title: Spectral Behavior of Solar Oscillations Modulated by Magnetic Variation

abstract:
  The principal aim of observational helioseismology is to determine mode
parameters of the solar oscillations as accurately as possible. Yet estimates
of the mode parameters are subject to many sources of noise, including
inevitable gaps in data, stochastic nature of excitation processes,
interferences among modes. Another uncertainty in frequency determination
results from a modulation of the oscillation frequency in itself. It is well
known that variation in the mean strength of the solar magnetic field modulates
the frequency. We consider effects of the solar magnetic field variation on the
spectral behavior of the power spectrum using a simple model. We show that the
solar magnetic field variation can cause unwanted sidelobes beside the main
peak in the power spectrum, and consequently show that the effect of the
frequency modulation due to the solar magnetic field variation can lead a bias
in frequency determinations. This effect should be considered seriously
particularly when the $ l \ne 0$ $p$-mode multiplets are analyzed to measure
the rotational splitting since the separations could be comparable. In addition
to a bias in frequency estimates, the line width is also likely to be
overestimated due to a line broadening. We therefore suggest that determination
of the mode parameters should be derived with due care considering the magnetic
field variation when a long data set is analyzed. The frequency modulation
should be taken into account in the analysis to make a solid conclusion on any
subtle dependence of the mode parameters, such as, that on the solar cycle. We
conclude by pointing out that a new method is required to accommodate the
stochastic force and the phase variation.


title:
The local stellar population of nova regions in the Large Magellanic
  Cloud

abstract:
  This study aims at identifying and understanding the parent population of
novae in the Large Magellanic Cloud (LMC) by studying the local, projected,
stellar population. The star formation history of the local environment around
novae is studied based on photometric data of stars and star clusters in the
nova neighbourhood, available in the OGLE II survey and star cluster
catalogues. The ages of stellar population within a few arcmin around novae
regions are estimated using isochrone fits to the V vs (V-I) colour-magnitude
diagrams. The fraction of stars in various evolutionary states are compared
using luminosity functions of the main-sequence stars and the red giant stars.
The age, density and luminosity function of the stellar population are
estimated around 15 novae. The upper limit of the age of the intermediate
stellar population is found to be 4 Gyr in all the regions, excepting the
region around the slow nova LMC 1948. Star formation in these regions is found
to have started between 4 - 2.0 Gyr, with a majority of the regions starting
the star formation at 3.2 Gyr. This star formation event lasted until 1.6 - 0.8
Gyr The star formation history of the underlying population of both the fast
and moderately fast novae indicate their parent population to be similar and
likely to be in the age range 3.2 - 1.0 Gyr. This is in good agreement with the
theoretical age estimates for Galactic cataclysmic variables. The region around
the slow nova shows a stellar population in the age range 1 - 10 Gyr, with a
good fraction belonging to an older population, consistent with the idea that
the progenitors of slow novae belong to older population.


title:
The coherent Raman scattering in astrophysics; application to a new
  model of quasar

abstract:
  The "Impulsive Stimulated Raman Scattering" (ISRS), is generally performed
using ultrashort laser pulses. It shifts the frequency of the laser beam
without any change of the wave surfaces and any appearance of extra lines. ISRS
works with the pulses which make the usual incoherent light provided that the
interactive medium is a low pressure gas having low frequency Raman
transitions, that is an hyperfine spectrum. ISRS has no intensity threshold,
but at low intensity level it becomes a linear effect, so that the relative
frequency shift $\Delta\nu/\nu$ is nearly constant in the spectrum. This linear
effect named "Incoherent Light, Coherent Raman Scattering" (ILCRS) may be
confused with a Doppler effect in astrophysics; it explains all optical
properties of the quasars, including the debatable ones, in particular the
width of the BAL lines, the infrared thermal radiation attributed to hot dust,
and the spectral discrepancies attributed to a variation of the hyperfine
constant.


title: GAIA and Population II Visual Binaries

abstract:
  The results of a kinematical population classification of 497 Hipparcos
orbital binaries are discussed. Less than 10% of the stars from the sample
belong to the thick disk. Only seven stars have halo kinematics. There are no
direct dynamical mass determinations for extreme halo stars. Some suggestions,
concerning Population II visual binaries for which ground-based astrometric
observations in combination with GAIA data will be useful in the future for the
better determination of orbits for long period Population II binaries, are
offered.


title:
Radiation hydrodynamics with neutrinos: Variable Eddington factor method
  for core-collapse supernova simulations

abstract:
  Neutrino transport and neutrino interactions in dense matter play a crucial
role in stellar core collapse, supernova explosions and neutron star formation.
Here we present a detailed description of a new numerical code for treating the
time and energy dependent neutrino transport in hydrodynamical simulations of
such events. The code is based on a variable Eddington factor method to deal
with the integro-differential character of the Boltzmann equation. The moments
of the neutrino distribution function and the energy and lepton number exchange
with the stellar medium are determined by iteratively solving the zeroth and
first order moment equations in combination with a model Boltzmann equation.
The latter is discretized on a grid of tangent rays. The integration of the
transport equations and the neutrino source terms is performed in a
time-implicit way. In the present version of the program, the transport part is
coupled to an explicit hydrodynamics code which follows the evolution of the
stellar plasma by a finite-volume method with piecewise parabolic
interpolation, using a Riemann solver for calculating the hydrodynamic states.
The neutrino source terms are implemented in an operator-split step. Neutrino
transport and hydrodynamics can be calculated with different spatial grids and
different time steppings. The structure of the described code is modular and
offers a high degree of flexibility for an application to relativistic and
multi-dimensional problems at different levels of refinement and accuracy. We
critically evaluate results for a number of test cases, including neutrino
transport in rapidly moving stellar media and approximate relativistic core
collapse, and suggest a path for generalizing the code to be used in
multi-dimensional simulations of convection in neutron stars and supernovae.


title: Planet accretion and the abundances of lithium isotopes

abstract:
  Planet accretion onto solar type stars may significantly change the stellar
atmospheric abundances of 6Li and 7Li if it takes place after the star has
arrived at the main sequence. Ingestion of planets at an earlier phase will not
affect theses abundances because of extensive pre-main sequence mixing and
burning. We present quantitative estimates of the main sequence evolution of
stellar surface lithium abundances after planet ingestion. At solar
metallicities, for stellar masses in the range ~ 1.3-1.1 M_sun, a large
fraction of the ingested 6Li is likely to be preserved during the whole main
sequence lifetime according to the standard model. Preservation of the less
fragile 7Li isotope occurs in a larger mass range ~ 1.3-0.9 M_sun. At high
metallicities typical of planet host stars, the ranges of masses are slightly
reduced essentially due to the thicker convective zones. Further reduction is
expected if non-standard processes cause extra-mixing of material below the
base of the convective zone, but even in this case there are stellar masses
where both isotopes are significantly preserved. We conclude that there is a
range of stellar effective temperature where migration and accretion of planets
and planetary material can be empirically tested using high-resolution
spectroscopy of the lithium isotopes.


title:
Cosmic ray acceleration at supergalactic accretion shocks: a new upper
  energy limit due to a finite shock extension

abstract:
  Accretion flows onto supergalactic-scale structures are accompanied with
large spatial scale shock waves. These shocks were postulated as possible
sources of ultra-high energy cosmic rays. The highest particle energies were
expected for perpendicular shock configuration in the so-called "Jokipii
diffusion limit", involving weakly turbulent conditions in the large-scale
magnetic field imbedded in the accreting plasma. For such configuration we
discuss the process limiting the highest energy that particles can obtain in
the first-order Fermi acceleration process due to finite shock extensions to
the sides, along and across the mean magnetic field. Cosmic ray outflow along
the shock structure can substantially lower (below ~10^18 eV for protons) the
upper particle energy limit for conditions considered for supergalactic shocks.


title:
On the Temperature and Intensity Distribution of the Galactic X-ray
  Plasma

abstract:
  We present the results of our investigation of the composition of the diffuse
soft X-ray background emission (SXRB). Combining data of the Leiden/Dwingeloo
HI Survey and the ROSAT All-Sky Survey (RASS), we set up a radiation transport
equation in order to model the SXRB. Two different techniques lead to the model
parameters: An image oriented approach which compares observed and modeled maps
of the 1/4 and 3/4 keV X-ray energy regime and a more analytic approach using
scatter diagrams. The analysis shows that only three independent components of
the emitting plasma (local, halo and extragalactic) are needed to explain the
SXRB. The results for the temperatures and X-ray intensities, which
characterize the three components, are given and compared to an alternative
model.


title: Timing analysis of the isolated neutron star RX J0720.4-3125

abstract:
  We present a combined analysis of XMM-Newton, Chandra and Rosat observations
of the isolated neutron star RXJ0720.4-3125, spanning a total period of \sim 7
years. We develop a maximum likelihood periodogramme for our analysis based on
the \Delta C-statistic and the maximum likelihood method, which are appropriate
for the treatment of sparse event lists. Our results have been checked "a
posteriori" by folding a further BeppoSAX dataset with the period predicted at
the time of that observation: the phase is found to be consistent. The study of
the spin history and the measure of the spin-down rate is of extreme importance
in discriminating between the possible mechanisms suggested for the nature of
the X-ray emission. The value of \dot P, here measured for the first time, is
\approx 10^{-14} s/s. This value can not be explained in terms of torque from a
fossil disk. When interpreted in terms of dipolar losses, it gives a magnetic
field of B \approx 10^{13} G, making also implausible that the source is
accreting from the underdense surroundings. On the other hand, we also find
unlikely that the field decayed from a much larger value (B\approx 10^{15} G,
as expected for a magnetar powered by dissipation of a superstrong field) since
this scenario predicts a source age of \approx 10^4 yrs, too young to match the
observed X-ray luminosity. The observed properties are more compatible with a
scenario in which the source is \approx 10^6 yrs old, and its magnetic field
has not changed substantially over the lifetime.


title: Torsionally excited methanol at 44.9 GHz

abstract:
  Using the Haystack Observatory 37-m radio telescope we have undertaken a
search for emission in the 2(0)-3(1)E rotational transition of methanol in its
first torsionally excited state (v_t=1) at 44.9 GHz. We examined seven galactic
sources -- six strong emitters of Class II methanol maser lines and Orion KL,
the only source where this line had been previously detected. We confirm (at a
level of 5\sigma) the previous detection and report two new detections -- a
reliable (9\sigma) detection in W3(OH) and a marginal (3.5\sigma) detection in
NGC 6334F. Upper limits for other sources are presented. Although we did not
see obvious signatures of maser amplification in this transition in any source,
arguments in favor of weak masing in W3(OH) are presented.


title: New Solar Seismic Models and the Neutrino Puzzle

abstract:
  The SoHO spacecraft made astrophysicists achieve a major breakthrough in the
knowledge of the Sun. In helioseismology, both GOLF and MDI experiments aboard
SoHO greatly improve the accuracy of seismic data. More specifically, the
detection of an enhanced number of low degree low order modes improves the
accuracy on the sound speed and density profiles in the solar core. After a
description of these profiles, we build solar seismic models. Different models
are considered and enable us to derive precise emitted neutrino fluxes. These
ones are validated by the seismic data and are in agreement with the recent
detected neutrinos, assuming 3 neutrino flavors. The seismic models are also
used to put limits on large scale magnetic fields in the solar interior. This
analysis puts some upper bounds of about 3x10^7 G in the radiative zone. Such a
field could slightly improve the emitted neutrino flux, which remains in
agreement with the Sudbury Neutrino Observatory result of 2001. From the models
we deduce gravity mode predictions, and the electron and neutron radial
densities that are useful to calculate the neutrino oscillations. We also begin
to discuss how the external magnetic field may influence such quantities.


title: Dynamical Masses of Elliptical Galaxies

abstract:
  Recent progress in the dynamical analysis of elliptical galaxy kinematics is
reviewed. Results reported briefly include (i) the surprisingly uniform
anisotropy structure of luminous ellipticals, (ii) their nearly flat (to $\sim
2R_e$) circular velocity curves, (iii) the Tully-Fisher and $M/L - L$ relations
and the connection to the Fundamental Plane, and (iv) the large halo mass
densities implied by the dynamical models.


title: The Galactic Bar

abstract:
  The Milky Way has a barred bulge. This article summarizes the current
understanding of the main structural parameters and pattern speed of the bar,
and compares predicted values for the microlensing optical depth with the bulge
microlensing observations.


title: Mass distribution in our Galaxy

abstract:
  This article summarizes recent work on the luminosity and mass distribution
of the Galactic bulge and disk, and on the mass of the Milky Way's dark halo. A
new luminosity model consistent with the COBE NIR data and the apparent
magnitude distributions of bulge clump giant stars has bulge/bar length of
$\simeq 3.5\kpc$, axis ratios of 1:(0.3-0.4):0.3, and short disk scale-length
($\simeq 2.1\kpc$). Gas-dynamical flows in the potential of this model with
constant M/L fit the terminal velocities in $10\deg\le |l| \le 50\deg$ very
well. The luminous mass distribution with this M/L is consistent with the
surface density of known matter near the Sun, but still underpredicts the
microlensing optical depth towards the bulge. Together, these facts argue
strongly for a massive, near-maximal disk in our $\sim L^\ast$, Sbc spiral
Galaxy. While the outer rotation curve and global mass distribution are not as
readily measured as in similar spiral galaxies, the dark halo mass estimated
from satellite velocities is consistent with a flat rotation curve continuing
on from the luminous mass distribution.


title: Timing study of the isolated neutron star RX J0720.4-3125

abstract:
  We present a combined analysis of XMM-Newton, Chandra and Rosat observations
of the isolated neutron star RX J0720.4-3125, spanning a total period of \sim 7
years. We develop a maximum likelihood periodogramme based on \Delta C
statistic and maximum likelihood method, which are appropriate for sparse event
lists. As an "a posteriori" check, we have folded a further BeppoSAX dataset
with the period predicted at the time of that observation, finding that the
phase is consistent. The value of the spin down rate, here measured for the
first time, is \approx 10^{-14} s/s and can not be explained in terms of
propeller or torque from a fossil disk. When interpreted in terms of dipolar
losses, it gives a magnetic field of B \approx 10^{13} G, making also
implausible that the source is accreting from the underdense surroundings. We
discuss the implications of this measure for the different mechanisms that have
been suggested to explain the X-ray emission. We conclude that the observed
properties are more compatible with a scenario in which the source is \approx
10^6 yrs old, and its magnetic field has not changed substantially over the
lifetime.


title: Cosmic Microwave Background anisotropies beyond the third peak

abstract:
  Forthcoming CMB experiments will allow us to accurately investigate the power
spectrum at very small scales ($\ell > 1000$). We predict the level of the
primary anisotropies, given the actual CMB measurements. The secondary
anisotropies generated after matter-radiation decoupling contribute additional
power in the tail of the CMB power spectrum. Together with the primary
anisotropies, we compute the predicted power spectra for three dominant
secondary effects induced by photon scattering. We predict these secondary
contributions in flat cosmological models for parameters in agreement (to
$2\sigma$) with the values allowed by current parameter estimates.


title:
High-Redshift Radio Galaxies as a Cosmological Tool: Exploration of a
  Key Assumption and Comparison with Supernova Results

abstract:
  There are many different approaches to using observations to constrain or
determine the global cosmological parameters that describe our universe.
Methods that rely upon a determination of the coordinate distance to
high-redshift sources are particularly useful because they do not involve
assumptions about the clustering properties of matter, or the evolution of this
clustering.
  Two of the methods currently being used to determine the coordinate distance
to high-redshift sources are the radio galaxy method and the supernova method.
These methods are similar in their dependence on the coordinate distance. Here,
the radio galaxy method is briefly described and results are presented. One of
the underlying assumptions of the method is explored. In addition, the method
is compared and contrasted to the supernova method. The constraints imposed on
global cosmological parameters by radio galaxies are consistent with those
imposed by supernovae.
  For a universe that is spatially flat with mean mass density $\Omega_m$ in
non-relativistic matter and mean mass density 1- $\Omega_m$ in quintessence,
radio galaxies alone indicate at 84 % confidence that the expansion of the
universe is accelerating at the current epoch. And, independent of whether or
not the universe is spatially flat, radio galaxies alone indicate at 95 %
confidence that $\Omega_m$ must be less than 0.6 at the current epoch.


title: Spectral Characteristics of X-ray Flashes compared to Gamma-Ray Bursts

abstract:
  X-ray flashes (XRFs) are a new type of fast transient source observed with
the BeppoSAX Wide Field Cameras (WFC) at a rate of about four per year. Apart
from their large fraction of 2-26 keV X-rays, the bulk properties of these
events are similar to those of classical gamma-ray bursts (GRBs). By
investigating the wide-band spectra of ten events detected in common with WFC
and BATSE, we explore the possibility that XRFs are a low-energy branch of the
GRB population. We find that XRF spectra are similar to those of GRBs, and that
their low peak energies could be an extension of known GRB properties.


title:
The origin of cyclic period changes in close binaries: the case of the
  Algol binary WW Cygni

abstract:
  Years to decade-long cyclic orbital period changes have been observed in
several classes of close binary systems including Algols, W Ursae Majoris and
RS Canum Venaticorum systems, and the cataclysmic variables. The origin of
these changes is unknown, but mass loss, apsidal motion, magnetic activity, and
the presence of a third body have all been proposed. In this paper we use new
CCD observations and the century-long historical record of the times of primary
eclipse for WW Cygni to explore the cause of these period changes. WW Cygni is
an Algol binary whose orbital period undergoes a 56 year cyclic variation with
an amplitude of approximately 0.02 days. We consider and reject the hypotheses
of mass transfer, mass loss, apsidal motion and the gravitational influence of
an unseen companion as the cause for these changes. A model proposed by
Applegate, which invokes changes in the gravitational quadrupole moment of the
convective and rotating secondary star, is the most likely explanation of this
star's orbital period changes. This finding is based on an examination of WW
Cygni's residual O-C curve and an analysis of the period changes seen in 66
other Algols. Variations in the gravitational quadrupole moment are also
considered to be the most likely explanation for the cyclic period changes
observed in several different types of binary systems.


title: Gravitational lenses magnify up to one third of the most distant quasars

abstract:
  Exceptionally bright quasars with redshifts up to z=6.28 have recently been
discovered. Quasars are thought to be powered by the accretion of gas onto
supermassive black holes at the centres of galaxies. Their maximum (Eddington)
luminosity is proportional to the mass of the black hole, and so these bright
quasars are inferred to have black holes with masses of more than a few billion
solar masses. The existence of such massive black holes poses a challenge to
models for the formation of structures in the early Universe, as it requires
that the black holes would grow so massive in less than a billion years after
the Big Bang. Here we show that up to a third of known quasars with z~6 will
have their observed flux magnified by a factor of 10 or more through
gravitational lensing by galaxies along the line of sight. The inferred
abundance of quasar host galaxies, as well as the luminosity density provided
by the quasars, are therefore substantially overestimated.


title: Cosmological constraints from the masses and abundances of L* galaxies

abstract:
  We place limits on the mean density of the universe and the slope of the
linear power spectrum around a megaparsec scale by comparing the universal mass
function to the observed luminosity function. Numerical simulations suggest
that the dark matter halo mass function at small scales depends only on
Omega_m(n_eff+3) independent of the overall power spectrum normalization.
Matching the halo abundance to the observed luminosity function requires
knowing the relation between the virial mass and luminosity (separately for
early and late type galaxies) and the fraction of galaxies that reside in
larger halos such as groups and clusters, all of which can be extracted from
the galaxy-galaxy lensing. We apply the recently derived values from SDSS and
find Omega_m(n_eff+3)= (0.15 \pm 0.05)/(1-f_dh), where f_dh accounts for the
possibility that some fraction of halos may be dark or without a bright central
galaxy. A model with Omega_m=0.25 and primordial n=0.8 or with Omega_m=0.2 and
n=1 agrees well with these constraints even in the absence of dark halos,
although with the current data somewhat higher values for Omega_m and n are
also acceptable.


title: Luminosity-metallicity relation for stars on the lower main sequence

abstract:
  We present a comparison of the predictions of stellar models with the
luminosity of the lower main sequence ($5.5 < M_V < 7.3$) using K dwarfs in the
Hipparcos catalog. The parallaxes of our comparison stars are known to better
than 15% and metallicities have been recently determined from photometry. A
major advantage of our comparison is that distances in our sample are known
with good accuracy, while tests that involve open and globular clusters are
constrained by potentially inaccurate distances. We show that the luminosity of
the lower main sequence relative to a fiducial (solar metallicity) isochrone is
a simple function of metallicity: $\Delta M_V = 0.84375 \times {\rm [ Fe/H]} -
0.04577$. We compare the data with a range of isochrones from the literature.
None of the models fit all the data, although some models do clearly better
than others. In particular, metal rich isochrones seem to be difficult to
construct.
  The relationship between luminosity, colour and metallicity for K dwarfs is
found to be very tight. We are thus able to derive metallicities for K dwarfs
based on their position in the Hipparcos colour-magnitude diagram with
accuracies better than 0.1 dex. The metallicity-luminosity relation for K
dwarfs leads to a new distance indicator with a wide range of possible
applications.


title: Gravitational Lensing of the SDSS High-Redshift Quasars

abstract:
  We predict the effects of gravitational lensing on the color-selected
flux-limited samples of z~4.3 and z>5.8 quasars, recently published by the
Sloan Digital Sky Survey (SDSS). Our main findings are: (i) The lensing
probability should be 1-2 orders of magnitude higher than for conventional
surveys. The expected fraction of multiply-imaged quasars is highly sensitive
to redshift and the uncertain slope of the bright end of the luminosity
function, beta_h. For beta_h=2.58 (3.43) we find that at z~4.3 and i*<20.0 the
fraction is ~4% (13%) while at z~6 and z*<20.2 the fraction is ~7% (30%). (ii)
The distribution of magnifications is heavily skewed; sources having the
redshift and luminosity of the SDSS z>5.8 quasars acquire median magnifications
of med(mu_obs)~1.1-1.3 and mean magnifications of <mu_obs>~5-50. Estimates of
the quasar luminosity density at high redshift must therefore filter out
gravitationally-lensed sources. (iii) The flux in the Gunn-Peterson trough of
the highest redshift (z=6.28) quasar is known to be f_lambda<3 10^-19
erg/sec/cm^2/Angstrom. Should this quasar be multiply imaged, we estimate a 40%
chance that light from the lens galaxy would have contaminated the same part of
the quasar spectrum with a higher flux. Hence, spectroscopic studies of the
epoch of reionization need to account for the possibility that a lens galaxy,
which boosts the quasar flux, also contaminates the Gunn-Peterson trough. (iv)
Microlensing by stars should result in ~1/3 of multiply imaged quasars in the
z>5.8 catalog varying by more than 0.5 magnitudes over the next decade. The
median equivalent width would be lowered by ~20% with respect to the intrinsic
value due to differential magnification of the continuum and emission-line
regions.


title:
TACMB-1: The Theory of Anisotropies in the Cosmic Microwave Background
  (Bibliographic Resource Letter)

abstract:
  This Resource Letter provides a guide to the literature on the theory of
anisotropies in the cosmic microwave background. Journal articles, web pages,
and books are cited for the following topics: discovery, cosmological origin,
early work, recombination, general CMB anisotropy references, primary CMB
anisotropies (numerical, analytical work), secondary effects,
Sunyaev-Zel'dovich effect(s), lensing, reionization, polarization, gravity
waves, defects, topology, origin of fluctuations, development of fluctuations,
inflation and other ties to particle physics, parameter estimation, recent
constraints, web resources, foregrounds, observations and observational issues,
and gaussianity.


title: Laminar Plasma Dynamos

abstract:
  A new kind of dynamo utilizing flowing laboratory plasmas has been
identified. Conversion of plasma kinetic energy to magnetic energy is verified
numerically by kinematic dynamo simulations for magnetic Reynolds numbers above
210. As opposed to intrinsically-turbulent liquid-sodium dynamos, the proposed
plasma dynamos correspond to laminar flow topology. Modest plasma parameters,
1-20 eV temperatures, 10^{19}-10^{20} m^{-3} densities in 0.3-1.0 m
scale-lengths driven by velocities on the order of the Alfven Critical
Ionization Velocity (CIV), self-consistently satisfy the conditions needed for
the magnetic field amplication. Growth rates for the plasma dynamos are
obtained numerically with different geometry and magnetic Reynolds numbers.
Magnetic-field-free coaxial plasma guns can be used to sustain the plasma flow
and the dynamo.


title:
The Luminosity & Mass Function of the Trapezium Cluster: From B stars to
  the Deuterium Burning Limit

abstract:
  We use the results of a new, multi-epoch, multi-wavelength, near-infrared
census of the Trapezium Cluster in Orion to construct and to analyze the
structure of its infrared (K band) luminosity function. Specifically, we employ
an improved set of model luminosity functions to derive this cluster's
underlying Initial Mass Function (IMF) across the entire range of mass from OB
stars to sub-stellar objects down to near the deuterium burning limit. We
derive an IMF for the Trapezium Cluster that rises with decreasing mass, having
a Salpeter-like IMF slope until near ~0.6 M_sun where the IMF flattens and
forms a broad peak extending to the hydrogen burning limit, below which the IMF
declines into the sub-stellar regime. Independent of the details, we find that
sub-stellar objects account for no more than ~22% of the total number of likely
cluster members. Further, the sub-stellar Trapezium IMF breaks from a steady
power-law decline and forms a significant secondary peak at the lowest masses
(10-20 times the mass of Jupiter). This secondary peak may contain as many as
\~30% of the sub-stellar objects in the cluster. Below this sub-stellar IMF
peak, our KLF modeling requires a subsequent sharp decline toward the planetary
mass regime. Lastly, we investigate the robustness of pre-main sequence
luminosity evolution as predicted by current evolutionary models, and we
discuss possible origins for the IMF of brown dwarfs.


title:
Modelling the spectral energy distribution of galaxies from the
  ultraviolet to submillimeter

abstract:
  We present results from a new modelling technique which can account for the
observed optical/NIR - FIR/submm spectral energy distributions (SEDs) of normal
star-forming galaxies in terms of a minimum number of essential parameters
specifying the star-formation history and geometrical distribution of stars and
dust. The model utilises resolved optical/NIR images to constrain the old
stellar population and associated dust, and geometry-sensitive colour
information in the FIR/submm to constrain the spatial distributions of young
stars and associated dust. It is successfully applied to the edge-on spirals
NGC891 and NGC5907. In both cases the young stellar population powers the bulk
of the FIR/sub-mm emission. The model also accounts for the observed surface
brightness distribution and large-scale radial brightness profiles in NGC891 as
determined using the Infrared Space Observatory (ISO) at 170 and 200 mcrions
and at 850 micron using SCUBA.


title:
The X-Ray Position and Infrared Counterpart of the Eclipsing X-Ray
  Pulsar OAO 1657-415

abstract:
  We have measured the precise position of the 38-s eclipsing X-ray pulsar OAO
1657-415 with the Chandra X-Ray Observatory: RA = 17h00m48.90s, Dec =
-41d39m21.6s, equninox J2000, error radius = 0.5 arcsec. Based on the
previously measured pulsar mass function and X-ray eclipse duration, this
10.4-d high-mass X-ray binary is believed to contain a B supergiant companion.
Deep optical imaging of the field did not detect any stars at the Chandra
source position, setting a limit of V>23. However, near-IR imaging revealed a
relatively bright star (J=14.1, H=11.9, K_s=10.7) coincident with the Chandra
position, and we identify this star as the IR counterpart of OAO 1657-415. The
IR colors and magnitudes and the optical non-detections for this star are all
consistent with a highly reddened B supergiant (A_V= 20.4 +/- 1.3) at a
distance of 6.4 +/- 1.5 kpc. This implies an X-ray luminosity of 3e36 erg/s
(2-10 keV). IR spectroscopy can verify the spectral type of the companion and
measure its radial velocity curve, yielding a neutron star mass measurement.


title:
Luminous Matter Distribution, Bulk Flows and Baryon Contents in
  Cosmological Models with a Local Void

abstract:
  First, we consider galaxy formation from the viewpoint of hierarchical
clustering theory and discuss the possibility that inhomogeneous models with a
local void may be compatible with the observed homogeneity of galactic
distributions found by recent redshift surveys, because their inhomogeneity can
be weakened by the difference in the feedback system of galaxy formation
between the inner and outer regions. Next, it is shown with the results of
numerical simulations that the observed inhomogeneity of two-point correlations
of galaxies can be accounted for by these models. Also, the natural appearance
of bulk flows for an off-central observer is shown. Finally the inhomogeneity
of baryon contents is discussed from the viewpoint of our inhomogeneous models.


title: High-resolution single-pulse studies of the Vela Pulsar

abstract:
  We present high-resolution multi-frequency single-pulse observations of the
Vela pulsar, PSR B0833-45, aimed at studying micro-structure, phase-resolved
intensity fluctuations and energy distributions at 1.41 and 2.30 GHz. We show
that the micro-pulse width in pulsars has a period dependence. Like individual
pulses, Vela's micro-pulses are highly elliptically polarized. There is a
strong correlation between Stokes parameters V and I in the micro-structure. We
show that the V/I distribution is Gaussian with a narrow width and that this
width appears to be constant as a function of pulse phase. The phase-resolved
intensity distributions of I are best fitted with log-normal statistics. Extra
emission components, i.e.``bump'' and ``giant micro-pulses'', discovered by
Johnston et al.(2001) are also present at 2.3 GHz. The bump component seems to
be an extra component superposed on the main pulse profile but does not appear
periodically. The giant micro-pulses are time-resolved and have significant
jitter in their arrival times. Their flux density distribution is best fitted
by a power-law, indicating a link between these features and ``classical''
giant pulses as observed for the Crab pulsar, (PSR B0531+21), PSR B1937+21 and
PSR B1821-24. We find that Vela contains a mixture of emission properties
representing both ``classical'' properties of radio pulsars (e.g.
micro-structure, high degree of polarization, S-like position angle swing,
orthogonal modes) and features which are most likely related to high-energy
emission (e.g. extra profile components, giant micro-pulses). It hence
represents an ideal test case to study the relationship between radio and
high-energy emission in significant detail.


title:
Line formation in convective stellar atmospheres. I. Granulation
  corrections for solar photospheric abundances

abstract:
  In an effort to estimate the largely unknown effects of photospheric
temperature fluctuations on spectroscopic abundance determinations, we have
studied the problem of LTE line formation in the inhomogeneous solar
photosphere based on detailed 2-dimensional radiation hydrodynamics simulations
of the convective surface layers of the Sun. By means of a strictly
differential 1D/2D comparison of the emergent equivalent widths, we have
derived "granulation abundance corrections" for individual lines, which have to
be applied to standard abundance determinations based on homogeneous 1D model
atmospheres in order to correct for the influence of the photospheric
temperature fluctuations. In general, we find a line strengthening in the
presence of temperature inhomogeneities as a consequence of the non-linear
temperature dependence of the line opacity. For many lines of practical
relevance, the magnitude of the abundance correction may be estimated from
interpolation in the tables and graphs provided with this paper. The
application of abundance corrections may often be an acceptable alternative to
a detailed fitting of individual line profiles based on hydrodynamical
simulations. The present study should be helpful in providing upper bounds for
possible errors of spectroscopic abundance analyses, and for identifying
spectral lines which are least sensitive to the influence of photospheric
temperature inhomogeneities.


title: Neutral hydrogen in dwarf galaxies I. The spatial distribution of HI

abstract:
  This paper is the first in a series presenting a sample of 29 late-type dwarf
galaxies, observed with the Westerbork Synthesis Radio Telescope (WSRT) in the
21-cm line of neutral atomic hydrogen (HI). The sample itself, the HI content
of and the HI distribution in the sample galaxies are briefly discussed. Four
sample galaxies were also detected in the continuum.


title: The role of multipolar magnetic fields in pulsar magnetospheres

abstract:
  We explore the role of complex multipolar magnetic fields in determining
physical processes near the surface of rotation powered pulsars. We model the
actual magnetic field as the sum of global dipolar and star-centered multipolar
fields. In configurations involving axially symmetric and uniform multipolar
fields, 'neutral points' and 'neutral lines' exist close to the stellar
surface. Also, the curvature radii of magnetic field lines near the stellar
surface can never be smaller than the stellar radius, even for very high order
multipoles. Consequently, such configurations are unable to provide an
efficient pair creation process above pulsar polar caps, necessary for plasma
mechanisms of generation of pulsar radiation. In configurations involving
axially symmetric and non-uniform multipoles, the periphery of the pulsar polar
cap becomes fragmented into symmetrically distributed narrow sub-regions where
curvature radii of complex magnetic field lines are less than the radius of the
star. The pair production process is only possible just above these
'favourable' sub-regions. As a result, the pair plasma flow is confined within
narrow filaments regularly distributed around the margin of the open magnetic
flux tube. Such a magnetic topology allows us to model the system of twenty
isolated sub-beams observed in PSR B0943+10 by Deshpande & Rankin (1999, 2001).
We suggest a physical mechanism for the generation of pulsar radio emission in
the ensemble of finite sub-beams, based on specific instabilities. We propose
an explanation for the subpulse drift phenomenon observed in some long-period
pulsars.


title:
Calibration of the Barnes-Evans relation using interferometric
  observations of Cepheids

abstract:
  Direct diameter observations of Cepheid variables are used to calibrate the
Barnes-Evans Cepheid surface brightness relation. Fifty-nine separate Cepheid
diameter measurements from four different optical interferometers are used to
calculate surface brightnesses as a function of magnitude and color. The linear
fit to Cepheid surface brightness versus color is in excellent agreement with
functions in the literature found using interferometric observations of
non-variable giant and supergiant stars (Fouque & Gieren 1997). Using these
relations the distance is calculated to delta Cephei, for which an independent
distance is known from trigonometric parallax. The distance from the relation
in this paper differs from that derived by the previously published relation by
4% but is still marginally within the combined errors. Both distances are well
within the errors of the distance derived from trigonometric parallax.


title:
Cosmic Shear and Power Spectrum Normalization with the Hubble Space
  Telescope

abstract:
  Weak lensing by large-scale structure provides a direct measurement of matter
fluctuations in the universe. We report a measurement of this `cosmic shear'
based on 271 WFPC2 archival images from the Hubble Space Telescope Medium Deep
Survey (MDS). Our measurement method and treatment of systematic effects were
discussed in an earlier paper. We measure the shear variance on scales ranging
from 0.7' to 1.4', with a detection significance greater than 3.8. This allows
us to measure the normalization of the matter power spectrum to be sigma8 =
(0.94 +/- 0.10 +/- 0.14) (0.3/Omega_m)^0.44 (0.21/Gamma)^0.15, in a LCDM
universe. The first 1sigma error includes statistical errors only, while the
latter also includes (gaussian) cosmic variance and the uncertainty in the
galaxy redshift distribution. Our results are consistent with earlier cosmic
shear measurements from the ground and from space. We compare our cosmic shear
results and those from other groups to the normalization from cluster abundance
and galaxy surveys. We find that the combination of four recent cosmic shear
measurements are somewhat inconsistent with the recent normalization using
these methods, and discuss possible explanations for the discrepancy.


title:
Statistics and multiwavelength synthesis models: towards a new
  generation of synthesis models

abstract:
  In this contribution I present my current work in a new generation of
evolutionary synthesis models that compute the multiwavelength energy
distribution (from gamma-rays to radio) as well as the associated dispersion
for young stellar systems. I will also show some statistical effects that may
appear in the analysis of surveys, like bimodal or multi-modal distributions
and bias when color indices computed by the codes are compared with
observations. Such new generation of synthesis models may be useful for the
analysis of the data expected from GTC.


title: Neutral hydrogen in dwarf galaxies. II. The kinematics of HI

abstract:
  This paper is the second in a series presenting a sample of 29 late-type
dwarf galaxies observed with the Westerbork Synthesis Radio Telescope in the
21-cm line of neutral hydrogen (HI). Here we present rotation curves, maps of
the velocity field and maps of the velocity dispersion across the sample
galaxies.


title:
Joint Cosmic Shear Measurements with the Keck and William Herschel
  Telescopes

abstract:
  The recent measurements of weak lensing by large-scale structure present
significant new opportunities for studies of the matter distribution in the
universe. Here, we present a new cosmic shear survey carried out with the
Echelle Spectrograph and Imager on the Keck II telescope. This covers a total
of 0.6 square degrees in 173 fields probing independent lines of sight, hence
minimising the impact of sample variance. We also extend our measurements of
cosmic shear with the William Herschel Telescope (Bacon, Refregier & Ellis
2000) to a survey area of 1 square degree. The joint measurements with two
independent telescopes allow us to assess the impact of instrument-specific
systematics, one of the major difficulties in cosmic shear measurements. For
both surveys, we carefully account for effects such as smearing by the point
spread function and shearing due to telescope optics. We find negligible
residuals in both cases and recover mutually consistent cosmic shear signals,
significant at the 5.1 sigma level. We present a simple method to compute the
statistical error in the shear correlation function, including non-gaussian
sample variance and the covariance between different angular bins. We measure
shear correlation functions for all fields and use these to ascertain the
amplitude of the matter power spectrum, finding sigma_8 (Omega_m/0.3)^0.68 =
0.97 \pm 0.13 with 0.14<Omega_m<0.65 in a Lambda-CDM model with Gamma=0.21.
These 68% CL uncertainties include sample variance, statistical noise, redshift
uncertainty, and the error in the shear measurement method. The results from
our two independent surveys are both consistent with measurements of cosmic
shear from other groups. We discuss how our results compare with current
normalisation from cluster abundance.


title: Variable stars in the core of the globular cluster M3

abstract:
  We present the results of a survey for variable stars in the core of the
globular cluster M3. Our findings include the discovery of eleven new or
suspected variables, including a possible W Vir, and the first period
determinations for thirteen previously known variables.


title: What are the Hot R Coronae Borealis Stars?

abstract:
  We investigate the evolutionary status of four stars: V348 Sgr, DY Cen and MV
Sgr in the Galaxy and HV 2671 in the LMC. These stars have in common random
deep declines in visual brightness which are characteristic for R Coronae
Borealis (RCB) stars. RCB stars are typically cool, hydrogen deficient
supergiants. The four stars studied in this paper are hotter (T$_{\rm eff}$ =
15-20 kK) than the majority of RCB stars (T$_{\rm eff}$ = 5000-7000 K).
Although these are commonly grouped together as the \emph{hot RCB stars} they
do not necessarily share a common evolutionary history. We present new
observational data and an extensive collection of archival and
previously-published data which is reassessed to ensure internal consistency.
We find temporal variations of various properties on different time scales
which will eventually help us to uncover the evolutionary history of these
objects. DY Cen and MV Sgr have typical RCB helium abundances which excludes
any currently known post-AGB evolutionary models. Moreover, their carbon and
nitrogen abundances present us with further problems for their interpretation.
V348 Sgr and HV 2671 are in general agreement with a born-again post-AGB
evolution and their abundances are similar to Wolf-Rayet central stars of PN.
The three Galactic stars in the sample have circumstellar nebulae which produce
forbidden line radiation (for HV 2671 we have no information). V348 Sgr and DY
Cen have low density, low expansion velocity nebulae (resolved in the case of
V348 Sgr), while MV Sgr has a higher density, higher expansion velocity nebula.


title:
On the Degeneracy Inherent in Observational Determination of the Dark
  Energy Equation of State

abstract:
  Using a specific model for the expansion rate of the Universe as a function
of scale factor, it is demonstrated that the equation of state of the dark
energy cannot be determined uniquely from observations at redshifts
$z\lesssim{\rm a few}$ unless the fraction of the mass density of the Universe
in nonrelativistic particles, $\Omega_M$, somehow can be found independently. A
phenomenological model is employed to discuss the utility of additional
constraints from the formation of large scale structure and the positions of
CMB peaks in breaking the degeneracy among models for the dark energy.


title:
The First Orbital Period for a Dwarf Nova in a Globular Cluster: V101 in
  M5

abstract:
  We report the first orbital period determination for a Dwarf Nova (DN) in a
glubular cluster: V101 in M5 has a period of 5.796 +- 0.036 hours. We derived
this period from I-band photometry acquired with the Calypso Observatory High
Resolution Camera operating with tip-tilt adaptive optics correction.
Observations from the South African Astronomical Observatory in the V-band were
also analyzed and exhibit a periodic signal of the same period. This orbital
period suggests that V101 has a secondary of mid to late K spectral type with
Mv = +8.2 +- 0.5. The predicted spectral type is consistent with previous
spectral observations in quiescence which show a fairly red continuum. From the
observed minimum brightness of V = 22.5, we derive a distance modulus of (m -
M)v = 14.3 +- 0.5 to the DN which supports V101's membership in the globular
cluster M5. Measurement of the ellipsoidality effect indicates that the orbital
plane of the V101 system is moderately inclined, but not enough to exhibit
eclipses.


title: Non-LTE Effects of Na I in the Atmosphere of HD209458b

abstract:
  The recent announcement that sodium absorption has been observed in the
atmosphere of HD209458b, the only EGP observed to transit its parent star, is
the first direct detection of an EGP atmosphere. We explore the possibility
that neutral sodium is {\em not} in local thermodynamic equilibrium (LTE) in
the outer atmosphere of irradiated EGPs and that the sodium concentration may
be underestimated by models that make the LTE assumption. Our results indicate
that it may not be necessary to invoke excessive photoionization, low
metallicity, or even high altitude clouds to explain the observations.


title:
Comment on ``Adiabatic stabilization: Observation of the surviving
  population''

abstract: This paper has been withdrawn by the authors.


title: Temperature Variations and Abundance Determinations in Planetary Nebulae

abstract:
  It is argued that an important fraction of PNe present large temperature
variations that are not due to observational errors nor to incomplete atomic
physics. Seven possible causes for these variations are reviewed, one of them
is presented for the first time.


title:
Systematic Effects on Tangential and Radial Arc Statistics: The Finite
  Source Size and Ellipticities of the Lens and Source

abstract:
  It has been recognized that the arc statistics of gravitational lensing is a
useful probe of the density profile of clusters of galaxies. We examine several
systematic effects which are important in predicting the number of arcs, with
particular attention to the difference between tangential and radial arcs.
First we derive an analytic expression of the cross section for radial arcs
taking account of the source size and find that the moderate source size
enhances the cross section for radial arcs while larger source size (\gtrsim
1'' in our example) suppresses the number of radial arcs. On the other hand,
tangential arcs are much less sensitive to the source size. Next we numerically
calculate the cross section for arcs considering the lens and source
ellipticities. We find that the numbers of both tangential and radial arcs are
highly enhanced by both ellipticities, by one or two orders of magnitude. The
number ratio of radial to tangential arcs is, however, not so affected if the
threshold axis ratio of arcs is large (\gtrsim 7). The number ratio therefore
still remains good statistics which probe the density profile of the lens
objects, if the source size effect is correctly taken into account.


title: The shape of rotation curves: models vs. observations

abstract:
  We discuss the shape and decomposition of rotation curves (RCs) of galaxies
formed within growing cold dark matter halos. The outer RC shape correlates
mainly with the surface brightness (SB), the luminous mass fraction, fd, and
the bulge fraction. In order the shapes of RC depend significantly on
luminosity, fd should be a strong function of mass (feedback). For the
preferred values of fd (\lesssim 0.03), the high SB models can be maximum disks
only when the halos have a shallow core. The low SB models are sub-maximum
disks. The residuals of the baryonic Tully-Fisher (TF) and disk mass-radius
relations show a clear anti-correlation among them, but when one passes to the
TF and luminosity-radius relations, the anti-correlation almost disappears.
Therefore, the observed lack of correlation among the residuals of the last two
relations should not be interpreted as an evidence of sub-maximal disks.


title:
Deep Near Infrared Observations of the X-ray Emitting Class 0 Protostar
  Candidates in the Orion Molecular Cloud-3

abstract:
  We obtained near infrared (NIR) imaging with the Subaru Telescope of the
class 0 protostar candidates in the Orion Molecular Cloud-3, two of which were
discovered to have X-ray emission by the Chandra X-ray Observatory. We found
strong evidence for the class~0 nature of the X-ray sources. First, our deep
K-band image shows no emission brighter than 19.6 mag from both of these X-ray
sources. Since class I protostars or class II T Tauri stars should be easily
detected in the NIR with this sensitivity, the lack of K-band detection
suggests that they are likely much more obscured than class I protostars.
Second, our H2 v=1-0 S(1) image shows a bubble-like feature from one of the
X-ray class 0 protostar candidates, which reinforces the idea that this is a
class 0 protostar. We also discuss the nature of nine NIR sources found in our
deep image based on their colors, spatial coincidence with millimeter cores,
and the properties of their X-ray counterparts.


title:
Binaries discovered by the SPY project. II. HE 1414-0848: a double
  degenerate with a mass close to the Chandrasekhar limit

abstract:
  In the course of our search for double degenerate (DD) binaries as potential
progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT
(ESO SN Ia Progenitor surveY - SPY) we discovered that the white dwarf HE
1414-0848 is a double-lined DA+DA binary with an orbital period of P = 12h 25m
39s. Semi-amplitudes of 128km/s and 100km/s are derived for the individual
components. The amplitude ratio and the measured difference in gravitational
redshift is used to estimate the masses of the individual components: 0.55Msol
and 0.71Msol. Hence the total mass of the HE 1414-0848 system is 1.26Msol, only
10% below the Chandrasekhar limit. The results of a model atmosphere analysis
are consistent with our mass estimated from the orbit. Temperatures of the
individual components are also determined. Possible scenarios for the formation
of this system are discussed. The system will merge due to loss of angular
momentum via gravitational wave radiation after two Hubble times. HE 1414-0848
does not qualify as a SN Ia progenitor, but it is the most massive close DD
known today.


title: Multiwavelength Rotation Curves to Test Dark Halo Central Shapes

abstract:
  We use Fabry-Perot Halpha spectroscopy, complemented with published HI radio
synthesis observations to derive high resolution rotation curves of spiral
galaxies. We investigate precisely their inner mass distribution and compare it
to CDM simulations predictions. Having verified the existence of the so-called
core-cusp problem, we find that the dark halo density inner slope is related to
the galaxy masses. Dwarf galaxies with V_max < 100 km/s have halo density inner
slope 0 < \gamma < 0.7 while galaxies with V_max > 100 km/s are best fitted by
\gamma >= 1.


title: Search for progenitors of supnernovae type Ia with SPY

abstract:
  We have started a large survey for double degenerate (DD) binaries as
potential progenitors of type Ia supernovae with the UVES spectrograph at the
ESO VLT (ESO SN Ia Progenitor surveY - SPY). About 400 white dwarfs were
checked for radial velocity variations during the first 15 months of this
project, twice the number of white dwarfs investigated during the last 20
years. We give an overview of the SPY project and present first results Fifty
four new DDs have been discovered, seven of them double lined (only 18 and 6
objects of these groups were known before, respectively). The final sample is
expected to contain 150 to 200 DDs. Eight new pre-cataclysmic binaries were
also detected. SPY is the first DD survey which encompasses also non-DA white
dwarfs. SPY produces an immense, unique sample of very high resolution white
dwarf spectra, which provides a lot of spin-off opportunities. We describe our
projects to exploit the SPY sample for the determination of basic parameters,
kinematics, and rotational velocities of white dwarfs. A catalogue with a first
subset of our white dwarf data has already been published by Koester et al.
2001.


title: Spatial distribution of galactic halos and their merger histories

abstract:
  We use a novel statistical tool, the mark correlation functions (MCFs), to
study clustering of galaxy-size halos as a function of their properties and
environment in a high-resolution numerical simulation of the LambdaCDM
cosmology. We applied MCFs using several types of continuous and discrete
marks: maximum circular velocity of halos, merger mark indicating whether halos
experienced or not a major merger in their evolution history, and a stripping
mark indicating whether the halo underwent a tidal stripping. We find that
halos which experienced a relatively early (z>1) major merger or mass loss (due
to tidal stripping) in their evolution histories are over-abundant in halo
pairs with separations < 3 Mpc/h. This result can be interpreted as spatial
segregation of halos with different merger histories, qualitatively similar to
the morphological segregation in the observed galaxy distribution. The analysis
presented in this paper demonstrate that MCFs provide powerful, yet
algorithmically simple, quantitative measures of segregation in the spatial
distribution of objects with respect to their various properties (marks).


title:
Measuring $\alpha$ in the Early Universe: CMB Temperature, Large-Scale
  Structure and Fisher Matrix Analysis

abstract:
  We extend our recent work on the effects of a time-varying fine-structure
constant $\alpha$ in the cosmic microwave background, by providing a thorough
analysis of the degeneracies between $\alpha$ and the other cosmological
parameters, and discussing ways to break these with both existing and/or
forthcoming data. In particular, we present the state-of-the-art CMB
constraints on $\alpha$, through a combined analysis of the BOOMERanG, MAXIMA
and DASI datasets. We also present a novel discussion of the constraints on
$\alpha$ coming from large-scale structure observations, focusing in particular
on the power spectrum from the 2dF survey. Our results are consistent with no
variation in $\alpha$ from the epoch of recombination to the present day, and
restrict any such (relative) variation to be less than about 4%. We show that
the forthcoming MAP and (particularly) Planck experiments will be able to break
most of the currently existing degeneracies between $\alpha$ and other
parameters, and measure $\alpha$ to better than percent accuracy.


title:
Mass Composition of Cosmic Rays in the Range 2 x 10^17 - 3 x 10^18
  Measured with Haverah Park Array

abstract:
  At the Haverah Park Array a number of air shower observables were measured
that are relevant to the determination of the mass composition of cosmic rays.
In this paper we discuss measurements of the risetime of signals in large area
water-Cherenkov detectors and of the lateral distribution function of the
water-Cherenkov signal. The former are used to demonstrate that the CORSIKA
code, using the QGSJET98 model, gives an adequate description of the data with
a low sensitivity, in this energy range, to assumptions about primary mass. By
contrast the lateral distribution is sufficiently well measured that there is
mass sensitivity. We argue that in the range 0.2-1.0 EeV the data are well
represented with a bi-modal composition of 34+-2 % protons and the rest iron.
We also discuss the systematic errors induced by the choice of hadronic model.


title:
On a probable manifestation of Hubble expansion at the local scales, as
  inferred from LLR data

abstract:
  Processing the data of lunar laser ranging (LLR), whose accuracy now reaches
a few millimeters, points to the effect of anomalous increase in the lunar
semimajor axis (with an excessive rate 1.3 cm/yr), which cannot be attributed
to the well-known tidal exchange of angular momentum between the Earth and
Moon. One of the possible interpretations of the above-mentioned anomaly may be
the "local" Hubble expansion with H = 33 +/- 5 (km/s)/Mpc. This small value of
the local Hubble constant (about two times less than at intergalactic scales)
can be reasonably explained if it is formed only by some kind of an unclumped
"dark matter" or "dark energy", while the other kinds of matter experienced a
gravitational instability, formed compact objects, and no longer contribute to
the formation of Hubble expansion at the local scales.


title:
Exotic meteoritic phenomena: The Tunguska event and anomalous low
  altitude fireballs -- manifestations of the mirror world?

abstract:
  There are a number of very puzzling meteoritic events including (a) The
Tunguska event. It is the only known example of a low altitude atmospheric
explosion. It is also the largest recorded event. Remarkably no fragments or
significant chemical traces have ever been recovered. (b) Anomalous low
altitude fireballs which (in some cases) have been observed to hit the ground.
The absence of fragments is particularly striking in these cases, but this is
not the only reason they are anomalous. On the other hand, there is strong
evidence that most of our galaxy is made from exotic dark material - `dark
matter'. Mirror matter is one well motivated dark matter candidate, since it is
dark and stable and it is required to exist if particle interactions are mirror
symmetric. If mirror matter is the dark matter, then some amount must exist in
our solar system. We demonstrate that the mirror matter theory allows for a
simple explanation for the puzzling meteoritic events [both (a) and (b)] if
they are due to mirror matter space-bodies. A direct consequence of this
explanation is that mirror matter fragments should exist in (or on) the ground
at various impact sites. The properties of this potentially recoverable
material depend importantly on the sign of the photon-mirror photon kinetic
mixing parameter, $\epsilon$. We argue that the broad characteristics of the
anomalous events suggests that $\epsilon$ is probably negative. Strategies for
detecting mirror matter in the ground are discussed.

categories: astro-ph cond-mat hep-ph physics.space-ph


title: A perspective on the CMB acoustic peak

abstract:
  CMB angular spectrum measurements suggest a flat universe. This paper
clarifies the relation between geometry and the spherical harmonic index of the
first acoustic peak ($\ell_{peak}$). Numerical and analytic calculations show
that $\ell_{peak}$ is approximately a function of $\Omega_K/\Omega_M$ where
$\Omega_K$ and $\Omega_M$ are the curvature ($\Omega_K > 0$ implies an open
geometry) and mass density today in units of critical density. Assuming
$\Omega_K/\Omega_M \ll 1$, one obtains a simple formula for $\ell_{peak}$, the
derivation of which gives another perspective on the widely-recognized
$\Omega_M$-$\Omega_\Lambda$ degeneracy in flat models. This formula for
near-flat cosmogonies together with current angular spectrum data yields
familiar parameter constraints.


title:
Heavy Element Abundances and Dust Depletions in the Host Galaxies of
  Three Gamma-Ray Bursts

abstract:
  We have derived the column densities of heavy elements in three gamma-ray
burst (GRB) optical transients, associated with the circumburst or interstellar
medium (ISM) of the host galaxy. In comparison with the same elements observed
in damped Lyman-alpha (DLA) systems along QSO sight lines, we find evidence for
much higher column densities of ZnII. The gap between the QSO-DLA and GRB-DLA
distributions is smoothly bridged by observations of the interstellar
absorption in the Milky Way and the Magellanic Clouds. Very small [Fe/Zn],
[Si/Zn], and [Cr/Zn] values in GRB-DLAs indicate large dust depletions. Once
the dust-to-metals ratios are determined, we find an optical extinction A_V ~ 1
mags, to be compared with typical A_V < 0.1 in most QSO-DLAs. Our inference of
high dust content appears to be in contradiction with the typical low reddening
previously found in GRBs. One possible way to reconcile is a dust grain-size
distribution biased towards big grains, which would give a grey extinction.
Possibly the small dust grains have been destroyed by the GRBs themselves. Our
findings support the idea that primarily optically selected QSOs probe mainly
low gas/dust regions of high redshift galaxies, while the more powerful GRBs
can be detected through denser regions of their ISM (molecular clouds and star
forming regions). Therefore GRB-DLAs and QSO-DLAs together provide a more
complete picture of the global properties of the interstellar medium in high
redshift galaxies.


title: UVES Be observations of early-G dwarfs in old clusters

abstract:
  We have obtained the first beryllium measurements of late F/early G-type
stars in the old open cluster M67 (4.5 Gyr) and in the intermediate age cluster
IC 4651 (1.7 Gyr). One member of the young cluster IC 2391 (~50 Myr) was also
observed. Our sample stars have effective temperatures within a range of +30 -
+380 K from the solar temperature. All our sample stars, including the Sun and
the young cluster star have, within the errors, the same Be abundance. This
result implies that late F/early G-type stars undergo very little (if any) Be
depletion during their main-sequence life-time. Since these stars have
undergone some Li depletion, our finding is indicative of shallow mixing, i.e.
of a mixing process that can transport surface material deep enough for Li
burning to occur, but not deep enough for Be burning. As shown in previous
studies, the Li vs. Be diagram is a powerful diagnostic of stellar interiors.
In this context, we do not find any evidence of correlated Li and Be depletion;
furthermore, a comparison with various models shows that the Be pattern of our
sample stars is compatible only with models including gravity waves. This class
of models, however, cannot reproduce the Li observations of M 67.


title:
A photometric study of the two poorly known northern open clusters NGC
  133 and NGC 1348

abstract:
  We present CCD UBVI observations obtained in the field of the previously
unstudied northern open clusters NGC 133 and NGC 1348. We argue that NGC 133 is
a heavily contaminated cluster, for which we identify 13 candidate members down
to $V$=14.50 mag on the basis of the position in the two-color Diagram .
Membership has been checked against proper motions from Tycho~2, whenever
available. The cluster turns out to have a reddening E$(B-V)=0.60\pm0.10$ mag,
to be $630\pm150$ pc distant from the Sun, and to have an age less than 10
Myrs. NGC 1348 is a more reddened cluster (E$(B-V)=0.85\pm0.15$ mag) for which
we isolate 20 members. The cluster lies at a distance of $1.9\pm0.5$ kpc away
from the Sun, and has an age greater than 50 Myrs.


title: Resolving the 47 Tucanae Distance Problem

abstract:
  We present new B, V and I-band photometry for a sample of 43 local subdwarfs
with HIPPARCOS parallax errors < 13%, in the metallicity range -1.0 < [Fe/H] <
-0.3, which we use to perform main sequence (MS) fitting to the Galactic
globular cluster 47 Tuc. This sample is many times larger than those used in
previous MS-fitting studies and also enables us to fit in two colour planes,
V/(B-V) and V/(V-I). With this enlarged subdwarf sample we investigate whether
the current discrepancy in empirical distance estimates for 47 Tuc, arising
from recent MS-fitting and white dwarf fitting results, is due to inaccuracies
in the MS-fitting method. Comparison of published photometries for 47 Tuc has
revealed systematic offsets which mean that the $(B-V)$ main-line used in
previous studies may be too blue by ~ 0.02 mag. We have derived main-lines in
V/(B-V) and V/(V-I) from the data of Kaluzny et al. (1998), which we have
recalibrated from the `secondary' standards in 47 Tuc of Stetson (2000). Using
an assumed cluster reddening of E(B-V)=0.04, our best-fit apparent distance
modulus is (m-M)V=13.37 (+0.10)(-0.11) in both colour planes, which implies a
cluster age of 11.0 +/-1.4 Gyr and leads to a dereddened distance modulus of
(m-M)0=13.25 (+0.06)(-0.07). Comparison with previous work shows that our
apparent distance modulus is ~0.2 mag smaller than those derived in previous
MS-fitting studies. The difference is accounted for by our preferred cluster
reddening and the recalibration of the cluster photometry, which has made the
main-line redder by an average of 0.02 mag in (B-V). Independent support for
our MS-fitting distance comes from consideration of the Red Clump in the
cluster, from which we derive a dereddened distance modulus of (m-M)0=13.31
+/-0.05, which is in agreement with the MS-fitting result. (Abridged)


title: Supermassive Black Hole Masses of AGNs with Elliptical Hosts

abstract:
  The recently discovered tight correlation between supermassive black hole
mass and central velocity dispersion suggests a possibility to estimate the
SMBH mass from the measured central velocity dispersion. However, for most AGNs
it is difficult to measure the central velocity dispersions of their host
galaxies directly. In this paper we adopt the fundamental plane for ellipticals
to estimate the central velocity dispersion and SMBH mass for a number of AGNs
with morphology parameters of their elliptical host galaxies obtained by the
HST imaging observations. The estimated SMBH masses of 63 BL Lac objects, 10
radio galaxies, 10 radio-loud quasars and 9 radio-quiet quasars are mostly in
the range of $10^{7.5} M_\odot$ to $10^{9} M_\odot$. No significant difference
in black hole mass is found for high-frequency peaked BL Lacs and low-frequency
peaked BL Lacs, as well as for radio galaxies and radio-loud quasars. The
Eddington ratios of radio galaxies are substantially smaller than those of
quasars. This suggests that the different observational features of radio-loud
AGNs may be mainly dominated by accretion rate rather than by the black hole
mass, which is in agreement with some evolutionary scenarios recently proposed
for radio-loud AGNs. Different from some previous claims, we found that the
derived mean SMBH mass for radio-loud quasars is only slightly larger than that
of radio-quiet quasars. Though their SMBH mass distributions are statistically
different, their Eddington ratio distributions are probably from the same
population. In addition, we noted that the relation between black hole mass and
host galaxy luminosity obtained using the fundamental plane provides further
arguments for a nonlinear scaling law between SMBH and galactic bulge mass.


title: CMB Power Spectrum Estimation for the Planck Surveyor

abstract:
  We use an iterative generalized least squares map-making algorithm, in
conjunction with Monte Carlo techniques, to obtain estimates of the angular
power spectrum from cosmic microwave background (CMB) maps. This is achieved by
characterizing and removing the instrumental noise contribution in multipole
space. This technique produces unbiased estimates and can be applied to an
arbitrary experiment. In this paper, we use it on realistic simulations of
Planck Low Frequency Instrument (LFI) observations, showing that it can lead to
fast and reliable estimation of the CMB angular power spectrum from megapixel
maps.


title: High-Resolution X-ray imaging and spectroscopy of SNR N103B

abstract:
  The X-ray emission from the young supernova remnant (SNR) N103B is measured
and analysed using the high-resolution cameras and spectrometers on board XMMM
and CHANDRA. The spectrum from the entire remnant is reproduced very well with
three plasma components of kT=0.55, 0.65, and 3.5 keV, corresponding roughly to
line emission by the O-K, Fe-L, and Fe-K species, respectively. Narrow band
images reveal different morphologies for each component. The kT=0.65keV
component, which dominates the emission measure (4.5E65m^{-3}), is in
ionisation equilibrium. This provides a lower limit of 3000 yrs to the age of
the remnant, which is considerably older than the previously assumed age of the
remnant (1500 yrs). Based on the measured energy of the Fe-K feature at 6.5
keV, the hot (3.5 keV) component is found to be recently shocked (~200 yrs) and
still ionising. The high elemental abundances of O and Ne and the low abundance
of Fe could imply that SNR N103B originated from a type II supernova (SN)
rather than a type Ia SN as previously thought.


title:
Probing the chemical abundances in distant galaxies with 10-m class
  telescopes

abstract:
  The determination of chemical abundances in star-forming galaxies and the
study of their evolution on cosmological timescales are powerful tools for
understanding galaxy formation and evolution. This contribution presents the
latest results in this domain. We show that detailed studies of chemical
abundances in UV-selected, HII and starburst nucleus galaxies, together with
the development of new chemical evolution models, put strong constraints on the
evolutionary stage of these objects in terms of star formation history.
Finally, we summarize our current knowledge on the chemical properties of
distant galaxies. Although the samples are still too small for statistical
studies, these results give insight into the nature and evolution of distant
star-forming objects and their link with present-day galaxies. No doubt that
the next large-scale spectroscopic surveys on 10-m class telescopes will shed
light on these fundamental issues.


title:
New distant companions to known nearby stars: I. GJ 4047B, GJ 718B, GJ
  747.2C, GJ 4100B, and GJ 4153B

abstract:
  In an ongoing survey for high proper motion stars at low galactic latitudes,
we have identified 5 previously uncatalogued common proper motion companions to
stars listed in the Preliminary Version of the Third Catalogue of Nearby Stars
(GJ stars). For each system, the relative proper motion between the components
is less than 5% of the common proper motion of the pair. Spectra of the pairs
have been obtained at the Lick 3-m Shane Telescope, confirming that the systems
are indeed wide separation binaries. The systems are classified as follows: GJ
4047AB = K5 V + M5 V, GJ 718AB = K5 V + M4.5 V, GJ 747.2ABC = (K7 V + K7 V) +
M4 Ve, GJ 4100AB = M1 V + M4.5 Ve, and GJ 4153AB = M0.5 V + M3.5 V. The total
area surveyed contains 346 Gliese stars, which suggests that approximately 1.5%
of the stars listed in the Preliminary Version of the Third Catalogue of Nearby
Stars have unrecognized proper motion companions. We predict that 15-50 more
new distant companions to GJ stars will be discovered in the Digitized Sky
Survey.


title:
Cosmological Information from Quasar-Galaxy Correlations induced by Weak
  Lensing

abstract:
  The magnification bias of large-scale structures, combined with galaxy
biasing, leads to a cross-correlation of distant quasars with foreground
galaxies on angular scales of the order of arc minutes and larger. The
amplitude and angular shape of the cross-correlation function w_QG contain
information on cosmological parameters and the galaxy bias factor. While the
existence of this cross-correlation has firmly been established, existing data
did not allow an accurate measurement of w_QG yet, but wide area surveys like
the Sloan Digital Sky Survey now provide an ideal database for measuring it.
However, w_QG depends on several cosmological parameters and the galaxy bias
factor. We study in detail the sensitivity of w_QG to these parameters and
develop a strategy for using the data. We show that the parameter space can be
reduced to the bias factor b, Omega_0 and sigma_8, and compute the accuracy
with which these parameters can be deduced from SDSS data. Under reasonable
assumptions, it should be possible to reach relative accuracies of the order of
5%-15% for b, Omega_0, and sigma_8. This method is complementary to other
weak-lensing analyses based on cosmic shear.


title: Fluctuation Spectrum from a Scalar-Tensor Bimetric Gravity Theory

abstract:
  Predictions of the CMB spectrum from a bimetric gravity theory
(gr-qc/0101126) are presented. The initial inflationary period in BGT is driven
by a vanishingly small speed of gravitational waves v_g in the very early
universe. This initial inflationary period is insensitive to the choice of
scalar field potential and initial values of the scalar field. After this
initial period of inflation, v_g will increase rapidly and the effects of a
potential will become important. We show that a quadratic potential introduced
into BGT yields an approximately flat spectrum with inflation parameters:
n_s=0.98, n_t=-0.027, alpha_s=-3.2e-4 and alpha_t=-5.0e-4, with r >= 0.014.


title: Bayesian Spectral Analysis of Metal Abandance Deficient Stars

abstract:
  Metallicity can be measured by analyzing the spectra in the X-ray region and
comparing the flux in spectral lines to the flux in the underlying
Bremsstrahlung continuum. In this paper we propose new Bayesian methods which
directly model the Poisson nature of the data and thus are expected to exhibit
improved sampling properties. Our model also accounts for the Poisson nature of
background contamination of the observations, image blurring due to instrument
response, and the absorption of photons in space. The resulting highly
structured hierarchical model is fit using the Gibbs sampler, data augmentation
and Metropolis-Hasting. We demonstrate our methods with the X-ray spectral
analysis of several "Metal Abundance Deficient" stars. The model is designed to
summarize the relative frequency of the energy of photons (X-ray or gamma-ray)
arriving at a detector. Independent Poisson distributions are more appropriate
to model the counts than the commonly used normal approximation. We model the
high energy tail of the ASCA spectrum of each of the stars as a combination of
a Bremsstrahlung continuum and ten narrow emission lines, included at positions
of known strong lines. Statistical analysis is based on two source observations
and one background observation. We use sequential Bayesian analysis for the two
source observations; the posterior distribution from the first analysis is used
to construct a prior for the second. Sensitivity of the final results to the
choise of prior is investigated by altering the prior.


title:
The rms peculiar velocity of galaxy clusters for different cluster
  masses and radii

abstract:
  We investigate the rms peculiar velocity of galaxy clusters in the Lambda
cold dark matter ($\Lambda$CDM) and tau cold dark matter ($\tau$CDM)
cosmological models using N-body simulations. Cluster velocities for different
cluster masses and radii are examined. To identify clusters in the simulations
we use two methods: the standard friends-of-friends (FOF) method and the
method, where the clusters are defined as the maxima of the density field
smoothed on the scale $R\sim 1h^{-1}$ Mpc (DENSMAX). If we use the DENSMAX
method, the size of the selected clusters is similar for all clusters. We find
that the rms velocity of clusters defined with the DENSMAX method is almost
independent of the cluster density and similar to the linear theory
expectations. The rms velocity of FOF clusters decreases with the cluster mass
and radius. In the $\Lambda$CDM model, the rms peculiar velocity of massive
clusters with an intercluster separation $d_{cl}=50h^{-1}$ Mpc is $\approx$15%
smaller than the rms velocity of the clusters with a separation
$d_{cl}=10h^{-1}$Mpc.


title: Bright loops in the solar corona

abstract:
  The heating of the solar corona and the puzzle of the slender high reaching
magnetic loops seen in observations from the Transition Region And Coronal
Explorer(TRACE) has been investigated through 3D numerical simulations, and
found to be caused by the well observed plasma flows in the photosphere
displacing the footpoints of magnetic loops in a nearly potential
configuration. It is found that even the small convective displacements cause
magnetic dissipation sufficient to heat the corona to temperatures of the order
of a million Kelvin. The heating is intermittent in both space and time - at
any one height and time it spans several orders of magnitude, and localized
heating causes transonic flows along field lines, which explains the observed
non-hydrostatic equilibrium of loops that are bright in emission measure.


title:
Star Formation History since z = 1.5 as Inferred from Rest-Frame
  Ultaviolet Luminosity Density Evolution

abstract:
  We investigate the evolution of the universal rest-frame ultraviolet
luminosity density from z = 1.5 to the present. We analyze an extensive sample
of multicolor data (U', B, V = 24.5) plus spectroscopic redshifts from the
Hawaii Survey Fields and the Hubble Deep Field. Our multicolor data allow us to
select our sample in the rest-frame ultraviolet (2500 angstrom) over the entire
redshift range to z = 1.5. We conclude that the evolution in the luminosity
density is a function of the form (1+z)^{1.7\pm1.0} for a flat lambda cosmology
and (1+z)^{2.4\pm1.0} for an Einstein-de Sitter cosmology.


title: Sample Variance Considerations for Cluster Surveys

abstract:
  We present a general statistical framework for describing the effect of
sample variance in the number counts of virialized objects and examine its
effect on cosmological parameter estimation. Specifically, we consider effects
of sample variance on the power spectrum normalization and properties of dark
energy extracted from current and future local and high-redshift samples of
clusters. We show that for future surveys that probe ever lower cluster masses
and temperatures, sample variance is generally comparable to or greater than
shot noise and thus cannot be neglected in deriving precision cosmological
constraints. For example, sample variance is usually more important than shot
variance in constraints on the equation of state of the dark energy from z < 1
clusters. Although we found that effects of sample variance on the
sigma_8-Omega_m constraints from the current flux and temperature limited X-ray
surveys are not significant, they may be important for future studies utilizing
the shape of the temperature function to break the sigma_8-Omega_m degeneracy.
We also present numerical tests clarifying the definition of cluster mass
employed in cosmological modelling and accurate fitting formula for the
conversion between different definitions of halo mass (e.g., virial vs. fixed
overdensity).


title:
Growth of a peanut shaped bulge via resonant trapping of stellar orbits
  in the vertical Inner Lindblad Resonances

abstract:
  We present a simple resonant Hamiltonian model for the vertical response of a
stellar disk to the growth of a bar perturbation. As a bar perturbation grows
stars become trapped in vertical Inner Lindblad resonances and are lifted into
higher amplitude orbits. The vertical structure of a boxy and peanut shaped
bulge as a function of radius and azimuthal angle in the galaxy plane can be
predicted from the strength and speed of the bar perturbation and the
derivatives of the gravitational potential. This model predicts that stars on
the outer side of the resonance are lifted higher than stars on the inner side,
offering an explanation for the sharp outer edge of the boxy/peanut.


title: Early-Type Halo Masses from Galaxy-Galaxy Lensing

abstract:
  We present measurements of the extended dark halo profiles of bright early
type galaxies at redshifts 0.1 to 0.9 obtained via galaxy-galaxy lensing
analysis of images taken at the CFHT using the UH8K CCD mosaic camera. Six half
degree fields were observed for a total of 2 hours each in I and V, resulting
in catalogs containing ~20 000 galaxies per field. We used V-I color and I
magnitude to select bright early type galaxies as the lens galaxies, yielding a
sample of massive lenses with fairly well determined redshifts and absolute
magnitudes M ~ M_* pm 1. We paired these with faint galaxies lying at angular
distances 20" to 60", corresponding to physical radii of 26 to 77 kpc (z = 0.1)
and 105 to 315 kpc (z = 0.9), and computed the mean tangential shear of the
faint galaxies. The shear falls off with radius roughly as expected for flat
rotation curve halos. The shear values were weighted in proportion to the
square root of the luminosity of the lens galaxy. Our results give a value for
the average mean rotation velocity of an L_* galaxy halo at r~50-200 kpc of v_*
= 238^{+27}_{-30} km per sec for a flat lambda (Omega_m0 = 0.3, Omega_l0 = 0.7)
cosmology (v_* = 269^{+34}_{-39} km per sec for Einstein-de Sitter), and with
little evidence for evolution with redshift. We find a mass-to-light ratio of
\~121\pm28h(r/100 kpc) and these halos constitute Omega ~0.04 pm 0.01 (r/100
kpc) of closure density.


title: Mass and Light in the Universe

abstract:
  We present a weak lensing and photometric study of six half by half degree
fields observed at the CFHT using the UH8K CCD mosaic camera. The fields were
observed for a total of 2 hours each in I and V, resulting in catalogs
containing ~ 20 000 galaxies per passband per field. We use V-I color and I
magnitude to select bright early type galaxies at redshifts 0.1 < z < 0.9. We
measure the gravitational shear from faint galaxies in the range 21 < m_I < 25
from a composite catalog and find a strong correlation with that predicted from
the early types if they trace the mass with mass-to-light ratio 300\pm75 h (in
solar units) for a flat (Omega_m0 = 0.3, Omega_l0 = 0.7) lambda cosmology and
400\pm100 h for Einstein-de Sitter. We make two-dimensional reconstructions of
the mass surface density. Cross-correlation of the measured mass surface
density with that predicted from the early type galaxy distribution shows a
strong peak at zero lag (significant at the 5.2-sigma level). We azimuthally
average the cross- and auto-correlation functions. We conclude that the
profiles are consistent with early type galaxies tracing mass on scales of > 45
arcsec (> 200 kpc at z = 0.5). We sub-divide our bright early type galaxies by
redshift and obtain similar conclusions. These mass-to-light ratios imply
Omega_m0 = 0.10\pm0.02 (Omega_m0 = 0.13\pm0.03 for Einstein-de Sitter) of
closure density.


title: The clustering of X-ray and sub-mm sources

abstract:
  It is becoming clear that luminous extragalactic X-ray and sub-mm sources are
essentially distinct populations. Thus, if high redshift sub-mm sources
represent massive spheroids in formation, there must be a time lag between the
major epoch of star-formation and the appearance of a visible quasar. Despite
this distinction, I find tentative evidence for a puzzling angular
cross-correlation between X-ray sources and bright sub-mm sources in two
independent fields. If this signal is due to large-scale structure it would
argue for a low redshift (z<2) for many of the SCUBA sources. Alternatively, I
suggest that the effect may be enhanced by gravitational lensing. The
exceptionally steep slope of the bright sub-mm counts makes this population
particularly prone to lensing bias. An apparent correlation may therefore be
produced if X-ray sources trace the intervening large scale structure.


title:
Chandra Observations of "The Antennae" Galaxies (NGC 4038/39): II.
  Detection and Analysis of Galaxian X-ray source

abstract:
  We report the detailed analysis of the X-ray properties of the discrete
sources detected in a long (72 ks) \chandra ACIS-S observation of the Antennae
galaxies. We detect 49 sources, down to a detection limit of ~ 10^{38} erg\s;
18 sources have Lx >10^{39} erg\s (Ultra Luminous X-ray sources; ULXs). Six of
the 49 sources have an extended component. Two sources show evidence for
variability during this observation, and three sources exhibit long term
variability in timescales of a few years. The spectra of the discrete sources
are diverse, suggesting different emission mechanisms, broadly correlated with
the source luminosity: the most luminous sources exhibit harder emission, while
the spectra of fainter sources appear softer. Spectra and variability suggest
that the ULXs may be binary accretion sources; Supernova remnants or hot ISM in
the Chandra beam may be responsible for some of the softer sources.


title:
The X-ray Source Population of "The Antennae" Galaxies: X-ray Properties
  from Chandra and Multiwavelength Associations

abstract:
  [abridged] We investigate the nature of the luminous X-ray source population
detected in a (72 ks) Chandra ACIS-S observation of NGC 4038/39, the Antennae
galaxies. We derive the average X-ray spectral properties of sources in
different luminosity ranges, and we correlate the X-ray positions with radio,
IR, and optical HST data. The X-ray sources are predominantly associated with
young stellar clusters, indicating that they belong to the young stellar
population. Based on both their co-added X-ray spectrum, and on the lack of
associated radio emission, we conclude that the Ultra Luminous X-ray sources
(ULXs), with Lx>10^{39} erg\s, are not young compact Supernova Remnants (SNR),
but accretion binaries. While their spectrum is consistent with those of ULXs
studied in nearby galaxies, and interpreted as the counterparts of intermediate
mass black-holes (M >10-1000 \msun), comparison with the position of
star-clusters suggests that some of the ULXs may be runaway binaries, thus
suggesting lower-mass binary systems. The co-added spectrum of the sources in
the 3x10^{38}-10^{39} erg\s luminosity range is consistent with those of
Galactic black-hole candidates. These sources are also on average displaced
from neighboring star clusters. The softer spectrum of the less luminous
sources suggests the presence of SNRs or of hot interstellar medium (ISM) in
the Chandra source extraction area. Comparison with HI and CO observations
shows that most sources are detected in the outskirts of large concentrations
of gas. The absorbing columns inferred from these observations would indeed
absorb X-rays up to 5 keV, so there may be several hidden X-ray sources.
Associated with these obscured regions we find 6 sources with heavily absorbed
X-ray spectra and absorption-corrected luminosities in the ULX range.


title:
The X-ray Luminosity Function of "The Antennae" Galaxies (NGC4038/39)
  and the Nature of Ultra-Luminous X-ray Sources

abstract:
  We derive the X-ray luminosity function (XLF) of the X-ray source population
detected in the Chandra observation of NGC4038/39 (the Antennae).
  We explicitly include photon counting and spectral parameter uncertainties in
our calculations. The cumulative XLF is well represented by a flat power law
($\alpha=-0.47$), similar to those describing the XLFs of other star-forming
systems (e.g. M82, the disk of M81), but different from those of early type
galaxies. This result associates the X-ray source population in the Antennae
with young High Mass X-ray Binaries. In comparison with less actively
star-forming galaxies, the XLF of the Antennae has a highly significant excess
of sources with luminosities above 10^{39} erg\s (Ultra Luminous Sources;
ULXs). We discuss the nature of these sources, based on the XLF and on their
general spectral properties, as well as their optical counterparts discussed in
Paper III. We conclude that the majority of the ULXs cannot be intermediate
mass black-holes (M > 10-1000 \msun) binaries, unless they are linked to the
remnants of massive Population III stars (the Madau & Rees model). Instead,
their spatial and multiwavelength properties can be well explained by beamed
emission as a consequence of supercritical accretion.
  Binaries with a neutron star or moderate mass black-hole (up to 20\msun), and
B2 to A type star companions would be consistent with our data. In the beaming
scenario, the XLF should exibit caracteristic breaks that will be visible in
future deeper observations of the Antennae.


title: Can neutrino-cooled accretion disk be an origin of gamma-ray bursts?

abstract:
  It is often considered that a massive torus with solar mass or so surrounding
a stellar-mass black hole may be a central engine of a gamma-ray burst. We
study the properties of such massive accretion tori (or disks) based on the
$\alpha$ viscosity model. For surface density exceeding about $10^{20}$ g
cm$^{-2}$, which realizes when about a solar-mass material is contained within
a disk with a size of $\sim 5 \times 10^6$ cm, we find that (1) luminosity of
photons is practically zero due to significant photon trapping, (2) neutrino
cooling dominates over advective cooling, (3) pressure of degenerate electrons
dominates over pressure of gas and photons, and (4) magnetic field strength
exceeds the critical value of about $4 \times 10^{13}$ G, even if we take 0.1 %
of the equi-partition value. The possible observable quantum electrodynamical
(QED) effects arising from super-critical fields are discussed. Most
interestingly, photon splitting may occur, producing significant number of
photons of energy below $\sim 511$ keV, thereby possibly suppressing e$^\pm$
pair creation.


title: Ionized iron K\alpha lines in AGN X-ray spectra

abstract:
  The Equivalent Widths (EW) of the He- and H-like iron lines produced in
photoionized, circumnuclear matter of AGN are calculated with respect to both
the reflected and the total continua. We found that the EWs with respect tothe
total continuum may be as large as a few tens of eV, making them observable in
bright Seyfert 1s by instruments on board Chandra and XMM-Newton. We apply our
calculations to the XMM-Newton spectrum of NGC 5506 and found a good agreement
with the data at the expense of a modest iron overabundance.


title: Compact groups in the UZC galaxy sample

abstract:
  Applying an automatic neighbour search algorithm to the 3D UZC galaxy
catalogue (Falco 1999) we have identified 291 compact groups (CGs) with
redshifts between 1000 and 10000 km/s. The sample is analysed to investigate
whether Triplets display kinematical and morphological characteristics similar
to higher order CGs (Multiplets). It is found that Triplets constitute low
velocity dispersion structures, have a gas-rich galaxy population and are
typically retrieved in sparse environments. Conversely Multiplets show higher
velocity dispersion, include few gas-rich members and are generally embedded
structures. Evidence hence emerges indicating that Triplets and Multiplets,
though sharing a common scale, correspond to different galaxy systems. Triplets
are typically field structures whilst Multiplets are mainly subclumps (either
temporarily projected or collapsing) within larger structures. Simulations show
that selection effects can only partially account for differences, but
significant contamination of Triplets by field galaxy interlopers could
eventually induce the observed dependences on multiplicity.


title: s-Process Nucleosynthesis in Low-Metallicity Stars

abstract:
  We have made a parametric study of s-process nucleosynthesis in the metal
poor ([Fe/H]=-2.7) stars LP625-44 and LP706-7. We find that a high neutron
exposure and a small overlap factor are necessary to fit the abundance pattern
observed in these two metal-deficient stars, particularly the abundance ratios,
Pb/Ba $\approx 1$ and Ba/Sr $\approx 10$. We have also constructed stellar
models to better understand how such s-process conditions could arise. We have
calculated a 2$M_\odot$ model star with metallicity [Fe/H]=-2.7 from the ZAMS
up to AGB phase. We find that for such low-metallicity stars the He convective
shell reaches the bottom of the overlying H-rich envelope at the second thermal
pulse. Protons are then carried into the hotter He burning layers and $^{13}$C
is formed as protons mix into the He shell. Subsequently, material in the
H-flash driven convective zone experiences a high neutron exposure due to the
$^{13}$C($\alpha$, n) reaction. This results in a new neutron-capture s-process
paradigm in which the abundances are characterized by only one neutron
exposure. We suggest that this new s-process site may be a significant
contributor to the s-process abundances in low-metallicity ([Fe/H] $\le -2.5$)
stars.


title: Search for diffuse neutrino flux from astrophysical sources with MACRO

abstract:
  Many galactic and extragalactic astrophysical sources are currently
considered promising candidates as high energy neutrino emitters. Astrophysical
neutrinos can be detected as upward-going muons produced in charged-current
interactions with the medium surrounding the detector. The expected neutrino
fluxes from various models start to dominate on the atmospheric neutrino
background at neutrino energies above some tens of TeV. We present the results
of a search for an excess of high energy upward-going muons among the sample of
data collected by MACRO during ~5.8 years of effective running time. No
significant evidence for this signal was found. As a consequence, an upper
limit on the flux of upward-going muons from high-energy neutrinos was set at
the level of 1.7 10^(-14) cm^(-2) s^(-1) sr^(-1).
  The corresponding upper limit for the diffuse neutrino flux was evaluated
assuming a neutrino power law spectrum. Our result was compared with
theoretical predictions and upper limits from other experiments.


title:
The Resonant Dynamical Evolution of Small Body Orbits Among Giant
  Planets

abstract:
  Mean motion resonances (MMRs) can lead either to chaotic or regular motion.
We report on a numerical experiment showing that even in one of the most
chaotic regions of the Solar System - the region of the giant planets, there
are numerous bands where MMRs can stabilize orbits of small bodies in a time
span comparable to their lifetimes. Two types of temporary stabilization were
observed: short period ($\sim10^{4}$ years) when a body was in a MMR with only
one planet and long period (over $10^{5}$ years) when a body is located in
overlapping MMRs with two or three planets.
  The experiment showed that the Main Belt region can be enriched by cometary
material in its pre-active state due to temporary resonant interactions between
small bodies and giant planets.


title: The near-infrared Hubble diagram for sub-mm galaxies

abstract:
  Determing the nature of the bright sub-mm sources and their role in the
process of galaxy formation is likely to be a major focus of extra-galactic
research over the next few years. In particular, we would like to know if these
sources are the progenitors of today's massive elliptical galaxies, or
alternatively arise from short-lived, albeit spectacular starbursts within
haloes of unexceptional mass. This question can be addressed from a number of
different directions, one of which is to compare the masses of sub-mm host
galaxies with those of other known massive high-redshift objects. Here I make a
first attempt to do this by exploring whether the few well-studied sub-mm/mm
sources are consistent with the well-established K-z relation for powerful
radio galaxies. Out to z = 3 this appears to be the case, providing evidence
that bright sub-mm sources are indeed destined to be massive ellipticals. At
higher redshifts there is a suggestion that sub-mm galaxies are signficantly
fainter at K than their radio-selected counterparts, but at present it is
unclear whether this indicates a significant difference in stellar mass or the
increasing impact of dust obscuration on the rest-frame light from the sub-mm
hosts.