title: On the minimum radius of strange stars with crust

abstract:
  The minimum value of the radius of strange star covered by the crust of
nuclear matter is determined. The results for the maximum possible thickness of
the crust (up to the neutron drip) as well as the possibility of thinner crust
postulated by some authors are discussed. The minimum radius of the strange
star with maximal crust is 5.5 km. The useful scaling formulae with respect to
the main parameters describing strange matter and the density at the bottom of
the crust are presented.


title: Population synthesis of wide binary millisecond pulsars

abstract:
  Four evolutionary channels leading to the formation of wide binary
millisecond pulsars are investigated. The majority of binary millisecond
pulsars are found to descend from systems in which the most massive component
undergoes a common-envelope phase prior to the supernova explosion leading to
the birth of the neutron star.
  The orbital period distribution of simulated samples of wide binary
millisecond pulsars is compared with the observed distribution of Galactic
binary millisecond pulsars for a variety of parameters describing the formation
and evolution of binaries. The distribution functions typically show a
short-period peak below 10 days and a long-period peak around 100 days. The
observed distribution is best reproduced by models with highly non-conservative
mass transfer, common-envelope efficiencies equal to or larger than unity, a
critical mass ratio for the delayed dynamical instability larger than 3, and no
or moderate supernova kicks at the birth of the neutron star. Few systems are
found with orbital periods longer than 200 days, irrespective of the accretion
efficiency of neutron stars. This occurs as a result of the upper limit on the
initial orbital periods beyond which the binary avoids the common-envelope
phase prior to the supernova explosion of the primary.


title: Classical dense matter physics:some basic methods and results

abstract:
  This is an intorduction to some of the basic methods and results of dense
matter physics.It is aimed at readers interested in astrophysical and physical
applications.


title:
Determination of Substellar Mass Function of Young Open Clusters Using
  2MASS and GSC Data

abstract:
  We present a statistical method to derive the mass functions of open clusters
using sky survey data such as the 2 Micron All Sky Survey and the Guide Star
Catalogue. We have used this method to derive the mass functions in the
stellar/substellar regime of three young, nearby open clusters, namely IC 348,
Sigma-Orionis and Pleiades. The mass function in the low mass range (M < 0.5
solar mass) is appreciably flatter than the stellar Salpeter function for all
three open clusters. The contribution of objects below 0.5 solar mass to the
total mass of the cluster is ~40% and the contribution of objects below 0.08
solar mass to the total is ~4%.


title:
Unveiling the Kinematics and Dynamics of Ionized Gas in the Nearby
  Irregular Galaxy NGC 4449

abstract:
  A detailed kinematic analysis of ionized gas in the nearby irregular galaxy
NGC 4449 is presented. Observations are conducted in the spectral lines of
Halpha and [SII]. Our scanning Fabry--Perot interferometric observations are
presented from both a global as well as a local perspective. We have analysed
the global velocity field, the spatially extended diffuse gaseous component
(DIG), the HII region populations, and, furthermore, have determined the
rotation curve based on the heliocentric radial velocities of the global Halpha
spatial distribution. Our results for NGC 4449 show that the optical velocity
field has a decreasing value in radial velocity along the optical bar from NE
to SW. The DIG component that permeates the entire galaxy was analysed (up to a
limiting surface brightness of ~ 3.165x10^-5 ergs cm$^-2 s^-1 steradian^-1). We
find that the diffuse gas component presents peculiar kinematical features such
as abrupt velocity gradients and highly supersonic velocity dispersions
(sigma~4 times the values of the nearest HII regions) but that its kinematical
and dynamical influence is important on both global and local scales. The
optical rotation curve of this nearby irregular shows that the NE sector
rotates like a solid body (V_rot~40 km s^-1 at R=2 kpc). For the SW side, our
results are not conclusive; the behavior of the gas at those locations is
chaotic. We conclude that the origin of such complex kinematics and dynamics is
undoubtedly related to the aftermath of an interaction experienced by this
galaxy in the past (abridged).


title: Subsurface magnetic fields from helioseismology

abstract:
  Using even-order frequency splitting coefficients of global p-modes it is
possible to infer the magnetic field in the solar interior as a function of
radial distance and latitude. Results obtained using GONG and MDI data are
discussed. While there is some signal of a possible magnetic field in the
convection zone, there is little evidence for any temporal variation of the
magnetic field in the solar interior. Limits on possible magnetic field in the
solar core are also discussed. It is generally believed that the solar dynamo
is located in the tachocline region. Seismic studies do not show any
significant temporal variation in the tachocline region, though a significant
latitudinal variation in the properties of the tachocline are found. There is
some evidence to suggest that the latitudinal variation is not continuous and
the tachocline may consist of two parts.


title:
The Effects of Shear and Rotation Anisotropy Upon the Process of
  Gravitational Instability

abstract:
  In this paper, we study the role of shear fields on the evolution of density
perturbations embedded in a Friedmann flat background universe, by studying the
evolution of a homogeneous ellipsoid model. In this context, we show that while
the effect of the shear is that of increasing the growth rate of the density
contrast of a mass element, the angular momentum acquired by the ellipsoid has
the right magnitude to counterbalance the shear. Finally, our result show that
initial asphericities and tidal interaction induce a slowing down of the
collapse after the system has broken away from the general expansion, in
perfect agreement with the previrialization conjecture (Peebles & Groth 1976;
Davis & Peebles 1977).


title: High velocity clumps and cluster of galaxies evolution

abstract:
  We study the effect of the interaction between small scale clumps having
velocities larger than the average escape velocity v_{\rm esc} and bound clumps
(having v<v_{\rm esc}), on clusters of galaxies evolution. We find that the
collapse of the bound clumps is accelerated with respect to the homogeneous
case (Gunn & Gott's model - Gunn & Gott 1972). A comparison between the
acceleration produced by this effect to the slowing down effect studied in Del
Popolo & Gambera (1998) shows that the magnitude of the slowing down effect is
larger than the acceleration produced by the effect studyed in this paper, only
in the outskirts of the cluster.


title: Computation of Light Scattering in Young Stellar Objects

abstract:
  A Monte Carlo light scattering code incorporating aligned non-spherical
particles is described. The major effects on the flux distribution, linear
polarisation and circular polarisation are presented, with emphasis on the
application to Young Stellar Objects (YSOs). The need for models with
non-spherical particles in order to successfully model polarisation data is
reviewed. The ability of this type of model to map magnetic field structure in
embedded YSOs is described. The possible application to the question of the
origin of biomolecular homochirality via UV circular polarisation in star
forming regions is also briefly discussed.


title: Solar supergranulation as a wavelike phenomenon

abstract:
  Supergranulation on the surface of the Sun is an organized cellular flow
pattern with a characteristic scale of 30 Mm. It is superficially similar to
the well understood granulation that operates at the 1.5 Mm natural scale of
convection, which has led to the conventional view that supergranulation has
its origin in the convective motion of cells of gas, though this does not
explain the observation that the supergranulation pattern appears to move
faster around the Sun than the bulk of its surface. A wave origin has been
proposed for supergranulation that may explain the superrotation, but it has
never had much support. Here we report that the supergranulation pattern has
oscillatory components with periods of 5-10 days, for which the best
explanation is a spectrum of traveling waves. We show that there is excess
power in the prograde and equatorward directions, which explains the
observation of superrotation.


title:
Probing drifting and nulling mechanisms through their interaction in PSR
  B0809+74

abstract:
  Both nulling and subpulse drifting are poorly understood phenomena. We probe
their mechanisms by investigating how they interact in PSR B0809+74. We find
that the subpulse drift is not aliased but directly reflects the actual motion
of the subbeams. The carousel-rotation time must then be over 200 seconds,
which is much longer than theoretically predicted.
  The drift pattern after nulls differs from the normal one, and using the
absence of aliasing we determine the underlying changes in the subbeam-carousel
geometry. We show that after nulls, the subbeam carousel is smaller, suggesting
that we look deeper in the pulsar magnetosphere than we do normally. The many
striking similarities with emission at higher frequencies, thought to be
emitted lower too, confirm this. The emission-height change as well as the
striking increase in carousel-rotation time can be explained by a post-null
decrease in the polar gap height. This offers a glimpse of the circumstances
needed to make the pulsar turn off so dramatically.


title:
The COMBO-17 Survey: Evolution of the Galaxy Luminosity Function from
  25,000 Galaxies with 0.2<z<1.2

abstract:
  We present a detailed empirical assessment of how the galaxy luminosity
function and stellar luminosity density evolves over the last half of the
universe's age (0.2<z<1.2) for galaxies of different spectral energy
distributions (SED). The results are based on ~25,000 galaxies (R<24) with
redshift measurements (sigma_z~0.03) and SEDs across 350..930 nm, derived from
medium-band photometry in 17 filters, observed as part of the COMBO-17 survey
(``Classifying Objects by Medium-Band Observations in 17 Filters'') over three
disjoint fields with a total area of 0.78 square degrees. Luminosity functions
(LF), binned in redshift and SED-type, are presented in the restframe passbands
of the SDSS r-band, the Johnson B-band and a synthetic UV continuum band at 280
nm. We find that the luminosity function depends strongly on SED-type at all
redshifts covered. The shape of the LF, i.e. the faint-end power-law slope,
does depend on SED type, but not on redshift. However, the redshift evolution
of the characteristic luminosity M* and density phi* depends strongly on
SED-type: (1) Early-type galaxies, defined as redder than a present-day
reference Sa spectrum, become drastically more abundant towards low redshift,
by a factor of 10 in the number density phi* from z=1.1 to now, and by a factor
of 4 in their contribution to the co-moving r-band luminosity density, j_r. (2)
Galaxies resembling present-day Sa- to Sbc-colours show a co-moving number
density and contribution to j_r that does not vary much with redshift. (3)
Galaxies with blue spectra reflecting strong star formation decrease towards
low redshift both in luminosity and density, and by a factor of 4 in their j_r
contribution. (abridged)


title: Galactic SNR candidates in the ROSAT all-sky survey

abstract:
  Identified radio supernova remnants (SNRs) in the Galaxy comprise an
incomplete sample of the SNR population due to various selection effects. ROSAT
performed the first all-sky survey with an imaging X-ray telescope, and thus
provides another window for finding SNRs and compact objects that may reside
within them. Performing a search for extended X-ray sources in the ROSAT
all-sky survey database about 350 objects were identified as SNR candidates in
recent years (Busser 1998). Continuing this systematic search, we have
reanalysed the ROSAT all-sky survey (RASS) data of these candidates and
correlated the results with radio surveys like NVSS, ATNF, Molonglo and
Effelsberg. A further correlation with SIMBAD and NED was performed for
subsequent identification purposes. About 50 of the 350 candidates turned out
to be likely galaxies or clusters of galaxies. We found 14 RASS sources which
are very promising SNR candidates and are currently subject of further
follow-up studies. We will provide the details of the identification campaign
and present first results.


title: Cumulative light curves of gamma-ray bursts and relaxation systems

abstract:
  The cumulative light curves of a large sample of gamma-ray bursts (GRBs) were
obtained by summing the BATSE counts. The smoothed profiles are much simpler
than the complex and erratic running light curves that are normally used. For
most GRBs the slope of the cumulative light curve (S) is approximately constant
over a large fraction of the burst. The bursts are modelled as relaxation
systems that continuously accumulate energy in the reservoir and
discontinuously release it. The slope is a measure of the cumulative power
output of the central engine. A plot of S versus peak flux in 64ms (P64ms)
shows a very good correlation over a wide range for both short and long GRBs.
No relationship was found between S and GRBs with known redshift. The standard
slope (S'), which is representative of the power output per unit time, is
correlated separately with P64ms for both sub-classes indicating more powerful
outbursts for the short GRBs. S' is also anticorrelated with GRB duration.
These results imply that GRBs are powered by accretion into a black hole.


title:
Continuum and Emission Line Strength Relations for a large Active
  Galactic Nuclei Sample

abstract:
  We report on the analysis of a large sample of 744 type 1 Active Galactic
Nuclei, including quasars and Seyfert 1 galaxies across the redshift range from
0 < z < 5 and spanning nearly 6 orders of magnitude in continuum luminosity. We
discuss correlations of continuum and emission line properties in the
rest-frame ultraviolet and optical spectral ranges. The well established
Baldwin Effect is detected for almost all emission lines from OVI1034 to
[OIII]5007. Their equivalent widths are significantly anti-correlated with the
continuum strength, while they are nearly independent of redshift. This is the
well known Baldwin Effect. Its slope beta, measured as log W_lambda ~ beta *
log lambda * L_lambda (1450A), shows a tendency to become steeper towards
higher luminosity. The slope of the Baldwin Effect also increases with the
ionization energy needed to create the individual lines. In contrast to this
general trend, the NV1240 equivalent width is nearly independent of continuum
luminosity and remains nearly constant. The overall line behaviors are
consistent with softer UV continuum shapes and perhaps increasing gas
metallicity in more luminous Active Galactic Nuclei.


title: Kerr black holes and time profiles of gamma-ray bursts

abstract:
  The cumulative light curves of gamma-ray bursts (GRBs) smooth the spiky
nature of the running light curve. The cumulative count increases in an
approximately linear way with time t for most bursts. In 19 out of 398 GRBs
with T90 > 2s, the cumulative light curve was found to increase with time as
\~t^2 implying a linear increase in the running light curve. The non-linear
sections last for a substantial fraction of the GRB duration, have a large
proportion of the cumulative count and many resolved pulses that usually end
with the highest pulse in the burst. The reverse behaviour was found in 11 GRBs
where the running light curve decreased with time and some bursts are good
mirror images of the increases. These GRBs are among the spectrally hardest
bursts observed by BATSE. The most likely interpretation is that these effects
are signatures of black holes that are either being spun up or down in the
accretion process. In the spin up case, the increasing Kerr parameter of the
black hole allows additional rotational and accretion energy to become
available for extraction. The process is reversed if the black hole is spun
down by magnetic field torques. The luminosity changes in GRBs are consistent
with the predictions of the BZ process and neutrino annihilation and thus
provide the link to spinning black holes. GRBs provide a new window for
studying the general relativistic effects of Kerr black holes.


title: Quantifying angular clustering in wide-area radio surveys

abstract:
  We quantify the angular clustering of radio galaxies in the NVSS and FIRST
radio surveys using the two-point correlation function and the moments of
counts-in-cells - both important points of comparison with theory. These
investigations consistently demonstrate that the slope of the correlation
function for radio galaxies agrees with that for optically-selected galaxies,
gamma = 1.8. We describe how to disentangle the imprint of galaxy clustering
from the two observational problems: resolution of radio galaxies into multiple
components and gradients in source surface density induced by difficulties in
processing "snapshot" radio observations (significant in both surveys below 15
mJy). This study disagrees in some respects with previous analyses of the
angular clustering of radio galaxies.


title: How well can we determine cluster mass profiles from weak lensing?

abstract:
  Weak gravitational lensing provides a direct way to study the mass
distribution of clusters of galaxies at large radii. Unfortunately, large scale
structure along the line of sight also contributes to the lensing signal, and
consequently affects the measurements. We quantify the effect of distant
uncorrelated large scale structure on the inferred mass profile of clusters as
measured from weak lensing. We consider NFW profiles, and find that large scale
structure is a major source of uncertainty for most practical situations, when
a model, with the mass M_200 and the concentration parameter c as free
parameters, is fit to the observations. We find that the best constraints are
found for clusters at intermediate redshifts (z~0.3). For a cluster at z=0.3,
optimal results are obtained when the lensing signal is measured out to 10-15
arcminutes. Measurements at larger radii do not improve the accuracy with which
the profile can be determined, contrary to what is expected when the
contribution from large scale structure is ignored. The true uncertainties in
M_200 and the concentration parameter c are ~2 times larger than when distant
large scale structure is not included in the error budget.


title: Did Globular Clusters Reionize the Universe?

abstract:
  A problem still unsolved in cosmology is the identification of the sources of
radiation able to reionize HI in the intergalactic medium (IGM) by z~6.
Theoretical works and observations seem to indicate that the fraction, f_esc,
of HI ionizing radiation emitted from galaxies that escapes into the IGM is
small in the local universe (f_esc < 10%). At high redshift galaxies are more
compact and probably gas rich implying smaller values of f_esc from their disks
or spheroids. But if the sites of star formation are displaced from the disk or
spheroid and the star formation efficiency of the proto-clusters is high, then
f_esc should be about one. This star formation scenario is consistent with
several models for globular clusters formation. Using simple arguments based on
the observed number of globular cluster systems in the local universe and
assuming that the oldest globular clusters formed before reionization and had
f_esc~1, I show that they produced enough ionizing photons to reionize the IGM
at z=6.


title: Substructure and the halo model of large-scale structure

abstract:
  We develop the formalism to include substructure in the halo model of
clustering. Real halos are not likely to be perfectly smooth, but have
substructure which has so far been neglected in the halo model -- our formalism
allows one to estimate the effects of this substructure on measures of
clustering. We derive expressions for the two-point correlation function, the
power-spectrum, the cross-correlation between galaxies and mass, as well as
higher order correlation functions. Simple forms of the formulae are obtained
for the limit in which the size of the subclumps and mass fraction in them is
small. Inclusion of substructure allows for a more accurate analysis of the
statistical effects of gravitational lensing. It can also bring the halo model
predictions into better agreement with the small-scale structure seen in recent
high resolution simulations of hierarchical clustering.


title: Chandra High Resolution Camera Imaging of GRS 1758-258

abstract:
  We observed the "micro-quasar" GRS 1758-258 four times with Chandra. Two
HRC-I observations were made in 2000 September-October spanning an
intermediate-to-hard spectral transition (identified with RXTE). Another HRC-I
and an ACIS/HETG observation were made in 2001 March following a hard-to-soft
transition to a very low flux state. Based on the three HRC images and the HETG
zero order image, the accurate position (J2000) of the X-ray source is RA = 18h
01m 12.39s, Dec = -25d 44m 36.1s (90% confidence radius = 0".45), consistent
with the purported variable radio counterpart. All three HRC images are
consistent with GRS 1758-258 being a point source, indicating that any bright
jet is less than ~1 light-month in projected length, assuming a distance of 8.5
kpc.


title: The EXPLORE Project: A Deep Search for Transiting Extra-Solar Planets

abstract:
  Searching for transits provides a very promising technique for finding
close-in extra-solar planets. Transiting planets present the advantage of
allowing one to determine physical properties such as mass and radius
unambiguously. The EXPLORE (EXtra-solar PLanet Occultation REsearch) project is
a transit search project carried out using wide-field CCD imaging cameras on
4-m class telescopes, and 8-10m class telescopes for radial velocity
verification of the photometric candidates. We describe some of the
considerations that go into the design of the EXPLORE transit search to
maximize the discovery rate and minimize contaminating objects that mimic
transiting planets. We show that high precision photometry (2 to 10 millimag)
and high time sampling (few minutes) are crucial for sifting out contaminating
signatures, such as grazing binaries. We have completed two searches using the
8k MOSAIC camera at the CTIO4m and the CFH12k camera at CFHT, with runs
covering 11 and 16 nights, respectively. We obtained preliminary light curves
for approximately 47,000 stars with better than ~1% photometric precision. A
number of light curves with flat-bottomed eclipses consistent with being
produced by transiting planets has been discovered. Preliminary results from
follow-up spectroscopic observations using the VLT UVES spectrograph and the
Keck HIRES spectrograph obtained for a number of the candidates are presented.
Data from four of these can be interpreted consistently as possible planet
candidates, although further data are still required for definitive
confirmations.


title: The Milky Way - Pulsars and Isolated Neutron Stars

abstract:
  CONTENTS The Milky Way -- Pulsars and Isolated Neutron Stars / Introduction:
Historical Overview / Physics and Astrophysics of Isolated Neutron Stars /
Rotation-powered Pulsars: The Magnetic Braking Model / High-energy Emission
Models / Magnetospheric Emission Models / Thermal Evolution of Neutron Stars /
Photospheric Emission from Cooling Neutron Stars / The Current Picture of
High-Energy Emission Properties of Isolated Neutron Stars / Young Neutron Stars
in Supernova Remnants / Crab-like Pulsars / Vela-like pulsars / Radio-silent
Neutron Stars in Supernova Remnants / Anomalous X-ray Pulsars and Soft
Gamma-Ray Repeaters / Thermal Emission from Middle-Aged Pulsars / Old Nearby
Radio Pulsars / Isolated Radio-quiet Neutron Stars / Recycled Millisecond
Pulsars / Impressive Achievements and Great Expectations / References


title:
Studies of the Relativistic Binary Pulsar PSR B1534+12: I. Timing
  Analysis

abstract:
  We have continued our long term study of the double-neutron-star binary
pulsar PSR B1534+12, using new instrumentation to make very high precision
measurements at the Arecibo Observatory. We have significantly improved our
solution for the astrometric, spin, and orbital parameters of the system, as
well as for the five "post-Keplerian" orbital parameters that can be used to
test gravitation theory. The results are in good agreement with the predictions
of general relativity.
  With the assumption that general relativity is the correct theory of gravity
in the classical regime, our measurements allow us to determine the masses of
the pulsar and its companion neutron star with high accuracy: 1.3332 \pm 0.0010
Msun and 1.3452 \pm 0.0010Msun, respectively. The small but significant mass
difference is difficult to understand in most evolutionary models, as the
pulsar is thought to have been born first from a more massive progenitor star
and then undergone a period of mass accretion before the formation of the
second neutron star.
  PSR B1534+12 has also become a valuable probe of the local interstellar
medium. We have now measured the pulsar distance to be 1.02 \pm 0.05 kpc,
giving a mean electron density along this line of sight of 0.011/cc. We
continue to measure a gradient in the dispersion measure, though the rate of
change is now slower than in the first years after the pulsar's discovery.


title:
Breit-Pauli R-matrix calculations for electron impact excitation of Fe
  XVII: a benchmark study

abstract:
  A comprehensive study of relativistic and resonance effects in electron
impact excitation of (e+Fe XVII) is carried out using the BPRM method in the
relativistic close coupling approximation. Two sets of eigenfunction expansions
are employed; first, up to the n = 3 complex corresponding 37 fine-structure
levels (37CC) from 21 LS terms; second, up to the n = 4 corresponding to 89
fine-structure levels (89CC) from 49 LS terms. In contrast to previous works,
the 37CC and the 89CC collision strengths exhibit considerable differences.
Denser and broader resonances due to n = 4 are present in the 89CC results both
above and {\it below} the 37 thresholds, thus significantly affecting the
collision strengths for the primary X-ray and EUV transitions within the first
37 n = 3 levels. Extensive study of other effects on the collision strengths is
also reported: (i) electric and magnetic multipole transitions E1, E2, E3 and
M1, M2, (ii) J-partial wave convergence of dipole and non-dipole transitions,
(iii) high energy behaviour compared to other approximations. Theortical
results are benchmarked against experiments to resolve longstanding
discrepancies -- collision strengths for the three prominent X-ray lines 3C, 3D
and 3E at 15.014, 15.265, and 15.456 \AA are in good agreement with two
independent measurements on Electron-Beam-Ion-Traps (EBIT). Finally, line
ratios from a collisional-radiative model using the new collisional rates are
compared with observations from stellar coronae and EBITs to illustrate
potential applications in laboratory and astrophysical plasmas.


title: The relative ages of LMC old clusters, and the case of NGC 1841

abstract:
  Using archival HST/WFPC2 imaging of 7 LMC globular clusters, and following
the methods outlined in our previous study, we have reached the tightest
constrain so far on their age dispersion, which cannot be greater than ~ 0.5
Gyr. We also confirm earlier results that their average age is comparable to
that of the metal-poor Galactic globulars. Evidence is also provided that NGC
1841 is younger than the rest of LMC globulars.


title:
The density profile and the wavelength dependence of compact radio
  source size

abstract:
  In the gaseous disk model, the density profile is derived from the mass and
energy conservation in the gravitational field of a central energy source.
Using the condition for emission, following from the induced character of
radiation process, we obtain the wavelength dependence of radio source size
which is consistent with observational data.


title:
Measuring Omega_0 with higher-order Quasar-Galaxy Correlations induced
  by Weak Lensing

abstract:
  Via the magnification bias, gravitational lensing by large-scale structures
causes angular cross-correlations between distant quasars and foreground
galaxies on angular scales of arc minutes and above. We investigate the
three-point cross-correlation between quasars and galaxy pairs measurable via
the second moment of the galaxy counts around quasars and show that it reaches
the level of a few per cent on angular scales near one arc minute. Combining
two- and three-point correlations, a skewness parameter can be defined which is
shown to be virtually independent on the shape and normalisation of the
dark-matter power spectrum. If the galaxy bias is linear and deterministic, the
skewness depends on the cosmic matter density parameter Omega_0 only;
otherwise, it can be used to probe the linearity and stochasticity of the bias.
We finally estimate the signal-to-noise ratio of a skewness determination and
find that around twenty thousand distant quasars e.g. from the Sloan Digital
Sky Survey should suffice for a direct measurement of Omega_0.


title:
Medium effects in the pion pole mechanism (photon photon --> pion-zero
  --> neutrino-R antineutrino-L (neutrino-L antineutrino-R)) of neutron star
  cooling

abstract:
  Nuclear medium effects in the neutrino cooling of neutron stars through the
exotic reaction channel \gamma \gamma --> \pi^0--> \nu_R \bar{\nu_L} (\nu_L
\bar{\nu_R}) are incorporated. Throughout the paper we discuss different
possibilities of right-handed neutrinos, massive left-handed neutrinos and
standard massless left-handed neutrinos (reaction is then allowed only with
medium modified vertices). It is demonstrated that multi-particle effects
suppress the rate of this reaction channel by 6-7 orders of magnitude that does
not allow to decrease existing experimental upper limit on the corresponding
\pi^0\nu\bar{\nu} coupling. Other possibilities of the manifestation of the
given reaction channel in differente physical situations, e.g. in the quark
color superconducting cores of some neutron stars, are also discussed. We
demonstrate that in the color-flavor-locked superconducting phase for
temperatures T < (0.1-10) MeV (depending on the effective pion mass and the
decay width) the process is feasibly the most efficient neutrino cooling
process, although the absolute value of the reaction is rather small.


title: Saturation of the corotation resonance in a gaseous disk

abstract:
  We determine the torque exerted in a steady state by an external potential on
a three-dimensional gaseous disk at a non-coorbital corotation resonance. Our
model accounts for the feedback of the torque on the surface density and
vorticity in the corotation region, and assumes that the disk has a barotropic
equation of state and a nonzero effective viscosity. The ratio of the torque to
the value given by the formula of Goldreich & Tremaine depends essentially on a
single dimensionless parameter, which quantifies the extent to which the
resonance is saturated. We discuss the implications for the eccentricity
evolution of young planets.


title: CMB limits on large-scale magnetic fields in an inhomogeneous universe

abstract:
  We use the cosmic microwave background temperature anisotropy to place limits
on large-scale magnetic fields in an inhomogeneous (perturbed Friedmann)
universe. If no assumptions are made about the spacetime geometry, only a weak
limit can be deduced directly from the CMB. In the special case where spatial
inhomogeneity is neglected to first order, the upper limit is much stronger,
i.e. a few nano-G


title:
A relativistic time variation of matter/space fits both local and cosmic
  data

abstract:
  Cosmic observations strongly support a time varying scenario for
matter/space. On the other hand, so far, observations at solar system scale
failed to identify any time variation on matter/space characteristics. To
explain both results it is enough to consider a time variation of physical
parameters liable to account for cosmic observations but satisfying Relativity
Principle at least at local scale (we called it Local Relativity Property).
Here, for the first time, a relativistic time varying scenario is defined from
redshift and Cosmic Microwave Background characteristics. It is showed that it
can match both cosmic and local data. Although undetectable in each local
measure, such relativistic scenario has detectable time dependent consequences
at Solar System scale, namely a receding component in the motion of the Moon, a
past warmer climate and, this being new, an accelerating component in Earth
rotation. A new class of cosmological models can now be explored, without
concepts like dark matter, valid at both local and cosmic scale, and such that
fundamental physical laws and Relativity Principle hold in any point of time
and space.


title:
Stability of strange stars (SS) derived from a realistic equation of
  state

abstract:
  A realistic equation of state (EOS) leads to realistic strange stars (ReSS)
which are compact in the mass radius plot, close to the Schwarzchild limiting
line (Dey et al 1998). Many of the observed stars fit in with this kind of
compactness, irrespective of whether they are X-ray pulsars, bursters or soft
$\gamma$ repeaters or even radio pulsars. We point out that a change in the
radius of a star can be small or large, when its mass is increasing and this
depends on the position of a particular star on the mass radius curve. We carry
out a stability analysis against radial oscillations and compare with the EOS
of other strange star (SS) models. We find that the ReSS is stable and an M-R
region can be identified to that effect.


title: The Orbit of the High-Mass X-Ray Binary Pulsar 1E1145.1-6141

abstract:
  Observations of the 297 s X-ray pulsar 1E1145.1-6141 with the Rossi X-Ray
Timing Explorer have revealed its 14.4 d eccentric orbit around its B
supergiant companion. The best-fit orbital elements are: P_orb = 14.365(2) d,
a_x sin i=99.4(18) light-s, e=0.20(3). No eclipses are detected, indicating
that the binary inclination is less than 55 deg.


title: A Parkes half-Jansky sample of GPS galaxies

abstract:
  This paper describes the selection of a new southern/equatorial sample of
Gigahertz Peaked Spectrum (GPS) radio galaxies, and subsequent optical CCD
imaging and spectroscopic observations using the ESO 3.6m telescope. The sample
consists of 49 sources with -40<\delta<+15 degrees, |b|>20 degrees, and
S(2.7GHz)>0.5 Jy, selected from the Parkes PKSCAT90 survey. About 80% of the
sources are optically identified, and about half of the identifications have
available redshifts. The R-band Hubble diagram and evolution of the host
galaxies of GPS sources are reviewed.


title: POX 186: A Dwarf Galaxy in the Process of Formation?

abstract:
  We present deep U, V and I band images of the "ultracompact" blue dwarf
galaxy POX 186 obtained with the Planetary Camera 2 of the Hubble Space
Telescope. We have also obtained a near-ultraviolet spectrum of the object with
the Space Telescope Imaging Spectrograph, and combine this with a new
ground-based optical spectrum. The images confirm the galaxy to be extremely
small, with a maximum extent of only 300 pc, a luminosity ~ 10^-4 L*, and an
estimated mass ~ 10^7 M(sun). Its morphology is highly asymmetric, with a tail
of material on its western side that may be tidal in origin. The U-band image
shows this tail to be part of a stream of material in which stars have recently
formed. Most of the star formation in the galaxy is however concentrated in a
central, compact (d ~ 10 - 15 pc) star cluster. The outer regions of the galaxy
are significantly redder than the cluster, with V - I colors consistent with a
population dominated by K and M stars. While these results rule out earlier
speculation that POX 186 is a protogalaxy, its morphology, mass and active star
formation suggest that it represents a recent (within ~ 10^8 yr) collision
between two clumps of stars of sub-galactic size (~ 100 pc). POX 186 may thus
be a very small dwarf galaxy that, dynamically speaking, is still in the
process of formation. This interpretation is supported by the fact that it
resides in a void, so its morphology cannot be explained as the result of an
encounter with a more massive galaxy. Clumps of stars this small may represent
the building blocks required by hierarchical models of galaxy formation, and
these results also support the recent "downsizing" picture of galaxy formation
in which the least massive objects are the last to form.


title: Jet-Induced Nucleosynthesis in Misaligned Microquasars

abstract:
  The jet axes and the orbital planes of microquasar systems are usually
assumed to be approximately perpendicular, eventhough this is not currently an
observational requirement. On the contrary, in one of the few systems where the
relative orientations are well-constrained, V4641Sgr, the jet axis is known to
lie not more than ~36 degrees from the binary plane. Such a jet, lying close to
the binary plane, and traveling at a significant fraction of the speed of light
may periodically impact the secondary star initiating nuclear reactions on its
surface. The integrated yield of such nuclear reactions over the age of the
binary system (less the radiative mass loss) will detectably alter the
elemental abundances of the companion star. This scenario may explain the
anomalously high Li enhancements (roughly ~20-200 times the sun's photospheric
value; or, equivalently, 0.1-1 times the average solar system value) seen in
the companions of some black-hole X-ray binary systems. (Such enhancements are
puzzling since Li nuclei are exceedingly fragile - being easily destroyed in
the interiors of stars - and Li would be expected to be depleted rather than
enhanced there.) Gamma-ray line signatures of the proposed process could
include the 2.22 MeV neutron capture line as well as the 0.478 MeV 7Li*
de-excitation line, both of which may be discernable with the INTEGRAL
satellite if produced in an optically thin region during a large outburst. For
very energetic jets, a relatively narrow neutral pion gamma-decay signature at
67.5 MeV could also be measurable with the GLAST satellite. We argue that about
10-20% of all microquasar systems ought to be sufficiently misaligned as to be
undergoing the proposed jet-secondary impacts.


title: X-ray Thread G0.13-0.11: A Pulsar Wind Nebula?

abstract:
  We have examined Chandra observations of the recently discovered X-ray thread
G0.13-0.11 in the Galactic center Radio Arc region. Part of the {\sl Chandra}
data was studied by Yusef-Zadeh, Law, & Wardle (2002), who reported the
detection of 6.4-keV line emission in this region. We find, however, that this
line emission is {\sl not} associated with G0.13-0.11. The X-ray spectra of
both G0.13-0.11 and the point-like source embedded are well characterized by a
power law. The 2 -- 10 keV band luminosities of these two components are $\sim
3.2\times 10^{33}{\rm ergs s^{-1}}$ (G0.13-0.11) and $\sim 7.5 \times10^{32}
{\rm ergs s^{-1}}$ (point source) at the Galactic center distance of 8 kpc. The
morphological, spectral, and luminosity properties strongly indicate that
G0.13-0.11 represents the leading-edge of a pulsar wind nebula, produced by a
pulsar (point source) moving in a strong magnetic field environment. The main
body of this pulsar wind nebula is likely traced by a bow-shaped radio feature,
which is apparently bordered by G0.13-0.11 and is possibly associated with the
prominent nonthermal radio filaments of the Radio Arc. We speculate that young
pulsars may be responsible for various unique nonthermal filamentary radio and
X-ray features observed in the Galactic center region.


title:
Quasi-molecular lines in Lyman wings of cool DA white dwarfs;
  Application to FUSE observations of G231-40

abstract:
  We present new theoretical calculations of the total line profiles of Lyman
alpha and Lyman beta which include perturbations by both neutral hydrogen AND
protons and all possible quasi-molecular states of H_2 and H_2^+. They are used
to improve theoretical modeling of synthetic spectra for cool DA white dwarfs.
  We compare them with FUSE observation of G231-40. The appearance of the line
wings between Lyman alpha and Lyman beta is shown to be sensitive to the
relative abundance of hydrogen ions and neutral atoms, and thereby to provide a
temperature diagnostic for stellar atmospheres and laboratory plasmas.


title:
N-body Gravitational Interactions: A General View and Some Heuristic
  Problems

abstract:
  We present some non-standard approaches to the N-body problem in an attempt
to overcome its epistemological limits. We provide, in a preliminary way,
not-ordinary insights and breakthroughs.


title: Intermediate- and High-Velocity Ionized Gas toward zeta Orionis

abstract:
  We combine UV spectra obtained with the HST/GHRS echelle, IMAPS, and
Copernicus to study the abundances and physical conditions in the predominantly
ionized gas seen at high (-105 to -65 km/s) and intermediate velocities (-60 to
-10 km/s) toward zeta Ori. We have high resolution (FWHM ~ 3.3-4.5 km/s) and/or
high S/N spectra for at least two significant ions of C, N, Al, Si, S, and Fe
-- enabling accurate estimates for both the total N(H II) and the elemental
depletions. C, N, and S have essentially solar relative abundances; Al, Si, and
Fe appear to be depleted by about 0.8, 0.3-0.4, and 0.95 dex, respectively.
While various ion ratios would be consistent with collisional ionization
equilibrium (CIE) for T ~ 25,000-80,000 K, the widths of individual
high-velocity absorption components indicate that T ~ 9000 K -- so the gas is
not in CIE. Analysis of the C II fine-structure excitation equilibrium yields
estimated densities (n_e ~ n_H ~ 0.1-0.2 cm^{-3}), thermal pressures (2 n_H T ~
2000-4000 cm^{-3}K), and thicknesses (0.5-2.7 pc) for the individual clouds. We
compare the abundances and physical properties derived for these clouds with
those found for gas at similar velocities toward 23 Ori and tau CMa, and also
with several models for shocked gas. While the shock models can reproduce some
features of the observed line profiles and some of the observed ion ratios,
there are also significant differences. The measured depletions suggest that
\~10% of the Al, Si, and Fe originally locked in dust in the pre-shock medium
may have been returned to the gas phase, consistent with predictions for the
destruction of silicate dust in a 100 km/s shock. The near-solar gas phase
abundance of carbon, however, seems inconsistent with the predicted longer time
scales for the destruction of graphite grains.


title: The r-process in the early Galaxy

abstract:
  We report Sr, Pd and Ag abundances for a sample of metal-poor field giants
and analyze a larger sample of Y, Zr, and Ba abundances. The [Y/Zr] and [Pd/Ag]
abundance ratios are similar to those measured for the r-process-rich stars CS
22892-052 and CS 31082-001. The [Pd/Ag] ratio is larger than predicted from the
solar-system r-process abundances. The constant[Y/Zr] and [Sr/Y] values in the
field stars places strong limits on the contributions of the weak s-process and
the main s-process to the light neutron-capture elements. Stars in the globular
cluster M 15 possess lower [Y/Zr] values than the field stars. There is a large
dispersion in [Y/Ba]. Because the r-process is responsible for the production
of the heavy elements in the early Galaxy, these dispersions require varying
light-to-heavy ratios in r-process yields.


title:
Discovery of New Milky Way Star Clusters Candidates in the 2MASS Point
  Source Catalog

abstract:
  A systematic search of the 2MASS point source catalog, covering 47% of the
sky, was carried out aiming to reveal any hidden globular clusters in our
Galaxy. Eight new star clusters were discovered by a search algorithm based on
finding peaks in the apparent stellar surface density, and a visual inspection
of their vicinities yielded additional two. They all are concentrated toward
the Galactic plane and are hidden behind up to Av=20 mag which accounts for
their late discovery. The majority of new clusters are associated with H II
regions or unidentified IRAS sources suggesting that they are young, probably
similar to Arches or open clusters. Only one candidate has morphology similar
to a globular cluster and the verification of its nature will require deeper
observations with higher angular resolution than the 2MASS data.


title: Star Formation Processes versus Planet Formation Processes

abstract:
  The processes of star formation are fundamentally different from those of
planet formation. Since the mass of a very-low-mass object alone doesn't allow
us to uniquely determine its basic nature, we have to look at its other
characteristics, such as its motion, its age, its atmospheric composition, its
internal structure and composition, etc., in order to ascertain its formation
mechanism.


title:
Precession of Isolated Neutron Stars II: Magnetic Fields and Type II
  Superconductivity

abstract:
  We consider the physics of free precession of a rotating neutron star with an
oblique magnetic field. We show that if the magnetic stresses are large enough,
then there is no possibility of steady rotation, and precession is inevitable.
Even if the magnetic stresses are not strong enough to prevent steady rotation,
we show that the minimum energy state is one in which the star precesses. Since
the moment of inertia tensor is inherently triaxial in a magnetic star, the
precession is periodic but not sinusoidal in time, in agreement with
observations of PSR 1828-11. However, the problem we consider is {\it not} just
precession of a triaxial body. If magnetic stresses dominate, the amplitude of
the precession is not set just by the angle between the rotational angular
velocity and any principal axis, which allows it to be small without
suppressing oscillations of timing residuals at harmonics of the precession
frequency. We argue that magnetic distortions can lead to oscillations of
timing residuals of the amplitude, period, and relative strength of harmonics
observed in PSR 1828-11 if magnetic stresses in its core are about 200 times
larger than the classical Maxwell value for its dipole field, and the stellar
distortion induced by these enhanced magnetic stresses is about 100-1000 times
larger than the deformation of the neutron star's crust. Magnetic stresses this
large can arise if the core is a Type II superconductor, or from toroidal
fields $\sim 10^{14}$ G if the core is a normal conductor. The observations of
PSR 1828-11 appear to require that the neutron star is slightly prolate.


title: A 15-Kiloparsec X-Ray Disk in the Elliptical Galaxy NGC 1700

abstract:
  We present Chandra observations of the young elliptical galaxy NGC 1700. The
X-ray isophotes are highly flattened between semimajor axes of 30 and 80
arcseconds, reaching a maximum ellipticity of approximately 0.65 at 60 arcsec
(15 kpc). The surface brightness profile in the spectrally soft, flattened
region is shallower than that of the starlight, indicating that the emission
comes from hot gas rather than stellar sources. The flattening is so extreme
that the gas cannot be in hydrostatic equilibrium in any plausible potential. A
likely alternative is that the gas has significant rotational support. A simple
model, representing isothermal gas distributed about a particular angular
momentum, can reproduce the X-ray morphology while staying consistent with
stellar kinematics. The specific angular momentum of the gas matches that of
the stars in the most isophotally distorted outer part of the galaxy, and its
cooling time matches the time since the last major merger. We infer that the
gas was acquired in that merger, which involved a pre-existing elliptical
galaxy with a hot ISM. The hot gas carried the angular momentum of the
encounter, and has since gradually settled into a rotationally flattened,
cooling disk.


title: Tidal Torques and Galactic Warps

abstract:
  (Abridged) We investigate how galactic disks react to external tidal torques.
We calculate the strength and radial dependence of torques on disks that arise
from a misalignment between the disk and the main axis system of a flattened
dark matter halo. We find that except for in the very inner regions, the
torques are well-described by a power law of the form $\tau \propto r^{-2.5}$.
The magnitude of the torque is large enough for the entire disk to react to the
torque in less than the Hubble time. We demonstrate analytically that disks
which are originally located in the $xy$-plane and which are subjected to a
torque around the x-axis tilt around the y-axis, as also found in fully
non-linear N-body simulations. We further demonstrate that that the torque
causes the radius of a chosen particle to increase with time. Investigations of
tilting disks which treat the disk as a set of solid rings thus may
systematically overestimate the effects of the torque by a factor of two. For
torques of the form we investigate, the inner regions of the disk react to the
torque faster than the outer regions, resulting in a trailing warp. We then
study the effect of the self-gravity of the disk in such a scenario using
numerical N-body models. Self-gravity flattens out the inner regions of the
disk, but these regions are tilted with respect to their initial plane followed
by a non-flat outer region whose tilt decreases with radius. The ``warp
radius,'' which marks the end of the inner flat disk, grows throughout the disk
at a rate that depends only on the strength of the torque and the local surface
density of the disk.


title:
Study of the Backgrounds for the Search for Proton Decay to 10^35 Y at
  the WIPP Site with the LANNDD Detector

abstract:
  We briefly describe the LANNDD 70-kT liquid argon TPC proposal for the WIPP
underground facility at Carlsbad, New Mexico. We, then, identify the key
backgrounds for the search for p -> K+ nu_bar to 10^35 years lifetime. The most
serious non-neutrino background is due to high-energy neutrons producing
strange particles in the detector. We show that this can be reduced to an
acceptable level by appropriate fiducial volume cuts.


title: The Progenitor of Supernova 1993J Revisited

abstract:
  From Hubble Space Telescope images with 0.05" resolution we identify four
stars brighter than V=25 mag within 2.5" of SN 1993J in M81 which contaminated
previous ground-based brightness estimates for the supernova progenitor.
Correcting for the contamination, we find that the energy distribution of the
progenitor is consistent with that of an early K-type supergiant star with M_V
\~ -7.0 +/- 0.4 mag and an initial mass of 13--22 Msun. The brightnesses of the
nearby stars are sufficient to account for the excess blue light seen from the
ground in pre-explosion observations. Therefore, the SN 1993J progenitor did
not necessarily have a blue companion, although by 2001, fainter blue stars are
seen in close proximity to the supernova. These observations do not strongly
limit the mass of a hypothetical companion. A blue dwarf star with a mass up to
30 Msun could have been orbiting the progenitor without being detected in the
ground-based images. Explosion models and observations show that the SN 1993J
progenitor had a helium-rich envelope. To test whether the helium abundance
could influence the energy distribution of the progenitor, we calculated model
supergiant atmospheres with a range of plausible helium abundances. The models
show that the pre-supernova colors are not strongly affected by the helium
abundance longward of 4000 A, and abundances ranging between solar and 90%
helium (by number) are all consistent with the observations.


title: FIRST J102347.6+003841: The First Radio-Selected Cataclysmic Variable

abstract:
  We have identified the 1.4 GHz radio source FIRST J102347.6+003841 (hereafter
FIRST J1023+0038) with a previously unknown 17th-mag Galactic cataclysmic
variable (CV). The optical spectrum resembles that of a magnetic (AM Herculis-
or DQ Herculis-type) CV. Five nights of optical CCD photometry showed
variations on timescales of minutes to hours, along with rapid flickering. A
re-examination of the FIRST radio survey data reveals that the radio detection
was based on a single 6.6 mJy flare; on two other occasions the source was
below the ~1 mJy survey limit. Several other magnetic CVs are known to be
variable radio sources, suggesting that FIRST J1023+0038 is a new member of
this class (and the first CV to be discovered on the basis of radio emission).
However, FIRST J1023+0038 is several optical magnitudes fainter than the other
radio-detected magnetic CVs. It remains unclear whether the source simply had a
very rare and extraordinarily intense radio flare at the time of the FIRST
observation, or is really an unusually radio-luminous CV; thus further
observations are urged.


title: Comment on "Black holes constrain varying constants"

abstract:
  A recent paper [DDL] claims that the increase of the proton electric charge e
leads to a (forbidden) decrease of black hole entropy, therefore, possible
evidence for variation of $\alpha=e^2/\hbar c$ [alpha] must be interpreted as a
decrease of the speed of light. We argue that purely theoretical consideration
of black holes possibly cannot give any model-independent limitations on
variation of fundamental constants.


title: Morphological Evolution of Distant Galaxies from Adaptive Optics Imaging

abstract:
  We report here on a sample of resolved, infrared images of galaxies at z~0.5
taken with the 10-m Keck Telescope's Adaptive Optics (AO) system. We regularly
achieve a spatial resolution of 0.05'' and are thus able to resolve both the
disk and bulge components. We have extracted morphological information for ten
galaxies and compared their properties to those of a local sample. The
selection effects of both samples were explicitly taken into account in order
to derive the unbiased result that disks at z~0.5 are ~0.6 mag arcsec^-2
brighter than, and about the same size as, local disks. The
no-luminosity-evolution case is ruled out at 90% confidence. We also find, in a
more qualitative analysis, that the bulges of these galaxies have undergone a
smaller amount of surface brightness evolution and have also not changed
significantly in size from z~0.5 to today. This is the first time this type of
morphological evolution has been measured in the infrared and it points to the
unique power of AO in exploring galaxy evolution.


title: A Lossy Method for Compressing Raw CCD Images

abstract:
  This paper describes a lossy method for compressing raw images produced by
CCDs or similar devices. The method is very simple: lossy quantization followed
by lossless compression using general-purpose compression tools such as gzip
and bzip2. A key feature of the method is that compressed images can be
converted to FITS files simply by decompressing with gunzip or bunzip2, and
this is a significant advantage for distributing compressed files. The degree
of quantization is chosen to eliminate low-order bits that over-sample the
noise, contain no information, and are difficult or impossible to compress. The
method is lossy but gives guarantees on the maximum absolute difference, the
expected mean difference, and the expected RMS difference between the
compressed and original images; these guarantees make it suitable for use on
raw images. The method consistently compresses images to roughly 1/5 of their
original size with a quantization such that no value changes by more than 1/2
of a standard deviation in the background. This is a dramatic improvement on
lossless compression. It appears that bzip2 compresses the quantized images to
within a few tens of percent of the theoretical limit.


title: Solar Supergranulation Waves Detected in Surface Doppler Shift

abstract:
  Recently Gizon, Duvall and Schou (2002) suggested that supergranulation has a
wave-like component. In this paper I show that the same phenomenon can be
observed using surface Doppler shift data, thereby confirming their
observations. I am also able to measure the dispersion relation to lower
wavenumbers and to extend the results for rotation and meridional flows beyond
+/-70 degrees latitude.


title: On Why Disks Generate Magnetic Towers and Collimate Jets

abstract:
  We show that accretion disks with magnetic fields in them ought to make jets
provided that their electrical conductivity prevents slippage and there is an
ambient pressure in their surroundings.
  We study equilibria of highly wound magnetic structures. General Energy
theorems demonstrate that they form tall magnetic towers whose height grows
with every turn at a velocity related to the circular velocity in the accretion
disk.
  The pinch effect amplifies the magnetic pressures toward the axis of the
towers whose stability is briefly considered.


title: The X-ray spectrum of the atoll source 4U 1608-52

abstract:
  The transient atoll source 4U 1608-52 had been extensively observed by the
Rossi X-ray Timing Explorer RXTE during its 1998 outburst. We analyse its X-ray
spectra as a function of inferred accretion rate from both the 1998 outburst
and from the non-outburst 1996 and 1998 data. We can fit all the spectra by a
model in which seed photons from the neutron star surface are Comptonized in a
boundary layer. The Comptonized emission illuminates the accretion disc
surface, producing an ionized, relativistically broadened reflection signature,
while the direct emission from the accretion disc can also be seen. The
evolution of the source can be explained if the main parameter driving the
spectral evolution is the average mass accretion rate, which determines the
truncation radius of the inner accretion disc. At low mass accretion rates, in
the island state, the disc truncates before reaching the neutron star surface
and the inner accretion flow/boundary layer is mostly optically thin. The disc
emission is at too low a temperature to be observed in the RXTE spectra, but
some of the seed photons from the neutron star can be seen directly through the
mostly optically thin boundary layer. At higher mass accretion rates, in the
banana state, the disc moves in and the boundary layer becomes much more
optically thick so its temperature drops. The disc can then be seen directly,
but the seed photons from the neutron star surface cannot as they are buried
beneath the increasingly optically thick boundary layer.


title:
On the black-hole mass -- radio luminosity relation for flat-spectrum
  radio-loud quasars

abstract:
  A new analysis of the connection between black-hole mass and radio luminosity
in radio-selected flat-spectrum quasars (FSQ) is presented. In contrast to
recent claims in the literature, we find no evidence that the black-hole masses
of radio-selected FSQ are systematically lower that those of luminous
optically-selected radio-loud quasars. The black-hole masses of the FSQ are
estimated via the virial black-hole mass estimator which utilizes the
line-width of the H$\beta$ emission line as a tracer of the central
gravitational potential. By correcting for the inevitable effects of
inclination, incurred due to the FSQ being viewed close to the line of sight,
we find that the black-hole masses of the FSQ with intrinsically powerful radio
jets are confined, virtually exclusively, to M_bh > 10^8 M_solar. This is in
good agreement with previous studies of optically selected FSQ and
steep-spectrum radio-loud quasars.
  Finally, following the application of a realistic Doppler boosting
correction, we find that the FSQ occupy a wide range in intrinsic radio
luminosity, and that many sources would be more accurately classified as
radio-intermediate or radio-quiet quasars. This range in radio luminosity
suggests that the FSQ are fully consistent with an upper boundary on radio
power of the form L_5GHz \propto M_bh^2.5.


title:
Lithium during the AGB evolution in young open clusters of the Large
  Magellanic cloud

abstract:
  We present the results of mid-resolution spectroscopy in the LiI 6708 AA
spectral region of Asymptotic Giant Branch (AGB) stars belonging to young open
clusters of the Large Magellanic Cloud. Most stars belong to the clusters NGC
1866 and NGC 2031, which have an age of ~ 150 Myr. Lithium lines of different
strength are detected in the spectra of stars evolving along the AGB, not
always in agreement with theoretical predictions. We also analyze the infrared
luminosities (ISOCAM data) of these stars, to discuss if their evolutionary
phase precedes or follows the lithium production stage.


title: Kinetic Sunyaev-Zeldovich effect from galaxy cluster rotation

abstract:
  We show how the temperature and the polarisation of the cosmic microwave
background are affected by bulk rotation of clusters of galaxies owing to the
kinetic Sunyaev-Zeldovich effect. The main effects of rotation are (i) a shift
of the position of the peak of the temperature fluctuation relative to the
center of the cluster by a few percent of the core radius and (ii) a tilt of
the direction of the plane of linear polarisation by several degrees.


title:
An Halpha nebula possibly associated with the central X-ray source in
  the G 266.1-1.2 supernova remnant

abstract:
  We report the discovery of a small Halpha nebula positionally coincident with
the candidate neutron star AX J0851.9-4617.4 located at the center of the
supernova remnant G 266.1-1.2. The nebula has a roughly circular shape with a
diameter of ~6'' and a flux of ~10^-2 photons cm^-2 s^-1 in the Halpha line.
Considering the uncertainties in the distance and energy output from the
putative neutron star, we find that such a flux can be explained either in a
bow-shock model or assuming that the nebular emission is due to
photo-ionization and heating of the ambient gas.


title:
Cosmological constraints from the local X-ray luminosity function of the
  most X-ray luminous galaxy clusters

abstract:
  We present precise constraints on the normalization of the power spectrum of
mass fluctuations in the nearby universe, sigma_8, as a function of the mean
local matter density, Omega_m. Using the observed local X-ray luminosity
function of galaxy clusters from the extended BCS and REFLEX studies, a
mass-luminosity relation determined from Chandra and ROSAT X-ray data and weak
gravitational lensing observations, and the mass function predicted by the
Hubble Volume simulations of Evrard et al., we obtain sigma_8 = (0.508\pm0.019)
Omega_m^-(0.253\pm0.024), with Omega_m < 0.34 at 68 per cent confidence. The
degeneracy between sigma_8 and Omega_m can be broken using Chandra measurements
of the X-ray gas mass fractions in dynamically relaxed clusters. Using this
information and including Gaussian priors on the mean baryon density of the
universe and the Hubble constant, we obtain sigma_8=0.695\pm0.042 and
Omega_m=0.287\pm0.036, for an assumed flat LambdaCDM cosmology (marginalized 68
per cent confidence limits). Our results are in good agreement with some recent
studies based on the local X-ray temperature function of clusters, the redshift
evolution of the X-ray luminosity and temperature functions of clusters, early
results from the Sloan Digitized Sky Survey, the most recent results from
studies of cosmic shear, and combined analyses of the 2dF galaxy redshift
survey and cosmic microwave background anisotropies.


title:
BeppoSAX/PDS identification of the true counterpart of the Piccinotti
  source H0917-074

abstract:
  High energy emission has been discovered serendipitously by the BeppoSAX/PDS
telescope in the ~1.3 degree field of view around the Piccinotti source
H0917-074. A re-pointing of BeppoSAX/NFI has allowed the association of this
emission with the Seyfert 2 galaxy MCG-1-24-12 which lies within the original
HEAO1/A2 error box of H0917-074. This is the first PDS serendipitous discovery
of a Seyfert 2 galaxy and the first detection of MCG-1-24-12 in the X-ray
domain. The measured 2-10 keV flux of MCG-1-24-12 is ~1 x 10^(-11) erg cm^(-2)
s^(-1) compatible with the Piccinotti HEAO-1/A2 observation. This is a factor
of ~6 greater than that observed from EXO0917.3-0722, originally suggested as
the counterpart of the Piccinotti source. The 2-10 keV spectrum of MCG-1-24-12
shows the presence of Fe K_alpha emission together with an absorption feature
at ~8.7 keV. At high energies, the Seyfert 2 still dominates and the observed
20-100 keV flux is ~4 x 10^(-11)erg cm^(-2) s^(-1).


title:
The Cosmic Ray Background as a Tool for Relative Calibration of
  Atmospheric Cherenkov Telescopes

abstract:
  The atmosphere is an intrinsic part of any ground based Cherenkov gamma-ray
telescope, and the telescope response is therefore sensitive to unpredictable
changes in the atmospheric transparency which are difficult to measure and
interpret in the absence of a calibrated beam of high energy gamma-rays. In
this paper, we use the detector response to Cherenkov emission from cosmic ray
initiated air showers to obtain a relative calibration for data obtained under
different instrumental and atmospheric conditions as well as over a range of
source angles to the Zenith. We show that such a relative calibration is useful
and efficient for data selection, for correcting the measured gamma-ray rate
and for inter-calibration between the elements of an array of Cherenkov
telescopes.


title: X- and Gamma-Ray Line Emission Processes

abstract:
  This chapter is intended to provide a general presentation of the atomic and
nuclear processes responsible for X-ray line and gamma-ray line emission in
various astrophysical environments. I consider line production from hot
plasmas, from accelerated particle interactions, from the decay of radioactive
nuclei synthesized in stars and from positron annihilation. Spectroscopic
properties of these emissions are discussed in the light of the detection
capabilities of modern space instruments.


title: Simulations of the Local Universe

abstract:
  The theory of structure formation predicts that galaxies form within extended
massive dark matter halos built from smaller pieces that collided and merged,
resulting in the hierarchy of galaxies, groups, and clusters observed today.
Here we present constrained numerical simulations designed to match the
observed local universe as well as possible and to study the formation,
evolution and present day properties of such dark matter halos in different
environments. Simulations have been done with different versions of the
Adaptive Refinement Tree (ART) N-body code, some of them including eulerian
gasdynamics.


title:
Constraining the Location of Microlensing Objects towards the LMC
  through Parallax Measurement in EAGLE Observations

abstract:
  We investigate the possibility of determining whether microlensing objects
towards the Large Magellanic Cloud (LMC) are in a Galactic thick disc, or are
in a Galactic halo, by using parallax measurements with an Earth-radius scale
baseline. Our method makes use of EAGLE (Extremely Amplified Gravitational
LEnsing) events which are microlensing events with an invisible faint source.
We show that the rate of EAGLE events is as high as that of normal microlensing
events, even if they are caused by dark stars in the Galactic thick disc. We
explore the possibility of measuring the parallax effect in EAGLE events
towards the LMC by using the {\it Hubble Space Telescope} (HST) or the {\it
Very Large Telescope} (VLT). We find that EAGLE events enlarge the opportunity
of parallax measurements by $4 \sim 10$ times relative to that in normal
microlensing events. We show that the parallax effect can be measured in
$\sim75%$ (from the HST) and $\sim 60%$ (from the VLT) of all EAGLE events if
most lenses are stars in the Galactic thick or thin disc, while $\sim 20%$
(from the HST) and $\sim 10%$ (from the VLT) can be measured if most lenses are
halo MACHOs. In combination with the finite source size effect observations, we
can strongly constrain the location of lenses.


title:
Extending the Shakura-Sunyaev approach to a strongly magnetized
  accretion disc model

abstract:
  We develop a model of thin turbulent accretion discs supported by magnetic
pressure of turbulent magnetic fields. This applies when the turbulent kinetic
and magnetic energy densities are greater than the thermal energy density in
the disc. Whether such discs survive in nature or not remains to be determined,
but here we simply demonstrate that self-consistent solutions exist when the
alpha-prescription for the viscous stress, similar to that of the original
Shakura-Sunyaev model, is used. We show that \alpha \sim 1 for the strongly
magnetized case and we calculate the radial structure and emission spectra from
the disc in the regime when it is optically thick. Strongly magnetized
optically thick discs can apply to the full range of disc radii for objects <
10^{-2} of the Eddington luminosity or for the outer parts of discs in higher
luminosity sources. In the limit that the magnetic pressure is equal to the
thermal or radiation pressure, our strongly magnetized disc model transforms
into the Shakura-Sunyaev model with \alpha=1. Our model produces spectra quite
similar to those of standard Shakura-Sunyaev models. In our comparative study,
we also discovered a small discrepancy in the spectral calculations of Shakura
and Sunyaev (1973).


title:
A test of arm-induced star formation in spiral galaxies from near-IR and
  H$\alpha$ imaging

abstract:
  We have imaged a sample of 20 spiral galaxies in H$\alpha$ and in the
near-infrared K band (2.2 um), in order to determine the location and strength
of star formation in these objects with respect to perturbations in the old
stellar population. We have found that star formation rates are significantly
enhanced in the vicinity of K band arms. We have also found that this
enhancement in star formation rate in arm regions correlates well with a
quantity that measures the relative strengths of shocks in arms. Assuming that
the K band light is dominated by emission from the old stellar population, this
shows that density waves trigger star formation in the vicinity of spiral arms.


title: X-ray QPOs in Black-Hole Binary Systems

abstract:
  We briefly review the properties and physical consequences of quasiperiodic
oscillations (QPOs) seen on many occasions in the X-ray emission from
black-hole binary systems. We also report on the discovery of QPOs at 164 and
328 Hz in GRS1915+105. These appear to be analogous to the harmonic systems of
high-frequency QPOs seen in XTEJ1550-564 and GROJ1655-40.


title: Inelastic Dark Matter at DAMA, CDMS and Future Experiments

abstract:
  The DAMA annual modulation signature, interpreted as evidence for a
spin-independent WIMP coupling, seems in conflict with null results from CDMS.
However, in models of ``inelastic dark matter'', the experiments are
compatible. Inelastic dark matter can arise in supersymmetric theories as the
real component of a sneutrino mixed with a singlet scalar. In contrast with
ordinary sneutrino dark matter, such particles can satisfy all experimental
constraints while giving the appropriate relic abundance. We discuss the
modifications to the signal seen at DAMA, in particular noting the strong
suppression of low energy events in both modulated and unmodulated components.
We discuss future experiments, with emphasis on distinguishing inelastic dark
matter from ordinary dark matter, and stressing the significance of experiments
with heavy target nuclei, such as xenon and tungsten.


title:
Structure of Disk Dominated Galaxies I. Bulge/Disk Parameters,
  Simulations, and Secular Evolution

abstract:
  (Abridged) A robust analysis of galaxy structural parameters, based on the
modeling of bulge and disk brightnesses in the BVRH bandpasses, is presented
for 121 face-on and moderately inclined late-type spirals. Each surface
brightness (SB) profile is decomposed into a sum of a generalized Sersic bulge
and an exponential disk. The reliability and limitations of our bulge-to-disk
(B/D) decompositions are tested with extensive simulations of galaxy brightness
profiles (1D) and images (2D). Galaxy types are divided into 3 classes
according to their SB profile shapes; Freeman Type-I and Type-II, and a third
``Transition'' class for galaxies whose profiles change from Type-II in the
optical to Type-I in the infrared. We discuss possible interpretations of
Freeman Type-II profiles. The Sersic bulge shape parameter for nearby Type-I
late-type spirals shows a range between n=0.1-2 but, on average, the underlying
surface density profile for the bulge and disk of these galaxies is adequately
described by a double-exponential distribution. We confirm a coupling between
the bulge and disk with a scale length ratio r_e/h=0.22+/-0.09, or
h_bulge/h_disk=0.13+/-0.06 for late-type spirals, in agreement with recent
N-body simulations of disk formation and models of secular evolution. This
ratio increases from ~0.20 for late-type spirals to ~0.24 for earlier types.
The similar scaling relations for early and late-type spirals suggest
comparable formation and/or evolution scenarios for disk galaxies of all Hubble
types.


title: How the BAL quasars are quiet

abstract:
  All properties of the quasars known by the author (quietness of the BAL
quasars, Lyman forest, iron in the high-z quasars...) are explained supposing
that the kernel of the quasar is surrounded by a halo containing an accretion
disk and magnetic satellites (no dark matter or fast jet, no variation of the
fine structure constant, no strange source of iron...). The key is taking into
account the coherent light-matter interactions.


title: Gravitational-Wave Radiation from Magnetized Accretion Disks

abstract:
  The detectability of gravitational wave (GW) radiation from accretion disks
is discussed based on various astrophysical contexts. In order to emit GW
radiation, the disk shape should lose axial symmetry. We point out that a
significant deformation is plausible in non-radiative hot accretion disks
because of enhanced magnetic activity, whereas it is unlikely for standard-type
cool disks. We have analyzed the 3D magnetohydrodynamical (MHD) simulation data
of magnetized accretion flow, finding non-axisymmetric density patterns. The
corresponding ellipticity is $\epsilon \sim 0.01$. The expected time variations
of GW radiation are overall chaotic, but there is a hint of quasi-periodicity.
GW radiation has no interesting consequence, however, in the case of close
binaries, because of very tiny disk masses. GW radiation is not significant,
either, for AGN because of very slow rotation velocities. The most promising
case can be found in gamma-ray bursts or supernovae, in which a massive torus
(or disk) with a solar mass or so may be formed around a stellar-mass compact
object as the result of a merger of compact objects, or by the fallback of
exploded material towards the center in a supernova. Although much more intense
GW radiation is expected before the formation of the torus, the detection of GW
radiation in the subsequent accretion phase is of great importance, since it
will provide a good probe to investigating their central engines.


title: Deep Transient Optical Fading in the WC9 Star WR 106

abstract:
  We discovered that the WR9-type star WR 106 (HDE 313643) underwent a deep
episodic fading in 2000. The depth of the fading (dV ~ 2.9 mag) surpassed those
of all known similar "eclipse-like" fadings in WR stars. This fading episode
was likely to be produced by a line-of-sight episodic dust formation rather
than a periodic enhancement of dust production in the WR-star wind during the
passage of the companion star though an elliptical orbit. The overall 2000
episode was composed of at least two distinct fadings. These individual fadings
seem to more support that the initial dust formation triggered a second dust
formation, or that the two independent dust formations occurred by the same
triggering mechanism rather than a stepwise dust formation. We also discuss on
phenomenological similarity of the present fading with the double fading of R
CrB observed in 1999-2000.


title:
Evolution and colours of helium-core white dwarf stars: the case of low
  metallicity progenitors

abstract:
  The present work is designed to explore the evolution of helium-core white
dwarf (HeWD) stars for the case of metallicities much lower than the solar one
(Z=0.001 and Z=0.0002). Evolution is followed in a self-consistent way with the
predictions of detalied and new non-grey atmospheres, time-dependent element
diffusion and the history of the white dwarf progenitor. Reliable initial
models for low mass HeWDs are obtained by applying mass loss rates to a 1msun
stellar model. The loss of angular momentum caused by gravitational wave
emission and magnetic stellar wind braking are considered. Model atmospheres,
based on a detailed treatment of the microphysics entering the WD atmosphere
enable us to provide accurate colours and magnitudes at both early and advanced
evolutionary stages. We find that most of our evolutionary sequences experience
several episodes of hydrogen thermonuclear flashes. In particular, the lower
the metallicity, the larger the minimum stellar mass for the occurrence fo
flashes induced by CNO cycle reactions. The existence of a mass-threshold for
the occurrence of diffusion-induced CNO flashes leadss to a marked dichotomy in
the age of our models. Another finding of this study is that our HeWD models
experience unstable hydrogen burning via PP nuclear reactions at late cooling
stages as a result of hydrogen chemically diffusing inwards. Such PP flashes
take place in models with very low metal content. We also find that models
experiencing CNO flashes exhibit a pronouncede turn-off in most of their
colours at M_V=16 approximately. Finally, colour-magnitude diagrams for our
models are presented and compared with recent observational data of HeWD
candidates in the globular clusters NGC 6397 and 47 Tucanae.


title: Probing Baryons in Galactic Halos and Gas Near Galaxies

abstract:
  We describe an extensive FUSE survey of highly ionized oxygen in the vicinity
of the Milky Way that serves as an example of the type of study that would be
desirable for other galactic systems. Understanding the origin of hot gas in
the vicinity of galaxies and its relationship to the intergalactic medium
presents a major observational challenge. Ultraviolet absorption-line
spectroscopy is currently the most direct means for comprehensive
investigations of the gas in galactic environments, but even with present (and
near-term) facilities the number of background objects available to probe
nearby galaxy halos and low-redshift cosmological structures is limited.
Studying these structures over a range of impact parameters and angular
separations would provide fundamental information about the baryonic content of
the hot gas, its physical conditions, and its origins. A large space telescope
optimized for high resolution spectroscopy in the 900-3200 Angstrom wavelength
region at a sensitivity sufficient to observe faint AGNs/QSOs at angular
separations of <1 degree would be ideal for such studies.


title: Cosmological Parameters from CMB measurements with the CBI

abstract:
  We derive cosmological parameters from the CBI measurements of the Cosmic
Microwave Background (CMB) angular power spectrum. Our results provide an
independent confirmation of the standard $\Omega_{\rm tot}=1$ $\Lambda$CDM
model within the adiabatic, inflationary paradigm. Above $\ell=2000$ the
observations show evidence of power in excess of that expected in the standard
models. We use hydrodynamical simulations to show how Sunyaev-Zeldovich Effect
(SZE) may account for the excess power for models with fluctuation amplitude
$\sigma_8\sim 1$ which is in the high end of the range allowed by the primary
CMB observations.


title:
Suppression of Entropy Perturbations in Multi--Field Inflation on the
  Brane

abstract:
  At energies higher than the brane tension, the dynamics of a scalar field
rolling down a potential are modified relative to the predictions of General
Relativity. The modifications imply, among other things, that steeper
potentials can be used to drive an epoch of slow--roll inflation. We
investigate the evolution of entropy and adiabatic modes during inflation
driven by two scalar fields confined on the brane. We show that the amount of
entropy perturbations produced during inflation is suppressed compared to the
predictions made by General Relativity. As a consequence, the initial
conditions do not matter in multiple field inflation in brane worlds if
inflation is driven at energies much higher than the brane tension.


title: Near and mid-infrared colours of star-forming galaxies in ELAIS fields

abstract:
  We present J and K-band near-infrared photometry of a sample of mid-infrared
sources detected by the Infrared Space Observatory (ISO) as part of the
European Large Area ISO-Survey (ELAIS) and study their classification and
star-forming properties. We have used the Preliminary ELAIS Catalogue for the
6.7 micron (LW2) and 15 micron (LW3) fluxes. All of the high-reliability LW2
sources and 80 per cent of the LW3 sources are identified in the near-IR survey
reaching K = 17.5 mag. The near- to mid-IR flux ratios can effectively be used
to separate stars from galaxies in mid-IR surveys. The stars detected in our
survey region are used to derive a new accurate calibration for the ELAIS
ISOCAM data in both the LW2 and LW3 filters. We show that near to mid-IR
colour-colour diagrams can be used to further classify galaxies, as well as
study star-formation. The ISOCAM ELAIS survey is found to mostly detect
strongly star-forming late-type galaxies, possibly starburst powered galaxies,
and it also picks out obscured AGN. The ELAIS galaxies yield an average mid-IR
flux ratio LW2/LW3 = 0.67 +/- 0.27. We discuss this [6.7/15] ratio as a star
formation tracer using ISO and IRAS data of a local comparison sample. We find
that the [K/15] ratio is also agood indicator of activity level in galaxies and
conclude that the drop in the [6.7/15] ratio seen in strongly star-forming
galaxies is a result of both an increase of 15 mic emission and an apparent
depletion of 6.7 mic emission. Near-IR data together with the mid-IR give the
possibility to estimate the relative amount of interstellar matter in the
galaxies.


title:
Causal perturbation theory in general FRW cosmologies II: superhorizon
  behaviour and initial conditions

abstract:
  We describe how causality and energy-momentum conservation constrain the
superhorizon behaviour of perturbation variables in a general FRW spacetime.
The effect of intrinsic curvature upon the horizon scale is discussed and
`white noise' results for the power spectra of generic `causally-seeded'
superhorizon perturbations are obtained. We present a detailed derivation of
the superhorizon energy density power spectrum for curved universes, and
provide elegant mathematical arguments for a curved universe analogue of the
Bessel function addition theorem. This yields physical insight into both the
familiar $k^4$ result for flat space and the $K \not= 0$ case: curvature
effects are seen to be evident from as early as half the curvature scale.
  We consider the implications of these results for the physically and
numerically significant issue of setting consistent initial conditions.


title:
Three-Dimensional Simulations of Parker, Magneto-Jeans, and Swing
  Instabilities in Shearing Galactic Gas Disks

abstract:
  We use 3D MHD simulations to investigate nonlinear development of the Parker,
magneto-Jeans (MJI), and swing mechanisms in galactic disks. The model disks
are local, isothermal, and begin from a vertically-stratified equilibrium. We
first construct axisymmetric equilibria and examine their stability. Finite
disk thickness reduces the critical Toomre Q parameter below unity; we find Q_c
\~ 0.75, 0.72, and 0.57 for \beta=\infty, 10, and 1 cases, respectively. We
then pursue fully 3D models. In non-self-gravitating cases, the peak density
enhancement from the `pure' Parker instability is less a factor of two. The
dominant growing modes have radial wavelengths comparable to the disk scale
height H, much shorter than the azimuthal wavelength (~10-20 H). Shearing
disks, being more favorable to midplane-symmetric modes, have somewhat
different late-time magnetic field profiles from nonshearing disks, but
otherwise saturated states are similar. Late-time velocity fluctuations at 10%
of the sound speed persist, but no characteristic structural signatures of
Parker modes remain in the new equilibria. In self-gravitating cases, the
development of density structure is qualitatively similar to our previous
results from thin-disk simulations. The Parker instability, although it may
help seed structure or tip the balance under marginal conditions, appears to
play a secondary role. In shearing disks with Q less than a threshold level ~
1, swing amplification can produce bound clouds of a few times the local Jeans
mass. The most powerful cloud-condensing mechanism appears to be the MJI. Our
simulations show that condensations of a local Jeans mass (~3\times 10^7 M_sun)
grow very rapidly, supporting the idea that MJI is at least partly responsible
for the formation of bound cloud complexes in spiral galaxies.


title:
The SN 1006 Remnant: Optical Proper Motions, Deep Imaging, Distance, and
  Brightness at Maximum

abstract:
  We report the first measurement of proper motions in the SN1006 remnant
(G327.6+14.6) based entirely on digital images. CCD images from three epochs
spanning a period of 11 years are used: 1987 from Las Campanas, and 1991 and
1998 from CTIO. Measuring the shift of delicate Balmer filaments along the
northwest rim of the remnant, we obtain proper motions of 280 +/- 8 mas/yr
along the entire length where the filaments are well defined, with little
systematic variation along the filaments. We also report very deep Halpha
imaging observations of the entire remnant that clearly show very faint
emission surrounding almost the entire shell, as well as some diffuse emission
regions in the (projected) interior. Combining the proper motion measurement
with a recent measurement of the shock velocity based on spectra of the same
filaments by Ghavamian et al. leads to a distance of 2.17 +/- 0.08 kpc to
SN1006. Several lines of argument suggest that SN1006 was a Type Ia event, so
the improved distance measurement can be combined with the peak luminosity for
SNeIa, as determined for events in galaxies with Cepheid-based distances, to
calculate the apparent brightness of the spectacular event that drew wide
attention in the eleventh century. The result, V_max = -7.5 =/- 0.4, lies
squarely in the middle of the wide range of estimates based on the historical
observations.


title:
The structure and stability of molecular cloud cores in external
  radiation fields

abstract:
  We have considered the thermal equilibrium in pre-protostellar cores in the
approximation where the dust temperature is independent of interactions with
the gas and where the gas is heated both by collisions with dust grains and
ionization by cosmic rays. We have then used these results to study the
stability of cores in the limit where thermal pressure dominates over magnetic
field and turbulence. We find that for cores with characteristics similar to
those observed, the gas and dust temperatures are coupled in the core interior.
As a consequence, the gas temperature like the dust temperature decreases
towards the center of these objects. The density structure computed taking into
account such deviations from isothermality are not greatly different from that
expected for an isothermal Bonnor-Ebert sphere. It is impossible in the
framework of these models to have a stable equilibrium core with mass above
about 5 solar masses and column density compatible with observed values. We
conclude from this that observed high mass cores are either supported by
magnetic field or turbulence or are already in a state of collapse. Lower mass
cores on the other hand have stable states and we conclude that the much
studied object B68 may be in a state of stable equilibrium if the internal gas
temperature is computed in self-consistent fashion. Finally we note that in
molecular clouds such as Ophiuchus and Orion with high radiation fields and
pressures, gas and dust temperatures are expected to be well coupled and hence
one expects temperatures to be relatively high as compared to low pressure
clouds like Taurus.


title:
Chemical Abundances in Twelve Red Giants of the Large Magellanic Cloud
  from High-Resolution Infrared Spectroscopy

abstract:
  High-resolution infrared spectra (R=50,000) have been obtained for twelve
red-giant members of the LMC with the Gemini South 8.3-meter telescope plus
Phoenix spectrometer. Quantitative chemical abundances of carbon-12, carbon-13,
nitrogen-14, and oxygen-16 were derived from molecular lines of CO, CN, and OH,
while sodium, scandium, titanium, and iron abundances were derived from neutral
atomic lines. The LMC giants have masses from about 1 to 4 solar masses and
span a metallicity range from [Fe/H]= -1.1 to -0.3. The program red giants all
show evidence of first dredge-up mixing, with low 12C/13C ratios, and low 12C
correlated with high 14N abundances. Comparisons of the oxygen-to-iron ratios
in the LMC and the Galaxy indicate that the trend of [O/Fe] versus [Fe/H] in
the LMC falls about 0.2 dex below the Galactic trend. Such an offset can be
modeled as due to an overall lower rate of supernovae per unit mass in the LMC
relative to the Galaxy, as well as a slightly lower ratio of supernovae of type
II to supernovae of type Ia.


title: Galactic winds in the intergalactic medium

abstract:
  We have performed hydrodynamical simulations to investigate the effects of
galactic winds on the high-redshift (z=3) universe. Strong winds suppress the
formation of low-mass galaxies significantly, and the metals carried by them
produce C IV absorption lines with properties in reasonable agreement with
observations. The winds have little effect on the statistics of the H I
absorption lines, because the hot gas bubbles blown by the winds fill only a
small fraction of the volume and because they tend to escape into the voids,
thereby leaving the filaments that produce these lines intact.


title:
Neutrino Clustering in Cold Dark Matter Halos : Implications for Ultra
  High Energy Cosmic Rays

abstract:
  We develop a method based on the collisionless Boltzmann equation to
calculate the gravitational clustering of relic neutrinos in realistic
cosmological models dominated by cold dark matter (CDM) and the cosmological
constant. This method can be used to estimate the phase-space distribution of
any light particles in CDM halos. We find that neutrinos with masses > 0.3 eV
cluster appreciably in dark matter halos above the galactic size. The resulting
neutrino overdensity above the cosmic mean neutrino density increases with both
the neutrino mass and the halo mass, ranging from about 10 for 0.3 eV neutrinos
in 10^13 M_sun halos, to about 1500 for 1.8 eV neutrinos in 10^15 M_sun halos.
We examine the implications of neutrino clustering for the Z-burst model of
ultra high energy cosmic rays (UHECR), which interprets the observed events at
E > 4 x 10^19 eV as decay products of Z-bosons from the resonant scattering
between relic and high energy neutrinos and anti-neutrinos. We estimate the
UHECR energy spectrum for various neutrino masses towards five of the most
massive clusters in the local universe (within 100 Mpc): Virgo, Perseus-Pisces,
Hydra, Centaurus, and Coma. The UHECR flux in the Z-burst model is expected to
be significantly higher towards these clusters if m_nu > 0.3 eV and nearly
isotropic otherwise.


title:
A Determination of H_0 with the CLASS Gravitational Lens B1608+656: III.
  A Significant Improvement in the Precision of the Time Delay Measurements

abstract:
  The gravitational lens CLASS B1608+656 is the only four-image lens system for
which all three independent time delays have been measured. This makes the
system an excellent candidate for a high-quality determination of H_0 at
cosmological distances. However, the original measurements of the time delays
had large (12-20%) uncertainties, due to the low level of variability of the
background source during the monitoring campaign. In this paper, we present
results from two additional VLA monitoring campaigns. In contrast to the ~5%
variations seen during the first season of monitoring, the source flux density
changed by 25-30% in each of the subsequent two seasons. We analyzed the
combined data set from all three seasons of monitoring to improve significantly
the precision of the time delay measurements; the delays are consistent with
those found in the original measurements, but the uncertainties have decreased
by factors of two to three. We combined the delays with revised isothermal mass
models to derive a measurement of H_0. Depending on the positions of the galaxy
centroids, which vary by up to 0.1 arcsec in HST images obtained with different
filters, we obtain H_0 = 61-65 km/s/Mpc, for (Omega_M,Omega_L) = (0.3,0.7). The
value of H_0 decreases by 6% if (Omega_M,Omega_L) = (1.0,0.0). The formal
uncertainties on H_0 due to the time delay measurements are +/- 1 (+/- 2)
km/s/Mpc for the 1-sigma (2-sigma) confidence limits. Thus, the systematic
uncertainties due to the lens model, which are on the order of +/- 15 km/s/Mpc,
now dominate the error budget for this system. In order to improve the
measurement of H_0 with this lens, new models that incorporate the constraints
provided by stellar dynamics and the optical/infrared Einstein ring seen in HST
images must be developed.


title: Gamma Rays From Rotation-Powered Pulsars

abstract:
  The seven known gamma-ray pulsars represent a very small fraction of the more
than 1000 presently known radio pulsars, yet they can give us valuable
information about pulsar particle acceleration and energetics. Although the
theory of acceleration and high-energy emission in pulsars has been studied for
over 25 years, the origin of the pulsed gamma rays is a question that remains
unanswered. Characteristics of the pulsars detected by the Compton Gamma-Ray
Observatory could not clearly distinguish between an emission site at the
magnetic poles (polar cap models) and emission from the outer magnetosphere
(outer gap models). There are also a number of theoretical issues in both type
of model which have yet to be resolved. The two types of models make
contrasting predictions for the numbers of radio-loud and radio-quiet gamma-ray
pulsars and of their spectral characteristics. GLAST will probably detect at
least 50 radio-selected pulsars and possibly many more radio-quiet pulsars.
With this large sample, it will be possible to fully test the model predictions
and finally resolve this longstanding question.


title: A Young Blue Tidal Stream in NGC 5128

abstract:
  Stellar streams in galaxy halos are the natural consequence of a history of
merging and accretion. We present evidence for a blue tidal stream of young
stars in the nearest giant elliptical galaxy, NGC 5128 (Centaurus A). Using
optical UBVR color maps, unsharp masking, and adaptive histogram equalization,
we detect a blue arc in the northwest portion of the galaxy that traces a
partial ellipse with an apocenter of 8 kpc. We also report the discovery of
numerous young star clusters that are associated with the arc. The brightest of
these clusters is spectroscopically confirmed, has an age of 350 Myr, and may
be a proto-globular cluster. It is likely that this arc, which is distinct from
the surrounding shell system and the young jet-related stars in the northeast,
is a tidally disrupted stellar stream orbiting the galaxy. Both the age derived
from the integrated optical colors of the stream and its dynamical disruption
timescale have values of 200-400 Myr. We propose that this stream of young
stars was formed when a dwarf irregular galaxy, or similar sized gas fragment,
underwent a tidally triggered burst of star formation as it fell into NGC 5128
and was disrupted 300 Myr ago. The stars and star clusters in this stream will
eventually disperse and become part of the main body of NGC 5128, suggesting
that the infall of gas-rich dwarfs plays a role in the building of stellar
halos and globular cluster systems.


title:
Effects of Resonance in Quasiperiodic Oscillators of Neutron Star
  Binaries

abstract:
  Using a large quantity of Rossi X-ray Timing Explorer data presented in the
literature I offer a detailed investigation into the accuracy of quasiperiodic
oscillations (QPO) frequency determination. The QPO phenomenon seen in X-ray
binaries is possibly a result of the resonance of the intrinsic (eigen)
oscillations and harmonic driving forces of the system. I show that the
resonances, in the presence of the damping of oscillations, occur at the
frequencies which are systematically and randomly shifted with respect to the
eigenfrequencies of the system. The shift value strongly depends on the damping
rate which is measured by the halfwidth of the QPO feature. Taking into account
this effect I analyze the QPO data for four Z-sources: Sco X-1, GX 340+0, GX
5-1, GX 17+2 and two atoll sources: 4U 1728-34, 4U 0614+09. The transition
layer model (TLM) predicts the existence of the invariant quantity: delta, an
inclination angle of the magnetospheric axis with respect to the normal to the
disk. I calculate delta and the error bars of delta using the resonance shift
and I find that the inferred delta-values are consistent with constants for
these four Z-sources, where horizontal branch oscillation and kilohertz
frequencies have been detected and correctly identified. It is shown that the
inferred delta are in the range between 5.5 and 6.5 degrees. I conclude that
the TLM seems to be compatible with data.