title:
Binary Aggregations in Hierarchical Galaxy Formation: The Evolution of
  the Galaxy Luminosity Function

abstract:
  We develop a semi-analytic model of hierarchical galaxy formation with an
improved treatment of the evolution of galaxies inside dark matter haloes. We
take into account not only dynamical friction processes building up the central
dominant galaxy, but also binary aggregations of satellite galaxies inside a
common halo described using the kinetic Smoluchowski equation. The description
of gas cooling, star formation and evolution, and Supernova feedback follows
the standard prescriptions widely used in semi-analytic modelling. We find that
binary aggregations are effective in depleting the number of small/intermediate
mass galaxies over the redshift range 1<z<3, thus flattening the slope of the
luminosity function at the faint end. At z~0 the flattening occurs for
-20<M_B<-18, but an upturn is obtained at the very faint end for M_B>-16. We
compare our predicted luminosity functions with those obtained from deep
multicolor surveys in the rest-frame B and UV bands for the redshift ranges
0<z<1 and 2.5<z<3.5, respectively. The comparison shows that the discrepancy of
the predictions of other semi-analytic models with the observations is
considerably reduced at z>1 and even more at z ~ 3 by the effect of binary
aggregations. The predictions from our dynamical model are discussed and
compared with the effects of complementary processes which may conspire in
affecting the shape of the luminosity function.


title: Complex X-ray spectral variability in Mkn 421 observed with XMM-Newton

abstract:
  The bright blazar Mkn 421 has been observed four times for uninterrupted
durations of ~ 9 - 13 hr during the performance verification and calibration
phases of the XMM-Newton mission. The source was strongly variable in all
epochs, with variability amplitudes that generally increased to higher energy
bands. Although the detailed relationship between soft (0.1 - 0.75 keV) and
hard (2 - 10 keV) band differed from one epoch to the next, in no case was
there any evidence for a measurable interband lag, with robust upper limits of
$| \tau | < 0.08 $ hr in the best-correlated light curves. This is in conflict
with previous claims of both hard and soft lags of ~1 hr in this and other
blazars. However, previous observations suffered a repeated 1.6 hr feature
induced by the low-Earth orbital period, a feature that is not present in the
uninterrupted XMM-Newton data. The new upper limit on $|\tau|$ leads to a lower
limit on the magnetic field strength and Doppler factor of $ B \delta^{1/3} \gs
4.7 $ G, mildly out of line with the predictions from a variety of homogeneous
synchrotron self-Compton emission models in the literature of $ B \delta^{1/3}
= 0.2 - 0.8 $ G. Time-dependent spectral fitting was performed on all epochs,
and no detectable spectral hysteresis was seen. We note however that the source
exhibited significantly different spectral evolutionary behavior from one epoch
to the next, with the strongest correlations in the first and last and an
actual divergance between soft and hard X-ray bands in the third. This
indicates that the range of spectral variability behavior in Mkn 421 is not
fully described in these short snippets; significantly longer uninterrupted
light curves are required, and can be obtained with XMM-Newton.


title: Photoevaporation of Clumps in Photodissociation Regions

abstract:
  We present the results of an investigation of the effects of Far Ultraviolet
(FUV) radiation from hot early type OB stars on clumps in star-forming
molecular clouds. Clumps in Photodissociation regions (PDRs) undergo external
heating which, if rapid, creates strong photoevaporative mass flows off the
clump surfaces, and drives shocks into the clumps, compressing them to high
densities. The clumps lose mass on relatively short timescales. The evolution
of an individual clump is found to be sensitive to its initial colunm density,
the temperature of the heated surface and the ratio of the ``turn-on time''
$t_{FUV}$ of the heating flux on a clump to its initial sound crossing-time
$t_{c}$.
  In this paper, we use spherical 1-D numerical hydrodynamic models as well as
approximate analytical models to study the evolution of turbulence-generated
and pressure-confined clumps in PDRs. Turbulent clumps evolve so that their
column densities are equal to a critical value determined by the local FUV
field, and typically have short photoevaporation timescales, $\sim 10^{4-5}$
years for a 1 M$_{\odot}$ clump in a typical star-forming region. Clumps that
are confined by an interclump medium may either get completely photoevaporated,
or may preserve a shielded core with a warm, dissociated, protective shell that
absorbs the incident FUV flux. We compare our results with observations of some
well-studied PDRs: the Orion Bar, M17SW, NGC 2023 and the Rosette Nebula. The
data are consistent with both interpretations of clump origin, with a slight
indication for favouring the turbulent model for clumps over pressure-confined
clumps.


title:
MgII Absorption Lines in z=2.974 Damped Lyman-alpha System toward
  Gravitationally Lensed QSO APM 08279+5255: Detection of Small-scale Structure
  in MgII Absorbing Clouds

abstract:
  1.02-1.16 micron spectra (R ~ 7,000) of the gravitationally lensed QSO APM
08279+5255 at z_em=3.911 were obtained during the commissioning run of IRCS,
the 1-5 micron near-infrared camera and spectrograph for the Subaru 8.2 m
Telescope. Strong MgII doublet at 2976,2800 angstrom and FeII (2600 angstrom),
FeII (2587 angstrom) absorption lines at z_abs=2.974 were clearly detected in
the rest-frame UV spectra, confirming the presence of a damped Lyman-alpha
system at the redshift as suggested by Petitjean et al. Also MgI (2853
angstrom) absorption line is probably detected. An analysis of the absorption
lines including velocity decomposition was performed. This is a first detailed
study of MgII absorption system at high redshift (z > 2.5) where the MgII
doublet shifts into the near-infrared in the observer's frame.
  The spectra of the lensed QSO pair A and B with 0.38 arcsec separation were
resolved in some exposure frames under excellent seeing condition. We extracted
the MgII doublet spectra of A and B separately. Although three velocity
components (v ~ -28, +5, +45 km/s) are known to exist in this MgII system
(Petitjean et al.), the v ~ +45 km/s absorption line was not detected toward
source B, showing that the +45 km/s MgII cloud lies only in the line of sight
to the source A. Our results suggests that the size of the MgII absorbing
clouds is as small as 200 pc, which corresponds to the separation of A and B at
the redshift of the absorber. This is the first direct detection of the
small-scale structure of MgII clouds at high-redshift, confirming the estimated
cloud sizes from photoionization model by Churchill and Charlton.


title: Detailed Structural Decomposition of Galaxy Images

abstract:
  We present a two-dimensional (2-D) fitting algorithm (GALFIT) designed to
extract structural components from galaxy images, with emphasis on closely
modeling light profiles of spatially well-resolved, nearby galaxies observed
with the Hubble Space Telescope. Our algorithm improves on previous techniques
in two areas, by being able to simultaneously fit a galaxy with an arbitrary
number of components, and with optimization in computation speed, suited for
working on large galaxy images. We use 2-D models such as the ``Nuker'' law,
the Sersic (de Vaucouleurs) profile, an exponential disk, and Gaussian or
Moffat functions. The azimuthal shapes are generalized ellipses that can fit
disky and boxy components. Many galaxies with complex isophotes, ellipticity
changes, and position-angle twists can be modeled accurately in 2-D. When
examined in detail, we find that even simple-looking galaxies generally require
at least three components to be modeled accurately, rather than the one or two
components more often employed. We illustrate this by way of 7 case studies,
which include regular and barred spiral galaxies, highly disky lenticular
galaxies, and elliptical galaxies displaying various levels of complexities. A
useful extension of this algorithm is to accurately extract nuclear point
sources in galaxies. We compare 2-D and 1-D extraction techniques on simulated
images of galaxies having nuclear slopes with different degrees of cuspiness,
and we then illustrate the application of the program to several examples of
nearby galaxies with weak nuclei.


title: Cosmic Rays from Microquasars: a Narrow Component to the CR Spectrum?

abstract:
  We propose that relativistic Galactic jets like those observed in GRS
1915+105 and GRO J1655-40 may produce small but measurable contributions to the
cosmic ray (CR) spectrum. If these jets contain cold protons and heavy ions (as
in SS433), it is plausible that this component will consist of a narrow
spectral feature, with a mean particle energy corresponding roughly to the bulk
kinetic particle energy in the beam, Gamma_jet m c^2, which, based on current
estimates of Gamma_jet, falls into the range of 3-10 GeV. The presence of
several sources with different Gamma_jet will lead to superposition of several
such peaks. Additionally, diffusive particle acceleration should produce a
powerlaw whose low energy cutoff at or above Gamma_jet^2 m c^2 would be visible
as another spectral feature. The large metallicities measured in several
microquasar companions suggest that this CR component could have an anomalous
composition compared to the bulk Galactic CRs. We provide estimates of the
effects of adiabatic losses, which pose the greatest challenge to models of
narrow band CR production in microquasar jets. While the total energy contained
in the microquasar CR component is highly uncertain, the CR spectrum in the
vicinity of microquasars would be severely affected. AMS02 will be able to
probe the low energy CR spectrum for such components and composition anomalies.
The spectrally peculiar gamma-ray emission produced by interaction of the ISM
with CRs surrounding microquasars might be detectable by GLAST. If the presence
of a microquasar CR proton component can be ruled out observationally, this
argument could be turned around in favor of electron-positron jets. We show
that existing OSSE/GRO and future INTEGRAL data on the Galactic 511 keV line
flux put interesting constraints on the particle content of microquasar jets.


title:
Assessing the Formation Scenarios for the Double Nucleus of M31 Using
  Two-Dimensional Image Decomposition

abstract:
  The double nucleus geometry of M31 is currently best explained by the
eccentric disk hypothesis of Tremaine, but whether the eccentric disk resulted
from the tidal disruption of an inbounding star cluster by a nuclear black
hole, or by an m=1 perturbation of a native nuclear disk, remains debatable. I
perform detailed 2-D decomposition of the M31 double nucleus in the Hubble
Space Telescope V-band to study the bulge structure and to address competing
formation scenarios of the eccentric disk. I deblend the double nucleus (P1 and
P2) and the bulge simultaneously using five Sersic and one Nuker components. P1
and P2 appear to be embedded inside an intermediate component (r_e=3.2") that
is nearly spherical (q=0.97+/-m0.02), while the main galaxy bulge is more
elliptical (q=0.81+/-0.01). The spherical bulge mass of 2.8x10^7 M_sol is
comparable to the supermassive black hole mass (3x10^7 M_sol). In the 2-D
decomposition, the bulge is consistent with being centered near the UV peak of
P2, but the exact position is difficult to pinpoint because of dust in the
bulge. P1 and P2 are comparable in mass. Within a radius r=1\arcsec of P2, the
relative mass fraction of the nuclear components is M_BH:M_bulge:P1: P2 =
4.3:1.2:1:0.7, assuming the luminous components have a common mass-to-light
ratio of 5.7. The eccentric disk as a whole (P1+P2) is massive, M ~ 2.1x10^7
M_sol, comparable to the black hole and the local bulge mass. As such, the
eccentric disk could not have been formed entirely out of stars that were
stripped from an inbounding star cluster. Hence, the more favored scenario is
that of a disk formed in situ by an m=1 perturbation, caused possibly by the
passing of a giant molecular cloud, or the passing/accretion of a small
globular cluster.


title:
The Correlations between Planetary Nebula Morphology and Central Star
  Evolution. Analysis of the Northern Galactic Sample

abstract:
  Northern Galactic Planetary nebulae (PNs) are studied to disclose possible
correlations between the morphology of the nebulae and the evolution of the
central stars (CSs). To this end, we have built the best database available to
date, accounting for homogeneity and completeness. We use updated statistical
distances, an updated morphological classification scheme, and we calculate
Zanstra temperatures for a large sample of PNs. With our study we confirm that
round, elliptical, and bipolar PNs have different spatial distributions within
the Galaxy, with average absolute distances to the Galactic plane 0.73, 0.38,
and 0.21 kpc respectively. We also find evidence that the distributions of the
central star's masses are different across these morphological groups, although
we do not find that CSs hosted by bipolar PNs are hotter, on average, than CSs
within round and elliptical PNs. Our results are in broad agreement with the
previous analyses, indicating that round, elliptical, and bipolar PNs evolve
from progenitors in different mass ranges, and may belong to different stellar
populations, as also indicated by the helium and nitrogen abundances of PNs of
different morphology.


title:
Joint Time--Frequency Analysis: a tool for exploratory analysis and
  filtering of non-stationary time series

abstract:
  It is the purpose of the paper to describe the virtues of time-frequency
methods for signal processing applications, having astronomical time series in
mind. Different methods are considered and their potential usefulness
respectively drawbacks are discussed and illustrated by examples. As areas
where one can hope for a successful application of joint time-frequency
analysis (JTFA), we describe specifically the problem of signal denoising as
well as the question of signal separation which allows to separate signals
(possibly overlapping in time or frequency, but) which are living on disjoint
parts of the time-frequency plane. Some recipes for practical use of the
algorithms are also provided.


title:
Comment on ``The Effect of Vacuum Polarization ... in Strongly
  Magnetized Plasmas'' by Ozel (astro-ph/0203449)

abstract:
  We have recently shown that in a highly magnetized neutron star atmospheric
plasma, vacuum polarization can induce resonant conversion of photon
polarization modes via a mechanism analogous to MSW neutrino oscillation. In a
recent paper Ozel has dismissed this mode conversion effect as ``mistakes''.
Here we explain why our arguments/calculations of this effect are correct.


title: Chandra Observations of the Disruption of the Cool Core in Abell 133

abstract:
  We present the analysis of a Chandra observation of the galaxy cluster Abell
133, which has a cooling flow core, a central radio source, and a diffuse,
filamentary radio source which has been classified as a radio relic.
  The X-ray image shows that the core has a complex structure. The most
prominent feature is a "tongue" of emission which extends from the central cD
galaxy to the northwest and partly overlaps the radio relic. One possibility is
that this tongue is produced by Kelvin-Helmholtz (KH) instabilities through the
interaction between the cold gas around the cD galaxy and hot intracluster
medium. We estimate the critical velocity and time scale for the KH instability
to be effective for the cold core around the cD galaxy. We find that the KH
instability can disrupt the cold core if the relative velocity is >~400 km
s^-1. We compare the results with those of clusters in which sharp, undisrupted
cold fronts have been observed; in these clusters, the low temperature gas in
their central regions has a more regular distribution. In contrast to Abell
133, these cluster cores have longer timescales for the disruption of the core
by the KH instability when they are normalized to the timescale of the cD
galaxy motion. Thus, the other cores are less vulnerable to KH instability.
Another possible origin of the tongue is that it is gas which has been uplifted
by a buoyant bubble of nonthermal plasma that we identify with the observed
radio relic. From the position of the bubble and the radio estimate of the age
of the relic source, we estimate avelocity of ~700 km s^-1 for the bubble. The
structure of the bubble and this velocity are consistent with numerical models
for such buoyant bubbles. (abridged)


title:
ST/STIS Spectroscopy of the White Dwarfs in the Short-Period Dwarf Novae
  LL And and EF Peg

abstract:
  We present new HST/STIS observations of the short-period dwarf novae LL And
and EF Peg during deep quiescence. We fit stellar models to the UV spectra and
use optical and IR observations to determine the physical parameters of the
whitedwarfs in the systems, the distances to the binaries, and the properties
of thesecondary stars. Both white dwarfs are relatively cool, having T_{eff}
near 15000K, and consistent with a mass of 0.6 M-sun. The white dwarf in LL And
appears to be of solar abundance or slightly lower while that in EF Peg is near
0.1-0.3 solar. LL And is found to be 760 pc away while EF Peg is closer at 380
pc. EF Peg appears to have an ~M5V secondary star, consistent with that
expected for its orbital period, while the secondary object in LL And remains a
mystery.


title: M31, M33 and the Milky Way: Similarities and Differences

abstract:
  The large galaxies in the Local Group, while all disk galaxies, have diverse
stellar populations. A better understanding of these differences, and a
physical understanding of the causes, requires more detailed study of the older
populations. This presents a significant challenge to GAIA but the scientific
returns are also significant.


title:
On the formation of neon-enriched donor stars in ultracompact X-ray
  binaries

abstract:
  We study the formation of neon-enriched donor stars in ultracompact X-ray
binaries (orbital periods P<80 min) and show that their progenitors have to be
low-mass (0.3 - 0.4 solar mass) ``hybrid'' white dwarfs (with CO cores and
thick helium mantles). Stable mass transfer is possible if in the initial
stages of mass exchange mass is lost from the system, taking away the specific
orbital angular momentum of the accretor (``isotropic re-emission''). The
excess of neon in the transferred matter is due to chemical fractionation of
the white dwarf which has to occur prior to the Roche lobe overflow by the
donor. The estimated lower limit of the orbital periods of the systems with
neon-enriched donors is close to 10 min. We show that the X-ray pulsar 4U
1626-67, which likely also has a neon-enriched companion, may have been formed
via accretion induced collapse of an oxygen-neon white dwarf accretor if the
donor was a hybrid white dwarf.


title:
Deviations from the Local Hubble Flow. I. The Tip of the Red Giant
  Branch as a Distance Indicator

abstract:
  The properties of the velocity field in the local volume (cz < 550 km/s) have
been difficult to constrain due to a lack of a consistent set of galaxy
distances. The sparse observations available to date suggest a remarkably quiet
flow, with little deviation from a pure Hubble law. However, velocity field
models based on the distribution of galaxies in the 1.2 Jy IRAS redshift
survey, predict a quadrupolar flow pattern locally with strong infall at the
poles of the local Supergalactic plane. We probe this velocity field and begin
to establish a consistent set of galactic distances. We have obtained images of
nearby galaxies in the I and V band from the W.M. Keck Observatory and in F814W
and F555W filters from the Hubble Space Telescope. Where these galaxies are
well resolved into stars we may use the Tip of the Red Giant Branch (TRGB) as a
distance indicator. Using a maximum likelihood analysis to quantitatively
measure the I magnitude of the TRGB we determine precise distances to seven
nearby galaxies: Leo I, Sextans B, NGC 1313, NGC 3109, UGC 03755, UGC 06456,
and UGC 07577.


title:
Variable stars in nearby galaxies. VI. Frequency-period distribution of
  Cepheids in IC 1613 and other galaxies of the Local Group

abstract:
  The frequency--period distribution and other properties of Cepheids in IC
1613 are discussed and compared with those of stars in our Galaxy (Milky Way),
LMC, SMC, M31 and M33. Taking into account the observational limitations and
related incompleteness, it is concluded that the frequency-period distribution
of Cepheids in IC 1613 is similar to that of SMC; we suspect that a much larger
number of stars exist in IC 1613 with a period of less than 2 d that have not
yet been detected. A discussion of the deficiency of fundamental mode Cepheids
with periods in the range 8 - 10 d in the Milky Way, M31 and M33 is reported.
The present data are not sufficient to verify if this is produced by a real
bimodal frequency--period distribution or whether depends on the lack of
pulsating stars in such a period range due to pulsational stability reasons.
Some arguments are presented in favor of a bimodal distribution that is a
function of the average metallicity. The Milky Way, M31 and M33 have the two
maxima located at the same periods, about 5 and 13 d, respectively. A comment
on very long period Cepheids is also given.


title:
Probing the Dark Side of Gravitational Clustering: Weak Lensing
  Statistics at Large Smoothing Angle

abstract:
  The weak lensing surveys have the potential to probe directly the clustering
statistics of dark matter in the universe. Recent studies have shown that it is
possible to predict analytically the whole probability distribution function
(pdf) and the bias associated with the collapsed objects in the highly
non-linear regime using the hierarchical ansatz. We extend such studies to the
quasi-linear regime where the hierarchical ansatz is replaced by the tree-level
perturbative calculations to an arbitrary order. It is shown how the generating
function techniques can be coupled with the perturbative calculations to
compute the complete pdf and the bias in the quasi-linear regime for the
weak-lensing convergence field. We study how these quantities depend on the
smoothing angle and the source red-shift in different realistic cosmological
scenarios. We show that it is possible to define a reduced convergence whose
statistics is similar to underlying 3D mass distribution for small smoothing
angle but it resembles projected mass distribution for large smoothing angles.
We have also compared our peturbative results with log-normal model for pdf and
bias and found a good agreement between the two analytical results.


title: The OH Megamaser Luminosity Function

abstract:
  We present the 1667 MHz OH megamaser luminosity function derived from a
single flux-limited survey. The Arecibo Observatory OH megamaser (OHM) survey
has doubled the number of known OH megamasers, and we list the complete catalog
of OHMs detected by the survey here, including three redetections of known
OHMs. OHMs are produced in major galaxy mergers which are (ultra)luminous in
the far-infrared. The OH luminosity function follows a power law in integrated
line luminosity, $\Phi \propto L_{OH}^{-0.64}$ per Mpc^3 per dex, and is
well-sampled for 10^{2.2} L(sun) < L_{OH} < 10^{3.8} L(sun). The OH luminosity
function is incorporated into predictions of the detectability and areal
density of OHMs in high redshift OH surveys for a variety of current and
planned telescopes and merging evolution scenarios parameterized by (1+z)^m in
the merger rate ranging from m=0 (no evolution) to m=8 (extreme evolution). Up
to dozens of OHMs may be detected per square degree per 50 MHz by a survey
reaching an rms noise of 100 microJy per 0.1 MHz channel. An adequately
sensitive ``OH Deep Field'' would significantly constrain the evolution
exponent m even if no detections are made. In addition to serving as luminous
tracers of massive mergers, OHMs may also trace highly obscured nuclear
starburst activity and the formation of binary supermassive black holes.


title: Variable Thermal Emission from Aql X-1 in Quiescence

abstract:
  We obtained four Chandra/ACIS-S observations beginning two weeks after the
end of the November 2000 outburst of the neutron star (NS) transient Aql X-1.
Over the five month span in quiescence, the X-ray spectra are consistent with
thermal emission from a NS with a pure hydrogen photosphere and
R_{\infty}=15.9+{0.8}-{2.9} (d/5 kpc) km at the optically implied X-ray column
density. We also detect a hard power-law tail during two of the four
observations. The intensity of Aql X-1 first decreased by 50+/-4% over three
months, then increased by 35+/-5% in one month, and then remained constant (<6%
change) over the last month. These variations in the first two observations
cannot be explained by a change in the power-law spectral component, nor in the
X-ray column density. Presuming that R_{\infty} is not variable and a pure
hydrogen atmosphere, the long-term changes can only be explained by variations
in the NS effective temperature, from kT_{eff, \infty}=130+3-5 eV, down to
113+3-4 eV, finally increasing to 118+9-4 eV for the final two observations.
During one of these observations, we observe two phenomena which were
previously suggested as indicators of quiescent accretion onto the NS:
short-timescale (<1e4 sec) variability (at 32+8-6% rms), and a possible
absorption feature near 0.5 keV. The possible absorption feature can
potentially be explained as due to a time-variable response in the ACIS
detector. Even so, such a feature has not been detected previously from a NS,
and if confirmed and identified, can be exploited for simultaneous measurements
of the photospheric redshift and NS radius.


title:
Global m=1 modes and migration of protoplanetary cores in eccentric
  protoplanetary discs

abstract:
  We calculate global $m=1$ modes with low pattern speed corresponding to
introducing a finite eccentricity into a protoplanetary disc. We consider disc
models which are either isolated or contain one or two protoplanets orbiting in
an inner cavity. Global modes that are strongly coupled to inner protoplanets
are found to have disc orbits which tend to have apsidal lines antialigned with
respect to those of the inner protoplanets. Other modes corresponding to free
disc modes may be global over a large range of length scales and accordingly be
long lived. We consider the motion of a protoplanet in the earth mass range
embedded in an eccentric disc and determine the equilibrium orbits which
maintain fixed apsidal alignment with respect to the disc gas orbits.
Equilibrium eccentricities are found to be comparable or possibly exceed the
disc eccentricity. We then approximately calculate the tidal interaction with
the disc in order to estimate the orbital migration rate. Results are found to
deviate from the case of axisymmetric disc with near circular protoplanet orbit
once eccentricities of protoplanet and disc orbits become comparable to the
disc aspect ratio in magnitude. Aligned protoplanet orbits with very similar
eccentricity to that of the gas disc are found to undergo litle eccentricity
change while undergoing inward migration in general. However, for significantly
larger orbital eccentricities, migration may be significantly reduced or even
reverse from inwards to outwards. Thus the existence of global non circular
motions in discs with radial excursions comparable to the semi-thickness may
have important consequences for the migration and survival of protoplanetary
cores in the earth mass range.


title: Lyman Break Galaxies and the Reionization of the Intergalactic Medium

abstract:
  Near-infrared observations of Lyman-break galaxies at redshifts z~3 are
beginning to provide constraints on ages, star-formation histories, dust
content, metallicities, and stellar masses. At present, uncertainties of more
than an order of magnitude are typical for many of these parameters. It is
nonetheless interesting to ask what the stellar-population models imply for the
existence and luminosities of Lyman-break galaxies at higher redshift. To this
end we examine the inferred star-formation rates in two well-studied samples of
galaxies as a function of redshift out to z = 10 for various best-fit and
limiting cases.
  Taken at face value, the generally young ages (typically 10^8 +- 0.5 yr) of
the z = 3 Lyman break galaxies imply that their stars were not present much
beyond z=4. By z = 6 the cosmic star-formation rate from the progenitors of
these galaxies is less than 10% of star-formation rate at z=3 +- 0.5, even for
maximally-old models, provided the derivative of the star-formation rate SFR(t)
is monotonic. The escaping Lyman-continuum radiation from such galaxies would
be insufficient to reionize the IGM. Thus other sources of ionizing photons
(e.g. very massive population III stars) may be needed, and the more normal
Lyman-break galaxies may be a phenomenon confined to redshifts z <~ 4. This
conclusion changes if SFR(t) was episodic, and we examine the parameters of
such bursty star-formation that might be consistent with both the z=2-4
luminosity functions and the z~3 spectral energy distributions.


title: A Revised Parallax and its Implications for RX J185635-3754

abstract:
  New astrometric analysis of four WFPC2 images of the isolated neutron star RX
J185635-3754 show that its distance is 117 +/- 12 pc, nearly double the
originally published distance. At the revised distance, the star's age is 5 x
10^5 years, its space velocity is about 185 km/s, and its radiation radius
inferred from thermal emission is approximately 15 km, in the range of many
equations of state both with and without exotic matter. These measurements
remove observational support for an extremely soft equation of state. The
star's birthplace is still likely to be in the Upper Sco association, but a
connection with zeta Oph is now unlikely.


title:
Constraining the past X-ray luminosity of AGN in clusters of galaxies:
  the role of resonant scattering

abstract:
  Only a small fraction of galactic nuclei in the nearby universe are luminous;
most of them are currently dim. We investigate the feasibility of constraining
the X-ray luminosity in the recent past (up to ~10^6 years ago) of the nucleus
of a cluster dominant galaxy by measuring the contribution of scattered
radiation from the central source to the surface brightness of the intracluster
gas dominated by thermal emission. We show that resonance X-ray lines present
an advantage over the adjacent continuum, because the relative contribution of
the scattered component is typically larger in the line case by a significant
factor of 3-10. As an example, we estimate the level of constraint that could
be derived from future fine spectroscopic observations on the past X-ray
luminosity of the nearby M87 and Cygnus A active galaxies. For instance,
scattered line radiation should be detectable from the Virgo cluster if the
X-ray luminosity of M87 was a few times 10^44 erg s^-1, or 10^-3 of its
Eddington luminosity, until a few times 10^5 years ago. For comparison, upper
limits inferred from the available XMM-Newton and Chandra X-ray continuum data
are typically 1-2 orders of magnitude weaker. The same method can be applied to
distant powerful quasars (at redshifts z~1 if they have cluster-like gaseous
coronae, as suggested by Rosat and Chandra observations of active galaxies at
z<1. Their surface brightness profiles in the X-ray continuum above ~10
keV>>kT/(1+z) (where T is the gas temperature) should be dominated by
redshifted scattered radiation from the quasar. Therefore, measurements with
forthcoming mirror-optics hard X-ray telescopes could give information on the
lifetime of quasars and parameters of the hot gas around them.


title: Lyman Break Galaxies in the NGST Era

abstract:
  With SIRTF and NGST in the offing, it is interesting to examine what the
stellar populations of z~3 galaxies models imply for the existence and nature
of Lyman-break galaxies at higher redshift. To this end, we ``turn back the
clock'' on the stellar population models that have been fit to optical and
infrared data of Lyman-break galaxies at z~3. The generally young ages
(typically 10^8 +- 0.5 yr) of these galaxies imply that their stars were not
present much beyond z=4. For smooth star-formation histories SFR(t) and
Salpeter IMFs, the ionizing radiation from early star-formation in these
galaxies would be insufficient to reionize the intergalactic medium at z~6, and
the luminosity density at z~4 would be significantly lower than observed. We
examine possible ways to increase the global star-formation rate at higher
redshift without violating the stellar-population constraints at z~3.


title: Is Cosmic Acceleration Really Recent?

abstract:
  In the standard cosmological paradigm cosmic acceleration is to only be a
very recent (viz. $z \leq 1$) phenomenon, with the universe being required to
be decelerating at all higher redshifts. We suggest that this particular
expectation of the standard model is to be viewed as a quite definitive test
not only of the model itself but also of the fine-tuning assumption on which
the expectation is based, with the expectation itself actually being readily
amenable to testing once the Hubble plot can be extended out to only $z=2$ or
so. Moreover, such a modest extension of the Hubble plot will also provide for
definitive testing of the non fine-tuned alternate conformal gravity theory, a
theory in which the universe is to accelerate both above and below $z=1$.


title: The Detectability of Orphan Afterglows

abstract:
  The realization that GRBs release a constant amount of energy implies that
the post jet-break afterglow evolution would be largely universal. For a given
redshift all afterglows should be detected up to a fixed observer angle. We
estimate the observed magnitude and the implied detectability of orphan
afterglows. We show that for reasonable limiting magnitudes ($m_{lim}=25$)
orphan afterglows would typically be detected from small ($\sim 10^\circ$)
angles away from the GRB jet axis. A detected orphan afterglow would generally
correspond to a "near-miss" of the GRB whose jet was pointing just slightly
away from us. With our most optimistic parameters we expect that 15 orphan
afterglows will be recorded in the SDSS and 35 transients will be recorded in a
dedicated 2m class telescope operating full time for a year in an orphan
afterglow search. The rate is smaller by a factor of 15 for our "canonical"
parameters. We show that for a given facility an optimal survey should be
shallower, covering larger area rather than deeper. The limiting magnitude
should not be, however, lower than $\sim$ 23rd as in this case more transients
from on-axis GRBs will be discovered than orphan afterglows. About 15% of the
transients could be discovered with a second exposure of the same area provided
that it follows after 3, 4 and 8 days for $m_{lim}=23$, 25 and 27.


title:
The Heavy Element Enrichment of Lyman alpha Clouds in the Virgo
  Supercluster

abstract:
  Using high S/N STIS echelle spectra (FWHM=7 km/s) of 3C 273, we constrain the
metallicities of two Lya clouds in the vicinity of the Virgo cluster. We detect
C II, Si II, and Si III absorption lines in the Lya absorber at z = 0.00530.
Previous observations with FUSE have revealed Ly beta - Ly theta lines at this
redshift, thereby accurately constraining N(H I). We model the ionization of
the gas and derive [C/H] = -1.2^{+0.3}_{-0.2}, [Si/C] = 0.2+/-0.1, and log
n_{H} = -2.8+/-0.3. The model implies a small absorber thickness, ~70 pc, and
thermal pressure p/k ~ 40 cm^{-3} K. It is most likely that the absorber is
pressure confined by an external medium because gravitational confinement would
require a very high ratio of dark matter to baryonic matter. Based on Milky Way
sight lines in which carbon and silicon abundances have been reliably measured
in the same interstellar cloud (including new measurements presented herein),
we argue that the overabundance of Si relative to C is not due to dust
depletion. Instead, this probably indicates that the gas has been predominately
enriched by Type II supernovae. Such enrichment is most plausibly provided by
an unbound galactic wind, given the absence of galaxies within a projected
distance of 100 kpc and the presence of galaxies capable of driving a wind at
larger distances. We also constrain the metallicity and physical conditions of
the Virgo absorber at z = 0.00337 based on detections of O VI and H I and an
upper limit on C IV. If this absorber is collisionally ionized, the O VI/C IV
limit requires T > 10^{5.3} K. For either collisional ionization or
photoionization, we find that [O/H] > -2.0 at z = 0.00337.


title: The Physics of the Knee in the Cosmic Ray Spectrum

abstract:
  Recent results from the KASCADE extensive air shower experiment are
presented. After briefly reviewing the status of the experiment we report on
tests of hadronic interaction models and emphasize the progress being made in
understanding the properties and origin of the knee at $E_{knee} ~ 4.10^{15}
eV. Analysing the muon- and hadron trigger rates in the KASCADE calorimeter as
well as the global properties of high energy hadrons in the shower core leads
us to conclude that QGSJET still provides the best overall description of EAS
data, being superior to DPMJET II-5 and neXus 2, for example. Performing high
statistics CORSIKA simulations and applying sophisticated unfolding techniques
to the electron and muon shower size distributions, we are able to successfully
deconvolute the all-particle energy spectrum into energy spectra of 4
individual primary mass groups (p, He, C, Fe). Each of these preliminary energy
distributions exhibits a knee like structure with a change of their knee
positions suggesting a constant rigidity of R ~ 2-3 PV.


title: Lensing Properties of Cored Galaxy Models

abstract:
  A method is developed to evaluate the magnifications of the images of
galaxies with lensing potentials stratified on similar concentric ellipses. A
simple contour integral is provided which enables the sums of the
magnifications of even parity or odd parity or the central image to be easily
calculated. The sums for pairs of images vary considerably with source
position, while the signed sums can be remarkably uniform inside the tangential
caustic in the absence of naked cusps. For a family of models in which the
potential is a power-law of the elliptic radius, the number of visible images
is found as a function of flattening, external shear and core radius. The
magnification of the central image depends on the core radius and the slope of
the potential. For typical source and lens redshifts, the missing central image
leads to strong constraints; the mass distribution in the lensing galaxy must
be nearly cusped, and the cusp must be isothermal or stronger. This is in
accord with the cuspy cores seen in high resolution photometry of nearby,
massive, early-type galaxies, which typically have the surface density falling
like distance^{-1.3} outside a break radius of a few hundred parsecs. Cuspy
cores by themselves can provide an explanation of the missing central images.
Dark matter at large radii may alter the slope of the projected density;
provided the slope remains isothermal or steeper and the break radius remains
small, then the central image remains unobservable. The sensitivity of the
radio maps must be increased fifty-fold to find the central images in
abundance.


title: Cosmology with GTC. A combined mm-optical galaxy cluster survey

abstract:
  The CMB Planck satellite (ESA) will provide a catalogue of nearly 30000
galaxy clusters (Sunyaev-Zel'dovich effect) between redshift 0 and approx. 2-3
(depending on the cosmological model). This hughe catalogue of clusters will
allow detailed studies of the evolution of the cluster population with redshift
which will constrain the cosmological model. The identification of the high
redshift clusters should be done with a large telescope (like GTC) since Planck
data alone will not provide any clue about the redshift of the clusters. In
this work we show that an optical follow up of only 300 clusters (randomly
selected from the Planck catalogue) is needed in order to distinguish models
with or without a cosmological constant.


title: Numerical Simulations of Kinematic Dynamo Action

abstract:
  Numerical simulations of kinematic dynamo action in steady and 3-d ABC flows
are presented with special focus on growth rates and multiple periods of the
prescribed velocity field. It is found that the difference in growth rate is
due to differences in the recycling of the weakest part of the magnetic field.
Differences in the topology in cases with and without stagnation points in the
imposed velocity field are also investigated, and it is found that the
cigar-like structures that develop in the classical A=B=C dynamos, are replaced
by ribbon structures in cases where the flow is without stagnation points.


title: Chemical composition of Galactic OB stars I. CNO abundances in O9 stars

abstract:
  We present NLTE abundances of CNO for a sample of four O9 stars in the
Galaxy, together with new determinations of their stellar parameters, $T_{\rm
eff}$, $\log g$, $\epsilon$(He) and microturbulence. These new analyses take
into account the effect of {\it line--blocking} in the spectral synthesis with
our classical NLTE, plane--parallel and hydrostatic model atmospheres. The
sample includes three O9 He normal stars: two dwarfs, HD 214680 and HD 34078,
and one supergiant, HD 209975, and one fast rotating giant with a preliminary
high He overabundance, HD 191423 with $\epsilon$(He)=0.20. We find first that
the consideration of microturbulence in the spectral synthesis for the fast
rotator leads to a considerably lower He abundance, $\epsilon$(He)=0.12. The
CNO abundances of the three He normal stars are in good agreement with the
values in the literature for Galactic B dwarfs with no evidence of mixing, and
show that they all have the same chemical composition. We also discuss however
the possible CNO contamination of the supergiant HD 209975. For the fast
rotator we find that the abundances show the trend of the CNO contamination: a
N overabundance together with C and O depletion. The N/C and N/O ratios of our
stars as a function of their projected rotational velocities are consistent
with the predictions of the recent evolutionary models of Meynet & Maeder
[Mey&Mae00].


title: Vacuum Gap Model for PSR B0943+10

abstract:
  PSR B0943+10 is known to show remarkably stable drifting subpulses, which can
be interpreted in terms of a circumferential motion of 20 sparks, each
completing one circulation around the periphery of the polar cap in 37 pulsar
periods. We use this observational constraint and argue that the vacuum gap
model can adequately describe the observed drift patterns. Further we
demonstrate that {\em only} the presence of strong non-dipolar surface magnetic
field can favor such vacuum gap formation. Subsequently, for the first time we
are able to constrain the parameters of the surface magnetic field, and model
the expected magnetic structure on the polar cap of PSR B0943+10 considering
the inverse Compton scattering photon dominated vacuum gap.


title:
Point field models for the galaxy point pattern. Modelling the
  singularity of the two-point correlation function

abstract:
  There is empirical evidence that the two-point correlation function of the
galaxy distribution follows, for small scales, reasonably well a power-law
expression $\xi(r)\propto r^{-\gamma}$ with $\gamma$ between 1.5 and 1.9.
Nevertheless, most of the point field models suggested in the literature do not
have this property.
  This paper presents a new class of models, which is produced by modifying
point fields commonly used in cosmology to mimic the galaxy distribution, but
where $\gamma=2$ is too large. The points are independently and randomly
shifted, leading to the desired reduction of the value of $\gamma$.


title: High-Resolution X-ray Imaging of the Colliding Wind Shock in WR147

abstract:
  We analyze new high-resolution Chandra X-ray images of the Wolf-Rayet binary
system WR147. This system contains a WN8 star with an early-type companion
located 0.6'' to its north, and is the only known early-type binary with a
separation on the sky large enough for the wind-wind collision between the
stars to currently be resolved at X-ray energies. The 5 ksec Chandra HRC-I
image provides the first direct evidence for spatially extended X-ray emission
in an early-type binary system. The X-ray emission peaks close to the position
of the radio bow shock and north of the WN8 star. A deeper X-ray image is
needed to accurately determine the degree of spatial extension, to exactly
align the X-ray and optical/radio frames, and to determine whether part of the
detected X-ray emission arises in the individual stellar winds. Simulated X-ray
images of the wind-wind collision have a FWHM consistent with the data, and
maximum likelihood fits suggest that a deeper observation may also constrain
the inclination and wind momentum ratio of this system. However, as the WR wind
dominates the colliding wind X-ray emission it appears unlikely that the
mass-loss rate and the terminal velocity of the companion wind can be
separately determined from X-ray observations. We also note an inconsistency
between numerical and analytical estimates of the X-ray luminosity ratio of the
stronger and weaker wind components, and conclude that the analytical results
are in error.


abstract:
  The Great Observatories Origins Deep Survey (GOODS) is designed to gather the
best and deepest multiwavelength data for studying the formation and evolution
of galaxies and active galactic nuclei, the distribution of dark and luminous
matter at high redshift, the cosmological parameters from distant supernovae,
and the extragalactic background light. The program uses the most powerful
space- and ground-based telescopes to cover two fields, each 10'x16', centered
on the Hubble Deep Field North and the Chandra Deep Field South, already the
sites of extensive observations from X-ray through radio wavelengths. GOODS
incorporates 3.6-24 micron observations from a SIRTF Legacy Program, four-band
ACS imaging from an HST Treasury Program, and extensive new ground-based
imaging and spectroscopy. GOODS data products will be made available on a rapid
time-scale, enabling community research on a wide variety of topics. Here we
describe the project, emphasizing its application for studying the mass
assembly history of galaxies.


title: ESO for GOODS' sake

abstract:
  Currently public ESO data sets pertinent to the CDFS/GOODS field are briefly
illustrated along with an indication on how to get access to them. Future ESO
plans for complementing the GOODS database with optical/IR imaging and optical
spectroscopy are also described.


title: Searching for Planets in the Hyades. I. The Keck Radial Velocity Survey

abstract:
  We describe a high-precision radial velocity search for jovian-mass
companions to main sequence stars in the Hyades star cluster. The Hyades
provides an extremely well controlled sample of stars of the same age, the same
metallicity, and a common birth and early dynamical environment. This sample
allows us to explore the dependence of the process of planet formation on only
a single independent variable: the stellar mass. In this paper we describe the
survey and summarize results for the first five years.


title:
Searching for Planets in the Hyades II: Some Implications of Stellar
  Magnetic Activity

abstract:
  The Hyades constitute a homogeneous sample of stars ideal for investigating
the dependence of planet formation on the mass of the central star. Due to
their youth, Hyades members are much more chromospherically active than stars
traditionally surveyed for planets using high precision radial velocity (RV)
techniques. Therefore, we have conducted a detailed investigation of whether
magnetic activity of our Hyades target stars will interfere with our ability to
make precise RV searches for substellar companions. We measure chromospheric
activity (which we take as a proxy for magnetic activity) by computing the
equivalent of the R'HK activity index from the Ca II K line. <R'HK> is not
constant in the Hyades: we confirm that it decreases with increasing
temperature in the F stars, and also find it decreases for stars cooler than
mid-K. We examine correlations between simultaneously measured R'HK and RV
using both a classical statistical test and a Bayesian odds ratio test. We find
that there is a significant correlation between R'HK and the RV in only 5 of
the 82 stars in this sample. Thus, simple Rprime HK-RV correlations will
generally not be effective in correcting the measured RV values for the effects
of magnetic activity in the Hyades. We argue that this implies long timescale
activity variations (of order a few years; i.e., magnetic cycles or growth and
decay of plage regions) will not significantly hinder our search for planets in
the Hyades if the stars are closely monitored for chromospheric activity. The
trends in the RV scatter (sigma'_v) with <R'HK>, vsini, and P_rot for our stars
is generally consistent with those found in field stars in the Lick planet
search data, with the notable exception of a shallower dependence of sigma'_v
on <R'HK> for F stars.


title:
Improved Astrometry and Photometry for the Luyten Catalog. I. Bright
  Stars

abstract:
  We outline the construction of an updated version of the New Luyten
Two-Tenths (NLTT) catalog of high proper motion stars, which will contain
improved astrometry and photometry for the vast majority of the ~59,000 stars
in NLTT. The bright end is constructed by matching NLTT stars to Hipparcos,
Tycho-2, and Starnet; the faint end by matching to USNO-A and 2MASS. In this
first paper, we detail the bright-end matching procedure. We show that for the
majority of stars in his catalog, Luyten measured positions accurate to 1" even
though he recorded his results much more coarsely. However, there is a long
tail of position errors, with one error as large as 11 deg. Proper-motion
errors for the stars with small position errors are 24 mas/yr (1 sigma) but
deteriorate to 34 mas/yr for stars with inferior positions. NLTT is virtually
100% complete for V<11.5 and |b|>15 deg, but completeness in this magnitude
range falls to about 75% at the Galactic plane. Incompleteness near the plane
is not uniform, but is rather concentrated in the interval -80<l<20, where the
Milky Way is brightest.


title: Dark Matter as Dense Color Superconductor

abstract:
  We discuss a novel cold dark matter candidate which is formed from the
ordinary quarks during the QCD phase transition when the axion domain wall
undergoes an unchecked collapse due to the tension in the wall. If a large
number of quarks is trapped inside the bulk of a closed axion domain wall, the
collapse stops due to the internal Fermi pressure. In this case the system in
the bulk, may reach the critical density when it undergoes a phase transition
to a color superconducting phase with the ground state being the quark
condensate, similar to BCS theory. If this happens, the new state of matter
representing the diquark condensate with a large baryon number B > 10^{20}
becomes a stable soliton-like configuration. Consequently, it may serve as a
novel cold dark matter candidate.


title:
Discovery of radio pulsations from the X-ray pulsar J0205+6449 in
  supernova remnant 3C58 with the Green Bank Telescope

abstract:
  We report the discovery with the 100 m Green Bank Telescope of 65 ms radio
pulsations from the X-ray pulsar J0205+6449 at the center of supernova remnant
3C58, making this possibly the youngest radio pulsar known. From our
observations at frequencies of 820 and 1375 MHz, the free electron column
density to PSR J0205+6449 is found to be 140.7 +- 0.3 pc/cc. The barycentric
pulsar period P and period derivative determined from a phase-coherent timing
solution are consistent with the values previously measured from X-ray
observations. The averaged radio profile of PSR J0205+6449 consists of one
sharp pulse of width ~ 3 ms ~ 0.05 P. The pulsar is an exceedingly weak radio
source, with pulse-averaged flux density in the 1400 MHz band of 0.045 mJy and
a spectral index of ~ -2.1. Its radio luminosity of ~ 0.5 mJy kpc^2 at 1400 MHz
is lower than that of ~ 99% of known pulsars and is the lowest among known
young pulsars.


title: 1-1.4 Micron Spectral Atlas of Stars

abstract:
  We present a catalog of J-band (1.08 um to 1.35 um) stellar spectra at low
resolution (R ~ 400). The targets consist of 105 stars ranging in spectral type
from O9.5 to M7 and luminosity classes I through V. The relatively featureless
spectra of hot stars, earlier than A4, can be used to remove the atmospheric
features which dominate ground-based J-band spectroscopy. We measure equivalent
widths for three absorption lines and nine blended features which we identify
in the spectra. Using detailed comparison with higher resolution spectra, we
demonstrate that low resolution data can be used for stellar classification,
since several features depend on the effective temperature and gravity. For
example The CN index (1.096 - 1.104 um) decreases with temperature, but the
strength of a blended feature at 1.28 um (consisting of primarily P beta)
increases. The slope of a star's spectrum can also be used to estimate its
effective temperature. The luminosity class of a star correlates with the ratio
of the Mg I (1.1831 um) line to a blend of several species at 1.16 um. Using
these indicators, a star can be classified to within several subclasses.
Fifteen stars with particularly high and low metal abundances are included in
the catalog and some spectral dependence on metal abundance is also found.


title: An Analytical Approach to the Spin-Distribution of Dark Halos

abstract:
  We derive the distribution of the dimensionless specific angular momentum of
dark matter halos, $P(j)$, in the framework of the standard tidal torque
theory, and explain the characteristic shape of $P(j)$ commonly observed in
N-body simulations. A scalar quantity (shear scalar), $r$, is introduced for
measuring the effective strength of the tidal torque force acting upon the halo
from the surrounding matter. It is found that the ubiquitous and broad shape of
$P(j)$ can mostly be attributed to the unique property of the shear scalar $r$,
and also that $P(j)$ is insensitve to the underlying collapse dynamics. Our
result demonstrates that although the shape of $P(j)$ is ubiquitous and close
to log-normal, the distribution is not exactly log-normal but decays
exponentially at the high angular momentum end, and drops slowly as a power-law
with an index 2 at the low angular momentum end.


title: Star Formation Rate from Dust Infrared Emission

abstract:
  We examine what types of galaxies the conversion formula from dust infrared
(IR) luminosity into the star formation rate (SFR) derived by
  Kennicutt (1998) is applicable to. The ratio of the observed IR luminosity,
$L_{\rm IR}$, to the intrinsic bolometric luminosity of the newly ($\la$ 10
Myr) formed stars,
  $L_{\rm SF}$, of a galaxy can be determined by a mean dust opacity in the
interstellar medium and the activity of the current star formation. We find
that these parameters area being $0.5 \le L_{\rm IR}/L_{\rm SF}
  \le 2.0$ is very large, and many nearby normal and active star-forming
galaxies really fall in this area. It results from offsetting two effects of a
small dust opacity and a large cirrus contribution of normal galaxies relative
to starburst galaxies on the conversion of the stellar emission into the dust
IR emission. In conclusion, the SFR determined from the IR luminosity under the
assumption of $L_{\rm IR}=L_{\rm SF}$ like Kennicutt (1998) is reliable within
a factor of 2 for all galaxies except for dust rich but quiescent galaxies and
extremely dust poor galaxies.


title:
Relativistic Outflow of Electron-Positron Pair Plasma from a Wien
  Equilibrium State

abstract:
  We investigate a novel mechanism of bulk acceleration for relativistic jets
of pure electron-positron pair plasma.We assumed that relativistically hot
plasma is optically thick for Compton scattering and then pair plasma coupled
dynamically to photons may establish quasi-Wien equilibria. We name such an
electron-positron pair plasma the "Wien-fireball". Assuming there is a
Wien-fireball, it is easy to form highly relativistic jets not only because
coupled photons do not cause radiation drag effect, but also because coupled
photons prevent catastrophic annihilation of pair plasma. It is found that the
Wien-fireball provides a very effective mechanism to form high power jets. And
the radiation of the Wien-fireball in blazars should be observed as MeV peaked
emission at infinity with an order of kinetic power of jets.


title:
Study of the X-Ray Background Spectrum and its Large-Scale Fluctuation
  with ASCA

abstract:
  We studied the energy spectrum and the large-scale fluctuation of the X-ray
background with the ASCA GIS based on the ASCA MSS and LSS observations. A
total of 91 fields with Galactic latitude |b|>10 deg were selected with a sky
coverage of 50 deg^2 and 4.2 Ms of exposure. For each field, sources brighter
than \sim 2\times 10^{-13}\ergs (2-10 keV) were eliminated. Spectral fits with
a single power-law model for the individual 0.7-10 keV spectra showed a
significant excess below \sim 2 keV, which could be expressed by an additional
thermal model with kT\simeq 0.4 keV or a steep power-law model with photon
index GS\simeq 6. The 0.5-2 keV intensities of the soft thermal component
varied significantly by 1\sigma=52^{+4}_{-5}%, and showed a maximum toward the
Galactic Center. This component is considered to be entirely Galactic. As for
the hard power-law component, an average photon index of 91 fields was obtained
to be GH = 1.412\pm 0.007\pm 0.025 and the average 2-10 keV intensity was
calculated as FH = (6.38\pm 0.04\pm 0.64)\times 10^{-8} \ergss. The Galactic
component is marginally detected in the hard band. The 2-10 keV intensities
shows a 1\sigma deviation of 6.49^{+0.56}_{-0.61}%, while deviation due to the
NXB is 3.2%. The observed deviation can be explained by the Poisson noise of
source count in the f.o.v. (\sim 0.5 deg^2), even assuming a single \logn
relation on the whole sky. Based on the observed fluctuation and the absolute
intensity, an acceptable region of the \logn relation was derived, showing a
consistent feature with the recent Chandra and XMM-Newton results. Fluctuation
of the spectral index was also examined, and it implied a large amount of hard
sources and a substantial variation in the intrinsic source spectra (GS\simeq
1.1\pm 1.0).


title:
Constraining the Rotation Rate of Transiting Extrasolar Planets by
  Oblateness Measurements

abstract:
  (Abridged) The solar system gas giant planets are oblate due to their rapid
rotation. A measurement of the planet's projected oblateness would constrain
the planet's rotational period. Planets that are synchronously rotating with
their orbital revolution will be rotating too slowly to be significantly
oblate; these include planets with orbital semi-major axes <~ 0.2AU (for M_P ~
M_J and M_* ~ M_sun). Jupiter-like planets in the range of orbital semi-major
axes 0.1 AU to 0.2 AU will tidally evolve to synchronous rotation on a
timescale similar to main sequence stars' lifetimes. In this case an oblateness
detection will help constrain the planet's tidal Q value.
  The projected oblateness of a transiting extrasolar giant planet is
measurable from a very high-photometric-precision transit light curve. For a
sun-sized star and a Jupiter-sized planet the normalized flux difference in the
transit ingress/egress light curve between a spherical and an oblate planet is
a few to 15 x 10^{-5} for oblateness similar to Jupiter and Saturn
respectively. The transit ingress and egress are asymmetric for an oblate
planet with an orbital inclination different from 90 degrees and a non-zero
projected obliquity. A photometric precision of 10^{-4} has been reached by HST
observations of the known transiting extrasolar planet HD209458b. In addition
several planned space missions (including MOST, MONS, Corot, and Kepler) will
study or find transiting giant planets with photometric precision <~ 10^{-5}.
In particular Kepler is expected to find ~40 transiting giant planets < 1 AU
with ~20 of those > 0.2 AU.


title: Cooling of Superfluid Neutron Stars

abstract:
  Cooling of neutron stars (NSs) with the cores composed of neutrons, protons,
and electrons is analyzed. The main cooling regulators are discussed: opening
of direct Urca process in a NS central kernel; superfluidity of nucleons in NS
interiors; surface layers of light (accreted) elements; strong surface magnetic
fields. An emphasis is paid on the cooling scenario with strong $^1$S$_0$
pairing of protons and weak $^3$P$_2$ pairing of neutrons in the NS core, as
well as strong $^1$S$_0$ pairing of neutrons in the NS crust. The theory
predicts three types of isolated cooling middle-aged NSs with distinctly
different properties: low-mass, slowly cooling NSs; medium-mass, moderately
cooling NSs; massive, rapidly cooling NSs. The theory is compared with
observations of isolated NSs -- pulsars and radio quiet NSs in supernova
remnants. The constraints on physical properties of NSs which can be inferred
from such a comparison are outlined.


title:
Rapid Oscillations in Cataclysmic Variables. XV. HT Camelopardalis (= RX
  J0757.0+6306)

abstract:
  We present photometry and spectroscopy of HT Camelopardalis, a recently
discovered X-ray-bright cataclysmic variable. The spectrum shows bright lines
of H, He I, and He II, all moving with a period of 0.059712(1) d, which we
interpret as the orbital period. The star's brightness varies with a strict
period of 515.0592(2) s, and a mean full amplitude of 0.11 mag. These
properties qualify it as a /bona fide/ DQ Herculis star (intermediate polar) --
in which the magnetism of the rapidly rotating white dwarf channels accretion
flow to the surface. Normally at V=17.8, the star shows rare and very brief
outbursts to V=12-13. We observed one in December 2001, and found that the 515
s pulse amplitude had increased by a factor of ~100 (in flux units). A
transient orbital signal may also have appeared.


title:
Stability and eccentricity of periodic orbit for two planets in a 1:1
  resonance

abstract:
  The nonlinear stability domain of Lagrange's celebrated 1772 solution of a
three-body problem is obtained numerically as a function of the masses of the
bodies and the common eccentricity of their Keplerian orbits. This domain shows
that this solution may be realized in extra-solar planetary systems similar to
those that have been discovered recently with two Jupiter-size planets orbiting
a solar-size star. For an exact 1:1 resonance, the Doppler shift variation in
the emitted light would be the same as for stars which have only a single
planetary companion. But it is more likely that in actual extra-solar planetary
systems there are deviations from such a resonance, raising the interesting
prospect that Lagrange's solution can be identified by an analysis of the
observations. The existence of another stable 1:1 resonance solution which
would have a more unambiguous Doppler shift signature is also discussed.


title:
Time Dependent Modeling of the Markarian 501 X-ray and TeV Gamma-Ray
  Data Taken During March and April, 1997

abstract:
  If the high-energy emission from TeV blazars is produced by the Synchrotron
Self-Compton (SSC) mechanism, then simultaneous X-ray and Gamma-ray
observations of these objects are a powerful probe of the electron (and/or
positron) populations responsible for this emission. Understanding the emitting
particle distributions and their evolution in turn allow us to probe physical
conditions in the inner blazar jet and test, for example, various acceleration
scenarios. By constraining the SSC emission model parameters, such observations
also allow us to predict the intrinsic (unabsorbed) Gamma-ray spectra of these
sources, a major uncertainty in current attempts to use the observed Gamma-ray
spectra to constrain the intensity of the extragalactic background at
optical/infrared wavelengths. As a next step in testing the SSC model and as a
demonstration of the potential power of coordinated X-ray and Gamma-ray
observations, we attempt to model in detail the X-ray and Gamma-ray light
curves of the TeV Blazar Mrk 501 during its April-May 1997 outburst using a
time dependent SSC emission model. Extensive, quasi-simultaneous X-ray and
gamma-ray coverage exists for this period. We discuss and explore
quantitatively several of the flare scenarios presented in the literature. We
show that simple two-component models (with a soft, steady X-ray component plus
a variable SSC component) involving substantial pre-acceleration of electrons
to Lorentz factors on the order of 1E+5 describe the data train surprisingly
well. All considered models imply an emission region that is strongly out of
equipartition and low radiative efficiencies (ratio between kinetic jet
luminosity and comoving radiative luminosity) of 1 per-mill and less.


title:
A New Look at the Evolution of Wolf-Rayet Central Stars of Planetary
  Nebulae

abstract:
  We construct a speculative scenario for the evolution of Wolf-Rayet central
stars of planetary nebula. It is clear from the latest infra-red observations
that a new perspective has to be adopted: the simultaneous presence of carbon-
and oxygen-rich dust (double dust chemistry), while being a rare phenomenon for
H-rich central stars, is found around the vast majority of cool Wolf-Rayet
central stars. This correlation between Wolf-Rayet characteristics and double
dust chemistry points to a common mechanism. Within the binary evolution
framework established by Soker, two scenarios are proposed, responsible for the
majority (80-85%) and minority (15-20%) of Wolf-Rayet central stars. In the
first scenario, proposed here for the first time, a low mass main sequence
star, brown dwarf or planet spirals into the Asymptotic Giant Branch (AGB) star
inducing extra mixing, hence a chemistry change, and terminating the AGB
evolution. In the second scenario, previously proposed, a close binary
companion is responsible for the formation of a disk around either the binary
or the companion. This long-lived disk harbors the O-rich dust.


title:
Analysis of the distribution of HII regions in external galaxies. IV The
  new galaxy sample. Position and Inclination angles

abstract:
  We have compiled a new sample of galaxies with published catalogs of HII
region coordinates. This sample, together with the former catalog of
Garcia-Gomez and Athanassoula (1991) will form the basis for subsequent studies
of the spiral structure in disc galaxies. In this paper we address the problem
of the deprojection of the galaxy images. For this purpose we use two
deprojection methods based on the HII region distribution and compare the
results with the values found in the literature using other deprojection
methods. Taking into account the results of all the methods, we propose optimum
values for the position and inclination angles of all the galaxies in our
sample.


title: Gravitational instability of slowly rotating isothermal spheres

abstract:
  We discuss the statistical mechanics of rotating self-gravitating systems by
allowing properly for the conservation of angular momentum. We study
analytically the case of slowly rotating isothermal spheres by expanding the
solutions of the Boltzmann-Poisson equation in a series of Legendre
polynomials, adapting the procedure introduced by Chandrasekhar (1933) for
distorted polytropes. We show how the classical spiral of Lynden-Bell & Wood
(1967) in the temperature-energy plane is deformed by rotation. We find that
gravitational instability occurs sooner in the microcanonical ensemble and
later in the canonical ensemble. According to standard turning point arguments,
the onset of the collapse coincides with the minimum energy or minimum
temperature state in the series of equilibria. Interestingly, it happens to be
close to the point of maximum flattening. We determine analytically the
generalization of the singular isothermal solution to the case of a slowly
rotating configuration. We also consider slowly rotating configurations of the
self-gravitating Fermi gas at non zero temperature.


title: The Cooling Neutron Star in 3C 58

abstract:
  The upper limit of the effective surface temperature of the neutron star (NS)
PSR J0205+6449 in the supernova remnant 3C 58 obtained recently by Slane et al.
(2002) is analyzed using a modern theory of NS cooling (Kaminker et al. 2002).
The observational limit can be explained by cooling of a superfluid NS with the
core composed of neutrons, protons and electrons, where direct Urca process is
forbidden. However, combined with the data on the surface temperatures of other
isolated NSs, it gives evidence (emphasized by Slane et al.) that direct Urca
process is open in the inner cores of massive NSs. This evidence turns out to
be less stringent than the evidence provided by the well known observations of
Vela and Geminga.


title:
Discovery of the Low-Redshift Optical Afterglow of GRB 011121 and Its
  Progenitor Supernova 2001ke

abstract:
  We present the discovery and follow-up observations of the afterglow of the
GRB 011121 and its associated supernova SN 2001ke. Images were obtained with
the OGLE 1.3m telescope in BVRI passbands, starting 10.3 hours after the burst.
The temporal analysis of our early data indicates a steep decay, independent of
wavelength with power-law index alpha=-1.72+/-0.05. There is no evidence for a
break in the light curve earlier than 2.5 days after the burst. The spectral
energy distribution determined from the early broad-band photometry is a
power-law with index beta=-0.66+/-0.13 after correcting for a large reddening.
Spectra, obtained with the Magellan 6.5m Baade telescope, reveal narrow
emission lines from the host galaxy which provide a redshift of z=0.362+/-0.001
to the GRB. We also present late R and J-band observations of the afterglow
between 7-17 days after the burst. The late-time photometry shows a large
deviation from the initial decline and our data combined with Hubble Space
Telescope photometry provide strong evidence for a supernova peaking about 12
rest-frame days after the GRB. The first spectrum ever obtained of a GRB
supernova at cosmological distance revealed a blue continuum. SN 2001ke was
more blue near maximum than SN 1998bw and faded more quickly which demonstrates
that a range of properties are possible in supernovae which generate GRB. The
blue color is consistent with a supernova interacting with circumstellar gas
and this progenitor wind is also evident in the optical afterglow. This is the
best evidence to date that classical, long gamma-ray bursts are generated by
core-collapse supernovae.


title: RXTE/OSSE Fits to the Hard State Spectrum of Cygnus X-1

abstract:
  We present three spectra of Cygnus X-1 in the low/hard state from 3-1000 keV
produced with RXTE and OSSE. We demonstrate that a pure thermal Comptonization
model, with Compton reflection fits the data well, with coronal temperatures of
about 90 keV, optical depths of about 1.3, and reflection fractions of about
0.25 $\times$ 2$\pi$. We find that no additional components are necessary to
fit the data, although the presence of an additional non-thermal component does
result in a marginal improvement to the goodness of the fit. Two of the
observations are fit better by an almost purely non-thermal Comptonization
model with $\Gamma_{inj}$ of $\sim$ 3.2 for the electrons and the other
parameters essentially the same as for the thermal model, while the third
observation is also consistent with this model. Observations that could break
this degeneracy are discussed. We also demonstrate that the low reflection
parameter (i.e. $R/2\pi<1$) is due to a lack of strong curvature in the 30-50
keV range of the spectrum and not due to ionization effects. The spectrum
changes very little over the three weeks of the observations, in accordance
with a three week correlation timescale found in the All Sky Monitor data. We
show that for a purely thermal corona, the radius of the corona must be between
$3\times 10^6$ and $1.5\times 10^{10}$ cm, while the radius of a hybrid corona
or a purely non-thermal corona is constrained to be between $10^8$ and $10^9$
cm.


title: The dominant X-ray wind in massive star binaries

abstract:
  We investigate which shocked wind is responsible for the majority of the
X-ray emission in colliding wind binaries, an issue where there is some
confusion in the literature, and which we show is more complicated than has
been assumed. We find that where both winds rapidly cool (typically close
binaries), the ratio of the wind speeds is often more important than the
momentum ratio, because it controls the energy flux ratio, and the faster wind
is generally the dominant emitter. When both winds are largely adiabatic
(typically long-period binaries), the slower and denser wind will cool faster
and the stronger wind generally dominates the X-ray luminosity.


title: Discovery of X-rays from Venus with Chandra

abstract:
  On January 10 and 13, 2001, Venus was observed for the first time with an
X-ray astronomy satellite. The observation, performed with the ACIS-I and
LETG/ACIS-S instruments on Chandra, yielded data of high spatial, spectral, and
temporal resolution. Venus is clearly detected as a half-lit crescent, with
considerable brightening on the sunward limb. The morphology agrees well with
that expected from fluorescent scattering of solar X-rays in the planetary
atmosphere. The radiation is observed at discrete energies, mainly at the
O-K_alpha energy of 0.53 keV. Fluorescent radiation is also detected from
C-K_alpha at 0.28 keV and, marginally, from N-K_alpha at 0.40 keV. An
additional emission line is indicated at 0.29 keV, which might be the signature
of the C 1s --> pi* transition in CO_2 and CO. Evidence for temporal
variability of the X-ray flux was found at the 2.6 sigma level, with
fluctuations by factors of a few times indicated on time scales of minutes. All
these findings are fully consistent with fluorescent scattering of solar
X-rays. No other source of X-ray emission was detected, in particular none from
charge exchange interactions between highly charged heavy solar wind ions and
atmospheric neutrals, the dominant process for the X-ray emission of comets.
This is in agreement with the sensitivity of the observation.


title:
The Parkes Multibeam Pulsar Survey -- II. Discovery and Timing of 120
  Pulsars

abstract:
  The Parkes multibeam pulsar survey is a sensitive survey of a strip of the
Galactic plane with $|b|<5\degr$ and $260\degr < l < 50\degr$ at 1374 MHz. Here
we report the discovery of 120 new pulsars and subsequent timing observations,
primarily using the 76-m Lovell radio telescope at Jodrell Bank. The main
features of the sample of 370 published pulsars discovered during the multibeam
survey are described. Furthermore, we highlight two pulsars: PSR J1734$-$3333,
a young pulsar with the second highest surface magnetic field strength among
the known radio pulsars, $B_s = 5.4\times10^{13}$ G, and PSR J1830$-$1135, the
second slowest radio pulsar known, with a 6-s period.


title: Studying large-scale structure with the 2dF Galaxy Redshift Survey

abstract:
  The 2dF Galaxy Redshift Survey is the first to observe more than 100,000
redshifts. This allows precise measurements of many of the key statistics of
galaxy clustering, in particular redshift-space distortions and the large-scale
power spectrum. This paper presents the current 2dFGRS results in these areas.
Redshift-space distortions are detected with a high degree of significance,
confirming the detailed Kaiser distortion from large-scale infall velocities,
and measuring the distortion parameter beta equiv Omega_m^{0.6}/b = 0.43 +-
0.07. The power spectrum is measured to < 10% accuracy for k > 0.02 h Mpc^{-1},
and is well fitted by a CDM model with Omega_m h = 0.20 +- 0.03 and a baryon
fraction of 0.15 +- 0.07. A joint analysis with CMB data requires Omega_m =
0.29 +- 0.05, assuming scalar fluctuations, but no priors on other parameters.
Two methods are used to determine the large-scale bias parameter: an internal
bispectrum analysis yields b = 1.04 +- 0.11, in very good agreement with the b
= 1.10 +- 0.08 obtained from a joint 2dFGRS+CMB analysis, again assuming scalar
fluctuations. These figures refer to galaxies of approximate luminosity 2L^*;
luminosity dependence of clustering is detected at high significance, and is
well described by b/b^* = 0.85 + 0.15(L/L^*).


title:
Formation and evolution of galactic disks with a multiphase numerical
  model

abstract:
  The formation and evolution of galactic disks are complex phenomena, where
gas and star dynamics are coupled through star formation and the related
feedback. The physical processes are so numerous and intricate that numerical
models focus, in general, on one or a few of them only. We propose here a
numerical model with particular attention to the multiphase nature of the
interstellar medium; we consider a warm gas phase (> 10^4 K), treated as a
continuous fluid by an SPH algorithm, and a cold gas phase (down to 10K),
fragmented in clouds, treated by a low-dissipation sticky particles component.
The two gas phases do not have the same dynamics, nor the same spatial
distribution. In addition to gravity, they are coupled through mass exchanges
due to heating/cooling processes, and supernovae feedback. Stars form out of
the cold phase, and re-inject mass to the warm phase through SN explosions and
stellar winds. The baryons are embedded in a live cold dark matter component.
  Baryonic disks, initially composed of pure gas, encounter violent
instabilities, and a rapid phase of star formation, that slows down
exponentially. Stars form in big clumps, that accumulate in the center to build
a bulge. Exponential metallicity gradients are obtained. External infall of gas
should be included to maintain a star formation rate in the disk comparable to
what is observed in present disk galaxies.


title:
ISO--LWS observations of the two nearby spiral galaxies: NGC6946 and
  NGC1313

abstract:
  (Abridged) We present the analysis of the main FIR fine structure lines
emission in NGC1313 and NGC6946. We calculate that a component probably
associated with the diffuse disks contributes <~40% in N6946 and ~30 % in N1313
to the total [CII] emission. The main PDR physical parameters responsible for
the neutral atomic gas emission in N1313 and N6946 do not significantly differ
from what Malhotra etal (2001) found by modelling the integrated emission of a
sample of 60 normal galaxies,although there are evidences for a beam averaged
contribution of a less active component inside NGC6946 higher than its
contribution in the integrated emission of normal galaxies. CO and [CII] in
N6946 are well correlated with a mean [CII]/CO ratio similar to that of the
normal galaxies sample. In N1313 the [CII]/CO seems to systematically increase
from the North to the south, along the S-shaped spiral arm, indicating much
more inhomogeneous conditions than in N6946. HI and [CII] in N6946 are
completely de-correlated, probably because they arise from different gas
components. In N1313 we successfully detect two distinct gas components: a
cirrus-like component where HI and [CII] are weakly correlated as observed in
our Galaxy, and a component associated with dense PDRs completely de-correlated
from HI as observed in N6946.Finally, we find that the HI residing in dense
PDRs and presumably recently photo-dissociated, constitutes a few % of the
total HI. In turn, this dense gas component produces most of the [CII] emission
emitted by the atomic neutral medium.


title: CTI history of the EPIC pn camera

abstract:
  The pn camera of EPIC is inherently robust against radiation damage effects.
Nevertheless, the knowledge of charge transfer inefficiency (CTI) of the pn
camera is crucial for obtaining the correct energy scale. We describe detailed
in-orbit monitoring of this effect, utilizing the internal calibration source.
We find that during the first two years in orbit the CTI increased by about 4%
for Al-K and by about 7% for Mn-K. The increases in the CTI are well within
expectations, with no measurable effect on the energy resolution.


title: On the pulsation parallax of the variable star RR Lyr

abstract:
  We show that a straightforward application of the predicted relation
connecting the absolute K magnitude of fundamental RR Lyrae variables to their
period and metal content, together with current evolutionary predictions on the
mass and luminosity of Horizontal Branch stars, supply a distance estimate to
the prototype star RR Lyr in close agreement with the recent parallax
determination by HST (Benedict et al. 2002), largely unaffected by the
interstellar extinction correction. Adopting <A_V>=0.12+-0.10 mag as a safe
estimate of the extinction correction to RR Lyr, we obtain a "pulsation"
parallax of 3.858+-0.131 mas which agrees quite well, and with a smaller formal
error, with the HST measurement (3.82+-0.20 mas) and with the weighted average
of HST, Hipparcos, and ground-based determinations (3.87+-0.19 mas). This
result suggests that near-infrared magnitudes and pulsation models could
constrain the distance to well-studied RR Lyrae stars, both in the field and in
globular clusters, with an accuracy better than current direct trigonometric
measurements.


title:
The Molecular Condensations Ahead of Herbig-Haro Objects. I.
  Multi-transition Observations of HH 2

abstract:
  We present a CSO and BIMA molecular line survey of the dense, quiescent
molecular environment ahead of HH2. The molecular gas is cold, 13 K, and
moderately dense, 3x10^5 cm^-3. A total of 14 species has been detected
(including different isotopes and deuterated species). The relative abundances
of the clump are compared with other dense molecular environments, including
quiescent dark clouds, and active low and high mass star forming regions. This
comparison confirms the peculiar chemical composition of the quiescent gas
irradiated by the HH objects. Thus, from this comparison, we found that the
HCO+, CH3OH and H2CO are strongly enhanced. SO and SO2 are weakly enhanced,
whereas HCN and CS are underabundant. The CN abundance is within the range of
value found in starless dark clouds, but it is low with respect to high mass
star forming regions. Finally, the chemical composition of HH2 confirms the
qualitative results of the Viti & Williams (1999) complex chemical model that
follows the chemical behavior of a molecular clump irradiated by a HH object.


title:
Measurement of the Solar Neutrino Capture Rate by the Russian-American
  Gallium Solar Neutrino Experiment During One Half of the 22-Year Cycle of
  Solar Activity

abstract:
  We present the results of measurements of the solar neutrino capture rate in
gallium metal by the Russian-American Gallium Experiment SAGE during slightly
more than half of a 22-year cycle of solar activity. Combined analysis of the
data of 92 runs during the 12-year period January 1990 through December 2001
gives a capture rate of solar neutrinos with energy more than 233 keV of 70.8
+5.3/-5.2 (stat.) +3.7/-3.2 (syst.) SNU. This represents only slightly more
than half of the predicted standard solar model rate of 128 SNU. We give the
results of new runs beginning in April 1998 and the results of combined
analysis of all runs since 1990 during yearly, monthly, and bimonthly periods.
Using a simple analysis of the SAGE results combined with those from all other
solar neutrino experiments, we estimate the electron neutrino pp flux that
reaches the Earth to be (4.6 +/- 1.1) E10/(cm^2-s). Assuming that neutrinos
oscillate to active flavors the pp neutrino flux emitted in the solar fusion
reaction is approximately (7.7 +/- 1.8) E10/(cm^2-s), in agreement with the
standard solar model calculation of (5.95 +/- 0.06) E10/(cm^2-s).


title:
Observation of periodic variable stars towards the galactic spiral arms
  by EROS II

abstract:
  We present the results of a massive variability search based on a photometric
survey of a six square degree region along the Galactic plane at ($l =
305^\circ$, $b = -0.8^\circ$) and ($l = 330^\circ$, $b = -2.5^\circ$). This
survey was performed in the framework of the EROS II (Exp\'erience de Recherche
d'Objets Sombres) microlensing program. The variable stars were found among
1,913,576 stars that were monitored between April and June 1998 in two
passbands, with an average of 60 measurements. A new period-search technique is
proposed which makes use of a statistical variable that characterizes the
overall regularity of the flux versus phase diagram. This method is well suited
when the photometric data are unevenly distributed in time, as is our case.
1,362 objects whose luminosity varies were selected. Among them we identified 9
Cepheids, 19 RR Lyrae, 34 Miras, 176 eclipsing binaries and 266 Semi-Regular
stars. Most of them are newly identified objects. The cross-identification with
known catalogues has been performed. The mean distance of the RR Lyrae is
estimated to be $\sim 4.9 \pm 0.3$ kpc undergoing an average absorption of
$\sim 3.4 \pm 0.2$ magnitudes. This distance is in good agreement with the one
of disc stars which contribute to the microlensing source star population.Our
catalogue and light curves are available electronically from the CDS,
Strasbourg and from our Web site http://eros.in2p3.fr.


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

abstract:
  We use HST broad band images, VLA and VLBI continuum data to study the three
dimensional orientation of jets relative to nuclear dust disks in 20 radio
galaxies. The comparison between the position angles of the jets with those of
the dust disks major axes shows a wide distribution, suggesting that they are
not aligned preferentially perpendicular to each other. We use a statistical
technique to determine the 3 dimensional distribution of angles between jets
and dust disks rotation axes. This analysis shows that the observations are
consistent with jets homogeneously distributed over a large region, extending
over polar caps of 55 degrees to 77 degrees, but seem to avoid lying close to
the plane of the dust disks. We argue that the lack of close alignment between
jets and dust disks axes is not likely to be caused by feeding the nucleus with
gas from mergers originated from random directions. We suggest that the
misalignment can be due by a warping mechanism in the accretion disk, like
self-irradiation instability or the Bardeen-Petterson effect, or that the
gravitational potential in the inner regions of the galaxy is misaligned with
respect to that of the dust disk.


title:
Multiple delays in QSO 0957+561: observational evidence and
  interpretation

abstract:
  Q0957+561A,B is a double-imaged quasar that has been intensively observed
during the last 10 years in different optical bands and with several
telescopes, and we concentrated on recent public data obtained at the Apache
Point Observatory (APO) and the Teide Observatory (TO). When an intrinsic event
appears in the light curve of Q0957+561A, its twin event (a similar feature) is
seen in the brightness record of Q0957+561B, and thus, one can measure the
corresponding time delay. The TO dataset includes two prominent twin events,
which were detected with a time separation of 425 +/- 4 days. On the other
hand, from the APO dataset, we found a clear evidence for two different time
delays associated with two pairs of twin events: 417.0 +/- 0.6 (APO main twin
events) and 432.0 +/- 1.9 days (APO secondary twin events), where the
APO(main)-APO(secondary) difference delay is of - 15 +/- 2 days. In agreement
with the Yonehara's idea, if the three pairs of twin events are originated
inside a standard hybrid source (accretion disk and circumnuclear stellar
region), the three measured time delays indicate that they do not come from a
common zone in the source. Therefore, we can consider that the prominent
features are caused by flares in a standard hybrid source and discuss on the
size and nature of the region of flares. In this paper it is showed that the
more plausible interpretation is that two of the three flares are generated at
distances (from the central black hole) larger than 90 pc. Some stellar
scenarios can explain the two flares far away from the black hole, while
phenomena in the accretion disk cannot cause them.


title:
Future Evolution of Nearby Large-Scale Structure in a Universe Dominated
  by a Cosmological Constant

abstract:
  We simulate the future evolution of the observed inhomogeneities in the local
universe assuming that the global expansion rate is dominated by a cosmological
constant. We find that within two Hubble times (~ 30 billion years) from the
present epoch, large-scale structures will freeze in comoving coordinates and
the mass distribution of bound objects will stop evolving. The Local Group will
get somewhat closer to the Virgo cluster in comoving coordinates, but will be
pulled away from the Virgo in physical coordinates due to the accelerated
expansion of the Universe. In the distant future there will only be one massive
galaxy within our event horizon, namely the merger product of the Andromeda and
the Milky Way galaxies. All galaxies that are not gravitationally bound to the
Local Group will recede away from us and eventually exit from our event
horizon. More generally, we identify the critical interior overdensity above
which a shell of matter around an object will remain bound to it at late times.


title:
Small Angular Scale CMB Anisotropies from CBI and BIMA: Early Universe
  or Local structures ?

abstract:
  The advent of high resolution cosmic microwave background (CMB) experiments
now allows studies on the temperature fluctuations at scales corresponding to
few arcminutes and below. Though the reported excess power at $\ell \sim 2000 -
6000$ by CBI and BIMA is roughly consistent with a secondary contribution
resulting from the Sunyaev-Zeldovich effect, this requires a higher
normalization for the matter power spectrum than measured by other means. In
addition to a local red-shift contribution, another strong possibility for
anisotropies at very small scales involve non-standard aspects of inflationary
models. To distinguish between contributions from early universe and local
structures, including a potential point source contribution, and to understand
the extent to which structures at low red-shifts contribute to small scale
temperature anisotropies, it maybe necessary to perform a combined study
involving CMB and the large scale structure. We suggest a cross-correlation of
the temperature data with a map of the large scale structure, such as the
galaxy distribution. For next generation small angular scale CMB experiments,
multi-frequency observations may be a necessary aspect to allow an additional
possibility to distinguish between these different scenarios.


title: An XMM-Newton survey of Extremely Red Objects

abstract:
  We present preliminary results of a 25 ks XMM-Newton observation of the
largest sample of Extremely Red Objects (EROs) available to date (about 450
sources), selected in a contiguous area of 700 arcmin^2 (Daddi et al. 2000).
Five of the 36 hard X-ray selected sources brighter than 7x10^{-15} erg cm^{-2}
s^{-1} in the 2-10 keV band are associated with EROs. All of the X-ray detected
EROs show rather extreme X-ray-to-optical flux ratios, suggesting the presence
of highly obscured AGN activity.


title:
Chandra Study of Young Stellar Objects in the NGC 1333 Star-forming
  Cloud

abstract:
  NGC 1333, a highly active star formation region within the Perseus molecular
cloud complex, has been observed with the ACIS-I detector on board the Chandra
X-ray Observatory. In our image with a sensitivity limit of ~ 1e28 erg/s, we
detect 127 X-ray sources, of which, 95 are known cluster members. The X-ray
luminosity function of the discovered YSO population spans a range of
1e28-3.2e31 erg/s in the 0.5-8 keV band. Comparison with K-band source counts
indicates that we detect all of the known cluster members with K < 12, and
about half of members with K > 12. We detect seven X-ray emitting YSOs which
drive optically visible jets as well as one deeply embedded object that has not
been detected in near-IR observations. The presence or absence of an outflows
does not appear to produce any difference in X-ray properties of YSOs. We also
find no systematic differences in X-ray luminosity distributions between two
complete subsamples of CTTs and WTTs. That suggests that there is no difference
in the astrophysical mechanism of WTT and CTT X-ray emission production.
Additional results include: the X-ray emission from two late-B stars which
illuminate the reflection nebula originates from unresolved late-type
companions; two T Tauri stars are discovered as previously unknown components
of visual binaries; and the X-ray counterpart of SVS 16 has the column density
much lower than that expected from near-IR photometry and thus its X-ray
luminosity is not anomalously high, as has been previously suggested.


title: Imaging low order CO emission from the z=4.12 QSO PSS 2322+1944

abstract:
  We present observations of CO 1-0 and CO 2-1 emission from the z = 4.12 QSO
PSS 2322+1944 using the Very Large Array. The CO emission is extended on a
spatial scale of 2''. This extension could reflect the double nature of the QSO
as seen in the optical, or could be diffuse emission with a (redshift
corrected) mean brightness temperature of 2.8 K for the CO 2-1 line. We find
the CO excitation conditions are lower than in two other IR-luminous z > 4
QSOs, suggesting the presence of a significant contribution from cooler, lower
density molecular gas (n(H_2) = 5x10^3 /cm^3), although such a conclusion is
complicated by the possibility of differential gravitational magnification.


title: Hot Settling Accretion Flow onto a Spinning Black Hole

abstract:
  We study the structure and properties of hot MHD accretion onto a Kerr black
hole. In such a system, the hole is magnetically coupled to the inflowing gas
and exerts a torque onto the accretion flow. A hot settling flow can form
around the hole and transport the angular momentum outward, to the outer edge
of the flow. Unlike other hot flows, such as advection- and
convection-dominated flows and inflow-outflow solutions (ADAFs, CDAFs, and
ADIOS), the properties of the hot settling flow are determined by the spin of
the central black hole, but are insensitive to the mass accretion rate.
Therefore, it may be possible to identify rapidly spinning BHs simply from
their broad-band spectra.
  Observationally, the hot settling flow around a Kerr hole is somewhat similar
to other hot flows in that they all have hard, power-law spectra and relatively
low luminosities. Thus, most black hole candidates in the low/hard and,
perhaps, intermediate X-ray state may potentially accrete via the hot settling
flow. However, a settling flow will be somewhat more luminous than
ADAFs/CDAFs/ADIOS, will exhibit high variability in X-rays, and may have
relativistic jets. This suggests that galactic microquasars and active galactic
nuclei may be powered by hot settling flows. We identify several galactic X-ray
sources as the best candidates.


title: M-type Vega-like stars

abstract:
  We carried out a search for M-type Vega-like stars by correlating the IRAS
Faint Source Catalog with Hipparcos selected M-type stars. Three stars with
apparent IRAS 25mu excess emission are shown instead to be non-IR-excess stars
from ground-based 11.7 and 17.9mu photometry. Two stars previously suggested to
have Vega-like mid-IR excess are also shown to be non-excess stars. These
results imply that other suggested mid-IR excess stars in the literature may
also be false excess stars. Detection threshold bias is apparently responsible
for these bogus IR excesses. Sixty micron excess emission from a previously
known M-type Vega-like star (GJ 803) is identified again.


title:
Eddington limit and radiative transfer in highly inhomogeneous
  atmospheres

abstract:
  Radiation dominated accretion disks are likely to be subject to the ``photon
bubble'' instability, which may lead to strong density inhomogeneities on
scales much shorter than the disk scale height. Such disks -- and magnetized,
radiation-dominated atmospheres in general -- could radiate well above the
Eddington limit without being disrupted. When density contrasts become large
over distances of order the photon mean free path, radiative transfer cannot be
described adequately using either the standard diffusion approximation or
existing prescriptions for flux-limited diffusion. Using analytical and Monte
Carlo techniques, we consider the effects of strong density gradients deep
within radiation- and scattering-dominated atmospheres. We find that radiation
viscosity -- i.e., the off-diagonal elements of the radiation stress tensor --
has an important effect on radiative transfer under such conditions. We compare
analytical and numerical results in the specific case of a plane-parallel
density wave structure and calculate Eddington enhancement factors due to the
porosity of the atmosphere. Our results can be applied to the study of
dynamical coupling between radiation forces and density inhomogeneities in
radiation dominated accretion disks in two or three dimensions.