title: Can Thin Disks Produce Anomalous X-Ray Pulsars?

abstract:
  We investigate whether young neutron stars with fall-back disks can produce
Anomalous X-Ray Pulsars (AXPs) within timescales indicated by the ages of
associated supernova remnants. The system passes through a propeller stage
before emerging as an AXP or a radio pulsar. The evolution of the disk is
described by a diffusion equation which has self-similar solutions with either
angular momentum or total mass of the disk conserved. We associate these two
types of solutions with accretor and propeller regimes, respectively. Our
numerical calculations of thin disk models with changing inner radius take into
account the super-critical accretion at the early stages, and electron
scattering and bound-free opacities with rich metal content. Our results show
that, assuming a fraction of the mass inflow is accreted onto the neutron star,
the fall-back disk scenario can produce AXPs for acceptable parameters.


title: Near-IR bright galaxies at z~2. Entering the spheroid formation epoch ?

abstract:
  Spectroscopic redshifts have been measured for 9 K-band luminous galaxies at
1.7 < z < 2.3, selected with Ks < 20 in the "K20 survey" region of the Great
Observatories Origins Deep Survey area. Star formation rates (SFRs) of ~100-500
Msun/yr are derived when dust extinction is taken into account. The fitting of
their multi-color spectral energy distributions indicates stellar masses M ~
10^11 Msun for most of the galaxies. Their rest-frame UV morphology is highly
irregular, suggesting that merging-driven starbursts are going on in these
galaxies. Morphologies tend to be more compact in the near-IR, a hint for the
possible presence of older stellar populations. Such galaxies are strongly
clustered, with 7 out of 9 belonging to redshift spikes, which indicates a
correlation length r_0 ~ 9-17 h^-1 Mpc (1 sigma range). Current semianalytical
models of galaxy formation appear to underpredict by a large factor (about 30)
the number density of such a population of massive and powerful starburst
galaxies at z ~ 2. The high masses and SFRs together with the strong clustering
suggest that at z ~ 2 we may have started to explore the major formation epoch
of massive early-type galaxies.


title: GRB 021219: the first Gamma-Ray Burst localized in real time with IBAS

abstract:
  On December 19, 2002, during the Performance and Verification Phase of
INTEGRAL, a Gamma-Ray Burst (GRB) has been detected and localized in real time
with the INTEGRAL Burst Alert System (IBAS). Here we present the results
obtained with the IBIS and SPI instruments. The burst had a time profile with a
single peak lasting about 6 s. The peak spectrum can be described by a single
power law with photon index $\Gamma$=1.6$\pm$0.1 and flux $\sim$3.7 photons
cm$^{-2}$ s$^{-1}$ (20 - 200 keV). The fluence in the same energy range is
9$\times10^{-7}$ erg cm$^{-2}$. Time resolved spectroscopy performed with
IBIS/ISGRI shows a clear hard to soft evolution of the spectrum.


title: Noncommutative Inflation and the CMB Multipoles

abstract:
  The first year results of WMAP tentatively indicate running of the spectral
index as well as a deficit of power in the low multipoles in the CMB spectrum.
The former can be rather easily understood in the noncommutative inflation
model, and the latter, as we shall show in this paper, still appears to be an
anomaly, even though the noncommutative inflation model already suppresses the
low multipoles to a certain degree. By fitting the power spectrum, we determine
the string scale to be $l_s\sim 4\times 10^{-29}$cm.


title: Classical Cepheid Pulsation Models: IX. New Input Physics

abstract:
  We constructed several sequences of classical Cepheid envelope models at
solar chemical composition ($Y=0.28, Z=0.02$) to investigate the dependence of
the pulsation properties predicted by linear and nonlinear hydrodynamical
models on input physics. To study the dependence on the equation of state (EOS)
we performed several numerical experiments by using the simplified analytical
EOS originally developed by Stellingwerf and the recent analytical EOS
developed by Irwin. Current findings suggest that the pulsation amplitudes as
well as the topology of the instability strip marginally depend on the adopted
EOS.
  We also investigated the dependence of observables predicted by theoretical
models on the mass-luminosity (ML) relation and on the spatial resolution
across the Hydrogen and the Helium partial ionization regions. We found that
nonlinear models are marginally affected by these physical and numerical
assumptions. In particular, the difference between new and old models in the
location as well as in the temperature width of the instability strip is on
average smaller than 200 K. However, the spatial resolution somehow affects the
pulsation properties. The new fine models predict a period at the center of the
Hertzsprung Progression ($P_{HP}=9.65$$-$9.84 days) that reasonably agree with
empirical data based on light curves ($P_{HP}=10.0\pm 0.5$ days;
\citealt{mbm92}) and on radial velocity curves ($P_{HP}=9.95\pm 0.05$ days;
\citealt{mall00}), and improve previous predictions by Bono, Castellani, and
Marconi (2000, hereinafter BCM00).


title: A long hard look at MCG-6-30-15 with XMM-Newton and BeppoSAX

abstract:
  We summarise the primary results from a 320 ks observation of the bright
Seyfert 1 galaxy MCG-6-30-15 with XMM-Newton and Beppo-SAX.


title:
Large-scale power in the CMB and new physics: an analysis using Bayesian
  model comparison

abstract:
  One of the most tantalizing results from the WMAP experiment is the
suggestion that the power at large scales is anomalously low when compared to
the prediction of the ``standard'' Lambda-CDM model. The same anomaly, although
with somewhat larger uncertainty, was also previously noted in the COBE data.
In this work we discuss possible alternate models that give better fits on
large scales and apply a model-comparison technique to select amongst them. We
find that models with a cut off in the power spectrum at large scales are
indeed preferred by data, but only by a factor of 3.6, at most, in the
likelihood ratio, corresponding to about ``1.5 sigma'' if interpreted in the
traditional manner. Using the same technique, we have also examined the
possibility of a systematic error in the measurement (or prediction) of the
large-scale power. Ignoring other evidence that the large-scale modes are
properly measured and predicted, we find this possibility somewhat more likely,
with roughly a 2.5 sigma evidence.


title: The role of ionization in symbiotic binaries

abstract:
  Processes of ionization and recombination often influence significantly the
observed spectrum produced by symbiotic stars in a very wide wavelength region.
Properties of the nebular spectrum provide important information on some
fundamental parameters and on geometric structure of symbiotic stars. This
paper reviews the recently recognized effects of ionization/recombination in
these binaries and summarizes first results. We concentrate in this review on
the continuum emission in the range from ultraviolet to near-IR wavelengths.


title: Chemical Evolution models of Local Group galaxies

abstract:
  Status quo and perspectives of standard chemical evolution models of Local
Group galaxies are summarized, discussing what we have learnt from them, what
we know we have not learnt yet, and what I think we will learn in the near
future. It is described how Galactic chemical evolution models have helped
showing that: i) stringent constraints on primordial nucleosynthesis can be
derived from the observed Galactic abundances of the light elements, ii) the
Milky Way has been accreting external gas from early epochs to the present
time, iii) the vast majority of Galactic halo stars have formed quite rapidly
at early epochs. Chemical evolution models for the closest dwarf galaxies,
although still uncertain so far, are expected to become extremely reliable in
the nearest future, thanks to the quality of new generation photometric and
spectroscopic data which are currently being acquired.


title: Point sources in the context of future SZ surveys

abstract:
  We look at the impact of Infra-Red (IR) and radio point sources on upcoming
large yield Sunyaev-Zel'dovich (SZ) cluster surveys such as APEX, SPT and ACT.
The IR and radio point source counts are based on observations by the the SCUBA
and WMAP instruments respectively. We show that the contributions from IR
source counts, when extrapolated from the SCUBA frequency of 350GHz to the
operating frequencies of these surveys (~100-300GHz), can be a significant
source of additional `noise' which needs to be accounted for in order to
extract the optimal science from these surveys. Alternatively, these surveys
give us an opportunity to study IR sources, their numbers and clustering
properties, opening a new window to the high redshift universe. For the radio
point sources, the contribution depends on a more uncertain extrapolation from
40GHz but is comparable to the IR near 200GHz. However, the radio signal may be
correlated with clusters of galaxies and have a disproportionately larger
effect.


title:
Measuring the Chaplygin gas equation of state from angular and
  luminosity distances

abstract:
  An exotic dark component, named generalized Chaplygin gas (Cg) and
parameterized by an equation of state $p = -A/\rho_{Cg}^{\alpha}$ where $A$ and
$\alpha$ are arbitrary constants, is one of the possible candidates for dark
energy as well as for a unified scenario of dark matter/energy. In this paper
we investigate qualitative and quantitative aspects of the angular size -
redshift test in cosmological models driven by such a dark component. We
discuss the prospects for constraining the Cg equation of state from
measurements of the angular size at low and high redshift radio sources and
also from a joint analysis involving angular size and supernova data. A
detailed discussion about the influence of the Cg on the minimal redshift at
which the angular size of an extragalactic source takes its minimal value is
also presented.


title: A Neutral Hydrogen Self-Absorption Cloud in the SGPS

abstract:
  Using data from the Southern Galactic Plane Survey (SGPS) we analyze an HI
self-absorption cloud centered on l = 318.0 deg, b = -0.5 deg, and velocity, v
= -1.1 km/s. The cloud was observed with the Australia Telescope Compact Array
(ATCA) and the Parkes Radio Telescope, and is at a near kinematic distance of
less than 400 pc with derived dimensions of less than 5 x 11 pc. We apply two
different methods to find the optical depth and spin temperature. In both
methods we find upper limit spin temperatures ranging from 20 K to 25 K and
lower limit optical depths ~ 1. We look into the nature of the HI emission and
find that 60-70% originates behind the cloud. We analyze a second cloud at the
same velocity centered on l = 319 deg and b = 0.4 deg with an upper limit spin
temperature of 20 K and a lower limit optical depth of 1.6. The similarities in
spin temperature, optical depth, velocity, and spatial location are evidence
the clouds are associated, possibly as one large cloud consisting of smaller
clumps of gas. We compare HI emission data with 12CO emission and find a
physical association of the HI self-absorption cloud with molecular gas.


title: The Size Distribution of Trans-Neptunian Bodies

abstract:
  [Condensed] We search 0.02 deg^2 for trans-Neptunian objects (TNOs) with
m<=29.2 (diameter ~15 km) using the ACS on HST. Three new objects are
discovered, roughly 25 times fewer than expected from extrapolation of the
differential sky density Sigma(m) of brighter objects. The ACS and other recent
TNO surveys show departures from a power law size distribution. Division of the
TNO sample into ``classical Kuiper belt'' (CKB) and ``Excited'' samples reveals
that Sigma(m) differs for the two populations at 96% confidence. A double power
law adequately fits all data. Implications include: The total mass of the CKB
is ~0.010 M_Earth, only a few times Pluto's mass, and is predominately in the
form of ~100 km bodies. The mass of Excited objects is perhaps a few times
larger. The Excited class has a shallower bright-end size distribution; the
largest objects, including Pluto, comprise tens of percent of the total mass
whereas the largest CKBOs are only ~2% of its mass. The predicted mass of the
largest Excited body is close to the Pluto mass; the largest CKBO is ~60 times
less massive. The deficit of small TNOs occurs for sizes subject to disruption
by present-day collisions, suggesting extensive depletion by collisions. Both
accretion and erosion appearing to have proceeded to more advanced stages in
the Excited class than the CKB. The absence of distant TNOs implies that any
distant (60 AU) population must have less than the CKB mass in the form of
objects 40 km or larger. The CKB population is sparser than theoretical
estimates of the required precursor population for short period comets, but the
Excited population could be a viable precursor population.


title: Relativistic Wind Bubbles and Afterglow Signatures

abstract:
  Highly magnetized, rapidly rotating compact objects are widely argued as
central energy sources of $\gamma$-ray bursts (GRBs). After the GRB, such a
magnetar-like object may directly lose its rotational energy through some
magnetically-driven processes, which produce an ultrarelativistic wind
dominated possibly by the energy flux of electron-positron pairs. The
interaction of such a wind with an outward-expanding fireball leads to a
relativistic wind bubble, being regarded as a relativistic version of the
well-studied Crab Nebula. We here explore the dynamics of this wind bubble and
its emission signatures. We find that when the injection energy significantly
exceeds the initial energy of the fireball, the bulk Lorentz factor of the wind
bubble decays more slowly than before, and more importantly, the reverse-shock
emission could dominate the afterglow emission, which yields a bump in
afterglow light curves. In addition, high polarization of the bump emission
would be expected if a toroidal magnetic field in the shocked wind dominates
over the random component.


title:
Deep Wide Field BVI CCD Photometry of the Sextans Dwarf Spheroidal
  Galaxy

abstract:
  We present deep wide field $VI$ CCD photometry of the Sextans dwarf
spheroidal galaxy (dSph) in the Local Group, covering a field of 42' x 28'
located at the center of the galaxy. Color-magnitude diagrams of the Sextans
dSph show well-defined red giant branch (RGB), blue horizontal branch (BHB),
prominent red horizontal branch (RHB), asymptotic giant branch (AGB), about 120
variable star candidates including RR Lyraes and anomalous Cepheids, about 230
blue stragglers (BSs), and main sequence (MS) stars. The distance to the galaxy
is derived using the $I$-band magnitude of the tip of the RGB at
I(TRGB)=15.95+/-0.04: (m-M)_0=19.90+/-0.06 for an adopted reddening of
E(B-V)=0.01. The mean metallicity of the RGB is estimated from the (V-I) color:
[Fe/H]=-2.1+/-0.1(statistical error) +/-0.2(standard calibration error) dex,
with a dispersion of sigma[Fe/H]=0.2 dex. The age of the MSTO of the main old
population is estimated to be similar to that of M92, and there are seen some
stellar populations with younger age. There is found to be one RGB bump at
V=19.95+/-0.05 mag (M_V=0.03 mag), and a weak brighter bump at V=19.35+/-0.05
mag(Mv=-0.58 mag) which is probably an AGB bump. The V-band luminosity function
of the RGB and MS stars is in general similar to that of M92, with a slight
excess of stars in the magnitude range brighter than the MSTO with respect to
that of M92. The bright BSs are more centrally concentrated than the faint BSs.
Significant radial gradients are seen for several kinds of populations: the
RHB, the red RGB, the red subgiant branch (SGB), and the bright BSs are more
centrally concentrated toward the center of the galaxy, compared with the BHB,
the blue RGB, the blue SGB, and the faint BSs, respectively.


title:
The Most Likely Sources of High Energy Cosmic-Ray Electrons in Supernova
  Remnants

abstract:
  Evidences of non-thermal X-ray emission and TeV gamma-rays from the supernova
remnants (SNRs) has strengthened the hypothesis that primary Galactic
cosmic-ray electrons are accelerated in SNRs. High energy electrons lose energy
via synchrotron and inverse Compton processes during propagation in the Galaxy.
Due to these radiative losses, TeV electrons liberated from SNRs at distances
larger than ~1 kpc, or times older than ~10^5 yr, cannot reach the solar
system. We investigated the cosmic-ray electron spectrum observed in the solar
system using an analytical method, and considered several candidate sources
among nearby SNRs which may contribute to the high energy electron flux.
Especially, we discuss the effects for the release time from SNRs after the
explosion, as well as the deviation of a source spectrum from a simple
power-law. From this calculation, we found that some nearby sources such as the
Vela, Cygnus Loop, or Monogem could leave unique signatures in the form of
identifiable structure in the energy spectrum of TeV electrons and show
anisotropies towards the sources, depending on when the electrons are liberated
from the remnant. This suggests that, in addition to providing information on
the mechanisms of acceleration and propagation of cosmic-rays, specific
cosmic-ray sources can be identified through the precise electron observation
in the TeV region.


title: Pulse emission mechanisms

abstract:
  High-energy and radio emission mechanisms for pulsars are reviewed. The
source region for high energy emission remains uncertain. Two preferred radio
emission mechanism are identified. Some difficulties may be resolved by
appealing to nonstationary pair creation distributed widely in height.


title:
The Distribution Function of the Phase Sum as a Signature of Phase
  Correlations Induced by Nonlinear Gravitational Clustering

abstract:
  We explore a signature of phase correlations in Fourier modes of dark matter
density fields induced by nonlinear gravitational clustering. We compute the
distribution function of the phase sum of the Fourier modes,
theta_k1+theta_k2+theta_k3, for triangle wavevectors satisfying k1+k2+k3=0, and
compare with the analytic prediction in perturbation theory recently derived by
one of us. Using a series of cosmological N-body simulations, we extensively
examine the time evolution and the dependence on the configuration of triangles
and the sampling volume. Overall we find that the numerical results are
remarkably consistent with the analytic formula from the perturbation theory.
Interestingly the validity of the perturbation theory at a scale k is
determined by P(k)/V_samp, the ratio of the power spectrum P(k) and the
sampling volume V_samp, not by k^3P(k) as in the case of the conventional
cosmological perturbation theory. Consequently this statistics of phase
correlations is sensitive to the size of the sampling volume itself. This
feature does not show up in more conventional cosmological statistics including
the one-point density distribution function and the two-point correlation
functions except as a sample-to-sample variation. Similarly if the sampling
volume size V_samp is fixed, the stronger phase correlation emerges first at
the wavevector where P(k) becomes largest, i.e., in linear regimes according to
the standard cosmological perturbation theory, while the distribution of the
phase sum stays fairly uniform in nonlinear regimes. The above feature can be
naturally understood from the corresponding density structures in real space as
we discuss in detail.


title: 3EG J2027+3429 another Blazar behind the Galactic Plane

abstract:
  We report on the association of an X-ray source (WGA J2025.1+3342),
serendipitously found with BeppoSAX in two separate observations, with the
unidentified EGRET source 3EG J2027+3429. The source is detected from 1 keV up
to about 100 keV, has a flat (0.6-1.5) spectrum and is highly variable both in
intensity and shape. The data indicate marginal evidence for an iron line in
the source rest frame. The overall X-ray luminosity is 4 10^{45} erg s^{-1}
typical of a quasar. The X-ray source is coincident in radio with a bright
object characterized by a flat spectrum over the band 0.3-10 GHz while in
optical it is identified with a quasar at redshift 0.22. All available data
indicate a SED compatible with a low frequency peaked or red blazar type
object. This identification is interesting because this is the second blazar
found behind the galactic plane in the direction of the Cygnus region.


title: Theoretical isochrones for the Delta a photometric system

abstract:
  We have calculated theoretical isochrones for the photometric Delta a system
to derive astrophysical parameters such as the age, reddening and distance
modulus for open clusters. The Delta a system samples the flux depression at
520 nm which is highly efficient to detect chemically peculiar (CP) objects of
the upper main sequence. The evolutionary status of CP stars is still a matter
of debate and very important to test, for example, the dynamo and diffusion
theories. In fact, the dynamo or fossil origin of the magnetic fields present
in this kind of stars it still not clear. Using the stellar evolutionary models
by Claret (1995), a grid of isochrones with different initial chemical
compositions for the Delta a system was generated. The published data of 23
open clusters were used to fit these isochrones with astrophysical parameters
(age, reddening and distance modulus) from the literature. As an additional
test, isochrones with the same parameters for Johnson UBV data of these open
clusters were also considered. The fits show a good agreement between the
observations and the theoretical grid. We find that the accuracy of fitting
isochrones to Delta a data without the knowledge of the cluster parameters is
between 5 and 15%.


title: Signatures of Galaxy Formation in the Intracluster Medium

abstract:
  The intergalactic gas in groups and clusters of galaxies bears the indelible
stamp of galaxy formation. We present a comparison between observations and
simple theoretical models indicating that radiative cooling governs the entropy
scale that sets the core radius of the intracluster medium. Entropy measured at
the radius 0.1 r_200 scales as T^2/3, in accord with cooling-threshold models
for the regulation of core entropy. Cooling of baryons to form galaxies is
likely to lead to feedback, and the signature of feedback may appear farther
out in the cluster. Entropy measured at the radius r_500 in all but the most
massive clusters exceeds the amount that can be generated by hierarchical
accretion. However, feedback that smoothes the density distribution of
accreting baryons, perhaps via galactic winds, can boost entropy production at
the accretion shock by a factor ~ 2-4. An initial comparison of entropy at
r_500 to smooth accretion models shows that smooth accretion is a plausible
explanation for this excess entropy and suggests that baryon accretion onto
groups was smoother than baryon accretion onto clusters.


title: A Molecular Gas Bridge between the Taffy Galaxies

abstract:
  The Taffy Galaxies system, UGC 12914/5, contains huge amounts of molecular
gas in the bridge region between the receding spirals after a direct collision.
$2 - 9 \times 10^9$M$_\odot$ of molecular gas is present between the galaxies,
more than the CO emission from the entire Milky Way! Such dense gas can only be
torn off by collisions between dense clouds, in this case with relative
velocities of about 800 $\kms$, such that the remnant cloud acquires an
intermediate velocity and is left in the bridge after separation of the
colliding galaxies. We suggest that after ionization in the collision front,
the gas cooled and recombined very quickly such that the density remained high
and the gas left the colliding disks in molecular form.


title: A Dedicated M-Dwarf Planet Search Using The Hobby-Eberly Telescope

abstract:
  We present first results of our planet search program using the 9.2 meter
Hobby-Eberly Telescope (HET) at McDonald Observatory to detect planets around
M-type dwarf stars via high-precision radial velocity (RV) measurements.
Although more than 100 extrasolar planets have been found around solar-type
stars of spectral type F to K, there is only a single M-dwarf (GJ 876, Delfosse
et al. 1998; Marcy et al. 1998; Marcy et al. 2001) known to harbor a planetary
system. With the current incompleteness of Doppler surveys with respect to
M-dwarfs, it is not yet possible to decide whether this is due to a fundamental
difference in the formation history and overall frequency of planetary systems
in the low-mass regime of the Hertzsprung-Russell diagram, or simply an
observational bias. Our HET M-dwarf survey plans to survey 100 M-dwarfs in the
next 3 to 4 years with the primary goal to answer this question. Here we
present the results from the first year of the survey which show that our
routine RV-precision for M-dwarfs is 6 m/s. We found that GJ 864 and GJ 913 are
binary systems with yet undetermined periods, while 5 out of 39 M-dwarfs reveal
a high RV-scatter and represent candidates for having short-periodic planetary
companions. For one of them, GJ 436 (rms = 20.6 m/s), we have already obtained
follow-up observations but no periodic signal is present in the RV-data.


title: Status of CMB Polarization Measurements from DASI and Other Experiments

abstract:
  We review the current status and future plans for polarization measurements
of the cosmic microwave background radiation, as well as the cosmology these
measurements will address. After a long period of increasingly sensitive upper
limits, the DASI experiment has detected the E-mode polarization and both the
DASI and WMAP experiments have detected the TE correlation. These detections
provide confirmation of the standard model of adiabatic primordial density
fluctuations consistent with inflationary models. The WMAP TE correlation on
large angular scales provides direct evidence of significant reionization at
higher redshifts than had previously been supposed. These detections mark the
beginning of a new era in CMB measurements and the rich cosmology that can be
gleaned from them.


title: Rotating black hole orbit functionals in the frequency domain

abstract:
  In many astrophysical problems, it is important to understand the behavior of
functions that come from rotating (Kerr) black hole orbits. It can be
particularly useful to work with the frequency domain representation of those
functions, in order to bring out their harmonic dependence upon the fundamental
orbital frequencies of Kerr black holes. Although, as has recently been shown
by W. Schmidt, such a frequency domain representation must exist, the coupled
nature of a black hole orbit's $r$ and $\theta$ motions makes it difficult to
construct such a representation in practice. Combining Schmidt's description
with a clever choice of timelike coordinate suggested by Y. Mino, we have
developed a simple procedure that sidesteps this difficulty. One first Fourier
expands all quantities using Mino's time coordinate $\lambda$. In particular,
the observer's time $t$ is decomposed with $\lambda$. The frequency domain
description is then built from the $\lambda$-Fourier expansion and the
expansion of $t$. We have found this procedure to be quite simple to implement,
and to be applicable to a wide class of functionals. We test the procedure
using a simple test function, and then apply it in a particularly interesting
case, the Weyl curvature scalar $\psi_4$ used in black hole perturbation
theory.


title: A Cluster of Compact Radio Sources in NGC 2024 (Orion B)

abstract:
  We present deep 3.6 cm radio continuum observations of the H II region NGC
2024 in Orion B obtained using the Very Large Array in its A-configuration,
with $0\rlap.{''}2$ angular resolution. We detect a total of 25 compact radio
sources in a region of $4' \times 4'$. We discuss the nature of these sources
and its relation with the infrared and X-ray objects in the region. At least
two of the radio sources are obscured proplyds whose morphology can be used to
restrict the location of the main ionizing source of the region. This cluster
of radio sources is compared with others that have been found in regions of
recent star formation.


title: Noise-Enhanced Parametric Resonance in Perturbed Galaxies

abstract:
  This paper describes how parametric resonances associated with a galactic
potential subjected to relatively low amplitude, strictly periodic
time-dependent perturbations can be impacted by pseudo-random variations in the
pulsation frequency, modeled as coloured noise. One aim thereby is to allow for
the effects of a changing oscillation frequency as the density distribution
associated with a galaxy evolves during violent relaxation. Another is to mimic
the possible effects of internal substructures, satellite galaxies, and or a
high density environment. The principal conclusion is that allowing for a
variable frequency does not vitiate the effects of parametric resonance; and
that, in at least some cases, such variations can increase the overall
importance of parametric resonance associated with systematic pulsations.


title: FUSE Spectra of the Black Hole Binary LMC X-3

abstract:
  Far-ultraviolet spectra of LMC X-3 were taken covering photometric phases
0.47 to 0.74 in the 1.7-day orbital period of the black-hole binary (phase zero
being superior conjunction of the X-ray source). The continuum is faint and
flat, but appears to vary significantly during the observations. Concurrent
RXTE/ASM observations show the system was in its most luminous X-ray state
during the FUSE observations. The FUV spectrum contains strong terrestrial
airglow emission lines, while the only stellar lines clearly present are
emissions from the O VI resonance doublet. Their flux does not change
significantly during the FUSE observations. These lines are modelled as two
asymmetrical profiles, including the local ISM absorptions due to C II and
possibly O VI. Velocity variations of O VI emission are consistent with the
orbital velocity of the black hole and provide a new constraint on its mass.


title: Magnetohydrodynamic Models for the Structure of Pulsar-Wind Nebulae

abstract:
  The Crab Nebula is well-described at optical wavelengths and above by a
steady-state magnetohydrodynamic model due to Kennel and Coroniti (1984). Can
this class of model describe other pulsar-wind nebulae? I exhibit simple
generalizations of KC models,for various values of sigma, the ratio of magnetic
to particle flux input at the wind shock. I calculate the evolution of the
electron spectrum and synchrotron emissivity in the nebula assuming spherical
symmetry, a steady state, and a purely toroidal magnetic field. Emission
profiles depend on the initial magnetic field B_0, the electron spectral index
s, and the angle of the toroidal axis with the line of sight, phi. I show
integrated spectra and radial profiles for various cases, along with predicted
variations of photon index Gamma with radius in X-rays. Most models predict
much smaller sizes in X-rays, and curves of Gamma(r) which do not resemble
observations. Further elaborations of the dynamics of PWNe seem necessary.


title: An Unusual Eclipse of a Pre-Main Sequence Star in IC 348

abstract:
  A solar-like pre-main sequence star (TJ 108 = H 187 = LRLL 35 = HMW 15) in
the extremely young cluster IC 348 has been found, which apparently experienced
an eclipse lasting ~3.5 years, much longer than has ever been detected for any
normal eclipsing binary. The light curve is flat-bottomed and rather symmetric,
with a depth of 0.66 mag in Cousins I. During eclipse, the system reddened by
\~0.17 mag in R-I. We argue that the eclipsing body is not a star because of
the small probability of detecting an eclipse in what would be a very widely
separated binary. Instead, it appears that the eclipse was caused by a
circumstellar or circumbinary cloud or disk feature which occulted the star, or
one of its components, if it is a binary system. We emphasize the importance of
more detailed study of this object, which appears to be a new member of a small
class of pre-main sequence stars whose variability can be firmly linked to
occultation by circumstellar (or circumbinary) matter.


title: Could Black-Hole X-Ray Binaries Be Detected in Globular Clusters?

abstract:
  We consider the implications of the presence of ~1 stellar-mass black hole
(BH) at the center of a dense globular cluster. We show that BH X-ray binaries
formed through exchange interactions are likely to have extremely low duty
cycles (<0.001), consistent with the absence of BH X-ray transients in Galactic
globular clusters. In contrast, we find that BH X-ray binaries formed through
tidal capture would be persistent, bright X-ray sources. Given the absence of
any such source and the very high interaction rates, we conclude that tidal
capture of a main-sequence star by a BH most likely leads to the complete
disruption of the star.


title:
A Search for Nitrogen Enriched Quasars in the Sloan Digital Sky Survey
  Early Data Release

abstract:
  A search for nitrogen-rich quasars in the Sloan Digital Sky Survey Early Data
Release (SDSS EDR) catalog has yielded 16 candidates, including five with very
prominent emission, but no cases with nitrogen emission as strong as in
Q0353-383. The quasar Q0353-383 has long been known to have extremely strong
nitrogen intercombination lines at lambda 1486 and lambda 1750 Angstroms,
implying an anomalously high nitrogen abundance of about 15 times solar. It is
still the only one of its kind known. A preliminary search through the EDR
using the observed property of the weak C IV emission seen in Q0353-383
resulted in a sample of 23 objects with unusual emission or absorption-line
properties, including one very luminous redshift 2.5 star-forming galaxy. We
present descriptions, preliminary emission-line measurements, and spectra for
all the objects discussed here.


title:
Alpha Magnetic Spectrometer (AMS02) experiment on the International
  Space Station (ISS)

abstract:
  The Alpha Magnetic Spectrometer experiment is realized in two phases. A
precursor flight (STS-91) with a reduced experimental configuration (AMS01) has
successfully flown on space shuttle Discovery in June 1998. The final version
(AMS02) will be installed on the International Space Station (ISS) as an
independent module in early 2006 for an operational period of three years. The
main scientific objectives of AMS02 include the searches for the antimatter and
dark matter in cosmic rays. In this work we will discuss the experimental
details as well as the improved physics capabilities of AMS02 on ISS.


title:
On the Nature of Collinder 121: Insights from the Low-Mass Pre-Main
  Sequence

abstract:
  We present a VI photometric catalogue towards the open cluster Cr 121.
XMM-Newton and ROSAT data are used to discover a low-mass pre-main sequence
(PMS) along this sight-line. de Zeeuw et al (1999) identified Cr 121 as a
moving group, using HIPPARCOS data, at a distance of 592 pc. We reject the
scenario that these low-mass PMS stars are associated with that association. By
considering the higher mass main sequence stellar membership of the groups
along this sight-line, the density of low-mass PMS stars and their age spread
we argue that the low-mass PMS stars are associated with a young, compact
cluster at a distance of 1050 pc. This is consistent with the original
description of Cr 121 (Collinder, 1931), and we argue that this distant compact
cluster should retain its original designation. The moving group detected by de
Zeeuw et al (1999) resembles a foreground association and we agree with Eggen
(1981) that this should be called CMa OB2.
  This study demonstrates that although the de Zeeuw et al (1999) census of OB
associations is an invaluable resource for studying local star formation, it
must be interpreted in the context other data when considering structure over
distances of the same order as the limits of the Hipparcos parallaxes.


title: Observational Constraints on Disk Heating as a Function of Hubble Type

abstract:
  Current understanding of the secular evolution of galactic disks suggests
that this process is dominated by two or more heating mechanisms, which
increase the random motions of stars in the disk. In particular, the
gravitational influence of giant molecular clouds and irregularities in the
spiral potential have been proposed to explain the observed velocity
dispersions in the solar neighborhood. Each of these mechanisms acts on
different components of the stellar velocities, which affects the ratio of the
vertical and radial components of the stellar velocity dispersion since the
relative strengths of giant molecular clouds and spiral irregularities vary
with Hubble type. A study of this ratio as function of Hubble type has the
potential to provide strong constraints on disk heating mechanisms. We present
major and minor axis stellar kinematics for four spiral galaxies of Hubble type
from Sa to Sbc, and use the data to infer the ratios sigma_z/sigma_R in the
galaxy disks. The results combined with two galaxies studied previously and
with Milky Way data show that the ratio is generally in the range 0.5 - 0.8.
There is a marginally significant trend of decreasing ratio with advancing
Hubble type, consistent with the predictions of disk heating theories. However,
the errors on individual measurements are large, and the absence of any trend
is consistent with the data at the 1-sigma level. As a byproduct of our study,
we find that three of the four galaxies in our sample have a central drop in
their stellar line-of-sight velocity dispersion, a phenomenon that is
increasingly observed in spiral galaxies. [ABRIDGED]


title: GRO J0422+32: The Lowest Mass Black Hole?

abstract:
  We have obtained optical and infrared photometry of the soft X-ray transient
GRO J0422+32. From this photometry, we find a secondary star spectral type of
M1, and an extinction of Av = 0.74 +/- 0.09. We present the first observed
infrared (J-, H-, and K-band) ellipsoidal variations, and model them with WD98,
a recent version of the Wilson-Devinney light curve modeling code. Assuming no
significant contamination of the infrared light curves, we find a lower limit
to the inclination angle of 43 degrees corresponding to an upper limit on the
mass of the compact object of 4.92 M_sun. Combining the models with the
observed spectral energy distribution of the system, the most likely value for
the orbital inclination angle is 45 +/- 2 degrees. This inclination angle
corresponds to a primary black hole mass of 3.97 +/- 0.95 M_sun. Thus we
contend that J0422+32 contains the lowest mass stellar black hole reported, and
the first to have a measured mass that falls in the 3 - 5 M_sun range.


title: Model-independent measurements of bar pattern speeds

abstract:
  The pattern speed in one of the fundamental parameters that determines the
structure of barred galaxies. This quantity is usually derived from indirect
methods or by employing model assumptions. The number of bar pattern speeds
derived using the model independent Tremaine and Weinberg technique is still
very limited. We present the results of model independent measurements of the
bar pattern speed in four galaxies ranging in Hubble type from SB0 to SBbc.
Three of the four galaxies in our sample are consistent with bars being fast
rotators. The lack of slow bars is consistent with previous observations and
suggests that barred galaxies do not have centrally concentrated dark matter
halos. This contradicts simulations of cosmological structure formation and
observations of the central mass concentration in nonbarred galaxies.


title: Chandra Multi-wavelength Project (ChaMP). I. First X-ray Source Catalog

abstract:
  The Chandra Multi-wavelength Project (ChaMP) is a wide-area (~14 deg^2)
survey of serendipitous Chandra X-ray sources, aiming to establish fair
statistical samples covering a wide range of characteristics (such as absorbed
AGNs, high z clusters of galaxies) at flux levels (fX ~ 10^-15 - 10^-14 erg
sec-1 cm-2) intermediate between the Chandra Deep surveys and previous
missions. We present the first ChaMP catalog, which consists of 991 near
on-axis, bright X-ray sources obtained from the initial sample of 62
observations. The data have been uniformly reduced and analyzed with techniques
specifically developed for the ChaMP and then validated by visual examination.
To assess source reliability and positional uncertainty, we perform a series of
simulations and also use Chandra data to complement the simulation study. The
false source detection rate is found to be as good as or better than expected
for a given limiting threshold. On the other hand, the chance of missing a real
source is rather complex, depending on the source counts, off-axis distance (or
PSF), and background rate. The positional error (95% confidence level) is
usually < 1" for a bright source, regardless of its off-axis distance while it
can be as large as 4" for a weak source (~20 counts) at a large off-axis
distance (Doff-axis > 8'). We have also developed new methods to find spatially
extended or temporary variable sources and those sources are listed in the
catalog.


title:
Chandra Multi-wavelength Project (ChaMP). II. First Results of X-ray
  Source Properties

abstract:
  We present the first results of ChaMP X-ray source properties obtained from
the initial sample of 62 observations. The data have been uniformly reduced and
analyzed with techniques specifically developed for the ChaMP and then
validated by visual examination. Utilizing only near on-axis, bright X-ray
sources (to avoid problems caused by incompleteness and the Eddington bias), we
derive the Log(N)-Log(S) relation in soft (0.5-2 keV) and hard (2-8 keV) energy
bands. The ChaMP data are consistent with previous results of ROSAT, ASCA and
Chandra deep surveys. In particular, our data nicely fill in the flux gap in
the hard band between the Chandra Deep Field data and the previous ASCA data.
We check whether there is any systematic difference in the source density
between cluster and non-cluster fields and also search for field-to-field
variations, both of which have been previously reported. We found no
significant field-to-field cosmic variation in either test within the
statistics (~1 sigma) across the flux levels included in our sample. In the
X-ray color-color plot, most sources fall in the location characterized by
photon index = 1.5-2 and NH = a few x 10^20 cm^2, suggesting that they are
typical broad-line AGNs. There also exist a considerable number of sources with
peculiar X-ray colors (e.g., highly absorbed, very hard, very soft). We confirm
a trend that on average the X-ray color hardens as the count rate decreases.
Since the hardening is confined to the softest energy band (0.3-0.9 keV), we
conclude it is most likely due to absorption. We cross-correlate the X-ray
sources with other catalogs and describe their properties in terms of optical
color, X-ray-to-optical luminosity ratio and X-ray colors.


title: The Anisotropy Search Program For the Pierre Auger Observatory

abstract:
  The Pierre Auger Southern Observatory in Argentina has begun taking data as
it is being developed up to a final enclosed area of 3000 square kilometres. A
key aspect of the project is to provide information on the origin of the
highest energy cosmic rays through understanding the arrival directions of
those particles. To avoid claims of a spurious anisotropy detection because
trials have not been properly accounted, the Auger Collaboration has agreed 'a
priori' to the analysis prescription presented here. It specifies the
following:
  1. The accumulation time for the (future) data set to be analyzed.
  2. The anisotropy 'targets', each assigned a chance probability level.
  3. The analysis procedure for each trial.
  A positive result will be claimed for any target search only if its chance
probability is less than its assigned level. The levels are chosen so that the
total chance probability for one or more positive results is 0.001.
  Exploratory searches beyond this prescription will be encouraged, but the
Auger Collaboration will not assign any confidence level to anisotropies that
may be discovered that way. Any such discovery would identify a good target for
a prescription to be used with a subsequent Auger data set.


title:
ASCA and RXTE Observations of Non-Thermal X-ray Emission from Galactic
  Supernova Remnants: G156.2+5.7

abstract:
  (Abridged) We are conducting a survey of Galactic shell-type supernova
remnants (SNRs) known or suspected to possess non-thermal components to their
X-ray emission using new and archived observations made with such X-ray
satellites as ROSAT, ASCA, RXTE, Chandra and XMM-Newton. This research is
intended to probe the phenomenon of cosmic-ray acceleration by Galactic SNRs
and estimate the maximum energy of cosmic-ray electrons accelerated by these
sources. To illustrate this work, we examine the X-ray spectrum of the
northwestern rim of an SNR suspected to have a non-thermal component to its
X-ray emission, G156.2+5.7 (RX J04591+5147), over the energy range of
approximately 0.7-12.0 keV using observations made by the ASCA GIS and the RXTE
PCA. We compare fits made to the non-thermal component using two models, a
simple power law and SRCUT. Both models give acceptable fits: the photon index
derived from the fit made with the power law model, 2.0 (+0.2, -0.5), is
comparable to values obtained for the bright rims of other SNRs with hard X-ray
spectra. Using the SRCUT model, we derive a value of 2.42 (+0.24, -0.23) x
10^17 Hz for the cutoff frequency: based on this value and assuming a mean
magnetic field strength of 14 microGauss, we estimate the cutoff energy of
cosmic-ray electrons accelerated by G156.2+5.7 to be approximately 32 TeV. This
energy value is well short of the "knee" feature of the cosmic-ray spectrum.


title:
An Adaptive Optics Survey of M6.0-M7.5 Stars: Discovery of Three Very
  Low Mass Binary Systems Including Two Probable Hyades Members

abstract:
  A survey of 30 nearby M6.0-M7.5 dwarfs with Ks<12 mag utilizing the Hokupa'a
adaptive optics system at the Gemini North Telescope has discovered 3 new
binary systems. All 3 systems have separations between 0.12-0.29 arcsec (3-10
AU) with similar mass ratios (q>0.8, Delta Ks<0.7). This result gives further
support to the suggestion that wide (a>20 AU) very low mass (M_{tot}<0.185
M_sun) binary systems are exceedingly rare or perhaps even non-existant. The
semimajor axis distribution of these systems peaks at ~5 AU, tighter than more
massive M and G binary distributions which have a broad peak at separations of
\~30 AU. We find a sensitivity-corrected binary fraction in the range of
5_{-2}^{+4}% for M6.0-M7.5 stars with separations a>3 AU. This binary frequency
is less than the ~32% measured among early M dwarfs over the same separation
range. Two of the low-mass binaries are probable Hyades open cluster members
based on proper motions, cluster membership probabilities, radial velocities,
and near-IR photometry. LP415-20 has the distinction of being the tightest (3.6
AU) multiple system ever spatially resolved in the cluster and the companions
of LP415-20 and LP475-855 are among the least massive objects ever resolved in
the Hyades with estimated masses of 0.081_{-0.010}^{+0.009} and
0.082_{-0.009}^{+0.009} M_{\sun}.


title: How to SYN in seven easy steps

abstract:
  The calculation of expected spectral line strengths and profiles is a
powerful tool for the analysis of the solar atmosphere, and other stellar
atmospheres. We present here a recipe in seven easy steps for the development
of such spectral synthesis software.


title: Can homogeneous extra dimensions be stabilized during matter domination?

abstract:
  We investigate cosmologies with homogeneous extra dimensions that can be
described by generalised Friedmann-Robertson-Walker metrics and give a brief
review on a general setup to describe a broad range of standard stabilization
and compactification mechanisms. These mechanisms allow for solutions to the
field equations with static extra dimensions if the universe is dominated by
radiation or an approximately constant energy-momentum tensor, as for example
due to a cosmological constant. During matter domination, however, there are no
static solutions for the extra dimensions and we therefore conclude that in
this setup it is not possible to construct stabilization mechanisms for the
whole evolution history of the universe. We furthermore show in detail that the
two possible approaches of discussing either the higher-dimensional field
equations directly or the dimensionally reduced and conformally transformed
theory, are exactly equivalent and thus lead to the same conclusions. Finally,
we indicate a possible way out of these difficulties.


title: Gravitational clustering in Static and Expanding Backgrounds

abstract:
  A brief summary of several topics in the study of gravitational many body
problem is given. The discussion covers both static backgrounds (applicable to
astrophysical systems) as well as clustering in an expanding background
(relevant for cosmology)


title:
Magnetic Fields and Ionized Gas in the Local Group Irregular Galaxies
  IC10 and NGC6822

abstract:
  We performed a high-sensitivity search for galaxy-scale magnetic fields by
radio polarimetry at 10.45GHz and 4.85GHz with the Effelsberg 100m radio
telescope, accompanied by Halpha imaging, for the two Local Group irregular
galaxies IC10 and NGC6822. Their star-forming bodies are small and rotate
slowly. IC10 is known to have a very high star-forming activity, resembling
blue compact dwarfs, while NGC6822 has a low overall star-formation level.
Despite very different current star formation rates, our Halpha imaging
revealed a large web of diffuse Halpha filaments and shells in both IC10 and
NGC6822. Some of them extend far away from the galaxy's main body. The total
power emission of both objects shows bright peaks either at the positions of
optically strong star-forming clumps (IC10) or individual HII regions or
supernova remnants (NGC6822). However, in both cases we detect a smoothly
distributed, extended component. In IC10 we found clear evidence for the
presence of a diffuse, mostly random magnetic field of ~14muG strength,
probably generated by a fluctuation dynamo. One of the Halpha-emitting
filaments appears to be associated with enhanced magnetic fields. We also
rediscuss the reddening of IC10 and its implications for its distance. In the
case of NGC6822 we found only very weak evidence for nonthermal emission,
except perhaps for some regions associated with local gas compression. We
detect in both galaxies small spots of polarized emission, indicative of
regular fields (~3muG), at least partly associated with local compressional
phenomena.


title: The Galactic population and birth rate of radio pulsars

abstract:
  We review current understanding of the underlying, as opposed to the
observed, pulsar population. The observed sample is heavily biased by selection
effects, so that surveys see less than 10% of all potentially observable
pulsars. We compare various techniques used to correct the sample for these
biases. By far the most significant recent development has been the discovery
of over 700 pulsars in the Parkes Multibeam (PM) survey. This new sample is far
less affected by selection effects and we use it to make a preliminary analysis
of the Galactic pulsar distribution, finding further evidence for a deficit of
pulsars in the inner Galaxy.


title:
On the filling factor of emitting material in the upper atmosphere of
  Epsilon Eri (K2 V)

abstract:
  The emission measure distribution in the upper transition region and corona
of Epsilon Eri is derived from observed emission line fluxes. Theoretical
emission measure distributions are calculated assuming that the radiation
losses are balanced by the net conductive flux. We discuss how the area factor
of the emitting regions as a function of temperature can be derived from a
comparison between these emission measure distributions. It is found that the
filling factor varies from ~0.2 in the mid transition region to ~1.0 in the
inner corona. The sensitivity of these results to the adopted ion fractions,
the iron abundance and other parameters is discussed. The area factors found
are qualitatively similar to the observed structure of the solar atmosphere,
and can be used to constrain two-component models of the chromosphere. Given
further observations, the method could be applied to investigate the trends in
filling factors with indicators of stellar activity.


title:
A Spontaneous Generation of the Magnetic Field and Suppression of the
  Heat Conduction in Cold Fronts

abstract:
  We have determined the physical mechanism responsible for the plasma
instabilities, which was first found by Ramani and Laval (1978), associated
with anisotropic velocity distributions induced by the temperature gradient in
which there are growing low frequency transverse magnetic waves, even in the
absence of background magnetic fields. We have shown that the physical
mechanism responsible for the growth of one of the modes is identical to the
Weibel instability. The nonlinear saturation level of the instability is also
provided by considering the wave-particle interactions. The non-linear
evolutions of the magnetic fields after the saturation are speculated. The
results are applied to the cold fronts which is one of the newly discovered
structures in clusters of galaxies by the Chandra X-ray observatory. We predict
the existence of the magnetic field of $\sim 10\mu$G tangential to the surface
over the entire region of the cold front surface and that the heat conduction
is significantly suppressed by the trapping of the electrons by the generated
magnetic fields. The instability may provide a new possibility on the origin of
cosmic magnetic field.


title: INTEGRAL/SPI ground calibration

abstract:
  Three calibration campaigns of the spectrometer SPI have been performed
before launch in order to determine the instrument characteristics, such as the
effective detection area, the spectral resolution and the angular resolution.
Absolute determination of the effective area has been obtained from simulations
and measurements. At 1 MeV, the effective area is 65 cm^2 for a point source on
the optical axis, the spectral resolution ~2.3 keV. The angular resolution is
better than 2.5 deg and the source separation capability about 1 deg. Some
temperature dependant parameters will require permanent in-flight calibration.


title: The frequency-dependence of drifting subpulse patterns

abstract:
  Drifting subpulse patterns in pulsar signals are frequently interpreted in
terms of a model in which a rotating ring of sparks on the polar cap gives rise
to emission from regions of the magnetsophere connected to the sparks by
dipolar magnetic field lines. The spacing of drift-bands in time depends on the
circulation rate of the polar cap pattern, but to first order the longitudinal
phase dependence of the subpulse modulation should obey a frequency-independent
relation determined by the geometrical configuration in a similar manner to the
polarization position angle. We present here observations at 272-1380 MHz of
PSR B0320+39 and PSR B0809+74, both of which show nearly linear drift in two
longitude regions, separated by a region of reduced modulation and accompanied
by a large step in the phase of the subpulse pattern. We show that the
observation of Bartel et al. (1981) that the subpulse spacing for PSR B0809+74
was 1.8 times greater at 102.5 MHz than at 1720 MHz is most likely an artifact
of the phase step, which is only present at high frequencies. The phase steps
can be understood as a consequence of observing overlapping offset images of
the polar cap spark pattern. We also detected more complicated,
frequency-dependent behaviour that would require that the images do not simply
differ by rotation about their centers. Detailed modelling of non-axisymmetric
refraction or distorted magnetic fields is suggested as a means of pursuing an
explanation for this phenomenon.


title:
The Chandra Multiwavelength Project: Optical Followup of Serendipitous
  Chandra Sources

abstract:
  We present followup optical g', r', and i', imaging and spectroscopy of
serendipitous X-ray sources detected in 6 archival Chandra, images included in
the Chandra, Multiwavelength Project (ChaMP). Of the 486 X-ray sources detected
between 3e-16 and 2e-13 (with a median flux of 3e-15 erg cm-2 s-1, we find
optical counterparts for 377 (78%), or 335 (68%) counting only unique
counterparts. We present spectroscopic classifications for 125 objects,
representing 75% of sources with r<21 optical counterparts (63% to r=22). Of
all classified objects, 63 (50%) are broad line AGN, which tend to be blue in
g-r colors. X-ray information efficiently segregates these quasars from stars,
which otherwise strongly overlap in these SDSS colors until z>3.5. We identify
28 sources (22%) as galaxies that show narrow emission lines, while 22 (18%)
are absorption line galaxies. Eight galaxies lacking broad line emission have
X-ray luminosities that require they host an AGN (logL_X>43). Half of these
have hard X-ray emission suggesting that high gas columns obscure both the
X-ray continuum and the broad emission line regions. We find objects in our
sample that show signs of X-ray or optical absorption, or both, but with no
strong evidence that these properties are coupled. ChaMP's deep X-ray and
optical imaging enable multiband selection of small and/or high-redshift groups
and clusters. In these 6 fields we have discovered 3 new clusters of galaxies,
two with z>0.4, and one with photometric evidence that it is at a similar
redshift.


title: Inertial modes of non-stratified superfluid neutron stars

abstract:
  We present results concerning adiabatic inertial-mode oscillations of
non-stratified superfluid neutron stars in Newtonian gravity, using the
anelastic and slow-rotation approximations. We consider a simple two-fluid
model of a superfluid neutron star, where one fluid consists of the superfluid
neutrons and the second fluid contains all the comoving constituents (protons,
electrons). The two fluids are assumed to be ``free'' in the sense that
vortex-mediated forces like mutual friction or pinning are absent, but they can
be coupled by the equation of state, in particular by entrainment. The
stationary background consists of the two fluids rotating uniformly around the
same axis with potentially different rotation rates. We study the special cases
of co-rotating backgrounds, vanishing entrainment, and the purely toroidal
r-modes, analytically. We calculate numerically the eigenfunctions and
frequencies of inertial modes in the general case of non co-rotating
backgrounds, and study their dependence on the relative rotation rate and
entrainment. In these non-stratified models we find avoided crossings only
between associated mode-pairs, eg. an ``ordinary'' mode and its ``superfluid''
counterpart, while other mode-frequencies generally cross as the background
parameters are varied. We confirm (for the first time in a mode calculation)
the onset of a ``two-stream instability'' at a critical relative background
rotation rate, and study some of the properties of this instability for the
inertial modes.


title: Continuum and Emission-Line Properties of Broad Absorption Line Quasars

abstract:
  We investigate the continuum and emission-line properties of 224 broad
absorption line quasars (BALQSOs) with 0.9<z<4.4 drawn from the Sloan Digital
Sky Survey (SDSS) Early Data Release (EDR), which contains 3814 bona fide
quasars. We find that low-ionization BALQSOs (LoBALs) are significantly
reddened as compared to normal quasars, in agreement with previous work.
High-ionization BALQSOs (HiBALs) are also more reddened than the average
nonBALQSO. Assuming SMC-like dust reddening at the quasar redshift, the amount
of reddening needed to explain HiBALs is E(B-V)~0.023 and LoBALs is
E(B-V)~0.077 (compared to the ensemble average of the entire quasar sample). We
find that there are differences in the emission-line properties between the
average HiBAL, LoBAL, and nonBAL quasar. These differences, along with
differences in the absorption line troughs, may be related to intrinsic quasar
properties such as the slope of the intrinsic (unreddened) continuum; more
extreme absorption properties are correlated with bluer intrinsic continua.
Despite the differences among BALQSO sub-types and nonBALQSOs, BALQSOs appear
to be drawn from the same parent population as nonBALQSOs when both are
selected by their UV/optical properties. We find that the overall fraction of
traditionally defined BALQSOs, after correcting for color-dependent selection
effects due to different SEDs of BALQSO and nonBALQSOs, is 13.4+/-1.2% and
shows no significant redshift dependence for 1.7<z<3.45. After a rough
completeness correction for the effects of dust extinction, we find that
approximately one in every six quasars is a BALQSO.


title: The UV Upturn: From M32 to Distant Clusters

abstract:
  I review the observational constraints on the stars responsible for the
upturn in the UV spectra of ellipticals, ranging from galaxies in the local
Universe to distant clusters. In nearby galaxies, this UV upturn is produced by
a minority population of extreme horizontal branch (EHB) stars, with the large
variations observed in the UV-to-optical flux ratio driven by variations in the
number of EHB stars, and not the type of UV-bright stars. Deep UV images of the
nearest elliptical galaxy, M32, show that it has a well-populated EHB, even
though it has the weakest UV upturn of any known elliptical galaxy. However,
M32 suffers from a striking dearth of the hot post-HB stars expected from
canonical evolutionary theory. As we observe to larger lookback times in more
distant galaxy clusters, the UV upturn fades, as predicted by theories of
stellar and galactic evolution, but does so gradually. Because the EHB stars do
not appear suddenly in the Universe, their presence is likely driven by a large
dispersion in the parameters that govern HB morphology.


title:
NEXXUS: A comprehensive ROSAT survey of coronal X-ray emission among
  nearby solar-like stars

abstract:
  We present a final summary of all ROSAT X-ray observations of nearby stars.
All available ROSAT observations with the ROSAT PSPC, HRI and WFC have been
matched with the CNS4 catalog of nearby stars and the results gathered in the
Nearby X-ray and XUV-emitting Stars data base, available via www from the Home
Page of the Hamburger Sternwarte at
http://www.hs.uni-hamburg.de/DE/For/Gal/Xgroup/nexxus. New volume-limited
samples of F/G-stars (d_lim = 14 pc), K-stars (d_lim = 12 pc), and M-stars
(d_lim = 6 pc) are constructed within which detection rates of more than 90 %
are obtained; only one star (GJ 1002) remains undetected in a pointed follow-up
observation. F/G-stars, K-stars and M-stars have indistinguishable surface
X-ray flux distributions, and the lower envelope of the observed distribution
at F_X \approx 10^4 erg/cm^2/sec is the X-ray flux level observed in solar
coronal holes. Large amplitude variations in X-ray flux are uncommon for
solar-like stars, but maybe more common for stars near the bottom of the main
sequence; a large amplitude flare is reported for the M star LHS 288. Long term
X-ray light curves are presented for Alpha Cen A/B and Gl~86, showing
variations on time scales of weeks and demonstrating that Alpha Cen B is a
flare star.


title: Primordial Nucleosynthesis

abstract:
  The primordial abundances of deuterium, helium-3, helium-4, and lithium-7
probe the baryon density of the Universe only a few minutes after the Big Bang.
Of these relics from the early Universe, deuterium is the baryometer of choice.
After reviewing the current observational status of the relic abundances (a
moving target!), the baryon density determined by big bang nucleosynthesis
(BBN) is derived. The temperature fluctuation spectrum of the cosmic background
radiation (CBR), established several hundred thousand years later, probes the
baryon density at a completely different epoch in the evolution of the
Universe. The excellent agreement between the BBN- and CBR-determined baryon
densities provides impressive confirmation of the standard model of cosmology,
permitting the study of extensions of the standard model. In combination with
the BBN- and/or CBR-determined baryon density, the relic abundance of 4He
provides an excellent chronometer, constraining those extensions of the
standard model which lead to a nonstandard early-Universe expansion rate.


title:
Hybrid Performance of the Pierre Auger Observatory and Reconstruction of
  Hybrid Events

abstract:
  The Pierre Auger Observatory is a``hybrid'' UHECR detector. The surface
detector (SD) and air fluorescence detector (FD) of the observatory are
designed for observation of cosmic ray showers in coincidence, with a 10% duty
cycle. The resulting data are expected to be superior in quality to those of
either the SD or FD operating individually. Hybrid operation, triggering, data
acquisition, and event reconstruction were successfully demonstrated during the
prototype phase of the project. This paper focuses on 75 hybrid events recorded
during a four month period of running with the prototype detectors in late 2001
and early 2002. The geometric technique for reconstruction of the hybrid events
is described and its advantages over the traditional FD-only method are
demonstrated. A lateral distribution for the water Cherenkov signals, derived
from these data, is presented.


title:
Interferometer Observations of Subparsec-scale Infrared Emission in the
  Nucleus of NGC 4151

abstract:
  We report novel, high-angular resolution interferometric measurements that
imply the near-infrared nuclear emission in NGC 4151 is unexpectedly compact.
We have observed the nucleus of NGC 4151 at 2.2 microns using the two 10-meter
Keck telescopes as an interferometer and find a marginally resolved source ~0.1
pc in diameter. Our measurements rule out models in which a majority of the K
band nuclear emission is produced on scales larger than this size. The
interpretation of our measurement most consistent with other observations is
that the emission mainly originates directly in the central accretion disk.
This implies that AGN unification models invoking hot, optically thick dust may
not be applicable to NGC 4151.


title:
The mass spectrum of metal-free Stars resulting from photodissociation
  feedback: A scenario for the formation of low-mass population III stars

abstract:
  The initial mass function (IMF) of metal-free stars that form in the initial
starburst of massive (virial temperatures >10^4K) metal-free protogalaxies is
studied. In particular, we focus on the effect of H2 photodissociation by
pre-existing stars on the fragmentation mass scale, presumedly determined by
the Jeans mass at the end of the initial free-fall phase, i.e., at the
so-called ``loitering phase,'' characterized by the local temperature minimum.
Photodissociation diminishes the Jeans mass at the loitering phase, thereby
reducing the fragmentation mass scale of primordial clouds. Thus, in a given
cloud, far ultraviolet (FUV) radiation from the first star, which is supposedly
very massive (about 10^3Msun), reduces the mass scale for subsequent
fragmentation. Through a series of similar processes the IMF for metal-free
stars is established. If FUV radiation exceeds a threshold level, the
star-forming clumps collapse solely through atomic cooling. Correspondingly,
the fragmentation scale drops discontinuously from a few time 10Msun to
sub-solar scales. In compact clouds (>1.6kpc for clouds of gas mass 10^8Msun),
this level of radiation field is attained, and sub-solar mass stars are formed
even in a metal-free environment. Consequently, the IMF becomes bi-modal, with
peaks at a few tenths of Msun and a few times 10Msun. The high-mass portion of
the IMF is found to be a very steep function of the stellar mass, xi_high(m)
being proportinal to m^{-5}. Therefore, the typical mass scale of metal-free
stars is significantly smaller than that of the very first stars. Also we study
the thermal instability in collapsing primordial prestellar clumps, and discuss
why the thermal instability occuring during the three-body H2 formation does
not appear to manifest itself in causing further fragmentation of such clumps.


title: Quintessence From The Decay of a Superheavy Dark Matter

abstract:
  We investigate the possibility of replacing the cosmological constant with
gradual condensation of a scalar field produced during the decay of a
superheavy dark matter. The advantage of this class of models to the ordinary
quintessence is that the evolution of the dark energy and the dark energy are
correlated and cosmological coincidence problem is solved. This model does not
need a special form for the quitessence potential and even a simple ${\phi}^4$
theory or an axion like scalar is enough to explain the existence of the Dark
Energy. We show that the model has an intrinsic feedback between energy density
of the dark matter and the scalar field such that for a large volume of the
parameter space the equation of state of the scalar field from very early in
the history of the Universe is very close to a cosmological constant. Other
aspects of this model are consistent with recent CMB and LSS observations.


title: Parallax and Distance Estimates for Fourteen Cataclysmic Variable Stars

abstract:
  I used the 2.4 m Hiltner telescope at MDM Observatory in an attempt to
measure trigonometric parallaxes for 14 cataclysmic variable stars. Techniques
are described in detail. In the best cases the parallax uncertainties are below
1 mas, and significant parallaxes are found for most of the program stars. A
Bayesian method which combines the parallaxes together with proper motions and
absolute magnitude constraints is developed and used to derive distance
estimates and confidence intervals. The most precise distance derived here is
for WZ Sge, for which I find 43.3 (+1.6, -1.5) pc. Six Luyten Half-Second stars
with previous precise parallax measurements were re-measured to test the
techniques, and good agreement is found.


title: Evidence for Flash Mixing in He-rich sdB Stars

abstract:
  We present FUSE spectra of three He-rich sdB stars. Two of these stars,
PG1544+488 and JL87, reveal extremely strong C III lines, suggesting that they
have mixed triple-alpha carbon from the deep interior out to their surfaces.
Using TLUSTY NLTE line-blanketed model atmospheres, we find that PG1544+488 has
a surface composition of 96% He, 2% C, and 1% N. JL87 shows a similar surface
enrichment of C and N but still retains a significant amount of hydrogen. In
contrast, the third star, LB1766, is devoid of hydrogen and strongly depleted
of carbon, indicating that its surface material has undergone CN-cycle
processing. We interpret these observations with new evolutionary calculations
which suggest that He-rich sdB stars with C-rich compositions arise from a
delayed helium-core flash on the white-dwarf cooling curve. During such a flash
the interior convection zone will penetrate into the stellar envelope, thereby
mixing the envelope with the He- and C-rich core. Such "flash-mixed" stars will
arrive on the extreme horizontal branch (EHB) with He- and C-rich surface
compositions and will be hotter than the hottest canonical EHB stars. Two types
of flash mixing are possible: "deep" and "shallow", depending on whether the
hydrogen envelope is mixed deeply into the site of the helium flash or only
with the outer layers of the core. Based on both their stellar parameters and
surface compositions, we suggest that PG1544+488 and JL87 are examples of
"deep" and "shallow" flash mixing, respectively.


title: A Dearth of Dark Matter in Ordinary Elliptical Galaxies

abstract:
  The kinematics of the outer parts of three intermediate-luminosity elliptical
galaxies have been studied using the Planetary Nebula Spectrograph. The
galaxies' velocity dispersion profiles are found to decline with radius;
dynamical modeling of the data indicates the presence of little if any dark
matter in these galaxies' halos. This surprising result conflicts with findings
in other galaxy types, and poses a challenge to current galaxy formation
theories.


title: The Dark Side of the Halo Occupation Distribution

abstract:
  We analyze the halo occupation distribution (HOD), the probability for a halo
of mass M to host a number of subhalos N, and two-point correlation function of
galaxy-size dark matter halos using high-resolution dissipationless simulations
of the concordance flat LCDM model. The halo samples include both the host
halos and the subhalos, distinct gravitationally-bound halos within the
virialized regions of larger host systems. We find that the first moment of the
HOD, <N>(M), has a complicated shape consisting of a step, a shoulder, and a
power law high-mass tail. The HOD can be described by a Poisson statistics at
high halo masses but becomes sub-Poisson for <N><4. We show that the HOD can be
understood as a combination of the probability for a halo of mass M to host a
central galaxy and the probability to host a given number Ns of satellite
galaxies. The former can be approximated by a step-like function, while the
latter can be well approximated by a Poisson distribution, fully specified by
its first moment <Ns>(M). We find that <Ns>~M^b with b~1 for a wide range of
number densities, redshifts, and different power spectrum normalizations. This
formulation provides a simple but accurate model for the halo occupation
distribution found in simulations. At z=0, the two-point correlation function
(CF) of galactic halos can be well fit by a power law down to ~100/h kpc with
an amplitude and slope similar to those of observed galaxies. At redshifts
z>~1, we find significant departures from the power-law shape of the CF at
small scales. If the deviations are as strong as indicated by our results, the
assumption of the single power law often used in observational analyses of
high-redshift clustering is likely to bias the estimates of the correlation
length and slope of the correlation function.


title: The Nature of Near-UV Selected Objects in the Chandra Deep Field South

abstract:
  We present the first results of the pure parallel near-UV observations with
WFPC2 in the Chandra Deep Field South. The main goal is to search for the
population of objects that contribute to the rise in the volume-averaged star
formation rate at intermediate redshifts (z<1). A total of 34 objects, were
identified in the WFPC2 images and their counterparts found in the ACS GOODS
images. We use template fitting of the spectral energy distributions to
classify the objects and found that 17 are starbursts, 9 are late-type, 2 are
early-type galaxies, and 6 are stars; two of the late-types and one of the
starbursts are X-ray sources. The colors of the starbursts were reproduced by
the stellar evolutionary synthesis code Starburst99 which shows a mixed
population of bursts with ages < 1 Gyr. Analysis of the light concentration,
asymmetry and clumpiness, shows that this sample is a mixed bag, containing
dwarf ellipticals, early and late-spirals and peculiar objects which resemble
mergers in progress.


title:
A Spectroscopic Technique for Measuring Stellar Properties of Pre-Main
  Sequence Stars

abstract:
  We describe a technique for deriving effective temperatures, surface
gravities, rotation velocities, and radial velocities from high resolution
near-IR spectra. The technique matches the observed near-IR spectra to spectra
synthesized from model atmospheres. For pre-main sequence stars, we use the
same matching process to also measure the amount of excess near-IR emission.
The information derived from high resolution spectra comes from line shapes and
the relative line strengths of closely spaced lines. The values for the stellar
parameters we derive are therefore independent of those derived from low
resolution spectroscopy and photometry. The new method offers the promise of
improved accuracy in placing young stellar objects on evolutionary model
tracks. We discuss the possible systematic effects on our determination of the
stellar parameters and evaluate the accuracy of the results derivable from high
resolution spectra. The analysis of high resolution near-IR spectra of MK
standards shows that the technique gives very accurate values for the effective
temperature. The biggest uncertainty in comparing our results with optical
spectral typing of MK standards is in the spectral type to effective
temperature conversion for the standards themselves. Even including this
uncertainty, the 1 sigma difference between the optical and IR temperatures for
3000-5800 K dwarfs is only 140 K. In a companion paper (Doppmann, Jaffe, &
White 2003), we present an analysis of heavily extincted young stellar objects
rho Oph.


title:
Stellar Properties of Pre-Main Sequence Stars from High Resolution
  Near-IR Spectra

abstract:
  We present high resolution (R=50,000) spectra at 2.2 um of 16 young stars in
the rho Ophiuchi dark cloud. Photospheric features are detected in the spectra
of 11 of these sources, all Class II young stellar objects. In 10 of these
sources, we measure effective temperatures, continuum veiling, and vsini
rotation from the shapes and strengths of atomic photospheric lines by
comparing to spectral synthesis models at 2.2 um. We measure surface gravities
in 2 stars from the integrated line flux ratio of the 12CO line region at 2.3
um and the Na I line region at 2.2 um. Although the majority (8/10) of the
Class II stars have similar effective temperatures (3530 K +/-100 K), they
exhibit a large spread in bolometric luminosities (factor ~8), as derived from
near-IR photometry. In the two stars where we have surface gravity measurements
from spectroscopy, the photometrically derived luminosities are systematically
higher than the spectroscopic luminosities. Our spectroscopic luminosities
result in older ages on the H-R diagram than is suggested by photometry at J or
K. Most of our sources show a substantially larger amount of continuum excess
than stellar flux at 2.2 um. The derived veiling values at K appear correlated
with mid-IR disk luminosity, and with Brackett gamma equivalent width,
corrected for veiling. The derived vsini rotation is substantial (12-39 km
s-1), but systematically less than the rotation measured in Class I.5 (flat)
and Class I sources from other studies in Ophiuchus.


title: A Study Of Very Inclined Showers In The Pierre Auger Observatory

abstract:
  The Engineering Array of the Auger Observatory has been running successfully
since 2001 and inclined showers have been recorded from the start. We have
analysed the events with zenith angle $>$ 70$^0$ recorded between May and
November 2002. The different algorithms developed to analyze these showers are
also discussed. An preliminary discussion of a reconstructed event having 20
detectors hit is presented. Inclined showers will be detected by the full Auger
Observatory and they will allow significant enhancement of the array aperture.
High energy events will be seen as spectacular events with 30 or 40 tanks
triggered and they will provide alternative information on muon content in air
showers.


title: Jet formation in BL Lacertae objects with different accretion modes

abstract:
  We estimate the masses of massive black holes in BL Lac objects from their
host galaxy luminosity. The power of jets and central optical ionizing
luminosity for a sample of BL Lac objects are derived from their extended radio
emission and the narrow-line emission, respectively. The maximal jet power can
be extracted from a standard thin accretion disk/spinning black hole is
calculated as a function of dimensionless accretion rate $\dot{m}$
($\dot{m}=\dot{M}/\dot{M}_{\rm Edd}$). Comparing with the derived jet power, we
find that the accretion disks in most BL Lac objects should not be standard
accretion disks. For a pure advection dominated accretion flow (ADAF), there is
an upper limit on its optical continuum luminosity due to the existence of an
upper limit $\dot{m}_{\rm crit}$ on the accretion rate. It is found that a pure
ADAF is too faint to produce the optical ionizing luminosity of BL Lac objects
derived from their narrow-line luminosity. We propose that an ADAF is present
in the inner region of the disk and it becomes a standard thin disk in the
outer region in most BL Lac objects, i.e., ADAF+SD(standard disk) scenario.
This ADAF+SD scenario can explain both the jet power and optical ionizing
continuum emission of these BL Lac objects. The inferred transition radii
between the inner ADAF and outer SD are in the range of $40-150 GM_{bh}/c^2$,
if the disks are accreting at the rate $\dot{m}=0.01$.


title:
On Recovering the Nonlinear Bias Function from Counts in Cells
  Measurements

abstract:
  We present a simple and accurate method to constrain galaxy bias based on the
distribution of counts in cells. The most unique feature of our technique is
that it is applicable to non-linear scales, where both dark matter statistics
and the nature of galaxy bias are fairly complex. First, we estimate the
underlying continuous distribution function from precise counts-in-cells
measurements assuming local Poisson sampling. Then a robust, non-parametric
inversion of the bias function is recovered from the comparison of the
cumulative distributions in simulated dark matter and galaxy catalogs.
Obtaining continuous statistics from the discrete counts is the most delicate
novel part of our recipe. It corresponds to a deconvolution of a (Poisson)
kernel. For this we present two alternatives: a model independent algorithm
based on Richardson-Lucy iteration, and a solution using a parametric skewed
lognormal model. We find that the latter is an excellent approximation for the
dark matter distribution, but the model independent iterative procedure is more
suitable for galaxies. Tests based on high resolution dark matter simulations
and corresponding mock galaxy catalogs show that we can reconstruct the
non-linear bias function down to highly non-linear scales with high precision
in the range of $-1 \le \delta \le 5$. As far as the stochasticity of the bias,
we have found a remarkably simple and accurate formula based on Poisson noise,
which provides an excellent approximation for the scatter around the mean
non-linear bias function. In addition we have found that redshift distortions
have a negligible effect on our bias reconstruction, therefore our recipe can
be safely applied to redshift surveys.


title: The high energy view of blazars

abstract:
  Beppo}SAX contributed substantially to our understanding of the physics of
blazars. This has been made possible mainly by its wide energy range and
especially by its high energy detector. Together with the information coming
from still higher energies we know at last the entire spectral energy
distribution (SED) of blazars. Different subclasses of blazars have different
SEDs, which seem to form a sequence, whose main parameter is the bolometric
luminosity. Physically, the blazar sequence can be the result of different
cooling rates by those electrons emitting most of the radiation we see. Blazars
are among the most active sources we know of, and the coordinated variability
at high energies gives very important clues about the physics of their jets:
initially, they must transport energy in a dissipationless way. They radiate
most of the entire bolometric luminosity we see at a preferred distance of a
few hundreds of Schwarzchild radii.For powerful blazars, the emitted radiation
must be a small fraction of the power transported by the jet, since the bulk of
it is required to energize the radio lobes. These are the jets which likely
have bulk relativistic speeds up to hundreds of kiloparsecs, as suggested by
the bright X-ray knots detected by Chandra in many extended jets.


title: Shocked gas layers surrounding the WR nebula NGC 2359

abstract:
  NGC 2359 is a Wolf-Rayet (W-R) nebula partially bound by a rather dense and
warm molecular cloud. We present the results derived from CO and $^{13}$CO
fully sampled maps of the molecular material with angular resolutions up to
12". We have detected three different velocity components, and determined their
spatial distribution and physical properties. The kinematics, morphology, mass
and density are clearly stratified with respect to the W-R star. These features
allow us to learn about the recent evolutionary history of HD 56925, because
the multiple layers could be associated to several energetic events which have
acted upon the surrounding circumstellar medium. Hence, a careful study of the
different shockfronts contain clues in determining the present and past
interaction of this evolved massive star with its surroundings. From the
analysis of the mass-loss history in massive stars like HD 56925, we suggest
that the multiple layers of shocked molecular gas are likely to be produced
during the earlier LBV phase and/or the actual W-R stage of HD 56925.


title: Starbirth in Galaxy Collisions

abstract:
  Young, massive star clusters are the most notable and significant end
products of violent star-forming episodes triggered by galaxy collisions,
mergers, and close encounters. Their contribution to the total luminosity
induced by such extreme conditions dominates, by far, the overall energy output
due to the gravitationally-induced star formation. The general characteristics
of these newly-formed clusters (such as their masses, luminosities, and sizes)
suggest that at least a fraction may eventually evolve into equal, or perhaps
slightly more massive, counterparts of the abundant old globular cluster
systems in the local Universe. Establishing whether or not such an evolutionary
connection exists requires our detailed knowledge of not only the physics
underlying the evolution of "simple" stellar populations, but also that of
cluster disruption in the time-dependent gravitational potentials of
interacting galaxies. Initial results seem to indicate that proto-globular
clusters do indeed continue to form today, which would support hierarchical
galaxy formation scenarios.


title:
The distance to the LMC cluster NGC 1866; clues from the cluster Cepheid
  population

abstract:
  (abridged) Recent investigations aimed at estimating the distance to the
young LMC cluster NGC1866 have made use of Red Clump stars in the surrounding
LMC field, together with empirical and theoretical Main-Sequence fitting
methods, and have found significantly different distances for the field and the
cluster, the latter being closer by in distance modulus by \Delta (DM) \sim
0.20 mag. In this paper we (re-)consider the Cepheid star population of
NGC1866, to try to shed some light on this discrepancy. By combining various
extensive photometric datasets in BVI and single-epoch 2MASS JHK photometry, PL
relationships for the cluster Cepheids are obtained. A comparison between the
field LMC and cluster PL relationships for the reddening free Wesenheit index
gives a firm determination of the distance between the cluster and the LMC main
body (0.04 mag in distance modulus, the cluster being more distant) which,
coupled to a model for the geometry of the LMC disk, provides \Delta (DM)
ranging between 0.0 and -0.11 mag. The simultaneous comparison of the PL
relationships in BVI for the cluster and LMC field gives an estimate of the
cluster reddening, which results to be E(B-V) = 0.12 \pm 0.02. This
determination is higher than the canonical value of 0.06 mag used in all
previous studies, but we show that it is not in contradiction with a
re-analysis of independent estimates. The cluster Main Sequence fitting
distance obtained with this new reddening is DM = 18.58 \pm 0.08, fully
compatible with the Red Clump value of DM = 18.53 \pm
0.07(random)^{+0.02}_{-0.05} (systematic) and the Cepheid constraint on \Delta
(DM).


title: Using Multi-Band Photometry to Classify Supernovae

abstract:
  Large numbers of supernovae (SNe) have been discovered in recent years, and
many more will be found in the near future. Once discovered, further study of a
SN and its possible use as an astronomical tool (e.g., as a distance estimator)
require knowledge of the SN type. Current classification methods rely almost
solely on the analysis of SN spectra to determine their type. However,
spectroscopy may not be possible or practical. We present a classification
method for SNe based on the comparison of their observed colors with synthetic
ones, calculated from a large database of multi-epoch optical spectra of nearby
events. Broadband photometry at optical wavelengths allows classification of
SNe up to z = 0.75, and the use of infrared bands extends it further to z =
2.5. We demonstrate the applicability of this method, outline the observational
data required to further improve the usefulness of the method, and discuss
prospects for its use on future SN samples. Community access to the tools
developed is provided by a dedicated website
(http://wise-obs.tau.ac.il/~dovip/typing).


title: Star formation rate in galaxies from UV, IR, and H-alpha estimators

abstract:
  Infrared (IR) luminosity of galaxies originating from dust emission can be
used as an indicator of the star formation rate (SFR). Inoue et al. (2000, IHK)
have derived a formula for the conversion from IR luminosity to SFR by using
the following three quantities: the fraction of Lyman continuum luminosity
absorbed by gas (f), the fraction of UV luminosity absorbed by dust (epsilon),
and the fraction of dust heating from old (>10^8 yr) stellar populations (eta).
We develop a method to estimate those three quantities based on the idea that
the various way of SFR estimates should return the same SFR. After applying our
method to samples of galaxies, the following results are obtained. First, our
method is applied to star-forming galaxies, finding that f~0.6, epsilon~0.5,
and eta~0.4 as representative values. Next, we apply the method to a starburst
sample, which shows larger extinction than the star-forming galaxy sample. With
the aid of f, epsilon, and eta, we estimate reliable SFRs. Moreover, the
H-alpha luminosity, if the H-alpha extinction is corrected by using the Balmer
decrement, is suitable for a statistical analysis of SFR, because the same
correction factor for the Lyman continuum extinction is applicable to both
normal and starburst galaxies over all the range of SFR. The metallicity
dependence of f and epsilon is also tested: Only the latter proves to have a
correlation with metallicity. As an extension of our result, we show that all
UV, H-alpha, and IR comoving luminosity densities at z=0 give a consistent SFR
(~ 3x10^{-2}h M_sun/Mpc^3). Useful formulae for SFR estimate are listed.


title:
UHECR Anisotropy from Luminous Infrared Galaxies - Predictions for the
  Pierre Auger Observatory

abstract:
  We consider the hypothesis that luminous infrared galaxies (LIRGs) are
sources of the UHECRs. By associating the AGASA triplet with the Arp 299 galaxy
we obtain reasonable values for Galactic and extragalactic magnetic fields. We
predict what the southern sky, to be seen by the Auger experiment, should look
like, so that the LIRG hypothesis could be verified soon.


title:
The Iron Abundance and Density Structure of the Inner Ring around SN
  1987A

abstract:
  We present a spectroscopic study of the inner circumstellar ring around SN
1987A. The aim is to determine the elemental abundances and density structure,
with particular emphasis on the abundance of iron. We acquired and analysed
optical spectra at the Anglo-Australian Telescope (AAT) between 1400 and 4300
days post-explosion. We also assembled from the literature all available
optical/near-IR line fluxes of the inner ring. The observed line light curves
were then compared with a photoionisation model for the inner ring. This
indicates an iron abundance of (0.20+-0.08) x solar which is lower than that
generally seen in the Large Magellanic Cloud (LMC).


title:
Non-radial instability of stalled accretion shocks: advective-acoustic
  cycle

abstract:
  The linear stability of stalled accretion shocks is investigated in the
context of core collapse of type II supernovae. We focus on a particular
instability mechanism based on the coupling of acoustic perturbations with
advected ones (vorticity, entropy). This advective-acoustic cycle takes place
between the shock and the nascent neutron star. Both adiabatic and
non-adiabatic processes may contribute to this coupling, but only adiabatic
ones are considered in this first approach. The growth time of the adiabatic
instability scales like the advection time, and is dominated by low degree
modes l=0,1,2. Non radial modes (l=1,2) found unstable by Blondin et al. (2003)
can be related to this mechanism.


title:
Revealing the active galactic nucleus in the superantennae through
  L-band spectroscopy

abstract:
  We present an L-band spectrum of the Ultraluminous Infrared Galaxy IRAS
19254-7245 (the Superantennae), obtained with VLT-ISAAC. The high signal to
noise ratio allows a study of the main spectral features with unprecedented
detail for an extragalactic source. We argue that the main energy source in the
IR is an obscured AGN. This is indicated by the low equivalent width of the 3.3
micron PAH feature, the broad absorption feature at 3.4 um, and the steep
continuum at lambda>3.7 um (f_lambda ~lambda^(2.7)). The substructure of the
3.4 um absorption feature indicates that the absorption is due to hydrocarbon
chains of 6-7 carbon atoms.


title: GRS 1915+105: The brightest Galactic black hole

abstract:
  We compare the evolution of spectral shape with luminosity in GRS 1915+105
with that of 'normal' black holes. The pathological time variability of GRS
1915+105 does not indicate that it belongs in a different class to all the
other objects. At comparable fraction of Eddington luminosity its spectra and
(more importantly) time variability behaviour are similar to that seen in the
'normal' black holes. Its unique limit-cycle variability only appears when it
radiates at uniquely high (super-Eddington) luminosities.


title: Nuclear Processes at Solar Energy

abstract:
  LUNA, Laboratory for Underground Nuclear Astrophysics at Gran Sasso, is
measuring fusion cross sections down to the energy of the nucleosynthesis
inside stars. Outstanding results obtained up to now are the cross-section
measurements within the Gamow peak of the Sun of $^{3}He(^{3}He,2p)^{4}He$ and
the $D(p,\gamma)^{3}He$. The former plays a big role in the proton-proton
chain, largely affecting the calculated solar neutrino luminosity, whereas the
latter is the reaction that rules the proto-star life during the pre-main
sequence phase. The implications of such measurements will be discussed.
Preliminary results obtained last year on the study of
$^{14}N(p,\gamma)^{15}O$, the slowest reaction of the CNO cycle, will also be
shown.


title: Astrophysical imaging with the Darwin IR interferometer

abstract:
  The proposed infrared space interferometry mission Darwin has two main aims:
(i) to detect and characterize exo-planets similar to the Earth, and (ii) to
carry out astrophysical imaging in the wavelength range 6 - 20 micron at a
sensitivity similar to JWST, but at an angular resolution up to 100 times
higher. In this contribution we will first briefly discuss the imaging
performance of the Darwin mission. We will then discuss how Darwin will
contribute in a very significant way to our understanding of the formation and
evolution of planets, stars, galaxies, and super-massive black-holes located at
the centers of galaxies.


title: Iron Line Diagnostics for the GRS 1915+105 Black Hole

abstract:
  The properties of the broad Fe line detected in two BeppoSAX observations of
the microquasar GRS 1915+105 are summarized.


title:
Intrinsic and dust-induced polarization in gamma-ray burst afterglows:
  the case of GRB 021004

abstract:
  Polarization measurements for the optical counterpart to GRB 021004 are
presented and discussed. Our observations were performed with the TNG and the
VLT-UT3 (Melipal) during the first and fourth night after the gamma-ray burst
discovery. We find robust evidence of temporal evolution of the polarization,
which is therefore, at least partially, intrinsic to the optical transient. We
do not find convincing evidence of wavelength dependence for the intrinsic
polarization of the transient, in agreement with current polarization models
for optical afterglows. We discuss the role of dust, both in our galaxy and in
the host, in modifying the transmitted polarization vector, showing how a
sizable fraction of the observed polarized flux is due to Galactic selective
extinction, while it is not possible to single out any clear contribution from
dust in the host galaxy. We discuss how our data compare to those obtained by
different groups showing that a two-component model is required to describe the
complete dataset. This is not surprising given the complex lightcurve of GRB
021004.


title: The z ~ 4 Lyman Break Galaxies: Colors and Theoretical Predictions

abstract:
  We investigate several fundamental properties of z ~ 4 Lyman-break galaxies
by comparing observations with the predictions of a semi-analytic model based
on the Cold Dark Matter theory of hierarchical structure formation. We use a
sample of B_{435}-dropouts from the Great Observatories Origins Deep Survey,
and complement the ACS optical B_{435}, V_{606}, i_{775}, and z_{850} data with
the VLT ISAAC J, H, and K_{s} observations. We extract B_{435}-dropouts from
our semi-analytic mock catalog using the same color criteria and magnitude
limits that were applied to the observed sample. We find that the i_{775} -
K_{s} colors of the model-derived and observed B_{435}-dropouts are in good
agreement. However, we find that the i_{775}-z_{850} colors differ
significantly, indicating perhaps that either too little dust or an incorrect
extinction curve have been used. Motivated by the reasonably good agreement
between the model and observed data we present predictions for the stellar
masses, star formation rates, and ages for the z ~ 4 Lyman-break sample. We
find that according to our model the color selection criteria used to select
our z ~ 4 sample surveys 67% of all galaxies at this epoch down to z_{850} <
26.5. We find that our model predicts a roughly 40% mass build-up between the z
\~ 4 and z ~ 3 epochs for the UV rest-frame L* galaxies. Furthermore, according
to our model, at least 50% of the total stellar mass resides in relatively
massive UV-faint objects that fall below our observational detection limit.