title:
Temperature Scale and Iron Abundances of Very Hot Central Stars of
  Planetary Nebulae

abstract:
  The determination of effective temperatures of very hot central stars
(Teff>70000K) by model atmosphere analyses of optical H and He line profiles is
afflicted with considerable uncertainty, primarily due to the lack of neutral
helium lines. Ionization balances of metals, accessible only with UV lines,
allow more precise temperature estimates. The potential of iron lines is
pointed out. At the same time iron and other metal abundances, hardly
investigated until today, may be derived from UV spectra. We describe recent
HST spectroscopy performed for this purpose.
  A search for iron lines in FUV spectra of the hottest H-deficient central
stars (PG1159-type, Teff>100000K) taken with FUSE was unsuccessful. The derived
deficiency is interpreted in terms of iron depletion due to n-capture
nucleosynthesis in intershell matter, which is now exposed at the stellar
surface as a consequence of a late He shell flash.


title: A Fabry-Perot Study of the Scd I galaxy NGC 5457

abstract:
  We have analyzed Halpha Fabry-Perot interferograms of NGC 5457 (M101) in
order to calculate the rotation curve. We have also isolated a sample of 263
HII regions and we determined for each one its radial velocity and velocity
dispersion. The rotation curve agrees with previous determinations and the mass
derived from it is 9.8E10 solar mass. The distribution of velocity dispersion
values of the HII regions presents a normal behavior, with a mean value of 30
km/sec.


title:
Discrete and diffuse X-ray emission in the nucleus and disk of the
  starburst spiral galaxy M83

abstract:
  We have studied the face-on, barred spiral M83 (NGC 5236) with Chandra.
Eighty-one point sources are detected (above 3.5-sigma) in the ACIS S3 image:
15 of them are within the inner 16 arcsec region (starburst nucleus, resolved
for the first time with Chandra), and 23 within the inner 60 arcsec (including
the bar). The luminosity distributions of the sources in the inner 60 arcsec
region (nucleus and stellar bar) is a single power law, which we interpret as
due to continuous, ongoing star formation. Outside this inner region, there is
a smaller fraction of bright sources, which we interpret as evidence of an
aging population from a past episode of star formation. About 50% of the total
emission in the nuclear region is unresolved; of this, about 70% can be
attributed to hot thermal plasma, and we interpret the rest as due to
unresolved point sources (eg, faint X-ray binaries). The unresolved X-ray
emission also shows differences between the nuclear region and the spiral arms.
In the nuclear region, the electron temperature of the thermal plasma is = 0.58
keV. In the spiral arms, the thermal component is at kT = 0.31 keV and a
power-law component dominates at energies >~1 keV. The high abundance of C, Ne,
Mg, Si and S with respect to Fe suggests that the interstellar medium is
enriched and heated by core-collapse supernova explosions and winds from
massive stars.


title: State transitions in LMC X-3

abstract:
  We carried out a multiwavelenght study of the black-hole candidate LMC X-3
with XMM-Newton. The system showed a transition to a low-hard state, in which
the X-ray spectrum was well fitted by a simple power law. It then returned to a
high-soft state, characterised by a strong disk-blackbody component. The
line-of-sight absorption column density is <~ 4 x 10^{20} cm^{-2} consistent
with the foreground Galactic absorption. This rules out wind accretion. We
argue that, despite LMC X-3 being a high-mass X-ray binary, Roche-lobe overflow
is the main mechanism of mass transfer. From UV/optical observations in the
low-hard state, we determine that the companion is a slightly evolved B5 star
with a mass M ~ 4.5 M_sun. This is indeed consistent with the secondary star
being close to filling its Roche lobe.


title: Radial Oscillations of Hybrid Stars

abstract:
  We study the effect of quark and nuclear matter mixed phase on the radial
oscillation modes of neutron stars. For this study we have considered recent
models from two classes of equations of state namely the relativistic mean
field theoretical models and models based on realistic nucleon-nucleon
interactions incorporating relativistic corrections and three body nuclear
interactions.


title: The nature of ultraluminous X-ray sources in nearby galaxies

abstract:
  The advanced capabilities of the Chandra and XMM-Newton observatories mean
that, for the first time, the detailed study of the brightest point-like X-ray
sources in nearby galaxies outside of the local group is a realistic aim. Here,
we present the results of a Chandra ACIS-S study of two of the nearest and
brightest sources in the rare ultraluminous (L(X) > 10^39 erg s^-1) X-ray
source (ULX) class, NGC 5204 X-1 and NGC 4559 X-1. When considered with new
optical integral field spectroscopy data this provides powerful diagnostics as
to the nature of these sources, in particular suggesting that NGC 5204 X-1 is a
high-mass X-ray binary, and showing new evidence linking it to the Galactic
microquasar phenomenon. We also find that both ULX appear to be located in
cavities in emission-line gas nebulae that surround the sources. In addition,
we present the results of a Chandra observation of the interacting galaxies NGC
4485/NGC 4490, a pair of late-type spiral galaxies that, remarkably, contain a
total of six ULX. We identify one as a supernovae, and the remainder as
probable black hole X-ray binaries. All six are located in star formation
regions, underlining the emerging link between ULX and active star formation
activity.


title: The intermediate-age open cluster NGC 2158

abstract:
  We report on $UBVRI$ CCD photometry of two overlapping fields in the region
of the intermediate-age open cluster NGC 2158 down to V=21. By analyzing
Colour-Colour (CC) and Colour-Magnitude Diagrams (CMD) we infer a reddening
$E_{B-V}= 0.55\pm0.10$, a distance of $3600 \pm 400$ pc, and an age of about 2
Gyr. Synthetic CMDs performed with these parameters (but fixing $E_{B-V}=0.60$
and $[{\rm Fe/H}]=-0.60$), and including binaries, field contamination, and
photometric errors, allow a good description of the observed CMD. The elongated
shape of the clump of red giants in the CMD is interpreted as resulting from a
differential reddening of about $\Delta E_{B-V}=0.06$ across the cluster, in
the direction perpendicular to the Galactic plane. NGC 2158 turns out to be an
intermediate-age open cluster with an anomalously low metal content. The
combination of these parameters together with the analysis of the cluster
orbit, suggests that the cluster belongs to the old thin disk population.


title:
Stochastic Correlation Model of Galactic Bulge Velocity Dispersions and
  Central Black Holes Masses

abstract:
  We consider the cosmological model in which a part of the Universe
\Omega_h\sim 10^-5 is in the form of primordial black holes with mass \sim
10^5M_\odot. These primordial black holes would be centers for growing
protogalaxies which experienced multiple mergers with ordinary galaxies. This
process of galaxies formation is accompanied by the merging of central black
holes in the galactic nuclei. It is shown that recently discovered correlations
between the central black holes and bulges of galaxies are naturally reproduced
in this scenario.


title: Abundance gradients and the role of SNe in M87/Virgo

abstract:
  We make a detailed measurement of the metal abundance profiles and metal
abundance ratios of the inner core of M87/Virgo observed by XMM-Newton during
the PV phase. We use multi temperature models for the inner regions and we
compare the plasma codes APEC and MEKAL. We confirm the strong heavy elements
gradient previously found by ASCA and BeppoSAX, but also find a significant
increase in light elements, in particular O. This fact together with the
constant O/Fe ratio in the inner 9 arcmin indicates an enhancement of
contribution in the core of the cluster not only by SNIa but also by SNII.


title: A Common Origin of Neutralino Stars and Supermassive Black Holes

abstract:
  To account for the microlensing events observed in the Galactic halo,
Gurevich, Zybin, and Sirota have proposed a model of gravitationally bound,
noncompact objects with masses of 0.01-1M_\odot. These objects are formed in
the expanding Universe from adiabatic density perturbations and consist of
weakly interacting particles of dark matter, for example, neutralinos. They
assumed the perturbation spectrum on some small scale to have a distinct peak.
We show that the existence of this peak would inevitably give rise to a large
number of primordial black holes (PBHs) with masses of \sim10^5M_\odot at the
radiation-dominated evolutionary stage of the Universe. Constraints on the
coefficient of nonlinear contraction and on the compactness parameter of
noncompact objects were derived from constraints on the PBH number density. We
show that noncompact objects can serve as gravitational lenses only at a large
PBH formation threshold, \delta_c > 0.5, or if noncompact objects are formed
from entropic density perturbations.


title: Source Detection in Simulated XMM-Newton Observations

abstract:
  We present preliminary results from our on-going study: Comparing and
optimizing source detection procedures for XMM images. By constructing
realistic spatial and spectral source distributions and ``observing'' these
through the XMM Science Simulator we study how source characteristics and
instrumental effects influence detection. We are currently undertaking a
statistical analysis on the outcome of running source detection algorithms on
the simulated EPIC pn and MOS images in various energy bands. Particular
emphasis is on the efficiency and reliability for detecting the faint, extended
emission from distant clusters of galaxies. Here we present simulated EPIC
images applicable to the XMM Large-scale Structure Survey (10 ksec pointings of
``blank fields''). However, we emphasize that our procedure is flexible,
including as many realistic source characteristics and instrumental effects as
possible, and yet modest in computational demand. As such it can be used for
simulating XMM data obtained from virtually any X-ray source. All simulation
products are made available at our website (http://www.astro.ku.dk/xcosmos/).


title: Shapelets: A New Method to Measure Galaxy Shapes

abstract:
  We present a new approach to measure the shapes of galaxies, a fundamental
task in observational astronomy. This approach is based on the decomposition of
a galaxy image into a series of orthogonal basis functions, or `shapelets'. Our
choice of basis functions, namely the Gauss-Hermite series, has a number of
remarkable properties under distortions, convolutions and noise, which makes
them particularly well suited for astrophysical applications. In particular, we
describe how they can be used to measure the shear induced by weak
gravitational lensing, with the precision required for upcoming surveys. We
also show how shapelets can be used to reconstruct images from interferometric
observations. Other application of shapelets, such as image compression, PSF
deconvolution, de-projection and the study of galaxy morphology, are also
briefly discussed.


title:
The Origin of the Correlation between the Spin Parameter and the Baryon
  Fraction of Galactic Disks

abstract:
  The puzzling correlation between the spin parameter lambda of galactic disks
and the disk-to-halo mass fraction fdisk is investigated. We show that such a
correlation arises naturally from uncertainties in determining the virial
masses of dark matter halos. This result leads to the conclusion that the halo
properties derived from fits to observed rotation curves are still very
uncertain which might explain part of the disagreements between cosmological
models and observations. We analyse lambda and fdisk as function of the adopted
halo virial mass. Reasonable halo concentrations require fdisk=0.01-0.07 which
is significantly smaller than the universal baryon fraction. Most of the
available gas either never settled into the galactic disks or was ejected
subsequently. In both cases it is not very surprising that the specific angular
momentum distribution of galactic disks does not agree with the cosmological
predictions which neglect these effects.


title: The Eagle's EGGs: fertile or sterile?

abstract:
  We present a deep, high spatial resolution (0.35 arcsec FWHM), near-infrared
(1-2.5 micron) imaging survey of the Eagle Nebula, M16, made with the VLT,
centred on the famous elephant trunks. We compare these data with the existing
HST optical images to search for evidence of ongoing or recent star formation
in the trunks, and in particular in the 73 small evaporating gaseous globules
(EGGs) on their surface. We find that two of the three HST trunks have
relatively massive YSOs in their tips. Most of the EGGs appear to be empty, but
some 15% of them do show evidence for associated young low-mass stars or brown
dwarfs: in particular, there is a small cluster of such sources seen at the
head of the largest trunk.


title: Cosmic alignment towards the radio Einstein ring PKS 1830-211 ?

abstract:
  Optical and near-IR Hubble Space Telescope and Gemini-North adaptive optics
images, further improved through deconvolution, are used to explore the
gravitationally lensed radio source PKS 1830-211. The line of sight to the
quasar at z=2.507 appears to be very busy, with the presence, within 0.5 arcsec
from the source of: (i) a possible galactic main-sequence star, (ii) a faint
red lensing galaxy visible only in H-band and (iii) a new object whose colors
and morphology match those of an almost face-on spiral. The V-I color and faint
I magnitude of the latter suggest that it is associated with the molecular
absorber seen towards PKS 1830-211, at z=0.89 rather than with the z=0.19 HI
absorber previously reported in the spectrum of PKS 1830-211. While this
discovery might ease the interpretation of the observed absorption lines, it
also complicates the modeling of the lensing potential well, hence decreasing
the interest in using this system as a mean to measure H_0 through the time
delay between the lensed images. This is the first case of a quasar lensed by
an almost face-on spiral galaxy.


title:
1.65 micron (H-band) surface photometry of galaxies. IX: photometric and
  structural properties of galaxies

abstract:
  As a result of a systematic NIR H-band (1.65 micron) imaging survey of normal
galaxies in the local universe, we are able to measure in a highly homogeneous
way photometric and structural properties for a sample of 1143 galaxies. We
base our analysis on a quantitative structural parameter, the concentration
index C_31, instead of relying on the galaxies' morphological classification.
The C_31 parameter provides a model independent, quantitative and continuous
characterization of the light distribution within galaxies, and it is thus to
be preferred to either the Hubble type or a parameter like the bulge-to-disk or
bulge-to-total light ratio. We find that galaxies can be completely described
by three parameters, namely: a scale parameter (the H-band luminosity), a shape
parameter (the concentration index C_31) and a colour parameter (e.g. the B-H
colour). At low luminosity dEs and dIs, having similar C_31, are
colour-discriminated, while at very high luminosity different C_31 discriminate
S0s from Scs, otherwise undistinguishable on the basis of their colour. A
single, monotonic relation exists between luminosity and mu_e in the H-band, as
opposed to the two separate regimes that are generally observed in the B-band.
As NIR luminosity traces quite accurately the galaxy mass distribution, this
relation re-enforces the indication in favour of a scale-dependent mass
collapse mechanism which produces higher surface-brightness and more centrally
peaked galaxies with increasing mass. However, the presence of high-luminosity
low-C_31 galaxies hints at other machanisms and physical properties (such as
angular momentum) playing an important role in galaxy formation. (abridged)


title: Supermassive Stars: Fact or Fiction?

abstract:
  Supermassive black holes are now realized to exist in the centers of most
galaxies. The recent discoveries of luminous quasars at redshifts higher than 6
require that these black holes were assembled already when the Universe was
less than a billion years old. They might originate from the collapse of
supermassive stars, a scenario which could ensure a sufficiently rapid
formation. Supermassive stars are dominated by photon pressure and radiate at
their Eddington limit, which drives their quasi-static evolution to a final
relativistic instability. Above some critical value of the metallicity, their
collapse can lead to a gigantic explosion, powered by the energy release due to
hydrogen burning, but below this critical metallicity their collapse inevitably
ends in the formation of a black hole, accompanied by the emission of huge
amounts of energy in the form of neutrinos. Although collapsing supermassive
stars are the most powerful known burst sources of neutrinos, the associated
conditions do not appear favorable for producing highly relativistic outflows
that can explain cosmic gamma-ray bursts.


title:
Strongly absorbed quiescent X-ray emission from the X-ray transient XTE
  J0421+56

abstract:
  We have observed the soft X-ray transient XTE J0421+56 in quiescence with
XMM-Newton. The observed spectrum is highly unusual being dominated by a broad
feature at 6.5 keV and can be modeled by a strongly absorbed continuum. The
spectra of X-ray transients observed so far are normally modeled using
Advection Dominated Accretion Flow models, black-bodies, power-laws, or by the
thermal emission from a neutron star surface. The strongly absorbed X-ray
emission of XTE J0421+56 could result from the compact object being embedded
within the dense circumstellar wind emitted from the supergiant B[e] companion
star.


title: Do NLS1s and ultrasoft AGN have irradiated, warped accretion disks?

abstract:
  When Beppo-SAX measured the 0.1--12 keV spectrum of RE J1034+396,
observations in the optical, UV and EUV were also taken within a few weeks.
This multiwavelength spectrum placed very strong constraints on its unusually
hot big blue bump component, which has been attributed to a high (almost
Eddington) rate of accretion onto a disk surrounding a low mass black hole.
However, while a simple, geometrically-thin accretion disk provides a good fit
to the UV to X-ray continuum, it leaves a residual flat and featureless
component in the optical. We propose that the disk is actually flared or warped
and that the central ionizing EUV/X-ray continuum is irradiating the outer
parts of the disk and boosting the optical/UV continuum flux. The relatively
narrow permitted lines may be due to a resulting disk wind. This physical
interpretation may explain the link between ultrasoft X-ray excesses and broad
line velocity in the AGN class as a whole. It may also have implications for
the possible relationship between ultrasoft AGN and galactic black holes.


title: Stellar Populations in Bulges of Spiral Galaxies

abstract:
  We have conducted a spectroscopic analysis of the bulges of a sample of 31
spiral galaxies, spanning the Hubble sequence from S0 to Scd type, in order to
study the radial distribution of their stellar population properties.


title: Quantum aspects of black holes

abstract:
  This is a brief introduction to quantum aspects of black holes, addressed at
an astrophysics-oriented audience. The topics are: The laws of black-hole
mechanics, Hawking radiation, interpretation of entropy, and primordial black
holes.


title: Hard X-ray afterglows of short GRBs

abstract:
  We report the discovery of a transient and fading hard X-ray emission in the
BATSE lightcurves of a sample of short gamma-ray bursts. We have summed each of
the four channel BATSE light curves of 76 short bursts to uncover the average
overall temporal and spectral evolution of a possible transient signal
following the prompt flux. We found an excess emission peaking ~30 s after the
prompt one, detectable for ~100 s. The soft power-law spectrum and the
time-evolution of this transient signal suggest that it is produced by the
deceleration of a relativistic expanding source, as predicted by the afterglow
model.


title:
Infrared Space Observatory Polarimetric Imaging of the Egg Nebula (RAFGL
  2688)

abstract:
  We present polarimetric imaging of the protoplanetary nebula RAFGL 2688
obtained at 4.5 microns with the Infrared Space Observatory (ISO). We have
deconvolved the images to remove the signature of the point spread function of
the ISO telescope, to the extent possible. The deconvolved 4.5 micron image and
polarimetric map reveal a bright point source with faint, surrounding
reflection nebulosity. The reflection nebula is brightest to the
north-northeast, in agreement with previous ground- and space-based infrared
imaging. Comparison with previous near-infrared polarimetric imaging suggests
that the polarization of starlight induced by the dust grains in RAFGL 2688 is
more or less independent of wavelength between 2 microns and 4.5 microns. This,
in turn, indicates that scattering dominates over thermal emission at
wavelengths as long as ~5 microns, and that the dust grains have characteristic
radii < 1 micron.


title:
The nuclei of radio galaxies in the UV: the signature of different
  emission processes

abstract:
  We have studied the nuclei of 28 radio galaxies from the 3CR sample in the UV
band. Unresolved nuclei (central compact cores, CCC) are observed in 10 of the
13 FR I, and in 5 of the 15 FR II. All sources that do not have a CCC in the
optical, do not have a CCC in the UV. Two FR I (3C 270 and 3C 296) have a CCC
in the optical but do not show the UV counterpart. Both of them show large
dusty disks observed almost edge-on, possibly implying that they play a role in
obscuring the nuclear emission. We have measured optical-UV spectral indices
alpha_o,UV between ~0.6 and ~7.0. BLRG have the flattest spectra and their
values of alpha_o,UV are also confined to a very narrow range. This is
consistent with radiation produced in a geometrically thin, optically thick
accretion disk. On the other hand, FR I nuclei, which are most plausibly
originated by synchrotron emission from the inner relativistic jet, show a wide
range of alpha_o,UV. There is a clear trend with orientation in that sources
observed almost edge-on or with clear signs of dust absorption have the
steepest spectra. These observations imply that in FR I obscuration can be
present, but the obscuring material is not in a ``standard'' geometrically
thick torus. The most striking difference between these absorbing structures
and the classic AGN ``tori'' resides in the lower optical depth of the FR I
obscuring material.


title:
Metal abundances and ionization conditions in a possibly dust-free
  damped Ly-alpha system at z=2.3

abstract:
  We have obtained a high resolution, high S/N UVES spectrum of the bright QSO
HE2243-6031 to analyze the damped Ly-alpha system (DLA) observed at z=2.33. The
metallicity of this system is 1/12 solar at a neutral hydrogen column density
of log N(HI)=20.7. From the observed ratios [Zn/Cr]=-0.01+/-0.05 and
[S/Si]=-0.06+/-0.03$ we conclude that dust is very likely absent from the ISM
of this protogalaxy. We observe an enhancement of the alpha/Fe-peak ratios of
+0.2 dex for various elements, a marked odd-even effect in Mn, and a strong
underabundance of N relative to Si and S, [N/Si,S]=-1 at [Si/H]=-0.86. All of
these ratios support an environment that is in an early evolutionary stage,
where the onset of star formation has begun only shortly before the DLA was
observed. We also perform a cloud-by-cloud analysis -- without precedent at
high redshift -- and find a tight correlation of all low-ionization species
with respect to FeII extending over 2.5 orders of magnitude in N(FeII). We
interpret this trend as being due to homogeneous physical conditions (very mild
ionization effects, common dust-destruction histories, same chemical
composition) and propose that this line of sight encounters absorbing clouds
that share a common environment. In addition, photoionization models show that
these single clouds are shielded from the external ionizing radiation, so the
fraction of ionized gas is small and, except for argon, does not influence the
measured metal abundances. The observed AlIII/low-ion ratios suggest the mildly
ionized gas occurs in shells surrounding neutral cores of AlII.


title: Gravitational wave background from Population III black hole formation

abstract:
  We study the generation of a stochastic gravitational wave (GW) background
produced from a population of core-collapse supernovae, which form black holes
in scenarios of structure formation. We obtain, for example, that the formation
of a population (Population III) of black holes, in cold dark matter scenarios,
could generate a stochastic GW background with a maximum amplitude of $h_{\rm
BG} \simeq 10^{-24}$ and corresponding closure energy density of
$\Omega_{\rm{GW}}\sim 10^{-7}$, in the frequency band $\nu_{\rm{obs}} \simeq
30-470 {\rm Hz}$ (assuming a maximum efficiency of generation of GWs, namely,
$\epsilon_{\rm GW_{\rm max}} = 7\times 10^{-4}$) for stars forming at redshifts
$z\simeq 30-10.$ We show that it will be possible in the future to detect this
isotropic GW background by correlating signals of a pair of `advanced' LIGO
observatories (LIGO III) at a signal-to-noise ratio of $\simeq 40$. We discuss
what astrophysical information could be obtained from a positive (or even a
negative) detection of such a GW background generated in scenarios such as
those studied here. One of them is the possibility of obtaining the initial and
final redshifts of the emission period from the observed spectrum of GWs.


title: A High Spectral Resolution Atlas of Comet 122P/de Vico

abstract:
  On 3 and 4 October, 1995, we obtained high spectral resolving power
(R=\lambda/\Delta\lambda = 60,000) observations of comet 122P/de Vico using the
2DCoude cross-dispersed echelle spectrograph on the 2.7-m telescope of McDonald
Observatory. The spectra cover the wavelength range from 3830A--10192A. The
spectra from 3830--5776A are continuous; from 5777--10192A there are increasing
interorder gaps. The comet was at a heliocentric distance of 0.66au and a
geocentric distance of 1.0au. Comet de Vico has a very high gas-to-dust ratio
and the spectra have excellent signal/noise. These two factors combined to
yield spectra with a large number of emission lines. We have collected
laboratory molecular line lists and have used these line lists in order to
identify as many of the detected lines as possible. We have identified 12,219
emission lines and have located another 4,055 lines which we cannot identify.
We present representative spectra and identifications along with a description
of our plans to make these spectra and identifications available to the
community. This atlas should prove a valuable tool for future studies of
comets.


title: Radio emission of the Moon before and after the Lunar Prospector impact

abstract:
  The direct impact of the American spacecraft Lunar Prospector into the Moon
on July 31, 1999 was accompanied by seismic effects comparable to a big
moonquake. Such an impact can be accompanied by radio seismic radiation of the
lunar surface layers. For registration of the lunar radio seismic radiation
after the Lunar Prospector impact radio observations of the Moon on two 64-m
radio telescopes at 13, 21, and 90 cm were conducted on July 30 - August 2,
1999. Changes of the radio temperature of the south polar regions after the
impact were detected. The Lunar Prospector impact may have been the cause of
these changes. Recommendations about the registration of the lunar radio
seismic radiation during the Leonid meteor showers are given.


title: Spin--Down Power in Astrophysics

abstract:
  While the accretion power in astrophysics has been studied in many
astronomical environments, the ``spin--down power'' is often neglected. In this
essay I demonstrate that the spin--down power alone may drive a rotating system
from sub-critical condition to critical condition with a small but finite
probability. In the case of an isolated spinning-down neutron star, the star
may undergo a quark--hadron phase transition in its center and become
observable as a soft gamma repeater or a cosmological gamma--ray burst. For a
spinning--down white dwarf, its Chandrasekhar mass limit will decrease and may
reach the stellar mass, then the star explodes to a type Ia supernova.
Gravitational wave detectors may be able to test these models.


title: MHD Models of Planetary Nebulae: Review

abstract:
  Hydrodynamical (HD) simulations played an important role in understanding the
dynamics and shaping of Planetary Nebulae (PNe) in the past century. However,
HD solutions are just a first order approach. The new millennium arrives with
the generalized understanding that the effects of magnetic fields (i.e., MHD)
are necessary to study the dynamics of PNe. Thus, B-fields introduce a whole
new number of physical possibilities for the modeling. We here review recent
advances in MHD modeling of PNe.


title: Microlensing Maps for the Milky Way Galaxy

abstract:
  At any instant, there are roughly 1000 ongoing microlensing events to sources
brighter than 20th magnitude in the Milky Way Galaxy. Large-scale maps of the
microlensing optical depth and the mean timescale are constructed for a number
of models of the Galactic bar and disk, incorporating the effects of streaming
and spiral structure. Freudenreich's model can reproduce the high optical
depths towards the Bulge. It is also in good agreement with the data towards
the spiral arms (except for the gamma Norma field). Spiral structure tends to
increase the optical depth by about 20% and the mean timescale by about 100%.
Different bar morphologies give characteristically different shaped contours,
especially at low Galactic latitudes (|b| < 2 degrees). These could be traced
out with a K band microlensing survey, consuming about 100 minutes per night on
a telescope like VISTA.


title:
Limits to the Cas A $^{44}$Ti Line Flux and Constraints on the Ejecta
  Energy and the Compact Source

abstract:
  Two long observations of Cas A supernova remnant were made by the \emph{Rossi
X-ray Timing Explorer} in 1996 and 1997 to search for hard X-ray line emission
at 67.9 and 78.4 keV from decay of $^{44}$Ti formed during the supernova event.
Continuum flux was detected up to 100 keV, but the $^{44}$Ti lines were not
detected. The 90% confidence upper limit to the line flux is 3.6$\times10^{-5}$
photons cm$^{-2}$s$^{-1}$. This is consistent with the recent \emph{BeppoSAX}
detection and with the \emph{CGRO}/COMPTEL detection of the companion
transition line flux for $^{44}$Sc decay. The mean \emph{BeppoSAX}--COMPTEL
flux indicates that 1.5$\pm$0.3 $\times10^{-4}$M$_\odot$ of $^{44}$Ti was
produced in the supernova explosion. Based upon recent theoretical
calculations, and optical observations suggesting a WN Wolf-Rayet progenitor
with an initial mass of $\geq$25 M$_\odot$, the observed $^{44}$Ti yield
implies that the Cas A supernova ejecta energy was $\sim2\times10^{51}$ ergs,
and as a result a neutron star was formed, rather than a black hole. We suggest
Cas A is possibly in the early stages of the AXP/SGR scenario in which the
push-back disk has yet to form, and when the disk does form, the accretion will
increase the luminosity to that of present-day AXP/SGRs and pulsed emission
will commence.


title: Exotic sources detected in the 1 Ms Chandra Deep Field North Survey

abstract:
  We provide constraints on optically faint (I>=24) X-ray sources, z>6 AGN,
Very Red Objects (VROs; I-K>=4), and optically faint radio sources using the 1
Ms Chandra Deep Field North survey. We argue that the majority of the optically
faint X-ray sources are obscured AGN at z=1-3. These sources comprise up to 50%
of the X-ray detected AGN. Approximately 30% of the optically faint X-ray
sources have properties consistent with those expected for z>6 AGN; however we
argue that the majority of these sources lie at lower redshifts. The constraint
we place on the source density of z>6 AGN (<~0.09 arcmin^{-2}) is below that
predicted by some models. Approximately 30% of the optically faint X-ray
sources are also VROs. Within the K<=20.1 VRO population, ~15% of the sources
are AGN dominated. Conversely, we present evidence suggesting that non-AGN
dominated VROs are detected at the flux limit of this 1 Ms Chandra survey.
Finally, we show that ~50% of the optically faint radio source population are
detected with X-ray emission. The majority of these sources appear to be
obscured AGN.


title: The Unique History of the Globular Cluster Omega Centauri

abstract:
  Using current observational data and simple dynamical modeling, we
demonstrate that Omega Cen is not special among the Galactic globular clusters
in its ability to produce and retain the heavy elements dispersed in the AGB
phase of stellar evolution. The multiple stellar populations observed in Omega
Cen cannot be explained if it had formed as an isolated star cluster. The
formation within a progenitor galaxy of the Milky Way is more likely, although
the unique properties of Omega Cen still remain a mystery.


title:
Magnetic flaring in the pre-main sequence Sun and implications for the
  early solar system

abstract:
  To address the role of energetic processes in the solar nebula, we provide a
detailed characterization of magnetic flaring in stellar analogs of the
pre-main sequence Sun based on 23 hours observations of 43 analogs of the young
Sun in the Orion Nebula Cluster obtained with the Chandra X-ray Observatory. We
find the X-ray luminosities are strongly elevated over main sequence levels
with average <log L_x> = 30.3 erg/s and <log L_x/L_*> = -3.9 (0.5-8 keV), and
dozens of flares are present. Analogs of the <= 1 My old pre-main sequence Sun
exhibit X-ray flares 10^{1.5} times more powerful and 10^{2.5} times more
frequent than the most powerful flares seen on the contemporary Sun.
Extrapolating the solar relationship between X-ray luminosity and proton
fluence, we infer that the young Sun exhibited a 10^5-fold enhancement in
energetic protons compared to contemporary levels. Unless the flare geometries
are unfavorable, this inferred proton flux on the disk is sufficient to produce
the observed meteoritic abundances of several important short-lived radioactive
isotopes. Our study thus strengthens the astronomical foundation for local
proton spallation models of isotopic anomalies in carbonaceous chondritic
meteorites. The radiation, particles and shocks produced by the magnetic
reconnection flares seen with Chandra may also have flash melted meteoritic
chondrules and produced excess 21-Ne seen in meteoritic grains.


title:
A Critical Examination of Hypernova Remnant Candidates in M101. II. NGC
  5471B

abstract:
  NGC 5471B has been suggested to contain a hypernova remnant because of its
extraordinarily bright X-ray emission. To assess its true nature, we have
obtained high-resolution images in continuum bands and nebular lines with the
Hubble Space Telescope, and high-dispersion long-slit spectra with the Kitt
Peak National Observatory 4-m echelle spectrograph. The images reveal three
supernova remnant (SNR) candidates in the giant HII region NGC 5471, with the
brightest one being the 77x60 pc shell in NGC 5471B. The Ha velocity profile of
NGC 5471B can be decomposed into a narrow component (FWHM = 41 km/s) from the
background HII region and a broad component (FWHM = 148 km/s) from the SNR
shell. Using the brightness ratio of the broad to narrow components and the Ha
flux measured from the WFPC2 Ha image, we derive an Ha luminosity of
(1.4+-0.1)x10^39 ergs/s for the SNR shell. The [SII]6716,6731 doublet ratio of
the broad velocity component is used to derive an electron density of ~700
cm^-3 in the SNR shell. The mass of the SNR shell is thus 4600+-500 Mo. With a
\~330 km/s expansion velocity implied by the extreme velocity extent of the
broad component, the kinetic energy of the SNR shell is determined to be
5x10^51 ergs. This requires an explosion energy greater than 10^52 ergs, which
can be provided by one hypernova or multiple supernovae. Comparing to SNRs in
nearby active star formation regions, the SNR shell in NGC 5471B appears truly
unique and energetic. We conclude that the optical observations support the
existence of a hypernova remnant in NGC 5471B.


title:
Faint Source Counts from the Off-source fluctuation Analysis on the
  Deepest Chandra Fields

abstract:
  We show the results of the fluctuation analysis applied to the off-source
areas from the two 1 Million second Chandra Deep Fields, including our new
results on the Chandra Deep Field-South (CDF-S) in the 0.5-2 keV band in
addition to those on the Chandra Deep Field-North (CDF-N), which have already
been reported. The distribution of the X-ray counts in cells has been compared
with the expectation from the Log N - Log S model to constrain the behavior of
the source number density down to a factor of several lower than the
source-detection limit. We show that our results are insensitive to the
non-uniformity of the non X-ray background (NXB). Our results show that the
number counts in the soft band (0.5-2 [keV]) continue to grow down to Sx =7e-18
erg/s/cm2, possibly suggesting the emergence of a new population and they agree
well with a prediction of star forming galaxies.


title: Detecting WIMPs in the Microwave Sky

abstract:
  The hierarchical clustering observed in cold dark matter simulations results
in highly clumped galactic halos. If the dark matter in our halo is made of
weakly interacting massive particles (WIMPs), their annihilation products
should be detectable in the higher density and nearby clumps. We consider WIMPs
to be neutralinos and calculate the synchrotron flux from their annihilation
products in the presence of the Galactic magnetic field. We derive a
self-consistent emission spectrum including pair annihilation, synchrotron
self-absorption, and synchrotron self-Compton reactions. The resulting
radiation spans microwave frequencies that can be observed over the
anisotropies in the cosmic microwave background. These synchrotron sources
should be identifiable as WIMP clumps, either by their spatial structure or by
their distinctive radio spectrum.


title:
The dynamical evolution of the circumstellar gas around low-and
  intermediate-mass stars I: the AGB

abstract:
  We have investigated the dynamical interaction of low- and-intermediate mass
stars (from 1 to 5 Msun) with their interstellar medium (ISM). In this first
paper, we examine the structures generated by the stellar winds during the
Asymptotic Giant Branch (AGB) phase, using a numerical code and the wind
history predicted by stellar evolution. The influence of the external ISM is
also taken into account. We find that the wind variations associated with the
thermal pulses lead to the formation of transient shells with an average
lifetime of 20,000 yr, and consequently do not remain recorded in the density
or velocity structure of the gas. The formation of shells that survive at the
end of the AGB occurs via two main processes: shocks between the shells formed
by two consecutive enhancements of the mass-loss or via continuous accumulation
of the material ejected by the star in the interaction region with the ISM. Our
models show that the mass of the circumstellar envelope increases appreciably
due to the ISM material swept up by the wind (up to 70 % for the 1 Msun stellar
model). We also point out the importance of the ISM on the deceleration and
compression of the external shells. According to our simulations, large regions
(up to 2.5 pc) of neutral gas surrounding the molecular envelopes of AGB stars
are expected. These large regions of gas are formed from the mass-loss
experienced by the star during the AGB evolution.


title: Nonlinear Couplings Between r-modes of Rotating Neutron Stars

abstract:
  The r-modes of neutron stars can be driven unstable by gravitational
radiation. While linear perturbation theory predicts the existence of this
instability, linear theory can't provide any information about the nonlinear
development of the instability. The subject of this paper is the weakly
nonlinear regime of fluid dynamics. In the weakly nonlinear regime, the
nonlinear fluid equations are approximated by an infinite set of oscillators
which are coupled together so that terms quadratic in the mode amplitudes are
kept in the equations of motion. In this paper, the coupling coefficients
between the r-modes are computed. The stellar model assumed is a polytropic
model where a source of buoyancy is included so that the Schwarzschild
discriminant is nonzero. The properties of these coupling coefficients and the
types of resonances possible are discussed in this paper. It is shown that no
exact resonance involving the unstable $l=m=2$ r-mode occur and that only a
small number of modes have a dimensionless coupling constant larger than unity.
However, an infinite number of resonant mode triplets exist which couple
indirectly to the unstable r-mode. All couplings in this paper involve the
l>|m| r-modes which only exist if the star is slowly rotating. This work is
complementary to that of Schenk et al (2002) who consider rapidly rotating
stars which are neutral to convection.


title: Toward a Possible Solution to the Cosmic Coincidence Problem

abstract:
  It is a mystery why the density of matter and the density of vacuum energy
are nearly equal today when they scale so differently during the expansion of
the Universe. We suggest a paradigm that might allow for a non-anthropic
solution to this cosmic coincidence problem. The fact that the half life of
Uranium 238 is very near to the age of the solar system is not considered a
coincidence since there are many nuclides with half lives ranging over a huge
range of time scales implying that there is likely to be some nuclide with a
half life near to any given time scale. Likewise it may be that the vacuum
field energy causing the universal acceleration today is just one of a large
ensemble of scalar field energies, which have dominated the Universe in the
past and then faded away. Given that in standard cosmology and particle physics
there are already several scalar fields that probably contribute to universal
vacuum energy (the Higgs field, the inflaton, and whatever quintessence/dark
energy field causes the current acceleration), the idea of a large ensemble of
fields does not seem far fetched. Predictions of the idea include: 1) The
current vacuum energy driving the acceleration is not constant and will
eventually fade away, 2) The ratio w of scalar field pressure to density is
currently changing and is not precisely negative one, 3) There were likely
periods of vacuum dominance and acceleration in the past, 4) the current phase
of acceleration will end but there may be additional periods of acceleration in
the future, 5) the ultimate fate of the Universe cannot be decided until the
nature of these fields is known, but the eventual sum of densities from all
scalar fields could be zero, as was usually assumed before the discovery of the
current universal acceleration.


title: Possible Origin of Lognormal Distributions in Gamma-Ray Bursts

abstract:
  We show that if the intrinsic break energy of Gamma-Ray Bursts (GRBs) is
determined by the product of more than three random variables the observed
break energy distribution becomes almost lognormal including the redshift
effect because of the central limit theorem. The excess from the lognormal
distribution at the low break energy is possibly due to the high redshift GRBs.
The same argument may also apply to the pulse duration, the interval between
pulses and so on.


title:
Spherical Gravitational Collapse and Accretion - Exact General
  Relativistic Description

abstract:
  In this paper, we consider the problems of spherical gravitational collapse
and accretion using a spherically symmetric, spatially homothetic spacetime,
that is, as an exact solution (cqg1) of the field equations of general
relativity. Properties of matter like its equation of state determine whether
the collapse becomes unstoppable or not since the spacetime under consideration
admits any equation of state for matter in it. We can therefore describe the
formation of a semi-stable object here. {\bf A black hole may form in the
unstoppable gravitational collapse and/or accretion but only as an infinite
red-shift surface that is, however, not a null hyper-surface.} Therefore,
spherical, astrophysical black holes will always be of this type. This result
will have important implications for observational astrophysics and other
considerations in General Relativity based on the conception of black hole as a
null hyper-surface.


title:
XMM-Newton sets the record straight: No X-ray emission detected from PSR
  J0631+1036

abstract:
  The pulsar PSR J0631+1036 was discovered during a radio search of Einstein
X-ray source error circles. A detection of a 288ms sinusoidal modulation in the
ASCA lightcurve, the same period as the radio pulsar, appeared to confirm the
association of the X-ray source and the pulsar. Its X-ray spectrum was said to
be similar to that of middle aged gamma-ray pulsars such as Geminga. However,
an XMM-Newton observation of the PSR J0631+1035 field, along with a re-analysis
of VLA data confirming the timing position of the pulsar, show a 75''
discrepancy in location of the X-ray source and the pulsar, and therefore these
cannot be the same object. The X-ray source appears to be the counterpart of an
A0 star, detected by the XMM-Newton Optical Monitor. No 288ms period was
detected from either the area around the pulsar or the bright X-ray source. The
upper limit on the X-ray luminosity with relation to the empirically observed
correlation between radio measured dE/dt and X-ray luminosity is discussed.


title: Relativistic Binaries in Globular Clusters

abstract:
  The galactic population of globular clusters are old, dense star systems,
with a typical cluster containing $10^4 - 10^6$ stars. As an old population of
stars, globular clusters contain many collapsed and degenerate objects. As a
dense population of stars, globular clusters are the scene of many interesting
close dynamical interactions between stars. These dynamical interactions can
alter the evolution of individual stars and can produce tight binary systems
containing one or two compact objects. In this review, we discuss the
theoretical models of globular cluster evolution and binary evolution,
techniques for simulating this evolution which lead to relativistic binaries,
and current and possible future observational evidence for this population.
Globular cluster evolution will focus on the properties that boost the
production of hard binary systems and on the tidal interactions of the galaxy
with the cluster, which tend to alter the structure of the globular cluster
with time. The interaction of the components of hard binary systems alters the
evolution of both bodies and can lead to exotic objects. Direct $N$-body
integrations and Fokker-Planck simulations of the evolution of globular
clusters that incorporate tidal interactions and lead to predictions of
relativistic binary populations are also discussed. We discuss the current
observational evidence for cataclysmic variables, millisecond pulsars, and
low-mass X-ray binaries as well as possible future detection of relativistic
binaries with gravitational radiation.


title: LSB Galaxies and the Tully-Fisher Relation

abstract:
  We present VLA HI imaging of four LSB galaxies which were thought to strongly
deviate from the TF relation based on Arecibo single-dish observations. We do
not detect three of the four targeted LSB galaxies in HI down to a 4-sigma
limit of 0.08Jy km/s. We find that two of the four of these LSBs have bright
galaxies which have contaminated the Arecibo signal. A further examination of
the Arecibo sample shows that five out of the six galaxies that were found to
deviate from TF have nearby bright galaxies and we conclude that possibly all
but one of the non-TF galaxies are contaminated by HI from nearby galaxies. The
sixth galaxy was not detected by us. A new observation by Arecibo did not
confirm the earlier detection. The integrated profiles of the bright galaxies
are consistent with the Arecibo results both in velocity range and amplitude,
which indicates that most of the extreme deviators from the TF relation must
have been affected by bright companions in this earlier HI survey. A more
recent determination of the sidelobe structure of the Arecibo beam supports our
conclusion and shows that the degree of sidelobe contamination was much larger
than could have been initially predicted. Hence, we have corrected the results
found in O'Neil et al. (2000) and have reconstructed the TF relation. These new
observations then show a) a reconstructed TF relation that has relatively large
scatter at all values of rotational velocity (possibly indicating the true
range in disk galaxy properties) and b) the presence of at least some red, gas
poor, LSB disks that indeed may be in an advanced evolutionary state as the
faded remnants of their former high surface brightness actively star forming
state.


title:
A New Channel to Search for Extra-solar Systems with Multiple Planets
  via Gravitational Microlensing

abstract:
  Gaudi, Naber & Sackett pointed out that if an event is caused by a lens
system containing more than two planets, all planets will affect the central
region of the magnification pattern, and thus the existence of the multiple
planets can be inferred by detecting additionally deformed anomalies from
intensive monitoring of high magnification events. Unfortunately, this method
has important limitations in identifying the existence of multiple planets and
determining their parameters due to the degeneracy of the resulting light curve
anomalies from those induced by a single planet and the complexity of multiple
planet lensing models. In this paper, we propose a new channel to search for
multiple planets via microlensing. The method is based on the fact that the
anomalies induced by multiple planets are well approximated by the
superposition of those of the single planet systems where the individual
planet-primary pairs act as independent lens systems. Then, if the source
trajectory passes both of the outer deviation regions induced by the individual
planets, one can unambiguously identify the existence of the multiple planets.
We illustrate that the probability of successively detecting light curve
anomalies induced by two Jovian-mass planets located in the lensing zone
through this channel will be substantial. Since the individual anomalies can be
well modeled by much simpler single planet lensing models, the proposed method
has an important advantage of allowing one to accurately determine the
parameters of the individual planets.


title:
HST-NICMOS Observations of Terzan 5: Stellar Content and Structure of
  the Core

abstract:
  We report results from HST-NICMOS imaging of the extremely dense core of the
globular cluster Terzan 5. This highly obscured bulge cluster has been
estimated to have one of the highest collision rates of any galactic globular
cluster, making its core a particularly conducive environment for the
production of interacting binary systems. We have reconstructed high-resolution
images of the central 19"x19" region of Terzan 5 by application of the drizzle
algorithm to dithered NIC2 images in the F110W, F187W, and F187N near-infrared
filters. We have used a DAOPHOT/ALLSTAR analysis of these images to produce the
deepest color-magnitude diagram (CMD) yet obtained for the core of Terzan 5. We
have also analyzed the parallel 11"X11" NIC1 field, centered 30" from the
cluster center and imaged in F110W and F160W, and an additional NIC2 field that
is immediately adjacent to the central field. This imaging results in a clean
detection of the red-giant branch and horizontal branch in the central NIC2
field, and the detection of these plus the main-sequence turnoff and the upper
main sequence in the NIC1 field. We have constructed an H versus J-H CMD for
the NIC1 field. We obtain a new distance estimate of 8.7 kpc, which places
Terzan 5 within less than 1 kpc of the galactic center. We have also determined
a central surface-density profile which results in a maximum likelihood
estimate of 7.9" +/- 0.6" for the cluster core radius. We discuss the
implications of these results for the dynamical state of Terzan 5.


title: Warm Molecular Layers in Protoplanetary Disks

abstract:
  We have investigated molecular distributions in protoplanetary disks,
adopting a disk model with a temperature gradient in the vertical direction.
The model produces sufficiently high abundances of gaseous CO and HCO+ to
account for line observations of T Tauri stars using a sticking probability of
unity and without assuming any non-thermal desorption. In regions of radius R >
10 AU, with which we are concerned, the temperature increases with increasing
height from the midplane. In a warm intermediate layer, there are significant
amounts of gaseous molecules owing to thermal desorption and efficient
shielding of ultraviolet radiation by the flared disk. The column densities of
HCN, CN, CS, H2CO, HNC and HCO+ obtained from our model are in good agreement
with the observations of DM Tau, but are smaller than those of LkCa15.
Molecular line profiles from our disk models are calculated using a
2-dimensional non-local-thermal-equilibrium (NLTE) molecular-line radiative
transfer code for a direct comparison with observations. Deuterated species are
included in our chemical model. The molecular D/H ratios in the model are in
reasonable agreement with those observed in protoplanetary disks.


title: Molecular Evolution in Collapsing Prestellar Cores

abstract:
  We have investigated the evolution and distribution of molecules in
collapsing prestellar cores via numerical chemical models, adopting the
Larson-Penston solution and its delayed analogues to study collapse. Molecular
abundances and distributions in a collapsing core are determined by the balance
among the dynamical, chemical and adsorption time scales. When the central
density n_H of a prestellar core with the Larson-Penston flow rises to 3 10^6
cm^{-3}, the CCS and CO column densities are calculated to show central holes
of radius 7000 AU and 4000 AU, respectively, while the column density of N2H+
is centrally peaked. These predictions are consistent with observations of
L1544. If the dynamical time scale of the core is larger than that of the
Larson-Penston solution owing to magnetic fields, rotation, or turbulence, the
column densities of CO and CCS are smaller, and their holes are larger than in
the Larson-Penston core with the same central gas density. On the other hand,
N2H+ and NH3 are more abundant in the more slowly collapsing core. Therefore,
molecular distributions can probe the collapse time scale of prestellar cores.
Deuterium fractionation has also been studied via numerical calculations. The
deuterium fraction in molecules increases as a core evolves and molecular
depletion onto grains proceeds. When the central density of the core is n_H=3
10^6 cm^{-3}, the ratio DCO+/HCO+ at the center is in the range 0.06-0.27,
depending on the collapse time scale and adsorption energy; this range is in
reasonable agreement with the observed value in L1544.


title:
Two-dimensional Distributions and Column Densities of Gaseous Molecules
  in Protoplanetary Disks II

abstract:
  We have investigated the two-dimensional (R,Z) distribution of deuterated
molecular species in circumstellar disks around young stellar objects. The
abundance ratios between singly deuterated and normal molecules (``D/H
ratios'') in disks evolve in a similar way as in molecular clouds.
Fractionation is caused by rapid exchange reactions that are exothermic because
of energy differences between deuterated and normal species. In the midplane
region, where molecules are heavily depleted onto grain surfaces, the D/H
ratios of gaseous molecules are higher than at larger heights. The D/H ratios
for the vertical column densities of NH3, H2O, and HCO+ are sensitive to the
temperature, and decrease significantly with decreasing radial distance for R <
300 AU. The analogous D/H ratios for CH4 and H2CO, on the other hand, are not
very sensitive to the temperature in the range (T=10-50 K) we are concerned
with, and do not decrease with decreasing R at R > 50 AU. The D/H
column-density ratios also depend on disk mass. In a disk with a larger mass,
the ratios of deuterated species to normal species are higher, because of
heavier depletion of molecules onto grains. In the second part of the paper, we
report molecular column densities for disks embedded in ambient cloud gas. Our
results suggest that CN and HCO+ can be tracers of gaseous disks, especially if
the central object is a strong X-ray source. Our results also suggest that the
radial distributions of CN, C2H, HCN, and H2CO may vary among disks depending
on the X-ray luminosity of the central star.


title:
Proper Motion Measurements of Pulsar B1951+32 in the Supernova Remnant
  CTB 80

abstract:
  Using the Very Large Array and the Pie Town antenna, we have measured the
position of the radio pulsar B1951+32 relative to nearby background radio
sources at four epochs between 1989 and 2000. These data show a clear motion
for the pulsar of (25 +/- 4) milliarcsec/yr at a position angle (252 +/- 7)
degrees (north through east), corresponding to a transverse velocity (240 +/-
40) km/s for a distance to the source of 2 kpc. The measured direction of
motion confirms that the pulsar is moving away from the center of its
associated supernova remnant, the first time that such a result has been
demonstrated. Independent of assumptions made about the pulsar birth-place, we
show that the measured proper motion implies an age for the pulsar of (64 +/-
18) kyr, somewhat less than its characteristic age of 107 kyr. This discrepancy
can be explained if the initial spin period of the pulsar was (27 +/- 6) ms.


title:
Triaxial Modeling of Halo Density Profiles with High-resolution N-body
  Simulations

abstract:
  We present a detailed non-spherical modeling of dark matter halos on the
basis of a combined analysis of the high-resolution halo simulations (12 halos
with $N\sim 10^6$ particles within their virial radius) and the large
cosmological simulations (5 realizations with $N=512^3$ particles in a
$100h^{-1}$Mpc boxsize). The density profiles of those simulated halos are well
approximated by a sequence of the concentric triaxial distribution with their
axis directions being fairly aligned. We characterize the triaxial model
quantitatively by generalizing the universal density profile which has
previously been discussed only in the framework of the spherical model. We
obtain a series of practically useful fitting formulae in applying the triaxial
model; the mass and redshift dependence of the axis ratio, the mean of the
concentration parameter, and the probability distribution functions of the the
axis ratio and the concentration parameter. These accurate fitting formulae
form a complete description of the triaxial density profiles of halos in Cold
Dark Matter models. Our current description of the dark halos will be
particularly useful in predicting a variety of nonsphericity effects, to a
reasonably reliable degree, including the weak and strong lens statistics, the
orbital evolution of galactic satellites and triaxiality of galactic halos, and
the non-linear clustering of dark matter. In addition, this provides a useful
framework for the non-spherical modeling of the intra-cluster gas, which is
crucial in discussing the gas and temperature profiles of X-ray clusters and
the Hubble constant estimated via the Sunyaev -- Zel'dovich effect.


title: Two Years of the X-ray Sky in M31

abstract:
  We have been monitoring M31 with HRC and ACIS onboard \chandra regularly in
the past two years. By combining eight \chandra ACIS-I observations taken
between 1999 to 2001, we have identified 204 X-ray sources within the central
$\sim 17\arcmin\times17\arcmin$ region of M31, with a detection limit of $\sim
1.6\times10^{35}$\lum. Of these 204 sources, 21 are identified with globular
clusters, 2 with supernova remnants (one of them is spatially resolved with
\chandra), and 8 with planetary nebula. By comparing individual images, about
50% of the sources are variable in time scales of months. We also found 14
transients. Combining all the available transients found in literatures, there
are 25 transients in M31 and M32 detected by \chandra and \xmm; we present some
of the long-term lightcurves by using the HRC, ACIS and \xmm data. The spectral
shape of 12 sources is shown to be variable, suggesting that they went through
state changes. The luminosity function of all the point sources is consistent
with previous observations (a broken power-law with a luminosity break at
$1.7\times10^{37}$\lum). However, when the X-ray sources in different regions
are considered separately, different luminosity functions are obtained. This
indicates that the star formation history might be different in different
regions.


title:
Lensed Density Perturbations in Braneworlds: An Alternative to
  Perturbations from Inflation

abstract:
  We consider a scenario in which our observable universe is a 3-dimensional
surface (3-brane) living in extra dimensions with a warped geometry. We show
that ``lensed'' density perturbations from other branes serve as possible seeds
for structure formation on our observable brane (without inflation), and, in
addition, provide constraints on braneworld scenarios with warped bulk
geometry. Due to the warped bulk metric, any perturbation generated on one
brane (or in the bulk matter) appears to an observer on a second brane to have
a significantly different amplitude. We analyze lensed perturbations in the
Randall-Sundrum type scenarios and the ``shortcut metric'' scenarios. For
Lorentz violating metrics in the bulk, we find the attractive possibility that
large density fluctuations that are causally produced elsewhere can lead to
small density fluctuations on our brane on superhorizon (acausal) length
scales, as required by structure formation. Our most interesting result is that
the ``shortcut metrics'' in which geodesics traverse the extra dimensions
provide an alternative to inflation with two important features: a possible
solution to the horizon problem and a mechanism to generate perturbations
necessary for structure formation.


title: The s-process in rotating AGB stars

abstract:
  We discuss the occurrence of the s-process during the radiative interpulse
phase of rotating AGB stars. Due to differential rotation, protons are mixed
into C12-rich layers after thermal pulses, in the course of the so called third
dredge up episode. We follow the time evolution of key isotope abundances in
the relevant layers with a post-processing code which includes time dependant
mixing and nucleosynthesis. In rotating AGB models, the mixing persists during
the entire interpulse phase due to the steep gradient of angular velocity at
the envelope-core interface. As the layers containing protons and C12, which
are formed this way, become hotter, a C13-pocket is formed in a natural way.
However, in this situation also N14 is formed and spread over the entire
C13-pocket. We include the neutron consuming N14(n,p) reaction in our network
and determine to what extent it reduces the production of trans-iron elements.
We propose that rotation may be responsible for the spread of efficiencies of
the C13 neutron source as required by observations.


title:
Radiation fields of disk, BLR and torus in quasars and blazars:
  implications for gamma-ray absorption

abstract:
  The radiation fields external to the jets and originating from within a few
parsecs from the black hole, are discussed in this paper. They are the direct
radiation from an accretion disk in symbiosis with jets, the radiation field
from the broad line region (BLR) surrounding the accretion disk, and the
infrared radiation from a dusty torus. The jet/disk symbiosis modifies the
energetics in the central parsec of AGN such that for a given accretion rate, a
powerful jet would occur at the expense of the disk luminosity, and
consequently the disk would less efficiently ionize the BRL clouds or heat the
dust in the torus, thereby affecting potentially important target photon fields
for interactions of gamma-rays, accelerated electrons and protons along the
jet.
  Motivated by unification schemes of active galactic nuclei, we briefly review
the evidence for the existence of broad line regions and small-scale dust tori
in BL Lacs and Fanaroff-Riley Class I (FR-I) radio galaxies. We propose that an
existing jet-accretion disk symbiosis can be extrapolated to provide a large
scale-symbiosis between other important dusty constituents of the blazar/FR-I
family. In the present paper, we discuss in the context of this symbiosis
interactions of GeV and TeV gamma-rays produced in the jet with the various
radiation fields external to the jet in quasars and blazars, taking account the
anisotropy of the radiation.


title:
The structure and radiation spectra of illuminated accretion discs in
  AGN. I. Moderate illumination

abstract:
  We present detailed computations of the vertical structure of an accretion
disc illuminated by hard X-ray radiation with the code {\sc titan-noar}
suitable for Compton thick media. The energy generated via accretion is
dissipated partially in the cold disc as well as in the X-ray source. We study
the differences between the case where the X-ray source is in the form of a
lamp post above the accretion disc and the case of a heavy corona. We consider
radiative heating via Comptonization together with heating via photo-absorption
on numerous heavy elements as carbon, oxygen, silicon, iron. The transfer in
lines is precisely calculated. A better description of the heating/cooling
through the inclusion of line transfer, a correct description of the
temperature in the deeper layers, a correct description of the entire disc
vertical structure, as well as the study of the possible coronal pressure
effect, constitute an improvement in comparison to previous works. We show that
exact calculations of hydrostatic equilibrium and determination of the disc
thickness has a crucial impact on the optical depth of the hot illuminated
zone. We assume a moderate illumination where the viscous flux equals the X-ray
radiation flux. A highly ionized skin is created in the lamp post model, with
the outgoing spectrum containing many emission lines and ionization edges in
emission or absorption in the soft X-ray domain, as well as an iron line at
$\sim 7 $ keV consisting of a blend of low ionization line from the deepest
layers and hydrogen and helium like resonance line from the upper layers, and
almost no absorption edge, contrary to the case of a slab of constant density.A
full heavy corona completely suppresses the highly ionized zone on the top of
the accretion disc and in such case the spectrum is featureless.


title:
The Imprint of Presupernova Winds on Supernova Remnant Evolution:
  Towards More Realistic Models for Type Ia Supernova Remnants and their
  Spectra

abstract:
  Supernova remnants are usually analysed in the light of hydrodynamical models
of the interaction of supernova ejecta with either a constant density ambient
medium or a circumstellar medium produced by a constant presupernova wind.
However, the ejection of energetic wind during the presupernova phase changes
the ambient medium structure and, consequently, the early supernova remnant
evolution. We have analysed the evolution of young remnants of type Ia
supernovae, focusing on the imprint of the presupernova wind history on the
supernova remnant structure and on the influence of the explosion mechanism. We
have found that the remnant evolution is most sensitive to the explosion
mechanism at ages not larger than a few hundred years, while the presupernova
history shows its influence at later epochs, before the Sedov phase sets in.


title: Chandra observations of Abell 2199

abstract:
  We present results from an analysis of two Chandra observations of the rich,
nearby galaxy cluster Abell 2199. We find evidence (having corrected for
projection effects) for radial gradients in temperature and metallicity in the
X-ray emitting gas: the temperature drops from kT~4.2 keV at R=200 kpc to 1.6
keV within R=5 kpc of the centre. The metallicity rises from ~0.3 solar at
R=200 kpc to ~0.7 solar at R=30 kpc before dropping to 0.3 solar within the
central 5 kpc. We find evidence for structure in the surface brightness
distribution associated with the central radio source 3C338. No evidence is
found for the gas having a large spread in temperature at any particular
location despite the cooling time being short (<10**9yr) within the central ~15
kpc. Heating and mass cooling rates are calculated for various assumptions
about the state of the gas.


title:
TeV gamma rays from the blazar H 1426+428 and the diffuse extragalactic
  background radiation

abstract:
  The detection of TeV gamma-rays from the blazar H 1426+428 at an integral
flux level of (4 +- 2(stat) +- 1(syst)) 10^(-12) erg cm^(-2) s^(-1) above 1 TeV
with the HEGRA imaging atmospheric Cherenkov telescope system is reported. H
1426+428 is located at a redshift of z=0.129, which makes it the most distant
source detected in TeV gamma-rays so far. The TeV radiation is expected to be
strongly absorbed by the diffuse extragalactic background radiation (DEBRA).
The observed energy spectrum of TeV photons is in good agreement with an
intrinsic power law spectrum of the source ~E^(-1.9) corrected for DEBRA
absorption. Statistical errors as well as uncertainties about the intrinsic
source spectrum, however, do not permit strong statements about the density of
the DEBRA infrared photon field.


title:
The central binary and surrounding nebula of the symbiotic star V1016
  Cygni

abstract:
  We present HST/WFPC2 images of the symbiotic star V1016 Cyg which, for the
first time, directly explore the inner regions of the nebula to AU scales at
optical wavelengths. They also suggest that the [OIII] 4959,5007 emission takes
place in a bipolar outflow. We use these images to determine the position of
the two stars and hence a projected binary separation of 84 AU (assuming a
distance of 2 kpc) and a position angle of 143.5 degrees. Furthermore, we
combine our images with VLA radio imaging which enables diagnostic tests to be
applied and properties of the circumstellar nebula to be determined. Finally we
have obtained archive HST/STIS spectra of V1016 Cyg with which we were able to
spatially resolve the source at various positions in the nebula. This enabled
discovery of the ultraviolet counterpart to the ~25 arcsec extended emission
found by Bang et al. (1992).


title:
Neutrino Flux Bounds and Prospects for High Energy and Ultrahigh Energy
  Neutrino Source Detection

abstract:
  After briefly reviewing various hadronic neutrino source models, we show how
to construct generic upper flux bounds. We then turn to the problem of neutrino
propagation through the inner Earth and neutrino detection in water-based
Cerenkov detectors. Applying the formalism thus developed to the
Mannheim-Protheroe-Rachen and the Waxman&Bahcall flux bounds, we find that
event rates of several hundred to thousand events per year might be possible in
next-generation neutrino telescopes. However, a tomography of the inner Earth
will face severe constraints due to the statistical error of the event rates to
be expected.


title: Halpha rotation curves: the soft core question

abstract:
  We present high resolution Halpha rotation curves of 4 late-type dwarf
galaxies and 2 low surface brightness galaxies (LSB) for which accurate HI
rotation curves are available from the literature. Observations are carried out
at Telescopio Nazionale Galileo (TNG). For LSB F583-1 an innovative dispersing
element was used, the Volume Phase Holographic (VPH) with a dispersion of about
0.35 A/pxl. We find good agreement between the Halpha data and the HI
observations and conclude that the HI data for these galaxies suffer very
little from beam smearing. We show that the optical rotation curves of these
dark matter dominated galaxies are best fitted by the Burkert profile. In the
centers of galaxies, where the N-body simulations predict cuspy cores and fast
rising rotation curves, our data seem to be in better agreement with the
presence of soft cores.


title: The Cosmological Constant Problem and Quintessence

abstract:
  I briefly review the cosmological constant problem and the issue of dark
energy (or quintessence). Within the framework of quantum field theory, the
vacuum expectation value of the energy momentum tensor formally diverges as
$k^4$. A cutoff at the Planck or electroweak scale leads to a cosmological
constant which is, respectively, $10^{123}$ or $10^{55}$ times larger than the
observed value, $\l/8\pi G \simeq 10^{-47}$ GeV$^4$. The absence of a
fundamental symmetry which could set the value of $\l$ to either zero or a very
small value leads to {\em the cosmological constant problem}. Most cosmological
scenario's favour a large time-dependent $\l$-term in the past (in order to
generate inflation at $z \gg 10^{10}$), and a small $\l$-term today, to account
for the current acceleration of the universe at $z \lleq 1$. Constraints
arising from cosmological nucleosynthesis, CMB and structure formation
constrain $\l$ to be sub-dominant during most of the intermediate epoch
$10^{10} < z < 1$. This leads to the {\em cosmic coincidence} conundrum which
suggests that the acceleration of the universe is a recent phenomenon and that
we live during a special epoch when the density in $\l$ and in matter are
almost equal. Time varying models of dark energy can, to a certain extent,
ameliorate the fine tuning problem (faced by $\l$), but do not resolve the
puzzle of cosmic coincidence. I briefly review tracker models of dark energy,
as well as more recent brane inspired ideas and the issue of horizons in an
accelerating universe. Model independent methods which reconstruct the cosmic
equation of state from supernova observations are also assessed. Finally, a new
diagnostic of dark energy -- `Statefinder', is discussed.


title:
Discovery of complex narrow X-ray absorption features from the low-mass
  X-ray binary GX13+1 with XMM-Newton

abstract:
  We report the detection of a complex of narrow X-ray absorption features from
the low-mass X-ray binary GX13+1 during 3 XMM-Newton observations in 2000 March
and April. The features are consistent with being due to resonant scattering of
the K_alpha and K_beta lines of He- and H-like iron (Fe xxv and Fe xxvi) and
H-like calcium (Ca xx) K_alpha. Only the Fe xxvi K_alpha line has been
previously observed from GX13+1. Due to the closeness in energy the Fe xxv and
Fe xxvi K_beta features may also be ascribed to Nixxvii and Nixxviii K_alpha,
respectively. We also find evidence for the presence of a deep (tau~0.2) Fe xxv
absorption edge at 8.83 keV. The equivalent widths of the lines do not show any
obvious variation on a timescale of a few days suggesting that the absorbing
material is a stable feature of the system and present during a range of
orbital phases.


title: Spectral properties of faint hard X-ray selected sources

abstract:
  We present preliminary results from a XMM-Newton spectroscopic survey of hard
(2 -10 keV) X-ray sources detected serendipitously in seven EPIC FOVs. All
observations were performed during the performance/verif ication phase. The
resulting sample consists of 39 sources with fluxes ranging from 3 to 80 $\t
imes$ 10$^{-14}$ erg cm$^{-2}$ s$^{-1}$ in the 2-10 keV band. Most of these
sources (23 out of 39, i.e. 60%) are fainter than 8 $\times $ 10$^{-14}$ erg
cm$^{-2}$ s$^{-1}$. The sources have been selected in order to obtain detailed
X-ray spectral inform ation, that are unprecedented at such low flux levels and
for such a large sample.
  To date we also have optical counterparts for 23 out of 39 objects, with
0.0058 $\leq$ $z$ $\leq$ 1.187.
  About 70% of the sources have spectra well fitted with a simple power law
model with Galactic absorption. For 9 objects (five of type 1, one of type 2
and three normal galaxies) absorption in excess to the Galactic one is
required. Additional emission/absorption components (i.e. soft excess, warm
absorber) are observed in 4 sources.


title: Magnetic Field Evolution in Accreting White Dwarfs

abstract:
  We discuss the evolution of the magnetic field of an accreting white dwarf.
We first show that the timescale for ohmic decay in the liquid interior is 8 to
12 billion years for a dipole field, and 4 to 6 billion years for a quadrupole
field. We then compare the timescales for ohmic diffusion and accretion at
different depths in the star, and for a simplified field structure and
spherical accretion, calculate the time-dependent evolution of the global
magnetic field at different accretion rates. In this paper, we neglect mass
loss by classical nova explosions and assume the white dwarf mass increases
with time. In this case, the field structure in the outer layers of the white
dwarf is significantly modified for accretion rates above the critical rate
(1-5) x 10^(-10) solar masses per year. We consider the implications of our
results for observed systems. We propose that accretion-induced magnetic field
changes are the missing evolutionary link between AM Her systems and
intermediate polars. The shorter ohmic decay time for accreting white dwarfs
provides a partial explanation of the lack of accreting systems with 10^9 G
fields. In rapidly accreting systems such as supersoft X-ray sources,
amplification of internal fields by compression may be important for Type Ia
supernova ignition and explosion. Finally, spreading matter in the polar cap
may induce complexity in the surface magnetic field, and explain why the more
strongly accreting pole in AM Her systems has a weaker field. We conclude with
speculations about the field evolution when classical nova explosions cause the
white dwarf mass to decrease with time.


title:
The HELLAS2XMM survey: II. Multiwavelength observations of P3: an X-ray
  bright, optically inactive galaxy

abstract:
  Recent X-ray surveys have clearly demonstrated that a population of optically
dull, X-ray bright galaxies is emerging at 2-10 keV fluxes of the order of
10^{-14} erg cm^{-2} s^{-1}. Although they might constitute an important
fraction of the sources responsible for the hard X-ray background, their nature
is still unknown. With the aim to better understand the physical mechanisms
responsible for the observed properties, we have started an extensive program
of multiwavelength follow-up observations of hard X-ray, optically quiet
galaxies discovered with XMM-Newton. Here we report the results of what can be
considered the first example of this class of objects: CXOUJ031238.9-765134,
originally discovered by Chandra, and optically identified by Fiore et al.
(2000) with an apparently normal early-type galaxy at z=0.159, usually known as
"FIORE P3". The analysis of the broad-band energy distribution suggests the
presence of a heavily obscured active nucleus.


title:
Chandra Observations of the QSO Pair Q2345+007: Binary Quasar or Massive
  Dark Lens?

abstract:
  The components of the wide (7.3") separation quasar pair Q2345+007A,B
(z=2.15) have the most strikingly similar optical spectra seen to date (Steidel
& Sargent 1991) yet no detected lensing mass, making this system the best
candidate known for a massive (1e14 Msun) dark matter lens system. Here we
present results from a 65ksec Chandra observation designed to investigate
whether it is a binary quasar or a gravitational lens. We find no X-ray
evidence for a lensing cluster to a (0.5-2keV) flux limit of 2e-15 cgs, which
is consistent with lensing only for a reduced baryon fraction. Using the
Chandra X-ray observations of the quasars themselves, together with new and
published optical measurements, we use the observed emission properties of the
quasars for further tests between the lens and binary hypotheses. Assuming
similar line-of-sight absorption to the images, we find that their X-ray
continuum slopes are inconsistent (Gamma_A=2.30 and Gamma_B=0.83) as are their
X-ray to optical flux ratios. The probability that B suffers absorption
sufficient to account for these spectral differences is negligible. We present
new optical evidence that the flux ratio of the pair is variable, so the
time-delay in a lens scenario could cause some of the discrepancies. However,
adequately large variations in overall spectral energy distribution are rare in
individual QSOs. All new evidence here weighs strongly toward the binary
interpretation. Q2345+007 thus may represent the highest redshift example known
of interaction-triggered but as-yet unmerged luminous AGN.


title: Cyclotron Emission and Thermalization of the CMB Spectrum

abstract:
  If there was a weak magnetic field in the early universe, cyclotron emission
could play an important role in the thermalization of the CMB. We study this
process in the tightly coupled primordial electron-photon plasma and find that
if the magnetic field is large enough so that the plasma effects allow emission
of cyclotron photons, this process will wipe out deviations from the black body
spectrum.


title:
Resolving the Composite Fe K-alpha Emission Line in the Galactic Black
  Hole Cygnus X-1 with Chandra

abstract:
  We observed the Galactic black hole Cygnus X-1 with the Chandra High Energy
Transmission Grating Spectrometer for 30 kiloseconds on 4 January, 2001. The
source was in an intermediate state, with a flux that was approximately twice
that commonly observed in its persistent low/hard state. Our best-fit model for
the X-ray spectrum includes narrow Gaussian emission line (E = 6.415 +/- 0.007
keV, FWHM = 80 (+28, -19) eV, W = 16 (+3, -2) eV) and broad line (E = 5.82
(+0.06, -0.07) keV, FWHM = 1.9 (+0.5, -0.3) keV, W = 140 (+70, -40) eV)
components, and a smeared edge at 7.3 +/- 0.2 keV (tau ~ 1.0). The broad line
profile is not as strongly skewed as those observed in some Seyfert galaxies.
We interpret these features in terms of an accretion disk with irradiation of
the inner disk producing a broad Fe K-alpha emission line and edge, and
irradiation of the outer disk producing a narrow Fe K-alpha emission line. The
broad line is likely shaped predominantly by Doppler shifts and gravitational
effects, and to a lesser degree by Compton scattering due to reflection. We
discuss the underlying continuum X-ray spectrum and these line features in the
context of diagnosing the accretion flow geometry in Cygnus X-1 and other
Galactic black holes.


title:
Unveiling the Progenitors of GRBs through Observations of their Host
  Galaxies

abstract:
  I discuss the possibility of differentiating between popular models for
gamma-ray bursts by using multiwavelength observations to constrain the
characteristics of their host galaxies, in particular the age of the stellar
populations.


title:
Probing the Invisible Universe: The Case for Far-IR/Submillimeter
  Interferometry

abstract:
  The question "How did we get here and what will the future bring?" captures
the human imagination and the attention of the National Academy of Science's
Astronomy and Astrophysics Survey Commitee (AASC). Fulfillment of this
"fundamental goal" requires astronomers to have sensitive, high angular and
spectral resolution observations in the far-infrared/submillimeter
(far-IR/sub-mm) spectral region. With half the luminosity of the universe and
vital information about galaxy, star and planet formation, observations in this
spectral region require capabilities similar to those currently available or
planned at shorter wavelengths. In this paper we summarize the scientific
motivation, some mission concepts and technology requirements for far-IR/sub-mm
space interferometers that can be developed in the 2010-2020 timeframe.


title:
The temporal characteristics of the Chandra X-ray Observatory high
  energy particle background

abstract:
  It was observed early on in the Chandra X-ray Observatory mission that the
background rates of the Advanced CCD Imaging Spectrometer (ACIS) were highly
variable on both short and long timescales. We present analysis of lightcurves
of the high energy (> 15 keV) ACIS background spanning most of the mission
lifetime. These high energy events are not produced by astrophysical X-rays,
but by the particle background, primarily energetic protons. Temporal
characteristics of both the quiescent background and background flares will be
discussed as well as correlations with Chandra's orbital position and the solar
activity cycle. The strength and frequency of background flares appear cyclic
with a quasi-annual period, most likely from the motion of Chandra's orbit
through the geomagnetic environment.


title: Searching for obscured supernovae in nearby starburst galaxies

abstract:
  We are currently carrying out a K_s band survey for core-collapse supernovae
in the nuclear (central kpc) regions of nearby starburst galaxies with the
INGRID near-IR camera at the WHT. In this article we concentrate in describing
mainly the observations and the real time processing of the SN search data,
which makes use of the ING's integrated data flow system.


title:
A Search for Gamma-Ray Bursts and Pulsars, and the Application of Kalman
  Filters to Gamma-Ray Reconstruction

abstract:
  Part I describes the analysis of periodic and transient signals in EGRET
data. A method to search for the transient flux from gamma-ray bursts
independent of triggers from other gamma-ray instruments is developed. Several
known gamma-ray bursts were independently detected, and there is evidence for a
previously unknown gamma-ray burst candidate. Statistical methods using maximum
likelihood and Bayesian inference are developed and implemented to extract
periodic signals from gamma-ray sources in the presence of significant
astrophysical background radiation. The analysis was performed on six pulsars
and three pulsar candidates. The three brightest pulsars, Crab, Vela, and
Geminga, were readily identified, and would have been detected independently in
the EGRET data without knowledge of the pulse period. No significant pulsation
was detected in the three pulsar candidates. Eighteen X-ray binaries were
examined. None showed any evidence of periodicity. In addition, methods for
calculating the detection threshold of periodic flux modulation were developed.
The future hopes of gamma-ray astronomy lie in the development of the Gamma-ray
Large Area Space Telescope, or GLAST. Part II describes the development and
results of the particle track reconstruction software for a GLAST science
prototype instrument beam test. The Kalman filtering method of track
reconstruction is introduced and implemented. Monte Carlo simulations, very
similar to those used for the full GLAST instrument, were performed to predict
the instrumental response of the prototype. The prototype was tested in a
gamma-ray beam at SLAC. The reconstruction software was used to determine the
incident gamma-ray direction. It was found that the simulations did an
excellent job of representing the actual instrument response.


title: SLOTT-AGAPE Data Processing

abstract:
  MEDEA Program (Microlensing Experiment Data-Analysis Software for Event with
Amplification) is here presented. It is developed to the pixel lensing analysis
used by SLOTT-AGAPE (Systematic Lensing Observation at Toppo Telescope -
Andromeda Gravitational Amplification Pixel Experiment) Collaboration. All
software components are fully automated and they can be used on-line and
off-line.


title: Lognormal Property of Weak Lensing Fields

abstract:
  The statistical property of the weak lensing fields is studied quantitatively
using the ray-tracing simulations. Motivated by the empirical lognormal model
that characterizes the probability distribution function(PDF) of the
three-dimensional mass distribution excellently, we critically investigate the
validity of lognormal model in the weak lensing statistics. Assuming that the
convergence field, $\kappa$, is approximately described by the lognormal
distribution, we present analytic formulae of convergence for the one-point PDF
and the Minkowski functionals. Comparing those predictions with ray-tracing
simulations in various cold dark matter models, we find that the one-point
lognormal PDF can describe the non-Gaussian tails of convergence fields
accurately up to $\nu\sim10$, where $\nu$ is the level threshold given by
$\nu\equiv\kappa/\var^{1/2}$, although the systematic deviation from lognormal
prediction becomes manifest at higher source redshift and larger smoothing
scales. The lognormal formulae for Minkowski functionals also fit to the
simulation results when the source redshift is low. Accuracy of the
lognormal-fit remains good even at the small angular scales, where the
perturbation formulae by Edgeworth expansion break down. On the other hand,
lognormal models does not provide an accurate prediction for the statistics
sensitive to the rare events such as the skewness and the kurtosis of
convergence. We therefore conclude that the empirical lognormal model of the
convergence field is safely applicable as a useful cosmological tool, as long
as we are concerned with the non-Gaussianity of $\nu\simlt5$ for low source
redshift samples.


title:
X-ray Study of Seventy-nine Distant Clusters of Galaxies: Discovery of
  Two Classes of Cluster Size

abstract:
  We have performed a uniform analysis of 79 clusters of galaxies with the
ROSAT HRI and ASCA to study the X-ray structure and evolution of clusters in
the redshift range 0.1 < z < 1. We determined the average X-ray temperatures
and the bolometric luminosities with ASCA and the spatial distributions of the
X-ray brightness with the ROSAT HRI by utilizing the isothermal beta-model. We
do not find any significant redshift dependence in the X-ray parameters
including the temperature, beta-model parameters, and the central electron
density. Among the parameters, the core radius shows the largest
cluster-to-cluster dispersions. We discovered that the histogram of the core
radius shows two peaks at 60 and 220 kpc. If we divide the cluster samples into
two subgroups corresponding to the two peaks in the core radius distribution,
they show differences in the X-ray and optical morphologies and in the X-ray
luminosity temperature relation. From these observational results, we suggest
that the clusters are divided into at least two subgroups according to the core
radius.


title: The ISO-LWS map of the Serpens cloud core. II. The line spectra

abstract:
  We present spectrophotometric ISO imaging with the LWS and the CAM-CVF of the
Serpens molecular cloud core. The LWS map is centred on the far infrared and
submillimetre source SMM1 and its size is 8' x 8'. The fine structure line
emission in [OI] and [CII] is extended and can be successfully modelled to
originate in a PDR with G_0 = 15 and n(H2) about 10^4 - 10^5 cm^-3. Extended
emission is also observed in the rotational line emission of H2O and high-J CO.
However, lack of sufficient angular resolution prevents us from excluding the
possibility that the emssion regions of these lines are point like, which could
be linked to the embedded objects SMM9 and SMM4. Toward the Class0 source SMM1,
the LWS observations reveal, in addition to fine structure line emission, a
rich spectrum of molecular lines. The sub-thermally excited and optically thick
CO, H2O and OH lines are tracing an about 10^3 AU source with temperatures
higher than 300 K and densities above 10^6 cm^-3. We show that geometry is of
concern for the correct interpretation of the data and based on 2D-radiative
transfer modelling of the disk/torus around SMM1, which successfully reproduces
the entire observed SED and the observed line profiles of CO isotopomers, we
can exclude the disk to be the source of the LWS-molecular line emission. The
CAM-CVF permits us to see a region of rotational H2 emission. This H2 gas has a
temperature of 10^3 K, which suggests that the heating of the gas is achieved
through relatively slow shocks. Although we are not able to establish any firm
conclusion regarding the detailed nature of the shock waves, our observations
of the molecular line emission from SMM1 can be explainable in terms of an
admixture of J-shocks and of C-shocks.


title: Iron Features in the XMM-Newton spectrum of NGC 4151

abstract:
  We present a detailed analysis of the hard X-ray (>2.5 keV) EPIC spectra from
the first observations of NGC 4151 made by XMM-Newton. We fit the spectra with
a model consisting of a power-law continuum modified by line-of-sight
absorption (arising in both partially photoionized and neutral gas) plus
additional iron-K emission and absorption features. This model provides an
excellent overall fit to the EPIC spectra. The iron K-alpha line is well
modelled as a narrow Gaussian component. In contrast to several earlier studies
based on data from ASCA, a relativistically broadened iron K-alpha emission
feature is not required by the XMM-Newton data. The upper limit on the flux
contained in any additional broad line is ~8% of that in the narrow line. The
measured intrinsic line width (sigma =32+_7 eV) may be ascribed to (i) the
doublet nature of the iron K-alpha line and (ii) emission from low ionization
states of iron, ranging from neutral up to ~FeXVII. The additional iron
absorption edge arises in cool material and implies factor ~2 overabundance of
iron in this component.


title: Cosmological parameter estimation and the inflationary cosmology

abstract:
  We consider approaches to cosmological parameter estimation in the
inflationary cosmology, focussing on the required accuracy of the initial power
spectra. Parametrizing the spectra, for example by power-laws, is well suited
to testing the inflationary paradigm but will only correctly estimate
cosmological parameters if the parametrization is sufficiently accurate, and we
investigate conditions under which this is achieved both for present data and
for upcoming satellite data. If inflation is favoured, reliable estimation of
its physical parameters requires an alternative approach adopting its detailed
predictions. For slow-roll inflation, we investigate the accuracy of the
predicted spectra at first and second order in the slow-roll expansion
(presenting the complete second-order corrections for the tensors for the first
time). We find that within the presently-allowed parameter space, there are
regions where it will be necessary to include second-order corrections to reach
the accuracy requirements of MAP and Planck satellite data. We end by proposing
a data analysis pipeline appropriate for testing inflation and for cosmological
parameter estimation from high-precision data.


title: Abundance gradients and the role of SNe in M87

abstract:
  We make a detailed measurement of the metal abundance profiles and metal
abundance ratios of the inner core of M87/Virgo observed by XMM-Newton during
the PV phase. We use multi temperature models for the inner regions and we
compare the plasma codes APEC and MEKAL. We confirm the strong heavy elements
gradient previously found by ASCA and BeppoSAX, but also find a significant
increase in light elements, in particular O. This fact together with the
constant O/Fe ratio in the inner 9 arcmin indicates an enhancement of
contribution in the core of the cluster not only by SNIa but also by SNII.


title: Strangelets and their possible astrophysical origin

abstract:
  We discuss the first-order phase transition of QCD at high temperature in the
universe and the possible formation of quark-matter lumps through cooling in
regions of increased pressure. We show tha similarity of results using
confinement and breaking of chiral symmetry. The inclusion of strange matter
may give stability to small drops, or strangelets, in the colour-flavour locked
phase possibly achieved in neutron stars that could reach a high-altitude
observatory like that of Chacaltaya as primary cosmic rays.


title:
Galactic Cosmic Rays from Superbubbles and the Abundances of Lithium,
  Beryllium, and Boron

abstract:
  In this article we study the galactic evolution of the LiBeB elements within
the framework of a detailed model of the chemical evolution of the Galaxy that
includes galactic cosmic ray nucleosynthesis by particles accelerated in
superbubbles. The chemical composition of the superbubble consists of varying
proportions of ISM and freshly supernova synthesized material. The
observational trends of 6 LiBeB evolution are nicely reproduced by models in
which GCR come from a mixture of 25% of supernova material with 75% of ISM,
except for 6 Li, for which maybe an extra source is required at low
metallicities. To account for 7 Li evolution several additional sources have
been considered (neutrino-induced nucleosynthesis, nova outbursts, C-stars).
The model fulfills the energetic requirements for GCR acceleration.


title:
The Power Spectrum for a Multi-Component Inflaton to Second-Order
  Corrections in the Slow-Roll Expansion

abstract:
  We derive the power spectrum $\mathcal P(k)$ of the density perturbations
produced during inflation up to second-order corrections in the standard
slow-roll approximation for an inflaton with more than one degree of freedom.
We also present the spectral index $n$ up to first-order corrections including
previously missing terms, and the running ${dn}/{d\ln k}$ to leading order.


title: Low-Temperature Direct Dark Matter Searches

abstract:
  Small cryogenic detectors with efficient background rejection now best longer
established and heavier direct dark matter searches. This paper reviews the
experiments, results and prospects.


title: Temporal and Spectral Properties of Gamma-Ray Flashes

abstract:
  The temporal and spectral properties of terrestrial gamma-ray flashes (TGFs)
are studied. The delay of low energy photons relative to high energy ones in
the gamma-ray variations of the TGFs with high signal to noise ratio has been
revealed by an approach of correlation analysis in the time domain on different
time scales. The temporal structures of the TGFs in high energy band are
usually narrower than that in low energy band. The spectral hardness has a
general trend of decreasing with time in a flash. The observed temporal and
spectral characteristics give constraints and valuable hints on the flash
production mechanism.