title:
A Diffuse X-Ray Source, AX J1843.8-0352: Association with the Radio
  Complex G28.6-0.1 and Identification of a New Supernova Remnant

abstract:
  ASCA discovered an extended source in the Scutum constellation. The X-ray
morphology is an elliptical shape elongated from north to south with a mean
diameter of about 10'. The image center is located at RA = 18h43m53s, DEC =
03D52'55'' (hereafter, AX J1843.8-0352). The north and south rims of AX
J1843.8-0352 are associated with non-thermal radio sources C and F of the
G28.6-0.1 complex (Helfand et al. 1989). The X-ray spectrum was fitted with a
model of either a thin thermal plasma in non-equilibrium ionization of a
temperature 5.4 keV or a power-law of photon index 2.1. The absorption column
is (2.4-4.0)E22 /cm2, which probably places this source in the Scutum arm. With
a reasonable distance assumption of about 7 kpc, we estimate the mean diameter
and X-ray luminosity to be ~20 pc and ~3E34 erg/s, respectively. Although a
Sedov solution for a thin thermal plasma model gives parameters of a young
shell-like SNR, no strong emission lines are found with the metal abundances
being ~solar. Thus, a more likely scenario for both the radio and X-ray spectra
and the morphologies is that AX J1843.8-0352 is a shell-like SNR which
predominantly emits synchrotron X-rays.


title: A relativistic jet from Cygnus X-1 in the low/hard X-ray state

abstract:
  We present the detection of a radio-emitting jet from the black-hole
candidate and X-ray binary source Cygnus X-1. Evidence of a bright core with a
slightly extended structure was found on milliarcsecond resolution observations
with the VLBA at 15.4 GHz. Later observations with the VLBA (and including the
phased up VLA) at 8.4 GHz show an extended jet-like feature extending to
approx. 15 mas from a core region, with an opening angle of < 2 degrees. In
addition, lower resolution MERLIN observations at 5 GHz show that the source
has < 10 per cent linear polarization. The source was in the low/hard X-ray
state during the observations, and the results confirm the existence of
persistent radio emission from an unresolved core and a variable relativistic
(> 0.6c) jet during this state.


title:
Monte Carlo cluster simulations to determine the rate of compact star
  inspiraling to a central galactic black hole

abstract:
  The capture and gradual inspiral of stellar mass objects by a massive black
hole at the centre of a galaxy has been proposed as one of the most promising
source of gravitational radiation to be detected by LISA. Unfortunately rate
estimates for this process suffer from many uncertainties. Here we report on
the use of our newly developed Monte Carlo stellar dynamics code to tackle this
problem. We present results from simple galactic nuclei models that demonstrate
the high potential of our approach and point out the aspects of the problem
where an improved treatment seems desirable.


title: Dwarf Galaxies and Star Clusters in Tidal Tails

abstract:
  We summarize the properties of tidal dwarf candidates in a sample of
interacting galaxies and classify objects in tidal tails depending on their
morphological appearance. New high-resolution dynamical models are needed to
understand how the different structures seen in tidal tails are formed.


title:
The Origin of the Density Distribution of Disk Galaxies: A New Problem
  for the Standard Model of Disk Formation

abstract:
  We present new models for the formation of disk galaxies that improve upon
previous models by following the detailed accretion and cooling of the baryonic
mass, and by using realistic distributions of specific angular momentum. Under
the assumption of detailed angular momentum conservation the disks that form
have density distributions that are more centrally concentrated than an
exponential. We examine the influence of star formation, bulge formation, and
feedback on the outcome of the surface brightness distributions of the stars.
Whereas the models are succesful in reproducing high surface brightness disks,
they fail to produce exponential disks of low surface brightness. In addition,
the models predict truncation radii in the gas that occur at too high surface
density. This signals a new problem for the standard model of disk formation:
if the baryonic component of the protogalaxies out of which disk galaxies form
have the same angular momentum distribution as the dark matter, disks are too
compact.


title:
Dynamics of gravitational clustering III. The quasi-linear regime for
  some non-Gaussian initial conditions

abstract:
  Using a non-perturbative method developed in a previous work (paper II), we
derive the probability distribution $P(\delta_R)$ of the density contrast
within spherical cells in the quasi-linear regime for some non-Gaussian initial
conditions. We describe three such models. The first one is a straightforward
generalization of the Gaussian scenario. It can be seen as a phenomenological
description of a density field where the tails of the linear density contrast
distribution would be of the form $P_L(\delta_L) \sim
e^{-|\delta_L|^{-\alpha}}$, where $\alpha$ is no longer restricted to 2 (as in
the Gaussian case). We derive exact results for $P(\delta_R)$ in the
quasi-linear limit. The second model is a physically motivated isocurvature CDM
scenario. Our approach needs to be adapted to this specific case and in order
to get convenient analytical results we introduce a simple approximation (which
is not related to the gravitational dynamics but to the initial conditions).
Then, we find a good agreement with the available results from numerical
simulations for the pdf of the linear density contrast for $\delta_{L,R} \ga
0$. We can expect a similar accuracy for the non-linear pdf $P(\delta_R)$.
Finally, the third model corresponds to the small deviations from Gaussianity
which arise in standard slow-roll inflation. We obtain exact results for the
pdf of the density field in the quasi-linear limit, to first-order over the
primordial deviations from Gaussianity.


title:
The 2dF Galaxy Redshift Survey: Galaxy luminosity functions per spectral
  type

abstract:
  We calculate the optical bj luminosity function of the 2dF Galaxy Redshift
Survey (2dFGRS) for different subsets defined by their spectral properties.
These spectrally selected subsets are defined using a new parameter, eta, which
is a linear combination of the first two projections derived from a Principal
Component Analysis. This parameter eta identifies the average emission and
absorption line strength in the galaxy rest-frame spectrum and hence is a
useful indicator of the present star formation. We use a total of 75,000
galaxies in our calculations, chosen from a sample of high signal-to-noise
ratio, low redshift galaxies observed before January 2001. We find that there
is a systematic steepening of the faint end slope (alpha) as one moves from
passive (alpha = -0.54) to active (alpha = -1.50) star-forming galaxies, and
that there is also a corresponding faintening of the rest-frame characteristic
magnitude M* - 5\log_10(h) (from -19.6 to -19.2). We also show that the
Schechter function provides a poor fit to the quiescent (Type 1) LF for very
faint galaxies (M - 5log_10(h) fainter than -16.0), perhaps suggesting the
presence of a significant dwarf population. The luminosity functions presented
here give a precise confirmation of the trends seen previously in a much
smaller preliminary 2dFGRS sample, and in other surveys. We also present a new
procedure for determining self-consistent K-corrections and investigate
possible fibre-aperture biases.


title: Gas in the central region of AGNs: ISM and supermassive gaseous objects

abstract:
  This is a starting point of future work on a more detailed study of early
evolutionary phases of galactic nuclei. We put into port the study of the
evolution of star accretion onto a supermassive gaseous object in the central
region of an active galactic nucleus, which was previously addressed
semi-analytically. For this purpose, we use a gaseous model of relaxing dense
stellar systems, whose equations are solved numerically. The model is shortly
described and some first model calculations for the specific case of black hole
mass growth in time are given. Similar concepts will be applied in future work
for a system in which there is a dense interstellar medium as a possible
progenitor of a black hole in the galactic centre.


title:
A measurement of the broad-band spectrum of XTE J1118+480 with BeppoSAX
  and its astrophysical implications

abstract:
  We report on results of a target of opportunity observation of the X-ray
transient XTE J1118+480 performed on 2000 April 14-15 with the Narrow Field
Instruments (0.1-200 keV) of the SAX satellite. The measured spectrum is a
power law with a photon index of ~1.7 modified by an ultrasoft X-ray excess and
a high-energy cutoff above ~100 keV. The soft excess is consistent with a
blackbody with temperature of ~40 eV and a low flux, while the cut-off power
law is well fitted by thermal Comptonization in a plasma with an electron
temperature of 100 keV and an optical depth of order of unity. Consistent with
the weakness of the blackbody, Compton reflection is weak. Though the data are
consistent with various geometries of the hot and cold phases of the accreting
gas, we conclude that a hot accretion disk is the most plausible model. The
Eddington ratio implied by recent estimates of the mass and the distance is
about 10^{-3}, which may indicate that advection is probably not the dominant
cooling mechanism. We finally suggest that the reflecting medium has a low
metallicity, consistent with location of the system in the halo.


title: High-Energy Neutrino Production through Photopion Processes in Blazars

abstract:
  The measured spectral energy distribution and variability time scale are used
to determine the radiation and magnetic-field energy densities in the
relativistic plasma that forms the gamma-ray emitting jet in the blazar 3C 279.
Assuming that protons are accelerated as efficiently as electrons to a maximum
energy determined by the size and magnetic field of the emitting region, we
calculate the emissivity of neutrinos produced by protons that interact with
the external radiation field intercepted by the jet. The external radiation
field provides the most important target photons for photomeson production of
high-energy neutrinos in flat spectrum radio quasars (FSRQs). Because of
photomeson interactions with this field, km^2 neutrino telescopes are predicted
to detect > 0.1-1 neutrinos per year from blazars such as 3C 279. BL Lac
objects are weaker neutrino sources if, as widely thought, their gamma-ray
emission is due to Compton-scattered synchrotron (SSC) radiation.


title:
Color Separation of Galaxy Types in the Sloan Digital Sky Survey Imaging
  Data

abstract:
  We study the optical colors of 147,920 galaxies brighter than g* = 21,
observed in five bands by the Sloan Digital Sky Survey (SDSS) over ~100 sq.
deg. of high Galactic latitude sky along the Celestial Equator. The
distribution of galaxies in the g*-r* vs. u*-g* color--color diagram is
strongly bimodal, with an optimal color separator of u*-r* = 2.22. We use
visual morphology and spectral classification of subsamples of 287 and 500
galaxies respectively, to show that the two peaks correspond roughly to early
(E, S0, Sa) and late (Sb, Sc, Irr) type galaxies, as expected from their
different stellar populations. We also find that the colors of galaxies are
correlated with their radial profiles, as measured by the concentration index
and by the likelihoods of exponential and de Vaucouleurs' profile fits. While
it is well known that late type galaxies are bluer than early type galaxies,
this is the first detection of a local minimum in their color distribution. In
all SDSS bands, the counts vs. apparent magnitude relations for the two color
types are significantly different, and indicate that the fraction of blue
galaxies increases towards the faint end.


title: Spectral Evolution of Circinus X-1 Along its Orbit

abstract:
  We report on the spectral analysis of Circinus X-1 observed by the ASCA
satellite in March 1998 along one orbital period. The luminosity of the source
(in the 0.1-100 keV band) ranges from $2.5 \times 10^{38}$ erg s$^{-1}$ at the
periastron (orbital phase 0.01) to $1.5 \times 10^{38}$ erg s$^{-1}$ at orbital
phase 0.3. From the spectral analysis and the lightcurve we argue that Cir X-1
shows three states along the orbital evolution. The first state is at the
orbital phase interval 0.97-0.3: the luminosity becames super-Eddington and a
strong flaring activity is present. In this state a shock could form in the
inner region of the system due to the super-Eddington accretion rate, producing
an outflow of ionized matter whose observational signature could be the
prominent absorption edge at $\sim 8.7$ keV observed in the energy spectrum at
these phases. In the second state, corresponding to the orbital phase interval
between 0.3 and 0.7, the accretion rate is sub-Eddington and we observe a
weaker outflow, with smaller hydrogen column: the absorption edge is now at
$\sim 8.3$ keV with an optical depth a factor of 2.5 to 6 smaller. The third
state corresponds to the orbital phase interval 0.78-0.97. In this state the
best fit model to the spectrum requires the presence of a partial covering
component, indicating that the emission from the compact object is partially
absorbed by neutral matter, probably the atmosphere of the companion star
and/or the accreting matter from the companion.


title:
Ultra High Energy Neutrino-Relic Neutrino Interactions In Dark Halos to
  Solve Infrared-Tev And GZK Cut-Off

abstract:
  Ultra High Energy Neutrino scattering on Relic Light Neutrinos in Dark
Galactic or Local Group lead to Z and WW,ZZ showering: the nucleon component of
the shower may overcome the GZK cut-off while the electro-magnetic tail at TeVs
up to EeVs energy may solve the Infrared-TeV cut-off in a natural way.
Different Gamma TeV puzzles may find a solution within this scenario: new
predictions on UHECR spectra in future data are derived.


title: 900-1200A interstellar extinction in the Galaxy, LMC, and SMC

abstract:
  We have derived far-ultraviolet extinction curves for stars in the Galaxy,
LMC, and SMC, from spectra of pairs of stars observed with the FUSE satellite,
matched in spectral type and with different amounts of reddening. The stars
were observed for other FUSE programs and were not selected for large
reddening. Thus, uncertainties in the derived extinction curves depend on the
photometric data. In the case of strongly reddened stars from the Galaxy, the
strong H2 absorption at the shortest wavelengths is an additional complication.
These initial results indicate that there is a family of extinction curves that
rise strongly to the Lyman limit, and extend the related extinction curves from
longer wavelengths.


title: DIRBE Minus 2MASS: the Cosmic Infrared Background at 3.5 Microns

abstract:
  Stellar fluxes from the 2MASS catalog are used to remove the contribution due
to Galactic stars from the intensity measured by DIRBE in 13 regions in the
North and South Galactic polar caps. Allowing for a constant calibration factor
between the DIRBE 3.5 micron intensity and the 2MASS 2.2 micron fluxes gives
very small pixel to pixel scatter. After subtracting the interplanetary and
Galactic foregrounds, a residual intensity of 16.1 +/- 4 kJy/sr or 13.8 +/- 3.4
nW/m^2/sr at 3.5 microns is found. A similar analysis at 2.2 microns gives a
residual intensity of 17.6 +/- 4.4 kJy/sr or 24 +/- 6 nW/m^2/sr. The intercepts
of the DIRBE minus 2MASS correlation at 1.25 microns show more scatter and are
a much smaller fraction of the foreground, leading to a weak limit on the CIRB
of 10.1 +/- 7.4 kJy/sr or 24.3 +/- 18 nW/m^2/sr (1 sigma).


title: Detection of ionized gas in the globular cluster 47 Tucanae

abstract:
  We report the detection of ionized intracluster gas in the globular cluster
47 Tucanae. Pulsars in this cluster with a negative period derivative, which
must lie in the distant half of the cluster, have significantly higher measured
integrated electron column densities than the pulsars with a positive period
derivative. We derive the plasma density within the central few pc of the
cluster using two different methods which yield consistent values. Our best
estimate of n_e = (0.067+-0.015)/cm^3 is about 100 times the free electron
density of the ISM in the vicinity of 47 Tucanae, and the ionized gas is
probably the dominant component of the intracluster medium.


title: Discovery of a cataclysmic variable with a sub-stellar companion

abstract:
  We find that the ROSAT source 1RXS J105010.3-140431 is a cataclysmic variable
with orbital period of 88.6 minutes and a spectrum closely resembling WZ Sge.
In particular, emission lines are flanked by Stark-broadened absorption wings
probably originating in the photosphere of a compact object. The Balmer
absorption lines can be modeled by the spectrum of a DA white dwarf with 13 000
$< T_{eff} <$ 24 000 K. The strong absorption lines allowed us to obtain direct
radial velocities of the white dwarf using the cross-correlation technique. We
find an extremely low white dwarf radial velocity half amplitude, $K_{wd}$ = 4
$\pm$ 1 km s$^{-1}$. This is consistent with the upper limit obtained from the
H$\alpha$ emission line wing K < 20 km s$^{-1}$. The corresponding mass
function is incompatible with a main sequence secondary, but is compatible with
a post orbital period minimum cataclysmic variable with a brown dwarf-like
secondary. The formal solution gives a secondary mass of 10-20 jovian masses.
Doppler maps for the emission lines and the hypothesis of black-body emission
indicate a steady state (T $\sim r^{-3/4}$) accretion disk mainly emitting in
H$\alpha$ and an optically thicker hotspot with a strong contribution to the
higher order Balmer lines and \ion{He}{I} 5875. As in other long cycle length
dwarf novae, evidence for inner disk removal is found from the analysis of the
emission lines.


title: Dwarf Galaxies in the Local Group and in the Local Volume

abstract:
  After summarizing the characteristics of different types of dwarf galaxies I
briefly review our current state of knowledge of dwarf galaxy evolution in the
Local Group, for which we now have a fairly detailed although by no means
comprehensive picture. All Local Group dwarfs studied to date contain an old
population, though its fraction varies considerably. The majority of the dwarf
companions of the Milky Way shows evidence for a common epoch of ancient star
formation. Spatial variations in star formation are frequently observed in many
dwarf galaxies in the Local Group and beyond. These spatial variations range
from a seemingly stochastic distribution of star-forming regions in gas-rich,
high-mass dwarfs to radial gradients in low-mass dwarfs. The global mode of
star formation may be either continuous with amplitude variations or episodic.
High-mass dwarf galaxies tend to form stars over a Hubble time, whereas
low-mass dwarfs eventually cease to form stars, possibly aided by environmental
effects. Much less is known about the content and properties of dwarf galaxies
in the Local Volume, which we are trying to remedy through a large
observational effort. Dwarf galaxies in the Local Volume follow a similar trend
with absolute magnitude, mean metallicity, and central surface brightness as
the Local Group dwarfs do, and appear to be subject to morphological
segregation.


title: Pair-production multiplicities in rotation-powered pulsars

abstract:
  We discuss the creation of electron-positron cascades in the context of
pulsar polar cap acceleration models and derive several useful analytic and
semi-analytic results for the spatial extent and energy response of the
cascade. Instead of Monte Carlo simulations, we use an integro- differential
equation which describes the development of the cascade energy spectrum in one
space dimension quite well, when it is compared to existing Monte Carlo models.
We reduce this full equation to a single integral equation, from which we can
derive useful results, such as the energy loss between successive generations
of photons and the spectral index of the response. We find that a simple
analytic formula represents the pair cascade multiplicity quite well, provided
that the magnetic field is below 10^12 Gauss, and that an only slightly more
complex formula matches the numerically-calculated cascade at all other field
strengths. Using these results, we find that cascades triggered by gamma rays
emitted through inverse Compton scattering of thermal photons from the neutron
star's surface, both resonant and non-resonant, are important for the dynamics
of the polar cap region in many pulsars.


title:
Off-Axis Cluster Mergers: Effects of a Strongly Peaked Dark Matter
  Profile

abstract:
  (Abridged) We present a parameter study of offset mergers between clusters of
galaxies. Using the Eulerian hydrodynamics/N-body code COSMOS, we simulate
mergers between nonisothermal, hydrostatic clusters with a steep central dark
matter density profile and a beta-model gas profile. We constrain global
properties of the model clusters using observed cluster statistical
relationships. We consider impact parameters between zero and five times the
scale radius and mass ratios of 1:1 and 1:3. The morphological changes,
relative velocities, and temperature jumps we observe agree with previous
studies using the King profile for the dark matter. We observe a larger jump in
X-ray luminosity (~4-10x) than in previous work, and we argue that this
increase is most likely a lower limit due to our spatial resolution. We
emphasize that luminosity and temperature jumps due to mergers may have an
important bearing on constraints on Omega derived from the observation of hot
clusters at high redshift. Shocks are relatively weak in the cluster cores;
hence they do not significantly increase the entropy there. Instead, shocks
create entropy in the outer regions, and this high-entropy gas is mixed with
the core gas during later stages of the merger. Ram pressure initiates mixing
by displacing the core gas from its potential center, causing it to become
convectively unstable. The resulting convective plumes produce large-scale
turbulent motions with eddy sizes up to several 100 kpc. This turbulence is
pumped by dark matter-driven oscillations in the gravitational potential. Even
after nearly a Hubble time these motions persist as subsonic turbulence in the
cluster cores, providing 5-10% of the support against gravity.


title:
The BIMA Survey of Nearby Galaxies (BIMA SONG): I. The Radial
  Distribution of CO Emission in Spiral Galaxies

abstract:
  We present the first results of the BIMA Survey of Nearby Galaxies (BIMA
SONG), an imaging survey of the CO J=(1-0) emission in 44 nearby spiral
galaxies at a typical resolution of 6". BIMA SONG differs from previous
high-resolution CO surveys in that: (1) CO brightness was not an explicit
selection criterion; (2) a larger area (200" diameter for most galaxies) of
each galaxy was imaged; and (3) fully-sampled single-dish CO data (55"
resolution) were obtained for over half of the sample galaxies, so all of the
CO flux is imaged in these galaxies. The radial distribution of stellar light
in galactic disks is generally characterized as an exponential. It is,
therefore, of interest to investigate whether the molecular gas, which is the
star-forming medium, has a similar distribution. Though our low-resolution
single-dish radial profiles of CO emission can be described by simple
exponentials, this is not true for the emission at our full 6" resolution. The
scale lengths of the CO disks are correlated with the scale lengths of the
stellar disks with a mean ratio of the scale lengths of about one. We also find
that:(1) there is also a weak correlation between the ratio of K-band to CO
luminosity and Hubble type; (2) in half of the galaxies presented here, CO
emission does not peak at the location of the stellar nucleus; (3) averaged
over the inner kiloparsec, the CO emission in one-half of the galaxies exhibits
an excess over that expected from an exponential disk which is similar to the
excess in stellar light caused by the bulge stars; and (4) this excess CO
emission may be due to an increase in the total molecular gas content in the
bulge region, or alternatively, to an increase in the CO emissivity caused by
the increased pressure of the bulge region.


title:
Discovery of water vapor around IRC+10216 as evidence for comets
  orbiting another star

abstract:
  Since 1995, astronomers have discovered planets with masses comparable to
that of Jupiter (318 times Earth's mass) in orbit around approximately 60
stars. Although unseen directly, the presence of these planets is inferred by
the small reflex motions that they gravitationally induce on the star they
orbit; these result in small periodic wavelength shifts in the stellar
spectrum. Since this method favors the detection of massive objects orbiting in
close proximity to the star, the question of whether these systems also contain
analogs of the smaller constituents of our Solar System has remained
unanswered. Using an alternative approach, we report here observations of an
aging carbon-star, IRC+10216, that reveal the presence of circumstellar water
vapor, a molecule not expected in measurable abundances around such a star and
thus a distinctive signature of an orbiting cometary system. The only plausible
explanation for this water vapor is that the recent evolution of IRC+10216 -
which is accompanied by a prodigious increase in its luminosity - is now
causing the vaporization of a collection of orbiting icy bodies, a process
first considered in a previous theoretical study.


title: Carbon Flashes in the Heavy Element Ocean on Accreting Neutron Stars

abstract:
  We show that burning of a small mass fraction of carbon in a neutron star
ocean is thermally unstable at low accumulated masses when the ocean contains
heavy ashes from the hydrogen burning rapid proton (rp) process. The key to
early unstable ignition is the low thermal conductivity of a heavy element
ocean. The instability requires accretion rates in excess of one-tenth the
Eddington limit when the carbon mass fraction is 0.1 or less. The unstable
flashes release 10^{42} to 10^{43} ergs over hours to days, and are likely the
cause of the recently discovered large Type I X-ray bursts (so-called
``superbursts'') from six Galactic low mass X-ray binaries. In addition to
explaining the energetics, recurrence times, and durations of the superbursts,
these mixed carbon/heavy element flashes have an accretion rate dependence of
unstable burning similar to that observed. Though the instability is present at
accretion rates near Eddington, there is less contrast with the accretion
luminosity there, explaining why most detections are made at accretion rates
between 0.1 and 0.3 Eddington. Future comparisons of time dependent
calculations with observations will provide new insights into the rp process.


title: Magnetic fields in barred galaxies. II. Dynamo models

abstract:
  We study the generation and maintenance of large-scale magnetic fields in
barred galaxies. We take a velocity field (with strong noncircular components)
from a published gas dynamical simulation of Athanassoula (1992), and use this
as input to a galactic dynamo calculation. Our work is largely motivated by
recent high quality VLA radio observations of the barred galaxy NGC 1097, and
we compare our results in detail with the regular magnetic fields deduced from
these observations. We are able to reproduce most of the conspicuous
large-scale features of the observed regular field, including the field
structure in the central regions, by using a simple mean-field dynamo model in
which the intensity of interstellar turbulence (more precisely, the turbulent
diffusivity) is enhanced by a factor of 2-6 in the dust lanes and near the
circumnuclear ring. We argue that magnetic fields can be dynamically important,
and therefore should be included in models of gas flow in barred galaxies.


title: Metals in the Universe and Diffuse Background Radiation

abstract:
  An attempt is made to guess the overall cosmic abundance of `metals' and the
contribution made by the energy released in their production to the total
intensity of extragalactic background light (EBL). With a comparable or
somewhat larger amount coming from white dwarfs, and a probably quite modest
contribution from AGNs, one can fairly easily account for the lower end of the
range of existing estimates for the total EBL intensity (50to 60 nwt m$^{-2}$
sterad$^{-1}$), but it seems more difficult should some higher estimates (90 to
100 in the same units) prove to be correct.


title: Annihilation Radiation in the Galaxy

abstract:
  Observations of annihilation radiation in the Galaxy are briefly reviewed. We
summarize astrophysical mechanisms leading to positron production, and recent
estimates for production rates from nova and supernova nucleosynthesis in the
Galaxy. The physical processes involved in the production of annihilation
radiation in the interstellar medium are described. These include positron
thermalization, charge exchange, radiative recombination, and direct
annihilation. Calculations of 2\gamma and 3\gamma spectra and the positronium
(Ps) fraction due to the annihilation of positrons in media containing H and He
at different temperatures and ionization states are presented. Quenching of Ps
by high temperature plasmas or dust could account for differences between 0.511
MeV and 3\gamma Ps continuum maps. These results are presented in the context
of the potential of INTEGRAL to map sites of annihilation radiation in the
Galaxy. Positron production by compact objects is also considered.


title:
Pair Production and Radiation Effects in Clouds Illuminated by Gamma Ray
  Sources

abstract:
  Many classes of gamma-ray sources, such as gamma-ray bursts, blazars, Seyfert
galaxies, and galactic black hole sources are surrounded by large amounts of
gas and dust. X-rays and gamma-rays that traverse this material will be
attenuated by Compton scattering and photoelectric absorption. One signature of
an intervening scattering cloud is radiation-hardening by electrons that have
been scattered and heated by the incident radiation, as illustrated by a Monte
Carlo calculation. Compton scattering provides backscattered photons that will
attenuate subsequent gamma rays through \gamma\gamma pair-production processes.
We calculate the pair efficiency for a cloud illuminated by gamma-ray burst
radiation. An analytic calculation of the flux of X-rays and gamma rays Thomson
scattered by an intervening cloud is presented. Illuminated clouds near GRBs
will form relativistic plasmas containing large numbers of electron-positron
pairs that can be detected within ~1-2 days of the explosion before expanding
and dissipating. Localized regions of pair annihilation radiation in the Galaxy
could reveal gamma-ray sources embedded in dense clouds, or sites of past GRB
explosions.


title: The Nuclear Disk in the Dwarf Elliptical Galaxy NGC 4486A

abstract:
  Many ellipticals contain nuclear disks of dust and gas. Some ellipticals
contain nuclear disks of stars that are distinct from the rest of the galaxy.
We show that the dwarf E2 galaxy NGC 4486A contains both -- it is a "Rosetta
stone" object that tells us how nuclear disks evolve. Its properties suggest
that, as accreted gas dissipates and settles toward the center, it forms stars
and builds a stellar disk. Secular growth may explain not only the most
distinct nuclear disks such as those in NGC 4486A but also some of the disky
distortions that are commonly seen in elliptical galaxies. That is, density
distributions may grow secularly cuspier. This would result in chaotic mixing
of stellar orbits in phase space and would tend to make an elliptical galaxy
evolve toward a more nearly axisymmetric shape.


title:
Membership of 23 stars towards the bulge globular clusters NGC 6528 and
  NGC 6553

abstract:
  Low resolution spectra of 23 stars towards the bulge globular clusters NGC
6528 and NGC 6553 are analysed. Radial velocities and atmospheric parameters
are derived in order to check their membership in the clusters. Effective
temperatures were obtained from photometric data for stars with Teff > 3800 K,
whereas for cooler stars, they were derived from equivalent widths of TiO
bands. Calibrations of W(TiO) as a function of stellar parameters based on a
grid of synthetic spectra are presented. Metallicities were derived from a
comparison of the observed spectra to a grid of synthetic spectra. The sample
comprises evolutionary stages from the Red Giant Branch to the Horizontal
Branch, with parameters in the range 3200 <= Teff <= 5000 K and -0.5 <= log g
<= 2.4. The mean metallicities obtained for NGC 6528 and NGC 6553 are [Fe/H] ~
-0.5 and -0.7, in both cases with [Mg/Fe] = +0.3; assuming the same
overabundance for the $\alpha$ elements O, Mg, Si, S, Ca and Ti, this gives
[Z/Zsolar] = -0.25 and -0.45. Membership verification by means of low
resolution spectra is a crucial step in preparing targets for high resolution
spectroscopy with 8m class telescopes.


title: MSX, 2MASS, and the LMC: A Combined Near and Mid Infrared View

abstract:
  The Large Magellanic Cloud (LMC) has been observed by both the Midcourse
Space Experiment (MSX) in the mid-infrared and the Two Micron All Sky Survey
(2MASS) in the near-infrared. We have performed a cross-correlation of the 1806
MSX catalog sources and nearly 1.4 million 2MASS catalogued point and extended
sources and find 1664 matches. Using the available color information, we
identify a number of stellar populations and nebulae, including main sequence
stars, giant stars, red supergiants, carbon- and oxygen-rich asymptotic giant
branch (AGB) stars, planetary nebulae, H II regions, and other dusty objects
likely associated with early-type stars. 731 of these sources have no previous
identification. We compile a listing of all objects, which includes photometry
and astrometry. The 8.3 micron MSX sensitivity is the limiting factor for
object detection: only the brighter red objects, specifically the red
supergiants, AGB stars, planetary nebulae and HII regions, are detected in the
LMC. The remaining objects are likely in the Galactic foreground. The spatial
distribution of the infrared LMC sources may contribute to understanding
stellar formation and evolution and the overall galactic evolution. We
demonstrate that a combined mid- and near-infrared photometric baseline
provides a powerful means of identifying new objects in the LMC for future
ground-based and space-based follow-up observations.


title:
Chandra Observation of the Radio Source / X-ray Gas Interaction in the
  Cooling Flow Cluster Abell 2052

abstract:
  We present a Chandra observation of Abell 2052, a cooling flow cluster with a
central cD that hosts the complex radio source 3C 317. The data reveal
``holes'' in the X-ray emission that are coincident with the radio lobes. The
holes are surrounded by bright ``shells'' of X-ray emission. The data are
consistent with the radio source displacing and compressing, and at the same
time being confined by, the X-ray gas. The compression of the X-ray shells
appears to have been relatively gentle and, at most, slightly transonic. The
pressure in the X-ray gas (the shells and surrounding cooler gas) is
approximately an order of magnitude higher than the minimum pressure derived
for the radio source, suggesting that an additional source of pressure is
needed to support the radio plasma. The compression of the X-ray shells has
speeded up the cooling of the shells, and optical emission line filaments are
found coincident with the brightest regions of the shells.


title: Tracking The Baryon Density From The Big Bang To The Present

abstract:
  The primordial abundances of deuterium, helium, and lithium probe the baryon
density of the universe only a few minutes after the Big Bang. Of these relics
from the early universe, deuterium is the baryometer of choice. After reviewing
the current observational status (a moving target!), the BBN baryon density is
derived and compared to independent estimates of the baryon density several
hundred thousand years after the Big Bang (as inferred from CMB observations)
and at present, more than 10 billion years later. The excellent agreement among
these values represents an impressive confirmation of the standard model of
cosmology, justifying -- indeed, demanding -- more detailed, quantitative
scrutiny. To this end, the corresponding BBN-predicted abundances of helium and
lithium are compared with observations to further test and constrain the
standard, hot, big bang cosmological model.


title:
Water Vapor in Carbon-rich AGB Stars from the Vaporization of Icy
  Orbiting Bodies

abstract:
  We argue that the presence of water vapor in the circumstellar outflow of a
carbon-rich AGB star is potentially a distinctive signature of extra-solar
cometary systems. Detailed models show that at suitable distances from the
star, water ice can survive well into the carbon-rich AGB phase; water vapor
abundances as large as 10^-6 could result from the vaporization of a collection
of orbiting icy bodies with a total mass comparable to what might have been
originally present in the solar system's Kuiper Belt. In particular, the
recently-reported detection by the Submillimeter Wave Astronomy Satellite of
water vapor in the circumstellar outflow of IRC+10216 can be explained if ~10
Earth masses of ice is present at a distance ~300 AU from that carbon-rich
star. Future observations with the Herschel Space Observatory (HSO, formerly
known as FIRST) will facilitate sensitive multi-transition observations of
water, yielding line ratios that can establish the radial distribution of water
vapor in IRC+10216. The greater sensitivity of HSO will also allow searches for
water vapor to be carried out in a much larger sample of carbon-rich AGB stars.


title: Soft X-ray Spectroscopy of Seyfert 2 Galaxies

abstract:
  Soft X-ray spectroscopy of Seyfert 2 galaxies offers perhaps the best method
to probe the possible connection between AGN activity and star formation.
Obscuration of powerful radiation from the inferred nucleus allows for detailed
study of circumnuclear emission regions. And soft X-ray spectroscopy of these
regions allows for robust discrimination between warm gas radiatively driven by
the AGN and hot collisionally-driven gas possibly associated with star
formation. A simple model of a (bi-)cone of gas photoionized and photoexcited
by a nuclear power-law continuum is sufficient to explain the soft X-ray
spectra of all Seyfert 2 galaxies so far observed by the XMM-Newton and Chandra
satellites. An upper limit of around 10 percent to an additional hot,
collisionally-driven gas contribution to the soft X-ray regime appears to hold
for five different Seyfert 2 galaxies, placing interesting constraints on
circumnuclear star formation.


title: High Resolution X-ray Spectroscopy of Seyfert 2 Galaxies

abstract:
  X-ray spectroscopy of Seyfert 2 galaxies provides an excellent probe of the
circumnuclear environment in active galactic nuclei. The grating experiments on
both Chandra and XMM-Newton have now provided the first high resolution spectra
of several of the brightest Seyfert 2's. We present Chandra HETG data on
Markarian 3 and XMM-Newton RGS data on NGC 1068. In both cases, the spectra are
dominated by emission lines due to radiative recombination following
photoionization, photoexcitation, and fluorescence. There is no evidence for
any significant contribution from collisionally-heated gas.


title:
KeV Astrophysics With GeV Beams; Blazing a New Trail on the Summitt of
  Nuclear Astrophysics

abstract:
  GeV beams of light ions and electrons are used for creating a high flux of
real and virtual photons, with which some problems in Nuclear Astrophysics are
studied. GeV 8B beams are used to study the Coulomb dissociation of 8B and thus
the 7Be(p,gamma)8B reaction. This reaction is one of the major source of
uncertainties in estimating the 8B solar neutrino flux and a critical input for
calculating the 8B Solar neutrino flux. The Coulomb dissociation of 8B appears
to provide a viable method for measuring the 7Be(p,gamma)8B reaction rate, with
a weighted average of the RIKEN1, RIKEN2, GSI1 and MSU published results of
S17(0) = 18.9 +/- 1.0 eV-b. This result however does not include a theoretical
error estimated to be +/- 10 %. GeV electron beams on the other hand, are used
to create a high flux of real and virtual photons at TUNL-HIGS and MIT-Bates,
respectively, and we discuss two new proposals to study the 12C(alpha,gamma)16O
reaction with real and virtual photons. The 12C(alpha,gamma)16O reaction is
essential for understanding Type II and Type Ia supernova. It is concluded that
virtual and real photons produced by GeV light ions and electron beams are
useful for studying some problems in Nuclear Astrophysics.


title: Accelerated Particles from Shocks Formed in Merging Clusters of Galaxies

abstract:
  Subcluster interactions within clusters of galaxies produce shocks that
accelerate nonthermal particles. We treat Fermi acceleration of nonthermal
electrons and protons by injecting power-law distributions of particles during
the merger event, subject to constraints on maximum particle energies. The
broadband nonthermal spectrum emitted by accelerated electrons and protons is
calculated during and following the subcluster interaction for a standard
parameter set. The intensity of gamma-ray emission from primary and secondary
processes is calculated and discussed in light of detection capabilities at
radio and gamma-ray energies.


title: Compact Objects and Accretion Disks

abstract:
  Recent developments in the spectropolarimetric study of compact objects,
specifically black holes (stellar and massive) and neutron stars are reviewed.
The lectures are organized around five topics: disks, jets, outflows, neutron
stars and black holes. They emphasize physical mechanisms and are intended to
bridge the gap between the fundamentals of polarimetry and the phenomenology of
observed cosmic sources of polarized radiation, as covered by the other
lecturers. There has been considerable recent progress in spectropolarimetry
from radio through optical frequencies and this is producing some unique
diagnostics of the physical conditions around compact objects. It is argued
that there is a great need to develop a correspondingly sensitive polarimetric
capability at ultraviolet through gamma-ray energies.


title: Gravitational Radiation Evolution of Accreting Neutron Stars

abstract:
  The gravitational-wave and accretion driven evolution of neutron stars in low
mass X-ray binaries and similar systems is analyzed, while the amplitude of the
radiating perturbation (here assumed to be an r-mode) remains small. If most of
the star is superfluid, with (temperature independent) mutual friction
dominating the ordinary (temperature dependent) shear viscosity, the amplitude
of the mode and the angular velocity of the star oscillate about their
equilibrium values with a period of at least a few hundred years. The resulting
oscillation of the neutron star temperature is also computed. For temperature
dependent viscosity, the general conditions for the equilibrium to be stable
are found.


title: Fractional diffusion of cosmic rays

abstract:
  We consider the propagation of galactic cosmic rays under assumption that the
interstellar medium is a fractal one. An anomalous diffusion equation in terms
of fractional derivatives is used to describe of cosmic ray propagation. The
anomaly in used model results from large free paths ("Levy flights") of
particles between galactic inhomogeneities and long time a particle stays in a
trap. An asymptotical solution of the anomalous diffusion equation for point
instantaneous and impulse sources with inverse power spectrum relating to
supernova bursts is found. It covers both subdiffusive and superdiffusive
regimes and is expressed in terms of the stable distributions. The energy
dependence of spectral exponent of observed particles in different regimes is
discussed.


title:
Mass composition of cosmic rays in anomalous diffusion model: comparison
  with experiment

abstract:
  We calculate the energy spectra and mass composition of cosmic rays in energy
region 1 - 10^8 GeV/particle under the assumption that cosmic rays propagation
in the Galaxy is described by anomalous diffusion equation. Our results and
comparisons with experimental data are presented.


title: Orbital decay of satellites crossing an accretion disc

abstract:
  Motion of stellar-mass satellites is studied around a massive compact body
which is surrounded by a gaseous slab of a stationary accretion disc. The
satellites suffer an orbital decay due to hydrodynamical interaction with the
disc medium (transitions across the disc, gap opening in the disc, density
waves) and gravitational radiation. Arbitrary orbital eccentricities and
inclinations are considered, and it is observed how the competing effects
depend on the parameters of the model, namely, the mass and compactness of the
orbiters, the osculating elements of their trajectories, and surface density of
the disc. These effects have a visible impact on the satellites long-term
motion, and they can produce observational consequences with respect to
galactic central clusters. It is shown that the satellite-disc collisions do
not impose serious restrictions on the results of gravitational wave
experiments if the disc medium is diluted and the orbiter is compact but they
are important in the case of environments with relatively high density. We thus
concentrate on application to accretion flows in which the density is not
negligible. We discuss the expected quasi-stationary structure of the cluster
that is established on sub-parsec scales within the sphere of gravitational
influence of the central object. Relevant to this region, we give the power-law
slopes defining the radial profile of modified clusters and we show that their
values are determined by satellite interaction with the accretion flow rather
than their initial distribution.


title:
Gravitational lensing statistical properties in general FRW cosmologies
  with dark energy component(s): analytic results

abstract:
  Various astronomical observations have been consistently making a strong case
for the existence of a component of dark energy with negative pressure in the
universe. It is now necessary to take the dark energy component(s) into account
in gravitational lensing statistics and other cosmological tests. By using the
comoving distance we derive analytic but simple expressions for the optical
depth of multiple image, the expected value of image separation and the
probability distribution of image separation caused by an assemble of singular
isothermal spheres in general FRW cosmological models with dark energy
component(s). We also present the kinematical and dynamical properties of these
kinds of cosmological models and calculate the age of the universe and the
distance measures, which are often used in classical cosmological tests. In
some cases we are able to give formulae that are simpler than those found
elsewhere in the literature, which could make the cosmological tests for dark
energy component(s) more convenient.


title:
Determining the Cosmic Equation of State Using Future Gravitational Wave
  Detectors

abstract:
  The expected chirp mass distribution of observed events for future
gravitational wave detectors is extensively investigated in the presence of an
exotic fluid component with an arbitrary equation of state, $-1 \leq \omega_x
\equiv p_x/\rho_x < 0$, i.e., the so-called dark energy component. The results
for a flat model dominated by a dark energy are compared to those for the
standard flat model dominated by cold dark matter. It is found that for a flat
universe the chirp mass distribution shows a sensitive dependence on
$\omega_x$, which may provide an independent and robust constraint on the
cosmic equation of state.


title: The Spectra of Red Quasars

abstract:
  We measure the spectral properties of a representative sub-sample of 187
quasars, drawn from the Parkes Half-Jansky, Flat-radio-spectrum Sample (PHFS).
Quasars with a wide range of rest-frame optical/UV continuum slopes are
included in the analysis: their colours range from 2 < B-K < 7.
  The median H-beta and [O III] emission-line equivalent widths of the red
quasar sub-sample are a factor of ten weaker than those of the blue quasar
sub-sample. Both the colours and the emission-line equivalent widths of the red
quasars can be explained by the addition of a featureless red synchrotron
continuum component to an otherwise normal blue quasar spectrum. The relative
strengths of the blue and red components span two orders of magnitude at
rest-frame 500nm. The blue component is weaker relative to the red component in
low optical luminosity sources. This suggests that the fraction of accretion
energy going into optical emission from the jet is greater in low luminosity
quasars.
  This synchrotron model does not, however, fit around 10% of the quasars,
which have both red colours and high equivalent width emission-lines. We
hypothesise that these red, strong-lined quasars have intrinsically weak Big
Blue Bumps.
  There is no discontinuity in spectral properties between the BL Lac objects
in our sample and the other quasars. The synchrotron emission component only
dominates the spectrum at longer wavelengths, so existing BL Lac surveys will
be biassed against high redshift objects.


title:
The transient X-ray pulsar 4U 0115+63 from quiescence to outburst
  through the centrifugal transition

abstract:
  We report on a BeppoSAX observation of the transient X-ray pulsar 4U 0115+63
close to periastron. This led to the discovery of a dramatic luminosity
variation from ~2x10^34 erg/s to ~5x10^36 erg/s (factor ~250) in less than 15
hr. The variation was accompanied by only minor (if any) changes in the emitted
spectrum and pulse fraction. On the contrary an observation near apastron
detected the source in a nearly constant state at a level of ~2x10^33 erg/s.
Direct accretion onto the neutron star surface encounters major difficulties in
explaining the source variability properties. When the different regimes
expected for a rotating magnetic neutron star subject to a variable inflow of
matter from its companion are taken into consideration, the results of BeppoSAX
observations of 4U 0115+63 can be explained naturally. In particular close to
apastron, the regime of centrifugal inhibition of accretion applies, whereas
the dramatic source flux variability observed close to periastron is readily
interpreted as the transition regime between direct neutron star accretion and
the propeller regime. In this centrifugal transition regime small variations of
the mass inflow rate give rise to very large luminosity variations. We present
a simple model for this transition, which we successfully apply to the X-ray
flux and pulse fraction variations measured by BeppoSAX.


title: Ram pressure stripping and galaxy orbits: The case of the Virgo cluster

abstract:
  We investigate the role of ram pressure stripping in the Virgo cluster using
N-body simulations. Radial orbits within the Virgo cluster's gravitational
potential are modeled and analyzed with respect to ram pressure stripping. The
N-body model consists of 10000 gas cloud complexes which can have inelastic
collisions. Ram pressure is modeled as an additional acceleration on the clouds
located at the surface of the gas distribution in the direction of the galaxy's
motion within the cluster. We made several simulations changing the orbital
parameters in order to recover different stripping scenarios using realistic
temporal ram pressure profiles. We investigate systematically the influence of
the inclination angle between the disk and the orbital plane of the galaxy on
the gas dynamics. We show that ram pressure can lead to a temporary increase of
the central gas surface density. In some cases a considerable part of the total
atomic gas mass (several 10^8 M_solar) can fall back onto the galactic disk
after the stripping event. A quantitative relation between the orbit parameters
and the resulting HI deficiency is derived containing explicitly the
inclination angle between the disk and the orbital plane. The comparison
between existing HI observations and the results of our simulations shows that
the HI deficiency depends strongly on galaxy orbits. It is concluded that the
scenario where ram pressure stripping is responsible for the observed HI
deficiency is consistent with all HI 21cm observations in the Virgo cluster.


title:
X-ray emission from young stars in Taurus-Auriga-Perseus: Luminosity
  functions and the rotation-activity-age relation

abstract:
  We report on a systematic search for X-ray emission from pre-main sequence
and young main sequence stars in the Taurus-Auriga-Perseus region. Our stellar
sample consists of all T Tauri stars from the Taurus-Auriga region, and all
late-type stars from the Pleiades and Hyades clusters which have been observed
by the ROSAT PSPC in pointed observations. We present the X-ray parameters for
all observed stars in tables, and study the connection between coronal X-ray
activity and stellar parameters for different subgroups of our sample. In
particular we compile X-ray luminosity functions (XLF), and discuss the
relations between X-ray emission and spectral type, age, and rotation, on the
largest sample so far.


title: Probing for Dark Matter within Spiral Galaxy Disks

abstract:
  We explore the relative importance of the stellar mass density as compared to
the inner dark halo, using the observed gas kinematics throughout the disk of
the spiral galaxy NGC 4254 (Messier 99). We perform hydrodynamical simulations
of the gas flow for a sequence of gravitational potentials in which we vary the
stellar disk contribution to the total potential. This stellar portion of the
potential was derived empirically from color corrected K-band photometry
reflecting the spiral arms in the stellar mass, while the halo was modelled as
an isothermal sphere. The simulated gas density and the gas velocity field are
then compared to the observed stellar spiral arm morphology and to the H-alpha
gas kinematics. We find that this method is a powerful tool to determine the
corotation radius of the spiral pattern and that it can be used to place an
upper limit on the mass of the stellar disk. For the case of the galaxy NGC
4254 we find R_cr = 7.5 +/- 1.1 kpc, or R_cr = 2.1 R_exp(K'). We also
demonstrate that for a maximal disk the prominent spiral arms of the stellar
component over-predict the non-circular gas motions unless an axisymmetric dark
halo component contributes significantly (>~ 1/3) to the total potential inside
2.2 K-band exponential disk scale lengths.


title:
BeppoSAX observations of the Narrow-Line Seyfert 1 galaxy RX
  J1702.5+3247

abstract:
  We report optical, radio and X-ray observations of the Narrow-Line Seyfert 1
galaxy RX J1702.5+3247. The soft (0.1-2 keV) X-ray flux, measured by BeppoSAX,
is characterized by strong variability on short time scales (< 500 sec). The
most extreme amplitude variations require a radiative efficiency exceeding the
maximum for a Kerr black hole, implying the presence of relativistic effects. A
comparison with archival ROSAT data reveals long term temporal and spectral
variability. The 0.1-10 keV spectrum is equally well fitted either by an
ionized reflection disk model, or by a broken power law plus a Gaussian line,
consistent with a hydrogen-like iron line at 6.97 keV from a highly ionized
accretion disk.


title: Formation of Spheroidal Galaxies: The Sub-MM View

abstract:
  The intensity of the Cosmic Far-IR Background and the strong evolution of
galaxies in the far-IR to mm wavelength range demonstrate that the bulk of
starlight emitted during the early phases of galaxy evolution was reprocessed
by dust. Therefore, the optical view of the galaxy formation process is highly
incomplete and biased, and must be complemented with far-IR/sub-mm
observations. We review the impact of sub-mm surveys on our understanding of
the evolutionary history of spheroidal galaxies. A recent model, bringing into
play also the inter-relationships between formation and early evolution of
spheroidal galaxies and quasars, is described and some implications are
outlined.


title: Cosmological constant and the fate of the DDM theory

abstract:
  We investigate the impact of the non-zero cosmological constant on the
classical decaying dark matter theory developed by the late Dennis Sciama. In
particular, we concentrate on the change in relevant values of cosmological
parameters in comparison to the high-precision estimates given by Sciama
(1997). It is shown that the appropriate changes in resulting parameter values
are such to make the DDM concept less plausible. This is in complete agreement
with recently reported observational results detrimental to this theory.


title: Spectra of binaries classified as lambda Boo stars

abstract:
  High angular resolution observations have shown that some stars classified as
lambda Boo are binaries with low values of angular separation and magnitude
difference of the components; therefore the observed spectrum of these objects
is a combination of those of the two components. These composite spectra have
been used to define spectroscopic criteria able to detect other binaries among
stars classified as lambda Boo. The application of this method to HD 111786 is
presented: the contribution of 5 components to the observed spectrum is
demonstrated by the shape of the O I 7774 Angstrom feature. This result makes
unreliable any attempt to perform an abundance analysis of this object which
therefore must be definitely rejected from the class of the peculiar lambda Boo
stars. This approach allowed us also to recognize that the SB2 star HD 153808
is in reality a triple system.


title:
A Multivariate Statistical Analysis of Spiral Galaxy Luminosities. II.
  Morphology-Dependent Multiwavelength Emission Properties

abstract:
  This is the second of two papers based on a systematic multi-wavelength (X,
B, H, 12$\mu$m, FIR, 6cm) statistical analysis of the {\it Einstein Observatory
Galaxy Catalog} sample of 234 `normal' S0/a-Irr galaxies. This sample is
representative of spiral galaxies (Paper I), and its wide wavelength coverage
provides a unique opportunity for a systematic exploration of the relations
among different emission bands, that can give novel insight on the different
emission processes and their relation to galaxian components, as a function of
galaxy morphology.


title: Cosmological perturbations in the bulk and on the brane

abstract:
  We study cosmological perturbations in a brane-world scenario where the
matter fields live on a four-dimensional brane and gravity propagates in the
five-dimensional bulk. We present the equations of motion in an arbitrary gauge
for metric perturbations in the bulk and matter perturbations on the brane.
Gauge-invariant perturbations are then constructed corresponding to
perturbations in longitudinal and Gaussian normal gauges. Longitudinal gauge
metric perturbations may be directly derived from three master variables
(separately describing scalar, vector and tensor metric perturbations) which
obey five-dimensional wave-equations. Gaussian normal gauge perturbations are
directly related to the induced metric perturbations on the brane with the
additional bulk degrees of freedom interpreted as an effective Weyl
energy-momentum tensor on the brane. We construct gauge-invariant perturbations
describing the effective density, momentum and pressures of this Weyl fluid at
the brane and throughout the bulk. We show that there exist gauge-invariant
curvature perturbations on the brane and in the bulk that are conserved on
large-scales when three-dimensional spatial gradients are negligible.


title:
Primordial space-time foam as an origin of cosmological
  matter-antimatter asymmetry

abstract:
  The possibility is raised that the observed cosmological matter-antimatter
asymmetry may reside in asymmetric space-time fluctuations and their interplay
with the St\"ckelberg-Feynman interpretation of antimatter. The presented
thesis also suggests that the effect of space-time fluctuations is to diminish
the fine structure constant in the past. Recent studies of the QSO absorption
lines provide a 4.1 standard deviation support for this prediction. Our
considerations suggest that in the presence of space-time fluctuations, the
principle of local gauge invariance, and the related notion of parallel
transport, must undergo fundamental changes.


title:
High-Resolution X-Ray Spectroscopy of the Accretion Disk Corona Source
  4U 1822-37

abstract:
  We present a preliminary analysis of the X-ray spectrum of the accretion disk
corona source, 4U 1822-37, obtained with the High Energy Transmission Grating
Spectrometer onboard the Chandra X-ray Observatory. We detect discrete emission
lines from photoionized iron, silicon, magnesium, neon, and oxygen, as well as
a bright iron fluorescence line. Phase-resolved spectroscopy suggests that the
recombination emission comes from an X-ray illuminated bulge located at the
predicted point of impact between the disk and the accretion stream. The
fluorescence emission originates in an extended region on the disk that is
illuminated by light scattered from the corona.


title:
The Shapes of Galaxies and Their Halos as Traced by Stars: The Milky Way
  Dark Halo and The LMC Disk

abstract:
  Stars and their kinematics provide one of the tools available for studies of
the shapes of galaxies and their halos. In this review I focus on two specific
applications: the shape of the Milky Way dark halo and the shape of the LMC
disk. The former is constrained by a variety of observations, but an accurate
determination of the axial ratio q_DH remains elusive. A very flattened Milky
Way dark halo with q_DH < 0.4 is ruled out, and values q_DH > 0.7 appear most
consistent with the data. Near-IR surveys have revealed that the LMC disk is
not approximately circular, as long believed, but instead has an axial ratio of
0.7 in the disk plane. The elongation is perpendicular to the Magellanic
Stream, indicating that it is most likely due to the tidal force of the Milky
Way. Equilibrium dynamical modeling of galaxies is important for many
applications. At the same time, detailed studies of tidal effects and tidal
streams have the potential to improve our understanding of both the Milky Way
dark halo and the structure of satellite galaxies such as the LMC.


title: Chemical Evolution of Clusters of Galaxies

abstract:
  The high metallicity of the intra-cluster medium (ICM) is generally
interpreted on the base of the galactic wind scenario for elliptical galaxies.
In this framework, we develop a toy-model to follow the chemical evolution of
the ICM, formulated in analogy to chemical models for individual galaxies. Just
as the ingredients for usual models are (a) the stellar yields, amount of
metals newly synthesized and re-ejected by stars; (b) the Star Formation Rate
and (c) the stellar Initial Mass Function (IMF), our model for clusters
involves: (a') ``galactic yields'' derived from galactic wind models of
ellipticals; (b') a parametric Galactic Formation Rate; (c') a
Press-Schechter-like Galactic Initial Mass Function.
  The model is used to test the response of the predicted metal content and
abundance evolution of the ICM to varying input galactic models. The resulting
luminosity function of cluster galaxies is also calculated, in order to
constrain model parameters.


title:
A Map of the Ionized Component of the Intermediate Velocity Cloud
  Complex K

abstract:
  The Wisconsin H-Alpha Mapper (WHAM) Northern Sky Survey is revealing that
many intermediate-velocity (|v_LSR| <= 100 km/s) neutral clouds and complexes
have an associated ionized component. We present the first map of the H-Alpha
emission from an intermediate- or high-velocity structure: Complex K. This
large, high-latitude feature stretches from l = 10 to 70 degrees, b = +30 to
+70 degrees and peaks in velocity over v_LSR ~ -60 to -80 km/s. The neutral and
ionized gas generally trace each other quite well in the complex, but the
detailed structure is not identical. In particular, the H-Alpha emission peaks
in brightness at slightly higher Galactic longitudes than corresponding 21 cm
features. The ionized gas has a peak H-Alpha intensity of 0.5 Rayleighs,
corresponding to an emission measure of 1.1 cm^-6 pc. Structures in the complex
are traced by WHAM down to about 0.1 Rayleighs (0.2 cm^-6 pc). Typical line
widths of the H-Alpha emission are ~ 30 km/s, limiting temperatures in the
ionized gas to < 20,000 K. If radiation is the primary ionizing mechanism, the
Lyman continuum flux required to sustain the most strongly emitting ionized
regions is 1.2 x 10^6 photons cm^-2 s^-1. There appears to be no local, stellar
source capable of maintaining the ionization of the gas; however, the required
ionizing flux is consistent with current models of the escape of Lyman
continuum radiation from OB stars in the disk and of ionizing radiation
produced by cooling supernova remnants.


title: Kinematics of Herbig-Haro Objects and Jets in the Orion Nebula

abstract:
  We have surveyed the inner 5' of the Orion Nebula by means of Halpha and
[NII] Fabry-Perot imaging spectroscopy to present a kinematical study of the
Herbig-Haro objects in the nebula. The objects studied in this work are HH 202,
203, 204, 529, 269 and other associated features. For HH 202 we find new
features that, because of their high velocities (up to 100 km/seg) indicate the
presence of an outflow that probably is a HH flow not catalogued previously. HH
202 could be only a part of this larger outflow. Large internal motions are
found in the fainter regions of HH 203-204, as well as evidence of transverse
density gradients that could account for the asymmetry in the brightness
distribution of HH 204. We report for the first time a high blueshifted
velocity (-118 km/seg) associated with HH 204, and show that the apex of HH 204
is indeed the zone of maximum velocity, in agreement with bow shock models. We
also studied the radial velocity field of HH 269 finding features associated
with the HH object. From our studies, we find kinematic evidence that suggests
that HH 203-204 and HH 202 are part of a big (aprox. 0.55 pc) bipolar HH
outflow.


title:
The Submillimeter Properties of the 1 Ms Chandra Deep Field North X-ray
  Sample

abstract:
  We present submillimeter observations for 136 of the 370 X-ray sources
detected in the 1 Ms exposure of the Chandra Deep Field North. Ten of the X-ray
sources are significantly detected in the submillimeter. The average X-ray
source in the sample has a significant 850 micron flux of 1.69+/-0.27 mJy. This
value shows little dependence on the 2-8 keV flux from 5e-16 erg/cm^2/s to
1e-14 erg/cm^2/s. The ensemble of X-ray sources contribute about 10% of the
extragalactic background light at 850 microns. The submillimeter excess is
found to be strongest in the optically faint X-ray sources that are also seen
at 20 cm, which is consistent with these X-ray sources being obscured and at
high redshift (z>1).


title: Anomalous diffusion of the cosmic rays: steady-state solution

abstract:
  We consider the propagation of galactic cosmic rays in the fractal
interstellar medium. Steady state solution of the fractional diffusion
equation, describing cosmic ray propagation, is found. We show that the
exponent of the steady state spectrum turns out to be equal to the exponent of
the cosmic ray spectrum above the "knee", that is approximately equal to 3.1.


title: Propagation of cosmic ray electrons in the Galaxy

abstract:
  We have made a new calculation of the cosmic ray electron spectrum using an
anomalous diffusion model to describe the propagation of electrons in the
Galaxy. The parameters defining the anomalous diffusion have been recently
determined from the study of nuclei propagation. The predicted electron
spectrum is in a good agreement with the measurements. The source spectral
index, found from experimental data, in this approach turns out to be equal to
2.95.


title: Theoretical Models of Multi-waveband QSO Luminosity Functions

abstract:
  Cosmological evolution of the QSO luminosity functions (LFs) at
NIR/optical/X-ray bands for 1.3 < z < 3.5 is investigated based on the
realistic QSO spectra. The accretion-disk theory predicts that although QSO
luminosities only depend on mass-accretion rate, \Mdot, QSO spectra have a
dependence on black-hole mass, M_{BH}, as well. The smaller M_{BH} is and/or
the larger \Mdot is, the harder becomes the QSO NIR/optical/UV spectrum. We
model disk spectra which can reproduce these features and calculated LFs for
redshift z ~ 3 with the assumption of new-born QSOs being shining at the
Eddington luminosity. The main results are: (i) the observed LFs at optical and
X-rays can be simultaneously reproduced. (ii) LFs at optical and X-ray bands
are not sensitive to M_{BH}, while LFs at NIR bands are; about one order of
magnitude difference is expected in volume number densities at L_{I, J} ~
10^{46} erg s^{-1} between the case that all QSOs would have the same spectral
shape as that of M_{BH} = 10^{9} M_sun and the case with M_{BH} = 10^{11}
M_sun. (iii) The resultant LFs at NIR are dominated by 10^{7} M_sun black-holes
at L_{I, J} ~ 10^{44} erg s^{-1}, and by 10^{11} M_sun black-holes at L_{I, J}
\~ 10^{46} erg s^{-1}. Future infrared observations from space(e.g.NGST) will
probe cosmological evolution of black hole masses. For redshift z < 3, on the
other hand, the observed optical/X-ray LFs can be fitted, if the initial QSO
luminosity L_0 is below the Eddington luminosity. Interestingly, the best
fitting values of l = L_0/L_{Edd} are different in B- and X-ray bands; l_B ~
2.5 l_X. The reason for this discrepancy is briefly discussed.


title: SN1A data and the CMB of Modified Curvature at short and long distances

abstract:
  The SN1a data, although inconclusive, when combined with other observations
makes a strong case that our universe is presently dominated by dark energy. We
investigate the possibility that large distance modifications of the curvature
of the universe would perhaps offer an alternative explanation of the
observation. Our calculations indicate that a universe made up of no dark
energy but instead, with a modified curvature at large scales, is not
scale-invariant, therefore quite likely it is ruled out by the CMB
observations. The sensitivity of the CMB spectrum is checked for the whole
range of mode modifications of large or short distance physics. The spectrum is
robust against modifications of short-distance physics and the UV cutoff when:
the initial state is the adiabatic vacuum, and the inflationary background
space is de Sitter.


title:
Non-linear evolution of thermally unstable slim accretion discs with a
  diffusive form of viscosity

abstract:
  We are carrying out a programme of non-linear time-dependent numerical
calculations to study the evolution of the thermal instability driven by
radiation pressure in transonic accretion discs around black holes. In our
previous studies we first investigated the original version of the slim-disc
model with low viscosity (parameter alpha = 0.001) for a stellar-mass (10 solar
masses) black hole, comparing the behaviour seen with results from local
stability analysis (which were broadly confirmed). In some of the unstable
models, we saw a violently evolving shock-like feature appearing near to the
sonic point. Next, we retained the original model simplifications but
considered a higher value of alpha = 0.1 and demonstrated the existence of
limit-cycle behaviour under suitable circumstances. The present paper describes
more elaborate calculations with a more physical viscosity prescription and
including a vertically integrated treatment of acceleration in the vertical
direction. Limit-cycle behaviour is still found for a model with alpha = 0.1,
giving a strong motivation to look for its presence in observational data.


title: Star Formation in a Complete Spectroscopic Survey of Galaxies

abstract:
  The 15R-North galaxy redshift survey is a uniform spectroscopic survey (S/N
$\sim $10) covering the range 3650---7400\AA for 3149 galaxies with median
redshift 0.05. The sample is 90% complete to $R=15.4$. The median slit covering
fraction is 24% of the galaxy, apparently sufficient to minimize the effects of
aperture bias on the EW(H$\alpha$).
  Forty-nine percent of the galaxes in the survey have one or more emission
lines detected at $\geq 2 \sigma$. In agreement with previous surveys, the
fraction of absorption-line galaxies increases steeply with galaxy luminosity.
  We use H$\beta$, O[III], H$\alpha$, and [N\II] to discriminate between
star-forming galaxies and AGNs.
  We use the EW(H$\alpha$ + [N\II]) to estimate the Scalo birthrate parameter,
$b$, the ratio of the current star formation rate to the time averaged star
formation rate.
  Finally, we examine the way galaxies of different spectroscopic type trace
the large-scale galaxy distribution.


title:
Intrinsic energy cut-off in diffusive shock acceleration: possible
  reason for non-detection of TeV-protons in SNRs

abstract:
  The linear theory of shock acceleration predicts the maximum particle energy
to be limited only by the acceleration time and the size of the shock. We study
the combined effect of acceleration nonlinearity (shock modification by
accelerated particles, that must be present in strong astrophysical shocks) and
propagation of Alfven waves that are responsible for particle confinement to
the shock front. We show that wave refraction to larger wave numbers in the
nonlinearly modified flow causes enhanced losses of particles in the momentum
range p_max/R < p < p_max, where R>1 is the nonlinear pre-compression of the
flow and p_max is a conventional maximum momentum, that could be reached if
there was no refraction.


title: Bayesian analysis of neutrinos observed from supernova SN 1987A

abstract:
  We present a Bayesian analysis of the energies and arrival times of the
neutrinos from supernova SN 1987A detected by the Kamiokande II, IMB, and
Baksan detectors, and find strong evidence for two components in the neutrino
signal: a long time scale component from thermal Kelvin-Helmholtz cooling of
the nascent neutron star, and a brief (~< 1 s), softer component similar to
that expected from emission by accreting material in the delayed supernova
scenario. In the context of this model, we show that the data constrain the
electron antineutrino rest mass to be less than 5.7 eV with 95% probability.
Our analysis takes advantage of significant advances that have occured in the
years since the detections in both our understanding of the supernova mechanism
and our ability to analyze sparse data. As a result there are substantial
differences between our inferences and those found in earlier studies. We find
that two-component models for the neutrino signal make the data >100 times more
probable than single-component models. In addition, the radius and binding
energy of the nascent neutron star implied by single-component models deviates
significantly from the values predicted by current neutron star models, whereas
those implied by models with an accretion component are in complete agreement
with the predictions. As a result, two-component models are hundreds to
thousands of times more probable than single-component models. The neutrino
data thus provide the first direct observational evidence in favor of the
delayed supernova scenario over the prompt scenario. (Abridged abstract)


title:
Evolutionary Binary Sequences for Low- and Intermediate-Mass X-ray
  Binaries

abstract:
  We present the results of a systematic study of the evolution of low- and
intermediate-mass X-ray binaries (LMXBs and IMXBs). Using a standard
Henyey-type stellar-evolution code and a standard model for binary
interactions, we have calculated 100 binary evolution sequences containing a
neutron star and a normal-type companion star, where the initial mass of the
secondary ranges from 0.6 to 7\Ms and the initial orbital period from $\sim 4
$hr to $\sim 100 $d. This grid of models samples the entire range of parameters
one is likely to encounter for LMXBs and IMXBs. The sequences show an enormous
variety of evolutionary histories and outcomes, where different mass-transfer
mechanisms dominate in different phases. Very few sequences resemble the
classical evolution of cataclysmic variables, where the evolution is driven by
magnetic braking and gravitational radiation alone. Many systems experience a
phase of mass transfer on a thermal timescale and may briefly become detached
immediately after this phase (for the more massive secondaries). In agreement
with previous results (\markcite{Tauris1}Tauris & Savonije 1999), we find that
all sequences with (sub-)giant donors up to $\sim 2\Ms$ are stable against
dynamical mass transfer. Sequences where the secondary has a radiative envelope
are stable against dynamical mass transfer for initial masses up to $\sim
4\Ms$. (abridged)


title:
Sensitivity of a Ground-Based Infrared Interferometer for Aperture
  Synthesis Imaging

abstract:
  Sensitivity limits of ground-based infrared interferometers using aperture
synthesis are presented. The motivation of this analysis is to compare an
interferometer composed of multiple large telescopes and a single giant
telescope with adaptive optics. In deriving these limits, perfect wavefront
correction by adaptive optics and perfect cophasing by fringe tracking are
assumed. We consider the case in which n beams are pairwise combined at
n(n-1)/2 detectors and the case in which all the n beams are combined at a
single detector. As a case study, we compare the point-source sensitivities of
interferometers composed of nine 10-m diameter telescopes and a 30-m diameter
single telescope with adaptive optics between 1 and 10 microns.


title:
Structural properties of spiral galaxies with and without an AGN:
  morphology and kinematics

abstract:
  The analysis of a sample of 30 isolated spiral galaxies with and without an
AGN results in active and control galaxies having similar bulge and disk
properties (since both samples are selected to match in morphological and bar
classification, they have similar bar percentages). Secondary bars seem also to
be indistinguishable. The central kinematics (both stellar and gas) are also
studied in order to put some constraints on the processes required to fuel
AGNs. Together with previous results, this points to AGNs being an episode of
the life of galaxies, providing that the fuel is available and the accumulation
mechanisms are at work.


title: Submillimeter CO Line Emission from Orion

abstract:
  Images of an 8 square minute region around the Orion KL source have been made
in the J=7-6 (806 GHz) and J=4-3 (461 GHz) lines of CO with angular resolutions
of 13" and 18". These data were taken employing on-the-fly mapping and position
switching techniques. Our J=7-6 data set is the largest image of Orion with the
highest sensitivity and resolution obtained so far in this line. Most of the
extended emission arises from a Photon Dominated Region (PDR), but 8% is
associated with the Orion ridge. For the prominent Orion KL outflow, we
produced ratios of the integrated intensities of our J=7-6 and 4-3 data to the
J=2-1 line of CO. Large Velocity Gradient (LVG) models fit the outflow ratios
better than PDR models. The LVG models give H_2 densities of ~10^5 per ccm. The
CO outflow is probably heated by shocks. In the Orion S outflow, the CO line
intensities are lower than for Orion KL. The 4-3/2-1 line ratio is 1.3 for the
blue shifted wing and 0.8 for the red shifted wing. Emission in the jet feature
extending 2' to the SW of Orion S was detected in the J=4-3 but not the J=7-6
line; the average 4-3/2-1 line ratio is ~1. The line ratios in the Orion S
outflow and jet features are consistent with both PDR and LVG models.
Comparisons of the intensities of the J=7-6 and J=4-3 lines from the Orion Bar
with PDR models show that the ratios exceed predictions by a factor of 2.
Either clumping or additional heating by mechanisms such as shocks, may be the
cause of this discrepancy.


title:
Recovering the Internal Dynamics and the Shapes of Galaxy Clusters:
  Virgo Cluster

abstract:
  We describe a method for recovering of the substructure, internal dynamics
and geometrical shapes of clusters of galaxies. Applying the method to the
Virgo cluster, we, first, reveal the substructure of the central 4 arc degree
field of the Virgo cluster by means of S-tree technique. The existence of three
main subgroups of galaxies is revealed and their dynamical characteristics are
estimated. Then, using the previously suggested technique (Gurzadyan and Rauzy
1997), the bulk flow velocities of the subgroups are evaluated based on the
distribution of the redshifts of the galaxies. The results enable us also to
obtain a secure indication of the elongation of the Virgo cluster and its
positional inclination.


title:
Confidence limits of evolutionary synthesis models III. On
  time-integrated quantities

abstract:
  Evolutionary synthesis models are a fundamental tool to interpret the
properties of observed stellar systems. In order to achieve a meaningful
comparison between models and real data, it is necessary to calibrate the
models themselves, i.e. to evaluate the dispersion due to the discreteness of
star formation as well as the possible model errors. In this paper we show that
linear interpolations in the log M - log t_k plane, that are customary in the
evaluation of isochrones in evolutionary synthesis codes, produce unphysical
results. We also show that some of the methods used in the calculation of
time-integrated quantities (kinetic energy, and total ejected masses of
different elements) may produce unrealistic results. We propose alternative
solutions to solve both problems. Moreover, we have quantified the expected
dispersion of these quantities due to stochastic effects in stellar
populations. As a particular result, we show that the dispersion in the 14N/12C
ratio increases with time.


title: Ionized Gas in Spheroids: The SAURON Survey

abstract:
  Early results are reported from the SAURON survey of the kinematics and
stellar populations of nearby cluster and field E, S0, and Sa galaxies. We
present maps of the Hbeta and [OIII] emission-line distribution and kinematics
for NGC 5813 and NGC 7742.


title: FLAIR-II spectroscopy of two DENIS J-band galaxy samples

abstract:
  As a pilot survey for the forthcoming 6dF Galaxy Redshift Survey,
spectroscopy of galaxies selected in J (1.2 mu) with the DENIS survey was
performed at the UKST using the FLAIR II multi-object spectroscope. 69 galaxy
redshifts (z's) were obtained in a high |b| field and an additional 12 z's in a
low latitude (b=-17 deg), obscured field. This study illustrates the
feasibility of obtaining z's with optical spectra on galaxies selected at much
longer wavelengths. It validated a very preliminary algorithm for star/galaxy
separation for high |b| DENIS objects, with 99% reliability for J < 13.9.
However, the FLAIR II z determinations required substantially longer
integration times to achieve 90% completeness than expected from previous
optical surveys at comparable depth. This is mainly due to a degradation in
overall fibre throughput due to known problems with ageing of the
prism-cement-fibre interface with exposure to UV light. Our low |b| (high
extinction) field required 2.5 times more exposure time for less than 50% of
successful z measurements. Among the J <= 13.9 galaxies with measured z's, only
37+/-6% display emission lines, in comparison with 60% of emission-line
galaxies (ELGs) in optical samples of comparable depth. The ELGs are, on
average, 0.5 mag bluer in B-J than non-ELGs of the same luminosity. We confirm
a previous optically-based result that the fraction of ELGs increases rapidly
with decreasing galaxy luminosity. The J-band luminosity function is estimated.
Our high latitude field displays a concentration of galaxies at cz ~ 38000 km/s
suggesting a possible supercluster. A radial velocity is reported for a galaxy
lying near the projected centre of the Abell 1434 cluster of galaxies, for
which no cluster z is currently available.


title: Carbon Monoxide in type II supernovae

abstract:
  Infrared spectra of two type II supernovae 6 months after explosion are
presented. The spectra exhibit a strong similarity to the observations of SN
1987A and other type II SNe at comparable epochs. The continuum can be fitted
with a cool black body and the hydrogen lines have emissivities that are
approximately those of a Case B recombination spectrum. The data extend far
enough into the thermal region to detect emission by the first overtone of
carbon monoxide. The molecular emission is modeled and compared with that in
the spectra of SN 1987A. It is found that the flux in the CO first overtone is
comparable to that found in SN 1987A. We argue that Carbon Monoxide forms in
the ejecta of all type II SNe during the first year after explosion.


title: X-ray spectral imaging and Doppler mapping of Cassiopeia A

abstract:
  A detailed X-ray spectral analysis of Cas A using a deep exposure from the
EPIC-MOS cameras on-board XMM-Newton is presented. Spectral fitting was
performed on a 15x15 grid of 20"x20" pixels using a two component
non-equilibrium ionisation model (NEI) giving maps of ionisation age,
temperature, interstellar column density, abundances and Doppler velocities.
The abundances of Si, S, Ar and Ca are strongly correlated. The abundance
ratios are consistent with the nucleosynthesis yield from the collapse of a 12
Msun progenitor. The abundance ratios Ne/Si, Mg/Si, Fe/Si and Ni/Si are very
variable and distinctly different from S/Si, Ar/Si and Ca/Si, in line with the
current explosive nucleosynthesis models. The ionisation age and temperature of
both NEI components varies considerably over the remnant. Accurate
determination of these parameters yield reliable Doppler velocities for both
components. The data are consistent with a plasma velocity of 2600 km/s at the
shock radius of 153" implying a primary shock velocity of 4000+/-500 km/s. The
Si-K and S-K line emission from the cool component is confined to a relatively
narrow shell with radius 100-150". This component is almost certainly ejecta
material which has been heated by a combination of the reverse shock and
heating of ejecta clumps as they plough through the medium which has been
pre-heated by the primary shock. The Fe-K line emission is expanding faster and
spans a radius range 110-170". The bulk of the Fe emission is confined to two
large clumps and it is likely that these too are the result of ablation from
ejecta bullets rather swept up circumstellar medium.


title:
A possible use for polarizers in imaging atmospheric Cherenkov
  telescopes

abstract:
  Cherenkov radiation produced in Extensive Air Showers shows a net
polarization. This article discusses its properties and physical origin, and
proposes an arrangement of polarizers potentially useful for Imaging
Atmospheric Cherenkov Telescopes.


title: Hydrodynamics of photoionized columns in the Eagle Nebula, M 16

abstract:
  We present hydrodynamical simulations of the formation, structure and
evolution of photoionized columns, with parameters based on those observed in
the Eagle Nebula. On the basis of these simulations we argue that there is no
unequivocal evidence that the dense neutral clumps at heads of the columns were
cores in the pre-existing molecular cloud. In our simulations, a variety of
initial conditions leads to the formation and maintenance of near-equilibrium
columns. Therefore, it is likely that narrow columns will often occur in
regions with large-scale inhomogeneities, but that observations of such columns
can tell us little about the processes by which they formed. The manner in
which the columns in our simulations develop suggests that their evolution may
result in extended sequences of radiation-induced star formation.


title: Population Synthesis and the Diagnostics of High-redshift Galaxies

abstract:
  The effect of redshift on the observation of distant galaxies is briefly
discussed emphasizing the possible sources of bias in the interpretation of
high-z data. A general energetic criterion to assess physical self-consistency
of evolutionary population synthesis models is also proposed, for a more
appropriate use of this important tool to investigate distinctive properties of
primeval galaxies.


title:
Observing the first galaxies - a case for an intermediate resolution
  multi-object IR spectrograph

abstract:
  We present a special science case for an intermediate resolution multi-object
IR spectrograph for the VLT. We have constructed new models for massive
Population III stars and metal-free stellar populations (see Schaerer 2001).
The properties of individual stars and integrated populations, including their
ionising fluxes and SEDs are discussed. We also study their dependence on the
poorly known IMF and the star formation history. The synthetic spectra are used
to simulate spectroscopic observations of the expected emission lines of Pop
III galaxies. We show that such an instrument should allow the detection and
efficient observations of the first galaxies with the VLT.


title: Radio and X-ray diffuse emission in six clusters of galaxies

abstract:
  Deep Very Large Array radio observations confirm the presence of halo and
relic sources in six clusters of galaxies (A115, A520, A773, A1664, A2254,
A2744) where a wide diffuse emission was previously found in the NRAO VLA Sky
Survey. New images at 1.4 GHz of these six clusters of galaxies are presented
and X-ray data obtained from the ROSAT archive are analyzed. The properties of
clusters hosting radio halos and relics are analyzed and discussed. A
correlation between the halo radio power and the cluster gravitational mass is
presented.


title: Cosmology studies with GRB afterglows

abstract:
  GRB afterglows close to their peak intensity are among the brightest sources
in the sky. We discuss how GRB optical-to-X-ray afterglows can be used as
probes of the metal enrichment of the interstellar matter in the GRB host
galaxies and of the heating history of the intergalactic matter in filaments
and outskirts of clusters of galaxies along the line of sight. The key points
of the proposed observation strategy are: 1) prompt GRB observations (from
minutes to a few hours); 2) coordinated O-UV and X-ray observations; and 3)
high resolution (1,500-6,000 in the 0.1-1 keV band and >10,000 in the OUV).


title: Colors and Spectra of Kuiper Belt Objects

abstract:
  We present new measurements of the optical colors of Kuiper Belt Objects,
principally from the Keck 10-m telescope. The measurements confirm the
existence of a wide spread in the B-V, V-R and R-I color indices (Luu and
Jewitt 1996). Relative to the sun, the Kuiper Belt Objects exhibit reflected
colors from nearly neutral to very red. The optical and optical-infrared (V-J)
color indices are mutually correlated, showing the presence of a single
reddening agent from 0.45 micron to 1.2 micron. On the other hand, we find no
evidence for linear correlations between the color and absolute magnitude (a
proxy for size), instantaneous heliocentric distance, semi-major axis, or with
any other orbital property. In this regard, the Kuiper Belt Objects differ from
the main-belt asteroids in which strong radial color gradients exist. We find
no statistically significant evidence for bimodal or other non-uniform color
distributions, either in our data, or in data previously reported to show such
evidence. The impact resurfacing hypothesis is re-examined in the light of the
new color data and is rejected as the primary cause of the observed color
dispersion. We also present new near-infrared reflection spectra of 1993 SC,
1996 TS_66, 1999 DE_9 and 2000 EB_173, taken at the Keck and Subaru telescopes.
These spectra, combined with others from the published literature, provide
independent evidence for compositional diversity in the Kuiper Belt. Objects
2000 EB_173, 1993 SC, and 1996 TS_66 are spectrally bland while 1999 DE_9 shows
solid-state absorption bands.


title: Limits on Pulsar Parameters for Pulsed detections with H.E.S.S

abstract:
  The non-detection of pulsed sub-TeV gamma-rays from EGRET pulsars proves that
the EGRET pulsed spectra of all gamma-ray pulsars should terminate at energies
below a few hundred GeV. The spectrum of a typical integrated pulse profile
predicted by the polar cap model resemble typically a hard component, followed
by a super exponential cutoff between 1 MeV (PSR B1509-58) and tens of GeV
(e.g. Crab, PSR B1951+32 etc). Using a topological trigger for the H.E.S.S.
Telescope System in the non-imaging mode, we show that H.E.S.S. should be able
to detect pulsed emission from PSR B1706-44 within a few hours if the cutoff
energy is above 30 GeV as suggested by EGRET observations. The recently
detected radio pulsar PSR J1837-0604 (pulsar period: 96 ms) associated with the
unidentified EGRET source GeV J1837-06010 should also be detectable within a
few hours if the source is pulsed and if its cutoff is similar to that of PSR
B1706-44. H.E.S.S. should even be able to image middle-aged, low-multiplicity
pulsars for which the mean photon energy is expected to be well above 10 GeV.
Such observations should provide important constraints on the final
evolutionary status of gamma-ray pulsars and millisecond pulsars in general.


title:
DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries
  and Cepheids. VIII. Additional Variables in the Field M33B Discovered with
  Image Subtraction

abstract:
  DIRECT is a project to obtain directly the distances to two Local Group
galaxies, M31 and M33, which occupy a crucial position near the bottom of the
cosmological distance ladder. As the first step of the DIRECT project we have
searched for detached eclipsing binaries (DEBs) and new Cepheids in the M31 and
M33 galaxies with 1m-class telescopes. In this eighth paper we present a
catalog of variable stars discovered in the data from the followup observations
of DEB system D33J013337.0+303032.8 in field M33B [(RA,Dec)= (23.48, 30.57),
J2000.0], collected with the Kitt Peak National Observatory 2.1m telescope. In
our search covering an area of 108 sq. arcmin. we have found 895 variable
stars: 96 eclipsing binaries, 349 Cepheids, and 450 other periodic, possible
long period or non-periodic variables. Of these variables 612 are newly
discovered. Their light curves were extracted using the ISIS image subtraction
package. For 77% of the variables we present light curves in standard V and B
magnitudes, with the remaining 23% expressed in units of differential flux. We
have discovered a population of first overtone Cepheid candidates and for six
of them we present strong arguments in favor of this interpretation. The
catalog of variables, as well as their photometry (about 9.2*10^4 BV
measurements) and finding charts, is available electronically via anonymous ftp
and the World Wide Web. The complete set of the CCD frames is available upon
request.


title:
Detailed Structure and Dynamics in Particle-in-Cell Simulations of the
  Lunar Wake

abstract:
  The solar wind plasma from the Sun interacts with the Moon, generating a wake
structure behind it, since the Moon is to a good approximation an insulator,
has no intrinsic magnetic field and a very thin atmosphere. The lunar wake in
simplified geometry has been simulated via a 1-1/2-D electromagnetic
particle-in-cell code, with high resolution in order to resolve the full phase
space dynamics of both electrons and ions. The simulation begins immediately
downstream of the moon, before the solar wind has infilled the wake region,
then evolves in the solar wind rest frame. An ambipolar electric field and a
potential well are generated by the electrons, which subsequently create a
counter-streaming beam distribution, causing a two-stream instability which
confines the electrons. This also creates a number of electron phase space
holes. Ion beams are accelerated into the wake by the ambipolar electric field,
generating a two stream distribution with phase space mixing that is strongly
influenced by the potentials created by the electron two-stream instability.
The simulations compare favourably with WIND observations.


title:
Conversion Problems: How (Not) to Determine Molecular Masses in Dwarf
  Galaxies

abstract:
  The determination of molecular gas masses in star forming dwarf irregular
galaxies is crucial to assess the star formation process in these objects. But
the derivation of the molecular gas content of dwarf galaxies has been a
long-standing problem. CO, as the only practical tracer of cold molecular gas,
has been (and to some extent still is) notoriously diffucult to detect. Yet,
star formation clearly takes place in many dwarf irregulars. This conference
contribution contrasts a number of methods commonly used to derive the
molecular gas contents of dwarf galaxies based on CO observations: Procedures
based on the virial theorem and those relying on radiative transfer arguments.
It is shown that both classes of methods have serious drawbacks. Still,
examples show that there seem to be real differences in the `correct'
conversion factor both between and within star forming dwarf irregular
galaxies.


title: The distance to the Vela pulsar gauged with HST parallax oservations

abstract:
  The distance to the Vela pulsar (PSR B0833-45) has been traditionally assumed
to be 500 pc. Although affected by a significant uncertainty, this value stuck
to both the pulsar and the SNR. In an effort to obtain a model free distance
measurement, we have applied high resolution astrometry to the pulsar V~23.6
optical counterpart. Using a set of five HST/WFPC2 observations, we have
obtained the first optical measurement of the annual parallax of the Vela
pulsar. The parallax turns out to be 3.4 +/- 0.7 mas, implying a distance of
294(-50;+76) pc, i.e. a value significantly lower than previously believed.
This affects the estimate of the pulsar absolute luminosity and of its emission
efficiency at various wavelengths and confirms the exceptionally high value of
the N_e towards the Vela pulsar. Finally, the complete parallax data base
allows for a better measurement of the Vela pulsar proper motion
(mu_alpha(cos(delta))=-37.2 +/- 1.2 mas/yr; mu_delta=28.2 +/- 1.3 mas/yr after
correcting for the peculiar motion of the Sun) which, at the parallax distance,
implies a transverse velocity of ~65 km/s. Moreover, the proper motion position
angle appears specially well aligned with the axis of symmetry of the X-ray
nebula as seen by Chandra. Such an alignment allows to assess the space
velocity of the Vela pulsar to be ~81 km/s.