title: Global Physical Conditions of the Interstellar Medium in Nearby Galaxies

abstract:
  Far-infrared spectra (43-197um) of 34 nearby galaxies obtained by the Long
Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO) were
analyzed to investigate the general properties of interstellar matter in
galaxies. The line fluxes of [CII]158um and [NII]122um relative to the total
far-infrared flux (FIR) decrease as the far-infrared color becomes bluer, while
the ratio of the [OI]63um flux to FIR does not show a systematic trend with the
color. The [OIII]88um to FIR ratio shows a large scatter with a weak trend of
increase with the color. We estimate the physical conditions of
photodissociation regions (PDRs) in the sample galaxies, such as the
far-ultraviolet radiation field intensity Go and the gas density n by assuming
that all the observed [OI]63um and far-infrared continuum emissions come from
PDRs. The present analysis suggests that the decrease in [CII]158um/FIR with
the far-infrared color may not be accounted for by the decrease in the
photoelectric heating efficiency owing to the increase in positive charges of
dust grains because a measure of the efficiency, Go/n, is found to stay
constant with the far-infrared color. Instead the decrease can be interpreted
in terms of either the increase in the collisional de-excitation of the [CII]
transition due to the increase in the gas density or the decrease in the
ionized component relative to the far-infrared intensity suggested by the
decrease in [NII]122um/FIR. Based on the present analysis, we derive average
relations of the far-infrared color with Go and n in galaxies, which can be
applied to the investigation of interstellar matter in distant galaxies.


title: Response of bare strange stars to energy input onto their surfaces

abstract:
  We study numerically the thermal emission of $e^+e^-$ pairs from a bare
strange star heated by energy input onto its surface; heating starts at some
moment, and is steady afterwards. The thermal luminosity in $e^+e^-$ pairs
increases to some constant value. The rise time and the steady thermal
luminosity are evaluated. Both normal and colour superconducting states of
strange quark matter are considered. The results are used to test the magnetar
model of soft gamma-ray repeaters where the bursting activity is explained by
fast decay of superstrong magnetic fields and heating of the strange star
surface. It is shown that the rise times observed in typical bursts may be
explained in this model only if strange quark matter is a superconductor with
an energy gap of more that 1 MeV.


title:
Simulations of Gas Flow from a Galactic Disk to the BH-dominated Central
  Disk

abstract:
  With a help of hydrodynamical models, we explore fundamental modes of gas
flow in central parts of a galaxy potential with non-axisymmetric perturbations
of various strengths. Our grid-based algorithm allows us to get a detailed
picture of gas dynamics down to about 10 pc from the galaxy center, where the
central black hole becomes dominant. Gas inflow in a bar with an Inner Lindblad
Resonance often stops at the nuclear ring. We find that embedded bars in
resonant coupling are unlikely to increase the inflow, but for certain gas
parameters in a single bar, inflow to the center develops in a spiral shock,
similar to the patterns observed in nuclear discs of real galaxies. The spiral
pattern persists for very weak non-axisymmetries of the potential.


title:
Using the Ca II Triplet to Trace Abundance Variations in Individual Red
  Giant Branch stars in Three Nearby Galaxies

abstract:
  Spectroscopic abundance determinations for stars spanning a Hubble time in
age are necessary in order to unambiguously determine the evolutionary
histories of galaxies. Using FORS1 in Multi-Object Spectroscopy mode on ANTU
(UT1) at the ESO-VLT on Paranal we obtained near infrared spectra from which we
measured the equivalent widths of the two strongest Ca II triplet lines to
determine metal abundances for a sample of Red Giant Branch stars, selected
from ESO-NTT optical (I, V-I) photometry of three nearby, Local Group,
galaxies: the Sculptor Dwarf Spheroidal, the Fornax Dwarf Spheroidal and the
Dwarf Irregular NGC 6822. The summed equivalent width of the two strongest
lines in the Ca II triplet absorption line feature, centered at 8500A, can be
readily converted into an [Fe/H] abundance using the previously established
calibrations by Armandroff & Da Costa (1991) and Rutledge, Hesser & Stetson
(1997). We measured metallicities for 37 stars in Sculptor, 32 stars in Fornax,
and 23 stars in NGC 6822, yielding more precise estimates of the metallicity
distribution functions for these galaxies than it is possible to obtain
photometrically. In the case of NGC 6822, this is the first direct measurement
of the abundances of the intermediate-age and old stellar populations. We find
metallicity spreads in each galaxy which are broadly consistent with the
photometric width of the Red Giant Branch, although the abundances of
individual stars do not always appear to correspond to their colour. This is
almost certainly predominantly due to a highly variable star formation rate
with time in these galaxies, which results in a non-uniform,
non-globular-cluster-like, evolution of the Ca/Fe ratio.


title: The distribution of mass around galaxies

abstract:
  We explore the distribution of mass about the expected sites of galaxy
formation in a high-resolution hydrodynamical simulation of a LCDM cosmology
which includes cooling, star-formation and feedback. We show that the evolution
of the galaxy bias is non-trivial and non-monotonic and that the bias is
stochastic. We discuss the galaxy-mass cross-correlation function and highlight
problems with the interpretation of galaxy-galaxy lensing as due to extended
dark matter halos around ``typical'' galaxies. Finally we show that the
``external shear'' around strong gravitational lenses is likely to be closely
aligned with the direction of the nearest massive galaxy and to have a
power-law distribution which can be predicted from the galaxy auto-correlation
function.


title:
Determination of the cosmological parameters from the Earth-Moon system
  evolution

abstract:
  We have obtained empirical laws for the variation of the Earth parameters
with geologic time that are in agreement with coral fossil data obtained by
Wells and Runcorn. Our model predicts that the day is lengthening at a rate of
2 ms/century at the present time. The length of the day when the Earth was
formed is found to be 6 hours and the synodic month to be 56 days. The angular
momentum of the Earth-Moon system is found to be increasing with time. The
origin of the presently observed acceleration of the Moon is explained. It is
predicted that the Moon is approaching the Earth at a present rate of 1.5
cm/year and with an acceleration of 20.6 arc sec/cy^2. It is shown that the
Moon has never been close to the Earth in last 4.5 million years.


title:
Seyfert-Type Dependences of Narrow Emission-Line Ratios and Physical
  Properties of High-Ionization Nuclear Emission-Line Regions in Seyfert
  Galaxies

abstract:
  In order to examine how narrow emission-line flux ratios depend on the
Seyfert type, we compiled various narrow emission-line flux ratios of 355
Seyfert galaxies from the literature. We present in this paper that the
intensity of the high-ionization emission lines, [Fe VII]6087, [Fe X]6374 and
[Ne V]3426, tend to be stronger in Seyfert 1 galaxies than in Seyfert 2
galaxies. In addition to these lines, [O III]4363 and [Ne III]3869, whose
ionization potentials are not high (< 100 eV), but whose critical densities are
significantly high (> 10^7 cm^-3), also exhibit the same tendency. On the other
hand, the emission-line flux ratios among low-ionization emission lines do not
show such a tendency. We point out that the most plausible interpretation of
these results is that the high-ionization emission lines arise mainly from
highly-ionized, dense gas clouds, which are located very close to nuclei, and
thus can be hidden by dusty tori. To examine the physical properties of these
highly-ionized dense gas clouds, photoionization model calculations were
performed. As a result, we find that the hydrogen density and the ionization
parameter of these highly-ionized dense gas clouds are constrained to be n_H >
10^6 cm^-3 and U > 10^-2, respectively. These lower limits are almost
independent both from the metallicity of gas clouds and from the spectral
energy distribution of the nuclear ionizing radiation.


title:
Interferometric Astrometry with Hubble Space Telescope Fine Guidance
  Sensor 3:The Parallax of the Cataclysmic Variable TV Columbae

abstract:
  TV Columbae (TV Col) is a 13th magnitude Intermediate Polar (IP) Cataclysmic
Variable (CV), with multiple periods found in the light curves. Past estimates
predicted a distance of 400 parsec to greater than 500 parsec. Recently
completed Hubble Space Telescope (HST) Fine Guidance Sensor (FGS)
interferometric observations allow us to determine the first trigonometric
parallax to TV Col. This determination puts the distance of TV Col at 368
-15+17 parsecs.
  CD-32 2376, a 10th magnitude Tycho Catalog star, is a reference star in the
TV Col frame. We find a distance of $127.7 -1+1 parsecs.


title: Multicolor Photometry of the Vela Pulsar

abstract:
  Multicolor photometry of the Vela pulsar (PSR B0833-45), updated by recent
HST/WFPC2 observations obtained in the 555W, 675W and 814W filters, is
presented. The available data provide the best characterization so far of the
pulsar spectral shape, which is dominated by a flat power law continuum with
spectral index \alpha = -0.2 +/- 0.2, consistent with the extrapolation in the
optical domain of the power law component of the X-ray spectrum detected by
Chandra. In addition, a marginally significant dip (~ 3 sigma) seems to be
present at about 6500 AA. Spectroscopic observations with the VLT, now in
progress, will undoubtly provide a much better assessment of the reality and
characteristics of this feature.


title: Omega_m - Different Ways to Determine the Matter Density of the Universe

abstract:
  A summary of various measurements of the mean matter density in the universe,
Omega_m, is presented. Results from very different kinds of methods using
various astronomical objects -- from supernovae to large-scale structure -- are
shown. There is a remarkable preference for Omega_m values around 0.3, but
there are also some measurements that favour a higher or a smaller value.


title: Probing the dark energy with quasar clustering

abstract:
  We show, through Monte Carlo simulations, that the Alcock-Paczynski test, as
applied to quasar clustering, is a powerful tool to probe the cosmological
density and equation of state parameters, Omega_{m0}, Omega_{x0} and w. By
taking into account the effect of peculiar velocities upon the correlation
function we obtain, for the Two-Degree Field QSO Redshift Survey (2QZ), the
predicted confidence contours for the cosmological constant (w = -1) and
spatially flat (Omega_{m0} + Omega_{x0}=1) cases. It turns out that, for w =
-1, the test is especially sensitive to the difference Omega_{m0} -
Omega_{Lambda 0}, thus being ideal to combine with CMB results. We also find
out that, for the flat case, it is competitive with future supernova and galaxy
number count tests, besides being complementary to them.


title: SCUBA Observations of NGC 1275

abstract:
  Deep SCUBA observations of NGC 1275 at 450 micron and 850 micron along with
the application of deconvolution algorithms have permitted us to separate the
strong core emission in this galaxy from the fainter extended emission around
it. The core has a steep spectral index and is likely due primarily to the AGN.
The faint emission has a positive spectral index and is clearly due to extended
dust in a patchy distribution out to a radius of $\sim$ 20 kpc from the
nucleus. These observations have now revealed that a large quantity of dust,
$\sim$ 6 $\times$ 10$^7$ $M_\odot$, 2 orders of magnitude larger than that
inferred from previous optical absorption measurements, exists in this galaxy.
We estimate the temperature of this dust to be $\sim$ 20 K (using an emissivity
index of $\beta$ = 1.3) and the gas/dust ratio to be 360. These values are
typical of spiral galaxies. The dust emission correlates spatially with the hot
X-ray emitting gas which may be due to collisional heating of broadly
distributed dust by electrons. Since the destruction timescale is short, the
dust cannot be replenished by stellar mass loss and must be externally
supplied, either via the infalling galaxy or the cooling flow itself.


title: Molecular Gas and Star Formation in NGC 3077

abstract:
  We present high resolution (~2.5'') CO(1-0) and CO(2-1) images of the central
kiloparsec of NGC 3077 made with the Owens Valley Millimeter Array. CO emission
is distributed in three major complexes which resolve into at least seven GMCs.
Two complexes are associated with the central starburst. A third, more distant
complex is not associated with strong star formation. The GMCs are ~70 pc in
size and contain ~10^{6} M_{\odot} of molecular gas. The Galactic conversion
factor appears applicable to NGC 3077, consistent with its solar metallicity.
Galactic rotation in NGC 3077 is detected for the first time in the molecular
gas. The molecular gas counterrotates with respect to the large scale HI tidal
bridge. The molecular clouds closest to the starburst have super-virial
linewidths, possibly related to the turbulence generated by the starburst. The
2.6 mm radio continuum flux indicates that thermal Bremsstrahlung dominates the
emission from the starburst region below 5 cm, and that the N_{Lyc} \simeq
3.7\times 10^{52} s^{-1} or ~3000 O7 stars, corresponds to a star formation
rate of 0.4 M_{\odot} yr^{-1}. At this rate the amount of molecular gas can
sustain star formation for only ~10 Myrs; thus NGC 3077 is a true starburst
galaxy. The derived age of the starburst is consistent with the inferred ages
of the superbubbles, which suggests that the burst is much younger than the age
of the M 81-M 82-NGC 3077 interaction. We suggest that it is caused by gas that
was pulled out of NGC 3077 during the interaction with M 81, raining back down
onto the galaxy.


title:
Detection of H2 Emission from Mira B in UV Spectra from the Hubble Space
  Telescope

abstract:
  We present ultraviolet spectra of Mira's companion star from the Space
Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space
Telescope (HST). The companion is generally assumed to be a white dwarf
surrounded by an accretion disk fed by Mira's wind, which dominates the UV
emission from the system. The STIS UV spectrum is dominated by numerous, narrow
H2 lines fluoresced by H I Ly-alpha, which were not detected in any of the
numerous observations of Mira B by the International Ultraviolet Explorer
(IUE). The high temperature lines detected by IUE (e.g., C IV 1550) still exist
in the STIS spectrum but with dramatically lower fluxes. The continuum fluxes
in the STIS spectra are also much lower, being more than an order of magnitude
lower than ever observed by IUE, and also an order of magnitude lower than
fluxes observed in more recent HST Faint Object Camera objective prism spectra
from 1995. Thus, the accretion rate onto Mira B was apparently much lower when
STIS observed the star, and this change altered the character of Mira B's UV
spectrum.


title: The 3D-structure of the LISM

abstract:
  We review what is currently known about the structure of interstellar
material in the solar neighborhood, emphasizing how observations from the
Hubble Space Telescope (HST) have improved our understanding of how
interstellar gas is distributed near the Sun. The nearby ISM is not uniform but
shows variations in both temperature and metal abundances on distance scales of
just a few parsecs. The observations also show that nearby gas does not have a
single uniform velocity vector. Instead, different components are often seen in
different directions for even very short lines of sight. However,
interpretation of these components remains difficult. It is uncertain whether
the components represent physically distinct clouds or perhaps are just
symptomatic of velocity gradients within the cloud. Finally, since it is the
local interstellar medium's interaction with the solar wind that is the primary
application of ISM studies considered in these proceedings, we also review how
the same HST data used to study the local ISM structure has also been used to
study both the heliospheric interaction with the solar wind and also
"astrospheric" interactions with the winds of other stars.


title: Controlling the False Discovery Rate in Astrophysical Data Analysis

abstract:
  The False Discovery Rate (FDR) is a new statistical procedure to control the
number of mistakes made when performing multiple hypothesis tests, i.e. when
comparing many data against a given model hypothesis. The key advantage of FDR
is that it allows one to a priori control the average fraction of false
rejections made (when comparing to the null hypothesis) over the total number
of rejections performed. We compare FDR to the standard procedure of rejecting
all tests that do not match the null hypothesis above some arbitrarily chosen
confidence limit, e.g. 2 sigma, or at the 95% confidence level. When using FDR,
we find a similar rate of correct detections, but with significantly fewer
false detections. Moreover, the FDR procedure is quick and easy to compute and
can be trivially adapted to work with correlated data. The purpose of this
paper is to introduce the FDR procedure to the astrophysics community. We
illustrate the power of FDR through several astronomical examples, including
the detection of features against a smooth one-dimensional function, e.g.
seeing the ``baryon wiggles'' in a power spectrum of matter fluctuations, and
source pixel detection in imaging data. In this era of large datasets and high
precision measurements, FDR provides the means to adaptively control a
scientifically meaningful quantity -- the number of false discoveries made when
conducting multiple hypothesis tests.


title: Strong Shocks and Supersonic Winds in Inhomogeneous Media

abstract:
  Many astrophysical flows occur in inhomogeneous media. The broad-line regions
(BLR) of active galactic nuclei (AGNs) are one of the important examples where
emission-line clouds interact with the outflow.
  We present results of a numerical study of the interaction of a steady,
planar shock / supersonic postshock flow with a system of embedded cylindrical
clouds in a two-dimensional geometry. Detailed analysis shows that the
interaction of embedded inhomogeneities with the shock / postshock wind depends
primarily on the thickness of the cloud layer and the arrangement of the clouds
in the layer, as opposed to the total cloud mass and the total number of
individual clouds. This allows us to define two classes of cloud distributions:
thin and thick layers. We define the critical cloud separation along the
direction of the flow and perpendicular to it. This definition allows us to
distinguish between the interacting and noninteracting regimes of cloud
evolution. Finally we discuss mass-loading in such systems.


title: Thermal Comptonization and Disk Thermal Reprocessing in NGC 3516

abstract:
  We present an application of the thermal Comptonization/disk reprocessing
model recently proposed by Zdziarski, Lubi\'nski, & Smith. We show that the
absence of strong optical variations in the presence of strong concurrent X-ray
variations, similar to those found by HST/RXTE monitoring observations of NGC
3516, can be explained by changing the geometry of the Comptonizing plasma
rather than the accretion disk itself. The total X-ray luminosity of the
Comptonizing plasma must decrease as its spatial extent increases. In contrast,
the disk inner radius must be roughly fixed in order not to produce
optical/ultraviolet color variations stronger than observed. By including
emission due to internal viscous dissipation in the disk, we can roughly match
the optical and X-ray flux levels and variability amplitudes seen from NGC 3516
during the HST/RXTE campaign.


title: The Nucleosynthetic Signature of Population III

abstract:
  Growing evidence suggests that the first generation of stars may have been
quite massive (~100-300 M_sun). Could these stars have left a distinct
nucleosynthetic signature? We explore the nucleosynthesis of helium cores in
the mass range M_He=64 to 133 Msun, corresponding to main-sequence star masses
of approximately 140 to 260 M_sun. Above M_He=133 M_sun, without rotation and
using current reaction rates, a black hole is formed and no nucleosynthesis is
ejected. For lighter helium core masses, ~40 to 63 M_sun, violent pulsations
occur, induced by the pair instability and accompanied by supernova-like mass
ejection, but the star eventually produces a large iron core in hydrostatic
equilibrium. It is likely that this core, too, collapses to a black hole, thus
cleanly separating the heavy element nucleosynthesis of pair instability
supernovae from those of other masses, both above and below. Indeed, black hole
formation is a likely outcome for all Population III stars with main sequence
masses between about 25 M_sun and 140 M_sun (M_He = 9 to 63 M_sun) as well as
those above 260 M_sun. Nucleosynthesis in pair-instability supernovae varies
greatly with the mass of the helium core which determines the maximum
temperature reached during the bounce. At the upper range of exploding core
masses, a maximum of 57 M_sun of Ni56 is produced making these the most
energetic and the brightest thermonuclear explosions in the universe.
Integrating over a distribution of masses, we find that pair instability
supernovae produce a roughly solar distribution of nuclei having even nuclear
charge, but are remarkably deficient in producing elements with odd nuclear
charge. Also, essentially no elements heavier than zinc are produced due to a
lack of s- and r-processes.


title: Orbital Evolution of Scattered Planets

abstract:
  A simple dynamical model is employed to study the possible orbital evolution
of scattered planets and phase plane analysis is used to classify the parameter
space and solutions. Our results reconfirm that there is always an increase in
eccentricity when the planet was scattered to migrate outward when the initial
eccentricity is zero. Applying our study on the Solar System and considering
the existence of the Kuiper Belt, this conclusion implies that Neptune was
dynamically coupled with the Kuiper Belt in the early phase of the Solar
System, which is consistent with the simulational model in Thommes, Duncan &
Levison (1999).


title: Spectrophotometric Evolution of Old Stellar Systems

abstract:
  Theoretical integrated spectrophotometric quantities, such as spectral line
indices in the Lick system (Hbeta, Mg2, Mg b, Fe5270, Fe5335), broadband color
indices (in the UBVRIHK and Washington CMT1 bandpasses), and surface brightness
fluctuation magnitudes and colors, ranging from far-UV to near-IR have been
consistently computed for simple stellar populations from our evolutionary
population synthesis code. The age range of -4 Gyr < Delta_t < +4 Gyr is
explored, where Delta_t = 0 Gyr is the currently favored mean age of inner halo
Galacitc globular clusters (Galactocentric radius < 8 kpc), ~ 12Gyr. The main
aim of this dissertation is to investigate the effects of post-red giant branch
stars on the integrated spectrophotometric quantities after employing detailed
systematic variation of horizontal-branch morphology with age and metallicity.


title: Neutron Capture Elements in s-Process-Rich, Very Metal-Poor Stars

abstract:
  We report abundance estimates for neutron-capture elements, including lead
(Pb), and nucleosynthesis models for their origin, in two carbon-rich, very
metal-poor stars, LP625-44 and LP706-7. These stars are subgiants whose surface
abundances are likely to have been strongly affected by mass transfer from
companion AGB stars that have since evolved to white dwarfs. The detections of
Pb, which forms the final abundance peak of the s-process, enable a comparison
of the abundance patterns from Sr (Z=38) to Pb (Z=82) with predictions of AGB
models. The derived chemical compositions provide strong constraints on the AGB
stellar models, as well as on s-process nucleosynthesis at low metallicity. The
present paper reports details of the abundance analysis for 16 neutron-capture
elements in LP 625-44, including the effects of hyperfine splitting and isotope
shifts of spectral lines for some elements. A Pb abundance is also derived for
LP706-7 by a re-analysis of a previously observed spectrum. We investigate the
characteristics of the nucleosynthesis pathway that produces the abundance
ratios of these objects using a parametric model of the s-process without
adopting any specific stellar model. The neutron exposure tau is estimated to
be about 0.7mb^-1, significantly larger than that which best fits solar-system
material, but consistent with the values predicted by models of moderately
metal-poor AGB stars. This value is strictly limited by the Pb abundance, in
addition to those of Sr and Ba. We also find that the observed abundance
pattern can be explained by a few recurrent neutron exposures, and that the
overlap of the material that is processed in two subsequent exposures is small
(the overlap factor r~0.1).


title:
What can we learn from the surface chemical composition of the optical
  companions of Soft X-ray transients?

abstract:
  Several evolutionary sequences with low--mass secondaries ($M_d $=1.25, 1.5
and 1.7$ M_\odot $) and black hole accretors ($M_{bh} $=5 and 10$ M_\odot$) are
calculated. The angular momentum losses due to magnetic braking and
gravitational wave radiation are included. Using full nuclear networks (p--p
and CNO cycles) we follow carefully the evolution of the surface composition of
the secondary star. We find that the surface chemical composition of the
secondary star may give additional information which helps to understand the
formation of soft X-ray transients with black holes as accretors. We show that
observations of isotope ratios $^{12}C/^{13}C$, $^{14}N/^{15}N$ and
$^{16}O/^{17}O $ with comparison to computed sequences allow estimates
independent from spectroscopy of the mass of the secondary component. We find
that our evolutionary calculations satisfactorily explain the observed $\it q =
M_{sg}/M_{bh}$ -- $P_{orb}$ distribution for Soft X-ray transients with orbital
periods less than one day. Using our evolutionary calculations we estimate
secondary masses and surface chemical abundances (C,N,O) for different systems.
We distinguished three different phases in the SXT's evolution. The optical
component shows (i) cosmic C, N, O abundances and $^{12}$C/$^{13}$C isotopic
ratio; (ii) cosmic C, N, O abundances but modified $^{12}$C/$^{13}$C ratio; and
(iii) depletion of C and enhanced of N abundances and strongly modified
isotopic ratios of C, N, O elements.


title: Is KPD 1930+2752 a good SN Ia progenitor?

abstract:
  We investigate the evolution of a binary system which initially has an
orbital period of 2^h 17^m and contains a 0.5 M_sun helium star with a white
dwarf companion of 0.97 M_sun, similarly to suggested SN Ia candidate
progenitor KPD 1930+2752. We show that the helium star completes core helium
burning and becomes a white dwarf before components merge. The most probable
outcome of the merger of components is formation of a massive white dwarf,
despite initially the total mass of the system is above the Chandrasekhar mass.


title: Fast Magnetosonic Waves Driven by Gravitational Waves

abstract:
  The propagation of a gravitational wave (GW) through a magnetized plasma is
considered. In particular, we study the excitation of fast magnetosonic waves
(MSW) by a gravitational wave, using the linearized general-relativistic
hydromagnetic equations. We derive the dispersion relation for the plasma,
treating the gravitational wave as a perturbation in a Minkowski background
space-time. We show that the presence of gravitational waves will drive
magnetosonic waves in the plasma and discuss the potential astrophysical
implications.


title: A study of Tycho's SNR at TeV energies with the HEGRA CT-System

abstract:
  Tycho's supernova remnant (SNR) was observed during 1997 and 1998 with the
  HEGRA Cherenkov Telescope System in a search for gamma-ray emission at
energies above
  ~1 TeV. An analysis of these data, ~65 hours in total, resulted in no
evidence for TeV gamma-ray emission. The 3sigma upper limit to the gamma-ray
flux (>1 TeV) from Tycho is estimated at 5.78x10^{-13} photons cm^{-2} s^{-1},
or 33 milli-Crab. We interpret our upper limit within the framework of the
following scenarios:
  (1) that the observed hard X-ray tail is due to synchrotron emission. A lower
limit on the magnetic field within Tycho may be estimated B>=22 microG,
assuming that the RXTE-detected
  X-rays were due to synchrotron emission. However, using results from a
detailed model of the ASCA emission, a more conservative lower limit B>=6
microG is derived.
  (2) the hadronic model of Drury, Aharonian & Voelk, and (3) the more recent
time-dependent kinetic theory of Berezhko & Voelk.
  Our upper limit lies within the range of predicted values of both hadronic
models, according to uncertainties in physical parameters of Tycho, and shock
acceleration details. In the latter case, the model was scaled to suit the
parameters of Tycho and re-normalised to account for a simplification of the
original model.
  We find that we cannot rule out Tycho as a potential contributor at an
average level to the Galactic cosmic-ray flux.


title:
The evolution of Omega(HI) and the epoch of formation of damped
  Lyman-alpha absorbers

abstract:
  We present a study of the evolution of the column density distribution,
f(N,z), and total neutral hydrogen mass in high-column density quasar absorbers
using candidates from a recent high-redshift survey for damped Lyman-alpha
(DLA) and Lyman limit system (LLS) absorbers. The observed number of LLS
(N(HI)> 1.6 * 10^{17} atom/cm^2) is used to constrain f(N,z) below the
classical DLA Wolfe et al. (1986) definition of 2 * 10^{20} atom/cm^2. The
joint LLS-DLA analysis shows unambiguously that f(N,z) deviates significantly
from a single power law and that a Gamma-law distribution of the form
f(N,z)=(f_*/N_*)(N/N_*)^{-Beta} exp(-N/N_*) provides a better description of
the observations. These results are used to determine the amount of neutral gas
contained in DLAs and in systems with lower column density. Whilst in the
redshift range 2 to 3.5, ~90% of the neutral HI mass is in DLAs, we find that
at z>3.5 this fraction drops to only 55% and that the remaining 'missing' mass
fraction of the neutral gas lies in sub-DLAs with N(HI) 10^{19} - 2 * 10^{20}
atom/cm^2. The characteristic column density, N_*, changes from 1.6 * 10^{21}
atom/cm^2 at z<3.5 to 2.9 * 10^{20} atom/cm^2 at z>3.5, supporting a picture
where at z>3.5, we are directly observing the formation of high column density
neutral hydrogen DLA systems from lower column density units. Moreover since
current metallicity studies of DLA systems focus on the higher column density
systems they may be giving a biased or incomplete view of global galactic
chemical evolution at z>3. After correcting the observed mass in HI for the
``missing'' neutral gas the comoving mass density now shows no evidence for a
decrease above z=2. (abridged)


title: Standing Shocks around Black Holes: An Analytical Study

abstract:
  We compute locations of sonic points and standing shock waves in a thin,
axisymmetric, adiabatic flow around a Schwarzschild black hole. We use
completely analytical method to achieve our goal. Our results are compared with
those obtained numerically and a good agreement is seen. Our results positively
prove the existence of shocks in centrifugal pressure dominated flows. We
indicate how our results could be used to obtain spectral properties and
frequencies of shock oscillations which may be directly related to the
quasi-periodic oscillations of hard X-rays.


title: Recovering true metal abundances of the ICM

abstract:
  Recovering the true average abundance of the intracluster medium (ICM) is
crucial for estimates of its global metal content, which in turn is linked to
its past evolution and to the star formation history of the stellar component
of the cluster. We analyze here how the presence of abundance gradients affects
commonly adopted estimates of the average abundance, assuming various plausible
ICM density and temperature profiles. We find that, adopting the observed
abundance gradients, the true average mass weighted abundance is less than
(although not largely deviating from) the commonly used emission weighted
abundance.


title:
The LBDS Hercules sample of mJy radio sources at 1.4 GHz - II. Redshift
  distribution, radio luminosity function, and the high-redshift cut-off

abstract:
  {Abridged} A combination of spectroscopy and broadband photometric redshifts
has been used to find the complete redshift distribution of the Hercules sample
of millijansky radio sources. These data have been used to examine the
evolution of the radio luminosity function (RLF) and its high-redshift cut-off.
  New redshifts have been measured for eleven sources, and a further ten upper
limits are given. The total number of sources with known redshifts in the
sample is now 47 (65%). We calculated broadband photometric redshifts for the
remaining one-third of the sample.
  For the luminosity range probed by the present study (P_1.4 > 10^24.5
W/Hz/sr), we use the V/V_max test to show conclusively that there is a deficit
of high-redshift (z > 2-2.5) objects. Comparison with the model RLFs of Dunlop
& Peacock (1990) shows that our data can now exclude pure luminosity evolution.
Two of the models of DP90, and the RLF deduced by direct binning of the data,
both favour a luminosity dependence for the high-redshift cut-off, with
lower-luminosity sources (P_1.4 \simeq 10^24 W/Hz/sr) in decline by z \simeq
1-1.5 while higher-luminosity sources (P_1.4 \simeq 10^{25-26} W/Hz/sr) decline
in comoving number density beyond z \simeq 2-2.5.


title: 12CO(1-0) observations of NGC 4848: a Coma galaxy after stripping

abstract:
  We study the molecular gas content and distribution in the Coma cluster
spiral galaxy NGC 4848. Plateau de Bure interferometric CO(1-0) observations
reveal a lopsided H_2 distribution with an off-center secondary maximum
coincident with the inner part of the HI. NGC 4848 is not at all deficient in
molecular gas as it contains M_H_2~4x10^9 M_solar. At the interface between the
CO and HI emission regions, about 8 kpc NW of the center, however, strong star
formation is present as witnessed by Halpha and radio continuum emission. This
is the region in which earlier Fabry-Perot observations revealed a
double-peaked Halpha line, indicating gas at two different velocities at the
same sky position. In order to understand these observations, we present the
results of numerical simulations of the ISM-ICM interaction. We suggest that
NGC 4848 already passed through the center of the cluster about 4x10^8 years
ago. At the observed stage ram pressure has no more direct dynamical influence
on the galaxy's ISM. We observe the galaxy when a fraction of the stripped gas
is falling back onto the galaxy. Ram pressure is thus a short-lived event with
longer-lasting consequences. The combination of ram-pressure and rotation
results in gas at different velocities colliding where the double-peaked Halpha
line is observed. Ram-pressure can thus result, after re-accretion, in
displaced molecular gas without the H_2 itself being pushed efficiently by the
ICM. A scenario where two interactions take place simultaneously is also
consistent with the available data but less probable on the basis of our
numerical simulations.


title:
First XMM-Newton observations of strongly magnetic cataclysmic variables
  I: spectral studies of DP Leo and WW Hor

abstract:
  We present an analysis of the X-ray spectra of two strongly magnetic
cataclysmic variables, DP Leo and WW Hor, made using XMM-Newton. Both systems
were in intermediate levels of accretion. Hard optically thin X-ray emission
from the shocked accreting gas was detected from both systems, while a soft
blackbody X-ray component from the heated surface was detected only in DP Leo.
We suggest that the lack of a soft X-ray component in WW Hor is due to the fact
that the accretion area is larger than in previous observations with a
resulting lower temperature for the re-processed hard X-rays. Using a
multi-temperature model of the post-shock flow, we estimate that the white
dwarf in both systems has a mass greater than 1 Msun. The implications of this
result are discussed. We demonstrate that the `soft X-ray excess' observed in
many magnetic cataclysmic variables can be partially attributed to using an
inappropriate model for the hard X-ray emission.


title: Chaotic motion and ballistic ejection of gravitating shells

abstract:
  It is shown that during the motion of two initially gravitationally bound
spherical shells, consisting of point particles moving along ballistic
trajectories, one of the shell may be expelled to infinity at subrelativistic
speed $v_{exp}\leq 0.25 c$. The problem is solved in Newtonian gravity. Motion
of two intersecting shells in the case when they do not runaway shows a chaotic
behaviour. We hope that this toy and oversimplyfied model can give nevertheless
a qualitative idea on the nature of the mechanism of matter outbursts from the
dense stellar clusters.


title: One year of Galileo dust data from the Jovian system: 1996

abstract:
  The dust detector system onboard Galileo records dust impacts in circumjovian
space since the spacecraft has been injected into a bound orbit about Jupiter
in December 1995. This is the sixth in a series of papers dedicated to
presenting Galileo and Ulysses dust data. We present data from the Galileo dust
instrument for the period January to December 1996 when the spacecraft
completed four orbits about Jupiter (G1, G2, C3 and E4). Data were obtained as
high resolution realtime science data or recorded data during a time period of
100 days, or via memory read-outs during the remaining times. Because the data
transmission rate of the spacecraft is very low, the complete data set (i. e.
all parameters measured by the instrument during impact of a dust particle) for
only 2% (5353) of all particles detected could be transmitted to Earth; the
other particles were only counted. Together with the data for 2883 particles
detected during Galileo's interplanetary cruise and published earlier, complete
data of 8236 particles detected by the Galileo dust instrument from 1989 to
1996 are now available. The majority of particles detected are tiny grains
(about 10 nm in radius) originating from Jupiter's innermost Galilean moon Io.
These grains have been detected throughout the Jovian system and the highest
impact rates exceeded $\rm 100 min^{-1}$. A small number of grains has been
detected in the close vicinity of the Galilean moons Europa, Ganymede and
Callisto which belong to impact-generated dust clouds formed by (mostly
submicrometer sized) ejecta from the surfaces of the moons (Kr\"uger et al.,
Nature, 399, 558, 1999). Impacts of submicrometer to micrometer sized grains
have been detected thoughout the Jovian system and especially in the region
between the Galilean moons.


title: The Highest Energy Emission Detected by EGRET from Blazars

abstract:
  Published EGRET spectra from blazars extend only to 10 GeV, yet EGRET has
detected approximately 2000 gamma-rays above 10 GeV of which about half are at
high Galactic latitude. We report a search of these high-energy gamma-rays for
associations with the EGRET and TeV detected blazars. Because the point spread
function of EGRET improves with energy, only ~2 gamma-rays are expected to be
positionally coincident with the 80 blazars searched, yet 23 gamma-rays were
observed. This collection of > 10 GeV sources should be of particular interest
due to the improved sensitivity and lower energy thresholds of ground-based TeV
observatories. One of the blazars, RGB0509+056, has the highest energy
gamma-rays detected by EGRET from any blazar with 2 > 40 GeV, and is a BL Lac
type blazar with unknown redshift.


title:
Modelling submillimetre spectra of the protostellar infall candidates
  NGC1333-IRAS2 and Serpens SMM4

abstract:
  We present a radiative transfer model, which is applicable to the study of
submillimetre spectral line observations of protostellar envelopes. The model
uses an exact, non-LTE, spherically symmetric radiative transfer `Stenholm'
method, which numerically solves the radiative transfer problem by the process
of `Lambda-iteration'. We also present submillimetre spectral line data of the
Class 0 protostars NGC1333-IRAS2 and Serpens SMM4. We examine the physical
constraints which can be used to limit the number and range of parameters used
in protostellar envelope models, and identify the turbulent velocity and tracer
molecule abundance as the principle sources of uncertainty in the radiative
transfer modelling. We explore the trends in the appearance of the predicted
line profiles as key parameters in the models are varied.
  We find that the separation of the two peaks of a typical infall profile is
dependent not on the evolutionary status of the collapsing protostar, but on
the turbulent velocity dispersion in the envelope. We also find that the line
shapes can be significantly altered by rotation.
  Fits are found for the observed line profiles of IRAS2 and SMM4 using
plausible infall model parameters. The density and velocity profiles in our
best fit models are inconsistent with a singular isothermal sphere model. We
find better agreement with a form of collapse which assumes non-static initial
conditions. We also find some evidence that the infall velocities are retarded
from free-fall towards the centre of the cloud, probably by rotation, and that
the envelope of SMM4 is rotationally flattened.


title: The dust temperature distribution in prestellar cores

abstract:
  We have computed the dust temperature distribution to be expected in a
pre-protostellar core in the phase prior to the onset of gravitational
instability. We have done this in the approximation that the heating of the
dust grains is solely due to the attenuated external radiation field and that
the core is optically thin to its own radiation. This permits us to consider
non spherically symmetric geometries. We predict the intensity distributions of
our model cores at millimeter and sub-millimeter wavelengths and compare with
observations of the well studied object L1544. We have also developed an
analytical approximation for the temperature at the center of spherically
symmetric cores and we compare this with the numerical calculations. Our
results show (in agreement with Evans et al. 2001) that the temperatures in the
nuclei of cores of high visual extinction (> 30 magnitudes) are reduced to
values of below ~8 K or roughly half of the surface temperature. This has the
consequence that maps at wavelengths shortward of 1.3 mm see predominantly the
low density exterior of pre-protostellar cores. It is extremely difficult to
deduce the true density distribution from such maps alone. We have computed the
intensity distribution expected on the basis of the models of Ciolek & Basu
(2000) and compared with the observations of L1544. The agreement is good with
a preference for higher inclinations (37 degrees instead of 16) than that
adopted by Ciolek & Basu (2000). We find that a simple extension of the
analytic approximation allows a reasonably accurate calculation of the dust
temperature as a function of radius in cores with density distributions
approximating those expected for Bonnor-Ebert spheres and suggest that this may
be a useful tool for future calculations of the gas temperature in such cores.


title:
Blue Stragglers, Young White Dwarfs and UV-excess stars in the core of
  47 Tuc

abstract:
  We used a set of archived HST/WFPC2 images to probe the stellar population in
the core of the nearby Galactic Globular Cluster (GGC) 47 Tuc. From the
ultraviolet (UV) Color Magnitude Diagrams (CMDs) obtained for ~4,000 stars
detected within the Planetary Camera (PC) field of view we have pinpointed a
number of interesting objects:
  (i) 43 blue stragglers stars (BSSs) including 20 new candidates;
  (ii) 12 bright (young) cooling white dwarfs (WDs) at the extreme blue region
of the UV-CMD; (iii) a large population of UV-excess (UVE) stars, lying between
the BSS and the WD sequences. The WD candidates identified here define a clean
pattern in the CMD, which define the WD cooling sequence. Moreover, both the
location on the UV-CMDs and the number of WDs are in excellent agreement with
the theoretical expectations. The UVE stars discovered here represent the
largest population of anomalous blue objects ever observed in a globular
cluster -- if the existence of such a large population is confirmed, we have
finally found the long-searched population of interacting binaries predicted by
the theory. Finally, we have investigated the feasibility of the optical
identification of the companions of the binary X-ray sources recently detected
by CHANDRA and of binary millisecond pulsars (MSPs) residing in the core of 47
Tuc. Unfortunately, the extreme faintness expected for the MSP companions
together with the huge stellar crowding in the cluster center prevent
statistically reliable identifications based only on positional coincidences.


title:
The shapes of dark matter dominated dwarf spheroidal stellar density
  profiles

abstract:
  A Bayesian likelihood analysis of the stellar density profile shapes of
several dark matter dominated Galactic dwarf spheroidal galaxies (dSphs) has
been completed. This analysis indicates that the inner power law, \rho \propto
r^{-\gamma}, of each of these profiles satisfies \gamma < 1.21 at greater than
99% confidence with a slight preference for \gamma \sim 0.7 . Speculating that
this bound on the stellar profiles may be related to the inner power law of the
underlying dark matter distribution reveals a statistical discrepancy with the
values favoured by recent N-body simulations of cold dark matter (CDM),
\gamma_{CDM} \sim 1.4-1.5 .


title: A list of peculiar velocities of RFGC galaxies

abstract:
  A list of radial velocities, HI line widths and peculiar velocities of 1327
galaxies from the RFGC catalogue has been compiled using actual observations
and literature data. The list can be used for studying bulk motions of
galaxies, construction of the field of peculiar velocities and other tasks.


title:
Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564.
  II. Ultraviolet Continuum and Emission-line Variability

abstract:
  We present results of an intensive two-month campaign of approximately daily
spectrophotometric monitoring of the narrow-line Seyfert 1 galaxy Akn 564 with
HST. The fractional variability amplitude of the continuum variations between
1365-3000 A is ~6%, about a factor 3 less than that found in typical Seyfert 1
galaxies over a similar period of time. However, large amplitude, short
time-scale flaring behavior is evident, with trough-to-peak flux changes of
about 18% in approximately 3 days. We present evidence for wavelength-dependent
continuum time delays, with the variations at 3000 A lagging behind those at
1365 A by about 1 day. These delays may be interpreted as evidence for a
stratified continuum reprocessing region, possibly an accretion-disk structure.
The Lyman-alpha 1216 emission-line exhibits flux variations of about 1%
amplitude.


title:
Scattered Light Models of Protostellar Envelopes: Multiple Outflow
  Cavities and Misaligned Circumstellar Disks

abstract:
  Ground based imaging, imaging polarimetry, and recent Hubble Space Telescope
WFPC2 and NICMOS images of protostars have revealed very complex scattered
light patterns that cannot be entirely explained by 2-D radiation transfer
models. We present here for the first time radiation transfer models of T Tau
and IRAS 04016+2610 that are fully 3-D, with the aim of investigating the
effects on image morphology of multiple illuminating sources and infalling
envelopes that have been shaped by multiple outflows. For T Tau we have
constructed scattered light models where the illumination of the surrounding
envelope is by a binary with each source surrounded by its own small
circumstellar disk or envelope. We find that the asymmetries in the WFPC2 image
of T Tau can be reproduced if the disks in the binary system are misaligned,
consistent with a recently discovered bipolar outflow believed to originate
from the secondary. For IRAS 04016+2610 we find that the observed scattered
light pattern can be reproduced by scattering in an envelope with cavities
carved by two sets of bipolar outflows, suggestive of an embedded binary
system.


title: Angular Momentum Evolution of Stars in the Orion Nebula Cluster

abstract:
  (Abridged) We present theoretical models of stellar angular momentum
evolution from the Orion Nebula Cluster (ONC) to the Pleiades and the Hyades.
We demonstrate that observations of the Pleiades and Hyades place tight
constraints on the angular momentum loss rate from stellar winds. The observed
periods, masses and ages of ONC stars in the range 0.2--0.5 M$_\odot$, and the
loss properties inferred from the Pleiades and Hyades stars, are then used to
test the initial conditions for stellar evolution models. We use these models
to estimate the distribution of rotational velocities for the ONC stars at the
age of the Pleiades (120 Myr). The modeled ONC and observed Pleiades
distributions of rotation rates are not consistent if only stellar winds are
included. In order to reconcile the observed loss of angu lar momentum between
these two clusters, an extrinsic loss mechanism such as protostar-accretion
disk interaction is required. Our model, which evolves the ONC stars with a
mass dependent saturation threshold normalized such that $\omega_{crit} = 5.4
\omega_\odot$ at 0.5 \m, and which includes a distribution of disk lifetimes
that is uniform over the range 0--6 Myr, is consistent with the Pleiades. This
model for disk-locking lifetimes is also consistent with inferred disk
lifetimes from the percentage of stars with infrared excesses observed in young
clusters. Different models, using a variety of initial period distributions and
different maximum disk lifetimes, are also compared to the Pleiades. For
disk-locking models that use a uniform distribution of disk lifetimes over the
range 0 to $\tau_{max}$, the acceptable range of the maximum lifetime is $3.5 <
\tau_{max} < 8.5$ Myr.


title:
Far-UV Observations of the Galactic Supersoft Binary RXJ0019.8+2156 (QR
  And)

abstract:
  FUSE spectra were obtained of the supersoft X-ray binary RX J0019.8+2156 (QR
And) during 16 consecutive spacecraft orbits, covering the binary orbit
(P=15.85 hr) with about 0.2 phase overlap. The spectrum is dominated by strong
H2 absorption (column density ~10**20 g/cm**2), which appears at a radial
velocity different from other interstellar absorption lines and may be
partially circumbinary. This absorption makes study of spectral features from
the binary system difficult. The only well-detected emission lines are He II,
1085A, and O VI, 1032A, (the other line of the O VI doublet, 1037A, is largely
obscured by strong H2 absorption). The O VI shows a P Cygni profile that varies
in velocity and strength with binary phase. We compare this with similar
changes seen in Balmer line profiles. We extract the FUV light curve and
compare it with the optical light curve. There is an eclipse in both wavelength
regions, but the FUV minimum lasts much longer, well beyond the visible light
egress. The FUV results are discussed in connection with the binary model and
mass flows within the system.


title: Mass Determinations of Star Clusters

abstract:
  Mass determinations are difficult to obtain and still frequently
characterised by deceptively large uncertainties. We review below the various
mass estimators used for star clusters of all ages and luminosities. We
highlight a few recent results related to (i) very massive old star clusters,
(ii) the differences and similarities between star clusters and cores of dwarf
elliptical galaxies, and (iii) the possible strong biases on mass determination
induced by tidal effects.


title:
The HI Content and Extent of Low Surface Brightness Galaxies - Could LSB
  Galaxies be Responsible for Damped Ly-alpha Absorption?

abstract:
  Low surface brightness galaxies, those galaxies with a central surface
brightness at least one magnitude fainter than the night sky, are often not
included in discussions of extragalactic gas at z < 0.1. In this paper we
review many of the properties of low surface brightness galaxies, including
recent studies which indicate low surface brightness systems may contribute far
more to the local HI luminosity function than previously thought. Additionally,
we use the known (HI) gas properties of low surface brightness galaxies to
consider their possible contribution to nearby damped Lyman-alpha absorbers.


title: A G1-like globular cluster in NGC 1023

abstract:
  The structure of a very bright (MV = -10.9) globular cluster in NGC 1023 is
analyzed on two sets of images taken with the Hubble Space Telescope. From
careful modeling of King profile fits to the cluster image, a core radius of
0.55+/-0.1 pc, effective radius 3.7+/-0.3 pc and a central V-band surface
brightness of 12.9+/-0.5 mag / square arcsec are derived. This makes the
cluster much more compact than Omega Cen, but very similar to the brightest
globular cluster in M31, G1 = Mayall II. The cluster in NGC 1023 appears to be
very highly flattened with an ellipticity of about 0.37, even higher than for
Omega Cen and G1, and similar to the most flattened clusters in the Large
Magellanic Cloud.


title: Thermal Conduction and the Stability of Hot Accretion Flows

abstract:
  Recently, Medvedev & Narayan (2001) discovered a new type of accretion flow,
a hot settling flow around a rapidly rotating neutron star. The flow is
cooling-dominated and energetically similar to the Shapiro, Lightman, & Eardley
(1976, SLE) solution. Since the SLE solution is known to be thermally unstable,
one might suspect that the new solution would also be unstable. However, due to
the very high temperature of the accreting gas, thermal conduction is very
strong and could suppress the thermal instability. We analyze the role of
thermal conduction in both the hot settling flow and the SLE solution. In the
hot settling flow collisions are very rare. Therefore, thermal transport occurs
via free streaming of electrons along tangled magnetic field lines. We find
that conduction is strong enough to make the flow marginally stable. In
contrast, in the cooler SLE solution, conduction is via collisional,
Spitzer-type transport. In this case, conduction is weaker, and we find that
the SLE solution is thermally unstable even in the presence of conduction.


title:
Modelling the orbital modulation of ultraviolet resonance lines in
  high-mass X-ray binaries

abstract:
  The stellar-wind structure in high-mass X-ray binaries (HMXBs) is
investigated through modelling of their ultraviolet (UV) resonance lines. For
the OB supergiants in two systems, Vela X-1 and 4U1700-37, high-resolution UV
spectra are available; for Cyg X-1, SMC X-1, and LMC X-4 low-resolution spectra
are used. In order to account for the non-monotonic velocity structure of the
stellar wind, a modified version of the Sobolev Exact Integration (SEI) method
by Lamers et al. (1987) is applied. The orbital modulation of the UV resonance
lines provides information on the size of the Stroemgren zone surrounding the
X-ray source. The amplitude of the observed orbital modulation (known as the
Hatchett-McCray effect), however, also depends on the density- and velocity
structure of the ambient wind. Model profiles are presented that illustrate the
effect on the appearance of the HM effect by varying stellar-wind parameters.
The q parameter of Hatchett & McCray (1977), as well as other parameters
describing the supergiant's wind structure, are derived for the 5 systems. The
X-ray luminosity needed to create the observed size of the Stroemgren zone is
consistent with the observed X-ray flux. The derived wind parameters are
compared to those determined in single OB supergiants of similar spectral type.
Our models naturally explain the observed absence of the HM effect in
4U1700-37. The orbital modulation in Vela X-1 indicates that besides the
Stroemgren zone other structures are present in the stellar wind (such as a
photo-ionization wake). The ratio of the wind velocity and the escape velocity
is found to be lower in OB supergiants in HMXBs than in single OB supergiants
of the same effective temperature.


title:
Chemical Evolution of Elliptical Galaxies as a Constraint to Galaxy
  Formation Scenarios

abstract:
  Elliptical galaxies are the main contributors to the chemical enrichment of
the intracluster and intergalactic medium; understanding how they form and
evolve enables us to get important hints on the amounts of energy and processed
matter that they eject into the ICM/IGM. Recent pieces of observational
evidence point to a strong connection between high redshift quasars and their
host galaxies. The aim of this paper is to prove that the main aspects of the
chemical evolution of the spheroids can be reproduced in the framework of a
model where the shining of the quasar is intimately related to the formation of
the galactic nucleus. A key assumption is that the quasars shone in an inverted
order with respect to the hierarchical one (i.e., stars and black holes in
bigger dark halos formed before those in smaller ones) during an early episode
of vigorous star formation. This scenario closely resembles the so-called
`inverse wind' model invoked to explain the observed increase of the [Mg/Fe]
ratio in the nuclei of ellipticals with increasing the galactic mass, the only
difference being that now the time for the occurrence of a galactic wind is not
determined by the energy input from supernovae, but is indeed the energy
injected by the quasar which regulates the onset of the wind phase.


title: Inflationary spectra in generalized gravity: Unified forms

abstract:
  The classical evolution and the quantum generation processes of the scalar-
and tensor-type cosmological perturbations in the context of a broad class of
generalized gravity theories are presented in unified forms. The exact forms of
final spectra of the two types of structures generated during a generalized
slow-roll inflation are derived. Results in generalized gravity are
characterized by two additional parameters which are the coupling between
gravity and field, and the nonminimal coupling in the kinetic part of the
field. Our general results include widely studied gravity theories and
inflation models as special cases, and show how the well known consistency
relation and spectra in ordinary Einstein gravity inflation models are affected
by the generalized nature of the gravity theories.


title: Circular Polarization of Circumstellar Water Masers around S Per

abstract:
  We present the first circular polarization measurements of circumstellar H2O
masers. Previously the magnetic field in circumstellar envelopes has been
estimated using polarization observations of SiO and OH masers. SiO masers are
probes of the high temperature and density regime close to the central star. OH
masers are found at much lower densities and temperatures, generally much
further out in the circumstellar envelope. The detection of the circular
polarization of the (6_16 - 5_23) rotational transition of the H2O maser could
be attributed to Zeeman splitting due to the magnetic field in the intermediate
temperature and density regime. The fields inferred here agree well with
predicted values for a combination of the r^{-2} dependence of a solar-type
magnetic field, and the coupling of the field to the high density masing
regions. We also discuss the unexpected narrowing of the circular polarization
spectrum.


title: Physical vacuum and cosmic coincidence problem

abstract:
  A framework is suggested in which the energy integrals of the Friedmann
cosmology are identified as genuine time-independent physical characteristics
for both vacuum and non-vacuum forms of cosmic energy. The integrals are found
to be numerically coincident within two orders of magnitude. It is assumed that
this coincidence reveals a symmetry that relates vacuum to non-vacuum forms of
cosmic energy at fundamental level. The symmetry shows the well-known cosmic
coincidence problem and the naturalness problem as two inter-related aspects of
a more general problem: Why are the energy integrals numerically coincident and
equal to $ \sim 10^{60} M_{Pl}^{-1}$? A simple kinetics model of cosmological
freeze out is used to examine how -- at least, in principle -- the electroweak
scale physics might explain the nature of the symmetry between vacuum and
non-vacuum cosmic energies and determine the value of the energy integrals in
terms of the fundamental energy scales.


title: Sulphur abundance in very metal-poor stars

abstract:
  We have obtained high-resolution high signal-to-noise spectra of the SI
near-infrared doublet at 8694 A in eight metal-poor stars with metallicities in
the range -0.6 <[Fe/H]< -3.0. Elemental sulphur abundances were derived for six
targets and upper limits were set for two of the most metal-poor stars in the
sample. The sulphur doublet at 8694.62 A has been detected in three stars
(HD19445, HD2665 and HD2796) with [Fe/H]< -1.9. Our observations combined with
those available in the literature indicate a monotonic increase of the [S/Fe]
ratio as [Fe/H] decreases, reaching values [S/Fe]~0.7-0.8 below [Fe/H]=-2. We
discuss plausible scenarios for interpretation of these results.


title:
Pulsar microstructure and its quasi-periodicities with the S2 VLBI
  system at a resolution of 62.5 nanoseconds

abstract:
  We report on a study of microstructure and its quasi-periodicities of three
pulsars at 1.65 GHz with the S2 VLBI system at a resolution of 62.5 ns, by far
the highest for any such statistical study yet. For PSR B1929+10 we found in
the average cross-correlation function (CCF) broad microstructure with a
characteristic timescale of 95+-10 mcs and confirmed microstructure with
characteristic timescales between 100 and 450 mcs for PSRs B0950+08 and
B1133+16. On a finer scale PSRs B0950+08, B1133+16 (component II) and B1929+10
show narrow microstructure with a characteristic timescale in the CCFs of ~10
mcs, the shortest found in the average CCF or autocorrelation function (ACF)
for any pulsar, apart perhaps for the Crab pulsar. Histograms of microstructure
widths are skewed heavily toward shorter timescales but display a sharp cutoff.
The shortest micropulses have widths between 2 and 7 mcs. No nanopulses or
unresolved pulse spikes were detected. Cross-power spectra of single pulses
show a large range of complexity with single spectral features representing
classic quasi-periodicities and broad and overlapping features with essentially
no periodicities at all. Significant differences were found for the two
components of PSR B1133+16 in every aspect of our statistical analysis of
micropulses and their quasi-periodicities. Asymmetries in the magnetosphere and
the hollow cone of emission above the polar cap of the neutron star may be
responsible for these differences.


title:
Characterising anomalous transport in accretion disks from X-ray
  observations

abstract:
  Whilst direct observations of internal transport in accretion disks are not
yet possible, measurement of the energy emitted from accreting astrophysical
systems can provide useful information on the physical mechanisms at work. Here
we examine the unbroken multi-year time variation of the total X-ray flux from
three sources: Cygnus X-1, the microquasar GRS1915+105, and for comparison the
nonaccreting Crab nebula. To complement previous analyses, we demonstrate that
the application of advanced statistical methods to these observational
time-series reveals important contrasts in the nature and scaling properties of
the transport processes operating within these sources. We find the Crab signal
resembles Gaussian noise; the Cygnus X-1 signal is a leptokurtic random walk
whose self-similar properties persist on timescales up to three years; and the
GRS1915+105 signal is similar to that from Cygnus X-1, but with self-similarity
extending possibly to only a few days. This evidence of self-similarity
provides a robust quantitative characterisation of anomalous transport occuring
within the systems.

categories: astro-ph physics.data-an physics.plasm-ph physics.space-ph


title:
Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564.
  III. Optical Observations and the Optical--UV--X-ray Connection

abstract:
  We present the results of a two-year long optical monitoring program of the
narrow-line Seyfert 1 galaxy Akn 564. The majority of this monitoring project
was also covered by X-ray observations (RXTE) and for a period of ~50 days, we
observed the galaxy in UV (HST) and X-rays (RXTE & ASCA) simultaneously with
the ground-based observations. Rapid and large-amplitude variations seen in the
X-ray band, on a daily and hourly time-scale, were not detected at optical and
UV wavelengths, which in turn exhibited much lower variability either on short
(one day) or long (several months) time-scales. The only significant optical
variations can be described as two 2--4 day events with ~10% flux variations.
We detect no significant optical line variations and thus cannot infer a
reverberation size for the broad-line region. Similarly, the large X-ray
variations seem to vanish when the light curve is smoothed over a period of 30
days. The UV continuum follows the X-rays with a lag of ~0.4 days, and the
optical band lags the UV band by ~2 days. No significant correlation was found
between the entire X-ray dataset and the optical band. Focusing on a 20-day
interval around the strongest optical event we detect a significant
X-ray--optical correlation with similar events seen in the UV and X-rays. Our
data are consistent with reprocessing models on the grounds of the energy
emitted in this single event. However, several large X-ray flares produced no
corresponding optical emission.


title: Pulsar Wind Nebulae in Evolved Supernova Remnants

abstract:
  For pulsars similar to the one in the Crab Nebula, most of the energy input
to the surrounding wind nebula occurs on a timescale of less than 1000 years;
during this time, the nebula expands into freely expanding supernova ejecta. On
a timescale 10,000 years, the interaction of the supernova with the surrounding
medium drives a reverse shock front toward the center of the remnant, where it
crushes the PWN (pulsar wind nebula). One- and two-dimensional, two-fluid
simulations of the crushing and re-expansion phases of a PWN show that (1)
these phases are subject to Rayleigh-Taylor instabilities that result in the
mixing of thermal and nonthermal fluids, and (2) asymmetries in the surrounding
interstellar medium give rise to asymmetries in the position of the PWN
relative to the pulsar and explosion site. These effects are expected to be
observable in the radio emission from evolved PWN because of the long lifetimes
of radio emitting electrons. The scenario can explain the chaotic and
asymmetric appearance of the Vela X PWN relative to the Vela pulsar without
recourse to a directed flow from the vicinity of the pulsar. The displacement
of the radio nebulae in G327.1--1.1, MSH15--56 (G326.3--1.8), G0.9+0.1, and W44
relative to the X-ray nebulae may be due to this mechanism. On timescales much
greater than the nebular crushing time, the initial PWN may be mixed with
thermal gas and become unobservable, so that even the radio emission is
dominated by recently injected particles.


title: A revision of the solar neighbourhood metallicity distribution

abstract:
  We present a revised metallicity distribution of dwarfs in the solar
neighbourhood. This distribution is centred on solar metallicity. We show that
previous metallicity distributions, selected on the basis of spectral type, are
biased against stars with solar metallicity or higher. A selection of G-dwarf
stars is inherently biased against metal rich stars and is not representative
of the solar neighbourhood metallicity distribution. Using a sample selected on
colour, we obtain a distribution where approximately half the stars in the
solar neighbourhood has a metallicity higher than [Fe/H]=0. The percentage of
mid-metal-poor stars ([Fe/H]$<$-0.5) is approximately 4 per cent, in agreement
with present estimates of the thick disc. In order to have a metallicity
distribution comparable to chemical evolution model predictions, we convert the
star fraction to mass fraction, and show that another bias against metal-rich
stars affects dwarf metallicity distributions, due to the colour (or spectral
type) limits of the samples. Reconsidering the corrections due to the
increasing thickness of the stellar disc with age, we show that the Simple
Closed-Box model with no instantaneous recycling approximation gives a
reasonable fit to the observed distribution. Comparisons with the
age-metallicity relation and abundance ratios suggest that the Simple
Closed-Box model may be a viable model of the chemical evolution of the Galaxy
at solar radius.


title:
Galaxies and Genes: Towards an Automatic Modeling of Interacting
  Galaxies

abstract:
  The main problems in modeling interacting galaxies are the extended parameter
space and the fairly high CPU costs of self-consistent N-body simulations.
Therefore, traditional modeling techniques suffer from either extreme CPU
demands or trapping in local optima (or both). A very promising alternative
approach are evolutionary algorithms which mimic natural adaptation in order to
optimize the numerical models. One main advantage is their very weak dependence
on starting points which makes them much less prone to trapping in local
optima. We present a Genetic Algorithm (GA) coupled with a fast (but not
self-consistent) restricted N-body solver. This combination allows us to
identify interesting regions of parameter space within only a few CPU hours on
a standard PC or a few CPU minutes on a parallel computer. Especially, we
demonstrate here the ability of GA-based fitting procedures to analyse
observational data automatically, provided the data are sufficiently accurate.


title: Searching for the Galactic Dark Matter

abstract:
  A straightforward interpretation of the MACHO microlensing results in the
direction of the Magellanic Clouds suggests that an important fraction of the
baryonic dark matter component of our Galaxy is in the form of old white
dwarfs. If correct, this has serious implications for the early generations of
stars that formed in the Universe and also on the manner in which galaxies
formed and enriched themselves in heavy elements. I examine this scenario in
some detail and in particular explore whether the searches currently being
carried out to locate local examples of these MACHOs can shed any light at all
on this scenario.


title: Properties of tidally-triggered vertical disk perturbations

abstract:
  We present a detailed analysis of the properties of warps and
tidally-triggered perturbations perpendicular to the plane of 47
interacting/merging edge-on spiral galaxies. The derived parameters are
compared with those obtained for a sample of 61 non-interacting edge-on
spirals. The entire optical (R-band) sample used for this study was presented
in two previous papers. We find that the scale height of disks in the
interacting/merging sample is characterized by perturbations on both large
(~disk cut-off radius) and short (~z0) scales, with amplitudes of the order of
280pc and 130pc on average, respectively. The size of these large (short)
-scale instabilities corresponds to 14% (6%) of the mean disk scale height.
This is a factor of 2 (1.5) larger than the value found for non-interacting
galaxies. A hallmark of nearly all tidally distorted disks is a scale height
that increases systematically with radial distance. The frequent occurrence and
the significantly larger size of these gradients indicate that disk asymmetries
on large scales are a common and persistent phenomenon, while local
disturbances and bending instabilities decline on shorter timescales. Nearly
all (93%) of the interacting/merging and 45% of the non-interacting galaxies
studied are noticeably warped. Warps of interacting/merging galaxies are ~2.5
times larger on average than those observed in the non-interacting sample, with
sizes of the order of 340pc and 140pc, respectively. This indicates that tidal
distortions do considerably contribute to the formation and size of warps.
However, they cannot entirely explain the frequent occurrence of warped disks.


title:
Sub-mm gravity: confronting the modified dynamics with
  higher-dimensional theories

abstract:
  We propose that future experiments aiming at the detection of deviations from
the inverse square gravitational law on submillimetric scales can be used to
test the modified Newtonian dynamics theory (MOND). Current experiments are
able to test the gravitational field of masses of approximately 1g at distances
around 200 micrometers, implying that they are probing accelerations well above
the MOND limit (1.2 X 10^{-8} cms^{-2}). We show that MONDian effects begin to
be important at the submillimetric level for masses below 1 mg. MOND makes
predictions that are clearly distinguishable from those expected in a scenario
with compact extra dimensions. This will enable direct confrontation between
the two theories if future experiments can improve their mass scales to the
milligram level.


title: HST photometry of Globular Clusters in the Sombrero Galaxy

abstract:
  We explore the rich globular cluster (GC) system of the nearby Sa galaxy
M104, the "Sombrero" (NGC 4594), using archive WFPC2 data. The GC colour
distribution is found to be bimodal at the > 99% level, with peaks at V-I =
0.96+/-0.03 and 1.21+/-0.03 (corrected for foreground reddening). The inferred
metallicities are very similar to those of globular clusters in our Galaxy and
M31. However the Sombrero reveals a much enhanced number of red (metal-rich)
GCs compared to other well-studied spirals. Because the Sombrero is dominated
by a huge bulge and only has a modest disk, we associate the two
sub-populations with the halo and bulge components respectively. Thus our
analysis supports the view that the metal-rich GCs in spirals are associated
with the bulge rather than with the disk. The Sombrero GCs have typical
effective (half-light) radii of about 2 pc with the red ones being about 30%
smaller than the blue ones. We identify many similarities between the
Sombrero's GC system and those of both late type spirals and early-type
galaxies. Thus both the GC system and the Hubble type of the Sombrero galaxy
appear to be intermediate in their nature.


title:
Measuring the galaxy power spectrum with multiresolution decomposition
  -- III. velocity field analysis

abstract:
  In this paper, we develop the method of analyzing the velocity field of
cosmic matter with a multiresolution decomposition. This is necessary in
calculating the redshift distortion of power spectrum in the discrete wavelet
transform (DWT) representation. We show that, in the DWT analysis, the velocity
field can be described by discrete variables, which are given by assignment of
the number density and velocity into the DWT modes. These DWT variables are
complete and not redundant. In this scheme, the peculiar velocity and pairwise
velocity of galaxies or particles are given by field variables. As a
consequence, the velocity dispersion (VD) and pairwise velocity dispersion
(PVD) are no longer measured by number-counting or pair-counting statistic, but
with the ensemble of the field variables, and therefore, they are free from the
bias due to the number-counting and pair-counting. We analyzed the VD and PVD
of the velocity fields given by the N-body simulation for models of the SCDM,
$\tau$CDM and $\Lambda$CDM. The spectrum (scale-dependence) of the VD and PVD
show that the length scale of the two-point correlation of the velocity field
is as large as few tens h$^{-1}$ Mpc. Although the VD and PVD show similar
behavior in some aspects, they are substantially different from each other. The
VD-to-PVD ratio shows the difference between the scale-dependencies of the VD
and PVD. More prominent difference between the VD and PVD is shown by
probability distribution function. The one-point distribution of peculiar
velocity is approximately exponential, while the pairwise velocity's is
lognormal, i.e. of long tail. This difference indicates that the cosmic
velocity field is typically intermittent.


title: A Multi-Threaded Fast Convolver for Dynamically Parallel Image Filtering

abstract:
  2D convolution is a staple of digital image processing. The advent of large
format imagers makes it possible to literally ``pave'' with silicon the focal
plane of an optical sensor, which results in very large images that can require
a significant amount computation to process. Filtering of large images via 2D
convolutions is often complicated by a variety of effects (e.g.,
non-uniformities found in wide field of view instruments). This paper describes
a fast (FFT based) method for convolving images, which is also well suited to
very large images. A parallel version of the method is implemented using a
multi-threaded approach, which allows more efficient load balancing and a
simpler software architecture. The method has been implemented within in a high
level interpreted language (IDL), while also exploiting open standards vector
libraries (VSIPL) and open standards parallel directives (OpenMP). The parallel
approach and software architecture are generally applicable to a variety of
algorithms and has the advantage of enabling users to obtain the convenience of
an easy operating environment while also delivering high performance using a
fully portable code.


title:
Shape Reconstruction and Weak Lensing Measurement with Interferometers:
  A Shapelet Approach

abstract:
  We present a new approach for image reconstruction and weak lensing
measurements with interferometers. Based on the shapelet formalism presented in
Refregier (2001), object images are decomposed into orthonormal Hermite basis
functions. The shapelet coefficients of a collection of sources are
simultaneously fit on the uv plane, the Fourier transform of the sky brightness
distribution observed by interferometers. The resulting chi-square fit is
linear in its parameters and can thus be performed efficiently by simple matrix
multiplications. We show how the complex effects of bandwidth smearing, time
averaging and non-coplanarity of the array can be easily and fully corrected
for in our method. Optimal image reconstruction, co-addition, astrometry, and
photometry can all be achieved using weighted sums of the derived coefficients.
As an example we consider the observing conditions of the FIRST radio survey
(Becker et al. 1995; White et al. 1997). We find that our method accurately
recovers the shapes of simulated images even for the sparse uv sampling of this
snapshot survey. Using one of the FIRST pointings, we find our method compares
well with CLEAN, the commonly used method for interferometric imaging. Our
method has the advantage of being linear in the fit parameters, of fitting all
sources simultaneously, and of providing the full covariance matrix of the
coefficients, which allows us to quantify the errors and cross-talk in image
shapes. It is therefore well-suited for quantitative shape measurements which
require high-precision. In particular, we show how our method can be combined
with the results of Refregier & Bacon (2001) to provide an accurate measurement
of weak lensing from interferometric data.


title: The Effects of a Stellar Encounter on a Planetesimal Disk

abstract:
  We investigate the effects of a passing stellar encounter on a planetesimal
disk through analytical calculations and numerical simulations, and derive the
boundary radius ($a_{\rm planet}$) outside which planet formation is inhibited
by disruptive collisions with high relative velocities.


title: X-Ray Microlensing of Bright Quasars

abstract:
  We calculated the expected microlens light curves for several accretion-flow
models and compared the results to find what aspects of distinct flow
structures can be extracted from the microlens light curves. As for the flow
models, we considered the standard disk, optically thin advection-dominated
flow, and the disk-corona model by Kawaguchi et al., which can nicely reproduce
the observed quasar spectra. The calculated microlens light curves of the
disk-corona model exhibit rapid soft X-ray and slow hard X-ray variations. This
is because the former is generated by Compton up-scattering of soft (optical --
UV) photons from the innermost part of the disk body, while the latter is
emitted via bremsstrahlung within the corona at relatively large radii.
Furthermore, an inhomogeneous emissivity distribution over the disk produces
humps in the microlens light curves because of enhanced microlens amplification
of the bright areas. It is hoped that black-hole accretion theory coupled with
future multi-wavelength microlens observations will be able to reveal such
spatial and temporal behaviors of flows in the vicinity of black holes.


title:
VLBI study of water maser emission in the Seyfert 2 galaxy NGC5793. I:
  Imaging blueshifted emission and the parsec-scale jet

abstract:
  We present the first result of VLBI observations of the blueshifted water
maser emission from the type 2 Seyfert galaxy NGC5793, which we combine with
new and previous VLBI observations of continuum emission at 1.7, 5.0, 8.4, 15,
and 22 GHz. Maser emission was detected earlier in single-dish observations and
found to have both red- and blueshifted features relative to the systemic
velocity. We could image only the blueshifted emission, which is located 3.6 pc
southwest of the 22 GHz continuum peak. The blueshifted emission was found to
originate in two clusters that are separated by 0.7 milliarcsecond (0.16 pc).
No compact continuum emission was found within 3.6 pc of the maser spot. A
compact continuum source showing a marginally inverted spectrum between 1.7 and
5.0 GHz was found 4.2 pc southwest of the maser position. The spectral turnover
might be due to synchrotron self-absorption caused by a shock in the jet owing
to collision with dense gas, or it might be due to free-free absorption in an
ionized screen possibly the inner part of a disk, foreground to the jet.
  The water maser may be part of a maser disk. If so, it would be rotating in
the opposite sense to the highly inclined galactic disk observed in CO
emission. We estimate a binding mass within 1 pc of the presumed nucleus to be
on the order of 10^7 Msun. Alternatively, the maser emission could result from
the amplification of a radio jet by foreground circumnuclear molecular gas. In
this case, the high blueshift of the maser emission might mean that the masing
region is moving outward away from the molecular gas surrounding an active
nucleus.


title:
Correlated perturbations from inflation and the cosmic microwave
  background

abstract:
  We compare the latest cosmic microwave background data with theoretical
predictions including correlated adiabatic and CDM isocurvature perturbations
with a simple power-law dependence. We find that there is a degeneracy between
the amplitude of correlated isocurvature perturbations and the spectral tilt. A
negative (red) tilt is found to be compatible with a larger isocurvature
contribution. Estimates of the baryon and CDM densities are found to be almost
independent of the isocurvature amplitude. The main result is that current
microwave background data do not exclude a dominant contribution from CDM
isocurvature fluctuations on large scales.


title: A giant stream of metal-rich stars in the halo of the galaxy M31

abstract:
  Recent observations have revealed streams of gas and stars in the halo of the
Milky Way that are the debris from interactions between our Galaxy and some of
its dwarf companion galaxies; the Sagittarius dwarf galaxy and the Magellanic
clouds. Analysis of the material has shown that much of the halo is made up of
cannibalized satellite galaxies, and that dark matter is distributed nearly
spherically in the Milky Way. It remains unclear, however, whether cannibalized
substructures are as common in the haloes of galaxies as predicted by
galaxy-formation theory. Here we report the discovery of a giant stream of
metal-rich stars within the halo of the nearest large galaxy, M31 (the
Andromeda galaxy). The source of this stream could be the dwarf galaxies M32
and NGC205, which are close companions of M31 and which may have lost a
substantial number of stars owing to tidal interactions. The results
demonstrate that the epoch of galaxy building still continues, albeit at a
modest rate, and that tidal streams may be a generic feature of galaxy haloes.


title: Observational Evidence for Galaxy Evolution in the Local Group

abstract:
  This review aims to give a summary of our understanding of galaxy evolution
as infered from studies of nearby galaxies; how observations made with the
Hubble Space Telescope have contributed significantly to our detailed
understanding of the older stellar populations in Local Group dwarf galaxies.
Recent results from VLT are also promising interesting future prospects for the
study of resolved stellar populations in nearby dwarf galaxies.


title: Infrared Observation of Hot Cores

abstract:
  We report on mid-infrared imaging of hot cores performed with SpectroCam-10
and TIMMI2. The observations aimed at the detection of thermal emission
presumably associated with the hot cores. Mid-infrared flux measurements are
required to improve the luminosity and optical depth estimates for these
sources. Results are presented for W3(H$_2$O), G9.62+0.19, G10.47+0.03, and the
possible hot core candidate G232.620+0.996. They illustrate that the morphology
of these sources cannot be described by simple geometries. Therefore,
line-of-sight effects and considerable extinction even at mid-infrared
wavelengths must not be neglected.


title: One-sided jet at milliarcsecond scales in LSI+61303

abstract:
  We present Very Long Baseline Interferometry (VLBI) observations of the high
mass X-ray binary LSI+61303, carried out with the European VLBI Network (EVN).
Over the 11 hour observing run, performed 10 days after a radio outburst, the
radio source showed a constant flux density, which allowed sensitive imaging of
the emission distribution. The structure in the map shows a clear extension to
the southeast. Comparing our data with previous VLBI observations we interpret
the extension as a collimated radio jet as found in several other X-ray
binaries. Assuming that the structure is the result of an expansion that
started at the onset of the outburst, we derive an apparent expansion velocity
of 0.003 c, which, in the context of Doppler boosting, corresponds to an
intrinsic velocity of at least 0.4 c for an ejection close to the line of
sight. From the apparent velocity in all available epochs we are able to
establish variations in the ejection angle which imply a precessing accretion
disk. Finally we point out that LSI+61303, like SS433 and Cygnus X-1, shows
evidence for an emission region almost orthogonal to the relativistic jet.


title: Arrays is Space to detect Upward Tau and Highest Altitude Showers

abstract:
  Ultra High Energy, UHE, upward Tau neutrinos Tau, anti-neutrino Tau, above
hundred TeVs and up to tens PeV energies, of relevant astrophysical nature, may
lead to UHE Taus and consequent Up-ward Tau air-Showers {UPTAUS} after
interaction on Earth crust surface. The UPTAUS discover may open a new UHE Tau
Neutrino Astrophysics. A new generation of Gamma, X, optical and Radio Arrays
in Space may discover, in the same Auger spirit, such up-coming Air-showers as
well as an additional Tau signal: the nearly Horizontal Tau AIR-Shower
{HORTAUS} originated by UHE neutrinos tau at 10^{19} eV energies arising from a
thin Earth crust corona at few tens of degree below the horizons; a degree
above the horizons, there should be over common diffused cosmic ray albedo, an
additional High Altitudes (nearly Horizontal) Showers {HIAS}, by more common
Cosmic Rays primaries at PeVs up to EeV and ZeV energies, both of hadronic or
of electro-magnetic $\gamma$ nature. Mini-arrays detectors in high Altitude
Balloons tails facing the horizons and the Earth below may also reveal both
UPTAUS, and HIAS, and more rarely HORTAUS. Gamma Burst, Cherenkov flashes and
rarer muons observed by high mountains peak arrays or high quota balloon array
may better probe UPTAUS and HORTAUS. Present and future X-Gamma satellites as
Beppo-Sax may be also able to discover HORTAUS and HIAS discovering transient
events by UHE source (as the Crab) while in occultation by Earth. Because of
the large shower distances and the Earth magnetic field, HIAS and HORTAUS
showers will be split in a {Twin-Beams} fan-shaped wide arc, orthogonal to the
terrestrial magnetic field, with a strong azimuths modulation. Gamma bursts
with rare single muons or neutrons at the horizon, associated with HIAS,
HORTAUS may be discovered by Glast and AMS satellite.


title: Radiation from the first forming stars

abstract:
  The evolution of radiation emitted during the dynamical collapse of
metal-free protostellar clouds is investigated within a spherically symmetric
hydrodynamical scheme that includes the transfer of radiation and the chemistry
of the primordial gas. The cloud centre collapses on a time scale of about
10^5-10^6 years, thanks to line cooling from molecular hydrogen (H2). For most
of the collapse time, when the evolution proceeds self-similarly, the
luminosity slowly rises up to about 10^36 erg/s and is essentially due to H2 IR
line emission. Later, continuum IR radiation provides an additional
contribution, which is mostly due to the accretion of an infalling envelope
upon a small hydrostatic protostellar core which develops in the centre. We
follow the beginning of the accretion phase, when the enormous accretion rate
(~ 0.1 Msun/yr) produces a very high continuum luminosity of about 10^36 erg/s.
Despite the high luminosities, the radiation field is unable to affect the gas
dynamics during the collapse and the first phases of accretion, because the
opacity of the infalling gas is too small; this is quite different from
present-day star formation. We also find that the protostellar evolution is
similar among clouds with different initial configurations, including those
resulting from 3D cosmological simulations of primordial objects; in
particular, the shape of the molecular spectra is quite universal. Finally, we
briefly discuss the detectability of this pristine cosmic star formation
activity.


title:
Optical Detection of a Variable Millisecond Pulsar Companion in 47
  Tucanae

abstract:
  Using results from radio and X-ray observations of millisecond pulsars in 47
Tucanae, and extensive HST U, V, I imaging of the globular cluster core, we
have derived a common astrometric solution good to < 0.1". A close positional
coincidence is found for 47 Tuc U, a 4.3 ms pulsar in a 0.429 day orbit,
detected in radio and X-rays, with an m_V = 20.9 blue star. Analysis of
extensive time series data for this optical candidate shows a 0.004 magnitude
semi-amplitude variation at the period and phase expected from the radio
ephemeris, and the optical variations are spatially coincident with the
candidate. This provides secure optical detection of the white dwarf companion
to the millisecond pulsar, the first such detection in a globular cluster,
allowing for comparisons to recent models for such companions with dependencies
on mass and age.


title:
Photometry and membership for low mass stars in the young open cluster
  NGC 2516

abstract:
  We present the results of a 0.86 square degree CCD photometric survey of the
open cluster NGC 2516, which has an age of about 150 Myr and may have a much
lower metallicity than the similarly-aged Pleiades. We select a preliminary
catalogue of 1254 low mass (between 0.2 and 2.0M_{sun}) cluster candidates, of
which about 70--80 percent are expected to be genuine. The mass function is
metallicity dependent, but consistent with a Salpeter-like law (dN/dlog M ~
M^{-alpha}, alpha=+1.47+/-0.11 or alpha=+1.67+/-0.11 for solar and half-solar
metallicities) between 0.7 and 3.0M_{sun}. At lower masses (between 0.3 and
0.7M_{sun}) there is a sharp fall in the mass function, with alpha=-0.75+/-0.20
(solar metallicity) or alpha=-0.49+/-0.13 (half-solar metallicity), which seems
inconsistent with the much flatter mass functions seen in the Pleiades and
field populations. We explain this by demonstrating that mass segregation has
been at work in NGC 2516 -- more than half the cluster low mass stars are
expected to lie outside out survey. The mass of NGC 2516 stars with mass
greater than 0.3M_{sun} inside our survey is 950-1200M_{sun}, depending on
metallicity and what corrections are applied for unresolved binarity.
Correcting for mass segregation increases this to ~1240-1560M_{sun}, about
twice the total mass of the Pleiades.


title:
The Infrared Continuum Radiation of NGC1808 : A PAH and Polarisation
  Study

abstract:
  The paper is devoted to the understanding of the infrared emission of nuclear
regions in galaxies. a) ISO data of NGC1808 are presented: spectro--photometry
from 5.1 to 16.4 mic., a 25"x25" map at 6 mic. and 170mic. photometry. b) The
data are complemented by a polarization measurement at 170 mic. (2.5+/-0.4% at
position angle 94+/-5deg) and a map at 6 mic. In the map, the degree of
polarisation goes up to 20% in the outer regions. We argue that the
polarisation is produced by emission of big grains and exclude very small
grains and PAHs or scattering and extinction. c) The mid infrared spectrum
shows, beside the main emission bands, a so far unknown plateau of PAH features
in the >13 mic.region. d) The total spectrum can be fit under the assumption of
optically thin emission. However, such a model fails to reproduce the 25mic.
point and implies that the mid infrared is due to very small grains and PAHs.
These particles would then also have to be responsible for the 6 mic.
polarisation, which is unlikely. e) To avoid these difficulties, we
successfully turn to a radiative transfer model whose major feature is the
existence of (hot spots) produced by the dust clouds around OB stars. We
demonstrate the decisive influence on the mid infrared spectrum of both the
PAHs and the hot spots.


title: P-mode observations on Alpha Cen A

abstract:
  We have made a clear detection of p-mode oscillations in the nearest
solar-like G2V star $\alpha$ Cen A with the CORALIE spectrograph on the 1.2-m
Swiss telescope at the ESO La Silla Observatory. We report the 5 nights of
observation on this star in May 2001 during which 1260 high precision radial
velocity measurements were obtained. The power spectrum clearly shows several
identifiable peaks between 1.7 and 3 mHz. The average large splitting of 105.7
$\mu$Hz and the amplitude of about 35 cm s$^{-1}$ of these modes are in
agreement with theoretical expectations.


title:
Large scale star formation in galaxies. II. The spirals NGC 3377A, NGC
  3507 and NGC 4394

abstract:
  The identification of young star groupings (YSG) in the three spiral galaxies
NGC 3377A, NGC 3507, NGC 4394 is obtained by mean of the statistical method
described in Paper I. We find 83, 90, 185 YSGs, respectively. An identification
map of YSGs, as well as their size distribution, their B-luminosity function,
their surface luminosity density radial behaviour, are presented and
comparatively discussed. These data, in addition to those in Paper I,
constitute a first sample suitable for seeking correlations among properties of
galaxies and their YSG, which we briefly discuss here.


title:
The Formation of Broad Emission Line Regions in Supernova-QSO Wind
  Interactions

abstract:
  We show that a cooled region of shocked supernova ejecta forms in a type II
supernova-QSO wind interaction, and has a density, an ionization parameter, and
a column density compatible with those inferred for the high ionization
component of the broad emission line regions in QSOs. The calculations are
based on the assumption that the ejecta flow is described initially by a
similarity solution investigated by Chevalier (1982) and Nadyozhin (1985) and
is spherically symmetric. Heating and cooling appropriate for gas irradiated by
a nearby powerful continuum source is included in our model, together with
reasonable assumptions for the properties of the QSO wind. The model results
are also in agreement with observational correlations and imply reasonable
supernova rates.


title:
Self-similar evolution of wind-blown bubbles with mass loading by
  hydrodynamic ablation

abstract:
  We present similarity solutions for adiabatic bubbles that are blown by winds
having time independent mechanical luminosities and that are each mass-loaded
by the hydrodynamic ablation of distributed clumps. The mass loading is
`switched-on' at a specified radius (with free-expansion of the wind interior
to this point) and injects mass at a rate per unit volume proportional to
M^delta r^lambda where delta = 4/3 (1) if the flow is subsonic (supersonic)
with respect to the clumps. In the limit of negligible mass loading a
similarity solution found by Dyson (1973) for expansion into a smooth ambient
medium is recovered. The presence of mass loading heats the flow, which leads
to a reduction in the Mach number of the supersonic freely-expanding flow, and
weaker jump conditions across the inner shock. In solutions with large mass
loading, it is possible for the wind to connect directly to the contact
discontinuity without first passing through an inner shock. For a solution that
gives the mass of swept-up ambient gas to be less than the sum of the masses of
the wind and ablated material, lambda < -2. Maximum possible values for the
ratio of ablated mass to wind mass occur when mass loading starts very close to
the bubble center and when the flow is supersonic with respect to the clumps
over the entire bubble radius. The maximum temperature in the bubble often
occurs near the onset of mass loading, and in some cases can be many times
greater than the post-inner-shock temperature. Our solutions are relevant to eg
stellar wind-blown bubbles, galactic winds, etc. This work complements Pittard
et al (2001) where it was assumed that clumps were evaporated through
conductive energy transport.