title: Deep griz GMOS Imaging of the Dwarf Irregular Galaxy Kar 50

abstract:
  Images obtained with the Gemini Multi-Object Spectrograph (GMOS) are used to
investigate the stellar content and distance of the dwarf irregular galaxy Kar
50. The brightest object is an HII region, and the bright stellar content is
dominated by stars with g'-r' < 0. The tips of the main sequence and the red
giant branch are tentatively identified near r' = 24.9 and i' = 25.5,
respectively. The galaxy has a blue integrated color with no significant color
gradient, and we conclude that Kar 50 has experienced a recent galaxy-wide
episode of star formation. The distance estimated from the brightest blue stars
indicates that Kar 50 is behind the M81 group, and this is consistent with the
tentative RGB-tip brightness. Kar 50 has a remarkably flat central surface
brightness profile, even at wavelengths approaching 1um, although there is no
evidence of a bar. In the absence of another large star-forming episode, Kar 50
will evolve into a very low surface brightness galaxy.


title:
Galaxy groups in the 2dF galaxy redshift survey: Luminosity and Mass
  Statistics

abstract:
  Several statistics are applied to groups and galaxies in groups in the Two
degree Field Galaxy Redshift Survey. Firstly we estimate the luminosity
functions for different subsets of galaxies in groups. The results are well
fitted by a Schechter function with parameters $M^{\ast}-5\log(h)=-19.90 \pm
0.03$ and $\alpha=-1.13\pm0.02$ for all galaxies in groups, which is quite
consistent with the results by Norberg et al. for field galaxies. When
considering the four different spectral types defined by Madgwick et al. we
find that the characteristic magnitude is typically brighter than in the field.
We also observe a steeper value, $\alpha=-0.76\pm 0.03$, of the faint end slope
for low star-forming galaxies when compared with the corresponding field value.
This steepening is more conspicuous, $\alpha=-1.10\pm 0.06$, for those galaxies
in more massive groups (${\mathcal M} \gsim 10^{14} h^{-1} M_{\odot}$) than the
obtained in the lower mass subset, $\alpha=-0.71\pm 0.04$ (${\mathcal
M}<10^{14} h^{-1} M_{\odot}$). Secondly, we compute group total luminosities
using Moore, Frenk & White prescriptions. We define a flux-limited group sample
using a new statistical tool developed by Rauzy. The resulting group sample is
used to determine the group luminosity function finding a good agreement with
previous determinations and semianalytical models. Finally, the group mass
function for the flux-limited sample is derived. An excellent agreement is
obtained when comparing our determination with analytical predictions over two
orders of magnitude in mass.


title: Simulations of the heating of the Galactic stellar disc

abstract:
  The velocity dispersion of nearby stars in the Galactic disc is well known to
increase substantially with age; this is the so-called Age-Velocity relation,
and is interpreted as a ``heating'' of the disc as a function of time. We have
studied the heating of the disc due to giant molecular clouds and halo black
holes, using simulations of the orbits of tracer stars embedded in a patch of
the local Galactic disc. We examine a range of masses and number densities of
the giant molecular cloud and halo black hole perturbers. The heating of the
stellar disc in the simulations is fit with a simple power law, and we also fit
this form to the best determinations of Age-Velocity relation as derived from
stars in the solar neighbourhood for which ages can be reliably assigned.
Observationally, the Age-Velocity relation remains poorly constrained and its
determination is probably still dominated by systematic errors. Our simulations
confirm the well known results that there are insufficient GMCs to heat the
Galactic disc appropriately. A range of dark halo black hole scenarios are
verified to heat the stellar disc in the manner expected from analytical
studies, and they reproduce the observed ratio of the stellar velocity
dispersions. Simulations featuring a combination of giant molecular clouds and
halo black holes can explain the observed heating of the stellar disc, but
since other perturbing mechanisms, such as spiral arms, are yet to be
included,we regard this solution as ad hoc.


title:
Pairwise velocity dispersion of galaxies at high redshift: theoretical
  predictions

abstract:
  We investigate the feasibility of determining the pairwise velocity
dispersion (PVD) for Lyman Break Galaxies (LBGs), and of using this quantity as
a discriminator among theoretical models. We find that when the Two Point
Correlation Function over the range of observable separations is fixed,
different schemes of galaxy formation will lead to significant changes in PVD,
while influence of different cosmogonies is invisible. Our test with mock
samples shows furthermore that one can discriminate among such models already
with currently available observational samples (if the measurement error of the
redshift is negligible) which have a typical error of $80\kms$. The error will
be reduced by a factor of 2 if the samples are increased four times. We also
show that an erroneous assumption about the geometry of the universe and
different infall models only slightly change the results. Therefore the PVD
will become another promising statistic to test galaxy formation models with
redshift samples of LBGs.


title:
Age and metallicity of a globular cluster in the dwarf spheroidal galaxy
  DDO78

abstract:
  We present the results of moderate resolution spectroscopy for a globular
cluster in the M81 group dwarf spheroidal galaxy DDO~78. The DDO78 globular
cluster, 4 Milky Way globular clusters, spectroscopic and radial velocity
standards were observed with the Long-slit spectrograph of the 6-m telescope
(SAO RAS, Russia). Lick spectrophotometric indices were determined in the
bandpasses adopted by Burstein et al. (1984). We have derived the mean
metallicity of the globular cluster in DDO78 to be [Fe/H] = -1.6 +- 0.1 dex by
taking the weighted mean of metallicities obtained from the strength of several
absorption features. We have estimated an age for the globular cluster of 9-12
Gyr similar to that found for the Galactic globular cluster NGC362, which
resembles our cluster by chemical abundance and integrated spectrophotometric
properties.


title: The Dynamical Interaction of AGN with their Galaxian Environments

abstract:
  Jet-driven shocks are responsible for an important fraction of the emission
of the narrow-line regions (NLRs) in many classes of AGN. However, this cannot
explain all observations. It is clear that the remaining sources are
photoionised by the active nucleus. The 2-d hydrodynamic models from the RSAA
group support an evolutionary scenario whereby the shock-excited NLRs are
initially jet-driven but later, ionizing photons from the central engine
replace shocks as the main excitation mechanism and shock induced star
formation may also become important. In their photoionized phase, dusty and
radiation-pressure dominated evolution produces a self-regulated NLR spectrum.
This model aso explains the coronal emission lines and fast (3000 km s$^{-1}$)
outflows seen in some Seyferts.


title: Structure and Dynamics of Candidate O Star Bubbles in N44

abstract:
  Dynamical studies of superbubbles and Wolf-Rayet ring nebulae show
discrepancies from the standard, adiabatic model for wind-blown bubbles. We
therefore study the physical properties and kinematics of three candidate
bubbles blown by single O stars, to evaluate whether these discrepancies are
also found in these simpler objects. Our sample candidates are N44F, N44J, and
N44M, in the outskirts of the HII complex N44 in the Large Magellanic Cloud. We
have obtained ground-based and HST emission-line images and high dispersion
echelle spectra for these objects. From the Halpha luminosities and the
[OIII]/Halpha ratios of these nebulae, we estimate the spectral types of the
ionizing stars to be O7V, O9.5V and O9.5V for N44F, N44J, and N44M,
respectively. We find that the observed expansion velocity of 12 km/s for N44F
is consistent with the stellar wind luminosity expected from the central
ionizing star, as predicted by the standard bubble model. The observed upper
limits for the expansion velocities of N44J and N44M are also compatible with
the expected values, within the uncertainties. We also report the discovery in
N44F of strongly-defined dust columns, similar to those seen in the Eagle
Nebula. The photoevaporation of these dense dust features may be kinematically
important and may actually govern the evolution of the shell. The inclusion of
photoevaporation processes may thus undermine the apparent agreement between
the observed bubble dynamics and the simple adiabatic models.


title: The link between symbiotic stars and chemically-peculiar red giants

abstract:
  Barium stars and technetium-poor, extrinsic S stars are binary systems with a
white dwarf companion, and with orbital elements similar to those of symbiotic
systems. One may thus wonder whether these various families of binary systems
involving red giant stars are somehow related. This question is actually
twofold: (i) Do barium and binary S stars exhibit some symbiotic activity? (ii)
Do symbiotic systems exhibit overabundances of s-process elements like barium
and S stars? This paper reviews the current situation regarding these two
questions.


title: SS433: the second Wolf-Rayet X-ray binary ?

abstract:
  We present mid-infrared spectrophotometric observations of SS433 with
ISOPHOT. The HeI+HeII lines in both spectra of SS433 and of the Wolf-Rayet star
WR147, a wind-colliding WN8+BO5 binary system, closely match. The 2.5-12 micron
continuum radiation is due to an expanding wind free-free emission in an
intermediate case between optically thick and optically thin regimes. The
inferred mass loss rate evaluation gives ~10^{-4} Msun/yr. Our results are
consistent with a Wolf-Rayet-like companion to the compact object in SS433. A
similar study for Cygnus X-3 confirms the Wolf-Rayet-like nature of its
companion, although with a later WN type than previously suggested.


title:
SSSPMJ0829-1309: A new nearby L dwarf detected in SuperCOSMOS Sky
  Surveys

abstract:
  The SuperCOSMOS Sky Surveys provide a complete coverage of the Southern sky
in three passbands (photographic B_J, R and I) and at different epochs (Hambly
et al. 2001a,b,c). These data are the basis for a new high proper motion survey
which aims at finding extremely red nearby dwarf stars and brown dwarfs. One of
the first candidates, which is relatively bright (I=16) but very red (R-I=2.8,
B_J-R=3.6), was detected in the equatorial zone by its large proper motion of
0.56 arcsec/yr. Spectroscopic follow-up observations with the 2.2m telescope of
the Calar Alto Observatory classified this object as L2 dwarf very similar to
the first free-floating L dwarf Kelu1 also discovered in a proper motion survey
by Ruiz et al. (1997). If we assume SSSPMJ0829-1309 to have the same luminosity
as Kelu1, we get a distance estimate for the new L dwarf of about 12pc since it
is about one magnitude brighter than Kelu1 in the SSS I and R bands. This makes
SSSPMJ0829-1309 one of the nearest objects of its class, well suited for
detailed investigations. We present a brief overview of all known nearby
(d<20pc) southern L dwarfs and give first proper motion values for
DENIS-PJ0255-47 and SDSSpJ1326-00 and an improved proper motion for LHS102B.


title: The Diversity of Extremely Red Objects

abstract:
  We present a multi-wavelength study of Extremely Red Objects (EROs) employing
deep RIzJHK photometry of a 8.5'x8.5' region to identify 68 EROs with R-K>5.3
and K<20.5 (5-sigma). This is combined with an extremely deep 1.4-GHz radio map
(sigma=3.5uJy), sensitive enough to detect an active galaxy with L_1.4>10^23
W/Hz at z>1 or a SFR of >25Mo/yr. We detect radio emission from 21 EROs at
>12.6uJy and resolve a third of these with our 1.6'' FWHM beam. The SEDs of
most of these radio EROs are consistent with dust-reddened starbursts at z~1.
At z~1 the radio luminosities of these EROs indicate far-infrared luminosities
of L_FIR>10^12 Lo, meaning half are ultraluminous infrared galaxies. We
conclude that >16+/-5% of EROs with K<20.5 are luminous infrared galaxies at
z>1. We also photometrically classify the EROs to investigate the mix of
dusty/active and evolved/passive systems in the radio-undetected EROs. We
suggest that at least 30%, and perhaps up to ~60%, of all EROs with R-K>5.3 and
K<20.5 are dusty, star-forming systems at z>1. The SFD in this optically faint
(R>26) population is rho^* (0.1-100Mo)=0.11+/-0.03 Mo/yr/Mpc^3, comparable to
that in H-alpha emitting galaxies at z~1, and greater than that in UV-selected
samples at these epochs. This support the claim of a strong increase in
obscured star formation at high redshifts. Using the observed counts of the
radio-detected EROs we model the break in the K-band number counts of all EROs
at K~19-20 and propose that the passive ERO class dominates the total
population in a narrow range around K~20, with dusty EROs dominating at fainter
magnitudes. [Abridged]


title: Long-term Neutrino Afterglows from Gamma-Ray Bursts

abstract:
  It is widely believed that multiwavelength afterglows of gamma-ray bursts
(GRBs) originate from relativistic blast waves. We here show that in such blast
waves, a significant fraction of the energy of shock-accelerated protons would
be lost due to pion production by interactions with afterglow photons. This
could lead to long-term production of $10^{16}$--$10^{18}$ eV neutrinos and
sub-TeV $\gamma$-rays that accompany with usual afterglows, provided that the
protons are accelerated to $10^{19}$ eV in the blast waves.


title:
Hemispheric Sunspot Numbers R_n and R_s: Catalogue and N-S asymmetry
  analysis

abstract:
  Sunspot drawings are provided on a regular basis at the Kanzelhoehe Solar
Observatory, Austria, and the derived relative sunspot numbers are reported to
the Sunspot Index Data Center in Brussels. From the daily sunspot drawings, we
derived the northern, R_n, and southern, R_s, relative sunspot numbers for the
time span 1975-2000. In order to accord with the International Sunspot Numbers
R_i, the R_n and R_s have been normalized to the R_i, which ensures that the
relation R_n + R_s = R_i is fulfilled. For validation, the derived R_n and R_s
are compared to the international northern and southern relative sunspot
numbers, which are available from 1992. The regression analysis performed for
the period 1992-2000 reveals good agreement with the International hemispheric
Sunspot Numbers. The monthly mean and the smoothed monthly mean hemispheric
Sunspot Numbers are compiled into a catalogue. Based on the derived hemispheric
Sunspot Numbers, we study the significance of N-S asymmetries and the
rotational behavior separately for both hemispheres. We obtain that about 60%
of the monthly N-S asymmetries are significant at a 95% level, whereas the
relative contributions of the northern and southern hemisphere are different
for different cycles. From the analysis of power spectra and autocorrelation
functions, we derive a rigid rotation with about 27 days for the northern
hemisphere, which can be followed for up to 15 periods. Contrary to that, the
southern hemisphere reveals a dominant period of about 28 days, whereas the
autocorrelation is strongly attenuated after 3 periods. These findings suggest
that the activity of the northern hemisphere is dominated by an active zone,
whereas the southern activity is mainly dominated by individual long-lived
sunspot groups.


title: GMOS Spectroscopy of SCUBA Galaxies Behind A851

abstract:
  We have identified counterparts to two submillimeter (submm) sources, SMM
J09429+4659 and SMM J09431+4700, seen through the core of the z=0.41 cluster
Abell 851. We employ deep 1.4-GHz observations and the far-infrared/radio
correlation to refine the submm positions and then optical and near-infrared
imaging to locate their counterparts. We identify an extremely red counterpart
to SMM J09429+4659, while GMOS spectroscopy with Gemini-North shows that the
R=23.8 radio source identified with SMM J09431+4700 is a hyperluminous infrared
galaxy (L_FIR~1.5x10^13 L_sun) at z=3.35, the highest spectroscopic redshift so
far for a galaxy discovered in the submm. The emission line properties of this
galaxy are characteristic of a narrow-line Seyfert-1, although the lack of
detected X-ray emission in a deep XMM-Newton observation suggests that the bulk
of the luminosity of this galaxy is derived from massive star formation. We
suggest that active nuclei, and the outflows they engender, may be an important
part of the evolution of the brightest submm galaxies at high redshifts.


title:
The very rich massive post-main-sequence star population of the open
  cluster Westerlund 1

abstract:
  We report the discovery of a population of Wolf-Rayet stars in the young
Galactic open cluster Westerlund 1. In an incomplete shallow spectroscopic
survey, we find six nitrogen-rich (WN) and five carbon-rich (WC) WR stars. We
also confirm the presence of a large population of yellow supergiants, some of
which are candidate hypergiants. Given this population, Westerlund 1 is likely
to be one of the most massive young clusters in the Local Group.


title: The Mean Number of Extra Micro-Image Pairs for Macro-Lensed Quasars

abstract:
  When a gravitationally lensed source crosses a caustic, a pair of images is
created or destroyed. We calculate the mean number of such pairs of
micro-images $<n>$ for a given macro-image of a gravitationally lensed point
source, due to microlensing by the stars of the lensing galaxy. This quantity
was calculated by Wambsganss, Witt & Schneider (1992) for the case of zero
external shear, $\gamma=0$, at the location of the macro-image. Since in
realistic lens models a non-zero shear is expected to be induced by the lensing
galaxy, we extend this calculation to a general value of $\gamma$. We find a
complex behavior of $<n>$ as a function of $\gamma$ and the normalized surface
mass density in stars $\kappa_*$. Specifically, we find that at high
magnifications, where the average total magnification of the macro-image is
$<\mu>=|(1-\kappa_*)^2-\gamma^2|^{-1}\gg 1$, $<n>$ becomes correspondingly
large, and is proportional to $<\mu>$. The ratio $<n>/<\mu>$ is largest near
the line $\gamma=1-\kappa_*$ where the magnification $<\mu>$ becomes infinite,
and its maximal value is 0.306. We compare our semi-analytic results for $<n>$
to the results of numerical simulations and find good agreement. We find that
the probability distribution for the number of extra image pairs is reasonably
described by a Poisson distribution with a mean value of $<n>$, and that the
width of the macro-image magnification distribution tends to be largest for
$<n>\sim 1$.


title:
A convolution integral representation of the thermal Sunyaev-Zel'dovich
  effect

abstract:
  Analytical expressions for the non-relativistic and relativistic
Sunyaev-Zel'dovich effect (SZE) are derived by means of suitable convolution
integrals. The establishment of these expressions is based on the fact that the
SZE disturbed spectrum, at high frequencies, possesses the form of a Laplace
transform of the single line distortion profile (structure factor).
Implications of this description of the SZE related to light scattering in
optically thin plasmas are discussed.


title: Mixing Time Scales in a Supernova-Driven Interstellar Medium

abstract:
  We study the mixing of chemical species in the interstellar medium (ISM).
Recent observations suggest that the distribution of species such as deuterium
in the ISM may be far from homogeneous. This raises the question of how long it
takes for inhomogeneities to be erased in the ISM, and how this depends on the
length scale of the inhomogeneities. We added a tracer field to the
three-dimensional, supernova-driven ISM model of Avillez (2000) to study mixing
and dispersal in kiloparsec-scale simulations of the ISM with different
supernova (SN) rates and different inhomogeneity length scales. We find several
surprising results. Classical mixing length theory fails to predict the very
weak dependence of mixing time on length scale that we find on scales of
25--500 pc. Derived diffusion coefficients increase exponentially with time,
rather than remaining constant. The variance of composition declines
exponentially, with a time constant of tens of Myr, so that large differences
fade faster than small ones. The time constant depends on the inverse square
root of the supernova rate. One major reason for these results is that even
with numerical diffusion exceeding physical values, gas does not mix quickly
between hot and cold regions.


title:
Galactic porosity and a star formation threshold for the escape of
  ionising radiation from galaxies

abstract:
  The spatial distribution of star formation within galaxies strongly affects
the resulting feedback processes. Previous work has considered the case of a
single, concentrated nuclear starburst, and also that of distributed single
supernovae (SNe). Here, we consider ISM structuring by SNe originating in
spatially distributed clusters having a cluster membership spectrum given by
the observed HII region luminosity function. We show that in this case, the
volume of HI cleared per SN is considerably greater than in either of the two
cases considered hitherto.
  We derive a simple relationship between the ``porosity'' of the ISM and the
star formation rate (SFR), and deduce a critical SFR_crit, at which the ISM
porosity is unity. This critical value describes the case in which the SN
mechanical energy output over a timescale t_e is comparable with the ISM
``thermal'' energy contained in random motions; t_e is the duration of SN
mechanical input per superbubble. This condition also defines a critical gas
consumption timescale t_exh, which for a Salpeter IMF and random velocities of
\simeq 10 km s-1 is roughly 10e10 years.
  We draw a link between porosity and the escape of ionising radiation from
galaxies, arguing that high escape fractions are expected if SFR >~ SFR_crit.
The Lyman Break Galaxies, which are presumably subject to infall on a timescale
< t_exh, meet this criterion, as is consistent with the significant leakage of
ionising photons inferred in these systems. We suggest the utility of this
simple parameterisation of escape fraction in terms of SFR for semi-empirical
models of galaxy formation and evolution and for modeling mechanical and
chemical feedback effects.


title: The Inflationary Perturbation Spectrum

abstract:
  Motivated by the prospect of testing inflation from precision cosmic
microwave background observations, we present analytic results for scalar and
tensor perturbations in single-field inflation models based on the application
of uniform approximations. This technique is systematically improvable,
possesses controlled error bounds, and does not rely on assuming the slow-roll
parameters to be constant. We provide closed-form expressions for the power
spectra and the corresponding scalar and tensor spectral indices.


title:
Magnetars in the Metagalaxy: An Origin for Ultra High Energy Cosmic Rays
  in the Nearby Universe

abstract:
  I show that the relativistic winds of newly born magnetars with khz initial
spin rates, occurring in all normal galaxies, can accelerate ultrarelativistic
light ions with an E^{-1} injection spectrum, steepening to E^{-2} at higher
energies, with an upper cutoff above 10^{21} eV. Interactions with the CMB
yield a spectrum in good accord with the observed spectrum of Ultra-High Energy
Cosmic Rays (UHECR), if ~ 5-10% of the magnetars are born with voltages
sufficiently high to accelerate the UHECR. The form the spectrum spectrum takes
depends on the gravitational wave losses during the magnetars' early spindown -
pure electromagnetic spindown yields a flattening of the E^3 J(E) spectrum
below 10^{20} eV, while a moderate GZK ``cutoff'' appears if gravitational wave
losses are strong enough. I outline the physics such that the high energy
particles escape with small energy losses from a magnetar's natal supernova,
including Rayleigh-Taylor ``shredding'' of the supernova envelope, expansion of
a relativistic blast wave into the interstellar medium, acceleration of the UHE
ions through surf-riding in the electromgnetic fields of the wind, and escape
of the UHE ions in the rotational equator with negligible radiation loss. The
abundance of interstellar supershells and unusually large supernova remnants
suggests that most of the initial spindown energy is radiated in khz
gravitational waves for several hours after each supernova, with effective
strains from sources at typical distances ~ 3 x 10^{-21}. Such bursts of
gravitational radiation should correlate with bursts of ultra-high energy
particles. The Auger experiment should see such bursts every few years.


title:
A McDonald Observatory Study of Comet 19P/Borrelly: Placing the Deep
  Space 1 Observations into a Broader Context

abstract:
  We present imaging and spectroscopic data on comet 19P/Borrelly that were
obtained around the time of the Deep Space 1 encounter and in subsequent
months. In the four months after perihelion, the comet showed a strong primary
(sunward) jet that is aligned with the nucleus' spin axis. A weaker secondary
jet on the opposite hemisphere appeared to became active around the end of
2001, when the primary jet was shutting down. We investigated the gas and dust
distributions in the coma, which exhibited strong asymmetries in the
sunward/anti-sunward direction. A comparison of the CN and C2 distributions
from 2001 and 1994 (during times when the viewing geometry was almost
identical) shows a remarkable similarity, indicating that the comet's activity
is essentially repeatable from one apparition to the next. We also measured the
dust reflectivities as a function of wavelength and position in the coma, and,
though the dust was very red overall, we again found variations with respect to
the solar direction. We used the primary jet's appearance on several dates to
determine the orientation of the rotation pole to be alpha = 214^{circ}, delta
= -5^{circ}. We compared this result to published images from 1994 to conclude
that the nucleus is near a state of simple rotation. However, data from the
1911, 1918 and 1925 apparitions indicate that the pole might have shifted by
5-10^{circ} since the comet was discovered. Using our pole position and the
published nongravitational acceleration terms, we computed a mass of the
nucleus of 3.3 times10^{16} g and a bulk density of 0.49 g cm^{-3} (with a
range of 0.29 < rho < 0.83 g cm^{-3}). This result is the least model-dependent
comet density known to date.


title: A Search for N2+ in Spectra of Comet C/2002C1 (Ikeya-Zhang)

abstract:
  We report low- and high-resolution spectra of comet C/2002 C1 (Ikeya-Zhang)
from McDonald Observatory. The comet had a well-developed ion tail including
CO+, CO2+, CH+, and H2O+. We used our high-resolution spectra to search for
N2+. None was detected and we placed upper limits on N2+/CO+ of 5.4 times
10^{-4}. N2+ was detected in the low-resolution spectra but we show that this
emission was probably telluric in origin (if cometary, we derive N2+/CO+ = 5.5
times 10^{-3}, still very low). We discuss the implications for the conditions
in the early solar nebula of the non-detection of N2+. These depend on whether
the H2O ice was deposited in the amorphous or crystalline form. If H2O was
deposited in its crystalline form, the detection of CO+ but not N2+ has
implications for H2O/H2 in the early solar nebula.


title: Three Epochs of Star Formation in the High Redshift Universe

abstract:
  We investigate the impact of an early population of massive stars on their
surroundings. Dissociation of molecular hydrogen by strong UV emission from
such stars is expected to produce a global transition in the cooling mechanism
of minihalos at a redshift of approximately 30, strongly inhibiting star
formation until more massive halos can collapse. Furthermore, chemical
enrichment from Pop III supernovae produces a second transition at z ~ 15-20,
when the mean metallicity of the universe exceeds a critical threshold and Pop
III star formation gives way to Pop II. We show that observations of high
redshift supernovae with the Next Generation Space Telescope (NGST) have the
potential to trace the cosmic star formation rate out to z >~ 20, provided that
Pop III supernovae are at least as bright as, and ideally brighter than, type
Ia supernovae. We also propose a mechanism for the formation of a novel
population of extremely low metallicity stars of intermediate mass at very high
redshifts, which we term Pop II.5. In our model shock compression, heating, and
subsequent cooling to high density reduces the fragment mass in primordial gas
to ~10 M_sun, allowing low mass stars to form. We predict the number density of
relic Pop II.5 stars in the Milky Way halo today and find that, with certain
assumptions, there should be ~ 10 kpc^{-3} in the solar neighborhood.


title: Seeing statistics at the upgraded 3.8m UK infrared telescope (UKIRT)

abstract:
  From 1991 until 1997, the 3.8m UK Infrared Telescope (UKIRT) underwent a
programme of upgrades aimed at improving its intrinsic optical performance.
This resulted in images with a FWHM of 0."17 at 2.2 um in September 1998. To
understand and maintain the improvements to the delivered image quality since
the completion of the upgrades programme, we have regularly monitored the
overall atmospheric seeing, as measured by radial displacements of subaperture
images (i.e. seeing-generated focus fluctuations), and the delivered image
diameters. The latter have been measured and recorded automatically since the
beginning of 2001 whenever the facility imager UFTI (UKIRT Fast Track Imager)
has been in use.
  In this paper we report the results of these measurements. We investigate the
relation between the delivered image diameter and the RMS atmospheric seeing
(as measured by focus fluctuations, mentioned above). We find that the best
seeing occurs in the second half of the night, generally after 2am HST and that
the best seeing occurs in the summer between the months of July and September.
We also find that the relationship between Zrms and delivered image diameter is
uncertain. As a result Zrms frequently predicts a larger FWHM than that
measured in the images.
  Finally, we show that there is no correlation between near-infrared seeing
measured at UKIRT and sub-mm seeing measured at the Caltech Submillimetre
Observatory (CSO).


title: Carbon stars in the Local Group

abstract:
  The current status of carbon stars in the Local Group and beyond, is
discussed. Although many carbon stars and late M-stars have been identified in
Local Group galaxies, a coherent understanding in terms of the chemical
evolution- and star formation history of a galaxy is still largely lacking.
Although a few major new surveys have been carried out over the last three
years, the observational data is still incomplete in many respects: 1) for some
of the larger galaxies only a small fraction in area has been surveyed so far,
2) surveys have been conducted using different techniques, and some of the
older surveys are incomplete in bolometric magnitude, 3) only for some galaxies
is there information about the late M-star population, or it is sometimes
unpublished even when the data is available, 4) not all galaxies in the Local
Group have been surveyed, 5) especially for some of the older work insufficient
data is available to determine bolometric magnitudes. I have correlated carbon
star positions with the 2MASS 2nd incremental data release to obtain $JHK$, and
bolometric magnitudes, to remedy this situation in some cases.
  From the existing observations one can derive the following: the formation of
carbon stars is both a function of metallicity and star-formation history. In
galaxies with a similar star formation history, there will be relatively more
carbon stars formed in the system with the lower metallicity. On the other
hand, the scarcity of AGB type carbon stars in some galaxies with the lowest
metallicity indicates that these systems have had a low, if any, star-formation
over the last few Gyrs.


title: A new measurement of zinc metallicity in a DLA at z=3.35

abstract:
  We present chemical abundance measurements in the z_abs=3.35045 Damped
Lyman-alpha (DLA) system observed in the UVES spectrum of the BAL quasar BR
1117-1329. We measure a neutral hydrogen column density N(HI)=6.9+/-1.7*10^{20}
atoms/cm2 and derive mean abundances relative to solar: [Si/H] = -1.26+/-0.13,
[Fe/H]=-1.51+/-0.13, [Ni/H]=-1.57+/-0.13, [Cr/H]=-1.36+/-0.13,
[Zn/H]=-1.18+/-0.13, [Al/H]>-1.25, [O/H]>-1.25 and [N/H]<-2.24. This is the
third measurement of Zn, an element mildly depleted onto dust grain, at
z_abs>3. The iron to zinc and chromium to zinc ratios, [Fe/Zn]=-0.33+/-0.05 and
[Cr/Zn]=-0.18+/-0.05 demonstrate that the absorber has a low dust content. The
nitrogen ratio [N/Si]<-0.98 suggests that the ``secondary'' N production
process is taking place in this DLA. Finally, this absorber does not seem to
present a convincing alpha-enhancement as shown by the alpha over Fe-peak
element ratios: [Si/Fe]=0.25+/-0.06, [Si/Cr]=0.10+/-0.06 and
[Si/Zn]=-0.08+/-0.06.


title: Effects of wind on radiation spectra from magnetized accretion disks

abstract:
  The effects of a wind on the emerging spectrum from an
inefficiently-radiating accretion flow in a global magnetic field are examined,
based on the analytic solution obtained recently by one of the present authors.
The results exhibit the steepening of the negative slope appearing in the
intermediate frequency range of bremsstrahlung spectrum and the decrease in the
luminosity ratio of thermal synchrotron to bremsstrahlung, in accordance with
the increasing wind strength. Both effects are due to a suppressed mass
accretion rate in the inner disk, caused by a mass loss in terms of wind.
  In order to demonstrate the reliability of this model, Sagittarius A^* (Sgr
A^*) and the nucleus of M 31, both of which have been resolved in an X-ray band
by Chandra, are taken up as the best candidates for the broadband spectral
fittings. Although the observed X-ray data are reproduced for these objects by
both of the inverse-Compton and the bremsstrahlung fittings, some evidence of
preference for the latter are recognized. The wind effects are clearly seen in
the latter fitting case, in which we can conclude that a widely extending
accretion disk is present in each nucleus, with no or only weak wind in Sgr A^*
and with a considerably strong wind in the nuclear region of M 31. Especially
in Sgr A^*, the inferred mass accretion rates are much smaller than the Bondi
rate whose estimate has become reliable due to Chandra. This fact strongly
suggests that the accretion in this object does not proceed like Bondi's
prediction, though its extent almost reaches the Bondi radius.


title:
To Circularize or Not to Circularize? -- Orbital Evolution of Satellite
  Galaxies

abstract:
  We investigated the orbital evolution of satellite galaxies using numerical
simulations. It has been long believed that the orbit suffers circularization
due to the dynamical friction from the galactic halo during orbital decay. This
circularization was confirmed by numerous simulations where dynamical friction
is added as external force. However, some of the resent N-body simulations
demonstrated that circularization is much slower than expected from approximate
calculations. We found that the dominant reason for this discrepancy is the
assumption that Coulomb logarithm log Lambda is constant, which has been used
in practically all recent calculations. Since the size of the satellite is
relatively large, accurate determination of the outer cutoff radius is crucial
to obtain good estimate for the dynamical friction. An excellent agreement
between $N$-body simulations and approximate calculations was observed when the
outer cutoff radius is taken to be the distance of the satellite to the center
of the galaxy. When satellite is at the perigalacticon, the distance to the
center is smaller and therefore log Lambda becomes smaller. As a result, the
dynamical friction becomes less effective.
  We apply our result to the Large Magellanic Cloud. We found that the expected
lifetime of the LMC is twice as long as that would be predicted with previous
calculations. Previous study predicts that the LMC will merge into the Milky
Way after 7 G years, while we found that the merging will take place after 14 G
years from now. Our result suggests that generally satellites formed around a
galaxy have longer lifetime than previous estimates.


title: Multipair contributions to the spin response of nuclear matter

abstract:
  We analyse the effect of non-central forces on the magnetic susceptibility of
degenerate Fermi systems. These include the presence of contributions from
transitions to states containing more than one quasiparticle-quasihole pair,
which cannot be calculated within the framework of Landau Fermi-liquid theory,
and renormalization of the quasiparticle magnetic moment, as well as explicit
non-central contributions to the quasiparticle interaction. Consequently, the
relationship between the Landau parameters and the magnetic susceptibility for
Fermi systems with non-central forces is considerably more complicated than for
systems with central forces. We use sum-rule arguments to place a lower bound
on the contribution to the static susceptibility coming from transitions to
multipair states.


title:
Magnetic white dwarfs in the Early Data Release of the Sloan Digital Sky
  Survey

abstract:
  We have identified 7 new magnetic DA white dwarfs in the Early Data Release
of the Sloan Digital Sky Survey. Our selection strategy has also recovered all
the previously known magnetic white dwarfs contained in the SDSS EDR,
KUV03292+0035 and HE0330-0002. Analysing the SDSS fibre spectroscopy of the
magnetic DA white dwarfs with our state-of-the-art model spectra, we find
dipole field strengths 1.5<=B_d<=63MG and effective temperatures
8500<=Teff<=39000K. As a conservative estimate, we expect that the complete
SDSS will increase the number of known magnetic white dwarfs by a factor 3.


title: Be/X-ray Binaries

abstract:
  A review of basic properties of Be/X-ray binaries is presented. These systems
(called also hard X-ray transients), which form the most numerous class of
massive X-ray binaries in the Galaxy, are composed of Be stars and neutron
stars (X-ray pulsars) on wide (orbital periods 17-263 d), usually eccentric
(eccentricities 0.1-0.9) orbits. The systems contain two quasi-Keplerian (ratio
of radial to orbital velocity components less than 0.01) discs: decretion disc
around Be star and accretion disc around neutron star. Both discs are
temporary: decretion disc disperses and refills on time scales of years
(dynamical evolution of the disc, formerly known as the "activity of a Be
star"), while accretion disc disperses and refills on time scales of weeks to
months (which is related to the orbital motion on an eccentric orbit and, on
some occasions, also to the major instabilities of the other disc). Accretion
disc might be absent over a longer period of time (years), if the other disc is
very weak or absent. The X-ray emission of Be/X-ray binaries has distinctly
transient nature and is controlled by the centrifugal gate mechanism, which, in
turn, is operated both by the periastron passages (Type I bursts) and by the
dynamical evolution of the decretion disc (both types of bursts). The X-ray
pulsars in these systems rotate at equilibrium periods (with the possible
exception of the slowest pulsars). Be/X-ray binaries are excellent laboratories
for investigation of both the evolutionary processes in the two discs and of
the evolution of the neutron star rotation.


title: Phase Transitions in Neutron Stars and Gravitational Wave Emission

abstract:
  We review the detectability of gravitational waves generated by oscillations
excited during a phase transition from hadronic matter to deconfined
quark-gluon matter in the core of a neutron star. Neutron star properties were
computed using a Boguta and Bodmer's based model and the MIT bag model. The
maximum energy available to excite mechanical oscillations into the star is
estimated by energy difference between the configurations with and without a
quark-gluon matter core. On basis of the planned sensitivity of present laser
interferometers (VIRGO or LIGO I) and those of the next generation (LIGO II),
the maximum volume to be proped by these experiments is determined. These
results are used as an indication of the potential detectability of neutron
stars as sources of gravitational waves. Our results indicate that the maximum
distance probed by the detectors of the first generation is well beyond M31,
whereas the second generation detectors will probably see phase transitions
events at distances two times longer, but certanly not yet attaining the Virgo
cluster.


title:
Damped Lyman alpha systems and disk galaxies: number density, column
  density distribution and gas density

abstract:
  We present a comparison between the observed properties of damped Lyman alpha
systems (DLAs) and the predictions of simple models for the evolution of
present day disk galaxies, including both low and high surface brightness
galaxies. We focus in particular on the number density, column density
distribution and gas density of DLAs, which have now been measured in
relatively large samples of absorbers. From the comparison we estimate the
contribution of present day disk galaxies to the population of DLAs, and how it
varies with redshift. Based on the differences between the models and the
observations, we also speculate on the nature of the fraction of DLAs which
apparently do not arise in disk galaxies.


title: Can annihilating Dark Matter be lighter than a few GeVs?

abstract:
  We estimate the gamma ray fluxes from the residual annihilations of Dark
Matter particles having a mass mdm \in [MeV, O(GeV)] and compare them to
observations. We find that particles lighter than O(100 MeV) are excluded
unless their cross section is S-wave suppressed.


title:
Magnetized Accretion-Ejection Structures: 2.5D MHD simulations of
  continuous Ideal Jet launching from resistive accretion disks

abstract:
  We present numerical magnetohydrodynamic (MHD) simulations of a magnetized
accretion disk launching trans-Alfvenic jets. These simulations, performed in a
2.5 dimensional time-dependent polytropic resistive MHD framework, model a
resistive accretion disk threaded by an initial vertical magnetic field. The
resistivity is only important inside the disk, and is prescribed as eta =
alpha_m V_AH exp(-2Z^2/H^2), where V_A stands for Alfven speed, H is the disk
scale height and the coefficient alpha_m is smaller than unity. By performing
the simulations over several tens of dynamical disk timescales, we show that
the launching of a collimated outflow occurs self-consistently and the ejection
of matter is continuous and quasi-stationary. These are the first ever
simulations of resistive accretion disks launching non-transient ideal MHD
jets. Roughly 15% of accreted mass is persistently ejected. This outflow is
safely characterized as a jet since the flow becomes super-fastmagnetosonic,
well-collimated and reaches a quasi-stationary state. We present a complete
illustration and explanation of the `accretion-ejection' mechanism that leads
to jet formation from a magnetized accretion disk. In particular, the magnetic
torque inside the disk brakes the matter azimuthally and allows for accretion,
while it is responsible for an effective magneto-centrifugal acceleration in
the jet. As such, the magnetic field channels the disk angular momentum and
powers the jet acceleration and collimation. The jet originates from the inner
disk region where equipartition between thermal and magnetic forces is
achieved. A hollow, super-fastmagnetosonic shell of dense material is the
natural outcome of the inwards advection of a primordial field.


title: A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra

abstract:
  (Abridged) We have searched for nuclear radio emission from a statistically
complete sample of 40 Sc galaxies within 30 Mpc that are optically classified
as star-forming objects, in order to determine whether weak AGNs might be
present. Only three nuclear radio sources were detected, in NGC 864, NGC 4123,
and NGC 4535. These galaxies have peak 6-cm radio powers of 10^{20} W/Hz at
arcsecond resolution, while upper limits of the non-detected galaxies typically
range from 10^{18.4} to 10^{20} W/Hz. The three nuclear radio sources all are
resolved and appear to have diffuse morphologies, with linear sizes of ~300 pc.
This strongly indicates that circumnuclear star formation has been detected in
these three H II galaxies. Comparison with previous 20-cm VLA results for the
detected galaxies shows that the extended nuclear radio emission has a flat
spectrum in two objects, and almost certainly is generated by thermal emission
from gas ionized by young stars in the centers of those galaxies. The 6-cm
radio powers are comparable to predictions for thermal emission that are based
on the nuclear H-alpha luminosities, and imply nuclear star formation rates of
0.08-0.8 solar masses/yr, while the low-resolution NRAO VLA Sky Survey implies
galaxy-wide star formation rates of 0.3-1.0 solar masses/yr in stars above 5
solar masses. Although the presence of active nuclei powered by massive black
holes cannot be definitively ruled out, the present results suggest that they
are likely to be rare in these late-type galaxies with H II spectra.


title: Interferometric Detection of Planets/Gaps in Protoplanetary Disks

abstract:
  We investigate the possibility to find evidence for planets in circumstellar
disks by infrared and submillimeter interferometry. Hydrodynamical simulations
of a circumstellar disk around a solar-type star with an embedded planet of 1
Jupiter mass are presented. On the basis of 3D radiative transfer simulations,
images of this system are calculated. These intensity maps provide the basis
for the simulation of the interferometers VLTI (equipped with the mid-infrared
instrument MIDI) and ALMA. While ALMA will provide the necessary basis for a
direct gap and therefore indirect planet detection, MIDI/VLTI will provide the
possibility to distinguish between disks with or without accretion on the
central star on the basis of visibility measurements.


title: Extrasolar Terrestrial Planets: Can We Detect Them Already?

abstract:
  With the example of Proxima Centauri we discuss the feasibility of detecting
terrestrial planets (1 to a few M_Earth) using the high precision radial
velocity (RV) technique. If a very high RV precision for M stars is achieved
even planets with these extremely low masses become detectable. For Proxima Cen
(M5V), one of the prime targets of our M-stars planet search program using the
UVES spectrograph & iodine cell at the ESO VLT UT2, we obtain a long term RV
precision of 2.5 m/s. Based on numerical simulations we determine that this
level of precision would have already allowed us to detect planets with m sin i
= 4 to 6 M_Earth inside the habitable zone of Proxima Cen.


title: Revealing the Focused Companion Wind in Cygnus X-1 with Chandra

abstract:
  We have analyzed a Chandra HETGS spectrum of the Galactic black hole Cygnus
X-1, obtained at a source flux which is approximately twice that commonly
observed in its persistent low-intensity, spectrally-hard state. We find a
myriad of absorption lines in the spectrum, including Ly-alpha lines and
helium-like resonance lines from Ne, Na, Mg, and Si. We calculate a
flux-weighted mean red-shift of ~100 km/s and a flux-weighted mean velocity
width of 800 km/s (FWHM) for lines from these elements. We also detect a number
of transitions from Fe XVIII-XXIV and Ni XIX-XX in absorption; however, the
identification of these lines is less certain and a greater range of shifts and
breadth is measured. Our observation occurred at a binary phase of phi = 0.76;
the lines observed are consistent with absorption in an ionized region of the
supergiant O9.7 Iab companion wind. The spectrum is extremely complicated in
that a range of temperatures and densities are implied. Prior Chandra HETGS
spectra of Cygnus X-1 were obtained in a similar transition state (at phi =
0.93) and in the low/hard state (at phi= 0.84). Considered together, these
spectra provide evidence for a companion wind that is focused as it flows onto
the black hole primary in this system.


title:
Eddington-limited X-ray Bursts as Distance Indicators. I. Systematic
  Trends and Spherical Symmetry in Bursts from 4U 1728-34

abstract:
  We investigate the limitations of thermonuclear X-ray bursts as a distance
indicator for the weakly-magnetized accreting neutron star 4U 1728-34. We
measured the unabsorbed peak flux of 81 bursts in public data from the Rossi
X-Ray Timing Explorer (RXTE). The distribution of peak fluxes was bimodal: 66
bursts exhibited photospheric radius expansion and were distributed about a
mean bolometric flux of 9.2e-8 erg/cm^2/s, while the remaining (non-radius
expansion) bursts reached 4.5e-8 erg/cm^2/s, on average. The peak fluxes of the
radius-expansion bursts were not constant, exhibiting a standard deviation of
9.4% and a total variation of 46%. These bursts showed significant correlations
between their peak flux and the X-ray colors of the persistent emission
immediately prior to the burst. We also found evidence for quasi-periodic
variation of the peak fluxes of radius-expansion bursts, with a time scale of
approximately 40 d. The persistent flux observed with RXTE/ASM over 5.8 yr
exhibited quasi-periodic variability on a similar time scale. We suggest that
these variations may have a common origin in reflection from a warped accretion
disk. Once the systematic variation of the peak burst fluxes is subtracted, the
residual scatter is only approximately 3%, roughly consistent with the
measurement uncertainties. The narrowness of this distribution strongly
suggests that i) the radiation from the neutron star atmosphere during
radius-expansion episodes is nearly spherically symmetric, and ii) the
radius-expansion bursts reach a common peak flux which may be interpreted as a
standard candle intensity.Adopting the minimum peak flux for the
radius-expansion bursts as the Eddington flux limit, we derive a distance for
the source of 4.4-4.8 kpc.


title:
On cosmological evolution with the Lambda-term and any linear equation
  of state

abstract:
  Recent observational indications of an accelerating universe enhance the
interest in studying models with a cosmological constant. We investigate
cosmological expansion (FRW metric) with $\Lambda>0$ for a general linear
equation of state $p=w\rho$, $w>-1$, so that the interplay between cosmological
vacuum and quintessence is allowed, as well.
  Four closed-form solutions (flat universe with any $w$, and $w=1/3$, $-1/3,
-2/3$) are given, in a proper compact representation. Various estimates of the
expansion are presented in a general case when no closed-form solutions are
available. For the open universe a simple relation between solutions with
different parameters is established: it turns out that a solution with some $w$
and (properly scaled) $\Lambda$ is expressed algebraically via another solution
with special different values of these parameters.
  The expansion becomes exponential at large times, and the amplitude at the
exponent depends on the parameters. We study this dependence in detail,
deriving various representations for the amplitude in terms of integrals and
series. The closed-form solutions serve as benchmarks, and the solution
transformation property noted above serves as a useful tool. Among the results
obtained, one is that for the open universe with relatively small cosmological
constant the amplitude is independent of the equation of state. Also, estimates
of the cosmic age through the observable ratio $\Omega_\Lambda/\Omega_M$ and
parameter $w$ are given; when inverted, they provide an estimate of $w$, i. e.,
the state equation, through the known $\Omega_\Lambda/\Omega_M$ and age of the
universe.


title:
X-ray Observations of Neutron Stars and Pulsars: First Results from
  XMM-Newton

abstract:
  The X-ray Multi-Mirror Mission XMM-Newton is ESA's largest observatory so
far; it is dedicated to explore the Universe in the 0.2 - 15 keV X-ray band of
the electromagnetic spectrum. Because of its large collecting area very faint
sources not accessible before can be observed and it is therefore the long
awaited instrument to study young pulsars and neutron stars in supernova
remnants, cooling neutron stars and millisecond pulsars at X-ray energies. The
high throughput of the instruments, which all are operated simultaneously,
provide high resolution spectral, spatial and temporal information from a
source during a single observation and make XMM-Newton unique and best suited
for pulsar studies. In this article we briefly describe the instrument
capabilities useful for pulsar observations and provide information on the
timing accuracy on the relative and absolute scale. We further provide
scientific results from observations of the Crab-pulsar, PSR J1617-5055 near
RCW 103, of young neutron stars in the supernova remnants RX J0852-4622,
Puppis-A and RCW 103 including 1E161348-5055.1 which is identified to be the
second binary in a supernova remnant. In addition we report on observations of
the cooling neutron star PSR B1055-52 and on the millisecond pulsar PSR
J0030+0451 which all were observed by XMM-Newton during the first two years of
scientific operation.


title: Central Mass Concentration and Bar Dissolution in Nearby Spiral Galaxies

abstract:
  We use data from the BIMA Survey of Nearby Galaxies (SONG) to investigate the
relationship between ellipticity and central mass concentration in barred
spirals. Existing simulations predict that bar ellipticity decreases as
inflowing mass driven by the bar accumulates in the central regions, ultimately
destroying the bar. Using the ratio of the bulge mass to the mass within the
bar radius as an estimate of the central mass concentration, we obtain
dynamical mass estimates from SONG CO 1-0 rotation curve data. We find an
inverse correlation between bar ellipticity and central mass concentration,
consistent with simulations of bar dissolution.


title: The Evolution of the Galaxy Cluster Luminosity-Temperature Relation

abstract:
  We analyzed the luminosity-temperature (L-T) relation for 2 samples of galaxy
clusters which have all been observed by the ASCA satellite. We used 32 high
redshift clusters (0.3<z<0.6), 53 low redshift clusters (z<0.3), and also the
combination of the low and high redshift datasets. We assumed a power law
relation between the bolometric luminosity of the galaxy cluster and its
integrated temperature and redshift (L_{bol,44}=C*T^alpha*(1+z)^A). The results
are consistent, independent of cosmology, with previous estimates of
L$\sim$T$^3$ found by other authors. We observed weak or zero evolution.


title: Outburst Photometry of the Eclipsing Dwarf Nova GY Cancri

abstract:
  We observed the ROSAT-selected eclipsing dwarf nova GY Cnc (=RX J0909.8+1849)
during the 2001 November outburst. We refined the orbital period to be
0.17544251(5) d. The fading portion of the outburst was indistinguishable from
those of typical dwarf novae with similar orbital periods. However, the
signature of orbital humps (or a hot spot) was far less prominently observed in
the orbital light curves and eclipse profiles than in usual dwarf novae with
similar orbital periods. The combination of low frequency of outbursts and the
apparent lack of slowly rising, long outbursts in GY Cnc is difficult to
reconcile within the standard framework of dwarf novae. We suspect that GY Cnc
may be the first above-the-gap counterpart of unusual eclipsing dwarf novae HT
Cas and IR Com.


title: Early-Phase Spectra of "Hypernova" SN 2002ap

abstract:
  The spectral evolution of the peculiar SN Ic 2002ap during the first 40 days
is presented. The spectra display very broad absorption features, which are
typical of "hypernovae". The maximum expansion velocity measured on the
earliest spectra exceeds 3 times 10^4 km s^{-1}. The spectrum of SN 2002ap at
the epoch of maximum brightness resembles that of SN 1997ef more than that of
SN 1998bw. The spectral evolution of SN 2002ap proceeds at about 1.5 times the
rate of SN 1997ef. The parameterized supernova spectrum synthesis code SYNOW
was used to perform line identification and deduce velocity information from
the early-phase spectra, which are heavily affected by line blending. The
photospheric velocity, as deduced from the fitting results and from the
blueshift of the \ion{Si}{2} lambda 6355 absorption minimum, is lower than in
previously studied hypernovae. At advanced epochs, the \ion{Si}{2} lambda 6355
absorption minimum becomes difficult to distinguish. This may be caused by the
growth of [\ion{O}{1}] lambda lambda 6300, 6364 emission. Together with the
rapid spectral evolution, this suggests that SN 2002ap should enter the nebular
phase sooner than previously studied hypernovae.


title:
AGAPEROS: Searching for variable stars in the LMC Bar II. Temporal and
  near-IR analysis of Long-Period Variables

abstract:
  We analysed the light curves of a large sample of long period variables in
the LMC from the AGAPEROS catalogue. The (non)regularity of the light change is
discussed in detail showing that the majority of the light curves cannot be
described properly by a single period. We show that semiregular and small
amplitude variability do not necessarily correlate as has been assumed in
several previous studies. Using near-infrared data from the DENIS survey we
correlate the light change with colours and luminosities of the objects. These
results are used to compare long period variables in the LMC with LPVs in the
Galactic Bulge and in the solar neighborhood.


title: Low-frequency QPO, Magnetic Flood and the states of GRS 1915+105

abstract:
  We sum up progress accomplished, since the last microquasar workshop, on the
physics of the Accretion-Ejection Instability (AEI), and its ability to explain
the properties of the low-frequency QPO of microquasars. These results concern
the basic theory of the instability, its numerical simulation and the resulting
modelisation of the QPO, as well as detailed observations of the QPO
properties. They converge to reinforce the `magnetic flood' scenario,
extrapolated from the AEI to explain the ~ 30 minutes cycles of G1915. We then
discuss directions in which this scenario might be extended toward a more
global view of the evolution of this source.


title:
Microscopic diffusion of partly ionized metals in the Sun and metal-poor
  stars

abstract:
  An improved microscopic diffusion in stars is presented considering in detail
the partly ionized stages of metals. Besides,the influence of degenerate
electron-gas and of the contribution of radiation to the total pressure has
been accounted for. The solution of the diffusion equations is then performed
following the scheme of Thoul et al. (1994). By defining one mean charged ion
per element very few modifications are necessary to solve the improved
diffusion scheme. (A portable FORTRAN routine is provided.) The change in the
sound-speed profile of a solar model obtained with the new diffusion
description is at most about 25% at r=0.6 R(sun). The biggest effect on
low-mass stars is expected near the turn-off, where the convective envelope is
shallowest. However, only a difference of at most 40 K in the effective
temperature could be observed when assuming either fully or partly ionized
metals in the diffusion equation. Nevertheless, the surface metal distribution
is strongly altered.


title:
Chandra X-ray Observation of the Orion Nebula Cluster. I Detection,
  Identification and Determination of X-ray Luminosities

abstract:
  In this first of two companion papers on the Orion Nebula Cluster (ONC), we
present our analysis of a 63 Ksec Chandra HRC-I observation that yielded 742
X-ray detections within the 30'x30' field of view. To facilitate our
interpretation of the X-ray image, here we collect a multi-wavelength catalog
of nearly 2900 known objects in the region by combining 17 different catalogs
from the recent literature. We define two reference groups: an infrared sample,
containing all objects detected in the K band, and an optical sample comprising
low extinction, well characterized ONC members. We show for both samples that
field object contamination is generally low.
  Our X-ray sources are primarily low mass ONC members. The detection rate for
optical sample stars increases monotonically with stellar mass from zero at the
brown dwarf limit to ~100% for the most massive stars but shows a pronounced
dip between 2 and 10 solar masses.
  We determine L_X and L_X/L_{bol} for all stars in our optical sample and
utilize this information in our companion paper to study correlations between
X-ray activity and other stellar parameters.


title:
Chandra X-ray Observation of the Orion Nebula Cluster. II Relationship
  between X-ray activity indicators and stellar parameters

abstract:
  Using the results of our first paper on the Chandra HRC observation of the
Orion Nebula Cluster (ONC), here we explore the relation between the coronal
activity of its 1-Myr-old pre-main sequence population and stellar parameters.
We find that median X-ray luminosities of low mass stars (M/M_sun < 3) increase
with increasing mass and decreasing stellar age. Brown dwarfs (0.03 < M/M_sun <
0.08) follow the same trend with mass. From M~0.1 to M~0.5M_sun, median
L_X/L_bol values increase by about half an order of magnitude and then remain
constant at ~10^-3.5 for the mass range from 0.5 to 3.0 M/M_sun. In these same
two mass ranges, L_X/L_bol remains roughly constant with age, until it drops by
more than two orders of magnitudes at the epoch when ~2-4M_sun stars are
expected to become fully radiative.
  We find a dependence of L_X and L_X/L_bol on circumstellar accretion
indicators and suggest three possible hypotheses for its origin. In spite of
improved X-ray and rotational data, correlations between activity indicators
and rotation remain elusive for these stars, possibly indicating that stars for
which rotational periods have been measured have reached some saturation level.
  Our study of X-ray activity vs. stellar mass leads us to propose that the few
HRC X-ray sources not associated with any optical/infrared counterpart trace a
yet to be discovered stellar population of deeply embedded, relatively massive
ONC members.


title: AE Aquarii: how CVs descend from supersoft binaries

abstract:
  AE Aquarii is a propeller system. It has the shortest spin period among
cataclysmic variables, and this is increasing on a 10^7 yr timescale. Its UV
spectrum shows very strong carbon depletion vs nitrogen and its secondary mass
indicates a star far from the zero-age main sequence. We show that these
properties strongly suggest that AE Aqr has descended from a supersoft X-ray
binary. We calculate the evolution of systems descending through this channel,
and show that many of them end as AM CVn systems. The short spindown timescale
of AE Aqr requires a high birthrate for such systems, implying that a
substantial fraction of cataclysmic variables must have formed in this way. A
simple estimate suggests that this fraction could be of order one-third of
current CVs. We emphasize the importance of measurements of the C/N abundance
ratio in CVs, particularly via the CIV1550 / NV1238 ratio, in determining how
large the observed fraction is.


title: Chandra Observations of Arp 220: The Nuclear Source

abstract:
  We present the first results from 60ks of observations of Arp 220 using the
ACIS-S instrument on Chandra. We report the detection of several sources near
the galaxy's nucleus, including a point source with a hard spectrum that is
coincident with the western radio nucleus B. This point source is mildly
absorbed (N_H ~ 3 x 10^22 cm^-2) and has an estimated luminosity of 4 x 10^40
erg/s. In addition, a fainter source may coincide with the eastern nucleus A.
Extended hard X-ray emission in the vicinity raises the total estimated nuclear
2-10 keV X-ray luminosity to 1.2 x 10^41 erg/s, but we cannot rule out a hidden
AGN behind columns exceeding 5 x 10^24 cm^-2. We also detect a peak of soft
X-ray emission to the west of the nucleus, and a hard point source 2.5 kpc from
the nucleus with a luminosity of 6 x 10^39 erg/s.


title:
The Kinematics and Physical Conditions pf the Ionized Gas in Markarian
  509. II. STIS Echelle Observations

abstract:
  We present observations of the UV absorption lines in the luminous Seyfert 1
galaxy Mrk 509, obtained with the medium resolution (lambda/Delta-lambda ~
40,000) echelle gratings of the Space Telescope Imaging Spectrograph on the
Hubble Space Telescope. The spectra reveal the presence of eight kinematic
components of absorption in Ly-alpha, C IV, and N V, at radial velocities of
-422, -328, -259, -62, -22, +34, +124, and +210 km s^-1 with respect to an
emission-line redshift of z = 0.03440, seven of which were detected in an
earlier Far Ultraviolet Spectrographic Explorer (FUSE) spectrum. The component
at -22 km s^-1 also shows absorption by Si IV. The covering factor and velocity
width of the Si IV lines were lower than those of the higher ionization lines
for this component, which is evidence for two separate absorbers at this
velocity. We have calculated photoionization models to match the UV column
densities in each of these components. Using the predicted O VI column
densities, we were able to match the O VI profiles observed in the FUSE
spectrum. Based on our results, none of the UV absorbers can produce the X-ray
absorption seen in simultaneous Chandra observations; therefore, there must be
more highly ionized gas in the radial velocity ranges covered by the UV
absorbers.


title: Discovery of a peculiar DQ white dwarf

abstract:
  We report the discovery of a new carbon rich white dwarf that was identified
during a proper motion survey for cool white dwarfs based on photographic
material used for the construction of the Guide Star Catalog II. Its large
proper motion (0.48 arcsec/yr) and faint apparent magnitude (V = 18.7) suggest
a nearby object of low luminosity. A low-resolution spectrum taken with the
William Herschel Telescope clearly shows strong C2 Deslandres-d'Azambuja and
Swan bands, which identify the star as a DQ white dwarf. The strength of the
Deslandres-d'Azambuja bands and the depression of the continuum in the
Swan-band region are signs of enhanced carbon abundance for the given Teff.
Comparison of our spectrophotometric data to published synthetic spectra
suggests 6000 K < Teff < 8000 K although further analysis with specialized
synthetic models appear necessary to derive both Teff and chemical composition.
Finally, the range of spatial velocity estimated for this object makes it a
likely member of the halo or thick disk population.


title: The Shape of Nereid's Phase Function Changed From 1998 To 1999 and 2000

abstract:
  We present well-sampled light curves of Nereid for 1999 and 2000 which show
symmetric shapes centered on opposition as is characteristic of a large
opposition surge. Surprisingly, the phase functions for 1999 and 2000 are
significantly different from the well-measured phase function for the year
1998, with the 1999 and 2000 curves being more peaked at low phase angles and
substantially brighter at high phase angles. We know of neither precedent nor
explanation for this mystery on Nereid.


title: On the Equation of State for Scalar Field

abstract:
  We consider Friedmann cosmologies with minimally coupled scalar field. Exact
solutions are found, many of them elementary, for which the scalar field energy
density, rho_f, and pressure, p_f, obey the equation of state (EOS)
p_f=w_f\rho_f. For any constant |w_f|<1 there exists a two-parameter family of
potentials allowing for such solutions; the range includes, in particular, the
quintessence (-1<w_f<0) and `dust' (w_f=0). The potentials are monotonic and
behave either as a power or as an exponent for large values of the field. For a
class of potentials satisfying certain inequalities involving their first and
second logarithmic derivatives, the EOS holds in which w_f=w_f(\f) varies with
the field slowly, as compared to the potential.


title:
HI Properties of Low Luminosity Star-Forming Galaxies in the KPNO
  International Spectroscopic Survey

abstract:
  New HI observations are presented for a complete sample of 109 low luminosity
star-forming galaxies taken from the KPNO International Spectroscopic Survey
(KISS), the first CCD-based wide-field objective-prism survey for emission-line
galaxies. This sample consists of all star-forming galaxies with M_B > -18.0
and cz < 11,000 km/s from the first Halpha-selected survey list. Overall, 97
out of 109 galaxies have been detected in HI. We confirm the weak trend of
increasing gas richness with decreasing luminosity found by previous authors.
Gas richness is also shown to be weakly anti-correlated with metallicity. The
dependence of star formation rates (SFRs) and HI gas depletion timescales on
metallicity is examined. The median solar metallicity based SFR and gas
depletion timescale are 0.1639 M_sun/yr and 5 Gyrs, respectively. Corrections
for variations in metallicity decreases SFRs by about 0.5 dex and increases gas
depletion timescales by an average of about 8 Gyrs. The majority of galaxies in
this sample still have large reservoirs of HI gas, and despite their large
current star formation rates, could have formed stars in a quasi-continuous
manner for a Hubble time. Finally, we present the first HI mass function for
low luminosity star-forming galaxies and show that this subpopulation
contributes 10-15% of the overall HI density in the local universe. We conclude
that if the HI mass function of the Universe does indeed have a steeply rising
low-mass slope as suggested by previous authors, it is not due to the
population of low luminosity star-forming galaxies.


title: Asymmetric Explosions of Type Ia Supernovae

abstract:
  The burning speed of a thermonuclear supernova front could be described by
the fractal model of combustion. We have examined the effects of magnetic
fields on the fractalization of the front considering a white dwarf with a
nearly dipolar magnetic field and found an intrinsic asymmetry on the velocity
field of the expanding plasma. For white dwarf's magnetic fields of 10^8-10^9 G
at the surface, and assuming a field roughly 10 times greater near the center,
we have found asymmetries in the velocity field > 10-20 % at rho ~ 10^8 g
cm^(-3), produced between the magnetic polar and the equatorial axis of the
remnant. This effect may be related to the asphericities inferred from
spectro-polarimetric observations of very young SN Ia remnants (for example: SN
1999by). In the present work, we analyse the dependence of the asymmetry with
the composition of the white dwarf progenitor.


title: Black hole mass and spin coevolution by mergers

abstract:
  Massive black holes appear to be present in the nuclei of almost all
galaxies, but their genesis and evolution are not well understood. As
astrophysical black holes are completely characterized by their masses and
spins, the observed joint distribution of these quantities contains important
clues to their history. We examine the coevolution of mass and spin in binary
merger growth scenarios. We find that holes are typically spun down by mergers.
Rapid rotation results only if the binary's larger member already spins quickly
and the merger with the smaller hole is consistently near prograde; or, if the
binary's mass ratio approaches one. If, as some observations have suggested,
observed black holes spin rapidly, then this limits the importance of merger
scenarios for the growth of black holes.


title:
Thermal and Nonthermal Emission from the Forward Shock in Tycho's
  Supernova Remnant

abstract:
  We present Chandra X-ray images of Tycho's supernova remnant that delineate
its outer shock as a thin, smooth rim along the straight northeastern edge and
most of the circular western half. The images also show that the Si and S
ejecta are highly clumpy, and have reached near the forward shock at numerous
locations. Most of the X-ray spectra that we examine along the rim show
evidence of line emission from Si and S ejecta, while the continuum is
well-represented by either a thermal or nonthermal model. If the continuum is
assumed to be thermal, the electron temperatures at the rim are all similar at
about 2 keV, while the ionization ages are very low, because of the overall
weakness of the line emission. These electron temperatures are substantially
below those expected for equilibration of the electron and ion temperatures,
assuming shock velocities inferred from radio and X-ray expansion measurements;
the electron to mean temperature ratios are <~0.1-0.2, indicating that
collisionless heating of the electrons at the shock is modest. The nonthermal
contribution to these spectra may be important, but cannot be strongly
constrained by these data. It could account for as much as half of the flux in
the 4-6 keV energy range, based on an extrapolation of the hard X-ray spectrum
above 10 keV.


title: The Submillimeter Properties of Extremely Red Objects

abstract:
  We use deep near-infrared and submillimeter observations of three massive
lensing cluster fields, A370, A851, and A2390, to determine the average
submillimeter properties of a K'-selected sample. The 38 Extremely Red Objects
(EROs; I-K'>4) with K'<21.25 have a very significant error-weighted mean
850-micron flux of 1.58 +/- 0.13 mJy. The ERO contribution to the 850-micron
background is 1.88 +/- 0.16 x 10^4 mJy per square degree, or about half the
background light. The 17 Very Red Objects (VROs; 3.5<I-K'<4) are also
significantly detected (1.32 +/- 0.19 mJy), bringing the combined VRO and ERO
contribution to 2.59 +/- 0.19 x 10^4 mJy per square degree. There is a
substantial systematic uncertainty (about a factor of two) in this value due to
field-to-field variation, but even with this uncertainty it is clear that a
large fraction of the 850-micron background arises from red objects. An
analysis of the VRO and ERO number counts shows that half of the population's
850-micron light arises in objects with demagnified magnitudes K'<20 and half
in fainter objects. On the basis of the I-J versus J-K' colors of the galaxies,
the bulk of the submillimeter signal appears to arise from the dusty starburst
galaxies in the red object population rather than from the high-redshift
elliptical galaxies.


title: Magnetic Fields via Polarimetry: Progress of Grain Alignment Theory

abstract:
  Most astrophysical systems, e.g. stellar winds, the diffuse interstellar
medium, molecular clouds, are magnetized with magnetic fields that influence
almost all of their properties. One of the most informative techniques of
magnetic field studies is based on the use of starlight polarization and
polarized emission arising from aligned dust. How reliable the interpretation
of the polarization maps in terms of magnetic fields is the issue that the
grain alignment theory addresses. Although grain alignment is a problem of half
a century standing, recent progress achieved in the field makes us believe that
we are approaching the solution of this mystery. I review basic physical
processes involved in grain alignment and discuss the niches for different
alignment mechanisms. I show why mechanisms that were favored for decades do
not look so promising right now, while the radiative torque mechanism ignored
for more than 20 years looks so attractive. I define the observational tests
and outline the circumstances when grain alignment theory predicts that new yet
untapped information of magnetic field structure is available through
polarimetry. In particular, I touch upon mapping magnetic fields in
circumstellar regions, interplanetary space and in comet comae.


title:
The Structure and X-ray Recombination Emission of a Centrally
  Illuminated Accretion Disk Atmosphere and Corona

abstract:
  We model an accretion disk atmosphere and corona photoionized by a central
X-ray continuum source. We calculate the opacity and radiation transfer for an
array of disk radii, to obtain the two-dimensional structure of the disk and
its X-ray recombination emission. The atmospheric structure is insensitive to
the viscosity alpha. We find a feedback mechanism between the disk structure
and the central illumination, which expands the disk and increases the solid
angle subtended by the atmosphere. We model the disk of a neutron star X-ray
binary. We map the temperature, density, and ionization structure of the disk,
and we simulate the high resolution spectra observable with the Chandra and
XMM-Newton grating spectrometers. The X-ray emission lines from the disk
atmosphere are detectable, especially for high-inclination binary systems. The
grating observations of two classes of X-ray binaries already reveal important
spectral similarities with our models. The line spectrum is very sensitive to
the structure of each atmospheric layer, and it probes the heating mechanisms
in the disk. The model spectrum is dominated by double-peaked lines of H-like
and He-like ions, plus weak Fe L. Species with a broad range of ionization
levels coexist at each radius: from Fe XXVI in the hot corona, to C VI at the
base of the atmosphere. The choice of stable solutions affects the spectrum,
since a thermal instability is present in the regime where the X-ray
recombination emission is most intense.


title:
Complex rotation with internal dissipation. Applications to cosmic-dust
  alignment and to wobbling comets and asteroids

abstract:
  Neutron stars, asteroids, comets, cosmic-dust granules, spacecraft, as well
as whatever other freely spinning body dissipate energy when they rotate about
any axis different from principal. We discuss the internal-dissipation-caused
relaxation of a freely precessing rotator towards its minimal-energy mode (mode
that corresponds to the spin about the maximal-inertia axis). While the body
nutates at some rate, the internal stresses and strains within the body
oscillate at frequencies both higher and lower than this rate. The internal
dissipation takes place mostly the second and higher harmonics. We discuss the
application of our findings to asteroids. Regarding the comets, estimates show
that the currently available angular resolution of spacecraft-based instruments
makes it possible to observe wobble damping within year- or maybe even
month-long spans of time. We also discuss cosmic-dust astrophysics; in
particular, the role played by precession damping in the dust alignment. We
show that this damping provides coupling of the grain's rotational and
vibrational degrees of freedom; this entails occasional flipping of dust grains
due to thermal fluctuations. During such a flip, grain preserves its angular
momentum, but the direction of torques arising from H2 formation reverses. As a
result, flipping grain will not rotate fast in spite of the action of
uncompensated H2 formation torques. The grains get ``thermally trapped,'' and
their alignment is marginal.

categories: astro-ph math-ph math.MP nlin.CD physics.class-ph physics.space-ph


title: Formation of Kuiper Belt Binaries

abstract:
  It appears that at least several percent of large Kuiper belt objects are
members of wide binaries. Physical collisions are too infrequent to account for
their formation. Collisionless gravitational interactions are more promising.
These provide two channels for binary formation. In each, the initial step is
the formation of a transient binary when two large bodies penetrate each
other's Hill spheres. Stabilization of a transient binary requires that it lose
energy. Either dynamical friction due to small bodies or the scattering of a
third large body can be responsible. Our estimates favor the former, albeit by
a small margin. We predict that most objects of size comparable to those
currently observed in the Kuiper belt are members of multiple systems. More
specifically, we derive the probability that a large body is a member of a
binary with semi-major axis of order a. The probability depends upon sigma, the
total surface density, Sigma, the surface density of large bodies having radius
R, and theta=10^-4, the angle subtended by the solar radius as seen from the
Kuiper belt. For (sigma/Sigma)R<a< R/theta, the probability is just (Sigma/rho
R)theta^-2, the optical depth of the large bodies divided by the solid angle
subtended by the Sun. For R<a<r_u=(sigma/Sigma)R, it varies inversely with
semimajor axis and reaches (sigma/rho R)theta^-2 at a=R. Based on current
surveys of the Kuiper belt, we estimate Sigma/rho=3 10^-4cm and R=100km. We
obtain sigma/rho=0.3cm by extrapolating the surface density deduced for the
minimum mass solar nebula. Rough predictions are: outside of the critical
separation r_u/a_odot=3'', the binary probability is 0.3%; at separations of
0.2'', comparable to current resolving capabilities, it reaches 5%, in
agreement with results from the HST binary survey by Brown.


title:
HST Proper Motion confirms the optical identification of the nearby
  pulsar PSR 1929+10

abstract:
  We report on the proper motion measurement of the proposed optical
counterpart of the X-ray/radio pulsar PSR 1929+10. Using images obtained with
the HST/STIS (average epoch 2001.73) we computed a yearly displacement of +97
+/- 1 mas yr^{-1} in RA and +46 +/- 1 mas yr^{-1} in Dec since the epoch
(1994.52) of the original HST/FOC detection. Both the magnitude and direction
of the optical proper motion components are found to be fully consistent with
the most recent VLBA radio measurements. This result provides an unambiguous
confirmation of the pulsar optical identification. In addition, we have used
the combined STIS/FOC datasets to derive information on the pulsar spectrum,
which seems characterized by a power law component, apparently unrelated to the
X-ray emission.


title: X-rays from Supernova Remnants

abstract:
  A summary of X-ray observations of supernova remnants is presented including
the explosion fragment A of the Vela SNR, Tycho, N132D, RX J0852-4622, the Crab
Nebula and the 'bulls eye', and SN 1987A, high-lighting the progress made with
Chandra and XMM-Newton and touching upon the questions which arise from these
observations and which might inspire future research.


title: Eta Carinae: The physical structure of the outer ejecta and the strings

abstract:
  The outer ejecta is part of the nebula around Eta Carinae. They are
filamentary, shaped irregularly and larger than the Homunculus, the central
bipolar nebula. While the Homuculus is mainly a reflection nebula, the outer
ejecta is an emission structure. However, we showed with kinematic analysis
that the outer ejecta (as the Homunculus) expands bi-directional despite of its
complex morphology. Radial velocities in the outer ejecta reach up to 2000km/s
and give rise to X-ray emission. An analysis showing the distribution of the
soft X-ray emission and its comparison to the optical emitting gas is presented
here. X-ray maxima are found in areas in which the expansion velocities are
highest. The temperature of 0.65 keV determined with the CHANDRA/ACIS data and
thermal equilibrium models indicates post-shock velocities of 750km/s, about
what was found in the spectra. In addition analysis of the new HST-STIS data
from the Strings--long, highly collimated structures in the outer ejecta--are
presented. The data show that the electron density of the Strings is of the
order of 10^4 cm^-3. The same value was detected for other structures in the
outer ejecta. With this density String 1 has a mass of about 3 10^-4 M_sun and
the total ejecta could be as massive as 0.5 M_sun.


title: Abundant molecular gas in the intergalactic medium of Stephan's Quintet

abstract:
  Stephan's Quintet (SQ) is a system consisting of at least four interacting
galaxies which is well known for its complex dynamical and star formation
history. It possesses a rich intergalactic medium (IGM), where hydrogen clouds,
both atomic and molecular, associated with two starbursts (refered to as SQ A
and B) have been found. In order to study the extent, origin and fate of the
intergalactic molecular gas and its relation to the formation of stars outside
galaxies and Tidal Dwarf Galaxies (TDGs), we mapped with the IRAM 30m antenna
the carbon monoxide (CO) towards several regions of the IGM in SQ. In both SQ A
and B, we detected unusually large amounts of molecular gas (3.1 times 10^9
msun and 7 times 10^8 msun, respectively). In contrast, no significant CO
detection was achieved towards HII regions south of the pair NGC 7318a/b
despite their high H alpha luminosities. The molecular gas is very extended in
both SQ A and SQ B, over areas of between 15 and 25 kpc. The CO clouds seem to
have otherwise different properties and may be of a different nature. The
integrated CO line of SQ A is in particular much wider than in SQ B. Its CO
spectrum shows emission at two velocities (6000 and 6700 km s^{-1}) that are
coincident with two HI lines. The strongest emission at 6000 km s^{-1} is
however spatially offset from the HI emission and situated on a ridge
south-east of the starburst region. In SQ B the CO emission coincides with that
of tracers of star formation (halpha, 15 mu m and radio continuum). The CO peak
lies slightly offset from the HI peak towards a steep HI gradient. This is
indicating that the molecular gas is forming in-situ, possibly in a region of
compressed HI, with subsequent star formation. The star forming region at SQ B
is the object in SQ that most resembles a TDG.


title: Recurrent microblazar activity in Cygnus X-1?

abstract:
  Recurrent flaring events at X- and soft gamma-ray energies have been recently
reported for the galactic black hole candidate Cygnus X-1. The observed fluxes
during these transient outbursts are far higher than what is observed in
``normal'' episodes. Here we suggest that the origin of this radiation is
non-thermal and produced by inverse Compton interactions between relativistic
electrons in the jet and external photon fields, with a dominant contribution
from the companion star field. The recurrent and relatively rapid variability
could be explained by the precession of the jet, which results in a variable
Doppler amplification.


title: Unabsorbed Seyfert 2 galaxies

abstract:
  We present a sample of 17 type 2 Seyfert galaxies which have an X-ray column
density lower than 10^{22} cm^{-2}. The Compton thin nature of these sources is
strongly suggested by isotropic indicators. We estimate the fraction of these
sources to be in the range of 10% - 30% of the population of type 2 Seyfert
galaxies. Furthermore, this fraction appears to increase progressively at lower
luminosities. The simple formulation of the Unified Model for Seyfert galaxies
is not applicable in such sources since the pc-scale molecular torus is not
likely to be responsible for the low column density observed, instead the
absorption observed is likely to originate at larger scales. According to this
hypothesis, in these objects the broad line regions are covered by some dusty
obscuring material. In particular, this could occur in objects with dust lanes,
patches or HII regions. However, we cannot rule out that in the lowest
luminosity sources the BLR is weak, absent or has faded away. This last
scenario is consistent with the predictions of some recent theoretical models
for low luminosity AGNs.


title:
Discovery of a very cool object with extraordinarily strong H(alpha)
  emission

abstract:
  We report on the finding of the strongest H(alpha) emission -pseudoequivalent
width of 705 Angstrom- known so far in a young, late type dwarf. This object,
named as SOri71, is a substellar candidate member of the 1-8 Myr star cluster
sigma Orionis. Due to its overluminous location in color-magnitude diagrams,
SOri71 might be younger than other cluster members, or a binary of similar
components. Its mass is in the range 0.021-0.012 M(sun), depending on
evolutionary models and possible binarity. The broad H(alpha) line of SOri71
appears asymmetric, indicative of high velocity mass motions in the H(alpha)
forming region. The origin of this emission is unclear at the present time. We
discuss three possible scenarios: accretion from a disk, mass exchange between
the components of a binary system, and emission from a chromosphere.


title: Radio Observations of Supernova Remnants

abstract:
  Supernovae release an enormous amount of energy into the interstellar medium.
Their remnants can observationally be traced up to several ten-thousand years.
So far more than 230 Galactic supernova remnants (SNRs) have been identified in
the radio range. Detailed studies of the different types of SNRs give insight
into the interaction of the blast wave with the interstellar medium. Shock
accelerated particles are observed, but also neutron stars left from the
supernova explosion make their contribution. X-ray observations in conjunction
with radio data constrain models of supernova evolution.
  A brief review of the origin and evolution of SNRs is given, which are
compared with supernova statistics and observational limitations. In addition
the morphology and characteristics of the different types of SNRs are
described, including some recent results and illustrated by SNRs images mostly
obtained with the Effelsberg 100-m telescope.


title: A Survey Searching for the Epoch of Assembling of Hubble Types

abstract:
  We have started a survey of galaxies at intermediate redshifts using the
HST-STIS parallel fields. Our main goal is to analyse the morphology of faint
galaxies in order to estimate the epoch of formation of the Hubble
classification sequence. The high resolution of STIS images (0.05'') is ideal
for this work and enable us to perform a morphological classification and to
analyse the internal structures of galaxies. We find that 40% of the 290
galaxies are early types and that there are more irregulars and ellipticals at
the fainter magnitudes.


title:
On Relativistic Corrections to Microlensing Effects: Applications to the
  Galactic Black Hole

abstract:
  The standard treatment of gravitational lensing by a point mass lens M is
based on a weak-field deflection angle a = 2/x, where x = (r c^2)/(2 G M) with
r the distance of closest approach to the mass of a lensed light ray. It was
shown that for a point mass lens, the total magnification and image centroid
shift of a point source remain unchanged by relativistic corrections of second
order in 1/x. This paper considers these issues analytically taking into
account the relativistic images, under three standard lensing configuration
assumptions, for a Schwarzschild black hole lens with background point and
extended sources having arbitrary surface brightness profiles. We apply our
results to the Galactic black hole for lensing scenarios where our assumptions
hold. We show that a single factor characterizes the full relativistic
correction to the weak-field image centroid and magnification. As the
lens-source distance increases, the relativistic correction factor strictly
decreases. In particular, we find that for point and extended sources about 10
pc behind the black hole (which is a distance significantly outside the tidal
disruption radius of a sun-like source), the relativistic correction factor is
miniscule, of order 10^{-14}. Therefore, for standard lensing configurations,
any detectable relativistic corrections to microlensing by the Galactic black
hole will most likely have to come from sources significantly closer to the
black hole.


title: BeppoSAX Observations of Synchrotron X-ray Emission from Radio Quasars

abstract:
  We present new BeppoSAX LECS, MECS, and PDS observations of four
flat-spectrum radio quasars (FSRQ) having effective spectral indices alpha_ro
and alpha_ox typical of high-energy peaked BL Lacs. Our sources have
X-ray-to-radio flux ratios on average ~ 70 times larger than ``classical'' FSRQ
and lie at the extreme end of the FSRQ X-ray-to-radio flux ratio distribution.
The collected data cover the energy range 0.1 - 10 keV (observer's frame),
reaching ~ 100 keV for one object. The BeppoSAX band in one of our sources, RGB
J1629+4008, is dominated by synchrotron emission peaking at ~ 2 x 10^16 Hz, as
also shown by its steep (energy index alpha_x ~ 1.5) spectrum. This makes this
object the FIRST known FSRQ whose X-ray emission is not due to inverse Compton
radiation. Two other sources display a flat BeppoSAX spectrum (alpha_x ~ 0.7),
with weak indications of steepening at low X-ray energies. The combination of
BeppoSAX and ROSAT observations, (non-simultaneous) multifrequency data, and a
synchrotron inverse Compton model suggest synchrotron peak frequencies ~ 10^15
Hz, although a better coverage of their spectral energy distributions is needed
to provide firmer values. If confirmed, these values would be typical of
``intermediate'' BL Lacs for which the synchrotron and inverse Compton
components overlap in the BeppoSAX band. Our sources, although firmly in the
radio-loud regime, have powers more typical of high-energy peaked BL Lacs than
of FSRQ, and indeed their radio powers put them near the low-luminosity end of
the FSRQ luminosity function. We discuss this in terms of an anti-correlation
between synchrotron peak frequency and total power, based on physical
arguments, and also as possibly due to a selection effect.


title:
The Chemical Composition of the 30 Doradus Nebula Derived from VLT
  Echelle Spectrophotometry

abstract:
  Echelle spectrophotometry of the 30 Doradus nebula in the LMC is presented.
The data consists of VLT UVES observations in the 3100 to 10350 A range. The
intensities of 366 emission lines have been measured, including 269 identified
permitted lines of H 0, He 0, C 0, C+, N+, N++, O 0, O+, Ne 0, Ne+, S+, S++, Si
0 , Si+, Si++, Ar+, and Mg+. Electron temperatures and densities have been
determined using different line intensity ratios. The He+, C++, O+, and O++
ionic abundances have been derived from recombination lines, these abundances
are almost independent of the temperature structure of the nebula.
Alternatively abundances from collisionally excited lines have been derived for
a large number of ions of different elements, these abundances depend strongly
on the temperature structure. Accurate t^2 values have been derived from the
Balmer continuum, and by comparing the C++, O+, and O++ ionic abundances
obtained from collisionally excited and recombination lines. The chemical
composition of 30 Doradus is compared with those of Galactic and extragalactic
HII regions. The values of Delta Y / Delta O, Delta Y / Delta Z, and Yp are
also discussed.


title:
Numerical methods for non-LTE line radiative transfer: Performance and
  convergence characteristics

abstract:
  Comparison is made between a number of independent computer programs for
radiative transfer in molecular rotational lines. The test models are
spherically symmetric circumstellar envelopes with a given density and
temperature profile. The first two test models have a simple power law density
distribution, constant temperature and a fictive 2-level molecule, while the
other two test models consist of an inside-out collapsing envelope observed in
rotational transitions of HCO+. For the 2-level molecule test problems all
codes agree well to within 0.2%, comparable to the accuracy of the individual
codes, for low optical depth and up to 2% for high optical depths (tau=4800).
The problem of the collapsing cloud in HCO+ has a larger spread in results,
ranging up to 12% for the J=4 population. The spread is largest at the radius
where the transition from collisional to radiative excitation occurs. The
resulting line profiles for the HCO+ J=4-3 transition agree to within 10%,
i.e., within the calibration accuracy of most current telescopes. The
comparison project and the results described in this paper provide a benchmark
for future code development, and give an indication of the typical accuracy of
present day calculations of molecular line transfer.


title:
Similarities and Differences between Relativistic Electron-Photon
  Cascades Developed in Matter, Photon Gas and Magnetic Field

abstract:
  We investigate properties of astrophysical electromagnetic cascades developed
in matter, photon gas and magnetic fields, and discuss similarities and
differences between characteristics of electron-photon showers developed in
these 3 substances.


title: Metal abundances in PG1159 stars from Chandra and FUSE spectroscopy

abstract:
  We investigate FUSE spectra of three PG1159 stars and do not find any
evidence for iron lines. From a comparison with NLTE models we conclude a
deficiency of 1-1.5 dex. We speculate that iron was transformed into heavier
elements. A soft X-ray Chandra spectrum of the unique H- and He-deficient star
H1504+65 is analyzed. We find high neon and magnesium abundances and confirm
that H1504+65 is the bare core of either a C-O or a O-Ne-Mg white dwarf.


title:
FUSE Spectroscopy of the Two Prototype White Dwarfs With Signatures of a
  Super-hot Wind

abstract:
  The O VIII phenomenon describes the occurrence of ultra-high ionization
absorption lines of the CNO elements (e.g. O VIII, N VII, C VI, and even Ne X)
in the optical spectra hot of DO WDs.


title: Astrophysics at the Highest Energy Frontiers

abstract:
  I discuss recent advances being made in the physics and astrophysics of
cosmic rays and cosmic gamma-rays at the highest observed energies as well as
the related physics and astrophysics of very high energy cosmic neutrinos. I
also discuss the connections between these topics.


title:
The H-alpha and Infrared Star Formation Rates for the Nearby Field
  Galaxy Survey

abstract:
  We investigate the H-alpha and infrared star formation rate (SFR) diagnostics
for galaxies in the Nearby Field Galaxy Survey (NFGS). For the 81 galaxies in
our sample, we derive H-alpha fluxes (included here) from integrated spectra.
There is a strong correlation between the ratio of far-infrared to optical
luminosities L(FIR)/L(H-alpha) and the extinction E(B-V) measured with the
Balmer decrement. Before reddening correction, the SFR(IR) and SFR(H-alpha) are
related to each other by a power-law. Correction of the SFR(H-alpha) for
extinction using the Balmer decrement and a classical reddening curve both
reduces the scatter in the SFR(IR)-SFR(H-alpha) correlation and results in a
much closer agreement (within ~10%) between the two SFR indicators. This SFR
relationship spans 4 orders of magnitude and holds for all Hubble types with
IRAS detections in the NFGS. A constant ratio between the SFR(IR) and
SFR(H-alpha) for all Hubble types, including early types (S0-Sab), suggests
that the IR emission in all of these objects results from a young stellar
population.