title:
Probing the HI Kinematics of the LMC: Toward Interpreting QAL
  Observations of Protogalactic Velocity Fields

abstract:
  We examine the gas kinematics of the LMC revealed by the high spatial and
velocity resolution HI data cube of the combined ATCA and Parkes telescope
surveys. We adopt an approach designed to facilitate comparisons with quasar
absorption line observations, in particular restricting our analysis to
pointings with HI column density satisfying the damped Lya (DLA) criterion. We
measure velocity widths for ~5000 random pointings to the LMC and find a median
value of ~40 km/s which modestly exceeds the value predicted by differential
rotation. This median is significantly lower than the median value observed for
the metal-line profiles of high z DLA. Therefore, assuming


title: Carbon Monoxide in the Type Ic SN 2000ew

abstract:
  We present K-band (1.9 -- 2.5 micron) spectra of the Type Ic SN 2000ew
observed with IRCS on the Subaru Telescope. These data show the first detection
of carbon monoxide (CO) emission in a Type Ic supernova. The detection of CO in
SN 2000ew provides further evidence that molecule formation may be a common
occurrence in core-collapse supernova ejecta. The spectrum also contains narrow
emission lines of [Fe II] and He I probably from dense clumps of hydrogen-poor
circumstellar gas surrounding SN 2000ew. Our spectrum of SN 2000ew shows no
trace of an unidentified feature seen near 2.26 micron, just blueward of the CO
emission, in the spectrum of SN 1987A and we discuss proposed detections of
this feature in other Type II supernovae.


title:
Nonthermal Radiation and Acceleration of Electrons in Clusters of
  Galaxies

abstract:
  Recent observations of excess radiation at extreme ultraviolet and hard X-ray
energies straddling the well known thermal soft X-ray emission have provided
new tools and puzzles for investigation of the acceleration of nonthermal
particles in the intercluster medium of clusters of galaxies. It is shown that
these radiations can be produced by the inverse Compton upscattering of the
cosmic microwave background photons by the same population of relativistic
electrons that produce the well known diffuse radio radiation via the
synchrotron mechanism. It is shown that the commonly discussed discrepancy
between the value of the magnetic field required for the production of these
radiation with that obtained from Faraday rotation measures could be resolved
by more realistic models and by considerations of observational selection
effects. In a brief discussion of the acceleration process it is argued that
the most likely scenario is reacceleration of injected relativistic electrons
involving shocks and turbulence. The seed electrons cannot be the background
thermal electrons because of energetic considerations, and a steady state
situation may not agree with the details of the observed spectra. Episodic
generation of shocks and turbulence or episodic injection of relativistic
electrons is a more likely scenario for acceleration.


title:
Looptop and Footpoint Impulsive Hard X-Rays and Stochastic Electron
  Acceleration in Solar Flares

abstract:
  The discovery of hard X-rays from tops of flaring loops by the HXT of YOHKOH
represents a significant progress in the understanding of solar flares. This
report describes the properties of 20 limb flares observed by YOHKOH from
October 1991 to August 1998, 15 of which show detectable impulsive looptop
emission. Considering the finite dynamic range (about a decade) of the
detection it can be concluded that looptop emission is a common feature of all
flares. The light curves and images of a representative flare are presented and
the statistical properties of the footpoint and looptop fluxes and spectral
indexes are summarized. The importance of these observations, and those
expected from RHESSI with its superior angular, spectral and temporal
resolution, in constraining the acceleration models and parameters is
discussed. briefly.


title:
Galaxy Number Counts in the Subaru Deep Field: Multi-band Analysis in a
  Hierarchical Galaxy Formation Model

abstract:
  Number counts of galaxies are re-analyzed using a semi-analytic model (SAM)
of galaxy formation based on the hierarchical clustering scenario. Faint
galaxies in the Subaru Deep Field (SDF) and the Hubble Deep Field (HDF) are
compared with our model galaxies. We have determined the astrophysical
parameters in the SAM that reproduce observations of nearby galaxies, and used
them to predict the number counts and redshifts of faint galaxies for three
cosmological models, the standard cold dark matter (CDM) universe, a flat
lambda-CDM, and an open CDM. The novelty of our SAM analysis is the inclusion
of selection effects arising from the cosmological dimming of surface
brightness of high-z galaxies, and from the absorption of visible light by
internal dust and intergalactic HI clouds. As was found in our previous work,
in which the UV/optical HDF galaxies were compared with our model galaxies, we
find that our SAM reproduces counts of near-IR SDF galaxies in low-density
models, and that the standard CDM universe is not preferred, as suggested by
other recent studies. Moreover, we find that simple prescriptions for (1) the
timescale of star formation being proportional to the dynamical time scale of
the formation of galactic disks, (2) the size of galactic disks being
rotationally supported with the same specific angular momentum as that of
surrounding dark halo, and (3) the dust optical depth being proportional to the
metallicity of cold gas, cannot completely explain all of observed data.
Improved prescriptions incorporating mild z-dependence for those are suggested
from our SAM analysis.


title: Unusually Increased Activity of GZ Cnc

abstract:
  GZ Cnc was discovered as a variable star by Takamizawa (Tmz V34), which
turned out to a cataclysmic variable (CV). Past studies have shown that this
object is a good candidate for a rarely outbursting, long-period dwarf nova.
Only three outbursts were recorded between 1999 and 2001. In 2002 March-May,
the object suddenly showed a dramatic increase of the outburst frequency. The
shortest observed interval was only 11 d. We suggest that the present behavior
may be interpreted as a clustering of short outbursts occasionally seen in
intermediate polars (magnetic CVs). The present activity can also be comparable
to V426 Oph, another dwarf nova which is known to show occasionally increased
activities. The resemblances in the X-ray properties and the outburst behavior
suggests that GZ Cnc and V426 Oph may comprise a new class of (weakly magnetic)
cataclysmic variables.


title:
The light curve of the semiregular variable L2 Puppis: I. A recent
  dimming event from dust

abstract:
  The nearby Mira-like variable L2 Pup is shown to be undergoing an
unprecedented dimming episode. The stability of the period rules out intrinsic
changes to the star, leaving dust formation along the line of sight as the most
likely explanation. Episodic dust obscuration events are fairly common in
carbon stars but have not been seen in oxygen-rich stars. We also present a
10-micron spectrum, taken with the Japanese IRTS satellite, showing strong
silicate emission which can be fitted with a detached, thin dust shell,
containing silicates and corundum.


title: QSOs from the variability and proper motion survey in the M3 field

abstract:
  We present results of the spectroscopical follow-up observations of QSO
candidates from a combined variability and proper motion (VPM) survey in a ~10
square degrees region centered on the globular cluster M3. The search is based
on a large number of digitised Schmidt plates with a time-baseline of three
decades. This paper reviews the candidate selection, the follow-up
spectroscopy, and general properties of the resulting QSO sample. In total, 175
QSOs and Sey1s were identified among the objects from the VPM survey, with 114
QSOs and 10 Sey1s up to the pre-estimated 90% completeness limit of the survey
at B_lim~19.7. The redshift range of the QSOs is 0.4<z<3. Among the 80 QSO
candidates of highest priority we confirm 75 QSOs/Sey1s and 2 NELGs. We present
magnitudes, colours, redshifts, and variability indices for all 181 identified
QSOs/Sey1s/NELGs and spectra for the 77 QSOs/Sey1s/NELGs from our spectroscopic
follow-up observations. The VPM survey uses selection criteria that are not
directly relying on the spectral energy distribution of QSOs. It is therefore
remarkable that the properties of the VPM QSOs do not significantly differ from
those of samples from colour selection or slitless spectroscopy. In particular,
we do not detect a substantial number of unusually red QSOs. The total surface
density of the brighter QSOs (17<=B<=18.5) in our search field is found to be
by a factor of ~1.8 larger than that derived from previous optical surveys.


title: Low mass dark matter halos in voids

abstract:
  Using numerical simulations and the Sheth-Tormen approximation we study the
mass function of dark matter halos in voids. We find that the void mass
function is significantly lower and its shape is different than that of the
field halos. We predict that in the standard LCDM model a void with radius 10
h^-1 Mpc should have 50 halos with circular velocity v_c > 50 km/s and 600
halos with v_c > 20 km/s.


title:
The status of Galactic field lambda Bootis stars in the post-Hipparcos
  era

abstract:
  The lambda Bootis stars are Population I, late B to early F-type stars, with
moderate to extreme (up to a factor 100) surface underabundances of most
Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). To
put constraints on the various existing theories that try to explain these
peculiar stars, we investigate the observational properties of lambda Bootis
stars compared to a reference sample of normal stars. Using various photometric
systems and Hipparcos data, we analyze the validity of standard photometric
calibrations, elemental abundances, and Galactic space motions. There
crystallizes a clear picture of a homogeneous group of Population I objects
found at all stages of their main-sequence evolution, with a peak at about 1
Gyr. No correlation of astrophysical parameters such as the projected
rotational velocities or elemental abundances with age is found, suggesting
that the a-priori unknown mechanism, which creates lambda Bootis stars, works
continuously for late B to early F-type stars in all stages of main-sequence
evolution. Surprisingly, the sodium abundances seem to indicate an interaction
between the stars and their local environment.


title: Lithium 6104A in Population II stars

abstract:
  We have obtained echelle spectroscopy of 14 Population II objects selected
from those previously observed by Bonifacio & Molaro (1997). For one object, HD
140283, we obtained exquisite data with the High Dispersion Spectrograph on the
Subaru Telescope, with S/N exceeding 1000 per 0.018A pixel. Li abundances have
been determined by spectral synthesis from both the 6708A resonance line and
also from 6104A subordinate feature. Firm detections of the weak line have been
made in seven objects, and upper limits are reported for the remainder. Our
6708A abundances agree with those reported by Bonifacio & Molaro at the
99%-confidence level. Abundances from the 6104A line hint at a higher Li
abundance than that determined from the resonance feature, but this evidence is
mixed; the weakness of the 6104A line and the large number of upper limits make
it difficult to draw firm conclusions. NLTE-corrections increase (rather than
eliminate) the size of the (potential) discrepancy, and binarity appears
unlikely to affect any abundance difference. The effect of multi-dimensional
atmospheres on the line abundances was also considered, although it appears
that use of 3-D (LTE) models could again act to increase the discrepancy, if
one is indeed present.


title: Kaon Condensates, Nuclear Symmetry Energy and Cooling of Neutron Stars

abstract:
  The cooling of neutron stars by URCA processes in the kaon-condensed neutron
star matter for various forms of nuclear symmetry energy is investigated. The
kaon-nucleon interactions are described by a chiral lagrangian. Nuclear matter
energy is parametrized in terms of the isoscalar contribution and the nuclear
symmetry energy in the isovector sector. High density behaviour of nuclear
symmetry energy plays an essential role in determining the composition of the
kaon-condensed neutron star matter which in turn affects the cooling
properties. We find that the symmetry energy which decreases at higher
densities makes the kaon-condensed neutron star matter fully protonized. This
effect inhibits strongly direct URCA processes resulting in slower cooling of
neutron stars as only kaon-induced URCA cycles are present. In contrast, for
increasing symmetry energy direct URCA processes are allowed in the almost
whole density range where the kaon condensation exists.


title:
Comptonization, the X-ray-radio correlation and the long-term
  periodicity in the chi-states of GRS 1915+105

abstract:
  We analyzed 139 chi-state observations of GRS 1915+105 with RXTE from 1997 to
2000 and found i) that the observations fall into two groups with different
Comptonization behavior, ii) that the slope of the hard X-ray component
correlates with the radio flux, thus revealing the interaction of jet and
corona, and iii) a 590 days long term periodicity in the hard X-ray and radio
components.


title:
On The Problem with Only Zeroth Landau Level Occupancy of Electrons /
  Protons in Strongly Magnetized Neutron Star Matter in $\beta$-equilibrium
  Condition- The Role of Anomalous Magnetic Moments

abstract:
  It is shown explicitly that if only the zeroth Landau level is occupied by
electrons in strongly magnetized neutron star matter in $\beta$-equilibrium
condition, then both the proton and neutron matter sectors become spin
symmetric. Whereas, the study of Pauli para-magnetism of neutron matter sector
shows that such a scenario is physically impossible. It is also shown that in
dense stellar hadronic matter in $\beta$-equilibrium in presence of strong
quantizing magnetic field, with $\sigma-\omega-\rho$ exchange type mean field
interaction and with the inclusion of magnetic dipole moments does not allow
electrons to occupy only the zeroth Landau level.


title: Supermassive black holes in scalar field galaxy halos

abstract:
  Ultra-light scalar fields provide an interesting alternative to WIMPS as halo
dark matter. In this paper we consider the effect of embedding a supermassive
black hole within such a halo, and estimate the absorption probability and the
accretion rate of dark matter onto the black hole. We show that the accretion
rate would be small over the lifetime of a typical halo, and hence that
supermassive central black holes can coexist with scalar field halos.


title:
On the Period-Luminosity-Colour-Metallicity relation and the pulsational
  characteristics of lambda Bootis type stars

abstract:
  The group of lambda Bootis type stars comprises late B- to early F-type,
Population I objects which are basically metal weak, in particular the Fe group
elements, but with the clear exception of C, N, O and S. The present work is a
continuation of the studies by Paunzen et al. (1998, A&A, 335, 533), who
presented first results on the pulsational characteristics of the lambda Bootis
stars. Since then, we have observed 22 additional objects; we found eight new
pulsators and confirmed another one. Furthermore, new spectroscopic data
(Paunzen, 2001, A&A, 373, 633) allowed us to sort out misidentified candidates
and to add true members to the group. From 67 members of this group, only two
are not photometrically investigated yet which makes our analysis highly
representative. We have compared our results on the pulsational behaviour of
the lambda Bootis stars with those of a sample of delta Scuti type objects. We
find that at least 70% of all lambda Bootis type stars inside the classical
instability strip pulsate, and they do so with high overtone modes (Q <
0.020d). Only a few stars, if any, pulsate in the fundamental mode. Compared to
the delta Scuti stars, the cool and hot borders of the instability strip of the
lambda Bootis stars are shifted by about 25mmag, towards smaller (b-y)0. Using
published abundances and the metallicity sensitive indices of the Geneva
7-colour and Stroemgren uvbybeta systems, we have derived [Z] values which
describe the surface abundance of the heavier elements for the group members.
We find that the Period-Luminosity-Colour relation for the group of lambda
Bootis stars is within the errors identical with that of the normal delta Scuti
stars. No clear evidence for a statistically significant metallicity term was
detected.


title:
A sample of southern Compact Steep Spectrum radio sources: The VLBI
  observations

abstract:
  A small sample of 7 southern Compact Steep Spectrum (CSS) radio sources has
been selected as part of the study of a larger flux-limited complete sample of
radio sources. High resolution images, using the VLBI network in the southern
hemisphere and the high resolution MERLIN array, are presented for all sources
in the CSS sample. The overall morphology of each source consists of
well-defined double lobes but with substantial diffuse and extended components
present. In the majority of cases only a fraction of the total flux density is
detected on the VLBI baselines, indicating the presence of larger extended
radio structures. However, all sources are unresolved at arcsecond scales and
are of sub-galactic size, with linear size in the range 0.1-2 kpc. The radio
properties of the sources agree well with CSS sources in other samples.


title: Perihelion motion due to the Poynting-Robertson effect

abstract:
  The force acting on a test particle moving around a body that is gravitating
and emitting electromagnetic radiation at the same time is computed up to the
second order in $1/c$, and the shift of perihelion is found. The total shift is
positive (the perihelion moves in the direction of particle revolution) and it
increases from zero to infinity as the radiation pressure to gravity ratio
increases from zero to 1. The additional shift caused by the radiation pressure
contains a term inversely proportional to eccentricity, therefore it may
dominate over the general relativistic shift if the orbit is round enough.


title: Multiple Light Echoes from Supernova 1993J

abstract:
  Using the technique of PSF-matched image subtraction, we have analyzed
archival HST/WFPC2 data to reveal details of at least two light-echo
structures, including some unknown before now, around SN 1993J in the galaxy
M81. In particular, we see one partial sheet of material 81 pc in front of the
SN and tilted ~60 deg relative to the disk plane of M81, and another 220 pc in
front of the SN, roughly parallel to the disk. The inferred echoing material is
consistent with the HI surface density detected in this region of M81's disk;
however, these data imply a fragmented covering factor for the echoing
structures. We discuss prospects for future (roughly annual) visits by HST to
image these and yet undiscovered echoes in the interstellar and circumstellar
environment of SN 1993J.


title: Far-Infrared OH fluorescent emission in Sagittarius B2

abstract:
  We present Infrared Space Observatory (ISO) observations of 16OH and 18OH
toward Sgr B2 with a spectral resolution of 35 km/s. The OH J=5/2-3/2 and
J=3/2-1/2 rotational lines of the 2Pi1/2 ladder are seen in emission while the
cross-ladder transitions (from the 2Pi3/2 J=3/2 to the J=1/2, 3/2 and 5/2
levels of the 2Pi1/2ladder), and the 2Pi3/2 J=5/2-3/2 and J=7/2-5/2 lines are
detected in absorption. The 18OH 2Pi3/2 J=5/2-3/2 Lambda-doublet at 120 mu is
also observed in absorption. All OH Lambda-doublets are resolved (except the 98
mu) and show, in addition to the strong absorption at the velocity of Sgr B2,
several velocity components associated to the gas surrounding Sgr B2 and to the
foreground clouds along the line of sight.
  No asymmetries in the line intensities of each doublet have been observed. We
have modeled the observations using a non-local radiative transfer code and
found that the OH absorption/emission must arise in a shell around Sgr B2 not
resolved by the ISO/LWS beam. The gas density is moderate, with upper limits of
10^4 cm^{-3} and 300 K in temperature. The OH abundance is high,(2-5)10^{-6}.
We argue that a widespread photon dominated region explains the enhancement of
OH abundance.


title:
Distant field BHB stars and the mass of the Galaxy I: Classification of
  halo A-type stars

abstract:
  This is the first in a series of three papers presenting a new calculation of
the mass of the Galaxy based on radial velocities and distances measured for a
sample of some 100 faint 16 < B < 20 field blue horizontal-branch (BHB) stars.
This study aims to reduce the uncertainty in the measured mass of the Galaxy by
increasing the number of halo objects at Galactocentric distances r>30 kpc with
measured radial velocities by a factor five. Faint A-type stars in the Galactic
halo have been identified from UBR photometry in six UK Schmidt fields. We
obtain accurate CCD photometry and spectra to classify these stars. This paper
describes our methods for separating out clean samples of BHB stars in a way
that is efficient in terms of telescope time required. We use the high
signal-to-noise ratio (S/N) spectra of A-type stars of Kinman, Suntzeff & Kraft
(published in 1994) to assess the reliability of two methods, and to quantify
the S/N requirements. First we revisit, refine and extend the hydrogen line
width versus colour relation as a classifier. The second method is new and
compares the shapes of the Balmer lines. Using the equivalent width of the Ca
II K line as an additional filter we find we can reproduce Kinman, Suntzeff &
Kraft's classifications with both methods.


title: Abundance determinations in HII regions and planetary nebulae

abstract:
  The methods of abundance determinations in HII regions and planetary nebulae
are described, with emphasis on the underlying assumptions and inherent
problems. Recent results on abundances in Galactic HII regions and in Galactic
and extragalactic Planetary Nebulae are reviewed.


title:
Luminosity Functions beyond the spectroscopic limit. I. Method and
  near-infrared LFs in the HDF-N and HDF-S

abstract:
  We have developed a Monte Carlo method to compute the luminosity function of
galaxies, based on photometric redshifts, which takes into account the
non-gaussianity of the probability functions, and the presence of degenerate
solutions in redshift. In this paper we describe the method and the mock tests
performed to check its reliability. The NIR luminosity functions and the
redshift distributions are determined for near infrared subsamples on the HDF-N
and HDF-S. The results on the evolution of the NIR LF, the stellar mass
function, and the luminosity density, are presented and discussed in view of
the implications for the galaxy formation models. The main results are the lack
of substantial evolution of the bright end of the NIR LF and the absence of
decline of the luminosity density up to a redshift z ~ 2, implying that most of
the stellar population in massive galaxies was already in place at such
redshift.


title:
Detection of new Optical Counterpart candidates to PSR B1951+32 with
  HST/WFPC2

abstract:
  There remain several definitive gamma-ray pulsars that are as yet undetected
in the optical regime. A classic case is the pulsar PSR B1951+32, associated
with the complex CTB 80 SNR. Previous ground based high speed 2-d optical
studies have ruled out candidates to V ~ 24. Hester (2000a) has reported an
analysis of archival HST/WFPC2 observations of the CTB 80 complex which suggest
a compact synchrotron nebula coincident with the pulsar's radio position.
Performing a similar analysis, we have identified a possible optical
counterpart within this synchrotron nebula at V ~ 25.5 - 26, and another
optical counterpart candidate nearby at V ~ 24.5. We assess the reality of
these counterpart candidates in the context of existing models of pulsar
emission.


title:
A model of nonlinear evolution and saturation of the turbulent MHD
  dynamo

abstract:
  The growth and saturation of magnetic field in conducting turbulent media
with large magnetic Prandtl numbers are investigated. This regime is very
common in low-density hot astrophysical plasmas. During the early (kinematic)
stage, weak magnetic fluctuations grow exponentially and concentrate at the
resistive scale, which lies far below the hydrodynamic viscous scale. The
evolution becomes nonlinear when the magnetic energy is comparable to the
kinetic energy of the viscous-scale eddies. A physical picture of the ensuing
nonlinear evolution of the MHD dynamo is proposed. Phenomenological
considerations are supplemented with a simple Fokker--Planck model of the
nonlinear evolution of the magnetic-energy spectrum. It is found that, while
the shift of the bulk of the magnetic energy from the subviscous scales to the
velocity scales may be possible, it occurs very slowly -- at the resistive,
rather than dynamical, time scale (for galaxies, this means that generation of
large-scale magnetic fields cannot be explained by this mechanism). The role of
Alfvenic motions and the implications for the fully developed isotropic MHD
turbulence are discussed.


title: Early-type galaxies in low-density environments

abstract:
  We describe the construction and study of an objectively-defined sample of
early-type galaxies in low-density environments. The sample galaxies are
selected from a recently-completed redshift survey using uniform and
readily-quantified isolation criteria, and are drawn from a sky area of ~700
deg^2, to a depth of 7000 k/ms and an apparent magnitude limit of b_J < 16.1.
Their early-type (E/S0) morphologies are confirmed by subsequent CCD imaging.
Five out of the nine sample galaxies show signs of morphological peculiarity
such as tidal debris or blue circumnuclear rings. We confirm that E/S0 galaxies
are rare in low-density regions, accounting for only ~8% of the total galaxy
population in such environments. We present spectroscopic observations of nine
galaxies in the sample, which are used, in conjunction with updated stellar
population models, to investigate star-formation histories. Environmental
effects on early-type galaxy evolution are investigated by comparison with a
sample of Fornax cluster E/S0s. Results from both samples are compared with
predictions from semi-analytic galaxy formation models. The Mg-sig relation of
E/S0s in low-density regions is shown to be indistinguishable from that of the
Fornax sample. Luminosity-weighted stellar ages and metallicities are
determined by considering various combinations of line-indices. At a given
luminosity, the E/S0 galaxies in low-density regions are younger than the E/S0s
in clusters (by ~2-3 Gyr), and also more metal-rich (by ~0.2 dex). We infer
that an anti-correlation of age and metallicity effects is responsible for
maintaining the zero-point of the Mg-sig relation. The youngest galaxies in our
sample show clear morphological signs of interaction. (Abridged)


title:
The shape of a small universe: signatures in the cosmic microwave
  background

abstract:
  We consider the most general parametrization of flat topologically compact
universes, complementing the work of Scannapieco, Levin and Silk to include
non-trivial shapes. We find that modifications in shape of the fundamental
domain will lead to distinct signatures in the anisotropy of the cosmic
microwave radiation. We make a preliminary assessment of the effect on three
statistics: the angular power spectrum, the distribution of identified
``circles'' on the surface of last scattering and the correlation function of
antipodal points.


title: The TeV spectrum of H1426+428

abstract:
  The BL Lac object H1426+428 was recently detected as a high energy gamma-ray
source by the VERITAS collaboration (Horan et al. 2002). We have reanalyzed the
2001 portion of the data used in the detection in order to examine the spectrum
of H1426+428 above 250 GeV. We find that the time-averaged spectrum agrees with
a power law of the shape dF/dE = 10^(-7.31 +- 0.15(stat) +- 0.16(syst)) x
E^(-3.50 +- 0.35(stat) +- 0.05(syst)) m^(-2)s^(-1)TeV^(-1) The statistical
evidence from our data for emission above 2.5 TeV is 2.6 sigma. With 95% c.l.,
the integral flux of H1426+428 above 2.5 TeV is larger than 3% of the
corresponding flux from the Crab Nebula. The spectrum is consistent with the
(non-contemporaneous) measurement by Aharonian et al. (2002) both in shape and
in normalization. Below 800 GeV, the data clearly favours a spectrum steeper
than that of any other TeV Blazar observed so far indicating a difference in
the processes involved either at the source or in the intervening space.


title:
New High Proper Motion Stars from the Digitized Sky Survey. I. Northern
  Stars with proper motion between 0.5 and 2.0 arcsec/yr at Low Galactic
  Latitudes

abstract:
  We have conducted a systematic search for high proper motion stars in the
Digitized Sky Survey, in the area of the sky north of -2.8 degrees in
declination and within 25 degrees of the galactic plane. Using the SUPERBLINK
software, a powerful automated blink comparator developed by us, we have
identified 601 stars in the magnitude range 9<r<20 with proper motions in the
range 0.5 to 2.0 arcsec/yr which have not been observed with the HIPPARCOS
satellite. Among those, we recovered 460 stars previously listed in Luyten's
proper motion catalogs (LHS, NLTT), and discovered 141 new high proper motion
stars, ranging in magnitude from R=13.0 to R=19.8. Only 9 stars from the Luyten
catalogs that were not observed by HIPPARCOS could not be recovered with
SUPERBLINK: 3 had proper motions larger than the search limit of the code
(>2.0\arcsec/yr), and 5 were missed because they were either too bright for
SUPERBLINK to handle or they are in the immediate proximity of very bright
stars. Only one of Luyten's stars (LHS1657) could not be recovered at all, even
by visual inspection of the POSS plates, and is now suspected to be bogus. The
very high success rate in the recovery by SUPERBLINK of faint Luyten stars
suggests that our new survey of high proper motion stars is at least 99 percent
complete for stars with proper motions 0.5 to 2.0 arcsec/yr down to R=19. This
paper includes a list of positions, proper motions, magnitudes, and finder
charts for all the new high proper motion stars.


title:
Correlation of the Quasi-Periodic Oscillation Frequencies of White
  Dwarf, Neutron Star, and Black Hole Binaries

abstract:
  Using data obtained in 1994 June/July with the Extreme Ultraviolet Explorer
deep survey photometer and in 2001 January with the Chandra X-ray Observatory
Low Energy Transmission Grating Spectrograph, we investigate the
extreme-ultraviolet (EUV) and soft X-ray oscillations of the dwarf nova SS Cyg
in outburst. We find quasi-periodic oscillations (QPOs) at nu_0 ~ 0.012 Hz and
nu_1 ~ 0.13 Hz in the EUV flux and at nu_0 ~ 0.0090 Hz, nu_1 ~ 0.11 Hz, and
possibly nu_2 ~ nu_0 + nu_1 ~ 0.12 Hz in the soft X-ray flux. These data,
combined with the optical data of Woudt & Warner for VW Hyi, extend the
Psaltis, Belloni, & van der Klis nu_high-nu_low correlation for neutron star
and black hole low-mass X-ray binaries (LMXBs) nearly two orders of magnitude
in frequency, with nu_low ~ 0.08 nu_high. This correlation identifies the
high-frequency quasi-coherent oscillations (so-called ``dwarf nova
oscillations'') of cataclysmic variables (CVs) with the kilohertz QPOs of
LMXBs, and the low-frequency QPOs of CVs with the horizontal branch
oscillations (or the broad noise component identified as such) of LMXBs.
Assuming that the same mechanisms produce the QPOs in white dwarf, neutron
star, and black hole binaries, we find that the data exclude the relativistic
precession model and the magnetospheric and sonic-point beat-frequency models
(as well as any model requiring the presence or absence of a stellar surface or
magnetic field); more promising are models that interpret QPOs as
manifestations of disk accretion onto any low-magnetic field compact object.


title: An ADAF in the Kerr metric: propagation of a wave pattern

abstract:
  Time evolution of an advection-dominated accretion flow is explored in terms
of relativistic fluid equations. An axially symmetric, vertically averaged mean
flow is constructed and then perturbed. An axisymmetric pattern is followed as
it propagates in the form of a wave towards the horizon of a rotating (Kerr)
black hole. Several assumptions are relaxed in comparison with previous works
(Manmoto et al. 1996).


title: The Stellar and Gas Kinematics of Several Irregular Galaxies

abstract:
  We present long-slit spectra of three irregular galaxies from which we
determinethe stellar kinematics in two of the galaxies (NGC 1156 and NGC 4449)
and ionized-gas kinematics in all three (including NGC 2366). We compare this
to the optical morphology and to the HI kinematics of the galaxies. In the
ionized gas, we see a linear velocity gradient in all three galaxies. In NGC
1156 we also detect a weak linear velocity gradient in the stars of (5+/-1/sin
i) km/s/kpc to a radius of 1.6 kpc. The stars and gas are rotating about the
same axis, but this is different from the major axis of the stellar bar which
dominates the optical light of the galaxy. In NGC 4449 we do not detect
organized rotation of the stars and place an upper limit of (3/sin i) km/s/kpc
to a radius of 1.2 kpc. For NGC 4449, which has signs of a past interaction
with another galaxy, we develop a model to fit the observed kinematics of the
stars and gas. In this model the stellar component is in a rotating disk seen
nearly face-on while the gas is in a tilted disk with orbits whose planes
precess in the gravitational potential. This model reproduces the apparent
counter-rotation of the inner gas of the galaxy. The peculiar orbits of the gas
are presumed due to acquisition of gas in the past interaction.


title:
Determination of the Linear Mass Power Spectrum From the Mass Function
  of Galaxy Clusters

abstract:
  We develop a new method to determine the linear mass power spectrum using the
mass function of galaxy clusters. We obtain the rms mass fluctuation sigma (M)
using the expression for the mass function in the Press & Schechter (1974),
Sheth, Mo & Tormen (2001) and Jenkins et al. (2001) formalisms. We apply
different techniques to recover the adimensional power spectrum Delta ^{2}(k)
from sigma (M) namely the k_{eff} approximation, the singular value
decomposition and the linear regularization method. The application of these
techniques to the tCDM and LCDM GIF simulations shows a high efficiency in
recovering the theoretical power spectrum over a wide range of scales. We
compare our results with those derived from the power spectrum of the spatial
distribution of the same sample of clusters in the simulations obtained by
application of the classical Feldman, Kaiser & Peacock (1994), FKP, method. We
find that the mass function based method presented here can provide a very
accurate estimate of the linear power spectrum, particularly for low values of
k. This estimate is comparable, or even better behaved, than the FKP solution.
The principal advantage of our method is that it allows the determination of
the linear mass power spectrum using the joint information of objects of a wide
range of masses without dealing with specific assumptions on the bias relative
to the underlying mass distribution.


title:
The planet search program at the ESO Coude Echelle spectrometer. III.
  The complete Long Camera survey results

abstract:
  We present the complete results of the planet search program carried out at
the ESO Coude Echelle Spectrometer (CES) on La Silla, using the Long Camera
from Nov. 1992 to April 1998. The CES survey has monitored 37 late-type (F8V -
M5V) stars in the southern hemisphere for variations in their differential
radial velocities (RV) in order to detect Doppler reflex motions caused by
planetary companions. This led to the discovery of the first extrasolar planet
in an Earth-like orbit around the young (ZAMS) and active G0V star iota
Horologii (Kuerster et al. 2000). Here we present the RV results for all survey
stars and perform a statistical examination of the whole data-set. Each star is
tested for RV variability, RV trends (linear and non-linear) and significant
periodic signals. Beta Hyi and eps Ind are identified as long-term,
low-amplitude RV variables. Furthermore, for 30 CES survey stars we determine
quantitative upper mass-limits for giant planets based on our long-term RV
results. We find that the CES Long Camera survey would have detected
short-period (51 Peg-type) planets around all 30 stars but no planets with m
sin i < 1 M_Jup at orbital separations larger than 2 AU. Finally, we
demonstrate that the CES planet search can be continued without applying
velocity corrections to the RV results coming from the currently installed Very
Long Camera at the CES.


title: The Structure of Winds in AGB Stars

abstract:
  Most dusty winds are described by a set of similarity functions of a single
independent variable that can be chosen as the overall optical depth at visual.
The self-similarity implies general scaling relations among the system
parameters, in agreement with observations. Dust drift through the gas has a
major impact on the structure of most winds.


title: On the mass function of star clusters

abstract:
  Clusters that form in total 10^3 < N < 10^5 stars (type II clusters) lose
their gas within a dynamical time as a result of the photo-ionising flux from O
stars. Sparser (type I) clusters get rid of their residual gas on a timescale
longer or comparable to the nominal crossing time and thus evolve approximately
adiabatically. This is also true for massive embedded clusters (type III) for
which the velocity dispersion is larger than the sound speed of the ionised
gas. On expelling their residual gas, type I and III clusters are therefore
expected to lose a smaller fraction of their stellar component than type II
clusters. We outline the effect this has on the transformation of the mass
function of embedded clusters (ECMF), which is directly related to the mass
function of star-cluster-forming molecular cloud cores, to the ``initial'' MF
of bound gas-free star clusters (ICMF). The resulting ICMF has, for a
featureless power-law ECMF, a turnover near 10^{4.5} Msun and a peak near 10^3
Msun. The peak lies around the initial masses of the Hyades, Praesepe and
Pleiades clusters. We also find that the entire Galactic population II stellar
spheroid can be generated if star formation proceeded via embedded clusters
distributed like a power-law MF with exponent 0.9 < beta < 2.6.


title:
Spectroscopic Detection of a Stellar-like Photosphere in an Accreting
  Protostar

abstract:
  We present the first spectrum of a highly veiled, strongly accreting
protostar which shows photospheric absorption features and demonstrates the
stellar nature of its central core. We find the spectrum of the luminous (L_bol
= 10 L_sun) protostellar source, YLW 15, to be stellar-like with numerous
atomic and molecular absorption features, indicative of a K5 IV/V spectral type
and a continuum veiling r_k = 3.0. Its derived stellar luminosity (3 L_sun) and
stellar radius (3.1 R_sun) are consistent with those of a 0.5 M_sun
pre-main-sequence star. However, 70% of its bolometric luminosity is due to
mass accretion, whose rate we estimate to be 1.6 E-6 M_sun / yr onto the
protostellar core. We determine that excess infrared emission produced by the
circumstellar accretion disk, the inner infalling envelope, and accretion
shocks at the surface of the stellar core of YLW 15 all contribute signifi-
cantly to its near-IR continuum veiling. Its projected rotation velocity v sin
i = 50 km / s is comparable to those of flat-spectrum protostars but
considerably higher than those of classical T Tauri stars in the rho Oph cloud.
The protostar may be magnetically coupled to its circumstellar disk at a radius
of 2 R_*. It is also plausible that this protostar can shed over half its
angular momentum and evolve into a more slowly rotating classical T Tauri star
by remaining coupled to its circumstellar disk (at increasing radius) as its
accretion rate drops by an order of magnitude during the rapid transition
between the Class I and Class II phases of evolution. The spectrum of WL 6 does
not show any photospheric absorption features, and we estimate that its
continuum veiling is r_k >= 4.6. Together with its low bolometric luminosity (2
L_sun), this dictates that its central core is very low mass, ~0.1 M_sun.


title:
Anisotropies in the Motions and Positions of the Galactic Globular
  Clusters

abstract:
  The velocity ellipsoid for 38 globular clusters with [Fe/H] <= -1.0 is
derived and shown to be significantly anisotropic with major axis directed
towards low Galactic latitude. Principal axes of the spatial distribution of
different groups of clusters are derived and compared with the velocity
ellipsoid. The metal poor cluster spatial distribution is significantly
flattened along an axis which coincides within the uncertainties with the major
axis of the velocity ellipsoid. Given the observed steep age-metallicity
relation for metal poor clusters, one speculative interpretation of the data is
that an initially flattened filament underwent a relatively rapid initial
transverse collapse forming satellite galaxies and metal poor globular clusters
while the protogalaxy collapsed and assembled more slowly along the filament
acquiring and/or redistributing angular momentum in the process.


title:
Parameterization of Dark-Energy Properties: a Principal-Component
  Approach

abstract:
  Considerable work has been devoted to the question of how to best
parameterize the properties of dark energy, in particular its equation of state
w. We argue that, in the absence of a compelling model for dark energy, the
parameterizations of functions about which we have no prior knowledge, such as
w(z), should be determined by the data rather than by our ingrained beliefs or
familiar series expansions. We find the complete basis of orthonormal
eigenfunctions in which the principal components (weights of w(z)) that are
determined most accurately are separated from those determined most poorly.
Furthermore, we show that keeping a few of the best-measured modes can be an
effective way of obtaining information about w(z).


title: Models of Irradiated Extrasolar Giant Planets

abstract:
  We review some of the characteristics of irradiated extrasolar giant planets
(EGPs), in anticipation of their direct detection from the ground and from
space. Spectral measurements are the key to unlocking their structural and
atmospheric characteristics and to determining the true differences between
giant planets and brown dwarfs. In this spirit, the theoretical spectral and
atmospheric calculations we summarize here are in support of the many searches
for EGPs to be conducted in the coming decade by astronomers from around the
world.


title: The Brown Dwarf Deficit in Taurus: Evidence for a Non-Universal IMF

abstract:
  We present the results of a deep, optical/IR wide field imaging survey of
selected fields in the nearby (d ~ 140 pc) Taurus star-forming region. We
report the discovery of 9 new members with spectral types M5.75-M9.5. We derive
an Initial Mass Function encompassing 54% of the known members in Taurus.
Comparison with dense regions like the Trapezium Cluster in Orion shows that
Taurus has produced x2 less brown dwarfs. We suggest that the lower frequency
of brown dwarfs in Taurus may result from the low-density star-forming
environment, leading to larger minimum Jeans masses.


title:
Constraints on the Baryonic Compression and Implications for the
  Fraction of Dark Halo Lenses

abstract:
  We predict the fraction of dark halo lenses, that is, the fraction of lens
systems produced by the gravitational potential of dark halos, on the basis of
a simple parametric model of baryonic compression. The fraction of dark halo
lenses primarily contains information on the effect of baryonic compression and
the density profile of dark halos, and is expected to be insensitive to
cosmological parameters and source population. The model we adopt comprises the
galaxy formation probability p_g(M) which describes the global efficiency of
baryonic compression and the ratio of circular velocities of galaxies to virial
velocities of dark halos gamma_v=v_c/v_{vir} which means how the inner
structure of dark halos is modified due to baryonic compression. The model
parameters are constrained from the velocity function of galaxies and the
distribution of image separations in gravitational lensing, although the
degeneracy between model parameters still remains. We show that the fraction of
dark halo lenses depends strongly on gamma_v and the density profile of dark
halos such as inner slope alpha. This means that the observation of the
fraction of dark halos can break the degeneracy between model parameters if the
density profile of dark halo lenses is fully settled. On the other hand, by
restricting gamma_v to physically plausible range we can predict the lower
limit of the fraction of dark halo lenses on the basis of our model. Our result
indicates that steeper inner cusps of dark halos (alpha >~ 1.5) or too
centrally concentrated dark halos are inconsistent with the lack of dark halo
lenses in observations.


title:
Dispersal of massive star products and consequences for galactic
  chemical evolution

abstract:
  The processes that disperse the products of massive stars from their birth
sites play a fundamental role in determining the observed abundances. I discuss
parameterizations for element dispersal and their roles in chemical evolution,
with an emphasis on understanding present-day dispersion and homogeneity in
metallicity. Turbulence dominates mixing processes, with characteristic
timescales of order 10^8 yr, implying significant dilution of metals into the
ISM. This permits a rough estimate of the metallicity distribution function of
enrichment events. Many systems, including the Milky Way and nearby galaxies,
show metallicity dispersions that as yet appear consistent with pure
inhomogeneous evolution. There are also systems like I Zw~18 that show strong
homogenization, perhaps tied to small galaxy size, high star formation rate,
and/or superwinds.


title: Inferring X-ray coronal structures from Zeeman-Doppler images

abstract:
  We have modelled the X-ray emission from the young rapid rotator AB Doradus
(P = 0.514 days) using as a basis Zeeman-Doppler maps of the surface magnetic
field. This allows us to reconcile the apparently conflicting observations of a
high X-ray emission measure and coronal density with a low rotational
modulation in X-rays. The technique is to extrapolate the coronal field from
the surface maps by assuming the field to be potential. We then determine the
coronal density for an isothermal corona by solving hydrostatic equilibrium
along each field line and scaling the plasma pressure at the loop footpoints
with the magnetic pressure. We set the density to zero along those field lines
that are open and those where at any point along their length the plasma
pressure exceeds the magnetic pressure. We then calculate the optically thin
X-ray emission measure and rotational modulation for models with a range of
coronal densities. Although the corona can be very extended, much of the
emission comes from high-latitude regions close to the stellar surface. Since
these are always in view as the star rotates, there is little rotational
modulation. We find that emission measures in the observed range of 10^52.8 -
10^53.3 per cubic centimetre can be reproduced with densities in the range 10^9
- 10^10.7 per cubic centimetre for coronae at temperatures of 10^6-10^7 K.


title:
Nonthermal radiation from clusters of galaxies: the role of merger
  shocks in particle acceleration

abstract:
  Nonthermal radiation is observed from clusters of galaxies in the radio, hard
X-rays, and possibly in the soft X-ray/UV bands. While it is known that
radiative processes related to nonthermal electrons are responsible for this
radiation, the sites and nature of particle acceleration are not known. We
investigate here the acceleration of protons and electrons in the shocks
originated during mergers of clusters of galaxies, where the Fermi acceleration
may work. We propose a semi-analytical model to evaluate the Mach number of the
shocks generated during clusters mergers and we use this procedure to determine
the spectrum of the accelerated particles for each one of the shocks produced
during the merger history of a cluster. We follow the proton component,
accumulated over cosmological time scales, and the short lived electron
component. We conclude that efficient particle acceleration, resulting in
nonthermal spectra that compare to observations, occurs mainly in minor
mergers, namely mergers between clusters with very different masses. Major
mergers, often invoked to be sites for the production of extended radio halos,
are found to have on average too weak shocks and are unlikely to result in
appreciable nonthermal activity.


title: Variation of Acoustic Power with Magnetic Field as seen in Gong+ Data

abstract:
  The acoustic spectra in sunspots are known to be richer in higher frequency
power. We have attempted a generalized study of the effect of magnetic fields
on the shape of the acoustic spectrum using GONG+ bread-board data (spatial
scale of ~ 2 arc-sec per pixel) of 11 May, 2000 and 12 June, 2000. The mean
power spectra of the velocity oscillations were obtained by averaging over
several spectra for different values of the magnetic field. With increasing
magnetic field, the acoustic power increases at higher frequencies and
decreases at lower frequencies with a transition at ~= 5 mHz. This behaviour is
slightly different from earlier results obtained from SOHO/MDI data.


title: Photon-Axion mixing in an inhomogeneous universe

abstract:
  We consider the dimming of photons from high redshift type 1a supernovae by
mixing with a pseudoscalar axion field in the intergalactic medium. We model
the electron density using a lognormal probability distribution and assume
frozen in magnetic fields. Assuming the magnetic fields are produced in the
early universe we are unable to obtain sufficient dimming in order to explain
the apparent acceleration without violating the bounds on the frequency
dependence of the dimming. We also show that any axion mixing leading to a
reduction in optical luminosities would also lead to a significant reduction in
the polarisation of UV light from intermediate redshift objects which may be
detected in the future.


title:
Fast CMB Power Spectrum Estimation of Temperature and Polarisation with
  Gabor Transforms

abstract:
  We extend the analysis of Gabor transforms on a Cosmic Microwave Background
(CMB) temperature map (Hansen, Gorski and Hivon 2002) to polarisation. We study
the temperature and polarisation power spectra on the cut sky, the so-called
pseudo power spectra. The transformation kernels relating the full-sky
polarisation power spectra and the polarisation pseudo power spectra are found
to be similar to the kernel for the temperature power spectrum. This fact is
used to construct a fast power spectrum estimation algorithm using the pseudo
power spectrum of temperature and polarisation as data vectors in a maximum
likelihood approach. Using the pseudo power spectra as input to the likelihood
analysis solves the problem of having to invert huge matrices which makes the
standard likelihood approach infeasible.


title: Science prospects with INTEGRAL

abstract:
  With the launch of ESA's INTEGRAL satellite in october 2002, a gamma-ray
observatory will be placed in orbit providing a multiwavelength coverage from a
few keV up to 10 MeV for the study of high energy phenomena in the universe.
Among the major scientific objectives of INTEGRAL are the study of compact
objects, and in particular of microquasars, stellar nucleosynthesis, high
energy transients, particle acceleration and interaction processes, and
galactic diffuse emission. In this review I will expose the science prospects
of INTEGRAL in the above mentioned fields.


title: An unidentified TeV source in the vicinity of Cygnus OB2

abstract:
  Deep observation (~113 hrs) of the Cygnus region at TeV energies using the
HEGRA stereoscopic system of air Cerenkov telescopes has serendipitously
revealed a signal positionally inside the core of the OB association Cygnus
OB2, at the edge of the 95% error circle of the EGRET source 3EG J2033+4118,
and ~0.5deg north of Cyg X-3. The centre of gravity of the source is RA
(J2000): 20hr 32m 07s +-9.2s (stat) +-2.2s (sys), Dec (J2000): +41deg 30' 30"
+-2.0' (stat) +-0.4' (sys). The source is steady, has a post-trial significance
of +4.6 sigma, indication for extension with radius 5.6' at the ~3sigma level,
and has a differential power-law flux with hard photon index of -1.9 +-0.3
(stat) +-0.3 (sys). The integral flux above 1 TeV amounts ~3% that of the Crab.
No counterpart for the TeV source at other wavelengths is presently identified,
and its extension would disfavour an exclusive pulsar or AGN origin. If
associated with Cygnus OB2, this dense concentration of young, massive stars
provides an environment conducive to multi-TeV particle acceleration and likely
subsequent interaction with a nearby gas cloud. Alternatively, one could
envisage gamma-ray production via a jet-driven termination shock.


title:
Directional scintillation detector for the detection of the wind of
  WIMPs

abstract:
  The quenching factor of the proton recoil in the stilbene scintillator was
measured with a 252Cf neutron source and was found to be 0.1 - 0.17 in the
recoil energy range between 300 keV and 3 MeV. It was found to depend on the
direction of the recoil proton. The directional anisotropy of the quenching
factor could be used to detect the wind of the WIMPs caused by the motion of
the earth around the galactic center.


title:
Investigation of the large-scale neutral hydrogen near the supernova
  remnant W28

abstract:
  The distribution and kinematics of neutral hydrogen have been studied in a
wide area around the supernova remnant W28. A 2.5 x 2.5 arcdeg field centered
at l = 6.5 arcdeg, b = 0 arcdeg was surveyed using the Parkes 64-m radio
telescope (HPBW 14.7 arcmin at lambda 21 cm). Even though W28 is located in a
complex zone of the Galactic plane, we have found different HI features which
are evidence of the interaction between W28 and its surrounding gas.


title: The ANTARES project

abstract:
  The ANTARES deep-sea neutrino telescope will be located at a depth of 2400 m
in the Mediterranean Sea. Deployment of the detector will commence this Autumn
and is expected to be completed by the end of 2004. With a surface area of the
order of 0.1 km^2 it will be one of the largest European detectors. The aim of
neutrino telescopes is to detect high-energy neutrinos from astrophysical
sources whilst also providing information on the early Universe. Successful
operation of ANTARES in a deep sea environment constitutes an important
milestone towards the ultimate goal of the construction of an underwater
neutrino telescope at the cubic-kilometre scale. The sky coverage of
astrophysical sources offered by a Mediterranean neutrino telescope is
complementary to any similar device at the South Pole. The current status of
the project is discussed and the expected performance of the detector is
described in the context of the scientific programme of the project which
comprises astrophysical studies, dark matter searches and neutrino
oscillations.


title: The supernova associated with GRB 020405

abstract:
  We use the very simple and successful Cannonball (CB) model of gamma ray
bursts (GRBs) and their afterglows (AGs) to analyze the observations of the
mildly extinct optical AG of the relatively nearby GRB 020405. We show that GRB
020405 was associated with a 1998bw-like supernova (SN) at the GRB's redshift
that appeared dimmer and redder than SN1998bw because of extinction in the host
and our Galaxy. The case for the SN/GRB association --advocated in the CB
model-- is becoming indubitable. We discuss the extent to which the GRB/SN
connection is model-dependent.


title:
Microlensing Searches for Extrasolar Planets: Current Status and Future
  Prospects

abstract:
  I review results from, and future prospects for, microlensing searches for
extrasolar planets. Analyses of well-sampled microlensing light curves by
several collaborations have demonstrated that current searches are sensitive to
Jupiter-mass planets with few AU separations from M-dwarfs in the Galactic
bulge. To date, however, no unambiguous planetary detections have been made.
Detailed analysis has shown that this null result implies that <33% of typical
stars (i.e. M-dwarfs) in the Galactic bulge have Jupiter-mass companions with
separations between 1.5 and 4 AU, and <45% have three-Jupiter-mass companions
between 1 and 7 AU. The recent dramatic increase in the number of alerts per
year will allow ongoing microlensing searches to probe companion fractions of a
few percent within a few years.


title: Dark halo densities, substructure, and the initial power spectrum

abstract:
  Although the currently favored cold dark matter plus cosmological constant
model for structure formation assumes an n=1 scale-invariant initial power
spectrum, most inflation models produce at least mild deviations from n=1.
Because the lever arm from the CMB normalization to galaxy scales is long, even
a small ``tilt'' can have important implications for galactic observations.
Here we calculate the COBE-normalized power spectra for several well-motivated
models of inflation and compute implications for the substructure content and
central densities of galaxy halos. Using an analytic model, normalized against
N-body simulations, we show that while halos in the standard (n=1) model are
overdense by a factor of ~6 compared to observations, several of our example
inflation+LCDM models predict halo densities well within the range of
observations, which prefer models with n ~ 0.85. We go on to use a
semi-analytic model (also normalized against N-body simulations) to follow the
merger histories of galaxy-sized halos and track the orbital decay, disruption,
and evolution of the merging substructure. Models with n ~0.85 predict a factor
of ~3 fewer subhalos at a fixed circular velocity than the standard $n = 1$
case. Although this level of reduction does not resolve the ``dwarf satellite
problem'', it does imply that the level of feedback required to match the
observed number of dwarfs is sensitive to the initial power spectrum. Finally,
the fraction of galaxy-halo mass that is bound up in substructure is consistent
with limits imposed by multiply imaged quasars for all models considered: f_sub
> 0.01 even for an effective tilt of n ~0.8.We conclude that, at their current
level, lensing constraints of this kind do not provide strong limits on the
primordial power spectrum.


title: Feedback Processes in Early-Type Galaxies

abstract:
  We present a phenomenological model of feedback in early-type galaxies that
tracks the evolution of the interstellar medium gas mass, metallicity, and
temperature. Modeling the star formation rate as a Schmidt law with a
temperature-dependent efficiency, we find that intermittent episodes of star
formation are common in moderate-size ellipticals. Our model is applicable in
the case in which the thermalization time from SN is sufficiently long that
spatial variations are relatively unimportant, an appropriate assumption for
the empirical parameters adopted here. The departure from a standard scenario
of passive evolution implies significantly younger luminosity-weighted ages for
the stellar populations of low-mass galaxies at moderate redshifts, even though
the more physically meaningful mass-weighted ages are changed only slightly.
Secondary bursts of star formation also lead to a natural explanation of the
large scatter in the NUV-optical relation observed in clusters at moderate
redshift and account for the population of E+A galaxies that display a
spheroidal morphology. As the late-time formation of stars in our model is due
to the gradual cooling of the interstellar medium, which is heated to
temperatures ~1 keV by the initial burst of supernovae, our conclusions do not
rely on any environmental effects or external mechanisms. Furthermore, a simple
estimate of the X-ray emission from this supernova heated gas leads to an L_X
vs L_B correlation that is in good agreement with observed values. Thus
feedback processes may be essential to understanding the observed properties of
early-type galaxies from the optical to the X-ray.


title: Planetesimal Formation by Gravitational Instability

abstract:
  We investigate the formation of planetesimals via the gravitational
instability of solids that have settled to the midplane of a circumstellar
disk. Vertical shear between the gas and a subdisk of solids induces turbulent
mixing which inhibits gravitational instability. Working in the limit of small,
well-coupled particles, we find that the mixing becomes ineffective when the
surface density ratio of solids to gas exceeds a critical value. Solids in
excess of this precipitation limit can undergo midplane gravitational
instability and form planetesimals. However, this saturation effect typically
requires increasing the local ratio of solid to gaseous surface density by
factors of two to ten times cosmic abundances, depending on the exact
properties of the gas disk. We discuss existing astrophysical mechanisms for
augmenting the ratio of solids to gas in protoplanetary disks by such factors,
and investigate a particular process that depends on the radial variations of
orbital drift speeds induced by gas drag. This mechanism can concentrate
millimeter sized chondrules to the supercritical surface density in < few x
10^6 years, a suggestive timescale for the disappearance of dusty disks in T
Tauri stars. We discuss the relevance of our results to some outstanding
puzzles in planet formation theory: the size of the observed solar system, and
the rapid type I migration of Earth mass bodies.


title: Pion production in the inner disk around Cygnus X-1

abstract:
  Neutron production via ^{4}He breakup and p(p, n{pi}^+)p is considered in the
innermost region of an accretion disk surrounding a Kerr Black Hole. These
reactions occur in a plasma in Wien equilibrium, where (radiatively produced)
pair production equals annihilation. Cooling of the disk is assumed to be due
to unsaturated inverse Comptonization of external soft photons and to the
energy needed to ignite both nuclear reactions. Assuming matter composition of
90% Hydrogen and 10% He, it is shown that, close to the border of this region,
neutron production is essentially from ^{4}He breakup. Close to the horizon,
the contribution from p(p, n{pi}^+)p to the neutron production is comparable to
that from the breakup. It is shown that the viscosity generated by the
collisions of the accreting matter with the neutrons may drive stationary
accretion, for accretion rates below a critical value. In this case, solution
to the disk equations is double-valued and for both solutions protons
overnumber the pairs. It is claimed that these solutions may mimic the states
of high and low luminosity observed in Cygnus X-1 and related sources. This
would be explained either by the coupling of thermal instability to the
peculiar behavior of the viscosity parameter alpha with the ion temperature
that may intermittently switch accretion off or by the impossibility of a
perfect tuning for both thermal and pair equilibrium in the disk, a fact that
forces the system to undergo a kind of limit cycle behavior around the upper
solution.


title: Stellar Companions to Stars with Planets

abstract:
  A combination of high-resolution and wide-field imaging reveals two binary
stars and one triple star system among the sample of the first 11 stars with
planets detected by radial velocity variations. High resolution speckle or
adaptive optics (AO) data probe subarcsecond scales down to the diffraction
limit of the Keck 10-m or Lick 3-m, and direct images or AO images are
sensitive to a wider field, extending to 10" or 38", depending upon the camera.
One of the binary systems -- HD 114762 -- was not previously known to be a
spatially resolved multiple system; additional data taken with the combination
of Keck adaptive optics and NIRSPEC are used to characterize the new companion.
The second binary system -- Tau Boo -- was a known multiple with two
conflicting orbital solutions; the current data will help constrain the
discrepant estimates of periastron time and separation. Another target -- 16
Cyg B -- was a known common proper motion binary, but the current data resolve
a new third component, close to the wide companion 16 Cyg A. Both the HD 114762
and 16 Cyg B systems harbor planets in eccentric orbits, while the Tau Boo
binary contains an extremely close planet in a tidally-circularized orbit.
Although the sample is currently small, the proportion of binary systems is
comparable to that measured in the field over a similar separation range.
Incorporating the null result from another companion search project lowers the
overall fraction of planets in binary systems, but the detections in our survey
reveal that planets can form in binaries separated by less than 50 AU.


title: Photometric parameters of edge-on galaxies from 2MASS observations

abstract:
  To analyze the vertical structure of edge-on galaxies, we have used images of
a large uniform sample of flat galaxies that have been taken during the 2MASS
all-sky survey. The photometric parameters, such as the radial scale length,
the vertical scale height, and the deprojected central surface brightness of
galactic disks have been obtained. We find a strong correlation between the
central surface brightness and the ratio of the vertical scale height to the
vertical scale length: the thinner the galaxy, the lower the central surface
brightness of its disk. The vertical scale height does not increase
systematically with the distance from the galaxy center in the frames of this
sample.


title:
The Likely Near-Infrared Counterpart to the Anomalous X-Ray Pulsar 1E
  1048.1-5937

abstract:
  We report our discovery of the likely near-infrared counterpart to the
anomalous X-ray pulsar (AXP) 1E1048.1-5937, using observations from the 6.5-m
Baade (Magellan-I) telescope in Chile. We derived a precise position for the
X-ray source using archival data from the Chandra X-Ray Observatory. This
position is inconsistent with a position reported earlier from XMM-Newton, but
we show that the originally reported XMM-Newton position suffered from attitude
reconstruction problems. Only two of the infrared objects in a 17 arcsec x 17
arcsec field containing the target have unusual colors, and one of these has
colors consistent with those of the identified counterparts of two other AXPs.
The latter object is also the only source detected within the 0.6 arcsec
Chandra error circle, and we identify it as the counterpart to 1E1048.1-5937.
This is the first AXP counterpart detected in multiple infrared bands, with
magnitudes J=21.7(3), H=20.8(3), and K=19.4(3). There is marginal evidence for
spectral flattening at longer wavelengths.


title: A High-Resolution Study of Eta Carinae's Outer Ejecta

abstract:
  Eta Carinae is a very luminous and unstable evolved star. Outflowing material
ejected during the star's giant eruption in 1843 surrounds it as a nebula which
consists of an inner bipolar region(the Homunculus) and the Outer Ejecta. The
outer ejecta is very filamentary and shaped irregularly. Kinematic analysis,
however, shows a regular bi-directional expansion despite of the complex
morphology. Radial velocities in the outer ejecta reach up to 2000 kms/s and
give rise to X-ray emission first detected by ROSAT. We will present a detailed
study of the outer ejecta based on HST images, high-resolution echelle spectra
for kinematic studies, images from CHANDRA/ACIS and HST-STIS spectra.


title: LBV (Candidate) Nebulae: Bipolarity and Outflows

abstract:
  The most massive evolved stars (above 50 M_sun) undergo a phase of extreme
mass loss in which their evolution is reversed from a redward to a blueward
motion in the HRD. In this phase the stars are known as Luminous Blue Variables
(LBVs) and they are located in the HRD close to the Humphreys-Davidson limit.
It is far from understood what causes the strong mass loss or what triggers the
so-called giant eruptions, active events in which in a short time a large
amount of mass is ejected. Here I will present results from a larger project
devoted to better understand LBVs through studying the LBV nebulae. These
nebulae are formed as a consequence of the strong mass loss. The analysis
concentrates on the morphology and kinematics of these nebulae. Of special
concern was the frequently observed bipolar nature of the LBV nebulae.
Bipolarity seems to be a general feature and strongly constrains models of the
LBV phase and especially of the formation of the nebulae. In addition we found
outflows from LBV nebulae, the first evidence for ongoing instabilities in the
nebulae.


title:
Measurement of the cosmic ray hadron spectrum up to 30 TeV at mountain
  altitude: the primary proton spectrum

abstract:
  The flux of cosmic ray hadrons at the atmospheric depth of 820 g/cm^2 has
been measured by means of the EAS-TOP hadron calorimeter (Campo Imperatore,
National Gran Sasso Laboratories, 2005 m a.s.l.). The hadron spectrum is well
described by a single power law : S(E_h) = (2.25 +- 0.21 +- 0.34(sys))
10^(-7)(E_h/1000)^(-2.79 +- 0.05) m^(-2) s^(-1) sr^(-1) GeV^(-1) over the
energy range 30 GeV-30 TeV. The procedure and the accuracy of the measurement
are discussed. The primary proton spectrum is derived from the data by using
the CORSIKA/QGSJET code to compute the local hadron flux as a function of the
primary proton spectrum and to calculate and subtract the heavy nuclei
contribution (basing on direct measurements). Over a wide energy range E_0 =
0.5-50 TeV its best fit is given by a single power law : S(E_0) = (9.8 +- 1.1
+- 1.6(sys)) 10^(-5) (E_0/1000)^(-2.80 +- 0.06) m^(-2) s^(-1) sr^(-1) GeV^(-1).
The validity of the CORSIKA/QGSJET code for such application has been checked
using the EAS-TOP and KASCADE experimental data by reproducing the ratio of the
measured hadron fluxes at the two experimental depths (820 and 1030 g/cm^2
respectively) at better than 10% in the considered energy range.


title:
Differential rotation and meridional flow in the solar supergranulation
  layer: Measuring the eddy viscosity

abstract:
  We measure the eddy viscosity in the outermost layers of the solar convection
zone by comparing the rotation law computed with the Reynolds stress resulting
from f-plane simulations of the angular momentum transport in rotating
convection with the observed differential rotation pattern. The simulations
lead to a negative vertical and a positive horizontal angular momentum
transport. The consequence is a subrotation of the outermost layers, as it is
indeed indicated both by helioseismology and the observed rotation rates of
sunspots. In order to reproduce the observed gradient of the rotation rate a
value of about 1.5 x 10^{13} cm/s for the eddy viscosity is necessary.
Comparison with the magnetic eddy diffusivity derived from the sunspot decay
yields a surprisingly large magnetic Prandtl number of 150 for the
supergranulation layer. The negative gradient of the rotation rate also drives
a surface meridional flow towards the poles, in agreement with the results from
Doppler measurements. The successful reproduction of the abnormally positive
horizontal cross correlation (on the northern hemisphere) observed for bipolar
groups then provides an independent test for the resulting eddy viscosity.


title: On the Temperature Structure of M87

abstract:
  We revisit the XMM-Newton observation of M87 focusing our attention on the
temperature structure. We find that spectra for most regions of M87 can be
adequately fit by single temperature models. Only in a few regions, which are
cospatial with the E and SW radio arms, we find evidence of a second
temperature. The cooler component (kT ~ 0.8-1 keV) fills a small volume
compared to the hotter component (kT ~ 1.6-2.5 keV), it is confined to the
radio arms rather than being associated with the potential well of the central
cD and is probably structured in blobs with typical sizes smaller than a few
100 pc. Thermal conduction must be suppressed for the cool blobs to survive in
the hotter ambient gas. Since the cool gas is observed only in those regions of
M87 where we have evidence of radio halos our results favor models in which
magnetic fields play a role in suppressing heat conduction. The entropy of the
cool blobs is in general smaller than that of the hot phase gas thus cool blobs
cannot originate from adiabatic evolution of hot phase gas entrained by buoyant
radio bubbles, as suggested by Churazov et al. (2001). An exploration of
alternative origins for the cool gas leads to unsatisfactory results.


title:
Strongly absorbed quiescent X-ray emission from the X-ray transient XTE
  J0421+56 (CI Cam) observed with XMM-Newton

abstract:
  We have observed the X-ray transient XTE J0421+56 in quiescence with
XMM-Newton. The observed spectrum is highly unusual being dominated by an
emission feature at ~6.5 keV. The spectrum can be fit using a partially covered
power-law and Gaussian line model, in which the emission is almost completely
covered (covering fraction of 0.98_{-0.06}^{+0.02}) by neutral material and is
strongly absorbed with an N_H of (5_{-2}^{+3}) x 10^{23} atom cm^{-2}. This
absorption is local and not interstellar. The Gaussian has a centroid energy of
6.4 +/- 0.1 keV, a width < 0.28 keV and an equivalent width of 940
^{+650}_{-460} eV. It can be interpreted as fluorescent emission line from
iron. Using this model and assuming XTE J0421+56 is at a distance of 5 kpc, its
0.5-10 keV luminosity is 3.5 x 10^{33} erg s^{-1}. The Optical Monitor onboard
XMM-Newton indicates a V magnitude of 11.86 +/- 0.03. The spectra of X-ray
transients in quiescence are normally modeled using advection dominated
accretion flows, power-laws, or by the thermal emission from a neutron star
surface. The strongly locally absorbed X-ray emission from XTE J0421+56 is
therefore highly unusual and could result from the compact object being
embedded within a dense circumstellar wind emitted from the supergiant B[e]
companion star. The uncovered and unabsorbed component observed below 5 keV
could be due either to X-ray emission from the supergiant B[e] star itself, or
to the scattering of high-energy X-ray photons in a wind or ionized corona,
such as observed in some low-mass X-ray binary systems.


title:
Rotation as a source of asymmetry in the double-peak lightcurves of the
  bright EGRET pulsars

abstract:
  We investigate the role of rotational effects in inducing asymmetry present
above ~5 GeV in the double-peak lightcurves of the bright EGRET pulsars: Vela,
Crab, and Geminga. According to Thompson 2001, the trailing peak dominates over
the leading peak above ~5 GeV consistently for all three pulsars, even though
this is not the case over the entire energy range of EGRET, i.e. above ~100
MeV. We present the results of Monte Carlo simulations of electromagnetic
cascades in a pulsar magnetosphere within a single-polar-cap scenario with
rotationally-induced propagation effects of the order of v/c (where v is the
local corotation velocity). We find that even in the case of nearly aligned
rotators with spin periods of P ~ 0.1 s rotation may lead to asymmetric (with
respect to the magnetic axis) magnetic photon absorption which in turn leads to
asymmetric gamma-ray pulse profiles. The resulting features - softer spectrum
of the leading peak and the dominance of the trailing peak above ~5 GeV - agree
qualitatively with the EGRET data of the bright gamma-ray pulsars.


title:
HST, VLT, and NTT imaging search for wide companions to bona-fide and
  candidate brown dwarfs in the Cha I dark cloud

abstract:
  We present results from a deep imaging search for companions around the young
bona-fide and candidate brown dwarfs Cha Ha 1 to 12 in the Cha I dark cloud,
performed with HST WFPC2 (R, I, Ha), VLT FORS1 (VRI), and NTT SofI (JHK). We
find 16 faint companion candidates around five primaries with separations
between 1.5" and 7" and magnitudes in R & I from 19 to 25 mag, i.e. up to 8 mag
fainter than the primaries. While most of these companion candidates are
probably unrelated background objects, there is one promising candidate, namely
1.5" SW off the M6-dwarf Cha Ha 5. This candidate is 3.8 to 4.7 mag fainter
than the primary and its colors are consistent with an early- to mid-L spectral
type. Assuming the same distance (140 pc) and absorption (0.47 mag in I) as
towards the primary, the companion candidate has log (L(bol)/L(odot) = -3.0 +-
0.3. At the age of the primary (1 to 5 Myrs), the faint object would have a
mass of 3 to 15 Jupiter masses according to Burrows et al. (1997) and Chabrier
& Baraffe (2000) models. The probability for this companion candidate to be an
unrelated fore- or background object is smaller than 0.7%, its colors are
marginally consistent with a strongly reddened background K giant. One other
companion candidate has infrared colors consistent with an early T-dwarf. In
addition, we present indications for Cha Ha 2 being a close (0.2") binary with
both components very close to the sub-stellar limit. Our detection limits are
such that we should have detected all companions above 1 Jup with separations
above 2" (320 AU) and all above 5 Jup at 0.35" (50 AU).


title: VLT spectra of the companion candidate Cha Ha 5/cc 1

abstract:
  We obtained optical and infrared spectra of Cha Ha 5/cc 1, a faint possibly
sub-stellar companion candidate next to the M6-type brown dwarf candidate Cha
Ha 5 in Cha I, using FORS1 and ISAAC at the VLT. The VRIJHK colors of Cha Ha
5/cc 1 are consistent with either an L-type companion or a K-type background
giant. Our spectra show that the companion candidate actually is a background
star.


title:
More on the determination of the coronal heating function from Yohkoh
  data

abstract:
  Two recent works have analyzed a solar large and steady coronal loop observed
with Yohkoh/SXT in two filter passbands to infer the distribution of the
heating along it. Priest et al. (2000) modelled the distribution of the
temperature obtained from filter ratio method with an analytical approach, and
concluded that the heating was uniform along the loop. Aschwanden (2001) found
that a uniform heating led to an unreasonably large plasma column depth along
the line of sight, and, using a two component loop model, that a
footpoint-heated model loop (with a minor cool component) yields more
acceptable physical solutions. We revisit the analysis of the same loop system,
considering conventional hydrostatic single loop models with uniformly
distributed heating, and with heating localized at the footpoints and at the
apex, and an unstructured background contribution extrapolated from the region
below the analyzed loop. The flux profiles synthesized from the loop models
have been compared in detail with those observed in both filter passbands with
and without background subtraction; we find that background-subtracted data are
fitted with acceptable statistical significance by a model of relatively hot
loop (~3.7 MK) heated at the apex, with a column depth ~1/10 of the loop
length. In discussing our results, we put warnings on the importance of aspects
of data analysis and modeling, such as considering diffuse background emission
in complex loop regions.


title:
On the correlation between radio and X-ray flux in Low/Hard state Black
  Holes

abstract:
  Radio emission from X-ray binary systems (XRBs) has developed in recent years
from being peculiar phenomenon to being recognised as an ubiquitous property of
several classes of XRBs. In this scenario the synchrotron emission is
interpreted as the radiative signature of jet-like outflows, some or all of
which may possess relativistic bulk motion. We have analysed a collection of
quasi-simultaneous radio/X-ray observations of Black Holes in the Low/Hard
X-ray state, finding evidence of a clear correlation between their fluxes over
many orders of magnitude in luminosity. Given that the correlation extends down
to GX 339-4 and V404 Cyg in quiescence, we can confidently assert that even at
accretion rates as low as ~ 10^{-5} dot{m}_{Edd} a powerful jet is being
formed. The normalisation of the correlation is very similar across a sample of
nine sources, implying that it is nearly independent of jet inclination angle.
Remarkably, V 404 Cyg is the second source (after GX 339-4) to show the
correlation S_{radio} proportional to S_{X}^{+0.7} from quiescent level up to
close to the High/Soft state transition. Moreover, assuming the same physics
and accretion:outflow coupling for all of these systems, the simplest
interpretation for the observed scenario is that outflows in Low/Hard state do
not have large bulk Lorentz factors.


title:
Why is it Difficult to Detect a Millisecond Pulsar in Neutron Star X-ray
  Binaries?

abstract:
  We explain why it is possible to detect directly X-ray emission from near the
surface of the neutron star (NS) in SAX J1808.4-3658 but not in most other
low-mass X-ray binaries (LMXBs), with the exception that emission from the
surface can be seen during bursts events. We show that the X-ray emission from
SAX J1808.4-3658 mostly originates in the Comptonization process in a
relatively optical thin hot region (with an optical depth $\tau_0$ around 4 and
temperature is around 20 keV). Such a transparent region does not prevent us
from detecting coherent X-ray pulsation due to hot spots on the NS surface.
When the characteristic scattering time in the region is of order of inverse
rotational frequency omega or higher then the amplitude of the harmonic
oscillation decays exponentially with (tau_0 x omega). We give a precise model
for the loss of modulation, such suppression of the QPO amplitude due to
scattering can explain the disappearance of kHz QPOs with increasing QPO
frequency. We also formulate general conditions under which the millisecond
X-ray pulsation can be detected in LMXBs.
  We demonstrate that the observed soft phase lag of the pulsed emission is a
result of the downscattering of the hard X-ray photons in the relatively cold
material near the NS surface. In the framework of this downscattering model we
propose a method to determine the atmosphere density in that region from
soft-lag measurements.


title:
Simultaneous measurements of water optical properties by AC9
  transmissometer and ASP-15 Inherent Optical Properties meter in Lake Baikal

abstract:
  Measurements of optical properties in media enclosing Cherenkov neutrino
telescopes are important not only at the moment of the selection of an adequate
site, but also for the continuous characterization of the medium as a function
of time. Over the two last decades, the Baikal collaboration has been measuring
the optical properties of the deep water in Lake Baikal (Siberia) where, since
April 1998, the neutrino telescope NT-200 is in operation. Measurements have
been made with custom devices. The NEMO Collaboration, aiming at the
construction of a km3 Cherenkov neutrino detector in the Mediterranean Sea, has
developed an experimental setup for the measurement of oceanographic and
optical properties of deep sea water. This setup is based on a commercial
transmissometer. During a joint campaign of the two collaborations in March and
April 2001, light absorption, scattering and attenuation in water have been
measured. The results are compatible with previous ones reported by the Baikal
Collaboration and show convincing agreement between the two experimental
techniques.


title:
Realistic Ionizing Fluxes for Young Stellar Populations from 0.05 to
  twice solar metallicity

abstract:
  We present a new grid of ionizing fluxes for O and Wolf-Rayet stars for use
with evolutionary synthesis codes and single star H II region analyses. A total
of 230 expanding, non-LTE, line-blanketed model atmospheres have been
calculated for five metallicities (0.05, 0.2, 0.4, 1 and 2 solar) using the
WM-basic code of Pauldrach et al. (2001) and the CMFGEN code of Hillier &
Miller (1998). The stellar wind parameters are scaled with metallicity for both
O and W-R stars. We incorporate the new models into Starburst99 (Leitherer et
al. 1999) and compare the ionizing outputs with Schaerer & Vacca (1998) and
Leitherer et al. (1999). The changes in the output ionizing fluxes are
dramatic, particularly below 228 A. We also find lower fluxes in the He I
continuum for Z > 0.4 solar and ages < 7 Myr because of the increased line
blanketing. We test the accuracy of the new models by constructing
photoionization models. We show that for the dwarf O star grid, He I 5876/H
beta decreases between Z = 1 and twice solar in a similar manner to
observations (e.g. Bresolin et al. 1999) due to the increased effect of line
blanketing. We therefore suggest that a lowering of the upper mass limit at
high abundances is not required to explain the observations. For the case of an
instantaneous burst, we plot the softness parameter "eta prime" against the
abundance indicator R_23. The new models are coincident with the data of
Bresolin et al. (1999), particularly during the W-R phase, unlike previous
models which over-predict the hardness of the ionizing radiation.


title:
The Millennium Galaxy Catalogue: 16 < B_MGC < 24 galaxy counts and the
  calibration of the local galaxy luminosity function

abstract:
  The Millennium Galaxy Catalogue (MGC) is a 37.5 deg^2, medium-deep, B-band
imaging survey along the celestial equator, taken with the Wide Field Camera on
the Isaac Newton Telescope. The survey region is contained within the regions
of both the Two Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan
Digital Sky Survey Early Data Release (SDSS-EDR). The survey has a uniform
isophotal detection limit of 26 mag arcsec^-2 and it provides a robust,
well-defined catalogue of stars and galaxies in the range 16 <= B_MGC < 24 mag.
  Here we describe the survey strategy, the photometric and astrometric
calibration, source detection and analysis, and present the galaxy number
counts that connect the bright and faint galaxy populations within a single
survey. We argue that these counts represent the state of the art and use them
to constrain the normalizations (phi*) of a number of recent estimates of the
local galaxy luminosity function. We find that the 2dFGRS, SDSS Commissioning
Data (CD), ESO Slice Project, Century Survey, Durham/UKST, Mt Stromlo/APM,
SSRS2, and NOG luminosity functions require a revision of their published phi*
values by factors of 1.05 +/- 0.05, 0.76 +/- 0.10, 1.02 +/- 0.22, 1.02 +/-
0.16, 1.16 +/- 0.28, 1.75 +/- 0.37, 1.40 +/- 0.26 and 1.01 +/- 0.39,
respectively. After renormalizing the galaxy luminosity functions we find a
mean local $\bj$ luminosity density of j_{b_J} = (1.986 +/- 0.031) x 10^8 h
L_{\odot} Mpc^-3.


title:
Modern Techniques in Galaxy Kinematics: CDI and the Planetary Nebula
  Spectrograph

abstract:
  We report here the successful commissioning of the PN.Spectrograph, the first
special-purpose instrument for the measurement of galaxy kinematics through the
PN population


title: Positron Fraction from Dark Matter Annihilation in the CMSSM

abstract:
  We investigate, if the cosmic ray positron fraction, as reported by the HEAT
and AMS collaborations, is compatible with the annihilation of neutralinos in
the supergravity inspired Constrained Minimal Supersymmetric Model (CMSSM),
thus complementing previous investigations, which did not consider constraints
from unification, electroweak symmetry breaking and the present Higgs limits at
LEP.
  We perform a global fit of all SUSY parameters to low energy constraints and
find that in the acceptable parameter regions the neutralino annihilation into
b-bbar quark pairs is the dominant channel and improves the fit to the
experimental positron fraction data considerably with respect to a fit with
background only. These fits are comparable to the fit for regions of parameter
space, where the annihilation into W^+ W^- pairs dominates. However, these
latter regions are ruled out by the present Higgs limit of 114 GeV from LEP in
combination with b->s gamma data.


title: On the Reality of the Accelerating Universe

abstract:
  Two groups recently deduced the positive value for the cosmological constant,
concluding at a high (>= 99%) confidence level that the Universe should be
accelerating. This conclusion followed from the statistical analysis of dozens
of high-redshift supernovae. In this paper this conclusion is discussed. From
the conservative frequentist's point of view the validity of null hypothesis of
the zero cosmological constant is tested by the classical statistical chi^2
test for the 60 supernovae listed in Perlmutter et al. 1999 (ApJ, 517, 565).
This sample contains 42 objects discovered in the frame of Supernova Cosmology
Project and 18 low-redshift object detected earlier. Excluding the event
SN1997O, which is doubtlessly an outlier, one obtains the result: The
probability for seeing a worse chi^2 - if the null hypothesis is true - is in
the 5% to 8% range, a value that does not indicate significant evidence againts
the null. If one excludes further five possible outliers, proposed to be done
by Perlmutter et al. 1999, then the sample of 54 supernovae is in an excellent
accordance with the null hypothesis. It also seems that upernovae from the
High-z Supernova Search Team does not change the acceptance of null hypothesis.
This means that the rejection of the Einstein equations with zero cosmological
constant - based on the supernova data alone - is still premature.


title:
HST Spectra of GW Librae: A Hot Pulsating White Dwarf in a Cataclysmic
  Variable

abstract:
  We have obtained Hubble Space Telescope UV spectra of the white dwarf in GW
Lib, the only known non-radially pulsating white dwarf in a cataclysmic
variable, and the first known DAZQ variable. The UV light curve reveals large
amplitude (10%) pulsationsin the UV with the same periods (646, 376 and 237 s)
as those seen at optical wavelengths, but the mean spectrum fits with an
average white dwarf temperature (14,700K for a 0.6M_{odot} white dwarf) that is
too hot to be in the normal instability strip for ZZ Ceti stars. A better fit
is achieved with a dual temperature model (with 63% of the white dwarf surface
at a temperature of 13300K and 37% at 17100K), and a higher mass (0.8M_{odot})
white dwarf with 0.1 solar metal abundance. Since the blue edge of the
instability strip moves to higher temperature with increasing mass, the lower
temperature of this model is within the instability strip. However, the
presence of accretion likely causes abundance and atmospheric temperature
differences in GW Lib compared to all known single white dwarf pulsators, and
the current models that have been capable of explaining ZZ Ceti stars may not
apply.


title:
Hydromagnetic Taylor--Couette flow: numerical formulation and comparison
  with experiment

abstract:
  Taylor--Couette flow in the presence of a magnetic field is a problem
belonging to classical hydromagnetics and deserves to be more widely studied
than it has been to date. In the nonlinear regime the literature is scarce. We
develop a formulation suitable for solution of the full three dimensional
nonlinear hydromagnetic equations in cylindrical geometry, which is motived by
the formulation for the magnetic field. It is suitable for study at finite
magnetic Prandtl numbers and in the small Prandtl number limit, relevant to
laboratory liquid metals. The method is used to determine the onset of
axisymmetric Taylor vortices, and finite amplitude solutions. Our results
compare well with existing linear and nonlinear hydrodynamic calculations and
with hydromagnetic experiments.


title: When is Uniform Rotation an Energy Minimum?

abstract:
  A simple variational calculation is presented showing that a uniformly
rotating barotropic fluid in an external potential attains a true energy
minimum if and only if the rotation profile is everywhere subsonic. If regions
of supersonic rotation are present, fluid variations exist that could take the
sytem to states of lower energy. In any given system, these states may or may
not be dynamically accessible, but their existence is important. It means that
extending the degrees of freedom available to the fluid (say by weak magnetic
fields) may open a path to fluid instabilities. Whether astrophysical gaseous
nebula tend toward states of uniform rotation or toward more Keplerian
core-disk systems appears to be largely a matter of whether the rotation
profile is transonic or not. The suggestion is made that the length scale
associated with coherent molecular cloud cores is related to the requirement
that the cores be stable and rotate subsonically.


title: Highly-Ionized High-Velocity Gas in the Vicinity of the Galaxy

abstract:
  We report the results of an extensive FUSE study of high velocity OVI
absorption along 102 complete sight lines through the Galactic halo. The high
velocity OVI traces a variety of phenomena, including tidal interactions with
the Magellanic Clouds, accretion of gas, outflow from the Galactic disk,
warm/hot gas interactions in a highly extended Galactic corona, and
intergalactic gas in the Local Group. We identify 85 high velocity OVI features
at velocities of -500 < v(LSR) < +500 km/s along 59 of the 102 sight lines.
Approximately 60% of the sky (and perhaps as much as 85%) is covered by high
velocity H+ associated with the high velocity OVI. Some of the OVI is
associated with known high velocity HI structures (e.g., the Magellanic Stream,
Complexes A and C), while some OVI features have no counterpart in HI 21cm
emission. The smaller dispersion in the OVI velocities in the GSR and LGSR
reference frames compared to the LSR is necessary (but not conclusive) evidence
that some of the clouds are extragalactic. Most of the OVI cannot be produced
by photoionization, even if the gas is irradiated by extragalactic background
radiation. Collisions in hot gas are the primary OVI ionization mechanism. We
favor production of some of the OVI at the boundaries between warm clouds and a
highly extended [R > 70 kpc], hot [T > 10^6 K], low-density [n < 10^-4 cm^-3]
Galactic corona or Local Group medium. A hot Galactic corona or Local Group
medium and the prevalence of high velocity OVI are consistent with predictions
of galaxy formation scenarios. Distinguishing between the various phenomena
producing high velocity OVI will require continuing studies of the distances,
kinematics, elemental abundances, and physical states of the different types of
high velocity OVI features found in this study. (abbreviated)


title: Hydromagnetic Taylor--Couette flow: wavy modes

abstract:
  We investigate magnetic Taylor--Couette flow in the presence of an imposed
axial magnetic field. First we calculate nonlinear steady axisymmetric
solutions and determine how their strength depends on the applied magnetic
field. Then we perturb these solutions to find the critical Reynolds numbers
for the appearance of wavy modes, and the related wavespeeds, at increasing
magnetic field strength. We find that values of imposed magnetic field which
alter only slightly the transition from circular--Couette flow to
Taylor--vortex flow, can shift the transition from Taylor--vortex flow to wavy
modes by a substantial amount. The results are compared against onset in the
absence of a magnetic field.


title: Magnetic instability in a sheared azimuthal flow

abstract:
  We study the magneto-rotational instability of an incompressible flow which
rotates with angular velocity Omega(r)=a+b/r^2 where r is the radius and $a$
and b are constants. We find that an applied magnetic field destabilises the
flow, in agreement with the results of Rudiger & Zhang 2001. We extend the
investigation in the region of parameter space which is Rayleigh stable. We
also study the instability at values of magnetic Prandtl number which are much
larger and smaller than Rudiger & Zhang. Large magnetic Prandtl numbers are
motivated by their possible relevance in the central region of galaxies
(Kulsrud & Anderson 1992). In this regime we find that increasing the magnetic
Prandtl number greatly enhances the instability; the stability boundary drops
below the Rayleigh line and tends toward the solid body rotation line. Very
small magnetic Prandtl numbers are motivated by the current MHD dynamo
experiments performed using liquid sodium and gallium. Our finding in this
regime confirms Rudiger & Zhang's conjecture that the linear magneto-rotational
instability and the nonlinear hydrodynamical instability (Richard & Zahn 1999)
take place at Reynolds numbers of the same order of magnitude.


title: Mid-Infrared Imaging of NGC 6334 I

abstract:
  We present high-resolution (<0.5") mid-infrared Keck II images of individual
sources in the central region of NGC 6334 I. We compare these images to images
at a variety of other wavelengths from the near infrared to cm radio continuum
and speculate on the nature of the NGC 6334 I sources. We assert that the
cometary shape of the UCHII region here, NGC 6334 F, is due to a champagne-like
flow from a source on the edge of a molecular clump and not a due to a bow
shock caused by the supersonic motion of the UCHII region through the
interstellar medium. The mid-infrared emission in concentrated into an arc of
dust that define the boundary between the UCHII region and the molecular clump.
This dust arc contains a majority of the masers in the region. We discuss the
nature of the four near-infrared sources associated with IRS-I 1, and suggest
that one of the sources, IRS1E, is responsible for the heating and ionizing of
the UCHII region and the mid-infrared dust arc. Infrared source IRS-I 2, which
has been thought to be a circumstellar disk associated with a linear
distribution of methanol masers, is found not to be directly coincident with
the masers and elongated at a much different position angle. IRS-I 3 is found
to be a extended source of mid-infrared emission coming from a cluster of young
dusty sources seen in the near-infrared.