title:
Discovery of a very luminous megamaser during a radio flare in the
  Seyfert 2 galaxy Mrk 348

abstract:
  We report the detection of a new H_2O megamaser in the Seyfert 2 galaxy Mrk
348 with the MPIfR 100 m telescope in Effelsberg. With an apparent isotropic
luminosity of L_H2O ~ 420 L_sun the maser is the third most luminous maser
discovered so far. The detected line is unusually broad (Delta v ~ 130 km/s),
is redshifted by ~130 km/s from the systemic velocity, and is asymmetric with a
pronounced blue wing. While evidence for obscuring material towards the nucleus
of this galaxy was found earlier, this detection is the first direct
observation of molecular material in the vicinity of the AGN. We also searched
for absorption from ammonia (NH_3) and cyclopropenylidene (C_3H_2) against the
bright radio nucleus. The H_2O line was only marginally detected in archival
data indicating that the maser flared recently in conjunction with a huge radio
continuum flare. Continuum and line flux density increased by a factor of
three, suggesting an unsaturated maser. The radio continuum flare has made Mrk
348 the most radio luminous megamaser galaxy known. It is pointed out that
megamaser galaxies contain a rather large fraction of galaxies with prominent
radio cores and it is speculated that the flare in the maser emission in Mrk
348 is related to the flare in the nuclear jet.


title: Global Spiral Modes in NGC 1566: Observations and Theory

abstract:
  We present an observational and theoretical study of the spiral structure in
galaxy NGC 1566. A digitized image of NGC 1566 in I-band was used for
measurements of the radial dependence of amplitude variations in the spiral
arms. We use the known velocity dispersion in the disk of NGC 1566, together
with its rotation curve, to construct linear and 2D nonlinear simulations which
are then compared with observations. A two-armed spiral is the most unstable
linear global mode in the disk of NGC 1566. The nonlinear simulations are in
agreement with the results of the linear modal analysis, and the theoretical
surface amplitude and the velocity residual variations across the spiral arms
are in qualitative agreement with the observations. The spiral arms found in
the linear and nonlinear simulations are considerably shorter than those
observed in the disk of NGC 1566. We argue therefore, that the surface density
distribution in the disk of the galaxy NGC 1566 was different in the past, when
spiral structure in NGC 1566 was linearly growing.


title: On the fate of gas in ultraluminous galaxies at low and high redshift

abstract:
  It is often suggested that the distant galaxies recently identified in 850
micron surveys with the SCUBA bolometer array on the JCMT Telescope are
high-redshift analogues to local ultraluminous infrared galaxies, based on
their similar spectral energy distributions and luminosities. We show that
these two populations of objects must differ in at least one fundamental way
from each other. This assertion is based on a consideration of the possible
fates of gas in the high redshift SCUBA galaxies, given the requirement that
they most evolve into some subset of the low-redshift galaxy population with a
comoving density of about 10^{-4} Mpc^{-3}. One possibility is that the SCUBA
galaxies have similar gas density profiles to local ultraluminous galaxies. If
this is the case, then they must derive almost all their power from AGNs, which
appears not to be the case for local ultraluminous galaxies, which are
predominantly star-formation powered. Another possibility is that the SCUBA
galaxies have more extended gas density profiles than local ultraluminous
galaxies. In this case they must be almost all star-formation powered, and much
of the star formation in the Universe can happen in these objects. Either way
there is a significant difference between the low- and high- redshift
populations.


title: Keck Studies of M31's Stellar Halo

abstract:
  We present Keck 10-meter/LRIS spectra of candidate red giants in the halo of
M31, located at a projected radius of R=19kpc on the minor axis. These
spectroscopic targets have been selected using a combination of UBRI-based and
morphological screening to eliminate background galaxies. Radial velocity
measurements are used to separate M31 halo giants from foreground Milky Way
dwarf stars, M31 disk stars, and residual background galaxies. The metallicity
of each M31 halo giant is measured using standard photometric and spectroscopic
techniques, the latter based on the strength of the CaII triplet. The various
[Fe/H] estimates are in rough agreement with one another. The data reveal a
large spread (>2dex) in [Fe/H] in M31's halo; there is no strong radial [Fe/H]
gradient. LRIS and HIRES spectra are also presented for red giants in five
dwarf spheroidal satellites of M31: AndI, AndIII, AndV, AndVI, and AndVII.
There appears to be a significant metallicity spread in AndVI and possibly in
AndI. The new radial velocity data on these outer dwarfs are used to constrain
the total mass of M31: the best estimate is under 10^(12)Msun, somewhat less
than the best estimate for the Milky Way.


title: A Tunable Echelle Imager

abstract:
  We describe and evaluate a new instrument design called a Tunable Echelle
Imager (TEI). In this instrument, the output from an imaging Fabry-Perot
interferometer is cross-dispersed by a grism in one direction and dispersed by
an echelle grating in the perpendicular direction. This forms a mosaic of
different narrow-band images of the same field on a detector. It offers a
distinct wavelength multiplex advantage over a traditional imaging Fabry-Perot
device.
  Potential applications of the TEI include spectrophotometric imaging and
OH-suppressed imaging by rejection.


title:
Detection of Dark Matter Concentrations in the Field of Cl 1604+4304
  from Weak Lensing Analysis

abstract:
  We present a weak-lensing analysis of a region around the galaxy cluster Cl
1604+4304 (z=0.897) on the basis of the deep observations with the HST/WFPC2.
We apply a variant of Schneider's aperture mass technique to the observed WFPC2
field and obtain the distribution of weak-lensing signal-to-noise (S/N) ratio
within the field. The resulting S/N map reveals a clear pronounced peak located
about 1.7 arcmin (850h_{50}^{-1} kpc at z=0.897) southwest of the second peak
associated with the optical cluster center determined from the dynamical
analysis of Postman et al. A non-linear finite-field inversion method has been
used to reconstruct the projected mass distribution from the observed shear
field. The reconstructed mass map shows a super-critical feature at the
location of the S/N peak as well as in the cluster central region. Assuming the
redshift distribution of field galaxies, we obtain the total mass in the
observed field to be 1.0 h_{50}^{-1} 10^{15} M_sun for <z>=1.0. The estimated
mass within a circular aperture of radius 280h_{50}^{-1} kpc centered on the
dark clump is 2.4h_{50}^{-1} 10^{14} M_sun. We have confirmed the existence of
the ` dark ' mass concentration from another deep HST observation with a
slightly different ~20 arcsec pointing.


title: Correlations between various hardness ratios of gamma-ray bursts

abstract:
  We study correlations between various hardness ratios of gamma-ray bursts
(GRBs) and investigate if there are any differences between the two classes of
the objects in the distributions of the ratios. The results suggest that,
statistically, the slope of the higher part of the spectrum of the long
duration bursts has nothing to do with that of the lower part; emissions at
higher energy bands from the bursts of both short and long duration classes
must be significantly different for different sources, while radiations at
lower energy bands of the objects are relatively similar; the spectrum of the
short duration bursts must be harder than that of the long duration bursts,
confirming what the well-known hardness-duration correlation reveals; the
profiles of the spectra between the long duration bursts must be more similar
than that between the short duration bursts. The long duration bursts would
share more common properties than the short duration bursts. A possible
interpretation is proposed with the concept of the Doppler boosting in the
relativistic beaming model in AGNs.


title:
Strange stars - linear approximation of the EOS and maximum QPO
  frequency

abstract:
  The equation of state of strange matter build of the u,d,s quarks in the
framework of the MIT bag model is studied. The scaling relations with bag
constant are discussed and applied to the determination of maximum frequency of
a particle in stable circular orbit around strange star. The highest QPO
frequency of 1.33 kHz observed so far is consistent with the strange stars
models for which the maximum QPO frequency is 1.7-2.4 kHz depending on the
strange quark mass and the QCD coupling constant. The linear approximation of
the equation of state is found and the parameters of this EOS are determined as
a functions of strange quark mass, QCD coupling constant and bag constant. This
approximation reproduces exact results within an error of the order of 1% and
can be used for the complete study of the properties of strange stars including
microscopic stability of strange matter and determination of the total baryon
number of the star.


title:
The cosmological lens equation in a universe with non zero cosmological
  constant

abstract:
  We derive and solve exactly the Dyer-Roeder equation in a
Friedman-Robertson-Walker cosmological model with non zero cosmological
constant. To take into account non homogeneous distribution of matter we use
the phenomenological clumpiness parameter. We propose also a general form of an
approximate solution which is simple enough to be useful in practical
applications and sufficiently accurate in the interesting range of redshifts.


title: The Circumstellar Environment of the TTS SU Aurigae

abstract:
  In this contribution we investigate how a disk determines the physical and
geometrical properties of the circumstellar environment of the T Tauri SU
Aurigae. Our model of the spectral energy distribution of this star includes
the central young star, a flat black disk and a diffuse envelope. We also
describe the inner interaction region between the disk and the star, the
magnetosphere, by analysing the accretion and wind signatures in several
spectral lines observed during the MUSICOS 96 campaign.


title: Comparing Tycho-2 Astrometry with UCAC1

abstract:
  The Tycho-2 Catalogue, released in February 2000, is based on the ESA
Hipparcos space mission data and various ground-based catalogs for proper
motions. An external comparison of the Tycho-2 astrometry is presented here
using the first U.S. Naval Observatory CCD Astrograph Catalog (UCAC1). The
UCAC1 data were obtained from observations performed at CTIO between February
1998 and November 1999, using the 206 mm aperture 5-element lens astrograph and
a 4k x 4k CCD. Only small systematic differences in position between Tycho-2
and UCAC1 up to 15 milliarcseconds (mas) are found, mainly as a function of
magnitude. The standard deviations of the distributions of the position
differences are in the 35 to 140 mas range, depending on magnitude. The
observed scatter in the position differences is about 30% larger than expected
from the combined formal, internal errors, also depending on magnitude. The
Tycho-2 Catalogue has the more precise positions for bright stars (V <= 10 mag)
while the UCAC1 positions are significantly better at the faint end (11 mag <=
V <= 12.5 mag) of the magnitude range in common. UCAC1 goes much fainter (to
R=16) than Tycho-2; however complete sky coverage is not expected before mid
2003.


title: A Search for Sub-TeV Gammas in Coincidence with Gamma Ray Bursts

abstract:
  We report on a study of sub-TeV ($E_\gamma > 10$ GeV) gamma-ray-induced muon
secondaries in coincidence with BATSE gamma ray bursts (GRBs). Each TeV gamma
ray striking the atmosphere produces $\approx$0.2 muons whose identity and
angle can be measured by the Project GRAND array. Eight GRB candidates were
studied; seven were selected based upon the optimum product of (detected BATSE
fluence) $\times$ (GRAND's acceptance). One candidate was added because it was
reported as a detection by the Milagrito collaboration. Seven candidates show a
positive, though not statistically significant, muon excess. The most
significant possible coincidence shows an excess of $466 \pm 171$ muons during
the BATSE T90 time interval. It is also of interest that the event with the
second most significant signal to noise (1.2$\sigma$) is the Milagrito event.
If our most significant event is real, the implied fluence of energetic ($> 10$
GeV) gammas necessary to account for the observed muon excess would require
that most of the GRB fluence arrived in the form of energetic gammas.


title:
FUSE Observations of Intrinsic Absorption in the Seyfert 1 Galaxy Mrk
  509

abstract:
  We present far-ultraviolet spectra of the Seyfert 1 galaxy Mrk 509 obtained
in 1999 November with the Far Ultraviolet Spectroscopic Explorer (FUSE). Our
data span the observed wavelength range 915-1185 A at a resolution of ~20 km/s.
The spectrum shows a blue continuum, broad OVI 1032,1038 emission, and a broad
CIII 977 emission line. Superposed on these emission components, we resolve
associated absorption lines of OVI 1032,1038, CIII 977, and Lyman lines through
Lzeta. Seven distinct kinematic components are present, spanning a velocity
range of -440 to +170 km/s relative to the systemic velocity. The absorption is
clustered in two groups, one centered at -370m km/s and another at the systemic
velocity. The blue-shifted cluster may be associated with the extended line
emission visible in deep images of Mrk 509 obtained by Phillips et al. Although
several components appear to be saturated, they are not black at their centers.
Partial covering or scattering permits ~7% of the broad-line or continuum flux
to be unaffected by absorption. Of the multiple components, only one has the
same ionization state and column density as highly ionized gas that produces
the OVII and OVIII ionization edges in X-ray spectra of Mrk 509.
  This paper will appear in a special issue of Astrophysical Journal Letters
devoted to the first scientific results from the FUSE mission.


title:
Halo Cores and Phase Space Densities: Observational Constraints on Dark
  Matter Physics and Structure Formation

abstract:
  We explore observed dynamical trends in a wide range of dark matter dominated
systems (about seven orders of magnitude in mass) to constrain hypothetical
dark matter candidates and scenarios of structure formation. First, we argue
that neither generic warm dark matter (collisionless or collisional) nor
self-interacting dark matter can be responsible for the observed cores on all
scales. Both scenarios predict smaller cores for higher mass systems, in
conflict with observations; some cores must instead have a dynamical origin.
Second, we show that the core phase space densities of dwarf spheroidals,
rotating dwarf and low surface brightness galaxies, and clusters of galaxies
decrease with increasing velocity dispersion like Q ~ sigma^-3 ~ M^-1, as
predicted by a simple scaling argument based on merging equilibrium systems,
over a range of about eight orders of magnitude in Q. We discuss the processes
which set the overall normalization of the observed phase density hierarchy. As
an aside, we note that the observed phase-space scaling behavior and density
profiles of dark matter halos both resemble stellar components in elliptical
galaxies, likely reflecting a similar collisionless, hierarchical origin. Thus,
dark matter halos may suffer from the same systematic departures from homology
as seen in ellipticals, possibly explaining the shallower density profiles
observed in low mass halos. Finally, we use the maximum observed phase space
density in dwarf spheroidal galaxies to fix a minimum mass for relativistically
decoupled warm dark matter candidates of roughly 700 eV for thermal fermions,
and 300 eV for degenerate fermions.


title: On the ongoing multiple blowout in NGC 604

abstract:
  Several facts regarding the structure of NGC 604 are examined here. The three
main cavities, produced by the mechanical energy from massive stars which in
NGC 604 are spread over a volume of 10$^6$ pc$^3$, are shown here to be
undergoing blowout into the halo of M33. High resolution long slit spectroscopy
is used to track the impact from massive stars while HST archive data is used
to display the asymmetry of the nebula.
  NGC 604 is found to be a collection of photoionized filaments and sections of
shells in direct contact with the thermalized matter ejected by massive stars.
The multiple blowout events presently drain the energy injected by massive
stars and thus the densest photoionized gas is found almost at rest and is
expected to suffer a slow evolution.


title: Keck Observations of the Hidden Quasar IRAS P09104+4109

abstract:
  We present imaging and spectro- polarimetric observations of the
ultraluminous infrared galaxy IRAS P09104+4109 using the Keck 10-m Telescope.
We detect the clear presence of broad Hb, Hg, and MgII 2800 emission lines in
the polarized flux spectra of the nucleus and of an extranuclear emission
region ~ 4" away, confirming the presence of a hidden central quasar. The
polarization of the broad Mg II emission line is high (~ 29%), consistent with
the remarkably high polarization (~ 30%-40%) observed in the extended continuum
emission. The narrow emission lines are polarized in a stratified fashion, with
the high ionization lines being polarized 0.7%-1.7% and [O II] essentially
unpolarized. The line polarizations are positively correlated with critical
density, ionization potential, and velocity width of the emission lines. This
indicates that the NLR may be partially shadowed by the putative torus, with
the higher ionization lines originating closer to the nucleus. One notable
characteristic of the extranuclear knot is that all species of Fe are markedly
absent in its spectrum, while they appear prominently in the nucleus. Our
favored interpretation is that there is a large amount of dust in the
extranuclear regions, allowing gaseous refractory metals to deposit. The
extended emission regions are most likely material shredded from nearby cluster
members and not gas condensed from the cooling flow or expelled from the
obscured quasar. Our data provide strong evidence for matter-bounded clouds in
addition to ionization-bounded clouds in the NLR. Ionization by pure velocity
shocks can be ruled out. Shocks with photoionizing precursors may be present,
but are probably not a dominant contributor to the energy input.


title: Scalar fields in an anisotropic closed universe

abstract:
  We study in this article a class of homogeneous, but anisotropic cosmological
models in which shear viscosity is included. Within the matter content we
consider a component (the quintessence component) determined by the barotropic
equations of state, $p=\alpha \rho$, with $\alpha < 0$. We establish conditions
under which a closed axisymmetrical cosmological model may look flat al low
redshift.


title: Boomerang returns unexpectedly

abstract:
  Experimental study of the anisotropy in the cosmic microwave background (CMB)
is gathering momentum. The eagerly awaited Boomerang results have lived up to
expectations. They provide convincing evidence in favor of the standard
paradigm: the Universe is close to flat and with primordial fluctuations which
are redolent of inflation. Further scrutiny reveals something even more
exciting however -- two hints that there may be some unforeseen physical
effects. Firstly the primary acoustic peak appears at slightly larger scales
than expected. Although this may be explicable through a combination of mundane
effects, we suggest it is also prudent to consider the possibility that the
Universe might be marginally closed. The other hint is provided by a second
peak which appears less prominent than expected. This may indicate one of a
number of possibilities, including increased damping length or tilted initial
conditions, but also breaking of coherence or features in the initial power
spectrum. Further data should test whether the current concordance model needs
only to be tweaked, or to be enhanced in some fundamental way.


title:
The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Young
  Clusters

abstract:
  We have obtained images of the Trapezium Cluster (140" x 140"; 0.3 pc x 0.3
pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object
Spectrometer (NICMOS). Combining these data with new ground-based K-band
spectra (R=800) and existing spectral types and photometry and the models of
D'Antona & Mazzitelli, we find that the distributions of ages of comparable
samples of stars in the Trapezium, rho Oph, and IC 348 indicate median ages of
\~0.4 Myr for the first two regions and ~1-2 Myr for the latter. The low-mass
IMFs in these sites of clustered star formation are similar over a wide range
of stellar densities and other environmental conditions. With current data, we
cannot rule out modest variations in the substellar mass functions among these
clusters. We then make the best estimate of the true form of the IMF in the
Trapezium by using the evolutionary models of Baraffe et al. and an empirically
adjusted temperature scale and compare this mass function to recent results for
the Pleiades and the field. All of these data are consistent with an IMF that
is flat or rises slowly from the substellar regime to about 0.6 Msun, and then
rolls over into a power law that continues from about 1 Msun to higher masses
with a slope similar to or somewhat larger than the Salpeter value of 1.35. For
the Trapezium, this behavior holds from our completeness limit of ~0.02 Msun
and probably, after a modest completeness correction, even from 0.01-0.02 Msun.
These data include ~50 likely brown dwarfs. We test the predictions of theories
of the IMF against various properties of the observed IMF.


title:
Photon Propagation Around Compact Objects and the Inferred Properties of
  Thermally Emitting Neutron Stars

abstract:
  Anomalous X-ray pulsars, compact non-pulsing X-ray sources in supernova
remnants, and X-ray bursters are three distinct types of sources for which
there are viable models that attribute their X-ray emission to thermal emission
from the surface of a neutron star. Inferring the surface area of the emitting
regions in such systems is crucial in assessing the viability of different
models and in providing bounds on the radii of neutron stars. We show that the
inferred areas of the emitting regions may be over- or under-estimated by a
factor of <=2, because of the geometry of the system and general relativistic
light deflection, combined with the effects of phase averaging. Such effects
make the determination of neutron-star radii uncertain, especially when
compared to the ~5% level required for constraining the equation of state of
neutron-star matter. We also note that, for a given spectral shape, the
inferred source luminosities and pulse fractions are anticorrelated because
they depend on the same properties of the emitting regions, namely their sizes
and orientations, i.e., brighter sources have on average weaker pulsation
amplitudes than fainter sources. We argue that this property can be used as a
diagnostic tool in distinguishing between different spectral models. As an
example, we show that the high inferred pulse fraction and brightness of the
pulsar RXS J1708-40 are inconsistent with isotropic thermal emission from a
neutron-star surface. Finally, we discuss the implication of our results for
surveys in the soft X-rays for young, cooling neutron stars in supernova
remnants and show that the absence of detectable pulsations from the compact
source at the center of Cas A (at a level of >=30%) is not a strong argument
againts its identification with a spinning neutron star.


title: The Magnetic Geometry of Pulsed Astrophysical Jets

abstract:
  Hypersonic, highly collimated, mass outflows ({\it jets}) are a ubiquitous
phenomena in astrophysics. While the character of the jets differ, many exhibit
some form of quasi-periodic clumping indicating the jet source is episodic or
{\it pulsed}. The presence of pulsed jets in so many astrophysical contexts
suggests a common formation mechanism. Such a process seems to have been found
in {\it Magneto-centrifugal launching}, the combination of magnetic and
centrifugal forces that occurs when a magnetized gaseous accretion disk orbits
a central gravitating source. Observations of strong magnetic fields in jets
are, however, rare or indirect. Thus the presence and effects of magnetic
fields in YSO jets remains an unresolved issue of the highest importance. In
this letter we focus on what should be expected of the structure of the fields
in pulsed YSO jets. We show that combining velocity variability with an initial
field configuration consistent with collimated, Magneto-centrifugally launched
jets leads to a clear set of predictions concerning the geometry and relative
strength of the magnetic field components in evolving YSO (and perhaps other)
jets.


title: Delayed Recombination

abstract:
  Under the standard model for recombination of the primeval plasma, and the
cold dark matter model for structure formation, recent measurements of the
first peak in the angular power spectrum of the cosmic microwave background
temperature indicate the spatial geometry of the universe is nearly flat. If
sources of Lya resonance radiation, such as stars or active galactic nuclei,
were present at z ~ 1000 they would delay recombination, shifting the first
peak to larger angular scales, and producing a positive bias in this measure of
space curvature. It can be distinguished from space curvature by its
suppression of the secondary peaks in the spectrum.


title: Time-series spectroscopy of the rapidly oscillating Ap star HR 3831

abstract:
  We present time-series spectroscopy of the rapidly oscillating Ap star HR
3831. This star has a dominant pulsation period of 11.7 minutes and a rotation
period of 2.85 days. We have analysed 1400 intermediate-resolution spectra of
the wavelength region 6100--7100 AA obtained over one week, using techniques
similar to those we applied to another roAp star, Alpha Cir.
  We confirm that the H-alpha velocity amplitude of HR 3831 is modulated with
rotation phase. Such a modulation was predicted by the oblique pulsator model,
and rules out the spotted pulsator model. However, further analysis of H-alpha
and other lines reveal rotational modulations that cannot easily be explained
using the oblique pulsator model. In particular, the phase of the pulsation as
measured by the width of the H-alpha line varies with height in the line.
  The variation of the H-alpha bisector shows a very similar pattern to that
observed in Alpha Cir, which we have previously attributed to a radial node in
the stellar atmosphere. However, the striking similarities between the two
stars despite the much shorter period of Alpha Cir (6.8 min) argues against
this interpretation unless the structure of the atmosphere is somewhat
different between the two stars. Alternatively, the bisector variation is a
signature of the degree l of the mode and not the overtone value n.
  High-resolution studies of the metal lines in roAp stars are needed to
understand fully the form of the pulsation in the atmosphere.


title:
Formation and evolution of dusty starburst galaxies I. A new method for
  deriving spectral energy distribution

abstract:
  We present a new numerical code which is designed to derive a spectral energy
distribution (SED) for an arbitrary spatial distribution of stellar and gaseous
components in a dusty starburst galaxy. We apply a ray tracing method to
numerical simulations and thereby estimate extinction and reemission of stellar
light by dusty gas in an explicitly self-consistent manner. By using this code,
we can investigate simultaneously dynamical and photometric evolution of a
dusty galaxy based on stellar and gaseous dynamical simulations. As an example,
we demonstrate when and how a major galaxy merger with dusty starburst becomes
an ultra-luminous infrared galaxy owing to strong internal dust extinction. We
furthermore discuss advantages and disadvantages of the present new code in
clarifying the nature and the origin of low and high redshift dusty starburst
galaxies.


title:
The Gravitational Lensing in Redshift-space Correlation Functions of
  Galaxies and Quasars

abstract:
  The gravitational lensing, as well as the velocity field and the cosmological
light-cone warp, changes the observed correlation function of high-redshift
objects. We present an analytical expression of 3D correlation function,
simultaneously including those three effects. When two objects are separated
over several hundreds Mpc along a line of sight, the observed correlation
function is dominated by the effect of gravitational lensing rather than the
intrinsic clustering. For a canonical lambda-CDM model, the lensing signals in
the galaxy-galaxy and galaxy-QSO correlations are beyond noise levels in
large-scale redshift surveys like the Sloan Digital Sky Survey.


title:
New CMB constraints on the cosmic matter budget: trouble for
  nucleosynthesis?

abstract:
  We compute the joint constraints on ten cosmological parameters from the
latest CMB measurements. The lack of a significant second acoustic peak in the
latest Boomerang and Maxima data favors models with more baryons than Big Bang
nucleosynthesis predicts, almost independently of what prior information is
included. The simplest flat inflation models with purely scalar scale-invariant
fluctuations prefer a baryon density 0.022 <h^2 Omega_b < 0.040 and a total
nonbaryonic (hot + cold) dark matter density 0.14 < h^2 Omega_dm < 0.32 at 95%
confidence, and allow reionization no earlier than z~30.


title:
Status Report of Project GRAND: An Extensive Air Shower Array of
  Proportional Wire Chambers

abstract:
  Project GRAND is an extensive air shower array utilizing position sensitive
detectors of proportional wire chambers. The 64 detectors deployed in a field
100 m x 100 m are located at 86.2 deg W and 41.7 deg N, at 220 m above sea
level. The project was completed about two years ago and has been taking data,
simultaneously on two triggers: 1) multiple-hit coincidence triggers which
collect data on extensive air showers, and 2) 200 Hz triggers which collect the
single tracks stored in each station during the last 5 msec.


title: Stochastic background of gravitational waves

abstract:
  A continuous stochastic background of gravitational waves (GWs) for burst
sources is produced if the mean time interval between the occurrence of bursts
is smaller than the average time duration of a single burst at the emission,
i.e., the so called duty cycle must be greater than one. To evaluate the
background of GWs produced by an ensemble of sources, during their formation,
for example, one needs to know the average energy flux emitted during the
formation of a single object and the formation rate of such objects as well. In
many cases the energy flux emitted during an event of production of GWs is not
known in detail, only characteristic values for the dimensionless amplitude and
frequencies are known. Here we present a shortcut to calculate stochastic
backgrounds of GWs produced from cosmological sources. For this approach it is
not necessary to know in detail the energy flux emitted at each frequency.
Knowing the characteristic values for the ``lumped'' dimensionless amplitude
and frequency we show that it is possible to calculate the stochastic
background of GWs produced by an ensemble of sources.


title:
Asymmetries of Secondary Cosmic Muons with High Statistics and Low
  Systematics

abstract:
  Project GRAND measures the asymmetries of secondary cosmic muons by
calculating the differences between the muons from the east and the muons from
the west for complete solar days. A similar north-south difference is also
presented. These muons are identified in single track data taken with the 64
stations of Project GRAND; the data cover a two year span with a total muon
sample of 30 billion muons.


title: Dark Matter Scaling Relations

abstract:
  We establish the presence of a dark matter core radius, for the first time in
a very large number of spiral galaxies of all luminosities. Contrary to common
opinion we find that the sizes of these cores and the " DM core problem" are
bigger for more massive spirals. As a result the Burkert profile provides an
excellent mass model for dark halos around disk galaxies. Moreover, we find
that the spiral dark matter core densities $\rho_{0}$ and core radii $r_{0}$
lie in the same scaling relation $\rho_{0}=4.5\times 10^-2 (r_{0}/kpc)^{-2/3}
M_{\odot}pc^{-3}$ of dwarf galaxies with core radii upto ten times more
smaller.


title: Secondary Cosmic Muon Angular Distributions with High Statistics

abstract:
  Project GRAND preents a map in right ascension and declination for single
cosmic secondary tracks which have been identified as muons. These muons are
measured in stations of proportional wire chambers (PWCs) which have a mean
angular resolution of 0.26 deg. A 50 mm steel plate interspersed with the PWCs
is used to distinguish muons from electrons. Two years of data are accumulated
in a map of right ascension and declination which covers all of the northern
hemisphere and a small portion of the southern hemisphere. The total number of
muon tracks in this data sample are 40 billion. Significant large angular
structure is found in this map; the deviations from average are small compared
to the average, but because of the high statistics, the deviations from average
are statistically significant to many standard deviations. Systematic effects
in the data are minimized by averaging over this two year period. These results
are similar to those obtained in previous data.


title:
A new component of the Galaxy as the origin of the LMC microlensing
  events

abstract:
  We suggest a new component of the Milky Way that can account for both the
optical depth and event durations implied by microlensing searches targeting
the Large Magellanic Cloud. This component, which represents less than 4% of
the total dark matter halo mass, consists of mainly old white dwarf stars in a
distribution that extends beyond the disk of the galaxy, but lies well within
the dark matter halo. It is consistent with recent evidence for a significant
population of white dwarfs detected in proper motion studies of the Hubble Deep
Field that cannot be accounted for by stars in the disk or spheroid. Further,
it evades all of the current observational constraints that restrict a halo
population of white dwarfs.


title: Cluster Mass Reconstruction by a Weak Shear Field

abstract:
  The tidal gravitational field of galaxy clusters causes a coherent distortion
of the images of background sources.
  Since the distribution of image distortions, namely the shear field, traces
the local gravitational potential of a deflector, it can be used to reconstruct
the two-dimensional mass distribution of clusters of galaxies.
  Moreover, the shear field can provide unique information on the redshift
distribution of high-redshift galaxies.
  In this review we summarize recently-developed parameter-free methods of
cluster-mass reconstruction based on the shear field, and we apply a
mass-reconstruction method to the cluster Abell 370 at redshift 0.375.


title: Double-Peaked Broad Emission Lines in NGC 4450 and Other LINERs

abstract:
  Spectra taken with HST reveal that NGC 4450 emits Balmer emission lines with
displaced double peaks and extremely high-velocity wings. This characteristic
line profile, previously seen in a few nearby LINERs and in a small fraction of
broad-line radio galaxies, can be interpreted as a kinematic signature of a
relativistic accretion disk. We can reproduce the observed profile with a model
for a disk with a radial range of 1000-2000 gravitational radii and inclined by
27 degrees along the line of sight. The small-aperture HST data also allow us
to detect, for the first time, the featureless continuum at optical wavelengths
in NGC 4450; the nonstellar nucleus is intrinsically very faint, with M_B =
-11.2 mag for D = 16.8 Mpc. We have examined the multiwavelength properties of
NGC 4450 collectively with those of other low-luminosity active nuclei which
possess double-peaked broad lines and find a number of common features. These
objects are all classified spectroscopically as "type 1" LINERs or closely
related objects. The nuclear luminosities are low, both in absolute terms and
relative to the Eddington rates. All of them have compact radio cores, whose
strength relative to the optical nuclear emission places them in the league of
radio-loud active nuclei. The broad-band spectral energy distributions of these
sources are most notable for their deficit of ultraviolet emission compared to
those observed in luminous Seyfert 1 nuclei and quasars. The double-peaked
broad-line radio galaxies Arp 102B and Pictor A have very similar attributes.
We discuss how these characteristics can be understood in the context of
advection-dominated accretion onto massive black holes.


title: Konus catalog of SGR activity to 2000

abstract:
  Observational data on the bursting activity of all five known Soft Gamma
Repeaters are presented. This information was obtained with Konus gamma-ray
burst experiments on board Venera 11-14, Wind, and Kosmos-2326 spacecraft in
the period from 1978 to 2000. These data on appearance rates, time histories,
and energy spectra of repeated soft bursts obtained with similar instruments
and collected together in a comparable form should be useful for further
studies of SGRs. (available at http://www.ioffe.rssi.ru/LEA/SGR/Catalog/).


title: Cosmic Phase Transitions

abstract:
  The sequence of phase transitions during the hot history of the universe is
followed within a phenomenological framework. Particular emphasis is put on the
QCD confinement transition, which is at reach under earth laboratory
conditions. A tepid inflationary scenario on the GUT scale with bubble grow at
moderate supercooling is discussed.


title:
A Flat Universe from High-Resolution Maps of the Cosmic Microwave
  Background Radiation

abstract:
  The blackbody radiation left over from the Big Bang has been transformed by
the expansion of the Universe into the nearly isotropic 2.73K Cosmic Microwave
Background. Tiny inhomogeneities in the early Universe left their imprint on
the microwave background in the form of small anisotropies in its temperature.
These anisotropies contain information about basic cosmological parameters,
particularly the total energy density and curvature of the universe. Here we
report the first images of resolved structure in the microwave background
anisotropies over a significant part of the sky. Maps at four frequencies
clearly distinguish the microwave background from foreground emission. We
compute the angular power spectrum of the microwave background, and find a peak
at Legendre multipole $\ell_{peak}=(197 \pm 6)$, with an amplitude
$DT_{200}=(69 \pm 8)\mu K$. This is consistent with that expected for cold dark
matter models in a flat (euclidean) Universe, as favoured by standard
inflationary scenarios.


title: Tidal dwarf candidates in a sample of interacting galaxies

abstract:
  We present deep optical B, V, R images of a sample of 10 interacting systems
which were selected for their resemblance to disturbed galaxies at high
redshift. Photometry is performed on knots in the tidal features of the
galaxies. We calculate a grid of evolutionary synthesis models with two
metallicities and various burst strengths for systems consisting of some
fraction of the stellar population of a progenitor spiral plus starburst. By
comparison with two-color diagrams we interpret the photometric data, select
from a total of about 100 condensations 36 star-forming objects that are
located in the tidal features and predict their further evolution. Being more
luminous by 4 mag than normal HII regions we argue that these objects could be
tidal dwarf galaxies or their progenitors, although they differ in number and
mean luminosity from the already known tidal dwarf galaxies typically located
at the end of tidal tails in nearby giant interacting systems. From comparison
with our models we note that all objects show young burst ages. The young
stellar component formed in these tidal dwarf candidates contributes up to 18%
to the total stellar mass at the end of the starburst and dominates the optical
luminosity. This may result in fading by up to 2.5 mag in B during the next 200
Myrs after the burst.


title: Cataclysmic variables as sources of gravitational waves

abstract:
  General Relativity predicts that binary systems of stars produce
gravitational waves of significant intensity. Here we are particularly
interested in the cataclysmic variable binaries (CVs). These systems emit low
frequency gravitational waves, $ f < 10^{-3} Hz$. We present here a catalog of
CVs and argue that part of them are capable of being detected by the Laser
Interferometer Space Antenna (LISA).


title: Magnetospheric Scattering and Emission in Millisecond Pulsars

abstract:
  We model the formation of magnetospheric components of millisecond pulsar
light curves, deriving an approximate model for the curved space, `swept-back'
dipole field and following photon emission, propagation, and scattering.
Magnetospheric pulse components are strongly affected by rapid rotation and
Schwarzschild effects.


title:
The Missing Link: Early Methane ("T") Dwarfs in the Sloan Digital Sky
  Survey

abstract:
  We report the discovery of three cool brown dwarfs which fall in the
effective temperature gap between the latest L dwarfs currently known, with no
methane absorption bands in the 1-2.5um range, and the previously known methane
(T) dwarfs, whose spectra are dominated by methane and water. The newly
discovered objects were detected as very red objects in the Sloan Digital Sky
Survey imaging data and have JHK colors between the red L dwarfs and the blue
Gl229B-like T dwarfs. They show both CO and methane absorption in their
near-infrared spectra in addition to water, with weaker methane absorption
features in the H and K bands than those in all other methane dwarfs reported
to date. Due to the presence of methane in these bands, we propose that these
objects are early T dwarfs. The three form part of the brown dwarf spectral
sequence and fill in the large gap in the overall spectral sequence from the
hottest main sequence stars to the coolest methane dwarfs currently known.


title:
The Ionization of the Local Interstellar Medium, as Revealed by FUSE
  Observations of N, O and Ar toward White Dwarf Stars

abstract:
  FUSE spectra of the white dwarf stars G191-B2B, GD 394, WD 2211-495 and WD
2331-475 cover the absorption features out of the ground electronic states of N
I, N II, N III, O I and Ar I in the far ultraviolet, providing new insights on
the origin of the partial ionization of the Local Interstellar Medium (LISM),
and for the case of G191-B2B, the interstellar cloud that immediately surrounds
the solar system. Toward these targets the interstellar abundances of Ar I, and
sometimes N I, are significantly below their cosmic abundances relative to H I.
In the diffuse interstellar medium, these elements are not likely to be
depleted onto dust grains. Generally, we expect that Ar should be more strongly
ionized than H (and also O and N whose ionizations are coupled to that of H via
charge exchange reactions) because the cross section for the photoionization of
Ar I is very high. Our finding that Ar I/H I is low may help to explain the
surprisingly high ionization of He in the LISM found by other investigators.
Our result favors the interpretation that the ionization of the local medium is
maintained by a strong EUV flux from nearby stars and hot gases, rather than an
incomplete recovery from a past, more highly ionized condition.


title: Dynamics of superconducting strings with chiral currents

abstract:
  We rederive, using an elementary formalism, the general solution to the
equations of motion for a superconducting string with a chiral (null) neutral
current, earlier obtained by Carter and Peter. We apply this solution to show
that the motion of such string loops is strictly periodic and analyze cusp-like
behavior and vorton solutions of arbitrary shape. We argue that this solution
can be used to approximately describe the dynamics of superconducting strings
with small non-chiral currents. We use this description to estimate the
electromagnetic radiation power from such strings.


title: Light Curves of Rapidly Rotating Neutron Stars

abstract:
  We consider the effect of rapid rotation on the light curves of neutron stars
with hot polar caps. For $P \approx 3$ms spin periods, the pulse fractions can
be as much as an order of magnitude larger than with simple slowly-rotating
(Schwarzschild) estimates. Doppler boosting, in particular, leads to
characteristic distortion and ``soft lags'' in the pulse profiles, which are
easily measurable in light curves with moderate energy resolution. With $\sim
10^5$ photons it should also be possible to isolate the more subtle distortions
of light travel time variations and frame dragging. Detailed analysis of high
quality millisecond pulsar data from upcoming X-ray missions must include these
effects.


title:
Remarks on the Boomerang results, the baryon density and the leptonic
  asymmetry

abstract:
  The very recent Boomerang results give an estimate of unprecedented precision
of the Cosmic Microwave Background anisotropies on sub--degree scales. A
puzzling feature for theoretical cosmology is the low amplitude of the second
acoustic peak. Through a qualitative discussion, we argue that a scarcely
considered category of flat models, with a leptonic asymmetry, a high baryon
density and a low cosmological constant seems to be in very good agreement with
the data, while still being compatible with big bang nucleosynthesis and some
other observational constraints. Although this is certainly not the only way to
explain the data, we believe that these models deserve to be included in
forthcoming likelihood analyses.


title:
Reionization of the Universe by Starlight and the Photoevaporation of
  Cosmological Minihalos

abstract:
  The first sources of ionizing radiation to condense out of the dark and
neutral IGM sent ionization fronts sweeping outward through their surroundings,
overtaking other condensed objects and photoevaporating them. This feedback of
universal reionization on cosmic structure formation is demonstrated here by
gas dynamical simulations, including radiative transfer, for the case of a
cosmological minihalo of dark matter and baryons exposed to an external source
of ionizing starlight, just after the passage of the global ionization front
created by the source.


title: EUVE Observations of OY Carinae in Superoutburst

abstract:
  The Extreme Ultraviolet Explorer (EUVE) satellite was used for three days
beginning on 1997 Mar 26.96 UT to obtain photometric and spectroscopic
observations of the eclipsing SU UMa-type dwarf nova OY Carinae in
superoutburst. Because of the longer time on source (143 ks), the larger number
of eclipses observed (17), and the higher count rate in the detector (0.5-2.2
counts/s), we are able to significantly strengthen previous reports that there
is little or no eclipse by the secondary of the EUV emission region of OY Car
in superoutburst. The mean EUVE spectrum extends from 70 to 190 A and contains
broad (FWHM~1 A) emission lines of N V, O V-O VI, Ne V-Ne VII, Mg IV-Mg VI, Fe
VI-Fe VIII, and possibly Fe XXIII. Good fits of the observed spectrum are
obtained with a model (similar to that of Seyfert 2 galaxies) wherein radiation
from the boundary layer and accretion disk is scattered into the line of sight
by the system's photoionized accretion disk wind. It is possible to trade off
continuum luminosity for wind optical depth, but reasonable models have a
boundary layer temperature T_{bl}=90-130 kK and a boundary layer and accretion
disk luminosity L_{bl}=L_{disk} ~4x10^{34} erg/s ~ 10 Lsun, corresponding to a
mass-accretion rate Mdota~10^{-8} Msun/yr; an absorbing column density
N_H=1.6-3.5x10^{19} cm^{-2}; and a wind mass-loss rate Mdotw~10^{-10} Msun/yr ~
0.01 Mdota. Because radiation pressure alone falls an order of magnitude short
of driving such a wind, magnetic forces must also play a role in driving the
wind of OY Car in superoutburst.


title:
Constraints on dark matter physics from dwarf galaxies through galaxy
  cluster haloes

abstract:
  One of the predictions of the standard CDM is that dark haloes have centrally
divergent density profiles. An extensive body of rotation curve observations of
dwarf and low surface brightness galaxies shows the dark haloes of those
systems to be characterized by soft constant density central cores. Several
physical processes have been proposed to produce soft cores in dark haloes,
each one with different scaling properties. With the aim of discriminating
among them we have examined the rotation curves of dark matter dominated dwarf
and low surface brightness galaxies and the inner mass profiles of two clusters
of galaxies lacking a central cD galaxy and with evidence of soft cores in the
centre. The core radii and central densities of these haloes scale in a well
defined manner with the depth of their potential wells, as measured through the
maximum circular velocity. As a result of our analysis we identify
self-interacting CDM as a viable solution to the core problem, where a
non-singular isothermal core is formed in the halo center surrounded by a
Navarro, Frenk, & White profile in the outer parts. We show that this
particular physical situation predicts core radii in agreement with
observations. Furthermore, using the observed scalings, we derive an expression
for the minimum cross section (\sigma) which has an explicit dependence with
the halo dispersion velocity (v). If m_x is the mass of the dark matter
particle: \sigma/m_x ~4 10^-25 (v/100 km s^-1)^-1 cm^2/Gev.


title: A critical-density closed Universe in Brans-Dicke theory

abstract:
  In a Brans-Dicke (BD) cosmological model, the energy density associated with
some scalar field decreases as $\displaystyle a^{{-2}(\frac{\omega_{o}+
{\frac12}%}{\omega_{o}+1})} $ with the scale factor $a(t)$ of the Universe,
giving a matter with an Equation of state $\displaystyle
p=-{1/3}(\frac{2+\omega_{o}}{1+\omega_{o}}) \rho $. In this model, the Universe
could be closed but still have a nonrelativistic-matter density corresponding
to its critical value, $\Omega_{o}=1$. Different cosmological expressions, such
as, luminosity distance, angular diameter, number count and ratio of the
redshift tickness-angular size, are determined in terms of the redshift for
this model.


title: An Exposition on Inflationary Cosmology

abstract:
  This paper is intended to offer a pedagogical treatment of cosmological
modeling and inflationary cosmology. In recent years, inflation has become
accepted as a standard scenario making predictions that are testable by
observations of the cosmic background. It is therefore manifest that anyone
wishing to pursue the study of cosmology and large-scale structure should have
this scenario at their disposal. The author hopes this paper will serve to
`bridge the gap' between technical and popular accounts of the subject.


title: First Estimations of Cosmological Parameters From BOOMERANG

abstract:
  The anisotropy of the cosmic microwave background radiation contains
information about the contents and history of the universe. We report new
limits on cosmological parameters derived from the angular power spectrum
measured in the first Antarctic flight of the BOOMERANG experiment. Within the
framework of inflation-motivated adiabatic cold dark matter models, and using
only weakly restrictive prior probabilites on the age of the universe and the
Hubble expansion parameter $h$, we find that the curvature is consistent with
flat and that the primordial fluctuation spectrum is consistent with scale
invariant, in agreement with the basic inflation paradigm. We find that the
data prefer a baryon density $\Omega_b h^2$ above, though similar to, the
estimates from light element abundances and big bang nucleosynthesis. When
combined with large scale structure observations, the BOOMERANG data provide
clear detections of both dark matter and dark energy contributions to the total
energy density $\Omega_{\rm {tot}}$, independent of data from high redshift
supernovae.


title: The hardness-duration correlation in the two classes of gamma-ray bursts

abstract:
  The well-known hardness-duration correlation of gamma-ray bursts (GRBs) is
investigated with the data of the 4B catalog. We find that, while the hardness
ratio and the duration are obviously correlated for the entire set of the 4B
catalog, they are not at all correlated for the two subsets divided at the
duration of 2 seconds. However, for other subsets with comparable sizes, the
two quantities are significantly correlated. The following conclusions are then
reached: (1) the existence of two classes of GRBs is confirmed; (2) the
hardness ratio and the duration are not at all correlated for any of the two
classes; (3) different classes of GRBs have different distributions of the
hardness ratio and the duration and it is this difference that causes the
correlation between the two quantities for the entire set of the bursts.


title:
Evidence consistent with the cosmological interpretation of quasar
  redshifts

abstract:
  In this letter, the old issue of whether redshifts of quasars are of
cosmological origin is investigated. We make a plot of absorption redshifts
versus emission redshifts for quasars with large amounts of data. Our study
shows that, almost all absorption redshifts are smaller than the corresponding
emission redshifts. The relation between the absorption and emission redshifts
predicted by current cosmological models is well obeyed. The result confirms
that redshifts of quasars are indeed distance indicators. It might be the most
obvious evidence found so far to be consistent with the cosmological
interpretation of quasar redshifts.


title:
Formulas for direct determination of real speed in Galactic superluminal
  sources

abstract:
  In this paper we show explicit and direct relations between the expected
quantities and the observed quantities for the components of Galactic
superluminal sources. Basic formulas for calculating the real speed and the
angle to the line of sight of the components from the data of proper motions
and the distance of the source are presented. We point out that the real speed
and the angle to the line of sight of components can be uniquely and directly
determined from the observed values of the proper motions and the distance of
the source. It is not necessary to calculate an intermediate quantity first and
then using the resulted value to calculate the two required quantities. The
process of the calculation is simple, and in this way, some extra uncertainties
are avoided.


title:
Globular Clusters in the dE,N galaxy NGC 3115 DW1: New Insights from
  Spectroscopy and HST Photometry

abstract:
  The properties of globular clusters in dwarf galaxies are key to
understanding the formation of globular cluster systems, and in particular in
verifying scenarios in which globular cluster systems of larger galaxies formed
(at least partly) from the accretion of dwarf galaxies. Here, we revisit the
globular cluster system of the dE,N galaxy NGC 3115 DW1 - a companion of the
nearby S0 galaxy NGC 3115 - adding Keck/LRIS spectroscopy and HST/WFPC2 imaging
to previous ground-based photometry. Spectra for seven globular clusters reveal
normal abundance ratios with respect to the Milky Way and M31 clusters, as well
as a relatively high mean metallicity ([Fe/H] = -1.0+/-0.1 dex). Crude
kinematics indicate a high velocity dispersion within 10 kpc which could either
be caused by dark matter dominated outer regions, or by the stripping of outer
globular clusters by the nearby giant galaxy NGC 3115. The total galaxy mass
out to 3 and 10 kpc lies between 10^10 and 10^11 solar masses and 2*10^10 and
4*10^11 solar masses, respectively, depending on the mass estimator used and
the assumptions on cluster orbits and systemic velocity. The HST imaging allows
measurement of sizes for two clusters, returning core radii around 2.0 pc,
similar to the sizes observed in other galaxies. Spectroscopy allows an
estimate of the degree of contamination by foreground stars or background
galaxies for the previous ground-based photometry, but does not require a
revision of previous results: NGC 3115 DW1 hosts around 60+/-20 clusters which
corresponds to a specific frequency of 4.9+/-1.9, on the high end for massive
dEs. Given its absolute magnitude (M_V=-17.7 mag) and the properties of its
cluster system, NGC 3115 DW1 appears to be a transition between a luminous dE
and low-luminosity E galaxy.


title: The STARE Project: A Transit Search for Hot Jupiters

abstract:
  The STARE instrument is a small aperture, wide-field, CCD-based telescope
that delivers high cadence time series photometry on roughly 40,000 stars in a
typical field centered on the galactic plane. In a two-month observing run on a
field, we obtain sufficient precision on roughly 4,000 stars to detect a
close-in Jupiter-sized companion in an edge-on orbit. We also used this
instrument to detect the planetary transits across the Sun-like star HD209458.
The project is now in its third season, and we have acquired a large dataset on
several fields. Given the frequency of close-in extrasolar planets found by the
radial velocity surveys, and the recent confirmation that at least some of
these are indeed gas giants, the STARE project should be able to detect roughly
a dozen Jupiter-sized planets in its existing dataset.


title: Halo occupation numbers and galaxy bias

abstract:
  We propose a heuristic model that displays the main features of realistic
theories for galaxy bias. We show that the low-order clustering statistics of
the dark-matter distribution depend almost entirely on the locations and
density profiles of dark-matter haloes. A hypothetical galaxy catalogue depends
on (i) the efficiency of galaxy formation, as manifested by the halo occupation
number -- the number of galaxies brighter than some sample limit contained in a
halo of a given mass; (ii) the location of these galaxies within their halo.
The first factor is constrained by the empirical luminosity function of groups.
For the second factor, we assume that one galaxy marks the halo centre, with
any remaining galaxies acting as satellites that trace the halo mass. These
simple assumptions amount to a recipe for non-local bias, in which the
probability of finding a galaxy is not a simple function of its local mass
density. We have applied this prescription to some CDM models of current
interest, and find that the predictions are close to the observed galaxy
correlations for a flat $\Omega=0.3$ model ($\Lambda$CDM), but not for an
$\Omega=1$ model with the same power spectrum ($\tau$CDM). This is an
inevitable consequence of cluster normalization for the power spectra:
cluster-scale haloes of given mass have smaller core radii for high $\Omega$,
and hence display enhanced small-scale clustering. Finally, the pairwise
velocity dispersion of galaxies in the $\Lambda$CDM model is lower than that of
the mass, allowing cluster-normalized models to yield a realistic Mach number
for the peculiar velocity field. This is largely due to the strong variation of
galaxy-formation efficiency with halo mass that is required in this model.


title: FUSE Observations of the Low-Redshift Lyman-beta Forest

abstract:
  We describe a moderate-resolution (20-25 km/s) FUSE study of the low-redshift
intergalactic medium. We report on studies of 7 extragalactic sightlines and 12
Ly-beta absorbers that correspond to Ly-alpha lines detected by HST/GHRS and
STIS. These absorbers appear to contain a significant fraction of the low-z
baryons and were a major discovery of the HST spectrographs. Using FUSE data,
with 40 mA (4-sigma) Lyb detection limits, we have employed the equivalent
width ratio of Lyb/Lya and occasionally higher Lyman lines, to determine the
doppler parameter, b, and accurate column densities, N(HI), for moderately
saturated lines. We detect Lyb absorption corresponding to all Lya lines with
EW > 200 mA. The Lyb/Lya ratios yield a preliminary distribution function of
doppler parameters, with mean <b> = 31.4 +/- 7.4 km/s and median b = 28 km/s,
comparable to values at redshifts z = 2.0-2.5. If thermal, these b-values
correspond to T(HI) ~ 50,000 K, although the inferred doppler parameters are
considerably less than the widths derived from Lya profile fitting,
<b(dopp)/b(width)> = 0.52. The typical increase in column density over that
derived from profile fitting is Delta[log N(HI)] = 0.3, but ranges up to 1.0
dex. Our data suggest that the low-z Lya absorbers contain sizable non-thermal
motions or velocity components in the line profile, perhaps arising from
cosmological expansion and infall.


title: FUSE Observations of O VI in High Velocity Clouds

abstract:
  We have used moderate-resolution (FWHM ~ 25 km/sec) spectra of AGNs and QSOs
observed by the Far Ultraviolet Spectroscopic Explorer (FUSE) to make the first
definitive measurements of absorption by hot gas in high velocity clouds (HVCs)
at large distances from the Galactic plane. Seven of the 11 sight lines studied
exhibit high velocity (|V(LSR)| > 100 km/sec) O VI 1031.93 A absorption with
log N(O VI) = 13.79-14.62. High velocity O VI absorption is detected in the
distant gas of H I HVC Complex C, the Magellanic Stream, several HVCs believed
to be in the Local Group, and the outer Galaxy. The fraction of O VI in HVCs
along the seven sight lines containing high velocity O VI averages about 30
percent, with a full range of 10-70 percent. The O VI detections imply that hot
(log T(K) = 5-6) collisionally-ionized gas is an important constituent of the
HVCs since O VI is difficult to produce by photoionization unless the path
lengths over which the absorption occurs are very large (>100 kpc). The
association of O VI with H I HVCs in many cases suggests that the O VI may be
produced at interfaces or mixing layers between the H I clouds and hot, low
density gas in the Galactic corona or Local Group. Alternatively, the O VI may
originate within cooling regions of hot gas clouds as they are accreted onto
the Galaxy.


title: FUSE Observations of Diffuse Interstellar Molecular Hydrogen

abstract:
  We describe a moderate-resolution FUSE mini-survey of H2 in the Milky Way and
Magellanic Clouds, using four hot stars and four AGN as background sources.
FUSE spectra of nearly every stellar and extragalactic source exhibit numerous
absorption lines from the H2 Lyman and Werner bands between 912 and 1120 A. One
extragalactic sightline, PKS 2155-304, with low N(HI) shows no detectable H2
and could be the "Lockman Hole" of molecular gas, of importance for QSO
absorption-line studies. We measure H2 column densities in low rotational
states (J = 0 and 1) to derive rotational and/or kinetic temperatures of
diffuse interstellar gas. The higher-J abundances can constrain models of the
UV radiation fields and gas densities. In three optically thick clouds toward
extragalactic sources, we find n(H) ~ 30-50 cm(-3) and cloud thicknesses of 2-3
pc. The rotational temperatures for H2 at high Galactic latitude, <T_01> = 107
+/- 17 K (seven sightlines) and 120 +/- 13 K (three optically thick clouds),
are higher than those in the Copernicus sample composed primarily of targets in
the disk. We find no evidence for great differences in the abundance or state
of excitation of H2 between sight lines in the Galaxy and those in the SMC and
LMC. In the future, we will probe the distribution and physical parameters of
diffuse molecular gas in the disk and halo and in the lower-metallicity
environs of the LMC and SMC.


title: On the Nature of Andromeda IV

abstract:
  Lying at a projected distance of 40' or 9 kpc from the centre of M31,
Andromeda IV is an enigmatic object first discovered during van den Bergh's
search for dwarf spheroidal companions to M31. Being bluer, more compact and
higher surface brightness than other known dwarf spheroidals, it has been
suggested that And IV is either a relatively old `star cloud' in the outer disk
of M31 or a background dwarf galaxy. We present deep HST WFPC2 observations of
And IV and the surrounding field which, along with ground-based long-slit
spectroscopy and Halpha imagery, are used to decipher the true nature of this
puzzling object. We find compelling evidence that And IV is a background galaxy
seen through the disk of M31. The moderate surface brightness (SB(V)~24), very
blue colour (V-I<~0.6), low current star formation rate (~0.001 solar mass/yr)
and low metallicity (~10% solar) reported here are consistent with And IV being
a small dwarf irregular galaxy, perhaps similar to Local Group dwarfs such as
IC 1613 and Sextans A. Although the distance to And IV is not tightly
constrained with the current dataset, various arguments suggest it lies in the
range 5<~D<~8 Mpc, placing it well outside the confines of the Local Group. It
may be associated with a loose group of galaxies, containing major members UGC
64, IC 1727 and NGC 784. We report an updated position and radial velocity for
And IV.


title: Radio Galaxy Clustering at z~0.3

abstract:
  Radio galaxies are uniquely useful as probes of large-scale structure as
their uniform identification with giant elliptical galaxies out to high
redshift means that the evolution of their bias factor can be predicted. As the
initial stage in a project to study large-scale structure with radio galaxies
we have performed a small redshift survey, selecting 29 radio galaxies in the
range 0.19<z<0.45 from a contiguous 40 square degree area of sky. We detect
significant clustering within this sample. The amplitude of the two-point
correlation function we measure is consistent with no evolution from the local
(z<0.1) value. This is as expected in a model in which radio galaxy hosts form
at high redshift and thereafter obey a continuity equation, although the
signal:noise of the detection is too low to rule out other models. Larger
surveys out to z~1 should reveal the structures of superclusters at
intermediate redshifts and strongly constrain models for the evolution of
large-scale structure.


title: 2MASS Extended Sources in the Zone of Avoidance

abstract:
  The Two Micron All Sky Survey (2MASS) is now underway and will provide a
complete census of galaxies as faint as 13.5 mag (3 mJy) at 2.2 microns for
most of the sky, and ~12.1 mag (10 mJy) for regions veiled by the Milky Way.
This census has already discovered nearby galaxies previously hidden behind our
Galaxy, and will allow delineation of large-scale structures in the
distribution of galaxies across the whole sky. Here we report the detection and
discovery of new extended sources from this survey for fields incorporating the
Galactic plane at longitudes between 40 and 70 deg. The area-normalized
detection rate is ~1-2 galaxies per deg^2 brighter than 12.1 mag (10 mJy),
roughly constant with Galactic latitude throughout the "Zone of Avoidance", of
which 85-95% are newly discovered sources. In conjunction with the deep HI
surveys, 2MASS will greatly increase the current census of galaxies hidden
behind the Milky Way.


title: New constraints on neutrino physics from Boomerang data

abstract:
  We have performed a likelihood analysis of the recent data on the Cosmic
Microwave Background Radiation (CMBR) anisotropy taken by the Boomerang
experiment. We find that this data places a strong upper bound on the radiation
density present at recombination. Expressed in terms of the equivalent number
of neutrino species the $2\sigma$ bound is N_nu < 13, and the standard model
prediction, N_nu = 3.04, is completely consistent the the data. This bound is
complementary to the one found from Big Bang nucleosynthesis considerations in
that it applies to any type of radiation, i.e. it is not flavour sensitive. It
also applies to the universe at a much later epoch, and as such places severe
limits on scenarios with decaying neutrinos. The bound also yields a firm upper
limit on the lepton asymmetry in the universe.


title: VLA Imaging of the Disk Surrounding the Nearby Young Star TW Hya

abstract:
  The TW Hya system is perhaps the closest analog to the early solar nebula. We
have used the Very Large Array to image TW Hya at wavelengths of 7mm and 3.6 cm
with resolutions 0.1 arcseconds (about 5 AU) and 1.0 arcseconds (about 50 AU),
respectively. The 7mm emission is extended and appears dominated by a dusty
disk of radius larger than 50 AU surrounding the star. The 3.6 cm emission is
unresolved and likely arises from an ionized wind or gyrosynchrotron activity.
The dust spectrum and spatially resolved 7mm images of the TW Hya disk are
fitted by a simple model with temperature and surface density described by
radial power laws, $T(r)\propto r^{-0.5}$ and $\Sigma(r) \propto r^{-1}$. These
properties are consistent with an irradiated gaseous accretion disk of mass
$\sim0.03~{\rm M_{\odot}}$ with an accretion rate $\sim10^{-8}~{\rm
M_{\odot}yr^{-1}}$ and viscosity parameter $\alpha = 0.01$. The estimates of
mass and mass accretion rates are uncertain as the gas-to-dust ratio in the TW
Hya disk may have evolved from the standard interstellar value.


title: Reflected Iron Line From a Source Above a Kerr Black Hole Accretion Disc

abstract:
  In this paper we present a fully relativistic approach to modelling both the
continuum emission and the reflected fluorescent iron line from a primary X-ray
source near a Kerr black hole. The X-ray source is located above an accretion
disc orbiting around the black hole. The source is assumed to be a static point
source located on an arbitrary position above the disc, on or off the axis of
rotation. We carry out Monte Carlo simulations in order to estimate the iron
line spectrum as well as its equivalent width. Because of the gravitational
lensing effect, an enhancement of the iron line is expected when the primary
source is located close to the central black hole. We find that for a source
located on the axis of rotation the enhancement is relatively modest. An
observer at inclination 30 degrees would measure an equivalent width of ~300eV
in the extreme case of a maximally rotating black hole and a source located at
height 1.5 gravitational radius from the centre. This corresponds to an
equivalent width enhancement factor of about 2 compared to the classical value
where no lensing effect comes into play. However, when allowing the source to
be located off the axis of rotation, much stronger enhancement can be obtained.
In the extreme case of a maximally rotating black hole and a source located
just above the approaching side of the disc, an observer at inclination 30d
egrees could measure an equivalent width as high as ~1.5 keV (i.e. ~10 times
the classical value). We also find that observers located at high inclination
angles observe a stronger line than observers at low inclination angles.


title:
The characteristics of high velocity O and B stars which are ejected
  from supernovae in binary systems

abstract:
  We perform binary population synthesis calculations to study the origin and
the characteristics of runaway O and B stars which are ejected by the supernova
explosion of the companion star in a binary system. The number of OB runaways
can be explained from supernova ejections only if: high mass stars are
preferentially formed in binaries, the initial mass ratio distribution is
strongly peaked to unity and stars are rejuvenated to zero age upon accretion
of mass from a companion star. Taking these requirements into consideration we
conclude that at most 30% of the runaway O stars but possibly all runaway B
stars obtain high velocities due to supernovae in evolving binaries. Stars
which obtain high velocities via supernova ejections have the following
characteristics: 1) at least 10% of the high velocity B stars and half the O
stars have a mass greater than the turn off mass of the cluster in which they
are born and would be observed as blue stragglers in the parent cluster, 2)
their equatorial rotational velocities are proportional to their space velocity
and 3) between 20% and 40% of the runaways have neutron star companions but
less than 1% are visible as radio pulsars in part of the orbit.


title: Evidence against or for topological defects in the BOOMERanG data ?

abstract:
  The recently released BOOMERanG data was taken as ``contradicting topological
defect predictions''. We show that such a statement is partly misleading.
Indeed, the presence of a series of acoustic peaks is perfectly compatible with
a non-negligible topological defects contribution. In such a mixed perturbation
model (inflation and topological defects) for the source of primordial
fluctuations, the natural prediction is a slightly lower amplitude for the
Doppler peaks, a feature shared by many other purely inflationary models. Thus,
for the moment, it seems difficult to rule out these models with the current
data.


title:
Interpretation of the Spatial Power Spectra of Neutral Hydrogen in the
  Galaxy and in the Small Magellanic Cloud

abstract:
  Recent 21 cm radio observations of H$_I$ regions in the Small Magellanic
Cloud, have revealed spatial power spectra of the intensity, which are quite
similar in shape to those previously deduced for the Galaxy. The similarity, in
spite the differences in the physical parameters between the Galaxy and the
SMC, suggests that the shape of the power spectra reflects some underlying
mechanism which is not too sensitive to the environmental specifics. In this
paper we present an interpretation for the observational power spectra in terms
of a large scale turbulence in the interstellar medium, in which the emitting
H$_I$ regions are embedded. The turbulence gives rise to density fluctuations
which lead to the observed intensity fluctuations, in the H$_I$ regions. The
observational power spectra are used to deduce the turbulence spectral
function.
  In the SMC, the turbulence largest eddies are comparable in scale to the SMC
itself. This implies that turbulent mixing should have smoothed out any large
scale abundance gradients. Indeed, this seems to be the case, observationally.
  The turbulence is also expected to amplify and shape up the large scale
magnetic field. Indeed, the observational data indicate the existence of a
large scale disordered field of the strength expected from energy equilibrium
with the turbulent velocity field. The large scale turbulence is most probably
generated by instabilities in the large scale flows induced by the tidal close
encounter with the LMC $ \sim 2\times 10^8{\rm yr}$ ago. The life-time of the
largest eddies is $\sim 4\times 10^8{\rm yr}$ so the turbulence had not yet
enough time to decay and persists even though the energy source is no longer
there.


title: Space-borne global astrometric surveys: the hunt for extra-solar planets

abstract:
  The proposed global astrometry mission {\it GAIA}, recently recommended
within the context of ESA's Horizon 2000 Plus long-term scientific program,
appears capable of surveying the solar neighborhood within $\sim$ 200 pc for
the astrometric signatures of planets around stars down to the magnitude limit
of $V$=17 mag, which includes late M dwarfs at 100 pc. Realistic end-to-end
simulations of the GAIA global astrometric measurements have yielded first
quantitative estimates of the sensitivity to planetary perturbations and of the
ability to measure their orbital parameters. Single Jupiter-mass planets around
normal solar-type stars appear detectable up to 150 pc ($V\le $12 mag) with
probabilities $\ge$ 50 per cent for orbital periods between $\sim$2.5 and
$\sim$8 years, and their orbital parameters measured with better than 30 per
cent accuracy to about 100 pc. Jupiter-like objects (same mass and period as
our giant planet) are found with similar probabilities up to 100 pc.These first
experiments indicate that the {\it GAIA} results would constitute an important
addition to those which will come from the other ongoing and planned
planet-search programs. These data combined would provide a formidable testing
ground on which to confront theories of planetary formation and evolution.


title:
Mapping IR Enhancements in Closely Interacting Spiral-Spiral Pairs. I.
  ISO~CAM and ISO~SWS Observations

abstract:
  Mid-infrared (MIR) imaging and spectroscopic observations are presented for a
well defined sample of eight closely interacting (CLO) pairs of spiral galaxies
that have overlapping disks and show enhanced far-infrared (FIR) emission. The
goal is to study the star formation distribution in CLO pairs, with special
emphasis on the role of 'overlap starbursts'. Observations were made with the
Infrared Space Observatory (ISO) using the CAM and SWS instruments. The ISO~CAM
maps, tracing the MIR emission of warm dust heated by young massive stars, are
compared to new ground based H$\alpha$ and R-band images. We identify three
possible subgroups in the sample, classified according to the star formation
morphology: (1) advanced mergers (Arp~157, Arp~244 and Arp~299), (2) severely
disturbed systems (Arp~81 and Arp~278), and (3) less disturbed systems
(Arp~276, KPG 347 and KPG 426). Localized starbursts are detected in the
overlap regions in all five pairs of subgroups (1) and (2), suggesting that
they are a common property in colliding systems. Except for Arp~244, the
'overlap starburst' is usually fainter than the major nuclear starburst in CLO
pairs. Star formation in 'less disturbed systems' is often distributed
throughout the disks of both galaxies with no 'overlap starburst' detected in
any of them. These systems also show less enhanced FIR emission, suggesting
that they are in an earlier interaction stage than pairs of the other two
subgroups where the direct disk collisions have probably not yet occurred.


title:
Interferometric Astrometry of the Low-mass Binary Gl 791.2 (= HU Del)
  Using Hubble Space Telescope Fine Guidance Sensor 3: Parallax and Component
  Masses

abstract:
  With fourteen epochs of fringe tracking data spanning 1.7y from Fine Guidance
Sensor 3 we have obtained a parallax (pi_abs=113.1 +- 0.3 mas) and perturbation
orbit for Gl 791.2A. Contemporaneous fringe scanning observations yield only
three clear detections of the secondary on both interferometer axes. They
provide a mean component magnitude difference, Delta V = 3.27 +- 0.10. The
period (P = 1.4731 yr) from the perturbation orbit and the semi-major axis (a =
0.963 +- 0.007 AU) from the measured component separations with our parallax
provide a total system mass M_A + M_B = 0.412 +- 0.009 M_sun. Component masses
are M_A=0.286 +- 0.006 M_sun and M_B = 0.126 +- 0.003 M_sun. Gl 791.2A and B
are placed in a sparsely populated region of the lower main sequence
mass-luminosity relation where they help define the relation because the masses
have been determined to high accuracy, with errors of only 2%.


title:
Age difference between the populations of binary and single F~stars
  revealed from HIPPARCOS data

abstract:
  We have compared the kinematics and metallicity of the main sequence binary
and single {\it uvby} F stars from the {\it HIPPARCOS} catalog to see if the
populations of these stars originate from the same statistical ensemble. The
velocity dispersions of the known unresolved binary F stars have been found to
be dramatically smaller than those of the single F stars. This suggests that
the population of these binaries is, in fact, younger than that of the single
stars, which is further supported by the difference in metal abundance: the
binaries turn out to be, on average, more metal rich than the single stars. So,
we conclude that the population of these binaries is indeed {\it younger} than
that of the single F stars. Comparison of the single F stars with the C
binaries (binary candidates identified in Suchkov & McMaster 1999) has shown,
on the other hand, that the latter stars are, on average, {\it older} than the
single F stars. We suggest that the age difference between the single F stars,
known unresolved binaries, and C binaries is associated with the fact that
stellar evolution in a binary systems depends on the binary components mass
ratio and separation, with these parameters being statistically very different
for the known binaries and C binaries (e.g., mostly substellar secondaries in C
binaries versus stellar secondaries in known binaries).
  In general we conclude that the populations of known binaries, C binaries,
and single F stars do not belong to the same statistical ensemble. The
implications of the discovered age difference between these populations along
with the corresponding differences in kinematics and metallicity should be
important not only for understanding the evolution of stars but also for the
history of star formation and the evolution of the local galactic disk.


title:
Implications of Recent Observational Discoveries for the Nature and
  Origin of Gamma-Ray Bursts

abstract:
  The discoveries that GRBs have X-ray, optical and radio afterglows have
connected the study of GRBs to the rest of astronomy, and revolutionized the
field. In this review, I discuss the implications that the observation of these
afterglows have for burst energies and luminosities, and for models of the
bursts and their afterglows. I describe recent evidence linking the long,
softer, smoother GRBs detected by BeppoSAX and core collapse supernovae.
Finally, I summarize recent work showing that, if these GRBs are due to the
collapse of massive stars, they may provide a powerful probe of the very high
redshift universe.


title:
Eclipsing Binaries as Astrophysical Laboratories: Internal Structure,
  Convective Core Overshooting and Evolution of the B-star Components of V380
  Cygni

abstract:
  New photometric solutions have been carried out on the important eccentric
eclipsing system V380 Cygni (B1.5II-III + B2V) from UBV differential
photoelectric photometry obtained by us. The photometric elements obtained from
the analysis of the light curves have been combined with the spectroscopic
solution recently published by Popper & Guinan and have led to the physical
properties of the system components. The effective temperature of the stars has
been determined by fitting IUE UV spectrophotometry to Kurucz model atmospheres
and compared with other determinations from broad-band and intermediate-band
standard photometry. The values of mass, absolute radius, and effective
temperature, for the primary and secondary stars are: 11.1+/-0.5 Mo, 14.7+/-0.2
Ro, 21350+/-400 K, and 6.95+/-0.25 Mo, 3.74+/-0.07 Ro, 20500+/-500 K,
respectively. In addition, a re-determination of the system's apsidal motion
rate has been done from the analysis of 12 eclipse timings obtained from 1923
to 1995. Using stellar structure and evolutionary models with modern input
physics, tests on the extent of convection in the core of the more massive star
of the system have been carried out. Both the analysis of the log g-log Teff
diagram and the apsidal motion study indicate a star with a larger convective
core, and thus more centrally condensed, than currently assumed. This has been
quantified in form of an overshooting parameter with a value of 0.6+/-0.1.
Finally, the tidal evolution of the system (synchronization and circularization
times) has also been studied.


title:
Infrared Observations of Hot Gas and Cold Ice toward the Low Mass
  Protostar Elias 29

abstract:
  We have obtained the full 1-200 um spectrum of the low luminosity (36 Lsun)
Class I protostar Elias 29 in the Rho Ophiuchi molecular cloud. It provides a
unique opportunity to study the origin and evolution of interstellar ice and
the interrelationship of interstellar ice and hot core gases around low mass
protostars. We see abundant hot CO and H2O gas, as well as the absorption bands
of CO, CO2, H2O and ``6.85 um'' ices. We compare the abundances and physical
conditions of the gas and ices toward Elias 29 with the conditions around
several well studied luminous, high mass protostars. The high gas temperature
and gas/solid ratios resemble those of relatively evolved high mass objects
(e.g. GL 2591). However, none of the ice band profiles shows evidence for
significant thermal processing, and in this respect Elias 29 resembles the
least evolved luminous protostars, such as NGC 7538 : IRS9. Thus we conclude
that the heating of the envelope of the low mass object Elias 29 is
qualitatively different from that of high mass protostars. This is possibly
related to a different density gradient of the envelope or shielding of the
ices in a circumstellar disk. This result is important for our understanding of
the evolution of interstellar ices, and their relation to cometary ices.


title:
Anisotropy of the Hubble Constant in a Cosmological Model with a Local
  Void on Scales of ~ 200 Mpc

abstract:
  A spherical cosmological model with a local void on scales of $\sim 200$ Mpc
and with an inhomogeneous Hubble constant was proposed in recent two papers.
This model explains consistently the observed properties of the cosmic bulk
flow, the accelerating behavior of type Ia supernovae and the CMB dipole
anisotropy without invoking a cosmological constant. As we are in a position
deviated from the center in the model, the anisotropy of the Hubble constant
appears owing to the directional difference of the distance from the observer
to the boundary of the void region. It is found that the anisotropy is
maximally about 6% of the constant in the region of $200 \sim 500$ Mpc from us.
This inhomogeneity and anisotropy of the Hubble constant are not so large as to
be inconsistent with the present observation. The detection of this anisotropy
in the future will be useful to clarify the implication of the inhomogeneity of
the Hubble constant.


title: Orbital dynamics of Cygnus X-3

abstract:
  Orbital-phased-resolved infrared spectra of Cygnus X-3 in outburst and
quiescence, including tomographic analysis, are presented. We confirm the
phasing of broad HeII and NV lines in quiescence, such that maximum blue shift
corresponds to the X-ray minimum at phase = 0.00 +/- 0.04. In outburst,
double-peaked HeI structures show a similar phasing with two significant
differences: (a) although varying in relative strength, there is continuous
line emission in blue and red peaks around the orbit, and (b) an absorption
component, ~1/4 of an orbit out of phase with the emission features, is
discerned. Doppler tomograms of the double-peaked profiles are consistent with
a disk-wind geometry, rotating at velocities of 1000 km/s. Regrettably, the
tomography algorithm will produce a similar ring structure from alternative
line sources if contaminated by overlying P Cygni profiles. This is certainly
the case in the strong 2.0587 micron HeI line, leading to an ambiguous solution
for the nature of double-peaked emission. The absorption feature, detected 1/4
of an orbit out of phase with the emission features, is consistent with an
origin in the He star wind and yields for the first time a plausible radial
velocity curve for the system. We directly derive the mass function of the
system, 0.027 M_sun. If we assume a neutron star accretor and adopt a high
orbital inclination, i > 60 degrees, we obtain a mass range for the He star of
5 M_sun < M_WR < 11 M_sun. Alternatively if the compact object is a black hole,
we estimate M_BH < 10 M_sun. We discuss the implications of these masses for
the nature and size of the binary system.


title:
Correlated V/R and IR photometric variations in the Be/X-ray binary LS I
  +61 235/RX J0146.9+6121

abstract:
  We report on the long-term variability of the Be/X-ray binary LS I +61 235/RX
J0146.9+6121. New optical spectroscopic and infrared photometric observations
confirm the presence of global one-arm oscillations in the circumstellar disc
of the Be star and allow us to derive a V/R quasi-period of 1240+-30 days.
Pronounced shell events, reminiscent of the spectacular variations in Be stars,
are also seen. We have found that the J, H and K infrared photometric bands
vary in correlation with the spectroscopic V/R variations, implying that the
one-armed disc oscillations are prograde. The effect of the oscillations is not
only seen in the Halpha line but also in the He I6678 and Paschen lines. Since
these lines are formed at different radii in the equatorial disc of the Be
star, such effect confirms the global nature of the perturbation. The Keplerian
disc has been found to be denser than the average of a sample of isolated Be
stars, which may be indicative of some kind of interaction with the compact
companion. Finally, from a Rossi X-ray Timing Explorer observation we derive a
spin period of the neutron star of 1404.5+-0.5 s.


title:
Comparison between Observed and Theoretical Red Giant Branch Luminosity
  Functions of Galactic Globular Clusters

abstract:
  V-band luminosity functions have been obtained for the upper main-sequence,
sub-giant branch and red giant branch of 18 galactic globular clusters from HST
data. A comparison with four sets of theoretical models has been performed. In
contrast with what was found in several previous works, a Good general
agreement has been found between the observed and theoretical LF at any
metallicity [M/H]<-0.7. Possible discrepancies at higher metallicity, in the
upper part of the RGB, need to be confirmed with further observational data and
by extending all the models to the most metal rich regime. The SGB shape has
been used to set an upper limit to the cluster age, and consequently a lower
limit on the cluster distance. A discussion on the still open problem of the
mismatch between the observed and theoretical RGB bump location is also
presented.


title:
ISO observations of a sample of Compact Steep Spectrum and GHz Peaked
  Spectrum Radio Galaxies

abstract:
  We present results from observations obtained with ISOPHOT, on board the ISO
satellite, of a representative sample of seventeen CSS/GPS radio galaxies and
of a control sample of sixteen extended radio galaxies spanning similar ranges
in redshift (0.2 <= z <= 0.8) and radio luminosity (P_2.7 GHz >= 10^26 W/Hz).
The observations have been performed at lambda = 60, 90, 174 and 200 microns.
Seven of the CSS/GPS sources have detections >= 3 sigma at one or more
wavelengths, one of which is detected at >= 5 sigma. By co-adding the data we
have obtained average flux densities at the four wavelengths. We found no
evidence that the FIR luminosities of the CSS/GPS sources are significantly
different from those of the extended objects and therefore there is not any
support for CSS/GPS sources being objects "frustrated" by an abnormally dense
ambient medium. The two samples were then combined, providing FIR information
on a new sample of radio galaxies at intermediate redshifts. We compare this
information with what previously known from IRAS and discuss the average
properties of radio galaxies in the redshift range 0.2 - 0.8. The FIR emission
cannot be accounted for by extrapolation of the synchrotron radio spectrum and
we attribute it to thermal dust emission. The average FIR luminosity is >=
6*10^11 L_sun. Over the observed frequency range the infrared spectrum can be
described by a power law with spectral index alpha >~1.0 +/- 0.2. Assuming the
emission to be due to dust, a range of temperatures is required, from >=80 K to
\~25 K. The dust masses required to explain the FIR emission range from 5*10^5
M_sun for the hotter component up to 2*10^8 M_sun for the colder one.
(abridged)


title: Acoustic Signatures in the Primary Microwave Background Bispectrum

abstract:
  If the primordial fluctuations are non-Gaussian, then this non-Gaussianity
will be apparent in the cosmic microwave background (CMB) sky. With their
sensitive all-sky observation, MAP and Planck satellites should be able to
detect weak non-Gaussianity in the CMB sky. On large angular scale, there is a
simple relationship between the CMB temperature and the primordial curvature
perturbation. On smaller scales; however, the radiation transfer function
becomes more complex. In this paper, we present the angular bispectrum of the
primary CMB anisotropy that uses the full transfer function. We find that the
bispectrum has a series of acoustic peaks that change a sign, and a period of
acoustic oscillations is twice as long as that of the angular power spectrum.
Using a single non-linear coupling parameter to characterize the amplitude of
the bispectrum, we estimate the expected signal-to-noise ratio for COBE, MAP,
and Planck experiments. We find that the detection of the primary bispectrum by
any kind of experiments should be problematic for the simple slow-roll
inflationary scenarios. We compare the sensitivity of the primary bispectrum to
the primary skewness and conclude that when we can compute the predicted form
of the bispectrum, it becomes a ``matched filter'' for detecting the
non-Gaussianity in the data, and much more powerful tool than the skewness. We
also show that MAP and Planck can separate the primary bispectrum from various
secondary bispectra on the basis of the shape difference. The primary CMB
bispectrum is a test of the inflationary scenario, and also a probe of the
non-linear physics in the very early universe.


title: Extreme Type IIp Supernovae as Yardsticks for Cosmology

abstract:
  Evolutionary effects with redshift of core collapse supernovae and their
application to cosmology have been studied based on an extensive grid of
stellar models between 13 and 25 Mo, and their light curves after the
explosion.
  With decreasing metallicity Z and increasing mass, progenitors tend to
explode as compact Blue Supergiants (BSG) and produce subluminous supernovae
which are about 1.5 mag. dimmer compared to 'normal' SNeII with Red Supergiant
(RSG) progenitors. Progenitors with small masses tend to explode as RSGs even
with low Z. The consequences are obvious for probing the chemical evolution.
  We identify 'extreme SNe IIp' supernovae as a rather homogeneous class which
may allow their use as standard candles for distance determination accurate
within 30 %. Due to their unique light curves, no spectra need to be taken for
their identification, and follow-up observations can be limited to a very small
dynamical range in brightness. This means that distance determination by
'extreme SNe IIp" are possible up to redshifts of about 3 using 8-meter class
telescopes. SIRTIF may push the limit by another magnitude.


title:
The exact solution of the Riemann problem with non-zero tangential
  velocities in relativistic hydrodynamics

abstract:
  We have generalised the exact solution of the Riemann problem in special
relativistic hydrodynamics for arbitrary tangential flow velocities. The
solution is obtained by solving the jump conditions across shocks plus an
ordinary differential equation arising from the self-similarity condition along
rarefaction waves, in a similar way as in purely normal flow. The dependence of
the solution on the tangential velocities is analysed, and the impact of this
result on the development of multidimensional relativistic hydrodynamic codes
(of Godunov type) is discussed.


title:
FUSE Observations of the Stellar Winds of Two O7 Supergiants in the
  Magellanic Clouds

abstract:
  We compare the stellar wind features in far-UV spectra of Sk -67 111, an O7
Ib(f) star in the LMC, with Sk 80, an O7 Iaf+ star in the SMC. The most
striking differences are that Sk 80 has a substantially lower terminal
velocity, much weaker O VI absorption, and stronger S IV emission. We have used
line-blanketed, hydrodynamic, non-LTE atmospheric models to explore the origin
of these differences. The far-UV spectra require systematically lower stellar
temperatures than previous determinations for O7 supergiants derived from
plane-parallel, hydrostatic models of photospheric line profiles. At these
temperatures, the O VI in Sk -67 111 must be due primarily to shocks in the
wind.


title:
Resolved Stellar Populations of Super-Metal-Rich Star Clusters in the
  Bulge of M31

abstract:
  We have applied the MCS image deconvolution algorithm (Magain, Courbin & Sohy
1998) to HST/WFPC2 V, I data of three M31 bulge globular clusters (G170, G177,
and G198) and control fields near each cluster. All three clusters are clearly
detected, with an increase in stellar density with decreasing radius from the
cluster centers; this is the first time that stars have been resolved in bulge
clusters in the inner regions of another galaxy. From the RGB slopes of the
clusters and the difference in I magnitude between the HB and the top of the
RGB, we conclude that these three clusters all have roughly solar metallicity,
in agreement with earlier integrated-light spectroscopic measurements. Our data
support a picture whereby the M31 bulge clusters and field stars were born from
the same metal-rich gas, early in the galaxy formation.


title:
Radial velocities of pulsating subdwarf B stars: KPD 2109+4401 and PB
  8783

abstract:
  High-speed spectroscopy of two pulsating subdwarf B stars, KPD 2109+4401 and
PB 8783, is presented. Radial motions are detected with the same frequencies as
reported from photometric observations and with amplitudes of ~2 km/sec in two
or more independent modes. These represent the first direct observations of
surface motion due to multimode non-radial oscillations in subdwarf B stars. In
the case of the sdB+F binary PB 8783, the velocities of both components are
resolved; high-frequency oscillations are found only in the sdB star and not
the F star. There also appears to be evidence for mutual motion of the binary
components. If confirmed, it implies that the F-type companion is >~1.2 times
more massive than the sdB star, while the amplitude of the F star acceleration
over 4 hours would constrain the orbital period to lie between 0.5 and 3.2d.