title: The cosmological evolution of BL Lacs: The REX point of view

abstract:
  We present the results on the cosmological evolution of BL Lac objects as
derived from a statistically complete sample of 44 BL Lacs selected from the
X-ray bright tail of the REX survey. With this sample, we have investigated the
cosmological properties of BL Lacs taking into account the radio, optical and
X-ray limits. We infer that no evolution is clearly visible down to the flux
limits reached by our sample. On the other hand, deeper samples are probably
needed in order to detect the negative evolution found in the EMSS sample. The
identification of such deeper sample, extracted from the REX survey, is in
progress.


title:
The Dependence of Dynamo $\alpha$-Effect on Reynolds Numbers, Magnetic
  Prandtl Number, and the Statistics of MHD Turbulence

abstract:
  We generalize the derivation of dynamo coefficient $\alpha$ of Field et al
(1999) to include the following two aspects: first, the de-correlation times of
velocity field and magnetic field are different; second, the magnetic Prandtl
number can be arbitrary. We find that the contributions of velocity field and
magnetic field to the $\alpha$ effect are not equal, but affected by their
different statistical properties. In the limit of large kinetic Reynolds number
and large magnetic Reynolds number, $\alpha$-coefficient may not be small if
the de-correlation times of velocity field and magnetic field are shorter than
the eddy turn-over time of the MHD turbulence. We also show that under certain
circumstances, for example if the kinetic helicity and current helicity are
comparable, $\alpha$ depends insensitively on magnetic Prandtl number, while if
either the kinetic helicity or the current helicity is dominated by the other
one, a different magnetic Prandtl number will significantly change the dynamo
$\alpha$ effect.


title: ROSAT HRI catalogue of X-ray sources in the SMC region

abstract:
  During the operational phase of the ROSAT satellite between 1990 and 1998 the
X-ray telescope pointed 71 times to the Small Magellanic Cloud (SMC) for
observations with the High Resolution Imager (HRI), covering a field of 5 deg x
5 deg. From this data a catalogue of 121 discrete X-ray sources was derived. By
cross-correlating the source catalogue with the SIMBAD data base and the TYCHO
catalogue, the systematic positional error of the HRI source positions could be
reduced. In total the X-ray position for 99 HRI sources was corrected yielding
positional errors between 1 arcsec and 16 arcsec. The HRI catalogue was also
cross-correlated with the catalogues derived from the ROSAT Position Sensitive
Propotional Counter (PSPC) pointings (Kahabka et al. 1999, Haberl et al. 2000).
For 75 HRI sources PSPC counterparts were found and thus hardness ratios are
given. With the help of the information obtained from the cross-correlations 56
HRI sources were identified with objects of known or proposed nature. Four
foreground stars, six supernova remnants, four supersoft sources, 12 X-ray
binaries, and one AGN were detected by the HRI. Based on the existence of a
likely optical counterpart or properties like hardness ratio and X-ray to
optical flux ratio, further 15 HRI sources were classified into different
source types.


title: Magnetic Fields are not ignorable in the dynamics of disks

abstract:
  Magnetic fields are considered to be dominant when
$\epsilon_{B}\geq\epsilon_{K}$, being $\epsilon_{B}=B^{2}/8\pi$ the magnetic
energy density and $\epsilon_{K}=1/2 \rho\theta^{2}$ the rotation energy
density, for a conventional moderate B= 1 $\mu$G. They are considered to be
negligible when $\epsilon_{B}<\epsilon_{K}$ for $B\sim 10 \mu$G. With no
assumption and no theoretical calculation, we show that magnetic fields cannot
be ignored in the outer parts of a galaxy like the Milky Way and in the whole
disk of a dwarf galaxy.


title: Stellar dynamics observations of a double nucleus in M 83

abstract:
  We report on the discovery of a double nucleus in M 83, based on measurements
of the line of sight velocity distribution of stars observed at near infrared
wavelengths with the VLT ISAAC spectrograph. We observe two peaks separated by
2.7" in the velocity dispersion profile of light from late-type stars measured
along a slit 0.6" wide, centered on the peak of K band emission and with P.A.
51.7 degrees. The first peak coincides with the peak of the K band light
distribution, widely assumed to be the galaxy nucleus. The second peak, of
almost equal strength, almost coincides with the center of symmetry of the
outer isophotes of the galaxy. The secondary peak location has little K band
emission, and appears to be significantly extincted, even at near infrared
wavelengths. It also lies along a mid-infrared bar, previously identified by
Gallais et al. (1991) and shows strong hydrogen recombination emission at 1.875
microns. If we interpret the observed stellar velocity dispersion as coming
from a virialized system, the two nuclei would each contain an enclosed mass of
13.2 x 10^6 M_sun within a radius of 5.4pc. These could either be massive star
clusters, or supermassive dark objects.


title:
Weighing 40 X-ray Luminous Clusters of Galaxies with Weak Gravitational
  Lensing

abstract:
  Deep two-color imaging of 40 clusters of galaxies with the NOT and the
University of Hawaii 2.24-m telescope is used to measure the weak gravitational
shear acting on faint background galaxies. From this, maps of the projected
cluster mass distribution are constructed, and the cluster masses are measured
within circular apertures of up to ~3 Mpc/h. The results are used to derive the
cluster mass function at z~0.2. The average mass-to-light ratio of the clusters
indicate a low-density Universe with Omega_0 around 0.25. Additional mass
concentrations are found along the lines of sight to the clusters, some of
which are most likely associated with clusters at z > 0.5. In addition, the
data are used to measure weak gravitational lensing due to large-scale
structures along the line of sight. The future prospects for this kind of
research with the NOT are briefly discussed.


title: Lensing Sunyaev-Zel'dovich Clusters

abstract:
  Full-sky microwave surveys like the upcoming Planck satellite mission will
detect of order 10^4 galaxy clusters through their thermal Sunyaev-Zel'dovich
effect. I investigate the properties of the gravitationally lensing subsample
of these clusters. The main results are: (1) The combined sample comprises
>~70% of the complete sample. (2) It is confined to redshifts 0.2+-0.1, and to
masses (5+-3) x 10^14 solar masses. (3) Using a particular measure for the weak
lensing effect, viz. the aperture mass, cluster masses can be determined with a
relative accuracy of ~20% if their density profile is known. Consequently, the
mass function of the combined sample can accurately be measured. (4) For
low-density universes, I predict a sharp peak in the measured (aperture) mass
function near 5 x 10^14 solar masses and explain its origin, showing that the
peak will be absent in high-density universes. (5) The location of the peak and
the exponential decrease of the mass function on its high-mass side will allow
the determination of the amplitude of the dark-matter power spectrum on the
cluster scale and the baryon fraction in clusters, and constrain the thermal
history of the intracluster gas.


title: Galaxies: The Long Wavelength View

abstract:
  Far-infrared spectroscopy obtained with the ISO LWS has shown that there is
strong variation (more than 2 orders of magnitude) in the [C II]/FIR ratios in
galaxies extending from blue compact dwarfs, to normal and starburst galaxies,
down to elliptical and ultraluminous galaxies (ULIGs). The variation in the
relative [C II] 158 micron line strength has been attributed to low metallicity
in blue compact dwarfs, high <G_o>/n for normal galaxies and ULIGs, soft
radiation fields in ellipticals, and extinction or enhanced abundance of dust
in ionized regions in ULIGs.
  Full ISO/LWS far-infrared (43 - 197 micron) spectra of six nearby IR-bright
galaxies reveal a dramatic progression of decreasing fine-structure line
emission from ionized species to molecular (OH and H2O) absorption line
dominated. The archetypical ULIG, Arp 220, lies at the absorption line
dominated end of this sequence. For Arp 220, radiative transfer models indicate
that it is optically thick in the FIR and that the water molecules observed in
absorption are radiatively excited. If extinction plays a role in the sequence
it appears from this analysis that the affected regions are heavily obscured
even in the far-infrared, while the detected line emission is not more obscured
in ULIGs than in starbursts. Linear correlation between polycyclic aromatic
hydrocarbon (PAH) 6.2 micron feature strength and the [C II] 158 micron line
strength in starbursts and ULIGs suggests a similar effect for these emitting
species, and that the detected PAH emission is not more obscured in ULIGs than
in lower luminosity starbursts.


title:
Morphological and kinematic signatures of a binary central star in the
  planetary nebula Hu 2-1

abstract:
  We present narrow-band optical images, VLA-A 3.6 cm continuum and H92alpha
emission line data and high resolution long-slit [N II] spectra of Hu 2-1. The
formation of Hu 2-1 appears dominated by anisotropic mass ejection during the
late AGB stage of its progenitor and by variable, ``precessing'' collimated
bipolar outflows during the proto-PN and/or early PN phases. The data strongly
support the existence of a binary central star at center of Hu 2-1: (1) the
brightness distribution of the bipolar lobes and inner shell is
point-symmetric, and the bipolar lobes show departures from axial symmetry; (2)
the position of the central star is off-center; (3) mass ejection towards the
equatorial plane is detected; (4) ``precessing'' collimated outflows are
present. Besides all this circumstantial evidences, the analysis of the
kinematics shows that the systemic velocity of the bipolar outflows does not
coincide with the systemic velocity of the nebula. We propose that this
velocity difference is a direct evidence of orbital motion of the ejection
source in a binary system. Assuming a reasonable range of masses for the
progenitor stars, the orbital velocity of ~10 km/s corresponds to a semi-major
axis of 9-27 AU and to a period of 25-80 yr. The formation of Hu 2-1 is
analyzed within current scenarios of PN formation with binary central stars.


title: A Lack of Planets in 47 Tucanae from an HST Search

abstract:
  We report results from a large Hubble Space Telescope project to observe a
significant (~34,000) ensemble of main sequence stars in the globular cluster
47 Tucanae with a goal of defining the frequency of inner-orbit, gas-giant
planets. Simulations based on the characteristics of the 8.3 days of
time-series data in the F555W and F814W WFPC2 filters show that ~17 planets
should be detected by photometric transit signals if the frequency of hot
Jupiters found in the solar neighborhood is assumed to hold for 47 Tuc. The
experiment provided high-quality data sufficient to detect planets. A full
analysis of these WFPC2 data reveals ~75 variables, but NO light curves
resulted for which a convincing interpretation as a planet could be made. The
planet frequency in 47 Tuc is at least an order of magnitude below that for the
solar neighborhood. The cause of the absence of close-in planets in 47 Tuc is
not yet known; presumably the low metallicity and/or crowding of 47 Tuc
interfered with planet formation, with orbital evolution to close-in positions,
or with planet survival.


title:
Diameters of delta Cephei and eta Aquilae Measured with the Navy
  Prototype Optical Interferometer

abstract:
  We have measured the diameters of the Cepheid variables delta Cephei (18
nights) and eta Aquilae (11 nights) with the Navy Prototype Optical
Interferometer. The primary results of these observations are the mean angular
diameters <theta(LD)> of these Cepheids: 1.520 +/- 0.014 milliseconds of arc
(mas) for delta Cep and 1.69 +/- 0.04 mas for eta Aql. We also report
limb-darkened diameters for the check stars in this program: for beta Lac,
theta(LD) = 1.909 +/- 0.011 mas, and for 12 Aql, theta(LD) = 2.418 +/- 0.010
mas. When combined with radius estimates from period-radius relations in the
literature, the Cepheid angular diameters suggest distances slightly smaller
than, but still consistent with, the Hipparcos distances. Pulsations are weakly
detected at a level of about 1.5 sigma to 2 sigma for both Cepheids.


title:
The Galactic Disk Distribution of Planetary Nebulae With Warm Dust
  Emission Features: I

abstract:
  We investigate the galactic disk distribution of a sample of planetary
nebulae characterised in terms of their mid-infrared spectral features. The
total number of galactic disk PNe with 8-13mum spectra is brought up to 74 with
the inclusion of 24 new objects, whose spectra we present for the first time.
54 PNe have clearly identified warm dust emission features, and form a sample
which we use to construct the distribution of the C/O chemical balance in
galactic disk PNe. The dust emission features complement the information on the
progenitor masses brought by the gas-phase N/O ratios: PNe with unidentified
infrared emission bands have the highest N/O ratios, while PNe with the
silicate signature have either very high N enrichment or close to none, and SiC
emission features coincide with a range of moderate N-enrichments. We find a
trend for a decreasing proportion of O-rich PNe towards the third and fourth
galactic quadrants. Two independent distance scales confirmed that the
proportion of O-rich PNe decreases from 30+-9% inside the solar circle, to
14+-7% outside. PNe with warm dust are also the youngest. PNe with no warm dust
are uniformly distributed in C/O and N/O ratios, and do not appear to be
confined to C/O~1. They also have higher 6cm fluxes, as expected from more
evolved PNe. We show that the IRAS fluxes are a good representation of the
bolometric flux for warm-dust PNe. The requirement F(12um)>0.5Jy should probe a
good portion of the galactic disk, and the dominant selection effects are
rooted in the PN catalogues.


title:
The Galactic Disk Distribution of Planetary Nebulae with Warm Dust
  Emission Features: II

abstract:
  Can the distribution of warm-dust compositions in IR-bright galactic disk PNe
be linked to the underlying stellar population? The PNe with warm dust emission
represent a homogeneous population, which is presumably young and minimally
affected by a possible dependence of PN lifetime on progenitor mass. The sample
in paper I thus allows testing the predictions of single star evolution,
through a comparison with synthetic distributions and under the assumption that
tip-of-the-AGB and PN statistics are similar. We construct a schematic model
for AGB evolution (adapted from Groenewegen & de Jong 1993), whose
free-parameters are calibrated with the luminosity function (LF) of C stars in
the LMC, the initial-final mass relation, and the range of PN compositions. The
observed metallicity gradient and distribution of star forming regions with
galactocentric radius (Bronfman et al. 2000) allow us to synthesise the
galactic disk PN progenitor population. We find the fraction of O-rich PNe,
f(O), is a tight constraint on AGB parameters. For our best model, a minimum PN
progenitor mass Mmin=1Msun predicts that about 50% of all young PNe should be
O-rich, compared to an observed fraction of 22%; thus Mmin=1.2Msun, at a 2sigma
confidence level. By contrast, current AGB models for single stars can account
neither for the continuous range of N enrichment (Leisy & Dennefeld 1996), nor
for the observation that the majority of very C-rich PNe have Peimbert type I
(paper I). f(O) is thus an observable much easier to model. The decrease in
f(O) with galactocentric radius, as reported in paper I, is a strong property
of the synthetic distribution, independent of Mmin. This trend reflects the
sensitivity of the surface temperature of AGB stars and of the core mass at the
first thermal pulse to the galactic metallicity gradient.


title:
CCD Photometry of the Globular Cluster NGC 4833 and Extinction Near the
  Galactic Plane

abstract:
  We present CCD photometry for the Galactic globular cluster NGC 4833. Our BVI
color magnitude diagrams (CMD) extend from above the red giant branch (RGB) tip
to several magnitudes below the main sequence turnoff. The principal sequences
of the cluster show the effects of differential reddening. We have created a
local extinction map, consistent with IRAS and COBE/DIRBE dust maps of the
region. We use our map to correct the colors and magnitudes of each star to the
value at the cluster center. The cluster horizontal branch (HB) is
predominately blueward of the instability strip with 13 confirmed RR Lyrae
variables and 5 additional RR Lyrae candidates. Using the 11 confirmed RR
Lyraes measured on our images, and the differential reddening corrected
photometry we calculate V(HB) = 15.56 +/- 0.063. We have used the simultaneous
reddening and metallicity method of Sarajedini (1994) to find the mean
reddening of the cluster E(B-V) = 0.32 +/- 0.03, and the mean metallicity
[Fe/H] = -1.83 +/- 0.14. As for the age of NGC 4833, we find provisional
evidence that NGC 4833 is 2 +/- 1 Gyr older than the average of M92 and M5. A
more definitive conclusion must await higher resolution imaging of the cluster
core where the effects of differential reddening are minimized.


title: The Topology of Weak Lensing Fields

abstract:
  The topology of weak lensing fields is studied using the 2-dimensional genus
statistic. Simulated fields of the weak lensing convergence are used to focus
on the effect of nonlinear gravitional evolution and to model the statistical
errors expected in observational surveys. For large smoothing angles, the
topology is in agreement with the predictions from linear theory. On smoothing
angles smaller than 10', the genus curve shows the non-Gaussian signatures of
gravitational clustering and differs for open and flat cold dark matter models.
Forthcoming surveys with areas larger than 10 square degrees should have
adequate signal-to-noise to measure the non-Gaussian shape and the
$\Omega$-dependence of the genus statistic.


title:
Physical Conditions in Circumstellar Gas surrounding SN 1987A 12 Years
  After Outburst

abstract:
  Two-dimensional spectra of Supernova 1987A were obtained on 1998 November
14-15 (4282 days after outburst) with the Space Telescope Imaging Spectrograph
(STIS) on board the Hubble Space Telescope (HST). The slit sampled portions of
the inner circumstellar ring at the east and west ansae as well as small
sections of both the northern and southern outer rings. The temperature and
density at these locations are estimated by nebular analysis of [N II], [O
III], and [S II] emission line ratios, and with time-dependent
photoionization/recombination models. The results from these two methods are
mutually consistent. The electron density in the inner ring is ~ 4000 cm-3 for
S II, with progressively lower densities for N II and O III. The electron
temperatures determined from [N II] and [O III] line ratios are ~11,000 K and
\~22,000 K, respectively. These results are consistent with evolutionary trends
in the circumstellar gas from similar measurements at earlier epochs. We find
that emission lines from the outer rings come from gas of lower density (n_e
\la 2000 cm-3) than that which emits the same line in the inner ring. The N/O
ratio appears to be the same in all three rings. Our results also suggest that
the CNO abundances in the northern outer ring are the same as in the inner
ring, contrary to earlier results of Panagia et al. (1996). Physical conditions
in the southern outer ring are less certain because of poorer signal-to-noise
data. The STIS spectra also reveal a weak Ha emission redshifted by ~100 km s-1
at p.a. 103\arcdeg that coincides with the recently discovered new regions that
are brightening (Lawrence et al. 2000). This indicates that the shock
interaction in the SE section of the inner ring commenced over a year before it
became apparent in HST images.


title:
Enhanced Microlensing by Stars Around the Black Hole in the Galactic
  Center

abstract:
  The effect of stars on the lensing properties of the supermassive black hole
in the Galactic Center is similar to the effect of planets on microlensing by a
star. We show that the dense stellar cluster around SgrA* increases by factors
of a few the probability of high-magnification lensing events of a distant
background source by the black hole. Conversely, the gravitational shear of the
black hole changes and enhances the microlensing properties of the individual
stars. The effect is largest when the source image lies near the Einstein
radius of the black hole 1.75"+/-0.20" for a source at infinity). We estimate
that the probability of observing at least one distant background star which is
magnified by a factor >5 in any infrared snapshot of the inner ~ 2" of the
Galactic Center is 1% with a K-band detection threshold of 20 mag. The largest
source of uncertainty in this estimate is the luminosity function of the
background stars. The gravitational shear of the black hole lengthens the
duration of high-magnification events near the Einstein radius up to a few
months, and introduces a large variety of lightcurve shapes that are different
from those of isolated microlenses. Identification of such events by image
subtraction can be used to probe the mass function, density and velocity
distributions of faint stars near the black hole, which are not detectable
otherwise.


title: Finding Pulsars at Parkes

abstract:
  There are many reasons why it is important to increase the number of known
pulsars. Not only do pulsar searches continue to improve statistical estimates
of, for example, pulsar birthrates, lifetimes and the Galactic distribution,
but they continue to turn up interesting and, in some cases, unique individual
pulsars. In the early days of pulsar astronomy, the Molonglo radio telescope
led the world as a pulsar detection instrument. However, the Parkes radio
telescope, with its frequency versatility and greater tracking ablility,
combined with sensitive receivers and powerful computer detection algorithms,
is now the world's most successful telescope at finding pulsars. The Parkes
multibeam survey, begun in 1997, by itself will come close to doubling the
number of known pulsars. Parkes has also been very successful at finding
millisecond pulsars, especially in globular clusters. One third of the known
millisecond pulsars have been found in just one cluster, 47 Tucanae.


title: The black-hole masses of Seyfert galaxies and quasars

abstract:
  The central black-hole masses of a sample of 30 luminous quasars are
estimated using H-beta FWHM measurements from a combination of new and
previously-published nuclear spectra. The quasar black-hole mass estimates are
combined with reverberation-mapping measurements for a sample of Seyfert
galaxies (Wandel 1999) in order to study AGN black-hole masses over a wide
range in nuclear luminosity. It is found that black-hole mass and bulge
luminosity are well correlated and follow a relation consistent with that
expected if black-hole and bulge mass are directly proportional. Contrary to
the results of Wandel (1999) no evidence is found that Seyfert galaxies follow
a different Mblack-Mbulge relation to quasars. However, the black-hole mass
distributions of the radio-loud and radio-quiet quasar sub-samples are found to
be significantly different, with the median black-hole mass of the radio-loud
quasars a factor of three larger than their radio-quiet counterparts. Finally,
utilizing the elliptical galaxy fundamental plane to provide stellar velocity
dispersion estimates, a comparison is performed between the virial H-beta
black-hole mass estimates and those of the Mblack-sigma correlations of
Gebhardt et al. (2000a) and Merritt & Ferrarese (2000). With the disc-like
geometry of the broad-line region adopted in this paper, the virial H-beta
black-hole masses indicate that the correct normalization of the black-hole vs.
bulge mass relation is Mblack=0.0025Mbulge, while the standard assumption of
purely random broad-line velocities leads to Mblack=0.0008Mbulge. The
normalization of Mblack=0.0025Mbulge provided by the disc model is in
remarkably good agreement with that inferred for our quasar sample using the
(completely independent) Mblack-sigma correlations.


title:
Gravitational waves, baryogenesis, and dark matter from primordial black
  holes

abstract:
  We discuss the hypothesis that the cosmological baryon asymmetry and entropy
were produced in the early Universe by the primordial black hole (PBHs)
evaporation.


title: Slow Jets in Seyfert Galaxies: NGC 1068

abstract:
  We have used the Very Long Baseline Array at 5 GHz to image the nucleus of
NGC 1068 at two epochs separated by 2.92 yr. No relative motion was detected
between the high brightness-temperature knots within components NE and C
relative to the nuclear component S1, placing an upper limit of 0.075 c on the
relative component speeds at distances of 21 pc and 43 pc from the AGN. The low
speed is consistent with the low bulk flow speed previously inferred from
indirect arguments based on ram pressure at the bow shock and on line emission
from the jet-cloud collision at cloud C. The components are probably shocks in
the jet, and the bulk flow speed could conceivably be higher than the limit
reported here.


title: Subaru Deep Survey I. Near-Infrared Observations

abstract:
  Deep near-infrared images of a blank 2'x2' section of sky near the Galactic
north pole taken by Subaru Telescope are presented. The total integration times
of the J and K' bands are 12.1 hours and 9.7 hours, resulting in 5-sigma
limiting magnitudes of 25.1 and 23.5 mag, respectively. The numbers of sources
within these limiting magnitudes found with an automated detection procedure
are 385 in the J band and 350 in K'. Based on photometric measurements of these
sources, we present number count vs. magnitude relations, color vs. magnitude
diagrams, size vs. color relationships, etc. The slope of the galaxy number
count plotted against the AB magnitude scale is about 0.23 in the 22 to 26 AB
magnitude range of both bands. The spatial number density of galaxies as well
as the slopes in the faint-end region given by the Subaru Deep Field (SDF)
survey is consistent with those given by HST-NICMOS surveys as expressed on the
AB magnitude diagram. Several sources having very large J-K' color are found
including a few K' objects without detection at J. In addition, a number of
faint Galactic stars are also detected, most of which are assigned to
M-subdwarfs, together with a few brown dwarf candidates.


title: On the stability of very massive primordial stars

abstract:
  The stability of metal-free very massive stars ($Z$ = 0; $M = 120 - 500
\msol$) is analyzed and compared with metal-enriched stars. Such zero-metal
stars are unstable to nuclear-powered radial pulsations on the main sequence,
but the growth time scale for these instabilities is much longer than for their
metal-rich counterparts. Since they stabilize quickly after evolving off the
ZAMS, the pulsation may not have sufficient time to drive appreciable mass loss
in Z = 0 stars. For reasonable assumptions regarding the efficiency of
converting pulsational energy into mass loss, we find that, even for the larger
masses considered, the star may die without losing a large fraction of its
mass. We find a transition between the $\epsilon$- and $\kappa$-mechanisms for
pulsational instability at $Z\sim 2\E{-4} - 2\E{-3}$. For the most metal-rich
stars, the $\kappa$-mechanism yields much shorter $e$-folding times, indicating
the presence of a strong instability. We thus stress the fundamental difference
of the stability and late stages of evolution between very massive stars born
in the early universe and those that might be born today.


title: Accretion Stream Mapping of HU Aquarii

abstract:
  We present a new mapping algorithm, the "Accretion Stream Mapping (ASM)"
which uses the full phase-coverage of a light curve to derive spatially
resolved intensity distributions along the accretion stream in magnetic
cataclysmic variables of AM Herculis type (polars). The surface of the
accretion stream is approximated as a duodecadon shaped tube. After
successfully testing this method on artificial data we applied it to emission
line light curves of Hbeta, Hgamma and He II lambda 4686 of the bright
eclipsing polar HU Aqr. We find Hydrogen and Helium line emission bright in the
threading region of the stream where the stream couples onto magnetic field
lines. It is particularly interesting, that the stream is bright on the
irradiated side, facing the white dwarf, which highlights the interplay of
collisional and radiative excitation/ionization.


title:
Origin of scaling structure and non-gaussian velocity distribution in
  self-gravitating ring model

abstract:
  Fractal structures and non-Gaussian velocity distributions are characteristic
properties commonly observed in virialized self-gravitating systems such as
galaxies or interstellar molecular clouds. We study the origin of these
properties using the one-dimensional ring model which we newly propose in this
paper. In this simple model, $N$ particles are moving, on a circular ring fixed
in the three dimensional space, with mutual interaction of gravity. This model
is suitable for accurate symplectic integration method by which we find the
phase transition in this system from extended-phase to collapsed-phase through
an interesting phase (\halo-phase) which has negative specific heat. In this
intermediate energy scale, there appear scaling properties, non-thermal and
non-Gaussian velocity distributions. In contrast, these peculiar properties are
never observed in other \gas and \core phases. Particles in each phase have
typical time scales of motion determined by the cutoff length $\xi$, the ring
radius $R$ and the total energy $E$. Thus all relaxation patterns of the system
are determined by these three time scales.


title: VLBI Observations of Five Compact Radio Sources

abstract:
  Five compact radio sources, include 0420-014, 1334-127, 1504-166, 2243-123,
and 2345-167, were observed at 5GHz by European VLBI (Very Long Baseline
Interferometry) Network (EVN) in June, 1996. The primary purpose of this
observation was to confirm their superluminal proper motions. Here, the results
of 1334-127, 1504-166, 2243-123 and 2345-167 are presented.


title: Hydrodynamic approach to the evolution of cosmological structures

abstract:
  A hydrodynamic formulation of the evolution of large-scale structure in the
Universe is presented. It relies on the spatially coarse-grained description of
the dynamical evolution of a many-body gravitating system. Because of the
assumed irrelevance of short-range (``collisional'') interactions, the way to
tackle the hydrodynamic equations is essentially different from the usual case.
The main assumption is that the influence of the small scales over the
large-scale evolution is weak: this idea is implemented in the form of a
large-scale expansion for the coarse-grained equations. This expansion builds a
framework in which to derive in a controlled manner the popular ``dust'' model
(as the lowest-order term) and the ``adhesion'' model (as the first-order
correction). It provides a clear physical interpretation of the assumptions
involved in these models and also the possibility to improve over them.


title:
A 421 d Activity Cycle in the BeX Recurrent Transient A0538-66 from
  MACHO monitoring

abstract:
  We present a ~ 5-yr optical light curve of the recurrent Be/X-ray transient
A0538-66 obtained as a by-product of the MACHO Project. These data reveal both
a long-term modulation at P = 420.8 +/- 0.8 d and a short-term modulation at
16.6510 +/- 0.0022 d which, within errors, confirms the previously found
orbital period. Furthermore, the orbital activity is only seen at certain
phases of the 421 d cycle suggesting that the long-term modulation is related
to variations in the Be star envelope.


title: Neutrinos and the Highest Energy Cosmic Rays

abstract:
  Observation of Ultra High Energy Cosmic Rays (UHECR) -whose energy exceeds
$10^20$eV- is still a puzzle for modern astrophysics. The transfer of more than
16 Joules to a microscopic particle can hardly be achieved, even in the most
powerful cosmic accelerators such as AGN's, GRB's or FR-II radio galaxy lobes.
Potential sources must also lie within 100 Mpc of the Earth as the interaction
length of protons, nuclei or photons is less than 10Mpc. However no visible
counterpart of those sources has been observed. Calling upon new physics such
as Topological Defect interactions or Super Massive Relic Particle decays is
therefore very tempting, but such objects are yet to be proven to exist. Due to
the very low flux of UHECR only very large dedicated experiments, such as the
Auger observatories, will allow to shed some light on the origin of those
cosmic rays. In this quest neutrinos, if they can be detected, are an
invaluable messengers of the nature of the sources.


title: On the detection of neutrino oscillations with Planck surveyor

abstract:
  The imprint of neutrino oscillations on the Cosmic Microwave Background (CMB)
anisotropy and polarization power spectra is evaluated in a $\Lambda$CHDM model
with two active neutrino flavors, consistent with the structure formation
models and the atmospheric neutrino oscillations data. We show the existence of
a significant overlap between the region of the oscillation parameter space
that can be measured by sc Planck surveyor and that implied by the atmospheric
neutrino oscillations data.


title: Infrared Spectra of Cooling Flow Galaxies

abstract:
  We have taken K-band spectra covering 7 cooling flow clusters. The spectra
show many of the 1-0S transitions of molecular Hydrogen, as well as some of the
higher vibrational transitions, and some lines of ionized Hydrogen. The line
ratios allow us to conclude that the rotational states of the first excited
vibrational state are in approximate LTE, so that densities above 10^5/ cm^3
are likely, but there is evidence that the higher vibrational states are not in
LTE. The lack of pressure balance between the molecular gas and the ionized
components emphasizes the need for dynamic models of the gas. The ratios of the
ionized to molecular lines are relatively constant but lower than from
starburst regions, indicating that alternative heating mechanisms are
necessary.


title:
Photometric Constraints on Chemical Evolution Models of Irregular
  Galaxies

abstract:
  Photometric properties of stellar populations that evolve according to
chemical evolution models developed by Carigi, Colin, & Peimbert (1999) and
Carigi & Peimbert (2001) are explored. Models explain the oxygen abundance and
gas mass fraction of irregular galaxies NGC 1560, I Zw 18, NGC 2366, and a
typical irregular galaxy. The photometric predictions help to narrow down the
range of possible chemical evolution models. Observed colors of I Zw 18 imply
an age of 10^8 - 10^9 yr for its dominant population, while 10^9 - 10^{10} yr
is an older age preferred by the rest of the galaxy sample. Observed colors are
in general, within errors, close to predicted. There is a tendency for the
observed (B-V) color to imply higher metallicities at a fixed age than (U-B)
(equivalently, (U-B) implies younger ages than (B-V)).


title: Late superhumps and the stream-disc impact in IY UMa

abstract:
  We use the hot spot eclipse times of the newly discovered deeply-eclipsing
dwarf nova IY UMa to trace out the shape of its disc during the late superhump
era. We find an eccentric disc. We show that the brightness of the stream-disc
impact region varies as expected with |deltaV|^2, where deltaV is the
differential velocity of the stream with respect to the velocity of the disc at
the impact point. We conclude that the hot spot is the source of late superhump
light.


title: An Empirical Procedure to Estimate Distances to Stellar Clusters

abstract:
  A most desirable feature of a standard candle to estimate astronomical
distances is robustness against changes in metallicity and age. It is argued
that the radii of main sequence stars with spectral types from solar to A0 show
predictable changes with metallicity, and detectable changes with evolution.
Such stars populate the solar neighborhood, and therefore benefit from
measurements of angular diameters. Also, reliable determinations of their
masses and radii are available from observations of eclipsing binaries. Three
empirical relationships are defined and suggested for estimating distances to
dwarfs from only BVK photometry. Comparison with HIPPARCOS trigonometric
parallaxes shows that the method provides errors of about 15% for a particular
star, which can be reduced to roughly 1.5% when applied to young clusters (age
<~ 1-2 Gyr) with ~ 100 stars of the appropriate spectral types. If reddening is
unknown, main sequence stars with effective temperatures close to 8000 K can
constrain it, although an estimate of R=A(V)/E(B-V) is required.


title: An RXTE Survey of Long-Term X-ray Variability in Seyfert 1 Galaxies

abstract:
  Data from the first three years of RXTE observations have been systematically
analyzed to yield a set of 300 day, 2-10 keV light curves with similarly
uniform, ~5 day sampling, for a total of nine Seyfert 1 galaxies. This is the
first X-ray variability survey to consistently probe time scales longer than a
few days in a large number of AGN. Comparison with ASCA data covering a similar
band but much shorter (~1 day) time scales shows that all the AGN are more
strongly variable on long time scales than on short time scales. This increase
is greatest for the highest-luminosity sources. The well-known anticorrelation
between source luminosity and variability amplitude is both stronger and
shallower in power-law slope when measured on long time scales. This is
consistent with a picture in which the X-ray variability of Seyfert 1s can be
can be described by a single, universal fluctuation power density shape for
which the cutoff moves to longer time scales for higher luminosity sources. All
of the Seyfert 1s exhibit stronger variability in the relatively soft 2-4 keV
band than in the harder 7-10 keV band. This effect is much too pronounced to be
explained by simple models based on either the dilution of the power-law
continuum by the Compton reflection component or on the hard X-rays being
produced in a static, pair-dominated, plane-parallel Comptonizing corona.


title: Evidence for a Long-period Planet Orbiting Epsilon Eridani

abstract:
  High precision radial velocity (RV) measurements spanning the years
1980.8--2000.0 are presented for the nearby (3.22 pc) K2 V star $\epsilon$ Eri.
These data, which represent a combination of six independent data sets taken
with four different telescopes, show convincing variations with a period of
$\approx$ 7 yrs. A least squares orbital solution using robust estimation
yields orbital parameters of period, $P$ = 6.9 yrs, velocity $K$-amplitude $=$
19 {\ms}, eccentricity $e$ $=$ 0.6, projected companion mass $M$ sin $i$ = 0.86
$M_{Jupiter}$, and semi-major axis $a_2$ $=$ 3.3 AU. Ca II H&K S-index
measurements spanning the same time interval show significant variations with
periods of 3 and 20 yrs, yet none at the RV period. If magnetic activity were
responsible for the RV variations then it produces a significantly different
period than is seen in the Ca II data. Given the lack of Ca II variation with
the same period as that found in the RV measurements, the long-lived and
coherent nature of these variations, and the high eccentricity of the implied
orbit, Keplerian motion due to a planetary companion seems to be the most
likely explanation for the observed RV variations. The wide angular separation
of the planet from the star (approximately 1 arc-second) and the long orbital
period make this planet a prime candidate for both direct imaging and
space-based astrometric measurements.


title:
Models for Accretion Disk Fluctuations through Self-Organized
  Criticality Including Relativistic Effects

abstract:
  The possibility that some of the observed X-ray and optical variability in
active galactic nuclei and galactic black hole candidates is produced in
accretion disks through the development of a self-organized critical state is
reconsidered. New simulations, including more complete calculations of
relativistic effects, do show that this model can produce light-curves and
power-spectra for the variability which agree with the range observed in
optical and X-ray studies of AGN and X-ray binaries. However, the universality
of complete self-organized criticality is not quite achieved. This is mainly
because the character of the variations depend quite substantially on the
extent of the unstable disk region. If it extends close to the innermost stable
orbit then a physical scale is introduced and the scale-free character of
self-organized criticality is vitiated. Significant dependence of the power
spectrum density slope on the type of diffusion within the disk and a weaker
dependence on the amount of differential rotation are noted. When general
relativistic effects are incorporated in the models, additional substantial
differences are produced if the disk is viewed from directions far from the
accretion disk axis.


title: ASCA Observation of an "X-ray Shadow" in the Galactic Plane

abstract:
  The diffuse X-ray background (DXB) emission near the Galactic plane ($l,b
\sim 25.6^{\circ},0.78^{\circ}$) has been observed with $ASCA$. The observed
region is toward a Galactic molecular cloud which was recently reported to cast
a deep X-ray shadow in the 0.5 $-$ 2.0 keV band DXB. The selection of this
particular region is intended to provide a constraint on the spatial
distribution of the DXB emission along the line of sight: i.e., the molecular
cloud is optically thick at $<$2 keV and so the bulk of the observed soft
X-rays {\it must} originate in the foreground of the cloud, which is at $\sim$3
kpc from the Sun. In the 0.8 $-$ 9.0 keV band, the observed spectrum is
primarily from multiple components of thermal plasmas. We here report a
detection of soft X-ray (0.5 $-$ 2 keV) emission from an $\sim10^{7}$ K thermal
plasma. Comparisons with the {\it ROSAT} data suggest that this soft X-ray
emission is absorbed by $N_H$ = 1 $-$ 3 $\times$ 10$^{21}$ cm$^{-2}$, which
implies a path-length through the soft X-ray emitting regions of $\la$1 kpc
from the Sun.


title: Weak Lensing Predictions at Intermediate Scales

abstract:
  As pointed out in previous studies, the measurement of the skewness of the
convergence field $\kappa$ will be useful in breaking the degeneracy among the
cosmological parameters constrained from weak lensing observations. The
combination of shot noise and finite survey volume implies that such a
measurement is likely to be done in a range of intermediate scales ($0.5'$ to
20') where neither perturbation theory nor the hierarchical ansatz apply. Here
we explore the behavior of the skewness of $\kappa$ at these intermediate
scales, based on results for the non-linear evolution of the mass bispectrum.
We combined different ray-tracing simulations to test our predictions, and we
find that our calculations describe accurately the transition from the weakly
non-linear to the strongly non-linear regime. We show that the single
lens-plane approximation remains accurate even in the non-linear regime, and we
explicitly calculate the corrections to this approximation. We also discuss the
prospects of measuring the skewness in upcoming weak lensing surveys.


title: A Fitting Formula for the Non-Linear Evolution of the Bispectrum

abstract:
  We present a fitting formula for the non-linear evolution of the bispectrum
in CDM models, obtained from measurements in high resolution numerical
simulations. The formula interpolates between the perturbative and highly
non-linear regimes, and generalizes previous results obtained for scale-free
initial conditions.


title:
Spectral Energy Distributions of T Tauri and Herbig Ae Disks: Grain
  Mineralogy, Parameter Dependences, and Comparison with ISO LWS Observations

abstract:
  We improve upon the radiative, hydrostatic equilibrium models of passive
circumstellar disks constructed by Chiang & Goldreich (1997). New features
include (1) account for a range of particle sizes, (2) employment of
laboratory-based optical constants of representative grain materials, and (3)
numerical solution of the equations of radiative and hydrostatic equilibrium
within the original 2-layer (disk surface + disk interior) approximation. We
explore how the spectral energy distribution (SED) of a face-on disk depends on
grain size distributions, disk geometries and surface densities, and stellar
photospheric temperatures. Observed SEDs of 3 Herbig Ae and 2 T Tauri stars,
including spectra from the Long Wavelength Spectrometer (LWS) aboard the
Infrared Space Observatory (ISO), are fitted with our models. Silicate emission
bands from optically thin, superheated disk surface layers appear in nearly all
systems. Water ice emission bands appear in LWS spectra of 2 of the coolest
stars. Infrared excesses in several sources are consistent with vertical
settling of photospheric grains. While this work furnishes further evidence
that passive reprocessing of starlight by flared disks adequately explains the
origin of infrared-to-millimeter wavelength excesses of young stars, we
emphasize how the SED alone does not provide sufficient information to
constrain particle sizes and disk masses uniquely.


title: Velocity Gradients in the Intracluster Gas of the Perseus Cluster

abstract:
  We report the results of spatially resolved X-ray spectroscopy of 8 different
ASCA pointings distributed symmetrically around the center of the Perseus
cluster. The outer region of the intracluster gas is roughly isothermal, with
temperature ~ 6-7 keV, and metal abundance ~ 0.3 Solar. Spectral analysis of
the central pointing is consistent with the presence of a cooling flow and a
central metal abundance gradient.
  A significant velocity gradient is found along an axis at a position angle of
\~135 deg, which is ~ 45 deg discrepant with the major axis of the X-ray
elongation. The radial velocity difference is found to be greater than 1000
km/s/Mpc at the 90% confidence level. Simultaneous fittings of GIS 2 & 3
indicate that the velocity gradient is significant at the 95% confidence level
and the F-test rules out constant velocities at the 99% level. Intrinsic short
and long term variations of gain are unlikely (P < 0.03) to explain the
velocity discrepancies.


title: RX J1420.4+5334 - another tidal disruption event?

abstract:
  We have discovered a transient X-ray source, RX J1420.4+5334, which displays
a ROSAT flux variation of >150 between the ROSAT All-Sky-Survey in 1990 and a
preceding pointed ROSAT observations in July 1990. Optical observations suggest
a non-active galaxy as the only visible counterpart. We therefore tentatively
identify RX J1420.4+5334 as a tidal disruption event in a non-active galaxy.


title: The Coma cluster luminosity function from ultraviolet to near-infrared

abstract:
  [Abridged] The Coma cluster luminosity function (LF) from ultraviolet (2000
AA) to the near-infrared (H band) is summarized. In the UV the LF is very
steep, much steeper than in the optical. The steep Coma UV LF implies that
faint and bright galaxies give similar contributions to the total UV flux and
to the total metal production rate. The Coma UV LF is dominated by star forming
galaxies, not by massive and large galaxies. The optical Coma LF is relatively
steep (alpha=-1.4) over the 11 magnitudes sampled. We found a clear steeping of
the FL going from B to R bands, indicative of the presence of a large number of
red dwarfs, as faint as three bright globular clusters. Furthermore, using
Hubble Space Telescope images, we discover that blends of globular clusters,
not resolved in individual components due to seeing, look like dwarf galaxies
when observed from the ground and are numerous and bright. The existence of
these fake extended sources increases the steepness of the LF at faint
magnitudes, if not deal on. The near-infrared LF was computed on a
near-infrared selected sample of galaxies which photometry is complete down to
the typical dwarf (M^*+5) luminosity. The Coma LF can be described by a
Schechter function with intermediate slope (alpha~-1.3), plus a dip at M_H~-22
mag. The shape of the Coma LF in H band is quite similar to the one found in
the B band. The similarity of the LF in the optical and H bands implies that in
the central region of Coma there is no new population of galaxies which is too
faint to be observed in the optical band (because dust enshrouded, for
instance), down to the magnitudes of dwarfs.


title: Implications for quintessence models from MAXIMA-1 and BOOMERANG-98

abstract:
  Prompted by the recent MAXIMA-1 and BOOMERANG-98 measurements of the cosmic
microwave background (CMB) anisotropy power spectrum, and motivated by the
results from the observation of high-redshift Type Ia supernovae, we
investigate CMB anisotropies in quintessence models in order to characterize
the nature of the dark energy today. We perform a Bayesian likelihood analysis,
using the MAXIMA-1 and BOOMERANG-98 published bandpowers, in combination with
COBE/DMR, to explore the space of quintessence parameters: the quintessence
energy density \Omega_\phi and equation of state w_\phi. We restrict our
analysis to flat, scale-invariant, inflationary adiabatic models. We find that
this simple class of inflationary models, with a quintessence component
\Omega_\phi < ~0.7, -1 < = w_\phi < ~-0.5, is in good agreement with the data.
Within the assumptions of our analysis, pure quintessence models seem to be
slightly favored, although the simple cosmological constant scenario is
consistent with the data.


title: Lensing properties of 7 damped Lyman-alpha absorbing galaxy-QSO pairs

abstract:
  Le Brun et al. (1997) presented the first identifications of the galaxies
giving rise to 7 intermediate redshift damped Ly-alpha (DLA) absorption
systems. Here, we study the gravitational lensing properties of these
foreground galaxies based on their observed optical appearance and on the
absence of any secondary lensed quasar image. We consider the possibility that
any secondary image be hidden due to extinction by dust, but find it unlikely.
We derive upper limits on the amplification factor affecting the luminosity of
the background quasars; in each case, this factor is found to be less than 0.3
mag. We also obtain upper limits on the total mass of the damped Ly-alpha
galaxies, within radii equal to the quasar impact parameters. Mass-to-light
ratios are found to be consistent with existing estimates based on X-ray
emission or on motion of dwarf satellites. Although we show that lensing is not
important in this sample, we note that existing DLA surveys used to determine
the cosmological density of gas at z<1 are based on samples of quasars brighter
than the ones considered here and for which the amplification bias is likely to
be stronger.


title:
The Discovery of a State Dependent Hard Tail in the X-ray Spectrum of
  the Luminous Z-source GX 17+2

abstract:
  We report results of a BeppoSAX (0.1-200 keV) observation of the Z-type low
mass X-ray binary GX 17+2. The source was on the so-called Horizontal and
Normal branches. Energy spectra were selected based on the source position in
the X-ray hardness-intensity diagram. The continuum could be fairly well
described by the sum of a ~0.6 keV blackbody, contributing ~10% of the observed
0.1-200 keV flux, and a Comptonized component, resulting from upscattering of
\~1 keV seed photons by an electron cloud with temperature of ~3 keV and
optical depth of ~10. Iron K-line and edge were also present at energies 6.7
and 8.5 keV, respectively. In the spectra of the Horizontal branch a hard tail
was clearly detected at energies above ~30 keV. It could be fit by a power law
of photon index ~2.7, contributing ~8% of the source flux. This component
gradually faded as the source moved towards the Normal branch, where it was no
longer detectable. We discuss the possible origin of this component and the
similarities with the spectra of Atoll sources and black hole X-ray binaries.


title:
A Broad Fe-Kalpha Emission Line in the X-Ray Spectrum of the Quasar 3C
  273

abstract:
  The Fe-K line, an important physical diagnostic in the X-ray spectra of AGN,
has been notoriously difficult to measure in the high-luminosity, radio-loud
quasar 3C 273 (z=0.158). On the few occasions that it has been detected its
intrinsic width has been thought to be narrow (FWHM < 10,000 km/s) with an
equivalent width (EW) of a few tens of eV.This was consistent with the general
trend that as one goes from low to high luminosity AGNs the Fe-K line goes from
being strong (EW ~200-300 eV) and broad (FWHM ~ 100,000 km/s) to being weak and
narrow, or absent altogether. Here we present the results of new ASCA and RXTE
observations, together with archival ASCA data, and show for the first time
that the Fe-K line in 3C 273 is as broad as that seen in Seyfert 1. The line is
resolved in two of the observations, with a mean Gaussian width of 0.8 +/- 0.3
keV, or FWHM of 0.3 +/- 0.1c. The smallest and largest EW measured is 43 +/- 34
eV, and 133 (+52,-53) eV respectively (quasar frame). The Compton-reflection
continuum is less than 10% of that expected from a centrally illuminated
semi-infinite, face-on, Compton-thick disk, confirming previous studies that
Compton reflection is negligible in 3C 273. The largest values of the Fe-K line
EW are under-predicted if the line originates in the disk, unless a time lag
longer than several days between line and continuum and/or an over-abundance of
Fe is invoked. We cannot unambiguously constrain the disk inclination angle.
About 60 deg is preferred for a cold disk, while a face-on disk is allowed if
the ionization state of Fe is H-like.


title:
Radial density and temperature profiles of the intracluster gas
  constructed jointly from the X-ray surface brightness measurement and the
  universal density profile

abstract:
  In this paper we have made an attempt to derive the radial profiles of
density and temperature of intracluster gas based on the two well-established
facts at present: the X-ray observed surface brightness of clusters described
by the standard beta model and the (NFW) universal density profile as the
underlying dark matter distribution. We have numerically solved the hydrostatic
equation by demanding that the volumed-averaged baryon fraction of a cluster
should asymptotically approach the universal value at its viral radius. We have
shown that the radial temperature variation derived from these constraints
differs significantly from the conventional polytropic equation of state: The
gas temperature profile may show a dramatic increase or decrease with outward
radius, depending sensitively on the beta parameter. A large beta value
(typically greater than 0.8) is required in order to ensure that the X-ray
temperature makes a drop at the virial radius. This indicates that either the
NFW profile is inappropriate to apply for the overall dark matter distribution
of clusters or other non-gravitational heating processes may play an important
role in the dynamical evolution of clusters.


title: Reconstruction of radial temperature profiles of galaxy clusters

abstract:
  In this Letter we present the radial temperature profiles of three X-ray
clusters (A119, A2255 and A2256) reconstructed from a combination of the X-ray
surface brightness measurements and the universal density profile as the
underlying dark matter distribution. Our algorithm is based on the hydrostatic
equilibrium for intracluster gas and the universality of the total baryon
fraction within the virial radius. The scaled temperature profiles of these
three clusters appear to be remarkably similar in shape, reflecting the
underlying structural regularity, although they are inconsistent with either
isothermality or a significant decline with increasing radius. Nevertheless, we
find a good agreement between our derived temperature profiles and the recent
analysis of 11 clusters observed with BeppoSAX (Irwin & Bregman 2000), which
provides a useful clue to resolving the temperature profile discrepancy raised
recently in literature. A comparison of our derived temperature profiles with
future spatially-resolved spectral measurements may constitute a critical test
for the standard model of structure formation and the conventional scenario for
dynamical properties of clusters.


title: Detection of spiral magnetic fields in two flocculent galaxies

abstract:
  Two flocculent galaxies NGC 3521 and NGC 5055 has been observed at 10.55GHz
with the Effelsberg 100m telescope. In both cases polarized emission reveals
substantial radial component of regular magnetic field - similar to that in
grand-designed spirals. Comparison with H_alpha distribution obtained at Lowell
Observatory is presented. Polarization models discussed, support modern
non-standard dynamo concepts for magnetic field generation in galaxies.


title: The origin of the HH7-11 outflow

abstract:
  New, high-sensitivity interferometric CO J=2-1 observations of the HH 7-11
outflow show that despite previous doubts, this system is powered by the Class
I source SVS 13. The molecular outflow from SVS 13 is formed by a shell with a
large opening angle at the base, which is typical of outflows from Class I
sources, but it also contains an extremely-high-velocity jet composed of
``molecular bullets'', which is more typical of Class 0 outflows. This suggests
that SVS 13 could be a very young Class I, which still keeps some features of
the previous evolutionary stage. We briefly discuss the nature of some sources
in the SVS 13 vicinity which are emitters of cm-wave continuum, but have no
counterpart at mm wavelengths.


title: Water and Dust Emission from W Hydrae

abstract:
  We construct a self-consistent model for the wind around W Hya by solving the
coupled equations describing the hydrodynamics and dust radiative transfer
problems. The model matches simultaneously the observed continuum radiation and
wind velocity profile. The water line emission is calculated next using the
water abundance as the only free parameter, fitted from the ISO observations of
Neufeld et al. (1996) and Barlow et al. (1996). The gas temperature is
determined from a thermal balance calculation that includes water as one of its
main components. Our model successfully fits all the observed water lines,
resolving a major discrepancy between the modeling results of the two observing
teams. The mass loss rate is 2.3 x 10^{-6} M_solar yr^{-1}, the water abundance
is 1.0 x 10^{-4} and the ortho:para ratio is 1:1.3.


title:
Extragalactic radio sources with hybrid morphology: implications for the
  Fanaroff-Riley dichotomy

abstract:
  We provide observational and theoretical perspectives on the currently much
debated issue of the Fanaroff-Riley (FR) morphological dichotomy of
extragalactic radio sources. In this context we introduce a new, albeit rare,
class of double radio sources in which the two lobes exhibit clearly different
FR morphologies. It is argued that such `HYbrid MOrphology Radio Sources', or
HYMORS, could be used to effectively constrain the theoretical mechanisms
proposed for the FR dichotomy. Basically, the existence of HYMORS supports
explanations for the FR dichotomy based upon jet interaction with the medium
external to the central engine, and appears quite difficult to reconcile with
the class of explanations that posit fundamental differences in the central
engine, such as black hole spin or jet composition, to be responsible for the
two FR classes of double radio sources.


title: VLT search for the infrared counterpart of 1E 1740.7-2942

abstract:
  We report the results of our search for the near infrared counterpart of the
microquasar 1E 1740.7-2942 using the VLT (Based on observations collected at
the European Southern Observatory, Chile (ESO No 63.H-0261)). For the first
time, several counterpart candidates have been found in our Ks-band images that
may be consistent with the best radio and X-ray positions available for 1E
1740.7-2942. However, the non-detection of variability between two observing
epochs and the positional uncertainty still remaining at the nearly less than 1
arcsec level prevent us from identifying an unambiguous counterpart.
Alternatively, the VLT images set new upper limits significantly deeper than
previously reported that constrain the binary companion to be later than B8 V
or earlier than G5 III.


title:
The Galaxy Environment of Quasars in the z~1.3 Clowes-Campusano Large
  Quasar Group

abstract:
  We report significant associated clustering in the field of a z=1.226 quasar
from the Clowes-Campusano LQG in the form of both a factor ~11 overdensity of
I-K>3.75 galaxies and red sequences of 15-18 galaxies at I-K~4.3, V-K~6.9
indicative of a population of massive ellipticals at the quasar redshift. The
quasar is located between two groups of these galaxies, with further clustering
extending over 2-3 Mpc. A band of V-I<1 galaxies bisects the two groups of red
sequence galaxies, and we suggest that the merging of these two groups has
triggered both this band of star-formation and the quasar.


title: Establishing The GZK Cutoff With Ultra High Energy Tau Neutrinos

abstract:
  The cosmic ray spectrum has been shown to extend well beyond 10^20 eV. With
nearly 20 events observed in the last 40 years, it is now established that
particles are accelerated or produced in the universe with energy near 10^21
eV. In all production models neutrinos and photons are part of the cosmic ray
flux. In acceleration models (bottom-up models), they are produced as
secondaries of the possible interactions of the accelerated charged particle,
in direct production models (top-down models) they are a dominant fraction of
the decay chain. In addition, hadrons above the GZK threshold energy will also
produce, along their path in the Universe, neutrinos and photons as secondaries
of the pion photo-production processes. Therefore, photons and in particular
neutrinos, are very distinctive signatures of the nature and distribution of
the potential sources of ultra high energy cosmic rays. In the following we
expose the identification capabilities of the Auger observatories. In the
hypothesis of nu_mu-->nu_tau oscillations with full mixing, special emphasis is
placed on the observation of tau neutrinos, with which Auger is able to
establish the GZK cutoff as well as to provide a strong and model independant
constraint on the top-down sources of ultra high energy cosmic rays.


title: Unusual Properties of X-Ray Emission near the Galactic Center

abstract:
  The X-ray spectrum in a $1^{\circ}\times1^{\circ}$ region of the Galactic
center observed with the ASCA satellite is examined in detail, following the
first report by Koyama et al. (1996, AAA 65.155.208). The observed spectrum
contains prominent emission lines from helium-like and hydrogen-like ions of
various elements, and is essentially the same all over the region. If the
observed spectrum is thermal emission from hot plasmas, it requires
multi-temperature plasma components, each at a different degree of ionization
and with a different amount of absorption. The absence of adiabatic cooling and
of systematic changes in the degree of ionization over the region is against
the Galactic center origin of hot plasmas. A significant broadening of the
helium-like and hydrogen-like iron K-lines is confirmed. The line width
corresponds to a rms velocity of $\sim3300$ km~s$^{-1}$, which far exceeds the
sound velocity in a plasma of $kT\sim14$ keV measured with the Ginga satellite.
These facts cast doubt on a thermal origin of the observed X-ray emission.


title:
The effect of a cusped matter distribution on the formation of brightest
  cluster members

abstract:
  We present N-body simulations of galaxy groups embedded in a common halo of
matter. We study the influence of the different initial conditions upon the
evolution of the group and show that denser configurations evolve faster, as
expected. We then concentrate on the influence of the initial radial density
profile of the common halo and of the galaxy distribution. We select two kinds
of density distributions, a singular profile (modeled by a Hernquist
distribution) and a profile with a flat core (modeled by a Plummer sphere). In
all cases we witness the formation of a central massive object due to mergings
of individual galaxies and to accretion of stripped material, but both its
formation history and its properties depend heavily on the initial
distribution. In Hernquist models the formation is due to a ``burst'' of
mergings in the inner parts, due to the large initial concentration of galaxies
in the center. The merging rate is much slower in the initial phases of the
evolution of a Plummer distribution, where the contribution of accretion to the
formation of the central object is much more important. The central objects
formed within Plummer distributions have projected density profiles which are
not in agreement with the radial profiles of observed brightest cluster
members, unless the percentage of mass in the common halo is small. On the
contrary the central object formed in initially cusped models has projected
radial profiles in very good agreement with those of brightest cluster members,
sometimes also showing luminosity excess over the $r^{1/4}$ law in the outer
parts, as is observed in cD galaxies.


title:
An Off-line Scan of the BATSE Daily Records and a Large Uniform Sample
  of Gamma-Ray Bursts

abstract:
  During a scan of the archival BATSE daily records covering the entire 9.1
years (TJD 8369-11690) of the BATSE operation, 3906 gamma-ray bursts (GRBs)
have been detected. 2068 of these GRBs are previously known BATSE triggers
while 1838 of them are new non-triggered bursts. It is important that all
events were detected in the same type of data and were processed with the same
procedure. Therefore these 3906 GRBs constitute a uniform sample. We have
created a publically available electronic data base containing this sample. We
describe the procedures of the data reduction, the selection of the GRB
candidates, and the statistical tests for possible non-GRB contaminations. We
also describe a novel test burst method used to measure the scan efficiency and
the information obtained using the test bursts. Our scan decreases the BATSE
detection threshold to ~0.1 photons/sec/cm2. As a first result, we show that
the differential log N - log P distribution corrected for the detection
efficiency extends to low brightnesses without any indication of a turn-over.
Any reasonable extrapolation of the new log N - log P to lower brightnesses
imply a rate of several thousands of GRBs in the Universe per year.


title:
Resolving the Mystery of X-ray Faint Elliptical Galaxies: Chandra X-ray
  Observations of NGC 4697

abstract:
  Chandra observations of the X-ray faint elliptical galaxy NGC 4697 resolve
much of the X-ray emission (61% within one effective radius) into ~80 point
sources, of which most are low mass X-ray binaries (LMXBs). These LMXBs provide
the bulk of the hard emission and much of the soft emission as well. Of the
remaining unresolved emission, it is likely that about half is from fainter
LMXBs, while the other half (~23% of the total emission) is from interstellar
gas. Three of the resolved sources are supersoft sources. In the outer regions
of NGC 4697, eight of the LMXBs (about 25%) are coincident with candidate
globular clusters, which indicates that globulars have a high probability of
containing X-ray binaries compared to the normal stellar population. The X-ray
luminosities (0.3-10 keV) of the resolved LMXBs range from ~5e37 to ~2.5e39
ergs/s. The luminosity function of the LMXBs has a "knee" at 3.2e38 ergs/s,
which is roughly the Eddington luminosity of a 1.4 M_sun neutron star (NS);
this knee might be useful as a distance indicator. The highest luminosity
source has the Eddington luminosity of a ~20 M_sun black hole (BH). The
presence of this large population of NS and massive BH stellar remnants in this
elliptical galaxy shows that it (or its progenitors) once contained a large
population of massive main sequence stars.


title:
Neutrino Processes in Supernovae and the Physics of Protoneutron Star
  Winds

abstract:
  In preparation for a set of hydrodynamical simulations of core-collapse
supernovae and protoneutron star winds, we investigate the rates of production
and thermalization of $\nu_\mu$ and $\nu_\tau$ neutrinos in dense nuclear
matter. Included are contributions from electron scattering, electron-positron
annihilation, nucleon-nucleon bremsstrahlung, and nucleon scattering. We find
that nucleon scattering dominates electron scattering as a thermalization
process at neutrino energies greater than $\sim$15 MeV. In addition,
nucleon-nucleon bremsstrahlung dominates electron-positron annihilation as a
production mechanism at low neutrino energies, near and below the $\nu_\mu$ and
$\nu_\tau$ neutrinospheres. Furthermore, we have begun a study of steady-state
general relativistic protoneutron star winds employing simple neutrino heating
and cooling terms. From this analysis we obtain acceleration profiles as well
as asymptotic lepton fractions and baryon entropies essential in assessing the
wind as a potential site for $r$-process nucleosynthesis.


title: Bound near-equatorial orbits around neutron stars

abstract:
  Recent discovery of kilohertz quasi-periodic brightness oscillations of low
mass X-ray binaries (LMXBs) has attracted attention to highly relativistic
periodic motion near accreting neutron stars. Most models proposed so far
involve (almost) inertial motion in the vicinity of the stars' innermost stable
circular orbits. In the present paper we study general-relativistic circular
and eccentric orbits around spinning neutron stars assuming the orbits are
slightly tilted with respect to the stars' equatorial planes. We develop
analytical and numerical techniques for integrating bound timelike geodesics in
fully relativistic neutron star spacetimes obtained by modern numerical codes.
We use equations of state of neutron star matter that span a broad range of
stiffness, while the explored range of masses M > 1.7 M(solar) and spin
frequencies nu_s < 600 Hz is motivated by the observations of LMXBs. We
investigate the general-relativistic effects of periastron advance and nodal
precession in the strong gravitational fields of rotating neutron stars and
compare quantitatively the associated orbital frequencies with the more readily
obtainable frequencies of orbits around Kerr black holes on the one hand, and
low-order post-Newtonian (PN) expansions, on the other. While Kerr results
approximate the periastron advance frequency much better than the PN
expressions, the retrograde torque caused by the high quadrupole moments of the
rotating stars clearly favours the PN approximation in the case of nodal
precession. The methods developed in the present paper are used in the
companion paper to test recent hypotheses regarding the origin of
quasi-periodic oscillations in accreting neutron star sources.


title: A nearly symmetric double-image gravitational lens

abstract:
  We report the discovery of a new double-image gravitational lens resulting
from our search for lenses in the southern sky. Radio source PMN J2004-1349 is
composed of two compact components separated by 1.13 arcseconds in VLA, MERLIN
and VLBA images. The components have a flux ratio of 1:1 at radio frequencies
ranging from 5 GHz to 22 GHz. The I-band optical counterpart is also an equal
double, with roughly the same separation and position angle as the radio
double. Upon subtraction of the components from the I-band image, we identify a
dim pattern of residuals as the lens galaxy. While the present observations are
sufficient to establish that J2004-1349 is a gravitational lens, additional
information will be necessary (such as the redshifts of the galaxy and quasar,
and precise astrometry and photometry of the lens galaxy) before constructing
detailed mass models.


title: Two classes of radio flares in the blazar PKS 0420$-$014

abstract:
  The two 5GHz VLBI (Very Long Baseline Interferometry) observations (1996 June
and 1997 November) presented in this paper, combined with several formerb VLBI
observations at 8.4GHz and 5GHz, suggest that the radio flares of the blazar
PKS 0420$-$014 can be divided into two classes according to their geometric
origins in 5 or 8.4GHz VLBI maps and the properties of light curves. One class
of flares, which we call {\it core flares}, originate from the core. Core
flares have large lags between the light curves at different frequencies, and
will probably lead to the ejection of new jet components. The other class of
flares, which we call {\it jet flares}, come from jet components. Jet flares
vary simultaneously at different wavelengths, and may due to the Doppler
boosting effect of rotating knots moving along a helical jet. The radio flare
in 1991, accompanied by a simultaneous gamma-ray flare, was identified as a
core flare.


title:
Relativistic Effects on Neutrino Pair Annihilation above a Kerr Black
  Hole with the Accretion Disk

abstract:
  Using idealized models of the accretion disk we investigate the relativistic
effects on the energy deposition rate via neutrino pair annihilation near the
rotation axis of a Kerr black hole. Neutrinos are emitted from the accretion
disk. The bending of neutrino trajectories and the redshift due to the disk
rotation and gravitation are taken into consideration. The Kerr parameter, $a$,
affects not only neutrinos' behavior but also the inner radius of the accretion
disk. When the deposition energy is mainly contributed by the neutrinos coming
from the central part, the redshift effect becomes dominant as $a$ becomes
large and the energy deposition rate is reduced compared with that neglecting
the relativistic effects. On the other hand, for small $a$ the bending effect
gets dominant and makes energy increase by factor 2 compared with that
neglecting the relativistic effects. For the disk with temperature gradient,
the energy deposition rate for a small inner radius of the accretion disk is
smaller than that estimated by neglecting the relativistic effects. The
relativistic effects, especially for large $a$, play a negative role in
avoiding the baryon contamination problem in gamma-ray bursts.


title: Numerous Old Starburst Galaxies in the Local Universe

abstract:
  Old starburst galaxies are deficient in O stars, and hence do not exhibit
strong line emission in the optical regime. However, there remain many B stars,
which are expected to heat dust grains and generate strong continuum emission
in the far-infrared. The IRAS data for a statistically complete sample of
nearby galaxies reveal for the first time that such objects are as numerous as
30-40% of the local galaxy population.


title: Radio continuum emission from M31 and M33

abstract:
  The radio emission from M31 (like HI, CO, FIR and H\alpha) is concentrated in
the '10 kpc ring', giving an impressive example that cosmic rays are produced
in star-forming regions. M31 and M33 have similar strengths of the total
magnetic field, but very different field structures: The field structure in M31
is exceptionally regular while that in M33 is rather irregular compared with
other spiral galaxies. In M33 the polarized intensity is highest between the
spiral arms, similar to most spiral galaxies, while in M31 total and polarized
emission both emerge from the ring. Star formation in M31 is probably too weak
to tangle the regular field. The high regularity of the field in the M31 ring
allows fast cosmic-ray propagation. As a consequence, there is no equipartition
between the energy densities of cosmic rays and total magnetic fields. Faraday
rotation measures show that the regular field in the ring is uni-directional,
signature of the basic axisymmetric dynamo mode with a pitch angle of only -12
degr. Faraday rotation of polarized background sources shows that the regular
field and thermal gas in M31 extend to at least 25 kpc radius. The regular
field in M33 forms an open spiral, a mixture of axisymmetric and higher modes,
with the largest pitch angle (\simeq 60 degr) observed in any spiral galaxy so
far. Vertical filaments in the NW and SE indicate interaction between the thin
and the thick disk of M31. The total emission in the central region of M31
follows the spiral and radial H\alpha filaments, while the polarized emission
is strongest on the inner edge of the southern spiral filament.


title:
Diffraction-limited bispectrum speckle interferometry and speckle
  polarimetry of the young bipolar outflow source S140 IRS1

abstract:
  We present bispectrum speckle interferometry and speckle polarimetry of the
deeply embedded infrared bipolar outflow source S140 IRS1, a massive
protostellar object in the L1204 molecular cloud. Using the SAO 6 m telescope,
we obtained 280 mas resolution polarization maps of S140 IRS1 as well as a
K-band image with diffraction-limited resolution lambda/D of 76 mas, which is
the highest angular resolution image of a young outflow source ever obtained in
the infrared. Our data suggest that the central source is marginally resolved
with a FWHM diameter of approximately 20 mas (~ 20 AU). The most remarkable
feature in our image is a bright extended and very clumpy structure pointing
away from the central source in exactly the same direction as the blue-shifted
CO outflow lobe. A centro-symmetric pattern of high polarization in this
feature suggests that we see scattered light from the central source. We
interprete this feature as the clumpy inner surface of a partially evacuated
cavity in the circumstellar envelope around IRS1, which has been excavated by
the strong outflow from IRS1.


title: Radio-Variability in Radio-Quiet Quasars and Low-Luminosity AGN

abstract:
  We report on two surveys of radio-weak AGN to look for radio variability. We
find significant variability with an RMS of 10-20% on a timescale of months in
radio-quiet and radio-intermediate quasars. This exceeds the variability of
radio cores in radio-loud quasars (excluding blazars), which vary only on a few
percent level. The variability in radio-quiet quasars confirms that the radio
emission in these sources is indeed related to the AGN. The most extremely
variable source is the radio-intermediate quasar III Zw 2 which was recently
found to contain a relativistic jet. In addition we find large amplitude
variabilities (up to 300% peak-to-peak) in a sample of nearby low-luminosity
AGN, Liners and dwarf-Seyferts, on a timescale of 1.5 years. The variability
could be related to the activity of nuclear jets responding to changing
accretion rates. Simultaneous radio/optical/X-ray monitoring also for
radio-weak AGN, and not just for blazars, is therefore a potentially powerful
tool to study the link between jets and accretion flows.


title: Mass estimates in short-period compact binaries

abstract:
  Using stellar models we investigate the relation between mass and the
spectral type of the secondary star in low-mass short-period compact binaries
such as cataclysmic variables and soft X-ray transients. Allowing for different
mass transfer rates and different system ages prior to mass transfer we find
that the secondaries should populate a band in the spectral type vs. mass
plane. The mass M_ms of a ZAMS star with the same spectral type as the donor is
effectively an upper limit to the donor mass. The lower mass limit for a given
spectral type depends on the mixing length parameter. If this is large, there
is no lower limit if the spectral type is later than K6. The band width
decreases from 0.4 M_sun at K6 to less than 0.2 M_sun at K0. If the mixing
length parameter is small, there is no lower mass limit if the spectral type is
later than M2, and the band width decreases from 0.2 M_sun at M2 to less than
0.1 M_sun for types earlier than K0. We also point out an error in the method
suggested by Beekman et al. (1997) to estimate the primary mass in a soft X-ray
transient.


title: Numerical study of the cosmic shear

abstract:
  We study cosmic shear statistics using the ray-tracing simulation combined
with a set of large $N$-body simulations. In this contribution, we first
describe our method. Then we show some selected results especially focusing on
effects of the deflection of light rays and the lens-lens coupling which are
neglected in making the theoretical predictions of the cosmic shear statistics.


title:
Exploring Galaxy Evolution from Infrared Number Counts and Cosmic
  Infrared Background

abstract:
  Recently reported infrared (IR) galaxy number counts and cosmic infrared
background (CIRB) all suggest that galaxies have experienced a strong evolution
sometime in their lifetime. We statistically estimate the galaxy evolution
history from these data. We find that an order of magnitude increase of the
far-infrared (FIR) luminosity at redshift z = 0.5 - 1.0 is necessary to
reproduce the very high CIRB intensity at 140 um reported by Hauser et al.
(1998). z \sim 0.75 and decreases to, even at most, a factor of 10 toward z
\sim 5, though many variants are allowed within these constraints. This
evolution history also satisfies the constraints from the galaxy number counts
obtained by IRAS, ISO and, roughly, SCUBA. The rapid evolution of the comoving
IR luminosity density required from the CIRB well reproduces the very steep
slope of galaxy number counts obtained by ISO. We also estimate the cosmic star
formation history (SFH) from the obtained FIR luminosity density, considering
the effect of the metal enrichment in galaxies. The derived SFH increases
steeply with redshift in 0 < z < 0.75, and becomes flat or even declines at z >
0.75. This is consistent with the SFH estimated from the reported ultraviolet
luminosity density. In addition, we present the performance of the Japanese
ASTRO-F FIR galaxy survey. We show the expected number counts in the survey. We
also evaluate how large a sky area is necessary to derive a secure information
of galaxy evolution up to z \sim 1 from the survey, and find that at least 50 -
300 deg^2 is required.


title: Searching for Extra Dimensions in the Early Universe

abstract:
  We investigate extra spatial dimensions ($D = 3+\epsilon$) in the early
universe using very high resolution molecular rotational spectroscopic data
derived from a large molecular cloud containing moderately cold carbon monoxide
gas at Z $\approx 6.42$. It turns out that the $\epsilon$-dependent quantum
mechanical wavelength transitions are solvable for a linear molecule and we
present the solution here. The CO microwave data allows a very precise
determination of $< \epsilon > = -0.00000657 \pm .10003032$. The probability
that $ < \epsilon > \neq 0$ is one in 7794, only 850 million years (using the
standard cosmology) after the Big Bang.


title: Implications of the Optical Observations of Neutron Stars

abstract:
  We show that observations of pulsars with pulsed optical emission indicate
that the peak flux scales according to the magnetic field strength at the light
cylinder. The derived relationships indicate that the emission mechanism is
common across all of the observed pulsars with periods ranging from 33ms to 385
ms and ages of 1000-300,000 years. It is noted that similar trends exist for
$\gamma$ ray pulsars. Furthermore the model proposed by Pacini (1971) and
developed by Pacini and Salvati (1983,1987) still has validity and gives an
adequate explanation of the optical phenomena.


title: Using the COBE/DMR data as a test-bed for normality assessments

abstract:
  A very important property of a statistical distribution is to know whether it
obeys Gaussian statistics or not. On the one hand, it is of paramount
importance in the context of CMB anisotropy studies, since deviations from a
Gaussian distribution could indicate the presence of uncorrected measurement
systematics, of remaining fluctuations contributed by foregrounds, of
deviations from the simplest models of inflation or of topological defects. On
the other hand, looking for a non-Gaussian signal is a very ill-defined task
and performances of various assessment methods may differ widely when applied
in different contexts.
  In previous studies, we introduced a sensitive wavelet-based method which we
apply here to the COBE/DMR data set, already extensively studied, using
different approaches. This provides an objective way to compare methods. It
turns out that our multi-scale wavelet decomposition is a sensitive method. Yet
we show that the results are rather sensitive to the choice of both the
decomposition scheme and the wavelet basis. We find that the detection of the
non-Gaussian signature is ``marginal'' with a probability of at most 99%.


title: First images on the sky from a hyper telescope

abstract:
  We show star images obtained with a miniature ``densified pupil imaging
interferometer'' also called a hyper-telescope. The formation of such images
violates a ``golden rule of imaging interferometers'' which appeared to forbid
the use of interferometric arrangements differing from a Fizeau interferometer.
These produce useless images when the sub-apertures spacing is much wider than
their size, owing to diffraction through the sub-apertures. The hyper-telescope
arrangement solves these problems opening the way towards multi-kilometer
imaging arrays in space. We experimentally obtain an intensity gain of 24 +- 3X
when a densified-pupil interferometer is compared to an equivalent Fizeau-type
interferometer and show images of the double star alpha Gem. The initial
results presented confirm the possibility of directly obtaining high resolution
and high dynamic range images in the recombined focal plane of a large
interferometer if enough elements are used.


title: Do Cluster Cooling Flows Survive Head-on Galaxy Cluster Mergers?

abstract:
  We report the results of recent numerical simulations of the head-on merger
of a cooling flow cluster with an infalling subcluster of galaxies. These
simulations examined the effects of different types of cluster mergers (with
16:1 and 4:1 mass ratios) on the evolution of cluster cooling flows (mass
accretion rates of 100 and 400 M/year. The 2-dimensional simulations were
performed with a Hydro/N-body code on a uniform grid with a resolution of 20
kpc.
  We find that the ram-pressure of the infalling gas is crucial in determining
the fate of the cooling flow as disruption occurs when a substantial amount of
subcluster gas reaches the primary's core. In such cases, the subcluster gas
can increase the central cooling time by displacing the high-density cooling
gas and by heating it via shocks and turbulent gas motions. Moreover, the fate
of a merging cooling flow is also dependent on its initial cooling time. In
cases where the initial cooling time is very small then, even if the flow is
disrupted, the central cooling time will remain less than a Hubble time and the
flow will likely re-establish itself. This has an important observational
consequence because such clusters will be classified as cooling flows even
though they have experienced a significant merger. In addition, there is a time
delay (1-2 Gyrs) between core-crossing and the point at which the central
cooling time of a disrupted flow becomes of order a Hubble time (abridged).


title: The GZK Feature in our Neighborhood of the Universe

abstract:
  We calculate numerically the spectrum of ultra-high energy cosmic rays on
Earth assuming that their sources are distributed in space like the observed
galaxies. We use the CfA2 and the PSCz galaxy redshift surveys to model the
local galaxy distribution, properly taking into account the galaxy selection
functions for each survey. When the survey selection effects are included, we
find that the local overdensity is only a factor of two, an order of magnitude
less than used in some earlier studies. An overdensity of two is not enough to
bridge the gap between the predicted number of events above $10^{20}$ eV and
the measured flux at these highest energies. This conclusion is particularly
strong for soft injection spectra ($\propto E^{-3}$) where the observed number
of events is 6 $\sigma$ higher than the expected one. However, if the injection
spectrum is hard ($\propto E^{-2}$), the small local overdensity helps bring
the present data within 2$\sigma$ of the low number of events predicted above
$10^{20}$ eV. In this case, the Greisen-Zatzepin-Kuzmin cutoff is not a {\it
cutoff} but rather a {\it feature} in the cosmic ray spectrum.


title:
Angular Signatures for Galactic Halo WIMP Scattering in Direct
  Detectors: Prospects and Challenges

abstract:
  Angular Sensitivity can provide a key additional tool which might allow
unambiguous separation of a signal due to Galactic halo WIMPs from other
possible backgrounds in direct detectors. We provide a formalism which allows a
calculation of the expected angular distribution of events in terrestrial
detectors with angular sensitivity for any incident distribution of Galactic
halo dark matter. This can be used as an input when studying the sensitivity of
specific detectors to halo WIMPs. We utilize this formalism to examine the
expected signature for WIMP dark matter using a variety of existing analytic
halo models in order to explore how uncertainty in the Galactic halo
distribution impact on the the event rates that may be required to separate a
possible WIMP signal from other terrestrial backgrounds. We find that as few as
30 events might be required to disentangle the signal from backgrounds if the
WIMP distribution resembles an isothermal sphere distribution. On the other
hand, for certain halo distributions, even detectors with fine scale resolution
may require in excess of a 100-400 events to distinguish a WIMP signal from
backgrounds using angular sensitivity. We also note that for finite thresholds
the different energy dependence of spin-dependent scattering cross sections may
require a greater number of events to discern a WIMP signal than for spin
independent interactions. Finally, we briefly describe ongoing studies aimed at
developing strategies to better exploit angular signatures, and the use of
N-body simulations to better model the expected halo distribution in predicting
the expected signature for direct WIMP detectors.


title:
III Zw 2: superluminal expansion and compact lobe expansion in a Seyfert
  galaxy

abstract:
  So far, all relativistically boosted jets with superluminal motion have only
been detected in typical radio galaxies with early type host galaxies. We have
now discovered superluminal motion in the Seyfert I galaxy III Zw 2, classified
as a spiral. The lower limit for the apparent expansion speed is 1.25 c.
Spectral and spatial evolution are closely linked. Before and after this rapid
expansion we have seen a period of virtually no expansion with an expansion
speed less than 0.04 c. However, at 15 GHz the picture is completely different.
III Zw 2 shows slow expansion ($\sim 0.6 c$) during the time of no expansion at
43 GHz and no expansion during the rapid expansion at 43 GHz. The difference
between the two frequencies is qualitatively explained by optical-depth effects
in an 'inflating- balloon model', describing the evolution of radio lobes on an
ultra-compact scale. The stop-and-go behavior could be explained by a jet
interacting with a molecular cloud or the molecular torus. Since III Zw 2 is
also part of a sample of so- called radio-intermediate quasars (RIQ), it
confirms earlier predictions of superluminal motion for this source, based on
the argument that RIQs could be relativistically boosted jets in radio-weak
quasars and Seyfert galaxies.


title: Cosmic Rays above $10^{14}$ eV

abstract:
  We briefly review the status of cosmic ray studies between $10^{14}$ eV and
the highest observed energies, namely a few times $10^{20}$ eV. Because of the
rather low incident fluxes in this energy range, the studies mostly rely on
ground based, large aperture detectors reconstructing the cosmic ray's
properties through the detection of the air-showers they generate by
interacting with the atmosphere. We stress the fact that many issues such as
the chemical composition of the cosmic rays, their acceleration mechanisms, the
structures displayed in their energy spectrum are mostly open questions which
may be answered by the next generation of experiments.


title:
The Formation of a Bound Star Cluster: From the Orion Nebula Cluster to
  the Pleiades

abstract:
  (shortened) Direct N-body calculations are presented of the formation of
Galactic clusters using GasEx, which is a variant of the code Nbody6. The
calculations focus on the possible evolution of the Orion Nebula Cluster (ONC)
by assuming that the embedded OB stars explosively drove out 2/3 of its mass in
the form of gas about 0.4 Myr ago. A bound cluster forms readily and survives
for 150 Myr despite additional mass loss from the large number of massive
stars, and the Galactic tidal field. This is the very first time that cluster
formation is obtained under such realistic conditions. The cluster contains
about 1/3 of the initial 10^4 stars, and resembles the Pleiades Cluster to a
remarkable degree, implying that an ONC-like cluster may have been a precursor
of the Pleiades. This scenario predicts the present expansion velocity of the
ONC, which will be measurable by upcoming astrometric space missions (DIVA and
GAIA). These missions should also detect the original Pleiades members as an
associated expanding young Galactic-field sub-population. The results arrived
at here suggest that Galactic clusters form as the nuclei of expanding OB
associations.


title: Red Giants in ISOGAL: Tracers of the Evolution of the Galaxy

abstract:
  The DENIS/ISOGAL near/mid-IR survey of the Milky Way for the first time
probes stellar populations in the innermost obscured regions of our galaxy.
Ages, metallicities and extinction-corrected luminosities are derived for these
stars individually by isochrone fitting to the preliminary IR photometry. A few
hundred AGB stars with thick circumstellar dust envelopes are identified. An
old metal-rich population dominates in the inner galactic Bulge, but there are
indications for the presence of a younger population. The inner Bulge has a
tri-axial shape, as traced by depth effects on the observed luminosity
distributions.


title: Eclipse mapping of accretion discs

abstract:
  The eclipse mapping method is an inversion technique that makes use of the
information contained in eclipse light curves to probe the structure, the
spectrum and the time evolution of accretion discs. In this review I present
the basics of the method and discuss its different implementations. I summarize
the most important results obtained to date and discuss how they have helped to
improve our understanding of accretion physics, from testing the theoretical
radial brightness temperature distribution and measuring mass accretion rates
to showing the evolution of the structure of a dwarf novae disc through its
outburst cycle, from isolating the spectrum of a disc wind to revealing the
geometry of disc spiral shocks. I end with an outline of the future prospects.


title: Tidal Tails and Galaxy Evolution

abstract:
  We review recent results on the tidal structures of spiral galaxies. Topics
included are general characteristics of tails; kinematics of tidal structures
and dark haloes of host galaxies; frequency of tidal distortions at z~1.


title:
Energy, entropy and mass scaling relations for elliptical galaxies.
  Towards a physical understanding of their photometric properties

abstract:
  In the present paper, we show that elliptical galaxies (Es) obey a scaling
relation between potential energy and mass. Since they are relaxed systems in a
post violent-relaxation stage, they are quasi-equilibrium gravitational systems
and therefore they also have a quasi-constant specific entropy.
  Assuming that light traces mass, these two laws imply that in the space
defined by the three S\'ersic law parameters (intensity Sigma_0, scale a and
shape nu), elliptical galaxies are distributed on two intersecting 2-manifolds:
the Entropic Surface and the Energy-Mass Surface.
  Using a sample of 132 galaxies belonging to three nearby clusters, we have
verified that ellipticals indeed follow these laws. This also implies that they
are distributed along the intersection line (the Energy-Entropy line), thus
they constitute a one-parameter family.
  These two physical laws (separately or combined), allow to find the
theoretical origin of several observed photometrical relations, such as the
correlation between absolute magnitude and effective surface brightness, and
the fact that ellipticals are located on a surface in the [log R_eff, -2.5 log
Sigma_0, log nu] space. The fact that elliptical galaxies are a one-parameter
family has important implications for cosmology and galaxy formation and
evolution models. Moreover, the Energy-Entropy line could be used as a distance
indicator.


title: Big Bang Nucleosynthesis and Related Observations

abstract:
  The current status of big bang nucleosynthesis is summarized. Particular
attention is paid to recent observations of He4 and Li7 and their systematic
uncertainties. Be and B are also discussed in connection to recent Li7
observations and the primordial Li7 abundance.


title:
New mechanism for the generation of primordial seeds for the cosmic
  magnetic fields

abstract:
  We discuss the inflationary production of magnetic seeds for the galactic
dynamo through the photon-graviphoton mixing typical of extended models of
local supersymmetry. An analisys of the allowed region in parameter space shows
that such a mechanism is compatible with existing phenomenological bounds on
the vector mass and on the mixing parameter, but requires a large enough mixing
that seems difficult to implement naturally in the context of a minimal
supersymmetric scenario.