title: Neutron star envelopes and thermal radiation from the magnetic surface

abstract:
  The thermal structure of neutron star envelopes is discussed with emphasis on
analytic results. Recent progress on the effect of chemical constitution and
high magnetic fields on the opacities and the thermal structure is further
reviewed in view of the application to pulsar cooling and magnetars.


title:
Anisotropic inverse Compton scattering in powerful radio galaxies: the
  case of 3C 295

abstract:
  Inverse Compton (IC) scattering of nuclear photons with relativistic
electrons in the lobes of powerful radio galaxies and quasars can give
detectable extended X-ray emission from the radio lobes if relativistic
electrons with a Lorentz factor gamma about 300 are present (Brunetti, Setti,
Comastri 1997). In general these electrons are not detected since they emit
synchrotron radiation at frequencies below the radio band, so that the study of
this effect provides a unique tool to measure the energy distribution of the
electron population in the radio lobes at gamma lower than 1000. In this paper
we reanalyze the Chandra observation of the powerful and compact radio galaxy
3C 295 for which the IC scattering of nuclear photons is expected to be an
important mechanism. We find strong evidence for extended and asymmetrical
X-ray emission associated with the radio lobes in the energy band 0.1--2 keV.
We show that both the luminosity and morphology of the extended X-ray emission
associated with the radio lobes, not compatible with other X-ray mechanisms,
can be best interpreted by the IC scattering with nuclear photons. We also show
that the relativistic electron energy distribution obtained from the
synchrotron radio emission can be extrapolated down to gamma about 100 thus
providing a first direct evidence on the electron spectrum in the lobes down to
lower energies.


title:
Hubble Space Telescope Images of Stephan's Quintet: Star Cluster
  Formation in a Compact Group Environment

abstract:
  Analysis of Hubble Space Telescope/Wide Field Planetary Camera 2 images of
Stephan's Quintet, Hickson Compact Group 92, yielded 115 candidate star
clusters (with V-I < 1.5). Unlike in merger remants, the cluster candidates in
Stephan's Quintet are not clustered in the inner regions of the galaxies; they
are spread over the debris and surrounding area. Specifically, these sources
are located in the long sweeping tail and spiral arms of NGC 7319, in the tidal
debris of NGC 7318B/A, and in the intragroup starburst region north of these
galaxies. Analysis of the colors of the clusters indicates several distinct
epochs of star formation that appear to trace the complex history of dynamical
interactions in this compact group.


title: Inflation, braneworlds and quintessence

abstract:
  Inflationary cosmology is developed in the second Randall-Sundrum braneworld
scenario, where the accelerated expansion arises through potentials that are
too steep to drive inflation in conventional cosmology. A relationship between
the scalar and tensor perturbation spectra is derived that is independent of
both the inflaton potential and the brane tension. It is found that a single
field with an inverse power law potential can act as both the inflaton and the
quintessence field for suitable values of the brane tension.


title: The Evolution of Dark-Matter Dominated Cosmological Halos

abstract:
  Adaptive SPH and N-body simulations were carried out to study the evolution
of the equilibrium structure of dark matter halos that result from the
gravitational instability and fragmentation of cosmological pancakes. Such
halos resemble those formed by hierarchical clustering from realistic initial
conditions in a CDM universe and, therefore, serve as a test-bed model for
studying halo dynamics. The dark matter density profile is close to the
universal halo profile identified previously from N-body simulations of
structure formation in CDM, with a total mass and concentration parameter which
grow linearly with scale factor a. When gas is included, this concentration
parameter is slightly larger than the pure N-body result. We also find that the
dark matter velocity distribution is less isotropic and more radial than found
by N-body simulations of CDM.


title:
Testing the transition layer model of quasi-periodic oscillations in
  neutron star X-ray binarie

abstract:
  We compare the theoretical predictions of the transition layer model with
some observational features of quasi-periodic oscillations (QPOs) in neutron
star X-ray binaries. We found that the correlation between horizontal branch
oscillation (HBO) frequencies and kilohertz (kHz) QPO frequencies, the
difference between the low-frequency QPOs in atoll sources and HBOs in Z
sources, and the correlation between the frequencies of low-frequency QPOs and
break frequencies can be well explained by the transition layer model, provided
the neutron star mass is around 1.4 solar mass and the angle between
magnetosphere equator and accretion disk plane is around 6 degree. The observed
decrease of peak separation between two kHz QPO frequencies with the increase
of kHz QPO frequencies and the increase of QPO frequencies with the increase of
inferred mass accretion rate are also consistent with the theoretical
predictions of transition layer model. In addition, we derive a simple equation
that can be adopted to estimate the angle ($\delta$) between magnetosphere
equator and accretion disk plane by use of the simultaneously observed QPO
frequency data. We estimate these angles, in the range of 4 to 8 degrees, for
five Z sources and two atoll sources. The nearly constant $\delta$ value for
each source, derived from the different sets of simultaneously observed QPO
frequency data, provides a strong test of the theoretical model. Finally, we
suggest that the similar transition layer oscillations may be also responsible
for the observed QPOs in accretion-powered millisecond X-ray pulsar and
Galactic black hole candidates.


title: Supernovae and the Nature of the Dark Energy

abstract:
  The use of Type Ia supernovae as calibrated standard candles is one of the
most powerful tools to study the expansion history of the universe and thereby
its energy components. While the analysis of some ~50 supernovae at redshifts
around z~0.5 have provided strong evidence for an energy component with
negative pressure, ``dark energy'', more data is needed to enable an accurate
estimate of the amount and nature of this energy. This might be accomplished by
a dedicated space telescope, the SuperNova / Acceleration Probe (2000; SNAP),
which aims at collecting a large number of supernovae with z<2.
  In this paper we assess the ability of the SNAP mission to determine various
properties of the ``dark energy.'' To exemplify, we expect SNAP, if operated
for three years to study Type Ia supernovae, to be able to determine the
parameters in a linear equation of state w(z)=w0 + w1 z to within a statistical
uncertainty of +-0.04 for w0 and +0.15,-0.17 for w1 assuming that the universe
is known to be flat and an independent high precision (sigma_{Omega_m}=0.015)
measurement of the mass density Omega_m, is used to constrain the fit. An
additional improvement can be obtained if a large number of low-z, as well as
high-z, supernovae are included in the sample.


title:
A ROSAT WFC observation of SW UMa: the EUV behaviour of dwarf novae in
  superoutburst explained

abstract:
  During re-processing and analysis of the entire ROSAT Wide Field Camera (WFC)
pointed observations database, we discovered a serendipitous, off-axis
detection of the cataclysmic variable SW UMa at the onset of its 1997 October
superoutburst. Although long outbursts in this SU UMa-type system are known to
occur every ~450 days, none had ever been previously observed in the extreme
ultra-violet (EUV) by ROSAT. The WFC observations began just ~13 hr after the
optical rise was detected. With a peak count rate of 4.5 count/s in the S1
filter, SW UMa was temporarily the third brightest object in the sky in this
waveband. Over the next ~19 hr the measured EUV flux dropped to <2 count/s
while the optical brightness remained essentially static at V~11. Similar
behaviour has also been recently reported in the EUV light curve of the related
SU UMa-type binary OY Car during superoutburst (Mauche and Raymond 2000). In
contrast, U Gem-type dwarf novae show no such early EUV dip during normal
outbursts. Therefore, this feature may be common in superoutbursts of SU
UMa-like systems. We expand on ideas first put forward by Osaki (1994, 1995)
and Mauche and Raymond (2000) and offer an explanation for this behaviour by
examining the interplay between the thermal and tidal instabilities which
affect the accretion disks in these systems.


title:
The Ultimate Future of the Universe, Black Hole Event Horizons,
  Holography, and the Value of the Cosmological Constant

abstract:
  Hawking has shown that if black holes were to exist in a universe that
expands forever, black holes would completely evaporate, violating unitarity. I
argue this means unitarity requires that the universe exist for only a finite
future proper time. I develop this argument, showing that unitarity also
requires the boundaries of all future sets to be Cauchy surfaces, and so no
event horizons can exist. Thus, the null generators of the surfaces of
astrophysical black holes must leave the surface in both time directions,
allowing non-spherical topologies for black hole surfaces. Since all
information eventually escapes astrophysical black holes, and since the null
surfaces defining astrophysical black holes are Cauchy surfaces, holography
automatically holds. I further show that unitarity requires the effective
cosmological constant to be zero eventually, since otherwise the universe would
expand forever.


title:
The influence of massive stars in the interstellar medium of IC 1613:
  the supernova remnant S8 and the nebula S3 associated with a WO star

abstract:
  We present a detailed kinematical analysis of two selected nebulae in the
Local Group irregular galaxy IC 1613. The nebulae are: S8, the only known
supernova remnant in this galaxy, and S3, a Wolf-Rayet nebula associated with
the only WO star in this galaxy. For S8, we have obtained and analyzed its
radial velocity field, where we found complex profiles which can be fitted by
several velocity components. These profiles also show the presence of high
velocity, low density gas. From this, we have obtained the expansion velocity,
estimated the preshock density and calculated the basic kinematical parameters
of this SNR. We suggest that in S8 we are seing a SNR partially hidden by dust.
This suggestion comes from the fact that the SNR is located between two
superbubbles where a ridge of obscured material unveils the existence of dust.
Moreover, we show that this hypothesis prevails when energetic arguments are
taken into account. In the case of S3, this nebula shows bipolar structure. By
means of its kinematics, we have analyzed its two lobes, the ``waist'', as well
as its relation with the nearest superbubbles. For the first time we are able
to see closed the NW lobe, showing a clover leaf shape. This fact allows a
better quantitative knowledge of the nebula as a whole. Furthermore, we found
evidence of an expansion motion in the NW lobe. In the light of our results, we
can express that these nebulae are the product of very massive stellar
evolution. It is surprising the influence these stars still have in shaping
their surrounding gas, and on the energy liberation towards the interstellar
medium of this galaxy.


title:
Genus statistics for galaxy clusters and nonlinear biasing of dark
  matter halos

abstract:
  We derive an analytic formula of genus for dark matter halos assuming that
the primordial mass density field obeys the random-Gaussian statistics. In
particular, we for the first time take account of the nonlinear nature of the
halo biasing, in addition to the nonlinear gravitational evolution of the
underlying mass distribution. We examine in detail the extent to which the
predicted genus for halos depends on the redshift, smoothing scale of the
density field, and the mass of those halos in representative cold dark matter
models. In addition to the full model predictions, we derive an explicit
perturbation formula for the halo genus which can be applied to a wider class
of biasing model for dark matter halos. With the empirical relation between the
halo mass and the luminosity/temperature of galaxy clusters, our prediction can
be compared with the upcoming cluster redshift catalogues in optical and X-ray
bands. Furthermore, we discuss the detectability of the biasing and
cosmological model dependence from the future data.


title:
Effects of Formation Epoch Distribution on X-Ray Luminosity and
  Temperature Functions of Galaxy Clusters

abstract:
  We investigate statistical properties of galaxy clusters in the context of
hierarchical clustering scenario, taking account of their formation epoch
distribution, motivated by the recent finding by Fujita and Takahara that X-ray
clusters form a fundamental plane, where the mass and formation epoch are
regarded as two independent parameters. Using the formalism which discriminates
between major merger and accretion, the epoch of a cluster formation is
identified with that of the last major merger. Since tiny mass accretion after
the formation does not much affect the core structure of clusters, the
properties of X-ray emission from clusters are determined by the total mass and
density at their formation time. Under these assumptions, we calculate X-ray
luminosity and temperature functions of galaxy clusters. We find that the
behavior of luminosity function is different from the model which does not take
account of formation epoch distribution, while the behavior of temperature
function is not much changed. In our model, luminosity function is shifted to a
higher luminosity and shows no significant evolution up to $z \sim 1$,
independent of cosmological models. The clusters are populated on the
temperature-luminosity plane with a finite dispersion. Since the simple scaling
model in which the gas temperature is equal to the virial temperature fails to
reproduce the observed luminosity-temperature relation, we also consider a
model which takes the effects of preheating into account. The preheating model
reproduces the observations much better.


title:
Implication of Omega_m through the Morphological Analysis of Weak
  Lensing Fields

abstract:
  We apply the morphological descriptions of two-dimensional contour map, the
so-called Minkowski functionals (the area fraction, circumference, and Euler
characteristics), to the convergence field $\kappa(\bm{\theta})$ of the
large-scale structure reconstructed from the shear map produced by the
ray-tracing simulations. The perturbation theory of structure formation has
suggested that the non-Gaussian features on the Minkowski functionals with
respect to the threshold in the weakly nonlinear regime are induced by the
three skewness parameters of $\kappa$ that are sensitive to the density
parameter of matter, $\Omega_{\rm m}$. We show that, in the absence of noise
due to the intrinsic ellipticities of source galaxies with which the
perturbation theory results can be recovered, the accuracy of $\Omega_{\rm m}$
determination is improved by $\sim 20%$ using the Minkowski functionals
compared to the conventional method of using the direct measure of skewness.


title: Stellar Populations and Chemical Evolution of Late--Type Dwarf Galaxies

abstract:
  Some aspects of the chemical evolution of late-type dwarf galaxies are
reviewed, together with their implications on three issues of cosmological
relevance: similarity to primeval galaxies, derivation of the primordial helium
abundance, contribution to the excess of faint blue galaxies. A more detailed
approach to model their evolution is suggested. The importance of deriving the
star formation history in these systems by studying their resolved stellar
populations is emphasized.


title:
Reproducing Cosmic Microwave Background anisotropies with mixed
  isocurvature perturbations

abstract:
  Recently high quality data of the cosmic microwave background anisotropies
have been published. In this work we study to which extent the cosmological
parameters determined by using this data depend on assumptions about the
initial conditions. We show that for generic initial conditions, not only the
best fit values are very different but, and this is our main result, the
allowed parameter range enlarges dramatically.


title: RXTE monitoring of Centaurus A

abstract:
  We report on the analysis from ~110 ks of X-ray observations of Centaurus A
carried out with the Proportional Counter Array (PCA) and the High Energy X-ray
Timing Experiment (HEXTE) instruments on Rossi X-ray Timing Explorer (RXTE)
during three monitoring campaigns over the last 4 years (10 ks in 1996, 74 ks
in 1998, and 25 ks in 2000). The joint PCA/HEXTE X-ray spectrum can be well
described by a heavily absorbed power law with photon index 1.8 and a narrow
iron line due to fluorescence of cold matter. The measured column depth
decreased by about 30% between 1996 and 2000, while the detected 2-10 keV
continuum flux remained constant between 1996 and 1998, but increased by 60% in
2000. Since in all three observations the iron line flux did not vary, a
corresponding decrease in equivalent width was noted. No appreciable evidence
for a reflection continuum in the spectrum was detected. We present the
interpretation of the iron line strength through Monte Carlo computations of
various geometries. No significant temporal variability was found in Cen A at
time scales from days to tens of minutes.


title: The High-Frequency QPOs in GRS 1915+105

abstract:
  We analyzed two 1996 observations of the Galactic Microquasar GRS 1915+105
taken with the Proportional Counter Array on board the Rossi X-ray Timing
Explorer. We focus on the properties of the high-frequency QPO as a function of
the `dip' oscillations, a factor of 1000 slower. In one observation, 1996 May
5th, we find that the energy spectrum of the QPO at ~65 Hz changes drastically
between the high-intervals and the dips, hardening during the dips to the point
that the QPO peak is no longer detected at low energies. In the second
observation, 1996 May 14th, although it has similar overall characteristics,
the 65 Hz QPO is not seen, but another broader QPO peak appears at 27 Hz, only
during the dips. This peak is too weak to obtain reliable information about its
spectrum. Our results indicate that the presence/absence of high-frequency
features in this enigmatic source are intimately linked to the slower
oscillations and variations that happen on longer time scales.


title: On spherically-symmetric accretion by a collisionless polytrope

abstract:
  An isolated, spherically-symmetric, self-gravitating, collisionless system is
always a polytrope when it reaches equilibrium (Nakamura 2000). This strongly
suggests as a corollary, however, that the same polytrope dominates its
precursor states, since the dynamical equations for its constituents can be
time-reversed. Moreover this assumption, which precludes a polytrope from ever
accreting 100% of the mass from an infalling shell, as a subsequent state will
eventually be a polytrope, is confirmed now by our finding that a collisionless
polytrope cannot accrete 100% of an infalling shell while simultaneously
guaranteeing that the entropy of the Universe as a whole increases. These
strictures are only evaded by the shedding of some mass. A polytrope must lose
mass to gain mass.
  We deduce from the time-reversible property of a collisionless polytrope that
the scalar sum, P, over constituent momenta in its rest frame is an independent
state variable that is conserved with respect to its surface radius through
interactions between a polytrope and an infalling shell. This new constraint,
together with conservation of energy, enables us (i) to show that an isolated
polytrope is indeed stable against spherically-symmetric mass-loss, which is
the essential content of our initial assumption; (ii) to calculate both the
velocity and the fraction of infall-mass returned to infinity, provided the
"accretion law" between the change in mass and surface radius is specified.
Numerical results confirm a frequent empirical finding (Livio 2000) that the
velocity of a mass outflow is of the same order of magnitude as the escape
velocity from the system.


title: The Sun as an X-ray Star: III. Flares

abstract:
  In previous works we have developed a method to convert solar X-ray data,
collected with the Yohkoh/SXT, into templates of stellar coronal observations.
Here we apply the method to several solar flares, for comparison with stellar
X-ray flares. Eight flares, from weak (GOES class C5.8) to very intense ones
(X9) are selected as representative of the flaring Sun. The emission measure
distribution vs. temperature, EM(T), of the flaring regions is derived from
Yohkoh/SXT observations in the rise, peak and decay of the flares. The EM(T) is
rather peaked and centered around $T \approx 10^7$ K for most of the time.
Typically, it grows during the rise phase of the flare, and then it decreases
and shifts toward lower temperatures during the decay, more slowly if there is
sustained heating. The most intense flare we studied shows emission measure
even at very high temperature ($T \approx 10^8$ K). Time-resolved X-ray spectra
both unfiltered and filtered through the instrumental responses of the
non-solar instruments ASCA/SIS and ROSAT/PSPC are then derived. Synthesized
ASCA/SIS and ROSAT/PSPC spectra are generally well fitted with single thermal
components at temperatures close to that of the EM(T) maximum, albeit two
thermal components are needed to fit some flare decays. ROSAT/PSPC spectra show
that solar flares are in a two-orders of magnitude flux range ($10^6 - 10^8$
erg cm$^{-2}$ s$^{-1}$) and a narrow PSPC hardness ratio range, however higher
than that of typical non-flaring solar-like stars.


title: How Recent is Cosmic Acceleration?

abstract:
  Possibly the most peculiar expectation of the standard fine-tuned
cosmological paradigm is that cosmic acceleration is to only be a very recent
(z<1) phenomenon, with the universe being required to be decelerating at all
higher redshifts. Detailed exploration of the Hubble plot out to z=2 or so will
not only provide an absolute test of this expectation but will also allow for
testing of conformal gravity, a non fine-tuned alternate cosmological theory
which provides equally good fitting to the current z<1 Hubble plot data while
requiring the universe to be accelerating at higher z instead. With both
standard and conformal gravity being found to be compatible with a very
recently reported z=1.7 data point, additional data points will thus be needed
to determine whether the universe is accelerating or decelerating above z=1.


title:
Spatial correlation functions and the pairwise peculiar velocity
  dispersion of galaxies in the PSCz survey: implications for the galaxy
  biasing in cold dark matter models

abstract:
  We report on the measurement of the two-point correlation function, and the
pairwise peculiar velocity of galaxies in the IRAS PSCz survey. We compute
these statistics first in redshift space, and then obtain the projected
functions which have simple relations to the real-space correlation functions
on the basis of the method developed earlier in analyzing the Las Campanas
Redshift Survey (LCRS) by Jing, Mo, & B\"orner (1998). We find that the real
space two-point correlation function can be fitted to a power law $\xi(r) =
(r_0/r)^{\gamma}$ with $\gamma=1.69$ and $r_0=3.70 \mpc$. The pairwise peculiar
velocity dispersion $\sigma_{12}(r_p)$ is close to $400 \kms$ at $r_p=3\mpc$
and decreases to about $150 \kms$ at $r_p \approx 0.2 \mpc$. These values are
significantly lower than those obtained from the LCRS. In order to understand
the implications of those measurements on the galaxy biasing, we construct mock
samples for a low density spatially-flat cold dark matter model ($\Omega_0 =
0.3$, $\lambda_0=0.7$, $\Gamma=0.2$, $\sigma_8=1$) using a set of
high-resolution N-body simulations. Applying a stronger cluster-underweight
biasing ($\propto M^{-0.25}$) than for the LCRS ($\propto M^{-0.08}$), we are
able to reproduce these observational data, except for the strong decrease of
the pairwise peculiar velocity at small separations. This is qualitatively
ascribed to the different morphological mixture of galaxies in the two
catalogues. Disk-dominated galaxy samples drawn from the theoretically
constructed GIF catalog yield results rather similar to our mock samples with
the simple cluster-underweight biasing.


title:
Rayleigh-Taylor Instabilities in Young Supernova Remnants Undergoing
  Efficient Particle Acceleration

abstract:
  We employ hydrodynamic simulations to study the effects of high shock
compression ratios, as expected for fast shocks with efficient particle
acceleration, on the convective instability of driven waves in supernova
remnants. We find that the instability itself does not depend significantly on
the compression ratio, but because the width of the interaction region between
the forward and reverse shocks can shrink significantly with increasing shock
compression, we find that convective instabilities can reach all the way to the
forward shock front if compression ratios are high enough.


title: Aspherical Supernovae: Hydrodynamics & Radiation Transport

abstract:
  Core collapse supernovae (SN) are the final stages of stellar evolution in
massive stars during which the central region collapses, forms a neutron star
(NS), and the outer layers are ejected. Recent explosion scenarios assumed that
the ejection is due to energy deposition by neutrinos into the envelope but
detailed models do not produce powerful explosions. There is new and mounting
evidence for an asphericity and, in particular, for axial symmetry in several
SNe which may be hard to reconcile within the spherical picture. This evidence
includes the observed high polarization and its variation with time, pulsar
kicks, high velocity iron-group and intermediate-mass elements material in
remnants & direct observations of the debris of SN87A.Any successful mechanism
must invoke some sort of axial symmetry for the explosion. As limiting case, we
consider jet-induced/dominated explosions of "classical" core collapse SNe. Our
study is based on detailed 3-D hydro and radiation transport models. The jet
properties and of the progenitor structure influence on the final density and
chemical structure. Our calculations show that low velocity, massive jets can
explain the observations. Both asymmetric ionization and density/chemical
distributions have been identified as crucial for the formation of asymmetric
photospheres. Even within the picture of jet-induced explosion, the latter
effect alone fails to explain early polarization in core collapse SNe with a
massive, hydrogen-rich envelopes such as SN1999em.


title:
n-Dimensional Gravity: Little Black Holes, Dark Matter, and Ball
  Lightning

abstract:
  The gravitational field, and radiation from quantized gravitational atoms and
little black holes (LBH) are analyzed in n-space, i.e. in all dimensions to
develop insights into possible additional compacted dimensions as predicted by
hierarchy and string theory. It is shown that the entropy of LBH is
significantly greater in higher dimensional space with potential implications
to the initial entropy of the universe. A case is made that LBH are the dark
matter of the universe, and can manifest themselves as the core energy source
of ball lightning (BL). The LBH incidence rate on earth is related to BL
occurrence and has the potential of aiding in the determination of the
distribution of LBH and hence dark matter in the universe. Examination of LBH
interactions with the atmosphere are found to be in accord with observations of
BL. Possibilities are explored as to why Hawking radiation has been undetected
in over 25 years. An alternate LBH tunneling radiation model is described.


title: A Chandra X-ray Study of NGC 1068 - I. Observations of Extended Emission

abstract:
  We report sub arc-second resolution X-ray imaging-spectroscopy of the
archetypal type 2 Seyfert galaxy NGC 1068 with the Chandra X-ray Observatory.
The observations reveal the detailed structure and spectra of the 13 kpc-extent
nebulosity previously imaged at lower resolution with ROSAT. The Chandra image
shows a bright, compact source coincident with the brightest radio and optical
emission; this source is extended by \simeq 1.5 arcsec (165 pc) in the same
direction as the nuclear optical line and radio continuum emission. Bright
X-ray emission extends \simeq 5 arcsec (550 pc) to the NE and coincides with
the NE radio lobe and gas in the narrow line region. The large-scale emission
shows trailing spiral arms and other structures. Numerous point sources
associated with NGC 1068 are seen. There is a very strong correlation between
the X-ray emission and the high excitation ionized gas seen in HST and
ground-based [O III] \lambda 5007 images. The X-rays to the NE of the nucleus
are absorbed by only the Galactic column density and thus originate from the
near side of the disk of NGC 1068. In contrast the X-rays to the SW are more
highly absorbed and must come from gas in the disk or on the far side of it.
This geometry is similar to that inferred for the narrow line region and radio
lobes. (Abstract truncated).


title: Small-Scale Interstellar Na I Structure Toward M92

abstract:
  We have used integral field echelle spectroscopy with the DensePak
fiber-optic array on the KPNO WIYN telescope to observe the central 27" x 43"
of the globular cluster M92 in the Na I D wavelength region at a spatial
resolution of 4". Two interstellar Na I absorption components are evident in
the spectra at LSR velocities of 0 km/s (Cloud 1) and -19 km/s (Cloud 2).
Substantial strength variations in both components are apparent down to scales
limited by the fiber-to-fiber separations. The derived Na I column densities
differ by a factor of 4 across the Cloud 1 absorption map and by a factor of 7
across the Cloud 2 map. Using distance upper limits of 400 and 800 pc for Cloud
1 and Cloud 2, respectively, the absorption maps indicate structure in the ISM
down to scales of 1600 and 3200 AU. The fiber-to-fiber Na I column density
differences toward M92 are comparable to those found in a similar study of the
ISM toward the globular cluster M15. Overall, the structures in the
interstellar components toward M92 have significantly lower column densities
than those toward M15. We interpret these low column density structures as
small-scale turbulent variations in the gas and compare them to the
larger-scale, higher column density variations toward M15, which may be the
hallmarks of actual H I structures.


title:
Quasar Evolution and the Baldwin Effect in the Large Bright Quasar
  Survey

abstract:
  From a large homogeneous sample of optical/UV emission line measurements for
993 quasars from the Large Bright Quasar Survey (LBQS), we study correlations
between emission line equivalent width and both restframe ultraviolet
luminosity (i.e., the Baldwin Effect) and redshift. Our semi-automated spectral
fitting accounts for absorption lines, fits blended iron emission, and provides
upper limits to weak emission lines. Use of a single large, well-defined sample
and consistent emission line measurements allows us to sensitively detect many
correlations, most of which have been previously noted. A new finding is a
significant Baldwin Effect in UV iron emission. Further analysis reveals that
the primary correlation of iron emission strength is probably with redshift,
implying an evolutionary rather than a luminosity effect. We show that for most
emission lines with a significant Baldwin Effect, and for some without,
evolution dominates over luminosity effects. This may reflect evolution in
abundances, in cloud covering factors, or overall cloud conditions such as
density and ionization. We find that in our sample, a putative correlation
between Baldwin Effect slope and the ionization potential is not significant.
Uniform measurements of other large quasar samples will extend the luminosity
and redshift range of such spectral studies and provide even stronger tests of
spectral evolution.


title: Deflection of Jets Induced by Jet-Cloud Interactions

abstract:
  A non--relativistic and relativistic model in which astrophysical jets are
deflected on passing through an isothermal high density region is analysed. The
criteria for the stability of jets due to the formation of internal shocks are
discussed.


title: A Search for Rapid Photometric Variability in Symbiotic Binaries

abstract:
  We report on our survey for rapid (time scale of minutes) photometric
variability in symbiotic binaries. These binaries are becoming an increasingly
important place to study accretion onto white dwarfs since they are candidate
Type Ia supernovae progenitors. Unlike in most cataclysmic variables, the white
dwarfs in symbiotics typically accrete from a wind, at rates greater than or
equal to 10^{-9} solar masses per year. In order to elucidate the differences
between symbiotics and other white dwarf accretors, as well as search for
magnetism in symbiotic white dwarfs, we have studied 35 primarily northern
symbiotic binaries via differential optical photometry. Our study is the most
comprehensive to date of rapid variability in symbiotic binaries. We have found
one magnetic accretor, Z And, previously reported by Sokoloski & Bildsten
(1999). In four systems (EG And, BX Mon, CM Aql, and BF Cyg), some evidence for
flickering at a low level (roughly 10 mmag) is seen for the first time. These
detections are, however, marginal. For 25 systems, we place tight upper limits
(order of mmag) on both aperiodic and periodic variability, highlighting a
major difference between symbiotics and cataclysmic variables. The remaining
five of the objects included in our sample (the 2 recurrent novae RS Oph and T
CrB, plus CH Cyg, o Ceti, and MWC 560) had previous detections of
large-amplitude optical flickering, and we present our extensive observations
of these systems in a separate paper. We discuss the impact of our results on
the ``standard'' picture of wind-fed accretion, and speculate on the
possibility that in most symbiotics, light from quasi-steady nuclear burning on
the surface of the white dwarf hides the fluctuating emission from accretion.


title: The Halo Black-Hole X-ray Transient XTE J1118+480

abstract:
  Optical spectra were obtained of the optical counterpart of the high latitude
soft X-ray transient XTE J1118+480 near its quiescent state with the new 6.5 m
MMT and the 4.2 m WHT. The spectrum exhibits broad, double-peaked, emission
lines of hydrogen from an accretion disk superposed with absorption lines of a
K7V-M0V secondary star. Cross-correlation of the 27 individual spectra with
late-type stellar template spectra reveals a sinusoidal variation in radial
velocity with amplitude K = 701 +/- 10 km/s and orbital period P = 0.169930 +/-
0.000004 d. The mass function, 6.1 +/- 0.3 solar masses, is a firm lower limit
on the mass of the compact object and strongly implies that it is a black hole.
Photometric observations (R-band) with the IAC 0.8 m telescope reveal
ellipsoidal light variations of full amplitude 0.2 mag. Modeling gives a large
mass ratio (M1/M2 ~ 20) and a high orbital inclination (i = 81 +/- 2 deg). Our
combined fits yield a mass of the black hole in the range M1 = 6.0-7.7 solar
masses (90% confidence) for plausible secondary star masses of M2 = 0.09-0.5
solar masses. The photometric period measured during the outburst is 0.5%
longer than our orbital period and probably reflects superhump modulations as
observed in some other soft X-ray transients. The estimated distance is d = 1.9
+/- 0.4 kpc corresponding to a height of 1.7 +/- 0.4 kpc above the Galactic
plane. The spectroscopic, photometric, and dynamical results indicate that XTE
J1118+480 is the first firmly identified black hole X-ray system in the
Galactic halo.


title:
Sensitivity of an underwater acoustic array to ultra-high energy
  neutrinos

abstract:
  We investigate the possibility of searching for ultra high energy neutrinos
in cosmic rays using acoustic techniques in ocean water. The type of
information provided by the acoustic detection is complementary to that of
other techniques, and the filtering effect of the atmosphere, imposed by the
fact that detection only happens if a shower fully develops in water, would
provide a clear neutrino identification. We find that it may be possible to
implement this technique with very limited resources using existing high
frequency underwater hydrophone arrays. We review the expected acoustic signals
produced by neutrino-induced showers in water and develop an optimal filtering
algorithm able to suppress statistical noise. The algorithm found is
computationally appropriate to be used as a trigger for the signal processors
available on existing arrays. We estimate the noise rates for a trigger system
on a very large size hydrophone array of the US Navy and find that, while a
higher density of hydrophones would be desirable, the existing system may
already provide useful data.


title:
Orbital perturbations on transiting planets: A possible method to
  measure stellar quadrupoles and to detect Earth-mass planets

abstract:
  The recent discovery of a planetary transit in the star HD 209458, and the
subsequent highly precise observation of the transit lightcurve with Hubble
Space Telescope, is encouraging to search for any phenomena that might induce
small changes in the light curve. Here we consider the effect of the quadrupole
moment of the parent star and of a possible second planet perturbing the orbit
of the transiting planet. Both of these cause a precession of the orbital plane
and of the periastron of the planet, which result in a long-term variation of
the duration and the period of the transits. For a transiting planet at 0.05
AU, either a quadrupole moment similar to that of the Sun or the gravitational
tug from an Earth-like planet on an orbit of semimajor axis ~ 0.2 AU and a
relative inclination near the optimal 45 degrees would cause a transit duration
time derivative of ~ 1 second per year.


title: A Chandra Study of the Circinus Galaxy Point-Source Population

abstract:
  We have used the Chandra X-ray Observatory to resolve spatially and
spectrally the X-ray emission from the Circinus Galaxy. We report here on the
nature of the X-ray emission from the off-nuclear point sources associated with
the disk of Circinus. We find that many of the serendipitous X-ray sources are
concentrated along the optical disk of the galaxy, but few have optical
counterparts within 1" of their X-ray positions down to V=23-25. At 3.8 Mpc,
their intrinsic 0.5-10 keV luminosities range from approx. 2E37 erg/s to 4E39
erg/s. One quarter of the sources are variable over the duration of the 67 ks
observation, and spectral fitting of these off-nuclear sources shows a diverse
range of spectral properties. The properties of the two strongest off-nuclear
sources are remarkable, with average X-ray luminosities of 3.7E39 erg/s and
3.4E39 erg/s. The former displays large and periodic flux variations every 7.5
hr and is well fit by a multicolor blackbody accretion-disk model with
T_in=1.35 keV, properties consistent with an eclipsing >50 M_sun black-hole
binary. The latter appears to be a young supernova remnant, as it coincides
with a non-thermal radio counterpart and an H\alpha-detected HII region. This
source exhibits both long-term (approx. 4 yr) X-ray variability and a 6.67-6.97
keV iron emission-line blend with a 1.6 keV equivalent width. These two objects
further support the notion that super-Eddington X-ray sources in nearby
galaxies can be explained by a mixture of intermediate-mass black holes in
X-ray binaries and young supernova remnants. (abridged)


title: The Balloon-borne Large Aperture Sub-millimetre Telescope

abstract:
  The Balloon-borne Large-Aperture Sub-millimetre Telescope (BLAST) will
operate on a Long Duration Balloon platform with large format bolometer arrays
at 250, 350 and 500 microns, initially using a 2m mirror, with plans to
increase to 2.5m. BLAST is a collaboration between scientists in the USA,
Canada, UK, Italy and Mexico. Funding has been approved and it is now in its
building phase. The test flight is scheduled for 2002, with the first long
duration flight the following year. The scientific goals are to learn about the
nature of distant extragalactic star forming galaxies and cold pre-stellar
sources by making deep maps both at high and low galactic latitudes. BLAST will
be useful for planning Herschel key projects which use SPIRE.


title:
Faint End of the Galaxy Luminosity Function: A Chronometer for Structure
  Formation?

abstract:
  There is accumulating evidence that the faint end of the galaxy luminosity
function might be very different in different locations. The luminosity
function might be sharply rising in rich clusters and flat or declining in
regions of low density. If galaxies form according to the model of hierarchical
clustering then there should be many small halos compared to the number of big
halos. If this theory is valid then there must be a mechanism that eliminates
at least the visible component of galaxies in low density regions. A plausible
mechanism is photoionization of the intergalactic medium at a time before the
epoch of galaxy formation in low density regions but after the epoch of
formation for systems that ultimately end up in rich clusters. The dynamical
timescales are found to accommodate this hypothesis in a flat universe with
Omega_m < 0.4.
  If this idea has validity, then upon surveying a variety of environments it
is expected that a dichotomy will emerge. There should be a transition between
high density / high frequency of dwarfs to lower density / low frequency of
dwarfs. This transition should ultimately be understood by the matching of
three timing considerations: (i) the collapse timescale of the transition
density, (ii) the timescale of reionization, and (iii) the linkage given by the
cosmic expansion timescale as controlled by the dark matter and dark energy
content of the universe.


title:
Finding out the velocity anisotropy parameter for some globular
  clusters: the case of stationary model

abstract:
  The problem of determination of the velocity anisotropy parameter (A) from
star density profiles in globular clusters is considered. The calculations are
performed for following clusters: M3, M12, M13, M15, M55, M56, Palomar 3,
Palomar 14, NGC5139 (Omega Centauri) and NGC6535. We found that for most
clusters is A=0. For M56 the parameter is calculated at limiting magnitudes
B=21.5 and B=19.0 and we found A=0.8 and A=0.3 respectively. For Omega Centauri
the anisotropy parameter is determined in three separate regions and we found:
A=0 for central region, A=0.1 for middle region and A=0.3 for halo.


title: The Dense Plasma Torus Around the Nucleus of an Active Galaxy NGC 1052

abstract:
  A subparsec-scale dense plasma torus around an active galactic nucleus (AGN)
is unveiled. We report on very-long-baseline interferometry (VLBI) observations
at 2.3, 8.4, and 15.4 GHz towards the active galaxy NGC 1052. The convex
spectra of the double-sided jets and the nucleus imply that synchrotron
emission is obscured through free--free absorption (FFA) by the foreground cold
dense plasma. A trichromatic image was produced to illustrate the distribution
of the FFA opacity. We found a central condensation of the plasma which covers
about 0.1 pc and 0.7 pc of the approaching and receding jets, respectively. A
simple explanation for the asymmetric distribution is the existence of a thick
plasma torus perpendicular to the jets. We also found an ambient FFA absorber,
whose density profile can be ascribed to a spherical distribution of the
isothermal King model. The coexistence of torus-like and spherical
distributions of the plasma suggests a transition from radial accretion to
rotational accretion around the nucleus.


title:
Recurrent novae as a progenitor system of Type Ia supernovae. I. RS
  Ophiuchi subclass --- Systems with a red giant companion

abstract:
  Theoretical light curves of four recurrent novae in outburst are modeled to
obtain various physical parameters. They are those with a red giant companion,
T CrB, RS Oph, V745 Sco, and V3890 Sgr. Our model includes irradiations of the
companion star and the accretion disk together with a shadowing effect on the
companion by the accretion disk. The early visual light curves are well
reproduced with a thermonuclear runaway model on a very massive white dwarf of
1.37 Mo for T CrB, 1.37 Mo for RS Oph with low metallicity (Z=0.004), 1.35 Mo
for V745 Sco, and 1.35 Mo for V3890 Sgr. Each envelope mass at the optical
maximum is also estimated to be 3 x 10^{-6}, 2 x 10^{-6}, 5 x 10^{-6}, and 3 x
10^{-6} Mo, indicating an average mass accretion rate of 0.4 x 10^{-7}, 1.2 x
10^{-7}, 0.9 x 10^{-7}, and 1.1 x 10^{-7} Mo/yr during the quiescent phase.
Although a large part of the envelope mass is blown in the wind, each WD can
retain a substantial part of the envelope mass after hydrogen burning ends.
Thus, we have obtained net mass-increasing rates of the WDs as 0.1 x 10^{-7},
0.12 x 10^{-7}, 0.05 x 10^{-7}, and 0.11 x 10^{-7} Mo/yr. These results
strongly indicate that the WDs in the recurrent novae have now grown up to near
the Chandrasekhar mass limit and will soon explode as a Type Ia supernova if
the WDs consist of carbon and oxygen. We also include a radiation-induced
warping instability of the accretion disk to reproduce the second peak of T CrB
outbursts. Thus, we have clarified the reason why only T CrB shows a secondary
maximum but the other three systems do not.


title: Revisiting the Cosmic Cooling Crisis

abstract:
  Recent measurements of the K-band luminosity function now provide us with
strong, reliable constraints on the fraction of baryons which have cooled.
Globally, this fraction is only about 5%, and there is no strong evidence that
it is significantly higher in clusters. Without an effective sub-grid feedback
prescription, the cooled gas fraction in any numerical simulation exceeds these
observational constraints, and increases with increasing resolution. This
compromises any discussion of galaxy and cluster properties based on results of
simulations which include cooling but do not implement an effective feedback
mechanism.


title:
The Environmental Dependence of the Infrared Luminosity and Stellar Mass
  Functions

abstract:
  We investigate the dependence of the galaxy infrared luminosity function (LF)
and the associated stellar mass function (SMF) on environment and spectral type
using photometry from the Two Micron All Sky Survey and redshifts from the Las
Campanas Redshift Survey for galaxies brighter than M_J<-19+5 log h. In the
field environment, galaxies with emission lines have LFs with much steeper
faint end slopes (alpha_J=-1.39) than galaxies without emission lines
(alpha_J=-0.59). In the cluster environment, however, even the non-emission
line galaxies have a steep faint-end LF (alpha_J=-1.22). There is also a
significant (95%) difference between the overall cluster and field LFs, $\Delta
\alpha_J=-0.34, \Delta M_J^\ast=-0.54$. All of these variations are more
pronounced in the SMFs, which we compute by relating the strength of the 4000 A
break in the optical spectra to a mass-to-light ratio.


title:
Robustness of the inflationary perturbation spectrum to trans-Planckian
  physics

abstract:
  It is investigated if predictions of the inflationary scenario regarding
spectra of scalar and tensor perturbations generated from quantum vacuum
fluctuations are robust with respect to a modification of the dispersion law
for frequencies beyond the Planck scale. For a large class of such
modifications of special and general relativity, for which the WKB condition is
not violated at super-high frequencies, the predictions remain unchanged. The
opposite possibility is excluded by the absence of large amount of created
particles due to the present Universe expansion. Creation of particles in the
quantum state minimizing the energy density of a given mode at the moment of
Planck boundary crossing is prohibited by the latter argument, too (contrary to
creation in the adiabatic vacuum state which is very small now).


title: Chemical Evolution of Bulges

abstract:
  We show our results from the application of the Multiphase chemical evolution
model to a set of Bulges of spiral galaxies


title: On the neutrino flux from Gamma Ray Bursts: an overview

abstract:
  Observations imply that gamma-ray bursts (GRBs) are produced by the
dissipation of the kinetic energy of a highly relativistic fireball.
Photo-meson interactions of protons with gamma-rays within the fireball
dissipation region are expected to convert a significant fraction of the
fireball energy into high energy neutrinos. In this talk we summarize the
results of an analysis of the internal shock model of GRBs, where production of
synchrotron photons and photo-meson neutrinos with energies about 10^14 eV are
self-consistently calculated. These neutrinos will be coincident with the GRB.
We show that the fraction of fireball energy converted into high energy
neutrinos is not sensitive to uncertainties in the fireball model parameters,
such as the expansion Lorentz factor and characteristic variability time. Other
processes of neutrinos emission from GRBs are also reviewed. Photomeson
interactions within the plasma region shocked by the reverse shock, may produce
a burst of 10^18 eV neutrinos following the GRB on the time scale of 10 s.
Inelastic p-n nuclear collisions result in the production of a burst of around
10 GeV neutrinos in coincidence with the GRB. Planned 1 km^3 neutrino
telescopes are expected to detect ten 100 TeV neutrino events and several 10^18
eV events, correlated with GRBs, per year. A suitably densely spaced detector
may allow the detection of several 10 GeV events per year.


title: Chemical Evolution along the Hubble sequence

abstract:
  We show a grid of multiphase models whose results are valid for any spiral
galaxy, using as input the luminosity or the rotation velocity and the
morphological type, measured by the classical index T from 1 to 10.


title: The Comptel 1.809 Mev Survey

abstract:
  We present the latest update of the 1.809 MeV sky survey obtained with
COMPTEL. Based on all observations taken since the launch of CGRO in spring
1991 to early summer this year we obtain 1.809 MeV all sky maps using different
imaging methods. The background is modelled on the basis of an adjacent energy
approach. We confirm the previously reported characteristics of the galactic
1.809 MeV emission, specifically excesses in regions away from the inner
Galaxy. The observed 1.8 MeV gamma-ray line is ascribed to the radioactive
decay of 26Al in the interstellar medium. 26Al has been found to be
predominantly synthesised in massive stars and their subsequent core-collapse
supernovae, which is confirmed in tracer comparisons. Due to this, one
anticipates flux enhancements aligned with regions of recent star formation,
such as apparently observed in the Cygnus and Vela regions.


title: A grid of chemical evolution models along the Hubble Sequence

abstract:
  We have computed a grid of multiphase chemical evolution models whose results
are valid for any spiral galaxy, using as input the maximum rotation velocity
and the morphological type or index T.


title: 56Co gamma-rays from SN1998bu: COMPTEL upper limits

abstract:
  The type Ia supernova SN1998bu in M96 was observed by COMPTEL for a total of
88 days starting 17 days after the first detection of the supernova. The
accumulated effective observation time was 4.14 Msec. The COMPTEL observations
were performed in a special instrument mode improving the low-energy
sensitivity. We generated images in the 847 keV and 1238 keV lines of 56Co,
using improved point spread functions for the low-energy mode. We do not detect
SN1998bu. A spectral analysis of our data also confirms the non-detection of
the supernova. We discuss the event for which our upper limits constrain the
standard supernova models.


title: The Cygnus Region: 26Al from OB Associations

abstract:
  The COMPTEL map of the 1.809 MeV gamma-ray line, which is attributed to the
radioactive decay of 26Al, shows significant excess emission in the Cygnus
region. Cygnus is a region of recent star formation activity, which is rich in
massive, early-type stars concentrated in OB associations.
  We perform population synthesis studies of this region to model the
production and distribution of 26Al, which is predominantly synthesized in
massive stars and distributed through stellar winds and core-collapse
supernovae. Our simulations of the Cygnus OB associations determine the
time-dependent production rate of 26Al. We also estimate the associated
production of radioactive 60Fe, which is primarily synthesized in core-collapse
supernovae. Gamma-ray line emission from this isotope has yet to be detected.
We also track the temporal evolution of the mechanical "luminosity" due to the
kinetic energy of stellar winds and supernova ejecta, and the ionizing EUV
emission from early-type stars. Together with a simple one-dimensional model of
the superbubble driven into the ISM by this energy flux one can constrain key
parameters of the stellar associations in the Cygnus region.


title: Gamma-Ray Line Emission from 7-Li and 7-Be Production by Cosmic-Rays

abstract:
  We calculate the total gamma-ray line emission at ~450 keV that accompanies
7-Li and 7-Be production by cosmic-ray interactions, including the delayed line
emission at 0.478 MeV from 7-Be radioactive decay. We present a new gamma-ray
spectroscopic test which has the potential to give direct information on the
nature of the interstellar regions into which 7-Be ions propagate and decay.
Finally, we evaluate the intensity of the predicted diffuse emission from the
central radian of the Galaxy.


title:
Radioactivities in Population Studies: 26Al and 60Fe from OB
  Associations

abstract:
  The observation of the interstellar 1.809 MeV decay-line of radioactive 26Al
by the imaging gamma-ray telescope COMPTEL have let to the conclusion, that
massive stars and their subsequent core-collapse supernovae are the dominant
sources of the interstellar 26Al abundance. Massive stars are known to affect
the surrounding interstellar medium by their energetic stellar winds and by the
emission of ionising radiation. We present a population synthesis model
allowing the correlated investigation of the gamma-ray emission characteristics
with integrated matter, kinetic energy and extreme ultra-violet radiation
emission of associations of massive stars. We study the time evolution of the
various observables. In addition, we discuss systematic as well as statistical
uncertainties affecting the model. Beside uncertainties in the input stellar
physics such as stellar rotation, mass loss rates or internal mixing
modifications due to a unknown binary component may lead to significant
uncertainties.


title:
Lithium abundances for 185 main-sequence stars - Galactic evolution and
  stellar depletion of lithium

abstract:
  We present a survey of lithium abundances in 185 main- sequence field stars
with Teff between 5600 and 6600 K and [Fe/H] from -1.4 to +0.2 based on
high-resolution spectra of 130 stars and a reanalysis of data from Lambert et
al. (1991). The survey takes advantage of improved ways of determining
effective temperature, metallicity, mass and age, offering an opportunity to
investigate the behaviour of Li as a function of these parameters. An
interesting result is the presence of a large gap in the Li-Teff plane, which
distinguishes `Hyades-like, Li-dip' stars from other stars. These Li-dip stars
have a well-defined mass, which decreases with metallicity. Stars above the
gap, when divided into four metallicity groups, may show a correlation between
Li abundance and stellar mass, but with a large dispersion that cannot be
explained by observational errors or differences in metallicity and age, which
ranges from 1.5 to 15 Gyr. This suggests that Li depletion occurs early in
stellar life and that other parameters, e.g. initial rotation velocity and/or
the rate of angular momentum loss, affect the degree of depletion. A comparison
of the distribution of stars in the Li-[Fe/H] plane with evolutionary models of
Romano et al. (1999) suggests that novae are a major source for the Li
production in the Galactic disk.


title:
OSSE and RXTE Observations of GRS 1915+105: Evidence for Non-thermal
  Comptonization

abstract:
  GRS 1915+105 was observed by the CGRO/OSSE 9 times in 1995-2000, and 8 of
those observations were simultaneous with those by RXTE. We present an analysis
of all of the OSSE data and of two RXTE-OSSE spectra with the lowest and
highest X-ray fluxes. The OSSE data show a power-law--like spectrum extending
up to ~600 keV without any break. We interpret this emission as strong evidence
for the presence of non-thermal electrons in the source. The broad-band spectra
cannot be described by either thermal or bulk-motion Comptonization, whereas
they are well described by Comptonization in hybrid thermal/ non-thermal
plasmas.


title: Macroscopic Hadronic Little Black Hole Interactions

abstract:
  Although the extraordinary weakness of gravity makes it by far the weakest of
the interactions, viewing little black holes (LBH) as a class of elementary
particles puts them in a league with hadrons as strongly interacting particles.
They interact strongly both in the subatomic and macroscopic realms. An
enormous universal gravitational attractive force ~ 10^43 /B 2 Newtons acts
between identical black holes for any mass M >> M Planck at a center-to-center
separation of 2 BR H (B > 1). For M ~ M Planck, there is a comparably large
repulsive force. The Hawking model of LBH radiation permits a luminosity from a
single LBH comparable to that of the entire universe, whereas this luminosity
is greatly attenuated in the Rabinowitz model. In interacting with each other,
and with large macroscopic bodies such as stars, neutron stars, and planets,
LBH can exhibit strong interactions with large-scale manifestations. Although
previously dismissed, an LBH is a potential candidate in accounting for the
1908 devastation of Tungus Siberia, since important LBH interactions were
overlooked. LBH passing through neutron star pulsars are capable of causing a
sudden change in frequency which may not be fully accounted for by other
theories. The existence of black holes is also discussed.


title: Ball Lightning: Manifestation of Cosmic Little Black Holes

abstract:
  A case is made that in encounters with the earth's atmosphere, astrophysical
little black holes (LBH) can manifest themselves as the core energy source of
balllightning (BL). Relating the LBH incidence rate on earth to BL occurrence
has the potential of shedding light on the distribution of LBH in the universe,
and their velocities relative to the earth. Most BL features can be explained
by a testable LBH model. Analyses are presented to support this model. LBH
produce complex and many-faceted interactions in air directly and via their
exhaust, resulting in excitation, ionization, and radiation due to processes
such as gravitational and electrostatic tidal force, bremsstrahlung, pair
production and annihilation, orbital electron near-capture by interaction with
a charged LBH. Gravitational interaction of atmospheric atoms with LBH can
result in an enhanced cross-section for polarization and ionization. An
estimate for the power radiated by BL ~ Watts is in agreement with observation.
An upper limit is found for the largest masses that can produce ionization and
polarization excitation. It is shown that the LBH high power exhaust radiation
is not prominent and its effects are consistent with observations.


title:
Time-Evolution of the Power Spectrum of the Black Hole X-ray Nova XTE
  J1550-564

abstract:
  We have studied the time evolution of the power spectrum of XTE J1550-564,
using X-ray luminosity time series data obtained by the Rossi X-Ray Timing
Explorer satellite. A number of important practical fundamental issues arise in
the analysis of these data, including dealing with time-tagged event data,
removal of noise from a highly non-stationary signal, and comparison of
different time-frequency distributions. We present two new methods to
understand the time frequency variations, and compare them to the dynamic power
spectrum of Homan et al. All of the approaches provide evidence that the QPO
frequency varies in a systematic way during the time evolution of the signal.


title: Funnel Flows from Disks to Magnetized Stars

abstract:
  This work considers flows from an accretion disk corotating with the aligned
dipole magnetic field of a rotating star. Ideal magnetohydrodynamics (MHD) is
assumed with the pressure and density related as $p \propto \rho^\gamma$ and
with $\rho {\bf v}^2 \ll {\bf B}^2/4\pi$, where ${\bf v}$ is the flow velocity.
This limit corresponds to the Alfv\'en radius for the disk accretion larger
than the corotation radius. Transonic flows, which go from subsonic motion near
the disk to supersonic inflow near the star, are shown to be possible only for
a narrow range of $R_d \sim r_c \equiv (GM/\Omega^2)^{1/3}$, where $R_d$ is the
radius at which the dipole field line intersects the disk, $r_c$ the corotation
radius, $M$ the mass of the star, and $\Omega$ its angular rotation rate. The
transonic flows have very different behaviors for $\gamma > 7/5$ and $< 7/5$.
In both cases, the plasma flow velocity ${\bf v}$ (which is parallel to ${\bf
B}$) increases with decreasing distance $R$ from the star. However, for $\gamma
>7/5$, the Mach number ${\cal M} \equiv |{\bf v}|/c_s$ (with $c_s$ the sound
speed) initially increases with $R$ decreasing from $R_d$, but for $R$
decreasing from $\approx 0.22 R_d$ (for $\gamma=5/3$)the Mach number
surprisingly {\it decreases}. In the other limit, $\gamma < 7/5$, ${\cal M}$
increases monotonically with decreasing $R$. Application of these results is
made to funnel flows to rotating magnetized neutron stars and young stellar
objects.


title: Wind Circulation in Selected Rotating Magnetic Early-B Stars

abstract:
  The rotating magnetic B stars have oblique dipolar magnetic fields and often
anomalous helium and metallic compositions. These stars develop co-rotating
torus-shaped clouds by channelling winds from their magnetic poles to an
anchored planar disk over the magnetic equator. The line absorptions from the
cloud can be studied as the complex rotates and periodically occults the star.
We describe an analysis of the clouds of four stars (HD184927, beta Cep, sigma
Ori E, and HR6684). From line synthesis models, we find that the metallic
compositions are spatially uniform over the stars' surfaces. Next, using the
Hubeny CIRCUS code, we demonstate that periodic UV continuum fluxes can be
explained by the absorption of low-excitation lines. The analysis also
quantifies the cloud temperatures, densities, and turbulences, which appear to
increase inward toward the stars. The temperatures range from about 12,000K for
the weak Fe lines up to temperatures of 33,000K for N V absorptions, which is
in excess of temperatures expected from radiative equilibrium.
  The spectroscopic hallmark of this stellar class is the presence of strong C
IV and N V resonance line absorptions at occultation phases and of redshifted
emissions at magnetic pole-on phases. The emissions have characteristics which
seem most compatible with the generation of high-energy shocks at the
wind-cloud interface, as predicted by Babel.


title:
FLIERs as stagnation knots from post-AGB winds with polar momentum
  deficiency

abstract:
  We present an alternative model for the formation of fast low-ionization
emission regions (FLIERs) in planetary nebulae that is able to account for many
of their attendant characteristics and circumvent the problems on the
collimation/formation mechanisms found in previous studies. In this model, the
section of the stellar wind flowing along the symmetry axis carries less
mechanical momentum than at higher latitudes, and temporarily develops a
concave or inverted shock geometry. The shocked ambient material is thus
refracted towards the symmetry axis, instead of away from it, and accumulates
in the concave section. The reverse is true for the outflowing stellar wind,
which in the reverse shock is refracted away from the axis. It surrounds the
stagnation region of the bow-shock and confines the trapped ambient gas. The
latter has time to cool and is then compressed into a dense "stagnation knot"
or "stagnation jet". In the presence of a variable stellar wind these features
may eventually overrun the expanding nebular shell and appear as detached
FLIERs. We present representative two and three-dimensional hydrodynamic
simulations of the formation and early evolution of stagnation knots and jets
and compare their dynamical properties with those of FLIERs in planetary
nebulae.
  Subject Headings: hydrodynamics - ISM: jets and outflows - ISM: kinematics
and dynamics - planetary nebulae: FLIERs and stagnation knots


title:
The X-ray spectra of optically selected Seyfert 2 galaxies. Are there
  any Sy2 galaxies with no absorption?

abstract:
  We present an X-ray spectral analysis of a sample of 8 bona-fide Seyfert 2
galaxies, selected on the basis of their high $[OIII]\lambda5007$ flux, from
the Ho et al. (1997) spectroscopic sample of nearby galaxies. We find that, in
general, the X-ray spectra of our Seyfert 2 galaxies are complex, with some our
objects having spectra different from the 'typical' spectrum of X-ray selected
Seyfert 2 galaxies. Two (NGC3147 and NGC4698) show no evidence for intrinsic
absorption. We suggest this is due to the fact that when the torus suppresses
the intrinsic medium and hard energy flux, underlying emission from the host
galaxy, originating in circumnuclear starbursts, and scattering from warm
absorbers contributes in these energy bands more significantly. Our asca data
alone cannot discriminate whether low absorption objects are Compton-thick AGN
with a strong scattered component or lack an obscuring torus. The most striking
example of our low absorption Seyfert 2 is NGC4698. Its spectrum could be
explained by either a dusty warm absorber or a lack of broad line clouds so
that its appearance as a Seyfert 2 is intrinsic and not due to absorption.


title: On the absorption feature in the prompt X-ray spectrum of GRB 990705

abstract:
  The absorption feature detected in the prompt X-ray emission of GRB 990705
bears important consequences. We investigate different production mechanisms
and we conclude that the absorbing material cannot be very close to the burster
and is likely to be moderately clumped. These properties challenge any model in
which the burst explodes in coincidence with the core-collapse of a massive
rotating star. We show that the straightforward interpretation of the
absorption feature as a photoionization K edge of neutral iron faces a severe
problem in that it requires a huge amount of iron in the close vicinity of the
burster. We then discuss an alternative scenario, in which iron ions are kept
in a high ionization state by the burst flux, and the absorption feature is
produced by resonant scattering from hydrogen-like iron, broadened by a range
outflow velocities. In this case the physical conditions and geometry of the
absorbing material are fully consistent with the presence of a young supernova
remnant surrounding the burst site at a radius R ~ 10^{16} cm. We finally
discuss how this remnant might affect the generation of afterglows with a
standard power-law flux decay.


title: A Study of Wavelength Calibration of NEWSIPS High-Dispersion Spectra

abstract:
  In this study we cross-correlate many IUE echellograms of a variety of stars
to evaluate systematic error sources in the wavelength zeropoint of all three
cameras. We first evaluated differences between the final archived ("NEWSIPS")
and the originally processed ("IUESIPS") spectra. These show a clear time
dependence in zeropoint for the SWP camera due to revisions in the IUESIPS
wavelength scale. Small IUESIPS - NEWSIPS differences are also found for the
LWR camera. We also examined wavelength zeropoint disparities between data
obtained both through the small and large entrance apertures and for
observations made by different target acquisition modes for faint and bright
stars. We found that velocities resulting from these alternative observing
modes are nil. For large-aperture observations the dominant error source is the
target position placement in the aperture. We searched for spurious trends with
time, and found only a suggestion of time trends for faint stars observed with
the SWP camera. We also discovered 1-day, +/-3 km/s sinusoidsal patterns in
intensive monitoring data which are ascribable to changes in telescope focus
resulting from thermal drifts. In the second part of the paper, we measured
mean zeropoint errors of NEWSIPS echellogram data against laboratory results by
using the GHRS spectral atlas of the 10 Lac. We find that the derived apparent
velocity difference for this star is -1 +/-3.5 km/s. Several less precise
comparisons lead to similar results. The zeropoints of the NEWSIPS-processed
LWP/LWR cameras are evaluated and are also found to be nearly zero (+/-5 km/s)
relative to HST atlases of Arcturus and Procyon atlas. These results do not
support result by Gonzalez-Riestra et al. that corrections should be introduced
to the wavelength scales of various NEWSIPS high-dispersion data products.


title: A semi-analytical approach to non-linear shock acceleration

abstract:
  Shocks in astrophysical fluids can generate suprathermal particles by first
order (or diffusive) Fermi acceleration. In the test particle regime there is a
simple relation between the spectrum of the accelerated particles and the jump
conditions at the shock. This simple picture becomes complicated when the
pressure of the accelerated particles becomes comparable with the pressure of
the shocked fluid, so that the non-linear backreaction of the particles becomes
non negligible and the spectrum is affected in a substantial way. Though only
numerical simulations can provide a fully self-consistent approach, a more
direct and easily applicable method would be very useful, and would allow to
take into account the non-linear effects in particle acceleration in those
cases in which they are important and still neglected. We present here a simple
semi-analytical model that deals with these non-linear effects in a
quantitative way. This new method, while compatible with the previous
simplified results, also provides a satisfactory description of the results of
numerical simulations of shock acceleration.


title: Radial Velocity Studies of Close Binary Stars.IV

abstract:
  Radial-velocity measurements and sine-curve fits to the orbital velocity
variations are presented for the fourth set of ten close binary systems: 44
Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc
(GSC 8-324), HT Vir. All systems are double-lined spectroscopic binaries with
only two of them not being contact systems (SW Lyn and GSC 8-324) and with five
(FI Boo, V2150 Cyg, V899 Her, EX Leo, V2377 Oph) being the recent photometric
discoveries of the Hipparcos satellite project. Five of the binaries are
triple-lined systems (44 Boo, V899 Her, VZ Lib, SW Lyn, HT Vir). Three (or
possibly four) companions in the triple-lined systems show radial-velocity
changes during the span of our observations suggesting that these are in fact
quadruple systems. Several of the studied systems are prime candidates for
combined light and radial-velocity synthesis solutions.


title:
High-resolution Near-Infrared Images and Models of the Circumstellar
  Disk in HH 30

abstract:
  We present Hubble Space Telescope (HST) Near-Infrared Camera and Multi-object
Spectrometer (NICMOS) observations of the reflection nebulosity associated with
the T Tauri star HH 30. The images show the scattered light pattern
characteristic of a highly inclined, optically thick disk with a prominent
dustlane whose width decreases with increasing wavelength. The reflected
nebulosity exhibits a lateral asymmetry in the upper lobe on the opposite side
to that reported in previously published Wide Field Planetary Camera 2 (WFPC2)
images. The radiation transfer model which most closely reproduces the data has
a flared accretion disk with dust grains larger than standard interstellar
medium grains by a factor of approximately 2.1. A single hotspot on the stellar
surface provides the necessary asymmetry to fit the images and is consistent
with previous modeling of the light curve and images. Photometric analysis
results in an estimated extinction of Av>~80; however, since the photometry
measures only scattered light rather than direct stellar flux, this a lower
limit. The radiative transfer models require an extinction of Av = 7,900.


title:
Radio Emission and the Timing Properties of the Hard X-ray State of GRS
  1915+105

abstract:
  We combine a complete sample of 113 pointed observations taken with the Rossi
X-ray Timing Explorer between 1996-1999, monitoring observations taken with the
Ryle telescope and the Green Bank Interferometer, and selected observations
with the Very Large Array to study the radio and X-ray properties of GRS
1915+105 when its X-ray emission is hard and steady. We establish that radio
emission always accompanies the hard-steady state of GRS 1915+105, but that the
radio flux density at 15.2 GHz and the X-ray flux between 2-200 keV are not
correlated. Therefore we study the X-ray spectral and timing properties of GRS
1915+105 using three approaches: first, by describing in detail the properties
of three characteristic observations, then by displaying the time evolution of
the timing properties during periods of both faint and bright radio emission,
and lastly by plotting the timing properties as a function of the the radio
flux density. We find that as the radio emission becomes brighter and more
optically thick, 1) the frequency of a ubiquitous 0.5-10 Hz QPO decreases, 2)
the Fourier phase lags between hard (11.5-60 keV) and soft (2-4.3 keV) in the
frequency range of 0.01-10 Hz change sign from negative to positive, 3) the
coherence between hard and soft photons at low frequencies decreases, and 4)
the relative amount of low frequency power in hard photons compared to soft
photons decreases. We discuss how these results reflect upon basic models from
the literature describing the accretion flow around black holes and the
possible connection between Comptonizing electrons and compact radio jets.


title: Explosions and Outflows during Galaxy Formation

abstract:
  We consider an explosion at the center of a halo which forms at the
intersection of filaments inside a cosmological pancake, a convenient test-bed
model for galaxy formation. ASPH/P3M simulations reveal that such explosions
are anisotropic. The energy and metals are channeled into the low density
regions, away from the pancake. The pancake remains essentially undisturbed,
even if the explosion is strong enough to blow away all the gas located inside
the halo and reheat the IGM surrounding the pancake. Infall quickly replenishes
this ejected gas and gradually restores the gas fraction as the halo continues
to grow. Estimates of the collapse epoch and SN energy-release for galaxies of
different mass in the CDM model can relate these results to scale-dependent
questions of blow-out and blow-away and their implication for early IGM heating
and metal enrichment and the creation of gas-poor dwarf galaxies.


title: The Equilibrium Structure of Cosmological Halos

abstract:
  We have derived an analytical model for the postcollapse equilibrium
structure of cosmological halos as nonsingular truncated isothermal spheres
(TIS) and compared this model with observations and simulations of cosmological
halos on all scales. Our model is in good agreement with the observations of
the internal structure of dark-matter-dominated halos from dwarf galaxies to
X-ray clusters. It reproduces many of the average properties of halos in CDM
simulations to good accuracy, including the density profiles outside the
central region, while avoiding the possible discrepancy at small radii between
observed galaxy and cluster density profiles and the singular density profiles
predicted by N-body simulations of the CDM model. While much attention has been
focused lately on this possible discrepancy, we show that the observed galaxy
rotation curves and correlations of halo properties nevertheless contain
valuable additional information with which to test the theory, despite this
uncertainty at small radii. The available data allows us to constrain the
fundamental cosmological parameters and also to put a unique constraint on the
primordial density fluctuation power spectrum at large wavenumbers (i.e. small
mass scale).


title: Chandra X-ray Observations of the X-ray Faint Elliptical Galaxy NGC 4697

abstract:
  (abridged) A Chandra ACIS S3 observation of the X-ray faint elliptical galaxy
NGC 4697 resolves much of the X-ray emission (61% of the counts from within one
effective radius) into 90 point sources, of which ~80 are low mass X-ray
binaries (LMXBs) associated with this galaxy. The dominance of LMXBs indicates
that X-ray faint early-type galaxies have lost much of their interstellar gas.
On the other hand, a modest portion of the X-ray emission from NGC 4697 is due
to hot gas. The X-ray emitting gas in NGC 4697 has a rather low temperature (kT
= 0.29 keV). The emission from the gas is very extended, with a much flatter
surface brightness profile than the optical light, and has an irregular,
L-shaped morphology. X-ray spectra of the resolved sources and diffuse emission
show that the soft X-ray spectral component, found in this and other X-ray
faint ellipticals with {\it ROSAT}, is due to interstellar gas. The cumulative
LMXB spectrum is well-fit by thermal bremsstrahlung at kT = 8.1 keV, without a
significant soft component. Three of the resolved sources in NGC 4697 are
supersoft sources. In the outer regions of NGC 4697, seven of the LMXBs (about
20%) 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 luminosity function of the LMXBs has a ``knee''
at 3.2 x 10^38 ergs/s, which is approximately the Eddington luminosity of a 1.4
Msun neutron star (NS). This knee appears to be a characteristic feature of the
LMXB population of early-type galaxies, and we argue that it separates black
hole and NS binaries. This characteristic luminosity could be used as a
distance estimator.


title: On OH line formation and oxygen abundances in metal-poor stars

abstract:
  The formation of the UV OH spectral lines has been investigated for a range
of stellar parameters in the light of 3D hydrodynamical model atmospheres. The
low atmospheric temperatures encountered at low metallicities compared with the
radiative equilibrium values enforced in classical 1D hydrostatic model
atmospheres have a profound impact on the OH line strengths. As a consequence,
the derived O abundances using 3D models are found to be systematically lower
by more than 0.6 dex at [Fe/H]=-3.0 compared with previous 1D analyses, casting
doubts on the recent claims for a monotonic increase in [O/Fe] towards lower
metallicities. In fact, taken at face value the resulting 3D LTE trend is in
rough agreement with the conventional [O/Fe] plateau. Caution must, however, be
exercised in view of the remaining assumptions in the 3D calculations. We have
verified that the stellar parameters remain essentially unchanged with 3D model
atmospheres provided that the infrared flux method, Hipparcos parallaxes and
FeII lines are utilised, leaving the 3D O abundances from OH lines largely
intact. Greater concern stems from possible departures from LTE in both the
line formation and the molecular equilibrium, which, if present, would increase
the derived O abundances again. Non-LTE line formation calculations with 1D
model atmospheres suggest no significant steepening of the [O/Fe] trend even if
the abundance corrections amount to about 0.2 dex for all investigated stellar
parameters. We note, however, that the 3D case may not necessarily be as
metallicity-independent. The apparent lack of laboratory or theoretical rate
coefficients at the relevant temperatures for the involved molecular reactions
unfortunately prevents a quantitative discussion on the possible effects of
non-equilibrium chemistry.


title:
Preheating in the Universe Suppressing High Energy Gamma-rays from
  Structure Formation

abstract:
  Structure formation in the universe can produce high energy gamma-rays from
shock-accelerated electrons, and this process may be the origin of the
extragalactic gamma-ray background (EGRB) as well as a part of the unidentified
sources detected by EGRET in the GeV band, if about 5% of the kinetic energy of
the shock is going into electron acceleration. However, we point out that the
production of gamma-rays may be severely suppressed if the collapsing matter
has been preheated by external entropy sources at the time of gravitational
collapse, as can be inferred from the luminosity-temperature (LT) relation of
galaxy clusters and groups. We also make a rough estimate of this effect by a
simple model, showing that the EGRB flux may be suppressed by a factor of about
30. Hence structure formation is difficult to be the dominant origin of EGRB if
preheating is actually responsible for the observed anomary in the LT relation.
The detectable number of gamma-ray clusters is also reduced, but about 5-10
forming clusters should still be detectable by EGRET all sky, and this number
is similar to that of the steady and high-latitude unidentified sources in the
EGRET catalog. The future GLAST mission should detect 10^2-10^3 gamma-ray
clusters of galaxies even if the intergalactic medium has been preheated.


title: A BeppoSAX view of transient black hole candidates in quiescence

abstract:
  We report on BeppoSAX observations of five transient black hole candidates
during their quiescent phase. We confirm these sources are X-ray faint,
improving on and complementing existing upper limits. We derive 1-10 keV upper
limits for GRO J0422+32, GRS 1009-45, 4U 1630-47 and XTE J1748-288, which range
from 2x10^32 erg/s to 5x10^34 erg/s. We positively detect GS 2023+338. Its
X-ray spectrum can be fit by a power law (photon index Gamma=1.9) or a thermal
bremsstrahlung (with kT= 7$ keV), converting in both cases to a 1-10 keV
unabsorbed luminosity of ~10^33 erg/s. These values are comparable to the ones
derived during an ASCA observation in 1994, indicating that the source remains
stable over a ~5 yr baseline.


title: The Cygnus X region: a nucleosynthesis laboratory for INTEGRAL

abstract:
  The detection of 1.809 MeV gamma-ray line emission from the Cygnus X complex
by the COMPTEL telescope is one of the most convincing proves of massive star
nucleosynthesis in our Galaxy. The Cygnus X complex is an extremely active
nearby region, containing several star forming regions, OB associations and
young open star clusters. It houses some of the most massive stars known in our
Galaxy and concentrates a large number of Wolf-Rayet stars. Thermal radio
continuum emission and intense [C II] line emission reveals widespread
ionisation, and at least 60 individual H II regions have been identified. In
order to understand the 1.809 MeV gamma-ray line emission from the Cygnus X
complex, and to compare the observations to theoretical nucleosynthesis
calculations, we modelled the multi-wavelength spectrum of the region by means
of an evolutionary synthesis model. Our investigation leads us to the following
conclusions: 1. Stellar wind ejection is the dominant mechanism for the
observed 26Al enrichment in the Cygnus X region. 2. Cyg OB2 is by far the
dominating massive star association in Cygnus X and 1.809 MeV line emission
from 26Al produced in this association should be detectable by the spectrometer
SPI on INTEGRAL. 3. There is only low supernova activity in the Cygnus X
complex and the 60Fe lines should be below INTEGRAL's detection sensitivity.
The detectability of an individual massive star cluster (Cyg OB2) by INTEGRAL
provides a fantastic opportunity for future nucleosynthesis studies using
gamma-ray line spectroscopy. We will explore the scientific potential of such
observations, and provide estimates for gamma-ray line intensity distributions
based on the massive star census of the Cygnus X region.


title:
Macrolensing signatures of large-scale violations of the weak energy
  condition

abstract:
  We present a set of simulations of the macrolensing effects produced by
large-scale cosmological violations of the energy conditions. These simulations
show how the appearance of a background field of galaxies is affected when
lensed by a region with an energy density equivalent to a negative mass ranging
from $10^{12}$ to $10^{17}$ solar masses. We compare with the macrolensing
results of equal amounts of positive mass, and show that, contrary to the usual
case where tangential arc-like structures are expected, there appear radial
arcs-runaway filaments-and a central void. These results make the cosmological
macrolensing produced by space-time domains where the weak energy conditions is
violated, observationally distinguishable from standard regions. Whether large
domains with negative energy density indeed exist in the universe can now be
decided by future observations of deep fields.


title:
Constraints on the Cosmic Equation of State using Gravitational Lensing
  Statistics with evolving galaxies

abstract:
  In this paper, observational constraints on the cosmic equation of state of
dark energy ($p = w \rho$) have been investigated using gravitational lensing
statistics. A likelihood analysis of the lens surveys has been carried out to
constrain the cosmological parameters $\Omega_{m}$ and $w$. Constraints on
$\Omega_{m}$ and $w$ are obtained in three different models of galaxy
evolution: no evolution model (comoving number density of galaxies remain
constant), Volmerange and Guiderdoni model and fast merging model. The last two
models consider the number evolution of galaxies in addition to the luminosity
evolution. The likelihood analysis shows that for the no-evolution case $w \leq
-0.04$ and $\Omega_{m}\leq 0.90$ at $1\sigma$ (68% confidence level). Similarly
for the Volmerange $&$ Guiderdoni Model the constraints are $w \leq -0.04$ and
$\Omega_{m} \leq 0.91$ at $1 \sigma$. In fast merging model the constraint
become weaker and it allows almost the entire range of parameters. For the case
of constant $\Lambda$ ($w =-1$), all the models permit $\Omega_{m} = 0.3$ with
68% CL which is consistent with the value of $\Omega_{m} $ inferred from
various other cosmological observations.


title: Predicted Planck Extragalactic Point Source Catalogue

abstract:
  An estimation of the number and amplitude (in flux) of the extragalactic
point sources that will be observed by the Planck Mission is presented in this
paper. The study is based on the Mexican Hat wavelet formalism introduced by
Cayon et al. 2000. Simulations at Planck observing frequencies are analysed,
taking into account all the possible cosmological, Galactic and Extragalactic
emissions together with noise. With the technique used in this work the Planck
Mission will produce a catalogue of extragalactic point sources above fluxes:
1.03 Jy (857 GHz), 0.53 Jy (545 GHz), 0.28 Jy (353 GHz), 0.24 Jy (217 GHz),
0.32 Jy (143 GHz), 0.41 Jy (100 GHz HFI), 0.34 Jy (100 GHz LFI), 0.57 Jy (70
GHz), 0.54 Jy (44 GHz) and 0.54 Jy (30 GHz), which are only slightly model
dependent (see text). Amplitudes of these sources are estimated with errors
below 15%. Moreover, we also provide a complete catalogue (for the point
sources simulation analysed) with errors in the estimation of the amplitude
below 10%. In addition we discuss the possibility of identifying different
point source populations in the Planck catalogue by estimating their spectral
indices.


title: Quantum Field Theoretic Description of Matter in the Universe

abstract:
  Quantum field theory at finite temperature and density can be used for
describing the physics of relativistic plasmas. Such systems are frequently
encountered in astrophysical situations, such as the early Universe, Supernova
explosions, and the interior of neutron stars. After a brief introduction to
thermal field theory the usefulness of this approach in astrophysics will be
exemplified in three different cases. First the interaction of neutrinos within
a Supernova plasma will be discussed. Then the possible presence of quark
matter in a neutron star core and finally the interaction of light with the
Cosmic Microwave Background will be considered.


title: X-Ray Probing of the Central Regions of Clusters of Galaxies

abstract:
  Results of ASCA X-ray study of central regions of medium-richness clusters of
galaxies are summarized, emphasizing differences between cD and non-cD
clusters. The intra-cluster medium (ICM) is likely to consist of two (hot and
cool) phases within $\sim 100$ kpc of a cD galaxy, where the ICM metallicity is
also enhanced. In contrast, the ICM in non-cD clusters appears to be isothermal
with little metallicity gradient right to the center. The gravitational
potential exhibits a hierarchical nesting around cD galaxies, while a total
mass-density profile with a central cusp is indicated for a non-cD cluster
Abell~1060. The iron-mass-to-light ratio of the ICM decreases toward the center
in both types of clusters, although it is radially constant in peripheral
regions. The silicon-to-iron abundance ratio in the ICM increases with the
cluster richness, but remains close to the solar ratio around cD galaxies.
These overall results are interpreted without appealing to the popular
cooling-flow hypothesis. Instead, an emphasis is put on the halo-in-halo
structure formed around cD galaxies.


title:
Light Curves of Jetted Gamma-Ray Burst Afterglows in Circumstellar
  Clouds

abstract:
  The afterglow emission from a spreading jet expanding in a circumstellar
cloud is discussed. Prompt X-ray radiation and a strong UV flash from the
reverse shock produced by the interaction of the jet with the cloud may destroy
and clear the dust out to about 30 pc within the initial solid angle of the
jet. As the sideways expansion of the jet becomes significant, most of the
optical radiation from the high-latitude part of the jet may be absorbed by the
dust outside the initial solid angle of the jet, but only the radiation from
the part within the initial solid angle can be observed. We analytically show
that the flux of the observational radiation decays as $\propto t^{-(p+1)}$
(where $p$ is the power-law index of the electron distribution) in the
relativistic phase. This preliminary result motivates us to perform numerical
calculations. Our results show that one break in the optical afterglow ligh
curve extends over a factor of $\sim 3$ in time rather than one decade in time
in the previous jet model. These results may provide a way to judge whether
GRBs locate in dense clouds or not. Finally, we carry out a detailed modelling
for the R-band afterglow of GRB 000926.


title: The anomalous properties of Markarian 1460

abstract:
  We present and discuss optical, near-infrared and HI measurements of the
galaxy Markarian 1460 at a distance of 19 Mpc in the Ursa Major Cluster. This
low-luminosity (M_B = -14) galaxy is unusual because (i) it is blue (B-R=0.8)
and has the spectrum of an HII galaxy, (ii) it has a light profile that is
smooth and well fit by an r^{1/4} and not an exponential function at all radii
larger than the seeing, and (iii) it has an observed central brightness of
about mu_B = 20 mag arcsec^{-2}, intermediate between those of elliptical
galaxies (on the bright mu_B side) and normal low-luminosity dwarf irregular
(on the low mu_B side) galaxies. No other known galaxy exhibits all these
properties in conjunction. On morphological grounds this galaxy looks like a
normal distant luminous elliptical galaxy, since the fundamental plane tells us
that higher luminosity normal elliptical galaxies tend to have lower
surface-brightnesses. Markarian 1460 has 2 X 10^7 M_sun of HI and a ratio
M(HI)/L_B of 0.2, which is low compared to typical values for star-forming
dwarf galaxies. From the high surface brightness and r^{1/4} profile, we infer
that the baryonic component of Markarian 1460 has become self-gravitating
through dissipative processes. From the colours, radio continuum, HI and
optical emission line properties, yet smooth texture, we infer that Markarian
1460 has had significant star formation as recently as about 1 Gyr ago but not
today.


title: Emission and Structure of Compact Fireballs

abstract:
  The possibility that the peak of the spectral energy distribution (SED) of
prompt GRB emission is produced on compact scales, prior to the acceleration of
the fireball to its terminal Lorentz factor is considered. It is argued that if
dissipation on these scales is associated with pair creation processes, then
the observed clustering of SED peaks can be accounted for quite naturally by
this mechanism. Further dissipation and processing of pairs and gamma rays at
larger radii, can give rise to a nonthermal extension of the spectrum up to a
rather high observed energy. If the nonthermal processes on these scales
conserve the total flux of fireball quanta, then the SED peak, which is
established on much smaller scales, will not be altered significantly. The
asymptotic bulk Lorentz factor in this model should exceed several hundred.


title:
The Nature of the Nuclear H2O Masers of NGC 1068: Reverberation and
  Evidence for a Rotating Disk Geometry

abstract:
  We report new (1995) Very Large Array observations and (1984 - 1999)
Effelsberg 100m monitoring observations of the 22 GHz H2O maser spectrum of the
Seyfert 2 galaxy NGC 1068. The sensitive VLA observations provide a
registration of the 22 GHz continuum emission and the location of the maser
spots with an accuracy of ~ 5 mas. Within the monitoring data, we find evidence
that the nuclear masers vary coherently on time-scales of months to years, much
more rapidly than the dynamical time-scale. We argue that the nuclear masers
are responding in reverberation to a central power source, presumably the
central engine. Between October and November 1997, we detected a simultaneous
flare of the blue-shifted and red-shifted satellite maser lines. Reverberation
in a rotating disk naturally explains the simultaneous flaring. There is also
evidence that near-infrared emission from dust grains associated with the maser
disk also responds to the central engine. We present a model in which an X-ray
flare results in both the loss of maser signal in 1990 and the peak of the
near-infrared light curve in 1994. In support of a rotating disk geometry for
the nuclear masers, we find no evidence for centripetal accelerations of the
redshifted nuclear masers; the limits are +/- 0.006 km/s/year, implying that
the masers are located within 2 degrees of the kinematic line-of-nodes. We also
searched for high velocity maser emission like that observed in NGC 4258. In
both VLA and Effelsberg spectra, we detect no high velocity lines between +/-
350 km/s to +/- 850 km/s relative to systemic, arguing that masers only lie
outside a radius of ~ 0.6 pc (1.9 light years) from the central engine
(assuming a distance of 14.4 Mpc).


title: On the Origin of the Colour-Magnitude Relation in the Virgo Cluster

abstract:
  We explore the origin of the colour-magnitude relation (CMR) of early type
galaxies in the Virgo cluster using spectra of very high S/N ratio for six
elliptical galaxies selected along the CMR. The data are analysed using a new
evolutionary stellar population synthesis model to generate galaxy spectra at
the resolution given by their velocity dispersions. In particular we use a new
age indicator that is virtually free of the effects of metallicity. We find
that the luminosity weighted mean ages of Virgo ellipticals are greater than ~8
Gyr, and show no clear trend with galaxy luminosity. We also find a positive
correlation of metallicity with luminosity, colour and velocity dispersion. We
conclude that the CMR is driven primarily by a luminosity-metallicity
correlation. However, not all elements increase equally with the total
metallicity and we speculate that the CMR may be driven by both a total
metallicity increase and by a systematic departure from solar abundance ratios
of some elements along the CMR. A full understanding of the role played by the
total metallicity, abundance ratios and age in generating the CMR requires the
analysis of spectra of very high quality, such as those reported here, for a
larger number of galaxies in Virgo and other clusters.


title: Status of Neutrino Oscillations

abstract:
  Solar and atmospheric neutrino data require physics beyond the Standard Model
of particle physics. The simplest, most generic, but not yet unique,
interpretation of the data is in terms of neutrino oscillations. I summarize
the results of the latest three-neutrino oscillation global fit of the data, in
particular the bounds on the angle $\theta_{13}$ probed in reactor experiments.
Even though not implied by the data, bi-maximal neutrino mixing emerges as an
attractive possibility either in hierarchical or quasi-degenerate neutrino
scenarios.


title: Iron line emission in X-ray afterglows

abstract:
  Recent observations of X-ray afterglows reveal the presence of a redshifted
Kalpha iron line in emission in four bursts. In GRB 991216, the line was
detected by the low energy grating of Chandra, which showed the line to be
broad, with a full width of ~15,000 km/s. These observations indicate the
presence of a >1 solar mass of iron rich material in the close vicinity of the
burst, most likely a supernova remnant. The fact that such strong lines are
observed less than a day after the trigger strongly limits the size of the
remnant, which must be very compact. If the remnant had the observed velocity
since the supernova explosion, its age would be less than a month. In this case
nickel and cobalt have not yet decayed into iron. We show how to solve this
paradox.