title: Infall variability in the Classical T Tauri system VZ Chamaeleonis

abstract:
  We present time series spectroscopy of the Classical T Tauri star VZ Cha. We
follow spectral variations at intermediate resolution over five successive
nights, or approximately two rotation periods. We see profile features which
persist on timescales longer than the expected infall time from the inner disc,
and we see expected evidence of rotational variations in the lines, but we also
note that rotation alone cannot produce all the observed variability and some
other mechanism must be invoked. The behaviour of H-alpha is observed to be
markedly different from that of the other lines. In particular, the evidence of
rotational effects is lacking at H-alpha, and the activity in the red and blue
wings of the line is not significantly correlated, in contrast to the other
Balmer lines.


title:
Interstellar Media in the Magellanic Clouds and other Local Group Dwarf
  Galaxies

abstract:
  I review the properties of the interstellar medium in the Magellanic Clouds
and Local Group dwarf galaxies. The more massive, star-forming galaxies show a
complex, multi-phase ISM full of shells and holes ranging from very cold phases
(a few 10 K) to extremely hot gas (> 10^6 K). In environments with high UV
radiation fields the formation of molecular gas is suppressed, while in dwarfs
with low UV fields molecular gas can form at lower than typical Galactic column
densities. There is evidence of ongoing interactions, gas accretion, and
stripping of gas in the Local Group dwarfs. Some dwarf galaxies appear to be in
various stages of transition from gas-rich to gas-poor systems. No ISM was
found in the least massive dwarfs.


title: Current constraints on the dark energy equation of state

abstract:
  We combine complementary datasets from Cosmic Microwave Background (CMB)
anisotropy measurements, high redshift supernovae (SN-Ia) observations and data
from local cluster abundances and galaxy clustering (LSS) to constrain the dark
energy equation of state parameterized by a constant pressure-to-density ratio
$w_Q$. Under the assumption of flatness, we find $w_Q < -0.85$ at 68% c.l.,
providing no significant evidence for quintessential behaviour different from
that of a cosmological constant. We then generalise our result to show that the
constraints placed on a constant $w_{Q}$ can be safely extended to dynamical
theories. We consider a variety of quintessential dynamical models based on
inverse power law, exponential and oscillatory scaling potentials. We find that
SN1a observations are `numbed' to dynamical shifts in the equation of state,
making the prospect of reconstructing $w(z)$, a challenging one indeed.


title:
Discovery of Very Extended Emission-Line Region around the Seyfert 2
  Galaxy NGC 4388

abstract:
  We found a very large, 35 kpc, emission-line region around the Seyfert type 2
galaxy NGC 4388, using deep narrow-band imaging with the prime focus camera
(Suprime-Cam) of the Subaru telescope. This region consists of many faint gas
clouds or filaments, and extends northeastwards from the galaxy. The typical
H-alpha luminosity L(H-alpha) of the clouds is 10^37 erg s^-1, and the total
L(H-alpha) of the region within 10 kpc from the nucleus is 2 x 10^38 erg s^-1,
which corresponds to an ionized gas mass of 10^5 M_solar. The map of the
emission-line intensity ratio I([OIII])/I(H-alpha) indicates that the inner (r
< 12 kpc) region of the VEELR may be excited by nuclear ionizing radiation. The
excitation mechanism of the outer (r > 12 kpc) region is unclear, but it is
likely that the nuclear radiation is also a dominant source of its ionization.
We discuss the origin of the ionized gas. Two plausible origins of the gas in
the VEELR are (i) the tidal debris resulting from a past interaction with a
gas-rich dwarf galaxy, i.e., a minor merger, or (ii) the interstellar medium of
NGC 4388, stripped by the ram pressure of the hot intracluster medium of the
Virgo cluster.


title: On the Formation of Multiple-Shells Around Asymptotic Giant Branch Stars

abstract:
  Two types of models for the formation of semi-periodic concentric multiple
shells (M-shells) around asymptotic giant branch (AGB) stars and in planetary
nebulae are compared against observations. Models that attribute the M-shells
to processes in an extended wind acceleration zone around AGB stars result in
an optically thick acceleration zone, which reduces the acceleration efficiency
in outer parts of the extended acceleration zone. This makes such models an
unlikely explanation for the formation of M-shells. Models which attribute the
M-shell to semi-periodic variation in one or more stellar properties are most
compatible with observations. The only stellar variation models on time scales
of 50-1500 years that have been suggested are based on an assumed solar-like
magnetic cycle. Although ad-hoc, the magnetic cycle assumption fits naturally
into the increasingly popular view that magnetic activity plays a role in
shaping the wind from upper AGB stars.


title: Solar-like oscillations of semiregular variables

abstract:
  Oscillations of the Sun and solar-like stars are believed to be excited
stochastically by convection near the stellar surface. Theoretical modeling
predicts that the resulting amplitude increases rapidly with the luminosity of
the star. Thus one might expect oscillations of substantial amplitudes in red
giants with high luminosities and vigorous convection. Here we present evidence
that such oscillations may in fact have been detected in the so-called
semiregular variables, extensive observations of which have been made by
amateur astronomers in the American Association for Variable Star Observers
(AAVSO). This may offer a new opportunity for studying the physical processes
that give rise to the oscillations, possibly leading to further information
about the properties of convection in these stars.


title: Deep Submillimeter Imaging of Dust Structures in Centaurus A

abstract:
  Images covering the central 450 by 100 arcsecond (about 8.0 by 2.0 kpc) of
NGC 5128 (Centaurus A) obtained using SCUBA at 850 and 450 micron with beam
sizes of 14.5 and 8 arcsecond respectively, are presented. These data are
compared with those obtained at other wavelengths, in particular the optical,
mid-infrared, and far-infrared continuum. The sensitive 850 and 450 micron
images show that the submillimeter (submm) continuum morphology and spectral
index distribution of Centaurus A comprise four regions: an unresolved AGN
core, an inner jet interacting with gas in the dust lane, an inner disk of
radius roughly 90 arcsecond, and colder outer dust. The inner disk has a high
surface brightness, reverse-S-shaped feature in the 850 and 450 micron images
that coincides with the regions of intense 7 and 15 micron continuum and a
region of active star-formation. The infrared (IR) and submm images appear to
reveal the same material as predicted by a geometric warped disk model
consisting of tilted rings. We suggest this scenario is more plausible than
that recently proposed in literature suggesting that the mid-IR emission in
Centaurus A is primarily from a bar, with a structure that is different from
the extended warped disk alone. A dust mass total of 2.2 million solar masses
has been calculated within a radius of 225 arcsecond, 45% of which is in the
star-forming region of radius about 90 arcsecond about the nucleus.


abstract:
  We report the discovery of a significant population of RR Lyrae variables in
the dwarf spheroidal galaxy Leo I. Based on 40 V and 22 B images of the galaxy
taken using the ESO Wide Field Imager we have identified so far 74 candidate RR
Lyrae's in two CCD's hosting the main body of the galaxy. Full coverage of the
light variations and pulsation periods have been obtained for 54 of them, 47 of
which are Bailey {\it ab}-type RR Lyrae's (RRab's) and 7 are {\it c}-type
(RRc's). The period distribution of the presently confirmed sample of RRab's
peaks at P=0\fd60, with a minimum period of 0\fd54. The pulsational properties
indicate for Leo I an intermediate Oosterhoff type, similar to other dwarf
galaxies in the Local Group and the LMC. However, the rather long minimum
period of the {\it ab}-type variables, and the significant number of RRab's
with long period and large amplitude, suggest that the bulk of the old
population in Leo I is more like the Oosterhoff type II globular clusters. The
most straightforward interpretation is that a range in metallicity is present
among the RR Lyrae's of Leo I, with a significant population of very metal-poor
stars. Alternatively, these OoII variables could be more evolved. The average
apparent magnitude of the RR Lyrae's across the full cycle is $<V(RR)>= 22.60
\pm 0.12$ mag, yielding a distance modulus $(m-M)_{V,0}= 22.04\pm 0.14$ mag for
Leo I on the ``long'' distance scale.


title: WINGS: a Wide-field Imaging Nearby Galaxy clusters Survey

abstract:
  We present a two-band, wide-field imaging survey of an X-ray selected sample
of 78 clusters in the redshift range z=0.03-0.07. The aim of the project is to
provide the astronomical community with a complete set of homogeneous,
CCD-based, surface photometry and morphological data of the nearby cluster
galaxies located within 1.5Mpc from the cluster center.


title:
SC1327-312 & SC1329-313: two galaxy groups in-between a major merging
  event observed with Beppo-SAX

abstract:
  We present the results of two Beppo-SAX observations of the poor clusters
SC1327-312 and SC1329-313. These objects are located in a huge structure,
formed by three ACO clusters, which is probably the remnant of one of the
largest and best studied major mergings known. Given the fact that these poor
clusters are in between two interacting ACO clusters, the aim of this work is
to study the physics of the intracluster medium and to look for the possible
presence of shocks.
  We derived the gas distribution profiles, the global (i.e. within 0.3 Mpc)
temperatures and abundances and the temperature profiles and maps for
SC1327-312 and SC1329-313. Also the presence of soft excess in LECS and hard
excess in PDS have been checked.
  We do not find evidence of regions where the gas is shocked or significantly
heated. The image of SC1327-312 seems rather symmetric, while the gas profile
of SC1329-313 shows disturbed, comet-like shaped isophotes, with the tail
pointing toward A3562 and a compression toward SC1327-312.
  The presence of multiphase gas in SC1329-313, as claimed by Hanami et al.
(1999) on ASCA data, has been found only at the 2 sigma confidence level.
  The lack of heating supports the hypothesis that the merging is at a late
stage, after the first core--core encounter, when the main shock front had the
time to travel to the external regions of the main clusters.


title:
BeppoSAX study of the X-ray binary XB 1832-330 located in the globular
  cluster NGC 6652

abstract:
  Results of a 2001 March 17-20 BeppoSAX observation of the X-ray binary XB
1832-330 located in the globular cluster NGC 6652 are presented. In contrast to
the majority of luminous globular cluster X-ray sources, the (0.1-200 keV)
BeppoSAX spectrum cannot be fit with a disk-blackbody and comptt Comptonization
model, unless partial covering is included. This confirms the ASCA detection of
partial covering by Mukai & Smale (2000). The best-fit spectral parameters are
similar to those of the globular cluster sources with orbital periods of <1 hr,
implying that XB 1832-330 is also an ultra-compact system. A plausible optical
candidate to XB 1832-330 has recently been discovered by Heinke et al. (2001)
which shows evidence for possible 0.92, 2.22, or 4.44 hr periodicities. We find
no evidence for any 2-10 keV periodic modulation at any of these periods with a
2 sigma upper limit to the semi-amplitude of any sinusoid of < 1.5%.


title: A Dynamical Origin for Brown Dwarfs

abstract:
  Brown dwarfs may have such low masses because they are prematurely ejected
from small unstable multiple systems, while the members are still actively
building up their masses. We demonstrate that this scenario is consistent with
all currently existing observations of brown dwarfs, and propose further
observational tests. We review the status of the latest realistic numerical
simulations of disintegrating small N clusters, which show that many of the
ejected members end up with masses that are substellar, drifting away from
their birth region with velocities rarely exceeding 2 km/s.


title:
The harmonic power spectrum of the soft X-ray background I. The data
  analysis

abstract:
  Fluctuations of the soft X-ray background are investigated using harmonic
analysis. A section of the ROSAT All-Sky Survey around the north galactic pole
is used. The flux distribution is expanded into a set of harmonic functions and
the power spectrum is determined. Several subsamples of the RASS have been used
and the spectra for different regions and energies are presented. The effects
of the data binning in pixels are assessed and taken into account. The spectra
of the analyzed samples reflect both small scale effects generated by strong
discrete sources and the large scale gradients of the XRB distribution. Our
results show that the power spectrum technique can be effectively used to
investigate anisotropy of the XRB at various scales. This statistics will
become a useful tool in the investigation of various XRB components.


title: Einstein's coefficients and the nature of thermal radio emission

abstract:
  The relations between Einstein's coefficients for spontaneous and induced
emission of radiation with account for the natural linewidth are obtained . It
is shown that thermal radio emission is stimulated one . Thermal radio emission
of non-uniform gas is considered .


title: The first compact objects in the MOND model

abstract:
  We trace the evolution of a spherically symmetric density perturbation in the
MOdified Newtonian Dynamics (MOND) model. The background cosmological model is
a $\Lambda$-dominated, low-$\Omega_b$ Friedmann model with no Cold Dark Matter.
We include thermal processes and non-equilibrium chemical evolution of the
collapsing gas. We find that the first density perturbations which collapse to
form luminous objects have mass $\sim 10^5 M_{\odot}$. The time of the final
collapse of these objects depends mainly on the value of the MOND acceleration
$a_0$ and also on the baryon density $\Omega_b$. For the "standard" value
$a_0=1.2\times 10^{-8}$ cm/s$^2$ the collapse starts at redshift $z \sim 160$
for $\Omega_b=0.05$ and $z \sim 110$ for $\Omega_b=0.02$.


title:
Reliability of astrophysical jet simulations in 2D: On inter-code
  reliability and numerical convergence

abstract:
  In the present paper, we examine the convergence behavior and inter-code
reliability of astrophysical jet simulations in axial symmetry. We consider
both, pure hydrodynamic jets and jets with a dynamically significant magnetic
field. The setups were chosen to match the setups of two other publications,
and recomputed with the MHD code NIRVANA. We show that NIRVANA and the two
other codes give comparable, but not identical results. We find that some
global properties of a hydrodynamical jet simulation, like e.g. the bow shock
velocity, converge at 100 points per beam radius (ppb) with NIRVANA. The
situation is quite different after switching on the toroidal magnetic field: In
this case, global properties converge even at 10 ppb. In both cases, details of
the inner jet structure and especially the terminal shock region are still
insufficiently resolved, even at our highest resolution of 70 ppb in the
magnetized case and 400 ppb for the pure hydrodynamic jet. In the case of our
highest resolution simulation, we can report two new features: First, small
scale Kelvin-Helmholtz instabilities are excited at the contact discontinuity
next to the jet head. This slows down the development of the long wavelength
Kelvin-Helmholtz instability and its turbulent cascade to smaller wavelengths.
Second, the jet head develops Rayleigh-Taylor instabilities which manage to
entrain an increasing amount of mass from the ambient medium with resolution.
This region extends in our highest resolution simulation over 2 jet radii in
the axial direction.


title:
Determining the location of Gamma-Ray Bursts through the evolution of
  their soft X-ray absorption

abstract:
  We investigate through dedicated numerical simulations the evolution of the
soft X-ray absorption properties of a cloud surrounding a gamma-ray burst
source. We show that the absorption properties of the material are strongly
modified by the ionization induced by the intense burst flux. We derive the
temporal evolution of the measured column density as a function of the density
and size of the absorbing medium. Even if their statistical significance is not
extremely compelling, we find that the detection in several bursts of variable
absorption during the gamma-ray phase can be accounted for if these bursts are
associated to overdense regions in molecular clouds with properties similar to
those of star formation globules. We fit our model variable column density to
the data of GRB 980329 and GRB 780506, showing that with this method the size,
density and density distribution of the material surrounding a burst can be
measured.


title: Non-linear radial oscillations of neutron stars: Mode-coupling results

abstract:
  The non-linear behaviour of oscillation modes in compact stars is a topic of
considerable current interest. Accurate numerical studies of such phenomena are
likely to require powerful new approaches to both fluid and spacetime
computations. We propose that a key ingredient of such methods will be the
non-linear evolution of deviations from the background stationary equilibrium
star. We investigate the feasibility of this approach by applying it to
non-linear radial oscillations of a neutron star, and explore numerically
various non-linear features of this problem, for a large range of amplitudes.
Quadratic and higher order mode coupling and non-linear transfer of energy is
demonstrated and analysed in detail.


title: Mode Switching Time Scales in the Classical Variable Stars

abstract:
  Near the edges of the instability strip the rate of stellar evolution is
larger than the growth-rate of the pulsation amplitude, and the same holds
whenever the star is engaged in pulsational mode switching. Stellar evolution
therefore controls both the onset of pulsation at the edges of the instability
strip and of mode switching inside it. Two types of switchings (bifurcations)
occur. In a soft bifurcation the switching time scale is the inverse harmonic
mean of the pulsational modal growth-rate and of the stellar evolution rate. In
a hard bifurcation the switching times can be substantially longer than the
thermal time scale which is typically of the order of a hundred periods for
Cepheids and RR Lyrae. We discuss some of the observational consequences, in
particular the paucity of low amplitude pulsators at the edges of the
instability strip.


title: Observed Smooth Energy Fitted by Parametrized Quintessence

abstract:
  This paper proposes two phenomenological quintessence potentials with
parameters fitted to the presently observed ratio $\rat$ of smooth energy to
clustered mass and limits on the equation of state parameter $w_Q(a)=P/\rhoq$,
for which the quintessence potential is now slow- or fast-rolling. These two
potentials are intended to illustrate rather different quintessence
phenomenology since tracking and into the near future. Neither can be a
fundamental potential derivable from present-day string theory.


title:
Rotational velocities of A-type stars I. Measurement of vsini in the
  southern hemisphere

abstract:
  Within the scope of a Key Programme determining fundamental parameters of
stars observed by HIPPARCOS, spectra of 525 B8 to F2-type stars brighter than
V=8 have been collected at ESO. Fourier transforms of several line profiles in
the range 4200-4500 A are used to derive vsini from the frequency of the first
zero. Statistical analysis of the sample indicates that measurement error is a
function of vsini and this relative error of the rotational velocity is found
to be about 6% on average. The results obtained are compared with data from the
literature. There is a systematic shift from standard values from Slettebak et
al. (1975), which are 10 to 12% lower than our findings. Comparisons with other
independent vsini values tend to prove that those from Slettebak et al. are
underestimated. This effect is attributed to the presence of binaries in the
standard sample of Slettebak et al., and to the model atmosphere they used.


title: Another bar in the Bulge

abstract:
  A map of the projected density of the old stellar population of the Galactic
Bulge region is reconstructed using 2MASS data. By making a combination of the
H and K photometric bands, it is possible to overcome the effect of reddening,
and thus penetrate the inner structure of the Galactic Bulge. The main
structure in the map corresponds to the well documented peanut shaped bar which
is formed by the inner parts of the Galactic disk as a result of dynamical
instabilities. As suggested by numerical simulations, the projected Z profile
of the bar, has an almost exponential shape. After subtracting the exponential
profile associated with the bar, a large residual appear near the Galactic
Center. This residual is elongated and asymmetrical, which suggest a bar
structure. Thus we arrive at the conclusion that in addition to the main bar a
smaller bar with a different orientation may exist in the central region of the
Milky Way. This finding makes the Milky Way very similar to a large number of
barred spiral Galaxies which show as well a smaller bar in their central
regions.


title:
Morphological Classification of Galaxies Using Artificial Neural
  Networks

abstract:
  The results of morphological galaxy classifications performed by humans and
by automated methods are compared. In particular, a comparison is made between
the eyeball classifications of 454 galaxies in the Sloan Digital Sky Survey
(SDSS) commissioning data (Shimasaku et al. 2001) with those of supervised
artificial neural network programs constructed using the MATLAB Neural Network
Toolbox package. Networks in this package have not previously been used for
galaxy classification. It is found that simple neural networks are able to
improve on the results of linear classifiers, giving correlation coefficients
of the order of 0.8 +/- 0.1, compared with those of around 0.7 +/- 0.1 for
linear classifiers. The networks are trained using the resilient
backpropagation algorithm, which, to the author's knowledge, has not been
specifically used in the galaxy classification literature. The galaxy
parameters used and the network architecture are both important, and in
particular the galaxy concentration index, a measure of the concentration of
light towards the centre of the galaxy, is the most significant parameter.
Simple networks are briefly applied to 29,429 galaxies with redshifts from the
SDSS Early Data Release. They give an approximate ratio of types E/S0:Sp:Irr of
14 +/- 5 : 86 +/- 12 : 0 +/- 0.1, which broadly agrees with the well known
approximate ratios of 20:80:1 observed at low redshift.


title:
Non-resonant nonlinear coupling of magnetohydrodynamic waves in
  inhomogeneous media

abstract:
  A new mechanism for the enhanced generation of compressible fluctuations by
Alfven waves is presented. A strongly nonlinear regime of Alfven wave
phase-mixing is numerically simulated in a one-dimensionally inhomogeneous
plasma of finite temperature. It is found that the inhomogeneity of the medium
determines the efficiency of nonlinear excitation of magnetoacoustic waves. The
level of the compressible fluctuations is found to be higher (up to the factor
of two) in inhomogeneous regions. The amplitude of the generated
magnetoacoustic wave can reach up to 30% of the source Alfven wave amplitude,
and this value is practically independent of the Alfven wave amplitude and the
steepness of Alfven speed profile. The highest amplitudes of compressible
disturbances are reached in plasmas with beta of about 0.5. The further growth
of the amplitude of compressible fluctuations is depressed by saturation.


title: Nonlinear MHD Waves in the Solar Wind Plasma Structures

abstract:
  We investigate the interaction of magnetohydrodynamic waves with plasma
density inhomogeneities. Our numerical study of the full MHD equations shows
that: (A) Plasma density inhomogeneities are a source of non-linear generation
of transverse compressive waves by a plane Alfven wave, and substantially
enhance (by about a factor of 2) the generation of the longitudinal compressive
waves. (B) Attained maximal values of the generated transverse compressive
waves are insensitive to the strength of the plasma density inhomogeneity and
the initial amplitude of the Alfven wave. (C) Efficiency of the generation
depends weakly upon the plasma beta parameter. The maximum generated amplitude
of transverse compressive wave, up to 32% of the initial Alfven wave amplitude,
is reached for about beta=0.5. The results obtained demonstrate that plasma
inhomogeneities enhance the efficiency of the non-linear wave coupling.


title: A Photometric Catalogue of Southern Emission-Line Stars

abstract:
  We present a catalogue of previously unpublished optical and infrared
photometry for a sample of 162 emission-line objects and shell stars visible
from the southern hemisphere. The data were obtained between 1978 and 1997 in
the Walraven (WULBV), Johnson/Cousins (UBV(RI)_c) and ESO and SAAO
near-infrared (JHKLM) photometric systems. Most of the observed objects are
Herbig Ae/Be (HAeBe) stars or HAeBe candidates appearing in the list of HAeBe
candidates of Th\'e et al. (1994), although several B[e] stars, LBVs and T
Tauri are also included in our sample. For many of the stars the data presented
here are the first photo-electric measurements in the literature. The resulting
catalogue consists of 1809 photometric measurements. Optical variability was
detected in 66 out of the 116 sources that were observed more than once. 15 out
of the 50 stars observed multiple times in the infrared showed variability at
2.2 microns (K band).


title: Nonlinear propagation of planet-generated tidal waves

abstract:
  The propagation and evolution of planet-generated density waves in
protoplanetary disks is considered. The evolution of waves, leading to the
shock formation and wake dissipation, is followed in the weakly nonlinear
regime. The local approach of Goodman & Rafikov (2001) is extended to include
the effects of surface density and temperature variations in the disk as well
as the disk cylindrical geometry and nonuniform shear. Wave damping due to
shocks is demonstrated to be a nonlocal process spanning a significant fraction
of the disk. Torques induced by the planet could be significant drivers of disk
evolution on timescales of the order 1-10 Myr even in the absence of strong
background viscosity. A global prescription for angular momentum deposition is
developed which could be incorporated into the study of gap formation in a
gaseous disk around the planet.


title: Anthropic Reasons for Non-Zero Flatness and Lambda

abstract:
  In some cosmological theories with varying constants there are anthropic
reasons why the expansion of the universe must not be too {\it close} to
flatness or the cosmological constant too close to zero. Using exact theories
which incorporate time-variations in $\alpha $ and in $G$ we show how the
presence of negative spatial curvature and a positive cosmological constant
play an essential role in bringing to an end variations in the scalar fields
driving time change in these 'constants' during any dust-dominated era of a
universe's expansion. In spatially flat universes with $\Lambda =0$ the fine
structure constant grows to a value which makes the existence of atoms
impossible.


title:
Is There an Advection-Dominated Accretion Flow in Radio Galaxies with
  Double-Peaked Balmer Lines?

abstract:
  In order to examine the prediction that the broad-line radio galaxies (BLRGs)
with double-peaked Balmer lines harbor an accretion disk characterized by an
advection-dominated accretion flow (ADAF) in their nuclei, we investigate
narrow emission-line flux ratios of the narrow-line regions which are
photoionized by the nuclear continuum radiation. We compile data from the
literature and confirm the pioneering work of Eracleous & Halpern that the
BLRGs with the double-peaked Balmer emission exhibit larger flux ratios of both
[O I]6300/[O III]5007 and [O II]3727/[O III]5007 than the BLRGs without the
double-peaked Balmer emission. To examine whether or not these properties are
attributed to the difference in the spectral energy distribution (SED) of the
ionizing radiation between the BLRGs with and without the double-peaked Balmer
emission, we perform photoionization model calculations using two types of
input continuum radiation; one has the strong big blue bump which is expected
for standard optically-thick accretion disks and another does not exhibit a
strong big blue bump as expected for optically-thin ADAFs. We find that the
data of the BLRGs with the double-peaked Balmer lines are consistent with the
models adopting the SED without a strong big blue bump while the data of the
BLRGs without the double-peaked emission lines are well described by the models
adopting the SED with a strong big blue bump. On the other hand, the observed
differences in the NLR emission is hard to be explain by the difference in the
contribution of shocks. These results support the idea that the double-peaked
Balmer lines arise at an outer region of an accretion disk which is illuminated
by an inner, geometrically-thick ADAF.


title:
A scaling law of interstellar depletions as a tool for abundance studies
  of Damped Ly alpha systems

abstract:
  An analytical expression is presented that allows dust depletions to be
estimated in different types of interstellar environments, including Damped Ly
alpha systems. The expression is a scaling law of a reference depletion pattern
and takes into account the possibility that the dust chemical composition may
vary as a function of the dust-to-metals ratio and of the intrinsic abundances
of the medium. Preliminary tests and applications of the proposed scaling law
are briefly reported.


title:
Near-infrared [Fe II] emission from supernova remnants and the supernova
  rate of starburst galaxies

abstract:
  In an effort to better calibrate the supernova rate of starburst galaxies as
determined from near-IR [Fe II] features, we report on a [Fe II] 1.644 microns
line-imaging survey of a sample of 42 optically-selected SNRs in M33. A wide
range of [Fe II] luminosities are observed within our sample (from less than 6
to 695 L_sun). Our data suggest that the bright [Fe II] SNRs are entering the
radiative phase and that the density of the local ISM largely controls the
amount of [Fe II] emission. We derive the following relation between the [Fe
II] 1.644 microns line luminosity of radiative SNRs and the electronic density
of the postshock gas, n_e: L_[Fe II] (L_sun) ~ 1.1 n_e (cm^-3). We also find a
correlation in our data between L_[Fe II] and the metallicity of the
shock-heated gas, but the physical interpretation of this result remains
inconclusive, as our data also show a correlation between the metallicity and
n_e. The dramatically higher level of [Fe II] emission from SNRs in the central
regions of starburst galaxies is most likely due to their dense environments,
although metallicity effects might also be important. The typical [Fe
II]-emitting lifetime of a SNR in the central regions of starburst galaxies is
found to be of the order of 10^4 yr. On the basis of these results, we provide
a new empirical relation allowing the determination of the current supernova
rate of starburst galaxies from their integrated near-IR [Fe II] luminosity.


title:
Spectral, polarisation and time-lag properties of GRS 1915+105 radio
  oscillations

abstract:
  We report high sensitivity dual-frequency observations of radio oscillations
from GRS 1915+105 following the decay of a major flare event in 2000 July. The
oscillations are clearly observed at both frequencies, and the time-resolved
spectral index traces the events between optically thin and thick states. While
previously anticipated from sparse observations and simple theory, this is the
first time a quasi-periodic signal has been seen in the radio spectrum, and is
a clear demonstration that flat radio spectra can arise from the combination of
emission from optically thick and thin regions. In addition, we measure the
linear polarisation of the oscillations, at both frequencies, at a level of
about 1--2%, with a flat spectrum. Cross-correlating the two light curves we
find a mean delay, in the sense that the emission at 8640 MHz leads that at
4800 MHz, of around 600 seconds. Comparison with frequency-dependent time
delays reported in the literature reveals that this delay is variable between
epochs. We briefly discuss possible origins for a varying time delay, and
suggest possible consequences.


title: Indices for SSPs with enhanced mix of alpha-elements

abstract:
  In this poster line strength indices for new Single Stellar Populations (SSP)
based on the recent stellar models with chemical compositions enhanced in the
alpha-elements (Salasnich et al. 2000) are presented. The SSP indices have been
calculated taking into account different methods to correct the
"Standard-Worthey Indices" for the real chemical composition of alpha-enhanced
isochrones.


title:
Analytic Approach to the Cloud-in-cloud Problem for Non-Gaussian Density
  Fluctuations

abstract:
  We revisit the cloud-in-cloud problem for non-Gaussian density fluctuations.
We show that the extended Press-Schechter (EPS) formalism for non-Gaussian
fluctuations has a flaw in describing mass functions regardless of type of
filtering. As an example, we consider non-Gaussian models in which density
fluctuations at a point obeys a \chi^2 distribution with \nu degrees of
freedom. We find that mass functions predicted by using an integral formula
proposed by Jedamzik, and Yano, Nagashima and Gouda, properly taking into
account correlation between objects at different scales, deviate from those
predicted by using the EPS formalism, especially for strongly non-Gaussian
fluctuations. Our results for the mass function at large mass scales are
consistent with those by Avelino and Viana obtained from numerical simulations.


title:
The BaSeL library as a basic tool to provide fundamental stellar
  parameters of future space missions: COROT and GAIA

abstract:
  COROT and GAIA are two future major space missions directly connected to most
of the stellar astrophysic questions, from stellar physics to evolution of
galaxies. We describe a project for the preparation of these two missions by
using the possibilities of the ``BaSeL'' models, a library of theoretical
stellar energy distributions, to provide automatically the fundamental stellar
parameters of the candidate stars. We present the results already obtained for
the stars of the COROT main programme.


title:
Temperature predictions for dust embedded AGB stars: how far can we go
  with synthetic near-infrared photometry ?

abstract:
  We discuss the possibilities of the BaSeL models in its lowest temperature
boundary (Teff ~ 2500 K for cool giants) to provide the Teff of AGB stars. We
present the first step of our work, by comparing our predictions for the AGB
star R Fornacis with the results of Lorenz-Martins & Lefevre (1994) based on
the dust spectral energy distribution.


title:
Atmospheric parameters for non-interacting eclipsing binaries:
  preliminary results from synthetic photometry

abstract:
  Double-lined spectroscopic binaries which are also eclipsing provide the most
accurate stellar data, and are consequently of first importance to improve
stellar evolution modelling. While the mass and radius of each component of
detached eclipsing binaries (EBs) can be accurately known, their temperature
Teff and chemical composition ([Fe/H]) are still uncertain. To contribute to
overcome these difficulties, we present metallicity-dependent Teff
determinations of 11 EBs (22 individual stars) from Stromgren synthetic
photometry. Inconsistencies suggesting new photometric observations are
discussed. Moreover, by exploring the best chi^2-fits to the photometric data,
we have re-derived their reddening.


title:
Significant discrepancies between stellar evolution models and
  solar-type eclipsing and visual binaries ?

abstract:
  Individual components of well-detached binary systems are assumed to be two
single-like stars with a common origin, i.e. they share the same chemical
composition and same age. Therefore, one expects to fit the observed parameters
of both components with a single isochrone at the same metallicity. We show
that serious problems appear for systems with accurate fundamental data
(eclipsing binaries in the field and in the Hyades, and a visual binary) in the
0.7-1.1 Msun mass range. We discuss and briefly review the results obtained so
far on these objects. Finally, in an attempt to solve this problem, we present
new projects, both on the theoretical and the observational sides.


title:
Non-iterative methods to estimate the in-flight noise properties of CMB
  detectors

abstract:
  We present a new approach for statistical inference on noise properties of
CMB anisotropy data. We consider a Maximum Likelihood parametric estimator to
recover the full dependence structure of the noise process. We also consider a
semiparametric procedure which is only sensitive to the low frequency behavior
of the noise spectral density. Both approaches are statistically robust and
computationally convenient in the case of long memory noise, even under
nonstationary circumstances. We show that noise properties can be consistently
derived by such procedures without resorting to currently used iterative
noise-signal methods. More importantly, we show that optimal (GLS) CMB maps can
be obtained from the observed timestream with the only knowledge of the noise
memory parameter, the outcome of our estimators.


title: Mkn 463 field observed by BeppoSAX

abstract:
  In this work we present the observation of the Mkn 463 field performed with
the MECS instrument on-board BeppoSAX in the 1.8-10.5 keV band. The Mkn 463
field is an example of an extragalactic field crowded with absorbed X-ray
sources: apart from the Seyfert 2 galaxy Mkn 463 and the well known QSO PG
1352+183 (the only object showing no absorption), two other objects are
detected with a column density in excess to the galactic value. The first 1SAX
J1353.9+1820 is a red QSO from the BeppoSAX High Energy Large Area Survey
(HELLAS). The second 1SAX J1355.4+1815 is optically unidentified, but its X-ray
spectral characteristics indicate that it too is an AGN hidden behind a large
column density.


title: The Sunyaev-Zeldovich Effect and Its Cosmological Significance

abstract:
  Comptonization of the cosmic microwave background (CMB) radiation by hot gas
in clusters of galaxies - the Sunyaev-Zeldovich (S-Z) effect - is of great
astrophysical and cosmological significance. In recent years observations of
the effect have improved tremendously; high signal-to-noise images of the
effect (at low microwave frequencies) can now be obtained by ground-based
interferometric arrays. In the near future, high frequency measurements of the
effect will be made with bolomateric arrays during long duration balloon
flights. Towards the end of the decade the PLANCK satellite will extensive S-Z
surveys over a wide frequency range. Along with the improved observational
capabilities, the theoretical description of the effect and its more precise
use as a probe have been considerably advanced. I review the current status of
theoretical and observational work on the effect, and the main results from its
use as a cosmological probe.


title: A search for new Galactic microquasars

abstract:
  A complete sample of bright ROSAT sources with hard XRB-like spectra in the
Galactic Plane (|b| < 15 deg.) has been tentatively identified with radio
sources in the GB6/PMN/NVSS surveys, and subsequently observed with the
Australia Telescope Compact Array and the Very Large Array. Most of them are
unresolved at the sub-arcsec scale and have flat or inverted spectra. Precise
radio coordinates have made unambiguous optical identifications possible,
which, after the removal of galaxies, yielded a final list of 40 microquasar
candidates. They are successfully going through the moderate dispersion
spectroscopy by the 4-m telescope of the Anglo-Australian Observatory. Our goal
is to obtain evidence for a characteristic accreting behaviour and establish
binarity, thence permitting actual microquasar classification. VLBI
observations of the brightest candidates are also underway. We expect some of
these objects could be QSOs, or radio galaxies, or cataclysmic variables.
However, this would be a valuable by-product of the proposed program.
Photometry of these objects dedicated to find possible eclipses and, also,
characteristic accreting disc driven flares.


title: RXTE Spectrum of A2319

abstract:
  The cluster of galaxies A2319 was observed in 1999 for 160 ks by the PCA and
HEXTE instruments aboard the RXTE satellite. No noticeable variability is seen
in the emission measured by either instrument over the 8 week observation.
Fitting the RXTE data by a single thermal component we obtain $kT = 8.6 \pm
0.1$ (90% confidence limits), a low iron abundance $Z_{F_e} \sim 0.16 \pm
0.02$, and large positive residuals below 6 keV and between 15 to 30 keV. The
quality of the fit is drastically improved if a second component is added. A
two-temperature model yields $kT_{1} \simeq 10.1 \pm 0.6$, $kT_{2}\simeq 2.8
\pm 0.6$, and of $Z_{F_e} \sim 0.23 \pm 0.03$. An equally good fit is obtained
by a combination of a primary thermal and a secondary nonthermal component,
with $kT \simeq 8.9 \pm 0.6$, and power-law index $\alpha \simeq 2.4 \pm 0.3$.
We have repeated the analysis by performing joint fits to both these RXTE
measurements and archival ASCA data. At most 25% of the RXTE secondary
component could be present in the ASCA data. Allowing for this difference, very
similar results were obtained, with only somewhat different values for the
temperature and power-law index in the latter model. The deduced value of
$\alpha$ is consistent with the measured spectrum of extended radio emission.
Identifying the power-law emission as Compton scattering of the radio-emitting
electrons by the CMB, we obtain $B \sim0.1-0.3$ $\mu G$ for the volume-averaged
magnetic field, and $\sim 4 \times 10^{-14}(R/2 Mpc)^{-3}$ erg cm$^{-3}$ for
the mean energy density of the emitting electrons in the central region (radius
R) of A2319.


title: Status of the Milagro Gamma Ray Observatory

abstract:
  The Milagro Gamma Ray Observatory, located at an altitude of 8,600 feet in
the Jemez Mountains of New Mexico, is the world's first large-area water
Cherenkov detector capable of continuously monitoring the entire sky for
sources of TeV gamma rays. It is uniquely capable of searching for transient
sources of VHE gamma rays. The core of the detector is a 60m x 80m x 8m pond
instrumented with 723 PMTs deployed in two layers. This part of the detector is
complete and has operated continuously since Jan. 2000. Initial studies
including searches for gamma-ray sources are ongoing, and preliminary results
are available. The final stage of construction is under way. We are deploying
170 auxiliary "outrigger" water Cherenkov detectors in an area of 40,000
square-meters surrounding the pond, which will significantly enhance our
ability to reject background and more accurately reconstruct the gamma-ray
direction and energy. In addition, we are lowering the energy threshold of the
detector by using custom processing to enable real-time intelligent triggering.
The lower energy threshold will significantly increase our sensitivity to
gamma-ray sources, and in particular to sources of cosmological origin, such as
GRBs, where the higher energy gamma-rays have sizable attenuation due to the
interaction with the intergalactic infra-red light.


title:
Coronal loop hydrodynamics. The solar flare observedon November 12 1980
  revisited: the UV line emission

abstract:
  We revisit a well-studied solar flare whose X-ray emission originating from a
simple loop structure was observed by most of the instruments on board SMM on
November 12 1980. The X-ray emission of this flare, as observed with the XRP,
was successfully modeled previously. Here we include a detailed modeling of the
transition region and we compare the hydrodynamic results with the UVSP
observations in two EUV lines, measured in areas smaller than the XRP rasters,
covering only some portions of the flaring loop (the top and the foot-points).
The single loop hydrodynamic model, which fits well the evolution of coronal
lines (those observed with the XRP and the \FeXXI 1354.1 \AA line observed with
the UVSP) fails to model the flux level and evolution of the \OV 1371.3 \AA
line.


title: An Atlas of FUSE Sight Lines Toward the Magellanic Clouds

abstract:
  We present an atlas of 57 Large Magellanic Cloud (LMC) and 37 Small
Magellanic Cloud (SMC) observations obtained with the Far Ultraviolet
Spectroscopic Explorer (FUSE) satellite. The atlas highlights twelve
interstellar absorption line transitions at a resolution of ~15 km/s. These
transitions cover a broad range of temperatures, ionization states, and
abundances. The species included are OVI, which probes hot (T~3x10^5 K) ionized
gas; CIII and FeIII, which probe warm (T~10^4 K) ionized gas; SiII, PII, CII,
FeII, and OI, warm neutral gas; and six different molecular hydrogen
transitions, which trace cold (T<=500 K) gas. We include Schmidt Halpha CCD
images of the region surrounding each sight line showing the morphology of warm
ionized gas in the vicinity, along with continuum images near each FUSE
aperture position. Finally, we present several initial scientific results
derived from this dataset on the interstellar medium of the Magellanic Clouds
and Galactic halo.


title:
X-ray Evidence for Spectroscopic Diversity of Type Ia Supernovae: XMM
  observation of the elemental abundance pattern in M87

abstract:
  We present the results of a detailed element abundance study of hot gas in
M87, observed by XMM-Newton. We choose two radial bins, 1'-3' and 8'-16'
(8'-14' for EMOS; hereafter the central and the outer zones), where the
temperature is almost constant, to carry out the detailed abundance
measurements of O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni using EPIC-PN (EPN) and
-MOS (EMOS) data. First, we find that the element abundance pattern in the
central compared to the outer zone in M87 is characterized by SN Ia enrichment
of a high (roughly solar) ratio of Si-group elements (Si, S, Ar, Ca) to Fe,
implying that Si burning in SN Ia is highly incomplete. In nucleosynthesis
modeling this is associated with either a lower density of the
deflagration-detonation transition and/or lower C/O and/or lower central
ignition density and observationally detected as optically subluminous SNe Ia
in early-type galaxies. Second, we find that SN Ia enrichment has a
systematically lower ratio of the Si-group elements to Fe by 0.2 dex in the
outer zone associated with the ICM of the Virgo cluster. We find that such a
ratio and even lower values by another 0.1 dex are a characteristic of the ICM
in many clusters using observed Si:S:Fe ratios as found with ASCA. Third, the
Ni/Fe ratio in the central zone of M87 is 1.5+/-0.3 solar (meteoritic), while
values around 3 times solar are reported for other clusters. In modeling of SN
Ia, this implies a reduced influence of fast deflagration SN Ia models in the
chemical enrichment of M87's ISM. Thus, to describe the SN Ia metal enrichment
in clusters, both deflagration as well as delayed detonation scenarios are
required, supporting a similar conclusion, derived from optical studies on SNe
Ia. Abridged.


title: The first close-up of the "flip-flop" phenomenon in a single star

abstract:
  We present temperature maps of the active late-type giant FK Com which
exhibit the first imagining record of the ``flip-flop'' phenomenon in a single
star. The phenomenon, in which the main part of the spot activity shifts 180
degrees in longitude, discovered a decade ago in FK Com, was reported later
also in a number of RS CVn binaries and a single young dwarf. With the surface
images obtained right before and after the ``flip-flop'', we clearly show that
the ``flip-flop'' phenomenon in FK Com is caused by changing the relative
strengths of the spot groups at the two active longitudes, with no actual spot
movements across the stellar surface, i.e. exactly as it happens in other
active stars.


title: AMiBA, XMM, and Cluster Surveys

abstract:
  The Array for Microwave Background Anisotropy (AMiBA) is an interferometric
array of 19 dishes co-mounted on a steerable platform and operating at 95GHz.
One of the main scientific aims of AMiBA is to conduct cluster surveys using
the Sunyaev-Zel'dovich (SZ) effect. Here we explore the potential of AMiBA as a
tailor-made SZ instrument for the study of cluster physics and cosmology via
cluster surveys out to the epoch of cluster formation. In particular, we
explore the potential of combining AMiBA cluster surveys with the XMM-LSS
(Large Scale Structure) survey.


title: Was GRB 990123 a unique optical flash?

abstract:
  GRB 990123 was a long, complex gamma-ray burst accompanied by an extremely
bright optical flash. We find different constraints on the bulk Lorentz of this
burst to be consistent with the speculation that the optical light is emission
from the reverse shock component of the external shock. Motivated by this
currently favoured idea, we compute the prompt reverse shock emission to be
expected for bursts in which multi-wavelength observations allow the physical
parameters to be constrained. We find that for reasonable assumptions about the
velocity of source expansion, a strong optical flash of approximately m_V=9 was
expected from the reverse shocks, which were usually found to be mildly
relativistic. The best observational prospects for detecting these prompt
flashes are highlighted, along with the possible reasons for the absence of
optical prompt detections in ongoing observations.


title:
XMM-EPIC observation of MCG-6-30-15: Direct evidence for the extraction
  of energy from aspinning black hole?

abstract:
  We present XMM-Newton European Photon Imaging Camera (EPIC) observations of
the bright Seyfert 1 galaxy MCG-6-30-15, focusing on the broad Fe K$\alpha$
line at ~6keV and the associated reflection continuum, which is believed to
originate from the inner accretion disk. We find these reflection features to
be extremely broad and red-shifted, indicating its origin from the very most
central regions of the accretion disk. It seems likely that we have caught this
source in the ``deep minimum'' state first observed by Iwasawa et al. (1996).
The implied central concentration of X-ray illumination is difficult to
understand in any pure accretion disk model. We suggest that we are witnessing
the extraction and dissipation of rotational energy from a spinning black hole
by magnetic fields connecting the black hole or plunging region to the disk.


title:
TEXES: A Sensitive High-Resolution Grating Spectrograph for the
  Mid-Infrared

abstract:
  We discuss the design and performance of TEXES, the Texas Echelon Cross
Echelle Spectrograph. TEXES is a mid-infrared (5-25 um) spectrograph with
several operating modes: high-resolution, cross-dispersed with a resolving
power of R=100,000, 0.5% spectral coverage, and a ~1.5 by 8" slit;
medium-resolution long-slit with R~15,000, 0.5% coverage, and a ~1.5 by 45"
slit; low-resolution long-slit with (delta lambda)~0.004 um, 0.25 um coverage,
and a ~1.5 by 45" slit; and source acquisition imaging with 0.33" pixels and a
25 by 25" field of view on a 3m telescope. TEXES has been used at the McDonald
Observatory 2.7m and the IRTF 3m telescopes, and has proven to be both
sensitive and versatile.


title:
Intracluster Planetary Nebulae in Virgo: Photometric selection,
  spectroscopic validation and cluster depth

abstract:
  We have imaged an empty area of 34'x34' one and a half degree north of the
Virgo cluster core to survey for intracluster planetary nebula candidates. We
have implemented and tested a fully automatic procedure for the selection of
emission line objects in wide-field images, based on the on-off technique from
Ciardullo and Jacoby. Freeman et al. have spectroscopically confirmed a sample
of intracluster planetary nebulae in one Virgo field. We use the photometric
and morphological properties of this sample to test our selection procedure. In
our newly surveyed Virgo field, 75 objects were identified as best candidates
for intracluster PNe.
  The luminosity function of the spectroscopically confirmed PNe shows a
brighter cut-off than the planetary nebula luminosity function for the inner
regions of M87. Such a brighter cut-off is also observed in the newly surveyed
field and indicates a smaller distance modulus, implying that the front end of
the Virgo cluster is closer to us by a significant amount: 14% closer (2.1 Mpc)
than M87 for the spectroscopic field, using the PN luminosity function distance
of 14.9 Mpc to M87, and 19% closer (2.8 Mpc) than M87 for the newly surveyed
field. Independent distance indicators (Tully-Fisher relation for Virgo spirals
and surface brightness fluctuations for Virgo ellipticals) agree with these
findings.
  From these two Virgo cluster fields there is no evidence that the surface
luminosity density for the diffuse stellar component in the cluster decreases
with radius. The luminosity surface density of the diffuse stellar population
is comparable to that of the galaxies.


title:
Interaction of Radio Lobes with the Hot Intracluster Medium: Driving
  Convective Outflow in Hydra A

abstract:
  The radio lobes of Hydra A lie within cavities surrounded by a rim of
enhanced X-ray emission in the intracluster gas. Although the bright rim
appears cooler than the surrounding gas, existing Chandra data do not exclude
the possibility that the rim is produced by a weak shock. A temperature map
shows that cool gas extends out along the radio axis of Hydra A. The age of the
radio source and equipartition pressure of the radio lobe argue against a
shock, and comparison with similar structure in the Perseus Cluster also
suggests that the rim is cool. We show that the cool bright rim cannot be the
result of shock induced cooling, or due to the effect of magnetic fields in
shocks. The most likely source of low entropy (cool) gas is entrainment by the
rising cavity. This requires some means of communicating the bouyant force on
the cavity to the surrounding gas. The magnetic field required to produce the
Faraday rotation in Hydra A has the appropriate properties for this, if the
Faraday screen is mainly in this bright rim. In Hydra A, the mass outflow due
to the rising cavities could be sufficient to balance cooling driven inflow, so
preventing the build up of low entropy gas in the cluster core.


title:
Anomalous Star-Formation Activity of Less-Luminous Galaxies in Cluster
  Environment

abstract:
  We discuss a correlation between star formation activity (SFA) and luminosity
of star-forming galaxies at intermediate redshifts of $0.2\le z\le 0.6$ in both
cluster and field environments. Equivalent width (EW) of [O{\sc ii}] is used
for measurement of the SFA, and $R$-band absolute magnitude, $M_R$, for the
luminosity. In less-luminous ($M_R \gsim -20.7$) galaxies, we find : (1) the
mean EW([O{\sc ii}]) of cluster galaxies is smaller than that of field
galaxies; but (2) some cluster galaxies have as large EW([O{\sc ii}]) as that
of actively star-forming field galaxies. Based on both our results, we discuss
a new possible mechanism for the Butcher-Oemler (BO) effect, assuming that the
luminosity of a galaxy is proportional to its dynamical mass. Our proposal is
that BO galaxies are less-massive cluster galaxies with smaller peculiar
velocities. They are then stable against Kelvin-Helmholtz instability (KHI),
and are not affected by tidal interaction between clusters and themselves.
Their interstellar medium (ISM) would be hardly stripped, and their SFA would
be little suppressed. Hence, as long as such galaxies keep up their SFA, the
fraction of blue galaxies in a cluster does not decrease. As a cluster becomes
virialized, however, such galaxies become more accelerated, the ISM available
for SFA is stripped by KHI, and their color evolves redward, which produces the
BO effect.


title:
The difficult discrimination of Impulse Stimulated Raman Scattering
  redshift against Doppler redshift

abstract:
  The Impulsive Stimulated Raman Scattering (ISRS) is a parametric light-matter
interaction which shifts the frequencies of two ultrashort laser light pulses
by a non-quantified transfer of energy. As ISRS has no threshold, the laser
pulses may be replaced by the pulses which constitute the ordinary incoherent
light. This replacement has the expected qualitative effect on the time
constants required to observe ISRS: nanosecond collisional time and Raman
period. It has also a qualitative effect, the frequency shifts become
independent on the intensity; thus we use a new name for this avatar of ISRS:
"Incoherent Light Coherent Raman Scattering" (ILCRS).
  The coherence makes ILCRS very different from the ordinary Raman effect
proposed as an alternative to Doppler effect in the past: ILCRS is a stronger
light-matter interaction, it does not blur the images, nether the spectra; the
beams which receive energy are in the thermal radiation.
  The shifts of the spectra produced either by a Doppler effect, or by ILCRS
are very similar. However ILCRS is subject to a dispersion which perturbs
slightly the spectra. ILCRS is the key of a model of quasars which explains all
observations, without any new matter or physical theory: no fast moving cloud,
no dark matter, no variation of the fine structure constant, no invisible
object.
  The redshifts and the thermal radiation produced by ILCRS should not be
neglected a priori.


title:
The Cepheid Period-Luminosity relation and the maser distance to NGC
  4258

abstract:
  In a recent paper describing HST observations of Cepheids in the spiral
galaxy NGC 4258, Newman et al. (2001) report that the revised calibrations and
methods for the Key Project on the Extragalactic Distance Scale yield that the
true distance modulus of this galaxy is 29.40+-0.09 mag, corresponding to a
metric distance of 7.6+-0.3 Mpc. This Cepheid distance, which holds for 18.50
mag as the true distance modulus of the LMC, is not significantly larger than
7.2+-0.5 Mpc, the value determined by Herrnstein et al. (1999) from purely
geometric considerations on the orbital motions of water maser sources.
However, if the metallicity difference D[O/H]~0.35 between NGC 4258 and LMC is
taken into account, then the Key Project methods lead to a
metallicity-corrected value of 29.47+-0.09 mag, with 18.50 mag for the LMC,
namely to a Cepheid distance of 7.8+-0.3 Mpc, which is 1.2 sigma from the maser
determination. In this paper we show that the metallicity correction on Cepheid
distance determinations, as suggested by pulsation models, might provide the
natural way of reaching a close agreement between Cepheid and maser distance to
NGC 4258 for a wide variety of LMC distance determinations.


title: A very rapid Extreme Scattering Event in the IDV source 0954+658

abstract:
  Extreme Scattering Events (ESEs) are dramatic variations of the flux density
at Gigahertz frequencies caused by ray path distortions within an isolated
inhomogeneity ("plasma lens") in the interstellar medium. These events are
characterized by a deep flux density minimum in the light curve with, in some
cases, surrounding maxima. The variability time scales range from weeks to
months. These phenomena show a strong frequency dependence, in which the
variability amplitudes increase with wavelength. During an Intraday Variability
(IDV) monitoring project (March 2000), a feature resembling an ESE-like event
appeared in the variable light curve of 0954+658, however with a time scale of
less than two days. We will discuss this effect and its implications for a
better description of the interstellar medium.


title: Hypernova Nucleosynthesis and Early Chemical Evolution

abstract:
  We review the characteristics of nucleosynthesis in 'Hypernovae', i.e.,
supernovae with very large explosion energies ($ \gsim 10^{52} $ ergs). The
hypernova yields compared to those of ordinary core-collapse supernovae show
the following characteristics: 1) Complete Si-burning takes place in more
extended region, so that the mass ratio between the complete and incomplete Si
burning regions is generally larger in hypernovae than normal supernovae. As a
result, higher energy explosions tend to produce larger [(Zn, Co)/Fe], smaller
[(Mn, Cr)/Fe], and larger [Fe/O], which could explain the trend observed in
very metal-poor stars. 2) Si-burning takes place in lower density regions, so
that the effects of $\alpha$-rich freezeout is enhanced. Thus $^{44}$Ca,
$^{48}$Ti, and $^{64}$Zn are produced more abundantly than in normal
supernovae. The large [(Ti, Zn)/Fe] ratios observed in very metal-poor stars
strongly suggest a significant contribution of hypernovae. 3) Oxygen burning
also takes place in more extended regions for the larger explosion energy. Then
a larger amount of Si, S, Ar, and Ca ("Si") are synthesized, which makes the
"Si"/O ratio larger. The abundance pattern of the starburst galaxy M82 may be
attributed to hypernova explosions. Asphericity in the explosions strengthens
the nucleosynthesis properties of hypernovae except for "Si"/O. We thus suggest
that hypernovae make important contribution to the early Galactic (and cosmic)
chemical evolution.


title:
Determination of proper motions and membership of the open star cluster
  NGC2548

abstract:
  Absolute proper motions, their corresponding errors and membership
probabilities of 501 stars in the intermediate-age open cluster NGC2548 region
are determined from MAMA measurements of 10 photographic plates. The plates
have the maximum epoch difference of 82 years and they were taken with the
double astrograph at Zo-Se station of Shanghai Observatory, which has an
aperture of 40 cm and a plate scale of 30"/mm. The average proper motion
precision is 1.18 mas/yr. These proper motions are used to determine the
membership probabilities of stars in the region. The number of stars with
membership probabilities higher than 0.7 is 165.


title:
Measuring the galaxy power spectrum with multiresolution decomposition
  -- IV. redshift distortion

abstract:
  In this paper, we develop a theory of redshift distortion of the galaxy power
spectrum in the discrete wavelet transform (DWT) representation. Because the
DWT power spectrum is dependent of both the scale and shape (configuration) of
the decomposition modes, it is sensitive to distortion of shape of the field.
On the other hand, the redshift distortion causes a shape distortion of
distributions in real space with respect to redshift space. Therefore, the
shape-dependent DWT power spectrum is useful to detect the effect of redshift
distortion. We first established the mapping between the DWT power spectra in
redshift and real space. The mapping depends on the redshift distortion effects
of (1) bulk velocity, (2) selection function and (3) pairwise peculiar
velocity. We then proposed $\beta$-estimators using the DWT off-diagonal power
spectra. These $\beta$-estimators are model-free even when the non-linear
redshift distortion effect is not negligible. Moreover, these estimators do not
rely on the assumption of whether the pairwise velocity dispersion being
scale-dependent. The tests with N-body simulation samples show that the
proposed $\beta$-estimators can yield reliable measurements of $\beta$ with
about 20% uncertainty for all popular dark matter models. We also develop an
algorithm for reconstruction of the power spectrum in real space from the
redshift distorted power spectrum. The numerical test also shows that the real
power spectrum can be well recovered from the redshift distorted power
spectrum.


title: A UBVR CCD Survey of the Magellanic Clouds

abstract:
  We present photometry and a preliminary interpretation of a UBVR survey of
the Large and Small Magellanic Clouds. We determine improved values for the
relative number of blue and red supergiants. We also compare the relative
number of Red Supergiants (RSGs) and Wolf-Rayet stars, demonstrating a strong,
tight correlation with metallicity, and reinvestigate the initial mass function
slope of massive stars found in the field.


title:
Determination of Nucleosynthetic Yields of Supernovae and Very Massive
  Stars from Abundances in Metal-Poor Stars

abstract:
  (Abridged) We determine the yields of Na to Ni for Type II supernovae (SNe
II) and the yield patterns of the same elements for Type Ia supernovae (SNe Ia)
and very massive (>100 M_sun) stars (VMS) using a phenomenological model of
stellar nucleosynthesis and the data on a number of stars with -4<[Fe/H]<-3, a
single star with [Fe/H]=-2.04, and the sun. We consider that there are two
distinct kinds of SNe II: the high-frequency SNe II(H) and the low-frequency
SNe II(L). We also consider that VMS were the dominant first-generation stars
formed from big bang debris. The yield patterns of Na to Ni for SNe II(H),
II(L), and Ia and VMS appear to be well defined. It is found that SNe II(H)
produce almost none of these elements, that SNe II(L) can account for the
entire solar inventory of Na, Mg, Si, Ca, Ti, and V, and that compared with SNe
II(L), VMS underproduce Na, Al, V, Cr, and Mn, overproduce Co, but otherwise
have an almost identical yield pattern. A comparison is made between the yield
patterns determined here from the observational data and those from ab initio
models of nucleosynthesis in SNe II and VMS. The evolution of the other
elements relative to Fe is shown to involve three distinct stages, the earliest
of which is directly related to the problems of early aggregation and
dispersion of baryonic matter. It is argued that the VMS contributions should
represent the typical composition of dispersed baryonic matter in the universe.


title: Constraints on the Cosmological Relativistic Energy Density

abstract:
  We discuss bounds on the cosmological relativistic energy density as a
function of redshift, reviewing the big bang nucleosynthesis and cosmic
microwave background bounds, updating bounds from large scale structure, and
introducing a new bound from the magnitude-redshift relation of Type Ia
supernovae. We conclude that the standard and well-motivated assumption that
relativistic energy is negligible during recent epochs is not necessitated by
extant data. We then demonstrate the utility of these bounds by constraining
the mass and lifetime of a hypothetical massive big bang relic particle.


title: New DA white dwarf evolutionary models and their pulsational properties

abstract:
  In this letter we investigate the pulsational properties of ZZ Ceti stars on
the basis of new white dwarf evolutionary models calculated in a
self-consistent way with the predictions of time dependent element diffusion
and nuclear burning. In addition, full account is taken of the evolutionary
stages prior to the white dwarf formation. Emphasis is placed on the trapping
properties of such models. By means of adiabatic, non-radial pulsation
calculations, we find, as a result of time dependent diffusion, a much weaker
mode trapping effect, particularly for the high-period regime of the pulsation
g-spectrum. This result is valid at least for models with massive hydrogen-rich
envelopes. Thus, mode trapping would not be an effective mechanism to explain
the fact that all the high periods expected from standard models of stratified
white dwarfs are not observed in the ZZ Ceti stars.


title:
The Origin of Radio Emission in Low-Luminosity Active Galactic Nuclei:
  Jets, Accretion Flows, or Both?

abstract:
  The low-luminosity active galactic nuclei in NGC 3147, NGC 4203, and NGC 4579
have been imaged at four frequencies with the Very Long Baseline Array. The
galaxies are unresolved at all frequencies, with size upper limits of
$10^3-10^4$ times the Schwarzschild radii of their central massive black holes.
The spectral indices between 1.7 and 5.0 GHz range from 0.2 to 0.4; one and
possibly two of the galaxies show spectral turnovers between 5.0 and 8.4 GHz.
The high brightness temperatures ($> 10^9$ K) and relatively straight spectra
imply that free-free emission and/or absorption cannot account for the slightly
inverted spectra. Although the radio properties of the cores superficially
resemble predictions for advection-dominated accretion flows, the radio
luminosities are too high compared to the X-ray luminosities. We suggest that
the bulk of the radio emission is generated by a compact radio jet, which may
coexist with a low radiative efficiency accretion flow.


title: IR Detection of Low-Mass Secondaries in Spectroscopic Binaries

abstract:
  This paper outlines an infrared spectroscopic technique to measure the radial
velocities of faint secondaries in known single-lined binaries. The paper
presents our H-band observations with the CSHELL and Phoenix spectrographs and
describes detections of three low-mass secondaries in main-sequence binaries:
G147-36, G164-67, and HD144284 with mass ratios of 0.562+-0.011, 0.423+-0.042,
and 0.380+-0.013, respectively. The latter is one of the smallest mass ratios
derived to date.


title:
The Importance of Shocks in the Ionization of the Narrow Line Region of
  Seyferts

abstract:
  We discuss the viability of shocks as the principal source of ionization for
the Narrow Line Region of Seyfert galaxies. We present the preliminary results
of [OIII]5007A and radio 3.6 cm imaging surveys of Seyferts, discuss the
effects of shocks in the ionization of two galaxies, and also calculate an
upper limit to the Hbeta luminosity that can be due to shocks in 36 galaxies
with unresolved radio emission. We show that, for favored values of the shock
parameters, that shocks cannot contribute more than ~15% of the ionizing
photons in most galaxies.


title: Testing the Unified Model with an Infrared Selected Sample of Seyferts

abstract:
  We present a series of statistical tests using homogeneous data and
measurements for a sample of Seyfert galaxies. These galaxies were selected
from mostly isotropic properties, their far infrared fluxes and warm infrared
colors, which provide a considerable advantage over the criteria used by most
investigators in the past, like ultraviolet excess. Our results provide strong
support for a Unified Model in which Seyferts 2's contain a torus seen more
edge-on than in Seyferts 1's and show that previous results showing the
opposite were most likely due to selection effects.


title: Heating and Ionization of X-Winds

abstract:
  In order to compare the x-wind with observations, one needs to be able to
calculate its thermal and ionization properties. We formulate the physical
basis for the streamline-by-streamline integration of the ionization and heat
equations of the steady x-wind. In addition to the well-known processes
associated with the interaction of stellar and accretion-funnel hot-spot
radiation with the wind, we include X-ray heating and ionization, mechanical
heating, and a revised calculation of ambipolar diffusion heating. The
mechanical heating arises from fluctuations produced by star-disk interactions
of the time dependent x-wind that are carried by the wind to large distances
where they are dissipated in shocks, MHD waves, and turbulent cascades. We
model the time-averaged heating by the scale-free volumetric heating rate,
$\Gamma_{\rm mech} = \alpha \rho v^3 s^{-1}$, where $\rho$ and $v$ are the
local mass density and wind speed, respectively, $s$ is the distance from the
origin, and $\alpha$ is a phenomenological constant. When we consider a
partially-revealed but active young stellar object, we find that choosing
$\alpha \sim 10^{-3}$ in our numerical calculations produces temperatures and
electron fractions that are high enough for the x-wind jet to radiate in the
optical forbidden lines at the level and on the spatial scales that are
observed. We also discuss a variety of applications of our thermal-chemical
calculations that can lead to further observational checks of x-wind theory.


title: Planet migration and gap formation by tidally-induced shocks

abstract:
  Gap formation in a gas disk triggered by disk-planet tidal interaction is
considered. Density waves launched by the planet are assumed to be damped as a
result of their nonlinear evolution leading to shock formation and its
subsequent dissipation. As a consequence wave angular momentum is transferred
to the disk,leading to evolution of its surface density. Planetary migration is
an important ingredient of the theory; effects of the planet-induced surface
density perturbations on the migration speed are considered. A gap is assumed
to form when a stationary solution for the surface density profile is no longer
possible in the frame of reference migrating with the planet. An analytical
limit on the planetary mass necessary to open a gap in an inviscid disk is
derived. The critical mass turns out to be smaller than mass M_1 for which
planetary Hill's radius equals disk scaleheight by a factor of at least Q^{5/7}
(Q is the Toomre stability parameter) depending on the strength of the
migration feedback. In viscous disks the critical planetary mass could vary
from about 0.1M_1 to M_1, depending on the disk viscosity. This implies that a
gap could be formed by a planet with mass 1-10 times bigger than the Earth mass
depending on the disk aspect ratio, viscosity, and planet's location in the
nebula.


title:
Relation between radio core length and black hole mass for active
  galactic nuclei

abstract:
  We explore the relation between the linear length of radio core and the
central black hole mass for a sample of radio-loud active galactic nuclei
(AGNs). An empirical relation between the size of the broad line region (BLR)
and optical luminosity is used to estimate the size of the BLR. The black hole
mass is derived from $\rm H_\beta$ line width and the radius of the BLR on the
assumption that the clouds in BLRs are orbiting with Keplerian velocities. A
significant intrinsic correlation is found between the linear length of the
core and the black hole mass, which implies that the jet formation is closely
related with the central black hole. We also find a strong correlation between
the black hole mass and the core luminosity.


title: Opacity in the jet of 3C309.1

abstract:
  The "core" of a radio source is believed to mark the frequency-dependent
location where the optical depth to synchrotron self--absorption tau_s~1. The
frequency dependence can be used for derive physical conditions of the radio
emitting region and the ambient environment near the central engine of the
radio source. In order to test and improve the models to derive this
information, we made multi-frequency dual-polarization observations of 3C309.1
in 1998.6, phase-referenced to the QSOs S5 1448+76 and 4C72.20 (S5 1520+72)
(4d26' and 1d49' away, respectively). We present here preliminary results from
these observations: total and polarized intensity maps, spectral information
deduced from these images, and the relative position of 3C309.1 with respect to
S5 1448+76 at different frequencies. Finally, we discuss briefly the observed
shift of the core position.


title:
The Munich Near-Infrared Cluster Survey (MUNICS) - Number density
  evolution of massive field galaxies to z ~ 1.2 as derived from the K-band
  selected survey

abstract:
  We derive the number density evolution of massive field galaxies in the
redshift range 0.4 < z < 1.2 using the K-band selected field galaxy sample from
the Munich Near-IR Cluster Survey (MUNICS). We rely on spectroscopically
calibrated photometric redshifts to determine distances and absolute magnitudes
in the rest-frame K-band. To assign mass-to-light ratios, we use an approach
which maximizes the stellar mass for any K-band luminosity at any redshift. We
take the mass-to-light ratio, M/L_K, of a Simple Stellar Population (SSP) which
is as old as the universe at the galaxy's redshift as a likely upper limit.
This is the most extreme case of pure luminosity evolution and in a more
realistic model M/L_K will probably decrease faster with redshift due to
increased star formation. We compute the number density of galaxies more
massive than 2 10^10 h^-2 solar masses, 5 10^10 h^-2 solar masses, and 1 10^11
h^-2 solar masses, finding that the integrated stellar mass function is roughly
constant for the lowest mass limit and that it decreases with redshift by a
factor of roughly 3 and by a factor of roughly 6 for the two higher mass
limits, respectively. This finding is in qualitative agreement with models of
hierarchical galaxy formation, which predict that the number density of ~ M*
objects is fairly constant while it decreases faster for more massive systems
over the redshift range our data probe.


title: The relation between far-UV and visible extinctions

abstract:
  For directions of sufficcient reddening (E(B-V) >~ 0.25), there is a simple
relation between the slope of the extinction curve in the far-UV and E(B-V).
Regardless of direction, the far-UV extinction curve is proportional to
1/lambda^n exp(-2e(B-V)/lambda) (lambda in micron, n = 4), in accordance with
the idea that reddened stars spectra are contaminated by scattered light
(Zagury, 2001b).
  This relation is not compatible with the standard theory of extinction which
states that far-UV and visible extinctions are due to different classes of
grains. In the standard theory model the two (far-UV and visible) extinctions
vary thus independently according to the proportion of each type of grains.
  In preceding papers I have shown that the standard theory cannot explain UV
observations of nebulae, and is contradicted by the UV spectra of stars with
very low reddening: for how long shall the standard theory be considered as the
interpretation of the extinction curve?


title:
Numerical convergence of physical variables in hydrodynamical
  simulations of cooling clusters

abstract:
  Results from hydrodynamical SPH simulations of galaxy clusters are used to
investigate the dependence of the final cluster X-ray properties on the
numerical resolution and the assumed models for the physical gas processes. Two
different spatially flat cosmological models have been considered: a
low-density cold dark matter universe with a vacuum energy density Omega_L=0.7
(LCDM) and a cold+hot dark matter model (CHDM). These simulations first include
radiative cooling and then also conversion of cold gas particles into stars.
When cold gas particles are allowed to convert into stars the final gas
profiles show a well defined core radius and the temperature profiles are
nearly flat. For the most massive test cluster in the LCDM model, these
simulations show a prominent cooling flow in the cluster core. This cluster was
analyzed in detail, running simulations with different star formation methods
and increasing numerical resolution. A comparison between different runs shows
that the results of simulations, based on star formation methods in which gas
conversion into stars is controlled by an efficiency parameter c_star, are
sensitive to the numerical resolution of the simulation. In this respect star
formation methods based instead on a local density threshold, as in Navarro and
White (1993), are shown to give more stable results. Final X-ray luminosities
are found to be numerically stable, with uncertainties of a factor two.


title: On the phase-space structure of the Milky Way dark-matter halo

abstract:
  We analyse a high resolution simulation of the formation of a cluster's
dark-matter halo in a $\Lambda$CDM cosmology (Springel et al. 2001). The
resolution achieved allows us to map the phase-space structure in detail, and
characterize its evolution and degree of lumpiness. Scaling down the cluster
halo to a Milky-Way size halo, we probe the substructure expected in the solar
neighbourhood. Here we specifically address the relevance of such substructure
for direct detection experiments aimed at determining the nature of
dark-matter.


title: The star-formation rate in the host of GRB 990712

abstract:
  We have observed the host galaxy of GRB 990712 at 1.4 GHz with the Australia
Telescope Compact Array, to obtain an estimate of its total star-formation
rate. We do not detect a source at the position of the host. The 2 sigma upper
limit of 70 microJy implies that the total star-formation rate is lower than
100 Msun/yr, using conservative values for the spectral index and cosmological
parameters. This upper limit is in stark contrast with recent reports of
radio/submillimeter-determined star-formation rates of roughly 500 Msun/yr for
two other GRB host galaxies. Our observations present the deepest
radio-determined star-formation rate limit on a GRB host galaxy yet, and show
that also from the unobscured radio point-of-view, not every GRB host galaxy is
a vigorous starburst.


title:
Detection of a vibration-rotation emission line of hydrogen deuteride
  toward Orion Peak 1: excitation coupling of HD to H_2

abstract:
  The 2.46um v=1-0 R(5) line of deuterated molecular hydrogen, HD, has been
detected in the Orion Peak~1 shock emission region, at a surface brightness of
(8.5 +/- 2.1) x 10^(-9) W m^(-2)sr^(-1) over a 6 arcsec^2 area. Comparison of
the column density of HD(v=1,J=6) with the column density of HD(v=0,J=6)
previously observed from ISO and the H_2 level column densities toward the same
region implies that the excitation of HD is similar to that of H_2 for these
energy levels, despite much higher spontaneous transition rates for HD. We
suggest that this rough equality is caused by the coupling of the HD levels to
those of H_2, due to strong reactive collisions, HD + H -> H_2 + D, in warm,
partially dissociated gas. The deuterium abundance implied by the combined ISO
and UKIRT measurements toward Orion Peak 1 is [D]/[H] = (5.1 +/- 1.9)x10^(-6).


title:
Spectroscopic Analysis of the DAB White Dwarf PG 1115+166: An Unresolved
  DA + DB Degenerate Binary

abstract:
  A spectroscopic analysis of the DAB white dwarf PG 1115+166 is presented. The
observed hydrogen and helium line profiles are shown to be incompatible with
model spectra calculated under the assumption of homogeneous or stratified
chemical compositions. In contrast, an excellent fit to the optical spectrum of
PG 1115+166 can be achieved if the object is interpreted as an unresolved
double degenerate composed of a hydrogen-line DA star and a helium-line DB
star. The atmospheric parameters obtained from the best fit are Teff=22,090 K
and log g=8.12 for the DA star, Teff=16,210 K and log g=8.19 for the DB star.
This binary interpretation is consistent with the results recently reported by
Burleigh et al. that PG 1115+166 also exhibits radial velocity variations. The
implications of this discovery with respect to the DAB spectral class are
discussed.


title: An Adaptive Optics Search for Companions to Stars with Planets

abstract:
  We have performed a Keck adaptive optics (AO) imaging survey of 25 extrasolar
planetary systems discovered by the radial velocity programs. Typically, the
high-resolution (FWHM~0.04") near-infrared images are able to detect point
sources at dH=10 at 1", L and T dwarfs at 0.5" to 2.0", and stars and brown
dwarfs at 3-10 AU and 10-100 AU from the targets. The AO images reveal 15 faint
sources (H=14-20) near the stars HD 37124, HD 168443, HD 187123, and HD 190228
out to a search radius of 3.3. We have obtained AO images at a second epoch for
five of the candidate companions at Keck and Gemini Observatories. The
resulting measurements of proper motions relative to the primary stars indicate
that these five sources are background stars. Given that the four primaries are
near the Galactic plane (|b|<6 deg), the remaining faint sources are also
likely to be background stars rather than substellar companions. We present the
companion detection limits for each target as a function of separation and
compare them to the sensitivities of radial velocity surveys, demonstrating the
complementary nature of the two techniques.


title:
Dust emission in massive star-forming regions with PRONAOS: the Orion
  and M17 molecular clouds

abstract:
  The balloon-borne submillimeter instrument PRONAOS has observed one square
degree areas towards the Orion and M17 molecular clouds. The 2' - 3.5'
resolution maps obtained in four wide wavelength bands between 200 microns and
600 microns, exhibit the dust distribution in these regions. We analyze the
temperature and spectral index of the dust, and we show the anticorrelation
between these two parameters. We derive estimations of the ISM column densities
and masses in these regions.


title:
Detecting HeliumII reionization from a sudden injection of entropy in
  the intergalactic medium

abstract:
  The temperature of the low-density intergalactic medium is set by the balance
between adiabatic cooling resulting from the expansion of the universe, and
photo-heating by the UV-background. A sudden injection of entropy from the
reionization will increase the temperature of the gas, leading to a broadening
of the hydrogen Lyman-alpha absorption lines produced in the IGM, and observed
in the spectra of background quasars. We present a method based on wavelets to
characterise objectively the line widths of such absorption lines. We use high
resolution hydrodynamical simulations to demonstrate that the algorithm can
detect changes in temperature of order of 50 per cent on scales > 5000 km/s. We
apply the method to a UVES/VLT spectrum of quasar 0055--269 (emission
redshift=3.7) and detect at the 99 per cent confidence level a sudden increase
in temperature below redshift z=3.3, which we interpret as evidence for
HeliumII reionization.


title: X-Ray Observations of Cygnus X-2

abstract:
  We report on a joint BeppoSAX/RossiXTE observation of the Z-type low mass
X-ray binary Cyg X-2. The source was in the so-called high overall intensity
state and in less than 24 hours went through all three branches of the Z-track.
The continuum x-ray spectrum could be described by the absorbed sum of a soft
thermal component, modeled as either a blackbody or a multicolor disk
blackbody, and a Comptonized component. The timing power spectrum showed
several components including quasiperiodic oscillations in the range 28-50 Hz
while the source was on the horizontal branch (horizontal branch oscillation;
HBO). We found that the HBO frequency was well correlated with the parameters
of the soft thermal component in the x-ray spectrum. We discuss implications of
this correlation for models of the HBO.


title: Discovery of Ghost Cavities in Abell 2597's X-ray Atmosphere

abstract:
  A Chandra image of the central 100 kpc of the Abell 2597 cluster of galaxies
shows bright, irregular, X-ray emission within the central dominant cluster
galaxy (CDG), and two low surface brightness cavities located 30 kpc from the
CDG's nucleus. Unlike the cavities commonly seen in other clusters, Abell
2597's ``ghost'' cavities are not coincident with the bright central radio
source. Instead, they appear to be associated with faint, extended radio
emission seen in a deep VLA radio map. We interpret the ghost cavities as
buoyantly-rising relics of a radio outburst that occurred between 50--100 Myr
ago. The demography of cavities in the few clusters studied thus far shows that
galactic radio sources experience recurrent outbursts on a $\sim 100$ Myr
timescale. Over the lifetime of a cluster, ghost cavities emerging from CDGs
deposit $\gae 10^{59-61}$ erg of energy into the intracluster medium. If a
significant fraction of this energy is deposited as magnetic field, it would
account for the high field strengths in the cooling flow regions of clusters.
The similarity between the central cooling time of the keV gas and the radio
cycling timescale suggests that feedback between cooling gas and the radio
source may be retarding or quenching the cooling flow.


title: Variable Stars in the Fornax Dwarf Galaxy

abstract:
  We present a search for variable stars in the Fornax dwarf galaxy covering an
area of 1/2 a square degree. We have ~30 epochs of VI data. We found and
determined periods for more than 500 RR Lyrae, 17 anomalous Cepheids, 6
Population II Cepheids. In addition we have 85 candidate Long Period Variables,
the majority of which were previously unknown. We estimated that the average
metal abundance of RR Lyrae stars is [Fe/H] ~ -1.6 dex.


title:
Gamma-ray bursts and black holes. Interpretation of the observational
  data

abstract:
  The paper relies upon the (Kuznetsov 2000), where the cosmic gamma - ray
bursts (GRBs) in clusters are shown to have an apparent shift relative to the
position of the source. Hence the main conclusion follows: only cluster of GRBs
ensures correct localization of the source whereas determining the direction of
arrival of a single GRB practically carries no information about the position
of its source. Generation of repeated GRBs in the activity phase of the source,
which amounts to 3-4 months and with the period of repetition of activity equal
to 4 years are most general properties of clusters. These properties precisely
correspond to the characteristics of manifestation of activity of X-ray NOVAE
(BHXN), thus pointing that the source of GRB clusters considered is a black
hole (BH) in the XN. The direct identification of the GRB source with the BHXN
GRO J0422+32 presented here this confirms. The investigated properties of GRB
clusters permit a final solution of 2 main problems of astrophysics: search for
black holes and origin of cosmic GRBs.


title:
Observations and models of the embedded phase of high-mass star
  formation

abstract:
  This paper is a review and an update on recent work on the physical and
chemical structure of the envelopes of newly born massive stars, at the stages
preceding ultracompact H II regions. It discusses methods and results to
determine total mass, temperature and density structure, ionization rate, and
depth-dependent chemical composition.


title: Effect of hyperon bulk viscosity on neutron-star r-modes

abstract:
  Neutron stars are expected to contain a significant number of hyperons in
addition to protons and neutrons in the highest density portions of their
cores. Following the work of Jones, we calculate the coefficient of bulk
viscosity due to nonleptonic weak interactions involving hyperons in
neutron-star cores, including new relativistic and superfluid effects. We
evaluate the influence of this new bulk viscosity on the gravitational
radiation driven instability in the r-modes. We find that the instability is
completely suppressed in stars with cores cooler than a few times 10^9 K, but
that stars rotating more rapidly than 10-30% of maximum are unstable for
temperatures around 10^10 K. Since neutron-star cores are expected to cool to a
few times 10^9 K within seconds (much shorter than the r-mode instability
growth time) due to direct Urca processes, we conclude that the gravitational
radiation instability will be suppressed in young neutron stars before it can
significantly change the angular momentum of the star.


title:
A standard stellar library for evolutionary synthesis. III. Metallicity
  calibration

abstract:
  We extend the colour calibration of the widely used BaSeL standard stellar
library (Lejeune, Cuisinier, & Buser 1997, 1998) to non-solar metallicities,
down to [Fe/H] ~ -2.0 dex. Surprisingly, we find that at the present epoch it
is virtually impossible to establish a unique calibration of UBVRIJHKL colours
in terms of stellar metallicity [Fe/H] which is consistent simultaneously with
both colour-temperature relations and colour-absolute magnitude diagrams (CMDs)
based on observed globular cluster photometry data and on published, currently
popular standard stellar evolutionary tracks and isochrones. The problem
appears to be related to the long-standing incompleteness in our understanding
of convection in late-type stellar evolution, but is also due to a serious lack
of relevant observational calibration data that would help resolve, or at least
further significant progress towards resolving this issue. In view of the most
important applications of the BaSeL library, we here propose two different
metallicity calibration versions: (1) the "WLBC 99" library, which consistently
matches empirical colour-temperature relations and which, therefore, should
make an ideal tool for the study of individual stars; and (2), the "PADOVA
2000" library, which provides isochrones from the Padova 2000 grid (Girardi et
al., 2000) that successfully reproduce Galactic globular-cluster
colour-absolute magnitude diagrams and which thus should prove particularly
useful for studies of collective phenomena in stellar populations in clusters
and galaxies.


title: X-ray Doppler Imaging of 44i Boo with Chandra

abstract:
  Chandra High-Energy Transmission Grating observations of the bright eclipsing
contact binary 44i Boo show X-ray line profiles which are Doppler-shifted by
orbital motions. The X-ray emission spectrum contains a multitude of lines
superimposed on a weak continuum, with strong lines of O VIII, Ne X, Fe XVII,
and Mg XII. The profiles of these lines from the total observed spectrum show
Doppler-broadened widths of ~ 550 km s^{-1}. Line centroids vary with orbital
phase, indicating velocity changes of > 180 km s^{-1}. The first-order light
curve shows significant variability, but no clear evidence for either primary
or secondary eclipses. Flares are observed for all spectral ranges;
additionally, the light curve constructed near the peak of the emission measure
distribution (T_e = 5 to 8 X 10^6 K) shows quiescent variability as well as
flares. The phase-dependences of line profiles and light curves together imply
that at least half of the emission is localized at high latitude. A simple
model with two regions on the primary star at relatively high latitude
reproduces the observed line profile shifts and quiescent light curve. These
first clear X-ray Doppler shifts of stellar coronal material illustrate the
power of Chandra.


title: Self-Interacting Dark Matter Halos and the Gravothermal Catastrophe

abstract:
  We study the evolution of an isolated, spherical halo of self-interacting
dark matter (SIDM) in the gravothermal fluid formalism. We show that the
thermal relaxation time, $t_r$, of a SIDM halo with a central density and
velocity dispersion of a typical dwarf galaxy is significantly shorter than its
age. We find a self-similar solution for the evolution of a SIDM halo in the
limit where the mean free path between collisions, $\lambda$, is everywhere
longer than the gravitational scale height, $H$. Typical halos formed in this
long mean free path regime relax to a quasistationary gravothermal density
profile characterized by a nearly homogeneous core and a power-law halo where
$\rho \propto r^{-2.19}$. We solve the more general time-dependent problem and
show that the contracting core evolves to sufficiently high density that
$\lambda$ inevitably becomes smaller than $H$ in the innermost region. The core
undergoes secular collapse to a singular state (the ``gravothermal
catastrophe'') in a time $t_{coll} \approx 290 t_r$, which is longer than the
Hubble time for a typical dark matter-dominated galaxy core at the present
epoch. Our model calculations are consistent with previous, more detailed,
N-body simulations for SIDM, providing a simple physical interpretation of
their results and extending them to higher spatial resolution and longer
evolution times. At late times, mass loss from the contracting, dense inner
core to the ambient halo is significantly moderated, so that the final mass of
the inner core may be appreciable when it becomes relativistic and radially
unstable to dynamical collapse to a black hole.


title: Quintessence and variation of the fine structure constant in the CMBR

abstract:
  We study dependence of the CMB temperature anisotropy spectrum on the value
of the fine structure constant $\alpha$ and the equation of state of the dark
energy component of the total density of the universe. We find that bounds
imposed on the variation of $\alpha$ from the analysis of currently available
CMB data sets can be significantly relaxed if one also allows for a change in
the equation of state.


title: New Constraints on the Nature of Radio Emission in Sagittarius A*

abstract:
  The mm to sub-mm spectrum of Sgr A* at the Galactic center, as well as its
polarization characteristics, are consistent with the inner 10 Schwarzschild
radii of a tight Keplerian emitting region of hot, magnetized, orbiting gas.
This plasma may also be the source through self-Comptonization of the X-rays
detected by Chandra. It has long been suspected that the circularization region
between the quasi-spherical infall at large radii, and this inner zone, is
responsible for producing the rest of Sgr A*'s spectrum. In this paper, we
report the results of a detailed study of this region. First, the combination
of existing cm and X-ray data preclude the possibility of producing the
observed strong 1.36 GHz radio flux via thermal synchrotron within a bounded
flow. If Sgr A*'s radio spectrum is produced by accreting gas, it appears that
a non-thermal particle distribution is a necessity. Second, if this is the
correct picture for how Sgr A*'s spectrum is produced, it appears that the
Chandra-detected X-rays may originate either from self-Comptonization in the
inner Keplerian region, or from optically-thin nonthermal synchrotron emission
in the much larger, circularization zone, extending up to 500 Schwarzschild
radii or more. This is a question that should be answered by upcoming broadband
observations, since the mm-bump and X-rays are strongly correlated in the
former case, whereas the X-rays are strongly correlated to the cm-radio flux in
the latter. In addition, X-rays produced in the circularized gas could show
periodic or quasi-periodic variations, but not those produced via nonthermal
synchrotron emission much farther out.