title:
The change from accretion via a thin disk to a coronal flow: dependence
  on the viscosity of the hot gas

abstract:
  We study the transition from the geometrically thin disk to the hot coronal
flow for accretion onto black holes. The efficiency of evaporation determines
the truncation of the geometrically thin disk as a function of the black hole
mass and the mass flow rate in the outer disk. The physics of the evaporation
was already described in detail in earlier work (Meyer et al. 2000b). We show
now that the value of the viscosity parameter for the coronal gas has a strong
influence on the evaporation efficiency. For smaller values of the viscosity
evaporation is less efficient. For a given mass flow rate from outside the
geometrically thin disk then extends farther inward. Spectral transitions
between soft and hard states are then expected for different mass flow rates in
the outer disk. The physics is the same for the cases of stellar and
supermassive black holes systems.


title: A fireworks model for Gamma-Ray Bursts

abstract:
  The energetics of the long duration GRB phenomenon is compared with models of
a rotating Black Hole (BH) in a strong magnetic field generated by an accreting
torus. A rough estimate of the energy extracted from a rotating BH with the
Blandford-Znajek mechanism is obtained with a very simple assumption: an
inelastic collision between the rotating BH and the torus. The GRB energy
emission is attributed to an high magnetic field that breaks down the vacuum
around the BH and gives origin to a e+- fireball. Its subsequent evolution is
hypothesized, in analogy with the in-flight decay of an elementary particle, to
evolve in two distinct phases. The first one occurs close to the engine and is
responsible of energizing and collimating the shells. The second one consists
of a radiation dominated expansion, which correspondingly accelerates the
relativistic photon--particle fluid and ends at the transparency time. This
mechanism simply predicts that the observed Lorentz factor is determined by the
product of the Lorentz factor of the shell close to the engine and the Lorentz
factor derived by the expansion. An anisotropy in the fireball propagation is
thus naturally produced, whose degree depends on the bulk Lorentz factor at the
end of the collimation phase.


title: X-ray properties of Red Active Galactic Nuclei

abstract:
  The Two Micron All Sky Survey (2MASS) is finding previously unidentified,
luminous red active galactic nuclei (AGN). This new sample has a space density
similar to, or greater than, previously known AGN, suggesting that a large
fraction of the overall population has been missed. Chandra observations of a
well-defined subset of these objects reveal that all are X-ray faint, with the
reddest sources being the faintest in X-rays. The X-ray hardness ratios cover a
wide range, generally indicating log NH ~21-23 /cm*2, but the softest sources
show no spectral evidence for intrinsic absorption. These characteristics
suggest that a mix of absorbed, direct emission and unabsorbed, scattered
and/or extended emission contributes to the X-ray flux, although we cannot rule
out the possibility that they are intrinsically X-ray weak. This population of
X-ray faint, predominantly broad-line objects could provide the missing
population of X-ray absorbed AGN required by current models of the cosmic X-ray
background. The existence of AGN which display both broad emission lines and
absorbed X-rays has important implications for unification schemes and
emphasizes the need for care in assigning classifications to individual AGN.


title:
A New Way to Detect Massive Black Holes in Galaxies: The Stellar
  Remnants of Tidal Disruption

abstract:
  We point out that the tidal disruption of a giant may leave a luminous
(10^35-10^39 ergs/s), hot (10-100 eV) stellar core. The ``supersoft'' source
detected by Chandra at the center of M31 may be such a core; whether or not it
is, the observations have shown that such a core is detectable, even in the
center of a galaxy. We therefore explore the range of expected observational
signatures and how they may be used to (1) test the hypothesis that the M31
source is a remnant of tidal stripping and (2) discover evidence of black holes
and disruption events in other galaxies.


title: A Search for Intra-group Planetary Nebulae in the M 81 Group

abstract:
  We present the initial results from an [O III] lambda 5007 survey for
intra-group planetary nebulae in the M 81 group of galaxies. A total of 0.36
square degrees of the survey have been analyzed thus far, and a total of four
intra-group candidates have been detected. These data allow us to probe the
physics of galaxy interactions in small groups, and give us an upper limit for
the density of intracluster starlight. We find that the M 81 group has less
than 3% of its stars in an intra-group component; this is much less than the
fraction found in richer galaxy clusters.


title:
Can a Dusty Warm Absorber Model Reproduce the Soft X-ray Spectra of
  MCG-6-30-15 and Mrk 766?

abstract:
  XMM-Newton RGS spectra of MCG-6-30-15 and Mrk 766 exhibit complex discrete
structure, which was interpreted in a paper by Branduardi-Raymont et al. (2001)
as evidence for the existence of relativistically broadened Lyman alpha
emission from carbon, nitrogen, and oxygen, produced in the inner-most regions
of an accretion disk around a Kerr black hole. This suggestion was subsequently
criticized in a paper by Lee et al. (2001), who argued that for MCG-6-30-15,
the Chandra HETG spectrum, which is partially overlapping the RGS in spectral
coverage, is adequately fit by a dusty warm absorber model, with no
relativistic line emission. We present a reanalysis of the original RGS data
sets in terms of the Lee et al. (2001) model, and demonstrate that spectral
models consisting of a smooth continuum with ionized and dust absorption alone
cannot reproduce the RGS spectra of both objects. The original relativistic
line model with warm absorption proposed by Branduardi-Raymont et al. (2001)
provides a superior fit to the RGS data, both in the overall shape of the
spectrum and in the discrete absorption lines. Limits on the amount of X-ray
absorption by dust particles are discussed. We also discuss a possible
theoretical interpretation for the putative relativistic Lyman alpha line
emission in terms of the photoionized surface layers of the inner regions of an
accretion disk.


title: Thermal Instability-Induced Interstellar Turbulence

abstract:
  We study the dynamics of phase transitions in the interstellar medium by
means of three-dimensional hydrodynamic numerical simulations. We use a
realistic cooling function and generic nonequilibrium initial conditions to
follow the formation history of a multiphase medium in detail in the absence of
gravity. We outline a number of qualitatively distinct stages of this process,
including a linear isobaric evolution, transition to an isochoric regime,
formation of filaments and voids (also known as "thermal" pancakes), the
development and decay of supersonic turbulence, an approach to pressure
equilibrium, and final relaxation of the multiphase medium. We find that 1%-2%
of the initial thermal energy is converted into gas motions in one cooling
time. The velocity field then randomizes into turbulence that decays on a
dynamical timescale E_k ~ t^-n, 1 < n < 2. While not all initial conditions
yield a stable two-phase medium, we examine such a case in detail. We find that
the two phases are well mixed with the cold clouds possessing a fine-grained
structure near our numerical resolution limit. The amount of gas in the
intermediate unstable phase roughly tracks the rms turbulent Mach number,
peaking at 25% when M_rms ~ 8, decreasing to 11% when M_rms ~ 0.4.


title: Measuring the Speed of Sound of Quintessence

abstract:
  Quintessence, a time-varying energy component that may account for the
accelerated expansion of the universe, can be characterized by its equation of
state and sound speed. In this paper, we show that if the quintessence density
is at least one percent of the critical density at the surface of last
scattering the cosmic microwave background anisotropy can distinguish between
models whose sound speed is near the speed of light versus near zero, which
could be useful in distinguishing competing candidates for dark energy.


title:
Stability of the Cyclotron Resonance Scattering Feature in Her X-1 with
  RXTE

abstract:
  Five observations of the hard X-ray spectrum of Her X-1 from \xte show that
the $\sim 41$ keV energy of the cyclotron scattering line is constant within
statistics of a few percent per observtion. Comparison with other observations
over many years indicates strongly that the centroid energy of this absorption
line has increased some time between 1991 and 1993 by 23%, from 34 keV to 41
keV. Moreover, the cutoff energy of the spectral continuum increased at the
same time from 16 keV to 20 keV, which is, within the statistical error of 5%,
in direct proportion to the centroid. This may be a sign thatboth these
characteristics of the spectrum are controlled in the same way by the magnetic
field strength in the region of scattering.


title: The Patchy Accretion Disc in HT Cassiopeiae

abstract:
  We have reconstructed the temperatures and surface densities in the quiescent
accretion disc in HT Cas by performing a "Physical Parameter Eclipse Mapping"
analysis of archival UBVR observations. Using a simple hydrogen slab model and
demanding a smooth, maximally artefact-free reconstruction, we derive a formal
distance to HT Cas of 207 +- 10 pc, significantly larger than the 133 +- 14 pc
we derive from a re-analysis of the data in the literature.
  We argue that the larger derived distance is probably incorrect but is not
produced by inaccuracies in our spectral model or optimization method. The
discrepancy can be resolved if the emission regions on the disc are patchy with
a filling factor of about 40% of the disc's surface. This solves the problem
with the high effective temperatures in the disc -- reducing them to around 6
500 K within a radius of 0.2 R_L1 -- and reduces the derived temperature of the
white dwarf and/or boundary layer from 22600 to 15500 K.
  We discuss several possible sources of the chromospheric emission and its
patchiness, including irradiation of the disc, thermal instabilities,
spiral-wave-like global structures, and magnetically active regions associated
with dynamo action and/or Balbus-Hawley instabilities.


title: B-modes in cosmic shear from source redshift clustering

abstract:
  Weak gravitational lensing by the large scale structure can be used to probe
the dark matter distribution in the Universe directly and thus to probe
cosmological models. The recent detection of cosmic shear by several groups has
demonstrated the feasibility of this new mode of observational cosmology. In
the currently most extensive analysis of cosmic shear, it was found that the
shear field contains unexpected modes, so-called B-modes, which are thought to
be unaccountable for by lensing. B-modes can in principle be generated by an
intrinsic alignment of galaxies from which the shear is measured, or may
signify some remaining systematics in the data reduction and analysis. In this
paper we show that B-modes in fact {\it are produced} by lensing itself. The
effect comes about through the clustering of source galaxies, which in
particular implies an angular separation-dependent clustering in redshift.
After presenting the theory of the decomposition of a general shear field into
E- and B-modes, we calculate their respective power spectra and correlation
functions for a clustered source distribution. Numerical and analytical
estimates of the relative strength of these two modes show that the resulting
B-mode is very small on angular scales larger than a few arcminutes, but its
relative contribution rises quickly towards smaller angular scales, with
comparable power in both modes at a few arcseconds. The relevance of this
effect with regard to the current cosmic shear surveys is discussed.


title: Location of Narrowband Spikes in Solar Flares

abstract:
  Narrowband spikes of the decimeter type have been identified in dynamic
spectrograms of Phoenix-2 of ETH Zurich and located in position with the Nancay
Radioheliograph at the same frequency. The spike positions have been compared
with the location of hard X-ray emission and the thermal flare plasma in soft
X-rays and EUV lines. The decimetric spikes are found to be single sources
located some 20" to 400" away from the flare site in hard or soft X-rays. In
most cases there is no bright footpoint nearby. In at least two cases the
spikes are near loop tops. These observations do not confirm the widely held
view that the spike emission is produced by some loss-cone instability masering
near the footpoints of flare loops. On the other hand, the large distance to
the flare sites and the fact that these spikes are all observed in the flare
decay phase make the analyzed spike sources questionable sites for the main
flare electron acceleration. They possibly indicate coronal post-flare
acceleration sites.


title: A non-linear theory of vertical resonances in accretion discs

abstract:
  An important and widely neglected aspect of the interaction between an
accretion disc and a massive companion with a coplanar orbit is the vertical
component of the tidal force. As shown by Lubow, the response of the disc to
vertical forcing is resonant at certain radii, at which a localized torque is
exerted, and from which a compressive wave (p mode) may be emitted. Although
these vertical resonances are weaker than the corresponding Lindblad
resonances, the m=2 inner vertical resonance in a binary star is typically
located within the tidal truncation radius of a circumstellar disc.
  In this paper I develop a general theory of vertical resonances, allowing for
non-linearity of the response, and dissipation by radiative damping and
turbulent viscosity. The problem is reduced to a universal, non-linear ordinary
differential equation with two real parameters. Solutions of the complex
non-linear Airy equation are presented to illustrate the non-linear saturation
of the resonance and the effects of dissipation. It is argued that the m=2
inner vertical resonance is unlikely to truncate the disc in cataclysmic
variable stars, but contributes to angular momentum transport and produces a
potentially observable non-axisymmetric structure.


title: A sub-mm imaging survey of ultracompact HII regions

abstract:
  We present the preliminary results of a sub-mm imaging survey of ultracompact
HII regions, conducted with the SCUBA bolometer array on JCMT.


title: Millisecond Pulsars as Probes of Mass Segregation in the Galactic Center

abstract:
  We propose a simple test for the existence of a cluster of black hole
remnants around Sgr A* that is based on a small sample of any type of Galactic
Center objects, provided they are substantially less massive than the black
holes and constitute part of an old (> 1 Gyr) population. The test relies on
the fact that, under the presence of such a cluster of heavy remnants and
because of energy equipartition, lower mass objects would be expelled from the
central regions and settle into a distribution very different than the cusp
expected to be induced by the supermassive black hole alone. We show that with
a sample of just 50 objects and using only their angular positions on the sky
relative to Sgr A* it is possible to clearly differentiate between a
distribution consistent with the presence of the cluster of black holes and a
power-law cusp distribution. We argue that millisecond pulsars might currently
be the best candidate to perform this test, because of the large uncertainties
involved in the age determination of less exotic objects. In addition, by
measuring their first and second period derivatives, millisecond pulsars offer
the rare opportunity of determining the complete phase space information of the
objects. We show that this extra information improves the detection of mass
segregation by about 30%.


title: BAIKAL experiment: status report

abstract:
  We review the present status of the Baikal Neutrino Project and present the
results obtained with the deep underwater neutrino telescope NT-200.


title:
Artifacts at 4.5 and 8.0 um in Short Wavelength Spectra from the
  Infrared Space Observatory

abstract:
  Spectra from the Short Wavelength Spectrometer (SWS) on ISO exhibit artifacts
at 4.5 and 8 um. These artifacts appear in spectra from a recent data release,
OLP 10.0, as spurious broad emission features in the spectra of stars earlier
than ~F0, such as alpha CMa. Comparison of absolutely calibrated spectra of
standard stars to corresponding spectra from the SWS reveals that these
artifacts result from an underestimation of the strength of the CO and SiO
molecular bands in the spectra of sources used as calibrators by the SWS.
Although OLP 10.0 was intended to be the final data release, these findings
have led to an additional release addressing this issue, OLP 10.1, which
corrects the artifacts.


title:
Empirical calibration of the near-IR Ca II triplet - III. Fitting
  functions

abstract:
  Using a near-IR stellar library of 706 stars with a wide coverage of
atmospheric parameters, we study the behaviour of the Ca II triplet strength in
terms of effective temperature, surface gravity and metallicity. Empirical
fitting functions for recently defined line-strength indices, namely CaT*, CaT
and PaT, are provided. These functions can be easily implemented into stellar
populations models to provide accurate predictions for integrated Ca II
strengths. We also present a thorough study of the various error sources and
their relation to the residuals of the derived fitting functions. Finally, the
derived functional forms and the behaviour of the predicted Ca II are compared
with those of previous works in the field.


title:
Can simulations reproduce the observed temperature-mass relation for
  clusters of galaxies?

abstract:
  It has become increasingly apparent that traditional hydrodynamical
simulations of galaxy clusters are unable to reproduce the observed properties
of galaxy clusters, in particular overpredicting the mass corresponding to a
given cluster temperature. Such overestimation may lead to systematic errors in
results using galaxy clusters as cosmological probes, such as constraints on
the density perturbation normalization sigma_8. In this paper we demonstrate
that inclusion of additional gas physics, namely radiative cooling and a
possible preheating of gas prior to cluster formation, is able to bring the
temperature-mass relation in the innermost parts of clusters into good
agreement with recent determinations by Allen, Schmidt & Fabian using Chandra
data.


title: Multiple starbursts in Blue Compact Galaxies

abstract:
  In this paper we present some results concerning the effects of two
instantaneous starbursts, separated by a quiescent period, on the dynamical and
chemical evolution of blue compact dwarf galaxies. In particular, we compare
the model results to the galaxy IZw18, which is a very metal-poor, gas-rich
dwarf galaxy, possibly experiencing its first or second burst of star
formation. We follow the evolution of a first weak burst of star formation
followed by a second more intense one occurring after several hundreds million
years. We find that a galactic wind develops only during the second burst and
that metals produced in the burst are preferentially lost relative to the
hydrogen gas. We predict the evolution of several chemical abundances (H, He,
C, N, O, \alpha-elements, Fe) in the gas inside and outside the galaxy, by
taking into account in detail the chemical and energetical contributions from
type II and Ia supernovae. We find that the abundances predicted for the star
forming region are in good agreement with the HII region abundances derived for
IZw18. We also predict the abundances of C, N and O expected for the HI gas to
be compared with future FUSE abundance determinations. We conclude that IZw18
must have experienced two bursts of star formation, one occurred \sim 300 Myr
ago and a present one with an age between 4-7 Myr. However, by taking into
account also other independent estimates, such as the color-magnitude diagram
and the spectral energy distribution of stars in IZw18, and the fact that real
starbursts are not instantaneous, we suggest that it is more likely that the
burst age is between 4 and 15 Myr.


title:
Coronal outflow dominated accretion discs: a new possibility for low
  luminosity black holes?

abstract:
  The spectral energy distributions of galactic black holes in the low/hard
state and of low-luminosity AGN possess many common features, the most
prominent being: compact, flat (or inverted) spectrum radio cores with high
brightness temperatures; excess red and infrared emission, often correlated
with the radio flux; an extremely weak (or absent) quasi-thermal hump and a
hard X-ray power-law with high energy cut-off. These sources are thought to be
accreting at low rates and advection (or convection) dominated accretion flows
are usually considered the best candidates to explain them. Here we present an
alternative possibility, involving strong, unbound, magnetic coronae generated
by geometrically thin, optically thick accretion discs at low accretion rates.
First we show that, if angular momentum transport in the disc is due to
magnetic turbulent stresses, the magnetic energy density and effective viscous
stresses inside the disc are proportional to the geometric mean of the total
(gas plus radiation) and gas pressure. Therefore the corona is less powerful in
a radiation pressure dominated disc, and the relative fraction of the power
liberated in the corona increases as the accretion rate decreases. Furthermore,
we discuss reasons why energetically dominant coronae are ideal sites for
launching powerful jets/outflows, both MHD and thermally driven. In analysing
the spectral properties of such coronal outflow dominated accretion discs, we
reach the important conclusion that if the jet/outflow is, as is likely,
radiatively inefficient, then so is the source overall, even without advection
of energy into the black hole being relevant for the dynamics of the accretion
flow.


title: Chromospherically young, kinematically old stars

abstract:
  We have investigated a group of stars known to have low chromospheric ages,
but high kinematical ages. Isochrone, chemical and lithium ages are estimated
for them. The majority of stars in this group show lithium abundances much
smaller than expected for their chromospheric ages, which is interpreted as an
indication of their old age. Radial velocity measurements in the literature
also show that they are not close binaries. The results suggest that they can
be formed from the coalescence of short-period binaries. Coalescence rates,
calculated taking into account several observational data and a maximum
theoretical time scale for contact, in a short-period pair, predict a number of
coalesced stars similar to what we have found in the solar neighbourhood.


title: A cookbook for the XMMSAS

abstract:
  This paper will give a short description of a `cookbook' for the XMM-Newton
data reduction software XMMSAS. This `cookbook' has been developed at the
Max-Planck-Institut f\"ur extraterrestrische Physik (MPE), Garching. The task
of this `cookbook' is to describe the necessary XMMSAS tasks and show examples
to make it easy for new users of the XMMSAS to understand the steps which have
to perform to reduce their XMM X-ray data.


title: Generalizing the MOND description of rotation curves

abstract:
  We present new mathematical alternatives for explaining rotation curves of
spiral galaxies in the MOND context. For given total masses, it is shown that
various mathematical alternatives to MOND, while predicting flat rotation
curves for large galactic radii, predict curves with different peculiar
features for smaller radii. They are thus testable against observational data.


title:
The BeppoSAX High Energy Large Area Survey -V. The nature of the hard
  X-ray source populations and its evolution

abstract:
  We present optical spectroscopic identifications of hard X-ray (5-10 keV)
selected sources belonging to the HELLAS sample obtained with BeppoSAX down to
a 5-10 keV flux limit of f_{5-10 keV}~3x10^-14 erg cm^-2 s^-1. The sample
consists of 118 sources. 25 sources have been identified trough correlations
with catalogues of known sources. 49 have been searched for spectroscopic
identification at the telescope. 13 fields resulted empty down to R=21. 37
sources have been identified with type 1 AGN and 9 with type 2 AGN. The
remaining are: 5 narrow emission line galaxies, 6 Clusters, 2 BL Lac, 1 Radio
Galaxy and 1 Star. Combining these objects with other hard X-ray selected AGNs
from ASCA and HEAO1, we find that the local luminosity function of type 1 AGN
in the 2-10 keV band is fairly well represented by a double-power-law-function.
There is evidence for significant cosmological evolution according to a pure
luminosity evolution (PLE) model L_X(z)~(1+z)^k, with k=2.12 and k=2.22 in a
(Omega_m,Omega_lambda)=(1.0,0.0) and in a (Omega_m,Omega_lambda)=(0.3,0.7)
cosmology, respectively. The data show an excess of faint high redshift type 1
AGN which is well modeled by a luminosity dependent density evolution (LDDE),
similarly to what observed in the soft X-rays. However, in both cosmologies,
the statistic is not significant enough to distinguish between the PLE and LDDE
models. The fitted models imply a contribution of AGN1 to the 2-10 keV X-ray
background from 35% up to 60%.


title:
Predicting the clustering properties of galaxy clusters detectable for
  the Planck satellite

abstract:
  We study the clustering properties of the galaxy clusters detectable for the
Planck satellite due to their thermal Sunyaev-Zel'dovich effect. We take the
past light-cone effect and the redshift evolution of both the underlying dark
matter correlation function and the cluster bias factor into account. A
theoretical mass-temperature relation allows us to convert the sensitivity
limit of a catalogue into a minimum mass for the dark matter haloes hosting the
clusters. We confirm that the correlation length is an increasing function of
the sensitivity limits defining the survey. Using the expected characteristics
of the Planck cluster catalogue, which will be a quite large and unbiased
sample, we predict the two-point correlation function and power spectrum for
different cosmological models. We show that the wide redshift distribution of
the Planck survey, will allow to constrain the cluster clustering properties up
to z=1. The dependence of our results on the main cosmological parameters (the
matter density parameter, the cosmological constant and the normalisation of
the density power-spectrum) is extensively discussed. We find that the future
Planck clustering data place only mild constraints on the cosmological
parameters, because the results depend on the physical characteristics of the
intracluster medium, like the baryon fraction and the mass-temperature
relation. Once the cosmological model and the Hubble constant are determined,
the clustering data will allow a determination of the baryon fraction with an
accuracy of few per cent.


title:
Peculiar velocity effects in high-resolution microwave background
  experiments

abstract:
  We investigate the impact of peculiar velocity effects due to the motion of
the solar system relative to the microwave background (CMB) on high resolution
CMB experiments. It is well known that on the largest angular scales the
combined effects of Doppler shifts and aberration are important; the lowest
Legendre multipoles of total intensity receive power from the large CMB
monopole in transforming from the CMB frame. On small angular scales aberration
dominates and is shown here to lead to significant distortions of the total
intensity and polarization multipoles in transforming from the rest frame of
the CMB to the frame of the solar system. We provide convenient analytic
results for the distortions as series expansions in the relative velocity of
the two frames, but at the highest resolutions a numerical quadrature is
required. Although many of the high resolution multipoles themselves are
severely distorted by the frame transformations, we show that their statistical
properties distort by only an insignificant amount. Therefore, cosmological
parameter estimation is insensitive to the transformation from the CMB frame
(where theoretical predictions are calculated) to the rest frame of the
experiment.


title: Measuring CMB polarisation with the Planck HFI

abstract:
  We describe the Planck HFI design and expected performances for measuring CMB
polarisation.


title: The Crab Nebula at 1.3 mm: evidence for a new synchrotron component

abstract:
  We present the results of 1.3 mm observations of the Crab Nebula, performed
with the MPIfR bolometer arrays at the IRAM 30-m telescope. The maps obtained,
of unprecedented quality at these wavelengths, allow a direct comparison with
high-resolution radio maps. Although the spatial structure of the Crab Nebula
does not change much from radio to millimetre wavelengths, we have detected
significant spatial variations of the spectral index between 20 cm and 1.3 mm.
The main effect is a spectral flattening in the inner region, which can be
hardly explained just in terms of the evolution of a single population of
synchrotron emitting electrons. We propose instead that this is the result of
the emergence of a second synchrotron component, that we have tried to extract
from the data. Shape and size of this component resemble those of the Crab
Nebula in X rays. However, while the more compact structure of the Crab Nebula
in X rays is commonly regarded as an effect of synchrotron downgrading, it
cannot be explained why a similar structure is present also at mm wavelengths,
where the electron lifetimes far exceed the nebular age. Our data, combined
with published upper limits on spatial variations of the radio spectral index,
also imply a low-energy cutoff for the distribution of electrons responsible
for this additional synchrotron component. Although no model has been developed
so far to explain the details of this component, one may verify that the total
number of the electrons responsible for it is in agreement with what predicted
by the classical pulsar-wind models, which otherwise are known to fail in
accounting for the number of radio emitting electrons. We have also detected a
spectral steepening at mm wavelengths in some elongated regions, whose
positions match those of radio synchrotron filaments.


title: On the large escape of ionizing radiation from GEHRs

abstract:
  A thorough analysis of well studied giant HII regions on galactic discs for
which we know the ionizing stellar population, the gas metallicity and the
Wolf-Rayet population, leads to photoionization models which can only match all
observed line intensity ratios ([OIII], [OII], [NII], [SII] and [SIII] with
respect to the intensity of H$\beta$), as well as the H$\beta$ luminosity and
equivalent width if one allows for an important escape of energetic ionizing
radiation. For the three regions presented here, the fractions of escaping
Lyman continuum photons amount to 10 to 73 % and, in all cases, the larger
fraction of escaping photons has energies between 13.6 and 24.4 eV. These
escaping photons clearly must have an important impact as a source of
ionization of the diffuse ionized gas (DIG) found surrounding many galaxies, as
well as of the intergalactic medium (IGM).


title: BaSeL: a library of synthetic spectra and colours for GAIA

abstract:
  The BaseL Stellar Library (BaSeL) is a library of synthetic spectra which has
already been used in various astrophysical applications (stellar clusters
studies, characterization and choice of the COROT potential targets, eclipsing
binaries,...). This library could provide useful indications to 1) choose the
best photometric system for the GAIA strategy by evaluating their expected
performances and 2) apply systematically the BaSeL models for any sample of
GAIA targets. In this context, we describe one of the future developments of
the BaSeL interactive web site to probe the GAIA photometric data: an automatic
determination of atmospheric parameters from observed colours.


title:
Optical Spectral Monitoring of XTE J1118+480 in Outburst: Evidence for a
  Precessing Accretion Disk?

abstract:
  We present spectroscopic observations of the X-ray transient XTE J1118+480
acquired during different epochs following the 2000 March outburst. We find
that the emission line profiles show variations in their double-peak structure
on time scales longer than the 4.1 hr orbital period. We suggest that these
changes are due to a tidally driven precessing disk. Doppler imaging of the
more intense Balmer lines and the HeII 4686 line shows evidence of a persistent
region of enhanced intensity superposed on the disk which is probably
associated with the gas stream, the hotspot or both. We discuss the possible
origins of the optical flux in the system and conclude that it may be due to a
viscously heated disk.


title:
The Intrinsic Shapes of Molecular Cloud Fragments over a Range of Length
  Scales

abstract:
  We decipher intrinsic three-dimensional shape distributions of molecular
clouds, cloud cores, Bok globules, and condensations using recently compiled
catalogues of observed axis ratios for these objects mapped in carbon monoxide,
ammonia, through optical selection, or in continuum dust emission. We apply
statistical techniques to compare assumed intrinsic axis ratio distributions
with observed projected axis ratio distributions. Intrinsically triaxial shapes
produce projected distributions which agree with observations. Molecular clouds
mapped in $^{12}$CO are intrinsically triaxial but more nearly prolate than
oblate, while the smaller cloud cores, Bok globules, and condensations are also
intrinsically triaxial but more nearly oblate than prolate.


title: A Jet-ADAF model for Sgr A*

abstract:
  The recent {\em Chandra} observation of the radio source at the center of our
Galaxy, Sgr A$^*$, puts new constraints on its theoretical models. The spectrum
is very soft, and the source is rapidly variable. We consider different models
to explain the observations. We find that the features of the x-ray spectrum
can be marginally explained with an advection-dominated accretion flow (ADAF)
model while it does not well fit the radio spectrum. An ADAF with strong winds
(ADIOS) model is not favored if we assume that the wind does not radiate.
Alternatively, we propose a coupled jet plus accretion disk model to explain
the observations for Sgr A$^*$. The accretion flow is described as an ADAF fed
by Bondi-Hoyle accretion of hot plasma in the Galactic Center region. A small
fraction of the accretion flow is ejected near the black hole, forming a jet
after passing through a shock. As a result, the electron temperature increases
to $\sim 2 \times 10^{11}{\rm K}$, which is about 10 times higher than the
highest temperature attained in the ADAF. The model is self-consistent since
the main jet parameters are determined by the underlying accretion disk at the
inner edge. The emergent spectrum of Sgr A$^*$ is the sum of the emission from
jet and underlying ADAF. The very strong Comptonization of synchrotron emission
from the jet dominates the bremsstrahlung from the ADAF, therefore, a very
short variability timescale is expected and the predicted X-ray slope and the
radio spectrum is in very good agreement with the observations.


title:
A Closer Look at the Soft X-ray Transient X1608-52: Long-term
  Optical/X-ray Observations

abstract:
  We report long-term simultaneous optical and (RXTE) X-ray observations of the
soft X-ray transient and low mass X-ray binary X1608-52 spanning from 1999 to
2001. In addition to the usual X-ray outburst and quiescent states, X1608-52
also exhibits an extended low intensity state during which the optical
counterpart, QX Nor, is found to be about two magnitudes brighter than during
quiescence. We detect optical photometric variability on a possible period of
0.5370 days with a semi-amplitude of ~0.27 mag in the I band. The modulation
could be orbital but is also consistent with a scenario invoking a superhump
with decreasing period. Observations of QX Nor during quiescence indicate an F
to G type main sequence secondary while theoretical considerations argue for an
evolved mass donor. Only an evolved mass donor would satisfy the condition for
the occurrence of superhumps.


title:
Observational Signatures of the Magnetic Connection between a Black Hole
  and a Disk

abstract:
  In this Letter we use a simple model to demonstrate the observational
signatures of the magnetic connection between a black hole and a disk: (1) With
the magnetic connection more energy is dissipated in and radiated away from
regions close to the center of the disk; (2) The magnetic connection can
produce a very steep emissivity compared to the standard accretion; (3) The
observational spectral signature of the magnetic connection can be robust.
These signatures may be identified with the observations of Chandra and
XMM-Newton. In fact, the steep emissivity index for the Seyfert 1 galaxy
MCG--6-30-15 inferred from the recent XMM-Newton observation is very difficult
to be explained with a standard accretion disk but can be easily explained with
the magnetic connection between a black hole and a disk.


title:
New Statistical Methods for Analysis of Large Surveys: Distributions and
  Correlations

abstract:
  The aim of this paper is to describe new statistical methods for
determination of the correlations among and distributions of physical
parameters from a multivariate data with general and arbitrary truncations and
selection biases. These methods, developed in collaboration with B. Efron of
Department of Statistics at Stanford, can be used for analysis of combined data
from many surveys with different and varied observational selection criteria.
For clarity we will use the luminosity function of AGNs and its evolution to
demonstrate the methods. We will first describe the general features of data
truncation and present a brief review of past methods of analysis. Then we will
describe the new methods and results from simulations testing their accuracy.
Finally we will present the results from application of the methods to a sample
of quasars.


title:
Discovery of a Cyclotron Resonance Scattering Feature in the X-ray
  Spectrum of XTE J1946+274

abstract:
  Observations of the transient accreting pulsar XTE J1946+274 made with the
Rossi X-ray Timing Explorer during the course of the 1998 September-November
outburst, reveal a cyclotron resonance scattering feature (or "cyclotron line")
in the hard X-ray spectrum near 35 keV. We determine a centroid energy of 36.2
+0.5/-0.7 keV, which implies a magnetic field strength of 3.1(1+z)x10^12 G,
where z is the gravitational redshift of the scattering region. The optical
depth, Tau = 0.33 +0.07/-0.06, and width, sigma = 3.37 +0.92/-0.75 keV, are
typical of known cyclotron lines in other pulsars. This discovery makes XTE
J1946+274 one of thirteen pulsars with securely detected cyclotron lines
resulting in direct magnetic field measurements.


title: Failed gamma-ray bursts and orphan afterglows

abstract:
  It is believed that orphan afterglow searches can help to measure the beaming
angle in gamma-ray bursts (GRBs). Great expectations have been put on this
method. We point out that the method is in fact not as simple as we originally
expected. Due to the baryon-rich environment that is common to almost all
popular progenitor models, there should be many failed gamma-ray bursts, i.e.,
fireballs with Lorentz factor much less than 100 -- 1000, but still much larger
than unity. In fact, the number of failed gamma-ray bursts may even be much
larger than that of successful bursts. Owing to the existence of these failed
gamma-ray bursts, there should be many orphan afterglows even if GRBs are due
to isotropic fireballs, then the simple discovery of orphan afterglows never
means that GRBs be collimated. Unfortunately, to distinguish a failed-GRB
orphan and a jetted but off-axis GRB orphan is not an easy task. The major
problem is that the trigger time is unknown. Some possible solutions to the
problem are suggested.


title: MSX Observations of Diffuse UV Emission in Orion

abstract:
  We have observed intense diffuse radiation in the UV (1400 A - 2600 A) from
three fields around M42 in Orion. Intensities of 20000 photons cm-2 s-1 sr-1
A-1 were observed to the east and west of M42 with 8000 photons cm-2 s-1 sr-1
A-1 south of the nebula. Enhanced emission, perhaps associated with a nearby
complex of molecular clouds observed in CO, was detected in one of the fields.
The IRAS 100 micron emission in that region is highly correlated with the UV
intensity with a UV-IR ratio of 40 photons cm-2 s-1 sr-1 A-1 (MJy sr-1)-1. In
the other two fields there was no structure in the diffuse emission nor was
there any correlation with the IRAS emission.


title: K-band luminosity (mass) segregation in AC118 at z=0.31

abstract:
  Using new observations of the galaxy cluster A118 at intermediate redshift
(z=0.31) in the Ks band, we were able to detect the cluster from the center to
half the Abell radius (1.5 Mpc, Ho=50 km/s/Mpc) and possibly to 2.0 Mpc. The
analysis of both the spatial distribution of galaxies of various luminosities
and of the luminosity function (LF) of galaxies in different cluster locations
strongly confirms and extends to larger clustercentric radii the luminosity
segregation found in a previous analysis of this cluster restricted to a
smaller cluster area: there is an excess of bright galaxies in the cluster core
(inside 250 Kpc) or a deficit of dwarfs in the remain part of the cluster.
Outside the cluster core and as far as 1.5 or even 2 Mpc, the giant-to-dwarf
ratio is constant. Because of the luminosity segregation, the LF of the AC118
shows a larger number of bright galaxies per unit dwarf in the core than in
other cluster locations. All non-core LFs, computed at several cluster
locations, are compatible each other. These results hold both including or
excluding the galaxies located in an overdensity found in the far South of
AC118 and in the second clump in galaxy density at the cluster North-West.
Since the near-infrared emission is a good tracer of the stellar mass, we
interpret the segregation found as a mass segregation.


title: The Size of IDV Jet Cores

abstract:
  Radio variability on timescales from a few hours to several days in
extragalactic flat-spectrum radio sources is generally classified as intra-day
variability (IDV). The origin of this short term variability is still
controversial and both extrinsic and intrinsic mechanisms must be considered
and may both contribute to the observed variations. The measured linear and
circular polarization of IDV sources constrains the low energy end of the
electron population. Any population of cold electrons within sources at or
above the equipartition temperature of 10^11 K depolarizes the emission and can
be ruled out. Intrinsic shock models are shown to either violate the large
fraction of sources displaying IDV or they do not relax the light travel time
argument for intrinsic variations. From structure function analysis, we further
conclude that interstellar scintillation also leads to tight size estimates
unless a very local cloud in the ISM is responsible for IDV.


title:
Cosmic Ray composition around the knee from EAS electromagnetic and muon
  data

abstract:
  We report the analysis of the Ne-Nmuon coincident events collected by the
MACRO/EAS-TOP collaboration at the Gran Sasso Laboratories. The result points
to a primary composition becoming heavier around the knee of the primary
spectrum (in the energy region 10**15-10**16 eV). The result is in very good
agreement with the measurements of EAS-TOP alone at the surface, wich detects
muons with energy Emuon > 1 GeV and uses the same (QGSJET) interaction model.


title: Ultra High Energy Cosmic Rays: present status and future prospects

abstract:
  Reasons for the current interest in cosmic rays above 10^19 eV are described.
The latest results on the energy spectrum, arrival direction distribution and
mass composition of cosmic rays are reviewed, including data that were reported
after the meeting in Blois in June 2001. The enigma set by the existence of
ultra high-energy cosmic rays remains. Ideas proposed to explain it are
discussed and progress with the construction of the Pierre Auger Observatory is
outlined.


title:
Study of CR primaries and their cascades at E0 = 10-100 TeV through
  EAS-TOP and MACRO

abstract:
  A measurement of the lateral distribution of Cherenkov light in Extensive Air
Showers (EAS) at E0 = 10-100 TeV and a study of the compatibility of the photon
number spectra with the expectations from the direct measurements of p and He
spectra and the Corsika-QGSJET propagation code in the atmosphere have been
performed at the National Gran Sasso Laboratories by the EAS-TOP and MACRO
arrays. The telescope array of EAS-TOP has been used as the Cherenkov light
detector. The muon tracking system of MACRO in the deep underground Gran Sasso
Laboratories (Emuon> 1.3 TeV) served as the EAS detector, including core
localization and arrival direction.


title:
Large-scale Correlation of Mass and Galaxies with the Lyman-alpha Forest
  Transmitted Flux

abstract:
  We present predictions of the correlation between the Lyman-alpha forest
absorption in quasar spectra and the mass within \sim 5 Mpc/h (comoving) of the
line of sight, using fully hydrodynamic and hydro-PM numerical simulations of
the cold dark matter model supported by present observations. The observed
correlation based on galaxies and the Lya forest can be directly compared to
our theoretical results, assuming that galaxies are linearly biased on large
scales. Specifically, we predict the average value of the mass fluctuation,
<delta_m>, conditioned to a fixed value of the Lya forest transmitted flux
delta_F, after they have been smoothed over a 10 Mpc/h cube and line of sight
interval, respectively. We find that <delta_m>/sigma_m as a function of
delta_F/sigma_F has a slope of 0.6 at this smoothing scale, where sigma_m and
sigma_F are the rms dispersions (this slope should decrease with the smoothing
scale). We show that this value is largely insensitive to the cosmological
model and other Lya forest parameters. Comparison of our predictions to
observations should provide a fundamental test of our ideas on the nature of
the Lya forest and the distribution of galaxies, and can yield a measurement of
the bias factor of any type of galaxies that are observed in the vicinity of
Lya forest lines of sight.


title: Radial Velocities for 889 Late-type Stars

abstract:
  We report radial velocities for 844 FGKM-type main sequence and subgiant
stars and 45 K giants, most of which had either low-precision velocity
measurements or none at all. These velocities differ from the standard stars of
Udry et al. by 0.035 km/s (RMS) for the 26 FGK standard stars in common. The
zero-point of our velocities differs from that of Udry et al.: (V_present -
V_Udry) = +0.053 km/s. Thus these new velocities agree with the best known
standard stars both in precision and zero-point, to well within 0.1 km/s.
  Nonetheless, both these velocities and the standards suffer from three
sources of systematic error, namely, convective blueshift, gravitational
redshift, and spectral type mismatch of the reference spectrum. These
systematic errors are here forced to be zero for G2V stars by using the Sun as
reference, with Vesta and day sky as proxies. But for spectral types departing
from solar, the systematic errors reach 0.3 km/s in the F and K stars and 0.4
km/s in M dwarfs.
  Multiple spectra were obtained for all 889 stars during four years, and 782
of them exhibit velocity scatter less than 0.1 km/s. These stars may serve as
radial velocity standards if they remain constant in velocity. We found 11 new
spectroscopic binaries and report orbital parameters for them.


title:
Nucleosynthesis in Massive Stars With Improved Nuclear and Stellar
  Physics

abstract:
  We present the first calculations to follow the evolution of all stable
nuclei and their radioactive progenitors in stellar models computed from the
onset of central hydrogen burning through explosion as Type II supernovae.
Calculations are performed for Pop I stars of 15, 19, 20, 21, and 25 M_sun
using the most recently available experimental and theoretical nuclear data,
revised opacity tables, neutrino losses, and weak interaction rates, and taking
into account mass loss due to stellar winds. A novel ``adaptive'' reaction
network is employed with a variable number of nuclei (adjusted each time step)
ranging from about 700 on the main sequence to more than 2200 during the
explosion. The network includes, at any given time, all relevant isotopes from
hydrogen through polonium (Z=84). Even the limited grid of stellar masses
studied suggests that overall good agreement can be achieved with the solar
abundances of nuclei between 16O and 90Zr. Interesting discrepancies are seen
in the 20 M_sun model and, so far, only in that model, that are a consequence
of the merging of the oxygen, neon, and carbon shells about a day prior to core
collapse. We find that, in some stars, most of the ``p-process'' nuclei can be
produced in the convective oxygen burning shell moments prior to collapse; in
others, they are made only in the explosion. Serious deficiencies still exist
in all cases for the p-process isotopes of Ru and Mo.


title:
Optical SETI: A Spectroscopic Search for Laser Emission from Nearby
  Stars

abstract:
  We have searched for nonastrophysical emission lines in the optical spectra
of 577 nearby F, G, K, and M main-sequence stars. Emission lines of
astrophysical origin would also have been detected, such as from a
time--variable chromosphere or infalling comets. We examined ~20 spectra per
star obtained during four years with the Keck/HIRES spectrometer at a
resolution of 5 km/s, with a detection threshold 3% of the continuum flux
level. We searched each spectrum from 4000-5000 angstroms for emission lines
having widths too narrow to be natural from the host star, as well as for lines
broadened by astrophysical mechanisms. We would have detected lasers that emit
a power, P>60 kW, for a typical beam width of ~0.01 arcsec (diffraction-limit
from a 10-m aperture) if directed toward Earth from the star. No lines
consisstent with laser emission were found.


title:
From old Globular Clusters to early Structures in the Universe: the
  Formation of old, metal-poor Halos around early-type Galaxies

abstract:
  Old, metal-poor globular clusters trace the formation and evolution of
early-type galaxies. Their are the best probes, at low redshift, of the
building-up of galaxy halos at high redshift. Their properties constrain the
characteristics of their progenitors. Recent results suggest that DLAs at z>3
are the likely hosts for their formation. Finally, they shed light on the old,
metal-poor halos probably present around all early-type galaxies.


title: A superburst from GX 3+1

abstract:
  I found one long X-ray flare from the X-ray burster GX 3+1 in almost 6 years
of observations with the RXTE All Sky Monitor (ASM). The event had a peak flux
of about 1.1 Crab (1.5-12 keV), lasted between 4.4 and 16.2 hours and exhibited
a fluence of more than about 5x10^{41} erg for a source distance of 5 kpc.
During the exponential-like decay, with an exponential decay time of 1.6 hours,
spectral softening is seen. The total ASM effective exposure time on GX 3+1 is
estimated to be around a year. The flare bears all the characteristics of the
recently discovered so-called superbursts in other X-ray burst sources.


title:
The Cut & Enhance method : selecting clusters of galaxies from the SDSS
  commissioning data

abstract:
  We describe an automated method, the Cut & Enhance method (CE) for detecting
clusters of galaxies in multi-color optical imaging surveys. This method uses
simple color cuts, combined with a density enhancement algorithm, to up-weight
pairs of galaxies that are close in both angular separation and color. The
method is semi-parametric since it uses minimal assumptions about cluster
properties in order to minimize possible biases. No assumptions are made about
the shape of clusters, their radial profile or their luminosity function. The
method is successful in finding systems ranging from poor to rich clusters of
galaxies, of both regular and irregular shape. We determine the selection
function of the CE method via extensive Monte Carlo simulations which use both
the real, observed background of galaxies and a randomized background of
galaxies. We use position shuffled and color shuffled data to perform the false
positive test. We have also visually checked all the clusters detected by the
CE method. We apply the CE method to the 350 deg^2 of the SDSS (Sloan Digital
Sky Survey) commissioning data and construct a SDSS CE galaxy cluster catalog
with an estimated redshift and richness for each cluster. The CE method is
compared with other cluster selection methods used on SDSS data such as the
Matched Filter (Postman et al. 1996, Kim et al. 2001), maxBCG technique (Annis
et al. 2001) and Voronoi Tessellation (Kim et al. 2001). The CE method can be
adopted for cluster selection in any multi-color imaging surveys.


title:
Variability of the X-ray P Cygni Line Profiles from Circinus X-1 Near
  Zero Phase

abstract:
  The luminous X-ray binary Circinus X-1 has been observed twice near zero
orbital phase using the High-Energy Transmission Grating Spectrometer (HETGS)
onboard Chandra. The source was in a high-flux state during a flare for the
first observation, and it was in a low-flux state during a dip for the second.
Spectra from both flux states show clear P Cygni lines, predominantly from
H-like and He-like ion species. These indicate the presence of a high-velocity
outflow from the Cir X-1 system which we interpret as an equatorial
accretion-disk wind, and from the blueshifted resonance absorption lines we
determine outflow velocities of 200 - 1900 km/s with no clear velocity
differences between the two flux states. The line strengths and profiles,
however, are strongly variable both between the two observations as well as
within the individual observations. We characterize this variability and
suggest that it is due to both changes in the amount of absorbing material
along the line of sight as well as changes in the ionization level of the wind.
We also refine constraints on the accretion-disk wind model using improved
plasma diagnostics such as the He-like Mg XI triplet, and we consider the
possibility that the X-ray absorption features seen from superluminal jet
sources can generally be explained via high-velocity outflows.


title: Chandra on Millisecond Pulsars in Globular Clusters

abstract:
  We summarize the x-ray properties of the complete samples of millisecond
pulsars (MSPs) detected in our Chandra observations of the globular clusters 47
Tuc and NGC 6397. The 47 Tuc MSPs are predominantly soft sources suggestive of
thermal emission from the neutron star polar cap and have x-ray luminosities in
a surprisingly narrow range (Lx ~--4 x 10^{30} erg/s). The single MSP in NGC
6397 is both hard and apparently extended, probably due to shocked hot gas
evaporating from its main sequence companion. In contrast to MSPs in the field
and the cluster M28, which show correlation between x-ray luminosity and
spindown luminosity Lx \propto \Edot^{\beta} with \beta ~1 - 1.4, the 47 Tuc
(and NGC 6397) sample display a relatively tight correlation with \beta = 0.5
+/-0.15. The correlations of Lx vs. P/2P-dot and light cylinder magnetic field
values are also different. It is possible the magnetic field configuration has
been altered (by episodic accretion) for old MSPs in dense cluster cores.


title:
The 1998 outburst of the X-ray transient XTE J2012+381 as observed with
  BeppoSAX

abstract:
  We report on the results of a series of X-ray observations of the transient
black hole candidate XTE J2012+381 during the 1998 outburst performed with the
BeppoSAX satellite. The observed broad-band energy spectrum can be described
with the superposition of an absorbed disk black body, an iron line plus a high
energy component, modelled with either a power law or a Comptonisation tail.
The source showed pronounced spectral variability between our five
observations. While the soft component in the spectrum remained almost
unchanged throughout our campaign, we detected a hard spectral tail which
extended to 200 keV in the first two observations, but became barely detectable
up to 50 keV in the following two. A further re-hardening is observed in the
final observation. The transition from a hard to a soft and then back to a hard
state occurred around an unabsorbed 0.1-200 keV luminosity of 10^38 erg/s (at
10 kpc). This indicates that state transitions in XTE 2012+281 are probably not
driven only by mass accretion rate, but additional physical parameters must
play a role in the evolution of the outburst.


title: Antiprotons from primordial black holes

abstract:
  Primordial black holes (PBHs) have motivated many studies since it was shown
that they should evaporate and produce all kinds of particles. Recent
experimental measurements of cosmic rays with great accuracy, theoretical
investigations on the possible formation mechanisms and detailed evaporation
processes have revived the interest in such astrophysical objects. This article
aims at using the latest developments on antiproton propagation models together
with new data from BESS, CAPRICE and AMS experiments to constrain the local
amount of PBH dark matter. Depending on the diffusion halo parameters and on
the details of emission mechanism, we derive an average upper limit of the
order of rho < 1.7E-33 g cm^-3.


title: Systematic Molecular Differentiation in Starless Cores

abstract:
  (Abridged) We present evidence that low-mass starless cores, the simplest
units of star formation, are systematically differentiated in their chemical
composition. Molecules including CO and CS almost vanish near the core centers,
where the abundance decreases by one or two orders of magnitude. At the same
time, N2H+ has a constant abundance, and the fraction of NH3 increases toward
the core center. Our conclusions are based on a study of 5 mostly-round
starless cores (L1498, L1495, L1400K, L1517B, and L1544), which we have
mappedin C18O(1-0), C17O(1-0), CS(2-1), C34S(2-1), N2H+(1-0), NH3(1,1) and
(2,2), and the 1.2 mm continuum. For each core we have built a model that fits
simultaneously the radial profile of all observed emission and the central
spectrum for the molecular lines. The observed abundance drops of CO and CS are
naturally explained by the depletion of these molecules onto dust grains at
densities of 2-6 10^4 cm-3. N2H+ seems unaffected by this process up to
densities of several 10^5, while the NH3 abundance may be enhanced by reactions
triggered by the disappearance of CO from the gas phase. With the help of our
models, we show that chemical differentiation automatically explains the
discrepancy between the sizes of CS and NH3 maps, a problem which has remained
unexplained for more than a decade. Our models, in addition, show that a
combination of radiative transfer effects can give rise to the previously
observed discrepancy in the linewidth of these two tracers. Although this
discrepancy has been traditionally interpreted as resulting from a systematic
increase of the turbulent linewidth with radius, our models show that it can
arise in conditions of constant gas turbulence.


title:
Some sources of systematic errors on CMB polarized measurements with
  bolometers

abstract:
  Some sources of systematic errors, specific to polarized CMB measurements
using bolometers, are examined. Although the evaluations we show have been made
in the context of the Planck mission (and more specifically the Planck HFI),
many of our conclusions are valid for other experiments as well.


title: Cepheids, Supernovae, Ho, and the Age of the Universe

abstract:
  The local expansion field is mapped using Cepheids, a complete sample of TF
distances, and nearby cluster distances. The large-scale field is mapped using
Cepheid-calibrated blue SNeIa. These data give Ho(local)=59.2+/-1.4 [km/s
Mpc^-1] and Ho(cosmic)=57.4+/-2.3. The intermediate expansion field (1200 < v <
10000km/s) is less well calibrated but fully consistent with Ho~60. Ho is
therefore (nearly) scale-invariant (high-density regions excluded). -- The P-L
relation of Cepheids is based on an improved zero point of (m-M)_{LMC}=18.56.
The slope of the P-L relation for P>10days, as judged from OGLE data (Udalski
et al. 1999) is flatter than anticipated, which tends to increase the above
values of Ho by 3.4 units. No significant metallicity effect on the Cepheid
distances seems to be indicated. For all practical purposes Ho=60 is
recommended with a systematic error of probably less than 10%. -- The
corresponding expansion age is T=15.7+/-1.5Gy (with Omega(Matter)=0.3,
Omega(Lambda)=0.7), which compares well with the formation time of 15+/-2Gy for
the apparently oldest globular cluster M107.


title:
Limits from CGRO/EGRET Data on the Use of Antimatter as a Power Source
  by Extraterrestrial Civilizations

abstract:
  I argue that the existence of cold antimatter in bulk is not permitted by the
Standard Model, so that if a gamma-ray signature from antiproton annihilation
were to be detected, it must represent either new physics or the action of
intelligence. Time variability of the signal would strongly support the second
alternative. The entire sky was scanned at the relevant energies (30- 928 MeV)
by the EGRET experiment on board the Compton Gamma Ray Observatory during
1991-1995. A search of this database for the antiproton annihilation signature
yielded only upper limits on the flux (an intriguing spectrum detected from QSO
2206+650 = 3EG J2206+6602 is probably not related to SETI). The all-sky,
longterm 99 upper limit is 2.3 x 10^{-8} photon/(cm2 s); it is a factor 10
worse in the Galactic plane due to the higher diffuse gamma-ray background
emission. I give brief, but quantitative, illustrations of what this limit
means for nearby intelligent activities.


title:
The Role of Strangeness in Astrophysics - an Odyssey through Strange
  Phases

abstract:
  The equation of state for compact stars is reviewed with special emphasis on
the role of strange hadrons, strange dibaryons and strange quark matter.
Implications for the properties of compact stars are presented. The importance
of neutron star data to constrain the properties of hypothetic particles and
the possible existence of exotic phases in dense matter is outlined. We also
discuss the growing interplay between astrophysics and heavy-ion physics.


title:
High resolution imaging of molecular line emission from high redshift
  QSOs

abstract:
  We present moderate (1'') and high resolution (0.2'') observations of the
CO(2-1) emission at 43 GHz, and radio continuum emission at 1.47 GHz, from the
z=4.7 QSO BRI 1202-0725 and the z=4.4 QSO BRI 1335--0417 using the Very Large
Array. The moderate resolution observations show that in both cases the CO
emission is spatially resolved into two components separated by 1'' for
1335-0417 and 4'' for 1202-0725. The high resolution observations show that
each component has sub-structure on scales of 0.2'' to 0.5'', with intrinsic
brightness temperatures > 20K. The CO ladder from (2-1) up to (7-6) suggests a
high kinetic temperature for the gas (70 K), and a high column density (10^{24}
cm^{-2}). In both sources the continuum-to-line ratio: L_{FIR}/L'_{CO(1-0)} =
335. All these characteristics (brightness temperature, excitation temperature,
column density, and continuum-to-line ratio) are comparable to conditions found
in low redshift, ultra-luminous nuclear starburst galaxies. We find that the CO
emitting regions in 1202-0725 and 1335-0417 must be close to face-on in order
to avoid having the gas mass exceed the gravitational mass, implying perhaps
unreasonably large rotational velocities. While this problem is mitigated by
lowering the CO luminosity-to-H_2 mass conversion factor (X), the required X
values become comparable to, or lower than, the minimum values dictated by
optically thin CO emission. We considered the possibility of magnification by
gravitational lensing in order to reduce the molecular gas masses.


title: What is the manifestation of a "quasar" at z > 10^{10} ?

abstract:
  The process of forming an image of a cosmological point source (CPS) in
condition of high optical depth is considered accounting for all types of
interactions. It is shown that the energy conservation law causes the size of
this image which is keeping constant over all redshifts of the CPSs. This
effect must be taken into account for the consideration of the angular power
spectrum of the CMBR. In particular, distant point sources and small scale
fluctuations which were damping before recombination will contribute their
energy in the region of angular scale \theta_0 \approx 20'.


title: Annealing of Silicate Dust by Nebular Shocks at 10 AU

abstract:
  Silicate dust grains in the interstellar medium are known to be mostly
amorphous, yet crystalline silicate grains have been observed in many
long-period comets and in protoplanetary disks. Annealing of amorphous silicate
grains into crystalline grains requires temperatures > 1000 K, but exposure of
dust grains in comets to such high temperatures is incompatible with the
generally low temperatures experienced by comets. This has led to the proposal
of models in which dust grains were thermally processed near the protoSun, then
underwent considerable radial transport until they reached the gas giant planet
region where the long-period comets originated. We hypothesize instead that
silicate dust grains were annealed in situ, by shock waves triggered by
gravitational instabilities. We assume a shock speed of 5 km/s, a plausible
value for shocks driven by gravitational instabilities. We calculate the peak
temperatures of micron and submicron amorphous pyroxene grains of chondritic
composition under conditions typical in protoplanetary disks at 5 - 10 AU. Our
results also apply to chondritic amorphous olivine grains. We show that {\it in
situ} thermal annealing of submicron and micron-sized silicate dust grains can
occur, obviating the need for large-scale radial transport.


title:
Time evolution of the linear perturbations of a rotating Newtonian
  polytrope

abstract:
  We present the results of numerical time evolutions of the linearised
perturbations of rapidly and rigidly rotating Newtonian polytropes while making
the Cowling approximation. The evolution code runs stably for hundreds of
stellar rotations, allowing us to compare our results with previously published
eigenmode calculations, for instance the f-mode calculations of Ipser &
Lindblom, and the r-mode calculations of Karino et al. The mode frequencies
were found to be in agreement within the expected accuracy. We have also
examined the inertial modes recently computed by Lockitch & Friedman, and we
were able to extend their slow-rotation results into the rapid rotation regime.
In the longer term, this code will provide a platform for studying a number of
poorly understood problems in stellar oscillation theory, such as the effect of
differential rotation and gravitational radiation reaction on normal mode
oscillations and, with suitable modifications, mode-mode coupling in the mildly
non-linear regime.


title:
The Solar Neighborhood VI: New Southern Stars Identified by Optical
  Spectroscopy

abstract:
  Broadband optical spectra are presented for 34 known and candidate nearby
stars in the southern sky. Spectral types are determined using a new method
that compares the entire spectrum with spectra of more than 100 standard stars.
We estimate distances to 13 candidate nearby stars using our spectra and new or
published photometry. Six of these stars are probably within 25 pc, and two are
likely to be within the RECONS horizon of 10 pc.


title: The Interstellar Medium of our Galaxy

abstract:
  The development of our understanding of the gaseous component of the
interstellar medium is reviewed. During the 20th century our picture of diffuse
material in space has grown from a simple model of isolated clouds in thermal
equilibrium with stellar radiation fields to one of a richly varied composite
of materials with a wide range of physical properties and morphologies. The
solar system interacts with this dynamical interstellar medium, which dominates
the properties of the interplanetary environment. Optical, radio, and UV
astronomy allow us to study the clouds which form the galactic environment of
the Sun. The composition and distribution of interstellar clouds in the disk
and halo tell us about the history of elemental formation in our galaxy, and
the past and future environment of the solar system.


title:
Radioseismology as a new method of investigations of meteor streams on
  the Moon and planets

abstract:
  Radioseismology is based on registration and interpretation of radio emission
of seismic origin. Non-thermal radio emission of the Moon was detectedat 13 and
21 cm on July 30 - August 2, 1999. Strong oscillations of the non-thermal lunar
radio flux at 25 mm were detected during the leonid meteor shower on November
17-18, 2000. The time of maxima of oscillations does not contradict theoretical
predictions about the existence of three maxima of the Leonid shower on the
Moon. These results can be explained as the detection of lunar radio emission
of seismic origin caused by meteoroid impacts. The implications of the
radioseismic method for determination of the intensity of meteor streams on the
Moon are described.


title: Probing SZ Source Detection with Gasdynamical Simulations

abstract:
  The huge worldwide investment in CMB experiments should make the
Sunyaev-Zeldovich (SZ) effect a key probe of the cosmic web in the near future.
For the promise to be realized, substantial development of simulation and
analysis tools to relate observation to theory is needed. The high nonlinearity
and dissipative/feedback gas physics lead to highly non-Gaussian patterns that
are much more difficult to analyze than Gaussian primary anisotropies for which
the procedures are reasonably well developed. Historical forecasts for what CMB
experiments might see used semi-analytic tools, including large scale map
constructions, with localized and simplified pressure structures distributed on
a point process of (clustered) sources. Hydro studies beyond individual
cluster/supercluster systems were inadequate, but now large-volume simulations
with high resolution are beginning to shift the balance. We illustrate this by
applying ``Gasoline'' (parallelized Tree+SPH) computations to construct SZ maps
and derive statistical measures. We believe rapid Monte Carlo simulations using
parameterized templates centered on point processes informed by optical and
other means on the observational side, and by hydro simulations on the theory
side, should play an important role in pipelines to analyze the new SZ field
data. We show that localized sources should dominate upcoming SZ experiments,
identify sources in the maps under filtering and noise levels expected for
these experiments, use the RCS photometric optical survey as an example of
redshift localization, and discuss whether cosmic web patterns such as
superclusters can be enhanced when such extra source information is supplied.


title:
Interstellar H-Alpha Line Profiles toward HD 93521 and the Lockman
  Window

abstract:
  We have used the Wisconsin H-Alpha Mapper (WHAM) facility to measure the
interstellar H-Alpha emission toward the high Galactic latitude O star HD 93521
(l = 183.1, b = +62.2). Three emission components were detected having radial
velocities of -10 km s^{-1}, -51 km s^{-1}, and -90 km s^{-1} with respect to
the local standard of rest (LSR) and H-Alpha intensities of 0.20 R, 0.15 R, and
0.023 R, respectively, corresponding to emission measures of 0.55 cm^{-6} pc,
0.42 cm^{-6} pc, and 0.06 cm^{-6} pc. We have also detected an H-Alpha emission
component at -1 km s^{-1} (LSR) with an intensity of 0.20 R (0.55 cm^{-6} pc)
toward the direction l = 148.5, b = +53.0, which lies in the region of
exceptionally low H I column density known as the Lockman Window. In addition,
we studied the direction l = 163.5, b = +53.5. Upper limits on the possible
intensity of Galactic emission toward this direction are 0.11 R at the LSR and
0.06 R at -50 km s^{-1}. We also detected and characterized twelve faint
(~0.03-0.15 R), unidentified atmospheric lines present in WHAM H-Alpha spectra.
Lastly, we have used WHAM to obtain [O I] 6300 spectra along the line of sight
toward HD 93521. We place an upper limit of 0.060 R on the [O I] intensity of
the -51 km s^{-1} component. If the temperature of the gas is 10,000 K within
the H-Alpha emitting region, the hydrogen ionization fraction n(H+)/n(H_total)
> 0.6.


title: From Current CMBology to its Polarization and SZ Frontiers circa TAW8

abstract:
  I highlight the remarkable advances in the past few years in CMB research on
total primary anisotropies, in determining the power spectrum, deriving
cosmological parameters from it, and more generally lending credence to the
basic inflation-based paradigm for cosmic structure formation, with a flat
geometry, substantial dark matter and dark energy, baryonic density in good
accord with that from nucleosynthesis, and a nearly scale invariant initial
fluctuation spectrum. Some parameters are nearly degenerate with others and CMB
polarization and many non-CMB probes are needed to determine them, even within
the paradigm. Such probes and their tools were the theme of the TAW8 meeting:
our grand future of CMB polarization, with AMiBA, ACBAR, B2K2, CBI, COMPASS,
CUPMAP, DASI, MAP, MAXIPOL, PIQUE, Planck, POLAR, Polatron, QUEST,
Sport/BaRSport, and of Sunyaev-Zeldovich experiments, also using an array of
platforms and detectors, e.g. AMiBA, AMI (Ryle+), CBI, CARMA (OVROmm+BIMA),
MINT, SZA, BOLOCAM+CSO, LMT, ACT. The SZ probe will be informed and augmented
by new ambitious attacks on other cluster-system observables discussed at TAW8:
X-ray, optical, weak lensing. Interpreting the mix is complicated by such
issues as entropy injection, inhomogeneity, non-sphericity, non-equilibrium,
and these effects must be sorted out for the cluster system to contribute to
``high precision cosmology'', especially the quintessential physics of the dark
energy that adds further mystery to a dark matter dominated Universe. We will
have to address ``Is it cluster evolution or is it cosmology?''. The answer
will be both, but we can be optimistic that, with the huge data influx,
computational power increase, and talented people joining the adventure, we can
handle both observationally, theoretically and phenomenologically.


title: Studies of Structure Formation and Cosmology with Galaxy Cluster Surveys

abstract:
  Surveys of galaxy clusters provide a promising method of testing models of
structure formation in the universe. Within the context of our standard
structure formation scenario, surveys provide measurements of the geometry of
the universe and the nature of the dark energy and dark matter. Cluster
catalogues will be constructed using some combination of X-ray,
optical/near--IR, and mm or cm-wave observations. These catalogues will be used
to study the cluster redshift and mass distributions along with the
correlations of the cluster spatial distribution. These measurements probe the
volume--redshift relation, the power spectrum of density fluctuations and the
evolution of galaxy cluster abundance. All are sensitive to the amount of dark
matter Omega_M, the amount of dark energy Omega_E, the equation of state of the
dark energy w(z) and any other parameter, which affects the expansion history
of the universe.


title: Mass/Light Variations with Environment

abstract:
  In the local part of the universe, a majority of the total mass is in only a
small number of groups with short dynamical times. The Virgo Cluster dominates
far out of proportion to its contribution in light. Ninety percent of the total
mass is in groups with 12.5 < log (M/M_sun) < 15.


title: The Masses of Lyman Break Galaxies

abstract:
  Data on galaxies at high redshift, identified by the Lyman-break photometric
technique, can teach us about how galaxies form and evolve. The stellar masses
and other properties of such Lyman break galaxies (LBGs) depend sensitively on
the details of star formation. In this paper we consider three different star
formation prescriptions, and use semi-analytic methods applied to the
now-standard $\Lambda$CDM theory of hierarchical structure formation to show
how these assumptions about star formation affect the predicted masses of the
stars in these galaxies and the masses of the dark matter halos that host them.
We find that, within the rather large uncertainties, recent estimates of the
stellar masses of LBGs from multi-color photometry are consistent with the
predictions of all three models. However, the estimated stellar masses are more
consistent with the predictions of two of the models in which star formation is
accelerated at high redshifts $z\gsim3$, and of these models the one in which
many of the LBGs are merger-driven starbursts is also more consistent with
indications that many high redshift galaxies are gas rich. The clustering
properties of LBGs have put some constraints on the masses of their host halos,
but due to similarities in the halo occupation of the three models we consider
and degeneracies between model parameters, current constraints are not yet
sufficient to distinguish between realistic models.


title:
Coherent Radio Pulses From GEANT Generated Electromagnetic Showers In
  Ice

abstract:
  Radio Cherenkov radiation is arguably the most efficient mechanism for
detecting showers from ultra-high energy particles of 1 PeV and above. Showers
occuring in Antarctic ice should be detectable at distances up to 1 km. We
report on electromagnetic shower development in ice using a GEANT Monte Carlo
simulation. We have studied energy deposition by shower particles and
determined shower parameters for several different media, finding agreement
with published results where available. We also report on radio pulse emission
from the charged particles in the shower, focusing on coherent emission at the
Cherenkov angle. Previous work has focused on frequencies in the 100 MHz to 1
GHz range. Surprisingly, we find that the coherence regime extends up to tens
of Ghz. This may have substantial impact on future radio-based neutrino
detection experiments as well as any test beam experiment which seeks to
measure coherent Cherenkov radiation from an electromagnetic shower. Our study
is particularly important for the RICE experiment at the South Pole.


title: Cosmic Microwave Background Anisotropy Measurement From Python V

abstract:
  We analyze observations of the microwave sky made with the Python experiment
in its fifth year of operation at the Amundsen-Scott South Pole Station in
Antarctica. After modeling the noise and constructing a map, we extract the
cosmic signal from the data. We simultaneously estimate the angular power
spectrum in eight bands ranging from large (l ~ 40) to small (l ~ 260) angular
scales, with power detected in the first six bands. There is a significant rise
in the power spectrum from large to smaller (l ~ 200) scales, consistent with
that expected from acoustic oscillations in the early Universe. We compare this
Python V map to a map made from data taken in the third year of Python. Python
III observations were made at a frequency of 90 GHz and covered a subset of the
region of the sky covered by Python V observations, which were made at 40 GHz.
Good agreement is obtained both visually (with a filtered version of the map)
and via a likelihood ratio test.


title: Wavelet tomography of the Galactic magnetic field. I. The method

abstract:
  We suggest a two-dimensional wavelet devised to deduce the large-scale
structure of a physical field (e.g., the Galactic magnetic field) from its
integrals along straight paths from irregularly spaced data points to a fixed
interior point (the observer). The method can be applied to the analysis of
pulsar rotation and dispersion measures in terms of the large-scale Galactic
magnetic field and electron density. The method does not use any 'a priori'
assumptions about the physical field and can be considered as an algorithm of
wavelet differentiation. We argue that a certain combination of the wavelet
transformation with model fitting would be most efficient in the interpretation
of the available pulsar RM data.


title: Massive molecular outflows

abstract:
  We present a mapping study of massive molecular outflows in 26 high-mass
star-forming regions at 11'' spatial resolution. Bipolar morpholgy is found in
80% of the sources and the collimation is higher than previously thought.
Additionally, we find that well known low-mass correlations continue up to the
high-mass regime, and accretion rates are around 10^(-4) Msun/yr rising as high
as 10^(-3) Msun/yr. A tight correlation between the outflow and the core mass
is established, implying that the accretion rate is a rather linear function of
the initial core mass. All the data suggest that massive outflows are
qualitatively similar and just quantitatively enhanced compared to their low
mass counterparts.


title: Acceleration of GRB outflows by Poynting flux dissipation

abstract:
  We study magnetically powered relativistic outflows in which a part of the
magnetic energy is dissipated internally by reconnection. For GRB parameters,
and assuming that the reconnection speed scales with the Alfven speed,
significant dissipation can take place both inside and outside the photosphere
of the flow. The process leads to a steady increase of the flow Lorentz factor
with radius. With an analytic model we show how the efficiency of this process
depends on GRB parameters. Estimates are given for the thermal and non-thermal
radiation expected to be emitted from the photosphere and the optically thin
part of the flow respectively.
  A critical parameter of the model is the ratio of Poynting flux to kinetic
energy flux at some initial radius of the flow. For a large value (> 100) the
non-thermal radiation dominates over the thermal component. If the ratio is
small (< 40) only prompt thermal emission is expected which can be identified
with X-ray flashes.


title: Singular spacetime and quantum probe

abstract:
  We examine the dependence of quantization on global properties of a classical
system. Quantization based on local properties may lead to ambiguities and
inconsistency between local and global symmetries of a quantum system. Our
quantization method based on global characteristics has sound foundation.
Presented results give insight into the nature of removable type singularity of
spacetime at the quantum level.


title:
FIRST-based survey of Compact Steep Spectrum sources I. MERLIN images of
  arc-second scale objects

abstract:
  Compact Steep Spectrum (CSS) sources are powerful extragalactic radio sources
with angular dimensions of the order of a few arcseconds or less. Such a
compactness is apparently linked to the youth of these objects. The majority of
CSSs investigated so far have been known since the early 1980s. This paper is
the first in a series where we report the results of an observational campaign
targeted on a completely new sample of CSSs which are significantly weaker than
those investigated before. The ultimate goal of that campaign is to find out
how ``weak'' CSSs compare to ``strong'', classical ones, especially with regard
to the morphologies. Here we present an analysis of morphological and physical
properties of five relatively large sources based on MERLIN observations at 1.6
and 5 GHz.


title: Effects of the magnetic fields on the helium white dwarfs structure

abstract:
  In this paper the effect of the magnetic field on the form of the equation of
state and helium white dwarfs structure are discussed. The influence of the
temperature and magnetic field on white dwarfs parameters have been
investigated. The mass-radius relations for different parameters were obtained.
The occurrence of unstable branches in the mass-radius relation are presented
for the temperature equals T=3 10^8 K and for different values of the strength
of magnetic field. Theoretical model of the star with two Landau levels is
obtained.


title:
Using Cepheids to determine the galactic abundance gradient II. Towards
  the galactic center

abstract:
  Based on spectra obtained at the Anglo-Australian Observatory, we present a
discussion of the metallicity of the galactic disc derived using Cepheids at
galactocentric distances 4-6 kpc. Our new results together with previous
gradient determination (Paper I) show that the overall abundance distribution
within the galactocentric distances 4-11 kpc cannot by represented by a single
gradient value. The distribution is more likely bimodal: it is flatter in the
solar neighbourhood with a small gradient, and steepens towards the galactic
center. The steepening begins at a distance of about 6.6 kpc.


title: Spectral Analysis of Bright Gamma Ray Bursts

abstract:
  We present the time integrated and time resolved spectral analysis of a
sample of bright bursts selected from the BATSE archive. We fitted four
different spectral models to the time integrated and time resolved spectra of
the flux pulses. We point out that the found (marginal) differences in the
parameter distributions can be ascribed to the different spectral shape of the
employed models and that a smoothly curved model best fits the observed
spectra. We characterize the spectral shape of bright bursts and compare the
low energy slope of the fitted spectra with the prediction N(E) = E^{-2/3} of
the synchrotron theory, finding that this limit is violated in a considerable
number of time resolved spectra around the peaks, both during the rise and
decay phase.


title:
Temporal properties of gamma-ray bursts as signatures of jets from the
  central engine

abstract:
  A comprehensive temporal analysis has been performed on the 319 brightest
GRBs with T90>2s from the BATSE current catalog. The rise times, fall times,
full-widths at half maximum (FWHM), pulse amplitudes and pulse areas were
measured and the frequency distributions are presented here. The distribution
of time intervals between pulses is not random but compatible with a lognormal
distribution when allowance was made for the 64 ms time resolution and a small
excess (5%) of long duration intervals that is often referred to as a
Pareto-Levy tail. A range of correlations are presented on pulse and burst
properties. The rise and fall times, FWHM and area of the pulses are highly
correlated with each other. The time intervals between pulses and pulse
amplitudes of neighbouring pulses are correlated with each other. It was also
found that the number of pulses, N, in GRBs is strongly correlated with the
fluence and the duration and that can explain the well known correlation
between duration and fluence. The GRBs were sorted into three catagories based
on N i.e. 3<=N<=12, 13<=N<=24, N>=25. The properties of pulses before and after
the stongest pulse were compared for the three catagories of bursts. This
analysis revealed that the GRBs with large numbers of pulses have narrower and
faster pulses and also larger fluences, longer durations and higher hardness
ratios than the GRBs with smaller numbers of pulses.


title: Spectroscopy of SN 1987A at 0.9-2.4 microns: Days 1348-3158

abstract:
  We present near-infrared spectroscopic observations of SN 1987A covering the
period 1358 to 3158 days post-explosion. This is the first time that IR spectra
of a supernova have been obtained to such late epochs. The spectra comprise
emission from both the ejecta and the bright, ring-shaped circumstellar medium
(CSM). The most prominent CSM emission lines are recombination lines of H I and
He I, and forbidden lines of [S III] and [Fe II]. The ejecta spectra include
allowed lines of H I, He I and Na I and forbidden lines of [Si I], [Fe I], [Fe
II], and possibly [S I]. The intensity ratios and widths of the H I ejecta
lines are consistent with a low-temperature Case B recombination spectrum
arising from non-thermal ionisation/excitation in an extended, adiabatically
cooled H-envelope, as predicted by several authors. The slow decline of the
ejecta forbidden lines, especially those of [Si I], indicates that pure
non-thermal excitation was taking place, driven increasingly by the decay of
44Ti. The ejecta iron exhibits particularly high velocities (4000-4500 km/s),
supporting scenarios where fast radioactive nickel is created and ejected just
after the core-bounce. In addition, the ejecta lines continue to exhibit
blueshifts with values about -200 km/s to -800 km/s to at least day 2000. These
blueshifts, which first appeared around day 600, probably indicate that very
dense concentrations of dust persist in the ejecta, although an alternative
explanation of asymmetry in the excitation conditions is not ruled out.


title: Temporal properties of the short gamma-ray bursts

abstract:
  A temporal analysis has been performed on a sample of 100 bright gamma-ray
bursts (GRBs) with T90<2s from the BATSE current catalog. The GRBs were
denoised using a median filter and subjected to an automated pulse selection
algorithm as an objective way of idenitifing the effects of neighbouring
pulses. The rise times, fall times, FWHM, pulse amplitudes and areas were
measured and the frequency distributions are presented here. All are consistent
with lognormal distributions. The distribution of the time intervals between
pulses is not random but consistent with a lognormal distribution. The time
intervals between pulses and pulse amplitudes are highly correlated with each
other. These results are in excellent agreement with a similar analysis that
revealed lognormal distributions for pulse properties and correlated time
intervals between pulses in bright GRBs with T90>2s. The two sub-classes of
GRBs appear to have the same emission mechanism which is probably caused by
internal shocks. They may not have the same progenitors because of the generic
nature of the fireball model.


title:
High-Energy Gamma Rays from Neutron Stars in Supernova Remnants: From
  EGRET to GLAST

abstract:
  At least three pulsars in supernova remnants were detected at E > 100 MeV by
EGRET on the Compton Gamma Ray Observatory. Efforts to search for additional
pulsars in the EGRET data have been unsuccessful due to limited statistics. An
example is the recently-discovered radio pulsar J2229+6114, where efforts to
search the EGRET data using several different methods failed to find
significant evidence of pulsation. The GLAST Large Area Telescope (LAT) will
have a much greater effective area and a narrower point-spread function than
EGRET. In addition, the field of view will be more than 4 times larger than
EGRET's, and the LAT will scan to avoid occultation by the earth, increasing by
a large factor the total number of photons detected. The greater rates of
photons from pulsar candidates and better discrimination of diffuse
interstellar emission will enhance the sensitivity of pulsation searches. These
improvements also offer the prospect of resolving point sources from extended
emission in some SNR to define the nature of the associations of EGRET sources
with SNR. Further, work with the GLAST LAT will benefit from ongoing
multiwavelength studies (e.g., for RX 1836.2+5925) that provide specific
candidate targets for gamma-ray studies.


title:
Abundances of Deuterium, Oxygen, and Nitrogen in the Local Interstellar
  Medium: Overview of First Results from the Far Ultraviolet Spectroscopic
  Explorer Mission

abstract:
  Observations obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE)
have been used to determine the column densities of D I, O I, and N I along
seven sight lines that probe the local interstellar medium (LISM) at distances
from 37 pc to 179 pc. Five of the sight lines are within the Local Bubble and
two penetrate the surrounding H I wall. Reliable values of N(H I) were
determined for five of the sight lines from HST data, IUE data, and published
EUVE measurements. The weighted mean of D I/H I for these five sight lines is
(1.52 +/- 0.08) x10-5 (1 sigma uncertainty in the mean). It is likely that the
D I/H I ratio in the Local Bubble has a single value. The D I/O I ratio for the
five sight lines within the Local Bubble is (3.76 +/- 0.20) x10-2. It is likely
that the O I column densities can serve as a proxy for H I in the Local Bubble.
The weighted mean for O I/H I for the seven FUSE sight lines is (3.03 +/-0.21)
x10-4, comparable to the weighted mean (3.43 +/- 0.15) x10-4 reported for 13
sight lines probing larger distances and higher column densities (Meyer et al.
1998, Meyer 2001). The FUSE weighted mean of N I/H I for the five sight lines
is half that reported by Meyer et al. (1997) for seven sight lines with larger
distances and higher column densities. This result combined with the
variability of O I/N I (six sight lines) indicates that at the low column
densities found in the LISM, nitrogen ionization balance is important. Thus,
unlike O I, N I cannot be used as a proxy for H I or as a metallicity indicator
in the LISM.
  Subject Headings: cosmology: observations- ISM: abundances- ISM: evolution -
Galaxy:abundances-Ultraviolet:ISM


title: UV Imaging Polarimetry of the peculiar Seyfert 2 galaxy Mrk 477

abstract:
  We present the results of UV imaging polarimetry of the Seyfert 2 galaxy Mrk
477 taken by the Faint Object Camera onboard the Hubble Space Telescope (HST).
  From a previous HST UV image (lambda ~ 2180A), Mrk 477 has been known to have
a pointlike bright UV hotspot in the central region, peculiar among nearby
Seyfert 2 galaxies. There are also claims of UV/optical variability, unusual
for a Seyfert 2 galaxy. Our data show that there is an off-nuclear scattering
region ~ 0."6 (~ 500 pc) NE from the hotspot. The data, after the subtraction
of the instrumental effect due to this bright hotspot region, might indicate
that the scattered light is also detected in the central 0."2 radius region and
is extended to a very wide angle. The hotspot location is consistent with the
symmetry center of the PA pattern, which represents the location of the hidden
nucleus, but our data do not provide a strong upper limit to the distance
between the symmetry center and the hotspot. We have obtained high spatial
resolution color map of the continuum which shows that the nuclear spiral arm
of 0."4 scale (~ 300pc) is significantly bluer than the off-nuclear mirror and
the hotspot region. The nature of the hotspot is briefly discussed.


title: Quasar Absorption Lines

abstract:
  The absorption lines observed in quasar spectra have given us a detailed
picture of the intergalactic medium and the metal abundance and kinematics of
high redshift galaxies. In this review, we present an introduction to the
field, starting with the techniques used for interpreting absorption line
spectra. We then survey the observational and theoretical development of our
understanding of the Lyman-alpha forest, the metal absorbers, and the damped
Ly-alpha absorbers. We conclude with a discussion of some of the remaining
outstanding issues, and prospects for the future.


title: Interacting Dark Matter disguised as Warm Dark Matter

abstract:
  We explore some of the consequences of Dark Matter-photon interactions on
structure formation, focusing on the evolution of cosmological perturbations
and performing both an analytical and a numerical study. We compute the cosmic
microwave background anisotropies and matter power spectrum in this class of
models. We find, as the main result, that when Dark Matter and photons are
coupled, Dark Matter perturbations can experience a new damping regime in
addition to the usual collisional Silk damping effect. Such Dark Matter
particles (having quite large photon interactions) behave like Cold Dark Matter
or Warm Dark Matter as far as the cosmic microwave background anisotropies or
matter power spectrum are concerned, respectively. These Dark Matter-photon
interactions leave specific imprints at sufficiently small scales on both of
these two spectra, which may allow to put new constraints on the acceptable
photon-Dark Matter interactions. Under the conservative assumption that the
abundance of 10^12 M_sol galaxies is correctly given by Cold Dark Matter, and
without any knowledge of the abundance of smaller objects, we obtain the limit
on the ratio of the Dark Matter-photon cross section to the Dark Matter mass
sigma_{gamma-DM} / m_DM < 10^-6 sigma_Thomson / 100 GeV \sim 6 * 10^-33 cm^2
GeV^-1 .


title: Adiabatic and entropy perturbations in cosmology

abstract:
  This PhD thesis presents a study of the effect and generation of
non-adiabatic perturbations in Cosmology. We study adiabatic (curvature) and
entropy (isocurvature) perturbations produced during a period of cosmological
inflation that is driven by multiple scalar fields with an arbitrary
interaction potential. A local rotation in field space is performed to separate
out the adiabatic and entropy modes. The resulting field equations show
explicitly how on large scales entropy perturbations can source adiabatic
perturbations if the background solution follows a curved trajectory in field
space, and how adiabatic perturbations cannot source entropy perturbations in
the long-wavelength limit. We show why one in general expects the adiabatic and
entropy perturbations to be correlated at the end of inflation. Then, we
consider two-field preheating after inflation, examining conditions under which
entropy perturbations can alter the large-scale curvature perturbation and
showing how our new formalism has advantages in numerical stability when the
background solution follows a non-trivial trajectory in field space. Then we
compare the latest cosmic microwave background data with theoretical
predictions including correlated adiabatic and CDM isocurvature perturbations.
We find that there is a degeneracy between the amplitude of correlated
isocurvature perturbations and the spectral tilt. We then study perturbations
in Randall-Sundrum-type brane-world cosmologies. The density perturbations
generate Weyl curvature in the bulk, which in turn backreacts on the brane via
stress-energy perturbations. Bulk effects produce a non-adiabatic mode, even
when the matter perturbations are adiabatic, and alter the background dynamics.