title:
Optical and near-infrared observations of hard serendipitous Chandra
  sources

abstract:
  We have been carrying out a successful observational programme targeted at
finding the highly obscured quasars that are thought to be the main
contributors to the hard X-ray background. Out of 56 sources so far studied
with optical and near-infrared imaging and spectroscopy, we have found three
definite and a further twelve possible Type II quasars. Few sources show
significant line emission, suggesting that the line photons are depleted by the
large columns of obscuring matter. The redshift distribution of our sources
shows a distinct peak at z~1. The broad-band colours and magnitudes of the
optical/near-infrared counterparts indicate that the light in these bands is
dominated by the continuum of a massive bright galaxy.


title:
Massive galaxy clusters as gravitational telescopes for distant
  supernovae

abstract:
  We investigate the potential of using massive clusters as gravitational
telescopes for searches and studies of supernovae of Type Ia and Type II in
optical and near-infrared bands at central wavelengths in the interval 0.8-1.25
microns. Using high-redshift supernova rates derived from the measured star
formation rate, we find the most interesting effects for the detection of
core-collapse SNe in searches at limiting magnitudes m_lim~25-26.5 mag, where
the total detection rate could be significantly enhanced and the number of
detectable events is considerable even in a small field. For shallower
searches, ~24, a net gain factor of up to 3 in the discovery rate could be
obtained, and yet a much larger factor for very high source redshifts. For
programs such as the GOODS/ACS transient survey, the discovery rate of
supernovae beyond z~2 could be significantly increased if the observations were
done in the direction of massive clusters. For extremely deep observations,
m_lim > 27 mag, or for very bright SNe (e.g. Type Ia) the competing effect of
field reduction by lensing dominates, and fewer supernovae are likely to be
discovered behind foreground clusters.


title:
Stringent limits on the existence of Planck time from stellar
  interferometry

abstract:
  We present a method of directly testing whether time is `grainy' on scales of
<= t_P = (hbar G/c^5)^0.5 ~ 5.4E-44 s, the Planck time. If the phenomenon
exists, the energy and momentum of a photon (quantities which are independently
measured) will be subject to ultimate uncertainties of the form dE/E ~ dp/p ~
(E/E_P)^a, where E=h/t_P and a~1, because surpassing these will lead to
`super-clocks' and `super-rulers'. A well-known consequence is random
perturbation of the photon dispersion equation by a correction term which to
lowest order modifies the equation to the form p^2 = E^2[1 +/- a_o(E/E_P)^a],
where a_o ~ 1 and c=1. As a result, the two wave velocities will fluctuate by
different amounts, so that after propagating a sufficiently large distance the
phase of the radiation will no longer be well-defined. Now, at optical
frequencies, the technique of stellar interferometry readily ascertains whether
light from an astronomical object retains is phase information upon arrival.
Currently the furthest star from which interference fringes were seen, S Ser,
is at ~ 1 kpc, implying that all models with a <= 13/15 are to be rejected. The
decisive step, of course, is to test the presence or not of the first order
term E/E_P itself (i.e. a=1); for this one must await the imminent observations
of extra-galactic sources at > 1 Mpc by the Very Large Telescope Interferometer
(the VLTI). Based upon the S Ser result, nonetheless, it is already possible to
conclude that there is no first order departure from exactness in time over
intervals ~ 4.2E-40 s (~10^4 times longer than the Planck time).


title: The Soft X-ray Spectrum from NGC 1068 Observed with LETGS on Chandra

abstract:
  Using the combined spectral and spatial resolving power of the Low Energy
Transmission Grating (LETGS) on board Chandra, we obtain separate spectra from
the bright central source of NGC 1068 (Primary region), and from a fainter
bright spot 4" to the NE (Secondary region). Both spectra are dominated by line
emission from H- and He-like ions of C through S, and from Fe L-shell ions, but
also include narrow radiative recombination continua, indicating that most of
the soft X-ray emission arises in low-temperature (kT few eV) photoionized
plasma. We confirm the conclusions of Kinkhabwala et al. (2002), based on
XMM-Newton RGS observations, that the entire nuclear spectrum can be explained
by recombination/radiative cascade following photoionization, and radiative
decay following photoexcitation, with no evidence for hot, collisionally
ionized plasma. In addition, this model also provides an excellent fit to the
spectrum of the Secondary region, albeit with radial column densities a factor
of three lower, as would be expected given its distance from the source of the
ionizing continuum. The remarkable overlap and kinematical agreement of the
optical and X-ray line emission, coupled with the need for a distribution of
ionization parameter to explain the X-ray spectra, collectively imply the
presence of a distribution of densities (over a few orders of magnitude) at
each radius in the ionization cone. Relative abundances of all elements are
consistent with Solar abundance, except for N, which is 2-3 times Solar. The
long wavelength spectrum beyond 30 A is rich of L-shell transitions of Mg, Si,
S, and Ar, and M-shell transitions of Fe. The velocity dispersion decreases
with increasing ionization parameter, as deduced from these long wavelength
lines and the Fe-L shell lines.


title:
Neutrino-Matter Interaction Rates in Supernovae: The Essential
  Microphysics of Core Collapse

abstract:
  Neutrino-matter interaction rates are central to the core collapse phenomenon
and, perhaps, to the viability of the mechanism of core-collapse supernova
explosions. In this paper we catalog and discuss the major neutrino scattering,
absorption, and production processes that together influence the outcome of
core collapse and the cooling of protoneutron stars. These are the essential
inputs into the codes used to simulate the supernova phenomenon and an
understanding of these processes is a prerequisite to continuing progress in
supernova theory.


title: The Optical Afterglows of Gamma-Ray Bursts

abstract:
  The optical afterglows of gamma-ray bursts can be used to probe the physics,
geometry, and environments of gamma-ray bursts. In this article I discuss the
how spectra and photometry can be used to constrain fireball parameters,
describe several types of breaks that might be observed in the optical decay,
and briefly review the late-time bumps and rapid variations in optical light
curves.


title:
Testing the Seyfert Unification Theory: Chandra HETGS Observations of
  NGC 1068

abstract:
  We present spatially resolved Chandra HETGS observations of the Seyfert 2
galaxy NGC 1068. X-ray imaging and high resolution spectroscopy are used to
test the Seyfert unification theory. Fe K-alpha emission is concentrated in the
nuclear region, as are neutral and ionized continuum reflection. This is
consistent with reprocessing of emission from a luminous, hidden X-ray source
by the obscuring molecular torus and X-ray narrow-line region (NLR). We detect
extended hard X-ray emission surrounding the X-ray peak in the nuclear region,
which may come from the outer portion of the torus. Detailed modeling of the
spectrum of the X-ray NLR confirms that it is excited by photoionization and
photoexcitation from the hidden X-ray source. K-shell emission lines from a
large range of ionization states of H-like and He-like N, O, Ne, Mg, Al, Si, S,
and Fe XVII-XXIV L-shell emission lines are modeled. The emission measure
distribution indicates roughly equal masses at all observed ionization levels
in the range log xi=1-3. We separately analyze the spectrum of an off-nuclear
cloud. We find that it has a lower column density than the nuclear region, and
is also photoionized. The nuclear X-ray NLR column density, optical depth,
outflow velocity, and electron temperature are all consistent with values
predicted by optical spectropolarimetry for the region which provides a
scattered view of the hidden Seyfert 1 nucleus.


title: Closed universe and the first Doppler-peak of the CMB spectrum

abstract:
  We study universe models which are intrinsically closed and are full of a
quintessence scalar field, besides the Cold Dark Matter component. We use these
to depict diverse flat Cold Dark Matter models. With the background geometry
specified by the Friedman-Robertson-Walker metric, we include among them the
standard Cold Dark Matter, the Cosmological Constant Cold Dark Matter and the
Dark Energy or Quintessence Cold Dark Matter models. After describing these
models, we determine the position of the first Doppler peak of the Cosmic
Microwave Background anisotropy spectrum for $\Omega_T$ close to one; we also
study the shift parameter $R$.


title:
Universal Behavior of Phase Correlations in Non-linear Gravitational
  Clustering

abstract:
  The large-scale structure of the Universe is thought to evolve by a process
of gravitational amplification from low-amplitude Gaussian noise generated in
the early Universe. The later, non-linear stages of gravitation-induced
clustering produce phase correlations with well-defined statistical properties.
In particular, the distribution of phase differences $D$ between neighboring
Fourier modes provides useful insights into the clustering phenomenon. Here we
develop an approximate theory for the probability distribution $D$ and test it
using a large battery of numerical simulations. We find a remarkable universal
form for the distribution which is well described by theoretical arguments.


title:
IRFM Temperature Calibrations for the Vilnius, Geneva, RI(C) and DDO
  Photometric Systems

abstract:
  We have used the infrared flux method (IRFM) temperatures of a large sample
of late type dwarfs given by Alonso et al. (1996a) to calibrate empirically the
relations Teff = f (colour, [Fe/H]) for the Vilnius, Geneva, RI(C) and DDO
photometric systems. The resulting temperature scale and intrinsic
colour-colour diagrams for these systems are also obtained. From this scale,
the solar colours are derived and compared with those of the solar twin 18 Sco.
Since our work is based on the same Teff and [Fe/H] values used by Alonso et
al. (1996b) to calibrate other colours, we now have an homogeneous calibration
for a large set of photometric systems.


title: Radiation pattern of the isolated pulsar PSR B1828-11

abstract:
  Based on the free precession model of the isolated pulsar PSR B1828-11, Link
& Epstein 2001) showed that the observed pulse durations require the radio beam
to have a non-standard shape: the beam duration is larger for beam sweeps
farthest from the dipole axis. In their analysis they assumed that the actual
precession period is ~ 500 d. Recent theoretical studies suggested that the
actual precession period might be ~ 1000 d as seen in observations (Rezania
2002, Wasserman 2002). In this paper, in a good agreement with the observed
data (Stairs et al. 2000), we model the changes of the pulse shape in a
precession cycle with period ~ 1000 d and find that the variation of the pulse
duration follows from a {\it standard} beam pattern in each cycle.


title: 2dF Spectroscopy of M104 Globular Clusters

abstract:
  We present preliminary results of 2dF spectroscopy of globular clusters in
The Sombrero (M104). We find 56 new clusters, and compile a total sample of 103
velocities combined with previous data. Our 2dF data extend out to 20 arcmin
radius (~50 kpc), much further than previous studies. In the combined sample,
we tentatively find a steep drop in the velocity dispersion with radius, which
might possibly indicate a truncated halo. There is no obvious solid-body
rotation over all radii, but separate fits for those clusters inside and
outside 25 kpc radius show tantalizing evidence for counter-rotation. The
projected mass estimator with isotropic orbits yields an M104 mass of 1.2x10^12
solar masses inside 50 kpc, and a (M/L)_B = 30: solid evidence for a dark
matter halo in this galaxy.


title:
High-Resolution {\it Chandra} Spectroscopy of tau Scorpii: A Narrow-Line
  X-ray Spectrum From a Hot Star

abstract:
  Long known to be an unusual early-type star by virtue of its hard and strong
X-ray emission, tau Scorpii poses a severe challenge to the standard picture of
O-star wind-shock X-ray emission. The Chandra HETGS spectrum now provides
significant direct evidence that this B0.2 star does not fit this standard
wind-shock framework. The many emission lines detected with the Chandra
gratings are significantly narrower than what would be expected from a star
with the known wind properties of tau Sco, although they are broader than the
corresponding lines seen in late-type coronal sources. While line ratios are
consistent with the hot plasma on this star being within a few stellar radii of
the photosphere, from at least one He-like complex there is evidence that the
X-ray-emitting plasma is located more than a stellar radius above the
photosphere. The Chandra spectrum of tau Sco is harder and more variable than
those of other hot stars, with the exception of the young magnetized O star
theta Ori C. We discuss these new results in the context of wind, coronal, and
hybrid wind-magnetic models of hot-star X-ray emission.


title: A Resource Letter on Physical Eschatology

abstract:
  This Resource Letter treats the nascent discipline of physical eschatology,
which deals with the future evolution of astrophysical objects, including the
universe itself, and is thus both a counterpart and a complement to
conventional cosmology. While sporadic interest in these topics has flared up
from time to time during the entire history of humanity, a truly physical
treatment of these issues has only become possible during the last quarter
century. This Resource Letter deals with these recent developments. It offers a
starting point for understanding what the physical sciences might say about the
future of our universe and its constituents. Journal articles, books, and web
sites are provided for the following topics: history and epistemology of
physical eschatology, the future of the Solar system, the future of stars and
stellar systems, the global future of the universe, information processing and
intelligent communities, as well as some side issues, like the possible vacuum
phase transition and the so-called Doomsday Argument.


title:
Forecast for the Next Eon: Applied Cosmology and the Long-Term Fate of
  Intelligent Beings

abstract:
  Cosmology seems extremely remote from everyday human practice and experience.
It is usually taken for granted that cosmological data cannot rationally
influence our beliefs about the fate of humanity -- and possible other
intelligent species -- except perhaps in the extremely distant future, when the
question of heat death (in an ever-expanding universe) becomes actual. Here, an
attempt is made to show that it may become a practical issue much sooner, if an
intelligent community wishes to maximize its creative potential. New
developments in the fields of anthropic self-selection and physical eschatology
give solid foundations to such a conclusion. This may open some new (and
possibly urgent) issues in the areas of future policy making and transhumanist
studies generally. It may also give us a slightly better perspective on the
SETI endeavor.

categories: astro-ph gr-qc physics.pop-ph physics.soc-ph


title: EXIST: Mission Design Concept and Technology Program

abstract:
  The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed very large
area coded aperture telescope array, incorporating 8m^2 of pixellated Cd-Zn-Te
(CZT) detectors, to conduct a full-sky imaging and temporal hard x-ray (10-600
keV) survey each 95min orbit. With a sensitivity (5sigma, 1yr) of ~0.05mCrab
(10-150 keV), it will extend the ROSAT soft x-ray (0.5-2.5keV) and proposed
ROSITA medium x-ray (2-10 keV) surveys into the hard x-ray band and enable
identification and study of sources ~10-20X fainter than with the ~15-100keV
survey planned for the upcoming Swift mission. At ~100-600 keV, the ~1mCrab
sensitivity is 300X that achieved in the only previous (HEAO-A4, non-imaging)
all-sky survey. EXIST will address a broad range of key science objectives:
from obscured AGN and surveys for black holes on all scales, which constrain
the accretion history of the universe, to the highest sensitivity and
resolution studies of gamma-ray bursts it will conduct as the Next Generation
Gamma-Ray Burst mission. We summarize the science objectives and mission
drivers, and the results of a mission design study for implementation as a free
flyer mission, with Delta IV launch. Key issues affecting the telescope and
detector design are discussed, and a summary of some of the current design
concepts being studied in support of EXIST is presented for the wide-field but
high resolution coded aperture imaging and very large area array of imaging CZT
detectors. Overall mission design is summarized, and technology development
needs and a development program are outlined which would enable the launch of
EXIST by the end of the decade, as recommended by the NAS/NRC Decadal Survey.


title:
Far and mid infrared observations of two ultracompact H II regions and
  one compact CO clump

abstract:
  Two ultracompact H II regions (IRAS 19181+1349 and 20178+4046) and one
compact molecular clump (20286+4105) have been observed at far infrared
wavelengths using the TIFR 1 m balloon-borne telescope and at mid infrared
wavelengths using ISO. Far infrared observations have been made simultaneously
in two bands with effective wavelengths of ~ 150 and ~ 210 micron, using liquid
3He cooled bolometer arrays. ISO observations have been made in seven spectral
bands using the ISOCAM instrument; four of these bands cover the emission from
Polycyclic Aromatic Hydrocarbon (PAH) molecules. In addition, IRAS survey data
for these sources in the four IRAS bands have been processed using the HIRES
routine. In the high resolution mid infrared maps as well as far infrared maps
multiple embedded energy sources have been resolved. There are structural
similarities between the images in the mid infrared and the large scale maps in
the far infrared bands, despite very different angular resolutions of the two.
Dust temperature and optical depth (tau_150 um) maps have also been generated
using the data from balloon-borne observations. Spectral energy distributions
(SEDs) for these sources have been constructed by combining the data from all
these observations. Radiation transfer calculations have been made to
understand these SEDs. Parameters for the dust envelopes in these sources have
been derived by fitting the observed SEDs. In particular, it has been found
that radial density distribution for three sources is diffrent. Whereas in the
case of IRAS 20178+4046, a steep distribution of the form r^-2 is favoured, for
IRAS 20286+4105 it is r^-1 and for IRAS 19181+1349 it the uniform distribution
(r^0). Line ratios for PAH bands have generally been found to be similar to
those for other compact H II regions but different from general H II regions.


title: RAVE: The RAdial Velocity Experiment

abstract:
  RAVE (RAdial Velocity Experiment) is an ambitious program to conduct an
all-sky survey (complete to V = 16) to measure the radial velocities,
metallicities and abundance ratios of 50 million stars using the 1.2-m UK
Schmidt Telescope of the Anglo-Australian Observatory (AAO), together with a
northern counterpart, over the period 2006 - 2010. The survey will represent a
giant leap forward in our understanding of our own Milky Way galaxy, providing
a vast stellar kinematic database three orders of magnitude larger than any
other survey proposed for this coming decade. RAVE will offer the first truly
representative inventory of stellar radial velocities for all major components
of the Galaxy.
  The survey is made possible by recent technical innovations in multi-fiber
spectroscopy; specifically the development of the 'Echidna' concept at the AAO
for positioning fibers using piezo-electric ball/spines. A 1m-class Schmidt
telescope equipped with an Echidna fiber-optic positioner and suitable
spectrograph would be able to obtain spectra for over 20 000 stars per clear
night.
  Although the main survey cannot begin until 2006, a key component of the RAVE
survey is a pilot program of 100 000 stars which may be carried out using the
existing 6dF facility in unscheduled bright time over the period 2003--2005.


title: The FeII Optical Emission in AGN

abstract:
  We investigated the optical FeII emission in a sample of about 215
low-redshift AGN (quasars and luminous Seyfert 1 galaxies). We find that a
scaled and broadened FeII template based on the I Zw 1 spectrum can
satisfactorily model the FeII emission in almost all sources in our sample. We
confirm that FWHM H$\beta$ and FeII$\lambda$4570 are strongly correlated. The
correlation is different for sources with FWHM(H$\beta$) greater than or less
than $\sim$4000 km s$^{-1}$. Sources with FWHM H$\beta$$\leq$ 4000 km s$^{-1}$
(Population A) show no difference between FWHM H$\beta$ and FeII while sources
with FWHM(H$\beta$) $\geq$ 4000 km s$^{-1}$ (Population B) show FWHM FeII that
is systematically smaller than FWHM H$\beta$. This may be telling us that FeII
emission in Pop. B sources comes from only the outermost part of the H$\beta$\
emitting region where the degree of ionization is lowest.


title:
An accretion model for the growth of the central black hole associated
  with ionization instability in quasars

abstract:
  A possible accretion model associated with the ionization instability of
quasar disks is proposed to address the growth of the central black hole
harbored in the host galaxy.The mass ratio between black hole and its host
galactic bulge is a nature consequence of our model.


title:
Star Cluster Formation and Disruption Time-Scales - II. Evolution of the
  Star Cluster System in M82's Fossil Starburst

abstract:
  ABRIDGED: We obtain new age and mass estimates for the star clusters in M82's
fossil starburst region B, based on improved fitting methods. Our new age
estimates confirm the peak in the age histogram attributed to the last tidal
encounter with M81; we find a peak formation epoch at slightly older ages than
previously published, log(t_peak / yr) = 9.04, with a Gaussian sigma of Delta
log(t_width) = 0.273. Cluster disruption has removed a large fraction of the
older clusters. Adopting the expression for the cluster disruption time-scale
of t_dis(M)= t_dis^4 (M/10^4 Msun)^gamma with gamma = 0.62 (Paper I), we find
that the ratios between the real cluster formation rates in the pre-burst phase
(log(t/yr) <= 9.4), the burst-phase (8.4 < log(t/yr) < 9.4) and the post-burst
phase (log(t/yr) <= 8.4) are about 1:2:1/40. The mass distribution of the
clusters formed during the burst shows a turnover at log(M_cl/Msun) ~ 5.3 which
is not caused by selection effects. This distribution can be explained by
cluster formation with an initial power-law mass function of slope alpha=2 up
to a maximum cluster mass of M_max = 3 x 10^6 Msun, and cluster disruption with
a normalisation time-scale t_dis^4 / t_burst = (3.0 +/- 0.3) x 10^{-2}. For a
burst age of 1 x 10^9 yr, we find that the disruption time-scale of a cluster
of 10^4 Msun is t_dis^4 ~ 3 x 10^7 years, with an uncertainty of approximately
a factor of two. This is the shortest disruption time-scale known in any
galaxy.


title: X-ray continuum variability of MCG-6-30-15

abstract:
  This paper presents a comprehensive examination of the X-ray continuum
variability of the bright Seyfert 1 galaxy MCG-6-30-15. The source clearly
shows the strong, linear correlation between rms variability amplitude and flux
first seen in Galactic X-ray binaries. The high frequency power spectral
density (PSD) of MCG-6-30-15 is examined in detail using a Monte Carlo fitting
procedure and is found to be well represented by a steep power-law at high
frequencies (with a power-law index alpha ~ 2.5), breaking to a flatter slope
(alpha ~ 1) below f_br ~ 0.6 - 2.0 x 10^-4 Hz, consistent with the previous
results of Uttley, McHardy & Papadakis. The slope of the power spectrum above
the break is energy dependent, with the higher energies showing a flatter PSD.
At low frequencies the variations between different energy bands are highly
coherent while at high frequencies the coherence is significantly reduced. Time
lags are detected between energy bands, with the soft variations leading the
hard. The magnitude of the lag is small (<200 s for the frequencies observed)
and is most likely frequency dependent. These properties are remarkably similar
to the temporal properties of the Galactic black hole candidate Cygnus X-1. The
characteristic timescales in these two types of source differ by ~10^5;
assuming that these timescales scale linearly with black hole mass then
suggests a black hole mass ~10^6 M_sun for MCG-6-30-15. We speculate that the
timing properties of MCG-6-30-15 may be analogous to those of Cyg X-1 in its
high/soft state and discuss a simple phenomenological model, originally
developed to explain the timing properties of Cyg X-1, that can explain many of
the observed properties of MCG-6-30-15.


title: Cosmology with the S-Z Effect

abstract:
  Extensive recent work on the Sunyaev-Zeldovich (S-Z) effect reflects major
progress in observational capabilities of interferometric arrays, the improved
quality of multi-frequency measurements with upcoming ground-based and
stratospheric bolometer arrays, and the intense theoretical and experimental
work on the small scale structure of the cosmic microwave background (CMB)
radiation. I briefly describe the effect and discuss its significance as a
major cosmological probe. Recent results for the gas mass fraction in clusters
and the Hubble constant (largely from measurements with the BIMA and OVRO
interferometric arrays) are discussed. Also reviewed are results from the first
determination of the CMB temperature at the redshifts of two clusters (from
measurements with the MITO and SuZIE experiments), and recent work on the CMB
anisotropy due to the S-Z effect.


title:
2D analytical modeling of distortion and sky background in multi-fiber
  spectrographs: the case of the Norris spectrograph at Palomar Mountain

abstract:
  A method for optimal reduction of data taken with multi-fiber spectrographs
is described, based on global correction of their geometrical distortion.
Though it was specifically developed for reducing observations performed at
Palomar Mountain using the Norris fiber spectrograph, this method can be
adapted to other types of multi-object spectrographs such as the multi-slit
ones. Combined with a 2D analytical interpolation of sky-background that
accounts for non-uniform spectral resolution, the Norris software package
achieves very high accuracy in airglow subtraction, even in the near infrared
(7000-9000A) where molecular band-emissions commonly induce strong artefacts
that preclude clean sky subtraction whenever standard image processing
techniques are used. Correlatively, an improvement by a factor of 2 on the
precision of radial velocities is achievable. Throughout the paper possible
improvements to the method are suggested for those devising similar packages
for other instruments.


title:
A Mass Model for Estimating the Gamma Ray Background of the Burst and
  Transient Source Experiment

abstract:
  Orbiting x-ray and gamma ray instruments are subject to large background
count rates due to local particle fluxes in the space environment. The ability
of an instrument to make calibrated measurements of the flux from a source of
interest is highly dependent on accurately determining the background level. We
present here a method of calculating the energy dependent background flux for
any point in the complete data set recorded by the Burst and Transient Source
Experiment (BATSE) in its nine year mission. The BATSE Mass Model (BAMM) uses a
Monte Carlo mass modelling approach to produce a data base of the gamma ray
background which is then filtered to simulate the background count rate with a
2.048 second time resolution. This method is able to reduce the variations in
the background flux by a factor of 8 - 10, effectively `flat-fielding' the
detector response. With flat-fielded BATSE data it should be possible to use
the Earth occultation technique to produce a hard x-ray all sky survey to the
1-2 mCrab sensitivity limit. BAMM is also capable of estimating the
contribution to the spectra measured from gamma ray sources due to the
reprocessing of source photons in inactive material surrounding a gamma ray
detector. Possible applications of this aspect of the model in the area of
Gamma Ray Burst spectral analysis are discussed.


title: A Puzzling Paucity of Double Peaked X-ray Pulsars

abstract:
  Accretion powered pulsars exhibit a variety of lightcurves. In this paper we
propose to classify the observed lightcurves as single or double pulsed.We
analyze the lightcurves of 86 accretion powered pulsars and assign them to
these classes. We present three datasets: first in which the classification can
be easily done, second for which the classification is more difficult and not
certain, and third for which we were unable to classify the pulsar because of
lack of published data. We analyze a simple model in which the angles between
the magnetic and rotation axis $\beta$, and between the rotation axis and the
line of sight $\theta$ are random, and show that it is inconsistent with the
data. We also present a model in whichthe angle between the magnetic axis and
rotation axis is restricted and compare it with the data. This leads to an
upper limit on the angle $\beta < 40^\circ$. We conclude that there must be a
mechanism that leads to alignment of the magnetic and spin axis in X-ray
pulsars.


title:
XMM-Newton spectral analysis of the Pulsar Wind Nebula within the
  composite SNR G0.9+0.1

abstract:
  We present a study of the composite supernova remnant G0.9+0.1 based on
observations by XMM-Newton. The EPIC spectrum shows diffuse X-ray emission from
the region corresponding to the radio shell. The X-ray spectrum of the whole
Pulsar Wind Nebula is well fitted by an absorbed power-law model with a photon
index Gamma ~ 1.9 and a 2-10 keV luminosity of about 6.5 X 10^34 d^2_10 erg
s^-1 (d_10 is the distance in units of 10 kpc). However, there is a clear
softening of the X-ray spectrum with distance from the core, which is most
probably related to the finite lifetime of the synchrotron emitting electrons.
This is fully consistent with the plerionic interpretation of the Pulsar Wind
Nebula, in which an embedded pulsar injects energetic electrons into its
surrounding region. At smaller scales, the eastern part of the arc-like
feature, which was first revealed by Chandra observations, shows indications of
a hard X-ray spectrum with a corresponding small photon index (Gamma=1.0 +-
0.7), while the western part presents a significantly softer spectrum
(Gamma=3.2 +- 0.7). A possible explanation for this feature is fast rotation
and subsequent Doppler boosting of electrons: the eastern part of the torus has
a velocity component pointing towards the observer, while the western part has
a velocity component in the opposite direction pointing away from the observer.


title:
The soft X-ray background towards the northern sky. A detailed analysis
  of the Milky Way halo

abstract:
  We present a correlation analysis of the diffuse X-ray background emission of
the ROSAT all-sky survey with the Leiden/Dwingeloo 21-cm HI line survey. We
derive a consistent model for the diffuse X-ray background emission over about
50% of the sky. Only three diffuse X-ray components are necessary to fit the
ROSAT data from 0.1 keV to 2.4 keV: a) the Local Hot Bubble, b) the Milky Way
Halo, and c) the extragalactic X-ray background. Only one temperature of the
hot coronal gas in the Milky Way Halo is needed. Our model predicts, that a
major fraction of the 1/4 keV and about 50% of the 3/4 keV diffuse X-ray
emission originates from the Milky Way Halo. We detect a difference between the
intensities towards the Galactic center and its anti-center, which is
consistent with the electron density distribution independently derived from
pulsar dispersion measurements.


title: The Peculiar Nebula Simeis 57: I. Ionized Gas and Dust Extinction

abstract:
  We present high resolution radio continuum maps of the Galactic nebula Simeis
57 (= HS 191 = G 80.3+4.7) made with the WSRT and the DRAObservatory at
frequencies of 609, 1412 and 1420 MHz. At optical and at radio wavelengths, the
nebula has a peculiar ``S'' shape, crossed by long, thin and straight
filaments. The radio maps, combined with other maps from existing databases,
show essentially all radio emission from the peculiar and complex nebula to be
thermal and optically thin. Although neither the distance nor the source of
excitation of Simeis 57 are known, the nebula can only have a moderate electron
density of typically n(e) = 100 cm-3. Its mass is also low, not exceeding some
tens of solar masses. Peak emission measures are 5000 pc cm-6.Obscuring dust is
closely associated with the nebula, but seems to occur mostly in front of it.
Extinctions vary from A(V) = 1.0 mag to A(V) = 2.8 mag with a mean of about 2
mag. The extinction and the far-infrared emission at 100 microns are
well-correlated.


title:
The 3-D composition of the Galactic interstellar medium. The hot phases
  and X-ray absorbing material

abstract:
  We present maps of the Galactic X-ray Halo and constrain the location of
X-ray absorbing gas using the X-ray radiation transfer as distance a indicator.
Based on a consistent model of the soft X-ray background (SXRB) and the ROSAT
all-sky survey, we derive the morphology of some components involved in the
SXRB. In particular we focus on their spatial and temperature distributions
across the sky. Starting from our SXRB model, we extract information on the
3-dimensional composition of the X-ray emitting and absorbing material. Using
this approach, it is possible to differentiate between absorbing gas within or
behind the Galactic X-ray Halo.


title:
Discriminating between unresolved point sources and "negative" SZ
  clusters in CMB maps

abstract:
  Clusters of galaxies produce negative features at wavelengths $\lambda >
1.25$ mm in CMB maps, by means of the thermal SZ effect, while point radio
sources produce positive peaks. This fact implies that a distribution of
unresolved SZ clusters could be detected using the negative asymmetry
introduced in the odd-moments of the brightness map (skewness and higher), or
in the probability distribution function (PDF) for the fluctuations, once the
map has been filtered in order to remove the contribution from primordial CMB
fluctuations from large scales. This property provides a consistency check to
the recent detections from CBI and BIMA experiments of an excess of power at
small angular scales, in order to confirm that they are produced by a
distribution of unresolved SZ clusters. However it will require at least 1.5 -
2 times more observing time than detection of corresponding power signal. This
approach could also be used with the data of the planned SZ experiments (e.g.
ACT, AMI, AMIBA, APEX, 8 m South Pole telescope).


title: Optical Observations of Blazars: the Perugia Monitoring

abstract:
  In eight years, during the blazar monitoring program performed with the
Perugia automatic telescope, we were able to collect about 20000 $BVR_cI_c$
photometric points, contributing to get knowledge on the optical flux history
of many sources brighter than magnitude $V=17.0$. This intensive and constant
optical monitoring is essential to perform studies and multiwavelength campains
about this class of AGN. We illustrate our program and some examples of data
and preliminary results.


title: SN1999E: Another piece in the SN-GRB connection puzzle

abstract:
  Detailed optical and near-IR observations of SN 1999E have confirmed early
suggestions that this supernova was indeed a twin of the peculiar type II SN
1997cy: it was exceptionally luminous and had evolved slowly, and the line
profiles had narrow peaks and broad wings, indicating interaction with the
circumstellar material. Nevertheless, the most intriguing characteristic was
that, in analogy to SN 1997cy, it exploded at a position consistent in time and
location with a BATSE event (GRB980910). The "a posteriori" probability that
the only two SNe with such an optical appearance are associated with two
different BATSE GRB is only 0.2%. This raises the possibility that some GRB are
associated with H--rich SNe.


title: Neutrinos from Pulsar Wind Bubbles as Precursors to Gamma-Ray Bursts

abstract:
  The supranova model for gamma-ray bursts (GRBs) has recently gained
popularity. In this scenario the GRB occurs weeks to years after a supernova
explosion, and is located inside a pulsar wind bubble (PWB). High energy
protons from the PWB can interact with photons from the rich radiation field
inside the PWB or collide with cold protons from the supernova remnant,
producing pions which decay into \sim 10-10^3 TeV neutrinos. The predicted
neutrino flux from the PWBs that host the GRBs should be easily detectable by
planned 1 km^2 detectors.


title:
Evidence for An Intermediate-Age, Metal-rich Population of Globular
  Clusters in NGC 4365

abstract:
  We present spectroscopy for globular clusters (GCs) in the elliptical galaxy
NGC 4365, obtained with the LRIS spectrograph on the Keck I telescope. Previous
studies have shown that the optical color distribution of GCs in NGC 4365 lacks
the bimodal structure that is common in globular cluster systems, showing only
a single broad peak. Measurements of Balmer line indices (Hbeta, Hgamma and
Hdelta) on the GC spectra support recent suggestions by Puzia et al., based on
optical and near-infrared photometry, that some of the clusters in NGC 4365 are
intermediate-age (2-5 Gyrs) and metal-rich (-0.4<[Z/H]<0) rather than old
(~10-15 Gyrs) and metal-poor. We also find some genuinely metal-poor, old
clusters, suggesting that the ages and metallicities of the two populations
conspire to produce the single broad distribution observed in optical colors.


title: Microflares in accretion disks

abstract:
  We have investigated the phenomenon of explosive chromospheric evaporation
from an accretion disk as a mechanism for fast variability in accreting sources
such as low mass X-ray binaries and active galactic nuclei. This has been done
in the context of advection dominated accretion flows, allowing both high and
low states to be considered. This mechanism can in principle produce
sub-millisecond timescales in binaries and sub-minute timescales in active
galaxies. However, even considering the possibility that large numbers of these
microflares may be present simultaneously, the power emitted from these
microflares probably amounts to only a small fraction of the total X-ray
luminosity.


title: Radio Polarization from the Galactic Plane in Cygnus

abstract:
  We present 1420 MHz (lambda=21cm) observations of polarized emission from an
area of 117 degree square in the Galactic plane in Cygnus, covering 82 < l <
95, -3.5 < b < +5.5, a complex region where the line of sight is directed
nearly along the Local spiral arm. The angular resolution is ~ 1', and
structures as large as 45' are fully represented in the images. Polarization
features bear little resemblance to features detected in total power: while the
polarized signal arises in diffuse Galactic synchrotron emission regions, the
appearance of the polarized sky is dominated by Faraday rotation occurring in
small-scale structure in the intervening Warm Ionized Medium. There is no
concentration of polarization structure towards the Galactic plane, indicating
that both the emission and Faraday rotation occur nearby. We develop a
conceptual framework for interpretation of the observations. We can detect only
that polarized emission which has its origin closer than the polarization
horizon, at a distance d_ph; more distant polarized emission is undetectable
because of depth depolarization (differential Faraday rotation) and/or beam
depolarization (due to internal and external Faraday dispersion). d_ph depends
on the instrument used (frequency and beamwidth) as well as the direction being
studied. In our data we find that d_ph ~ 2 kpc, consistent with the
polarization features originating in the Local arm.


title: The Evolution of Nova Remnants

abstract:
  In this review I concentrate on describing the physical characteristics and
evolution of the nebular remnants of classical novae. I also refer as
appropriate to the relationship between the central binary and the ejected
nebula, particularly in terms of remnant shaping. Evidence for remnant
structure in the spectra of unresolved novae is reviewed before moving on to
discuss resolved remnants in the radio and optical domains. As cited in the
published literature, a total of 5 remnants have now been resolved in the radio
and 44 in the optical. This represents a significant increase since the time of
the last conference. We have also made great strides in understanding the
relationship of remnant shape to the evolution of the outburst and the
properties of the central binary. The results of various models are presented.
Finally, I briefly describe new results relating to the idiosyncratic remnant
of GK Per (1901) which help to explain the apparently unique nature of the
evolving ejecta before concluding with a discussion of outstanding problems and
prospects for future work.


title: ROSAT-HRI investigation of the NGC 507 X-ray halo

abstract:
  We present an X-ray investigation of the elliptical galaxy NGC 507. We make
use of archival Rosat HRI, PSPC and Chandra data, to connect the large-scale
structure of the halo to the core morphology. Our analysis shows that the halo
core (r<2-3 r_e) and the external halo (r>3 r_e) are characterised by different
dynamical properties and suggests a different origin of the two components. The
halo core has a complex morphology with a main X-ray emission peak, coincident
with the center of the optical galaxy, and several secondary peaks. The spatial
and spectral analysis of the central peak shows that this feature is produced
by denser hot gas in the galaxy core. Our data support the scenario where the
gas is kinetically heated by stellar mass losses. Comparison with previously
published studies suggest that the core of X-ray extended galaxies is
associated to the stellar distribution and has similar properties to the X-ray
halo of compact galaxies. The secondary peaks are due instead to interactions
between the radio-emitting plasma and the surrounding ISM. We found that the
energy input by the central radio source in the ISM may be large enough to
prevent gas from cooling. The total mass profile shows the presence of a dark
matter halo extending on cluster scales which is likely to be associated with
the whole cluster rather than with NGC 507. This structure is typical of many
X-ray bright Early-Type galaxies and may explain the spatial and spectral
differences with X-ray compact galaxies largely debated in literature. Finally
we discuss the nature of the point sources detected in the HRI FOV.


title: A massive warm baryonic halo in the Coma cluster

abstract:
  Several deep PSPC observations of the Coma cluster reveal a very large-scale
halo of soft X-ray emission, substantially in excess of the well known
radiation from the hot intra-cluster medium. The excess emission, previously
reported in the central region of the cluster using lower-sensitivity EUVE and
ROSAT data, is now evident out to a radius of 2.6 Mpc, demonstrating that the
soft excess radiation from clusters is a phenomenon of cosmological
significance. The X-ray spectrum at these large radii cannot be modeled
non-thermally, but is consistent with the original scenario of thermal emission
from warm gas at ~ 10^6 K. The mass of the warm gas is on par with that of the
hot X-ray emitting plasma, and significantly more massive if the warm gas
resides in low-density filamentary structures. Thus the data lend vital support
to current theories of cosmic evolution, which predict that at low redshift
\~30-40 % of the baryons reside in warm filaments converging at clusters of
galaxies.


title:
Interferometric Observations of Formaldehyde in the Protoplanetary Disk
  around LkCa15

abstract:
  Emission from the $2_{12}-1_{11}$ line of H$_2$CO has been detected and
marginally resolved toward LkCa15 by the Nobeyama Millimeter Array. The column
density of H$_2$CO is higher than that observed in DM Tau and than predicted by
theoretical models of disk chemistry; also the line-intensity profile is less
centrally peaked than that for CO. A similar behavior is observed in other
organic gaseous molecules in the LkCa 15 disk.


title:
Subaru high resolution spectroscopy of complex metal absorption lines of
  QSO HS1603+3820

abstract:
  We present a high resolution spectrum of the quasar, HS1603+3820
(z_em=2.542), observed with the High Dispersion Spectrograph (HDS) on Subaru
Telescope. This quasar, first discovered in the Hamburg/CfA Quasar Survey, has
11 C IV lines at 1.96 < z_abs < 2.55. Our spectrum covers 8 of the 11 C IV
lines at z_abs > 2.29 and resolves some of them into multiple narrow components
with b < 25 km/s because of the high spectral resolution R=45000, while other
lines show broad profiles (b > 65 km/s). We use three properties of C IV lines,
specifically, time variability, covering factor, and absorption line profile,
to classify them into quasar intrinsic absorption lines (QIALs) and spatially
intervening absorption lines (SIALs). The C IV lines at 2.42 < z_abs < 2.45 are
classified as QIALs in spite of their large velocity shifts from the quasar.
Perhaps they are produced by gas clouds ejected from the quasar with the
velocity of v_ej = 8000 km/s -- 10000 km/s. On the other hand, three C IV lines
at 2.48 < z_abs < 2.55 are classified as SIALs, which suggests there exist
intervening absorbers near the quasar. We, however, cannot rule out QIALs for
the two lines at z_abs ~ 2.54 and 2.55, because their velocity shifts, 430 km/s
blueward and 950 km/s redward of the quasar, are very small. The C IV line at
z_abs ~ 2.48 consists of many narrow components, and has also corresponding
low-ionization metal lines (Al II, Si II, and Fe II). The velocity distribution
of these low-ionization ions is concentrated at the center of the system
compared to that of high-ionization C IV ion. Therefore we ascribe this system
of absorption lines to an intervening galaxy.


title: Aperiodic variability of low-mass X-ray binaries at very low frequencies

abstract:
  We have obtained discrete Fourier power spectra of a sample of persistent
low-mass neutron-star X-ray binaries using long-term light curves from the All
Sky Monitor on board the Rossi X-ray Timing Explorer. Our aim is to investigate
their aperiodic variability at frequencies in the range 1 x 10^{-7}-5 x 10^{-6}
Hz and compare their properties with those of the black-hole source Cyg X-1. We
find that the classification scheme that divides LMXBs into Z and atoll sources
blurs at very low frequencies. Based on the long-term (~ years) pattern of
variability and the results of power-law fits (P ~ v^{-a}) to the 1 x 10^{-7}-5
x 10^{-6} Hz power density spectra, low-mass neutron-star binaries fall into
three categories. Type I includes all Z sources, except Cyg X-2, and the atoll
sources GX9+1 and GX13+1. They show relatively flat power spectra (a < 0.9) and
low variability (rms < 20%). Type II systems comprise 4U 1636-53, 4U 1735-44
and GX3+1. They are more variable (20% < rms < 30%) and display steeper power
spectra (0.9 < a < 1.2) than Type I sources. Type III systems are the most
variable (rms > 30%) and exhibit the steepest power spectra (a > 1.2). The
sources 4U 1705-44, GX354-0 and 4U 1820-30 belong to this group. GX9+9 and Cyg
X-2 appear as intermediate systems in between Type I and II and Type II and III
sources, respectively. We speculate that the differences in these systems may
be caused by the presence of different types of mass-donor companions. Other
factors, like the size of the accretion disc and/or the presence of weak
magnetic fields, are also expected to affect their low-frequency X-ray
aperiodic varibility.


title: Observational constraints on the afterglow of GRB 020531

abstract:
  We present the data acquired by the TAROT automated observatory on the
afterglow of GRB 020531. Up to now, no convincing afterglow emission has been
reported for this short/hard GRB at any wavelength, including X-ray and
optical. The combination of our early limits, with other published data allows
us to put severe constraints on the afterglow magnitude and light curve. The
limiting magnitude is 18.5 in R band, 88 minutes after the GRB, and the decay
slope power law index could be larger than 2.2.


title:
The Hubble Diagram of Type Ia Supernovae as a Function of Host Galaxy
  Morphology

abstract:
  (Abridged) We present new results on the Hubble diagram of distant type Ia
supernovae (SNe Ia) segregated according to the type of host galaxy. This makes
it possible to check earlier evidence for a cosmological constant by explicitly
comparing SNe residing in galaxies likely to contain negligible dust with the
larger sample. The cosmological parameters derived from these SNe Ia hosted by
presumed dust-free early-type galaxies supports earlier claims for a
cosmological constant, which we demonstrate at 5 sigma significance, and the
internal extinction implied is small even for late-type systems (A_B<0.2).
Thus, our data demonstrate that host galaxy extinction is unlikely to
systematically dim distant SNe Ia in a manner that would produce a spurious
cosmological constant. We classify the host galaxies of 39 distant SNe
discovered by the Supernova Cosmology Project (SCP) using the combination of
HST STIS imaging, Keck ESI spectroscopy and ground-based broad-band photometry.
We compare with a low-redshift sample of 25 SNe Ia. The scatter observed in the
SNe Ia Hubble diagrams correlates closely with host galaxy morphology. We find
the scatter in the SNe Ia Hubble diagram is smallest for SNe occurring in
early-type hosts and largest for those occurring in late-type galaxies.
Moreover, SNe residing in early-type hosts appear only ~0.14+/-0.09 mag
brighter in their light-curve-width-corrected luminosity than those in
late-type hosts, implying only a modest amount of dust extinction even in the
late-type systems.


title: The runaway black hole GRO J1655-40

abstract:
  We have used the Hubble Space Telescope to measure the motion in the sky and
compute the galactocentric orbit of the black hole X-ray binary GRO J1655-40.
The system moves with a runaway space velocity of $112\pm 18$ km s$^{-1}$ in a
highly eccentric ($e = 0.34\pm 0.05$) orbit. The black hole was formed in the
disk at a distance greater than 3 kpc from the Galactic centre and must have
been shot to such an eccentric orbit by the explosion of the progenitor star.
The runaway linear momentum and kinetic energy of this black hole binary are
comparable to those of solitary neutron stars and millisecond pulsars. GRO
J1655-40 is the first black hole for which there is evidence for a runaway
motion imparted by a natal kick in a supernova explosion.


title:
Direct detection of WIMPs with conventional (non-cryogenic) detectors.
  Experimental review

abstract:
  An overview of the current status of WIMP direct searches with conventional
detectors is presented, emphasizing strategies, achievements and prospects.


title:
Star Formation in Sculptor Group Dwarf Irregular Galaxies and the Nature
  of "Transition" Galaxies

abstract:
  We present new H-alpha narrow band imaging of the HII regions in eight
Sculptor Group dwarf irregular (dI) galaxies. Comparing the Sculptor Group dIs
to the Local Group dIs, we find that the Sculptor Group dIs have, on average,
lower values of SFR when normalized to either galaxy luminosity or gas mass
(although there is considerable overlap between the two samples). The
properties of ``transition'' (dSph/dIrr) galaxies in Sculptor and the Local
Group are also compared and found to be similar. The transition galaxies are
typically among the lowest luminosities of the gas rich dwarf galaxies.
Relative to the dwarf irregular galaxies, the transition galaxies are found
preferentially nearer to spiral galaxies, and are found nearer to the center of
the mass distribution in the local cloud. While most of these systems are
consistent with normal dI galaxies which currently exhibit temporarily
interrupted star formation, the observed density-morphology relationship (which
is weaker than that observed for the dwarf spheroidal galaxies) indicates that
environmental processes such as ``tidal stirring'' may play a role in causing
their lower SFRs.


title:
Very Light Jets I. Axisymmetric Parameter Study and Analytic
  Approximation

abstract:
  The propagation of extragalactic jets is studied by a series of twelve
axisymmetric hydrodynamic simulations. Motivated by observational constraints,
but unlike most previous simulations, the regime of jet to external medium
density (eta) from 10^-5 to 10^-2 is explored, for Mach numbers (M) between 2.6
and 26. The computational domain contained the bow shocks for the whole
simulation time. The bow shocks are found to be spherical at source sizes below
a critical value r1 (blastwave phase), which can reach up to 10 jet radii.
[...] The numerical work is complemented by an analytic approach for the
spherical phase. Extending previous work, the radial force balance could be
integrated for arbitrary background density and energy input, which results in
a global solution. The analytic results are shown to be consistent with the
numerical work, and a lower limit to r1 can be calculated, which falls below
the numerical results by a few jet radii. It is shown explicitely how a King
density distribution changes the discussed aspects of the bow shock
propagation. Because the jet head propagates very fast in the blastwave phase,
it turns out that it is not possible to ``frustrate'' a jet by a high density
environment. This is very important for the class of small radio galaxies
(compact symmetric objects / GHz peaked sources): They have to be young. During
its blastwave phase, a powerful jet can transfer typically 10^60 erg to the
environmental gas. This is enough to balance the radiative losses in a cooling
flow, if one of the cluster galaxies harbours a powerful jet every Gigayear.


title:
On the optical--infra-red continuum emission from equatorial discs of
  supergiant B[e] stars

abstract:
  Two models of the circumstellar disc around supergiant B[e] stars are
discussed: an equatorial wind model produced by wind bi-stability, and a
Keplerian viscous disc model. Both models are successful in providing a site
for dust formation once they have cooled sufficiently. However, the
optical--infra-red continuum is calculated and it is found that both models
have significant trouble in accounting for observations. In particular the
optical--near-IR emission is accounted for, but the dust emission is
underestimated by at least an order of magnitude. Variations in the structure
of the models (the temperature variation with radius, the density structure and
the dust opacity) are investigated to assess how (in)appropriate the standard
models are for supergiant B[e] star discs. Changing the temperature structure,
and making simple dust opacity changes within the disc has little effect on the
resultant continuum emission. By altering the density structure of the discs,
the continuum may be accounted for by both models: the equatorial wind model
requires a very flat density profile which is impossible to explain with any
accelerating wind, and the viscous disc model's density structure is required
to fall off less steeply with radius than would have been expected, although
this may be explained from consideration of viscous processes in the disc. It
is recognised that both theoretical interpretations have difficulties and
unsolved problems.


title:
Results of the ESO-SEST Key Programme on CO in the Magellanic Clouds.
  IX. The giant LMC HII region complex N11

abstract:
  We present maps and a catalogue containing the J=1-0 12CO parameters of 29
individual molecular clouds in the second-brightest LMC star formation complex,
N11. In the southwestern part of N11, molecular clouds occur in a ring or shell
surrounding the major OB star association LH9. In the northeastern part, a
chain of molecular clouds delineates the rim of one of the so-called supergiant
shells in the LMC. The well-defined clouds have dimensions close to those of
the survey beam (diameters of 25 pc or less). Some of the clouds were also
observed in J=2-1 12CO, and in the lower two transitions of 13CO. Clouds mapped
with a twice higher angular resolution in J=2-1 12CO show substructure with
dimensions once again comparable to those of the mapping beam. The few clouds
for which we could model physical parameters have fairly warm (T(kin) = 60 -
150 K) and moderately dense (n(H2) = 3000 cm-3) gas. The northeastern chain of
CO clouds, although lacking in diffuse intercloud emission, is characteristic
of the more quiescent regions of the LMC and appears to have been subject to
relatively little photo-processing. The clouds forming part of the southwestern
shell or ring, however, are almost devoid of diffuse intercloud emission and
also exhibit other characteristics of an extreme photon-dominated region (PDR).


title:
Rapid Variability and Annual Cycles in the Characteristic Time-scale of
  the Scintillating Source PKS 1257-326

abstract:
  Rapid radio intra-day variability (IDV) has been discovered in the southern
quasar PKS 1257-326. Flux density changes of up to 40% in as little as 45
minutes have been observed in this source, making it, along with PKS 0405-385
and J1819+3845, one of the three most rapid IDV sources known. We have
monitored the IDV in this source with the Australia Telescope Compact Array
(ATCA) at 4.8 and 8.6 GHz over the course of the last year, and find a clear
annual cycle in the characteristic time-scale of variability. This annual cycle
demonstrates unequivocally that interstellar scintillation is the cause of the
rapid IDV at radio wavelengths observed in this source. We use the observed
annual cycle to constrain the velocity of the scattering material, and the
angular size of the scintillating component of PKS 1257-326. We observe a time
delay, which also shows an annual cycle, between the similar variability
patterns at the two frequencies. We suggest that this is caused by a small (~10
microarcsecond) offset between the centroids of the 4.8 and 8.6 GHz components,
and may be due to opacity effects in the source. The statistical properties of
the observed scintillation thus enable us to resolve source structure on a
scale of ~10 microarcseconds, resolution orders of magnitude higher than
current VLBI techniques allow. General implications of scintillation for the
physical properties of sources and the turbulent ISM are discussed.


title:
Short-lived p-nuclides in the early solar system and implications on the
  nucleosynthetic role of X-ray binaries

abstract:
  The data available for short-lived $p$-nuclides are used in an open nonlinear
model of the chemical evolution of the Galaxy in order to discuss the origin of
extinct radionuclides, the stellar sources of $p$-nuclides, and the chronology
of solar system formation. It is concluded that the observed abundances of
$^{97}$Tc, $^{98}$Tc, $^{92}$Nb, and $^{146}$Sm in the early solar system are
consistent with nucleosynthesis in type II supernovae during continuous
chemical evolution of the Galaxy and a subsequent short isolation of the
presolar molecular cloud from fresh nucleosynthetic inputs. However, further
work on supernova models is needed before $p$-radionuclides will comprise
reliable cosmochronometers. Despite these limitations, we argue that niobium-92
can be used to test whether the {\it rp}-process contributed to the synthesis
of light {\it p}-nuclides in the Mo-Ru region.


title: Near IR Spectroscopy of Active Galactic Nuclei

abstract:
  Using the VLT together with the near infrared instrument ISAAC, we have
obtained medium spectral and high spatial resolution observations of a sample
of nearby Seyfert galaxies in the H-band. This band is particularly suited for
stellar population studies since the stellar component dominates over the AGN
nucleus. The H-band also includes the peak contribution from cool stars. The
AGN spectra are very rich in strong metallic lines which are sensitive to
stellar luminosity class. For 4 out of 5 galaxies the central velocity
dispersions are found to be significantly lower than reported in previous
studies. Gradients in the stellar population within the central regions were
searched for, together with evidence for dilution of the stellar spectral
features within the nucleus.


title: Quiet Sun magnetic fields at high spatial resolution

abstract:
  We present spectro-polarimetric observations of Inter-Network magnetic fields
at the solar disk center. A Fabry-Perot spectrometer was used to scan the two
Fe I lines at 6301.5 A and 6302.5 A. High spatial resolution (0.5")
magnetograms were obtained after speckle reconstruction. The patches with
magnetic fields above noise cover approximately 45% of the observed area. Such
large coverage renders a mean unsigned magnetic flux density of some 20 G (or
20 Mx/cm^2), which exceeds all previous measurements. Magnetic signals occur
predominantly in intergranular spaces. The systematic difference between the
flux densities measured in the two iron lines leads to the conclusion that,
typically, we detect structures with intrinsic field strengths larger than 1kG
occupying only 2% of the surface.


title: Radio galaxies and the star formation history of the universe

abstract:
  Multi-wavelength observations made in the last decade suggest that the
universe underwent an intense phase of star formation in the past (z > 1). This
intensive activity is commonly attributed to a higher galaxy merger rate when
the universe was a fraction of its present age. We examine the role of the
powerful radio sources whose comoving density is known to be a few orders of
magnitude higher at z ~ 2, the `quasar era'. Taking into account recent models
for the temporal evolution of the size and luminosity of a powerful double
radio source, as well as Lambda-CDM simulations of the cosmic web of baryonic
material at different redshifts, we argue that during the quasar era a high
fraction of the volume of the web was occupied by the lobes of double radio
sources. Widespread compression of protostellar clouds, triggered by the high
pressure of the synchrotron plasma of the radio lobes, can thus be expected to
have played a significant role in the global star formation history of the
universe. These lobes can also yield a rather high level of magnetization of
the intergalactic medium at these early cosmic epochs.


title:
Bragg gratings in multi-mode fiber optics for wavelength calibration of
  GAIA and RAVE spectra

abstract:
  We propose a new technique, the use of FBGs (fiber Bragg gratings), for
accurate, easy and low cost wavelength calibration of GAIA, RAVE and follow-ups
spectra at local Observatories. FBGs mark the spectra with absorption lines,
freely defined in number and position during the fibers manufacturing. The
process goes in parallel with the science exposure and through the same optical
train and path, thus ensuring the maximum return in wavelength calibration
accuracy. Plans to manufacture and test FBGs for the CaII/Paschen region are
underway at the Astronomical Observatory of Padova.


title: Time variation of fundamental constants: two phenomenological models

abstract:
  Time variation of fundamental constants, a strong signal of new physics, is
analyzed comparing extant data with two phenomenological models. Results are
discussed.


title: Magnetic Field in Supernovae

abstract:
  A relatively modest value of the initial rotation of the iron core, a period
of ~ 6-31 s, will give a very rapidly rotating protoneutron star and hence
strong differential rotation with respect to the infalling matter. Under these
conditions, a seed field is expected to be amplified by the MRI and to grow
exponentially. Exponential growth of the field on the time scale Omega^{-1} by
the magnetorotational instability (MRI) will dominate the linear growth process
of field line "wrapping" with the same characteristic time. The shear is
strongest at the boundary of the newly formed protoneutron star. Modest initial
rotation velocities of the iron core result in sub-Keplerian rotation and a
sub-equipartition magnetic field that nevertheless produce substantial MHD
luminosity and hoop stresses: saturation fields of order 10^{15} - 10^{16} G
develop ~ 300 msec after bounce with an associated MHD luminosity of ~ 10^{49}
- 10^{53} erg s^{-1}. Bi-polar flows driven by this MHD power can affect or
even cause the explosions associated with core-collapse supernovae. If the
initial rotation is too slow, then there will not be enough rotational energy
to power the supernova despite the high luminosities. The MRI should be active
and may qualitatively alter the flow if a black hole forms directly or after a
fall-back delay.


title: MEDEA: a real time imaging pipeline for pixel lensing

abstract:
  Pixel lensing is a technique used to search for baryonic components of dark
matter (MACHOs) and allows to detect microlensing events even when the target
galaxies are not resolved into individual stars. Potentially, it has the
advantage to provide higher statistics than other methods but, unfortunately,
traditional approaches to pixel lensing are very demanding in terms of
computing time. We present the new, user friendly, tool MEDEA (Microlensing
Experiment Data-Analysis Software for Events with Amplification). The package
can be used either in a fully automatic or in a semi-automatic mode and can
perform an on-line identification of events by means of a two levels trigger
and a quasi-on-line data analysis. The package will find application in the
exploration of large databases as well as in the exploitation of specifically
tailored future surveys.


title:
Using Multiwavelength Observations to Determine the Black Hole Mass and
  Accretion Rate in the Type 1 Seyfert Galaxy NGC 5548

abstract:
  We model the spectral energy distribution of the type 1 Seyfert galaxy NGC
5548, fitting data from simultaneous optical, UV, and X-ray monitoring
observations. We assume a geometry consisting of a hot central Comptonizing
region surrounded by a thin accretion disk. The properties of the disk and the
hot central region are determined by the feedback occurring between the hot
Comptonizing region and thermal reprocessing in the disk that, along with
viscous dissipation, provides the seed photons for the Comptonization process.
The constraints imposed upon this model by the multiwavelength data allow us to
derive limits on the central black hole mass, $M \la 2 \times 10^7$ \Msun, the
accretion rate, $\Mdot \la 2.5\times 10^5$ M$_\odot^2$yr$^{-1}/M$, and the
radius of the transition region between the thin outer disk and the
geometrically thick, hot inner region, $\sim 2$--5$\times 10^{14}$ cm.


title: Long-lived neutralino and ultra-high energy cosmic rays

abstract:
  Secondary photons from decays of metastable neutralinos can contribute to the
ultra-high energy cosmic ray flux. The neutralino production rate is too low in
acceleration mechanisms to affect the cosmic ray spectrum without emitting
enormous energy in photons and neutrinos. However, in top-down models with
sources not concentrated in galactic halos, neutralino decays change the
spectrum significantly. We estimate the parameters of a model in which photons
from neutralino decays are responsible for cosmic ray events with energies
above 10^20 eV, and figure out distinctive experimental signatures for this
model.


title: Expansion of the R4 Water Maser Arc Near Cepheus A HW 2

abstract:
  We present new (April 2000) MERLIN observations of the H2O masers located
near the protostar Cepheus A HW2. The MERLIN observations detect many of the
structures found in earlier (1996) VLBA observations of Torrelles and
collaborators, and the changed positions of these structures are compatible
with the VLBA proper motions and astrometric uncertainties. The radius of
curvature of the R4 structure of maser arcs appears to have grown by a factor
of two, and the displacement of the arcs between 1996 and 2000 are compatible
with expansion about a common center. In addition, the MERLIN observations
detect red-shifted masers not previously found; taken with the newly discovered
masers, the R4 structure now resembles patchy emission from an elliptical ring.
We demonstrate that a simple bow-shock model cannot simultaneously account for
the shape and the velocity gradient of the R4 structure. A model involving a
slow, hydromagnetic shock propagating into a rotating, circumstellar disk
better describes the maser spot kinematics and luminosities. In this model, the
central mass is 3 solar masses, and we demonstrate that the mass of the disk is
negligible in comparison. The expansion velocity of the post-shock gas, roughly
5 km / s, is slow compared to the average shock velocity (roughly 13 km / s)
suggesting that the post-shock gas is magnetically supported with a
characteristic field strength of roughly 30 mG. We speculate that the expanding
maser rings R4 and R5 may be generated by periodic, instability-driven winds
from young stars that periodically send spherical shocks into the surrounding
circumstellar material.


title:
Observational consequences of fine structure line optical depths on
  infrared spectral diagnostics

abstract:
  It has long been known that infrared fine structure lines of abundant ions,
like the [O III] 88 micron line, can become optically thick in H II regions
under certain high luminosity conditions. This could mitigate their potential
as diagnostic tools, especially if the source is too dusty for optical
spectroscopy to otherwise determine the system's parameters. We examined a
series of photoionization calculations which were designed to push the nebulae
into the limit where many IR lines should be quite optically thick. We find
that radiative transfer effects do not significantly change the observed
emission line spectrum. This is due to a combination of grain absorption of the
hydrogen ionizing continuum and the fact that the correction for stimulated
emission in these lines is large. Given these results, and the likelihood that
real objects have non-thermal line broadening, it seems unlikely that line
optical depth presents a problem in using these lines as diagnostics of the
physical conditions or chemical composition.


title:
Schechter vs. Schechter: Sub-Arcsecond Gravitational Lensing and Inner
  Halo Profiles

abstract:
  Sub-arcsecond lensing statistics depend sensitively on the inner mass
profiles of low-mass objects and the faint-end slopes of the Schechter
luminosity function and the Press-Schechter mass function. By requiring the
luminosity and mass functions to give consistent predictions for the
distribution of image separation below 1'', we show that dark matter halos with
masses below 10^12 M_sun cannot have a single type of profile, be it the
singular isothermal sphere (SIS) or the shallower ``universal'' dark matter
profile. Instead, consistent results are achieved if we allow a fraction of the
halos at a given mass to be luminous with the SIS profile, and the rest be dark
with an inner logarithmic slope shallower than -1.5 to compensate for the
steeper faint-end slope of the mass function compared with the luminosity
function. We quantify how rapidly the SIS fraction must decrease with
decreasing halo mass, thereby providing a statistical measure for the
effectiveness of feedback processes on the baryon content in low-mass halos.


title:
Cosmological Origin of the Stellar Velocity Dispersions in Massive
  Early-Type Galaxies

abstract:
  We show that the observed upper bound on the line-of-sight velocity
dispersion of the stars in an early-type galaxy, sigma<400km/s, may have a
simple dynamical origin within the LCDM cosmological model, under two main
hypotheses. The first is that most of the stars now in the luminous parts of a
giant elliptical formed at redshift z>6. Subsequently, the stars behaved
dynamically just as an additional component of the dark matter. The second
hypothesis is that the mass distribution characteristic of a newly formed dark
matter halo forgets such details of the initial conditions as the stellar
"collisionless matter" that was added to the dense parts of earlier generations
of halos. We also assume that the stellar velocity dispersion does not evolve
much at z<6, because a massive host halo grows mainly by the addition of
material at large radii well away from the stellar core of the galaxy. These
assumptions lead to a predicted number density of ellipticals as a function of
stellar velocity dispersion that is in promising agreement with the Sloan
Digital Sky Survey data.


title:
Elemental Abundances in the Broad Emission Line Region of Quasars at
  Redshifts larger than 4

abstract:
  We present observations of 11 high redshift quasars ($3.9 \la z \la 5.0$)
observed with low spectral resolution in the restframe ultraviolet using FORS 1
at the VLT UT 1. The emission-line fluxes of strong permitted and
intercombination ultraviolet emission lines are measured to estimate the
chemical composition of the line emitting gas. Comparisons to photoionization
calculations indicate gas metallicities in the broad emission line region in
the range of solar to several times solar. The average of the mean metallicity
of each high-z quasar in this sample is $Z/Z_\odot = 4.3 \pm 0.3$. Assuming a
chemical evolution time scale of $\tau_{evol} \simeq 0.5 - 0.8$ Gyrs, we derive
a redshift of $z_f \simeq 6 {\rm to} 8$ for the onset of the first major star
formation episode (H$_o = 65$ km s$^{-1}$ Mpc$^{-1}$, $\Omega_M = 0.3$,
$\Omega_\Lambda = 0.7$), corresponding to an age of the universe of several
$10^8$ yrs at this epoch. We note that this epoch is also supposed to be the
era of re-ionization of the universe.


title: Ionized Gas in the First 10 kpc of the Interstellar Galactic Halo

abstract:
  We present FUSE observations of the post-asymptotic giant branch star von
Zeipel 1128 (l=42.5, b=+78.7; z=10.0 kpc), located in the globular cluster
Messier 3. The FUSE observations cover the wavelength range 905-1187 Ang at ~20
km/s (FWHM) resolution. These data exhibit many photospheric and interstellar
absorption lines, including absorption from ions associated with the warm
neutral, warm ionized, and highly-ionized phases of the interstellar medium
along this sight line. Ionized hydrogen represents >12%, most likely ~45%, of
the total hydrogen column along this sight line, most of it associated with the
warm ionized phase. The warm ionized and neutral media toward von Zeipel 1128
have very similar gas-phase abundances and kinematics: the neutral and ionized
gases in this region of the thick disk are closely related. Strong O VI
absorption is seen with the same central velocity as the warm ionized gas,
though the O VI velocity dispersion is much higher (sigma=32 km/s). Virtually
all of the O VI is found at velocities where lower-ionization gas is seen,
suggesting the O VI and WNM/WIM probes are tracing different portions of the
same structures (e.g., the O VI may reside in interfaces surrounding the
WNM/WIM clouds). We see no evidence for interstellar absorption associated with
the globular cluster Messier 3 itself nor with the circumstellar environment of
von Zeipel 1128. Neither high velocity cloud absorption (with v(LSR)>125 km/s)
nor high velocity-dispersion gas (with sigma~60 km/s) is seen toward von Zeipel
1128. [Abridged]


title:
Chandra X-Ray Observatory observations of the globular cluster M28 and
  its millisecond pulsar B1821-24

abstract:
  We report here the results of the first Chandra X-Ray Observatory
observations of the globular cluster M28 (NGC 6626). 46 X-ray sources are
detected, of which 12 lie within one core radius of the center. We show that
the apparently extended X-ray core emission seen with the ROSAT HRI is due to
the superposition of multiple discrete sources for which we determine the X-ray
luminosity function down to a limit of about 6xE30 erg/s. For the first time
the unconfused phase-averaged X-ray spectrum of the 3.05-ms pulsar B1821--24 is
measured and found to be best described by a power law with photon index ~ 1.2.
Marginal evidence of an emission line centered at 3.3 keV in the pulsar
spectrum is found, which could be interpreted as cyclotron emission from a
corona above the pulsar's polar cap if the the magnetic field is strongly
different from a centered dipole. The unabsorbed pulsar flux in the 0.5--8.0
keV band is ~3.5xE-13 ergs/s/cm^2. Spectral analysis of the 5 brightest
unidentified sources is presented. Based on the spectral parameters of the
brightest of these sources, we suggest that it is a transiently accreting
neutron star in a low-mass X-ray binary, in quiescence. Fitting its spectrum
with a hydrogen neutron star atmosphere model yields the effective temperature
T_eff^\infty = 90^{+30}_{-10} eV and the radius R_NS^\infty =
14.5^{+6.9}_{-3.8} km. In addition to the resolved sources, we detect fainter,
unresolved X-ray emission from the central core of M28. Using the
Chandra-derived positions, we also report on the result of searching archival
Hubble Space Telescope data for possible optical counterparts.


title:
Massive Ellipticals at High Redshift: NICMOS Imaging of Z~1 Radio
  Galaxies

abstract:
  We present deep, continuum images of eleven high-redshift (0.811 < z < 1.875)
3CR radio galaxies observed with NICMOS. Our images probe the rest-frame
optical light where stars are expected to dominate the galaxy luminosity. The
rest-frame UV light of eight of these galaxies demonstrates the well-known
``alignment effect''. Most of the radio galaxies have rounder, more symmetric
morphologies at rest-frame optical wavelengths. Here we show the most direct
evidence that in most cases the stellar hosts are normal elliptical galaxies
with de Vaucouleurs law light profiles. For a few galaxies very faint traces of
the UV-bright aligned component are also visible in the infrared images. We
derive both the effective radius and surface-brightness for nine of eleven
sample galaxies by fitting surface-brightness models to them. We find their
sizes are similar to those of local FRII radio source hosts and are in general
larger than other local galaxies. The derived host galaxy luminosities are very
high and lie at the bright end of luminosity functions constructed at similar
redshifts. The galaxies in our sample are also brighter than the rest-frame
size--surface-brightness locus defined by the low-redshift sources. Passive
evolution roughly aligns the z ~ 1 galaxies with the low-redshift samples. The
optical host is sometimes centered on a local minimum in the rest-frame UV
emission, suggesting the presence of substantial dust obscuration. We also see
good evidence of nuclear point sources in three galaxies. Overall, our results
are consistent with the hypothesis that these galaxies have already formed the
bulk of their stars at redshifts greater than z >~ 2, and that the AGN
phenomenon takes place within otherwise normal, perhaps passively evolving,
galaxies. (abridged)


title:
Binarity in Brown Dwarfs: T Dwarf Binaries Discovered with the Hubble
  Space Telescope WPFC2

abstract:
  (abridged) We present the discovery of two T dwarf binaries, 2MASS
1225-2739AB and 2MASS 1534-2952AB, identified in a sample of ten T dwarfs
imaged with the Hubble Space Telescope Wide Field Planetary Camera 2. The
separations of the two binary systems are 0{\farcs}282$\pm$0{\farcs}005 and
0{\farcs}065$\pm$0{\farcs}007, implying projected separations of 3.17$\pm$0.14
and 1.0$\pm$0.3 AU, respectively. The observed binary fraction of our HST
sample, 20$^{+17}_{-7}$%, is consistent with results obtained for late-M and L
field dwarfs, and implies a bias-corrected binary fraction of 9$^{+15}_{-4}$%
for $a \gtrsim 1$ AU and $q \gtrsim 0.4$, significantly lower than the binary
fractions of F--G and early-type M dwarf stars. Neither of the T binaries have
separations $a \gtrsim 10$ AU, consistent with results from other brown dwarf
binary searches. We conclude that tidal disruption by passing stars or Giant
Molecular Clouds, which limits the extent of wide stellar binaries, plays no
role in eliminating wide brown dwarf binaries, implying either disruption very
early in the formation process (ages $\lesssim 1-10$ Myr) or a formation
mechanism which precludes such systems. We find that the maximum binary
separation in the brown dwarf regime appears to scale as M$_{total}^2$, a
possible clue to the physical mechanism which restricts wide substellar
systems.


title: Dynamical evolution of star clusters in tidal fields

abstract:
  We report results of a large set of N-body calculations aimed to study the
evolution of multi-mass star clusters in external tidal fields. Our clusters
start with the same initial mass-functions, but varying particle numbers,
orbital types and density profiles. Our main focus is to study how the stellar
mass-function and other cluster parameters change under the combined influence
of stellar evolution, two-body relaxation and the external tidal field. We find
that the lifetimes of star clusters moving on similar orbits scale as T sim
T_RH^x, where T_RH is the relaxation time, and the exponent x depends on the
initial concentration of the cluster and is around x approx 0.75. From the
results for the lifetimes, we predict that between 53% to 67% of all galactic
globular clusters will be destroyed within the next Hubble time. Low-mass stars
are preferentially lost and the depletion is strong enough to turn initially
increasing mass-functions into mass-functions which decrease towards the
low-mass end. The details of this depletion are insensitive to the starting
condition of the cluster. The preferential depletion of low-mass stars from
star clusters leads to a decrease of their mass-to-light ratios except for a
short period close to final dissolution. The fraction of compact remnants is
increasing throughout the evolution and they are more strongly concentrated
towards the cluster cores than main-sequence stars. For a sample of galactic
globular clusters with well observed parameters, we find a correlation between
the observed slope of the mass-function and the lifetimes predicted by us. It
seems possible that galactic globular clusters started with a mass-function
similar to what one observes for the average mass-function of the galactic disc
and bulge. (Abridged)


title: The Poynting-Robertson Effect and Secular Changes of Orbital Elements

abstract:
  The Poynting-Robertson (P-R) effect has been applied to meteoroids for
several decades. It is well known that the P-R effect produces only changes in
the orbital plane of the particle. The differential equations governing the
secular changes in both eccentricity and semi-major axis are known since the
time of Robertson, provided the initial orbits are not near circular. A
disadvantage of this type of osculating orbital elements is that it cannot be
applied to motion of arbitrarily shaped particles. Relevant type of osculating
orbital elements is discussed. It's application to the P-R effect is presented
and simple analytical formulae for secular changes in both eccentricity and
semi-major axis are derived.


title:
Sub-au imaging of water vapour clouds around four Asymptotic Giant
  Branch stars

abstract:
  We present MERLIN maps of the 22-GHz H2O masers around four low-mass
late-type stars (IK Tau U Ori, RT Vir and U Her), made with an angular
resolution of ~ 15 milliarcsec and a velocity resolution of 0.1 km s-1. The H2O
masers are found in thick expanding shells with inner radii ~ 6 to 16 au and
outer radii four times larger. The expansion velocity increases radially
through the H2O maser regions, with logarithmic velocity gradients of 0.5--0.9.
IK Tau and RT Vir have well-filled H2O maser shells with a spatial offset
between the near and far sides of the shell, which suggests that the masers are
distributed in oblate spheroids inclined to the line of sight. U Ori and U Her
have elongated poorly-filled shells with indications that the masers at the
inner edge have been compressed by shocks; these stars also show OH maser
flares. MERLIN resolves individual maser clouds, which have diameters of 2 -- 4
au and filling factors of only ~ 0.01 with respect to the whole H2O maser
shells. The CSE velocity structure gives additional evidence the maser clouds
are density bounded. Masing clouds can be identified over a similar timescale
to their sound crossing time (~2 yr) but not longer. The sizes and observed
lifetimes of these clouds are an order of magnitude smaller than those around
red supergiants, similar to the ratio of low-mass:high-mass stellar masses and
sizes. This suggests that cloud size is determined by stellar properties, not
local physical phenomena in the wind.


title: Stellar population gradients in Seyfert 2 galaxies

abstract:
  We study the variation of the stellar population properties as a function of
distance from the nucleus for a sample of 35 Seyfert 2 galaxies using the
technique of stellar population synthesis. We sample regions at the galaxies
with dimensions in the range 200 x 200 to 400 x 400 pc and compare the
synthesis results with those of a control sample of non-Seyfert galaxies. We
find that both at the nucleus and up to 3 kpc from it the oldest age component
(10 Gyr) presents a smaller contribution to the total flux in the Seyfert than
in the non-Seyfert galaxies of the same Hubble type, while the components
younger than 100 Myr present a larger contribution in the Seyfert's than in
non-Seyferts. In addition, while for the non-Seyferts clear gradients are
present, in which the contribution of the oldest components decrease with
distance from the nucleus and the contribution of the 1 Gyr component increases
-- we do not find such gradients in most Seyferts. These results suggest that
the AGN-starburst connection is a large scale phenomenon affecting not only the
inner few hundred parsecs, but the inner kiloparsecs.


title: On the evidence for brown-dwarf secondary stars in cataclysmic variables

abstract:
  We present the K-band spectrum of the cataclysmic variable LL And, obtained
using NIRSPEC on Keck-II. The spectrum shows no evidence for the absorption
features observed by Howell & Ciardi (2001), which these authors used to claim
a detection of a brown-dwarf secondary star in LL And. In light of our new
data, we review the evidence for brown-dwarf secondary stars in this and other
cataclysmic variables.


title:
The 3--D ionization structure of NGC 6818: a Planetary Nebula threatened
  by recombination

abstract:
  Long-slit NTT+EMMI echellograms of NGC 6818 (the Little Gem) at nine equally
spaced position angles, reduced according to the 3-D methodology introduced by
Sabbadin et al. (2000a,b), allowed us to derive: the expansion law, the
diagnostics and ionic radial profiles, the distance and the central star
parameters, the nebular photo-ionization model, the 3-D reconstruction in He
II, [O III] and [N II], the multicolor projection and a series of movies. The
Little Gem results to be a young (3500 years), optically thin (quasi-thin in
some directions) double shell (Mion~0.13 Msun) at a distance of 1.7 kpc, seen
almost equatorial on: a tenuous and patchy spherical envelope (r~0.090 pc)
encircles a dense and inhomogeneous tri-axial ellipsoid (a/2~0.077 pc,
a/b~1.25, b/c~1.15) characterized by a hole along the major axis and a pair of
equatorial, thick moustaches. NGC 6818 is at the start of the recombination
phase following the luminosity decline of the 0.625 Msun central star, which
has recently exhausted the hydrogen shell nuclear burning and is rapidly moving
toward the white dwarf domain (log T*~5.22 K; log(L*/Lsun)~3.1). The nebula is
destined to become thicker and thicker, with an increasing fraction of neutral,
dusty gas in the outermost layers. Only over some hundreds of years the plasma
rarefaction due to the expansion will prevail against the slower and slower
stellar decline, leading to a gradual re-growing of the ionization front. The
exciting star of NGC 6818 (mV~17.06) is a visual binary: a faint, red companion
(mV~17.73) appears at 0.09 arcsec in PA=190deg, corresponding to a separation
>=150 AU and to an orbital period >=1500 years


title: Feeding the active nucleus of NGC 1097

abstract:
  We discuss the signatures of an evolving accretion disk around the nucleus of
NGC 1097, based on observations of its double-peaked H-alpha emission-line
profile which cover a time span of 10 yrs. The monitoring of the profile has
allowed us to better constrain the inner radius of the accretion disk, and to
propose a scenario in which the ionizing source is getting dimmer and making
the peak of the disk emissivity to drift inwards.


title: Evolution of UV -- NIR Structural Properties of Cluster Galaxies

abstract:
  We study the structure and the internal colour gradients of cluster galaxies
from UV to NIR restframe, in the redshift range z=0.21-0.64. Structural
parameters (half light radius r_e, mean surface brightness mu_e and Sersic
index n) are derived. This data set constitutes the first large (N ~ 270)
sample of cluster galaxies whose internal structure in UV, optical (OPT) and
NIR (U-, V- and H-band restframe) can be investigated up to a look-back time of
~6 Gyr (Omega_m=0.3, Omega_Lambda=0.7 and H_0=70 Km/s/Mpc). Galaxies are
classified as spheroids or disks according to the shape of the light profile,
and the evolution of the two populations are investigated separately. On
average, both spheroids and disks are more concentrated at longer wavelengths:
the galaxy sizes become smaller from UV to NIR, while Sersic indices increase.
This trend shows an evolution in disks, where the mean ratio of optical to NIR
Sersic indices decreases from z=0.31 to z=0.64. Colour gradients are on average
negative at all redshifts and are stronger in disks than in spheroids.
  Colour gradients and central colours are compared with models of metallicity,
age, and dust extinction gradients. Metallicity turns out to be the primary
driver of colour gradients in spheroids, the age gradient being constrained to
be smaller than ~25%. For disks, two kinds of models fit the present data: (i)
age gradients (in the range [30,50]%) with significant dust extinction, and
(ii) `pure' dust models, in which the gradients of colour excess are a factor
of two higher in EIS 0048 than in the other clusters. Since colour gradients of
disks seem not to correlate significantly with inclination, we argue that age
gradient models could represent a more likely explanation of the present data,
in agreement with what expected on the basis of hierarchical merging scenarios.


title: XMM-Newton observation of PG 0844 + 349

abstract:
  In a ~ 20 ksec XMM-Newton observation the X-ray transient radio-quiet quasar
PG 0844+349 was found in a historically high state compared to previous X-ray
observations. The quasar showed a featureless spectrum with a strong soft
excess over the extrapolation of a hard power law. Comptonization models or a
broken power law with Gamma_{soft} ~ 2.75, Gamma_{hard} ~ 2.25 and a break
energy of E_{break} ~ 1.35 keV represent acceptable descriptions of the
spectral continuum. In the Comptonization models the temperature of the
Comptonizing gas is considerably lower than generally found in (broad line)
Seyfert galaxies whereas the optical depth is much higher. As a similar
behavior has been seen in NLSy1 galaxies, it might be an indicator of the
different physical conditions in these two classes of AGN. During the
XMM-Newton observation the flux of PG 0844+349 varied achromatically in a
smooth, nearly linear fashion, by ~ 25 % on time scales of a few thousand
seconds, which puts some constraints on current models of Comptonizing
accretion disk coronae.


title:
Observational Constraints on General Relativistic Energy Conditions,
  Cosmic Matter Density and Dark Energy from X-Ray Clusters of Galaxies and
  Type-Ia Supernovae

abstract:
  New observational constraints on the cosmic matter density $\Omega_m$ and an
effectively redshift-independent equation of state parameter $w_x$ of the dark
energy are obtained while simultaneously testing the strong and null energy
conditions of general relativity on macroscopic scales. The combination of
REFLEX X-ray cluster and type-Ia supernova data shows that for a flat Universe
the strong energy condition might presently be violated whereas the null energy
condition seems to be fulfilled. This provides another observational argument
for the present accelerated cosmic expansion and the absence of exotic physical
phenomena related to a broken null energy condition. The marginalization of the
likelihood distributions is performed in a manner to include a large fraction
of the recently discussed possible systematic errors involved in the
application of X-ray clusters as cosmological probes. This yields for a flat
Universe, $\Omega_m=0.29^{+0.08}_{-0.12}$ and $w_x=-0.95^{+0.30}_{-0.35}$
($1\sigma$ errors without cosmic variance). The scatter in the different
analyses indicates a quite robust result around $w_x=-1$, leaving little room
for the introduction of new energy components described by quintessence-like
models or phantom energy. The most natural interpretation of the data is a
positive cosmological constant with $w_x=-1 or something like it.


title: On binary pulsars and the force of gravity

abstract:
  The energy-momentum budget of the astrophysical systems can be studied by the
exact local conservation equation derived by Landau and Lifshitz. We show that
a similar equation is valid for the Einstein-Cartan gravity. We reanalyze a
binary pulsar system using the Landau-Lifshitz conservation equation and show
that the orbital period change rate can be completely understood as a curvature
backreaction process. Taking into account the detailed theoretical and
observational research of relativistic binary pulsar systems, especially the
system of Hulse and Taylor, we conclude that general relativity and
astrophysical observations rule out the existence of gravitational radiation.
We comment upon the LIGO GW events and their alternative explanation.


title: Xray observations of high redshift radio galaxies

abstract:
  I summarize Xray properties of high redshift radio galaxies, beginning with a
brief review of what has been learned from Xray observations of low redshift
powerful radio galaxies (in particular, Cygnus A), and then turning to Chandra
observations of four high redshift radio galaxies. Hot Xray emitting
atmospheres of the type seen in low redshift clusters are not detected in the
high redshift sources, suggesting that these systems are not yet virialized
massive clusters, but will likely evolve into such. Xray emission from highly
obscured AGN is detected in all cases. Extended Xray emission is also seen, and
the extended emission is clearly aligned with the radio source, and on a
similar spatial scale. Multiple mechanisms are proposed for this radio-Xray
alignment, including inverse Compton scattering of photons from the AGN (the
'Brunetti mechanism'), and thermal emission from ambient gas that is shocked
heated by the expanding radio source. The pressure in the high filling factor
shocked gas is adequate to confine the radio source and the low filling factor
optical line emitting clouds.


title:
Reprocessing the Hipparcos Intermediate Astrometric Data of
  spectroscopic binaries: II. Systems with a giant component

abstract:
  By reanalyzing the Hipparcos Intermediate Astrometric Data of a large sample
of spectroscopic binaries containing a giant, we obtain a sample of 29 systems
fulfilling a carefully derived set of constraints and hence for which we can
derive an accurate orbital solution. Of these, one is a double-lined
spectroscopic binary and six were not listed in the DMSA/O section of the
catalogue. Using our solutions, we derive the masses of the components in these
systems and statistically analyze them. We also briefly discuss each system
individually.


title: An Infrared View of Local Universe AGN

abstract:
  We summarize recent results on the infrared (IR) nuclear properties of
Seyfert galaxies. 100% of all Seyfert 1-1.9$ and ~50% of all Seyfert 2s in the
CfA and RSA samples observed with HST/NICMOS show nuclear point sources at
1.6micron. We find that the unresolved emission is variable in 9 out of the 14
Seyferts with duplicate observations, indicating a non-stellar origin. We have
also put together non-stellar 0.4-16micron spectral energy distributions (SEDs)
for the entire CfA sample of Seyfert galaxies. The shape of the SEDs for a
complete sample of AGN can be used to constrain torus models.We report a good
correlation between the IR and hard X-ray luminosities of local universe AGN
suggesting that their mid-IR emission is approximately an isotropic property,
and thus can be used as an indicator of the AGN luminosity. Finally we show
that the hard X-ray and mid-IR luminosities appear to be related to the black
hole mass in AGN.


title: Massive star formation in Luminous Infrared Galaxies

abstract:
  We present HST/NICMOS observations of a sample of LIRGs. We show that active
star formation appears to be occurring not only in the bright nuclei of these
galaxies, but also in luminous super-star clusters and giant HII regions with
ages of up to 20-40Myr. This population of bright clusters and HII regions is
unprecedented in normal galaxies and emphasizes the effects of the extreme star
formation in LIRGs.