title: Radial Velocity of the Phoenix Dwarf Galaxy: Linking Gas and Hi Gas

abstract:
  We present the first radial velocity measurement of the stellar component of
the Local Group dwarf galaxy Phoenix, using FORS1 at the VLT UT1 (ANTU)
telescope. From the spectra of 31 RGB stars, we derive an heliocentric optical
radial velocity of Phoenix Vo=-52 +/- 6 \kms. On the basis of this velocity,
and taking into account the results of a series of semi-analytical and
numerical simulations, we discuss the possible association of the HI clouds
observed in the Phoenix vicinity. We conclude that the characteristics of the
HI cloud with heliocentric velocity --23 \kms are consistent with this gas
having been associated with Phoenix in the past, and lost by the galaxy after
the last event of star formation in the galaxy, about 100 Myr ago. Two possible
scenarios are discussed: the ejection of the gas by the energy released by the
SNe produced in that last event of star formation, and a ram-pressure stripping
scenario. Both in the SNe ejection case and in the ram-pressure sweeping
scenario, the distances and relative velocities imply that the HI cloud is not
gravitationally bound to Phoenix, since this would require a Phoenix total mass
about an order of magnitude larger than its total estimated mass. Finally, we
discuss the possibility that Phoenix may be a bound Milky Way satellite. The
minimum required mass of the Milky Way for Phoenix to be bound is $M_{MW}(<450
{\rm kpc}) \ge 1.2 \times 10^{12}$ M$_{\odot}$ which comfortably fits within
most current estimates.


title: Formation of contact in massive close binaries

abstract:
  We present evolutionary calculations for 74 close binaries systems with
initial primary masses in the range 12...25 M_sun, and initial secondary masses
between 6 and 24 M_sun. The initial periods were chosen such that mass overflow
starts during the core hydrogen burning phase of the primary (Case A), or
shortly thereafter (Case B). We assume conservative evolution for contact-free
systems, i.e., no mass or angular momentum loss from those system except due to
stellar winds. We investigate the borderline between contact-free evolution and
contact, as a function of the initial system parameters. We also investigate
the effect of the treatment of convection, and found it relevant for contact
and supernova order in Case A systems, particularly for the highest considered
masses. For Case B systems we find contact for initial periods above
approximate 10 days and below. However, in that case (and for not too large
periods) contact occurs only after the mass ratio has been reversed, due to the
increased fraction of the donor's convective envelope. As most In all Cases we
find contact for mass ratios below approximate 0.65. We derive the observable
properties of our systems after the major mass transfer event, where the mass
gainer is a main sequence or supergiant O or early B type star, and the mass
loser is a helium star. We point out that the assumption of conservative
evolution for contact-free systems could be tested by finding helium star
companions to O stars.


title: Non-linear fluid dynamics of eccentric discs

abstract:
  A new theory of eccentric accretion discs is presented. Starting from the
basic fluid-dynamical equations in three dimensions, I derive the fundamental
set of one-dimensional equations that describe how the mass, angular momentum
and eccentricity vector of a thin disc evolve as a result of internal stresses
and external forcing. The analysis is asymptotically exact in the limit of a
thin disc, and allows for slowly varying eccentricities of arbitrary magnitude.
The theory is worked out in detail for a Maxwellian viscoelastic model of the
turbulent stress in an accretion disc. This generalizes the conventional alpha
viscosity model to account for the non-zero relaxation time of the turbulence,
and is physically motivated by a consideration of the nature of
magnetohydrodynamic turbulence. It is confirmed that circular discs are
typically viscously unstable to eccentric perturbations, as found by
Lyubarskij, Postnov & Prokhorov, if the conventional alpha viscosity model is
adopted. However, the instability can usually be suppressed by introducing a
sufficient relaxation time and/or bulk viscosity. It is then shown that an
initially uniformly eccentric disc does not retain its eccentricity as had been
suggested by previous analyses. The evolutionary equations should be useful in
many applications, including understanding the origin of planetary
eccentricities and testing theories of quasi-periodic oscillations in X-ray
binaries.


title: Gas dynamics and disk formation in 3:1 mergers

abstract:
  We performed N-body/SPH simulations of merging gas rich disk-galaxies with a
mass ratio of 3:1. A stellar disk and bulge component and a dark halo is
realized with collisionless particles, the gas is simulated using SPH
particles. In this paper we focus on the gas dynamics in mergers and its
influence on the structure of the final merger remnant, neglecting star
formation. During the merger around $8\times 10^9 M_{\odot}$ of gas accumulate
in the central region of the merger remnant (inside 300 pc). Part of the gas
falls to the center, channeled by a tidally induced bar in the more massive
galaxy. A peak accretion rate of 150 solar masses/year is reached when the two
galaxy centers merge. It is likely that the gas will experience a central
starburst and/or fuel a central black hole. The gas in the outer regions
accumulates in dense knots within tidal tails which could lead to the formation
of open clusters or dwarf satellites. Later on, the gas knots loose angular
momentum by dynamical friction and also sink to the center of the remnant,
thereby increasing the central gas content. In the end, the gas settles in a
central power-law disk with surface density $\Sigma \propto r^{-2}$ surrounded
by dense, orbiting gas clumps. The stellar profile is of de Vaucouleurs-type,
like in simulations of pure stellar mergers


title: Cosmic Supernova Rate History and Type Ia Supernova Progenitors

abstract:
  Adopting a single degenerate scenario for Type Ia supernova progenitors with
the metallicity effect, we make a prediction of the cosmic supernova rate
history as a composite of the supernova rates in spiral and elliptical
galaxies, and compare with the recent observational data up to z ~ 0.55.


title:
Radio Properties of the Shapley Concentration. IV. The A3528 Cluster
  Complex

abstract:
  We report and discuss the results of a 22 cm radio survey carried out with
the Australia Telescope Compact Array (ATCA) covering the A3528 complex, a
chain formed by the merging ACO clusters A3528-A3530-A3532, located in the
central region of the Shapley Concentration. Simultaneous 13 cm observations
are also presented. Our final catalogue includes a total of 106 radio sources
above the flux density limit of 0.8 mJy. By cross correlation with optical and
spectroscopic catalogues we found 32 optical counterparts, nine of them
belonging tothe A3528 complex. We explored the effects of cluster mergers on
the radio emission properties of radio galaxies by means of the radio
luminosity function (RLF) and radio source counts. We found that the radio
source counts are consistent with the background counts, as already found for
the A3558 complex (Paper III). The RLF for this complex is consistent, both in
shape and normalisation, with the general cluster luminosity function for
early-type galaxies derived by Ledlow & Owen (LO96). This result is different
from what we obtained for the A3558 merging complex, whose RLF is significantly
lower than LO96. We propose that the different stage of the merger is
responsible for the different RLFs in the two cluster complexes in the core of
the Shapley Concentration. The early stage of merger for the A3528 complex,
proposed by many authors, may have not yet affected the radio properties of
cluster galaxies, while in the more much advanced merger in the A3558 region we
actually see the effects of this process on the radio emission.


title:
Propagation of gamma-rays in massive binary Cen X-3: Interaction of
  cascade gamma-rays with the massive star

abstract:
  We consider the propagation of very high energy (VHE) gamma-rays in the
radiation field of the massive star of binary system Cen X-3. VHE gamma-rays or
electrons, injected by the compact object close to the surface of a massive
companion, develop inverse Compton pair (ICS) cascades. Based on the Monte
Carlo simulations, we obtain the fraction of secondary cascade photons which
collide with the surface of the massive companion in Cen X-3 system. The
distribution of photons falling on the surface of the massive star is
investigated. These photons interact with the atmosphere of the star and should
excite different gamma-ray lines (nuclear, electron-positron annihilation
line). We estimate that these gamma-ray lines can be likely detected by the
INTEGRAL telescopes.


title: Magnetically Collimated Jets with High Mass Flux

abstract:
  Recent numerical simulations and analytical models of magnetically collimated
plasma outflows from a uniformly rotating central gravitating object and/or a
Keplerian accretion disk have shown that relatively low mass and magnetic
fluxes reside in the produced jet. Observations however indicate that in some
cases, as in jets of YSO's, the collimated outflow carries higher fluxes than
these simulations predict. A solution to this problem is proposed here by
assuming that jets with high mass flux originate in a central source which
produces a noncollimated outflow provided that this source is surrounded by a
rapidly rotating accretion disk. The relatively faster rotating disk produces a
collimated wind which then forces all the enclosed outflow from the central
source to be collimated too. This conclusion is confirmed by self-consistent
numerical solutions of the full set of the MHD equations.


title: Formation of ellipticals by unequal mass mergers

abstract:
  Collisionless N-body simulations of merging disk-galaxies with mass ratios
($\eta$) of 1:1, 2:1, 3:1, and 4:1 have been performed using direct summation
with the special purpose hardware GRAPE. The simulations are used to examine
whether the formation of elliptical galaxies can be explained in the context of
the merger scenario. The photometric, kinematical and isophotal properties of
the merger remnants are investigated and turn out to be in very good agreement
with observations of giant elliptical galaxies. We conclude that equal mass
mergers lead to slowly rotating, anisotropic remnants having predominantly boxy
isophotes. Mergers with a mass ratio of 3:1 and 4:1, on the other hand, are
fast isotropic rotators with disky isophotes. Projection effects can explain
the observed scatter in the kinematical and isophotal properties of elliptical
galaxies.


title: Host Galaxies and the Spectral Variability of Quasars

abstract:
  Brightness variability of QSOs is associated with variations of the spectral
energy distribution in the optical-UV range. The observed change of the
spectral shape depends on the contribution of the host galaxy. Simulations,
taking into account luminosities and spectra expected for the host galaxies,
are compared with the observed spectral variability of a complete QSO sample.


title: Zero-metallicity stars I. Evolution at constant mass

abstract:
  We present extensive evolutionary models of stars with initial
zero-metallicity, covering a large range of initial masses (i.e. 0.7 <= M <=
100 Msun). Calculations are carried out at constant mass, with updated input
physics, and applying an overshooting scheme to convective boundaries. The
nuclear network includes all the important reactions of the p-p chain,
CNO-cycle and alpha-captures, and is solved by means of a suitable
semi-implicit method. The evolution is followed up to the thermally pulsing AGB
in the case of low- and intermediate-mass stars, or to the onset of carbon
burning in massive stars. The main evolutionary features of these models are
discussed, also in comparison with models of non-zero metallicity. Among
several interesting aspects, particular attention has been paid to describe: i)
the first synthesis of 12C inside the stars, that may suddenly trigger the
CNO-cycle causing particular evolutionary features; ii) the pollution of the
stellar surface by the dredge-up events, that are effective only within
particular mass ranges; iii) the mass limits which conventionally define the
classes of low-, intermediate-, and high-mass stars on the basis of common
evolutionary properties, including the upper mass limit for the achievement of
super-Eddington luminosities before C-ignition in the high-mass regime; and iv)
the expected pulsational properties of zero-metallicity stars. All relevant
information referring to the evolutionary tracks and isochrones is made
available in computer-readable format at http://pleiadi.pd.astro.it .


title:
Near-Infrared Spectroscopy of the Cassiopeia A and Kepler Supernova
  Remnants

abstract:
  Near-infrared spectra (0.95 - 2.4 micron) of the Cassiopeia A and Kepler
supernova remnants (SNRs) are presented. Low-dispersion (R = 700) spectra were
obtained for five bright fast-moving ejecta knots (FMKs) at two locations on
the main shell and for three bright circumstellar knots (QSFs) near the
southwest rim of Cas A. The main shell FMKs in Cas A exhibit a sparse
near-infrared spectrum dominated by [S II] 1.03 micron emission with a handful
of other, fainter emission lines. Among these are two high-ionization silicon
lines, [Si VI] 1.96 micron and [Si X] 1.43 micron, which have been detected in
AGNs and novae but never before in a supernova remnant. The near-infrared
spectra of circumstellar QSFs in Cas A show a much richer spectrum, with strong
He I 1.083 micron emission and over a dozen bright [Fe II] lines. Observed [Fe
II] line ratios indicate electron densities of 5 - 9 * 10^4 cm^-3 in the QSFs.
The Cas A QSF data are quite similar to the observed spectrum of a bright
circumstellar knot along the northwest rim of the Kepler SNR, which also shows
strong He I and [Fe II] emission with a measured electron density of 2.5 - 3 *
10^4 cm^-3. Finally, we present J- and K-band images of Cas A. The K-band image
shows faint diffuse emission which has no optical or mid-infrared counterpart
but is morphologically similar to radio continuum maps and may be infrared
synchrotron radiation.


title: Gamma-Ray Bursts: Afterglow Implications, Progenitor Clues and Prospects

abstract:
  Gamma-ray bursts (GRB) are sudden, intense flashes of gamma-rays which, for a
few blinding seconds, light up in an otherwise fairly dark gamma-ray sky. They
are detected at the rate of about once a day, and while they are on, they
outshine every other gamma-ray source in the sky, including the sun. Major
advances have been made in the last three or four years, including the
discovery of slowly fading x-ray, optical and radio afterglows of GRBs, the
identification of host galaxies at cosmological distances, and finding evidence
for many of them being associated with star forming regions and possibly
supernovae. Progress has been made in understanding how the GRB and afterglow
radiation arises in terms of a relativistic fireball shock model. These
advances have opened new vistas and questions on the nature of the central
engine, the identity of their progenitors, the effects of the environment, and
their possible gravitational wave, cosmic ray and neutrino luminosity. The
debates on these issues indicate that GRB remain among the most mysterious
puzzles in astrophysics.


title: Chandra Observations of "The Antennae" Galaxies (NGC 4038/39)

abstract:
  We report the results of a deep Chandra ACIS pointing at the merging system
NGC 4038/39. We detect an extraordinarily luminous population of X-ray sources,
with luminosity well above that of XRBs in M31 and the Milky Way. If these
sources are unbeamed XRBs, our observations may point to them being 10-100Mo
black hole counterparts. We detect an X-ray bright hot ISM, with features
including bright superbubbles associated with the actively star-forming knots,
regions where hot and warm (H$\alpha$) ISM intermingle, and a large-scale
outflow.


title:
Gravitational microlensing of planets: the influence of planetary phase
  and caustic orientation

abstract:
  Recent studies have demonstrated that detailed monitoring of gravitational
microlensing events can reveal the presence of planets orbiting the microlensed
source stars. With the potential of probing planets in the Galactic Bulge and
Magellanic Clouds, such detections greatly increase the volume over which
planets can be found. This paper expands on these original studies by
considering the effect of planetary phase on the form of the resultant
microlensing light curve. It is found that crescent-like sources can undergo
substantially more magnification than a uniformly illuminated disk, the model
typically employed in studying such planets. In fact, such a circularly
symmetric model is found to suffer a minimal degree of magnification when
compared to the crescent models. The degree of magnification is also a strong
function of the planet's orientation with respect to the microlensing caustic.
The form of the magnification variability is also strongly dependent on the
planetary phase and from which direction it is swept by the caustic, providing
further clues to the geometry of the planetary system. As the amount of light
reflected from a planet also depends on its phase, the detection of extreme
crescent-like planets requires the advent of 30-m class telescopes, while light
curves of planets at more moderate phases can be determined with today's 10-m
telescopes.


title:
Quasi-local evolution of cosmic gravitational clustering in the weakly
  non-linear regime

abstract:
  We investigate the weakly non-linear evolution of cosmic gravitational
clustering in phase space by looking at the Zel'dovich solution in the discrete
wavelet transform (DWT) representation. We show that if the initial
perturbations are Gaussian, the relation between the evolved DWT mode and the
initial perturbations in the weakly non-linear regime is quasi-local. That is,
the evolved density perturbations are mainly determined by the initial
perturbations localized in the same spatial range. Furthermore, we show that
the evolved mode is monotonically related to the initial perturbed mode. Thus
large (small) perturbed modes statistically correspond to the large (small)
initial perturbed modes. We test this prediction by using QSO Ly$\alpha$
absorption samples. The results show that the weakly non-linear features for
both the transmitted flux and identified forest lines are quasi-localized. The
locality and monotonic properties provide a solid basis for a DWT
scale-by-scale Gaussianization reconstruction algorithm proposed by Feng & Fang
(Feng & Fang, 2000) for data in the weakly non-linear regime. With the
Zel'dovich solution, we find also that the major non-Gaussianity caused by the
weakly non-linear evolution is local scale-scale correlations. Therefore, to
have a precise recovery of the initial Gaussian mass field, it is essential to
remove the scale-scale correlations.


title: The lives and deaths of star clusters near the Galactic center

abstract:
  We study the evolution and observability of young, compact star clusters near
the Galactic center, such as the Arches and Quintuplet systems. The clusters
are modeled by integrating the equations of motion of all stars while
accounting for the internal evolution of stars and binaries, as well as the
effect of the Galactic tidal field. We find that clusters within 150 pc of the
Galactic center dissolve within ~55 Myr, but their projected densities drop
below the background density in the direction of the Galactic center within
only a few Myr, effectively making these clusters undetectable after that time.
Detailed observations of the Arches cluster, taken at face value, suggest that
its mass function is unusually flat and that the cluster contains an
overabundance of stars more massive than 20 Msun. Our dynamical analysis,
however, shows that the observed characteristics of the Arches cluster are
consistent with a perfectly normal initial mass function. The observed
anomalies are then caused by a combination of observational selection effects
and the dynamical evolution of the cluster. We calibrate the current parameters
of the Arches cluster using a normal initial mass function and conclude that
the cluster is more massive than 40000 Msun, has a half mass radius of about
0.35 pc and is located between 50 and 90 pc from the Galactic center.


title:
Surface Photometric Calibration of the Infrared Tully-Fisher Relation
  Using Cepheid-based Distances of Galaxies

abstract:
  Infrared J and H surface photometry are carried out for nearby 12 galaxies
whose distances have been accurately measured via HST Cepheid observations.
Using the total, isophotal, and surface-photometric aperture magnitudes we
calibrate the infrared luminosity-line width relation (IRTF). It is found that
IRTF changes its slope at log W_{20}^c=2.45 in all the examined magnitude
systems. The apparent scatter of IRTF is not significantly reduced when surface
photometric magnitudes are used instead of the conventionally used synthetic
aperture magnitude H_{-0.5}. It is also shown that the color (I-H)_T of the
nearby calibrator galaxies is redder by 0.2mag than the Coma cluster galaxies,
but such a trend is not clearly visible for the Ursa Major mostly because of
poor statistics. The color offset of the Coma is analogous to that previously
found in I_T-H_{-0.5}. From the present calibration of H-band IRTF, we obtain
the distance to the Coma cluster to be m-M=34.94 +/- 0.13mag, where no account
is taken of the I-H color problem. Using the CMB-rest recession velocity of the
Coma cluster we obtain H_0=73 +/- 4 km/s/Mpc.


title:
The r-Process in Neutrino-Driven Winds from Nascent, "Compact" Neutron
  Stars of Core-Collapse Supernovae

abstract:
  We present calculations of r-process nucleosynthesis in neutrino-driven winds
from the nascent neutron stars of core-collapse supernovae. A full dynamical
reaction network for both the alpha-rich freezeout and the subsequent r-process
is employed. The physical properties of the neutrino-heated ejecta are deduced
from a general relativistic model in which spherical symmetry and steady flow
are assumed. Our results suggest that proto-neutron stars with a large
compaction ratio provide the most robust physical conditions for the r-process.
The third peak of the r-process is well reproduced in the winds from these
``compact'' proto-neutron stars even for a moderate entropy, \sim 100-200 N_A
k, and a neutrino luminosity as high as \sim 10^{52} ergs s^{-1}. This is due
to the short dynamical timescale of material in the wind. As a result, the
overproduction of nuclei with A \lesssim 120 is diminished (although some
overproduction of nuclei with A \approx 90 is still evident). The abundances of
the r-process elements per event is significantly higher than in previous
studies. The total-integrated nucleosynthesis yields are in good agreement with
the solar r-process abundance pattern. Our results have confirmed that the
neutrino-driven wind scenario is still a promising site in which to form the
solar r-process abundances. However, our best results seem to imply both a
rather soft neutron-star equation of state and a massive proto-neutron star
which is difficult to achieve with standard core-collapse models. We propose
that the most favorable conditions perhaps require that a massive supernova
progenitor forms a massive proto-neutron star by accretion after a failed
initial neutrino burst.


title:
The MACHO Project LMC Variable Star Inventory: X. The R Coronae Borealis
  Stars

abstract:
  We report the discovery of eight new R Coronae Borealis (RCB) stars in the
Large Magellanic Cloud (LMC) using the MACHO project photometry database. The
discovery of these new stars increases the number of known RCB stars in the LMC
to thirteen. We have also discovered four stars similar to the Galactic
variable DY Per. These stars decline much more slowly and are cooler than the
RCB stars. The absolute luminosities of the Galactic RCB stars are unknown
since there is no direct measurement of the distance to any Galactic RCB star.
Hence, the importance of the LMC RCB stars. We find a much larger range of
absolute magnitudes (M(V) = -2.5 to -5 mag) than inferred from the small
pre-MACHO sample of LMC RCB stars. It is likely that there is a temperature -
M(V)relationship with the cooler stars being intrinsically fainter. Cool (~5000
K) RCB stars are much more common than previously thought based on the Galactic
RCB star sample. Using the fairly complete sample of RCB stars discovered in
the MACHO fields, we have estimated the likely number of RCB stars in the
Galaxy to be ~3,200. The SMC MACHO fields were also searched for RCB stars but
none were found.


title:
A Pair of Compact Red Galaxies at Redshift 2.38, Immersed in a 100 kpc
  Scale Ly-alpha Nebula

abstract:
  We present Hubble Space Telescope (HST) and ground-based observations of a
pair of galaxies at redshift 2.38, which are collectively known as 2142-4420 B1
(Francis et al. 1996). The two galaxies are both luminous extremely red objects
(EROs), separated by 0.8 arcsec. They are embedded within a 100 kpc scale
diffuse Ly-alpha nebula (or blob) of luminosity ~10^44 erg/s.
  The radial profiles and colors of both red objects are most naturally
explained if they are young elliptical galaxies: the most distant yet found. It
is not, however, possible to rule out a model in which they are abnormally
compact, extremely dusty starbursting disk galaxies. If they are elliptical
galaxies, their stellar populations have inferred masses of ~10^11 solar masses
and ages of ~7x10^8 years. Both galaxies have color gradients: their centers
are significantly bluer than their outer regions. The surface brightness of
both galaxies is roughly an order of magnitude greater than would be predicted
by the Kormendy relation. A chain of diffuse star formation extending 1 arcsec
from the galaxies may be evidence that they are interacting or merging.
  The Ly-alpha nebula surrounding the galaxies shows apparent velocity
substructure of amplitude ~ 700 km/s. We propose that the Ly-alpha emission
from this nebula may be produced by fast shocks, powered either by a galactic
superwind or by the release of gravitational potential energy.


title:
Binned Cosmic Microwave Background Anisotropy Power Spectra: Peak
  Location

abstract:
  We use weighted mean and median statistics techniques to combine individual
cosmic microwave background (CMB) anisotropy detections and determine binned,
multipole-space, CMB anisotropy power spectra. The resultant power spectra are
peaked. The derived weighted-mean CMB anisotropy power spectrum is not a good
representation of the individual measurements in a number of multipole-space
bins, if the CMB anisotropy is Gaussian and correlations between individual
measurements are small. This could mean that some observational error bars are
underestimated, possibly as a consequence of undetected systematic effects.
Discarding the most discrepant 5% of the measurements alleviates but does not
completely resolve this problem. The median-statistics power spectrum of this
culled data set is not as constraining as the weighted-mean power spectrum.
Nevertheless it indicates that there is more power at multipoles $\ell \sim
150-250$ than is expected in an open cold dark matter (CDM) model, and it is
more consistent with a flat CDM model. Unlike the weighted-mean power spectrum,
the median-statistics power spectrum at $\ell \sim 400-500$ does not exclude a
second peak in the flat CDM model.


title:
Ground-based exoplanet near-infrared search by imaging and spectroscopy:
  3 new companion candidates in TWA

abstract:
  We report first results from our ground-based infrared imaging search for
sub-stellar companions (brown dwarfs and giant planets) of young (up to 100
Myrs) nearby (up to 100 pc) stars, where companions should be well separated
from the central stars and still relatively bright due to ongoing accretion
and/or contraction. Our observations are performed mainly with SOFI and SHARP
at the ESO 3.5m NTT on La Silla (imaging) and with ISAAC at the ESO 8.2m Antu
(VLT-UT1) on Cerro Paranal (imaging and spectroscopy), all in the H- and
K-bands. Here, we present new companion candidates around three T Tauri stars
(TWA-8 A, RXJ1121.1-3845, and RXJ1121.3-3447 N) in the TW Hya group, which
would have been sub-stellar if at the same distance and age as the T Tauri
stars, but are found to be background stars by spectroscopy.


title:
Cosmic Rays in the Energy Range of the Knee - Recent Results from
  KASCADE --

abstract:
  A brief motivation for studying cosmic rays at energies 10^14 < E < 10^17 eV
is given. Besides astrophysical interests in identifying and understanding
their sources, there are also particle physics aspects related to their
transport properties in the galaxy or to their detection via extensive air
showers. The KASCADE air shower experiment taking data at Forschungszentrum
Karlsruhe (Germany) provides important information to both of these topics of
particle-astrophysics research. A target of particular interest is the
so-called 'knee' in the cosmic ray energy spectrum at E_k = 4 x 10^15 eV.
Recent results adding knowledge to an understanding its origin will be
presented as well as results on tests of high-energy hadronic interaction
models required for air shower simulations.


title: Photometric study of the double cluster h and chi Persei

abstract:
  We present uvbybeta CCD photometry of the central region of the double
cluster h and chi Persei. We identify 350 stars, of which 214 were not included
in Oosterhof catalogue. Our magnitude limit V=16.5 allows us to reach early F
spectral type and obtain very accurate fits to the ZAMS. We derive reddening
values of E(b-y)=0.44+-0.02 for h Persei and E(b-y)=0.39+-0.05 for chi Persei.
  From the ZAMS fitting, we derive distance moduli V0-Mv=11.66+-0.20 and
V0-Mv=11.56+-0.20 for h and chi Persei respectively. These values are perfectly
compatible with both clusters being placed at the same distance and having
identical reddenings. The shift in the main-sequence turnoff and isochrone
fitting, however, show that there is a significant age difference between both
clusters, with the bulk of stars in h Persei being older than chi Persei. There
is, however, a significant population of stars in h Persei which are younger
than chi Persei. All this argues for at least three different epochs of star
formation, corresponding approximately to log t=7.0, 7.15 and 7.3.


title: Ionized Iron Lines in X-ray Reflection Spectra

abstract:
  We present results from new calculations of the X-ray reflection spectrum
from ionized accretion discs. These computations improve on our previous models
by including the condition of hydrostatic balance in the vertical direction,
following the work of Nayakshin, Kazanas & Kallman. We find that an ionized Fe
K$\alpha$ line is prominent in the reflection spectra for a wide variety of
physical conditions. The results hold for both gas and radiation pressure
dominated discs and when the metal abundances have been varied.


title: Radiative transfer for the FIRST era

abstract:
  This paper presents a brief overview of some recent advances in numerical
radiative transfer, which may help the molecular astrophysics community to
achieve new breakthroughs in the interpretation of spectro-(polarimetric)
observations.


title: Radiative transfer in molecular lines

abstract:
  The highly convergent iterative methods developed by Trujillo Bueno and
Fabiani Bendicho (1995) for radiative transfer (RT) applications are
generalized to spherical symmetry with velocity fields. These RT methods are
based on Jacobi, Gauss-Seidel (GS), and SOR iteration and they form the basis
of a new NLTE multilevel transfer code for atomic and molecular lines. The
benchmark tests carried out so far are presented and discussed. The main aim is
to develop a number of powerful RT tools for the theoretical interpretation of
molecular spectra.


title: Relativistic Blastwaves and Synchrotron Emission

abstract:
  Relativistic shocks accelerate particles by the first order Fermi mechanism.
These particles then emit synchrotron emission in the post shock gas. We have
developed a numerical code which integrates the relativistic Euler equations
for fluid dynamics with a general equation of state, together with the
Liouville equation for the accelerated particles. We present tests of this code
and, in addition, we use it to study the gamma ray burst afterglow predicted by
the fireball model, along with the hydrodynamics of a relativistic blastwave.
  We find that, while, broadly speaking, the behaviour of the emission is
similar to that already predicted with semi-analytic approaches, the detailed
behaviour is somewhat different. The ``breaks'' in the synchrotron spectrum
behave differently with time, and the spectrum above the final break is harder
than previously expected. These effects are due to the incorporation of the
geometry of the (spherical) blastwave, along with relativistic beaming and
adiabatic cooling of the energetic particles leading to a mix, in the observed
spectrum, between recently injected "uncooled" particles and the older "cooled"
population in different parts of the evolving, inhomogeneous flow.


title:
The effect of stellar evolution upon Population II Contact Binaries in
  the Period-Color Relation. I. Equal-Mass, Marginal Contact Systems

abstract:
  Field W UMa binaries observe a well known Period-Color Relation such that
systems containing more massive stars are bluer and have longer orbital periods
than those systems with lower mass components. However, it has been known for a
decade that metal-poor W UMa's are too blue, have too short an orbital period,
or both. Correcting the observed color for the reduced line blanketing in the
atmosphere of a Pop II star only accounts for part of the observed discrepancy.
As others have suggested, and Rucinski (2000) show, the smaller radii of Pop II
stars and the correspondingly shorter orbital periods are responsible for the
remainder. In this paper I investigate the effect of evolution upon the
location in the period-color plane. This paper addresses the restricted case of
equal mass components in critical contact with their inner Roche lobes, but
should be applicable to the more general cases to the extent that the relative
sizes of stellar components are preserved with metallicity changes.
  The calculated metallicity-age dependent Period-Color Relations substantially
agree with Rucinski & Duerbeck's (1997) empirically derived corrections to the
Period-Color Relation over most of the investigated range of periods. However,
our predictions deviate to a greater degree as stellar age increases since
their parameterization does not include the effect of evolution.


title:
The Pearson-Readhead Survey of Compact Extragalactic Radio Sources From
  Space. I. The Images

abstract:
  We present images from a space-VLBI survey using the facilities of the VLBI
Space Observatory Programme (VSOP), drawing our sample from the well-studied
Pearson-Readhead survey of extragalactic radio sources. Our survey has taken
advantage of long space-VLBI baselines and large arrays of ground antennas,
such as the Very Long Baseline Array and European VLBI Network, to obtain high
resolution images of 27 active galactic nuclei, and to measure the core
brightness temperatures of these sources more accurately than is possible from
the ground. A detailed analysis of the source properties is given in
accompanying papers. We have also performed an extensive series of simulations
to investigate the errors in VSOP images caused by the relatively large holes
in the (u,v) plane when sources are observed near the orbit normal direction.
We find that while the nominal dynamic range (defined as the ratio of map peak
to off-source error) often exceeds 1000:1, the true dynamic range (map peak to
on-source error) is only about 30:1 for relatively complex core-jet sources.
For sources dominated by a strong point source, this value rises to
approximately 100:1. We find the true dynamic range to be a relatively weak
function of the difference in position angle (PA) between the jet PA and (u,v)
coverage major axis PA. For low signal-to-noise regions typically located down
the jet away from the core, large errors can occur, causing spurious features
in VSOP images that should be interpreted with caution.


title:
DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries
  and Cepheids. VII. Additional Variables in the Field M33A Discovered with
  Image Subtraction

abstract:
  DIRECT is a project to obtain directly the distances to two Local Group
galaxies, M31 and M33, which occupy a crucial position near the bottom of the
cosmological distance ladder. As the first step of the DIRECT project we have
searched for detached eclipsing binaries (DEBs) and new Cepheids in the M31 and
M33 galaxies with 1m-class telescopes. In this seventh paper we present a
catalog of variable stars discovered in the data from the followup observations
of DEB system D33J013346.2+304439.9 in field M33A [(RA,Dec)= (23.55, 30.72),
J2000.0], collected with the Kitt Peak National Observatory 2.1m telescope. In
our search covering an area of 108 sq. arcmin. we have found 434 variable
stars: 63 eclipsing binaries, 305 Cepheids, and 66 other periodic, possible
long period or non-periodic variables. Of these variables 280 are newly
discovered, mainly short-period and/or faint Cepheids. Their light curves were
extracted using the ISIS image subtraction package. For 85% of the variables we
present light curves in standard V and B magnitudes, with the remaining 15%
expressed in units of differential flux. We have discovered a population of
first overtone Cepheid candidates and for eight of them we present strong
arguments in favor of this interpretation. We also report on the detection of a
non-linearity in the KPNO T2KA and T1KA cameras. The catalog of variables, as
well as their photometry (about 7.8*10^4 BV measurements) and finding charts,
is available electronically via anonymous ftp and the World Wide Web. The
complete set of the CCD frames is available upon request.


title:
Observations of the bright radio sources in the North Celestial Pole
  region at the RATAN-600 radio telescope

abstract:
  A survey of the North Celestial Pole region using the RATAN-600 radio
telescope at five frequencies in the range 2.3 to 21.7 GHz is described.
Sources were chosen from the NVSS catalogue. The flux densities of 171 sources
in the Declination range +75 to +88 are presented; typical flux density errors
are 5-10 percent including calibration errors. About 20 percent of the sources
have flat spectra or a flat component.


title:
The Pearson-Readhead Survey of Compact Extragalactic Radio Sources From
  Space. II. Analysis of Source Properties

abstract:
  We have performed a multi-dimensional correlation analysis on the observed
properties of a statistically complete core-selected sample of compact
radio-loud active galactic nuclei, based on data from the VLBI Space Observing
Programme (Paper I) and previously published studies. Our sample is drawn from
the well-studied Pearson-Readhead (PR) survey, and is ideally suited for
investigating the general effects of relativistic beaming in compact radio
sources. In addition to confirming many previously known correlations, we have
discovered several new trends that lend additional support to the beaming
model. These trends suggest that the most highly beamed sources in
core-selected samples tend to have a) high optical polarizations; b) large
pc/kpc-scale jet misalignments; c) prominent VLBI core components; d)
one-sided, core, or halo radio morphology on kiloparsec scales; e) narrow
emission line equivalent widths; and f) a strong tendency for intraday
variability at radio wavelengths. We have used higher resolution space and
ground-based VLBI maps to confirm the bi-modality of the jet misalignment
distribution for the PR survey, and find that the sources with aligned parsec-
and kiloparsec-scale jets generally have arcsecond-scale radio emission on both
sides of the core. The aligned sources also have broader emission line widths.
We find evidence that the BL Lacertae objects in the PR survey are all highly
beamed, and have very similar properties to the high-optically polarized
quasars, with the exception of smaller redshifts. A cluster analysis on our
data shows that after partialing out the effects of redshift, the luminosities
of our sample objects in various wave bands are generally well-correlated with
each other, but not with other source properties.


title: BATSE Observations of Fast X-ray Transients Detected by BeppoSAX-WFC

abstract:
  The BeppoSAX Wide Field Cameras have been successful in detecting gamma-ray
bursts in the 2--26 keV energy range. While most detected bursts are also
strong emitters at higher energies, a significant fraction have anomalously low
gamma-ray flux. The nature of these "Fast X-ray Transients" (FXTs), and their
relation to gamma-ray bursts (GRBs), is unknown. We use BATSE untriggered
continuous data to examine the >20 keV gamma-ray properties of the events
detected in common with BeppoSAX. Temporal and spectral characteristics, such
as peak flux, fluence, duration, and spectrum are compared to the full
population of triggered BATSE GRBs. We find that FXTs have softer spectra than
most triggered bursts, but that they are consistent with the extrapolated
hardness expected for low-intensity GRBs.


title: GRB 000418: A Hidden Jet Revealed?

abstract:
  We report on optical, near-infrared and centimeter radio observations of
GRB000418 which allow us to follow the evolution of the afterglow from 2 to 200
days after the gamma-ray burst. In modeling these broad-band data, we find that
an isotropic explosion in a constant density medium is unable to simultaneously
fit both the radio and optical data. However, a jet-like outflow with an
opening angle of 10-20 degress provides a good description of the data. The
evidence in favor of a jet interpretation is based on the behavior of the radio
light curves, since the expected jet break is masked at optical wavelengths by
the light of the host galaxy. We also find evidence for extinction, presumably
arising from within the host galaxy, with A(V)=0.4 mag, and host flux densities
of F_R=1.1 uJy and F_K=1.7 uJy. These values supercede previous work on this
burst due to the availability of a broad-band data set allowing a global
fitting approach. A model in which the GRB explodes into a wind-stratified
circumburst medium cannot be ruled out by these data. However, in examining a
sample of other bursts (e.g. GRB990510, GRB000301C) we favor the jet
interpretation for GRB000418.


title: FUSE Observations of Interstellar Gas toward the SMC Star Sk 108

abstract:
  We discuss the interstellar absorption lines found in FUSE spectra of the
Wolf-Rayet binary Sk 108, located in the northeastern part of the main ``bar''
of the Small Magellanic Cloud. The spectra cover the wavelength range 988-1187
Angstroms, at a resolution of about 12,000 and S/N of 20--40. We use detailed
component information from higher resolution near-UV and optical spectra to
model the far-UV lines of similarly distributed species. Both the Galactic and
SMC gas toward Sk 108 seem to be predominantly neutral, though a significant
fraction of the SMC gas is ionized. The column densities of P II, S II, and Ar
I are consistent with essentially solar ratios, relative to N(Zn II), in both
the Galactic and SMC gas; the column density of N I remains somewhat uncertain.
  Molecular hydrogen is present in the Galactic gas, with properties similar to
those found in low mean density Galactic lines of sight and in the Galactic gas
toward several other LMC and SMC stars. We report a tentative detection of H_2
in the SMC gas for J = 1 and 3, with rotational level populations consistent
with an excitation temperature of order 1000 K -- similar to the H_2 found in
diffuse Galactic gas toward zeta Pup. Strong absorption from N III, S III, and
Fe III has revealed a significant ionized component, particularly in the SMC; O
VI is present, but relatively weak, especially in the Galactic gas. The N(C
IV)/N(O VI) ratio varies somewhat within the SMC --- suggesting that several
processes may contribute to the observed high ion abundances.


title: The VIMOS Mask Preparation Software

abstract:
  The main scientific characteristic of VIMOS (VIsible Multi Object
Spectrograph, to be placed on ESO Very Large Telescope) is its high
multiplexing capability, allowing astronomers to obtain up to 800 spectra per
exposure. To fully exploit such a potential a dedicated tool, the VIMOS Mask
Preparation Software (MPS), has been designed. The MPS provides the astronomer
with tools for the selection of the objects to be spectroscopically observed,
including interactive object selection, handling of curved slits, and an
algorithm for automatic slit positioning that derives the most effective
solution in terms of number of object selected per field. The slit positioning
algorithm must take into account both the initial list of user's preferred
objects, and the constraints imposed either by the instrument characteristics
or by the requirement of having easily reduceable data. The number of possible
slit combinations in a field is in any case very high (10^73), and the task of
slits maximization cannot be solved through a purely combinational approach. We
have introduced an innovative approach, based on the analysis of the function
(Number of slits)/(slit length) vs. (slit length). The algorithm has been fully
tested with good results, and it will be distributed to the astronomical
community for the observation preparation phase.


title: The composition of circumstellar gas and dust in 51 Oph

abstract:
  We analyze ISO archive data of the nearby bright emission-line star 51 Oph,
previously classified as a proto-planetary system similar to beta Pic. The
infrared spectrum reveals the presence of gas-phase emission bands of hot
(approx 850 K) CO, CO_2, H_2O and NO. In addition to this, partially
crystalline silicate dust is present. The solid-state bands and the energy
distribution are indicative of dust that has formed recently, rather than of
debris dust. The presence of hot molecular gas and the composition of the
circumstellar dust are highly unusual for a young star and are reminiscent of
what is found around evolved (AGB) stars, although we exclude the possibility
of 51 Oph belonging to this group. We suggest several explanations for the
nature of 51 Oph, including a recent episode of mass loss from a Be star, and
the recent destruction of a planet-sized body around a young star.


title: Beaming in Gamma-Ray Bursts: Evidence for a Standard Energy Reservoir

abstract:
  Gamma-ray bursts (GRBs) are the most brilliant objects in the Universe but
efforts to estimate the total energy released in the explosion -- a crucial
physical quantity -- have been stymied by their unknown geometry: spheres or
cones. We report on a comprehensive analysis of GRB afterglows and derive their
conical opening angles. We find that the gamma-ray energy release, corrected
for geometry, is narrowly clustered around 5x10**50 erg. We draw three
conclusions. First, the central engines of GRBs release energies that are
comparable to ordinary supernovae, suggesting a connection. Second, the wide
variation in fluence and luminosity of GRBs is due entirely to a distribution
of opening angles. Third, only a small fraction of GRBs are visible to a given
observer and the true GRB rate is at least a factor of 500 times larger than
the observed rate.


title:
FUSE Observations of Outflowing OVI in the Dwarf Starburst Galaxy
  NGC1705

abstract:
  We report FUSE far-UV spectroscopy of the prototypical dwarf starburst galaxy
NGC 1705. These data allow us for the first time to probe the coronal-phase gas
(T = 10E5 to 10E6 K) that may dominate the radiative cooling of the
supernova-heated ISM and thereby determine the dynamical evolution of
starburst-driven outflows. We detect a broad (100 km/s) and blueshifted (by 80
km/s) OVI absorption-line arising in the previously-known galactic outflow. The
properties of the OVI absorption are inconsistent with the standard superbubble
model in which this gas arises in a conductive interface inside the outer
shell. We show that the superbubble in NGC 1705 is blowing out of the galaxy
ISM. During blow-out, coronal-phase gas can be created by hydrodynamical mixing
as hot gas rushes out through fissures in the fragmenting shell of cool gas. As
the coronal gas cools radiatively, it can naturally produce the observed OVI
column density and outflow speed. The OVI data show that the cooling rate in
the coronal-phase gas is less than about 10% of the supernova heating rate.
Since the X-ray luminosity from hotter gas is even smaller, we conclude that
radiative losses are insignificant. The outflow should be able to vent its
metals and kinetic energy out of the galaxy. This process has potentially
important implications for the evolution of dwarf galaxies and the IGM.


title: The plasma-solid transition

abstract:
  Using a criterion proposed by Salpeter and standard solid-state physics,we
have determined conditions for the occurence of the plasma-solid
transition.Possible astrophysical applications are discussed.


title:
Critical Test of the Self-Similar Cosmological Paradigm: Anomalously Few
  Planets Orbiting Low-Mass Red Dwarf Stars

abstract:
  The incidence of planetary systems orbiting red dwarf stars with masses less
than 0.4 solar masses provides a crucial observational test for the
Self-Similar Cosmological paradigm. The discrete self-similarity of the
paradigm mandates the prediction of anomalously few planetary systems
associated with these lowest mass red dwarf stars, in contrast to conventional
astrophysical assumptions. Ongoing observational programs are rapidly
collecting the data necessary for testing this prediction and preliminary
results are highly encouraging. A definitive verdict on the prediction should
be available in the near future.


title: WFPC2 Images of the Central Regions of Early-Type Galaxies - I. The Data

abstract:
  We present high resolution R-band images of the central regions of 67
early-type galaxies obtained with the Wide Field and Planetary Camera 2 (WFPC2)
aboard the Hubble Space Telescope (HST). Our sample strikingly confirms the
complex morphologies of the central regions of early-type galaxies. In
particular, we detect dust in 43 percent of all galaxies, and evidence for
embedded stellar disks in a remarkably large fraction of 51 percent. In 14 of
those galaxies the disk-like structures are misaligned with the main galaxy,
suggesting that they correspond to stellar bars in S0 galaxies. We analyze the
luminosity profiles of the galaxies in our sample, and classify galaxies
according to their central cusp slope. To a large extent we confirm the clear
dichotomy found in previous HST surveys: bright, boxy ellipticals with shallow
inner cusps (`core' galaxies) on one hand and faint, disky ellipticals with
steep central cusps (`power-law' galaxies) on the other hand. The advantages
and shortcomings of classification schemes utilizing the extrapolated central
cusp slope are discussed, and it is shown that this cusp slope might be an
inadequate representation for galaxies whose luminosity profile slope changes
smoothly with radius rather than resembling a broken power-law. In fact, we
find evidence for an `intermediate' class of galaxies, that cannot
unambiguously be classified as either core or power-law galaxies, and which
have central cusp slopes and absolute magnitudes intermediate between those of
core and power-law galaxies.


title:
JHK Standard Stars for Large Telescopes: the UKIRT Fundamental and
  Extended Lists

abstract:
  We present high-precision JHK photometry with the 3.8m UK Infrared Telescope
(UKIRT) of 83 standard stars, 28 from the widely used preliminary list known as
the "UKIRT Faint Standards" (Casali & Hawarden, 1992), referred to here as the
Fundamental List, and 55 additional stars referred to as the Extended List. The
stars have 9.4<K<15.0 and most should be readily observable with imaging array
detectors in normal operating modes on telescopes of up to 10m aperture. Many
are accessible from the southern hemisphere. Arcsec-accuracy positions (J2000,
Epoch ~1998) are given, together with optical photometry and spectral types
from the literature, where available, or inferred from the J-K colour. Finding
charts are provided for stars with proper motions exceeding 0.3"/yr. On 30
nights between late 1994 and early 1998 the stars from the Fundamental List,
which were used as standards for the whole programme, were observed on an
average of 10 nights each, and those from the Extended List 6 nights. The
average internal standard error of the mean results for K is 0.005 mag; for J-H
it is 0.003 mag for the Fundamental List stars and 0.006 mag for the Extended
List; for H-K the average is 0.004 mag. The results are on the natural system
of the IRCAM3 imager, which used a 256x256 InSb detector array with "standard"
JHK filters, behind gold-coated fore-optics and a gold- or silver-dielectric
coated dichroic. We give colour transformations onto the CIT, Arcetri and
LCO/Palomar NICMOS systems, and preliminary transformations onto the system
defined by the new Mauna Kea Observatory filter set.


title:
Protoplanetary Disks in the Nearest Star-Forming Cloud: Mid-Infrared
  Imaging and Optical Spectroscopy of MBM 12 Members

abstract:
  The recent identification of several groups of young stars within 100 parsecs
of the Sun has generated widespread interest. Given their proximity and
possible age differences, these systems are ideally suited for detailed studies
of star and planet formation. Here we report on the first investigation of
protoplanetary disks in one such group, the high-latitude cloud MBM 12 at a
distance of $\sim$65 pc. We present mid-infrared observations of the eight
candidate pre-main-sequence (PMS) members and the two main-sequence (MS) stars
in the same line-of-sight which may or may not be associated with the group. We
have also derived H$\alpha$ and Li line widths from medium-resolution optical
spectra. We report the discovery of significant mid-infrared excess from six
PMS stars --LkH$\alpha$ 262, LkH$\alpha$ 263, LkH$\alpha$ 264, E02553+2018,
RXJ0258.3+1947 and S18 --presumably due to optically thick circumstellar disks.
Our flux measurements for the other two PMS stars and the two MS stars are
consistent with photospheric emission, allowing us to rule out dusty inner
disks. The disks we have found in MBM 12 represent the nearest known sample of
very young protoplanetary systems, and thus are prime targets for
high-resolution imaging at infrared and millimeter wavelengths.


title: The Trans-Relativistic Blast Wave Model for SN 1998bw and GRB 980425

abstract:
  The spatiotemporal coincidence of supernova (SN) 1998bw and gamma-ray burst
(GRB) 980425 and this supernova's unusual optical and radio properties have
prompted many theoretical models that produce GRBs from supernovae. We review
the salient features of our simple, spherical model in which an energetic
supernova explosion shock accelerates a small fraction of the progenitor's
stellar envelope to mildly relativistic velocities. This material carries
sufficient energy to produce a weak GRB and a bright radio supernova through an
external shock against a dense stellar wind.


title: Efficient N-body Realisations of axisymmetric Galaxies and Haloes

abstract:
  We present an efficient method for building equilibrium multi-component
galaxies with non-spherical haloes and bulges. The gist of our approach is to
tailor the velocity ellipsoid directly to the geometry of the mass
distribution. Thus we avoid computing the anisotropic velocity dispersions
which leads to large savings in the cpu budget. The computational time of the
algorithm for triaxial equilibria scales linearly with the number of particles,
N. The approximate solution to the velocity field causes structural relaxation:
tests with N = 50,000 show that fluctuations of the inertia tensor (not
exceeding the 10 per cent level) disappear within one half of a revolution at
the half-mass radius. At later times equilibrium properties settle to values
close to those sought from the initial conditions.
  A disc component is then added as described by Hernquist (1993).
Incorporating the above algorithm to his code BuildGal, test runs show that the
stability of the disc against vertical heating is not substantially modified by
using our method.
  The code, MaGali, is made generally available.


title:
Chandra Observation of RXJ1720.1+2638: a Nearly Relaxed Cluster with a
  Fast Moving Core?

abstract:
  We have analyzed the Chandra observation of the distant (z=0.164) galaxy
cluster RXJ1720.1+2638 in which we find sharp features in the X-ray surface
brightness on opposite sides of the X-ray peak: an edge at about 250 h_50^{-1}
kpc to the South-East and a plateau at about 130 h_50^{-1} kpc to the
North-West. The surface brightness edge and the plateau can be modeled as a gas
density discontinuity (jump) and a slope change (break). The temperature
profiles suggest that the jump and the break are the boundaries of a central,
group-size (d=380h_50^{-1} kpc), dense, cold (T=4 keV) gas cloud, embedded in a
diffuse hot (T=10 keV) intracluster medium. The density jump and the
temperature change across the discontinuity are similar to the ``cold fronts''
discovered by Chandra in A2142 and A3667, and suggest subsonic motion of this
central gas cloud with respect to the cluster itself. The most natural
explanation is that we are observing a merger in the very last stage before the
cluster becomes fully relaxed. However, the data are also consistent with an
alternative scenario in which RXJ1720.1+2638 is the result of the collapse of
two co-located density perturbations, the first a group-scale perturbation
collapse followed by a second cluster-scale perturbation collapse that
surrounded, but did not destroy, the first one. We also show that, because of
the core motion, the total mass inside the cluster core, derived under the
assumption of hydrostatic equilibrium, may underestimate the true cluster mass.
If widespread, such motion may partially explain the discrepancy between X-ray
and the strong lensing mass determinations found in some clusters.


title: Dusty Nuclear Disks and Filaments in Early Type Galaxies

abstract:
  We examine the dust properties of a nearby distance-limited sample of early
type galaxies using the WFPC2 of the Hubble Space Telescope. Dust is detected
in 29 out of 67 galaxies (43%), including 12 with small nuclear dusty disks. In
a separate sample of 40 galaxies biased for the detection of dust by virtue of
their detection in the IRAS 100 micron band, dust is found in ~78% of the
galaxies, 15 of which contain dusty disks. In those galaxies with detectable
dust, the apparent mass of the dust correlates with radio and far infrared
luminosity, becoming more significant for systems with filamentary dust. A
majority of IRAS and radio detections are also associated with dusty galaxies
rather than dustless galaxies. This indicates that thermal emission from
clumpy, filamentary dust is the main source of the far-IR radiation in early
type galaxies. Dust in small disk-like morphology tends to be well aligned with
the major axis of the host galaxies, while filamentary dust appears to be more
randomly distributed with no preference for alignment with any major galactic
structure. This suggests that, if the dusty disks and filaments have a common
origin, the dust originates externally and requires time to dynamically relax
and settle in the galaxy potential in the form of compact disks. More galaxies
with visible dust than without dust display emission lines, indicative of
ionized gas, although such nuclear activity does not show a preference for
dusty disk over filamentary dust. There appears to be a weak relationship
between the mass of the dusty disks and central velocity dispersion of the
galaxy, suggesting a connection with a similar recently recognized relationship
between the latter and the black hole mass.


title: The Host Galaxy and the Environment of the z = 1.195 Quasar 3C 190

abstract:
  We present deep imaging and spectroscopic observations of the z = 1.195
quasar 3C 190 and its immediate environment. The quasar is surrounded by an
asymmetric low-surface-brightness envelope in which there are also several
galaxies with characteristic dimensions of 3-5 kpc. Some of these form a linear
structure some 50 kpc long in projection, offset from the quasar and almost
perpendicular to the radio axis. Spectroscopy of this feature indicates the
presence of a starburst component as well as stars a few 10^8 years old.
Velocities of the emission- line gas associated with H II regions in the linear
feature are difficult to reconcile with any reasonable model that is also
consistent with the observed morphology. One possible scenario is an edge-on
disk in an extremely massive (~10^12 solar mass) halo; another is two
independent chain galaxies, with the apparent alignment being fortuitous.
Taking into account all of the types of extended material we find in the
vicinity of 3C 190, we appear to be witnessing a relatively brief phase in the
development of a spheroidal galaxy, in which merging is proceeding nearly
simultaneously in a variety of different regimes. This system may be one of the
clearest examples yet found for the mechanism by which many elliptical galaxies
and bulges of early-type spirals form in the early Universe.


title:
Seven (and a half) reasons to believe in Mirror Matter: From neutrino
  puzzles to the inferred Dark matter in the Universe

abstract:
  Parity and time reversal are obvious and plausible candidates for fundamental
symmetries of nature. Hypothesising that these symmetries exist implies the
existence of a new form of matter, called mirror matter. The mirror matter
theory (or exact parity model) makes four main predictions: 1) Dark matter in
the form of mirror matter should exist in the Universe (i.e. mirror galaxies,
stars, planets, meteoroids...), 2) Maximal ordinary neutrino - mirror neutrino
oscillations if neutrinos have mass, 3) Orthopositronium should have a shorter
effective lifetime than predicted by QED (in "vacuum" experiments) because of
the effects of photon-mirror photon mixing and 4) Higgs production and decay
rate should be 50% lower than in the standard model due to Higgs mirror - Higgs
mixing (assuming that the seperation of the Higgs masses is larger than their
decay widths). At the present time there is strong experimental/observational
evidence supporting the first three of these predictions, while the fourth one
is not tested yet because the Higgs boson, predicted in the standard model of
particle physics, is yet to be found. This experimental/observational evidence
is rich and varied ranging from the atmospheric and solar neutrino deficits,
MACHO gravitational microlensing events, strange properties of extra-solar
planets, the existence of "isolated" planets, orthopositronium lifetime
anomaly, Tunguska and other strange "meteor" events including perhaps, the
origin of the moon. The purpose of this article is to provide a not too
technical review of these ideas along with some new results.


title: Spectral Energy Distributions of Blazars: Facts and Speculations

abstract:
  We discuss the present knowledge about the Spectral Energy Distributions
(SEDs) of blazars within a unified approach emphasizing overall similarities.
The properties of the average SEDs of different samples of blazars suggest that
more powerful sources contain on average less energetic particles. Detailed
studies of TeV emitting blazars show that the energy of the particles emitting
the bulk of the power increases during flares. A framework for a general
theoretical understanding is proposed. We present recent results on the SEDs of
a group of blazars with emission lines, allowing to estimate both the
luminosity in the jet and the luminosity of the accretion disk. Implications
for the origin of the power carried by relativistic jets are considered.


title: Dyadosphere bending of light

abstract:
  In the context of the static and spherically symmetric solution of a charged
compact object, we present the expression for the bending of light in the
region just outside the event horizon (the dyadosphere) where vacuum
polarization effects are taken into account.


title: Comparison of source detection procedures for XMM-Newton images

abstract:
  Procedures based on current methods to detect sources in X-ray images are
applied to simulated XMM images. All significant instrumental effects are taken
into account, and two kinds of sources are considered -- unresolved sources
represented by the telescope PSF and extended ones represented by a b-profile
model. Different sets of test cases with controlled and realistic input
configurations are constructed in order to analyze the influence of confusion
on the source analysis and also to choose the best methods and strategies to
resolve the difficulties.
  In the general case of point-like and extended objects the mixed approach of
multiresolution (wavelet) filtering and subsequent detection by SExtractor
gives the best results. In ideal cases of isolated sources, flux errors are
within 15-20%. The maximum likelihood technique outperforms the others for
point-like sources when the PSF model used in the fit is the same as in the
images. However, the number of spurious detections is quite large.
  The classification using the half-light radius and SExtractor stellarity
index is succesful in more than 98% of the cases. This suggests that average
luminosity clusters of galaxies (L_[2-10] ~ 3x10^{44} erg/s) can be detected at
redshifts greater than 1.5 for moderate exposure times in the energy band below
5 keV, provided that there is no confusion or blending by nearby sources.
  We find also that with the best current available packages, confusion and
completeness problems start to appear at fluxes around 6x10^{-16} erg/s/cm^2 in
[0.5-2] keV band for XMM deep surveys.


title:
An analytic function fit to Monte-Carlo X- and gamma-ray spectra from
  Thomson thick thermal/nonthermal hybrid plasmas

abstract:
  We suggest a simple fitting formula to represent Comptonized X- and gamma-ray
spectra from a hot ($kT_e \gtrsim 10$ keV), Thomson thick ($\tau_T \gtrsim 5$)
hybrid thermal/nonthermal plasma in spherical geometry with homogeneous
soft-photon injection throughout the Comptonizing region. We have used this
formula to fit a large data base of Monte-Carlo generated photon spectra, and
provide correlations between the physical parameters of the plasma and the fit
parameters of our analytic fit function. These allow us to construct Thomson
thick Comptonization spectra without performing computer intensive Monte Carlo
simulations of the high-Thomson-depth hybrid-plasma Comptonization problem. Our
formulae can easily be used in data analysis packages such as XSPEC, thus
rendering rapid $\chi^2$ fitting of such spectra to real data feasible.


title: Detection of a Hard Tail in the X-ray Spectrum of the Z Source GX 349+2

abstract:
  We present the results of a BeppoSAX observation of the Z source GX 349+2
covering the energy range 0.1-200 keV. The presence of flares in the light
curve indicates that the source was in the flaring branch during the BeppoSAX
observation. We accumulated energy spectra separately for the non-flaring
intervals and the flares. In both cases the continuum is well described by a
soft blackbody ($k T_{BB} \sim 0.5$ keV) and a Comptonized spectrum
corresponding to an electron temperature of $k T_e \sim 2.7$ keV, optical depth
$\tau \sim 10$ (for a spherical geometry), and seed photon temperature of $k
T_W \sim 1$ keV. All temperatures tend to increase during the flares. In the
non-flaring emission a hard tail dominates the spectrum above 30 keV. This can
be fit by a power law with photon index $\sim 2$, contributing $\sim 2%$ of the
total source luminosity over the BeppoSAX energy range. A comparison with hard
tails detected in some soft states of black hole binaries suggests that a
similar mechanism could originate these components in black hole and neutron
star systems.


title:
ESO Imaging Survey. Deep Public Survey: Infrared Data for the Chandra
  Deep Field South

abstract:
  This paper presents new J and Ks near-infrared data obtained from
observations of the Chandra Deep Field South (CDF-S) conducted at the ESO 3.5m
New Technology Telescope (NTT). These data were taken as part of the ongoing
Deep Public Survey (DPS) being carried out by the ESO Imaging Survey (EIS)
program, extending the EIS-DEEP survey. Combined these surveys now provide a
contiguous coverage over an area of 400 square arcmin in the near-infrared,
nearly matching that covered by the deep X-ray observations of Chandra, four
times the area of the original EIS-DEEP survey. The paper briefly describes the
observations and the new techniques being employed for pipeline processing
jittered infrared observations, which include unbiased de-fringing and
sky-background subtraction, pixel-based astrometry and stacking and pixel
registration based on a multi-resolution decomposition of the images. The
astrometric solution is based on a pre-release of the GSC-II catalog and has an
accuracy of < 0.15 arcsec. The final images for 12 pointings presented here
reach median 5 sigma limiting magnitudes of J_AB~23.4 and K_AB~22.6 as measured
within an aperture 2xFWHM. The frame to frame variation of the photometric
zero-point is estimated to be <0.09 mag. The data are publicly available in the
form of fully calibrated J and Ks pixel maps and source lists extracted for
each pointing. These data can be requested through the URL
``http://www.eso.org/eis''.


title: Discovery of Radio Emission from the Brown Dwarf LP944-20

abstract:
  Brown dwarfs are classified as objects which are not massive enough to
sustain nuclear fusion of hydrogen, and are distinguished from planets by their
ability to burn deuterium. Old (>10 Myr) brown dwarfs are expected to possess
short-lived magnetic fields and, since they no longer generate energy from
collapse and accretion, weak radio and X-ray emitting coronae. Several efforts
have been undertaken in the past to detect chromospheric activity from the
brown dwarf LP944-20 at X-ray and optical wavelengths, but only recently an
X-ray flare from this object was detected. Here we report on the discovery of
quiescent and flaring radio emission from this source, which represents the
first detection of persistent radio emission from a brown dwarf, with
luminosities that are several orders of magnitude larger than predicted from an
empirical relation between the X-ray and radio luminosities of many stellar
types. We show in the context of synchrotron emission, that LP944-20 possesses
an unusually weak magnetic field in comparison to active dwarf M stars, which
might explain the null results from previous optical and X-ray observations of
this source, and the deviation from the empirical relations.


title: A Catalog and Atlas of Cataclysmic Variables - The Living Edition

abstract:
  The Catalog and Atlas of Cataclysmic Variables (Edition 1 - 1993) and Edition
2 - 1997) has been a valuable source of information for the cataclysmic
variable (CV) community. However, the goal of having a central location for all
objects is slowly being lost as each new edition is generated. There can also
be a long time delay between new information becoming available on an object
and its publication in the catalog. To eliminate these concerns, as well as to
make the catalog more accessible, we have created a web site which will contain
a ``living'' edition of the catalog. We have also added orbital period
information, as well as finding charts for novae, to the catalog.


title:
Analytic Study of Grid Star and Reference Star Selection for the Space
  Interferometry Mission

abstract:
  Grid stars and reference stars provide the fundamental global and local
astrometric reference frames for observations by the Space Interferometry
Mission. They must therefore be astrometrically stable at the ~1 uas level. I
present simple formulae in closed form to estimate contamination of these
frames by motions due to stellar companions that go undetected in a
radial-velocity (RV) survey of specified precision. The contamination rate
depends almost entirely on the binary-period distribution function and not on
the details of the mass or eccentricity distributions. Screening by a modest RV
survey (sigma_rv=60 m/s) can reduce the fraction of grid stars having
detectable unmodeled accelerations to <<1%. Reference-star selection promises
to be much more challenging, partly because the requirements of astrometric
stability are more severe and partly because the required density of sources is
about 100 times higher, which latter implies that less satisfactory candidates
will have to be accepted. The tools presented here can help design a
reference-star selection strategy, but a full treatment of the problem will
require better knowledge of their companions in the planetary mass range.


title: Constraints on Warm Dark Matter from Cosmological Reionization

abstract:
  We study the constraints that high-redshift structure formation in the
universe places on warm dark matter (WDM) dominated cosmological models. We
modify the extended Press-Schechter formalism to derive the halo mass function
in WDM models. We show that our predictions agree with recent numerical
simulations at low redshift over the halo masses of interest. Applying our
model to galaxy formation at high redshift, we find that the loss of power on
small scales, together with the delayed collapse of low-mass objects, results
in strong limits on the root-mean-square velocity dispersion v_rms of the WDM
particles at z=0. For fermions decoupling while relativistic, these limits are
equivalent to constraints on the mass m_X of the particles. The presence of a 4
billion solar mass black hole at z=5.8, believed to power the quasar SDSS
1044-1215, implies m_X > 0.5 keV (or v_rms < 0.10 km/s), assuming that the
quasar is unlensed and radiating at or below the Eddington limit. Reionization
by z=5.8 also implies a limit on m_X. If high-redshift galaxies produce
ionizing photons with an efficiency similar to their z=3 counterparts, we find
m_X > 1.2 keV (or v_rms < 0.03 km/s). However, given the uncertainties in
current measurements from the proximity effect of the ionizing background at
redshift 3, values of m_X as low as 0.75 keV (v_rms = 0.06 km/s) are not ruled
out. The limit weakens further if, instead, the ionizing-photon production
efficiency is greater at high z, but this limit will tighten considerably if
reionization is shown in the future to have occurred at higher redshifts. WDM
models with m_X < 1 keV (v_rms > 0.04 km/s) produce a low-luminosity cutoff in
the high-redshift galaxy luminosity function which is directly detectable with
the Next Generation Space Telescope (abridged).


title: Space, Time, and Matter: Cosmological Parameters 2001

abstract:
  Over the past three years, our confidence in the inferred values of
cosmological parameters has increased dramatically, confirming that the flat
matter dominated Universe that dominated cosmological model building for the
past 20 years does not correspond to the Universe in which we live. I review
recent developments here and quote best fit current values for fundamental
cosmological parameters.


title:
Detecting high redshift evolved galaxies as the hosts of optically faint
  hard X-ray sources

abstract:
  We combine deep Subaru near-infrared images of the massive lensing clusters
A2390 and A370 with Keck optical data to map the spectral energy distributions
(SEDs) of Chandra X-ray sources lying behind the clusters. The three sources
behind A2390 are found to have extremely red colors with SEDs consistent with
evolved galaxies at redshifts z>1.4. One source has extremely anomalous colors,
which we interpret as evidence for a type Sa SED at a redshift around 2.5. The
photometric redshift of another source has been confirmed at z=1.467 from
near-infrared spectroscopy using the CISCO spectrograph on Subaru. Mapping of
optically faint hard X-ray sources may prove to be an extremely efficient way
to locate luminous evolved galaxies at high redshifts.


title: Chemical Compositions of Four Metal-poor Giants

abstract:
  We present the chemical compositions of four K giants CS 22877-1, CS
22166-16, CS22169-35 and BS 16085 - 0050 that have [Fe/H] in the range -2.4 to
-3.1. Metal-poor stars with [Fe/H] < -2.5 are known to exhibit considerable
star - to - star variations of many elements. This quartet confirms this
conclusion. CS 22877-1 and CS 22166-16 are carbon-rich. There is significant
spread for [$\alpha$/Fe] within our sample where [$\alpha$/Fe] is computed from
the mean of the [Mg/Fe], and [Ca/Fe] ratios. BS 16085 - 0050 is remarkably
$\alpha$ enriched with a mean [$\alpha$/Fe] of $+$0.7 but CS 22169-35 is
$\alpha$-poor. The aluminium abundance also shows a significant variation over
the sample. A parallel and unsuccessful search among high-velocity late-type
stars for metal-poor stars is described.


title:
Surprises from a deep ASCA spectrum of a Broad Absorption Line Quasar
  PHL 5200

abstract:
  We present a deep ($\sim$85 ksec) ASCA observation of the prototype Broad
Absorption Line Quasar (BALQSO) PHL 5200. This is the best X-ray spectrum of a
BALQSO yet. We find that (1) the source is not intrinsically X-ray weak, (2)
the line of sight absorption is very strong with N_H=5 x 10^{23} cm^{-2}, (3)
the absorber does not cover the source completely; the covering fraction is
about 90%. This is consistent with the large optical polarization observed in
this source, implying multiple lines of sight. The most surprising result of
this observation is that (4) the spectrum of this BALQSO is not exactly similar
to other radio-quiet quasars. The hard X-ray spectrum of PHL 5200 is steep with
the power-law spectral index alpha ~1.5. This is similar to the steepest hard
X-ray slopes observed so far. At low redshifts, such steep slopes are observed
in narrow line Seyfert 1 galaxies, believed to be accreting at a high Eddington
rate. This observation strengthens the analogy between BALQSOs and NLS1
galaxies and supports the hypothesis that BALQSOs represent an early
evolutionary state of quasars (Mathur 2000). It is well accepted that the
orientation to the line of sight determines the appearance of a quasar; age
seems to play a significant role as well.


title: Precision Timing Measurements of PSR J1012+5307

abstract:
  We present results and applications of high precision timing measurements of
the millisecond pulsar J1012+5307. Combining our radio observations with
results based on optical observations, we derive complete 3-D velocity
information for this system. Correcting for Doppler effects, we derive the
intrinsic spin parameters of this pulsar and a characteristic age of 8.6 +/-
1.9 Gyr. Our upper limit for the orbital eccentricity of only 8 * 10^-7 (68%
C.L.) is the smallest ever measured for a binary system. We demonstrate that
this makes the pulsar an ideal laboratory to test certain aspects of
alternative theories of gravitation. Our precise measurements suggest
deviations from a simple pulsar spin-down timing model, which are consistent
with timing noise and the extrapolation of the known behaviour of slowly
rotating pulsars.


title:
Spatially Resolved Millimeter Spectroscopy of the Gravitational Lens PKS
  1830-211

abstract:
  This paper presents data from the BIMA interferometer showing spatially
resolved absorption spectra of the gravitationally lensed quasar PKS 1830-211.
High-resolution (1.2 km/s) spectra were taken in two spectral windows centered
on the redshifted frequencies of the HCO+(2-1) and HCN(2-1) molecular
transitions. There is no molecular absorption in the northeast image but the
southwest image reveals optically thick absorbing gas at these transition
frequencies. Further analyses conclude that the spectra are consistent with
completely saturated absorption in the southwest image and the line profiles
suggest that the absorbing medium is complex, perhaps containing multiple
components and small scale structure. The absorption occurs along a pencil beam
through the lensing galaxy which is thought to be a late type spiral oriented
almost face on. However, the spectra show absorption spanning more than 60 km/s
which is difficult to explain for this scenario.


title:
Observational constraints on inflation models with nonminimal scalar
  field

abstract:
  We present the power spectra of the scalar- and tensor-type structures
generated in an inflation model based on the nonminimally coupled scalar field
with a self coupling. By comparing the contributions of these structures to the
anisotropy of the cosmic microwave background radiation with the four year COBE
DMR data we derive strong constraints on model parameters and the inflation
model.


title:
The Metal-rich Globular Cluster NGC6553: Observations with WFPC2, STIS,
  and NICMOS

abstract:
  We present a HST study of the metal-rich globular cluster NGC6553 using
WFPC2, NICMOS and STIS. Our primary motivation is to calibrate the STIS
broad-band LP magnitude against $V_{555}$ and $I_{814}$ magnitudes for stars of
known metallicity and absolute (visual) magnitude, for application to our study
of LMC globular clusters. NGC6553 has been shown in earlier studies to have a
very unusual colour-magnitude diagram, so we also use our data to investigate
the reddening, distance, luminosity function and structure of this cluster. We
deduce a higher metallicity and smaller distance modulus than did some previous
studies, but emphasise that very large patchy extinction on small angular
scales prohibits accurate determination of the parameters of this cluster. The
horizontal branch of NGC6553 in ($V,V-I$) is tilted at an angle close to that
of the reddening vector. We show that extinction does not, however, explain the
tilt, which is presumably a metallicity effect. The colour-magnitude diagram
shows an apparent second turnoff some 1.5 magnitudes fainter than that of the
cluster. We show that this is most likely the background Galactic bulge:
however, in that case, the colour-magnitude diagram of NGC6553 is not a good
match to that of the field bulge population. The cluster is probably more
metal-rich than is the mean field bulge star.


title:
TVD Scheme for the Numerical Simulation of the Axisymmetrical
  Selfgravitating MHD Flows

abstract:
  The explicit quasi-monotonic conservative TVD scheme and numerical method for
the solution of the gravitational MHD equations are developed. The 2D numerical
code for the simulation of multidimensional selfgravitating MHD flows on the
Eulerian cylindrical grid is constructed. The results of test calculations show
that the code has a good mathematical and computational properties and can be
applied to the solution of a wide class of plasma physics and astrophysics
problems. We have simulated, for example, a collapse of magnetized rotating
protostellar clouds.


title: Are Cen a and M87 Tev Gamma-Ray Sources?

abstract:
  In this paper, we identify Cen A and M87, two nearby Fanaroff-Riley I (FRI)
radio galaxies, with high-energy-peaked BL Lac-like (HBL-like) objects by
investigating their spectral energy distributions (SEDs). The SED peak of Cen A
at $\sim$150 keV, which was generally believed to be the peak of
inverse-Compton emission as in the case of 3C 273, is found to be actually the
peak of synchrotron emission. The synchrotron emission of M87 peaks in the far
UV band. We summarize the properties of $\gamma$-ray-loud blazars, especially
those of TeV BL Lac objects, and generalize them to HBL-like FRI radio galaxies
according to the unified scheme of BL Lac objects and FRI radio galaxies. We
infer that Cen A may have a peak in its Compton component power output at
$\sim$1 TeV, and that M87 may have a Compton emission peak at $\sim$0.1 TeV.
For Cen A, the estimated TeV $\gamma$-ray flux during outburst is F(0.25 $-$ 30
TeV) = 6.4$\times10^{-9}$ erg cm$^{-2}$s$^{-1}$, and for M87, F(0.25 $-$ 30
TeV) = 1.1$\times10^{-11}$ erg cm$^{-2}$s$^{-1}$. Both fluxes are detectable by
TeV detectors available today, and hence Cen A and M87 are TeV $\gamma$-ray
source candidates. By investigating the long term variability, we predict that
Cen A will undergo an outburst in the near future and will be detectable at the
TeV $\gamma$-ray energy range using the CANGAROO and the German-French-Italian
experiment HESS TeV $\gamma$-ray telescopes.


title: Gravitational Radiation from Gamma-Ray Bursts

abstract:
  Gamma Ray Bursts (GRBs) are the most relativistic objects known so far,
involving, on one hand an ultra-relativistic motion with a Lorentz factor
$\Gamma > 100$ and on the other hand an accreting newborn black hole. The two
main routes leading to this scenario: binary neutron star mergers and Collapsar
- the collapse of a rotating star to a black hole, are classical sources for
gravitational radiation. Additionally one expect a specific a gravitational
radiation pulse associated with the acceleration of the relativistic ejecta. I
consider here the implication of the observed rates of GRBs to the possibility
of detection of a gravitational radiation signal associated with a GRB.
Unfortunately I find that, with currently planned detectors it is impossible to
detect the direct gravitational radiation associated with the GRB. It is also
quite unlikely to detect gravitational radiation associated with Collapsars.
However, the detection of gravitational radiation from a neutron star merger
associated with a GRB is likely.


title: The Hipparcos observations and the mass of sub-stellar objects

abstract:
  The Hipparcos Intermediate Astrometric Data have been used lately to estimate
the inclination of the orbital plane of candidate extrasolar planets. Whereas
most of these investigations derive almost face-on orbits, we show that the
astrometric data are seldom precise enough to undertake such studies and that
the `face-on' result might be just a spurious effect of the method.


title: TeV Neutrinos and GeV Photons from Shock Breakout in Supernovae

abstract:
  We show that as a Type II supernova shock breaks out of its progenitor star,
it becomes collisionless and may accelerate protons to energies >10 TeV.
Inelastic nuclear collisions of these protons produce a ~1 hr long flash of TeV
neutrinos and 10 GeV photons, about 10 hr after the thermal (10 MeV) neutrino
burst from the cooling neutron star. A Galactic supernova in a red supergiant
star would produce a photon and neutrino flux of ~10^{-4} erg/cm^2 s. A km^2
neutrino detector will detect ~100 muons, thus allowing to constrain both
supernova models and neutrino properties.


title:
A Closed Non-Collapsing 3-D Universe Predicting A New Source of Gravity
  and Dark Mass

abstract:
  Could one start from scratch, ignore relativity theory and quantum theory,
create and expand our 3-D universe with no singularities, have the mathematical
model predict correctly all of the cosmological parameters, provide the origins
and understanding of time, energy, gravity and some of quantum behavior inside
our 3-D universe and do all of that with just high school algebra and a little
calculus? The answer is: Yes, it has been done and includes many falsifiable
predictions. For the mathematical model, some new physical concepts are needed
together with some older physical concepts such as the scaling of radiation and
matter with the expansion and the idea that clumps of mass locally curve our
3-D space. Instead of assuming roll-up dimensional changes of space that
occurred sometime in the past, here the major postulate is that such an ongoing
dimensional change of space drives our universe yet today. The first paper,
astro-ph/0102071, presented the predicted magnitudes of the new model for
supernova Ia and the excellent fit with the astronomical measurements without
the cosmological constant. This second paper will present more of the theory
and other important predictions.


title: Overconstrained dynamics in galaxy redshift surveys

abstract:
  The least-action principle (LAP) method is used on four galaxy redshift
surveys to measure the density parameter Omega_m and the matter and
galaxy-galaxy power spectra. The datasets are PSCz, ORS, Mark III and SFI. The
LAP method is applied on the surveys simultaneously, resulting in an
overconstrained dynamical system that describes the cosmic overdensities and
velocity flows. The system is solved by relaxing the constraint that each
survey imposes upon the cosmic fields. A least-squares optimization of the
errors that arise in the process yields the cosmic fields and the value of
Omega_m that is the best fit to the ensemble of datasets. The analysis has been
carried out with a high-resolution Gaussian smoothing of 500 km/s and over a
spherical selected volume of radius 9,000 km/s. We have assigned a weight to
each survey, depending on their density of sampling, and this parameter
determines their relative influence in limiting the domain of the overall
solution. The influence of each survey on the final value of Omega_m, the
cosmographical features of the cosmic fields and the power spectra largely
depends on the distribution function of the errors in the relaxation of the
constraints. We find that PSCz and Mark III are closer to the final solution
than ORS and SFI. The likelihood analysis yields Omega_m= 0.37\pm 0.01 to
1sigma level. PSCz and SFI are the closest to this value, whereas ORS and Mark
III predict a somewhat lower Omega_m. The model of bias employed is a
scale-dependent one, and we retain up to 42 bias coefficients b_{rl} in the
spherical harmonics formalism. The predicted power spectra are estimated in the
range of wavenumbers 0.02-0.49h Mpc^{-1}, and we compare these results with
measurements recently reported in the literature.


title: Complexity in Cosmology

abstract:
  The question of the nature of galaxy clustering and the possible homogeneity
of galaxy distribution is one of the fundamental problem of cosmology. It is
well established that galaxy structures are characterized, up to a certain
scale, by fractal properties. The possible crossover to homogeneity is instead
still matter of debate. However, independently on the specific value of the
homogeneity scale, the fractal nature of galaxy clustering requires new methods
and theoretical concepts developed in the area of statistical physics and
complexity. In this lecture we discuss a new perspective on the problem of
cosmological structures formation, both from the experimental and the
theoretical points of view. This new perspective leads to a very interesting
and constructive interaction between the fields of cosmic structures,
statistical physics and complexity with very challenging open problems which we
also discuss.


title: Turbulent Dynamos and Magnetic Helicity

abstract:
  It is shown that the turbulent dynamo $\alpha$-effect converts magnetic
helicity from the turbulent field to the mean field when the turbulence is
electromagnetic while the magnetic helicity of the mean-field is transported
across space when the turbulence is electrostatic or due to the electron
diamagnetic effect. In all cases, however, the dynamo effect strictly conserves
the total helicity except for resistive effects and a small battery effect.
Implications for astrophysical situations, especially for the solar dynamo, are
discussed.


title: Large Circumbinary Dust Grains Around Evolved Giants?

abstract:
  We have detected continuum emission at 450 microns, 850 microns and 1.35
millimeters from SS Lep (or 17 Lep), 3 Pup and probably BM Gem, likely or
confirmed binary systems consisting of at least one evolved giant. The observed
submillimeter fluxes are probably emitted by grains rather than ionized gas.
The dust temperature is greater than 70 K within 6 arcseconds of each source.
To explain why grains are so cold near the star, we suggest that the emission
at wavelengths greater than 450 microns is produced by particles as large as
0.1 millimeter in radius, and that these large particles probably have grown by
coagulation in circumbinary orbiting disks.


title:
NICMOS observations of high redshift radio galaxies: witnessing the
  formation of bright elliptical galaxies?

abstract:
  We present the results of a near infrared imaging program of a sample of 19
radio galaxies with redshift between 1.7 and 3.2, using the NICMOS Camera 2 on
the Hubble Space Telescope. The galaxies were observed in H-band which, for 18
of the 19 targets, samples the rest-frame optical emission longwards of the
4000 A break. The images show a wide range of morphologies, from unresolved to
compact systems, to systems with substructures such as multiple emission peaks,
to systems comprised of several components spread over large areas. The
morphologies of 5 of the lowest redshift targets are well represented by a de
Vaucouleurs profile, consistent with them being elliptical galaxies. Their
average effective radius is a factor of 2 smaller than that of z=1 3CR radio
galaxies at similar restframe wavelengths. The near infrared continuum light is
generally well aligned with the radio axis and the aligned light has typical
V-H colors of around 3.5-4. For several galaxies where WFPC2 images were
available, we computed a high resolution map of the optical-to-infrared
spectral indices: all multi-component systems present net color gradients
between the various clumps. We argue that in these galaxies the continuum
emission has probably a stellar origin. Finally in many cases we observe nearby
faint objects close to the radio sources. The number density of these faint
objects is slightly higher than what is found in the deep NICMOS parallel
observations of random fields. These objects also tend to be aligned with the
radio sources axis, suggesting that they may be related to the presence of the
AGN. (shortened astro-ph version)


title: TeV observations of SNRs and unidentified sources

abstract:
  A review of very high energy gamma-ray astronomy is presented. Particular
attention is paid to the atmospheric Cherenkov imaging technique whose
employment has resulted in detections of both galactic and extra-galactic
objects at energies above 300GeV. Next generation ground-based telescopes
promise to increase our knowledge of extreme astrophysical objects as they
begin to operate over the next few years.


title:
Understanding Spectral Variability and Time Lags in Accreting Black
  Holes

abstract:
  I review the temporal/spectral data of accreting black hole sources paying
most attention to the properties of the temporal variability such as photon
energy dependent auto- and cross-correlation functions, average shot profiles
and hardness ratios, and the Fourier frequency dependent time/phase lags. These
statistics characterize spectral changes at short time scales that are
otherwise impossible to study by direct spectral analysis. The data provide
strong constraints on the theoretical models for X-ray production in accreting
black holes. Models for the spectral variability of the Comptonized component
are briefly reviewed. It is also shown that Compton reflection can have
significant impact on the observed temporal characteristics.


title: Magnetic flaring in pre-main sequence stars

abstract:
  Observations of nearby star forming clouds with imaging X-ray telescopes have
revealed that X-ray emission is elevated $10^1-10^4$ above main sequence levels
in low-mass pre-main sequence (PMS) stars. The variability and spectral X-ray
evidence, together with circularly polarized radio continuum flares seen in a
few cases, strongly argues for an origin in magnetic reconnection flares. These
high levels of magnetic activity are present from the earliest protostellar
phase to the main sequence. After a brief review of past observations, three
astrophysical issues are raised: the location of the flaring magnetic fields,
the origin of these fields, and the effects of flare high-energy photons and
particles on the environs. New results from Chandra observations of a
well-defined samples of PMS solar analogues are presented, giving an improved
view of magnetic flaring in the early Sun.


title: The Cosmological Tests

abstract:
  Recent observational advances have considerably improved the cosmological
tests, adding to the lines of evidence, and showing that some issues under
discussion just a few years ago may now be considered resolved or irrelevant.
Other issues remain, however, and await resolution before the great program of
testing the relativistic Friedmann-Lemaitre model, that commenced in the 1930s,
may at last be considered complete.


title:
Diffuse Extragalactic Background Light versus Deep Galaxy Counts in the
  Subaru Deep Field: Missing Light in the Universe?

abstract:
  Deep optical and near-infrared galaxy counts are utilized to estimate the
extragalactic background light (EBL) coming from normal galactic light in the
universe. Although the slope of number-magnitude relation of the faintest
counts is flat enough for the count integration to converge, considerable
fraction of EBL from galaxies could still have been missed in deep galaxy
surveys because of various selection effects including the cosmological dimming
of surface brightness of galaxies. Here we give an estimate of EBL from galaxy
counts, in which these selection effects are quantitatively taken into account
for the first time, based on reasonable models of galaxy evolution which are
consistent with all available data of galaxy counts, size, and redshift
distributions. We show that the EBL from galaxies is best resolved into
discrete galaxies in the near-infrared bands (J, K) by using the latest data of
the Subaru Deep Field; more than 80-90% of EBL from galaxies has been resolved
in these bands. Our result indicates that the contribution by missing galaxies
cannot account for the discrepancy between the count integration and recent
tentative detections of diffuse EBL in the K-band (2.2 micron), and there may
be a very diffuse component of EBL which has left no imprints in known galaxy
populations.