title:
Adaptive Optics Integral Field Spectroscopy of the Young Stellar Objects
  in LkH_alpha 225

abstract:
  Progress in understanding the embedded stars in LkHa225 has been hampered by
their variability, making it hard to compare data taken at different times, and
by the limited resolution of the available data, which cannot probe the small
scales between the two stars. In an attempt to overcome these difficulties, we
present new near-infrared data on this object taken using the ALFA adaptive
optics system with the MPE 3D integral field spectrometer and the near-infrared
camera Omega-Cass. The stars themselves have K-band spectra which are dominated
by warm dust emission, analagous to class I-II for low mass YSOs, suggesting
that the stars are in a phase where they are still accreting matter. On the
other hand, the ridge of continuum emission between them is rather bluer,
suggestive of extincted and/or scattered stellar light rather than direct dust
emission. The compactness of the CO emission seen toward each star argues for
accretion disks (which can also account for much of the K-band veiling) rather
than a neutral wind. In contrast to other YSOs with CO emission, LkHa225 has no
detectable Br_gamma emission. Additionally there is no H_2 detected on the
northern star, although we do confirm that the strongest H_2 emission is on the
southern star, where we find it is excited primarily by thermal mechanisms. A
second knot of H_2 is observed to its northeast, with a velocity shift of
-75kms and a higher fraction of non-thermal emission. This is discussed with
reference to the H2O maser, the molecular outflow, and [S II] emission observed
between the stars.


title: The INTEGRAL Burst Alert System

abstract:
  We describe the INTEGRAL Burst Alert System (IBAS): the automatic software
developed at the INTEGRAL Science Data Center to allow the rapid distribution
of the coordinates of the Gamma-Ray Bursts detected by INTEGRAL. IBAS is
implemented as a ground based system, working on the near-real time telemetry
stream. It is expected that the system will detect more than one GRB per month
in the field of view of the main instruments. Positions with an accuracy of a
few arcminutes will be distributed to the community for follow-up observations
within a few tens of seconds of the event. The system will also upload commands
to optimize the possible detection of bursts in the visible band with the
INTEGRAL Optical Monitor Camera.


title:
On Echo Outbursts and ER UMa Supercycles in SU UMa-type Cataclysmic
  Variables

abstract:
  I present a variation on Osaki's tidal-thermal-instability model for SU UMa
behavior. I suggest that in systems with the lowest mass ratios, the
angular-momentum dissipation in an eccentric disk is unable to sustain the disk
on the hot side of the thermal instability. This decoupling of the tidal and
thermal instabilities in systems with q < 0.07 allows a better explanation of
the `echo' outbursts of EG Cnc and the short supercycles of RZ LMi and DI UMa.
The idea might also apply to the soft X-ray transients.


title: The origin of the mid- and far-infrared emission in AGN

abstract:
  The relation between the X-ray emission, the infrared emission and the
coronal line emission in a sample of the brightest known Seyfert galaxies is
analyzed. A close relationship between the absorption-corrected soft X-ray
emission and both the mid-infrared and the coronal line emission is found among
the Seyfert type 2 objects studied in this work. Being both the coronal line
and the X-ray emissions main tracers of the AGN activity, their relation with
the mid-infrared emission adds further support to the claim that the
mid-infrared emission is primarily due to dust heated directly by the central
AGN. No apparent relationship between the soft X-ray emission and the coronal
line and/or the mid-infrared emissions is seen within Seyfert 1 objects, the
number of objects of this class in the sample is comparatively smaller though.
That discrepancy is partially due to the fact that the soft X-ray emission in
the Seyfert 1s is systematically larger by at least one order of magnitude than
that in their Seyfert 2 counterparts. Finally, the hard X-ray emission in both
Seyfert types shows unrelated to the mid-infrared and coronal line emissions.


title:
Optical studies of the X-ray transient XTE J2123-058 - II.
  Phase-resolved spectroscopy

abstract:
  We present time-resolved spectroscopy of the soft X-ray transient XTE
J2123-058 in outburst. A useful spectral coverage of 3700-6700A was achieved
spanning two orbits of the binary, with single epoch coverage extending to
\~9000A. The optical spectrum approximates a steep blue power-law, consistent
with emission on the Rayleigh-Jeans tail of a hot black body spectrum. The
strongest spectral lines are HeII 4686A and CIII/NIII 4640A (Bowen blend) in
emission. Their relative strengths suggest that XTE J2123-058 was formed in the
Galactic plane, not in the halo. Other weak emission lines of HeII and CIV are
present and Balmer lines show a complex structure, blended with HeII. HeII
4686A profiles show a complex multiple S-wave structure with the strongest
component appearing at low velocities in the lower-left quadrant of a Doppler
tomogram. H alpha shows transient absorption between phases 0.35-0.55. Both of
these effects appear to be analogous to similar behaviour in SW Sex type
cataclysmic variables. We therefore consider whether the spectral line
behaviour of XTE J2123-058 can be explained by the same models invoked for
those systems.


title: Far-Infrared Source Counts and the Diffuse Infrared Background

abstract:
  The cosmic far-infrared background is now well measured from 140 micron to 1
mm. Uncertainties remain at 100 micron (and even more at 60 micron). These are
dominated by limitations of the zodiacal model. The nature of sources
dominating the background near its maximum are beginning to be studied through
deep surveys carried out with ISOPHOT. These surveys show very steep number
counts and fluctuations of the background due to unresolved sources.


title: Intrinsic Shapes of Molecular Cloud Cores

abstract:
  We conduct an analysis of the shapes of molecular cloud cores using recently
compiled catalogs of observed axis ratios of individual cores mapped in ammonia
or through optical selection. We apply both analytical and statistical
techniques to deproject the observed axis ratios in order to determine the true
distribution of cloud core shapes. We find that neither pure oblate nor pure
prolate cores can account for the observed distribution of core shapes.
Intrinsically triaxial cores produce distributions which agree with
observations. The best-fit triaxial distribution contains cores which are more
nearly oblate than prolate.


title:
The peculiar cluster HS 327 in the Large Magellanic Cloud: can OH/IR
  stars and carbon stars be twins?

abstract:
  The obscured OH/IR star IRAS05298-6957 in the LMC was recently noticed to be
member of the small double cluster HS 327 that also contains a carbon star (van
Loon et al., 1998, A&A 329, 169). Hence they are coeval and have (nearly) the
same progenitor mass, which can only be understood if Hot Bottom Burning (HBB)
has prevented IRAS05298-6957 from being a carbon star. We present extensive
visual and near-IR photometric data for >10^4 stars in and around HS 327, and
spectroscopic data for some of the brightest AGB stars amongst these.
Colour-magnitude diagrams are used to estimate the age for the cluster and its
members, and luminosities are derived for the stars for which spectra have been
obtained. The age for IRAS05298-6957 and the carbon star is estimated to be
about 200 Myr. This corresponds to a Main-Sequence progenitor mass of about 4.0
M_sun --- the first direct measurement of the lower mass threshold for HBB.
This agrees with stellar evolution models that, however, fail to reproduce the
low luminosity of the carbon star.


title: Variable Unidentified Gamma-Ray Sources Near the Galactic Plane

abstract:
  In a recent paper, Romero et al. (1999) have presented the results of a
positional correlation analysis of the low-latitude unidentified gamma-ray
sources in the Third EGRET catalog with complete lists of galactic objects like
supernova remnants, early type stars with strong stellar winds, and OB
associations (considered as pulsar tracers). We have now carried out a study of
those 42 sources at |b|<10 deg for which no counterpart was found at all. A
variability analysis shows that this sample contains a population of sources
with high levels of variability at gamma-rays. The surface density of these
variable sources is 5 times higher than what is expected for unidentified AGNs
seen through the Galactic plane. We discuss the origin of this presumed
Galactic population of gamma-ray objects and the role that INTEGRAL could play
in their physical identification.


title:
Excitation of stellar p-modes by turbulent convection: 1. Theoretical
  formulation

abstract:
  Stochatic excitation of stellar oscillations by turbulent convection is
investigated and an expression for the power injected into the oscillations by
the turbulent convection of the outer layers is derived which takes into
account excitation through turbulent Reynolds stresses and turbulent entropy
fluctuations. This formulation generalizes results from previous works and is
built so as to enable investigations of various possible spatial and temporal
spectra of stellar turbulent convection. For the Reynolds stress contribution
and assuming the Kolmogorov spectrum we obtain a similar formulation than those
derived by previous authors. The entropy contribution to excitation is found to
originate from the advection of the Eulerian entropy fluctuations by the
turbulent velocity field. Numerical computations in the solar case in a
companion paper indicate that the entropy source term is dominant over Reynold
stress contribution to mode excitation, except at high frequencies.


title:
Discovery of a Cyclotron Resonant Scattering Feature in the RXTE
  Spectrum of 4U 0352+309 (X Per)

abstract:
  We have discovered a ~29 keV Cyclotron Resonant Scattering Feature (CRSF) in
the X-Ray spectrum of 4U 0352+309 (X Per) using observations taken with the
Rossi X-Ray Timing Explorer. 4U 0352+309 is a persistent low luminosity (L_x =
4.2x10^34 ergs/s) X-ray pulsar, with a 837 s period and which accretes material
from the Be star X Per. The X-Ray spectrum, unusual when compared to brighter
accreting pulsars, may be due to the low mass accretion rate and could be
typical of the new class of persistent low luminosity Be/X-Ray binary pulsars.
We attempted spectral fits with continuum models used historically for 4U
0352+309, and found that all were improved by the addition of a CRSF at ~29
keV. The model that best fit the observations is a combination of a 1.45+/-0.02
keV blackbody with a 5.4x10^8 cm^2 area, and a power-law with a 1.83+/-0.03
photon index modified by the CRSF. In these fits the CRSF energy is
28.6+1.5-1.7 keV, implying a magnetic field strength of 2.5(1+z)x10^12 G in the
scattering region (where z is the gravitational redshift). Phase resolved
analysis shows that the blackbody and cyclotron line energies are consistent
with being constant through the pulse.


title: Excitation of stellar p-modes by turbulent convection : 2. The Sun

abstract:
  Acoustic power and oscillation amplitudes of radial oscillations computed for
a solar model are compared with solar seismic observations. The oscillations
are assumed stochastically excited by turbulence. The numerical computations
are based upon a theoretical formulation of the power going into solar like
oscillation modes as proposed by Samadi et al. (2000) in a companion paper.
This formulation allows to investigate several assumptions concerning
properties of the stellar turbulence. We find that the entropy source plays a
dominant role in the stochastic excitation compared with the Reynold stress
source in agreement with Goldreich et al. (1994). We consider several turbulent
kinetic energy spectra suggested by different observations of the solar
granulation. Differences between turbulent spectra manifest themselves by large
differences in the computed oscillation powers at high oscillation frequency.
Two free parameters which are introduced in the description of the turbulence
enter the expression for the acoustic power. These parameters are adjusted in
order to fit to the solar observations of the surface velocity oscillations.
The best fit is obtained with the kinetic energy spectrum deduced from the
observations of the solar granulation by Nesis et al. (1993); the corresponding
adjusted parameters are found to be compatible with the theoretical upper limit
which can be set on these parameters. The adopted theoretical approach improves
the agreement between solar seismic observations and numerical results.


title:
MAPCUMBA : a fast iterative multi-grid map-making algorithm for CMB
  experiments

abstract:
  The data analysis of current Cosmic Microwave Background (CMB) experiments
like BOOMERanG or MAXIMA poses severe challenges which already stretch the
limits of current (super-) computer capabilities, if brute force methods are
used. In this paper we present a practical solution to the optimal map making
problem which can be used directly for next generation CMB experiments like
ARCHEOPS and TopHat, and can probably be extended relatively easily to the full
PLANCK case. This solution is based on an iterative multi-grid Jacobi algorithm
which is both fast and memory sparing. Indeed, if there are N_tod data points
along the one dimensional timeline to analyse, the number of operations is
O(N_tod ln N_tod) and the memory requirement is O(N_tod). Timing and accuracy
issues have been analysed on simulated ARCHEOPS and TopHat data, and we discuss
as well the issue of the joint evaluation of the signal and noise statistical
properties.


title:
On Local Approximations to the Nonlinear Evolution of Large-Scale
  Structure

abstract:
  We present a comparative analysis of several methods, known as local
Lagrangian approximations, which are aimed to the description of the nonlinear
evolution of large-scale structure. We have investigated various aspects of
these approximations, such as the evolution of a homogeneous ellipsoid,
collapse time as a function of initial conditions, and asymptotic behavior. As
one of the common features of the local approximations, we found that the
calculated collapse time decreases asymptotically with the inverse of the
initial shear. Using these approximations, we have computed the cosmological
mass function, finding reasonable agreement with N-body simulations and the
Press-Schechter formula.


title: The Radio Galaxy Populations of Nearby Northern Abell Clusters

abstract:
  We report on the use of the NRAO VLA Sky Survey (NVSS) to identify radio
galaxie s in eighteen nearby Abell clusters. The listings extend from the cores
of the clusters out to radii of 3 Mpc, which corresponds to 1.5 Abell radii and
approximately four orders of magnitude in galaxy density. To create a truly
useful catalog, we have collected optical spectra for nearly all of the
galaxies lacking public velocity measurements. Consequently, we are able to
discriminate between those radio galaxies seen in projection on the cluster and
those which are in actuality cluster members. The resulting catalog consists of
329 cluster radio galaxies plus 138 galaxies deemed foreground/background
objects, and new velocity measurements are reported for 273 of these radio
galaxies.
  The motivation for the catalog is the study of galaxy evolution in the
cluster environment. The radio luminosity function (RLF) is a powerful tool in
the identification of active galaxies, as it is dominated by star-forming
galaxies at intermediate luminosities and active galactic nuclei (AGN) at
higher luminosities. The flux limit of the NVSS allows us to identify AGN and
star- forming galaxies down to star formation rates (SFR) less than 1 solar
mass per year. This sensitivity, coupled with the all-sky nature of the NVSS,
allows us to produce a catalog of considerable depth and breadth. In addition
to these data, we report detected infrared fluxes and upper limits obtained
from IRAS data. It is hoped that this database will prove useful in a number of
potential studies of the effect of environment on galaxy evolution.


title: G28.17+0.05: An unusual giant HI cloud in the inner Galaxy

abstract:
  New 21 cm HI observations have revealed a giant HI cloud in the Galactic
plane that has unusual properties. It is quite well defined, about 150 pc in
diameter at a distance of 5 kpc, and contains as much as 100,000 Solar Masses
of atomic hydrogen. The outer parts of the cloud appear in HI emission above
the HI background, while the central regions show HI self-absorption. Models
which reproduce the observations have a core with a temperature <40 K and an
outer envelope as much as an order of magnitude hotter. The cold core is
elongated along the Galactic plane, whereas the overall outline of the cloud is
approximately spherical. The warm and cold parts of the HI cloud have a
similar, and relatively large, line width of approximately 7 km/s. The cloud
core is a source of weak, anomalously-excited 1720 MHz OH emission, also with a
relatively large line width, which delineates the region of HI self-absorption
but is slightly blue-shifted in velocity. The intensity of the 1720 MHz OH
emission is correlated with N(H) derived from models of the cold core. There is
12CO emission associated with the cloud core. Most of the cloud mass is in
molecules, and the total mass is > 200,000 Solar Masses. In the cold core the
HI mass fraction may be 10 percent. The cloud has only a few sites of current
star formation. There may be about 100 more objects like this in the inner
Galaxy; every line of sight through the Galactic plane within 50 degrees of the
Galactic center probably intersects at least one. We suggest that G28.17+0.05
is a cloud being observed as it enters a spiral arm and that it is in the
transition from the atomic to the molecular state.


title:
Constraints on Stirring and Dissipation of MHD Turbulence in Molecular
  Clouds

abstract:
  We discuss constraints on the rates of stirring and dissipation of MHD
turbulence in molecular clouds. Recent MHD simulations suggest that turbulence
in clouds decays rapidly, thus providing a significant source of energy input,
particularly if driven at small scales by, for example, bipolar outflows. We
quantify the heating rates by combining the linewidth-size relations, which
describe global cloud properties, with numerically determined dissipation
rates. We argue that, if cloud turbulence is driven on small internal scales,
the $^{12}$CO flux (enhanced by emission from weakly supersonic shocks) will be
much larger than observed; this, in turn, would imply excitation temperatures
significantly above observed values. We reach two conclusions: (1) small-scale
driving by bipolar outflows cannot possibly account for cloud support and yield
long-lived clouds, unless the published MHD dissipation rates are seriously
overestimated; (2) driving on large scales (comparable to the cloud size) is
much more viable from an energetic standpoint, and if the actual net
dissipation rate is only slightly lower than what current MHD simulations
estimate, then the observationally inferred lifetimes and apparent virial
equilibrium of molecular clouds can be explained.


title: The Variable Diffuse Continuum Emission of Broad Line Clouds

abstract:
  We investigate the wavelength-dependent intensity and reverberation
properties of the UV-optical diffuse continuum emission expected from broad
emission line gas. The locally optimally emitting clouds picture is adopted,
with the cloud distribution functions in gas density and distance from the
ionizing source determined by a fit to the mean UV emission line spectrum from
the 1993 HST campaign of NGC5548 in our previous paper. The model Balmer
continuum's strength and variability characteristics are in agreement with
those derived from the observations of NGC5548. A key prediction is a
wavelength dependent lag across the UV-optical spectrum which can broadly mimic
the signature from X-ray reprocessing in an accretion disk, calling into
question the discovery claims of the latter in NGC7469. The influence of the
diffuse continuum on the optical continuum may result in a small yet
significant underestimation of the characteristic sizes of the regions emitting
the optical emission lines. Its contribution can also alter the inferred
spectral energy distribution of the UV-optical continuum, even well outside the
spectral region near the well-known Balmer jump. The reverberation of the
diffuse continuum emitted by the BLR may account for perhaps one-third of the
observed effect that the 1350-5100 Angstrom continuum becomes bluer as it
becomes brighter (even after accounting for non-variable optical starlight).
And as in other models of the broad emission line gas, a significant yet
unobserved Lyman jump is predicted. (abridged)


title: Radiative Transfer in Obliquely Illuminated Accretion Disks

abstract:
  The illumination of an accretion disk around a black hole or neutron star by
the central compact object or the disk itself often determines its spectrum,
stability, and dynamics. The transport of radiation within the disk is in
general a multi-dimensional, non-axisymmetric problem, which is challenging to
solve. Here, I present a method of decomposing the radiative transfer equation
that describes absorption, emission, and Compton scattering in an obliquely
illuminated disk into a set of four one-dimensional transfer equations. I show
that the exact calculation of the ionization balance and radiation heating of
the accretion disk requires the solution of only one of the one-dimensional
equations, which can be solved using existing numerical methods. I present a
variant of the Feautrier method for solving the full set of equations, which
accounts for the fact that the scattering kernels in the individual transfer
equations are not forward-backward symmetric. I then apply this method in
calculating the albedo of a cold, geometrically thin accretion disk.


title: Optical Spectroscopy of Type Ib/c Supernovae

abstract:
  We present 84 spectra of Type Ib/c and Type IIb supernovae (SNe), describing
the individual SNe in detail. The relative depths of the helium absorption
lines in the spectra of the SNe Ib appear to provide a measurement of the
temporal evolution of the SN, with He I 5876 and He I 7065 growing in strength
relative to He I 6678 over time. Light curves for three of the SNe Ib provide a
sequence for correlating the helium-line strengths. We find that some SNe Ic
show evidence for weak helium absorption, but most do not. Aside from the
presence or absence of the helium lines, there are other spectroscopic
differences between SNe Ib and SNe Ic. On average, the O I 7774 line is
stronger in SNe Ic than in SNe Ib. In addition, the SNe Ic have distinctly
broader emission lines at late times, indicating either a consistently larger
explosion energy and/or lower envelope mass for SNe Ic than for SNe Ib. While
SNe Ib appear to be basically homogeneous, the SNe Ic are quite heterogeneous
in their spectroscopic characteristics. Three SNe Ic that may have been
associated with gamma-ray bursts are also discussed; two of these have clearly
peculiar spectra, while the third seems fairly typical.


title: TeV Gamma-Ray Astronomy in the new Millennium

abstract:
  The field of TeV gamma-ray astronomy is reviewed with emphasis on its
relation to the origin of cosmic rays. The discovery of TeV photons from
supernova remnants and active galaxies has provided the first direct
observational link between specific astrophysical objects and particle
production at the TeV scale. TeV gamma-ray observations constrain the high end
of the electromagnetic spectrum, a regime most sensitive for testing particle
acceleration and emission models. TeV telescopes have made important
contributions to the understanding of blazars and supernova remnants, however,
it will take the next generation atmospheric Cherenkov telescopes and
satellite-based gamma-ray detectors to unravel the mystery of hadronic
cosmic-ray sources.
  A short review of TeV observations is followed by a discussion of the
capabilities and scientific potential of the next generation ground-based
atmospheric Cherenkov telescopes.


title:
PICsIM - the INTEGRAL/IBIS/PICsIT Observation Simulation Tool for
  Prototype Software Evaluation

abstract:
  The INTEGRAL satellite is an observatory-class gamma-ray telescope due for
launch in early 2002. It comprises two main instruments, one optimised for
imaging (IBIS) and the other for spectroscopy (SPI). The PICsIT telescope is
the high energy (150 keV - 10 MeV) plane of the IBIS imager and consists of 8
individual modules of 512 detection elements. The modules are arranged in a 4 x
2 pattern, while the pixels are in a 16 x 32 array. This layout, which includes
a dead area equivalent to one pixel width between each module, together with
the event selection procedure, which (in standard mode) does not allow the
identification of coincidences between separate modules, leads to a
non-uniformity of the background which is significantly different for
single-site events and for multiple energy deposits. Other sources of
background variations range from the separate low energy detector, situated
immediately above the PICsIT plane, to the large mass of the SPI telescope at a
short distance to one side. The algorithms for performing all the imaging and
spectral deconvolution for PICsIT are currently being produced for delivery to
the INTEGRAL Science Data Centre. In order to maximise the information which
may be extracted from the PICsIT data, we have designed a prototyping
environment which consists of a GUI to a highly structured and modular set of
procedures which allows the easy simulation of observations from the data
collection phase through to the final image production and analysis.


title:
DISCoS - a detector-independent software for the on-ground testing and
  calibration of scientific payloads using the ESA Packet Telemetry and
  Telecommand Standards

abstract:
  The ESA Packet Telemetry and Telecommand Standards accommodate the
requirements of a great variety of scientific space missions, thus providing a
standard basis for cost-effective and technically compatible developments of
on-board and on-ground data handling systems for a wide range of projects. This
paper describes the design and the implementation of a detector-independent
software, running on Unix platforms, which has been developed for the near real
time acquisition, archiving, and basic processing of the ESA based telemetry
and telecommand data produced during the on ground testing and calibration of
various X- and $\gamma$-ray space borne detectors.


title:
Population synthesis for double white dwarfs. II. Semi-detached systems:
  AM CVn stars

abstract:
  We study two models for AM CVn stars: white dwarfs accreting (i) from a
helium white dwarf companion and (ii) from a helium-star donor. We show that in
the first model possibly no accretion disk forms at the onset of mass transfer.
The stability and the rate of mass transfer then depend on the tidal coupling
between the accretor and the orbital motion. In the second model the formation
of AM CVn stars may be prevented by detonation of the CO white dwarf accretor
and the disruption of the system. With the most favourable conditions for the
formation of AM CVn stars we find a current Galactic birth rate of 6.8 10^{-3}
yr^{-1}. Unfavourable conditions give 1.1 10^{-3} yr^{-1}. The expected total
number of the systems in the Galaxy is 9.4 10^{7} and 1.6 10^{7}, respectively.
We model very simple selection effects to get some idea about the currently
expected observable population and discuss the (quite good) agreement with the
observed systems.


title: The Connection between BL Lacs and FSRQs

abstract:
  We discuss the features that mark the Flat Spectrum Radio Quasars from the BL
Lacertae objects. We propose that FSRQs exceeding L = 10^{46} erg/s are powered
by black hole accreting at rates dm/dt = 1 - 10; their power is dominated by
the disk components, thermal and BZ. Instead, sources accreting at rates
10^{-3} < dm/dt < 10^{-2} radiate in the BL Lac mode; here the power is mainly
non-thermal, and is driven by the rotational energy stored in a Kerr hole which
sustains L < 10^{46} erg/s in the jet frame for Gyrs. The two populations may
be even linked if around the same objects dm/dt drops in time; then some
negative cosmological evolution is expected for the newborn BL Lacs fed by the
dying FSRQs. Further implications are discussed.


title: Circumstellar masers in the Magellanic Clouds

abstract:
  We have searched for 22 GHz H2O and 43/86/129 GHz SiO masers in bright IRAS
point sources in the SMC and LMC, to test whether the kinematics of the mass
loss from these stars depends on metallicity. H2O masers were detected in the
red supergiants IRAS04553-6825 and IRAS05280-6910, and tentatively in the
luminous IR object IRAS05216-6753 and the AGB star IRAS05329-6708. SiO masers
were detected in IRAS04553-6825. The outflow velocity increases between the H2O
masing zone near the dust-formation region and the more distant OH masing zone
from 18 to 26 km/s for IRAS04553-6825 and from 6 to 17 km/s for IRAS05280-6910.
The total sample of LMC targets is analysed in comparison with circumstellar
masers in the Galactic Centre. The photon fluxes of circumstellar masers in the
LMC are very similar to those in the Galactic Centre. The expansion velocities
in the LMC appear to be 20% lower than for similarly bright OH masers in the
Galactic Centre, but the data are consistent with no difference in expansion
velocity. OH/IR stars in the LMC appear to have slower accelerating envelopes
than OH/IR stars in the Galactic Centre. Masers in the LMC have blue-asymmetric
emission profiles. This may be due to the amplification of stellar and/or
free-free radiation, rather than the amplification of dust emission, and may be
more pronounced in low metallicity envelopes. SiO maser strength increases with
the photometric amplitude at 2.2 micron but is independent of the photometric
amplitude at 10 micron. This suggests a strong connection between shocks in the
dust-free SiO masing zone and the dust formation process. Appendices describe
H2O maser emission from R Dor in the Milky Way, optical echelle spectroscopy of
IRAS04553-6825, and the properties of masers in the Galactic Centre (Abridged).


title:
Cluster AgeS Experiment. CCD photometry of SX Phoenicis variables in the
  globular cluster M 55

abstract:
  We present CCD photometry of SX Phe variables in the field of the globular
cluster M 55. We have discovered 27 variables, three of which are probable
members of the Sagittarius dwarf galaxy. All of the SX Phe stars in M 55 lie in
the blue straggler region of the cluster color-magnitude diagram. Using period
ratio information we have identified the radial pulsation modes for one of the
observed variables. Inspection of the period-luminosity distribution permits
the probable identifications of the pulsation modes for most of the rest of the
stars in the sample. We have determined the slope of the period-luminosity
relation for SX Phe stars in M 55 pulsating in the fundamental mode. Using this
relation and the HIPPARCOS data for SX Phe itself, we have estimated the
apparent distance modulus to M 55 to be (m-M)_V=13.86 +- 0.25 mag.


title: The Void Phenomenon

abstract:
  Advances in theoretical ideas on how galaxies formed have not been strongly
influenced by the advances in observations of what might be in the voids
between the concentrations of ordinary optically selected galaxies. The theory
and observations are maturing, and the search for a reconciliation offers a
promising opportunity to improve our understanding of cosmic evolution. I
comment on the development of this situation and present an update of a nearest
neighbor measure of the void phenomenon that may be of use in evaluating
theories of galaxy formation.


title: Oscillation power as a diagnostic tool for stellar turbulent spectra

abstract:
  Recent observations and theoretical studies support the theory that
solar-type oscillations are intrinsically stable but excited stochastically by
the turbulent convection in the outer layers of the star. The acoustic noise
generated by the convective motion depends on the details of the turbulent
energy spectrum. In this paper we present a general formulation for the
acoustic noise generation rate based on previous works by other authors. In
this general formulation any model for the spatial turbulent energy spectrum
and for the turbulent time spectrum can be assumed. We compute acoustic power
spectra and oscillation amplitudes of radial oscillations for models of the Sun
and Procyon A. The results are compared with recent observations.


title:
Oscillation power as a test of stellar turbulence : Scanning the HR
  diagram

abstract:
  The acoustic power injected by turbulent convection into solar-like
oscillations depends on the details of the turbulent spectrum. A theoretical
formulation for the oscillation power is developed which generalizes previous
ones. The formulation is first calibrated on a solar model in such a way as to
reproduce the solar seismic data. This allows to investigate different
assumptions about the stellar turbulent spectrum. We next explore consequences
of the assumed turbulent description for some potentially solar-like
oscillating stars. Large differences are found in the oscillation power of a
given star when using different turbulent spectra as well as in a star to star
comparison. Space seismic observations of such stars will be valuable for
discriminating between several turbulent models.


title: Cosmic shear surveys

abstract:
  Gravitational weak shear produced by large-scale structures of the universe
induces a correlated ellipticity distribution of distant galaxies. The
amplitude and evolution with angular scale of the signal depend on cosmological
models and can be inverted in order to constrain the power spectrum and the
cosmological parameters. We present our recent analysis of 50 uncorrelated VLT
fields and the very first constrains on ($\Omega_m,\sigma_8$) and the nature of
primordial fluctuations based on the join analysis of present-day cosmic shear
surveys.


title: Correlation of the South Pole 94 data with 100microns and 408 MHz maps

abstract:
  We present a correlation between the ACME/SP94 CMB anisotropy data at 25 to
45 GHz with the IRAS/DIRBE data and the Haslam 408 MHz data. We find a marginal
correlation between the dust and the Q-band CMB data but none between the CMB
data and the Haslam map. While the amplitude of the correlation with the dust
is larger than that expected from naive models of dust emission it does not
dominate the sky emission.


title: Simulations of black hole-neutron star binary coalescence

abstract:
  We show the results of dynamical simulations of the coalescence of black
hole-neutron star binaries. We use a Newtonian Smooth Particle Hydrodynamics
code, and include the effects of gravitational radiation back reaction with the
quadrupole approximation for point masses, and compute the gravitational
radiation waveforms. We assume a polytropic equation of state determines the
structure of the neutron star in equilibrium, and use an ideal gas law to
follow the dynamical evolution. Three main parameters are explored: (i) The
distribution of angular momentum in the system in the initial configuration,
namely tidally locked systems vs. irrotational binaries; (ii) The stiffness of
the equation of state through the value of the adiabatic index Gamma (ranging
from Gamma=5/3 to Gamma=3); (iii) The initial mass ratio q=M(NS)/M(BH). We find
that it is the value of Gamma that determines how the coalescence takes place,
with immediate and complete tidal disruption for Gamma less than 2, while the
core of the neutron star survives and stays in orbit around the black hole for
Gamma=3. This result is largely independent of the initial mass ratio and spin
configuration, and is reflected directly in the gravitational radiation signal.
For a wide range of mass ratios, massive accretion disks are formed
(M(disk)~0.2 solar masses), with baryon-free regions that could possibly give
rise to gamma ray bursts.


title: The Equilibrium State of Molecular Regions in the Outer Galaxy

abstract:
  A summary of global properties and an evaluation of the equilibrium state of
molecular regions in the outer Galaxy are presented from the decomposition of
the FCRAO Outer Galaxy Survey and targeted 12CO and 13CO observations of four
giant molecular cloud complexes. The ensemble of identified objects includes
both small, isolated clouds and clumps within larger cloud complexes. 12CO
velocity dispersions show little variation with cloud sizes for radii less than
10 pc. It is demonstrated that the internal motions of regions with molecular
masses greater than 10**4 msuns are bound by self gravity, yet, the constituent
clumps of cloud complexes and isolated molecular clouds with M < 10**3 msuns
are not in self gravitational equilibrium. The required external pressures to
maintain the equilibrium of this population are (1-2)x10**4 cm-3-K.


title: Astrophysical Limits on Massive Dark Matter

abstract:
  Annihilations of weakly interacting dark matter particles provide an
important signature for the possibility of indirect detection of dark matter in
galaxy halos. These self-annihilations can be greatly enhanced in the vicinity
of a massive black hole. We show that the massive black hole present at the
centre of our galaxy accretes dark matter particles, creating a region of very
high particle density. Consequently the annihilation rate is considerably
increased, with a large number of $e^+e^-$ pairs being produced either directly
or by successive decays of mesons. We evaluate the synchrotron emission (and
self-absorption) associated with the propagation of these particles through the
galactic magnetic field, and are able to constrain the allowed values of masses
and cross sections of dark matter particles.


title:
The Evolutionary Status of Isolated Dwarf Irregular Galaxies II. Star
  Formation Histories and Gas Depletion

abstract:
  The results of UBV and H alpha imaging of a large sample of isolated dwarf
irregular galaxies are interpreted in the context of composite stellar
population models. The observed optical colors are best fit by composite
stellar populations which have had approximately constant star formation rates
for at least 10 Gyr. The galaxies span a range of central surface brightness,
from 20.5 to 25.0 mag arcsec^{-2}; there is no correlation between surface
brightness and star formation history. Although the current star formation
rates are low, it is possible to reproduce the observed luminosities without a
major starburst episode. The derived gas depletion timescales are long,
typically ~20 Gyr. These results indicate that dwarf irregular galaxies will be
able to continue with their slow, but constant, star formation activity for at
least another Hubble time.
  The sample of isolated dIs is compared to a sample of star bursting dwarf
galaxies taken from the literature. The star bursting dwarf galaxies have many
similar properties; the main difference between these two types of gas-rich
dwarf galaxies is that the current star formation is concentrated in the center
of the star bursting systems while it is much more distributed in the quiescent
dIs. This results in pronounced color gradients for the starbursting dwarf
galaxies, while the majority of the quiescent dwarf irregular galaxies have
minor or non-existent color gradients. Thus, the combination of low current
star formation rates, blue colors, and the lack of significant color gradients
indicates that star formation percolates slowly across the disk of normal dwarf
galaxies in a quasi-continuous manner.


title: Neutron Star Pulsations and Instabilities

abstract:
  Gravitational radiation (GR) drives an instability in certain modes of
rotating stars. This instability is strong enough in the case of the r-modes to
cause their amplitudes to grow on a timescale of tens of seconds in rapidly
rotating neutron stars. GR emitted by these modes removes angular momentum from
the star at a rate which would spin it down to a relatively small angular
velocity within about one year, if the dimensionless amplitude of the mode
grows to order unity. A pedagogical level discussion is given here on the
mechanism of GR instability in rotating stars, on the relevant properties of
the r-modes, and on our present understanding of the dissipation mechanisms
that tend to suppress this instability in neutron stars. The astrophysical
implications of this GR driven instability are discussed for young neutron
stars, and for older systems such as low mass x-ray binaries. Recent work on
the non-linear evolution of the r-modes is also presented.


title: Millimeter observations of radio-loud active galaxies

abstract:
  In order to study the nature of the far-infrared emission observed in
radio-loud active galaxies, we have obtained 1.2 mm observations with the IRAM
30 m telescope for a sample of eight radio-loud active galaxies. In all objects
we find that the 1.2 mm emission is dominated by non-thermal emission. An
extrapolation of the non-thermal radio spectrum indicates that the contribution
of synchrotron emission to the far-infrared is less than 10% in quasars, and
negligible in the radio galaxies. The quasars in the sample show signs of
relativistic beaming at millimeter wavelengths, and the quasar 3C334 shows
evidence for strong variability.


title: Neutron Stars as Sources of High Energy Particles - the case of RPP

abstract:
  Highly magnetised rapidly spinning neutron stars are widely considered to be
natural sites for acceleration of charged particles. Powerful acceleration
mechanism due to unipolar induction is thought to operate in the magnetospheres
of isolated neutron stars, bringing the particles to ultrarelativistic energies
at the expense of the neutron star rotational energy, with inevitable emission
of high energy photons. The aim of this review is to present basic ingredients
of modern models of magnetospheric activity of rotation powered pulsars in the
context of high-energy radiation from these objects. Several aspects of pulsar
activity are addressed and related to spectacular results of pulsar
observations with two major satellite missions of the past - CGRO and ROSAT. It
is then argued that high sensitivity experiments of the future - GLAST, VERITAS
and MAGIC - will be vital for a progress in our understanding of pulsar
magnetospheric processes. In a conservative approach rotation powered pulsars
are not expected to be the sources of UHE Cosmic Rays. However, several
scenarios have been proposed recently to explain the UHECR events above the GZK
limit with the help of acceleration processes in the immediate surrounding of
newly born pulsars. Major features of these scenarios are reviewed along with
references to contemporary models of magnetospheric activity.


title: The Mass and Structure of the Pleiades Star Cluster from 2MASS

abstract:
  We present the results of a large scale search for new members of the
Pleiades star cluster using 2MASS near-infrared photometry and proper motions
derived from POSS plates digitized by the USNO PMM program. The search extends
to a 10 degree radius around the cluster, well beyond the presumed tidal
radius, to a limiting magnitude of R ~ 20, corresponding to ~ 0.07 M_sun at the
distance and age of the Pleiades. Multi-object spectroscopy for 528 candidates
verifies that the search was extremely effective at detecting cluster stars in
the 1 - 0.1 M_sun mass range using the distribution of H_alpha emission
strengths as an estimate of sample contamination by field stars.
  When combined with previously identified, higher mass stars, this search
provides a sensitive measurement of the stellar mass function and dynamical
structure of the Pleiades. The degree of tidal elongation of the halo agrees
well with current N body simulation results. Tidal truncation affects masses
below ~ 1 M_sun. The cluster contains a total mass ~ 800 M_sun. Evidence for a
flatter mass function in the core than in the halo indicates the depletion of
stars in the core with mass less than ~ 0.5 M_sun, relative to stars with mass
\~1 - 0.5 M_sun, and implies a preference for very low mass objects to populate
the halo or escape. The overall mass function is best fitted with a lognormal
form that becomes flat at ~ 0.1 M_sun. Whether sufficient dynamical evaporation
has occurred to detectably flatten the initial mass function, via preferential
escape of very low mass stars and brown dwarfs, is undetermined, pending better
membership information for stars at large radial distances.


title: Chaos in Pseudo-Newtonian Black Holes with Halos

abstract:
  The Newtonian as well as the special relativistic dynamics are used to study
the stability of orbits of a test particle moving around a black hole plus a
dipolar halo. The black hole is modeled by either the usual monopole potential
or the Paczynki-Wiita pseudo-Newtonian potential. The full general relativistic
similar case is also considered. The Poincare section method and the Lyapunov
characteristic exponents show that the orbits for the pseudo-Newtonian
potential models are more unstable than the corresponding general relativistic
geodesics.


title:
Time-Variable Emission from Transiently Accreting Neutron Stars In
  Quiescence due to Deep Crustal Heating

abstract:
  Transiently accreting neutron stars in quiescence (Lx<10^34 erg/s) have been
observed to vary in intensity by factors of few, over timescales of days to
years. If the quiescent luminosity is powered by a hot NS core, the core
cooling timescale is much longer than the recurrence time, and cannot explain
the observed, more rapid variability. However, the non-equilibrium reactions
which occur in the crust during outbursts deposit energy in iso-density shells,
from which the thermal diffusion timescale to the photosphere is days to years.
The predicted magnitude of variability is too low to explain the observed
variability unless - as is widely believed - the neutrons beyond the
neutron-drip density are superfluid. Even then, variability due to this
mechanism in models with standard core neutrino cooling processes is less than
50 per cent - still too low to explain the reported variability. However,
models with rapid core neutrino cooling can produce variability by a factor as
great as 20, on timescales of days to years following an outburst. Thus, the
factors of few intensity variability observed from transiently accreting
neutron stars can be accounted for by this mechanism only if rapid core cooling
processes are active.


title: A New Pupil for Detecting Extrasolar Planets

abstract:
  The challenge for optical detection of terrestial planet is the 25 magnitude
brightness contrast between the planet and its host star. This paper introduces
a new pupil design that produces a very dark null along its symmetry axis. By
changing the shape of the pupil, we can control the depth and location of this
null. This null can be further enhanced by combining this pupil with a rooftop
nuller or cateye nuller and an aperture stop. The performance of the optical
system will be limited by imperfections in the mirror surface. If the star is
imaged with and without the nuller, then we can characterize these
imperfections and then correct them with a deformable mirror. The full optical
system when deployed on a 6 $\times$ 10 m space telescope is capable of
detecting Earthlike planets around stars within 20 parsecs. For an Earthlike
planet around a nearby stars (10 parsecs), the telescope can characterize its
atmosphere by measuring spectral lines in the 0.3 - 1.3 micron range.


title: On the trispectrum as a gaussian test for cosmology

abstract:
  In the standard model for structure formation, bound objects originate from
the gravitational collapse of small perturbations arising from quantum
fluctuations with random phases. In other scenarios, based on defects,
structures are seeded by localized energy density. In principle, it is possible
to differentiate between these models on the basis of their statistical
properties; only in the former case is the initial density field an
almost-perfect random gaussian field. In this paper, we investigate the use of
the trispectrum of the galaxy density field, which is the connected four-point
function in Fourier space, as a discriminant between gaussian and non-gaussian
models. It has the advantage of having only weak non-linear growth. We define a
related statistic $\tau$ which, as a test of the gaussian hypothesis, is
independent of cosmology, the power spectrum and biasing, in real space, and
which is, in principle, a measure of the departure from gaussian statistics.
For galaxy redshift surveys, the statistic depends on cosmology and bias only
through the potentially observable parameter $\beta$. We compute the expected
errors on the estimate of $\tau$, and demonstrate with numerical simulations
that it can be a useful discriminant of models, with the important proviso that
any bias is linear on large scales. Whether it is the most effective method is
uncertain and depends on the nature of the departure from gaussianity.


title: The Cosmic Star-Formation History: The UV finds most

abstract:
  This is a summary of arguments in favor of observing high-redshift star
formation in the UV as presented at the Ringberg meeting in September 2000. The
most rapidly star-forming galaxies are very dusty, easier to detect at 850um
than in the UV, but less rapidly star-forming galaxies are less obscured by
dust and as a result the comparatively faint galaxies that hosted most
high-redshift star formation are easiest to detect in the UV. The correlation
of star-formation rate and dust obscuration implies that extremely luminous
dusty galaxies are usually as bright in the UV as the less luminous dust-free
galaxies, and that any UV survey at a given redshift 0<z<~3 deep enough to
detect the majority of the UV luminosity density will detect the majority of
IR-selected galaxies as well. Little star formation occurs in galaxies that are
completely hidden from UV surveys. I review recent attempts to estimate
star-formation rates for high-redshift galaxies from UV data alone. The
strength of UV surveys is that they detect large numbers of high-redshift
galaxies, even ones that are intrinsically very faint, in large and
representative comoving volumes. The weakness is that star-formation rates are
difficult to estimate for the detected galaxies. IR surveys complement them
perfectly: star-formation rates can be estimated with reasonable confidence,
but only small regions of the sky can be surveyed and only the most luminous
sources can be detected. Multiwavelength cooperation, not conflict, will lead
to future progress in this field.


title:
On The Non Thermal Emission and Acceleration of Electrons in Coma and
  Other Clusters of Galaxies

abstract:
  Some clusters of galaxies in addition to thermal bremsstrahlung (TB), emit
diffuse radiation from the intercluster medium (ICM) at radio, EUV and hard
x-ray (HXR) ranges. The radio radiation is due to synchrotron by relativistic
electrons, and the inverse Compton (IC) scattering by the cosmic microwave
background radiation of the same electrons is the most natural source for the
HXR and perhaps the EUV emissions. However, simple estimates give a weaker
magnetic field than that suggested by Faraday rotation measurements.
Consequently, non-thermal bremsstrahlung (NTB) and TB have also been suggested
as sources of these emissions. We show that NTB cannot be the source of the
HXRs and that the difficulty with the low magnetic field in the IC model is
alleviated if we take into account the effects of observational bias,
nonisotropic pitch angle distribution and spectral breaks. We derive a spectrum
for the radiating electrons and discuss acceleration scenarios. We show that
continuous and in situ acceleration in the ICM of the background thermal
electrons requires unreasonably high energy input and acceleration of injected
relativistic electrons gives rise to a much flatter spectrum than desired,
unless a large fraction of electrons escape the ICM, in which case one obtains
EUV and HXR emissions extending well beyond the boundaries of the cluster. A
continuous emission by a cooling spectrum resulting from interaction with ICM
of electrons accelerated elsewhere also suffers from similar shortcomings. The
most likely scenario appears to be an episodic injection-acceleration model,
whereby one obtains a time dependent spectrum that for certain phases of its
evolution satisfies all the requirements.


title: High time-resolution observations of the Vela pulsar

abstract:
  We present high time resolution observations of single pulses from the Vela
pulsar (PSR B0833-45) made with a baseband recording system at observing
frequencies of 660 and 1413 MHz. We have discovered two startling features in
the 1413 MHz single pulse data. The first is the presence of giant micro-pulses
which are confined to the leading edge of the pulse profile. One of these
pulses has a peak flux density in excess of 2500 Jy, more than 40 times the
integrated pulse peak. The second new result is the presence of a large
amplitude gaussian component on the trailing edge of the pulse profile. This
component can exceed the main pulse in intensity but is switched on only
relatively rarely. Fluctutation spectra reveal a possible periodicity in this
feature of 140 pulse periods. Unlike the rest of the profile, this component
has low net polarization and emits predominantly in the orthogonal mode. This
feature appears to be unique to the Vela pulsar. We have also detected
microstructure in the Vela pulsar for the first time. These same features are
present in the 660 MHz data. We suggest that the full width of the Vela pulse
profile might be as large as 10 ms but that the conal edges emit only rarely.


title: Gamma-Ray Bursts: Afterglows and Central Engines

abstract:
  Gamma-ray bursts (GRBs) are most intense transient gamma-ray events in the
sky when they are on together with the strong evidences (i.e. the isotropic and
inhomogeneous distribution of GRBs detected by BASTE) that they are located at
cosmological distances, which make them the most energetic events ever known.
For example, the observed radiation energies of some GRBs are equivalent to
convert more than one solar mass energy into radiation completely. This is
thousand times stronger than that of supernova explosion. Unconventional energy
mechanisms and extremely high conversion efficiency for these mysterious events
are required. The discovery of host galaxies and association with supernovae in
the cosmological distances by the recently launched satellite of BeppoSAX and
ground based radio and optical telescopes in GRB afterglow provides further
support to the cosmological origin of GRBs and put strong constraints on
central engines of GRBs. It is the aim of this article to review the possible
central engines, energy mechanisms, dynamical and spectral evolution of GRBs,
especially focusing on the afterglows in multi-wavebands.


title:
Are You Ready to FLY in the Universe ? A Multi-platform N-body Tree Code
  for Parallel Supercomputers

abstract:
  The code we describe (FLY) is a newly written code (using the tree N-body
method), for three-dimensional self-gravitating collisionless systems
evolution. FLY is a fully parallel code based on the tree Barnes-Hut algorithm
and periodical boundary conditions are implemented by means of the Ewald
summation technique. FLY is based on the one-side communication paradigm to
share data among the processors, that access to remote private data avoiding
any kind of synchronism. The code was originally developed on CRAY T3E system
using the logically SHared MEMory access routines (SHMEM) but it runs also on
SGI ORIGIN systems and on IBM SP by using the Low-Level Application Programming
Interface routines (LAPI). This new code reaches good performance in all
systems where it has been well-tested. This performance allows us today to
consider the code FLY among the most powerful parallel codes for tree N-body
simulations. The FLY version 1.1 is freely available on
http://www.ct.astro.it/fly/ and it will be maintained and upgraded with new
releases.


title: The effect of reionization on the COBE normalization

abstract:
  We point out that the effect of reionization on the microwave anisotropy
power spectrum is not necessarily negligible on the scales probed by COBE. It
can lead to an upward shift of the COBE normalization by more than the
one-sigma error quoted ignoring reionization. We provide a fitting function to
incorporate reionization into the normalization of the matter power spectrum.


title: Discovery of a kHz QPO in 2S 0918-549

abstract:
  We report the discovery of a kilohertz quasi-periodic oscillation (kHz QPO)
in the low-mass X-ray binary (LMXB) 2S 0918-549. The kHz QPO has a frequency of
1156+-9 Hz, a FWHM of 70+-20 Hz, and a fractional rms amplitude of 18%+-2%. We
also detected for the first time a type I X-ray burst in this source. The
compact object must therefore be a neutron star. Finally, we were able to
classify the source as an atoll source exhibiting the full complement of
spectral/timing states of this class (island and banana). From the peak burst
flux an upper limit on the persistent luminosity can be derived of 0.5% of the
Eddington luminosity, making 2S 0918-549 one of the least luminous LMXBs
showing a kHz QPO. We compare the fractional rms amplitudes of the upper kHz
QPO across the ensemble of LMXBs. We find a strong anticorrelation with
luminosity. In LMXBs with luminosities ~100 times lower than those of
Z-sources, the fractional rms amplitude is a factor ~10 larger.


title: Magnetized gravitational waves

abstract:
  We investigate the influence of cosmic magnetic fields on gravitational wave
perturbations, and find exact solutions on large scales. We show that a
large-scale magnetic field can generate large-scale non-decaying gravitational
waves. In the general case where gravitational waves are generated by other
mechanisms, a large-scale magnetic field introduces a new decaying tensor mode
and modifies the non-decaying mode. The direct effect of the magnetic field is
to damp the gravitational waves, while an indirect magneto-curvature effect can
either damp or boost the waves. A magnetic field also leads to a breaking of
statistical isotropy, and the magnetic imprint on the tensor spectrum in
principle provides a means of detecting a primordial field.


title:
Deep VLT spectroscopy of the z=2.49 Radio Galaxy MRC 2104-242: Evidence
  for a metallicity gradient in its extended emission line region

abstract:
  We present spectroscopic observations of the rest-frame UV line emission
around radio galaxy MRC 2104-242 at z=2.49, obtained with FORS1 on VLT Antu.
The morphology of the halo is dominated by two spatially resolved regions. Lya
is extended by >12 arcsec along the radio axis, CIV and HeII are extended by ~8
arcsec. The overall spectrum is typical for that of high redshift radio
galaxies. The most striking spatial variation is that NV is present in the
spectrum of the region associated with the center of the galaxy hosting the
radio source, the northern region, while absent in the southern region.
Assuming that the gas is photoionized by a hidden quasar, the difference in NV
emission can be explained by a metallicity gradient within the halo. This is
consistent with a scenario in which the gas is associated with a massive
cooling flow or originates from the debris of the merging of two or more
galaxies.


title:
Near-infrared Integral Field Spectroscopy and Mid-infrared Spectroscopy
  of the Starburst Galaxy M82

abstract:
  We present new observations of the central regions of the starburst galaxy
M82 consisting of near-infrared H- and K-band integral field spectroscopy from
the MPE 3D instrument, and 2.4-45 micron spectroscopy from the Short Wavelength
Spectrometer (SWS) on board ISO. These measurements are used, together with
data from the literature, to re-examine the issue of extinction, determine the
physical conditions of the interstellar medium, and characterize the
composition of the stellar populations. We find that purely foreground
extinction cannot reproduce the global relative intensities of H recombination
lines from optical to radio wavelengths. A good fit is provided by a
homogeneous mixture of dust and sources, and with a visual extinction of 52
mag. The SWS data provide evidence for deviations from commonly assumed
extinction laws between 3 and 10 micron. The fine-structure lines of Ne, Ar,
and S detected with SWS imply an electron density of about 300 cm^{-3}, and
abundance ratios Ne/H and Ar/H nearly solar and S/H one-fourth solar. The
excitation of the ionized gas indicates an average temperature for the OB stars
of 37400 K, with little spatial variation. A random distribution of gas clouds
and ionizing clusters and an ionization parameter of about 10^{-2.3} represent
well the star-forming regions. From population synthesis and the
mass-to-K-light ratio, we conclude that the near-infrared continuum emission
across the starburst regions is dominated by red supergiants with average
temperatures ranging from 3600 K to 4500 K, and roughly solar metallicity. Our
data rule out significant contributions from older metal-rich giants in the
central few tens of parsecs of M82.


title: SuperAGILE: the X-ray Monitor of the AGILE gamma-ray Mission

abstract:
  SuperAGILE is the X-ray stage of the AGILE gamma-ray mission. It is devoted
to monitor X-ray (10-40 keV) sources with a sensitivity better than 10 mCrabs
in 50 ks and to detect X-ray transients in a field of view of 1.8 sr, well
matched to that of the gamma-ray tracker, with few arc-minutes position
resolution and better than 5 us timing resolution. SuperAGILE is designed to
exploit one additional layer of four Si microstrip detectors placed on top of
the AGILE tracker, and a system of four mutually orthogonal one-dimensional
coded masks to encode the X-ray sky. The total geometric area is 1444 cm^2. Low
noise electronics based on ASIC technology composes the front-end read out. We
present here the instrumental and astrophysical performances of SuperAGILE as
derived by analytical calculations, Monte Carlo simulations and experimental
tests on a prototype of the silicon microstrip detector and front-end
electronics.


title:
On the peak radio and X-ray emission from neutron star and black hole
  candidate X-ray transients

abstract:
  We have compiled and analysed reports from the literature of
(quasi-)simultaneous observations of X-ray transients at radio and X-ray
wavelengths and compared them with each other and with more unusual
radio-bright sources such as Cygnus X-3, GRS 1915+105 and Circinus X-1. There
exists a significant (>97% likelihood) positive (rank) correlation between the
peak X-ray flux P_X and radio flux density P_R for the black hole candidate
(BHC) systems, and a marginally significant positive (rank) correlation for the
neutron star (NS) systems. This is further evidence for a coupling between
accretion and outflows in X-ray binary systems, in this case implying a
relation between peak disc-accretion-rate and the number of synchroton-emitting
electrons ejected. However, we also show that the distribution of `radio
loudness', P_R/P_X, is significantly different for the two samples, in the
sense that the BHCs generally have a higher ratio of P_R/P_X. The origin of
this discrepancy is uncertain, but probably reflects differences in the
energetics and/or radiative efficiency of flows around the neutron stars and
black holes; we briefly discuss some of these possibilities. We conclude that
these data point to the formation of a mildly relativistic jet whose luminosity
is a function of the accretion rate, in the majority, if not all, of X-ray
transient outbursts, but whose relation to the observed X-ray emission is
dependent on the nature of the accreting compact object. (Abridged).


title: A catalogue of soft X-ray sources in the galactic center region

abstract:
  We present a catalogue of 107 point-like X-ray sources derived from a
systematic analysis of all the ROSAT PSPC observations of the galactic center
region performed in 1992-1993. Besides SgrA*, the massive black hole at the
galactic center, 41 X-ray sources have been positionally associated with
already classified objects. Twenty are identified with foreground stars and
five with known Low Mass X-ray Binaries. The majority of the sources in our
catalogue still remains unidentified. They are hard and/or severely absorbed
and probably represent a large population of X-ray binaries located in the
galactic center region, accreting at low accretion rates, and still largely
unknown.


title:
From nuclei to atoms and molecules: the chemical history of the early
  Universe

abstract:
  The "dark age" of the Universe is generally pointed out as the period between
the recombination epoch and the horizon of current observations (z=5-6). The
arrow of time in the cosmic history describes the progression from simplicity
to complexity, because the present Universe is clumpy and complicated unlike
the homogeneous early Universe. Thus it is crucial to know the nature of the
constituents, in order to understand the conditions of the formation of the
first bound objects. In this paper we analyse the chemical history of this
"dark age" through the creation of the primordial nuclei to the formation of
the first atoms and molecules. Then we will describe the consequences of the
molecular formation on the birth of the proto-objects. In this context we will
mention the important works of Dennis W. Sciama who influenced a large number
of theorists -cosmologists and astronomers- on this new field of research
dedicated to primordial molecules.


title: The Far-Infrared/Radio Correlation in Nearby Abell Clusters

abstract:
  A comprehensive study of the effect of the cluster environment on the far-
infrared (FIR)/radio correlation in nearby Abell clusters is presented. Using
the cluster radio galaxy database from Miller & Owen (2001) and optical
spectroscopy and high resolution radio images to remove AGN, we assess the
FIR/radio correlation of cluster galaxies from the centers of the clusters out
well past the classical Abell radius. The FIR/radio correlation is shown to
hold quite well for star forming galaxies, and the FIR and radio fluxes for
cluster AGN are also well correlated. In the case of AGN, the relative radio-
to-FIR fluxes are greater and the scatter in the correlation is larger than
those seen for star forming galaxies. We also find that there is a rare but
statistically significant excess of star forming galaxies with enhanced radio
emission in the centers of the clusters, and that the degree of this
enhancement is typically a factor of two or three. The FIR/radio correlation
for cluster star forming galaxies is also tested against line-of-sight velocity
relative to the cluster systemic velocities, but no significant correlation is
found. While the radial dependence of the FIR/radio correlation is consistent
with the model wherein ram pressure increases the cluster galaxies' magnetic
field strengths through compression, the velocity data do not confirm this
model. Although a contribution from ram pressure can not be ruled out, the
thermal pressure due to the ICM alone is an equally viable alternative. The
high resolution radio images largely reject the hypothesis that the increased
radio emission arises from an AGN component, strengthening the claim that the
change in the correlation is caused by a change in the environment of the
galaxies.


title: Fast Zonal Field Dynamo in Collisionless Kinetic Alfven Wave Turbulence

abstract:
  The possibility of fast dynamo action by collisionless kinetic Alfven Wave
turbulence is demonstrated. The irreversibility necessary to lock in the
generated field is provided by electron Landau damping, so the induced electric
field does not vanish with resistivity. Mechanisms for self-regulation of the
system and the relation of these results to the theory of alpha quenching are
discussed. The dynamo-generated fields have symmetry like to that of zonal
flows, and thus are termed zonal fields.


title:
X-ray Observations of Neutron Star Binaries: Evidence for Millisecond
  Spins

abstract:
  High amplitude X-ray brightness oscillations during thermonuclear X-ray
bursts were discovered with the Rossi X-ray Timing Explorer (RXTE) in early
1996. Spectral and timing evidence strongly supports the conclusion that these
oscillations are caused by rotational modulation of the burst emission and that
they reveal the spin frequency of neutron stars in low mass X-ray binaries
(LMXB), a long sought goal of X-ray astronomy. I briefly review the status of
our knowledge of these oscillations. So far 10 neutron star systems have been
observed to produce burst oscillations, interestingly, the observed frequencies
cluster in a fairly narrow range from about 300 - 600 Hz, well below the
break-up frequency for most modern neutron star equations of state (EOS). This
has led to suggestions that their spin frequencies may be limited by the loss
of angular momentum due to gravitational wave emission. Connections with
gravity wave rotational instabilities will be briefly described.


title: On Turbulent Reconnection

abstract:
  We examine the dynamics of turbulent reconnection in 2D and 3D reduced MHD by
calculating the effective dissipation due to coupling between small-scale
fluctuations and large-scale magnetic fields. Sweet-Parker type balance
relations are then used to calculate the global reconnection rate. Two
approaches are employed -- quasi-linear closure and an eddy-damped fluid model.
Results indicate that despite the presence of turbulence, the reconnection rate
remains inversely proportional to $\sqrt{R_m}$, as in the Sweet-Parker
analysis. In 2D, the global reconnection rate is shown to be enhanced over the
Sweet-Parker result by a factor of magnetic Mach number. These results are the
consequences of the constraint imposed on the global reconnection rate by the
requirement of mean square magnetic potential balance. The incompatibility of
turbulent fluid-magnetic energy equipartition and stationarity of mean square
magnetic potential is demonstrated.


title: Chandra X-ray observations of the 3C295 cluster core

abstract:
  We examine the properties of the X-ray gas in the central regions of the
distant (z=0.46), X-ray luminous cluster of galaxies surrounding the powerful
radio source 3C 295, using observations made with the Chandra Observatory.
Between radii of 50-500 kpc, the cluster gas is approximately isothermal with
an emission-weighted temperature, kT ~5 keV. Within the central 50 kpc radius
this value drops to kT ~3.7 keV. The spectral and imaging Chandra data indicate
the presence of a cooling flow within the central 50 kpc radius of the cluster,
with a mass deposition rate of approximately 280 solar masses per year. We
estimate an age for the cooling flow of 1-2 Gyr, which is approximately one
thousand times older than the central radio source. We find no evidence in the
X-ray spectra or images for significant heating of the X-ray gas by the radio
source. We report the detection of an edge-like absorption feature in the
spectrum for the central 50 kpc region, which may be due to oxygen-enriched
dust grains. The implied mass in metals seen in absorption could have been
accumulated by the cooling flow over its lifetime. Combining the results on the
X-ray gas density profile with radio measurements of the Faraday rotation
measure in 3C295, we estimate the magnetic field strength in the region of the
cluster core to be B ~12 \muG.


title:
Luminosity Function of Gamma-Ray Bursts Derived Without Benefit of
  Redshifts

abstract:
  We show that the Euclidean value of <V/Vmax> for gamma-ray bursts (GRB)
selected on a timescale of 1024 ms is correlated with spectral hardness. The
value of <V/Vmax> ranges from 0.42 for soft bursts to 0.26 for the hardest
bursts. Given that the Euclidean value of <V/Vmax> for cosmological objects in
a well defined sample is a distance indicator, the hard bursts must reside at
larger redshifts and therefore be more luminous than the soft bursts. The
resulting luminosity-hardness correlation cannot be shown explicitly due to the
small number of observed GRB redshifts at the present time. Based on the
<V/Vmax>-hardness correlation, we derive the luminosity function of GRBs
without using any redshifts, but we have to make an assumption how the comoving
GRB rate varies with redshift. We present luminosity functions for three models
of the GRB rate as a function of redshift, based on star formation rates. The
peak luminosity functions are approximately broken power laws with an
isotropic-equivalent break luminosity of around 10^51.5 erg s^-1 in the 50-300
keV range and total local rate densities of 0.5 Gpc^-3 y^-1. Predicted GRB
counts as a function of flux and redshift are presented. Based on the GRB
luminosity function, we carry out a simulation to produce the
luminosity-hardness correlation, which shows that the hardest GRBs are about 20
times more luminous than the softest ones.


title: Chaotic Motion Around Prolate Deformed Bodies

abstract:
  The motion of particles in the field of forces associated to an axially
symmetric attraction center modeled by a monopolar term plus a prolate
quadrupole deformation is studied using Poincare surface of sections and
Lyapunov characteristic numbers. We find chaotic motion for certain values of
the parameters, and that the instability of the orbits increases when the
quadrupole parameter increases. A general relativistic analogue is briefly
discussed.


title:
The structure of radiative shock waves. III. The model grid for
  partially ionized hydrogen gas

abstract:
  The grid of the models of radiative shock waves propagating through partially
ionized hydrogen gas with temperature 3000K <= T_1 <= 8000K and density
10^{-12} gm/cm^3 <= \rho_1 <= 10^{-9}gm/cm^3 is computed for shock velocities
20 km/s <= U_1 <= 90 km/s. The fraction of the total energy of the shock wave
irreversibly lost due to radiation flux ranges from 0.3 to 0.8 for 20 km/s <=
U_1 <= 70 km/s. The postshock gas is compressed mostly due to radiative cooling
in the hydrogen recombination zone and final compression ratios are within 1
<\rho_N/\rho_1 \lesssim 10^2, depending mostly on the shock velocity U_1. The
preshock gas temperature affects the shock wave structure due to the
equilibrium ionization of the unperturbed hydrogen gas, since the rates of
postshock relaxation processes are very sensitive to the number density of
hydrogen ions ahead the discontinuous jump. Both the increase of the preshock
gas temperature and the decrease of the preshock gas density lead to lower
postshock compression ratios. The width of the shock wave decreases with
increasing upstream velocity while the postshock gas is still partially ionized
and increases as soon as the hydrogen is fully ionized. All shock wave models
exhibit stronger upstream radiation flux emerging from the preshock outer
boundary in comparison with downstream radiation flux emerging in the opposite
direction from the postshock outer boundary. The difference between these
fluxes depends on the shock velocity and ranges from 1% to 16% for 20 km/s <=
U_1 <= 60 km/s. The monochromatic radiation flux transported in hydrogen lines
significantly exceeds the flux of the background continuum and all shock wave
models demonstrate the hydrogen lines in emission.


title: The central kiloparsec-scale structure of galaxies

abstract:
  This review summarizes some aspects of the central kiloparsec scale structure
of galaxies, and in particular spiral galaxies, elliptical galaxies and merger
remnants. The focus is on results from optical and near-IR imaging and
spectroscopy, with emphasis on recent work with the Hubble Space Telescope.


title:
The Taurus Tunable Filter Field Galaxy Survey: Sample Selection and
  Narrowband Number-Counts

abstract:
  Recent evidence suggests a falling volume-averaged star-formation rate (SFR)
over z ~ 1. It is not clear, however, the extent to which the selection of such
samples influences the measurement of this quantity. Using the Taurus Tunable
Filter (TTF) we have obtained an emission-line sample of faint star-forming
galaxies over comparable lookback times: the TTF Field Galaxy Survey. By
selecting through emission-lines, we are screening galaxies through a quantity
that scales directly with star-formation activity for a given choice of initial
mass function. The scanning narrowband technique furnishes a galaxy sample that
differs from traditional broadband-selected surveys in both its volume-limited
nature and selection of galaxies through emission-line flux. Three discrete
wavelength intervals are covered, centered at H-alpha redshifts z = 0.08, 0.24
and 0.39.
  Galaxy characteristics are presented and comparisons made with existing
surveys of both broadband and emission-line selection. When the number-counts
of emission-line objects are compared with those expected on the basis of
existing H-alpha surveys, we find an excess of ~ 3 times at the faintest
limits. While these detections are yet to be independently confirmed,
inspection of the stronger subsample of galaxies detected in both the line and
continuum (line-on-continuum subsample; 13 %) is sufficient to support an
excess population. This increase in the emission-line field population implies
higher star-formation densities over z ~ 0.4. However, further study in the
form of multi-object spectroscopic follow-up is necessary to quantify this and
confirm the faintest detections in the sample.


title: Ballooning Instability in Polar Caps of Accreting Neutron Stars

abstract:
  We assess the stability of Kruskal-Schwarzschild (magnetic Rayleigh-Taylor)
type modes for accreted matter on the surface of a neutron star confined by a
strong (>= 1.E12 G) magnetic field. Employing the energy principle to analyze
the stability of short-wavelength ballooning modes, we find that line-tying to
the neutron star crust stabilizes these modes until the overpressure at the top
of the neutron star crust exceeds the magnetic pressure by a factor ~ 8(a/h),
where a and h are respectively the lateral extent of the accretion region and
the density scale height. The most unstable modes are localized within a
density scale height above the crust. We calculate the amount of mass that can
be accumulated at the polar cap before the onset of instability.


title:
An Improved Measurement of the Hubble Constant from the
  Sunyaev-Zeldovich Effect

abstract:
  We present a determination of the Hubble constant from measurements of the
Sunyaev-Zeldovich Effect (SZE) in an orientation-unbiased sample of 7 z < 0.1
galaxy clusters. With improved X-ray models and a more accurate 32-GHz
calibration, we obtain H_O = 64+14-11 +/- 14_sys km/s/Mpc. for a standard CDM
cosmology, or 66+14-11 +/- 15_sys km/s/Mpc for a flat LambdaCDM cosmology. In
combination with X-ray cluster measurements and the BBN value for Omega_B, we
find Omega_M = 0.32 +/- 0.05.


title: The Hubble Constant from SZE Measurements in Low-Redshift Clusters

abstract:
  We present a determination of the Hubble constant from measurements of the
Sunyaev-Zeldovich Effect (SZE) in an orientation-unbiased sample of 7 z < 0.1
galaxy clusters. With improved X-ray models and a more accurate 32-GHz
calibration, we obtain H_O = 64+14-11 +/- 14_sys km/s/Mpc. for a standard CDM
cosmology, or 66+14-11 +/- 15_sys km/s/Mpc for a flat LambdaCDM cosmology. The
random uncertainty in this result is dominated by intrinsic CMB anisotropies,
and the systematic uncertainty is chiefly due to uncertainties in the X-ray
spectral models. The implications of this result and future prospects for the
method are discussed.


title: Preliminary Results from the Cosmic Background Imager

abstract:
  The Cosmic Background Imager (CBI) is a 13-element interferometer designed to
image intrinsic anisotropies in the cosmic microwave background (CMB) on
arcminute scales. A review of the capabilities of the instrument is presented,
together with a discussion of observations which have been taken over the past
9 months from the Atacama desert of Chile. We present preliminary
high-resolution mosaiced images of the CMB obtained from recent CBI data and
discuss topics which the CBI will address in the near future.


title: Can Geometric Test Probe the Cosmic Equation of State ?

abstract:
  Feasibility of the geometric test as a probe of the cosmic equation of state
of the dark energy is discussed assuming the future 2dF QSO sample. We examine
sensitivity of the QSO two-point correlation functions, which are theoretically
computed incorporating the light-cone effect and the redshift distortions, as
well as the nonlinear effect, to a bias model whose evolution is
phenomenologically parameterized. It is shown that the correlation functions
are sensitive on a mean amplitude of the bias and not to the speed of the
redshift evolution. We will also demonstrate that an optimistic geometric test
could suffer from confusion that a signal from the cosmological model can be
confused with that from a stochastic character of the bias.


title:
Toy model for a two-dimensional accretion disk dominated by Poynting
  flux

abstract:
  We discuss the effect of the Poynting flow on the magnetically dominated thin
accretion disk, which is simplified to a two-dimensional disk on the equatorial
plane. It is shown in the relativistic formulation that the Poynting flux by
the rotating magnetic field with Keplerian angular velocity can balance the
energy and angular momentum conservation of a steady accretion flow.


title:
Extended Lyman Alpha Emission Around Young Quasars: a Constraint on
  Galaxy Formation

abstract:
  The early stage in the formation of a galaxy inevitably involves a spatially
extended distribution of infalling, cold gas. If a central luminous quasar
turned on during this phase, it would result in significant extended Lyman
alpha emission, possibly accompanied by other lines. For halos condensing at
redshifts between 3 < z < 8 and having virial temperatures between 2 x 10^5 K
and 2 x 10^6 K, this emission results in a ``fuzz'' of characteristic angular
diameter of a few arcseconds, and surface brightness between 10^-18 and 10^-16
erg/s/cm^2/asec^2. The fuzz around bright, high redshift quasars could be
detected in deep narrow band imaging with current telescopes, providing a
direct constraint on galaxy formation models. The absence of detectable fuzz
might suggest that most that most of the protogalaxy's gas settles to a
self-gravitating disk before a quasar turns on. However, continued gas infall
from large radii, or an on-going merger spreading cold gas over a large solid
angle, during the luminous quasar phase could also result in extended
Ly$\alpha$ emission, and can be constrained by deep narrow band imaging.


title: Shock Acceleration of Cosmic Rays - a critical review

abstract:
  Motivated by recent unsuccessful efforts to detect the predicted flux of TeV
gamma-rays from supernova remnants, we present a critical examination of the
theory on which these predictions are based. Three crucial problems are
identified: injection, maximum achievable particle energy and spectral index.
In each case significant new advances in understanding have been achieved,
which cast doubt on prevailing paradigms such as Bohm diffusion and
single-fluid MHD. This indicates that more realistic analytical models, backed
by more sophisticated numerical techniques should be employed to obtain
reliable predictions. Preliminary work on incorporating the effects of
anomalous transport suggest that the resulting spectrum should be significantly
softer than that predicted by conventional theory.


title: WIMP searches with superheated droplet detectors: Status and Prospects

abstract:
  SIMPLE (Superheated Instrument for Massive ParticLE searches) employs
superheated droplet detectors (SDDs) to search for Weakly Interacting Massive
Particle (WIMP) dark matter. As a result of the intrinsic SDD insensitivity to
minimum ionizing particles and high fluorine content of target liquids,
competitive WIMP limits were already obtained at the early prototype stage. We
comment here on the expected immediate increase in sensitivity of the program
and on future plans to exploit this promising technnique.

categories: astro-ph cond-mat.soft hep-ex hep-ph nucl-ex physics.ins-det


title: The broad-line radio galaxy story

abstract:
  In this paper I discuss the issue of the so-called 25 micron-peakers, which
were discovered with IRAS, and consist almost solely of broad-line radio
galaxies. I find that this peak is caused by the absence of colder dust that
emits at 60 micron and not by an excess of hot dust, as suggested by the name.
On optical images, the 25 micron-peakers show a lack of extended dust. The
peakers are consistent with being in a later evolutionary stage, in which all
the extended dust has been formed into stars and the dust torus is smaller. If
the 60 micron dust is heated by stars, there might be a correlation between the
star-formation rate and the power of the AGN.


title:
Stellar Associations and their Field East of LMC 4 in the Large
  Magellanic Cloud

abstract:
  We report about the stellar content and the luminosity and mass functions of
three stellar associations and their field located on the north-east edge of
the super-bubble LMC 4 in the Large Magellanic Cloud.


title: Absorption Systems in the Spectra of 66 z > 4 Quasars

abstract:
  We present high signal-to-noise, 5 A resolution (FWHM) spectra of 66 z \ga 4
bright quasars obtained with the 4 m Cerro Tololo Inter-American Observatory
and 4.2 m William Hershel telescopes. The primary goal of these observations
was to undertake a new survey for intervening absorption systems detected in
the spectra of background quasars. We look for both Lyman-limit systems (column
densities N(HI) > 1.6 * 10^{17} atoms cm-2) and damped Ly-alpha systems (column
densities N(HI) > 2 * 10^{20} atoms cm-2). This work resulted in the discovery
of 49 Lyman-limit systems, 15 of which are within 3000 km s-1 of the quasar
emission and thus might be associated with the quasar itself, 26 new damped
Ly-alpha absorption candidates, 15 of which have z>3.5 and numerous metal
absorption systems. In addition ten of the quasars presented here exhibit
intrinsic broad absorption lines.


title: Kinematic Projecting of Pulsar Profiles

abstract:
  We suggest a technique for construction of profiles of incoherent pulsar
emission using instantaneous angular distribution indicatrix of radiation from
relativistic source moving in the neutron star magnetosphere. In the general
case the indicatrix depends on the kinematic parameters of radiation source
such as velocity and acceleration. The method is illustrated by calculation of
the profiles of pulsar radiation based on synchrotron radiation indicatrix.
This technique can be easily generalized for the case of other types of
relativistic particles radiation. The considered profiles are compared with
observed ones. A good agreement was found with profiles of gamma-pulsars -
Geminga, Crab and Vela.


title: Infrared Imaging Data Reduction Software and Techniques

abstract:
  We describe the InfraRed Data Reduction (IRDR) software package, a small ANSI
C library of fast image processing routines for automated pipeline reduction of
infrared (dithered) observations. We developed the software to satisfy certain
design requirements not met in existing packages (e.g., full weight map
handling) and to optimize the software for large data sets (non-interactive
tasks that are CPU and disk efficient). The software includes stand-alone C
programs for tasks such as running sky frame subtraction with object masking,
image registration and coaddition with weight maps, dither offset measurement
using cross-correlation, and object mask dilation. Although we currently use
the software to process data taken with CIRSI (a near-IR mosaic imager), the
software is modular and concise and should be easy to adapt/reuse for other
work. IRDR is available from anonymous ftp to ftp.ast.cam.ac.uk in pub/sabbey.


title: Lensing by Lyman Limit Systems: Determining the Mass to Gas Ratio

abstract:
  We present a new method to determine the total mass-to-neutral gas ratio in
Lyman-limits systems. The method exploits the relation between the neutral
hydrogen column density and the magnification of background sources due to the
weak gravitational lensing that these systems induce. Because weak lensing does
not provide a direct measure of mass, one must use this relation in a
statistical sense to solve for the average mass-to-gas ratio and its
distribution. We use a detailed mock catalog of quasars (sources) and
Lyman-limit systems (lenses) to demonstrate the applicability of this approach
through our ability to recover the parameter. This mock catalog also allows us
to check for systematics in the method and to sketch its limitations. For a
universal constant mass-to-gas ratio and a sample of N quasars, we obtain an
unbiased estimate of its value with 95% confidence limits (independent of its
actual value) of +/- 140 {10^5/N)^0.5.


title: Monte Carlo Simulations of Dense Galactic Nuclei

abstract:
  We have developed a new numerical code to simulate the joint evolution of a
massive black hole (MBH) and a surrounding stellar cluster at the center of a
galaxy. The physics treated in the simulations include: 2-body relaxation,
stellar collisions (using a large set of "SPH" hydrodynamical simulations) and
tidal disruption of stars by the MBH. In particular, we investigate the rates
of star disruptive events that provide the MBH with gas to accrete.


title:
Soft X-ray properties of a spectroscopically selected sample of
  interacting and isolated Seyfert galaxies

abstract:
  We present a catalogue of ROSAT detected sources in the sample of
spectroscopically selected Seyfert 1 and Seyfert 2 galaxies of Rafanelli et al.
(1995). The catalogue contains 102 Seyfert 1 and 36 Seyfert 2 galaxies. The
identification is based on X-ray contour maps overlaid on optical images taken
from the Digitized Sky Survey. We have derived the basic spectral and timing
properties of the X-ray detected Seyfert galaxies. For Seyfert 1 galaxies a
strong correlation between photon index and X-ray luminosity is detected. We
confirm the presence of generally steeper X-ray continua in narrow-line Seyfert
1 galaxies (NLS1s) compared to broad-line Seyfert 1 galaxies. Seyfert 2
galaxies show photon indices similar to those of NLS1s. Whereas a tendency for
an increasing X-ray luminosity with increasing interaction strength is found
for Seyfert 1 galaxies, such a correlation is not found for Seyfert 2 galaxies.
For Seyfert 1 galaxies we found also a strong correlation for increasing
far-infrared luminosity with increasing interaction strength. Both NLS1s and
Seyfert 2 galaxies show the highest values of far-infrared luminosity compared
to Seyfert 1 galaxies, suggesting that NLS1s and Seyfert 2 galaxies host strong
(cirumnuclear) starformation. For variable Seyfert galaxies we present the
X-ray light curves obtained from the ROSAT All-Sky Survey and from ROSAT PSPC
and HRI pointed observations. Besides the expected strong short- and long-term
X-ray variability in Seyfert 1 galaxies, we find indications for X-ray flux
variations in Seyfert 2 galaxies.


title: Starbursts in ultraluminous infrared galaxies - fueling and properties

abstract:
  The properties of starbursts in ultraluminous infrared galaxies are
discussed, with particular emphasis on the fueling, the amount of extinction
and the intrinsic properties of the nuclear starbursts. It is shown by the
example of NGC6240 that the H_2 vibrational lines can be used to measure the
rate of gas inflow into the potential well, which is sufficient to fuel a
nuclear starburst of the intensity required to account for the far-infrared
emission. It is shown that in Arp220 the faintness of all tracers of ionized
gas can be accounted for by Lyman continuum absorption by dust within the
ionized regions, combined with significant (but not extreme) extinction; there
is no reason to invoke the presence of extreme extinction, an old starburst, or
an additional non-stellar power source in Arp220.


title:
A Monte Carlo Code to Investigate Stellar Collisions in Dense Galactic
  Nuclei

abstract:
  Stellar collisions have long been envisioned to be of great importance in the
center of galaxies where densities of 1e6 stars per cubic pc or higher are
attained. Not only can they play a unique dynamical role by modifying stellar
masses and orbits, but high velocity disruptive encounters occurring in the
vicinity of a massive black hole can also be an occasional source of fuel for
the starved central engine. In the past few years, we have been building a
comprehensive table of SPH (Smoothed Particle Hydrodynamics) collision
simulations for main sequence stars. This database is now integrated as a
module into our Henon-like Monte Carlo code. The combination of SPH collision
simulations with a Monte Carlo cluster evolution code seems ideally suited to
study the frequency, characteristics and effects of stellar collisions during
the long term evolution of galactic nuclei.


title: ISOCAM-CVF 5-12 mum Spectroscopy of Ultraluminous Infrared Galaxies

abstract:
  We present low resolution mid infrared spectra of 16 ultraluminous infrared
galaxies (ULIRGs) obtained with the CVF spectroscopy mode of ISOCAM on board
the Infrared Space Observatory ISO. Our sample completes previous ISO
spectroscopy of ultra- and hyperluminous infrared galaxies towards higher
luminosities. The combined samples cover an infrared luminosity range of
\~10^{12 -13.1} Lo. For about half of the high luminosity ULIRGs studied here,
strong aromatic emission bands suggest starburst dominance. Other spectra are
dominated by a strong AGN-related continuum with weak superposed emission
features of uncertain nature. An improved method to quantitatively characterize
the relative contribution of star formation and AGN activity to the
mid-infrared emission of ULIRGs is presented. As dominant source of the
bolometric luminosity, starbursts prevail at the lower end and AGNs at the
higher end of this range. The transition between mostly starburst and mostly
AGN powered occurs at ~10^{12.4}$ to $10^{12.5} Lo, and individual luminous
starbursts are found up to ~10^{12.65} Lo.


title:
Jet stability and the generation of superluminal and stationary
  components

abstract:
  We present a numerical simulation of the response of an expanding
relativistic jet to the ejection of a superluminal component. The simulation
has been performed with a relativistic time-dependent hydrodynamical code from
which simulated radio maps are computed by integrating the transfer equations
for synchrotron radiation. The interaction of the superluminal component with
the underlying jet results in the formation of multiple conical shocks behind
the main perturbation. These trailing components can be easily distinguished
because they appear to be released from the primary superluminal component,
instead of being ejected from the core. Their oblique nature should also result
in distinct polarization properties. Those appearing closer to the core show
small apparent motions and a very slow secular decrease in brightness, and
could be identified as stationary components. Those appearing farther
downstream are weaker and can reach superluminal apparent motions. The
existence of these trailing components indicates that not all observed
components necessarily represent major perturbations at the jet inlet; rather,
multiple emission components can be generated by a single disturbance in the
jet. While the superluminal component associated with the primary perturbation
exhibits a rather stable pattern speed, trailing components have velocities
that increase with distance from the core but move at less than the jet speed.
The trailing components exhibit motion and structure consistent with the
triggering of pinch modes by the superluminal component.


title: The inner nebula and central binary of the symbiotic star HM Sge

abstract:
  We present contemporaneous HST WFPC2 and VLA observations of the symbiotic
nova HM Sge. We identify a number of discreet features at spatial scales
smaller than approximately 0.1 arcsec embedded in the extended nebula, with
radio and optical emission well correlated in the inner 1 arcsec. For the first
time we measure the positions of the binary components of a symbiotic star
directly. We estimate the projected angular binary separation to be 40+/-9
milli-arcsec, with the binary axis at position angle 130+/-10 degrees. The
latter is consistent with previous estimates made by indirect methods. The
binary separation is consistent with a previous estimate of 50 au if the
distance is 1250+/-280 pc. Temperature and density diagnostics show two
distinct regions in the surrounding nebula, with a cool wedge to the
south-west. An extinction map indicates the true interstellar extinction to be
no more than E(B-V) = 0.35. This is consistent with a minimum distance of
approximatelly 700 pc, but this would be reduced if there is a circumstellar
contribution to the minimum in the extinction map. The extinction map also
suggests a patchy dust distribution. We suggest that a southern concentration
of dust and the south-west wedge are associated with the cool component wind.
Alternatively, the southern dust concentration is the cause of the cool wedge,
as it shields part of the nebula from the hot component radiation field.


title: Visual Spectroscopy of Asteroids at San Pedro Martir

abstract:
  We present low resolution reflectance spectra over the wavelength range
5000-10000\AA for 4 asteroids (3 belonging to the Nysa family and one
near-Earth asteroid) obtained at the San Pedro Martir Observatory (Mexico)
using the 2.1 m telescope. Though the limited wavelength range covered often
makes a classification difficult, the analysis of the available data reveals
that two asteroids of the Nysa family, (2007) McCuskey and (3130) Hillary, are
probably of F-type and (3384) Daliya of S-type. Near-Earth asteroid (3908) Nyx
(Amor asteroid) shows a spectrum, within the limits of our signal-to-noise
ratio (S/N), consistent with a V-type taxonomic classification and may be a
fragment excavated from Vesta by an impact.