title:
Modeling Charge Transfer Inefficiency in the Chandra Advanced CCD
  Imaging Spectrometer

abstract:
  The front-illuminated (FI) CCDs in the Advanced CCD Imaging Spectrometer
(ACIS) on the Chandra X-ray Observatory (Chandra) were damaged in the extreme
environment of the Earth's radiation belts, causing charge traps that result in
enhanced charge transfer inefficiency (CTI) during parallel readout. This
causes row-dependent gain, event grade `morphing' (spatial redistribution of
charge) and energy resolution degradation.
  The ACIS back-illuminated (BI) CCDs also exhibit pronounced CTI due to their
manufacturing. It is mild enough that position-dependent energy resolution is
not seen, but it is present in both parallel and serial registers. This CTI
also changes the gain and event grades, in a spatially complicated way as
parallel and serial CTI interact.
  Given these realities, we have developed and tuned a phenomenological model
of CTI for both FI and BI CCDs and incorporated it into our Monte Carlo
simulations of the ACIS CCDs. It models charge loss and the spatial
redistribution of charge (trailing), thus reproducing the spatially-dependent
gain and grade distribution seen in all ACIS CCDs and the row-dependent energy
resolution seen in the FI devices. Here we explore the evidence for CTI,
compare our simulations to data, and present a technique for CTI correction
based on forward modeling.


title:
The Impact of Galaxies on their Environment from Observations of
  Gravitationally lensed QSOs

abstract:
  Observations of absorption systems in close, multiple lines of sight to
gravitationally lensed QSOs can be used to infer the density fluctuations and
motions of the gas clouds giving rise to the Lyman alpha forest phenomenon and
to QSO metal absorption lines. We describe a survey of lensed QSOs with the
Keck HIRES instrument and argue that one can derive limits on the frequency and
importance of hydrodynamical disturbances inflicted by galaxies on the
surrounding gas from such data. We discuss differences between the kinematic
properties of low density unsaturated Lyman alpha forest absorption systems,
high ionization CIV absorption systems, and low ionization gas visible in SiII
and CII. The general intergalactic medium appears to show very little
turbulence, but the presumable denser CIV systems exhibit evidence of having
been stirred repeatedly (by winds ?) in the past on time scales similar to
those governing stellar feedback and possibly galaxy mergers. The quiescence of
the low density IGM can be used to put upper limits on the incidence and
energetics of galactic winds on a cosmological time scale.


title: Adaptive Ray Tracing for Radiative Transfer around Point Sources

abstract:
  We describe a novel adaptive ray tracing scheme to solve the equation of
radiative transfer around point sources in hydrodynamical simulations. The
angular resolution adapts to the local hydrodynamical resolution and hence is
of use for adaptive meshes as well as adaptive smooth particle hydrodynamical
simulations. Recursive creation of rays ensures ease of implementation. The
multiple radial integrations needed to solve the time dependent radiative
transfer are sped up significantly using a quad-tree once the rays are cast.
Simplifications advantageous for methods with one radiation source are briefly
discussed. The suggested method is easily generalized to speed up Monte Carlo
radiative transfer techniques. In summary a nearly optimal use of long
characteristics is presented and aspects of its implementation and comparison
to other methods are given.


title: Pulsar Scintillation in the Local ISM: Loop I and Beyond

abstract:
  Recent pulsar scintillation measurements from Ooty, in conjunction with those
from Parkes and other large radio telescopes, are used for a systematic
investigation of the Local Interstellar Medium (LISM) towards the general
direction of the Loop I Bubble. For several pulsars, clear evidence is found
for an enhanced level of scattering which is over and above what can be
accounted for by the enhanced scattering model for the Local Bubble. These
results are interpreted in terms of enhanced scattering due to turbulent plasma
associated with the Loop I shell. Useful constraints are obtained for the
scattering properties of the shell. The inferred value for the scattering
measure for the Loop I shell is found to be ~0.3 pc m^{-20/3}. Assuming a shell
thickness ~5-10 pc, this implies an average strength of scattering in the shell
that is ~100-200 times larger than that in the ambient ISM. An alternative
explanation, where the enhanced level of scattering is due to a possible
"interaction zone" between the Local Bubble and the Loop I Bubble, is also
considered; it is found to be somewhat less satisfactory in explaining the
observations. The best fit value for the scattering measure for such an
interaction zone region is estimated to be ~1.1 pc m^{-20/3}.
  Further, several pulsars beyond ~1 kpc are found to show enhanced levels of
scattering over and above that expected from this "two-bubble model." For some
of the low-latitude pulsars, this is found to be due to enhanced scattering
from plasma inside the intervening Sagittarius spiral arm. We discuss the
implications of our results for the interpretation of scintillation data and
for the general understanding of the LISM.


title: Extragalactic Planetary Nebulae

abstract:
  Planetary nebulae (PNe) can be used to trace intermediate and old stellar
populations in galaxies and the intracluster medium out to approximately 20
Mpc. PNe can be easily identified with narrow-band surveys, and their chemical
abundances and radial velocities can be measured with multi-slit or multi-fiber
spectrographs. We briefly review what has been accomplished to date, and
include tables (with references) that summarize the observations of PNe in 42
galaxies and in the intracluster media of the Virgo and Fornax clusters. The
surveys for intracluster PNe suggest that between 20% and 50% of the clusters'
total stellar mass is in the intracluster medium! We illustrate the utility of
PNe for dynamical studies by presenting results from a recently completed
survey of Cen A (NGC 5128) with the NOAO mosaic camera on the CTIO 4-m
telescope. The PNe and globular cluster surveys extend respectively to
distances of 80 Kpc and 50 Kpc. We compare the kinematics of the stars in Cen A
(736 PN velocities) to the kinematics of the red and blue globular clusters
(188 clusters with measured velocities). The latter include 125 newly confirmed
globular clusters from our survey.


title: Agns and Clusters in Chandra Deep Fields

abstract:
  The Chandra X-ray Satellite already observed several deep fields, including
the two 1 Megasec exposures of the Chandra Deep Field South (CDFS) and North.
We review here the main findings from the CDFS. The LogN-LogS relations show
the resolution of the X-ray background into point sources at the level of
83-99% in the 1-2 keV band and 65-98% in the 2-10 keV band, given the
uncertainties in the unresolved value. The so called ``spectral paradox'' is
solved by a hard, faint population of sources constituted mostly by nearby
(z<1) absorbed (Type II) AGNs with hard-band luminosities L~10^{42}-10^{44}
erg/s. When comparing these results to other deep fields in the X-ray band, we
find that the AGNs detected in 0.1 deg^2 of the CDFS are representative of the
AGNs population as a whole. However, we also noticed an excess in the hard
counts in two Chandra deep fields. If we include this excess and average it
among the observed fields, the total contribution of the XRB can grow of about
7%. Finally, we discuss briefly the properties of the Intra Cluster Medium
imaged at high z, showing no evolution in clusters properties up to z~1.


title:
A candidate of a type-2 QSO at z=0.9: Large X-ray absorption with a
  strong broad-H-alpha emission line

abstract:
  Deep hard X-ray and near infrared observations of a type-2 radio-quiet QSO
candidate at z=0.9, AXJ08494+4454, are reported. The 0.5-10keV Chandra X-ray
Observatory spectrum of AXJ08494+4454 is hard, and is explained well with a
power-law continuum absorbed by a hydrogen column density of 2x10^23 cm^-2. The
2-10keV luminosity of the object reaches hard X-ray luminosity of QSOs. The
large X-ray absorption and the large intrinsic luminosity support the original
identification of AXJ08494+4454 as a type-2 radio-quiet QSO. Nevertheless, the
deep Subaru/IRCS J-band spectroscopic observation suggests the presence of a
strong broad H-alpha emission line from AXJ08494+4454. If real, the broad
H-alpha emission line has a velocity width of 9400+-1000 km/s, which
corresponds to a typical broad-Balmer line velocity width of a luminous QSO.
The existence of the strong broad H-alpha line means that the object is not a
type-2 QSO, but a luminous cousin of a Seyfert 1.9 galaxy in the source-frame
optical spectrum. The Balmer decrement of broad lines, and the broad H-alpha
emission to the hard X-ray luminosity ratio suggest that the nucleus is
affected by dust extinction with A_V of 1-3 mag in the optical wavelength. The
estimated amount of dust extinction is much smaller than that expected from the
X-ray column density.


title: Substructure in the Coma Cluster: Giants vs Dwarfs

abstract:
  The processes that form and shape galaxy clusters, such as infall, mergers
and dynamical relaxation, tend to generate distinguishable differences between
the distributions of a cluster's giant and dwarf galaxies. Thus the dynamics of
dwarf galaxies in a cluster can provide valuable insights into its dynamical
history. With this in mind, we look for differences between the spatial and
velocity distributions of giant (b<18) and dwarf (b>18) galaxies in the Coma
cluster. Our redshift sample contains new measurements from the 2dF and WYFFOS
spectrographs, making it more complete at faint magnitudes than any previously
studied sample of Coma galaxies. It includes 745 cluster members - 452 giants
and 293 dwarfs. We find that the line-of-sight velocity distribution of the
giants is significantly non-Gaussian, but not that for the dwarfs. A battery of
statistical tests of both the spatial and localised velocity distributions of
the galaxies in our sample finds no strong evidence for differences between the
giant and dwarf populations. These results rule out the cluster as a whole
having moved significantly towards equipartition, and they are consistent with
the cluster having formed via mergers between dynamically-relaxed subclusters.


title: Influence of Rotation on Pulsar Radiation Characteristics

abstract:
  We present a relativistic model for pulsar radio emission by including the
effect of rotation on coherent curvature radiation by bunches. We find that
rotation broadens the width of leading component compared to the width of
trailing component. We estimate the component widths in the average pulse
profiles of about 24 pulsars, and find that 19 of them have a broader leading
component. We explain this difference in the component widths by using the
nested cone emission geometry.
  We estimate the effect of pulsar spin on the Stokes parameters, and find that
the inclination between the rotation and magnetic axes can introduce an
asymmetry in the circular polarization of the conal components. We analyze the
single pulse polarization data of PSR B0329+54 at 606 MHz, and find that in its
conal components, one sense of circular polarization dominates in the leading
component while the other sense dominates in the trailing component. Our
simulation shows that changing the sign of the impact parameter changes the
sense of circular polarization as well as the swing of polarization angle.


title: Nonrelativistic Electron-Electron Thermal Bremsstrahlung Gaunt Factor

abstract:
  With the launch of the Chandra X-Ray Observatory and XMM-Newton, X-ray
astronomy has entered an era of precision science. The precision observational
data taken by these satellites require precision basic physics data for their
analysis. The present authors have recently published a series of papers in
which they have reported the results of the accurate calculations of the
electron-ion thermal bremsstrahlung which are particularly suited for the
analysis of the high-temperature galaxy clusters. In this paper we will present
accurate analytic fitting formulae for the nonrelativistic electron-electron
thermal bremsstrahlung Gaunt factor which will be useful for the analysis of
the X-ray observational data taken by the Chandra X-Ray Observatory and
XMM-Newton. With the publication of the present paper X-ray astronomers will be
provided with an accurate thermal bremsstrahlung Gaunt factor which has an
overall accuracy better than 1% for the temperature range 6.0 <log T[K] < 8.5.


title:
Improving the Prospects for Detecting Extrasolar Planets in
  Gravitational Microlensing in 2002

abstract:
  Gravitational microlensing events of high magnification have been shown to be
promising targets for detecting extrasolar planets. However, only a few events
of high magnification have been found using conventional survey techniques.
Here we demonstrate that high magnification events can be readily found in
microlensing surveys using a strategy that combines high frequency sampling of
target fields with online difference imaging analysis. We present 10
microlensing events with peak magnifications greater than 40 that were detected
in real-time towards the Galactic Bulge during 2001 by MOA. We show that Earth
mass planets can be detected in future events such as these through intensive
follow-up observations around the event peaks. We report this result with
urgency as a similar number of such events are expected in 2002.


title: Hypothesis of a daemon kernel of the Earth

abstract:
  The paper considers the fate of the electrically charged (Ze~10e) Planckian
elementary black holes - daemons - making up the dark matter (DM) of the
Galactic disk, which, as follows from our measurements, were trapped by the
Earth during 4.5 Gyr in an amount of ~10^24. Due to their huge mass
(~2x10^(-8)kg), these particles settle down to the Earth's center to form a
kernel. Assuming the excess flux of 10-20 TW over the heat flux level produced
by known sources, which is quoted by many researchers, to be due to the energy
liberated in the outer kernel layers in daemon-stimulated proton decay of iron
nuclei, we have come to the conclusion that the Earth's kernel is presently
measured in few fractions of meter in size. The observed mantle flux of 3He
(and the limiting 3He/4He ~ 10^(-4) ratio itself) can be provided if at least
one 3He(or 3T) nucleus is emitted in a daemon-stimulated decay of ~100-1000 Fe
nuclei. This could remove actually the only objection to the hot origin of the
Earth and to its original melting. The high energy liberation at the center of
the Earth drives two-phase two-dimensional convection in its inner core (IC),
with rolls oriented along the rotation axis. This provides an explanation for
the numerous features in the IC structure revealed in the recent years. The
energy release in the kernel grows continuously as the number of daemons in it
increases. Therefore the global tectonic activity, which had died out after the
initial differentiation and cooling off of the Earth was reanimated ~2 Gyr ago
by the rearrangement and enhancement of convection in the mantle as a result of
the increasing outward energy flow. It is pointed out that as the kernel
continues to grow, the tectonic activity will become intensified rather than
die out, as this was believed before.


title: Globular Clusters around Galaxies in Groups

abstract:
  We have obtained deep photometry of NGC 1199 (in the compact group HCG 22)
and NGC 6868 (in the Telescopium loose group) with the Keck II and the VLT-I
telescopes. Both galaxies are the optically brightest galaxy of their groups.
NGC 1199 has two companion galaxies at a median projected distance of only 33
kpc and, based in its peculiar internal structure and large X-ray halo, NGC
6868 has been proposed to be a merger remnant. Our analysis of $B$ and $R$
images uncovered a population of globular clusters around both galaxies, with
total (and local) specific frequency S_N = 3.6\pm1.8 (3.4\pm1.5) for NGC 1199
and S_N = 1.8\pm1.1 (0.8\pm0.4) for NGC 6868. The radial profile of the
globulars of NGC 1199 follows the light distribution of the galaxy and can be
fitted by a power--law and a ``core model'' with a very steep slope (\alpha =
2.5\pm0.3). In the case of NGC 6868, the profile of the globulars is well
fitted by a power--law and a ``core model'' profile of slope 1.4\pm0.3 and is
shallower than the galaxy light distribution. Maximum-likelihood fitting of two
Gaussians to the globular cluster color distribution yields a high significance
for multi-modality with peaks centered at (B-R)_0 = 1.13\pm0.04 and 1.42\pm0.04
(NGC 1199) and (B-R)_0=1.12\pm0.07 and 1.42\pm0.07 (NGC 6868). NGC 1199 and NGC
6868 are good examples of galaxies where the group environment are likely to
have affected their dynamical evolution. We find that for NGC 1199, the
properties of the globular cluster system are similar to those for other
systems around external elliptical galaxies located in less dense environments,
but with a very steep radial profile. In the case of NGC 6868, we find a
regular radial profile and color distribution and a comparatively low specific
frequency for the globular cluster system of the galaxy.


title: Supercluster Properties as a Cosmological Probe

abstract:
  We investigate the supercluster shape properties of the all-sky observed
(Abell/ACO) and simulated (Virgo data) cluster catalogues using an approach
based on differential geometry. We reliably identify rich superclusters by
applying percolation statistics to both observed and mock cluster populations,
the latter being constructed following the observational requirements of the
Abell/ACO sample extended out to $z_{\rm max}\leq 0.114$. We apply a set of
shape diagnostics in order to study in a thorough way the morphological
features of superclusters with $\geq 8$ cluster members. Results demonstrate
that filamentarity is the dominant shape feature of superclusters. On comparing
data and models, we show that the $\Lambda$CDM ($\Omega_{\Lambda}=1-\Omega_{\rm
m}=0.7$) model performs better than $\tau$CDM, which is excluded at a high
confidence level, in agreement with other recent large scale structure studies.


title: The Gravitational Million-Body Problem

abstract:
  We review what has been learned recently using N-body simulations about the
evolution of globular clusters. While simulations of star clusters have become
more realistic, and now include the evolution of single and binary stars, the
prospect of reaching large enough N is still a distant one. Nevertheless more
restricted kinds of simulations have recently brought valuable progress for
certain problems of current observational interest, including the origin and
structure of tidal tails of globular clusters. In addition, such simulations
have forced us to rethink some basic aspects of stellar dynamics, including, in
particular, the process of escape. Finally we turn to faster, approximate
methods for studying star cluster dynamics, where the role of N-body
simulations is one of calibration.


title: On the "initial" Angular Momentum of Galaxies

abstract:
  Spherical density profiles and specific angular momentum profiles of Dark
Matter halos found in cosmological N-body simulations have been measured
extensively. The distribution of the total angular momentum of dark matter
halos is also used routinely in semi-analytic modeling of the formation of disk
galaxies. However, it is unclear whether the initial (i.e. at the time the halo
is assembled) angular momentum distributions of baryons is related to the dark
matter at all. Theoretical models for ellipticities in weak lensing studies
often rely on an assumed correlation of the angular momentum vectors of dark
matter and gas in galaxies. Both of these assumptions are shown to be in
reasonable agreement with high resolution cosmological smoothed particle
hydrodynamical simulations that follow the dark matter as long as only
adiabatic gas physics are included. However, we argue that in more realistic
models of galaxy formation one expects pressure forces to play a significant
role at turn--around. Consequently the torquing force on DM and baryons will be
uncorrelated and their respective angular momenta are not expected to align. An
SPH simulation with ad-hoc feedback is presented that illustrates these
effects. Massive low redshift elliptical galaxies may be a notable exception
where "light may trace mass".


title: The Fundamental Properties of Early-type Galaxies in the Coma Cluster

abstract:
  We report the results of a high quality spectral study of early-type galaxies
within the Coma Cluster core. Stellar population analysis using Lick/IDS
indices to break the age/metallicity degeneracy are presented, probing their
formation history and properties. A clear metallicity trend and a dominant
single age population are found.


title:
Nodal and Periastron Precession of Inclined Orbits in the Field of a
  Rotating Black Hole

abstract:
  The inclination of low-eccentricity orbits is shown to significantly affect
the orbital parameters, in particular, the Keplerian, nodal precession, and
periastron rotation frequencies, which are interpreted in terms of observable
quantities. For the nodal precession and periastron rotation frequencies of
low-eccentricity orbits in a Kerr field, we derive a Taylor expansion in terms
of the Kerr parameter at arbitrary orbital inclinations to the black-hole spin
axis and at arbitrary radial coordinates. The particle radius, energy, and
angular momentum in the marginally stable circular orbits are calculated as
functions of the Kerr parameter $j$ and parameter $s$ in the form of Taylor
expansions in terms of $j$ to within $O[j^6]$. By analyzing our numerical
results, we give compact approximation formulas for the nodal precession
frequency of the marginally stable circular orbits at various $s$ in the entire
range of variation of Kerr parameter.


title:
Evidence for Accretion: High-Resolution X-ray Spectroscopy of the
  Classical T Tauri Star TW Hydrae

abstract:
  We present high resolution X-ray spectra of the X-ray bright classical T
Tauri star, TW Hydrae, covering the wavelength range of 1.5-25 AA. The
differential emission measure derived from fluxes of temperature-sensitive
emission lines shows a plasma with a sharply peaked temperature distribution,
peaking at log T = 6.5. Abundance anomalies are apparent, with iron very
deficient relative to oxygen, while neon is enhanced relative to oxygen.
Density-sensitive line ratios of Ne IX and O VII indicate densities near log
n_e = 13. A flare with rapid (~1 ks) rise time was detected during our 48 ksec
observation; however, based on analysis of the emission-line spectrum during
quiescent and flaring states, the derived plasma parameters do not appear
strongly time-dependent. The inferred plasma temperature distribution and
densities are consistent with a model in which the bulk of the X-ray emission
from TW Hya is generated via mass accretion from its circumstellar disk.
Assuming accretion powers the X-ray emission, our results for log n_e suggest
an accretion rate of ~10^{-8} M_sun yr^{-1}.


title: Stellar differential rotation from direct starspot tracking

abstract:
  On the Sun, the rotation periods of individual sunspots not only trace the
latitude dependence of the surface rotation rate, but also provide clues as to
the amount of subsurface fluid shear. In this paper we present the first
measurements of stellar differential rotation made by tracking the rotation of
individual starspots with sizes comparable to the largest sunspots. To achieve
this we re-analyse four sequences of densely-sampled, high signal-to-noise
echelle spectra of AB Doradus spanning several stellar rotations in 1996
December. Using spectral subtraction, least-squares deconvolution and
matched-filter analysis, we demonstrate that it is possible to measure directly
the velocity amplitudes and rotation periods of large numbers of individual
starspots at low to intermediate latitude. We derive values for the equatorial
rotation rate and the magnitude of the surface differential rotation, both of
which are in excellent agreement with those obtained by Donati & Collier
Cameron (1997) from cross-correlation of Doppler images derived a year earlier
in 1995 December, and with a re-analysis of the 1996 data by the method of
Donati et al (2000). The differences between the rotation rates of individual
spots and the fitted differential rotation law are substantially greater than
the observational errors. The smaller spots show a greater scatter about the
mean relation than the larger ones, which suggests that buffeting by turbulent
supergranular flows could be responsible.


title: Where the Very Bright Matter is a Standard Ruler

abstract:
  Where's the matter? The answer seems to be: ``distributed according to a
power spectrum with at least one feature (local maximum) near 120-130h^-1Mpc''.
Analyses of the Iovino, Clowes & Shaver quasar candidate catalogue at z~2 and
the 2dF Quasar Survey 10K Release (2QZ-10K) support this claim, which has
previously been made both for low redshift survey analyses and for high z~3)
redshift surveys will be presented. This feature (i) offers a comoving standard
ruler which can lift the matter density-cosmological constant
(Omega_m-Omega_Lambda) degeneracy and (ii) might be due either to baryonic
acoustic oscillations or to Planck epoch physics which survives through
inflation. (i) The 95% confidence constraint from the 2QZ-10K is Omega_m=
0.25\pm0.15, Omega_Lambda=0.60{\pm0.35}. This constraint is independent of
cosmic microwave background constraints and type Ia supernovae constraints. The
only assumptions required are (a) that the Universe satisfies a perturbed
Friedmann-Lema\^{\i}tre-Robertson-Walker model with a possibly non-zero
cosmological constant, (b) that the density perturbations in this model on
large scales (>> 10h^-1Mpc) remain small (``linear'') and approximately
spatially fixed in comoving coordinates, (c) that the statistics (power
spectrum or correlation function) of the perturbations are redshift
independent, and (d) that quasar redshifts are cosmological.


title: Topological Lensing: Is the Matter Both Here and There?

abstract:
  If the Universe satisfies a perturbed Friedmann-Lema\^{\i}tre model, then the
bright matter (e.g. radio-loud active galactic nuclei, RLAGNs) may be
topologically lensed by global geometry. The generation of candidate
topological lensing pairs of RLAGNs, which may be double images of single
objects seen at very different celestial positions, provides very easily
falsifiable (given moderate telescope time) cosmological geometry hypotheses.


title: Limits on WIMP Dark Matter

abstract:
  The current state searches for dark matter in the form of Weakly Interacting
Massive Particles (WIMPs) using both direct and indirect techniques is
reviewed. Advances in recent years by various direct search experiments,
utilising technology able to record the nuclear recoil events expected from
elastic scattering by WIMPs, have allowed progress towards lower limits to be
made. In particular, the Edelweiss and CDMS collaborations are achieving
sensitiviy able to challenge data from DAMA interpreted as evidence for WIMPs
of mass in the region of 60 GeV. Meanwhile, indirect searches, based on
observing the annihilation products of neutralino-neutralino interactions in
the Earth, Sun and Galaxy, have produced intriguing results. For instance,
analysis by Superkamiokande now suggests limits comparable with the best direct
search results.


title: SDSS J124602.54+011318.8: A Highly Luminous Optical Transient at z=0.385

abstract:
  We report the discovery of a highly luminous optical transient (OT), SDSS
J124602.54+011318.8, associated with a galaxy at a redshift of 0.385. In this
paper we consider the possibility that the OT may be a GRB afterglow. Three
sets of images and two sets of spectra were obtained as part of the normal
operations of the Sloan Digital Sky Survey (SDSS). In the first two image sets,
observed two nights apart, the object appears as a point source at
$r^{*}\approx 17$. The third image set, observed about 410 days later, shows an
extended source which is more than 2.5 magnitudes fainter. The spectra were
observed about 400 and 670 days after the first two image sets, and both show
an apparently normal galaxy at a redshift of 0.385. Associating the OT with the
galaxy, the absolute magnitude was $M_{r^*}=-24.8$, which is over 4 magnitudes
brighter than the most luminous supernova ever measured. The spectral energy
distributions of the galaxy-subtracted OT derived from the first two image sets
are well-fit by single power-laws with indices of $\beta_{\nu}=-0.92$ and -1.29
respectively, similar to most GRB afterglows. Based upon the luminosity of the
OT, non-detections in contemporaneous ROTSE-I images, and the change in
spectral slope, the OT, if an afterglow, was likely discovered early during a
``plateau'' or slowly-fading phase. The discovery of a GRB afterglow at this
stage of the SDSS is consistent with expectations, but only if the optical
emission is much less strongly beamed than the gamma-rays. We emphasize that
other explanations for the OT cannot be ruled out; a recent follow-up study by
[galyam02] provides strong evidence that this source is in fact an unusual AGN.


title:
Spectroscopic Signatures of Convection in the Spectrum of Procyon.
  Fundamental Parameters and Iron Abundance

abstract:
  We have observed the spectrum of Procyon A (F5IV) from 4559 to 5780 A with a
S/N of ~ 1e3 and a resolving power of 2e5. We have measured the line bisectors
and relative line shifts of a large number of Fe I and Fe II lines, comparing
them to those found in the Sun. A three-dimensional(3D) hydrodynamical model
atmosphere has been computed and is tested against observations. The model
reproduces in detail most of the features observed, although we identify some
room for improvement. At all levels, the comparison of the 3D time-dependent
calculations with the observed spectral lines shows a much better agreement
than for classical homogeneous models, making it possible to refine previous
estimates of the iron abundance, the projected rotational velocity, the
limb-darkening, and the systemic velocity of the Procyon binary system.
  The difference between the iron abundance determined with the 3D model and
its
  1D counterpart is <~ 0.05 dex. We find consistency between the iron abundance
derived from Fe I and Fe II lines, suggesting that departures from LTE in the
formation of the studied lines are relatively small. The scatter in the iron
abundance determined from different lines still exceeds the expectations from
the uncertainties in the atomic data, pointing out that one or more components
in the modeling can be refined further.


title:
Disclosing the true nature of the Sy 2 galaxy NGC 3281: one more
  Compton-thick source

abstract:
  We present the BeppoSAX broad-band X-ray spectrum of the Seyfert 2 galaxy NGC
3281. The source high-energy spectrum is characterized by the nuclear
transmitted component, with an absorbing column density of about 2 10^24 cm^-2,
while the MECS spectrum is reflection-dominated, with a prominent (EW about
0.5-1.2 keV) iron K_alpha emission line. The source is detected at only the 5
sigma significance level in the LECS band, because of the strong obscuration
which hampers at low energies the direct view of the active nucleus harbored in
NGC 3281. BeppoSAX results are consistent with the scenario where NGC 3281 is
inclined more than 60 degrees with respect to the line-of-sight. Combining the
N_H value obtained from the present X-ray analysis with the A_V measurement, a
N_H/A_V about 50 times the Galactic value is derived.


title: Mass Segregation in Globular Clusters

abstract:
  We present the results of a new study of mass segregation in two-component
star clusters, based on a large number of numerical N-body simulations using
our recently developed dynamical Monte Carlo code. Specifically, we follow the
dynamical evolution of clusters containing stars with individual masses m_1 as
well as a tracer population of objects with individual masses m_2=\mu m_1,
using N=10^5 total stars. For heavy tracers, which could represent stellar
remnants such as neutron stars or black holes in a globular cluster, we
characterize in a variety of ways the tendency for these objects to concentrate
in or near the cluster core. In agreement with simple theoretical arguments, we
find that the characteristic time for this mass segregation process varies as
1/\mu. For models with very light tracers (\mu <~ 10^-2), which could represent
free-floating planets or brown dwarfs, we find the expected depletion of light
objects in the cluster core, but also sometimes a significant enhancement in
the halo. Using these results we estimate the optical depth to gravitational
microlensing by planetary mass objects or brown dwarfs in typical globular
clusters. For some initial conditions, the optical depth in the halo due to
very low-mass objects could be much greater than that of luminous stars. If we
apply our results to M22, using the recent null detection of Sahu, Anderson, &
King (2001), we find an upper limit of ~25% at the 63% confidence level for the
current mass fraction of M22 in the form of very low-mass objects.


title:
Higher Order Moments of the Angular Distribution of Galaxies from Early
  SDSS Data

abstract:
  We present initial results for counts in cells statistics of the angular
distribution of galaxies in early data from the Sloan Digital Sky Survey
(SDSS). We analyze a rectangular stripe $2.5^\circ$ wide, covering
approximately 160 sq. degrees, containing over $10^6$ galaxies in the apparent
magnitude range $18 < r^\prime < 22$, with areas of bad seeing, contamination
from bright stars, ghosts, and high galactic extinction masked out. This survey
region, which forms part of the SDSS Early Data Release, is the same as that
for which two-point angular clustering statistics have recently been computed.
The third and fourth moments of the cell counts, $s_3$ (skewness) and $s_4$
(kurtosis), constitute the most accurate measurements to date of these
quantities (for $r^\prime < 21$) over angular scales $0.015^\circ-0.3^\circ$.
They display the approximate hierarchical scaling expected from non-linear
structure formation models and are in reasonable agreement with the predictions
of $\Lambda$-dominated cold dark matter models with galaxy biasing that
suppresses higher order correlations at small scales. The results are in
general consistent with previous measurements in the APM, EDSGC, and Deeprange
surveys. These results suggest that the SDSS imaging data are free of
systematics to a high degree and will therefore enable determination of the
skewness and kurtosis to 1% and less then 10%, as predicted by Colombi,
Szapudi, & Szalay (1998).


title:
The Highest Energy Cosmic Rays, Gamma Rays and Neutrinos: Facts, Fancy
  and Resolution

abstract:
  Although cosmic rays were discovered 90 years ago, we do not know how and
where they are accelerated. There is compelling evidence that the highest
energy cosmic rays are extra-galactic -- they cannot be contained by our
galaxy's magnetic field anyway because their gyroradius exceeds its dimensions.
Elementary elementary-particle physics dictates a universal upper limit on
their energy of $5\times10^{19}$ eV, the so-called Greisen-Kuzmin-Zatsepin
cutoff; however, particles in excess of this energy have been observed, adding
one more puzzle to the cosmic ray mystery. Mystery is nonetheless fertile
ground for progress: we will review the facts and mention some very speculative
interpretations. There is indeed a realistic hope that the oldest problem in
astronomy will be resolved soon by ambitious experimentation: air shower arrays
of $10^4$ km$^2$ area, arrays of air Cerenkov detectors and kilometer-scale
neutrino observatories.


title: Numerical Simulations of Incompressible MHD Turbulence

abstract:
  The study of incompressible magnetohydrodynamic (MHD) turbulence gives useful
insights on many astrophysical problems. We describe a pseudo-spectral MHD code
suitable for the study of incompressible turbulence. We review our recent works
on direct three-dimensional numerical simulations for MHD turbulence in a
periodic box. In those works, we use a pseudo-spectral code to solve the
incompressible MHD equations. We first discuss the structure and properties of
turbulence as functions of scale. The results are consistent with the scaling
law recently proposed by Goldreich & Sridhar. The scaling law is based on the
concept of scale-dependent isotropy: smaller eddies are more elongated than
larger ones along magnetic field lines. This scaling law substantially changes
our views on MHD turbulence. For example, as noted by Lazarian & Vishniac, the
scaling law can provide a fast reconnection rate. We further discuss how the
study of incompressible MHD turbulence can help us to understand physical
processes in interstellar medium (ISM) by considering imbalanced cascade and
viscous damped turbulence.


title:
Cosmological Relativity: Determining the Universe by the Cosmological
  Redshift

abstract:
  Using cosmological relativity theory, we derive the formula for the
cosmological redshift written explicitly in terms of 1 - "Omega", where "Omega"
= "rho"/"rho"_c is the ratio of the average mass density to the critical
"closure" density. Based on the present-day data of observed redshifts, we
conclude that "Omega" is less than one.


title:
Spectral analysis of the sdO K 648, the exciting star of the planetary
  nebula Ps 1 in the globular cluster M 15 (NGC 7078)

abstract:
  We present a spectral analysis of the sdO central star K 648 based on
medium-resolution optical and high-resolution UV spectra. The photospheric
parameters are determined by means of state-of-the-art NLTE model atmosphere
techniques.
  We found Teff = 39 +/- 2 kK and log g = 3.9 +/- 0.2. The helium (He/H=0.08)
and oxygen (O/H=0.001) abundances are about solar while carbon is enriched by a
factor of 2.5 (C/H=0.001). Nitrogen (N/H = 10**(-6), [N/H] = -2.0) appears at a
sub-solar value. However, these metal abundances are much higher than the
cluster's metallicity M 15: [Fe/H] = -2.25).
  The surface composition appears to be a mixture of the original hydrogen-rich
material and products of helium burning (3 alpha process) which have been mixed
up to the surface. The abundances of He, C, and N are consistent with the
nebular abundance, while O is considerably more abundant in the photosphere
than in the nebula.
  From a comparison of its position in the log Teff - log g plane with
evolutionary calculations a mass of 0.57 (+0.02, -0.01) Msun and a luminosity
of 3810 +/- 1200 Lsun are deduced.
  Our spectroscopic distance d = 11.1 (+2.4, -2.9) kpc is in agreement with the
distance of M 15 as determined by Alves et al. (2000).
  From the GHRS spectra we measure a radial velocity of vrad = -130 km/sec.


title: Spectroscopy of Globular Clusters in M81

abstract:
  We present moderate-resolution spectroscopy of globular clusters (GCs) around
the Sa/Sb spiral galaxy M81 (NGC 3031). Sixteen candidate clusters were
observed with the Low Resolution Imaging Spectrograph on the Keck I telescope.
All are confirmed as bona fide GCs, although one of the clusters appears to
have been undergoing a transient event during our observations. In general, the
M81 globular cluster system (GCS) is found to be very similar to the Milky Way
(MW) and M31 systems, both chemically and kinematically. A kinematic analysis
of the velocities of 44 M81 GCS, (the 16 presented here and 28 from previous
work) strongly suggests that the red, metal-rich clusters are rotating in the
same sense as the gas in the disk of M81. The blue, metal-poor clusters have
halo-like kinematics, showing no evidence for rotation. The kinematics of
clusters whose projected galactocentric radii lie between 4 and 8 kpc suggest
that they are rotating much more than those which lie outside these bounds. We
suggest that these rotating, intermediate-distance clusters are analogous to
the kinematic sub-population in the metal-rich, disk GCs observed in the MW and
we present evidence for the existence of a similar sub-population in the
metal-rich clusters of M31. With one exception, all of the M81 clusters in our
sample have ages that are consistent with MW and M31 GCs. One cluster may be as
young as a few Gyrs. The correlations between absorption-line indices
established for MW and M31 GCs also hold in the M81 cluster system, at least at
the upper end of the metallicity distribution (which our sample probes). On the
whole, the mean metallicity of the M81 GCS is similar to the metallicity of the
MW and M31 GCSs. The projected mass of M81 is similar to the masses of the MW
and M31. Its mass profile indicates the presence of a dark matter halo.


title:
Far-Infrared/Millimetre Emission in 3C Ssources. Dust in Radio Galaxies
  and Quasars

abstract:
  We present far-infrared and millimetric observations of a sample of 3C
objects. Millimetre data were taken at 1.25 mm with the IRAM 30m antenna
feeding the MPIfR bolometer array. Mid-infrared (MIR) and far-infrared (FIR)
photometry were carried out with the ISOCAM and ISOPHOT cameras on the ISO
Satellite. Additional FIR IRAS observations are also included. We present the
entire Spectral Energy Distributions (SEDs) from the UV to radio and discuss
the emitting mechanisms. Two composite spectra, one for the radio galaxies and
one for the radio quasars, are built in the object rest frame. While the SEDs
of the two classes differ, they are indistinguishable in the MIR and FIR range
where they probably arise as thermal emission from a dusty torus and a
larger-scale (cooler) dust distribution in the host galaxy.


title: Polarization of X-ray emission from the Sgr B2 cloud

abstract:
  The Sgr B2 giant molecular cloud is claimed to be an "X-ray reflection
nebula" - the reprocessing site of a powerful flare of the Sgr A* source,
occurred few hundred years ago. The shape of the X-ray spectrum and the
strength of the iron fluorescent line support this hypothesis. We argue that
the most clean test of the origin of X-rays from Sgr B2 would be a detection of
polarized emission from this source.


title:
Broad-band gravitational-wave pulses from binary neutron stars in
  eccentric orbits

abstract:
  Maximum gravitational wave emission from binary stars in eccentric orbits
occurs near the periastron passage. We show that for a stationary distribution
of binary neutron stars in the Galaxy, several high-eccentricity systems with
orbital periods in the range from tens of minutes to several days should exist
that emit broad gravitational-wave pulses in the frequency range 1-100 mHz. The
space interferometer LISA could register the pulsed signal from these system at
a signal-to-noise ratio level $S/N>5\sqrt{5}$ in the frequency range $\sim
10^{-3}-10^{-1}$ Hz during one-year observational time. Some detection
algorithms for such a signal are discussed.


title: Systematics of Microwave Polarimetry with the Planck LFI

abstract:
  The Planck Low Frequency Instrument will recover polarization by differencing
the outputs from radiometers sensitive to orthogonal polarizations. We contrast
the systematic errors that afflict such a system with those that affect
correlation polarimeters; the Planck design has some important advantages when
measuring very weak signals such as the CMB. We also review systematic effects
arising from the choice of scan strategy for all-sky mapping missions like
Planck.[For the Planck-LFI consortium].


title: The Impact of Massive Stars on the Formation of Young Stellar Clusters

abstract:
  Massive OB stars play an important role in the evolution of molecular clouds
and star forming regions. The OB stars both photo--ionize molecular gas as well
as sweep up and compress interstellar gas through winds, ionization fronts, and
supernovae. In this contribution, we examine the effect massive stars have on
the formation of young stellar clusters. We first discuss the processes by
which OB stars destroy cluster--forming molecular cores, and hence terminate
star formation. We overview observational evidence that OB stars forming in
young stellar clusters destroy their parental cores on a timescale of 0.1 Myr,
and we discuss some of the implications of this result. We then summarize
extensive observations of the NGC 281 molecular cloud complex, and present
evidence that two types of triggered star formation are occurring in this
complex. Our goal is to underscore the impact massive stars have on cluster
formation over distances ranging from 0.1 pc to 300 pc.


title: Concentrations and Assembly Histories of Dark Matter Halos

abstract:
  We study the relation between the density profiles of dark matter halos and
their mass assembly histories, using a statistical sample of halos in a
high-resolution N-body simulation of the LCDM cosmology. For each halo at z=0,
we identify its merger-history tree, and determine concentration parameters
c_vir for all progenitors, thus providing a structural merger tree for each
halo. We fit the mass accretion histories by a universal function with one
parameter, the formation epoch a_c, defined when the log mass accretion rate
dlog M/doga falls below a critical value. We find that late forming galaxies
tend to be less concentrated, such that c_vir ``observed'' at any epoch a_obs
is strongly correlated with a_c via c_vir=c_1 a_obs/a_c. Scatter about this
relation is mostly due to measurement errors in c_vir and a_c, implying that
the actual spread in c_vir for halos of a given mass can be mostly attributed
to scatter in a_c. Because of the direct connection between halo concentration
and velocity rotation curves, and because of probable connections between halo
mass assembly history and star formation history, the tight correlation between
these properties provides an essential new ingredient for galaxy formation
modeling.


title: Spectroscopy of blue supergiants in NGC 300

abstract:
  We have obtained VLT low-resolution (~5 A) multi-object spectroscopy in the
4,000-5,000 A spectral range of about 70 blue supergiant candidates in the
Sculptor Group spiral galaxy NGC 300. We present a detailed spectral catalog
containing identification, magnitudes, colors and spectral types. We employ
synthetic spectra to determine metal abundances for two A0 supergiants of the
sample. In agreement with the expectations, the star closer to the galactic
center is found to be more metal rich than the object at a larger
galactocentric distance. Using the Balmer Hbeta line profile we have estimated
the mass-loss rate for one of the brightest A2 supergiants in the sample. We
determined the wind momentum of the star and compared it to the value expected
from the empirical wind momentum-luminosity relationship (WLR) for A-type
supergiants of Kudritzki et al. (1999). Good agreement is obtained.


title: Basic Approach to the Problem of Cosmological Constant and Dark Energy

abstract:
  Most of the calculations done to obtain the value of the cosmological
constant use methods of quantum gravity, a theory that has not been established
as yet, and a variety of results are usually obtained. The numerical value of
the cosmological constant is then supposed to be inserted in the Einstein field
equations, hence the evolution of the Universe will depend on the calculated
value. Here we present a fundamental approach to the problem. The theory
presented here uses a Riemannian four-dimensional presentation of gravitation
in which the coordinates are those of Hubble, i.e. distances and velocity
rather than space and time. We solve these field equations and show that there
are three possibilities for the Universe to expand but only the accelerating
Universe is possible. From there we calculate the cosmological constant and
find that its value is given by 1.934x10^(-35)s^-2. This value is in excellent
agreement with the measurements obtained by the High-Z Supernova Team and the
Supernova Cosmology Project. Finally it is shown that the three-dimensional
space of the Universe is Euclidean, as the Boomerang experiment shows.


title:
Constraints Imposed by a High Magnetic Field on Models for the EUV
  Emission in the Coma Cluster

abstract:
  A variety of models have been explored in regard to the origin of the excess
extreme ultraviolet (~ 0.1 keV) emission in the Coma cluster. It is now
established that the flux is non-thermal and the only non-thermal source
mechanism that appears viable is inverse Compton emission produced by ~ 100 MeV
electrons interacting with the cosmic microwave background photons. All but one
of the models that have been proposed require a cluster magnetic field < 1
micro G. However, recent observations strongly suggest the magnetic field in
the Coma cluster is ~ 5 micro G. We investigate the constraints on models
imposed by a 5 micro G cluster field and find a limited class of models that
are compatible with this constraint. We also investigate the possibility that
the excess hard (40-60 keV) X-ray emission in the cluster is produced by
inverse Compton emission with the same electron population that produces the
EUV excess. We find no scenarios that are compatible with a large cluster
magnetic field, and consequently in this case these two components must be
unrelated.


title: Dissipation of non-linear circularly polarized Alfven waves

abstract:
  We study propagating Alfven waves by solving the time-dependent equations of
magnetohydrodynamics (MHD) in one dimension numerically. In a homogeneous
medium the circularly polarized Alfven wave is an exact solution of the ideal
MHD equations, and therefore it does not suffer from any dissipation. A
high-amplitude linearly polarized Alfven wave, on the other hand, steepens and
form current sheets, in which the Poynting flux is lost. In a stratified
medium, however, a high-amplitude circularly polarized Alfven wave can also
lose a significant fraction of its Poynting flux.


title: High-resolution studies of massive star-forming regions

abstract:
  We summarize the status of our program of near-infrared adaptive optics
observations of ultracompact HII regions. By means of selected results we
demonstrate the usefulness of this technique for disentangling the complexity
of massive star-forming regions. The primary scientific aims of our study are
the identification of the ionizing stars, the characterization of the stellar
population, the clarification of the role of dust for the excitation of the HII
region and, last but not least, the search for circumstellar disks surrounding
high-mass stars. We present results obtained by adaptive optics observations
and additional measurements for G45.45+0.06, G5.89-0.39, and G309.92+0.48 to
illustrate our scientific objectives.


title:
The Double Quasar HE1104-1805: a case study for time delay determination
  with poorly sampled lightcurves

abstract:
  We present a new determination of the time delay of the gravitational lens
system HE1104-1805 ('Double Hamburger') based on a previously unpublished
dataset. We argue that the previously published value of dt_(A-B)=0.73 years
was affected by a bias of the employed method. We determine a new value of
dt_(A-B)=0.85+/-0.05 years (2 sigma confidence level), using six different
techniques based on non interpolation methods in the time domain. The result
demonstrates that even in the case of poorly sampled lightcurves, useful
information can be obtained with regard to the time delay. The error estimates
were calculated through Monte Carlo simulations. With two already existing
models for the lens and using its recently determined redshift, we infer a
range of values of the Hubble parameter: Ho=48+/-4 km/s Mpc^-1 (2 sigma) for a
singular isothermal ellipsoid (SIE) and Ho=62+/-4 km/s Mpc^-1 (2 sigma) for a
constant mass-to-light ratio plus shear model (M/L+gamma). The possibly much
larger errors due to systematic uncertainties in modeling the lens potential
are not included in this error estimate.


title:
Numerical Convergence of Hydrodynamical SPH Simulations of Cooling
  Clusters

abstract:
  The results from hydrodynamical TREESPH simulations of galaxy clusters are
used to investigate the dependence of the final cluster X-ray properties upon
the numerical resolution and the assumed star formation models for the cooled
gas. A comparison between runs with different star formation methods shows that
the results of simulations, based on star formation methods in which gas
conversion into stars is controlled by an efficiency parameter c_{star}, are
sensitive to the simulation numerical resolution. In this respect star
formation methods based instead on a local density threshold, are shown to give
more stable results. Final X-ray luminosities are found to be numerically
stable, with uncertainties of a factor 2.


title:
Constraints on Omega_B from the nucleosynthesis of 7Li in the standard
  Big Bang

abstract:
  We update Standard Big Bang Nucleosynthesis (SBBN) calculations on the basis
of recent nuclear physics compilations (NACRE in particular), experimental and
theoretical works. By a Monte--Carlo technique, we calculate the uncertainties
on the light element yields (4He, D, 3He, 7Li) related to nuclear reactions.
The results are compared to observations that are thought to be representative
of the corresponding primordial abundances. It is found that 7Li could lead to
more stringent constraints on the baryonic density of the universe (Omega_B)
than deuterium, because of much higher observation statistics and an easier
extrapolation to primordial values. The confrontation of SBBN results with 7Li
observations is of special interest since other independent approaches have
also recently provided Omega_B.h^2 values: i) the anisotropies of the Cosmic
Microwave Background by the BOOMERANG, CBI, DASI and MAXIMA experiments and ii)
the Lyman-alpha forest at high redshift. Comparison between these results
obtained by different methods provides a test of their consistency and could
provide a better determination of the baryonic density in the universe.
However, the agreement between Omega_B.h^2 values deduced from SBBN calculation
and 7Li observation on the one hand and CMB observations on the other hand is
only marginal.


title:
PLANCK: systematic effects induced by periodic fluctuations of arbitrary
  shape

abstract:
  A fundamental requirement in the new generation of high resolution Cosmic
Microwave Background imaging experiments is a strict control of systematic
errors that must be kept at micro-K level in the final maps. Some of these
errors are of celestial origin, while others will be generated by periodic
fluctuations of the satellite environment. These environment instabilities will
cause fluctuations in the measured signal output thus generating correlated
effects in the reconstructed maps. In this paper we present an analytical study
of the impact of periodic signal fluctuations on the measured sky maps produced
by the Planck survey. In particular we show how it is possible to estimate
analytically the damping factor of the peak-to-peak amplitude of the
fluctuation at the instrument output after the projection in the final maps.


title: Microlensing by Compact Objects associated to Gas Clouds

abstract:
  We investigate gravitational microlensing of point-like lenses surrounded by
diffuse gas clouds. Besides gravitational bending, one must also consider
refraction and absorption phenomena. According to the cloud density, the light
curves may suffer small to large deviations from Paczynski curves, up to
complete eclipses. Moreover, the presence of the cloud endows this type of
microlensing events with a high chromaticity and absorption lines recognizable
by spectral analysis. It is possible that these objects populate the halo of
our galaxy, giving a conspicuous contribution to the fraction of the baryonic
dark matter. The required features for the extension and the mass of the cloud
to provide appreciable signatures are also met by several astrophysical
objects.


title: Highly accurate calculation of rotating neutron stars

abstract:
  A new spectral code for constructing general-relativistic models of rapidly
rotating stars with an unprecedented accuracy is presented. As a first
application, we reexamine uniformly rotating homogeneous stars and compare our
results with those obtained by several previous codes. Moreover, representative
relativistic examples corresponding to highly flattened rotating bodies are
given.


title: Optical SETI with Air Cerenkov Telescopes

abstract:
  We propose using large Air Cerenkov Telescopes (ACT's) to search for optical,
pulsed signals from extra-terrestrial intelligence. Such dishes collect tens of
photons from a nanosecond-scale pulse of isotropic equivalent power of tens of
solar luminosities at a distance of 100 pc. The field of view for giant ACT's
can be on the order of ten square degrees, and they will be able to monitor 10
to 10$^2$ stars simultaneously for nanosecond pulses of about 6th mag or
brighter. Using the Earth's diameter as a baseline, orbital motion of the
planet could be detected by timing the pulse arrival times.


title:
An empirical method to estimate the LMC distance using B-stars in
  eclipsing binary systems

abstract:
  We present a new method to determine the distance to B-stars in eclipsing
binary systems. The method is completely empirical, and it is based on the
existence of a very tight linear relationship between the V-band ``zero
magnitude angular diameter'' and the Stroemgren colour index c1 for B-stars; we
have empirically calibrated this relationship using local single B-stars with
accurate angular diameters, and B-stars in eclipsing binaries with precise
radii and parallax determinations. By studying the differential behaviour of
this relationship as predicted by theoretical stellar evolution models, we find
that it is independent of the stellar metallicities for a range of [Fe/H]
values between the solar one and that of young stars in the Magellanic Clouds.
The method, which also provides the value of the reddening to the system, is
discussed in detail, together with a thorough estimate of the associated
errors. We conclude that accurate Stroemgren photometry obtainable with 1.5
m-class telescopes of the LMC eclipsing binaries HV 2274 and HV 982 will allow
to obtain an empirical LMC distance with an accuracy of the order of 0.13 mag.


title: Mass segregation of different populations inside the cluster NGC6101

abstract:
  We have used ESO telescopes at La Silla and the Hubble Space Telescope (HST)
in order to obtain accurate B,V,I CCD photometry for the stars located within
200" (~= 2 half-mass radii, r_h = 1.71') from the center of the cluster NGC
6101. Color-Magnitude Diagrams extending from the red-giant tip to about 5
magnitudes below the main-sequence turnoff MSTO (V = 20.05 +- 0.05) have been
constructed.
  The following results have been obtained from the analysis of the CMDs: a)
The overall morphology of the main branches confirms previous results from the
literature, in particular the existence of a sizeable population of 73 "blue
stragglers", which had been already partly detected (27).They are considerably
more concentrated than either the subgiant branch or the main sequence stars,
and have the same spatial distribution as the horizontal branch stars (84%
prob. from K-S test). An hypothesis on the possible BSS progeny is also
presented. b) The HB is narrow and the bulk of stars is blue, as expected for a
typical metal-poor globular cluster. c) The derived magnitudes for the HB and
the MSTO, $V(ZAHB) = 16.59+-0.10, V(TO) = 20.05+-0.05, coupled with the values
E(B-V) = 0.1, [Fe/H] = -1.80, Y = 0.23 yield a distance modulus (m-M)_V = 16.23
and an age similar to other ``old'' metal-poor globular clusters. In
particular, from the comparison with theoretical isochrones, we derive for this
cluster an age of 13 Gyrs. d) By using the large statistical sample of Red
Giant Branch (RGB) stars, we detected with high accuracy the position of the
bump in the RGB luminosity function. This observational feature has been
compared with theoretical prescriptions, yielding a good agreement within the
current theoretical and observational uncertainties.


title:
Star formation and chemical evolution in SPH simulations: a statistical
  approach

abstract:
  In Smoothed Particles Hydrodynamics (SPH) codes with a large number of
particles, star formation as well as gas and metal restitution from dying stars
can be treated statistically. This approach allows to include detailed chemical
evolution and gas re-ejection with minor computational effort. Here we report
on a new statistical algorithm for star formation and chemical evolution,
especially conceived for SPH simulations with large numbers of particles, and
for parallel SPH codes.
  For the sake of illustration, we present also two astrophysical simulations
obtained with this algorithm, implemented into the Tree-SPH code by Lia &
Carraro (2000). In the first one, we follow the formation of an individual
disc-like galaxy, predict the final structure and metallicity evolution, and
test resolution effects. In the second one we simulate the formation and
evolution of a cluster of galaxies, to demonstrate the capabilities of the
algorithm in investigating the chemo-dynamical evolution of galaxies and of the
intergalactic medium in a cosmological context.


title: 75 kpc trails of ionized gas behind two Irr galaxies in A1367

abstract:
  In a 6h Halpha exposure of the N-W region of the cluster of galaxies A1367 we
discovered a 75 kpc cometary emission of ionized gas trailing behind two
Irregular galaxies. The Halpha trails correspond in position and length with
tails of syncrotron radiation. At the galaxy side opposite to the tails the two
galaxies show bright HII regions aligned along arcs, where the star formation
takes place at the prodigeous rate of about 1 solar mass per yr. From the
morphology of the galaxies and of the trailing material, we infer that the two
galaxies are suffering from ram pressure due to their high velocity motion
through the cluster IGM. We estimate that about 10^9 solar masses of gas,
probably ionized in the giant HII regions, is swept out forming the tails. The
tails cross each other at some 100 kpc from the present galaxy location,
indicating that a major tidal event occurred some about 5x10^7 yr ago. We
exclude that mutual harassment produced the observed morphology and we show
with numerical simulations that it could have marginally aided ram pressure
stripping by loosening the potential well of the galaxies.


title: High-Mass Stars as Early Signpost of Cluster Formation

abstract:
  The connection between high-mass stars and young stellar clusters has been
well established by near-IR observations showing young massive stars in HII
regions surrounded by clusters of lower mass stars. Mm-wave observations show
that these clusters form in approx. 1000 Msol dense cores. Interestingly, the
mm-wave observations of very active cluster-forming regions also reveal the
presence of seemingly quiescent dense massive cores, which contain few signs of
ongoing star formation. In the W3 Main region we find an approx. 1000 Msol mass
dense core which contains no mid-IR or cm-continuum sources. Near-IR imaging
has failed to detect any embedded sources. Yet, we suggest that this region is
at an early stage of cluster formation. This is given support by comparative
observations of the NGC 6334 GMC. Here, we find another quiescent massive 1000
Msol core without mid-IR sources, HII regions, or a detectable near-IR cluster.
Motivated by the presence of CH3OH and H2O masers in this IR-quiet core, we
have searched for and detected a bipolar outflow driven by a young massive star
deeply embedded in the core. The presence of an embedded high-mass star
strengthens our arguments that IR-quiet cores are at an early stage of cluster
formation. We propose that masers and outflows from very deeply embedded (and
consequently IR-quiet) high-mass stars are among the first incipient signposts
of cluster formation in massive cores. Accordingly, we have undertaken a SEST
survey of 46 CH3OH maser clusters which are not coincident with IRAS sources or
HII regions. From this sample, we detected outflows in transitions of SiO
toward 15 of the maser clusters. These sources have now been observed at 1200
micron with SIMBA, the 37-multichannel bolometer at SEST. Each one is
associated with a bright 1 mm point source.


title: Flexible Automatic Scheduling For Autonomous Telescopes: The MAJORDOME

abstract:
  We have developped a new method for the scheduling of astronomical automatic
telescopes, in the framework of the autonomous TAROT instrument. The MAJORDOME
software can handle a variety of observations, constrained, periodic, etc., and
produces a timeline for the night, which may be modified at any time to take
into account the specific conditions of the night. The MAJORDOME can also
handle target of opportunity observations without delay.


title:
Separation of the Galactic Synchrotron Foreground and the CMB
  Polarization Measurements

abstract:
  The polarization of the CMBR represents a powerful test for modern cosmology.
It allows to break the degeneracy of fundamental cosmological parameters, and
also to observe the contribution of gravitational waves background to the CMBR
anisotropy. To observe the CMBR polarization several experiments are either in
progress or planned and SPOrt is one of the most promising planned by ESA. At
the same time the observation of the CMBR polarization is a difficult task and
one of the reasons is the presence of polarized foreground emission. For
instance, galactic polarized synchrotron emission (according to some estimates)
can completely mimic the polarization of the CMBR. Nevertheless, one can use
mathematical properties of the spherical harmonics of the distribution of
radiation over the sky to separate different contributions. In this paper the
mathematical properties of the polarized synchrotron foreground and the
physical mechanism that produces it are discussed. The separation of
synchrotron polarization from the polarization generated by density
cosmological perturbations is discussed as well.


title: Photometry and Spectroscopy of Eclipsing Binaries in omega Centauri

abstract:
  Detached eclipsing double line spectroscopic binaries are accurate distance
indicators. They can be used for the direct determination of distances to
globular clusters in which such systems can be identified. The results of major
photometric surveys aimed at identification of variable stars in omega Cen are
summarized. Over 43 eclipsing binaries have been identified so far in the
cluster field of which only 8 objects are true detached systems. Distance and
age determinations are presented for the system OGLEGC-17. The apparent
distance modulus is (m-M)_{V}=14.09\pm 0.04 and the age of this binary is
tau=11.8\pm 0.6 Gyr.


title: An Empirical View to the Early Chemical Evolution of Bulge/Disk Galaxies

abstract:
  Scaling from the empirical metal yield as measured in clusters of galaxies,
it is inferred that early in the evolution of the Galaxy the bulge stellar
population has produced $\sim 10^9\msun$ of metals, at least 5 times more than
the total metal content of the bulge today. It is argued that an early galactic
wind from the starbursting bulge has pre-enriched a vast region around it, with
these metals being able to enrich to $\sim 1/10$ solar of order of $5\times
10^{11}\msun$ of pristine material. From the empirical evidence that bulges
come before disks, it is inferred that the Milky Way disk formed out of this
pre-enriched material, which accounts for the scarcity of metal poor stars in
the solar neighborhood, the so-called `G-Dwarf Problem'. High redshift
observations are now becoming able to efficiently explore the $1.2\lsim z\lsim
3$ region of the universe, when disk formation and morphological
differentiation may have taken place.


title: Tracing Matter with Weak Lensing Surveys

abstract:
  Gravitational weak lensing maps the location of (dark) matter at all scales.
The lens-induced distortion field traces gravity fields and can be used to
reconstruct the mass distribution in galaxies, groups, clusters of galaxies or
large-scale structures. From these reconstructions, one can in principle
recover where the matter is, what are its properties and how it is coupled with
light and baryons. In the following, we review the present status of weak
lensing analysis and discuss the most recent results regarding matter
properties in the universe.


title: A unified equation of state of dense matter and neutron star structure

abstract:
  An equation of state (EOS) of neutron star matter, describing both the
neutron star crust and the liquid core, is calculated. It is based on the
effective nuclear interaction SLy of the Skyrme type, which is particularly
suitable for the application to the calculation of the properties of very
neutron rich matter (Chabanat et al. 1997, 1998). The structure of the crust,
and its EOS, is calculated in the T=0 approximation, and under the assumption
of the ground state composition. The crust-core transition is a very weakly
first-order phase transition, with relative density jump of about one percent.
The EOS of the liquid core is calculated assuming (minimal) n-p-e-mu
composition. Parameters of static neutron stars are calculated and compared
with existing observational data on neutron stars. The minimum and maximum
masses of static neutron stars are 0.094 M_sun and 2.05 M_sun, respectively.
Effects of rotation on the minimum and the maximum mass of neutron stars are
briefly discussed.


title: Observations of Anomalous X-ray Pulsars

abstract:
  We review recent results obtained from observations of Anomalous X-ray
Pulsars at different wavelengths (X-rays, Optical, IR and Radio) with
particular emphasis on results obtained by BeppoSAX. Proposed models for AXPs
are briefly presented and critically discussed in the light of these results.


title:
Measurement of the Cosmic-Ray Antiproton to Proton Abundance Ratio
  between 4 and 50 GeV

abstract:
  We present a new measurement of the antiproton to proton abundance ratio,
pbar/p, in the cosmic radiation. The HEAT-pbar instrument, a balloon borne
magnet spectrometer with precise rigidity and multiple energy loss measurement
capability, was flown successfully in Spring 2000, at an average atmospheric
depth of 7.2 g/cm^2. A total of 71 antiprotons were identified above the
vertical geomagnetic cut-off rigidity of 4.2 GV. The highest measured proton
energy was 81 GeV. We find that the pbar/p abundance ratio agrees with that
expected from a purely secondary origin of antiprotons produced by primary
protons with a standard soft energy spectrum.


title: The Ghost of Sagittarius and Lumps in the Halo of the Milky Way

abstract:
  We identify new structures in the halo of the Milky Way Galaxy from
positions, colors and magnitudes of five million stars detected in the Sloan
Digital Sky Survey. Most of these stars are within 1.26 degrees of the
celestial equator. We present color-magnitude diagrams (CMDs) for stars in two
previously discovered, tidally disrupted structures. The CMDs and turnoff
colors are consistent with those of the Sagittarius dwarf galaxy, as had been
predicted. In one direction, we are even able to detect a clump of red stars,
similar to that of the Sagittarius dwarf, from stars spread across 110 square
degrees of sky. Focusing on stars with the colors of F turnoff objects, we
identify at least five additional overdensities of stars. Four of these may be
pieces of the same halo structure, which would cover a region of the sky at
least 40 degrees in diameter, at a distance of 11 kpc from the Sun (18 kpc from
the center of the Galaxy). The turnoff is significantly bluer than that of
thick disk stars, and closer to the Galactic plane than a power-law spheroid.
We suggest two models to explain this new structure. One possibility is that
this new structure could be a new dwarf satellite of the Milky Way, hidden in
the Galactic plane, and in the process of being tidally disrupted. The other
possibility is that it could be part of a disk-like distribution of stars which
is metal-poor, with a scale height of approximately 2 kpc and a scale length of
approximately 10 kpc. The fifth overdensity, which is 20 kpc away, is some
distance from the Sagittarius dwarf streamer orbit and is not associated with
any known structure in the Galactic plane. It is likely that there are many
smaller streams of stars in the Galactic halo.


title:
Seismic Test of Solar Models, Solar Neutrinos and Implications for
  Metal-Rich Accretion

abstract:
  The Sun is believed to have been the recipient of a substantial amount of
metal-rich material over the course of its evolution, particularly in the early
stages of the Solar System. With a long diffusion timescale, the majority of
this accreted matter should still exist in the solar convection zone, enhancing
its observed surface abundance, and implying a lower-abundance core. While
helioseismology rules out solar models with near-zero metallicity cores, some
solar models with enhanced metallicity in the convection zone might be viable,
as small perturbations to the standard model. Because of the reduced interior
opacity and core temperature, the neutrino flux predicted for such models is
lower than that predicted by the standard solar model. This paper examines how
compatible inhomogeneous solar models of this kind are with the observed low
and intermediate degree p-mode oscillation data, and with the solar neutrino
data from the SNO Collaboration. We set an upper limit on how much metal-rich
accretion took place during the early evolution of the Sun at about 2 Earth
masses of iron (or about 40 Earth masses of meteoric material).


title: Star Streams in the Milky Way Halo

abstract:
  The last 10-20 years has seen a profound shift in views of how the Galaxy's
halo formed. The idea of a monolithic early collapse of a single system (Eggen,
Lynden-Bell and Sandage 1962) has been challenged by observations at high
redshift and by cosmological models of structure formation. These findings
imply that we should see clear evidence of hierarchical formation processes in
nearby galaxies. Recent studies of our Galaxy, made possible by large-scale CCD
surveys such as the Sloan Digital Sky Survey (SDSS), have begun to reveal
tantalizing evidence of substructure in the outer halo. We review evidence for
tidal streams associated with known Milky Way satellites and for star streams
whose progenitors are still unknown. This includes results from the SDSS and
our own ongoing pencil-beam halo survey, the Spaghetti survey.


title: ZEPLIN IV: A One Ton Ultimate WIMP Detector

abstract:
  We describe the research and development program carried out by the UCLA -
Torino group leading to the ZEPLIN II detector under construction for the
Boulby Laboratory. Knowledge of ZEPLIN II performance will help in the design
and construction of ZEPLIN IV. This detector could be located at a U.S.
underground laboratory (WIPP site or others) or elsewhere. We show that a
detector of this size is required to observe SUSY WIMPS.


title: Simulating the Formation of the Local Galaxy Population

abstract:
  We simulate the formation and evolution of the local galaxy population
starting from initial conditions with a smoothed linear density field which
matches that derived from the IRAS 1.2 Jy galaxy survey. Our simulations track
the formation and evolution of all dark matter haloes more massive than 10e+11
solar masses out to a distance of 8000 km/s from the Milky Way. We implement
prescriptions similar to those of Kauffmann et al. (1999) to follow the
assembly and evolution of the galaxies within these haloes. We focus on two
variants of the CDM cosmology: an LCDM and a tCDM model. Galaxy formation in
each is adjusted to reproduce the I-band Tully-Fisher relation of Giovanelli et
al. (1997). We compare the present-day luminosity functions, colours,
morphology and spatial distribution of our simulated galaxies with those of the
real local population, in particular with the Updated Zwicky Catalog, with the
IRAS PSCz redshift survey, and with individual local clusters such as Coma,
Virgo and Perseus. We also use the simulations to study the clustering bias
between the dark matter and galaxies of differing type. Although some
significant discrepancies remain, our simulations recover the observed
intrinsic properties and the observed spatial distribution of local galaxies
reasonably well. They can thus be used to calibrate methods which use the
observed local galaxy population to estimate the cosmic density parameter or to
draw conclusions about the mechanisms of galaxy formation. To facilitate such
work, we publically release our z=0 galaxy catalogues, together with the
underlying mass distribution.


title:
A CS J = 5 -> 4 Mapping Survey Towards High Mass Star Forming Cores
  Associated with H2O Masers

abstract:
  In this survey we have systematically mapped 63 cloud cores in the CS J = 5
-> 4 line towards a sample of high mass star forming cores with water masers
(Plume et al. 1992, Plume et al. 1997) using the CSO. From the CS spectra and
maps we determine cloud core sizes, virial masses, a mass spectrum, and a
size-linewidth relationship.


title: Dust Continuum Observations of Massive Star Forming Regions

abstract:
  We have observed 51 high mass star forming cores associated with water masers
at 350 micron. The spectral energy distributions (SEDs) and dust continuum
normalized radial intensity profiles were modeled for 28 sources using a
one-dimensional dust radiative transfer code assuming a power law density
distribution in the envelope n = n_0 (r/r_0)^{-p}. The best fit density power
law exponent, p, ranged from 1.0 to 2.5 with a mean value of p = 1.72. We
determined the dust masses for the modeled cores and found a mean mass of 209
M_{sun}.


title: Dust and Molecular Emission from the S235 Star Forming Region

abstract:
  We present the results of a multi-faceted study of the high-mass star-forming
region S235. With the CalTech Submillimeter Observatory (CSO), we have observed
and/or mapped over fifty molecular transitions and 350 micron dust emission in
an attempt to learn more about the chemistry, kinematics, and mass distribution
within this rich region. We have found two dust cores that are not resolved in
our molecular line observations and suggest that one of these is a less evolved
star-forming core.


title: Early Phases and Initial Conditions for Massive Star Formation

abstract:
  Our knowledge of the initial conditions and early stages of high mass star
formation is very limited. We will review recent surveys of regions in the
early stages of massive star formation using molecular tracers of high density
and dust continuum emission and consider the status of evolutionary schemes.
Comparison to the situation for low mass, relatively isolated star formation
will be used to illustrate the outstanding issues in massive star formation.
The problem of initial conditions is particularly acute because there is a lack
of observational evidence for regions capable of forming massive stars BEFORE
star formation actually begins. By analogy with the Pre-Protostellar Cores
(PPCs) studied for low-mass star formation, one might call such regions
Pre-Proto-cluster Cores (PPclCs). We will conclude with some speculation about
what such cores might look like and possibilities for their detection.


title:
Confrontation of Intracluster and Interstellar Gas in Cluster-Centered
  Elliptical Galaxies: M87 in Virgo and NGC 4874 in Coma

abstract:
  X-ray observations of M87 in the Virgo cluster and NGC 4874 in Coma reveal
that the gas temperature beyond about 50 kpc from these cD galaxies is
comparable to the virial temperature of the cluster, 3 or 9 keV respectively,
but within the optical galaxy the temperature drops to the galactic virial
temperature, about 1 keV. We show that these steep thermal (and density)
gradients follow naturally from the usual cooling inflow assumptions without
recourse to thermal conductivity. To avoid unobserved central mass
concentrations, most of the gas must radiatively cool (``dropout'') before it
flows to the galactic core, i.e. the gas must be multiphase. Recent XMM spectra
of M87 indicate single phase flow at every radius with no apparent radiative
cooling to low temperatures. However, the X-ray spectral evidence for
multiphase cooling beginning at lower temperatures near 1 keV (within about 10
kpc) may be less apparent and may have escaped detection. Finally, we show that
the standard decomposition method used by X-ray observers to determine the mass
flow dM/dt(r) may fail rather badly due to small deviations from perfectly
steady state flow. When applied to our slightly non-steady computed flows, this
decomposition (incorrectly) gives the usual result, dM/dt proportional to r,
and overestimates the mass dropout dM/dt(r) at large radii.


title:
CS J = 7 -> 6 Mapping of Massive Star Formation Regions Associated with
  Water Masers

abstract:
  Twenty-four cores have been mapped in CS J = 7 -> 6 at the CSO. From the
spectra we determine core sizes and virial masses. Combining results from the
CS and dust continuum studies for M8E, we use Monte Carlo simulations for the
CS emission to determine radial profiles.


title: NGC 2362: a Template for Early Stellar Evolution

abstract:
  We present UBVRI photometry for the young open cluster NGC 2362. From
analysis of the appropriate color-color and color-magnitude diagrams we derive
the fundamental parameters of the NGC 2362 cluster to be: age = 5 (+1-2) Myr,
distance = 1480 pc, E(B-V)=0.10 mag. The cluster age was independently
determined for both high mass (2.1 - 36Msun) and low mass (0.7 - 1.2Msun) stars
with excellent agreement between the ages derived using post-main sequence and
pre-main sequence evolutionary tracks for the high and low mass stars
respectively. Analysis of this cluster's color-magnitude diagram reveals a well
defined pre-main sequence (covering DeltaV ~ 9 magnitudes in V and extending
from early A stars to near the hydrogen burning limit) which makes this cluster
an ideal laboratory for pre-main sequence evolution studies.


title:
Proposal for Determining the Total Masses of Eccentric Binaries Using
  Signature of Periastron Advance in Gravitational Waves

abstract:
  We propose a new method for determining total masses of low frequency
eccentric binaries (such as, neutron star binaries with orbital frequency
$f\gsim 10^{-3}$Hz) from their gravitational waves.
  In this method we use the frequency shift caused by periastron advance, and
it works even at low frequency band where chirp signal due to radiation
reaction is difficult to be measured. It is shown that the total masses of
several Galactic neutron star binaries might be measured accurately (within a
few percent error) by LISA with operation period of $\sim 10$ years.


title: Globular Clusters and the Mira Period-Luminosity Relation

abstract:
  A globular cluster distance scale based on Hipparcos parallaxes of subdwarfs
has been used to derive estimates of M_K for cluster Miras, including one in
the SMC globular cluster NGC121. These lead to a zero-point of the Mira
infrared period-luminosity relation, PL(K), in good agreement with that derived
from Hipparcos parallaxes of nearby field Miras. The mean of these two
estimates together with data on LMC Miras yields an LMC distance modulus of
18.60 +/- 0.10 in evident agreement with a metallicity corrected Cepheid
modulus (18.59 +/- 0.10).
  The use of luminous AGB stars as extragalactic population indicators is also
discussed.


title:
Big Bang Nucleosynthesis, Population III, and Stellar Genetics in the
  Galactic Halo

abstract:
  The diverse isotopic and elemental signatures produced in different
nucleosynthetic sites are passed on to successive generations of stars. By
tracing these chemical signatures back through the stellar populations of the
Galaxy, it is possible to unravel its nucleosynthetic history and even to study
stars which are now extinct. This review considers recent applications of
"stellar genetics" to examine the earliest episodes of nucleosynthesis in the
Universe, in Population III stars and the Big Bang.


title: Detection of non-random patterns in large-scale structure

abstract:
  A new method for analyzing the morphological features of point patterns is
presented. The method is taken from the study of molecular liquids, where it
has been introduced for making a statistical description of anisotropic
distributions. The statistical approach is based on the spherical harmonic
expansion of angular correlations.


title: The production of proton and lepton fluxes in near Earth orbit

abstract:
  Substantial fluxes of protons and leptons with energies below the geomagnetic
cutoff have been measured by the AMS experiment at altitudes of 370-390 Km, in
the latitude interval +/- 51.7 degrees. The production mechanisms of the
observed trapped fluxes are investigated in detail by means of the FLUKA Monte
Carlo simulation code. All known processes involved in the interaction of the
cosmic rays with the atmosphere (detailed descriptions of the magnetic field
and atmospheric density, as well as the electromagnetic and nuclear interaction
processes) are included in the simulation. The results are presented and
compared with the experimental data, indicating good agreement with the
observed fluxes. The impact of secondary proton flux on particle production in
atmosphere is briefly discussed.


title:
The New Emerging Model for the Structure of Cooling Cores in Clusters of
  Galaxies

abstract:
  New X-ray observations with XMM-Newton show a lack of spectral evidence for
large amounts of cooling and condensing gas in the centers of galaxy clusters
believed to harbour strong cooling flows. The paper reexplores the cooling flow
scenario in the light of the new observations. We explore the diagnostics of
the temperature structure of cooling cores with XMM-spectroscopy, tests for
intracluster X-ray absorption towards central AGN, the effect of metal
abundance inhomogeneities, and the implications of high resolution images in
the centers of clusters. We find no evidence of intrinsic absorption in the
center of the cooling flows of M87 and the Perseus cluster. We further consider
the effect of cluster rotation in cooling flow regions in the frame of cosmic
structure evolution models. Also the heating of the core regions of clusters by
jets from a central AGN is reconsidered. We find that the power of the AGN jets
as estimated by their interaction effects with the intracluster medium in
several examples is more then sufficient to heat the cooling flows and to
reduce the mass deposition rates. We explore in more detail which requirements
such a heating model has to fulfill to be consistent with all observations,
point out the way such a model could be constructed, and argue that such model
building seems to be successful. In summary it is argued that most
observational evidence points towards much lower mass deposition rates than
previously inferred in the central region of clusters thought to contain strong
cooling flows.


abstract:
  New X-ray observations with XMM-Newton show a lack of spectral evidence for
large amounts of cooling and condensing gas in the centers of galaxy clusters
believed to harbour strong cooling flows. Here, we explore these diagnostics of
the temperature structure of cooling cores with XMM-spectroscopy. We further
find no evidence of intrinsic absorption in the center of the cooling flows of
M87 and the Perseus cluster. To explain these findings we consider the heating
of the core regions of clusters by jets from a central AGN. We find that the
power of the AGN jets as estimated by their interaction effects with the
intracluster medium in several examples is more then sufficient to heat the
cooling flows. We explore which requirements such a heating model has to
fulfill and find a very promising scenario of self-regulated Bondi accretion of
the central black hole. In summary it is argued that most observational
evidence points towards much lower mass deposition rates than previously
inferred for cooling flow clusters.


title: High resolution polarimetry of the inner Galaxy

abstract:
  We present our results from the Southern Galactic Plane Survey, an effort to
map the fourth quadrant of the Milky Way in linear polarization at a frequency
of 1.4 GHz and at a resolution of 1-2 arcmin. These data are a powerful probe
of both the turbulence and large-scale structure of magneto-ionic gas, and have
revealed a variety of new features in the interstellar medium.


title: Environments of Quasars in the Context of Large-Scale Structure

abstract:
  We are looking at quasar environment in the context of large-scale structure
(LSS) - a new approach, giving a more informed interpretation of quasar-galaxy
correlations. This paper presents our first results for a sample of z ~ 0.3
quasars. We are using Voronoi tessellation applied in colour (B_J - R) slices
for the detection of galaxy clusters and the minimal spanning tree (MST) to
delineate the large-scale structure. This new cluster-detection method allows
us to find reliably galaxy clusters at z < 0.3 from SuperCOSMOS measurements of
UK Schmidt plates. By reconstructing the large-scale structure in a relatively
narrow redshift band (0.2 < z < 0.3), we show that quasars follow the
large-scale structure traced by galaxy clusters. None of the quasars in our
radio-quiet sample is located in the central area of a galaxy cluster. Two
quasars, found in a very rich environment, are actually located between two
very close galaxy clusters, consistent with results on z ~ 1 quasars suggesting
that cluster merg ers may be involved in one of the quasar formation
mechanisms.


title: Monitoring the Evolution of the X-ray Remnant of SN 1987A

abstract:
  We report on the results of our monitoring program of the remnant of SN 1987A
with the Advanced CCD Imaging Spectrometer (ACIS) on board the {\it Chandra
X-ray Observatory}. Two new observations have been performed in AO2, bringing
the total to four monitoring observations over the past two years. Over this
time period, new techniques for correction of ``Charge Transfer Inefficiency
(CTI)'' and for use of charge spreading to provide angular resolution somewhat
better than the pixel size of the CCD detector have become available at Penn
State. We have processed all four observations using sub-pixel resolution to
obtain the highest possible angular resolution, and using our CTI correction
software to provide more reliable spectral analysis and flux estimations.
  The high angular resolution images indicate that the X-ray bright knots are
convincingly correlated with the optical spots, primarily at $\la$1 keV, while
higher energy photons are very well correlated with radio images. Our data also
provide marginal evidence for radial expansion of the X-ray remnant at a rate
of 5200 $\pm$ 2100 km s$^{-1}$. The X-ray flux appears to linearly increase by
$\sim$60% over the 18 month period of these observations. The spectrum is
dominated by broad complexes of atomic emission lines and can be fit with a
simple model of a plane-parallel shock with electron temperatures of $kT$
$\sim$ 2 $-$ 4 keV and a postshock electron density of $n_{e}$ $\sim$ 210 $-$
420 cm$^{-3}$. The implied 0.5 $-$ 10 keV band luminosity in 2001 April is
$\sim$1.3 $\times$ 10$^{35}$ ergs s$^{-1}$; as of that date, we still observe
no direct evidence for the central point source, with an upper limit on the
{\it observed} luminosity of $L_{X}$ $\sim$ 5.5 $\times$ 10$^{33}$ ergs
s$^{-1}$ in the 2 $-$ 10 keV band.


title: The Galactic Halo from Microlensing

abstract:
  The status of the microlensing search for galactic dark matter in the form of
massive astronomical compact halo objects (machos) is reviewed. Unresolved
issues are discussed, as well as possible ways to solve these.


title:
A wide-field spectroscopic survey of the cluster of galaxies
  Cl0024+1654. II. A high-speed collision?

abstract:
  The mass distribution of the rich cluster of galaxies Cl0024+1654 has
frequently been used to constrain the nature of dark matter yet a model
consistent with all the observational data has been difficult to construct. In
this paper we analyse the three-dimensional structure of this cluster using new
spectroscopic information on ~300 galaxies within a projected radius of 3
Mpc/h. These data reveal an unusual foreground component of galaxies separated
from the main cluster by 3000 km/s. We use numerical simulations to show that a
high speed collision along the line of sight between Cl0024+1654 and a second
cluster of slightly smaller mass can reproduce the observed peculiar redshift
distribution. The collision dramatically alters the internal mass distribution
of the bound remnants, creating constant density cores from initially cuspy
dark matter profiles and scattering galaxies to large projected radii. Our
results can reconcile the inferred mass profile from gravitational lensing with
predictions from hierarchical structure formation models, while at the same
time resolving the mass discrepancy that results from a comparison between
lensing, velocity dispersion and X-ray studies.


title: Europium abundances in F and G disk dwarfs

abstract:
  Europium abundances for 74 F and G dwarf stars of the galactic disk have been
determined from the 4129.7 A Eu II line. The stars were selected from the
sample of Edvardsson et al. (1993) and [Eu/Fe] shows a smaller scatter and a
slightly weaker trend with [Fe/H] than found by Woolf et al. (1995). The data
of the two analyses are homogenized and merged. We also discuss the adopted
effective temperature scale.


title: A search for radio emission from Galactic supersoft X-ray sources

abstract:
  We have made a deep search for radio emission from all the northern
hemisphere supersoft X-ray sources using the VLA and MERLIN telescopes, at 5
and 8.4 GHz. Three previously undetected sources: T Pyx, V1974 Cygni and RX
J0019.8+2156 were imaged in quiescence using the VLA in order to search for any
persistent emission. No radio emission was detected in any of the VLA fields
down to a typical 1 sigma RMS noise of 20 uJy/beam, however, 17 new point
sources were detected in the fields with 5 GHz fluxes between 100 and 1500 uJy
giving an average 100 uJy-source density of around 200 per square degree,
comparable to what was found in the MERLIN HDF survey. The persistent source AG
Draconis was observed by MERLIN to provide a confirmation of previous VLA
observations and to investigate the source at a higher resolution. The core is
resolved at the milliarcsec scale into two components which have a combined
flux of around 1 mJy. It is possible that we are detecting nebulosity which is
becoming resolved out by the higher MERLIN resolution. We have investigated
possible causes of radio emission from a wind environment, both directly from
the secondary star, and also as a consequence of the high X-ray luminosity from
the white dwarf. There is an order of magnitude discrepancy between observed
and modelled values which can be explained by the uncertainty in fundamental
quantities within these systems.


title: Discovery of Reflection Nebulosity Around Five Vega-like Stars

abstract:
  Coronagraphic optical observations of six Vega-like stars reveal reflection
nebulosities, five of which were previously unknown. The nebulosities
illuminated by HD 4881, HD 23362, HD 23680, HD 26676, and HD 49662 resemble
that of the Pleiades, indicating an interstellar origin for dust grains. The
reflection nebulosity around HD 123160 has a double-arm morphology, but no
disk-like feature is seen as close as 2.5 arcsec from the star in K-band
adaptive optics data. We demonstrate that uniform density dust clouds
surrounding HD 23362, HD 23680 and HD 123160 can account for the observed
12-100 micron spectral energy distributions. For HD 4881, HD 26676, and HD
49662 an additional emission source, such as from a circumstellar disk or
non-equilibrium grain heating, is required to fit the 12-25 micron data. These
results indicate that in some cases, particularly for Vega-like stars located
beyond the Local Bubble (>100 pc), the dust responsible for excess thermal
emission may originate from the interstellar medium rather than from a
planetary debris system.


title: Comparison of cosmological models using Bayesian theory

abstract:
  Using the Bayesian theory of model comparison, a new cosmological model due
to John and Joseph [M. V. John and K. Babu Joseph, Phys. Rev. D 61, 87304
(2000)] is compared with the standard \Omega_{\Lambda} \neq 0 cosmological
model. Their analysis based on the recent apparent magnitude-redshift data of
Type Ia supernovas found evidence against the new model; our more careful
analysis finds instead that this evidence is not strong. On the other hand, we
find that the angular size-redshift data from compact (milliarcsecond) radio
sources do not discriminate between the two models. Our analysis serves as an
example of how to compare the relative merits of cosmological models in
general, using the Bayesian approach.


title: Further Evidence for Large Intrinsic Redshifts

abstract:
  An examination of the positions and redshifts of the compact, QSO-like
objects reported near the Seyfert 2 galaxy NGC 1068 has revealed many
relationships that suggest strongly that the objects have been ejected from the
galaxy. Although some of the same relations have been found for the compact
objects near NGC 3516, the higher number of sources near NGC 1068 has resulted
in a detailed physical model. The results indicate that the objects have been
expelled in at least four similarly structured ejection events from a point
near the center of NGC 1068 within the last 6 million years, with very modest
velocities between 10,000 and 20,000 km/s. From the age and rotation angle of
successive events, the rotation period of the central object is calculated to
be approximately 10 million yrs, in good agreement with the nuclear rotation
period obtained from kinematic studies of NGC 1068. The large redshifts of the
objects cannot be explained by their modest ejection velocities and require an
additional, large intrinsic component.