title: Gravitational Radiation From Cosmological Turbulence

abstract:
  An injection of energy into the early Universe on a given characteristic
length scale will result in turbulent motions of the primordial plasma. We
calculate the stochastic background of gravitational radiation arising from a
period of cosmological turbulence, using a simple model of isotropic
Kolmogoroff turbulence produced in a cosmological phase transition. We also
derive the gravitational radiation generated by magnetic fields arising from a
dynamo operating during the period of turbulence. The resulting gravitational
radiation background has a maximum amplitude comparable to the radiation
background from the collision of bubbles in a first-order phase transition, but
at a lower frequency, while the radiation from the induced magnetic fields is
always subdominant to that from the turbulence itself. We briefly discuss the
detectability of such a signal.


title: Workshop summary and the future

abstract:
  We present a tentative summary of the many very interesting issues that have
been addresses at this workshop, focussing in particular on the perspectives
for measuring the polarization power spectra of the Cosmic Microwave Background
produced by scalar and tensor perturbations, in the presence of foregrounds.


title:
New Insights from a study of the Globular Cluster Systems of 60
  Early-Type Galaxies

abstract:
  We present the results of our detailed WFPC2-based photometric study of the
globular cluster systems (GCS) of over 60 elliptical and S0 galaxies.
Approximately 50\% of the GCSs of ellipticals, and at least 15-20\% of S0s
reveal bimodality in the color distribution. We trace the variation in GCS
properties with Hubble type and discuss the implications on the various models
of galaxy (and cluster system) formation. We also provide evidence that the
globular cluster luminosity function is an excellent distance indicator with an
accuracy comparable to the surface brightness fluctuation method.


title:
A uniform analysis of the Lyman alpha forest at z = 0-5: III. HST FOS
  Spectral Atlas

abstract:
  We analyzed the absorption line spectra of all quasars observed with the high
resolution gratings of the Faint Object Spectrograph on board the Hubble Space
Telescope. We examined 788 spectra for 334 quasars, and present line lists and
identifications of absorption lines in the spectra of 271 of them. Analysis of
the statistics of the Ly-alpha and metal absorption systems are presented in
companion papers (Dobrzycki et al. 2001; Scott et al. 2001; Morita et al.
2001). The data and several analysis products are available electronically and
on the authors' web site.


title:
A uniform analysis of the Lyman alpha forest at z = 0-5: IV. The
  clustering and evolution of clouds at z < 1.7

abstract:
  We present results on the evolution and clustering of Ly-alpha lines at low
z. The sample contains 1298 Ly-alpha lines from 165 quasar spectra mined from
the archives of the HST/FOS. Our sample extends to z=1.7, slightly higher than
the sample analyzed by the HST Quasar Absorption Line Key Project. We confirm
the Key Project result that the number density evolution of Ly-alpha lines at
low z can be described by a power law that is significantly flatter than that
found at high z. We find gamma=0.54+/-0.21 for lines with equivalent widths
greater than 0.24 A, and gamma=0.60+/-0.14 using a variable EQW threshold,
somewhat steeper than obtained previously. We find that the difference is
likely attributable to different coverage of the two samples. The results
concerning gamma are not significantly affected if one includes Ly-alpha lines
from metal systems. Object to object fluctuations in the number of lines
detected are small, indicating a high degree of uniformity in the IGM on large
scales. We find marginal evidence that weak and strong lines undergo different
evolution. We find weak clustering for Ly-alpha lines at Delta(V)<500 km/s,
weaker than earlier analysis by Ulmer of a subsample of the Key Project data.
We see no correlations for metal system-Ly-alpha forest or extensive metal
system-Ly-alpha forest combinations.


title:
Chaos and the continuum limit in the gravitational N-body problem II.
  Nonintegrable potentials

abstract:
  This paper continues a numerical investigation of orbits evolved in `frozen,'
time-independent N-body realisations of smooth time-independent density
distributions corresponding to both integrable and nonintegrable potentials,
allowing for N as large as 300,000. The principal focus is on distinguishing
between, and quantifying, the effects of graininess on initial conditions
corresponding, in the continuum limit, to regular and chaotic orbits. Ordinary
Lyapunov exponents X do not provide a useful diagnostic for distinguishing
between regular and chaotic behaviour. Frozen-N orbits corresponding in the
continuum limit to both regular and chaotic characteristics have large positive
X even though, for large N, the `regular' frozen-N orbits closely resemble
regular characteristics in the smooth potential. Viewed macroscopically both
`regular' and `chaotic' frozen-N orbits diverge as a power law in time from
smooth orbits with the same initial condition. There is, however, an important
difference between `regular' and `chaotic' frozen-N orbits: For regular orbits,
the time scale associated with this divergence t_G ~ N^{1/2}t_D, with t_D a
characteristic dynamical time; for chaotic orbits t_G ~ (ln N) t_D. At least
for N>1000 or so, clear distinctions exist between phase mixing of initially
localised orbit ensembles which, in the continuum limit, exhibit regular versus
chaotic behaviour. For both regular and chaotic ensembles, finite-N effects are
well mimicked, both qualitatively and quantitatively, by energy-conserving
white noise with amplitude ~ 1/N. This suggests strongly that earlier
investigations of the effects of low amplitude noise on phase space transport
in smooth potentials are directly relevant to real physical systems.


title: The Ionized Stellar Wind in Vela X-1 During Eclipse

abstract:
  We present a first analysis of a high resolution X-ray spectrum of the
ionized stellar wind of Vela X-1 during eclipse. The data were obtained with
the High Energy Transmission Grating Spectrometer onboard the Chandra X-ray
Observatory. The spectrum is resolved into emission lines with fluxes between
0.02 and 1.04x10^4 ph/cm^2/s. We identify lines from a variety of charge
states, including fluorescence lines from cold material, a warm photoionized
wind. We can exclude signatures from collisionally ionized plasmas. For the
first time we identify fluorescence lines from L-shell ions from lower Z
elements. We also detect radiative recombination continua from a kT = 10 eV
(1.2 x 10^5 K) photoionized optically thin gas. The fluorescence line fluxes
infer the existence of optically thick and clumped matter within or outside the
warm photoionized plasma.


title: Completeness in Weak Lensing Searches for Clusters

abstract:
  Using mock observations of numerical simulations, we investigate the
completeness and efficiency of searches for galaxy clusters in weak lensing
surveys. While it is possible to search for high mass objects directly as
density enhancements using weak lensing, we find that line-of-sight projection
effects can be quite serious. For the search methods that we consider, to
obtain high completeness requires acceptance of a very high false-positive
rate. The false positive rate can be reduced only by significantly degrading
the completeness. Both completeness and efficiency are dependent upon the
filter used in the search and the desired mass threshold, emphasizing that a
measurement of the 3D mass function from gravitational lensing is affected by a
number of biases which mix `cosmological' and observational issues.


title: Electric Field Screening by Pairs in the Presence of Returning Positrons

abstract:
  We solve the one-dimensional Poisson equation along a magnetic field line,
both analytically and numerically, for a given current density incorporating
effects of returning positrons. We find that the number of returning positrons
per one primary electrons should be smaller than unity, and the returning of
positrons occurs only in a very short braking distance scale. As a result, for
realistic polar cap parameters, the accelerating electric field will not be
screened out; thus, the model fails to be self-consistent. A previous belief
that pair creation with a pair density higher than the Goldreich-Julian density
immediately screens out the electric field is unjustified. We suggest some
possibilities to resolve this difficulty.


title: 220 GHZ Zenith Atmospheric Transparency at Iao, Hanle

abstract:
  We present 220 GHz (1.36 mm) measurements of zenith optical depth obtained to
characterise the Indian Astronomical Observatory, Hanle (Ladakh, India) during
the period from late December 1999 to early May 2000 and early October 2000 to
September 2001. The data were sampled at an interval of 10 minutes. We describe
the automated 220 GHz tipping radiometer used, its basic principle, operation,
data acquisition method and data reduction scheme in detail. The 220 GHz
opacity is found to be less than 0.06 for a significant fraction (40%) of the
time during the winter months, indicating that Hanle is one of the good
observing sites for submillimeter-wave astronomy. We make a preliminary
correlation with the precipitable water vapour derived from surface relative
humidity and air temperature measurements made during the same period with a
weather station installed at the site. We also compare the Hanle site with
other high-altitude sites like Mauna Kea and Atacama desert.


title:
A Search for Water Maser Emission in Southern AGN and Star Forming
  Galaxies -- Discovery of a Maser in the Edge-on Galaxy IRASF01063-8034

abstract:
  We report the cumulative results of five surveys for water maser emission at
1.35 cm wavelength in 131 active galactic nuclei (AGNs) and star-forming
galaxies, conducted at the Parkes Observatory between 1993 and 1998. We
detected one new maser, in the edge-on galaxy IRASF01063-8034, which exhibits a
single, about 0.1 Jy spectral feature at 4282+/-6 km/s (heliocentric) with an
unusually large 54+/-16 km/s half-power full width. The centroid velocity of
the emission increased to 4319.6+/-0.6 km/s (38+/-2 km/s width) over the 13
days between discovery and confirmation of the detection. A similarly broad
linewidth and large change in velocity has been noted for the maser in NGC1052,
wherein jet activity excites the emission. Neither optical spectroscopy,
radio-infrared correlations, nor infrared colors provide compelling evidence of
unusual activity in the nucleus of IRASF01063-8034. Since the galaxy appears to
be outwardly normal at optical and infrared wavelengths, detection of a water
maser therein is unique. The maser emission is evidence that the galaxy harbors
an AGN that is probably obscured by the edge-on galactic disk. The detection
highlights the possibility that undetected AGNs could be hidden in other
relatively nearby galaxies. No other maser emission features have been
identified at velocities between 3084 km/s and 6181 km/s.


title:
HD 209458: Physical Parameters of the Parent Star and the Transiting
  Planet

abstract:
  The Sun-like star HD209458 harbors a close-in giant planet which transits
across the star's disk, and thus allows an unprecedented access to the basic
parameters of the planet, given a certain knowledge of the basic parameters of
the star, namely its mass and radius. We present theoretical stellar evolution
model calculations for HD 209458 and discuss the uncertainties involved in
deriving the stellar mass and radius. We derive the mass, M=1.06 Msun, radius,
R=1.18 Rsun,and age, t=5.2 Gyr of the star with uncertainties of 10% or more.
The dominant sources of uncertainty remain to be the helium abundance estimate
and the treatment of convection, even after an optimistic estimate for the
effective temperature of the star. However, we find that in deriving the radius
of the planet, R_p, the relevant stellar model input is the M/R relation, which
runs orthogonal to a degeneracy in the transit light curve solution and greatly
improves the estimate of R_p. Theoretically the M/R relation has a lower
uncertainty than the M and R separately. We estimate the planet radius and mass
to be R_p =1.42 +0.10/-0.13 R_J and M_p =0.69 +/- 0.02 M_J.


title: Triggered star formation in expanding shells

abstract:
  We discuss fragmentation processes which induce star formation in dense walls
of expanding shells. The influence of the energy input, the ISM scale-height
and speed of sound in the ambient medium is tested. We formulate the condition
for the gravitational fragmentation of expanding shells: if the total surface
density of the disc is higher than a certain critical value, shells are
unstable. The value of the critical density depends on the energy of the shell
and the sound speed in the ISM.


title: Spatially resolved STIS spectra of WR+OB binaries with colliding winds

abstract:
  We present spatially resolved spectra of the visual WR+OB massive binaries
WR86, WR146, and WR147, obtained with the Space Telescope Imaging Spectrograph
on board the Hubble Space Telescope. The systems are classified as follows:
WR86 = WC7 + B0 III, WR146 = WC6 + O8 I-IIf, WR147 = WN8 + O5-7 I-II(f). Both
WR146 and WR147 are known to have strong non-thermal radio emission arising in
a wind-wind collision shock zone between the WR and OB components. We find that
the spectra of their O companions show Halpha profiles in emission, indicative
of large mass-loss rates, and consistent with the colliding-wind model. Our
spectra indicate that the B component in WR86 has a low mass-loss rate, which
possibly explains the fact that WR86, despite being a long period WR+OB binary,
was not found to be a strong non-thermal radio emitter. Because of the small
mass-loss rate of the B star component in WR86, the wind collision region must
be closer to the B star and smaller in effective area, hence generating smaller
amounts of non-thermal radio emission. Absolute magnitudes for all the stars
are estimated based on the spectral types of the components (based on the
tables by Schmidt-Kaler for OB stars, and van der Hucht for WR stars), and
compared with actual, observed magnitude differences. While the derived
luminosities for the WC7 and B0 III stars in WR86 are consistent with the
observed magnitude difference, we find a discrepancy of at least 1.5 magnitudes
between the observed luminosities of the components in each of WR146 and WR147
and the absolute magnitudes expected from their spectral types. In both cases,
it looks as though either the WR components are about 2 magnitudes too bright
for their spectral types, or that the O components are about 2 magnitudes too
faint. We discuss possible explanations for this apparent discrepancy.


title: The X-ray Spectrum of Cyg X-2

abstract:
  The spectra of disc accreting neutron stars generally show complex curvature,
and individual components from the disc, boundary layer and neutron star
surface cannot be uniquely identified. Here we show that much of the confusion
over the spectral form derives from inadequate approximations for
comptonization and for the iron line. There is an intrinsic low energy cutoff
in comptonised spectra at the seed photon energy. It is very important to model
this correctly in neutron star systems as these have expected seed photon
temperatures (from either the neutron star surface, inner disc or self-absorbed
cyclotron) of ~1 keV, clearly within the observed X-ray energy band. There is
also reflected continuum emission which must accompany the observed iron line,
which distorts the higher energy spectrum. We illustrate these points by a
reanalysis of the GINGA spectra of Cyg X-2 at all points along its Z track, and
show that the spectrum can be well fit by models in which the low energy
spectrum is dominated by the disc, while the higher energy spectrum is
dominated by comptonised emission from the boundary layer, together with its
reflected spectrum from a relativistically smeared, ionised disc.


title: Optical identifications of High Frequency Peakers

abstract:
  We present CCD observations of 13 objects from a complete sample of 55 bright
High Frequency Peaker (HFP) radio sources, and provide optical identification
for 12 of them. Images in R and V filters have been used to derive some
additional information concerning the host of the radio source. Three hosts are
likely to be galaxies, one resulted slightly extended, while the remaining 8
are likely distant quasars. Based on these identifications and those available
in the literature, we find that the fraction of quasars in our HFP sample is
significantly higher than in samples of Compact Steep-Spectrum and GHz-Peaked
Spectrum radio sources.


title:
Spectral Energy Distributions of 3C 279 revisited: BeppoSAX observations
  and variability models

abstract:
  We present the BeppoSAX observations of 3C 279 performed in 1997 January
13-23 simultaneously with gamma-ray pointings with EGRET on board CGRO and
optical observations at the Torino Observatory (1997 January 11-18). ISO data
close to this epoch are also available. We compare the derived Spectral Energy
Distribution with those obtained at all other epochs with adequate
multiwavelength coverage. Simple spectral models fitted to the multiepoch SEDs
suggest that changes in intensity can be ascribed mainly to the variation of
the bulk Lorentz factor of the plasma in the jet.


title: Models of Quintessential Inflation

abstract:
  A unified approach to quintessence and inflation is investigated with the use
of a single scalar field. It is argued that successful potentials have to
approximate a combination of exponential and inverse power-law decline in the
limit of large values of the scalar field. A class of such potentials is
studied analytically and it is found that quintessential inflation is indeed
possible. Successful models, not involving more than two natural mass scales,
are obtained, which do not require fine-tuning of initial conditions and do not
result in eternal acceleration.


title:
CMB: The ultimate test for theoretical models aiming at describing the
  very early universe

abstract:
  In this talk, I will illustrate how one can use the cosmic microwave
background anisotropy measurements, in order to test theoretical models aiming
at describing the early universe.


title: A measure of gravitational entropy and structure formation

abstract:
  Increasing inhomogeneity due to gravitational clumping reflects increasing
gravitational entropy in a time evolving universe. Starting from an ensemble of
uniformly distributed particles it is demonstrated that gravitational
clustering is subject to a specific quantization rule for the amount of
increase of gravitational entropy during the formation of inhomogeneities. The
gain of gravitational entropy at each higher order merging process within the
system is shown to result as a natural consequence from an extremal condition
involved. The resulting discrete spectrum of nested, bound structures of
specific mass and radius, ranging from the particle physics scale to galaxies
and super clusters, provides a unified view of fundamental inhomogeneity scales
in the universe from gravitational entropy considerations. Consequently, also
the gravitational arrow of time points in the direction of stepwise increasing
entropy or inhomogeneity, respectively.


title:
Annual Modulation in the Variability Properties of the IDV-Source
  0917+624 ?

abstract:
  There is new evidence which identifies seasonal changes of the variability
time scale in intraday variable sources with refractive interstellar
scintillation effects. Such a RISS-model takes the annual change of the Earth
velocity relative to the scattering medium into account. In September 1998 we
found a remarkable prolongation of the variability time scale in the IDV-source
0917+624 with only small variations in flux density during a period of 5 days.
This was explained as a seasonal effect, in which the velocity vector of the
Earth and the interstellar medium nearly canceled. In order to further
investigate the applicability of the model for 0917+624, we performed an
Effelsberg 6cm-flux monitoring program over the course of one year. Since
September 2000, the source appears to be remarkably inactive and yet (May
2001), no return to its normal, faster and stronger variability pattern is
observed. Here, our observational results and a possible explanation for the
current quiescence are presented.


title: The evolution of field early-type galaxies to z~0.7

abstract:
  We have measured the Fundamental Plane (FP) parameters for a sample of 30
field early-type galaxies (E/S0) in the redshift range 0.1<z<0.66. We find
that: i) the FP is defined and tight out to the highest redshift bin; ii) the
intercept \gamma evolves as d\gamma/dz=0.58+0.09-0.13 (for \Omega=0.3,
\Omega_{\Lambda}=0.7), or, in terms of average effective mass to light ratio,
as d\log(M/L_B)/dz=-0.72+0.11-0.16, i.e. faster than is observed for cluster
E/S0 -0.49+-0.05. In addition, we detect [OII] emission >5\AA in 22% of an
enlarged sample of 42 massive E/S0 in the range 0.1<z<0.73, in contrast with
the quiescent population observed in clusters at similar z. We interpret these
findings as evidence that a significant fraction of massive field E/S0
experiences secondary episodes of star-formation at z<1.


title:
On the duration of the subsonic propeller state of neutron stars in
  wind-fed mass-exchange close binary systems

abstract:
  The condition for the subsonic propeller - accretor state transition of
neutron stars in wind-fed mass-exchange binary systems is discussed. I show
that the value of the break period, at which the neutron star change its state
to accretor, presented by Davies & Pringle (1981) is underestimated by a factor
of 7.5. The correct value is P_{\rm br} = 450 \mu_{30}^{16/21}
\dot{M}_{15}^{-5/7} (M/M_{\sun})^{-4/21} s. This result forced us to reconsider
some basic conclusions on the efficiency of the propeller spindown mechanism.


title:
Supersonic propeller spindown of neutron stars in wind-fed mass-exchange
  close binaries

abstract:
  The supersonic propeller spindown of a neutron star moving in a strong
stellar wind of its massive companion is discussed. I show that the supersonic
propeller model presented by Davies & Pringle (1981}) is self-consistent if the
strength of the stellar wind of the normal companion is \dot{M}_{\rm c} \la 2.2
10^{18} (M_{\rm ns}/M_{\sun}) V_8 g/s. Under these conditions the model can be
used for the interpretation of the long-period pulsars in Be/X-ray transients.
The spin history of the neutron star in the long period Be/X-ray transient
A0535+26 is considered.


title: Chandra/HETGS Spectroscopy of the Anomalous X-ray Pulsar 4U 0142+61

abstract:
  We report on a 25 ks observation of the anomalous X-ray pulsar 4U 0142+61
with the High Energy Transmission Grating Spectrometer (HETGS) on the Chandra
X-ray Observatory. The continuum spectrum is consistent with previous
measurements and is well fit by an absorbed power-law + blackbody model with
photon index Gamma=3.3+/-0.4 and blackbody temperature kT=0.418+/-0.013 keV.
The pulsar frequency was 0.1150966+/-0.0000017 Hz and the pulse fractions were
between 8.7% and 21%, which are also consistent with past measurements. No
evidence was found for emission or absorption lines with an upper limit of ~50
eV on the equivalent width of a broad feature in the 2.5-13 A (0.95-4.96 keV)
range. The absence of a proton cyclotron line strongly constrains magnetar
atmosphere models and hence the magnetic field strength of the neutron star.
For the energy range given above, the allowed magnetic field strengths of 4U
0142+61 are B<1.9x 10^14 G and B>9.8x 10^14 G.


title:
Constraints on the Accuracy of Photometric Redshifts Derived from BLAST
  and Herschel/SPIRE Sub-mm Surveys

abstract:
  More than 150 galaxies have been detected in blank-field millimetre and
sub-millimetre surveys. However the redshift distribution of sub-mm galaxies
remains uncertain due to the difficulty in identifying their optical-IR
counterparts, and subsequently obtaining their spectroscopic emission-line
redshifts. In this paper we discuss results from a Monte-Carlo analysis of the
accuracy with which one can determine redshifts from photometric measurements
at sub-millimetre-FIR wavelengths. The analysis takes into account the
dispersion in colours introduced by including galaxies with a distribution of
SEDs, and by including photometric and absolute calibration errors associated
with real observations. We present examples of the probability distribution of
redshifts for individual galaxies detected in the future BLAST and
Herschel/SPIRE surveys. We show that the combination of BLAST and 850um
observations constrain the photometric redshifts with sufficient accuracy to
pursue a program of spectroscopic follow-up with the 100m GBT.


title:
On the Probability Distribution of Cosmological Microlensing Optical
  Depths

abstract:
  It is conventional to calculate the probability of microlensing for a
cosmologically distant source based on the Press-Gunn approximation that the
lensing objects are uniformly and randomly distributed in the intervening space
with a constant comoving density. Here we investigate more realistic
cosmological microlensing statistics by considering the strong spatial
clustering of likely lensing objects with each other in galaxies and their
association with the clumps of dark matter that make up the massive halos of
galaxies. The distribution of microlensing optical depth (kappa) along randomly
chosen sight lines is calculated as is the conditional distribution of kappa
along sight lines near one which is strongly microlensed. Our overall result is
that the Press-Gunn approximation is a useful order-of-magnitude approximation
if the massive halos of galaxies are made of dark compact objects but that it
fails badly and can be qualitatively misleading in the more likely case in
which only the ordinary stellar populations of galaxies are the dominant source
of cosmological microlensing events. In particular, we find that microlensing
by stars is limited to of order 1 percent of high redshift sources at any one
time. Furthermore, even though only a small fraction of high redshift sources
are multiply-imaged (by galaxies), it is these sources that are most likely to
be microlensed by stars. Consequently, microlensing by stars is usually
observed at kappa's near 1 where the simple isolated point mass lens
approximation is not appropriate. However, if CDM halos are composed of
condensed objects, then more than 10 percent of high redshift sources are
microlensed at any given time. The vast majority of these sources are not
multiply-imaged, and have kappa's smaller than 0.01.


title: Radio Properties of Pinwheel Nebulae

abstract:
  A small number of dusty Wolf-Rayet stars have been resolved into pinwheel
nebulae, defined by their ``rotating'' spiral dust shells observed in the
infrared. This morphology is naturally explained by dust formation associated
with colliding winds in a binary system. In order to confirm and further
explore this hypothesis, we have observed the known pinwheel nebulae (WR 104
and WR 98a) as well as the suspected binary WR 112 at multiple radio
wavelengths with the Very Large Array to search for non-thermal radio emission
from colliding winds. The spectrum of each target is nearly flat between 5 and
22 GHz, consistent with the presence of non-thermal emission that is reduced at
low frequencies by free-free absorption. This emission must lie outside the
radio ``photosphere,'' leading us to estimate a lower limit to the physical
size of the non-thermal emitting region that is larger than expected from
current theory. Based on a radio and infrared comparison to WR 104 and 98a, we
conclude that WR 112 is a likely candidate pinwheel nebula, but its temporal
variability indicates an eccentric binary orbit or a pinwheel viewed nearly
edge-on. A sensitive radio survey of IR-bright WRs would stringently test the
hypothesis that colliding winds lie at the heart of_all_ dusty WR systems. We
also discuss the effects of dust obscuration in the ultra-violet and how
radio-determined mass-loss rates of pinwheel nebulae (and dusty WR stars in
general) may be underestimated due to shadowing effects.


title:
Chandra observations of NGC 253. II: On the origin of diffuse X-ray
  emission in the halos of starburst galaxies

abstract:
  We present a detailed case study of the diffuse X-ray and H-alpha emission in
the halo of NGC 253, a nearby edge-on starburst galaxy driving a galactic
superwind. The arcsecond spatial resolution of the Chandra ACIS instrument
allows us to study the spatial and spectral properties of the diffuse X-ray
emitting plasma with greatly superior spatial and spectral resolution compared
to previous X-ray instruments. We find statistically significant structure
within the X-ray diffuse emission on angular scales down to ~10 arcsec (~130
pc). There is no statistically significant evidence for any spatial variation
in the spectral properties of the diffuse emission, over scales from ~400 pc to
\~3 kpc. We show that the X-shaped soft X-ray morphology of the superwind,
previously revealed by ROSAT, is matched by very similar X-shaped H-alpha
emission, extending at least 8 kpc above the plane of the galaxy. In the
northern halo the X-ray emission appears to lie slightly interior to the
boundary marked by the H-alpha emission. The total 0.3-2.0 keV energy band
X-ray luminosity of the northern halo, L_X ~ 5e38 erg/s, is very similar to the
halo H-alpha luminosity of L_Ha ~ 4e38 erg/s, both of which are a small
fraction of the estimated wind energy injection rate of ~1e42 erg/s from
supernovae in the starburst. We show that there are a variety of models that
can simultaneously explain spatially-correlated X-ray and H-alpha emission in
the halos of starburst galaxies. These findings indicate that the physical
origin of the X-ray-emitting million-degree plasma in superwinds is closely
linked to the presence of much cooler and denser T ~ 1e4 K gas, not only within
the central kpc regions of starbursts, but also on ~10 kpc-scales within the
halos of these galaxies. (Abridged)


title: Searching for Failed Supernovae With Astrometric Binaries

abstract:
  Stars in the mass range 8 Msun<M<30 Msun are thought to end their lives as
luminous supernovae that leave behind a neutron star. However, if a substantial
fraction of these stars instead ended as black-hole remnants, without producing
a supernova (a `failed' supernova), how would one know? We show that, under
plausible assumptions, the Hipparcos catalog should contain about 30 f_{fail}
astrometric binaries with black-hole companions, where f_{fail} is the fraction
of supernovae that fail. Since no black-hole astrometric binaries are found in
Hipparcos, one might like to conclude that such failed supernovae are very
rare. However, the most important assumption required for this argument, the
initial companion mass function (ICMF) of G stars (the majority of Hipparcos
stars) in the high-mass companion regime, is without any observational basis.
We show how the ICMF of G stars can be measured using the Full-Sky Astrometric
Explorer (FAME), thereby permitting an accurate measurement of the rate of
supernovae that fail.


title: Chandra Detection of a TypeII Quasar at z=3.288

abstract:
  We report on observations of a TypeII quasar at redshift z=3.288, identified
as a hard X-ray source in a 185 ks observation with the Chandra X-ray
Observatory and as a high-redshift photometric candidate from deep, multiband
optical imaging. CXOJ084837.9+445352 (hereinafter CXO52) shows an unusually
hard X-ray spectrum from which we infer an absorbing column density N(H) =
(4.8+/-2.1)e23 / cm2 (90% confidence) and an implied unabsorbed 2-10 keV
rest-frame luminosity of L(2-10) = 3.3e44 ergs/s, well within the quasar
regime. Hubble Space Telescope imaging shows CXO52 to be elongated with slight
morphological differences between the WFPC2 F814W and NICMOS F160W bands.
Optical and near-infrared spectroscopy of CXO52 show high-ionization emission
lines with velocity widths ~1000 km/s and flux ratios similar to a Seyfert2
galaxy or radio galaxy. The latter are the only class of high-redshift TypeII
luminous AGN which have been extensively studied to date. Unlike radio
galaxies, however, CXO52 is radio quiet, remaining undetected at radio
wavelengths to fairly deep limits, f(4.8GHz) < 40 microJy. High-redshift TypeII
quasars, expected from unification models of active galaxies and long-thought
necessary to explain the X-ray background, are poorly constrained
observationally with few such systems known. We discuss recent observations of
similar TypeII quasars and detail search techniques for such systems: namely
(1) X-ray selection, (2) radio selection, (3) multi-color imaging selection,
and (4) narrow-band imaging selection. Such studies are likely to begin
identifying luminous, high-redshift TypeII systems in large numbers. We discuss
the prospects for these studies and their implications to our understanding of
the X-ray background.


title: The Spectral Energy Distribution of the Seyfert galaxy Ton S180

abstract:
  We present spectral results from a multi-satellite, broad-band campaign on
the Narrow-line Seyfert 1 galaxy Ton S180 performed at the end of 1999. We
discuss the spectral-energy distribution of the source, combining simultaneous
Chandra, ASCA and EUVE data with contemporaneous FUSE, HST, and ground-based
optical and infra-red data. The resulting SED shows that most of the energy is
emitted in the 10 -- 100 eV regime, which must be dominated by the primary
energy source. No spectral turnover is evident in the UV regime. This, the
strong soft X-ray emission, and the overall shape of the SED indicate that
emission from the accretion disk peaks between 15 and 100 eV. High resolution
FUSE spectra showing UV absorption due to O VI and the lack of detectable X-ray
absorption in the Chandra spectrum demonstrate the presence of a low column
density of highly ionized gas along our line-of-sight. The highly-ionized state
of the circumnuclear gas is most likely linked to the high luminosity and steep
spectrum of the active nucleus. Given the strong ionizing flux in Ton S180, it
is possible that the clouds within a few tens of light days of the central
source are too highly ionized to produce much line emission. Thus the narrow
width of the emission lines in Ton S180 is due to the emission arising from
large radii.


title: A gamma Doradus star campaign

abstract:
  We report on the results from a large photometric campaign on thirty five
gamma Dor star candidates undertaken at the Institute of Astronomy of the
University of Leuven in the framework of the Flanders -- South-Africa grant. An
overview of the data, as well as the results of the analysis of the obtained
time series are presented, the main conclusion being that nine stars are
thought to be multiperiodic gamma Dor stars and eight monoperiodic. We also
performed a photometric mode identification for two stars of the sample by
comparing the amplitude ratios in the different passbands of the Geneva
photometric system. Both stars seem to pulsate in non-radial modes of degree
l=1.


title: Effects of Strong Magnetic Fields in Strange Baryonic Matter

abstract:
  We investigate the effects of very strong magnetic fields upon the equation
of state of dense bayonic matter in which hyperons are present. In the presence
of a magnetic field, the equation of state above nuclear density is
significantly affected both by Landau quantization and magnetic moment
interactions, but only for field strengths $B>5\times10^{18}$ G. The former
tends to soften the EOS and increase proton and lepton abundances, while the
latter produces an overall stiffening of the EOS. Each results in a supression
of hyperons relative to the field-free case. The structure of a neutron star
is, however, primarily determined by the magnetic field stress. We utilize
existing general relativistic magneto-hydrostatic calculations to demonstrate
that maximum average fields within a stable neutron are limited to values $B\le
1-3 \times10^{18}$ G. This is not large enough to significantly influence
particle compositions or the matter pressure, unless fluctuations dominate the
average field strengths in the interior or configurations with significantly
larger field gradients are considered.


title:
Chaos in cuspy triaxial galaxies with a supermassive black hole: a
  simple toy model

abstract:
  This paper summarises an investigation of chaos in a toy potential which
mimics much of the behaviour observed for the more realistic triaxial
generalisations of the Dehnen potentials, which have been used to model cuspy
triaxial galaxies both with and without a supermassive black hole. The
potential is the sum of an anisotropic harmonic oscillator potential,
  V_o=(1/2)*(a^{2}x^{2}+b^{2}y^{2}+c^{2}z^{2}), and a spherical Plummer
potential,
  V_o=-M_{BH}/(r^{2}+e^{2})^{1/2} with r^{2}=x^{2}+y^{2}+z^{2}. Attention
focuses on three issues related to the properties of ensembles of chaotic
orbits which impact on chaotic mixing and the possibility of constructing
self-consistent equilibria: (1) What fraction of the orbits are chaotic? (2)
How sensitive are the chaotic orbits, i.e., how large are their largest (short
time) Lyapunov exponents? (3) To what extent is the motion of chaotic orbits
impeded by Arnold webs, i.e.,, how `sticky' are the chaotic orbits? These
questions are explored as functions of the axis ratio a:b:c, black hole mass
M_BH, softening length e, and energy E with the aims of understanding how the
manifestations of chaos depend on the shape of the system and why the black
hole generates chaos. The simplicity of the model makes it amenable to a
perturbative analysis. That it mimics the behaviour of more complicated
potentials suggests that much of this behaviour should be generic.


title: Ram Pressure and Anomalous Shell Formation in HoII

abstract:
  Neutral hydrogen VLA D-array observations of the dwarf irregular galaxy HoII,
a prototype galaxy for studies of shell formation, are presented. The
large-scale HI morphology is reminiscent of ram pressure and is unlikely caused
by interactions. A case is made for intragroup gas in poor and compact groups
like the M81 group, to which HoII belongs. Numerous shortcomings of the
supernova explosions and stellar winds scenario to create the shells in HoII
are highlighted, and it is suggested that ram pressure may be able to reconcile
the observations available.


title: Objective-Prism Emission-Line Searches for Active Galactic Nuclei

abstract:
  Objective-prism surveys for UV-excess and emission-line objects, especially
the First and Second Byurakan Surveys, have been central to the study of active
galactic nuclei (AGNs). We review previous line-selected surveys for AGNs and
discuss their contribution to our understanding of the AGN phenomena. In
addition, we present results from the KPNO International Spectroscopic Survey,
a modern digital objective-prism survey for emission line objects. This survey
is discovering substantial numbers of new AGNs, in particular low-luminosity
AGNs and LINERs.


title:
Genesis: How the Universe Began According to Standard Model Particle
  Physics

abstract:
  I show that the mutual consistency of the Bekenstein Bound, the Standard
Model (SM) of particle physics, and general relativity implies that the
universe began in a unique state. I solve the coupled EYM equations for this
unique state, show how the horizon problem is solved, and how SM baryogenesis
naturally results from the triangle anomoly. Since the SU(2) winding number
state is thus non-zero, the universe is not in the QCD ground state, and this
plausibly yields a (small) positive cosmological constant. Since the initial
state is unique, it is necessarily homogeneous and isotropic, as required by
the Bekenstein Bound. Wheeler-DeWitt quantization implies an $S^3$ cosmology
must be very close to flat if the universe is to be classical today. I show
that the spectrum of any classical gauge field (or interacting massless scalar
field) in a FRW universe necessarily obeys the Wien displacement law and the
corresponding quantized field the Planck distribution law with the reciprocal
of the scale factor playing the role of temperature, even if the fields have
zero temperature. Thus the CBR could even today be a pure SU(2) electroweak
field at zero temperature coupled to the Higgs field, in spite of early
universe inverse double Compton and thermal bremsstrahlung.Such a CBR would not
couple to right-handed electrons, and this property can be detected with a
Penning trap or even using the late 1960's CBR detector with appropriate
filters. I argue that ultrahigh energy (UHE) Genesisf.tex Genesisf.tex cosmic
ray protons would not produce pions by interacting with such a CBR, and thus
the existence of such protons may constitute an observation of this CBR
property.


title: The merger stage of the ultra-luminous infrared galaxy IRAS 03158+4227

abstract:
  We examine the merger stage of IRAS 03158+4227, one of the most luminous
ULIRGs from the IRAS 2 Jy sample. Deep optical images are presented along with
high-resolution NIR images and optical low-resolution spectra. IRAS 03158+4227
is confirmed as a component of an equal-luminosity binary galaxy with a nuclei
separation of 47 / (h/75) kpc. A long lopsided tail emanating from the
companion, which harbours an active nucleus, is the most prominent peculiar
feature of the binary. The results of numerical simulations admit the
interpretation of this structure as a product of the tidal interaction between
the two components. If the infrared-activity of IRAS 03158+4227 is also
dynamically triggered by this process, this would implicate that the ULIRG
phenomenon is not restricted to the final stage of a binary merger.
Alternatively, the system may be a multiple merger where the partner(s)
has/have already coalesced.


title: Channeled blast wave behavior based on longitudinal instabilities

abstract:
  To address the important issue of how kinetic energy of collimated blast
waves is converted into radiation, Pohl & Schlickeiser (2000) have recently
investigated the relativistic two-stream instability of electromagnetic
turbulence. They have shown that swept-up matter is quickly isotropized in the
blast wave, which provides relativistic particles and, as a result, radiation.
Here we present new calculations for the electrostatic instability in such
systems. It is shown that the electrostatic instability is faster than the
electromagnetic instability for highly relativistic beams. However, even after
relaxation of the beam via the faster electrostatic turbulence, the beam is
still unstable with respect to the electromagnetic waves, thus providing the
isotropization required for efficient production of radiation. While the
emission spectra in the model of Pohl and Schlickeiser have to be modified, the
basic characteristics persist.


title:
The Detection of Circumnuclear X-ray Emission from the Seyfert Galaxy
  NGC 3516

abstract:
  We present the first high-resolution, X-ray image of the circumnuclear
regions of the Seyfert 1 galaxy NGC 3516, using the Chandra X-ray Observatory
(CXO). All three of the CXO observations reported were performed with one of
the two grating assemblies in place, and here we restrict our analysis to
undispersed photons (i.e. those detected in the zeroth-order). A
previously-unknown X-ray source is detected approx 6 arcsec (1.1 h_{75}^{-1}
kpc) NNE of the nucleus (position angle approx 29 degrees) which we designate
CXOU 110648.1+723412. Its spectrum can be characterized as a power law with a
photon index Gamma ~ 1.8--2.6, or as thermal emission with a temperature
kT~0.7--3 keV. Assuming a location within NGC 3516, isotropic emission implies
a luminosity L ~ 2--8e39 h_{75}^{-2} erg s^{-1} in the 0.4--2 keV band. If due
to a single point source, the object is super-Eddington for a 1.4 M_sun neutron
star. However, multiple sources or a small, extended source cannot be excluded
using the current data. Large-scale extended X-ray emission is also detected
out to ~10 arcsec (~1.7 h_{75}^{-1} kpc) from the nucleus to the NE and SW, and
is approximately aligned with the morphologies of the radio emission and
extended narrow emission line region (ENLR). The mean luminosity of this
emission is 1--5e37 h_{75}^{-2} erg s^{-1} arcsec^{-2}, in the 0.4--2 keV band.
Unfortunately the current data cannot usefully constrain its spectrum. These
results are consistent with earlier suggestions of circumnuclear X-ray emission
in NGC 3516. If the extended emission is due to scattering of the nuclear X-ray
continuum, then the pressure in the X-ray emitting gas is at least two orders
of magnitude too small to provide the confining medium for the ENLR clouds.


title: Antimatter as a probe for physical processes in the early Universe

abstract:
  The whole set of astrophysical data indicates that our Universe is globally
baryon asymmetrical. Nevertheless a possibility of existence of relatively
small amount of sufficiently large antimatter regions is not excluded. Such
regions can survive the annihilation with surrounding matter only in the case
if their sizes exceed a certain scale. It is shown that quantum fluctuations of
a complex scalar field caused by inflation can generate large antimatter
domains progenitors, which contribute insignificantly to the total volume of
the Universe. The resulting distribution and evolution of such antimatter
regions could cause every galaxy to be a harbour of an anti--star globular
cluster. The existence of one of such anti -- star globular cluster in our
Galaxy, does not contradict the observed $\gamma$ -- ray background, but the
expected fluxes of $\bar{^4He}$ and $\bar{^3He}$ from such an antimatter object
can be searched for in PAMELA experiment and are definitely accessible for the
sensitivity of coming AMS02 experiment.


title: Star Formation in the Local Universe

abstract:
  We present preliminary results of a long-term study aimed at answering a
number of open questions on the evolution of starbursts in local galaxies. The
project employes mainly HST data from the ultraviolet to the red of the stellar
continuum and of the nebular emission from the galaxies. Here we concentrate on
NGC5253 and NGC5236 (M83), that form a dwarf--massive galaxy pair at about 4
Mpc distance. The recent star formation history of the centers of the two
galaxies is investigated in order to identify similarities and differences in
the evolution of their central starbursts.


title:
Chandra Observations of the Components of Clusters, Groups, and Galaxies
  and their Interactions

abstract:
  We discuss two themes from Chandra observations of galaxies, groups, and
clusters. First, we review the merging process as seen through the high angular
resolution of Chandra. We present examples of sharp, edge-like surface
brightness structures ``cold fronts'', the boundaries of the remaining cores of
merger components and the Chandra observations of CL0657, the first clear
example of a strong cluster merger shock. In addition to reviewing already
published work, we present observations of the cold front around the elliptical
galaxy NGC1404 which is infalling into the Fornax cluster and we discuss
multiple ``edges'' in ZW3146. Second, we review the effects of relativistic,
radio-emitting plasmas or ``bubbles'', inflated by active galactic nuclei, on
the hot X-ray emitting gaseous atmospheres in galaxies and clusters. We review
published work and also discuss the unusual X-ray structures surrounding the
galaxies NGC4636 and NGC507.


title:
The K20 survey. I. Disentangling old and dusty star-forming galaxies in
  the ERO population

abstract:
  We present the results of VLT optical spectroscopy of a complete sample of 78
EROs with R-Ks\geq5 over a field of 52 arcmin^2. About 70% of the 45 EROs with
Ks\leq19.2 have been spectroscopically identified with old passively evolving
and dusty star-forming galaxies at 0.7<z<1.5. The two classes are about equally
populated and for each of them we present and discuss the average spectrum.
  From the old ERO average spectrum and for Z=Z_{\odot} we derive a minimum age
of \sim 3 Gyr, corresponding to a formation redshift of z_f \gtsima 2.4. PLE
models with such formation redshifts well reproduce the density of old EROs
(consistent with being passively evolving ellipticals), whereas the predictions
of the current hierarchical merging models are lower than the observed
densities by large factors (up to an order of magnitude). From the average
spectrum of the star-forming EROs we estimate a substantial dust extinction
with E(B-V) \gtsima 0.5. The star formation rates, corrected for the average
reddening, suggest a significant contribution from EROs to the cosmic
star-formation density at z \sim 1.


title:
Dissecting the luminosity function of the Coma cluster of galaxies using
  CFHT wide field images

abstract:
  [Abridged] We determined the luminosity function (LF) of the Coma cluster
galaxies selected by luminosity, and the LF bi-variate in central brightness.
The Coma cluster and control fields were imaged using the CFH12K (42x28 arcmin)
and UH8K (28x28 arcmin) wide-field cameras at the CFHT. Selected HST images
were used for testing. Quantities were derived from measurements in at least
two colors, which have the following features: (1) Galaxies as faint as three
times the luminosity of the brightest globular clusters are in the completeness
region of our data. (2) We have a complete census (in the explored region) of
low surface brightness galaxies with central surface brightness galaxies almost
as low as the faintest so far cataloged ones. (3) The explored area is among
the largest ever sampled with CCDs at comparable depth for any cluster of
galaxies. (4) The error budget includes all sources of errors known to date.
Using HST images we also discovered that blends of globular clusters, not
resolved in individual components due to seeing, look like dwarf galaxies when
observed from the ground and are numerous and bright. The derived Coma LF is
relatively steep (alpha=-1.4) over the 11 magnitudes sampled, but the slope and
shape depend on color. A large population of faint low surface brightness
galaxies was discovered, representing the largest contributor (in number) to
the LF at faint magnitudes. We found a clear progression for a faintening of
the LF from high surface brightness galaxies (mu~20 mag/arcsec2) to galaxies of
very faint central brightnesses (mu~24.5 mag/arcsec2), and some evidence for a
steepening. Compact galaxies, usually classified as stars and therefore not
included in the LF, are found to be a minor population in Coma.


title: A Novel Approach to Non linear Shock Acceleration

abstract:
  First order Fermi acceleration at astrophysical shocks is often invoked as a
mechanism for the generation of non-thermal particles. This mechanism is
especially simple in the approximation that the accelerated particles behave
like test particles, not affecting the shocked fluid. Many complications enter
the calculations when the accelerated particles have a backreaction on the
fluid, in which case we may enter the non linear regime of shock acceleration.
In this paper we summarize the main features of a semi-analytical approach to
the study of the non linearity in shock acceleration, and compare some of the
results with previous attempts and with the output of numerical simulations.


title: Helioseismology as a New Constraint on SUSY Dark Matter

abstract:
  The presence of dark matter in the solar neighbourhood can be tested in the
framework of stellar evolution theory by using the new results of
helioseismology. If weakly interacting massive particles accumulate in the
center of the Sun, they can provide an additional mechanism for transferring
energy from the solar core. The presence of these particles produces a change
in the local luminosity of the Sun of the order of 0.1%, which is now within
the reach of seismic solar experiments. We find that typical WIMPs with a mass
of 60 GeV, annihilation cross-section of 10^{-32} cm^3/sec, and scalar
scattering interaction between 10^{-36} cm^2 and 10^{-41} cm^2, the lower end
of this range being that suggested by the DAMA direct detection experiment,
modify the radial profile of the square of the sound speed in the solar core by
\~ 0.1 %. This level of change is strongly constrained by the most recent
helioseismological results. Significantly more massive WIMPs have a much
smaller effect on the solar core temperature profile. However future
helioseismological experiments have the potential exploring most, if not all,
of the WIMP parameter space accessible to current and planned direct detection
experiments.


title: Ultra-High Energy Cosmic Rays: The Annihilation of Super-Heavy Relics

abstract:
  We investigate the possibility that ultra-high energy cosmic rays (UHECRs)
originate from the annihilation of relic superheavy (SH) dark matter in the
Galactic halo. In order to fit the data on UHECRs, a cross section of
$<\sigma_Av>\sim 10^{-26}\textrm{cm}^2 (M_X/10^{12} \textrm{GeV})^{3/2}$ is
required if the SH dark matter follows a Navarro--Frenk--White (NFW) density
profile. This would require extremely large-$l$ contributions to the
annihilation cross section. An interesting finding of our calculation is that
the annihilation in sub-galactic clumps of dark matter dominates over the
annihilations in the smooth dark matter halo, thus implying much smaller values
of the cross section needed to explain the observed fluxes of UHECRs.


title: Lyman Continuum Escape from Inhomogeneous ISM

abstract:
  We have studied the effects of gas density inhomogeneities on the escape of
ionising Lyman continuum (Lyc) photons from Milky Way-type galaxies via 3D
numerical simulations using the Monte Carlo radiative transfer code CRASH
(Ciardi et al. 2001). To this aim a comparison between a smooth Gaussian
distribution (GDD) and an inhomogeneous, fractal one (FDD) has been made with
realistic assumptions for the ionising stellar sources based on available data
in the solar neighborhood. In both cases the escape fraction f_esc increases
with ionisation rate N_gamma (although for the FDD with a flatter slope) and
they become equal at N_gamma = 2*10^50 s^-1 where f_esc = 0.11. FDD allows
escape fractions of the same order also at lower N_gamma, when Lyc photon
escape is sharply suppressed by GDD. Values of the escape fraction as high as
0.6 can be reached (GDD) for N_gamma ~ 9*10^50 s^-1, corresponding to a star
formation rate (SFR) of roughly 2 M_o yr^-1; at this ionising luminosity the
FDD is less transparent (f_esc ~ 0.28). If high redshift galaxies have gas
column densities similar to local ones, are characterized by such high SFRs and
by a predominantly smooth (i.e.turbulence free) interstellar medium, our
results suggest that they should considerably contribute to - and possibly
dominate - the cosmic UV background.


title:
Profile Shapes for Optically Thick X-ray Emission Lines from Stellar
  Winds

abstract:
  We consider the consequences of appreciable line optical depth for the
profile shape of X-ray emission lines formed in stellar winds. The hot gas is
thought to arise in distributed wind shocks, and the line formation is
predominantly via collisional excitation followed by radiative decay. Such
lines are often modelled as optically thin, but the theory has difficulty
matching resolved X-ray line profiles. We suggest that for strong lines of
abundant metals, newly created photons may undergo resonance scattering,
modifying the emergent profile. Using Sobolev theory in a spherically symmetric
wind, we show that thick-line resonance scattering leads to emission profiles
that still have blueshifted centroids like the thin lines, but which are
considerably less asymmetric in appearance. We focus on winds in the
constant-expansion domain, and derive an analytic form for the profile shape in
the limit of large line and photoabsorptive optical depths. Our theory is
applied to published {\it Chandra} observations of the O star $\zeta$ Pup.


title: An inhomogeneous fractal cosmological model

abstract:
  We present a cosmological model in which the metric allows for an
inhomogeneous Universe with no intrinsic symmetries (Stephani models),
providing the ideal features to describe a fractal distribution of matter.
Constraints on the metric functions are derived using the expansion and
redshift relations and allowing for scaling number counts, as expected in a
fractal set. The main characteristics of such a cosmological model are
discussed.


title: Baryon bias and structure formation in an accelerating universe

abstract:
  In most models of dark energy the structure formation stops when the
accelerated expansion begins. In contrast, we show that the coupling of dark
energy to dark matter may induce the growth of perturbations even in the
accelerated regime. In particular, we show that this occurs in the models
proposed to solve the cosmic coincidence problem, in which the ratio of dark
energy to dark matter is constant. Depending on the parameters, the growth may
be much faster than in a standard matter-dominated era. Moreover, if the dark
energy couples only to dark matter and not to baryons, as requested by the
constraints imposed by local gravity measurements, the baryon fluctuations
develop a constant, scale-independent, large-scale bias which is in principle
directly observable. We find that a lower limit to the baryon bias b>0.5
requires the total effective parameter of state w_e=1+p/rho to be larger than
0.6 while a limit b>0.73 would rule out the model.


title:
Does Dark Matter at the Center and in the Halo of the Galaxy Consist of
  the Same Particles?

abstract:
  After a discussion of the properties od degenerate fermion balls, we analize
the orbits of the star S0-1, which has the smallest projected distance to Sgr
A*, in the supermassive black hole as well as in the fermion ball scenarios of
the Galactic center. It is shown that both scenarios are consistent with the
data,as measured during the last six yiers by Genzel ae al. and Ghez et al.. We
then consider a self-gravitating ideal fermion gas at nonzero temperature as a
model for the Galactic halo. The Galactic halo of mass ~2 x 10^12 Msol enclosed
within a radius of ~200 kpc implies the existence of a supermassive compact
dark object at the Galactic center that is in hydrostatic and thermal
equilibrium with the halo. The central object has a maximal mass of ~2.3 x 10^6
Msol within a minimal radius of ~18 mpc for fermion masses ~15 keV. We thus
conclude that both the supermassive compact dark object and the halo could be
made of the same weakly interacting ~15 keV particle.


title:
Systematic Construction of Exact 2-D MHD Equilibria with Steady,
  Compressible Flow in Cartesian Geometry and Uniform Gravity

abstract:
  We present a systematic method for constructing two-dimensional
magnetohydrodynamic equilibria with compressible flow in Cartesian geometry.
This systematic method has already been developed in spherical geometry and
applied in modelling solar and stellar winds and outflows (Vlahakis &
Tsinganos,1998) but is derived here in Cartesian geometry in the context of the
solar atmosphere for the first time. Using the method we find several new
classes of solutions, some of which generalise known solutions, including the
Kippenhahn & Schl\"uter (1957) and Hood & Anzer (1990) solar prominence models
and the Tsinganos, Surlantzis & Priest (1993) coronal loop model with flow, and
some of which are completely new. Having developed the method in full and
summarised the several classes of solutions, we explore in a some detail one of
the classes to illustrate the general construction method. From one of the new
classes of solutions we calculate two loop-like solutions, one of which is the
first exact two-dimensional magnetohydrodynamic equilibrium with
trans-Alfv\'enic flow.


title: An unusually massive stellar black hole in the Galaxy

abstract:
  Here we report a measurement of the orbital period and mass function of GRS
1915+105 which allow us to deduce a mass of 14 +- 4 solar masses for its black
hole. This large mass provides a challenge for black hole formation scenarios
in binaries, since black holes with masses above 5-7 solar masses are hard to
explain. Also, the mass estimate allows us to understand the unique X-ray
variability of GRS 1915+105 as being due to instabilities of a
radiation-pressure dominated disk radiating near the Eddington limit. Finally,
several models are constrained which relate observable X-ray properties to the
spin of black holes in microquasars. Once further calibrated, these relations
may soon turn into a valuable tool to study relativistic effects in strong
gravitational fields.


title:
The tidal effects on the lithium abundance of binary systems with giant
  component

abstract:
  We analise the behavior of lithium abundance as a function of effective
temperature, projected rotational velocity, orbital period and eccentricity for
a sample of 68 binary systems with giant component and orbital period ranging
from about 10 to 6400 days. For these binary systems the Li abundances show a
gradual decrease with temperature, paralleling the well established result for
single giants. We have also observed a dependence of lithium content on
rotation. Binary systems with moderate to high rotation present also moderate
to high Li content. This study shows also that synchronized binary systems with
giant component seems to retain more of their original lithium than the
unsynchronized systems. For orbital periods lower than 100 to 250 days,
typically the period of synchronization for this kind of binary systems,
lithium depleted stars seems to be unusual. The suggestion is made that there
is an 'inhibited zone' in which synchronized binary systems with giant
component having lithium abundance lower than a threshold level should be
unusual.


title: GRS 1915+105

abstract:
  I summarize recent near-infrared spectroscopy of the microquasar GRS 1915+105
with the ESO/VLT which allowed to (i) identify the donor and (ii) measure the
orbital period and radial velocity amplitude. Assuming that the jet ejections
occur perpendicular to the accretion disk and orbital plane, the mass of the
black hole is determined to M = 14 +- 4 solar masses. I discuss the
implications of this mass determination on (a) the understanding of the
large-amplitude X-ray variability in GRS 1915+105, (b) binary formation
scenarios, and (c) models to explain the stable QPO frequencies in GRS 1915+105
and GRO J1655-40.


title:
The Aquarius Superclusters - I. Identification of Clusters and
  Superclusters

abstract:
  We study the distribution of galaxies and galaxy clusters in a 10^deg x 6^deg
field in the Aquarius region. In addition to 63 clusters in the literature, we
have found 39 new candidate clusters using a matched-filter technique and a
counts-in-cells analysis. From redshift measurements of galaxies in the
direction of these cluster candidates, we present new mean redshifts for 31
previously unobserved clusters, while improved mean redshifts are presented for
35 other systems. About 45% of the projected density enhancements are due to
the superposition of clusters and/or groups of galaxies along the line of
sight, but we could confirm for 72% of the cases that the candidates are real
physical associations similar to the ones classified as rich galaxy clusters.
On the other hand, the contamination due to galaxies not belonging to any
concentration or located only in small groups along the line of sight is ~ 10%.
Using a percolation radius of 10 h^{-1} Mpc (spatial density contrast of about
10), we detect two superclusters of galaxies in Aquarius, at z = 0.086 and at z
= 0.112, respectively with 5 and 14 clusters. The latter supercluster may
represent a space overdensity of about 160 times the average cluster density as
measured from the Abell et al. (1989) cluster catalog, and is possibly
connected to a 40 h^{-1} Mpc filament from z ~ 0.11 to 0.14.


title: Keck Spectroscopy of Young and Old Star Clusters in NGC 1023

abstract:
  We present Keck/LRIS spectra for 11 old globular clusters in the S0-type
galaxy NGC 1023 and 2 young blue clusters in the nearby companion NGC 1023A.
Analysis of the spectra of 7 old clusters with sufficient S/N shows generally
good agreement between spectroscopic and previous photometric metallicity
estimates, but the integrated colors of two clusters are too blue for their
spectroscopic metallicities. Although the cluster ages are not well
constrained, they are most likely similar to those of Milky Way globular
clusters and certainly older than about 5 Gyr. The brightest GC in the sample
shows enhanced cyanogen, possibly indicating an abundance anomaly similar to
that observed in some M31 globular clusters. For the two blue clusters in NGC
1023A we estimate ages between 125 and 500 Myr, based on their strong Balmer
lines. The total masses are about 80000 Msun and 60000 Msun for a Miller-Scalo
IMF and Z=0.004, making these objects similar to the young populous clusters in
the LMC. It is suggested that the two young clusters might have formed during a
period of enhanced star formation activity in NGC 1023A, stimulated by a close
encounter with NGC 1023.


title: Deep Westerbork 1.4 GHz Imaging of the Bootes Field

abstract:
  We present the results from our deep (16x12 hour) Westerbork Synthesis Radio
Telescope (WSRT) observations of the approximately 7 square degree Bootes Deep
Field, centered at 14h32m05.75s, 34d16'47.5" (J2000). Our survey consists of 42
discrete pointings, with enough overlap to ensure a uniform sensitivity across
the entire field, with a limiting sensitivity of 28 microJy (1 sigma rms). The
catalog contains 3172 distinct sources, of which 316 are resolved by the
13"x27" beam. The Bootes field is part of the optical/near-infrared imaging and
spectroscopy survey effort conducted at various institutions. The combination
of these data sets, and the deep nature of the radio observations will allow
unique studies of a large range of topics including the redshift evolution of
the luminosity function of radio sources, the K-z relation and the clustering
environment of radio galaxies, the radio / far-infrared correlation for distant
starbursts, and the nature of obscured radio loud AGN.


title: Detection of an Extrasolar Planet Atmosphere

abstract:
  We report high precision spectrophotometric observations of four planetary
transits of HD 209458, in the region of the sodium resonance doublet at 589.3
nm. We find that the photometric dimming during transit in a bandpass centered
on the sodium feature is deeper by (2.32 +/- 0.57) x 10^{-4} relative to
simultaneous observations of the transit in adjacent bands. We interpret this
additional dimming as absorption from sodium in the planetary atmosphere, as
recently predicted from several theoretical modeling efforts. Our model for a
cloudless planetary atmosphere with a solar abundance of sodium in atomic form
predicts more sodium absorption than we observe. There are several
possibilities that may account for this reduced amplitude, including reaction
of atomic sodium into molecular gases and/or condensates, photoionization of
sodium by the stellar flux, a low primordial abundance of sodium, or the
presence of clouds high in the atmosphere.


title: Neutrinos from active galactic nuclei as a diagnostic tool

abstract:
  Active galactic nuclei (AGN) are known as sources of high energy gamma-rays.
The emission probably results from non-thermal radiation of relativistic jets
belonging to the AGN. Earlier investigations of these processes have suggested
that neutrinos are among the radiation products of the jets and may be used to
discriminate between hadrons and leptons as primary particles for the
production of the high energy emission. It is shown that the neutrino flux is
correlated with the flux of TeV gamma-rays. This allows to distinctly search
for neutrino emissions from the jets of AGN by using the TeV gamma-ray light
curves to drastically reduce the temporal and spatial parameter space. Given
the observed TeV photon fluxes from nearby BL Lacs the neutrino signal from AGN
may be detectable with future neutrino observatories as least as sensitive as
IceCube.


title: Two-Dimensional Topology of the 2dF Galaxy Redshift Survey

abstract:
  We study the topology of the publicly available data released by the 2dFGRS.
The 2dFGRS data contains over 100,000 galaxy redshifts with a magnitude limit
of b_J=19.45 and is the largest such survey to date. The data lie over a wide
range of right ascension (75 degree strips) but only within a narrow range of
declination (10 degree and 15 degree strips). This allows measurements of the
two-dimensional genus to be made.
  The NGP displays a slight meatball shift topology, whereas the SGP displays a
bubble like topology. The current SGP data also have a slightly higher genus
amplitude. In both cases, a slight excess of overdense regions are found over
underdense regions. We assess the significance of these features using mock
catalogs drawn from the Virgo Consortium's Hubble Volume LCDM z=0 simulation.
We find that differences between the NGP and SGP genus curves are only
significant at the 1 sigma level. The average genus curve of the 2dFGRS agrees
well with that extracted from the LCDM mock catalogs.
  We compare the amplitude of the 2dFGRS genus curve to the amplitude of a
Gaussian random field with the same power spectrum as the 2dFGRS and find,
contradictory to results for the 3D genus of other samples, that the amplitude
of the GRF genus curve is slightly lower than that of the 2dFGRS. This could be
due to a a feature in the current data set or the 2D genus may not be as
sensitive as the 3D genus to non-linear clustering due to the averaging over
the thickness of the slice in 2D. (Abridged)


title:
Breaking the Redshift Deadlock - I: Constraining the star formation
  history of galaxies with sub-millimetre photometric redshifts

abstract:
  Future extragalactic sub-millimetre and millimetre surveys have the potential
to provide a sensitive census of the level of obscured star formation in
galaxies at all redshifts. While in general there is good agreement between the
source counts from existing SCUBA (850um) and MAMBO (1.25mm) surveys of
different depths and areas, it remains difficult to determine the redshift
distribution and bolometric luminosities of the sub-millimetre and millimetre
galaxy population. This is principally due to the ambiguity in identifying an
individual sub-millimetre source with its optical, IR or radio counterpart
which, in turn, prevents a confident measurement of the spectroscopic redshift.
Additionally, the lack of data measuring the rest-frame FIR spectral peak of
the sub-millimetre galaxies gives rise to poor constraints on their rest-frame
FIR luminosities and star formation rates. In this paper we describe
Monte-Carlo simulations of ground-based, balloon-borne and satellite
sub-millimetre surveys that demonstrate how the rest-frame FIR-sub-millimetre
spectral energy distributions (250-850um) can be used to derive photometric
redshifts with an r.m.s accuracy of +/- 0.4 over the range 0 < z < 6. This
opportunity to break the redshift deadlock will provide an estimate of the
global star formation history for luminous optically-obscured galaxies [L(FIR)
> 3 x 10^12 Lsun] with an accuracy of 20 per cent.


title: Radial Velocities of Dwarf Spheroidal Galaxies in the M81 Group

abstract:
  Long-slit observations of 4 dwarf spheroidal galaxies in the M81 group are
presented. We have obtained a heliocentric velocity of globular cluster
candidate located near the center of DDO78 to be +55 +- 10 km/s by
cross-correlation with template stars. We estimated a heliocentric radial
velocity of -116 +- 21 km/s for an HII region seen in the K 61.
  A red diffuse object near the K64 center is found to be a remote galaxy with
a heliocentric velocity of +46530 km/s.


title: Cosmic Inversion: Reconstructing primordial spectrum from CMB anisotropy

abstract:
  We investigate the possibility of reconstructing the initial spectrum of
density fluctuations from the cosmic microwave background (CMB) anisotropy. As
a first step toward this program, we consider a spatially flat, CDM dominated
universe. In this case, it is shown that, with a good accuracy, the initial
spectrum satisfies a first order differential equation with the source
determined by the CMB angular correlation function. The equation is found to
contain singularities arising from zeros of the acoustic oscillations in the
transfer functions. Nevertheless, we find these singularities are not fatal,
and the equation can be solved nicely. We test our method by considering simple
analytic forms for the transfer functions. We find the initial spectrum is
reproduced within 5% accuracy even for a spectrum that has a sharp spike.


title: A Planet Candidate in the Stellar Triple System HD178911

abstract:
  We report the detection of a low-mass companion orbiting the solar-type star
HD178911B, the distant component of the stellar triple system HD178911. The
variability of HD178911B was first detected using radial-velocity measurements
obtained with the HIRES spectrograph mounted on the 10-m Keck1 telescope at the
W.M. Keck Observatory (Hawaii, USA). We then started an intense radial-velocity
follow up of the star with the ELODIE echelle spectrograph mounted on the
1.93-m telescope at the Observatoire de Haute-Provence (France) in order to
derive its orbital solution. The detected planet candidate has an orbital
period of 71.5 days and a minimum mass of 6.3 Jupiter masses. We performed a
spectral analysis of the star, which shows that the lithium abundances in the
system are similar to those in another known planet-hosting wide binary stellar
system, 16 Cyg. In both systems the lithium is undetected in the atmosphere of
the visual secondary harboring the planetary companion, but is easily detected
in the spectrum of the visual primary. We discuss this similarity and its
ramifications.


title:
Statistical Mechanics of the Self-gravitating gas with two or more kinds
  of Particles

abstract:
  We study the statistical mechanics of the self-gravitating gas at thermal
equilibrium with two kinds of particles. We start from the partition function
in the canonical ensemble which we express as a functional integral over the
densities of the two kinds of particles for a large number of particles. The
system is shown to possess an infinite volume limit when (N_1,N_2,V)->infty,
keeping N_1/V^{1/3} and N_2/V^{1/3} fixed. The saddle point approximation
becomes here exact for (N_1,N_2,V)->infty.It provides a nonlinear differential
equation on the particle densities. For the spherically symmetric case, we
compute the densities as functions of two dimensionless physical parameters:
eta_1=G m_1^2 N_1/[V^{1/3} T] and eta_2=G m_2^2 N_2/[V^{1/3} T] (where G is
Newton's constant, m_1 and m_2 the masses of the two kinds of particles and T
the temperature). According to the values of eta_1 and eta_2 the system can be
either in a gaseous phase or in a highly condensed phase.The gaseous phase is
stable for eta_1 and eta_2 between the origin and their collapse values. The
gas is inhomogeneous and the mass M(R) inside a sphere of radius R scales with
R as M(R) propto R^d suggesting a fractal structure. The value of d depends in
general on eta_1 and eta_2 except on the critical line for the canonical ensem-
ble where it takes the universal value d simeq 1.6 for all values of N_1/N_2.
The equation of state is computed.It is found to be locally a perfect gas
equation of state. Thermodynamic functions are computed as functions of eta_1
and eta_2. They exhibit a square root Riemann sheet with the branch points on
the critical canonical line. This treatment is further generalized to the
self-gravitating gas with n-types of particles.


title: Gamma-ray astronomy

abstract:
  This paper summarizes recents results in gamma-ray astronomy, most of which
were derived with data from ground-based gamma-ray detectors. Many of the
contributions presented at this conference involve multiwavelength studies
which combine ground-based gamma-ray measurements with optical data or
space-based X-ray and gamma-ray measurements. Besides measurements of the
diffuse emission from the Galaxy, observations of blazars, gamma-ray bursts,
and supernova remnants this paper also covers theoretical models for the
acceleration of radiating particles and their emission mechanisms in these
sources.


title:
The influence of dynamic tides on the apsidal-motion rate in close
  binaries with an evolved main-sequence star

abstract:
  The validity of the classical formula for the rate of secular apsidal motion
in close binaries is investigated for a sequence of models of a 5 solar mass
star ranging from the last stages of the C12 -> N14 reaction to the phase where
hydrogen is exhausted in the core. For binaries with short orbital periods, the
apsidal-motion rates predicted by the classical formula deviate from the rates
determined within the framework of the theory of dynamic tides due to the
effects of the compressibility of the stellar fluid and due to resonances of
dynamic tides with free oscillation modes of the component stars (Smeyers &
Willems 2001). As the star evolves on the main sequence, the deviations caused
by the compressibility of the stellar fluid increase with increasing radius of
the star. The additional deviations caused by the resonances are largest near
the end of the core-hydrogen burning phase. Both of these deviations increase
with increasing values of the orbital eccentricity.


title:
Numerical study of the magnetorotational instability in weakly
  magnetised accretion disks: Resolution dependence of the Shakura-Sunyaev
  alpha

abstract:
  In this letter, we present numerical calculations made to investigate the
possible resolution dependence of the Shakura & Sunyaev (1973) viscosity
parameter alpha from local magnetohydrodynamic simulations of the
magnetorotational instability (MRI). We find that the values of alpha do indeed
depend significantly on the numerical resolution but also that when the highest
resolutions attainable by the computational resources available are used, the
growth of the alpha-parameter seems to saturate. The values of alpha are at
most of the order of 10^(-3), which indicates that the sole presence of
turbulence due to dynamo generated magnetic field in the disk is not enough to
reproduce alphas of the order unity which could explain some observational
results (e.g. Cannizzo 1993).


title: On the Origin of Cosmic Rays

abstract:
  The problem in identifying the sites of origin of Galactic Cosmic Rays (CRs)
is reviewed. Recent observational evidence from very-high energy (VHE, energies
above 100 GeV) gamma-ray measurements is in contradiction with the surmise that
synchrotron radiation from relativistic electrons is indicative for hadron
acceleration. It rather points to a CR-acceleration efficiency of supernova
remnants (SNRs) below one percent, much less than the value required if these
objects were to be the main sources of Galactic cosmic rays (about 30%).
Observations of CR anisotropy and the emission of low-energy (energy < 10 GeV)
gamma-rays from the Galactic disk indicate that the sources of low-energy
cosmic rays are distributed with a Galactocentric radial scale length in the
order of 25 +- 10 kpc, much larger than expected if SNRs are the main sources
of CRs. These two facts - together with the body of evidence from CR isotope
abundances - strongly suggest that a new class of astrophysical objects -
distinct from SNRs and located manly in the outer reaches of our Galaxy - is
the major source of hadronic CRs in our Galaxy. The basic observational
features of ultra high-energy (UHE, energy > 10^{19} eV) CRs are most naturally
understood if the same CR sources accelerate CRs up to the highest observed CR
energies. Proposals for the nature of a new source class are mentioned. The
origin of CRs is still as much shrouded in mystery as it was in 1957, when
Philip Morrison wrote a seminal review about CR origin. The potential for
discoveries is thus great.


title: Inflationary Cosmology: Status and Prospects

abstract:
  This article gives a brief overview of the status of attempts to constrain
inflation using observations, and examines prospects for future developments.


title: Time-dependent correlations of inflationary perturbations

abstract:
  We show that if the primordial classical perturbations were generated by the
gravitational particle creation during inflation, and followed by an evolution
of quantum-to-classical transition,the time dependent correlation of these
perturbations is long-tailed with a correlation time larger than the
Hubble-time. Consequently, the inflationary perturbations are locally
scale-scale correlated. Hence, the interaction of the fields during inflation
can be explored via the detection of the local scale-scale correlation of the
CMB fluctuations.


title:
The influence of free neutrons on dynamics and radiation of
  astrophysical plasmas

abstract:
  We present arguments in favor of the presence of free neutrons in plasmas
generated by compact astrophysical objects and find conditions necessary for
the formation of the neutron component. The broad range of phenomena caused by
neutrons includes both dynamical (sources' variability, transition of fireballs
to the two-flow regime) and kinetic (fission of helium nuclei by neutrons,
electromagnetic cascade, emission in annihilation and nuclear lines, neutrino
losses) effects. The presented theory can be applied to internal regions of
accretion disks, jets in microquasars, and gamma-ray burst (GRB) fireballs.


title:
A submillimetre difference between radio galaxies and radio quasars:
  evidence for quasar-heated dust and synchronized submillimetre and radio
  source activity

abstract:
  We present submillimetre photometry of 11 3CR and 6CE radio quasars of
similar 151-MHz radio luminosity and redshifts to the radio galaxies studied at
1.3<z<2 by Archibald et al. (2001). We detect all bar one quasar at 850
microns, and five quasars are confirmed as dusty hyperluminous objects by
detections at shorter wavelengths. Our observations reveal a clear difference
between the submillimetre luminosity distributions of the radio quasars and a
matched sample of radio galaxies: the quasars are ~5-times brighter than the
radio galaxies and >~2-times brighter accounting for possible synchrotron
contamination. This difference is in quantitative agreement with a
receding-torus unified scheme for radio sources in which the torus opening
angle depends on quasar optical luminosity, provided that there is a close
relationship between the optical and submillimetre luminosities. The
implication is that quasar-heated dust dominates the submillimetre emission for
powerful radio quasars at z~1.5. We find a significant anti-correlation between
submillimetre/far-infrared luminosity L_FIR and radio source age in the sense
that hyperluminous quasars tend to be associated with young (<10^7 yr) sources.
This suggests that the processes controlling L_FIR are synchronized with the
jet-triggering event and that L_FIR declines on a ~10^7 yr timescale. There is
evidence for a small amount of obscuration in the hyperluminous quasars from
reddening and associated or broad absorption lines. We speculate that shortly
after jet triggering, dust is more widely distributed than at later times and
is heated by the quasar nucleus and/or a short-lived synchronized starburst.


title: Dynamical Masses of Young Star Clusters in NGC 4038/4039

abstract:
  In order to estimate the masses of the compact, young star clusters in the
merging galaxy pair, NGC 4038/4039 (``the Antennae''), we have obtained medium
and high resolution spectroscopy using ISAAC on VLT-UT1 and UVES on VLT-UT2 of
five such clusters. The velocity dispersions were estimated using the stellar
absorption features of CO at 2.29 microns and metal absorption lines at around
8500 \AA, including lines of the Calcium Triplet. The size scales and light
profiles were measured from HST images. From these data and assuming Virial
equilibrium, we estimated the masses of five clusters. The resulting masses
range from 6.5 x 10^5 to 4.7 x 10^6 M_sun. These masses are large, factor of a
few to more than 10 larger than the typical mass of a globular cluster in the
Milky Way. The mass-to-light ratios for these clusters in the V- and K-bands in
comparison with stellar synthesis models suggest that to first order the IMF
slopes are approximately consistent with Salpeter for a mass range of 0.1 to
100 M_sun. However, the clusters show a significant range of possible IMF
slopes or lower mass cut-offs and that these variations may correlate with the
interstellar environment of the cluster. Comparison with the results of
Fokker-Planck simulations of compact clusters with properties similar to the
clusters studied here, suggest that they are likely to be long-lived and may
lose a substantial fraction of their total mass. This mass loss would make the
star clusters obtain masses which are comparable to the typical mass of a
globular cluster.


title: Optical and near-infrared observations of Anomalous X-ray pulsars

abstract:
  We present recent results of our program of deep optical and near-infrared
observations of AXPs. We find that the counterpart to AXP 4U 0142+61 has a
peculiar spectral energy distribution. The counterpart is remarkably bright in
the near-infrared, but is not detected in the B band. We also present the
possible detection of a second AXP counterpart, namely that of AXP 1E 2259+586.


title: Long-Term Monitoring of Anomalous X-ray Pulsars

abstract:
  We report on long-term monitoring of anomalous X-ray pulsars (AXPs) using the
Rossi X-ray Timing Explorer. Using phase-coherent timing, we find a wide
variety of behaviors among the sources, ranging from high stability (in 1E
2259.1+586 and 4U 0142+61), to instabilities so severe that phase-coherent
timing is not possible (in 1E 1048.1-5937). We note a correlation in which
timing stability in AXPs decreases with increasing spin-down rate. The timing
stability of soft gamma repeaters in quiescence is consistent with this trend,
which is similar to one seen in radio pulsars. We consider high signal-to-noise
ratio average pulse profiles as a function of energy for each AXP, and find a
variety of behaviors. We find no large variability in pulse morphology nor in
pulsed flux as a function of time.


title: Molecular gas at intermediate redshifts

abstract:
  We present Giant Metrewave Radio Telescope (GMRT) observations of OH
absorption in B3~1504+377 ($z \sim 0.673$) and PKS 1413+135 ($z \sim 0.247$).
OH has now been detected in absorption towards four intermediate redshift
systems, viz. the lensing galaxies towards B~0218+357 ($z \sim 0.685$; Kanekar
et al. 2001) and 1830-211 ($z \sim 0.886$; Chengalur et al. 1999), in addition
to the two systems listed above. All four systems also give rise to well
studied millimetre wavelength molecular line absorption from a host of
molecules, including HCO$^+$. Comparing our OH data with these millimetre line
transitions, we find that the linear correlation between $N_{\rm OH}$ and
$N_{\rm HCO^+}$ found in molecular clouds in the Milky Way (Liszt & Lucas 1996)
persists out to $z \sim 1$. It has been suggested (Liszt & Lucas 1999) that OH
is a good tracer of ${\rm H_2}$, with $N_{\rm H_2}/N_{\rm OH} \approx 10^7$
under a variety of physical conditions. We use this relationship to estimate
$N_{\rm H_2}$ in these absorbers. The estimated $N_{\rm H_2}$ is $\ga 10^{22}$
in all four cases and substantially different from estimates based on CO
observations.


title: BATSE Observations of Gamma-Ray Burst Tails

abstract:
  I discuss in this paper the phenomenon of post-burst emission in BATSE
gamma-ray bursts at energies traditionally associated with prompt emission. By
summing the background-subtracted signals from hundreds of bursts, I find that
tails out to hundreds of seconds after the trigger may be a common feature of
long events (duration greater than 2s), and perhaps of the shorter bursts at a
lower and shorter-lived level. The tail component appears independent of both
the duration (within the long GRB sample) and brightness of the prompt burst
emission, and may be softer. Some individual bursts have visible tails at
gamma-ray energies and the spectrum in at least a few cases is different from
that of the prompt emission.


title: Hydrogen-Poor Disks in Compact X-Ray Binaries

abstract:
  We show that accretion disks in several compact X-ray binaries with
hydrogen-depleted donors are likely subject to a thermal ionization
instability, unless they are strongly irradiated. These disks are particularly
interesting in that their MHD-turbulent properties in the neutral phase may be
quite different from those of standard, hydrogen-rich disks.


title:
The Global Content, Distribution, and Kinematics of Interstellar O VI in
  the Large Magellanic Cloud

abstract:
  We present FUSE observations of interstellar O VI absorption towards 12
early-type stars in the Large Magellanic Cloud (LMC). O VI 1031.926 Ang
absorption at LMC velocities is seen towards all 12 stars. The observed columns
are in the range log N(O VI)=13.9 to 14.6, with a mean of 14.37. The
observations probe several sight lines projected onto known superbubbles, but
these show relatively little (if any) enhancement in O VI column density
compared to sight lines towards relatively quiescent regions of the LMC. The
observed LMC O VI absorption is broad, with Gaussian dispersions of 30 to 50
km/sec, implying temperatures T<(2-5)x10^6 K. The O VI absorption is typically
displaced -30 km/sec from the corresponding low-ionization absorption
associated with the bulk of the LMC gas. The properties of the LMC O VI
absorption are very similar to those of the Milky Way halo. The average column
density of O VI and the dispersion of the individual measurements about the
mean are identical to those measured for the halo of the Milky Way, even though
the metallicity of the LMC is a factor of ~2.5 lower than the Milky Way. Much
of the LMC O VI may arise in a vertically-extended distribution similar to the
Galactic halo. If the observed O VI absorption is tracing a radiatively cooling
galactic fountain flow, the mass flow rate from one side of the LMC disk is of
the order 1 Msun/yr, with a mass flux per unit area of the disk ~0.02
Msun/yr/kpc^2. (abridged)


title: Magnetic helicity in stellar dynamos: new numerical experiments

abstract:
  The theory of large scale dynamos is reviewed with particular emphasis on the
magnetic helicity constraint in the presence of closed and open boundaries. In
the presence of closed or periodic boundaries, helical dynamos respond to the
helicity constraint by developing small scale separation in the kinematic
regime, and by showing long time scales in the nonlinear regime where the scale
separation has grown to the maximum possible value. A resistively limited
evolution towards saturation is also found at intermediate scales before the
largest scale of the system is reached. Larger aspect ratios can give rise to
different structures of the mean field which are obtained at early times, but
the final saturation field strength is still decreasing with decreasing
resistivity. In the presence of shear, cyclic magnetic fields are found whose
period is increasing with decreasing resistivity, but the saturation energy of
the mean field is in strong super-equipartition with the turbulent energy. It
is shown that artificially induced losses of small scale field of opposite sign
of magnetic helicity as the large scale field can, at least in principle,
accelerate the production of large scale (poloidal) field. Based on mean field
models with an outer potential field boundary condition in spherical geometry,
we verify that the sign of the magnetic helicity flux from the large scale
field agrees with the sign of alpha. For solar parameters, typical magnetic
helicity fluxes lie around 10^{47} Mx^2 per cycle.


title:
Local and nonlocal magnetic diffusion and alpha-effect tensors in shear
  flow turbulence

abstract:
  Various approaches to estimate turbulent transport coefficients from
numerical simulations of hydromagnetic turbulence are discussed. A quantitative
comparison between the averaged magnetic field obtained from a specific
three-dimensional simulation of a rotating turbulent shear flow in a slab and a
simple one-dimensional alpha-omega dynamo model is given. A direct
determination of transport coefficients is attempted by calculating the
correlation matrix of different components of the field and its derivatives.
The alpha-effect operating on the toroidal field is found to be negative and of
similar magnitude as the value obtained previously by correlating the
electromotive force with the mean magnetic field. The turbulent diffusion of
the toroidal field is comparable to the kinematic viscosity that was determined
earlier by comparing the stress with the shear. However, the turbulent
diffusion of the radial field component is smaller and can even be formally
negative. The method is then modified to obtain the spectral dependence of the
turbulent transport coefficients on the wavenumber. There is evidence for
nonlocal behavior in that most of the response comes from the smallest
wavenumbers corresponding to the largest scale possible in the simulation.


title: Hydromagnetic turbulence in computer simulations

abstract:
  In ordinary turbulence research it has been a long standing tradition to
solve the equations in spectral space giving the best possible accuracy. This
is indeed a natural choice for incompressible problems with periodic
boundaries, but it is no longer optimal in many astrophysical circumstances. It
is argued that lower order spatial derivatives schemes are unacceptable in view
of their low overall accuracy, even when mass, momentum, and energy are
conserved to machine accuracy. High order finite difference schemes are
therefore found to be quite efficient and physically appropriate. They are also
easily and efficiently implemented on massively parallel computers. High order
schemes also yield sufficient overall accuracy. Our code uses centered finite
differences which make the adaptation to other problems simple. Since the code
is not written in conservative form, conservation of mass, energy and momentum
can be used to monitor to quality of the solution. A third order Runge-Kutta
scheme with 2N-storage is used for calculating the time advance.


title: Vacuum Decay Constraints on a Cosmological Scalar Field

abstract:
  If the potential of a scalar field, Phi, which currently provides the ``dark
energy'' of the universe, has a negative minimum -M_0^4, then
quantum-mechanical fluctuations could nucleate a bubble of Phi at a negative
value of the potential. The bubble would expand at the speed of light. Given
that no such bubble enveloped us in the past, we find that any minimum in
V(Phi) must be separated from the current Phi value by more than min{1.5M_0,
0.21M_Pl}, where M_Pl is the Planck mass. We also show that vacuum decay
renders a cyclic or ekpyrotic universe with M_0^4 > 10^{-10}M_Pl^4, untenable.


title: Normal Modes of Rotating Magnetic Stars

abstract:
  We investigate the effect of a magnetic field on the global oscillation modes
of a rotating fluid star in the magnetohydrodynamic approximation. We present
general equations for the modification of any type of fluid mode due to a
general magnetic field which is not aligned with the star's spin axis. In the
case of any internal dipole magnetic field we derive the equations for the
frequency corrections to the r-modes. We solve for the frequency correction
explicitly for the case when the internal dipole field is force-free, including
the uniform density case. In the weak-field limit, the spatial form of the
r-mode velocity perturbation is unchanged, but the magnitude of the frequency
in the rotating frame increases.


title:
Abundances in Stars from the Red Giant Branch Tip to Near the Main
  Sequence Turn Off in M71: III. Abundance Ratios

abstract:
  We present abundance ratios for 23 elements with respect to Fe in a sample of
stars with a wide range in luminosity, from luminous giants to stars near the
turnoff, in the globular cluster M71. The analyzed spectra, obtained with HIRES
at the Keck Observatory, are of high dispersion (R=35,000). We find that the
neutron capture, the iron peak and the alpha-element abundance ratios show no
trend with Teff, and low scatter around the mean between the top of the RGB and
near the main sequence turnoff. The alpha-elements Mg, Ca, Si and Ti are
overabundant relative to Fe. The anti-correlation between O and Na abundances,
observed in other metal poor globular clusters, is detected in our sample and
extends to the main sequence. A statistically significant correlation between
Al and Na abundances is observed among the M71 stars in our sample, extending
to Mv = +1.8, fainter than the luminosity of the RGB bump in M5. Lithium is
varying, as expected, and Zr may be varying from star to star as well. M71
appears to have abundance ratios very similar to M5 whose bright giants were
studied by Ivans et al. (2001), but seems to have a smaller amplitude of
star-to-star variations at a given luminosity, as might be expected from its
higher metallicity. The results of our abundance analysis of 25 stars in M71
provide sufficient evidence of abundance variations at unexpectedly low
luminosities to rule out the mixing scenario. Either alone or, even more
powerfully, combined with other recent studies of C and N abundances in M71
stars, the existence of such abundance variations cannot be reproduced within
the context of our current understanding of stellar evolution.


title: Optical Spectra of Supernovae

abstract:
  Supernova flux and polarization spectra bring vital information on the
geometry, physical conditions, and composition structure of the ejected matter.
For some supernovae the circumstellar matter is also probed by the observed
spectra. Some of this information can be inferred directly from the observed
line profiles and fluxes, but because of the Doppler broadening and severe line
blending, interpretation often involves the use of synthetic spectra. The
emphasis in this Chapter is on recent results obtained with the help of
synthetic spectra.