title: The spatial distribution of the far-infrared emission in NGC 253

abstract:
  We study the far-infrared emission properties of the nearby starburst galaxy
NGC 253 based on IRAS maps and an ISOPHOT map at 180 microns. Based on the
analysis of the light profiles, we have been able to identify three main
structural components: an unresolved nuclear component, an exponential disk,
and a kiloparsec scale bar.In addition, we also found a ring structure at the
end of the bar that is particularly conspicuous at 12 microns. The Spectral
Energy Distribution (SED) of each morphological component has been modeled as
thermal dust emission at different temperatures. The unresolved nuclear
component is dominated by cold dust emission (T ~ 50 K), whereas the disk
emission is dominated by very cold dust (T ~ 16 K) plus a contribution from
cold dust (T ~ 55 K). The bar emission corresponds mainly to cold dust (T ~ 23
K) plus a warm component (T ~ 148 K). We detect an extension of the disk
emission due to very cold dust, which contributes a large fraction (94%) of the
total dust mass of the galaxy. The estimated total dust mass is 8.2 +/- 10^7
Msun.


title:
On The Origin of HI in Galaxies: Photodissociation and the ``Schmidt
  Law'' for Global Star Formation

abstract:
  Young stars in the disks of galaxies produce HI from their parent H2 clouds
by photodissociation. This process is widespread in late-type galaxies, and
follows the distribution of Far-UV photons produced primarily by B-type stars.
An estimate of the amount of dissociated gas can be made using observed Far-UV
fluxes and simple approximations for the physics of photodissociation. This
leads to the startling conclusion that much, and perhaps even all, of the HI in
galaxy disks can be produced in this way. This result offers a simple, but
inverse, cause-effect explanation for the ``Schmidt Law'' of Global Star
Formation in galaxies.


title: HI 21cm absorption beyond the epoch of re-ionization

abstract:
  We explore the possibility of detecting HI 21cm absorption by the neutral
intergalactic medium (IGM) toward very high redshift radio sources. The epoch
considered is between the time when the first ionizing sources form and when
the bulk of the neutral IGM becomes ionized. Due to the extreme Ly-alpha
opacities of the neutral IGM, objects within this 'gray age' can only be
observed at wavelengths longer than about 1micron. We use the latest
simulations of the evolution of the IGM in the context of LambdaCDM structure
formation models constrained by observations of the highest redshift QSOs to
predict the optical depth as a function of frequency of the neutral IGM due to
the HI 21cm line. We then simulate radio spectra assuming observational
parameters for future large area radio telescopes. These spectra show that HI
21cm absorption studies could be a powerful probe of the rich structure of the
neutral IGM prior to the epoch of reionization, including 1% absorption by the
mean neutral IGM, plus deeper, narrow lines (5% and a few km/s). Most of the
variations in transmissivity are due to the mild density inhomogeneities with
typical values of the cosmic overdensity of about 10, precisely the structures
that at later times give rise to the Ly-alpha forest. We also consider
sensitivity limits and the evolution of radio source populations, and conclude
that it is reasonable to hypothesize the existence of an adequate number of
high-z radio sources against which such absorption studies could be performed.


title:
Neutrino-induced Collapse of Bare Strange Stars Via TeV-scale Black Hole
  Seeding

abstract:
  There is increasing observational evidence for the existence of strange
stars: ultra-compact objects whose interior consists entirely of deconfined
quark matter. If confirmed, their existence places constraints on the rate of
formation of microscopic black holes in models which invoke a TeV-scale Planck
mass. In such models, black holes can form with ~TeV masses through nuclear
interactions of particles with PeV and greater energies. Once formed, these
black hole states are unstable to Hawking radiation, and rapidly decay.
However, if such a black hole forms in the interior of a strange star, the
density is high enough that the decay may be counterbalanced by accretion, and
the black hole can grow, leading to subsequent catastropic collapse of the
star. A guaranteed source of ultra-high energy particles is provided by the
cosmogenic Greisen neutrinos, as well as by ultra-high energy cosmic rays, and
the implied lifetimes for strange stars are extremely short, contrary to
observations. The observed lifetimes of strange star candidates thus
effectively exclude Planck mass scales of less than ~2 TeV with comparable
black hole masses, for up to 2 extra dimensions. Seeding of strange star
collapse in scenarios with a larger number of extra-dimensions or with higher
mass black holes remains a possibility, and may provide another channel for the
origin of gamma-ray bursts.


title: Black Hole Mass Estimates of Radio Selected Quasars

abstract:
  The black hole (BH) mass in the centre of AGN has been estimated for a sample
of radio-selected flat-spectrum quasars to investigate the relationship between
BH mass and radio properties of quasars. We have used the virial assumption
with measurements of the H$\beta$ FWHM and luminosity to estimate the central
BH mass. In contrast to previous studies we find no correlation between BH mass
and radio power in these AGN. We find a range in BH mass similar to that seen
in radio-quiet quasars from previous studies. We believe the reason that the
low BH mass radio-loud quasars have not been measured in previous studies is
due to optical selection effects which tend to miss the less optically luminous
radio-loud sources.


title: The metallicities of UM151, UM408 and A1228+12 revisited

abstract:
  We present the results of new spectrophotometry and heavy element abundance
determinations for 3 dwarf galaxies UM151, UM408 and A1228+12 (RMB132). These
galaxies have been claimed in the literature to have very low metallicities,
corresponding to log(O/H)+12 < 7.65, that are in the metallicity range of some
candidate local young galaxies. We present higher S/N data for these three
galaxies. UM151 and UM408 have significantly larger metallicities: log(O/H)+12
= 8.5 and 7.93, respectively. For A1228+12 our new log(O/H)+12 = 7.73 is close
to that recalculated from earlier data (7.68). Thus, the rederived
metallicities allow us to remove these objects from the list of galaxies with Z
< 1/20 Z_Sun.


title:
New Method for ISOCAM Data Reduction - II. Mid-Infrared Extragalactic
  Source Counts in the Southern ELAIS Field

abstract:
  We present the 15 micron extragalactic source counts from the Final Analysis
Catalogue of the European Large Area ISO Survey southern hemisphere field S1,
extracted using the Lari method. The large number of extragalactic sources
(about 350) detected over this area between 0.5 and 100 mJy guarantee a high
statistical significance of the source counts in the previously poorly covered
flux density range between IRAS and the Deep ISOCAM Surveys. The bright counts
in S1 (> 2mJy) are consistent with a flat, Euclidean slope, suggesting the
dominance of a non-evolving population. In contrast, at fainter fluxes (< 2
mJy) our counts show a strong departure from no evolution models, with a very
steep super-Euclidean slope down to our flux limit. Strong luminosity and
density evolution is needed at least for the population of star-forming
galaxies, together with a luminosity break around 10^10.8 Lsun in their local
luminosity function in order to reproduce our sharp increase of the counts
below 2 mJy and the redshift distributions observed for 15 micron sources at
different flux levels. The contribution of the strongly evolving starburst
population (down to 50 microJy) to the 15 micron cosmic background is estimated
to be 2.2 nW m^-2 sr^-1 (67% of the total mid-infrared background estimate).


title: A BeppoSax view of the Centaurus Cluster

abstract:
  We present results from the analysis of a BeppoSAX observation of the
Centaurus Cluster. The radial metal abundance profile shows evidence of a large
enhancement in the core, where Ab $>$ 1 (sol. units). The temperature map
indicates that the cluster is characterized by a gradient oriented in the NW/SE
direction, with cooler gas in the NW and hotter gas in the SE (\Delta kT \sim 1
keV). In hard X-rays, where the PDS detects emission with a flux of $2.2 \times
10^{-11}$ erg/cm^2/s in the 20-200 keV band, the spectrum lies above the
extrapolation of the cluster thermal emission. We discuss several possible
interpretations for the hard excess finding that none is completely
satisfactory.


title:
A comparison of neutron star blackbody luminosities in LMXB with the
  theory of accretion flow spreading on the stellar surface

abstract:
  We present a comparison of the results of the ASCA survey of LMXB with the
Inogamov and Sunyaev theory of accretion flow spreading on the surface of
neutron stars. The ASCA survey of LMXB of Church and Balucinska-Church (2001)
revealed a systematic variation of the luminosity of blackbody emission from
the neutron star spanning 3 decades in total X-ray luminosity suggesting that
the level of blackbody emission is controlled by the physics of the inner
disk/stellar interface, which we can hope to understand. Two types of
explanation exist: firstly that there is radial flow between the inner disk and
star at all vertical positions above the orbital plane so that the height of
the disk directly determines the area of star emitting. Secondly, the height of
the emitting region on the star is not directly related to the disk properties
but depends on the mass accretion rate as suggested by Inogamov and Sunyaev
(1999) in their theory of accretion flow spreading on the stellar surface. We
find that the survey results for the emitting area agree with this theory at
the lowest luminosities. However, for higher luminosities, the blackbody
emission is stronger than predicted by spreading theory suggesting that the
emitting area is controlled by radial flow between disk and star.


title: Bulges on the Fundamental Plane of Early-Type Galaxies

abstract:
  In an ongoing effort to study the formation and evolution of galactic bulges
we have investigated the position of 19 bulges of type S0-Sbc on the
fundamental plane (FP). We find that bulges, both in B and K band, lie close to
but slightly below the FP defined by ellipticals and S0s, i.e. are slightly
brighter. There are hints that bulges of later morphological type are situated
below the other bulges in our sample. The FP results are consistent with the
picture, obtained from our recent analysis of HST-colours, that bulges are old,
except for the Sbc galaxies. The fact that bulges lie so close to the FP of
ellipticals and S0s implies that their formation epoch must have been similar,
at most about 2.5 Gyr earlier, than cluster Es and S0s, and and that the
surrounding disk does not significantly affect their structure.


title: Giant Radio Pulses from the Millisecond Pulsar PSR B1937+21 at 327 MHz

abstract:
  Seven giant radio pulses were recorded from the millisecond pulsar PSR
B1937+21 during $\approx$ 8.1 minutes observation by the Ooty Radio Telescope
(ORT) at 326.5 MHz. Although sparse, these observations support most of the
giant pulse behavior reported at higher radio frequencies (430 to 2380 MHz).
Within the main componentof the integrated profile, they are emitted only in a
narrow ($\la$ 47 $\mu$s) window of pulse phase, close to its peak. This has
important implications for doing super-high precision timing of PSR B1937+21 at
low radio frequencies.


title:
RXTE observations of single pulses of PSR B0531+21: II Test for radio
  behavior

abstract:
  This article is the second in the series that analyze about 1.87 million
periods of Crab pulsar, observed by the PCA detector aboard the RXTE x-ray
observatory. At these energies the pulsar displays none of the three phenomena
that are often seen in normal radio pulsars -- ``pulse nulling'', ``systematic
sub pulse drifting'' and ``mode changing''. Presence or absence of these three
behavior in the Crab pulsar, at radio wavelengths, something that has not been
rigorously established yet, might be important for a satisfactory understanding
of the above three phenomena.


title:
Radio Profile Instability in the Millisecond Pulsar PSR J0437-4715 due
  to Spiky Emission

abstract:
  The instability in one of the components of the radio integrated profile (IP)
of the millisecond pulsar PSr J0437-4715 is correlated with the occurrence of
the spiky emission in that component. It is speculated that the instability in
other components is also due to the spiky emission. This might have important
implications for interpreting the individual components of the IP as
independent beams or regions of emission.


title: On the precession of the isolated pulsar PSR B1828-11

abstract:
  Analysis of both pulse timing and pulse shape variations of the isolated
pulsar PSR B1828-11 shows highly correlated and strong Fourier power at periods
\~ 1000, 500, and 250 d (Stairs et al. 2000). The only description based on a
free precession of star's rigid crust coupled to the magnetic dipole torque,
explains the 500-component, as the fundamental Fourier frequency, with its
harmonic 250-component (Link & Epstein 2001). In this paper, we show that if
the dipole moment vector varies with time with a period nearly equal to the
longest (probably fundamental) observed period (~ 1000 d), the dipole torque
may produce the all other harmonics. We also find the second and fourth
harmonics at periods ~ 500 and 250 d are dominant for small wobble angle ~ 3^o
and large field's inclination angle 89^o.


title:
A new approach in data reduction: proper handling of random errors and
  image distortions

abstract:
  Data reduction procedures are aimed to minimize the impact of data
acquisition imperfections on the measurement of data properties with a
scientific meaning for the astronomer. To achieve this purpose, appropriate
arithmetic manipulations with data and calibration frames must be performed.
Furthermore, a full understanding of all the possible measurements relies on a
solid constraint of their associated errors. We discuss different strategies
for obtaining realistic determinations of final random errors. In particular,
we highlight the benefits of considering the data reduction process as the full
characterization of the raw-data frames, but avoiding, as far as possible, the
arithmetic manipulation of that data until the final measure and analysis of
the image properties. This philosophy will be used in the pipeline data
reduction for ELMER and EMIR.


title: The Peculiar Galaxy NGC7332

abstract:
  We present a detailed study of the edge-on S0 galaxy NGC7332. We show that
this object lies significantly below the fundamental plane of early-type
galaxies. To understand this behaviour, we have carried out observations with
the Integral Field Spectrograph SAURON, which give us a detailed view of the
internal kinematics and gas and stars in this galaxy.


title: The Multi-Component Nature of the Vela Pulsar Nonthermal X-ray Spectrum

abstract:
  We report on our analysis of a 274 ks observation of the Vela pulsar with the
Rossi X-Ray Timing Explorer (RXTE). The double-peaked, pulsed emission at 2 -
30 keV, which we had previously detected during a 93 ks observation, is
confirmed with much improved statistics. There is now clear evidence, both in
the spectrum and the light curve, that the emission in the RXTE band is a blend
of two separate non-thermal components. The spectrum of the harder component
connects smoothly with the OSSE, COMPTEL and EGRET spectrum and the peaks in
the light curve are in phase coincidence with those of the high-energy light
curve. The spectrum of the softer component is consistent with an extrapolation
to the pulsed optical flux, and the second RXTE pulse is in phase coincidence
with the second optical peak. In addition, we see a peak in the 2-8 keV RXTE
pulse profile at the radio phase.


title:
A peculiar spectral state transition of 4U1705--44: when an Atoll looks
  like a Z

abstract:
  We report on a clear spectral state transition of the neutron star low-mass
X-ray binary 4U1705-44 observed by the Rossi X-ray Timing Explorer. In the
X-ray color-color diagram (CCD), the source, classified as an Atoll, samples
the upper parts of a Z, starting from and returning to the left bottom of the
Z. We follow the path of 4U1705-44 on its CCD, model its broad band X-ray/hard
X-ray spectrum, and compute the Fourier power density spectrum of its X-ray
variability. The spectral transitions of 4U1705-44 are shown to be primarily
associated with changes in the temperature of the Comptonizing electrons. In
the hard state (top branch of the Z), the source evolves from left to right on
the CCD, while its luminosity smoothly increases.
  Our observations can be interpreted in the framework of a model made of a
truncated accretion disk of varying inner radius and an inner flow merging
smoothly with the neutron star boundary layer. The spectral evolution could be
driven by changes in the truncation radius of the disk; e.g. the soft to hard
transition could be caused by the disk moving outwards. If this model is
correct, then our data show that the disk truncation radius is not set by the
instantaneous mass accretion rate, as derived from the source bolometric
luminosity.
  Comparing the power density spectra of 4U1705-44 and Z sources when they
occupy similar branches of the Z, we show that the most significant difference
is on the diagonal branch, on which the power density spectra of 4U1705-44
remain similar to the ones measured on the top branch of the Z (hard state).


title: A Search for OH Megamasers at z > 0.1. III. The Complete Survey

abstract:
  We present the final results from the Arecibo Observatory OH megamaser
survey. We discuss in detail the properties of the remaining 18 OH megamasers
detected in the survey, including 3 redetections. We place upper limits on the
OH emission from 85 nondetections and examine the properties of 25 ambiguous
cases for which the presence or absence of OH emission could not be determined.
The complete survey has discovered 50 new OH megamasers (OHMs) in
(ultra)luminous infrared galaxies ([U]LIRGs) which doubles the sample of known
OHMs and increases the sample at z>0.1 sevenfold. The Arecibo OH megamaser
survey indicates that the OHM fraction in LIRGs is an increasing function of
the far-IR luminosity (L_{FIR}) and far-IR color, reaching a fraction of
roughly one third in the warmest ULIRGs. Significant relationships between OHMs
and their hosts are few, primarily due to a mismatch in size scales of measured
properties and an intrinsic scatter in OHM properties roughly equal to the span
of the dataset. We investigate relationships between OHMs and their hosts with
a variety of statistical tools including survival analysis, partial correlation
coefficients, and a principal component analysis. There is no apparent OH
megamaser ``fundamental plane.'' We compile data on all previously known OHMs
and evaluate the possible mechanisms and relationships responsible for OHM
production in merging systems. The OH-FIR relationship is reexamined using the
doubled OHM sample and found to be significantly flatter than previously
thought: L_{OH} ~ L_{FIR}^{1.2 +/- 0.1}. This near-linear dependence suggests a
mixture of saturated and unsaturated masers, either within individual galaxies
or across the sample.


title: Adaptive Optics Near-Infrared Spectroscopy of the Sgr A* Cluster

abstract:
  We present K-band $\lambda/\Delta\lambda$ ~ 2600 spectroscopy of five stars
(K ~ 14 - 16 mag) within 0.''5 of Sgr A*, the radio source associated with the
compact massive object suspected to be a 2.6 x 10$^{6}$ \msun black hole at the
center of our Galaxy. High spatial resolution of ~ 0.''09, and good strehl
ratios of ~ 0.2 achieved with adaptive optics on the 10-meter Keck telescope
make it possible to measure moderate-resolution spectra of these stars
individually for the first time. Two stars (S0-17 and S0-18) are identified as
late-type stars by the detection of CO bandhead absorption in their spectra.
Their absolute K magnitudes and CO bandhead absorption strengths are consistent
with early K giants. Three stars (S0-1, S0-2, and S0-16), with r$_{proj}$ $<$
0.0075 pc (~ 0.''2) from Sgr A*, lack CO bandhead absorption, confirming the
results of earlier lower spectral and lower spatial resolution observations
that the majority of the stars in the Sgr A* Cluster are early-type stars. The
absolute K magnitudes of the early-type stars suggest that they are late O -
early B main sequence stars of ages $<$ 20 Myr. The presence of young stars in
the Sgr A* Cluster, so close to the central supermassive black hole, poses the
intriguing problem of how these stars could have formed, or could have been
brought, within its strong tidal field.


title: Predictions and Observations in Theories with Varying Couplings

abstract:
  We consider a toy universe containing conventional matter and an additional
real scalar field, and discuss how the requirements of gauge and diffeomorphism
invariance essentially single out a particular set of theories which might
describe such a world at low energies. In these theories, fermion masses and
g-factors, as well as the electromagnetic coupling turn to be scalar field
dependent; fermion charges and the gravitational coupling might be assumed to
be constant. We then proceed to study the impact of a time variation of the
scalar field on measurements of atomic spectra at high redshifts. Light
propagation is not affected by a sufficiently slow change of the fine structure
constant, but changes of the latter as well as variations of fermion masses and
g-factors do affect the observed atomic spectra. Finally, we prove the
independence of these predictions on the chosen conformal frame, in a further
attempt to address differing views about the subject expressed in the
literature.


title: Scaling of voids and fractality in the galaxy distribution

abstract:
  We study here, from first principles, what properties of voids are to be
expected in a fractal point distribution and how the void distribution is
related to its morphology. We show this relation in various examples and apply
our results to the distribution of galaxies. If the distribution of galaxies
forms a fractal set, then this property results in a number of scaling laws to
be fulfilled by voids. Consider a fractal set of dimension $D$ and its set of
voids. If voids are ordered according to decreasing sizes (largest void has
rank R=1, second largest R=2 and so on), then a relation between size $\Lambda$
and rank of the form $\Lambda (R) \propto R^{-z}$ must hold, with $z = d/D$,
and where $d$ is the euclidean dimension of the space where the fractal is
embedded. The physical restriction $D < d$ means that $z > 1$ in a fractal set.
The average size $\bar \Lambda$ of voids depends on the upper ($\Lambda_u$) and
the lower ($\Lambda_l$) cut-off as ${\bar \Lambda} \propto \Lambda_u^{1-D/d}
\Lambda_l^{D/d}$. Current analysis of void sizes in the galaxy distribution do
not show evidence of a fractal distribution, but are insufficient to rule it
out. We identify possible shortcomings of current void searching algorithms,
such as changes of shape in voids at different scales or merging of voids, and
propose modifications useful to test fractality in the galaxy distribution.


title:
Constraining the Lifetime of QSOs with Present-day Mass Function of
  Supermassive Black Holes

abstract:
  Using the theoretical models of the QSO formation, we can reproduce optical
QSO luminosity functions (LFs) at high redshifts (z > 2.2). Two different
models can reproduce LFs successfully, though the lifetime of QSOs, t_Q, and
the relation between the black hole mass and the host halo mass are different
each other; t_Q = 10^6yr, in one model, t_Q > 10^7yr, in other models. Here, we
propose a method to break this degeneracy.
  We calculate the mass function of supermassive black holes (SMBHs) at z=2.5,
and compare the result with the current mass function obtained by Salucci et
al.(1999). In the shorter lifetime model, the mass function at z=2.5 exceeds
that of z=0.0 by one order of magnitude, then it should be ruled out. We
conclude that the lifetime is at least t_Q > 10^7yr.
  Next, we examine the difference of the formation epoch of SMBHs existing at
z=3.0 for each model under the model assumptions. We simply discuss the
difference of formation epoch as another possible model-discriminator.


title: New Tests of Magnetospheric Accretion in T Tauri Stars

abstract:
  We examine 3 analytic theories of magnetospheric accretion onto classical T
Tauri stars under the assumption that the magnetic field strength does not vary
appreciably from star to star. From these investigations we derive predicted
relationships among the stellar mass, radius, rotation period, and disk
accretion rate. Data from 5 studies of the accretion parameters of CTTSs are
used to test the predicted correlations. We generally find that the data do not
display the predicted correlations except for that predicted by the model of
Shu et al. as detailed by Ostriker and Shu and extended here to include
non-dipole field topologies. Their identification of the trapped flux as an
important quantity in the model appears to be critical for reconciling the
observed data to the theory. While the data do generally support the extended
Ostriker and Shu predictions, only one of the two studies for which the
requisite data exist show the highest correlation when considering all the
relevant parameters. This suggests great care must be taken when trying to use
existing observations to test the theory.


title:
Shell Shock and Cloud Shock: Results from Spatially-Resolved X-ray
  Spectroscopy with Chandra in the Cygnus Loop

abstract:
  We use the Chandra X-ray Observatory to analyze interactions of the blast
wave and the inhomogeneous interstellar medium on the western limb of the
Cygnus Loop supernova remnant. This field of view includes an initial
interaction between the blast wave and a large cloud, as well as the encounter
of the shock front and the shell that surrounds the cavity of the supernova
progenitor. Uniquely, the X-rays directly trace the shock front in the dense
cloud, where we measure temperature kT = 0.03 keV. We find kT~0.2 keV in
regions where reflected shocks further heat previously-shocked material.
Applying one-dimensional models to these interactions, we determine the
original blast wave velocity v_bw~330 km/s in the ambient medium. We do not
detect strong evidence for instabilities or non-equilibrium conditions on the
arcsecond scales we resolve. These sensitive, high-resolution data indicate no
exceptional abundance variations in this region of the Cygnus Loop.


title: Modeling the Formation of Clouds in Brown Dwarf Atmospheres

abstract:
  Because the opacity of clouds in substellar mass object (SMO) atmospheres
depends on the composition and distribution of particle sizes within the cloud,
a credible cloud model is essential for accurately modeling SMO spectra and
colors. We present a one--dimensional model of cloud particle formation and
subsequent growth based on a consideration of basic cloud microphysics. We
apply this microphysical cloud model to a set of synthetic brown dwarf
atmospheres spanning a broad range of surface gravities and effective
temperatures (g_surf = 1.78 * 10^3 -- 3 * 10^5 cm/s^2 and T_eff = 600 -- 1600
K) to obtain plausible particle sizes for several abundant species (Fe,
Mg2SiO4, and Ca2Al2SiO7). At the base of the clouds, where the particles are
largest, the particle sizes thus computed range from ~5 microns to over 300
microns in radius over the full range of atmospheric conditions considered. We
show that average particle sizes decrease significantly with increasing brown
dwarf surface gravity. We also find that brown dwarfs with higher effective
temperatures have characteristically larger cloud particles than those with
lower effective temperatures. We therefore conclude that it is unrealistic when
modeling SMO spectra to apply a single particle size distribution to the entire
class of objects.


title: Measuring the mass of high-z galaxies with NGST

abstract:
  We discuss dynamical mass measurements of high-z galaxies with the Next
Generation Space Telescope (NGST). In particular, we review some of the
observational limits with the current instrument/telescope generation, we
discuss the redshift limits and caveats for absorption and emission lines
studies with NGST, and the existence of suitable targets at high redshift. We
also briefly summarize strengths and weaknesses of proposed NGST instruments
for dynamical studies.


title:
Exploring Halo Substructure with Giant Stars IV: The Extended Structure
  of the Ursa Minor Dwarf Spheroidal

abstract:
  We present a large area photometric survey of the Ursa Minor dSph. We
identify UMi giant star candidates extending to ~3 deg from the center of the
dSph. Comparison to previous catalogues of stars within the tidal radius of UMi
suggests that our photometric luminosity classification is 100% accurate. Over
a large fraction of the survey area, blue horizontal branch stars associated
with UMi can also be identified. The spatial distribution of both the UMi giant
stars and the BHB stars are remarkably similar, and a large fraction of both
samples of stars are found outside the tidal radius of UMi. An isodensity
contour map of the stars within the tidal radius of UMi reveals two
morphological peculiarities: (1) The highest density of dSph stars is offset
from the center of symmetry of the outer isodensity contours. (2) The overall
shape of the outer contours appear S-shaped. We find that previously determined
King profiles with ~50' tidal radii do not fit well the distribution of our UMi
stars. A King profile with a larger tidal radius produces a reasonable fit,
however a power law with index -3 provides a better fit for radii > 20'. The
existence of UMi stars at large distances from the core of the galaxy, the
peculiar morphology of the dSph within its tidal radius, and the shape of its
surface density profile all suggest that UMi is evolving significantly due to
the tidal influence of the Milky Way. However, the photometric data on UMi
stars alone does not allow us to determine if the candidate extratidal stars
are now unbound or if they remain bound to the dSph within an extended dark
matter halo. (Abridged)


title:
Studies of galaxies in voids. I. HI observations of Blue Compact
  Galaxies

abstract:
  We present here results of studies of the properties of galaxies located in
very low density environments. We observed 26 blue compact galaxies (BCGs) from
the Second Byurakan (SBS) and Case surveys located in voids with the radial
velocities V < 11000 km/s, two BCGs in the void behind the Virgo cluster and 11
BCGs in denser environments. HI fluxes and profile widths, as well as estimates
of total HI masses, are presented for the 27 detected galaxies (of which 6 are
in three galaxy pairs and are not resolved by the radiotelescope beam).
Preliminary comparisons of void BCGs with similar objects from intermediate
density regions - in the general field and the Local Supercluster (sub-samples
of BCGs in the SBS zone) and in the dense environment of the Virgo Cluster (a
BCD sample) - are performed using the hydrogen-to-blue-luminosity ratio
M(HI)/L_B. We find that for the same blue luminosity, for M_B > -18.0, BCGs in
lower density environment have on average more HI. The slope (beta) of the
M(HI)/L_B proportional to L^(beta) for BCGs shows a trend of steepening with
decreasing bright galaxy density, being very close to zero for the densest
environment considered here and reaching (beta) = -0.4 for voids.


title: The Radio Properties of Composite LINER/HII Galaxies

abstract:
  Arcsec-resolution VLA observations -- newly obtained as well as published --
of 40 nearby galaxies are discussed, completing a study of the radio properties
of a magnitude-limited sample of nearby galaxies of the composite LINER/HII
type. Our results reveal an overall detection rate of at least 25% AGN
candidates among these composite sources. The general properties of these AGN
candidates, as compared to non-AGN composite sources and HII galaxies, are
discussed.


title: Search for Hot Gas in the Local Group with ASCA

abstract:
  An X-ray study was made to examine whether some part of the soft X-ray
background is coming from hot gas in the Local Group. For this purpose, four
consecutive pointings were made with ASCA toward a sky region between M 31 and
M 33, which is close to the direction of the center of the Local Group. By
comparing the X-ray surface brightness in this sky direction with that in
another blank sky region near the north equatorial pole, an upper limit on any
soft excess X-ray background was determined to be 2.8$\times10^{-9}$ erg
cm$^{-2}$ s$^{-1}$ sr$^{-1}$ with a 90% confidence level statistical error.
Assuming an optically thin thermal bremsstrahlung energy spectrum
(Raymond-Smith model) for a temperature of 1 keV and a $\beta$-model electron
density distribution for a core radius of 100 kpc for the X-ray halo, the upper
limit of the central plasma density was obtained to be 1.3$\times10^{-4}$
cm$^{-3}$. The plasma column density is too low to contribute significantly to
the observed quadrupole anisotropy in the cosmic microwave background.


title: The Late-Time Radio Spectrum of SN1993J

abstract:
  We present VLA radio continuum measurements of SN1993J in M81 at the
frequencies of 0.32 (P-band), 1.3 and 1.7 (L-band), 4.9 (C-band), 8.5 (X-band),
and 14.9 (U-band) GHz carried out on December 17 and 21, 2000, about 2820 days
after the supernova explosion. We find that a power-law spectrum, free-free
absorbed by an homogeneous, or clumpy, distribution of ionized gas yields the
best fit to the radio data. A combined homogeneous-clumpy model is not favored,
but neither totally excluded. This result contrasts with the modeling of the
early ($t \lessim $230 days) radio emission from SN1993J, where a mixture of
homogeneous and clumpy absorbers appeared to be necessary to adequately
describe the behavior of the light curves. The radio spectrum of supernova
SN1993J between 0.32 and 14.9 GHz is well characterized by $\alpha = -0.67 \pm
0.02 $ ($S_\nu \propto \nu^\alpha$), typical of an optically thin radio
supernova. A fit to the radio spectra of SN1993J from $\sim$ 70 up to 2820 days
shows that the observed spectral index of SN1993J has been slowly evolving
since $t\sim$1000 days on, with the observed spectral index changing from
$\alpha \approx -1$ to $\alpha=-0.67$. This spectral evolution seems to suggest
that, in addition to the radiative (synchrotron) losses, adiabatic cooling and
ionization (Coulomb) losses at the lowest frequencies might be contributing
significantly to the integrated electron spectrum.


title: Mass of Clusters in Simulations

abstract:
  We show that dark matter haloes, in n--body simulations, have a boundary
layer (BL) with precise features. In particular, it encloses all dynamically
stable mass while, outside it, dynamical stability is lost soon. Particles can
pass through such BL, which however acts as a confinement barrier for dynamical
properties. BL is set by evaluating kinetic and potential energies (T(r) and
W(r)) and calculating R=-2T/W. Then, on BL, R has a minimum which closely
approaches a maximum of w= -dlog W/dlog r. Such $Rw$ ``requirement'' is
consistent with virial equilibrium, but implies further regularities. We test
the presence of a BL around haloes in spatially flat CDM simulations, with or
without cosmological constant. We find that the mass M_c, enclosed within the
radius r_c, where the $Rw$ requirement is fulfilled, closely approaches the
mass M_{dyn}, evaluated from the velocities of all particles within r_c,
according to the virial theorem. Using r_c we can then determine an individual
density contrast Delta_c for each virialized halo, which can be compared with
the "virial" density contrast $\Delta_v ~178 \Omega_m^{0.45}$ (Omega_m: matter
density parameter) obtained assuming a spherically symmetric and unperturbed
fluctuation growth. The spread in Delta_c is wide, and cannot be neglected when
global physical quantities related to the clusters are calculated, while the
average Delta_c is ~25 % smaller than the corresponding Delta_v; moreover if
$M_{dyn}$ is defined from the radius linked to Delta_v, we have a much worse
fit with particle mass then starting from {\it Rw} requirement.


title: The B3-VLA CSS sample. II: VLBA images at 18 cm

abstract:
  VLBA observations at 18 cm are presented for 28 Compact Steep-spectrum radio
Sources (CSSs) from the B3-VLA CSS sample. These sources were unresolved in
previous VLA observations at high frequencies or their brightness distribution
was dominated by an unresolved steep spectrum component. More than half of them
also showed a low frequency turnover in their radio spectrum. The VLBA images
display in most cases a compact symmetric structure. Only in a minority of
cases complex morphologies are present.


title: The B3-Vla CSS sample. III: Evn & Merlin images at 18 cm

abstract:
  EVN and MERLIN observations at 18 cm are presented for 18 Compact
Steep--spectrum radio Sources (CSSs) from the B3-VLA CSS sample. These sources
were marginally resolved in previous VLA A-configuration observations at 4.9
and 8.4 GHz or had peculiar morphologies, two of them looking like core-jets.
The MERLIN images basically confirm the VLA structures at 8.4 GHz while the EVN
and/or the combined images reveal several additional details.


title: Inflation and non--Gaussianity

abstract:
  We study non-Gaussian signatures on the cosmic microwave background (CMB)
radiation predicted within inflationary models with non-vacuum initial states
for cosmological perturbations. The model incorporates a privileged scale,
which implies the existence of a feature in the primordial power spectrum. This
broken-scale-invariant model predicts a vanishing three-point correlation
function for the CMB temperature anisotropies (or any other odd-numbered-point
correlation function) whilst an intrinsic non-Gaussian signature arises for any
even-numbered-point correlation function. We thus focus on the first
non-vanishing moment, the CMB four-point function at zero lag, namely the
kurtosis, and compute its expected value for different locations of the
primordial feature in the spectrum, as suggested in the literature to conform
to observations of large scale structure. The excess kurtosis is found to be
negative and the signal to noise ratio for the dimensionless excess kurtosis
parameter is equal to $| S/N | \simeq 4 \times 10^{-4}$, almost independently
of the free parameters of the model. This signature turns out to be
undetectable. We conclude that, subject to current tests, Gaussianity is a
generic property of single field inflationary models. The only uncertainty
concerning this prediction is that the effect of back-reaction has not yet been
properly incorporated. The implications for the trans-Planckian problem of
inflation are also briefly discussed.


title:
Nonradial and nonpolytropic astrophysical outflows. V. Acceleration and
  collimation of self-similar winds

abstract:
  An exact model for magnetized and rotating outflows, underpressured at their
axis, is analysed by means of a nonlinear separation of the variables in the
two-dimensional governing magnetohydrodynamic (MHD) equations for axisymmetric
plasmas. The outflow starts subsonically and subAlfv\'enically from the central
gravitating source and its surrounding accretion disk and after crossing the
MHD critical points, high values of the Alfv\'en Mach number may be reached.
Three broad types of solutions are found: (a) collimated jet-type outflows from
efficient magnetic rotators where the outflow is confined by the magnetic hoop
stress; (b) collimated outflows from inefficient magnetic rotators where the
outflow is cylindrically confined by thermal pressure gradients; and (c)
radially expanding wind-type outflows analogous to the solar wind. In most of
the cases examined cylindrically collimated (jet-type) outflows are naturally
emerging with thermal and magnetic effects competing in the acceleration and
the confinement of the jet. The interplay of all MHD volumetric forces in
accelerating and confining the jet is displayed along all its length and for
several parameters. The solutions may be used for a physical understanding of
astrophysical outflows, such as those associated with young stellar objects,
planetary nebulae, extragalactic jets, etc.


title: A Spectropolarimetric Atlas of Seyfert 1 Galaxies

abstract:
  We present optical spectropolarimetry of the nuclei of 36 Seyfert 1 galaxies,
obtained with the William Herschel and the Anglo-Australian Telescopes from
1996 to 1999. In 20 of these, the optical emission from the active nucleus is
intrinsically polarized. We have measured a significant level of polarization
in a further 7 objects but these may be heavily contaminated by Galactic
interstellar polarization. The intrinsically polarized Seyfert 1s exhibit a
variety of characteristics, with the average polarization ranging from < 0.5 to
5 per cent and many showing variations in both the degree and position angle of
polarization across the broad H alpha emission line. We identify a small group
of Seyfert 1s that exhibit polarization properties similar to those of Seyfert
2 galaxies in which polarized broad-lines have been discovered. These objects
represent direct observational evidence that a Seyfert 2-like far-field polar
scattering region is also present in Seyfert 1s. Several other objects have
features that can be explained in terms of equatorial scattering of line
emission from a rotating disk. We propose that much of the diversity in the
polarization properties of Seyfert galaxies can be understood in terms of a
model involving both equatorial and polar scattering, the relative importance
of the two geometries as sources of polarized light being determined
principally by the inclination of the system axis to the line-of-sight.


title: Current status of weak gravitational lensing

abstract:
  Weak gravitational lensing of distant galaxies by foreground structures has
proven to be a powerful tool to study the mass distribution in the universe.
Nowadays, attention has shifted from clusters of galaxies to the statistical
properties of the large scale structures and the halos of (field) galaxies.
These applications have become feasible with the advent of panoramic cameras on
4m class telescopes. In this review we will give an overview of recent advances
in this fast evolving field of astronomy. We start with a discussion of the
recent measurements of weak lensing by large scale structure (``cosmic
shear''), which can be used to constrain cosmological parameters. We also show
how weak lensing can be used to measure the relation between galaxies and dark
matter (galaxy biasing) directly. Another area that benefitted greatly from the
current data is the weak lensing by galaxies (galaxy-galaxy lensing). Weak
lensing provides a unique probe of the gravitational potential on large scales.
Hence, in the context of dark matter, it can provide constrains on the extent
and shapes of dark matter halos. Furthermore, it can test alternative theories
of gravity (without dark matter). The best constraint comes from the first
detection of the anisotropy of the lensing signal around lens galaxies, which
suggest that the dark matter halos are flattened. An isotropic signal, as
predicted by MOND, is excluded with 99% confidence.


title: Loop Corrections to Scalar Quintessence Potentials

abstract:
  The stability of scalar quintessence potentials under quantum fluctuations is
investigated both for uncoupled models and models with a coupling to fermions.
We find that uncoupled models are usually stable in the late universe. However,
a coupling to fermions is severely restricted. We check whether a graviton
induced fermion-quintessence coupling is compatible with this restriction.


title: Generalized Chaotic Inflation

abstract:
  We investigate inflation driven by the evolution of highly excited quantum
states within the framework of out of equilibrium field dynamics. The
self-consistent evolution of these quantum states and the scale factor is
studied analytically and numerically. It is shown that the time evolution of
these quantum states lead to two consecutive stages of inflation under
conditions that are the quantum analogue of slow-roll. The evolution of the
scale factor during the first stage has new features that are characteristic of
the quantum state. During this initial stage the quantum fluctuations in the
highly excited band build up an effective homogeneous condensate with a
non-perturbatively large amplitude as a consequence of the large number of
quanta. The second stage of inflation is similar to the usual classical chaotic
scenario but driven by this effective condensate. The excited quantum modes are
already superhorizon in the first stage and do not affect the power spectrum of
scalar perturbations. Thus, this novel scenario provides a field theoretical
justification for chaotic scenarios driven by a classical homogeneous scalar
field of large amplitude.


title:
Observations of the X-ray Afterglows of GRB011211 and GRB001025 by
  XMM-Newton

abstract:
  We present the XMM-Newton observations of X-ray afterglows of the gamma-ray
bursts GRB 011211 and GRB 001025. For GRB 011211 XMM detected fading X-ray
object with an average flux in 0.2-10 keV declining from 2.7$\times10^{-13}$
erg cm$^{-2}$ s$^{-1}$ during the first 5 ks of 27-ks observation to
1.0$\times10^{-13}$ erg cm$^{-2}$ s$^{-1}$ toward the end of the observation.
The spectrum of the afterglow can be fit to a power law with
alpha=2.16$\pm$0.03 modified for the Galactic absorption. No significant
evolution of spectral parameters has been detected during the observation.
Similar X-ray spectrum with alpha=2.01$\pm$0.09 has been observed by the XMM
from the GRB 001025. The non-detection of any extra absorption in these spectra
above the Galactic value is an interesting fact and may impose restrictions to
the favorable GRB models involving burst origin in star-forming regions.
Finally we discuss soft X-ray lines from GRB 011211 reported by Reeves et
al.(2002) and conclude that there is no definitive evidence for the presense of
these lines in the spectrum.


title:
On the coorbital corotation torque in a viscous disk and its impact on
  planetary migration

abstract:
  We evaluate the coorbital corotation torque on a planet on a fixed circular
orbit embedded in a viscous protoplanetary disk, for the case of a steady flow
in the planet frame. This torque can be evaluated just from the flow properties
at the separatrix between the librating (horseshoe) and circulating
streamlines. A stationary solution is searched for the flow in the librating
region. When used to evaluate the torque exerted by the circulating material of
the outer and inner disk on the trapped material of the librating region, this
solution leads to an expression of the coorbital corotation torque in agreement
with previous estimates. An analytical expression is given for the corotation
torque as a function of viscosity. Lastly, we show that additional terms in the
torque expression can play a crucial role. In particular, they introduce a
coupling with the disk density profile perturbation (the `dip' which surrounds
the planet) and add to the corotation torque a small, positive fraction of the
one-sided Lindblad torque. As a consequence, the migration could well be
directed outwards in very thin disks (aspect ratio smaller than a few percent).
This 2D analysis is especially relevant for mildly embedded protoplanets
(sub-Saturn sized objects).


title:
Line-driven winds, ionizing fluxes and UV-spectra of hot stars at
  extremely low metallicity. I. Very massive O-stars

abstract:
  Wind models of very massive stars with metallicities in a range from 1E-4 to
1.0 solar are calculated using a new treatment of radiation driven winds with
depth dependent radiative force multipliers and a comprehensive list of more
than two million spectral lines in NLTE. The models are tested by a comparison
with observed stellar wind properties of O stars in the Galaxy and the SMC.
Satisfying agreement is found. The calculations yield mass-loss rates, wind
velocities, wind momenta and wind energies as a function of metallicity and can
be used to discuss the influence of stellar winds on the evolution of very
massive stars in the early universe and on the interstellar medium in the early
phases of galaxy formation. The normal scaling laws, which predict stellar
mass-loss rates and wind momenta to decrease as a power law with metal
abundance break down at a certain threshold. Analytical fit formulae for
mass-loss rates are provided as a function of stellar parameters and
metallicity. The new wind models are applied to calculate ionizing fluxes and
observable spectra of very massive stars as a function of metallicity using the
new hydrodynamic, non-LTE line-blanketed flux constant model atmosphere code
developed by Pauldrach et al. Numbers of ionizing photons for the crucial
ionization stages are given. For a fixed effective temperature the He II
ionizing emergent flux depends very strongly on metallicity but also on stellar
luminosity. A strong dependence on metallicity is also found for the C III, Ne
II and O II ionizing photons, whereas the H I and He I ionizing flux is almost
independent of metallicity. We also calculate UV spectra for all the models and
discuss the behaviour of significant line features as a function of
metallicity.


title:
The co-orbital corotation torque in a viscous disk: numerical
  simulations

abstract:
  The torque felt by a non-accreting protoplanet on a circular orbit embedded
in a uniform surface density protoplanetary disk is analyzed by means of
time-dependent numerical simulations. Varying the viscosity enables one to
disentangle the Lindblad torque (which is independent of viscosity) from the
corotation torque, which saturates at low viscosity and is unsaturated at high
viscosity. The dependence of the corotation torque upon the viscosity and upon
the width of the librating zone is compared with previous analytical
expressions, and shown to be in agreement with those. The effect of the
potential smoothing respectively on the Lindblad torque and on the corotation
torque is investigated, and the question of whether 3D effects and their impact
on the total torque sign and magnitude can be modeled by an adequate smoothing
prescription in a 2D simulation is addressed. As a side result, this study
shows that the total torque acting on a Neptune-sized protoplanet is positive
in a sufficiently thin, viscous disk (H/r < 4%, \alpha > 10^-2), but the inward
migration time of smaller bodies is still very short, making it unlikely that
they reach the torque reversal mass before having migrated all the way to the
central object.


title: On Fossil Disk Models of Anomalous X-Ray Pulsars

abstract:
  Currently, two competing models are invoked in order to explain the
observable properties of Anomalous X-ray Pulsars (AXPs). One model assumes that
AXP emission is powered by a strongly magnetized neutron star - i.e., a
magnetar. Other groups have postulated that the unusually long spin periods
associated with AXPs could, instead, be due to accretion. As there are severe
observational constraints on any binary accretion model, fossil disk models
have been suggested as a plausible alternative. Here we analyze fossil disk
models of AXPs in some detail, and point out some of their inherent
inconsistencies. For example, we find that, unless it has an exceptionally high
magnetic field strength, a neutron star in a fossil disk cannot be observed as
an AXP if the disk opacity is dominated by Kramers' law. However, standard
alpha-disk models show that a Kramers opacity must dominate for the case log B
> 12, making it unlikely that a fossil disk scenario can successfully produce
AXPs. Additionally, we find that in order to sufficiently spin down a neutron
star in a fossil disk, an unusually efficient propeller torque must be used.
Such torques are inconsistent with observations of other accreting sytems -
particularly High Mass X-ray Binaries. Thus, our analysis lends credence to the
magnetar model of AXPs.


title: Off-Axis Neutrino Scattering in GRB Central Engines

abstract:
  The search for an understanding of an energy source great enough to explain
the gamma-ray burst (GRB) phenomena has attracted much attention from the
astrophysical community since its discovery. In this paper we extend the work
of K. Asano and T. Fukuyama, and J. D. Salmonson and J. R. Wilson, and analyze
the off-axis contributions to the energy-momentum deposition rate (MDR) from
the neutrino anti-neutrino collisions above a rotating black hole/thin
accretion disk system. Our calculations are performed by imaging the accretion
disk at a specified observer using the full geodesic equations, and calculating
the cumulative MDR from the scattering of all pairs of neutrinos and
anti-neutrinos arriving at the observer. Our results shed light on the beaming
efficiency of GRB models of this kind. Although we confirm Asano and Fukuyama's
conjecture as to the constancy of the beaming for small angles away from the
axis; nevertheless, we find the dominant contribution to the MDR comes from
near the surface of the disk with a tilt of approximately \pi/4 in the
direction of the disk's rotation. We find that the MDR at large radii is
directed outward in a conic section centered around the symmetry axis and is
larger, by a factor of 10 to 20, than the on-axis values. By including this
off-axis disk source, we find a linear dependence of the MDR on the black hole
angular momentum (a). In addition, we find that scattering is directed back
onto the black hole in regions just above the horizon of the black hole. This
gravitational ``in scatter'' may provide an observable high energy signature of
the central engine, or at least another channel for accretion.


title: Is the Cosmic Microwave Background Circularly Polarized?

abstract:
  The primordial anisotropies of the cosmic microwave background (CMB) are
linearly polarized via Compton-scattering. The Faraday conversion process
during the propagation of polarized CMB photons through regions of the
large-scale structure containing magnetized relativistic plasma, such as galaxy
clusters, will lead to a circularly polarized contribution. Though the
resulting Stokes-V parameter is of order 10^-9 at frequencies of 10 GHz, the
contribution can potentially reach the total Stokes-U at low frequencies due to
the cubic dependence on the wavelength. In future, the detection of circular
polarization of CMB can be used as a potential probe of the physical properties
associated with relativistic particle populations in large-scale structures.


title:
X-ray properties of Lyman Break Galaxies in the Hubble Deep Field North
  region

abstract:
  We describe the X-ray properties of a large sample of $z\sim3$ Lyman Break
Galaxies (LBGs) in the region of the Hubble Deep Field North, derived from the
1 Ms public Chandra observation. Of our sample of 148 LBGs, four are detected
individually. This immediately gives a measure of the bright AGN fraction in
these galaxies of $\sim 3$~per cent, which is in agreement with that derived
from the UV spectra. The X-ray color of the detected sources indicates that
they are probably moderately obscured. Stacking of the remainder shows a
significant detection ($6\sigma$) with an average luminosity of $3.5 \times
10^{41}$~erg s$^{-1}$ per galaxy in the rest frame 2-10 keV band. We have also
studied a comparison sample of 95 z$\sim 1$ ``Balmer Break'' galaxies. Eight of
these are detected directly, with at least two clear AGN based on their high
X-ray luminosity and very hard X-ray spectra respectively. The remainder are of
relatively low luminosity ($<10^{42}$~erg s$^{-1}$), and the X-rays could arise
from either AGN or rapid star-formation. The X-ray colors and evidence from
other wavebands favor the latter interpretation. Excluding the clear AGN, we
deduce a mean X-ray luminosity of $6.6 \times 10^{40}$~erg s$^{-1}$, a factor
$\sim 5$ lower than the LBGs. The average ratio of the UV and X-ray
luminosities of these starforming galaxies $L_{\rm UV}/L_{\rm X}$, however, is
approximately the same at $z = 1$ as it is at $z = 3$. This scaling implies
that the X-ray emission follows the current star formation rate, as measured by
the UV luminosity. We use our results to constrain the star formation rate at
$z\sim 3$ from an X-ray perspective (truncated).


title: Inflation, cold dark matter, and the central density problem

abstract:
  A problem with high central densities in dark halos has arisen in the context
of LCDM cosmologies with scale-invariant initial power spectra. Although n=1 is
often justified by appealing to the inflation scenario, inflationary models
with mild deviations from scale-invariance are not uncommon and models with
significant running of the spectral index are plausible. Even mild deviations
from scale-invariance can be important because halo collapse times and
densities depend on the relative amount of small-scale power. We choose several
popular models of inflation and work out the ramifications for galaxy central
densities. For each model, we calculate its COBE-normalized power spectrum and
deduce the implied halo densities using a semi-analytic method calibrated
against N-body simulations. We compare our predictions to a sample of dark
matter-dominated galaxies using a non-parametric measure of the density. While
standard n=1, LCDM halos are overdense by a factor of 6, several of our example
inflation+CDM models predict halo densities well within the range preferred by
observations. We also show how the presence of massive (0.5 eV) neutrinos may
help to alleviate the central density problem even with n=1. We conclude that
galaxy central densities may not be as problematic for the CDM paradigm as is
sometimes assumed: rather than telling us something about the nature of the
dark matter, galaxy rotation curves may be telling us something about inflation
and/or neutrinos. An important test of this idea will be an eventual consensus
on the value of sigma_8, the rms overdensity on the scale 8 h^-1 Mpc. Our
successful models have values of sigma_8 approximately 0.75, which is within
the range of recent determinations. Finally, models with n>1 (or sigma_8 > 1)
are highly disfavored.


title: Scalar field dark energy and Cosmic Microwave Background

abstract:
  A dynamical scalar field represents the simplest generalization of a pure
Cosmological Constant as a candidate to explain the recent evidence in favour
of the accelerated cosmic expansion. We review the dynamical properties of such
a component, and argue that, even if the background expectation value of this
field is fixed and the equation of state is the same as a Cosmological
Constant, scalar field fluctuations can still be used to distinguish the two
components. We compare predicted spectra of Cosmic Microvave Background (CMB)
anisotropies in tracking scalar field cosmologies with the present CMB data, in
order to get constraints on the amount and equation of state of dark energy.
High precision experiments like SNAP, {\sc Planck} and {\sc SNfactory},
together with the data on Large Scale Structure, are needed to probe this issue
with the necessary accuracy. Here we show the intriguing result that, with a
strong prior on the value of the Hubble constant today, the assumption of a
flat universe, and consistency relations between amplitude and spectral index
of primordial gravitational waves, the present CMB data at $1\sigma$ give
indication of a dark energy equation of state larger than -1, while the
ordinary Cosmological Constant is recovered at $2\sigma$.


title:
Half lives and Rates for Electron Capture on Drip Line Nuclei and for
  Beta Decay with 65 < A <100

abstract:
  The half lives are calculated for the process of $\beta^\pm$ decay and
electron capture for nuclei in mass range $\sim$ 65 - 100 relevant for the core
of a massive star at late burning stage of steller evolution that leads to
supernova explosion. The rates of electron capture process are also computed
for nuclei relevant during presupernova stage of massive stars. These half
lives and rates are calculated by expressing $\beta^\pm$ Gamow-Teller decay
strengths in terms of smoothed bivariate strength densities. These strength
densities are constructed in the framework of spectral averaging theory for two
body nuclear Hamiltonian in a large nuclear shell model space. The method has a
natural extension to weak interaction rates for r and rp-processes.


title:
BVI time series data of the Galactic Globular Cluster NGC3201. I. RR
  Lyrae stars

abstract:
  We present Johnson BV, and Kron-Cousins I-band time series data collected
over three consecutive nights in a region of 13 arcmin^2 centered on the
Galactic Globular Cluster (GGC) NGC3201. The time sampling of current CCD data
allowed us to derive accurate light curves, and in turn mean magnitudes and
colors for a sample of 53 RR Lyrae. To overcome the thorny problem of
differential reddening affecting this cluster, we derived new empirical
relations connecting the intrinsic (B-V) and (V-I) colors of fundamental
($RR_{ab}$) RR Lyrae to the luminosity amplitude, the metallicity, and the
pulsation period. The key features of these relations are the following: i)
they rely on stellar parameters which are not affected by reddening; ii) they
supply accurate estimates of intrinsic colors across the fundamental
instability strip and cover a wide metallicity range; iii) they were derived by
neglecting the RR Lyrae that are affected by amplitude modulation. Moreover,
the zero-point of the E(B-V) reddening scale was empirically checked using the
large sample of RR Lyrae in M3 (Corwin & Carney 2001), a GGC affected by a
vanishing reddening. According to these relations we estimated individual
reddenings for RR Lyrae in our sample and the main results we found are the
following: i) the mean cluster reddening based on E(B-V) color excesses is
<E(B-V)>=0.30\pm0.03. iii) According to current individual E(B-V) and E(V-I)
reddenings and theoretical predictions for Horizontal-Branch stars, we found
that the true distance modulus for this cluster is 13.32\pm0.06 mag. iv) The
comparison between present luminosity amplitudes and estimates available in the
literature discloses that approximately 30% of fundamental RR Lyrae are
affected by amplitude modulation (Blazhko effect).


title: General Topology of the Universe

abstract:
  General topology of the universe is descibed. It is concluded that topology
of the present universe is greater or stronger than the topology of the
universe in the past and topology of the future universe will be stronger or
greater than the present topology of the universe. Consequently, the universe
remains unbounded.


title:
Radiation pressure instability driven variability in the accreting black
  holes

abstract:
  The time dependent evolution of the accretion disk around black hole is
computed. The classical description of the $\alpha$-viscosity is adopted so the
evolution is driven by the instability operating in the innermost
radiation-pressure dominated part of the accretion disk. We assume that the
optically thick disk always extends down to the marginally stable orbit so it
is never evacuated completely. We include the effect of the advection, coronal
dissipation and vertical outflow. We show that the presence of the corona
and/or the outflow reduce the amplitude of the outburst. If only about half of
the energy is dissipated in the disk (with the other half dissipated in the
corona and carried away by the outflow) the outburst amplitude and duration are
consistent with observations of the microquasar GRS 1915+105. Viscous evolution
explains in a natural way the lack of direct transitions from the state C to
the state B in color-color diagram of this source. Further reduction of the
fraction of energy dissipated in the optically thick disk switches off the
outbursts which may explain why they are not seen in all high accretion rate
sources being in the Very High State.


title:
The Spectrum of the Millisecond Pulsar J0218+4232 - Theoretical
  Interpretations

abstract:
  We interpret the unique high-energy spectrum of the millisecond pulsar PSR
J0218+4232 within polar cap scenarios. We show that the spectral data from
BeppoSAX (Mineo et al.2000) and EGRET (Kuiper et al 2000) impose very
restrictive limitations on possible radiation mechanisms, energy spectrum of
radiating charges as well as viewing geometry. Theoretical spectra are able to
reproduce the data, however, this can be achieved provided very special --
unusual within the conventional polar cap picture -- conditions are satisfied.
Those include off-beam viewing geometry along with one of the following
alternatives: 1) strong acceleration of secondary pairs; 2) broad energy
distribution of primary electrons extending down to $10^5$ MeV; 3)
high-altitude synchrotron emission.


title: Cosmological limit on the neutrino mass

abstract:
  We have performed a careful analysis of constraints on the neutrino mass from
current cosmological data. Combining data from the cosmic microwave background
and the 2dF galaxy survey yields an upper limit on the sum of the three
neutrino mass eigenstates of \sum m_nu < 3 eV (95% conf.), without including
additional priors. Including data from SNIa observations, Big Bang
nucleosynthesis, and HST Hubble key project data on H_0 tightens the limit to
\sum m_nu < 2.5 eV (95% conf.). We also perform a Fisher matrix analysis which
illustrates the cosmological parameter degeneracies affecting the determination
of \sum m_nu.


title: The dependence of observed gamma-ray pulsar spectra on viewing geometry

abstract:
  We calculate the gamma-ray lightcurves and spectra of rotation powered
pulsars for a wide range of observer's viewing angles, and inclination angles
of the magnetic axis to the rotation axis. We show how the shapes of the
observed phase-averaged spectra as well as energy-integrated pulse profiles
depend on the orientation for classical and millisecond pulsars.


title: X-ray Line Emission from Supernova Ejecta Fragments

abstract:
  We show that fast moving isolated fragments of a supernova ejecta composed of
heavy elements should be sources of K_alpha X-ray line emission of the SN
nuclear-processed products. Supersonic motion of the knots in the intercloud
medium will result in a bow-shock/knot-shock structure creation. Fast
nonthermal particles accelerated by Fermi mechanism in the MHD collisionless
shocks diffuse through a cold metallic knot, producing the X-ray emission. We
modeled the X-ray emission from a fast moving knot of a mass M ~ 10^{-3} \Msun,
containing about 10^{-4} \Msun of any metal impurities like Si, S, Ar, Ca, Fe.
The fast electron distribution was simulated using the kinetic description. We
accounted for nonlinear effects of shock modification by the nonthermal
particles pressure. The K_alpha line emission is most prominent for the knots
propagating through dense molecular clouds. The bow shock should be a radiative
wave with a prominent infrared and optical emission. In that case the X-ray
line spectrum of an ejecta fragment is dominated by the low ionization states
of the ions with the metal line luminosities reaching L_x \gsim 10^{31} erg/s.
High resolution XMM and Chandra observations are able to detect the line
emission from the knots at distances up to a few kpcs. The knots propagating
through tenuous interstellar matter are of much fainter surface brightness but
long-lived. The line spectra with higher ionization states of the ions are
expected in that case. Compact dense knots could be opaque for some X-ray lines
and that is important for their abundances interpretation. The ensemble of
unresolved knots of galactic supernovae can contribute substantially to the
iron line emission observed from the Galactic Center region and the Galactic
ridge.


title:
Relation between dust and radio luminosity in optically selected early
  type galaxies

abstract:
  We have surveyed an optical/IR selected sample of nearby E/S0 galaxies with
and without nuclear dust structures with the VLA at 3.6 cm to a sensitivity of
100 $\mu$Jy. We can construct a Radio Luminosity Function (RLF) of these
galaxies to ~10^19 W/Hz and find that ~50% of these galaxies have AGNs at this
level. The space density of these AGNs equals that of starburst galaxies at
this luminosity. Several dust-free galaxies have low luminosity radio cores,
and their RLF is not significantly less than that of the dusty galaxies.


title: Emission lines in GRBs constrain the total energy reservoir

abstract:
  The emission features observed in the X-ray afterglow of Gamma Ray Bursts are
extremely powerful. Since they last at least for several hours, they imply
energies of the order of 1e49 ergs. This in turn implies that the energy
contained in the illuminating continuum thought to be responsible of the line
production must exceed 1e51 ergs. This is a strong lower limit to the energy
reservoir of Gamma Ray Bursts, which is independent of collimation and beaming,
and bears important consequences on the possible collimation of the fireball
radiation and the density of the medium surrounding the burst.


title: Numerical simulations of radiation from blazar jets

abstract:
  We present a description of our numerical code BLAZAR. This code calculates
spectra and light curves of blazars during outbursts. The code is based on a
model in which the non-thermal flares in blazars are produced in thin shells
propagating down a conical jet with relativistic velocities. Such shells may
represent layers of a shocked plasma, enclosed between the forward and reverse
fronts of an internal shock. In the model adopted by us, the production of
non-thermal radiation is assumed to be dominated by electrons and positrons
which are accelerated directly, rather then injected by pair cascades. The code
includes synchrotron emission and inverse-Compton process as the radiation
mechanisms. Both synchrotron photons and external photons are included as the
seed photons for Comptonization. At the present stage, the code is limited to
treat the inverse Compton process only within the Thomson limit and is
specialized to model radiation production in the flat spectrum radio quasars.
As an example, we present the results of modeling an outburst in 3C 279 - the
most extensively monitored gamma-ray - bright quasar.


title: Spectroscopic study of blue compact galaxies: I. The spectra

abstract:
  Blue compact galaxies are compact objects that are dominated by intense star
formation. Most of them have dramatically different properties compared to the
Milky Way and many other nearby galaxies. Using the IRAS, HI data, and optical
spectra, we wanted to measure the current star formation rates, stellar
components, metallicities, and star formation histories and evolution of a
large blue compact galaxy sample. We anticipate that our study will be useful
as a benchmark for studies of emission line galaxies at high redshift.
  In the first paper of this series, we describe the selection, spectroscopic
observation, data reduction and calibration, and spectrophotometric accuracy of
a sample of 97 luminous blue compact galaxies.
  We present a spectrophotometric atlas of rest-frame spectra, as well as
tables of the recession velocities and the signal-to-noise ratios. The
recession velocities of these galaxies are measured with an accuracy of
  $\delta$V $<$ 67 km s$^{-1}$. The average signal-to-noise ratio of sample
spectra is $\sim$ 51. The spectral line strengths, equivalent widths and
continuum fluxes are also measured for the same galaxies and will be analyzed
in the next paper of this series. The atlas and tables of measurements will be
made available electronically.


title:
Intrinsic spectra and energetics of BeppoSAX Gamma-Ray Bursts with known
  redshifts

abstract:
  We present the main results of a study of spectral and energetics properties
of twelve gamma-ray bursts (GRBs) with redshift estimates. All GRBs in our
sample were detected by BeppoSAX in a broad energy range (2-700 keV). From the
redshift estimates and the good-quality BeppoSAX time-integrated spectra we
deduce the main properties of GRBs in their cosmological rest frames. All
spectra in our sample are satisfactorily represented by the Band model with no
significant soft X-ray excesses or spectral absorptions. We find a positive
correlation between the estimated total (isotropic) energies in the 1-10000 keV
energy range (E_rad) and redshifts z. Interestingly, more luminous GRBs are
characterized also by larger peak energies E_p of their EF(E) spectra.
Furthermore, more distant GRBs appear to be systematically harder in the X-ray
band compared to GRBs with lower redshifts. We discuss how selection and data
truncation effects could bias our results and give possible explanations for
the correlations that we found.


title: A Low/Hard State Outburst of XTE J1550-564

abstract:
  We present the results of the analysis of 11 RXTE/PCA observations of the
January 2002 outburst of the black-hole transient XTE J1550-564. The outburst
was rather short, with an e-folding time of ~11 days in the PCA band 3-25 keV.
The source was seen in an extreme low/hard state. The energy spectra could be
fitted with a power law slightly steepening (Gamma ~ 1.4 to ~1.5) in time, with
a high-energy cutoff decreasing from ~300 keV to ~100 keV and some additional
features between 6 and 7 keV, while the 3-150 keV flux decreased by a factor of
17. The power spectra were fitted with two broad Lorentzian components, whose
characteristic frequencies decreased with the source flux, and whose fractional
rms contribution was rather constant. The timing parameters derived can be
identified with those observed in other systems. These results show that,
although during previous, more luminous, outbursts, a very complex behavior was
observed, at low luminosities XTE J1550-564 behaves in a way comparable to most
Black-Hole Candidates.


title:
First Stars II. Elemental abundances in the extremely metal-poor star CS
  22949--037: A diagnostic of early massive supernovae

abstract:
  CS 22949--037 is one of the most metal-poor giants known ([Fe/H]$
\approx-4.0$), and it exhibits large overabundances of carbon and nitrogen
(Norris et al.). Using VLT-UVES spectra of unprecedented quality, regarding
resolution and S/N ratio, covering a wide wavelength range (from $\lambda =
350$ to 900 nm), we have determined abundances for 21 elements in this star
over a wide range of atomic mass. The major new discovery is an exceptionally
large oxygen enhancement, [O/Fe] $= 1.97\pm0.1$, as measured from the [OI] line
at 630.0 nm. We find an enhancement of [N/Fe] of $2.56\pm 0.2$, and a milder
one of [C/Fe] $= 1.17\pm$0.1, similar to those already reported in the
literature. This implies $Z_{\star}=0.01 Z_{\odot}$. We also find carbon
isotopic ratios $^{12}$C/$^{13}$C$ =4\pm2.0$ and $^{13}$C/$^{14}$N$ =0.03
^{+0.035}_{-0.015}$, close to the equilibrium value of the CN cycle. Lithium is
not detected. Na is strongly enhanced ([Na/Fe] $= +2.1 \pm 0.2$), while S and K
are not detected. The silicon-burning elements Cr and Mn are underabundant,
while Co and Zn are overabundant ([Zn/Fe]$ = +0.7$). Zn is measured for the
first time in such an extremely metal-poor star. The abundances of the
neutron-capture elements Sr, Y, and Ba are strongly decreasing with the atomic
number of the element: [Sr/Fe] $\approx +0.3$, [Y/Fe] $\approx -0.1$, and
[Ba/Fe] $\approx -0.6$. Among possible progenitors of CS 22949--037, we discuss
the pair-instability supernovae. Such very massive objects indeed produce large
amounts of oxygen, and have been found to be possible sources of primary
nitrogen. Other scenarios are also discussed. A 30-40$M_{\odot}$ supernova,
with fallback, seems the most likely progenitor for CS 22949--037.


title:
Magnetic Fluctuations with a Zero Mean Field in a Random Fluid Flow with
  a Finite Correlation Time and a Small Magnetic Diffusion

abstract:
  Magnetic fluctuations with a zero mean field in a random flow with a finite
correlation time and a small yet finite magnetic diffusion are studied.
Equation for the second-order correlation function of a magnetic field is
derived. This equation comprises spatial derivatives of high orders due to a
non-local nature of magnetic field transport in a random velocity field with a
finite correlation time. For a random Gaussian velocity field with a small
correlation time the equation for the second-order correlation function of the
magnetic field is a third-order partial differential equation. For this
velocity field and a small magnetic diffusion with large magnetic Prandtl
numbers the growth rate of the second moment of magnetic field is estimated.
The finite correlation time of a turbulent velocity field causes an increase of
the growth rate of magnetic fluctuations. It is demonstrated that the results
obtained for the cases of a small yet finite magnetic diffusion and a zero
magnetic diffusion are different. Astrophysical applications of the obtained
results are discussed.


title:
Building the bridge between Damped Ly-alpha Absorbers and Lyman Break
  galaxies

abstract:
  In 2000, we started the program ``Building the Bridge between Damped Ly-alpha
Absorbers and Lyman-Break Galaxies: Ly-alpha Selection of Galaxies'' at the
European Southern Observatory's Very Large Telescope. This project is an
attempt to use Ly-alpha selection of high-z galaxies to bridge the gap between
absorption- and emission-selected galaxies by creating a large database of z=3
galaxies belonging to the abundant population of faint (R>25.5) galaxies probed
by the Damped Ly-alpha Absorbers (DLAs). Here we present the first results of
our program, namely the results from a deep Ly-alpha study of the field of the
z=2.85 DLA towards Q2138-4427.


title:
The detection of the Sc-44 nuclear de-excitation lines and hard X-ray
  emission from Cas A

abstract:
  We discuss the detection of Sc-44 (product of Ti-44) in the supernova remnant
Cas A with the BeppoSAX-PDS instrument, and elaborate on the nature of the hard
X-ray continuum, which is not only important for correctly estimating the Sc-44
flux, but is interesting in its own right. We apply the lower hybrid wave
electron acceleration model to the hard X-ray data and use upper limits on the
cosmic ray injection spectrum to infer that B > 2 mG. We conclude with the
prospects of observing nuclear decay lines and electron-positron annihilation
in Cas A with INTEGRAL.


title: Inflation and Braneworlds: Degeneracies and Consistencies

abstract:
  Scalar and tensor perturbations arising in an inflationary braneworld
scenario driven by a single scalar field are considered, where the bulk on
either side of the brane corresponds to Anti-de Sitter spaces with different
cosmological constants. A consistency relation between the two spectra is
derived and found to have an identical form to that arising in standard
single-field inflation based on conventional Einstein gravity. The dS/CFT
correspondence may provide further insight into the origin of this degeneracy.
Possible ways of lifting such a degeneracy are discussed.


title: The physical properties of the Ly-Alpha forest at z > 1.5

abstract:
  Combining a new, increased dataset of 8 QSOs covering the Ly-alpha forest at
redshifts 1.5 < z < 3.6 from VLT/UVES observations with previously published
results, we have investigated the properties of the Ly-alpha forest at 1.5 < z
< 4. We have fitted Voigt profiles to the Ly-alpha absorption lines as in
previous studies, and have, for two QSOs, fitted Ly-alpha at z ~ 2.2 and higher
order of Lyman lines down to 3050 Angstrom simultaneously. For a given HI
column density range, the Ly-alpha forest at 1.5 < z < 4 shows the monotonic
evolution, in terms of the line number density and the HI opacity. For higher
column density clouds at 10^{14} cm^(-2),there is a variation in the line
number density from sightline to sightline at z < 2.5. This variation is
stronger for higher column density systems, probably due to more
gravitationally evolved structures at lower z. The correlation strength of the
step optical depth correlation function shows the strong evolution from z ~ 3.3
to z ~ 2.1, although there is a large scatter along different sightlines. The
analyses of the Ly-beta forest at z ~ 2.2 are, in general, in good agreement
with those of the Ly-alpha forest.


title: Telling Three from Four Neutrinos with Cosmology

abstract:
  New results, namely the independent determination of the deuterium abundance
in several quasar absorption systems, and the complementary determination of
the cosmological baryon density by observations of anisotropies in the cosmic
microwave background (CMB), allow for a reevaluation of the constraints on the
relativistic particle content of the universe at primordial nucleosynthesis.
Expressed in terms of the neutrino energy density, we find 1.7 < N_\nu < 3.5
(95% CL). In particular, we show that phenomenological four neutrino models
including a sterile state (not participating in SU(2)_L x U(1)_Y interactions)
unavoidably thermalize a fourth neutrino, and are highly disfavored in the
standard minimal model of primordial nucleosynthesis, if the systematic
uncertainty in the primordial helium abundance is small. We describe plausible
extensions of the minimal model which evade this constraint.


title: HST Imaging of a z=1.55 Old Galaxy Group

abstract:
  We present high-resolution imaging in the rest-frame optical of the weak
radio source LBDS53W091. Previous optical spectroscopy has shown that this
object has an evolved stellar population of age >3Gyr at z=1.55, determined
from the amplitude of rest-frame UV spectral breaks. We have obtained deep
Hubble Space Telescope imaging over 10 orbits with NICMOS camera 2, using the
F160W H-band filter (1.6microns) which is a good approximation to the
rest-frame R-band. Our observations reveal a radial light profile which is well
fit by a de Vaucouleurs' r^{1/4} law, with a scale length of r_e=0.3"
(3kpc/h_{50} for Omega_M=0.3 and Omega_{Lambda}=0). The elliptical morphology
of the radio galaxy indicates a dynamically-evolved old system, consistent with
the spectroscopic results. Some surrounding objects lie on the color:magnitude
relation for a cluster at z=1.55, and are likely to be associated. The group of
galaxies are somewhat more luminous than the fundamental plane of ellipticals
at z=0 subject to (1+z)^4 surface brightness dimming, but are consistent with
estimates of the fundamental plane at high redshift subject to passive
luminosity evolution from a formation epoch of z>3.


title: Modified-Entropy Models for the Intracluster Medium

abstract:
  We present a set of cluster models that link the present-day properties of
clusters to the processes that govern galaxy formation. These models treat the
entropy distribution of the intracluster medium as its most fundamental
property. Because convection strives to establish an entropy gradient that
rises with radius, the observable properties of a relaxed cluster depend
entirely on its dark-matter potential and the entropy distribution of its
uncondensed gas. Guided by simulations, we compute the intracluster entropy
distribution that arises in the absence of radiative cooling and supernova
heating by assuming that the gas-density distribution would be identical to
that of the dark matter. The lowest-entropy gas would then fall below a
critical entropy threshold at which the cooling time equals a Hubble time.
Radiative cooling and whatever feedback is associated with it must modify the
entropy of that low-entropy gas, changing the overall entropy distribution
function and thereby altering the observable properties of the cluster. Using
some phenomenological prescriptions for entropy modification based on the
existence of this cooling threshold, we construct a remarkably realistic set of
cluster models. The surface-brightness profiles, mass-temperature relation, and
luminosity-temperature relation of observed clusters all naturally emerge from
these models. By introducing a single adjustable parameter related to the
amount of intracluster gas that can cool within a Hubble time, we can also
reproduce the observed temperature gradients of clusters and the deviations of
cooling-flow clusters from the standard luminosity-temperature relation.


title: On the progenitor of the Type Ic supernova 2002ap

abstract:
  This letter presents wide-field optical and and NIR UBVRI,Halpha,K' images of
the galaxy M74 which were taken between 0.6-8.3 years before the discovery of
the Type Ic SN2002ap. We have located the position of the SN on these images
with an accuracy of 0.3''. We find no sign of a progenitor object on any of the
images. The deepest of these images is the B-band exposure which has a
sensitivity limit corresponding to an absolute magnitude of M_B <= -6.3. From
our observed limits, we rule out as the progenitor all evolved states of single
stars with initial masses greater than 20Msol unless the WR phase has been
entered. Two popular theories for the origin of Type Ic SNe are the core
collapse of massive stars when they are in the WR phase, or the core collapse
of a massive star in an interacting binary which has had its envelope stripped
through mass transfer. Our prediscovery images are sensitive only to the most
luminous ~30% of WR stars, leaving a substantial fraction of typical WR stars
as viable progenitors. The energetics measured from modelling the spectral
evolution of SN 2002ap suggest an explosion of a 5Msol C+O core. While WR stars
generally have measured final masses greater than this, the uncertainties
associated with the explosion model, stellar evolutionary calculations and mass
measurements suggest we cannot definitively rule out a WR star progenitor. The
alternative scenario is that the progenitor was a star of initial mass
20-25Msol which was part of an interacting binary. We discuss future
observations which will provide further constraints on the nature of the
progenitor.


title:
The evolutionary status of Sher25 - implications for blue supergiants
  and the progenitor of SN1987A

abstract:
  The blue supergiant Sher25 in the massive Galactic cluster NGC3603 is
surrounded by a striking emission line nebula. The nebula contains an
equatorial ring and probable bi-polar outflows, and is similar in morphology,
mass and kinematics to the structure visible around SN1987A. It has been
suggested that both nebulae were ejected while Sher25 and the progenitor of
SN1987A were in previous red supergiant phases. We present optical
high-resolution spectra of Sher25 and a model photosphere and unified stellar
wind analysis which determines atmospheric parameters, mass-loss rate and
photospheric abundances. We compare CNO abundances to other Galactic B-type
supergiants and find that Sher25 does not appear extreme or abnormal in terms
of its photospheric nitrogen and helium abundances. The C/N and N/O ratios are
compared to surface abundances predicted by stellar evolutionary calculations
and are incompatible with the star having a previous red-supergiant phase. The
nebula is likely to have been ejected while the star was a blue supergiant. The
results are compatible with some degree of rotationally induced mixing having
occurred while the star was on or near the main-sequence. Our analsysis
suggests the star has a relatively normal stellar wind and mass-loss rate, and
sits comfortably within the wind momentum-luminosity relationship. In light of
the evidence regarding massive evolved early-type stars in the Galaxy we
suggest there is no object which shows clear evidence of having had a previous
red supergiant phase and hence of undergoing blue loops in the HR diagram.
[ABRIDGED]


title: Estimating Fixed Frame Galaxy Magnitudes in the SDSS

abstract:
  Broad-band measurements of flux for galaxies at different redshifts measure
different regions of the rest-frame galaxy spectrum. Certain astronomical
questions, such as the evolution of the luminosity function of galaxies,
require transforming these magnitudes into redshift-independent quantities. To
prepare to address these astronomical questions, investigated in detail in
subsequent papers, we fit spectral energy distributions (SEDs) to broad band
photometric observations, in the context of the optical observations of the
Sloan Digital Sky Survey (SDSS). Linear combinations of four spectral templates
can reproduce the five SDSS magnitudes of all galaxies to the precision of the
photometry. Expressed in the appropriate coordinate system, the locus of the
coefficients multiplying the templates is planar, and in fact nearly linear.
The resulting reconstructed SEDs can be used to recover fixed frame magnitudes
over a range of redshifts. This process yields consistent results, in the sense
that within each sample the intrinsic colors of similar type galaxies are
nearly constant with redshift. We compare our results to simpler interpolation
methods and galaxy spectrophotometry from the SDSS. The software that generates
these results is publicly available and easily adapted to handle a wide range
of galaxy observations.


title:
MACHO Photometry of Two LMC Be X-ray Transients, EXO 0531-66 and H
  0544-665

abstract:
  Long-term variations are well-known in Be X-ray binaries, and are attributed
to non-orbital changes in the structure of the Be circumstellar (equatorial)
disc. However, the timescales involved are so long (tens of days, to years)
that systematic studies have been very restricted. The ~8 year MACHO monitoring
of the Large Magellanic Cloud (LMC) therefore presents an ideal opportunity to
undertake such studies of Be X-ray systems that lie within the monitored
fields. Here we present MACHO observations of two LMC Be X-ray transients, EXO
0531-66 and H 0544-665, the light curves of which show substantial (~0.5 mag)
long-term variations. However, our analysis shows little evidence for any
periodic phenomena in the light curves of either source. We find an upper limit
for detection of a short (1-100 d) periodicity in the V- and R-band light
curves of EXO 0531-66 of 0.041 mag and 0.047 mag semi-amplitude, respectively.
The upper limits for the V- and R-band data of H 0544-665 are 0.054 mag and
0.075 mag semi-amplitude, respectively. Both EXO 0531-66 and H 0544-665 become
redder as they brighten, possibly due to variations in the structure of the
equatorial disc around the Be star. Spectra of both sources show H$\alpha$
emission; for EXO 0531-66 we find the emission varies over time, thereby
confirming its optical identification.


title: Sub-horizon Perturbation Behavior in Extended Quintessence

abstract:
  In the general context of scalar-tensor theories, we consider a model in
which a scalar field coupled to the Ricci scalar in the gravitational sector of
the Lagrangian, is also playing the role of an ``Extended Quintessence'' field,
dominating the energy content of the Universe at the present time. In this
framework, we study the linear evolution of the perturbations in the
Quintessence energy density, showing that a new phenomenon, named here
``gravitational dragging'', can enhance the scalar field density perturbations
as much as they reach the non-linear regime. The possibility of dark energy
clumps formation is thus discussed.


title: A Search for CO Absorption in the Transmission Spectrum of HD 209458b

abstract:
  We observed one transit of the extrasolar planet HD 209458b with the NIRSPEC
spectrograph on the Keck II telescope. Using time series of low-noise
observations in the wavelength range 2.0 micron to 2.5 micron, we searched for
extra absorption from the 1st overtone rotation-vibration band of CO near 2.3
micron. This was not detected, with a detection limit that fails to test simple
models of the planetary atmosphere by a factor of about 3. Great improvements
in the detectability of the CO spectrum features could be realized by observing
a transit that is centered near stellar meridian passage, and in better
weather. Since it appears that similar observations taken under better
circumstances might succeed, we describe our analysis procedures in detail.


title:
Crossing the `Yellow Void' -- Spatially Resolved Spectroscopy of the
  Post- Red Supergiant IRC+10420 and Its Circumstellar Ejecta

abstract:
  IRC +10420 is one of the extreme hypergiant stars that define the empirical
upper luminosity boundary in the HR diagram. During their post--RSG evolution,
these massive stars enter a temperature range (6000-9000 K) of increased
dynamical instability, high mass loss, and increasing opacity, a
semi--forbidden region, that de Jager and his collaborators have called the
`yellow void'. We report HST/STIS spatially resolved spectroscopy of IRC +10420
and its reflection nebula with some surprising results. Long slit spectroscopy
of the reflected spectrum allows us to effectively view the star from different
directions. Measurements of the double--peaked Halpha emission profile show a
uniform outflow of gas in a nearly spherical distribution, contrary to previous
models with an equatorial disk or bipolar outflow. Based on the temperature and
mass loss rate estimates that are usually quoted for this object, the wind is
optically thick to the continuum at some and possibly all wavelengths.
Consequently the observed variations in apparent spectral type and inferred
temperature are changes in the wind and do not necessarily mean that the
underlying stellar radius and interior structure are evolving on such a short
timescale. To explain the evidence for simultaneous outflow and infall of
material near the star, we propose a `rain' model in which blobs of gas
condense in regions of lowered opacity outside the dense wind. With the
apparent warming of its wind, the recent appearance of strong emission, and a
decline in the mass loss rate, IRC +10420 may be about to shed its opaque wind,
cross the `yellow void', and emerge as a hotter star.


title: Formation and Evolution of Microquasar GRS 1915+105

abstract:
  Using the StarTrack population synthesis code we analyze the possible
formation channels of the Galactic microquasar GRS 1915+105 harboring the most
massive known stellar black hole. We find that we are able to reproduce the
evolution and the current state of GRS 1915+105 in a model with lowered wind
mass loss rates in massive stars. We conclude that the existence of GRS
1915+105 implies that stellar winds in massive stars are a factor of two
weaker, but still within observational bounds, than used in stellar models. We
discuss the mass transfer initiated by the massive primary in binaries which
are the possible precursors of systems harboring massive black holes. We show
that such mass transfer evolution is neither clear case B nor C, but instead is
initiated during the core helium burning phase of the massive donor star, the
progenitor of the black hole. We also argue that massive black holes do not
receive any kicks at their formation and are formed through direct collapse of
progenitor star without accompanying supernova explosion.


title: Galaxy Evolution tool: Construction and Applications

abstract:
  We present a dual-infall galactic chemical evolution model which uses a new
set of stellar yields calculated by Limongi et al (2001) to constrain the
amount of iron-peak elements ejected by massive stars. The age-metallicity
relation, G-dwarf distribution and evolution of abundance ratios are predicted
using Galaxy Evolution tool (GEtool), a software package currently being
developed to self-consistenly model the chemical and spectral evolution of disk
galaxies. A comparison with results obtained using the Woosley & Weaver (1995)
core-collapse supernova models suggests that the observed behaviour of key
abundance patterns cannot be reproduced if the iron yield of massive stars
increases with initial mass.


title:
Migration of matter from the Edgeworth-Kuiper and main asteroid belts to
  the Earth

abstract:
  A considerable portion of near-Earth objects could have come from the
trans-Neptunian belt. Some of them have aphelia deep inside Jupiter's orbit
during more than 1 Myr.


title:
Comparison of simulated longitudinal profiles of hadronic air showers
  with MASS2 balloon data

abstract:
  The KASKADE and CORSIKA air shower generators are compared to the data
collected by MASS2 balloon experiment in 1991. The test of longitudinal profile
for proton, helium and muon flux production provide good constraints on these
air shower generators. KASKADE and CORSIKA especially with the new simulator
UrQMD for low energies are found to fit these data well. This study is limited
to a comparison of longitudinal profiles and therefore does not provide
constraints on the overall shower development.


title: The Jet-Disk Connection and Blazar Unification

abstract:
  We discuss the relation between the power carried by relativistic jets and
the nuclear power provided by accretion, for a group of blazars including FSRQs
and BL Lac objects. They are characterized by good quality broad band X-ray
data provided by the Beppo SAX satellite. The jet powers are estimated using
physical parameters determined from uniformly modelling their spectral energy
distributions (SEDs). Our analysis indicates that for Flat Spectrum Radio
Quasars the total jet power is of the same order as the accretion power. We
suggest that blazar jets are likely powered by energy extraction from a rapidly
spinning black hole through the magnetic field provided by the accretion disk.
FSRQs must have large BH masses (10^8 - 10^9 solar masses) and high, near
Eddington accretion rates. For BL Lac objects the jet luminosity is larger than
the disk luminosity. This can be understood within the same scenario if BL Lac
objects have masses similar to FSRQ but accrete at largely subcritical rates,
whereby the accretion disk radiates inefficiently. Thus the ``unification'' of
the two classes into a single blazar population, previously proposed on the
basis of a spectral sequence governed by luminosity, finds a physical basis.