title: Interstellar Carbon in Translucent Sightlines

abstract:
  We report interstellar C II column densities or upper limits determined from
weak absorption of the 2325.4029 A intersystem transition observed in six
translucent sightlines with STIS. The sightlines sample a wide range of
interstellar characteristics including total-to-selective extinction, R_{V} =
2.6 - 5.1; average hydrogen density along the sightline, <n(H)> = 3 - 14
cm^{-3}; and fraction of H in molecular form, 0 - 40%. Four of the sightlines,
those toward HD 37021, HD 37061, HD 147888 and HD 207198, have interstellar
gas-phase abundances that are consistent with the diffuse sightline ratio of
161 +/- 17 carbon atoms in the gas per million hydrogen nuclei. We note that
while it has a gas-phase carbon abundance that is consistent with the other
sightlines, a large fraction of the C II toward HD 37061 is in an excited
state. The sightline toward HD 152590 has a measured interstellar gas-phase
carbon abundance that is well above the diffuse sightline average; the column
density of C in this sightline may be overestimated due to noise structure in
the data. Toward HD 27778 we find a 3 sigma abundance upper limit of <108 C
atoms in the gas per million H, a substantially enhanced depletion of C as
compared to the diffuse sightline value. The interstellar characteristics
toward HD 27778 are otherwise not extreme among the sample except for an
unusually large abundance of CO molecules in the gas.


title:
Indirect searches for SUSY Dark Matter with the MAGIC Cherenkov
  Telescope

abstract:
  Neutralinos are the natural well-motivated candidates to provide the
non-baryonic dark matter of the universe which may produce detectable signals
through their annihilation into neutrinos, photons or positrons. Due to its
high flux sensitivity and low energy threshold, the MAGIC Cherenkov telescope
could potentially detect the neutralino annihilation high energy photon
products. In the framework of minimal supergravity, the neutralino SUSY
parameter space can be scanned in different benchmark scenarios defined after
accelerator and cosmology constraints. Moreover, the neutralino density
profiles in galaxy halos and sub-halos have to be understood to infer which is
the optimal observation region to be explored by the MAGIC telescope for the
detection of neutralino photon signatures within our Galaxy and our Local
Group.


title: Astrophysical inputs on the SUSY dark matter annihilation detectability

abstract:
  If dark matter (DM), which is considered to constitute most of the mass of
galaxies, is made of supersymmetric (SUSY) particles, the centers of galaxies
should emit gamma-rays produced by their self-annihilation. We present accurate
estimates of continuum gamma-ray fluxes due to neutralino annihilation in the
central regions of the Milky Way. We use detailed models of our Galaxy, which
satisfy available observational data, and include some important physical
processes, which were previously neglected. Our models predict that spatially
extended annihilation signal should be detected at high confidence levels by
incoming experiments assuming that neutralinos make up most of the DM in the
Universe and that they annihilate according to current SUSY models.


title: The Nearby Supernova Factory

abstract:
  The Nearby Supernova Factory (SNfactory) is an ambitious project to find and
study in detail approximately 300 nearby Type Ia supernovae (SNe~Ia) at
redshifts 0.03<z<0.08. This program will provide an exceptional data set of
well-studied SNe in the nearby smooth Hubble flow that can be used as
calibration for the current and future programs designed to use SNe to measure
the cosmological parameters. The first key ingredient for this program is a
reliable supply of Hubble-flow SNe systematically discovered in unprecedented
numbers using the same techniques as those used in distant SNe searches. In
2002, 35 SNe were found using our test-bed pipeline for automated SN search and
discovery. The pipeline uses images from the asteroid search conducted by the
Near Earth Asteroid Tracking group at JPL. Improvements in our subtraction
techniques and analysis have allowed us to increase our effective SN discovery
rate to ~12 SNe/month in 2003.


title: A search for microquasar candidates at low galactic latitudes

abstract:
  Recent studies of relativistic jet sources in the Galaxy, also known as
microquasars, have been very useful in trying to understand the
accretion/ejection processes that take place near compact objects. However, the
number of sources involved in such studies is still small. In an attempt to
increase the number of known microquasars we have carried out a search for new
Radio Emitting X-ray Binaries (REXBs). These sources are the ones to be
observed later with VLBI techniques to unveil their possible microquasar
nature. To this end, we have performed a cross-identification between the X-ray
ROSAT all sky survey Bright Source Catalog (RBSC) and the radio NRAO VLA Sky
Survey (NVSS) catalogs under very restrictive selection criteria for sources
with |b|<5 degrees. We have also conducted a deep observational radio and
optical study for six of the selected candidates. At the end of this process
two of the candidates appear to be promising, and deserve additional
observations aimed to confirm their proposed microquasar nature.


title:
Probing Newton's Constant on Vast Scales: DGP Gravity, Cosmic
  Acceleration and Large Scale Structure

abstract:
  The nature of the fuel that drives today's cosmic acceleration is an open and
tantalizing mystery. The braneworld theory of Dvali, Gabadadze, and Porrati
(DGP) provides a context where late-time acceleration is driven not by some
energy-momentum component (dark energy), but rather is the manifestation of the
excruciatingly slow leakage of gravity off our four-dimensional world into an
extra dimension. At the same time, DGP gravity alters the gravitational force
law in a specific and dramatic way at cosmologically accessible scales. We
derive the DGP gravitational force law in a cosmological setting for spherical
perturbations at subhorizon scales and compute the growth of large-scale
structure. We find that a residual repulsive force at large distances gives
rise to a suppression of the growth of density and velocity perturbations.
Explaining the cosmic acceleration in this framework leads to a present day
fluctuation power spectrum normalization sigma_8 <= 0.8 at about the two-sigma
level, in contrast with observations. We discuss further theoretical work
necessary to go beyond our approximations to confirm these results.


title:
EVN and MERLIN observations of microquasar candidates at low galactic
  latitudes

abstract:
  In an attempt to increase the number of known microquasars, Paredes et al.
(2002) have presented a long-term project focused on the search for new objects
of this type. They performed a cross-identification between X-ray and radio
catalogs under very restrictive selection criteria for sources with |b|<5
degrees, and obtained a sample of 13 radio-emitting X-ray sources. Follow-up
observations of 6 of these sources with the VLA provided accurate coordinates,
which were used to discover optical counterparts for all of them. We have
observed these six sources with the EVN and MERLIN at 5 GHz. Five of the six
objects have been detected and imaged, presenting different morphologies: one
source has a two-sided jet, three sources have one-sided jets, and one source
is compact. With all the presently available information, we conclude that two
of the sources are promising microquasar candidates in our Galaxy.


title: Phenomenological aspects of dark energy dominated cosmologies

abstract:
  In this thesis we study some observational consequences of dark energy
dominated cosmologies. After reviewing the main characteristics of
quintessential models of dark energy, by using the SN Ia data and the position
of the CMB peaks we constrain a class of parameterized scalar field potentials.
Going beyond constraining specific classes models, we introduce a
parameterization of the dark energy equation of state. Such an approach allows
us to study in a model independent way the imprint dark energy leaves in the
CMB power spectrum. Finally we develop a formalism to model localized CMB
anisotropies and compute analytical formulae for the power spectrum and the
bispectrum.


title: Optical spectroscopy of microquasar candidates at low galactic latitudes

abstract:
  We report optical spectroscopic observations of a sample of 6 low-galactic
latitude microquasar candidates selected by cross-identification of X-ray and
radio point source catalogs for |b|<5 degrees. Two objects resulted to be of
clear extragalactic origin, as an obvious cosmologic redshift has been measured
from their emission lines. For the rest, none exhibits a clear stellar-like
spectrum as would be expected for genuine Galactic microquasars. Their
featureless spectra are consistent with being extragalactic in origin although
two of them could be also highly reddened stars. The apparent non-confirmation
of our candidates suggests that the population of persistent microquasar
systems in the Galaxy is more rare than previously believed. If none of them is
galactic, the upper limit to the space density of new Cygnus X-3-like
microquasars within 15 kpc would be 1.1\times10^{-12} per cubic pc. A similar
upper limit for new LS 5039-like systems within 4 kpc is estimated to be
5.6\times10^{-11} per cubic pc.


title: Gravitational Lensing of the Microwave Background by Galaxy Clusters

abstract:
  Galaxy clusters will distort the pattern of temperature anisotropies in the
microwave background via gravitational lensing. We create lensed microwave
background maps using clusters drawn from numerical cosmological simulations. A
distinctive dipole-like temperature fluctuation pattern is formed aligned with
the underlying microwave temperature gradient. For a massive cluster, the
characteristic angular size of the temperature distortion is a few arcminutes
and the characteristic amplitude a few micro-Kelvin. We demonstrate a simple
technique for estimating the lensing deflection induced by the cluster;
microwave background lensing measurements have the potential to determine the
mass distribution for some clusters with good accuracy on angular scales up to
a few arcminutes. Future high-resolution and high-sensitivity microwave
background maps will have the capability to detect lensing by clusters; we
discuss various systematic limitations on probing cluster masses using this
technique.


title: Three Form Inflation

abstract:
  It is noted that inflation driven by a three form with arbitrary self
coupling satisfies a consistency relation $n_S-1=2n_T$, between spectral
indices of scalar and tensor cosmological perturbations. The standard
consistency relation for the ratio of the amplitudes of perturbations is only
valid for quadratic self coupling of the three form.


title: Spontaneous violation of the energy conditions

abstract:
  A decade ago, it was shown that a wide class of scalar-tensor theories can
pass very restrictive weak field tests of gravity and yet exhibit
non-perturbative strong field deviations away from General Relativity. This
phenomenon was called `Spontaneous Scalarization' and causes the (Einstein
frame) scalar field inside a neutron star to rapidly become inhomogeneous once
the star's mass increases above some critical value. For a star whose mass is
below the threshold, the field is instead nearly uniform (a state which
minimises the star's energy) and the configuration is similar to the General
Relativity one. Here, we show that the spontaneous scalarization phenomenon is
linked to another strong field effect: a spontaneous violation of the weak
energy condition.


title:
Spectra and Diagnostics for the Direct Detection of Wide-Separation
  Extrasolar Giant Planets

abstract:
  We calculate as a function of orbital distance, mass, and age the theoretical
spectra and orbit-averaged planet/star flux ratios for representative
wide-separation extrasolar giant planets (EGPs) in the optical, near-infrared,
and mid-infrared. Stellar irradiation of the planet's atmosphere and the
effects of water and ammonia clouds are incorporated and handled in a
consistent fashion. We include predictions for 12 specific known EGPs. In the
process, we derive physical diagnostics that can inform the direct EGP
detection and remote sensing programs now being planned or proposed.
Furthermore, we calculate the effects of irradiation on the spectra of a
representative companion brown dwarf as a function of orbital distance.


title:
Effect of energy losses and interactions during diffusive shock
  acceleration: applications to SNR, AGN and UHE Cosmic Rays

abstract:
  I discuss the shape of the high energy end of the spectrum of particles
arising from diffusive shock acceleration in the presence of (i) additional
diffusive escape from the accelerator, (ii) continuous energy losses, (iii)
energy changes arising from interactions. The form of the spectrum near cut-off
is sensitive to these processes as well as to the momentum-dependence of the
diffusion coefficients and the compression ratio, and so the spectrum of any
radiation emitted by the accelerated particles may reflect the physical
conditions of the acceleration region. Results presented in this paper have
applications in interpreting the spectral energy distributions of many types of
astrophysical object including supernova remnants (SNR), active galactic nuclei
(AGN) and acceleration sources of ultra high energy cosmic rays (UHE CR).
Except for extremely nearby sources, spectral features imprinted on the
spectrum of UHE CR during the acceleration process will be largely eroded
during propagation, but the spectrum of UHE neutrinos produced in interactions
of UHE CR with radiation, both during cosmic ray acceleration and subsequent
propagation through the cosmic microwave background radiation, contains
sufficient information to determine the cut-off momentum of the UHE CR just
after acceleration for reasonable assumptions. Observation of these UHE
neutrinos by the Pierre Auger Observatory may help in identifying the sources
of the highest energy cosmic rays.


title:
Testing Radiatively-Inefficient Accretion Flow Theory: an XMM-Newton
  Observation of NGC 3998

abstract:
  We present the results of a 10 ks XMM-Newton observation of NGC 3998, a
``type-I'' LINER galaxy. Our goal is to test the extent to which
radiatively-inefficient accretion flow (RIAF) models and/or scaled-down AGN
models are consistent with the observed properties of NGC 3998. The upper-limit
for narrow Fe-K emission derived from a combined fit of the XMM-Newton and
BeppoSAX spectra is 25 eV, which is one of the strictest limits to date for any
AGN. This significantly rules out Fe-K emission as is expected to be observed
in typical Seyfert 1 galaxies. The lack of any reflection features suggests
that any optically-thick, geometrically-thin accretion disk must be truncated,
probably at a radius of order 100-300 R_s. RIAF models fit the UV to X-ray
spectral energy distribution of NGC 3998 reasonably well. In these models the
mid-IR flux also constrains the emission from any outer thin disk component
that might be present. The UV to X-ray SED is also consistent with a
Comptonized thin disk with a very low accretion rate, in which case the lack of
Fe-K emission may be due to an ionized accretion disk. Accretion models in
general do not account for the observed radio flux of NGC 3998, and the radio
flux may be due to a jet. Recent jet models may also be consistent with the
nuclear fluxes of NGC 3998 in general, including the X-ray, optical/UV and
mid-IR bands. We also derive nuclear fluxes using archival HST WFPC2 data to
constrain the SED of NGC 3998. We discuss a possible OM U band and USNO-B
detection of the NGC 3998 ULX.


title: The Statistical Properties of Galaxies Containing ULXs

abstract:
  We present a statistical analysis of the properties of galaxies containing
ultraluminous X-ray objects (ULXs). Our primary goal is to establish the
fraction of galaxies containing a ULX as a function of ULX luminosity. Our
sample is based on ROSAT HRI observations of galaxies. We find that ~ 12% of
galaxies contain at least one ULX with L_X > 10^39 erg/s and ~ 1% of galaxies
contain at least one ULX with L_X > 10^40 erg/s. These ULX frequencies are
lower limits since ROSAT HRI observation would miss absorbed ULXs (i.e., with
N_H >~ 10^21 cm^-2) and those within ~ 10" of the nucleus (due to the
positional error circle of the ROSAT HRI). The Hubble type distribution of
galaxies with a ULX differs significantly from the distribution of types for
nearby RC3 galaxies, but does not differ significantly from the galaxy type
distribution of galaxies observed by the HRI in general. We find no increase in
the mean FIR luminosity or FIR / K band luminosity ratio for galaxies with a
ULX relative to galaxies observed by the HRI in general, however this result is
also most likely biased by the soft bandpass of the HRI and the relatively low
number of high SFR galaxies observed by the HRI with enough sensitivity to
detect a ULX.


title: The Carnegie Observatories Astrophysics Series

abstract:
  On the occasion of the Centennial of the Carnegie Institution of Washington,
Carnegie Observatories held a series of four astrophysics symposia in Pasadena
from October 2002 to February 2003. The topics of the symposia were:
  (1) Coevolution of Black Holes and Galaxies [Ed. L. C. Ho]
  (2) Measuring and Modeling the Universe [Ed. W. L. Freedman]
  (3) Clusters of Galaxies: Probes of Cosmological Structure and Galaxy
Evolution [Ed. J. S. Mulchaey, A. Dressler, and A. Oemler]
  (4) Origin and Evolution of the Elements [Ed. A. McWilliam and M. Rauch]
  The invited papers of the symposia, which have been peer-reviewed and
carefully edited, will be published in 2004 by Cambridge University Press, as
the first four volumes of the Carnegie Observatories Astrophysics Series. The
papers from the contributed talks and posters, along with the full set of the
invited papers, are available electronically at
http://www.ociw.edu/ociw/symposia/series/. The purpose of this note is to alert
the community of the availability of this resource.


title: Black Hole Demography from Nearby Active Galactic Nuclei

abstract:
  A significant fraction of local galaxies show evidence of nuclear activity. I
argue that the bulk of this activity, while energetically not remarkable,
derives from accretion onto a central massive black hole. The statistics of
nearby active galactic nuclei thus provide an effective probe of black hole
demography. Consistent with the picture emerging from direct dynamical studies,
the local census of nuclear activity strongly suggests that most, perhaps all,
galaxies with a significant bulge component contain a central massive black
hole. Although late-type galaxies appear to be generally deficient in nuclear
black holes, there are important exceptions to this rule. I highlight two
examples of dwarf, late-type galaxies that contain active nuclei powered by
intermediate-mass black holes.


title: What Can We Learn from Nearby AGNs?

abstract:
  This contribution reviews the properties of nuclear activity in nearby
galaxies, with emphasis on their implications for the demography of nuclear
black holes and the nature of accretion flows in the regime of very low
accretion rates.


title: Propagation of electromagnetic waves in space plasma

abstract:
  Coherent Raman Effect on Incoherent Light (CREIL), shifts the frequencies of
normally incoherent light without any blurring of the images or altering the
order of the spectra. CREIL operates in gases having quadrupolar resonances in
the megaherz range, and it is easily confused with Doppler effects. When CREIL
is taken into account, the propagation of light in cosmic low pressure gases
involves a complex combination of absorptions and frequency shifts. Current
star theory predicts very bright accreting neutron stars. These should be
small, very hot objects surrounded by dirty atomic hydrogen. CREIL predicts
spectra for these stars that have exactly the characteristics found in the
spectra of the quasars. The intrinsic redshifting in the extended photosphere
of Quasars as defined by CREIL events drastically reduces both the size and
distance to quasars, and clearly identifies the missing neutron stars as
quasar-like objects. A full interpretation of quasar spectra does not require
jets, dark matter, a variation of the fine structure constant, or an early
synthesis of iron. CREIL is useful in explaining other astrophysical problems,
such as redshifting proportional to the path of light through the corona of the
Sun. CREIL radiation transfers may explain the blueshifting of radio signals
from Pioneer 10 and 11.


title: Supernova constraints on alternative models to dark energy

abstract:
  The recent observations of type Ia supernovae suggest that the universe is
accelerating now and decelerated in the recent past. This may be the evidence
of the breakdown of the standard Friedmann equation. The Friedmann equation
$H^2\sim \rho$ is modified to be a general form $H^2=g(\rho)$. Three models
with particular form of $g(\rho)$ are considered in detail. The supernova data
published by \citet{tonry}, \citet{ddsg} and \citet{raknop03} are used to
analyze the models. After the best fit parameters are obtained, we then find
out the transition redshift $z_{\rm T}$ when the universe switched from the
deceleration phase to the acceleration phase.


title:
Cosmic Star Formation History and the Future Observation of Supernova
  Relic Neutrinos

abstract:
  We investigate the flux and event rate of supernova relic neutrinos (SRNs)
and discuss their implications for the cosmic star formation rate. As reference
models, we adopt the supernova rate model based on recent observations and the
supernova neutrino spectrum numerically calculated by several groups. In the
detection energy range E_e>10 MeV, which will possibly be a background-free
region in the near future, the SRN event rate is found to be 1-2 yr^{-1} at a
water Cerenkov detector with a fiducial volume of 22.5 kton, depending on the
adopted neutrino spectrum. We also simulate the expected signal with one set of
the reference models by using the Monte Carlo method and then analyze these
pseudodata with several free parameters, obtaining the distribution of the
best-fit values for them. In particular, we use a parameterization such that
R_{SN}(z)=R_{SN}^0 (1+z)^\alpha, where R_{SN}(z) is the comoving supernova rate
density at redshift z and R_{SN}^0 and \alpha are free parameters, assuming
that the supernova neutrino spectrum and luminosity are well understood by way
of a future Galactic supernova neutrino burst or the future development of
numerical supernova simulations. The obtained 1\sigma errors for these two
parameters are found to be \delta\alpha /\alpha = 30% (7.8%) and \delta
R_{SN}^0/ R_{SN}^0 = 28% (7.7%) for a detector with an effective volume of 22.5
kton 5 yr (440 kton 5 yr), where one of the parameters is fixed. On the other
hand, if we fix neither of the values for these two parameters, the expected
errors become rather large, \delta\alpha /\alpha = 37% and \delta R_{SN}^0/
R_{SN}^0 = 55%, even with an effective volume of 440 kton 5 yr.


title: Primordial Structure of Massive Black Hole Clusters

abstract:
  We describe a mechanism of the primordial black holes formation that can
explain the existence of a population of supermassive black holes in galactic
bulges. The mechanism is based on the formation of black holes from closed
domain walls. The origin of such domain walls could be a result of the
evolution of an effectively massless scalar field during inflation. The initial
non-equilibrium distribution of the scalar field imposed by background
de-Sitter fluctuations gives rise to the spectrum of black holes, which covers
a wide range of masses -- from superheavy ones down to deeply subsolar. The
primordial black holes of smaller masses are concentrated around the most
massive ones within a fractal-like cluster.


title: Chandra X-ray observations of Young Clusters I. NGC2264 Data

abstract:
  We present results of a Chandra observation of a field in NGC 2264. The
observations were taken with the ACIS-I camera with an exposure time of 48.1
ks. We present a catalog of 263 sources, which includes X-ray luminosity,
optical and infrared photometry and X-ray variability information. We found 41
variable sources, 14 of which have a flare-like light curve, and 2 of which
have a pattern of a steady increase or decrease over a 10 hour period. The
optical and infrared photometry for the stars identified as X-ray sources are
consistent with most of these objects being pre-main sequence stars with ages
younger than 3 Myr.


title:
Effects of Quasi-Orthogonal EMission Modes on the Rotation Measures of
  Pulsars

abstract:
  We report here the discovery of a significant source of systematic error in
the rotation measure determinations of pulsars. Conventional analysis of high
sensitivity polarimetric observations of PSR B2016+28 display variation of the
rotation measure of $\pm$15 rad m$^{-2}$ (around the mean value of -34.6 rad
m$^{-2}$) across the pulse profile. Analysis of single pulse data shows that
this variation is an artifact of the incoherent superposition of
quasi-orthogonal polarisation modes along with the frequency dependence of
relative strength and/or quasi-orthogonality of the modes. Quasi-orthogonal
polarization is common among pulsars, and therefore this effect needs to be
taken into account in the interpretation of pulsar rotation measures.


title: A Circumstellar Disc in a High-Mass Star Forming Region

abstract:
  We present an edge-on Keplerian disc model to explain the main component of
the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1 N.
The brightness distribution and spectrum of the line of bright masers are
successfully modeled with high amplification of background radio continuum
emission along velocity coherent paths through a maser disc. The bend seen in
the position-velocity diagram is a characteristic signature of differentially
rotating discs. For a central mass of 30 solar masses, suggested by other
observations, our model fixes the masing disc to have inner and outer radii of
about 350 AU and 1000 AU.


title: Radio Astronomical Polarimetry and Point-Source Calibration

abstract:
  A mathematical framework is presented for use in the experimental
determination of the polarimetric response of observatory instrumentation.
Elementary principles of linear algebra are applied to model the full matrix
description of the polarization measurement equation by least-squares
estimation of non-linear, scalar parameters. The formalism is applied to
calibrate the center element of the Parkes Multibeam receiver using
observations of the millisecond pulsar, PSR J0437-4715, and the radio galaxy,
3C 218 (Hydra A).


title: A major outburst from the X-ray binary RX J0520.5-6932

abstract:
  We report on the analysis of 8 years of MAssive Compact Halo Objects (MACHO)
data for the source RX J0520.5-6932. A regular period of 24.4 days has been
confirmed, however this is manifest almost entirely in the red part of the
spectrum. A major outburst, lasting approximately 200 days, was observed which
increased the apparent brightness of the object by approximately 0.15
magnitudes without significantly altering its V-R colour index. This outburst
was also seen in X-ray data. The evidence from this analysis points to the
identification of this object as a Be/X-ray binary with a periodically variable
circumstellar disk and a very early optical counterpart.


title: Galactic Structure and Evolution: a decade of surveys

abstract:
  Surveys of the local and distant Universe are the means to test and improve
our models of galaxy formation. Substantial successes in the models are
evident, while there is also considerable recent progress in identifying what
remains to be learned. The key weaknesses of present models are related to
merging histories, and small-scale structures, which are both significantly at
variance with observations. Observers are polite, and often emphasise their
agreements with models. Data are objective, and show us the way to focus future
surveys, to allow improved understanding and knowledge.


title:
Magnetic floods: a scenario for the variability of the microquasar GRS
  1915+105

abstract:
  We present a scenario for the variability of the microquasar GRS 1915+105.
This starts from previous works, leading to the tentative identification of the
Accretion-Ejection Instability as the source of the low-frequency
Quasi-Periodic Oscillation of microquasars and other accreting sources. We
follow the physics of this instability: its conditions (the magnetic field and
geometry adapted to MHD jet models), its instability criterion, and its
consequences (cooling down of the disk, heating and excitation of the corona).
Comparing them to the observed properties of the source, in particular the
detailed properties of its spectral states, we first derive a model for the
$\sim$ 30 minutes cycles often exhibited by GRS 1915+105. In our model this is
a limit cycle determined by the advection of poloidal magnetic flux to the
inner region of the disk, and its destruction by reconnection (leading to
relativistic ejections) with the magnetic flux trapped in the vicinity of the
central source. We show how it leads to natural explanations for observed
behaviors of GRS 1915+105, including the three basic states of Belloni et al
(2000). We then discuss how this could be extrapolated further to understand
the longer-term variability of this and other microquasars.


title:
Discovery of an anomalous Sub Giant Branch in the Color Magnitude
  Diagram of omega Centauri

abstract:
  Using deep high-resolution multi-band images taken with the Very Large
Telescope and the Hubble Space Telescope, we discovered a new anomalous
sequence in the Color Magnitude Diagram of omega Cen. This feature appears as a
narrow, well-defined Sub Giant Branch (SGB-a), which merges into the Main
Sequence of the dominant cluster population at a magnitude significantly
fainter than the cluster Turn-Off (TO). The simplest hypothesis assumes that
the new feature is the extension of the anomalous Red Giant Branch (RGB-a)
metal-rich population discovered by Lee et al. (1999) and Pancino et al.
(2000). However, under this assumption the interpretation of the SGB-a does not
easily fit into the context of a self-enrichment scenario within omega Cen. In
fact, its TO magnitude, shape and extension are not compatible with a young,
metal-rich population, as required by the self-enrichment process. The TO level
of the SGB-a suggests indeed an age as old as the main cluster population,
further supporting the extra-cluster origin of the most metal rich stars, as
suggested by Ferraro, Bellazzini & Pancino (2002). Only accurate measurements
of radial velocities and metal abundances for a representative sample of stars
will firmly establish whether or not the SGB-a is actually related to the RGB-a
and will finally shed light on the origin of the metal rich population of omega
Cen.


title: Elliptical galaxy nuclei activity powered by infalling globular clusters

abstract:
  Globular cluster systems evolve, in galaxies, due to internal and external
dynamics and tidal phenomena. One of the causes of evolution, dynamical
friction, is responsible for the orbital decay of massive clusters into the
innermost galactic regions. It is found that these clusters are effective
source of matter to feed a central galactic black hole such to make it grow and
shine as an AGN.


title: Gravitational Lensing in Standard and Alternative Cosmologies

abstract:
  This thesis contributes to the field of gravitational lensing (GL) and
observational cosmology. We discuss the use of gravitational lensing as a tool
in search of exotic objects in the Universe. In the next chapter the
concordance of an alternative cosmological model with the current gravitational
lensing observations is explored and also a non-minimally coupled effective
gravity theory that supports non-topological solitonic solutions is considered.
In the last chapter we study propagation of light in strong gravitational
field. Using geometrical optics approach we show that massless particles with
spin deviate from the geodesic motion. We demonstrate that the velocity of
photon propagating in a Kerr black hole background remains subluminal.


title:
Low-frequency gravitational radiation from coalescing massive black hole
  binaries in hierarchical cosmologies

abstract:
  We compute the expected gravitational wave signal from coalescing massive
black hole (MBH) binaries at the center of galaxies in a hierarchical structure
formation scenario in which seed holes of intermediate mass form far up in the
dark halo merger tree. The merger history of DM halos and MBHs is followed from
z=20 to the present in a LCDM cosmology. MBHs get incorporated through halo
mergers into larger and larger structures, sink to the center owing to
dynamical friction against the DM background, accrete cold material in the
merger remnant, and form MBH binary systems. Stellar dynamical interactions
cause the hardening of the binary at large separations, while gravitational
wave emission takes over at small radii and leads to the final coalescence of
the pair. The integrated emission from inspiraling MBH binaries results in a
gravitational wave background (GWB). The characteristic strain spectrum has the
standard h_c(f)\propto f^{-2/3} behavior only in the range 1E-9<f<1E-6 Hz. At
lower frequencies the orbital decay of MBH binaries is driven by the ejection
of background stars, and h_c(f) \propto f. At higher frequencies, f>1E-6 Hz,
the strain amplitude is shaped by the convolution of last stable circular orbit
emission. We discuss the observability of inspiraling MBH binaries by the
planned LISA. Over a 3-year observing period LISA should resolve this GWB into
discrete sources, detecting ~60 (~250) individual events above a S/N=5 (S/N=1)
confidence level. (Abridged)


title: Redshift distortions in one-dimensional power spectra

abstract:
  We present a model for one-dimensional (1D) matter power spectra in redshift
space as estimated from data provided along individual lines of sight. We
derive analytic expressions for these power spectra in the linear and nonlinear
regimes, focusing on redshift distortions arising from peculiar velocities. In
the linear regime, redshift distortions enhance the 1D power spectra only on
small scales, and do not affect the power on large scales. This is in contrast
to the effect of distortions on three-dimensional (3D) power spectra estimated
from data in 3D space, where the enhancement is independent of scale. For CDM
cosmologies, the 1D power spectra in redshift and real space are similar for
wavenumbers $q<0.1h/Mpc$ where both have a spectral index close to unity,
independent of the details of the 3D power spectrum. Nonlinear corrections
drive the 1D power spectrum in redshift space into a nearly universal shape
over scale $q<10h/Mpc$, and suppress the power on small scales as a result of
the strong velocity shear and random motions. The redshift space, 1D power
spectrum is mostly sensitive to the amplitude of the initial density
perturbations. Our results are useful in particular for power spectra computed
from the SDSS quasars sample.


title: Nuclear liquid-gas phase transition and supernovae evolution

abstract:
  It is shown that the large density fluctuations appearing at the onset of the
first order nuclear liquid-gas phase transition can play an important role in
the supernovae evolution. Due to these fluctuations, the neutrino gas may be
trapped inside a thin layer of matter near the proto-neutron star surface. The
resulting increase of pressure may induce strong particle ejection a few
hundred milliseconds after the bounce of the collapse, contributing to the
revival of the shock wave. The Hartree-Fock+RPA scheme, with a finite-range
nucleon-nucleon effective interaction, is employed to estimate the effects of
the neutrino trapping due to the strong density fluctuations, and to discuss
qualitatively the consequences of the suggested new scenario.


title: Anisotropic Stars: Exact Solutions and Stability

abstract:
  I report on recent work concerning the existence and stability of
self-gravitating spheres with anisotropic pressure. After presenting new exact
solutions, Chandrasekhar's variational formalism for radial perturbations is
generalized to anisotropic objects and applied to investigate their stability.
It is shown that anisotropy can not only support stars of mass M and radius R
with 2M/R > 8/9 and arbitrarily large surface redshifts, but that stable
configurations exist for values of the adiabatic index smaller than the
corresponding isotropic value.


title: TASI Lectures: Introduction to Cosmology

abstract:
  These proceedings summarize lectures that were delivered as part of the 2002
and 2003 Theoretical Advanced Study Institutes in elementary particle physics
(TASI) at the University of Colorado at Boulder. They are intended to provide a
pedagogical introduction to cosmology aimed at advanced graduate students in
particle physics and string theory.


title: The extinction law in high redshift galaxies

abstract:
  We estimate the dust extinction laws in two intermediate redshift galaxies.
The dust in the lens galaxy of LBQS1009-0252, which has an estimated lens
redshift of zl~0.88, appears to be similar to that of the SMC with no
significant feature at 2175 A. Only if the lens galaxy is at a redshift of
zl~0.3, completely inconsistent with the galaxy colors, luminosity or location
on the fundamental plane, can the data be fit with a normal Galactic extinction
curve. The dust in the zl=0.68 lens galaxy for B0218+357, whose reddened image
lies behind a molecular cloud, requires a very flat ultraviolet extinction
curve with (formally) R(V)=12 +- 2. Both lens systems seem to have unusual
extinction curves by Galactic standards.


title:
Constraining Alternate Models of Black Holes: Type I X-ray Bursts on
  Accreting Fermion-Fermion and Boson-Fermion Stars

abstract:
  The existence of black holes remains open to doubt until other conceivable
options are excluded. With this motivation, we consider a model of a compact
star in which most of the mass consists of dark particles of some kind, and a
small fraction of the mass is in the form of ordinary nucleonic gas. The gas
does not interact with the dark matter other than via gravity, but collects at
the center as a separate fermionic fluid component. Depending on whether the
dark mass is made of fermions or bosons, the objects may be called
fermion-fermion stars or boson-fermion stars, respectively. For appropriate
choices of the mass of the dark matter particles, these objects are viable
models of black hole candidates in X-ray binaries. We consider models with a
dark mass of 10 solar masses and a range of gas mass from 10^{-6} to nearly one
solar mass, and analyse the bursting properties of the models when they accrete
gas. We show that all the models would experience thermonuclear Type I X-ray
bursts at appropriate mass accretion rates. Since no Type I bursts have been
reported from black hole candidates, the models are ruled out. The case for
identifying black hole candidates in X-ray binaries as true black holes is thus
strengthened.


title: The complex soft X-ray spectrum of NGC 4151

abstract:
  We present a detailed analysis of the complex soft X-ray spectrum of NGC 4151
measured by the RGS instruments aboard XMM-Newton. The XMM-Newton RGS spectra
demonstrate that the soft X-ray emission is extremely rich in X-ray emission
lines and radiative recombination continua (RRC), with no clear evidence for
any underlying continuum emission. Line emission, and the associated RRC, are
clearly detected from hydrogen-like and helium-like ionization states of neon,
oxygen, nitrogen and carbon. The measured lines are blueshifted with a velocity
of between ~100-1000 km/s, with respect to the systemic velocity of NGC 4151,
approximately consistent with the outflow velocities of the absorption lines
observed in the UV, suggestive of an origin for the UV and soft X-ray emission
in the same material. Plasma diagnostics imply a range of electron temperatures
of ~1-5x10^4 K and electron densities of between 10^8-10^10 cm^-3. The soft
X-ray spectrum of NGC 4151 is extremely similar to that of NGC 1068, suggesting
that the soft X-ray excesses observed in many Seyfert galaxies may be composed
of similar emission features. Modelling the RGS spectra in terms of emission
from photoionized and photoexcited gas in an ionization cone reproduces all of
the hydrogen-like and helium-like emission features observed in the soft X-ray
spectrum of NGC 4151 in detail and confirms the correspondence between the soft
X-ray emission in NGC 4151 and NGC 1068.


title:
Does the detection of X-ray emission from SN1998bw support its
  association with GRB980425?

abstract:
  We show that the recent identification of X-ray emission from SN1998bw is
naturally explained as synchrotron emission from a shock driven into the wind
surrounding the progenitor by a mildly relativistic shell ejected by the
supernova, the existence of which was inferred earlier from radio observations.
X-ray observations imply a shell energy E~10^{49.7}erg, and constrain the
initial shell velocity \beta*c and normalized wind mass loss rate,
\dot{m}=(\dot{M}/10^{-5}M_sun/yr)/(v_w/10^3 km/s), to satisfy
\beta^3*\dot{m}~10^{-1.5}. The inferred energy is consistent with energy
estimates based on radio observations provided \dot{m}~0.04, in which case
radio observations imply \beta~0.8, consistent with the X-ray constraint
\beta^3*\dot{m}~10^{-1.5}. While X-ray observations allow to determine the
parameters characterizing the pre-explosion wind and the mildly relativistic
shell ejected by SN1998bw, they do not provide evidence for existence of an
off-axis "standard" GRB jet associated with SN1998bw, that may have produced
GRB980425. However, as recently pointed out in (astro-ph/0310320), the lack of
observational signatures typically expected to be produced by such an off-axis
jet on a 1yr time scale, may be due to a low \dot{m}<0.1, which implies that an
off-axis jet will become observable only on >10yr time scale.


title:
The Becklin-Neugebauer Object as a Runaway B Star, Ejected 4000 years
  ago from the theta^1C system

abstract:
  We attempt to explain the properties of the Becklin-Neugebauer (BN) object as
a runaway B star, as originally proposed by Plambeck et al. (1995). This is one
of the best-studied bright infrared sources, located in the Orion Nebula
Cluster -- an important testing ground for massive star formation theories.
  From radio observations of BN's proper motion, we trace its trajectory back
to Trapezium star theta^1C, the most massive (45 Msun) in the cluster and a
relatively tight (17 AU) visual binary with a B star secondary. This origin
would be the most recent known runaway B star ejection event, occurring only
\~4000 yr ago and providing a unique test of models of ejection from multiple
systems of massive stars. Although highly obscured, we can constrain BN's mass
(~7 Msun) from both its bolometric luminosity and the recoil of theta^1C.
Interaction of a runaway B star with dense ambient gas should produce a compact
wind bow shock. We suggest that X-ray emission from this shocked gas may have
been seen by Chandra: the offset from the radio position is ~300 AU in the
direction of BN's motion. Given this model, we constrain the ambient density,
wind mass-loss rate and wind velocity. BN made closest approach to the massive
protostar, source ``I'', 500 yr ago. This may have triggered enhanced accretion
and thus outflow, consistent with previous interpretations of the outflow being
a recent (~10^3 yr) "explosive" event.


title: On the Low Progenitor Mass of the Binary Pulsar J0737-3039B

abstract:
  The observed orbital parameters of the recently discovered binary pulsar
J0737-3039 are used to constrain the progenitor system. In particular, the
small observed eccentricity and the small inferred peculiar velocity imply that
during the formation of the second NS in the system, a very small mass Delta M
<~ 0.15 Msun, was ejected. A progenitor more massive than 1.4 Msun is unlikely
and a progenitor more massive than 2.3 Msun is practically ruled out. We
therefore argue that the companion removed most of the progenitor envelope
prior to its collapse. The second collapse may have been a SN of Type Ib, or
more probably, of Type Ic. Alternatively, it could have been a bare collapse,
an option which is kinematically favored. Future constraints on the peculiar
motion could solidify this constraint on the mass loss. A future determination
of the pulsars' spin vectors and proper motion could allow us the complete
determination of the conditions during the second collapse.


title: Redshifted 21cm Signatures Around the Highest Redshift Quasars

abstract:
  The Ly-alpha absorption spectrum of the highest redshift quasars indicates
that they are surrounded by giant HII regions, a few Mpc in size. The neutral
gas around these HII regions should emit 21cm radiation in excess of the Cosmic
Microwave Background, and enable future radio telescopes to measure the
transverse extent of these HII regions. At early times, the HII regions expand
with a relativistic speed. Consequently, their measured sizes along the
line-of-sight (via Ly-alpha absorption) and transverse to it (via 21 cm
emission) should have different observed values due to relativistic time-delay.
We show that the combined measurement of these sizes would directly constrain
the neutral fraction of the surrounding intergalactic medium (IGM) as well as
the quasar lifetime. Based on current number counts of luminous quasars at z>6,
an instrument like LOFAR should detect >2 redshifted 21cm shells per field
(with a radius of 11 degrees) around active quasars as bright as those already
discovered by SDSS, and >200 relic shells of inactive quasars per field. We
show that Ly-alpha photons from the quasar are unable to heat the IGM or to
couple the spin and kinetic temperatures of atomic hydrogen beyond the edge of
the HII region. The detection of the IGM in 21cm emission around high redshift
quasars would therefore gauge the presence of a cosmic Ly-alpha background
during the reionization epoch.


title: Magnetar Spindown, Hyper-Energetic Supernovae, and Gamma Ray Bursts

abstract:
  The Kelvin-Helmholtz cooling epoch, lasting tens of seconds after the birth
of a neutron star in a successful core-collapse supernova, is accompanied by a
neutrino-driven wind. For magnetar-strength ($\sim10^{15}$ G) large scale
surface magnetic fields, this outflow is magnetically-dominated during the
entire cooling epoch.Because the strong magnetic field forces the wind to
co-rotate with the protoneutron star,this outflow can significantly effect the
neutron star's early angular momentum evolution, as in analogous models of
stellar winds (e.g. Weber & Davis 1967). If the rotational energy is large in
comparison with the supernova energy and the spindown timescale is short with
respect to the time required for the supernova shockwave to traverse the
stellar progenitor, the energy extracted may modify the supernova shock
dynamics significantly. This effect is capable of producing hyper-energetic
supernovae and, in some cases, provides conditions favorable for gamma ray
bursts. We estimate spindown timescales for magnetized, rotating protoneutron
stars and construct steady-state models of neutrino-magnetocentrifugally driven
winds. We find that if magnetars are born rapidly rotating, with initial spin
periods ($P$) of $\sim1$ millisecond, that of order $10^{51}-10^{52}$ erg of
rotational energy can be extracted in $\sim10$ seconds. If magnetars are born
slowly rotating ($P\gtrsim10$ ms) they can spin down to periods of $\sim1$
second on the Kelvin-Helmholtz timescale.


title: A comparison of cosmological models using recent supernova data

abstract:
  We study the expansion history of the universe up to a redshift of z=1.75
using the 194 recently published SnIa data by Tonry et. al. and Barris et. al.
In particular we find the best fit forms of several cosmological models and
$H(z)$ ansatze, determine the best fit values of their parameters and rank them
according to increasing value of $\chi_{min}^2$ (the minimum value of $\chi^2$
for each $H(z)$ ansatz). We use a prior of $\Omega_{0m} = 0.3$ and assume flat
geometry of the universe. No prior assumptions are made about validity of
energy conditions. The fitted models are fourteen and include SCDM, LCDM, dark
energy with constant equation of state parameter $w$ (quiessence), third order
polynomial for $H(1+z)$, Chaplygin gas, Cardassian model, $w(z)=w_0 + w_1 z$,
$w(z)=w_0 + z w_1/(1+z)$, an oscillating ansatz for $H(z)$ etc. All these
models with the exception of SCDM are consistent with the present data.
However, the quality of the fit differs significantly among them and so do the
predicted forms of $w(z)$ and $H(z)$ at best fit. The worst fit among the
data-consistent models considered corresponds to the simplest model LCDM
($\chi_{min}^2 = 198.7$ for $\Omega_{0m} = 0.34$) while the best fit is
achieved by the three parameter oscillating ansatz ($\chi_{min}^2 = 194.1$).
Most of the best fit ansatze have an equation of state parameter $w(z)$ that
varies between $w(z) \simeq -1$ for $z<0.5$ to $w(z) > 0$ for $z>1$. This
implies that the sign of the pressure of the dark energy may be alternating as
the redshift increases. The goodness of fit of the oscillating $H(z)$ ansatz
lends further support to this possibility.


title: The Evolution of Tidal Debris

abstract:
  Galaxy interactions expel a significant amount of stars and gas into the
surrounding environment. I review the formation and evolution of the tidal
debris spawned during these collisions, and describe how this evolution depends
on the large scale environment in which the galaxies live. In addition to
acting as a long-lived tracer of the interaction history of galaxies, the
evolution of this material -- on both large scales and small -- has important
ramifications for galactic recycling processes, the feeding of the intracluster
light and intracluster medium within galaxy clusters, and the delayed formation
of galactic disks and dwarf galaxies.


title: Cepheids and Long Period Variables in NGC 4395

abstract:
  Repeated imaging observations of NGC 4395 were made with the WIYN 3.5 m and
the KPNO 2.1 m telescopes. From the photometry of the resolved brighter stars
in this galaxy eleven Cepheids with periods ranging between 12 and 90 days have
been identified. The true distance modulus has been derived from the apparent
distance moduli in g, r and i. The distance modulus is 28.02 +/- 0.18 based on
the LMC P-L relation by Sandage et al. 2003; this corresponds to a distance of
4.0 +/- 0.3 Mpc. Using the P-L relation from Madore & Freedman 1991, the
distance modulus is 28.15 +/- 0.18; which corresponds to a distance of 4.3 +/-
0.4 Mpc. The reddening is calculated to be E(g-r) = 0.06 +/- 0.08 and E(r-i) =
0.10 +/- 0.08, again from the distance moduli mu_g, mu_r and mu_i. In addition,
37 other variables have been detected, the majority of which have definite
periods. They are probably all red long period variables.


title: Self-Calibration of Cluster Dark Energy Studies: Counts in Cells

abstract:
  Cluster number counts can constrain the properties of dark energy if and only
if the evolution in the relationship between observable quantities and the
cluster mass can be calibrated. Next generation surveys with ~10000 clusters
will have sufficient statistics to enable some degree of self-calibration. The
excess variance of counts due to the clustering of clusters provides such an
opportunity and can be measured from the survey without additional
observational cost. It can minimize the degradation in dark energy constraints
due to an unknown power law evolution in the mass-observable relation improving
constraints on the dark energy equation of state by a factor of 2 or more to
sigma(w)=0.06 for a deep 4000 deg2 survey.


title:
A multi-wavelength scattered light analysis of the dust grain population
  in the GG Tau circumbinary ring

abstract:
  We present the first 3.8 micron image of the dusty ring surrounding the young
binary system GG Tau, obtained with the W. M. Keck II 10m telescope's adaptive
optics system. This is the longest wavelength at which the ring has been
detected in scattered light so far, allowing a multi-wavelength analysis of the
scattering properties of the dust grains present in this protoplanetary disk in
combination with previous, shorter wavelengths, HST images. We find that the
scattering phase function of the dust grains in the disk is only weakly
dependent on the wavelength. This is inconsistent with dust models inferred
from observations of the interstellar medium or dense molecular clouds. In
particular, the strongly forward-throwing scattering phase function observed at
3.8 micron implies a significant increase in the population of large (>~1
micron) grains, which provides direct evidence for grain growth in the ring.
However, the grain size distribution required to match the 3.8 micron image of
the ring is incompatible with its published 1 micron polarization map, implying
that the dust population is not uniform throughout the ring. We also show that
our 3.8 micron scattered light image probes a deeper layer of the ring than
previous shorter wavelength images, as demonstrated by a shift in the location
of the inner edge of the disk's scattered light distribution between 1 and 3.8
micron. We therefore propose a stratified structure for the ring in which the
surface layers, located ~50 AU above the ring midplane, contain dust grains
that are very similar to those found in dense molecular clouds, while the
region of the ring located ~25 AU from the midplane contains significantly
larger grains. This stratified structure is likely the result of vertical dust
settling and/or preferred grain growth in the densest parts of the ring.


title:
Magnetars: Time Evolution, Superfluid Properties, and Mechanism of
  Magnetic Field Decay

abstract:
  We calculate the coupled thermal evolution and magnetic field decay in
relativistic model neutron stars threaded by superstrong magnetic fields (B >
10^{15} G). Our main goal is to evaluate how such ``magnetars'' evolve with
time and how field decay modifies the transitions to core superfluidity and
cooling dominated by surface X-ray emission. Observations of a thermal X-ray
spectral component and fast timing noise place strong constraints on the
presence of a superfluid core. We find that the transition to core
superfluidity can be significantly delayed by field decay in the age range ~
10^3-10^5 yrs. The mechanism of Hall drift is related to the stability of the
core magnetic field, and to currents flowing outward through the crust. The
heating effect is enhanced if it is continuous rather than spasmodic.
Condensation of a heavy element layer at the surface is shown to cause only
modest changes in the outward conduction of heat.


title: The Extended Methanol Maser Emission in W51

abstract:
  The European VLBI Network (EVN) has been used to make phase referenced,
wide-field (several arcminute) spectral line observations of the 6.7-GHz
methanol maser emission towards W51. In the W51main region, the bulk of the
methanol is offset from an UCHII region. This probably indicates the methanol
emission arises at the interface of the expanding UCHII region and not from an
edge-on circumstellar disc, as previously suggested. Near the W51 IRS2 region,
the methanol emission is associated with a very compact, extremely embedded
source supporting the hypothesis that methanol masers trace the earliest stages
of massive star formation. As well as these two previously well studied sites
of star formation, many previously unknown regions star formation are detected,
demonstrating that methanol masers are powerful means of detection young
massive stars.


title:
Gravitational Radiation from Rotational Core Collapse: Effects of
  Magnetic Fields and Realistic Equation of States

abstract:
  We perform a series of two-dimensional, axisymmetric, magnetohydrodynamic
simulations of the rotational collapse of a supernova core. In order to
calculate the waveforms of the gravitational wave, we derive the quadrupole
formula including the contributions from the electromagnetic fields. Recent
stellar evolution calculations imply that the magnetic fields of the toroidal
components are much stronger than those of the poloidal ones at the
presupernova stage. Thus, we systematically investigate the effects of the
toroidal magnetic fields on the amplitudes and waveforms. Furthermore, we
employ the two kinds of the realistic equation of states, which are often used
in the supernova simulations. Then, we investigate the effects of the equation
of states on the gravitational wave signals. With these computations, we find
that the peak amplitudes are lowered by an order of 10% for the models with the
strongest toroidal magnetic fields. However, the peak amplitudes are mostly
within sensitivity range of laser interferometers such as TAMA and the first
LIGO for a source at a distance of 10 kpc. Furthermore, we point out that the
amplitudes of second peaks are still within the detection limit of the first
LIGO for the source, although the characteristics of second peaks are reduced
by the magnetic fields. We stress the importance of the detection, since it
will give us information about the angular momentum distribution of massive
evolved stars. When we compare the gravitational waves from the two realistic
equation of states, significant differences are not found, except that the
typical frequencies of the gravitational wave become slightly higher for the
softer equation of state.


title: Cool carbon stars in the halo: a new survey based on 2MASS

abstract:
  We present the first results of a new survey for finding cool N-type carbon
(C) stars in the halo of the Galaxy. Candidates were first selected in the
2MASS Second Incremental Release database with JHKs colours typical of red AGB
C stars and Ks < 13, and susequently checked through slit spectroscopy. 27 new
halo C stars were discovered, and a detailed study of their properties are
given (distance, radial velocity, variablility, proper motion, colors etc). It
is found that most probably all these stars are true luminous AGB stars, rather
than C dwarfs. It is finally found that about half of these stars belong to the
Sgr Stream. (this abstract was shortened)


title: Searching for Dark Matter-Can it be directly detected?

abstract:
  In this paper we review the theoretical issues involved in the direct
detection of supersymmetric (SUSY) dark matter. After a brief discussion of the
allowed SYSY parameter space we focus on the determination of the traditional
neutralino detection rates, in experiments which measure the energy of the
recoiling nucleus, such as the coherent and spin induced rates and the
dependence of the rate on the motion of the Earth (modulation effect). Then we
examine the novel features appearing in directional experiments, which detect
the recoiling nucleus in a given direction. Next we estimate the branching
ratios for transitions to accessible excited nuclear levels. Finally we comment
on the event rates leading to the atom ionization and subsequent detection of
the outgoing electrons.


title: Averaging the spectral shapes

abstract:
  The methods of obtaining the average spectral shape in a low statistics
regime are presented. Different approaches to averaging are extensively tested
with simulated spectra, based on the ASCA responses. The issue of binning up
the spectrum before fitting is discussed together with the choice of statistic
used to model the spectral shape. The best results are obtained with methods in
which input data are represented by probability density functions. Application
of weights, representing the coverage between the input and output bins,
slightly improves the resolution of averaging.


title: NGC 4569: recent evidence for a past ram pressure stripping event

abstract:
  Deep 21-cm HI line observations of the Virgo cluster spiral galaxy NGC 4569
have been obtained with the VLA in its D configuration and with the Effelsberg
100-m telescope. A low surface density arm was discovered in the west of the
galaxy, whose velocity field is distinct from that of the overall disk
rotation. The observed gas distribution, velocity field, and velocity
dispersion are compared to snapshots of dynamical simulations that include the
effects of ram pressure. Two different scenarios were explored: (i) ongoing
stripping and (ii) a major stripping event that took place about 300 Myr ago.
It is concluded that only the post-stripping scenario can reproduce the main
observed characteristics of NGC 4569. It is not possible to determine if the
gas disk of NGC 4569 had already been truncated before it underwent the ram
pressure event that lead to its observed HI deficiency.


title:
Updated Toulouse solar models including the diffusion-circulation
  coupling and the effect of $\mu$-gradients

abstract:
  New solar models are presented, which have been computed with the most recent
physical inputs (nuclear reaction rates, equation of state, opacities,
microscopic diffusion). Rotation-induced mixing has been introduced in a way
which includes the feed-back effect of the $\mu$-gradient induced by helium
settling. A parametrization of the tachocline region below the convective zone
has also been added in the computations. The sound velocities have been
computed in the models and compared to the seismic sun. Our best model is
described in some detail. Besides the new physical inputs, the most important
improvement concerns the computations of $\mu$-gradients during the solar
evolution and their influence in slowing down rotation-induced mixing. This
process can explain why lithium is depleted in the present Sun while beryllium
is not, and meanwhile why $^3$He has not increased at the solar surface for at
least 3 Gyrs.


title:
The X-Ray Binary X2127+119 in M15: Evidence for a Very-Low-Mass,
  Stripped-Giant Companion

abstract:
  We present integral field spectroscopy of X2127+119, the luminous X-ray
binary in the globular cluster M15, obtained with INTEGRAL/WYFFOS on the
William Herschel Telescope. We find that tomograms of HeII 4686 line profiles
appear to be incompatible with the previously-assumed view of X2127+119, in
which the binary consists of a 1.4-solar-mass neutron star and a 0.8-solar-mass
sub-giant companion near the main-sequence turn-off for M15. Our data imply a
much smaller mass ratio M_2/M_x of 0.1. We find that models of X2127+119 with
black-hole compact objects give a poor fit to our data, while a neutron-star
compact object is consistent with the data, implying that X2127+119's companion
may have a much lower mass (~0.1 solar masses) than previously assumed. As an
0.1-solar-mass main-sequence star would be unable to fill its Roche lobe in a
binary with X2127+119's orbital period (17.1 hours), the companion is likely to
be the remnant of a significantly more massive star which has had most of its
envelope stripped away.


title: Modeling the Multi-wavelength Universe: the assembly of massive galaxies

abstract:
  Pan-chromatic galaxy surveys are providing tightening constraints on the
global mass assembly history, and high-resolution imaging of large fields is
telling us when and where stars were formed. How well are state-of-the-art
hierarchical galaxy formation models currently doing at reproducing these
observations? I present results here that suggest that hierarchical models are
doing quite well at reproducing the global star formation and stellar mass
assembly history obtained from galaxies selected in the optical and Near IR.
However, the same models fail to reproduce two very important populations at
high redshift: quiescent red spheroids and vigorously star-forming,
dust-enshrouded starbursts. This mismatch carries important lessons about how
star formation is triggered and regulated in early galaxies, and may force us
to consider new ideas about the formation of massive spheroids.


title: A Very Large Array 3.6cm continuum survey of Galactic Wolf-Rayet stars

abstract:
  We report the results of a survey of radio continuum emission of Galactic
Wolf-Rayet stars north of declination -46 degrees. The observations were
obtained at 8.46 GHz (3.6cm) using the Very Large Array (VLA), with an angular
resolution of about 6 x 9 arcsec and typical rms noise of 0.04 mJy/beam. Our
survey of 34 WR stars resulted in 15 definite and 5 probable detections, 13 of
these for the first time at radio wavelengths. All detections are unresolved.
Time variations in flux are confirmed in the cases of WR98a, WR104, WR105 and
WR125. WR79a and WR89 are also variable in flux and we suspect they are also
non-thermal emitters. Thus, of our sample 20-30% of the detected stars are
non-thermal emiters. Average mass loss rates determinations obtained excluding
definite and suspected non-thermal cases give similar values for WN (all
subtypes) and WC5-7 stars, while a lower value was obtained for WC8-9 stars.
Uncertainties in stellar distances largely contribute to the observed scatter
in mass loss rates. Upper limits to the mass loss rates were obtained in cases
of undetected sources or for sources which probably show additional non-thermal
emission.


title:
Potential--density pairs for spherical galaxies and bulges: the
  influence of scalar fields

abstract:
  A family of potential--density pairs has been found for spherical halos and
bulges of galaxies in the Newtonian limit of scalar--tensor theories of
gravity. The scalar field is described by a Klein--Gordon equation with a
source that is coupled to the standard Poisson equation of Newtonian gravity.
The net gravitational force is given by two contributions: the standard
Newtonian potential plus a term stemming from massive scalar fields. General
solutions have been found for spherical systems. In particular, we compute
potential--density pairs of spherical galactic systems, and some other
astrophysical quantities that are relevant to generating initial conditions for
spherical galaxy simulations.


title:
Electron Inertial Effects on Rapid Energy Redistribution at Magnetic
  X-points

abstract:
  The evolution of non-potential perturbations to a current-free magnetic
X-point configuration is studied, taking into account electron inertial effects
as well as resistivity. Electron inertia is shown to have a negligible effect
on the evolution of the system whenever the collisionless skin depth is less
than the resistive scale length. Non-potential magnetic field energy in this
resistive MHD limit initially reaches equipartition with flow energy, in
accordance with ideal MHD, and is then dissipated extremely rapidly, on an
Alfvenic timescale that is essentially independent of Lundquist number. In
agreement with resistive MHD results obtained by previous authors, the magnetic
field energy and kinetic energy are then observed to decay on a longer
timescale and exhibit oscillatory behavior, reflecting the existence of
discrete normal modes with finite real frequency. When the collisionless skin
depth exceeds the resistive scale length, the system again evolves initially
according to ideal MHD. At the end of this ideal phase, the field energy decays
typically on an Alfvenic timescale, while the kinetic energy (which is equally
partitioned between ions and electrons in this case) is dissipated on the
electron collision timescale. The oscillatory decay in the energy observed in
the resistive case is absent, but short wavelength structures appear in the
field and velocity profiles, suggesting the possibility of particle
acceleration in oppositely-directed current channels. The model provides a
possible framework for interpreting observations of energy release and particle
acceleration on timescales down to less than a second in the impulsive phase of
solar flares.


title:
Three-dimensional dust radiative-transfer models: The Pinwheel Nebula of
  WR104

abstract:
  We present radiative-transfer modelling of the dusty spiral Pinwheel Nebula
observed around the Wolf-Rayet/OB-star binary WR104. The models are based on
the three-dimensional radiative-transfer code TORUS, modified to include an
adaptive mesh that allows us to adequately resolve both the inner spiral turns
(sub-AU scales) and the outer regions of the nebula (distances of 10^4 AU from
the central source). The spiral model provides a good fit to both the spectral
energy distribution and Keck aperture masking interferometry, reproducing both
the maximum entropy recovered images and the visibility curves. We deduce a
dust creation rate of 8+-1 x 10^{-7} solar masses per year, corresponding to
approximately 2% by mass of the carbon produced by the Wolf-Rayet star.
Simultaneous modelling of the imaging and spectral data enables us to constrain
both the opening-angle of the wind-wind collision interface and the dust grain
size. We conclude that the dust grains in the inner part of the Pinwheel nebula
are small (~100A), in agreement with theoretical predictions, although we
cannot rule out the presence of larger grains (~1 micron) further from the
central binary. The opening angle of the wind-wind collision interface appears
to be about 40 degrees, in broad agreement with the wind parameters estimated
for the central binary. We discuss the success and deficiencies of the model,
and the likely benefits of applying similar techniques to the more the more
complex nebulae observed around other WR/O star binaries.


title: Scaling behaviour of a scalar field model of dark matter halos

abstract:
  Galactic dark matter is modelled by a scalar field. In particular, it is
shown that an analytically solvable toy model with a non-linear
self-interaction potential U(Phi) leads to dark halo models which have the form
of quasi-isothermal spheres. We argue that these fit better the observed
rotation curves of galaxies than the centrally cusped halos of standard cold
dark matter. The scalar field model predicts a proportionality between the
central densities of the dark halos and the inverse of their core radii. We
test this prediction successfully against a set of rotation curves of low
surface brightness galaxies and nearby bright galaxies.


title: Simulating the metal enrichment of the ICM

abstract:
  We present results from Tree+SPH simulations of a galaxy cluster, aimed at
studying the metal enrichment of the intra--cluster medium (ICM). The
simulation code includes a fairly advanced treatment of star formation, as well
as the release of energy feedback and detailed yields from both type-II and
type-Ia supernovae, also accurately accounting for the lifetimes of different
stellar populations. We perform simulations of a cluster with virial mass ~
3.9x 10^14 Msun, to investigate the effect of varying the feedback strength and
the stellar initial mass function (IMF). Although most of the models are able
to produce acceptable amounts of Fe mass, we find that the profiles of the iron
abundance are always steeper than observed. The [O/Fe] ratio is found to be
sub--solar for a Salpeter IMF, with [O/Fe] -0.2 at R >~ 0.1R200, whereas
increasing to super-solar values in central regions, as a result of recent star
formation. Using a top--heavier IMF gives a larger [O/Fe] over the whole
cluster, at variance with observations. On the other hand, the adoption of a
variable IMF, which becomes top-heavier at z>2, provides a roughly solar [O/Fe]
ratio. Our results indicate that our simulations still lack a feedback
mechanism which should quench star formation at low redshift and transport
metals away from the star forming regions.


title: Effective geometry in Astrophysics

abstract:
  The effective metric is introduced by means of two examples (non-linear
electromagnetism and hydrodynamics),along with applications in Astrophysics. A
sketch of the generality of the effect is also given.


title: Halo Model Analysis of Cluster Statistics

abstract:
  We use the halo model formalism to provide expressions for cluster abundances
and bias, as well as estimates for the correlation matrix between these
observables. Off-diagonal elements due to scatter in the mass tracer scaling
with mass are included, as are observational effects such as biases/scatter in
the data, detection rates (completeness), and false detections (purity). We
apply the formalism to a hypothetical volume limited optical survey where the
cluster mass tracer is chosen to be the number of member galaxies assigned to a
cluster. Such a survey can strongly constrain $\sigma_8$
($\Delta\sigma_8\approx 0.05$), the power law index $\alpha$ where
$<N_{gal}|m>= 1+(m/M_1)^\alpha$ ($\Delta\alpha\approx0.03$), and perhaps even
the Hubble parameter ($\Delta h\approx 0.07$). We find cluster abundances and
bias not well suited for constraining $\Omega_m$ or the amplitude $M_1$. We
also find that without bias information $\sigma_8$ and $\alpha$ are degenerate,
implying constraints on the former are strongly dependent on priors used for
the latter and vice-versa. The degeneracy stems from an intrinsic scaling
relation of the halo mass function, and hence it should be present regardless
of the mass tracer used in the survey.


title: A Briefing on the Ekpyrotic/Cyclic Universe

abstract:
  This is a short overview of the ekpyrotic/cyclic model of the universe, an
alternative to the standard big bang inflationary paradigm.


title:
Formation Rate, Evolving Luminosity Function, Jet Structure, and
  Progenitors for Long Gamma-Ray Bursts

abstract:
  We constrain the isotropic luminosity function (LF) and formation rate of
long gamma-ray bursts (GRBs) by fitting models 'jointly' to both the observed
differential peak flux and redshift distributions. We find evidence supporting
an evolving LF, where the luminosity scales as (1+z)^delta with an optimal
delta of 1.0\pm 0.2. For a single power-law LF, the best slope is ~ -1.57 with
an upper luminosity of 10^53.3 erg/s, while the best slopes for a double
power-law LF are approximately -1.6 and -2.6 with a break luminosity of 10^52.7
erg/s. Our finding implies a jet model intermediate between the universal
structured epsilon(theta) proportional to theta^-2 model and the
quasi-universal Gaussian structured model. For the uniform jet model our result
is compatible with an angle distribution between 2 and 15 grades. Our best
constrained GRB formation rate histories increase from z=0 to z=2 by a factor
of ~30 and then continue increasing slightly. We connect these histories to
that of the cosmic star formation history, and compare with observational
inferences up to z~6. GRBs could be tracing the cosmic rates of both the normal
and obscured star formation regimes. We estimate a current GRB event rate in
the Milky Way of ~5 10^-5 yr^-1, and compare it with the birthrate of massive
close WR+BH binaries with orbital periods of hours. The agreement is rather
good suggesting that these systems could be the progenitors of the long GRBs.


title:
Effect of Differential Rotation on the Maximum Mass of Neutron Stars:
  Realistic Nuclear Equations of State

abstract:
  The merger of binary neutron stars is likely to lead to differentially
rotating remnants. In this paper, we survey several cold nuclear equations of
state (EOSs) and numerically construct models of differentially rotating
neutron stars in general relativity. For each EOS we tabulate maximum allowed
masses as a function of the degree of differential rotation. We also determine
effective polytropic indices, and compare the maximum allowed masses with those
for the corresponding polytropes. We consistently find larger mass increases
for the polytropes, but even for the nuclear EOSs we typically find maximum
masses 50% higher than the corresponding values for nonrotating (TOV) stars. We
evaluate our findings for the six observed binary neutron star (pulsar)
systems, including the recently discovered binary pulsar J0737-3039. For each
EOS we determine whether their merger will automatically lead to prompt
collapse to a black hole, or whether the remnant can be supported against
collapse by uniform rotation (possibly as a supramassive star) or differential
rotation (possibly as a hypermassive star). For hypermassive stars, delayed
collapse to a black hole is likely. For the most recent EOSs we survey the
merger remnants can all be supported by rotation against prompt collapse, but
their actual fate will depend on the nonequilibrium dynamics of the coalescence
event. Gravitational wave observations of coalescing binary neutron stars may
be able to distinguish these outcomes -- no, delayed or prompt collapse -- and
thereby constrain possible EOSs.


title: The Tidal Circularization Cutoff Period of the Old Open Cluster NGC188

abstract:
  Based on a sample of 45 main-sequence solar-type spectroscopic binaries we
find the tidal circularization cutoff in the open cluster NGC 188 (age 7 Gyr)
to be well-defined at a period of 15.0 days. When compared to shorter tidal
circularization cutoff periods in the younger clusters M67 and the Hyades, this
result establishes that tidal circularization processes are effective in
solar-type main-sequence binaries for timescales longer than 1 Gyr. This result
is in contrast to the theoretical prediction by Zahn & Bouchet that tidal
circularization due to equilibrium tides is ineffective for late-type main
sequence stars, and that tidal circularization cutoff periods are instead set
only by pre-main-sequence tidal circularization. The NGC 188 cutoff period is
also longer than can be explained by present theories of tidal circularization
due to dynamical tides.


title:
Doppler Shifts and Broadening and the Structure of the X-ray Emission
  from Algol

abstract:
  In a study of Chandra High Energy Transmission Grating spectra of Algol, we
clearly detect Doppler shifts caused by the orbital motion of Algol B. These
data provide the first definitive proof that the X-ray emission of Algol is
dominated by the secondary, in concordance with expectations that Algol A (B8)
is X-ray dark. The measured Doppler shifts are slightly smaller than expected,
implying an effective orbital radius of about 10 Rsolar, instead of 11.5 Rsolar
for the Algol B center of mass. This could be caused by a small contribution of
X-ray flux from Algol A (10-15%), possibly through accretion. The more likely
explanation is an asymmetric corona biased toward the system center of mass by
the tidal distortion of the surface of Algol B. Analysis of the strongest lines
indicates excess line broadening of ~150 km/s above that expected from thermal
motion and surface rotation. Possible explanations include turbulence, flows or
explosive events, or rotational broadening from a radially extended corona. We
favor the latter scenario and infer that a significant component of the corona
at temperatures <10^7 K has a scale height of order the stellar radius. This is
supported by the shape of the X-ray lightcurve and the shallow dip at secondary
eclipse. We also examine the O VII intercombination and forbidden lines in a
Low Energy Transmission Grating Spectrograph observation and find no change in
their relative line fluxes as the system goes from quadrature to primary
eclipse. Since these lines are strongly affected by UV irradiation from Algol
A, this supports the conjecture that the corona of Algol B at temperatures of
several million K must be significantly extended and/or located toward the
poles to avoid being shadowed from Algol A during primary eclipse.


title: N2H+ Observations of Molecular Cloud Cores in Taurus

abstract:
  N2H+ observations of molecular cloud cores in Taurus with the Nobeyama 45 m
radio telescope are reported. We compare ``cores with young stars'' with
``cores without young stars''. The differences in core radius, linewidth, and
core mass are small. Linewidth is dominated by thermal motions in both cases.
N2H+ maps show that the intensity distribution does not differ much between
cores without stars and those with stars. This is in contrast to the result
previously obtained in H13CO+ toward Taurus molecular cloud cores. Larger
degree of depletion of H13CO+ in starless cores will be one possible
explanation for this difference. We studied the physical state of molecular
cloud cores in terms of ``critical pressure'' for the surface (external)
pressure. There is no systematic difference between starless cores and cores
with stars in this analysis. Both are not far from the critical state for
pressure equilibrium. We suggest that molecular cloud cores in which thermal
support is dominated evolve toward star formation by keeping close to the
critical state. This result is in contrast with that obtained in the
intermediate-mass star forming region OMC-2/3, where molecular cloud cores
evolve by decreasing the critical pressure appreciably. We investigate the
radial distribution of the integrated intensity. Cores with stars are found to
have shallow (-1.8 to -1.6) power-law density profiles.


title:
Stochastic Acceleration of Electrons and Protons. I. Acceleration by
  Parallel Propagating Waves

abstract:
  Stochastic acceleration of electrons and protons by waves propagating
parallel to the large scale magnetic fields of magnetized plasmas is studied
with emphasis on the feasibility of accelerating particles from a thermal
background to relativistic energies and with the aim of determining the
relative acceleration of the two species in one source. In general, the
stochastic acceleration by these waves results in two distinct components in
the particle distributions, a quasi-thermal and a hard nonthermal, with the
nonthermal one being more prominent in hotter plasmas and/or with higher level
turbulence. This can explain many of the observed features of solar flares.
Regarding the proton to electron ratio, we include the effects of $^4$He in the
dispersion relation and the damping of the turbulent waves by the thermal
background plasma. The relative acceleration of protons and electrons is very
sensitive to the ratio of the electron plasma frequency to its gyro-frequency.
Protons are preferentially accelerated in weakly magnetized plasmas. The
formalism developed here is applicable to the acceleration of other ion species
and to other astrophysical systems.


title:
High-speed Keck II and RXTE spectroscopy of Cygnus X-2: (I) Three X-ray
  components revealed by correlated variability

abstract:
  We have performed simultaneous X-ray and optical spectroscopic observations
of the Low Mass X-ray Binary Cygnus X-2. We have used a new data system
attached to the Low Resolution Imaging Spectrograph instrument on Keck II to
obtain spectra with a mean time resolution of 72.075 milliseconds, simultaneous
with pointed X-ray observations using the PCA onboard XTE. In this paper, we
have analysed the variability in both wavebands on timescales of 16 seconds.
During our observations Cygnus X-2 covered all three branches of the Z-curve,
allowing us to study how the changes in X-ray spectral state affect the optical
emission. As the optical flux rises the X-ray intensity first rises on the
Horizontal Branch (0<S_z<1) but then falls on the Normal Branch (1<S_z<2) and
Flaring Branch (2<S_z<3), where S_z is a rank number characterising the
position on the Z-curve. This linear increase in the optical flux with S_z
indicates the optical flux is a good predictor of the accretion rate (possibly
normalized by its own long-term average) inferred from the Z-state S_z. We have
used this correlation to decompose the total X-ray count-rate into three
distinct spectral components.


title:
On the determination of age and mass functions of stars in young open
  star clusters from the analysis of their luminosity functions

abstract:
  Based on the CCD observations of remote young open clusters NGC 2383, NGC
2384, NGC 4103, NGC 4755, NGC 7510 and Hogg 15, we constructed their observed
luminosity functions (LFs). The observed LFs are corrected for field star
contamination determined with the help of galactic star count model. In the
case of Hogg 15 and NGC 2383 we also considered the additional contamination
from neighbouring clusters NGC 4609 and NGC 2384 respectively. These
corrections provided the realistic pattern of cluster LF in the vicinity of the
MS turn on point and at fainter magnitudes, revealed the so called H-feature
arising due to transition of the Pre-MS phase to MS, which is dependent on the
cluster age. The theoretical LFs were constructed representing a cluster
population model with continuous star formation for a short time scale and a
power law Initial Mass Function (IMF) and these were fitted to the observed LF.
As a result we are able to determine for each cluster a set of parameters,
describing cluster population (the age, duration of star formation, IMF slope
and percentage of field star contamination). It was found that in spite of the
non-monotonic behaviour of observed LFs, cluster IMFs can be described as the
power law functions with slopes similar to Salpeter's value. The present MS
turn on cluster ages are several times lower than those derived from the
fitting of theoretical isochrones to the turn off region of the upper Main
Sequences.


title:
On the use of X-rays to determine dynamical properties of elliptical
  galaxies

abstract:
  The X-ray emitting interstellar medium of early type galaxies is often used
as a tool to determine their total mass M and stellar orbital anisotropy beta
profiles, based on the hypothesis of hydrostatic equilibrium for the hot gas.
Here we investigate the effects that deviations from equilibrium have on M and
beta estimates, by using simple analytical calculations and hydrodynamical
simulations representative of gas rich galaxies. We show that the deviations of
the X-ray determined beta^{est} and M^{est} from the true values are linked by
a remarkably simple relation; in particular, M is underestimated if beta is
overestimated, and more radially anisotropic orbital distributions than true
are deduced in presence of gas infall velocities of the order of the local
stellar velocity dispersion (as are likely in the central regions of galactic
cooling flows). The results of this analysis are applied to the most thoroughly
investigated bright elliptical, NGC4472. We show that beta^{est} recently
derived from X-rays corresponds to a galaxy that is unstable by radial orbit
instability. Then, assuming as true beta and M the optically derived values, we
show that the differences beta^{est}-beta and M^{est}-M agree with the
predictions found here in the case of lack of hydrostatic equilibrium, which
points to the latter as a possible explanation for the discrepancies
(abridged).


title:
X-ray flares reveal mass and angular momentum of the Galactic Center
  black hole

abstract:
  We have analysed the light curve of the two brightest X-ray flares from the
Galactic Center black hole, one flare observed by XMM-Newton on October 3, 2002
(Porquet et al. 2003), and the other flare observed by Chandra on October 26,
2000 (Baganoff et al. 2001). The power density spectra show five distinct peaks
at periods of ~ 100 s, 219 s, 700 s, 1150 s, and 2250 s common to both
observations within their estimated measurement uncertainties. The power
density spectrum of the recently reported infrared flare of June 16, 2003
(Genzel et al. 2003) shows distinct peaks at two, if not three, periods
(including the 1008 +/- 120 s infrared period), which are consistent with the
X-ray periods. The remaining two periods could not be covered by the infrared
measurements. Each period can be identified with one of the characteristic
gravitational cyclic modes associated with accretion disks, i.e. either
Lense-Thirring precession, Kepler orbital motion and the vertical and radial
epicyclic oscillation modes, in such a way that a consistent value for the
black hole mass of M_BH = 2.72^{+0.12}_{-0.19} x 10^6 M_odot and the angular
momentum $a$ = 0.9939^{+0.0026}_{-0.0074} is obtained. The available data on
M_BH derived from studies of the orbital motion of the S2 (S0-2) star (Schoedel
et al. 2002, Ghez et al. 2003) agree with our findings. Finally we discuss some
implications of the fairly high value for the angular momentum.


title: Extragalactic jets: the high energy view

abstract:
  I review the current knowledge of high-energy emission from extragalctic
jets. First I discuss gamma-ray emission from blazars, which provides us
numerous precious information on the innermost portions of the relativistic
jets. I describe the constraints on the dynamics of the jet from the subpc to
the pc scale provided by recent VLBI studies of TeV sources, together with the
modelling of the emission from the blazar jet. Finally I discuss high energy
emission from large scale jets as seen by Chandra and I report on the expected
gamma-ray emission from large-scale regions of jets.


title: On the relationship between MOND and DM

abstract:
  Numerous astrophysical observations have shown that classical Newtonian
dynamics fails on galactic scales and beyond, if only visible matter is taken
into account. The two most popular theoretical concepts dealing with this
problem are Dark Matter (DM) and Modified Newtonian Dynamics (MOND). In the
first part of this paper it is demonstrated that a generalized MOND equation
can be derived in the framework of Newtonian Dark Matter theory. For systems
satisfying a fixed relationship between the gravitational fields caused by DM
and visible matter, this generalized MOND equation reduces to the traditional
MOND law, first postulated by Milgrom. Therefore, we come to the conclusion
that traditional MOND can also be interpreted as special limit case of DM
theory. In the second part, a formal derivation of the Tully-Fisher relation is
discussed.


title:
Chandra/ACIS Subpixel Event Repositioning. II. Further Refinements and
  Comparison between Backside and Front-side Illuminated X-ray CCDs

abstract:
  We further investigate subpixel event repositioning (SER) algorithms in
application to Chandra X-ray Observatory (CXO) CCD imaging. SER algorithms have
been applied to backside illuminated (BI) Advanced CCD Imaging Spectrometer
(ACIS) devices, and demonstrate spatial resolution improvements in Chandra/ACIS
observations. Here a new SER algorithm that is charge split dependent is added
to the SER family. We describe the application of SER algorithms to frontside
illuminated (FI) ACIS devices. The results of SER for FI CCDs are compared with
those obtained from SER techniques applied to BI CCD event data. Both simulated
data and Chandra/ACIS observations of the Orion Nebular Cluster were used to
test and evaluate the achievement of the various SER techniques.


title: Further Clues to the Nature of Composite LINER/HII Galaxies

abstract:
  We have analyzed new, archival and published high resolution radio and X-ray
observations of a sample of composite LINER/HII galaxies known to exhibit
AGN-like properties. Five of the 16 AGN candidates have milliarcsecond-scale
detections and are found to display a compact, flat spectrum, high brightness
temperature radio core, four of which also exhibit extended radio emission.
Five of the eight AGN candidates with available high resolution X-ray
observations were found to possess a hard X-ray nuclear source, two of which
have no milliarcsecond radio detection. The combined high resolution radio and
X-ray data yield a 50% detection rate of low luminosity AGN among the AGN
candidates, which translates into a 12% detection rate for the entire composite
LINER/HII sample. In the sources where the AGN has been unambiguously detected,
the ionizing power of the AGN is not sufficient to generate the observed
emission lines, unless the hard X-rays are heavily obscured. We attempt to
apply a canonical advection-dominated accretion flow (ADAF) and jet model to
the sample sources in order to explain the observed radio and X-ray emission.
While ADAFs may be responsible for the observed emission in submillijansky
radio cores like NGC 7331, they do not appear consistent with the radio
emission observed in the milliarcsecond-scale radio detected cores; the latter
sources are more likely to have an energetically important contribution from a
radio-emitting jet.


title: omega-Centauri - an Ultra Compact Dwarf Galaxy ?

abstract:
  A new formation scenario for omega-Cen is presented, in which omega-Cen has
formed from a star cluster complex (= super-cluster). The star-burst which has
led to the formation of this cluster of star clusters was triggered by the
infall and destruction of a gas-rich dwarf galaxy during the early build-up
phase of the Milky Way. While the star clusters in the super-cluster merge on a
few crossing times scale, which is always longer than the individual cluster
formation time-scale, they capture stars from the destroyed dwarf galaxy very
efficiently. This process makes it possible to explain the age-spread, the
spatial and the kinematical differences of the populations observed in
omega-Cen. This formation scenario places omega-Cen into the same class of
objects as the ultra-compact dwarf galaxies (UCDs) and the faint fuzzy star
clusters (FFs).


title:
WIYN Survey for Carbon Stars in the M31 and Cetus Dwarf Spheroidal
  Galaxies: Evolutionary Implications

abstract:
  We report results of a photometric survey with the WIYN telescope for carbon
stars in the M 31 dwarf spheroidal (dSph) companions And III, And V, And VI,
and And VII, as well as in the relatively isolated Local Group dSph Cetus. We
find three carbon-star candidates in And VII and one carbon star in each And VI
and Cetus. Comparing the carbon star content with other Local Group dwarf
galaxies, we argue against the presence of substantial intermediate-age stellar
populations in the all of the galaxies surveyed with the exception of And VII.
We discuss these results in the context of the origin of the Andromeda dSphs
and conclude that these are ancient galaxies, most of which ceased star
formation long before the main merger events in M31. The M31 dSphs therefore
show less diversity in star formation histories than the Galactic dSph
companions, or the M31 dE companions, as illustrated by NGC147 which was
surveyed as a calibration object. All of our dSph targets except And V have
candidate carbon stars below the tip of the RGB, which resemble CH stars found
in globular clusters. We estimate that 0.3% of stars in the dSphs are CH stars,
presumably as a result of C pollution from a binary companion. Comparisons with
CH star frequencies in globular clusters could constrain the impact of dense
environments on the frequency of this form of binary star evolution.


title: QSO + galaxy association and discrepant redshifts in NEQ3

abstract:
  Spectroscopy and deep imaging of the group NEQ3 are presented. This system is
formed by three compact objects with relative separations of ~2.6 and ~2.8
arcsec, and a lenticular galaxy at ~17 arcsec from the geometric centre of the
group. A diffuse filament is located on a line joining the three compact
objects and the main galaxy. Analysis of these observations confirms the
redshift previously known for three of the objects (z=0.1239 for the main
galaxy, and z=0.1935 and 0.1939 for two of the compact objects). We have also
determined the previously unknown redshift of the third compact object as
z=0.2229. Using the relative strength and width of the main spectral lines, we
have classified the compact objects as two HII galaxies and one QSO (the object
at z=0.1935). With cross-correlation techniques, we have tentatively estimated
the redshift of the filament as z=0.19 (although a weaker component also
appears at z=0.12) so that it is probably associated with the halo of the two
compact objects at this redshift. The two objects at redshift ~0.19 represent
possibly one of the more clear examples of starburst (and perhaps QSO activity)
driven by interaction. These, and the relation between these two objects and
the other two at (~0.12 and ~0.22) make the nature of this system intriguing,
being difficult to explain the whole association on conventional scenarios.


title:
Detection of polarization from the E^4\Pi-A^4\Pi system of FeH in
  sunspot spectra

abstract:
  Here we report the first detection of polarization signals induced by the
Zeeman effect in spectral lines of the E^4\Pi-A^4\Pi system of FeH located
around 1.6 $\mu$m. Motivated by the tentative detection of this band in the
intensity spectrum of late-type dwarfs, we have investigated the full Stokes
sunspot spectrum finding circular and linear polarization signatures that we
associate with the FeH lines of the E^4\Pi-A^4\Pi band system. We investigate
the Zeeman effect in these molecular transitions pointing out that in Hund's
case (a) coupling the effective Land\'e factors are never negative. For this
reason, the fact that our spectropolarimetric observations indicate that the
Land\'e factors of pairs of FeH lines have opposite signs, prompt us to
conclude that the E^4\Pi-A^4\Pi system must be in intermediate angular momentum
coupling between Hund's cases (a) and (b). We emphasize that theoretical and/or
laboratory investigations of this molecular system are urgently needed for
exploiting its promising diagnostic capabilities.


title:
On the Excess Dispersion in the Polarization Position Angle of Pulsar
  Radio Emission

abstract:
  The polarization position angles (PA) of pulsar radio emission occupy a
distribution that can be much wider than what is expected from the average
linear polarization and the off-pulse instrumental noise. Contrary to our
limited understanding of the emission mechanism, the excess dispersion in PA
implies that pulsar PAs vary in a random fashion. An eigenvalue analysis of the
measured Stokes parameters is developed to determine the origin of the excess
PA dispersion. The analysis is applied to sensitive, well-calibrated
polarization observations of PSR B1929+10 and PSR B2020+28. The analysis
clarifies the origin of polarization fluctuations in the emission and reveals
that the excess PA dispersion is caused by the isotropic inflation of the data
point cluster formed by the measured Stokes parameters. The inflation of the
cluster is not consistent with random fluctuations in PA, as might be expected
from random changes in the orientation of the magnetic field lines in the
emission region or from stochastic Faraday rotation in either the pulsar
magnetosphere or the interstellar medium. The inflation of the cluster, and
thus the excess PA dispersion, is attributed to randomly polarized radiation in
the received pulsar signal. The analysis also indicates that orthogonal
polarization modes (OPM) occur where the radio emission is heavily modulated.
In fact, OPM may only occur where the modulation index exceeds a critical value
of about 0.3.