title:
GeV photons from up-scattering of supernova shock breakout X-rays by an
  outside GRB jet

abstract:
  Shock breakout X-ray emission has been reported for the first time from a
supernova connected with a gamma-ray burst, namely GRB060218/SN2006aj. The
gamma-ray emission and the power-law decaying X-ray afterglow are ascribed to a
highly relativistic jet, while the thermal soft X-rays are thought to be
produced when the radiation-dominated shock breaks from the optically thick
stellar wind. We study the inverse Compton emission of the breakout thermal
soft X-rays scattered by relativistic electrons in the jet forward shock, which
is expected to be at larger radii than the breakout shock. This IC emission
produces sub-GeV to GeV photons, which may be detectable by GLAST. The
detection of such GeV photons simultaneously with the supernova shock breakout
emission would give evidence for the presence of a GRB jet ahead of the shock
while the shock is breaking out. The anisotropic scattering between the X-rays
and relativistic electrons may lead to large angle emission outside of the jet
opening angle. This has implications for the detection of GeV photons from
burstless type Ib/c hypernova shock breakout, which due to its more isotropic
emission might be observed with wide-field X-ray cameras such as LOBSTER.


title: Imaging the Dust Trail and Neckline of 67P/Churyumov-Gerasimenko

abstract:
  We report on the results of nearly 10 hours of integration of the dust trail
and neckline of comet 67P/Churyumov-Gerasimenko (67P henceforth) using the Wide
Field Imager at the ESO/MPG 2.2m telescope in La Silla. The data was obtained
in April 2004 when the comet was at a heliocentric distance of 4.7 AU outbound.
67P is the target of the Rosetta spacecraft of the European Space Agency.
Studying the trail and neckline can contribute to the quantification of
mm-sized dust grains released by the comet. We describe the data reduction and
derive lower limits for the surface brightness. In the processed image, the
angular separation of trail and neckline is resolved. We do not detect a coma
of small, recently emitted grains.


title:
A large stellar evolution database for population synthesis studies. II.
  Stellar models and isochrones for an alpha-enhanced metal distribution

abstract:
  [Abridged] We present a large, new set of stellar evolution models and
isochrones for an alpha-enhanced metal distribution typical of Galactic halo
and bulge stars; it represents a homogeneous extension of our stellar model
library for a distribution already presented in Pietrinferni et al.(2004). The
effect of the alpha-element enhancement has been properly taken into account in
the nuclear network, opacity, equation of state and, for the first time, the
bolometric corrections, and color transformations. This allows us to avoid the
inconsistent use - common to all alpha-enhanced model libraries currently
available - of scaled-solar bolometric corrections and color transformations
for alpha-enhanced models and isochrones. We show how bolometric corrections to
magnitudes obtained for the U,B portion of stellar spectra for T_{eff}<=6500K,
are significantly affected by the metal mixture, especially at the higher
metallicities. We also provide complete sets of evolutionary models for
low-mass, He-burning stellar structures covering the whole metallicity range,
to enable synthetic horizontal branch simulations. We compare our database with
several widely used stellar model libraries from different authors, as well as
with various observed color magnitude and color-color diagrams (Johnson-Cousins
BVI and near infrared magnitudes, Stromgren colors) of Galactic field stars and
globular clusters. We also test our isochrones comparing integrated optical
colors and Surface Brightness Fluctuation magnitudes with selected globular
cluster data. We find a general satisfactory agreement with the empirical
constraints.


title: Characterizing stellar populations in spiral disks

abstract:
  It is now possible to measure detailed spectral indices for stellar
populations in spiral disks. We propose to interpret these data using
evolutionary synthesis models computed from the Star Formation Histories
obtained from chemical evolutionary models. We find that this technique is a
powerful tool to discriminate between old and young stellar populations. We
show an example of the power of Integral Field spectroscopy in unveiling the
spatial distribution of populations in a barred galaxy.


title:
Observational constraints on energetic particle diffusion in young SNRs:
  amplified magnetic field and maximum energy

abstract:
  Constraints on the diffusion and acceleration parameters in five young
supernova remnants (SNRs) are derived from the observed thickness of their
X-ray rims, as limited by the synchrotron losses of the highest energy
electrons, assuming uniform and isotropic turbulence. It is shown that the
magnetic field must be amplified up to values between 250 and 500 microGauss in
the case of Cas A, Kepler, and Tycho, or ~ 100 microGauss in the case of SN
1006 and G347.3-0.5. The diffusion coefficient at the highest electron energy
can also be derived from the data, by relating the X-ray energy cutoff to the
acceleration timescale. Values typically between 1 and 10 times the Bohm
diffusion coefficient are found to be required. We also find interesting
constraints on the energy dependence of the diffusion coefficient. This favours
diffusion regimes between the Kraichnan and the Bohm regime, and rejects
turbulence spectrum indices larger than ~ 3/2. Finally, the maximum energy of
the accelerated particles is found to lay between 10^13 and 5 10^13 eV for
electrons, and around Z \times 8 10^14 eV at most for nuclei (or ~ 2.5 times
less if a Bohm diffusion regime is assumed), roughly independently of the
compression ratio assumed at the shock. Even by taking advantage of the
uncertainties on the measured parameters, it appears very difficult for the
considered SNRs in their current stage of evolution to produce protons up to
the knee of the cosmic-ray spectrum, at ~ 3 10^15 eV, and essentially
impossible to accelerate Fe nuclei up to either the ankle at ~ 3 10^18 eV or
the second knee at ~ 5 10^17 eV.


title: Evidence for precession of the isolated neutron star RX J0720.4-3125

abstract:
  The XMM-Newton spectra of the isolated neutron star RX J0720.4-3125 obtained
over 4.5 years can be described by sinusoidal variations in the inferred
blackbody temperature, the size of the emitting area and the depth of the
absorption line with a period of 7.1 +/- 0.5 years, which we suggest to be the
precession period of the neutron star. Precession of a neutron star with two
hot spots of different temperature and size, probably not located exactly in
antipodal positions, may account for the variations in the X-ray spectra,
changes in the pulsed fraction, shape of the light curve and the phase-lag
between soft and hard energy bands observed from RX J0720.4-3125. An
independent sinusoidal fit to published and new pulse timing residuals from a
coherent analysis covering ~12 years yields a consistent period of 7.7 +/- 0.6
years supporting the precession model.


title:
Study of time lags in HETE-2 Gamma-Ray Bursts with redshift: search for
  astrophysical effects and Quantum Gravity signature

abstract:
  The study of time lags between spikes in Gamma-Ray Burst light curves in
different energy bands as a function of redshift may lead to the detection of
effects due to Quantum Gravity. We present an analysis of 15 Gamma-Ray Bursts
with measured redshift, detected by the HETE-2 mission in order to measure time
lags related to astrophysical effects and search for Quantum Gravity signature
in the framework of an extra-dimension string model. The wavelet transform
method is used both for de-noising the light curves and for the detection of
sharp transitions. The use of photon tagged data allows us to consider various
energy ranges and to evaluate systematic effects due to selections and cuts.
The analysis of maxima and minima of the light curves leads to no significant
Quantum Gravity effect. A lower limit at 95% Confidence Level on the Quantum
Gravity scale parameter of 2x10**15 GeV is set.


title:
Analysis of the Luminosity-Stellar Mass-Metallicity Relation in
  cosmological simulations

abstract:
  We study the Luminosity-Metallicity Relation and the Stellar Mass-Metallicity
Relation by performing chemo-dynamical simulations in a cosmological scenario.
Our results predict a tight linear correlation between oxygen chemical
abundance and luminosity for galactic systems up to z=3. The
Luminosity-Metallicity Relation evolves with redshift in such a way that
systems at a given oxygen abundance were ~3 dex brighter at z=3 compared to
local ones, in good agreement with observations. We determin also a
characteristic stellar mass M_c~10^(10.2) M_sun/h above which the Stellar
Mass-Metallicity Relation starts to flatten. We encounter that this mass arises
as a consequence of the hierarchical aggregation of structure in a LCDM
universe and segregates two galactic populations with different astophysical
properties.


title: Bulk Motion of Ultrarelativistic Conical Blazar Jets

abstract:
  Allowing for the conical shape of ultrarelativistic blazar jets with opening
angles of a few degrees on parsec-scales we show that their bulk Lorentz
factors and viewing angles can be much larger than the values usually inferred
by combining their flux variability and proper motion measurements. This is in
accord with our earlier finding that such ultrarelativistic (Lorentz factor,
Gamma > 30) conical jets can reconcile the relatively slow apparent motions of
VLBI knots in TeV blazars with the extremely fast flows implied by their rapid
gamma-ray variability. This jet geometry also implies that de-projected jet
opening angles will typically be significantly underestimated from VLBI
measurements. In addition, de-projected jet lengths will be considerably
overestimated if high Lorentz factors and significant opening angles are not
taken into account.


title:
Active Galactic Nuclei: Unification, Blazar Variability and the Radio
  Galaxy/Cosmology Interface

abstract:
  We first review some basic properties of the most important classes of active
galactic nuclei (AGN), including quasars, blazars, Seyfert galaxies and radio
galaxies. The most commonly accepted type of scheme designed to individually
unify the radio-loud and radio-quiet categories of AGN is based upon three
parameters: black hole mass, accretion rate, and our orientation to the
accretion flow. Some recent evidence from optical microvariability of several
classes of AGN points in favor of a strong unification scheme that unites both
radio-loud and radio-quiet categories. An important question concerning the
nature of blazars and other AGN whose jet emission appears to dominate their
spectral energy distributions involves the velocities of those flows. A variety
of apparently contradictory observations can be reconciled if such flows are
ultrarelativistic but have an opening angle of a few degrees. Radio galaxies
(RGs) were much more numerous at redshifts ~2 than they are today. Combining
this fact with the realization that older RGs at such redshifts are very
difficult to detect, and with cosmological simulations of the growth of
structure in the universe has led us to propose that RG lobes have impacted a
significant fraction of the cosmic web of baryons. These impacts may have
triggered extensive star formation and perhaps even engendered new galaxies;
they also probably played important roles in the spreading of magnetic fields
and heavier elements into the intergalactic medium.


title: Nearby debris disk systems with high fractional luminosity reconsidered

abstract:
  By searching the IRAS and ISO databases we compiled a list of 60 debris disks
which exhibit the highest fractional luminosity values (fd>10^-4) in the
vicinity of the Sun (d<120pc). Eleven out of these 60 systems are new
discoveries. Special care was taken to exclude bogus disks from the sample. We
computed the fractional luminosity values using available IRAS, ISO, and
Spitzer data, and analysed the galactic space velocities of the objects. The
results revealed that stars with disks of high fractional luminosity often
belong to young stellar kinematic groups, providing an opportunity to obtain
improved age estimates for these systems. We found that practically all disks
with fd>5x10^-4 are younger than 100Myr. The distribution of the disks in the
fractional luminosity versus age diagram indicates that (1) the number of old
systems with high fd is lower than was claimed before; (2) there exist many
relatively young disks of moderate fractional luminosity; and (3) comparing the
observations with a current theoretical model of debris disk evolution a
general good agreement could be found.


title:
The multiwavelength afterglow of GRB 050721: a puzzling rebrightening
  seen in the optical but not in the X-ray

abstract:
  Context. GRB050721 was detected by Swift and promptly followed-up, in the
X-ray by Swift itself and, in the optical band, by the VLT operated, for the
first time, in rapid response mode. A multiwavelength monitoring campaign was
performed in order to study its afterglow behavior. Aims. We present the
analysis of the early and late afterglow emission in both the X-ray and optical
bands, as observed by Swift, a robotic telescope, and the VLT. We compare early
observations with late afterglow observations obtained with Swift and the VLT
in different bands in order to constrain the density of the medium in which the
fireball is expanding. Methods. We have analyzed both the X-ray and the optical
light curves and compared the spectral energy distribution of the afterglow at
two different epochs. Results. We observed an intense rebrightening in the
optical band at about one day after the burst which was not seen in the X-ray
band. This is the first observation of a GRB afterglow in which a rebrightening
is observed in the optical but not in the X-ray band. The lack of detection in
X-ray of such a strong rebrightening at lower energies can be described with a
variable external density profile. In such a scenario, the combined X-ray and
optical observations allow us to derive the matter density at 10^15 cm from the
burst. This is about a factor of 10 higher than in the inner region.


title:
Jet-dominated advective systems: radio and X-ray luminosity dependence
  on the accretion rate

abstract:
  We present a novel method to measure the accretion rate of radio emitting
X-ray binaries (XRBs) and active galactic nuclei (AGN) independently of the
X-ray luminosity. The radio emission of the jet is used as a tracer for the
accretion rate and is normalised using sources of known accretion rates: island
state neutron stars and efficiently radiating black holes close to a state
transition. We show that the radio power in black holes and neutron stars is
comparable for a given mass accretion rate and verify empirically the assumed
analytic scaling of the radio luminosity with accretion rate. As our accretion
measure is independent of the X-ray luminosities, we can search for radiatively
inefficient accretion in black holes by comparing the X-ray luminosities with
the accretion rate in XRBs and AGN. While the X-ray luminosity of efficiently
radiating objects scales linearly with accretion rate, the scaling of hard
state black holes is quadratical, in agreement with theoretical models. We show
that the turnover from the inefficient quadratic scaling to the linear scaling
has to occur at accretion rates of 1-10 % Eddington both in XRBs and AGN. The
comparison of both accretion states supports the idea that in a black hole in
the hard state some accretion power is advected into the black hole while the
jet power exceeds the X-ray luminosity: these are therefore jet-dominated
advective systems.


title:
Velocity dispersion, mass and the luminosity function of the fossil
  cluster RX J1416.4+2315

abstract:
  We study the properties of the fossil cluster RX J1416.4+2315 through g' and
i'-band imaging and spectroscopy of 25 member galaxies. The system is at a mean
redshift of 0.137 and has a velocity dispersion of 584 km s^-1. Superimposed
onto one quadrant of the cluster field there is a group of five galaxies at a
mean redshift of 0.131, which, if included as part of the cluster, increases
the velocity dispersion to 846 km/s. The central object of RX J1416.4+2315 is a
normal elliptical galaxy, with no cD envelope. The luminosity function of the
system, estimated by the number counts, and statistical background correction,
in the range -22.6< M_g'< -16.6, is well fitted by a Schechter function with
M_g'^* = -21.2 +/- 0.8 and alpha = -1.2 +/- 0.2 (H_0 = 70 km s^-1 Mpc^-1,
Omega_M=0.3, Omega_Lambda=0.7). The luminosity function obtained from the
spectroscopically confirmed members in both g' and i' bands agrees with the
photometric results. The mass of the system, M 0.9 \times 10^14 h^-1_70 M_sun,
its M/L of 445 h_70 M_sun/L_B_sun and L_X of 11 10^43 h^-2_70 ergs s^-1
(bolometric) suggest that this system is the second example of known fossil
cluster, after RX J1552.2+2013, confirmed in the literature.


title: FH Leonis, the first dwarf nova member of a multiple star system?

abstract:
  Sudden brightenings of HD 96273 or BD+07 2411B were observed with the
HIPPARCOS satellite in 1992,which still require a convincing explanation. A new
analysis of all known data of these two stars is given, including additional
information on the Balmer line equivalent widths. The brightenings can be
explained as SU UMa type dwarf nova outbursts, superimposed on the combined
light of two normal F and G type main sequence stars. Since the hypothetical
dwarf nova turns out to be located at the same distance as HD 96273 and BD+07
2411B, we possibly see here the first case of a cataclysmic variable as a
member of a multiple star system. Questions on history and evolution, as well
as possible ways to confirm this interpretation, are briefly outlined.


title:
New DQ white dwarfs in the Sloan Digital Sky Survey DR4: confirmation of
  two sequences

abstract:
  Using photometric selection criteria, and in a final step visual inspection
of spectra, we find 65 DQ white dwarfs in the Data Release 4 of the Sloan
Digital Sky Survey. 37 of these are new identifications, three more are
reclassified DQ from DC, the other 25 have been described as DQ before in the
literature. We derive effective temperatures and carbon abundances for 60 of
these stars. The results confirm the main conclusions of Dufour et al.(2005).
The majority of stars defines a clear sequence in the C abundance vs. Teff
diagram, with high abundances found at high Teff and vice versa. We also
confirm with high significance a second sequence with an abundance about 1 dex
higher at the same Teff, and discuss the nature and possible origin of the
high-C sequence.


title:
Asteroseismic inferences on GW Vir variable stars in the frame of new PG
  1159 evolutionary models

abstract:
  An adiabatic, nonradial pulsation study of GW Vir stars is presented. The
pulsation calculations are based on PG1159 evolutionary sequences with
different stellar massess artificially derived from a full evolutionary
sequence of 0.5895 Mo that has been computed taking into account the
evolutionary history of the progenitor star. The artificial sequences were
constructed by appropriately scaling the stellar mass of the 0.5895 Mo sequence
well before the models reach the low-luminosity, high-gravity stage of the GW
Vir domain. We compute g-mode pulsation periods appropriate to GW Vir variable
stars. The implications for the mode-trapping properties of our PG 1159 models
are discussed at length. We found that the mode-trapping features
characterizing our PG 1159 models are mostly fixed by the stepped shape of the
core chemical profile left by prior convective overshooting. This is
particularly true at least for the range of periods observed in GW Vir stars.
In addition, we make asteroseismic inferences about the internal structure of
the GW Vir stars PG 1159-035, PG 2131+066, PG 1707+427 and PG 0122+200.


abstract:
  This submission has been removed by arXiv administrators because it is a
duplicate of astro-ph/0603735.


title: Understanding Infrared Galaxy Populations: the SWIRE Legacy Survey

abstract:
  We discuss spectral energy distributions, photometric redshifts, redshift
distributions, luminosity functions, source-counts and the far infrared to
optical luminosity ratio for sources in the SWIRE Legacy Survey. The spectral
energy distributions of selected SWIRE sources are modelled in terms of a
simple set of galaxy and quasar templates in the optical and near infrared, and
with a set of dust emission templates (cirrus, M82 starburst, Arp 220
starburst, and AGN dust torus) in the mid infrared. The optical data, together
with the IRAC 3.6 and 4.5 mu data, have been used to determine photometric
redshifts. For galaxies with known spectroscopic redshifts there is a notable
improvement in the photometric redshift when the IRAC data are used, with a
reduction in the rms scatter from 10% in (1+z) to 5%. While further
spectroscopic data are needed to confirm this result, the prospect of
determining good photometric redshifts for the 2 million extragalactic objects
in SWIRE is excellent. The distribution of the different infrared sed types in
the L{ir}/L{opt} versus L{ir} plane, where L{ir} and L{opt} are the infrared
and optical bolometric luminosities, is discussed. Source-counts at 24, 70 and
160 mu are discussed, and luminosity functions at 3.6 and 24 mu are presented.


title: Swift XRT Observations of the Afterglow of XRF 050416A

abstract:
  Swift discovered XRF 050416A with the BAT and began observing it with its
narrow field instruments only 64.5 s after the burst onset. Its very soft
spectrum classifies this event as an X-ray flash. The afterglow X-ray emission
was monitored up to 74 days after the burst. The X-ray light curve initially
decays very fast, subsequently flattens and eventually steepens again, similar
to many X-ray afterglows. The first and second phases end about 172 and 1450 s
after the burst onset, respectively. We find evidence of spectral evolution
from a softer emission with photon index Gamma ~ 3.0 during the initial steep
decay, to a harder emission with Gamma ~ 2.0 during the following evolutionary
phases. The spectra show intrinsic absorption in the host galaxy. The
consistency of the initial photon index with the high energy BAT photon index
suggests that the initial phase of the X-ray light curve may be the low-energy
tail of the prompt emission. The lack of jet break signatures in the X-ray
afterglow light curve is not consistent with empirical relations between the
source rest-frame peak energy and the collimation-corrected energy of the
burst. The standard uniform jet model can give a possible description of the
XRF 050416A X-ray afterglow for an opening angle larger than a few tens of
degrees, although numerical simulations show that the late time decay is
slightly flatter than expected from on-axis viewing of a uniform jet. A
structured Gaussian-type jet model with uniform Lorentz factor distribution and
viewing angle outside the Gaussian core is another possibility, although a full
agreement with data is not achieved with the numerical models explored.


title:
Spitzer 4.5 micron Luminosity-Metallicity and Mass-Metallicity Relations
  for Nearby Dwarf Irregular Galaxies

abstract:
  For a sample of 25 dwarf irregular galaxies with distances D < 5 Mpc and
measured oxygen abundances, we present results derived from stellar masses and
galaxy luminosities from near-infrared imaging with IRAC on the Spitzer Space
Telescope. We have constructed the appropriate luminosity-metallicity (L-Z) and
mass-metallicity (M-Z) relations, and compared these relations with their
corresponding relations from the Sloan Digital Sky Survey (SDSS). We obtain the
following results. 1. The dispersion in the near-infrared L-Z relation is
reduced with respect to the dispersion in the optical L-Z relation, which
agrees with expectations for reduced variations of stellar mass-to-light ratios
at longer wavelengths compared to optical wavelengths. 2. The dispersion in the
optical L-Z relation is similar over approximately 11 mag in optical
luminosity. 3. With our constructed M-Z relation, we have extended the SDSS M-Z
relation to lower masses by about 2.5 dex in stellar mass. 4. The dispersion in
the M-Z relation appears to be comparable over a range of 5.5 dex in stellar
mass.


title: Newtonian and Pseudo-Newtonian Hill Problem

abstract:
  A pseudo-Newtonian Hill problem based on the Paczynski-Wiita pseudo-Newtonian
potential that reproduces general relativistic effects is presented and
compared with the usual Newtonian Hill problem. Poincare maps, Lyapunov
exponents and fractal escape techniques are employed to study bounded and
unbounded orbits. In particular we consider the systems composed by Sun, Earth
and Moon and composed by the Milky Way, the M2 cluster and a star. We find that
some pseudo-Newtonian systems - including the M2 system - are more stable than
their Newtonian equivalent.


title:
Magnetic Field Decay and Period Evolution of Anomalous X-Ray Pulsars in
  the Context of Quark Stars

abstract:
  We discuss a model wherein soft gamma-ray repeaters (SGRs), anomalous X-ray
pulsars (AXPs), and radio quiet isolated neutron stars (RQINSs) are all compact
objects exhibiting superconductivity, namely color-flavor locked quark stars.
In particular we calculate the magnetic field decay due to the expulsion of
spin-induced vortices from the star's superfluid-superconducting interior, and
the resultant spin-down rate. We find that, for initial parameters
characteristic of AXPs/SGRs ($10^{13}<B<10^{14}~\rm{G}$; $3<P<12~\rm{s}$), the
magnetic field strengths and periods remain unchanged within a factor of two
for timescales of the order of $5\times 10^{5} - 5\times 10^{7}~\rm{yrs}$ given
a quark star of radius $10~\rm{km}$. Within these timescales, we show that the
observed period clustering in RQINSs can be explained by compactness, as well
as calculate how the magnetic field and period evolve in a manner concurrent
with RQINS observations.


title:
Quasars Probing Quasars I: Optically Thick Absorbers Near Luminous
  Quasars

abstract:
  With close pairs of quasars at different redshifts, a background quasar
sightline can be used to study a foreground quasar's environment in absorption.
We search 149 moderate resolution background quasar spectra, from Gemini, Keck,
the MMT, and the SDSS to survey Lyman Limit Systems (LLSs) and Damped Ly-alpha
systems (DLAs) in the vicinity of 1.8 < z < 4.0 luminous foreground quasars. A
sample of 27 new quasar-absorber pairs is uncovered with column densities, 17.2
< log (N_HI/cm^2) < 20.9, and transverse (proper) distances of 22 kpc/h < R <
1.7 Mpc/h, from the foreground quasars. If they emit isotropically, the implied
ionizing photon fluxes are a factor of ~ 5-8000 times larger than the ambient
extragalactic UV background over this range of distances. The observed
probability of intercepting an absorber is very high for small separations: six
out of eight projected sightlines with transverse separations R < 150 kpc/h
have an absorber coincident with the foreground quasar, of which four have log
N_HI > 10^19. The covering factor of log N_HI > 10^19 absorbers is thus ~ 50 %
(4/8) on these small scales, whereas < 2% would have been expected at random.
There are many cosmological applications of these new sightlines: they provide
laboratories for studying fluorescent Ly-alpha recombination radiation from
LLSs, constrain the environments, emission geometry, and radiative histories of
quasars, and shed light on the physical nature of LLSs and DLAs.


title: Quark deconfinement in neutron star cores: The effects of spin-down

abstract:
  We study the role of spin-down in driving quark deconfinement in the high
density core of isolated neutron stars. Assuming spin-down to be solely due to
magnetic braking, we obtain typical timescales to quark deconfinement for
neutron stars that are born with Keplerian frequencies. Employing different
equations of state (EOS), we determine the minimum and maximum neutron star
masses that will allow for deconfinement via spin-down only. We find that the
time to reach deconfinement is strongly dependent on the magnetic field and
that this time is least for EOS that support the largest minimum mass at zero
spin, unless rotational effects on stellar structure are large. For a fiducial
critical density of $5\rho_0$ for the transition to the quark phase
($\rho_0=2.5\times10^{14}$g/cm$^3$ is the saturation density of nuclear
matter), we find that neutron stars lighter than $1.5M_{\odot}$ cannot reach a
deconfined phase. Depending on the EOS, neutron stars of more than
$1.5M_{\odot}$ can enter a quark phase only if they are spinning faster than
about 3 milliseconds as observed now, whereas larger spin periods imply that
they are either already quark stars or will never become one.


title: Very Cool Close Binaries

abstract:
  We present new observations of cool <6000K and low mass <1Msun binary systems
that have been discovered by searching several modern stellar photometric
databases. The search has led to a factor of 10 increase in the number of known
cool close eclipsing binary systems.


title: Interstellar Dust at the Magnetic Wall of the Heliosphere. II

abstract:
  Several sets of data show that small interstellar grains captured in
interstellar magnetic fields draped over the heliosphere appear to polarize the
light of nearby stars. The maximum polarization direction is offset in ecliptic
longitude by about +35 from the upwind direction, and the polarization peak is
enhanced for stars near the ecliptic plane. A band of weak polarization
stretches through the southern ecliptic hemisphere to the downwind direction.
The interstellar field at the heliosphere is directed towards l=105 deg,
forming an angle of about 75 deg. with the inflowing gas. Grain alignment is
stable in the low density LIC, and is disrupted about 600 times more slowly
than in dense clouds. The polarization vanishes where the outer heliosheath
magnetic fields become tangled or reconnect. The dust in the local cloud
appears to be primarily olivines. The distribution of polarization depends on
the solar cycle phase.


title:
Does Sgr A* Have an Intrinsic Magnetic Moment Instead of an Event
  Horizon?

abstract:
  In previous work we have developed a general relativistic, magnetospheric
eternally collapsing object (MECO) model for black hole candidates and shown
that the model is consistent with broad band spectral and luminosity
characteristics and accounts for the radio/x-ray luminosity correlations of
both galactic black hole candidates (GBHC) and active galactic nuclei (AGN). We
show here that the MECO model can: a) satisfy the luminosity constraints that
have been claimed as proof of an event horizon for Sgr A*, b) reconcile the low
bolometric luminosity with the expected Bondi accretion rate for Sgr A* by
means of a magnetic propeller driven outflow, c) account for the Sgr A* NIR and
x-ray luminosities, the general characteristics of its broad band spectrum, and
the sequence of flares in different spectral ranges as well as the pattern of
its observed orthogonal polarizations. We also include specific predictions for
images that may be obtained in sub-millimeter to NIR wavelengths in the near
future. Additional future tests for the presence of an intrinsic magnetic
moment for Sgr A* will require global solutions for electron density and
magnetic field distributions in a Bondi accretion flow into a compact, rotating
magnetic dipole. These will provide for definitive tests in the form of
detailed calculations of spectral and spatial luminosity distributions and
polarization maps for direct comparison with high resolution images of Sgr A*.


title:
White Dwarf - Red Dwarf Systems Resolved with the Hubble Space
  Telescope: I. First Results

abstract:
  First results are presented for a Hubble Space Telescope Advanced Camera for
Surveys snapshot study of white dwarfs with likely red dwarf companions. Of 48
targets observed and analyzed so far, 27 are totally or partially resolved into
two or more components, while an additional 15 systems are almost certainly
unresolved binaries. These results provide the first direct empirical evidence
for a bimodal distribution of orbital separations among binary systems
containing at least one white dwarf.


title:
Testing Low-Mass Stellar Models: Three New Detached Eclipsing Binaries
  below 0.75 Msun

abstract:
  Full tests to stellar models below 1 Msun have been hindered until now by the
scarce number of precise measurements of the stars' most fundamental
parameters: their masses and radii. With the current observational techniques,
the required precision to distinguish between different models (errors < 2-3 %)
can only be achieved using detached eclipsing binaries where 1) both stars are
similar in mass, i.e. q = M1/M2 ~ 1.0, and 2) each star is a main sequence
object below 1 Msun.
  Until 2003 only three such binaries had been found and analyzed in detail.
Two new systems were published in 2005 (Creevey et al.; Lopez-Morales & Ribas),
almost doubling the previous number of data points. Here we present preliminary
results for 3 new low-mass detached eclipsing binaries. These are the first
studied systems from our sample of over 41 new binaries (Shaw & Lopez-Morales,
this proceedings). We also provide an updated comparison between the
Mass-Radius and the Mass-Teff relations predicted by the models and the
observational data from detached eclipsing binaries.


title:
Earth azimuth effect in the bank of search templates for an all sky
  search of the continuous gravitational wave

abstract:
  We study the problem of all sky search in reference to continuous
gravitational wave (CGW) whose wave-form are known in advance. We employ the
concept of Fitting Factor and study the variation in the bank of search
templates with different Earth azimuth at t=0. We found that the number of
search templates varies significantly. Hence, accordingly, the computational
demand for the search may be reduced up to two orders by time shifting the
data.


title: A Century of Cosmology

abstract:
  In the century since Einstein's anno mirabilis of 1905, our concept of the
Universe has expanded from Kapteyn's flattened disk of stars only 10 kpc across
to an observed horizon about 30 Gpc across that is only a tiny fraction of an
immensely large inflated bubble. The expansion of our knowledge about the
Universe, both in the types of data and the sheer quantity of data, has been
just as dramatic. This talk will summarize this century of progress and our
current understanding of the cosmos.


title:
Formation of Spiral-Arm Spurs and Bound Clouds in Vertically Stratified
  Galactic Gas Disks

abstract:
  (Abridged) We investigate the growth of spiral-arm substructure in vertically
stratified, self-gravitating, galactic gas disks, using local numerical MHD
simulations. Our new models extend our previous 2D studies (Kim & Ostriker
2002), which showed that a magnetized spiral shock in a thin disk can undergo
magneto-Jeans instability (MJI), resulting in interarm spur structures and
massive fragments. Similar spur features have recently been seen in
high-resolution observations of several galaxies. Here, we consider two sets of
numerical models: 2D models that use a thick-disk gravitational kernel, and 3D
runs with explicit vertical stratification. When disks are sufficiently
magnetized and self-gravitating, the result in both sorts of models is the
growth of spiral-arm substructure similar to that in our previous razor-thin
models. Reduced self-gravity in thick disks increases the spur spacing to ~10
times the Jeans length at the arm peak. Bound clouds that form from spur
fragmentation have masses ~(1-3)x10^7 Msun each, a factor ~3-8 times larger
than in razor-thin models with the same gas surface density and stellar spiral
arm strength. We find that unmagnetized or weakly magnetized 2D models are
unstable to the wiggle instability (WI) previously identified by Wada & Koda
(2004), and proposed as a potential spur- and clump-forming mechanism.
However,our fully 3D models do not show this effect. Non-steady motions and
strong vertical shear prevent coherent vortical structures from forming,
evidently suppressing the WI that appears in 2D (isothermal) runs. We also find
no clear traces of Parker instability in the nonlinear spiral arm substructures
that emerge (in self-gravitating models), although conceivably Parker modes may
help seed the MJI at early stages since azimuthal wavelengths are similar.


title:
A self-consistent model of isolated neutron stars: the case of the X-ray
  pulsar RX J0720.4-3125

abstract:
  We present a unified explanation for the observed properties of the isolated
neutron star RX J0720.4-3125 by obtaining, for the first time, a
self-consistent model that accounts simultaneously for the observed X-ray
spectrum and optical excess, the pulsed fraction, the observed spectral feature
around 0.3 keV, and the long--term spectral evolution. By fitting the
parameters of our realistic self--consistent models to all archival XMM--Newton
observations and available optical data, we show that all observed properties
are consistent with a normal neutron star with a proper radius of about 12 km,
a temperature at the magnetic pole of about 100 eV and a magnetic field
strength of 2-3 x 10^{13} G, with no need to invoke additional emission and
absorption components nor exotic internal composition. The observed variability
of the effective temperature, strength of the spectral feature, and pulsed
fraction are in good agreement with the predictions of our model in which the
star is subject to free precession, producing changes in the angle between the
magnetic field and the rotation axis of tens of degrees with a periodicity of 7
years, as pointed out by other authors on the basis of phenomenological models.
In addition to the evidence of internal toroidal components, we also find
strong evidence of non-dipolar magnetic fields, since all spectral properties
are better reproduced with models with strong quadrupolar components.


title: Observational constraints and cosmological parameters

abstract:
  I discuss the extraction of cosmological parameter constraints from the
recent WMAP 3-year data, both on its own and in combination with other data.
The large degeneracies in the first year data can be largely broken with the
third year data, giving much better parameter constraints from WMAP alone. The
polarization constraint on the optical depth is crucial to obtain the main
results, including n_s < 1 in basic six-parameter models. Almost identical
constraints can also be obtained using only temperature data with a prior on
the optical depth. I discuss the modelling of secondaries when extracting
parameter constraints, and show that the effect of CMB lensing is about as
important as SZ and slightly increases the inferred value of the spectral
index. Constraints on correlated matter isocurvature modes are not radically
better than before, and the data is consistent with a purely adiabatic
spectrum. Combining WMAP 3-year data with data from the Lyman-alpha forest
suggests somewhat higher values for sigma_8 than from WMAP alone.


title:
Photometric studies of three multiperiodic Beta Cephei stars: Beta CMa,
  15 CMa and KZ Mus

abstract:
  We have carried out single and multi-site photometry of the three Beta Cephei
stars Beta and 15 CMa as well as KZ Mus. For the two stars in CMa, we obtained
270 h of measurement in the Stromgren uvy and Johnson V filters, while 150 h of
time-resolved Stromgren uvy photometry was acquired for KZ Mus. All three stars
are multi-periodic variables, with three (Beta CMa) and four (15 CMa, KZ Mus)
independent pulsation modes. Two of the mode frequencies of 15 CMa are new
discoveries and one of the known modes showed amplitude variations over the
last 33 years. Taken together, this explains the star's diverse behaviour
reported in the literature fully.
  Mode identification by means of the amplitude ratios in the different
passbands suggests one radial mode for each star. In addition, Beta CMa has a
dominant l=2 mode while its third mode is nonradial with unknown l. The
nonradial modes of 15 CMa, which are l <= 3, form an almost equally split
triplet that, if physical, would imply that we see the star under an
inclination angle larger than 55 degrees. The strongest nonradial mode of KZ
Mus is l=2, followed by the radial mode and a dipole mode. Its weakest known
mode is nonradial with unknown l, confirming previous mode identifications for
the star's pulsations.
  The phased light curve for the strongest mode of 15 CMa has a descending
branch steeper than the rising branch. A stillstand phenomenon during the rise
to maximum light is indicated. Given the low photometric amplitude of this
nonradial mode this is at first sight surprising, but it can be explained by
the mode's aspect angle.


title: Synthetic Super AGB Stars

abstract:
  We describe our first attempt at modelling nucleosynthesis in massive AGB
stars which have undergone core carbon burning, the super-AGB stars. We fit a
synthetic model to detailed stellar evolution models in the mass range
9<=M/Msun<=11.5 (Z=0.02), and extrapolate these fits to the end of the AGB. We
determine the number of thermal pulses and AGB lifetime as a function of mass
and mass-loss prescription. Our preliminary nucleosynthesis calculations show
that, for a reasonable mass-loss rate, the effect of hot-bottom burning in
super-AGB stars on the integrated yield of a stellar population is not large.
There are many uncertainties, such as mass-loss and convective overshooting,
which prevent accurate yield calculations. However, as potential progenitors of
electron-capture supernovae, these stars may contribute 7% of non-type-Ia
supernovae.


title: Unveiling supergiant fast X-ray transient sources with INTEGRAL

abstract:
  Supergiant high mass X-ray binaries (SGXBs) are believed to be rare objects,
as stars in the supergiant phase have a very short lifetime and to date only
about a dozen of them have been discovered. They are known to be persistent and
bright X-ray sources. INTEGRAL is changing this classical picture as its
observations are revealing the presence of a new subclass of SGXBs which have
been labelled as supergiant fast X-ray transients (SFXTs) as they are strongly
characterized by fast X-ray outbursts lasting less than a day, typically a few
hours. We report on IBIS detections of newly discovered fast X-ray outbursts
from 10 sources, four of which have been recently optically identified as
supergiant high mass X-ray binaries. In particular for one of them, IGR
J11215-5952, we observe fast X-ray transient behaviour for the first time. The
remaining six sources (IGR J16479-4514, IGR J16418-4532, XTE J1743-363, IGR
J16195-4945=AX J161929-4945, AX J1749.1-2733, IGR J17407-2808) are still
unclassified, however they can be considered as candidate SFXTs because of
their similarity to the known SFXTs.


title:
Population synthesis of s-process element enhanced stars: Constraining
  the 13C efficiency

abstract:
  We study s-process element abundance ratios in stars by carrying out stellar
population synthesis, using a rapid synthetic stellar evolution code which
includes an up-to-date treatment of AGB nucleosynthesis and evolution. In
contrast to other studies, we find that a large spread in the 13C efficiency
parameter (13C_eff) is not needed to explain the observed spread in the ratios
of heavy s-process to light s-process elements ([hs/ls]), but this comes
naturally from the range of different initial stellar masses and their time
evolution. As a result, the 13C efficiency needed for fitting most stars in the
galactic disk is constrained to 1 < 13C_eff < 2.5. In the same fashion we also
study the [Pb/Ce] ratios of lead stars and find out that for low metallicities
13C_eff is approximately 0.5.


title: Searching for a gigamaser in APM08279+5255, and other short stories

abstract:
  Bolometer arrays on large antennas at high, dry sites have unveiled a dusty
population of massive, luminous galaxies - submillimetre galaxies, or SMGs -
which make a significant contribution to the star-formation rate density at z >
1. The most crucial piece of information required to derive the history of
obscured star formation is the redshift distribution of this galaxy population,
N(z), which breaks degeneracies in the models and allows the mass and dynamics
of the galaxies to be explored via high-resolution three-dimensional imaging in
CO and by determining their level of clustering. Many SMGs are extremely faint,
optically; some have no plausible counterparts, even in the IR, making the
determination of an unbiased N(z) very difficult. The arrival of Herschel and
next-generation ground-based submm cameras will likely exacerbate this
so-called `redshift deadlock'. Here, we report the first test of a new method
for determining redshifts, based on the observed dependence of maser and IR
luminosities. We have searched the dusty, lensed, hyperluminous quasar,
APM08279+5255, for the 1612-, 1665- and 1667-MHz hydroxyl lines as well as the
22-GHz water line. At z = 3.9 these are shifted to 329, 340 and 4,538MHz. Our
relatively shallow test data reveal no convincing maser activity but we set a
meaningful constraint on the OH maser luminosity and we approach the expected
thermal noise levels, meaning progress is possible. As an aside, we present
deep new submm and radio imaging of this field. Using a simple shift-and-add
technique we uncover a new submm galaxy, conceivably at the redshift of
APM08279+5255.


title:
A Comprehensive Study of 2 000 Narrow Line Seyfert 1 Galaxies from the
  Sloan Digital Sky Survey: I. The Sample

abstract:
  This is the first paper in a series dedicated to the study of the
emission-line and continuum properties of narrow line Seyfert 1 galaxies
(NLS1s). We carried out a systematic search for NLS1s from objects assigned as
``QSOs'' or ``galaxies'' in the spectroscopic sample of the Sloan Digital Sky
Survey Data Release 3 (SDSS DR3) by a careful modeling of their emission lines
and continua. The result is a uniform sample comprising $\sim 2~000$ NLS1. This
sample dramatically increases the number of known NLS1 by a factor of $\sim 10$
over previous compilations. This paper presents the parameters of the prominent
emission lines and continua, which were measured accurately with typical
uncertainties $<10%$. Taking advantage of such an unprecedented large and
uniform sample with accurately measured spectral parameters, we carried out
various statistical analysis, some of which were only possible for the first
time (abbreviated).


title:
New methods for approximating general relativity in numerical
  simulations of stellar core collapse

abstract:
  We review various approaches to approximating general relativistic effects in
hydrodynamic simulations of stellar core collapse and post-bounce evolution.
Different formulations of a modified Newtonian gravitational potential are
presented. Such an effective relativistic potential can be used in an otherwise
standard Newtonian hydrodynamic code. An alternative approximation of general
relativity is the assumption of conformal flatness for the three-metric, and
its extension by adding second post-Newtonian order terms. Using a code which
evolves the coupled system of metric and fluid equations, we apply the various
approximation methods to numerically simulate axisymmetric models for the
collapse of rotating massive stellar cores. We compare the collapse dynamics
and gravitational wave signals (which are extracted using the quadrupole
formula), and thereby assess the quality of the individual approximation
method. It is shown that while the use of an effective relativistic potential
already poses a significant improvement compared to a genuinely Newtonian
approach, the two conformal-flatness-based approximation methods yield even
more accurate results, which are qualitatively and quantitatively very close to
those of a fully general relativistic code even for rotating models which
almost collapse to a black hole.


title: Will black holes eventually engulf the universe?

abstract:
  The Babichev-Dokuchaev-Eroshenko model for the accretion of dark energy onto
black holes has been extended to deal with black holes with non-static metrics.
The possibility that for an asymptotic observer a black hole with large mass
will rapidly increase and eventually engulf the Universe at a finite time in
the future has been studied by using reasonable values for astronomical
parameters. It is concluded that such a phenomenon is forbidden for all black
holes in quintessential cosmological models.


title: The GLAST mission, LAT and GRBs

abstract:
  The GLAST Large Area Telescope (LAT) is the next generation satellite
experiment for high-energy gamma-ray astronomy. It is a pair conversion
telescope built with a plastic anticoincidence shield, a segmented CsI
electromagnetic calorimeter, and the largest silicon strip tracker ever built.
It will cover the energy range from 30 MeV to 300 GeV, shedding light on many
issues left open by its predecessor EGRET. One of the most exciting science
topics is the detection and observation of gamma-ray bursts (GRBs). In this
paper we present the work done so far by the GRB LAT science group in studying
the performance of the LAT detector to observe GRBs. We report on the
simulation framework developed by the group as well as on the science tools
dedicated to GRBs data analysis. We present the LAT sensitivity to GRBs
obtained with such simulations, and, finally, the general scheme of GRBs
detection that will be adopted on orbit.


title: Challenges in optics for Extremely Large Telescope instrumentation

abstract:
  We describe and summarize the optical challenges for future instrumentation
for Extremely Large Telescopes (ELTs). Knowing the complex instrumental
requirements is crucial for the successful design of 30-60m aperture
telescopes. After all, the success of ELTs will heavily rely on its
instrumentation and this, in turn, will depend on the ability to produce large
and ultra-precise optical components like light-weight mirrors, aspheric
lenses, segmented filters, and large gratings. New materials and manufacturing
processes are currently under study, both at research institutes and in
industry. In the present paper, we report on its progress with particular
emphasize on volume-phase-holographic gratings, photochromic materials,
sintered silicon-carbide mirrors, ion-beam figuring, ultra-precision surfaces,
and free-form optics. All are promising technologies opening new degrees of
freedom to optical designers. New optronic-mechanical systems will enable
efficient use of the very large focal planes. We also provide exploratory
descriptions of "old" and "new" optical technologies together with suggestions
to instrument designers to overcome some of the challenges placed by ELT
instrumentation.


title: Superclusters of galaxies from the 2dF redshift survey. I. The catalogue

abstract:
  We use the 2dF Galaxy Redshift Survey data to compile catalogues of
superclusters for the Northern and Southern regions of the 2dFGRS, altogether
543 superclusters at redshifts 0.009 < z < 0.2. We analyse methods of compiling
supercluster catalogues and use results of the Millennium Simulation to
investigate possible selection effects and errors. We find that the most
effective method is the density field method using smoothing with an
Epanechnikov kernel of radius 8 Mpc/h. We derive positions of the highest
luminosity density peaks and find the most luminous cluster in the vicinity of
the peak, this cluster is considered as the main cluster and its brightest
galaxy the main galaxy of the supercluster. In catalogues we give equatorial
coordinates and distances of superclusters as determined by positions of their
main clusters. We also calculate the expected total luminosities of the
superclusters.


title:
Turbulent diffusion in protoplanetary discs: the effect of an imposed
  magnetic field

abstract:
  We study the effect of an imposed vertical magnetic field on the turbulent
mass diffusion properties of magnetorotational turbulence in protoplanetary
discs. It is well-known that the effective viscosity generated by the
turbulence depends strongly on the magnitude of such an external field. In this
letter we show that the turbulent diffusion of the flow also grows, but that
the diffusion coefficient does not rise with increasing vertical field as fast
as the viscosity does. The vertical Schmidt number, i.e. the ratio between
viscosity and vertical diffusion, can be close to 20 for high field magnitudes,
whereas the radial Schmidt number is increased from below unity to around 3.5.
Our results may have consequences for the interpretation of observations of
dust in protoplanetary discs and for chemical evolution modelling of these
discs.


title: Fragmentation of star-forming clouds enriched with the first dust

abstract:
  The thermal and fragmentation properties of star-forming clouds have
important consequences on the corresponding characteristic stellar mass. The
initial composition of the gas within these clouds is a record of the
nucleosynthetic products of previous stellar generations. In this paper we
present a model for the evolution of star-forming clouds enriched by metals and
dust from the first supernovae, resulting from the explosions of metal-free
progenitors with masses in the range 12 - 30 Msun and 140 - 260 Msun. Using a
self-consistent approach, we show that: (i) metals depleted onto dust grains
play a fundamental role, enabling fragmentation to solar or sub-solar mass
scales already at metallicities Zcr = 10^{-6} Zsun; (ii) even at metallicities
as high as 10^{-2} Zsun, metals diffused in the gas-phase lead to fragment mass
scales which are ~ 100 Msun; (iii) C atoms are strongly depleted onto amorphous
carbon grains and CO molecules so that CII plays a minor role in gas cooling,
leaving OI as the main gas-phase cooling agent in low-metallicity clouds. These
conclusions hold independently of the assumed supernova progenitors and suggest
that the onset of low-mass star formation is conditioned to the presence of
dust in the parent clouds.


title:
Gravitational effects on the high energy emission of accreting black
  holes

abstract:
  We extend the investigation of general relativistic effects on the observed
X-ray continuum of Kerr black holes in the context of the light bending model
(Miniutti & Fabian, 2004). Assuming a ring-like illuminating source,
co-rotating with the underlying accretion disk, we study the shape and
normalisation of the primary and disc reflected continuum as well as the
dependence of the observed spectrum on the line of sight for various source
heights and radii. These calculations are performed using Monte-Carlo methods
to compute the angle dependent reflection spectrum from the disc. The effects
of general relativity are illustrated by a comparison with Newtonian and
Special Relativity calculations. We find that relativistic distortions can
strongly affect the shape of the reflected spectrum. Light bending can
dramatically increase the observable reflected flux and reduce the primary
emission. In addition, multiple reflections due to the reflected photons
deflected toward the disc can alter significantly the shape of the spectrum
above 10 keV. Large variations of the ring radius at constant height can lead
to an (unobserved) anti-correlation between primary and reflected flux. In
another side, the variability behaviour of several sources can be reproduced if
the ring source radius is small (<5 r_g), and its height varies by a large
factor. In particular, a non-linear flux-flux relation, similar to that
observed in several sources, can be produced. We compare our model with the
flux-flux plot of NGC4051, and find an agreement for low inclination angles
(<20 deg.), ring source radius <3 r_g and a height varying between 0.5 to 10
r_g.


title: The Ultraluminous X-ray Source in Holmberg IX and its Environment

abstract:
  We present optical observations of an ultraluminous X-ray source (ULX) in
Holmberg IX, a dwarf galaxy near M81. The ULX has an average X-ray luminosity
of some 10^{40} erg/s. It is located in a huge (400pc x 300pc) ionized nebula
being much larger than normal supernova remnants. From the observed emission
lines (widths and ratios) we find that the structure is due to collisional
excitation by shocks, rather than by photoionization.
  We identify the optical counterpart to be a 22.8 mag blue star (M_V=-5.0)
belonging to a small stellar cluster. From isochrone fitting of our
multi-colour photometry we determine a cluster age of 20 to 50 Myr. We also
discovered strong stellar HeII4686 emission (equivalent width of 10 A) which
proves the identification with the X-ray source, and which suggests the
presence of an X-ray heated accretion disc around the putative black hole.


title: The Ultraluminous X-ray Source IC342 X-1 and its Environment

abstract:
  We present optical observations of a ULX in the nearby spiral galaxy IC 342.
This variable source has an average X-ray luminosity of some 10^{40} erg/s. At
the position of the source there is an ionized nebula (the "Tooth") having huge
dimensions (280 x 130 pc), much larger than normal supernova remnants. Our
optical spectra reveal highly supersonic expansion velocities and emission line
ratios typical of SNRs. It has been claimed that two [OIII] 5007 bright regions
in the nebula might be indicative of excitation by non-isotropic emission from
the ULX. However, our continuum subtracted [OIII] 5007 image reveals that
O^{++} ions are rather smoothly distributed in the nebula, fully consistent
with shock excitation. Within the nebula we find two candidate stars (V=24.0 &
24.6) in the Chandra X-ray error circle. Both are substantially reddened being
consistent with the patchy interstellar absorption. We will discuss the nature
of this source in the framework of what is currently known about optical
counterparts of ULXs.


title:
Contributions to the Nearby Stars (NStars) Project: Spectroscopy of
  Stars Earlier than M0 within 40 parsecs: The Southern Sample

abstract:
  We are obtaining spectra, spectral types and basic physical parameters for
the nearly 3600 dwarf and giant stars earlier than M0 in the Hipparcos catalog
within 40pc of the Sun. Here we report on results for 1676 stars in the
southern hemisphere observed at Cerro Tololo Interamerican Observatory and
Steward Observatory. These results include new, precise, homogeneous spectral
types, basic physical parameters (including the effective temperature, surface
gravity, and metallicity, [M/H]) and measures of the chromospheric activity of
our program stars. We include notes on astrophysically interesting stars in
this sample, the metallicity distribution of the solar neighborhood and a table
of solar analogues. We also demonstrate that the bimodal nature of the
distribution of the chromospheric activity parameter log R'HK depends strongly
on the metallicity, and we explore the nature of the ``low-metallicity''
chromospherically active K-type dwarfs.


title: Ultraluminous X-ray Sources: Bubbles and Optical Counterparts

abstract:
  Optical studies of ultraluminous X-ray sources (ULX) in nearby galaxies have
turned out to be instrumental in discriminating between various models
including the much advertised intermediate mass black hole hypothesis and
various beaming scenarios. Here we report on ESO VLT and SUBARU observations of
ULX that have revealed the parent stellar clusters with ages of some 60 million
years in two cases. Thus we are able to derive upper limits of about 8 M_sun
for the mass donors in these systems. The optical counterparts are dominated by
X-ray heated accretion disks, and the discovery of the HeII4686 emission line
now allows to derive dynamical masses in these systems. Apparent radial
velocity variations of 300 km/s have been detected in NGC 1313 X-2 which, if
confirmed by further observations, would exclude the presence of IMBH in these
systems.


title:
Scaling of Black Hole Accretion Discs from Gamma-Ray Bursts and Black
  Hole X-Ray Binaries to Active Galactic Nuclei

abstract:
  I consider how physical processes scale over eight orders of magnitude in
black hole mass, from stellar masses in gamma-ray bursts (GRB) and black-hole
X-ray binaries (BHXRB) to supermassive active galactic nuclei (AGN). Accretion
rates onto stellar mass black holes range over more than sixteen orders of
magnitude, from the lower luminosity BHXRB to GRB. These enormous parameter
ranges correspond to qualitative as well as quantitative differences in
behavior. The fundamental questions involve the balance between nonequilibrium
and thermalized plasmas. When energy fluxes exceed a critical value $\sim
10^{29}$ erg/cm$^2$s, as in GRB, a black-body equilibrium pair plasma forms. At
the lower fluxes found in AGN, BHXRB and microquasars, accretion power
electrodynamically accelerates a small number of very energetic particles,
explaining their non-thermal spectra and the high energy gamma-ray emission of
blazars. Ultra-high energy cosmic rays may be accelerated by massive black
holes, otherwise undetectable, with very low thermal luminosities. New-born
fast high-field pulsars may be in the black-body equilibrium regime, resembling
SGR in permanent outburst. I also consider the question, significant for the
acceleration of nonthermal particles in GRB outflows, of whether collisionless
plasmas interpenetrate rather than forming hydrodynamic shocks, and propose
this as an alternative to internal shock models of GRB.


title:
Jet Breaks in Short Gamma-Ray Bursts. I: The Uncollimated Afterglow of
  GRB 050724

abstract:
  We report the results of the \chandra observations of the \swift-discovered
short Gamma-Ray Burst GRB 050724. \chandra observed this burst twice, about two
days after the burst and a second time three weeks later. The first \chandra
pointing occurred at the end of a strong late-time flare. About 150 photons
were detected during this 49.3 ks observation in the 0.4-10.0 keV range. The
spectral fit is in good agreement with spectral analysis of earlier \swift XRT
data. In the second \chandra pointing the afterglow was clearly detected with 8
background-subtracted photons in 44.6 ks. From the combined \swift XRT and
\chandra-ACIS-S light curve we find significant flaring superposed on an
underlying power-law decay slope of $\alpha$=0.98$^{+0.11}_{-0.09}$. There is
no evidence for a break between about 1 ks after the burst and the last
\chandra pointing about three weeks after the burst. The non-detection of a jet
break places a lower limit of 25$^{\circ}$ on the jet opening angle, indicating
that the outflow is less strongly collimated than most previously-reported long
GRBs. This implies that the beaming corrected energy of GRB 050724 is at least
$4\times 10^{49}$ ergs.


title: Debris Disks Around White Dwarfs: The DAZ Connection

abstract:
  We present near-infrared spectroscopic observations of 20 previously known
DAZ white dwarfs obtained at the NASA Infrared Telescope Facility. Two of these
white dwarfs (G29-38 and GD362) are known to display significant K-band
excesses due to circumstellar debris disks. Here we report the discovery of
excess K-band radiation from another DAZ white dwarf, WD0408-041 (GD56). Using
spectroscopic observations, we show that the excess radiation cannot be
explained by a stellar or substellar companion, and is likely to be caused by a
warm debris disk. Our observations strengthen the connection between the debris
disk phenomena and the observed metal abundances in cool DAZ white dwarfs.
However, we do not find any excess infrared emission from the most metal rich
DAZs with $T_{\rm eff}=$ 16000 -- 20000 K. This suggests that the metal
abundances in warmer DAZ white dwarfs may require another explanation.


title: A Large Dark Matter Core in the Fornax Dwarf Spheroidal Galaxy?

abstract:
  We use measurements of the stellar velocity dispersion profile of the Fornax
dwarf spheroidal galaxy to derive constraints on its dark matter distribution.
Though the data are unable to distinguish between models with small cores and
those with cusps, we show that a large > 1 kpc dark matter core in Fornax is
highly implausible. Irrespective of the origin of the core, reasonable
dynamical limits on the mass of the Fornax halo constrain its core radius to be
no larger than 700 pc. We derive an upper limit core radius of 300 pc by
demanding that the central phase space density of Fornax not exceed that
directly inferred from the rotation curves of low-mass spiral galaxies.
Further, if the halo is composed of warm dark matter then phase-space
constraints force the core to be quite small in order to avoid conservative
limits from the Ly alpha forest power spectrum, implying a core radius < 85 pc.
We discuss our results in the context of the idea that the extended globular
cluster distribution in Fornax can be explained by the presence of a large 1.5
kpc core. A self-consistent core of this size would be drastically inconsistent
with the expectations of standard warm or cold dark matter models, and would
also require an unreasonably massive dark matter halo, with a maximum circular
velocity of 200 km/s.


title:
Early Star Formation, Nucleosynthesis, and Chemical Evolution in
  Proto-Galactic Clouds

abstract:
  We present numerical simulations to describe the nucleosynthesis and
evolution of pre-Galactic clouds in a model which is motivated by cold dark
matter simulations of hierarchical galaxy formation. We adopt a SN-induced
star-formation mechanism and follow the chemical enrichment and energy input by
Type II and Type Ia SNe. We utilize metallicity-dependent yields and include
finite stellar lifetimes. We derive the metallicity distribution functions, the
age-metallicity relation, and relative elemental abundances for a number of
alpha- and Fe-group elements. We find that the dispersion of the metallicity
distribution function of the outer halo is reproduced by contributions from
clouds with different initial conditions. Clouds with initial masses greater
than that of present globular clusters are found to survive the first 0.1 Gyr,
suggesting that such systems may have contributed to the formation of the first
stars, and could have been self-enriched. More massive clouds are only stable
when one assumes an initial mass function that is not biased towards massive
stars. The predicted relative abundances of some alpha- and Fe-group elements
show good agreement with the observed values down to metallicities below [Fe/H]
= -4 when the iron yields are reduced relative to stellar models. The observed
scatter is also reproduced for many elements including the observed bifurcation
in [alpha/Fe] for stars with low [Fe/H]. However, the predicted dispersion may
be too large for some alpha elements unless a limited range of progenitor
masses is assumed. The results suggest that the low-mass SNeII were absent at
the very low metallicities, and that the upper mass limit for the first stars
that contributed to nucleosynthesis may be < 40 solar masses.


title: Late-time Inhomogeneity and the Acceleration of the Universe

abstract:
  The inhomogeneous distribution of matter in the non-linear regime of
galaxies, clusters of galaxies and voids is described by an exact, spherically
symmetric inhomogeneous solution of Einstein's gravitational field equations,
corresponding to an under-dense void. The solution becomes the homogeneous and
isotropic Einstein-de Sitter solution for a red shift $z > 10-20$, which
describes the matter dominated CMB data with small inhomogeneities. A spatial
volume averaging of physical quantities is introduced and the averaged time
evolution expansion parameter $\theta$ can give rise in the late-time universe
to a volume averaged deceleration parameter $<q>$ that is negative for a
positive matter density. This allows for a region of accelerated expansion
which does not require a cosmological constant. A negative deceleration
parameter can be derived by this volume averaging procedure from the
Lema\^{i}tre-Tolman-Bondi open void solution, which describes the late-time
non-linear regime associated with galaxies and under-dense voids and solves the
``coincidence'' problem.


title: Eridanus - A Supergroup in the Local Universe?

abstract:
  We examine a possible supergroup in the direction of the Eridanus
constellation using 6dF Galaxy Survey second data release (6dFGS DR2) positions
and velocities together with 2MASS and HyperLEDA photometry. We perform a
friends-of-friends analysis to determine which galaxies are associated with
each substructure before examining the properties of the constituent galaxies.
The structure is made up of three individual groups that are likely to merge to
form a cluster of mass 7x10^13 Msolar. We conclude that this structure is a
supergroup. We also examine the colours, morphologies and luminosities of the
galaxies in the region with respect to their local projected surface density.
We find that the colours of the galaxies redden with increasing density, the
median luminosities are brighter with increasing environmental density and the
morphologies of the galaxies show a strong morphology-density relation. The
colours and luminosities of the galaxies in the supergroup are already similar
to those of galaxies in clusters, however the supergroup contains more
late-type galaxies, consistent with its lower projected surface density. Due to
the velocity dispersion of the groups in the supergroup, which are lower than
those of clusters, we conclude that the properties of the constituent galaxies
are likely to be a result of merging or strangulation processes in groups
outlying this structure.


title:
Are There Radical Cyanogen Abundance Differences Between Galactic
  Globular Cluster RGB and AGB Stars?

abstract:
  [Abridged] Norris et al. (1981) found that there was a distinct lack of
cyanogen-strong (CN-strong) stars in their sample of AGB stars, as compared to
their sample of RGB stars (which had roughly equal numbers of CN-normal and
CNstrong stars). Similar features have been discovered in the AGB populations
of other clusters. Unfortunately all of these studies suffer from low AGB star
counts so the conclusions are not necessarily robust -- larger, statistically
signifcant, sample sizes are needed.
  We outline the results of a literature search for relevant CN observations
and describe our observing proposal to test the suggestion that there are
substantial abundance differences between the AGB and RGB in galactic globular
clusters. The literature search revealed that the AGB star counts for all
studies (which are not, in general, studies about AGB stars in particular) are
low, usually being < or = 10. The search also revealed that the picture may not
be consistent between clusters. Although most clusters appear to have CN-weak
AGBs, at least two seem to have CN-strong AGBs (M5 & 47 Tuc). To further
complicate the picture, clusters often appear to have a combination of both
CN-strong and CN-weak stars on their AGBs -- although one population tends to
dominate. Again, all these assertions are however based on small sample
sizes.We aim to increase the sample sizes by an order of magnitude using
existing high quality photometry in which the AGB and RGB can be reliably
separated. For the observations we will use a wide-field, low- to
mid-resolution multi-object spectroscope. With the new information we hope to
ascertain whether significant abundance differences really exist.


title:
The Topology and Polarisation of Subbeams Associated with the `Drifting'
  Subpulse Emission of Pulsar B0943+10 -- IV. Q-to-B-Mode Recovery Dynamics

abstract:
  Pulsar B0943+10 is well known for its `B' (burst) mode, characterized by
accurately drifting subpulses, in contrast to its chaotic `Q' (quiet) mode. Six
new Arecibo observations at 327 MHz with durations of 2+ hours each have shed
considerable light on the modal dynamics of this pulsar. Of these, three were
found to be exclusively `B' mode, and three were discovered to exhibit
transitions from the `Q' to the `B' mode. One of these observations has
permitted us to determine the circulation time of the subbeam carousel in the
`Q' mode for the first time, at some 36.4$\pm$0.9 stellar rotation periods. The
onset of the `B' mode is then observed to commence similarly in all three
observations. The initial circulation time is about 36 periods and relaxes to
nearly 38 periods in a roughly exponential fashion with a characteristic time
of some 1.2 hours. This is the longest characteristic time ever found in a
mode-switching pulsar. Moreover, just after the `B'-mode onset the pulsar
exhibits a symmetrical resolved-double profile form with a somewhat stronger
trailing component, but this second component slowly dies away leaving the
usual single `B'-mode profile with the longitude of the magnetic axis falling
at about its trailing half power point. Thus it would appear that Q-to-B- and
B-to-Q-transitions have different characteristic times. Some speculations are
given on the nature of this slow modal alternation.


title:
Towards Determination of the Initial Flavor Composition of
  Ultrahigh-energy Neutrino Fluxes with Neutrino Telescopes

abstract:
  We propose a simple but useful parametrization of the flavor composition of
ultrahigh-energy neutrino fluxes produced from distant astrophysical sources:
$\phi^{}_e : \phi^{}_\mu : \phi^{}_\tau = \sin^2 \xi \cos^2 \zeta : \cos^2 \xi
\cos^2 \zeta : \sin^2 \zeta$. We show that it is possible to determine or
constrain $\xi$ and $\zeta$ by observing two independent neutrino flux ratios
at the second-generation neutrino telescopes, provided three neutrino mixing
angles and the Dirac CP-violating phase have been well measured in neutrino
oscillations. Any deviation of $\zeta$ from zero will signify the existence of
cosmic $\nu^{}_\tau$ and $\bar{\nu}^{}_\tau$ neutrinos at the source, and an
accurate value of $\xi$ can be used to test both the conventional mechanism and
the postulated scenarios for cosmic neutrino production.


title:
Running Spectral Index in Noncommutative Inflation and WMAP Three Year
  Results

abstract:
  A model independent analysis shows that the running of the spectral index of
the three year WMAP results can be nicely realized in noncommutative inflation.
We also re-examine some concrete noncommutative inflation models. We find that
a large tensor-scalar ratio is required, corresponding to a low number of
e-folds before the end of inflation in some simple models.


title:
An XMM-Newton view of the young open cluster NGC 6231 -- I. The
  catalogue

abstract:
  This paper is the first of a series dedicated to the X-ray properties of the
young open cluster NGC 6231. Our data set relies on an XMM-Newton campaign of a
nominal duration of 180 ks and reveals that NGC 6231 is very rich in the X-ray
domain too. Indeed, 610 X-ray sources are detected in the present field of
view, centered on the cluster core. The limiting sensitivity of our survey is
approximately 6E-15 erg/s/cm^2 but clearly depends on the location in the field
of view and on the source spectrum. Using different existing catalogues, over
85% of the X-ray sources could be associated with at least one optical and/or
infrared counterpart within a limited cross-correlation radius of 3 arcsec at
maximum. The surface density distribution of the X-ray sources presents a
slight N-S elongation. Once corrected for the spatial sensitivity variation of
the EPIC instruments, the radial profile of the source surface density is well
described by a King profile with a central density of about 8 sources per
arcmin^2 and a core radius close to 3.1arcmin. The distribution of the X-ray
sources seems closely related to the optical source distribution. The expected
number of foreground and background sources should represent about 9% of the
detected sources, thus strongly suggesting that most of the observed X-ray
emitters are physically belonging to NGC 6231. Finally, beside a few bright but
soft objects -- corresponding to the early-type stars of the cluster -- most of
the sources are relatively faint (~5E-15 erg/s/cm^2) with an energy
distribution peaked around 1.0-2.0 keV.


title: Lifetime of nuclear velocity dispersion drops in barred galaxies

abstract:
  We have made hydro/N-body simulations with and without star formation to shed
some light on the conditions under which a central kinematically cold stellar
component (characterized by a velocity dispersion drop or \sigma-drop) could be
created in a hot medium (e.g. a bulge) and survive enough time to be observed.
We found that the timescale for a \sigma-drop formation could be short (less
than 500 Myr) whereas its lifetime could be long (more than 1 Gyr) provided
that the central region is continuously or regularly fed by fresh gas which
leads to a continuous star formation activity. Star formation in the central
region, even at a low rate as 1M_{sol} yr^{-1}, is mandatory to sustain a
permanent \sigma-drop by replacing heated particles by new low-\sigma ones. We
moreover show that as soon as star formation is switched off, the \sigma-drop
begins to disappear.


title:
SCUBA polarisation observations of the magnetic fields in the prestellar
  cores L1498 and L1517B

abstract:
  We have mapped linearly polarized dust emission from the prestellar cores
L1498 and L1517B with the James Clerk Maxwell Telescope (JCMT) using the
Submillimetre Common User Bolometer Array (SCUBA) and its polarimeter SCUBAPOL
at a wavelength of 850um. We use these measurements to determine the
plane-of-sky magnetic field orientation in the cores. In L1498 we see a
magnetic field across the peak of the core that lies at an offset of 19 degrees
to the short axis of the core. This is similar to the offsets seen in previous
observations of prestellar cores. To the southeast of the peak, in the
filamentary tail of the core, we see that the magnetic field has rotated to lie
almost parallel to the long axis of the filament. We hypothesise that the field
in the core may have decoupled from the field in the filament that connects the
core to the rest of the cloud. We use the Chandrasekhar-Fermi (CF) method to
measure the plane-of-sky field strength in the core of L1498 to be 10 +/- 7 uG.
  In L1517B we see a more gradual turn in the field direction from the northern
part of the core to the south. This appears to follow a twist in the filament
in which the core is buried, with the field staying at a roughly constant 25
degree offset to the short axis of the filament, also consistent with previous
observations of prestellar cores. We again use the CF method and calculate the
magnetic field strength in L1517B also to be 30 +/- 10 uG. Both cores appear to
be roughly virialised. Comparison with our previous work on somewhat denser
cores shows that, for the denser cores, thermal and non-thermal (including
magnetic) support are approximately equal, while for the lower density cores
studied here, thermal support dominates.


title:
Dynamical age of the universe as a constraint on the parametrization of
  dark energy equation of state

abstract:
  The dynamical age of the universe depends upon the rate of the expansion of
the universe, which explicitly involves the dark energy equation of state
parameter $w(z)$. Consequently, the evolution of $w(z)$ has a direct imprint on
the age of the universe. We have shown that the dynamical age of the universe
as derived from CMB data can be used as an authentic criterion, being
independent of the priors like the present value of the Hubble constant $H_{0}$
and the cosmological density parameter $\Omega_{M}^{0}$, to constrain the range
of admissible values of $w$ for quiessence models and to test the physically
viable parametrizations of the equation of state $w(z) $ in kinessence models.
An upper bound on variation of dark energy density is derived and a relation
between cosmological density parameters and the transition redshift is
established.


title:
Radio, X-ray, and gamma-ray Emission Models of the Colliding Winds
  Binary WR 140

abstract:
  We use hydrodynamical models of the wind-collision region (WCR) in the
archetype colliding-wind system WR140 to determine the spatial and spectral
distribution of the radio, X-ray and gamma-ray emission from shock accelerated
electrons. Our calculations are for orbital phase 0.837 when the observed radio
emission is close to maximum. Using the observed thermal X-ray emission
together with the radio emission to constrain the mass-loss rates, we find that
the O-star mass-loss rate is consistent with recent reductions for O4-5
supergiants. We demonstrate that radio VLBI observations of the WCR fail to
constrain the opening angle. The observed low frequency turnover at ~3 GHz in
the radio emission is due to free-free absorption, since models based on the
Razin effect have an unacceptably large fraction of energy in non-thermal
particles. The index of the non-thermal electron energy distribution is flatter
than the canonical value for diffusive shock acceleration, namely p<2. Several
mechanisms are discussed that could lead to such an index. Tighter constraints
on p and the nature of the shocks in WR140 will be obtained from future
observations at MeV and GeV energies, for which we generally predict lower
fluxes than previous work. Since the high stellar photon fluxes prevent the
acceleration of electrons beyond gamma > 1e5-1e6, TeV emission from CWB systems
will provide unambiguous evidence of pion-decay emission from accelerated ions.
We finish by commenting on the emission and physics of the multiple wind
collisions in dense stellar clusters, paying particular attention to the
Galactic Centre (abridged).


title:
The search for extrasolar planets: Study of line bisectors and its
  relation with precise radial velocity measurements

abstract:
  (Abridged) To this purpose, in the course of the thesis work we prepared a
suitable software in order to use the same spectra acquired for radial velocity
determinations (i.e., with the spectrum of the Iodine cell imprinted on) to
measure variations of the stellar line profiles. This is a novel approach, that
can be of general utility in all high precision radial velocity surveys based
on iodine cell data. This software has then been extensively used on data
acquired within our survey, allowing a proper insight into a number of
interesting cases, where spurious estimates of the radial velocities due to
activity or contamination by light from the companions were revealed. The same
technique can also be considered to correct the measured radial velocities, in
order to search for planets around active stars.


title: Magnetorotational supernovae with jets

abstract:
  We present results of 2D simulation of magnetorotational (MR) supernova
accompanied by jet formation in the core collapse supernova explosion. Initial
magnetic field used in the simulations has dipole-like symmetry. Contrary to
the simulations of MR supernova with initial quadrupole-like magnetic field,
where the matter was ejected mainly near the equatorial plane, in presence of
the dipole-like initial magnetic field the supernova explosion is developing
preferably along a rotational axis, and leads to formation of a protojet. We
expect that protojet propagation through the envelope of the star will be
accompanied by its collimation. The magnetorotational instability (MRI) was
found in simulations, similar to the earlier considered case of the
quadrupole-like initial magnetic field. Our estimations show that the
characteristic time for the reconnection of the magnetic field is much larger
than the MRI development time. The supernova explosion energy for the
dipole-like field is about $0.61\cdot 10^{51}$erg, and about $0.13M_\odot$ of
mass was ejected during the explosion.


title:
Possible relation between galactic flat rotational curves and the
  Pioneers' anomalous acceleration

abstract:
  We consider a generic minimal modification of the Newtonian potential, that
is a modification that introduces only one additional dimensional parameter.
The modified potential depends on a function whose behavior for large and small
distances can be fixed in order to obtain respectively (i) galactic flat
rotational curves and (ii) a universal constant acceleration independent of the
masses of the interacting bodies (Pioneer anomaly). Then using a dimensional
argument we show that the Tully-Fisher relation for the maximal rotational
velocity of spiral galaxies follows without any further assumptions. This
result suggests that the Pioneer anomalous acceleration and the flat rotational
curves of galaxies could have a common origin in a modified gravitational
theory. The relation of these results with the Modified Newtonian Dynamics
(MOND) is discussed.


title: van Stockum--Bonnor Spacetimes of Rigidly Rotating Dust

abstract:
  Stationary, axisymmetric and asymptotically flat spacetimes of dust of which
trajectories are integral curves of the time translation Killing vector are
investigated. The flow has no Newtonian limit. Asymptotic flatness implies the
existence of singularities of the curvature scalar that are distributions and
that are not isolated from regularity regions of the flow. The singularities
are closely related to the presence of additional stresses that contribute
negative active mass to the total (Komar) mass, which is zero for
asymptotically flat spacetimes. Several families of solutions are constructed
and a multipole expansion is presented.


title: Dwarf galaxies in the Dynamically Evolved NGC 1407 Group

abstract:
  The NGC 1407 Group stands out among nearby structures by its properties that
suggest it is massive and evolved. It shares properties with entities that have
been called fossil groups: the 1.4 magnitude differential between the dominant
elliptical galaxy and the second brightest galaxy comes close to satisfying the
definition that has been used to define the fossil class. There are few
intermediate luminosity galaxies, but a large number of dwarfs in the group. We
estimate there are 250 group members to the depth of our survey. The slope of
the faint end of the luminosity function (reaching M_R = -12) is alpha = -1.35.
Velocities for 35 galaxies demonstrate that this group with one dominant galaxy
has a mass of 7 X 10^13 M_sun and M/L_R = 340. Two galaxies in close proximity
to NGC 1407 have very large blueshifts. The most notable is the second
brightest galaxy, NGC 1400, with a velocity of -1072 km/s with respect to the
group mean. We report the detection of X-ray emission from this galaxy and from
the group.


title:
The Star Formation Histories of the Bulge and Disk of M31 from Gemini
  North+NIRI/Altair and HST/NICMOS

abstract:
  We discuss H and K observations of three fields in the bulge and disk of M31
obtained with the Altair adaptive optics system and NIRI instrument on Gemini
North. These are the highest resolution and deepest near-infrared observations
obtained to date of the inner regions of M31, and demonstrate the promise of
ground-based adaptive optics for studying the crowded regions of nearby
galaxies. We have combined our observations with previously published
HST/NICMOS observations of nine M31 fields and have derived the coarse star
formation histories of M31's bulge and inner disk. From fits to the M_K
luminosity functions, we find the stellar population mix to be dominated by
old, nearly solar-metallicity stars. The old populations, which we define as
having age >~6 Gyr, indeed dominate the star formation histories at all radii
independent of the relative contributions of bulge and disk stars. Although all
of our fields contain some bulge contribution, our results suggest that there
is no age difference between the bulge and disk to the limit of our precision.


title: Cosmic Reionization Redux

abstract:
  We show that numerical simulations of reionization that resolve the Lyman
Limit systems (and, thus, correctly count absorptions of ionizing photons) have
converged to about 10% level for 5<z<6.2 and are in reasonable agreement
(within 10%) with the SDSS data in this redshift interval. The SDSS data thus
constraint the redshift of overlap of cosmic HII regions to z_{OVL} =
6.1+-0.15. At higher redshifts, the simulations are far from convergence on the
mean Gunn-Peterson optical depth, but achieve good convergence for the mean
neutral hydrogen fraction. The simulations that fit the SDSS data, however, do
not have nearly enough resolution to resolve the earliest episodes of star
formation, and are very far from converging on the precise value of the optical
depth to Thompson scattering - any value between 6 and 10% is possible,
depending on the convergence rate of the simulations and the fractional
contribution of PopIII stars. This is generally consistent with the third-year
WMAP results, but much higher resolution simulation are required to come up
with the sufficiently precise value for the Thompson optical depth that can be
statistically compared with the WMAP data.


title:
Unipolar Inductor Model coupled to GW emission: energy budget and model
  application to RX J0806+15 and RX J1914+24

abstract:
  We further discuss the Unipolar Inductor Model (UIM) coupled to GW emission
(Dall'Osso et al. 2005) and compare it to observed properties of the two
candidate ultrashort period binaries RX J0806+15 and RX J1914+24 . We consider
the measured orbital periods, period derivatives and inferred X-ray
luminosities of these two sources and find constraints on system parameters in
order for the model to account for them. We find that these properties point to
the two sources being in different regimes of the UIM, with the requirement of
low magnetic moment primaries ($\sim 10^{30} G cm^3$) for both. Given this weak
magnetization, RX J0806+15 has a sufficiently low luminosity that it can be
interpreted as having a primary spin almost synchronous to and just slightly
slower than the orbital motion. Its measured orbital spin-up is only slightly
affected by spin-orbit coupling and is mostly due to GW emission. RX J1914+24,
on the other hand, is too bright in X-rays and has too slow an orbital spin-up
for the same regime to apply. We suggest that this binary system may be
emitting GWs at a significantly higher rate than implied by its measured
$\dot{\omega}_o = 6 \times 10^{-17} rad s^{-2}$. The latter is explained, in
this framework, by the primary spin being slightly faster than the orbital
motion ($\alpha <or= 1.1$). In this case, the associated spin-orbit coupling
transfers to the orbit a significant amount of angular momentum, thus partially
balancing that lost to GW emission. All expectations can be tested in the near
future to confirm the viability of the model.


title:
Clumpiness of Dark Matter and Positron Annihilation Signal: Computing
  the odds of the Galactic Lottery

abstract:
  The small-scale distribution of dark matter in Galactic halos is poorly
known. Several studies suggest that it could be very clumpy, which turns out to
be of paramount importance when investigating the annihilation signal from
exotic particles (e.g. supersymmetric or Kaluza-Klein). In this paper we focus
on the annihilation signal in positrons. We estimate the associated
uncertainty, due to the fact that we do not know exactly how the clumps are
distributed in the Galactic halo. To this aim, we perform a statistical study
based on analytical computations, as well as numerical simulations. In
particular, we study the average and variance of the annihilation signal over
many Galactic halos having the same statistical properties. We find that the
so-called boost factor used by many authors should be handled with care, as i)
it depends on energy and ii) it may be different for positrons, antiprotons and
gamma rays, a fact which has not received any attention before. As an
illustration, we use our results to discuss the positron spectrum measurements
by the HEAT experiment.


title:
Can Experiments Studying Ultrahigh Energy Cosmic Rays Measure the
  Evolution of the Sources?

abstract:
  Interactions between cosmic ray protons and the photons of the cosmic
microwave background radiation, as well as the expansion of the universe, cause
cosmic rays to lose energy in a way that depends on the distance from the
cosmic nray source to the earth. Because of this, there is a correlation
between cosmic ray energies and the average redshift of their origin. This
correlation may be exploited to measure the evolution of the sources of cosmic
rays.
  Sky surveys of Quasi Stellar Objects (QSO's) and Active Galactic Nuclei
(AGN's), made at optical and x-ray wavelengths, are consistent in showing that
the evolution of such objects exhibits a break at a redshift, z, of about 1.6.
At smaller redshifts, the luminosity density of QSO's and AGN's follows a
$(1+z)^m$ distribution, with $m \sim 2.6$, and exhibit a much flatter
distribution above the break. Measurements of the star formation rate are also
consistent with this picture.
  If QSO's and AGN's are sources of ultrahigh energy cosmic rays the break in
their evolution should appear in the cosmic ray spectrum at an energy of about
$10^{17.6}$ eV. This is the energy of the second knee.


title: VW Hyi: optical spectroscopy and Doppler tomography

abstract:
  We present high quality optical spectroscopy of the SU UMa-subtype dwarf
nova, VW Hyi taken while the system was in quiescence. An S-wave is executed by
the emission cores of the Hydrogen Balmer lines and by the emission lines of He
I, Ca II, Fe II and He II. Using Doppler tomography we show it originates in
the accretion stream-disc impact region. The He II emission is strongly
phase-dependent, suggesting it originates exclusively within a hot cavity at
the initial impact. We map the ionization structure of the stream-disc
interaction region. One possible interpretation of this is that the Balmer
hotspot lies downstream of the He II hotspot in the outer accretion disc, with
the He I and Ca II hotspots at intermediate locations between the two. This
suggests that Balmer emission is suppressed until material has cooled somewhat
downstream of the impact site and is able to recombine. We favour a phase
offset of 0.15+/-0.04 between the photometric ephemeris and inferior
conjunction of the mass donor. The white dwarf contributes significantly to the
optical continuum, with broad Balmer absorption and narrow Mg II 4481
absorption clearly apparent. This latter feature yields the gravitational
redshift: v_grav=38+/-21 km s^-1, so M_1=0.71+0.18-0.26 M_sun. This implies
M_2=0.11 +/- 0.03 M_sun and hence the donor is not a brown dwarf. A prominent
Balmer jump is also observed. We note that the previously accepted system
parameters for both VW Hyi and WX Hyi incoporate an algebraic error, and we
provide a recalculated M_1(q) plane for WX Hyi.


title: Non-Gaussianities in two-field inflation

abstract:
  We study the bispectrum of the curvature perturbation on uniform energy
density hypersurfaces in models of inflation with two scalar fields evolving
simultaneously. In the case of a separable potential, it is possible to compute
the curvature perturbation up to second order in the perturbations, generated
on large scales due to the presence of non-adiabatic perturbations, by
employing the $\delta N$-formalism, in the slow-roll approximation. In this
case, we provide an analytic formula for the nonlinear parameter $f_{NL}$. We
apply this formula to double inflation with two massive fields, showing that it
does not generate significant non-Gaussianity; the nonlinear parameter at the
end of inflation is slow-roll suppressed. Finally, we develop a numerical
method for generic two-field models of inflation, which allows us to go beyond
the slow-roll approximation and confirms our analytic results for double
inflation.


title: An Internet Database of Ultraviolet Lightcurves for Seyfert Galaxies

abstract:
  Using the Multimission Archives at Space Telescope (MAST), we have extracted
spectra and determined continuum light curves for 175 Seyfert Galaxies that
have been observed with the International Ultraviolet Explorer (IUE) and the
Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST). To obtain
the light curves as a function of Julian Date, we used fix bins in the object's
rest frame, and measured small regions (between 30 and 60 Angstroms) of each
spectrum's continuum flux in the range 1150 Angstroms to 3200 Angstroms. We
provide access to the UV light curves and other basic information about the
observations in tabular and graphical form via the Internet at
http://www.chara.gsu.edu/PEGA/IUE/.


title:
From Supermassive Black Holes to Dwarf Elliptical Nuclei: a Mass
  Continuum

abstract:
  Considerable evidence suggests that supermassive black holes reside at the
centers of massive galactic bulges. At a lower galactic mass range, many dwarf
galaxies contain extremely compact nuclei that structurally resemble massive
globular clusters. We show that both these types of central massive objects
(CMO's) define a single unbroken relation between CMO mass and the luminosity
of their host galaxy spheroid. Equivalently, M_CMO is directly proportional to
the host spheroid mass over 4 orders of magnitude. We note that this result has
been simultaneously and independently identified by Cote et al. (2006), see
also Ferrarese et al. (2006). We therefore suggest that the dE,N nuclei may be
the low-mass analogs of supermassive black holes, and that these two types of
CMO's may have both developed starting from similar initial formation
processes. The overlap mass interval between the two types of CMO's is small,
and suggests that for M_CMO > 10^7 M_sun, the formation of a black hole was
strongly favored, perhaps because the initial gas infall to the center was too
rapid and violent for star formation to occur efficiently.


title: Constraining the size of the narrow line region in distant quasars

abstract:
  We propose a proper method to measure the size of the narrow line region
(NLR) in distant quasars. The apparent angular size of the NLR is, in general,
too small to resolve technically. However, it is possible to map the NLR if
with gravitational lensing. In our method, we directly compare the observed
image of the NLR with the expected lensed images of the NLR for various source
sizes and lens models. Seeking the best fit image via the comparison
procedures, we can obtain the best-fit size and the best-fit lens model. We
apply this method to the two-dimensional spectroscopic data of a famous lensed
quasar, Q2237+0305. If the lens galaxy resembles the applied lens model, an
upper limit to the NLR size can be set 750 pc. Further, we examine how the
fitting results will be improved by future observations, taking into account
the realistic observational effects, such as seeing. Future observations will
provide us more stringent constraints on the size of the NLR and on the density
profile of the lens galaxy.