title:
The nature of the mid-infrared population from optical identifications
  of the ELAIS-S1 sample

abstract:
  We present a multi-wavelength catalog (15 um, R, K-band, 1.4 GHz flux) plus
spectroscopic identifications for 406 15 um sources detected in the ELAIS
region S1, over the flux density range 0.5<S<150 mJy. 332 (~82%) sources are
optically identified down to R~23.0. Spectra or bona fide stellar
identifications are obtained for 290 objects. The areal coverage, MIR and
optical completeness of the sample are discussed in order to allow statistical
and evolutionary analyses. Two main spectroscopic classes have been found to
dominate the MIR extragalactic population: z<0.5 star-forming galaxies (from
absorbed to extreme starbursts: nuL_nu~10^8-10^11 L_odot), which account for
\~75% of the sources, and AGN (both type 1 and 2), which account for ~25% of
the sources. About 20% of the extragalactic sources are dust-enshrouded
starburst galaxies [e(a) spectra], and all the starburst galaxies appear more
dust extincted in the optical than nearby normal galaxies. We also identified
91 stellar objects (~22% of the MIR sources). The counts for starburst galaxies
and AGN down to 0.6 mJy have been derived. A general trend is found in the
optical-MIR SED of the galaxies, where the MIR-luminous objects have larger MIR
to optical luminosity ratios.


title:
Can microlensing fold caustics reveal a second stellar limb-darkening
  coefficient?

abstract:
  Dense high-precision photometry of microlensed stars during a fold-caustic
passage can be used to reveal their intensity profiles from which the
temperature of the stellar atmosphere as function of fractional radius can be
derived. While the capabilities of current microlensing follow-up campaigns
such as PLANET allow a precise measurement of linear limb-darkening
coefficients, the residual signal of a second coefficient characterizing
square-root limb darkening is ~ 25 times smaller which prevents a proper
determination except for unlikely cases of very high caustic-peak-to-outside
relative magnifications with no adequate event being observed so far or for
source stars passing over a cusp singularity. Although the presence of limb
darkening can be well established from the data, a reliable measurement of the
index of an underlying power-law cannot be obtained.


title: Curvaton scenario with low scale inflation revisited

abstract:
  In its simplest form the curvaton paradigm requires the Hubble parameter
during inflation to be bigger than $10^8 \GeV$, but this bound may be evaded in
non-standard settings. In the heavy curvaton scenario the curvaton mass
increases significantly after the end of inflation. We reanalyze the bound in
this set up, taking into account the upper bound on the curvaton mass from
direct decay. We obtain $H_* > 10^8 \GeV$ if the mass increase occurs at the
end of inflation, and $H_* > 10^{-14} \GeV$ if it occurs just before
nucleosynthesis. We then discuss two implementations of the heavy curvaton.
Parameters are constrained in these explicit models, and as a result even
obtaining TeV scale inflation is hard to obtain.


title: BeppoSAX observations of the quasar Markarian 205

abstract:
  We present the first BeppoSAX observation (0.1 to 220 keV) of the quasar Mrk
205. We have searched for the unusual Fe line profile claimed in the XMM-Newton
spectrum which has been widely discussed in recent literature. We find no
evidence for a broad, ionized Fe line component in our data. We detect for the
first time a Compton hump in this object. Besides, when this component is
included in the fit, the line strength diminishes, in agreement with a recent
re-analysis of the XMM-Newton data, but with better constraints on the
reflection component thanks to the PDS instrument (15-220 keV). We interpret
this fact as another indication for illumination of a distant and cold material
rather than reprocessing in the highly ionized inner parts of an accretion
disk. We cannot constrain the presence of a high energy cutoff but we confirm
the existence of a variable soft excess (one year timescale).


title: Using Chandra/LETG spectra to probe stellar coronae

abstract:
  We probe the relationship between surface magnetic fields and the X-ray
emitting corona in the rapidly rotating star AB Dor. Circularly polarised
spectra have been inverted to produce a surface (photospheric) magnetic field
map. This surface map has been extrapolated to model AB Dor's coronal field
topology and X-ray light curve. Chandra/LETG light curves of AB Dor from the
same epoch show intrinsic variability at the 30% level. Period analysis
indicates a fraction of this is due to rotational modulation. We measure
velocity shifts in emission line centroids as a function of rotation period and
find evidence of rotational modulation (max. vel. ~40+/- 13km/s). This
modulation may indicate the presence of a localised X-ray emitting region at
mid-to-high latitudes.


title: The X-ray luminosity function of galaxies in the Coma cluster

abstract:
  The XMM-Newton survey of the Coma cluster of galaxies covers an area of 1.86
square degrees with a mosaic of 16 pointings and has a total useful integration
time of 400 ksec. Detected X-ray sources with extent less than 10" were
correlated with cataloged galaxies in the Coma cluster region. The redshift
information, which is abundant in this region of the sky, allowed us to
separate cluster members from background and foreground galaxies. For the
background sources, we recover a typical LogN-LogS in the flux range 1.e-15 -
1.e-13 ergs/s/cm^2 in the 0.5-2.0 keV band. The X-ray emission from the cluster
galaxies exhibits X-ray colors typical of thermal emission. The luminosities of
Coma galaxies lie in the 1.e39-1.e41 ergs/s interval in the 0.5-2.0 keV band.
The luminosity function of Coma galaxies reveals that their X-ray activity is
suppressed with respect to the field by a factor of 5.6, indicating a lower
level of X-ray emission for a given stellar mass.


title: Ground-State SiO Maser Emission Toward Evolved Stars

abstract:
  We have made the first unambiguous detection of vibrational ground-state
maser emission from SiO toward six evolved stars. Using the Very Large Array,
we simultaneously observed the v=0, J=1-0, 43.4-GHz, ground-state and the v=1,
J=1-0, 43.1-GHz, first excited-state transitions of SiO toward the oxygen-rich
evolved stars IRC+10011, o Ceti, W Hya, RX Boo, NML Cyg, and R Cas and the
S-type star chi Cyg. We detected at least one v=0 SiO maser feature from six of
the seven stars observed, with peak maser brightness temperatures ranging from
10,000 K to 108,800 K. In fact, four of the seven v=0 spectra show multiple
maser peaks, a phenomenon which has not been previously observed. Ground-state
thermal emission was detected for one of the stars, RX Boo, with a peak
brightness temperature of 200 K. Comparing the v=0 and the v=1 transitions, we
find that the ground-state masers are much weaker with spectral characteristics
different from those of the first excited-state masers. For four of the seven
stars the velocity dispersion is smaller for the v=0 emission than for the v=1
emission, for one star the dispersions are roughly equivalent, and for two
stars (one of which is RX Boo) the velocity spread of the v=0 emission is
larger. In most cases, the peak flux density in the v=0 emission spectrum does
not coincide with the v=1 maser peak. Although the angular resolution of these
VLA observations were insufficient to completely resolve the spatial structure
of the SiO emission, the SiO spot maps produced from the interferometric image
cubes suggest that the v=0 masers are more extended than their v=1
counterparts.


title: A Second Stellar Color Locus: a Bridge from White Dwarfs to M stars

abstract:
  We report the discovery of a locus of stars in the SDSS g-r vs. u-g
color-color diagram that connects the colors of white dwarfs and M dwarfs.
While its contrast with respect to the main stellar locus is only ~1:2300, this
previously unrecognized feature includes 863 stars from the SDSS Data Release
1. The position and shape of the feature are in good agreement with predictions
of a simple binary star model that consists of a white dwarf and an M dwarf,
with the components' luminosity ratio controlling the position along this
binary system locus. SDSS DR1 spectra for 47 of these objects strongly support
this model. The absolute magnitude--color distribution inferred for the white
dwarf component is in good agreement with the models of Bergeron et al. (1995).


title: Color-Induced Displacement double stars in SDSS

abstract:
  We report the first successful application of the astrometric color-induced
displacement technique (CID, the displacement of the photocenter between
different bandpasses due to a varying contribution of differently colored
components to the total light), originally proposed by Wielen (1996) for
discovering unresolved binary stars. Using the Sloan Digital Sky Survey (SDSS)
Data Release 1 with 2.5 million stars brighter than 21m in the u and g bands,
we select 419 candidate binary stars with CID greater than 0.5 arcsec. The SDSS
colors of the majority of these candidates are consistent with binary systems
including a white dwarf and any main sequence star with spectral type later
than ~K7. The astrometric CID method discussed here is complementary to the
photometric selection of binary stars in SDSS discussed by Smolcic et al.
(2004), but there is considerable overlap (15%) between the two samples of
selected candidates. This overlap testifies both to the physical soundness of
both methods, as well as to the astrometric and photometric quality of SDSS
data.


title: Gamma-Ray Burst Intensity Distributions

abstract:
  We use the lag-luminosity relation to calculate self-consistently the
redshifts, apparent peak bolometric luminosities L_B, and isotropic energies
E_iso for a large sample of BATSE gamma-ray bursts. We consider two different
forms of the lag-luminosity relation; for both forms the median redshift for
our burst database is 1.6. We model the resulting E_iso sample with power law
and Gaussian probability distributions without redshift evolution, both of
which are reasonable models. The power law model has an index of
alpha_E=1.76+/-0.05 (95% confidence), where p(E_iso) propto E_iso^(-alpha_E).
The simple universal jet profile model suggested but did not require alpha_E=2,
and subsequent physically reasonable refinements to this model permit greater
diversity in alpha_E, as well as deviations from a power law; therefore our
observed E_iso probability distribution does not disprove the universal jet
model.


title:
Extracting energy from black holes: Short-GRBs, Long-GRBs and GRB
  afterglows

abstract:
  The extractable energy from a black hole, as origin of the Gamma-Ray Burst
(GRB) phenomenon is reviewed.


title: The Evolutionary History of Local Group Irregular Galaxies

abstract:
  Irregular (Irr) galaxies are gas-rich objects with recent or ongoing star
formation. In absence of spiral density waves, star formation occurs largely
stochastically. The scattered star-forming regions tend to be long-lived and
migrate slowly. Older populations have a spatially more extended and regular
distribution. In fast-rotating Irrs high star formation rates with stronger
concentration toward the galaxies' center are observed, and cluster formation
is facilitated. In slowly or nonrotating dwarf Irrs (dIrrs) star formation
occurs more quiescently, and the formation of OB associations is common. Irrs
and dIrrs tend to experience continuous star formation with amplitude
variations and to continue to form stars for another Hubble time. Irrs exhibit
lower effective yields than spirals, and [alpha/Fe] ratios below the solar
value. This may be indicative of fewer Type II SNe and lower astration rates in
their past. Alternatively, many metals may be lost from the shallow galaxy
potential wells due to selective winds. The differences in the
metallicity-luminosity relation between dIrrs and dwarf spheroidals (which,
despite their lower masses, tend to have too high a metallicity for their
luminosity as compared to dIrrs) further supports the idea of slow astration
and slow enrichment in dIrrs. The current data on age-metallicity relations are
still too sparse to distinguish between infall, leaky-box, and closed-box
models. The preferred location of dIrrs in the outer parts of galaxy groups and
clusters and in the field as well as the positive correlation between gas
content and distance from massive galaxies indicate that these dIrrs probably
have not yet experienced significant interactions or galaxy harassment.
(Abridged)


title:
The Star Formation Rate of the Universe at z~6 from the Hubble Ultra
  Deep Field

abstract:
  We determine the abundance of i'-band drop-outs in the recently-released
HST/ACS Hubble Ultra Deep Field (UDF). Since the majority of these sources are
likely to be z~6 galaxies whose flux decrement between the F775W i'-band and
F850LP z'-band arises from Lyman-alpha absorption, the number of detected
candidates provides a valuable upper limit to the unextincted star formation
rate at this redshift. We demonstrate that the increased depth of UDF enables
us to reach an 8-sigma limiting magnitude of z'(AB)=28.5 (equivalent to
1.5/h{70}^2 M_sun/yr at z=6, or 0.1 L*(UV) for the z~3 U-drop population),
permitting us to address earlier ambiguities arising from the unobserved form
of the luminosity function. We identify 54 galaxies (and only one star) at
z'(AB)<28.5 with (i'-z')>1.3 over the deepest 11arcmin^2 portion of the UDF
field. The characteristic luminosity (L*) is consistent with values observed at
z~3. The faint end slope (alpha) is less well constrained, but is consistent
with only modest evolution. The main change appears to be in the number density
(Phi*). Specifically, and regardless of possible contamination from cool stars
and lower redshift sources, the UDF data support our previous result that the
star formation rate at z~6 was at least x6 LESS than at z~3 (Stanway, Bunker &
McMahon 2003). This declining comoving star formation rate (0.005
h{70}M_sun/yr/Mpc^3 at z~6 for a Salpeter IMF) poses an interesting challenge
for models which suggest that L>0.1L* star forming galaxies at z~6 reionized
the universe. The
  short-fall in ionizing photons might be alleviated by galaxies
  fainter than our limit, or a radically different IMF.
  Alternatively, the bulk of reionization might have occurred at z>>6.


title: Viscosity and Rotation in Core-Collapse Supernovae

abstract:
  We construct models of core-collapse supernovae in one spatial dimension,
including rotation, angular momentum transport, and viscous dissipation
employing an alpha-prescription. We compare the evolution of a fiducial 11
M_sun non-rotating progenitor with its evolution including a wide range of
imposed initial rotation profiles (1.25<P_0<8 s, where P_0 is the initial,
approximately solid-body, rotation period of the iron core). This range of P_0
covers the region of parameter space from where rotation begins to modify the
dynamics (P_0~8 s) to where angular velocities at collapse approach Keplerian
(P_0~1 s). Assuming strict angular momentum conservation, all models in this
range leave behind neutron stars with spin periods <10 ms, shorter than those
of most radio pulsars, but similar to those expected theoretically for
magnetars at birth. A fraction of the gravitational binding energy of collapse
is stored in the free energy of differential rotation. This energy source may
be tapped by viscous processes, providing a mechanism for energy deposition
that is not strongly coupled to the mass accretion rate through the stalled
supernova shock. This effect yields qualitatively new dynamics in models of
supernovae. We explore several potential mechanisms for viscosity in the
core-collapse environment: neutrino viscosity, turbulent viscosity caused by
the magnetorotational instability (MRI), and turbulent viscosity by entropy-
and composition-gradient-driven convection. We argue that the MRI is the most
effective. We find that for rotation periods in the range P_0<~5 s, and a range
of viscous stresses, that the post-bounce dynamics is significantly effected by
the inclusion of this extra energy deposition mechanism; in several cases we
obtain strong supernova explosions.


title: The Formation and Evolution of the First Massive Black Holes

abstract:
  The first massive astrophysical black holes likely formed at high redshifts
(z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations.
These black holes grow by mergers and gas accretion, evolve into the population
of bright quasars observed at lower redshifts, and eventually leave the
supermassive black hole remnants that are ubiquitous at the centers of galaxies
in the nearby universe. The astrophysical processes responsible for the
formation of the earliest seed black holes are poorly understood. The purpose
of this review is threefold: (1) to describe theoretical expectations for the
formation and growth of the earliest black holes within the general paradigm of
hierarchical cold dark matter cosmologies, (2) to summarize several relevant
recent observations that have implications for the formation of the earliest
black holes, and (3) to look into the future and assess the power of
forthcoming observations to probe the physics of the first active galactic
nuclei.


title:
Bar Diagnostics in Edge-On Spiral Galaxies. III. N-Body Simulations of
  Disks

abstract:
  Present in over 45% of local spirals, boxy and peanut-shaped bulges are
generally interpreted as edge-on bars and may represent a key phase in the
evolution of bulges. Aiming to test such claims, the kinematic properties of
self-consistent 3D N-body simulations of bar-unstable disks are studied. Using
Gauss-Hermite polynomials to describe the stellar kinematics, a number of
characteristic bar signatures are identified in edge-on disks: 1) a major-axis
light profile with a quasi-exponential central peak and a plateau at moderate
radii (Freeman Type II profile); 2) a ``double-hump'' rotation curve; 3) a
sometime flat central velocity dispersion peak with a plateau at moderate radii
and occasional local central minimum and secondary peak; 4) an h3-V correlation
over the projected bar length. All those kinematic features are spatially
correlated and can easily be understood from the orbital structure of barred
disks. They thus provide a reliable and easy-to-use tool to identify edge-on
bars. Interestingly, they are all produced without dissipation and are
increasingly realized to be common in spirals, lending support to bar-driven
evolution scenarios for bulge formation. So called ``figure-of-eight''
position-velocity diagrams are never observed, as expected for realistic
orbital configurations. Although not uniquely related to triaxiality,
line-of-sight velocity distributions with a high velocity tail (i.e. an h3-V
correlation) appear as particularly promising tracers of bars. The stellar
kinematic features identified grow in strength as the bar evolves and vary
little for small inclination variations. Many can be used to trace the bar
length. Comparisons with observations are encouraging and support the view that
boxy and peanut-shaped bulges are simply thick bars viewed edge-on.


title: The Power of Exploratory Chandra Observations

abstract:
  With its excellent spatial resolution, low background, and hard-band
response, the Chandra X-ray Observatory is ideal for performing exploratory
surveys. These efficient, sensitive observations can place constraints on
fundamental properties of a quasar continuum including the X-ray luminosity,
the ratio of X-ray to UV power, and the X-ray spectral shape. To demonstrate
the power of such surveys to provide significant insight, we consider two
examples, a Large Bright Quasar Survey sample of broad absorption line quasars
and a sample of Sloan Digital Sky Survey (SDSS) quasars with extreme CIV
blueshifts. In both cases, exploratory Chandra observations provide important
information for a physical understanding of UV spectroscopic differences in
quasars.


title: Observational constraints on cosmology from modified Friedmann equation

abstract:
  Recent measurements of type Ia supernovae as well as other concordant
observations suggest that the expansion of our universe is accelerating. A dark
energy component has usually been invoked as the most feasible mechanism for
the acceleration. However, the effects arising from possible extra dimensions
can mimic well the role of a dark energy through a modified Friedmann equation.
In this work, we investigate some observational constraints on a scenario in
which this modification is given by $H^2 = {8\pi G \over 3} (\rho +C\rho^n)$.
We mainly focus our attention on the constraints from recent measurements of
the dimensionless coordinate distances to type Ia supernovae and Fanaroff-Riley
type IIb radio galaxies compiled by Daly and Djorgovski (2003) and the X-ray
gas mass fractions in clusters of galaxies published by Allen et al.
(2002,2003). We obtain the confidence region on the power index $n$ of the
modificative term and the density parameter $\Omega_m$ of the universe from a
combined analysis of these databases. It is found that $n=0.06^{+0.22}_{-0.18}$
and $\Omega_m=0.30^{+0.02}_{-0.02}$, at the 95.4% confidence level, which is
consistent within the errors with the standard $\Lambda$CDM model. These
parameter ranges give a universe whose expansion swithes from deceleration to
acceleration at a redshift between 0.52 to 0.73.


title: Probing Dark Matter and Dark Energy with Space-Based Weak Lensing

abstract:
  Weak lensing provides a direct measure of the distribution of mass in the
universe, and is therefore a uniquely powerful probe of dark matter. Weak
lensing can also be used to measure the twin phenomenon of dark energy, via its
effect upon the cosmological growth rate of structures. Essential for this
technique are well-resolved images of background galaxies out to large
distances. As a concrete example of the surveys that will become available by
the end of the decade, we consider the planned Supernova/Acceleration Probe
(SNAP) space telescope. Detailed simulations of space-based images,
manufactured using the shapelets formalism, enable us to quantitatively predict
the future sensitivity to weak lensing shear. The high number density of
galaxies resolved from space will enable maps of dark matter to be produced in
two and three dimensions, with a resolution superior to that from the ground.
Such observations will also afford reduced systematics for high-precision
measurements of weak lensing statistics. These will be used to set tight
constraints on cosmological parameters. In particular, the parameter for
equation of state of dark energy, w, will be measured using weak lensing with a
precision comparable to and somewhat orthogonal to constraints from other
methods.


title: Automated Classification of 2000 Bright IRAS Sources

abstract:
  An Artificial Neural Network (ANN) has been employed using a supervised
back-propagation scheme to classify 2000 bright sources from the Calgary
database of IRAS (Infrared Astronomy Satellite) spectra in the wavelength
region of 8-23 microns. The data base has been classified into 17
pre-determined classes based on spectral morphology. We have been able to
classify more than 80 percent of the 2000 sources correctly at the first
instance. The speed and robustness of the scheme will allow us to classify the
whole of LRS database, containing more than 50,000 sources in the future.


title: Clusters in Very High Energy Cosmic Rays

abstract:
  Arrival directions of cosmic rays with the energy E>4.10^{19} eV are analyzed
by using data of the Yakutsk and AGASA (Japan) extensive air showers (EAS)
arrays. It is supposed that the clusters can be formed as a result of decay of
superheavy particles. The consequences of this supposition compare with
experimental data.


title: Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks

abstract:
  Major-axis long-slit stellar kinematics was obtained for 30 edge-on spiral
galaxies, 24 with a boxy/peanut-shaped (B/PS) bulge. B/PS bulges are present in
>45% of highly inclined systems and much work suggests that they are the
edge-on projection of thick bars. Profiles of the mean stellar velocity V, the
velocity dispersion sigma, and the asymmetric (h3) and symmetric (h4)
deviations from a Gaussian are presented. Comparing those with N-body bar
diagnostics, we find bar signatures in 80% of our sample. B/PS bulge galaxies
typically show a double-hump rotation curve with an intermediate dip or
plateau. They often show a flat central velocity dispersion profile accompanied
by a secondary peak or plateau and >=40% have a local central sigma minimum.
The h3 profiles display up to 3 slope reversals and h3 is normally correlated
with V over the presumed bar length, contrary to expectations from axisymmetric
disks. Those characteristic bar signatures strengthen the case for a close link
between B/PS bulges and bars. h3 is anti-correlated with V in the very center
of most galaxies, indicating that they additionally harbor cold and dense
decoupled nearly axisymmetric central stellar disks. These coincide with
previously identified star-forming ionized-gas disks in the gas-rich systems,
and we argue that they formed out of gas inflow driven by the bar. As suggested
by N-body models, h3 appears to be a reliable tracer of asymmetries in disks,
allowing to discriminate between axisymmetric and barred disks seen in
projection. B/PS bulges (and thus a large fraction of all bulges) appear to be
made-up mostly of disk material which has acquired a large vertical extent
through bar-driven vertical instabilities. Their formation is thus probably
dominated by secular evolution processes rather than merging. [Abridged]


title:
A Hybrid Cosmological Hydrodynamic/N-body Code Based on a Weighted
  Essentially Non-Oscillatory Scheme

abstract:
  We present a newly developed cosmological hydrodynamics code based on
weighted essentially non-oscillatory (WENO) schemes for hyperbolic conservation
laws. WENO is a higher order accurate finite difference scheme designed for
problems with piecewise smooth solutions containing discontinuities, and has
been successfully applied for problems involving both shocks and complicated
smooth solution structures. We couple hydrodynamics based on the WENO scheme
with standard Poisson solver - particle-mesh (PM) algorithm for evolving the
self-gravitating system. The third order low storage total variation
diminishing (TVD) Runge-Kutta scheme has been used for the time integration of
the system. To test accuracy and convergence rate of the code, we subject it to
a number of typical tests including the Sod shock tube in multidimensions, the
Sedov blast wave and formation of the Zeldovich pancake. These tests validate
the WENO hydrodynamics with fast convergence rate and high accuracy. We also
evolve a low density flat cosmological model ($\Lambda$CDM) to explore the
validity of the code in practical simulations.


title:
Self-enrichment of Galactic halo globular clusters: stimulated star
  formation and consequences for the halo metallicity distribution

abstract:
  We explore the self-enrichment hypothesis for globular cluster formation with
respect to the star formation aspect. Following this scenario, the massive
stars of a first stellar generation chemically enrich the globular progenitor
cloud up to Galactic halo metallicities and sweep it into an expanding
spherical shell of gas. This paper investigates the ability of this swept
proto-globular cloud to become gravitationally unstable and, therefore, to seed
the formation of second generation stars which may later on form a globular
cluster. We use a simple model based on a linear perturbation theory for
transverse motions in a shell of gas to demonstrate that the pressures by which
the progenitor clouds are bound and the supernova numbers required to achieve
Galactic halo metallicities support the successful development of the shell
transverse collapse. Interestingly, the two parameters controling the
metallicity achieved through self-enrichment, namely the number of supernovae
and the external pressure, also rule the surface density of the shell and thus
its ability to undergo a transverse collapse. Such a supernova-induced origin
for the globular cluster stars opens therefore the way to the understanding of
the halo metallicity distributions. This model is also able to explain the
lower limit of the halo globular cluster metallicity.


title:
Radial Velocity Variations in Pulsating Ap Stars III. The Discovery of
  16.21 min Oscillations in Beta CrB

abstract:
  We present the analysis of 3 hrs of a rapid time series of precise stellar
radial velocity (RV) measurements (sigma = 4.5 m/s) of the cool Ap star Beta
CrB. The integrated RV measurements spanning the wavelength interval 5000-6000
Ang. show significant variations (false alarm probability = 10^-5) with a
period of 16.21 min (nu = 1028.17 micro Hz) and an amplitude of 3.54 +/- 0.56
m/s. The RV measured over a much narrower wavelength interval reveals one
spectral feature at 6272 Ang. pulsating with the same 16.21 min period and an
amplitude of 138 +/- 23 m/s. These observations establish Beta CrB to be a
low-amplitude rapidly oscillating Ap star.


title:
Predicted rotation signatures in MHD disc winds and comparison to DG Tau
  observations

abstract:
  Motivated by the first detections of rotation signatures in the DG Tau jet
(Bacciotti et al. 2002), we examine possible biases affecting the relation
between detected rotation signatures and true azimuthal velocity for
self-similar MHD disc winds, taking into account projection, convolution as
well as excitation gradients effects. We find that computed velocity shifts are
systematically smaller than the true underlying rotation curve. When outer
slower streamlines dominate the emission, we predict observed shifts increasing
with transverse distance to the jet axis, opposite to the true rotation
profile. Determination of the full transverse rotation profile thus requires
high angular resolution observations (< 5 AU) on an object with dominant inner
faster streamlines. Comparison of our predictions with HST/STIS observations of
DG Tau clearly shows that self-similar, warm MHD disc wind models with lambda =
13 and an outer radius of the disc ~ 3 AU are able to reproduce detected
velocity shifts, while cold disc wind models (lambda > 50) are ruled out for
the medium-velocity component in the DG Tau jet.


title:
The early build-up of dust in galaxies: A study of Damped Ly alpha
  Systems

abstract:
  We present a study of the early build-up of dust in high redshift galaxies.
The study is based on the analysis of 38 Damped Ly alpha systems (DLAs) for
which we derive the fraction of iron atoms in dust form, f_{Fe}. The sample is
representative of metal-poor galaxies in the redshift range 0.6 </= z </= 3.4
selected on the basis of their absorption HI column density (N(HI) >/= 2 x
10^{20} atoms cm^{-2}). We find that the dust fraction increases with
metallicity, from f_{Fe}~0 at [Fe/H] ~ -2 dex, up to f_{Fe} ~ 0.9 at solar
metallicity; the increase is fast below [Fe/H] ~ -1 dex and mild at higher
metallicities. We also find some evidence for an increase of f_{Fe} with cosmic
time; a large fraction of the systems younger than ~3 Gyr has f_{Fe} </~ 0.5.
These results indicate the dust-to-metal ratio increases in the course of
chemical evolution, at variance with the hypothesis of an approximately
constant dust-to-metal ratio, commonly adopted in models of galactic evolution.
This hypothesis is consistent with local and high-redshift data only when the
metallicity is relatively high ([Fe/H] >/~ -1 dex). The results of this work
suggest that the main mechanisms of dust formation may be rather sensitive to
the level of metallicity attained by a galaxy in the course of its chemical
evolution. A metallicity-dependent dust production by SNe II seems to be the
most promising mechanism for explaining the rise of f_{Fe} at [Fe/H] </~ -1
dex.


title: X-ray polarization properties of the accretion column in magnetic CVs

abstract:
  The accretion column in magnetic Cataclysmic Variables may have a not
negligible Thomson optical depth. A fraction of the thermal radiation from the
post-shock region may therefore be scattered - and then polarized - before
escaping the column. Moreover, part of the thermal radiation is reflected - and
again polarized - by the White Dwarf surface. We show that X-ray polarimetry
can provide valuable, and probably unique informations on the geometry and
physical parameters of the accretion column by calculating, by means of Monte
Carlo simulations, the expected polarization properties of magnetic CVs as a
function of the geometrical parameters (assuming a cylindrical geometry) and
the Thomson optical depth of the column. We find that degrees of polarization
as high as about 4% can be present, and apply our calculations to the
archetypal magnetic CV, AM Herculis.


title: Handling of Atomic Data

abstract:
  State-of-the-art NLTE model-atmosphere codes have arrived at a high level of
numerical sophistication and are now useful tools to analyze high-quality
spectra from the infrared to the X-ray wavelength range. The capacity of
current computers permit calculations which include line spectra from all
elements from hydrogen up to the iron group. The lack of reliable atomic data
has become a critical problem for further progress.
  We summarize available sources of atomic data, and discuss how these are
implemented in the Tuebingen Model-Atmosphere Package TMAP. We describe our
Iron Opacity Interface IrOnIc which is used to calculate opacities of
iron-group elements from Kurucz's and the Opacity Project's data.
  We propose general use of the Tuebingen Model-Atom Database TMAD, which would
allow an easy exchange of ready-to-use model atoms between all model-atmosphere
groups. The comparison of model-atmosphere calculations would then be much
easier, and would save a great deal of manpower that is presently consumed
preparing suitable model atoms for spectral analyses.


title:
Consistency between the radio and MIR faint source counts using the
  radio-MIR correlation

abstract:
  We show from the recent extrapolation of the radio-FIR correlation to the MIR
that the 20 cm and 15 um differential source counts are likely to come from the
same parent population.


title:
The Impact of High Pressure Cluster Environment on the X-ray Luminosity
  of Coma Early-type Galaxies

abstract:
  We present an observational study of the Lx vs Lb sigma^2 relation for
early-type galaxies in the Coma cluster based on the XMM-Newton survey data.
Compared to a similar relation for a sample dominated by field early-type
galaxies, the Coma cluster galaxies show a flatter slope. Our calculations show
that adiabatic compression produces a flattening in the Lx vs Lb sigma^2
relation that is in remarkable agreement with the observed effect. Our scenario
is further supported by the observed compactness of the X-ray emission of Coma
galaxies.


title: The Mid-IR luminosity function of galaxies in the ELAIS Southern fields

abstract:
  We present the first determination of the 15micron luminosity functio
galaxies from the European Large Area ISO survey (ELAIS) southern fields. We
have adopted a new criterion to separate the quiescent, non-evolving and the
starburst, evolving populations based on the ratio of mid-infrared to optical
luminosities. Strong evolution is suggested by our data for the starburst
galaxy population, while normal spiral galaxies are consistent with no
evolution. The starburst population must evolve both in luminosity and in
density with rates of the order L(z) (1+z)^(3.5) and rho(z) (1+z)^3.8 up to
z~1. The evolutionary parameters of our model have been tested by comparing the
model predictions with other observables, like source counts at all flux
density levels (from 0.1 to 300 mJy) and redshift distributions and luminosity
functions at high-z (0.7 < z < 1.0 from HDF-N data). The agreement between our
model predictions and the observed data is remarkably good. We use our data to
estimate the star-formation density of the Universe up to z=0.4 and we use the
luminosity function model to predict the trend of the star-formation history up
to z=1.


title:
Black hole mass estimation with a relation between the BLR size and
  emission line luminosity of AGN

abstract:
  An empirical relation between the broad line region (BLR) size and optical
continuum luminosity is often adopted to estimate the BLR size and then the
black hole mass of AGNs. However, optical luminosity may not be a good
indicator of photoionizing luminosity for extremely radio-loud AGNs because the
jets usually contribute significantly to the optical continuum. Therefore, the
black hole masses derived for blazar-type AGNs with this method are probably
overestimated. Here we first derived a tight empirical relation between the BLR
size and the H$_\beta$ emission line luminosity, $R(\rm{light-days})=
24.05(L_{H_\beta}/10^{42} ergs s^{-1})^{0.68}$, from a sample of 34 AGNs with
the BLR size estimated with the reverberation mapping technique. Then we
applied this relation to estimate the black hole masses of some AGNs and found
that for many extremely radio-loud AGNs the black hole masses obtained with the
$R-L_{H_\beta}$ relation are systematically lower than those derived previously
with the $R-L_{5100\AA}$ relation, while for radio-quiet and slightly
radio-loud AGNs the results obtained with these two methods are almost the
same. The difference of black hole masses estimated with these two relations
increases with the radio-loudness for extremely radio-loud AGNs, which is
consistent with the fact that their equivalent widths of H$_{\beta}$ emission
line become smaller at higher radio-loudness. If the small H$_{\beta}$
equivalent widths of extremely radio-loud AGNs are indeed caused by the beaming
effect, we argue that the optical emission line luminosity may be a better
tracer of ionizing luminosity for blazar-type AGNs and the black hole mass
derived with the $R-L_{H_\beta}$ relation are probably more accurate.


title: Young Massive Star Clusters in Normal Galaxies

abstract:
  Young star clusters with masses similar to those of classical old globular
clusters are observed not only in starbursts, mergers or otherwise disturbed
galaxies, but also in normal spiral galaxies. Some young clusters with masses
as high as ~10^6 Msun have been found in the disks of isolated spirals.
Dynamical mass estimates are available for a few of these clusters and are
consistent with Kroupa-type IMFs. The luminosity (and possibly mass-) functions
of young clusters are usually well approximated by power-laws. Thus, massive
clusters at the tail of the distribution are naturally rare, but appear to be
present whenever clusters form in large numbers. While bound star clusters may
generally form with a higher efficiency in environments of high star formation
rate, many of the apparent differences between clusters in starbursts and
``normal'' galaxies might be simply due to sampling effects.


title: Spectral Types and Masses of White Dwarfs in Globular Clusters

abstract:
  White dwarfs in globular clusters offer additional possibilities to determine
distances and ages of globular clusters, provided their spectral types and
masses are known. We therefore started a project to obtain spectra of white
dwarfs in the globular clusters NGC 6397 and NGC 6752. All observed white
dwarfs show hydrogen-rich spectra and are therefore classified as DA. Analysing
the multi-colour photometry of the white dwarfs in NGC 6752 yields an average
gravity of log g = 7.84 and 0.53 Msolar as the most probable average mass for
globular cluster white dwarfs. Using this average gravity we try to determine
independent temperatures by fitting the white dwarf spectra. While the stellar
parameters determined from spectroscopy and photometry usually agree within the
mutual error bars, the low resolution and S/N of the spectra prevent us from
setting constraints stronger than the ones derived from the photometry alone.
For the same reasons the white dwarf spectra obtained for NGC 6397
unfortunately do not provide an independent distance estimate of sufficient
accuracy to distinguish between the long and short distance scale for globular
clusters.


title: Interstellar Polarization in M31

abstract:
  The wavelength dependence of interstellar polarization due to dust in M31 has
been observed along four sightlines. Only one sightline had been measured
previously.The globular clusters, S78, S150, S233 and Baade 327 were used as
point sources to probe the interstellar dust in M31. The Serkowski law produces
good fits for all the sightlines although the relationship between K and
lambda(max) may be different from that found in the Galaxy. The results of this
study imply that the slope K/lambda(max) may be significantly larger in M31.
The Serkowski curves are significantly narrower than those of the same
lambda(max) in the Galaxy and may require extreme modifications to the size
distributions of silicate particles. The fits for the four sightlines reveal
values of lambda(max) ranging from 4800 to 5500 A. These are consistent with
average values of lambda(max) measured in the Galaxy and the Magellanic Clouds.
The range measured for M31 corresponds to R(V) values of 2.7 to 3.1. The range
in R(V) seen in the Galaxy is 2.5 to 5.5 implying, for this small sample, that
the average size ofinterstellar grains in M31 is typically smaller than that
seen for Galactic grains if the nature of the grains is the same. Also, the
polarization efficiency for these sightlines is large although some bias is
expected since sightlines known to have significant interstellar polarization
were selected for the sample.


title:
Spectral characteristics of water megamaser galaxies II: ESO 103-G035,
  TXS 2226-184, and IC 1481

abstract:
  Long-slit optical emission-line spectra of the H2O megamaser galaxies ESO
103-G03, TXS 2226-184, and IC 1481 are evaluated in order to look for
characteristics typical for water-megamaser galaxies. We present rotation
curves, line ratios, electron densities, temperatures, and Hbeta luminosities.
The successful line-profile decompositions rest on d-Lorentzians with an
additional parameter d to adjust the wings, rather than Gaussians or
Lorentzians as basic functions. No significant velocity gradient is found along
the major axis in the innermost 2 kpc of TXS 2226-184. IC 1481 reveals a
spectrum suggestive of a vigorous starburst in the central kiloparsec 10^8
years ago. None of the three galaxies shows any hints for outflows nor special
features which could give clues to the presence of H2O megamaser emission. The
galaxies are of normal Seyfert-2 (ESO 103-G035) or LINER (TXS 2226-184, IC
1481) type.


title: Evidence of Halo Microlensing in M31

abstract:
  We report results from intensive monitoring of two fields on either side of
M31,emphasizing microlensing involving stars and masses in M31. These results
stem from the three-year VATT/Columbia survey of variability on 3d to 2m
timescales. Observations were conducted intensively from 1997-1999, with
baselines 1995-now,at the Vatican Advanced Technology Telescope, MDM 1.3-meter,
and Isaac Newton telescopes, totaling about 200 epochs. The two fields cover
560 square arcmin total, along the minor axis on either side of M31. Candidate
microlensing events are subject to tests to distinguish microlenses from
variable stars. Fourprobable microlensing events total, compared to carefully
computed event rate and efficiency models, indicate a marginally significant
microlensing activity above expectations for the stellar lenses alone in M31
(and the Galaxy) acting as lenses. Maximum likelihood analyses of the event
distribution in timescale and across the face of M31 indicates a microlensing
dark matter halo fraction consistent with that seen in our Galaxy towards the
LMC (Alcock et al. 2000). For a nearly singular isothermal sphere model, we
find a microlensing halo mass fraction f=0.29 +0.30/-0.13 of total dark matter,
and a poorly constrained lensing component mass 0.02 to 1.5 solar mass, 1 sigma
limits). This study is the prototype for a larger one approaching completion;
between them there is significant evidence for asymmetry in the distribution of
microlensing events across the face of M31, and a large population of halo
microlensing objects. (Abridged)


title: Jeans instability in the linearized Burnett regime

abstract:
  Jeans instability is derived for the case of a low density self-gravitating
gas beyond the Navier-Stokes equations. The Jeans instability criterium is
shown to depend on a Burnett coefficient if the formalism is taken up to fourth
order in the wave number. It is also shown that previously known viscosity
corrections to the Jeans wave-number are enhanced if the full fourth order
formalism is applied to the stability analysis.


title:
Discovery of a Jet-Like Structure at the High Redshift QSO CXOMP
  J084128.3+131107

abstract:
  The Chandra Multiwavelength Project (ChaMP) has discovered a jet-like
structure associated with a newly recognized QSO at redshift z=1.866. The
system was 9.4 arcmin off-axis during an observation of 3C 207. Although
significantly distorted by the mirror PSF, we use both a raytrace and a nearby
bright point source to show that the X-ray image must arise from some
combination of point and extended sources, or else from a minimum of three
distinct point sources. We favor the former situation, as three unrelated
sources would have a small probability of occurring by chance in such a close
alignment. We show that interpretation as a jet emitting X-rays via inverse
Compton (IC) scattering on the cosmic microwave background (CMB) is plausible.
This would be a surprising and unique discovery of a radio-quiet QSO with an
X-ray jet, since we have obtained upper limits of 100 microJy on the QSO
emission at 8.46 GHz, and limits of 200 microJy for emission from the putative
jet.


title:
On the Lack of Thermal Emission from the Quiescent Black Hole XTE
  J1118+480: Evidence for the Event Horizon

abstract:
  A soft component of thermal emission is very commonly observed from the
surfaces of quiescent, accreting neutron stars. We searched with Chandra for
such a surface component of emission from the dynamical black-hole candidate
XTE J1118+480 (= J1118), which has a primary mass of about 8 solar masses. None
was found, as one would expect if the compact X-ray source is a bona fide black
hole that possesses an event horizon. The X-ray spectrum of J1118 is
well-fitted by a simple power-law model. In our search for a thermal component,
we fitted our Chandra data to a power-law model (with slope and column density
fixed) plus a series of nine hydrogen-atmosphere models with radii ranging from
9/8 to 2.8 Schwarzschild radii. For the more compact models, we included the
important effect of self-irradiation of the atmosphere. Because of the
extremely low column density to J1118, we obtained very strong limits on a
hypothetical thermal source: kT(infinity) < 0.011 keV and L(infinity) < 9.4E30
erg/s (99% confidence level). In analogy with neutron stars, we examine two
possible sources of thermal radiation from a hypothetical surface of J1118:
deep crustal heating and accretion in quiescence. We conclude that if J1118
possesses a surface composed of normal nuclear matter, we would have detected
thermal radiation from this surface. The absence of thermal radiation indicates
that J1118 is a true black hole with an event horizon.


title:
Theoretical and Observational Agreement on Mass Dependence of Cluster
  Life Times

abstract:
  Observations and N-body simulations both support a simple relation for the
disruption time of a cluster as a function of its mass of the form: t_dis = t_4
* (M/10^4 Msun)^gamma. The scaling factor t_4 seems to depend strongly on the
environment. Predictions and observations show that gamma ~ 0.64 +/- 0.06.
Assuming that t_dis ~ M^0.64 is caused by evaporation and shocking implies a
relation between the radius and the mass of a cluster of the form: r_h ~
M^0.07, which has been observed in a few galaxies. The suggested relation for
the disruption time implies that the lower mass end of the cluster initial mass
function will be disrupted faster than the higher mass end, which is needed to
evolve a young power law shaped mass function into the log-normal mass function
of old (globular) clusters.


title: The Star Cluster Population of M51

abstract:
  We present the age and mass distribution of star clusters in M51. The
structural parameters are found by fitting cluster evolution models to the
spectral energy distribution consisting of 8 HST-WFPC2 pass bands. There is
evidence for a burst of cluster formation at the moment of the second encounter
with the companion NGC5195 (50-100 Myr ago) and a hint for an earlier burst
(400-500 Myr ago). The cluster
  IMF has a power law slope of -2.1. The disruption time of clusters is
extremely short (< 100 Myr for a 10^4 Msun cluster).


title:
On the contribution of microlensing to X-ray variability of
  high-redshifted QSOs

abstract:
  We consider a contribution of microlensing in X-ray variability of
high-redshifted QSOs. Such an effect could be caused by stellar mass objects
(SMO) located in a bulge or/and in a halo of this quasar as well as at
cosmological distances between an observer and a quasar. Here, we not
considerability of microlensing caused by deflectors in our Galaxy since it is
well-known from recent MACHO, EROS and OGLE observations that the corresponding
optical depth for the Galactic halo and the Galactic bulge is lower than
$10^{-6}$. Cosmologically distributed gravitational microlenses could be
localized in galaxies (or even in bulge or halo of gravitational macrolenses)
or could be distributed in a uniform way. We have analyzed both cases of such
distributions. As a result of our analysis, we obtained that an optical depth
for microlensing caused by stellar mass objects is usually small for quasar
bulge and quasar halo gravitational microlens distributions ($\tau\sim
10^{-4}$). On the other hand, the optical depth for gravitational microlensing
caused by cosmologically distributed deflectors could be significant and could
reach $10^{-2} - 0.1$ at $z\sim 2$. It means that cosmologically distributed
deflectors may significantlly contribute to the X-ray variability of
high-redshifted QSOs ($z>2$). Considering that upper limit of the optical depth
($\tau\sim 0.1$) corresponds to the case when dark matter forms cosmologically
distributed deflectors, therefore observations of X-ray variations of unlensend
QSOs can be used for the estimation of the dark matter fraction of microlenses.


title:
Galaxy-galaxy weak lensing in SDSS: intrinsic alignments and shear
  calibration errors

abstract:
  Galaxy-galaxy lensing has emerged as a powerful probe of the dark matter
halos of galaxies, but is subject to contamination if intrinsically aligned
satellites of the lens galaxy are used as part of the source sample. We present
a measurement of this intrinsic shear using 200,747 lens galaxies from the
Sloan Digital Sky Survey (SDSS) spectroscopic sample and a sample of satellites
selected using photometric redshifts. The mean intrinsic shear at transverse
separations of 30--446$h^{-1}$ kpc is constrained to be
$-0.0062<\Delta\gamma<+0.0066$ (99.9 per cent confidence, including identified
systematics), which limits contamination of the galaxy-galaxy lensing signal to
at most $\sim 15$ per cent on these scales. We present these limits as a
function of transverse separation and lens luminosity. We furthermore
investigate shear calibration biases in the SDSS, which can also affect
galaxy-galaxy lensing, and conclude that the shear amplitude is calibrated to
better than 18 per cent. This includes noise-induced calibration biases in the
ellipticity, which are small for the sample considered here, but which can be
more important if low signal-to-noise or poorly resolved source galaxies are
used.


title:
Constraints on Scalar-Field Dark Energy from the Cosmic Lens All-Sky
  Survey Gravitational Lens Statistics

abstract:
  We use the statistics of strong gravitational lensing based on the Cosmic
Lens All-Sky Survey (CLASS) data to constrain cosmological parameters in a
spatially-flat, inverse power-law potential energy density, scalar-field dark
energy cosmological model. The lensing-based constraints are consistent with,
but weaker than, those derived from Type Ia supernova redshift-magnitude data,
and mildly favor the Einstein cosmological constant limit of this dark energy
model.


title:
Black Hole Mass Determinations From Orbit Superposition Models are
  Reliable

abstract:
  We show that orbit-superposition dynamical models (Schwarzschild's method)
provide reliable estimates of nuclear black hole masses and errors when
constructed from adequate orbit libraries and kinematic data. We thus rebut two
recent papers that argue that BH masses obtained from this method are
unreliable. These papers claim to demonstrate that the range of allowable BH
masses derived from a given dataset is artificially too narrow as a result of
an inadequate number of orbits in the library used to construct dynamical
models. This is an elementary error that is easily avoided. We describe a
method to estimate the number and nature of orbits needed for the library. We
provide an example that shows that this prescription is adequate, in the sense
that the range of allowable BH masses is not artificially narrowed by use of
too few orbits. A second point raised by critics is that kinematic data are
generally obtained with insufficient spatial resolution to obtain a reliable
mass. We make the distinction between unreliable determinations and imprecise
ones. We show that there are several different properties of a kinematic
dataset that can lead to imprecise BH determinations, but none of the
attributes we have investigated leads to an unreliable determination. In short,
the degree to which the BH radius of influence is resolved by spectroscopic
observations is already reflected in the BH-mass error envelope, and is not a
hidden source of error. The BH masses published by our group and the Leiden
group are reliable.


title: Mixed inflaton and curvaton perturbations

abstract:
  A recent variant of the inflationary paradigm is that the ``primordial''
curvature perturbations come from quantum fluctuations of a scalar field,
subdominant and effectively massless during inflation, called the ``curvaton'',
instead of the fluctuations of the inflaton field. We consider the situation
where the primordial curvature perturbations generated by the quantum
fluctuations of an inflaton and of a curvaton field are of the same order of
magnitude. We compute the curvature perturbation and its spectrum in this case
and we discuss the observational consequences.


title:
LISA Measurement of Gravitational Wave Background Anisotropy:
  Hexadecapole Moment via a Correlation Analysis

abstract:
  We discuss spatial fluctuations in the gravitational wave background arising
from unresolved Galactic binary sources, such as close white dwarf binaries,
due to the fact the galactic binary source distribution is anisotropic. We
introduce a correlation analysis of the two data streams of the Laser
Interferometer Space Antenna (LISA) to extract spherical harmonic coefficients,
in an independent manner, of the hexadecapole moment ($l=4$) related to the
projected two-dimensional density distribution of the binary source population.
The proposed technique complements and improves over previous suggestions in
the literature to measure the gravitational wave background anisotropy based on
the time modulation of data as LISA orbits around the Sun. Such techniques,
however, are restricted only to certain combinations of spherical harmonic
coefficients of the galaxy with no ability to separate them individually. With
LISA, $m=2,3$ and 4 coefficients of the hexadecapole ($l=4$) can be measured
with signal-to-noise ratios at the level of 10 and above in a certain
coordinate system. In addition to the hexadecapole coefficients, when combined
with the time modulation analysis, the correlation study can also be used, in
principle, to measure quadrupole coefficients of the binary distribution.


title: High Energy Emission from the Double Pulsar system J0737-3039

abstract:
  We discuss the effects of particle acceleration at the bow shocks expected in
the binary pulsar system J0737-3039, due to the wind from pulsar A interacting
with both the interstellar medium (ISM), and with the magnetosphere of pulsar
B. In this model, we find that the likeliest source for the X-rays observed by
Chandra is the emission from the shocked wind of pulsar A as it interacts with
the ISM. In this case, for favorable model parameter values, better statistics
might help Chandra marginally resolve the source. A consequence of the model is
a power law high energy spectrum extending up to $\lesssim$ 60 keV, at a level
of $\sim 2 \times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$.


title: A ROSAT Bright Source Catalog Survey with the Swift Satellite

abstract:
  We consider the prospects for a complete survey of the 18,811 sources of the
ROSAT All-Sky Survey Bright Source Catalog (BSC) with NASA's Swift gamma-ray
burst (GRB) mission. By observing each BSC source for 500 s with the
satellite's imaging X-ray and UV/optical telescopes, this "Swift Bright
(Source) Catalog Survey" (Swift-BCS) would derive <5'' source positions for all
BSC sources that have not faded substantially from their ROSAT-era flux levels,
and provide 0.2-10 keV X-ray and UV or optical flux measurements. The
improvement by a factor of 10 to 30 in the two-dimensional localization for
these sources will enable optical identifications or deep limits in nearly
every case, fulfilling the promise of the BSC as a multiwavelength catalog, and
allowing the full enumeration of its rare source populations. Since the
Swift-BCS can be accomplished with 10% of the time on-orbit, for a three-year
mission, and since its targets will be of lower priority than active
afterglows, it will not conflict with the primary Swift mission of GRB
follow-up observations. Moreover, the BSC targets can be scheduled so as to
advance the secondary goals of Swift: Daily monitoring of the full sky in the
hard X-ray band (source fluxes of >~20 mCrab, 10-100 keV) with the wide-field
Burst Alert Telescope (BAT); and a two-year all-sky BAT survey down to >~1
mCrab. The resulting expansion of the catalog of identified X-ray sources from
2000 to 18,000 will provide a greatly-enriched set of targets for observation
by XMM-Newton, Chandra, and future high-energy observatories.


title: Far-UV Spectroscopic Analyses of Four Central Stars of Planetary Nebulae

abstract:
  We analyze the Far-UV/UV spectra of four central stars of planetary nebulae
with strong wind features -- NGC 2371, Abell 78, IC 4776 and NGC 1535, and
derive their photospheric and wind parameters by modeling high-resolution FUSE
(Far-Ultraviolet Spectroscopic Explorer) data in the Far-UV and HST-STIS and
IUE data in the UV with spherical non-LTE line-blanketed model atmospheres.
Abell 78 is a hydrogen-deficient transitional [WR]-PG 1159 object, and we find
NGC 2371 to be in the same stage, both migrating from the constant-luminosity
phase to the white dwarf cooling sequence with Teff ~= 120 kK, Mdot ~= 5x10^-8
Msun/yr. NGC 1535 is a ``hydrogen-rich'' O(H) CSPN, and the exact nature of IC
4776 is ambiguous, although it appears to be helium burning. Both objects lie
on the constant-luminosity branch of post-AGB evolution and have Teff ~= 65 kK,
Mdot ~= 1x10^-8 Msun/yr. Thus, both the H-rich and H-deficient channels of PN
evolution are represented in our sample. We also investigate the effects of
including higher ionization stages of iron (up to FeX) in the model atmosphere
calculations of these hot objects (usually neglected in previous analyses), and
find iron to be a useful diagnostic of the stellar parameters in some cases.
The Far-UV spectra of all four objects show evidence of hot (T ~ 300 K)
molecular hydrogen in their circumstellar environments.


title:
Hydra Observations of Aluminum Abundances in the Red Giants of the
  Globular Clusters M80 and NGC 6752

abstract:
  Aluminum and other metal abundances were determined in 21 red giants in the
globular clusters NGC 6752 and M80 as part of a larger study to determine
whether the aluminum distribution on the red giant branch is related to the
second parameter effect that causes clusters of similar metallicity to display
different horizontal branch morphologies. The observations were obtained of the
Al I lines near 6700 Angstroms with the CTIO Blanco 4-m telescope and Hydra
multi-object spectrograph. The spectra have a resolving power of 18000 or 9400,
with typical S/N ratios of 100-200. Mean [Fe/H] values obtained from the
spectra are -1.58 for NGC 6752 and -1.73 for M80; this represents the first
spectroscopic iron abundance determination for M80. Both NGC 6752 and M80
display a spread in aluminum abundance, with mean [Al/Fe] ratios of +0.51 and
+0.37, respectively. No trend in the variation of the mean Al abundance with
position on the giant branch is discernible in either cluster with our small
sample.


title:
SPIFFI observations of the starburst SMMJ14011+0252: Already old, fat,
  and rich by z = 2.565

abstract:
  Using the SPectrometer for Infrared Faint Field Imaging (SPIFFI) on the ESO
VLT, we have obtained J, H, and K band integral field spectroscopy of the z =
2.565 luminous submillimeter galaxy SMMJ14011+0252. A global spectrum reveals
the brighter of this spatially resolved system's two components as an intense
starburst that is remarkably old, massive, and metal-rich for the early epoch
at which it is observed. We see a strong Balmer break implying a > 100 Myr
timescale for continuous star formation, as well as nebular emission line
ratios implying a supersolar oxygen abundance on large spatial scales. Overall,
the system is rapidly converting a large baryonic mass into stars over the
course of only a few hundred Myr. Our study thus adds new arguments to the
growing evidence that submillimeter galaxies are more massive than Lyman break
galaxies, and more numerous at high redshift than predicted by current
semi-analytic models of galaxy evolution.


title:
Measuring Fundamental Parameters of Substellar Objects. I: Surface
  Gravities

abstract:
  (abridged) We present an analysis of high resolution optical spectra for a
sample of very young, mid- to late M, low-mass stellar and substellar objects
in Upper Sco and Taurus. Effective temperatures (T_eff) and surface gravities
are derived from a multi-feature spectral analysis using TiO, NaI and KI,
through comparison with the latest synthetic spectra. In combination, they
allow us to determine T_eff to within 50K and gravity to within 0.25 dex. Our
high-resolution analysis does not require extinction estimates. Moroever, it
yields T_eff and gravities independent of theoretical evolutionary models. We
find that our gravities for most of the sample agree remarkably well with the
isochrone predictions for the likely cluster ages. However, discrepancies
appear in our coolest targets: these appear to have significantly lower gravity
(by up to 0.75 dex) than our hotter objects, even though our entire sample
covers a relatively narrow range in T_eff (about 300K). This drop in gravity is
also implied by inter-comparisons of the data alone, without recourse to
synthetic spectra. We consider, and argue against, dust opacity, cool stellar
spots or metallicity differences leading to the observed spectral effects; a
real decline in gravity is strongly indicated. Such gravity variations are
contrary to the predictions of the evolutionary tracks, causing improbably low
ages to be inferred from the tracks for our coolest targets. We venture that
these results may arise from evolutionary model uncertainties related to
accretion, deuterium-burning and/or convection effects. Finally, when combined
with photometry and distances, our technique for deriving gravities and
temperatures provides a way of obtaining masses and radii for substellar
objects independent of evolutionary models, as presented in Paper II.


title:
Modified Gravitational Theory as an Alternative to Dark Energy and Dark
  Matter

abstract:
  The problem of explaining the acceleration of the expansion of the universe
and the observational and theoretical difficulties associated with dark matter
and dark energy are discussed. The possibility that Einstein gravity does not
correctly describe the large-scale structure of the universe is considered and
an alternative gravity theory is proposed as a possible resolution to the
problems.


title: X-rays from HH 80, HH 81, and the Central Region

abstract:
  We report detections of X-rays from HH 80 and HH 81 with the ACIS instrument
on the Chandra X-ray Observatory. These are among the most luminous HH sources
in the optical and they are now the most luminous known in X-rays. These X-rays
arise from the strong shocks that occur when the southern extension of this
bipolar outflow slams into the ambient material. There is a one-to-one
correspondence between regions of high X-ray emission and high H? emission. The
X-ray luminosities of HH 80 and HH 81 are 4.5 and 4.3 x 1031 erg s-1,
respectively, assuming the measured low-energy absorption is not in the
sources. The measured temperature of the HH plasma is not as large as that
expected from the maximum velocities seen in the extended tails of the optical
emission lines. Rather it is consistent with the ~106 K temperature of the
?narrow? core of the optical lines. There is no observed emission from HH 80
North, the northern extension of the bipolar flow, based upon a measurement of
lower sensitivity. We imaged the central region of the bipolar flow revealing a
complex of X-ray sources including one near, but not coincident with the
putative power source in the radio and infrared. This source, CXOPTM
J181912.4-204733, has no counterparts at other wavelengths and is consistent in
luminosity and spectrum with a massive star with AV ~ 90 mag. It may contribute
significantly to the power input to the complex. Alternatively, this emission
might be extended X-rays from outflows close to the power source. We detect 94
X-ray sources overall in this area of star formation.


title:
Observational constraints on cosmic strings: Bayesian analysis in a
  three dimensional parameter space

abstract:
  Current data exclude cosmic strings as the primary source of primordial
density fluctuations. However, in a wide class of inflationary models, strings
can form at later stages of inflation and have potentially detectable
observational signatures. We study the constraints from WMAP and SDSS data on
the fraction of primordial fluctuations sourced by local cosmic strings. The
Bayesian analysis presented in this brief report is restricted to the minimal
number of parameters. Yet it is useful for two reasons. It confirms the results
of Pogosian et al (2003) using an alternative statistical method. Secondly, it
justifies the more costly multi-parameter analysis. Already, varying only three
parameters -- the spectral index and the amplitudes of the adiabatic and string
contributions -- we find that the upper bound on the cosmic string contribution
is of order 10%. We expect that the full multi-parameter study, currently
underway, will likely loosen this bound.


title:
Measuring Fundamental Parameters of Substellar Objects. II: Masses and
  Radii

abstract:
  We present mass and radius derivations for a sample of very young, mid- to
late M, low-mass stellar and substellar objects in Upper Sco and Taurus. In a
previous paper, we determined effective temperatures and surface gravities for
these targets, from an analysis of their high-resolution optical spectra and
comparisons to the latest synthetic spectra. We now derive extinctions, radii,
masses and luminosities by combining our previous results with observed
photometry, surface fluxes from the synthetic spectra and the known cluster
distances. These are the first mass and radius estimates for young, very low
mass bodies that are independent of theoretical evolutionary models (though our
estimates do depend on spectral modeling). We find that for most of our sample,
our derived mass-radius and mass-luminosity relationships are in very good
agreement with the theoretical predictions. However, our results diverge from
the evolutionary model values for the coolest, lowest-mass targets: our
inferred radii and luminosities are significantly larger than predicted for
these objects at the likely cluster ages, causing them to appear much younger
than expected. We suggest that uncertainties in the evolutionary models - e.g.,
in the choice of initial conditions and/or treatment of interior convection -
may be responsible for this discrepancy. Finally, two of our late-M objects
(USco 128 and 130) appear to have masses close to the deuterium-fusion boundary
(9--14 Jupiters, within a factor of 2). This conclusion is primarily a
consequence of their considerable faintness compared to other targets with
similar extinction, spectral type and temperature (difference of 1 mag). Our
result suggests that the faintest young late-M or cooler objects may be
significantly lower in mass than the current theoretical tracks indicate.


title:
Large Cosmic Variance in the Clustering Properties of Lyman Alpha
  Emitters at z~5

abstract:
  We reported in a previous paper the discovery of large-scale structure of
Lyman Alpha emitters (LAEs) at z=4.86+-0.03 with a projected size of 20 Mpc x
50 Mpc in narrow-band data of a 25' x 45' area of the Subaru Deep Field
(Omega_0=0.3, lambda_0=0.7, H0=70 km/s/Mpc). However, the surveyed area, which
corresponds to 55 Mpc x 100 Mpc, was not large enough that we can conclude that
we are seeing a typical distribution of z~5 LAEs. In this Letter, we report the
results of follow-up imaging of the same sky area using a new narrow-band
filter (NB704, lambda_c=7046 A and FWHM=100 A) to detect LAEs at z=4.79, i.e.,
LAEs lying closer to us by 39 Mpc on average than the z=4.86 objects. We detect
51 LAEs at z=4.79+-0.04 down to NB704=25.7, and find that their sky
distribution is quite different from the z=4.86 LAEs'. The clustering of z=4.79
LAEs is very weak on any scales and there is no large-scale high- contrast
structure. The shape and the amplitude of the angular correlation function are
thus largely different between the two samples. These results demonstrate a
large cosmic variance in the clustering properties of LAEs on scales of ~ 50
Mpc.


title: Temperature response of Earth to the annual solar irradiance cycle

abstract:
  We directly determine the sensitivity and time delay of Earth's surface
temperature response to annual solar irradiance variations from 60 years of
data. A two-layer energy balance model is developed to interpret the results.
Explaining both the resulting low sensitivity and time delay of 1-2 months
requires negative feedback.


title: A Transition in the Accretion Properties of Radio-Loud Active Nuclei

abstract:
  We present evidence for the presence of a transition in the accretion
properties of radio-loud sources. For a sample of radio galaxies and radio-loud
quasars, selected based on their extended radio properties, the accretion rate
is estimated from the black hole mass and nuclear luminosity. The inferred
distribution is bimodal, with paucity of sources at accretion rates, in
Eddington units, of order ~ 10^{-2} - assuming a radiative efficiency of 10 per
cent - and possibly spanning one-two orders of magnitude. Selection biases are
unlikely to be responsible for such behavior; we discuss possible physical
explanations, including a fast transition to low accretion rates, a change in
the accretion mode/actual accretion rate/radiative efficiency, the lack of
stable disc solutions at intermediate accretion rates or the inefficiency of
the jet formation processes in geometrically thin flows. This transition might
be analogous to spectral states (and jet) transitions in black hole binary
systems.


title: High-resolution radio imaging of young supernovae

abstract:
  The high resolution obtained through the use of VLBI gives an unique
opportunity to directly observe the interaction of an expanding radio supernova
with its surrounding medium. We present here results from our VLBI observations
of the young supernovae SN 1979C, SN 1986J, and SN 2001gd.


title: The environment of Tycho: possible interaction with molecular cloud

abstract:
  The Tycho supernova remnant (SNR), as one of the few historical SNRs, has
been widely studied in various wavebands. Observations show evidence that Tycho
is expanding in a medium with density gradient and possibly interacting with
dense ambient medium toward the northeast direction. From the FCRAO CO survey
of the outer Galaxy, we have identified a patch of molecular clouds in this
area and have conducted a follow-up observation with Nobeyama 45m radio
telescope. The high-resolution (16\arcsec) Nobeyama data shows that a large
molecular cloud surrounds the SNR along the northeastern boundary. We suggest
that the Tycho SNR and the molecular cloud are located in the Perseus arm and
that the dense medium interacting with the SNR is possibly the molecular cloud.
We also discuss the possible connection between the molecular cloud and the
Balmer-dominated optical filaments, and suggest that the preshock gas may be
accelerated within the cosmic ray and/or fast neutral precursor.


title: The Dipole Anisotropy of the First All-Sky X-ray Cluster Sample

abstract:
  We combine the recently published CIZA galaxy cluster catalogue with the
XBACs cluster sample to produce the first all-sky catalogue of X-ray clusters
in order to examine the origins of the Local Group's peculiar velocity without
the use of reconstruction methods to fill the traditional Zone of Avoidance.
The advantages of this approach are (i) X-ray emitting clusters tend to trace
the deepest potential wells and therefore have the greatest effect on the
dynamics of the Local Group and (ii) our all-sky sample provides data for
nearly a quarter of the sky that is largely incomplete in optical cluster
catalogues. We find that the direction of the Local Group's peculiar velocity
is well aligned with the CMB as early as the Great Attractor region 40 h^-1 Mpc
away, but that the amplitude of its dipole motion is largely set between 140
and 160 h^-1 Mpc. Unlike previous studies using galaxy samples, we find that
without Virgo included, roughly ~70% of our dipole signal comes from mass
concentrations at large distances (>60 h^-1 Mpc) and does not flatten,
indicating isotropy in the cluster distribution, until at least 160 h^-1 Mpc.
We also present a detailed discussion of our dipole profile, linking observed
features to the structures and superclusters that produce them. We find that
most of the dipole signal can be attributed to the Shapley supercluster
centered at about 150 h^-1 Mpc and a handful of very massive individual
clusters, some of which are newly discovered and lie well in the Zone of
Avoidance.


title: The Structure of Brown Dwarf Circumstellar Disks

abstract:
  We present synthetic spectra for circumstellar disks that are heated by
radiation from a central brown dwarf. Under the assumption of vertical
hydrostatic equilibrium, our models yield scaleheights for brown dwarf disks in
excess of three times those derived for classical T Tauri (CTTS) disks. If the
near-IR excess emission observed from brown dwarfs is indeed due to
circumstellar disks, then the large scaleheights we find could have a
significant impact on the optical and near-IR detectability of such systems.
Our radiation transfer calculations show that such highly flared disks around
brown dwarfs will result in a large fraction of obscured sources due to
extinction of direct starlight by the disk over a wide range of sightlines. The
obscured fraction for a 'typical' CTTS is less than 20%. We show that the
obscured fraction for brown dwarfs may be double that for CTTS, but this
depends on stellar and disk mass. We also comment on possible confusion in
identifying brown dwarfs via color-magnitude diagrams: edge-on CTTS display
similar colors and magnitudes as a face-on brown dwarf plus disk systems.


title:
The Distance to NGC 5904 (M 5) via the Subdwarfs Main Sequence Fitting
  Method

abstract:
  We present a determination of the distance modulus of the globular cluster
NGC 5904 (M 5), obtained by means of the subdwarf main-sequence fitting on the
(V,V-I) color-magnitude diagram. The subdwarf sample has been selected from the
HIPPARCOS catalog in a metallicity range homogeneous with the cluster ([Fe/H]
\~= -1.1). Both the cluster and the subdwarfs have been observed with the same
telescope+instrument+filters setup (namely, ESO-NTT equipped with the SUSI2
camera), in order to preserve homogeneity and reduce systematic uncertainties.
A set of archival HST data has then been used to obtain a deep and precise
ridge line. These have been accurately calibrated in the ground photometric
system by using the NTT data and used to fit the cluster distance modulus. By
adopting the most commonly accepted values for the reddening, E(B-V) = 0.035
and 0.03, we obtain respectively mu_0 = 14.44 +- 0.09 +- 0.07 and mu_0 = 14.41
+- 0.09 +- 0.07, in agreement with recent determinations.


title: Does Cosmological Vacuum Energy Density have an Electric Reason ?

abstract:
  Rather uncomplicated calculations by hand display a surprising connection
between the energy density of the vacuum and the diameter and age of the
universe. Among other things, the result explains the observation of the
accelerated expansion of the universe.


title: XMM-Newton survey of the Local Group galaxy M 33

abstract:
  In an XMM-Newton raster observation of the bright Local Group spiral galaxy M
33 we study the population of X-ray sources (X-ray binaries, supernova
remnants) down to a 0.2--4.5 keV luminosity of 10^35 erg/s -- more than a
factor of 10 deeper than earlier ROSAT observations. EPIC hardness ratios and
optical and radio information are used to distinguish between different source
classes. The survey detects 408 sources in an area of 0.80 square degree. We
correlate these newly detected sources with earlier M 33 X-ray catalogues and
information from optical, infra-red and radio wavelengths. As M 33 sources we
detect 21 supernova remnants (SNR) and 23 SNR candidates, 5 super-soft sources,
and 2 X-ray binaries (XRBs). There are 267 sources classified as hard, which
may either be XRBs or Crab-like SNRs in M 33 or background AGN. The 44
confirmed and candidate SNRs more than double the number of X-ray detected SNRs
in M 33. 16 of these are proposed as SNR candidates from the X-ray data for the
first time. On the other hand, there are several sources not connected to M 33:
five foreground stars, 30 foreground star candidates, 12 active galactic
nucleus candidates, one background galaxy and one background galaxy candidate.
Extrapolating from deep field observations we would expect 175 to 210
background sources in this field. This indicates that about half of the sources
detected are sources within M 33.


title: A note on solid pulsars

abstract:
  After a brief introduction to the necessary of quark stars in modelling
pulsars, I present a qualitative analysis of the solidification of quark matter
with low-temperature but high-density. The reason, that a solid neutron star
could not be possible, is also given.


title: WX Cen (= WR 48c) - a possible type Ia Supernova progenitor

abstract:
  We confirm the orbital period of WX Cen (WR 48c) determined by Diaz & Steiner
(1995) and refined its value to P = 0.416 961 5 d. The light curve of this
object has an amplitude of 0.32 magnitudes and has a V-shaped narrow minimum,
similar to the ones seen in V Sge, V617 Sgr and in Compact Binary Supersoft
Sources - CBSS. The He II Pickering series decrement shows that the system has
significant amount of hydrogen. The He II 4686 emission lines became weaker
between the 1991 and 2000/2002 observations, indicating distinct levels of
activity. The Balmer lines show variable features with V = -2900 km/s in
absorption and with V = +/- 3500 km/s in emission. These highly variable events
remind the satellites in emission of CBSS. We estimate the color excess as
E(B-V)=0.63. Given the distance-color excess relation in the direction of WX
Cen, this implies a distance of 2.8 kpc. Interstellar absorption of the Na I D
lines show components at -4.1 km/s, which corresponds to the velocity of the
Coalsack, and three other components a -23.9, -32.0 and -39.0 km/s. These
components are also seen with similar strengths in field stars that have
distances between 1.8 and 2.7 kpc. The intrinsic color of WX Cen is (B-V)0=-0.2
and the absolute magnitude, Mv = -0.5. Extended red wings in the strong
emission lines are seen. A possible explanation is that the system has a
spill-over stream similar to what is seen in V617 Sgr. We predict that when
observed in opposite orbital phase, blue wings would be observed. The velocity
of the satellite-like feature is consistent with the idea that the central star
is a white dwarf with a mass of M ~ 0.9 Msun. With the high accretion rate
under consideration, the star may become a SN Ia in a time-scale of 5 X 10^6
years.


title: Simulating Galaxy Clusters - III: Properties of the Intracluster Stars

abstract:
  Cosmological (LCDM) TreeSPH simulations of galaxy clusters have been
performed, invoking star-formation, chemical evolution with non-instantaneous
recycling, metal dependent radiative cooling, strong star-burst and/or AGN
driven super-winds, effects of a meta-galactic UV field and thermal conduction.
Results for two clusters, one Virgo-like (T~3 keV) and one (sub) Coma-like (T~6
keV), are presented. At z=0, the stellar contents of both clusters consist of a
central dominant (cD) galaxy surrounded by galaxies and intracluster (IC)
stars. The IC stars are found to contribute 20-40% of the total cluster B-band
light and to form at a mean redshift z_f~3, on average about 0.5 Gyr prior to
the stars in galaxies. UBVRIJHK surface brightness profiles of the IC star
populations are presented; the profile of the larger cluster matches the
observed V-band profile of the cD in Abell 1413 (T~8 keV). The IC stellar
populations have B-R=1.4-1.5, comparable to larger E galaxies. The mean
[Fe/H]~0.0 in the central part of the cluster (r~100 kpc) decreasing to about
-0.3 at r_vir. The IC stars are alpha-element enhanced, with a weak trend of
[O/Fe] increasing with r, and an overall [O/Fe]~0.4 dex. The IC stars are
kinematically colder than the galaxies: The velocity dispersions of the IC
stars are at r~100-500 kpc only about half of those of the galaxies increasing
to about 70% at r=1-2 Mpc. The projected velocity dispersion in the Virgo-like
cluster at R>~50 kpc is 300-600 km/s depending on orientation and R. Rotation
is dynamically insignificant for the IC stars. The velocity distributions of IC
stars and galaxies are in one cluster highly radially anisotropic, in the other
close to isotropic.


title:
An X-ray measurement of Titan's atmospheric extent from its transit of
  the Crab Nebula

abstract:
  Saturn's largest satellite, Titan, transited the Crab Nebula on 5 January
2003. We observed this astronomical event with the {\it Chandra} X-ray
Observatory. An ``occultation shadow'' has clearly been detected and is found
to be larger than the diameter of Titan's solid surface. The difference gives a
thickness for Titan's atmosphere of 880 $\pm$ 60 km. This is the first
measurement of Titan's atmospheric extent at X-ray wavelengths. The value
measured is consistent with or slightly larger than those estimated from
earlier Voyager observations at other wavelengths. We discuss the possibility
of temporal variations in the thickness of Titan's atmosphere.


title:
Photospheric magnetic field and surface differential rotation of the FK
  Com star HD 199178

abstract:
  We present spectropolarimetric observations of the FK Com star HD 199178
obtained between 1998 December and 2003 August at the Telescope Bernard Lyot
(Observatoire du Pic du Midi, France). We report the detection of a
photospheric magnetic field and reconstruct its distribution by means of
Zeeman-Doppler Imaging. We observe large regions where the magnetic field is
mainly azimuthal, suggesting that the dynamo processes generating the magnetic
activity of HD 199178 may be active very close to the stellar surface. We
investigate the rapid evolution of surface brightness and magnetic structures
from a continuous monitoring of the star over several weeks in 2002 and 2003.
We report that significant changes occur in the distribution of cool spots and
magnetic regions on typical timescales of the order of 2 weeks. Our
spectropolarimetric observations also suggest that the surface of HD 199178 is
sheared by differential rotation, with a difference in rotation rate between
equatorial and polar regions of the order of 1.5 times that of the Sun.


title:
Probing Dark Energy with Supernovae : Bias from the time evolution of
  the equation of state

abstract:
  Observation of thousands of type Ia supernovae should offer the most direct
approach to probe the dark energy content of the universe. This will be
undertaken by future large ground-based surveys followed by a space mission
(SNAP/JDEM). We address the problem of extracting the cosmological parameters
from the future data in a model independent approach, with minimal assumptions
on the prior knowledge of some parameters. We concentrate on the comparison
between a fiducial model and the fitting function and adress in particular the
effect of neglecting (or not) the time evolution of the equation of state. We
present a quantitative analysis of the bias which can be introduced by the
fitting procedure. Such bias cannot be ignored as soon as the statistical
errors from present data are drastically improved.


title: Neutrino Experiments and Their Implications

abstract:
  Recent developments in solar, reactor, and accelerator neutrino physics are
reviewed. Implications for neutrino physics, solar physics, nuclear two-body
physics, and r-process nucleosynthesis are briefly discussed.


title: Spatial Variation of the X-ray spectrum of the Crab Nebula

abstract:
  We present spectral analysis of the Crab Nebula obtained with the {\it
Chandra} X-ray observatory. The X-ray spectrum is characterized by a power-law
whose index varies across the nebula. The variation can be discussed in terms
of the particle injection from the pulsar in two different directions: the
equatorial plane containing the torus and the symmetry axis along the jet. In
the equatorial plane, spectra within the torus are the hardest, with photon
index $\alpha \approx 1.9$, and are almost independent of the surface
brightness. At the periphery of the torus, the spectrum gradually softens in
the outer, lower surface brightness regions, up to $\alpha \approx 3.0$. This
indicates that synchrotron losses become significant to X-ray emitting
particles at the outer boundary of the torus. We discuss the nature of the
torus, incorporating information from observations at other wavelengths.
Spectral variations are also seen within the southern jet. The core of the jet
is the hardest with $\alpha \approx$ 2.0, and the outer sheath surrounding the
core becomes softer with $\alpha$ up to 2.5 at the outermost part. Based on the
similarity between the spectra of the jet core and the torus, we suggest that
the electron spectra of the particles injected from the pulsar are also similar
in these two different directions. The brightness ratio between the near and
far sides of the torus can be explained by Doppler boosting and relativistic
aberration; however, the observed ratio cannot be derived from the standard
weakly magnetized pulsar wind model. We also found a site where an optical
filament comprised of supernova ejecta is absorbing the soft X-ray emission
($<$ 2 keV).


title:
A study of the expanding envelope of Nova V1974 Cyg 1992 based on IUE
  high resolution spectroscopy

abstract:
  We have carried out a detailed analysis of the IUE archival high resolution
spectra of the classical nova V1974 Cyg 1992. In addition to the P Cygni and
emission lines, two shortward shifted absorption systems are present. Evidence
is given that these absorptions originate in two separate expanding shells,
outside the wind layers where the emission lines are formed. The outer main
shell, containing most of the matter ejected at outburst, produces the
so-called ``principal absorption line system'', and the inner faster moving
second shell produces the so-called ``diffuse--enhanced absorption line
system''. The outflow velocity of the two shells increases exponentially with
time reaching a value of about 1750 km/s and 2900 km/s, respectively. We
suggest that the acceleration of the shells is the result of increasing
line-radiation pressure due to the UV-brightening of the star as the effective
radius decreases. Around day 60 the second shell has overtaken the slower
moving principal system shell, and merged with it. This explains: the sudden
disappearance of the diffuse line system near that date, the upward jump of 240
km/s in velocity of the principal system and the first detection of hard X-ray
emission on day 63. This velocity jump indicates that the main shell is about 4
times more massive than the second shell. The deceleration suffered by the
diffuse-enhanced system after the shock provides a shock temperature of about
1.6 KeV, in fairly good agreement with the temperature of the observed hard
X-ray emission.


title: Phenomenological parameterization of quintessence

abstract:
  We propose a simple phenomenological parameterization of quintessence with a
time-varying equation of state. In particular, it accounts for the possibility
of early dark energy. The quintessence potential can be reconstructed in terms
of the present fraction in dark energy, the present equation of state and the
amount of early dark energy.


title:
Testing and comparing tachyon inflation to single standard field
  inflation

abstract:
  We compare the standard single scalar field inflationary predictions with
those of an inflationary phase driven by a tachyon field. A slow-roll formalism
is defined for tachyon inflation and we derive the spectra of scalar and tensor
perturbations as well as the consistency relations. At lowest order the
predictions of standard and tachyon inflation are the same. Higher order
deviations are present and their observational relevance is discussed. We
discuss the observational consequences of some typical inflationary tachyon
potentials and compare them with recent data. All the models predict a negative
and very small running of the scalar spectral index, and they consistently lie
within the 1$\sigma$ contour of the data set. However, the regime of blue
scalar spectral index and large gravity waves is not explored by these models.


title: What is the lowest possible reheating temperature?

abstract:
  We study models in which the universe exits reheating at temperatures in the
MeV regime. By combining light element abundance measurements with cosmic
microwave background and large scale structure data we find a fairly robust
lower limit on the reheating temperature of T_RH > 4 MeV at 95% C.L. However,
if the heavy particle whose decay reheats the universe has a direct decay mode
to neutrinos, there are some small islands left in parameter space where a
reheating temperature as low as 1 MeV is allowed. The derived lower bound on
the reheating temperature also leads to very stringent bounds on models with
$n$ large extra dimensions. For n=2 the bound on the compactification scale is
M > 2000 TeV, and for n=3 it is 100 TeV. These are currently the strongest
available bounds on such models.


title:
New dark energy constraints from supernovae, microwave background and
  galaxy clustering

abstract:
  Using the spectacular new high redshift supernova observations from the
HST/GOODS program and previous supernova, CMB and galaxy clustering data, we
make the most accurate measurements to date of the dark energy density rho_X as
a function of cosmic time, constraining it in a rather model-independent way,
assuming a flat universe. We find that Einstein's vanilla scenario where
rho_X(z) is constant remains consistent with these new tight constraints, and
that a Big Crunch or Big Rip is more than 50 gigayears away for a broader class
of models allowing such cataclysmic events. We discuss popular pitfalls and
hidden priors: parametrizing the equation-of-state w_X(z) assumes positive dark
energy density and no Big Crunch, and the popular parametrization w_X(z)=w_0
+w_0' z has nominally strong constraints from CMB merely because w_0' > 0
implies an unphysical exponential blow-up rho_X ~ e^{3 w_0' z}.


title: The Complete Star Formation History of the Universe

abstract:
  The determination of the star-formation history of the Universe is a key goal
of modern cosmology, as it is crucial to our understanding of how structure in
the Universe forms and evolves. A picture has built up over recent years,
piece-by-piece, by observing young stars in distant galaxies at different times
in the past.
  These studies indicated that the stellar birthrate peaked some 8 billion
years ago, and then declined by a factor of around ten to its present value.
Here we report on a new study which obtains the complete star formation history
by analysing the fossil record of the stellar populations of 96545 nearby
galaxies. Broadly, our results support those derived from high-redshift
galaxies elsewhere in the Universe. We find, however, that the peak of star
formation was more recent - around 5 billion years ago. Our study also shows
that the bigger the stellar mass of the galaxy, the earlier the stars were
formed. This striking result indicates a very different formation history for
high- and low-mass formation.


title:
Baryonic Conversion Tree: The global assembly of stars and dark matter
  in galaxies from the SDSS

abstract:
  Using the spectroscopic sample of the SDSS DR1 we measure how gas was
transformed into stars as a function of time and stellar mass: the baryonic
conversion tree (BCT). There is a clear correlation between early star
formation activity and present-day stellar mass: the more massive galaxies have
formed about 80% of their stars at $z>1$, while for the less massive ones the
value is only about 20%. By comparing the BCT to the dark matter merger tree,
we find indications that star formation efficiency at $z>1$ had to be about a
factor of two higher than today ($\sim 10%$) in galaxies with present-day
stellar mass larger than $2 \times 10^{11}M_\odot$, if this early star
formation occurred in the main progenitor. Therefore, the LCDM paradigm can
accommodate a large number of red objects. On the other hand, in galaxies with
present-day stellar mass less than $10^{11}$ M$_{\odot}$, efficient star
formation seems to have been triggered at $z \sim 0.2$. We show that there is a
characteristic mass (M$_* \sim 10^{10}$ M$_{\odot}$) for feedback efficiency
(or lack of star formation). For galaxies with masses lower than this, feedback
(or star formation suppression) is very efficient while for higher masses it is
not. The BCT, determined here for the first time, should be an important
observable with which to confront theoretical


title:
The effect of gravitational-wave recoil on the demography of massive
  black holes

abstract:
  The coalescence of massive black hole (MBH) binaries following galaxy mergers
is one of the main sources of low-frequency gravitational radiation. A
higher-order relativistic phenomenon, the recoil as a result of the non-zero
net linear momentum carried away by gravitational waves, may have interesting
consequences for the demography of MBHs at the centers of galaxies. We study
the dynamics of recoiling MBHs and its observational consequences. The
``gravitational rocket'' may: i) deplete MBHs from late-type spirals, dwarf
galaxies, and stellar clusters; ii) produce off-nuclear quasars, including
unusual radio morphologies during the recoil of a radio-loud source; and iii)
give rise to a population of interstellar and intergalactic MBHs.


title: Photometric Identification of Young Stripped-Core Supernovae

abstract:
  We present a method designed to identify the spectral type of young (less
than ~30 days after explosion) and nearby (z < ~0.05) supernovae (SNe) using
their broad-band colors. In particular, we show that stripped-core SNe (i.e.,
hydrogen deficient core-collapse events, spectroscopically defined as SNe Ib
and SNe Ic, including broad-lined SN 1998bw-like events) can be clearly
distinguished from other types of SNe. Using the full census of nearby SNe
discovered during the year 2002, we estimate the impact that prompt multi-band
photometry, obtained by 1m class telescopes, would have on the early
identification of stripped-core events. Combining this new approach with
ongoing spectroscopic follow-up programs, one can expect ~20 nearby,
stripped-core events to be identified, each year, around, or before, maximum
light. Follow-up studies, including prompt, multi-epoch optical spectroscopy
and spectropolarimetry, as well as radio and X-ray observations, could greatly
increase our understanding of these events, and shed new light on their
association with cosmological gamma-ray bursts.


title: Evolutionary Population Synthesis for Binary Stellar Populations

abstract:
  We present integrated colours, integrated spectral energy distributions, and
absorption-line indices, for instantaneous burst solar-metallicity binary
stellar populations with ages in the range 1 - 15Gyr. By comparing the results
for populations with and without binary interactions we show that the inclusion
of binary interactions makes the appearance of the population substantially
bluer -- this is the case for each of the quantities we have considered. This
effect raises the derived age and metallicity of the population. Therefore it
is necessary to consider binary interactions in order to draw accurate
conclusions from evolutionary population synthesis work.