title: HI Imaging the Low Red-shift Cosmic Web

abstract:
  Only in recent years has the realization emerged that galaxies do not
dominate the universal baryon budget but are merely the brightest pearls of an
underlying Cosmic Web. Although the gas in these inter-galactic filaments is
moderately to highly ionized, QSO absorption lines have shown that the surface
area increases dramatically in going down to lower HI column densities. The
first image of the Cosmic Web in HI emission has just been made of the Local
Group filament connecting M31 and M33. The corresponding HI distribution
function is in very good agreement with that of the QSO absorption lines,
confirming the 30-fold increase in surface area expected between 10^19 cm^-2
and 10^17 cm^-2. The critical observational challenge is crossing the "HI
desert", the range of log(N_HI) from about 19.5 down to 18, over which
photo-ionization by the intergalactic radiation field produces an exponential
decline in the neutral fraction from essentially unity down to a few percent.
Nature is kinder again to the HI observer below log(N_HI)=18, where the neutral
fraction decreases only very slowly with log(N_HI). With the SKA we can begin
the systematic study of the Cosmic Web beyond the Local Group. With moderate
integration times, the necessary resolution and sensitivity can be achieved out
to distances beyond the Virgo cluster. When combined with targeted optical and
UV absorption line observations, the total baryonic masses and enrichment
histories of the Cosmic Web will be determined over the complete range of
environmental over-densities.


title: R Coronae Borealis Stars at Minimum Light -- UW Cen

abstract:
  Two high-resolution optical spectra of the R Coronae Borealis star UW Cen in
decline are discussed. A spectrum from mid-1992 when the star had faded by
three magnitudes shows just a few differences with the spectrum at maximum
light. The ubiquitous sharp emission lines seen in R CrB at a similar drop
below maximum light are absent. In contrast, a spectrum from mid-2002 when the
star was five magnitudes below maximum light shows an array of sharp emission
lines and a collection of broad emission lines. Comparisons are made with
spectra of R CrB obtained during the deep 1995-1996 minimum. The many common
features are discussed in terms of a torus-jet geometry.


title: Wavelength Shifts in Solar-Type Spectra

abstract:
  Spectral-line displacements away from the wavelengths naively expected from
the Doppler shift caused by stellar radial motion may originate as convective
shifts (correlated velocity and brightness patterns in the photosphere), as
gravitational redshifts, or perhaps be induced by wave motions. Absolute
lineshifts, in the past studied only for the Sun, are now accessible also for
other stars thanks to astrometric determination of stellar radial motion, and
spectrometers with accurate wavelength calibration.
  Comparisons between spectroscopic apparent radial velocities and
astrometrically determined radial motions reveal greater spectral blueshifts in
F-type stars than in the Sun (as theoretically expected from their more
vigorous convection), further increasing in A-type stars (possibly due to
atmospheric shockwaves).
  An important near-future development to enable a further analysis of stellar
surface structure will be the study of wavelength variations across spatially
resolved stellar disks, e.g., the center-to-limb wavelength changes along a
stellar diameter, and their spatially resolved time variability.


title:
New analysis of the two carbon-rich stars CS 22948-27 and CS 29497-34 :
  binarity and neutron-capture elements

abstract:
  We have carried out a new determination of abundances in the very metal-poor
CH/CN strong stars CS 29497-34 and CS 22948-27, using high-resolution spectra
obtained with the HARPS spectrograph at the 3.6m telescope of ESO, La Silla,
that covers the range 400 - 690 nm at a resolution of R = 100,000. Both stars
are found to be long period binaries. It is confirmed that the abundance
patterns show an enhancement of all the alpha-elements (like Mg, Ca), of the
proton capture elements (like Na and Al) and a strong enrichment in "r" and "s"
process elements, where the s-enrichment is probably due to a mass transfer
episode from a companion in its AGB phase. The possible origins of the
abundance pattern and especially of the strong enhancement of both "s" and "r"
elements are discussed.


title: New release of the ELODIE library

abstract:
  We present ELODIE.3, an updated release of the ELODIE library originally
published in Prugniel & Soubiran (2001). It is part of the spectrophotometric
resources available in the HyperLeda database where the spectra can be
visualized or downloaded in FITS format. The ELODIE library includes 1962
spectra of 1388 stars obtained with the ELODIE spectrograph at the Observatoire
de Haute-Provence 193cm telescope in the wavelength range 400 to 680 nm. It
provides a large coverage of atmospheric parameters : Teff from 3000 K to 60000
K, log g from -0.3 to 5.9 and [Fe/H] from -3.2 to +1.4. The library is given at
two resolutions: R=42000, with the flux normalized to the pseudo-continuum,
R=10000 calibrated in physical flux (reduced above earth atmosphere) with a
broad-band photometric precision of 2.5% and narrow-band precision of 0.5%. A
grid of interpolated spectra is also given, which has been used for synthesis
of stellar population with PEGASE-HR (Le Borgne et al. 2004). Compared to the
previous version we have doubled the size of the library, corrected some
identification errors, improved the external stellar parameters and the
reduction procedure. A detailed description is available at the ELODIE.3
website : http://www.obs.u-bordeaux1.fr/m2a/soubiran/elodie_library.html


title:
The Discovery of a High Redshift X-ray Emitting QSO Very Close to the
  Nucleus of NGC 7319

abstract:
  A strong X-ray source only 8" from the nucleus of the Sy2 galaxy NGC 7319 in
Stephan's Quintet has been discovered by Chandra. We have identified the
optical counterpart and show it is a QSO with $z_e = 2.114$. It is also a ULX
with $L_x = 1.5 x 10^{40} erg sec^{-1}$. From the optical spectra of the QSO
and interstellar gas in the galaxy (z = .022) we show that it is very likely
that the QSO and the gas are interacting.


title: Masses of star clusters in the nuclei of bulge-less spiral galaxies

abstract:
  In the last decade star clusters have been found in the centers of spiral
galaxies across all Hubble types. We here present a spectroscopic study of the
exceptionally bright (10^6 - 10^8 Lsun) but compact (Re ~ 5 pc) nuclear star
clusters in very late type spirals with UVES at the VLT. We find the velocity
dispersions of the nine clusters in our sample to range from 13 to 34 km/s.
Using photometric data from the HST/WFPC2 and spherically symmetric dynamical
models we determine masses between 8*10^5 and 6*10^7 Msun. The mass to light
ratios range from 0.2 to 1.5 in the I band. This indicates a young mean age for
most clusters, in agreement with previous studies. Given their high masses and
small sizes we find that nuclear clusters are among the objects with the
highest mean surface density known (up to 10^5 Msun pc^-2). From their
dynamical properties we infer that, rather than small bulges, the closest
structural kin of nuclear clusters appear to be massive compact star clusters.
This includes such different objects as globular clusters, "super star
clusters", ultra compact dwarf galaxies and the nuclei of dwarf elliptical
galaxies. It is a challenge to explain why, despite the wildly different
current environments, all different types of massive star clusters share very
similar and structural properties. A possible explanation links UCDs and
massive globular clusters to nuclear star clusters through stripping of
nucleated dwarf galaxies in a merger event. The extreme properties of this type
of clusters would then be a consequence of their location in the centers of
their respective host galaxies.


title:
Properties of serendipitous X-ray flares discovered in XMM-Newton
  observations

abstract:
  We present the results of a search of the XMM-Newton public data archive for
stellar X-ray flares. We find eight flaring sources for which we identify 7
optical counterparts. Three of these sources have distance estimates which
allow us to determine their luminosities. Based on the decay time of the flares
and their luminosity we derive loop half-lengths of ~2-7x10^10 cm and emission
measures of ~10^54 cm^-3: these are similar to values derived for other stellar
flaring sources. One of the stars shows two flares in close succession. We
discuss the likelihood of this double event being either sympathetic or
homologous in nature. A comparison to a pair of similar flares on the Sun
suggests that homology is the more likely process driving the flare event.


title:
The Microlensing Planet Finder: Completing the Census of Extrasolar
  Planets in the Milky Way

abstract:
  The Microlensing Planet Finder (MPF) is a proposed Discovery mission that
will complete the first census of extrasolar planets with sensitivity to
planets like those in our own solar system. MPF will employ a 1.1m aperture
telescope, which images a 1.3 sq. deg. field-of-view in the near-IR, in order
to detect extrasolar planets with the gravitational microlensing effect. MPF's
sensitivity extends down to planets of 0.1 Earth masses, and MPF can detect
Earth-like planets at all separations from 0.7AU to infinity. MPF's extrasolar
planet census will provide critical information needed to understand the
formation and frequency of extra solar planetary systems similar to our own.


title: Dynamo action in M-dwarfs

abstract:
  Magnetic activity in M-dwarfs present enigmatic questions: On the one hand
they have higher field strengths and larger filling factors than the magnetic
field on the Sun, on the other hand, they are fully convective and their
atmospheres are more neutral, hence they do not have an undershoot layer for
magnetic flux storage and as we show here, cannot have small-scale dynamo
action in their photospheres either. We present a discussion of these facts and
propose a new numerical model to investigate M-dwarf magnetism.


title: Solar System Science with SKA

abstract:
  Radio wavelength observations of solar system bodies reveal unique
information about them, as they probe to regions inaccessible by nearly all
other remote sensing techniques and wavelengths. As such, the SKA will be an
important telescope for planetary science studies. With its sensitivity,
spatial resolution, and spectral flexibility and resolution, it will be used
extensively in planetary studies. It will make significant advances possible in
studies of the deep atmospheres, magnetospheres and rings of the giant planets,
atmospheres, surfaces, and subsurfaces of the terrestrial planets, and
properties of small bodies, including comets, asteroids, and KBOs. Further, it
will allow unique studies of the Sun. Finally, it will allow for both indirect
and direct observations of extrasolar giant planets.


title:
Irradiation of accretion discs in active galactic nuclei due to warm
  absorber

abstract:
  The presence of the warm absorber of considerable optical depth is seen in
many AGN. We show that this medium may affect significantly the optical/UV
spectrum of an AGN by backscattering a fraction of the total radiation flux
towards the disc surface. We consider in detail the case when the disk extends
down to a marginally stable orbit, all the emission comes from the disk surface
and the scattering medium forms a cone around the symmetry axis. Disc
irradiation results in much flatter optical/UV continuum than predicted by
standard disc models. The effect depends both on the total optical depth of the
warm absorber and on the specific density distribution of this medium so the
analysis of the optical/UV continuum allows to obtain constraints for the warm
absorber complementary to those obtained from the soft X-ray data analysis. We
give results for two exemplary sources - RE J1034+396 and PG1211+143, and for
the bluest composite quasar spectrum of Richards et al. obtained from SDSS.


title: Ultra High Energy Cosmic Rays Spectra in Top-Down models

abstract:
  In this work we present a detailed computation of the spectra of UHECR in the
top-down scenario. We compare the spectra of hadrons obtained by two different
methods in QCD and supersymmetric (SUSY) QCD with large primary energies
$\sqrt{s}$ up to $10^{16}$ GeV. The two methods discussed are a Monte Carlo
(MC) simulation and the evolution of the hadron fragmentation functions as
described by the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) equations.
The hadron spectra obtained by the two methods agree fairly well in the
interesting energy range $10^{-5}M_{X}<E<0.3M_{X}$ ($M_X$ is the energy scale
of the process $M_{X}\ge 10^{12}$ GeV). We have also computed the spectra of
photons, neutrinos and nucleons obtaining a good agreement with other published
results. The consistency of the spectra computed by different methods allows us
to consider the spectral shape as a signature of the production model for
UHECR, such as the decay of super heavy relic particles or topological defects.


title: Radio emission from cosmic ray air showers: Monte Carlo simulations

abstract:
  We present time-domain Monte Carlo simulations of radio emission from cosmic
ray air showers in the scheme of coherent geosynchrotron radiation. Our model
takes into account the important air shower characteristics such as the lateral
and longitudinal particle distributions, the particle track length and energy
distributions, a realistic magnetic field geometry and the shower evolution as
a whole. The Monte Carlo approach allows us to retain the full polarisation
information and to carry out the calculations without the need for any
far-field approximations. We demonstrate the strategies developed to tackle the
computational effort associated with the simulation of a huge number of
particles for a great number of observer bins and illustrate the robustness and
accuracy of these techniques. We predict the emission pattern, the radial and
the spectral dependence of the radiation from a prototypical 10^17 eV vertical
air shower and find good agreement with our analytical results (Huege & Falcke
2003) and the available historical data. Track-length effects in combination
with magnetic field effects surprisingly wash out any significant asymmetry in
the total field strength emission pattern in spite of the magnetic field
geometry. While statistics of total field strengths alone can therefore not
prove the geomagnetic origin, the predicted high degree of polarisation in the
direction perpendicular to the shower and magnetic field axes allows a direct
test of the geomagnetic emission mechanism with polarisation-sensitive
experiments such as LOPES. Our code provides a robust, yet flexible basis for
detailed studies of the dependence of the radio emission on specific shower
parameters and for the inclusion of additional radiation mechanism in the
future.


title:
Constraints on higher-dimensional gravity from the cosmic shear
  three-point correlation function

abstract:
  With the developments of large galaxy surveys or cosmic shear surveys it is
now possible to map the dark matter distribution at truly cosmological scales.
Detailed examinations of the statistical properties of the dark matter
distribution reveal the detail of the large-scale structure growth of the
Universe. In particular it is shown here that the behavior of the density field
bi-spectrum is sensitive to departure from normal gravity in a way which
depends only weakly on the background evolution. The cosmic shear bispectrum
appears to be particularly sensitive to changes in the Poisson equation: we
show that the current cosmic shear data can already be used to infer
constraints on the scale of a possible higher-dimensional gravity, above 2
h^{-1}Mpc.


title:
Multiwavelength study of X-ray emitting A- and B-stars testing the
  companion hypothesis

abstract:
  We report on the first results of a multi-wavelength approach to test the
hypothesis that the X-ray emission from intermediate-mass stars is generated by
late-type magnetically active companions. Our high spatial resolution
observations of A/B-type stars in the IR using adaptive optics uncover
hypothetical companion stars at arcsecond separations from the primary. The
same targets are then followed-up in X-rays with Chandra to pinpoint the X-ray
source. Finally, those A/B-type stars that are still detected with Chandra are
studied with IR spectroscopy, where we search for temperature sensitive
features indicating the existence of even closer cool companions.


title: Microquasars as high-energy gamma-ray sources

abstract:
  Galactic microquasars are certainly one of the most recent additions to the
field of high energy astrophysics and have attracted increasing interest over
the last decade. However, the high energy part of the spectrum of microquasars
is the most poorly known, mainly due the lack of sensitive instrumentation in
the past. Microquasars are now primary targets for all of the observatories
working in the X-ray and gamma-ray domains. They also appear as the possible
counterparts for some of the unidentified sources of high-energy gamma-rays
detected by the experiment EGRET on board the satellite COMPTON-GRO. This paper
provides a general review of the main observational results obtained up to now
as well as a summary of the scenarios for production of high-energy gamma-rays
at the present moment.


title: Microquasar models for 3EG J1828+0142 and 3EG J1735-1500

abstract:
  Microquasars are promising candidates to emit high-energy gamma-rays.
Moreover, statistical studies show that variable EGRET sources at low galactic
latitudes could be associated with the inner spiral arms. The variable nature
and the location in the Galaxy of the high-mass microquasars, concentrated in
the galactic plane and within 55 degrees from the galactic center, give to
these objects the status of likely counterparts of the variable low-latitude
EGRET sources. We consider in this work the two most variable EGRET sources at
low-latitudes: 3EG J1828+0142 and 3EG J1735-1500, proposing a microquasar model
to explain the EGRET data in consistency with the observations at lower
energies (from radio frequencies to soft gamma-rays) within the EGRET error
box.


title: On the Nature of the variable gamma-ray sources in the Galaxy

abstract:
  Population studies of EGRET gamma-ray sources indicate that there is a
distinctive population of bright sources at low galactic latitudes. The sources
have a distribution consistent with that of young galactic objects, with a
concentration toward the inner spiral arms. There is a subgroup that displays
strong variability with timescales from days to months. Following an earlier
suggestion by Kaufman Bernado et al. (2002), we explore the possibility that
these sources could be high-mass microquasars. Detailed models for the
gamma-ray emission that include inverse Compton interactions of electrons in
the relativistic jets and photons from all local fields (stellar UV photons,
synchrotron photons, soft X-ray photons from the accretion disk, and hard X-ray
photons from a corona) are presented. We conclude that microquasars are
excellent candidates for the parent population of the subgroup of variable
low-latitude EGRET sources.


title:
Prospects for radio detection of ultra-high energy cosmic rays and
  neutrinos

abstract:
  The origin and nature of the highest energy cosmic ray events is currently
the subject of intense investigation by giant air shower arrays and fluorescent
detectors. These particles reach energies well beyond what can be achieved in
ground-based particle accelerators and hence they are fundamental probes for
particle physics as well as astrophysics. Because of the scarcity of these
high-energy particles, larger and larger ground-based detectors have been
built. The new generation of digital radio telescopes may play an important
role in this, if properly designed. Radio detection of cosmic ray showers has a
long history but was abandoned in the 1970's. Recent experimental developments
together with sophisticated air shower simulations incorporating radio emission
give a clearer understanding of the relationship between the air shower
parameters and the radio signal, and have led to resurgence in its use.
Observations of air showers by the SKA could, because of its large collecting
area, contribute significantly to measuring the cosmic ray spectrum at the
highest energies. Because of the large surface area of the moon, and the
expected excellent angular resolution of the SKA, using the SKA to detect radio
Cherenkov emission from neutrino-induced cascades in lunar regolith will be
potentially the most important technique for investigating cosmic ray origin at
energies above the photoproduction cut-off. (abridged)


title:
The ELODIE Planet Search: Synthetic View of the Survey and its Global
  Detection Threshold

abstract:
  In this paper, we give a synthetic view of the ELODIE Planet Search Survey: a
short description of our instrument and the surveyed sample as well as a brief
review of our detections. Moreover, we have obtained, through numerical
simulations, the global survey sensitivity: a detection probability map in the
secondary mass versus orbital period diagram. We use this map for correcting
our total number of detections for observational biases. Finally, we derive the
fraction of our sample stars hosting at least one giant planet: 4% +/- 1% of
our sample stars host at least one giant planet more massive than 0.5
Jupiter-mass with a period shorter than 1500 days.


title:
Magnetically Driven Accretion Flows in the Kerr Metric IV: Dynamical
  Properties of the Inner Disk

abstract:
  This paper continues the analysis of a set of general relativistic 3D MHD
simulations of accreting tori in the Kerr metric with different black hole
spins. We focus on bound matter inside the initial pressure maximum, where the
time-averaged motion of gas is inward and an accretion disk forms. We use the
flows of mass, angular momentum, and energy in order to understand dynamics in
this region. The sharp reduction in accretion rate with increasing black hole
spin reported in Paper I of this series is explained by a strongly
spin-dependent outward flux of angular momentum conveyed electromagnetically;
when a/M > 0.9, this flux can be comparable to the inward angular momentum flux
carried by the matter. In all cases, there is outward electromagnetic angular
momentum flux throughout the flow; in other words, contrary to the assertions
of traditional accretion disk theory, there is in general no "stress edge", no
surface within which the stress is zero. The retardation of accretion in the
inner disk by electromagnetic torques also alters the radial distribution of
surface density, an effect that may have consequences for observable properties
such as Compton reflection. The net accreted angular momentum is sufficiently
depressed by electromagnetic effects that in the most rapidly-spinning black
holes mass growth can lead to spindown. Spinning black holes also lose energy
by Poynting flux; this rate is also a strongly increasing function of black
hole spin, rising to 10% or more of the rest-mass accretion rate at very high
spin. As the black hole spins faster, the path of the Poynting flux changes
from being predominantly within the accretion disk to predominantly within the
funnel outflow.


title:
High Redshift HCN Emission: Dense Star-Forming Molecular Gas in IRAS
  F10214+4724

abstract:
  Hydrogen cyanide emission in the J=1-0 transition has been detected at
redshift z=2.2858 in IRAS F10214+4724 using the Green Bank Telescope . This is
the second detection of HCN emission at high redshift. The large HCN line
luminosity in F10214 is similar to that in the Cloverleaf (z=2.6) and the
ultra-luminous infrared galaxies Mrk231 and Arp220. This is also true of the
ratio of HCN to CO luminosities. The ratio of far-infrared luminosity to HCN
luminosity, an indicator of the star formation rate per solar mass of dense
gas, follows the correlation found for normal spirals and infrared luminous
starburst galaxies. F10214 clearly contains a starburst that contributes,
together with its embedded quasar, to its overall infrared luminosity. A new
technique for removing spectral baselines in the search for weak, broad
emission lines is presented.


title: Numerical estimation of densities

abstract:
  [Abridged] We present a novel technique, dubbed FiEstAS, to estimate the
underlying density field from a discrete set of sample points in an arbitrary
multidimensional space. FiEstAS assigns a volume to each point by means of a
binary tree. Density is then computed by integrating over an adaptive kernel.
As a first test, we construct several Monte Carlo realizations of a Hernquist
profile and recover the particle density in both real and phase space. At a
given point, Poisson noise causes the unsmoothed estimates to fluctuate by a
factor ~2 regardless of the number of particles. This spread can be reduced to
about 1 dex (~26 per cent) by our smoothing procedure. [...] We conclude that
our algorithm accurately measure the phase-space density up to the limit where
discreteness effects render the simulation itself unreliable. Computationally,
FiEstAS is orders of magnitude faster than the method based on Delaunay
tessellation that Arad et al. employed, making it practicable to recover
smoothed density estimates for sets of 10^9 points in 6 dimensions.


title:
Hubble Space Telescope Observations of Element Abundances in
  Low-redshift Damped Lyman-alpha Galaxies and Implications for the Global
  Metallicity-Redshift Relation

abstract:
  Most models of cosmic chemical evolution predict that the mass-weighted mean
interstellar metallicity of galaxies should rise with time from a low value
$\sim 1/30$ solar at $z \sim 3$ to a nearly solar value at $z = 0$. In the
absence of any selection effects, the damped Lyman-alpha absorbers (DLAs) in
quasar spectra are expected to show such a rise in global metallicity. However,
it has been difficult to determine whether or not DLAs show this effect,
primarily because of the very small number of DLA metallicity measurements at
low redshifts. In an attempt to put tighter constraints on the low-redshift end
of the DLA metallicity-redshift relation, we have observed Zn II and Cr II
lines in four DLAs at $0.09 < z < 0.52$, using the Space Telescope Imaging
Spectrograph (STIS) onboard the Hubble Space Telescope (HST). These
observations have provided the first constraints on Zn abundances in DLAs with
$z < 0.4$. In all the three DLAs for which our observations offer meaningful
constraints on the metallicity, the data suggest that the metallicities are
much lower than the solar value. These results are consistent with recent
imaging studies indicating that these DLAs may be associated with dwarf or low
surface brightness galaxies. We combine our results with higher redshift data
from the literature to estimate the global mean metallicity-redshift relation
for DLAs. We find that the global mean metallicity shows at most a slow
increase with decreasing redshift. ...(Please see the paper for the complete
abstract).


title: Astrometric Discovery of GJ 164B

abstract:
  We discovered a low-mass companion to the M-dwarf GJ 164 with the CCD-based
imaging system of the Stellar Planet Survey (STEPS) astrometric program. The
existence of GJ 164B was confirmed with Hubble Space Telescope NICMOS imaging
observations. A high-dispersion spectral observation in V sets a lower limit of
delta m> 2.2 mag between the two components of the system. Based upon our
parallax value of 0.082 +/- 0.008, we derive the following orbital parameters:
P = 2.04 +/- 0.03 y, a = 1.03 +/- 0.03 AU, and Mtotal = 0.265 +/- 0.020 MSun.
The component masses are MA = 0.170 +/- 0.015 MSun and MB = 0.095 +/- 0.015
MSun. Based on its mass, colors, and spectral properties, GJ 164B has spectral
type M6-8 V.


title: Thirty Meter Telescopes and Gravitational Lensing

abstract:
  Diffraction limited 30m class telescopes will play an important role in
gravitational lensing studies, coming online in approximately 2015. As imaging
telescopes they will complement the ~6m JWST, probing to smaller angular scales
in greatly magnified objects near critical lines and for measuring shear of
objects below the JWST angular scale, such as luminous super-star clusters at
high redshift. The high source density will allow more detailed mass mapping in
the weak lensing regime and will be useful in breaking the cosmology-lens
potential degeneracy in strong lensing. As multi-object spectrographs 30m
telescopes should provide spectra over the entire optical and near infrared
spectrum region. The statistical distribution of redshifts needed to invert
projected shear measurements and calibration of photometric redshifts for
``tomography'' will be available to flux levels around 5-10 nano-Jansky (approx
29.5 m_AB). However, a one nJy object is expected to require ~500 hours to
acquire a redshift, which is most of the dark time in an observing season.
Accordingly ``gravitational telescopes'' will be an important tool for probing
the very faint high redshift universe, magnifying a few square arc-seconds at a
time by factors of 10-1000.


title:
Collapsed and Extended Cold Dark Matter Haloes in Softened N-Body
  Gravity

abstract:
  The statistical mechanics of N cold dark matter (CDM) particles interacting
via a softened gravitational potential is reviewed in the microcanonical
ensemble and mean-field limit. A phase diagram for the system is computed as a
function of the total energy E and gravitational softening length epsilon. For
softened systems, two stable phases exist: a collapsed phase, whose radial
density profile rho(r) is a central Dirac cusp, and an extended phase, for
which rho(r) has a central core and rho(r) ~ r^{-2.2} at large r. It is shown
that many N-body simulations of CDM haloes in the literature inadvertently
sample the collapsed phase only, even though this phase is unstable when there
is zero softening. Consequently, there is no immediate reason to expect
agreement between simulated and observed profiles unless the gravitational
potential is appreciably softened in nature.


title: Casimir Effect in a Supersymmetry-Breaking Brane-World as Dark Energy

abstract:
  A new model for the origin of dark energy is proposed based on the Casimir
effect in a supersymmetry-breaking brane-world. Supersymmetry is assumed to be
preserved in the bulk while broken on a 3-brane. Due to the boundary conditions
imposed on the compactified extra dimensions, there is an effective Casimir
energy induced on the brane. The net Casimir energy contributed from the
graviton and the gravitino modes as a result of supersymmetry-breaking on the
brane is identified as the observed dark energy, which in our construction is a
cosmological constant. We show that the smallness of the cosmological constant,
which results from the huge contrast in the extra-dimensional volumes between
that associated with the 3-brane and that of the bulk, is attainable under very
relaxed conditions.


title: Mass Models for Spiral Galaxies from 2-D Velocity Maps

abstract:
  We model the mass distributions of 40 high surface brightness spiral galaxies
inside their optical radii, deriving parameters of mass models by matching the
predicted velocities to observed velocity maps. We use constant mass-to-light
disk and bulge models, and we have tried fits with no halo and with three
different halo density profiles. The data require a halo in most, but not all,
cases, while in others the best fit occurs with negligible mass in the luminous
component, which we regard as unphysical. All three adopted halo profiles lead
to fits of about the same quality, and our data therefore do not constrain the
functional form of the halo profile. The halo parameters display large
degeneracies for two of the three adopted halo functions, but the separate
luminous and dark masses are better constrained. However, the fitted disk and
halo masses vary substantially between the adopted halo models, indicating that
even high quality 2-D optical velocity maps do not provide significant
constraints on the dark matter content of a galaxy. We demonstrate that data
from longslit observations are likely to provide still weaker constraints. We
conclude that additional information is needed in order to constrain the
separate disk and halo masses in a galaxy.


title:
Correcting for the alias effect when measuring the power spectrum using
  FFT

abstract:
  Because of mass assignment onto grid points in the measurement of the power
spectrum using the Fast Fourier Transform (FFT), the raw power spectrum $\la
|\delta^f(k)|^2\ra$ estimated with FFT is not the same as the true power
spectrum $P(k)$. In this paper, we derive the formula which relates $\la
|\delta^f(k)|^2\ra$ to $P(k)$. For a sample of $N$ discrete objects, the
formula reads: $\la |\delta^f(k)|^2\ra=\sum_{\vec n}
[|W(\kalias)|^2P(\kalias)+1/N|W(\kalias)|^2]$, where $W(\vec k)$ is the Fourier
transform of the mass assignment function $W(\vec r)$, $k_N$ is the Nyquist
wavenumber, and $\vec n$ is an integer vector. The formula is different from
that in some of previous works where the summation over $\vec n$ is neglected.
For the NGP, CIC and TSC assignment functions, we show that the shot noise term
$\sum_{\vec n} 1/N|W(\kalias)|^2]$ can be expressed by simple analytical
functions. To reconstruct $P(k)$ from the alias sum $\sum_{\vec
n}|W(\kalias)|^2 P(\kalias)$, we propose an iterative method. We test the
method by applying it to an N-body simulation sample, and show that the method
can successfully recover $P(k)$. The discussion is further generalized to
samples with observational selection effects.


title:
3C 345: the historical light curve (1967-1990) from the digitized plates
  of the Asiago Observatory

abstract:
  In the frame of a large project to digitize the plate archives of the Italian
and Vatican Astronomical Observatories, we have already performed the
digitization of all available plates of the field of the quasar 3C345. The
plates, approximately 100, were taken with the three telescopes of the Asiago
Observatory (122 cm, 182 cm, 67/90 cm Schmidt Telescope) in the period from
1967 to 1990. We present here essentially new data, mostly in the B band, about
the variability of 3C 345 and also of other four objects (3 quasars and the
active galaxy NGC 6212) in the same field, in that period. Beyond the well
known 3C 345 itself, also the other three quasars show variability, with a
range of 2.0 mag for Q1 and Q2, 1 mag for Q3. The low level variability
detected for the nucleus of NGC 6212 is more suspicious, and should be
confirmed by linear detector data.


title: Late stages of stellar evolution with the Square Kilometer Array

abstract:
  Stars at the end of their lives return much of their mass back to the ISM.
This process is the main source of dust in the ISM, and potentially a source of
large molecules. I discuss several areas where SKA will have major impact on
our understanding of the mass loss and the circumstellar processes. The
resulting requirements for SKA, including frequency coverage and location, are
discussed.


title:
Detection of non-radial g-mode pulsations in the newly discovered PG1159
  star HE 1429-1209

abstract:
  We performed time-series photometry of the PG1159-type star HE 1429-1209,
which was recently discovered in the ESO SPY survey. We show that the star is a
low-amplitude (about 0.05 mag) non-radial g-mode pulsator with a period of
919s. HE 1429-1209 is among the hottest known post-AGB stars (Teff=160000 K)
and, together with the known pulsator RX J2117.1+3412, it defines empirically
the blue edge of the GW Vir instability strip in the HRD at high luminosities.


title:
North-South Neutrino Heating Asymmetry in Strongly Magnetized and
  Rotating Stellar Cores

abstract:
  We perform a series of two-dimensional magnetohydrodynamic simulations of
supernova cores. Since the distributions of the angular momentum and the
magnetic fields of strongly magnetized stars are quite uncertain, we
systematically change the combinations of the strength of the angular momentum,
the rotations law, the degree of differential rotation, and the profiles of the
magnetic fields to construct the initial conditions. By so doing, we estimate
how the rotation-induced anisotropic neutrino heating are affected by the
strong magnetic fields through parity-violating effects and first investigate
how the north-south asymmetry of the neutrino heating in a strongly magnetized
supernova core could be. As for the microphysics, we employ a realistic
equation of state based on the relativistic mean field theory and take into
account electron captures and the neutrino transport via the neutrino leakage
scheme. With these computations, we find that the parity-violating corrections
reduce $ \lesssim 0.5 %$ of the neutrino heating rate than that without the
magnetic fields in the vicinity of the north pole of a star, on the other hand,
enhance about $ \lesssim 0.5 %$ in the vicinity of the south pole. If the
global asymmetry of the neutrino heating in the both of the poles develops in
the later phases, the newly born neutron star might be kicked toward the north
pole in the subsequent time.


title:
Bayesian Statistics and Parameter Constraints on the Generalized
  Chaplygin Gas Model using SNe Ia Data

abstract:
  The type Ia supernovae (SNe Ia) observational data are used to estimate the
parameters of a cosmological model with cold dark matter and the generalized
Chaplygin gas model (GCGM). The GCGM depends essentially on five parameters:
the Hubble constant, the parameter $\bar{A}$ related to the velocity of the
sound, the equation of state parameter $\alpha$, the curvature of the Universe
and the fraction density of the generalized Chaplygin gas (or the cold dark
matter). The parameter $\alpha$ is allowed to take negative values and to be
greater than 1. The Bayesian parameter estimation yields $\alpha = -
0.86^{+6.01}_{-0.15}$, $H_0 = 62.0^{+1.32}_{-1.42} km/Mpc.s$, $\Omega
_{k0}=-1.26_{-1.42}^{+1.32}$, $\Omega_{m0} = 0.00^{+0.86}_{-0.00}$,
$\Omega_{c0} = 1.39^{+1.21}_{-1.25}$, $\bar A =1.00^{+0.00}_{-0.39}$, $t_0 =
15.3^{+4.2}_{-3.2}$ and $q_0 = -0.80^{+0.86}_{-0.62}$, where $t_0$ is the age
of the Universe and $q_0$ is the value of the deceleration parameter today. Our
results indicate that a Universe completely dominated by the generalized
Chaplygin gas is favoured, what reinforces the idea that the this gas may unify
the description for dark matter and dark energy, at least as the SNe Ia data is
concerned. A closed and accelerating Universe is also favoured. The traditional
Chaplygin gas model (CGM), $\alpha = 1$ is not ruled out, even if it does not
give the best-fitting. Particular cases with four or three independent free
parameters are also analysed.


title: Differential rotation of main sequence F stars

abstract:
  The differential rotation of a 1.2 $M_\odot$ zero age MS star (spectral type
F8) is computed and the results are compared with those from a similar model of
the Sun. The rotation pattern is determined by solving the Reynolds equation
including the convective energy transport. The latter is anisotropic due to the
Coriolis force causing a horizontal temperature gradient of ~ 7 K between the
poles and the equator. Comparison of the transport mechanisms of angular
momentum (the eddy viscosity, the $\Lambda$-effect and the meridional flow)
shows that for the F star the $\Lambda$-effect is the most powerful transporter
for rotation periods of 7 d or less. In the limit of very fast rotation the
$\Lambda$-effect is balanced by the meridional flow alone and the rotation is
nearly rigid. The rotation pattern found for the F star is very similar to the
solar rotation law, but the horizontal shear is about twice the solar value. As
a function of the rotation period, the total equator-pole difference of the
angular velocity has a (slight) maximum at a period of 7 d and (slowly)
vanishes in both the limiting cases of very fast and very slow rotation. A
comparison of the solar models with those for the F-type star shows a much
stronger dependence of the differential surface rotation on the stellar
luminosity rather than on the rotation rate.


title: The Lifetimes and Evolution of Molecular Cloud Cores

abstract:
  We discuss the lifetimes and evolution of clumps and cores formed as
turbulent density fluctuations in nearly isothermal molecular clouds. In the
non-magnetic case, clumps are unlikely to reach a hydrostatic state, and
instead are expected to either proceed directly to collapse, or else
``rebound'' towards the mean pressure and density of the parent cloud.
Rebounding clumps are delayed in their re-expansion by their self-gravity. From
a simple virial calculation, we find re-expansion times of a few free-fall
times. In the magnetic case, we present a series of driven-turbulence,
ideal-MHD isothermal numerical simulations in which we follow the evolution of
clumps and cores in relation to the magnetic criticality of their ``parent
clouds'' (the numerical boxes). In subcritical boxes, magnetostatic clumps do
not form. A few moderately-gravitationally bound clumps form which however are
dispersed by the turbulence in < 1.3 Myr. An estimate of the ambipolar
diffusion (AD) time scale t_AD in these cores gives t_AD > 1.3 Myr, only
slightly longer than the dynamical times. In supercritical boxes, some cores
become locally supercritical and collapse in typical times ~ 1 Myr. We also
observe longer-lived supercritical cores that however do not collapse because
they are smaller than the local Jeans length. Fewer clumps and cores form in
these simulations than in their non-magnetic counterpart. Our results suggest
that a) A fraction of the cores may not form stars, and may correspond to some
of the observed starless cores. b) Cores may be out-of-equilibrium structures,
rather than quasi-magnetostatic ones. c) The magnetic field may help reduce the
star formation efficiency by reducing the probability of core formation, rather
than by significantly delaying the collapse of individual cores.


title:
The VVDS data reduction pipeline: introducing VIPGI, the VIMOS
  Interactive Pipeline and Graphical Interface

abstract:
  The VIMOS VLT Deep Survey (VVDS), designed to measure 150,000 galaxy
redshifts, requires a dedicated data reduction and analysis pipeline to process
in a timely fashion the large amount of spectroscopic data being produced. This
requirement has lead to the development of the VIMOS Interactive Pipeline and
Graphical Interface (VIPGI), a new software package designed to simplify to a
very high degree the task of reducing astronomical data obtained with VIMOS,
the imaging spectrograph built by the VIRMOS Consortium for the European
Southern Observatory, and mounted on Unit 3 (Melipal) of the Very Large
Telescope (VLT) at Paranal Observatory (Chile). VIPGI provides the astronomer
with specially designed VIMOS data reduction functions, a VIMOS-centric data
organizer, and dedicated data browsing and plotting tools, that can be used to
verify the quality and accuracy of the various stages of the data reduction
process. The quality and accuracy of the data reduction pipeline are comparable
to those obtained using well known IRAF tasks, but the speed of the data
reduction process is significantly increased, thanks to the large set of
dedicated features. In this paper we discuss the details of the MOS data
reduction pipeline implemented in VIPGI, as applied to the reduction of some
20,000 VVDS spectra, assessing quantitatively the accuracy of the various
reduction steps. We also provide a more general overview of VIPGI capabilities,
a tool that can be used for the reduction of any kind of VIMOS data.


title:
Monte Carlo techniques for time-dependent radiative transfer in 3-D
  supernovae

abstract:
  Monte Carlo techniques based on indivisible energy packets are described for
computing light curves and spectra for 3-D supernovae. The radiative transfer
is time-dependent and includes all effects of O(v/c). Monte Carlo quantization
is achieved by discretizing the initial distribution of 56Ni into radioactive
pellets. Each pellet decays with the emission of a single energy packet
comprising gamma-ray photons representing one line from either the 56Ni or the
56Co decay spectrum. Subsequently, these energy packets propagate through the
homologously-expanding ejecta with appropriate changes in the nature of their
contained energy as they undergo Compton scatterings and pure absorptions.
  The 3-D code is tested by applying it to a spherically-symmetric SN in which
the transfer of optical radiation is treated with a grey absorption
coefficient. This 1-D problem is separately solved using Castor's co-moving
frame moment equations. Satisfactory agreement is obtained.
  The Monte Carlo code is a platform onto which more advanced treatments of the
interactions of matter and radiation can be added. Some of these have already
been developed and tested in previous papers and are summarized here.


title:
Unveiling the nature of three INTEGRAL sources through optical
  spectroscopy

abstract:
  The results of an optical spectroscopy campaign performed at the Astronomical
Observatory of Bologna in Loiano (Italy) on three hard X-ray sources detected
by INTEGRAL (IGR J17303-0601, IGR J18027-1455 and IGR J21247+5058) are
presented. These data have allowed a determination of the nature for two of
them, with IGR J17303-0601 being a low mass X-ray binary in the Galaxy and IGR
J18027-1455 a background Type 1 Seyfert galaxy at redshift z = 0.035. IGR
J21247+5058, instead, has a quite puzzling spectroscopic appearance, with a
broad, redshifted H_alpha complex superimposed onto a `normal' F/G-type
Galactic star continuum: these features, together with the spatially coincident
extended radio emission, might suggest a chance alignment between a relatively
nearby star and a background radio galaxy. These results underline the still
non-negligible importance of smaller telescopes in modern astrophysics.


title: RX J2130.6+4710 - an eclipsing white dwarf - M-dwarf binary star

abstract:
  (Abridged) We report the detection of eclipses in the close white-dwarf -
M-dwarf binary star RXJ2130.6+4710. We estimate that the spectral type of the
M-dwarf is M3.5Ve or M4Ve. We estimate that the effective temperature of the
white dwarf is Teff = 18000K +- 1000K. We have used the width of the primary
eclipse and duration of totality measured precisely from Ultracam u' data
combined with the amplitude of the ellipsoidal effect in the I band and the
semi-amplitudes of the spectroscopic orbits to derive masses and radii for the
M-dwarf and white dwarf. The M-dwarf has a mass of 0.555 +- 0.023 solar masses
and a radius of 0.534 +- 0.053 solar radii, which is a typical radius for stars
of this mass. The mass of the white dwarf is 0.554 +- 0.017 solar masses and
its radius is 0.0137 +- 0.0014 solar radii, which is the radius expected for a
carbon-oxygen white dwarf of this mass and effective temperature RXJ2130.6+4710
is a rare example of a pre-cataclysmic variable star which will start mass
transfer at a period above the period gap for cataclysmic variables.


title: The VLT-VIMOS Mask Preparation Software

abstract:
  VIMOS (VIsible Multi-Object Spectrograph) is a multi-object imaging
spectrograph installed at the VLT (Very large Telescope) at the ESO (European
Southern Observatory) Paranal Observatory, especially suited for survey work.
VIMOS is characterized by its very high multiplexing factor: it is possible to
take up to 800 spectra with 10 arcsec long slits in a single exposure. To fully
exploit its multiplexing potential, we designed and implemented a dedicated
software tool: the VIMOS Mask Preparation Software (VMMPS), which allows the
astronomer to select the objects to be spectroscopically observed, and provides
for automatic slit positioning and slit number maximization within the
instrumental constraints. The output of VMMPS is used to manufacture the slit
masks to be mounted in the instrument for spectroscopic observations.


title:
INTEGRAL observations of the PSR B1259-63 / SS2883 system after the 2004
  periastron passage

abstract:
  The millisecond pulsar PSR B1259-63 and the Be star SS2883 are situated in a
highly eccentric binary system, with orbital period ~3.4 years. We report on
hard X-ray observations obtained with the INTEGRAL satellite close to the 2004
periastron passage. These are the first imaging observations of this system in
the hard X-ray range (>20 keV) and allow the emission of PSR B1259-63 to be
separated from that of a nearby unidentified variable source which may have
contaminated previous hard X-ray observations of this system. Using the
IBIS/ISGRI instrument we measured a flux of ~2--6 mCrab in the 20--200 keV
range, with a power law spectrum of photon index of 1.3 +/- 0.5.


title: The role of an accretion disk in AGN variability

abstract:
  Optically thick accretion disks are considered to be important ingredients of
luminous AGN. The claim of their existence is well supported by observations
and recent years brought some progress in understanding of their dynamics.
However, the role of accretion disks in optical/UV/X-ray variability of AGN is
not quite clear. Most probably, in short timescales the disk reprocesses the
variable X-ray flux but at longer timescales the variations of the disk
structure lead directly to optical/UV variations as well as affect, or even
create, the X-ray variability pattern. We urgently need a considerable progress
in time-dependent disk models to close the gap between the theory and the
stream of data coming from the AGN monitoring.


title:
The gravitational wave signal from massive black hole binaries and its
  contribution to the LISA data stream

abstract:
  Massive black hole binaries, with masses in the range 1E3-1E8 Msun, are
expected to be the most powerful sources of gravitational radiation at mHz
frequencies, and hence are among the primary targets for the planned Laser
Interferometer Space Antenna (LISA). We extend and refine our previous analysis
(Sesana et al. 2004), detailing the gravitational wave signal expected from a
cosmological population of massive black hole binaries. As done in our previous
paper, we follow the merger history of dark matter halos, the dynamics of the
massive black holes they host, and their growth via gas accretion and binary
coalescences in a LCDM cosmology. Stellar dynamical processes dominates the
orbital evolution of black hole binaries at large separations, while
gravitational wave emission takes over at small radii, causing the final
coalescence of the pairs. We show that the GW signal from this population, in a
3 year LISA observation, will be resolved into approx 90 discrete events with
S/N>5, among which approx. 35 will be observed above threshold until
coalescence. These "merging events" involve relatively massive binaries, M=10E5
Msun, in the redshift range 2<z<6. The remaining approx. 55 events come from
higher redshift, less massive binaries (M=5E3 Msun at z>6) and, although their
S/N integrated over the duration of the observation can be substantial, the
final coalescence phase is at too high frequency to be directly observable by
space-based interferometers such as LISA. LISA will be able to detect a
fraction approx. 90% of all the coalescences of massive black hole binaries
occurring at z=5. The residual confusion noise from unresolved massive black
hole binaries is expected to be at least an order of magnitude below the
estimated stochastic noise.


title:
Constraints on the ionization sources of the high redshift intergalactic
  medium

abstract:
  Constraints on the ionization structure of the Intergalactic Medium are
derived as directly imposed by observations in conjunction with the results of
numerical simulations for structure formation. Under the assumption that the
population of sources dominating the UV ionizing background at z<6 is the same
population which reionized the IGM, it is shown that consistency with
measurements of the mean LyA transmitted flux at high redshifts requires the
epoch of hydrogen reionization of the IGM to have occurred at a redshift z <
11, independent of the space density of the sources. The upper limit on the
reionization redshift depends only on the shape of the UV spectra of the
sources. Consistency with constraints on the reionization epoch from WMAP
requires the sources of photoionization to have had hard spectra, such as QSOs
or Population III stars. The only way to escape these conclusions is either:
1.the sources which dominate the photoionization background at z<6 are the
remnants of a population that was a much more prodigious source of ionizing
photons at earlier times, or 2.the sources responsible for the photoionization
of the IGM are an unknown population that contributes negligibly to the
ionization of the IGM at z<6. The contribution of QSOs to the UV background is
also estimated based on recent surveys.


title:
XMM-Newton observations of Extremely Red Objects and the link with
  luminous, X-ray obscured Quasars

abstract:
  We present the results of a deep (about 80 ks) XMM-Newton survey of the
largest sample of near-infrared selected Extremely Red Objects (R-K>5)
available to date to K_S< 19.2. At the relatively bright X-ray fluxes (F_{2-10
keV}> 4x10^{-15} cgs) and near-infrared magnitude probed by the present
observations, the fraction of AGN (i.e., X-ray detected) among the ERO
population is small (~3.5%); conversely, the fraction of EROs among hard X-ray
selected sources is much higher (~20%). The X-ray properties of EROs detected
in our XMM-Newton observation indicate absorption in excess of 10^{22} cm^{-2}
in a large fraction of them. We have also considered additional samples of
X-ray detected EROs available in the literature. X-ray spectral analysis of the
highest S/N sources unambiguously indicates that large columns of cold gas
(even >10^{23} cm^{-2}) are the rule rather than the exception. The X-ray,
optical, and near-infrared properties of those X-ray selected EROs with a
spectroscopic or photometric redshift nicely match those expected for quasars
2, the high-luminosity, high-redshift obscured AGNs predicted in baseline XRB
synthesis models. A close correlation is detected between X- and K-band fluxes.
For the AGN EROs this is consistent, under reasonable assumptions, with the
relation established locally between the host galaxies and their central black
holes. This suggest that the majority of EROs are powered by massive black
holes accreting, on average, at about 0.03-0.1 of the Eddington limit.


title: HETGS Spectroscopy of a Coronally Active Contact Binary, VW Cep

abstract:
  Short-period binaries represent extreme cases in the generation of stellar
coronae via a rotational dynamo. Such stars are important for probing the
origin and nature of coronae in the regimes of rapid rotation and activity
saturation. VW Cep (P=0.28 d) is relatively bright, partially eclipsing, and
very active object. We present preliminary results from Chandra X-ray
spectroscopy with the High Energy Transmission Grating. Light curves show
flaring and rotational modulation, but no strong eclipses. Emission lines are
broader than instrumental, indicating emission from both binary components.
Velocity modulation of emission lines is indicative of geometric structure of
the emitting plasma. The emission measure shows a broad range of temperatures
and strong peak.


title:
Extragalactic Water Masers, Geometric Estimation of H_o and
  Characterization of Dark Energy

abstract:
  High precision estimation of the equation of state of dark energy depends on
constraints external to analyses of Cosmic Microwave Background fluctuations. A
geometric estimation of the local expansion rate, H_o, would provide the most
direct and robust constraint. Traditional techniques to estimate H_o have
depended on observations of standard candles for which systematic effects can
be 10% or more. Observations of water maser sources in the accretion disks that
feed the central engines of active galaxies enable simplified, robust, and
largely geometric analyses. Many thousand maser sources will be discovered in
studies with the SKA, owing to its great sensitivity. Spectroscopic monitoring
and interferometric mapping - with intercontinental baselines - will allow
estimation of H_o to 1% and possibly better.


title: New Insights into Solar Wind Physics from SOHO

abstract:
  The Solar and Heliospheric Observatory (SOHO) was launched in December 1995
with a suite of instruments designed to answer long-standing questions about
the Sun's internal structure, its extensive outer atmosphere, and the solar
wind. This paper reviews the new understanding of the physical processes
responsible for the solar wind that have come from the past 8 years of SOHO
observations, analysis, and theoretical work. For example, the UVCS instrument
on SOHO has revealed the acceleration region of the fast solar wind to be far
from simple thermal equilibrium. Evidence for preferential acceleration of
ions, 100 million K ion temperatures, and marked departures from Maxwellian
velocity distributions all point to specific types of collisionless heating
processes. The slow solar wind, typically associated with bright helmet
streamers, has been found to share some of the nonthermal characteristics of
the fast wind. Abundance measurements from spectroscopy and visible-light
coronagraphic movies from LASCO have led to a better census of the plasma
components making up the slow wind. The origins of the solar wind in the
photosphere and chromosphere have been better elucidated with disk spectroscopy
from the SUMER and CDS instruments. Finally, the impact of the solar wind on
spacecraft systems, ground-based technology, and astronauts has been greatly
aided by having continuous solar observations at the Earth-Sun L1 point, and
SOHO has set a strong precedent for future studies of space weather.


title:
Pulse Shapes From Rapidly-Rotating Neutron Stars: Equatorial Photon
  Orbits

abstract:
  We demonstrate that fitted values of stellar radius obtained by fitting
theoretical light curves to observations of millisecond period X-ray pulsars
can significantly depend on the method used to calculate the light curves. The
worst-case errors in the fitted radius are evaluated by restricting ourselves
to the case of light emitted and received in the equatorial plane of a
rapidly-rotating neutron star. First, using an approximate flux which is
adapted to the one-dimensional nature of such an emission region, we show how
pulse shapes can be constructed using an exact spacetime metric and fully
accounting for time-delay effects. We compare this to a method which
approximates the exterior spacetime of the star by the Schwarzschild metric,
inserts special relativistic effects by hand, and neglects time-delay effects.
By comparing these methods, we show that there are significant differences in
these methods for some applications, for example pulse timing and constraining
the stellar radius. In the case of constraining the stellar radius, we show
that fitting the approximate pulse shapes to the full calculation yields errors
in the fitted radius of as much as about +/- 10%, depending on the rotation
rate and size of the star as well as the details describing the emitting
region. However, not all applications of pulse shape calculations suffer from
significant errors: we also show that the calculation of the soft-hard phase
lag for a 1 keV blackbody does not strongly depend on the method used for
calculating the pulse shapes.


title: User Guide for the Discrete Dipole Approximation Code DDSCAT 6.1

abstract:
  DDSCAT 6.1 is a software package which applies the discrete dipole
approximation (DDA) to calculate scattering and absorption of electromagnetic
waves by targets with arbitrary geometries and complex refractive index. DDSCAT
6.1 allows accurate calculations of electromagnetic scattering from targets
with size parameters 2 pi a_eff/lambda < 15 provided the refractive index m is
not large compared to unity (|m-1| < 2). DDSCAT 6.1 includes support for MPI
and FFTW. We also make available a "plain" distribution of DDSCAT 6.1 that does
not include support for MPI, FFTW, or netCDF, but is much simpler to install
than the full distribution.
  The DDSCAT package is written in Fortran and is highly portable. The program
supports calculations for a variety of target geometries (e.g., ellipsoids,
regular tetrahedra, rectangular solids, finite cylinders, hexagonal prisms,
etc.). Target materials may be both inhomogeneous and anisotropic. It is
straightforward for the user to import arbitrary target geometries into the
code, and relatively straightforward to add new target generation capability to
the package. DDSCAT automatically calculates total cross sections for
absorption and scattering and selected elements of the Mueller scattering
intensity matrix for specified orientation of the target relative to the
incident wave, and for specified scattering directions.


title: Streaming Instabilities in Protoplanetary Disks

abstract:
  Interpenetrating streams of solids and gas in a Keplerian disk produce a
local, linear instability. The two components mutually interact via aerodynamic
drag, which generates radial drift and triggers unstable modes. The secular
instability does not require self-gravity, yet it generates growing particle
density perturbations that could seed planetesimal formation. Growth rates are
slower than dynamical, but faster than radial drift, timescales. Growth rates,
like streaming velocities, are maximized for marginal coupling (stopping times
comparable dynamical times). Fastest growth occurs when the solid to gas
density ratio is order unity and feedback is strongest. Curiously, growth is
strongly suppressed when the densities are too nearly equal. The relation
between background drift and wave properties is explained by analogy with
Howard's semicircle theorem. The three-dimensional, two-fluid equations
describe a sixth order (in the complex frequency) dispersion relation. A
terminal velocity approximation allows simplification to an approximate cubic
dispersion relation. To describe the simplest manifestation of this
instability, we ignore complicating (but possibly relevant) factors like
vertical stratification, dispersion of particle sizes, turbulence, and
self-gravity. We consider applications to planetesimal formation and compare
our work to other studies of particle-gas dynamics.


title: Current Observational Constraints on Cosmic Doomsday

abstract:
  In a broad class of dark energy models, the universe may collapse within a
finite time t_c. Here we study a representative model of dark energy with a
linear potential, V(\phi)=V_0(1+\alpha\phi). This model is the simplest
doomsday model, in which the universe collapses rather quickly after it stops
expanding. Observational data from type Ia supernovae (SNe Ia), cosmic
microwave background anisotropy (CMB), and large scale structure (LSS) are
complementary in constraining dark energy models. Using the new SN Ia data
(Riess sample), the CMB data from WMAP, and the LSS data from 2dF, we find that
the collapse time of the universe is t_c > 42 (24) gigayears from today at 68%
(95%) confidence.


title:
Tramp Novae Between Galaxies in the Fornax Cluster: Tracers of
  Intracluster Light

abstract:
  We report the results of a survey for novae in and between the galaxies of
the Fornax cluster. Our survey provides strong evidence that intracluster novae
exist and that they provide a useful, independent measure of the intracluster
light in Fornax. We discovered six strong nova candidates in six distinct
epochs spanning eleven years from 1993 to 2004. The data were taken with the 4m
and the 1.5m telescopes at CTIO. The spatial distribution of the nova
candidates is consistent with $\sim$16-41% of the total light in the cluster
being in the intracluster light, based on the ratio of the number of novae we
discovered in intracluster space over the total number of novae discovered plus
a simple completeness correction factor. This estimate is consistent with
independent measures of intracluster light in Fornax and Virgo using
intracluster planetary nebulae. The accuracy of the intracluster light
measurement improves with each survey epoch as more novae are discovered.


title: Designer Cosmology

abstract:
  We highlight the flexibility of the IPSO experiment-design framework by
contrasting its application to CMB, weak lensing and redshift surveys. We
illustrate the latter with a 10 parameter MCMC D-optimisation of a dark energy
redshift survey. When averaged over a standard dark energy model space the
resulting optimal survey typically has only one or two redshift bins, located
at z<2. By exploiting optimisation we show how the statistical power of such
surveys is significantly enhanced. Experiment design is aided by the richness
of the figure of merit landscape which means one can impose secondary
optimisation criteria at little cost. For example, one may choose either to
maximally test a single model (such as \Lambda CDM) or to get the most general
model-independent constraints possible (e.g. on a whole space of dark energy
models). Such freedom points to a future where cosmological experiments become
increasingly specialised and optimisation increasingly important.


title: The L to T Dwarf Transition

abstract:
  While the precise mechanism responsible for the L to T dwarf transition
remains unclear, it is clearly caused by changing cloud characteristics. Here
we briefly review data relevant to understanding the nature of the transition
and argue that changing atmospheric dynamics produce the transition by opening
holes through the global iron and silicate cloud decks. Other possibilities,
such as a sudden vertical collapse in these cloud decks are also considered.
Any acceptable model of the L to T transition must ultimately connect changing
cloud properties to the underlying atmospheric dynamics.


title:
Testing the Reality of Strong Magnetic Fields on T Tauri Stars: The
  Naked T Tauri Star Hubble 4

abstract:
  High resolution optical and infrared (IR) echelle spectra of the naked
(diskless) T Tauri star Hubble 4 are presented. The K band IR spectra include 4
Zeeman sensitive Ti I lines along with several magnetically insensitive CO
lines. Detailed spectrum synthesis combined with modern atmospheric models is
used to fit the optical spectra of Hubble 4 in order to determine its key
stellar parameters: Teff = 4158 +/- 56 K; log(g) = 3.61 +/- 0.50; [M/H] = -0.08
+/- 0.05; vsini = 14.6 +/- 1.7 km/s . These stellar parameters are used to
synthesize K band spectra to compare with the observations. The magnetically
sensitive Ti I lines are all significantly broadened relative to the lines
produced in the non-magnetic model, while the magnetically insensitive CO lines
are well matched by the basic non-magnetic model. Models with magnetic fields
are synthesized and fit to the Ti I lines. The best fit models indicate a
distribution of magnetic field strengths on the stellar surface characterized
by a mean magnetic field strength of 2.51 +/- 0.18 kG. The mean field is a
factor of 2.0 greater than the maximum field strength predicted by pressure
equipartition arguments. To confirm the reality of such strong fields, we
attempt to refit the observed profiles using a two component magnetic model in
which the field strength is confined to the equipartition value representing
plage-like regions in one component, and the field is allowed to vary in a
cooler component representing spots. It is shown that such a model is
inconsistent with the optical spectrum of the TiO bandhead at 7055 Angstroms.


title:
The Blue Straggler and Main-sequence Binary Population of the Low-Mass
  Globular Cluster Palomar 13

abstract:
  We present high-precision VI photometry of stars from the middle of the giant
branch to about 5 magnitudes below the main-sequence turnoff in the globular
cluster Palomar 13 based on images obtained with the Keck II 10m telescope. We
tabulate a complete sample of blue stragglers in the cluster out to about 18
core radii. The blue straggler population is significantly more centrally
concentrated than the giant star sample, which is in turn significantly more
centrally concentrated than the main-sequence star sample. Palomar 13 has one
of the highest specific frequencies of blue stragglers of any known globular
cluster, but the specific frequency of blue stragglers in the outskirts of the
cluster does not increase as has been seen in denser clusters. We also identify
a group of faint blue stragglers (bluer than the turnoff, but having about the
same magnitude) that outnumbers the brighter stragglers by more than a factor
of 2. The cluster's color-magnitude diagram shows a large excess of stars to
the red of the main sequence, indicating that the cluster's binary fraction is
at least 30% +/- 4%, which appears to be similar to that of the low-mass
cluster E3 but significantly higher than that of the more massive clusters Pal
5 and NGC 288.


title:
Oxygen Abundances and Chemical Evolution in Low Surface Brightness
  Galaxies

abstract:
  We report the oxygen abundances of the HII regions of a sample of low surface
brightness (LSB) galaxies. We provide analytic functions describing the McGaugh
(1991) calibration of the R_23 method. We use this and the equivalent width
(EW) method to determine oxygen abundances, and also make direct estimates in a
few cases where the temperature sensitive [OIII] 4363 line is available. We
find LSB galaxies to be metal poor, consistent with the L-Z relation of other
galaxies. The large gas mass fractions of these objects provide an interesting
test of chemical evolution models. We find no obvious deviation from the
closed-box model of galactic chemical evolution. Based on our abundance and gas
mass fraction measurements, we infer that LSB galaxies are not fundamentally
different than other galaxy types but are perhaps at an early stage of
evolution.


title:
The Nature of the Molecular Environment within 5 pc of the Galactic
  Center

abstract:
  We present a detailed study of molecular gas in the central 10pc of the
Galaxy through spectral line observations of four rotation inversion
transitions of NH3 made with the VLA. Updated line widths and NH3(1,1)
opacities are presented, and temperatures, column densities, and masses are
derived. We examine the impact of Sgr A East on molecular material at the
Galactic center and find that there is no evidence that the expansion of this
shell has moved a significant amount of the 50 km/s GMC. The western streamer,
however, shows strong indications that it is composed of material swept-up by
the expansion of Sgr A East. Using the mass and kinematics of the western
streamer, we calculate an energy of E=(2-9)x10^{51} ergs for the progenitor
explosion and conclude that Sgr A East was most likely produced by a single
supernova. The temperature structure of molecular gas in the central ~20pc is
also analyzed in detail. We find that molecular gas has a ``two-temperature''
structure similar to that measured by Huttemeister et al. (2003a) on larger
scales. The largest observed line ratios, however, cannot be understood in
terms of a two-temperature model, and most likely result from absorption of
NH3(3,3) emission by cool surface layers of clouds. By comparing the observed
NH3 (6,6)-to-(3,3) line ratios, we disentangle three distinct molecular
features within a projected distance of 2pc from Sgr A*. Gas associated with
the highest line ratios shows kinematic signatures of both rotation and
expansion. The southern streamer shows no significant velocity gradients and
does not appear to be directly associated with either the circumnuclear disk or
the nucleus. The paper concludes with a discussion of the line-of-sight
arrangement of the main features in the central 10pc.


title:
The Discovery of Extended Thermal X-ray Emission from PKS 2152-699:
  Evidence for a `Jet-cloud' Interaction

abstract:
  A Chandra ACIS-S observation of PKS 2152-699 reveals thermal emission from a
diffuse region around the core and a hotspot located 10" northeast from the
core. This is the first detection of thermal X-ray radiation on kiloparsec
scales from an extragalactic radio source. Two other hotspots located 47"
north-northeast and 26" southwest from the core were also detected. Using a
Raymond-Smith model, the first hotspot can be characterized with a thermal
plasma temperature of 2.6$\times10^6$ K and an electron number density of 0.17
cm$^{-3}$. These values correspond to a cooling time of about 1.6$\times10^7$
yr. In addition, an emission line from the hotspot, possibly Fe xxv, was
detected at rest wavelength 10.04\AA.
  The thermal X-ray emission from the first hotspot is offset from the radio
emission but is coincident with optical filaments detected with broadband
filters of HST/WFPC2. The best explanation for the X-ray, radio, and optical
emission is that of a `jet-cloud' interaction.
  The diffuse emission around the nucleus of PKS 2152-699 can be modeled as a
thermal plasma with a temperature of 1.2$\times10^7$ K and a luminosity of
1.8$\times10^{41}$ erg s$^{-1}$. This emission appears to be asymmetric with a
small extension toward Hotspot A, similar to a jet. An optical hotspot (EELR)
is seen less than an arcsecond away from this extension in the direction of the
core. This indicates that the extension may be caused by the jet interacting
with an inner ISM cloud, but entrainment of hot gas is unavoidable. Future
observations are discussed.


title:
Subaru Deep Spectroscopy of a Star-forming Companion Galaxy of BR
  1202-0725 at $z=4.7$

abstract:
  We present deep spatially-resolved optical spectroscopy of the NW companion
galaxy of the quasar BR 1202-0725 at $z=4.7$. Its rest-frame UV spectrum shows
star-forming activity in the nuclear region. The Ly$\alpha$ emission profile is
symmetric with wavelength while its line width is unusually wide (FWHM $\simeq
1100$ km s$^{-1}$) for such a high-$z$ star-forming galaxy. Spectrum taken
along the Ly$\alpha$ nebula elongation, which is almost along the minor axis of
the companion host galaxy, reveals that off-nuclear Ly$\alpha$ nebulae have
either flat-topped or multi-peaked profiles along the extension. All these
properties can be understood in terms of superwind activity in the companion
galaxy. We also find a diffuse continuum component around the companion, which
shows similar morphology to that of Ly$\alpha$ nebula, and is most likely due
to scattering of the quasar light at dusty halo around the companion. We argue
that the superwind could expel dusty material out to the halo region, making a
dusty halo for scattering.


title:
Science with the Square Kilometer Array: Motivation, Key Science
  Projects, Standards and Assumptions

abstract:
  The Square Kilometer Array (SKA) represents the next major, and natural, step
in radio astronomical facilities, providing two orders of magnitude increase in
collecting area over existing telescopes. In a series of meetings, starting in
Groningen, the Netherlands (August 2002) and culminating in a `science retreat'
in Leiden (November 2003), the SKA International Science Advisory Committee
(ISAC), conceived of, and carried-out, a complete revision of the SKA science
case (to appear in New Astronomy Reviews). This preface includes: (i) general
introductory material, (ii) summaries of the key science programs, and (iii) a
detailed listing of standards and assumptions used in the revised science case.


title:
Searching for a holographic connection between dark energy and the low-l
  CMB multipoles

abstract:
  We consider the angular power spectrum in a finite universe with different
boundary conditions and perform a fit to the CMB, LSS and supernova data. A
finite universe could be the consequence of a holographic constraint, giving
rise to an effective IR cutoff at the future event horizon. In such a model
there is a cosmic duality relating the dark energy equation of state and the
power spectrum, which shows a suppression and oscillatory behaviour that is
found to describe the low l features extremely well. However, much of the
discussion here will also apply if we actually live inside an expanding bubble
that describes our universe. The best fit to the CMB and LSS data turns out to
be better than in the standard Lambda-CDM model, but when combined with the
supernova data, the holographic model becomes disfavored. We speculate on the
possible implications.


title:
Material enhancement in protoplanetary nebulae by particle drift through
  evaporation fronts

abstract:
  Solid material in a protoplanetary nebula is subject to vigorous
redistribution processes relative to the nebula gas. Meter-sized particles
drift rapidly inwards near the nebula midplane, and material evaporates when
the particles cross a condensation/evaporation boundary. The material cannot be
removed as fast in its vapor form as it is being supplied in solid form, so its
concentration increases locally by a large factor (more than an order of
magnitude under nominal conditions). As time goes on, the vapor phase
enhancement propagates for long distances inside the evaporation boundary
(potentially all the way in to the star). Meanwhile, material is enhanced in
its solid form over a characteristic lengthscale outside the evaporation
boundary. This effect is applicable to any condensible (water, silicates, {\it
etc.}). Three distinct radial enhancement/depletion regimes can be discerned by
use of a simple model. Meteoritics applications include oxygen fugacity and
isotopic variations, as well as isotopic homogenization in silicates. Planetary
system applications include more robust enhancement of solids in Jupiter's core
formation region than previously suggested. Astrophysical applications include
differential, time-dependent enhancement of vapor phase CO and H$_2$O in the
terrestrial planet regions of actively accreting protoplanetary disks.


title: Kinematics of Diffuse Interstellar Clouds :Recent GMRT Results

abstract:
  A high latitude HI 21 cm-line absorption survey toward extragalactic sources
was recently completed using the Giant Meterwave Radio Telescope (GMRT). A
total of 104 sources with mod(b) > 15 deg. and with a 21 cm flux density
greater than 1 Jy were observed for about 120 hours. With an optical depth
detection limit of about 0.01 this is the most sensitive high-latitude survey
as yet. Most of the detected HI 21 cm-line absorption features belong to a
population with a velocity dispersion of about 7.6 km/s. These are the
'standard' HI clouds and have been well-studied for decades. However, we also
detect a second population of absorbing clouds with a velocity dispersion of
about 21 km/s. About 20 percent of the total number of absorbing clouds belong
to this population. This new population of 'fast' clouds can be identified with
a similar velocity dispersion Ca II absorbing clouds and with the Halo clouds
recently detected in HI emission from Green Bank.


title: Cosmology with the Square Kilometre Array

abstract:
  We argue that the Square Kilometre Array has the potential to make both
redshift (HI) surveys and radio continuum surveys that will revolutionize
cosmological studies, provided that it has sufficient instantaneous
field-of-view that these surveys can cover a hemisphere in a timescale ~1 yr.
Adopting this assumption, we focus on two key experiments which will yield
fundamental new measurements in cosmology, characterizing the properties of the
mysterious dark energy which dominates the dynamics of today's Universe.
Experiment I will map out ~10^9 HI galaxies to redshift z~1.5, providing the
premier measurement of the clustering power spectrum of galaxies: accurately
delineating the acoustic oscillations and the `turnover'. Experiment II will
quantify the cosmic shear distortion of ~10^10 radio continuum sources,
determining a precise power spectrum of the dark matter, and its growth as a
function of cosmic epoch. We contrast the performance of the SKA in precision
cosmology with that of other facilities which will, probably or possibly, be
available on a similar timescale. We conclude that data from the SKA will yield
transformational science as the direct result of four key features: (i) the
immense cosmic volumes probed, exceeding future optical redshift surveys by
more than an order of magnitude; (ii) well-controlled systematic effects such
as the narrow `k-space window function' for Experiment I and the
accurately-known `point-spread function' for Experiment II; (iii) the ability
to measure with high precision large-scale modes in the clustering power
spectra, for which nuisance effects such as non-linear structure growth,
peculiar velocities and `galaxy bias' are minimised; and (iv) different
degeneracies between key parameters to those which are inherent in the CMB.


title: Extending and Exploring the 2 cm Survey Sample

abstract:
  We present new results from the VLBA 2 cm Survey, an imaging survey of active
galactic nuclei (AGN) at sub-milliarcsecond resolution. We extend the
structural variability monitoring program of more than 130 extragalactic
parsec-scale radio jets from over 170 AGN to a total of eight years. The sample
is explored further in time for all sources, and intensively for individual
objects. We report new detailed results on the compact sources III Zw 2, AO
0235+16, and NRAO 512.


title: A Conceptual Tour About the Standard Cosmological Model

abstract:
  With the beginning of the XXIst century, a physical model of our Universe,
usually called the Standard Cosmological Model (SCM), is reaching an important
level of consolidation, based on accurate astrophysical data and also on
theoretical developments. In this paper we review the interplay between the
basic concepts and observations underlying this model. The SCM is a complex and
beautiful building, recieving inputs from many branches of physics. Major
topics reviewed are: General Relativity and the cosmological constant, the
Cosmological Principle and Friedmann-Robertson-Walker-Lemaitre models, Hubble
diagrams and dark energy, large scale structure and dark matter, the cosmic
microwave background, Big Bang nucleosynthesis, and inflation.


title: Eclipsing binaries in open clusters. III. V621 Per in chi Persei

abstract:
  V621 Persei is a detached eclipsing binary in the open cluster chi Persei
which is composed of an early B-type giant star and a main sequence secondary
component. From high-resolution spectroscopic observations and radial
velocities from the literature, we determine the orbital period to be 25.5 days
and the primary velocity semiamplitude to be K = 64.5 +/- 0.4 km/s. No trace of
the secondary star has been found in the spectrum. We solve the discovery light
curves of this totally-eclipsing binary and find that the surface gravity of
the secondary star is log(g_B) = 4.244 +/- 0.054 (cm/s). We compare the
absolute masses and radii of the two stars in the mass--radius diagram, for
different possible values of the primary surface gravity, to the predictions of
stellar models. We find that log(g_A) is approximately 3.55, in agreement with
values found from fitting Balmer lines with synthetic profiles. The expected
masses of the two stars are 12 Msun and 6 Msun, and the expected radii are 10
Rsun and 3 Rsun. The primary component is near the blue loop stage in its
evolution.


title:
On the theory of canonical perturbations and its application to Earth
  rotation

abstract:
  Both orbital and rotational dynamics employ the method of variation of
parameters. We express, in a non-perturbed setting, the coordinates (Cartesian,
in the orbital case, or Eulerian in the rotation case) via the time and six
adjustable constants called elements (orbital elements or rotational elements).
If, under disturbance, we use this expression as ansatz and endow the
"constants" with time dependence, then the perturbed velocity (Cartesian or
angular) will consist of a partial derivative with respect to time and a
so-called convective term, one that includes the time derivatives of the
variable "constants." Out of sheer convenience, the so-called Lagrange
constraint is often imposed. It nullifies the convective term and, thereby,
guarantees that the functional dependence of the velocity upon the time and
"constants" stays, under perturbation, the same as it used to be in the
undisturbed setting.
  When the dynamical equations, written in terms of the "constants," are
demanded to be symplectic (and the "constants" make conjugated pairs $ Q, P$),
these "constants" are called Delaunay elements, in the orbital case, or Andoyer
elements, in the rotational case. The Andoyer and Delaunay sets of elements
share a feature not visible with a naked eye: in certain cases, the standard
equations render these elements non-osculating.
  Hence, even though the Andoyer variables in the Kinoshita-Souchay theory are
introduced in a precessing frame of the Earth orbit, they nevertheless return
the angular velocity relative to an inertial frame.


title: Radial Distribution of Dust Grains Around HR 4796A

abstract:
  We present high-dynamic-range images of circumstellar dust around HR 4796A
that were obtained with MIRLIN at the Keck II telescope at lambda = 7.9, 10.3,
12.5 and 24.5 um. We also present a new continuum measurement at 350 um
obtained at the Caltech Submillimeter Observatory. Emission is resolved in Keck
images at 12.5 and 24.5 um with PSF FWHM's of 0.37" and 0.55", respectively,
and confirms the presence of an outer ring centered at 70 AU. Unresolved excess
infrared emission is also detected at the stellar position and must originate
well within 13 AU of the star. A model of dust emission fit to flux densities
at 12.5, 20.8, and 24.5 um indicates dust grains are located 4(+3/-2) AU from
the star with effective size, 28+/-6 um, and an associated temperature of
260+/-40 K.
  We simulate all extant data with a simple model of exozodiacal dust and an
outer exo-Kuiper ring. A two-component outer ring is necessary to fit both Keck
thermal infrared and HST scattered-light images. Bayesian parameter estimates
yield a total cross-sectional area of 0.055 AU^2 for grains roughly 4 AU from
the star and an outer-dust disk composed of a narrow large-grain ring embedded
within a wider ring of smaller grains. The narrow ring is 14+/-1 AU wide with
inner radius 66+/-1 AU and total cross-sectional area 245 AU^2. The outer ring
is 80+/-15 AU wide with inner radius 45+/-5 AU and total cross-sectional area
90 AU^2. Dust grains in the narrow ring are about 10 times larger and have
lower albedos than those in the wider ring. These properties are consistent
with a picture in which radiation pressure dominates the dispersal of an
exo-Kuiper belt.


title:
A Parameter Study of Type II Supernova Light Curves Using 6 M_odot He
  Cores

abstract:
  Results of numerical calculations of Type II supernova light curves are
presented. The model progenitor stars have 6 $M{_\odot}$ cores and various
envelopes, originating from a numerically evolved 20 $M{_\odot}$ star. Five
parameters that affect the light curves are examined: the ejected mass, the
progenitor radius, the explosion energy, the $^{56}$Ni mass, and the extent of
$^{56}$Ni mixing. The following affects have been found: 1) the larger the
progenitor radius the brighter the early--time light curve, with little affect
on the late--time light curve, 2) the larger the envelope mass the fainter the
early light curve and the flatter the slope of the late light curve, 3) the
larger the explosion energy the brighter the early light curve and the steeper
the slope of the late light curve, 4) the larger the $^{56}$Ni mass the
brighter the overall light curve after 20 to 50 days, with no affect on the
early light curve, 5) the more extensive the $^{56}$Ni mixing the brighter the
early light curve and the steeper the late light curve. The primary parameters
affecting the light curve shape are the progenitor radius and the ejected mass.
The secondary parameters are the explosion energy, $^{56}$Ni mass and $^{56}$Ni
mixing. I find that while in principle the general shape and absolute magnitude
of a light curve indicate a unique set of parameters, in practice it is
difficult to avoid some ambiguity in the parameters. I find that the
nickel--powered diffusion wave and the recombination of helium produce a
prominent secondary peak in all our calculations. The feature is less prominent
when compositional mixing, both $^{56}$Ni mixing and mixing between the
hydrogen and helium layers, occurs. The model photospheric temperatures and
velocities are presented, for comparison to observation.


title:
3-D numerical simulations of rotating jets: The case of the DG Tau
  microjet

abstract:
  We here present results of three-dimensional Smoothed Particle hydro and
magnetohydrodynamics simulations of rotating jets, also including the effects
of radiative cooling, precession and velocity variability. Using initial
conditions and parameters which are particularly suitable for the DG Tau
microjet, we have been able to approximately reproduce its complex knotty
morphology and kinematics. We have also obtained radial velocity maps which are
in good agreement with the data obtained by Bacciotti et al., thus indicating
that their interpretation that the DG Tau microjet is rotating is correct.
Finally, we have found that a magnetic field of the order of ~ 0.5 mG is
sufficient to collimate the jet against the lateral expansion that is caused by
the centrifugal forces.


title: Full-star Type Ia supernova explosion models

abstract:
  We present full-star simulations of Type Ia supernova explosions on the basis
of the standard Chandrasekhar-mass deflagration model. Most simulations so far
considered only one spatial octant and assumed mirror symmetry to the other
octants. Two full-star models are evolved to homologous expansion and compared
with previous single-octant simulations. Therefrom we analyze the effect of
abolishing the artificial symmetry constraint on the evolution of the flame
surface. It turns out that the development of asymmetries depends on the chosen
initial flame configuration. Such asymmetries of the explosion process could
possibly contribute to the observed polarization of some Type Ia supernova
spectra.


title: DNOs and QPOs in Cataclysmic Variables

abstract:
  We describe some of the recent observations of Dwarf Nova Oscillations and
Quasi-Periodic Oscillations in cataclysmic variable stars. The similarities to
high frequency QPOs seen in X-Ray binaries make this an increasingly useful
field to explore. Our principal new result is the discovery of 1:2:3 harmonic
structure in the DNOs of VW Hyi late in outburst. Similar structure is seen in
the QPOs of some black hole and neutron star X-Ray binaries. In VW Hyi there is
a sudden frequency-doubling when the DNO period reaches ~39 s. This first
harmonic increases in period to ~28 s at which point the second harmonic
appears. Both harmonics continue with increasing period, together or
separately, with an occasional appearance of the fundamental, until the latter
reaches ~105 s, by which time VW Hyi has fallen to its quiescent magnitude. We
also report the first extensive observations of DNOs in a dwarf nova (OY Car)
in quiescence. These are lpDNOs (longer period DNOs) and show similar short
time scale properties to the DNOs and lpDNOs seen in outburst.


title: A fast directional continuous spherical wavelet transform

abstract:
  A fast algorithm for Antoine and Vandergheynst's (1998) directional
continuous spherical wavelet transform (CSWT) is presented. Computational
requirements are reduced by a factor of O(\sqrt{N}), when N is the number of
pixels on the sphere. The spherical Mexican hat wavelet Gaussianity analysis of
the WMAP 1-year data performed by Vielva et al. (2003) is reproduced and
confirmed using the fast CSWT. The proposed extension to directional analysis
is inherently afforded by the fast CSWT algorithm.


title: Photometric Monitoring of Open Clusters I. The Survey

abstract:
  Open clusters, which have age, abundance, and extinction information from
studies of main-sequence turn off stars, are the ideal location in which to
determine the mass-luminosity-radius relation for low-mass stars. We have
undertaken a photometric monitoring survey of open clusters in the Galaxy
designed to detect low-mass eclipsing binary systems through variations in
their relative light curves. Our aim is to provide an improved calibration of
the mass-luminosity-radius relation for low-mass stars and brown dwarfs, to
test stellar structure and evolution models, and to help quantify the
contribution of low-mass stars to the global mass census in the Galaxy. In this
paper we present our survey, describing the data and outlining the analysis
techniques. We study six nearby open clusters, with a range of ages from $\sim
0.2$ to 4 Gyr and metallicities from approximately solar to -0.2dex. We monitor
a field-of-view of > 1 square degree per target cluster, well beyond the
characteristic cluster radius, over timescales of hours, days, and months with
a sampling rate optimised for the detection of eclipsing binaries with periods
of hours to days. Our survey depth is designed to detect eclipse events in a
binary with a primary star of $\lesssim 0.3~M_{\sun}$. Our data have a
photometric precision of $\sim 3$ mmag at $I\approx 16$.


title:
Interaction of Supermassive Black Holes with their Stellar and Dark
  Matter Environments

abstract:
  A review of recent theoretical work on the interactions of supermassive
single and binary black holes with their nuclear environments, highlighting
ways in which the observed structure of nuclei can be used to constrain the
formation history of black holes.


title:
Rocket and FUSE Observations of IC 405: Differential Extinction and
  Fluorescent Molecular Hydrogen

abstract:
  We present far-ultraviolet spectroscopy of the emission/reflection nebula IC
405 obtained by a rocket-borne long-slit spectrograph and the Far Ultraviolet
Spectroscopic Explorer. Both data sets show a rise in the ratio of the nebular
surface brightness to stellar flux (S/F_*) of approximately two orders of
magnitude towards the blue end of the far-UV bandpass. Scattering models using
simple dust geometries fail to reproduce the observed S/F_* for realistic grain
properties. The high spectral resolution of the FUSE data reveals a rich
fluorescent molecular hydrogen spectrum ~1000" north of the star that is
clearly distinguished from the steady blue continuum. The S/F_* remains roughly
constant at all nebular pointings, showing that fluorescent molecular hydrogen
is not the dominant cause for the blue rise. We discuss three possible
mechanisms for the ``Blue Dust'': differential extinction of the dominant star
(HD 34078), unusual dust grain properties, and emission from nebular dust. We
conclude that uncertainties in the nebular geometry and the degree of dust
clumping are most likely responsible for the blue rise. As an interesting
consequence of this result, we consider how IC 405 would appear in a spatially
unresolved observation. If IC 405 was observed with a spatial resolution of
less than 0.4 pc, for example, an observer would infer a far-UV flux that was
2.5 times the true value, giving the appearance of a stellar continuum that was
less extinguished than radiation from the surrounding nebula, an effect that is
reminiscent of the observed ultraviolet properties of starburst galaxies.


title:
A $\lambda$20cm Survey of the Galactic Center Region I: Detection of
  Numerous Linear Filaments

abstract:
  We present a sensitive $\lambda$20cm VLA continuum survey of the Galactic
center region using new and archival data based on multi-configuration
observations taken with relatively uniform {\it uv} coverage. The high dynamic
range images cover the regions within $-2^\circ < l < 5^\circ$ and $-40' < b <
40'$ with a spatial resolution of $\approx30''$ and 10$''$. The wide field
imaging technique is used to construct a low-resolution mosaic of 40
overlapping pointings. The mosaic image includes the Effelsburg observations
filling the low spatial frequency {\it uv} data. We also present high
resolution images of twenty three overlapping fields using DnC and CnB array
configurations. The survey has resulted in a catalog of 345 discrete sources as
well as 140 images revealing structural details of HII regions, SNRs, pulsar
wind nebulae and more than 80 linear filaments distributed toward the complex
region of the Galactic center. These observations show the evidence for an
order of magnitude increase in the number of faint linear filaments with
typical lengths of few arcminutes. Many of the filaments show morphological
characteristics similar to the Galactic center nonthermal radio filaments
(NRFs). The linear filaments are not isolated but are generally clustered in
star forming regions where prominent NRFs had been detected previously. The
extensions of many of these linear filaments appear to terminate at either a
compact source or a resolved shell-like thermal source. A relationship between
the filaments, the compact and extended thermal sources as well as a lack of
preferred orientation for many RFs should constrain models that are proposed to
explain the origin of nonthermal radio filaments in the Galactic center.


title:
Flux and energy modulation of redshifted iron emission in NGC3516:
  implications for the black hole mass

abstract:
  We report the tentative detection of the modulation of a transient,
redshifted Fe Kalpha emission feature in the X-ray spectrum of the Seyfert
galaxy NGC3516. The detection of the spectral feature at 6.1 keV, in addition
to a stable 6.4 keV line, has been reported previously. We find on re-analysing
the XMM-Newton data that the feature varies systematically in flux at intervals
of 25 ks. The peak moves in energy between 5.7 keV and 6.5 keV. The spectral
evolution of the feature agrees with Fe K emission arising from a spot on the
accretion disc, illuminated by a corotating flare located at a radius of (7-16)
rg, modulated by Doppler and gravitational effects as the flare orbits around
the black hole. Combining the orbital timescale and the location of the
orbiting flare, the mass of the black hole is estimated to be (1-5)e+7 Msun,
which is in good agreement with values obtained from other techniques.