title: The Kepler equation for inspiralling compact binaries

abstract:
  Compact binaries consisting of neutron stars / black holes on eccentric orbit
undergo a perturbed Keplerian motion. The perturbations are either of
relativistic origin or are related to the spin, mass quadrupole and magnetic
dipole moments of the binary components. The post-Newtonian motion of such
systems decouples into radial and angular parts. We present here for the first
time the radial motion of such a binary encoded in a generalized Kepler
equation, with the inclusion of all above-mentioned contributions, up to linear
order in the perturbations. Together with suitably introduced parametrizations,
the radial motion is solved completely.


title:
Is there a relationship between the mass of a SMBH and the kinetic
  energy of its host elliptical galaxy?

abstract:
  We use a restricted sample of elliptical galaxies, whose kinematical
parameters inside the semimajor axis were calculated correcting the effect of
the integration of the light along the line of sight, in order to analyze a
possible relationship between the mass of a Supermassive Black Hole (SMBH) and
the kinetic energy of random motions in the host galaxy. We find $M_{BH}
\propto (M_{G} \sigma^{2})^\alpha$ with $0.87 \leq \alpha \leq 1$ depending on
the different fitting methods and samples used. This result could be
interpreted as a new fundamental relationship or as a new way to explain the
old $M_{BH} - \sigma$ law. In fact, the relations of the velocity dispersion
both with the mass of the SMBH ($M_{BH} \propto \sigma^{4.12}$) and with the
mass of the host galaxy ($M_{G} \propto \sigma^{2.16}$) induce us to infer an
almost direct proportionality: $M_{BH} \propto M_{G} \sigma^{2}$. A similar
relationship is found for the total kinetic energy involving the rotation
velocity too.


title: Multi-wavelength analysis of the field of the dark burst GRB 031220

abstract:
  We have collected and analyzed data taken in different spectral bands (from
X-ray to optical and infrared) of the field of GRB031220 and we present results
of such multiband observations. Comparison between images taken at different
epochs in the same filters did not reveal any strong variable source in the
field of this burst. X-ray analysis shows that only two of the seven Chandra
sources have a significant flux decrease and seem to be the most likely
afterglow candidates. Both sources do not show the typical values of the R-K
colour but they appear to be redder. However, only one source has an X-ray
decay index (1.3 +/- 0.1) that is typical for observed afterglows. We assume
that this source is the best afterglow candidate and we estimate a redshift of
1.90 +/- 0.30. Photometric analysis and redshift estimation for this object
suggest that this GRB can be classified as a Dark Burst and that the
obscuration is the result of dust extinction in the circum burst medium or
inside the host galaxy.


title: The autoparametric 3:2 resonance in conservative systems

abstract:
  In the resonance model, high-frequency quasi-periodic oscillations (QPOs) are
supposed to be a consequence of nonlinear resonance between modes of
oscillations occurring within the innermost parts of an accretion disk. Several
models with a prescribed mode--mode interaction were proposed in order to
explain the characteristic properties of the resonance in QPO sources. In this
paper, we examine nonlinear oscillations of a system having two degrees of
freedom and we show that this case could be particularly relevant for QPOs. We
present a very convenient way how to study autoparametric resonances of a fully
general system using the method of multiple scales. We concentrate to
conservative systems and discuss their behavior near the 3:2 parametric
resonance.


title:
Nonradial and nonpolytropic astrophysical outflows VIII. A GRMHD
  generalization for relativistic jets

abstract:
  Steady axisymmetric outflows originating at the hot coronal magnetosphere of
a Schwarzschild black hole and surrounding accretion disk are studied in the
framework of general relativistic magnetohydrodynamics (GRMHD). The assumption
of meridional self-similarity is adopted for the construction of
semi-analytical solutions of the GRMHD equations describing outflows close to
the polar axis. In addition, it is assumed that relativistic effects related to
the rotation of the black hole and the plasma are negligible compared to the
gravitational and other energetic terms. The constructed model allows us to
extend previous MHD studies for coronal winds from young stars to spine jets
from Active Galactic Nuclei surrounded by disk-driven outflows. The outflows
are thermally driven and magnetically or thermally collimated. The collimation
depends critically on an energetic integral measuring the efficiency of the
magnetic rotator, similarly to the non relativistic case. It is also shown that
relativistic effects affect quantitatively the depth of the gravitational well
and the coronal temperature distribution in the launching region of the
outflow. Similarly to previous analytical and numerical studies, relativistic
effects tend to increase the efficiency of the thermal driving but reduce the
effect of magnetic self-collimation.


title: The dwarf galaxy DDO 47: testing cusps hiding in triaxial halos

abstract:
  We present HI data of the dwarf galaxy DDO 47, aimed at testing the
hypothesis that dark halo triaxiality might induce non-circular motions
resulting in rotation curves best fitted by cored halos, even if the dark
matter halo is intrinsically cuspy. We performed a harmonic decomposition of
the velocity field in order to search for alleged non-circular motions needed
to ``hide'' a cusp: in DDO 47 non-circular motions are globally at a level of
2-3 km s$^{-1}$, far from being sufficient to reconcile the observed rotation
curve with the $\Lambda$CDM predictions. We conclude that the dark matter halo
around DDO 47 is truly cored and that a cusp cannot be hidden by non-circular
motions. More details are shown in Gentile et al. (2006, ApJL in press,
astro-ph/0506538).


title: A survey for pulsars in EGRET error boxes

abstract:
  As part of an effort to associate the unidentified EGRET gamma-ray sources
with pulsars, error boxes for 19 sources were searched using Arecibo at
327-MHz. The sources were chosen to be out-of-plane and possibly associated
with the Gould belt, a nearby starburst region with an enhanced production rate
of core-collapse supernovae. The search revealed one new 597-ms pulsar,
J2243+1518, within the error box of the EGRET source 3EG J2243+1509. The
spin-down energy loss rate of the new pulsar is not nearly sufficient to power
the gamma-ray source and so the pulsar is very unlikely to be associated.
Simulations we have carried out show that any pulsars at Gould belt distances
should have been detected by the survey. This suggests that either the EGRET
sources associated with the Gould belt are not pulsars, or that the minimum of
the pulsar luminosity function is lower than the ~1.5 mJy kpc^2 inferred from
the population of normal pulsars.


title:
Photo-chemical evolution of elliptical galaxies II. The impact of
  merging-induced starbursts

abstract:
  The effects of late gas accretion episodes and subsequent merger-induced
starbursts on the photo-chemical evolution of elliptical galaxies are studied
and compared to the picture of galaxy formation occurring at high redshift with
an unique and intense starburst modulated by a very short infall, as suggested
by Pipino & Matteucci (2004, Paper I). By means of the comparison with the the
colour-magnitude relations and the [<Mg/Fe>_V]-sigma relation observed in
ellipticals, we conclude that either bursts involving a gas mass comparable to
the mass already transformed into stars during the first episode of star
formation and occurring at any redshift, or bursts occurring at low redshift
(i.e. z<0.2) and with a large range of accreted mass, are ruled out. These
models fail in matching the above relations even if the initial infall
hypothesis is relaxed, and the galaxies form either by means of more
complicated star formation histories or by means of the classical monolithic
model. On the other hand, galaxies accreting a small amount of gas at high
redshift (i.e. z>3) produce a spread in the model results, with respect to
Paper I best model, which is consistent with the observational scatter of the
color-magnitude relations, although there is only marginal agreement with the
[<Mg/Fe>_V]-sigma relation. Therefore, only small perturbations to the standard
scenario seem to be allowed. We stress that the strongest constraints to galaxy
formation mechanisms are represented by the chemical abundances, whereas the
colours can be reproduced under several different hypotheses.


title: Close binary systems among very low mass stars and brown dwarfs

abstract:
  Using Monte Carlo simulations and published radial velocity surveys we have
constrained the frequency and separation (a) distribution of very low mass star
(VLM) and brown dwarf (BD) binary systems. We find that simple Gaussian
extensions of the observed wide binary distribution, with a peak at 4 au and
0.6< sigma_{log(a/au)}<1.0, correctly reproduce the observed number of close
binary systems, implying a close (a<2.6 au) binary frequency of 17-30 per cent
and overall frequency of 32-45 per cent. N-body models of the dynamical decay
of unstable protostellar multiple systems are excluded with high confidence
because they do not produce enough close binary VLMs/BDs. The large number of
close binaries and high overall binary frequency are also completely
inconsistent with published smoothed particle hydrodynamical modelling and
argue against a dynamical origin for VLMs/BDs.


title: Near-UV to near-IR disk-averaged Earth's reflectance spectra

abstract:
  We report 320 to 1020nm disk-averaged Earth reflectance spectra obtained from
Moon's Earthshine observations with the EMMI spectrograph on the NTT at ESO La
Silla (Chile). The spectral signatures of Earth atmosphere and ground
vegetation are observed. A vegetation red-edge of up to 9% is observed on
Europe and Africa and ~2% upon Pacific Ocean. The spectra also show that Earth
is a blue planet when Rayleigh scattering dominates, or totally white when the
cloud cover is large.


title: The Wolf-Rayet hydrogen puzzle -- an observational point of view

abstract:
  Significant amounts of hydrogen were found in very hot early-type single WN
stars in the SMC and the LMC. Recently, we found similar evidence in the
Wolf-Rayet star of a short-period LMC binary. We discuss here the relevance of
hydrogen for WR star classification, models, the relation to metallicity, and
the GRB progenitors.


title:
Multifrequency VLA radio observations of the X-ray cavity cluster of
  galaxies RBS797: evidence of differently oriented jets

abstract:
  We report on the peculiar activity of the radio source located at the center
of the cooling flow cluster RBS797 (z=0.35), the first distant cluster in which
two pronounced X-ray cavities have been discovered. New multifrequency (1.4,
4.8, and 8.4 GHz) observations obtained with the Very Large Array clearly
reveal the presence of radio emission on three different scales showing
orientation in different directions, all of which indicates that RBS797
represents a very peculiar case. The lowest resolution images show large-scale
radio emission characterized by amorphous morphology and a steep spectrum,
extended on a scale of hundreds of kpc. On a scale of tens of kpc, there is
evidence of 1.4 GHz radio emission elongated in the northeast-southwest
direction exactly towards the holes detected in X-rays. The highest resolution
image shows the details of the innermost 4.8 GHz radio jets on a kpc scale;
they are remarkably oriented in a direction that is perpendicular to that of
the extended structure detected at a lower resolution. We therefore find
evidence of a strong interaction between the central radio source and the
intra-cluster medium in RBS797. We suggest a scenario in which the 1.4 GHz
emission filling the X-ray cavities consists of buoyant bubbles of radio
emitting plasma that are created by twin jets in the past and whose expansion
has displaced the thermal gas that was formerly in the X-ray holes, whereas the
two jets visible at 4.8 GHz are related to the present nuclear activity that
has restarted at a different position angle from the original outburst that
created the outer radio lobes. The total radio luminosity is ~ 10^42 erg/s,
corresponding to a factor of a few thousand times less than the estimated
cooling luminosity.


title: Truncated disc versus extremely broad iron line in XTE J1650-500

abstract:
  There is growing evidence from both spectral and timing properties that there
is a truncated inner accretion disc in low mass accretion rate Galactic black
hole systems. The detection of extremely smeared relativistic iron lines in
some of these systems is the only current piece of evidence which conflicts
with this geometrical interpretation of the low/hard state. Here we show that
the line width in the BeppoSAX data of a bright low/hard state of the transient
black hole XTE J1650-500 is indeed consistent with extreme relativistic
effects. However, the relativistic smearing can be significantly reduced if
there is also resonance iron K line absorption from an outflowing disc wind.
The iron line smearing is then completely compatible with a truncated disc, so
gives no information on the black hole spin.


title:
Lithium abundances in exoplanet host stars as test of planetary
  formation scenarii

abstract:
  Following the observations of Israelian et al. 2004, we compare different
evolutionary models in order to study the lithium destruction processes and the
planetary formation scenarii.


title: A New Exact Method for Line Radiative Transfer

abstract:
  We present a new method, the Coupled Escape Probability (CEP), for exact
calculation of line emission from multi-level systems, solving only algebraic
equations for the level populations. The CEP formulation of the classical
two-level problem is a set of {\em linear equations}, and we uncover an exact
analytic expression for the emission from two-level optically thick sources
that holds as long as they are in the "effectively thin" regime. In comparative
study of a number of standard problems, the CEP method outperformed the leading
line transfer methods by substantial margins.
  The algebraic equations employed by our new method are already incorporated
in numerous codes based on the escape probability approximation. All that is
required for an exact solution with these existing codes is to augment the
expression for the escape probability with simple zone-coupling terms. As an
application, we find that standard escape probability calculations generally
produce the correct cooling emission by the CII 158 mic line but not by the
$^3$P lines of OI.


title:
Helium diffusion during the evolution of solar-type stars :
  asteroseismic tests

abstract:
  The element diffusion, described by Michaud (1970), is now recognized to
occur in all kinds of stars. We attempt to give evidence of signatures of
helium diffusion below the convective zone by the way of asteroseismology.


title: Is there a galactic component for the ultra high energy cosmic rays?

abstract:
  Under the hypothesis that Gamma Ray Burst (GRB) might be responsible for the
origin of Ultra High Energy Cosmic Ray (UHECR), we propose a two component
(galactic and extra-galactic) model for the UHECR origin. The model is based on
two facts. The first is the anisotropies found in the angular distribution of
GRBs from BATSE catalog. Second is that, of all the located long-GRBs, only
approximately 15 percent of them have their spectroscopic redshift determined,
and some 38 percent of them have a X-ray, optical, or radio afterglow. So far,
in short-GRBs, no afterglow and no red shift have been detected, suggesting
that these GRB sources are inside or close to our Galaxy. This two component
model for the UHECR is further supported by the experimental evidences of an
UHECR excess around $10^{18}$ eV from the direction of the galactic central
region. The model offers in a natural way an explanation for the presence of
cosmic rays with energies beyond the Greisen-Zatsepin-Kuz'min (GZK) cutoff.


title: Molecular Clouds as Ensembles of Transient Cores

abstract:
  We construct models of molecular clouds that are considered as ensembles of
transient cores. Each core is assumed to develop in the background gas of the
cloud, grow to high density and decay into the background. The chemistry in
each core responds to the dynamical state of the gas and to the gas-dust
interaction. Ices are deposited on the dust grains in the core's dense phase,
and this material is returned to the gas as the core expands to low density.
The cores of the ensemble number typically one thousand and are placed randomly
in position within the cloud, and are assigned a random evolutionary phase.
  The models are used to generate molecular line contour maps of a typical dark
cloud. These maps are found to represent extremely well the characteristic
features of observed maps of the dark cloud L673, which has been observed at
both low and high resolutions. The computed maps are found to exhibit the
general morphology of the observed maps, and to generate similar sizes of
emitting regions, molecular column densities, and the separations between peaks
of emissions of various molecular species. The models give insight into the
nature of molecular clouds and the dynamical processes occurring within them,
and significantly constrain dynamical and chemical processes in the
interstellar medium.


title: Some Systematic Properties of Rotation Curves

abstract:
  The rotation curves of spiral galaxies obey strong scaling relations. These
include the Tully-Fisher and baryonic Tully-Fisher relations, and the mass
discrepancy--acceleration relation. These relations can be used to place
constraints on the mass-to-light ratios of stars. Once the stellar mass is
constrained, the distribution of dark matter follows. The shape of the dark
matter distribution is consistent with the expectations of NFW halos exterior
to 1 kpc, but the amplitude is wrong. This is presumably related to the
long-standing problem of the normalization of the Tully-Fisher relation and may
imply a downturn in the amplitude of the power spectrum at small scales. More
fundamentally, the persistent success of MOND remains a troubling fact.


title:
Redshifts from Spitzer Spectra for Optically Faint, Radio Selected
  Infrared Sources

abstract:
  Spectra have been obtained with the Infrared Spectrograph on the Spitzer
Space Telescope for 18 optically faint sources (R > 23.9,mag) having f(nu)
(24um) > 1.0,mJy and having radio detections at 20 cm to a limit of 115
microJy. Sources are within the Spitzer First Look Survey. Redshifts are
determined for 14 sources from strong silicate absorption features (12 sources)
or strong PAH emission features (2 sources), with median redshift of 2.1.
Results confirm that optically faint sources of ~1 mJy at 24um are typically at
redshifts z ~ 2, verifying the high efficiency in selecting high redshift
sources based on extreme infrared to optical flux ratio, and indicate that 24um
sources which also have radio counterparts are not systematically different
than samples chosen only by their infrared to optical flux ratios. Using the
parameter q = log[f(nu)(24um)/f(nu)(20 cm)] 17 of the 18 sources observed have
values of 0<q<1, in the range expected for starburst-powered sources, but only
a few of these show strong PAH emission as expected from starbursts, with the
remainder showing absorbed or power-law spectra consistent with an AGN
luminosity source. This confirms previous indications that optically faint
Spitzer sources with f(nu)(24um) > 1.0mJy are predominately AGN and represent
the upper end of the luminosity function of dusty sources at z ~ 2. Based on
the characteristics of the sources observed so far, we predict that the nature
of sources selected at 24um will change for f(nu)(24um) < 0.5 mJy to sources
dominated primarily by starbursts.


title: High mass star formation in the infrared dark cloud G11.11-0.12

abstract:
  We report detection of moderate to high-mass star formation in an infrared
dark cloud (G11.11-0.12) where we discovered class II methanol and water maser
emissions at 6.7 GHz and 22.2 GHz, respectively. We also observed the object in
ammonia inversion transitions. Strong emission from the (3,3) line indicates a
hot (~60 K) compact component associated with the maser emission. The line
width of the hot component (4 km/s), as well as the methanol maser detection,
are indicative of high mass star formation. To further constrain the physical
parameters of the source, we derived the spectral energy distribution (SED) of
the dust continuum by analysing data from the 2MASS survey, HIRAS, MSX, the
Spitzer Space Telescope, and interferometric 3mm observations. The SED was
modelled in a radiative transfer program: a) the stellar luminosity equals 1200
L_sun corresponding to a ZAMS star of 8 M_sun; b) the bulk of the envelope has
a temperature of 19 K; c) the mass of the remnant protostellar cloud in an area
8x10^17 cm or 15 arcsec across amounts to 500M_sun, if assuming standard dust
of the diffuse medium, and to about 60 M_sun, should the grains be fluffy and
have ice mantles; d) the corresponding visual extinction towards the star is a
few hundred magnitudes. The near IR data can be explained by scattering from
tenuous material above a hypothetical disk. The class II methanol maser lines
are spread out in velocity over 11 km/s. To explain the kinematics of the
masing spots, we propose that they are located in a Kepler disk at a distance
of about 250 AU. The dust temperatures there are around 150 K, high enough to
evaporate methanol--containing ice mantles.


title: Causes and Consequences of Magnetic Field Changes in Neutron Stars

abstract:
  Because of the quantum fluid properties of a neutron star core's neutrons and
protons, its magnetic field is expected to be coupled strongly to its spin.
This predicts a simple evolution of the surface-field of such stars as they
spin down or, less commonly, are spun up. Consequences and comparisons with
observations are given for properties of solitary spinning down pulsars,
including their glitches and spin-down ages, X-ray pulsars, and the formation
and pulse characteristics of Millisecond Pulsars. For none of these is there a
present conflict between model predictions and what has been observed.


title: Cloudshine: New Light on Dark Clouds

abstract:
  We present new deep near-infrared images of dark clouds in the Perseus
molecular complex. These images show beautiful extended emission which we model
as scattered ambient starlight and name ``cloudshine''. The brightness and
color variation of cloudshine complicates the production of extinction maps,
the best tracer of column density in clouds. However, since the profile of
reflected light is essentially a function of mass distribution, cloudshine
provides a new way to study the structure of dark clouds. Previous work has
used optical scattered light to study the density profile of tenuous clouds;
extending this technique into the infrared provides a high-resolution view into
the interiors of very dense clouds, bypassing the complexities of using thermal
dust emission, which is biased by grain temperature, or molecular tracers,
which have complicated depletion patterns. As new wide-field infrared cameras
are used to study star-forming regions at greater depth, cloudshine will be
widely observed and should be seen as a new high-resolution tool, rather than
an inconvenience.


title: Building Galaxies with Simulations

abstract:
  We present an overview of some of the issues surrounding current models of
galaxy formation, highlighting recent insights obtained from cosmological
hydrodynamic simulations. Detailed examination of gas accretion processes show
a hot mode of gas cooling from near the halo's virial temperature, and a
previously underappreciated cold mode where gas flows in along filaments on
dynamical timescales, emitting its energy in line radiation. Cold mode
dominates in systems with halo masses slightly smaller than the Milky Way and
below, and hence dominates the global accretion during the heydey of galaxy
formation. This rapid accretion path enables prompt assembly of massive
galaxies in the early universe, and results in $z\sim 4$ galaxy properties in
broad agreement with observations, with the most massive galaxies being the
most rapid star formers. Massive galaxies today are forming stars at a much
reduced rate, a trend called downsizing. The trend of downsizing is naturally
reproduced in simulations, owing to a transition from cold mode accretion in
the early growth phase to slower hot mode accretion once their halos grow
large. However, massive galaxies at the present epoch are still observed to
have considerably redder colors than simulations suggest, suggesting that star
formation is not sufficiently truncated in models by the transition to hot
mode, and that another process not included in current simulations is required
to suppress star formation.


title: A High Resolution Map of 12CO J=6-5 Emission in the Starburst Galaxy M82

abstract:
  We present a map of 12CO J=6-5 emission of the nuclear region of the nearby
starburst galaxy M82 at resolution 7" taken with the James Clerk Maxwell
Telescope (JCMT). This is the highest resolution map yet available at this
transition. A detailed quantitative comparison is made with emission at 12CO
J=1-0 at the same resolution yielding new insights into the excitation of
molecular gas in this galaxy. The excitation is found to be highest in the
central area of the starburst region where the ratio r_61 = 12CO J=6-5/12CO
J=1-0 is as high as 0.5, compared to the mean value over the starburst region
of 0.24. The excitation ratio peaks along the inner edge of the molecular ring
outlined by atomic and molecular gas at lower excitation, and also in two spurs
extending northward from the disk toward the outflow associated with the
supwerwind. Emission with higher than avarage excitation is also found to be
associated with the supershell surrounding the luminous SNR candidate 41.9+58,
and possibly on a larger scale in gas whose orbits are strongly influenced by
the stellar bar. The higher excitation in M82 is likely to be caused
predominantly by local increases in kinetic temperature and/or geometric
filling factor of a pre-existing higher excitation component, and less likely
to be caused by local increases in gas density.


title: Ultra High Energy Cosmic Rays and the Auger Observatory

abstract:
  In this proceeding we present the construction status and the performances of
the Pierre Auger Observatory together with the first results obtained with our
initial 18 month of data. In particular, we discuss our search for anisotropy
near the Galactic Center, our limit on the photon fraction at the highest
energies and our first estimate of the cosmic ray spectrum above 3 EeV. All of
the material presented in this proceeding was extracted from the numerous Auger
contributions to the 29th ICRC proceedings.


title: Super-acceleration as Signature of Dark Sector Interaction

abstract:
  We show that an interaction between dark matter and dark energy generically
results in an effective dark energy equation of state of w<-1. This arises
because the interaction alters the redshift-dependence of the matter density.
An observer who fits the data treating the dark matter as non-interacting will
infer an effective dark energy fluid with w<-1. We argue that the model is
consistent with all current observations, the tightest constraint coming from
estimates of the matter density at different redshifts. Comparing the
luminosity and angular-diameter distance relations with LambdaCDM and phantom
models, we find that the three models are degenerate within current
uncertainties but likely distinguishable by the next generation of dark energy
experiments.


title: Variable accretion and outflow in young brown dwarfs

abstract:
  We report on the first dedicated monitoring campaign of spectroscopic
variability in young brown dwarfs. High-resolution optical spectra of six
targets in nearby star-forming regions were obtained over 11 nights between
2005 January-March on the Magellan 6.5m telescope. We find significant
variability in Halpha and a number of other emission lines related to accretion
and outflow processes on a variety of timescales ranging from hours to weeks to
years. The most dramatic changes are seen for 2M1207, 2M1101 and ChaI-ISO217.
We observe possible accretion rate changes by about an order of magnitude in
two of these objects, over timescales of weeks (2M1207) or hours (2M1101). The
accretion 'burst' seen in 2M1101 could be due to a 'clumpy' flow. We also see
indications for changes in the outflow rate in at least three objects. In one
case (ISO217), there appears to be a ~1-hour time lag between outflow and
accretion variations, consistent with a scenario in which the wind originates
from the inner disk edge. Our variability study supports a close to edge-on
inclination for the brown dwarf LS-RCrA 1. The fact that all targets in our
sample show variations in accretion and/or outflow indicators suggests that
studies of young brown dwarf properties should be based either on large samples
or time series. As an example, we demonstrate that the large scatter in the
recently found accretion rate vs. mass relationship can be explained primarily
with variability. The observed profile variations imply asymmetric accretion
flows in brown dwarfs, which, in turn, is evidence for magnetic funneling by
large-scale fields. We show that accreting sub-stellar objects may harbor
magnetic fields with ~kG strength (abridged).


title:
A Spitzer Space Telescope Infrared Survey of Supernova Remnants in the
  Inner Galaxy

abstract:
  Using Infrared Array Camera (IRAC) images at 3.6, 4.5, 5.8, and 8 microns
from the GLIMPSE Legacy science program on the Spitzer Space Telescope, we
searched for infrared counterparts to the 95 known supernova remnants that are
located within galactic longitudes 65>|l|>10 degrees and latitudes |b|<1
degree. Eighteen infrared counterparts were detected. Many other supernova
remnants could have significant infrared emission but are in portions of the
Milky Way too confused to allow separation from bright HII regions and
pervasive mid-infrared emission from atomic and molecular clouds along the line
of sight. Infrared emission from supernova remnants originates from synchrotron
emission, shock-heated dust, atomic fine-structure lines, and molecular lines.
The detected remnants are G11.2-0.3, Kes 69, G22.7-0.2, 3C 391, W 44, 3C 396,
3C 397, W 49B, G54.4-0.3, Kes 17, Kes 20A, RCW 103, G344.7-0.1, G346.6-0.2, CTB
37A, G348.5-0.0, and G349.7+0.2. The infrared colors suggest emission from
molecular lines (9 remnants), fine-structure lines (3), and PAH (4), or a
combination; some remnants feature multiple colors in different regions. None
of the remnants are dominated by synchrotron radiation at mid-infrared
wavelengths. The IRAC-detected sample emphasizes remnants interacting with
relatively dense gas, for which most of the shock cooling occurs through
molecular or ionic lines in the mid-infrared.


title: To Be or Not To Be: Very Young Globular Clusters in M31

abstract:
  We present observations made with the newly commissioned Keck laser-guide
star adaptive optics system of 6 objects in M31 that are alleged in multiple
recent studies to be young globular clusters (GCs); all are supposed to have
ages less than 5 Gyr. The resulting FWHM of the PSF core in our images is ~70
mas. The four youngest of these objects are asterisms; they are with certainty
not young GCs in M31. Based on their morphology, the two oldest are GCs in M31.
While the M31 GCs with ages 5 -- 8 Gyr appear to be mostly genuine, it appears
that many of the alleged very young GCs in M31 are spurious identifications.
This problem will be even more severe in studies of the GC systems of more
distant spiral galaxies now underway, for which imaging at the spatial
resolution of our observations in M31 may not be adequate to detect sample
contamination by asterisms.


title:
X-ray constraints on the dark matter profile of a very relaxed cluster
  of galaxies

abstract:
  We have analyzed an XMM-Newton observation of the cluster Abell 2589. Apart
from a low-level asymmetry in the central region, the cluster appears very
relaxed and does not show presence of a central AGN. We derived constraints for
the radial temperature, density and, assuming hydrostatic equilibrium, mass
profiles. We find that the best fit to the dark matter profile is given by the
Sersic-like profile proposed by Navarro et al. (2004). The NFW model does not
provide a good fit. We also tested whether the central stellar component could
affect the profile through the adiabatic contraction model but were unable to
distinguish it from a simple "dark matter + stars" modeling.


title:
The color signature of the transit of HD 209458: Discrepancies between
  stellar atmospheric models and observations

abstract:
  Exoplanetary transits produce a double-horned color signature that is
distinct from both binaries and blends and can thus be used to separate
exoplanets from false positives in transit searches. Color photometry with
precision sufficient to detect this signal in transits of HD 209458 is
available in the literature. Analysis of these observations reveals that, while
the signature does exhibit the expected shape, it is significantly stronger
than PHOENIX atmospheric models predict.


title:
Spectral distortions to the Cosmic Microwave Background from the
  recombination of hydrogen and helium

abstract:
  The recombination of hydrogen and helium at z~1000-7000 gives unavoidable
distortions to the Cosmic Microwave Background (CMB) spectrum. We present a
detailed calculation of the line intensities arising from the Ly-alpha (2p-1s)
and two-photon (2s-1s) transitions for the recombination of hydrogen, as well
as the corresponding lines from helium. We give an approximate formula for the
strength of the main recombination line distortion on the CMB in different
cosmologies, this peak occurring at about 170 microns. We also find a
previously undescribed long wavelength peak (which we call the
pre-recombination peak) from the lines of the 2p-1s transitions, which are
formed before significant recombination of the corresponding atoms occurred.
Detailed calculations of the two-photon emission line shapes are presented here
for the first time. The frequencies of the photons emitted from the two-photon
transition have a wide spectrum and this causes the location of the peak of the
two-photon line of hydrogen to be located almost at the same wavelength as the
main Ly-alpha peak. The helium lines also give distortions at similar
wavelengths, so that the combined distortion has a complex shape. The detection
of this distortion would provide direct supporting evidence that the Universe
was indeed once a plasma. Moreover, the distortions are a sensitive probe of
physics during the time of recombination. Although the spectral distortion is
overwhelmed by dust emission from the Galaxy, and is maximum at wavelengths
roughly where the cosmic far-infrared background peaks, it may be able to
tailor an experiment to detect its non-trivial shape.


title: Gas phase water in the surface layer of protoplanetary disks

abstract:
  Recent observations of the ground state transition of HDO at 464 GHz towards
the protoplanetary disk of DM Tau have detected the presence of water vapor in
the regions just above the outer disk midplane (Ceccarelli et al 2005). In the
absence of non-thermal desorption processes, water should be almost entirely
frozen onto the grain mantles and HDO undetectable. In this Letter we present a
chemical model that explores the possibility that the icy mantles are
photo-desorbed by FUV (6eV < h nu < 13.6eV) photons. We show that the average
Interstellar FUV field is enough to create a layer of water vapor above the
disk midplane over the entire disk. Assuming a photo-desorption yield of
10^{-3}, the water abundance in this layer is predicted to be ~ 3 x 10^{-7} and
the average H2O column density is ~ 1.6x 10^{15} cm^{-2}. The predictions are
very weakly dependent on the details of the model, like the incident FUV
radiation field, and the gas density in the disk. Based on this model, we
predict a gaseous HDO/H2O ratio in DM Tau of ~1%. In addition, we predict the
ground state transition of water at 557 GHz to be undetectable with ODIN and/or
HSO-HIFI.


title: Lithium isotopic abundances in metal-poor halo stars

abstract:
  Very high-quality spectra of 24 metal-poor halo dwarfs and subgiants have
been acquired with ESO's VLT/UVES for the purpose of determining Li isotopic
abundances. The derived 1D, non-LTE 7Li abundances from the LiI 670.8nm line
reveal a pronounced dependence on metallicity but with negligible scatter
around this trend. Very good agreement is found between the abundances from the
LiI 670.8nm line and the LiI 610.4nm line. The estimated primordial 7Li
abundance is $7Li/H = 1.1-1.5 x 10^-10, which is a factor of three to four
lower than predicted from standard Big Bang nucleosynthesis with the baryon
density inferred from the cosmic microwave background. Interestingly, 6Li is
detected in nine of our 24 stars at the >2sigma significance level. Our
observations suggest the existence of a 6Li plateau at the level of log 6Li =
0.8; however, taking into account predictions for 6Li destruction during the
pre-main sequence evolution tilts the plateau such that the 6Li abundances
apparently increase with metallicity. Our most noteworthy result is the
detection of 6Li in the very metal-poor star LP815-43. Such a high 6Li
abundance during these early Galactic epochs is very difficult to achieve by
Galactic cosmic ray spallation and alpha-fusion reactions. It is concluded that
both Li isotopes have a pre-Galactic origin. Possible 6Li production channels
include proto-galactic shocks and late-decaying or annihilating supersymmetric
particles during the era of Big Bang nucleosynthesis. The presence of 6Li
limits the possible degree of stellar 7Li depletion and thus sharpens the
discrepancy with standard Big Bang nucleosynthesis.


title:
Modelling the evolution of dusty starburst galaxies in multi-band deep
  surveys

abstract:
  We model the constraints set on the evolution of dusty starburst galaxies by
the current deep extragalactic surveys performed in the far-infrared with $\it
Spitzer$, and at radio wavelengths with the VLA. Our models fit the number
counts in all the available spectral bands well, and also provide a reasonably
close match to the redshift distribution of the $\it Spitzer$ detections. We
find: 1.) dusty starburst galaxies with infrared burst phases triggered by
galactic interactions at redshift $z \sim 1-2$ are good candidates to fit the
$\it Spitzer$ results at $24\mu m$, $70 \mu m$ and $160 \mu m$, assuming
plausible strengths for the PAH features for the infrared luminous sources. An
Arp220-like spectral energy distribution (SED) for Ultraluminous Infrared
Galaxies (ULIGs) of $L_{\rm ir}>10^{12} L_{\odot}$ and one like that of M82 for
Luminous Infrared Galaxies (LIGs) of $L_{\rm ir}\sim 10^{11-12} L_{\odot}$ give
a successful fit to the $\it Spitzer$ $24\mu m$ and $\rm ISOCAM 15\mu m$ number
counts at flux levels of $S_{\nu}< 1 mJy$; 2.) the strong evolution of the
number density of the ULIGs from redshift $z\sim 0$ to $\sim 1$ predicted by
our models is consistent with the current deep $\rm 1.4 GHz$ radio surveys and
accounts for the upturn in the $\rm 1.4 GHz$ differential counts at the sub-mJy
flux level; and 3.) comparing with number counts at near infrared bands, as
well as the background measurements using DIRBE and 2MASS, shows that only a
fraction of the stellar mass in the Universe is included in our models of dusty
starburst mergers at $z \sim 1 - 2$.


title:
The GSC-II-based survey of ancient cool white dwarfs I. The sample of
  spectroscopically confirmed WDs

abstract:
  The GSC-II white dwarf survey was designed to identify faint and high proper
motion objects, which we used to define a new and independent sample of cool
white dwarfs. With this survey we aim to derive new constraints on the halo
white dwarf space density. Also, these data can provide information on the age
of thick disk and halo through the analysis of the luminosity function. On the
basis of astrometric and photometric parameters, we selected candidates with mu
> 0.28 as/yr and R_F > 16 in an area of 1150 square degrees. Then, we separated
white dwarfs from late type dwarfs and subdwarfs by means of the reduced proper
motion diagram. Finally, spectroscopic follow-up observations were carried out
to confirm the white dwarf nature of the selected candidates. We found 41 white
dwarfs of which 24 are new discoveries. Here we present the full sample and for
each object provide positions, absolute proper motions, photometry, and
spectroscopy.


title: Discovery of a nearby M9 dwarf

abstract:
  We report the discovery of a new M9.0 dwarf at only 8.2 pc, which we
identified in our search for nearby ultracool dwarf (I-J >= 3.0, later than
M8.0) in the DENIS database. We measure a very high proper motion of 2.5
arc-sec/yr. The PC3 index measured from its low-resolution spectrum gives a
spectrophotometric distance of 8.2 pc. This makes it the third closest M9.0
dwarf.


title: Water in the envelopes and disks around young high-mass stars

abstract:
  Single-dish spectra and interferometric maps of (sub)mm lines of H2O-18 and
HDO are used to study the chemistry of water in eight regions of high-mass star
formation. The spectra indicate HDO excitation temperatures of ~110 K and
column densities in an 11'' beam of ~2x10^14 cm^-2 for HDO and ~2x10^17 cm^-2
for H2O, with the N(HDO)/N(H2O) ratio increasing with decreasing temperature.
Simultaneous observations of CH3OH and SO2 indicate that 20-50% of the
single-dish line flux arises in the molecular outflows of these objects. The
outflow contribution to the H2O-18 and HDO emission is estimated to be 10-20%.
Radiative transfer models indicate that the water abundance is low (~10^-6)
outside a critical radius corresponding to a temperature in the protostellar
envelope of ~100 K, and `jumps' to H2O/H2 ~ 10^-4 inside this radius. This
value corresponds to the observed abundance of solid water and together with
the derived HDO/H2O abundance ratios of ~1/1000 suggests that the origin of the
observed water is evaporation of grain mantles. This idea is confirmed in the
case of AFGL 2591 by interferometer observations of HDO, H2O-18 and SO2 lines,
which reveal compact (~800 AU) emission with a systematic velocity gradient.
This size is similar to that of the 1.3 mm continuum towards AFGL 2591, from
which we estimate a mass of ~0.8 M0, or ~5% of the mass of the central star. We
speculate that we may be observing a circumstellar disk in an almost face-on
orientation.


title:
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses II. SDSS
  J0924+0219: the redshift of the lensing galaxy, the quasar spectral
  variability and the Einstein rings

abstract:
  (Abridged) We present our VLT/FORS1 deep spectroscopic observations of the
gravitationally lensed quasar SDSS J0924+0219, as well as archival HST/NICMOS
and ACS images of the same object. The two-epoch spectra, obtained in the Multi
Object Spectroscopy (MOS) mode, allow for very accurate flux calibration,
spatial deconvolution of the data, and provide the redshift of the lensing
galaxy z=0.394 +/- 0.001. These spectra, taken 15 days apart, show only slight
continuum variations, while the broad emission lines display obvious changes in
the red wing of the Mg II line, in the Fe II bands, and in the central part of
the C III] line. Even though variations in the line profiles are present, we do
not see any significant differences between the continuum and emission line
flux ratios of images A and B of the quasar. Spatial deconvolution of the HST
images reveals a double Einstein ring. One ring corresponds to the lensed
quasar host galaxy at z=1.524 and a second bluer one, is the image either of a
star-forming region in the host galaxy, or of another unrelated lower redshift
object. We find that a broad range of lens models gives a satisfactory fit to
the data. However, they predict very different time delays, making SDSS
J0924+0219 an object of particular interest for photometric monitoring. In
addition, the lens models reconstructed using exclusively the constraints from
the Einstein rings, or using exclusively the astrometry of the quasar images,
are not compatible. This suggests that substructures play an important role in
SDSS J0924+0219.


title:
A self-consistent model of a 22 GHz water maser in a dusty environment
  near late-type stars

abstract:
  We study the conditions for operation of the 22 GHz ortho-water maser in a
dusty medium near late-type stars. The main physical processes, such as
exchange of energy between dust and gas in the radiation field of a star,
radiative cooling by water molecules and pumping of water masers are described
self-consistently. We show that the presence of dust grains of various types
(or of one type with size distribution) strongly affects the maser action. The
pumping mechanism based on the presence of the dust of different optical
properties is able to explain water masers in the silicate carbon star V778
Cyg. However, the masers in the winds from asymptotic giant branch stars
require an additional source of heating, for instance due to the dust drift
through the gas.


title: Galaxy Groups in the 2dFGRS: the number density of groups

abstract:
  The abundance of galaxy clusters as a function of mass is determined using
the 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue. This is used to
estimate the amplitude of the matter fluctuation spectrum, parametrised by the
linear theory rms density fluctuations in spheres of 8Mpc/h, sigma_8. The
best-fitting value for this parameter is highly correlated with the mean matter
density in the Universe, Omega_m, and is found to satisfy
sigma_8=0.25Omega_m^{-0.92-4.5(Omega_m-0.22)^2}+/-10%(statistical)+/-20%
(systematic) for 0.18<Omega_m<0.50, assuming that Omega_m+Omega_Lambda=1. This
gives sigma_8=0.89 when Omega_m=0.25. A ~20% correction has been applied to
undo the systematic bias inherent in the measurement procedure. Mock
catalogues, constructed from large cosmological N-body simulations, are used to
help understand and model these systematic errors. The abundance of galaxy
groups as a function of group bj band luminosity is also determined. This is
used in conjunction with the halo mass function, determined from simulations,
to infer the variation of halo mass-to-light ratio over four orders of
magnitude in halo mass. The mass-to-light ratio shows a minimum value of
100hM_sol/L_sol in the bj band at a total group luminosity of L_bJ ~
5.10^9Lsol/h^2. Together with the observed Tully-Fisher relation, this implies
that the observed rotation speed of Tully-Fisher galaxies is within ~10% of the
typical circular speed of haloes hosting brightest galaxies of the same
luminosity.


title: A New Asteroseismic Diagram For Solar-type Stars

abstract:
  We propose a new kind of seismic diagram, based on the determination of the
locations of sharp acoustic features inside a star. We show that by combining
the information about the position of the base of the convective envelope or
the second helium ionisation zone with a measure of the average large
separation, it is possible to constrain the unknown parameters characterising
the physical processes in the stellar interior. We demonstrate the application
of this technique to the analysis of mock data for a CoRoT target star.


title: Resolving the Fe xxv Triplet with Chandra in Cen X-3

abstract:
  We present the results of a 45 ks Chandra observation of the high-mass X-ray
binary Cen X--3 at orbital phases between 0.13 and 0.40 (in the eclipse
post-egress phases). Here we concentrate on the study of discrete features in
the energy spectrum at energies between 6 and 7 keV, i.e. on the iron
K$_\alpha$ line region, using the High Energy Transmission Grating Spectrometer
on board the Chandra satellite. We clearly see a K$_\alpha$ neutral iron line
at $\sim 6.40$ keV and were able to distinguish the three lines of the
\ion{Fe}{25} triplet at 6.61 keV, 6.67 keV, and 6.72 keV, with an equivalent
width of 6 eV, 9 eV, and 5 eV, respectively. The equivalent width of the
K$_\alpha$ neutral iron line is 13 eV, an order of magnitude lower than
previous measures. We discuss the possibility that the small equivalent width
is due to a decrease of the solid angle subtended by the reflector.


title:
Effects of "extra-mixing" processes on the periods of high-order gravity
  modes in main-sequence stars

abstract:
  In main-sequence stars, the chemical composition gradient that develops at
the edge of the convective core is responsible for a non-uniform period spacing
of high-order gravity modes. In this work we investigate, in the case of a 1.6
Msun star, the effects on the period-spacing of extra mixing processes in the
core (such as diffusion and overshooting).


title: Forming sub-horizon black holes at the end of inflation

abstract:
  Previous authors have calculated the mass function of primordial black holes
only on scales which are well outside the horizon at the end of inflation. Here
we extend the calculation to sub-horizon scales, on which the density
perturbation never becomes classical. Regarding the formation of black holes as
a `measurement' of the (high peaks) of the density perturbation, we estimate a
mass function by assuming that black holes form as soon as inflation ends, in
those rare regions where the Bardeen potential exceeds a threshold value of
$Psi_c\simeq 0.5$.


title: On the origin of warps and the role of the intergalactic medium

abstract:
  In this paper we consider the viability of these non-gravitational torques to
take the gas off the plane. We show that magnetically generated warps are
clearly flawed because they would wrap up into a spiral in less than two or
three galactic rotations. The inclusion of any magnetic diffusivity to dilute
the wrapping effect, causes the amplitude of the warp to damp. We also consider
observational consequences of the accretion of an intergalactic plane-parallel
flow at infinity. We have computed the amplitude and warp asymmetry in the
accretion model, for a disc embedded in a flattened dark matter halo, including
self-consistently the contribution of the modes with azimuthal wavenumbers m=0
and m=1. This model predicts quite asymmetric warps, maximum gas displacements
on the two sides in the ratio 3:2 for the preferred Galactic parameters,and the
presence of a fraction ~3.5% of U-shaped warps, at least. The azimuthal
dependence of the moment transfer by the ram pressure would produce a strong
asymmetry in the thickness of the HI layer and asymmetric density distributions
in z, in conflict with observational data for the warp in our Galaxy and in
external galaxies. The amount of accretion that is required to explain the
Galactic warp would give gas scaleheights in the far outer disc that are too
small. We conclude that accretion of a flow with no net angular momentum,
cannot be the main and only cause of warps.


title:
Light Variations of the Anomalous Central Star of Planetary Nebula Sh
  2-71

abstract:
  We present an analysis of light variations in UBVRI of the anomalous object
in the center of planetary nebula Sh 2-71. We refined the linear ephemeris of
the light maxima to JD{max} = 2449862.0 + 68.101 (E-96), but also identified
long-term, obviously non-periodic variations. The latter manifest themselves in
large O-C shifts, a variable profile of light curves (hereafter LC) and changes
in the mean brightness of the object. Our spectroscopic observations suggested
the presence of a superdense nebula in the center of Sh 2-71.


title: The Warped Nuclear Disk of Radio Galaxy 3C 449

abstract:
  Among radio galaxies containing nuclear dust disks, the bipolar jet axis is
generally observed to be perpendicular to the disk major axis. The FR I radio
source 3C 449 is an outlier to this statistical majority, as it possesses a
nearly parallel jet/disk orientation on the sky. We examine the 600 pc dusty
disk in this galaxy with images from the Hubble Space Telescope. We find that a
colormap of the disk exhibits a twist in its isocolor contours (isochromes). We
model the colormap by integrating galactic starlight through an absorptive
disk, and find that the anomalous twist in the isochromes can be reproduced in
the model with a vertically thin, warped disk. The model predicts that the disk
is nearly perpendicular to the jet axis within 100 pc of the nucleus. We
discuss physical mechanisms capable of causing such a warp. We show that
precessional models or a torque on the disk arising from a possible binary
black hole in the AGN causes precession on a timescale that is too long to
account for the predicted disk morphology. However, we estimate that the
pressure in the X-ray emitting interstellar medium is large enough to perturb
the disk, and argue that jet-driven anisotropy in the excited ISM may be the
cause of the warp. In this way, the warped disk in 3C 449 may be a new
manifestation of feedback from an active galactic nucleus.


title: The XMM-Newton View of GRS1915+105

abstract:
  (abridged) Two XMM-Newton observations of the black-hole binary GRS1915+105
were triggered in 2004, during a long "plateau" state of the source. (...)
While the light curves show just small amplitude variations (a few percent) at
timescales longer than a few seconds, a QPO is seen at about 0.6 Hz (...). The
pn spectrum is well fitted without invoking thermal disk emission, on the base
of four main components: a primary one (...), absorbed by cold matter with
abundances different than those of standard ISM; reprocessing from an ionized
disk; emission and absorption lines; and a soft X-ray excess around 1 keV.
However, the latter is not confirmed by the RGS spectra, whose difference from
the EPIC-pn ones actually lacks of a fully satisfactory explanation. If real,
the soft X-ray excess may be due to reflection from an optically thin,
photoionized disk wind; in this case it may yield a way to disentangle
intrinsic from interstellar absorption.


title:
The Thermal State of the Accreting White Dwarf in AM Canum Venaticorum
  Binaries

abstract:
  We calculate the heating and cooling of the accreting white dwarf (WD) in the
ultracompact AM Canum Venaticorum (AM CVn) binaries and show that the WD can
contribute significantly to their optical and ultraviolet emission. We estimate
the WD's effective temperature, Teff, using the optical continuum for a number
of observed binaries, and show that it agrees well with our theoretical
calculations. Driven by gravitational radiation losses, the time averaged
accretion rate, <Mdot>, decreases monotonically with increasing Porb, covering
six orders of magnitude. If the short period (Porb<10 min) systems accrete at a
rate consistent with gravitational radiation via direct impact, we predict
their unpulsed optical/UV light to be that of the Teff>50,000$ K accreting WD.
At longer Porb we calculate the Teff and absolute visual magnitude, M_V, that
the accreting WD will have during low accretion states, and find that the WD
naturally crosses the pulsational instability strip. Discovery and study of
pulsations could allow for the measurement of the accumulated helium mass on
the accreting WD, as well as its rotation rate. Accretion heats the WD core,
but for Porb>40 minutes, the WD's Teff is set by its cooling as <Mdot>
plummets. For the two long period AM CVn binaries with measured parallaxes, GP
Com and CE 315, we show that the optical broadband colors and intensity are
that expected from a pure helium atmosphere WD. This confirms that the WD
brightness sets the minimum light in wide AM CVn binaries, allowing for
meaningful constraints on their population density from deep optical searches,
both in the field and in Globular Clusters.


title: Collapse of magnetized hypermassive neutron stars in general relativity

abstract:
  Hypermassive neutron stars (HMNSs) -- equilibrium configurations supported
against collapse by rapid differential rotation -- are possible transient
remnants of binary neutron star mergers. Using newly developed codes for
magnetohydrodynamic simulations in dynamical spacetimes, we are able to track
the evolution of a magnetized HMNS in full general relativity for the first
time. We find that secular angular momentum transport due to magnetic braking
and the magnetorotational instability results in the collapse of an HMNS to a
rotating black hole, accompanied by a gravitational wave burst. The nascent
black hole is surrounded by a hot, massive torus undergoing quasistationary
accretion and a collimated magnetic field. This scenario suggests that HMNS
collapse is a possible candidate for the central engine of short gamma-ray
bursts.


title: The satellite distribution of M31

abstract:
  (Abridged) The spatial distribution of the Galactic satellite system plays an
important role in Galactic dynamics and cosmology, where its successful
reproduction is a key test of simulations of galaxy halo formation. Here, we
examine its representative nature by conducting an analysis of the
3-dimensional spatial distribution of the M31 subgroup of galaxies. We begin by
a discussion of distance estimates and incompleteness concerns, before
revisiting the question of membership of the M31 subgroup. Comparison of the
distribution of M31 and Galactic satellites relative to the galactic disks
suggests that the Galactic system is probably modestly incomplete at low
latitudes by ~20%. We find that the radial distribution of satellites around
M31 is more extended than the Galactic subgroup; 50% of the Galactic satellites
are found within ~100kpc of the Galaxy, compared to ~200kpc for M31. We search
for ``ghostly streams'' of satellites around M31, in the same way others have
done for the Galaxy, and find several. The lack of M31-centric kinematic data,
however, means we are unable to probe whether these streams represent real
physical associations. Finally, we find that the M31 satellites are
asymmetrically distributed with respect to our line-of-sight to this object, so
that the majority of its satellites are on its near side with respect to our
line-of-sight. We quantify this result and find it to be significant at the ~3
sigma level. Until such time as a satisfactory explanation for this finding is
presented, our results warn against treating the M31 subgroup as complete,
unbiased and relaxed.


title: An IR-Selected Galaxy Cluster at z = 1.41

abstract:
  We report the discovery of a galaxy cluster at z = 1.41. ISCS J143809+341419
was found in the Spitzer/IRAC Shallow Survey of the Bootes field in the NOAO
Deep Wide-Field Survey carried out by IRAC. The cluster candidate was initially
identified as a high density region of objects with photometric redshifts in
the range 1.3 < z < 1.5. Optical spectroscopy of a limited number of objects in
the region shows that 5 galaxies within a ~120 arcsec diameter region lie at z
= 1.41 +/- 0.01. Most of these member galaxies have broad--band colors
consistent with the expected spectral energy distribution of a
passively--evolving elliptical galaxy formed at high redshift. The redshift of
ISCS J143809+341419 is the highest currently known for a
spectroscopically-confirmed cluster of galaxies.


title: The velocity anisotropy - density slope relation

abstract:
  One can solve the Jeans equation analytically for equilibrated dark matter
structures, once given two pieces of input from numerical simulations. These
inputs are 1) a connection between phase-space density and radius, and 2) a
connection between velocity anisotropy and density slope, the \alpha-\beta
relation. The first (phase-space density v.s. radius) has already been analysed
through several different simulations, however the second (\alpha-\beta
relation) has not been quantified yet. We perform a large set of numerical
experiments in order to quantify the slope and zero-point of the \alpha-\beta
relation. We find strong indication that the relation is indeed an attractor.
When combined with the assumption of phase-space being a power-law in radius,
this allows us to conclude that equilibrated dark matter structures indeed have
zero central velocity anisotropy \beta_0 = 0, central density slope of \alpha_0
= -0.8, and outer anisotropy of \beta_\infty = 0.5.


title:
Colors of Luminous Bulges in Cluster MS1054-03 and Field Galaxies at
  Redshifts z ~ 0.83

abstract:
  Using HST images, we separate the bulge-like (pbulge) and disk-like (pdisk)
components of 71 galaxies in the rich cluster MS1054-03 and of 21 in the field.
Our key finding is that luminous pbulges are very red with restframe U-B ~
0.45, while predicted colors are bluer by 0.20 mag. Moreover, these very red
colors appear to be independent of environment, pbulge luminosity, pdisk color,
and pbulge fraction. These results challenge any models of hierarchical galaxy
formation that predict the colors of distant (z ~ 0.8) luminous field and
cluster bulges would differ. Our findings also disagree with other claims that
30% to 50% of bright bulges and ellipticals at z ~ 1 are very blue (U-B < 0).


title: XTE J1739-302 as a Supergiant Fast X-ray Transient

abstract:
  XTE J1739-302 is a transient X-ray source with unusually short outbursts,
lasting on the order of hours. Here we give a summary of X-ray observations we
have made of this object in outburst with the Rossi X-ray Timing Explorer
(RXTE) and at a low level of activity with the Chandra X-ray Observatory, as
well as observations made by other groups. Visible and infrared spectroscopy of
the mass donor of XTE J1739-302 are presented in a companion paper. The X-ray
spectrum is hard both at low levels and in outburst, but somewhat variable, and
there is strong variability in the absorption column from one outburst to
another. Although no pulsation has been observed, the outburst data from
multiple observatories show a characteristic timescale for variability on the
order of 1500-2000 s. The Chandra localization (right ascension 17h 39m 11.58s,
declination -30o 20' 37.6'', J2000) shows that despite being located less than
2 degrees from the Galactic Center and highly absorbed, XTE J1739-302 is
actually a foreground object with a bright optical counterpart. The combination
of a very short outburst timescale and a supergiant companion is shared with
several other recently-discovered systems, forming a class we designate as
Supergiant Fast X-ray Transients (SFXTs). Three persistently bright X-ray
binaries with similar supergiant companions have also produced extremely short,
bright outbursts: Cyg X-1, Vela X-1, and 1E 1145.1-6141.


title: Locking of the Rotation of Disk-Accreting Magnetized Stars

abstract:
  We investigate the rotational equilibrium state of a disk accreting
magnetized stars using axisymmetric magnetohydrodynamic (MHD) simulations. In
this ``locked'' state, the spin-up torque balances the spin-down torque so that
the net average torque on the star is zero. We investigated two types of
initial conditions, one with a relatively weak stellar magnetic field and a
high coronal density, and the other with a stronger stellar field and a lower
coronal density. We observed that for both initial conditions the rotation of
the star is locked to the rotation of the disk. In the second case, the radial
field lines carry significant angular momentum out of the star. However, this
did not appreciably change the condition for locking of the rotation of the
star. We find that in the equilibrium state the corotation radius $r_{co}$ is
related to the magnetospheric radius $r_A$ as $r_{co}/r_A\approx 1.2-1.3$ for
case (1) and $r_{co}/r_A\approx 1.4-1.5$ for case (2). We estimated periods of
rotation in the equilibrium state for classical T Tauri stars, dwarf novae and
X-ray millisecond pulsars.


title:
2D non-LTE Modeling for Axi-symmetric Winds. II. A Short Characteristic
  Solution for Radiative Transfer in Rotating Winds

abstract:
  We present a new radiative transfer code for axi-symmetric stellar
atmospheres and compare test results against 1D and 2D models with and without
velocity fields. The code uses the short characteristic method with
modifications to handle axi-symmetric and non-monotonic 3D wind velocities, and
allows for distributed calculations. The formal solution along a characteristic
is evaluated with a resolution that is proportional to the velocity gradient
along the characteristic. This allows us to accurately map the variation of the
opacities and emissivities as a function of frequency and spatial coordinates,
but avoids unnecessary work in low velocity regions. We represent a
characteristic with an impact-parameter vector p (a vector that is normal to
the plane containing the characteristic and the origin) rather than the
traditional unit vector in the direction of the ray. The code calculates the
incoming intensities for the characteristics by a single latitudinal
interpolation without any further interpolation in the radiation angles. Using
this representation also provides a venue for distributed calculations since
the radiative transfer can be done independently for each p.


title:
The X-ray Jet in Centaurus A: Clues on the Jet Structure and Particle
  Acceleration

abstract:
  We report detailed studies of the X-ray emission from the kpc scale jet in
the nearest active galaxy, Cen A. 41 compact sources were found within the jet,
13 of which were newly identified. We construct the luminosity function for the
detected jet-knots and argue that the remaining emission is most likely to be
truly diffuse, rather than resulting from the pile-up of unresolved faint
knots. The transverse jet profile reveals that the extended emission has the
intensity peak at the jet boundaries. We note that limb-brightened jet
morphologies have been observed previously at radio frequencies in some jet
sources, but never so clearly at higher photon energies. Our result therefore
supports a stratified jet model, consisting of a relativistic outflow including
a boundary layer with a velocity shear. In addition, we found that the X-ray
spectrum of the diffuse component is almost uniform across and along the jet.
We discuss this spectral behavior within a framework of shock and stochastic
particle acceleration processes. We note some evidence for a possible spectral
hardening at the outer sheath of the jet. Due to the limited photon statistics
of the present data, further deep observations of Cen A are required to
determine the reality of this finding, however we note that the existence of
the hard X-ray features at outer jet boundaries would provide an important
challenge to theories for the evolution of ultra-relativistic particles within
the jets.


title: Discovery of a Wide Low-mass Binary System in Upper Scorpius

abstract:
  Using the near-infrared spectrometer SpeX and its slit-viewing camera at the
IRTF, I have resolved a low-mass member of the Upper Scorpius OB association
into a double star. From K-band images of the pair, DENIS-P J161833.2-251750.4
A and B, I measure a separation of 0.96" and a magnitude difference of dK=0.42
mag. I present resolved 0.8-2.5 micron spectroscopy of the two objects, both of
which exhibit signatures of youth in the shape of their H- and K-band continua,
demonstrating that both are members of Upper Scorpius rather than field stars.
In addition, through a comparison to optically-classified pre-main-sequence
objects, I derive a spectral type near M5 for each component, corresponding to
a mass of ~0.15 Msun with the evolutionary models of Chabrier and Baraffe. The
probability that this pair is composed of unrelated M-type members of Upper
Scorpius is ~10^-5. When added to the recent discoveries of other wide, easily
disrupted low-mass binaries, this new system further establishes that the
formation of low-mass stars and brown dwarfs does not require ejection from
multiple systems. These observations also indicate that wide low-mass binaries
can form in OB associations as well as in smaller clusters where the previously
known wide pairs have been found. Thus, the available data show no perceptible
effect of star-forming environment on the prevalence of loosely bound low-mass
systems.


title:
The Energy Dependence of Neutron Star Surface Modes and X-ray Burst
  Oscillations

abstract:
  We calculate the photon energy dependence of the pulsed amplitude of neutron
star (NS) surface modes. Simple approximations demonstrate that it depends most
strongly on the bursting NS surface temperature. This result compares well with
full integrations that include Doppler shifts from rotation and general
relativistic corrections to photon propagation. We show that the energy
dependence of type I X-ray burst oscillations agrees with that of a surface
mode, lending further support to the hypothesis that they originate from
surface waves. The energy dependence of the pulsed emission is rather
insensitive to the NS inclination, mass and radius, or type of mode, thus
hindering constraints on these parameters. We also show that, for this
energy-amplitude relation, the majority of the signal (relative to the noise)
comes in the 2-25 keV band, so that the current burst oscillation searches with
the Rossi X-Ray Timing Explorer are close to optimal. The critical test of the
mode hypothesis for X-ray burst oscillations would be a measurement of the
energy dependence of burst oscillations from an accreting millisecond pulsar.


title: The Disk Fractions of Brown Dwarfs in IC 348 and Chamaeleon I

abstract:
  Using the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope, we
have obtained mid-infrared photometry for 25 and 18 low-mass members of the IC
348 and Chamaeleon I star-forming clusters, respectively (>M6, M<=0.08 Msun).
We find that 42+/-13% and 50+/-17% of the two samples exhibit excess emission
indicative of circumstellar disks. In comparison, the disk fractions for
stellar members of these clusters are 33+/-4% and 45+/-7% (M0-M6, 0.7
Msun>=M>=0.1 Msun). The similarity of the disk fractions of stars and brown
dwarfs is consistent with a common formation mechanism and indicates that the
raw materials for planet formation are available around brown dwarfs as often
as around stars.


title: The Age of AB Dor

abstract:
  We have derived a new age estimate for the nearby young star AB Dor and have
investigated the resulting implications for testing theoretical evolutionary
models with the data reported by Close and coworkers for the low-mass companion
AB Dor C. Using color-magnitude diagrams, we find that the AB Dor moving group
is roughly coeval with the Pleiades (100-125 Myr) and is clearly older than IC
2391 (35-50 Myr). In fact, based on a comparison of the kinematics of AB Dor
and the Pleiades, we suggest that the stars identified by Zuckerman and
coworkers as members of a moving group with AB Dor are remnants of the large
scale star-formation event that formed the Pleiades. Using the age of 50+50/-20
Myr adopted by Close, the luminosity predicted by the models of Chabrier and
Baraffe for AB Dor C is larger than the value reported by Close, but is still
within the quoted uncertainties. Meanwhile, the agreement is good when our age
estimate for AB Dor C is adopted. Thus, we find no evidence in the data
presented by Close for AB Dor C to suggest that previous studies using the
models of Chabrier and Baraffe and bolometric luminosity as the mass indicator
have significantly underestimated the masses of young low-mass stars and brown
dwarfs.


title:
Testing Theoretical Evolutionary Models with AB Dor C and the Initial
  Mass Function

abstract:
  We assess the constraints on the evolutionary models of young low-mass
objects that are provided by the measurements of the companion AB Dor C by
Close and coworkers and by a new comparison of model-derived IMFs of
star-forming regions to the well-calibrated IMF of the solar neighborhood.
After performing an independent analysis of Close's imaging and spectroscopic
data for AB Dor C, we find that AB Dor C is not detected at a significant level
(SN 1.2) in the SDI images when one narrow-band image is subtracted from
another, but that it does appear in the individual SDI frames as well as the
images at JHK. Using the age of 75-150 Myr for AB Dor from Luhman, Stauffer, &
Mamajek, the luminosity predicted by the models of Chabrier & Baraffe is
consistent with the value that we estimate. We measure a spectral type of
M6+/-1 from the K-band spectrum of AB Dor C, which is earlier than the value of
M8+/-1 from Close and is consistent with the model predictions when a dwarf
temperature scale is adopted. In a test of these models at much younger ages,
we show that the low-mass IMFs that they produce for star-forming regions are
similar to the IMF of the solar neighborhood. If the masses of the low-mass
stars and brown dwarfs in these IMFs of star-forming regions were
underestimated by a factor of two as suggested by Close, then the IMF
characterizing the current generation of Galactic star formation would have to
be radically different from the IMF of the solar neighborhood.


title:
Observations of the X-ray Burster MX 0836-42 by the INTEGRAL and RXTE
  Orbiting Observatories

abstract:
  We present the results of our study of the emission from the transient
burster MX 0836-42 using its observations by the INTEGRAL and RXTE X-ray and
gamma-ray observatories in the period 2003-2004. The source's broadband X-ray
spectrum in the energy range 3-120 keV has been obtained and investigated for
the first time. We have detected 39 X-ray bursts from this source. Their
analysis shows that the maximum 3-20 keV flux varies significantly from burst
to burst, F ~ (0.5-1.5)x10^{-8} erg cm^{-2} s^{-1}. Using the flux at the
maximum of the brightest detected burst, we determined an upper limit for the
distance to the source, D ~ 8 kpc.


title:
Are neutron stars crushed? Gravitomagnetic tidal fields as a mechanism
  for binary-induced collapse

abstract:
  Numerical simulations of binary neutron stars by Wilson, Mathews, and
Marronetti indicated that neutron stars that are stable in isolation can be
made to collapse to black holes when placed in a binary. This claim was
surprising as it ran counter to the Newtonian expectation that a neutron star
in a binary should be more stable, not less. After correcting an error found by
Flanagan, Wilson and Mathews found that the compression of the neutron stars
was significantly reduced but not eliminated. This has motivated us to ask the
following general question: Under what circumstances can general-relativistic
tidal interactions cause an otherwise stable neutron star to be compressed? We
have found that if a nonrotating neutron star possesses a current-quadrupole
moment, interactions with a gravitomagnetic tidal field can lead to a
compressive force on the star. If this current quadrupole is induced by the
gravitomagnetic tidal field, it is related to the tidal field by an
equation-of-state-dependent constant called the gravitomagnetic Love number.
This is analogous to the Newtonian Love number that relates the strength of a
Newtonian tidal field to the induced mass quadrupole moment of a star. The
compressive force is almost never larger than the Newtonian tidal interaction
that stabilizes the neutron star against collapse. In the case in which a
current quadrupole is already present in the star (perhaps as an artifact of a
numerical simulation), the compressive force can exceed the stabilizing one,
leading to a net increase in the central density of the star. This increase is
small (<~1%) but could, in principle, cause gravitational collapse in a star
that is close to its maximum mass.


title: QPOs in microquasars and Sgr A*: measuring the black hole spin

abstract:
  In all four microquasars which show double peak kHz QPOs, the ratio of the
two frequencies is 3:2. This strongly supports the suggestion that twin peak
kHz QPOs are due to a resonance between some modes of accretion disk
oscillations. Here, we stress that fits to observations of the hypothetical
resonances between vertical and radial epicyclic frequencies (particularly of
the parametric resonance) give an accurate estimate of the spin for the three
microquasars with known mass. Measurement of double peak QPOs frequencies in
the Galaxy centre seems also to be consistent with the 3:2 ratio established by
previous observations in microquasars, however the Sgr A* data are rather
difficult for the same exact analysis. If confirmed, the 3:2 ratio of double
peak QPOs in Sgr A* would be of a fundamental importance for the black hole
accretion theory and the precise measurement could help to solve the question
of QPOs nature.


title:
Dynamical properties of Ultraluminous Infrared Galaxies I: Mass ratio
  conditions for ULIRG activity in interacting pairs

abstract:
  We present first results from our Very Large Telescope large program to study
the dynamical evolution of Ultraluminous Infrared Galaxies (ULIRGs), which are
the products of mergers of gas-rich galaxies. The full data set consists of
high resolution, long-slit, H- and K-band spectra of 38 ULIRGs and 12 QSOs
(between 0.042<z<0.268). In this paper, we present the sources that have not
fully coalesced, and therefore have two distinct nuclei. This sub-sample
consists of 21 ULIRGs, the nuclear separation of which varies between 1.6 and
23.3 kpc. From the CO bandheads that appear in our spectra, we extract the
stellar velocity dispersion, sigma, and the rotational velocity, V_rot. The
stellar dispersion equals 142 km/s on average, while V_rot is often of the same
order. We combine our spectroscopic results with high-resolution infrared (IR)
imaging data to study the conditions for ULIRG activity in interacting pairs.
We find that the majority of ULIRGs are triggered by almost equal-mass major
mergers of 1.5:1 average ratio. Less frequently, 3:1 encounters are also
observed in our sample. However, less violent mergers of mass ratio >3:1
typically do not force enough gas into the center to generate ULIRG
luminosities.


title: Physical conditions in the ISM towards HD185418

abstract:
  We have developed a complete model of the hydrogen molecule as part of the
spectral simulation code Cloudy. Our goal is to apply this to spectra of
high-redshift star-forming regions where H2 absorption is seen, but where few
other details are known, to understand its implication for star formation. The
microphysics of H2 is intricate, and it is important to validate these
numerical simulations in better-understood environments. This paper studies a
well-defined line-of-sight through the Galactic interstellar medium (ISM) as a
test of the microphysics and methods we use. We present a self-consistent
calculation of the observed absorption-line spectrum to derive the physical
conditions in the ISM towards HD185418, a line-of-sight with many observables.
We deduce density, temperature, local radiation field, cosmic ray ionization
rate, chemical composition and compare these conclusions with conditions
deduced from analytical calculations. We find a higher density, similar
abundances, and require a cosmic ray flux enhanced over the Galactic background
value, consistent with enhancements predicted by MHD simulations.


title:
Narrow-Band Survey of the GOODS Fields: Search for Lyman-Alpha Emitters
  at z = 5.7

abstract:
  We present results from optical narrow-band lambda_c = 8150A ~ and Delta
lambda = 120A) observations of the Great Observatories Origins Deep Survey
(GOODS) fields, using Suprime-Cam on the Subaru Telescope. Using these
narrow-band data, we then perform a survey of Lyman alpha Emitters (LAEs) at
z~5.7. The LAE survey covers an area of approx 320 arcmin^2 and a co-moving
volume of ~8.0 x 10^4 Mpc^3. We found a total of 10 (GOODS-N) and 4 (GOODS-S)
LAE candidates at z~5.7. We perform a study of the spatial distribution, space
density, and star formation properties of the LAEs at z~5.7.


title:
Reconstruction of $5D$ Cosmological Models From Equation of State of
  Dark Energy

abstract:
  We consider a class of five-dimensional cosmological solutions which contains
two arbitrary function $\mu(t)$ and $\nu(t)$. We found that the arbitrary
function $\mu(t)$ contained in the solutions can be rewritten in terms of the
redshift $z$ as a new arbitrary function $f(z)$. We further showed that this
new arbitrary function $f(z)$ could be solved out for four known parameterized
equations of state of dark energy. Then the $5D$ models can be reconstructed
and the evolution of the density and deceleration parameters of the universe
can be determined.


title: A deep XMM-Newton serendipitous survey of a middle-latitude area

abstract:
  The radio quiet neutron star 1E1207.4-5209 has been the target of a 260 ks
XMM-Newton observation, which yielded, as a by product, an harvest of about 200
serendipitous X-ray sources above a limiting flux of 2E-15 erg/cm2/s, in the
0.3-8 keV energy range. In view of the intermediate latitude of our field (b~10
deg), it comes as no surprise that the logN-logS distribution of our
serendipitous sources is different from those measured either in the Galactic
Plane or at high galactic latitudes. Here we shall concentrate on the analysis
of the brightest sources in our sample, which unveiled a previously unknown
Seyfert-2 galaxy.


title: The optical counterpart to the peculiar X-ray transient XTE J1739-302

abstract:
  The weak X-ray transient XTE J1739-302, characterized by extremely short
outbursts, has recently been identified with a reddened star. Here we present
spectroscopy and photometry of the counterpart, identifying it as a O8Iab(f)
supergiant at a distance of ~2.3 kpc. XTE J1739-302 becomes thus characterized
as the prototype of the new class of Supergiant Fast X-ray Transients. The
optical and infrared spectra of the counterpart to XTE J1739-302 do not reveal
any obvious characteristics setting it apart from other X-ray binaries with
supergiant companions, which display a very different type of X-ray lightcurve.


title:
High spatial resolution study of the inner environment around two young
  planetary nebulae

abstract:
  We present observations of the dusty emission from the young planetary
nebulae Hen2-113 and CPD-56 obtained with VLT/NACO, VLTI/MIDI. The central
stars of these two objects are Wolf-Rayet stars of the same spectral type
[WC10]. They share an impressive number of characteristics and are located at
similar distance, making the detection of any differences in their close
environment of great interest. Hen2-113 exhibits a clear ring-like structure of
about 0.4 arcsec in diameter, superimposed to a more diffuse environment
visible in L', M' and 8.7 micron bands. No clear core could be detected for
this object with MIDI through the N band. The dusty environment of CPD-568032
is much more compact, dominated by a bright, barely resolved, core whereas the
visible nebula exhibits an amazing complexity. From MIDI 8.7 micron acquisition
images (dominated by PAHs emission), the extension and geometry of the core
have been estimated and compared to the STIS/HST observations (De Marco et al.,
1997 and 2002). Moreover, high SNR fringes at low level have been detected with
projected baselines between 40 and 45 meters. This clear signal is interpreted
in terms of the bright inner rim of a dusty disk exposed to the flux from the
Wolf-Rayet star. The geometrical parameters of the N band flux distribution are
well constrained by means of simple geometrical models and a simple radiative
transfer model has been developed to extract the physical parameters of the
disk.


title: Swift observations of the X-ray bright GRB 050315

abstract:
  This paper discusses Swift observations of the gamma-ray burst GRB 050315
(z=1.949) from 80 s to 10 days after the onset of the burst. The X-ray light
curve displayed a steep early decay (t^-5) for ~200 s and several breaks.
However, both the prompt hard X-ray/gamma-ray emission (observed by the BAT)
and the first ~ 300 s of X-ray emission (observed by the XRT) can be explained
by exponential decays, with similar decay constants. Extrapolating the BAT
light curve into the XRT band suggests the rapidly decaying, early X-ray
emission was simply a continuation of the fading prompt emission; this strong
similarity between the prompt gamma-ray and early X-ray emission may be related
to the simple temporal and spectral character of this X-ray rich GRB. The
prompt (BAT) spectrum was a steep down to 15 keV, and appeared to continue
through the XRT bandpass, implying a low peak energy, inconsistent with the
Amati relation. Following the initial steep decline the X-ray afterglow did not
fade for ~1.2*10^4 s, after which time it decayed with a temporal index of
alpha ~ 0.7, followed by a second break at ~2.5*10^5 s to a slope of alpha ~ 2.
The apparent `plateau' in the X-ray light curve, after the early rapid decay,
makes this one of the most extreme examples of the steep-flat-steep X-ray light
curves revealed by Swift. If the second afterglow break is identified with a
jet break then the jet opening angle was theta_0 ~ 5 deg, and implying E_gamma
> 10^50 erg.


title:
Abundances from disentangled component spectra of close binary stars: An
  observational test of an earlz mixing in high-mass stars

abstract:
  Recent theoretical calculations of stellar evolutionary tracks for rotating
high-mass stars suggests that the chemical composition of the surface layers
changes even whilst the star is evolving on the Main Sequence. The abundance
analysis of binary components with precisely known fundamental stellar
quantities allows a powerful comparison with theory. The observed spectra of
close binary stars can be separated into the individual spectra of the
component stars using the method of spectral disentangling on a time-series of
spectra taken over the orbital cycle. Recently, Pavlovski & Hensberge (2005,
A&A, 439, 309) have shown that, even with moderately high line-broadening,
metal abundances can be derived from disentangled spectra with a precision of
0.1 dex. In a continuation of this project we have undertaken a detailed
abundance analysis of the components of another two high-mass binaries, V453
Cyg, and V380 Cyg. Both binaries are well-studied systems with modern
solutions. The components are close to the TAMS and therefore very suitable for
an observational test of early mixing in high-mass stars.


title:
Probable member stars of the gravitational theory-testing globular
  clusters AM 1, Pal 3 and Pal 14

abstract:
  Some of the Galactic outer halo globular clusters are excellent tools to
probe gravitational theories in the regime of weak accelerations (Baumgardt et
al. 2005). The measurement of the line-of-sight velocity dispersion among stars
in these clusters will differentiate between the validity of Newtonian dynamics
(low velocity dispersion) and the possiblity of modified Newtonian dynamics
(MOND) or dark matter dominated globular clusters (high velocity dispersion).
In this paper, the properties of probable member stars of the three best-case
gravitational theory-testing clusters AM 1, Pal 3 and Pal 14 are presented. The
member selection is based on VLT photometry in Johnson BV. The positions of the
stars were determined with an accuracy of the order <=0.2 arcsec, allowing
their direct use for follow-up spectroscopy. The distance, reddening, age, and
metallicities of the clusters were estimated from isochrone fitting.
Furthermore, improved structural parameters, like central coordinates,
ellipticit


title: The nature of the 'knee' in the cosmic ray energy spectrum

abstract:
  In view of recent developments attention is directed again at two aspects of
the well known 'knee' in the cosmic ray energy spectrum at 3 PeV: the mass of
the predominant particles at this energy and their source. It is inevitable in
a subject such as this that ideas - and conclusions - evolve. Earlier, we had
used a particular acceleration model and the nature of the local ISM to infer
that the particles are mainly oxygen nuclei. Initially no specific source was
identified. More recently, however, we have specified the Monogem Ring
supernova remnant (SNR) as the likely source; this is at just the right
distance and age and the energies are reasonable. Concerning the mass
composition at the knee, a quantity more difficult to determine, recent direct
measurements, which extend to higher energies than hitherto, show a likely
flattening in the spectrum above 10^4 GeV/nucleon for He-nuclei, a flattening
which, if extrapolated to higher energies, would meet the measured spectrum in
the knee region. The other nuclei do not show this feature. He-nuclei in the
knee region would also be marginally consistent with KASCADE EAS data, although
there are serious problems with EAS mass estimates in that experiment.
Concerning the acceleration, recent models applied to the Monogem Ring SNR
allow a satisfactory explanation in terms of either oxygen or helium, but with
the latter being a distinct possibility and perhaps more likely.


title: Nonlinear bending waves in Keplerian accretion discs

abstract:
  The nonlinear dynamics of a warped accretion disc is investigated in the
important case of a thin Keplerian disc with negligible viscosity and
self-gravity. A one-dimensional evolutionary equation is formally derived that
describes the primary nonlinear and dispersive effects on propagating bending
waves other than parametric instabilities. It has the form of a derivative
nonlinear Schroedinger equation with coefficients that are obtained explicitly
for a particular model of a disc. The properties of this equation are analysed
in some detail and illustrative numerical solutions are presented. The
nonlinear and dispersive effects both depend on the compressibility of the gas
through its adiabatic index Gamma. In the physically realistic case Gamma<3,
nonlinearity does not lead to the steepening of bending waves but instead
enhances their linear dispersion. In the opposite case Gamma>3, nonlinearity
leads to wave steepening and solitary waves are supported. The effects of a
small effective viscosity, which may suppress parametric instabilities, are
also considered. This analysis may provide a useful point of comparison between
theory and numerical simulations of warped accretion discs.


title: Long-term remnant evolution of compact binary mergers

abstract:
  We investigate the long-term evolution and observability of remnants
originating from the merger of compact binary systems and discuss the
differences to supernova remnants. Compact binary mergers expel much smaller
amounts of mass at much higher velocities, as compared to supernovae and
therefore the free expansion phase of the remnant will be short (~ 1 - 10 yr).
In general the remnants will be observable for a considerable time (~ 10^6 -
10^7 yr). Events releasing large amounts of kinetic energy may be responsible
for a subsample of observed giant HI holes of unknown origin as compact
binaries merge far away from star forming regions. If the ejecta consist
primarily of actinides, on long timescales the expelled material will contain
mainly the few quasi-stable nuclei in the actinides range. Consequently the
abundance of each isotope in the ejecta might be of the order of a few percent.
During their decay some actinides will produce observational signatures in form
of gamma ray lines. We particularly investigate the gamma ray emission of Am
243, Cm 247, Cm 248 and Bi 208 and estimate their observability in nearby
remnants. Detections of the gamma ray lines with INTEGRAL will be possible only
in very advantageous cases but these remnants are promising targets for future
instruments using focusing optics for soft gamma rays. Due to the low mass
expelled in mergers and due to the lack of free electrons in the ejecta, the
merger remnants might be significantly fainter in bremsstrahlung and
synchrotron radiation than comparable supernova remnants. Hence merger remnants
might represent a candidate for very recently discovered 'dark accelerators'
which are hard gamma ray sources with no apparent emission in other bands.


title: Long Baseline Interferometry of Be Stars

abstract:
  We give an introduction to interferometrical concepts and their applicability
to Be stars. The first part of the paper concentrates on a short historic
overview and basic principles of two-beam interferometric observations. In the
second part, the VLTI/MIDI instrument is introduced and its first results on Be
stars, obtained on alpha Ara and delta Cen, are outlined.


title: Anisotropic thermal emission from magnetized neutron stars

abstract:
  The thermal emission from isolated neutron stars is not well understood. The
X-ray spectrum is very close to a blackbody but there is a systematic optical
excess flux with respect to the extrapolation to low energy of the best
blackbody fit. This fact, in combination with the observed pulsations in the
X-ray flux, can be explained by anisotropies in the surface temperature
distribution.We study the thermal emission from neutron stars with strong
magnetic fields in order to explain the origin of the anisotropy. We find
(numerically) stationary solutions in axial symmetry of the heat
transportequations in the neutron star crust and the condensed envelope. The
anisotropy in the conductivity tensor is included consistently. The presence of
magnetic fields of the expected strength leads to anisotropy in the surface
temperature. Models with toroidal components similar to or larger than the
poloidal field reproduce qualitatively the observed spectral properties and
variability of isolated neutron stars. Our models also predict spectral
features at energies between 0.2 and 0.6 keV.


title: Constraints on the IMF of the first stars

abstract:
  Motivated by theoretical predictions that first stars were predominantly very
massive, we investigate the physics of the transition from an early epoch
dominated by massive Pop III stars to a later epoch dominated by familiar
low-mass Pop II/I stars by means of a numerically-generated catalogue of dark
matter halos coupled with a self-consistent treatment of chemical and radiative
feedback. Depending on the strength of the chemical feedback, Pop III stars can
contribute a substantial fraction (several percent) of the cosmic star
formation activity even at moderate redshifts, z = 5. We find that the three z
= 10 sources tentatively detected in NICMOS UDFs should be powered by Pop III
stars, if these are massive; however, this scenario fails to reproduce the
derived WMAP electron scattering optical depth. Instead, both the UDFs and WMAP
constraints can be fulfilled if stars at any time form with a more standard,
slightly top-heavy, Larson IMF in the range 1 Msun < M < 100 Msun.


title: Massive Stellar Content of Giant HII Regions in M 33 and M 101

abstract:
  Far-ultraviolet (900-1200A) spectral synthesis of nine giant extragalactic
HII regions in M 33 and M 101 is performed to study their massive stellar
content. Several parameters are quantified, predicted, and compared to the
literature: age, stellar mass, IMF slope, number of O-type and Wolf-Rayet
stars, Halpha and 5500A continuum fluxes. The results of this particular
technique are consistent with other methods and observations. This work shows
that a total stellar mass of a few 10^3 Msun is needed to populate the IMF bins
well enough at high masses to obtain accurate results from the spectral
synthesis technique in the far-ultraviolet. A flat IMF slope seems to
characterize better the stellar line profiles of these objects, which is likely
the first sign of a small number statistic effect on the IMF. Finally, the HII
region NGC 5461 is identified as a good candidate for hosting a second
generation of stars, not yet seen at far-ultraviolet wavelengths.


title: A New Mechanism for Core-Collapse Supernova Explosions

abstract:
  We present a new mechanism for core-collapse supernova explosions that relies
upon acoustic power generated in the inner core as the driver. In our
simulation using an 11-solar-mass progenitor, a strong advective-acoustic
oscillation a la Foglizzo with a period of ~25-30 milliseconds (ms) arises ~200
ms after bounce. Its growth saturates due to the generation of secondary
shocks, and kinks in the resulting shock structure funnel and regulate
subsequent accretion onto the inner core. However, this instability is not the
primary agent of explosion. Rather, it is the acoustic power generated in the
inner turbulent region and most importantly by the excitation and sonic damping
of core g-mode oscillations. An l=1 mode with a period of ~3 ms grows to be
prominent around ~500 ms after bounce. The accreting protoneutron star is a
self-excited oscillator. The associated acoustic power seen in our
11-solar-mass simulation is sufficient to drive the explosion. The angular
distribution of the emitted sound is fundamentally aspherical. The sound pulses
radiated from the core steepen into shock waves that merge as they propagate
into the outer mantle and deposit their energy and momentum with high
efficiency. The core oscillation acts like a transducer to convert accretion
energy into sound. An advantage of the acoustic mechanism is that acoustic
power does not abate until accretion subsides, so that it is available as long
as it may be needed to explode the star. [abridged]


title: Using the Parallel Virtual Machine for Everyday Analysis

abstract:
  A review of the literature reveals that while parallel computing is sometimes
employed by astronomers for custom, large-scale calculations, no package
fosters the routine application of parallel methods to standard problems in
astronomical data analysis. This paper describes our attempt to close that gap
by wrapping the Parallel Virtual Machine (PVM) as a scriptable S-Lang module.
Using PVM within ISIS, the Interactive Spectral Interpretation System, we've
distributed a number of representive calculations over a network of 25+ CPUs to
achieve dramatic reductions in execution times. We discuss how the approach
applies to a wide class of modeling problems, outline our efforts to make it
more transparent for common use, and note its growing importance in the context
of the large, multi-wavelength datasets used in modern analysis.