title:
Spin-Kick Correlation in Neutron Stars: Alignment Conditions and
  Implications

abstract:
  Recent observations of pulsar wind nebulae and radio polarization profiles
revealed a tendency of the alignment between the spin and velocity directions
in neutron stars. We study the condition for spin-kick alignment using a toy
model, in which the kick consists of many off-centered, randomly-oriented
thrusts. Both analytical considerations and numerical simulations indicate that
spin-kick alignment cannot be easily achieved if the proto-neutron star does
not possess some initial angular momentum, contrary to some previous claims. To
obtain the observed spin-kick misalignment angle distribution, the initial spin
period of the neutron star must be smaller than the kick timescale. Typically,
an initial period of a hundred milliseconds or less is required.


title: Star-forming QSO host galaxies

abstract:
  The recent finding of substantial masses of cold molecular gas as well as
young stellar populations in the host galaxies of quasars is at odds with
results of Hubble Space Telescope imaging studies, since the latter appear to
yield mature, quiescent early type hosts. It is demonstrated here that the
characterization as `quiescent' is incorrect. Radio and far-infrared properties
of both the HST sample and a larger comparison sample of uv-excess selected
radio-quiet QSOs are consistent with substantial recent star-formation
activity.


title: The role of microquasars in astroparticle physics

abstract:
  I present an overview of past, present and future research on microquasars
and jets, showing that microquasars, i.e. galactic jet sources, are among the
best laboratories for high energy phenomena and astroparticle physics. After
reminding the analogy with quasars, I focus on one of the best microquasar
representatives, probably the archetype, namely GRS 1915+105, and present
accretion and ejection phenomena, showing that only a multi-wavelength approach
allows a better understanding of phenomena occurring in these sources.
Thereafter, I review jets at different scales: compact jets, large-scale jets,
and the interactions between ejection and the surrounding medium. I finish this
review by showing that microquasars are good candidates to be emitters of
astroparticles: very high energy photons, cosmic rays and neutrinos.


title:
The Spectral Energy Distribution of Dust Emission in the Edge-on Spiral
  Galaxy NGC 4631 as seen with Spitzer and JCMT

abstract:
  We explore the nature of variations in dust emission within an individual
galaxy using 3.6 - 160 micron Spitzer Space Telescope observations and 450 and
850 micron James Clerk Maxwell Telescope observations of the edge-on Sd spiral
galaxy NGC 4631 with the goals of understanding the relation between polycyclic
aromatic hydrocarbons (PAH) and dust emission, studying the variations in the
colors of the dust emission, and searching for possible excess submillimeter
emission compared to what is anticipated based on dust models applied to the
mid- and far-infrared data. PAH emission at 8 micron is found to correlate best
with hot dust emission at 24 micron on kiloparsec scales, although the relation
breaks down on scales equal to hundreds of parsecs, possibly because of
differences in the mean free paths between the photons that excite the PAHs and
heat the dust and possibly because the PAHs are destroyed by the hard radiation
fields in the centers of some star formation regions. The ratio of 8 micron PAH
emission to 160 micron cool dust emission appears to be a function of radius.
The 70/160 and 160/450 micron flux density ratios are remarkably constant even
though the surface brightness varies by a factor of 25 in each wave band, which
suggests that the emission is from dust heated by a nearly-uniform radiation
field. Globally, we find an excess of 850 micron emission relative to what
would be predicted by dust models. The 850 micron excess is highest in regions
with low 160 micron surface brightness, although the strength and statistical
significance of this result depends on the model fit to the data. We rule out
variable emissivity functions or ~4 K dust as the possible origins of this 850
micron emission, but we do discuss the other possible mechanisms that could
produce the emission.


title: Binary Stars in the Orion Nebula Cluster

abstract:
  We report on a high-spatial-resolution survey for binary stars in the
periphery of the Orion Nebula Cluster, at 5 - 15 arcmin (0.65 - 2 pc) from the
cluster center. We observed 228 stars with adaptive optics systems, in order to
find companions at separations of 0.13" - 1.12" (60 - 500 AU), and detected 13
new binaries. Combined with the results of Petr (1998), we have a sample of 275
objects, about half of which have masses from the literature and high
probabilities to be cluster members. We used an improved method to derive the
completeness limits of the observations, which takes into account the elongated
point spread function of stars at relatively large distances from the adaptive
optics guide star. The multiplicity of stars with masses >2 M_sun is found to
be significantly larger than that of low-mass stars. The companion star
frequency of low-mass stars is comparable to that of main-sequence M-dwarfs,
less than half that of solar-type main-sequence stars, and 3.5 to 5 times lower
than in the Taurus-Auriga and Scorpius-Centaurus star-forming regions. We find
the binary frequency of low-mass stars in the periphery of the cluster to be
the same or only slightly higher than for stars in the cluster core (<3 arcmin
from theta1C Ori). This is in contrast to the prediction of the theory that the
low binary frequency in the cluster is caused by the disruption of binaries due
to dynamical interactions. There are two ways out of this dilemma: Either the
initial binary frequency in the Orion Nebula Cluster was lower than in
Taurus-Auriga, or the Orion Nebula Cluster was originally much denser and
dynamically more active.


title:
Quasi-stationary Electromagnetic Effects in Conductors and
  Superconductors in Schwarzchild Space-time

abstract:
  The general principles needed to compute the effect of a stationary
gravitational field on the quasistationary electromagnetic phenomena in normal
conductors and superconductors are formulated from general relativistic point
of view. Generalization of the skin effect, that is the general relativistic
modification of the penetration depth (of the time-dependent magnetic field in
the conductor) due to its relativistic coupling to the gravitational field is
obtained. The effect of the gravitational field on the penetration and
coherence depths in superconductors is also studied. As an illustration of the
foregoing general results, we discuss their application to superconducting
systems in the outer core of neutron stars. The relevance of these effects to
electrodynamics of magnetized neutron stars has been shown.


title:
Tomography of the intergalactic medium with Ly-alpha forests in close
  QSO pairs

abstract:
  We study the three-dimensional distribution of non virialised matter at z~2
using high resolution spectra of QSO pairs and simulated spectra drawn from
cosmological hydrodynamical simulations. We have collected the largest sample
of QSO pairs ever observed with UVES at the ESO-VLT, with angular separations
between ~1 and 14 arcmin. The observed correlation functions of the transmitted
flux in the HI Lyman alpha forest along and transverse to the lines of sight
are in good agreement implying that the distortions in redshift space due to
peculiar velocities are small. The clustering signal is significant up to
velocity separations of ~200 km/s, or about 3 h^{-1} comoving Mpc. The regions
at lower overdensity (rho/<rho> < 6.5) are still clustered but on smaller
scales (Delta v < 100 km/s). The observed and simulated correlation functions
are compatible at the 3 sigma level. A better concordance is obtained when only
the low overdensity regions are selected for the analysis or when the effective
optical depth of the simulated spectra is increased artificially, suggesting a
deficiency of strong lines in the simulated spectra. We found that also a lower
value of the power-law index of the temperature-density relation for the Lyman
alpha forest gas improves the agreement between observed and simulated results.
If confirmed, this would be consistent with other observations favouring a late
HeII reionization epoch (at z~3). We remark the detection of a significant
clustering signal in the cross correlation coefficient at a transverse velocity
separation Delta v_{\perp} ~500 km/s whose origin needs further investigation.


title:
Mid-infrared Identification of 6 cm Radio Source Counterparts in the
  Extended Groth Strip

abstract:
  A new 6-cm survey of almost 0.6 square degrees to a limit of 0.55-mJy/beam
(10-sigma) finds 37 isolated radio sources and 7 radio source pairs (not
necessarily physical companions). IRAC counterparts are identified for at least
92% of the radio sources within the area of deep IRAC coverage, which includes
31 isolated sources and 6 pairs. This contrasts with an identification rate of
<74% to R<23.95 in visible light. Eight of the IRAC galaxies have power law
spectral energy distributions, implying that the mid-infrared emission comes
from a powerful AGN. The remaining 26 IRAC galaxies show stellar emission in
the mid-infrared, probably in most of these galaxies because the stellar
emission is bright enough to outshine an underlying AGN. The infrared colors
suggest that the majority of these galaxies are bulge-dominated and have
redshifts between approximately 0.5 and 1.0. Visible spectra from the DEEP2
redshift survey, available for 11 galaxies, are consistent with this
suggestion. The IRAC galaxies fall into two distinct groups in a
color-magnitude diagram, one group (the "stripe") includes all the AGN. The
other group (the "blue clump") has blue 3.6 to 8 micron colors and a small
range of 8 micron magnitudes. This separation should be useful in classifying
galaxies found in other radio surveys.


title: Cosmic Supernova Rates and the Hubble Sequence

abstract:
  We compute the type Ia, Ib/c and II supernova (SN) rates as functions of the
cosmic time for galaxies of different morphological types. We use four
different chemical evolution models, each one reproducing the features of a
particular morphological type: E/S0, S0a/b, Sbc/d and Irr galaxies. We
essentially describe the Hubble sequence by means of decreasing efficiency of
star formation and increasing infall timescale. These models are used to study
the evolution of the SN rates per unit luminosity and per unit mass as
functions of cosmic time and as functions of the Hubble type. Our results
indicate that: (i) the observed increase of the SN rate per unit luminosity and
unit mass from early to late galaxy types is accounted for by our models. Our
explanation of this effect is related to the fact that the latest Hubble types
have the highest star formation rate per unit mass; (ii) By adopting a Scalo
(1986) initial mass function in spiral disks, we find that massive single stars
ending their lives as Wolf-Rayet objects are not sufficient to account for the
observed type Ib/c SN rate per unit mass. Less massive stars in close binary
systems can give instead a significant contribution to the local Ib/c SN rates.
On the other hand, with the assumption of a Salpeter (1955) IMF for all galaxy
types, single massive WR stars are sufficient to account for the observed type
Ib/c SN rate. (iii) Our models allow us to reproduce the observed type Ia SN
rate density up to redshift z~1. We predict an increasing type Ia SN rate
density with redshift, reaching a peak at redshift z >= 3, because of the
contribution of massive spheroids.


title: Planetary nebulae abundances and stellar evolution

abstract:
  A summary is given of planetary nebulae abundances from ISO measurements. It
is shown that these nebulae show abundance gradients (with galactocentric
distance), which in the case of neon, argon, sulfur and oxygen (with four
exceptions) are the same as HII regions and early type star abundance
gradients. The abundance of these elements predicted from these gradients at
the distance of the Sun from the center are exactly the solar abundance. Sulfur
is the exception to this; the reason for this is discussed. The higher solar
neon abundance is confirmed; this is discussed in terms of the results of
helioseismology. Evidence is presented for oxygen destruction via ON cycling
having occurred in the progenitors of four planetary nebulae with bilobal
structure. These progenitor stars had a high mass, probably greater than 5
solar masses. This is deduced from the high values of He/H and N/H found in
these nebulae. Formation of nitrogen, helium and carbon are discussed. The high
mass progenitors which showed oxygen destruction are shown to have probably
destroyed carbon as well. This is probably the result of hot bottom burning.


title:
The galaxy-galaxy lensing contribution to the cosmic shear two point
  function

abstract:
  We note that galaxy-galaxy lensing by non-spherical galaxy halos produces a
net anti-correlation between the shear of background galaxies and the
ellipticity of foreground galaxies. This anti-correlation would contaminate the
tomographic cosmic shear two point function if the effect were not taken into
account. We compare the size of the galaxy-galaxy lensing contribution to the
change in the cosmic shear two-point correlation function due to a change in
the dark energy equation of state w of 1%. We find them comparable on scales
<~5 arcmin for NFW galaxy profiles, and out to much larger scales for SIE
profiles. However the galaxy-galaxy lensing signal has a characteristic spatial
and redshift pattern which should allow it to be removed.


title:
Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH
  Model in the Post-Spitzer Era

abstract:
  Infrared (IR) emission spectra are calculated for dust composed of mixtures
of amorphous silicate and graphitic grains, including varying amounts of
polycyclic aromatic hydrocarbon (PAH) particles. The models are constrained to
reproduce the average Milky Way extinction curve. The calculations include the
effects of single-photon heating. Updated IR absorption properties for the PAHs
are presented, that are consistent with observed emission spectra, including
those newly obtained by Spitzer Space Telescope. We find a size distribution
for the PAHs that results in emission band ratios consistent with observed
spectra of the Milky Way and other galaxies. Emission spectra are presented for
various intensities of the illuminating starlight. We calculate how the
efficiency of emission into different IR bands depends on PAH size; the strong
7.7um emission feature is produced mainly by PAH particles containing <1000 C
atoms. We show how the emission spectrum depends on U, the starlight intensity
relative to the local interstellar radiation field. The submm and far-infrared
emission is compared to the observed emission from the local interstellar
medium. Using a simple distribution function, we calculate the emission
spectrum for dust heated by a distribution of starlight intensities, such as
occurs within galaxies. The models are parameterized by the PAH mass fraction
qpah, the lower cutoff Umin, and the fraction gamma of the dust heated by
starlight with U>Umin. We present graphical procedures using IRAC and MIPS
photometry to estimate qpah, Umin, and gamma, the fraction f_PDR of the dust
luminosity coming from photodissociation regions with U>100, and the total dust
mass Mdust.


title: The Intrinsic Size of Sagittarius A* from 0.35 cm to 6 cm

abstract:
  We present new high-resolution observations of Sagittarius A* at wavelengths
of 17.4 to 23.8 cm with the Very Large Array in A configuration with the Pie
Town Very Long Baseline Array antenna. We use the measured sizes to calibrate
the interstellar scattering law and find that the major axis size of the
scattering law is smaller by ~6% than previous estimates. Using the new
scattering law, we are able to determine the intrinsic size of Sgr A* at
wavelengths from 0.35 cm to 6 cm using existing results from the VLBA. The new
law increases the intrinsic size at 0.7 cm by ~20% and <5% at 0.35 cm. The
intrinsic size is 13^{+7}_{-3} Schwarzschild radii at 0.35 cm and is
proportional to lambda^gamma, where gamma is in the range 1.3 to 1.7.


title: Hybrid Detection of UHECR with the Pierre Auger Observatory

abstract:
  The Pierre Auger Observatory detects ultra-high energy cosmic rays by
implementing two complementary air-shower techniques. The combination of a
large ground array and fluorescence detectors, known as the "hybrid" concept,
means that a rich variety of measurements can be made on a single shower,
providing much improved information over what is possible with either detector
alone. In this paper the hybrid reconstruction approach and its performance are
described.


title:
Probing the Evolution of IR Properties of z~6 Quasars: Spitzer
  Observations

abstract:
  We present Spitzer observations of thirteen z~6 quasars using the Infrared
Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). All
the quasars except SDSS J000552.34-000655.8 (SDSS J0005-0006) were detected
with high S/N in the four IRAC channels and the MIPS 24um band, while SDSS
J0005-0006 was marginally detected in the IRAC 8.0um band, and not detected in
the MIPS 24um band. We find that most of these quasars have prominent emission
from hot dust as evidenced by the observed 24um fluxes. Their spectral energy
distributions (SEDs) are similar to those of low-redshift quasars at rest-frame
0.15-3.5 um, suggesting that accretion disks and hot-dust structures for these
sources already have reached maturity. However, SDSS J0005-0006 has an unusual
SED that lies significantly below low-redshift SED templates at rest-frame 1
and 3.5 um, and thus shows a strong near-IR (NIR) deficit and no hot-dust
emission. Type I quasars with extremely small NIR-to-optical flux ratios like
SDSS J0005-0006 are not found in low-redshift quasar samples, indicating that
SDSS J0005-0006 has different dust properties at high redshift. We combine the
Spitzer observations with X-ray, UV/optical, mm/submm and radio observations to
determine bolometric luminosities for all the quasars. We find that the four
quasars with central black-hole mass measurements have Eddington ratios of
order unity.


title: Estimation of Polarized Power Spectra by Gibbs sampling

abstract:
  Earlier papers introduced a method of accurately estimating the angular
cosmic microwave background (CMB) temperature power spectrum based on Gibbs
sampling. Here we extend this framework to polarized data. All advantages of
the Gibbs sampler still apply, and exact analysis of mega-pixel polarized data
sets is thus feasible. These advantages may be even more important for
polarization measurements than for temperature measurements. While approximate
methods can alias power from the larger E-mode spectrum into the weaker B-mode
spectrum, the Gibbs sampler (or equivalently, exact likelihood evaluations)
allows for a statistically optimal separation of these modes in terms of power
spectra. To demonstrate the method, we analyze two simulated data sets: 1) a
hypothetical future CMBPol mission, with the focus on B-mode estimation; and 2)
a Planck-like mission, to highlight the computational feasibility of the
method.


title: Hall Magnetohydrodynamics of weakly-ionized plasma

abstract:
  We show that the Hall scale in a weakly ionized plasma depends on the
fractional ionization of the medium and, Hall MHD description becomes important
whenever the ion-neutral collision frequency is comparable to the ion-gyration
frequency, or, the ion-neutral collisional mean free path is smaller than the
ion gyro-radius. Wave properties of a weakly-ionized plasma also depends on the
fractional ionization and plasma Hall parameters, and whistler mode is the most
dominant mode in such a medium. Thus Hall MHD description will be important in
astrophysical disks, dark molecular clouds, neutron star crusts, and, solar and
planetary atmosphere.


title: Probing Dark Energy with Constellation-X

abstract:
  Constellation-X (Con-X) will carry out two powerful and independent sets of
tests of dark energy based on X-ray observations of galaxy clusters, providing
comparable accuracy to other leading dark energy probes. The first group of
tests will measure the absolute distances to clusters, primarily using
measurements of the X-ray gas mass fraction in the largest, dynamically relaxed
clusters, but with additional constraining power provided by follow-up
observations of the Sunyaev-Zel'dovich (SZ) effect. As with supernovae studies,
such data determine the transformation between redshift and true distance,
d(z), allowing cosmic acceleration to be measured directly. The second,
independent group of tests will use the exquisite spectroscopic capabilities of
Con-X to determine scaling relations between X-ray observables and mass.
Together with forthcoming X-ray and SZ cluster surveys, these data will help to
constrain the growth of structure, which is also a strong function of
cosmological parameters.


title:
On-sky results of the adaptive optics MACAO for the new IR-spectrograph
  CRIRES at VLT

abstract:
  The adaptive optics MACAO has been implemented in 6 focii of the VLT
observatory, in three different flavors. We present in this paper the results
obtained during the commissioning of the last of these units, MACAO-CRIRES.
CRIRES is a high-resolution spectrograph, which efficiency will be improved by
a factor two at least for point-sources observations with a NGS brighter than
R=15. During the commissioning, Strehl exceeding 60% have been observed with
fair seeing conditions, and a general description of the performance of this
curvature adaptive optics system is done.


title: MACAO-CRIRES, a step towards high-resolution spectroscopy

abstract:
  High resolution spectroscopy made an important step ahead 10 years ago,
leading for example to the discovery of numerous exoplanets. But the IR did not
benefit from this improvement until very recently. CRIRES will provide a
dramatic improvement in the 1-5 micron region in this field. Adaptive optics
will allow us increasing both flux and angular resolution on its spectra. This
paper describes the adaptive optics of CRIRES, its main limitations, its main
components, the principle of its calibration with an overview of the methods
used and the very first results obtained since it is installed in the
laboratory.


title: CGCG 480-022: A distant lonesome merger?

abstract:
  We present a complete analysis, which includes morphology, kinematics,
stellar populations and N-body simulations of CGCG 480-022, the most distant
(cz=14317 km/s) isolated galaxy studied so far in such detail. The results all
support the hypothesis that this galaxy has suffered a major merger event with
a companion of ~0.1 times its mass. Morphology reveals the presence of a
circumnuclear ring and possibly further ring debris. The radial velocity curve
looks symmetrical, whilst the velocity dispersion increases with radius
reaching values that do not correspond to a virialized system. Moreover, this
galaxy deviates significantly from the Fundamental Plane and the Faber-Jackson
relation. The stellar population analysis show that the ring is younger and
more metal-rich, which suggest that it has undergone a fairly recent burst of
star formation. Both morphological and dynamical results are in broad
agreeement with our N-body simulations.


title:
The globular cluster mass/low mass X-ray binary correlation:implications
  for kick velocity distributions from supernovae

abstract:
  Optical and X-ray studies of six nearby galaxies show that the probability a
globular cluster will be an X-ray source is consistent with being linearly
proportional to its mass. We show that this result is consistent with some
recent estimates of the velocity kick distributions for isolated radio pulsars
-- those which are the sum of two Maxwellians, with the slower distribution at
about 100 km/sec -- so long as a large fraction of the retained binaries are in
binary systems with other massive stars. We confirm that over a large sample of
galaxies, metallicity is clearly a factor in determining whether a globular
cluster will contain an X-ray binary, and we estimate the transformations
between color and metallicity for a large number of optical filter
combinations. We also show that the core interaction rate is roughly linearly
proportional to the stellar mass of a globular cluster for the Milky Way when
one bins the clusters by mass.


title:
Spectropolarimetry of PKS 0040-005 and the Orientation of Broad
  Absorption Line Quasars

abstract:
  We have used the Very Large Telescope (VLT) to obtain spectropolarimetry of
the radio-loud, double-lobed broad absorption line (BAL) quasar PKS 0040-005.
We find that the optical continuum of PKS 0040-005 is intrinsically polarized
at 0.7% with an electric vector position angle nearly parallel to that of the
large-scale radio axis. This result is naturally explained in terms of an
equatorial scattering region seen at a small inclination, building a strong
case that the BAL outflow is not equatorial. In conjunction with other recent
results concerning radio-loud BAL quasars, the era of simply characterizing
these sources as ``edge-on'' is over.


title:
Chemical differentiation in regions of high-mass star formation I. CS,
  dust and N2H^+ in southern sources

abstract:
  Aims. Our goals are to compare the CS, N2H+ and dust distributions in a
representative sample of high-mass star forming dense cores and to determine
the physical and chemical properties of these cores. Methods. We compare the
results of CS(5-4) and 1.2 mm continuum mapping of twelve dense cores from the
southern hemisphere presented in this work, in combination with our previous
N2H+(1-0) and CS(2-1) data. We use numerical modeling of molecular excitation
to estimate physical parameters of the cores. Results. Most of the maps have
several emission peaks (clumps). We derive basic physical parameters of the
clumps and estimate CS and N2H+ abundances. Masses calculated from LVG
densities are higher than CS virial masses and masses derived from continuum
data, implying small-scale clumpiness of the cores. For most of the objects,
the CS and continuum peaks are close to the IRAS point source positions. The
CS(5-4) intensities correlate with continuum fluxes per beam in all cases, but
only in five cases with the N2H+(1-0) intensities. The study of spatial
variations of molecular integrated intensity ratios to continuum fluxes reveals
that I(N2H+)/F{1.2} ratios drop towards the CS peaks for most of the sources,
which can be due to a N2H+ abundance decrease. For CS(5-4), the I(CS)/F{1.2}
ratios show no clear trends with distance from the CS peaks, while for CS(2-1)
such ratios drop towards these peaks. Possible explanations of these results
are considered. The analysis of normalized velocity differences between CS and
N2H+ lines has not revealed indications of systematic motions towards CS peaks.


title: Eclipsing Binary Stars in Open Clusters

abstract:
  The study of detached eclipsing binaries in open clusters can provide
stringent tests of theoretical stellar evolutionary models, which must
simultaneously fit the masses, radii, and luminosities of the eclipsing stars
and the radiative properties of every other star in the cluster. We review
recent progress in such studies and discuss two unusually interesting objects
currently under analysis. GV Carinae is an A0m + A8m binary in the Southern
open cluster NGC 3532; its eclipse depths have changed by 0.1 mag between 1990
and 2001, suggesting that its orbit is being perturbed by a relatively close
third body. DW Carinae is a high-mass unevolved B1V + B1V binary in the very
young open cluster Collinder 228, and displays double-peaked emission in the
centre of the Halpha line which is characteristic of Be stars. We conclude by
pointing out that the great promise of eclipsing binaries in open clusters can
only be satisfied when both the binaries and their parent clusters are
well-observed, a situation which is less common than we would like.


title:
Revised WMAP constraints on neutrino masses and other extensions of the
  minimal $\Lambda$CDM model

abstract:
  Recently, two issues concerning the three-year WMAP likelihood code were
pointed out. On large angular scales ($l \lesssim 30$), a sub-optimal
likelihood approximation resulted in a small power excess. On small angular
scales ($l \gtrsim 300$), over-subtraction of unresolved point sources produced
a small power deficit. For a minimal six-parameter cosmological model, these
two effects conspired to decrease the value of $n_s$ by $\sim 0.7 \sigma$. In
this paper, we study the change in preferred parameter ranges for more
extensive cosmological models, including running of $n_s$, massive neutrinos,
curvature, and the equation of state for dark energy. We also include
large-scale structure and supernova data in our analysis. We find that the
parameter ranges for $\alpha_s$, $\Omega_k$ and $w$ are not much altered by the
modified analysis. For massive neutrinos the upper limit on the sum of the
neutrino masses decreases from $M_\nu < 1.90$eV to $M_\nu < 1.57$eV when using
the modified WMAP code and WMAP data only. We also find that the shift of $n_s$
to higher values is quite robust to these extensions of the minimal
cosmological model.


title: Accurate stellar masses in the multiple system T Tau

abstract:
  The goal of this study is to obtain accurate estimates for the individual
masses of the components of the tight binary system T Tau S in order to settle
the ongoing debate on the nature of T Tau Sa, a so-called infrared companion.
We take advantage of the fact that T Tau S belongs to a triple system composed
of two hierarchical orbits to simultaneously analyze the motion of T Tau Sb in
the rest frames of T Tau Sa and T Tau N. With this method, it is possible to
pinpoint the location of the center of mass of T Tau S and, thereby, to
determine individual masses for T Tau Sa and T Tau Sb with no prior assumption
about the mass/flux ratio of the system. This improvement over previous studies
of the system results in much better constraints on orbital parameters. We find
individual masses of 2.73+/-0.31 Msun for T Tau Sa and of 0.61+/-0.17 Msun for
T Tau Sb (in agreement with its early-M spectral type), including the
uncertainty on the distance to the system. These are among the most precise
estimates of the mass of any Pre-Main Sequence star, a remarkable result since
this is the first system in which individual masses of T Tauri stars can be
determined from astrometry only. This model-independent analysis confirms that
T Tau Sa is an intermediate-mass star, presumably a very young Herbig Ae star,
that may possess an almost edge-on disk.


title:
Halo and Galaxy Formation Histories from the Millennium Simulation:
  Public release of a VO-oriented and SQL-queryable database for studying the
  evolution of galaxies in the LambdaCDM cosmogony

abstract:
  The Millennium Run is the largest simulation of the formation of structure
within the $\Lambda$CDM cosmogony so far carried out. It uses $10^{10}$
particles to follow the dark matter distribution in a cubic region
500$h^{-1}$Mpc on a side, and has a spatial resolution of 5 $h^{-1}$kpc.
Application of simplified modelling techniques to the stored output of this
calculation allows the formation and evolution of the $\sim 10^7$ galaxies more
luminous than the Small Magellanic Cloud to be simulated for a variety of
assumptions about the detailed physics involved. As part of the activities of
the German Astrophysical Virtual Observatory we have used a relational database
to store the detailed assembly histories both of all the haloes and subhaloes
resolved by the simulation, and of all the galaxies that form within these
structures for two independent models of the galaxy formation physics. We have
created web applications that allow users to query these databases remotely
using the standard Structured Query Language (SQL). This allows easy access to
all properties of the galaxies and halos, as well as to the spatial and
temporal relations between them and their environment. Information is output in
table format compatible with standard Virtual Observatory tools and protocols.
With this announcement we are making these structures fully accessible to all
users. Interested scientists can learn SQL, gain familiarity with the database
design and test queries on a small, openly accessible version of the Millennium
Run (with volume 1/512 that of the full simulation). They can then request
accounts to run similar queries on the databases for the full simulations.


title:
The formation of an eccentric gap in a gas disk by a planet in an
  eccentric orbit

abstract:
  We investigate the effect of a planet on an eccentric orbit on a two
dimensional low mass gaseous disk. At a planet eccentricity above the planet's
Hill radius divided by its semi-major axis, we find that the disk morphology
differs from that exhibited by a disk containing a planet in a circular orbit.
An eccentric gap is created with eccentricity that can exceed the planet's
eccentricity and precesses with respect to the planet's orbit. We find that a
more massive planet is required to open a gap when the planet is on an
eccentric orbit. We attribute this behavior to spiral density waves excited at
corotation resonances that increase the disk's eccentricity and exert a torque
opposite in sign to that exerted by the Lindblad resonances. The reduced torque
makes it more difficult for waves driven by the planet to overcome viscous
inflow in the disk. Spectral energy distributions of transitional disks may
reveal the presence of an eccentric planet if they are matched by an inner edge
comprising a range of temperatures set by the semi-major axis and eccentricity
of the hole.


title: Hybrid protoneutron stars with the MIT bag model

abstract:
  We study the hadron-quark phase transition in the interior of protoneutron
stars. For the hadronic sector, we use a microscopic equation of state
involving nucleons and hyperons derived within the finite-temperature
Brueckner-Bethe-Goldstone many-body theory, with realistic two-body and
three-body forces. For the description of quark matter, we employ the MIT bag
model both with a constant and a density-dependent bag parameter. We calculate
the structure of protostars with the equation of state comprising both phases
and find maximum masses below 1.6 solar masses. Metastable heavy hybrid
protostars are not found.


title:
Methods for improving open cluster fundamental parameters applied to M
  52 and NGC 3960

abstract:
  We derive accurate parameters related to the CMD, structure and dynamical
state of M52 and NGC3960, whose fields are affected by differential reddening.
Compared to open clusters in different dynamical states studied with similar
methods, the core and overall parameters of M52 are consistent with an open
cluster more massive than 1000Mo and ~60Myr old, with some mass segregation in
the inner region. The core of NGC3960 is in an advanced dynamical state with
strong mass segregation in the core/halo region, while the somewhat flat
overall MF (x~1.07) suggests low-mass star evaporation. The excess stellar
density in the core may suggest post-core collapse. The dynamical evolution of
NGC3960 may have been accelerated by the tidal Galactic field, since it lies
\~0.5kpc inside the Solar circle.


title: The bright spiky emission of pulsar B0656+14

abstract:
  We present a detailed study of the single radio pulses of PSR B0656+14, a
pulsar also known to be a strong pulsed source of high-energy emission. Despite
the extensive studies at high-energy wavelengths, there is little or no
published work on its single-pulse behaviour in the radio band. In this report
we rectify this omission. We have found that the shape of the pulse profile of
PSR B0656+14 requires an unusually long timescale to achieve stability (over
25,000 pulses at 327 MHz). This instability is caused by very bright and narrow
pulses with widths and luminosities comparable to those observed for the RRATs.
Many pulses are bright enough to qualify as "giant pulses", but are broader
than those usually meant by this term. At 327 MHz the brightest pulse was about
116 times brighter than the average pulse. Although the most powerful pulses
peak near the centre of the profile, occasional sudden strong pulses are also
found on the extreme leading edge of the profile. One of them has a peak flux
of about 2000 times the average flux at that pulse longitude. No "break" in the
pulse-energy distributions is observed, but nevertheless there is evidence of
two separate populations of pulses: bright pulses have a narrow "spiky"
appearance consisting of short quasi-periodic bursts of emission with
microstructure, in contrast to the underlying weaker broad pulses. Furthermore,
the spiky pulses tend to appear in clusters which arise and dissipate over
about 10 periods. We demonstrate that the spiky emission builds a narrow and
peaked profile, whereas the weak emission produces a broad hump, which is
largely responsible for the shoulders in the total emission profiles at both
high and low frequencies.


title:
A Comparison of Ultraluminous X-ray Sources in NGC 1399 and the Antennae
  Galaxies (NGC 4038/4039)

abstract:
  The temporal and spectral properties of ultraluminous X-ray sources (ULXs,
L>2x10^39 ergs/s) and bright X-ray sources (L>3x10^38 ergs/s) are examined and
compared in two extremely different host environments: the old elliptical
galaxy NGC 1399 and the young, starforming Antennae galaxies (NGC 4038/4039).
ULXs in NGC 1399 show little variability on either long or short time scales.
Only 1 of 8 ULXs and 10 of 63 bright sources in NGC 1399 are variable at a
confidence level of 90%. On long timescales, the NGC 1399 sources are steadier
than most Galactic black hole X-ray binaries, but similar to GRS 1915+105. The
outburst duration of the NGC 1399 sources is about 20 yrs, again, similar to
that of GRS 1915+105. The bright X-ray sources in NGC 1399 may be black hole
X-ray binaries with giant star companions similar to GRS 1915+105. The
brightest ULX (PSX-1) in NGC 1399 is coincident with a globular cluster, shows
a hard spectrum with a photon index around 1.5, and has a nearly constant
luminosity around 5x10^39 erg/s. It may be an intermediate-mass black hole
(IMBH) in a hard spectral state. In contrast to NGC 1399, the ULXs in the
Antennae are all variable and a large fraction of the bright sources (9 of 15)
are also variable. The variability and luminosity of ULXs in the Antennae
suggest they are black hole high mass X-ray binaries accreting via Roche-lobe
overflow. A flare with a duration of about 5 ks is found from Antennae X-42.
The most luminous ULX, X-16, with a very hard spectrum (Gamma=1.0~1.3) and a
luminosity which varies by a factor of 10, could be an IMBH candidate.


title: Studies of Neutron Stars at Optical/IR Wavelengths

abstract:
  In the last years, optical studies of Isolated Neutron Stars (INSs) have
expanded from the more classical rotation-powered ones to other categories,
like the Anomalous X-ray Pulsars (AXPs) and the Soft Gamma-ray Repeaters
(SGRs), which make up the class of the magnetars, the radio-quiet INSs with
X-ray thermal emission and, more recently, the enigmatic Compact Central
Objects (CCOs) in supernova remnants. Apart from 10 rotation-powered pulsars,
so far optical/IR counterparts have been found for 5 magnetars and for 4 INSs.
In this work we present some of the latest observational results obtained from
optical/IR observations of different types of INSs.


title:
The Structure of Jupiter, Saturn, and Exoplanets: Key Questions for
  High-Pressure Experiments

abstract:
  We give an overview of our current understanding of the structure of gas
giant planets, from Jupiter and Saturn to extrasolar giant planets. We focus on
addressing what high-pressure laboratory experiments on hydrogen and helium can
help to elucidate about the structure of these planets.


title: Galaxy Luminosities in 2PIGG groups

abstract:
  We derive composite luminosity functions (LF) for galaxies in groups and
examine the behaviour of the LF as a function of group luminosity (used as an
indicator of group or halo mass). We consider both the entire galaxy population
and split galaxies into red and blue (quiescent and star forming) samples, in
order to examine possible mechanisms behind observed variations of galaxy
properties with environment. We find evidence that $M^*$ brightens and $\alpha$
steepens with group luminosity, until a threshold value where the LF parameters
stabilize at those found in rich clusters. The effect is seen in the total LF
and for the blue and red galaxies separately. The behaviour of the quiescent
and star-forming samples is qualitatively consistent with variations resulting
from interactions and mergers, where mergers build the bright end of the
luminosity function at the same time as dwarf irregulars have their star
formation quenched and evolve into dwarf ellipticals. These processes appear to
take place preferentially in low luminosity groups and to be complete at a
group luminosity of -22.5 in $B$, corresponding to a halo mass of order
$10^{13.5} M_{\odot}$.


title: Collapsars in Three Dimensions

abstract:
  We present the results of 3-dimensional simulations of the direct collapse to
a black hole of a rotating, 60-solar-mass, zero metallicity, population III
star. Because the structure of this star (angular momentum, density and
temperature profiles) is similar to many collapsar gamma-ray burst progenitors,
these calculations have implications beyond the fate of population III stars.
These simulations provide a first 3-dimensional look at a realistic collapsar
progenitor, and the results are very different from any previous 2-dimensional
calculations. If the angular momentum of the progenitor is high,
non-axisymmetric instabilities in the collapsing core cause spiral structures
to form, and these structures shape later outflows. These outflows are driven
by the imbalance between viscous heating and inefficient neutrino cooling and
ultimately develop into a 1e52 erg explosion. Without magnetic fields, this
collapse will not produce relativistic jets, but the explosion is indeed a
hypernova. We conclude with a discussion of the implications of such
calculations on the explosions, nucleosynthesis, neutrino flux and
gravitational wave emission from the collapse of massive stars.


title: On the progenitor of SN 2005gl and the nature of Type IIn supernovae

abstract:
  We present a study of the type IIn supernova (SN) 2005gl, in the relatively
nearby (d~66 Mpc) galaxy NGC 266. Photometry and spectroscopy of the SN
indicate it is a typical member of its class. Pre-explosion Hubble Space
Telescope (HST) imaging of the location of the SN, along with a precise
localization of this event using the Laser-Guide-Star assisted Adaptive Optics
(LGS-AO) system at Keck Observatory, are combined to identify a luminous
(M_V=-10.3) point source as the possible progenitor of SN 2005gl. If the source
is indeed a single star, it was likely a member of the class of luminous blue
variable stars (LBVs). This finding leads us to consider the possible general
association of SNe IIn with LBV progenitors. We find this is indeed supported
by observations of other SNe, and the known properties of LBV stars. For
example, we argue that should the prototypical Galactic LBV eta Carina explode
in a phase similar to its current state, it will likely produce a type IIn SN.
We discuss our findings in the context of current ideas about the evolution of
massive stars, and review the census of SNe with identified progenitors. We
introduce the concept of the progenitor-SN map as a convenient means to discuss
the present status and future prospects of direct searches for SN progenitors.
We conclude that this field has matured considerably in recent years, and the
transition from anecdotal information about rare single events to robust
associations of progenitor classes with specific SN types has already begun.


title: Measuring M dwarf Winds with DAZ White Dwarfs

abstract:
  Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, show
evidence for ongoing accretion of material onto their surfaces. Some DAZs are
known to have unresolved M dwarf companions, which could account for the
observed accretion through a stellar wind. I combine observed Ca abundances of
the DAZs with information on the orbital separation of their M dwarf companions
to infer the mass loss rate of the M dwarfs. I find that for three of the six
known DAZs with M dwarf companions, a stellar wind can plausibly explain the
observed accretion on the white dwarfs assuming Bondi-Hoyle accretion of solar
abundance stellar winds on the order of 10$^{-14}-10^{-16}\Msun$ yr$^{-1}$. The
rest of the sample have companions with orbits $\gtorder$ 1~AU, and require
companion mass loss rates of $> 10^{-11}\Msun$ yr$^{-1}$. I conclude that there
must be an alternative explanation for accretion of material onto DAZs with
widely separated companions. The inferred winds for two of the close binaries
are orders of magnitude smaller than typically assumed for the angular momentum
loss of red dwarf-white dwarf pairs due to magnetic braking from a stellar wind
and may seriously affect predictions for the formation rate of CVs with low
mass companions.


title: Energy Conditions and Supernovae Observations

abstract:
  In general relativity, the energy conditions are invoked to restrict general
energy-momentum tensors on physical grounds. We show that in the standard
Friedmann-Lemaitre-Robertson-Walker approach to cosmological modelling where
the equation of state of the cosmological fluid is unknown, the energy
conditions provide model-independent bounds on the behavior of the distance
modulus of cosmic sources as a function of the redshift. We use both the gold
and the legacy samples of current type Ia supenovae to carry out a
model-independent analysis of the energy conditions violation in the context of
standard cosmology.


title:
Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift
  Universe

abstract:
  Observations of the high-redshift Universe with the 21 cm hyperfine line of
neutral hydrogen promise to open an entirely new window onto the early phases
of cosmic structure formation. Here we review the physics of the 21 cm
transition, focusing on processes relevant at high redshifts, and describe the
insights to be gained from such observations. These include measuring the
matter power spectrum at z~50, observing the formation of the cosmic web and
the first luminous sources, and mapping the reionization of the intergalactic
medium. The epoch of reionization is of particular interest, because large HII
regions will seed substantial fluctuations in the 21 cm background. We also
discuss the experimental challenges involved in detecting this signal, with an
emphasis on the Galactic and extragalactic foregrounds. These increase rapidly
toward low frequencies and are especially severe for the highest redshift
applications. Assuming that these difficulties can be overcome, the redshifted
21 cm line will offer unique insight into the high-redshift Universe,
complementing other probes but providing the only direct, three-dimensional
view of structure formation from z~200 to z~6.


title:
Nonthermal gamma-ray and X-ray flashes from shock breakout in gamma-ray
  bursts/supernovae

abstract:
  Thermal X-ray emission which is simultaneous with the prompt gamma-rays has
been detected for the first time from a supernova connected with a gamma-ray
burst (GRB), namely GRB060218/SN2006aj. It has been interpreted as arising from
the breakout of a mildly relativistic, radiation-dominated shock from a dense
stellar wind surrounding the progenitor star. There is also evidence for the
presence of a mildly relativistic ejecta in GRB980425/SN1998bw, based on its
X-ray and radio afterglow. Here we study the process of repeated bulk Compton
scatterings of shock breakout thermal photons by the mildly relativistic
ejecta. During the shock breakout process, a fraction of the thermal photons
would be repeatedly scattered between the pre-shock material and the shocked
material as well as the mildly relativistic ejecta and, as a result, the
thermal photons get boosted to increasingly higher energies. This bulk motion
Comptonization mechanism will produce nonthermal gamma-ray and X-ray flashes,
which could account for the prompt gamma-ray burst emission in low-luminosity
supernova-connected GRBs, such as GRB060218. A Monte Carlo code has been
developed to simulate this repeated scattering process, which confirms that a
significant fraction of the thermal photons get "accelerated" to form a
nonthermal component, with a dominant luminosity. This interpretation for the
prompt nonthermal emission of GRB060218 may imply that either the usual
internal shock emission from highly relativistic jets in these low-luminosity
GRBs is weak, or alternatively, that there are no highly relativistic jets in
this peculiar class of bursts.


title: The accelerating universe and a limiting curvature proposal

abstract:
  We consider the hypothesis of a limiting minimal curvature in gravity as a
way to construct a class of theories exhibiting late-time cosmic acceleration.
Guided by the minimal curvature conjecture (MCC) we are naturally lead to a set
of scalar tensor theories in which the scalar is non-minimally coupled both to
gravity and to the matter Lagrangian. The model is compared to the Lambda Cold
Dark Matter concordance model and to the observational data using the gold
SNeIa sample of Riess et. al. (2004). An excellent fit to the data is achieved.
We present a toy model designed to demonstrate that such a new, possibly
fundamental, principle may be responsible for the recent period of cosmological
acceleration. Observational constraints remain to be imposed on these models.


title: An Eccentric Hot Jupiter Orbiting the Subgiant HD 185269

abstract:
  We report the detection of a Jupiter-mass planet in a 6.838 day orbit around
the 1.28 solar mass subgiant HD 185269. The eccentricity of HD 185269b (e =
0.30) is unusually large compared to other planets within 0.1 AU of their
stars. Photometric observations demonstrate that the star is constant to
+/-0.0001 mag on the radial velocity period, strengthening our interpretation
of a planetary companion. This planet was detected as part of our radial
velocity survey of evolved stars located on the subgiant branch of the H-R
diagram--also known as the Hertzsprung Gap. These stars, which have masses
between 1.2 and 2.5 solar masses, play an important role in the investigation
of the frequency of extrasolar planets as a function of stellar mass.


title: First Constraints on Rings in the Pluto System

abstract:
  Simple theoretical calculations have suggested that small body impacts onto
Pluto's newly discovered small satellites, Nix and Hydra, are capable of
generating time-variable rings or dust sheets in the Pluto system. Using
HST/ACS data obtained on 2006 February 15 and 2006 March 2, we find no
observational evidence for such a ring system and present the first constraints
on the present-day I/F and optical depth of a putative ring system. At the
1500-km radial resolution of our search, we place a 3-sigma upper limit on the
azimuthally-averaged normal I/F of ring particles of 5.1x10^-7 at a distance of
42,000 km from the Pluto-Charon barycenter, the minimum distance for a
dynamically stable ring (Stern et al., 1994; Nagy et al., 2006); 4.4x10^-7 at
the orbit of Nix; and 2.5x10^-7 at the orbit of Hydra. For an assumed ring
particle albedo of 0.04 (0.38), these I/F limits translate into 3-sigma upper
limits on the normal optical depth of macroscopic ring particles of 1.3x10^-5
(1.4x10^-6), 1.1x10^-5 (1.2x10^-6), 6.4x10^-6 (6.7x10^-7), respectively. Were
the New Horizons spacecraft to fly through a ring system with optical depth of
1.3x10^-5, it would collide with a significant number of potentially damaging
ring particles. We therefore recommend that unless tighter constraints can be
obtained, New Horizons cross the putative ring plane within 42,000 km of the
Pluto-Charon barycenter, where rings are dynamically unstable. We derive a
crude estimate of the lifetime of putative ring paritcles of 900 years.


title: X-Ray Scattering by Nonspherical Grains. I. Oblate Spheroids

abstract:
  We calculate the scattering of X-rays by interstellar dust, for a dust model
that reproduces the observed wavelength-dependent extinction and polarization
of starlight. On interstellar sightlines that produce appreciable starlight
polarization, we predict that the dust-scattered X-ray halo around point
sources will have measurable azimuthal asymmetry due to scattering by
partially-aligned nonspherical grains. We calculate the expected halo
asymmetry. X-ray halo asymmetry provides a new test of interstellar dust
models.


title:
A Survey and Analysis of Spitzer Infrared Spectrograph Spectra of T
  Tauri Stars in Taurus

abstract:
  We present mid-infrared spectra of T Tauri stars in the Taurus star-forming
region obtained with the Spitzer Infrared Spectrograph (IRS). For the first
time, the 5-36 micron spectra of a large sample of T Tauri stars belonging to
the same star-forming region is studied, revealing details of the mid-infrared
excess due to dust in circumstellar disks. We analyze common features and
differences in the mid-IR spectra based on disk structure, dust grain
properties, and the presence of companions. Our analysis encompasses spectral
energy distributions from the optical to the far-infrared, a morphological
sequence based on the IRS spectra, and spectral indices in IRS wave bands
representative of continuum emission. By comparing the observed spectra to a
grid of accretion disk models, we infer some basic disk properties for our
sample of T Tauri stars, and find additional evidence for dust settling.


title:
Characterizing Bars at z~0 in the optical and NIR: Implications for the
  Evolution of Barred Disks with Redshift

abstract:
  Critical insights on galaxy evolution stem from the study of bars. With the
advent of HST surveys that trace bars in the rest-frame optical out to z~1, it
is critical to provide a reference baseline for bars at z~0 in the optical
band. We present results on bars at z~0 in the optical and NIR bands based on
180 spirals from OSUBSGS. (1) The deprojected bar fraction at z~0 is ~60% +/-6%
in the NIR H-band and ~44% +/-6% in the optical B-band. (2) The results before
and after deprojection are similar, which is encouraging for high-redshift
studies that forego deprojection. (3) Studies of bars at z~0.2-1.0 (lookback
time of 3-8 Gyr) have reported an optical bar fraction of ~30% +/-6%, after
applying cutoffs in absolute magnitude (M_V < -19.3), bar size (a_bar >= 1.5
kpc), and bar ellipticity (e_bar >= 0.4). Applying these exact cutoffs to the
OSUBSGS data yields a comparable optical B-band bar fraction at z~0 of ~
34%+/-6%. This rules out scenarios where the optical bar fraction in bright
disks declines strongly with redshift. (4) Most (~70%) bars have moderate to
high strentgh or ellipticity (0.50 <= e_bar <= 0.75). There is no bimodality in
the distribution of e_bar. The H-band bar fraction and e_bar show no
substantial variation across RC3 Hubble types Sa to Scd. (5) RC3 bar types
should be used with caution. Many galaxies with RC3 types "AB" turn out to be
unbarred and RC3 bar classes "B" and "AB" have a significant overlap in e_bar.
(6) Most bars have sizes below 5 kpc. Bar and disk sizes correlate, and most
bars have a_bar/R_25~0.1-0.5. This suggests that the growths of bars and disks
are intimately tied.


title:
Searching for Low Surface-brightness Galaxies in the Hubble Ultra Deep
  Field: Implications for the Star Formation Efficiency in Neutral Gas at z ~ 3

abstract:
  (Abridged) The Kennicutt--Schmidt law relates the face-on star formation rate
(SFR) per unit area with the face-on gaseous column density in nearby galaxies.
Applying this relation to damped Lya absorption systems (DLAs) of neutral
hydrogen column density N > 1.6x10^21 cm^-2 leads to an estimate that three
percent of the sky should be covered with extended sources brighter than
mu_V~28.4 mag arcsec^-2, if DLAs at redshift z=[2.5,3.5] undergo in situ star
formation. We test this hypothesis by searching the Hubble Ultra Deep Field
(UDF) F606W image for low surface-brightness features of angular sizes, ranging
between theta_dla=0.25" and 4.0". Our search yields upper limits on the
comoving SFR densities that are between factors of 30 and 100 lower than
predictions, suggesting a reduction by more than a factor of 10 in star
formation efficiency at z~3. We consider several mechanisms that could reduce
star formation efficiency at high redshift. We find that the cosmological
increase with redshift of the critical surface density for the Toomre
instability may be sufficient to suppress star formation to the levels implied
by the UDF observations. However, the uncertainties are such that Toomre
instabilities may still exist. In that case star formation at column densities
less than 10^22 cm^-2 may be suppressed by the low molecular content of the DLA
gas. The upper limits on in situ star formation reduce the predicted
metallicities at z~3 to be significantly lower than observed, and reduce the
heat input in the gas to be substantially lower than the inferred cooling
rates. In contrast, the radiative output from compact Lyman Break Galaxies
(LBGs) with R<27 is sufficient to balance the comoving cooling rate.


title:
Understanding the saturation of proton-driven Weibel instabilities and
  implications for astrophysics

abstract:
  The linear growth rate and saturation level of magnetic fields for Weibel
instabilities driven by ion temperature anisotropy, defined as
$\alpha=(T_\perp/T_\parallel)-1$ where $T_\perp$ and $T_\parallel$ are ion
temperatures perpendicular and parallel to the wave vector, are derived in the
small $\alpha$-limit. It is shown that the ratio of the saturated magnetic
energy to the initial ion energy scales as the fourth power of the electron to
ion mass ratio, $m/M$, for an initially unmagnetized plasma with $\alpha\leq
M/m$. Particle-in-cell simulations confirm the mass scaling and also show that
the electron energy gain is of the same order of magnitude as the magnetic
field energy. This implies that the Weibel instabilities cannot provide a
faster-than-Coulomb collisionless mechanism to equilibrate ion-electron plasmas
with ions initially much hotter than electrons, a key component in
low-luminosity astrophysical accretion flows. The results here also show that
the large $\alpha$-limit formulae used in the study of magnetic field
generation in collisionless shocks are only valid if $\alpha\geq M/m$.


title: TeV Astrophysics, A Review

abstract:
  In this paper I briefly review recent progress in the field of ground-based
gamma ray astrophysics.


title: New Self-Similar Solutions of Polytropic Gas Dynamics

abstract:
  We explore semi-complete self-similar solutions for the polytropic gas
dynamics involving self-gravity under spherical symmetry, examine behaviours of
the sonic critical curve, and present new asymptotic collapse solutions that
describe `quasi-static' asymptotic behaviours at small radii and large times.
These new `quasi-static' solutions with divergent mass density approaching the
core can have self-similar oscillations. Earlier known solutions are
summarized. Various semi-complete self-similar solutions involving such novel
asymptotic solutions are constructed, either with or without a shock. In
contexts of stellar core collapse and supernova explosion, a hydrodynamic model
of a rebound shock initiated around the stellar degenerate core of a massive
progenitor star is presented. With this dynamic model framework, we attempt to
relate progenitor stars and the corresponding remnant compact stars: neutron
stars, black holes, and white dwarfs.


title:
Visible spectroscopy of 2003 UB313: Evidence for N2 ice on the surface
  of the largest TNO?

abstract:
  The recent discovery of two large trans-Neptunian objects (TNOs) 2003 UB313
and 2005 FY9, with surface properties similar to those of Pluto, provides an
exciting new laboratory for the study of processes considered for Pluto and
Triton: volatile mixing and transport; atmospheric freeze-out and escape, ice
chemistry, and nitrogen phase transitions. We studied the surface composition
of TNO 2003 UB313, the first known TNO larger than Pluto. We report a visible
spectrum covering the 0.35-0.95 microns spectral range, obtained with the 4.2m
William Herschel Telescope at "El Roque de los Muchachos" Observatory (La
Palma, Spain). The visible spectrum of this TNO presents very prominent
absorpt- ions bands formed in solid CH4. At wavelengths shorter than 0.6 micron
the spectrum is almost featureless and slightly red (S'=4%). The icy-CH4 bands
are significantly stronger than those of Pluto and slightly weaker than those
observed in the spectrum of another giant TNO, 2005 FY9, implying that methane
is more abundant on its surface than in Pluto's and close to that of the
surface of 2005 FY9. A shift of 15 +/-3 A relative to the position of the bands
of the spectrum of laboratory CH4 ice is observed in the bands at larger
wavelengths (e.g. around 0.89 microns), but not at shorter wavelengths (the
band around 0.73 microns is not shifted) this may be evidence for a vertical
compositional gradient. Purer methane could have condensed first while 2003
UB313 moved towards aphelion during the last 200 years, and as the atmosphere
gradually collapsed, the composition became more nitrogen-rich as the last,
most volatile components condensed, and CH4 diluted in N2 is present in the
outer surface layers.


title: Enhancement and suppression of heat transfer by MHD turbulence

abstract:
  We study of the effect of turbulence on heat transfer within magnetized
plasmas for energy injection velocities both larger and smaller that the Alfven
speed. We find that in the latter regime the heat transfer is partially
suppressed, while in the former regime the effects of turbulence depend on the
intensity of driving. In fact, the scale l at which the turbulent velocity is
equal the Alfven velocity is a new important parameter. When the electron mean
free path is larger than l, the stronger the the turbulence, the lower thermal
conductivity by electrons is. The turbulent motions, however, induces their own
advective heat transport, which, for the parameters of intracluster medium
(ICM) provides effective heat diffusivity that exceeds the classical Spitzer
value.


title: SINS of Viscosity Damped Turbulence

abstract:
  The problems with explaining the Small Ionized and Neutral Structures (SINS)
appealing to turbulence stem from inefficiency of the Kolmogorov cascade in
creating large fluctuations at sufficiently small scales. However, other types
of cascades are possible. When magnetic turbulence in a fluid with viscosity
that is much larger than resistivity gets to a viscous damping scale, the
turbulence does not vanish. Instead, it gets into a different new regime.
Viscosity-damped turbulence produces fluctuations on the small scales. Magnetic
fields sheared by turbulent motions by eddies not damped by turbulence create
small scale filaments that are confined by the external plasma pressure. This
creates small scale density fluctuations. In addition, extended current sheets
create even stronger density gradients that accompany field reversals in the
plane perpendicular to mean magnetic field. Those can be responsible for the
SINS formation. This scenario is applicable to partially ionized gas. More
studies of reconnection in the viscosity dominated regime are necessary to
understand better the extend to which the magnetic reversals can compress the
gas.


title:
Theoretical approaches to particle propagation and acceleration in
  turbulent intergalactic medium

abstract:
  Intercluster medium is expected to be turbulent with turbulence being
superAlfvenic at large scales. Magnetic fields substantially modify the
turbulent cascade when the turbulence reaches the scales at which the
fluctuation velocity gets less than the Alfven velocity. At those scales it is
possible to consider three cascades, of fast, slow and Alfven modes with little
energy exchange between them. As Alfvenic and slow modes are anisotropic they
marginally scatter and accelerate cosmic rays, while fast modes dominate the
processes. However, in the presence of cosmic rays the turbulence is modified
as cosmic rays transfer the energy of compressible motions (i.e. slow and fast
modes) from large scales to the scale of cosmic ray Larmor radius. This results
in generation of a new small-scale Alfvenic component which is not a part of
the ordinary MHD cascade. This component does scatter and accelerate cosmic
rays. In addition, magnetic reconnection in turbulent medium accelerates cosmic
rays. The complexity of the intracluster turbulence calls for observational
studies. A new technique Velocity Coordinate Spectrum (VCS) is particularly
promising for studies of velocity fluctuations with a new generation of X-ray
observatories.


title:
Intermittency of Magnetohydrodynamic Turbulence: Astrophysical
  Perspective

abstract:
  Intermittency is an essential property of astrophysical fluids, which
demonstrate an extended inertial range. As intermittency violates
self-similarity of motions, it gets impossible to naively extrapolate the
properties of fluid obtained computationally with relatively low resolution to
the actual astrophysical situations. In terms of Astrophysics, intermittency
affects turbulent heating, momentum transfer, interaction with cosmic rays,
radio waves and many more essential processes. Because of its significance,
studies of intermittency call for coordinated efforts from both theorists and
observers. In terms of theoretical understanding we are still just scratching a
surface of a very rich subject. We have some theoretically well justified
models that are poorly supported by experiments, we also have She-Leveque
model, which could be vulnerable on theoretical grounds, but, nevertheless, is
well supported by experimental and laboratory data. I briefly discuss a rather
mysterious property of turbulence called ``extended self-similarity'' and the
possibilities that it opens for the intermittency research. Then I analyze
simulations of MHD intermittency performed by different groups and show that
their results do not contradict to each other. Finally, I discuss the
intermittency of density, intermittency of turbulence in the
viscosity-dominated regime as well as the intermittency of polarization of
Alfvenic modes. The latter provides an attractive solution to account for a
slower cascading rate that is observed in some of the numerical experiments. I
conclude by claiming that a substantial progress in the field may be achieved
by studies of the turbulence intermittency via observations.


title: Grain Alignment, Polarization and Magnetic Fields

abstract:
  Aligned non-spherical dust particles polarize starlight passing through the
dust cloud. They also emit polarized far infrared and sub-mm radiation.
Substantial progress in understanding of grain alignment theory makes the
interpretation of the polarized radiation in terms of underlying magnetic
fields much more reliable. I discuss a number of fundamental processes that
affect grain alignment. In particular, I shall discuss how subtle effects
related to nuclear spins of the atoms alter the dynamics of dust grains. I
shall discuss how the theory explains the existing observational data and
demonstrate when the polarization can and cannot be interpreted in terms of the
underlying magnetic fields.


title: Coherent Development of Neutrino Flavor in the Supernova Environment

abstract:
  We calculate coherent neutrino and antineutrino flavor transformation in the
supernova environment, for the first time including a self-consistent treatment
of forward scattering-induced coupling and entanglement of intersecting
neutrino/antineutrino trajectories. For the atmospheric neutrino mass-squared
difference we find that in the normal (inverted) mass hierarchy the more
tangentially-propagating (radially-propagating) neutrinos and antineutrinos can
initiate collective, simultaneous medium-enhanced flavor conversion of these
particles across broad ranges of energy and propagation direction. Accompanying
alterations in neutrino/antineutrino energy spectra and/or fluxes could affect
supernova nucleosynthesis and the expected neutrino signal.


title:
Density Fluctuations in MHD Turbulence: Spectra, Intermittency and
  Topology

abstract:
  We perform three-dimensional (3D) compressible MHD simulations over many
dynamical times for an extended range of sonic and Alfven Mach numbers and
analyze the statistics of 3D density and 2D column density, which include
probability distribution functions, spectra, skewness, kurtosis, She-Leveque
exponents, and genus. In order to establish the relation between the statistics
of the observables, i.e. column densities, and the underlying 3D statistics of
density, we analyze the effects of cloud boundaries. We define the parameter
space for 3D measures to be recovered from column densities. In addition, we
show that for subsonic turbulence the spectra of density fluctuations are
consistent with k^-7/3 in the case of a strong magnetic field and k^-5/3 in the
case of a weak magnetic field. For supersonic turbulence we confirm the earlier
findings of the shallow spectra of density and Kolmogorov spectra of the
logarithm of density. We find that the intermittencies of the density and
velocity are very different.


title:
A pulsational distance to Omega Centauri based on Near-Infrared
  Period-Luminosity relations of RR Lyrae stars

abstract:
  We present new Near-Infrared (J,K) magnitudes for 114 RR Lyrae stars in the
globular cluster Omega Cen (NGC 5139) which we combine with data from the
literature to construct a sample of 180 RR Lyrae stars with J and K mean
magnitudes on a common photometric system. This is presently the largest such
sample in any stellar system. We also present updated predictions for J,K-band
Period-Luminosity relations for both fundamental and first-overtone RR Lyrae
stars, based on synthetic horizontal branch models with metal abundance ranging
from Z=0.0001 to Z=0.004. By adopting for the Omega Cen variables with measured
metal abundances an alpha-element enhancement of a factor of 3 (about 0.5 dex)
with respect to iron we find a true distance modulus of 13.70 (with a random
error of 0.06 and a systematic error of 0.06), corresponding to a distance
d=5.5 Kpc (with both random and systematic errors equal to 0.03 Kpc). Our
estimate is in excellent agreement with the distance inferred for the eclipsing
binary OGLEGC-17, but differ significantly from the recent distance estimates
based on cluster dynamics and on high amplitude Delta Scuti stars.


title:
Sensitivity of an underwater Cerenkov km3 telescope to TeV neutrinos
  from Galactic Microquasars

abstract:
  In this paper are presented the results of Monte Carlo simulations on the
capability of the proposed NEMO-km$^3$ telescope to detect TeV muon neutrinos
from Galactic microquasars. For each known microquasar we compute the number of
detectable events, together with the atmospheric neutrino and muon background
events. We also discuss the detector sensitivity to neutrino fluxes expected
from known microquasars, optimizing the event selection also to reject the
background; the number of events surviving the event selection are given. The
best candidates are the steady microquasars SS433 and GX339-4 for which we
estimate a sensitivity of about $5\cdot10^{-11}$ erg/cm$^2$ s; the predicted
fluxes are expected to be well above this sensitivity. For bursting
microquasars the most interesting candidates are Cygnus X-3, GRO J1655-40 and
XTE J1118+480: their analyses are more complicated because of the stochastic
nature of the bursts.


title: Survival of a brown dwarf after engulfment by a red giant star

abstract:
  (Summary of paper) High resolution optical spectroscopy of the white dwarf
WD0137-349 reveals a weak Halpha line in emission, due to a low mass companion
in a close orbit. Using this emission feature, and the narrow NLTE core of the
white dwarf's Halpha absorption line, we measure the orbital period at 116
minutes, the separation at 0.65Rsun, and the mass ratio m2/m1 = K1/K2 =
0.134+/-0.006. From the mass of the white dwarf (0.39+/-0.035Msun) we derive a
mass for the companion of 0.053+/-0.006Msun. This is well below the limit of
about 0.075Msun commonly used to distinguish stars from brown dwarfs. The
observed infrared flux distribution of WD0137-349 is also consistent with a
model of an old brown dwarf spectral type mid T or slightly earlier. The system
is detached, and the brown dwarf must have survived a previous phase of common
envelope evolution, providing a key observational test for models of this
interaction.


title: Pulsar Braking Indices, Glitches and Energy Dissipation In Neutron Stars

abstract:
  Almost all pulsars with anomalous positive $\ddot \Omega $ measurements
(corresponding to anomalous braking indices in the range 5$<n<$100), including
all the pulsars with observed large glitches ($\Delta\Omega/\Omega$ $>$
10$^{-7}$) as well as post glitch or interglitch $\ddot \Omega$ measurements
obey the scaling between $\ddot \Omega$ and glitch parameters originally noted
in the Vela pulsar. Negative second derivative values can be understood in
terms of glitches that were missed or remained unresolved. We discuss the
glitch rates and a priori probabilities of positive and negative braking
indices according to the model developed for the Vela pulsar. This behavior
supports the universal occurrence of a nonlinear dynamical coupling between the
neutron star crust and an interior superfluid component. The implied lower
limit to dynamical energy dissipation in a neutron star with spindown rate
$\dot \Omega$ is $\dot E_{diss}> 1.7 \times 10 ^{-6} \dot E_{rot}$. Thermal
luminosities and surface temperatures due to dynamical energy dissipation are
estimated for old neutron stars which are spinning down as rotating magnetic
dipoles beyond the pulsar death line.


title:
An optical search for Low Surface Brightness Galaxies in the Arecibo HI
  Strip Survey

abstract:
  In order to estimate the contribution of low surface brightness (LSB)
galaxies to the local (z<0.1) galaxy number density, we performed an optical
search for LSB candidates in a 15.5 deg^2 part of the region covered by the 65
deg^2 blind Arecibo HI Strip Survey (AHISS). Object detection and galaxy
profile fitting were done with analytical algorithms. The detection efficiency
and the selection effects were evaluated using large samples of artificial
galaxies. Our final catalogue is diameter-limited and contains 306 galaxies
with diameters >18" at the limiting surface brightness of mu_{B,lim}=25.2+-0.31
mag/arcsec^2. Of these 306 galaxies, 148 were not catalogued previously. Our
results indicate that low surface brightness galaxies contribute at least to 30
% to the local galaxy number density. Without additional distance information,
choosing the limiting diameter and the surface brightness at which the diameter
is measured is crucial. Depending on these choices, diameter-limited optical
catalogues are either biased against LSB galaxies, or contaminated with
cosmologically dimmed high surface brightness galaxies, which affects the
implied surface brightness distribution. The comparison to the AHISS showed
that although optical surveys detect more galaxies per deg^2 than HI surveys,
their drawback is the need for spectroscopic follow up observations to derive
distances. Blind HI surveys have no diameter limits, but tend to miss gas-poor
galaxies and all galaxies which lie outside their redshift limits. HI and
optical surveys thus provide complementary information and sample different
parts of the LSB galaxy population.


title: The Infrared Emission from the Narrow Line Region

abstract:
  We present models for the mid- and far- infrared emission from the Narrow
Line Region (NLR) of Active Galactic Nuclei (AGN). Using the MAPPINGS III code
we explore the effect of typical NLR parameters on the spectral characteristics
of the IR emission. These include useful IR emission line ratio diagnostic
diagrams for the determination of these parameters, as well as Star
formation--AGN mixing diagnostics. We also examine emission line to continuum
correlations which would assist in separating the IR emission arising from the
NLR from that coming from the inner torus. We find for AGN like NGC 1068 and
NGC 4151 that the NLR only contributes ~10% to the total IRAS 25 mum flux, and
that other components such as a dusty torus are necessary to explain the total
AGN IR emission.


title:
Particle Accelerator in Pulsar Magnetospheres: Super Goldreich-Julian
  Current with Ion Emission from the Neutron Star Surface

abstract:
  We investigate the self-consistent electrodynamic structure of a particle
accelerator in the Crab pulsar magnetosphere on the two-dimensional poloidal
plane, solving the Poisson equation for the electrostatic potential together
with the Boltzmann equations for electrons, positrons and gamma-rays. If the
trans-field thickness of the gap is thin, the created current density becomes
sub-Goldreich-Julian, giving the traditional outer-gap solution but with
negligible gamma-ray luminosity. As the thickness increases, the created
current increases to become super-Goldreich-Julian, giving a new gap solution
with substantially screened acceleration electric field in the inner part. In
this case, the gap extends towards the neutron star with a small-amplitude
positive acceleration field, extracting ions from the stellar surface as a
space-charge-limited flow. The acceleration field is highly unscreened in the
outer magnetosphere, resulting in a gamma-ray spectral shape which is
consistent with the observations.


title:
Chaotic zone boundary for low free eccentricity particles near an
  eccentric planet

abstract:
  We consider particles with low free or proper eccentricity that are orbiting
near planets on eccentric orbits. Via collisionless particle integration we
numerically find the location of the boundary of the chaotic zone in the
planet's corotation region. We find that the distance in semi-major axis
between the planet and boundary depends on the planet mass to the 2/7 power and
is independent of the planet eccentricity, at least for planet eccentricities
below 0.3. Our integrations reveal a similarity between the dynamics of
particles at zero eccentricity near a planet in a circular orbit and with zero
free eccentricity particles near an eccentric planet. The 2/7 law has been
previously explained by estimating the semi-major at which the first order mean
motion resonances are large enough to overlap. Orbital dynamics near an
eccentric planet could differ due to first order corotation resonances that
have strength proportional to the planet's eccentricity. However, we find the
corotation resonance width at low free eccentricity is small. Also the first
order resonance width at zero free eccentricity is the same as that for a zero
eccentricity particle near a planet in a circular orbit. This accounts for
insensitivity of the chaotic zone width to planet eccentricity. Particles at
zero free eccentricity near an eccentric planet have similar dynamics to those
at zero eccentricity near a planet in a circular orbit.


title: Infrared Properties of Close Pairs of Galaxies

abstract:
  We discuss spectroscopy and infrared photometry for a complete sample of ~
800 galaxies in close pairs objectively selected from the CfA2 redshift survey.
We use 2MASS to compare near infrared color-color diagrams for our sample with
the Nearby Field Galaxy Sample and with a set of IRAS flux-limited pairs from
Surace et al. We construct a basic statistical model to explore the physical
sources of the substantial differences among these samples. The model explains
the spread of near infrared colors and is consistent with a picture where
central star formation is triggered by the galaxy-galaxy interaction before a
merger occurs. For 160 galaxies we report new, deep JHK photometry within our
spectroscopic aperture and we use the combined spectroscopic and photometric
data to explore the physical conditions in the central bursts. We find a set of
objects with H-K >= 0.45 and with a large F(FIR)/F(H). We interpret the very
red H-K colors as evidence for 600-1000 K dust within compact star-forming
regions, perhaps similar to super-star clusters identified in individual
well-studied interacting galaxies. The galaxies in our sample are candidate
``hidden'' bursts or, possibly, ``hidden'' AGN. Over the entire pair sample,
both spectroscopic and photometric data show that the specific star formation
rate decreases with the projected separation of the pair. The data suggest that
the near infrared color-color diagram is also a function of the projected
separation; all of the objects with central near infrared colors indicative of
bursts of star formation lie at small projected separation.


title: X-ray Properties of Intermediate-mass Black Holes in Active Galaxies

abstract:
  We present a pilot study of the X-ray properties of intermediate-mass
(~10^5-10^6 M_sun) black holes in active galaxies using the Chandra X-ray
telescope. Eight of the 10 active galaxies are detected with a significance of
at least 3 sigma, with X-ray luminosities in the range L_(0.5-2 keV) ~
10^41-10^43 ergs/s. The optical-to-X-ray flux ratios are consistent with
expectations, given the known correlations between alpha_ox and ultraviolet
luminosity, while a couple of objects appear to be anomalously X-ray weak. The
range of 0.5--2 keV photon indices we measure, 1 < Gamma_s < 2.7, is entirely
consistent with values found in samples of more luminous sources with more
massive black holes. Black hole mass evidently is not a primary driver of soft
X-ray spectral index. On the other hand, we do find evidence for a correlation
between X-ray power-law slope and both X-ray luminosity and Eddington ratio,
which may suggest that X-ray emission mechanisms weaken at high Eddington
ratio. Such a weakening may explain the X-ray weakness of one of our most
optically luminous objects.


title:
Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies:
  III. Emission Line Diagnostics of Ensembles of Evolving HII Regions

abstract:
  We build, as far as theory will permit, self consistent model HII regions
around central clusters of aging stars. These produce strong emission line
diagnostics applicable to either individual HII regions in galaxies, or to the
integrated emission line spectra of disk or starburst galaxies. The models
assume that the expansion and internal pressure of individual HII regions is
driven by the net input of mechanical energy from the central cluster, be it
through winds or supernova events. This eliminates the ionization parameter as
a free variable, replacing it with a parameter which depends on the ratio of
the cluster mass to the pressure in the surrounding interstellar medium. These
models explain why HII regions with low abundances have high excitation, and
demonstrate that at least part of the warm ionized medium is the result of
overlapping faint, old, large, and low pressure HII regions. We present line
ratios (at both optical and IR wavelengths) which provide reliable abundance
diagnostics for both single HII regions or for integrated galaxy spectra, and
we find a number that can be used to estimate the mean age of the cluster stars
exciting individual HII regions.


title: Shock-cloud interaction in the Vela SNR II. Hydrodynamic model

abstract:
  In the framework of the study of the X-ray and optical emission in supernova
remnants we focus on an isolated X-ray knot in the northern rim of the Vela SNR
(Vela FilD), whose X-ray emission has been studied and discussed in Paper I. We
aim at understanding the physical origin of the X-ray and optical emission in
FilD, at understanding the role of the different physical processes at work,
and at obtaining a key for the interpretation of future X-ray observations of
SNRs. To this end we have pursued an accurate ``forward'' modeling of the
interaction of the Vela SNR shock with an ISM cloud. We perform hydrodynamic
simulations and we directly compare the observables synthesized from the
simulations with the data. We explore four different model setups, choosing the
values of the physical parameters on the basis of our preliminary analysis of
the X-ray data. We synthesize X-ray emission maps and spectra filtered through
the XMM-Newton EPIC-MOS instrumental response. The impact of a shock front at 6
million Kelvin on an elliptical cloud 30 times denser than the ambient medium
describes well the shock-cloud interaction processes in the Vela FilD region in
terms of spectral properties and morphology of the X-ray and optical emission.
The bulk of the X-ray emission in the FilD knot originates in the cloud
material heated by the transmitted shock front, but significant X-ray emission
is also associated to the cloud material, which evaporates, as an effect of
thermal conduction, in the intercloud medium. The physical origin of the FilD
optical emission is associated to thermal instabilities. In the FilD knot the
X-ray emission associated to the reflected shock front is negligible.


title:
Why your model parameter confidences might be too optimistic -- unbiased
  estimation of the inverse covariance matrix

abstract:
  AIMS. The maximum-likelihood method is the standard approach to obtain model
fits to observational data and the corresponding confidence regions. We
investigate possible sources of bias in the log-likelihood function and its
subsequent analysis, focusing on estimators of the inverse covariance matrix.
Furthermore, we study under which circumstances the estimated covariance matrix
is invertible. METHODS. We perform Monte-Carlo simulations to investigate the
behaviour of estimators for the inverse covariance matrix, depending on the
number of independent data sets and the number of variables of the data
vectors. RESULTS. We find that the inverse of the maximum-likelihood estimator
of the covariance is biased, the amount of bias depending on the ratio of the
number of bins (data vector variables), P, to the number of data sets, N. This
bias inevitably leads to an -- in extreme cases catastrophic -- underestimation
of the size of confidence regions. We report on a method to remove this bias
for the idealised case of Gaussian noise and statistically independent data
vectors. Moreover, we demonstrate that marginalisation over parameters
introduces a bias into the marginalised log-likelihood function. Measures of
the sizes of confidence regions suffer from the same problem. Furthermore, we
give an analytic proof for the fact that the estimated covariance matrix is
singular if P>N.


title: Model Atmosphere Analysis of the Weakly Magnetic DZ White Dwarf G165-7

abstract:
  A reanalysis of the strongly metal-blanketed DZ white dwarf G165-7 is
presented. An improved grid of model atmospheres and synthetic spectra is used
to analyze BVRI, JHK, and ugriz photometric observations as well as a high
quality Sloan Digital Sky Survey spectrum covering the energy distribution from
3600 to 9000 A. The detection of splitting in several lines of Ca, Na, and Fe,
suggesting a magnetic field of Bs~650 kG, is confirmed by spectropolarimetric
observations that reveal as much as +/- 7.5% circular polarization in many of
the absorption lines, most notably Na, Mg, and Fe. Our combined photometric and
spectroscopic fit yields Teff = 6440 K, log g=7.99, log H/He=-3.0 and log
Ca/He=-8.1. The other heavy elements have solar ratios with respect to calcium,
with the exception of Na and Cr that had to be reduced by a factor of two and
three, respectively. A crude polarization model based upon the observed local
spectral flux gradient yields a longitudinal field of 165 kG, consistent with
the mean surface field inferred from the Zeeman splitting. The inclusion of
this weak magnetic field in our synthetic spectrum calculations, even in an
approximate fashion, is shown to improve our fit significantly.


title:
Spectral State Transitions of the Ultraluminous X-ray Sources X-1 and
  X-2 in NGC 1313

abstract:
  X-ray spectral state transitions are a key signature of black hole X-ray
binaries and follow a well-defined pattern. We examined 12 XMM-Newton
observations of the nearby spiral galaxy NGC 1313, which harbors two compact
ultraluminous X-ray sources (ULXs), X-1 and X-2, in order to determine if the
state transitions in ULXs follow the same pattern. For both sources, the
spectra were adequately fitted by an absorbed power-law with the addition of a
low temperature (kT=0.1~0.3 keV) disk blackbody component required in 6 of the
12 observations. As the X-ray luminosity of X-1 increases to a maximum at
3x10^40 ergs/s, the power-law photon index softens to 2.5-3.0. This behavior is
similar to the canonical spectral state transitions in Galactic black hole
binaries, but the source never enters the high/soft or thermal dominant state
and instead enters the steep power-law state at high luminosities. X-2 has the
opposite behavior and appears to be in the hard state, with a photon index of
Gamma=1.7-2.0 at high luminosity, but can soften to Gamma=2.5 at the lower
luminosities.


title: Spin Exchange Rates in Electron-Hydrogen Collisions

abstract:
  The spin temperature of neutral hydrogen, which determines the 21 cm optical
depth and brightness temperature, is set by the competition between radiative
and collisional processes. In the high-redshift intergalactic medium, the
dominant collisions are typically those between hydrogen atoms. However,
collisions with electrons couple much more efficiently to the spin state of
hydrogen than do collisions with other hydrogen atoms and thus become important
once the ionized fraction exceeds ~1%. Here we compute the rate at which
electron-hydrogen collisions change the hydrogen spin. Previous calculations
included only S-wave scattering and ignored resonances near the n=2 threshold.
We provide accurate results, including all partial wave terms through the
F-wave, for the de-excitation rate at temperatures T_K < 15,000 K; beyond that
point, excitation to n>=2 hydrogen levels becomes significant. Accurate
electron-hydrogen collision rates at higher temperatures are not necessary,
because collisional excitation in this regime inevitably produces Lyman-alpha
photons, which in turn dominate spin exchange when T_K > 6200 K even in the
absence of radiative sources. Our rates differ from previous calculations by
several percent over the temperature range of interest. We also consider some
simple astrophysical examples where our spin de-excitation rates are useful.


title:
On the Physics of Type I X-ray Bursts on Accreting Neutron Stars at High
  Accretion Rates

abstract:
  We investigate the effect of the hot CNO cycle breakout reaction
15O(alpha,gamma)19Ne on the occurrence of type I X-ray bursts on accreting
neutron stars. For f_rp <~ 0.1, where f_rp is a dimensionless factor by which
we multiply the 15O(alpha,gamma)19Ne reaction rate of Caughlan & Fowler (1988),
our model predicts that bursts should occur only for accretion rates below a
critical value of approximately 0.3 times the Eddington limit. This agrees with
observations. For larger values of f_rp, including the standard choice f_rp =
1, the model switches to a new regime in which bursts occur all the way up to
roughly the Eddington limit. Since the latter regime disagrees with
observations, we suggest that the true 15O(alpha,gamma)19Ne reaction rate is
lower than usually assumed.


title: Dynamical Evolution of Globular Clusters in Hierarchical Cosmology

abstract:
  We test the hypothesis that metal-poor globular clusters form within disk
galaxies at redshifts z>3. Numerical simulations demonstrate that giant gas
clouds, which are cold and dense enough to produce massive star clusters,
assemble naturally in hierarchical models of galaxy formation at high redshift.
Do model clusters evolve into observed globular clusters or are they disrupted
before present as a result of the dynamical evolution? To address this
question, we calculate the orbits of model clusters in the time-variable
gravitational potential of a Milky Way-sized galaxy, using the outputs of a
cosmological N-body simulation. We find that at present the orbits are
isotropic in the inner 50 kpc of the Galaxy and preferentially radial at larger
distances. All clusters located outside 10 kpc from the center formed in
satellite galaxies, some of which are now tidally disrupted and some of which
survive as dwarf galaxies. The spatial distribution of model clusters is
spheroidal and the fit to the density profile has a power-law slope of 2.7. The
combination of two-body relaxation, tidal shocks, and stellar evolution drives
the evolution of the cluster mass function from an initial power law to a
peaked distribution, in agreement with observations. However, not all initial
conditions and not all evolution scenarios are consistent with the observed
mass function of the Galactic globular clusters. The successful models require
the average cluster density to be constant initially for clusters of all mass
and to remain constant with time. Synchronous formation of all clusters at a
single epoch (z=4) and continuous formation over a span of 1.6 Gyr (between z=9
and z=3) are both consistent with the data. For both formation scenarios, we
provide online catalogs of the main physical properties of model clusters.


title: Stellar Encounters with Massive Star-Disk Systems

abstract:
  The dense, clustered environment in which massive stars form can lead to
interactions with neighboring stars. It has been hypothesized that collisions
and mergers may contribute to the growth of the most massive stars. In this
paper we extend the study of star-disk interactions to explore encounters
between a massive protostar and a less massive cluster sibling using the
publicly available SPH code GADGET-2. Collisions do not occur in the parameter
space studied, but the end state of many encounters is an eccentric binary with
a semi-major axis ~ 100 AU. Disk material is sometimes captured by the
impactor. Most encounters result in disruption and destruction of the initial
disk, and periodic torquing of the remnant disk. We consider the effect of the
changing orientation of the disk on an accretion driven jet, and the evolution
of the systems in the presence of on-going accretion from the parent core.


title:
Prospects for the Characterization and Confirmation of Transiting
  Exoplanets via the Rossiter-McLaughlin Effect

abstract:
  The Rossiter-McLaughlin (RM) effect is the distortion of stellar spectral
lines that occurs during eclipses or transits, due to stellar rotation. We
assess the future prospects for using the RM effect to measure the alignment of
planetary orbits with the spin axes of their parent stars, and to confirm
exoplanetary transits. We compute the achievable accuracy for the parameters of
interest, in general and for the 5 known cases of transiting exoplanets with
bright host stars. We determine the requirements for detecting the effects of
differential rotation. For transiting planets with small masses or long periods
(as will be detected by forthcoming satellite missions), the velocity anomaly
produced by the RM effect can be much larger than the orbital velocity of the
star. For a terrestrial planet in the habitable zone of a Sun-like star found
by the Kepler mission, it will be difficult to use the RM effect to confirm
transits with current instruments, but it still may be easier than measuring
the spectroscopic orbit.


title:
Search for Oxygen Emission from Warm-Hot Intergalactic Medium around
  A2218 with Suzaku

abstract:
  We searched for redshifted O emission lines from the possible warm-hot
intergalactic medium (WHIM) surrounding the cluster of galaxies A2218 at
z=0.1756 using the XIS instrument on Suzaku. This cluster is thought to have an
elongated structure along the line of sight based on previous studies. We
studied systematic uncertainties in the spectrum of the Galactic emission and
in the soft X-ray response of the detectors due to the contamination building
up on the XIS filters. We detected no significant redshifted O lines, and set a
tight constraint on the intensity with upper limits for the surface brightness
of OVII and OVIII lines of 1.1 x 10^-7 and 3.0 x 10^-7 photons cm^-2 s^-1
arcmin^-2, respectively. These upper limits are significantly lower than the
previously reported fluxes from the WHIM around other clusters of galaxies. We
also discuss the prospect for the detection of the WHIM lines with Suzaku XIS
in the future.


title:
A deep mosaic of [O III] 5007 A CCD images of the environment of the LBV
  star P Cygni

abstract:
  A mosaic of six, deep, CCD images in the light of the [O III] 5007 A nebular
emission line has been obtained with the 1.3-m Skinakas (Crete) telescope of
the filamentary nebulosity surrounding P Cygni. The [O III] 5007 A line
discriminates against confusing galactic H II regions along the same
sight-lines and the new mosaic did not include the 4.8 mag. central star; a
source of artifacts in the previous lower angular resolution observations. New
giant `lobes' and `shells' are found to be clustered around P Cygni which must
be the relics of historic eruptions between 2400 and up to ~10^5 yr ago.