title: The Spatial Distribution of Brown Dwarfs in Taurus

abstract:
  By combining photometry from the 2MASS Point Source Catalog and the USNO-B1.0
Catalog with optical and infrared spectroscopy, I have performed a search for
young brown dwarfs in an area of 225 deg^2 encompassing all of the Taurus
star-forming region (1 Myr). From this work, I have discovered 22 new members
of Taurus, five of which were independently found by Guieu and coworkers.
Sixteen of these new members have spectral types later than M6 and thus are
likely to be brown dwarfs according to the theoretical evolutionary models of
Chabrier and Baraffe. After adding these new members to the previously known
members of Taurus, I have compared the spatial distributions of stars and brown
dwarfs across the entire region. I find no statistically significant difference
between these two distributions. Taurus does not contain the large, extended
population of brown dwarfs that has been predicted by some embryo ejection
models for the formation of brown dwarfs. However, these results are consistent
with other ejection models, as well as models in which stars and brown dwarfs
share a common formation mechanism.


title: A Survey for New Members of Taurus with the Spitzer Space Telescope

abstract:
  We present the results of a search for new members of the Taurus star-forming
region using the Infrared Array Camera (IRAC) aboard the Spitzer Space
Telescope}. With IRAC images of 29.7 deg^2 of Taurus at 3.6, 4.5, 5.8, and 8.0
um, we have identified sources with red mid-infrared colors indicative of
disk-bearing objects and have obtained optical and infrared spectra of 23 of
these candidate members. Through this work, we have discovered 13 new members
of Taurus, two of which have spectral types later than M6 and thus are likely
to be brown dwarfs according to the theoretical evolutionary models of Chabrier
and Baraffe. This survey indicates that the previous census of Taurus has a
completeness of ~80% for members with disks. The new members that we have found
do not significantly modify the previously measured distributions of Taurus
members as a function of position, mass, and extinction. For instance, we find
no evidence for a population of highly reddened brown dwarfs (A_K~2) that has
been missed by previous optical and near-infrared surveys, which suggests that
brown dwarf disks are not significantly more flared than disks around stars. In
addition to the new members, we also present IRAC photometry for the 149
previously known members that appear within this survey, which includes 27
objects later than M6.


title: The Atacama Cosmology Telescope Project: A Progress Report

abstract:
  The Atacama Cosmology Telescope is a project to map the microwave background
radiation at arcminute angular resolution and high sensitivity in three
frequency bands over substantial sky areas. Cosmological signals driving such
an experiment are reviewed, and current progress in hardware construction is
summarized. Complementary astronomical observations in other wavebands are also
discussed.


title:
Radioelectric Field Features of Extensive Air Showers Observed with
  CODALEMA

abstract:
  Based on a new approach to the detection of radio transients associated with
extensive air showers induced by ultra high energy cosmic rays, the
experimental apparatus CODALEMA is in operation, measuring about 1 event per
day corresponding to an energy threshold ~ 5. 10^16 eV. Its performance makes
possible for the first time the study of radio-signal features on an
event-by-event basis. The sampling of the magnitude of the electric field along
a 600 meters axis is analyzed. It shows that the electric field lateral spread
is around 250 m (FWHM). The possibility to determine with radio both arrival
directions and shower core positions is discussed.


title:
Chemical sensitivity to the ratio of the cosmic-ray ionization rates of
  He and H2 in dense clouds

abstract:
  Aim: To determine whether or not gas-phase chemical models with homogeneous
and time-independent physical conditions explain the many observed molecular
abundances in astrophysical sources, it is crucial to estimate the
uncertainties in the calculated abundances and compare them with the observed
abundances and their uncertainties. Non linear amplification of the error and
bifurcation may limit the applicability of chemical models. Here we study such
effects on dense cloud chemistry. Method: Using a previously studied approach
to uncertainties based on the representation of rate coefficient errors as log
normal distributions, we attempted to apply our approach using as input a
variety of different elemental abundances from those studied previously. In
this approach, all rate coefficients are varied randomly within their log
normal (Gaussian) distribution, and the time-dependent chemistry calculated
anew many times so as to obtain good statistics for the uncertainties in the
calculated abundances. Results: Starting with so-called ``high-metal''
elemental abundances, we found bimodal rather than Gaussian like distributions
for the abundances of many species and traced these strange distributions to an
extreme sensitivity of the system to changes in the ratio of the cosmic ray
ionization rate zeta\_He for He and that for molecular hydrogen zeta\_H2. The
sensitivity can be so extreme as to cause a region of bistability, which was
subsequently found to be more extensive for another choice of elemental
abundances. To the best of our knowledge, the bistable solutions found in this
way are the same as found previously by other authors, but it is best to think
of the ratio zeta\_He/zeta\_H2 as a control parameter perpendicular to the
''standard'' control parameter zeta/n\_H.


title: Modeling the hard states of XTE J1550--564 during its 2000 outburst

abstract:
  We study hard states of the black-hole binary XTE J1550--564 during its 2000
outburst. In order to explain those states at their highest luminosities,
$L\sim 10%$ of the Eddington luminosity, $L_{\rm E}$, we propose a specific hot
accretion flow model. We point out that the highest values of the hard-state
$L$ are substantially above the $L$ an advection-dominated accretion flow
(ADAF) can produce, $\sim 0.4\alpha^2 L_{\rm E}$, which is only $\sim
(3$--$4)%L_{\rm E}$ even for $\alpha$ as high as 0.3. On the other hand, we
successfully explain the hard states with $L\sim (4$--$10)%$ using the luminous
hot accretion flow (LHAF) model. As $10%L_{\rm E}$ is also roughly the highest
luminosity an LHAF can produce, such an agreement between the predicted and
observed highest luminosities provides by itself strong support for this model.
Then, we study multi-waveband spectral variability during the 2000 outburst. In
addition to the primary maxima in the optical light curves, secondary maxima
were detected after the transition from the very high state to the hard state.
We show that the secondary maxima are well modeled by synchrotron emission from
a jet formed during the state transition. We argue that the absence of the
corresponding secondary peak in the X-ray light curve indicates that the X-ray
jet emission, regardless of its radiative process, synchrotron or its
Comptonization, is not important in the hard state compared to the emission
from the accretion flow.


title: Cosmic Rays at the Knee

abstract:
  Several kinds of measurements are combined in an attempt to obtain a
consistent estimate of the spectrum and composition of the primary cosmic
radiation through the knee region. Assuming that the knee is a signal of the
high-energy end of a galactic cosmic-ray population, I discuss possible
signatures of a transition to an extra-galactic population and how they might
be detected.


title:
Bubbles in Planetary Nebulae and Clusters of Galaxies: Slowly Precessing
  Jets

abstract:
  I derive the condition for narrow jets with varying axis, e.g., precessing
jets, to inflate more or less spherical (fat) bubbles in planetary nebulae and
clusters of galaxies. This work follows a previous work dealing with wide jets,
i.e., having a wide opening angle. The expressions derive here are
qualitatively and quantitatively similar to the conditions for inflating fat
bubbles by non-precessing wide jets. This follows the similar physical cause of
inflating fat bubbles, which is that the jet deposits energy inside the bubble.
Fat bubbles in planetary nebulae (and similar stellar systems) and in clusters
of galaxies, are likely to be formed by wide jets, precessing jets, or other
jets whose axis is not constant relative to the medium they expand into.


title: Puzzled by GRB 060218

abstract:
  We study the optical-UV/X-ray spectral energy distribution of GRB 060218
during the prompt phase and during what seems to be the afterglow phase. The
results are puzzling, since if the opt-UV and the X-ray emission belong to a
single backbody (BB), then its luminosity is too large, and this BB cannot be
interpreted as the signature of the shock breakout of the supernova. There are
also serious problems in associating the emission expected by the supernova
shock breakout with either the opt-UV or the X-ray emission. In the former case
we derive too small ejecta velocities; in the latter case, on the contrary, the
required velocity is too large, corresponding to the large radius of a BB
required to peak close to the UV band. We then present what we think is the
most conservative alternative explanation, namely a synchrotron spectrum,
self-absorbed in the opt-UV and extending up to the X-ray band, where we
observe the emission of the most energetic electrons, which are responsible for
the exponential roll-over of the spectrum. The obtained fit can explain the
entire spectrum except the BB observed in the X-rays, which must be a separate
component. The puzzling feature of this interpretation is that the same model
is required to explain the spectrum also at later times, up to 1e5 s, because
the opt-UV emission remains constant in shape and also (approximately) in
normalisation. In this case the observed X-ray flux is produced by self-Compton
emission. Thus the prompt emission phase should last for ~1e5 s or more.
Finally, we show that the BB observed in X-rays, up to 7000 seconds, can be
photospheric emission from the cocoon or stellar material, energized by the GRB
jet at radii comparable to the stellar radius (i.e. 1e10-1e11 cm), not very far
from where this material becomes transparent (e.g. 1e12 cm).


title:
Rotational Modulation of the Radio Emission from the M9 Dwarf TVLM
  513-46546: Broadband Coherent Emission at the Substellar Boundary?

abstract:
  The Very Large Array was used to observe the ultracool, rapidly rotating M9
dwarf TVLM 513-46546 simultaneously at 4.88 GHz and 8.44 GHz. The radio
emission was determined to be persistent, variable and periodic at both
frequencies with a period of ~2 hours. This periodicity is in excellent
agreement with the estimated period of rotation of the dwarf based on its v sin
i of ~60 km/s. This rotational modulation places strong constraints on the
source size of the radio emitting region and hence the brightness temperature
of the associated emission. We find the resulting high brightness temperature,
together with the inherent directivity of the rotationally modulated component
of the emission, difficult to reconcile with incoherent gyrosynchrotron
radiation. We conclude that a more likely source is coherent, electron
cyclotron maser emission from the low density regions above the magnetic poles.
This model requires the magnetic field of TVLM 513-46546 to take the form of a
large-scale, stable, dipole or multipole with surface field strengths up to at
least 3kG. We discuss a mechanism by which broadband, persistent electron
cyclotron maser emission can be sustained in the low density regions of the
magnetospheres of ultracool dwarfs. A second nonvarying, unpolarized component
of the emission may be due to depolarization of the coherent electron cyclotron
maser emission or alternatively, incoherent gyrosynchrotron or synchrotron
radiation from a population of electrons trapped in the large-scale magnetic
field.


title: Abundances and Behavior of 12CO, 13CO, and C2 in Translucent Sight Lines

abstract:
  Using UV spectra obtained with FUSE, HST, and/or IUE, we determine
interstellar column densities of 12CO, 13CO, and/or C_2 for ten Galactic sight
lines with 0.37<E(B-V)<0.72. The N(CO)/N(H_2) ratio varies over a factor of 100
in this sample, due primarily to differences in N(CO). For a given N(H_2),
published models of diffuse and translucent clouds predict less CO than is
observed. The J=1-3 rotational levels of 12CO are sub-thermally populated in
these sight lines, with T_ex typically between 3 and 7 K. In general, there is
no significant difference between the excitation temperatures of 12CO and 13CO.
Fits to the higher resolution CO line profiles suggest that CO (like CN) is
concentrated in relatively cold, dense gas. We obtain C_2 column densities from
the F-X (1-0) and (0-0) bands (1314 and 1341 A), the D-X (0-0) band (2313 A),
and the A-X (3-0) and (2-0) bands (7719 and 8757 A). Comparisons among those
N(C_2) yield a set of mutually consistent f-values for the UV and optical C_2
bands, but also reveal some apparent anomalies within the F-X (0-0) band. Both
the kinetic temperature inferred from the C_2 rotational populations (up to
J=18) and the excitation temperature T_02(C_2) are generally smaller than the
corresponding T_01(H_2). Incorporating additional data for K I, HD, CH, C_2,
C_3, CN, and CO from the literature (for a total sample of 74 sight lines), we
find that (1) CO is most tightly correlated with CN; (2) the ratios 12CO/H_2
and 13CO/H_2 both are fairly tightly correlated with the density indicator
CN/CH (but C_2/H_2 is not); and (3) the ratio 12CO/13CO is somewhat
anti-correlated with both CN/CH and N(CO). Sight lines with 12CO/13CO below the
average local Galactic value of 12C/13C appear to sample colder, denser gas in
which isotope exchange reactions have enhanced 13CO, relative to 12CO.


title: A look at disk-jet connections in stellar-mass black holes

abstract:
  Connections between accretion disks and jets in accreting black holes are
anticipated theoretically. In recent years, potential evidence for such
connections has been emerging, most vividly in the convenient regime of
stellar-mass black holes. In this contribution, various lines of evidence for
disk-jet connections are briefly examined, from the standpoint of an observer
focused on the role of the disk. While many lines of investigation may be
promising in the future, obtaining multi-wavelength lightcurves and correlating
jet flux in the radio band with physical parameters and phenomena tied to the
accretion disk in X-rays may be the most direct.


title:
Fundamental Parameters and Abundances of Metal-Poor Stars: The SDSS
  Standard BD +17 4708

abstract:
  The atmospheric parameters and iron abundance of the Sloan Digital Sky Survey
(SDSS) spectrophotometric standard star BD +17 4708 are critically examined
using up-to-date Kurucz model atmospheres, LTE line formation calculations, and
reliable atomic data. We find Teff = 6141+-50 K, log g = 3.87+-0.08, and
[Fe/H]=-1.74+-0.09. The line-of-sight interstellar reddening, bolometric flux,
limb-darkened angular diameter, stellar mass, and the abundances of Mg, Si, and
Ca are also obtained. This star is a unique example of a moderately metal-poor
star for which the effective temperature can be accurately constrained from the
observed spectral energy distribution (corrected for reddening). Such analysis
leads to a value that is higher than most spectroscopic results previously
reported in the literature (~5950 K). We find that the ionization balance of Fe
lines is satisfied only if a low Teff (~5950 K) is adopted. With our preferred
Teff (6141 K), the mean iron abundance we obtain from the FeII lines is lower
by about 0.15 dex than that from the FeI lines, and therefore, the discrepancy
between the mean iron abundance from FeI and FeII lines cannot be explained by
overionization by UV photons as the main non-LTE effect. We also comment on
non-LTE effects and the importance of inelastic collisions with neutral H atoms
in the determination of oxygen abundances in metal-poor stars from the 777 nm
OI triplet. (Abridged)


title:
The impact of mergers on relaxed X-ray clusters - I. Dynamical evolution
  and emergent transient structures

abstract:
  We report on the analysis of a suite of SPH simulations (incorporating
cooling and star formation) of mergers involving idealised X-ray clusters whose
initial conditions resemble relaxed clusters with cool compact cores observed
by Chandra and XMM. The simulations sample the most interesting, theoretically
plausible, range of impact parameters and progenitor mass ratios. We find that
all mergers evolve via a common progression. We illustrate this progression in
the projected gas density, X-ray surface brightness, SZ, temperature, and gas
entropy maps. Several different classes of transient ``cold front''-like
features can arise over the course of a merger. We find that all of these
classes are present in Chandra and XMM observations of merging systems and
propose a naming scheme for these features: ``comet-like'' tails, bridges,
plumes, streams and edges. In none of the cases considered do the initial cool
compact cores of the primary and the secondary get destroyed during the course
of the mergers. We quantify the evolving morphology of our mergers using
centroid variance, power ratios and offset between the X-ray and the projected
mass maps. We find that the centroid variance best captures the dynamical state
of the cluster. Placing the system at z=0.1, we find that all easily identified
observable traces of the secondary disappear from a simulated 50 ks Chandra
image following the second pericentric passage. The system, however, takes
approximately 2 additional Gyrs to relax and virialize. Temperature
fluctuations at the level of 20% can persist in the final systems well past the
point of virialization, suggesting that that the existence of temperature
fluctuations, in and of themselves, do not necessarily indicate a disturbed or
unrelaxed system.


title:
The Spitzer Survey of the Small Magellanic Cloud: S3MC Imaging and
  Photometry in the Mid- and Far-Infrared Wavebands

abstract:
  We present the initial results from the Spitzer Survey of the Small
Magellanic Cloud (S3MC), which imaged the star-forming body of the Small
Magellanic Cloud (SMC) in all seven MIPS and IRAC wavebands. We find that the
F_8/F_24 ratio (an estimate of PAH abundance) has large spatial variations and
takes a wide range of values that are unrelated to metallicity but
anticorrelated with 24 um brightness and F_24/F_70 ratio. This suggests that
photodestruction is primarily responsible for the low abundance of PAHs
observed in star-forming low-metallicity galaxies. We use the S3MC images to
compile a photometric catalog of ~400,000 mid- and far-infrared point sources
in the SMC. The sources detected at the longest wavelengths fall into four main
categories: 1) bright 5.8 um sources with very faint optical counterparts and
very red mid-infrared colors ([5.8]-[8.0]>1.2), which we identify as YSOs. 2)
Bright mid-infrared sources with mildly red colors (0.16<[5.8]-[8.0]<0.6),
identified as carbon stars. 3) Bright mid-infrared sources with neutral colors
and bright optical counterparts, corresponding to oxygen-rich evolved stars.
And, 4) unreddened early B stars (B3 to O9) with a large 24 um excess. This
excess is reminiscent of debris disks, and is detected in only a small fraction
of these stars (<5%). The majority of the brightest infrared point sources in
the SMC fall into groups one to three. We use this photometric information to
produce a catalog of 282 bright YSOs in the SMC with a very low level of
contamination (~7%).


title:
Bound-State Effects on Light-Element Abundances in Gravitino Dark Matter
  Scenarios

abstract:
  If the gravitino is the lightest supersymmetric particle and the long-lived
next-to-lightest sparticle (NSP) is the stau, the charged partner of the tau
lepton, it may be metastable and form bound states with several nuclei. These
bound states may affect the cosmological abundances of Li6 and Li7 by enhancing
nuclear rates that would otherwise be strongly suppressed. We consider the
effects of these enhanced rates on the final abundances produced in Big-Bang
nucleosynthesis (BBN), including injections of both electromagnetic and
hadronic energy during and after BBN. We calculate the dominant two- and
three-body decays of both neutralino and stau NSPs, and model the
electromagnetic and hadronic decay products using the PYTHIA event generator
and a cascade equation. Generically, the introduction of bound states drives
light element abundances further from their observed values; however, for small
regions of parameter space bound state effects can bring lithium abundances in
particular in better accord with observations. We show that in regions where
the stau is the NSP with a lifetime longer than 10^3-10^4 s, the abundances of
Li6 and Li7 are far in excess of those allowed by observations. For shorter
lifetimes of order 1000 s, we comment on the possibility in minimal
supersymmetric and supergravity models that stau decays could reduce the Li7
abundance from standard BBN values while at the same time enhancing the Li6
abundance.


title: Debris Disk Evolution Around A Stars

abstract:
  We report 24 and/or 70 um measurements of ~160 A-type main-sequence stars
using the Multiband Imaging Photometer for Spitzer (MIPS). Their ages range
from 5 to 850 Myr based on estimates from the literature (cluster or moving
group associations) or from the H-R diagram and isochrones. The thermal
infrared excess is identified by comparing the deviation (~3% and ~15% at the
1-\sigma level at 24 and 70 um, respectively) between the measurements and the
synthetic Kurucz photospheric predictions. Stars showing excess infrared
emission due to strong emission lines or extended nebulosity seen at 24 um are
excluded from our sample; therefore, the remaining infrared excesses are likely
to arise from circumstellar debris disks. At the 3-sigma confidence level, the
excess rate at 24 and 70 um is 32% and >=33% (with an uncertainty of 5%),
considerably higher than has been found for old solar analogs and M dwarfs. Our
measurements place constraints on the fractional dust luminosities and
temperatures in the disks. We find that older stars tend to have lower
fractional dust luminosity than younger ones. While the fractional luminosity
from the excess infrared emission follows a general 1/t relationship, the
values at a given stellar age vary by at least two orders of magnitude. We also
find that (1) older stars possess a narrow range of temperature distribution
peaking at colder temperatures, and (2) the disk emission at 70 um persists
longer than that at 24 um. Both results suggest that the debris-disk clearing
process is more effective in the inner regions.


title: The Extreme Physics Explorer

abstract:
  Some tests of fundamental physics - the equation of state at supra-nuclear
densities, the metric in strong gravity, the effect of magnetic fields above
the quantum critical value - can only be measured using compact astrophysical
objects: neutron stars and black holes. The Extreme Physics Explorer is a
modest sized (~500 kg) mission that would carry a high resolution (R ~300)
X-ray spectrometer and a sensitive X-ray polarimeter, both with high time
resolution (~5 ?s) capability, at the focus of a large area (~5 sq.m), low
resolution (HPD~1 arcmin) X-ray mirror. This instrumentation would enable new
classes of tests of fundamental physics using neutron stars and black holes as
cosmic laboratories.


title:
QED can explain the non-thermal emission from SGRs and AXPs :
  Variability

abstract:
  Owing to effects arising from quantum electrodynamics (QED),
magnetohydrodynamical fast modes of sufficient strength will break down to form
electron-positron pairs while traversing the magnetospheres of strongly
magnetised neutron stars. The bulk of the energy of the fast mode fuels the
development of an electron-positron fireball. However, a small, but potentially
observable, fraction of the energy ($\sim 10^{33}$ ergs) can generate a
non-thermal distribution of electrons and positrons far from the star. This
paper examines the cooling and radiative output of these particles. Small-scale
waves may produce only the non-thermal emission. The properties of this
non-thermal emission in the absence of a fireball match those of the quiescent,
non-thermal radiation recently observed non-thermal emission from several
anomalous X-ray pulsars and soft-gamma repeaters. Initial estimates of the
emission as a function of angle indicate that the non-thermal emission should
be beamed and therefore one would expect this emission to be pulsed as well.
According to this model the pulsation of the non-thermal emission should be
between 90 and 180 degrees out of phase from the thermal emission from the
stellar surface.


title: Coherent Synchrotron Radiation for Laminar Flows

abstract:
  We investigate the effect of shear in the flow of charged particle equilibria
that are unstable to the Coherent Synchrotron Radiation (CSR) instability.
  Shear may act to quench this instability because it acts to limit the size of
the region with a fixed phase relation between emitters.
  The results are important for the understanding of astrophysical sources of
coherent radiation where shear in the flow is likely.


title: Gravitational Wave Sources from New Physics

abstract:
  Forthcoming advances in direct gravitational wave detection from kilohertz to
nanohertz frequencies have unique capabilities to detect signatures from or set
meaningful constraints on a wide range of new cosmological phenomena and new
fundamental physics. A brief survey is presented of the post-inflationary
gravitational radiation backgrounds predicted in cosmologies that include
intense new classical sources such as first-order phase transitions,
late-ending inflation, and dynamically active mesoscopic extra dimensions. LISA
will provide the most sensitive direct probes of such phenomena near TeV
energies or Terascale. LISA will also deeply probe the broadband background,
and possibly bursts, from loops of cosmic superstrings predicted to form in
current models of brane inflation.


title: The yields of r-process elements and chemical evolution of the Galaxy

abstract:
  The supernova yields of r-process elements are obtained as a function of the
mass of their progenitor stars from the abundance patterns of extremely
metal-poor stars on the left-side [Ba/Mg]-[Mg/H] boundary with a procedure
proposed by Tsujimoto and Shigeyama. The ejected masses of r-process elements
associated with stars of progenitor mass $M_{ms}\leq18M_{\odot}$ are infertile
sources and the SNe II with 20$M_{\odot}\leq M_{ms}\leq 40M_{\odot}$are the
dominant source of r-process nucleosynthesis in the Galaxy. The ratio of these
stars 20$M_{\odot}\leq M_{ms}\leq40M_{\odot}$ with compared to the all massive
stars is about $\sim$18%. In this paper, we present a simple model that
describes a star's [r/Fe] in terms of the nucleosynthesis yields of r-process
elements and the number of SN II explosions. Combined the r-process yields
obtained by our procedure with the scatter model of the Galactic halo, the
observed abundance patterns of the metal-poor stars can be well reproduced


title:
The DEEP2 galaxy redshift survey: the evolution of the blue fraction in
  groups and the field

abstract:
  We explore the behavior of the blue galaxy fraction over the redshift range
0.75 <= z <= 1.3 in the DEEP2 Survey, both for field galaxies and for galaxies
in groups. The primary aim is to determine the role that groups play in driving
the evolution of galaxy colour at high z. The colour segregation observed
between local group and field samples is already in place at z ~ 1: DEEP2
groups have a significantly lower blue fraction than the field. At fixed z,
there is also a correlation between blue fraction and galaxy magnitude, such
that brighter galaxies are more likely to be red, both in groups and in the
field. In addition, there is a negative correlation between blue fraction and
group richness. In terms of evolution, the blue fraction in groups and the
field remains roughly constant from z=0.75 to z ~ 1, but beyond this redshift
the blue fraction in groups rises rapidly with z, and the group and field blue
fractions become indistinguishable at z ~ 1.3. Careful tests indicate that this
effect does not arise from known systematic or selection effects. To further
ensure the robustness of this result, we build on previous mock DEEP2
catalogues to develop mock catalogues that reproduce the colour-overdensity
relation observed in DEEP2 and use these to test our methods. The convergence
between the group and field blue fractions at z ~ 1.3 implies that DEEP2 galaxy
groups only became efficient at quenching star formation at z ~ 2; this result
is broadly consistent with other recent observations and with current models of
galaxy evolution and hierarchical structure growth. (Abridged.)


title: Inferring the emission regions for different kinds of gamma-ray bursts

abstract:
  Using a theoretical model describing pulse shapes, we have clarified the
relations between the observed pulses and their corresponding timescales, such
as the angular spreading time, the dynamic time as well as the cooling time. We
find that the angular spreading timescale caused by curvature effect of
fireball surface only contributes to the falling part of the observed pulses,
while the dynamic one in the co-moving frame of the shell merely contributes to
the rising portion of pulses provided the radiative time is negligible. In
addition, the pulses resulted from the pure radiative cooling time of
relativistic electrons exhibit properties of fast rise and slow decay (a
quasi-FRED) profile together with smooth peaks. Besides, we interpret the
phenomena of wider pules tending to be more asymmetric to be a consequence of
the difference in emission regions. Meanwhile, we find the intrinsic emission
time is decided by the ratios of lorentz factors and radii of the shells
between short and long bursts. Based on the analysis of asymmetry, our results
suggest that the long GRB pulses may occur in the regions with larger radius,
while the short bursts could locate at the smaller distance from central
engine.


title: Bayesian Inference from Observations of Solar-Like Oscillations

abstract:
  Stellar oscillations can provide a wealth of information about a star, which
can be extracted from observed time series of the star's brightness or radial
velocity. In this paper we address the question of how to extract as much
information as possible from such a dataset. We have developed a Markov Chain
Monte Carlo (MCMC) code that is able to infer the number of oscillation
frequencies present in the signal and their values (with corresponding
uncertainties), without having to fit the amplitudes and phases. Gaps in the
data do not have any serious consequences for this method; in cases where
severe aliasing exists, any ambiguity in the frequency determinations will be
reflected in the results. It also allows us to infer parameters of the
frequency pattern, such as the large separation Delta nu. We have previously
applied this method to the star nu Indi (Bedding et al 2006), and here we
describe the method fully and apply it to simulated datasets, showing that the
code is able to give correct results even when some of the model assumptions
are violated. In particular, the non-sinusoidal nature of the individual
oscillation modes due to stochastic excitation and damping has no major impact
on the usefulness of our approach.


title:
Kinematic Control of the Inertiality of the System of Tycho-2 and UCAC2
  Stellar Proper Motions

abstract:
  Based on the Ogorodnikov-Milne model, we analyze the proper motions of
Tycho-2 and UCAC2 stars. We have established that the model component that
describes the rotation of all stars under consideration around the Galactic y
axis differs significantly from zero at various magnitudes. We interpret this
rotation found using the most distant stars as a residual rotation of the
ICRS/Tycho-2 system relative to the inertial reference frame. For the most
distant ($d\approx900$ pc) Tycho-2 and UCAC2 stars, the mean rotation around
the Galactic y axis has been found to be $M_{13}=-0.37\pm0.04$ mas yr$^{-1}$.
The proper motions of UCAC2 stars with magnitudes in the range $12-15^m$ are
shown to be distorted appreciably by the magnitude equation in
$\mu_\alpha\cos\delta$, which has the strongest effect for northern-sky stars
with a coefficient of $-0.60\pm0.05$ mas yr$^{-1}$ mag$^{-1}$. We have detected
no significant effect of the magnitude equation in the proper motions of UCAC2
stars brighter than $\approx11^m$.


title: Halo Stars Near the Hydrogen-Burning Limit: The M/L Subdwarf Transition

abstract:
  We present the first far-red spectra of the L subdwarf 2MASS
J16262034+3925190 and the late M/early L subdwarf 2MASS J16403197+1231068. We
confirm the ultracool subdwarf nature of these objects. 2M1626+3925 shows
strong K I absorption, like an L4 dwarf, and is very similar to, but hotter
than, the late L subdwarf 2MASS J05325346+8246465. It is unambiguously an L
subdwarf. 2M1640+1231 is very similar to SSSPM J1444-2019, which has been
classified as sdM9 or early sdL. In contrast to the hotter M subdwarfs, L
subdwarfs are characterized by not only enhanced hydrides but also strong TiO.
Progress in a classification system requires identification of more subdwarfs
to map out their variations.


title:
The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of A Wide, Low
  Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating
  Wide Binaries?

abstract:
  We imaged five objects near the star forming clouds of Ophiuchus with the
Keck Laser Guide Star AO system. We resolved Allers et al. (2006)'s #11 (Oph
16222-2405) and #16 (Oph 16233-2402) into binary systems. The #11 object is
resolved into a 243 AU binary, the widest known for a very low mass (VLM)
binary. The binary nature of #11 was discovered first by Allers (2005) and
independently here during which we obtained the first spatially resolved R~2000
near-infrared (J & K) spectra, mid-IR photometry, and orbital motion estimates.
We estimate for 11A and 11B gravities (log(g)>3.75), ages (5+/-2 Myr),
luminosities (log(L/Lsun)=-2.77+/-0.10 and -2.96+/-0.10), and temperatures
(Teff=2375+/-175 and 2175+/-175 K). We find self-consistent DUSTY evolutionary
model (Chabrier et al. 2000) masses of 17+4-5 MJup and 14+6-5 MJup, for 11A and
11B respectively. Our masses are higher than those previously reported (13-15
MJup and 7-8 MJup) by Jayawardhana & Ivanov (2006b). Hence, we find the system
is unlikely a ``planetary mass binary'', (in agreement with Luhman et al. 2007)
but it has the second lowest mass and lowest binding energy of any known
binary. Oph #11 and Oph #16 belong to a newly recognized population of wide
(>100 AU), young (<10 Myr), roughly equal mass, VLM stellar and brown dwarf
binaries. We deduce that ~6+/-3% of young (<10 Myr) VLM objects are in such
wide systems. However, only 0.3+/-0.1% of old field VLM objects are found in
such wide systems. Thus, young, wide, VLM binary populations may be
evaporating, due to stellar encounters in their natal clusters, leading to a
field population depleted in wide VLM systems.


title: The Sloan Digital Sky Survey Monitor Telescope Pipeline

abstract:
  The photometric calibration of the Sloan Digital Sky Survey (SDSS) is a
multi-step process which involves data from three different telescopes: the
1.0-m telescope at the US Naval Observatory (USNO), Flagstaff Station, Arizona
(which was used to establish the SDSS standard star network); the SDSS 0.5-m
Photometric Telescope (PT) at the Apache Point Observatory (APO), New Mexico
(which calculates nightly extinctions and calibrates secondary patch transfer
fields); and the SDSS 2.5-m telescope at APO (which obtains the imaging data
for the SDSS proper).
  In this paper, we describe the Monitor Telescope Pipeline, MTPIPE, the
software pipeline used in processing the data from the single-CCD telescopes
used in the photometric calibration of the SDSS (i.e., the USNO 1.0-m and the
PT). We also describe transformation equations that convert photometry on the
USNO-1.0m u'g'r'i'z' system to photometry the SDSS 2.5m ugriz system and the
results of various validation tests of the MTPIPE software. Further, we discuss
the semi-automated PT factory, which runs MTPIPE in the day-to-day standard
SDSS operations at Fermilab. Finally, we discuss the use of MTPIPE in current
SDSS-related projects, including the Southern u'g'r'i'z' Standard Star project,
the u'g'r'i'z' Open Star Clusters project, and the SDSS extension (SDSS-II).


title: Status and recent results of the Pierre Auger Observatory

abstract:
  The Pierre Auger Observatory aims to determine the nature and origin of the
ultra-high energy cosmic rays (UHECR). The Auger hybrid detector combines
fluorescence observations of extended air showers, initiated in the atmosphere
by these most energetic particles, with measures of the shower front at the
ground level by its large array of Cherenkov water tanks. This allows to
improve considerably the precision on reconstructed primary cosmic ray
parameters, and to make important cross-calibrations between two techniques at
these energies, unreachable with accelerator experiments. The Southern Auger
site in Argentina is close to completion. The first measure of the primary
cosmic rays energy spectrum, the anisotropy search results, and the limit on
the photon fraction in the UHECR are discussed.


title: A Search for Molecular Gas in Low Luminosity Radio Galaxies

abstract:
  We discuss CO spectral line data of a volume-limited sample of 23 nearby
(z<0.03) low luminosity radi galaxies, selected from the B2 catalogue. Most of
such objects (16/23) have HST imaging. Our aim is to establish the distribution
of molecular gas masses in low luminosity radio galaxies, in comparison with
other radio source samples, confirm the suggestion that the CO is in ordered
rotation, determine its relation to the dust disks observed in these objects
with HST and establish targets for future interferometric imaging.


title:
Spin of Stellar-Mass Black Holes Estimated by a Model of Quasi-Periodic
  Oscillations

abstract:
  We have proposed in previous papers that the high-frequency pair QPOs
observed in black-hole binaries with frequency ratio 3:2 are inertial-acoustic
oscillations (nearly horizontal oscillations with no node in the vertical
direction) or g-mode oscillations, which are resonantly excited on warped
relativistic disks. The resonance occurs through horizontal motions. In this
model the dimensionless spin parameter $a_*$ of the central sources can be
estimated when their masses are known from other observations. This estimate is
done for three sources (GRO J1665-40, XTE J1550-564, GRS 1915+105). For all of
them we have $a_*\leq 0.45$.


title: Hardness Ratio Estimation in Low Counting X-ray Photometry

abstract:
  Hardness ratios are commonly used in X-ray photometry to indicate spectral
properties roughly. It is usually defined as the ratio of counts in two
different wavebands. This definition, however, is problematic when the counts
are very limited. Here we instead define hardness ratio using the $\lambda$
parameter of Poisson processes, and develop an estimation method via Bayesian
statistics. Our Monte Carlo simulations show the validity of our method. Based
on this new definition, we can estimate the hydrogen column density for the
photoelectric absorption of X-ray spectra in the case of low counting
statistics.


title: Analysis of galactic tides and stars on CDM microhalos

abstract:
  A special purpose N-body simulation has been built to understand the tidal
heating of the smallest dark matter substructures ($10^{-6}\msun$ and 0.01pc)
from the grainy potential of the Milky Way due to individual stars in the disk
and the bulge. To test the method we first run simulations of single encounters
of microhalos with an isolated star, and compare with analytical predictions of
the dark particle bound fraction as a function of impact parameter. We then
follow the orbits of a set of microhalos in a realistic flattened Milky Way
potential. We concentrate on (detectable) microhalos passing near the Sun with
a range of pericenter and apocenter. Stellar perturbers near the orbital path
of a microhalo would exert stochachstic impulses, which we apply in a Monte
Carlo fashion according to the Besancon model for the distribution of stars of
different masses and ages in our Galaxy. Also incorporated are the usual
pericenter tidal heating and disk-shocking heating. We give a detailed
diagnosis of typical microhalos and find microhalos with internal tangential
anisotropy are slightly more robust than the ones with radial anisotropy. In
addition, the dark particles generally go through of a random walk in velocity
space and diffuse out of the microhalos.
  We show that the typical destruction time scales are strongly correlated with
the stellar density averaged along a microhalo's orbit over the age of the
stellar disk. We also present the morphology of a microhalo at several epochs
which may hold the key to dark matter detections.


title: ESO Imaging survey: Optical Deep Public Survey

abstract:
  This paper presents new five passbands (UBVRI) optical wide-field imaging
data accumulated as part of the DEEP Public Survey (DPS) carried out as a
public survey by the ESO Imaging Survey (EIS) project. Out of the 3 square
degrees originally proposed, the survey covers 2.75 square degrees, in at least
one band (normally R), and 1.00 square degrees in five passbands. The median
seeing, as measured in the final stacked images, is 0.97", ranging from 0.75"
to 2.0". The median limiting magnitudes (AB system, 2" aperture, 5 sigma
detection limit) are U_(AB)=25.65, B_(AB)=25.54, V_(AB)=25.18, R_(AB) = 24.8
and I_(AB)=24.12 mag, consistent with those proposed in the original survey
design. The paper describes the observations and data reduction using the EIS
Data Reduction System and its associated EIS/MVM library. The quality of the
individual images were inspected, bad images discarded and the remaining used
to produce final image stacks in each passband, from which sources have been
extracted. Finally, the scientific quality of these final images and associated
catalogs was assessed qualitatively by visual inspection and quantitatively by
comparison of statistical measures derived from these data with those of other
authors as well as model predictions, and from direct comparison with the
results obtained from the reduction of the same dataset using an independent
(hands-on) software system. Finally to illustrate one application of this
survey, the results of a preliminary effort to identify sub-mJy radio sources
are reported. To the limiting magnitude reached in the R and I passbands the
success rate ranges from 66 to 81% (depending on the fields). These data are
publicly available at CDS.


title:
R-process Experimental Campaign at the National Superconducting
  Cyclotron Laboratory

abstract:
  A JINA/VISTARS r-process campaign was completed at the A1900 Fragment
Separator of the National Superconducting Cyclotron Laboratory in the fall of
2005. The purpose of the campaign was the measurement of the beta-decay
half-lives and beta-delayed neutron-emission probabilities of different unknown
neutron-rich nuclei participating in the r-process. Details of this campaign
will be presented.


title: Brownian Motion of Stars, Dust, and Invisible Matter

abstract:
  Treating the motion of a dust particle suspended in a liquid as a random
walk, Einstein in 1905 derived an equation describing the diffusion of the
particle's probability distribution in configuration space. Fokker and Planck
extended this work to describe the velocity distribution of the particles.
Their equation and its solutions have been applied to many problems in nature
starting with the motion of Brownian particles in a liquid. Chandrasekhar
derived the Fokker-Planck equation for stars and showed that long-range
gravitational encounters provide a drag force, dynamical friction, which is
important in the evolution of star clusters and the formation of galaxies. In
certain circumstances, Fokker-Planck evolution also describes the evolution of
dark (invisible) matter in the universe. In the early universe, the thermal
decoupling of weakly interacting massive particles from the plasma of
relativistic leptons and photons is governed by Fokker-Planck evolution. The
resulting dissipation imprints a minimum length scale for cosmic density
fluctuations. Still later, these density fluctuations produce stochastic
gravitational forces on the dark matter as it begins to cluster under gravity.
The latter example provides an exact derivation of the Fokker-Planck equation
without the usual assumption of Markovian dynamics.


title:
Kinematics, Substructure and Luminosity-weighted Dynamics of Six Nearby
  Galaxy Groups

abstract:
  We have redefined group membership of six southern galaxy groups in the local
universe (mean cz < 2000 km/s) based on new redshift measurements from our
recently acquired Anglo-Australian Telescope 2dF spectra. For each group, we
investigate member galaxy kinematics, substructure, luminosity functions and
luminosity-weighted dynamics. Our calculations confirm that the group sizes,
virial masses and luminosities cover the range expected for galaxy groups,
except that the luminosity of NGC 4038 is boosted by the central starburst
merger pair. We find that a combination of kinematical, substructural and
dynamical techniques can reliably distinguish loose, unvirialised groups from
compact, dynamically relaxed groups. Applying these techniques, we find that
Dorado, NGC 4038 and NGC 4697 are unvirialised, whereas NGC 681, NGC 1400 and
NGC 5084 are dynamically relaxed.


title:
Magnetically Dominated Strands of Cold Hydrogen in the Riegel-Crutcher
  Cloud

abstract:
  We present new high resolution (100 arcsec) neutral hydrogen (H I)
self-absorption images of the Riegel-Crutcher cloud obtained with the Australia
Telescope Compact Array and the Parkes Radio Telescope. The Riegel-Crutcher
cloud lies in the direction of the Galactic center at a distance of 125 +/- 25
pc. Our observations resolve the very large, nearby sheet of cold hydrogen into
a spectacular network of dozens of hair-like filaments. Individual filaments
are remarkably elongated, being up to 17 pc long with widths of less than ~0.1
pc. The strands are reasonably cold, with spin temperatures of 40 K and in many
places appearing to have optical depths larger than one. Comparing the H I
images with observations of stellar polarization we show that the filaments are
very well aligned with the ambient magnetic field. We argue that the structure
of the cloud has been determined by its magnetic field. In order for the cloud
to be magnetically dominated the magnetic field strength must be > 30
microGauss.


title: Magnetic field in supernova remnant SN 1987A

abstract:
  A nonlinear kinetic theory of cosmic ray (CR) acceleration in supernova
remnants is employed to investigate the properties of the remnant SN 1987A. It
is shown that a large downstream magnetic field ~10 mG is required to fit the
existing observational data. Such a strong field together with the strong shock
modification due to CR backreaction provides the steep and concave
radioemission spectrum and considerable synchrotron cooling of high energy
electrons which diminish their X-ray synchrotron flux below the observed
Chandra flux which has to be considered as an upper limit for nonthermal X-ray
emission. The expected gamma-ray energy flux at TeV-energies at the current
epoch is 2x10^{-13} erg/(cm^2 s).


title:
Time delay by primordial density fluctuations: its biasing effect on the
  observed mean curvature of the Universe

abstract:
  In this paper we specifically studied one aspect of foreground primordial
matter density perturbations: the relative gravitational time delay between a
pair of light paths converging towards an observer and originating from two
points on the last scattering surface separated by the physical scale of an
acoustic oscillation. It is found that time delay biases the size of acoustic
oscillations {\it systematically} towards smaller angles, or larger harmonic
numbers $\ell$, i.e. the mean geometry as revealed by CMB light becomes that of
an open Universe if $\Omega=1$. Since the effect is second order, its standard
deviation $\delta\ell/\ell \sim (\delta\Phi)^2$ where $(\delta\Phi)^2 \sim
10^{-9}$ is the normalization of the primordial matter spectrum $P(k)$, the
consequence is too numerically feeble to warrant a re-interpretion of WMAP
data. If, however, this normalization were increased to $\delta\Phi \gtrsim
0.01$ which is still well within the perturbation limit, the shift in the
positions of the acoustic peaks would have been substantial enough to implicate
inflationary $\Lambda$CDM cosmology. Thus $\Omega$ is not the only parameter
(and by deduction inflation cannot be the only mechanism) of relevance to the
understanding of {\it observed} large scale geometry. The physics that explains
why $\delta\Phi$ is so small also plays a crucial role, but since this is a
separate issue independent of inflation, might it be less artificial to look
for an alternative solution to the flatness problem altogether?


title:
The first XMM-Newton observations of the Soft Gamma-ray Repeater SGR
  1900+14

abstract:
  A ~50 ks XMM-Newton observation of SGR 1900+14 has been carried out in
September 2005, after almost three years during which no bursts were detected
from this soft gamma-ray repeater. The 0.8-10 keV spectrum was well fit by a
power law plus blackbody model with photon index 1.9+/-0.1, temperature
kT=0.47+/-0.02 keV and N_H = (2.12+/-0.08)x10^22 cm^-2, similar to previous
observations of this source. The flux was ~5x10^{-12} erg/cm2/s, a factor 2
dimmer than the typical value and the smallest ever seen from SGR 1900+14. The
long term fading of the persistent emission has been interrupted by the recent
burst reactivation of the source. A target of opportunity XMM-Newton
observation performed in April 2006 showed a flux ~15% higher. This variation
was not accompanied by significant changes in the spectrum, pulsed fraction and
light curve profile. We searched for emission and absorption lines in the
spectra of the two observations, with negative results and setting tight upper
limits of 50-200 eV (3 sigma), depending on the assumed line energy and width,
on the equivalent width of lines in the 1-9 keV range.


title: Measuring proper motions of isolated neutron stars with Chandra

abstract:
  The excellent spatial resolution of the Chandra observatory offers the
unprecedented possibility to measure proper motions at X-ray wavelength with
relatively high accuracy using as reference the background of extragalactic or
remote galactic X-ray sources. We took advantage of this capability to
constrain the proper motion of RX J0806.4-4123 and RX J0420.0-5022, two X-ray
bright and radio quiet isolated neutron stars (INSs) discovered by ROSAT and
lacking an optical counterpart. In this paper, we present results from a
preliminary analysis from which we derive 2 sigma upper limits of 76 mas/yr and
138 mas/yr on the proper motions of RX J0806.4-4123 and RX J0420.0-5022
respectively. We use these values together with those of other ROSAT discovered
INSs to constrain the origin, distance and evolutionary status of this
particular group of objects. We find that the tangential velocities of radio
quiet ROSAT neutron stars are probably consistent with those of 'normal'
pulsars. Their distribution on the sky and, for those having accurate proper
motion vectors, their possible birth places, all point to a local population,
probably created in the part of the Gould Belt nearest to the earth.


title: The Metallicity of Galaxy Disks: Infall versus Outflow

abstract:
  Both gas accretion (infall) and winds (outflow) change a galaxy's metallicity
and gas fraction, lowering the effective yield. Low effective yields in
galaxies with rotation speeds < 120 km/s have been widely interpreted as the
onset of SN-driven winds below a characteristic galaxy mass, but gas accretion
is also a viable explanation. However, calculations presented here prove: (1)
that metal-enriched outflows are the only mechanism that can significantly
reduce the effective yield, but only for gas-rich systems; (2) that it is
nearly impossible to reduce the effective yield of a gas-poor system, no matter
how much gas is lost or accreted; and (3) that any subsequent star formation
drives the effective yield back to the closed-box value. Thus, only gas-rich
systems with low star formation rates (such as dwarf irregulars) can produce
and maintain low effective yields, while massive gas-poor galaxies can never
show low effective yields, even after experiencing substantial infall and/or
outflow. The drop in effective yield seen in low mass galaxies is therefore
less likely to be due to the onset of SN-driven winds than to the galaxies'
surface densities falling entirely below the Kennicutt SF threshold. Additional
calculations confirm that the fraction of baryonic mass lost through winds
varies only weakly with galaxy mass, shows no sharp upturn at any mass scale,
and does not require that >15% of baryons have been lost by galaxies of any
mass. SN feedback is therefore unlikely to be effective for removing large
amounts of gas from low mass disk galaxies. In addition, the dependence between
metal-loss and galaxy mass is sufficiently weak that massive galaxies dominate
metal enrichment of the IGM. The calculations in this paper provide limiting
cases for any arbitrary chemical evolution history, as proven in an Appendix.


title: Specsim: The MIRI Medium Resolution Spectrometer Simulator

abstract:
  MIRI, the Mid-InfraRed Instrument, is one of four instruments being built for
the James Webb Space Telescope, and is developed jointly between an
EuropeanConsortium and the US. In this paper we present a software data
simulator for one of MIRI's four instruments: the Integral Field Unit (IFU)
Medium Resolution Spectrometer (MIRI-MRS), the first mid-infrared IFU
spectrograph, and one of the first IFUs to be used in a space mission. To give
the MIRI community a preview of the properties of the MIRI-MRS data products
before the telescope is operational, the Specsim tool has been developed to
model, in software, the operation of the spectrometer. Specsim generates
synthetic data frames approximating those which will be taken by the instrument
in orbit. The program models astronomical sources and generates detector frames
using the predicted and measured optical properties of the telescope and MIRI.
These frames can then be used to illustrate and inform a range of operational
activities, including data calibration strategies and the development and
testing of the data reduction software for the MIRI-MRS. Specsim will serve as
a means of communication between the many consortium members by providing a way
to easily illustrate the performance of the spectrometer under different
circumstances, tolerances of components and design scenarios.


title:
Establishing HZ43 A, Sirius B, and RX J185635-3754 as soft X-ray
  standards: a cross-calibration between the Chandra LETG+HRC-S, the EUVE
  spectrometer, and the ROSAT PSPC

abstract:
  The absolute calibration of space-borne instruments in the soft X-ray regime
rests strongly on model spectra of hot white dwarfs.
  We analyze the Chandra LETG+HRC-S observations of the white dwarfs HZ43 A and
Sirius B and of the neutron star RX J185635-3754 in order to resolve current
uncertainties in the soft X-ray spectral fluxes and photospheric parameters of
the three stars. We have obtained improved parameters for which fit the
observations from the optical to the soft X-ray regime. Our approach allows us
to quote their absolute spectral fluxes at selected wavelengths which may aid
the calibration of other space-borne instruments.


title: Dusty waves on a starry sea: the mid-infrared view of M31

abstract:
  Mid-infrared observations of the Andromeda galaxy, M31, obtained with the
Infrared Array Camera on board the Spitzer Space Telescope, are presented. The
image mosaics cover areas of approximate 3.7deg x 1.6deg and include the
satellite galaxies M32 and NGC 205. The appearance of M31 varies dramatically
in the different mid-infrared bands, from the smooth bulge and disk of the old
stellar population seen at 3.6um to the well-known '10 kpc ring' dominating the
8um image. The similarity of the 3.6um and optical isophotes and nearly
constant optical-mid-infrared color over the inner 400 arcsec confirms that
there is no significant extinction at optical wavelengths in M31's bulge. The
nuclear colors indicate the presence of dust but not an infrared-bright
nucleus. The integrated 8um non-stellar luminosity implies a star formation
rate of 0.4 Msun/yr, consistent with other indicators that show M31 to be a
quiescent galaxy.


title: GALEX UV Color Relations for Nearby Early-Type Galaxies

abstract:
  We use GALEX/optical photometry to construct color-color relationships for
early-type galaxies sorted by morphological type. We have matched objects in
the GALEX GR1 public release and the first IR1.1 internal release, with the RC3
early-type galaxies having a morphological type -5.5<T<-1.5 with mean error in
T<1.5, and mean error on (B-V)T<0.05. After visual inspection of each match, we
are left with 130 galaxies with a reliable GALEX pipeline photometry in the
far-UV and near-UV bands. This sample is divided into Ellipticals (-5.5<T<-3.5)
and Lenticulars (-3.5<T<-1.5). After correction for the Galactic extinction,
the color-color diagrams FUV-NUV vs. (B-V)_{Tc} are plotted for the two
subsamples. We find a tight anti-correlation between the FUV-NUV and (B-V)_{Tc}
colors for Ellipticals, the UV color getting bluer when the (B-V)_{Tc} get
redder. This relationship very likely is an extension of the color-metallicity
relationship into the GALEX NUV band. We suspect that the main source of the
correlation is metal line blanketing in the NUV band. The FUV-NUV vs B-V
correlation has larger scatter for lenticular galaxies; we speculate this
reflects the presence of low level star formation. If the latter objects (i.e.
those that are blue both in FUV-NUV and B-V) are interpreted as harboring
recent star formation activity, this would be the case for a few percent (~4%)
of Ellipticals and ~15% of Lenticulars; this would make about 10% of early-type
galaxies with residual star formation in our full sample of 130 early-type
galaxies. We also plot FUV-NUV vs. the Mg_2 index and central velocity
dispersion. We find a tight anti-correlation between FUV-NUV and the Mg_2
index(...).


title:
Processing of turbulence-layer wind speed with Generalized SCIDAR
  through wavelet analysis

abstract:
  We describe a new method involving wavelet transforms for deriving the wind
velocity associated with atmospheric turbulence layers from
  Generalized SCIDAR measurements. The algorithm analyses the cross-correlation
of a series of scintillation patterns separated by lapses of Dt,
  2Dt, 3Dt, 4Dt and 5Dt using wavelet transforms. Wavelet analysis provides the
position, direction and altitude of the different turbulence layers detected in
each cross-correlation. The comparison and consistency of the turbulent layer
displacements in consecutive cross-correlations allow the determination of
their velocities and avoid misidentifications associated with noise and/or
overlapping layers. To validate the algorithm, we have compared the velocity of
turbulence layers derived on four nights with the wind vertical profile
provided by balloon measurements. The software is fully automated and is able
to analyse huge amounts of Generalized SCIDAR measurements.


title:
Gravitational Waves from Compact Objects Accreting onto Active Galactic
  Nuclei

abstract:
  We consider a model in which massive stars form in a self-gravitating
accretion disk around an active galactic nucleus. These stars may evolve and
collapse to form compact objects on a time scale shorter than the accretion
time, thus producing an important family of sources for LISA. Assuming the
compact object formation/inspiral rate is proportional to the steady-state gas
accretion rate, we use the observed extra-galactic X-ray luminosity function to
estimate expected event rates and signal strengths. We find that these sources
will produce a continuous low-frequency background detectable by LISA if more
than >~ 1% of the accreted matter is in the form of compact objects. For
compact objects with m >~ 10 Msun, the last stages of the inspiral events
should be resolvable above a few mHz, at a rate of ~10-100 per year.


title: The effect of red noise on planetary transit detection

abstract:
  Since the discovery of short-period exoplanets a decade ago, photometric
surveys have been recognized as a feasible method to detect transiting hot
Jupiters. Many transit surveys are now under way, with instruments ranging from
10-cm cameras to the Hubble Space Telescope. However, the results of these
surveys have been much below the expected capacity, estimated in the dozens of
detections per year. One of the reasons is the presence of systematics (``red
noise'') in photometric time series. In general, yield predictions assume
uncorrelated noise (``white noise''). In this paper, we show that the effect of
red noise on the detection threshold and the expected yields cannot be
neglected in typical ground-based surveys. We develop a simple method to
determine the effect of red noise on photometric planetary transit detections.
This method can be applied to determine detection thresholds for transit
surveys. We show that the detection threshold in the presence of systematics
can be much higher than with the assumption of white noise, and obeys a
different dependence on magnitude, orbital period and the parameters of the
survey. Our method can also be used to estimate the significance level of a
planetary transit candidate (to select promising candidates for spectroscopic
follow-up). We apply our method to the OGLE planetary transit search, and show
that it provides a reliable description of the actual detectionthreshold with
real correlated noise. We point out in what way the presence of red noise could
be at least partly responsible for the dearth of transiting planet detections
from existing surveys, and examine some possible adaptations in survey planning
and strategy. Finally, we estimate the photometric stability necessary to the
detection of transiting ``hot Neptunes''.


title: Early spectral evolution of Nova Sgr 2004 (V5114 Sgr)

abstract:
  We present optical and near-infrared spectral evolution of the Galactic nova
V5114 Sgr (2004) during few months after the outburst. We use multi-band
photometry and line intensities derived from spectroscopy to put constrains on
the distance and the physical conditions of the ejecta of V5114 Sgr. The nova
showed a fast decline (t_2 \simeq 11 days) and spectral features of FeII
spectroscopic class. It reached M_V = -8.7 \pm 0.2 mag at maximum light, from
which we derive a distance of 7700 \pm 700 kpc and a distance from the galactic
plane of about 800 pc. Hydrogen and Oxygen mass of the ejecta are measured from
emission lines, leading to 10^{-6} and 10^{-7} M_\odot, respectively. We
compute the filling factor of the ejecta to be in the range 0.1 -- 10^{-3} . We
found the value of the filling factor to decrease with time. The same is also
observed in other novae, then giving support to the idea that nova shells are
not homogeneously filled in, rather being the material clumped in relatively
higher density blobs less affected by the general expanding motion of the
ejecta.


title:
INTEGRAL spectral variability study of the atoll 4U 1820-30: first
  detection of hard X-ray emission

abstract:
  We study the 4-200 keV spectral and temporal behaviour of the low mass X-ray
binary 4U 1820-30 with INTEGRAL during 2003-2005. This source as been observed
in both the soft (banana) and hard (island) spectral states. A high energy
tail, above 50 keV, in the hard state has been observed for the first time.
This places the source in the category of X-ray bursters showing high-energy
emission. The tail can be modeled as a soft power law component, with the
photon index of ~2.4, on top of thermal Comptonization emission from a plasma
with the electron temperature of kT_e~6 keV and optical depth of \tau~4.
Alternatively, but at a lower goodness of the fit, the hard-state broad band
spectrum can be accounted for by emission from a hybrid, thermal-nonthermal,
plasma. During this monitoring the source spent most of the time in the soft
state, usual for this source, and the >~4 keV spectra are represented by
thermal Comptonization with kT_e~3 keV and \tau~6-7.


title:
Gravitational Recoil from Binary Black Hole Mergers: the Close-Limit
  Approximation

abstract:
  [abridged] The coalescence of a binary black hole system is one of the main
sources of gravitational waves that present and future detectors will study.
Apart from the energy and angular momentum that these waves carry, for
unequal-mass binaries there is also a net flux of linear momentum that implies
a recoil velocity of the resulting final black hole in the opposite direction.
We present a computation of the recoil velocity based on the close-limit
approximation scheme, which gives excellent results for head-on and grazing
collisions of black holes when compared to full numerical relativistic
calculations. We obtain a maximum recoil velocity of ~ 64 km/s for a symmetric
mass ratio eta = M_1 M_2/(M_1+M_2)^2 ~ 0.19 and an initial proper separation of
4 M, where M is the total ADM mass of the system. This separation is the
maximum at which the close-limit approximation is expected to provide accurate
results. If we supplement this estimate with PN calculations up to the
innermost stable circular orbit, we obtain a lower bound for the recoil
velocity, with a maximum around 84 km/s. This is a lower bound because it
neglects the initial merger phase. We can however obtain a rough estimate by
using PN methods or the close-limit approximation. Since both methods are known
to overestimate the amount of radiation, we obtain in this way an upper bound
for the recoil with maxima in the range of 220-265 km/s. We also provide
non-linear fits to these estimated upper and lower bounds. These estimates are
subject to uncertainties related to issues such as the choice of initial data
and higher effects in perturbation theory. Nonetheless, our estimates are
consistent with previous results in the literature and suggest a narrower range
of possible recoil velocities.


title:
A Hard-to-Soft State Transition during A Luminosity Decline of Aquila
  X-1

abstract:
  We have discovered a spectral transition from the low/hard (LH) state to the
high/soft (HS) state when Aquila X-1 was {\em declining} in observations made
with the {\it Rossi X-Ray Timing Explorer (RXTE)}. The 2--200 keV energy flux
corresponding to the state transition is $1.1\times{10}^{-9} ergs cm^{-2}
s^{-1}$, an order of magnitude lower than observed in the past. The 2--200 keV
peak flux of the following HS state is $1.6\times{10}^{-9} ergs cm^{-2}
s^{-1}$. The relation between the luminosity of the hard-to-soft state
transition and the peak luminosity of the following HS state confirms the
linear relation found previously. This implies that the luminosity of the
hard-to-soft state transition is not determined solely by the mass accretion
rate, but appears to be determined by the peak luminosity of the soft X-ray
outburst. We also found that the LH-to-HS state transition occurred at a
luminosity similar to that of the corresponding HS-to-LH state transition,
i.e., there is no apparent hysteresis. These results provide additional
evidence that the mass in the accretion disk affects the luminosity of the
hard-to-soft state transition, and that the accretion flow that powers the LH
state is related to the accretion flow that powers the HS state at a later
time.


title: Can Cosmic Structure form without Dark Matter?

abstract:
  One of the prime pieces of evidence for dark matter is the observation of
large overdense regions in the universe. Since we know from the cosmic
microwave background that the regions that contained the most baryons when the
universe was ~400,000 years old were overdense by only one part in ten
thousand, perturbations had to have grown since then by a factor greater than
$(1+z_*)\simeq 1180$ where $z_*$ is the epoch of recombination. This enhanced
growth does not happen in general relativity, so dark matter is needed in the
standard theory. We show here that enhanced growth can occur in alternatives to
general relativity, in particular in Bekenstein's relativistic version of
MOdified Newtonian Dynamics (MOND). The vector field introduced in that theory
for a completely different reason plays a key role in generating the
instability that produces large cosmic structures today.


title: Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars

abstract:
  We discuss color selection of rare objects in a wide-field, multiband survey
spanning from the optical to the mid-infrared. Simple color criteria
simultaneously identify and distinguish two of the most sought after
astrophysical sources: the coolest brown dwarfs and the most distant quasars.
We present spectroscopically-confirmed examples of each class identified in the
IRAC Shallow Survey of the Bootes field of the NOAO Deep Wide-Field Survey. ISS
J142950.9+333012 is a T4.5 brown dwarf at a distance of approximately 42 pc,
and ISS J142738.5+331242 is a radio-loud quasar at redshift z=6.12. Our
selection criteria identify a total of four candidates over 8 square degrees of
the Bootes field. The other two candidates are both confirmed 5.5<z<6 quasars,
previously reported by Cool et al. (2006). We discuss the implications of these
discoveries and conclude that there are excellent prospects for extending such
searches to cooler brown dwarfs and higher redshift quasars.


title: Sensitivity of solar f-mode travel times to internal flows

abstract:
  We compute f-mode travel-time sensitivity kernels for flows. Using a
two-dimensional model, we show that it is important to account for several
systematic effects, such as the foreshortening and the projection of the
velocity vector onto the line of sight. Correcting for these effects is
necessary before any data inversion is attempted away from the center of the
solar disk.


title:
Two-component magnetohydrodynamical outflows around young stellar
  objects Interplay between stellar magnetospheric winds and disc-driven jets

abstract:
  We present the first-ever simulations of non-ideal magnetohydrodynamical
(MHD) stellar magnetospheric winds coupled with disc-driven jets where the
resistive and viscous accretion disc is self-consistently described. These
innovative MHD simulations are devoted to the study of the interplay between a
stellar wind (having different ejection mass rates) and an MHD disc-driven jet
embedding the stellar wind. The transmagnetosonic, collimated MHD outflows are
investigated numerically using the VAC code. We first investigate the various
angular momentum transports occurring in the magneto-viscous accretion disc. We
then analyze the modifications induced by the interaction between the two
components of the outflow. Our simulations show that the inner outflow is
accelerated from the central object's hot corona thanks to both the thermal
pressure and the Lorentz force. In our framework, the thermal acceleration is
sustained by the heating produced by the dissipated magnetic energy due to the
turbulence. Conversely, the outflow launched from the resistive accretion disc
is mainly accelerated by the magneto-centrifugal force.}{The simulations show
that the MHD disc-driven outflow extracts angular momentum more efficiently
than do viscous effects in near-equipartition, thin-magnetized discs where
turbulence is fully developed. We also show that, when a dense inner stellar
wind occurs, the resulting disc-driven jet has a different structure, namely a
magnetic structure where poloidal magnetic field lines are more inclined
because of the pressure caused by the stellar wind. This modification leads to
both an enhanced mass-ejection rate in the disc-driven jet and a larger radial
extension that is in better agreement with the observations, besides being more
consistent.


title: Searching for a Stochastic Background of Gravitational Waves with LIGO

abstract:
  The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
$\Omega_{\rm GW} < 6.5 \times 10^{-5}$. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.


title:
The spin and shape of dark matter haloes in the Millennium simulation of
  a LambdaCDM universe

abstract:
  We investigate the spins and shapes of over a million dark matter haloes
identified at z=0 in the Millennium simulation. Our sample spans halo masses
ranging from dwarf galaxies to rich galaxy clusters. The very large dynamic
range of this simulation enables the distribution of spins and shapes and their
variation with halo mass and environment to be characterised with unprecedented
precision. We compare results for haloes identified using different algorithms,
including a novel one based on the branches of the halo merger trees. We
investigate (and remove) biases in the estimate of angular momentum introduced
by both the algorithms themselves and by numerical effects. We find that for
this many objects, the traditional lognormal function is no longer an adequate
description of the distribution of the dimensionless spin parameter lambda, and
we provide a different function that gives a better fit. The variation of spin
with halo mass is weak but detectable, although the trend depends strongly on
the halo definition used. The haloes exhibit a range of shapes, with a
preference for prolateness over oblateness. More massive haloes tend to be less
spherical and more prolate. We find that the more spherical haloes have spin in
the median, and those closest to spherical have a spin independent of mass. The
most massive have a spin independent of shape. The majority of haloes have
their angular momentum vector aligned with their minor axis and perpendicular
to their major axis. We find that higher tend to be more clustered, with a
stronger effect for more massive haloes. (abridged)


title: Hydrodynamics of Supernova Evolution in the Winds of Massive Stars

abstract:
  Core-Collapse supernovae arise from stars greater than 8 $\msun$. These stars
lose a considerable amount of mass during their lifetime, which accumulates
around the star forming wind-blown bubbles. Upon the death of the star in a
spectacular explosion, the resulting SN shock wave will interact with this
modified medium. We study the evolution of the shock wave, and investigate the
properties of this interaction. We concentrate on the evolution of the SN shock
wave in the medium around a 35 solar mass star. We discuss the hydrodynamics of
the resulting interaction, the formation and growth of instabilities, and
deviations from sphericity.


title:
AGN and Starburst Classification from Spitzer Mid-Infrared Spectra for
  High Redshift SWIRE Sources

abstract:
  Spectra have been obtained with the Infrared Spectrograph (IRS) on the
Spitzer Space Telescope for 20 sources in the Lockman Hole field of the SWIRE
survey. The sample is divided between sources with indicators of an obscured
AGN, based primarily on X-ray detections of optically-faint sources, and
sources with indicators of a starburst, based on optical and near-infrared
spectral energy distributions (SEDs) which show a luminosity peak from stellar
photospheric emission. Ten of the 11 AGN sources have IRS spectra which show
silicate absorption or are power laws; only one AGN source shows PAH emission
features. All 9 of the sources showing starburst SEDs in the near-infrared show
PAH emission features in the IRS spectra. Redshifts are determined from the IRS
spectra for all 9 starbursts (1.0 < z < 1.9) and 8 of the 11 AGN (0.6 < z <
2.5). Classification as AGN because of an X-ray detection, the classification
as AGN or starburst derived from the photometric SED, and the IRS spectroscopic
classification as AGN (silicate absorption) or starburst (PAH emission) are all
consistent in 18 of 20 sources. The surface density for starbursts which are
most luminous in the mid-infrared is less than that for the most luminous AGN
within the redshift interval 1.7 < z < 1.9. This result implies that
mid-infrared source counts at high redshift are dominated by AGN for
f(24micron) > 1.0 mJy.


title: The concentration-velocity dispersion relation in galaxy groups

abstract:
  Based on results from cold dark matter N-body simulations we develop a
dynamical model for the evolution of subhaloes within host haloes of galaxy
groups. Only subhaloes more massive than 5 times 10^8 M_{sol} at the time of
accretion are examined because they are massive enough to possibly host
luminous galaxies. As they orbit within a growing host potential the subhaloes
are subject to tidal stripping and dynamical friction. We consider groups of
equal mass (M_{vir} = 3.9 times 10^{13} M_{sol}) at redshift z=0 but with
different concentrations associated with different formation times. We
investigate the variation of subhaloe (or satellite galaxy) velocity dispersion
with host concentration and/or formation time. In agreement with the Jeans
equation the velocity dispersion of subhaloes increases with the host
concentration. Between concentrations ~5 and ~20 the subhaloe velocity
dispersions increase by ~25 per cent. By applying a simplified tidal disruption
criterion, i.e. rejection of all subhaloes with a tidal truncation radius below
3 kpc at z=0, the central velocity dispersion of 'surviving' subhaloes
increases substantially for all concentrations. The enhanced central velocity
dispersion among surviving subhaloes is caused by a lack of slow tangential
motions. Additionally, we present a fitting formula for the velocity anisotropy
parameter \beta(r) which does not depend on concentration if the group-centric
distances are scaled by r_s, the characteristic radius of the NFW-profile.


title: The impact and rotational lightcurves of Comet 9P/Tempel 1

abstract:
  UVES and HIRES high-resolution spectra of comet 9P/Tempel 1 are used to
investigate the impact and rotational light curves of various species with a
view toward building a simple model of the distribution and activity of the
sources. The emission by OH, NH, CN, C3, CH, C2, NH2 and OI, are analyzed, as
well as the light scattered by the dust. It is found that a simple model
reproduces fairly well the impact lightcurves of all species combining the
production of the observed molecules and the expansion of the material
throughout the slit. The rotational light curve for each species is explained
in terms of a single model with three sources.


title: Secular evolution in galaxies

abstract:
  New observations in favour of a significant role of secular evolution are
reviewed: central star formation boosted in pseudo-bulge barred galaxies,
relations between bulge and disk, evidence for rejuvenated bulges. Numerical
simulations have shown that secular evolution can occur through a cycle of bar
formation and destruction, in which the gas plays a major role. Since bars are
weakened or destroyed in gaseous disks, the high frequency of bars observed
today requires external cold gas accretion, to replenish the disk and allow a
new bar formation. The rate of gas accretion from external filaments is
compatible with what is observed in cosmological simulations.


title:
Empirical Models for Dark Matter Halos. II. Inner profile slopes,
  dynamical profiles, and rho/sigma^3

abstract:
  We have recently shown that both the Prugniel-Simien model and Sersic's
function (hereafter referred to as the Einasto model when applied to internal
density profiles) describe simulated dark matter halos better than an NFW-like
model with equal number of parameters. Here we provide analytical expressions
for the logarithmic slopes of these models, and compare them with data from
real galaxies. Depending on the Einasto parameters of the dark matter halo, one
can expect an extrapolated, inner (0.01--1 kpc), logarithmic profile slope
ranging from -0.2 to -1.5, with a typical value at 0.1 kpc around -0.7.
Application of this (better fitting) model therefore alleviates some of the
past disagreement with observations on this issue. We additionally provide
useful expressions for the concentration and assorted scale radii: r_s, r_{-2},
r_e, R_e, r_virial, and r_max -- the radius where the circular velocity profile
has its maximum value. We also present the circular velocity profiles and the
radial behavior of rho(r)/sigma(r)^3 for both the Einasto and Prugniel-Simien
models. We find this representation of the phase-space density profile to be
well approximated by a power-law with slope slightly shallower than -2 near
r=r_{-2}.


title:
Empirical Models for Dark Matter Halos. III. The Kormendy relation and
  the log(rho_e)-log(R_e) relation

abstract:
  We have recently shown that the 3-parameter density-profile model from
Prugniel & Simien provides a better fit to simulated, galaxy- and
cluster-sized, dark matter halos than an NFW-like model with arbitrary inner
profile slope gamma (Paper I). By construction, the parameters of the
Prugniel-Simien model equate to those of the Sersic R^{1/n} function fitted to
the projected distribution. Using the Prugniel-Simien model, we are therefore
able to show that the location of simulated (10^{12} M_sun) galaxy-sized dark
matter halos in the <mu>_e-log(R_e) diagram coincides with that of brightest
cluster galaxies, i.e., the dark matter halos appear consistent with the
Kormendy relation defined by luminous elliptical galaxies. These objects are
also seen to define the new, and equally strong, relation log(rho_e) = 0.5 -
2.5log(R_e), in which rho_e is the internal density at r=R_e. Simulated
(10^{14.5} M_sun) cluster-sized dark matter halos and the gas component of real
galaxy clusters follow the relation log(rho_e) = 2.5[1 - log(R_e)]. Given the
shapes of the various density profiles, we are able to conclude that while
dwarf elliptical galaxies and galaxy clusters can have dark matter halos with
effective radii of comparable size to the effective radii of their baryonic
component, luminous elliptical galaxies can not. For increasingly large
elliptical galaxies, with increasingly large profile shapes `n', to be dark
matter dominated at large radii requires dark matter halos with increasingly
large effective radii compared to the effective radii of their stellar
component.


title:
Mid-InfraRed imaging of the circumstellar dust around three Herbig Ae
  stars : HD135344, CQTau, HD163296

abstract:
  Planet formation has been known for many years to be tied to the spatial
distribution of gas and dust in disks around young stars. To constrain planet
formation models, imaging observations of protoplanetary disks are required. In
this framework, we have undertaken a mid-infrared imaging survey of Herbig Ae
stars, which are pre-main sequence stars of intermediate mass still surrounded
by a large amount of circumstellar material. The observations were made at a
wavelength of 20.5 $\mu$m with the CAMIRAS camera mounted at the Cassegrain
focus of the Canada France Hawaii Telescope.
  We report the observations of three stars, HD135344, CQTau and HD163296. The
circumstellar material around the three objects is spatially resolved. The
extensions feature a disk like shape. The images provide direct information on
two key parameters of the disk : its inclination and its outer radius. The
outer radius is found to be quite different from the one deduced from disk
models only constrained by fitting the Spectral Energy Distribution of the
object. Other parameters of the disk, such as flaring, dust mass have been
deduced from fitting both the observed extension and the spectral energy
distribution with sophisticated disk models.
  Our results show how important imaging data are to tighten constraints on the
disk model parameters.


title: Gas flows and bars in galaxies

abstract:
  Dynamical evolution of spiral galaxies is strongly dependent on
non-axisymmetric patterns that develop from gravitational instabilities, either
spontaneously or externally triggered.
  Some evolutionary sequences are described through which a galaxy could
possibly concentrate mass and build bulges, how external gas accretion from
cosmic filaments could be funneled to the galaxy disks, and intermittently
driven to the galaxy center, to form nuclear starbursts and fuel an active
nucleus. The frequency of both bars and lopsidedness can be used to constrain
the gas accretion rate.


title:
Influence of the frictional heating on the wind line-profiles of SMC
  stars

abstract:
  We study the influence of the frictional heating on the wind line-profiles of
SMC stars. For this purpose we use our NLTE wind code to obtain consistent
occupation numbers of studied levels and our radiative transfer code to solve
the radiative transfer equation in moving media. We compare predicted wind line
profiles calculated with and without frictional heating for a low-luminosity
SMC star with a weak wind and discuss the relevance of frictional heating as a
solution of a "weak-wind problem" for this star.


title:
Ellipsoidal Variability and Long Secondary Periods in MACHO Red Giant
  Stars

abstract:
  We present a period-luminosity-amplitude analysis of 5899 red giant and
binary stars in the Large Magellanic Cloud, using publicly available
observations of the MACHO project. For each star, we determined new periods,
which were double-checked in order to exclude aliases and false periods. The
period-luminosity relations confirm the existence of a short-period,
small-amplitude P-L sequence at periods shortward of Seq. A. We point out that
the widely accepted sequence of eclipsing binaries between Seqs. C and D, known
as Seq. E, does not exist. The correct position for Seq. E is at periods a
factor of two greater, and the few stars genuinely lying between Seq. C and D
are under-luminous Mira variables, presumably enshrouded in dust. The true Seq.
E overlaps with the sequence of Long Secondary Periods (Seq. D) and their P-L
relation is well described by a simple model assuming Roche geometry. The
amplitudes of LSPs have properties that are different from both the pulsations
and the ellipsoidal variations, but they are more similar to the former than
the latter, arguing for pulsation rather than binarity as the origin of the LSP
phenomenon.


title:
Rapid interstellar scintillation of PKS B1257-326: two-station pattern
  time delays and constraints on scattering and microarcsecond source structure

abstract:
  We report measurements of time delays of up to 8 minutes in the centimeter
wavelength variability patterns of the intra-hour scintillating quasar PKS
1257-326 as observed between the VLA and the ATCA on three separate epochs.
These time delays confirm interstellar scintillation as the mechanism
responsible for the rapid variability, at the same time effectively ruling out
the coexistence of intrinsic intra-hour variability in this source. The time
delays are combined with measurements of the annual variation in variability
timescale exhibited by this source to determine the characteristic length scale
and anisotropy of the quasar's intensity scintillation pattern, as well as
attempting to fit for the bulk velocity of the scattering plasma responsible
for the scintillation. We find evidence for anisotropic scattering and highly
elongated scintillation patterns at both 4.9 and 8.5 GHz, with an axial ratio >
10:1, extended in a northwest direction on the sky. The characteristic scale of
the scintillation pattern along its minor axis is well determined, but the high
anisotropy leads to degenerate solutions for the scintillation velocity. The
decorrelation of the pattern over the baseline gives an estimate of the major
axis length scale of the scintillation pattern. We derive an upper limit on the
distance to the scattering plasma of no more than 10 pc.


title:
Time-dependent hydrogen ionisation in the solar chromosphere. I: Methods
  and first results

abstract:
  An approximate method for solving the rate equations for the hydrogen
populations was extended and implemented in the three-dimensional radiation
(magneto-)hydrodynamics code CO5BOLD. The method is based on a model atom with
six energy levels and fixed radiative rates. It has been tested extensively in
one-dimensional simulations. The extended method has been used to create a
three-dimensional model that extends from the upper convection zone to the
chromosphere. The ionisation degree of hydrogen in our time-dependent
simulation is comparable to the corresponding equilibrium value up to 500 km
above optical depth unity. Above this height, the non-equilibrium ionisation
degree is fairly constant over time and space, and tends to be at a value set
by hot propagating shock waves. The hydrogen level populations and electron
density are much more constant than the corresponding values for statistical
equilibrium, too. In contrast, the equilibrium ionisation degree varies by more
than 20 orders of magnitude between hot, shocked regions and cool, non-shocked
regions. The simulation shows for the first time in 3D that the chromospheric
hydrogen ionisation degree and electron density cannot be calculated in
equilibrium. Our simulation can provide realistic values of those quantities
for detailed radiative transfer computations.


title: Exploration of the $\ps-\pb$ Relation for Wind-Fed X-Ray Pulsars

abstract:
  We have investigated the relation between the orbital periods ($\pb$) and the
spin periods ($\ps$) of wind-fed X-ray pulsars in high-mass X-ray binaries
(HMXBs), based on population synthesis calculations of the spin evolution of
neutron stars during the pre-HMXB stage. We show that most of the neutron stars
either have steady accretion or still reside in the radio pulsar phase when the
donor star starts evolving off the main sequence. In the former case the values
of $\ps$ can be decelerated to be $\sim 10^2-10^3$ s depending on $\pb$. We
briefly discuss the possible origin of the $\ps-\pb$ correlation in Be/X-ray
binaries, and the existence of HMXBs with main sequence donors. We have also
investigated the evolution of the inclination angle between the magnetic and
spin axes of neutron stars in a massive binary, suggesting secular alignment of
the magnetic and spin axes during their evolution.


title: Radial solitary waves in periodic variable stars

abstract:
  It is shown that the oscillations of brightness in classical Cepheids and
other 'pulsating' variable stars are caused rather by the passing of radial
solitary waves through the photosphere of a star, than by pulsations of a star.
Radial solitary waves also determine the oscillations of brightness in some
other types of periodic variable stars ordinary not considered as pulsating
stars.


title:
Young stellar populations in early-type galaxies in the Sloan Digital
  Sky Survey

abstract:
  We use a purely data-driven rectified factor analysis to identify early-type
galaxies with recent star formation in DR4 of the SDSS Spectroscopic Catalogue.
We compare the spectra and environment of these galaxies with `normal'
early-types, and a sample of independently selected E+A galaxies. We calculate
the projected local galaxy surface density (Sigma_5 and Sigma_10) for each
galaxy in our sample, and find that the dependence, on projected local density,
of the properties of E+As is not significantly different from that of
early-types with young stellar populations, dropping off rapidly towards denser
environments, and flattening off at densities < 0.1-0.3 Mpc^-2. The dearth of
E+A galaxies in dense environments confirms that E+As are most likely the
products of galaxy-galaxy merging or interactions, rather than star-forming
galaxies whose star formation has been quenched by processes unique to dense
environments. We see a tentative peak in the number of E+A galaxies at Sigma_10
\~ 0.1-0.3 Mpc^-2, which may represent the local galaxy density at which the
rate of galaxy-galaxy merging or interaction rate peaks. Analysis of the
spectra of our early-types with young stellar populations suggests that they
have a stellar component dominated by F stars, ~ 1-4 Gyr old, together with a
mature, metal-rich population characteristic of `typical' early-types. The
young stars represent > 10% of the stellar mass in these galaxies. This,
together with the similarity of the environments in which this `E+F' population
and the E+A galaxy sample are found, suggests that E+F galaxies used to be E+A
galaxies, but have evolved by a further ~ one to a few Gyr. Our factor analysis
is sensitive enough to identify this hidden population. (Abridged)


title:
Galaxy clusters at 0.6 < z < 1.4 in the UKIDSS Ultra Deep Survey Early
  Data Release

abstract:
  We present the first cluster catalogue extracted from the UKIRT Infrared Deep
Sky Survey Early Data Release. The catalogue is created using UKIDSS Ultra Deep
Survey infrared J and K data combined with 3.6 micro-m and 4.5 micro-m Spitzer
bands and optical BVRi'z' imaging from the Subaru Telescope over 0.5 square
degrees in the Subaru XMM-Newton Deep Field. We have created a new
cluster-detection algorithm, based on the Friends-Of-Friends and Voronoi
Tessellation methods, which utilises probability distribution functions derived
from a photometric redshift analysis. We employ mock catalogues to understand
the selection effects and contamination associated with the algorithm. The
cluster catalogue contains 13 clusters at redshifts 0.61 <= z <= 1.39 with
luminosities 10 L* <~ L_tot <~ 50 L*, corresponding to masses 5 x 10^13 M_sun
<~ M_cluster <~ 3 x 10^14 M_sun for (M/M_sun) / (L/L_sun) = 75h. The measured
sky surface density of ~ 10 deg^-2 for high-redshift (z=0.5-1.5), massive
(>10^14 M_sun) clusters is precisely in line with theoretical predictions
presented by Kneissl et al. (2001).


title:
Local stability of self-gravitating fluid disks made of two components
  in relative motion

abstract:
  Context. We consider a simple self-gravitating disk, made of two fluid
components characterized by different effective thermal speeds and interacting
with one another only through gravity; two-component models of this type have
often been considered in order to estimate the impact of the cold interstellar
medium on gravitational instabilities in star-dominated galaxy disks.
  Aims. This simple model allows us to produce a unified description of
instabilities in non-viscous self-gravitating disks, some originating from
Jeans collapse, and others from the relative motion between the two components.
In particular, the model suggests that the small streaming velocity between the
two components associated with the so-called asymmetric drift may be the origin
of instability for suitable non-axisymmetric perturbations.
  Methods. The result is obtained by examining the properties of a local,
linear dispersion relation for tightly wound density waves in such
two-component model. The parameters characterizing the equilibrium model and
the related dispersion relation allow us to recover as natural limits the
cases, known in the literature, in which the relative drift between the two
components is ignored.
  Results. Dynamically, the instability is similar to (although gentler than)
that known to affect counter-rotating disks. However, in contrast to the
instability induced by counter-rotation, which is a relatively rare phenomenon,
the mechanism discussed in this paper is likely to be rather common in nature.
  Conclusions. We briefly indicate some consequences of the instability on the
evolution of galaxy disks and possible applications to other astrophysical
systems, in particular to protostellar disks and accretion disks.


title: Torsional Oscillations of Relativistic Stars with Dipole Magnetic Fields

abstract:
  We present the formalism and numerical results for torsional oscillations of
relativistic stars endowed with a strong dipole magnetic field. We do a
systematic search of parameter space by computing torsional mode frequencies
for various values of the harmonic index $\ell$ and for various overtones,
using an extended sample of models of compact stars, varying in mass,
high-density equation of state and crust model. We show that torsional mode
frequencies are sensitive to the crust model if the high-density equation of
state is very stiff. In addition, torsional mode frequencies are drastically
affected by a dipole magnetic field, if the latter has a strength exceeding
roughly $10^{15}$G and we find that the magnetic field effects are sensitive to
the adopted crust model. Using our extended numerical results we derive
empirical relations for the effect of the magnetic field on torsional modes as
well as for the crust thickness. We compare our numerical results to observed
frequencies in SGRs and find that certain high-density EoS and mass values are
favored over others in the non-magnetized limit. On the other hand, if the
magnetic field is strong, then its effect has to be taken into account in
attempts to formulate a theory of asteroseismology for magnetars.