title:
Multiwavelength Observations of the Blazar Mrk 421 in December 2002 and
  January 2003

abstract:
  We report on a multiwavelength campaign on the TeV gamma-ray blazar Markarian
(Mrk) 421 performed during December 2002 and January 2003. These target of
opportunity observations were initiated by the detection of X-ray and TeV
gamma-ray flares with the All Sky Monitor (ASM) on board the Rossi X-ray Timing
Explorer (RXTE) and the 10 m Whipple gamma-ray telescope.The campaign included
observational coverage in the radio (University of Michigan Radio Astronomy
Observatory), optical (Boltwood, La Palma KVA 0.6m, WIYN 0.9m), X-ray (RXTE
pointed telescopes), and TeV gamma-ray (Whipple and HEGRA) bands.
  At TeV energies, the observations revealed several flares at intermediate
flux levels, peaking between 1 and 1.5 times the flux from the Crab Nebula.
While the time averaged spectrum can be fitted with a single power law of
photon index Gamma =2.8, we find some evidence for spectral variability.
Confirming earlier results, the campaign reveals a rather loose correlation
between the X-ray and TeV gamma-ray fluxes. In one case, a very strong X-ray
flare is not accompanied by a comparable TeV gamma-ray flare. Although the
source flux was variable in the optical and radio bands, the sparse sampling of
the optical and radio light curves does not allow us to study the correlation
properties in detail.
  We present a simple analysis of the data with a synchrotron-self Compton
model, emphasizing that models with very high Doppler factors and low magnetic
fields can describe the data.


title: Nonlinear Criterion for the Stability of Molecular Clouds

abstract:
  Dynamically significant magnetic fields are routinely observed in molecular
clouds, with mass-to-flux ratio lambda = (2 pi sqrt{G}) (Sigma/B) ~ 1 (here
Sigma is the total column density and B is the field strength). It is widely
believed that ``subcritical'' clouds with lambda < 1 cannot collapse, based on
virial arguments by Mestel and Spitzer and a linear stability analysis by
Nakano and Nakamura. Here we confirm, using high resolution numerical models
that begin with a strongly supersonic velocity dispersion, that this criterion
is a fully nonlinear stability condition. All the high-resolution models with
lambda <= 0.95 form ``Spitzer sheets'' but collapse no further. All models with
lambda >= 1.02 collapse to the maximum numerically resolvable density. We also
investigate other factors determining the collapse time for supercritical
models. We show that there is a strong stochastic element in the collapse time:
models that differ only in details of their initial conditions can have
collapse times that vary by as much as a factor of 3. The collapse time cannot
be determined from just the velocity dispersion; it depends also on its
distribution. Finally, we discuss the astrophysical implications of our
results.


title:
Detection with RHESSI of high frequency X-ray oscillations in the tail
  of the 2004 hyperflare from SGR 1806-20

abstract:
  The recent discovery of high frequency oscillations in giant flares from SGR
1806-20 and SGR 1900+14 may be the first direct detection of vibrations in a
neutron star crust. If this interpretation is correct it offers a novel means
of testing the neutron star equation of state, crustal breaking strain, and
magnetic field configuration. Using timing data from RHESSI, we have confirmed
the detection of a 92.5 Hz Quasi-Periodic Oscillation (QPO) in the tail of the
SGR 1806-20 giant flare. We also find another, stronger, QPO at higher
energies, at 626.5 Hz. Both QPOs are visible only at particular (but different)
rotational phases, implying an association with a specific area of the neutron
star surface or magnetosphere. At lower frequencies we confirm the detection of
an 18 Hz QPO, at the same rotational phase as the 92.5 Hz QPO, and report the
additional presence of a broad 26 Hz QPO. We are however unable to make a
robust confirmation of the presence of a 30 Hz QPO, despite higher countrates.
We discuss our results in the light of neutron star vibration models.


title: Linear Cosmological Structure Limits on Warm Dark Matter

abstract:
  I consider constraints from observations on a cutoff scale in clustering due
to free streaming of the dark matter in a warm dark matter cosmological model
with a cosmological constant. The limits are derived in the framework of a
sterile neutrino warm dark matter universe, but can be applied to gravitinos
and other models with small scale suppression in the linear matter power
spectrum. With freedom in all cosmological parameters including the free
streaming scale of the sterile neutrino dark matter, limits are derived using
observations of the fluctuations in the cosmic microwave background, the 3D
clustering of galaxies and 1D clustering of gas in the Lyman-alpha (Ly-alpha)
forest in the Sloan Digital Sky Survey (SDSS), as well as the Ly-alpha forest
in high-resolution spectroscopic observations. In the most conservative case,
using only the SDSS main-galaxy 3D power-spectrum shape, the limit is m_s >
0.11 keV; including the SDSS Ly-alpha forest, this limit improves to m_s > 1.7
keV. More stringent constraints may be placed from the inferred matter power
spectrum from high-resolution Ly-alpha forest observations, which has
significant systematic uncertainties; in this case, the limit improves to m_s >
3.0 keV (all at 95% CL).


title: On the Relation Between Hot Jupiters & the Roche Limit

abstract:
  Many of the known extrasolar planets are ``hot Jupiters,'' giant planets with
orbital periods of just a few days. We use the observed distribution of hot
Jupiters to constrain the location of its inner edge in the mass--period
diagram. If we assume a slope corresponding to the classical Roche limit, then
we find that the edge corresponds to a separation close to_twice_ the Roche
limit, as expected if the planets started on highly eccentric orbits that were
later circularized. In contrast, any migration scenario would predict an inner
edge right at the Roche limit, which applies to planets approaching on nearly
circular orbits. However, the current sample of hot Jupiters is not sufficient
to provide a precise constraint simultaneously on both the location and slope
of the inner edge.


title: Observational confirmation of the Sun's CNO cycle

abstract:
  Gamma rays from a solar flare in Active Region 10039 on 23 July 2002 with the
RHESSI spacecraft spectrometer indicate that the CNO cycle occurs at the solar
surface, in electrical discharges along closed magnetic loops. At the two feet
of the loop, H ions are accelerated to energy levels that surpass Coulomb
barriers for the C-12[H-1, gamma]N-13 and N-14[H-1, gamma]O-15 reactions. First
x-rays appear along the discharge path. Next annihilation of positrons from
N-13 and O-15 [half-life = 10 m and 2 m] produce bright spots of 0.511 MeV
gammas at the loop feet. As C-13 increases from positron decay of N-13, the
C-13[He-4, n]O-16 reaction produces neutrons and then the 2.2 MeV emission line
appears from n-capture on H-1. These results suggest that the CNO cycle changed
the N-15/N-14 ratio in the solar wind and at the solar surface over geologic
time, and this ratio may contain an important historical record of climate
changes related to sunspot activity.


title:
Improving the Efficiency of Markov Chain Monte Carlo for Analyzing the
  Orbits of Extrasolar Planets

abstract:
  Precise radial velocity measurements have led to the discovery of ~170
extrasolar planetary systems. Understanding the uncertainties in the orbital
solutions will become increasingly important as the discovery space for
extrasolar planets shifts to planets with smaller masses and longer orbital
periods. The method of Markov chain Monte Carlo (MCMC) provides a rigorous
method for quantifying the uncertainties in orbital parameters in a Bayesian
framework (Ford 2005a). The main practical challenge for the general
application of MCMC is the need to construct Markov chains which quickly
converge. The rate of convergence is very sensitive to the choice of the
candidate transition probability distribution function (CTPDF). Here we explain
one simple method for generating alternative CTPDFs which can significantly
speed convergence by one to three orders of magnitude. We have numerically
tested dozens of CTPDFs with simulated radial velocity data sets to identify
those which perform well for different types of orbits and suggest a set of
CTPDFs for general application. Additionally, we introduce other refinements to
the MCMC algorithm for radial velocity planets, including an improved treatment
of the uncertainties in the radial velocity observations, an algorithm for
automatically choosing step sizes, an algorithm for automatically determining
reasonable stopping times, and the use of importance sampling for including the
dynamical evolution of multiple planet systems. Together, these improvements
make it practical to apply MCMC to multiple planet systems. We demonstrate the
improvements in efficiency by analyzing a variety of extrasolar planetary
systems.


title: What do Multiple Planet Systems Teach us about Planet Formation?

abstract:
  For centuries, our knowledge of planetary systems and ideas about planet
formation were based on a single example, our solar system. During the last
thirteen years, the discovery of ~170 planetary systems has ushered in a new
era for astronomy. I review the surprising properties of extrasolar planetary
systems and discuss how they are reshaping theories of planet formation. I
focus on how multiple planet systems constrain the mechanisms proposed to
explain the large eccentricities typical of extrasolar planets. I suggest that
strong planet-planet scattering is common and most planetary systems underwent
a phase of large eccentricities. I propose that a planetary system's final
eccentricities may be strongly influenced by how much mass remains in a
planetesimal disk after the last strong planet-planet scattering event.


title: Newtonian versus relativistic nonlinear cosmology

abstract:
  Both for the background world model and its linear perturbations Newtonian
cosmology coincides with the zero-pressure limits of relativistic cosmology.
However, such successes in Newtonian cosmology are not purely based on Newton's
gravity, but are rather guided ones by previously known results in Einstein's
theory. The action-at-a-distance nature of Newton's gravity requires further
verification from Einstein's theory for its use in the large-scale nonlinear
regimes. We study the domain of validity of the Newtonian cosmology by
investigating weakly nonlinear regimes in relativistic cosmology assuming a
zero-pressure and irrotational fluid. We show that, first, if we ignore the
coupling with gravitational waves the Newtonian cosmology is exactly valid even
to the second order in perturbation. Second, the pure relativistic correction
terms start appearing from the third order. Third, the correction terms are
independent of the horizon scale and are quite small in the large-scale near
the horizon. These conclusions are based on our special (and proper) choice of
variables and gauge conditions. In a complementary situation where the system
is weakly relativistic but fully nonlinear (thus, far inside the horizon) we
can employ the post-Newtonian approximation. We also show that in the
large-scale structures the post-Newtonian effects are quite small. As a
consequence, now we can rely on the Newtonian gravity in analyzing the
evolution of nonlinear large-scale structures even near the horizon volume.


title: Location of the solar dynamo and near-surface shear

abstract:
  The location of the solar dynamo is discussed in the context of new insights
into the theory of nonlinear turbulent dynamos. It is argued that, from a
dynamo-theoretic point of view, the bottom of the convection zone is not a
likely location and that the solar dynamo may be distributed over the
convection zone. The near surface shear layer produces not only east-west field
alignment, but it also helps the dynamo disposing of its excess small scale
magnetic helicity.


title: Distributed versus tachocline dynamos

abstract:
  Arguments are presented in favor of the idea that the solar dynamo may
operate not just at the bottom of the convection zone, i.e. in the tachocline,
but it may operate in a more distributed fashion in the entire convection zone.
The near-surface shear layer is likely to play an important role in this
scenario.


title: Connection between active longitudes and magnetic helicity

abstract:
  A two-dimensional mean field dynamo model is solved where magnetic helicity
conservation is fully included. The model has a negative radial velocity
gradient giving rise to equatorward migration of magnetic activity patterns. In
addition the model develops longitudinal variability with activity patches
travelling in longitude. These patches may be associated with active
longitudes.


title:
The relation between circular velocity and central velocity dispersion
  in low surface brightness galaxies

abstract:
  We analyzed a sample of high and low surface brightness (HSB and LSB) disc
galaxies and elliptical galaxies to investigate the correlation between the
circular velocity (Vc) and the central velocity dispersion (sigma). We better
defined the previous Vc-sigma correlation for HSB and elliptical galaxies,
especially at the lower end of the sigma values. Elliptical galaxies with Vc
based on dynamical models or directly derived from the HI rotation curves
follow the same relation as the HSB galaxies in the V-sigma plane. On the
contrary, the LSB galaxies follow a different relation, since most of them show
either higher Vc (or lower sigma) with respect to the HSB galaxies. This argues
against the relevance of baryon collapse in the radial density profile of the
dark matter haloes of LSB galaxies. Moreover, if the Vc-sigma relation is
equivalent to one between the mass of the dark matter halo and that of the
supermassive black hole, these results suggest that the LSB galaxies host a
supermassive black hole with a smaller mass compared to HSB galaxies of equal
dark matter halo. On the other hand, if the fundamental correlation of SMBH
mass is with the halo Vc, then LSBs should have larger black hole masses for
given bulge sigma.


title: Analytic Results for a Flat Universe Dominated by Dust and Dark Energy

abstract:
  We find the solution for the scale factor in a flat Universe driven by dust
plus a component characterized by a constant parameter of state which dominates
in the asymptotic future. We also present an analytic formula (in terms of
hypergeometric functions) for the past light cone in such a universe. As
applications of this result, we give analytic expressions for the Luminosity
Distance and for the Acoustic Scale, where the latter determines the peaks
positions in the pattern of CMB anisotropies.


title: Massive Black Hole Binaries from Collisional Runaways

abstract:
  Recent theoretical work has solidified the viability of the collisional
runaway scenario in young dense star clusters for the formation of very massive
stars (VMSs), which may be precursors to intermediate-mass black holes (IMBHs).
We present first results from a numerical study of the collisional runaway
process in dense star clusters containing primordial binaries. Stellar
collisions during binary scattering encounters offer an alternate channel for
runaway growth, somewhat independent of direct collisions between single stars.
We find that clusters with binary fractions >~10% yield two VMSs via
collisional runaways, presenting the exotic possibility of forming IMBH--IMBH
binaries in star clusters. We discuss the implications for gravitational wave
observations, and the impact on cluster structure.


title: G359.95-0.04: Pulsar Candidate Near Sgr A*

abstract:
  We report the discovery of a prominent nonthermal X-ray feature located near
the Galactic center that we identify as an energetic pulsar wind nebula. This
feature, G359.95-0.04, lies 1 lyr north of Sgr A* (in projection), is
comet-like in shape, and has a power law spectrum that steepens with increasing
distance from the putative pulsar. The distinct spectral and spatial X-ray
characteristics of the feature are similar to those belonging the rare class of
ram-pressure confined pulsar wind nebulae. The luminosity of the nebula at the
distance of \sgra, consistent with the inferred X-ray absorptions, is 1 10^{34}
ergs s^{-1} in the 2--10 keV energy band. The cometary tail extends back to a
region centered at the massive stellar complex IRS 13 and surrounded by
enhanced diffuse X-ray emission, which may represent an associated supernova
remnant. Furthermore, the inverse Compton scattering of the strong ambient
radiation by the nebula consistently explains the observed TeV emission from
the Galactic center. We also briefly discuss plausible connections of
G359.95-0.04 to other high-energy sources in the region, such as the young
stellar complex IRS 13 and SNR Sgr A East.


title: Testing a new analytic model for gravitational lensing probabilities

abstract:
  We study gravitational lensing with a multiple lens plane approach, proposing
a simple analytical model for the probability distribution function (PDF) of
the dark matter convergence, kappa, for the different lens planes in a given
cosmology as a function of redshift and smoothing angle, theta. The model is
fixed solely by the variance of kappa, which in turn is fixed by the amplitude
of the power spectrum, sigma_8. We test the PDF against a high resolution
Tree-Particle-Mesh simulation and find that it is far superior to the Gaussian
or the lognormal, especially for small values of theta << 1 arcmin and at large
values of kappa relevant to strong lensing. With this model, we predict the
probabilities of strong lensing by a single plane or by multiple planes. We
find that for theta ~ 10 arcsec, a single plane accounts for almost all (~ 98%)
of the strong lensing cases for source redshift unity. However, for a more
typical source redshift of 4, about 12% of the strong lensing cases will result
from the contribution of a secondary clump of matter along the line of sight,
introducing a systematic error in the determination of the surface density of
clusters, typically overestimating it by about 2-5%. We also find that matter
inhomogenieties introduce a dispersion in the value of the angular diameter
distance about its cosmological mean. The probable error relative to the mean
increases with redshift to a value of about 8% for z ~ 6 and theta ~ 10 arcsec.


title: The soft X-ray properties of quasars in the Sloan Digital Sky Survey

abstract:
  We use the ROSAT All Sky Survey (RASS) to study the soft X-ray properties of
a homogeneous sample of 46,420 quasars selected from the third data release of
the Sloan Digital Sky Survey (SDSS). Optical luminosities, both at rest-frame
2500\AA ($L_{2500}$) and in [OIII] ($L_{[\rm{OIII}]}$) span more than three
orders of magnitude, while redshifts range over $0.1<z<5.4$. We detect 3366
quasars directly in the observed 0.1--2.4 keV band. Sub-samples of radio-loud
and radio-quiet objects (RLQs and RQQs) are obtained by cross-matching with the
FIRST catalogue. We study the distribution of X-ray luminosity as a function of
optical luminosity, redshift and radio power using both individual detections
and stacks of complete sets of similar quasars. At every optical luminosity and
redshift $\log L_{2\kev}$ is, to a good approximation, normally distributed
with dispersion $\sim 0.40$, at least brightwards of the median X-ray
luminosity. This median X-ray luminosity of quasars is a power law of optical
luminosity with index $\sim 0.53$ for $L_{2500}$ and $\sim 0.30$ for
$L_{[\rm{OIII}]}$. RLQs are systematically brighter than RQQs by about a factor
of 2 at given optical luminosity. The zero-points of these relations increase
systematically with redshift, possibly in different ways for RLQs and RQQs.
Evolution is particularly strong at low redshift and if the optical luminosity
is characterised by $L_{[\rm{OIII}]}$. At low redshift and at given
$L_{[\rm{OIII}]}$ the soft X-ray emission from type II AGN is more than 100
times weaker than that from type I AGN.


title:
Short-living supermassive magnetar model for the early X-ray flares
  following short GRBs

abstract:
  We suggest a short-living supermassive magnetar model to account for the
X-ray flares following short $\gamma-$ray bursts. In this model, the central
engine of the short $\gamma-$ray bursts is a supermassive millisecond magnetar.
The X-ray flares are powered by the dipole radiation of the magnetar. When the
magnetar has lost a significant part of its angular momentum, it collapses to a
black hole and the X-ray flares disappear abruptly. Two important predictions
of this model are (i) X-ray flares much more energetic than that detected in
GRB 050724 may be detectable in the coming months and years by the XRT onboard
{\it Swift}. (ii) The short GRBs with X-ray flares may occur outside of their
host galaxy.


title:
Morphology and Evolution of Simulated and Optical Clusters: A
  Comparative Analysis

abstract:
  We have made a comparative study of morphological evolution in simulated DM
halos and X-ray brightness distribution, and in optical clusters. Samples of
simulated clusters include star formation with supernovae feedback, radiative
cooling, and simulation in the adiabatic limit at three different redshifts, z
= 0.0, 0.10, and 0.25. The optical sample contains 208 ACO clusters within
redshift, $z \leq 0.25$. Cluster morphology, within 0.5 and 1.0 h$^{-1}$ Mpc
from cluster center, is quantified by multiplicity and ellipticity.
  We find that the distribution of the dark matter halos in the adiabatic
simulation appear to be more elongated than the galaxy clusters. Radiative
cooling brings halo shapes in excellent agreement with observed clusters,
however, cooling along with feedback mechanism make the halos more flattened.
  Our results indicate relatively stronger structural evolution and more clumpy
distributions in observed clusters than in the structure of simulated clusters,
and slower increase in simulated cluster shapes compared to those in the
observed one.
  Within $z \leq 0.1$, we notice an interesting agreement in the shapes of
clusters obtained from the cooling simulations and observation. We also notice
that the different samples of observed clusters differ significantly in
morphological evolution with redshift. We highlight a few possibilities
responsible for the discrepancy in morphological evolution of simulated and
observed clusters.


title:
Direct Detection of Intermediate Mass Compact Objects via
  Submillilensing

abstract:
  A galaxy-sized halo may contain a large number of intermediate mass (10^{2-4}
solar mass) compact objects (IMCOs), which can be intermediate mass black holes
(IMBHs) or the CDM subhalos. We propose to directly detect the IMBHs by
observing multiply imaged QSO-galaxy lens systems with a high angular
resolution (~ 0.03mas), which would be achieved by the next-VLBI space
missions. The silhouette of the IMBHs would appear as an either monopole-like
or dipole-like variation at the scale of the Einstein radius against the QSO
jets. As a byproduct, we can also directly detect the 10^{4-5} solar mass CDM
subhalos. From a measurement of the local distortion in the surface brightness
of the QSO jet, we can make a distinction between a point mass (corresponding
to an IMBH) and an extended structure (corresponding to a CDM subhalo). It
would be a unique probe of the IMCOs whose nature has been under the veil of
mistery.


title: Gamma Ray Bursts as cosmological tools

abstract:
  The use of Gamma Ray Bursts as ``standard candles'' has been made possible by
the recent discovery of a very tight correlation between their rest frame
intrinsic properties. This correlation relates the GRB prompt emission peak
spectral energy E_peak to the energy E_gamma corrected for the collimation
angle theta_jet of these sources. The possibility to use GRBs to constrain the
cosmological parameters and to study the nature of Dark Energy are very
promising.


title:
NGC 6791: an exotic open cluster or the nucleus of a tidally disrupted
  galaxy?

abstract:
  We report on high resolution Echelle spectroscopy of 20 giant stars in the
Galactic old open clusters NGC 6791 obtained with Hydra at the WIYN telescope.
High precision radial velocity allow us to isolate 15 {\it bona fide} cluster
members. From 10 of them we derive a global [M/H]=+0.39$\pm$0.05. We therefore
confirm that NGC 6791 is extremely metal rich, exhibits a few marginally
sub-solar abundance ratios, and within the resolution of our spectra does not
show evidences of spread in metal abundance. With these new data we re-derive
the cluster fundamental parameters suggesting that it is about 8 Gyr old and
4.3 kpc far from the Sun. The combination of its chemical properties, age,
position, and Galactic orbit hardly makes NGC 6791 a genuine Population I open
cluster. We discuss possible interpretations of the cluster peculiarities
suggesting that the cluster might be what remains of a much larger system,
whose initial potential well could have been sufficient to produce high
metallicity stars, and which has been depopulated by the tidal field of the
Galaxy. Alternatively, its current properties may be explained by the
perturbation of the Galactic bar on an object originated well inside the solar
ring, where the metal enrichment had been very fast.


title: Inhomogeneity-Induced Cosmic Acceleration in a Dust Universe

abstract:
  It is the common consensus that the expansion of a universe always slows down
if the gravity provided by the energy sources therein is attractive and
accordingly one needs to invoke dark energy as a source of anti-gravity for
understanding the cosmic acceleration. To examine this point we find
counter-examples for a spherically symmetric dust fluid described by the
Lemaitre-Tolman-Bondi solution without singularity. Thus, the validity of this
naive consensus is indeed doubtful and the effects of inhomogeneities should be
restudied. These counter-intuitive examples open a new perspective on the
understanding of the evolution of our universe.


title: Burning of an hadronic star into a quark or a hybrid star

abstract:
  We study the hydrodynamical transition from an hadronic star into a quark or
a hybrid star. We discuss the possible mode of burning, using a fully
relativistic formalism and realistic Equations of State in which hyperons can
be present. We take into account the possibility that quarks form a diquark
condensate. We also discuss the formation of a mixed phase of hadrons and
quarks, and we indicate which region of the star can rapidly convert in various
possible scenarios. An estimate of the final temperature of the system is
provided. We find that the conversion process always corresponds to a
deflagration and never to a detonation. Hydrodynamical instabilities can
develop on the front. We estimate the increase in the conversion's velocity due
to the formation of wrinkles and we find that, although the increase is
significant, it is not sufficient to transform the deflagration into a
detonation in essentially all realistic scenarios. Concerning convection, it
does not always develop. In particular the system does not develop convection
if hyperons are not present in the initial phase and if the newly formed quark
phase is made of ungapped (or weakly gapped) quarks. At the contrary, the
process of conversion from ungapped quark matter to gapped quarks always allows
the formation of a convective layer. Finally, we discuss possible astrophysical
implications of our results.


title:
Interrelation between radio and X-ray signatures of drifting subpulses
  in pulsars

abstract:
  We examined a model of partially screened gap region above the polar cap, in
which the electron-positron plasma generated by sparking discharges coexists
with thermionic flow ejected by the bombardment of the surface beneath these
sparks. Our special interest was the polar cap heating rate and the subpulse
drifting rate, both phenomena presumably associated with sparks operating at
the polar cap. We investigated correlation between the intrinsic drift rate and
polar cap heating rate and found that they are coupled to each other in such a
way that the thermal X-ray luminosity $L_x$ from heated polar cap depends only
on the observational tertiary subpulse drift periodicity $\hat{P}_3$ (polar cap
carousel time). Within our model of partially screened gap we derived the
simple formula relating $L_x$ and $\hat{P}_3$, and showed that it holds for
PSRs B0943$+$10 and B1133+16, which are the only two pulsars in which both
$L_x$ and $\hat{P}_3$ are presently known.


title:
Short gamma-ray bursts from binary neutron star mergers in globular
  clusters

abstract:
  The first locations of short gamma-ray bursts (GRBs) in elliptical galaxies
suggest they are produced by the mergers of double neutron star (DNS) binaries
in old stellar populations. Globular clusters, where the extreme densities of
very old stars in cluster cores create and exchange compact binaries
efficiently, are a natural environment to produce merging NSs. They also allow
some short GRBs to be offset from their host galaxies, as opposed to DNS
systems formed from massive binary stars which appear to remain in galactic
disks. Starting with a simple scaling from the first DNS observed in a galactic
globular, which will produce a short GRB in ~300My, we present numerical
simulations which show that ~10-30% of short GRBs may be produced in globular
clusters vs. the much more numerous DNS mergers and short GRBs predicted for
galactic disks. Reconciling the rates suggests the disk short GRBs are more
beamed, perhaps by both the increased merger angular momentum from the DNS
spin-orbit alignment (random for the DNS systems in globulars) and a larger
magnetic field on the secondary NS.


title:
Asymmetric neutrino propagation in newly born magnetized strange stars:
  GRB and kicks

abstract:
  We consider the early cooling evolution of strongly magnetized strange stars
in a CFL phase with high gap Delta > 100 MeV. We demonstrate how this model may
explain main features of the gamma-ray burst phenomena and also yield a strong
star kick. The mechanism is based on beaming of neutrino emission along the
magnetic vortex lines. We show that for sufficiently high initial temperatures
T_0 ~ 30 - 60 MeV and surface magnetic fields B_s ~ 10^{15} - 10^{17} G, the
energy release within the narrow beam is up to 10^{52} erg with a magnetic
field dependent time scale between 10^{-2} s (for a smaller magnetic field) to
10 s. The above mechanism together with the parity violation of the
neutrino-producing weak interaction processes in a magnetic field allow for the
strange star kick. The higher the magnetic field the larger is the stars kick
velocity. These velocities may cover the same range as observed pulsar kick
velocities.


title: Interacting X-ray Binaries in Globular Clusters: 47Tuc vs. NGC 6397

abstract:
  Our deep Chandra exposures of 47Tuc and moderate exposures of NGC 6397 reveal
a wealth of new phenomena for interacting X-ray binaries (IXBs) in globular
clusters. In this (late) Review, updated since the conference, I summarize
recent and ongoing analysis of the millisecond pulsars, the compact binaries
containing white dwarfs and neutron stars, and the chromospherically active
binaries in both globular clusters. Spectral variability analysis enables new
insights into source properties and evolutionary history. These binary
populations, now so ``easily'' visible, are large enough that their properties
and spatial distributions reveal new hints of compact object formation and
binary interactions with their parent cluster. Neutron stars appear
overabundant, relative to white dwarfs, in 47Tuc vs. NGC 6397. The IXBs
containing neutron stars (i.e., MSPs and qLMXBs), as the most massive and
ancient compact binary sample, may trace the protocluster disk in 47Tuc,
whereas compact binaries may have been ejected preferentially along the cluster
rotation equator during the recent core collapse in NGC 6397.


title:
EXIST: All-Sky Hard X-ray Imaging and Spectral-Temporal Survey for Black
  Holes

abstract:
  The Energetic X-ray Imaging Survey Telescope (EXIST) is under study for the
proposed Black Hole Finder Probe, one of the three Einstein Probe missions in
NASA's proposed Beyond Einstein Program. EXIST would have unique capabilities:
it would survey the full sky at 5-600 keV each 95min orbit with 0.9-5 arcmin,
10microsec - 45min, and ~0.5-5 keV resolution to locate sources to 10arcsec and
enable black holes to be surveyed and studied on all scales. With 5sigma survey
sensitivity (0.5-1y) Fx(40-80 keV) ~5 x 10^-13 cgs, or comparable to the ROSAT
soft X-ray (0.3-2.5 keV) sky survey, a large sample (~2-4 x 10^4) of obscured
AGN will be identified and a complete sample of accreting stellar mass BHs in
the Galaxy will be found. The all-sky/all-time coverage will allow rare events
to be measured, such as possible stellar disruption flares from dormant AGN out
to ~200 Mpc. A large sample (~2-3/day) of GRBs will be located (<~10arcsec) at
sensitivities and bandwidths much greater than previously and likely yield the
highest redshift events and constraints on Pop III BHs. An outline of the
mission design from the ongoing concept study is presented.


title:
Deviations from passive evolution - star formation and the UV excess in
  z~1 radio galaxies

abstract:
  Galaxy colours are determined for two samples of 6C and 3CR radio sources at
z~1, differing by a factor of ~6 in radio power. Corrections are made for
emission line contamination and the presence of any nuclear point source, and
the data analysed as a function of both redshift and the radio source
properties. The galaxy colours are remarkably similar for the two populations,
and the UV excess evolves with radio source size similarly in both samples,
depsite the fact that the alignment effect is more extensive for the more
powerful 3CR radio galaxies. These results seem to suggest that the alignment
effect at these redshifts does not scale strongly with radio power, and is
instead more closely dependent on galaxy mass (which is statistically
comparable for the two samples). However, it is likely that the presence of
relatively young (< several 10^8 years old) stellar populations has
considerably contaminated the K-band flux of these systems, particularly in the
case of the more powerful 3CR sources, which are ~0.5mag more luminous than the
predictions of passive evolution models at z~1. The higher luminosity of the
3CR alignment effect is balanced by emission at longer wavelengths, thereby
leading to comparable colours for the two samples.


title:
Frequency of Hot Jupiters and Very Hot Jupiters from the OGLE-III
  Transit Surveys Toward the Galactic Bulge and Carina

abstract:
  We derive the frequencies of hot Jupiters (HJs) with 3--5 day periods and
very hot Jupiters (VHJs) with 1-3 day periods by comparing the planets actually
detected in the OGLE-III survey with those predicted by our models. The models
are constructed following Gould & Morgan (2003) by populating the line of sight
with stars drawn from the Hipparcos catalog. Using these, we demonstrate that
the number of stars with sensitivity to HJs and VHJs is only 4--16% of those in
the OGLE-III fields satisfying the spectroscopic-followup limit of V_max<17.5.
Hence, the frequencies we derive are much higher than a naive estimate would
indicate. We find that at 90% confidence the fraction of stars with planets in
the two period ranges is (1/310)(1^{+1.39}_{-0.59}) for HJs and
(1/690)(1^{+1.10}_{-0.54}) for VHJs. The HJ rate is statistically
indistinguishable from that found in radial velocity (RV) studies. However, we
note that magnitude-limited RV samples are heavily biased toward metal-rich
(hence, planet-bearing) stars, while transit surveys are not, and therefore we
expect that more sensitive transit surveys should find a deficit of HJs as
compared to RV surveys. The detection of 3 transiting VHJs, all with periods
less than 2 days, is marginally consistent with the complete absence of such
detections in RV surveys. The planets detected are consistent with being
uniformly distributed between 1.00 and 1.25 Jovian radii, but there are too few
in the sample to map this distribution in detail.


title:
A Cosmic Milestone: Constraints from Metal-Poor Halo Stars on the
  Cosmological Reionization Epoch

abstract:
  Theoretical studies and current observations of the high-redshift
intergalactic medium (IGM) indicate that at least two cosmic transitions occur
by the time the universe reaches gas metallicities of about $10^{-3}$ of solar
values. These are the cosmological reionization of the IGM, and the transition
from a primordial to present-day mode of star formation. We quantify this
relation through new calculations of the ionizing radiation produced in
association with the elements carbon, oxygen and silicon observed in Galactic
metal-poor halo stars, which are likely second-generation objects formed in the
wake of primordial supernovae. We demonstrate that sufficient ionizing photons
per baryon are created by enrichment levels of [Fe/H] of about -3 in the
environment of metal-poor halo stars to provide the optical depth in the cosmic
microwave background of about 0.1 detected by $WMAP$. We show, on a star by
star basis, that a genuine cosmic milestone in IGM ionization and star
formation mode occurred at metallicities of $10^{-4}$ to $10^{-3}$ solar in
these halo stars. This provides an important link in the chain of evidence for
metal-free first stars having dominated the process of reionization by redshift
6. We conclude that many of the Fe-poor halo stars formed close to the end of
or soon after cosmological reionization, making them the ideal probe of the
physical conditions under which the transition from first- to second-generation
star formation happened in primordial galaxies.


title:
Cosmic evolution of the galaxy mass and luminosity functions by
  morphological type from multi-wavelength data in the CDF-South

abstract:
  We constrain the evolution of the galaxy mass and luminosity functions from
the analysis of (public) multi-wavelength data in the Chandra Deep Field South
(CDFS) area, obtained from the GOODS and other projects, and including very
deep high-resolution imaging by HST/ACS. Our reference catalogue of faint
high-redshift galaxies, which we have thoroughly tested for completeness and
reliability, comes from a deep (S(3.6micron)>1 microJy) image by IRAC on the
Spitzer Observatory. These imaging data in the field are complemented with
extensive optical spectroscopy by the ESO VLT/FORS2 and VIMOS spectrographs,
while deep K-band VLT/ISAAC imaging is also used to derive further
complementary statistical constraints and to assist the source identification
and SED analysis. We have selected a highly reliable IRAC 3.6micron sub-sample
of 1478 galaxies with S(3.6)>10microJy, 47% of which have spectroscopic
redshift, while for the remaining objects both COMBO-17 and Hyperz are used to
estimate the photometric redshift. This very extensive dataset is exploited to
assess evolutionary effects in the galaxy luminosity and stellar mass
functions, while luminosity/density evolution is further constrained with the
number counts and redshift distributions. The deep ACS imaging allows us to
differentiate these evolutionary paths by morphological type, which our
simulations show to be reliable at least up to z=1.5 for the two main early-
(E/S0) and late-type (Sp/Irr) classes. These data, as well as our direct
estimate of the stellar mass function above M=10^(10)M_sun for the spheroidal
subclass, consistently evidence a progressive dearth of such objects to occur
starting at z=0.7, paralleled by an increase in luminosity. (abridged)


title: Relic keV sterile neutrinos and reionization

abstract:
  A sterile neutrino with mass of several keV can account for cosmological dark
matter, as well as explain the observed velocities of pulsars. We show that
X-rays produced by the decays of these relic sterile neutrinos can boost the
production of molecular hydrogen, which can speed up the cooling of gas and the
early star formation, which can, in turn, lead to a reionization of the
universe at a high enough redshift to be consistent with the WMAP results.


title: Turbulent Structure of a Stratified Supernova-Driven Interstellar Medium

abstract:
  To study how supernova feedback structures the turbulent interstellar medium,
we construct 3D models of vertically stratified gas stirred by discrete
supernova explosions, including vertical gravitational field and parametrized
heating and cooling. The models reproduce many observed characteristics of the
Galaxy such as global circulation of gas (i.e., galactic fountain) and the
existence of cold dense clouds in the galactic disk. Global quantities of the
model such as warm and hot gas filling factors in the midplane, mass fraction
of thermally unstable gas, and the averaged vertical density profile are
compared directly with existing observations, and shown to be broadly
consistent. We find that energy injection occurs over a broad range of scales.
There is no single effective driving scale, unlike the usual assumption for
idealized models of incompressible turbulence. However, >90% of the total
kinetic energy is contained in wavelengths shortward of 200 pc. The shape of
the kinetic energy spectrum differs substantially from that of the velocity
power spectrum, which implies that the velocity structure varies with the gas
density. Velocity structure functions demonstrate that the phenomenological
theory proposed by Boldyrev is applicable to the medium. We show that it can be
misleading to predict physical properties such as the stellar initial mass
function based on numerical simulations that do not include self-gravity of the
gas. Even if all the gas in turbulently Jeans unstable regions in our
simulation is assumed to collapse and form stars in local freefall times, the
resulting total collapse rate is significantly lower than the value consistent
with the input supernova rate. Supernova-driven turbulence inhibits star
formation globally rather than triggering it.


title: Properties of Flares-Generated Seismic Waves on the Sun

abstract:
  The solar seismic waves excited by solar flares (``sunquakes'') are observed
as circular expanding waves on the Sun's surface. The first sunquake was
observed for a flare of July 9, 1996, from the Solar and Heliospheric
Observatory (SOHO) space mission. However, when the new solar cycle started in
1997, the observations of solar flares from SOHO did not show the seismic
waves, similar to the 1996 event, even for large X-class flares during the
solar maximum in 2000-2002. The first evidence of the seismic flare signal in
this solar cycle was obtained for the 2003 ``Halloween'' events, through
acoustic ``egression power'' by Donea and Lindsey. After these several other
strong sunquakes have been observed. Here, I present a detailed analysis of the
basic properties of the helioseismic waves generated by three solar flares in
2003-2005. For two of these flares, X17 flare of October 28, 2003, and X1.2
flare of January 15, 2005, the helioseismology observations are compared with
simultaneous observations of flare X-ray fluxes measured from the RHESSI
satellite. These observations show a close association between the flare
seismic waves and the hard X-ray source, indicating that high-energy electrons
accelerated during the flare impulsive phase produced strong compression waves
in the photosphere, causing the sunquake. The results also reveal new physical
properties such as strong anisotropy of the seismic waves, the amplitude of
which varies significantly with the direction of propagation. The waves travel
through surrounding sunspot regions to large distances, up to 120 Mm, without
significant decay. These observations open new perspectives for helioseismic
diagnostics of flaring active regions on the Sun and for understanding the
mechanisms of the energy release and transport in solar flares.


title: Parametrization of K-essence and Its Kinetic Term

abstract:
  We construct the non-canonical kinetic term of a k-essence field directly
from the effective equation of state function $w_k(z)$, which describes the
properties of the dark energy. Adopting the usual parametrizations of equation
of state we numerically reproduce the shape of the non-canonical kinetic term
and discuss some features of the constructed form of k-essence.


title: Where Are the Baryons? II: Feedback Effects

abstract:
  Numerical simulations of the intergalactic medium have shown that at the
present epoch a significant fraction (40-50%) of the baryonic component should
be found in the (T~10^6K) Warm-Hot Intergalactic Medium (WHIM) - with several
recent observational lines of evidence indicating the validity of the
prediction. We here recompute the evolution of the WHIM with the following
major improvements: (1) galactic superwind feedback processes from galaxy/star
formation are explicitly included; (2) major metal species (O V to O IX) are
computed explicitly in a non-equilibrium way; (3) mass and spatial dynamic
ranges are larger by a factor of 8 and 2, respectively, than in our previous
simulations. Here are the major findings: (1) galactic superwinds have dramatic
effects, increasing the WHIM mass fraction by about 20%, primarily through
heating up warm gas near galaxies with density 10^{1.5}-10^4 times the mean
density. (2) the fraction of baryons in WHIM is increased modestly from the
earlier work but is ~40-50%. (3) the gas density of the WHIM is broadly peaked
at a density 10-20 times the mean density, ranging from underdense regions to
regions that are overdense by 10^3-10^4. (4) the median metallicity of the WHIM
is 0.18 Zsun for oxygen with 50% and 90% intervals being (0.040,0.38) and
(0.0017,0.83).


title: Where Are the Baryons? III: Non-Equilibrium Effects and Observables

abstract:
  Numerical simulations of the intergalactic medium have shown that at the
present epoch a significant fraction (40-50%) of the baryonic component should
be found in the (T~10^6K) Warm-Hot Intergalactic Medium (WHIM) - with several
recent observational lines of evidence indicating the validity of the
prediction. We here recompute the evolution of the WHIM with the following
major improvements: (1) galactic superwind feedback processes from galaxy/star
formation are explicitly included; (2) major metal species (O V to O IX) are
computed explicitly in a non-equilibrium way; (3) mass and spatial dynamic
ranges are larger by a factor of 8 and 2, respectively, than in our previous
simulations. We find: (1) non-equilibrium calculations produce significantly
different results from ionization equilibrium calculations. (2) The abundance
of O VI absorption lines based on non-equilibrium simulations with galactic
superwinds is in remarkably good agreement with latest observations, implying
the validity of our model, while the predicted abundances for O VII and O VIII
absorption lines appear to be lower than observed but the observational
errorbars are currently very large. The expected abundances for O VI (as well
as Lyman alpha), O VII and O VIII absorption systems are in the range 50-100
per unit redshift at EW=1km/s decreasing to 10-20 per unit redshift at
EW=10km/s. The number of O VI absorption lines with EW>100km/s is very small,
while there are about 1-3 lines per unit redshift for O VII and O VIII
absorption lines at EW=100km/s. (3) Emission lines, primarily O VI and \lya in
the UV and O VII and O VIII in the soft X-rays are potentially observable by
future missions. The number of emission lines per unit redshift that may be
detectable by planned UV and soft X-ray missions are in the order of 0.1-1.


title: Detection and Fundamental Applications of Individual First Galaxies

abstract:
  First galaxies formed within halos of mass M=E7.5-E9 Msun at z=30-40 in the
standard cold dark matter (CDM) universe may each display an extended hydrogen
21-cm absorption halo against the cosmic microwave background with a brightness
temperature decrement of del T=-(100-150)mK at a radius 0.3 < r < 3.0 comoving
Mpc, corresponding to an angular size of 10-100 arcseconds. A 21-cm tomographic
survey in the redshift shell z=30-40 (at 35-45MHz), which could be carried out
by the next generation of radio telescopes, is expected to be able to detect
millions of first galaxies and may prove exceedingly profitable in enabling (at
least) four fundamental applications for cosmology and galaxy formation. First,
it may yield direct information on star formation physics in first galaxies.
Second, it could provide a unique and sensitive probe of small-scale power in
the standard cosmological model hence physics of dark matter and inflation.
Third, it would allow for an independent, perhaps "cleaner" characterization of
interesting features on large scales in the power spectrum such as the baryonic
oscillations. Finally, possibly the most secure, each 21-cm absorption halo is
expected to be highly spherical and faithfully follow the Hubble flow. By
applying the Alcock-Paczynski test to a significant sample of first galaxies,
one may be able to determine the dark energy equation of state with an accuracy
likely only limited by the accuracy with which the matter density can be
determined independently.


title: Shears from shapelets

abstract:
  Accurate measurement of gravitational shear from images of distant galaxies
is one of the most direct ways of studying the distribution of mass in the
universe. We describe an implementation of a technique that is based on the
shapelets formalism.
  The shapelets technique describes PSF and observed images in terms of
Gauss-Hermite expansions (Gaussians times polynomials). It allows the various
operations that a galaxy image undergoes before being registered in a camera
(gravitational shear, PSF convolution, pixelation) to be modeled in a single
formalism, so that intrinsic ellipticities can be derived in a single modeling
step.
  The resulting algorithm, and tests of it on idealized data as well as more
realistic simulated images from the STEP project, are described. Results are
very promising, with attained calibration accuracy better than four percent (1
percent for round PSFs) and PSF ellipticity correction better than a factor of
20. Residual calibration problems are discussed.


title: Neutrino Telescopy in the Mediterranean Sea

abstract:
  The observation of high-energy extraterrestrial neutrinos is one of the most
promising future options to increase our knowledge on non-thermal processes in
the universe. Neutrinos are e.g. unavoidably produced in environments where
high-energy hadrons collide; in particular this almost certainly must be true
in the astrophysical accelerators of cosmic rays, which thus could be
identified unambiguously by sky observations in "neutrino light". On the one
hand, neutrinos are ideal messengers for astrophysical observations since they
are not deflected by electromagnetic fields and interact so weakly that they
are able to escape even from very dense production regions and traverse large
distances in the universe without attenuation. On the other hand, their weak
interaction poses a significant problem for detecting neutrinos. Huge target
masses up to gigatons must be employed, requiring to instrument natural
abundances of media such as sea water or antarctic ice. The first generation of
such neutrino telescopes is taking data or will do so in the near future, while
the second-generation projects with cubic-kilometre size is under construction
or being prepared. This report focuses on status and prospects of current
(ANTARES, NEMO, NESTOR) and future (KM3NeT) neutrino telescope projects in the
Mediterranean Sea.


title: Dust Size Growth and Settling in a Protoplanetary Disk

abstract:
  We have studied dust evolution in a quiescent or turbulent protoplanetary
disk by numerically solving coagulation equation for settling dust particles,
using the minimum mass solar nebular model. As a result, if we assume an
ideally quiescent disk, the dust particles settle toward the disk midplane to
form a gravitationally unstable layer within 2x10^3 - 4x10^4 yr at 1 - 30 AU,
which is in good agreement with an analytic calculation by Nakagawa, Sekiya, &
Hayashi (1986) although they did not take into account the particle size
distribution explicitly. In an opposite extreme case of a globally turbulent
disk, on the other hand, the dust particles fluctuate owing to turbulent motion
of the gas and most particles become large enough to move inward very rapidly
within 70 - 3x10^4 yr at 1 - 30 AU, depending on the strength of turbulence.
Our result suggests that global turbulent motion should cease for the
planetesimal formation in protoplanetary disks.


title: Accelerating Universe: Observational Status and Theoretical Implications

abstract:
  This is a pedagogical review of the recent observational data obtained from
type Ia supernova surveys that support the accelerating expansion of the
universe. The methods for the analysis of the data are reviewed and some of the
theoretical implications obtained from their analysis are discussed.


title: Radioactive 26Al and massive stars in the Galaxy

abstract:
  Gamma-rays from radioactive 26Al (half life ~7.2 10^5 yr) provide a
'snapshot' view of ongoing nucleosynthesis in the Galaxy. The Galaxy is
relatively transparent to such gamma-rays, and emission has been found
concentrated along the plane of the Galaxy. This led to the conclusion1 that
massive stars throughout the Galaxy dominate the production of 26Al. On the
other hand, meteoritic data show locally-produced 26Al, perhaps from spallation
reactions in the protosolar disk. Furthermore, prominent gamma-ray emission
from the Cygnus region suggests that a substantial fraction of Galactic 26Al
could originate in localized star-forming regions. Here we report high spectral
resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that
the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide
origin. We determine a present-day equilibrium mass of 2.8 (+/-0.8) M_sol of
26Al. We use this to estimate that the frequency of core collapse (i.e. type
Ib/c and type II) supernovae to be 1.9(+/- 1.1) events per century.


title: The Offline Software Framework of the Pierre Auger Observatory

abstract:
  The Pierre Auger Observatory is designed to unveil the nature and the origins
of the highest energy cosmic rays. The large and geographically dispersed
collaboration of physicists and the wide-ranging collection of simulation and
reconstruction tasks pose some special challenges for the offline analysis
software. We have designed and implemented a general purpose framework which
allows collaborators to contribute algorithms and sequencing instructions to
build up the variety of applications they require. The framework includes
machinery to manage these user codes, to organize the abundance of
user-contributed configuration files, to facilitate multi-format file handling,
and to provide access to event and time-dependent detector information which
can reside in various data sources. A number of utilities are also provided,
including a novel geometry package which allows manipulation of abstract
geometrical objects independent of coordinate system choice. The framework is
implemented in C++, and takes advantage of object oriented design and common
open source tools, while keeping the user side simple enough for C++ novices to
learn in a reasonable time. The distribution system incorporates unit and
acceptance testing in order to support rapid development of both the core
framework and contributed user code.


title: Charge screening effect on hadron-quark mixed phase in compact stars

abstract:
  We study the charge screening effect in the hadron-quark mixed phase. By
including the charge screening effect, rearrangement of charged particles
occurs and some part becomes locally charge-neutral. As a result the equation
of state for the mixed phase becomes close to that given by the Maxwell
construction, which means that the Maxwell construction would effectively gain
the physical meaning again even in the system with two or more chemical
potentials. We also discuss the interplay of the surface tension and the
Coulomb interaction. Both effects would restrict the region of the mixed phase
in the core of hybrid stars.


title: The Discovery of Two New Satellites of Pluto

abstract:
  Pluto's first known moon, Charon, was discovered in 1978 (Christy 1978) and
has a diameter about half that of Pluto (Buie 1992,Young 1994, Sicardy 2005),
which makes it larger relative to its primary than any other moon in the Solar
System. Previous searches for other satellites around Pluto have been
unsuccessful (Stern 1991, Stern 1994, Stern 2003), but they were not sensitive
to objects <=150 km in diameter and there are no fundamental reasons why Pluto
should not have more satellites (Stern 1994). Here we report the discovery of
two additional moons around Pluto, provisionally designated S/2005 P1
(hereafter P1) and S/2005 P2 (hereafter P2), which makes Pluto the first Kuiper
belt object (KBO) known to have multiple satellites. These new satellites are
much smaller than Charon (diameter~1200 km), with P1 ranging in diameter from
60-165 km depending on the surface reflectivity, and P2 about 20% smaller than
P1. Although definitive orbits cannot be derived, both new satellites appear to
be moving in circular orbits in the same orbital plane as Charon, with orbital
periods of ~38 days (P1) and ~25 days (P2). The implications of the discovery
of P1 and P2 for the origin and evolution of the Pluto system, and for the
satellite formation process in the Kuiper belt, are discussed in a companion
paper (Stern 2006).


title: A Magnetar Flare in the BATSE Catalog?

abstract:
  To identify extragalactic magnetar flares, we have searched for their
periodic tails by generating Lomb periodograms of the emission following short
bursts detected by the Burst and Transient Source Experiment (BATSE). Out of
358 short bursts examined, one has a significant tail periodicity (T = 13.8 s,
P = 4 x 10^-5). The most probable host galaxy for this burst is "The Fireworks
Galaxy" NGC 6946 (d = 5.9 Mpc). At this distance, the energy of the spike, (2.7
+/- 0.3) x 10^44 ergs, is akin to those of the galactic magnetar giant flares,
as are its duration (~ 0.4 s) and temperature (250 +/- 60 keV). For the tail
emission, however, our estimated temperature of 60 +/- 5 keV is harder and the
energy release of (4.3 +/- 0.8) x 10^45 ergs is larger than those of the
galactic magnetar flares. Regardless of the host, such a large ratio of
tail-to-spike energy would imply that magnetar flare tails might be detectable
out to further distances than previously thought.


title:
QPOs during magnetar flares are not driven by mechanical normal modes of
  the crust

abstract:
  Quasi-Periodic Oscillations (QPOs) have been observed during three powerful
magnetar flares, from SGR0526-66, SGR1806-20 and SGR1900+14. These QPOs have
been commonly interpreted as being driven by the mechanical modes of the
magnetar's solid crust which are excited during the flare. Here we show that
this interpretation is in sharp contradiction with the conventional magnetar
model. Firstly, we show that a magnetar crustal mode decays on the timescale of
at most a second due to the emission of Alfven waves into the neutron-star
interior. A possible modification is then to assume that the QPOs are
associated with the magnetars' global modes. However, we argue that at the
frequencies of the observed QPOs, the neutron-star core is likely to support a
continuum of Magneto-Hydrodynamic (MHD) normal modes. We demonstrate this on a
completely solvable toy model which captures the essential physics of the
system. We then show that the frequency of the global mode of the whole star is
likely to have a significant imaginary component, and its amplitude is likely
to decay on a short timescale. This is not observed. Thus we conclude that
either (i) the origin of the QPO is in the magnetar's magnetosphere, or (ii)
the magnetic field has a special configuration: either it is expelled from the
magnetar's core prior to the flares, or its poloidal component has very small
coherence length.


title:
Evolving Transport induced by a Surface Wave Propagating along a
  Vacuum-Matter Interface

abstract:
  Hydrodynamic derivation of the entrainment of matter induced by a surface
elastic wave propagating along the flexible vacuum-matter interface is
conducted by considering the nonlinear coupling between the interface and the
rarefaction effect. The critical reflux values associated with the product of
the second-order (unit) body forcing and the Reynolds number (representing the
viscous dissipations) decrease as the Knudsen number (representing the
rarefaction measure) increases from zero to 0.1. We obtained the critical
bounds for matter-freezed or zero-volume-flow-rate states corresponding to
specific Reynolds numbers and wave numbers which might be linked to the
evolution of the Universe. Our results also show that for positive evolution of
the matter their might be existence of negative pressure.


title:
The red rain phenomenon of Kerala and its possible extraterrestrial
  origin

abstract:
  A red rain phenomenon occurred in Kerala, India starting from 25th July 2001,
in which the rainwater appeared coloured in various localized places that are
spread over a few hundred kilometers in Kerala. Maximum cases were reported
during the first 10 days and isolated cases were found to occur for about 2
months. The striking red colouration of the rainwater was found to be due to
the suspension of microscopic red particles having the appearance of biological
cells. These particles have no similarity with usual desert dust. An estimated
minimum quantity of 50,000 kg of red particles has fallen from the sky through
red rain. An analysis of this strange phenomenon further shows that the
conventional atmospheric transport processes like dust storms etc. cannot
explain this phenomenon. The electron microscopic study of the red particles
shows fine cell structure indicating their biological cell like nature. EDAX
analysis shows that the major elements present in these cell like particles are
carbon and oxygen. Strangely, a test for DNA using Ethidium Bromide dye
fluorescence technique indicates absence of DNA in these cells. In the context
of a suspected link between a meteor airburst event and the red rain, the
possibility for the extraterrestrial origin of these particles from cometary
fragments is discussed.


title:
Understanding the Nuclear Gas Dispersion in Early-Type Galaxies in the
  Context of Black Hole Demographics

abstract:
  (abridged) We analyze and model HST /STIS observations of a sample of 27
galaxies; 16 Fanaroff & Riley Type I radio galaxies and 11 (more) normal
early-type galaxies. We focus here on what can be learned from the nuclear
velocity dispersion (line width) of the gas as a complement to the many studies
dealing with gas rotation velocities. We find that the dispersion in a STIS
aperture of ~0.1''-0.2'' generally exceeds the large-scale stellar velocity
dispersion of the galaxy. This is qualitatively consistent with the presence of
central BHs, but raises the question whether the excess gas dispersion is of
gravitational or non-gravitational origin and whether the implied BH masses are
consistent with our current understanding of BH demography(as predicted by the
M-sigma relation between BH mass and stellar velocity dispersion). To address
this we construct dynamical models for the gas, both thin disk models and
models with more general axis ratios and velocity anisotropies. For the normal
galaxies the nuclear gas dispersions are adequately reproduced assuming disks
around BHs with masses that follow the M-sigma relation. In contrast, the gas
dispersions observed for the radio galaxies generally exceed those predicted by
any of the models. We attribute this to the presence of non-gravitational
motions in the gas that are similar to or larger than the gravitational
motions. The non- gravitational motions are presumably driven by the active
galactic nucleus (AGN), but we do not find a relation between the radiative
output of the AGN and the non-gravitational dispersion. It is not possible to
uniquely determine the BH mass for each galaxy from its nuclear gas dispersion.
However, for the sample as a whole the observed dispersions do not provide
evidence for significant deviations from the M-sigma relation.


title:
High resolution spectroscopy of stars with transiting planets. The cases
  of OGLE-TR-10, 56, 111, 113, and TrES-1

abstract:
  Context: During the past years photometric surveys, later complemented by
follow-up radial-velocity measurements, have revealed the presence of several
new extra-solar transiting planets, in very short period orbits. Many of the
host stars are extremely faint (V$\sim$16), making high-precision spectroscopic
measurements challenging. Aims: We have used the UVES spectrograph (VLT-UT2
telescope) to obtain high resolution spectra of 5 stars hosting transiting
planets, namely for OGLE-TR-10, 56, 111, 113 and TrES-1. The immediate
objective is to derive accurate stellar parameters and chemical abundances.
Methods: The stellar parameters were derived from an LTE analysis of a set of
FeI and FeII lines. Results: Complementing the spectroscopic information with
photometric transit curves and radial-velocity data from the literature, we
have then refined the stellar and planetary radii and masses. The obtained data
were also used to study and discuss the relation between the stellar
metallicity and orbital period of the planets.


title: Spectroscopic Survey of Red Giants in the SMC. I: Kinematics

abstract:
  We present a spectroscopic survey of 2046 red giant stars, distributed over
the central 4x2 kpc of the Small Magellanic Cloud (SMC). After fitting and
removing a small velocity gradient across the SMC (7.9 km/s/deg oriented at 10
deg E of N), we measure an rms velocity scatter of 27.5+-0.5 km/s. The line of
sight velocity distribution is well-characterized by a Gaussian and the
velocity dispersion profile is nearly constant as a function of radius. We find
no kinematic evidence of tidal disturbances. Without a high-precision
measurement of the SMC's proper motion, it is not possible to constrain the
SMC's true rotation speed from our measured radial-velocity gradient. However,
even with conservative assumptions, we find that v < sigma and hence that the
SMC is primarily supported by its velocity dispersion. We find that the shape
of the SMC, as measured from the analysis of the spatial distribution of its
red giant stars, is consistent with the degree of rotational flattening
expected for the range of allowed v/sigma values. As such, the properties of
the SMC are consistent with similar low luminosity spheroidal systems. We
conclude that the SMC is primarily a low luminosity spheroid whose irregular
visual appearance is dominated by recent star formation. A simple virial
analysis using the measured kinematics implies an enclosed mass within 1.6 kpc
of between 1.4 and 1.9x10^9 Mo, and a less well constrained mass within 3 kpc
of between 2.7 and 5.1x10^9 Mo.


title: Eclipsing binaries in ASAS catalog

abstract:
  ASAS is a long term project to monitor bright variable stars over the whole
sky. It has discovered 50,122 variables brighter than V < 14 mag south of
declination +28 degrees, and among them 11,099 eclipsing binaries. We present a
preliminary analysis of 5,384 contact, 2,957 semi-detached, and 2,758 detached
systems. The statistics of the distribution provides a qualitative confirmation
of decades old idea of Flannery and Lucy that W UMa type binaries evolve
through a series of relaxation oscillations: ASAS finds comparable number of
contact and semidetached systems. The most surprising result is a very small
number of detached eclipsing binaries with periods P < 1 day, the systems
believed to be the progenitors of W UMa stars. As many (perhaps all) contact
binaries have companions, there is a possibility that some were formed in a
Kozai cycle, as suggested by Eggleton and his associates.


title: The metallicity of the old open cluster NGC 6791

abstract:
  We have observed four red clump stars in the very old and metal-rich open
cluster NGC 6791 to derive its metallicity, using the high resolution
spectrograph SARG mounted on the TNG. Using a spectrum synthesis technique we
obtain an average value of [Fe/H] = +0.47 (+/- 0.04, rms=0.08) dex. Our method
was tested on mu Leo, a well studied metal-rich field giant. We also derive
average oxygen and carbon abundances for NGC 6791 from synthesis of [O I] at
6300 A and C_2 at 5086 A, finding [O/Fe] =~ -0.3 and [C/Fe] =~ -0.2.


title:
Linear and Bayesian Planet Detection Algorithms for the Terrestrial
  Planet Finder

abstract:
  Current plans call for the first Terrestrial Planet Finder mission, TPF-C, to
be a monolithic space telescope with a coronagraph for achieving high contrast.
The coronagraph removes the diffracted starlight allowing the nearby planet to
be detected. In this paper, we present a model of the planet measurement and
noise statistics. We utilize this model to develop two planet detection
algorithms, one based on matched filtering of the PSF and one using Bayesian
techniques. These models are used to formulate integration time estimates for a
planet detection with desired small probabilities of false alarms and missed
detections.


title: UV-optical colours as probes of early-type galaxy evolution

abstract:
  We have studied ~2100 early-type galaxies in the SDSS DR3 which have been
detected by the GALEX Medium Imaging Survey (MIS), in the redshift range 0 < z
< 0.11. Combining GALEX UV photometry with corollary optical data from the
SDSS, we find that, at a 95 percent confidence level, at least ~30 percent of
galaxies in this sample have UV to optical colours consistent with some recent
star formation within the last Gyr. In particular, galaxies with a NUV - r
colour less than 5.5 are very likely to have experienced such recent star
formation, taking into account the possibility of a contribution to NUV flux
from the UV upturn phenomenon. We find quantitative agreement between the
observations and the predictions of a semi-analytical LCDM hierarchical merger
model and deduce that early-type galaxies in the redshift range 0 < z < 0.11
have ~1 to 3 percent of their stellar mass in stars less than 1 Gyr old. The
average age of this recently formed population is ~300 to 500 Myrs. We also
find that monolithically evolving galaxies, where recent star formation can be
driven solely by recycled gas from stellar mass loss, cannot exhibit the blue
colours (NUV - r < 5.5) seen in a significant fraction (~30 percent) of our
observed sample.


title: Selection and Characterization of Interesting Grism Spectra

abstract:
  Observations with the ACS Wide Field Camera and G800L grism can produce
thousands of spectra within a single WFC field producing a potentially rich
treasure trove of information. However, the data are complicated to deal with.
Here we describe algorithms to find and characterize spectra of emission line
galaxies and supernovae using tools we have developed in conjunction with off
the shelf software.


title:
INTEGRAL/RossiXTE high-energy observation of a state transition of GX
  339-4

abstract:
  On 2004 August 15, we observed a fast (shorter than 10 hours) state
transition in the bright black-hole transient GX 339-4 simultaneously with
RossiXTE and INTEGRAL. This transition was evident both in timing and spectral
properties. Combining the data from PCA, HEXTE and IBIS, we obtained good
quality broad-band (3-200 keV) energy spectra before and after the transition.
These spectra indicate that the hard component steepened. Also, the high-energy
cutoff that was present at ~70 keV before the transition was not detected after
the transition. This is the first time that an accurate determination of the
broad-band spectrum across such a transition has been measured on a short time
scale. It shows that, although some spectral parameters do not change abruptly
through the transition, the high-energy cutoff increases/disappears rather
fast. These results constitute a benchmark on which to test theoretical models
for the production of the hard component in these systems.


title: Bubbles in Planetary Nebulae and Clusters of Galaxies: Jet Bending

abstract:
  We study the bending of jets in binary stellar systems. A compact companion
accretes mass from the slow wind of the mass-losing primary star, forms an
accretion disk, and blows two opposite jets. These fast jets are bent by the
slow wind. Disregarding the orbital motion, we find the dependence of the
bending angle on the properties of the slow wind and the jets. Bending of jets
is observed in planetary nebulae which are thought to be the descendants of
interacting binary stars. For example, in some of these planetary nebulae the
two bubbles (lobes) which are inflated by the two opposite jets, are displaced
to the same side of the symmetry axis of the nebula. Similar displacements are
observed in bubble pairs in the center of some clusters and groups of galaxies.
We compare the bending of jets in binary stellar systems with that in clusters
of galaxies.


title: Massive Protoplanetary Disks in the Trapezium Region

abstract:
  (abridged) We determine the disk mass distribution around 336 stars in the
young Orion Nebula cluster by imaging a 2.5' x 2.5' region in 3 mm continuum
emission with the Owens Valley Millimeter Array. For this sample of 336 stars,
we observe 3 mm emission above the 3-sigma noise level toward ten sources, six
of which have also been detected optically in silhouette against the bright
nebular background. In addition, we detect 20 objects that do not correspond to
known near-IR cluster members. Comparisons of our measured fluxes with longer
wavelength observations enable rough separation of dust emission from thermal
free-free emission, and we find substantial dust emission toward most objects.
For the ten objects detected at both 3 mm and near-IR wavelengths, eight
exhibit substantial dust emission. Excluding the high-mass stars and assuming a
gas-to-dust ratio of 100, we estimate circumstellar masses ranging from 0.13 to
0.39 Msun. For the cluster members not detected at 3 mm, images of individual
objects are stacked to constrain the mean 3 mm flux of the ensemble. The
average flux is detected at the 3-sigma confidence level, and implies an
average disk mass of 0.005 Msun, comparable to the minimum mass solar nebula.
The percentage of stars in Orion surrounded by disks more massive than ~0.1
Msun is consistent with the disk mass distribution in Taurus, and we argue that
massive disks in Orion do not appear to be truncated through close encounters
with high-mass stars. Comparison of the average disk mass and number of massive
dusty structures in Orion with similar surveys of the NGC 2024 and IC 348
clusters constrains the evolutionary timescales of massive circumstellar disks
in clustered environments.


title: Spatially Resolving the Inner Disk of TW Hya

abstract:
  We present Keck Interferometer observations of TW Hya that spatially resolve
its emission at 2 micron wavelength. Analyzing these data together with
existing K-band veiling and near-infrared photometric measurements, we conclude
that the inner disk consists of optically thin, sub-micron-sized dust extending
from ~4 AU to within 0.06 AU of the central star. The inner disk edge may be
magnetospherically truncated. Even if we account for the presence of gas in the
inner disk, these small dust grains have survival times against radiation
blow-out that are orders of magnitude shorter than the age of the system,
suggesting continual replenishment through collisions of larger bodies.


title: The First Scientific Results from the Pierre Auger Observatory

abstract:
  The southern site of the Pierre Auger Observatory is under the construction
near Malargue in Argentina and now more than 60% of the detectors are
completed. The observatory has been collecting data for over 1 year and the
cumulative exposure is already similar to that of the largest forerunner
experiments. The hybrid technique provides model-independent energy
measurements from the Fluorescence Detector to calibrate the Surface Detector.
Based on this technique, the first estimation of the energy spectrum above 3
EeV has been presented and is discussed in this paper.


title:
The effect of environment on the UV colour-magnitude relation of
  early-type galaxies

abstract:
  We use \textit{GALEX} (Galaxy Evolution Explorer) near-UV (NUV) photometry of
a sample of early-type galaxies selected in \textit{SDSS} (Sloan Digital Sky
Survey) to study the UV color-magnitude relation (CMR). $NUV-r$ color is an
excellent tracer of even small amounts ($\sim 1$% mass fraction) of recent
($\la 1$ Gyr) star formation and so the $NUV-r$ CMR allows us to study the
effect of environment on the recent star formation history. We analyze a
volume-limited sample of 839 visually-inspected early-type galaxies in the
redshift range $0.05 < z < 0.10$ brighter than $M_{r}$ of -21.5 with any
possible emission-line or radio-selected AGN removed to avoid contamination. We
find that contamination by AGN candidates and late-type interlopers highly bias
any study of recent star formation in early-type galaxies and that, after
removing those, our lower limit to the fraction of massive early-type galaxies
showing signs of recent star formation is roughly $30 \pm 3%$ This suggests
that residual star formation is common even amongst the present day early-type
galaxy population.
  We find that the fraction of UV-bright early-type galaxies is 25% higher in
low-density environments. However, the density effect is clear only in the
lowest density bin. The blue galaxy fraction for the subsample of the brightest
early-type galaxies however shows a very strong density dependence, in the
sense that the blue galaxy fraction is lower in a higher density region.


title:
A Chandra Snapshot Survey of Representative High-Redshift Radio-Loud
  Quasars from the Parkes-MIT-NRAO Sample

abstract:
  We present the results of Chandra ACIS-S snapshot observations of six
radio-loud quasars (RLQs) at z=3.5-4.7. These observations sample luminous RLQs
with moderate-to-high radio-loudness (R=200-9600) and aim to connect the X-ray
properties of radio-quiet quasars (R<10) and highly radio-loud blazars (R>1000)
at high redshift. This work extends a study by Bassett et al. (2004) which used
similar methods to examine z > 4 RLQs with moderate radio-loudness (R=40-400).
All of our targets are clearly detected. A search for extended X-ray emission
associated with kpc-scale radio jets revealed only limited evidence for X-ray
extension in our sample: three sources showed no evidence of X-ray extension,
and the other three had 3-30% of their total X-ray fluxes extended >1 arcsec
away from their X-ray cores. Additionally, we do not observe any systematic
flattening of the optical-to-X-ray spectral index (alpha_{ox}) compared to
low-redshift quasars. These results suggest that kpc-scale X-ray jet emission
is not dominated by inverse-Compton scattering of CMB-seed photons off jet
electrons. We measured X-ray continuum shapes and performed individual and
joint spectral fits of our data combined with eight archival RLQs. A single
power-law model acceptably fit the data. We added an intrinsic absorption
component to our model, and neither the moderate-R nor the high-R fits set a
lower bound on N_H. Our spectral results suggest that intrinsic absorption does
not strongly depend on radio-loudness, and high-R sources have flatter power
laws than moderate-R sources. Overall, our high-redshift RLQs have basic X-ray
properties consistent with similar RLQs in the local universe.


title: Discrete Cosmological Self-Similarity And Delta Scuti Stars

abstract:
  Within the context of a fractal paradigm that emphasizes nature's
well-stratified hierarchical organization, the delta Scuti class of variable
stars is investigated for evidence of discrete cosmological self-similarity.
Methods that were successfully applied to the RR Lyrae class of variable stars
are used to identify Atomic Scale analogues to delta Scuti stars and their
relevant range of energy levels. The mass, pulsation mode and fundamental
oscillation period of a well-studied delta Scuti star are shown to be
quantitatively self-similar to the counterpart parameters of a uniquely
identified Atomic Scale analogue. Several additional tests confirm the
specificity of the discrete fractal relationship.


title: Are Ti44-Producing Supernovae Exceptional?

abstract:
  According to standard models supernovae produce radioactive $^{44}$Ti, which
should be visible in gamma-rays following decay to $^{44}$Ca for a few
centuries. $^{44}Ti production is believed to be the source of cosmic
$^{44}$Ca, whose abundance is well established. Yet, gamma-ray telescopes have
not seen the expected young remnants of core collapse events. The $^{44}$Ti
mean life of $\tau \simeq$ 89 y and the Galactic supernova rate of $\simeq$
3/100 y imply $\simeq$ several detectable $^{44}Ti gamma-ray sources, but only
one is clearly seen, the 340-year-old Cas A SNR. Furthermore, supernovae which
produce much $^{44}Ti are expected to occur primarily in the inner part of the
Galaxy, where young massive stars are most abundant. Because the Galaxy is
transparent to gamma-rays, this should be the dominant location of expected
gamma-ray sources. Yet the Cas A SNR as the only one source is located far from
the inner Galaxy (at longitude 112 degree). We evaluate the surprising absence
of detectable supernovae from the past three centuries. We discuss whether our
understanding of SN explosions, their $^{44}Ti yields, their spatial
distributions, and statistical arguments can be stretched so that this apparent
disagreement may be accommodated within reasonable expectations, or if we have
to revise some or all of the above aspects to bring expectations in agreement
with the observations. We conclude that either core collapse supernovae have
been improbably rare in the Galaxy during the past few centuries, or
$^{44}Ti-producing supernovae are atypical supernovae. We also present a new
argument based on $^{44}$Ca/$^{40}$Ca ratios in mainstream SiC stardust grains
that may cast doubt on massive-He-cap Type I supernovae as the source of most
galactic $^{44}$Ca.


title:
The Alignment between the Distribution of Satellites and the Orientation
  of their Central Galaxy

abstract:
  We use galaxy groups selected from the Sloan Digital Sky Survey to examine
the alignment between the orientation of the central galaxy (defined as the
brightest group member) and the distribution of satellite galaxies. By
construction, we therefore only address the alignment on scales smaller than
the halo virial radius. We find a highly significant alignment of satellites
with the major axis of their central galaxy. This is in qualitative agreement
with the recent study of Brainerd (2005), but inconsistent with several
previous studies who detected a preferential minor axis alignment. The
alignment strength in our sample is strongest between red central galaxies and
red satellites. On the contrary, the satellite distribution in systems with a
blue central galaxy is consistent with isotropic. We also find that the
alignment strength is stronger in more massive haloes and at smaller projected
radii from the central galaxy. In addition, there is a weak indication that
fainter (relative to the central galaxy) satellites are more strongly aligned.
We present a detailed comparison with previous studies, and discuss the
implications of our findings for galaxy formation.


title:
Second-order perturbations of a zero-pressure cosmological medium:
  comoving vs. synchronous gauge

abstract:
  Except for the presence of gravitational wave source term, the relativistic
perturbation equations of a zero-pressure irrotational fluid in a flat
Friedmann world model coincide exactly with the Newtonian ones to the second
order in perturbations. Such a relativistic-Newtonian correspondence is
available in a special gauge condition (the comoving gauge) in which all the
variables are equivalently gauge invariant. In this work we compare our results
with the ones in the synchronous gauge which has been used often in the
literature. Although the final equations look simpler in the synchronous gauge,
the variables have remnant gauge modes. Except for the presence of the gauge
mode for the perturbed order variables, however, the equations in the
synchronous gauge are gauge invariant and can be exactly identified as the
Newtonian hydrodynamic equations in the Lagrangian frame. In this regard, the
relativistic equations to the second order in the comoving gauge are the same
as the Newtonian hydrodynamic equations in the Eulerian frame. We resolve
several issues related to the two gauge conditions often to fully nonlinear
orders in perturbations.


title: Downsizing of Star-Forming Galaxies by Gravitational Processes

abstract:
  There is observed a trend that a lower mass galaxy forms stars at a later
epoch. This downsizing of star-forming galaxies has been attributed to
hydrodynamical or radiative feedback processes that regulate star formation.
However, here we explain the downsizing by gravitational processes alone, in
the bottom-up scenario where galaxies evolve from subgalactic-scale objects.
Within a region of the initial density field that is to evolve into a lower
mass galaxy, subgalactic-scale fluctuation is of a smaller amplitude. The
formation of subgalactic-scale objects, i.e., gravitational collapse of the
subgalactic-scale fluctuation, and the subsequent onset of star formation
accordingly occur at a later epoch for a lower mass galaxy. As a function of
galaxy mass, we calculate the peak epoch of formation of subgalactic-scale
objects. The peak epoch is consistent with the peak epoch of star formation
derived from observations. [abridged]


title:
Jupiter's composition: sign of a (relatively) late formation in a
  chemically evolved protosolar disk

abstract:
  It has been proposed that the enrichment in noble gases found by Galileo in
Jupiter's atmosphere can be explained by their delivery inside cold
planetesimals. We propose instead that this is a sign that the planet formed in
a chemically evolved disk and that noble gases were acquired mostly in gaseous
form during the planet's envelope capture phase. We show that the combined
settling of grains to the disk midplane in the cold outer layers, the
condensation of noble gases onto these grains at temperatures below 20-30K, and
the evaporation from high disk altitudes effectively lead to a progressive,
moderate enrichment of the disk. The fact that noble gases are vaporized from
the grains in the hot inner disk regions (e.g. Jupiter formation region) is not
a concern because a negative temperature gradient prevents convection from
carrying the species into the evaporating region. We show that the ~2 times
solar enrichment of Ar, Kr, Xe in Jupiter is hence naturally explained by a
continuous growth of the planet governed by viscous diffusion in the protosolar
disk in conjunction with an evaporation of the disk and its progressive
enrichment on a million years timescale.


title: Light Bending as a Probe of the Nature of Dark Energy

abstract:
  We study the bending of light for static spherically symmetric (SSS)
space-times which include a dark energy contribution. Geometric dark energy
models generically predict a correction to the Einstein angle written in terms
of the distance to the closest approach, whereas a cosmological constant
$\Lambda$ does not. While dark energy is associated with a repulsive force in
cosmological context, its effect on null geodesics in SSS space-times can be
attractive as for the Newtonian term. This dark energy contribution may be not
negligible with respect to the Einstein prediction in lensing involving
clusters of galaxies. Strong lensing may therefore be useful to distinguish
$\Lambda$ from other dark energy models.


title: Two new candidate ultra-compact X-ray binaries

abstract:
  We present the identification of the optical counterparts to the low-mass
X-ray binaries 1A 1246-588 and 4U 1812-12. We determine the X-ray position of
1A 1246-588 from ROSAT/PSPC observations and find within the error circle a
blue star with V=19.45, B-V=0.22 and R-I=0.22 which we identify as the
counterpart. Within the Chandra error circle of 4U 1812-12, a single star is
present which appears blue with respect to the stars in the vicinity. It has
R=22.15, R-I=1.53. Distance estimates for both systems indicate that the
optical counterparts are intrinsically faint, suggesting that they are
ultra-compact X-ray binaries. These identifications would increase the number
of candidate ultra-compact X-ray binaries from 2 to 4, whereas orbital periods
are measured for only 7 systems in the Galactic disk.


title: Spectroscopy of the candidate pre-CV LTT 560

abstract:
  We present preliminary results on spectroscopic data of the candidate
pre-cataclysmic variable LTT 560. A fit to the flux-calibrated spectrum reveals
the temperature of the white-dwarf primary to be T_eff = 7000 - 7500 K, and
confirms the result of previous studies on the detection of an M5V secondary
star. The analysis of radial velocity data from spectral features attributed to
the primary and the secondary star shows evidence for low-level accretion.


title: Formation flying for a Fresnel lens observatory mission

abstract:
  The employment of a large area Phase Fresnel Lens (PFL) in a gamma-ray
telescope offers the potential to image astrophysical phenomena with
micro-arcsecond angular resolution. In order to assess the feasibility of this
concept, two detailed studies have been conducted of formation flying missions
in which a Fresnel lens capable of focussing gamma-rays and the associated
detector are carried on two spacecraft separated by up to 10$^6$ km. These
studies were performed at the NASA Goddard Space Flight Center Integrated
Mission Design Center (IMDC) which developed spacecraft, orbital dynamics, and
mission profiles. The results of the studies indicated that the missions are
challenging but could be accomplished with technologies available currently or
in the near term. The findings of the original studies have been updated taking
account of recent advances in ion thruster propulsion technology.


title:
Comparative Direct Analysis of Type Ia Supernova Spectra. II. Maximum
  Light

abstract:
  A comparative study of near-maximum-light optical spectra of 24 Type Ia
supernovae (SNe Ia) is presented. The spectra are quantified in two ways, and
assigned to four groups. Seven "core-normal" SNe Ia have very similar spectra,
except for strong high-velocity CaII absorption in SN 2001el. Seven SNe Ia are
assigned to a "broad-line" group, the most extreme of which is SN 1984A. Five
SNe Ia, including SN 1991bg, are assigned to a "cool" group. Five SNe Ia,
including SN 1991T, are assigned to a "shallow-silicon" group. Comparisons with
SYNOW synthetic spectra provide a basis for discussion of line identifications,
and an internally consistent quantification of the maximum-light spectroscopic
diversity among SNe Ia. The extent to which SN Ia maximum-light spectra appear
to have a continuous distribution of properties, rather than consisting of
discrete subtypes, is discussed.


title:
Effective temperature scale and bolometric corrections from 2MASS
  photometry

abstract:
  This paper presents a method to determine effective temperatures, angular
semi-diameters and bolometric corrections for population I and II FGK type
stars based on V and 2MASS IR photometry. Accurate calibration is accomplished
by using a sample of solar analogues, whose average temperature is assumed to
be equal to the solar effective temperature of 5777 K. By taking into account
all possible sources of error we estimate associated uncertainties better than
1% in effective temperature and in the range 1.0-2.5% in angular semi-diameter
for unreddened stars. Comparison of our new temperatures with other
determinations extracted from the literature indicates, in general, remarkably
good agreement. These results suggest that the effective temperaure scale of
FGK stars is currently established with an accuracy better than 0.5%-1%. The
application of the method to a sample of 10999 dwarfs in the Hipparcos
catalogue allows us to define temperature and bolometric correction (K band)
calibrations as a function of (V-K), [m/H] and log g. Bolometric corrections in
the V and K bands as a function of effective temperature, [m/H] and log g are
also given. We provide effective temperatures, angular semi-diameters, radii
and bolometric corrections in the V and K bands for the 10999 FGK stars in our
sample with the corresponding uncertainties.


title:
Better age estimations using UV-optical colours: breaking the
  age-metallicity degeneracy

abstract:
  We demonstrate that the combination of GALEX UV photometry in the FUV (~1530
angstroms) and NUV (~2310 angstroms) passbands with optical photometry in the
standard U,B,V,R,I filters can efficiently break the age-metallicity
degeneracy. We estimate well-constrained ages, metallicities and their
associated errors for 42 GCs in M31, and show that the full set of
FUV,NUV,U,B,V,R,I photometry produces age estimates that are ~90 percent more
constrained and metallicity estimates that are ~60 percent more constrained
than those produced by using optical filters alone. The quality of the age
constraints is comparable or marginally better than those achieved using a
large number of spectrscopic indices.


title: Conformal Transformations and Accelerated Cosmologies

abstract:
  A cosmological theory that predicts a late-time accelerated attractor with a
constant dark matter to dark energy ratio can be said to solve the Coincidence
Problem. Such cosmologies are naturally generated in the context of
non-standard gravity theories under conformal transformation because of the
resulting couplings between scalar fields and matter. The present work examines
four classes of these transformed theories and finds that only a small
subset--those with a single scalar field--are capable of solving the
Coincidence Problem.


title: The Paths of Quintessence

abstract:
  The structure of the dark energy equation of state phase plane holds
important information on the nature of the physics. We explain the bounds of
the freezing and thawing models of scalar field dark energy in terms of the
tension between the steepness of the potential vs. the Hubble drag.
Additionally, we extend the phase plane structure to modified gravity theories,
examine trajectories of models with certain properties, and categorize regions
in terms of scalar field hierarchical parameters, showing that dark energy is
generically not a slow roll phenomenon.


title: Twin-peak quasiperiodic oscillations as an internal resonance

abstract:
  Two inter-related peaks occur in high-frequency power spectra of X-ray
lightcurves of several black-hole candidates. We further explore the idea that
a non-linear resonance mechanism, operating in strong-gravity regime, is
responsible for these quasi-periodic oscillations (QPOs). By extending the
multiple-scales analysis of Rebusco, we construct two-dimensional phase-space
sections, which enable us to identify different topologies governing the system
and to follow evolutionary tracks of the twin peaks. This suggests that the
original (Abramowicz and Kluzniak) parametric-resonance scheme can be viewed as
an ingenuous account of the QPOs model with an internal resonance. We show an
example of internal resonance in a system with up to two critical points, and
we describe a general technique that permits to treat other cases in a
systematical manner. A separatrix divides the phase-space sections into regions
of different topology: inside the libration region the evolutionary tracks
bring the observed twin-peak frequencies to an exact rational ratio, whereas in
the circulation region the observed frequencies remain off resonance. Our
scheme predicts the power should cyclically be exchanged between the two
oscillations. Likewise the high-frequency QPOs in neutron-star binaries, also
in black-hole sources one expects, as a general property of the non-linear
model, that slight detuning pushes the twin-peak frequencies out of sharp
resonance.


title:
GRB efficiency and Possible Physical Processes Shaping the Early
  Afterglow

abstract:
  The discovery by Swift that a good fraction of Gamma Ray Bursts (GRBs) have a
slowly decaying X-ray afterglow phase led to the suggestion that energy
injection into the blast wave takes place several hundred seconds after the
burst. This implies that right after the burst the kinetic energy of the blast
wave was very low and in turn the efficiency of production of $\gamma$-rays
during the burst was extremely high, rendering the internal shocks model
unlikely. We re-examine the estimates of kinetic energy in GRB afterglows and
show that the efficiency of converting the kinetic energy into gamma-rays is
moderate and does not challenge the standard internal shock model. We also
examine several models, including in particular energy injection, suggested to
interpret this slow decay phase. We show that with proper parameters, all these
models give rise to a slow decline lasting several hours. However, even those
models that fit all X-ray observations, and in particular the energy injection
model, cannot account self-consistently for both the X-ray and the optical
afterglows of well monitored GRBs such as GRB 050319 and GRB 050401. We
speculate about a possible alternative resolution of this puzzle.