title: Estimators for local non-Gaussianities

abstract:
  We study the Likelihood function of data given f_NL for the so-called local
type of non-Gaussianity. In this case the curvature perturbation is a
non-linear function, local in real space, of a Gaussian random field. We
compute the Cramer-Rao bound for f_NL and show that for small values of f_NL
the 3-point function estimator saturates the bound and is equivalent to
calculating the full Likelihood of the data. However, for sufficiently large
f_NL, the naive 3-point function estimator has a much larger variance than
previously thought. In the limit in which the departure from Gaussianity is
detected with high confidence, error bars on f_NL only decrease as 1/ln Npix
rather than Npix^-1/2 as the size of the data set increases. We identify the
physical origin of this behavior and explain why it only affects the local type
of non-Gaussianity, where the contribution of the first multipoles is always
relevant. We find a simple improvement to the 3-point function estimator that
makes the square root of its variance decrease as Npix^-1/2 even for large
f_NL, asymptotically approaching the Cramer-Rao bound. We show that using the
modified estimator is practically equivalent to computing the full Likelihood
of f_NL given the data. Thus other statistics of the data, such as the 4-point
function and Minkowski functionals, contain no additional information on f_NL.
In particular, we explicitly show that the recent claims about the relevance of
the 4-point function are not correct. By direct inspection of the Likelihood,
we show that the data do not contain enough information for any statistic to be
able to constrain higher order terms in the relation between the Gaussian field
and the curvature perturbation, unless these are orders of magnitude larger
than the size suggested by the current limits on f_NL.


title: The X-ray Properties of Optically-Selected Galaxy Clusters

abstract:
  We stacked the X-ray data from the ROSAT All Sky Survey for over 4,000
clusters selected from the 2MASS catalog and divided into five richness
classes. We detected excess X-ray emission over background at the center of the
stacked images in all five richness bins. The interrelationships between the
mass, X-ray temperature and X-ray luminosity of the stacked clusters agree well
with those derived from catalogs of X-ray clusters. Poisson variance in the
number of galaxies occupying halos of a given mass leads to significant
differences between the average richness at fixed mass and the average mass at
fixed richness that we can model relatively easily using a simple model of the
halo occupation distribution. These statistical effects probably explain recent
results in which optically-selected clusters lie on the same X-ray
luminosity-temperature relations as local clusters but have lower optical
richnesses than observed for local clusters with the same X-ray properties.
When we further binned the clusters by redshift, we did not find significant
redshift-dependent biases in the sense that the X-ray luminosities for massive
clusters of fixed optical richness show little dependence on redshift beyond
that expected from the effects of Poisson fluctuations. Our results demonstrate
that stacking of RASS data from optically selected clusters can be a powerful
test for biases in cluster selection algorithms.


title: Tachyon dark energy models: dynamics and constraints

abstract:
  We explore the dynamics of dark energy models based on a Dirac-Born-Infeld
(DBI) tachyonic action, studying a range of potentials. We numerically
investigate the existence of tracking behaviour and determine the present-day
value of the equation of state parameter and its running, which are compared
with observational bounds. We find that tachyon models have quite similar
phenomenology to canonical quintessence models. While some potentials can be
selected amongst many possibilities and fine-tuned to give viable scenarios,
there is no apparent advantage in choosing a DBI scalar field instead of a
Klein-Gordon one.


title: The bright optical flash from GRB 060117

abstract:
  We present a discovery and observation of an extraordinarily bright prompt
optical emission of the GRB 060117 obtained by a wide-field camera atop the
robotic telescope FRAM of the Pierre Auger Observatory from 2 to 10 minutes
after the GRB. We found rapid average temporal flux decay of alpha = -1.7 +-
0.1 and a peak brightness R = 10.1 mag. Later observations by other instruments
set a strong limit on the optical and radio transient fluxes, unveiling an
unexpectedly rapid further decay. We present an interpretation featuring a
relatively steep electron-distribution parameter p ~ 3.0 and providing a
straightforward solution for the overall fast decay of this optical transient
as a transition between reverse and forward shock.


title: On the efficiency of Fermi acceleration at relativistic shocks

abstract:
  It is shown that Fermi acceleration at an ultra-relativistic shock wave
cannot operate on a particle for more than 1 1/2 Fermi cycle (i.e., u -> d -> u
-> d) if the particle Larmor radius is much smaller than the coherence length
of the magnetic field on both sides of the shock, as is usually assumed. This
conclusion is shown to be in excellent agreement with recent numerical
simulations. We thus argue that efficient Fermi acceleration at
ultra-relativistic shock waves requires significant non-linear processing of
the far upstream magnetic field with strong amplification of the small scale
magnetic power. The streaming or transverse Weibel instabilities are likely to
play a key role in this respect.


title: Arc sensitivity to cluster ellipticity, asymmetries and substructures

abstract:
  We investigate how ellipticity, asymmetries and substructures separately
affect the ability of galaxy clusters to produce strong lensing events, i.e.
gravitational arcs, and how they influence the arc morphologies and fluxes.
This is important for those studies aiming, for example, at constraining
cosmological parameters from statistical lensing, or at determining the inner
structure of galaxy clusters through gravitational arcs. We do so by creating
two-dimensional gradually smoothed, differently elliptical and asymmetric
versions of some numerical models. On average, we find that the contributions
of ellipticity, asymmetries and substructures amount to ~40%, ~10% and ~30% of
the total strong lensing cross section, respectively. However, our analysis
shows that substructures play a more important role in less elliptical and
asymmetric clusters, even if located at large distances from the cluster
centers (~1Mpc/h). Conversely, their effect is less important in highly
asymmetric lenses. The morphology, position and flux of individual arcs are
strongly affected by the presence of substructures in the clusters. Removing
substructures on spatial scales <~50kpc/h, roughly corresponding to mass scales
<~5 10^{10}M_\odot/h, alters the image multiplicity of ~35% of the sources used
in the simulations and causes position shifts larger than 5'' for ~40% of the
arcs longer than 5''. We conclude that any model for cluster lens cannot
neglect the effects of ellipticity, asymmetries and substructures. On the other
hand, the high sensitivity of gravitational arcs to deviations from regular,
smooth and symmetric mass distributions suggests that strong gravitational
lensing is potentially a powerfull tool to measure the level of substructures
and asymmetries in clusters.


title: The Large-Scale Structure view on the Galaxy-Quasar-AGN connection

abstract:
  Combined investigations of the clustering properties of galaxies of different
spectral type and high-redshift quasars strongly suggest local ellipticals to
be the parent population of optically bright Active Galactic Nuclei (AGN).
However, the picture gets more blurred when one extends the analysis to that
class of AGNs which show enhanced radio emission. Objects belonging to this
class in fact are found to be associated with structures which are about an
order of magnitude more massive than those that host radio-quiet AGNs. Also,
masses for the black holes engines of radio-enhanced AGN emission turn out to
be systematically higher than those which fuel 'normal' quasars. On the other
hand, the level of radio-activity in radio-luminous objects does not seem to be
connected with black hole/host galaxy mass, at variance with what found in the
optical case. These results, together with evidences for different cosmological
evolutions of different types of AGNs pose a serious challenge to all those
models aiming at providing a unified picture for black hole-powered sources.


title: Probing the Low-Luminosity XLF in Normal Elliptical Galaxies

abstract:
  We present the first low luminosity (LX > 5 - 10 1036 erg s-1) X-ray
luminosity functions (XLFs) of low-mass X-ray binaries (LMXBs) determined for
two typical old elliptical galaxies, NGC 3379 and NGC 4278. Because both
galaxies contain little diffuse emission from hot ISM and no recent significant
star formation (hence no high-mass X-ray binary contamination), they provide
two of the best homogeneous sample of LMXBs. With 110 and 140 ks Chandra ACIS
S3 exposures, we detect 59 and 112 LMXBs within the D25 ellipse of NGC 3379 and
NGC 4278, respectively. The resulting XLFs are well represented by a single
power-law with a slope (in a differential form) of 1.9 0.1. In NGC 4278, we can
exclude the break at LX ~ 5 x 1037 erg s-1 that was recently suggested to be a
general feature of LMXB XLFs. In NGC 3379 instead we find a localized excess
over the power law XLF at ~4 x 1037 erg s-1, but with a marginal significance
of ~1.6s. Because of the small number of luminous sources, we cannot constrain
the high luminosity break (at 5 x 1038 erg s-1) found in a large sample of
early type galaxies. While the optical luminosities of the two galaxies are
similar, their integrated LMXB X-ray luminosities differ by a factor of 4,
consistent with the relation between the X-ray to optical luminosity ratio and
the globular cluster specific frequency.


title:
The Eccentricity-Mass Distribution of Exoplanets: Signatures of
  Different Formation Mechanisms?

abstract:
  We examine the distributions of eccentricity and host star metallicity of
exoplanets as a function of their mass. Planets with M sin i >~ 4 M_J have an
eccentricity distribution consistent with that of binary stars, while planets
with M sin i <~ 4 M_J are less eccentric than binary stars and more massive
planets. In addition, host star metallicities decrease with planet mass. The
statistical significance of both of these trends is only marginal with the
present sample of exoplanets. To account for these trends, we hypothesize that
there are two populations of gaseous planets: the low-mass population forms by
gas accretion onto a rock-ice core in a circumstellar disk and is more abundant
at high metalliticities, and the high-mass population forms directly by
fragmentation of a pre-stellar cloud. Planets of the first population form in
initially circular orbits and grow their eccentricities later, and may have a
mass upper limit from the total mass of the disk that can be accreted by the
core. The second population may have a mass lower limit resulting from
opacity-limited fragmentation. This would roughly divide the two populations in
mass, although they would likely overlap over some mass range. If most objects
in the second population form before the pre-stellar cloud becomes highly
opaque, they would have to be initially located in orbits larger than ~30 AU,
and would need to migrate to the much smaller orbits in which they are
observed. The higher mean orbital eccentricity of the second population might
be caused by the larger required intervals of radial migration, and the brown
dwarf desert might be due to the inability of high-mass brown dwarfs to migrate
inwards sufficiently in radius.


title:
DEMON: a Proposal for a Satellite-Borne Experiment to study Dark Matter
  and Dark Energy

abstract:
  We outline a novel satellite mission concept, DEMON, aimed at advancing our
comprehension of both dark matter and dark energy, taking full advantage of two
complementary methods: weak lensing and the statistics of galaxy clusters. We
intend to carry out a 5000 sqdeg combined IR, optical and X-ray survey with
galaxies up to a redshift of z~2 in order to determine the shear correlation
function. We will also find ~100000 galaxy clusters, making it the largest
survey of this type to date. The DEMON spacecraft will comprise one IR/optical
and eight X-ray telescopes, coupled to multiple cameras operating at different
frequency bands. To a great extent, the technology employed has already been
partially tested on ongoing missions, therefore ensuring improved reliability.


title:
Smooth Light Curves from a Bumpy Ride: Relativistic Blast Wave
  Encounters a Density Jump

abstract:
  Some GRB afterglow light curves show significant variability, which often
includes episodes of rebrightening. This was attributed in several cases to
large fluctuations in the external density. Here we examine the effect of a
sharp increase in the external density on the light curve by considering, for
the first time, a full treatment of both the hydrodynamic evolution and the
radiation in this scenario. To this end we develop a semi-analytic model for
the light curve and carry out several elaborate numerical simulations using a
1D hydrodynamic code together with a synchrotron radiation code.Two spherically
symmetric cases are explored in detail: a density jump in a uniform external
medium, and a wind termination shock. Contrary to previous works, we find that
even a sharp (step function) and large (by a factor of $a>>1$) increase in the
external density does not produce sharp features in the light curve, and cannot
account for significant temporal variability. For a wind termination shock, the
light curve smoothly transitions between the asymptotic power-laws over about
one decade in time, and there is no rebrightening in the optical or X-rays to
serve as a clear observational signature. For a sharp jump in a uniform density
we find that the maximal deviation $\Delta\alpha_max$ of the temporal decay
index $\alpha$ from its asymptotic value, is bounded (e.g., $\Delta\alpha_max
<0.4$ for $a=10$); $\Delta\alpha_max$ slowly increases with $a$, converging to
$\Delta\alpha_{max} \approx 1$ at very large $a$ values. Therefore, no optical
rebrightening is expected here as well. In the X-rays, while the asymptotic
flux is unaffected by the density jump, the fluctuations in $\alpha$ are found
to be comparable to those in the optical. Finally, we discuss the implications
of our results for the origin of the fluctuations in several afterglows.


title:
Refining a relativistic, hydrodynamic solver: Admitting
  ultra-relativistic flows

abstract:
  We have undertaken the simulation of hydrodynamic flows with bulk Lorentz
factors in the range 10^2--10^6. We discuss the application of an existing
relativistic, hydrodynamic primitive-variable recovery algorithm to a study of
pulsar winds, and, in particular, the refinement made to admit such
ultra-relativistic flows. We show that an iterative quartic root finder breaks
down for Lorentz factors above 10^2 and employ an analytic root finder as a
solution. We find that the former, which is known to be robust for Lorentz
factors up to at least 50, offers a 24% speed advantage. We demonstrate the
existence of a simple diagnostic allowing for a hybrid primitives recovery
algorithm that includes an automatic, real-time toggle between the iterative
and analytical methods. We further determine the accuracy of the iterative and
hybrid algorithms for a comprehensive selection of input parameters and
demonstrate the latter's capability to elucidate the internal structure of
ultra-relativistic plasmas. In particular, we discuss simulations showing that
the interaction of a light, ultra-relativistic pulsar wind with a slow, dense
ambient medium can give rise to asymmetry reminiscent of the Guitar nebula
leading to the formation of a relativistic backflow harboring a series of
internal shockwaves. The shockwaves provide thermalized energy that is
available for the continued inflation of the PWN bubble. In turn, the bubble
enhances the asymmetry, thereby providing positive feedback to the backflow.


title:
Spiral stellar density waves and the flattening of abundance gradients
  in the warm gas component of spiral galaxies

abstract:
  Motivated by recent observations of plateaus and minima in the radial
abundance distributions of heavy elements in the Milky Way and some other
spiral galaxies, we propose a dynamical mechanism for the formation of such
features around corotation. Our numerical simulations show that the
non-axisymmetric gravitational field of spiral density waves generates cyclone
and anticylone gas flows in the vicinity of corotation. The anticyclones
flatten the pre-existing negative abundance gradients by exporting many more
atoms of heavy elements outside corotation than importing inside it. This
process is very efficient and forms plateaus of several kiloparsec in size
around corotation after two revolution periods of a galaxy. The strength of
anticyclones and, consequently, the sizes of plateaus depend on the pitch angle
of spiral arms and are expected to increase along the Hubble sequence.


title: Coherent synchrotron emission from cosmic ray air showers

abstract:
  Coherent synchrotron emission by particles moving along semi-infinite tracks
is discussed, with a specific application to radio emission from air showers
induced by high-energy cosmic rays. It is shown that in general, radiation from
a particle moving along a semi-infinite orbit consists of usual synchrotron
emission and modified impulsive bremsstrahlung. The latter component is due to
the instantaneous onset of the curved trajectory of the emitting particle at
its creation. Inclusion of the bremsstrahlung leads to broadening of the
radiation pattern and a slower decay of the spectrum at the cut-off frequency
than the conventional synchrotron emission. Possible implications of these
features for air shower radio emission are discussed.


title: Substructure around M31 : Evolution and Effects

abstract:
  We investigate the evolution of a population of 100 dark matter satellites
orbiting in the gravitational potential of a realistic model of M31. We find
that after 10 Gyr, seven subhalos are completely disrupted by the tidal field
of the host galaxy. The remaining satellites suffer heavy mass loss and
overall, 75% of the mass initially in the subhalo system is tidally stripped.
Not surprisingly, satellites with pericentric radius less than 30 kpc suffer
the greatest stripping and leave a complex structure of tails and streams of
debris around the host galaxy. Assuming that the most bound particles in each
subhalo are kinematic tracers of stars, we find that the halo stellar
population resulting from the tidal debris follows an r^{-3.5} density profile
at large radii. We construct B-band photometric maps of stars coming from
disrupted satellites and find conspicuous features similar both in morphology
and brightness to the observed Giant Stream around Andromeda. An assumed star
formation efficiency of 5-10% in the simulated satellite galaxies results in
good agreement with the number of M31 satellites, the V-band surface brightness
distribution, and the brightness of the Giant Stream. During the first 5 Gyr,
the bombardment of the satellites heats and thickens the disk by a small
amount. At about 5 Gyr, satellite interations induce the formation of a strong
bar which, in turn, leads to a significant increase in the velocity dispersion
of the disk.


title: Magellan Spectroscopy of AGN Candidates in the COSMOS Field

abstract:
  We present spectroscopic redshifts for the first 466 X-ray and radio-selected
AGN targets in the 2 deg^2 COSMOS field. Spectra were obtained with the IMACS
instrument on the Magellan (Baade) telescope, using the nod-and-shuffle
technique. We identify a variety of Type 1 and Type 2 AGN, as well as red
galaxies with no emission lines. Our redshift yield is 72% down to i_AB=24,
although the yield is >90% for i_AB<22. We expect the completeness to increase
as the survey continues. When our survey is complete and additional redshifts
from the zCOSMOS project are included, we anticipate ~1100 AGN with redshifts
over the entire COSMOS field. Our redshift survey is consistent with an
obscured AGN population that peaks at z~0.7, although further work is necessary
to disentangle the selection effects.


title: High-energy Emission from Pulsar Magnetospheres

abstract:
  A synthesis of the present knowledge on gamma-ray emission from the
magnetosphere of a rapidly rotating neutron star is presented, focusing on the
electrodynamics of particle accelerators. The combined curvature, synchrotron,
and inverse-Compton emission from ultra-relativistic positrons and electrons,
which are created by two-photon and/or one-photon pair creation processes, or
emitted from the neutron-star surface, provide us with essential information on
the properties of the accelerator -- electric potential drop along the magnetic
field lines. A new accelerator model, which is a mixture of traditional
inner-gap and outer gap models, is also proposed, by solving the Poisson
equation for the electrostatic potential together with the Boltzmann equations
for particles and gamma-rays in the two-dimensional configuration and
two-dimensional momentum spaces.


title: VZ Velorum: 116 years of a Mira star

abstract:
  Using the Harvard College Observatory Photographic Plate Collection and
recent CCD observations by the ASAS project we have reconstructed the light
variations of the southern pulsating red giant star VZ Velorum between 1890 and
early 2006. Contrary to an early report on its low-amplitude semiregular
nature, we found a relatively stable Mira-like light curve with a mean period
of 318 days and amplitude up to 7 magnitudes. The latest observations show
evidence for a slightly shorter period (312 days). However, the difference does
not exceed the intrinsic period jitter often seen in Mira type variables.


title: The HII Region of a Primordial Star

abstract:
  The concordance model of cosmology and structure formation predicts the
formation of isolated very massive stars at high redshifts in dark matter
dominated halos of 10^5 to 10^6 Msun. These stars photo-ionize their host
primordial molecular clouds, expelling all the baryons from their halos. When
the stars die, a relic HII region is formed within which large amounts of
molecular hydrogen form which will allow the gas to cool efficiently when
gravity assembles it into larger dark matter halos. The filaments surrounding
the first star hosting halo are largely shielded and provide the pathway for
gas to stream into the halo when the star has died. We present the first fully
three dimensional cosmological radiation hydrodynamical simulations that follow
all these effects. A novel adaptive ray casting technique incorporates the time
dependent radiative transfer around point sources. This approach is fast enough
so that radiation transport, kinetic rate equations, and hydrodynamics are
solved self-consistently. It retains the time derivative of the transfer
equation and is explicitly photon conserving. This method is integrated with
the cosmological adaptive mesh refinement code enzo, and runs on distributed
and shared memory parallel architectures. Where applicable the three
dimensional calculation not only confirm expectations from earlier one
dimensional results but also illustrate the multi-fold hydrodynamic
complexities of HII regions. In the absence of stellar winds the circumstellar
environments of the first supernovae and putative early gamma-ray bursts will
be of low density ~1 cm^-3. Albeit marginally resolved, ionization front
instabilities lead to cometary and elephant trunk like small scale structures
reminiscent of nearby star forming regions.


title: Ongoing Star Formation in the BL Lacertae object PKS 2005-489

abstract:
  We present VLT long slit optical spectroscopy of the luminous BL Lacertae
object PKS 2005-489. The high signal-to-noise ratio and the good spatial
resolution of the data allow us to detect the signatures of ongoing star
formation in an extended rotating ring, at ~4 kpc from the nucleus. We find
that the ring is almost perpendicular to the radio axis and its total star
formation rate is ~1 MSol/yr. We briefly discuss the concomitant presence of
recent star formation and nuclear activity.


title:
High-resolution X-ray spectroscopy of the Narrow line Seyfert 1 galaxy
  NGC 4051 with Chandra LETGS

abstract:
  We study the absorption and emission properties of the photoionised gas near
one of the brightest and most variable AGN, the Seyfert galaxy NGC 4051, in
order to constrain the geometry, dynamics and ionisation structure of the
outflow. We analyse two observations taken with the Low Energy Transmission
Grating Spectrometer (LETGS) of Chandra. We study the spectra of both
observations and investigate the spectral response to a sudden, long-lasting
flux decrease of a factor of 5 that occurred during the second observation. We
confirm the preliminary detection of a highly ionised component with an outflow
velocity of -4500 km/s, one of the highest velocity outflow components seen in
a Seyfert 1 galaxy. The sudden drop in intensity by a factor of five during the
second observation causes a drop in ionisation parameter of a similar magnitude
in the strongest and main ionisation component (v = -610 km/s), allowing us for
the first time to determine the recombination time of this component and
thereby its distance in a robust way. We find an upper limit to the distance of
10^15 m, ruling out an origin in the narrow emission line region. In addition,
an emission component producing strong radiative recombination continua of C VI
and C V appears during the low state. This can be explained by emission from an
ionised skin of the accretion disk at a distance of only ~4x10^12 m from the
black hole. Finally, the spectra contain a broad relativistic O VIII line with
properties similar to what was found before in this source with XMM-Newton;
this line has disappeared during the low flux state, consistent with the
disappearance of the inner part of the accretion disk during that low flux
state. (abridged)


title:
Necessary and sufficient condition for hydrostatic equilibrium in
  general relativity

abstract:
  We present explicit examples to show that the `compatibility criterion' is
capable of providing a {\em necessary} and {\em sufficient} condition for any
regular configuration to be compatible with the state of hydrostatic
equilibrium. This conclusion is drawn on the basis of the finding that the
$M-R$ relation gives the necessary and sufficient condition for dynamical
stability of equilibrium configurations only when the compatibility criterion
for these configurations is appropriately satisfied. In this regard, we
construct an appropriate sequence composed of core-envelope models on the basis
of compatibility criterion, such that each member of this sequence satisfies
the extreme case of causality condition $v = c = 1$ at the centre. The maximum
stable value of $u \simeq 0.3389$ (which occurs for the model corresponding to
the maximum value of mass in the mass-radius relation) and the corresponding
central value of the local adiabatic index, $(\Gamma_1)_0 \simeq 2.5911$, of
this model are found fully consistent with those of the corresponding {\em
absolute} values, $u_{\rm max} \leq 0.3406$, and $(\Gamma_1)_0 \leq 2.5946$,
which impose strong constraints on these parameters of such models. In addition
to this example, we also study dynamical stability of pure adiabatic polytropic
configurations on the basis of variational method for the choice of the `trial
function', $\xi =re^{\nu/4}$, as well as the mass-central density relation,
since the compatibility criterion is appropriately satisfied for these models.
The results of this example provide additional proof in favour of the statement
regarding compatibility criterion mentioned above.


title:
Deep Near-Infrared Imaging af an Embedded Cluster in the Extreme Outer
  Galaxy: Census of Supernovae Triggered Star Formation

abstract:
  While conducting a near-infrared (NIR) survey of ``Digel Clouds'', which are
thought to be located in the extreme outer Galaxy (EOG), Kobayashi & Tokunaga
found star formation activity in ``Cloud 2'', a giant molecular cloud at the
Galactic radius of ~ 20 kpc. Additional infrared imaging showed two embedded
young clusters at the densest regions of the molecular cloud. Because the
molecular cloud is located in the vicinity of a supernova remnant (SNR) HI
shell, GSH 138-01-94, it was suggested that the star formation activity in
Cloud 2 was triggered by this expanding HI shell. We obtained deep J (1.25 um),
H (1.65 um) and K (2.2 um) images of one of the embedded clusters in Cloud 2
with high spatial resolution (FWHM ~0".3) and high sensitivity (K ~ 20 mag, 10
sigma). We identified 52 cluster members. The estimated stellar density (~ 10
pc^{-2}) suggests that the cluster is a T-association. This is the deepest NIR
imaging of an embedded cluster in the EOG. The observed K-band luminosity
function (KLF) suggests that the underlying initial mass function (IMF) of the
cluster down to the detection limit of ~ 0.1 M_sun is not significantly
different from the typical IMFs in the field and in the near-by star clusters.
The overall characteristics of this cluster appears to be similar to those of
other embedded clusters in the far outer Galaxy. The estimated age of the
cluster from the KLF, which is less than 1 Myr, is consistent with the view
that the star formation was triggered by the HI shell whose age was estimated
at 4.3 Myr (Stil & Irwin). The 3-dimensional geometry of SNR shell, molecular
cloud and the embedded cluster, which is inferred from our data, as well as the
cluster age strongly suggest that the star formation in Cloud 2 was triggered
by the SNR shell.


title:
Estimations of orbital parameters of exoplanets from transit photometry
  by using dynamical constraints

abstract:
  The probability of the detection of Earth-like exoplanets may increase in the
near future after the launch of the space missions using the transit photometry
as observation method. By using this technique only the semi-major axis of the
detected planet can be determined, and there will be no information on the
upper limit of its orbital eccentricity. However, the orbital eccentricity is a
very important parameter, not only from a dynamical point of view, since it
gives also information on the climate and the habitability of the Earth-like
planets. In this paper a possible procedure is suggested for confining the
eccentricity of an exoplanet discovered by transit photometry if an already
known giant planet orbits also in the system.


title:
Instantaneous Radio Spectra of Giant Pulses from the Crab Pulsar from
  Decimeter to Decameter Wavelengths

abstract:
  The results of simultaneous multifrequency observations of giant radio pulses
from the Crab pulsar, PSR B0531+21, at 23, 111, and 600 MHz are presented and
analyzed. Giant pulses were detected at a frequency as low as 23 MHz for the
first time. Of the 45 giant pulses detected at 23 MHz, 12 were identified with
counterparts observed simultaneously at 600 MHz. Of the 128 giant pulses
detected at 111 MHz, 21 were identified with counterparts observed
simultaneously at 600 MHz. The spectral indices for the power-law frequency
dependence of the giant-pulse energies are from -3.1 to -1.6. The mean spectral
index is -2.7 +/- 0.1 and is the same for both frequency combinations (600-111
MHz and 600-23 MHz). The large scatter in the spectral indices of the
individual pulses and the large number of unidentified giant pulses suggest
that the spectra of the individual giant pulses do not actually follow a simple
power law. The observed shapes of the giant pulses at all three frequencies are
determined by scattering on interstellar plasma irregularities. The scatter
broadening of the pulses and its frequency dependence were determined as
tau_sc=20*(f/100)^(-3.5 +/- 0.1) ms, where the frequency f is in MHz.


title: Hot Flashers and He Dwarfs in Galactic Globulars

abstract:
  We revisit the evolutionary scenario for Hot Flasher low-mass structures,
where mass loss delays the He flash till the initial phases of their White
Dwarf cooling sequence. Our aim has been to test the theoretical results
vis-a-vis different assumptions about the efficiency of mass loss. To this
purpose, we present evolutionary models covering a fine grid of masses, as
obtained assuming a single episode of mass loss in a Red Giant model of 0.86 Mo
with Z=0.0015. We find a reasonable agreement with previous evolutionary
investigations, showing that for the given metallicity late Hot Flashers are
predicted to cover the mass range M=0.4975 to M= 0.4845 Mo, all models igniting
the He-flash with a mass of the H-rich envelope as given by about Me=0.00050.
The ignition mechanism is discussed in some details, showing the occurrence of
a bifurcation in the evolutionary history of stellar structures at the lower
mass limit for He ignition. Below such a critical mass, the structures miss the
He ignition, cooling down as a Hot Flasher-Manque' He White Dwarfs We predict
that these structures will cool down, reaching the luminosity logL/Lo=-1 in a
time at the least five times longer than the corresponding cooling time of a
normal CO White Dwarf. On very general grounds, one expects that old stellar
clusters with a sizeable population of Hot Flasher should likely produce at
least a similar amount of slow-cooling He White Dwarfs. According to this
result, in a cluster where 20% of Red Giants escape the He burning phase, one
expects roughly twice as White Dwarfs than in a normal cluster where all Red
Giants undergo their He flash


title: Distances to Anomalous X-ray Pulsars using Red Clump Stars

abstract:
  We identify `red clump stars' - core helium-burning giants - among 2MASS
stars and use them to measure the run of reddening with distance in the
direction of each of the Galactic Anomalous X-ray Pulsars (AXP). We combine
this with extinction estimates from X-ray spectroscopy to infer distances and
find that the locations of all AXP are consistent with being in Galactic spiral
arms. We also find that the 2-10 keV luminosities implied by our distances are
remarkably similar for all AXPs, being all around 1.3e35 erg s-1. Furthermore,
using our distances to estimate effective black-body emitting radii, we find
that the radii are tightly anti-correlated with pulsed fraction, and somewhat
less tightly anti-correlated with black-body temperature. We find no obvious
relationship of any property with the dipole magnetic field strength inferred
from the spin-down rate.


title: Dark matter clustering: a simple renormalization group approach

abstract:
  I compute a renormalization group (RG) improvement to the standard
beyond-linear-order Eulerian perturbation theory (PT) calculation of the power
spectrum of large-scale density fluctuations in the Universe. At z=0, for a
power spectrum matching current observations, lowest order RGPT appears to be
as accurate as one can test using existing numerical simulation-calibrated
fitting formulas out to at least k~=0.3 h/Mpc; although inaccuracy is
guaranteed at some level by approximations in the calculation (which can be
improved in the future). In contrast, standard PT breaks down virtually as soon
as beyond-linear corrections become non-negligible, on scales even larger than
k=0.1 h/Mpc. This extension in range of validity could substantially enhance
the usefulness of PT for interpreting baryonic acoustic oscillation surveys
aimed at probing dark energy, for example. I show that the predicted power
spectrum converges at high k to a power law with index given by the fixed-point
solution of the RG equation. I discuss many possible future directions for this
line of work. The basic calculation of this paper should be easily
understandable without any prior knowledge of RG methods, while a rich
background of mathematical physics literature exists for the interested reader.


title:
On the effect of overshooting as predicted by the modelling of the
  pre-main sequence evolution of a 2 solar-mass star

abstract:
  We discuss the effects of convective overshooting in the PMS evolution of
intermediate mass stars, by analysing in detail the early evolution towards the
main sequence of a 2 M_sun stellar model. These effects can be extremely
important in the end of the PMS, when the abundances in CNO elements approach
the equilibrium in the centre. We provide a possible physical explanation on
why a moderate amount of overshooting produces, as the star approaches the
ZAMS, an extra loop in the evolutionary tracks on the HR diagram.
  An interesting feature is that there is a very well defined amount of
overshooting (for a given stellar mass and chemical composition) beyond which a
loop is produced. For smaller amounts of overshooting such a loop does not take
place and the evolutionary tracks are similar to the ones obtained by Iben
(1965). The amount of overshooting needed to produce the loop decreases with
stellar mass.
  We discuss the underlining physical reasons for the behaviour predicted by
the evolution models and argue that it provides a crucial observational test
for convective overshooting in the core of intermediate mass stars.


title: GRB 050315: A step toward the uniqueness of the overall GRB structure

abstract:
  Using the Swift data of GRB 050315, we progress on the uniqueness of our
theoretically predicted Gamma-Ray Burst (GRB) structure as composed by a
proper-GRB (P-GRB), emitted at the transparency of an electron-positron plasma
with suitable baryon loading, and an afterglow comprising the so called "prompt
emission" as due to external shocks. Thanks to the Swift observations, the
P-GRB is identified and for the first time we can theoretically fit detailed
light curves for selected energy bands on a continuous time scale ranging over
10^6 seconds. The theoretically predicted instantaneous spectral distribution
over the entire afterglow is presented, confirming a clear hard-to-soft
behavior encompassing, continuously, the "prompt emission" all the way to the
latest phases of the afterglow.


title:
Simulating Anisotropic Thermal Conduction in Supernova Remnants I :
  Numerics and the Evolution of Remnants

abstract:
  Anisotropic thermal conduction plays an important role in various
astrophysical systems. One of the most stringent tests of thermal conduction
can be found in supernova remnants. In this paper we study anisotropic thermal
conduction and examine the physical nature of the flux of thermal conduction in
the classical and saturated limits. We also present a temporally second-order
accurate implicit-explicit scheme for the time-update of thermal conduction
terms within a numerical MHD scheme.
  Several simulations of supernova remnants are presented for a range of ISM
parameters. The role of thermal conduction in such remnants has been studied.
We find that thermal conduction produces cooler temperatures and higher
densities in the hot gas bubbles that form in the remnants. The effect of
thermal conduction in changing the thermal characteristics of the hot gas
bubble increases as the remnant propagates through denser ISMs. Remnants
evolving in denser ISMs are shown to make a faster transition to a
centre-bright x-ray morphology, with the trend emerging earlier in hard x-rays
than in the soft x-rays.


title: A Cloudy/Xspec Interface

abstract:
  We discuss new functionality of the spectral simulation code CLOUDY which
allows the user to calculate grids with one or more initial parameters varied
and formats the predicted spectra in the standard FITS format. These files can
then be imported into the x-ray spectral analysis software XSPEC and used as
theoretical models for observations. We present and verify a test case.
Finally, we consider a few observations and discuss our results.


title: Inflation with large gravitational waves

abstract:
  It is well known that in manifestly Lorentz invariant theories with
nontrivial kinetic terms, perturbations around some classical backgrounds can
travel faster than light. These exotic "supersonic" models may have interesting
consequences for cosmology and astrophysics. In particular, one can show that
in such theories the contribution of the gravitational waves to the CMB
fluctuations can be significantly larger than that in standard inflationary
models. This increase of the tensor-to-scalar perturbation ratio leads to a
larger B-component of the CMB polarization, thus making the prospects for
future detection much more promising. Interestingly, the spectral index of
scalar perturbations and mass of the scalar field considered in the model are
practically indistinguishable from the standard case. Whereas the energy scale
of inflation and hence the reheating temperature can be much higher compared to
a simple chaotic inflation.


title: Stability in MaVaN Models

abstract:
  Mass-varying neutrino (MaVaN) models propose a source of dark energy in a new
scalar field called the acceleron. Recent work has shown that nonrelativistic
neutrino fields in these theories are unstable to inhomogeneous fluctuations,
and form structures that no longer behave as dark energy. One might expect that
in multiple-neutrino models, the lighter species could continue to act as a
source for the acceleron, generating dark energy without the help of heavier
species. This paper shows that by considering the evolution of the acceleron
field for a large class of models, the result of any neutrino component
becoming unstable is that all components become unstable within a short time on
cosmological scales. An alternate model employing a second scalar field in a
hybrid potential is shown to have stable MaVaN dark energy even in the presence
of unstable heavier components.


title: The lack of binaries among hot horizontal branch stars: M80 and NGC5986

abstract:
  We present preliminary results of a our search for close (period P < 10 days)
binary systems among hot (Teff > 20000 K) horizontal branch stars in globular
clusters M80 and NGC5986. We measured radial velocity variations of 11 targets
in M80 and 5 in NGC5986, spectroscopically observed at medium resolution
(R=4100) during four nights at VLT-FORS2. We found one close binary candidate
in M80, showing statistically significative radial velocity variations, and no
clear evidence in NGC5986. These results confirm the lack of close binaries
among hot horizontal branch stars in globular clusters, as already found in
NGC6752, at variance with what observed among hot subdwarfs in the field.


title: Globular Cluster Formation in Mergers

abstract:
  Mergers of gas-rich galaxies lead to gravitationally driven increases in gas
pressure that can trigger intense bursts of star and cluster formation.
Although star formation itself is clustered, most newborn stellar aggregates
are unbound associations and disperse. Gravitationally bound star clusters that
survive for at least 10-20 internal crossing times (~20-40 Myr) are relatively
rare and seem to contain <10% of all stars formed in the starbursts. The most
massive young globular clusters formed in present-day mergers exceed omega Cen
by an order of magnitude in mass, yet appear to have normal stellar initial
mass functions.
  In the local universe, recent remnants of major gas-rich disk mergers appear
as protoelliptical galaxies with subpopulations of typically 100-1000 young
metal-rich globular clusters in their halos. The evidence is now strong that
these "second-generation" globular clusters formed from giant molecular clouds
in the merging disks, squeezed into collapse by large-scale shocks and high gas
pressure rather than by high-velocity cloud-cloud collisions. Similarly, first-
generation metal-poor globular clusters may have formed during cosmological
reionization from low-metallicity giant molecular clouds squeezed by the
universal reionization pressure.


title:
Double-Layer Silicon PIN Photodiode X-Ray Detector for a Future X-ray
  Timing Mission

abstract:
  A double-layer silicon detector consisting of two 500micron-thick silicon PIN
photodiodes with independent readouts was mounted in a vacuum chamber and
tested with X-ray sources. The detector is sensitive from 1-30 keV with an
effective area of 6 mm^2. The detector performs best at -35 C with an energy
resolution of 220 eV (FWHM, full width at half maximum) at 5.9 keV, and is able
to operate at room temperature, +25 C, with moderate resolution around 760 eV
(FWHM). The response of the top layer sensor is highly uniform across the
sensitive area. This large-format silicon detector is appropriate for future
X-ray timing missions.


title:
Identification of the OGLE-2003-BLG-235/MOA-2003-BLG-53 Planetary Host
  Star

abstract:
  We present the results of HST observations of the host star for the first
definitive extrasolar planet detected by microlensing. The light curve model
for this event predicts that the lens star should be separated from the source
star by ~6mas at the time of the HST images. If the lens star is a late G, K or
early M dwarf, then it will be visible in the HST images as an additional
source of light that is blended with the source image. Unless the lens and
source have exactly the same colors, its presence will also be revealed by a
systematic shift between centroids of the source plus lens in different filter
bands. The HST data indicates both of these effects: the HST source that
matches the position of the source star is 0.21 magnitudes brighter in the
ACS/HRC-F814W filter than the microlensing model predicts, and there is an
offset of ~0.7mas between the centroid of this source in the F814W and F435W
filter bands. We conclude the planetary host star has been detected in these
HST images, and this identification of the lens star enables a complete
solution of the lens system. The lens parameters are determined with a Bayesian
analysis, averaging over uncertainties in the measured parameters, interstellar
extinction, and allowing for the possibility of a binary companion to the
source star. This yields a stellar mass of M_* = 0.63(+0.07/-0.09) M_solar and
a planet mass of M_p = 2.6 (+0.8/-0.6) M_Jup at an orbital separation of 4.3
(+2.5/-0.8) AU. Thus, the lens system resembles our own Solar System, with a
planet of ~3 Jupiter-masses in a Jupiter-like orbit around a star of two-thirds
of a Solar mass. These conclusions can be tested with future HST images, which
should reveal a broadening of the blended source-plus-lens point spread
function due to the relative lens-source proper motion.


title: Spitzer 24 micron Survey of Debris Disks in the Pleiades

abstract:
  We performed a 24 micron 2 Deg X 1 Deg survey of the Pleiades cluster, using
the MIPS instrument on Spitzer. Fifty four members ranging in spectral type
from B8 to K6 show 24 micron fluxes consistent with bare photospheres. All Be
stars show excesses attributed to free-free emission in their gaseous
envelopes. Five early-type stars and four solar-type stars show excesses
indicative of debris disks. We find a debris disk fraction of 25 % for B-A
members and 10 % for F-K3 ones. These fractions appear intermediate between
those for younger clusters and for the older field stars. They indicate a decay
with age of the frequency of the dust-production events inside the planetary
zone, with similar time scales for solar-mass stars as have been found
previously for A-stars.


title: Fe II Emission in 14 Low-Redshift Quasars: I - Observations

abstract:
  We present the spectra of 14 quasars with a wide coverage of rest wavelengths
from 1000 to 7300 A. The redshift ranges from z = 0.061 to 0.555 and the
luminosity from M_{B} = -22.69 to -26.32. We describe the procedure of
generating the template spectrum of Fe II line emission from the spectrum of a
narrow-line Seyfert 1 galaxy I Zw 1 that covers two wavelength regions of
2200-3500 A and 4200-5600 A. Our template Fe II spectrum is semi-empirical in
the sense that the synthetic spectrum calculated with the CLOUDY
photoionization code is used to separate the Fe II emission from the Mg II
line. The procedure of measuring the strengths of Fe II emission lines is
twofold; (1) subtracting the continuum components by fitting models of the
power-law and Balmer continua in the continuum windows which are relatively
free from line emissions, and (2) fitting models of the Fe II emission based on
the Fe II template to the continuum-subtracted spectra. From 14 quasars, we
obtained the Fe II fluxes in five wavelength bands, the total flux of Balmer
continuum, and the fluxes of Mg II, Halpha, and other emission lines, together
with the full width at half maxima (FWHMs) of these lines. Regression analysis
was performed by assuming a linear relation between any two of these
quantities. Eight correlations were found with a confidence level higher than
99%. The fact that six of these eight are related to FWHM or M_{BH} may imply
that M_{BH} is a fundamental quantity that controls Gamma or the spectral
energy distribution (SED) of the incident continuum, which in turn controls the
Fe II emission. Furthermore, it is worthy of noting that Fe II(O1)/Fe II(U1) is
found to tightly correlate with Fe II(O1)/Mg II, but not with Fe II(U1)/Mg II.


title: Ultra-Compact Stellar Systems in the Fornax Galaxy Cluster

abstract:
  Our VLT (FLAMES) observations near NGC1399 investigate the connection between
ultra-compact dwarf galaxies (UCDs), NGC1399 globular clusters and
intra-cluster globulars. We have uncovered 30 faint compact stellar systems in
the Fornax galaxy cluster, adding to 62 bright UCDs previously reported. The
magnitude limit of these stellar systems extends down to the globular cluster
domain. We detect a filament of UCDs and globular clusters stretching across
NGC1399 and find weak evidence for its rotation. These compact stellar systems
not only congregate around several cluster galaxies but are also widely
distributed through intra-cluster space.


title: Neutrino Oscillation Effects on Supernova Light Element Synthesis

abstract:
  Neutrino oscillations affect light element synthesis through the
neutrino-process in supernova explosions. The 7Li and 11B yields produced in a
supernova explosion of a 16.2 solar-mass star model increase by factors of 1.9
and 1.3 in the case of large mixing angle solution with normal mass hierarchy
and sin^{2}2theta_{13} > 0.002 compared with those without the oscillations. In
the case of inverted mass hierarchy or nonadiabatic 13-mixing resonance, the
increment of their yields is much smaller. Neutrino oscillations raise the
reaction rates of charged-current neutrino-process reactions in the region
outside oxygen-rich layers. The number ratio of 7Li/11B could be a tracer of
normal mass hierarchy and relatively large theta_{13}, still satisfying
sin^{2}2theta_{13} < 0.1, through future precise observations in stars having
strong supernova component.


title: A Detection of [CII] line emission in the z=4.7 QSO BR1202-0725

abstract:
  We present ~3'' resolution imaging of the z=4.7 QSO BR1202-0725 at 900 micron
from the Submillimeter Array. The two submillimeter continuum components are
clearly resolved from each other, and the positions are consistent with
previous lower frequency images. In addition, we detect [CII] line emission
from the northern component. The ratio of [CII] to far-infrared luminosity is
0.04% for the northern component, and an upper limit of < 0.03% is obtained for
the southern component. These ratios are similar to the low values found in
local ultraluminous galaxies, indicating that the excitation conditions are
different from those found in local field galaxies. X-ray emission is detected
by Chandra from the southern component at
L$_{0.5-2keV}=3\times10^{45}$~erg~s$^{-1}$, and detected at 99.6% confidence
from the northern component at L$_{0.5-2keV}\sim3\times10^{44}$erg~s$^{-1}$,
supporting the idea that BR1202-0725 is a pair of interacting galaxies at z=4.7
that each harbor an active nucleus.


title: Standard and non-standard primordial neutrinos

abstract:
  The standard cosmological model predicts the existence of a cosmic neutrino
background with a present density of about 110 cm^{-3} per flavour, which
affects big-bang nucleosynthesis, cosmic microwave background anisotropies, and
the evolution of large scale structures. We report on a precision calculation
of the cosmic neutrino background properties including the modification
introduced by neutrino oscillations. The role of a possible
neutrino-antineutrino asymmetry and the impact of non-standard
neutrino-electron interactions on the relic neutrinos are also briefly
discussed.


title:
Submillimeter Wave Astronomy Satellite observations of comet 9P/Tempel 1
  and Deep Impact

abstract:
  On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its
goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on
the nucleus and ejecting material into the coma of the comet. NASA's
Submillimeter Wave Astronomy Satellite (SWAS) observed the 1(10)-1(01)
ortho-water ground-state rotational transition in comet 9P/Tempel 1 before,
during, and after the impact. No excess emission from the impact was detected
by SWAS and we derive an upper limit of 1.8e7 kg on the water ice evaporated by
the impact. However, the water production rate of the comet showed large
natural variations of more than a factor of three during the weeks before and
after the impact. Episodes of increased activity with Q(H2O)~1e28 molecule/s
alternated with periods with low outgassing (Q(H2O)<~5e27 molecule/s). We
estimate that 9P/Tempel 1 vaporized a total of N~4.5e34 water molecules (~1.3e9
kg) during June-September 2005. Our observations indicate that only a small
fraction of the nucleus of Tempel 1 appears to be covered with active areas.
Water vapor is expected to emanate predominantly from topographic features
periodically facing the Sun as the comet rotates. We calculate that appreciable
asymmetries of these features could lead to a spin-down or spin-up of the
nucleus at observable rates.


title: Bianchi Type VII_h Models and the WMAP 3-year Data

abstract:
  Context. A specific example of Bianchi Type VIIh models, i.e. those including
universal rotation (vorticity) and differential expansion (shear), has been
shown in Jaffe et al. (2005) to correlate unexpectedly with the WMAP first-year
data. Aims. We re-assess the signature of this model in the WMAP 3-year data.
Methods. The cross-correlation methods are described in Jaffe et al. (2006a).
We use the WMAP 3-year data release, including maps for individual years, and
perform additional comparisons to assess the influence of both noise and
residual foregrounds and eliminate potential non-cosmological sources for the
correlation. Results. We confirm that the signal is detected in both the
combined 3-year data and the individual yearly sky maps at a level consistent
with our original analysis. The significance of the correlation is not affected
by either noise or foreground residuals. Conclusions. The results of our
previous study are unchanged.


title:
Braneworld inflation from an effective field theory after WMAP
  three-year data

abstract:
  In light of the results from the WMAP three-year sky survey, we study an
inflationary model based on a single-field polynomial potential, with up to
quartic terms in the inflaton field. Our analysis is performed in the context
of the Randall-Sundrum II braneworld theory, and we consider both the
high-energy and low-energy (i.e. the standard cosmology case) limits of the
theory. We examine the parameter space of the model, which leads to both
large-field and small-field inflationary type solutions. We conclude that small
field inflation, for a potential with a negative mass square term, is in
general favored by current bounds on the tensor-to-scalar perturbation ratio
rs.


title:
About universes with scale-related total masses and their abolition of
  presently outstanding cosmological problems

abstract:
  Cosmological consequences of a strictly valid total energy conservation for
the whole universe are investigated in this paper. Interestingly enough as one
consequence of ergodically behaving universes very specific scaling laws with
the diameter R of the universe can be derived for relevant cosmic quantities.
Especially the 1/R^2- scaling of mass - and vacuum energy - density then
automatically leads to a vanishing cosmic curvature parameter k=0 and also
reveals, that for such universes no horizon problem occurs. In addition the
longstanding problem of observationally indicated very low cosmic vacuum
energies in contrast to the very large quantumfield estimates is easily solved
when the vacuum energy density decay with 1/R^2 is taken into account
reconciling presently observed vacuum energy density values with those from
theoretical expectations. We also suggest why the mass of the universe can
permanently increase and can in fact grow up from a Planck mass as a pure
vacuum fluctuation.


title:
Testing the inverse-Compton catastrophe scenario in the intra-day
  variable blazar S5 0716+71: II. A search for intra-day variability at
  millimetre wavelengths with the IRAM 30 m telescope

abstract:
  We report on a densely time sampled polarimetric flux density monitoring of
the BL Lac object S5 0716+71 at 86 GHz and 229 GHz with the IRAM 30 m telescope
within a coordinated broad spectral band campaign, centred around an INTEGRAL
observation during November 10 to 16, 2003. Our aim was to search for
signatures of inverse-Compton "catastrophes". At 86 GHz, making use of a new
calibration strategy, we reach a relative rms accuracy of the flux density
measurements of 1.2%. At this frequency, S5 0716+71 showed no intra-day
variability, but showed remarkable inter-day variability with a flux density
increase of 34% during the first four observing days, which can not be
explained by source extrinsic causes. The 86 GHz linear polarization fraction
of S5 0716+71 was unusually large 15.0+-1.8%. Inter-day variability in linear
polarization at 86 GHz, with significance level >~95%; sigma_P/<P>=15% and
sigma_chi=6 deg., was also observed. From the emission variations at the
synchrotron turnover frequency (~86 GHz) we compute an apparent brightness
temperature T_B,app>1.4x10^14K at a redshift of 0.3, which exceeds by two
orders of magnitude the inverse-Compton limit. A relativistic correction for
T_B,app with a Doppler factor delta > 7.8 brings the observed brightness
temperature down to the inverse Compton limit. A more accurate lower limit of
delta > 14.0, is obtained from the comparison of the 86 GHz synchrotron flux
density and the upper limits for the synchrotron self-Compton flux density
obtained from the INTEGRAL observations. The relativistic beaming of the
emission by this high Doppler factor explains the non-detection of
"catastrophic" inverse-Compton avalanches by INTEGRAL.


title:
Structure and flux variability in the VLBI jet of BL Lacertae during the
  WEBT campaigns (1995--2004)

abstract:
  BL Lacertae has been the target of several observing campaigns by the Whole
Earth Blazar Telescope (WEBT) collaboration and is one of the best studied
blazars at all accessible wavelengths. A recent analysis of the optical and
radio variability indicates that part of the radio variability is correlated
with the optical light curve. Here we present an analysis of a huge VLBI data
set including 108 images at 15, 22, and 43 GHz obtained between 1995 and 2004.
The aim of this study is to identify the different components contributing to
the single-dish radio light curves. We obtain separate radio light curves for
the VLBI core and jet and show that the radio spectral index of single-dish
observations can be used to trace the core variability. Cross-correlation of
the radio spectral index with the optical light curve indicates that the
optical variations lead the radio by about 100 days at 15 GHz. By fitting the
radio time lags vs. frequency, we find that the power law is steeper than
expected for a freely expanding conical jet in equipartition with energy
density decreasing as the square of the distance down the jet as in the
K\"onigl model. There is a section of the compact radio jet where the emission
is weak such that flares propagating down the jet are bright first in the core
region with a secondary increase in flux about 1.0 mas from the core. This
illustrates the importance of direct imaging to the interpretation of
multi-wavelength light curves that can be affected by several distinct
components at any given time. We discuss how the complex behaviour of the light
curves and correlations can be understood within the framework of a precessing
helical jet model.


title: The light curves of type Ia Supernova 2004fu

abstract:
  CCD UBVRI photometry is presented for type Ia supernova 2004fu in NGC 6949.
The light and colour curves are typical for this class of objects, absolute
magnitude at maximum and decline rate are in agreement with the relationship
between these parameters, established for SNe Ia.


title:
Few Skewed Disks Found in First Closure-Phase Survey of Herbig Ae/Be
  stars

abstract:
  Using the 3-telescope IOTA interferometer on Mt. Hopkins, we report results
from the first near-infrared (lambda=1.65 mu) closure-phase survey of Young
Stellar Objects (YSOs). These closure phases allow us to unambiguously detect
departures from centrosymmetry (i.e., skew) in the emission pattern from YSO
disks on the scale of ~4 milliarcseconds, expected from generic ``flared disk''
models. Six of fourteen targets showed small, yet statistically-significant,
non-zero closure phases, with largest values from the young binary system MWC
361-A and the (pre-main sequence?) Be star HD 45677. Our observations are quite
sensitive to the vertical structure of the inner disk and we confront the
predictions of the ``puffed-up inner wall'' models of Dullemond, Dominik, and
Natta (DDN). Our data support disks models with curved inner rims because the
expected emission appear symmetrically-distributed around the star over a wide
range of inclination angles. In contrast, our results are incompatible with the
models possessing vertical inner walls because they predict extreme skewness
(i.e., large closure phases) from the near-IR disk emission that is not seen in
our data. In addition, we also present the discovery of mysterious H-band
``halos'' (~5-10% of light on scales 0.01-0.50 arcsec) around a few objects, a
preliminary ``parametric imaging'' study for HD 45677, and the first
astrometric orbit for the young binary MWC 361-A.


title: Long-term variation in distribution of sunspot groups

abstract:
  We studied the relation between the distribution of sunspot groups and the
Gleissberg cycle. As the magnetic field is related to the area of the sunspot
groups, we used area-weighted sunspot group data. On the one hand, we confirm
the previously reported long-term cyclic behaviour of the sum of the northern
and southern sunspot group mean latitudes, although we found a somewhat longer
period (P~104 years). We introduced the difference between the ensemble average
area of sunspot groups for the two hemispheres, which turns out to show similar
behaviour. We also investigated a further aspect of the Gleissberg cycle where
while in the 19th century the consecutive Schwabe cycles are sharply separated
from each other, one century later the cycles overlap each other more and more.


title:
Observations of the Hot Horizontal-Branch Stars in the Metal-Rich Bulge
  Globular Cluster NGC 6388 - Indications of Helium Enrichment and a Lesson in
  Crowded Field Spectroscopy

abstract:
  (abridged) The metal-rich bulge globular cluster NGC6388 shows a distinct
blue horizontal-branch tail with a strong upward tilt in its colour-magnitude
diagram. Several noncanonical scenarios have been proposed to explain these
puzzling observations. In order to test the predictions of these scenarios, we
have obtained medium resolution spectra to determine the atmospheric parameters
of a sample of the blue HB stars in NGC 6388. Using the medium resolution
spectra, we determine effective temperatures, surface gravities and helium
abundances by fitting the observed Balmer and helium lines with appropriate
theoretical stellar spectra. As we know the distance to the cluster, we can
verify our results by determining masses for the stars. During the data
reduction we took special care in subtracting the background, which is
dominated by the overlapping spectra of cool stars. The physical parameters of
the blue HB stars near 10,000 K support the helium pollution scenario. The low
gravities and masses found for the hot blue tail stars, however, are probably
caused by problems with the data reduction, most likely due to remaining
background light in the spectra, which would affect the fainter hot blue tail
stars much more strongly than the brighter cool blue tail stars. Our study of
the hot blue tail stars in NGC 6388 illustrates the obstacles which are
encountered when attempting to determine the atmospheric parameters of hot HB
stars in very crowded fields using ground-based observations. We discuss these
obstacles and offer possible solutions for future projects.


title: Dynamics of the fast solar tachocline: II. Migrating field

abstract:
  We present detailed numerical calculations of the fast solar tachocline based
on the assumption that the dynamo field dominates over the dynamics of the
tachocline. In the present paper of the series, we focus on three shortfalls of
the earlier models. First, instead of the simple oscillating dipole poloidal
field we study the more general magnetic field structures reminiscent of the
butterfly diagram. The migrating field is prescribed as the observed
axisymmetric radial magnetic field Stenflo (1988, 1994). Our results are in
good agreement with our analitical estimate and our previous works in
Forgacs-Dajka & Petrovay (2001,2002), but the polar "dip" in isorotational
surfaces is strongly reduced in this case. On the other hand, a more realistic
model should have a magnetic diffusivity decreasing significantly inside the
radiative interior, so we also explore the effect of diffusivity and magnetic
Prandtl number varying with depth. We found that the downwards decreasing
magnetic diffusivity and Prandtl number have no significant effect on the
solution, although the temporal variation of the tachocline thickness has
decreased.


title:
K-Band Observations of Boxy Bulges. I. Morphology and Surface Brightness
  Profiles

abstract:
  Kn-band images, unsharp-masked images, as well as major-axis and vertically-
summed surface brightness profiles are presented for 30 edge-on spiral
galaxies, most with a boxy or peanut-shaped (B/PS) bulge. Such galaxies have
more complex morphologies than galaxies of other bulge types, more often
showing (off-)centered X structures, secondary major-axis maxima and
spiral-like structures. Those features are also observed in N-body simulations
of barred discs and may trace the main bar orbit families. The surface
brightness profiles of galaxies with a B/PS bulge are also more complex, with
typically 3 or more clearly separated regions, including a flat intermediate
region (Freeman Type II profiles). Those radial breaks offer evidence for
bar-driven transfer of angular momentum and radial redistribution of material.
The profiles also suggest a rapid variation of the scaleheight of the disc
material, contrary to conventional wisdom but again as expected from vertical
resonances and instabilities in barred discs. The steep inner region of the
surface brightness profiles is often shorter than the isophotally thick part of
the galaxies, itself always shorter than the flat region of the profiles.
Contrary to the standard `bulge + disc' model, we thus propose that galaxies
with a B/PS bulge are composed of a thin concentrated disc (a disc-like bulge)
contained within a partially thick bar (the B/PS bulge) and a thin outer disc.
The inner disc likely formed secularly through bar-driven processes and is
responsible for the steep inner region of the surface brightness profiles,
while the bar is responsible for the flat region and the thick complex
morphological structures observed. Those components are strongly coupled
dynamically and are formed mostly of the same (disc) material. [Abridged]


title:
Submillimeter vibrationally excited water emission from the peculiar red
  supergiant VY CMa

abstract:
  Vibrationally excited emission from the SiO and H2O molecules probes the
innermost circumstellar envelopes of oxygen-rich red giant and supergiant
stars. VY CMa is the most prolific known stellar emission source in these
molecules. Observations were made to search for rotational lines in the lowest
vibrationally excited state of H2O. The APEX telescope was used for
observations of H2O lines at frequencies around 300 GHz. Two vibrationally
excited H2O lines were detected, a third one could not be found. In one of the
lines we find evidence for weak maser action, similar to known (sub)millimeter
H2O lines. We find that the other line's intensity is consistent with thermal
excitation by the circumstellar infrared radiation field. Several SiO lines
were detected together with the H2O lines.


title:
Energy spectra of gamma-rays, electrons and neutrinos produced at
  proton-proton interactions in the very high energy regime

abstract:
  We present new parametrisations of energy spectra of secondary particles,
$\pi$-mesons, gamma-rays, electrons and neutrinos, produced in inelastic
proton-proton collisions. The simple analytical approximations based on
imulations of proton-proton interactions using the public available SIBYLL
code, provide very good accuracy for energy distributions of secondary products
in the energy range above 100 GeV. Generally, the recommended analytical
formulae deviate from the simulated distributions within a few percent over a
large range of $x=E_i/E_p$ - the fraction of energy of the incident proton
transferred to the secondaries. Finally, we describe an approximate procedure
of continuation of calculations towards low energies, down to the threshold of
$\pi$-meson production.


title:
Bright Localized Near-Infrared Emission at 1-4 AU in the AB Aurigae Disk
  Revealed by IOTA Closure Phases

abstract:
  We report on the detection of localized off-center emission at 1-4 AU in the
circumstellar environment of the young stellar object AB Aurigae. We used
closure phase measurements in the near-infrared made at the long baseline
interferometer IOTA, the first obtained on a young stellar object using this
technique. When probing sub-AU scales, all closure phases are close to zero
degrees, as expected given the previously-determined size of the AB Aurigae
inner dust disk. However, a clear closure phase signal of -3.5 +/- 0.5 degrees
is detected on one triangle containing relatively short baselines, requiring a
high degree of non-point symmetry from emission at larger (AU-sized) scales in
the disk. We have not identified any alternative explanation for these closure
phase results and demonstrate that a ``disk hot spot'' model can fit our data.
We speculate that such asymmetric near-infrared emission detected might arise
as a result of localized viscous heating due to a gravitational instability in
the AB Aurigae disk, or to the presence of a close stellar companion or
accreting sub-stellar object.


title: The VIMOS VLT Deep Survey: the faint type-1 AGN sample

abstract:
  We present the type-1 active galactic nuclei (AGN) sample extracted from the
VIMOS VLT Deep Survey first observations of 21000 spectra in 1.75 square
degree. This sample, which is purely magnitude limited, free of morphological
or color selection biases, contains 130 broad line AGN (BLAGN) spectra with
redshift up to 5. Our data are divided into a wide (Iab < 22.5) and a deep (Iab
< 24) subsample containing 56 and 74 objects respectively. Because of its depth
and selection criteria, this sample is uniquely suited to study the population
of faint type-1 AGN. Our measured surface density (~ 472 +- 48 BLAGN per square
degree with Iab < 24) is significantly higher than that of any other optically
selected sample of BLAGN with spectroscopic confirmation. By applying a
morphological and color analysis to our AGN sample we find that: (1)~23% of the
AGN brighter than Iab=22.5 are classified as extended; this percentage
increases to ~42% for those with z < 1.6; (2) a non-negligible fraction of our
BLAGN are lying close to the color space area occupied by stars in u*-g' versus
g'-r' color-color diagram. This leads us to the conclusion that classical
optical ultraviolet preselection technique, if employed at such deep magnitudes
(Iab=22.5) in conjuction with a preselection of point-like sources, can miss
miss up to ~35% of the AGN population. Finally, we present a composite spectrum
of our sample of objects. While the continuum shape is very similar to that of
the SDSS composite at short wavelengths, it is much redder than it at lambda >
3000 A. We interpret this as due to significant contamination from emission of
the host galaxies, as expected from the faint absolute magnitudes sampled by
our survey.


title:
SuperCam, a 64-pixel heterodyne imaging array for the 870 micron
  atmospheric window

abstract:
  We report on the development of SuperCam, a 64 pixel, superheterodyne camera
designed for operation in the astrophysically important 870 micron atmospheric
window. SuperCam will be used to answer fundamental questions about the physics
and chemistry of molecular clouds in the Galaxy and their direct relation to
star and planet formation. The advent of such a system will provide an order of
magnitude increase in mapping speed over what is now available and
revolutionize how observational astronomy is performed in this important
wavelength regime. Unlike the situation with bolometric detectors, heterodyne
receiver systems are coherent, retaining information about both the amplitude
and phase of the incident photon stream. From this information a high
resolution spectrum of the incident light can be obtained without multiplexing.
SuperCam will be constructed by stacking eight, 1x8 rows of fixed tuned, SIS
mixers. The IF output of each mixer will be connected to a low-noise, broadband
MMIC amplifier integrated into the mixer block. The instantaneous IF bandwidth
of each pixel will be ~2 GHz, with a center frequency of 5 GHz. A spectrum of
the central 500 MHz of each IF band will be provided by the array spectrometer.
Local oscillator power is provided by a frequency multiplier whose output is
divided between the pixels by using a matrix of waveguide power dividers. The
mixer array will be cooled to 4K by a closed-cycle refrigeration system.
SuperCam will reside at the Cassegrain focus of the 10m Heinrich Hertz
telescope (HHT). A prototype single row of the array will be tested on the HHT
in 2006, with the first engineering run of the full array in late 2007. The
array is designed and constructed so that it may be readily scaled to higher
frequencies.


title: Globular Clusters in Dwarf Galaxies

abstract:
  Recent work on globular cluster systems in dwarf galaxies outside the Local
Group is reviewed. Recent large imaging surveys with the Hubble Space Telescope
and follow-up spectroscopy with 8-m class telescopes now allow us to compare
the properties of massive star clusters in a wide range of galaxy types and
environments. This body of work provides important constraints for theories of
galaxy and star cluster formation and evolution.


title: X-ray Selected Intermediate-Redshift Groups of Galaxies

abstract:
  We present spectroscopic confirmation of nine moderate redshift galaxy groups
and poor clusters selected from the ROSAT Deep Cluster Survey. The groups span
the redshift range z=0.23-0.59 and have between 4 and 20 confirmed members. The
velocity dispersions of these groups range from 125 to 650 km/s. Similar to
X-ray groups at low redshift, these systems contain a significant number of
early-type galaxies. Therefore, the trend for X-ray luminous groups to have
high early-type fractions is already in place by at least z=0.5. In 4 of the 9
groups, the X-ray emission is clearly peaked on the most luminous early-type
galaxy in the group. However, in several cases the central galaxy is composed
of multiple luminous nuclei, suggesting that the brightest group galaxy may
still be undergoing major mergers. In at least 3 of the groups in our sample, a
dominant early-type galaxy is not found at the center of the group potential.
This suggests that many of our groups are not dynamically evolved despite their
high X-ray luminosities. While similar systems have been identified at low
redshift, the X-ray luminosities of the intermediate redshift examples are one
to three orders of magnitude higher than those of their low redshift
counterparts. We suggest that this may be evidence for group downsizing: while
massive groups are still in the process of collapsing and virializing at
intermediate redshifts, only low-mass groups are in the process of forming at
the present day.


title: X-ray Properties of Intermediate-Redshift Groups of Galaxies

abstract:
  We have undertaken a multiwavelength project to study the relatively unknown
properties of groups and poor clusters of galaxies at intermediate redshifts.
In this paper, we describe the XMM-Newton observations of six X-ray selected
groups with 0.2<z<0.6. The X-ray properties of these systems are generally in
good agreement with the properties of low-redshift groups. They appear to
follow the scaling relations between luminosity, temperature, and velocity
dispersion defined by low-redshift groups and clusters. The X-ray emission in
four of the six groups is also centered on a dominant early-type galaxy. The
lack of a bright elliptical galaxy at the peak of the group X-ray emission is
rare at low-redshifts, and the other two groups may be less dynamically
evolved. We find indications of excess entropy in these systems over
self-similar predictions out to large radii. We also confirm the presence of at
least one X-ray luminous AGN associated with a group member galaxy and find
several other potential group AGN.


title:
Using the Active Collimator and Shield Assembly of an EXIST-Type Mission
  as a Gamma-Ray Burst Spectrometer

abstract:
  The Energetic X-ray Imaging Survey Telescope (EXIST) is a mission design
concept that uses coded masks seen by Cadmium Zinc Telluride (CZT) detectors to
register hard X-rays in the energy region from 10 keV to 600 keV. A partially
active or fully active anti-coincidence shield/collimator with a total area of
between 15 and 35 square meters will be used to define the field of view of the
CZT detectors and to suppress the background of cosmic-ray-induced events. In
this paper, we describe the use of a sodium activated cesium iodide
shield/collimator to detect gamma-ray bursts (GRBs) and to measure their energy
spectra in the energy range from 100 keV up to 10 MeV. We use the code GEANT4
to simulate the interactions of photons and cosmic rays with the spacecraft and
instrument and the code DETECT2000 to simulate the optical properties of the
scintillation detectors. The shield collimator achieves a nu-F-nu sensitivity
of 3 x 10^(-9) erg cm^(-2) s^(-1) and 2 x 10^(-8) erg cm^(-2) s^(-1) at 100 keV
and 600 keV, respectively. The sensitivity is well matched to that of the coded
mask telescope. The broad energy coverage of an EXIST-type mission with active
shields will constrain the peak of the spectral energy distribution (SED) for a
large number of GRBs. The measurement of the SED peak may be key for
determining photometric GRB redshifts and for using GRBs as cosmological
probes.


title: Nuclear Star Clusters in Edge-on Galaxies

abstract:
  From observations of edge-on, late-type galaxies, we present morphological
evidence that some nuclear star clusters have experienced in situ star
formation. We find three nuclear clusters that, viewed from the edge-on
perspective, have both a compact disk-like component and a spheroidal
component. In each cluster, the disk components are closely aligned with the
major axis of the host galaxy and have bluer colors than the spheroidal
components. We spectroscopically verify that one of the observed multiple
component clusters has multiple generations of stars. These observations lead
us to suggest a formation mechanism for nuclear star clusters, in which stars
episodically form in compact nuclear disks, and then lose angular momentum,
eventually forming an older spheroid.


title:
Mass-dependent Color Evolution of Field Galaxies Back to z~3 Over the
  Wide Range of Stellar Mass

abstract:
  We use deep multi-band optical and near-infrared data for four general
fields, GOODS-South, HDF North/South, and IRAC UDF in GOODS-North to
investigate the evolution of the observed rest-frame U-V color of field
galaxies as a function of the stellar mass. In these four fields, the U-V color
distributions of the galaxies at each mass and redshift interval are very
similar. At 0.3<z<2.7, we found that more massive galaxies always tend to have
a redder U-V color. High- and low-mass galaxies exhibit quite different color
evolutions. As seen in our previous study in HDF-N, the color distribution of
low-mass (M_stellar < 3x10^9M_solar) galaxies becomes significantly bluer with
an increase in the redshift. This evolution of the average color can be
explained by a constant star formation rate model with z_form~4. On the other
hand, the average color of high-mass galaxies (M_stellar > 3x10^10M_solar)
evolves more strongly at a high redshift. Such mass-dependent color
distribution and its evolution indicate that galaxies with a larger stellar
mass appear to have shorter star-formation timescales, and on an average, they
form the larger fraction of their stars in the earlier epoch.


title: KM3NeT: Towards a km3 Mediterranean Neutrino Telescope

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". To establish
neutrino astronomy beyond the detection of single events, neutrino telescopes
of km3 scale are needed. In order to obtain full sky coverage, a corresponding
detector in the Mediterranean Sea is required to complement the IceCube
experiment currently under construction at the South Pole. The groups pursuing
the current neutrino telescope projects in the Mediterranean Sea, ANTARES, NEMO
and NESTOR, have joined to prepare this future installation in a 3-year,
EU-funded Design Study named KM3NeT. This report will highlight some of the
physics issues to be addressed with the KM3NeT detector and will outline the
path towards its realisation, with a focus on the upcoming Design Study.


title: The CMB as a dark energy probe

abstract:
  We give a brief review of the known effects of a dynamical vacuum
cosmological component, the dark energy, on the anisotropies of the cosmic
microwave background (CMB). We distinguish between a "classic" class of
observables, used so far to constrain the average of the dark energy abundance
in the redshift interval in which it is relevant for acceleration, and a
"modern" class, aiming at the measurement of its differential redshift
behavior. We show that the gravitationally lensed CMB belongs to the second
class, as it can give a measure of the dark energy abundance at the time of
equality with matter, occurring at about redshift 0.5. Indeed, the dark energy
abundance at that epoch influences directly the lensing strength, which is
injected at about the same time, if the source is the CMB. We illustrate this
effect focusing on the curl (BB) component of CMB polarization, which is
dominated by lensing on arcminute angular scales. An increasing dark energy
abundance at the time of equality with matter, parameterized by a rising first
order redshift derivative of its equation of state today, makes the BB power
dropping with respect to a pure LambdaCDM cosmology, keeping the other
cosmological parameters and primordial amplitude fixed. We briefly comment on
the forthcoming probes which might measure the lensing power on CMB.


title: INTEGRAL and XMM-Newton observations of LSI +61 303

abstract:
  LSI +61 303 is one of the few X-ray binaries with Be star companion from
which both radio and high-energy gamma-ray emission have been observed. We
present XMM-Newton and INTEGRAL observations which reveal variability of the
X-ray spectral index of the system. The X-ray spectrum is hard (photon index ~
1.5) during the orbital phases of both high and low X-ray flux. However, the
spectrum softens at the moment of transition from high to low X-ray state. The
spectrum of the system in the hard X-ray band does not reveal the presence of a
cut-off (or, at least a spectral break) at 10-60 keV energies, expected if the
compact object is an accreting neutron star. The observed spectrum and spectral
variability can be explained if the compact object in the system is a rotation
powered pulsar.


title: Six Myths on the Virial Theorem for Interstellar Clouds

abstract:
  It has been paid little or no attention to the implications that turbulent
fragmentation has on the validity of at least six common assumptions on the
Virial Theorem (VT), which are: (i) the only role of turbulent motions within a
cloud is to provide support against collapse, (ii) the surface terms are
negligible compared to the volumetric ones, (iii) the gravitational term is a
binding source for the clouds, (iv) the sign of the second-time derivative of
the moment of inertia determines whether the cloud is contracting or expanding,
(v) interstellar clouds are in Virial Equilibrium (VE), and (vi) Larson's
(1981) relations are the observational proof that clouds are in VE.
Interstellar clouds cannot fulfill these assumptions, however, because
turbulent fragmentation will induce flux of mass, moment and energy between the
clouds and their environment, and will favor local collapse while may disrupt
the clouds within a dynamical timescale. It is argued that, although the
observational and numerical evidence suggests that interstellar clouds are not
in VE, the so-called ``Virial Mass'' estimations, which actually should be
called ``energy-equipartition mass'' estimations, are good order-of magnitude
estimations of the actual mass of the clouds just because observational surveys
will tend to detect interstellar clouds appearing to be close to energy
equipartition. However, since clouds are actually out of VE, as suggested by
asymmetrical line profiles, they should be transient entities. These results
are compatible with observationally-based estimations for rapid star formation.
, and call into question the models for the star formation efficiency based on
clouds being in VE.


title:
Influence of Thermalisation on Electron Injection in Supernova Remnant
  Shocks

abstract:
  Within a test-particle description of the acceleration process in parallel
nonrelativistic shocks, we present an analytic treatment of the electron
injection. We estimate the velocity distribution of the injected electrons as
the product of the post-shock thermal distribution of electrons times the
probability for electrons with a given velocity to be accelerated; the
injection efficiency is then evaluated as the integral of this velocity
distribution. We estimate the probability of a particle to be injected as that
of going back to the upstream region at least once. This is the product of the
probability of returning to the shock from downstream times that of recrossing
the shock from downstream to upstream. The latter probability is expected to be
sensitive to details of the process of electron thermalisation within the
(collisionless) shock, a process that is poorly known. In order to include this
effect, for our treatment we use results of a numerical, fully kinetic study,
by Bykov & Uvarov (1999). According to them, the probability of recrossing
depends on physics of thermalisation through a single free parameter (Gamma),
which can be expressed as a function of the Mach number of the shock, of the
level of electron-ion equilibration, as well as of the spectrum of turbulence.
It becomes apparent, from our analysis, that the injection efficiency is
related to the post-shock electron temperature, and that it results from the
balance between two competing effects: the higher the electron temperature, the
higher the fraction of downstream electrons with enough velocity to return to
the shock and thus to be ready to cross the shock from downstream to upstream;
at the same time, however, the higher the turbulence, which would hinder the
crossing.


title:
Cold dark matter cosmology conflicts with fluid mechanics and
  observations

abstract:
  Cold dark matter hierarchical clustering (CDMHC) cosmology based on the Jeans
1902 criterion for gravitational instability gives predictions about the early
universe contrary to fluid mechanics and observations. Jeans neglected
viscosity, diffusivity, and turbulence: factors that determine gravitational
structure formation and contradict small structures (CDM halos) forming from
non-baryonic dark matter particle candidates. From hydro-gravitational-dynamics
(HGD) cosmology, viscous-gravitational fragmentation produced supercluster
(10^46 kg), cluster, and galaxy-mass (10^42 kg) clouds in the primordial plasma
with the large fossil density turbulence (rho_o ~ 3x10-17 kg m-3) of the first
fragmentation at 10^12 s, and a protogalaxy linear and spiral clump morphology
reflecting maximum stretching near vortex lines of the plasma turbulence at the
10^13 s plasma-gas transition. Gas protogalaxies fragmented into
proto-globular-star-cluster mass (10^36 kg) clumps of protoplanet gas clouds
that are now frozen as earth-mass (10^24-^25 kg) Jovian planets of the baryonic
dark matter, about 30,000,000 rogue planets per star. Observations contradict
the CDMHCC prediction of large explosive Population III first stars at 10^16 s,
but support the immediate gentle formation of small Population II first stars
at 10^13 s in globular-star-clusters from HGD.


title: Angular Correlation Function of Quasars from SDSS DR3

abstract:
  We estimate the two-point angular correlation function (CF) of quasars from
SDSS DR3 using a special method of comparison random catalog generation. The
best-fit value for the CF power-law index is found to be $\alpha=0.78\pm0.18$
on the $2<\theta<250$ $arcmin$ interval. This is lower (though in marginal
agreement) than earlier result of \markcite{{\it Myers et al.} (2005)} based on
SDSS DR1 catalogue of photometrically-classified quasars.


title: The XMM Cluster Survey: A Massive Galaxy Cluster at z=1.45

abstract:
  We report the discovery of XMMXCS J2215.9-1738, a massive galaxy cluster at z
=1.45, which was found in the XMM Cluster Survey. The cluster candidate was
initially identified as an extended X-ray source in archival XMM data. Optical
spectroscopy shows that 6 galaxies within a 60 arcsec diameter region lie at z
= 1.45 +/- 0.01. Model fits to the X-ray spectra of the extended emission yield
kT = 7.4 (+2.7,-1.8) keV (90 % confidence); if there is an undetected central
X-ray point source then kT = 6.5 (+2.6,-1.8) keV. The bolometric X-ray
luminosity is Lx = 4.4 (+0.8,-0.6) x 10^44 ergs/s over a 2 Mpc radial region.
The measured Tx, which is the highest known for a cluster at z > 1, suggests
that this cluster is relatively massive for such a high redshift. The redshift
of XMMXCS J2215.9-1738 is the highest currently known for a
spectroscopically-confirmed cluster of galaxies.


title: The Spin of the Near-Extreme Kerr Black Hole GRS 1915+105

abstract:
  Based on a spectral analysis of the X-ray continuum that employs a fully
relativistic accretion-disk model, we conclude that the compact primary of the
binary X-ray source GRS 1915+105 is a rapidly-rotating Kerr black hole. We find
a lower limit on the dimensionless spin parameter of a* greater than 0.98. Our
result is robust in the sense that it is independent of the details of the data
analysis and insensitive to the uncertainties in the mass and distance of the
black hole. Furthermore, our accretion-disk model includes an advanced
treatment of spectral hardening. Our data selection relies on a rigorous and
quantitative definition of the thermal state of black hole binaries, which we
used to screen all of the available RXTE and ASCA data for the thermal state of
GRS 1915+105. In addition, we focus on those data for which the accretion disk
luminosity is less than 30% of the Eddington luminosity. We argue that these
low-luminosity data are most appropriate for the thin alpha-disk model that we
employ. We assume that there is zero torque at the inner edge of the disk, as
is likely when the disk is thin, although we show that the presence of a
significant torque does not affect our results. Our model and the model of the
relativistic jets observed for this source constrain the distance and black
hole mass and could thus be tested by determining a VLBA parallax distance and
improving the measurement of the mass function. Finally, we comment on the
significance of our results for relativistic-jet and core-collapse models, and
for the detection of gravitational waves.


title:
The Solar Heavy Element Abundances: II. Constraints from Stellar
  Atmospheres

abstract:
  Estimates of the bulk metal abundance of the Sun derived from the latest
generation of model atmospheres are significantly lower than the earlier
standard values. In Paper I we demonstrated that a low solar metallicity is
inconsistent with helioseismology if the quoted errors in the atmospheres
models (of order 0.05 dex) are correct. In this paper we undertake a critical
analysis of the solar metallicity and its uncertainty from a model atmospheres
perspective, focusing on CNO. We argue that the non-LTE corrections for
abundances derived from atomic features are overestimated in the recent
abundance studies, while systematic errors in the absolute abundances are
underestimated. If we adopt the internal consistency between different
indicators as a measure of goodness of fit, we obtain intermediate abundances
[C/H] = 8.44 +/- 0.06, [N/H] = 7.96 +/- 0.10 and [O/H] = 8.75 +/- 0.08. The
errors are too large to conclude that there is a solar abundance problem, and
permit both the high and low scales. However, the center-to-limb continuum flux
variations predicted in the simulations appear to be inconsistent with solar
data, which would favor the traditional thermal structure and lead to high CNO
abundances of (8.52, 7.96, 8.80) close to the seismic scale. We argue that
further empirical tests of non-LTE corrections and the thermal structure are
required for precise absolute abundances. The implications for beryllium
depletion and possible sources of error in the numerical simulations are
discussed.


title: Cosmology and Astrophysical Constraints of Gauss-Bonnet Dark Energy

abstract:
  Cosmological consequences of a string-motivated dark energy scenario
featuring a scalar field coupled to the Gauss-Bonnet invariant are
investigated. We study the evolution of the universe in such a model,
identifying its key properties. The evolution of the homogeneous background and
cosmological perturbations, both at large and small scales, are calculated. The
impact of the coupling on galaxy distributions and the cosmic microwave
background is examined. We find the coupling provides a mechanism to viably
onset the late acceleration, to alleviate the coincidence problem, and
furthermore to effectively cross the phantom divide at the present while
avoiding a Big Rip in the future. We show the model could explain the present
cosmological observations, and discuss how various astrophysical and
cosmological data, from the Solar system, supernovae Ia, cosmic microwave
background radiation and large scale structure constrain it.


title:
A Simultaneous Optical and X-ray Variability Study of the Orion Nebula
  Cluster. I. Incidence of Time-Correlated X-ray/Optical Variations

abstract:
  We present a database of $BVRI$ time-series photometry of the Orion Nebula
Cluster obtained with two ground-based telescopes at different longitudes to
provide simultaneous coverage with the 13-d Chandra observation of the cluster.
The resulting database of simultaneous optical and X-ray light curves for some
800 pre--main-sequence (PMS) stars represents, by a factor of hundreds, the
largest synoptic, multi--wavelength-regime, time-series study of young stars to
date. This database will permit detailed analyses of the relationship between
optical and X-ray variability among a statistically significant ensemble of PMS
stars, with the goal of elucidating the origins of PMS X-ray production. In
this first paper, we present the optical observations, describe the combined
X-ray/optical database, and perform an analysis of time-correlated variability
in the optical and X-ray light curves. We identify 40 stars (representing 5% of
our study sample) with possible time-correlated optical and X-ray variability.
Examples of both positive and negative time-correlations are found, possibly
representing X-ray flares and persistent coronal features associated with both
cool and hot surface spots (i.e. magnetically active regions and accretion
shocks). We also find two possible examples of "white-light" flares coincident
with X-ray flares; these may correspond to the impulsive heating phase in
solar-analog flares. However, though interesting, these represent unusual
cases. More generally, we find very little evidence to suggest a direct causal
link between the sources of optical and X-ray variability in PMS stars. The
conclusion that accretion is a primary driver of X-ray production in PMS stars
is not supported by our findings.