title: Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System

abstract:
  We determine the stellar, planetary, and orbital properties of the transiting
planetary system HD 209458, through a joint analysis of high-precision radial
velocities, photometry, and timing of the secondary eclipse. Of primary
interest is the strong detection of the Rossiter-McLaughlin effect, the
alteration of photospheric line profiles that occurs because the planet occults
part of the rotating surface of the star. We develop a new technique for
modeling this effect, and use it to determine the inclination of the planetary
orbit relative to the apparent stellar equator [lambda = (-4.4 +/- 1.4)
degrees], and the line-of-sight rotation speed of the star [v*sin(I) = (4.70
+/- 0.16) km/s]. The uncertainty in these quantities has been reduced by an
order of magnitude relative to the pioneering measurements by Queloz and
collaborators. The small but nonzero misalignment is probably a relic of the
planet formation epoch, because the expected timescale for tidal
coplanarization is larger than the age of the star. Our determination of
v*sin(I) is a rare case in which rotational line broadening has been isolated
from other broadening mechanisms.


title:
Emission-line spectroscopy of Damped Lyman Alpha Systems: The case of
  SBS 1543+593/HS 1543+5921

abstract:
  We report HST/STIS spectroscopy and Gemini/GMOS-N imaging of the Damped Lyman
Alpha (DLA) system toward HS 1543+5921 caused by the host star-forming galaxy
(SFG) SBS 1543+593. The Gemini image shows new morphological details of this
well resolved DLA galaxy. In combination with previous optical spectra, the new
UV spectra enable us to compare for the first time, ionized and neutral
gas-phase alpha-element abundances derived from emission- and absorption-line
spectroscopy, in a bona fide DLA galaxy. The abundances we determine using
emission-line diagnostics agree with those from absorption-line diagnostics. We
present our results on a metallicity versus redshift diagram that combines
local HII regions and SFGs with high-redshift DLAs, and discuss implications
for the chemical evolution of galaxies.


title:
Impact of Dark Matter Substructure on the Matter and Weak Lensing Power
  Spectra

abstract:
  We explore the effect of substructure in dark matter halos on the power
spectrum and bispectrum of matter fluctuations and weak lensing shear. By
experimenting with substructure in a cosmological N = 512^3 simulation, we find
that when a larger fraction of the host halo mass is in subhalos, the resulting
power spectrum has less power at 1 < k < 100 h Mpc^{-1} and more power at k >
100 h Mpc^{-1}. We explain this effect using an analytic halo model including
subhalos, which shows that the 1 < k < 100 h Mpc^{-1} regime depends
sensitively on the radial distribution of subhalo centers while the interior
structure of subhalos is important at k > 100 h Mpc^{-1}. The corresponding
effect due to substructures on the weak lensing power spectrum is up to about
11% at angular scale l < 10^4. Predicting the nonlinear power spectrum to a few
percent accuracy for future surveys would therefore require large cosmological
simulations that also have exquisite numerical resolution to model accurately
the survivals of dark matter subhalos in the tidal fields of their hosts.


title: Probing the Local Group Medium Toward Mkn 421 with Chandra and FUSE

abstract:
  We report the detection of highly-ionized gas at z~0 seen in resonant UV and
X-ray absorption lines toward the z=0.03 blazar Mkn 421. A total of 13 X-ray
and 3 UV lines were measured (or upper limits derived), including three lines
in the OVII K-series and K\alpha transitions from neon, carbon, and nitrogen.
  From the three OVII lines we derive a 2\sigma Doppler parameter constraint of
24<b<55 km/s. The FUSE spectrum shows strong Galactic low--velocity OVI 1032A
absorption as well as a possible weak OVI high-velocity component (HVC). The
Doppler parameter of the low-velocity OVI measured with FUSE is ~3\sigma higher
than that derived from the OVII line ratios, indicating that the OVII and
Galactic OVI arise in different phases. This velocity dispersion, along with
limits on the gas temperature and density from the X-ray line ratios (assuming
a single phase with collisional ionization equilibrium plus photoionization)
are all consistent with an extragalactic absorber. However, the OVII Doppler
parameter is inconsistent with the high temperature required to produce the
observed OVI_HVC/OVII ratio, implying that the HVC is probably not related to
the OVII. In addition, the OVI_K\alpha line detected by Chandra implies a
column density ~4 times higher than the 1032A absorption. Although an
extragalactic absorber is fully consistent with the measured column density
ratios, a Galactic origin cannot be ruled out given the uncertainties in the
available data.


title:
Chandra X-ray Observations of the Young Stellar Cluster NGC 6193 in the
  Ara OB1 Association

abstract:
  A 90 ks Chandra HETG observation of the young stellar cluster NGC 6193 in the
southern Ara OB1 association detected 43 X-ray sources in a 2' x 2' core region
centered on the young O stars HD 150135 (O6.5V) and HD 150136 (O3+O6V). The
cluster is dominated by exceptionally bright X-ray emission from the two O
stars, which are separated by only 10 arcsecs. The X-ray luminosity of HD
150136 is log Lx = 33.39 (ergs/s), making it one of the most luminous O-star
X-ray sources known. All of the fainter X-ray sources in the core region have
near-IR counterparts, but JHK photometry provides little evidence for near-IR
excesses. These core sources have typical mean photon energies of 2 keV and
about one-third are variable. It is likely that some are young low-mass stars
in the cluster, but cluster membership remains to be determined. Grating
spectra show that the X-ray properties of HD 150135 and HD 150136 are similar,
but not identical. Both have moderately broadened unshifted emission lines and
their emission is dominated by cool plasma, pointing to a wind shock origin.
However, the emission of HD 150136 is slightly hotter and 4 times more luminous
than its optical twin HD 150135. We discuss the possibility that a radiative
colliding wind shock contributes to the prodigious X-ray output of the
short-period (2.66 d) binary HD 150136. A surprising result is that the X-ray
emission of HD 150136 is slowly variable on a timescale of less than one day.
The origin of the variability is not yet known, but the observed behavior
suggests that it is an occultation effect.


title: B-Inflation

abstract:
  We propose a novel model of inflation based on a large class of covariant
effective actions containing only the second derivatives of a scalar field. The
initial conditions leading to the inflationary solutions in this model are
rather generic. The graceful exit from the inflationary regime is natural once
the first order derivative terms are included.


title:
Radiative Effect on Particle Acceleration via Relativistic
  Electromagnetic Expansion

abstract:
  The radiation damping effect on the diamagnetic relativistic pulse
accelerator (DRPA) is studied in two-and-half dimensional Particle-in-Cell
(PIC) simulation with magnetized electron-positron plasmas. Self-consistently
solved radiation damping force converts particle energy to radiation energy.
The DRPA is still robust with radiation, and the Lorentz factor of the most
high energy particles reach more than two thousand before they decouple from
the electromagnetic pulse. Resulted emitted power from the pulse front is lower
in the radiative case than the estimation from the non-radiative case due to
the radiation damping. The emitted radiation is strongly linearly polarized and
peaked within few degrees from the direction of Poynting flux.


title: Spot the differences: The X-ray spectrum of SU Aur compared to TW Hya

abstract:
  We present high-resolution Chandra HETGS X-ray spectra of the classical T
Tauri star SU Aur. The quiescent X-ray emission is dominated by a 20-40 MK
plasma, which contrasts strongly with the cool 3 MK plasma dominating the X-ray
emission of the CTTS TW Hya. A large flare occurred during the first half of
our 100 ks observation, and we have modelled the emitting plasma both during
this flare and during the apparently quiescent periods. During the flare, an
extremely high temperature plasma component (at least 60 MK) accounts for the
bulk of the emission. There is an indication of the presence of Fe XXVI
emission at 1.78 Angstrom, which is maximally formed at 130 MK.


title:
The Non-Monotonic Dependence of Supernova and Remnant Formation on
  Progenitor Rotation

abstract:
  Traditional models of core collapse suggest the issue of successful versus
failed supernova explosions and neutron star versus black hole formation
depends monotonically on the mass (and metallicity) of the progenitor star.
Here we argue that the issue of success or failure of the explosion or other
possible outcomes may depend non--monotonically on the rotation of the
progenitor star even at fixed progenitor mass and composition. We have computed
"shellular" models of core collapse for a star of 15 M_solar with initial
central angular velocity, Omega_0, in the range 0.1 -- 8 rad/s until a few
hundred ms after bounce to explore qualitative trends. The non--monotonic
behavior will be manifested in the rotation of the proto--neutron star and
hence in the strength of the associated magnetic field that will be generated
by shear in that rotating environment. We estimate that our maximally rotating
and shearing models generate toroidal fields approaching or exceeding 10^17G,
strengths nearing dynamical significance.


title: Deconfinement and color superconductivity in cold neutron stars

abstract:
  We study the deconfinement transition of hadronic matter into quark matter in
neutron star conditions in the light of color superconductivity. Deconfinement
is considered to be a first order phase transition that conserves color and
flavor. It gives a short-lived {($\tau \sim \tau_{weak}$)} transitory
colorless-quark-phase that is {\it not} in $\beta$-equilibrium. We deduce the
equations governing deconfinement when quark pairing is allowed and find the
regions of the parameter space (pairing gap $\Delta$ versus bag constant $B$)
where deconfinement is possible inside cold neutron stars. We show that for a
wide region of ($B,\Delta$) a pairing pattern is reachable within a strong
interaction timescale, and the resulting ``2SC-like'' phase is preferred
energetically to the unpaired phase. We also show that although $\beta$-stable
hybrid star configurations are known to be possible for a wide region of the
($B,\Delta$)-space, many of these configurations could not form in practice
because deconfinement is forbidden, i.e. the here studied non-$\beta$-stable
\emph{intermediate} state cannot be reached.


title:
The Evolution of Damped Lyman-alpha Absorbers: Metallicities and Star
  Formation Rates

abstract:
  The damped Lyman-alpha (DLA) and sub-DLA quasar absorption lines provide
powerful probes of the evolution of metals, gas, and stars in galaxies. One
major obstacle in trying to understand the evolution of DLAs and sub-DLAs has
been the small number of metallicity measurements at z < 1.5, an epoch spanning
\~70 % of the cosmic history. In recent surveys with the Hubble Space Telescope
and Multiple Mirror Telescope, we have doubled the DLA Zn sample at z < 1.5.
Combining our results with those at higher redshifts from the literature, we
find that the global mean metallicity of DLAs does not rise to the solar value
at low redshifts. These surprising results appear to contradict the near-solar
mean metallicity observed for nearby (z ~ 0) galaxies and the predictions of
cosmic chemical evolution models based on the global star formation history.
Finally, we discuss direct constraints on the star formation rates (SFRs) in
the absorber galaxies from our deep Fabry-Perot Ly-alpha imaging study and
other emission-line studies in the literature. A large fraction of the observed
heavy-element quasar absorbers at 0 < z < 3.4 appear to have SFRs substantially
below the global mean SFR, consistent with the low metallicities observed in
the spectroscopic studies.


title:
An analysis of the distribution of background star polarization in dark
  clouds

abstract:
  The polarization observed for stars background to dark clouds (Bok Globules)
is often used as diagnostic to study the ongoing star formation processes in
these clouds. Such polarization in the optical have been reported for eight
nearby clouds CB3, CB25, CB39, CB52, CB54, CB58, CB62 and CB246 in one of our
previous work (Sen et. al. 2000). With a view to understand the origin of this
polarization, the the present work attempts are made to look for any possible
relation between this observed polarization and other physical parameters in
the cloud (like temperature, turbulence etc.). The observed polarization does
not seem to be clearly related to the dust and gas temperatures (T_d and T_g)
in the cloud as expected from the Davis-Greenstein grain alignment mechanism
(Davis & Greenstein, 1952). However, the average observed polarization p_av
appears to be related to the turbulence delta V (measured by 12CO line width)
by the mathematical relation p_av=2.95exp(-0.24delta V). The possible realtion
between the direction of polarization vector and other physical parameters are
also discussed. For this analysis, in addition to the data on above eight
clouds, the data on CB4 (Kane et. al., 1995) are also included for comparison.


title:
Axisymmetric collapse simulations of rotating massive stellar cores in
  full general relativity: Numerical study for prompt black hole formation

abstract:
  We perform axisymmetric simulations for gravitational collapse of a massive
iron core to a black hole in full general relativity. The iron cores are
modeled by $\Gamma = 4/3$ equilibrium polytrope for simplicity and a parametric
equation of state is adopted during the collapse. Performing simulations for a
wide variety of initial conditions changing the mass, the angular momentum, the
rotational velocity profile of the core, and the parameters of the equations of
state (which are chosen so that the maximum mass of the cold spherical
polytrope is $\approx 1.6M_{\odot}$), a criterion for the prompt black hole
formation is clarified in terms of them. It is found that (i) with the increase
of the thermal energy generated by shocks, the threshold mass for the prompt
black hole formation is increased by 20--40%, (ii) the rotational centrifugal
force increases the threshold mass by $\alt 25%$, (iii) with the increase of
the degree of differential rotation, the threshold mass is also increased, and
(iv) the amplification factors shown in the results (i)--(iii) depend
sensitively on the equation of state. We also find that the collapse dynamics
and the structure of the shock formed at the bounce depend strongly on the
stiffness of the adopted equation of state. In particular, as a new feature, a
strong bipolar explosion is observed for the collapse of rapidly rotating iron
cores with an equation of state which is stiff in subnuclear density and soft
in supranuclear density. Gravitational waves are computed in terms of a
quadrupole formula. It is also found that the waveform depends sensitively on
the equations of state.


title:
The HST view of the nuclear emission line region in low luminosity
  radio-galaxies

abstract:
  We study the properties of the emission line regions in two samples of low
luminosity radio-galaxies (LLRG), focusing on the compact emission line region
(CELR) revealed to be a characteristic feature of these objects by HST
narrow-band imaging. We find a strong correlation between line and optical
continuum nuclear emission, suggesting that the optical cores (most likely of
non thermal origin) can be directly associated to the source of ionizing
photons, i.e. that we are seeing a jet-ionized narrow line region. A photon
budget argument indicates that the optical nuclear sources produce a sufficient
photon flux provided that the covering factor of the circum-nuclear gas is
rather large, on average ~ 0.3. Analysis of HST images and spectra suggests
that the CELR may take the form of a pc-scale, high filling factor, structure,
possibly an optically thin torus. Estimates of the CELR mass lead to values as
small as 10 - 1000 solar masses and photon counting sets a limit to the BLR
mass of 0.01 solar masses. When considered together with the low accretion rate
and the tenuous torus structure, a general paucity of gas in the innermost
regions of LLRG emerges as the main characterizing difference from more
powerful AGN.


title: Molecular Gas in Compact Galaxies

abstract:
  New observations of 11 compact galaxies in the 12CO J=2-1 and J=3-2
transitions and literature data have been used to construct accurate line
ratios in matched beams allowing LVG modelling of physical parameters. Fitting
a single gas component to observed line ratios tends to produce physically
unrealistic results, and is often not possible at all. Much better results are
obtained by modelling two distinct gas components. The molecular gas is usually
warm (T(kin)=50-150 K) and at least partially dense (n(H2)>3000 cm3). Most of
the gas-phase carbon in these galaxies is in atomic form; only a small fraction
(5%) is in carbon monoxide. Beam-averaged CO column densities are low,
typically 10(16) cm2 but molecular hydrogen column densities are high, of the
order of 10(22) cm2 and confirm large CO-to-H2 conversion factors, typically X
= 10(21)-10(22) cm2(K kms-1) found in low-metallicity environments by other
methods. From CO spectroscopy, three different types of molecular environment
are distinguished in compact galaxies. Type I (high rotational and isotopic
ratios) corresponds to hot and dense molecular clouds dominated by star-forming
regions. Type II has lower ratios, similar to the mean found for
infrared-luminous galaxies in general, and corresponds to environments engaged
in, but not dominated by, star-forming activity. Type III, characterized by low
12CO (2--1)/(1--0) ratios, corresponds to mostly inactive environments of
relatively low density.


title: A deep survey of brown dwarfs in Orion with Gemini

abstract:
  We report the results of a deep near infrared (JHK) survey of the outer parts
of the Trapezium Cluster with Gemini South/Flamingos. 396 sources were detected
in a 26 arcmin^2 area, including 138 brown dwarf candidates, defined as M<0.075
Msun for an assumed age of 1 Myr. Only 33 of the brown dwarf candidates are
planetary mass candidates (PMCs) with estimated masses in the range
0.003<M<0.012Msun. In an extinction limited sample (A(V)<5) complete to
approximately 0.005 Msun (5 Mjup) the mass function appears to drop by a factor
of 2 at the deuterium burning threshold, i.e. at planetary masses. After
allowing for background contamination it is likely that planetary mass objects
at 3-13 Mjup number <10% of the cluster population, with an upper limit of 13%.
Analysis of the spatial distribution of stars and brown dwarf candidates
suggests that brown dwarfs and very low mass stars (M<0.1 Msun) are less likely
than more massive stars to have wide (>150 AU) binary companions. This result
has modest statistical significance (96%) in our data but is supported at 93%
confidence by analysis of an completely independent sample taken from the
Subaru data of Kaifu et al.(2000). There is a statistically very significant
excess of both stars and brown dwarfs with small separations from each other
(<6 arcsec or 2600 AU). This appears to be due to the presence of small N
subgroups, which are likely to be dynamically unstable in the long term. Hence
these results are consistent with the 'ejected stellar embryo' hypothesis for
brown dwarf formation (Reipurth & Clarke 2001). We also report the discovery of
two new bipolar nebulae, which are interpreted as Class I protostars.


title: Growth of perturbations in dark matter coupled with quintessence

abstract:
  We consider the evolution of linear perturbations in models with a nonminimal
coupling between dark matter and scalar field dark energy. Growth of matter
inhomogeneities in two examples of such models proposed in the literature are
investigated in detail. Both of these models are based on a low-energy limit of
effective string theory action, and have been previously shown to naturally
lead to late acceleration of the universe. However, we find that these models
can be ruled out by taking properly into account the impact of the scalar field
coupling on the formation of structure in the dark matter density. In
particular, when the transition to acceleration in these models begins, the
interaction with dark energy enchances the small scale clustering in dark
matter much too strongly. We discuss the the role of an effective small scale
sound speed in such models with a coupled dark sector.


title: Non-equilibrium beta processes in superfluid neutron star cores

abstract:
  The influence of nucleons superfluidity on the beta relaxation time of
degenerate neutron star cores, composed of neutrons, protons and electrons, is
investigated. We numerically calculate the implied reduction factors for both
direct and modified Urca reactions, with isotropic pairing of protons or
anisotropic pairing of neutrons. We find that due to the non-zero value of the
temperature and/or to the vanishing of anisotropic gaps in some directions of
the phase-space, superfluidity does not always completely inhibit beta
relaxation, allowing for some reactions if the superfluid gap amplitude is not
too large in respect to both the typical thermal energy and the chemical
potential mismatch. We even observe that if the ratio between the critical
temperature and the actual temperature is very small, a suprathermal regime is
reached for which superfluidity is almost irrelevant. On the contrary, if the
gap is large enough, the composition of the nuclear matter can stay frozen for
very long durations, unless the departure from beta equilibrium is at least as
important as the gap amplitude. These results are crucial for precise
estimation of the superfluidity effect on the cooling/slowing-down of pulsars
and we provide online subroutines to be implemented in codes for simulating
such evolutions.


title:
Optimal Choice of the Softening Length and Time-Step in N-body
  Simulations

abstract:
  A criterion for the choice of optimal softening length $\epsilon$ and
time-step $dt$ for $N$-body simulations of a collisionless stellar system is
analyzed. Plummer and Hernquist spheres are used as models to follow how
changes in various parameters of an initially equilibrium stable model depend
on $\epsilon$ and $dt$. These dependences are used to derive a criterion for
choosing $\epsilon$ and $dt$. The resulting criterion is compared to Merritt's
criterion for choosing the softening length, which is based on minimizing the
mean irregular force acting on a particle with unit mass. Our criterion for
choosing $\epsilon$ and $dt$ indicate that $\epsilon$ must be a factor of 1.5-2
smaller than the mean distance between particles in the densest regions to be
resolved. The time-step must always be adjusted to the chosen $\epsilon$ (the
particle must, on average, travel a distance smaller than $0.5\epsilon$ during
one time-step). An algorithm for solving N-body problems with adaptive
variations of the softening length is discussed in connection with the task of
choosing $\epsilon$, but is found not to be promising.


title: The sensitivity of Lick indices to abundance variations

abstract:
  We present results of model atmosphere/line formation calculations which
quantitatively test how the 21 classical and four higher-order Balmer-line
Lick/IDS indices (Worthey et al. 1994; Worthey & Ottaviani 1997) depend on
individual elemental abundances (of carbon, nitrogen, oxygen, magnesium, iron,
calcium, natrium, silicon, chromium, titanium) and overall metallicity in
various stellar evolutionary stages and at various metallicities. At low
metallicities the effects of an overall enhancement of alpha-elements are also
investigated. The general results obtained by Tripicco & Bell (1995) at solar
metallicity are confirmed, while details do differ. Tables are given detailing
to which element every index reacts significantly, as a function of
evolutionary stage and composition.
  This work validates a number of assumptions implicitly made in the stellar
population models of Thomas, Maraston & Bender (2003), which utilized the
results of Tripicco & Bell (1995) to include the effects of element abundance
ratios variations. In particular, these computations confirm that fractional
changes to index strengths computed at solar metallicity (and solar age) can be
applied over a wide range of abundances and ages, also to model old stellar
populations with non-solar abundance ratios. The use of metallicity-dependent
response functions is, however, required for the proper modelling of the
Balmer-line indices. While H beta still responds only moderately to abundance
ratio variations, the higher-order Balmer indices H gamma and H delta display
very strong dependencies at high metallicities. As shown in Thomas, Maraston &
Korn (2004), this result allows to remove systematic effects in age
determinations based on different Balmer-line indices. (abridged)


title:
Generalised 3D-reconstruction method of a dipole anisotropy in
  cosmic-ray distributions

abstract:
  We develop a method to study the anisotropy of a cosmic-ray angular
distribution, using both the right ascension and the declination of the arrival
directions. It generalises the full-sky coverage method of Sommers (2001) to
partial-sky coverage experiments. When the angular distribution consists of a
dipolar modulation of an otherwise isotropic flux, the method allows one to
reconstruct the dipole amplitude and the dipole orientation in 3D space. We
analyse in detail the statistical properties of the method, introducing the
concept of reconstruction power, and show that it is generally more powerful
than the standard Rayleigh analysis in right ascension. We clarify the link
between the traditionally-used first harmonic amplitude and the true, physical
dipole amplitude, and we investigate the variation of the reconstruction powers
as a function of the dipole orientation. We illustrate the method by computing
the amplitude and angular reconstruction powers of the Pierre Auger
Observatory, with the Southern site alone and with both Southern and Northern
sites. In this particular case, we find that the building of a similar site in
the Northern hemisphere would decrease the time needed for the method to reveal
a significant departure from an isotropic cosmic-ray distribution by a factor
of about eight.


title: Stability properties of some perfect fluid cosmological models

abstract:
  Flat FRW perfect fluid cosmologies can be reproduced as particular solutions
of suitable field theoretical models. Here we investigate the stability of
perfect fluid model trajectories with respect to sets of trajectories of the
corresponding field models having generic initial conditions. It is shown that
the trajectories of barotropic perfect fluid models and those of the Chaplygin
gas model are stable. The total probability to reach the Chaplygin gas regime
early enough to achieve a matter dominated stage having a realistic duration is
calculated for a scalar field model assuming a natural measure in the space of
initial conditions taken near a cosmological singularity. An example is
presented of a two-fluid cosmological model where the stability is partially
absent.


title:
The evolution of the timing properties of the black-hole transient GX
  339-4 during its 2002/2003 outburst

abstract:
  We present the results of the timing and color analysis of more than two
hundred RXTE/PCA observations of the bright black-hole transient GX 339-4
obtained during its 2002/2003 outburst. The color-intensity evolution of the
system, coupled to the properties of its fast time variability, allow the
identification of four separate states. Depending on the state, strong noise is
detected, together with a variety of quasi-periodic oscillations at frequencies
from 0.2 to 8 Hz. We present a characterization of the timing parameters of
these states and compare them to what has been observed in other systems. These
results, together with those obtained from energy spectra, point towards a
common evolution of black-hole transients through their outbursts.


title:
Halpha-Derived Star-Formation Rates For Three z ~ 0.75 EDisCS Galaxy
  Clusters

abstract:
  We present Halpha-derived star-formation rates (SFRs) for three z ~ 0.75
galaxy clusters. Our 1 sigma flux limit corresponds to a star-formation rate of
0.10-0.24 solar mass per year, and our minimum reliable Halpha + [N II]
rest-frame equivalent width is 10\AA. We show that Halpha narrowband imaging is
an efficient method for measuring star formation in distant clusters. In two
out of three clusters, we find that the fraction of star-forming galaxies
increases with projected distance from the cluster center. We also find that
the fraction of star-forming galaxies decreases with increasing local galaxy
surface density in the same two clusters. We compare the median rate of star
formation among star-forming cluster galaxies to a small sample of star-forming
field galaxies from the literature and find that the median cluster SFRs are
\~50% less than the median field SFR. We characterize cluster evolution in
terms of the mass-normalized integrated cluster SFR and find that the z ~ 0.75
clusters have more SFR per cluster mass on average than the z <= 0.4 clusters
from the literature. The interpretation of this result is complicated by the
dependence of the mass-normalized SFR on cluster mass and the lack of
sufficient overlap in the mass ranges covered by the low and high redshift
samples. We find that the fraction and luminosities of the brightest starburst
galaxies at z ~ 0.75 are consistent with their being progenitors of the
post-starburst galaxies at z ~ 0.45 if the post-starburst phase lasts several
(~5) times longer than the starburst phase.


title: System Parameters of the Transiting Extrasolar Planet HD 209458b

abstract:
  We derive improved system parameters for the HD 209458 system using a model
that simultaneously fits both photometric transit and radial velocity
observations. The photometry consists of previous Hubble Space Telescope STIS
and FGS observations, twelve I-band transits observed between 2001-2003 with
the Mt. Laguna Observatory 1m telescope, and six Stromgren b+y transits
observed between 2001-2004 with two of the Automatic Photometric Telescopes at
Fairborn Observatory. The radial velocities were derived from Keck/HIRES
observations. The model properly treats the orbital dynamics of the system, and
thus yields robust and physically self-consistent solutions. Our set of system
parameters agrees with previously published results though with improved
accuracy. For example, applying robust limits on the stellar mass of
0.93-1.20Msun, we find 1.26 < Rplanet < 1.42 Rjup and 0.59 < Mplanet < 0.70
Mjup. We can reduce the uncertainty on these estimates by including a stellar
mass-radius relation constraint, yielding Rplanet = 1.35 +/- 0.07 Rjup and
Mplanet = 0.66 +/- 0.04 Mjup. Our results verify that the planetary radius is
10-20% larger than predicted by planet evolution models, confirming the need
for an additional mechanism to slow the evolutionary contraction of the planet.
A revised ephemeris is derived, T0=2452854.82545 + 3.52474554E (HJD), which now
contains an uncertainty in the period of 0.016s and should facilitate future
searches for planetary satellites and other bodies in the HD 209458 system.


title: What is L*?: Anatomy of the Galaxy Luminosity Function

abstract:
  Using the empirical relations between the central galaxy luminosity and the
halo mass, and between the total galaxy luminosity in a halo and the halo mass,
we construct the galaxy luminosity function (LF). To the luminosity of the
central galaxy in a halo of a given mass we assign log-normal scatter with a
mean calibrated against the observations. In halos where the total galaxy
luminosity exceeds that of the central galaxy, satellite galaxies are
distributed as a power-law in luminosity. Combined with the halo mass function,
this description reproduces the observed characteristics of the galaxy LF,
including a shape consistent with the Schechter function. When all galaxies are
included, regardless of the environment or the Hubble type, the Schechter L* is
the luminosity scale above which the central galaxy luminosity-halo mass
relation flattens; L* corresponds to ~10^{13}Msun on the halo mass scale. In
surveys where central galaxies in massive clusters are neglected, either by
design or because of the cosmic variance, L* is simply the mean luminosity of
central galaxies in halos at the upper end of the selected mass range. The
smooth, exponential decay of the Schechter function toward high luminosities
reflects the intrinsic scatter in the central galaxy luminosity-halo mass
relation. In addition to the LF, the model successfully reproduces the observed
dependence of galaxy clustering bias on luminosity.


title: Dark Matter and Stellar Mass in the Luminous Regions of Disk Galaxies

abstract:
  We investigate the correlations among stellar mass (M_*), disk scale length
(R_d), and rotation velocity at 2.2 disk scale lengths (V_2.2) for a sample of
81 disk-dominated galaxies (disk/total >= 0.9) selected from the SDSS. We
measure V_2.2 from long-slit H-alpha rotation curves and infer M_* from galaxy
i-band luminosities (L_i) and g-r colors. We find logarithmic slopes of
2.60+/-0.13 and 3.05+/-0.12 for the L_i-V_2.2 and M_*-V_2.2 relations, somewhat
shallower than most previous studies, with intrinsic scatter of 0.13 dex and
0.16 dex. Our direct estimates of the total-to-stellar mass ratio within
2.2R_d, assuming a Kroupa IMF, yield a median ratio of 2.4 for M_*>10^10 Msun
and 4.4 for M_*=10^9-10^10 Msun, with large scatter at a given M_* and R_d. The
typical ratio of the rotation speed predicted for the stellar disk alone to the
observed rotation speed at 2.2R_d is ~0.65. The distribution of R_d at fixed
M_* is broad, but we find no correlation between disk size and the residual
from the M_*-V_2.2 relation, implying that this relation is an approximately
edge-on view of the disk galaxy fundamental plane. Independent of the assumed
IMF, this result implies that stellar disks do not, on average, dominate the
mass within 2.2R_d. We discuss our results in the context of infall models of
disk formation in cold dark matter halos. A model with a disk-to-halo mass
ratio m_d=0.05 provides a reasonable match to the R_d-M_* distribution for spin
parameters \lambda ranging from ~0.04-0.08, and it yields a reasonable match to
the mean M_*-V_2.2 relation. A model with m_d=0.1 predicts overly strong
correlations between disk size and M_*-V_2.2 residual. Explaining the wide
range of halo-to-disk mass ratios within 2.2R_d requires significant scatter in
m_d values, with systematically lower m_d for galaxies with lower $M_*$.


title: Crossing the Phantom Divide Barrier with Scalar Tensor Theories

abstract:
  There is accumulating observational evidence (based on SnIa data) that the
dark energy equation of state parameter $w$ may be evolving with time and
crossing the phantom divide barrier $w=-1$ at recent times. The confirmation of
these indications by future data would indicate that minimally coupled
quintessence can not reproduce the observed expansion rate $H(z)$ for any
scalar field potential. Here we explicitly demonstrate that scalar tensor
theories of gravity (extended quintessence) can predict crossing of the phantom
divide barrier. We reconstruct phenomenologically viable scalar-tensor
potentials $F(\Phi)$ and $U(\Phi)$ that can reproduce a polynomial best fit
expansion rate $H(z)$ and the corresponding dark energy equation of state
parameter $w(z)$ crossing the $w=-1$ line. The form of the reconstructed scalar
tensor potentials is severely constrained but is not uniquely determined. This
is due to observational uncertainties in the form of $H(z)$ and also because a
single observed function $H(z)$ does not suffice for the reconstruction of the
two potential functions $F(\Phi)$ and $U(\Phi)$.


title: Revealing the Supernova Remnant Population of M33 with Chandra

abstract:
  We present results of a search for supernova remnants (SNRs) in archival
Chandra images of M33. We have identified X-ray SNRs by comparing the list of
Chandra, X-ray sources in M33 with tabulations of SNR candidates identified
from (1) elevated [S II]/Halpha ratios in the optical, and (2) radio spectral
indices. Of the 98 optically known SNRs in M33, 22 have been detected at >
3-sigma level in the soft band (0.35-1.1 keV). At least four of these SNR
candidates are spatially extended based on a comparison of the data to
simulated images of point sources. Aside from the optically matching SNRs, we
have found one soft X-ray source in M33 which exhibits no optical emission and
is coincident with a known radio source. The radio spectral index of this
source is consistent with particle acceleration in shocks, leading us to
suggest that it is a non-radiative SNR. We have also found new optical
counterparts to two soft X-ray SNRs in M33. Pending confirmation from optical
spectroscopy, the identification of these two optical counterparts increases
the total number of known optically emitting SNRs in M33 to 100. This brings
the total number of identified SNRs with X-ray counterparts, including those
exclusively detected by the XMM-Newton survey of M33, to 37 SNRs. We find that
while there are a similar number of confirmed X-ray SNRs in M33 and the LMC
with X-ray luminosities in excess of 1e35 ergs/s, nearly 40% of the LMC SNRs
are brighter than 1e36 ergs/s, while only 13% of the M33 sample exceed this
luminosity. The differences in luminosity distributions cannot be fully
explained by uncertainty in spectral model parameters, and is not fully
accounted for by abundance differences between the galaxies (abridged).


title: A statistical study of 233 pulsar proper motions

abstract:
  We present and analyse a catalogue of 233 pulsars with proper motion
measurements. The sample contains a wide variety of pulsars including recycled
objects and those associated with globular clusters or supernova remnants.
After taking the most precise proper motions for those pulsars for which
multiple measurements are available, the majority of the proper motions (58%)
are derived from pulsar timing methods, 41% using interferometers and the
remaining 1% using optical telescopes. Many of the 1-D and 2-D speeds
(referring to speeds measured in one coordinate only and the magnitudes of the
transverse velocities respectively) derived from these measurements are
somewhat lower than earlier estimates because of the use of the most recent
electron density model in determining pulsar distances. The mean 1-D speeds for
the normal and recycled pulsars are 152(10) and 54(6) km/s respectively. The
corresponding mean 2-D speeds are 246(22) and 87(13) km/s. PSRs B2011+38 and
B2224+64 have the highest inferred 2-D speeds of ~1600 km/s. We study the mean
speeds for different subsamples and find that, in general, they agree with
previous results. Applying a novel deconvolution technique to the sample of 73
pulsars with characteristic ages less than 3 Myr, we find the mean 3-D pulsar
birth velocity to be 400(40) km/s. The distribution of velocities is well
described by a Maxwellian distribution with 1-D rms sigma=265 km/s. There is no
evidence for a bimodal velocity distribution. The proper motions for PSRs
B1830-08 and B2334+61 are consistent with their proposed associations with the
supernova remnants W41 and G114.3+0.3 respectively.


title: Discovery of a high-redshift Einstein ring

abstract:
  We report the discovery of a partial Einstein ring of radius 1.48arcsec
produced by a massive (and seemingly isolated) elliptical galaxy. The
spectroscopic follow-up at the VLT reveals a 2L* galaxy at z=0.986, which is
lensing a post-starburst galaxy at z=3.773. This unique configuration yields a
very precise measure of the mass of the lens within the Einstein radius,
(8.3e11 +- 0.4)/h70 Msolar. The fundamental plane relation indicates an
evolution rate of d [log (M/L)B] / dz = -0.57+-0.04, similar to other massive
ellipticals at this redshift. The source galaxy shows strong interstellar
absorption lines indicative of large gas-phase metallicities, with fading
stellar populations after a burst. Higher resolution spectra and imaging will
allow the detailed study of an unbiased representative of the galaxy population
when the universe was just 12% of its current age.


title: Statefinder diagnostic for holographic dark energy model

abstract:
  In this paper we study the holographic dark energy model proposed by Li from
the statefinder viewpoint. We plot the evolutionary trajectories of the model
with $c=1$ in the statefinder parameter-planes. The statefinder diagrams
characterize the properties of the holographic dark energy and show the
discrimination between this scenario and other dark energy models. We also
perform a statefinder diagnostic to the holographic dark energy model in cases
of different $c$ which given by three fits to observational data. The result
indicates that from the statefinder viewpoint $c$ plays a significant role in
this model and should thus be determined seriously by future high precision
experiments.


title: Optical Monitoring of PKS 1510-089: A Binary Black Hole System?

abstract:
  Three deep flux minima were observed with nearly the same time-scales and
intervals for the blazar PKS 1510-089 in the past few years. A binary black
hole system was proposed to be at the nucleus of this object, and a new minimum
was predicted to occur in 2002 March. We monitored this source with a 60/90 cm
Schmidt telescope from 2002 February to April. In combination with the data
obtained by Xie et al. (2004) in the same period, we presented for the 2002
minimum a nearly symmetric light curve, which would be required by an eclipsing
model of a binary black hole system. We also constrained the time-scale of the
minimum to be 35 min, which is more consistent with the time-scales ~42 min of
the three previous minima than the 89 min time-scale given by the same authors.
The wiggling miniarcsecond radio jet observed in this object is taken as a
further evidence for the binary black hole system. The `coupling' of the
periodicity in light curve and the helicity in radio jet is discussed in the
framework of a binary black hole system.


title: Magnetic-field generation in helical turbulence

abstract:
  We investigate analytically the amplification of a weak magnetic field in a
homogeneous and isotropic turbulent flow lacking reflectional symmetry (helical
turbulence). We propose that the spectral distributions of magnetic energy and
magnetic helicity can be found as eigenmodes of a self-adjoint,
Schr\"odinger-type system of evolution equations. We argue that large-scale and
small-scale magnetic fluctuations cannot be effectively separated, and that the
conventional alpha-model is, in general, not an adequate description of the
large-scale dynamo mechanism. As a consequence, the correct numerical modeling
of such processes should resolve magnetic fluctuations down to the very small,
resistive scales.


title:
Non-Gaussianity due to Possible Residual Foreground Signals in WMAP
  1st-year Data Using Spherical Wavelet Approaches

abstract:
  We perform multi-scale non-Gaussianity detection and localization to the
Wilkinson Microwave Anisotropy Probe (WMAP) first-year data in both wavelet and
real spaces. Such an analysis is facilitated by spherical wavelet transform and
inverse transform techniques developed by the YAWtb team. Skewness and kurtosis
as test statistics are calculated on scales from about $1^{\circ}$ to
$30^{\circ}$ on the sky as well as toward different directions using
anisotropic spherical Morlet wavelet (SMW). A maximum deviation from Gaussian
simulations with a right tail probability of $\sim 99.9%$ is detected at an
angular scale of $\sim12^{\circ}$ at an azimuthal orientation of $\sim
0^{\circ}$ on the sky. In addition, some significant non-Gaussian spots have
been identified and localized in real space from both the combined Q-V-W map
recommended by the WMAP team and the Tegmark foreground-cleaned map. Systematic
effects due to beams and noise can be rejected as the source of this
non-Gaussianity. Several tests show that residual foreground contamination may
significantly contribute to this non-Gaussian feature. It is thus still
premature to do more precise tests on the non-Gaussianity of the intrinsic CMB
fluctuations before we can identify the origin of these foreground signals,
understand their nature, and finally remove them from the CMB maps completely.


title: Disc-Disc Encounters between Low-Mass Protoplanetary Accretion Discs

abstract:
  Simulations of the collapse and fragmentation of turbulent molecular clouds
and dense young clusters show that encounters between disc-surrounded stars are
relatively common events which should significantly influence the resulting
disc structure. In turn this should alter the accretion rate of disc matter
onto the star and the conditions under which planet formation occurs. Although
the effects of star-disc encounters have been previously investigated, very
little is known about encounters where both stars are surrounded by discs. In
this paper encounters of such disc-disc systems are studied quantitatively. It
is found that for low-mass discs ($M_D$= 0.01 $M_\sun$) the results from
star-disc encounters can be straightforwardly generalized to disc-disc
encounters as long as there is no mass transport between the discs. Differences
to star-disc encounters occur naturally where significant amounts of matter are
transported between the discs. In this case it is found that although the mass
distribution does not change significantly, matter caught onto highly eccentric
orbits is transported surprisingly far inside the disc. The captured mass
partly replenishes the disc, but has a much lower angular momentum. This can
lead to a reduction of the angular momentum in the entire disc and thus
considerably increased accretion shortly after the encounter as well as in the
long term.


title: Can gamma-ray bursts constrain quintessence?

abstract:
  Using the narrow clustering of the geometrically corrected gamma-ray energies
released by gamma-ray bursts, we investigate the possibility of using these
sources as standard candles to probe cosmological parameters such as the matter
density Omega_m and the cosmological constant energy density Omega_Lambda. By
simulating different samples of gamma-ray bursts, we find that Omega_m can be
determined with accuracy ~7% with data from 300 sources. We also show that, if
Omega = 1 is due to a quintessence field, some of the models proposed in the
literature may be discriminated from a Universe with cosmological constant, by
a similar-sized sample of gamma-ray bursts.


title:
Late-epoch optical and near-infrared observations of the GRB000911
  afterglow and its host galaxy

abstract:
  We present the results of an optical and near-infrared (NIR) monitoring
campaign of the counterpart of Gamma-Ray Burst (GRB) 000911, located at
redshift z=1.06, from 5 days to more than 13 months after explosion. Our
extensive dataset is a factor of 2 larger and spans a time interval about 4
times longer than the ones considered previously for this GRB afterglow; this
allows a more thorough analysis of its light curve and of the GRB host galaxy
properties. The afterglow light curves show a single power-law temporal
decline, modified at late times by light from a host galaxy with moderate
intrinsic extinction, and possibly by an emerging supernova (SN). The afterglow
evolution is interpreted within the classical "fireball" scenario as a weakly
collimated adiabatic shock propagating in the interstellar medium. The presence
of a SN light curve superimposed on the non-thermal afterglow emission is
investigated: while in the optical bands no significant contribution to the
total light is found from a SN, the NIR J-band data show an excess which is
consistent with a SN as bright as the known hypernova SN1998bw. If the SN
interpretation is true, this would be the farthest GRB-associated SN, as well
as the farthest core-collapse SN, discovered to date. However, other possible
explanations of this NIR excess are also investigated. Finally, we studied the
photometric properties of the host, and found that it is likely to be a
slightly reddened, subluminous, extreme starburst compact galaxy, with
luminosity about 0.1 L*, an age of about 0.5 Gyr and a specific Star Formation
Rate (SFR) of approximately 30 Msol yr-1 (L/L*)-1. This is the highest specific
SFR value for a GRB host inferred from optical/NIR data.


title: A Multiplicity Survey of the Rho Ophiuchi Molecular Clouds

abstract:
  We present a volume-limited multiplicity survey with magnitude cutoff (K =<
10.5 mag) of 158 young stellar objects located within or in the vicinity of the
Rho Ophiuchi Dark Cloud. With exception of eleven already well observed
objects, all sources have been observed by us in the K-band with 3.5m
telescopes by using speckle techniques. The separation range covered by our
survey is [0.13'',6.4''], where the lower limit is given by the diffraction
limit of the telescopes and the upper limit by confusion with background stars.
The multiplicity survey is complete for flux ratios => 0.1 (=< 2.5 mag) at the
diffraction limit. After taking the background density into account the degree
of multiplicity is 29.1%+-4.3% and thus only marginally higher than the value
23.5%+-4.8%derived for the given separation range for the main-sequence
solar-like stars in the solar neighbourhood (Duquennoy & Mayor 1991). We
discuss the implications of these findings.


title:
Soft X-ray Transmission Spectroscopy of Warm/Hot Intergalactic Medium
  with XEUS

abstract:
  We discuss the detectability of Warm/Hot Intergalactic medium (WHIM) via the
absorption lines toward bright point sources with a future X-ray satellite
mission, XEUS. While we consider bright QSOs as specific examples, the
methodology can be applied to bright GRB afterglows. We create mock absorption
spectra for bright QSOs (more than 20 QSOs over the all sky) using a light-cone
output of a cosmological hydrodynamic simulation. We assume that WHIM is under
collisional and photo-ionization equilibrium. If WHIM has a constant
metallicity of $Z=0.1Z_\odot$, approximately 2 O{\sc vii} absorption line
system with $>3\sigma$ will be detected on average along a random line-of-sight
toward bright QSOs up to $z=0.3$ for 30 ksec exposure.


title: The Surprising Anisotropy of Fast Rotating, Disky Elliptical Galaxies

abstract:
  The projected kinematical properties of unequal-mass merger remnants of disk
galaxies are analysed and shown to agree well with observations of disky, fast
rotating elliptical galaxies. This supports the major merger hypothesis of
early-type galaxy formation. However, in contrast to previous claims, the
merger remnants are very anisotropic with values of the anisotropy parameter
that are similar to equal-mass merger remnants that form boxy, slowly rotating
ellipticals. Including gas in the simulations does not change this result
although the line-of-sight velocity profile and the intrinsic orbital structure
are strongly affected by the presenceof gas. The kinematical difference between
boxy and disky ellipticals appears not to be the amount of anisotropy but
rather rotation and the shape of the velocity dispersion tensor. The apparent
isotropy of observed disky ellipticals is shown to result from inclination
effects. Even small inclination angles strongly reduce the measured anisotropy
of fast rotating systems, seen in projection. A second problem is the limited
amount of information that is available when measuring only the central
velocity dispersion and a characteristic rotation and ellipticity. Methods are
investigated that allow a better determination of the intrinsic anisotropy of
fast rotating early-type galaxies with known inclination angles.


title:
V453 Oph: a s-process enriched, but carbon-deficient RV Tauri star of
  low intrinsic metallicity

abstract:
  This paper reports the detection of a heavy element enriched RV Tauri
variable with an abundance pattern that differs significantly from a standard
s-process enriched object: V453 Oph. Based on optical high-resolution spectra,
we determined that this object of low intrinsic metallicity ([Fe/H] = -2.2) has
a mild, but significant, enrichment ([s/Fe] ~ +0.5) of heavy elements for which
the distribution points to slow neutron capture nucleosynthesis. This result is
strengthened by a comparative analysis to the non-enriched RV Tauri star DS Aqr
([s/Fe] = 0.0). Although V453 Oph is the first RV Tauri star showing a strong
s-process signature, it is NOT accompanied by C enhancement, challenging our
current nucleosynthetic models of post-AGB stars that predict a simultaneous
enrichment in C and s-process elements. The low N abundance excludes CN cycling
as being responsible for the low C abundance. We explore three different
scenarios to explain the heavy element distribution in this evolved object: an
enrichment of the parental cloud, an accretion scenario in which the chemical
patterns were acquired by mass transfer in a binary system and an intrinsic
enrichment by dredge-up.


title: Supernovae: Explosions in the Cosmos

abstract:
  In this article, a broad perspective of supernovae, their classification and
mechanism is given. Later, the astrophysical significance of supernovae is
discussed in brief.


title: New Jupiter and Saturn formation models meet observations

abstract:
  The wealth of observational data about Jupiter and Saturn provides strong
constraints to guide our understanding of the formation of giant planets. The
size of the core and the total amount of heavy elements in the envelope have
been derived from internal structure studies by Saumon & Guillot (2004). The
atmospheric abundance of some volatile elements has been measured {\it in situ}
by the {\it Galileo} probe (Mahaffy et al. 2000, Wong et al. 2004) or by remote
sensing (Briggs & Sackett 1989, Kerola et al. 1997). In this Letter, we show
that, by extending the standard core accretion formation scenario of giant
planets by Pollack et al. (1996) to include migration and protoplanetary disk
evolution, it is possible to account for all of these constraints in a
self-consistent manner.


title:
An application of Green-function methods to gravitational radiation
  theory

abstract:
  Previous work in the literature has studied gravitational radiation in
black-hole collisions at the speed of light. In particular, it had been proved
that the perturbative field equations may all be reduced to equations in only
two independent variables, by virtue of a conformal symmetry at each order in
perturbation theory. The Green function for the perturbative field equations is
here analyzed by studying the corresponding second-order hyperbolic operator
with variable coefficients, instead of using the reduction method from the
retarded flat-space Green function in four dimensions. After reduction to
canonical form of this hyperbolic operator, the integral representation of the
solution in terms of the Riemann function is obtained. The Riemann function
solves a characteristic initial-value problem for which analytic formulae
leading to the numerical solution are derived.


title:
Dynamical and photometric imprints of feedback processes on the early
  evolution of E/S0 galaxies

abstract:
  We show that the observed Velocity Dispersion Function of E/S0 galaxies
matches strikingly well the distribution function of virial velocities of
massive halos virializing at z > 1.5, as predicted by the standard hierarchical
clustering scenario in a \LambdaCDM cosmology, for a constant ratio sigma/V_vir
= 0.55 \pm 0.05, close to the value expected at virialization if it typically
occurred at z > 3. This strongly suggests that dissipative processes and later
merging events had little impact on the matter density profile. Adopting the
above sigma/V_vir ratio, the observed relationships between photometric and
dynamical properties which define the fundamental plane of elliptical galaxies,
such as the luminosity-sigma (Faber-Jackson) and the luminosity-effective
radius relations, as well as the M_BH-sigma relation, are nicely reproduced.
Their shapes turn out to be determined by the mutual feedback of star-formation
(and supernova explosions)and nuclear activity, along the lines discussed by
Granato et al. (2004). To our knowledge, this is the first semi-analytic model
for which simultaneous fits of the fundamental plane relations and of the
epoch-dependent luminosity function of spheroidal galaxies have been presented.


title: Long-Term INTEGRAL and RXTE Observations of the X-Ray Pulsar LMC X-4

abstract:
  We analyze the observations of the X-ray pulsar LMC X-4 performed by the
INTEGRAL observatory and the All-Sky Monitor (ASM) of the RXTE observatory over
a wide energy range. The observed hard X-ray flux from the source is shown to
change by more than a factor of 50 (from ~70 mCrab in the high state to ~1.3
mCrab in the low state) on the time scale of the accretion-disk precession
period, whose mean value for 1996-2004 was determined with a high accuracy,
Pprec=30.275+/-0.004 days. In the low state, a flare about 10 h in duration was
detected from the source; the flux from the source increased by more than a
factor of 4 during this flare. The shape of the pulsar's broadband spectrum is
essentially invariable with its intensity; no statistically significant
features associated with the possible resonance cyclotron absorption line were
found in the spectrum of the source.


title: The puzzling case of GRB 990123: multiwavelength afterglow study

abstract:
  We report on the BeppoSAX data analysis of the afterglow of Gamma-Ray Burst
(GRB) 990123, one of the brightest GRBs detected by BeppoSAX. Mainly due to its
exceptional brightness, this is the only source for which the Wide Field
Cameras have allowed an early detection of the X-ray afterglow between about 20
and 60 min after the GRB trigger. Besides, again for the first time,
high-energy emission from the afterglow was detected up to 60 keV. For the
X-ray afterglow we found a power-law decay with index alpha = 1.46 +/- 0.04;
the spectrum has a power-law shape with photon index Gamma about 1.9. The
backward extrapolation of the afterglow decay smoothly reconnects with the late
GRB emission, thus suggesting that both emissions are produced by the same
phenomenon. An extensive set of multiwavelength observations for the GRB 990123
afterglow made during the BeppoSAX pointing was collected from the literature.
The hard X-ray to radio range coverage allowed to construct a spectral flux
distribution and to perform an analysis of the GRB afterglow in the context of
the "fireball" model. We also report the results of temporal and spectral
analysis of an X-ray source serendipitously observed about 22 arcmin north of
the GRB afterglow, along with the optical spectroscopy of its possible
counterpart to establish the nature of this source.


title: L-band (3.5 micron) IR-excess in massive star formation, I. 30 Doradus

abstract:
  L-band data of 30 Doradus at 3.5 micron taken with SPIREX (South Pole
Infrared Explorer) is presented. The photometry was combined with 2MASS JHK
data at 1.25-2.2 micron. Colour-colour and colour-magnitude diagrams are
constructed and used to determine the sources with infrared excess. These are
interpreted as circumstellar disks, and enable the fraction of sources with
disks (the cluster disk fraction or CDF) to be determined. We find that ~42% of
the sources detected at L-band in 30 Doradus have an IR-excess.


title: Molecular Gas and Nuclear Activity in Radio Galaxies Detected by IRAS

abstract:
  This paper reports the latest results from a millimeter-wave (CO)
spectroscopic survey of IRAS-detected radio galaxies with L_1.4GHz ~ 10^23-28
W/Hz in the redshift range z ~ 0.02-0.15. The IRAS flux-limited sample contains
33 radio galaxies with different radio morphologies and a broad range of
infrared luminosities L_IR = 10^9-12 L_sun), allowing for an investigation of
(a) whether low-z radio-selected AGN reside in molecular gas-rich host galaxes,
and (b) whether the CO properties are correlated with the properties of the
host galaxy or the AGN. All of the radio galaxies in Mazzarella et al. (1993)
and Mirabel et al. (1989) have been reobserved. Three new CO detections have
been made, raising the total number of CO detections to nine and setting the
survey detection rate at ~ 25%. Many of the CO lines have double-peaked
profiles, and the CO line widths are broad (average Delta v_FWHM ~ 500+/-130
km/s), exceeding the average CO widths of both ultraluminous infrared galaxies
(300+/-90 km/s) and Palomar-Green QSOs (260+/-160 km/s), and thus being
indicative of massive host galaxies. The CO luminosities translate into
molecular gas masses of ~ 0.4-7x10^9 M_sun, however, the 3-sigma CO upper
limits for nondetections do not rule out a molecular gas mass as high as that
of the Milky Way (~ 3x10^9 M_sun). Optical images of eight out of nine
molecular gas-rich radio galaxies show evidence of close companions and/or
tidal features. Finally, there is no obvious correlation between radio power
and molecular gas mass. However, it is notable that only one F-R II galaxy out
of 12 is detected in this CO survey; the remaining detections are of galaxies
hosting F-R I and compact radio jets.


title:
POLAR, a compact detector for Gamma Ray Bursts photon polarization
  measurements

abstract:
  The design and the simulated performances of a compact detector dedicated to
the measurement of GRB photon polarization is presented. Such a detector would
permit to answer the question ``are most of the GRB strongly polarized?'' in a
mission of one year in space.


title: Formation and evolution of primordial black holes after hybrid inflation

abstract:
  We examine the formation and evolution of primordial black holes (PBH's)
after hybrid inflation. Our goal is to assess the effects of various
theoretical uncertainties on the extrapolation from a given inflation model to
a spectrum of primordial black hole masses. The context of our work is an
examination of the possibility [Chen and Adler (2003), MacGibbon (1987)] that
the dark matter is comprised of Planck-mass black hole remnants (BHR's). As an
example we focus on a particular scenario [Chen (2003)] in which the black
holes form from quantum perturbations that were generated during hybrid
inflation. We find the correspondence between hybrid inflation parameters and
the range of initial PBH masses that would allow BHR's to comprise the dark
matter, taking account of the possible early presence of radiation and its
accretion onto the PBH's.


title:
The puzzling case of GRB 990123: prompt emission and broad-band
  afterglow modeling

abstract:
  We report on BeppoSAX simultaneous X- and gamma-ray observations of the
bright GRB 990123. We present the broad-band spectrum of the prompt emission,
including optical, X- and gamma-rays, confirming the suggestion that the
emission mechanisms at low and high frequencies must have different physical
origins. In the framework of the standard fireball model, we discuss the X-ray
afterglow observed by the NFIs and its hard X-ray emission up to 60 keV several
hours after the burst, detected for about 20 ks by the PDS. Considering the
2-10 keV and optical light curves, the 0.1-60 keV spectrum during the 20 ks in
which the PDS signal was present and the 8.46 GHz upper limits, we find that
the multi-wavelength observations cannot be readily accommodated by basic
afterglow models. While the temporal and spectral behavior of the optical
afterglow is possibly explained by a synchrotron cooling frequency between the
optical and the X-ray energy band during the NFIs observations, in X-rays this
assumption only accounts for the slope of the 2-10 keV light curve, but not for
the flatness of the 0.1-60 keV spectrum. Including the contribution of Inverse
Compton (IC) scattering, we solve the problem of the flat X-ray spectrum and
justify the hard X-ray emission; we suggest that the lack of a significant
detection of 15-60 keV emission in the following 75 ks and last 70 ks spectra,
should be related to poorer statistics rather than to an important suppression
of IC contribution. However, considering also the radio band data, we find the
8.46 GHz upper limits violated. On the other hand, leaving unchanged the
emission mechanism requires modifying the hydrodynamics by invoking an ambient
medium whose density rises rapidly with radius and by having the shock losing
energy. Thus we are left with an open puzzle which requires further inspection.


title:
A boxy bulge in the Milky Way. Inversion of the stellar statistics
  equation with 2MASS data

abstract:
  Inverting the stellar statistics equation from 2MASS star counts, we obtain
the 3D density distribution of the Galactic bulge as well as its luminosity
function in the K-band. This results in a boxy bulge with axial ratios
1:0.5:0.4 and a major axis angle with respect to the Sun-galactic center of
$20^\circ-35^\circ $.


title:
Supernova Remnants in the Magellanic Clouds. V. The Complex Interior
  Structure of the N206 SNR

abstract:
  The N206 supernova remnant (SNR) in the Large Magellanic Cloud (LMC) has long
been considered a prototypical "mixed morphology" SNR. Recent observations,
however, have added a new twist to this familiar plot: an elongated,
radially-oriented radio feature seen in projection against the SNR face.
Utilizing the high resolution and sensitivity available with the Hubble Space
Telescope, Chandra, and XMM-Newton, we have obtained optical emission-line
images and spatially resolved X-ray spectral maps for this intriguing SNR. Our
findings present the SNR itself as a remnant in the mid to late stages of its
evolution. X-ray emission associated with the radio "linear feature" strongly
suggests it to be a pulsar-wind nebula (PWN). A small X-ray knot is discovered
at the outer tip of this feature. The feature's elongated morphology and the
surrounding wedge-shaped X-ray enhancement strongly suggest a bow-shock PWN
structure.


title: Neutrino Detection with Inclined Air Showers

abstract:
  The possibilities of detecting high energy neutrinos through inclined showers
produced in the atmosphere are addressed with an emphasis on the detection of
air showers by arrays of particle detectors. Rates of inclined showers produced
by both down-going neutrino interactions and by up-coming $\tau$ decays from
earth-skimming neutrinos as a function of shower energy are calculated with
analytical methods using two sample neutrino fluxes with different spectral
indices. The relative contributions from different flavors and charged, neutral
current and resonant interactions are compared for down-going neutrinos
interacting in the atmosphere. No detailed description of detectors is
attempted but rough energy thresholds are implemented to establish the ranges
of energies which are more suitable for neutrino detection through inclined
showers. Down-going and up-coming rates are compared.


title: The heavy elements mixture and the stellar cluster age

abstract:
  Recent analyses of solar spectroscopic data (see Asplund, Grevesse & Sauval
2004 and references therein) suggest a significative variation of the heavy
elements abundance. The change of heavy mixture might affect the determination
of the clusters age for two different reasons: the change of theoretical
isochrones at fixed metallicity and the variation of the inferred cluster
metallicity from the observed [Fe/H]. The first point is analyzed discussing
the effects of updating the metal distribution on theoretical evolutionary
tracks and isochrones for metallicities suitable for the galactic globular and
open clusters and for the bulk population of the Large Magellanic Clouds. The
maximum variation of the estimated age ($\approx$0.5 Gyr), although not
negligible, is still within the present uncertainty. The second point is
addressed by comparing present theoretical predictions with the very precise
observational data of the Hyades cluster from the Hypparcos satellite.


title:
Self-consistent radiative effect on relativistic electromagnetic
  particle acceleration

abstract:
  We study the radiation damping effect on the relativistic acceleration of
electron-positron plasmas with two-and-half-dimensional particle-in-cell (PIC)
simulation. Particles are accelerated by Poynting flux via the diamagnetic
relativistic pulse accelerator (DRPA), and decelerated by the self-consistently
solved radiation damping force. With $\Omega_{ce}/\omega_{pe}\geq 10$, the
Lorentz factor of the highest energy particles reaches gamma>100, and the
acceleration still continues. The emitted radiation is peaked within few
degrees from the direction of Poynting flux and strongly linearly polarized,
which may be detectable in gamma-ray burst(GRB) observations. We also show that
the DRPA is insensitive to the initial supporting currents.


title:
Radiative transfer problem in dusty galaxies: effects of non-isotropic
  multiple scattering

abstract:
  We investigate the effects of multiple anisotropic light scattering by
interstellar dust particles on photometric profiles of disk galaxy models
computed using an iterative ray-tracing radiative transfer modeling code. It is
shown that anisotropic scattering must be fully accounted for in at least the
first scattering event for all considered cases. At the same time scattering
terms of the order higher than 5th can be safely approximated using the
isotropic phase function. The effects of isotropic approximation are most
significant in the galaxy models seen face-on with dust population extending
beyond the stellar disk, therefore the applicability of isotropic approximation
to a higher-order (2 to 5) scattering terms depends on the assumed galaxy model
parameters, namely, the optical depth, scattering albedo and the distribution
of interstellar dust with respect to stars.


title:
Radiative transfer problem in dusty galaxies: iteration scaling
  approximation

abstract:
  We investigate the applicability and accuracy of the iteration scaling
approximation, proposed by Kylafis and Bahcall (1987). It is shown, that while
this method provides results sufficiently close to the exact solution of
radiative transfer problem, care must be taken in cases when the distribution
of interstellar dust significantly differs from that of light sources. The
problem is successfully circumvented by using the ratio of scattered light
distributions obtained in the first two iterations.


title: Stochastic chemical enrichment in metal-poor systems I. Theory

abstract:
  A stochastic model of the chemical enrichment of metal-poor systems by
core-collapse (Type II) supernovae is presented, allowing for large-scale
mixing of the enriched material by turbulent motions and cloud collisions in
the interstellar medium. Infall of pristine material is taken into account by
following the evolution of the gas density in the medium. Analytical
expressions were derived for the number of stars enriched by a given number of
supernovae, as well as for the amount of mass with which the ejected material
from a supernova is mixed before being locked up in a subsequently formed star.
It is shown that for reasonable values of the gas density (~0.1 cm-3) and of
the supernova rate (~0.25 kpc-3 Myr-1) of the Galactic halo, the resulting
metallicity distributions of the extreme Population II stars show a distinct
cut-off at [Fe/H] ~= -4. In fact, by assuming no low-mass Population III stars
were able to form out of the primordial interstellar medium, the derived
fraction of stars below [Fe/H] = -4 is in agreement with observations.
Moreover, the probability is high that even the most metal-poor stars observed
to date have been enriched by several contributing supernovae. This partly
explains the relatively small star-to-star scatter in many chemical-abundance
ratios for stars down to [Fe/H] = -4, as recently found in several
observational studies. Contribution from the thermonuclear (Type Ia) supernovae
is found to be negligible over almost the entire extremely metal-poor regime.
(***abridged***)


title: Using gravitational-wave standard sirens

abstract:
  Gravitational waves (GWs) from supermassive binary black hole (BBH) inspirals
are potentially powerful standard sirens (the GW analog to standard candles)
(Schutz 1986, 2002). Because these systems are well-modeled, the space-based GW
observatory LISA will be able to measure the luminosity distance (but not the
redshift) to some distant massive BBH systems with 1-10% accuracy. This
accuracy is largely limited by pointing error: GW sources generally are poorly
localized on the sky. Localizing the binary independently (e.g., through
association with an electromagnetic counterpart) greatly reduces this
positional error. An electromagnetic counterpart may also allow determination
of the event's redshift. In this case, BBH coalescence would constitute an
extremely precise (better than 1%) standard candle visible to high redshift. In
practice, gravitational lensing degrades this precision, though the candle
remains precise enough to provide useful information about the
distance-redshift relation. Even if very rare, these GW standard sirens would
complement, and increase confidence in, other standard candles.


title:
Stochastic chemical enrichment in metal-poor systems II. Abundance
  ratios and scatter

abstract:
  A stochastic model of the chemical enrichment of metal-poor systems by
core-collapse supernovae is used to study the scatter in stellar abundance
ratios. The resulting scatter in abundance ratios, e.g. as functions of the
overall metallicity, is demonstrated to be crucially dependent on the as yet
uncertain supernovae yields. The observed abundance ratios and their scatters
therefore have diagnostic power as regards the yields. The relatively small
star-to-star scatter observed in many chemical abundance ratios, e.g. by Cayrel
et al. (2004) for stars down to [Fe/H] = -4, is tentatively explained by the
averaging of a large number of contributing supernovae and by the cosmic
selection effects favoring contributions from supernovae in a certain mass
range for the most metal-poor stars. The scatter in observed abundances of
alpha-elements is understood in terms of observational errors only, while
additional spread in yields or sites of nucleosynthesis may affect the odd-even
elements Na and Al. For the iron-group elements we find systematically too high
predicted Cr/Fe and Cr/Mg ratios, as well as differences between the different
sets of yields, both in terms of predicted abundance ratios and scatter. The
semi-empirical yields recently suggested by Francois et al. (2004) are found to
lead to scatter in abundance ratios significantly greater than observed, when
applied in the inhomogeneous models. "Spurs", very narrow sequences in
abundance-ratio diagrams, may disclose a single-supernova origin of the
elements of the stars on the sequence. Verification of the existence of such
features, called single supernova sequences (SSSs), is challenging. This will
require samples of several hundred stars with abundance ratios observed to
accuracies of 0.05 dex or better.


title:
The metal enrichment of elliptical galaxies in hierarchical galaxy
  formation models

abstract:
  We investigate the metal enrichment of elliptical galaxies in the framework
of hierarchical models of galaxy formation. The semi-analytical model we use in
this Letter, which has been used to study the metal enrichment of the
intracluster medium (ICM) by Nagashima et al., includes the effects of flows of
gas and metals both into and out of galaxies and the processes of metal
enrichment due to both type Ia and type II supernovae. We adopt a solar
neighbourhood IMF for star formation in discs, but consider models in which
starbursts have either a solar neighbourhood IMF or a top-heavy IMF. We find
that the alpha-element abundance in ellipticals is consistent with observed
values only if the top-heavy IMF is used. This result is consistent with our
previous study on the metal enrichment of the ICM. We also discuss the
abundance ratio of alpha elements to iron as a function of velocity dispersion
and metallicity. We find that models with a top-heavy IMF match the alpha/Fe
ratios observed in typical L_* ellipticals, but none of the models reproduce
the observed increase of alpha/Fe with velocity dispersion.


title: Close Binaries as the Progenitors of the Brightest Planetary Nebulae

abstract:
  We investigate the possible progenitors of the planetary nebulae (PNs) which
populate the top 0.5 mag of the [O III] 5007 planetary nebula luminosity
function (PNLF). We show that the absolute luminosity of the PNLF cutoff
demands that the central stars of these most luminous planetaries be greater
than 0.6 Msun, and that such high-mass PN cores must exist in every galaxy. We
also use the bolometric-luminosity specific PN number density to show that in
early-type galaxies, [O III]-bright planetaries are relatively rare, with only
about 10% of stars evolving to these bright magnitudes. We demonstrate that the
combination of these two facts implies that either all early-type systems
contain a small, smoothly distributed component of young (< 1 Gyr old) stars,
or another mechanism exists for creating high-core mass planetaries. We argue
that binary-star evolution is this second mechanism, and demonstrate that blue
stragglers have the appropriate core properties and number density to explain
the observations. We discuss the implications of this alternative mode of
stellar evolution, and speculate on how coalesced binaries might affect the use
of PNs for measuring a galaxy's star-formation history and chemical evolution.


title: Millisecond Proto-Magnetars & Gamma Ray Bursts

abstract:
  In the seconds after core collapse and explosion, a thermal neutrino-driven
wind emerges from the cooling, deleptonizing newly-born neutron star. If the
neutron star has a large-scale magnetar-strength surface magnetic field and
millisecond rotation period, then the wind is driven primarily by
magneto-centrifugal slinging, and only secondarily by neutrino interactions.
The strong magnetic field forces the wind to corotate with the stellar surface
and the neutron star's rotational energy is efficiently extracted. As the
neutron star cools, and the wind becomes increasingly magnetically-dominated,
the outflow becomes relativistic. Here I review the millisecond magnetar model
for long-duration gamma ray bursts and explore some of the basic physics of
neutrino-magnetocentrifugal winds. I further speculate on some issues of
collimation and geometry in the millisecond magnetar model.


title:
Effects of new long-range interaction: Recombination of relic Heavy
  neutrinos and antineutrinos

abstract:
  If stable Heavy neutrinos of 4th generation possess their own Coulomb-like
interaction, recombination of pairs of Heavy neutrinos and antineutrinos can
play important role in their cosmological evolution and lead to observable
consequences. In particular, effect of this new interaction in the annihilation
of neutrino-antineutrino pairs can account for $\gamma$-flux observed by EGRET.


title: Far Infrared Observations of Radio Quasars and FR II Radio Galaxies

abstract:
  We report MIPS photometry of 20 radio-loud quasars and galaxies at 24 and 70
um (and of five at 160 um). We combine this sample with additional sources
detected in the far infrared by IRAS and ISO for a total of 47 objects,
including 23 steep spectrum Type I AGNs: radio-loud quasars and broad line
radio galaxies; and 24 Type II AGNs: narrow line and weak line FR II radio
galaxies. Of this sample, the far infrared emission of all but 3C 380 appears
to be dominated by emission by dust heated by the AGN and by star formation.
The AGN appears to contribute more than 50% of the far infrared luminosity in
most of sources. It is also expected that the material around the nucleus is
optically thin in the far infrared. Thus, the measurements at these wavelengths
can be used to test the orientation-dependent unification model. As predicted
by the model, the behavior of the sources is consistent with the presence of an
obscuring circumnuclear torus; in fact, we find it may still have significant
optical depth at 24 um.In addition, as expected for the radio-loud quasars,
there is a significant correlation between the low frequency radio (178 MHz)
and the 70 um emission, two presumably isotropic indicators of nuclear
activity. This result is consistent with the simple unified scheme. However,
there is a population of radio galaxies that are underluminous at 70 um
compared with the radio-loud quasars and hence are a challenge to the simple
unified model.


title:
An Analytic Model for the Axis-Ratio Distribution of Dark Matter Halos
  from the Primordial Gaussian Density Field

abstract:
  We present an analytic expression for the axis ratio distribution of triaxial
dark matter halos driven from physical principles. Adopting the picture of
triaxial collapse based on the Zel'dovich approximation, we derive analytically
both the minor-to-major and the conditional intermediate-to-major axis ratio
distributions, and examine how they depend on the halo mass, redshift, and
cosmology. Our analytic model is tested against the simulation data given by
Jing & Suto in 2002, and found to reproduce the conditional
intermediate-to-major axis ratio distribution successfully and the
minor-to-major axis ratio distribution approximately. However, the trends of
our analytic axis-ratio distributions with mass and redshift are opposite to
what is found in N-body simulations. This failure of our analytic model puts a
limitation on analytic approaches based on the Lagrangian theory to the halo
ellipticity. Given the overall agreement with the simulation results, our model
provides a new theoretical step toward using the axis-ratio distribution of
dark halos as a cosmological probe. We also discuss several possibilities to
improve the model.


title: Ep-Eiso Correlation in a Multiple Subjet Model of Gamma-Ray Bursts

abstract:
  We perform Monte Carlo simulations to study Ep-Eiso correlation in the
context of a multiple subjet model (or inhomogeneous jet model) for gamma-ray
bursts (GRBs), X-ray--rich GRBs (XRRs), and X-ray flashes (XRFs). For a single
subjet, we find that Ep prop. Eiso^0.4 for large viewing angles. For the
multiple subjet model in which all the subjets have the same intrinsic
properties, off-axis events show Ep prop. Eiso^a with 0.4<a<0.5. If the
intrinsic properties of the subjets are distributed so that on-axis emission of
each subjet follows a correlation Ep prop. Liso^1/2, we obtain the Amati
correlation (Ep prop. Eiso^1/2) over three orders of magnitude in Ep. Although
the scatter around the Amati correlation is large in the simulation, the
results are consistent with the observed properties of GRBs with known
redshifts and the BASTE GRBs with pseudo redshifts derived from the
lag-luminosity correlation. We also calculate the event rates, the redshift
distributions, and the T90 duration distributions of GRBs, XRRs, and XRFs which
can be detected by HETE-2, assuming that the source redshift distribution is in
proportion to the cosmic star formation rate. It is found that the event rates
of three classes are comparable, that the average redshift of the XRRs is a
little larger than those of the GRBs and the XRFs, and that short XRRs arise
when a single subjet is viewed off-axis or viewed on-axis with slightly high
redshift.


title: An absorbed view of a new class of INTEGRAL sources

abstract:
  The European gamma-ray observatory INTEGRAL has found a group of hard X-ray
sources which are highly absorbed, i.e., with column densities higher than
about 10^{23}/cm^2. Here I give an overview of this class of INTEGRAL sources.
The X-ray, as well as the optical/IR, properties of these sources and their
location in the sky suggest that they belong to the class of high-mass X-ray
binaries, some of them possibly long-period X-ray pulsars. The donors in these
binaries are most probably giant or supergiant stars. I suggest that the soft
X-ray spectrum below ~5 keV of IGR J16318-4848, as well as in several other
X-ray binaries (e.g., XTE J0421+56), can be described by emission from a
compact object which is strongly absorbed by a partionally ionised dense
envelope.


title:
Color Gradients in Early-type Galaxies: Dependence on Environment and
  Redshift

abstract:
  Color gradients in early-type galaxies contain valuable clues about their
formation and evolutionary histories and mechanisms. We examine color gradients
in 1,700 early-type galaxies in 159 galaxy clusters spanning a redshift range
of 0.05 to 0.2. We find that color gradients strongly depend on the environment
where galaxies reside, with steeper color gradients in poor rather than rich
clusters. No dependence of color gradients on galaxy luminosity is found in
either rich or poor clusters. The difference in color gradients can be
explained by a change in the internal metallicity and/or an age gradient in
these galaxies. Our results support a reasonable picture whereby young
early-type galaxies form in a dissipative collapse process, and then undergo
increased (either major or minor) merging activity in richer rather than in
poor clusters.


title:
Color--Magnitude Diagrams and Luminosity Functions down to the Hydrogen
  Burning Limit. III. A Preliminary HST Study of NGC6791

abstract:
  Using HST ACS/WFC images, we derive the color--magnitude diagram of the old,
metal-rich open cluster NGC 6791 to nearly 29th magnitude in V, which is the
neighborhood of the hydrogen-burning limit.Comparison with isochrones leads to
a discussion of the distance modulus, the reddening, and the age of the
cluster. By making a statistical correction for field stars we derive a
preliminary luminosity function, and a very tentative mass function. The white
dwarf sequence is clearly shown, and has been discussed in a separate paper.


title: Gravoturbulent formation of planetesimals

abstract:
  We explore the effect of magnetorotational turbulence on the dynamics and
concentrations of boulders in local box simulations of a sub-Keplerian
protoplanetary disc. The solids are treated as particles each with an
independent space coordinate and velocity. We find that the turbulence has two
effects on the solids. 1) Meter and decameter bodies are strongly concentrated,
locally up to a factor 100 times the average dust density, whereas decimeter
bodies only experience a moderate density increase. The concentrations are
located in large scale radial gas density enhancements that arise from a
combination of turbulence and shear. 2) For meter-sized boulders, the
concentrations cause the average radial drift speed to be reduced by 40%. We
find that the densest clumps of solids are gravitationally unstable under
physically reasonable values for the gas column density and for the dust-to-gas
ratio due to sedimentation. We speculate that planetesimals can form in a dust
layer that is not in itself dense enough to undergo gravitational
fragmentation, and that fragmentation happens in turbulent density fluctuations
in this sublayer.


title:
MACHe3, a prototype for non-baryonic dark matter search: KeV event
  detection and multicell correlation

abstract:
  Superfluid He3 at ultra-low temperatures (100 microKelvins) is a sensitive
medium for the bolometric detection of particles. MACHe3 (MAtrix of Cells of
Helium 3) is a project for non-baryonic dark matter search using He3 as a
sensitive medium. Simulations made on a high granularity detector show a very
good rejection to background signals. A multicell prototype including 3
bolometers has been developed to allow correlations between the cells for
background event discrimination. One of the cells contains a low activity Co57
source providing conversion electrons of 7.3 and 13.6 keV to confirm the
detection of low energy events. First results on the multicell prototype are
presented. A detection threshold of 1 keV has been achieved. The detection of
low energy conversion electrons coming from the Co57 source is highlighted as
well as the cosmic muon spectrum measurement. The possibility to reject
background events by using the correlation among the cells is demonstrated from
the simultaneous detection of muons in different cells.


title: A new method to search for a cosmic ray dipole anisotropy

abstract:
  We propose a new method to determine the dipole (and quadrupole) component of
a distribution of cosmic ray arrival directions, which can be applied when
there is partial sky coverage and/or inhomogeneous exposure. In its simplest
version it requires that the exposure only depends on the declination, but it
can be easily extended to the case of a small amplitude modulation in right
ascension. The method essentially combines a $\chi^2$ minimization of the
distribution in declination to obtain the multipolar components along the
North-South axis and a harmonic Rayleigh analysis for the components involving
the right ascension direction.


title: Halo Geometry and Dark Matter Annihilation Signal

abstract:
  We study the impact of the halo shape and geometry on the expected weakly
interacting massive particle (WIMP) dark matter annihilation signal from the
galactic center. As the halo profile in the innermost region is still poorly
constrained, we consider different density behaviors like flat cores, cusps and
spikes, as well as geometrical distortions. We show that asphericity has a
strong impact on the annihilation signal when the halo profile near the
galactic center is flat, but becomes gradually less significant for cuspy
profiles, and negligible in the presence of a central spike. However, the
astrophysical factor is strongly dependent on the WIMP mass and annihilation
cross-section in the latter case.


title:
A model for the population of helium stars in the Galaxy I. Low-mass
  stars

abstract:
  By means of population synthesis we model the Galactic ensemble of helium
stars. It is assumed that all helium stars are formed in binaries. Under this
assumption, single helium stars are produced by the mergers of helium remnants
of components of close binaries (mainly, by merging helium white dwarfs) and by
disruption of binaries with helium components in supernovae explosions. The
estimate of the total birthrate of helium stars in the Galaxy is 0.043
yr$^{-1}$, their total number is estimated as $4 \times 10^6$. The rate of
binarity in the total sample is 76%. We construct a subsample of low-mass
($M_{\rm He} \lesssim 2 \ms$) helium stars limited by observational selection
effects: stellar magnitude ($V_{\rm He} \leq 16$), ratio of stellar magnitudes
of components in binaries ($V_{\rm He}\leq V_{\rm comp}$), lower limit of the
semiamplitude of radial velocity that is necessary for discovery of binarity
($K_{min}=30$ km/s). The parameters of this ``observable'' sample are in
satisfactory agreement with the parameters of the observed ensemble of sdB
stars. In particular, in the selection-limited sample binarity rate is 58%. We
analyze the relations between orbital periods and masses of helium stars and
their companions in systems with different combinations of components. We
expect that overwhelming majority ($\sim 90$%) of unobserved components in
binary sdB stars are white dwarfs, predominantly, carbon-oxygen ones.


title: INTEGRAL High Energy Observations of 2S 0114+65

abstract:
  We report the first INTEGRAL timing and spectral analysis of the high mass
X-ray binary source 2S 0114+65 at high energies (5-100 keV). The pulse period
was found at 2.668 hr with a high pulsed fraction, ~80% in both the 20-40 keV
and 40-80 keV energy bands. The spin-up trend over ~8 years was measured to be
-8.9 * 10^{-7}. The hard X-ray spectrum obtained with JEM-X/ISGRI is well
described by a high energy exponential cut-off power law model where the
estimated luminosity is 1.8 * 10^{36} erg/s in the 5-100 keV energy band, for a
source distance of 7.2 kpc. We tentatively identify a cyclotron resonance
scattering feature at ~22 keV with one harmonic, implying a magnetic field of
2.5 * 10^{12} G.


title: Options for a nondedicated mission to test the Pioneer anomaly

abstract:
  The Doppler-tracking data of the Pioneer 10 and 11 spacecraft show an
unmodelled constant acceleration in the direction of the inner Solar System.
Serious efforts have been undertaken to find a conventional explanation for
this effect, all without success at the time of writing. Hence the effect,
commonly dubbed the Pioneer anomaly, is attracting considerable attention.
Unfortunately, no other space mission has reached the long-term navigation
accuracy to yield an independent test of the effect. To fill this gap we
discuss strategies for an experimental verification of the anomaly via an
upcoming space mission. Emphasis is put on two plausible scenarios:
nondedicated concepts employing either a planetary exploration mission to the
outer Solar System or a piggybacked micro-spacecraft to be launched from a
mother spacecraft travelling to Saturn or Jupiter. The study analyses the
impact of a Pioneer anomaly test on the system and trajectory design for these
two paradigms. It is found that both paradigms are capable of verifying the
Pioneer anomaly and determine its magnitude at 10% level. Moreover the concepts
can discriminate between the most plausible classes of models of the anomaly, a
central force, a blueshift of the radio signal and a drag-like force. The
necessary adaptions of the system and mission design do not impair the
planetary exploration goals of the missions.


title:
Searching for galaxy clusters using the aperture mass statistics in 50
  VLT fields

abstract:
  Application of the aperture mass (Map-) statistics provides a weak lensing
method for the detection of cluster-sized dark matter halos. We present a new
aperture filter function and maximise the effectiveness of the Map-statistics
to detect cluster-sized halos using analytical models. We then use weak lensing
mock catalogues generated from ray-tracing through N-body simulations, to
analyse the effect of image treatment on the expected number density of halos.
Using the Map-statistics, the aperture radius is typically several arcminutes,
hence the aperture often lies partly outside a data field, consequently the
signal-to-noise ratio of a halo detection decreases. We study these border
effects analytically and by using mock catalogues. We find that the expected
number density of halos decreases by a factor of two if the size of a field is
comparable to the diameter of the aperture used. We finally report on the
results of a weak lensing cluster search applying the Map-statistics to 50
randomly selected fields which were observed with FORS1 at the VLT. Altogether
the 50 VLT fields cover an area of 0.64 square degrees. The I-band images were
taken under excellent seeing conditions (average seeing 0.6 arcsec.) which
results in a high number density of galaxies used for the weak lensing analysis
(26/sq.arcmin). In five of the VLT fields, we detect a significant Map-signal
which coincides with an overdensity of the light distribution. These detections
are thus excellent candidates for shear-selected clusters.


title: Mirror World and Axion: Relaxing Cosmological Bounds

abstract:
  The cosmological (upper) limit on the Peccei-Quinn constant, related to the
primordial oscillations of the axion field, can be relaxed for a mirror axion
model. The simple reason is that the mirror world is colder and so the behavior
of the axion temperature-dependent mass is dominated by the contribution from
the mirror sector. So the coherent oscillations start earlier and
correspondingly the axion mass density \Omega_a h^2 is reduced.


title:
Spurious 'active longitudes' in parametric models of heavily spotted
  eclipsing binaries

abstract:
  In this paper, size distributions of starspots extrapolated from the case of
the Sun, are modelled on the eclipsing binary SV Cam to synthesise images of
stellar photospheres with high spot filling factors. These spot distributions
pepper the primary's surface with spots, many of which are below the resolution
capabilities of eclipse mapping and Doppler imaging techniques. The lightcurves
resulting from these modelled distributions are used to determine the
limitations of image reconstruction from photometric data. Surface brightness
distributions reconstructed from these lightcurves show distinctive spots on
the primary star at its quadrature points. It is concluded that two-spot
modelling or chi-squared minimisation techniques are more susceptible to
spurious structures being generated by systematic errors, arising from
incorrect assumptions about photospheric surface brightness, than simple
Fourier analysis of the light-curves.


title:
GRBs and SGRs by high energy leptons showering in blazing gamma jets:
  are SGRs sources of EeV CRs?

abstract:
  The apparently huge energy budget of the gamma ray burst GRB 990123 led to
the final collapse of the isotropic fireball model, forcing even the most
skeptical to consider a beamed Jet emission correlated to a supernova (SN)
explosion. Similarly the surprising giant flare from the soft gamma repeater
SGR 1806-20 that occurred on 2004 December 27, may induce the crisis of the
magnetar model. If the apparently huge energy associated to this flare has been
radiated isotropically, the magnetar should have consumed at once most of (if
not all) the energy stored in the magnetic field. On the contrary we think that
a thin collimated precessing jet, blazing on-axis, may be the source of such
apparently huge bursts with a moderate output power. We discuss the possible
role of the synchrotron emission and electromagnetic showering of PeV electron
pairs from muon bundles. A jet made of muons may play a key role in avoiding
the opacity of the SN-GRB radiation field. We propose a similar mechanism to
explain the emission of SGRs. In this case we also examine the possibility of a
primary hadronic jet that would produce ultra relativistic e+ e- (1 - 10 PeV)
from pion- muon or neutron decay. Such electron pairs would emit a few hundreds
keV radiation from their interaction with the galactic magnetic field, as it is
observed in the intense gamma ray flare from SGR 1806-20. A thin precessing jet
from a pulsar may naturally explain the negligible variation of the spin
frequency. A correlation between SGR 1806-20, SGR 1900 +14, Cygnus and the
AGASA excess of EeV cosmic rays (CRs) has been found; we suggest that a robust
EeV signal may be detected by AUGER or Milagro in the near future.