title:
Discovery of kHz QPOs and shifted frequency correlations in the
  accreting millisecond pulsar XTE J1807--294

abstract:
  We report the discovery of twin kHz QPOs in the X ray flux of XTE J1807--294,
the fourth accreting millisecond pulsar (AMP). This is the second AMP
exhibiting twin kHz QPOs. In contrast to the first case, SAX J1808.4--3658, the
frequency separation $\Delta\nu$ between the kHz QPOs is consistent with the
pulse frequency (190.6 Hz), not with half that value, confirming for the first
time from pulsation measurements the inference, based on burst oscillations,
that 'slow rotators' (spin frequency less than 400 Hz) have $\Delta\nu$
approximately equal to the spin frequency. While the QPOs move in frequency
together over a range of more than 200 Hz, $\Delta\nu$ remains constant with an
average value of 205$\pm$6 Hz. Variability components were found in the 5--130
Hz range similar to those seen in other LMXBs. The correlations between the QPO
and noise frequencies are also similar to those in other sources, but shifted
by a factor of 1.59 in kHz QPO frequencies, similar to the factor 1.45 shift
found for SAX J1808.4--3658. Our results argue in favour of a spin-related
formation mechanism for twin kHz QPOs and against a spin-related cause of the
shift in the frequency correlations.


title: Factorial moment studies of Cherenkov images

abstract:
  In this paper we study factorial moments of simulated Cherenkov images of
TACTIC type gamma ray telescope for cosmic gamma rays and proton segregation. A
comprative and supplemnetary studies between factorial moments and Hillas
parameters using ANN is discussed.


title: Search for multifractal features in Cherenkov arrival time

abstract:
  Extensive air shower products are fractal in nature. Both simulated and
experimental Cherenkov images display multifractal properties. In this paper we
explore the possibility of searching multifractal features in Cherenkov arrival
times.


title: New insights on the complex planetary nebula Hen 2-113

abstract:
  We report infrared observations of the planetary nebula Hen 2-113 obtained
with VLT/NACO, VLTI/MIDI, VLT/ISAAC and TIMMI at the ESO 3.6m. Hen 2-113
exhibits a clear ring-like structure superimposed to a more diffuse environment
visible in the L' (3.8$\mu$m), M' (4.78$\mu$m) and 8.7$\mu$m bands. No clear
core at 8.7$\mu$m and no fringes through the N band could be detected for this
object with MIDI. A qualitative interpretation of the object structure is
proposed using a diabolo-like geometrical model. The PAH content of the nebula
was also studied with ISAAC and TIMMI observations. This indicates that the
PAHs are mostly concentrated towards the lobes of the diabolo and the bipolar
lobes of the nebula. In L' band, a void $0.3\arcsec$ in diameter was discovered
with NACO around the central source. The L' and M' fluxes from the central
source were derived from NACO data indicating an important infrared excess with
respect to the expected stellar emission based on stellar models and short
wavelength data. The observed flux from this source in the L' and M' is about
300 and 800 times respectively than those expected from a model including only
the central star. Moreover, the central object appears resolved in L' band with
measured FWHM about 155 mas. This infrared excess can be explained by emission
from a cocoon of hot dust (T$\sim$1000K) with a total mass
$\sim10^{-9}$M$\_{\odot}$.


title:
Post-inflationary behavior of adiabatic perturbations and
  tensor-to-scalar ratio

abstract:
  We explain why it is so difficult and perhaps even impossible to increase the
cosmological tensor-to-scalar perturbation ratio during the post-inflationary
evolution of the universe. Nevertheless, contrary to some recent claims, tensor
perturbations can be relatively large in the simplest inflationary models which
do not violate any rules of modern quantum field theory.


title:
Back to the basis - observations support spherically closed dynamic
  space

abstract:
  A holistic view of the cosmological appearance and development of space is
obtained by studying space as a spherically closed surface of a 4-sphere in a
zero energy balance between motion and gravitation. Such an approach
re-establishes Einstein's original view of the cosmological structure of the
universe but instead of forcing space to be static with a cosmology constant,
it lets it contract or expand while constantly maintaining a balance between
the energies of motion and gravitation within the structure. In spherically
closed dynamic space the fourth dimension is purely metric in its nature; time
can be treated as a universal scalar, and the line element cdt in the fourth
dimension gets the meaning of the distance that space moves at velocity c in
time differential dt. The rest energy of matter appears as the energy of motion
due to the motion of space in the direction of the 4-radius of the structure.
All velocities in space are related to the 4-velocity of space, and the local
state of rest appears as a property of the local energy system rather than as
the state of an observer. Relativistic phenomena and cosmological predictions
can be derived in closed mathematical form and the picture of cosmology is
cleared; the Euclidean appearance of distant space is predicted and no dark
energy or free parameters are needed to explain the magnitude/redshift
relations of distant objects.


abstract:
  We report on the XMM-Newton observation of the bright Seyfert 1 galaxy,
MCG+8-11-11. Data from the EPIC/p-n camera, the Reflection Gratings
Spectrometers (RGS) and the Optical Monitor (OM) have been analyzed. The p-n
spectrum is well fitted by a power law, a spectrally unresolved Fe Kalpha line,
a Compton reflection component (whose large value, when compared to the iron
line equivalent width, suggests iron underabundance), and absorption by warm
material. Absorption lines are apparent in the RGS spectra, but their
identification is uncertain and would require large matter velocities. The UV
fluxes measured by the OM are well above the extrapolation of the X-ray
spectrum, indicating the presence of a UV bump.


title: INTEGRAL observations of recurrent fast X-ray transient sources

abstract:
  Fast X-ray Transients (FXTs) are believed to be non-recurrent bright X-ray
sources lasting less than a day and occuring at serendipitous positions, they
can best detected and discovered by instruments having a sufficiently wide
field of view and high sensitivity. The IBIS/ISGRI instrument onboard INTEGRAL
is particularly suited to detect new or already known fast X-ray transient
sources. We report on IBIS/ISGRI detection of newly discovered outbursts of
three fast transient sources located at low Galactic latitude: SAX
J1818.6-1703; IGR J16479-4514; IGR J17391-302/XTE J1739-302. The reported
results confirm and strengthen the very fast transient nature of these sources,
given that all their newly detected outbursts have a duration less than about 3
hours. Additionally, they provide the first evidence for a possible recurrent
fast transient behaviour as all three sources were detected in outburst by
ISGRI more than once during the last 2 years.


title: Linearly polarized X-ray flares following short gamma-ray bursts

abstract:
  Soft X-ray flares were detected to follow the short-duration gamma-ray burst
GRB 050724. The temporal properties of the flares suggest that they are likely
due to the late time activity of the central engine. We argue that if short
GRBs are generated through compact star mergers, as is supported by the recent
observations, the jet powering the late X-ray flares must be launched via
magnetic processes rather than via neutrino-antineutrino annihilations. As a
result, the X-ray flares following short GRBs are expected to be linearly
polarized. The argument may also apply to the X-ray flares following long GRBs.
Future observations with the upcoming X-ray polarimeters will test this
prediction.


title:
New Optical and Near-Infrared Surface Brightness Fluctuations Models.
  II. Young and Intermediate Age Stellar Populations

abstract:
  We present theoretical surface-brightness fluctuations (SBF) amplitudes for
single-burst stellar populations of young and intermediate age ($25 Myr \leq t
\leq 5 Gyr$), and $Z=0.0003$, 0.001, 0.004, 0.008, 0.01, 0.02, and 0.04. We pay
attention to the contribution of thermal-pulses asymptotic giant branch
(TP-AGB) stars. The sensitivity of the predicted SBF to changes in the
mass-loss scenario along the TP-AGB phase is examined. Below 0.6-$1 Gyr$ both
optical and NIR SBF models exhibit a strong dependence on age and mass loss. We
also evaluate SBF amplitudes by using Monte Carlo techniques to reproduce the
random variation in the number of stars experiencing bright and fast
evolutionary phases (Red Giant Branch, AGB, TP-AGB). We provide constraints
upon the faintest integrated flux of real stellar populations required to
derive reliable and meaningful SBF measurements. We analyze a technique for
deriving SBF amplitudes of star clusters from the photometry of individual
stars, and estimate the indetermination due to statistical effects, which may
impinge on the procedure. The first optical SBF measurements for 11 Large
Magellanic Cloud (LMC) star rich clusters - with age ranging from few $Myr$ to
several $Gyr$ - are derived by using Hubble Space Telescope observations. The
measurements are successfully compared to our SBF predictions, thus providing a
good agreement with models of metallicity $Z = 0.0001$-0.01. A mass loss as a
power-law function of the TP-AGB star luminosity is required in order to
properly reproduce the optical SBF data of the LMC clusters. We suggest how to
overcome the general problem of SBF models in reproducing the details of the
near-infrared SBF measurements of the Magellanic Cloud star clusters.


title: Hydrostatic models for the rotation of extra-planar gas in disk galaxies

abstract:
  We show that fluid stationary models are able to reproduce the observed,
negative vertical gradient of the rotation velocity of the extra-planar gas in
spiral galaxies. We have constructed models based on the simple condition that
the pressure of the medium does not depend on density alone (baroclinic instead
of barotropic solutions: isodensity and isothermal surfaces do not coincide).
As an illustration, we have successfully applied our method to reproduce the
observed velocity gradient of the lagging gaseous halo of NGC 891. The fluid
stationary models discussed here can describe a hot homogeneous medium as well
as a "gas" made of discrete, cold HI clouds with an isotropic velocity
dispersion distribution. Although the method presented here generates a density
and velocity field consistent with observational constraints, the stability of
these configurations remains an open question.


title: Processing challenges in the XMM-Newton slew survey

abstract:
  The great collecting area of the mirrors coupled with the high quantum
efficiency of the EPIC detectors have made XMM-Newton the most sensitive X-ray
observatory flown to date. This is particularly evident during slew exposures
which, while giving only 15 seconds of on-source time, actually constitute a
2-10 keV survey ten times deeper than current "all-sky" catalogues. Here we
report on progress towards making a catalogue of slew detections constructed
from the full, 0.2-12 keV energy band and discuss the challenges associated
with processing the slew data. The fast (90 degrees per hour) slew speed
results in images which are smeared, by different amounts depending on the
readout mode, effectively changing the form of the point spread function. The
extremely low background in slew images changes the optimum source searching
criteria such that searching a single image using the full energy band is seen
to be more sensitive than splitting the data into discrete energy bands. False
detections due to optical loading by bright stars, the wings of the PSF in very
bright sources and single-frame detector flashes are considered and techniques
for identifying and removing these spurious sources from the final catalogue
are outlined. Finally, the attitude reconstruction of the satellite during the
slewing manoeuver is complex. We discuss the implications of this on the
positional accuracy of the catalogue.


title:
Optical Monitoring of PKS 2155-304 during August-September 2004 with the
  KVA telescope

abstract:
  The southern gamma-ray blazar PKS 2155-304 is one of the brightest and most
intensively studied prototypes of BL Lac object. PKS 2155-304 has recently
aroused the interest of Cherenkov telescope projects like HESS and MAGIC, the
former having already observed the source in 2002 and 2003. This blazar was
monitored with the KVA optical telescope (R-band intranight photometry and
unfiltered polarization observations), in the frame of a new HESS
multiwavelength campaign performed in August-September 2004.


title: The baryon fraction in hydrodynamical simulations of galaxy clusters

abstract:
  We study the baryon mass fraction in a set of hydrodynamical simulations of
galaxy clusters performed using the Tree+SPH code GADGET-2. We investigate the
dependence of the baryon fraction upon the radiative cooling, star formation,
feedback through galactic winds, conduction and redshift. Both the cold stellar
component and the hot X-ray emitting gas have narrow distributions that, at
large cluster-centric distances r>R500, are nearly independent of the physics
included in the simulations. Only the non-radiative runs reproduce the gas
fraction inferred from observations of the inner regions (r ~ R2500) of massive
clusters. When cooling is turned on, the excess star formation is mitigated by
the action of galactic winds, but yet not by the amount required by
observational data. The baryon fraction within a fixed overdensity increases
slightly with redshift, independent of the physical processes involved in the
accumulation of baryons in the cluster potential well. In runs with cooling and
feedback, the increase in baryons is associated with a larger stellar mass
fraction that arises at high redshift as a consequence of more efficient gas
cooling. For the same reason, the gas fraction appears less concentrated at
higher redshift. We discuss the possible cosmological implications of our
results and find that two assumptions generally adopted, (1) mean value of Yb =
fb / (Omega_b/Omega_m) not evolving with redshift, and (2) a fixed ratio
between f_star and f_gas independent of radius and redshift, might not be
valid. In the estimate of the cosmic matter density parameter, this implies
some systematic effects of the order of Delta Omega_m/Omega_m < +0.15 for
non-radiative runs and Delta Omega_m/Omega_m ~ +0.05 and < -0.05 for radiative
simulations.


title: Pulsar Astrometry at the Microarcsecond Level

abstract:
  Determination of pulsar parallaxes and proper motions addresses fundamental
astrophysical questions. We have recently finished a VLBI astrometry project to
determine the proper motions and parallaxes of 27 pulsars, thereby doubling the
total number of pulsar parallaxes. Here we summarise our astrometric technique
and present the discovery of a pulsar moving in excess of 1000 km/s. As an
example of the application of high precision pulsar astrometry we also infer
the identification of 2 pulsars originating from a disrupted binary in the
Cygnus Superbubble.


title:
Detection of large scale intrinsic ellipticity-density correlation from
  the Sloan Digital Sky Survey and implications for weak lensing surveys

abstract:
  The power spectrum of weak lensing shear caused by large-scale structure is
an emerging tool for precision cosmology, in particular for measuring the
effects of dark energy on the growth of structure at low redshift. One
potential source of systematic error is intrinsic alignments of ellipticities
of neighbouring galaxies (II correlation) that could mimic the correlations due
to lensing. A related possibility pointed out by Hirata and Seljak (2004) is
correlation between the intrinsic ellipticities of galaxies and the density
field responsible for gravitational lensing shear (GI correlation). We present
constraints on both the II and GI correlations using 265 908 spectroscopic
galaxies from the SDSS, and using galaxies as tracers of the mass in the case
of the GI analysis. The availability of redshifts in the SDSS allows us to
select galaxies at small radial separations, which both reduces noise in the
intrinsic alignment measurement and suppresses galaxy- galaxy lensing (which
otherwise swamps the GI correlation). While we find no detection of the II
correlation, our results are nonetheless statistically consistent with recent
detections found using the SuperCOSMOS survey. In contrast, we have a clear
detection of GI correlation in galaxies brighter than L* that persists to the
largest scales probed (60 Mpc/h) and with a sign predicted by theoretical
models. This correlation could cause the existing lensing surveys at z~1 to
underestimate the linear amplitude of fluctuations by as much as 20% depending
on the source sample used, while for surveys at z~0.5 the underestimation may
reach 30%. (Abridged.)


title:
X-Ray and Optical Flux Anomalies in the Quadruply Lensed QSO 1RXS
  J1131-1231

abstract:
  Optical and X-ray observations of the quadruply imaged quasar 1RXS J1131-1231
show flux ratio anomalies among the images factors of ~2 in the optical and
\~3-9 in X-rays. Temporal variability of the quasar seems an unlikely
explanation for the discrepancies between the X-ray and optical flux ratio
anomalies. The negative parity of the most affected image and the decreasing
trend of the anomalies with wavelength suggest microlensing as a possible
explanation; this would imply that the source of optical radiation in RXS J1131
is ~10^4 R_g in size for a black hole mass of ~10^8 M_sun. We also present
evidence for different X-ray spectral hardness ratios among the four images.


title:
Going with the flow: can the base of jets subsume the role of compact
  accretion disk coronae?

abstract:
  The hard state of X-ray binaries (XRBs) is characterized by a power law
spectrum in the X-ray band, and a flat/inverted radio/IR spectrum associated
with occasionally imaged compact jets. It has generally been thought that the
hard X-rays result from Compton upscattering of thermal accretion disk photons
by a hot, coronal plasma whose properties are inferred via spectral fitting.
Interestingly, these properties-especially those from certain magnetized corona
models-are very similar to the derived plasma conditions at the jet footpoints.
Here we explore the question of whether the `corona' and `jet base' are in fact
related, starting by testing the strongest premise that they are synonymous. In
such models, the radio through the soft X-rays are dominated by synchrotron
emission, while the hard X-rays are dominated by inverse Compton at the jet
base - with both disk and synchrotron photons acting as seed photons. The
conditions at the jet base fix the conditions along the rest of the jet, thus
creating a direct link between the X-ray and radio emission. We also add to
this model a simple iron line and convolve the spectrum with neutral
reflection. After forward-folding the predicted spectra through the detector
response functions, we compare the results to simultaneous radio/X-ray data
obtained from the hard states of the Galactic XRBs GX339-4 and Cygnus X-1.
Results from simple Compton corona model fits are also presented for
comparison. We demonstrate that the jet model fits are statistically as good as
the single-component corona model X-ray fits, yet are also able to address the
simultaneous radio data.


title: Limits on non-Gaussianities from WMAP data

abstract:
  We develop a method to constrain the level of non-Gaussianity of density
perturbations when the 3-point function is of the "equilateral" type.
Departures from Gaussianity of this form are produced by single field models
such as ghost or DBI inflation and in general by the presence of higher order
derivative operators in the effective Lagrangian of the inflaton. We show that
the induced shape of the 3-point function can be very well approximated by a
factorizable form, making the analysis practical. We also show that, unless one
has a full sky map with uniform noise, in order to saturate the Cramer-Rao
bound for the error on the amplitude of the 3-point function, the estimator
must contain a piece that is linear in the data. We apply our technique to the
WMAP data obtaining a constraint on the amplitude f_NL^equil of "equilateral"
non-Gaussianity: -366 < f_NL^equil < 238 at 95% C.L. We also apply our
technique to constrain the so-called "local" shape, which is predicted for
example by the curvaton and variable decay width models. We show that the
inclusion of the linear piece in the estimator improves the constraint over
those obtained by the WMAP team, to -27 < f_NL^local < 121 at 95% C.L.


title:
Interstellar Scintillation Observations of 146 Extragalactic Radio
  Sources

abstract:
  From 1979--1996 the Green Bank Interferometer was used by the Naval Research
Laboratory to monitor the flux density from 146 compact radio sources at
frequencies near 2 and 8 GHz. We filter the ``light curves'' to separate
intrinsic variations on times of a year or more from more rapid interstellar
scintilation (ISS) on times of 5--50 d. Whereas the intrinsic variation at 2
GHz is similar to that at 8 GHz (though diminished in amplitude), the ISS
variation is much stronger at 2 than at 8 GHz. We characterize the ISS
variation by an rms amplitude and a timescale and examine the statistics of
these parameters for the 121 sources with significant ISS at 2 GHz. We model
the scintillations using the NE2001 Galactic electron model assuming the
sources are brightness-limited.
  We find the observed rms amplitude to be in general agreement with the model,
provided that the compact components of the sources have about 50% of their
flux density in a component with maximum brightness temperatures
$10^{11}$--$10^{12}$K. Thus our results are consistent with cm-wavelength VLBI
studies of compact AGNs, in that the maximum brightness temperatures found are
consistent with the inverse synchrotron limit at $3 \times 10^{11}$ K, boosted
in jet configurations by Doppler factors up to about 20. The average of the
observed 2 GHz ISS timescales is in reasonable agreement with the model at
Galactic latitudes above about 10\de. At lower latitudes the observed
timescales are too fast, suggesting that the transverse plasma velocity
increases more than expected beyond about 1 kpc.


title: Getting Its Kicks: A VLBA Parallax for the Hyperfast Pulsar B1508+55

abstract:
  The highest velocity neutron stars establish stringent constraints on natal
kicks, asymmetries in supernova core collapse, and the evolution of close
binary systems. Here we present the first results of a long-term pulsar
astrometry program using the VLBA. We measure a proper motion and parallax for
the pulsar B1508+55, leading to model-independent estimates of its distance
(2.37+0.23-0.20 kpc) and transverse velocity (1083+103-90 km/s), the highest
velocity directly measured for a neutron star. We trace the pulsar back from
its present Galactic latitude of 52.3 degrees to a birth site in the Galactic
plane near the Cyg OB associations, and find that it will inevitably escape the
Galaxy. Binary disruption alone is insufficient to impart the required birth
velocity, and a natal kick is indicated. A composite scenario including a large
kick along with binary disruption can plausibly account for the high velocity.


title:
Constraining the photometric properties of MgII absorbing galaxies with
  the SDSS

abstract:
  Using a sample of nearly 700 quasars with strong (W_0(2796)>0.8 Angstrom)
MgII absorption lines detected in the Early Data Release of the SDSS, we
demonstrate the feasibility of measuring the photometric properties of the
absorber systems by stacking SDSS imaging data. As MgII lines can be observed
in the range 0.37<z_abs<2.2, the absorbing galaxies are in general not
identified in SDSS images, but they produce systematic light excesses around
QSOs which can be detected with a statistical analysis. In this Letter we
present a 6-sigma detection of this effect over the whole sample in i-band,
rising to 9.4-sigma for a low-redshift subsample with 0.37<z_abs<=0.82. We use
a control sample of QSOs without strong MgII absorption lines to quantify and
remove systematics with typical 10-20% accuracy. The signal varies as expected
as a function of absorber redshift. For the low z_abs subsample we can reliably
estimate the average luminosities per MgII absorber system in the g, r, and i
bands and find them to be compatible with a few-hundred-Myr old stellar
population of M_r ~ -21 in the rest frame. Colors are also consistent with
typical absorbing galaxies resembling local Sb-c spirals. Our technique does
not require any spectroscopic follow-up and does not suffer from confusion with
other galaxies arising along the line-of-sight. It will be applied to larger
samples and other line species in upcoming studies.


title:
Halo Model at Its Best: Constraints on Conditional Luminosity Functions
  from Measured Galaxy Statistics

abstract:
  (Summary) Using the conditional luminosity function (CLF) -- the luminosity
distribution of galaxies in a dark matter halo -- as the fundamental building
block, we present an empirical model for the galaxy distribution. The model
predictions are compared with the published luminosity function and clustering
statistics from Sloan Digital Sky Survey (SDSS) at low redshifts, and galaxy
correlation functions from COMBO-17 survey at a redshift of 0.6, DEEP2 survey
at a redshift of unity, and Great Observatories Deep Origins Survey (GOODS) at
a redshift around 3. The comparison with statistical measurements allows us to
constrain certain parameters related to analytical descriptions that describe
the relation between a dark matter halo and its central galaxy luminosity, its
satellite galaxy luminosity, and the fraction of early- and late-type galaxies
of that halo. The single parameter best constrained by clustering measurements
is the total satellite galaxy luminosity averaged over the halo mass
distribution probed by the galaxy sample. For SDSS, $<L_{\rm sat}>
=(2.1^{+0.8}_{-0.4}) \times 10^{10}$ h${-2}$ L$_{\sun}$, while for GOODS at $z
\sim 3$, $<L_{\rm sat}> < 2 \times 10^{11}$ h$^{-2}$ L$_{\sun}$. Quantities
such as the fraction of satellite galaxies at a given galaxy luminosity are not
strongly constrained with SDSS data. We use our CLFs to establish probability
distribution of halo mass in which galaxies of a given luminosity could be
found either at halo centers or as satellites. Finally, to help establish
further properties of the galaxy distribution, we propose the measurement of
cross-clustering between galaxies divided into two distinctly different
luminosity bins.


title:
Chemical enrichment of the complex hot ISM of the Antennae Galaxies: II.
  Physical properties of the hot gas and supernova feedback

abstract:
  We investigate the physical properties of the interstellar medium (ISM) in
the merging pair of galaxies known as The Antennae (NGC 4038/39), using the
deep coadded ~411 ks Chandra ACIS-S data set. The method of analysis and some
of the main results from the spectral analysis, such as metal abundances and
their variations from ~0.2 to ~20-30 times solar, are described in Paper I
(Baldi et al. submitted). In the present paper we investigate in detail the
physics of the hot emitting gas, deriving measures for the hot-gas mass (~10^
M_sun), cooling times (10^7-10^8 yr), and pressure (3.5x10^-11-2.8x10^-10 dyne
cm^-2). At least in one of the two nuclei (NGC 4038) the hot-gas pressure is
significantly higher than the CO pressure, implying that shock waves may be
driven into the CO clouds. Comparison of the metal abundances with the average
stellar yields predicted by theoretical models of SN explosions points to SNe
of Type II as the main contributors of metals to the hot ISM. There is no
evidence of any correlation between radio-optical star-formation indicators and
the measured metal abundances. Although due to uncertainties in the average gas
density we cannot exclude that mixing may have played an important role, the
short time required to produce the observed metal masses (<=2 Myr) suggests
that the correlations are unlikely to have been destroyed by efficient mixing.
More likely, a significant fraction of SN II ejecta may be in a cool phase, in
grains, or escaping in hot winds. In each case, any such fraction of the ejecta
would remain undetectable with soft X-ray observations.


title: Long-term trends in radiation damage of Chandra X-ray CCDs

abstract:
  Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the
focal plane instruments on the Chandra X-ray Observatory, suffered radiation
damage from exposure to soft protons during passages through the Earth's
radiation belts. Current operations require ACIS to be protected during
radiation belt passages to prevent this type of damage, but there remains a
much slower and more gradual increase. We present the history of ACIS charge
transfer inefficiency (CTI), and other measures of radiation damage, from
January 2000 through June 2005. The rate of CTI increase is low, of order 1e-6
per year, with no indication of step-function increases due to specific solar
events. Based on the time history and CCD location of the CTI increase, we
speculate on the nature of the damaging particles.


title:
Evidence for J and H-band excess in classical T Tauri stars and the
  implications for disk structure and estimated ages

abstract:
  We argue that classical T Tauri stars (cTTs) possess significant non-
photospheric excess in the J and H bands. We first show that normalizing the
spectral energy distributions (SEDs) of cTTs to the J-band leads to a poor fit
of the optical fluxes, while normalizing the SEDs to the Ic-band produces a
better fit to the optical bands and in many cases reveals the presence of a
considerable excess at J and H. NIR spectroscopic veiling measurements from the
literature support this result. We find that J and H-band excesses correlate
well with the K-band excess, and that the J-K and H-K colors of the excess
emission are consistent with that of a black body at the dust sublimation
temperature (~ 1500-2000 K). We propose that this near-IR excess originates at
a hot inner rim, analogous to those suggested to explain the near-IR bump in
the SEDs of Herbig Ae/Be stars. To test our hypothesis, we use the model
presented by Dullemond et al. (2001) to fit the photometry data between 0.5 um
and 24 um of 10 cTTs associated with the Chamaeleon II molecular cloud. The
models that best fit the data are those where the inner radius of the disk is
larger than expected for a rim in thermal equilibrium with the photospheric
radiation field alone. In particular, we find that large inner rims are
necessary to account for the mid infrared fluxes (3.6-8.0 um) obtained by the
Spitzer Space Telescope. Finally, we argue that deriving the stellar
luminosities of cTTs by making bolometric corrections to the J-band fluxes
systematically overestimates these luminosities. The overestimated luminosities
translate into underestimated ages when the stars are placed in the H-R
diagram. Thus, the results presented herein have important implications for the
dissipation timescale of inner accretion disks.


title: Optical Morphology Evolution of Infrared Luminous Galaxies in GOODS-N

abstract:
  We combine optical morphologies and photometry from HST, redshifts from Keck,
and mid-infrared luminosities from Spitzer for an optically selected sample
of~800 galaxies in GOODS-N to track morphology evolution of infrared luminous
galaxies (LIRGs) since redshift z=1. We find a 50% decline in the number of
LIRGs from z~1 to lower redshift, in agreement with previous studies. In
addition, there is evidence for a morphological evolution of the populations of
LIRGs. Above z=0.5, roughly half of all LIRGs are spiral, the
peculiar/irregular to spiral ratio is ~0.7, and both classes span a similar
range of L_{IR} and M_B. At low-z, spirals account for one-third of LIRGs, the
peculiar to spiral fraction rises to 1.3, and for a given M_B spirals tend to
have lower IR luminosity than peculiars. Only a few percent of LIRGs at any
redshift are red early-type galaxies. For blue galaxies (U-B < 0.2), M_B is
well correlated with log(L_{IR}) with an RMS scatter (about a bivariate linear
fit) of ~0.25 dex in IR luminosity. Among blue galaxies that are brighter than
M_B = -21, 75% are LIRGs, regardless of redshift. These results can be
explained by a scenario in which at high-z, most large spirals experience an
elevated star formation rate as LIRGs. Gas consumption results in a decline of
LIRGs, especially in spirals, to lower redshifts.


title:
A refined ephemeris and phase resolved X-ray spectroscopy of the Geminga
  pulsar

abstract:
  We present a refined phase-connected post-glitch ephemeris for the Geminga
pulsar that is a good fit to all the post-glitch data from EGRET, ASCA, and
XMM. We also present the results of phase-resolved spectroscopy of two XMM
X-ray observations of the Geminga pulsar obtained in 2002 and 2004. An
investigation is made into a previously claimed existence of a small hot spot
on the neutron star surface. We conclude that that interpretation was more
likely an artifact of an overly restrictive assumption used to fit the
phase-resolved spectra, namely, that the spectral index of the non-thermal
component is constant. When we allow the spectral index to vary as a function
of rotation phase, we find systematic variations in spectral index, and such
fits do not require an additional, hot blackbody component.


title: Local Pancake Defeats Axis of Evil

abstract:
  Among the biggest surprises revealed by COBE and confirmed by WMAP
measurements of the temperature anisotropy of the CMB are the anomalous
features in the 2-point angular correlation function on very large angular
scales. In particular, the $\ell = 2$ quadrupole and $\ell = 3$ octopole terms
are surprisingly planar and aligned with one another, which is highly unlikely
for a statistically isotropic Gaussian random field, and the axis of the
combined low-$\ell$ signal is perpendicular to ecliptic plane and the plane
defined by the dipole direction. Although this $< 0.1 %$ 3-axis alignment might
be explained as a statistical fluke, it is certainly an uncomfortable one,
which has prompted numerous exotic explanations as well as the now well known
``Axis of Evil'' (AOE) nickname. Here, we present a novel explanation for the
AOE as the result of weak lensing of the CMB dipole by local large scale
structures in the local universe, and demonstrate that the effect is
qualitatively correct and of a magnitude sufficient to fully explain the
anomaly.


title: New spectroscopic confirmations of high-redshift galaxy clusters

abstract:
  We present new spectroscopic data in the field of five high-redshift (z>=0.6)
candidate galaxy clusters, drawn from the EIS Cluster Candidate Catalog. A
total of 327 spectra were obtained using FORS1 at the VLT, out of which 266 are
galaxies with secure redshifts. In this paper, we use these data for confirming
the existence of overdensities in redshift space at the approximate same
location as the matched-filter detections in the projected distribution of
galaxies from the EIS I-band imaging survey. The spectroscopic redshifts,
associated to these overdensities, are consistent but, in general, somewhat
lower than those predicted by the matched-filter technique. Combining the
systems presented here with those analyzed earlier, we have spectroscopically
confirmed a total of nine overdensities in the redshift range 0.6<z<1.3,
providing an important first step in building an optically-selected,
high-redshift sample for more detailed studies, complementing those based on
the few available X-ray selected systems.


title:
Spectra of High-Redshift Type Ia Supernovae and a Comparison with their
  Low-Redshift Counterparts

abstract:
  We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which
were discovered by the Supernova Cosmology Project as part of a campaign to
measure cosmological parameters. The spectra are used to determine the redshift
and classify the supernova type, essential information if the supernovae are to
be used for cosmological studies. Redshifts were derived either from the
spectrum of the host galaxy or from the spectrum of the supernova itself. We
present evidence that these supernovae are of Type Ia by matching to spectra of
nearby supernovae. We find that the dates of the spectra relative to maximum
light determined from this fitting process are consistent with the dates
determined from the photometric light curves, and moreover the spectral
time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We
also show that the expansion velocities measured from blueshifted CaHK are
consistent with those measured for low-redshift Type Ia supernovae. From these
first-level quantitative comparisons we find no evidence for evolution in SNIa
properties between these low- and high-redshift samples. Thus even though our
samples may not be complete, we conclude that there is a population of SNe Ia
at high redshift whose spectral properties match those at low redshift.


title:
A Study of the Gravitational Wave Pulsar Signal with orbital and
  spindown Effects

abstract:
  In this work we present analytic and numerical treatments of the
gravitational wave signal from a pulsar which includes spindown. We consider
phase corrections to a received monochromatic signal due to rotational and
elliptical orbital motion of the Earth, as well as perturbations due to Jupiter
and the Moon. We discuss the Fourier transform of such a signal, which is
expressed in terms of well known special functions and lends itself to a
tractable numerical analysis.


title: The hard X-ray view of Giga-Hertz Peaked Spectrum Radio Galaxies

abstract:
  We present the first broadband X-ray observations of four Giga-Hertz Peaked
Spectrum (GPS) radio galaxies at redshift <~1 performed by Chandra and
XMM-Newton. These observations more than double the number of members of this
class with measured spectra in hard (E > 2 keV) X-rays. All sources were
detected. Their radio-to-X-ray spectral energy distributions are similar,
except for PKS0941-080, which is X-ray under-luminous by about two orders of
magnitude. The comparison between the full sample of GPS galaxies with
measurements in hard X-rays and a control sample of radio galaxies rules out
intrinsic X-ray weakness as causing a lower detection rate of GPS sources in
X-ray surveys. Four out of seven GPS galaxies exhibit high X-ray column
densities, whereas for the remaining three this measurement is hampered by the
poor spectral statistics. Bearing in mind the low number statistics in both the
GPS and the control sample, the average column density measured in GPS galaxies
is larger than in FRI or Broad Line Region FR II radio galaxies, but consistent
with that measured in High-Excitation FRII galaxies. This leads to a location
the absorbing gas in an obscuring ``torus'', which prevents us from observing
the nuclear region along lines-of-sight perpendicular to the radio axis. This
interpretation is supported by the discovery of rapid (timescale ~1000 s) X-ray
variability in the GPS galaxy COINSJ0029+3456, and by an almost
order-of-magnitude difference between the HI column density measured in radio
and X-rays in PKS0500+019.


title: Planetary Nebulae as a Chemical Evolution Tool: Abundance Gradients

abstract:
  We have studied the time variation of the radial abundance gradients using
samples of planetary nebulae, open clusters, cepheids and other young objects.
Based on the analysis of O/H and S/H abundances for planetary nebulae and
metallicities of the remaining objects, we concluded that the gradients have
been flattening out in the last 8 Gyr with an average rate of the order of
0.005 - 0.010 dex/(kpc Gyr). We have estimated the errors involved in the
determination of the gradients, and concluded that the existence of systematic
abundance variations is more likely than a simple statistical dispersion around
a mean value.


title: Spectral energy distributions of a large sample of BL Lacertae objects

abstract:
  We have collected a large amount of multifrequency data for the objects in
the Metsahovi Radio Observatory BL Lacertae sample and computed their spectral
energy distributions (SED). This is the first time the SEDs of BL Lacs have
been studied with a sample of over 300 objects. The synchrotron components of
the SEDs were fitted with a parabolic function to determine the synchrotron
peak frequency. We checked the dependence between luminosities at several
frequency bands and synchrotron peak frequency to test the blazar sequence
scenario, which states that the source luminosity depends on the location of
the synchrotron peak. We also calculated broad band spectral indices and
plotted them against each other and the peak frequency. The range of peak
frequencies in our study was considerably extended compared to previous
studies. There were 22 objects for which log\nu_{peak}>19. The data shows that
at 5 GHz, 37 GHz and 5500 A there is negative correlation between luminosity
and nu_{peak}. There is no significant correlation between source luminosity at
synchrotron peak and peak frequency. Several low radio luminosity-low energy
peaked BL Lacs were found. The negative correlation between broad band spectral
indices and nu_{peak} is also significant, although there is substantial
scatter. Therefore we find that neither alpha_{rx} nor alpha_{ro} can be used
to determine the synchrotron peak of BL Lacs. On the grounds of our results we
conclude that the blazar sequence scenario is not valid. In all our results the
BL Lac population is continuous with no hint of the bimodality of the first BL
Lac samples.


title:
Fast Optical Photometry of Galaxies: Observations of Short-Lived Flare
  Events

abstract:
  We have monitored two bright galaxies, M85 and NGC7331, on timescales as
short as 0.01s. In the optical, we discovered an unusual burst coincident with
the galaxy M85. We registered a sudden onset with a characteristic time of less
than 10ms with subsequent quasi-exponential decay within approximately 1s and
an amplitude of 2.5mag in the V-band. In the course of high-speed monitoring
with two Crimean telescopes operated synchronously, in both independent
instruments we have registered one coincident event occurring in NGC7331 with a
duration of ~0.6s. The amplitudes range from ~3mag to ~0.3mag in the U-band and
I-band, respectively. Merging of an intermediate-mass black hole with a small
black hole or normal star seems to be the most plausible mechanism responsible
for short bursts. Our observations support the hypothesis concerning the
existence of intermediate-mass black holes in the centers of galaxies and in
dense globular clusters.


title:
A toy model for coupling accretion disk oscillations to the neutron star
  spin

abstract:
  Lee, Abramowicz & Kluzniak (2004) demonstrated numerically that rotation of
neutron star couples with oscillations of its accretion disk, and excites
resonances. No specific coupling was assumed, but magnetic field was suggested
as the most likely one. Following this idea, we show (Petri 2005) that if the
neutron star is non-axially symmetric and rotating, its gravity may provide the
coupling and excite resonances. Here, we return to the original suggestion that
the coupling is of a magnetic origin, and demonstrate how does it work in terms
of a simple, analytic toy-model.


title:
A sensitive search for CO J=1-0 emission in 4C 41.17: high-excitation
  molecular gas at z=3.8

abstract:
  We report sensitive imaging observations of the CO J=1-0 line emission in the
powerful high-redshift radio galaxy 4C 41.17 (z=3.8) with the NRAO Very Large
Array (VLA), conducted in order to detect the large concomitant H_2 gas
reservoir recently unveiled in this system by De Breuck et al (2005) via the
emission of the high excitation J=4-3 line. Our observations fail to detect the
J=1-0 line but yield sensitive lower limits on the R_43=(4-3)/(1-0) brightness
temperature ratio of R_43 ~ 0.55 - >1.0 for the bulk of the H_2 gas mass. Such
high ratios are typical of the high-excitation molecular gas phase ``fueling''
the star formation in local starbursts, but quite unlike these objects, much of
the molecular gas in 4C 41.17 seems to be in such a state, and thus
participating in the observed starburst episode. The widely observed and unique
association of highly excited molecular gas with star forming sites allows CO
line emission with large (high-J)/(low-J) intensity ratios to serve as an
excellent ``marker'' of the spatial distribution of star formation in distant
dust-obscured starbursts, unaffected by extinction.


title:
An empirical temperature calibration for the Delta a photometric system.
  I. The B-type stars

abstract:
  We establish an empirical effective temperature calibration of main sequence,
luminosity class V to III B-type stars for the Delta a photometric system which
was originally developed to detect magnetic chemically peculiar objects of the
upper main sequence (early B-type to early F-type) at 5200A. However, this
system provides the index (g1-y) which shows an excellent correlation with
(B-V) as well as (b-y) and can be used as an indicator of the effective
temperature. This is supplemented by a very accurate color-magnitude diagram, y
or V versus (g1-y), which can be used, for example, to determine the reddening,
distance and age of an open cluster. This makes the Delta a photometric system
an excellent tool to investigate the Hertzsprung-Russell-Diagram (HRD) in more
detail. Using the reddening-free parameters and already established
calibrations within the Stromgren uvbybeta, Geneva 7-color and Johnson UBV
systems, a polynomial fit of third degree for the averaged effective
temperatures to the individual (g1-y)0 values was derived. For this purpose,
data from the literature as well as new observations were taken resulting in
225 suitable bright normal B-type objects. The statistical mean of the error
for this sample is 238K which is sufficient to investigate the HRD of distant
galactic open clusters as well as extragalactic aggregates in the future.


title:
The use of Planetary Nebulae precursors in the study of Diffuse
  Interstellar Bands

abstract:
  We present the first results of a systematic search for Diffuse Interstellar
Bands in a carefully selected sample of post-AGB stars observed with high
resolution optical spectroscopy. These stars are shown to be ideal targets to
study this old, intriguing astrophysical problem. Our results suggest that the
carrier(s) of these bands may not be present in the circumstellar environments
of these evolved stars. The implications of the results obtained on the
identification of the still unknown carrier(s) are discussed.


title: Why are massive O-rich AGB stars in our Galaxy not S-stars?

abstract:
  We present the main results derived from a chemical analysis carried out on a
large sample of galactic O-rich AGB stars using high resolution optical
spectroscopy (R~40,000-50,000) with the intention of studying their lithium
abundances and/or possible s-process element enrichment. Our chemical analysis
shows that some stars are lithium overabundant while others are not. The
observed lithium overabundances are interpreted as a clear signature of the
activation of the so-called ``Hot Bottom Burning'' (HBB) process in massive
galactic O-rich AGB stars, as predicted by the models. However, these stars do
not show the zirconium enhancement (taken as a representative for the s-process
element enrichment) associated to the third dredge-up phase following thermal
pulses. Our results suggest that the more massive O-rich AGB stars in our
Galaxy behave differently from those in the Magellanic Clouds, which are both
Li- and s-process-rich (S-type stars). Reasons for this unexpected result are
discussed. We conclude that metallicity is probably the main responsible for
the differences observed and suggest that it may play a more important role
than generally assumed in the chemical evolution of AGB stars.


title: The Carina dSph galaxy: where is the edge?

abstract:
  Recent cosmological N-body simulations suggest that current empirical
estimates of tidal radii in dSphs might be underestimated by at least one order
of magnitude. To constrain the plausibility of this theoretical framework, we
undertook a multiband (U,B,V,I) survey of the Carina dSph. Deep B,V data of
several fields located at radial distances from the Carina center ranging from
0.5 to 4.5 degrees show a sizable sample of faint blue objects with the same
magnitudes and colors of old, Turn-Off stars detected across the center. We
found that the (U-V,B-I) color-color plane is a robust diagnostic to split
stars from background galaxies. Unfortunately, current U,I-band data are too
shallow to firmly constrain the real extent of Carina.


title: The First Chandra Field

abstract:
  Before the official first-light images, the Chandra X-Ray Observatory
obtained an X-ray image of the field to which its focal plane was first
exposed. We describe this historic observation and report our study of the
first Chandra field. Chandra's Advanced CCD Imaging Spectrometer (ACIS)
detected 15 X-ray sources, the brightest being dubbed ``Leon X-1'' to honor the
Chandra Telescope Scientist, Leon Van Speybroeck. Based upon our analysis of
the X-ray data and spectroscopy at the European Southern Observatory (ESO; La
Silla, Chile), we find that Leon X-1 is a Type-1 (unobscured) active galactic
nucleus (AGN) at a redshift z=0.3207. Leon X-1 exhibits strong Fe II emission
and a broad-line Balmer decrement that is unusually flat for an AGN. Within the
context of the Eigenvector-1 correlation space, these properties suggest that
Leon X-1 may be a massive (> 10**{9} solar mass) black hole, accreting at a
rate approaching its Eddington limit.


title: Cosmic Ray Acceleration by E-Parallel Reconnection of Force-Free Fields

abstract:
  We propose that nearly every accelerated CR was part of the parallel current
that maintains all force-free (f-f) magnetic fields. Charged particles are
accelerated by the E-parallel (to the magnetic filed B) produced by
reconnection. The inferred total energy in extra-galactic cosmic rays is
10^(60) ergs per galaxy spacing volume, provided that acceleration mechanisms
assumed do not preferentially only accelerate ultra high energy cosmic rays
(UHECRs). This total energy is about 10^5 times the parent galactic CR or
magnetic energy. The formation energy of supermassive black holes (SMBHs) at
galaxy centers, 10^(62) ergs, becomes the only feasible source. An efficient
dynamo process converts gravitational free energy into magnetic energy in an
accretion disk around a SMBH. Aided by Keplerian winding, this dynamo converts
a poloidal seed field into f-f fields, which are transported into the general
inter-galactic medium (IGM). This magnetic energy is also efficiently converted
into particle energies, as evidenced by the radiation from energetic particles.
CRs of the IGM are then the result of the continuing dissipation, in a Hubble
time, of this magnetic energy, by acceleration within the f-f fields confined
within the super-galactic walls and filaments of large scale structures. In
addition, most UHECRs are diffusively lost to the galactic voids before the GZK
attenuation time, 10^8 years and hence are lost from view. Similarly within the
galaxy we expect that the winding by accretion are the sources of galactic CR
acceleration. [edited]


title: HI 21cm probes of reionization, and beyond

abstract:
  I review the potential for observing cosmic reionization using the HI 21cm
line of neutral hydrogren. Studies include observations of the evolution of
large scale structure of the IGM (density, excitation temperature, and neutral
fraction), through HI 21cm emission, as well as observations of small to
intermediate scale structure through absorption toward the first discrete radio
sources. I summarize predictions for the HI signals, then consider capabilities
of facilities being built, or planned, to detect these signals. I also discuss
the significant observational challenges.


title: Optical properties of the NGC 5328 group of galaxies

abstract:
  We present the results of a photometric and spectroscopic study of seven
members of the NGC 5328 group of galaxies, a chain of galaxies spanning over
200 kpc (H_0 = 70 km/s/Mpc). We analyze the galaxy structure and study the
emission line properties of the group members looking for signatures of star
formation and AGN activity. We finally attempt to infer, from the modeling of
line-strength indices, the stellar population ages of the early-type members.
We investigate also the presence of a dwarf galaxy population associated with
the bright members.
  The group is composed of a large fraction of early-type galaxies including
NGC 5328 and NGC 5330, two bona fide ellipticals at the center of the group. In
both galaxies no recent star formation episodes are detected by the H_beta vs.
MgFe indices of these galaxies. 2MASX J13524838-2829584 has extremely boxy
isophotes which are believed to be connected to a merging event: line strength
indices suggest that this object probably had a recent star formation episode.
A warped disc component emerges from the model subtracted image of 2MASX
J13530016-2827061 which is interpreted as a signature of an ongoing interaction
with the rest of the group.
  Ongoing star formation and nuclear activity is present in the projected
outskirts of the group. The two early-type galaxies 2MASX J13523852-2830444 and
2MASX J13525393-2831421 show spectral signatures of star formation, while a
Seyfert 2 type nuclear activity is detected in MCG -5-33-29.


title: The outer disks of galaxies: "To be or not to be truncated?"

abstract:
  We have in recent years come to view the outer parts of galaxies as having
vital clues about their formation and evolution. Here, we would like to briefly
present our results from a complete sample of nearby, late-type, spiral
galaxies, using data from the SDSS survey, especially focused on the stellar
light distribution in the outer disk. Our study shows that only the minority of
late-type galaxies show a classical, exponential Freeman Type I profile down to
the noise limit, whereas the majority exhibit either downbending (stellar
truncation as introduced 1979 by Piet van der Kruit) or upbending profiles.


title: Millimeter observations of obscured Spitzer 24 micron sources

abstract:
  We present MAMBO 1.2mm observations of 40 extragalactic sources from the
Spitzer First Look Survey that are bright in the mid-infrared (S_24um>1mJy) but
optically obscured (log_10 (nu F_nu (24um))/(nu F_nu (0.7um))>1). We use these
observations to search for cold dust emission, probing the similarity of their
spectral energy distributions to star forming infrared galaxies or obscured
AGN. The sample as a whole is well detected at mean S_1.2mm=0.74+-0.09mJy and
S_1.2mm/S_24um=0.15+-0.03. Seven (three) of the sources are individually
detected at >3sigma (>5sigma) levels. Mean millimeter fluxes are higher for
sources with the reddest mid-infrared/optical colors. Optically faint but with
relatively low mm to mid-infrared ratio, the typical SEDs are inconsistent with
redshifted SED shapes of local star-forming infrared galaxies. They also differ
from SEDs of typical submillimeter selected galaxies, with the 24um sources
that are individually detected by MAMBO possibly representing intermediate
objects. Compared to star-forming galaxies, a stronger but optically obscured
mid-infrared component without associated strong far-infrared emission has to
be included. This component may be due to luminous optically obscured AGN,
which would represent a significant part of the high redshift AGN population.


title: Specific Star Formation Rates

abstract:
  We present results from a study to determine how star formation contributes
to galaxy growth since redshift z=1.5. Using galaxies from the MUnich
Near-Infrared Cluster Survey (MUNICS) and the FORS Deep Field (FDF), we
investigate the specific star formation rate (SSFR, star formation rate [SFR]
per unit galaxy stellar mass) as a function of galaxy stellar mass and
redshift. We test the compatibility of our results with a sample drawn from a
larger volume using the Sloan Digital Sky Survey. We find that the SSFR
decreases as galaxy stellar mass increases, suggesting that star formation
contributes more to the growth of low-mass galaxies than high-mass galaxies at
all redshifts in this study. We also find a ridge in the SSFR that runs
parallel to lines of constant SFR and decreases by a factor of 10 from z=1 to
today, matching the results of the evolution in SFR density seen in the
``Lilly-Madau'' diagram. The ridge evolves independently of galaxy stellar mass
to a particular turnover mass at the high mass end. Galaxies above the turnover
mass show a sharp decrease in SSFR compared to the average at that epoch, and
the turnover mass increases with redshift.


title: Swift-UVOT detection of GRB 050318

abstract:
  We present observations of GRB 050318 by the Ultra-Violet and Optical
Telescope (UVOT) on-board the Swift observatory. The data are the first
detections of a Gamma Ray Burst (GRB) afterglow decay by the UVOT instrument,
launched specifically to open a new window on these transient sources. We
showcase UVOTs ability to provide multi-color photometry and the advantages of
combining UVOT data with simultaneous and contemporaneous observations from the
high-energy detectors on the Swift spacecraft. Multiple filters covering
1,800-6,000 Angstroms reveal a red source with spectral slope steeper than the
simultaneous X-ray continuum. Spectral fits indicate that the UVOT colors are
consistent with dust extinction by systems at z = 1.2037 and z = 1.4436,
redshifts where absorption systems have been pre-identified. However, the data
can be most-easily reproduced with models containing a foreground system of
neutral gas redshifted by z = 2.8 +/- 0.3. For both of the above scenarios,
spectral and decay slopes are, for the most part, consistent with fireball
expansion into a uniform medium, provided a cooling break occurs between the
energy ranges of the UVOT and Swifts X-ray instrumentation.


title: Chemical composition of evolved stars of high galactic latitude

abstract:
  We have carried out abundance analysis for a sample of high galactic latitude
supergiants in search of evolved stars. We find that HD 27381 has atmospheric
parameters and an abundance pattern very similar to that of the post-AGB star
HD 107369. HD 10285 and HD 25291 are moderately metal-poor and show the
influence of mixing that has brought the products of NeNa cycle to the surface.
The high galactic latitude B supergiant HD 137569 shows selective depletion of
refractory elements normally seen in post-AGB stars. We find that the high
velocity B type star HD 172324 shows moderate deficiency of Fe group elements
but the CNO abundances are very similar to that of disk B supergiants. The
observed variations in the radial velocities, transient appearance of emission
components in hydrogen line profiles and doubling of O I lines at 7774\AA
support the possibility of this star being a pulsating variable or a binary
star.


title:
Shapes of clusters and groups of galaxies: Comparison of model
  predictions with observations

abstract:
  We study the properties of the 3-dimensional and projected shapes of haloes
using high resolution numerical simulations and observational data where the
latter comes from the 2PIGG (Eke et al. 2004) and SDSS-DR3GC group catalogues
(Merchan & Zandivarez 2005). We investigate the dependence of halo shape on
characteristics such as mass and number of members. In the 3-dimensional case,
we find a significant correlation between the mass and halo shape; massive
systems are more prolate than small haloes. We detect a source of strong
systematics in estimates of the triaxiality of a halo, which is found to be a
strong function of the number of members; LCDM haloes usually characterised by
triaxial shapes, slightly bent toward prolate forms, appear more oblate when
taking only a small subset of the halo particles. The ellipticities of observed
2PIGG and SDSS-DR3GC groups are found to be strongly dependent on the number of
group members, so that poor groups appear more elongated than rich ones.
However, this is again an artifact caused by poor statistics and not an
intrinsic property of the galaxy groups, nor an effect from observational
biases. We interpret these results with the aid of a GALFORM mock 2PIGG
catalogue. When comparing the group ellipticities in mock and real catalogues,
we find an excellent agreement between the trends of shapes with number of
group members. When carefully taking into account the effects of low number
statistics, we find that more massive groups are consistent with more elongated
shapes. Finally, our studies find no significant correlations between the shape
of observed 2PIGG or SDSS-DR3GC groups with the properties of galaxy members
such as colour or spectral type index.


title: A 3D Spectral Anelastic Hydrodynamic Code for Shearing, Stratified Flows

abstract:
  We have developed a three-dimensional (3D) spectral hydrodynamic code to
study vortex dynamics in rotating, shearing, stratified systems (e.g. the
atmosphere of gas giant planets, protoplanetary disks around newly forming
protostars). The time-independent background state is stably stratified in the
vertical direction and has a unidirectional linear shear flow aligned with one
horizontal axis. Superposed on this background state is an unsteady, subsonic
flow that is evolved with the Euler equations subject to the anelastic
approximation to filter acoustic phenomena. A Fourier-Fourier basis in a set of
quasi-Lagrangian coordinates that advect with the background shear is used for
spectral expansions in the two horizontal directions. For the vertical
direction, two different sets of basis functions have been implemented: (1)
Chebyshev polynomials on a truncated, finite domain, and (2) rational Chebyshev
functions on an infinite domain. Use of this latter set is equivalent to
transforming the infinite domain to a finite one with a cotangent mapping, and
using cosine and sine expansions in the mapped coordinate. The nonlinear
advection terms are time integrated explicitly, whereas the Coriolis force,
buoyancy terms, and pressure/enthalpy gradient are integrated semi-implicitly.
We show that internal gravity waves can be damped by adding new terms to the
Euler equations. The code exhibits excellent parallel performance with the
Message Passing Interface (MPI). As a demonstration of the code, we simulate
the merger of two 3D vortices in the midplane of a protoplanetary disk.


title: Magnetic collimation of the relativistic jet in M87

abstract:
  We apply a two-zone MHD model to the jet of M87. The model consists of an
inner relativistic outflow, which is surrounded by a non-relativistic outer
disk-wind. The outer disk-wind collimates very well through magnetic
self-collimation and confines the inner relativistic jet into a narrow region
around the rotation axis. Further, we show by example, that such models
reproduce very accurately the observed opening angle of the M87 jet over a
large range from the kiloparsec scale down to the sub-parsec scale.


title: Quasars as Probes of Late Reionization and Early Structure Formation

abstract:
  Observations of QSOs at z ~ 5.7 - 6.4 show the appearance of Gunn-Peterson
troughs around z ~ 6, and a change in the slope of the IGM optical depth tau(z)
near z ~ 5.5. These results are interpreted as a signature of the end of the
reionization era, which probably started at considerably higher redshifts.
However, there also appears to be a substantial cosmic variance in the
transmission of the IGM, both along some lines of sight, and among different
lines of sight, in this intriguing redshift regime. We suggest that this is
indicative of a spatially uneven reionization, possibly caused by the
bias-driven primordial clustering of the reionization sources. There is also
some independent evidence for a strong clustering of QSOs at z ~ 4 - 5 and
galaxies around them, supporting the idea of the strong biasing of the first
luminous sources at these redshifts. Larger samples of high-z QSOs are needed
in order to provide improved, statistically significant constraints for the
models of these phenomena. We expect that the Palomar-Quest (PQ) survey will
soon provide a new set of QSOs to be used as cosmological probes in this
redshift regime.


title: L and T Dwarf Models and the L to T Transition

abstract:
  Using a model for refractory clouds, a novel algorithm for handling them, and
the latest gas-phase molecular opacities, we have produced a new series of L
and T dwarf spectral and atmosphere models as a function of gravity and
metallicity, spanning the \teff range from 2200 K to 700 K. The correspondence
with observed spectra and infrared colors for early- and mid-L dwarfs and for
mid- to late-T dwarfs is good. We find that the width in infrared
color-magnitude diagrams of both the T and L dwarf branches is naturally
explained by reasonable variations in gravity and, therefore, that gravity is
the "second parameter" of the L/T dwarf sequence. We investigate the dependence
of theoretical dwarf spectra and color-magnitude diagrams upon various cloud
properties, such as particle size and cloud spatial distribution. In the region
of the L$\to$T transition, we find that no one cloud-particle-size and gravity
combination can be made to fit all the observed data. Furthermore, we note that
the new, lower solar oxygen abundances of Allende-Prieto, Lambert, & Asplund
(2002) produce better fits to brown dwarf data than do the older values.
Finally, we discuss various issues in cloud physics and modeling and speculate
on how a better correspondence between theory and observation in the
problematic L$\to$T transition region might be achieved.


title: Discovery of Outlying, High-Velocity Oxygen-Rich Ejecta in Cassiopeia A

abstract:
  Hubble Space Telescope images of the young Galactic supernova remnant
Cassiopeia A reveal a far larger population of outlying, high-velocity knots of
ejecta with a broader range of chemical properties than previously suspected.
We identify three main classes of outer ejecta: 1) Knots dominated by [N II]
6548,6583 emission; 2) Knots dominated by oxygen emission lines especially [O
II] 7319,7330; and 3) Knots with emission line strengths similar to the [S II]
strong FMK ejecta commonly seen in the main emission shell. The discovery of a
significant population of O-rich ejecta situated in between the suspected
N-rich outer photospheric layer and S-rich FMK-like ejecta suggests that the
Cas A progenitor's chemical layers were not completely disrupted by the
supernova explosion outside of the remnant's NE and SW high velocity `jet'
regions. In addition, we find the majority of O-rich outer ejecta at projected
locations out beyond (v = 6500 - 9000 km/s) the remnant's fastest moving
Fe-rich X-ray emission material (6000 km/s) seen in Chandra and XMM data along
the eastern limb. This suggests that penetration of Fe-rich material up through
the S and Si-rich mantle did not extend past the progenitor's N or O-rich outer
layers for at least this section of the remnant.


title: Detection of Giant Pulses in pulsar PSR J1752+2359

abstract:
  We report the detection of Giant Pulses (GPs) in the pulsar PSR J1752+2359.
About one pulse in 270 has a peak flux density more than 40 times the peak flux
density of an average pulse (AP), and the strongest GP is as large as 260. The
energy of the strongest GP exceeds the energy of the average pulse by a factor
of 200 which is greater than in other known pulsars with GPs. PSR J1752+2359 as
well as the previously detected pulsars PSR B0031-07 and PSR B1112+50, belong
to the first group of pulsars found to have GPs without a strong magnetic field
at the light cylinder.


title: Dip in UHECR and Transition from Galactic to Extragalactic Cosmic Rays

abstract:
  The dip is a feature in the diffuse spectrum of UHE protons in energy range
$1\times 10^{18} - 4\times 10^{19}$ eV, which is caused by electron-positron
pair production on CMB photons. Calculated for power-law generation spectrum
with index $\gamma_g=2.7$, the shape of the dip is confirmed with high accuracy
by data of Akeno - AGASA, HiRes, Yakutsk and Fly's Eye detectors. The predicted
shape of the dip is robust: it is valid for the rectilinear and diffusive
propagation, for different discretenesses in the source distribution, for local
source overdensity and deficit, for source inhomogeneities on scale $\ell \lsim
100$ Mpc etc. Below the characteristic energy $E_c \approx 1\times 10^{18}$ eV
the spectrum of the dip flattens for both diffusive and rectilinear
propagation, and more steep galactic spectrum becomes dominant at $E < E_c$.
The energy of transition $E_{\rm tr} < E_c$ approximately coincides with the
position of the second knee $E_{2kn}$ observed in the cosmic ray spectrum. The
critical energy $E_c$ is determined by the energy $E_{\rm eq} = 2.3\times
10^{18}$ eV, where adiabatic and pair-production energy losses are equal. Thus,
position of the second knee is explained by proton energy losses on CMB
photons.


title: High-energy emission of fast rotating white dwarfs

abstract:
  The process of energy release in the magnetosphere of a fast rotating,
magnetized white dwarf can be explained in terms of the canonical spin-powered
pulsar model. Applying this model to the white dwarf companion of the low mass
close binary AE Aquarii leads us to the following conclusions. First, the
system acts as an accelerator of charged particles whose energy is limited to
E_p < 3 TeV and which are ejected from the magnetosphere of the primary with
the rate L_kin < 10^{32} erg/s. Due to the curvature radiation of the
accelerated primary electrons the system should appear as a source of soft
gamma-rays (~ 100 keV) with the luminosity < 3x10^{27} erg/s. The TeV emission
of the system is dominated by the inverse Compton scattering of optical photons
on the ultrarelativistic electrons. The optical photons are mainly contributed
by the normal companion and the stream of material flowing through the
magnetosphere of the white dwarf. The luminosity of the TeV source depends on
the state of the system (flaring/quiet) and is limited to < 5x10^{29} erg/s.
These results allow us to understand a lack of success in searching for the
high-energy emission of AE Aqr with the Compton Gamma-ray Observatory and the
Whipple Observatory.


title: On One Model of the Geometrical Quintessence

abstract:
  A cosmological model with modification of the Einstein-Hilbert action by the
correction $f(R)\propto \beta R^n$ is considered. Such way of the description
of the ``geometrical'' dark energy has been introduced repeatedly and the
coefficients of the model were chosen to be fit against some observational
data. In this paper the unambiguous choice of parameters $n$ and $\beta$ is
proposed from the follow reasons: the exponent $n$ close to 1.2953 follows from
the request for the evolution of the Universe after recombination to be close
to the evolution of the flat FRW model with cold dark matter and the reasonable
age of the Universe defines the magnitude of the coefficient $\beta$. Such a
model corresponding to the evolution of the Universe with the dynamical
$\Lambda$-term describes well enough the observational data.


title: Isolated and non-isolated dark matter halos and the NFW profile

abstract:
  We compare the conclusions reached using the coarse-graining technique
employed by Henriksen (2004) for a one degree of freedom (per particle)
collisionless system, to those presented in a paper by Binney (2004) based on
an exact one degree of freedom model. We find agreement in detail but in
addition we show that the isolated 1D system is self-similar and therefore
unrelaxed. Fine graining of this system recovers much less prominent wave-like
structure than in a spherically symmetric isotropic 3D system. The rate of
central flattening is also reduced in the 1D system. We take this to be
evidence that relaxation of collisionless systems proceeds ultimately by way of
short wavelength Landau damping. N-body systems, both real and simulated, can
be trapped in an incompletely relaxed state because of a break in the cascade
of energy to small scales. This may be due to the rapid dissipation of the
small scale oscillations in an isolated system, to the existence of conserved
quantities such as angular momentum, or to the failure in simulations to
resolve sub-Jeans length scales. Such a partially relaxed state appears to be
the NFW state, and is to be expected especially in young systems. The NFW core
is shown to be isolated. In non-isolated systems continuing coarse-grained
relaxation should be towards a density core in solid body rotation.


title:
3-D Models of Embedded High-Mass Stars: Effects of a Clumpy
  Circumstellar Medium

abstract:
  We use 3-D radiative transfer models to show the effects of clumpy
circumstellar material on the observed infrared colors of high mass stars
embedded in molecular clouds. We highlight differences between 3-D clumpy and
1-D smooth models which can affect the interpretation of data. We discuss
several important properties of the emergent spectral energy distribution
(SED): More near-infrared light (scattered and direct from the central source)
can escape than in smooth 1-D models. The near- and mid-infrared SED of the
same object can vary significantly with viewing angle, depending on the clump
geometry along the sightline. Even the wavelength-integrated flux can vary with
angle by more than a factor of two. Objects with the same average circumstellar
dust distribution can have very different near-and mid-IR SEDs depending on the
clump geometry and the proximity of the most massive clump to the central
source.
  Although clumpiness can cause similar objects to have very different SEDs,
there are some observable trends. Near- and mid-infrared colors are sensitive
to the weighted average distance of clumps from the central source and to the
magnitude of clumpy density variations (smooth-to-clumpy ratio). Far-infrared
emission remains a robust measure of the total dust mass. We present simulated
SEDs, colors, and images for 2MASS and Spitzer filters. We compare to
observations of some UCHII regions and find that 3-D clumpy models fit better
than smooth models. In particular, clumpy models with fractal dimensions in the
range 2.3-2.8, smooth to clumpy ratios of <50%, and density distributions with
shallow average radial density profiles fit the SEDs best.


title: The Demographics of Long-Period Comets

abstract:
  The absolute magnitude and perihelion distributions of long-period comets are
derived, using data from the Lincoln Near-Earth Asteroid Research (LINEAR)
survey. The results are surprising in three ways. Firstly, the flux of comets
through the inner solar system is much lower than some previous estimates.
Secondly, the expected rise in comet numbers to larger perihelia is not seen.
Thirdly, the number of comets per unit absolute magnitude does not
significantly rise to fainter magnitudes. These results imply that the Oort
cloud contains many fewer comets than some previous estimates, that small
long-period comets collide with the Earth too infrequently to be a plausible
source of Tunguska-style impacts, and that some physical process must have
prevented small icy planetesmals from reaching the Oort cloud, or have rendered
them unobservable. A tight limit is placed on the space density of interstellar
comets, but the predicted space density is lower still. The number of
long-period comets that will be discovered by telescopes such as SkyMapper,
Pan-Starrs and LSST is predicted, and the optimum observing strategy discussed.


title:
Keck High-Resolution Spectroscopy of Outflows in Infrared Luminous
  Galaxies

abstract:
  Several recent studies have determined that large quantities of neutral gas
are outflowing from the nuclei of almost all infrared-luminous galaxies. These
measurements show that winds in infrared-luminous galaxies play a significant
role in the evolution of galaxies and the intergalactic medium at redshifts z >
1, when infrared-luminous galaxies dominated the star formation rate of the
universe. These conclusions rely on moderate resolution spectra (FWHM > 65
km/s) of the NaI D absorption line and the assumption that there are no
unresolved, saturated velocity components. For the first time, we present high
resolution spectra (FWHM = 13 km/s) of massive, infrared-luminous galaxies. The
five galaxies in our sample are known to host outflows on the basis of previous
observations. With the present observations, all NaI D velocity components are
resolved with tau(NaI D1 5896 A) < 6. The column densities we measure are
consistent within the errors with those measured from moderate-resolution
observations. This confirms that the mass, momentum, and energy of outflowing
gas in infrared-luminous galaxies have been measured correctly by previous
studies.


title:
Big-bang nucleosynthesis in Brans-Dicke cosmology with a varying
  $\Lambda$ term related to WMAP

abstract:
  We investigate the big-bang nucleosynthesis in a Brans-Dicke model with a
varying $\Lambda$ term using the Monte-Carlo method and likelihood analysis. It
is found that the cosmic expansion rate differs appreciably from that of the
standard model. The produced abundances of $^4$He, D, and barely Li are
consistent with the observed ones within the uncertainties in nuclear reaction
rates when the baryon to photon ratio $\eta = (5.47 - 6.64)\times 10^{-10}$,
which is in agreement with the value deduced from WMAP.


title:
Kinematics of globular cluster systems and the formation of early-type
  galaxies

abstract:
  We numerically investigate the kinematic properties of globular cluster
systems (GCSs) in E/S0 galaxies formed from dissipationless merging of spiral
galaxies. The metal-poor globular clusters (MPCs) and metal-rich clusters
(MRCs) in the merger progenitors are initially assumed to have spatial
distributions consistent with the Milky Way GC system. Our principal results,
which can be tested against observations, are as follows. Both MPCs and MRCs in
elliptical galaxies formed from major mergers can exhibit significant rotation
at large radii ($\sim$20 kpc) due to the conversion of initial orbital angular
momentum into intrinsic angular momentum of the remnant. MPCs show higher
central velocity dispersions than MRCs for most major merger models. $V_{\rm
m}/{\sigma}_{0}$ (where $V_{\rm m}$ and ${\sigma}_{0}$, are the GCS maximum
rotational velocity and central velocity dispersion of respectively) ranges
from 0.2--1.0 and 0.1--0.9 for the MPCs and MRCs respectively, within $6R_{\rm
e}$ for the remnant elliptical. For most merger remnant ellipticals, $V_{\rm
m}/{\sigma}_{0}$ of GCSs within $6R_{\rm e}$ is greater than that of the field
stars within $2R_{\rm e}$. The radial profiles of rotational velocities and
velocity dispersions of the GCSs depend upon the orbital configuration of the
merger progenitors, their mass-ratios, and the viewing angle. For example, more
flattened early-type galaxies, formed through mergers with small mass ratios
($\sim$ 0.1), show little rotation in the outer MRCs. Two-dimensional (2D)
velocity dispersion distributions of the GCSs of merger remnant ellipticals are
generally flattened for both MPCs and MRCs, reflecting the fact that the GCSs
have anisotropic velocity dispersions (abridged).


title: Conserved non-linear quantities in cosmology

abstract:
  We give a detailed and improved presentation of our recently proposed
formalism for non-linear perturbations in cosmology, based on a covariant and
fully non-perturbative approach. We work, in particular, with a covector
combining the gradients of the energy density and of the local number of
e-folds to obtain a non-linear generalization of the familiar linear uniform
density perturbation. We show that this covector obeys a remarkably simple
conservation equation which is exact, fully non-linear and valid at all scales.
We relate explicitly our approach to the coordinate-based formalisms for linear
perturbations and for second-order perturbations. We also consider other
quantities, which are conserved on sufficiently large scales for adiabatic
perturbations, and discuss the issue of gauge invariance.


title:
Joint constraints on the lepton asymmetry of the Universe and neutrino
  mass from the Wilkinson Microwave Anisotropy Probe

abstract:
  We use the Wilkinson Microwave Anisotropy Probe (WMAP) data on the spectrum
of cosmic microwave background anisotropies to put constraints on the present
amount of lepton asymmetry L, parameterized by the dimensionless chemical
potential (also called degeneracy parameter) xi and on the effective number of
relativistic particle species. We assume a flat cosmological model with three
thermally distributed neutrino species having all the same mass and chemical
potential, plus an additional amount of effectively massless exotic particle
species. The extra energy density associated to these species is parameterized
through an effective number of additional species DeltaN_oth$. We find that
0<|xi|<1.1 and correspondingly 0<|L|<0.9 at 2sigma, so that WMAP data alone
cannot firmly rule out scenarios with a large lepton number; moreover, a small
preference for this kind of scenarios is actually found. We also discuss the
effect of the asymmetry on the estimation of other parameters and in particular
of the neutrino mass. In the case of perfect lepton symmetry, we obtain the
standard results. When the amount of asymmetry is left free, we find \sum m_nu
< 3.6 eV at 2sigma. Finally we study how the determination of |L| is affected
by the assumptions on DeltaN_oth. We find that lower values of the extra energy
density allow for larger values of the lepton asymmetry, effectively ruling
out, at 2sigma level, lepton symmetric models with DeltaN_oth=0.


title:
First limit on WIMP cross section with low background CsI(Tl) crystal
  detector

abstract:
  The Korea Invisible Mass Search (KIMS) collaboration has been carrying out
WIMP search experiment with CsI(T$\ell$)crystal detectors at the YanYang
Underground Laboratory. A successful reduction of the internal background of
the crystal is done and a good pulse shape discrimination is achieved. We
report the first result on WIMP search obtained with 237 kg$\cdot$days data
using one full-size CsI(T$\ell$)crystal of 6.6 kg mass.


title:
The HELLAS2XMM survey. VII. The hard X-ray luminosity function of AGN up
  to z=4: more absorbed AGN at low luminosities and high redshifts

abstract:
  We have determined the cosmological evolution of the density of AGN and of
their Nh distribution as a function of the un-absorbed 2-10 keV luminosity up
to redshift 4. We used the HELLAS2XMM sample combined with other published
catalogs, yielding a total of 508 AGN. Our best fit is obtained with a
luminosity-dependent density evolution (LDDE) model where low luminosity
(Lx~10^43 erg s^-1) AGN peak at z~0.7, while high luminosity AGN (Lx>10^45 erg
s^-1) peak at z~2.0. A pure luminosity evolution model (PLE) can instead be
rejected. There is evidence that the fraction of absorbed (Nh>10^22 cm^-2) AGN
decreases with the intrinsic X-ray luminosity, and increases with the redshift.
Our best fit solution provides a good fit to the observed counts, the cosmic
X-ray background, and to the observed fraction of absorbed AGN as a function of
the flux in the 10^-15<S(2-10)<10^-10 erg s^-1 cm^-2 range. We find that the
absorbed, high luminosity (Lx>10^44 erg s^-1) AGN have a density of 267 deg^-2
at fluxes S(2-10)>10^-15 erg s^-1 cm^-2. Using these results, we estimate a
density of supermassive black holes in the local Universe of 3.2 (h^2_70) x
10^5 M_sol Mpc^-3, which is consistent with the recent measurements of the
black hole mass function in the local galaxies.


title: Observational Constraints on a Variable Dark Energy Model

abstract:
  We study the effect of a phenomenological parameterized quintessence model on
low, intermediate and high redshift observations. At low and intermediate
redshifts, we use the Gold sample of supernova Type Ia (SNIa) data and recently
observed size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS),
to put constraint on the parameters of the quintessence model. At the high
redshift, the same fitting procedure is done using WAMP data, comparing the
location of acoustic peak with that obtain from the dark energy model. As a
complementary analysis in a flat universe, we combine the results from the
SNIa, CMB and SDSS. The best fit values for the model parameters are $\Omega_m
= 0.27^{+0.02}_{-0.02}$ (the present matter content) and
$w_0=-1.45^{+0.35}_{-0.60}$ (dark energy equation of state). Finally we
calculate the age of universe in this model and compare it with the age of old
stars and high redshift objects


title:
Smoothed Particle Magnetohydrodynamics III. Multidimensional tests and
  the div B = 0 constraint

abstract:
  In two previous papers (Price & Monaghan 2004a,b) (papers I,II) we have
described an algorithm for solving the equations of Magnetohydrodynamics (MHD)
using the Smoothed Particle Hydrodynamics (SPH) method. The algorithm uses
dissipative terms in order to capture shocks and has been tested on a wide
range of one dimensional problems in both adiabatic and isothermal MHD. In this
paper we investigate multidimensional aspects of the algorithm, refining many
of the aspects considered in papers I and II and paying particular attention to
the code's ability to maintain the div B = 0 constraint associated with the
magnetic field. In particular we implement a hyperbolic divergence cleaning
method recently proposed by Dedner et al. (2002) in combination with the
consistent formulation of the MHD equations in the presence of non-zero
magnetic divergence derived in papers I and II. Various projection methods for
maintaining the divergence-free condition are also examined. Finally the
algorithm is tested against a wide range of multidimensional problems used to
test recent grid-based MHD codes. A particular finding of these tests is that
in SPMHD the magnitude of the divergence error is dependent on the number of
neighbours used to calculate a particle's properties and only weakly dependent
on the total number of particles. Whilst many improvements could still be made
to the algorithm, our results suggest that the method is ripe for application
to problems of current theoretical interest, such as that of star formation.


title:
MAMBO 1.25mm observations of 3CR radio galaxies and quasars at z=1.5: On
  the debate of the unified schemes

abstract:
  In order to explore the nature of the 850 micron flux difference between
powerful radio galaxies and steep radio-spectrum quasars at z=1.5 reported by
Willott et al. (2002), we have observed 9 sources from their sample of 11
quasars at 1.25 mm. For 7 sources the 1.25 mm fluxes are much brighter than one
would expect from a purely thermal dust model fitted to the submm data,
providing evidence for the synchrotron nature of the observed 1.25 mm
radiation. If we extrapolate a power-law synchrotron spectrum to shorter
wavelengths, then for 6 of the 9 sources also the 850 micron fluxes are
dominated by synchrotron radiation. We discuss how far the (sub)-millimetre
data can be interpreted in accordance with the orientation-dependent unified
schemes for powerful radio galaxies and quasars. In this case the results
challenge the reported evidence for the receding torus model and for the
evolutionary trend of a declining dust luminosity with increasing projected
size of the radio lobes.


title:
XMM-Newton X-ray and optical observations of the globular clusters M 55
  and NGC 3201

abstract:
  We have observed two low concentration Galactic globular clusters with the
X-ray observatory XMM-Newton. We detect 47 faint X-ray sources in the direction
of M 55 and 62 in the field of view of NGC 3201. Using the statistical Log
N-Log S relationship of extragalactic sources derived from XMM-Newton Lockman
Hole observations, to estimate the background source population, we estimate
that very few of the sources (1.5+/-1.0) in the field of view of M 55 actually
belong to the cluster. These sources are located in the centre of the cluster
as we expect if the cluster has undergone mass segregation. NGC 3201 has
approximately 15 related sources, which are centrally located but are not
constrained to lie within the half mass radius. The sources belonging to this
cluster can lie up to 5 core radii from the centre of the cluster which could
imply that this cluster has been perturbed. Using X-ray (and optical, in the
case of M 55) colours, spectral and timing analysis (where possible) and
comparing these observations to previous X-ray observations, we find evidence
for sources in each cluster that could be cataclysmic variables, active
binaries, millisecond pulsars and possible evidence for a quiescent low mass
X-ray binary with a neutron star primary, even though we do not expect any such
objects in either of the clusters, due to their low central concentrations. The
majority of the other sources are background sources, such as AGN.


title: A broadband leptonic model for gamma-ray emitting microquasars

abstract:
  Observational and theoretical studies point to microquasars (MQs) as possible
counterparts of a significant fraction of the unidentified gamma-ray sources
detected so far. At present, a proper scenario to explain the emission beyond
soft X-rays from these objects is not known, nor what the precise connection is
between the radio and the high-energy radiation. We develop a new model where
the MQ jet is dynamically dominated by cold protons and radiatively dominated
by relativistic leptons. The matter content and power of the jet are both
related with the accretion process. The magnetic field is assumed to be close
to equipartition, although it is attached to and dominated by the jet matter.
For the relativistic particles in the jet, their maximum energy depends on both
the acceleration efficiency and the energy losses. The model takes into account
the interaction of the relativistic jet particles with the magnetic field and
all the photon and matter fields. Such interaction produces significant amounts
of radiation from radio to very high energies through synchrotron, relativistic
Bremsstrahlung, and inverse Compton (IC) processes. Variability of the emission
produced by changes in the accretion process (e.g. via orbital eccentricity) is
also expected. The effects of the gamma-ray absorption by the external photon
fields on the gamma-ray spectrum have been taken into account, revealing clear
spectral features that might be observed. This model is consistent to the
accretion scenario, energy conservation laws, and current observational
knowledge, and can provide deeper physical information of the source when
tested against multiwavelength data.


title:
Metallicities, relative ages and kinematics of stellar populations in
  omega Centauri

abstract:
  We present results of an extensive spectroscopic survey of Subgiant stars in
the stellar system omega Centauri. Using infrared CaII triplet lines, we
derived metallicities and radial velocities for more than 250 stars belonging
to different stellar populations of the system. We find that the most metal
rich component, the anomalous Sub Giant Branch (SGB-a), has a metallicity of
[Fe/H] -0.6 fully compatible with that determined along the anomalous Red Giant
Branch (RGB-a). Our analysis suggests that the age of this component and of the
other metal-intermediate (-1.4 < [Fe/H] < -1.0) stellar populations of the
system are all comparable to that of the dominant metal poor population within
2 Gyr regardless of any choice of helium abundance. These results impose severe
constraints on the time-scale of the enrichment process of this stellar system,
excluding the possibility of an extended star formation period. The radial
velocity analysis of the entire sample demonstrates that only the
metal-intermediate populations are kinematically cooler than the others.


title: The Calar Alto lunar occultation program: update and new results

abstract:
  We present an update of the lunar occultation program which is routinely
carried out in the near-IR at the Calar Alto Observatory. A total of 350 events
were recorded since our last report (Fors et al. 2004). In the course of eight
runs we have observed, among others, late-type giants, T-Tauri stars, and
infrared sources. Noteworthy was a passage of the Moon close to the galactic
center, which produced a large number of events during just a few hours in July
2004. Results include the determinations of the angular diameter of RZ Ari, and
the projected separations and brightness ratios for one triple and 13 binary
stars, almost all of which representing first time detections. Projected
separations range from 0.09arcsec to 0.007arcsec. We provide a quantitative
analysis of the performance achieved in our observations in terms of angular
resolution and sensitivity, which reach about 0.003arcsec and K~8.5mag,
respectively. We also present a statistical discussion of our sample, and in
particular of the frequency of detection of binaries among field stars.


title: Best median values for cosmological parameters

abstract:
  Our procedure to obtain best values for cosmological parameters from five
recent multiparameter fits is as follows. We first study the values quoted for
$r, \alpha_s, w+1 (w_0+1), w_1$ and $\Omega_k$, arriving at the conclusion that
they do not differ significantly from zero, and their correlations to other
parameters are insignificant. In what follows they can be therefore fixed. The
neutrino mass sum $\Sigma m_{\nu}$ also does not differ significantly from
zero, but since neutrinos are massive their sum must be included as a free
parameter. We then compare the values obtained in five large flat-space
determinations of the parameters $\Sigma m_{\nu}, \omega_b, \omega_m, h, \tau,
n_s, A_s$ and $\sigma_8$. For these we compute the medians and the
17-percentile and 83-percentile errors by a described procedure.


title: The Dark Gravity model predictions for Gravity Probe B

abstract:
  The previous version of this article gave erroneous predictions. The correct
uptodate predictions can be found in the section devoted to gravitomagnetism in
the living review of the Dark Gravity theory: gr-qc/0610079 The most natural
prediction is zero frame dragging and the same geodetic effect as predicted by
GR. However, a straightforward extension of the theory could lead to the same
frame-dragging as in GR.


title: DIM light on Black Hole X-ray Transients

abstract:
  The current model for the outburst of stellar-mass black holes X-ray binaries
is the disk instability model (DIM). An overview of this model and a discussion
of its theoretical and observational challenges are given.


title: Dark gravity and cosmology

abstract:
  The previous version of this article was a first attempt to confront the Dark
Gravity theory to cosmological data. However, more recent developments lead to
the conclusion that the cosmological principle is probably not valid in Dark
Gravity so that this kind of analysis is at best very premature. A more recent
and living review of the Dark Gravity theory can be found in gr-qc/0610079


title: The dark gravity model and the formation of large scale structures


title: The Remarkable Be Star HD110432

abstract:
  HD110432 has gained considerable attention because it is a hard, variable
X-ray source similar to gamma Cas. From time-serial echelle data obtained over
two weeks during 2005 January and February, we find several remarkable
characteristics in the star's optical spectrum. The line profiles show rapid
variations on some nights which can be most likely be attributed to irregularly
occurring and short-lived migrating subfeatures. Such features have only been
observed to date in gamma Cas and AB Dor, two stars for which it is believed
magnetic fields force circumstellar clouds to corotate over the stellar
surface. The star's optical spectrum also exhibits a number of mainly FeII and
HeI emission features with profiles typical of an optically thin disk viewed
edge-on. Using spectral synthesis techniques, we find that its temperature is
9800K +/-300K, that its projected area is a remarkably large 100 stellar areas,
and its emitting volume resides at a distance of 1 AU from the star. We also
find that the star's absorption profiles extend to +/-1000 km/s, a fact which
we cannot explain. Otherwise, HD110432 and gamma Cas share similarly peculiar
X-ray and optical characteristics such as high X-ray temperature, erratic X-ray
variability on timescales of a few hours, optical emission lines, and
submigrating features in optical line profiles. Because of these similarities,
we suggest that this star is a new member of a select class of "gamma Cas
analogs."


title: Spectral energy distribution of the gamma-ray microquasar LS 5039

abstract:
  The microquasar LS 5039 has recently been detected as a source of very high
energy (VHE) $\gamma$-rays. This detection, that confirms the previously
proposed association of LS 5039 with the EGRET source 3EG~J1824$-$1514, makes
of LS 5039 a special system with observational data covering nearly all the
electromagnetic spectrum. In order to reproduce the observed spectrum of LS
5039, from radio to VHE $\gamma$-rays, we have applied a cold matter dominated
jet model that takes into account accretion variability, the jet magnetic
field, particle acceleration, adiabatic and radiative losses, microscopic
energy conservation in the jet, and pair creation and absorption due to the
external photon fields, as well as the emission from the first generation of
secondaries. The radiative processes taken into account are synchrotron,
relativistic Bremsstrahlung and inverse Compton (IC). The model is based on a
scenario that has been characterized with recent observational results,
concerning the orbital parameters, the orbital variability at X-rays and the
nature of the compact object. The computed spectral energy distribution (SED)
shows a good agreement with the available observational data.


title: Comment on "Damping of Tensor Modes in Cosmology"

abstract:
  We provide an analytic solution to the short wave length limit of the
integro-differential equation describing the damping of the tensor modes of
gravitational waves.