title:
A Computational Guide to Physics of Eclipsing Binaries. Paper I.
  Demonstrations and Perspectives

abstract:
  PHOEBE (PHysics Of Eclipsing BinariEs) is a modeling package for eclipsing
binary stars, built on top of the widely used WD program (Wilson & Devinney
1971). This introductory paper overviews most important scientific extensions
(incorporating observational spectra of eclipsing binaries into the
solution-seeking process, extracting individual temperatures from observed
color indices, main-sequence constraining and proper treatment of the
reddening), numerical innovations (suggested improvements to WD's Differential
Corrections method, the new Nelder & Mead's downhill Simplex method) and
technical aspects (back-end scripter structure, graphical user interface).
While PHOEBE retains 100% WD compatibility, its add-ons are a powerful way to
enhance WD by encompassing even more physics and solution reliability. The
operability of all these extensions is demonstrated on a synthetic
main-sequence test binary; applications to real data will be published in
follow-up papers. PHOEBE is released under the GNU General Public License,
which guarranties it to be free, open to anyone interested to join in on future
development.


title: Bulk viscosity driving the acceleration of the Universe

abstract:
  The possibility that the present acceleration of the universe is driven by a
kind of viscous fluid is exploited. At background level this model is similar
to the generalized Chaplygin gas model (GCGM). But, at perturbative level, the
viscous fluid exhibits interesting properties. In particular the oscillations
in the power spectrum that plagues the GCGM are not present. Possible
fundamental descriptions for this viscous dark energy are discussed.


title:
Self-Calibration of Cluster Dark Energy Studies: Observable-Mass
  Distribution

abstract:
  The exponential sensitivity of cluster number counts to the properties of the
dark energy implies a comparable sensitivity to not only the mean but also the
actual_distribution_ of an observable mass proxy given the true cluster mass.
For example a 25% scatter in mass can provide a ~50% change in the number
counts at z~2 for the upcoming SPT survey. Uncertainty in the scatter of this
amount would degrade dark energy constraints to uninteresting levels. Given the
shape of the actual mass function, the properties of the distribution may be
internally monitored by the shape of the_observable_ mass function. An
arbitrary evolution of the scatter of a mass-independent Gaussian distribution
may be self-calibrated to allow a measurement of the dark energy equation of
state of Delta w ~0.1. External constraints on the mass_variance_ of the
distribution that are more accurate than Delta var < 0.01 at z~1 can further
improve constraints by up to a factor of 2. More generally, cluster counts and
their sample variance measured as a function of the observable provide internal
consistency checks on the assumed form of the observable-mass distribution that
will protect against misinterpretation of the dark energy constraints.


title: Bounds on Cosmic Strings from WMAP and SDSS

abstract:
  We find the constraints from WMAP and SDSS data on the fraction of
cosmological fluctuations sourced by local cosmic strings using a Markov Chain
Monte Carlo (MCMC) analysis. In addition to varying the usual 6 cosmological
parameters and the string tension ($\mu$), we also varied the amount of
small-scale structure on the strings. Our results indicate that cosmic strings
can account for up to 7 (14)% of the total power of the microwave anisotropy at
68 (95)% confidence level. The corresponding bound on the string mass per unit
length, within our string model, is $G\mu < 1.8 (2.7) \times 10^{-7}$ at 68
(95)% c.l., where this constraint has been altered from what appears below
following the correction of errors in our cosmic string code outlined in a
recent erratum, astro-ph/0604141. We also calculate the B-type polarization
spectra sourced by cosmic strings and discuss the prospects of their detection.


title:
Evolution in the Cluster Early-type Galaxy Size-Surface Brightness
  Relation at z =~ 1

abstract:
  We investigate the evolution in the distribution of surface brightness, as a
function of size, for elliptical and S0 galaxies in the two clusters RDCS
J1252.9-2927, z=1.237 and RX J0152.7-1357, z=0.837. We use multi-color imaging
with the Advanced Camera for Surveys on the Hubble Space Telescope to determine
these sizes and surface brightnesses. Using three different estimates of the
surface brightnesses, we find that we reliably estimate the surface brightness
for the galaxies in our sample with a scatter of < 0.2 mag and with systematic
shifts of \lesssim 0.05 mag. We construct samples of galaxies with early-type
morphologies in both clusters. For each cluster, we use a magnitude limit in a
band which closely corresponds to the rest-frame B, to magnitude limit of M_B =
-18.8 at z=0, and select only those galaxies within the color-magnitude
sequence of the cluster or by using our spectroscopic redshifts. We measure
evolution in the rest-frame B surface brightness, and find -1.41 \+/- 0.14 mag
from the Coma cluster of galaxies for RDCS J1252.9-2927 and -0.90 \+/- 0.12 mag
of evolution for RX J0152.7-1357, or an average evolution of (-1.13 \+/- 0.15)
z mag. Our statistical errors are dominated by the observed scatter in the
size-surface brightness relation, sigma = 0.42 \+/- 0.05 mag for RX
J0152.7-1357 and sigma = 0.76 \+/- 0.10 mag for RDCS J1252.9-2927. We find no
statistically significant evolution in this scatter, though an increase in the
scatter could be expected. Overall, the pace of luminosity evolution we measure
agrees with that of the Fundamental Plane of early-type galaxies, implying that
the majority of massive early-type galaxies observed at z =~ 1 formed at high
redshifts.


title: On gravitational lensing by quadrupole potentials

abstract:
  We study gravitational lensing by quadrupole potentials within the linearized
gravity approximation and the integration over the unperturbed photon
trajectory. It is well known that the quadrupole potential contribution to the
deviation angle is much smaller than that of the monopole one. We show,
however, that quadrupole potentials can change the photon polarization vector,
but there is no contribution from the monopole term to the first order. The
effect is maximal when the axis of the quadrupole is tangential to the photon
trajectory and it is proportional to the frequency(rate) of the quadrupole
moment of the deflector. The second order correction of the monopole potential
to the polarization is canceled away by the renormalization of the polarization
vector.


title:
Evolution in the Color-Magnitude Relation of Early-Type Galaxies in
  Clusters of Galaxies at z~=1

abstract:
  We present a study of the color evolution of elliptical and S0 galaxies in
six clusters of galaxies inside the redshift range 0.78 < z < 1.27. For each
cluster, we used imaging from the Hubble Space Telescope to determine
morphological types by both an automated technique and from visual inspection.
We performed simulations to determine the accuracy of the automated
classifications and found a success rate of ~75% at m(L*) or brighter
magnitudes for most of our HST imaging data with the fraction of late--type
galaxies identified as early--type galaxies to be ~10% at m(L*) to ~20% at
m(L*)+2. From ground based optical and near-infrared imaging, we measured the
zero-point and scatter in the color--magnitude relation of the early-type
populations, which when combined with Stanford et al. (1998), yields a sample
of cluster early--type galaxies that span a lookback time of 9 gigayears from
the present. We see the colors of the early--type cluster members become bluer
with increasing redshift. We fit a set of models to the change in the color as
a function of redshift with the best fitting values ranging from a formation
redshift of 3^+2_-1 to 5_-3. The large scatter in resulting formation epochs,
which depends on the details of the models used, implies that we can conclude
that the oldest stars in the elliptical galaxies appear to have formed at
redshifts of z>3. We find possible evolution in the scatter of the colors, with
some high redshift clusters showing scatter as small as the Coma cluster but
others showing much larger scatter. Those clusters with a small scatter imply
either a formation redshift of at least z ~ 3 or a smaller spread in the range
of formation redshifts at lower redshifts, assuming a Gaussian distribution of
star-formation around the mean epoch.


title: Pioneer anomaly? Gravitational pull due to the Kuiper belt

abstract:
  In this work we study the gravitational influence of the material extending
from Uranus orbit to the Kuiper belt and beyond on objects moving within these
regions. We conclude that a density distribution given by $\rho(r)=\frac{1}{r}$
(for $r\geq 20 UA$) generates a constant acceleration towards the Sun on those
objects, which, with the proper amount of mass, accounts for the blue shift
detected on the Pioneers space crafts. We also discuss the effect of this
gravitational pull on Neptune, and comment on the possible origin of such a
matter distribution.


title: A Merger-Driven Scenario for Cosmological Disk Galaxy Formation

abstract:
  (Abridged) The violent hierarchical nature of the LCDM cosmology poses
serious difficulties for the formation of disk galaxies. To help resolve these
issues, we describe a new, merger-driven scenario for the cosmological
formation of disk galaxies at high redshifts that supplements the standard
model based on dissipational collapse.In this picture, large gaseous disks may
be produced from high-angular momentum mergers of systems that are
gas-dominated, i.e. M_gas/(M_gas +M_star > 0.5 at the height of the merger.
Pressurization from the multiphase structure of the interstellar medium
prevents the complete conversion of gas into stars during the merger, and if
enough gas remains to form a disk, the remnant eventually resembles a disk
galaxy. We perform numerical simulations of galaxy mergers to study how
supernovae feedback strength, supermassive black hole growth and feedback,
progenitor gas fraction, merger mass-ratio, and orbital geometry impact the
formation of remnant disks. We find that disks can build angular momentum
through mergers and the degree of rotational support of the baryons in the
merger remnant is primarily related to feedback processes associated with star
formation. Disk-dominated remnants are restricted to form in mergers that are
gas-dominated at the time of final coalescence and gas-dominated mergers
typically require extreme progenitor gas fractions (>80%). We also show that
the formation of rotationally-supported stellar systems in mergers is not
restricted to idealized orbits, or major or minor mergers. We suggest that the
hierarchical nature of the LCDM cosmology and the physics of the interstellar
gas may act together to form spiral galaxies by building the angular momentum
of disks through early, gas-dominated mergers.


title: NGC 770: A Counter-Rotating Core in a Low-Luminosity Elliptical Galaxy

abstract:
  We present evidence for a counter-rotating core in the low-luminosity (M_B =
-18.2) elliptical galaxy NGC 770 based on internal stellar kinematic data. This
counter-rotating core is unusual as NGC 770 is not the primary galaxy in the
region and it lies in an environment with evidence of on-going tidal
interactions. We discovered the counter-rotating core via single-slit Keck/ESI
echelle spectroscopy; subsequent integral field spectroscopy was obtained with
the Gemini/GMOS IFU. The counter-rotating region has a peak rotation velocity
of 21 km/s as compared to the main galaxy's rotation speed of greater than 45
km/s in the opposite direction. The counter-rotating region extends to a radius
of 4'' (0.6 kpc), slightly smaller than the half-light radius of the galaxy
which is 5.3'' (0.8 kpc) and is confined to a disk whose scale height is less
than 0.8'' (0.1 kpc). We compute an age and metallicity of the inner
counter-rotating region of 3 +/- 0.5 Gyr and [Fe/H] = 0.2 +/- 0.2 dex, based on
Lick absorption-line indices. The lack of other large galaxies in this region
limits possible scenarios for the formation of the counter-rotating core. We
discuss several scenarios and favor one in which NGC 770 accreted a small
gas-rich dwarf galaxy during a very minor merging event. If this scenario is
correct, it represents one of the few known examples of merging between two
dwarf-sized galaxies.


title:
The Magnetic Field of the Large Magellanic Cloud: A New Way of Studying
  Galactic Magnetism

abstract:
  We present a study of the Faraday rotation of extragalactic sources lying
behind the Large Magellanic Cloud. These data represent the most detailed study
yet of magnetic field structures in any external galaxy, and are a
demonstration of how magnetic fields in galaxies will best be studied with
future instruments.


title:
Stellar Lyman-alpha Emission Lines in the Hubble Space Telescope
  Archive: Intrinsic Line Fluxes and Absorption from the Heliosphere and
  Astrospheres

abstract:
  We search the Hubble Space Telescope (HST) archive for previously unanalyzed
observations of stellar H I Lyman-alpha emission lines, our primary purpose
being to look for new detections of Lyman-alpha absorption from the outer
heliosphere, and to also search for analogous absorption from the astrospheres
surrounding the observed stars. The astrospheric absorption is of particular
interest because it can be used to study solar-like stellar winds that are
otherwise undetectable. We find and analyze 33 HST Lyman-alpha spectra in the
archive. All the spectra were taken with the E140M grating of the Space
Telescope Imaging Spectrograph (STIS) instrument on board HST. The HST/STIS
spectra yield 4 new detections of heliospheric absorption (70 Oph, Xi Boo, 61
Vir, and HD 165185) and 7 new detections of astrospheric absorption (EV Lac, 70
Oph, Xi Boo, 61 Vir, Delta Eri, HD 128987, and DK UMa), doubling the previous
number of heliospheric and astrospheric detections. When combined with previous
results, 10 of 17 lines of sight within 10 pc yield detections of astrospheric
absorption. This high detection fraction implies that most of the ISM within 10
pc must be at least partially neutral, since the presence of H I within the ISM
surrounding the observed star is necessary for an astrospheric detection. In
contrast, the detection percentage is only 9.7% (3 out of 31) for stars beyond
10 pc. Our Lyman-alpha analyses provide measurements of ISM H I and D I column
densities for all 33 lines of sight, and we discuss some implications of these
results. Finally, we measure chromospheric Lyman-alpha fluxes from the observed
stars. We use these fluxes to determine how Lyman-alpha flux correlates with
coronal X-ray and chromospheric Mg II emission, and we also study how
Lyman-alpha emission depends on stellar rotation.


title: Weak Lensing Mass Reconstruction using Wavelets

abstract:
  This paper presents a new method for the reconstruction of weak lensing mass
maps. It uses the multiscale entropy concept, which is based on wavelets, and
the False Discovery Rate which allows us to derive robust detection levels in
wavelet space. We show that this new restoration approach outperforms several
standard techniques currently used for weak shear mass reconstruction. This
method can also be used to separate E and B modes in the shear field, and thus
test for the presence of residual systematic effects. We concentrate on large
blind cosmic shear surveys, and illustrate our results using simulated shear
maps derived from N-Body Lambda-CDM simulations with added noise corresponding
to both ground-based and space-based observations.


title:
Cosmological non-Gaussian Signature Detection: Comparing Performance of
  Different Statistical Tests

abstract:
  Currently, it appears that the best method for non-Gaussianity detection in
the Cosmic Microwave Background (CMB) consists in calculating the kurtosis of
the wavelet coefficients. We know that wavelet-kurtosis outperforms other
methods such as the bispectrum, the genus, ridgelet-kurtosis and
curvelet-kurtosis on an empirical basis, but relatively few studies have
compared other transform-based statistics, such as extreme values, or more
recent tools such as Higher Criticism (HC), or proposed `best possible' choices
for such statistics.
  In this paper we consider two models for transform-domain coefficients: (a) a
power-law model, which seems suited to the wavelet coefficients of simulated
cosmic strings; and (b) a sparse mixture model, which seems suitable for the
curvelet coefficients of filamentary structure. For model (a), if power-law
behavior holds with finite 8-th moment, excess kurtosis is an asymptotically
optimal detector, but if the 8-th moment is not finite, a test based on extreme
values is asymptotically optimal. For model (b), if the transform coefficients
are very sparse, a recent test, Higher Criticism, is an optimal detector, but
if they are dense, kurtosis is an optimal detector. Empirical wavelet
coefficients of simulated cosmic strings have power-law character, infinite
8-th moment, while curvelet coefficients of the simulated cosmic strings are
not very sparse. In all cases, excess kurtosis seems to be an effective test in
moderate-resolution imagery.


title: Optimal Estimation of Non-Gaussianity

abstract:
  We systematically analyze the primordial non-Gaussianity estimator used by
the Wilkinson Microwave Anisotropy Probe (WMAP) science team with the basic
ideas of estimation theory in order to see if the limited Cosmic Microwave
Background (CMB) data is being optimally utilized. The WMAP estimator is based
on the implicit assumption that the CMB bispectrum, the harmonic transform of
the three-point correlation function, contains all of the primordial
non-Gaussianity information in a CMB map. We first demonstrate that the
Signal-to-Noise (S/N) of an estimator based on CMB three-point correlation
functions is significantly larger than the S/N of any estimator based on
higher-order correlation functions; justifying our choice to focus on the
three-point correlation function. We then conclude that the estimator based on
the three-point correlation function, which was used by WMAP, is optimal,
meaning it saturates the Cramer-Rao Inequality when the underlying CMB map is
nearly Gaussian. We quantify this restriction by demonstrating that the
suboptimal character of our estimator is proportonal to the square of the
fiducial non-Gaussianity, which is already constrained to be extremely small,
so we can consider the WMAP estimator to be optimal in practice. Our
conclusions do not depend on the form of the primordial bispectrum, only on the
observationally established weak levels of primordial non-Gaussianity.


title: The DEEP Groth Strip Survey. I. The Sample

abstract:
  The Deep Extragalactic Exploratory Probe (DEEP) is a multi-phase research
program dedicated to the study of the formation and evolution of galaxies and
of large scale structure in the distant Universe. This paper describes the
first five-year phase, denoted DEEP1. A series of ten DEEP1 papers will discuss
a range of scientific topics (e.g., the study of photometric and spectral
properties of a general distant galaxy survey, the evolution observed in galaxy
populations of varied morphologies). The observational basis for these studies
is the Groth Survey Strip field, a 127 square arcminute region which has been
observed with the Hubble Space Telescope in both broad I-band and V-band
optical filters and with the Low Resolution Imaging Spectrograph on the Keck
Telescopes. Catalogs of photometric and structural parameters have been
constructed for 11,547 galaxies and stars at magnitudes brighter than 29, and
spectroscopy has been conducted for a magnitude-color weighted subsample of 818
objects. We evaluate three independent techniques for constructing an imaging
catalog for the field from the HST data, and discuss the depth and sampling of
the resultant catalogs. The selection of the spectroscopic subsample is
discussed, and we describe the multifaceted approach taken to prioritizing
objects of interest for a variety of scientific subprograms. A series of Monte
Carlo simulations then demonstrates that the spectroscopic subsample can be
adequately modeled as a simple function of magnitude and color cuts in the
imaging catalog.


title:
A Comparison of surface brightness profiles for ultra-compact dwarfs and
  dwarf elliptical nuclei: implications for the `threshing' scenario

abstract:
  Using imaging from the Hubble Space Telescope, we derive surface brightness
profiles for ultra-compact dwarfs in the Fornax cluster and for the nuclei of
dwarf elliptical galaxies in the Virgo cluster. Ultra-compact dwarfs are more
extended and have higher surface brightnesses than typical dwarf nuclei, while
the luminosities, colors, and sizes of the nuclei are closer to those of
Galactic globular clusters. This calls into question the production of
ultra-compact dwarfs via ``threshing'' whereby the lower surface brightness
envelope of a dwarf elliptical is removed by tidal processes, leaving behind a
bare nucleus. Threshing may still be a viable model if the relatively bright
Fornax ultra compact dwarfs considered here are descended from dwarf
ellipticals whose nuclei are at the upper end of their luminosity and size
distributions.


title: Stability of strange stars (SS) under radial oscillation

abstract:
  A realistic Equation of State (EOS) leads to strange stars (ReSS) which are
compact in the mass radius plot, close to the Schwarzchild limiting line (Dey
et al. 1998). We carry out a stability analysis under radial oscillations and
compare with the EOS of other SS models. We find that the ReSS is stable and an
M-R region can be identified to that effect.


title:
Multiplicity Amongst Wide Brown Dwarf Companions to Nearby Stars: Gliese
  337CD

abstract:
  We present Lick Natural Guide Star Adaptive Optics observations of the L8
brown dwarf Gliese 337C, which is resolved for the first time into two closely
separated (0"53+/-0"03), nearly equal magnitude components with a K_s flux
ratio of 0.93+/-0.10. Companionship is inferred from the absence of a 3"6
offset source in 2MASS or photographic plate images, implying that the observed
secondary component is a co-moving late-type dwarf. With a projected separation
of 11 AU and nearly equal-magnitude components, Gliese 337CD has properties
similar to other known companion and field substellar binaries. Its long
orbital period (estimated to be ~140-180 yr) inhibits short-term astrometric
mass measurements, but the Gliese 337CD system is ideal for studying the L/T
transition at a fixed age and metallicity. From a compilation of all known
widely separated (>~100 AU) stellar/brown dwarf multiple systems, we find
evidence that the binary fraction of brown dwarfs in these systems is notably
higher than that of field brown dwarfs, 45(+15)(-13)% versus 18(+7)(-4)% for
analogous samples. We speculate on possible reasons for this difference,
including the possibility that dynamic (ejection) interactions which may form
such wide pairs preferentially retain binary secondaries due to their greater
combined mass and/or ability to absorb angular momentum.


title: Indirect Search for Dark Matter

abstract:
  Possible dark matter candidates are reviewed as well as indirect search
methods based on annihilation or decay channels of these particles. Neutralino
is presently the best particle candidate and its annihilation produces high
energy neutrinos, antiprotons, positrons and gamma-rays. To date, only upper
limits on neutrino fluxes from the center of the Earth or the Sun, were
established by different experiments. Antiprotons detected by the BESS
collaboration, if issued from the follow up hadronization of the annihilation
process, exclude neutralino masses higher than 100 GeV. The EGRET gamma-ray
residual emission seen at high galactic latitudes above 1 GeV could be
explained by neutralino annihilations if: i) the dark matter profile is "cored"
and ii) the neutralino mass is < 50 GeV. Sterile neutrinos in the keV mass
range are a possible candidate to constitute warm dark matter. These particles
may provide an adequate free streaming mass able to solve "some" difficulties
present in the cold dark matter scenario at small scales and could also explain
the natal kick of pulsars. MeV particles, dubbed "light" dark matter, proposed
to explain the extended 511 keV line emission from the galactic center will
also be discussed.


title:
Effects of gravitational darkening on the determination of fundamental
  parameters in fast rotating B-type stars

abstract:
  In this paper we develop a calculation code to account for the effects
carried by fast rotation on the observed spectra of early-type stars. Stars are
assumed to be in rigid rotation and the grid of plane-parallel model
atmospheres used to represent the gravitational darkening are calculated by
means of a non-LTE approach. Attention is paid on the relation between the
apparent and parent non-rotating counterpart stellar fundamental parameters and
apparent and true vsini parameters as a function of the rotation rate
Omega/Omega_c, stellar mass and inclination angle. It is shown that omission of
gravitational darkening in the analysis of chemical abundances of CNO elements
can produce systematic overestimation or underestimation, depending on the
lines used, rotational rate and inclination angle. The proximity of Be stars to
the critical rotation is re-discussed by correcting not only the vsini of 130
Be stars, but also their effective temperature and gravity to account for
stellar rotationally induced geometrical distortion and for the concomitant
gravitational darkening effect. We concluded that the increase of the vsini
estimate is accompanied by an even higher value of the stellar equatorial
critical velocity, so that the most probable average rate of angular velocity
of Be stars attains Omega/Omega_c ~ 0.88.


title: Predicted and empirical radii of RR Lyrae stars

abstract:
  We present new theoretical Period-Radius-Metallicity (PRZ) relations for RR
Lyrae stars. Current predictions are based on a large set of nonlinear,
convective models that cover a broad range of chemical abundances and input
parameters. We also provide new and homogeneous estimates of angular diameters
for a sample of field RR Lyrae stars using a recent calibration of the
Barnes-Evans surface brightness relation. Predicted and empirical radii are,
within the errors, in reasonable agreement, but in the short-period range the
latter present a larger scatter. As a working hypothesis we suggest that this
discrepancy might be due to the occurrence either of nonlinear features such as
bumps or a steep rising branch. New distance determination for RR Lyr itself is
in very good agreement with HST trigonometric parallax and with pulsation
parallax.


title: Long-lag, Wide-Pulse Gamma-Ray Bursts

abstract:
  Currently, the best available probe of the early phase of gamma-ray burst
(GRB) jet attributes is the prompt gamma-ray emission, in which several
intrinsic and extrinsic variables determine GRB pulse evolution. Bright,
usually complex bursts have many narrow pulses that are difficult to model due
to overlap. However, the relatively simple, long spectral lag, wide-pulse
bursts may have simpler physics and are easier to model. In this work we
analyze the temporal and spectral behavior of wide pulses in 24 long-lag
bursts, using a pulse model with two shape parameters -- width and asymmetry --
and the Band spectral model with three shape parameters. We find that pulses in
long-lag bursts are distinguished both temporally and spectrally from those in
bright bursts: the pulses in long spectral lag bursts are few in number, and ~
100 times wider (10s of seconds), have systematically lower peaks in nu*F(nu),
harder low-energy spectra and softer high-energy spectra. We find that these
five pulse descriptors are essentially uncorrelated for our long-lag sample,
suggesting that at least five parameters are needed to model burst temporal and
spectral behavior. However, pulse width is strongly correlated with spectral
lag; hence these two parameters may be viewed as mutual surrogates. We infer
that accurate formulations for estimating GRB luminosity and total energy will
depend on several gamma-ray attributes, at least for long-lag bursts. The
prevalence of long-lag bursts near the BATSE trigger threshold, their
predominantly low nF(n) spectral peaks, and relatively steep upper power-law
spectral indices indicate that Swift will detect many such bursts.


title:
The first observed stellar X-ray flare oscillation: Constraints on the
  flare loop length and the magnetic field

abstract:
  We present the first X-ray observation of an oscillation during a stellar
flare. The flare occurred on the active M-type dwarf AT Mic and was observed
with XMM-Newton. The soft X-ray light curve (0.2-12 keV) is investigated with
wavelet analysis. The flare's extended, flat peak shows clear evidence for a
damped oscillation with a period of around 750 s, an exponential damping time
of around 2000 s, and an initial, relative peak-to-peak amplitude of around
15%. We suggest that the oscillation is a standing magneto-acoustic wave tied
to the flare loop, and find that the most likely interpretation is a
longitudinal, slow-mode wave, with a resulting loop length of (2.5 +- 0.2) e10
cm. The local magnetic field strength is found to be (105 +- 50) G. These
values are consistent with (oscillation-independent) flare cooling time models
and pressure balance scaling laws. Such a flare oscillation provides an
excellent opportunity to obtain coronal properties like the size of a flare
loop or the local magnetic field strength for the otherwise
spatially-unresolved star.


title: Quantum Electrodynamical Effects in Dusty Plasmas

abstract:
  A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is
predicted. Its existence depends on the interaction of an intense circularly
polarized electromagnetic wave with a dusty plasma, where quantum
electrodynamical photon-photon scattering is taken into account. Specifically,
we consider a dusty electron-positron-ion plasma, and show that the propagation
of the new mode is admitted. It could be of significance for the physics of
supernova remnants and in neutron star formation.


title: Testing GR with the Double Pulsar: Recent Results

abstract:
  This first ever double pulsar system consists of two pulsars orbiting the
common center of mass in a slightly eccentric orbit of only 2.4-hr duration.
The pair of pulsars with pulse periods of 22 ms and 2.8 sec, respectively,
confirms the long-proposed recycling theory for millisecond pulsars and
provides an exciting opportunity to study the works of pulsar magnetospheres by
a very fortunate geometrical alignment of the orbit relative to our
line-of-sight. In particular, this binary system represents a truly unique
laboratory for relativistic gravitational physics. This contribution serves as
an update on the currently obtained results and their consequences for the test
of general relativity in the strong-field regime. A complete and more
up-to-date report of the timing results will be presented elsewhere shortly.


title: The first WIMPy halos

abstract:
  Dark matter direct and indirect detection signals depend crucially on the
dark matter distribution. While the formation of large scale structure is
independent of the nature of the cold dark matter (CDM), the fate of
inhomogeneities on sub-galactic scales, and hence the present day CDM
distribution on these scales, depends on the micro-physics of the CDM
particles. We study the density contrast of Weakly Interacting Massive
Particles (WIMPs) on sub-galactic scales. We calculate the damping of the
primordial power spectrum due to collisional damping and free-streaming of
WIMPy CDM and show that free-streaming leads to a CDM power spectrum with a
sharp cut-off at about $10^{-6} M_\odot$. We also calculate the transfer
function for the growth of the inhomogeneities in the linear regime, taking
into account the suppression in the growth of the CDM density contrast after
matter-radiation equality due to baryons and show that our analytic results are
in good agreement with numerical calculations. Combining the transfer function
with the damping of the primordial fluctuations we produce a WMAP normalized
primordial CDM power spectrum, which can serve as an input for high resolution
CDM simulations. We find that the smallest inhomogeneities typically have
co-moving radius of about 1 pc and enter the non-linear regime at a redshift of
$60 \pm 20$. We study the effect of scale dependence of the primordial power
spectrum on these numbers and also use the spherical collapse model to make
simple estimates of the properties of the first generation of WIMP halos to
form. We find that the very first WIMPy halos may have a significant impact on
indirect dark matter searches.


title:
Warp signatures of the Galactic disk as seen in mid infrared from
  Midcourse Space Experiment

abstract:
  The gross features in the distribution of stars as well as warm (T >~ 100 K)
interstellar dust in the Galactic disk have been investigated using the recent
mid infrared survey by Midcourse Space Experiment (MSX) at 8, 12, 14 & 21
micron bands. An attempt has been made to determine the location of the
Galactic mid-plane at various longitudes, using two approaches : (i) fitting
exponential functions to the latitude profiles and (ii) statistical
indicators.The former method is successful for the inner Galaxy (-90 < l < 90),
and quantifies characteristic angular scales along latitude, which have been
translated to linear scale heights (z_h) and radial length scales (R_l) using
geometric description of the Galactic disk. The distribution of warm dust in
the Galactic disk is found to be characterised by R_l < 6 kpc and 60 < z_h <~
100 pc, in agreement with other studies. The location of the Galactic mid-plane
as a function of longitude, for stars as well as warm dust, has been searched
for signatures of warp-like feature in their distribution, by fitting sinusoid
with phase and amplitude as parameters. In every case, the warp signature has
been detected. An identical analysis of the DIRBE/COBE data in all its ten
bands covering the entire infrared spectrum (1.25-240 micron), also leads to
detection of warp signatures with very similar phase as found from the MSX
data. Our results have been compared with those from other studies.


title: Understanding galaxy formation with ISO deep surveys

abstract:
  We present the results obtained through the various ISO extragalactic deep
surveys. While IRAS revealed the existence of galaxies forming stars at a rate
of a few tens (LIRGs) or even hundreds (ULIRGs) solar masses in the local
universe, ISO not only discovered that these galaxies were already in place at
redshift one, but also that they are not the extreme objects that we once
believed them to be. Instead they appear to play a dominant role in shaping
present-day galaxies as reflected by their role in the cosmic history of star
formation and in producing the cosmic infrared background detected by the COBE
satellite in the far infrared to sub-millimeter range.


title:
Three XMM-Newton observations of the Anomalous X-ray Pulsar 1E
  1048.1-5937: long term variations in spectrum and pulsed fraction

abstract:
  We report the results of a recent (July 2004) XMM-Newton Target of
Opportunity observation of the Anomalous X-ray pulsar 1E 1048.1-5937, together
with a detailed re-analysis of previous observations carried out in 2000 and
2003. In July 2004 the source had a 2-10 keV flux of 6.2$\times10^{-12}$ erg
cm$^{-2}$ s$^{-1}$ and a pulsed fraction P$_F$=0.68. The comparison of the
three data sets shows the presence of an anti-correlation between flux and
pulsed fraction, implying that previous estimates of the source energetics
based on the assumption of a large and constant pulsed fraction might be
significantly underestimated. The source spectrum is well described by a power
law plus blackbody model (kT~0.63 keV, photon index $\Gamma$~2.7-3.5) or,
alternatively, by the sum of two blackbodies of which the hotter is Comptonized
by relativistic electrons. In this case the temperatures are kT${_1}$~0.2-0.3
keV and kT${_2}$~0.4-0.5 keV and the emitting area of the cooler component is
consistent with the whole neutron star surface. The long term luminosity
variation of a factor >~2 is accompanied by relatively small variations in the
spectral shape. Phase resolved spectroscopy indicates a harder spectrum in
correspondence of the pulse maximum. No spectral features have been detected
with 4$\sigma$ limits on the equivalent width in the range ~10-220 eV,
depending on line energy and width.


title: Radial velocity moments of dark matter haloes

abstract:
  Using cosmological N-body simulations we study the radial velocity
distribution in dark matter haloes focusing on the lowest-order even moments,
dispersion and kurtosis. We determine the properties of ten massive haloes in
the simulation box approximating their density distribution by the NFW formula
characterized by the virial mass and concentration. We also calculate the
velocity anisotropy parameter of the haloes and find it mildly radial and
increasing with distance from the halo centre. The radial velocity dispersion
of the haloes shows a characteristic profile with a maximum, while the radial
kurtosis profile decreases with distance starting from a value close to
Gaussian near the centre. We therefore confirm that dark matter haloes possess
intrinsically non-Gaussian, flat-topped velocity distributions. We find that
the radial velocity moments of the simulated haloes are quite well reproduced
by the solutions of the Jeans equations obtained for the halo parameters with
the anisotropy measured in the simulations. We also study the radial velocity
moments for a composite cluster made of ten haloes out to ten virial radii. In
this region the velocity dispersion decreases systematically to reach the value
of the background, while kurtosis increases from below to above the Gaussian
value of 3 signifying a transition from a flat-topped to a strongly peaked
velocity distribution with respect to the Gaussian, which can be interpreted as
the dominance of ordered flow with a small dispersion. We illustrate the
transition by showing explicitly the velocity distribution of the composite
cluster in a few radial bins.


title: Radio synchrotron spectra for a leaky box approximation

abstract:
  The synchrotron emission observed from many astrophysical objects is commonly
modelled to arise from relativistic electrons in an emission region occupied by
a spatially homogeneous, but tangled magnetic field. However, we know that
magnetic fields embedded in ionised gases tend to form flux ropes interspersed
with regions of much lower magnetic field strengths. Here we develop a full
description of the evolution of the energy distribution of relativistic
electrons in a plasma divided into two distinct regions with different
strengths of the magnetic field. Electrons are able to continuously leak from
the low-field region into the high-field region. The model becomes fully
analytic for physically reasonable assumptions. We show that such a leaky box
model produces two distinct breaks in the electron energy distributions which
give rise to three breaks in the resulting synchrotron spectrum. The spectral
slopes in between the breaks are in general not constant and thus allow for
significant curvature of the spectrum. These spectra are consistent with
spatially resolved observations of the radio spectra of the lobes of radio
galaxies. The exact form of the spectra depends on the adopted diffusion rate.
The leaky box model significantly extends the time over which synchrotron
emission can be detected at a given frequency compared to the usually assumed
case of homogeneous magnetic fields. The spectral ages inferred for the
electron population from standard techniques for the leaky box model are
considerably younger than their real age.


title:
Homogeneous Photometry IV: On the Standard Sequence in the Globular
  Cluster NGC2419

abstract:
  A new analysis of CCD-based BVRI broad-band photometry for the globular
cluster NGC2419 is presented, based on 340 CCD images either donated by
colleagues or retrieved from public archives. The calibrated results have been
made available through my Web site. I compare the results of my analysis with
those of an independent analysis of a subset of these data by Saha et al.
(2005, PASP, 117, 37), who have found a color-dependent discrepancy of up to
0.05 mag between their I-band photometry and mine for stars in this cluster. I
conclude that a major part of the discrepancy appears to be associated with
small (a few hundredths of a second) shutter-timing errors in the MiniMos
camera on the WIYN 3.5-m telescope. Smaller contributions to the anomaly likely
come from (a) a color-scale error with a maximum amplitude of ~ +/-0.02 mag in
my secondary standard list as of September 2004; and (b) statistical effects
arising from the previous study's use of a relatively small number of
standard-star observations to determine a comparatively large number of fitting
parameters in the photometric transformations.


title: Supporting the GLAST User Community

abstract:
  The Gamma-ray Large Area Space Telescope (GLAST) Science Support Center
(GSSC) is the scientific community's interface with GLAST. The GSSC will
provide data, analysis software and documentation. In addition, the GSSC will
administer the guest investigator program for NASA HQ. Consequently, the GSSC
will provide proposal preparation tools to assist proposers in assessing the
feasibility of observing sources of interest.


title: A Phoenix Modelatmosphere Grid For GAIA

abstract:
  We present the results of a set of model atmospheres and synthetic spectra
computed with the PHOENIX code. The models cover a range of effective
temperatures 2700 K <= T_eff <= 10 000 K, gravities (-0.5 <= log(g)<= 5.5) and
metalicities (-4.0 <= [Z/H] <= +0.5). In addition, variations of alpha elements
are considered for each metalicity. The models are computed with a homogeneous
set of input data in order to allow for direct relative comparison between the
models. For example, all models use a mixing length of l/H_p = 2.0. We provide
synthetic spectra with a resolution of 0.2 nm from the UV to the infrared for
all models. We give a brief overview of the input physics and show illustrative
results. All synthetic spectra are available via ftp:
ftp.hs.uni-hamburg.de/pub/outgoing/phoenix/GAIA


title:
Structural Parameters of the Hot Pulsating B Subdwarf PG 1219+534 from
  Asteroseismology

abstract:
  We have carried out a detailed asteroseismic analysis of PG 1219+534. Our
analysis leads to the identification of the (k,l) indices of nine periods
observed in the star PG 1219+534, and to the determination of its structural
parameters. The periods all correspond to low-order acoustic modes with
adjacent values of k and with l=0, 1, 2, and 3. They define a band of unstable
modes, in close agreement with nonadiabatic pulsation theory. Furthermore, the
average dispersion between the nine observed periods and the periods of the
corresponding nine theoretical modes of the optimal model is only ~0.6%,
comparable to the results of a similar analysis carried out by Brassard et al.
(2001) on the rapid sdB pulsator PG 0014+067. On the basis of our combined
spectroscopic and asteroseismic analysis, the inferred global structural
parameters of PG 1219+534 are Teff = 33,600 +/- 370 K, log g = 5.8071 +/-
0.0057, log Menv/M* = -4.254 +/- 0.147, M* = 0.457 +/- 0.012 Msun, R/Rsun =
0.1397 +/- 0.0028, and L/Lsun = 22.01 +/- 1.85. Combined with detailed model
atmosphere calculations, we estimate, in addition, that this star has an
absolute visual magnitude MV = 4.62 +/- 0.06 and is located at a distance d =
531 +/- 23 pc (using V = 13.24 +/- 0.20). Finally, if we interpret the absence
of fine structure (frequency multiplets) as indicative of a slow rotation rate
of that star, we further find that PG 1219+534 rotates with a period longer
than 3.4 days, and has a maximum rotational broadening velocity of Vsin i <~
2.1 km/s.


title: The white dwarf cooling sequence in NGC 6791

abstract:
  In the old, populous, and metal-rich open cluster NGC 6791 we have used deep
HST/ACS images to track the white dwarf cooling sequence down to m_F606W~28.5.
The white dwarf luminosity function shows a well defined peak at m_F606W~27.4,
and a bending to the blue in the color--magnitude diagram. If this peak
corresponds to the end of the white dwarf cooling sequence the comparison with
theoretical isochrones provides a cluster age estimate of ~2.4 Gyr, in sharp
contrast with the age of 8--9 Gyr inferred from the main-sequence turn-off. If
the end is at fainter magnitudes, the peak at m_F606W~27.4 is even more
enigmatic. We discuss possible causes, none of them very convincing.


title:
Development of Bubble Chambers With Enhanced Stability and Sensitivity
  to Low-Energy Nuclear Recoils

abstract:
  The viability of using a Bubble Chamber for rare event searches and in
particular for the detection of dark matter particle candidates is considered.
Techniques leading to the deactivation of inhomogeneous nucleation centers and
subsequent enhanced stability in such a detector are described. Results from
prototype trials indicate that sensitivity to low-energy nuclear recoils like
those expected from Weakly Interacting Massive Particles can be obtained in
conditions of near total insensitivity to minimum ionizing backgrounds. An
understanding of the response of superheated heavy refrigerants to these
recoils is demonstrated within the context of existing theoretical models. We
comment on the prospects for the detection of supersymmetric dark matter
particles with a large $CF_{3}I$ chamber.


title:
Maximum elastic deformations of compact stars with exotic equations of
  state

abstract:
  I make the first estimates of maximum elastic quadrupole deformations
sustainable by alternatives to conventional neutron stars. Solid strange quark
stars might sustain maximum ellipticities (dimensionless quadrupoles) up to a
few times $10^{-4}$ rather than a few times $10^{-7}$ for conventional neutron
stars, and hybrid quark-baryon or meson-condensate stars might sustain up to
$10^{-5}$. Most of the difference is due to the shear modulus, which can be up
to $10^{33}$ erg/cm$^3$ rather than $10^{30}$ erg/cm$^3$ in the inner crust of
a conventional neutron star. Maximum solid strange star ellipticities are
comparable to upper limits obtained for several known pulsars in a recent
gravitational-wave search by LIGO. Maximum ellipticities of the more robust
hybrid model will be detectable by LIGO at initial design sensitivity. A large
shear modulus also strengthens the case for starquakes as an explanation for
frequent pulsar glitches.


title: The Distribution of Satellite Galaxies: The Great Pancake

abstract:
  The 11 known satellite galaxies within 250 kpc of the Milky Way lie close to
a great circle on the sky. We use high resolution N-body simulations of
galactic dark matter halos to test if this remarkable property can be
understood within the context of the cold dark matter cosmology. We construct
halo merger trees from the simulations and use a semianalytic model to follow
the formation of satellite galaxies. We find that in all 6 of our simulations,
the 11 brightest satellites are indeed distributed along thin, disk-like
structures analogous to that traced by the Milky Way's satellites. This is in
sharp contrast to the overall distributions of dark matter in the halo and of
subhalos within it which, although triaxial, are not highly aspherical. We find
that the spatial distribution of satellites is significantly different from
that of the most massive subhalos but is similar to that of the subset of
subhalos that had the most massive progenitors at earlier times. The elongated
disk-like structure delineated by the satellites has its long axis aligned with
the major axis of the dark matter halo. We interpret our results as reflecting
the preferential infall of satellites along the spines of a few filaments of
the cosmic web.


title: Gemini Deep Deep Survey VI: Massive Hdelta-strong galaxies at z=1

abstract:
  We show that there has been a dramatic decline in the abundance of massive
galaxies with strong Hdelta stellar absorption lines from z=1.2 to the present.
These ``Hdelta-strong'', or HDS, galaxies have undergone a recent and rapid
break in their star-formation activity. Combining data from the Gemini Deep
Deep and the Sloan Digital Sky Surveys to make mass-matched samples
(M*>=10^10.2 Msun), with 25 and 50,255 galaxies, respectively), we find that
the fraction of galaxies in an HDS phase has decreased from about 50% at z=1.2
to a few percent today. This decrease in fraction is due to an actual decrease
in the number density of massive HDS systems by a factor of 2-4, coupled with
an increase in the number density of massive galaxies by about 30 percent. We
show that this result depends only weakly on the threshold chosen for the
Hdelta equivalent width to define HDS systems (if greater than 4 A) and
corresponds to a (1+z)^{2.5\pm 0.7} evolution. Spectral synthesis studies of
the high-redshift population using the PEGASE code, treating Hdelta_A, EW[OII],
Dn4000, and rest-frame colors, favor models in which the Balmer absorption
features in massive Hdelta-strong systems are the echoes of intense episodes of
star-formation that faded about 1 Gyr prior to the epoch of observation. The
z=1.4-2 epoch appears to correspond to a time at which massive galaxies are in
transition from a mode of sustained star formation to a relatively quiescent
mode with weak and rare star-formation episodes. We argue that the most likely
local descendants of the distant massive HDS galaxies are passively evolving
massive galaxies in the field and small groups.


title:
Constraints on Topological Defects Energy Density from First-Year WMAP
  Results

abstract:
  We compare the predictions of hybrid inflationary models that produce both
adiabatic fluctuations and topological defects to first year WMAP results. We
use a Markov Chain Monte Carlo method to constrain the contribution of cosmic
strings and textures to the CMB angular power spectrum. Marginalizing this
contribution over the cosmological parameters of a power law flat LCDM model,
we place a 95% upper limit of 23% on the topological defects contribution to
density fluctuations, the maximum likelihood being of order 4%. This
corresponds to an upper limit on the string scale of G\mu \leq 3.2 \times
10^{-7}. We also explore the degeneracies between the defects contribution and
other cosmological parameters.


title:
On the gamma-ray spectra radiated by protons accelerated in SNR shocks
  near molecular clouds: The case of SNR RX J1713.7-3946

abstract:
  Cosmic rays (CRs) are thought to be accelerated in SNRs. The most favorable
situation for proving that the main, hadronic CR component is accelerated there
is when CRs interact with dense gases, such as molecular clouds (MC) which
surround the SN shock. Here, a new mechanism of spectrum formation in partially
ionized gases near SNRs is proposed. Using an analytic model of nonlinear
diffusive shock acceleration, we calculate the spectra of protons and estimate
the resulting $\gamma$-ray emission occurring when the SNR shock approaches a
MC. We show that the spectrum develops a break in the TeV range and that its
GeV component is suppressed. These modifications to the standard theory occur
because of the proximity of the partially ionized MC-gas and because of the
physics of particle and Alfven wave propagation inside the gas. Possible
applications of the new spectra to the recent CANGAROO and HESS observations of
the SNR RX J1713.7-3946 are discussed.


title:
Potential Vorticity Evolution of a Protoplanetary Disk with An Embedded
  Protoplanet

abstract:
  We present two-dimensional inviscid hydrodynamic simulations of a
protoplanetary disk with an embedded planet, emphasizing the evolution of
potential vorticity (the ratio of vorticity to density) and its dependence on
numerical resolutions. By analyzing the structure of spiral shocks made by the
planet, we show that progressive changes of the potential vorticity caused by
spiral shocks ultimately lead to the excitation of a secondary instability. We
also demonstrate that very high numerical resolution is required to both follow
the potential vorticity changes and identify the location where the secondary
instability is first excited. Low-resolution results are shown to give the
wrong location. We establish the robustness of a secondary instability and its
impact on the torque onto the planet. After the saturation of the instability,
the disk shows large-scale non-axisymmetry, causing the torque on the planet to
oscillate with large amplitude. The impact of the oscillating torque on the
protoplanet's migration remains to be investigated.


title: On Precision Measurement of the Mean Curvature

abstract:
  Very small mean curvature is a robust prediction of inflation worth rigorous
checking. Since current constraints are derived from determinations of the
angular-diameter distance to the CMB last-scattering surface, which is also
affected by dark energy, they are limited by our understanding of the dark
energy. Measurements of luminosity or angular-diameter distances to redshifts
in the matter-dominated era can greatly reduce this uncertainty. With a one
percent measurement of the distance to z=3, combined with the CMB data expected
from Planck, one can achieve sigma(\Omega_k h^2) \sim 10^{-3}. A non-zero
detection at this level would be evidence against inflation or for unusually
large curvature fluctuations on super-Hubble scales.


title: The length of stellar bars in SB galaxies and N-body simulations

abstract:
  We have investigated the accuracy and reliability of six methods used to
determine the length of stellar bars in galaxies or N-body simulations. All
these methods use ellipse fitting and Fourier decomposition of the surface
brightness. We have applied them to N-body simulations that include stars, gas,
star formation, and feedback. Stellar particles were photometrically calibrated
to make B and K-band mock images. Dust absorption is also included. We discuss
the advantages and drawbacks of each method, the effects of projection and
resolution, as well as the uncertainties introduced by the presence of dust.
The use of N-body simulations allows us to compare the location of Ultra
Harmonic Resonance (UHR or 4/1) and corotation (CR) with measured bar lengths.
We show that the minimum of ellipticity located just outside the bulk of the
bar is correlated with the corotation, whereas the location of the UHR can be
approximated using the phase of the fitted ellipses or the phase of the m=2
Fourier development of the surface brightness. We give evidence that the
classification of slow/fast bars, based on the ratio R = Rcr/Rbar could
increase from 1 (fast bar) to 1.4 (slow bar) just by a change of method. We
thus conclude that one has to select the right bar-length estimator depending
on the application, since these various estimators do not define the same
physical area.


title:
On the Estimation of Solar Energetic Particle Injection Timing from
  Onset Times near Earth

abstract:
  We examine the accuracy of a common technique for estimating the start time
of solar energetic particle injection based on a linear fit to the observed
onset time versus 1/(particle velocity). This is based on a concept that the
first arriving particles move directly along the magnetic field with no
scattering. We check this by performing numerical simulations of the transport
of solar protons between 2 and 2000 MeV from the Sun to the Earth, for several
assumptions regarding interplanetary scattering and the duration of particle
injection, and analyzing the results using the inverse velocity fit. We find
that in most cases, the onset times align close to a straight line as a
function of inverse velocity. Despite this, the estimated injection time can be
in error by several minutes. Also, the estimated path length can deviate
greatly from the actual path length along the interplanetary magnetic field.
The major difference between the estimated and actual path lengths implies that
the first arriving particles cannot be viewed as moving directly along the
interplanetary magnetic field.


title:
Influence of two updated nuclear reaction rates on the evolution of low
  and intermediate mass stars

abstract:
  Two key reactions of hydrostatic nuclear burning in stars have recently been
revised by new experimental data - the 14N(p,gamma)15O and triple alpha
reaction rates. We investigate how much the new rates influence the evolution
of low-mass, metal-poor and metal-free, stars and of an intermediate-mass star
of solar-type composition. We concentrate on phases of helium ignition or
thermally unstable helium burning. Our global result is that the new triple
alpha rate has no significant influence on such stars, but that there is a
noticable, though small, effect of the new 14N(p,gamma)15O rate, in particular
on the core helium flash and the blue loop during core helium burning in the
intermediate-mass star.


title:
The Serendipitous XMM-Newton Cluster Athens Survey (SEXCLAS): Sample
  selection and the cluster log N - log S

abstract:
  In this paper we serendipitously identify X-ray cluster candidates using
XMM-Newton archival observations complemented by 5-band optical photometric
follow-up observations (r~23 mag) as part of the X-ray Identification (XID)
programme. Our sample covers an area of ~2.1 sq. deg (15 XMM-Newton fields) and
comprises a total of 21 (19 serendipitous + 2 target) extended X-ray sources to
the limit f(0.5-2keV) ~ 6x10^{-15} cgs with a high probability (> 99.9%) of
being extended on the XMM-Newton images. Of the 21 cluster candidates 7 are
spectroscopically confirmed in the literature. Exploiting the optical data
available for these fields we discover that 68% of the X-ray cluster candidates
are associated with optical galaxy overdensities. We also attempt to constrain
the redshifts of our cluster candidates using photometric methods. We thus
construct the photometric redshift distribution of galaxies in the vicinity of
each X-ray selected cluster candidate and search for statistically significant
redshift peaks against that of the background distribution of field galaxies.
Comparison of the photometric with spectroscopic redshift estimates for the
confirmed clusters suggest that our simple method is robust out to z~0.5. For
clusters at higher z, deeper optical data are required to estimate reliable
photometric redshifts. Finally, using the sample of the 19 serendipitous X-ray
selected cluster candidates we estimate their surface density down to
f(0.5-2keV) ~ 6x10^{-15} cgs and find it to be in fair agreement with previous
and recent studies.


title:
Time variations of the narrow FeII and HI spectral emission lines from
  the close vicinity of Eta Carinae during the spectral event of 2003

abstract:
  The spectrum of Eta Carinae and its ejecta shows slow variations over a
period of 5.5 years. However, the spectrum changes drastically on a time scale
of days once every period called the 'spectral event'. We report on variations
in the narrow emission line spectrum of gas condensations (the Weigelt blobs)
close to the central star during a spectral event. The rapid changes in the
stellar radiation field illuminating the blobs make the blobs a natural
astrophysical laboratory to study atomic photoprocesses. The different
responses of the HI Paschen lines, fluorescent <FeII> lines and forbidden
[FeII] lines allow us to identify the processes and estimate physical
conditions in the blobs. This paper is based on observations from the Pico dos
Dias Observatory (LNA/Brazil) during the previous event in June 2003.


title: Pulsar shadow as the origin of double notches in radio pulse profiles

abstract:
  We present the model of eclipsing a rotating, spatially extended source of
directional emission by a central absorber, and apply it to the pulsar
magnetosphere. The model assumes the radially extended inward radio emission
along the local direction of the magnetic field, and the pulsar as the
absorber. The geometry of the magnetic field lines of the rotating dipole is
favourable for the double eclipse events, which we identify with the double
notches observed in pulse profiles of nearby pulsars. For pulsars with large
dipole inclinations 70 <~ alpha <~ 110 deg the double notches are predicted to
occur within a narrow phase range of 20 to 30 deg before the main radio peak.
Application of the model to PSR B0950+08 establishes it as a nearly orthogonal
rotator (alpha =~ 75 deg, beta =~ -10 deg) with many pulse components naturally
interpreted in terms of the inward radio emission from a large range of
altitudes. The inward components include the intermittently strong, leading
component of the main pulse, which would traditionally have been interpeted as
a conal emission in the outward direction. The model also identifies the
magnetic field lines along which the radially extended inward radio emission
occurs in B0950+08. These have a narrow range of the footprint parameter s
close to 1.1 (closed field line region, near the last open field lines). We
describe directional characteristics of inward emission from the radially
extended region and compare them with characteristics of extended outward
emission. Our work shows that pulse profiles of at least some pulsars may be a
superposition of both inward and outward emission.


title: Binary star formation from ring fragmentation

abstract:
  We present a simple model of binary star formation based on the assumption
that rotating prestellar cores collapse to form rings and these rings then
fragment into protostars. We assume that each ring spawns a small number (N <=
6) of protostars, and that the condensation of the protostars is sufficiently
rapid that they can subsequently be treated as point masses. We simulate the
dynamical evolution of a ring of N stars and record the properties of the
single stars, binaries and higher multiples that form as a result of the
dissolution of the ring. The masses of the individual stars in a ring are drawn
from a log-normal distribution with dispersion \sigma. This part of the model
is perfomed for many different realizations of the ring, to obtain good
statistics. The second part of the model is to convolve the results of these
dimensionless simulations, first with the distribution of core masses, which
yields the distributions of multiplicity,mass ratio and eccentricity, as a
function of primary mass; and second with the distribution of core angular
momenta, which yields the distributions of semi-major axis and period, again as
a function of primary mass. Using the observed distribution of core masses, and
the observed distribution of core angular momenta, our model is able to
reproduce the observed IMF, the observed high multiplicity frequency of
pre-Main Sequence stars, the observed distribution of separations, and -- for
long-period systems -- the observed distributions of eccentricity and
mass-ratio, provided we invoke N = 4 or 5 and $\sigma = 0.6$. We presume that
the reduced multiplicity frequency in the field, compared with young clusters,
is the result of dynamical interactions between stars formed in different cores
but the same cluster, following ring dissolution.


title: Reversals of radio emission direction in PSR B1822-09

abstract:
  The pulse profile of pulsar B1822-09 exhibits a very peculiar kind of mode
changing: a "precursor" appearing just in front of the Main-Pulse (MP) exhibits
periods of nulling, during which an interpulse (IP) becomes detectable at
rotation phase separated by roughly 180 deg from the precursor. We propose that
this bizarre phenomenon, which requires an information transfer between the two
components, occurs by means of reversal of a direction of coherent radio
emission generated in the same emission region. This interpretation naturally
explains the lack of weak radio emission in the off-pulse regions, as well as
the problem of information transfer between emission regions associated with
the MP precursor and the IP. The reversals also imply nulling. The model has
profound physical implications: (i) the mechanism of coherent radio emission
must allow radiation into two, opposite, intermittently changing directions;
(ii) the radio waves must be able to propagate through inner regions of the
neutron star magnetosphere with strong magnetic field. Most importantly, the
model implies inward radio emission in pulsar magnetosphere.


title:
Infrared afterglow of GRB041219 as a result of reradiation on dust in a
  circumstellar cloud

abstract:
  Observations of gamma ray bursts (GRB) afterglows in different spectral bands
provide a most valuable information about their nature, as well as about
properties of surrounding medium. Powerful infrared afterglow was observed from
the strong GRB041219. Here we explain the observed IR afterglow in the model of
a dust reradiation of the main GRB signal in the envelope surrounding the GRB
source. In this model we do not expect appearance of the prompt optical
emission which should be absorbed in the dust envelope. We estimate the
collimation angle of the gamma ray emission, and obtain restrictions on the
redshift (distance to GRB source), by fitting the model parameters to the
observational data.


title: Absolute magnitudes for late-type dwarf stars for Sloan photometry

abstract:
  We present a new formula for absolute magnitude determination for late-type
dwarf stars as a function of (g-r) and (r-i) for Sloan photometry. The absolute
magnitudes estimated by this approach are brighter than those estimated by
colour-magnitude diagrams, and they reduce the luminosity function rather close
to the luminosity function of Hipparcos.


title: Evolution of non-linear cosmological perturbations

abstract:
  We define fully non-perturbative generalizations of the uniform density and
comoving curvature perturbations, which are known, in the linear theory, to be
conserved on sufficiently large scales for adiabatic perturbations. Our
non-linear generalizations are defined geometrically, independently of any
coordinate system. We give the equations governing their evolution on all
scales. Also, in order to make contact with previous works on first and second
order perturbations, we introduce a coordinate system and show that previous
results can be recovered, on large scales, in a remarkably simple way, after
restricting our definitions to first and second orders in a perturbative
expansion.


title: FUSE Observations of RX J0513.9-6951

abstract:
  FUSE observations were obtained in July 2003 during 1.2 cycles of the
0.76-day binary orbit of RX J0513.9-6951. Radial velocity measurements of the
broad O VI emission profile show a semiamplitude of K~26 km/sec, which is much
smaller than the value of 117 km/sec measured from 2001 FUSE data. Narrow O VI
emissions show no measurable velocity variation. The mean velocity of the broad
O VI emission is red-shifted by ~500 km/sec with respect to both the systemic
and narrow emission-line velocities. Spectral difference plots show
phase-related changes in the broad emission profile. Other phase-related
changes such as line and continuum variations are also smaller than in the 2001
spectra. We describe a moving broad absorption feature near 1020A as possible O
VI outflow associated with a precessing jet. We discuss the implications for
the stellar masses if the 2003 broad O VI velocities outline the compact star's
orbital motion.


title: The Red Giant Branch Tip and Bump of the Leo II dwarf spheroidal galaxy

abstract:
  We present V and I photometry of a 9.4' X 9.4' field centered on the dwarf
spheroidal galaxy Leo II. The Tip of the Red Giant Branch is identified at
I^{TRGB}=17.83 +/- 0.03 and adopting <[M/H]> = -1.53 +/- 0.2 from the
comparison of RGB stars with Galactic templates, we obtain a distance modulus
(m-M)_0=21.84 +/- 0.13, corresponding to a distance D=233 +/- 15 Kpc. Two
significant bumps have been detected in the Luminosity Function of the Red
Giant Branch. The fainter bump (B1, at V=21.76 +/- 0.05) is the RGB bump of the
dominant stellar population, while the actual nature of the brightest one (B2,
at V=21.35 +/- 0.05) cannot be firmly assessed on the basis of the available
data, it can be due to the Asymptotic Giant Branch Clump of the main population
or it may be a secondary RGB bump. The luminosity of the main RGB bump (B1)
suggests that the majority of RGB stars in Leo II belongs to a population that
is ~4 gyr younger than the classical Galactic globular clusters. The stars
belonging to the He-burning Red Clump are shown to be significantly more
centrally concentrated than RR Lyrae and Blue Horizontal Branch stars, probing
the existence of an age/metallicity radial gradient in this remote dwarf
spheroidal.


title: Velocity Dispersion of Excited H2

abstract:
  We present a study of the high rotational bands (J > 2) of H2 toward 4 early
type galactic stars: HD 73882, HD 192639, HD 206267, and HD 207538. In each
case, the velocity dispersion - characterized by the spectrum fitting parameter
b - increases with the level of excitation, a phenomenon that has previously
been detected by the Copernicus and IMAPS observatories. In particular, we show
with 4 sigma confidence that for HD 192639 it is not possible to fit all J
levels with a single b value, and that higher b values are needed for the
higher levels. The amplitude of the line broadening, which can be as high as 10
km s^-1, makes explanations such as inhomogeneous spatial distribution
unlikely. We investigate a mechanism in which the broadening is due to the
molecules that are rotationally excited through the excess energy acquired
after their formation on a grain (H2-formation pumping). We show that different
dispersions would be a natural consequence of this mechanism. We note however
that such process would require a formation rate 10 times higher then what was
inferred from other observations. In view of the difficulty to account for the
velocity dispersion as thermal broadening (T would be around 10,000 K), we
conclude then that we are most certainly observing some highly turbulent warm
layer associated with the cold diffuse cloud. Embedded in a magnetic field, it
could be responsible for the high quantities of CH+ measured in the cold
neutral medium.


title:
Relativistic Magnetohydrodynamics In Dynamical Spacetimes: Numerical
  Methods And Tests

abstract:
  Many problems at the forefront of theoretical astrophysics require the
treatment of magnetized fluids in dynamical, strongly curved spacetimes. Such
problems include the origin of gamma-ray bursts, magnetic braking of
differential rotation in nascent neutron stars arising from stellar core
collapse or binary neutron star merger, the formation of jets and magnetized
disks around newborn black holes, etc. To model these phenomena, all of which
involve both general relativity (GR) and magnetohydrodynamics (MHD), we have
developed a GRMHD code capable of evolving MHD fluids in dynamical spacetimes.
Our code solves the Einstein-Maxwell-MHD system of coupled equations in
axisymmetry and in full 3+1 dimensions. We evolve the metric by integrating the
BSSN equations, and use a conservative, shock-capturing scheme to evolve the
MHD equations. Our code gives accurate results in standard MHD code-test
problems, including magnetized shocks and magnetized Bondi flow. To test our
code's ability to evolve the MHD equations in a dynamical spacetime, we study
the perturbations of a homogeneous, magnetized fluid excited by a gravitational
plane wave, and we find good agreement between the analytic and numerical
solutions.


title:
Excitation Of MHD Modes With Gravitational Waves: A Testbed For
  Numerical Codes

abstract:
  We consider a gravitational wave oscillating in an initially homogeneous,
magnetized fluid. The fluid is perfectly conducting and isentropic, and the
magnetic field is initially uniform. We find analytic solutions for the case in
which the gravitational wave is linear and unaffected by the background fluid
and field. Our solutions show how gravitational waves can excite three
magnetohydrodynamic (MHD) modes in the fluid: Alfven waves, and both fast and
slow magnetosonic waves. Our analytic solutions are particularly useful for
testing numerical codes designed to treat general relativistic MHD in dynamical
spacetimes, as we demonstrate in a companion paper.


title:
Dense Cloud Ablation and Ram Pressure Stripping of the Virgo Spiral NGC
  4402

abstract:
  We present optical, HI and radio continuum observations of the highly
inclined Virgo Cluster Sc galaxy NGC 4402, which show evidence for ram-pressure
stripping and dense cloud ablation. VLA HI and radio continuum maps show a
truncated gas disk and emission to the northwest of the main disk emission. In
particular, the radio continuum emission is asymmetrically extended to the
north and skewed to the west. The Halpha image shows numerous HII complexes
along the southern edge of the gas disk, possibly indicating star formation
triggered by the ICM pressure. BVR images at 0.5" resolution obtained with the
WIYN Tip-Tilt Imager show a remarkable dust lane morphology: at half the
optical radius, the dust lane of the galaxy curves up and out of the disk,
matching the HI morphology. Large dust plumes extend upward for ~1.5 kpc from
luminous young star clusters at the SE edge of the truncated gas disk. These
star clusters are very blue, indicating very little dust reddening, which
suggests dust blown away by an ICM wind at the leading edge of the interaction.
To the south of the main ridge of interstellar material, where the galaxy is
relatively clean of gas and dust, we have discovered 1 kpc long linear dust
filaments with a position angle that matches the extraplanar radio continuum
tail; we interpret this angle as the projected ICM wind direction. One of the
observed dust filaments has an HII region at its head. We interpret these dust
filaments as large, dense clouds which were initially left behind as the
low-density ISM is stripped, but are then ablated by the ICM wind. These
results provide striking new evidence on the fate of molecular clouds in
stripped cluster galaxies.


title: XMM-Newton observation of the drifting pulsar B0943+10

abstract:
  Radio pulsar subpulse drifting has been interpreted as rotation of sub-beams
(sparks) of pair plasma produced by intermittent breakdowns of an inner vacuum
gap above the pulsar polar cap. This model also predicts strong thermal X-ray
emission from the polar cap caused by inflowing particles created in spark
discharges. We have observed the best-studied drifting pulsar B0943+10 with
XMM-Newton and detected a point source coincident with the radio pulsar
position. Its spectrum could be fitted with a thermal blackbody model, although
a power-law model is also acceptable. The thermal fit gives a bolometric
luminosity L_bol ~ 5 x 10^{28} erg/s and a surface area A ~ 10^3 (T/3MK)^{-4}
m^2, much smaller than the conventional polar cap area, 6 x 10^4 m^2. Such
thermal radiation can be interpreted as emitted from footprints of sparks
drifting in an inner gap of a height h ~ 0.1 - 0.2 r_pc, where r_pc is the
polar cap radius. However, the original vacuum gap model by Ruderman and
Sutherland requires some modification to reconcile the X-ray and radio data.


title:
Discovery of a 105 ms X-ray Pulsar in Kesteven 79: On the Nature of
  Compact Central Objects in Supernova Remnants

abstract:
  We report the discovery of 105-ms X-ray pulsations from the compact central
object (CCO) in the supernova remnant Kes 79 using data acquired with the
Newton X-Ray Multi-Mirror Mission. Two observations of the pulsar taken 6 days
apart yield an upper limit on its spin-down rate of dP/dt < 7E-14 s/s and no
evidence for binary orbital motion. The implied energy loss rate is dE/dt <
2E36 ergs/s, surface magnetic field strength is B_p < 3E12 G, and spin-down age
is t > 24 kyr. The latter exceeds the remnant's estimated age, suggesting that
the pulsar was born spinning near its current period. The X-ray spectrum of PSR
J1852+0040 is best characterized by a blackbody model of temperature kT_BB =
0.44 +/- 0.03 keV, radius R_BB approx. 0.9 km, and L_bol = 3.7E33 ergs/s at d =
7.1 kpc. The sinusoidal light curve is modulated with a pulsed fraction of
>45%, suggestive of a small hot spot on the surface of the rotating neutron
star. The lack of a discernible pulsar wind nebula is consistent with an
interpretation of PSR J1852+0040 as a rotation-powered pulsar whose spin-down
luminosity falls below the empirical threshold for generating bright wind
nebulae, dE/dt_c approx. 4E36 ergs/s. The age discrepancy implies that its
dE/dt has always been below dE/dt_c, perhaps a distinguishing property of the
CCOs. Alternatively, the X-ray spectrum of PSR J1852+0040 suggests a
low-luminosity AXP, but the weak inferred B_p field is incompatible with a
magnetar theory of its X-ray luminosity. So far, we cannot exclude accretion
from a fall-back disk. The ordinary spin parameters discovered from PSR
J1852+0040 highlight the difficulty that existing theories of isolated neutron
stars have in explaining the high luminosities and temperatures of CCO thermal
X-ray spectra.


title:
A New Radio Catalog of Compact HII Regions in the Milky Way II. The 1.4
  GHz Data

abstract:
  We utilize a new VLA Galactic plane catalog at 1.4 GHz covering the first and
second Galactic quadrants (340 deg <l< 120 deg, |b|<0.8 deg with |b|< 1.8 deg
for 350 deg <l< 40 deg and |b|<2.5 deg for 100 deg <l<105 deg) in conjunction
with the MSX6C Galactic plane mid-infrared catalog to supplement and better
understand our 5 GHz catalog (Giveon et al. 2005). A radio catalog of this
region was first published by Zoonematkermani et al. (1990), but we have
re-reduced the data with significantly improved calibration and mosaicing
procedures, resulting in more than a tripling of the number of 1.4 GHz sources
detected. Comparison of the new 1.4 GHz catalog and the MSX6C catalog resulted
in a sample of 556 matches, out of which we estimate only 11 to be chance
coincidences. Most of the matches show red MSX colors. The scale height of
their Galactic latitude distribution is 24'-28' (FWHM) or ~60-70 pc (for a
distance of 8.5 kpc), depending on longitude. The latitude distribution
flattens out significantly above l~40 deg and the number of matches drops off
sharply.


title:
$XMM-Newton$ $\Omega$ project: III. Gas mass fraction shape in high
  redshift clusters

abstract:
  We study the gas mass fraction, $f\_{\rm gas},$ behavior in $XMM-Newton$
$\Omega$ project. The typical $f\_{\rm gas}$ shape of high redshift galaxy
clusters follows the global shape inferred at low redshift quite well. This
result is consistent with the gravitational instability picture leading to self
similar structures for both the dark and baryonic matter. However, the mean
$f\_{\rm gas} in distant clusters shows some differences to local ones,
indicating a departure from strict scaling. This result is consistent with the
observed evolution in the luminosity-temperature relation. We quantitatively
investigate this departure from scaling laws. Within the local sample we used,
a moderate but clear variation of the amplitude of the gas mass fraction with
temperature is found, a trend that weakens in the outer regions. These
variations do not explain departure from scaling laws of our distant clusters.
An important implication of our results is that the gas fraction evolution, a
test of the cosmological parameters, can lead to biased values when applied at
radii smaller than the virial radius. From our $XMM$ clusters, the apparent gas
fraction at the virial radius is consistent with a non-evolving universal value
in a high matter density model and not with a concordance.


title: Born-Infeld Phantom Gravastars

abstract:
  We construct new gravitational vacuum star solutions with a Born-Infeld
phantom replacing the de Sitter interior. The model allows for a wide range of
masses and radii required by phenomenology, and can be motivated from low
energy string theory.


title: Transient acceleration from a hybrid Chaplygin gas

abstract:
  We extend the Chaplygin gas model for dark matter and dark energy unification
by promoting the Chaplygin gas parameter A to the potential for an extra scalar
with canonical kinetic energy. The hybrid model allows for accelerated Hubble
expansion to be a transient effect around redshift zero.


title:
A HST study of the stellar populations in the cometary dwarf irregular
  galaxy NGC 2366

abstract:
  We present V and I photometry of the resolved stars in the cometary dwarf
irregular galaxy NGC 2366, using Wide Field Planetary Camera 2 images obtained
with the Hubble Space Telescope. The resulting color-magnitude diagram reaches
down to I~26.0 mag. It reveals not only a young population of blue
main-sequence stars (age <30 Myr) but also an intermediate-age population of
blue and red supergiants (20 Myr<age<100 Myr), and an older evolved populations
of asymptotic giant branch (AGB) stars (age >100 Myr) and red giant branch
(RGB) stars (age >1 Gyr). The measured magnitude I=23.65+/-0.10 mag of the RGB
tip results in a distance modulus m-M=27.67+/-0.10, which corresponds to a
distance of 3.42+/-0.15 Mpc, in agreement with previous distance
determinations. The youngest stars are associated with the bright complex of
HII regions NGC 2363=Mrk 71 in the southwest extremity of the galaxy. As a
consequence of the diffusion and relaxation processes of stellar ensembles, the
older the stellar population is, the smoother and more extended is its spatial
distribution. An underlying population of older stars is found throughout the
body of NGC 2366. The most notable feature of this older population is the
presence of numerous relatively bright AGB stars. The number ratio of AGB to
RGB stars and the average absolute brightness of AGB stars in NGC 2366 are
appreciably higher than in the BCD VII Zw 403, indicating a younger age of the
AGB stars in NGC 2366. In addition to the present burst of age <100 Myr, there
has been strong star formation activity in the past of NGC 2366, from ~100 Myr
to <3 Gyr ago.


title:
Differential Emission Measure Determination of Collisionally Ionized
  Plasma: II. Application to Hot Stars

abstract:
  In a previous paper we have described a technique to derive constraints on
the differential emission measure (DEM) distribution, a measure of the
temperature distribution, of collisionally ionized hot plasmas from their X-ray
emission line spectra. We apply this technique to the Chandra/HETG spectra of
all of the nine hot stars available to us at the time this project was
initiated. We find that DEM distributions of six of the seven O stars in our
sample are very similar but that theta Ori has an X-ray spectrum characterized
by higher temperatures. The DEM distributions of both of B stars in our sample
have lower magnitudes than those of the O stars and one, tau Sco, is
characterized by higher temperatures than the other, beta Cru. These results
confirm previous work in which high temperatures have been found for theta Ori
and tau Sco and taken as evidence for channeling of the wind in magnetic
fields, the existence of which are related to the stars' youth. Our results
demonstrate the utility of our method for deriving temperature information for
large samples of X-ray emission line spectra.


title: Acceleration of Plasma Flows Due to Reverse Dynamo Mechanism

abstract:
  The "reverse-dynamo" mechanism - the amplification/generation of fast plasma
flows by micro scale (turbulent) magnetic fields via magneto-fluid coupling is
recognized and explored. It is shown that macro-scale magnetic fields and flows
are generated simultaneously and proportionately from micro scale fields and
flows. The stronger the micro-scale driver, the stronger are the macro-scale
products. Stellar and astrophysical applications are suggested.


title: Intrinsic Redshifts and the Tully-Fisher Distance Scale

abstract:
  The Tully-Fisher relationship (TFR) has been shown to have a relatively small
observed scatter of ~ +/-0.35 mag implying an intrinsic scatter < +/-0.30 mag.
However, when the TFR is calibrated from distances derived from the Hubble
relation for field galaxies scatter is consistently found to be +/-0.64 to
+/-0.84 mag. This significantly larger scatter requires that intrinsic TFR
scatter is actually much larger than +/-0.30 mag, that field galaxies have an
intrinsic TFR scatter much larger than cluster spirals, or that field galaxies
have a velocity dispersion relative to the Hubble flow in excess of 1000 km
s-1. Each of these potential explanations faces difficulties contradicted by
available data and the results of previous studies. An alternative explanation
is that the measured redshifts of galaxies are composed of a cosmological
redshift component predicted from the value of the Hubble Constant and a
superimposed intrinsic redshift component previously identified in other
studies. This intrinsic redshift component may exceed 5000 km s-1 in individual
galaxies. In this alternative scenario a possible value for the Hubble Constant
is 55-60 km s-1 Mpc-1.


title: Can we escape from the big rip in the achronal cosmic future?

abstract:
  Recently Pedro F. Gonzalez-Diaz had shown that phantom energy can results in
achronal cosmic future where the wormholes become infinite before the
occurrence of the big rip singularity. After that, while the phantom energy
continues its accretion, any wormhole becomes the Einstein-Rosen bridge. Pedro
F. Gonzalez-Diaz has suggested that such objects can be used by an advanced
civilization as the means of escape from the big rip. Using the Bekenstein
Bound we'll show that it is impossible due to the very strong upper bound laid
on the total amount of information which can be sent through this bridge.


title: Cosmological Bounds on Spatial Variations of Physical Constants

abstract:
  We derive strong observational limits on any possible large-scale spatial
variation in the values of physical 'constants' whose space-time evolution is
driven by a scalar field. The limits are imposed by the isotropy of the
microwave background on large angular scales in theories which describe space
and time variations in the fine structure constant, the electron-proton mass
ratio, and the Newtonian gravitational constant, G. Large-scale spatial
fluctuations in the fine structure constant are bounded by 2x10^-9 and
1.2x10^-8 in the BSBM and VSL theories respectively, fluctuations in the
electron-proton mass ratio by 9x10^-5 in the BM theory and fluctuations in G by
3.6x10^-10 in Brans-Dicke theory. These derived bounds are significantly
stronger than any obtainable by direct observations of astrophysical objects at
the present time.


title:
A Log-Quadratic Relation Between the Nuclear Black-Hole Masses and
  Velocity Dispersions of Galaxies

abstract:
  We demonstrate that a log-linear relation does not provide an adequate
description of the correlation between the masses of Super-Massive Black-Holes
(SMBH, M_bh) and the velocity dispersions of their host spheroid (sigma). An
unknown relation between log(M_bh) and log(sigma) may be expanded to second
order to obtain a log-quadratic relation of the form log(M_bh)=alpha+beta
log(sigma/200) + beta_2[log(sigma/200)]^2. We perform a Bayesian analysis using
the Nuker sample, and solve for beta, beta_2 and alpha, in addition to the
intrinsic scatter (delta). We find unbiased parameter estimates of
beta=4.2+/-0.37, beta_2=1.6+/-1.3 and delta=0.275+/-0.05. At the 80% level the
M_bh-sigma relation does not follow a uniform power-law. Indeed, over the
velocity range 70km/s<sigma<380km/s the logarithmic slope of the best fit
relation varies between 2.7 and 5.1, which should be compared with a power-law
estimate of 4.02+/-0.33. Assuming no systematic offset, single epoch virial
SMBH masses estimated for AGN follow the same log-quadratic M_bh-sigma relation
as the Nuker sample, but extend it downward in mass by an order of magnitude.
The log-quadratic term in the M_bh-sigma relation has a significant effect on
estimates of the local SMBH mass function at M_bh>10^9 solar masses, leading to
densities of SMBHs with M_bh>10^10 solar masses that are several orders of
magnitude larger than inferred from a log-linear relation. We also estimate
unbiased parameters for the SMBH-bulge mass relation. With a parameterisation
log(M_bh)=alpha_b + beta_b log(M_b/10^{11}) + beta_2b[log(M_b/10^{11})]^2, we
find beta_b=1.15+/-0.18 and beta_2b=0.12+/-0.14. We determined an intrinsic
scatter delta_b=0.41+/-0.07 which is ~50% larger than the scatter in the
M_bh-sigma relation.


title:
Supersymmetric dark matter search via spin-dependent interaction with
  He3

abstract:
  The potentialities of MIMAC-He3, a MIcro-tpc MAtrix of Chambers of Helium 3,
for supersymmetric dark matter search are discussed within the framework of
effective MSSM models without gaugino mass unification at the GUT scale. A
phenomenological study has been done to investigate the sensitivity of the
MIMAC-He3 detector to neutralinos (m > 6 GeV/c2) via spin-dependent interaction
with He3 as well as its complementarity to direct and indirect detection
experiments. Comparison with other direct dark matter searches will be
presented in a WIMP model-independent framework.


title: On the evidence for discs around Blue Straggler stars

abstract:
  Recent observations of blue stragglers by De Marco et al. (2004) have
revealed continuum deficits on the blue side of the Balmer discontinuity,
leading these authors to infer the presence of discs around the stars. This
intriguing possibility may throw light on aspects of the mechanisms responsible
for at least some of these objects; current theories of blue straggler
formation invoke stellar collisions or interacting binaries, both of which
appear capable of forming a circumstellar disc.
  However, by synthesizing photospheric spectra for models of rotating blue
stragglers, we demonstrate that the Balmer jump enhancements can be wholly
attributed to the influence of oblateness and gravity darkening on the
formation of the continuum. Therefore, we are led to conclude that the
observations of De Marco et al. can be ascribed a more prosaic explanation,
that of rapid stellar rotation arising from the merger/interaction formation
process.


title:
Variation of the line profile moments for stars pulsating in distorted
  oblique non-radial modes

abstract:
  We derive expressions and develop a numerical technique for the analysis of
the line profile moment variations for stars pulsating in oblique non-radial
modes. This represents an extension of the widely used spectroscopic moment
mode identification method to the oblique distorted pulsations observed in
rapidly oscillating Ap stars. We demonstrate that a non-axisymmetric
superposition of the pulsation and rotation velocity fields results in a
qualitatively new behaviour of some of the line profile characteristics. It is
found that for the majority of roAp stars the second moment varies with the
pulsation frequency rather than with its first harmonic even for axisymmetric
modes. We also identify pulsation observables which do not change during
pulsation cycle but are modulated by the stellar rotation and can contribute to
the variability of the stellar spectra averaged over many pulsation cycles. As
an illustration of the new version of the moment technique, we compute
rotational modulation of the pulsational changes of the line profile moments
for the oblique axisymmetric dipolar pulsation modes with different parameters.
It is also shown that a distortion of the oblique dipolar modes predicted by
the recent theoretical studies of the stellar magneto-acoustic oscillations can
be readily diagnosed through the moment analysis. In particular, the shape of
the pulsation phase modulation for the radial velocity and the second moment is
very sensitive to non-axisymmetric pulsation components, whereas the rotational
modulation of the second moment amplitude is best suited to reveal axisymmetric
magnetically induced distortion of pulsations.


title:
Charges in gravitational fields: from Fermi, via Hanni-Ruffini-Wheeler,
  to the "electric Meissner effect"

abstract:
  Recent developments in obtaining a detailed model for gamma ray bursts have
shown the need for a deeper understanding of phenomena described by solutions
of the Einstein-Maxwell equations, reviving interest in the behavior of charges
close to a black hole. In particular a drastic difference has been found
between the lines of force of a charged test particle in the fields of
Schwarzschild and Reissner-Nordstrom black holes. This difference characterizes
a general relativistic effect for the electric field of a charged test particle
around a (charged) Reissner-Nordstrom black hole similar to the "Meissner
effect" for a magnetic field around a superconductor. These new results are
related to earlier work by Fermi and Hanni-Ruffini-Wheeler.


title: Further Evidence for Intrinsic Redshifts in Normal Spiral Galaxies

abstract:
  Evidence from galaxy absolute magnitudes, linear diameters, and HyperLeda
images is presented which strongly supports the interpretation that some normal
spiral galaxies can contain large non-cosmological (intrinsic) redshifts in
excess of 5000 km s-1.


title: The stars of the galactic center

abstract:
  We consider the origin of the so-called S stars orbiting the supermassive
black hole at the very center of the Galaxy. These are usually assumed to be
massive main-sequence stars. We argue instead that they are the remnants of
low-to-intermediate mass red giants which have been scattered on to near-radial
orbits and tidally stripped as they approach the central black hole. Such stars
retain only low-mass envelopes and thus have high effective temperatures. Our
picture simultaneously explains why S stars have tightly-bound orbits, and the
observed depletion of red giants in the very center of the Galaxy.


title: Alternative Multipole Vectors for the CMB Temperature Fluctuations

abstract:
  We introduce new, low-$\ell$, multipole vectors for the CMB temperature
fluctuations. A very strong alignment of the quadrupole and octopole vectors is
observed as well as a remarkably low declination of these vectors with respect
to the galactic plane.


title: HI shells in the outer Milky Way

abstract:
  We present results of a method for an automatic search for HI shells in 3D
data cubes and apply it to the Leiden-Dwingeloo HI survey of the northern Milky
Way. In the 2nd Galactic quadrant, where identifications of structures are not
substantially influenced by overlapping, we find nearly 300 structures. The
Galactic distribution of shells has an exponential profile in the radial
direction with a scale length of 3 kpc. In the z direction, one half of the
shells are found at distances smaller than 500 pc. We also calculate the
energies necessary to create the shells: there are several structures with
energies greater than 10 E_SN but only one with an energy exceeding 100 E_SN.
Their size distribution, corrected for distance effects, is approximated by a
power-law with an index 2.1. Our identifications provide a lower limit to the
filling factor of shells in the outer Milky Way: f_2D = 0.4 and f_3D = 0.05.


title:
The 24 micron Luminosity Function of spectroscopic SWIRE sources from
  the Lockman validation field

abstract:
  A spectroscopic follow-up of SWIRE sources from the Lockman Validation Field
has allowed the determination of the SWIRE 24 micron Luminosity Function (LF).
The spectroscopic sample was chosen above a 24 micron flux limit at 260 microJy
and an r-band optical limit of r<21. A spectroscopic completeness of 82.5% was
achieved. We found the median redshift for the sample to be z_med=0.29.
Markov-Chain Monte-Carlo (MCMC) and Maximum Likelihood Estimator (MLE)
techniques were employed to fit a parametric LF. Our result of the local LF
(LLF) is consistent with the local 25 micron determination from Shupe et al.
1998. We split the sample at a redshift of z_split=0.36 and find strong
evidence for galaxy evolution.


title: A Dynamical Simulation of the Debris Disk Around HD 141569A

abstract:
  We study the dynamical origin of the structures observed in the
scattered-light images of the resolved debris disk around HD 141569A. We
explore the roles of radiation pressure from the central star, gas drag from
the gas disk, and the tidal forces from two nearby stars in creating and
maintaining these structures. We use a simple one-dimensional axisymmetric
model to show that the presence of the gas helps confine the dust and that a
broad ring of dust is produced if a central hole exists in the disk. This model
also suggests that the disk is in a transient, excited dynamical state, as the
observed dust creation rate applied over the age of the star is inconsistent
with submillimeter mass measurements. We model in two dimensions the effects of
a fly-by encounter between the disk and a binary star in a prograde, parabolic,
coplanar orbit. We track the spatial distribution of the disk's gas,
planetesimals, and dust. We conclude that the surface density distribution
reflects the planetesimal distribution for a wide range of parameters. Our most
viable model features a disk of initial radius 400 AU, a gas mass of 50
M_earth, and beta = 4 and suggests that the system is being observed within
4000 yr of the fly-by periastron. The model reproduces some features of HD
141569A's disk, such as a broad single ring and large spiral arms, but it does
not reproduce the observed multiple spiral rings or disk asymmetries nor the
observed clearing in the inner disk. For the latter, we consider the effect of
a 5 M_Jup planet in an eccentric orbit on the planetesimal distribution of HD
141569A.


title: Gravitational Lensing of Distant Supernovae

abstract:
  We use a series of ray-tracing experiments to determine the magnification
distribution of high-redshift sources by gravitational lensing. We determine
empirically the relation between magnification and redshift, for various
cosmological models. We then use this relation to estimate the effect of
lensing on the determination of the cosmological parameters from observations
of high-z supernovae. We found that, for supernovae at redshifts z<1.8, the
effect of lensing is negligible compared to the intrinsic uncertainty in the
measurements. Using mock data in the range 1.8<z<8, we show that the effect of
lensing can become significant. Hence, if a population of very-high-z
supernovae was ever discovered, it would be crucial to fully understand the
effect of lensing, before these SNe could be used to constrain cosmological
models.