title:
K-band Properties of Galaxy Clusters and Groups: Luminosity Function,
  Radial Distribution and Halo Occupation Number

abstract:
  We explore the near-infrared (NIR) $K$-band properties of galaxies within 93
galaxy clusters and groups using data from the 2MASS. We use X-ray properties
of these clusters to pinpoint cluster centers and estimate cluster masses. By
stacking all these systems, we study the shape of the cluster luminosity
function and the galaxy distribution within the clusters. We find that the
galaxy profile is well described by the NFW profile with a concentration
parameter c~3, with no evidence for cluster mass dependence of the
concentration. Using this sample, whose masses span the range from
$3\times10^{13}M_\odot$ to $2\times10^{15}M_\odot$, we confirm the existence of
a tight correlation between total galaxy NIR luminosity and cluster binding
mass, which indicates that NIR light can serve as a cluster mass indicator.
  From the observed galaxy profile, together with cluster mass profile
measurements from the literature, we find that the \mlr is a weakly decreasing
function of cluster radius, and that it increases with cluster mass. We also
derive the mean number of galaxies within halos of a given mass. We find that
the mean number scales as $N\propto M^{0.84\pm0.04}$ for galaxies brighter than
$M_K=-21$, indicating high mass clusters have fewer galaxies per unit mass than
low mass clusters. Using published observations at high redshift, we show that
higher redshift clusters have higher mean occupation number than nearby systems
of the same mass. By comparing the luminosity function & radial distribution of
galaxies in low mass and high mass clusters, we show that there is a marked
decrease in the number density of galaxies fainter than $M_*$ as one moves to
higher mass clusters; in addition, extremely luminous galaxies are more
probable in high mass clusters.


title:
Using Local Group Galaxies to Investigate the Influence of Blending on
  Cepheid Distances and the Cosmological Distance Scale

abstract:
  We investigate the influence of blending on the Cepheid distance scale using
two Local Group galaxies, M31 and M33. Blending leads to systematically low
distances to galaxies observed with the HST, and therefore to systematically
high estimates of H_0. High-resolution HST images are compared to our
ground-based data, obtained as part of the DIRECT project, for a sample of 22
Cepheids in M31 and 102 Cepheids in M33. For a sample of 22 Cepheids in M31,
the average (median) flux contribution from luminous companions not resolved on
the ground-based images in the V-band, S_V, is about 19% (12%) of the flux of
the Cepheid. For 102 Cepheids in M33 the average (median) values of S_V, S_I,
S_B are 23% (13%), 28% (20%), 28% (15%). For 64 Cepheids in M33 with periods in
excess of 10 days the average (median) S_V, S_I, S_B are 16% (7%), 23% (12%),
20% (10%).


title: A CCD Imaging Search for Wide Metal-Poor Binaries

abstract:
  We explored the regions within a radius of 25 arcsec around 473 nearby,
low-metallicity G- to M-type stars using (VR)I optical filters and
small-aperture telescopes. About 10% of the sample was searched up to angular
separations of 90 arcsec. We applied photometric and astrometric techniques to
detect true physical companions to the targets. The great majority of the
sample stars was drawn from the Carney-Latham surveys; their metallicities
range from roughly solar to [Fe/H]=-3.5 dex. Our I-band photometric survey
detected objects that are between 0 and 5 mag fainter (completeness) than the
target stars; the maximum dynamical range of our exploration is 9 mag. We also
investigated the literature and inspected images from the Digitized Sky Surveys
to complete our search. By combining photometric and proper motion
measurements, we retrieved 29 previously known companions, and identified 13
new proper motion companions. Near-infrared 2MASS photometry is provided for
the great majority of them. Low-resolution optical spectroscopy (386-1000 nm)
was obtained for eight of the new companion stars. These spectroscopic data
confirm them as cool, late-type, metal-depleted dwarfs, with spectral classes
from esdK7 to sdM3. After comparison with low-metallicity evolutionary models,
we estimate the masses of the proper motion companion stars to be in the range
0.5-0.1 Msol. They are orbiting their primary stars at projected separations
between ~32 and ~57000 AU. These orbital sizes are very similar to those of
solar-metallicity stars of the same spectral types. Our results indicate that
about 15% of the metal-poor stars have stellar companions at large orbits,
which is in agreement with the binary fraction observed among main sequence G-
to M-type stars and T Tauri stars.


title: Nonsingular FRW cosmology and nonlinear electrodynamics

abstract:
  The possibility to avoid the cosmic initial singularity as a consequence of
nonlinear effects on the Maxwell eletromagnetic theory is discussed. For a flat
FRW geometry we derive the general nonsingular solution supported by a magnetic
field plus a cosmic fluid and a nonvanishing vacuum energy density. The
nonsingular behavior of solutions with a time-dependent $\Lambda(t)$-term are
also examined. As a general result, it is found that the functional dependence
of $\Lambda(t)$ can uniquely be determined only if the magnetic field remains
constant. All these models are examples of bouncing universes which may exhibit
an inflationary dynamics driven by the nonlinear corrections of the magnetic
field.


title: Self-Magnetization of charged particles and Bose-Einstein Condensation

abstract:
  We discuss the Bose-Einstein condensation of relativistic vector charged
particles in a strong external magnetic field in very dense matter, as may be
paired spin-up electrons. We show that for electrons such systems may maintain
self-consistently magnetic fields of order in between the interval
$10^{10}-10^{13}$ Gauss. This could be the origin of large magnetic fields in
some white dwarfs, but may also impose bounds due to the arising of strong
anisotropy in the pressures, which may produce a transverse collapse of the
star.


title: M31-RV evolution and its alleged multi-outburst pattern

abstract:
  The photometric evolution of M31-RV has been investigated on 1447 plates of
the Andromeda galaxy obtained over half a century with the Asiago telescopes.
M31-RV is a gigantic stellar explosion that occurred during 1988 in the Bulge
of M31 and that was characterized by the appearance for a few months of an M
supergiant reaching M_bol=-10. The 1988 outburst has been positively detected
on Asiago plates, and it has been the only such event recorded over the period
covered by the plates (1942-1993). In particular, an alleged previous outburst
in 1967 (Sharov 1990, SvAL, 16, 199) is excluded by the more numerous and
deeper Asiago plates, with relevant implication for the interpretative models
of this unique event. We outline a close analogy in spectral and photometric
evolution with those of V838 Mon which exploded in our Galaxy in 2002. The
analogy is found to extend also to the closely similar absolute magnitude at
the time of the sudden drop in photospheric temperature that both M31-RV and
V838 Mon exhibited. These similarities, in spite of the greatly differing
metallicity, age and mass of the two objects, suggest that the same, universal
and not yet identified process was at work in both cases.


title: CMB-Cluster Lensing

abstract:
  Clusters of galaxies are powerful cosmological probes, particularly if their
masses can be determined. One possibility for mass determination is to study
the cosmic microwave background (CMB) on small angular scales and observe
deviations from a pure gradient due to lensing of massive clusters. I show
that, neglecting contamination, this technique has the power to determine
cluster masses very accurately, in agreement with estimates by Seljak and
Zaldarriaga (1999). However, the intrinsic small scale structure of the CMB
significantly degrades this power. The resulting mass constraints are useless
unless one imposes a prior on the concentration parameter c. With even a modest
prior on c, an ambitious CMB experiment (0.5' resolution and 1 microK per
pixel) could determine masses of high redshift (z>0.5) clusters with ~ 30%
accuracy.


title: Neutrino emission in neutron matter from magnetic moment interactions

abstract:
  Neutrino emission drives neutron star cooling for the first several hundreds
of years after its birth. Given the low energy ($\sim$ keV) nature of this
process, one expects very few nonstandard particle physics contributions which
could affect this rate. Requiring that any new physics contributions involve
light degrees of freedom, one of the likely candidates which can affect the
cooling process would be a nonzero magnetic moment for the neutrino. To
illustrate, we compute the emission rate for neutrino pair bremsstrahlung in
neutron-neutron scattering through photon-neutrino magnetic moment coupling. We
also present analogous differential rates for neutrino scattering off nucleons
and electrons that determine neutrino opacities in supernovae. Employing
current upper bounds from collider experiments on the tau magnetic moment, we
find that the neutrino emission rate can exceed the rate through neutral
current electroweak interaction by a factor two, signalling the importance of
new particle physics input to a standard calculation of relevance to neutron
star cooling. However, astrophysical bounds on the neutrino magnetic moment
imply smaller effects.


title: Purely kinetic k-essence as unified dark matter

abstract:
  We examine k-essence models in which the Lagrangian p is a function only of
the derivatives of a scalar field phi and does not depend explicity on phi. The
evolution of phi for an arbitrary functional form for p can be given in terms
of an exact analytic solution. For quite general conditions on the functional
form of p, such models can evolve to a state characterized by a density scaling
with the scale factor as rho = rho_0 + rho_1(a/a_0)^{-3}, but with a sound
speed c_s^2 << 1 at all times. Such models can serve as a unified model for
dark matter and dark energy, while avoiding the problems of the generalized
Chaplygin gas models, which are due to a non-negligible sound speed in these
models. A dark energy component with c_s << 1 serves to suppress cosmic
microwave background fluctuations on large angular scales.


title:
Witnessing the gradual slow-down of powerful extragalactic jets: The
  X-ray -- optical -- radio connection

abstract:
  A puzzling feature of the {\it Chandra}--detected quasar jets is that their
X-ray emission decreases faster along the jet than their radio emission,
resulting to an outward increasing radio to X-ray ratio. In some sources this
behavior is so extreme that the radio emission peak is located clearly
downstream of that of the X-rays. This is a rather unanticipated behavior given
that the inverse
  Compton nature of the X-rays and the synchrotron radio emission are
attributed to roughly the same electrons of the jet's non-thermal electron
distribution. In this note we show that this morphological behavior can result
from the gradual deceleration of a relativistic flow and that the offsets in
peak emission at different wavelengths carry the imprint of this deceleration.
This notion is consistent with another recent finding, namely that the jets
feeding the terminal hot spots of powerful radio galaxies and quasars are still
relativistic with Lorentz factors $\Gamma \sim 2-3$. The picture of the
kinematics of powerful jets emerging from these considerations is that they
remain relativistic as they gradually decelerate from Kpc scales to the hot
spots, where, in a final collision with the intergalactic medium, they
slow-down rapidly to the subrelativistic velocities of the hot spot advance
speed.


title:
Far Ultraviolet Spectroscopic Explorer Spectroscopy of Absorption and
  Emission Lines from the Narrow-Line Seyfert 1 Galaxy NGC 4051

abstract:
  We present three Far Ultraviolet Spectroscopic Explorer (FUSE) observations
of the Narrow-Line Seyfert 1 galaxy NGC4051. The most prominent features in the
far-ultraviolet (FUV) spectrum are the OVI emission and absorption lines and
the HI Lyman series absorption lines which are detected up to the Lyman edge.
We also identify weak emission from NIII, CIII, and HeII. The CIII line shows
absorption while none is detected in the NIII and HeII lines. In HI and CIII we
detect two main absorption systems at outflow velocities of -50+/-30 and
-240+/-40 km/s, as well as a possible third one at ~ -450 km/s. These systems
are consistent in velocity with the 10 absorption systems found previously in
CIV, NV, and SiIV, though the individual systems are blended together in the
FUV spectrum. We estimate column densities of the two main absorption systems
and find that the HI column density is lower for systems with larger outflow
velocity. We detect no flux or spectral variations of NGC4051 at FUV
wavelengths during three epochs spanning one year. This is consistent with the
optical light curve which shows no variations between the three epochs. It is
also consistent with the X-ray light curve which shows consistent flux levels
at the three epochs of the FUSE observations, although the X-ray light curve
shows strong variations on much shorter timescales.


title:
A Probable z~7 Galaxy Strongly Lensed by the Rich Cluster Abell 2218:
  Exploring the Dark Ages

abstract:
  We discuss the observational properties of a remarkably faint triply-imaged
galaxy revealed in a deep z-band ACS observation of the lensing cluster A2218.
A well-constrained mass model for the cluster, which incorporates the outcome
of recent Keck spectroscopic campaigns, suggests that the triple system arises
via a z>6 source viewed at high magnification (~x25). Optical and IR photometry
from HST and Keck confirms the lensing hypothesis and suggests a significant
discontinuity occurs in the spectral energy distribution within 9250-9850A. If
this break is associated with Gunn-Peterson absorption from neutral
hydrogen,6.6<z<7.1 is inferred. Deep Keck spectroscopy conducted using both
optical and IR spectrographs fails to reveal any prominent emission lines in
this region. However, an IR stellar continuum is detected whose decline below
9800A suggests a spectroscopic redshift of z~7. Regardless of the precise
redshift, the source is remarkably compact (<1 kpc) and faint (z=28.0) yet is
undergoing vigorous star formation at a rate ~2.6 Mo/yr. An intriguing property
is the steep slope of the UV continuum implied by the photometry which may
suggest that the source is representative of an early population of galaxies
responsible for cosmic reionization. Independent verification of these results
is highly desirable but our attempts highlight the difficulty of studying such
sources with present facilities and the challenges faced in pushing back the
frontiers of the observable universe beyond z~6.5.


title: Imprint of Intergalactic Shocks on the Radio Sky

abstract:
  Strong intergalactic shocks are a natural consequence of structure formation
in the universe. They are expected to deposit large fractions of their energy
in relativistic electrons (xi_e~0.05 according to SNR observations) and
magnetic fields (xi_B~0.01 according to cluster halo observations). We
calculate the synchrotron emission from such shocks using an analytical model,
calibrated with a hydrodynamical LCDM simulation. The resulting signal composes
a large fraction of the extragalactic radio background (ERB) below 500 MHz. The
associated angular fluctuations dominate the sky for frequencies nu<10 GHz and
angular scales arcmin-deg (after a modest removal of point sources), provided
that xi_e*xi_B>3*10^-4. The fluctuating signal is most pronounced for nu<500
MHz, dominating the sky even for xi_e*xi_B=5*10^-5. The signal will be easily
observable by next generation radio telescopes such as LOFAR and SKA, and is
marginally observable with present telescopes. It may be identified using
cross-correlations with tracers of large scale structure, possibly even in
existing <10 GHz CMB anisotropy maps and high resolution ~1 GHz radio surveys.
Detection of the signal will provide the first identification of intergalactic
shocks and of the WHIM, and gauge the unknown intergalactic magnetic field. We
show that existing observations of the diffuse <500 MHz radio background are
well fit by a simple, double-disk Galactic model, precluding a direct
identification of the diffuse ERB. Modelling the frequency-dependent anisotropy
pattern observed at very low (1-10 MHz) frequencies can disentangle the
distributions of Galactic cosmic-rays, ionized gas and magnetic fields. Space
missions such as ALFA will thus provide important insight into the structure
and composition of our Galaxy (abridged).


title:
A simple model for hydromagnetic instabilities in the presence of a
  constant magnetic field

abstract:
  In this paper we study a simple model consisting of a dilute fully ionized
plasma in the presence of the gravitational and a constant magnetic field to
analyze the propagation of hydromagnetic instabilities. In particular we show
that the so called Jeans instability is in principle affected by the presence
of the magnetic field. A brief discussion is made attempting to assess this
influence in the stage of the evolution of the Universe where structures were
formed. The most logical conclusion is that if magnetic fields existed in those
times their magnitudes were too small to modify Jeans' mass. Our results places
limits of the possible values of seed magnetic fields consistent with the
formation structures in the Universe. These values are within the range of the
results obtained by other authors.


title:
The 21 centimeter emission from the reionization epoch: extended and
  point source foregrounds

abstract:
  Fluctuations in the redshifted 21 centimeter emission from neutral hydrogen
probe the epoch of reionization. We examine the observability of this signal
and the impact of extragalactic foreground radio sources. We use cosmological
simulations to predict the angular correlation functions of intensity
fluctuations due to unresolved radio galaxies, cluster radio halos and relics
and free-free emission from the interstellar and intergalactic medium at the
frequencies and angular scales relevant for the proposed 21cm tomography. In
accord with previous findings, the brightness temperature fluctuations due to
foreground sources are much larger than those from the primary 21cm signal at
all scales. In particular, diffuse cluster radio emission, which has been
previously neglected, provides the most significant foreground contamination.
However, we show that the contribution to the angular fluctuations at scales
\theta > 1' is dominated by the spatial clustering of bright foreground
sources. This excess can be removed if sources above flux levels S > 0.1 mJy
are detected and removed. Hence, efficient source removal may be sufficient to
allow the detection of angular fluctuations in the 21cm emission free of
extragalactic foregrounds at \theta > 1 arcmin. In addition, the removal of
sources above S=0.1 mJy also reduces the foreground fluctuations to roughly the
same level as the 21cm signal at scales \theta < 1 arcmin. This should allow
the substraction of the foreground components in frequency space, making it
possible to observe in detail the topology and history of reionization.


title: Early Estimation of Microlensing Event Magnifications

abstract:
  Gravitational microlensing events with high peak magnifications provide a
much enhanced sensitivity to the detection of planets around the lens star.
However, estimates of peak magnification during the early stages of an event by
means of chi^2 minimization frequently involve an overprediction, making
observing campaigns with strategies that rely on these predictions inefficient.
  I show that a rudimentary Bayesian formulation, incorporating the known
statistical characteristics of a detection system, produces much more accurate
predictions of peak magnification than chi^2 minimisation. Implementation of
this system will allow efficient follow-up observing programs that focus solely
on events that contribute to planetary abundance statistics.


title: Cosmic Topology: a Brief Overview

abstract:
  Questions such as whether we live in a spatially finite universe, and what
its shape and size may be, are among the fundamental open problems that high
precision modern cosmology needs to resolve. These questions go beyond the
scope of general relativity (GR), since as a (local) metrical theory GR leaves
the global topology of the universe undetermined. Despite our present-day
inability to predict the topology of the universe, given the wealth of
increasingly accurate astro-cosmological observations it is expected that we
should be able to detect it. An overview of basic features of cosmic topology,
the main methods for its detection, and observational constraints on
detectability are briefly presented. Recent theoretical and observational
results related to cosmic topology are also discussed.


title:
The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other
  Cool Dwarf Discoveries

abstract:
  We present the discovery of seven new T dwarfs identified in the Two Micron
All Sky Survey. Low-resolution (R$\sim$150) 0.8--2.5 micron spectroscopy
obtained with the IRTF SpeX instrument reveal the characteristic H$_2$O and
CH$_4$ bands in the spectra of these brown dwarfs. Comparison to spectral
standards observed with the same instrument enable us to derive classifications
of T3 to T7 for the objects in this sample. Moderate-resolution (R$\sim$1200)
near-infrared spectroscopy for a subset of these discoveries reveal K I line
strengths consistent with previously observed trends with spectral type.
Follow-up imaging observations provide proper motion measurements for these
sources, ranging from $<$ 0$\farcs$1 to 1$\farcs$55 yr$^{-1}$. One object,
2MASS 0034+0523, has a spectrophotometric distance placing it within 10 pc of
the Sun. This source also exhibits a depressed K-band peak reminiscent of the
peculiar T dwarf 2MASS 0937+2931, and may be a metal-poor or old, high-mass
brown dwarf. We also present low resolution SpeX data for a set of M and L-type
dwarf, subdwarf, and giant comparison stars used to classify 59 additional
candidates identified as background stars. These are primarily M5-M8.5 dwarfs,
many exhibiting H I Paschen $\gamma$, but include three candidate ultracool M
subdwarfs and one possible early-type L subdwarf.


title: Multi-wavelength Diameters of Nearby Miras and Semiregulars

abstract:
  We have used optical interferometry to obtain multi-wavelength visibility
curves for eight red giants over the wavelength range 650--1000 nm. The
observations consist of wavelength-dispersed fringes recorded with MAPPIT
(Masked APerture-Plane Interference Telescope) at the 3.9-m Anglo-Australian
Telescope. We present results for four Miras (R Car, $o$ Cet, R Hya, R Leo) and
four semi-regular variables (R Dor, W Hya, L$_2$ Pup, $\gamma$ Cru). All stars
except $\gamma$ Cru show strong variations of angular size with wavelength. A
uniform-disk model was found to be a poor fit in most cases, with Gaussian (or
other more tapered profiles) preferred. This, together with the fact that most
stars showed a systematic increase in apparent size toward the blue and a
larger-than-expected linear size, even in the red, all point toward significant
scattering by dust in the inner circumstellar environment. Some stars showed
evidence for asymmetric brightness profiles, while L$_2$ Pup required a
two-component model, indicating an asymmetrical circumstellar dust shell.


title:
Iron Kalpha emission from the low-luminosity Active Galaxies M81 and NGC
  4579

abstract:
  We report on XMM-Newton spectroscopy of the low-luminosity active galaxies
(LLAGN) M81 and NGC4579 both of which have known black hole masses and
well-sampled spectral energy distributions (SED). The iron Kalpha line profiles
from both the LLAGN can be described in terms of two components - a narrow line
at 6.4 keV and a moderately broad line (FWHM = 20000 km/s) arising from highly
ionized, He-like or H-like species (E \sim 6.8 keV). We interpret the broad
lines arising from an accretion disk the inner edge of which is restricted to
large radii (r_{in} \sim 100 r_g). However, the Eddington ratio, {L}/{L_{Edd}},
of these sources, is 3 - 4 orders of magnitude lower than that required to
photo-ionize a cold disk to He-like iron. We suggest that the lines can be
explained as collisionally ionized X-ray lines arising from the transition
region between a hot (radiatively inefficient) flow in the inner regions and a
cold disk outside r \sim 100r_g. The accretion flow geometry probed by our
XMM-Newton observations is consistent with the truncated disk models proposed
to explain the SED of LLAGNs.


title: The formation of Kuiper-belt Binaries through Exchange Reactions

abstract:
  Recent observations have revealed an unexpectedly high binary fraction among
the Trans-Neptunian Objects (TNOs) that populate the Kuiper-belt. The
discovered binaries have four characteristics they comprise a few percent of
the TNOs, the mass ratio of their components is close to unity, their internal
orbits are highly eccentric, and the orbits are more than 100 times wider than
the primary's radius. In contrast, theories of binary asteroid formation tend
to produce close, circular binaries. Therefore, a new approach is required to
explain the unique characteristics of the TNO binaries. Two models have been
proposed. Both, however, require extreme assumptions on the size distribution
of TNOs. Here we show a mechanism which is guaranteed to produces binaries of
the required type during the early TNO growth phase, based on only one
plausible assumption, namely that initially TNOs were formed through
gravitational instabilities of the protoplanetary dust layer.


title: The high energy X-ray tail of Eta Car revealed by BeppoSAX

abstract:
  We report on the June 2000 long (100 ks) BeppoSAX exposure that has unveiled
above 10 keV a new very high energy component of the X-ray spectrum of Eta Car
extending to at least 50 keV. We find that the 2-150 keV spectrum is best
reproduced by a thermal + non-thermal model. The thermal component dominates
the 2-10 keV spectral range with kT_h=5.5 +/- 0.3 keV and log NH_h=22.68 +/-
0.01. The spectrum displays a prominent iron emission line centred at 6.70 keV.
Its equivalent width of 0.94 keV, if produced by the thermal source, gives a
slightly sub-solar iron abundance ([Fe/H]=-0.15 +/- 0.02).
  The high energy tail above 10 keV is best fitted by a power law with a photon
index of 2.42 +/- 0.04. The integrated 13-150 keV luminosity of ~12 L-sun is
comparable to that of the 2-10 keV thermal component. The present result can be
explained, in the Eta Car binary star scenario, by Comptonisation of low
frequency radiation by high energy electrons, probably generated in the
colliding wind shock front, or in instabilities in the wind of the S Dor
primary star. It is possible that the high energy tail had largely weakened
near the minimum of the 5.53 yr cycle. With respect to the thermal component,
it probably has a longer recovering time like that of the highest excitation
optical emission lines. Both features can be associated with the large
absorption measured by BeppoSAX at phase 0.05.


title: Single-Mode versus multimode interferometry: a performance study

abstract:
  We compare performances of ground-based single-mode and multimode (speckle)
interferometers in the presence of partial Adaptive Optics correction of
atmospheric turbulence. It is first shown that for compact sources (i.e.
sources smaller than the Airy disk of a single telescope) not entirely resolved
by the interferometer, the remarkable property of spatial filtering of
single-mode waveguides coupled with AO correction significantly reduces the
speckle noise which arises from residual wavefront corrugations. Focusing on
those sources, and in the light of the AMBER experiment (the near infrared
instrument of the VLTI), we show that single-mode interferometry produces a
better Signal-to-Noise Ratio on the visibility than speckle interferometry.
This is true for bright sources (K < 5), and in any case as soon as Strehl
ratio of 0.2 is achieved. Finally, the fiber estimator is much more robust --
by two orders of magnitude -- than the speckle estimator with respect to Strehl
ratio variations during the calibration procedure. The present analysis
theoretically explains why interferometry with fibers can produce visibility
measurements with a very high precision, 1% or less


title: A catalogue of absorption-line systems in QSO spectra

abstract:
  We present a new catalog of absprption-line systems identified in the quasar
spectra. It contains data on 821 QSOs and 8558 absorption systems comprizing
16139 absorption lines with measured redshifts in the QSO spectra. The catalog
includes absorption-line systems consisting of lines of heavy elements, lines
of neutral hydrogen, Lyman limit systems, damped Ly\alpha absorption systems,
and broad absorption-line systems. The catalog is available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/412/707 and at
www.ioffe.ru/astro/QC. Using the data of the present catalog we also discuss
redshift distributions of absorption-line systems.


title: A variable ultra-luminous X-ray source in the colliding galaxy NGC 7714

abstract:
  We studied the colliding galaxy NGC 7714 with two XMM-Newton observations,
six months apart. The galaxy contains two bright X-ray sources: we show that
they have different physical nature. The off-nuclear source is an accreting
compact object, one of the brightest ultraluminous X-ray sources (ULXs) found
to date. It showed spectral and luminosity changes between the two
observations, from a low/soft to a high/hard state; in the high state, it
reached L_x ~ 6 x 10^{40} erg/s. Its lightcurve in the high state suggests
variability on a ~ 2-hr timescale. Its peculiar location, where the tidal
bridge between NGC 7714 and NGC 7715 joins the outer stellar ring of NGC 7714,
makes it an interesting example of the connection between gas flows in
colliding galaxies and ULX formation. The nuclear source (L_x ~ 10^{41} erg/s)
coincides with a starburst region, and is the combination of thin thermal
plasma emission and a point-source contribution (with a power-law spectrum).
Variability in the power-law component between the two observations hints at
the presence of a single, bright point source (L_x >~ 3 x 10^{40} erg/s):
either a hidden AGN or another ULX.


title: Separating the kinetic SZ effect from primary CMB fluctuations

abstract:
  In the present work, we propose a new method aiming at extracting the kinetic
Sunyaev-Zel'dovich (KSZ) temperature fluctuations embedded in the primary
anisotropies of the cosmic microwave background (CMB). We base our study on
simulated maps without noise and we consider very simple and minimal
assumptions. Our method essentially takes benefit from the spatial correlation
between KSZ and the Compton parameter distribution associated with the thermal
Sunyaev-Zel'dovich (TSZ) effect of the galaxy clusters, the later can be
obtained by means of multi-frequency based component separation techniques. We
reconstruct the KSZ signal by interpolating the CMB fluctuations without making
any hypothesis besides the CMB fluctuations are Gaussian distributed. We
present two ways of estimating the KSZ fluctuations, after the interpolation
step. In the first way we use a blind technique based on canonical Principal
Component Analysis, while the second uses a minimisation criterion based on the
fact that KSZ dominates a small angular scales and that it follows a
non-Gaussian distribution. We show using the correlation between the input and
reconstructed KSZ map that the latter can be reconstructed in a very
satisfactory manner (average correlation coefficient between 0.62 and 0.90),
furthermore both the retrieved KSZ power spectrum and temperature fluctuation
distribution are in quite good agreement with the original signal. The ratio
between the input and reconstructed power spectrum is indeed very close to one
up to a multipole $\ell\sim 200$ in the best case. The method presented here
can be considered as a promising starting point to identify in CMB observations
the temperature fluctuation associated with the KSZ effect.


title: Models for extremely metal-poor halo stars

abstract:
  Two alternative scenarios concerning the origin and evolution of extremely
metal-poor halo stars are investigated. The first one assumes that the stars
have been completely metal-free initially and produced observed carbon and
nitrogen overabundances during the peculiar core helium flash typical for
low-mass Population-III stars. The second scenario assumes that the initial
composition resulted from a mixture of primordial material with ejecta from a
single primordial supernovae. Both scenarios are shown to have problems in
reproducing C, N, and O abundances simultaneously, and both disagree with
observed 12C/13C-ratios,though in different directions. We concentrate on the
most iron-poor, carbon-rich object of this class, HE0107-5240, and conclude
that the second scenario presently offers the more promising approach to
understand these objects, in particular because evolutionary tracks match
observations very well.


title: Regular Motions in Extra-Solar Planetary Systems

abstract:
  This paper is a review of the dynamics of a system of planets. It includes
the study of averaged equations in both non-resonant and resonant systems and
shows the great deal of situations in which the angle between the two
semi-major axes oscillates around a constant value. It introduces the
Hamiltonian equations of the $N$-planet problem and Poincar\'e's reduction of
them to $3N$ degrees of freedom with a detailed discussion of the
non-osculating ``canonical'' heliocentric Keplerian elements that should be
used with Poincar\'e relative canonical variables. It also includes Beaug\'e's
approximation to expand the disturbing function in the exoplanetary case where
masses and eccentricities are large. The paper is concluded with a discussion
of systems captured into resonance and their evolution to symmetric and
asymmetric stationary solutions with apsidal corotation.


title: The associated system of HE2347-4342

abstract:
  We present an analysis of the complex associated system of the high-redshift
QSO HE2347-4342. Absorption features of HI, CIII, CIV, NV, and OVI with up to
16 components occur in the optical spectral range located up to 1500 km/s
redwards from the emission line. Apparently, CIV and NV show the line locking
effect. A quantivative analysis of the line distribution comparing simulated
spectra with randomly distributed doublets reveals, however, no statistical
evidence for its physical reality. Using photoionization calculations to
emulate the observed ion column densities we constrain the quasar's spectral
energy distribution. Absorbers in the velocity range of 200 - 600 km/s can be
modelled successfully with a spectral index of alpha ~ -3 at energies higher
than 3 - 4 Ryd, which is an energy distribution similar to the QSO continuum
suggested by Mathews & Ferland (1987). The analysis of a group of high velocity
absorbers (v > 1300 km/s) leads to a harder energy distribution. The large
amount of helium (log N(HeII) > 16.3) associated with these absorbers implies
that they are responsible for the observed absence of the proximity effect
(Reimers et al. 1997). Clouds located more distant from the quasar may be
shielded from the high energy part of the quasar continuum due to optically
thick absorption shortward of 228 Angstrom by the high velocity absorbers. A
group of absorbers with 900 < v < 1200 km/s, in particular a cloud at 1033
km/s, which has the most reliable column density measurements, can be modelled
neither with photoionzation nor under the assumption of collisionally ionized
gas.


title: The stellar population associated with IRAS source 16132-5039

abstract:
  We report the discovery of a young massive stellar cluster and infrared
nebula in the direction of the CS molecular cloud associated to the IRAS point
source 16132-5039. The analysis of the mid-infrared images from the more
accurate MSX catalog, reveled that there are two independent components
associated with the IRAS source. The integral of the spectral energy
distribution for these components, between 8.28 $\mu$m and 100 $\mu$m, gave
lower limits for the bolometric luminosity of the embedded objects of $8.7
\times 10^4 L_\odot$ and $9 \times 10^3 L_\odot$, which corresponds to ZAMS O8
and B0.5 stars, respectively. The number of Lyman continuum photons expected
from the stars that lie along the reddening line for early-type stars is about
1.7 $ \times$ 10$^{49}$ s$^{-1}$, enough to produce the detected flux densities
at 5 GHz. The NIR spectrum of the nebula increases with frequency, implying
that free-free emission cannot be the main source of the extended luminosity,
from which we conclude that the observed emission must be mainly dust scattered
light. A comparison of the cluster described in this paper with the young
stellar cluster associated with the IRAS source 16177-5018, which is located at
the same distance and direction, shows that the mean visual absorption of the
newly discovered cluster is about 10 magnitudes smaller and it contains less
massive stars, suggesting that it was formed from a less massive molecular
cloud.


title: Weighing the cusp at the Galactic Centre

abstract:
  This paper has been withdrawn temporarily by the authors. As stars close to
the galactic centre have short orbital periods it has been possible to trace
large fractions of their orbits in the recent years. Previously the data of the
orbit of the star S2 have been fitted with Keplerian orbits corresponding to a
massive black hole (MBH) with a mass of M$_{BH}$=3-4$\times10^6$M_sun implying
an insignificant cusp mass.However, it has also been shown that the central
black hole resides in a ~1'' diameter stellar cluster of a priori unknown mass.
In a spherical potential which is neither Keplerian nor harmonic, orbits will
precess resulting in inclined rosetta shaped trajectories on the sky. In this
case, the assumption of non-Keplerian orbits is a more physical approach. It is
also the only approach through which cusp mass information can be obtained via
stellar dynamics of the cusp members. This paper presents the first exemplary
modelling efforts in this direction. Using positional and radial data of star
S2, we find that there could exist an unobserved extended mass component of
several 10$^5$M$_{\odot}$ forming a so-called 'cusp' centred on the black hole
position. Considering only the fraction of the cusp mass M$_{S2_{apo}}$ within
the apocenter of the S2 orbit we find as an upper limit that
M$_{S2_{apo}}$/(M$_{BH}$ + M$_{S2_{apo}}$) $\le$ 0.05. A large extended cusp
mass, if present, is unlikely to be composed of sub-solar mass constituents,
but could be explained rather well by a cluster of high M/L stellar remnants,
which we find to form a stable configuration.


title: Cosmology and Gravitostatics

abstract:
  In gravitostatics, the minimally generalized Newtonian theory, the simplest
cosmological model implies a cosmological redshift with acceleration parameter
-1. If the gravitational potential satisfies a wave equation, the total mass
density (visible plus dark) is one third of the critical density, in good
agreement with observation. There is no horizon problem and no need to invoke
dark energy.


title:
Models for the Gravitational Field of the Galactic Bar. An Application
  to Stellar Orbits in the Galactic Plane and Orbits of Some Globular Clusters

abstract:
  We built three models for the gravitational field of the Galactic bar. These
models are an inhomogeneous ellipsoid, an inhomogeneous prolate spheroid, and a
superposition of four inhomogeneous ellipsoids. Among the three models, the
superposition provides our best approximation to the observed boxy mass
distribution of the Galactic bar. Adding the bar component to an axisymmetric
Galactic model, we have calculated stellar midplane orbits and orbits of some
globular clusters with known kinematical data. For all models we find a secular
dispersion effect upon the orbital energy and angular momentum, as measured in
the Galactic inertial frame. This effect might be relevant to explain the
orbital prograde-retrograde distribution of globular clusters. For the stellar
kinematics, we study the connection between the sense of orbital motion in the
midplane and the onset of chaos in the presence of the bar. In the inner region
of the bar, chaos is induced by an axisymmetric central component (bulge) and
it arises in orbits that change its orbital sense from prograde to retrograde
and vice versa as seen from an inertial reference frame. Outside the bar
region, chaos appears only in prograde orbits. Our results concerning such
connection are consistent and extend those obtained for midplane orbits in the
presence of only a spiral pattern in the axisymmetric Galactic model.


title:
The Central Region of Barred Galaxies: Molecular Environment,
  Starbursts, and Secular Evolution

abstract:
  Despite compelling evidence that stellar bars drive gas into the inner 1--2
kpc or circumnuclear (CN) region of galaxies, there are few large, high
resolution studies of the CN molecular gas and star formation (SF). We study a
sample of local barred non-starbursts and starbursts with high-resolution CO,
optical, Ha, RC, Br-gamma, and HST data, and find the following. (1) The inner
kpc of bars differs markedly the outer disk and hosts molecular gas surface
densities Sigma-gas-m of 500-3500 Msun pc-2, gas mass fractions of 10--30 %,
and epicyclic frequencies of several 100--1000 km s-1 kpc-1.Consequently,
gravitational instabilities can only set in at high gas densities and grow on a
short timescale (few Myr). This high density, short timescale, `burst' mode may
explain why powerful starbursts tend to be in the CN region of galaxies. (2) We
suggest that the variety in CO morphologies is due to different stages of
bar-driven inflow. At late stages, most of the CN gas is inside the outer inner
Lindblad resonance (OILR), and has predominantly circular motions. Across the
sample, we find bar pattern speeds with upper limits of 43 to 115 km s-1 kpc-1
and OILR radii of > 500 pc. (3) Barred starbursts and non-starbursts have CN
SFRs of 3--11 and 0.1--2 Msun yr-1, despite similar CN gas mass. Sigma-gas-m in
the starbursts is larger (1000--3500 Msun pc-2) and close to the Toomre
critical density over a large region. (4) Molecular gas makes up 10%--30% of
the CN dynamical mass (6--30 x 10^9 Msun).In the starbursts, it fuels CN SFRs
of 3--11 Msun yr-1, building young, massive, high V/sigma components. We
present evidence for such a pseudo-bulge in NGC 3351. Implications for secular
evolution along the Hubble sequence are discussed.


title: The Interaction of Radio Sources and X-ray-Emitting Gas in Cooling Flows

abstract:
  Recent observations of the interactions between radio sources and the
X-ray-emitting gas in cooling flows in the cores of clusters of galaxies are
reviewed. The radio sources inflate bubbles in the X-ray gas, which then rise
buoyantly outward in the clusters transporting energy to the intracluster
medium (ICM). The bright rims of gas around the radio bubbles are cool, rather
than hot, and do not show signs of being strongly shocked. Energy deposited
into the ICM over the lifetime of a cluster through several outbursts of a
radio source helps to account for at least some of the gas that is missing in
cooling flows at low temperatures.


title:
On the Relationship Between the Optical Emission-Line and X-ray
  Luminosities in Seyfert 1 Galaxies

abstract:
  We have explored the relationship between the [O III] $\lambda$5007 and the
2--10 keV luminosities for a sample of Broad- and Narrow-Line Seyfert 1
galaxies (BLSy1 and NLSy1, respectively). We find that both types of Seyferts
span the same range in luminosity and possess similar [O III]/X-ray ratios. The
NLSy1s are more luminous than BLSy1s, when normalized to their central black
hole masses, which is attributed to higher mass accretion rates. However, we
find no evidence for elevated [O III]/X-ray ratios in NLSy1s, which would have
been expected if they had excess EUV continuum emission compared to BLSy1s.
Also, other studies suggest that the gas in narrow-line regions (NLR) of NLSy1s
and NLSy1s span a similar range in ionization, contrary to what is expected if
those of the former are exposed to a stronger flux of EUV radiation. The
simplest interpretation is that, like BLSy1s, a large EUV bump is not present
in NLSy1s. However, we show that the [OIII]/X-ray ratio can be lowered as a
result of absorption of the ionizing continuum by gas close to the central
source, although there is no evidence that intrinsic line-of-sight absorption
is more common among NLSy1s, as would be expected if there were a larger amount
of circumnuclear gas. Other possible explanations include: 1) anisotropic
emission of the ionizing radiation, 2) higher gas densities in the NLR of
NLSy1s, resulting in lower average ionization, or 3) the presence of strong
winds in the the nuclei of NLSy1s which may drive off much of the gas in the
narrow-line region, resulting in lower cover fraction and weaker [O III]
emission.


title:
Did Something Decay, Evaporate, or Annihilate during Big Bang
  Nucleosynthesis?

abstract:
  Results of a detailed examination of the cascade nucleosynthesis resulting
from the putative hadronic decay, evaporation, or annihilation of a primordial
relic during the Big Bang nucleosynthesis (BBN) era are presented. It is found
that injection of energetic nucleons around cosmic time 1000 sec may lead to an
observationally favored reduction of the primordial Li7/H yield by a factor 2 -
3. Moreover, such sources also generically predict the production of the Li6
isotope with magnitude close to the as yet unexplained high Li6 abundances in
low-metallicity stars. The simplest of these models operate at fractional
contribution to the baryon density Omega_b h^2> 0.025, slightly larger than
that inferred from standard BBN. Though further study is required, such
sources, as for example due to the decay of the next-to-lightest supersymmetric
particle into GeV gravitinos or the decay of an unstable gravitino in the TeV
range of abundance \Omega_G h^2\sim 5\times 10^{-4} show promise to explain
both the Li6 and Li7 abundances in low metallicity stars.


title:
Microlensing of the Broad Emission Line Region in the Quadruple Lens
  SDSS J1004+4112

abstract:
  We present seven epochs of spectroscopy on the quadruply imaged quasar SDSS
J1004+4112, spanning observed-frame time delays from 1 to 322 days. The spectra
reveal differences in the emission lines between the lensed images.
Specifically, component A showed a strong enhancement in the blue wings of
several high-ionization lines relative to component B, which lasted at least 28
days (observed frame) then faded. Since the predicted time delay between A and
B is <30 days, our time coverage suggests that the event was not intrinsic to
the quasar. We attribute these variations to microlensing of part of the broad
emission line region of the quasar, apparently resolving structure in the
source plane on a scale of ~10^{16} cm at z=1.734. In addition, we observed
smaller differences in the emission line profiles between components A and B
that persisted throughout the time span, which may also be due to microlensing
or millilensing. Further spectroscopic monitoring of this system holds
considerable promise for resolving the structure of the broad emission line
region in quasars.


title: VOBOZ: An Almost-Parameter-Free Halo-Finding Algorithm

abstract:
  We have developed an algorithm to find haloes in an N-body dark matter
simulation, called VOBOZ (VOronoi BOund Zones), which has as little dependence
on free parameters as we can manage. By using the Voronoi diagram, we achieve
nonparametric, `natural' measurements of each particle's density and set of
neighbors. We then eliminate much of the ambiguity in merging sets of particles
together by identifying every possible density peak, and measuring the
probability that each does not arise from Poisson noise. This probability could
be interpreted as a measure of a halo's sub-haloness, and might be of use to
researchers of the halo model. The first parameter in VOBOZ controls the
subtlety of particle unbinding, and may be eliminated if one is cavalier with
processor time; even if one is not, the results saturate to the parameter-free
answer when the parameter is sufficiently small. The only parameter which
remains, an outer density cut-off, does not influence whether or not haloes are
identified, nor does it have any effect on subhaloes; it only affects the
masses returned for supercluster haloes.


title: The Evolution of the Intergalactic Medium Transmission to Redshift Six

abstract:
  We have measured the transmission of the Lyman alpha forest produced by
neutral hydrogen scattering in the intergalactic medium between redshifts 2 and
6.3 using high signal to noise, high resolution (R > 5000) observations of 50
quasars spread over the redshift range. We use a uniform set of 15 Angstrom
intervals covering Lyman alpha, Lyman beta, and Lyman gamma absorption regions
to tabulate the forest transmission as a function of redshift. The transmitted
fractions show a relatively smooth evolution over the entire range of
redshifts, which can be modelled with a smoothly decreasing ionization rate.
Previous claims of an abrupt change at a redshift of approximately 6 appear in
part to be a consequence of an incorrect conversion of Lyman beta to Lyman
alpha optical depths. The tabulated transmissions can be used to calculate the
colors of objects with a specified input spectrum as a function of redshift. We
calculate the colors of a flat f_nu galaxy with a large intrinsic continuum
break, as an important example.


title:
A Systematic Study of Radio-Induced X-ray Cavities in Clusters, Groups,
  and Galaxies

abstract:
  We present an analysis of sixteen galaxy clusters, one group and one galaxy
drawn from the Chandra X-ray Observatory's data archive. These systems possess
prominent X-ray surface brightness depressions associated with cavities or
bubbles that were created by interactions between powerful radio sources and
the surrounding hot gas. The minimum energy associated with the cavities ranges
between pV~10^55 erg in galaxies, groups, and poor clusters to pV~10^60 erg in
rich clusters. We evaluate the hypothesis that cooling in the hot gas can be
quenched by energy injected into the surrounding gas by the rising bubbles.
Nearly half of the systems in this study may have instantaneous mechanical
luminosities large enough to balance cooling, at least for a short period of
time, if the cavities are filled with a relativistic gas. We find a trend or
upper envelope in the distribution of central X-ray luminosity versus
instantaneous mechanical luminosity with the sense that the most powerful
cavities are found in the most X-ray luminous systems. Such a trend would be
expected if many of these systems produce bubbles at a rate that scales in
proportion to the cooling rate of the surrounding gas. Finally, we use the
X-ray cavities to measure the mechanical power of radio sources over six
decades of radio luminosity, independently of the radio properties themselves.
We find that the ratio of the instantaneous mechanical (kinetic) luminosity to
the 1.4 GHz synchrotron luminosity ranges from a few to roughly a thousand.
This wide range implies that the 1.4 GHz synchrotron luminosity is an
unreliable gauge of the mechanical power of radio sources.


title:
Self-bound CFL stars in binary systems : are they "hidden" among the
  black hole candidates?

abstract:
  The identification of black holes is one of the most important tasks of
modern astrophysics. Candidates have been selected among binary stars based on
a high mass function, and seriously considered when the lower mass limit
exceeds ~ 3 solar masses. More recently the absence of (Type I) thermonuclear
bursts has been advanced as an additional criterion in favor of the black hole
interpretation, since the absence of a solid surface naturally precludes the
accumulation and ignition of accreting material. We discuss in this Letter the
possibility that self-bound stars made of CFL-paired quarks mimic the behavior
of at least the low-mass end black holes as a result of a) higher maximum
masses than ordinary neutron stars b) low steady luminosities due to the bare
surface properties c) impossibility of generating Type I bursts because of the
complete absence of normal matter crusts at their surfaces. These features
caution about a positive identification of event horizons based on the lack of
bursts.


title: Nonlinear Parker Instability with the Effect of Cosmic-Ray Diffusion

abstract:
  We present the results of linear analysis and two-dimensional local
magnetohydrodynamic (MHD) simulations of the Parker instability, including the
effects of cosmic rays (CRs), in magnetized gas disks (galactic disks). As an
unperturbed state for both the linear analysis and the MHD simulations, we
adopted an equilibrium model of a magnetized two-temperature layered disk with
constant gravitational acceleration parallel to the normal of the disk. The
disk comprises a thermal gas, cosmic rays and a magnetic field perpendicular to
the gravitational accelerartion. Cosmic ray diffusion along the magnetic field
is considered; cross field-line diffusion is supposed to be small and is
ignored. We investigated two cases in our simulations. In the mechanical
perturbation case we add a velocity perturbation parallel to the magnetic field
lines, while in the explosional perturbation case we add cosmic ray energy into
a sphere where the cosmic rays are injected. Linear analysis shows that the
growth rate of the Parker instability becomes smaller if the coupling between
the CR and the gas is stronger (i.e., the CR diffusion coefficient is smaller).
Our MHD simulations of the mechanical perturbation confirm this result. We show
that the falling matter is impeded by the CR pressure gradient, this causes a
decrease in the growth rate. In the explosional perturbation case, the growth
of the magnetic loop is faster when the coupling is stronger in the early
stage. However, in the later stage the behavior of the growth rate becomes
similar to the mechanical perturbation case.


title: Cosmic ray threshold anomaly and kinematics in the dS spacetime

abstract:
  We present a covariant framework of kinematics in the dS spacetime, which is
a natural postulate of recent astronomical observations ($\Lambda>0)$.
One-particle states are presented explicitly. It is noticed that the dispersion
relation of free particles is dependent on the degrees of freedom of angular
momentum and spin. This fact can be referred to as the effects of the
cosmological constant on kinematics of particles. The kinematics in dS
spacetime is used to investigate the phenomenon of ultra high energy cosmic
rays. We emphasize the possibility of solving the threshold anomalies of the
interactions between ultra high energy cosmic rays and soft photons in the
covariant framework of kinematics in the dS spacetime.


title: Detection of Knots and Jets in IRAS 06061+2151

abstract:
  We report detection of a Young Stellar Object with an evidence for an outflow
in the form of knots in the molecular hydrogen emission line (2.121 micron)
towards the massive star forming region IRAS 06061+2151. Near-infrared images
reveal IRAS 06061+2151 to be a cluster of at least five sources, four of which
seem to be early B type young stellar objects, in a region of 12 arcsec
surrounded by a nebulosity. The presence of the knots that are probably similar
to the HH objects in the optical wavelengths, suggests emerging jets from one
of the cluster members. These jets appear to excite a pair of knot-like objects
(Knot-NW and Knot-SE) and extend over a projected size of 0.5pc. The driving
source for the jets is traced back to a member of the cluster whose position in
the H-Ks/J-H color-color diagram indicates that it is a Class 1 type
pre-mainsequence star. We also obtained K band spectra of the brightest source
in the cluster and of the nearby nebular matter. The spectra show molecular
hydrogen emission lines but do not show Brackett gamma line at 2.167 micron.
These spectra suggest that the excitation of the molecular hydrogen lines is
probably due to a mild shock.


title:
The IC2118 association: new T Tauri stars in high-latitude molecular
  clouds

abstract:
  We identified new pre-main sequence stars in the region of high-latitude
molecular clouds associated with the reflection nebula IC2118, around l = 208
degr and b = -27 degr. The stars were selected as T Tauri candidates in
objective prism plates obtained with the Schmidt telescope of Konkoly
Observatory. Results of spectroscopic follow-up observations, carried out with
the FLAIR spectrograph installed on the UK Schmidt and with ALFOSC on Nordic
Optical Telescope, are presented in this paper. Based on spectral types,
presence of emission lines and lithium absorption line, we identified five
classical T Tauri stars and a candidate weak-line T Tauri star projected on the
molecular clouds, as well as two candidate pre-main sequence stars outside the
nebulous region. Using the near infrared magnitudes obtained from the 2MASS All
Sky Catalog. we determined the masses and ages of these stars. We found that
the five classical T Tauri stars projected on the clouds are physically related
to them, whereas the other stars are probably background objects. Adopting a
distance of 210 pc for IC2118 (Kun et al. 2001) and using Palla & Stahler's
(1999) evolutionary tracks we derived an average age of 2.5 million yrs and a
mass interval of 0.4--1.0 M_sun for the members of the IC2118 association.


title:
Asteroseismology of the Beta Cephei star Nu Eridani: Interpretation and
  applications of the oscillation spectrum

abstract:
  The oscillation spectrum of Nu Eri is the richest known for any variable of
the Beta Cephei type. We interpret the spectrum in terms of normal mode
excitation and construct seismic models of the star. The frequency data
combined with data on mean colours sets the upper limit on the extent of
overshooting from the convective core. We use data on rotational splitting of
two dipole (l=1) modes (g_1 and p_1) to infer properties of the internal
rotation rate. Adopting a plausible hypothesis of nearly uniform rotation in
the envelope and increasing rotation rate in the mu-gradient zone, we find that
the mean rotation rate in this zone is about three times faster than in the
envelope. In our standard model only the modes in the middle part of the
oscillation spectrum are unstable. To account for excitation of a possible
high-order g-mode at nu = 0.43 c/d as well as p-modes at nu > 6 c/d we have to
invoke an overabundance of Fe in the driving zone.


title: Propagation and Dynamics of Relativistic Jets

abstract:
  We investigate the dynamics and morphology of jets propagating into the
interstellar medium using 2D relativistic hydrodynamic simulations. The
calculations are performed assuming axisymmetric geometry and trace a long
propagation of jets. The jets are assumed to be 'light' with the density ratio
between the beam to the ambient gas much less than unity. We examine the
mechanism for the appearance of vortices at the head of jets in the hot spot.
Such vortices are known as a trigger of a deceleration phase which appears
after a short phase in which one dimensional analysis is dominant. We find that
an oblique shock at the boundary rim near the end of the beam strongly affects
the flow structure in and around the hot spot. Weakly shocked gas passed
through this oblique shock and becomes a trigger for the generation of
vortices. We also find the parameter dependence of these effects for the
propagation and dynamics of the jets. The jet with slower propagation velocity
is weakly pinched, has large vortices and shows very complex structure at the
head of the jets and extended synchrotron emissivity.


title: Models of the Knee in the Energy Spectrum of Cosmic Rays

abstract:
  The origin of the knee in the energy spectrum of cosmic rays is an
outstanding problem in astroparticle physics. Numerous mechanisms have been
proposed to explain the structure in the all-particle spectrum. In the article
basic ideas of several models are summarized, including diffusive acceleration
of cosmic rays in shock fronts, acceleration via cannonballs, leakage from the
Galaxy, interactions with background particles in the interstellar medium, as
well as new high-energy interactions in the atmosphere. The calculated energy
spectra and mean logarithmic masses are compiled and compared to results from
direct and indirect measurements.


title:
The 2D Continuum Radiative Transfer Problem: Benchmark Results for Disk
  Configurations

abstract:
  We present benchmark problems and solutions for the continuum radiative
transfer (RT) in a 2D disk configuration. The reliability of three Monte-Carlo
and two grid-based codes is tested by comparing their results for a set of
well-defined cases which differ for optical depth and viewing angle. For all
the configurations, the overall shape of the resulting temperature and spectral
energy distribution is well reproduced. The solutions we provide can be used
for the verification of other RT codes.We also point out the advantages and
disadvantages of the various numerical techniques applied to solve the RT
problem.


title: A transonic collisionless model of the solar wind

abstract:
  Because of the semi-collisional nature of the solar wind, the collisionless
or exospheric approach as well as the hydrodynamic one are both inaccurate.
However, the advantage of simplicity makes them useful for enlightening some
basic mechanisms of solar wind acceleration. Previous exospheric models have
been able to reproduce winds that were already nearly supersonic at the
exobase, the altitude above which there are no collisions. In order to allow
transonic solutions, a lower exobase has to be considered, in which case the
protons are experiencing a non-monotonic potential energy profile. This is done
in the present work. In this model, the electron velocity distribution in the
corona is assumed non-thermal. Parametric results are presented and show that
the high acceleration obtained does not depend on the details of the
non-thermal distributions. This acceleration seems, therefore, to be a robust
result produced by the presence of a sufficient number of suprathermal
electrons. A method for improving the exospheric description is also given,
which consists in mapping particle orbits in terms of their invariants of
motion.


title: Extended Mosaic Observations with the Cosmic Background Imager

abstract:
  Two years of microwave background observations with the Cosmic Background
Imager (CBI) have been combined to give a sensitive, high resolution angular
power spectrum over the range 400 < l < 3500. This power spectrum has been
referenced to a more accurate overall calibration derived from WMAP. The data
cover 90 deg^2 including three pointings targeted for deep observations. The
uncertainty on the l > 2000 power previously seen with the CBI is reduced.
Under the assumption that any signal in excess of the primary anisotropy is due
to a secondary Sunyaev-Zeldovich anisotropy in distant galaxy clusters we use
CBI, ACBAR, and BIMA data to place a constraint on the present-day rms mass
fluctuation sigma_8. We present the results of a cosmological parameter
analysis on the l < 2000 primary anisotropy data which show significant
improvements in the parameters as compared to WMAP alone, and we explore the
role of the small-scale cosmic microwave background data in breaking parameter
degeneracies.


title: Asteroseismic determination of helium abundance in stellar envelopes

abstract:
  Intermediate degree modes of the solar oscillations have previously been used
to determine the solar helium abundance to a high degree of precision. However,
we cannot expect to observe such modes in other stars. In this work we
investigate whether low degree modes that should be available from space-based
asteroseismology missions can be used to determine the helium abundance, Y, in
stellar envelopes with sufficient precision. We find that the oscillatory
signal in the frequencies caused by the depression in \Gamma_1 in the second
helium ionisation zone can be used to determine the envelope helium abundance
of low mass main sequence stars. For frequency errors of 1 part in 10^4, we
expect errors \sigma_Y in the estimated helium abundance to range from 0.03 for
0.8M_sun stars to 0.01 for 1.2M_sun stars. The task is more complicated in
evolved stars, such as subgiants, but is still feasible if the relative errors
in the frequencies are less than 10^{-4}.


title:
Protostellar Angular Momentum Evolution during Gravoturbulent
  Fragmentation

abstract:
  Using hydrodynamic simulations we investigate the rotational properties and
angular momentum evolution of prestellar and protostellar cores formed from
gravoturbulent fragmentation of interstellar gas clouds. We find the specific
angular momentum j of prestellar cloud cores in our models to be on average
comparable to the observed values. A fraction of prestellar cores is
gravitationally unstable and goes into collapse to build up protostars and
protostellar systems. Their specific angular momentum is one order of magnitude
lower than their parental cores and in agreement with observations of
main-sequence binaries.
  The ratio of rotational to gravitational energy of protostellar cores in the
model turns out to be very similar to the observed values. We find, that it is
roughly conserved during the main collapse phase. This leads to j proportional
to M^{2/3}, where j is specific angular momentum and M core mass. Although the
temporal evolution of the angular momentum of individual protostars or
protostellar systems is complex and highly time variable, this correlation
holds well in a statistical sense for a wide range of turbulent environmental
parameters. In addition, high turbulent Mach numbers result in the formation of
more numerous protostellar cores with, on average, lower mass. Therefore,
models with larger Mach numbers result in cores with lower specific angular
momentum. We find, however, no dependence on the spatial scale of the
turbulence. Our models predict a close correlation between the angular momentum
vectors of neighboring protostars during their main accretion phase. Possible
observational signatures are aligned disks and parallel outflows. The latter
are indeed observed in some low-mass isolated Bok globules.


title: The Large Scale Distribution of Galaxies in the Shapley Supercluster

abstract:
  We present new results of our wide-field redshift survey of galaxies in a 182
square degree region of the Shapley Supercluster (SSC) based on observations
with the FLAIR-II spectrograph on the UK Schmidt Telescope. We present new
measurements to give a total sample of redshifts for 710 bright (R<16.6)
galaxies, of which 464 are members of the SSC (8000<v<18000 kms). Our data
reveal that the main plane of the SSC extends further than previously realised,
filling the whole extent of our survey region of 10 degrees by 20 degrees on
the sky (35 Mpc by 70 Mpc). There is also a significant structure associated
with the slightly nearer Abell 3571 cluster complex with a caustic structure
evident out to a radius of 6 Mpc. These galaxies seem to link two previously
identified sheets of galaxies and establish a connection with a third one at
v=15000 kms. They also tend to fill the gap of galaxies between the foreground
Hydra-Centaurus region and the more distant SSC. We calculate galaxy
overdensities of 5.0+/-0.1 over the 182 square degree region surveyed and
3.3+/-0.1 in a 159 square degree region excluding rich clusters.


title:
Spectral Statistics and Luminosity Function of a Hard X-ray Complete
  Sample of Brightest AGNs

abstract:
  We investigated the statistics of the X-ray spectral properties of a complete
flux-limited sample of bright AGNs from HEAO-1 all-sky catalogs to provide the
bright end constraint of the evolution of AGN hard X-ray luminosity function
(HXLF) and the AGN population synthesis model of the X-ray background. Spectral
studies have been made using ASCA and XMM-Newton observation data for almost
all AGNs in this sample.


title: Wind Accretion by a Binary Stellar System and Disk Formation

abstract:
  I calculate the specific angular momentum of mass accreted by a binary system
embedded in the dense wind of a mass losing asymptotic giant branch star. The
accretion flow is of the Bondi-Hoyle-Lyttleton type. For most of the relevant
parameters space the flow is basically an isothermal high Mach number accretion
flow. I find that when the orbital plane of the accreting binary system and the
orbital plane of the triple system are not parallel to each other, the accreted
mass onto one or two of the binary system components has high specific angular
momentum. For a large fraction of triple-star systems, accretion disks will be
formed around one or two of the stars in the binary system, provided that the
mass ratio of the two stars in the accreting binary system is >0.5. Such disks
may blow jets which shape the descendant planetary nebula. The jets' axis will
be almost parallel to the orbital plane of the triple-star system. One jet is
blown outward relative to the wind, while the other jet pass near the mass
losing star, and is more likely to be slowed down or deflected. I find that
during the final asymptotic giant branch phase, when mass loss rate is very
high, accretion disk may form for orbital separation between the accreting
binary systems and the mass losing star of up to 400-800 AU. I discuss the
implications for the shape of the descendant planetary nebula, and list several
planetary nebulae which may have been shaped by an accreting binary star
system, i.e., by a triple star system.


title: The DRAO 26-m Large Scale Polarization Survey at 1.41 GHz

abstract:
  The Effelsberg telescope as well as the DRAO synthesis telescope are
currently surveying the Galactic polarized emission at 21 cm in detail. These
new surveys reveal an unexpected richness of small-scale structures in the
polarized sky. However, observations made with synthesis or single-dish
telescopes are not on absolute intensity scales and therefore lack information
about the large-scale distribution of polarized emission to a different degree.
Until now, absolutely calibrated polarization data from the Leiden/Dwingeloo
polarization surveys are used to recover the missing spatial information.
However, these surveys cannot meet the requirements of the recent survey
projects regarding sampling and noise and new polarization observation were
initiated to complement the Leiden/Dwingeloo Survey. In this paper we will
outline the observation and report on the progress for a new polarization
survey of the northern sky with the 26-m telescope of the DRAO.


title:
A halo approach to the evaluation of the cross-correlation between the
  SZ sky and galaxy survey

abstract:
  Using a purely analytic approach to gaseous and dark matter halos, we study
the cross-correlation between the Sunyaev-Zel'dovich (SZ) sky and galaxy survey
under flat sky approximation, in an attempt to acquire the redshift information
of the SZ map. The problem can be greatly simplified when it is noticed that
the signals of the SZ-galaxy correlation arise only from hot gas and galaxies
inside the same massive halos (i.e. clusters), and field galaxies make almost
no contribution to the cross-correlation. Under the assumption that both the
hot gas and galaxies trace the common gravitational potential of dark halos, we
calculate the expected cross SZ-galaxy power spectra for the WMAP/Planck SZ
maps and the SDSS galaxy sample at small scales $100<l<1000$. It turns out,
however, that it is not presently feasible to measure such small angular cross
power spectra because of the high noise levels at $l>400$ with the WMAP/Planck
experiments. Future SZ observations with better angular resolutions and
sufficiently wide sky coverages will be needed if this technique is applied for
the statistical measurement of redshift distribution of the SZ sources.


title:
Detection and Investigation of the Properties of Dark Electric Matter
  Objects: The First Results and Prospects

abstract:
  Negative Dark Electric Matter Objects, daemons, have been detected by means
of ZnS(Ag) scintillator screens. These objects are apparently relic elementary
Planckian black holes. The scintillations in ZnS(Ag) are excited by electrons
and nucleons ejected as the daemon captures a nucleus of Zn (or S). By
catalyzing the decay of protons in the remainder of the nucleus, the daemon
becomes capable of capturing a new nucleus, and so on. The time elapsed between
successive captures (scintillations) is used to estimate the daemon velocity
and the proton decay time (~1 microsec). The flux of daemons with velocities
from ~5 to ~30 km/s is ~10-9 cm-2s-1 and varies with a period of 0.5 yr. This
could indicate a preferred direction of the flux, which is a result of the
Sun's moving relative to daemons in the Galactic disk and of their capture into
helio- and geocentric orbits. Daemons crowd at the centres of the Earth, the
Sun, and the Galaxy, where they catalyze proton decay, a process capable of
accounting from a common standpoint a variety of observations and phenomena
unexplained heretofore.


title:
Magnesium abundances in mildly metal-poor stars from different
  indicators

abstract:
  We present magnesium abundances derived from high resolution spectra using
several Mg I and two high excitation Mg II lines for 19 metal-poor stars with
[Fe/H] values between -1.1 and +0.2. The main goal is to search for systematic
differences in the derived abundances between the two ionisation state lines.
Our analysis shows that the one-dimensional LTE and N-LTE study finds a very
good agreement between these features. The [Mg/Fe] vs. [Fe/H] relationship
derived, despite the small sample of stars, is also in agreement with the
classical figure of increasing [Mg/Fe] with decreasing metallicity. We find a
significant scatter however, in the [Mg/Fe] ratio at [Fe/H]$\sim -0.6$ which is
currently explained as a consequence of the overlap at this metallicity of
thick and thin disk stars, which were probably formed from material with
different nucleosynthesis histories. We speculate on the possible consequences
of the agreement found between Mg I and Mg II lines on the very well known
oxygen problem in metal-poor stars. We also study the [O/Mg] ratio in the
sample stars using oxygen abundances from the literature and find that the
current observations and nucleosynthetic predictions from type II supernovae
disagree. We briefly discuss some alternatives to solve this discrepancy.


title: Unidentified EGRET Sources

abstract:
  A brief summary of the main properties of the unidentified gamma-ray sources
detected by EGRET is presented, with particular emphasis on the different
populations and their phenomenological characteristics.


title: Faraday Rotation and Depolarization of Galactic Radio Emission

abstract:
  A joint action of depth and bandwidth depolarization in the interstellar
medium is considered using a model of N homogeneous synchrotron layers with
Faraday rotation. The bandwidth depolarization can be used in multifrequency
polarimetric observations of Galactic diffuse synchrotron radio emission to
investigate the interstellar ionized medium and magnetic field in the direction
to the Faraday-thick objects of known distances.


title: Astrophysical Origins of Ultrahigh Energy Cosmic Rays

abstract:
  In the first part of this review we discuss the basic observational features
at the end of the cosmic ray energy spectrum. We also present there the main
characteristics of each of the experiments involved in the detection of these
particles. We then briefly discuss the status of the chemical composition and
the distribution of arrival directions of cosmic rays. After that, we examine
the energy losses during propagation, introducing the Greisen-Zaptsepin-Kuzmin
(GZK) cutoff, and discuss the level of confidence with which each experiment
have detected particles beyond the GZK energy limit. In the second part of the
review, we discuss astrophysical environments able to accelerate particles up
to such high energies, including active galactic nuclei, large scale galactic
wind termination shocks, relativistic jets and hot-spots of Fanaroff-Riley
radiogalaxies, pulsars, magnetars, quasar remnants, starbursts, colliding
galaxies, and gamma ray burst fireballs. In the third part of the review we
provide a brief summary of scenarios which try to explain the super-GZK events
with the help of new physics beyond the standard model. In the last section, we
give an overview on neutrino telescopes and existing limits on the energy
spectrum and discuss some of the prospects for a new (multi-particle)
astronomy. Finally, we outline how extraterrestrial neutrino fluxes can be used
to probe new physics beyond the electroweak scale.


title:
Unveiling Su Aurigae in the near Infrared: New high spatial resolution
  results using Adaptive Optics

abstract:
  We present here new results on circumstellar nebulosity around SU Aurigae, a
T-Tauri star of about 2 solar mass and 5 Myrs old at 152 pc in the J, H and K
bands using high resolution adaptive optics imaging (0$\farcs$30) with the Penn
state IR Imaging Spectrograph (PIRIS) at the 100 inch Mt. Wilson telescope.
  A comparison with HST STIS optical (0.2 to 1.1 micron) images shows that the
orientation of the circumstellar nebulosity in the near-IR extends from PAs 210
to 270 degrees in H and K bands and up to 300 degrees in the J band. We call
the circumstellar nebulosity seen between 210 to 270 degrees as 'IR
nebulosity'. We find that the IR nebulosity (which extends up to 3.5 arcsecs in
J band and 2.5 arcsecs in the K band) is due to scattered light from the
central star. The IR nebulosity is either a cavity formed by the stellar
outflows or part of the circumstellar disk. We present a schematic
3-dimensional geometrical model of the disk and jet of SU Aur based on STIS and
our near-IR observations. According to this model the IR nebulosity is a part
of the circumstellar disk seen at high inclination angles. The extension of the
IR nebulosity is consistent with estimates of the disk diameter of 50 to 400 AU
in radius, from earlier mm, K band interferometric observations and SED
fittings.


title: Evolution of massive and magnetized protoplanetary disks

abstract:
  We present global 2D and 3D simulations of self-gravitating magnetized tori.
We used the 2D calculations to demonstrate that the properties of the MRI are
not affected by the presence of self-gravity: MHD turbulence and enhanced
angular momentum transport follow the linear growth of the instability. In 3D,
we have studied the interaction between an $m=2$ gravitational instability and
MHD turbulence. We found its strength to be significantly decreased by the
presence of the latter, showing that both instabilities strongly interact in
their non-linear phases. We discuss the consequences of these results.


title:
The superluminal motion of Gamma-Ray-Burst sources and the complex
  afterglow of GRB 030329

abstract:
  The source of the very bright Gamma-Ray Burst GRB 030329 is close enough to
us for there to be a hope to measure or significantly constrain its putative
superluminal motion. Such a phenomenon is expected in the ``Cannonball'' (CB)
model of GRBs. Recent precise data on the optical and radio afterglow of this
GRB --which demonstrated its very complex structure-- allow us to pin down the
CB-model's prediction for the afterglow-source position as a function of time.
It has been stated that (the unpublished part of) the new radio data
``unequivocably disprove'' the CB model. We show how greatly exaggerated that
obituary announcement was, and how precise a refined analysis of the data would
have to be, to be still of interest.


title:
Optical Imaging of Very Luminous Infrared Galaxy Systems: Photometric
  Properties and Late Evolution

abstract:
  A sample of 19 low redshift (0.03$<$z$<$0.07) very luminous infrared galaxy
(VLIRG: $10^{11}L_\odot< $ L[8-1000 $\mu$m] $ < 10^{12} L_\odot$) systems (30
galaxies) has been imaged in $B$, $V$, and $I$. These objects cover a
luminosity range that is key to linking the most luminous infrared galaxies
with the population of galaxies at large. We have obtained photometry for all
of these VLIRG systems, the individual galaxies (when detached), and their
nuclei, and the relative behavior of these classes has been studied in optical
color-magnitude diagrams. The photometric properties of the sample are also
compared with previously studied samples of ULIRGs. The mean observed
photometric properties of VLIRG and ULIRG samples, considered as a whole, are
indistinguishable at optical wavelengths. This suggests that not only ULIRG,
but also the more numerous population of VLIRGs, have similar rest-frame
optical photometric properties as the submillimeter galaxies (SMG), reinforcing
the connection between low-{\it z} LIRGs -- high-{\it z} SMGs. When the nuclei
of the {\it young} and {\it old} interacting systems are considered separately,
some differences between the VLIRG and the ULIRG samples are found. In
particular, the old VLIRGs are less luminous and redder than old ULIRG systems.
If confirmed with larger samples, this behavior suggests that the late-stage
evolution is different for VLIRGs and ULIRGs. Specifically, as suggested from
spectroscopic data, the present photometric observations support the idea that
the activity during the late phases of VLIRG evolution is dominated by
starbursts, while a higher proportion of ULIRGs could evolve into a QSO type of
object.


title: On the Black Hole Mass - Bulge Mass Relation

abstract:
  We have re-examined the relation between the mass of the central black holes
in nearby galaxies, M_bh, and the stellar mass of the surrounding spheroid or
bulge, M_bulge. For a total of 30 galaxies bulge masses were derived through
Jeans equation modeling or adopted from dynamical models in the literature. In
stellar mass-to-light ratios the spheroids and bulges span a range of a factor
of eight. The bulge masses were related to well-determined black hole masses
taken from the literature. With these improved values for M_bh, compared to
Magorrian et al. (1998), and our redetermination of M_bulge, we find the
M_bh-M_bulge relation becomes very tight. We find M_bh ~ M_bulge^(1.12+/-0.06)
with an observed scatter of < 0.30 dex, a fraction of which can be attributed
to measurement errors. The scatter in this relation is therefore comparable to
the scatter in the relations of M_bh with sigma and the stellar concentration.
These results confirm and refine the work of Marconi and Hunt (2003). For
M_bulge~5x10^10 M_sun the median black hole mass is 0.14% +/- 0.04% of the
bulge mass.


title: Young Massive Clusters in Merging and Starburst Galaxies

abstract:
  The currently available empirical evidence on the star formation processes in
the extreme, high-pressure environments induced by galaxy encounters, mostly
based on high-resolution Hubble Space Telescope imaging observations, strongly
suggests that star CLUSTER formation is an important and perhaps even the
dominant mode of star formation in the starburst events associated with galaxy
interactions. The production of young massive star clusters (YSCs) seems to be
a hallmark of intense star formation, particularly in interacting and starburst
galaxies. Their sizes, luminosities, and mass estimates are entirely consistent
with what is expected for young Milky Way-type globular clusters (GCs). YSCs
are important because of what they can tell us about GC formation and evolution
(e.g., initial characteristics and early survival rates). They are also of
prime importance as probes of the formation and (chemical) evolution of their
host galaxies, and of the initial mass function in the extreme environments
required for cluster formation. Recent evidence lends support to the scenario
that Milky Way-type GCs (although more metal rich), which were once thought to
be the oldest building blocks of galaxies, are still forming today.


title: The X-ray Bursts from the Magnetar Candidate 1E 2259+586

abstract:
  We present a statistical analysis of the X-ray bursts observed from the 2002
June 18 outburst of the Anomalous X-ray Pulsar (AXP) 1E 2259+586, observed with
the Proportional Counter Array aboard the Rossi X-ray Timing Explorer. We show
that the properties of these bursts are similar to those of Soft
Gamma-Repeaters (SGRs). The similarities we find are: the burst durations
follow a log-normal distribution which peaks at 99 ms, the differential burst
fluence distribution is well described by a power law of index -1.7, the burst
fluences are positively correlated with the burst durations, the distribution
of waiting times is well described by a log-normal distribution of mean 47 s,
and the bursts are generally asymmetric with faster rise than fall times.
However, we find several quantitative differences between the AXP and SGR
bursts. Specifically, there is a correlation of burst phase with pulsed
intensity, the AXP bursts we observed exhibit a wider range of durations, the
correlation between burst fluence and duration is flatter than for SGRs, the
observed AXP bursts are on average less energetic than observed SGR bursts, and
the more energetic AXP bursts have the hardest spectra - the opposite of what
is seen for SGRs. We conclude that the bursts are sufficiently similar that
AXPs and SGRs can be considered united as a source class yet there are some
interesting differences that may help determine what physically differentiates
the two closely related manifestations of neutron stars.


title: Linearized Bekenstein Varying Alpha Models

abstract:
  We study the simplest class of Bekenstein-type, varying $\alpha$ models, in
which the two available free functions (potential and gauge kinetic function)
are Taylor-expanded up to linear order. Any realistic model of this type
reduces to a model in this class for a certain time interval around the present
day. Nevertheless, we show that no such model is consistent with all existing
observational results. We discuss possible implications of these findings, and
in particular clarify the ambiguous statement (often found in the literature)
that ``the Webb results are inconsistent with Oklo''.


title:
GX 339-4: the distance, state transitions, hysteresis and spectral
  correlations

abstract:
  We study X-ray and variability and distance of GX 339-4. We derive d>7 kpc,
based on recent determination of the binary parameters. We study data from the
Ginga/ASM, the CGRO/BATSE, and the RXTE/ASM, PCA and HEXTE. From 1987 to 2004,
GX 339-4 underwent 15 outbursts and went through all known states of black-hole
binaries. We also present the PCA data from the initial stage of the 2004
outburst. We then study colour-colour and colour-flux correlations. In the hard
state, there is a strong anticorrelation between the 1.5-5 and 3-12 keV
spectral slopes, which we explain by thermal Comptonization of disc photons.
There is also a softening of the spectrum above 3 keV with the increasing flux
that becomes stronger with increasing energy up to 200 keV. This indicates an
anticorrelation between the electron temperature and luminosity, explained by
hot accretion models. In addition, we see a variable broad-band slope with a
pivot at 200 keV. We confirm the presence of pronounced hysteresis, with the
hard-to-soft state transitions occurring at much higher (and variable)
luminosities than the soft-to-hard transitions. We fit the ASM data with a
model consisting of an outer accretion disc and a hot inner flow. State
transitions are associated then with variations in the disc truncation radius,
which we fit as 6GM/c^2 in the soft state and several times that in the hard
state. The disappearence of the inner disc takes place at a lower accretion
rate than its initial appearance due to the dependence of the transitions on
the source history. We provide further evidence against the X-ray emission in
the hard state being nonthermal synchrotron, and explain the observed
radio-X-ray correlation by the jet power being correlated with the accretion
power.


title: Grain size distributions and photo-electric heating in ionized media

abstract:
  Ever since the pioneering study of Spitzer, it has been widely recognized
that grains play an important role in the heating and cooling of photo-ionized
environments. A detailed code is necessary to model grains in a photo-ionized
medium. In this paper we will use the spectral synthesis code Cloudy for this
purpose. The grain model of this code has recently undergone a comprehensive
upgrade. Part of this is the newly developed hybrid grain charge model, which
will be described in detail. This model allows discrete charge states of very
small grains to be modelled accurately while simultaneously avoiding the
overhead of fully resolving the charge distribution of large grains, thus
making the model both accurate and computationally efficient. A comprehensive
comparison with the fully resolved charge state models of Weingartner & Draine
(2001) shows that the agreement is very satisfactory for realistic size
distributions. The effect of the grain size distribution on the line emission
from photo-ionized regions is studied by taking standard models for an H II
region and a planetary nebula and adding a dust component to the models with
varying grain size distributions. A comparison of the models shows that varying
the size distribution has a dramatic effect on the emitted spectrum, and
affects the ionization balance as well. These results clearly demonstrate that
the grain size distribution is an important parameter in photo-ionization
models.


title:
Photoionized Gas in Dark-Matter Minihalos in the Galactic Halo and Local
  Group

abstract:
  (Abridged) We present computations of the metals photoionization structures
of pressure supported gas clouds in gravitationally dominant DM minihalos in
the extended Galactic halo or LG environment. We consider low-metallicity
(0.1-0.3 solar) clouds that are photoionized by the metagalactic radiation
field, and which are pressure-confined by a hot external medium. We study the
properties of LCDM Burkert (and NFW) minihalos with circular velocities 12-30
km/s. We present results for the volume densities and projected column
densities of low-ions, CII, NI, OI, SiII and SII, produced in the neutral
cores, and high-ions, CIV, NV, OVI, SiIII, SiIV, and SIII produced in the
ionized envelopes. We examine the possible relationships between the compact HI
high-velocity clouds (CHVCs), dwarf galaxies, and high-velocity ionized CIV
absorbers, within the context of photoionized minihalo models. In
pressure-confined (P/k ~50 K/cm^3) mini-halo models for the CHVCs the
photoionization states are much lower than in the CIV absorbers. However, for
lower bounding pressures (<~1 K/cm^3) in more massive dwarf galaxy scale halos,
the photoionization states in the outer envelopes resemble those observed in
the CIV HVCs. An important exception is OVI for which our photoionization
models underpredict the relative abundances by about an order-of-magnitude,
suggesting that additional processes are at play as concluded by Sembach et al.
For the cloud size-scales expected in median LCDM Burkert halos, a metallicity
of 0.3 solar is required to produce absorption-line strengths comparable to
those in the CIV HVCs. We argue that fully ionized and starless "dark galaxies"
could be detectable in the local universe as UV metal line absorbers with
ionization states similar to the CIV absorbers.


title:
The Production of HI in Photodissociation Regions and A Comparison with
  CO(1-0) Emission

abstract:
  The gas at the surfaces of molecular clouds in galaxies is heated and
dissociated by photons from young stars both near and far. HI resulting from
the dissociation of molecular hydrogen H2 emits hyperfine line emission at 21
cm, and warmed CO emits dipole rotational lines such as the 2.6 mm line of
CO(1-0). We use previously developed models for photodissociation regions
(PDRs) to compute the intensities of these HI and CO(1-0) lines as a function
of the total volume density n in the cloud and the far ultraviolet flux G0
incident upon it and present the results in units familiar to observers. The
intensities of these two lines behave differently with changing physical
conditions in the PDR, and, taken together, the two lines can provide a
ground-based radio astronomy diagnostic for determining n and G0 separately in
distant molecular clouds. This diagnostic is particularly useful in the range
Gzero <~ 100, 10 cm^{-3} <~ n <~ 10^5 cm^{-3}, which applies to a large
fraction of the volume of the interstellar medium in galaxies. If the molecular
cloud is located near discrete sources of far-UV (FUV) emission, the
PDR-generated HI and CO(1-0) emission on the cloud surface can be more easily
identified, appearing as layered ``blankets'' or ``blisters'' on the side of
the cloud nearest to the FUV source. As an illustration, we consider the
Galactic object G216 -2.5, i.e. ``Maddalena's Cloud'', which has been
previously identified as a large PDR in the Galaxy. We determine that this
cloud has n ~ 200 cm^{-3}, G0 ~ 0.8, consistent with other data.


title: Modified Newtonian dynamics from acceleration fluctuations

abstract:
  A speculative mathematical model is used to generate the modified Newtonian
dynamics called MOND from fluctuations of the number of quanta of quantized
acceleration. The one new parameter can be chosen either to make the transition
to modification comparable to that obtained from the functions used to fit data
with MOND, or to make the modification at larger accelerations comparable in
magnitude to the unexplained accelerations of Pioneer 10 and 11.


title:
The repeating microlensing event OGLE-2003-BLG-095: A plausible case for
  microlensing of a binary source

abstract:
  The apparently repeating microlensing event OGLE-2003-BLG-095 is analyzed.
Data were obtained from the OGLE Internet archive and exist in the public
domain. The source is relatively bright, with an unmagnified (but possibly
blended) $I$-band magnitude of 15.58, and the signal-to-noise ratio of the data
is excellent. The light curve shows two distinct, smooth peaks characteristic
of a double microlensing event. It can be modeled as either (1) microlensing by
a binary lens or (2) microlensing of a binary source, with the latter model
providing a statistically superior fit. However due to apparent low-amplitude
variability of the source, the interpretation is somewhat ambiguous.
OGLE-2003-BLG-095 is only the second possible case in the literature for
microlensing of a well-resolved binary source.


title:
FIRST-2MASS Sources Below the APM Detection Threshold: A Population of
  Highly Reddened Quasars

abstract:
  We have constructed a sample of bright near-infrared sources which are
detected at radio wavelengths but undetected on the POSS I plates in order to
search for a population of dust-obscured quasars. Optical and infrared
spectroscopic followup of the sample has led to the discovery of seventeen
heavily reddened quasars (B-K>6.5), fourteen of which are reported here for the
first time. This has allowed us to define a region in the R-K, J-K color plane
in which 50% of the radio-selected objects are highly reddened quasars. We
compare the surface density of this previously overlooked population to that of
UVX- radio-selected quasars, finding that they make up ~20% of the total quasar
population for K < 15.5.


title:
Latest Supernova data in the framework of Generalized Chaplygin Gas
  model

abstract:
  We use the most recent Type-Ia Supernova data in order to study the dark
energy - dark matter unification approach in the context of the Generalized
Chaplygin Gas (GCG) model. Rather surprisingly, we find that data allow models
with $\alpha > 1$. We have studied how the GCG adjusts flat and non-flat
models, and our results show that GCG is consistent with flat case upto 68%
confidence level. Actually this holds even if one relaxes the flat prior
assumption. We have also analysed what one should expect from a future
experiment such as SNAP. We find that there is a degeneracy between the GCG
model and a XCDM model with a phantom-like dark energy component.


title:
Warm dust and aromatic bands as quantitative probes of star-formation
  activity

abstract:
  We combine samples of spiral galaxies and starburst systems observed with
ISOCAM to investigate the reliability of mid-infrared (MIR) dust emission as a
quantitative tracer of star formation (SF) activity. The total sample covers
very diverse galactic environments and probes a much wider dynamic range in SF
rate density than previous similar studies. We find that both the monochromatic
15 micron continuum and the 5-8.5 micron emission constitute excellent
indicators of the SF rate as quantified by the Lyman continuum luminosity
L_Lyc, within specified validity limits which are different for the two
tracers. Normalized to projected surface area, the 15 micron luminosity S_15ct
is directly proportional to S_Lyc over several orders of magnitude. Two regimes
are distinguished from the relative offsets in the observed relation: the
proportionality factor increases by a factor of ~ 5 between quiescent disks in
spiral galaxies, and moderate to extreme star-forming environments in
circumnuclear regions of spirals and in starburst systems. The transition
occurs near S_Lyc ~ 10^2 L_sun pc^{-2} and is interpreted as due to very small
dust grains starting to dominate the emission at 15 microns over aromatic
species above this threshold. The 5-8.5 micron luminosity per unit area is also
proportional to S_Lyc, with a single conversion factor from the most quiescent
objects in the sample up to S_Lyc ~ 10^4 L_sun pc^{-2}, where the relation then
flattens. The turnover is attributed to depletion of aromatic band carriers in
the harsher conditions prevailing in extreme starbursts. The observed relations
provide empirical calibrations useful for estimating SF rates from mid-IR
observations in deeply embedded HII regions and obscured starbursts, and for
predictions from evolutionary synthesis models.