title: X-ray emission from T Tauri stars

abstract:
  We have modelled the X-ray emission of T Tauri stars assuming that they have
isothermal, magnetically-confined coronae. These coronae extend outwards until
either the pressure of the hot coronal gas overcomes the magnetic field, or, if
the corona interacts with a disk before this happens, by the action of the disk
itself. This work is motivated by the results of the Chandra Orion Ultradeep
Project (COUP) that show an increase in the X-ray emission measure with
increasing stellar mass. We find that this variation (and its large scatter)
result naturally from the variation in the sizes of the stellar coronae. The
reduction in the magnitude of the X-ray emission due to the presence of a disk
stripping the outer parts of the stellar corona is most pronounced for the
lower mass stars. The higher mass stars with their greater surface gravities
have coronae than typically do not extend out as far as the inner edge of the
disk and so are less affected by it. For these stars, accretion takes place
along open field lines that connect to the disk. By extrapolating surface
magnetograms of young main sequence stars we have examined the effect on the
X-ray emission of a realistic degree of field complexity. We find densities
consistent with estimates from modelling of individual flares. A simple dipole
field in contrast gives densities typically an order of magnitude less. We
suggest that T Tauri stars have coronal fields that are slightly more extended
than their main sequence counterparts, but not as extended as a purely dipolar
fields.


title: The Proper Motion of the Large Magellanic Cloud: A Reanalysis

abstract:
  We have determined the proper motion (PM) of the Large Magellanic Cloud (LMC)
relative to four background quasi-stellar objects, combining data from two
previous studies made by our group, and new observations carried out in four
epochs not included the original investigations. The new observations provided
a significant increase in the time base and in the number of frames, relative
to what was available in our previous studies. We have derived a total LMC PM
of $\mu$ = ($+2.0\pm$0.1) mas yr$^{-1}$, with a position angle of $\theta$ =
(62.4$\pm$3.1)$^\circ$. Our new values agree well with most results obtained by
other authors, and we believe we have clarified the large discrepancy between
previous results from our group. Using published values of the radial velocity
for the center of the LMC, in combination with the transverse velocity vector
derived from our measured PM, we have calculated the absolute space velocity of
the LMC. This value, along with some assumptions regarding the mass
distribution of the Galaxy, has in turn been used to calculate the mass of the
Milky Way. Our measured PM also indicates that the LMC is not a member of a
proposed stream of galaxies with similar orbits around our galaxy.


title:
High Velocity Spectroscopic Binary Orbits from Photoelectric Radial
  Velocities: BD +82 565A

abstract:
  The spectroscopic orbit of a circumpolar high-proper-motion visual binary BD
+82 565 A component is determined from 57 CORAVEL radial velocity measurements.
A short period P = 12.69 d and a moderate eccentricity e = 0.30 are obtained.
The visual system AB has a projected spatial separation ~830 AU. The system's
barycenter velocity V_0 = -86.7 km/s, the transverse velocity V_t = 118.7 km/s
and the Galactic spatial velocity components U = -62.6 km/s, V = -84.1 km/s and
W = -84.2 km/s give evidence that it belongs to the thick disk of the Galaxy.


title: GRB Cosmology and the First Stars

abstract:
  Gamma-Ray Bursts (GRBs) are unique probes of the cosmic star formation
history and the state of the intergalactic medium up to the redshifts of the
first stars. In particular, the ongoing {\it Swift} mission might be the first
observatory to detect individual Population~III stars, provided that the
massive, metal-free stars were able to trigger GRBs. {\it Swift} will
empirically constrain the redshift at which Population~III star formation was
terminated, thus providing crucial input to models of cosmic reionization and
metal enrichment.


title: Exotic populations in Galactic Globular Clusters

abstract:
  Recent high-resolution observations of the central region of Galactic
globular clusters have shown the presence of a large variety of exotic stellar
objects whose formation and evolution may be strongly affected by dynamical
interactions. In this paper I review the main properties of two classes of
exotic objects: the so-called Blue Stragglers stars and the recently identified
optical companions to Millisecond pulsar.
  Both these class of objects are invaluable tools to investigate the binary
evolution in very dense environments and are powerful tracers of the dynamical
history of the parent cluster.


title: SDSS Pre-Burst Observations of Recent Gamma-Ray Burst Fields

abstract:
  In this paper, we present Sloan Digital Sky Survey (SDSS) photometry and
spectroscopy in the fields of 24 gamma-ray bursts (GRBs) observed by Swift,
including bursts localized by Swift, HETE-2, and INTEGRAL, after December 2004.
After this bulk release, we plan to provide individual releases of similar data
shortly after the localization of future bursts falling in the SDSS survey
area. These data provide a solid basis for the astrometric and photometric
calibration of follow-up afterglow searches and monitoring. Furthermore, the
images provided with this release will allow observers to find transient
objects up to a magnitude fainter than possible with Digitized Sky Survey image
comparisons.


title: Constraining Lorentz violations with Gamma Ray Bursts

abstract:
  Gamma ray bursts are excellent candidates to constrain physical models which
break Lorentz symmetry. We consider deformed dispersion relations which break
the boost invariance and lead to an energy-dependent speed of light. In these
models, simultaneously emitted photons from cosmological sources reach Earth
with a spectral time delay that depends on the symmetry breaking scale. We
estimate the possible bounds which can be obtained by comparing the spectral
time delays with the time resolution of available telescopes. We discuss the
best strategy to reach the strongest bounds. We compute the probability of
detecting bursts that improve the current bounds. The results are encouraging.
Depending on the model, it is possible to build a detector that within several
years will improve the present limits of 0.015 m_pl.


title:
Structure formation in modified gravity models alternative to dark
  energy

abstract:
  We study structure formation in phenomenological models in which the
Friedmann equation receives a correction of the form
$H^{\alpha}/r_c^{2-\alpha}$, which realize an accelerated expansion without
dark energy. In order to address structure formation in these model, we
construct simple covariant gravitational equations which give the modified
Friedmann equation with $\alpha=2/n$ where $n$ is an integer. For $n=2$, the
underlying theory is known as a 5D braneworld model (the DGP model). Thus the
models interpolate between the DGP model ($n=2, \alpha=1$) and the LCDM model
in general relativity ($n \to \infty, \alpha \to 0$). Using the covariant
equations, cosmological perturbations are analyzed. It is shown that in order
to satisfy the Bianchi identity at a perturbative level, we need to introduce a
correction term $E_{\mu \nu}$ in the effective equations. In the DGP model,
$E_{\mu \nu}$ comes from 5D gravitational fields and correct conditions on
$E_{\mu \nu}$ can be derived by solving the 5D perturbations. In the general
case $n>2$, we have to assume the structure of a modified theory of gravity to
determine $E_{\mu \nu}$. We show that structure formation is different from a
dark energy model in general relativity with identical expansion history and
that quantitative features of the difference crucially depend on the conditions
on $E_{\mu \nu}$, that is, the structure of the underlying theory of modified
gravity. This implies that it is essential to identify underlying theories in
order to test these phenomenological models against observational data and,
once we identify a consistent theory, structure formation tests become
essential to distinguish modified gravity models from dark energy models in
general relativity.


title: GMOS Spectroscopy of the S0 galaxy NGC 3115

abstract:
  We present Gemini GMOS longslit spectroscopy of the isolated S0 galaxy NGC
3115. We have determined kinematical data and Lick/IDS absorption line-strength
indices for the major axis out to around 9 kpc and for the minor axis out to
around 5 kpc (around 2Re). Using stellar population models which include the
effects of variable [alpha/Fe] ratios we derive metallicities, abundance ratios
and ages for the stellar population of NGC 3115. We find that [alpha/Fe]
remains fairly constant with increasing radius at around [alpha/Fe] = 0.17 for
the major axis but increases rapidly for the minor axis to around [alpha/Fe] =
0.3. We also find that to first order this behaviour can be explained by a
simple spheroid + disc model, where the spheroid has [alpha/Fe] = 0.3 and the
disc shows close to solar abundance ratios. The disc also appears considerably
younger than the spheroid, having an age of around 6 Gyr compared to 12 Gyr for
the spheroid. We compare these results to those previously presented for the
globular cluster system of NGC 3115.


title: Surface density jumps as planet traps

abstract:
  [Abridged] The tidal torque exerted by a protoplanetary disk with power law
surface density and temperature profiles onto an embedded protoplanetary embryo
is generally a negative quantity that leads to the embryo inwards migration.
Here we investigate how the tidal torque balance is affected at a disk surface
density radial jump. The jump has two consequences :
  - it affects the differential Lindblad torque. In particular if the disk is
merely empty on the inner side, the differential Lindblad torque almost amounts
to the large negative outer Lindblad torque.
  - It affects the corotation torque, which is a quantity very sensitive to the
local gradient of the disk surface density. In particular if the disk is
depleted on the inside and if the jump occurs radially over a few pressure
scale-heights, the corotation torque is a positive quantity that is much larger
than in a power-law disk.
  We show by means of customized numerical simulations of low mass planets
embedded in protoplanetary nebulae with a surface density jump that the second
effect is dominant, that is that the corotation torque largely dominates the
differential Lindblad torque on the edge of a central depletion. As a
consequence the type I migration of low mass objects reaching the jump should
be halted, and all these objects should be trapped there.


title:
Lyman break galaxies, Lya emitters and a radio galaxy in a protocluster
  at z=4.1

abstract:
  We present deep HST/ACS observations in g,r,i,z towards the z=4.1 radio
galaxy TN J1338-1942 and its overdensity of >30 spectroscopically confirmed Lya
emitters (LAEs). We select 66 g-band dropouts to z=27, 6 of which are also a
LAE. Although our color-color selection results in a relatively broad redshift
range centered on z=4.1, the field of TN J1338-1942 is richer than the average
field at the >5 sigma significance, based on a comparison with GOODS. The
angular distribution is filamentary with about half of the objects clustered
near the radio galaxy, and a small, excess signal (2 sigma) in the projected
pair counts at separations of <10" is interpreted as being due to physical
pairs. The LAEs are young (a few x 10^7 yr), small (<r_50> = 0.13") galaxies,
and we derive a mean stellar mass of ~10^8-9 Msun based on a stacked K-band
image. We determine star formation rates, sizes, morphologies, and
color-magnitude relations of the g-dropouts and find no evidence for a
difference between galaxies near TN J1338-1942 and in the field. We conclude
that environmental trends as observed in clusters at much lower redshift are
either not yet present, or are washed out by the relatively broad selection in
redshift. The large galaxy overdensity, its corresponding mass overdensity and
the sub-clustering at the approximate redshift of TN J1338-1942 suggest the
assemblage of a >10^14 Msun structure, confirming that it is possible to find
and study cluster progenitors in the linear regime at z>4.


title:
Low-Redshift Cosmic Baryon Fluid on Large Scales and She-Leveque
  Universal Scaling

abstract:
  We investigate the statistical properties of cosmic baryon fluid in the
nonlinear regime, which is crucial for understanding the large-scale structure
formation of the universe. With the hydrodynamic simulation sample of the
Universe in the cold dark matter model with a cosmological constant, we show
that the intermittency of the velocity field of cosmic baryon fluid at redshift
z=0 in the scale range from the Jeans length to about 16 Mpc/h can be extremely
well described by She-Leveque's universal scaling formula. The baryon fluid
also possesses the following features: (1) for volume weight statistics, the
dissipative structures are dominated by sheets, and (2) the relation between
the intensities of fluctuations is hierarchical. These results imply that the
evolution of highly evolved cosmic baryon fluid is similar to a fully developed
turbulence.


title:
Bump Cepheids in the Magellanic Clouds: Metallicities, the Distances to
  the LMC and SMC, and the Pulsation-Evolution Mass Discrepancy

abstract:
  We utilize nonlinear pulsation models to reproduce the observed light and
color curves for two samples of bump Cepheid variables, 19 from the Large
Magellanic Cloud and 9 from the Small Magellanic Cloud. This analysis
determines the fundamental parameters mass, luminosity, effective temperature,
metallicity, distance and reddening for the sample of stars. The use of light
curve shape alone to determine metallicity is a new modelling technique
introduced here.
  The metallicity, distance and reddening distributions for the two samples are
in agreement with those of similar stellar populations in the literature. The
distance modulus of the Large Magellanic Cloud is determined to be
18.54$\pm$0.018 and the distance modulus of the Small Magellanic Cloud is
determined to be 18.93$\pm$0.024. The mean Cepheid metallicities are $Z =
0.0091\pm0.0007$ and $0.0050\pm0.0005$ for the LMC and SMC, respectively.
  The masses derived from pulsation analysis are significantly less than those
predicted by stellar evolutionary models with no or mild convective core
overshoot. We show that this discrepancy can not be accounted for by
uncertainties in our input opacities or in mass-loss physics. We interpret the
observed mass discrepancy in terms of enhanced internal mixing in the vicinity
of the convective core during the main-sequence lifetime and find that the
overshoot parameter $\Lambda_{c}$ rises from 0.688$\pm$0.009H_p at the mean LMC
metallicity to 0.746$\pm$0.009H_p in the SMC.


title:
The Born and Lens-Lens Corrections to Weak Gravitational Lensing Angular
  Power Spectra

abstract:
  We revisit the estimation of higher order corrections to the angular power
spectra of weak gravitational lensing. Extending a previous calculation of
Cooray and Hu, we find two additional terms to the fourth order in potential
perturbations of large-scale structure corresponding to corrections associated
with the Born approximation and the neglect of line-of-sight coupling of two
foreground lenses in the standard first order result. These terms alter the
convergence ($\kappa\kappa$), the lensing shear E-mode ($\epsilon\epsilon$),
and their cross-correlation ($\kappa\epsilon$) power spectra on large angular
scales, but leave the power spectra of the lensing shear B-mode ($\beta\beta$)
and rotational ($\omega\omega$) component unchanged as compared to previous
estimates. The new terms complete the calculation of corrections to weak
lensing angular power spectra associated with both the Born approximation and
the lens-lens coupling to an order in which the contributions are most
significant. Taking these features together, we find that these corrections are
unimportant for any weak lensing survey, including for a full sky survey
limited by cosmic variance.


title: MMT Survey for Intervening MgII Absorption

abstract:
  We present the results from a spectroscopic survey for intervening MgII
absorption in the spectra of 381 background QSOs conducted at the Multiple
Mirror Telescope. This survey complements our earlier SDSS EDR MgII survey,
extending our results to lower redshift ($z \simeq 0.15$) and weaker MgII
$\lambda2796$ rest equivalent width ($W_0^{\lambda2796} \simeq 0.1$\AA). We
confirm two major results from that survey: the transition in the
$W_0^{\lambda2796}$ distribution at $W_0^{\lambda2796} \approx 0.3$\AA, and the
$W_0^{\lambda2796}$-dependent evolution of the incidence of systems. The nature
of $\partial^2N/\partial z \partial W_0^{\lambda2796}$ is consistent with the
idea that multiple physically-distinct components/processes contribute to the
incidence of MgII absorption systems in a $W_0$-dependent manner and evolve at
different rates. A significant decrease in the total proper absorption cross
section is detected in our MMT data for systems as weak as 1.0 \AA $\le
W_0^{\lambda2796} < 1.5$\AA at $z\lesssim 0.4$. We discuss this $W_0$-dependent
evolution in the context of the evolution of galaxy structures, processes
including superwinds and interactions, and damped-Ly$\alpha$ absorbers. We also
consider the possibility that the observed redshift and $W_0^{\lambda2796}$
dependence of the incidence of absorption in spectroscopic surveys for
low-ion/neutral gas results from the effects of dust-induced extinction.


title: Recent Results on Interstellar Turbulence

abstract:
  The statistical properties of interstellar turbulence are studied by means of
three-dimensional high-resolution HD and MHD simulations of a SN-driven ISM. It
is found that the longitudinal and transverse turbulent length scales have time
averaged (over a period of 50 Myr) ratios of 0.5-0.6, almost similar to the one
expected for isotropic homogeneous turbulence. The mean characteristic size of
the larger eddies is found to be ~75 pc. Furthermore, the scalings of the
structure functions measured in the simulated disk show unambiguous departure
from the Kolmogorv (1941) model being consistent with the latest intermittency
studies of supersonic turbulence (Politano & Pouquet 1995; Boldyrev 2002). Our
results are independent of the resolution, indicating that convergence has been
reached, and that the unresolved smaller dissipative scales do not feed back on
the larger ones.


title: GeV-TeV and X-ray flares from gamma-ray bursts

abstract:
  The recent detection of delayed X-ray flares during the afterglow phase of
gamma-ray bursts (GRBs) suggests an inner-engine origin, at radii inside the
deceleration radius characterizing the beginning of the forward shock afterglow
emission. Given the observed temporal overlapping between the flares and
afterglows, there must be inverse Compton (IC) emission arising from such flare
photons scattered by forward shock afterglow electrons. We find that this IC
emission produces GeV-TeV flares, which may be detected by GLAST and
ground-based TeV telescopes. We speculate that this kind of emission may
already have been detected by EGRET from a very strong burst--GRB940217. The
enhanced cooling of the forward shock electrons by the X-ray flare photons may
suppress the synchrotron emission of the afterglows during the flare period.
The detection of GeV-TeV flares combined with low energy observations may help
to constrain the poorly known magnetic field in afterglow shocks. We also
consider the self-IC emission in the context of internal-shock and
external-shock models for X-ray flares. The emission above GeV from internal
shocks is low, while the external shock model can also produce GeV-TeV flares,
but with a different temporal behavior from that caused by IC scattering of
flare photons by afterglow electrons. This suggests a useful approach for
distinguishing whether X-ray flares originate from late central engine activity
or from external shocks.


title:
Physical and Chemical Structure of Protoplanetary Disks with Grain
  Growth

abstract:
  We calculate the physical structure of protoplanetary disks by evaluating the
gas density and temperature self-consistently and solving separately for the
dust temperature. The effect of grain growth is taken into account by assuming
a power-law size distribution and varying the maximum radius of grains a_max.
In our fiducial model with a_max=10um, the gas is warmer than the dust in the
surface layer of the disk, while the gas and dust have the same temperature in
deeper layers. In the models with larger a_max, the gas temperature in the
surface layer is lower than in the fiducial model because of reduced
photo-electric heating rates from small grains, while the deeper penetration of
stellar radiation warms the gas at intermediate height. A detailed chemical
reaction network is solved at outer radii (r \ge 50 AU). Vertical distributions
of some molecular species at different radii are similar, when plotted as a
function of hydrogen column density Sigma_H from the disk surface.
Consequently, molecular column densities do not much depend on disk radius. In
the models with larger a_max, the lower temperature in the surface layer makes
the geometrical thickness of the disk smaller, and the gaseous molecules are
confined to smaller heights. However, if we plot the vertical distributions of
molecules as a function of Sigma_H, they do not significantly depend on a_max.
The dependence of the molecular column densities on a_max is not significant,
either. Notable exceptions are HCO+, H3+ and H2D+, which have smaller column
densities in the models with larger a_max.


title:
Two-Current-Sheet Reconnection Model of Interdependent Flare and Coronal
  Mass Ejection

abstract:
  Time-dependent resistive magnetohydrodynamic simulations are carried out to
study a flux rope eruption caused by magnetic reconnection with implication in
coexistent flare-CME (coronal mass ejection) events. An early result obtained
in a recent analysis of double catastrophe of a flux rope system is used as the
initial condition, in which an isolated flux rope coexists with two current
sheets: a vertical one below and a transverse one above the flux rope. The flux
rope erupts when reconnection takes place in the current sheets, and the flux
rope dynamics depends on the reconnection sequence in the two current sheets.
Three cases are discussed: reconnection occurs (1) simultaneously in the two
current sheets, (2) first in the transverse one and then in the vertical, and
(3) in an order opposite to case 2. Such a two-current-sheet reconnection
exhibits characteristics of both magnetic breakout for CME initiation and
standard flare model. We argue that both breakout-like and tether-cutting
reconnections may be important for CME eruptions and associated surface
activities.


title: Dense Stellar Systems as Laboratories for Fundamental Physics

abstract:
  Galactic nuclei and globular clusters act as laboratories in which nature
experiments with normal stars, neutron stars and black holes, through
collisions and through the formation of bound states, in the form of binaries.
The main difference with the usual Earth-based laboratories is that we cannot
control the experiments. Instead, we have no choice but to create virtual
laboratories on Earth, in order to simulate all the relevant physics in
large-scale computational experiments. This implies a realistic treatment of
stellar dynamics, stellar evolution, and stellar hydrodynamics.
  Each of these three fields has its own legacy codes, workhorses that are
routinely used to simulate star clusters, stars, and stellar collisions,
respectively. I outline the main steps that need to be taken in order to embed
and where needed transform these legacy codes in order to produce a far more
modular and robust environment for modeling dense stellar systems.
  The time is right to do so: within a few years computers will reach the
required speed, in the Petaflops range, to follow a star cluster with a million
stars for ten billion years, while resolving the internal binary and multiple
star motions. By that time simulation software will be the main bottleneck in
our ability to analyze dense stellar systems. Only through full-scale
simulations will we be able to critically test our understanding of the
`microphysics' of stellar collisions and their aftermath, in a direct
comparison with observations.


title: Capturing Halos at High Redshifts

abstract:
  We study the evolution of the mass function of dark matter halos in the
concordance LCDM model at high redshift. We employ overlapping
(multiple-realization) numerical simulations to cover a wide range of halo
masses, 10^7-10^{15}h^{-1}M_\odot, with redshift coverage beginning at z=20.
The Press-Schechter mass function is significantly discrepant from the
simulation results at high redshifts. Of the more recently proposed mass
functions, our results are in best agreement with Warren et al. (2005). The
statistics of the simulations -- along with good control over systematics --
allow for fits accurate to the level of 20% at all redshifts. We provide a
concise discussion of various issues in defining and computing the halo mass
function, and how these are addressed in our simulations.


title: XMM-Newton X-ray spectroscopy of classical T Tauri stars

abstract:
  We present results from a comparative study of XMM-Newton observations of
four classical T Tauri stars (CTTS), namely BP Tau, CR Cha, SU Aur and TW Hya.
In these objects coronal, i.e. magnetic, activity and as recently shown,
magnetically funneled accretion are the processes likely to be responsible for
the generation of X-ray emission. Variable X-ray emission with luminosities in
the order of $10^{30}$ erg/s is observed for all targets. We investigate light
curves as well as medium and high-resolution X-ray spectra to determine the
plasma properties of the sample CTTS and to study the origin of their X-ray
emission and its variability. The emission measure distributions and observed
temperatures differ significantly and the targets are dominated either by
plasma at high densities as produced by accretion shocks or by predominantly
hotter plasma of coronal origin. Likewise the variability of the X-ray
luminosity is found to be generated by both mechanisms. Cool plasma at high
densities is found in all stars with detected \ion{O}{vii} triplet emission,
prevented only for SU~Aur due to strong absorption. A general trend is present
in the abundance pattern, with neon being at solar value or enhanced while
oxygen, iron and most other metals are depleted, pointing to the presence of
the inverse FIP effect in active coronae and possibly grain formation in
evolved disks. We find that both accretion shocks and coronal activity
contribute to the observed X-ray emission of the targets. While coronal
activity is the dominant source of X-ray activity in the majority of the CTTS,
the fraction for each process differs significantly between the individual
objects.


title:
Star formation in the nearby universe: the ultraviolet and infrared
  points of view

abstract:
  This work presents the main ultraviolet (UV) and far-infrared (FIR)
properties of two samples of nearby galaxies selected from the GALEX ($\lambda
= 2315$\AA, hereafter NUV) and IRAS ($\lambda = 60\mu$m) surveys respectively.
They are built in order to get detection at both wavelengths for most of the
galaxies. Star formation rate (SFR) estimators based on the UV and FIR
emissions are compared. Systematic differences are found between the SFR
estimators for individual galaxies based on the NUV fluxes corrected for dust
attenuation and on the total IR luminosity. A combined estimator based on NUV
and IR luminosities seems to be the best proxy over the whole range of values
of SFR. Although both samples present similar average values of the birthrate
parameter b, their star-formation-related properties are substantially
different: NUV-selected galaxies tend to show larger values of $b$ for lower
masses, SFRs and dust attenuations, supporting previous scenarios for the star
formation history (SFH). Conversely, about 20% of the FIR-selected galaxies
show high values of $b$, SFR and NUV attenuation. These galaxies, most of them
being LIRGs and ULIRGs, break down the downsizing picture for the SFH, however
their relative contribution per unit volume is small in the local Universe.
Finally, the cosmic SFR density of the local Universe is estimated in a
consistent way from the NUV and IR luminosities.


title: A high accuracy computed water line list

abstract:
  A computed list of H$_{2}$$^{16}$O infra-red transition frequencies and
intensities is presented. The list, BT2, was produced using a discrete variable
representation two-step approach for solving the rotation-vibration nuclear
motions. It is the most complete water line list in existence, comprising over
500 million transitions (65% more than any other list) and it is also the most
accurate (over 90% of all known experimental energy levels are within 0.3
cm$^{-1}$ of the BT2 values). Its accuracy has been confirmed by extensive
testing against astronomical and laboratory data.
  The line list has been used to identify individual water lines in a variety
of objects including: comets, sunspots, a brown dwarf and the nova-like object
V838 Mon. Comparison of the observed intensities with those generated by BT2
enables physical values to be derived for these objects. The line list can also
be used to provide an opacity for models of the atmospheres of M-dwarf stars
and assign previously unknown water lines in laboratory spectra.


title:
The RR Lyrae distance scale from near-infrared photometry: current
  results

abstract:
  We present new observational results on the RR Lyrae K-band Period-Luminosity
relation (PLK). Data on the Galactic globular clusters NGC 3201 and NGC 4590
(M68), and on the Large Magellanic Cloud cluster Reticulum are shown. We
compare the observed slopes of the PLK relations for these three clusters with
those predicted by pulsational and evolutionary models, finding a fair
agreement. Trusting on this finding we decided to adopt these theoretical
calibrations to estimate the distance to the target clusters,finding a good
agreement with optical-based RR Lyrae distances, but with a smaller formal
scatter.


title: A microquasar model applied to unidentified gamma-ray sources

abstract:
  Among unidentified gamma-ray sources in the galactic plane, there are some
that present significant variability and have been proposed to be high-mass
microquasars. To deepen the study of the possible association between variable
low galactic latitude gamma-ray sources and microquasars, we have applied a
leptonic jet model based on the microquasar scenario that reproduces the
gamma-ray spectrum of three unidentified gamma-ray sources, 3EG J1735-1500, 3EG
J1828+0142 and GRO J1411-64, and is consistent with the observational
constraints at lower energies. We conclude that if these sources were generated
by microquasars, the particle acceleration processes could not be as efficient
as in other objects of this type that present harder gamma-ray spectra.
Moreover, the dominant mechanism of high-energy emission should be synchrotron
self-Compton (SSC) scattering, and the radio jets may only be observed at low
frequencies. For each particular case, further predictions of jet physical
conditions and variability generation mechanisms have been made in the context
of the model. Although there might be other candidates able to explain the
emission coming from these sources, microquasars cannot be excluded as
counterparts. Observations performed by the next generation of gamma-ray
instruments, like GLAST, are required to test the proposed model.


title: Element abundances of unevolved stars in the open cluster M 67

abstract:
  We determined the metallicity ([Fe/H]), together with O, Na, Mg, Al, Si, Ca,
Ti, Cr and Ni abundances for a sample of 10 unevolved or slightly evolved stars
belonging to the open cluster M 67. We find an average metallicity [Fe/H]=0.03
+/- 0.01, in very good agreement with previous determinations. All the [X/Fe]
abundance ratios are very close to solar. The star-to-star scatter in [Fe/H]
and [X/Fe] ratios for all elements, including oxygen, is lower than 0.05 dex,
implying that the large dispersion in lithium reported in previous studies is
not due to differences in these element abundances. We also find that, when
using a homogeneous scale, the abundance pattern of unevolved stars in our
sample is very similar to that of evolved stars, suggesting that, at least in
this cluster, RGB and clump stars have not undergone any chemical processing.
Finally, our results show that M 67 has a chemical composition that is
representative of the solar neighborhood.


title:
Effects of metallicity, star formation conditions and evolution in B and
  Be stars. I: Large Magellanic Cloud, field of NGC 2004

abstract:
  Spectroscopic observations of hot stars belonging to the young cluster
LMC-NGC 2004 and its surrounding region were carried out with the VLT-GIRAFFE
facilities in MEDUSA mode. We determine fundamental parameters (Teff, logg,
vsini, and radial velocity), for all B and Be stars in the sample thanks to a
code developed in our group. The effect of fast rotation (stellar flattening
and gravitational darkening) are taken into account in this study. We also
determine the age of observed clusters. We compare the mean vsini obtained for
field and cluster B and Be stars in the Large Magellanic Cloud (LMC) with the
ones in the Milky Way (MW). We find, in particular, that Be stars rotate faster
in the LMC than in the MW, in the field as well as in clusters. We discuss the
relations between vsini, metallicity, star formation conditions and stellar
evolution by comparing the LMC with the MW. We conclude that Be stars begin
their Main Sequence life with an initial rotational velocity greater than the
one of B stars. It is probable that only part of the B stars, with a sufficient
initial rotational velocity, can become Be stars. This result may explain the
differences in the proportion of Be stars in clusters with similar ages.


title: XMM-Newton observations of PSr B1259-63 near the 2004 periastron passage

abstract:
  PSR B1259-63 is in a highly eccentric 3.4 year orbit with a Be star and
crosses the Be star disc twice per orbit, just prior to and just after
periastron. Unpulsed radio, X-ray and gamma-ray emission observed from the
binary system is thought to be due to the collision of pulsar wind with the
wind of Be star. We present here the results of new XMM-Newton observations of
the PSR B1259-63 system during the beginning of 2004 as the pulsar approached
the disc of Be star.We combine these results with earlier unpublished X-ray
data from BeppoSAX and XMM-Newton as well as with ASCA data. The detailed X-ray
lightcurve of the system shows that the pulsar passes (twice per orbit) through
a well-defined gaussian-profile disk with the half-opening angle (projected on
the pulsar orbit plane) ~18.5 deg. The intersection of the disk middle plane
with the pulsar orbital plane is inclined at ~70 deg to the major axis of the
pulsar orbit. Comparing the X-ray lightcurve to the TeV lightcurve of the
system we find that the increase of the TeV flux some 10--100 days after the
periastron passage is unambiguously related to the disk passage. At the moment
of entrance to the disk the X-ray photon index hardens from 1.8 up to 1.2
before returning to the steeper value 1.5. Such behaviour is not easily
accounted for by the model in which the X-ray emission is synchrotron emission
from the shocked pulsar wind. We argue that the observed hardening of the X-ray
spectrum is due to the inverse Compton or bremsstrahlung emission from 10-100
MeV electrons responsible for the radio synchrotron emission.


title:
{Interstellar Plasma Weather Effects in Long-term Multi-frequency Timing
  of Pulsar B1937+21

abstract:
  We report here on variable propagation effects in over twenty years of
multi-frequency timing analysis of pulsar PSR B1937+21 that determine
small-scale properties of the intervening plasma as it drifts through the sight
line. The phase structure function derived from the dispersion measure
variations is in remarkable agreement with that expected from the Kolmogorov
spectrum, with a power law index of $3.66\pm 0.04$, valid over an inferred
scale range of 0.2--50 A.U. The observed flux variation time scale and the
modulation index, along with their frequency dependence, are discrepant with
the values expected from a Kolmogorov spectrum with infinitismally small inner
scale cutoff, suggesting a caustic-dominated regime of interstellar optics.
This implies an inner scale cutoff to the spectrum of $\sim 1.3\times 10^9$
meters. Our timing solutions indicate a transverse velocity of 9 km sec$^{-1}$
with respect to the solar system barycenter, and 80 km sec$^{-1}$ with respect
to the pulsar's LSR. We interpret the frequency dependent variations of DM as a
result of the apparent angular broadening of the source, which is a sensitive
function of frequency ($\propto\nu^{-2.2}$). The error introduced by this in
timing this pulsar is $\sim$2.2 $\mu$s at 1 GHz. The timing error introduced by
``image wandering'' from the slow, nominally refractive scintillation effects
is about 125 nanosec at 1 GHz. The error accumulated due to positional error
(due to image wandering) in solar system barycentric corrections is about 85
nanosec at 1 GHz.


title: Generation of magnetic field from cosmological perturbations

abstract:
  We discuss generation of magnetic field from cosmological perturbations. We
consider the evolution of three component plasma (electron, proton and photon)
evaluating the collision term between elecrons and photons up to the second
order. The collision term is shown to induce electric current, which then
generate magnetic field. There are three contributions, two of which can be
evaluated from the first-order quantities, while the other one is fluid
vorticity which is purely second order. We compute numerically the magnitudes
of the former contributions and shows that the amplitude of the produced
magnetic field is about $\sim 10^{-19} {\rm G}$ at 10kpc comoving scale at
present. Compared to astrophysical and inflationary mechanisms for seed-field
generation, our study suffers from much less ambiguities concerning unknown
physics and/or processes.


title: Braking the Gas in the beta Pictoris Disk

abstract:
  (Abridged) The main sequence star beta Pictoris hosts the best studied
circumstellar disk to date. Nonetheless, a long-standing puzzle has been around
since the detection of metallic gas in the disk: radiation pressure from the
star should blow the gas away, yet the observed motion is consistent with
Keplerian rotation. In this work we search for braking mechanisms that can
resolve this discrepancy. We find that all species affected by radiation force
are heavily ionized and dynamically coupled into a single fluid by Coulomb
collisions, reducing the radiation force on species feeling the strongest
acceleration. For a gas of solar composition, the resulting total radiation
force still exceeds gravity, while a gas of enhanced carbon abundance could be
self-braking. We also explore two other braking agents: collisions with dust
grains and neutral gas. Grains surrounding beta Pic are photoelectrically
charged to a positive electrostatic potential. If a significant fraction of the
grains are carbonaceous (10% in the midplane and larger at higher altitudes),
ions can be slowed down to satisfy the observed velocity constraints. For
neutral gas to brake the coupled ion fluid, we find the minimum required mass
to be $\approx$ 0.03 $M_\earth$, consistent with observed upper limits of the
hydrogen column density, and substantially reduced relative to previous
estimates. Our results favor a scenario in which metallic gas is generated by
grain evaporation in the disk, perhaps during grain-grain collisions. We
exclude a primordial origin for the gas, but cannot rule out the possibility of
its production by falling evaporating bodies near the star. We discuss the
implications of this work for observations of gas in other debris disks.


title: XMM-Newton and Chandra observations of SHEEP sources

abstract:
  We present Chandra and XMM observations of 12 bright (f(2-10 keV)
  > 10^-13 cgs) sources from the ASCA SHEEP (Search for the High Energy
  Extragalactic Population) survey. Most of these have been either not observed
or not detected previously with the ROSAT mission and therefore they constitute
a sample biased towards hard sources. The Chandra observations are important in
locating with accuracy the optical counterpart of the X-ray sources. Optical
spectroscopic observations show that our sample is associated with both
narrow-line (NL) (six objects), and
  Broad-Line (BL) AGN (five objects) with one source remaining unidentified.
  Our sources cover the redshift range 0.04 to 1.29 spanning luminosities from
10^42 to 10^45 cgs (2-10 keV). The NL sources have preferentially lower
redshift (and luminosity) compared with the BL ones. This can be most easily
explained in a model where the NL AGN are intrinsically less luminous than the
BL ones in line with the results of Steffen et al.
  The X-ray spectral fittings show a roughly equal number of obscured
(N_H>10^22 cgs) and unobscured (N_H<10^22 cgs) sources.
  There is a clear tendency for obscured sources to be associated with
  NL AGN and unobscured sources with BL ones. However, there is a marked
exception with the highest obscuring column observed at a BL AGN at a redshift
of z=0.5.


title: Turbulence, magnetic fields and plasma physics in clusters of galaxies

abstract:
  Observations of galaxy clusters show that the intracluster medium (ICM) is
likely to be turbulent and is certainly magnetized. The properties of this
magnetized turbulence are determined both by fundamental nonlinear
magnetohydrodynamic interactions and by the plasma physics of the ICM, which
has very low collisionality. Cluster plasma threaded by weak magnetic fields is
subject to firehose and mirror instabilities. These saturate and produce
fluctuations at the ion gyroscale, which can scatter particles, increasing the
effective collision rate and, therefore, the effective Reynolds number of the
ICM. A simple way to model this effect is proposed. The model yields a
self-accelerating fluctuation dynamo whereby the field grows explosively fast,
reaching the observed, dynamically important, field strength in a fraction of
the cluster lifetime independent of the exact strength of the seed field. It is
suggested that the saturated state of the cluster turbulence is a combination
of the conventional isotropic magnetohydrodynamic turbulence, characterized by
folded, direction-reversing magnetic fields and an Alfv\'en-wave cascade at
collisionless scales. An argument is proposed to constrain the reversal scale
of the folded field. The picture that emerges appears to be in qualitative
agreement with observations of magnetic fields in clusters.


title: Alternative proposal to modified Newtonian dynamics

abstract:
  From a study of conserved quantities of the so-called Modified Newtonian
Dynamics (MOND) we propose an alternative to this theory. We show that this
proposal is consistent with the Tully-Fisher law, has conserved quantities
whose Newtonian limit are the energy and angular momentum, and can be useful to
explain cosmic acceleration. The dynamics obtained suggests that, when
acceleration is very small, time depends on acceleration. This result is
analogous to that of special relativity where time depends on velocity.


title: On Dark Matter Self-Interactions from Higher Dimensional Gravity

abstract:
  It has recently been suggested that in a brane world scenario with large
extra dimensions, short distance gravitational interactions can enhance the
dark matter scattering cross-section in a velocity dependent way. Such a
modification may then help to address possible problems with non-interacting
cold dark matter on galactic and sub-galactic scales. We argue that,
considering the singular character of the higher dimensional Newtonian
potential, the scattering cross-section is UV-dependent, depending ultimately
on the underlying quantum gravity theory considered. We demonstrate that for a
wide class of unitary short distance regularizations, the actual cross-section
is velocity-independent and does not significantly affect dark matter
substructure. We comment on the problem of thermalization of ultra-light cold
dark matter by gravitational interactions in the early universe.


title: Dark Matter and the CACTUS Gamma-Ray Excess from Draco

abstract:
  The CACTUS atmospheric Cherenkov telescope collaboration recently reported a
gamma-ray excess from the Draco dwarf spheroidal galaxy. Draco features a very
low gas content and a large mass-to-light ratio, suggesting as a possible
explanation annihilation of weakly interacting massive particles (WIMPs) in the
Draco dark-matter halo. We show that with improved angular resolution, future
measurements can determine whether the halo is cored or cuspy, as well as its
scale radius. We find the relevant WIMP masses and annihilation cross sections
and show that supersymmetric models can account for the required gamma-ray
flux. The annihilation cross section range is found to be not compatible with a
standard thermal relic dark-matter production. We compute for these
supersymmetric models the resulting Draco gamma-ray flux in the GLAST energy
range and the rates for direct neutralino detection and for the flux of
neutrinos from neutralino annihilation in the Sun. We also discuss the
possibility that the bulk of the signal detected by CACTUS comes from direct
WIMP annihilation to two photons and point out that a decaying-dark-matter
scenario for Draco is not compatible with the gamma-ray flux from the Galactic
center and in the diffuse gamma-ray background.


title:
News from the "Dentist's Chair": Observations of AM 1353-272 with the
  VIMOS IFU

abstract:
  The galaxy pair AM 1353-272 nicknamed "The Dentist's Chair" shows two ~30 kpc
long tidal tails. Previous observations using multi-slit masks showed that they
host up to seven tidal dwarf galaxies. The kinematics of these tidal dwarfs
appeared to be decoupled from the surrounding tidal material. New observations
of the tip of the southern tidal tail with the VIMOS integral field unit
confirm the results for two of these genuine tidal dwarfs but raise doubts
whether the velocity gradient attributed to the outermost tidal dwarf candidate
is real. We also discuss possible effects to explain the observational
difference of the strongest velocity gradient seen in the slit data which is
undetected in the new integral field data, but arrive at no firm conclusion.
Additionally, low-resolution data covering most of the two interacting partners
show that the strongest line emitting regions of this system are the central
parts.


title:
Probing the cosmic star formation using long Gamma-Ray Bursts: New
  constraints from the Spitzer Space Telescope

abstract:
  We report on IRAC-4.5mic, IRAC-8.0mic and MIPS-24mic deep observations of 16
Gamma-Ray Burst (GRBs) host galaxies performed with the Spitzer Space
Telescope, and we investigate in the thermal infrared the presence of evolved
stellar populations and dust-enshrouded star-forming activity associated with
these objects. Our sample is derived from GRBs that were identified with
sub-arcsec localization between 1997 and 2001, and only a very small fraction
(~20%) of the targeted sources is detected down to f_4.5mic ~3.5microJy and
f_24mic ~85microJy (3sigma). This likely argues against a population dominated
by massive and strongly-starbursting (i.e., SFR > ~100 Msol/yr) galaxies as it
has been recently suggested from submillimeter/radio and optical studies of
similarly-selected GRB hosts. Furthermore we find evidence that some GRBs do
not occur in the most infrared-luminous regions -- hence the most actively
star-forming environments -- of their host galaxies. Should the GRB hosts be
representative of all star-forming galaxies at high redshift, models of
infrared galaxy evolution indicate that > ~50% of GRB hosts should have f_24mic
> ~100microJy. Unless the identification of GRBs prior to 2001 was prone to
strong selection effects biasing our sample against dusty galaxies, we infer in
this context that the GRBs identified with the current techniques can not be
directly used as unbiased probes of the global and integrated star formation
history of the Universe.


title:
Missing GRB host galaxies in deep mid-infrared observations:
  implications on the use of GRBs as star formation tracers

abstract:
  We report on the first mid-infrared observations of 16 GRB host galaxies
performed with the Spitzer Space Telescope, and investigate the presence of
evolved stellar populations and dust-enshrouded star-forming activity
associated with GRBs. Only a very small fraction of our sample is detected by
Spitzer, which is not consistent with recent works suggesting the presence of a
GRB host population dominated by massive and strongly-starbursting galaxies
(SFR > ~100 Msol/yr). Should the GRB hosts be representative of star-forming
galaxies at high redshift, models of galaxy evolution indicate that >~50% of
GRB hosts would be easily detected at the depth of our mid-infrared
observations. Unless our sample suffers from a strong observational bias which
remains to be understood, we infer in this context that the GRBs identified
with the current techniques can not be directly used as unbiased probes of the
global and integrated star formation history of the Universe.


title: A VLT-UVES spectrscopic analysis of C-rich Fe-poor stars

abstract:
  Large surveys of very metal-poor stars have revealed in recent years that a
large fraction of these objects were carbon-rich, analogous to the more
metal-rich CH-stars. The abundance peculiarities of CH-stars are commonly
explained by mass-transfer from a more evolved companion. In an effort to
better understand the origin and importance for Galactic evolution of Fe-poor,
C-rich stars, we present abundances determined from high-resolution and high
signal-to-noise spectra obtained with the UVES instrument attached to the
ESO/VLT. Our analysis of carbon-enhanced objects includes both CH stars and
more metal-poor objects, and we explore the link between the two classes. We
also present preliminary results of our ongoing radial velocity monitoring.


title:
Stacking weak lensing signals of SZ clusters to constrain cluster
  physics

abstract:
  We show how to place constraints on cluster physics by stacking the weak
lensing signals from multiple clusters found through the Sunyaev-Zeldovich (SZ)
effect. For a survey that covers about 200 sq. deg. both in SZ and weak lensing
observations, the slope and amplitude of the mass vs. SZ luminosity relation
can be measured with few percent error for clusters at z~0.5. This can be used
to constrain cluster physics, such as the nature of feedback. For example, we
can distinguish a pre-heated model from a model with a decreased accretion rate
at more than 5sigma. The power to discriminate among different
non-gravitational processes in the ICM becomes even stronger if we use the
central Compton parameter y_0, which could allow one to distinguish between
models with pre-heating, SN feedback and AGN feedback, for example, at more
than 5sigma. Measurement of these scaling relations as a function of redshift
makes it possible to directly observe e.g., the evolution of the hot gas in
clusters. With this approach the mass-L_SZ relation can be calibrated and its
uncertainties can be quantified, leading to a more robust determination of
cosmological parameters from clusters surveys. The mass-L_SZ relation
calibrated in this way from a small area of the sky can be used to determine
masses of SZ clusters from very large SZ-only surveys and is nicely
complementary to other techniques proposed in the literature.


title: Quasars and their host galaxies

abstract:
  This review attempts to describe developments in the fields of quasar and
quasar host galaxies in the past five. In this time period, the Sloan and 2dF
quasar surveys have added several tens of thousands of quasars, with Sloan
quasars being found to z>6. Obscured, or partially obscured quasars have begun
to be found in significant numbers. Black hole mass estimates for quasars, and
our confidence in them, have improved significantly, allowing a start on
relating quasar properties such as radio jet power to fundamental parameters of
the quasar such as black hole mass and accretion rate. Quasar host galaxy
studies have allowed us to find and characterize the host galaxies of quasars
to z>2. Despite these developments, many questions remain unresolved, in
particular the origin of the close relationship between black hole mass and
galaxy bulge mass/velocity dispersion seen in local galaxies.


title:
Permitted Oxygen Abundances and the Temperature Scale of Metal-Poor
  Turn-Off Stars

abstract:
  We use high quality VLT/UVES published data of the permitted OI triplet and
FeII lines to determine oxygen and iron abundances in unevolved (dwarfs,
turn-off, subgiants) metal-poor halo stars. The calculations have been
performed both in LTE and NLTE, employing effective temperatures obtained with
the new infrared flux method (IRFM) temperature scale by Ramirez & Melendez,
and surface gravities from Hipparcos parallaxes and theoretical isochrones. A
new list of accurate transition probabilities for FeII lines, tied to the
absolute scale defined by laboratory measurements, has been used. We find a
plateau in the oxygen-to-iron ratio over more than two orders of magnitude in
iron abundance (-3.2 < [Fe/H] < -0.7), with a mean [O/Fe] = 0.5 dex (sigma =
0.1 dex), independent of metallicity, temperature and surface gravity.
According to the new IRFM Teff scale, the temperatures of turn-off halo stars
strongly depend on metallicity, a result that is in excellent qualitative and
quantitative agreement with stellar evolution calculations, which predict that
the Teff of the turn-off at [Fe/H] = -3 is about 600-700 K higher than that at
[Fe/H] = -1.


title: Analysis of the rotational properties of Kuiper belt objects

abstract:
  We use optical data on 10 Kuiper Belt objects (KBOs) to investigate their
rotational properties. Of the 10, three (30%) exhibit light variations with
amplitude delta_m >= 0.15 mag, and 1 out of 10 (10%) has delta_m >= 0.40 mag,
which is in good agreement with previous surveys. These data, in combination
with the existing database, are used to discuss the rotational periods, shapes,
and densities of Kuiper Belt objects. We find that, in the sampled size range,
Kuiper Belt objects have a higher fraction of low amplitude lightcurves and
rotate slower than main belt asteroids. The data also show that the rotational
properties and the shapes of KBOs depend on size. If we split the database of
KBO rotational properties into two size ranges with diameter larger and smaller
than 400 km, we find that: (1) the mean lightcurve amplitudes of the two groups
are different with 98.5% confidence, (2) the corresponding power-law shape
distributions seem to be different, although the existing data are too sparse
to render this difference significant, and (3) the two groups occupy different
regions on a spin period vs. lightcurve amplitude diagram. These differences
are interpreted in the context of KBO collisional evolution.


title:
Modelling of isolated radio pulsars and magnetars on the fossil field
  hypothesis

abstract:
  We explore the hypothesis that the magnetic fields of neutron stars are of
fossil origin. For parametrised models of the distribution of magnetic flux on
the Main Sequence and of the birth spin period of the neutron stars, we
calculate the expected properties of isolated radio pulsars in the Galaxy using
as our starting point the initial mass function and star formation rate as a
function of galacto-centric radius. We then use the 1374 MHz Parkes Multi-Beam
Survey of isolated radio pulsars to constrain the parameters in our model and
to deduce the required distribution of magnetic fields on the main sequence. We
find agreement with observations for a model with a star formation rate that
corresponds to a supernova rate of 2 per century in the Galaxy from stars with
masses in the range 8 - 45 solar masses and predict 447,000 active pulsars in
the Galaxy with luminosities greater than 0.19 mJy kpc^2. The progenitor OB
stars have a field distribution which peaks near 46 Gauss with about 8 percent
of stars having fields in excess of 1,000 Gauss. The higher field progenitors
yield a population of 24 neutron stars with fields in excess of 10^14 Gauss,
periods ranging from 5 to 12 seconds, and ages of up to 100,000 years, which we
identify as the dominant component of the magnetars. We also predict that high
field neutron stars (log B>13.5) originate preferentially from higher mass
progenitors and have a mean mass of 1.6 solar masses, which is significantly
above the mean mass of 1.4 solar masses calculated for the overall population
of radio pulsars.


title: Cyclotron emission effect on CMB spectral distortions

abstract:
  We investigated the role of the cyclotron emission (CE) associated to cosmic
magnetic fields (MF) on the evolution of cosmic microwave background (CMB)
spectral distortions. We computed the photon and energy injection rates by
including spontaneous and stimulated emission and absorption. These CE rates
have been compared with those of bremsstrahlung (BR) and double Compton
scattering (DC), for realistic CMB distorted spectra at various cosmic epochs.
For reasonable MF strengths we found that the CE contribution to the evolution
of the CMB spectrum is much smaller than the BR and DC contributions. The
constraints on the energy exchanges at various redshifts can be then derived,
under quite general assumptions, by considering only Compton scattering (CS),
BR, and DC, other than the considered dissipation process. Upper limits to the
CMB polarization degree induced by CE have been estimated.


title: Methanol Masers and Star Formation

abstract:
  Methanol masers which are traditionally divided into two classes provide
possibility to study important parts of the star forming regions: Class~II
masers trace vicinities of the massive YSOs while class~I masers are likely to
trace more distant parts of the outflows where newer stars can form. There are
many methanol transitions which produce observed masers. This allows to use
pumping analysis for estimation of the physical parameters in the maser
formation regions and its environment, for the study of their evolution.
Extensive surveys in different masing transitions allow to conclude on the
values of the temperatures, densities, dust properties, etc. in the bulk of
masing regions. Variability of the brightest masers is monitored during several
years. In some cases it is probably caused by the changes of the dust
temperature which follow variations in the brightness of the central YSO
reflecting the character of the accretion process. A unified catalogue of the
class II methanol masers consisting of more than 500 objects is compiled.
Analysis of the data shows that: physical conditions within the usual maser
source vary considerably; maser brightness is determined by parameters of some
distinguished part of the object - maser formation region; class II methanol
masers are formed not within the outflows but in the regions affected by their
propagation. It is shown that the "near" solutions for the kinematic distances
to the sources can be used for statistical analysis. The luminosity function of
the 6.7 GHz methanol masers is constructed. It is shown that improvement of the
sensitivity of surveys can increase number of detected maser sources
considerably.


title: The Physics of Core-Collapse Supernovae

abstract:
  Supernovae are nature's grandest explosions and an astrophysical laboratory
in which unique conditions exist that are not achievable on Earth. They are
also the furnaces in which most of the elements heavier than carbon have been
forged. Scientists have argued for decades about the physical mechanism
responsible for these explosions. It is clear that the ultimate energy source
is gravity, but the relative roles of neutrinos, fluid instabilities, rotation
and magnetic fields continue to be debated.


title: The influence of grain rotation on the structure of dust aggregates

abstract:
  We study the effect of rotation during the collision between dust aggregates,
in order to address a mismatch between previous model calculations of Brownian
motion driven aggregation and experiments. We show that rotation during the
collision does influence the shape and internal structure of the aggregates
formed. The effect is limited in the ballistic regime when aggregates can be
considered to move on straight lines during a collision. However, if the
stopping length of an aggregate becomes smaller than its physical size,
extremely elongated aggregates can be produced. We show that this effect may
have played a role in the inner regions of the solar nebula where densities
were high.


title: The distribution of ejected brown dwarfs in clusters

abstract:
  We examine the spatial distribution of brown dwarfs produced by the decay of
small-N stellar systems as expected from the embryo ejection scenario. We model
a cluster of several hundred stars grouped into 'cores' of a few stars/brown
dwarfs. These cores decay, preferentially ejecting their lowest-mass members.
Brown dwarfs are found to have a wider spatial distribution than stars, however
once the effects of limited survey areas and unresolved binaries are taken into
account it can be difficult to distinguish between clusters with many or no
ejections. A large difference between the distributions probably indicates that
ejections have occurred, however similar distributions sometimes arise even
with ejections. Thus the spatial distribution of brown dwarfs is not
necessarily a good discriminator between ejection and non-ejection scenarios.


title:
Exploring variations in the fundamental constants with ELTs: The CODEX
  spectrograph on OWL

abstract:
  Cosmological variations in the fine structure constant, alpha, can be probed
through precise velocity measurements of metallic absorption lines from
intervening gas clouds seen in spectra of distant quasars. Data from the
Keck/HIRES instrument support a variation in alpha of 6 parts per million. Such
a variation would have profound implications, possibly providing a window into
the extra spatial dimensions required by unified theories such as
string/M-theory. However, recent results from VLT/UVES suggest no variation in
alpha. The COsmic Dynamics EXperiment (CODEX) spectrograph currently being
designed for the ESO OWL telescope (Pasquini et al 2005) with a resolution high
enough to properly resolve even the narrowest of metallic absorption lines,
R>150,000, will achieve a 2-to-3 order-of-magnitude precision increase in
Delta\alpha/alpha. This will rival the precision available from the Oklo
natural fission reactor and upcoming satellite-borne atomic clock experiments.
Given the vital constraints on fundamental physics possible, the ELT community
must consider such a high-resolution optical spectrograph like CODEX.


title: [O III] emission line in narrow-line Seyfert 1 galaxies

abstract:
  Three sets of two-component profiles are used to simultaneously model the [O
III]$\lambda\lambda$4959, 5007 and H$\beta$ lines for the Fe II-subtracted
spectra of 149 narrow line Seyfert 1 galaxies (NLSls) from the Sloan Digital
Sky Survey (SDSS). Using the linewidth of the narrow/core component of [O
III]$\lambda$5007 to trace the stellar velocity dispersion instead of using the
total linewidth of [O III]$\lambda$5007, we found that the SDSS NLSls are still
deviated from the $M_{bh}-\sigma$ relation found in the nearby inactive
galaxies, suggesting that the linewidth of the [O III] narrow/core component is
likely not a good tracer of bulge velocity dispersion in NLSls, since some
other studies indicate that NLS1s, like other AGN, should follow the
$M_{bh}-\sigma$ relation. If we assume that the [O III]5007/H$\beta_{n}$ line
ratio emitted in narrow line region ranges from one to ten, 63 objects are
found to satisfied with this criterion and their H$\beta$ broad components
should be used to calculate their virial black hole masses. These 63 objects
are statically consistent with the $M_{bh}-\sigma_{[O III]}$ relation. With the
Chandra observation of some SDSS NLSls, for one object in these 63 objects,
J143030.22-001115.1, we found that it can't be classified as a genuine NLS1.
Its narrow component of H$\beta$ is coming from narrow line regions (NLRs).
This is consistent with its very flat hard X-ray spectrum found by williams et
al. (2004).


title:
A fluid os strings as a viable candidate to the dark side of the
  universe

abstract:
  We investigate the possibility that part of the dark matter is not made out
of the usual cold dark matter (CDM) dustlike particles, but is under the form
of a fluid of strings with barotropic factor $w_s = -1/3$ of cosmic origin. To
this aim, we split the dark matter density parameter in two terms and
investigate the dynamics of a spatially flat universe filled with baryons, CDM,
fluid of strings and dark energy, modeling this latter as a cosmological
constant or a negative pressure fluid with a constant equation of state $w <
0$. To test the viability of the models and to constrain their parameters, we
use the Type Ia Supernovae Hubble diagram and the data on the gas mass fraction
in galaxy clusters. We also discuss the weak field limit of a model comprising
a significant fraction of dark matter in the form of a fluid of strings and
show that this mechanism makes it possible to reduce the need for the elusive
and up to now undetected CDM. We finally find that a model comprising both a
cosmological constant and a fluid of strings fits very well the data and
eliminates the need of phantom dark energy thus representing a viable candidate
to alleviate some of the problems plaguing the dark side of the universe.


title: A new approach of analyzing GRB light curves

abstract:
  We estimated the Txx quantiles of the cumulative GRB light curves using our
recalculated background. The basic information of the light curves was
extracted by multivariate statistical methods. The possible classes of the
light curves are also briefly discussed.


title:
The Two Young Star Disks in the Central Parsec of the Galaxy:
  Properties, Dynamics and Formation

abstract:
  We report the definite spectroscopic identification of 41 OB supergiants,
giants and main sequence stars in the central parsec of the Galaxy. Detection
of their absorption lines have become possible with the high spatial and
spectral resolution and sensitivity of the adaptive optics integral field
spectrometer SPIFFI/SINFONI on the ESO VLT. Several of these OB stars appear to
be helium and nitrogen rich. Almost all of the ~80 massive stars now known in
the central parsec (central arcsecond excluded) reside in one of two somewhat
thick (<|h|/R>~0.14) rotating disks. These stellar disks have fairly sharp
inner edges (R~1") and surface density profiles that scale as R^{-2}. We do not
detect any OB stars outside the central 0.5 pc. The majority of the stars in
the clockwise system appear to be on almost circular orbits, whereas most of
those in the `counter-clockwise' disk appear to be on eccentric orbits. Based
on its stellar surface density distribution and dynamics we propose that IRS
13E is an extremely dense cluster (core density > 3x10^8 sunmass/pc^3), which
has formed in the counter-clockwise disk. The stellar contents of both systems
are remarkably similar, indicating a common age of ~6+/-2 Myr. The K-band
luminosity function of the massive stars suggests a top-heavy mass function and
limits the total stellar mass contained in both disks to ~1.5x10^4 sunmass. Our
data strongly favor in situ star formation from dense gas accretion disks for
the two stellar disks. This conclusion is very clear for the clockwise disk and
highly plausible for the counter-clockwise system.


title: First Results from IceCube

abstract:
  IceCube is a 1 km$^3$ neutrino observatory being built to study neutrino
production in active galactic nuclei, gamma-ray bursts, supernova remnants, and
a host of other astrophysical sources. High-energy neutrinos may signal the
sources of ultra-high energy cosmic rays. IceCube will also study many
particle-physics topics: searches for WIMP annihilation in the Earth or the
Sun, and for signatures of supersymmetry in neutrino interactions, studies of
neutrino properties, including searches for extra dimensions, and searches for
exotica such as magnetic monopoles or Q-balls. IceCube will also study the
cosmic-ray composition.
  In January, 2005, 60 digital optical modules (DOMs) were deployed in the
South Polar ice at depths ranging from 1450 to 2450 meters, and 8 ice-tanks,
each containing 2 DOMs were deployed as part of a surface air-shower array. All
76 DOMs are collecting high-quality data. After discussing the IceCube physics
program and hardware, I will present some initial results with the first DOMs.


title: A rotating disk around the very young massive star AFGL 490

abstract:
  We observed the embedded, young 8--10 Msun star AFGL 490 at subarcsecond
resolution with the Plateau de Bure Interferometer in the C17O (2--1)
transition and found convincing evidence that AFGL 490 is surrounded by a
rotating disk. Using two-dimensional modeling of the physical and chemical disk
structure coupled to line radiative transfer, we constrain its basic
parameters. We obtain a relatively high disk mass of 1 Msun and a radius of ~
1500 AU. A plausible explanation for the apparent asymmetry of the disk
morphology is given.


title:
Nonlinear perturbations for dissipative and interacting relativistic
  fluids

abstract:
  We develop a covariant formalism to study nonlinear perturbations of
dissipative and interacting relativistic fluids. We derive nonlinear evolution
equations for various covectors defined as linear combinations of the spatial
gradients of the local number of e-folds and of some scalar quantities
characterizing the fluid, such as the energy density or the particle number
density. For interacting fluids we decompose perturbations into adiabatic and
entropy components and derive their coupled evolution equations, recovering and
extending the results obtained in the context of the linear theory. For
non-dissipative and noninteracting fluids, these evolution equations reduce to
the conservation equations that we have obtained in recent works. We also
illustrate geometrically the meaning of the covectors that we have introduced.


title:
The late time evolution of Gamma-Ray Bursts: ending hyperaccretion and
  producing flares

abstract:
  We consider the properties of a hyperaccretion model for gamma-ray bursts
(GRBs) at the late time when the mass supply rate is expected to decrease with
time. We point out that the region in the vicinity of the accretor and the
accretor itself can play an important role in determining the rate and time
behavior of the accretion and ultimately the energy output. Motivated by
numerical simulations and theoretical results, we conjecture that the energy
release can be repeatedly stopped and then restarted by the magnetic flux
accumulated around the accretor. We propose that the episode or episodes when
the accretion resumes correspond to X-ray flares discovered recently in a
number of GRBs.


title: Clockwise Stellar Disk and the Dark Mass in the Galactic Center

abstract:
  Two disks of young stars have recently been discovered in the Galactic
Center. The disks are rotating in the gravitational field of the central black
hole at radii r=0.1-0.3 pc and thus open a new opportunity to measure the
central mass. We find that the observed motion of stars in the clockwise disk
implies M=4.3+/-0.5 million solar masses for the fiducial distance to the
Galactic Center R_0=8 kpc and derive the scaling of M with R_0. As a tool for
our estimate we use orbital roulette, a recently developed method. The method
reconstructs the three-dimensional orbits of the disk stars and checks the
randomness of their orbital phases. We also estimate the three-dimensional
positions and orbital eccentricities of the clockwise-disk stars.


title: Dark Fluid: a complex scalar field to unify dark energy and dark matter

abstract:
  In this article, we examine a model which proposes a common explanation for
the presence of additional attractive gravitational effects -- generally
considered to be due to dark matter -- in galaxies and in clusters, and for the
presence of a repulsive effect at cosmological scales -- generally taken as an
indication of the presence of dark energy. We therefore consider the behavior
of a so-called dark fluid based on a complex scalar field with a conserved
U(1)-charge and associated to a specific potential, and show that it can at the
same time account for dark matter in galaxies and in clusters, and agree with
the cosmological observations and constraints on dark energy and dark matter.


title:
Short GRB and binary black hole standard sirens as a probe of dark
  energy

abstract:
  Observations of the gravitational radiation from well-localized, inspiraling
compact object binaries can measure absolute source distances with high
accuracy. When coupled with an independent determination of redshift through an
electromagnetic counterpart, these standard sirens can provide an excellent
probe of the expansion history of the Universe and the dark energy. Short
gamma-ray bursts, if produced by merging neutron star binaries, would be
standard sirens with known redshifts detectable by ground-based GW networks
such as LIGO-II, Virgo, and AIGO. Depending upon the collimation of these GRBs,
a single year of observation of their gravitational waves can measure the
Hubble constant to about 2%. When combined with measurement of the absolute
distance to the last scattering surface of the cosmic microwave background,
this determines the dark energy equation of state parameter w to 9%. Similarly,
supermassive binary black hole inspirals will be standard sirens detectable by
LISA. Depending upon the precise redshift distribution, 100 sources could
measure w at the 4% level.


title: The Lyth Bound and the End of Inflation

abstract:
  We derive an extended version of the well-known Lyth Bound on the total
variation of the inflaton field, incorporating higher order corrections in slow
roll. We connect the field variation $\Delta\phi$ to both the spectral index of
scalar perturbations and the amplitude of tensor modes. We then investigate the
implications of this bound for ``small field'' potentials, where the field
rolls off a local maximum of the potential. The total field variation during
inflation is {\em generically} of order $m_{\rm Pl}$, even for potentials with
a suppressed tensor/scalar ratio. Much of the total field excursion arises in
the last e-fold of inflation and in single field models this problem can only
be avoided via fine-tuning or the imposition of a symmetry. Finally, we discuss
the implications of this result for inflationary model building in string
theory and supergravity.


title: The N-Body Approach to Disk Galaxy Evolution

abstract:
  I review recent progress from $N$-body simulations in our understanding of
the secular evolution of isolated disk galaxies. I describe some of the recent
controversies in the field which have been commonly attributed to numerics. The
numerical methods used are widely used in computational astronomy and the
problems encountered are therefore of wider interest.


title: On the Formation of Gas Giant Planets on Wide Orbits

abstract:
  A new suite of three dimensional radiative, gravitational hydrodynamical
models is used to show that gas giant planets are unlikely to form by the disk
instability mechanism at distances of ~100 AU to ~200 AU from young stars. A
similar result seems to hold for the core accretion mechanism. These results
appear to be consistent with the paucity of detections of gas giant planets on
wide orbits by infrared imaging surveys, and also imply that if the object
orbiting GQ Lupus is a gas giant planet, it most likely did not form at a
separation of ~100 AU. Instead, a wide planet around GQ Lup must have undergone
a close encounter with a third body that tossed the planet outward to its
present distance from its protostar. If it exists, the third body may be
detectable by NASA's Space Interferometry Mission.


title:
Average Extinction Curves and Relative Abundances for QSO Absorption
  Line Systems at 1 <= z_abs < 2

abstract:
  We have studied a sample of 809 Mg II absorption systems with 1.0 < z_abs <
1.86 in the spectra of SDSS QSOs, with the aim of understanding the nature and
abundance of the dust and the chemical abundances in the intervening absorbers.
Normalized, composite spectra were derived, for abundance measurements, for the
full sample and several sub-samples, chosen on the basis of the line strengths
and other absorber and QSO properties. Average extinction curves were obtained
for the sub-samples by comparing their geometric mean spectra with those of
matching samples of QSOs without absorbers in their spectra. There is clear
evidence for the presence of dust in the intervening absorbers. The 2175 A
feature is not present in the extinction curves, for any of the sub-samples.
The extinction curves are similar to the SMC extinction curve with a rising UV
extinction below 2200 A. The absorber rest frame colour excess, E(B-V), derived
from the extinction curves, depends on the absorber properties and ranges from
< 0.001 to 0.085 for various sub-samples. The column densities of several ions
do not show such a correspondingly large variation. The depletion pattern is
similar to halo clouds in the Galaxy. Assuming an SMC gas-to-dust ratio we find
a trend of increasing abundance with decreasing extinction; systems with N_H I
\~ 10^{20} cm^{-2} show solar abundance of Zn. The large velocity spread of
strong Mg II systems seems to be mimicked by weak lines of other elements. The
ionization of the absorbers, in general appears to be low. QSOs with absorbers
are, in general, at least three times as likely to have highly reddened spectra
as compared to QSOs without any absorption systems in their spectra.


title: Spatial Distribution of Faint Fuzzy Star Clusters in NGC 5195

abstract:
  We present a study of a faint fuzzy star cluster system in the nearby SB0
galaxy NGC 5195 interacting with the famous spiral galaxy NGC 5194 (M51), based
on HST ACS BVI mosaic images taken by the Hubble Heritage Team. We have found
about 50 faint fuzzy star clusters around NGC 5195 which are larger than
typical globular clusters with effective radii r_eff > 7 pc and red with (V-I)
> 1.0. They are mostly fainter than M_V ~ 8.3 mag. From the comparison of BVI
photometry of these clusters with the simple stellar population models, we find
that they are as massive as ~ 10^5 M_sun and older than 1 Gyr. Strikingly, most
of these clusters are found to be scattered in an elongated region almost
perpendicular to the northern spiral arm of NGC 5194, and the center of the
region is slightly north of the NGC 5195 center, while normal compact red
clusters of NGC 5195 are located around the bright optical body of the host
galaxy. This is in contrast against the cases of NGC 1023 and NGC 3384 where
spatial distribution of faint fuzzy clusters shows a ring structure around the
host galaxy. We suggest that at least some faint fuzzy clusters are
experiencing tidal interactions with the companion galaxy NGC 5194 and must be
associated with the tidal debris in the western halo of NGC 5195.


title:
The comparison of velocity distribution between Adhesion approximation
  and the Euler-Jeans-Newton model

abstract:
  For the evolution of density fluctuation in nonlinear cosmological dynamics,
adhesion approximation (AA) is proposed as a phenomenological model, which is
especially useful for describing nonlinear evolution. However, the origin of
the artificial viscosity in AA is not clarified. Recently, Buchert and
Dom\'{\i}nguez report if the velocity dispersion of the dust fluid is regarded
as isotropic, it works on a principle similar to viscosity or effective
pressure, and they consider isotropic velocity dispersion as the origin of the
artificial viscosity in AA. They name their model the Euler-Jeans-Newton (EJN)
model. In this paper, we focus on the velocity distribution in AA and the EJN
model and examine the time evolution in both models. We find the behavior of AA
differs from that of the EJN model, i.e., although the peculiar velocity in the
EJN model oscillates, that in AA is monotonically decelerated due to viscosity
without oscillation. Therefore it is hard to regard viscosity in AA as
effective pressure in the EJN model.


title:
Compact strange stars with a medium dependence in gluons at finite
  temperature

abstract:
  The possible existence of strange stars in the universe will help in the
understanding of various properties of quantum chromodynamics, like asymptotic
freedom and chiral symmetry restoration, which is otherwise very difficult to
prove in laboratory experiments. Strange star properties were calculated using
large $N_c$ approximation with built-in chiral symmetry restoration. A
relativistic Hartree Fock calculation was performed using the Richardson
potential as an interquark interaction. This potential has the asymptotic
freedom and a confinement-deconfinement mechanism built into it and the present
calculation employs an application of this potential with modified two scale
parameters $\Lambda$ and $\Lambda^{\prime}$, to find a new set of equations of
state for strange quark matter. The linear confinement string tension from
lattice calculations is 350 $MeV$ and the Coulomb -like part has the parameter
100 $MeV$ from deep inelastic scattering experiments. We also consider the
effect of temperature, $T$, on gluon mass in a simple way, in addition to the
usual density dependence, and find that the transition $T$ from hadronic matter
to strange matter is at 80 MeV, close to the 100 MeV estimated in litarature.
Therefore formation of strange stars may be the only signal for formation of
quark-gluon plasma with asymptotic freedom and chiral symmetry restoration and
this may be observable through many processes -such as for example through
delayed $\gamma$ ray afterglow.


title: The structure of Planetary Nebulae: theory vs. practice

abstract:
  This paper - the first of a short series dedicated to the long-stan ding
astronomical problem of de-projecting the bi-dimensional apparent morpholog y
of a three-dimensional mass of gas - focuses on the density distribution in
real Planetary Nebulae (and all types of expanding nebulae). We introduce some
basic theoretical notions, discuss the observational methodology and develope
the accurate procedure for the determination of the matter radial profile
within the sharp portion of nebula in the plane of the sky identified by the
zero-velocity-pixel-column (zvpc) of high-resolution spectral images. Moreover,
a series of evolutive snapshots is presented, combining illustrative examples
of model- and true-Planetary Nebulae. Last, the general and specific
applications of the method (and some caveats) are discussed.


title:
Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic
  Variables, IV. Observations of Frequency Doubling and Tripling in VW Hyi

abstract:
  We present new observations of the rapid oscillations in the dwarf nova VW
Hyi, made late in outburst. These dwarf nova oscillations (DNOs) increase in
period until they reach 33 s, when a transition to a strong 1st harmonic and
weak fundamental takes place. After further period increase the 2nd harmonic
appears; often all three components are present simultaneously. This 1:2:3
frequency suite is similar to what has been seen in some neutron star and black
hole X-Ray binaries, but has not previously been seen in a cataclysmic
variable. When studied in detail the fundamental and 2nd harmonic vary
similarly in phase, but the 1st harmonic behaves independently, though keeping
close to twice the frequency of the fundamental. The fundamental period of the
DNOs, as directly observed or inferred from the harmonics, increases to ~100 s
before the oscillation disappears as the star reaches quiescence. Its maximum
period is close to that of the `longer period' DNOs observed in VW Hyi. The
quasi-periodic oscillations (QPOs), which have fundamental periods 400 -- 1000
s, behave in the same way, showing 1st and 2nd harmonics at approximately the
same times as the DNOs. We explore some possible models. One in which the
existence of the 1st harmonic is due to transition from viewing a single
accretion region to viewing two regions, and the rate of accretion onto the
primary is modulated at the frequency of the 1st harmonic, as in the `beat
frequency model', can generate the suite of DNO frequencies observed. But the
behaviour of the QPOs is not yet understood.


title: New radio halos and relics in clusters of galaxies

abstract:
  We present here new images of relics and halo sources in rich cluster of
galaxies and the correlation between the halo radio surface brightness versus
the cluster bolometric X-ray luminosity.


title:
Why the fundamental plane of black hole activity is not simply a
  distance driven artifact

abstract:
  The fundamental plane of black hole activity is a non-linear correlation
among radio core luminosity, X-ray luminosity and mass of all accreting black
holes, both of stellar mass and supermassive, found by Merloni, Heinz and Di
Matteo (2003) and, independently, by Falcke, Koerding and Markoff (2004). Here
we further examine a number of statistical issues related to this correlation.
In particular, we discuss the issue of sample selection and quantify the bias
introduced by the effect of distance in two of the correlated quantities. We
demonstrate that the fundamental plane relation cannot be a distance artifact,
and that its non-linearity must represent an intrinsic characteristic of
accreting black holes. We also discuss possible future observational strategies
to improve our understanding of this correlation.


title: A Catalog of Transient X-ray Sources in M31

abstract:
  From October 1999 to August 2002, 45 transient X-ray sources were detected in
M31 by Chandra and XMM-Newton. We have performed spectral analysis of all
XMM-Newton and Chandra ACIS detections of these sources, as well as flux
measurements of Chandra HRC detections. The result is absorption-corrected
X-ray lightcurves for these sources covering this 2.8 year period, along with
spectral parameters for several epochs of the outbursts of most of the
transient sources. We supply a catalog of the locations, outburst dates, peak
observed luminosities, decay time estimates, and spectral properties of the
transient sources, and we discuss similarities with Galactic X-ray novae. Duty
cycle estimates are possible for 8 of the transients and range from 40% to 2%;
upper limits to the duty cycles are estimated for an additional 15 transients
and cover a similar range. We find 5 transients which have rapid decay times
and may be ultra-compact X-ray binaries. Spectra of three of the transients
suggest they may be faint Galactic foreground sources. If even one is a
foreground source, this suggests a surface density of faint transient X-ray
sources of >~1 deg$^{-2}$.


title:
FIRST-based survey of Compact Steep Spectrum sources, IV. Multifrequency
  VLBA observations of very compact objects

abstract:
  Evidence has been mounting recently that activity in some radio-loud AGNs
(RLAGNs) can cease shortly after ignition and that perhaps even a majority of
very compact sources may be short-lived phenomena because of a lack of stable
fuelling from the black hole. Thus, they can fade out before having evolved to
large, extended objects. Re-ignition of the activity in such objects is not
ruled out. With the aim of finding more examples of these objects and to
investigate if they could be RLAGNs switched off at very early stages of their
evolution, multifrequency VLBA observations of six sources with angular sizes
significantly less than an arcsecond, yet having steep spectra, have been made.
Observations were initially made at 1.65 GHz using the VLBA with the inclusion
of Effelsberg telescope. The sources were then re-observed with the VLBA at 5,
8.4 and 15.4 GHz. All the observations were carried out in a snapshot mode with
phase referencing. One of the sources studied, 0809+404, is dominated by a
compact component but also has diffuse, arcsecond-scale emission visible in VLA
images. The VLBI observations of the "core" structure have revealed that this
is also diffuse and fading away at higher frequencies. Thus, the inner
component of 0809+404 could be a compact fading object. The remaining five
sources presented here show either core-jet or edge-brightened double-lobed
structures indicating that they are in an active phase. The above result is an
indication that the activity of the host galaxy of 0809+404 may be
intermittent. Previous observations obtained from the literature and those
presented here indicate that activity had ceased once in the past, then
restarted, and has recently switched off again.


title:
Millimag Precision Photometry of Southern Bright Stars with a 1-m
  Telescope and a Standard CCD

abstract:
  This paper summarizes a three night observing campaign aimed at achieving
milli-magnitude precision photometry of bright stars (V < 9.0) with the 1-meter
Swope telescope at Las Campanas Observatory. The test targets were the main
sequence stars HD205739 and HD135446. The results show that, by placing a
concentric diaphragm in front of the aperture of the telescope, it is possible
to avoid saturation and to achieve a photometric precision of 0.0008-0.0010 mag
per data point with a cadence of less than 4 minutes. It is also possible to
reach an overall precision of less that 0.0015 mags for time series of 6 hours
or more. The photometric precision of this setup is only limited by
scintillation. Scintillation could be reduced, and therefore the photometric
precision could be further improved, by using a neutral density filter instead
of the aperture stop. Given that the expected median depth of extrasolar planet
transits of about 0.01 mags, and their typical duration of several hours, the
results of this paper show that 1-m telescopes equipped with standard CCDs can
be used to detect planet transits as shallow as 0.002 mags around bright stars.


title:
The Anisotropy of Galactic Cosmic Rays as a Product of Stochastic
  Supernova Explosions

abstract:
  We study the effect of the stochastic character of supernova explosions on
the anisotropy of galactic cosmic rays below the knee. We conclude that if the
bulk of cosmic rays are produced in supernova explosions the observed small and
nearly energy independent amplitude of the anisotropy and its phase are to the
large extent determined by the history of these explosions in the vicinity of
the solar system, namely by the location and the age of the supernova remnants,
within a few kpc, which give the highest contribution to the total intensity at
the present epoch. Among the most important factors which result in the small
magnitude and the energy independence of the anisotropy amplitude are the mixed
primary mass composition, the effect of the Single Source and the Galactic
Halo. Special attention is given to the phase of the anisotropy. It is shown
that the excessive flux from the Outer Galaxy can be due to the location of the
solar system at the inner edge of the Orion Arm which has the enhanced density
and rate of supernova explosions.


title:
A VIMOS-IFU survey of $z \sim 0.2$ massive lensing galaxy clusters:
  constraining cosmography

abstract:
  We present an integral field spectroscopy survey of rich clusters of galaxies
aimed at studying their lensing properties. Thanks to knowledge of the
spectroscopic caracteristics of more than three families of multiple images in
a single lens, one is able in principle to derive constraints on the geometric
cosmological parameters. We show that this ambitious program is feasible and
present some new results, in particular the redshift measurement of the giant
arc in A2667 and the resdshift confirmation of the counter-image of the radial
arc in MS2137--23. Prospects for the future of such program are presented.


title: Estimation of the detectability of optical orphan afterglows

abstract:
  By neglecting sideways expansion of gamma-ray burst (GRB) jets and assuming
their half-opening angle distribution, we estimate the detectability of orphan
optical afterglows. This estimation is carried out by calculating the durations
of off-axis optical afterglows whose flux density exceeds a certain
observational limit. We show that the former assumption leads to more
detectable orphans, while the latter suppresses the detectability strongly
compared with the model with half-opening angle $\theta_j=0.1$. We also
considered the effects of other parameters, and find that the effects of the
ejecta energy $E_j$ and post-jet-break temporal index $-\alpha_2$ are important
but that the effects of the electron-energy distribution index $p$, electron
energy equipartition factor $\epsilon_e$, and environment density $n$ are
insignificant. If $E_j$ and $\alpha_2$ are determined by other methods, one can
constrain the half-opening angle distribution of jets by observing orphan
afterglows. Adopting a set of "standard" parameters, the detectable rate of
orphan afterglows is about $1.3\times 10^{-2} {deg}^{-2} {yr}^{-1}$, if the
observed limiting magnitude is 20 in R-band.


title: The broadband afterglow of GRB 030328

abstract:
  We here report on the photometric, spectroscopic and polarimetric monitoring
of the optical afterglow of the Gamma-Ray Burst (GRB) 030328 detected by
HETE-2. We found that a smoothly broken power-law decay provides the best fit
of the optical light curves, with indices alpha_1 = 0.76 +/- 0.03, alpha_2 =
1.50 +/- 0.07, and a break at t_b = 0.48 +/- 0.03 d after the GRB. Polarization
is detected in the optical V-band, with P = (2.4 +/- 0.6)% and theta = (170 +/-
7) deg. Optical spectroscopy shows the presence of two absorption systems at z
= 1.5216 +/- 0.0006 and at z = 1.295 +/- 0.001, the former likely associated
with the GRB host galaxy. The X-ray-to-optical spectral flux distribution
obtained 0.78 days after the GRB was best fitted using a broken power-law, with
spectral slopes beta_opt = 0.47 +/- 0.15 and beta_X = 1.0 +/- 0.2. The
discussion of these results in the context of the "fireball model" shows that
the preferred scenario is a fixed opening angle collimated expansion in a
homogeneous medium.


title: A New Color-Magnitude Diagram for Palomar 11

abstract:
  We present new photometry for the Galactic thick disk globular cluster
Palomar 11 extending well past the main sequence turn-off in the V and I bands.
This photometry shows noticeable red giant and subgiant branches. The
difference in magnitude between the red horizontal branch (red clump) and the
subgiant branch is used to determine that Palomar 11 has an age of 10.4+/-0.5
Gyr. The red clump is used to derive a distance d_\sun=14.3+/-0.4 kpc, and a
mean cluster reddening of E(V-I)=0.40+/-0.03. There is differential reddening
across the cluster, of order \delta E(V-I)~0.07. The colour magnitude diagram
of Palomar 11 is virtually identically to that of the thick disk globular
cluster NGC 5927, implying that these two clusters have a similar age and
metallicity. Palomar 11 has a slightly redder red giant branch than 47 Tuc,
implying that Palomar 11 is 0.15 dex more metal-rich, or 1 Gyr older than 47
Tuc. Ca II triplet observations (Rutledge et al. 1997) favour the hypothesis
that Palomar 11 is the same age as 47 Tuc, but slightly more metal-rich.


title: Modelling the Galaxy Bimodality: Shutdown Above a Critical Halo Mass

abstract:
  We reproduce the blue and red sequences in the observed joint distribution of
colour and magnitude for galaxies at low and high redshifts using hybrid
N-body/semi-analytic simulations of galaxy formation. The match of model and
data is achieved by mimicking the effects of cold flows versus shock heating
coupled to feedback from active galactic nuclei (AGNs), as predicted by Dekel &
Birnboim (2006). After a critical epoch z=3, only haloes below a critical
shock-heating mass 10^12MSun enjoy gas supply by cold flows and form stars,
while cooling and star formation are shut down abruptly above this mass. The
shock-heated gas is kept hot because being dilute it is vulnerable to feedback
from energetic sources such as AGNs in their self-regulated mode. The shutdown
explains in detail the bright-end truncation of the blue sequence at ~L*, the
appearance of luminous red-and-dead galaxies on the red sequence starting
already at z~2, the colour bimodality, its strong dependence on environment
density and its correlations with morphology and other galaxy properties.
Before z~2-3, even haloes above the shock-heating mass form stars by cold
streams penetrating through the hot gas. This explains the bright star-forming
galaxies at z~3-4, the early appearance of massive galaxies on the red
sequence, the high cosmological star-formation rate at high redshifts and the
subsequent low rate at low redshifts.


title:
Photoelectric Emission from Dust Grains Exposed to Extreme Ultraviolet
  and X-ray Radiation

abstract:
  Photoelectric emission from dust plays an important role in grain charging
and gas heating. To date, detailed models of these processes have focused
primarily on grains exposed to soft radiation fields. We provide new estimates
of the photoelectric yield for neutral and charged carbonaceous and silicate
grains, for photon energies exceeding 20 eV. We include the ejection of
electrons from both the band structure of the material and the inner shells of
the constituent atoms, as well as Auger and secondary electron emission. We
apply the model to estimate gas heating rates in planetary nebulae and grain
charges in the outflows of broad absorption line quasars. For these
applications, secondary emission can be neglected; the combined effect of inner
shell and Auger emission is small, though not always negligible. Finally, we
investigate the survivability of dust entrained in quasar outflows. The lack of
nuclear reddening in broad absorption line quasars may be explained by
sputtering of grains in the outflows.