title:
X-ray Emission from Orion Nebula Cluster Stars with Circumstellar Disks
  and Jets

abstract:
  We investigate the X-ray and near-infrared emission properties of a sample of
pre-main sequence (PMS) stellar systems in the Orion Nebula Cluster (ONC) that
display evidence for circumstellar disks (``proplyds'') and optical jets in
Hubble Space Telescope (HST) imaging. Approximately 70% of ~140 proplyds were
detected as X-ray sources in the Chandra Orion Ultradeep Program observation of
the ONC, including ~25% of proplyds that do not display central stars in HST
imaging. Many proplyds display near-infrared excesses, suggesting disk
accretion is ongoing onto the central, PMS stars. Among circumstellar disks
that are detected in absorption in HST imaging, we find that X-ray absorbing
column and apparent disk inclination are well correlated, providing insight
into the disk scale heights and metal abundances of UV- and X-ray-irradiated
protoplanetary disks. Jet sources display some of the largest near-infrared
excesses among the X-ray-detected proplyds, suggesting that the origin of the
jets is closely related to ongoing, PMS stellar accretion. Some jet sources
display double-peaked X-ray spectral energy distributions, with soft components
indicative of strong shocks in the jet collimation region. These results
support models in which circumstellar disks collimate and/or launch jets from
young stellar objects and, furthermore, demonstrate that star-disk-jet
interactions may contribute to PMS X-ray emission.


title: Li in NGC 6752 and the formation of globular clusters

abstract:
  Li abundances for 9 Turnoff (TO) stars of the intermediate metallicity
cluster ([Fe/H]=-1.4) NGC6752 are presented. The cluster is known to show
abundance anomalies and anticorrelations observed in both evolved and main
sequence stars. We find that Li abundance anticorrelates with Na (and N) and
correlates with O in these Turn-Off stars. For the first time we observe Pop II
hot dwarfs systematically departing from the Spite plateau. The observed
anticorrelations are in qualitative agreement with what is expected if the
original gas were contaminated by Intermediate Mass AGB - processed material.
However, a quantitative comparison shows that none of the existing models can
reproduce all the observations at once. The very large amount of processed gas
present in the cluster does not imply a 'pollution', but rather that the whole
protocluster cloud was enriched by a previous generation of stars. We finally
note that the different abundance patterns in NGC 6397 and NGC 6752 imply
different ejecta of the preenrichment composition for the two clusters.


title: The search for the host galaxy of the gamma-ray burst GRB 000214

abstract:
  We present UBVRI-band observations taken ~300 days after the BeppoSAX
gamma-ray burst GRB 000214. This GRB did not show a detectable optical
afterglow, however due to the localization of a previously unknown, fading,
X-ray source at a tentative redshift in the range 0.37-0.47, we have searched
with the ESO 3.6 m telescope for objects with photometric redshifts consistent
with the mentioned X-ray redshift range. We report four host galaxy candidates,
which might be the subject of future spectroscopic observations in order to
confirm their redshifts.


title: The Metallicity Distribution Function of Field Stars in M31's Bulge

abstract:
  We have used Hubble Space Telescope Wide Field Planetary Camera 2
observations to construct a color-magnitude diagram (CMD) for the bulge of M31
at a location ~1.6 kpc from the galaxy's center. Using scaled-solar abundance
theoretical red giant branches with a range of metallicities, we have
translated the observed colors of the stars in the CMD to abundances and
constructed a metallicity distribution function (MDF) for this region. The MDF
shows a peak at [M/H]~0 with a steep decline at higher metallicities and a more
gradual tail to lower metallicities. This is similar in shape to the MDF of the
Milky Way bulge but shifted to higher metallicities by ~0.1 dex. As is the case
with the Milky Way bulge MDF, a pure closed box model of chemical evolution,
even with significant pre-enrichment, appears to be inconsistent with the M31
bulge MDF. However, a scenario in which an initial infall of gas enriched the
bulge to an abundance of [M/H] ~ -1.6 with subsequent evolution proceeding as a
closed box provides a better fit to the observed MDF. The similarity between
the MDF of the M31 bulge and that of the Milky Way stands in stark contrast to
the significant differences in the MDFs of their halo populations. This
suggests that the bulk of the stars in the bulges of both galaxies were in
place before the accretion events that occurred in the halos could influence
them.


title: The dynamical disconnection of sunspots from their magnetic roots

abstract:
  After a dynamically active emergence phase, magnetic flux at the solar
surface soon ceases to show strong signs of the subsurface dynamics of its
parent magnetic structure. This indicates that some kind of disconnection of
the emerged flux from its roots in the deep convection zone should take place.
We propose a mechanism for the dynamical disconnection of the surface flux
based upon the buoyant upflow of plasma along the field lines. Such flows arise
in the upper part of a rising flux loop during the final phases of its buoyant
ascent towards the surface. The combination of the pressure buildup by the
upflow and the cooling of the upper layers of an emerged flux tube by radiative
losses at the surface lead to a progressive weakening of the magnetic field in
several Mm depth. When the field strength has become sufficiently low,
convective motions and the fluting instability disrupt the flux tube into thin,
passively advected flux fragments, thus providing a dynamical disconnection of
the emerged part from its roots. We substantiate this scenario by considering
the quasi-static evolution of a sunspot model under the effects of radiative
cooling, convective energy transport, and pressure buildup by a prescribed
inflow at the bottom of the model. For inflow speeds in the range shown by
simulations of thin flux tubes, we find that the disconnection takes place in a
depth between 2 and 6 Mm for disconnection times up to 3 days.


title: The evolution of early-type galaxies at z~1 from the K20 survey

abstract:
  We have performed VLT spectroscopy of an almost complete sample of 18
early-type galaxies with 0.88 < z < 1.3 plus two at z=0.67, selected from the
K20 survey, and derived the velocity dispersion for 15+2 of them. By combining
these data with HST and VLT images, we study the Fundamental Plane (FP), the
Faber-Jackson and the Kormendy relations at z~1, and compare them with the
local ones. The FP at z~1 keeps a remarkably small scatter, and shows both an
offset and a rotation, which we interpret in terms of evolution of the
mass-to-light ratio, and possibly of the size. We show evidence that the
evolution rate depends on galaxy mass, being faster for less massive galaxies.
We discuss the possible factors driving the evolution of spheroids and compare
our results with the predictions of the hierachical models of galaxy formation.


title:
On the V-type asteroids outside the Vesta family. I. Interplay of
  nonlinear secular resonances and the Yarkovsky effect: the cases of 956 Elisa
  and 809 Lundia

abstract:
  Among the largest objects in the main belt, asteroid 4 Vesta is unique in
showing a basaltic crust. It is also the biggest member of the Vesta family,
which is supposed to originate from a large cratering event about 1 Gyr ago
(Marzari et al. 1996). Most of the members of the Vesta family for which a
spectral classification is available show a V-type spectra. Before the
discovery of 1459 Magnya (Lazzaro et al. 2000) and of several V-type NEA (Xu
1995), all the known V-type asteroids were members of the Vesta family.
Recently two V-type asteroids, 809 Lundia and 956 Elisa, (Florczak et al. 2002)
have been discovered well outside the limits of the family, near the Flora
family. We currently know 22 V-type asteroids outside the family, in the inner
asteroid belt. In this work we investigate the possibility that these objects
are former family members that migrated to their current positions via the
interplay of Yarkovsky effect and nonlinear secular resonances. The main
dynamical feature of 956 Elisa and 809 Lundia is that they are currently inside
the 2(g-g6)+s-s6 (z2 by Milani and Knezevic, 1993) secular resonance. Our
investigations show that members of the Vesta dynamical family may drift in
three-body and weak secular resonances until they are captured in the strong z2
secular resonance. Only asteroids with diameters larger than 16 km can remain
in one of the three-body or secular resonances long enough to reach the region
of the z2 resonance. This two-step mechanism of capture into the z2 resonance
could explain: i) the current resonant orbits of 956 Elisa and 809 Lundia, ii)
why their size is significantly larger than that of the typical member of the
Vesta family, and iii) provide a lower limit on the Vesta family age.


title:
X-ray observations of the edge-on star-forming galaxy NGC891 and its
  supernova SN1986J

abstract:
  We present XMM-Newton observations of NCG891, a nearby edge-on spiral galaxy.
We analyse the extent of the diffuse emission emitted from the disk of the
galaxy, and find that it has a single temperature profile with best fitting
temperature of 0.26 keV, though the fit of a dual-temperature plasma with
temperatures of 0.08 and 0.30 keV is also an acceptable fit. There is a
considerable amount of diffuse X-ray emission protruding from the disk in the
NW direction out to approximately 6 kpc. We analyse the point source population
using a Chandra observation, using a maximum likelihood method to find that the
slope of the cumulative luminosity function of point sources in the galaxy is
-0.77^{+0.13}_{-0.1}. Using a sample of other local galaxies, we compare the
X-ray and infrared properties of NGC891 with those of 'normal' and starburst
spiral galaxies, and conclude that NGC891 is most likely a starburst galaxy in
a quiescent state. We establish that the diffuse X-ray luminosity of spirals
scales with the far infra-red luminosity as L_X \propto L_FIR ^{0.87 +- 0.07},
except for extreme starbursts, and NGC891 does not fall in the latter category.
We study the supernova SN1986J in both XMM-Newton and Chandra observations, and
find that the X-ray luminosity has been declining with time more steeply than
expected (L_X \propto t^-3).


title:
Far-Infrared Spectral Energy Distributions of Embedded Protostars and
  Dusty Galaxies: I. Theory for Spherical Sources

abstract:
  We present analytic radiative transfer solutions for the spectra of
unresolved, spherically symmetric, centrally heated, dusty sources. We find
that the dust thermal spectrum possesses scaling relations that provide a
natural classification for a broad range of sources, from low-mass protostars
to dusty galaxies. In particular, we find that, given our assumptions, spectral
energy distributions (SEDs) can be characterized by two distance-independent
parameters, the luminosity-to-mass ratio, $L/M$, and the surface density,
$\Sigma$, for a set of two functions, namely, the density profile and the
opacity curve. The goal is to use SEDs as a diagnostic tool in inferring the
large-scale physical conditions in protostellar and extragalactic sources, and
ultimately, evolutionary parameters. Our approach obviates the need to use SED
templates in the millimeter to far-infrared region of the spectrum; this is a
common practice in the extragalactic community that relies on observed
correlations established at low redshift that may not necessarily extend to
high redshift. Further, we demarcate the limited region of parameter space in
which density profiles can be inferred from the SED, which is of particular
import in the protostellar community as competing theories of star formation
are characterized by different density profiles. The functionality of our model
is unique in that in provides for a self-consistent analytic solution that we
have validated by comparison with a well-tested radiative transfer code (DUSTY)
to find excellent agreement with numerical results over a parameter space that
spans low-mass protostars to ultra-luminous infrared galaxies (ULIRGS).


title:
Stars beyond Galaxies: The Origin of Extended Luminous Halos around
  Galaxies

abstract:
  (Abridged) We use numerical simulations to investigate the origin and
structure of the luminous halos that surround isolated galaxies. These stellar
structures extend out to several hundred kpc away from a galaxy, and consist of
stars shed by merging subunits during the many accretion events that
characterize the hierarchical assembly of galaxies. Such origin suggests that
outer luminous halos are ubiquitous and that they should appear as an excess of
light over extrapolations of the galaxy's inner profile beyond its traditional
luminous radius. The mass profile of the accreted stellar component is well
approximated by a model where the logarithmic slope steepens monotonically with
radius; from -3 at the luminous edge of the galaxy to -4 or steeper near the
virial radius of the system. Such spatial distribution is consistent with that
of Galactic and M31 globular clusters, suggesting that many of the globulars
were brought in by accretion events, in a manner akin to the classic
Searle-Zinn scenario. The outer stellar spheroid is supported by a velocity
dispersion tensor with a substantial and radially increasing radial anisotropy.
These properties distinguish the stellar halo from the dark matter component,
which is more isotropic in velocity space, as well as from some tracers of the
outer spheroid such as satellite galaxies. Most stars in the outer halo formed
in progenitors that have since merged with the central galaxy; very few stars
in the halo are contributed by satellites that survive as self-bound entities
at the present. These features are in reasonable agreement with recent
observations of the outer halo of the MW, of M31, and of other isolated
spirals, and suggest that all of these systems underwent an early period of
active merging, as envisioned in hierarchical models of galaxy formation.


title:
CAIRNS: The Cluster And Infall Region Nearby Survey III. Environmental
  Dependence of H-alpha Properties of Galaxies

abstract:
  We investigate the environmental dependence of star formation in cluster
virial regions and infall regions as part of CAIRNS (Cluster And Infall Region
Nearby Survey), a large spectroscopic survey of the infall regions surrounding
nine nearby rich clusters of galaxies. Our long-slit spectroscopy yields
estimates of star formation rates in environments from cluster cores to the
general large-scale structure. The fraction of galaxies with current star
formation in their inner disks as traced by H-alpha emission increases with
distance from the cluster and converges to the ``field'' value only at 2-3
virial radii, in agreement with other investigations. However, among galaxies
with significant current star formation (EW[Ha]geq2\AA), there is no difference
in the distribution of EW[Ha] inside and outside the virial radius. This
surprising result, first seen by Carter et al., suggests that (1) star
formation is truncated on either very short timescales or only at moderate and
high redshifts or (2) that projection effects contaminate the measurement. The
number density profiles of star-forming and non-star-forming galaxies indicate
that, among galaxies projected inside the virial radius, at least half of the
former and 20% of the latter are ``infall interlopers,'' galaxies in the infall
region but outside the virial region. The kinematics of star-forming galaxies
in the infall region closely match those of absorption-dominated galaxies. This
result shows that the star forming galaxies in the infall regions are not
interlopers from the field and excludes one model of the backsplash scenario of
galaxy transformation. Finally, we quantify systematic uncertainties in
estimating the global star formation in galaxies from their inner disks.


title: The Recent and Continuing Assembly of Field Ellipticals by Red Mergers

abstract:
  We present a study of tidal debris associated with 126 nearby red galaxies
selected from the MUSYC and NDWFS surveys. In the full sample 67 galaxies (53%)
show morphological signatures of tidal interactions, consisting of broad fans
of stars, tails, and other asymmetries at very faint surface brightness levels.
When restricting the sample to the 86 bulge-dominated early-type galaxies the
fraction of tidally disturbed galaxies rises to 71%, which implies that for
every ``normal'' undisturbed elliptical there are two which show clear signs of
interactions. The tidal features are red and smooth, and often extend over >50
kpc. Of the tidally distorted galaxies about 2/3 are remnants and 1/3 are
interacting with a companion galaxy. The companions are usually bright red
galaxies as well: the median R-band luminosity ratio of the tidal pairs is
0.31, and the median color difference after correcting for the slope of the
color-magnitude relation is -0.02 in B-R. If the ongoing mergers are
representative for the progenitors of the remnants ~35% of bulge-dominated
galaxies experienced a merger with mass ratio >1:4 in the recent past. With
further assumptions it is estimated that the present-day mass accretion rate of
galaxies on the red sequence is 0.09+-0.04 per Gyr. For a constant or
increasing mass accretion rate with redshift, we find that red mergers may lead
to an evolution of a factor of >~2 in the stellar mass density in luminous red
galaxies over the redshift range 0<z<1, consistent with recent studies of the
evolution of the luminosity density. We conclude that most of today's field
elliptical galaxies were assembled at low redshift through "dry" mergers of
gas-poor, bulge-dominated systems. [ABRIDGED]


title:
GRB 050509b: the elusive optical/nIR/mm afterglow of a short-duration
  GRB

abstract:
  We present multiwavelength (optical/near infrared/millimetre) observations of
a short duration gamma-ray burst detected by Swift (GRB 050509b) collected
between 0 seconds and ~18.8 days after the event. No optical, near infrared or
millimetre emission has been detected in spite of the well localised X-ray
afterglow, confirming the elusiveness of the short duration events. We also
discuss the possibility of the burst being located in a cluster of galaxies at
z= 0.225 or beyond. In the former case, the spectral energy distribution of the
neighbouring, potential host galaxy, favours a system harbouring an evolved
dominant stellar population (age ~360 Myr), unlike most long duration GRB host
galaxies observed so far, i.e. thus giving support to a compact binary merger
origin. Any underlying supernova that could be associated with this particular
event should have been at least 3 magnitudes fainter than the type Ib/c SN
1998bw and 2.3 magnitudes fainter than a typical type Ia SN.


title: On the stability of Dark Energy with Mass-Varying Neutrinos

abstract:
  An interesting dynamical model for dark energy which does not require
extremely light scalar fields such as quintessence, and at the same time
explains the (near-) coincidence between the neutrino and dark energy densities
is the model of dark energy coupled to mass varying neutrinos (MaVaNs). Despite
the attractions of this model, we show that, generically, this model contains a
catastrophic instability which occurs when neutrinos become non-relativistic.
As a result of this instability, as neutrinos become non-relativistic, they
condense into neutrino nuggets which redshift away similar to cold dark matter,
and thus cease to act as dark energy. Any stable MaVaNs dark energy model is
extremely contrived, and is virtually indistinguishable from a cosmological
constant.


title: CO in HI Self-Absorbed Clouds in Perseus

abstract:
  We have observed 12CO J = 2-1 and J = 1-0, and 13CO J = 1-0 emission in two
regions of HI Self-Absorption (HISA) in Perseus: a small, isolated HISA feature
called the globule and a more extended HISA cloud called the complex. Using
both Large Velocity Gradient and Monte Carlo radiative transfer codes we found
that, in the globule, N(12CO) < 6.0x10^15 cm-2 which, using PDR models, implies
that N(H_2) < 9.9x10^20 cm-2. In the complex we found that the H_2 column
densities ranged from 1.2 - 2.2 x 10^21 cm-2. By comparing the HISA and CO
observations we are able to constrain the physical conditions and atomic gas
fraction (f). In the globule, 8 K < T_spin < 22 K and 0.02 < f < 0.2 depending
on whether the (unknown) gas density is 10^2, 10^3, or 10^4 cm-3. In the
complex, 12 K < T_spin < 24 K, 0.02 < f < 0.05, and we were also able to
constrain the gas density (100 < n < 1200 cm-3). These results imply that the
gas in the HISA clouds is colder and denser than that usually associated with
the atomic ISM and, indeed, is similar to that seen in molecular clouds. The
small atomic gas fractions also imply that there is a significant molecular
component in these HISA clouds, even when little or no 12CO is detected. The
level of 12CO detected and the visual extinction due to dust is consistent with
the idea that these HISA clouds are undergoing a transition from the atomic to
molecular phase.


title:
Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A
  Reverberation-Based Measurement of the Black Hole Mass

abstract:
  A reverberation-mapping program on NGC 4395, the least-luminous known Seyfert
1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the
Hubble Space Telescope, yields a measurement of the mass of the central black
hole of 360,000 solar masses. The observations consist of two visits of 5
orbits each, in 2004 April and July. During each of these visits, the UV
continuum varied by at least 10% (rms) and only C IV 1549 showed corresponding
variations large enough to reliably determine the emission-line lag, which was
measured to be of order one hour for both visits. The size of the C IV-emitting
region is about a factor of three smaller than expected if the slope of the
broad-line region radius-luminosity relationship is identical to that for the
H-beta emission line. NGC 4395 is underluminous even for its small black hole
mass; the Eddington ratio of 0.0012 is lower than that of any other active
galactic nucleus for which a black hole mass measurement has been made by
emission-line reverberation.


title:
On the possibility of a helium white dwarf donor in the presumed
  ultracompact binary 2S 0918-549

abstract:
  2S 0918-549 is a low-mass X-ray binary (LMXB) with a low optical to X-ray
flux ratio. Probably it is an ultracompact binary with an orbital period
shorter than 60 min. Such binaries cannot harbor hydrogen rich donor stars. As
with other (sometimes confirmed) ultracompact LMXBs, 2S 0918-549 is observed to
have a high neon-to-oxygen abundance ratio (Juett et al. 2001) which has been
used to argue that the companion star is a CO or ONe white dwarf. However,
type-I X-ray bursts have been observed from several of these systems implying
the presence of hydrogen or helium on the neutron star surface. In this paper,
we argue that the companion star in 2S 0918-549 is a helium white dwarf We
first present a Type I X-ray burst from 2S 0918-549 with a long duration of 40
minutes. We show that this burst is naturally explained by accretion of pure
helium at the inferred accretion rate of ~0.01 times the Eddington accretion
rate. At higher accretion rates of ~0.1 Eddington, hydrogen is required to
explain long duration bursts. However, at low rates the long duration is due to
the large amount of helium that accumulates prior to the burst. We show that it
is possible to form a helium white dwarf donor in an ultracompact binary if
accretion starts during the first ascent of the giant branch, when the core is
made of predominantly helium. Furthermore, this scenario naturally explains the
high neon-to-oxgen ratio, without requiring a CO or ONe white dwarf companion.
The only observational aspect of 2S 0918-549 that we cannot explain is the
absence of helium lines in the optical spectrum. Model calculations of optical
accretion disk spectra need to be carried out in order to obtain limits on the
helium abundance.


title: A search for HI in some peculiar faint dwarf galaxies

abstract:
  We present a deep Giant Metrewave Radio Telescope (GMRT) search for HI 21 cm
emission from three dwarf galaxies, viz. POX 186, SC 24 and KKR 25. Based, in
part, on previous single dish HI observations, these galaxies have been
classified as a BCD, a dwarf irregular and a transition galaxy respectively.
However, in conflict with previous single dish detections, we do not detect HI
in SC 24 or KKR 25. We suggest that the previous single dish measurements were
probably confused with the local galactic emission. In the case of POX 186, we
confirm the previous non detection of HI but with substantially improved limits
on its HI mass. Our derived upper limits on the HI mass of SC 24 and KKR 25 are
similar to the typical HI mass limit for dwarf spheroidal galaxies, whereas in
the case of POX 186, we find that its gas content is somewhat smaller than is
typical of BCD galaxies.


title: Statistics of Voids in the 2dF Galaxy Redshift Survey

abstract:
  We present a statistical analysis of voids in the 2dF galaxy redshift survey
(2dFGRS). In order to detect the voids, we have developed two robust
algorithms. We define voids as non-overlapping maximal spheres empty of halos
or galaxies with mass or luminosity above a given one. We search for voids in
cosmological $N$-Body simulations to test the performance of our void finders.
We obtain and analyze the void statistics for several volume-limited samples
for the North Galactic Strip (NGP) and the South Galactic Strip (SGP)
constructed from the 2dFGRS full data release. We find that the results
obtained from the NGP and the SGP are statistically compatible. From the
results of several statistical tests we conclude that voids are essentially
uncorrelated, with at most a mild anticorrelation and that there is a
dependence of the void number density on redshift at least at the 99.5%
confidence level. We develop a technique to correct the distortion caused by
the fact that we use the redshift as the radial coordinate. We calibrate this
technique with mock catalogues and find that the correction might be of some
relevance to carry out accurate inferences from void statistics. We study the
statistics of the galaxies inside nine nearby voids. We find that galaxies in
voids are not randomly distributed: they form structures like filaments. We
also obtain the galaxy number density profile in voids. This profile follow a
similar but steeper trend to that follow by halos in voids.


title: Signatures of Planets in Spatially Unresolved Disks

abstract:
  Main sequence stars are commonly surrounded by debris disks, composed of cold
dust continuously replenished by a reservoir of undetected dust-producing
planetesimals. In a planetary system with a belt of planetesimals (like the
Solar System's Kuiper Belt) and one or more interior giant planets, the
trapping of dust particles in the mean motion resonances with the planets can
create structure in the dust disk, as the particles accumulate at certain
semimajor axes. Sufficiently massive planets may also scatter and eject dust
particles out of a planetary system, creating a dust depleted region inside the
orbit of the planet. In anticipation of future observations of spatially
unresolved debris disks with the Spitzer Space Telescope, we are interested in
studying how the structure carved by planets affects the shape of the disk's
spectral energy distribution (SED), and consequently if the SED can be used to
infer the presence of planets. We numerically calculate the equilibrium spatial
density distributions and SEDs of dust disks originated by a belt of
planetesimals in the presence of interior giant planets in different planetary
configurations, and for a representative sample of chemical compositions. The
dynamical models are necessary to estimate the enhancement of particles near
the mean motion resonances with the planets, and to determine how many
particles drift inside the planet's orbit. Based on the SEDs and predicted
$\it{Spitzer}$ colors we discuss what types of planetary systems can be
distinguishable from one another and the main parameter degeneracies in the
model SEDs.


title: AGN Outflows in a Cosmological Context

abstract:
  We combine cosmological simulations with an AGN luminosity function
constrained by optical surveys in order to create a realistic AGN distribution
in which to model AGN outflows. The outflows are modeled with assumptions of
spherical symmetry and energy conservation. We study the importance of the
kinetic luminosity of AGN outflows in determining the fractional volume of the
IGM filled with outflows as a function of redshift. We find that kinetic
luminosities of < 10% of the bolometric luminosities are required or the entire
IGM would be filled with outflows at z=0. We also examine the effects of
varying the AGN lifetime and the bias parameter, which describes how tightly
correlated AGN are to high density regions. We find that longer lifetimes
(tau_{AGN} ~ 1 Gyr), as well as small bias parameters increase the filling
fraction.


title:
Probing the inner 200 AU of low-mass protostars with the Submillimeter
  Array: Dust and organic molecules in NGC1333-IRAS2A

abstract:
  The Submillimeter Array has opened a new window to study the innermost warm
and dense regions of the envelopes and disks around deeply embedded protostars.
This paper presents high-angular resolution (< 2'') submillimeter observations
of the class 0 young stellar object NGC1333-IRAS2A. Dust continuum emission and
lines of complex organic molecules such as CH3OCH3 and CH3OCHO, high excitation
CH3OH transitions, deuterated methanol CH3OD as well as lines of CO, HCN,
H13CN, SO and SO2 are detected on < 200 AU scales. The observations are
interpreted using detailed radiative transfer models of the physical and
chemical structure, consistent with both single-dish and interferometer data.
The continuum emission is explained by an extended envelope and a compact but
resolved component, presumably a circumstellar disk with a diameter of 200-300
AU and a mass of a few times 0.01-0.1 M_sun. If related to the rotation of the
envelope, then the size of this disk suggests a centrifugal barrier of 200-300
AU, which implies that the temperature in the envelope does not increase above
100 K. Its large size also suggests that the build-up of disks proceeds rapidly
throughout the early protostellar stages. The smaller (< 100 AU) disks found
around other deeply embedded protostars may be a result of tidal truncation.
The high-resolution observations of SO can be explained with a simple constant
abundance, ~1E-9, constrained through single-dish observations, whereas those
of H13CN and the organic species require high abundances, increased by one to
two orders of magnitude, or an additional compact source of emission at small
scales. The compact molecular emission could originate in a hot core region of
the inner envelope, but a more likely reservoir is the circumstellar disk.


title: Stellar Cluster Fiducial Sequences with the Advanced Camera for Surveys

abstract:
  We present color-magnitude diagrams of five Galactic globular clusters and
one Galactic open cluster spanning a wide range of metallicity (-2.1 < [Fe/H] <
+0.3), as observed in the F606W (broad V) and F814W (I) bands with the Advanced
Camera for Surveys (ACS) on the Hubble Space Telescope. These clusters are part
of two large ACS programs measuring the star formation history in the Andromeda
halo, tidal stream, and outer disk. In these programs, the clusters serve as
empirical isochrones and as calibrators for the transformation of theoretical
isochrones to the ACS bandpasses. To make these data more accessible to the
community, for each cluster, we provide a ridge line tracing the stars on the
main sequence, subgiant branch, and red giant branch, plus the locus of stars
on the horizontal branch. In addition, we provide the transformation of the
Victoria-Regina isochrones to the ACS bandpasses.


title: A complete view of the broad-line radio galaxy 4C+74.26 with XMM-Newton

abstract:
  This paper presents a timing study and broadband spectral analysis of the
broad-line radio galaxy 4C+74.26 based on a 35 ks XMM-Newton observation. As
found in previous datasets, the source exhibits no evidence for rapid
variability, and its 0.2-10 keV lightcurve is well fit by a constant. An
excellent fit to the pn 0.3-12 keV spectrum was found using a continuum that
combines an ionized and a neutral reflector, augmented by both cold and warm
absorption. There is no evidence for a soft excess. The column of cold
absorption was greater than the Galactic value with an intrinsic column of
\~1.9\times 10^{21} cm^{-2}. Evidence for the warm absorber was found from O
VII and O VIII absorption edges with maximum optical depths of \tau_{O VII}=0.3
and \tau_{O VIII}=0.03, respectively. A joint pn-MOS fit increased the O VIII
optical depth to \tau_{O VIII}=0.1. A simple, one-zone warm absorber model
yielded a column of ~9\times 10^{20} cm^{-2} and an ionization parameter of
\~60. Partial covering models provide significantly worse fits than ones
including a relativistically broadened Fe K line, strengthening the case for
the existence of such a line. On the whole, the X-ray spectrum of 4C+74.26
exhibits many features typical of both a radio-loud quasar (excess absorption)
and radio-quiet Seyfert~1 galaxies (\fe emission and warm absorption). We also
show that a spurious absorption line at ~8 keV can be created by the
subtraction of an instrumental Cu K\alpha emission line.


title:
Dust outflows and inner gaps generated by massive planets in debris
  disks

abstract:
  Main sequence stars are commonly surrounded by debris disks, formed by cold
far-IR-emitting dust that is thought to be continuously replenished by a
reservoir of undetected dust-producing planetesimals. We have investigated the
orbital evolution of dust particles in debris disks harboring massive planets.
Small dust grains are blown out by radiation pressure, as is well known; in
addition, gravitational scattering by the giant planets also creates an outflow
of large grains. We describe the characteristics of this large-particle outflow
in different planetary architectures and for different particle sizes. In
addition, the ejection of particles is responsible for the clearing of dust
inside the orbit of the planet. We study the efficiency of particle ejection
and the resulting dust density contrast inside and outside the orbit of the
planet, as a function of the planet's mass and orbital elements and the
particle size. We discuss its implications for exo-planetary debris disks and
for the interpretation of in-situ dust detection experiments on space probes
traveling in the outer solar system.


title: Photometric Accretion Signatures Near the Substellar Boundary

abstract:
  Multi-epoch imaging of the Orion equatorial region by the Sloan Digital Sky
Survey has revealed that significant variability in the blue continuum persists
into the late-M spectral types, indicating that magnetospheric accretion
processes occur below the substellar boundary in the Orion OB1 association. We
investigate the strength of the accretion-related continuum veiling by
comparing the reddening-invariant colors of the most highly variable stars
against those of main sequence M dwarfs and evolutionary models. A gradual
decrease in the g band veiling is seen for the cooler and less massive members,
as expected for a declining accretion rate with decreasing mass. We also see
evidence that the temperature of the accretion shock decreases in the very low
mass regime, reflecting a reduction in the energy flux carried by the accretion
columns. We find that the near-IR excess attributed to circumstellar disk
thermal emission drops rapidly for spectral types later than M4. This is likely
due to the decrease in color contrast between the disk and the cooler stellar
photosphere. Since accretion, which requires a substantial stellar magnetic
field and the presence of a circumstellar disk, is inferred for masses down to
0.05 Msol we surmise that brown dwarfs and low mass stars share a common mode
of formation.


title: Introduction to Dark Energy and Dark Matter

abstract:
  In an introductory manner, the nature of dark energy is addressed, how it is
observed and what further tests are needed to reconstruct its properties.
Several theoretical approaches to dark energy will be discussed. Finally, the
dark matter, especially WIMPs, is introduced.


title: A helium-hydrogenic molecular atmosphere of neutron star 1E1207.4-5209

abstract:
  A model of a mixed helium-hydrogenic atmosphere of the isolated neutron star
1E1207.4-5209 is proposed. It is based on the assumption that the main
components in the atmosphere are the exotic molecular ions $He_2^{3+}$ and
$H_3^{2+}$ with the presence of $He^{+}, (HeH)^{2+}, H_2^{+}$ under a surface
magnetic field $\approx 4.4 \times 10^{13}$ G. In addition to two absorption
features observed by {\it Chandra} observatory (Sanwal et al, 2002) the model
predicts one more narrow absorption feature at $\approx 400$ eV.


title: The Nonradial Oscillation Node Precession of Neutron Stars

abstract:
  The standing wave nodes of nonradial oscillations on a neutron star crust
will drift with a definite angle velocity around rotational pole due to the
rotation of neutron stars. This is called the nonradial oscillation node
precession of neutron stars. This article estimated the precession velocity and
pointed out that it merely lies on the star's rotation velocity and the angular
order of spherical harmonic $l$ by one order approximation. If we suppose that
oscillations effect the particles' escaping from the polar cap of a neutron
star, so that the antinode and node areas of the standing waves have different
radiative intensity, several unusual conclusions are acquired by reviewing the
observation of pulsars which had already been taken as neutron stars. For
example, the drifting subpulse period $P_{3}$ can be gotten from the width of
subpulses and order $l$; the larger velocity drift may produce the peak
structure of average pulse profiles; the dissimilar radiation phenomena between
neighboring periods generated from drift provide a reasonable explanation of
interpulses which have been found on some pulsars.


title:
Increase in the Absorption Length of Inclined Extensive Air Showers with
  Different Selection Types

abstract:
  The dependence of the number of extensive air showers (EAS) on the zenith
angle is obtained in groups with a constant solid-angle step with different
election types at separations between stations of 500 and 1000 m by using the
Yakutsk EAS array data. A bend point is formed at the zenith angle
approximately of 50 deg. This point shifts with the increasing energy in the
direction corresponding to the shift of the cascade-curve maximum depth with
the variation of energy. The boundaries of change of these dependences obtained
separately at the distances between stations of 500 and 1000 m are different
that may be caused by the uncertainty of the lateral distribution function
(LDF) used. Thereby, energies of showers detected by the stations with a
different separation are not joined.


title:
Seasonal Variations of Extensive Air Showers with Energies from 10**17
  to 10**18 eV

abstract:
  The seasonal variations of extensive air showers (EAS) registered at the
Yakutsk EAS array are considered. The dependence of variations on the
atmospheric pressure is significantly expressed. The dependence on an air
temperature is not found.


title: Probing the interior of neutron stars with gravitational waves

abstract:
  We show here how the internal structure of a neutron star can be inferred
from its gravitational wave spectrum. Under the premise that the frequencies
and damping rates of a few $w$-mode oscillations are found, we apply an
inversion scheme to determine its mass, radius and density distribution. In
addition, accurate equation of state of nuclear matter can also be determined.


title:
The XMM-Newton Detection of Diffuse Inverse Compton X-rays from Lobes of
  the FR-II Radio Galaxy 3C98

abstract:
  The XMM-Newton observation of the nearby FR-II radio galaxy 3C 98 is
reported. In two exposures on the target, faint diffuse X-ray emission
associated with the radio lobes was significantly detected, together with a
bright X-ray active nucleus, of which the 2 -- 10 keV intrinsic luminosity is
(4 -- 8) \times 10^{42} erg s-1. The EPIC spectra of the northern and southern
lobes are reproduced by a single power law model modified by the Galactic
absorption, with a photon index of 2.2-0.5+0.6 and 1.7-0.6+0.7 respectively.
These indices are consistent with that of the radio synchrotron spectrum, 1.73
+- 0.01 The luminosity of the northern and southern lobes are measured to be
8.3-2.6+3.3 \times 10^{40} erg s-1 and 9.2-4.3+5.7 \times 10^{40} erg s-1,
respectively, in the 0.7 -- 7 keV range. The diffuse X-ray emission is
interpreted as an inverse-Compton emission, produced when the
synchrotron-emitting energetic electrons in the lobes scatter off the cosmic
microwave background photons. The magnetic field in the lobes is calculated to
be about 1.7 \mu G, which is about 2.5 times lower than the value estimated
under the minimum energy condition. The energy density of the electrons is
inferred to exceed that in the magnetic fields by a factor of 40 -- 50.


title:
The quiescent Hubble flow, local dark energy tests, and pairwise
  velocity dispersion in a $\Omega = 1$ universe

abstract:
  We review the increasing evidence for the cosmological relevance of the cold
local Hubble flow. New observations, N-body simulations and other theoretical
arguments are discussed, supporting our previous suggestion that the
cosmological vacuum or uniform dark energy can have locally observable
consequencies, especially a lower velocity scatter in DE dominated regions. The
apparent contradiction between the slight dependence of the growth factor on
$\Omega_{\Lambda}$ and the significant influence of dark energy in realistic
N-body calculations is clarified. An interesting new result is that in the
standard $\Lambda$ cosmology, gravitation dominates around a typical matter
fluctuation up to about the correlation length $r_0$, and we tentatively link
this with the high pairwise velocity dispersion on scales up to several Mpc, as
measured from galaxy redshift-space correlations. Locally, the smooth Hubble
flow on similar scales is consistent with N-body simulations including
$\Omega_{\Lambda} \approx 0.7$ and a low density contrast in the Local Volume,
which make it generally vacuum-dominated beyond 1 - 2 Mpc from galaxies and
groups. We introduce a useful way to view the Hubble flow in terms of "zero
gravity" spheres aound galaxies: e.g. a set of non-intersecting spheres,
observed to be expanding, actually participates in accelerating expansion. The
observed insensitiveness of the local velocity dispersion to galaxy mass is
explained as an effect of the vacuum, too.


title: Extinction Correction for Type Ia Supernova Rates. I. The Model

abstract:
  In this paper we present and discuss a new Monte Carlo approach aimed at
correcting the observed Supernova (SN) rates for the effects of host galaxy
dust extinction. The problem is addressed in a general way and the model
includes SN position distributions, SN light curve and spectral library, dust
properties and distribution as input ingredients. Even though the recipe we
propose is in principle applicable to all SN types, in this paper we illustrate
the use of our model only for Type Ia. These represent in fact the simplest
test case, basically due to their spectroscopic homogeneity which, to a first
approximation, allows one to treat them all in the same way. This test case
shows that the final results do not depend critically on the spiral arm dust
geometry, while the total amount of dust, its properties and the size of the
galactic bulge do have a strong effect. With the availability of more complete
spectral libraries and a more accurate knowledge of SN spatial distribution,
the method we propose here can be easily extended to Core Collapses events.


title: Stellar populations and Lya emission in two lensed z>~6 galaxies

abstract:
  We present an analysis of two strongly lensed galaxies at z=6.56 and z ~ 7
for which multi-band photometric and spectroscopic observations are available.
For one source the data include recent HST and Spitzer observations. Using an
SED fitting technique considering a number of parameters we attempt to
constrain the properties of their stellar populations and their intrinsic Lya
emission. The following main results are obtained for the individual galaxies:
* Triple arc in Abell 2218: The most likely redshift of this source is z ~
6.0-7.2. SED fits indicate generally a low extinction but do not strongly
constrain the star formation (SF) history. Best fits have typical ages of ~3 to
400 Myr. The apparent 4000Ang break observed recently from combination of
IRAC/Spitzer and HST observations, can also equally well be reproduced with the
template of a young (~3-5 Myr). The estimated SFR is typically ~1 Msun/yr, in
agreement with previous estimates. The unknowns on the age and star formation
history could easily explain the apparent absence of Lya in this galaxy. *
Abell 370 HCM 6A: The available Lya and continuum observations indicate two
possible solutions: 1) a young burst or ongoing constant SF with non-negligible
extinction or 2) a composite young+"old" stellar population. In the first case
one obtains a best fit A_V ~ 0.5-1.8 at a 1 sigma level. In consequence we
obtain SFR ~ 11-41 Msun/yr, higher than earlier estimates, and we estimate a
fairly high total luminosity (L ~ (1-4)*10^{11} Lsun) for this galaxy, in the
range LIRG. A Lya transmission of ~23-90% is estimated from our best fit
models. Other properties remain largely unconstrained. In case of composite
stellar populations the SFR, mass, and luminosity estimate is lower. The two
scenarios may be distinguishable with IRAC/Spitzer observations at 3.6 and 4.5
micron.


title: On the nature of nearby GRB/SN host galaxies

abstract:
  We present and discuss optical diagnostics of the low redshift (z<0.2)
galaxies that are known to have hosted supernovae associated with gamma-ray
bursts (GRBs). The three galaxies are all actively starforming sub-luminous
(L<L*) galaxies with relatively low metallicities (Z<Zsun). We find no evidence
for substantial internal extinction within any of the galaxies. We derive star
formation rates (SFR) based on H-alpha luminosities, as well as specific star
formation rates (SFFR, star formation rate per unit luminosity). For GRB 980425
(SN 1998bw) we use photometry of the supernova environment to estimate the mass
of the progentitor to > 30 Msun. These three host galaxies have global
properties (luminosities, SFR, SSFR, metallicity, colour, reddening) that
resemble those of more distant GRB host galaxies. We also compare the host
galaxies with a sample of Blue Compact Galaxies (BCGs) in the local universe,
and show that these samples have similar properties.


title: The tidal stripping of satellites

abstract:
  We present an improved analytic calculation for the tidal radius of
satellites and test our results against N-body simulations.
  The tidal radius in general depends upon four factors: the potential of the
host galaxy, the potential of the satellite, the orbit of the satellite and
{\it the orbit of the star within the satellite}. We demonstrate that this last
point is critical and suggest using {\it three tidal radii} to cover the range
of orbits of stars within the satellite. In this way we show explicitly that
prograde star orbits will be more easily stripped than radial orbits; while
radial orbits are more easily stripped than retrograde ones. This result has
previously been established by several authors numerically, but can now be
understood analytically. For point mass, power-law (which includes the
isothermal sphere), and a restricted class of split power law potentials our
solution is fully analytic. For more general potentials, we provide an equation
which may be rapidly solved numerically. Over short times ($\simlt 1-2$ Gyrs
$\sim 1$ satellite orbit), we find excellent agreement between our analytic and
numerical models. Over longer times, star orbits within the satellite are
transformed by the tidal field of the host galaxy. In a Hubble time, this
causes a convergence of the three limiting tidal radii towards the prograde
stripping radius. Beyond the prograde stripping radius, the velocity dispersion
will be tangentially anisotropic.


title: Optimal slit orientation for long multi-object spectroscopic exposures

abstract:
  Historically, long-slit spectroscopic observations were carried out using the
parallactic angle for the slit orientation if slit loss was an important
consideration (either to maximize the signal-to-noise or to do
spectrophotometry). This requires periodic realignment of the slit position
angle as the parallactic angle changes. This is not possible for multi-slit
observations where one slit position angle must be chosen for the entire
exposure. Common wisdom suggests using the parallactic angle at the meridian
(HA=0). In this paper, I examine what the best strategy is for long, multi-slit
exposures. I find that in extreme cases (very long exposure time) the best
choice is to orient the slit \emph{perpendicular} to the parallactic angle at
the meridian. There are two effects to consider: the increasing dispersion with
increasing airmass and the changing angle between the parallactic angle and the
slit. In the case of \emph{traditional} slit orientation, the two effects
amplify each other, thus rendering a significant fraction of the observation
useless. Using the perpendicular orientation, the two processes work against
each other, thus most of the observation remains useful. I will use, as an
example, our 8 hour Lockman Hole observations using the Keck telescope, but
generic methods are given to evaluate a particular observation. I also make the
tools available to the community.


title: Binary systems and stellar mergers in massive star formation

abstract:
  We present a model for the formation of high-mass close binary systems in the
context of forming massive stars through gas accretion in the centres of
stellar clusters. A low-mass wide binary evolves under mass accretion towards a
high-mass close binary, attaining system masses of order 30-50 solar masses at
separations of order 1 AU. The resulting high frequency of binary systems with
two massive components is in agreement with observations. These systems are
typically highly eccentric and may evolve to have periastron separations less
than their stellar radii. Mergers of these binary systems are therefore likely
and can lead to the formation of the most massive stars, circumventing the
problem of radiation pressure stopping the accretion. The stellar density
required to induce binary mergers is one million stars per cubic parsec, or
approximately one percent that required for direct stellar collisions.


title:
The VVDS-VLA Deep Field II. Optical and near infrared identifications of
  VLA S(1.4GHz)>80 microJy sources in the VIMOS VLT Deep Survey VVDS-02h field

abstract:
  In this paper we present the optical and near-infrared identifications of the
1054 radio sources detected in the 20cm deep radio survey down to a 5sigma flux
limit of about 80 microJy obtained with the VLA in the VIMOS VLT Deep Survey
VVDS-02h deep field. Using U,B,V,R,I and K data, we identified 718 radio
sources (~74% of the whole sample). The photometric redshift analysis shows
that, in each magnitude bin, the radio sample has a higher median photometric
redshift than the whole optical sample, while the median (V-I) color of the
radio sources is redder than the median color of the whole optical sample.
These results suggest that radio detection is preferentially selecting galaxies
with higher intrinsic optical luminosity. From the analysis of the optical
properties of the radio sources as function of the radio flux, we found that
while about 35% of the radio sources are optically unidentified in the higher
radio flux bin (S> 1.0 mJy), the percentage of unidentified sources decreases
to about 25% in the faintest bins (S< 0.5 mJy). The median I magnitude for the
total sample of radio sources,i.e. including also the unidentified ones, is
brighter in the faintest radio bins than in the bin with higher radio flux.
This suggests that most of the faintest radio sources are likely to be
associated to relatively lower radio luminosity objects at relatively modest
redshift, rather than radio-powerful, AGN type objects at high redshift.


title: Mid-infrared spectra of PAH emission in Herbig AeBe stars

abstract:
  We present spectra of four Herbig AeBe stars obtained with the Infrared
Spectrograph (IRS). on the Spitzer Space Telescope. All four of the sources
show strong emission from polycyclic aromatic hydrocarbons (PAHs), with the 6.2
um emission feature shifted to 6.3 um and the strongest C-C skeletal-mode
feature occuring at 7.9 um instead of at 7.7 um as is often seen. Remarkably,
none of the four stars have silicate emission. The strength of the 7.9 um
feature varies with respect to the 11.3 um feature among the sources,
indicating that we have observed PAHs with a range of ionization fractions. The
ionization fraction is higher for systems with hotter and brighter central
stars. Two sources, HD 34282 and HD 169142, show emission features from
aliphatic hydrocarbons at 6.85 and 7.25 um. The spectrum of HD 141569 shows a
previously undetected emission feature at 12.4 um which may be related to the
12.7 um PAH feature. The spectrum of HD 135344, the coolest star in our sample,
shows an unusual profile in the 7-9 um region, with the peak emission to the
red of 8.0 um and no 8.6 um PAH feature.


title: Cosmological expansion and the uniqueness of gravitational action

abstract:
  Modified theories of gravity have recently been studied by several authors as
possibly viable alternatives to the cosmological concordance model. Such
theories attempt to explain the accelerating expansion of the universe by
changing the theory of gravity, instead of introducing dark energy. In
particular, a class of models based on higher order curvature invariants,
so-called $f(R)$ gravity models, has drawn attention. In this letter we show
that within this framework, the expansion history of the universe does not
uniquely determine the form of the gravitational action and it can be radically
different from the standard Einstein-Hilbert action. We demonstrate that for
any barotropic fluid, there always exists a class of $f(R)$ models that will
have exactly the same expansion history as that arising from the
Einstein-Hilbert action. We explicitly show how one can extend the
Einstein-Hilbert action by constructing a $f(R)$ theory that is equivalent on
the classical level. Due to the classical equivalence between $f(R)$ theories
and Einstein-Hilbert gravity with an extra scalar field, one can also hence
construct equivalent scalar-tensor theories with standard expansion.


title: SXP 323 - an unusual X-ray binary system in the Small Magellanic Cloud

abstract:
  Spectroscopic observations taken with the VLT/UVES telescope/instrument are
presented of the unusual Small Magellanic Cloud (SMC) X-ray binary system SXP
323 = AX J0051-733. This system shows a clear modulation at 0.71d in long term
optical photometry which has been proposed as the binary period of this system.
The high resolution optical spectra, taken at a range of phases during the
0.71d cycle, rule out this possibility. Instead it is suggested that this
long-term effect is due to Non Radial Pulsations (NRP) in the Be star companion
to SXP 323. In addition, the spectra show clear evidence for major changes in
the (V/R) ratio of the double peaks of the Balmer lines indicative of
asymmetries in the circumstellar disk. The complex structure of the
interstellar lines are also discussed in the context of the SMC structure.


title: Modeling a coronal loop heated by MHD-turbulence nanoflares

abstract:
  We model the hydrodynamic evolution of the plasma confined in a coronal loop,
30000 km long, subject to the heating of nanoflares due to intermittent
magnetic dissipative events in the MHD turbulence produced by loop footpoint
motions. We use the time-dependent distribution of energy dissipation along the
loop obtained from a hybrid shell model, occurring for a magnetic field of
about 10 G in corona; the relevant heating per unit volume along the loop is
used in the Palermo-Harvard loop plasma hydrodynamic model. We describe the
results focussing on the effects produced by the most intense heat pulses,
which lead to loop temperatures between 1 and 1.5 MK.


title:
The projection factor of delta Cephei A calibration of the
  Baade-Wesselink method using the CHARA Array

abstract:
  Cepheids play a key role in astronomy as standard candles for measuring
intergalactic distances. Their distance is usually inferred from the
Period-Luminosity relationship, calibrated using the semi-empirical
Baade-Wesselink method. Using this method, the distance is known to a
multiplicative factor, called the projection factor. Presently, this factor is
computed using numerical models - it has hitherto never been measured directly.
Based on our new interferometric measurements obtained with the CHARA Array and
the already published parallax, we present a geometrical measurement of the
projection factor of a Cepheid, delta Cep. The value we determined, p =
1.27$\pm$0.06, confirms the generally adopted value of p = 1.36 within 1.5
sigmas. Our value is in line with recent theoretical predictions of Nardetto et
al. (2004).


title: Direct reconstruction of the quintessence potential

abstract:
  We describe an algorithm which directly determines the quintessence potential
from observational data, without using an equation of state parametrisation.
The strategy is to numerically determine observational quantities as a function
of the expansion coefficients of the quintessence potential, which are then
constrained using a likelihood approach. We further impose a model selection
criterion, the Bayesian Information Criterion, to determine the appropriate
level of the potential expansion. In addition to the potential parameters, the
present-day quintessence field velocity is kept as a free parameter. Our
investigation contains unusual model types, including a scalar field moving on
a flat potential, or in an uphill direction, and is general enough to permit
oscillating quintessence field models. We apply our method to the `gold' Type
Ia supernovae sample of Riess et al. (2004), confirming the pure cosmological
constant model as the best description of current supernovae
luminosity-redshift data. Our method is optimal for extracting quintessence
parameters from future data.


title:
X-ray absorption lines suggest matter infalling onto the central
  black-hole of Mrk 509

abstract:
  Evidence for both red- and blue-shifted absorption lines due to ionized Fe in
the X-ray spectrum of the Seyfert 1 galaxy Mrk 509 are reported. These features
appear to be transient on time-scales as short as ~20 ks, and have been
observed with two different satellites, BeppoSAX and XMM-Newton. The red- and
blue-shifted lines are found at E~5.5 keV and ~8.1-8.3 keV (rest-frame),
respectively. The first is seen in one out of six BeppoSAX observations, the
latter is seen by both satellites. Under the assumption that the absorption is
due to either H- or He-like Iron, the implied velocities for the absorbing
matter are v~0.15-0.2 c, in both outward and inward directions. An alternative
explanation in terms of gravitational red-shift for the ~5.5 keV line cannot be
ruled out with the current data. We argue, however, that the temporal patterns
and sporadic nature of the lines are more easily reconciled with models which
predict important radial motions close to the central black hole, such as the
``aborted jet'' model, the ``thundercloud'' model, or magneto-hydrodynamical
models of jets and accretion-disks.


title: Cosmic rays at ultra high energies (Neutrinos!)

abstract:
  Resonant photopion production with the cosmic microwave background predicts a
suppression of extragalactic protons above the famous Greisen-Zatsepin-Kuzmin
cutoff at about E_{GZK} ~ 5 x 10^10 GeV. Current cosmic ray data measured by
the AGASA and HiRes Collaborations do not unambiguously confirm the GZK cutoff
and leave a window for speculations about the origin and chemical composition
of the highest energy cosmic rays. In this work we analyze the possibility of
strongly interacting neutrino primaries and derive model-independent
quantitative requirements on the neutrino-nucleon inelastic cross section for a
viable explanation of the cosmic ray data. Search results on weakly interacting
cosmic particles from the AGASA and RICE experiments are taken into account
simultaneously. Using a flexible parameterization of the inelastic
neutrino-nucleon cross section we find that a combined fit of the data does not
favor the Standard Model neutrino-nucleon inelastic cross section, but
requires, at 90 % confidence level, a steep increase within one energy decade
around E_{GZK} by four orders of magnitude. We illustrate such an enhancement
within some extensions of the Standard Model. The impact of new cosmic ray data
or cosmic neutrino search results on this scenario, notably from the Pierre
Auger Observatory soon, can be immediately evaluated within our approach.


title: Limits on Enhanced Radio Wave Scattering by Supernova Remnants

abstract:
  We report multifrequency observations with the NRAO Very Long Baseline Array
(VLBA) of the compact radio sources J0128+6306 and J0547+2721, which are viewed
through the supernova remnants G127.1+0.5 and S147, respectively. Observations
were made at frequencies of 1.427, 1.667, 2.271, and 4.987 GHz. The lines of
sight to these sources pass through the shock wave and upstream and downstream
turbulent layers of their respective supernova remnants, and thus might detect
cosmic-ray generated turbulence produced during the Fermi acceleration process.
For both sources, we detect interstellar scattering, characterized by a
component of the angular size which scales as the square of the observing
wavelength. The magnitude of the scattering is characterized by an effective
scattering angular size theta_S0 at a frequency of 1 GHz of 13.2 +/- 2.6
milliarcseconds (mas) for J0128+6306 and 6.7 +/- 2.2 mas for J0547+2721. These
angular sizes are consistent with the ``incidental'' scattering for any line of
sight out of the galaxy at similar galactic latitudes and longitudes. There is
therefore no evidence for enhanced turbulence at these supernova remnants. We
establish upper limits to the supernova remnant-associated scattering measures
of 8.1-14.8 m^-20/3-pc for J0128+6306 and 3.0 m^-20/3-pc for J0547+2721.


title: Highly ionized absorbers at high redshift

abstract:
  We investigate the existence of a metal-rich OVI population in 10 high
spectral resolution quasar spectra and define observational criteria for this
class of absorbers. The low temperatures of nearly half of all OVI absorbers
(redshifts 2.0 to 2.6), implied by their line widths, are too low for
collisional ionization to be a dominant process. We estimate the oxygen
abundance under the assumption of photoionization; a striking result is the
bimodal distribution of [O/H] with median values close to 0.01 (0.5) solar for
the metal-poor (metal-rich) populations. We present the first estimate of the
OVI column density distribution and fit a single power-law index of ~-1.7 and a
normalization of f(N)= 2.3e(-13) at log N(OVI) ~ 13.5, both with a ~30%
uncertainty. The value of the index is similar to that found for CIV surveys,
whereas the normalization factor is about ten times higher. We use f(N) to
derive dn/dz and the cosmic density, Omega_b(OVI), selecting a limited column
density range not strongly affected by incompleteness or sample variance. We
find some decline of dn/dz with z. The cosmic OVI density derived from f(N),
Omega_b(OVI) ~ 3.5e(-7), is 2.3 times higher than the value estimated using the
observed OVI sample (of which the metal-rich population contributes ~35%),
easing the problem of missing metals at high z (~1/4 of the produced metals)
but not solving it. We find that the majority of the metal-rich absorbers are
located within ~450 km/s of strong Ly-a lines and show that, contrary to the
metal-poor absorbers, this population cannot be in hydrostatic equilibrium. All
of the OVI absorber properties imply that there are two distinct populations:
metal-poor absorbers tracing the intergalactic medium and metal-rich absorbers
associated with active sites of star formation.


title: The Metallicity - Kinematics Relation in Large-N(HI) Absorbers

abstract:
  Sloan Digital Sky Survey (SDSS) quasar spectroscopy is yielding a database of
strong low-ionization MgII absorbers over the redshift interval 0.36<z<2.28
which is over two orders of magnitude larger than anything previously
assembled. HST UV spectroscopy has been used to measure neutral hydrogen column
densities for a small subset of them. These data empirically show that MgII
absorbers with rest equivalent widths $W^{\lambda2796}_0 \ge 0.6$ \AA have a
mean neutral hydrogen column density that is roughly constant at $N(HI) \approx
4 \times 10^{20}$ atoms cm$^{-2}$, with individual systems lying in the damped
Ly-alpha (DLA) and sub-DLA regimes. Since the MgII doublets generally exhibit
saturation, the $W^{\lambda2796}_0$ values are an indication of the absorbers'
velocity spreads. Thus, we can study neutral-gas-phase metallicities as a
function of kinematics by forming SDSS composite spectra and measuring weak
unsaturated metal lines that form in neutral gas (e.g., CrII, FeII, MnII, SiII,
ZnII) as a function of $W^{\lambda2796}_0$. We use this method on SDSS
composite spectra to show how metallicity and kinematics are positively
correlated for large N(HI) absorbers, including trends related to dust
depletion and the enhancement of alpha-elements. We also discuss the need to
account for selection effects in DLA surveys, and we make inferences about
models for DLA absorption and their contribution to cosmic star formation.


title:
Quasi-periodic Oscillations in the X-ray Light Curves from Relativistic
  Tori

abstract:
  We use a relativistic ray-tracing code to analyze the X-ray emission from a
pressure-supported oscillating relativistic torus around a black hole. We show
that a strong correlation exists between the {\it intrinsic} frequencies of the
torus normal modes and the {\it extrinsic} frequencies seen in the observed
light curve power spectrum. This correlation demonstrates the feasibility of
the oscillating-torus model to explain the multiple peaks seen in black hole
high-frequency quasi-periodic oscillations. Using an optically thin,
monochromatic emission model, we also determine how a relativistically
broadened emission line and the amplitude of the X-ray modulations are
dependent on the observer's inclination angle and on the torus oscillation
amplitudes. Observations of these features can provide important information
about the torus as well as the black hole.


title: Dynamical models of Kuiper Belt dust in the inner and outer Solar System

abstract:
  We report several results related to the dynamical evolution of dust produced
in the Kuiper Belt (KB). We show that its particle size frequency distribution
in space is greatly changed from the distribution at production, as a results
of the combined effects of radiation forces and the perturbations of the
planets. We estimate the contribution of KB dust to the zodiacal cloud by
calculating the radial profile of its number density near the ecliptic. We also
study the contribution of KB dust to the population of interplanetary dust
particles (IDPs) collected at Earth, by calculating geocentric encounter
velocities and capture rates. Our models show, in contrast with previous
studies, that KB dust grains on Earth-crossing orbits have high eccentricities
and inclinations and, therefore, their encounter velocities are similar to
those of cometary grains and not to asteroidal grains. We estimate that at most
25% in number of captured IDPs have cometary or KB origin; the KB contribution
may be as low as 1%-2%. We present the velocity field of KB dust throughout the
solar system; this, together with the number density radial profile, is
potentially useful for planning spacecraft missions to the outer solar system.


title: Large non-Gaussianity in multiple-field inflation

abstract:
  We investigate non-Gaussianity in general multiple-field inflation using the
formalism we developed in earlier papers. We use a perturbative expansion of
the non-linear equations to calculate the three-point correlator of the
curvature perturbation analytically. We derive a general expression that
involves only a time integral over background and linear perturbation
quantities. We work out this expression explicitly for the two-field slow-roll
case, and find that non-Gaussianity can be orders of magnitude larger than in
the single-field case. In particular, the bispectrum divided by the square of
the power spectrum can easily be of O(1-10), depending on the model. Our result
also shows the explicit momentum dependence of the bispectrum. This conclusion
of large non-Gaussianity is confirmed in a semi-analytic slow-roll
investigation of a simple quadratic two-field model.


title: A Medium Resolution Near-Infrared Spectral Atlas of O and Early B Stars

abstract:
  We present intermediate resolution (R ~ 8,000 - 12,000) high signal-to-noise
H- and K-band spectroscopy of a sample of 37 optically visible stars, ranging
in spectral type from O3 to B3 and representing most luminosity classes.
Spectra of this quality can be used to constrain the temperature, luminosity
and general wind properties of OB stars, when used in conjunction with
sophisticated atmospheric model codes. Most important is the need for
moderately high resolutions (R > 5000) and very high signal-to-noise (S/N >
150) spectra for a meaningful profile analysis. When using near-infrared
spectra for a classification system, moderately high signal-to-noise (S/N ~
100) is still required, though the resolution can be relaxed to just a thousand
or two. In the appendix we provide a set of very high quality near-infrared
spectra of Brackett lines in six early-A dwarfs. These can be used to aid in
the modeling and removal of such lines when early-A dwarfs are used for
telluric spectroscopic standards.


title:
Infrared Properties of Star Forming Dwarf Galaxies: I. Dwarf Irregular
  Galaxies in the Local Volume

abstract:
  A sample of 34 dwarf irregular galaxies in the Local Volume, most nearer than
5 Mpc, has been imaged in the near-infrared (NIR) in J and K_s at CFHT in
Hawaii and OAN-SPM in Mexico. In CFHT images, stars brighter than M_Ks=-7.5
were resolved. In most cases, the resolved population represents less than 5%
of the total NIR flux in K_s. Although exponential at large radii, surface
brightness profiles for the unresolved component flatten in the centres. They
can be fitted across the whole range of radii with a hyperbolic secant (sech)
defined as a function of two parameters: the central surface brightness and the
scale length of the exponential. Isophotal, total, and fitted sech magnitudes
have been calculated for all galaxies for which the unresolved component was
detected, along with semimajor axes. The scale length and the semimajor axes
correlate linearly with absolute isophotal magnitude. The same is true for
colors and the central brightness. More luminous dIs tend to be larger, redder
and brighter in the centre. The Tully-Fisher relation shows considerable
scatter, but residuals are tied to surface brightness. The galaxies appear to
lie in a ``fundamental plane'' defined by the sech absolute magnitude, the sech
central surface brightness, and the HI line-width. The rms of residuals in M_K
is only 0.4 mag, which implies that the plane can be used to evaluate the
distances of star-forming dwarfs. Color-magnitude diagrams are presented for 29
galaxies in which stars were resolved. Most show a finger centered around
J-K_s=1 mag. In some cases, there is a red tail extending to J-K_s=2.5 mag.
(Abstract slightly shortened).


title: Smoothing spline primordial power spectrum reconstruction

abstract:
  We reconstruct the shape of the primordial power spectrum (PPS) using a
smoothing spline. Our adapted smoothing spline technique provides a
complementary method to existing efforts to search for smooth features in the
PPS, such as a running spectral index. With this technique we find no
significant indication with WMAP first-year data that the PPS deviates from
Harrison-Zeldovich and no evidence for loss of power on large scales. We also
examine the effect on the cosmological parameters of the additional PPS
freedom. Smooth variations in the PPS are not significantly degenerate with
other cosmological parameters, but the spline reconstruction greatly increases
the errors on the optical depth and baryon fraction.


title:
New Estimates of the Solar-Neighborhood Massive-Stars Birthrate and the
  Galactic Supernova Rate

abstract:
  The birthrate of stars of masses > 10 solar masses is estimated from a sample
of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sun and the result
extrapolated to estimate the galactic supernova rate contributed by such stars.
The solar-neighborhood galactic-plane massive star birthrate is estimated at
176 stars per cubic kpc per million years. Based on a model where the galactic
stellar density distribution comprises a disk plus central hole like that of
the dust infrared emission (Drimmel & Spergel 2001 ApJ 556, 181) the galactic
supernova rate is estimated as probably not less than 1 nor more than 2 per
century and the number of O3-B2 dwarfs within the solar circle as ~ 200,000.


title:
Erupting Cataclysmic Variable Stars in the Nearest Globular Cluster, NGC
  6397: Intermediate Polars?

abstract:
  NGC 6397 is the closest globular cluster, and hence the ideal place to search
for faint stellar populations such as cataclysmic variables (CVs). HST and
Chandra observers have identified nine certain and likely CVs in this nearby
cluster, including several magnetic CV candidates. We have combined our recent
UV imagery with archival HST images of NGC 6397 to search for new CV candidates
and especially to look for dwarf nova-like eruptive events. We find remarkable
and somewhat unexpected dwarf nova-like eruptions of the two well-known
cataclysmic systems CV2 and CV3. These two objects have been claimed to be {\it
magnetic} CVs, as indicated by their helium emission-line spectra. Magnetic
fields in CVs are usually expected to prevent the disk instability that leads
to dwarf nova eruptions. In fact, most field magnetic CVs are observed to not
undergo eruptions. Our observations of the dwarf nova eruptions of CV2 and CV3
can be reconciled with these objects' HeII emission lines if both objects are
infrequently-erupting intermediate polars, similar to EX Hya. If this is the
case for most globular cluster CVs then we can reconcile the many X-ray and UV
bright CV candidates seen by Chandra and HST with the very small numbers of
erupting dwarf novae observed in cluster cores.


title: Is the Cepheus E Outflow driven by a Class 0 Protostar?

abstract:
  New early release observations of the Cepheus E outflow and its embedded
source, obtained with the Spitzer Space Telescope, are presented. We show the
driving source is detected in all 4 IRAC bands, which suggests that traditional
Class 0 classification, although essentially correct, needs to accommodate the
new high sensitivity infrared arrays and their ability to detected deeply
embedded sources. The IRAC, MIPS 24 and 70 microns new photometric points are
consistent with a spectral energy distribution dominated by a cold, dense
envelope surrounding the protostar. The Cep E outflow, unlike its more famous
cousin the HH 46/47 outflow, displays a very similar morphology in the near and
mid-infrared wavelengths, and is detected at 24 microns. The interface between
the dense molecular gas (where Cep E lies) and less dense interstellar medium,
is well traced by the emission at 8 and 24 microns, and is one of the most
exotic features of the new IRAC and MIPS images. IRS observations of the North
lobe of the flow confirm that most of the emission is due to the excitation of
pure H2 rotational transitions arising from a relatively cold (Tex~700 K) and
dense (N{H}~9.6E20 cm-2 molecular gas.


title:
Morphologies in a Cluster of Extremely Red Galaxies with Old Stellar
  Populations at z=1.34

abstract:
  We have identified a clustering of red galaxies from deep optical/IR images
obtained as part of the Institute for Astronomy Deep Survey. Photometric
spectral-energy distributions indicate that most of these galaxies comprise
nearly pure old stellar populations at a redshift near 1.4, and Keck
spectroscopy of the three brightest red galaxies confirm this interpretation
and give redshifts ranging from 1.335 to 1.338. Four of the galaxies are close
together on the sky and less than 30" from an R=13.5 star, and we have obtained
deep adaptive-optics imaging of this group. Detailed analysis and modeling of
the surface-brightness profiles of these galaxies shows that two are normal
ellipticals, one is an S0, and one appears to be an essentially pure disk of
old stars, with no significant bulge. All four are highly relaxed, symmetric
systems. While the old, bulgeless disk galaxy represents a type that is rare at
the present epoch, the other three galaxies have structural parameters that are
essentially indistinguishable from those of present-day galaxies and differ
only in the age of their stellar populations.


title: The First Miniquasar

abstract:
  We investigate the environmental impact of the first active galactic nuclei
that may have formed ~150 Myr after the big bang in low-mass ~10^6 Msun
minihaloes. Using Enzo, an adaptive-mesh refinement cosmological hydrodynamics
code, we carry out three-dimensional simulations of the radiative feedback from
`miniquasars' powered by intermediate-mass black holes. We follow the
non-equilibrium multispecies chemistry of primordial gas in the presence of a
point source of X-ray radiation, which starts shining in a rare high-sigma peak
at z=21 and emits a power-law spectrum in the 0.2-10 keV range. We find that,
after one Salpeter time-scale, the miniquasar has heated up the simulation box
to a volume-averaged temperature of 2800 K. The mean electron and H2 fractions
are now 0.03 and 4e-5: the latter is 20 times larger than the primordial value,
and will delay the buildup of a uniform UV photodissociating background. The
net effect of the X-rays is to reduce gas clumping in the IGM by as much as a
factor of 3. While the suppression of baryonic infall lowers the gas mass
fraction at overdensities delta in the range 20-2000, enhanced molecular
cooling increases the amount of dense material at delta>2000. In many haloes
within the proximity of our miniquasar the H2-boosting effect of X-rays is too
weak to overcome heating, and the cold and dense gas mass actually decreases.
We find little evidence for an entropy floor in gas at intermediate densities
preventing gas contraction and H2 formation. Overall, the radiative feedback
from X-rays enhances gas cooling in lower-sigma peaks that are far away from
the initial site of star formation, thus decreasing the clustering bias of the
early pregalactic population, but does not appear to dramatically reverse or
promote the collapse of pregalactic clouds as a whole. (abridged)


title:
The Build-up of the Colour-Magnitude Relation as a Function of
  Environment

abstract:
  We discuss the environmental dependence of galaxy evolution based on deep
panoramic imaging of two distant clusters taken with Suprime-Cam as part of the
PISCES project. By combining with the SDSS data as a local counterpart for
comparison, we construct a large sample of galaxies that spans wide ranges in
environment, time, and stellar mass (or luminosity). We find that colours of
galaxies, especially those of faint galaxies ($M_V>M_V^*+1$), change from blue
to red at a break density as we go to denser regions. Based on local and global
densities of galaxies, we classify three environments: field, groups, and
clusters. We show that the cluster colour-magnitude relation is already built
at $z=0.83$. In contrast to this, the bright-end of the field colour-magnitude
relation has been vigorously built all the way down to the present-day and the
build-up at the faint-end has not started yet. A possible interpretation of
these results is that galaxies evolve in the 'down-sizing' fashion. That is,
massive galaxies complete their star formation first and the truncation of star
formation is propagated to smaller objects as time progresses. This trend is
likely to depend on environment since the build-up of the colour-magnitude
relation is delayed in lower-density environments. Therefore, we may suggest
that the evolution of galaxies took place earliest in massive galaxies and in
high density regions, and it is delayed in less massive galaxies and in lower
density regions.


title:
Lightning Stars: Anomalous Photoproduction in Neutron Stars via
  Parametric Resonance Mechanism

abstract:
  In this work we propose a new mechanism for photoproduction inside a neutron
star based on Parametric Resonance phenomenon as firstly applied to
Inflationary Cosmology. Our assumptions are based on the pion condensation
model by Harrington and Shepard. We show that a huge number of photons are
created which, on turns, reheats the matter in the star's core. Thus, we argue
that Parametric Resonance can be effective during a brief period out of an
neutron star lifetime leading to an anomalous uprising variation of its
brightness departing from the black body radiation at regularly spaced
frequencies. In adition, a time periodic signal is obtained in moderate (not
exponential) regimes. We argue also that our PR mechanism offers a simple and
feasible explanation for some recent observations of giant flares from neutron
stars.


title: Gradient expansion(s) and dark energy

abstract:
  Motivated by recent claims stating that the acceleration of the present
Universe is due to fluctuations with wavelength larger than the Hubble radius,
we present a general analysis of various perturbative solutions of fully
inhomogeneous Einstein equations supplemented by a perfect fluid. The
equivalence of formally different gradient expansions is demonstrated. If the
barotropic index vanishes, the deceleration parameter is always positive
semi-definite.


title: Silicate emissions in active galaxies - From LINERs to QSOs

abstract:
  We report the first detection of ~10 and ~18 micron silicate dust emissions
in a low-luminosity active galactic nucleus (AGN), obtained in Spitzer-IRS 7-37
micron spectroscopy of the Type 1 LINER galaxy NGC3998. Silicate emissions in
AGN have only recently been detected in several quasars. Our detection counters
suggestions that silicate emissions are present only in the most luminous AGN.
The silicate features may be signatures of a dusty ``obscuring torus'' viewed
face-on as postulated for Type 1 AGN. However, the apparently cool (~200 K)
dust is inconsistent with theoretical expectations of much hotter torus walls.
Furthermore, not all Type 1 objects are silicate emission sources.
Alternatively, the silicate emission may originate in dust not directly
associated with a torus. We find that the long-wavelength (>20 micron) tail of
the emission in NGC3998 is significantly weaker than in the sample of bright
QSOs recently presented by Hao et al. The 10 micron profile in our NGC3998
spectrum is inconsistent with ``standard'' silicate ISM dust. This may indicate
differences in the dust composition, grain size distribution, or degree of
crystallization. The differences between NGC3998, QSOs, and Galactic templates
suggest that there are significant environmental variations.


title: Wiggly cosmic strings accrete dark energy

abstract:
  This paper deals with a study of the cylindrically symmetric accretion of
dark energy with equation of state $p=w\rho$ onto wiggly straight cosmic
strings. We have obtained that when $w>-1$ the linear energy density in the
string core gradually increases tending to a finite maximum value as time
increases for all considered dark energy models. On the regime where the
dominant energy condition is violated all such models predict a steady
decreasing of the linear energy density of the cosmic strings as phantom energy
is being accreted. The final state of the string after such an accretion
process is a wiggleless defect. It is argued however that if accreation of
phantom energy would proceed by successive quantum steps then the defect would
continue losing linear energy density until a minimum nonzero value which can
be quite smaller than that corresponding to the unperturbed string.


title:
XMM-Newton observations of the Lockman Hole IV: spectra of the brightest
  AGN

abstract:
  This paper presents the results of a detailed X-ray spectral analysis of a
sample of 123 X-ray sources (46 being type-1 AGN and 28 type-2 AGN) detected
with XMM-Newton in the Lockman Hole field. Using a single power law model our
sources' average spectral slope hardens at faint 0.5-2 keV fluxes but not at
faint 2-10 keV fluxes. We explain the effect in terms of an increase in X-ray
absorption at faint fluxes. The average spectral slope of our sources is ~1.9
with an intrinsic dispersion of ~0.28. We detected X-ray absorption in 37% of
the sources, ~10% in type-1 AGN and ~77% in type-2 AGN. Using X-ray fluxes
corrected for absorption, the fraction of absorbed objects and the absorbing
column density distribution did not vary with X-ray flux. Our type-1 and type-2
AGN do not appear to have different continuum shapes, but the distribution of
intrinsic absorption is different among both classes. A significant fraction of
our type-2 AGN (5 out of 28) were found to display no substantial absorption.
We discuss possible interpretations to this in terms of Compton-thick AGN and
intrinsic Broad Line Region properties. An emission line compatible with Fe
Kalpha was detected in 8 sources with rest frame equivalent widths 120-1000 eV.
The AGN continuum or intrinsic absorption did not depend on X-ray luminosity
and/or redshift. Soft excess emission was detected in 18 objects, but only in 9
could we fit this spectral component with a black body model. The 0.5-2 keV
luminosities of the fitted black body were not significantly different in
type-1 and type-2 AGN, although the temperatures were slightly higher in type-2
AGN than in type-1 AGN. For 9 sources (including 1 type-1 AGN and 3 type-2 AGN)
a scattering model provided a better fit of the soft excess emission.


title: Particle acceleration timescales in relativistic shear flows

abstract:
  We review the acceleration of energetic particles in relativistic
astrophysical jets characterized by a significant velocity shear. The possible
formation of power-law momentum spectra is discussed and typical acceleration
timescales are determined for a variety of different conditions such as
parallel and azimuthal shear flows. Special attendance is given to the analysis
of parallel shear flows with either a linear decreasing or a Gaussian-type
velocity profile. It is shown that in the presence of a gradual shear flow and
a particle mean free path scaling with the gyroradius, synchrotron radiation
losses may no longer be able to stop the acceleration once it has started to
work efficiently. Finally, the relevance of shear acceleration in small- and
large-scale relativistic jets is addressed.


title: Periodic variability and binary black hole systems in blazars

abstract:
  We consider the periodic modulation of emission from jets in blazar-type
sources. A differential Doppler boosting origin, associated with the helical
motion of a radiating component, is analyzed for different periodic driving
sources including orbital motion and jet precession in a binary black hole
system (BBHS). We emphasize that for non-ballistic helical motion classical
travel time effects can lead to strong shortening effects, such that the
observed period may be a factor $\gamma_b^2$ smaller than the underlying
driving period, where $\gamma_b$ denotes the bulk Lorentz factor of the jet
flow. The relevance of the above noted scenarios is discussed for the BL Lac
object AO 0235+16.


title:
Expectations for the Deep Impact collision from cometary nuclei
  modelling

abstract:
  Using the cometary nucleus model developed by Espinasse et al. (1991), we
calculate the thermodynamical evolution of Comet 9P/Tempel 1 over a period of
360 years. Starting from an initially amorphous cometary nucleus which
incorporates an icy mixture of H2O and CO, we show that, at the time of Deep
Impact collision, the crater is expected to form at depths where ice is in its
crystalline form. Hence, the subsurface exposed to space should not be
primordial. We also attempt an order-of-magnitude estimate of the heating and
material ablation effects on the crater activity caused by the 370 Kg
projectile released by the DI spacecraft. We thus show that heating effects
play no role in the evolution of crater activity. We calculate that the CO
production rate from the impacted region should be about 300-400 times higher
from the crater resulting from the impact with a 35 m ablation than over the
unperturbed nucleus in the immediate post-impact period. We also show that the
H2O production rate is decreased by several orders of magnitude at the crater
base just after ablation.


title:
The MultiSite Spectroscopic Telescope campaign: 2m spectroscopy of the
  V361 Hya variable PG1605+072

abstract:
  We present results and analysis for the 2m spectroscopic part of the
MultiSite Spectroscopic Telescope (MSST) campaign undertaken in May/June 2002.
The goal of the project was to observe the pulsating subdwarf B star PG1605+072
simultaneously in velocity and photometry and to resolve as many of the >50
known modes as possible, which will allow a detailed asteroseismological
analysis. We have obtained over 150 hours of spectroscopy, leading to an
unprecedented noise level of only 207m/s. We report here the detection of 20
frequencies in velocity, with two more likely just below our detection
threshold. In particular, we detect 6 linear combinations, making PG1605+072
only the second star known to show such frequencies in velocity. We investigate
the phases of these combinations and their parent modes and find relationships
between them that cannot be easily understood based on current theory. These
observations, when combined with our simultaneous photometry, should allow
asteroseismology of this most complicated of sdB pulsators.


title: Modified Newtonian Dynamics in the Milky Way

abstract:
  Both microlensing surveys and radio-frequency observations of gas flow imply
that the inner Milky Way is completely dominated by baryons, contrary to the
predictions of standard cold dark matter (CDM) cosmology. We investigate the
predictions of the Modified Newtonian Dynamics (MOND) formula for the Galaxy
given the measured baryon distribution. Satisfactory fits to the
observationally determined terminal-velocity curve are obtained for different
choices of the MOND's interpolating function mu(x). However, with simple
analytical forms of mu(x), the local circular speed v_c(R_0) can be as large as
220 km/s only for values of the parameter a_0 that are excluded by observations
of NGC 3198. Only a numerically specified interpolating function can produce
v_c(R_0)=220 km/s, which is therefore an upper limit in MOND, while the
asymptotic velocity is predicted to be v_c(infty)=170+-5 km/s. The data are
probably not consistent with the functional form of mu(x) that has been
explored as a toy model in the framework of Bekenstein's covariant theory of
gravity.


title:
X-ray absorption and re-emission from an ionised outflow in the Type 1
  QSO 2MASS 234449+1221

abstract:
  We report on the analysis of a short XMM-Newton observation of the reddened
Type 1 QSO 2MASS 234449+1221 first identified in the Two Micron All-Sky Survey.
The underlying X-ray continuum is found to be typical of a broad-line active
galaxy, with photon index Gamma ~ 1.9. Low energy absorption can be modelled by
a column N_H ~ 10^22 cm^{-2} of moderately ionised gas or a smaller column of
cold gas. Addition of a soft X-ray emission component significantly improves
the fit in both cases. With the assumption that the soft X-ray flux represents
emission from gas photoionised by the incident X-ray continuum, a comparison of
the absorbed and emitted luminosities indicates a covering factor of ~ 8-17%.
The unusual opportunity to simultaneously observe and quantify ionised
absorption and emission in 2MASS 234449+1221 is due to the relatively large
opacity (for a Type 1 AGN) of the absorbing gas, which depresses the normally
strong continuum below ~ 1 keV. A comparison of the soft X-ray emission of
2MASS 234449+1221 with that of other Type 1 and Type 2 AGN suggests the
existence of an inner turbulent extension to ionised outflows, not detected in
current high resolution X-ray spectra.


title:
Hubble Space Telescope ultraviolet spectroscopy of blazars: emission
  lines properties and black hole masses

abstract:
  The ultraviolet (UV) spectra of 16 blazars (<z> ~1) from the archives of the
Hubble Space Telescope Faint Object Spectrograph have been analyzed in order to
study in a systematic way the properties oftheir broad UV emission lines. We
find that the luminosities of the most prominent and intense lines, Ly_alpha
and C IV lambda1549, are similar to those of normal radio-loud quasars at
comparable redshifts. However, the equivalent widths of blazar lines are
significantly smaller than those of radio-loud quasars. Therefore, while the
intrinsic broad line region luminosity of blazars appears to be
indistinguishable from that of radio-loud quasars, their continuum must be
comparatively higher, most probably due to relativistic beaming. We have
combined the UV luminosities of the de-beamed continuum with the emitting gas
velocity to derive estimates of the masses of the central supermassive black
holes. The size of the broad line region was computed in two ways: 1) via an
empirical relationship between UV continuum luminosity and broad line region
size, and 2) through the external photon density required by blazar models to
reproduce the inverse Compton components observed at gamma-rays. The second
method yields significantly different results from the first method, suggesting
that it provides only a very rough estimate or a lower limit on the size of the
broad line region. We find that the average mass of the central black holes in
blazars is ~2.8e8 Msun, with a large dispersion, comparable to those computed
for other radio-loud active galactic nuclei.


title:
The INT Photometric H-alpha Survey of the Northern Galactic Plane
  (IPHAS)

abstract:
  The INT Photometric Halpha Survey of the Northern Galactic Plane (IPHAS) is a
1800 square degrees CCD survey of the northern Milky Way spanning the latitude
range -5 < b < +5 (degrees) and reaching down to r' ~ 20 (10-sigma). It may
increase the number of known northern emission line sources by an order of
magnitude. Representative observations and an assessment of point-source data
from IPHAS, now underway, are presented. The data obtained are Wide Field
Camera images in Halpha narrow-band, and Sloan r' and i' broad-band, filters.
We simulate IPHAS (r' - Halpha, r' - i') point-source colours using a
spectrophotometric library of stellar spectra and available filter transmission
profiles: this gives expected colours for (i) solar-metallicity stars, without
Halpha emission, and (ii) emission line stars. Comparisons with Aquila field
observations show that simulated normal star colours reproduce the data well
for spectral types earlier than M. Spectroscopic follow-up of a Cepheus field
confirms that sources lying above the main stellar locus in the (r' - Halpha,
r' - i') plane are emission line objects, with very few failures. Examples of
Halpha deficit objects -- a white dwarf and a carbon star -- are shown to be
readily distinguished by their IPHAS colours. The role IPHAS can play in
studies of nebulae is discussed briefly, and illustrated by a
continuum-subtracted mosaic image of the SNR, Shajn 147. The final catalogue of
IPHAS point sources will contain photometry on ~80 million objects. (abridged)


title:
Deep Photometry of the Globular Cluster M5: Distance Estimates from
  White Dwarf and Main Sequence Stars

abstract:
  We present deep VI photometry of stars in the globular cluster M5 (NGC 5904)
based on images taken with the Hubble Space Telescope. The resulting
color-magnitude diagram reaches below V ~ 27 mag, revealing the upper 2-3
magnitudes of the white dwarf cooling sequence, and main sequence stars eight
magnitudes and more below the turn-off. We fit the main sequence to subdwarfs
of known parallax to obtain a true distance modulus of (m-M)_0 = 14.45 +/- 0.11
mag. A second distance estimate based on fitting the cluster white dwarf
sequence to field white dwarfs with known parallax yielded (m-M)_0 = 14.67 +/-
0.18 mag. We couple our distance estimates with extensive photometry of the
cluster's RR Lyrae variables to provide a calibration of the RR Lyrae absolute
magnitude yielding M_V(RR) = 0.42 +/- 0.10 mag at [Fe/H] = -1.11 dex. We
provide another luminosity calibration in the form of reddening-free Wasenheit
functions. Comparison of our calibrations with predictions based on recent
models combining stellar evolution and pulsation theories shows encouraging
agreement. (Abridged)


title:
Photometric Periodicities of Be/X-ray Pulsars in the Small Magellanic
  Cloud

abstract:
  Analysis of the longterm photometric variability of 7 Be/X-ray-pulsar systems
in the Small Magellanic Cloud has been carried out. We find a variety of types
of variability are present, including: longterm irregular changes, periodic
orbital outbursts due to interaction between the stars (weeks to months),
low-amplitude quasi-periodic variations of the equatorial disk (days), and
nonradial pulsations of the Be primary star (hours). This is the first time
nonradial pulsations have been identified in Be/X-ray binaries, although they
were previously known in some single Be stars.