title:
An iterative destriping technique for diffuse background polarization
  data

abstract:
  We describe a simple but effective iterative procedure specifically designed
to destripe Q and U Stokes parameter data as those collected by the SPOrt
experiment onboard the International Space Station (ISS). The method is general
enough to be useful for other experiments, both in polarization and total
intensity. The only requirement for the algorithm to work properly is that the
receiver knee frequency must be lower than the signal modulation frequency,
corresponding in our case to the ISS orbit period. Detailed performances of the
technique are presented in the context of the SPOrt experiment, both in terms
of added rms noise and residual correlated noise.


title:
Statistical characterisation of full-disk EUV/XUV solar irradiance and
  correlation with solar activity

abstract:
  We investigate the distribution of fluctuations in solar irradiance when
integrated over the full disk, obtained using extreme ultraviolet/soft X-ray
observations from the SOHO CELIAS/SEM instrument. This time series sums over
both the contributions of single distinguishable flares, and of many other
processes. By detrending we select events with timescales of less than a few
hours such as waves, slow flows, and CMEs. The statistics generated by this
range of phenomena can be characterised by power-law-tailed distributions. We
show that (i) during the high-activity period 2000 Jan-June the tail exponent
a(T)=1.5 +/- 0.1; (ii) during the low-activity period 1996 Jan-June a(T)=3.0
+/- 0.2; and (iii) in general a(T) decreases with increasing activity.


title: The Chemical Composition of Carbon C(N) stars

abstract:
  A chemical study of normal Galactic C(N) carbon stars is presented.
Abundances of Li, CNO isotopes and s-elements are derived. The derived
abundances of s-elements nicely agree with theoretical s-process
nucleosynthesis predictions during the AGB phase. However, the figures obtained
for Li and the 12C/13C ratios might imply the existence of a non-standard
mixing process during the AGB phase operating preferentially in low mass stars.
The intrinsic or extrinsic nature of C(N) stars is also discussed.


title: A new view of k-essence

abstract:
  K-essence models, relying on scalar fields with non-canonical kinetic terms,
have been proposed as an alternative to quintessence in explaining the observed
acceleration of the Universe. We consider the use of field redefinitions to
cast k-essence in a more familiar form. While k-essence models cannot in
general be rewritten in the form of quintessence models, we show that in
certain dynamical regimes an equivalence can be made, which in particular can
shed light on the tracking behaviour of k-essence. In several cases, k-essence
cannot be observationally distinguished from quintessence using the homogeneous
evolution, though there may be small effects on the perturbation spectrum. We
make a detailed analysis of two k-essence models from the literature and
comment on the nature of the fine tuning arising in the models.


title: The 2dF QSO Redshift Survey - XI. The QSO Power Spectrum

abstract:
  We present a power spectrum analysis of the final 2dF QSO Redshift Survey
catalogue containing 22652 QSOs. Utilising the huge volume probed by the QSOs,
we can accurately measure power out to scales of ~500Mpc and derive new
constraints, at z~1.4, on the matter and baryonic contents of the Universe.
Importantly, these new cosmological constraints are derived at an intermediate
epoch between the CMB observations at z~1000, and local (z~0) studies of
large-scale structure; the average QSO redshift corresponds to a look-back time
of approximately two-thirds of the age of the Universe. We find that the
amplitude of clustering of the QSOs at z~1.4 is similar to that of present day
galaxies. The power spectra of the QSOs at high and low redshift are compared
and we find little evidence for any evolution in the amplitude. Assuming a
lambda cosmology to derive the comoving distances, r(z), to the QSOs, the power
spectrum derived can be well described by a model with shape parameter
Gamma=0.13+-0.02. If an Einstein-de Sitter model r(z) is instead assumed, a
slightly higher value of Gamma=0.16+-0.03 is obtained. A comparison with the
Hubble Volume LCDM simulation shows very good agreement over the whole range of
scales considered. A standard (Omega_m=1) CDM model, however, predicts a much
higher value of Gamma than is observed, and it is difficult to reconcile such a
model with these data. We fit CDM model power spectra (assuming scale-invariant
initial fluctuations), convolved with the survey window function, and corrected
for redshift space distortions, and find that models with baryon oscillations
are slightly preferred, with the baryon fraction Omega_b/Omega_m=0.18+-0.10.
The overall shape of the power spectrum provides a strong constraint on
Omega_m*h (where h is the Hubble parameter), with Omega_m*h=0.19+-0.05.


title: Radio galaxies: unification and dust properties

abstract:
  The 2002 status of unification models for extragalactic radio sources is
examined, with particular emphasis on the dust properties of these objects.


title: Gamma Ray Bursts in Pulsar Wind Bubbles: Observational implications

abstract:
  We present the main observational features expected for Gamma-Ray Bursts
(GRBs) that occur inside pulsar wind bubbles (PWBs). This is the most natural
outcome of the supranova model, where initially a supernova (SN) explosion
takes place, leaving behind a supra-massive neutron star, which loses its
rotational energy over a time t_sd and collapses to a black hole, triggering a
GRB. We find that the time delay, t_sd, between the SN and GRB events is the
most important parameter that determines the behavior of the system. We
consider the afterglow, prompt GRB and PWB emission. Constraints on the model
are derived for a spherical PWB, from current afterglow observations and the
lack of direct detection of the PWB emission. We find that a simple spherical
model cannot account for the X-ray features detected in some afterglows,
together with the typical afterglow emission that was observed for the same
GRBs. The discrepancies with observations may be reconciled by resorting to a
non-spherical geometry, where the PWB is elongated along the polar axis.
Finally, we predict that the inverse Compton upscattering of PWB photons by the
relativistic electrons of the afterglow (external Compton) should lead to high
energy emission during the early afterglow that may explain the GeV photons
detected by EGRET for a few GRBs, and should be detectable by future missions
such as GLAST.


title: Fitting Dynamical Models to Observations of Globular Clusters

abstract:
  The basic ingredients of models for the internal dynamics of globular
clusters are reviewed, with an emphasis on the description of equilibrium
configurations. The development of progressive complexity in the models is
traced, concentrating on the inclusion of velocity anisotropy, rotation, and
integrals of motion other than energy. Applications to observations of
extragalactic globulars and to combined radial-velocity and proper-motion
datasets are discussed.


title: The Globular Cluster Luminosity Function

abstract:
  The main aspects of the globular cluster luminosity function needing to be
explained by a general theory of cluster formation are reviewed, and the
importance of simultaneously understanding globular cluster systematics (the
fundamental plane) within such a theory is pointed out.


title: Is Primordial He Truly from Big Bang ?

abstract:
  Population III stars are now believed to contribute to the observed Near
Infrared Background (NIRB) and heavy element pollution of the intergalactic
medium. Here we show that a Pop III contribution to the primordial He abundance
consistent with NIRB constraints, might mask a lower value for the Big Bang
Nucleosynthesis (BBN) He abundance.


title:
Star Cluster Formation and Evolution in Nearby Starburst Galaxies: I.
  Systematic Uncertainties

abstract:
  (ABBREVIATED:) The large majority of extragalactic star cluster studies done
to date have essentially used two or three-passband aperture photometry,
combined with theoretical stellar population synthesis models, to obtain age,
mass and extinction estimates, and sometimes also metallicities. The accuracy
to which this can be done depends on the choice of passband combination and,
crucially, also on the wavelength range covered. Understanding the systematic
uncertainties is of the utmost importance for a well-balanced interpretation of
the properties of extragalactic star cluster systems. We simultaneously obtain
ages, metallicities and extinction values for ~300 clusters in the nearby
starburst galaxy NGC 3310, based on archival Hubble Space Telescope
observations from the ultraviolet (UV) to the near-infrared (NIR). We show
that, for ages 6 <= log(age/yr) <= 9, and if one can only obtain partial
coverage of the spectral energy distribution (SED), an optical passband
combination of at least four filters including BOTH blue AND red passbands
results in the most representative age distribution. We find that while
blue-selected passband combinations lead to age distributions that are slightly
biased towards younger ages due to the age-metallicity degeneracy,
red-dominated passband combinations should be avoided. NGC 3310 underwent a
global burst of cluster formation ~3x10^7 yr ago. This coincides closely with
the last tidal interaction or merger with a low-metallicity galaxy that likely
induced the formation of the large fraction of clusters with (significantly)
subsolar metallicities. The observed cluster system has a median mass of
<log(m/Msun)> = 5.25 +- 0.1, obtained from scaling the appropriate model SEDs
for known masses to the observed cluster SEDs.


title: Draco -- A Failure of the Tidal Model

abstract:
  We test whether the structural properties of the nearby dwarf spheroidal
(dSph) galaxy Draco, a well-studied Milky Way companion, can be reconciled with
the suggestion that dSphs are unbound tidal remnants with a large depth extent
along the line of sight. In order to apply the observational test of this
hypothesis suggested by Klessen & Zhao, we use public photometric data from the
Sloan Digital Sky Survey (SDSS) to explore the width of Draco's blue horizontal
branch over a range of areas covering 0.06 square degrees to 6.25 square
degrees centered on Draco. The SDSS database is the only currently existing
database with sufficient depth and area coverage to permit a stringent test of
the tidal models. We show that blue horizontal branch stars extend beyond the
previously inferred limiting radii of Draco, consistent with the observed
absence of a truncated stellar surface density profile of this dSph. We
calculate new models for a galaxy without dark matter, using Draco's
morphological properties as constraints. The resulting models are unable to
reproduce the narrow observed horizontal branch width of Draco, which stays
roughly constant regardless of the field of view. We conclude that Draco cannot
be the remnant of a tidally disrupted satellite, but is probably strongly
dark-matter dominated. (ABSTRACT ABBREVIATED)


title: A two-component ionized reflection model of MCG--6-30-15

abstract:
  Ionized reflection has often been considered as the explanation for the
unusual Fe K variability observed in MCG--6-30-15. In this paper, we test this
model using a 325 ks observation of MCG--6-30-15 by XMM-Newton and BeppoSAX.
The data are fit between 2.5 and 80 keV with the constant density models of
Ross & Fabian. The best fit ionized reflection model requires the Fe K line to
be split into two reprocessing events: one from the inner disc to build up the
red wing, and the other from the outer accretion disc to fit the blue horn. The
implied geometry is a disc which becomes strongly warped or flared at large
radii. A good fit was obtained with a solar abundance of iron and a reflection
fraction (R) of unity for the inner reflector. The combination of the two
reflection spectra can appear to have R>2 as required by the BeppoSAX data. The
inner reflector has an ionization parameter \log \xi =3.8, but the outer one is
neutral with an inner radius ~70 gravitational radii (r_g), corresponding to a
light crossing time of about an hour for a 10^7 Msun black hole. Applying this
model to time-resolved spectra shows that the inner reflector becomes more
ionized as the source brightens. This reduces the strength of the red wing at
high flux states. The X-ray source is constrained to arise from a narrow
annulus at ~5 r_g, with only 6 per cent of the 2-10 keV flux due to the outer
reprocessor. This amount of localized energy generation is extremely difficult
to produce without resorting to other energy sources such as the black hole
spin. In fact, all the Fe K models fit to XMM-Newton spectra of MCG--6-30-15
require a large increase in energy production at the inner edge of the
accretion disc.


title: The nature of X-ray selected EROs

abstract:
  We report on the X-ray, optical, near-infrared, submillimetre and radio
properties of five Extremely Red Objects (EROs) selected at X-ray wavelengths
by XMM-Newton in the Lockman Hole field. They all have enough counts in the
X-ray band to allow spectral fitting: four are most probably obscured,
Compton-thin AGN with redshift dependent absorbing column densities of 10^22 -
10^24 cm-2, whilst the fifth is best fitted by a thermal spectrum and is likely
to be a massive elliptical galaxy in a deep gravitational potential. Their
optical/near-infrared colours and sizes suggest that X-ray selected EROs
comprise a mixture of dusty 'starburst' galaxies and non-dusty galaxies that
are dominated by either star-light or light from an active nucleus. The colour
diagnostics are supported by the submillimetre and radio data: the two AGN with
'starburst' colours have submillimetre or radio flux densities that imply large
star-formation rates, whilst those with 'elliptical' colours do not. The one
source detected in the submillimetre waveband has narrow emission lines at a
redshift of 1.45. Although the bulk of its radio emission originates from
processes other than star formation, it is most probably a radio-quiet
ultraluminous infrared galaxy.


title: X-ray Variability and Emission Process of the Radio Jet in M87

abstract:
  We monitored the M87 jet with the ACIS-S detector on Chandra with 5
observations between 2002 Jan and 2002 Jul. Our goal was to determine the
presence and degree of variability in morphology, intensity, and spectral
parameters. We find strong variability of the core and HST-1, the knot lying
0.8" from the core. These observations were designed to constrain the X-ray
emission process: whereas synchrotron emission would necessitate the presence
of extremely high energy electrons with a halflife of a few years or less,
inverse Compton emission from a relativistic jet would arise from low energy
electrons with very long halflives. Currently, all indications point to a
synchrotron process for the X-ray emission from the M87 jet. We give key
parameters for a ``modest beaming'' synchrotron model.


title: A Regularized Free Form Estimator for Dark Energy

abstract:
  We construct a simple, regularized estimator for the dark energy equation of
state by using the recently introduced linear response approximation. We show
that even a simple regularization substantially improves the performance of the
free form fitting approach. The use of linear response approximation allows an
analytic construction of maximum likelihood estimator, in a convenient and easy
to use matrix form. We show that in principle, such regularized free form
fitting can give us an unbiased estimate of the functional form of the equation
of state of dark energy. We show the efficacy of this approach on a simulated
SNAP class data, but it is easy to generalize this method to include other
cosmological tests. We provide a possible explanation for the sweet spots seen
in other reconstruction methods.


title:
CL 1358+62: Characterizing the Physical Properties of Cluster Galaxies
  at z=0.33

abstract:
  [Abridged] We examine the physical properties of 173 cluster members in
CL1358+62 (z=0.33) from HST WFPC2 imaging taken in the F606W & F814W filters
(rest-frame B & V) over a 2.2x2.2 Mpc^2 field. Structural parameters are
measured for each member by fitting a PSF-convolved, two component model to
their 2D surface brightness distribution. We examine bulge+disk models using
three different bulge profiles (de Vaucouleurs, Sersic, and exponential), and
rigorously test the robustness of our results by analyzing several thousand
artificial galaxies in the same manner as the cluster data. Combining
structural parameters with ground-based spectroscopy, we test for correlations
between morphological characteristics, current star formation, total galaxy
colors, and cluster substructure. We find that: (1) Using a de Vaucouleurs
bulge, bulge-to-total ratios and Hubble type (-5<T<8) are strongly correlated
(99% CL), but the scatter is large and early-type spirals are not reliably
distinguished from E's and S0's based on (B/T). (2) The low luminosity
ellipticals in our sample are likely to be face-on S0 galaxies. (3) High galaxy
asymmetry and strong [OII] emission are strongly correlated for disk-dominated
members. (4) There exists a small population (~5%) of bulge-dominated members
whose significant [OII] emission (<-5A) suggest they harbor AGN. (5) At these
redshifts, determining the correct Sersic index can be highly unreliable.


title:
Evolutionary models for cool brown dwarfs and extrasolar giant planets.
  The case of HD 20945

abstract:
  We present evolutionary models for cool brown dwarfs and extra-solar giant
planets. The models reproduce the main trends of observed methane dwarfs in
near-IR color-magnitude diagrams. We also present evolutionary models for
irradiated planets, coupling for the first time irradiated atmosphere profiles
and inner structures. We focus on HD 209458-like systems and show that
irradiation effects can substantially affect the radius of sub-jovian mass
giant planets. Irradiation effects, however, cannot alone explain the large
observed radius of HD 209458b. Adopting assumptions which optimise irradiation
effects and taking into account the extension of the outer atmospheric layers,
we still find $\sim$ 20% discrepancy between observed and theoretical radii. An
extra source of energy seems to be required to explain the observed value of
the first transit planet.


title:
The Measurement of the Light Deflection from Jupiter: Experimental
  Results

abstract:
  We have determined the relativistic light deflection of the quasar J0842+1835
as Jupiter passed within 3.7' on 2002 September 8, by measuring the time delay
using the VLBA and Effelsberg radio telescopes at 8.4 GHz. At closest approach,
General Relativity (GR) predicts a radial (static) deflection of 1190
microarcsec, and tangential (retarded) deflection in the direction of Jupiter's
motion of 51 microarcsec. Our experiment achieved an rms position error of <10
microarcsec, and measured this retarded deflection to be 0.98 +/- 0.19 (rms
error) times that predicted by GR. The increase positional accuracy for this
VLBI phase referencing experiment was achieved by using two calibrator sources.
Comments on the interpretation of this experiment are given.


title: WMAP Constraints on varying $\alpha$ and the Promise of Reionization

abstract:
  We present up-to-date constraints on the value of the fine-structure constant
at the epoch of decoupling from the recent observations made by the Wilkinson
Microwave Anisotropy Probe (WMAP) satellite. In the framework of models we
considered, a positive (negative) variation of the value of $\alpha$ at
decoupling with respect to the present-day value is now bounded to be smaller
than 2% (6%) at 95% confidence level. We point out that the existence of an
early reionization epoch as suggested by the above measurements will, when more
accurate cosmic microwave background polarization data is available, lead to
considerably tighter constraints. The so-called `reionization bump', in
particular, will be extremely useful for this purpose. We find that constraints
on $\alpha$ can in principle only be as small as $0.1 %$ using CMB data
alone--tighter constraints will require further (non-CMB) priors.


title: Chaotic Loss Cones, Black Hole Fueling and the M-Sigma Relation

abstract:
  In classical loss cone theory, stars are supplied to a central black hole via
gravitational scattering onto low angular momentum orbits. Higher feeding rates
are possible if the gravitational potential near the black hole is
non-axisymmetric and the orbits are chaotic. Motivated by recently published,
self-consistent models, we evaluate rates of stellar capture and disruption in
triaxial nuclei. Rates are found to substantially exceed those in
collisionally-resupplied loss cones, as long as an appreciable fraction of the
orbits are centrophilic. The mass captured by a black hole after a given time
in a steep nucleus scales as the fifth power of the velocity dispersion, and
the accumulated mass in 10^10 yr is of the correct order to reproduce the
M-sigma relation. Triaxiality can solve the "final parsec problem" of decaying
black hole binaries by increasing the flux of stars into the binary's loss
cone.


title: Was the Universe Reionized by Massive Population-III Stars?

abstract:
  The WMAP satellite has measured a large optical depth to electron scattering
after cosmological recombination of 0.17+-0.04, implying significant
reionization of the primordial gas only ~200 million years after the big bang.
However, the most recent overlap of intergalactic HII regions must have occured
at z<9 based on the Lyman-alpha forest constraint on the thermal history of the
intergalactic medium. Here we argue that a first generation of metal-free stars
with a heavy (rather than Salpeter) mass function is therefore required to
account for much of the inferred optical depth. This conclusion holds if
feedback regulates star formation in early dwarf galaxies as observed in
present-day dwarfs.


title: A Quadruple-Phase Strong Mg II Absorber at z~0.9902 Toward PG 1634+706

abstract:
  The z=0.9902 system along the quasar PG 1634+706 line of sight is a strong
MgII absorber (W(2796)>0.3A) with only weak CIV absorption (it is
``CIV-deficient''). To study this system, we used high-resolution spectra from
both HST/STIS (R=30,000) and Keck/HIRES (R=45,000). These spectra cover key
transitions, such as MgI, MgII, FeII, SiII, CII, SiIII, CIII, SiIV, and CIV.
Assuming a Haardt and Madau extragalactic background spectrum, we modeled the
system with a combination of photoionization and collisional ionization. Based
on a comparison of synthetic spectra to the data profiles, we infer the
existence of the following four phases of gas: i) Seven MgII clouds have sizes
of 1-1000pc and densities of 0.002-0.1/cm^3, with a gradual decrease in density
from blue to red. The MgII phase gives rise to most of the CIV absorption and
resembles the warm, ionized inter-cloud medium of the Milky Way; ii) Instead of
arising in the same phase as MgII, MgI is produced in separate, narrow
components with b~0.75km/s. These small MgI pockets (~100AU) could represent a
denser phase (~200/cm^3) of the interstellar medium (ISM), analogous to the
small-scale structure observed in the Milky Way ISM; iii) A ``broad phase''
with a Doppler parameter, b~60km/s, is required to consistently fit Ly-alpha,
Ly-beta, and the higher-order Lyman-series lines. A low metallicity (log Z <=
-2) for this phase could explain why the system is ``CIV-deficient'', and also
why NV and OVI are not detected. This phase may be a galactic halo or it could
represent a diffuse medium in an early-type galaxy; iv) The strong absorption
in SiIV relative to CIV could be produced in an extra, collisionally ionized
phase with a temperature of T~60,000K. The collisional phase could exist in
cooling layers that are shock-heated by supernovae-related processes.


title:
The First Measurement of Spectral Lines in a Short-Period Star Bound to
  the Galaxy's Central Black Hole: A Paradox of Youth

abstract:
  We have obtained the first detection of spectral absorption lines in one of
the high-velocity stars in the vicinity of the Galaxy's central supermassive
black hole. Both Brgamma (2.1661 micron) and He I (2.1126 micron) are seen in
absorption in S0-2 with equivalent widths (2.8+-0.3 Ang & 1.7+-0.4 Ang) and an
inferred stellar rotational velocity (220+-40 km/s) that are consistent with
that of an O8-B0 dwarf, which suggests that it is a massive (~15 Msun), young
(<10 Myr) main sequence star. This presents a major challenge to star formation
theories, given the strong tidal forces that prevail over all distances reached
by S0-2 in its current orbit (130 - 1900 AU) and the difficulty in migrating
this star inward during its lifetime from further out where tidal forces should
no longer preclude star formation. The radial velocity measurements (-510+-40
km/s) and our reported proper motions for S0-2 strongly constrain its orbit,
providing a direct measure of the black hole mass of 4.1(+-0.6)x10^6(Ro/8kpc)^3
Msun. The Keplerian orbit parameters have uncertainities that are reduced by a
factor of 2-3 compared to previously reported values and include, for the first
time, an independent solution for the dynamical center; this location, while
consistent with the nominal infrared position of Sgr A*, is localized to a
factor of 5 more precisely (+-2 milli-arcsec). Furthermore, the ambiguity in
the inclination of the orbit is resolved with the addition of the radial
velocity measurement, indicating that the star is behind the black hole at the
time of closest approach and counter-revolving against the Galaxy. With further
radial velocity measurements in the next few years, the orbit of S0-2 will
provide the most robust estimate of the distance to the Galactic Center.


title:
Star Formation History of Omega Centauri Imprinted in Elemental
  Abundance Patterns

abstract:
  The star formation history of the globular cluster Omega Centauri is
investigated in the context of an inhomogeneous chemical evolution model in
which supernovae induce star formation. The proposed model explains recent
observations for Omega Cen stars, and divides star formation into three epochs.
At the end of the first epoch, ~ 70% of the gas was expelled by supernovae. AGB
stars then supplied s-process elements to the remaining gas during the first
interval of ~300 Myr. This explains the observed sudden increase in Ba/Fe
ratios in Omega Cen stars at [Fe/H] ~ -1.6. Supernovae at the end of the second
epoch were unable to expel the gas. Eventually, Type Ia supernovae initiated
supernova-induced star formation, and remaining gas was stripped when the
cluster passed through the newly formed disk of the Milky Way. The formation of
Omega Cen is also discussed in the framework of globular cluster formation
triggered by cloud-cloud collisions. In this scenario, the relative velocity of
clouds in the collision determines the later chemical evolution in the
clusters. A head-on collision of proto-cluster clouds with a low relative
velocity would have converted less than 1% of gas into stars and promoted the
subsequent chemical evolution by supernova-driven star formation. This is
consistent with present observed form of Omega Cen. In contrast, the other
Galactic globular clusters are expected to have formed from more intense
head-on collisions, and the resultant clouds would have been too thin for
supernovae to accumulate enough gas to form the next generation of stars. This
explains the absence of chemical evolution in these other globular clusters.


title:
High Resolution Calculations of Merging Neutron Stars II: Neutrino
  Emission

abstract:
  The remnant resulting from the merger of two neutron stars produces neutrinos
in copious amounts. In this paper we present the neutrino emission results
obtained via Newtonian, high-resolution simulations of the coalescence event.
These simulations use three-dimensional smoothed particle hydrodynamics
together with a nuclear, temperature dependent equation of state and a
multi-flavour neutrino leakage scheme. We present the details of our scheme,
discuss the neutrino emission results from a neutron star coalescence and
compare them to the core-collapse supernova case where neutrino emission has
been studied for several decades. The average neutrino energies are similar to
those in the supernova case, but contrary to the latter, the luminosities are
dominated by electron-type antineutrinos which are produced in the hot,
neutron-rich, thick disk of the merger remnant. The cooler parts of this disk
contain substantial fractions of heavy nuclei, which, however, do not influence
the overall neutrino emission results significantly. Our total neutrino
luminosities from the merger event are considerably lower than those found in
previous investigations. This has serious consequences for the ability to
produce a gamma-ray burst via neutrino annihilation. The neutrinos are emitted
preferentially along the initial binary rotation axis, an event seen
``pole-on'' would appear much brighter in neutrinos than a similar event seen
``edge-on''.


title: Can dark energy be decaying?

abstract:
  We explore the fate of the universe given the possibility that the density
associated with `dark energy' may decay slowly with time. Decaying dark energy
is modeled by a homogeneous scalar field which couples minimally to gravity and
whose potential has {\em at least one} local quadratic maximum. Dark energy
decays as the scalar field rolls down its potential, consequently the current
acceleration epoch is a transient. We examine two models of decaying dark
energy. In the first, the dark energy potential is modeled by an analytical
form which is generic close to the potential maximum. The second potential is
the cosine, which can become negative as the field evolves, ensuring that a
spatially flat universe collapses in the future. We examine the feasibility of
both models using observations of high redshift type Ia supernovae. A maximum
likelihood analysis is used to find allowed regions in the $\lbrace m,
\phi_0\rbrace$ plane ($m$ is the tachyon mass modulus and $\phi_0$ the initial
scalar field value; $m\sim H_0$ and $\phi_0\sim M_P$ by order of magnitude).
For the first model, the time for the potential to drop to half its maximum
value is larger than $\sim 8$ Gyrs. In the case of the cosine potential, the
time left until the universe collapses is always greater than $\sim 18$ Gyrs
(both estimates are presented for $\om = 0.3$, $m/H_0 \sim 1$, $H_0 \simeq 70$
km/sec/Mpc, and at the 95.4% confidence level).


title: Jet-formation in accreting black hole systems and in GRB

abstract:
  Most powerful jets are observed to emanate from accreting black hole systems.
Recent quasi-stationary radiative MHD calculations reveal that jet-launching
start in the innermost region of a transition layer (:TL), which is located
between the disk and the corona. The plasma in the TL is dominated by
virial-hot protons, advective, highly magnetic-diffusive and rotates
super-Keplerian. The amplified toroidal magnetic field (TMF) in the TL reach
values beyond equipartition with respect to the electron thermal energy,
thereby considerably enhancing the Poynting energy flux and yielding
gravitationally unbound electron-proton outflows with a positive Bernoulli
number.
  We speculate that beaming jets in GRBs may possess similar properties,
provided that the GRB-progenitors have rotational energy sufficient for forming
a nearly Keplerian and massive disk.


title: The far infrared CO line emission of Orion BN/KL

abstract:
  We present observations towards one of the closest regions of high mass star
formation, Orion BN/KL, performed at both low resolution mode (grating mode)
and high resolution mode (Fabry-Perot) with the Long Wavelength Spectrometer on
board the Infrared Space Observatory. We detected the CO rotational lines from
Jup = 15 to Jup = 45. While the lines with Jup<= 32 are spectrally unresolved,
the higher lying lines show a broadened profile. Finally, we detected two 13CO
lines, namely at Jup = 18 and 24, from which we could derive the opacities of
the relative 12CO lines. The LVG analysis of the observed line spectrum allows
to distinguish three main physical components with different temperatures,
densities and column densities: 1) lines with Jup< 20 originate mainly in the
diffuse photodissociation region surrounding the source; 2) lines with Jup
between 20 and 30 originate in the high velocity outflow (plateau) emanating
from IrC2; 3) lines with Jup > 32 originate in the hot and dense gas of the
shocked component of the outflow. We discuss how future observations with HIFI,
onboard the Far Infrared Space Telescope (FIRST) will allow to spectrally and
spatially disentangle the three components, and, consequently, characterise
more precisely the Orion BN/KL star forming region.


title: Water emission in NGC1333-IRAS4: Probing its surrounding envelope

abstract:
  Sun like stars are born from the collapse of fragment of molecular clouds.
During the first embedded phase (the so called class 0/1), the protostar is
surrounded by a collapsing envelope, whose physical and chemical structure
would set up the initial conditions of the proto-stellar disk which may
eventually form planets. In this contribution, we show how spectroscopic far
infrared to millimeter observations can be a powerful diagnostic to derive the
chemical and physical structure of the innermost regions of envelopes
collapsing around solar type protostars, where disk are believe to form. Our
claim is based on the simultaneous modeling of the dynamics, chemistry and
radiative transfer in a protostellar envelope. Here we present a study of a
class 0 protostar NGC1333-IRAS4, obtained using ISO-LWS observations of water
far-infrared lines. We show the derived physical and chemical structure of the
protostar, namely the density and temperature profiles, as well as the water
abundance across the envelope. Besides, the mass of the central protostar and
its accretion rate can be constrained by these observations and modeling,
yielding an alternative method to measure these two poorly know parameters.


title: Reconstructing the primordial power spectrum

abstract:
  We reconstruct the shape of the primordial power spectrum from the latest
cosmic microwave background data, including the new results from the Wilkinson
Microwave Anisotropy Probe (WMAP), and large scale structure data from the two
degree field galaxy redshift survey (2dFGRS). We tested four parameterizations
taking into account the uncertainties in four cosmological parameters. First we
parameterize the initial spectrum by a tilt and a running spectral index,
finding marginal evidence for a running spectral index only if the first three
WMAP multipoles (ell=2,3,4) are included in the analysis. Secondly, to
investigate further the low CMB large scale power, we modify the conventional
power-law spectrum by introducing a scale above which there is no power. We
find a preferred position of the cut at k_c ~ 3e-4 /Mpc although k_c=0 (no cut)
is not ruled out. Thirdly we use a model independent parameterization, with 16
bands in wavenumber, and find no obvious sign of deviation from a power law
spectrum on the scales investigated. Furthermore the values of the other
cosmological parameters defining the model remain relatively well constrained
despite the freedom in the shape of the initial power spectrum. Finally we
investigate a model motivated by double inflation, in which the power spectrum
has a break between two characteristic wavenumbers. We find that if a break is
required to be in the range 0.01 < k Mpc <0.1 then the ratio of amplitudes
across the break is constrained to be 1.23 +/- 0.14. Our results are consistent
with a power law spectrum that is featureless and close to scale invariant over
the wavenumber range 0.005 ~< k Mpc ~< 0.15, with a hint of a decrease in power
on the largest scales.


title: The Local Interstellar Spectrum of Cosmic Ray Electrons

abstract:
  The direct measurements of electrons and positrons over the last 30 years,
corrected for the solar effect in the force-field approximation, are
considered. The resulting overall electron spectrum may be fitted with a single
power law above few GeV with spectral index ($\gamma_{-} = 3.41 \pm 0.02$),
consistent with the spectral index of the positron spectrum ($\gamma_{+} = 3.40
\pm 0.06$), therefore suggesting a common acceleration process for both
species. We propose that the engine was a shock wave originating from the last
supernova explosion among those that formed the local bubble. In addition, at
low energy, the electron spectrum measured during the last $A+$ solar phase is
damped, whereas the positron spectrum is well represented by a single power law
down to the lowest inferred local interstellar energy (0.8 GeV). We suggest
that this difference arises from a time- and charge-dependent effect of the
solar modulation that is not taken into account by the force-field
approximation.


title:
Anisotropies in the redshift-space correlations of galaxy groups and
  clusters I: Simulated catalogues

abstract:
  We analyse the correlation function of mock galaxy clusters in redshift
space. We constructed several mock catalogues designed to mimic the selection
biases inherent in a variety of observational surveys. We explore different
effects that contribute to the distortion of the clustering pattern; the
pairwise velocity distribution of galaxy systems, coherent bulk motions,
redshift errors and systematics in cluster identification. Our tests show that
the redshift-space clustering pattern of galaxy systems is highly influenced by
effects associated with the identification procedure from two dimensional
surveys. These systems show a spuriously large correlation amplitude, an effect
that is present and even stronger in a subsample whose angular positions
coincide with 3-dimensional identified clusters. The use of a small number of
redshift measurements in the determination of the cluster distance has a
smaller impact on the measured correlation function. We show that an angular
incompleteness in redshift surveys, such as that present in the 2dFGRS 100k
public release, has no significant effect in the results. We suggest that the
nature of projection effects arise mainly from structures along the line of
sight in the filamentary large-scale clustering pattern. Thus spectroscopic
surveys are the only means of providing unbiased cluster samples.


title: The Janus head of the HD 12661 planetary system

abstract:
  In this work we perform a global analysis of the radial velocity curve of the
HD 12661 system. Orbital fits that are obtained by the genetic and gradient
algorithms of minimization reveal the proximity of the system to the 6:1 mean
motion resonance. The orbits are locked in the secular resonance with apsidal
axes librating about 180 deg with the full amplitude $\simeq (90,180) deg$. Our
solution incorporates the mutual interaction between the companions. The
stability analysis with the MEGNO fast indicator shows that the system is
located in an extended stable zone of quasi-periodic motions. These results are
different from those obtained on the basis of the orbital fit published by
Fischer et al. (2003)


title:
Anisotropies in the redshift-space correlations of galaxy groups and
  clusters II: Analysis of observational cluster samples

abstract:
  We study the redshift space correlation function of galaxy clusters for
observational samples constructed in different surveys. We explore correlation
amplitudes, pairwise velocity distributions and bias factors. Systematics in
cluster identification procedures are the main source of biased estimates of
the correlation amplitude and inferred velocity dispersions. By comparing our
results with those of numerical simulations we explore the strong influence on
the clustering distortion pattern in redshift space from effects associated
with the cluster identification procedure from two dimensional surveys as is
the case of Abell and APM clusters. The identification of clusters in X-ray
surveys improves this situation, although there are still systematic effects
which are probably due to identification of optical sources in the
determination of cluster redshifts. These systematics are particularly strong
for the most luminous X-ray selected clusters in the Extended Bright Cluster
Survey, which exhibits very large anisotropies, comparable to those present in
the Abell catalogue. Our results demonstrate that forthcoming large redshift
surveys will be extremely important for the construction of new samples of
groups and clusters as well as improving the determination of optical and X-ray
selected cluster distances, essential for reliable analyses of the large scale
structure.


title:
Highly extinguished emission line outflows in the young radio source PKS
  1345+12

abstract:
  (Abridged) We present new, intermediate resolution spectra (~4A) of the
compact radio source PKS 1345+12. Our spectra clearly show extended line
emission (~20kpc) consistent with the asymmetric halo of diffuse emission
observed in optical and infra-red images. In the nucleus we observe complex
emission line profiles requiring 3 Gaussian components (narrow, intermediate
and broad). The broadest component (FWHM ~2000 km/s) is blue shifted by ~2000
km/s with respect to the galaxy halo and HI absorption. We interpret this as
material in outflow. We find evidence for high reddening and measure
E(B-V)>0.92 for the broadest component. From [S II]6716,6731 we estimate
electron densities of n_e<150cm^{-3}, n_{e}>5300 cm^{-3} and n_{e}>4200 cm^{-3}
for the regions emitting the narrow, intermediate and broad components
respectively. We calculate a total mass of line emitting gas of M_{gas}<10^6
solar masses. Not all emission line profiles can be reproduced by the same
model: [O I]6300,6363 and [S II] require separate, unique models. We argue that
PKS 1345+12 is a young radio source whose nuclear regions are enshrouded in a
dense cocoon of gas and dust. The radio jets are expanding, sweeping material
out of the nuclear regions. Emission originates from three kinematically
distinct regions though gradients (e.g. density, ionisation potential,
acceleration) must exist across the regions responsible for the emission of the
intermediate and broad components.


title: The surprising Far-UV spectrum of the polar BY Camelopardalis

abstract:
  We report on the first far-UV observations of the asynchronous polar BY Cam
made by the Far-Ultraviolet Spectroscopic Explorer (FUSE). The source is known
to exhibit the most extreme NV/CIV emission resonance line ratio observed among
polars. The FUSE observations reveal a OVI resonance line weaker than in the
prototype of polars, AM Her, with the absence of a detectable narrow component.
The OVI broad line is detected with an equivalent width of the same order as in
AM Her, the blueward doublet component is clearly present but the redward
component is strongly affected by H2 absorption. The presence of a strong NIII
line and weak CIII lines also confirms the peculiar CNO line flux. We compare
the resonance CNO line intensities with the predictions of the CLOUDY plasma
code coupled to a geometrical model of the accretion column. Varying the
temperature and/or intensity of the ionising spectrum is unable to reproduce
the observed broad line ratios. A solution is obtained by significantly
altering the element abundances with a strong depletion of C, overabundance of
N and a weak underabundance of O. This confirms previous suggestions of
non-solar abundances which may result from redistribution in the accreted
material following nova outbursts and/or the secondary nuclear evolution. A
very significant H2 absorption is observed in front of the source, a possible
indication for either the existence of a dense interstellar cloud or of
circumstellar material.


title: Inertial modes of neutron stars with the superfluid core

abstract:
  We investigate the modal properties of inertial modes of rotating neutron
stars with the core filled with neutron and proton superfluids, taking account
of entrainment effects between the superfluids. In this paper, the entrainment
effects are modeled by introducing a parameter $\eta$ so that no entrainment
state is realized at $\eta=0$. We find that inertial modes of rotating neutron
stars with the superfluid core are split into two families, which we call
ordinary fluid inertial modes ($i^o$-mode) and superfluid inertial modes
($i^s$-mode). The two superfluids in the core counter-move for the $i^s$-modes.
For the $i^o$-modes, $\kappa_0=\lim_{\Omega\to 0}\omega/\Omega$ is only weakly
dependent on the entrainment parameter $\eta$, where $\Omega$ and $\omega$ are
the angular frequency of rotation and the oscillation frequency observed in the
corotating frame of the star, respectively. For the $i^s$-modes, on the other
hand, $|\kappa_0|$ almost linearly increases as $\eta$ increases. Avoided
crossings as functions of $\eta$ are therefore quite common between $i^o$- and
$i^s$-modes. We find that some of the $i^s$-modes that are unstable against the
gravitational radiation reaction at $\eta=0$ become stable when $\eta$ is
larger than $\eta_{crit}$, the value of which depends on the mode. Since the
radiation driven instability associated with the current multipole radiation is
quite weak for the inertial modes and the mutual friction damping in the
superfluid core is strong, the instability caused by the inertial modes will be
easily suppressed unless the entrainment parameter $\eta$ is extremely small
and the mutual friction damping is sufficiently weak.


title:
Accretion disk assembly and survival during the disruption of a neutron
  star by a black hole

abstract:
  We study the formation of accretion disks resulting from dynamical three
dimensional binary coalescence calculations, where a neutron star is tidally
disrupted before being swallowed by its black hole companion. By subsequently
assuming azimuthal symmetry we are able to follow the time dependence of the
disk structure for a few tenths of a second. Although the disruption of a
neutron star leads to a situation where violent instabilities redistribute mass
and angular momentum within a few dynamical timescales, enough gas mass remains
in the orbiting debris to catalyse the extraction of energy from the hole at a
rate adequate to power a short-lived gamma ray burst.


title:
An XMM-Newton Observation of 4U1755-33 in Quiescence: Evidence for a
  Fossil X-Ray Jet

abstract:
  We report an XMM-Newton observation of the Low mass X-ray Binary (LMXB) and
black hole candidate 4U1755-33. This source had been a bright persistent source
for at least 25 yrs, but in 1995 entered an extended quiescent phase. 4U1755-33
was not detected with an upper limit to the 2-10 keV luminosity of 5.10^31
erg/s (assuming a distance of 4 kpc) - consistent with the luminosity of other
black hole candidates in a quiescent state. An unexpected result is the
discovery of a narrow 7' long X-ray jet-like feature centered on the position
of 4U1755-33. The spectrum of the jet is similar to that observed from other
galactic and extragalactic jets thought to be associated with accreting black
holes. The detection of a fossil jet provides additional evidence supporting
the black hole candidacy of 4U1755-33. The spectral properties of three bright
serendipitous sources in the field are reported and it is suggested these are
background active galactic nuclei (AGN).


title: Excavation of the first stars

abstract:
  The external pollution of the first stars in the Galaxy is investigated. The
first stars were born in clouds composed of the pristine gas without heavy
elements. These stars accreted gas polluted with heavy elements while they
still remained in the cloud. As a result, it is found that they exhibit a
distribution with respect to the surface metallicity. We have derived the
actual form of this distribution function. This metallicity distribution
function strongly suggests that the recently discovered most metal-deficient
star HE0107-5240 with [Fe/H]=-5.3 was born as a metal-free star and accreted
gas polluted with heavy elements. Thus the heavy elements such as Fe in
HE0107-5240 must have been supplied from supernovae of later generations
exploding inside the cloud in which the star had been formed. The elemental
abundance pattern on the surface of stars suffering from such an external
pollution should not be diverse but exhibit the average pattern of numerous
supernovae. Future observations for a number of metal-deficient stars with
[Fe/H]<-5 will be able to prove or disprove this external pollution scenario.
Other possibilities to produce a star with this metallicity are also discussed.


title:
First Results from the HI Jodrell All Sky Survey: Inclination-Dependent
  Selection Effects in a 21-cm Blind Survey

abstract:
  Details are presented of the HI Jodrell All Sky Survey (HIJASS). HIJASS is a
blind neutral hydrogen (HI) survey of the northern sky, being conducted using
the multibeam receiver on the Lovell Telescope at Jodrell Bank. HIJASS covers
the velocity range -3500 km/s to 10000 km/s with a velocity resolution of 18.1
km/s and a spatial positional accuracy of ~2.5 arcmin. Thus far about 1115 sq
deg have been surveyed. We describe the methods of detecting galaxies within
the HIJASS data and of measuring their HI parameters. The properties of the
resulting HI-selected sample of galaxies are described. Of the 222 sources so
far confirmed, 170 (77 per cent) are clearly associated with a previously
catalogued galaxy. A further 23 sources (10 percent) lie close (within 6
arcmin) to a previously catalogued galaxy for which no previous redshift
exists. A further 29 sources (13 per cent) do not appear to be associated with
any previously catalogued galaxy. The distributions of peak flux, integrated
flux, HI mass and cz are discussed. We show, using the HIJASS data, that HI
self-absorption is a significant, but often overlooked, effect in galaxies with
large inclination angles to the line of sight. Properly accounting for it could
increase the derived HI mass density of the local Universe by at least 25 per
cent. The effect this will have on the shape of the HI Mass Function will
depend on how self-absorption affects galaxies of different morphological types
and HI masses. We also show that galaxies with small inclinations to the line
of sight may also be excluded from HI-selected samples, since many such
galaxies will have observed linewidths which are too narrow for them to be
distinguished from narrow-band radio frequency interference.


title: Dark matter and visible baryons in M33

abstract:
  In this paper we present new measurements of the gas kinematics in M33 using
the CO J=1-0 line. The resulting rotational velocities complement previous
21-cm line data for a very accurate and extended rotation curve. The implied
dark matter mass, within the total gaseous extent, is a factor 5 higher than
the visible baryonic mass. Dark matter density profiles with an inner cusp as
steep as R^{-1}, are compatible with M33 data. The dark matter concentrations
required for fitting the M33 rotation curve are very low but marginally
consistent with halos forming in a standard Cold Dark Matter cosmology. The M33
virialized dark halo is at least 50 times more massive than the visible baryons
and its size is comparable with the M33-M31 separation. Inner cusps as steep as
R^{-1.5} are ruled out, while halo models with a large size core of constant
density are consistent with the M33 data. A central spheroid of stars is needed
and we evaluate its dynamical mass range. Using accurate rotational velocity
gradients and the azimuthally averaged baryonic surface densities, we show that
a disk instability can regulate the star formation activity in M33. Considering
the gaseous surface density alone, the predicted outer star formation threshold
radius is consistent with the observed drop of the H-alpha surface brightness
if a shear rate criterion is used. The classical Toomre criterion predicts
correctly the size of the unstable region only when the stellar or dark halo
gravity, derived in this paper, is added to that of the gaseous disk.


title: Far-UV FUSE spectra of peculiar magnetic cataclysmic variables

abstract:
  We present far-UV spectra of the three magnetic cataclysmic variables (MCVs)
BY Cam, V1309 Ori and AE Aqr obtained with the FUSE satellite. These MCVs have
revealed strongly unusual NV and CIV UV resonance lines. The FUSE spectra
exhibit broad OVI lines as well as a strong NIII line at 991A, while the CIII
1175A line is nearly absent, supporting non-solar CNO abundances of the
accreting matter in these sources. The spectrum of BY Cam shows molecular H2
lines which might be of circumstellar nature. The flaring activity of AE Aqr is
also observed in the far-UV range. The radial velocities of the broad OVI
components in AE Aqr are orbitally modulated and would indicate an emission
region close to the magnetosphere.


title: Decay of Magnetic Fields in the Early Universe

abstract:
  We study the evolution of a stochastic helical magnetic field generated in
the early Universe after the electroweak phase transition, using standard
magnetohydrodynamics (MHD). We find how the coherence length xi, magnetic
energy E_M and magnetic helicity H evolve with time. We show that the
self-similarity of the magnetic power spectrum alone implies that xi ~ t^{1/2}.
This in turn implies that magnetic helicity decays as H ~ t^{-2s}, and that the
magnetic energy decays as E_M ~ t^{-0.5-2s}, where s is inversely proportional
to the magnetic Reynolds number Re_M. These laws improve on several previous
estimates.


title: Chemical evolution of the M82 B fossil starburst

abstract:
  M82 B is an old starburst site located in the eastern part of the M82 disc.
We derive the distributions of age and metallicity of the star clusters located
in this region of M82 by using theoretical evolutionary population synthesis
models. Our analysis is based on the comparison of the $BVIJ$ photometry
obtained by de Grijs et al. (2001) with the colours of single-generation
stellar populations. We show that M82 B went through a chemical enrichment
phase up to super-solar metallicities around the time of the last close
encounter between M82 and its large neighbour galaxy M81. We date and confirm
the event triggering the enhanced cluster formation at about 1 Gyr ago. At
almost the same time an additional, distinct subpopulation of metal-poor
clusters formed in the part of M82 B nearest to the galactic centre. The
formation of these peculiar clusters may be related to infall of circumgalactic
gas onto M82 B.


title:
Simulations of the Effects of Stripping and Accretion on Galaxy Haloes
  in Clusters

abstract:
  We present results from a series of hydrodynamic simulations investigating
ram pressure stripping of galactic haloes as the host galaxy falls radially
into a cluster. We perform a parameter study comprising of variations in
initial gas content, gas injection rate (via stellar mass loss processes),
galaxy mass and amplitude of infall. From the simulation results we track
variations in both physical quantities (e.g. gas mass) and directly observable
quantities (e.g. X-ray luminosities). The luminosity of the galaxy's X-ray halo
is found to compare favourably with the observationally determined correlation
with optical blue band luminosity (L_X:L_B) relation. Factors affecting the
X-ray luminosity are explored and it is found that the gas injection rate is a
dominant factor in determining the integrated luminosity. Observational
properties of the material stripped from the galaxy, which forms an X-ray wake,
are investigated and it is found that wakes are most visible around galaxies
with a substantial initial gas content, during their first passage though the
cluster. We define a statistical skewness measure which may be used to
determine the direction of motion of a galaxy using X-ray observations.
Structures formed in these simulations are similar to the cold fronts seen in
observation of cluster mergers where a sharp increase in surface brightness is
accompanied by a transition to a cooler region.


title: The infrared supernova rate in starburst galaxies

abstract:
  We report the results of our ongoing search for extincted supernovae (SNe) at
near-infrared wavelengths. We have monitored at 2.2 micron a sample of 46
Luminous Infrared Galaxies and detected 4 SNe. The number of detections is
still small but sufficient to provide the first estimate of supernova rate at
near-infrared wavelengths. We measure a SN rate ofv 7.6+/-3.8 SNu which is an
order of magnitude larger than observed in quiescent galaxies. On the other
hand, the observed near-infrared rate is still a factor 3-10 smaller than that
estimated from the far-infrared luminosity of the galaxies. Among various
possibilities, the most likely scenario is that dust extinction is so high
(Av>30) to obscure most SNe even in the near-IR.
  The role of type Ia SNe is also discussed within this context. We derive the
type Ia SN rate as a function of the stellar mass of the galaxy and find a
sharp increase toward galaxies with higher activity of star formation. This
suggests that a significant fraction of type Ia SNe are associated with young
stellar populations.
  Finally, as a by-product, we give the average K-band light curve of
core-collapse SNe based on all the existing data, and review the relation
between SN rate and far-infrared luminosity.


title: Spectroscopic binaries in the open cluster Trumpler 16 revisited

abstract:
  We have recalculated the orbits of 3 binary systems, members of the open
cluster Trumpler 16 in the Carina region. We have added new observations to
those available in the literature. Also, we have also tried to find the orbital
periods for two suspected binary systems in the same cluster. We have improved
considerably the precision of some of the orbital parameters.


title:
Microlensing towards the Magellanic Clouds: Nature of the Lenses and
  Implications for Dark Matter

abstract:
  (Abridged) A close scrutiny of the microlensing results towards the
Magellanic clouds reveals that the stars within the Magellanic clouds are major
contributors as lenses, and the contribution of MACHOs to dark matter is 0 to
5%. The principal results which lead to this conclusion are the following.
  (i) Out of the ~17 events detected so far towards the Magellanic Clouds, the
lens locations have been determined for four events where the lenses are most
likely within the Magellanic clouds.
  (ii) If caused by MACHOs, the event timescales would imply that the MACHOs in
the direction of the LMC and the SMC have masses of the order of 0.5 and 2
solar masses, respectively. This is inconsistent with even the most flattened
model of the Galaxy. If caused by stars within the Magellanic Clouds, the
masses of the lenses are of the order of 0.2 solar mass for both the LMC as
well as the SMC.
  (iii) The fact that the two observed binary events are caused by lenses
within the Magellanic Clouds would suggest that there should be a total of ~20
events caused by lenses within the Magellanic Clouds. This implies that most of
the microlensing events observed so far are probably caused by stars within the
Magellanic Clouds.
  (iv) If the microlensing events are caused by MACHOs of 0.5 solar mass, ~15
events should have been detected by now towards the SMC, with timescales of ~40
days. The fact that both the events detected towards the SMC have been shown to
be due to self-lensing places severe constraints on the MACHO contribution and
suggests that the contribution of MACHOs to dark matter is consistent with
zero, with an upper limit of 5%.


title: Adiabatic Modes in Cosmology

abstract:
  We show that the field equations for cosmological perturbations in Newtonian
gauge always have an adiabatic solution, for which a quantity ${\cal R}$ is
non-zero and constant in all eras in the limit of large wavelength, so that it
can be used to connect observed cosmological fluctuations in this mode with
those at very early times. There is also a second adiabatic mode, for which
${\cal R}$ vanishes for large wavelength, and in general there may be
non-adiabatic modes as well. These conclusions apply in all eras and whatever
the constituents of the universe, under only a mild technical assumption about
the wavelength dependence of the field equations for large wave length. In the
absence of anisotropic inertia, the perturbations in the adiabatic modes are
given for large wavelength by universal formulas in terms of the
Robertson--Walker scale factor. We discuss an apparent discrepancy between
these results and what appears to be a conservation law in all modes found for
large wavelength in synchronous gauge: it turns out that, although equivalent,
synchronous and Newtonian gauges suggest inequivalent assumptions about the
behavior of the perturbations for large wavelength.


title: Hidden starburst in Seyfert 1 Galaxies

abstract:
  We report the detection of the 3.3 mu Polycyclic Aromatic Hydrocarbon (PAH)
feature in two Seyfert 1 galaxies - NGC 3227 and Mrk 766, and one QSO - Mrk
478, observed with SpeX at IRTF at a spectral resolution not previously
attained for this type of objects. Except for NGC 3227, this is the first time
that the 3.3 mu PAH emission is detected in Mrk 766 and Mrk 478. The widths of
the emission, reported also for the first time, are rather similar, ranging
from 450 A to 550 A. The luminosity of the 3.3 mu PAH emission measured in the
QSO Mrk 478 places it at a level similar of that found in starburst and
infrared luminous galaxies and implies that this object is having a vigorous
burst of star formation. The spatial resolution of the spectra allows us to
constrain the location of the star-forming region to the inner 1 Kpc for the
QSO and 150 pc for the Seyferts. Our results support the idea that these
objects resides in molecular gas-rich galaxies and that their observed infrared
excess is primarily due to star formation, as previously indicated by CO and
H_2 observations. We also report, for Mrk 1239, the presence of a broad
emission feature centred at 3.43 mu, not previosly detected in an extragalactic
object and whose origin is not yet clear.


title:
Changing look: from Compton-thick to Compton-thin, or the re-birth of
  fossil AGN

abstract:
  We discuss the properties of a small sample of Seyfert 2 galaxies whose X-ray
spectrum changed appearance on time scales of years, becoming
reflection-dominated from Compton-thin, or viceversa. A reflection--dominated
spectrum is usually taken as evidence of Compton-thick absorption, but we
instead argue that such a spectrum is due to a temporary switching--off of the
nuclear radiation. The observations discussed here may help explaining
mismatches between optical and X-ray classifications, and provide new strong
and direct evidence of the presence of more than one cold circumnuclear region
in Seyfert 2 galaxies.


title:
Time evolution of X-ray coronal activity in PMS stars; a possible
  relation with the evolution of accretion disks

abstract:
  We investigate the evolution of X-ray stellar activity from the age of the
youngest known star forming regions (SFR), < 1Myr, to about 100 Myr, i.e. the
zero age main sequence (ZAMS) for a ~ 1M_sun star. We consider five SFR of
varying age (Rho Ophiuchi, the Orion Nebula Cluster, NGC 2264, Chamaeleon I,
and Eta Chamaeleontis) and two young clusters (the Pleiades and NGC 2516).
Optical and X-ray data for these regions are retrieved both from archival
observations and recent literature, and reanalyzed here in a consistent manner
so to minimize systematic differences in the results. We study trends of L_X
and L_X/L_bol as a function of stellar mass and association age. For low mass
stars (M < 1M_sun) we observe an increase in L_X/L_bol in the first 3-4 Myr and
a subsequent leveling off at the saturation level (L_X/L_bol ~ -3). Slowly
evolving very low mass stars then retain saturated levels down to the oldest
ages here considered, while for higher mass stars activity begins to decline at
some age after ~10^7 years. We find our data consistent with the following
tentative picture: low mass PMS stars with no circumstellar accretion disk have
saturated activity, consistently with the activity-Rossby number relation
derived for MS stars. Accretion and/or the presence of disks somehow lowers the
observed activity levels; disk dissipation and/or the decrease of mass
accretion rate in the first few Myrs of PMS evolution is therefore responsible
for the observed increase of L_X/L_bol with time.


title: The Local Hole in the Galaxy Distribution: New Optical Evidence

abstract:
  We present a new CCD survey of galaxies within the N and S strips of the
2dFGRS areas. We use the new CCD data to check the photographic photometry
scales of the 2dFGRS, APMBGC, APM-Stromlo Redshift Survey, Durham-UKST (DUKST)
survey, Millenium Galaxy Catalogue (MGC) and Sloan Digital Sky Survey (SDSS).
We find evidence for scale and zero-point errors in the 2dFGRS northern field,
DUKST and APM data of 0.10, 0.24 and 0.31 mag. respectively; we find excellent
agreement with the MGC and SDSS photometry. We find conclusive evidence that
the S counts with B<17 mag are down by ~30% relative to both the N counts and
to the models of Metcalfe et al. We further compare the n(z) distributions from
the B<17 mag. DUKST and B<19.5 2dFGRS redshift surveys using the corrected
photometry. While the N n(z) from 2dFGRS appears relatively homogeneous over
its whole range, the S n(z) shows a 30% deficiency out to z=0.1; at higher
redshifts it agrees much better with the N n(z) and the homogeneous model n(z).
The DUKST n(z) shows that the S `hole' extends over a 20 by 75 degree squared
area. The troughs with z<0.1 in the DUKST n(z) appear deeper than for the
fainter 2dFGRS data. This may be evidence that the local galaxy distribution is
biased on >50 h-1 Mpc scales which is unexpected in a Lambda-CDM cosmology.
Finally, since the Southern local void persists over the full area of the APM
and APMBGC with a ~25% deficiency in the counts below B~17, this means that its
extent is ~300 h-1 Mpc by 300 h-1 Mpc on the sky as well as ~300 h-1 Mpc in the
redshift direction. Such a 25% deficiency extending over ~10^7 h-3 Mpc^3 may
imply that the galaxy correlation function's power-law behaviour extends to
\~150 h-1 Mpc with no break and show more excess large-scale power than
detected in the 2dFGRS correlation function or expected in the Lambda-CDM
cosmology.


title: The Local Hole in the Galaxy Distribution: Evidence from 2MASS

abstract:
  Using the bright galaxy counts from the 2 Micron All Sky Survey (2MASS)
second incremental release, two techniques for probing large-scale structure at
distances of ~150 h-1 Mpc are investigated. First, we study the counts from two
sets of six 5 degree by ~80 degree strips in the two galactic caps. In the six
southern strips a deficit of ~30% was found relative to a predicted homogeneous
distribution at K~11. These strips were also in good agreement with a model
incorporating the radial density function of the southern 2dF Galaxy Redshift
Survey (2dFGRS), which shows a deep underdensity between ~90 and 180 h-1 mpc.
These results indicate a very large `local hole' in the Southern Galactic Cap
(SGC) to >150 h-1 Mpc with a linear size across the sky of ~200 h-1 Mpc, but
with a significantly lower mean underdensity of ~30% than that suggested by the
bright APM SGC counts. The counts in the northern set of strips are low overall
but indicate a more varied pattern. When all the available 2MASS data with
|b|>30 were aggregated, they indicated underdensities of ~18% and ~30% at K~11
for the northern and southern areas respectively. Our second method uses the
ratio of the counts with 11.38<K<12.38 to 12.88<K<13.38 binned in 25 degree
squared areas; the counts from these areas provide a smoothed map over the sky
of the slope in the counts between K=11.38 and 13.38. The resulting map picks
out known rich clusters, demonstrating usefulness as a probe of LSS at
distances of <150 h-1 Mpc. Interestingly, the map also shows large regions,
\~100 degrees across, of steep counts in both hemispheres. Thus, the present
2MASS data suggest the presence of a potentially huge contiguous void
stretching from south to north, indicating the possible presence of significant
power on scales of >300 h-1 Mpc in the galaxy power spectrum.


title:
Spin-perpendicular kicks from evanescent binaries formed in the
  aftermath of rotational core-collapse and the nature of the observed bimodal
  distribution of pulsar peculiar velocities

abstract:
  If rotating core collapse leads to the formation of a proto-neutron star
binary in super-close orbit, then the lighter star, propelled toward the
minimum stable mass, explodes. The neutron star (or black hole) that remains
acquires a spin-perpendicular kick of very large amplitude. Kicks of the type
are required to explain the geodesic precession in double neutron star binaries
such as B1913+16. On the contrary, spin-kick alignment has been claimed for the
Vela and Crab pulsars whose kicks are relatively small. We propose that the
larger kick component, when present in a pulsar, results from the disruption of
an evanescent proto-neutron star binary and is spin perpendicular; the smaller
kick component is associated to some other mechanism that leads to less
vigorous kicks, predominantly parallel to the spin, because of phase averaging.
This gives rise to a "bimodal distribution" in the peculiar velocities of
neutron stars, as observed in the pulsar sample. The kick velocity is found to
scale with the mass of the star that remains as M^(-2/3). This scenario can
explain the run-away black hole GRO J1655-40, the first to show evidence for a
natal kick.


title: Planck scale still safe from stellar images

abstract:
  The recent paper of Lieu and Hillman [1] that a possible, (birefringence
like) phase difference ambiguity coming from Planck effects would alter stellar
images of distant sources is questioned. Instead for {\em division of
wavefront} interference and diffraction phenomena, initial (lateral) coherence
is developed simply by propagation of rays (cf. van Cittert-Zernike theorem).
This case is strongly immune to quantum gravity influences that could tend to
reduce phase coherence. The phase ambiguity, if actually present, could reduce
any underlying polarization of the light rays.


title: STELIB: a library of stellar spectra at R~2000

abstract:
  We present STELIB, a new spectroscopic stellar library, available at
http://webast.ast.obs-mip.fr/stelib . STELIB consists of an homogeneous library
of 249 stellar spectra in the visible range (3200 to 9500A), with an
intermediate spectral resolution (~3A) and sampling (1A). This library includes
stars of various spectral types and luminosity classes, spanning a relatively
wide range in metallicity. The spectral resolution, wavelength and spectral
type coverage of this library represents a substantial improvement over
previous libraries used in population synthesis models. The overall absolute
photometric uncertainty is 3%.


title: On the Detectability of the Cosmic Dark Ages: 21-cm Lines from Minihalos

abstract:
  In the standard Cold Dark Matter (CDM) theory of structure formation,
virialized minihalos (with T_vir = 10,000 K or less) form in abundance at high
redshift (z > 6), during the cosmic "dark ages." The hydrogen in these
minihalos, the first nonlinear baryonic structures to form in the universe, is
mostly neutral and sufficiently hot and dense to emit strongly at the 21-cm
line. We calculate the emission from individual minihalos and the radiation
background contributed by their combined effect. Minihalos create a "21-cm
forest" of emission lines. We predict that the angular fluctuations in this
21-cm background should be detectable with the planned LOFAR and SKA radio
arrays, thus providing a direct probe of structure formation during the "dark
ages." Such a detection will serve to confirm the basic CDM paradigm while
constraining the background cosmology parameters, the shape of the
power-spectrum of primordial density fluctuations, the onset and duration of
the reionization epoch, and the conditions which led to the first stars and
quasars. We present results here for the currently-favored, flat LCDM model,
for different tilts of the primordial power spectrum. These minihalos will also
cause a "21-cm forest" of absorption lines, as well, in the spectrum of radio
continuum sources at high redshift, if the latter came into existence before
the end of reionization.


title: Density Profiles of Dark Halos from their Mass Accretion Histories

abstract:
  We use the universal mass accretion history recently reported for simulations
of halo formation in the cold dark matter model (CDM) to analyze the formation
and growth of a single halo. We derive the time-dependent density profile three
different ways, based upon three approximations of successively greater
realism: equilibrium, radial orbits, and a fluid approximation. For the
equilibrium model, the density profile is well-fit by either an NFW or Moore
profile over a limited range of radii and scale factors. For the radial orbit
model, we find profiles which are generally steeper than the NFW profile, with
an inner logarithmic slope approaching -2, consistent with a purely radial
collisionless system. In the fluid approximation, we find good agreement with
the NFW and Moore profiles for radii resolved by N-body simulations (r/r_200 >
0.01), and an evolution of concentration parameter nearly identical to that
found in N-body simulations. The evolving structure of cosmological halos is
therefore best understood as the effect of a time-varying rate of mass infall
on a smoothly distributed, isotropic, collisionless fluid.


title:
Measuring the cosmological background of relativistic particles with
  WMAP

abstract:
  We show that the first year results of the Wilkinson Microwave Anisotropy
Probe (WMAP) constrain very efficiently the energy density in relativistic
particles in the universe. We derive new bounds on additional relativistic
degrees of freedom expressed in terms of an excess in the effective number of
light neutrinos Delta N_eff. Within the flat LambdaCDM scenario, the allowed
range is Delta N_eff < 6 (95% CL) using WMAP data only, or -2.6 < Delta N_eff <
4 with the prior H_0= 72 \pm 8 km/s/Mpc. When other cosmic microwave background
and large scale structure experiments are taken into account, the window
shrinks to -1.6 < Delta N_eff < 3.8. These results are in perfect agreement
with the bounds from primordial nucleosynthesis. Non-minimal cosmological
models with extra relativistic degrees of freedom are now severely restricted.


title: Metallicity effects in Photon Dominated Regions: Clumpy clouds

abstract:
  Several galaxies, such as dwarfs and Irregulars as well as outer galactic
clouds have low metallicity. At low metallicities a reduction in the amount of
dust and heavy elements plays a significant role on the chemistry as well as
the heating and cooling of the gas in the molecular regions, called as Photon
Dominated Regions (PDRs). We present here the effects of reduced metallicity in
PDRs and study the important PDR cooling lines ([CII], [CI] and CO). Moreover
many observational evidences suggest that molecular clouds are clumpy. We model
the molecular emission from galaxies incorporating a mass spectrum of clumps.
We also compare our results with the semi-analytical results obtained by
Bolatto et al. (1999).


title: Photoevaporation of Minihalos during Reionization

abstract:
  We present the first gas dynamical simulations of the photoevaporation of
cosmological minihalos overtaken by the ionization fronts which swept through
the IGM during reionization in a LCDM universe, including the effects of
radiative transfer. We demonstrate the phenomenon of I-front trapping inside
minihalos, in which the weak, R-type fronts which traveled supersonically
across the IGM decelerated when they encountered the dense, neutral gas inside
minihalos, becoming D-type I-fronts, preceded by shock waves. For a minihalo
with virial temperature T_vir < 10,000 K, the I-front gradually burned its way
through the minihalo which trapped it, removing all of its baryonic gas by
causing a supersonic, evaporative wind to blow backwards into the IGM, away
from the exposed layers of minihalo gas just behind the advancing I-front.
  Such hitherto neglected feedback effects were widespread during reionization.
N-body simulations and analytical estimates of halo formation suggest that
sub-kpc minihalos such as these, with T_vir < 10,000 K, were so common as to
dominate the absorption of ionizing photons. This means that previous estimates
of the number of ionizing photons per H atom required to complete reionization
which neglected this effect may be too low. Regardless of their effect on the
progress of reionization, however, the minihalos were so abundant that random
lines of sight thru the high-z universe should encounter many of them, which
suggests that it may be possible to observe the processes described here in the
absorption spectra of distant sources.


title:
A new map of neutrino cosmology - revised bounds on the number of
  neutrino species and the cosmological lepton asymmetry from WMAP data

abstract: The paper has been withdrawn


title:
Multi-Color Light Curves of Type Ia Supernovae on the Color-Magnitude
  Diagram: a Novel Step Toward More Precise Distance and Extinction Estimates

abstract:
  We show empirically that fits to the color-magnitude relation of Type Ia
supernovae after optical maximum can provide accurate relative extragalactic
distances. We report the discovery of an empirical color relation for Type Ia
light curves: During much of the first month past maximum, the magnitudes of
Type Ia supernovae defined at a given value of color index have a very small
magnitude dispersion; moreover, during this period the relation between $B$
magnitude and $B-V$ color (or $B-R$ or $B-I$ color) is strikingly linear, to
the accuracy of existing well-measured data. These linear relations can provide
robust distance estimates, in particular, by using the magnitudes when the
supernova reaches a given color. After correction for light curve strech factor
or decline rate, the dispersion of the magnitudes taken at the intercept of the
linear color-magnitude relation are found to be around 0$^m$.08 for the
sub-sample of supernovae with \BVm $\le 0^m.05$, and around 0$^m$.11 for the
sub-sample with \BVm $\le 0^m.2$. This small dispersion is consistent with
being mostly due to observational errors. The method presented here and the
conventional light curve fitting methods can be combined to further improve
statistical dispersions of distance estimates. It can be combined with the
magnitude at maximum to deduce dust extinction. The slopes of the
color-magnitude relation may also be used to identify intrinsically different
SN Ia systems. The method provides a tool that is fundamental to using SN Ia to
estimate cosmological parameters such as the Hubble constant and the mass and
dark energy content of the universe.


title:
CHANDRA/VLA Follow-up of TeV J2032+4131, the Only Unidentified TeV
  Gamma-ray Source

abstract:
  The HEGRA Cherenkov telescope array group recently reported a steady and
extended unidentified TeV gamma-ray source lying at the outskirts of Cygnus
OB2. This is the most massive stellar association known in the Galaxy,
estimated to contain ~2600 OB type members alone. It has been previously argued
that the large scale shocks and turbulence induced by the multiple interacting
supersonic winds from the many young stars in such associations may play a role
in accelerating Galactic cosmic rays. Indeed, Cyg OB2 also coincides with the
non-variable MeV-GeV range unidentified EGRET source, 3EG 2033+4118. We report
on the near-simultaneous follow-up observations of the extended TeV source
region with the CHANDRA X-ray Observatory and the Very Large Array (VLA) radio
telescope obtained in order to explore this possibility. Analysis of the CO,
HI, and IRAS 100 micron emissions shows that the TeV source region coincides
with an outlying sub-group of powerful OB stars which have evacuated or
destroyed much of the ambient atomic, molecular and dust material, and which
may be related to the very high-energy emissions. An interesting SNR-like
structure is also revealed near the TeV source region in the CO, HI and radio
emission maps. Applying a numerical simulation which accurately tracks the
radio to gamma-ray emission from primary hadrons as well as primary and
secondary e+/-, we find that the broadband spectrum of the TeV source region
favors a predominantly nucleonic - rather than electronic - origin of the
high-energy flux, though deeper X-ray and radio observations are needed to
confirm this. A very reasonable, ~0.1%, conversion efficiency of Cyg OB2's
extreme stellar wind mechanical luminosity to nucleonic acceleration to ~PeV
(10^15 eV) energies is sufficient to explain the multifrequency emissions.


title:
N-body simulations with two-orders-of-magnitude higher performance using
  wavelets

abstract:
  Noise is a problem of major concern for N-body simulations of structure
formation in the early Universe, of galaxies and plasmas. Here for the first
time we use wavelets to remove noise from N-body simulations of disc galaxies,
and show that they become equivalent to simulations with two orders of
magnitude more particles. We expect a comparable improvement in performance for
cosmological and plasma simulations. Our wavelet code will be described in a
following paper, and will then be available on request.


title: Serendipitous discovery of seven new southern L-dwarfs

abstract:
  We report the discovery of seven hitherto unknown L-dwarfs found as a result
of a spectroscopic search for distant AGB stars. Their far-red and
near-infrared colours are very similar to known dwarfs of the same spectral
type. One new object is among the ~30 brightest L-dwarfs, with K_s=12.12, and
is nearby, ~20pc. Using low resolution spectroscopy from the Danish 1.54 m ESO
telescope, spectral types in the range L0.5 - L5 are derived for these seven
L-dwarfs by direct comparison to L-type standards taken from Kirkpatrick et al.
(1999). Distances are determined from existing calibrations, and together with
measured proper motions, yield kinematics for the seven new dwarfs consistent
with that expected for the solar neighbourhood disk population.


title: Formation of the First Stars by Accretion

abstract:
  The process of star formation from metal-free gas is investigated by
following the evolution of accreting protostars with emphasis on the properties
of massive objects. The main aim is to establish the physical processes that
determine the upper mass limit of the first stars. Although the consensus is
that massive stars were commonly formed in the first cosmic structures, our
calculations show that their actual formation depends sensitively on the mass
accretion rate and its time variation. Even in the rather idealized case in
which star formation is mainly determined by dot{M}acc, the characteristic mass
scale of the first stars is rather uncertain. We find that there is a critical
mass accretion rate dot{M}crit = 4 10^{-3} Msun/yr that separates solutions
with dot{M}acc< dot{M}crit in which objects with mass >> 100 Msun can form,
provided there is sufficient matter in the parent clouds, from others
(dot{M}acc > dot{M}crit) where the maximum mass limit decreases as dot{M}acc
increases. In the latter case, the protostellar luminosity reaches the
Eddington limit before the onset of hydrogen burning at the center via the
CN-cycle. This phase is followed by a rapid and dramatic expansion of the
radius, possibly leading to reversal of the accretion flow when the stellar
mass is about 100Msun. (abridged)


title: Intercalibration of Cherenkov Telescopes in Telescope Arrays

abstract:
  A simple analysis technique is described which allows to intercalibrate the
response of imaging atmospheric Cherenkov telescopes in stereoscopic telescope
arrays at a level of 1-2%.


title: Search for TeV gamma ray emission from the Andromeda galaxy

abstract:
  Using the HEGRA system of imaging atmospheric Cherenkov telescopes, the
Andromeda galaxy (M31) was surveyed for TeV gamma ray emission. Given the large
field of view of the HEGRA telescopes, three pointings were sufficient to cover
all of M31, including also M32 and NGC205. No indications for point sources of
TeV gamma rays were found. Upper limits are given at a level of a few percent
of the Crab flux. A specific search for monoenergetic gamma-ray lines from
annihilation of supersymmetric dark matter particles accumulating near the
center of M31 resulted in flux limits in the 10^-13/cm^2s range, well above the
predicted MSSM flux levels except for models with pronounced dark-matter spikes
or strongly enhanced annihilation rates.


title:
G0.087-0.087, a highly polarized flat spectrum filament near the
  Galactic Centre Arc

abstract:
  32 GHz observations with the Effelsberg 100-m telescope revealed a highly
polarized Galactic Centre filament: G0.087-0.087, running parallel to the
well-known Arc structure. It has a similar flat spectrum, but it is an order of
magnitude weaker. G0.087-0.087 is about 2.5' or 6.2 pc long and located at the
western boundary of the expanding molecular cloud G0.11-0.11. This unusual
cloud is also visible in X-rays and known to interact on its eastern periphery
with the Arc. Acceleration of highly relativistic particles at the surface of
G0.11-0.11 seems necessary to explain the properties of both structures. The
new filament supports previous findings on the existence of a strong poloidal
magnetic field throughout the Galactic Centre region.


title: The recent X-ray history of NGC 5506

abstract:
  We present a detailed discussion of the spectral and spatial components of
NGC 5506, based on XMM-Newton, Chandra and BeppoSAX observations. The overall
picture consists of a nucleus absorbed by cold gas with column density of
$\approx10^{22}$ cm$^{-2}$ and surrounded by a Compton-thick torus, whose
existence is inferred by a cold reflection component and an iron K$\alpha$
line. On a much larger scale, a photoionized gas extended on $\approx350$ pc
reprocesses the nuclear radiation, producing a soft excess and ionized iron
lines. Noteworthy, we find no evidence for the presence of the accretion disc.


title: Optical and near-infrared observations of the GRB020405 afterglow

abstract:
  (Abridged) We report on observations of the optical and NIR afterglow of
GRB020405. Ground-based optical observations started about 1 day after the GRB
and spanned a period of ~10 days; archival HST data extended the coverage up to
70 days after the GRB. We report the first detection of the afterglow in NIR
bands. The detection of emission lines in the optical spectrum indicates that
the GRB is located at z = 0.691. Absorptions are also detected at z = 0.691 and
at z = 0.472. The latter system is likely caused by clouds in a galaxy located
2 arcsec southwest of the GRB host. Hence, for the first time, the galaxy
responsible for an intervening absorption system in the spectrum of a GRB
afterglow is identified. Optical and NIR photometry indicates that the decay in
all bands follows a single power law of index alpha = 1.54. The late-epoch VLT
and HST points lie above the extrapolation of this power law, so that a plateau
is apparent in the VRIJ light curves at 10-20 days after the GRB. The light
curves at epochs later than day ~20 after the GRB are consistent with a
power-law decay with index alphaprime = 1.85. We suggest that this deviation
can be modeled with a SN having the same temporal profile as SN2002ap, but 1.3
mag brighter at peak, and located at the GRB redshift. Alternatively, a shock
re-energization may be responsible for the rebrightening. A polarimetric R-band
measurement shows that the afterglow is polarized, with P = 1.5 % and theta =
172 degrees. Optical-NIR spectral flux distributions show a change of slope
across the J band which we interpret as due to the presence of nu_c. The
analysis of the multiwavelength spectrum within the fireball model suggests
that a population of relativistic electrons produces the optical-NIR emission
via synchrotron in an adiabatically expanding blastwave, and the X-rays via IC.


title: X-rays from Cataclysmic Variables

abstract:
  Cataclysmic Variables are a distinct class of interacting binaries,
transferring mass from a donor star to a degenerate accretor, a white dwarf. We
here review X-ray observations of these systems, with some emphasis on what has
been achieved in the last decade.


title: Dynamical Evolution of Planets in Disks

abstract:
  We study the evolution of a system consisting of two protoplanets still
embedded in a protoplanetary disk. Results of two different numerical
approaches are presented. In the first kind of model the motion of the disk
material is followed by fully viscous hydrodynamical simulations, and the
planetary motion is determined by N-body calculations including exactly the
gravitational potential from the disk material. In the second kind we only
solve the N-body part and add additional analytically given forces which model
the effect of the torques of the disk. This type of modeling is of course
orders of magnitudes faster than the full hydro-model. Another advantage of
this two-fold approach is the possibility of adjusting the otherwise unknown
parameters of the simplified model.
  The results give very good agreement between the methods. Using two different
initial setups for the planets and disk, we obtain in the first case a resonant
trapping into the 3:1 resonance, and in the second case a trapping into the 2:1
resonance. Resonant capture leads to a rise in the eccentricity and to an
alignment of the of the spatial orientation of orbits. The characteristics of
the numerical results agree very favorably with those of 3 observed planetary
systems (GJ 876, HD 82943, and 55 Cnc) known to be in mean motion resonances.


title: Quantum corrections to microscopic diffusion constants

abstract:
  We review the state of the art regarding the computation of the resistance
coefficients in conditions typical of the stellar plasma, and compare the
various results studying their effect on the solar model. We introduce and
discuss for the first time in an astrophysical context the effect of quantum
corrections to the evaluation of the resistance coefficients, and provide
simple yet accurate fitting formulae for their computation. Although the
inclusion of quantum corrections only weakly modifies the solar model, their
effect is growing with density, and thus might be of relevance in case of
denser objects like, e.g., white dwarfs.


title:
Coded-Mask Imaging in Gamma-Ray Astronomy - Separating the Real and
  Imaginary parts of a Complex subject

abstract:
  The concept of coded mask imaging in theory and in practice is reviewed, with
particular emphasis on image reconstruction techniques. The techniques are
simple in principle but become more complicated when one takes into account
real, `as-built', instruments, as opposed to idealised imaginary ones.
Procedures are discussed with particular reference to the instruments of
Integral.


title: Chandra and XMM-Newton observations of Tololo 0109-383

abstract:
  We present and discuss Chandra and XMM-Newton observations of the Seyfert 2
galaxy and Compton-thick absorbed source, Tololo~0109-383. The hard X-ray
emission (i.e. above $\sim$2 keV), is dominated by a spatially unresolved
reflection component, as already discovered by previous ASCA and BeppoSAX
observ ations. The soft X-ray emission is partly ($\sim$15%) extended over
about 1 kpc. Below 2 keV, the spectrum is very steep and two emission lines,
probably due to recombination to He-like ions of oxygen and neon, are clearly
present. Combining X-rays and optical information taken from the literature, we
propose an overall scenario for the nuclear regions of this source.


title: Follow-up of the 9C survey: Initial results

abstract:
  We present initial results from a follow-up of the 9C survey, complete to 25
mJy at 15 GHz, designed to assemble and investigate a sample of young
radiosources. We have made radio continuum maps of 111 sources at frequencies
spanning 1.4-43 GHz, and classified them according to their radio size and
spectral index between 1.4 and 4.8 GHz. We find that selection at 15 GHz is
twice as efficient at picking Gigahertz Peaked Spectrum (GPS) sources as
selection at 5 GHz. Optical follow-up has now begun; imaging of GPS and compact
steep spectrum sources suggests that a significant fraction of the host
galaxies have close companions or disturbed morphologies.


title: Is the present expansion of the universe really accelerating?

abstract:
  The current observations are usually explained by an accelerating expansion
of the present universe. However, with the present quality of the supernovae Ia
data, the allowed parameter space is wide enough to accommodate the
decelerating models as well. This is shown by considering a particular example
of the dark energy equation-of-state $w_\phi\equiv p_\phi/\rho_\phi=-1/3$,
which is equivalent to modifying the \emph{geometrical curvature} index $k$ of
the standard cosmology by shifting it to $(k-\alpha)$ where $\alpha$ is a
constant. The resulting decelerating model is consistent with the recent CMB
observations made by WMAP, as well as, with the high redshift supernovae Ia
data including SN 1997ff at $z= 1.755$. It is also consistent with the newly
discovered supernovae SN 2002dc at $z=0.475$ and SN 2002dd at $z=0.95$ which
have a general tendency to improve the fit.


title:
Spherical collapse and mass function of rich clusters in models with
  curvature and cosmological constant

abstract:
  We have analyzed the dependences of the threshold value of amplitude of
linear density fluctuation collapsed at the current epoch, $\delta_c$, and its
overdensity after virialization, $\Delta_c$, on matter density content, 3D
curvature parameter and cosmological constant. Though the range for the
threshold values of perturbation amplitude is quite narrow - $1.55\le
\delta_c\le 1.75$ in the region of parameters $-0.4\le\Omega_k\le0.4$,
$0\le\Omega_{\Lambda}\le 1$, $0.1\le\Omega_m\le 1$, the difference in the
concentrations of rich clusters of galaxies (calculated within the
Press-Schechter formalism framework) with real and with canonical values of
$\delta_c$ reaches, and for some models exceeds, 30%. The range of changes for
the overdensity after virialization, $\Delta_c$, is considerably wider for the
same region of parameters: $60\le\Delta_c\le180$. It results into difference up
to $\sim40$% between the X-ray temperatures of gas, as calculated for these
values and for the canonical value of $\Delta_c=178$. Also we have found
analytical approximations of the dependences
$\delta_c(\Omega_m,\Omega_{\Lambda})$ and $\Delta_c(\Omega_m,\Omega_{\Lambda})$
with their accuracies for above mentioned region of parameters being no worse
than 0.2% and 1.7% respectively.


title:
Galaxies as Fluctuations in the Ionizing Background Radiation at Low
  Redshift

abstract:
  Some Lyman continuum photons are likely to escape from most galaxies, and
these can play an important role in ionizing gas around and between galaxies,
including gas that gives rise to Lyman alpha absorption. Thus the gas
surrounding galaxies and in the intergalactic medium will be exposed to varying
amounts of ionizing radiation depending upon the distances, orientations, and
luminosities of any nearby galaxies. The ionizing background can be
recalculated at any point within a simulation by adding the flux from the
galaxies to a uniform quasar contribution. Normal galaxies are found to almost
always make some contribution to the ionizing background radiation at redshift
zero, as seen by absorbers and at random points in space. Assuming that about 2
percent of ionizing photons escape from a galaxy like the Milky Way, we find
that normal galaxies make a contribution of at least 30 to 40 percent of the
assumed quasar background. Lyman alpha absorbers with a wide range of neutral
column densities are found to be exposed to a wide range of ionization rates,
although the distribution of photoionization rates for absorbers is found to be
strongly peaked. On average, less highly ionized absorbers are found to arise
farther from luminous galaxies, while local fluctuations in the ionization rate
are seen around galaxies having a wide range of properties.


title:
The optical to soft X-ray spectrum of the ultrasoft broad-line AGN RE
  J2248-511

abstract:
  We present a series of monitoring observations of the ultrasoft broad-line
AGN RE J2248-511 with XMM-Newton. Previous X-ray observations showed a
transition from a very soft state to a harder state five years later. We find
that the ultrasoft X-ray excess has re-emerged, yet there is no change in the
hard power-law. Reflection models with a reflection fraction of >15, and
Comptonisation models with two components of different temperatures and optical
depths can be fit to the spectrum, but cannot be constrained. The best
representation of the spectrum is a model consisting of two blackbodies
(kT~90,200 eV) plus a power-law (Gamma=1.8). We also present simultaneous
optical and infrared data showing that the optical spectral slope also changes
on timescales of years. If the optical to X-ray flux comes primarily from a
Comptonised accretion disk we obtain estimates for the black hole mass of ~1e8
solar, accretion rate ~0.8xEddington and disk inclination cosi>0.8.