title:
A hot story with many tales: the qWR star HD 45166. I- Observations and
  system parameters

abstract:
  The binary star HD 45166 has been observed since 1922 but its orbital period
has not yet been found. It is considered a peculiar Wolf-Rayet star, and its
assigned classification varied along the years. High-resolution spectroscopic
observations show that the spectrum, in emission and in absorption, is quite
rich. The emission lines have great diversity of widths and profiles. The
Hydrogen and Helium lines are systematically broader than the CNO lines.
Assuming that HD 45166 is a double-line spectroscopic binary, it presents an
orbital period of P = 1.596 days, with an eccentricity of e = 0.18. In
addition, a search for periodicity using standard techniques reveals that the
emission lines present at least two other periods, of 5 hours and of 15 hours.
The secondary star has a spectral type of B7 V and, therefore, should have a
mass of about 4.8 solar masses. Given the radial velocity amplitudes, we
determined the mass of the hot (primary) star as being 4.2 solar masses and the
inclination angle of the system, i = 0.77 degr. As the eccentricity of the
orbit is non zero, the Roche lobes increase and decrease as a function of the
orbital phase. At periastron, the secondary star fills its Roche lobe. The
distance to the star has been re-determined as d = 1.3 kpc and a color excess
of E(B-V)=0.155 has been derived. This implies an absolute B magnitude of -0.6
for the primary star and -0.7 for the B7 star. We suggest that the discrete
absorption components (DACs) observed in the ultraviolet with a periodicity
similar to the orbital period may be induced by periastron events.


title: Nonlinear Evolution of the Magnetothermal Instability in Two Dimensions

abstract:
  In weakly magnetized, dilute plasmas in which thermal conduction along
magnetic field lines is important, the usual convective stability criterion is
modified. Instead of depending on entropy gradients, instability occurs for
small wavenumbers when (dP/dz)(dln T/dz) > 0, which we refer to as the Balbus
criterion. We refer to the convective instability that results in this regime
as the magnetothermal instability (MTI). We use numerical MHD simulations which
include anisotropic electron heat conduction to follow the growth and
saturation of the MTI in two-dimensional, plane parallel atmospheres that are
unstable according to the Balbus criterion. The linear growth rates measured in
the simulations agree with the weak field dispersion relation. We investigate
the effect of strong fields and isotropic conduction on the linear properties
and nonlinear regime of the MTI. In the nonlinear regime, the instability
saturates and convection decays away, when the atmosphere becomes isothermal.
Sustained convective turbulence can be driven if there is a fixed temperature
difference between the top and bottom edges of the simulation domain, and if
isotropic conduction is used to create convectively stable layers that prevent
the formation of unresolved, thermal boundary layers. The largest component of
the time-averaged heat flux is due to advective motions. These results have
implications for a variety of astrophysical systems, such as the temperature
profile of hot gas in galaxy clusters, and the structure of radiatively
inefficient accretion flows.


title:
"PAH" emission bands in selected planetary nebulae: a study of the
  behaviour with gas phase C/O ratio

abstract:
  Airborne and space-based low-resolution spectroscopy in the 1980s discovered
tantalizing quantitative relationships between the gas phase C/O abundance
ratio in planetary nebulae (PNe) and the fractions of total far-infrared
luminosity radiated by the 7.7 and 11.3 micron bands (the C=C stretch and C-H
bend, respectively), of polycyclic aromatic hydrocarbons. Only a very small
sample of nebulae was studied in this context, limited by airborne observations
of the 7.7 micron band, or the existence of adequate IRAS Low Resolution
Spectrometer data for the 11.3 micron band. To investigate these trends
further, we have expanded the sample of planetaries available for this study
using Infrared Space Observatory (ISO) low-resolution spectra secured with the
Short Wavelength Spectrometer (SWS) and the Long Wavelength Spectrometer (LWS).
The new sample of 43 PNe, of which 17 are detected in PAH emission, addresses
the range from C/O=0.2-13 with the objective of trying to delineate the
pathways by which carbon dust grains might have formed in planetaries. For the
7.7-micron and 11.3- micron bands, we confirm that the ratio of band strength
to total infrared luminosity is correlated with the nebular C/O ratio.
Expressed in equivalent width terms, the cut-on C/O ratio for the 7.7-micron
band is found to be 0.6(+0.2,-0.4), in good accord with that found from
sensitive ground-based measurements of the 3.3-micron band too.


title:
Integrated spectral analysis of 18 concentrated star clusters in the
  Small Magellanic Cloud

abstract:
  We present in this study flux-calibrated integrated spectra in the range
3600-6800A for 18 concentrated SMC clusters. Cluster reddening values were
estimated by interpolation between the extinction maps of Burstein & Heiles
(1982, AJ, 87, 1165) and Schlegel et al. (1998, ApJ, 500, 525). The cluster
parameters were derived from the template matching procedure by comparing the
line strengths and continuum distribution of the cluster spectra with those of
template cluster spectra with known parameters and from the equivalent width
(EW) method. In this case, new calibrations were used together with diagnostic
diagrams involving the sum of EWs of selected spectral lines. A very good
agreement between ages derived from both methods was found. The final cluster
ages obtained from the weighted average of values taken from the literature and
the present measured ones range from 15 Mr (e.g. L51) to 7 Gyr (K3). Metal
abundances have been derived for only 5 clusters from the present sample, while
metallicity values directly averaged from published values for other 4 clusters
have been adopted. Combining the present cluster sample with 19 additional SMC
clusters whose ages and metal abundances were put onto a homogeneous scale, we
analyse the age and metallicity distributions in order to explore the SMC star
formation history and its spatial extent. By considering the distances of the
clusters from the SMC centre instead of their projections onto the right
ascension and declination axes, the present age-position relation suggests that
the SMC inner disk could have been related to a cluster formation episode which
reached the peak ~2.5 Gyr ago. Evidence for an age gradient in the inner SMC
disk is also presented.


title:
The 2MASS galaxy angular power spectrum: Probing the galaxy distribution
  to Gigaparsec scales

abstract:
  We present an angular power spectrum analysis of the 2MASS full release
extended source catalogue. The main sample used includes 518,576 galaxies below
an extinction-corrected magnitude of K=13.5 and limited to |b|>20. The power
spectrum results provide an estimate of the galaxy density fluctuations at
extremely large scales, r<1000 Mpc. We compare this with mock predictions
constructed from the LCDM Hubble Volume mock catalogue. We find that over the
range 1<l<100 the 2MASS C_l is steeper than that for the Hubble Volume model.
However, in the linear regime (l<30) there is good agreement between the two.
We investigate in detail the effects of possible sources of systematic error.
Converting linear power spectrum predictions for the form of the
three-dimensional matter power spectrum, P(k), and assuming a flat CDM
cosmology, a primordial n_s=1 spectrum and negligible neutrino mass, we perform
fits to the galaxy angular power spectrum at large linear scales (l<30,
corresponding to r>50 Mpc). We obtain constraints on the galaxy power spectrum
shape of Gamma=0.14+/-0.02, in good agreement with previous estimates inferred
at smaller scales. We also constrain the galaxy power spectrum normalisation to
(sigma_8 b_K)^2=1.36+/-0.10; in combination with previous constraints on
sigma_8 we infer a K-band bias of b_K=1.39+/-0.12. We are also able to provide
weak constraints on Omega_m h and Omega_b/Omega_m. These results are based on
the usual assumption that the errors derived from the Hubble Volume mocks are
applicable to all other models. If we instead assume that the error is
proportional to the C_l amplitude then the constraints weaken; for example it
becomes more difficult to reject cosmologies with lower Gamma.


title:
Structure and stellar content analysis of the open cluster M11 with
  2MASS photometry

abstract:
  An overall analysis of the structure and stellar content of M11 is presented,
thanks to the wide-angle 2MASS spatial coverage. We derive photometric and
structural parameters and discuss the spatial dependance of the luminosity and
mass functions. Photometric parameters basically agree with previous ones
mostly based on the optical. We obtained a core radius of 1.23pc and a tidal
radius of 29pc. In particular, the cluster is populous enough so that the tidal
radius could be obtained by fitting the three-parameter King profile to the
radial distribution of stars. We analyzed the spatial distribution of mass
functions, finding that the the slope changes from -0.73 in the core to +2.88
in the outer halo. The spatial distribution of mass function slopes derived
from 2MASS agrees with that derived from optical CCD data, which further
confirms the reliability of 2MASS data for future analyses of this kind at
comparable observational limits. We detect mass segregation up to distances
from the center of ~20arcmin. We emphasize that the mass function slope in the
core is flatter than anywhere else as a consequence of mass segregation. The
derived total cluster mass is ~11000 solar masses.


title: Period Relation for the 2:1 resonance in the GJ876 planetary system

abstract:
  The recent radial velocity Keck data for GJ876 in Laughlin et al. (2005) is
shown to be in good agreement, apart from a 6 m/s scatter, with a theoretical
calculation (Nauenberg, 2002) based on orbital parameters from a fit to the
earlier Keck data. The time variation of the periods of the inner and outer
planets, which are locked in a near 2:1 resonance, are evaluated, and their
mean values, Pi and Po, are shown to satisfy closely the relation Po/Pi=2+Po/P,
where P is the period for the retrograde precesion of the common mean
periastron of these planets.


title: Fitting Photometry of Blended Microlensing Events

abstract:
  We reexamine the usefulness of fitting blended lightcurve models to
microlensing photometric data. We find agreement with previous workers (e.g.
Wozniak & Paczynski) that this is a difficult proposition because of the
degeneracy of blend fraction with other fit parameters. We show that follow-up
observations at specific point along the lightcurve (peak region and wings) of
high magnification events are the most helpful in removing degeneracies. We
also show that very small errors in the baseline magnitude can result in
problems in measuring the blend fraction, and study the importance of
non-Gaussian errors in the fit results. The biases and skewness in the
distribution of the recovered blend fraction is discussed. We also find a new
approximation formula relating the blend fraction and the unblended fit
parameters to the underlying event duration needed to estimate microlensing
optical depth.


title:
Evolution of Stellar Bars in Live Axisymmetric Halos: Recurrent Buckling
  and Secular Growth

abstract:
  Evolution of stellar bars in disk galaxies is accompanied by dynamical
instabilities and secular changes. Following the vertical buckling instability,
the bars are known to weaken dramatically and develop a pronounced boxy/peanut
shape when observed edge-on. Using high-resolution N-body simulations of
stellar disks embedded in live axisymmetric dark matter halos, we have
investigated the long-term changes in the bar morphology, specifically the
evolution of the bar size, its vertical structure and exchange of angular
momentum. We find that following the initial buckling, the bar resumes its
growth from deep inside the corotation radius and follows the Ultra-Harmonic
resonance thereafter. We also find that this secular bar growth triggers a
spectacular secondary vertical buckling instability which leads to the
appearance of characteristic boxy/peanut/X-shaped bulges. The secular bar
growth is crucial for the recurrent buckling to develop. Furthermore, the
secondary buckling is milder, persists over a substantial period of time, ~3
Gyr, and can have observational counterparts. Overall, the stellar bars show
recurrent behavior in their properties and evolve by increasing their linear
and vertical extents, both dynamically and secularly. We also demonstrate
explicitly that the prolonged growth of the bar is mediated by continuous
angular momentum transfer from the disk to the surrounding halo, and that this
angular momentum redistribution is resonant in nature -- a large number of
lower resonances trap disk and halo particles and this trapping is robust, in a
broad agreement with the earlier results in the literature.


title: Galactic structure from the Calar Alto Deep Imaging Survey (CADIS)

abstract:
  We used 1627 faint (15.5< R<23) stars in five fields of the Calar Alto Deep
Imaging Survey (CADIS) to estimate the structure parameters of the Galaxy. The
results were derived by applying two complementary methods: first by fitting
the density distribution function to the measured density of stars
perpendicular to the Galactic plane, and second by modelling the observed
colors and apparent magnitudes of the stars in the field, using Monte Carlo
simulations. The best-fitting model of the Galaxy is then determined by
minimising the C-statistic, a modified chisquared. Our model includes a double
exponential for the stellar disk with scaleheights h_1 and h_2 and a power law
halo with exponent alpha. 24480 different parameter combinations have been
simulated. Both methods yield consistent results: the best fitting parameter
combination is alpha=3.0 (or alpha=2.5, if we allow for a flattening of the
halo with an axial ratio of (c/a)=0.6), h_1=300 pc, h_2=900 pc, and the
contribution of thick disk stars to the disk stars in the solar neighbourhood
is found to be between 4 and 10%.


title: A Radio Transient 0.1 pc from Sagittarius A*

abstract:
  We report the discovery of a transient radio source 2.7 arcsec (0.1 pc
projected distance) South of the Galactic Center massive black hole,
Sagittarius A*. The source flared with a peak of at least 80 mJy in March 2004.
The source was resolved by the Very Large Array into two components with a
separation of ~0.7 arcsec and characteristic sizes of ~0.2 arcsec. The two
components of the source faded with a power-law index of 1.1 +/- 0.1. We detect
an upper limit to the proper motion of the Eastern component of ~3 x 10^3 km
s^-1 relative to Sgr A*. We detect a proper motion of ~10^4 km s^-1 for the
Western component relative to Sgr A*. The transient was also detected at X-ray
wavelengths with the Chandra X-ray Observatory and the XMM-Newton telescope and
given the designation CXOGC J174540.0-290031. The X-ray source falls in between
the two radio components. The maximum luminosity of the X-ray source is ~10^36
erg s^-1, significantly sub-Eddington. The radio jet flux density predicted by
the X-ray/radio correlation for X-ray binaries is orders of magnitude less than
the measured flux density. We conclude that the radio transient is the result
of a bipolar jet originating in a single impulsive event from the X-ray source
and interacting with the dense interstellar medium of the Galactic Center.


title: Galaxy Cluster Masses Without Non-Baryonic Dark Matter

abstract:
  We apply the modified acceleration law obtained from Einstein gravity coupled
to a massive skew symmetric field, F_{\mu\nu\lambda}, to the problem of
explaining X-ray galaxy cluster masses without exotic dark matter. Utilizing
X-ray observations to fit the gas mass profile and temperature profile of the
hot intracluster medium (ICM) with King beta-models, we show that the dynamical
masses of the galaxy clusters resulting from our modified acceleration law fit
the cluster gas masses for our sample of 106 clusters without the need of
introducing a non-baryonic dark matter component. We are further able to show
for our sample of 106 clusters that the distribution of gas in the ICM as a
function of radial distance is well fit by the dynamical mass distribution
arising from our modified acceleration law without any additional dark matter
component. In previous work, we applied this theory to galaxy rotation curves
and demonstrated good fits to our sample of 101 LSB, HSB and dwarf galaxies
including 58 galaxies that were fit photometrically with the single parameter
(M/L)_{stars}. The results there were qualitatively similar to those obtained
using Milgrom's phenomenological MOND model, although the determined galaxy
masses were quantitatively different and MOND does not show a return to
Keplerian behavior at extragalactic distances. The results here are compared to
those obtained using Milgrom's phenomenological MOND model which does not fit
the X-ray galaxy cluster masses unless an auxiliary dark matter component is
included.


title:
Correlation between radio luminosity and X-ray timing frequencies in
  neutron star and black hole X-ray binaries

abstract:
  We report on correlations between radio luminosity and X-ray timing features
in X-ray binary systems containing low magnetic field neutron stars and black
holes. The sample of neutron star systems consists of 4U 1728-34, 4U 1820-34,
Ser X-1, MXB 1730-335, GX 13+1, the millisecond X-ray pulsars SAX J1808.4-3658
and IGR J00291+5934, and these are compared with the black hole system GX
339-4. The analysis has been done using data from pointed observations of the
Rossi X-ray Timing Explorer coordinated with radio observations. In the neutron
star systems the radio luminosity L_{R} is correlated with the characteristic
frequency of the L_{h} Lorentzian component detected contemporaneously in the
power spectrum, and anticorrelated with its strength. Similarly, in the black
hole system GX 339-4 L_{R} is correlated with the frequency of the L_{\ell}
component in the power spectrum, and anti-correlated with its strength. The
index of a power-law fit to the correlation is similar in both cases, L_{R}
\propto \nu^{~1.4} and L_{R} \propto (rms)^{-2.3}. At lower timing frequencies,
the radio luminosity is further found to be correlated with the characteristic
(break) frequency of the L_{b} component of the power spectra in the neutron
stars and, marginally, with the equivalent break frequency in GX 339-4. We
briefly discuss the coupling between the innermost regions of the accretion
disc and the production of the jet and, from the behaviour of the ms accreting
X-ray pulsars, the possible role of the NS magnetic field.


title: Parameterizing the Power Spectrum: Beyond the Truncated Taylor Expansion

abstract:
  The power spectrum is traditionally parameterized by a truncated Taylor
series: $ln P(k) = ln P_* + (n_*-1) ln(k/k_*) + {1/2} n'_* ln^2(k/k_*)$. It is
reasonable to truncate the Taylor series if $|n'_* ln(k/k_*)| << |n_*-1|$, but
it is not if $|n'_* ln(k/k_*)| \gtrsim |n_*-1|$. We argue that there is no good
theoretical reason to prefer $|n'_*| << |n_*-1|$, and show that current
observations are consistent with $|n'_* ln(k/k_*)| ~ |n_*-1|$ even for
$|ln(k/k_*)| ~ 1$. Thus, there are regions of parameter space, which are both
theoretically and observationally relevant, for which the traditional truncated
Taylor series parameterization is inconsistent, and hence it can lead to
incorrect parameter estimations. Motivated by this, we propose a simple
extension of the traditional parameterization, which uses no extra parameters,
but that, unlike the traditional approach, covers well motivated inflationary
spectra with $|n'_*| ~ |n_*-1|$. Our parameterization therefore covers not only
standard-slow-roll inflation models but also a much wider class of inflation
models. We use this parameterization to perform a likelihood analysis for the
cosmological parameters.


title: Astrophysical bounds on supersymmetric dark-matter Q-balls

abstract:
  Stable baryonic Q-balls, which appear in supersymmetric extensions of the
Standard Model, could form at the end of cosmological inflation from
fragmentation of the Affleck -- Dine condensate. We reconsider astrophysical
constraints on such Q-balls as dark matter candidates. Baryonic Q-balls
interact with matter by absorbing the baryon number and, effectively, leading
to a rapid baryon number non-conservation. We have recently shown that this
process can occur at a much faster rate than that used in previous
calculations. As a consequence, stability of neutron stars imposes a stringent
constraint on the types of Q-balls that can be dark matter. Only the Q-balls
that correspond to baryonic flat directions lifted by baryon-number violating
operators are allowed as dark-matter candidates.


title:
Disentangling the wind and the disk in the close surrounding of the
  young stellar object MWC297 with AMBER/VLTI

abstract:
  The young stellar object MWC297 is a B1.5Ve star exhibiting strong hydrogen
emission lines. This object has been observed by the AMBER/VLTI instrument in
2-telescope mode in a sub-region of the K spectral band centered around the Br
gamma line at 2.1656 microns. The object has not only been resolved in the
continuum with a visibility of 0.50+/-0.10, but also in the Br gamma line,
where the flux is about twice larger, with a visibility about twice smaller
(0.33+/-0.06). The continuum emission is consistent with the expectation of an
optically thick thermal emission from dust in a circumstellar disk. The
hydrogen emission can be understood by the emission of a halo above the disk
surface. It can be modelled as a latitudinal-dependant wind model and it
explains the width, the strength and the visibibility through the emission
lines. The AMBER data associated with a high resolution ISAAC spectrum
constrains the apparent size of the wind but also its kinematics.


title:
Observational Constraints on Accelerating Brane Cosmology with Exchange
  between the Bulk and Brane

abstract:
  We explore observational constraints on a cosmological brane-world scenario
in which the bulk is not empty. Rather, exchange of mass-energy between the
bulk and the bane is allowed. The evolution of matter fields to an observer on
the brane is then modified due to new terms in the energy momentum tensor
describing this exchange. We investigate the constraints from various
cosmological observations on the flow of matter from the bulk into the brane.
Interestingly, we show that it is possible to have a $\Lambda = 0$ cosmology to
an observer in the brane which satisfies standard cosmological constraints
including the CMB temperature fluctuations, Type Ia supernovae at high
redshift, and the matter power spectrum. This model even accounts for the
observed suppression of the CMB power spectrum at low multipoles. In this
cosmology, the observed cosmic acceleration is attributable to the flow of
matter from the bulk to the brane. A peculiar aspect of this cosmology is that
the present dark-matter content of the universe may be significantly larger
than that of a $\Lambda$CDM cosmology. Its influence, however, is offset by the
dark-radiation term. Possible additional observational tests of this new
cosmological paradigm are suggested.


title: Indirect evidence for short period magnetic cycles in W UMa stars

abstract:
  Complex period variations of five W UMa type binaries (AB And, OO Aql, DK
Cyg, V566 Oph, U Peg) were investigated by analyzing their O--C diagrams, and
several common features were found. Four of the five systems show secular
period variations at a constant rate on the order of |dP / dt 1/P | ~ 10E-7
1/yr. In the case of AB And, OO Aql, and U Peg a high-amplitude, nearly
one-century long quasi-sinusoidal pattern was also found. It might be explained
as light-time effect, or by some magnetic phenomena, although the mathematical,
and consequently the physical, parameters of these fits are very problematic,
as the obtained periods are very close to the length of the total data range.
The most interesting feature of the studied O--C diagrams is a low amplitude
(2-4 x 10E-3 d) modulation with a period around 18--20 yr in four of the five
cases. This phenomenon might be indirect evidence of some magnetic cycle in
late-type overcontact binaries as an analog to the observed activity cycles in
RS CVn systems.


title:
Radio pulsars around intermediate mass black holes in super stellar
  clusters

abstract:
  We study accretion in binaries hosting an intermediate mass black hole (IMBH)
of 1000 solar masses, and a donor star more massive than 15 solar masses. These
systems experience an active X-ray phase characterized by luminosities varying
over a wide interval, from <10^36 erg/s up to a few 10^40 erg/s typical of the
ultra luminous X-ray sources (ULXs). Roche lobe overflow on the zero-age main
sequence and donor masses above 20 solar masses can maintain a long-lived
accretion phase at the level required to feed a ULX source. In wide systems,
wind transfer rates are magnified by the focusing action of the IMBH yielding
wind luminosities around 10^38 erg/s. These high mass-IMBH binaries can be
identified as progenitors of IMBH-radio pulsar (PSR) binaries. We find that the
formation of an IMBH-PSR binary does not necessarely require the transit
through a ULX phase, but that a ULX can highlight a system that will evolve
into an IMBH-PSR, if the mass of the donor star is constrained to lie within 15
to 30 solar masses. We show that binary evolution delivers the pre-exploding
helium core in an orbit such that after explosion, the neutron star has a very
high probability to remain bound to the IMBH, at distances of 1-10 AU. The
detection of an IMBH-PSR binary in the Milky Way has suffered, so far, from the
same small number of statistics limit affecting the population of ULXs in our
Galaxy. Ongoing deeper surveys or next generation radio telescopes like SKA
will have an improved chance to unveil such intriguing systems. Timing analysis
of a pulsar orbiting around an IMBH would weigh the black hole in the still
uncharted interval of mass around 1000 solar masses


title: Spatial Evidence for Transition Radiation in a Solar Radio Burst

abstract:
  Microturbulence, i.e. enhanced fluctuations of plasma density, electric and
magnetic fields, is of great interest in astrophysical plasmas, but occurs on
spatial scales far too small to resolve by remote sensing, e.g., at ~ 1-100 cm
in the solar corona. This paper reports spatially resolved observations that
offer strong support for the presence in solar flares of a suspected radio
emission mechanism, resonant transition radiation, which is tightly coupled to
the level of microturbulence and provides direct diagnostics of the existence
and level of fluctuations on decimeter spatial scales. Although the level of
the microturbulence derived from the radio data is not particularly high,
<\Delta n^2 >/n^2 ~ 10^{-5}$, it is large enough to affect the charged particle
diffusion and give rise to effective stochastic acceleration. This finding has
exceptionally broad astrophysical implications since modern sophisticated
numerical models predict generation of much stronger turbulence in relativistic
objects, e.g., in gamma-ray burst sources.


title:
Inductive and Electrostatic Acceleration in Relativistic Jet-Plasma
  Interactions

abstract:
  We report on the observation of rapid particle acceleration in numerical
simulations of relativistic jet-plasma interactions and discuss the underlying
mechanisms. The dynamics of a charge-neutral, narrow, electron-positron jet
propagating through an unmagnetized electron-ion plasma was investigated using
a three-dimensional, electromagnetic, particle-in-cell computer code. The
interaction excited magnetic filamentation as well as electrostatic plasma
instabilities. In some cases, the longitudinal electric fields generated
inductively and electrostatically reached the cold plasma wave-breaking limit,
and the longitudinal momentum of about half the positrons increased by 50% with
a maximum gain exceeding a factor of 2 during the simulation period. Particle
acceleration via these mechanisms occurred when the criteria for Weibel
instability were satisfied.


title:
Using transport coefficients of cosmic rays in turbulent magnetic fields
  to determine hybrid viscosity in hot accretion disks around AGN

abstract:
  The nature of the viscosity operative in hot, two-temperature accretion disks
around AGN has been a long-standing, unsolved problem. It has been previously
suggested that protons, in conjunction with the turbulent magnetic field that
is likely to exist in the accretion disk, might be crucial in providing this
viscosity. Several authors have recently determined diffusion coefficients for
charged particles (cosmic rays) propagating in turbulent magnetic fields by
means of extensive Monte Carlo simulations. We use the diffusion coefficients
for protons determined by these simulations to find the effective mean free
path for protons in hot accretion disks. This in turn yields good estimates of
the viscosity due to energetic protons embedded in the turbulent magnetic field
of a hot, two-temperature accretion disk. We combine this with a simple
two-temperature accretion disk model to determine the Shakura-Sunyaev $\alpha$
viscosity parameter arising out of this mechanism. We find that protons
diffusing in the turbulent magentic field embedded in a hot accretion d isk
provide a physically reasonable source of viscosity in hot accretion disks
around AGN.


title:
VITRUV - Imaging close environments of stars and galaxies with the VLTI
  at milli-arcsec resolution

abstract:
  The VITRUV project has the objective to deliver milli-arcsecond
spectro-images of the environment of compact sources like young stars, active
galaxies and evolved stars to the community. This instrument of the VLTI second
generation based on the integrated optics technology is able to combine from 4
to 8 beams from the VLT telescopes. Working primarily in the near infrared, it
will provide intermediate to high spectral resolutions and eventually
polarization analysis. This paper summarizes the result from the concept study
led within the Joint Research Activity advanced instruments of the OPTICON
program.


title:
A Vertical Resonances of G-Mode Oscillations in Warped Disks and QPOs in
  Low-Mass X-Ray Binaries

abstract:
  Resonant oscillations in warped disks are examined in order to explain
high-frequency QPOs and horizontal-branch QPOs in low-mass X-ray binaries.
Different from our previous work, addressed to the same subjects, we relax in
this paper the assumption that the disks are isothermal in the vertical
direction. That is, the pressure, density, and temperature are assumed to be
distributed in the vertical direction with a polytropic relation, and the
polytropic index changes as the disk state changes. By this generalization and
by some subsidiaries we can qualitatively explain, within the framework of our
resonance model, observed large frequency variations in neutron-star QPOs and
little variations in black-hole QPOs. We consider vertical resonances of g-mode
oscillations, since they are most appropriate to explain observations.


abstract:
  I present an analysis of the XMM-Newton observations of four millisecond
pulsars, J0437-4715, J2124-3358, J1024-0719, and J0034-0534. The new data
provide strong evidence of thermal emission in the X-ray flux detected from the
first three objects. This thermal component is best interpreted as radiation
from pulsar polar caps covered with a nonmagnetic hydrogen atmosphere. A
nonthermal power-law component, dominating at energies E>3 keV, can also be
present in the detected X-ray emission. For PSR J0437-4715, the timing analysis
reveals that the shape and pulsed fraction of the pulsar light curves are
energy dependent. This, together with the results obtained from the
phase-resolved spectroscopy, supports the two-component (thermal plus
nonthermal) interpretation of the pulsar's X-ray radiation. Highly significant
pulsations have been found in the X-ray flux of PSRs J2124-3358 and J1024-0719.
For PSR J0034-0534, a possible X-ray counterpart of the radio pulsar has been
suggested. The inferred properties of the detected thermal emission are
compared with predictions of radio pulsar models.


title: Observing the Seyfert 2 nucleus of NGC 1068 with the VLT Interferometer

abstract:
  Dusty tori have been suggested to play a crucial role in determining the
physical characteristics of active galactic nuclei (AGN), but investigation of
their properties has stalled for lack of high resolution mid-IR imaging.
Recently, a long-awaited breakthrough in this field was achieved: NGC 1068, a
nearby AGN, was the first extragalactic object to be observed with a mid-IR
interferometer, thereby obtaining the needed angular resolution to study the
alleged torus.
  In this proceeding, first the field of AGN research is briefly reviewed, with
an emphasis on models of dusty tori. Second, the general properties of the key
object NGC 1068 are discussed. Third, the MIDI mid-IR interferometric data set
is presented together with a first attempt to interpret this data in the
context of tori models. Fourth, preliminary MIDI interferometric spectra of the
nucleus of the nearby starbursting galaxy Circinus are presented. Finally, we
briefly discuss the prospects of ESA's Darwin mission for observing nearby and
distant AGN. This mission will allow detailed mapping of tori of low luminosity
AGN such as NGC 1068 up to redshifts of 1 - 2 and more luminous AGN up to
redshift of 10 and beyond (abridged).


title: Optimal Softening for N-Body Halo Simulations

abstract:
  We propose to determine the optimal softening length in N-body halo
simulations by minimizing the ensemble-average acceleration error at a small
radius r0. This strategy ensures that the error never exceeds the optimal value
beyond r0. Furthermore, we derive semi-analytic formulae for calculating the
acceleration error due to the discreteness of particles and softened gravity,
which are validated by direct N-body force calculations. We estimate that
current state-of-the-art halo simulations suffer >~6% acceleration error at 1%
of the halo virial radius. The error grows rapidly toward the center and could
contribute significantly to the uncertainties of inner halo properties.


title: Topological signatures in CMB temperature anisotropy maps

abstract:
  We propose an alternative formalism to simulate CMB temperature maps in
$\Lambda$CDM universes with nontrivial spatial topologies. This formalism
avoids the need to explicitly compute the eigenmodes of the Laplacian operator
in the spatial sections. Instead, the covariance matrix of the coefficients of
the spherical harmonic decomposition of the temperature anisotropies is
expressed in terms of the elements of the covering group of the space. We
obtain a decomposition of the correlation matrix that isolates the topological
contribution to the CMB temperature anisotropies out of the simply connected
contribution. A further decomposition of the topological signature of the
correlation matrix for an arbitrary topology allows us to compute it in terms
of correlation matrices corresponding to simpler topologies, for which closed
quadrature formulae might be derived. We also use this decomposition to show
that CMB temperature maps of (not too large) multiply connected universes must
show ``patterns of alignment'', and propose a method to look for these
patterns, thus opening the door to the development of new methods for detecting
the topology of our Universe even when the injectivity radius of space is
slightly larger than the radius of the last scattering surface. We illustrate
all these features with the simplest examples, those of flat homogeneous
manifolds, i.e., tori, with special attention given to the cylinder, i.e.,
$T^1$ topology.


title: A Complete N-body Model of the Old Open Cluster M67

abstract:
  The old open cluster M67 is an ideal testbed for current cluster evolution
models because of its dynamically evolved structure and rich stellar
populations that show clear signs of interaction between stellar, binary and
cluster evolution. Here we present the first truly direct N-body model for M67,
evolved from zero age to 4 Gyr taking full account of cluster dynamics as well
as stellar and binary evolution. Our preferred model starts with 12000 single
stars and 12000 binaries placed in a Galactic tidal field at 8.0 kpc from the
Galactic Centre. Our choices for the initial conditions and for the primordial
binary population are explained in detail. At 4 Gyr, the age of M67, the total
mass has reduced by 90% as a result of mass loss and stellar escapes. The mass
and half-mass radius of luminous stars in the cluster are a good match to
observations although the model is more centrally concentrated than
observations indicate. The stellar mass and luminosity functions are
significantly flattened by preferential escape of low-mass stars. We find that
M67 is dynamically old enough that information about the initial mass function
is lost, both from the current luminosity function and from the current mass
fraction in white dwarfs. The model contains 20 blue stragglers at 4 Gyr which
is slightly less than the 28 observed in M67. Nine are in binaries. The blue
stragglers were formed by a variety of means and we find formation paths for
the whole variety observed in M67. Both the primordial binary population and
the dynamical cluster environment play an essential role in shaping the
population. A substantial population of short-period primordial binaries (with
periods less than a few days) is needed to explain the observed number of blue
stragglers in M67.


title:
Optical identification of ISO far-infrared sources in the Lockman Hole
  using a deep VLA 1.4 GHz continuum survey

abstract:
  By exploiting the far-infrared(FIR) and radio correlation, we have performed
the Likelihood-Ratio analysis to identify optical counterparts to the
far-infrared sources in the Lockman Hole. Using the likelihood ratio analysis
and the associated reliability, 44 FIR sources have been identified with radio
sources. Redshifts have been obtained for 29 out of 44 identified sources. One
hyper-luminous infrared galaxy (HyLIRG) with and four ultraluminous infrared
galaxies (ULIRGs) are identified in our sample. The space density of the FIR
sources at z = 0.3-0.6 is 4.6\times 10^{-5}Mpc^{-3}, implying a rapid evolution
of the ULIRG population. Most of \ISO FIR sources have their FIR-radio ratios
similar to star-forming galaxies ARP 220 and M82. At least seven of our FIR
sources show evidence for the presence of an active galactic nucleus (AGN) in
optical emission lines, radio continuum excess, or X-ray activity. Three out of
five (60%) of the ULIRG/HyLIRGs are AGN galaxies. Five of the seven AGN
galaxies are within the ROSAT X-ray survey field, and two are within the
XMM-Newton survey fields. X-ray emission has been detected in only one source,
1EX030, which is optically classified as a quasar. The non-detection in the
XMM-Newton 2-10 keV band suggests a very thick absorption obscuring the central
source of the two AGN galaxies. Several sources have an extreme FIR luminosity
relative to the optical R-band, L(90\mu\mathrm{m})/L(R) > 500, which is rare
even among the local ULIRG population. While source confusion or blending might
offer an explanation in some cases, they may represent a new population of
galaxies with an extreme activity of star formation in an undeveloped stellar
system -- i.e., formation of bulges or young ellipticals.


title:
Spectroscopic Study of SU UMa-type Dwarf Nova YZ Cnc during its 2002
  Superoutburst

abstract:
  We report time-resolved spectroscopic observations of the SU Ursae Majoris
dwarf nova, YZ Cnc, for 2 nights over 11 hrs during its 2002 January
superoutburst. The spectra only show absorption-line profiles in the first day.
But the lines display blue and red troughs, with ``W'' profiles in the second
day. The radial velocity curve of the absorption troughs and emission peaks of
H$\beta$ has an amplitude of $49\pm10$ km s$^{-1}$ and a phase offset of
$-0.07\pm0.04$, which are very similar to those measured in quiescence;
however, the $\gamma$ velocity deviates strongly from the systemic velocity
measured in quiescence, showing variation of the order of $\pm$60 km s$^{-1}$.
And large shifts of $\sim$70 km s$^{-1}$ and $\sim$0.09, for the
orbital-averaged velocity and phase respectively, are also found in our
observations. All these phenomena can be well explained with a precession of an
eccentric disk and we conclude that these phenomena are the characteristic
products of an eccentric accretion disk.


title:
Low-energy absorption towards the ultra-compact binary 4U1850-087
  located in the globular cluster NGC6712

abstract:
  We report the results of two XMM-Newton observations of the ultra-compact
low-mass X-ray binary 4U1850-087 located in the galactic globular cluster
NGC6712. A broad emission feature at 0.7keV was detected in an earlier ASCA
observation and explained as the result of an unusual Ne/O abundance ratio in
the absorbing material local to the source. We find no evidence for this
feature and derive Ne/O ratios in the range 0.14-0.21, consistent with that of
the interstellar medium. During the second observation, when the source was 10%
more luminous, there is some evidence for a slightly higher Ne/O ratio and
additional absorption. Changes in the Ne/O abundance ratio have been detected
from another ultra-compact binary, 4U1543-624. We propose that these changes
result from an X-ray induced wind which is evaporated from an O and Ne rich
degenerate donor. As the source X-ray intensity increases so does the amount of
evaporation and hence the column densities and abundance ratio of Ne and O.


title:
Influence of local treatments of convection upon solar p mode excitation
  rates

abstract:
  We compute the rates P at which acoustic energy is injected into the solar
radial p modes for several solar models. The solar models are computed with two
different local treatments of convection: the classical mixing-length theory
(MLT hereafter) and Canuto et al (1996)'s formulation (CGM hereafter). Among
the models investigated here, our best models reproduce both the solar radius
and the solar luminosity at solar age and the observed Balmer line profiles.
For the MLT treatment, the rates P do depend significantly on the properties of
the atmosphere whereas for the CGM's treatment the dependence of P on the
properties of the atmosphere is found smaller than the error bars attached to
the seismic measurements. The excitation rates P for modes associated with the
MLT models are significantly underestimated compared with the solar seismic
constraints. The CGM models yield values for P closer to the seismic data than
the MLT models. We conclude that the solar p-mode excitation rates provide
valuable constraints and according to the present investigation clearly favor
the CGM treatment with respect to the MLT, although neither of them yields
values of P as close to the observations as recently found for 3D numerical
simulations.


title: Variable stars in Fornax dwarf spheroidal galaxy

abstract:
  We present the first results of a variable star search in the field and in
the globular clusters of the Fornax dwarf spheroidal galaxy. Variable stars
were identified using the Image Subtraction Technique (Alard 2000) on
time-series data obtained with the ESO 2.2 m and the Magellan 6.5 m telescopes.
The variable star sample includes RR Lyrae stars, Dwarf Cepheids and Anomalous
Cepheids. The pulsation properties (namely: periods, light curves,
period-amplitude relations and classification in Oosterhoff types) of Fornax
variables from the present study are discussed in some detail.


title:
Elliptical Galaxies with Emission Lines from the Sloan Digital Sky
  Survey

abstract:
  We present the results of 11 elliptical galaxies with strong nebular emission
lines during our study of star formation history along the Hubble sequence.
After removing the dilution from the underlying old stellar populations by use
of stellar population synthesis model, we derive the accurate fluxes of all
emission lines for these objects, which are later classified with emission line
ratios into one Seyfert 2, six LINERs and four HII galaxies. We also identify
one HII galaxy (A1216+04) as a hitherto unknown Wolf-Rayet galaxy from the
presence of the Wolf-Rayet broad bump at 4650 \AA. We propose that the
star-forming activities in elliptical galaxies are triggered by either
galaxy-galaxy interaction or the merging of a small satellite/a massive star
cluster, as already suggested by recent numerical simulations.


title:
Higher Criticism Statistic: Detecting and Identifying Non-Gaussianity in
  the WMAP First Year Data

abstract:
  Higher Criticism is a recently developed statistic for non-Gaussian
detection, proposed in Donoho & Jin 2004. We find that Higher Criticism is
useful for two purposes. First, Higher Criticism has competitive detection
power, and non-Gaussianity is detected at the level 99% in the first year WMAP
data. We find that the Higher Criticism value of WMAP is outside the 99%
confidence region at a wavelet scale of 5 degrees (99.46% of Higher Criticism
values based on simulated maps are below the values for WMAP). Second, Higher
Criticism offers a way to locate a small portion of data that accounts for the
non-Gaussianity. Using Higher Criticism, we have successfully identified a ring
of pixels centered at (l\approx 209 deg, b\approx -57 deg), which seems to
account for the observed detection of non-Gaussianity at the wavelet scale of 5
degrees. Note that the detection is achieved in wavelet space first. Second, it
is always possible that a fraction of pixels within the ring might deviate from
Gaussianity even if they do not appear to be above the 99% confidence level in
wavelet space. The location of the ring coincides with the cold spot detected
in Vielva et al. 2004 and Cruz et al. 2005.


title: WINGS: a WIde-field Nearby Galaxy-cluster Survey. I - Optical imaging

abstract:
  This is the first paper of a series that will present data and scientific
results from the WINGS project, a wide-field, multiwavelength imaging and
spectroscopic survey of galaxies in 77 nearby clusters. The sample was
extracted from the ROSAT catalogs with constraints on the redshift
(0.04<z<0.07) and distance from the galactic plane (|b|>20). The global goal of
the WINGS project is the systematic study of the local cosmic variance of the
cluster population and of the properties of cluster galaxies as a function of
cluster properties and local environment. This data collection will allow to
define a local 'Zero-Point' reference against which to gauge the cosmic
evolution when compared to more distant clusters. The core of the project
consists of wide-field optical imaging of the selected clusters in the B and V
bands. We have also completed a multi-fiber, medium resolution spectroscopic
survey for 51 of the clusters in the master sample. In addition, a NIR (JK)
survey of ~50 clusters and an H_alpha + UV survey of some 10 clusters are
presently ongoing, while a very-wide-field optical survey has also been
programmed. In this paper we briefly outline the global objectives and the main
characteristics of the WINGS project. Moreover, the observing strategy and the
data reduction of the optical imaging survey (WINGS-OPT) are presented. We have
achieved a photometric accuracy of ~0.025mag, reaching completeness to V~23.5.
Field size and resolution (FWHM) span the absolute intervals (1.6-2.7)Mpc and
(0.7-1.7)kpc, respectively, depending on the redshift and on the seeing. This
allows the planned studies to get a valuable description of the local
properties of clusters and galaxies in clusters.


title: The recurrent ultra-luminous X-ray transient NGC 253 ULX1

abstract:
  We present the results of ROSAT and XMM-Newton observations of the recurrent
ultraluminous X-ray source (ULX) NGC 253 ULX1. This transient is one of the few
ULXs that was detected during several outbursts. The luminosity reached 1.4
10^39 erg s^-1 and 0.5 10^39 erg s^-1 in the detections by ROSAT and
XMM-Newton, respectively, indicating a black hole X-ray binary with a mass of
the compact object of >11 M_sun. It is highly unlikely that this source is a
foreground source or a background AGN. In the ROSAT detection NGC 253 ULX1
showed significant variability, whereas the luminosity was constant in the
detection from XMM-Newton. The XMM-Newton EPIC spectra are well-fit by a
bremsstrahlung model (kT=2.24 keV, N_H=1.74 10^20 cm^-2), which can be used to
describe a comptonized plasma. No counterpart was detected in the optical I, R,
B, NUV and FUV bands to limits of 22.9, 24.2, 24.3, 22 and 23 mag,
respectively, pointing at a X-ray binary with a low mass companion.


title:
Quantitative Morphology of Galaxies from the SDSS I: Luminosity in
  Bulges and Disks

abstract:
  In the first paper of this series we use the publicly available code Gim2D to
model the r- and i-band images of all galaxies in a magnitude-limited sample of
roughly 1800 morphologically classified galaxies taken from the Sloan Digital
Sky Survey. The model is a concentric superposition of two components, each
with elliptical isophotes with constant flattening and position angle. The disk
luminosity profile is assumed exponential, while the bulge is assumed to have a
de Vaucouleurs or a Sersic profile. We find that the parameters returned by
Gim2D depend little on the waveband or bulge profile used; their formal
uncertainties are usually small. Nevertheless, for bright galaxies the measured
distribution of b/a, the apparent disk flattening, deviates strongly from the
expected uniform distribution, showing that the `disk' identified by the code
frequently corresponds to an intrinsically 3-dimensional structure rather than
to a true thin disk. We correct approximately for this systematic problem using
the observed statistics of the b/a distribution and estimate, as a function of
absolute magnitude, the mean fractions of galaxy light in disks and in `pure
bulge' systems (those with no detectable disk). For the brightest galaxies the
disk light fraction is about 10% and about 80% are `pure bulge' systems. For
faint galaxies most of the light is in disks and we do not detect a `pure
bulge' population. Averaging over the galaxy population as a whole, we find
that 54 \pm 2% of the local cosmic luminosity density at both r and i comes
from disks and 32 \pm 2% from `pure bulge' systems. The remaining 14 \pm 2%
comes from bulges in galaxies with detectable disks.


title: Scaling Dark Energy in a Five-Dimensional Bouncing Cosmological Model

abstract:
  We consider a 5-dimensional Ricci flat bouncing cosmological model in which
the 4-dimensional induced matter contains two components at late times - the
cold dark matter (CDM)+baryons and dark energy. We find that the arbitrary
function $f(z)$ contained in the solution plays a similar role as the potential
$V(\phi)$ in quintessence and phantom dark energy models. To resolve the
coincidence problem, it is generally believed that there is a scaling stage in
the evolution of the universe. We analyze the condition for this stage and show
that a hyperbolic form of the function $f(z)$ can work well in this property.
We find that during the scaling stage (before $z\approx 2$), the dark energy
behaves like (but not identical to) a cold dark matter with an adiabatic sound
speed $c_{s}^{2}\approx 0$ and $p_{x}\approx 0$. After $z\approx 2$, the
pressure of dark energy becomes negative. The transition from deceleration to
acceleration happens at $z_{T}\approx 0.8$ which, as well as other predictions
of the $5D$ model, agree with current observations.


title:
Impact of a new Cherenkov light parameterisation on the reconstruction
  of shower profiles from Auger hybrid data

abstract:
  The light signal measured by fluorescence telescopes receives - strongly
depending on the shower geometry with respect to the detector - a
non-negligible contribution from additionally produced Cherenkov light. This
Cherenkov contribution has to be accounted for to determine primary parameters
properly. In comparison to the previous ansatz used by other experiments, the
impact of a new analytical description of Cherenkov light production in EAS on
the Auger event reconstruction is investigated.


title: New CO observations and simulations of the NGC 4438/NGC 4435 system

abstract:
  NGC 4438 is a highly perturbed spiral with a stellar tidal tail and
extraplanar molecular gas, now very HI deficient, crossing the center of the
Virgo cluster at high speed. Various authors have attributed the perturbed
appearance to the ram pressure of the intracluster medium, the tidal
interaction with NGC 4435, and an ISM-ISM collision between the ISM of NGC 4438
and NGC 4435. We present new CO observations covering virtually all of NGC 4438
and the center of NGC 4435 and detailed simulations including all of the above
effects. For the first time CO is detected in NGC 4435. In NGC 4438 we find
double line profiles at distances up to 40" to the west and south-west and
redshifted lines with respect to galactic rotation in the south of the center.
The lack of gas to the North and East coupled with the large gaseous extent to
the West and the redshifted and double line profiles can only be reproduced
with a ram pressure wind. NGC 4438 is most probably on its first passage
through the cluster center and has been stripped of its HI only over the past
100 Myr. While an ISM-ISM collision between NGC 4435 and NGC 4438 may occur,
the effect is not significant compared to ram pressure and tidal forces, not
surprising for the passage of an S0 galaxy 5-10 kpc from the center of NGC
4438. We also detect narrow CO lines, in the absence of detected HI, in the
northern tidal arm some 15 kpc from the center of NGC 4438. This can be
understood from the simulations assuming a few percent of the gas is too dense
to experience the ram pressure wind. NGC 4438 has changed greatly over the past
100 Myr due to its plunge through the center of the Virgo cluster and the
interaction with the S0 NGC 4435.


title:
Constraints on parameters of B-type pulsators from combined multicolour
  photometry and radial velocity data. I. $\beta$ Cephei stars

abstract:
  We analyze data on pulsation amplitudes and phases for two $\beta$ Cephei
stars, $\delta$ Cet and $\nu$ Eri. Str\"omgren photometry and radial velocity
measurements are used simultaneously to obtain constraints on mean parameters
of the stars and identification of the excited modes. The inference about the
radial mode order and mean star parameters is based on comparison of certain
complex parameter, $f$, determined from data, with its counterpart derived from
linear nonadiabatic modelling of stellar oscillations. The theoretical $f$
values are very sensitive to the adopted opacity data. In our modelling we rely
on the data from OPAL and OP projects. Significant differences were found. New
seismic models of $\nu$ Eri were constructed with both the OPAL and OP
opacities.


title: Upper Limits on a Stochastic Background of Gravitational Waves

abstract:
  The Laser Interferometer Gravitational Wave Observatory (LIGO) has performed
a third science run with much improved sensitivities of all three
interferometers. We present an analysis of approximately 200 hours of data
acquired during this run, used to search for a stochastic background of
gravitational radiation. We place upper bounds on the energy density stored as
gravitational radiation for three different spectral power laws. For the flat
spectrum, our limit of Omega_0<8.4e-4 in the 69-156 Hz band is ~10^5 times
lower than the previous result in this frequency range.


title:
Can pulsating PG1159 stars place constraints on the occurrence of core
  overshooting?

abstract:
  The present letter is aimed at exploring the influence of overshooting during
the central helium burning in pre-white dwarf progenitors on the pulsational
properties of PG1159 stars. To this end we follow the complete evolution an
intermediate-mass white dwarf progenitor from the zero age main sequence
through the thermally pulsing and born-again phases to the domain of the PG1159
stars. Our results suggest that the presence of mode-trapping features in the
period spacings of these hot pulsating stars could result from structure in the
carbon-oxygen core. We find in particular that in order to get enough core
structure consistent with observational demands, the occurrence of overshoot
episodes during the central helium burning is needed. This conclusion is valid
for thick helium envelopes like those predicted by our detailed evolutionary
calculations. If the envelope thickness were substantially smaller, then the
occurrence of core overshooting would be more difficult to disentangle from the
effects related to the envelope transition zones.


title: SINFONI Observations of Starclusters in Starburst Galaxies

abstract:
  We have used ESO's new NIR IFS SINFONI during its Science Verification period
to observe the central regions of local starburst galaxies. Being Science
Verification observations, the aim was two-fold: to demonstrate SINFONI's
capabilities while obtaining information on the nature of starclusters in
starburst galaxies. The targets chosen include a number of the brighter
clusters in NGC1808 and NGC253. Here we present first results.


title: Non-linear Structure Formation in Cosmologies with Early Dark Energy

abstract:
  We argue that a few per cent of "Early Dark Energy" can be detected by the
statistics of nonlinear structures. The presence of Dark Energy during linear
structure formation is natural in models where the present tiny Dark-Energy
density is related to the age of the Universe rather than a new fundamental
small parameter. Generalisation of the spherical collapse model shows that the
linear collapse parameter delta_c is lowered. The corresponding relative
enhancement of weak gravitational lensing on arc-minute scales lowers the value
of sigma_8 inferred from a given lensing amplitude as compared to Lambda-CDM.
In presence of Early Dark Energy, structures grow slower, such that for given
sigma_8 the number of galaxies and galaxy clusters is substantially increased
at moderate and high redshift. For realistic models, the number of clusters
detectable through their thermal Sunyaev-Zel'dovich effect at redshift unity
and above, e.g. with the Planck satellite, can be an order of magnitude larger
than for Lambda-CDM.


title: Magnetic fields around late-type stars using water maser observations

abstract:
  We present the analysis of the circular polarization, due to Zeeman
splitting, of the water masers around a sample of late-type stars to determine
the magnetic fields in their circumstellar envelopes. The magnetic field
strengths in the water maser regions around the Mira variable stars U Ori and U
Her are shown to be several Gauss while those of the supergiants S Per, NML Cyg
and VY CMa are several hundred mG. We also show that large scale magnetic
fields permeate the CSE of an evolved star; the polarization of the water
masers around VX Sgr reveals a dipole field structure. We shortly discuss the
coupling of the magnetic field with the stellar outflow, as such fields could
possibly be the cause of distinctly aspherical mass-loss and the resulting
aspherical planetary nebulae.


title:
Rossi X-ray Timing Explorer Observations of the X-ray Pulsar EXO
  1722-363 - a Candidate Eclipsing Supergiant System

abstract:
  Observations made of the X-ray pulsar EXO 1722-363 using the Proportional
Counter Array and All Sky Monitor on board the Rossi X-ray Timing Explorer
reveal the orbital period of this system to be 9.741 +/- 0.004 d from periodic
changes in the source flux. The detection of eclipses, together with the values
of the pulse and orbital periods, suggest that this source consists of a
neutron star accreting from the stellar wind of an early spectral type
supergiant companion. Pulse timing measurements were also obtained but do not
strongly constrain the system parameters. The X-ray spectra can be well fitted
with a model consisting of a power law with a high energy cutoff and, for some
spectra, a blackbody component with a temperature of approximately 0.85 keV.


title:
Long-Term Evolution of Massive Black Hole Binaries. II. Binary Evolution
  in Low-Density Galaxies

abstract:
  We use direct-summation N-body integrations to follow the evolution of binary
black holes at the centers of galaxy models with large, constant-density cores.
Particle numbers as large as 400K are considered. The results are compared with
the predictions of loss-cone theory, under the assumption that the supply of
stars to the binary is limited by the rate at which they can be scattered into
the binary's influence sphere by gravitational encounters. The agreement
between theory and simulation is quite good; in particular, we are able to
quantitatively explain the observed dependence of binary hardening rate on N.
We do not verify the recent claim of Chatterjee, Hernquist & Loeb (2003) that
the hardening rate of the binary stabilizes when N exceeds a particular value,
or that Brownian wandering of the binary has a significant effect on its
evolution. When scaled to real galaxies, our results suggest that massive black
hole binaries in gas-poor nuclei would be unlikely to reach gravitational-wave
coalescence in a Hubble time.


title:
Vertical modes of two-dimensional dust coulomb clusters in complex
  plasmas

abstract:
  The vertical as well as horizontal oscillation modes in a thermally excited
two-dimensional (2D) dust coulomb cluster were investigated for particle
numbers between and using both a box_tree simulation and an analytical method.
The horizontal mode spectra is shown to agree with published results while the
vertical mode spectra obtained from the box_tree simulation and the analytical
method are shown to agree with one another. The maximum frequency of the
vertical modes is shown to be the vertical oscillation frequency of the whole
system acting as a solid plane and the frequency is shown to decrease as the
mode number l decreases. The oscillation patterns of the vertical modes are
also investigated. For clusters with large numbers of particles, the high
frequency modes are shown to have oscillation patterns similar in shape to
Bessel-Fourier functions with various index m and n. For specified values of n,
modes with higher m (except for) have lower frequencies and for specified m,
modes with higher n have lower frequencies. For low frequency modes, the
largest amplitude particle motion is concentrated in a few inner rings with the
outer rings remaining almost motionless. This is in contrast to the horizontal
modes where the strongest motion of the particles is concentrated in the inner
rings at high frequency. For clusters with small numbers of particles (), these
modes where the strongest vertical motion is concentrated in the inner rings
does not exist resulting in oscillation magnitudes for all the modes appearing
in the shape of Bessel-Fourier functions.


title: The Structure of Close Binaries in Two Dimensions

abstract:
  The structure and evolution of close binary stars has been studied using the
two-dimensional (2D) stellar structure algorithm developed by Deupree (1995).
We have calculated a series of solar composition stellar evolution sequences of
binary models, where the mass of the 2D model is 8Msun with a point-mass 5Msun
companion. We have also studied the structure of the companion in 2D, by
considering the zero-age main-sequence (ZAMS) structure of a 5Msun model with
an 8Msun point-mass companion. In all cases the binary orbit was assumed to be
circular and co-rotating with the rotation rate of the stars. We considered
binary models with three different initial separations, a = 10, 14 and 20Rsun.
These models were evolved through central hydrogen burning or until the more
massive star expanded to fill its critical potential surface or Roche lobe. The
calculations show that evolution of the deep interior quantities is only
slightly modified from those of single star evolution. Describing the model
surface as a Roche equipotential is also satisfactory until very close to the
time of Roche lobe overflow, when the self gravity of the model about to lose
mass develops a noticeable aspherical component and the surface time scale
becomes sufficiently short that it is conceivable that the actual surface is
not an equipotential.


title: Cosmic Growth History and Expansion History

abstract:
  The cosmic expansion history tests the dynamics of the global evolution of
the universe and its energy density contents, while the cosmic growth history
tests the evolution of the inhomogeneous part of the energy density. Precision
comparison of the two histories can distinguish the nature of the physics
responsible for the accelerating cosmic expansion: an additional smooth
component - dark energy - or a modification of the gravitational field
equations. With the aid of a new fitting formula for linear perturbation growth
accurate to 0.05-0.2%, we separate out the growth dependence on the expansion
history and introduce a new growth index parameter \gamma that quantifies the
gravitational modification.


title:
A Census of Optical and Near-Infrared Selected Star-Forming and
  Passively Evolving Galaxies at Redshift Z~2

abstract:
  Using the extensive multi-wavelength data in the GOODS-North field, we
construct and draw comparisons between samples of optical and near-IR selected
star-forming and passively evolving galaxies at redshifts 1.4<z<2.6. We find
overlap at the 70-80% level in samples of z~2 star-forming galaxies selected by
their optical (UGR) and near-IR (BzK) colors when subjected to common K-band
limits. Deep Chandra data indicate a 25% AGN fraction among near-IR selected
objects, much of which occurs among near-IR bright objects (K<20; Vega).
Stacking the X-ray emission for the star-forming galaxies, we find the SFR
distributions of UGR, BzK, and J-K>2.3 galaxies (Distant Red Galaxies; DRGs)
are very similar as a function of K, with K<20 galaxies having <SFR>~120
Msun/yr, a factor of two to three higher than those with K>20.5. The absence of
X-ray emission from the reddest DRGs and BzK galaxies with z-K>3 indicates they
must have declining star formation histories to explain their red colors and
low SFRs. While the M/L ratio of passively-evolving galaxies may be larger on
average, the Spitzer/IRAC data indicate that their inferred stellar masses do
not exceed the range spanned by optically selected galaxies, suggesting that
the disparity in current SFR may not indicate a fundamental difference between
optical and near-IR selected massive galaxies (M* > 10^11 Msun). We consider
the contribution of UGR, BzK, DRG, and submillimeter galaxies (SMGs) to the
SFRD at z~2, taking into account sample overlap. The total SFRD in the interval
1.4<z<2.6 of UGR and BzK galaxies to K=22, and DRGs to K=21 is ~ 0.10+/-0.02
Msun/yr/Mpc^3. Optically-selected galaxies to R=25.5 and K=22 account for ~70%
of this total. Of the radio-selected SMGs to S(850 micron)~4 mJy with redshifts
1.4<z<2.6, >80% could be selected by the UGR, BzK, and/or DRG criteria.


title: Microlensing of Circumstellar Disks

abstract:
  We investigate the microlensing effects on a source star surrounded by a
circumstellar disk, as a function of wavelength. The microlensing light curve
of the system encodes the geometry and surface brightness profile of the disk.
In the mid- and far-infrared, the emission of the system is dominated by the
thermal emission from the cold dusty disk. For a system located at the Galactic
center, we find typical magnifications to be of order 10-20% or higher,
depending on the disk surface brightness profile, and the event lasts over one
year. At around 20 microns, where the emission for the star and the disk are
comparable, the difference in the emission areas results in a chromatic
microlensing event. Finally, in the near-infrared and visible, where the
emission of the star dominates, the fraction of star light directly reflected
by the disk slightly modifies the light curve of the system which is no longer
that of a point source. In each case, the corresponding light curve can be used
to probe some of the disk properties. A fraction of 0.1% to 1% optical
microlensing events are expected to be associated with circumstellar disk
systems. We show that the lensing signal of the disk can be detected with
sparse follow-up observations of the next generation space telescopes. While
direct imaging studies of circumstellar disks are limited to the solar
neighborhood, this microlensing technique can probe very distant disk systems
living in various environments and has the potential to reveal a larger
diversity of circumstellar disks.


title: The Effects of Reionization on Lyman-alpha Galaxy Surveys

abstract:
  Searches for Lyman-alpha emission lines are among the most effective ways to
identify high-redshift galaxies. They are particularly interesting because they
probe not only the galaxies themselves but also the ionization state of the
intergalactic medium (IGM). The observed line strengths depend on the amount by
which each photon is able to redshift away from line center before encountering
neutral gas and hence on the size distribution of HII regions surrounding the
sources. Here, we use an analytic model of that size distribution to study the
effects of reionization on the luminosity function of Lyman-alpha emitters and
their observed spatial distribution. Our model includes the clustering of
high-redshift galaxies and thus contains ionized bubbles much larger than those
expected around isolated galaxies. As a result, Lyman-alpha emitting galaxies
remain visible earlier in reionization: we expect the number counts to decline
by only a factor ~2 (or 10) when the mean ionized fraction falls to x_i~0.75
(or 0.5) in the simplest model. Moreover, the absorption is not uniform across
the sky: galaxies remain visible only if they sit inside large bubbles, which
become increasingly rare as x_i decreases. Thus, the size distribution also
affects the apparent clustering of Lyman-alpha selected galaxies. On large
scales, it traces that of the large bubbles, which in our model are more biased
than the galaxies. On small scales, the clustering increases rapidly as x_i
decreases because large HII regions surround strong galaxy overdensities, so a
survey automatically selects only those galaxies with neighbours. The
transition between these two regimes occurs at the characteristic bubble size.
Hence, large Lyman-alpha galaxy surveys have the potential to measure directly
the size distribution of HII regions during reionization.


title: Angular power spectrum of the FastICA CMB component from BEAST data

abstract:
  We present the angular power spectrum of the CMB component extracted with
FastICA from the Background Emission Anisotropy Scanning Telescope (BEAST)
data. BEAST is a 2.2 meter off-axis telescope with a focal plane comprising 8
elements at Q (38-45 GHz) and Ka (26-36 GHz) bands. It operates from the UC
White Mountain Research Station at an altitude of 3800 meters. The BEAST CMB
angular power spectrum has been already calculated by O'Dwyer et.al. using only
the Q band data. With two input channels FastICA returns two possible
independent components. We found that one of these two has an unphysical
spectral behaviour while the other is a reasonable CMB component. After a
detailed calibration procedure based on Monte-Carlo (MC) simulations we
extracted the angular power spectrum for the identified CMB component and found
a very good agreement with the already published BEAST CMB angular power
spectrum and with the WMAP data.


title: The Disc-Jet Connection

abstract:
  A large body of theoretical and computational work shows that jets - modelled
as magnetized disk winds - exert an external torque on their underlying disks
that can efficiently remove angular momentum and act as major drivers of disk
accretion. These predictions have recently been confirmed in direct HST
measurements of the jet rotation and angular momentum transport in low mass
protostellar systems. We review the theory of disc winds and show that their
physics is universal and scales to jets from both low and high mass star
forming regions. This explains the observed properties of outflows in massive
star forming regions, before the central massive star generates an ultracompact
HII region. We also discuss the recent numerical studies on the formation of
massive accretion disks and outflows through gravitational collapse, including
our own work on 3D Adaptive Mesh simulations (using the FLASH code) of the
hydromagnetic collapse of an initial rotating, and cooling Bonner-Ebert sphere.
Magnetized collapse gives rise to outflows. Our own simulations show that both
a jet-like disk wind on sub AU scales, and a larger scale molecular outflow
occur (Banerjee and Pudritz 2005).


title:
Sun's retrograde motion and violation of even-odd cycle rule in sunspot
  activity

abstract:
  The sum of sunspots number over an odd numbered 11 yr sunspot cycle exceeds
that of its preceding even numbered cycle, and it is well known as Gnevyshev
and Ohl rule (or G--O rule) after the names of the authors who discovered it in
1948. The G--O rule can be used to predict the sum of sunspot numbers of a
forthcoming odd cycle from that of its preceding even cycle. But this is not
always possible because occasionally the G--O rule is violated. So far no
plausible reason is known either for the G--O rule or the violation of this
rule. Here we showed the epochs of the violation of the G--O rule are close to
the epochs of the Sun's retrograde orbital motion about the centre of mass of
the solar system (i.e., the epochs at which the orbital angular momentum of the
Sun is weakly negative). Using this result easy to predict the epochs of
violation of the G--O rule well in advance. We also showed that the solar
equatorial rotation rate determined from sunspot group data during the period
1879--2004 is correlated/anti-correlated to the Sun's orbital torque during
before/after 1945. We have found the existence of a statistically significant
$\sim$ 17 yr periodicity in the solar equatorial rotation rate. The
implications of these findings for understanding the mechanism behind the solar
cycle and the solar-terrestrial relationship are discussed.


title: A survey of NB921 dropouts in the Subaru Deep Field

abstract:
  In order to search for high-redshift galaxies beyond $z = 6.6$ in the Subaru
Deep Field, we have investigated NB921-dropout galaxies where NB921 is the
narrowband filter centered at 919.6 nm with FWHM of 13.2 nm for the Suprime-Cam
on the Subaru Telescope. There are no secure NB921-dropout candidates brighter
than $z^\prime = 25.5$. Based on this result, we discuss the UV luminosity
function of star-forming galaxies at $z > 6.6$.


title: Observational studies of stellar black hole binaries and ULXs

abstract:
  We outline a framework for understanding the X-ray spectra of high mass
accretion rate stellar black holes based on X-ray data from RXTE and ASCA.
Three spectral regimes can be separated out by the behaviour of the observed
disk luminosity and temperature. The well established "standard regime" is seen
when the disk dominates the spectrum, where only a small fraction of the
luminosity is emitted in the power law tail. These spectra generally satisfy
the standard relation expected for thermal emission from a constant area,
namely that the disk bolometric luminosity, Ldisk, is proportional to its
maximum temperature, Tin^4. However, at higher luminosities this starts to
change to Tin^2. This "apparently standard regime" is still dominated by the
disk emission, but this difference luminosity-temperature relation and subtle
changes in spectral shape may show that another cooling process is required in
addition to radiative cooling. At intermediate luminosities there is an
anomalous regime (or weak very high state) where the disk temperature and
luminosity are less clearly related. These spectra are characterized by the
presence of a much stronger comptonized tail indicating high energy electrons.
When observed disk emission is corrected for the the effects of comptonisation
then these points lie back on the standard relation. The growth of this
comptonising corona is also clearly linked to the quasi-periodic oscillations,
as these are observed preferentially in the anomalous regime. This presented
picture was found to explain the spectral behavior of both black hole binaries
in our Galaxy and LMC. Spectral evolution of several bright ULXs observed with
ASCA were also successfully explained in the same picture.


title:
Disentangling the composite continuum of symbiotic binaries I. S-type
  systems

abstract:
  We describe a method of disentangling the composite,0.12-5 microns continuum
of symbiotic binaries.The observed SED is determined by the IUE/HST archival
spectra and flux-points corresponding to the optical UBVRI and infrared JHKLM
photometric measurements. The modeled SED is given by superposition of fluxes
from the cool giant, hot stellar source and nebula including the effect of the
Rayleigh scattering process and considering influence of the iron curtain
absorptions.We applied this method to 21 S-type symbiotic stars during
quiescence, activity and eclipses.


title:
The large scale structure of the Galactic magnetic field and High Energy
  Cosmic Ray anisotropy

abstract:
  The magnetic field in our Galaxy is not well known and is difficult to
measure. A spiral regular field in the disk between the Galactic arms is
favored by observations, however it is still controversial if the field
reverses from arm to arm. The parity of the field across the Galactic plane is
also not well established. In this letter we demonstrate that cosmic ray
protons in the energy range 10^18 to 10^19 eV, if accelerated near the center
of the Galaxy, can probe the large scale structure of the Galactic Magnetic
Field. In particular if the field is of even parity, and the spiral field
reverses direction from arm to arm, i.e. if it is bi-symmetric (BSS), ultra
high energy protons will predominantly come from the Southern Galactic
hemisphere, and predominantly from the Northern Galactic hemisphere if the
field is of even parity and axi-symmetric (ASS). There is no sensitivity to the
BSS or ASS configurations if the field is of odd parity.


title: Mapping extreme-scale alignments of quasar polarization vectors

abstract:
  Based on a new sample of 355 quasars with significant optical polarization
and using complementary statistical methods, we confirm that quasar
polarization vectors are not randomly oriented over the sky with a probability
often in excess of 99.9%. The polarization vectors appear coherently oriented
or aligned over huge (~ 1 Gpc) regions of the sky located at both low (z ~ 0.5)
and high (z ~ 1.5) redshifts and characterized by different preferred
directions of the quasar polarization. In fact, there seems to exist a regular
alternance along the line of sight of regions of randomly and aligned
polarization vectors with a typical comoving length scale of 1.5 Gpc.
Furthermore, the mean polarization angle \bar{\theta} appears to rotate with
redshift at the rate of ~ 30\degr per Gpc. The symmetry of the the \bar{\theta}
-z relation is mirror-like, the mean polarization angle rotating clockwise with
increasing redshift in North Galactic hemisphere and counter-clockwise in the
South Galactic one. These characteristics make the alignment effect difficult
to explain in terms of local mechanisms, namely a contamination by interstellar
polarization in our Galaxy. While interpretations like a global rotation of the
Universe can potentially explain the effect, the properties we observe
qualitatively correspond to the dichroism and birefringence predicted by
photon-pseudoscalar oscillation within a magnetic field. Interestingly, the
alignment effect seems to be prominent along an axis not far from preferred
directions tentatively identified in the CMB maps. Although many questions and
more particularly the interpretation of the effect remain open, alignments of
quasar polarization vectors appear as a promising new way to probe the Universe
and its dark components at extremely large scales.


title:
Atmospheric Profiles at the Southern Pierre Auger Observatory and their
  Relevance to Air Shower Measurement

abstract:
  The dependence of atmospheric conditions on altitude and time have to be
known at the site of an air shower experiment for accurate reconstruction of
extensive air showers and their simulations. The height-profile of atmospheric
depth is of particular interest as it enters directly into the reconstruction
of longitudinal shower development and of the primary energy and mass of cosmic
rays. For the southern part of the Auger Observatory, the atmosphere has been
investigated in a number of campaigns with meteorological radio soundings and
with continuous measurements of ground-based weather stations. Focussing on
atmospheric depth and temperature profiles, temporal variations are described
and monthly profiles are developed. Uncertainties of the monthly atmospheres
that are currently applied in the Auger reconstruction are discussed.


title: Nearby star cluster formation: Probes of cosmological galaxy evolution

abstract:
  (abridged) The old Star Cluster (SC) systems surrounding any sofar
investigated galaxy represent a powerful tool for the understanding of the
cosmological evolution of their host galaxies. Phases of enhanced cluster
formation can be identified by reliably age dating the clusters. These are
symptoms of violent star formation, results of intense starbursts as commonly
seen in merging nearby galaxies and high-z forming galaxies. However, the young
SC systems of nearby merging galaxies and the old SC systems of nearby passive
galaxies (most likely resulting from high-z starburst events of these galaxies)
appear to be significantly different in terms of their mass functions. Whether
this difference originates in differences in the formation physics/environment
or is only due to dynamical evolution of the cluster systems is currently a hot
issue. A main diagnostic for the survival probability of a newly formed cluster
is most likely its compactness, since less compact, fluffy clusters are more
vulnerable to destructive interactions with the galactic environment of the
cluster. For these reasons, we developed
  1) a tool to significantly improve photometry of nearby SCs (which appear
resolved on high-resolution images, provided e.g. by HST), by accurately
measuring and taking the cluster size into account, and
  2) a tool to effectively determine ages and masses (plus metallicities and
extinctions) of SCs from multi-wavelength photometry, ranging from the UV to
the NIR.


title: The zero-crossing scale and the problem of galaxy bias

abstract:
  One of the main problems in the studies of large scale galaxy structures
concerns the relation of the correlation properties of a certain population of
objects with those of a selected subsample of it, when the selection is
performed by considering physical quantities like luminosity or mass. I
consider the case where the sampling is defined as in the simplest thresholding
selection scheme of the peaks of a Gaussian random field as well as the case of
the extraction of point distributions in high density regions from
gravitational N-body simulations. I show that an invariant scale under sampling
is represented by the zero-crossing scale of \xi(r). By considering recent
measurements in the 2dF and SDSS galaxy surveys I note that the zero-point
crossing length has not yet been clearly identified, while a dependence on the
finite sample size related to the integral constraint is manifest. I show that
this implies that other length scales derived from \xi(r) are also affected by
finite size effects. I discuss the theoretical implications of these results,
when considering the comparison of structures formed in N-body simulations and
observed in galaxy samples, and different tests to study this problem.


title: O stars with weak winds: the Galactic case

abstract:
  We study the stellar and wind properties of a sample of Galactic O dwarfs to
track the conditions under which weak winds (i.e mass loss rates lower than ~
1e-8 Msol/yr) appear. The sample is composed of low and high luminosity dwarfs
including Vz stars and stars known to display qualitatively weak winds.
Atmosphere models including non-LTE treatment, spherical expansion and line
blanketing are computed with the code CMFGEN. Both UV and Ha lines are used to
derive wind properties while optical H and He lines give the stellar
parameters. Mass loss rates of all stars are found to be lower than expected
from the hydrodynamical predictions of Vink et al. (2001). For stars with log
L/Lsol > 5.2, the reduction is by less than a factor 5 and is mainly due to the
inclusion of clumping in the models. For stars with log L/Lsol < 5.2 the
reduction can be as high as a factor 100. The inclusion of X-ray emission in
models with low density is crucial to derive accurate mass loss rates from UV
lines. The modified wind momentum - luminosity relation shows a significant
change of slope around this transition luminosity. Terminal velocities of low
luminosity stars are also found to be low. The physical reason for such weak
winds is still not clear although the finding of weak winds in Galactic stars
excludes the role of a reduced metallicity. X-rays, through the change in the
ionisation structure they imply, may be at the origin of a reduction of the
radiative acceleration, leading to lower mass loss rates. A better
understanding of the origin of X-rays is of crucial importance for the study of
the physics of weak winds.


title:
Investigation of flat spectrum radio sources by the interplanetary
  scintillation method at 111 MHz

abstract:
  Interplanetary scintillation observations of 48 of the 55 Augusto et al.
(1998) flat spectrum radio sources were carried out at 111 MHz using the
interplanetary scintillation method on the Large Phased Array (LPA) in Russia.
Due to the large size of the LPA beam ($1\degr \times 0.5\degr$) a careful
inspection of all possible confusion sources was made using extant large radio
surveys: 37 of the 48 sources are not confused. We were able to estimate the
scintillating flux densities of 13 sources, getting upper limits for the
remaining 35. Gathering more or improving extant VLBI data on these sources
might significantly improve our results. This proof-of-concept project tells us
that compact ($<1''$) flat spectrum radio sources show strong enough
scintillations at 111 MHz to establish/constrain their spectra (low-frequency
end).


title: The Galaxy in the cosmological context

abstract:
  A new view on our Galaxy has recently emerged, with large consequences on its
formation scenarios. Not only new dwarf satellites have been detected, still
orbiting and tidally disrupting, but also a multitude of stellar streams or
tidal debris have been observed suggesting the formation of the halo through
successive accretions. The large scatter in the age-metallicity relation in the
solar neighborhood points towards several accretion episodes, while the
chemical evolution of the disk requires a more or less continuous gas infall.
The global kinematics and morphology refined by large surveys such as 2MASS
suggest the existence of two embedded bars, as is frequently observed in
external galaxies. The mass of the central black hole has been refined through
stellar proper motions, and is compatible with the M$_{bh}$-$\sigma$ relation
valid for all bulges. The baryonic dark matter is no longer thought to lie in
compact objects, and on the contrary, more dark cold gas is revealed by
gamma-ray observations. The star forming history can be built, and confronted
to numerical models of galaxy evolution both through hierarchical and secular
scenarios. Our Galaxy plays thus the role of a prototype to probe galaxy
formation theories, and in particular thin and thick disk formation.


title:
The Stellar Halo Metallicity - Luminosity Relationship for Spiral
  Galaxies

abstract:
  The stellar halos of spiral galaxies bear important chemo-dynamical
signatures of galaxy formation. We present here the analysis of 89
semi-cosmological spiral galaxy simulations, spanning ~ 4 magnitudes in total
galactic luminosity. These simulations sample a wide variety of merging
histories and show significant dispersion in halo metallicity at a given total
luminosity - more than a factor of ten in metallicity. Our preliminary analysis
suggests that galaxies with a more extended merging history possess halos which
have younger and more metal rich stellar populations than the stellar halos
associated with galaxies with a more abbreviated assembly. A correlation
between halo metallicity and its surface brightness has also been found,
reflecting the correlation between halo metallicity and its stellar mass. Our
simulations are compared with recent Hubble Space Telescope observations of
resolved stellar halos in nearby spirals.


title: The subpulse modulation properties of pulsars at 21 cm

abstract:
  We present the results of a systematic, unbiased search for subpulse
modulation of 187 pulsars performed with the Westerbork Synthesis Radio
Telescope (WSRT) in the Netherlands at an observing wavelength of 21 cm. Using
new observations and archival WSRT data we have expanded the list of pulsars
which show the drifting subpulse phenomenon by 42, indicating that at least one
in three pulsars exhibits this phenomenon. The real fraction of pulsars which
show the drifting phenomenon is likely to be larger than some 55%. The majority
of the analysed pulsars show subpulse modulation (170), of which the majority
were not previously known to show subpulse modulation and 30 show clear
systematic drifting. The large number of new drifters we have found allows us,
for the first time, to do meaningful statistics on the drifting phenomenon. We
find that the drifting phenomenon is correlated with the pulsar age such that
drifting is more likely to occur in older pulsars. Pulsars which drift more
coherently seem to be older and have a lower modulation index. There is no
significant correlation found between P3 and other pulsar parameters (such as
the pulsar age), as has been reported in the past. There is no significant
preference of drift direction and the drift direction is not found to be
correlated with pulsar parameters. None of the four complexity parameters
predicted by different emission models (Jenet & Gil 2003) are shown to be
inconsistent with the set of modulation indices of our sample of pulsars.
Therefore none of the models can be ruled out based on our observations. We
also present results on some interesting new individual sources like a pulsar
which shows similar subpulse modulation in both the main- and interpulse and
six pulsars with opposite drift senses in different components.


title:
Discovery of X-ray eclipses from the transient source CXOGC
  J174540.0-290031 with XMM-Newton

abstract:
  We present the XMM-Newton observations obtained during four revolutions in
Spring and Summer 2004 of CXOGC J174540.0-290031, a moderately bright transient
X-ray source, located at only 2.9" from SgrA*. We report the discovery of sharp
and deep X-ray eclipses, with a period of 27,961+/-5 s and a duration of about
1,100+/-100 s, observed during the two consecutive XMM revolutions from August
31 to September 2. No deep eclipses were present during the two consecutive XMM
revolutions from March 28 to April 1, 2004. The spectra during all four
observations are well described with an absorbed power law continuum. While our
fits on the power law index over the four observations yield values that are
consistent with Gamma=1.6-2.0, there appears to be a significant increase in
the column density during the Summer 2004 observations, i.e. the period during
which the eclipses are detected. The intrinsic luminosity in the 2-10 keV
energy range is almost constant with 1.8-2.3 x 10^34 (d_8kpc)^2 erg/s over the
four observations. In the framework of eclipsing semidetached binary systems,
we show that the eclipse period constrains the mass of the assumed
main-sequence secondary star to less than 1.0 M_odot. Therefore, we deduce that
CXOGC J174540.0-290031 is a low-mass X-ray binary (LMXB). Moreover the eclipse
duration constrains the mass of the compact object to less than about 60
M_odot, which is consistent with a stellar mass black hole or a neutron star.
The absence of deep X-ray eclipses during the Spring 2004 observations could be
explained if the centroid of the X-ray emitting region moves from a position on
the orbital plane to a point above the compact object, possibly coincident with
the base of the jet which was detected in radio at this epoch. [Abstract
truncated].


title:
Search for nearby stars among proper motion stars selected by
  optical-to-infrared photometry III. Spectroscopic distances of 322 NLTT stars

abstract:
  Distance estimates based on low-resolution spectroscopy and Two Micron All
Sky Survey (2MASS) J magnitudes are presented for a large sample of 322 nearby
candidates from Luyten's NLTT catalogue. Mainly relatively bright (typically 7
< K_s < 11) and red high proper motion stars have been selected according to
their 2MASS magnitudes and optical-to-infrared colours (+1 < R-K_s < +7). Some
LHS stars previously lacking spectroscopy have also been included. We have
classified the majority of the objects as early-M dwarfs (M2-M5). More than 70%
of our targets turned out to lie within the 25 pc horizon of the catalogue of
nearby stars, with 50 objects placed within 15 pc and 8 objects being closer
than 10 pc. Three objects in the 10 pc sample have no previously published
spectral type: LP 876-10 (M4), LP 870-65 (M4.5), and LP 869-26 (M5). A large
fraction of the objects in our sample (57%) have independent distance
estimates, mainly by the recent efforts of Reid and collaborators. Our distance
determinations are generally in good agreement with theirs. 11 rather distant
(d > 100 pc) objects have also been identified, including a probable halo, but
relatively hot (T_eff = 13000 K) white dwarf (LHS 1200) and 10 red dwarfs with
extremely large tangential velocities (250 < v_t < 1150 km/s). Altogether,
there are 11 red dwarfs (including one within 70 pc) with tangential velocities
larger than about 250 km/s. All these objects are suspected to be in fact
subdwarfs, if so, their distances would be only about half of our original
estimates. The three most extreme objects in that respect are the K and early M
dwarfs LP 323-168, LHS 5343 and LP 552-21 with corrected distances between 180
pc and 400 pc and resulting tangential velocities still larger than about 400
km/s.


title:
A VSA search for the extended Sunyaev-Zel'dovich Effect in the Corona
  Borealis Supercluster

abstract:
  We present interferometric imaging at 33 GHz of the Corona Borealis
supercluster, using the extended configuration of the Very Small Array. A total
area of 24 deg^2 has been imaged, with an angular resolution of 11 arcmin and a
sensitivity of 12 mJy/beam. The aim of these observations is to search for
Sunyaev-Zel'dovich (SZ) detections from known clusters of galaxies in this
supercluster and for a possible extended SZ decrement due to diffuse warm/hot
gas in the intercluster medium. We measure negative flux values in the
positions of the ten richest clusters in the region. Collectively, this implies
a 3.0-sigma detection of the SZ effect. In the clusters A2061 and A2065 we find
decrements of approximately 2-sigma. Our main result is the detection of two
strong and resolved negative features at -70+-12 mJy/beam (-157+-27 microK) and
-103+-10 mJy/beam (-230+-23 microK), respectively, located in a region with no
known clusters, near the centre of the supercluster. We discuss their possible
origins in terms of primordial CMB anisotropies and/or SZ signals related to
either unknown clusters or to a diffuse extended warm/hot gas distribution. Our
analyses have revealed that a primordial CMB fluctuation is a plausible
explanation for the weaker feature (probability of 37.82%). For the stronger
one, neither primordial CMB (probability of 0.33%) nor SZ can account alone for
its size and total intensity. The most reasonable explanation, then, is a
combination of both primordial CMB and SZ signal. Finally, we explore what
characteristics would be required for a filamentary structure consisting of
warm/hot diffuse gas in order to produce a significant contribution to such a
spot taking into account the constraints set by X-ray data.


title: MACHOs in M31? Absence of evidence but not evidence of absence

abstract:
  We present results of a microlensing survey toward the Andromeda Galaxy (M31)
carried out during four observing seasons at the Isaac Newton Telescope (INT).
This survey is part of the larger microlensing survey toward M31 performed by
the Microlensing Exploration of the Galaxy and Andromeda (MEGA) collaboration.
Using a fully automated search algorithm, we indentify 14 candidate
microlensing events, three of which are reported here for the first time.
Observations obtained at the Mayall telescope are combined with the INT data to
produce composite lightcurves for these candidates. The results from the survey
are compared with theoretical predictions for the number and distribution of
events. These predictions are based on a Monte Carlo calculation of the
detection efficiency and disk-bulge-halo models for M31. The models provide the
full phase-space distribution functions for the lens and source populations and
are motivated by dynamical and observational considerations. They include
differential extinction and span a wide range of parameter space characterised
primarily by the mass-to-light ratios for the disk and bulge. For most models,
the observed event rate is consistent with the rate predicted for self-lensing
-- a MACHO halo fraction of 30% or higher can be ruled at the 95% confidence
level. The event distribution does show a large near-far asymmetry hinting at a
halo contribution to the microlensing signal. Two candidate events are located
at particularly large projected radii on the far side of the disk. These events
are difficult to explain by self lensing and only somewhat easier to explain by
MACHO lensing. A possibility is that one of these is due to a lens in a giant
stellar stream.