title: New Grids of ATLAS9 Model Atmospheres

abstract:
  New opacity distribution functions (ODFs) for several metallicities have been
computed. The main improvements upon previous ODFs computed by Kurucz (1990)
are: (1) the replacement of the solar abundances from Anders & Grevesse (1989)
with those from Grevesse & Sauval (1998); (2) the replacement of the TiO lines
provided by Kurucz (1993) with the TiO lines from Schwenke (1998), as
distributed by Kurucz (1999a); (3) the addition of the H2O lines from Partridge
& Schwenke (1997) as distributed by Kurucz (1999b); (4) the addition of the
HI-HI and HI-H+ quasi-molecular absorptions near 1600 A and 1400 A computed
according to Allard et al. (1998). Other minor improvements are related with
some changes in a few atomic and molecular data. New grids of ATLAS9 model
atmospheres for Teff from 3500K to 50000K and logg from 0.0 dex to 5.0 dex have
been computed for several metallicities with the new ODFs. Preliminary
comparisons of the results from the old and new models have shown differences
in the energy distributions of stars cooler than 4500K, in the ultraviolet
energy distribution of metal-poor A-type stars, in the U-B and u-b color
indices for Teff<7000K and in all the color indices for Teff<4250K.


title:
Determination of the Night Sky Background around the Crab pulsar using
  its optical pulsation

abstract:
  The poor angular resolution of imaging gamma-ray telescopes is offset by the
large reflector areas of next generation telescopes such as MAGIC (17~m
diameter), which makes the study of optical emission associated with some
gamma-ray sources feasible. Furthermore, the extremely fast time response of
photomultipliers (PMs) makes them ideal detectors for fast (subsecond) optical
transients and periodic sources like pulsars. The optical pulse of the Crab
pulsar was detected with the HEGRA CT1 central pixel using a modified PM,
similar to the future MAGIC camera PMs. The purpose of these periodic
observations was to determine the light of the night sky (LONS) for the
galactic anticenter Crab region.Our results are between 2.5 and 3 times larger
than the previously measured LONS (outside the galactic plane), as expected
since the Crab pulsar is in the galactic plane, which implies a slightly higher
energy threshold for Crab observations, if the higher value of CT1 measured
LONS rate for galactic sources is used.


title: Crust cooling curves of accretion-heated neutron stars

abstract:
  We discuss the recent efforts to use a sub-class of neutron-star X-ray
transients (the quasi-persistent transients) to probe the properties of
neutron-star crusts and cores. Quasi-persistent X-ray transients experience
accretion episodes lasting years to decades, instead of the usual weeks to
months of ordinary, short-duration transients. These prolonged accretion
episodes should significantly heat the crusts of the neutron stars in these
systems, bringing the crusts out of thermal equilibrium with their neutron-star
cores. When these systems are back in quiescence, i.e. when no more accretion
onto the neutron-star surfaces occurs, then the crusts should thermally radiate
in X-rays, cooling them down until they are again in thermal equilibrium with
the cores. In this chapter we discuss the recent X-ray monitoring campaigns we
performed (using the X-ray satellites Chandra and XMM-Newton) to study several
quasi-persistent neutron-star X-ray transients in their quiescent states. These
observations gave us, for the first time, a detailed look into the cooling
curves of accretion heated neutron-star crusts. In this chapter, we discuss how
these crust cooling curves can provide insight into the structure of neutron
stars.


title:
The role of the time step and overshooting in the modelling of PMS
  evolution: the case of EK Cephei

abstract:
  We have produced detailed evolutionary models of the binary EK Cep using the
CESAM stellar evolution code (Morel 1997). A $\chi^2$-minimisation was
performed to derive the most reliable set of modelling parameters. We have
found that an evolutionary age of about 26.8 Myrs fits both components in the
same isochrone. The positions of EK Cep A and B in the HR diagram are
consistent (within the observational uncertainties) with our results.
  Our revised calibration shows clearly that EK Cep is in the beginning of the
main sequence, while EK Cep B is indeed a PMS star. Such a combination allows
for a precise age determination of the binary, and provides a strict test of
the modelling. In particular we have found that the definition of the time step
in calculating the PMS evolution is crucial to reproduce the observations. A
discussion of the optimal time step for calculating PMS evolution is presented.
  The fitting to the radii of both components is a more difficult task;
although we managed to do it for EK Cep B, EK Cep A has a lower radius than our
best models.
  We further studied the effect of the inclusion of a moderate convective
overshooting; the calibration of the binary is not significantly altered, but
the effect of the inclusion of overshooting can be dramatic in the approach to
the main sequence of stars with masses high enough to burn hydrogen through the
CNO cycle on the main sequence.


title: Dying Radio Galaxies In Clusters

abstract:
  We report the recent discovery of three `dying' radio galaxies belonging to
the WENSS minisurvey sample: WNB1734+6407, WNB1829+6911 and WNB1851+5707. These
sources have been selected on the basis of their extremely steep broad-band
radio spectra, which is a strong indication that these objects either belong to
the rare class of dying radio galaxies or that we are observing `fossil' radio
plasma remaining from a previous nuclear activity. Deep spectral index images
obtained with the Very Large Array confirmed that in these sources the central
engine has ceased to be active for a significant fraction of their lifetime
although their extended lobes have not yet completely faded away. In one case,
WNB1829+6911, fossil radio lobes are seen in conjunction with newly restarting
jets. We found that each source is located (at least in projection) at the
center of an X-ray emitting cluster. We argue that their intriguing association
with clusters implies that the pressure of the dense intracluster medium,
perhaps a cooling flow, prevents quick liquidation of a fossil radio lobe
through adiabatic expansion. On statistical ground we deduce that the duration
of the dying phase for a radio source in cluster is one order of magnitude
higher with respect to that of a radio galaxy in the field.


title: XMM-Newton study of A3562 and its immediate Shapley environs

abstract:
  Using the mosaic of six XMM-Newton observations, we study the hydrodynamic
state of the A3562, a cluster in the center of the Shapley Supercluster. The
X-ray image reveals a sharp surface brightness gradient within the core of
A3562, a 200 kpc ridge extending to the south-west. A nearby group, SC1329-313,
imaged within this program also exhibits a tail aligned with the ridge. Study
of the pressure and entropy identified the ridge with a 40% pressure
enhancement. An associated Mach number of 1.15 relative to a polytropic sound
speed for a 5 keV plasma requires the velocity of the group to be 1400 km/s,
while the projected velocity difference between the cluster and the group
amounts to 1200-1500 km/s. Apparent disruption of the group, if attributed to
the ram pressure, also requires the velocity of the group in the cluster frame
to amount to 1700+/-150 km/s. The sharp surface brightness gradient at the
center is identified with a contact discontinuity, which together with dove
tails in the the large-scale entropy distribution reveals a sloshing of the BCG
in response to the passage of the SC1329-313 group. Using the extent of the
low-entropy tails in A3562 we estimate the amplitude of sloshing motion to be
200/h_70 kpc and the oscillation frequency 1 Gyr.


title:
Obscured star formation in the central region of the dwarf galaxy
  NGC5253

abstract:
  We present HST/NICMOS observations (1.1-2.2micron) and 1.9-4.1micron
spectroscopy of the central region of the dwarf galaxy NGC5253. The HST/NICMOS
observations reveal the presence of a nuclear double star cluster separated by
0.3-0.4arcsec or 6-8pc (for a distance d=4.1Mpc). The double star cluster, also
a bright double source of Pa-alpha emission, appears to be coincident with the
double radio nebula detected at 1.3cm. The eastern near-infrared star cluster
(C1) is identified with the youngest optical cluster, whereas the western star
cluster (C2), although it is almost completely obscured in the optical, becomes
the brightest star cluster in the central region of NGC 5253 at wavelengths
longer than 2micron. Both clusters are extremely young with ages of
approximately 3.5 million years old. C2 is more massive than C1 by a factor of
6 to 20 (M(C2)= 7.7 x 10^5 - 2.6 x 10^6Msun, for a Salpeter IMF in the mass
range 0.1-100Msun). Analysis of the circumnuclear spectrum excluding C1 and C2,
as well as of a number of other near-infrared selected clusters with a range of
(young) ages, suggests that the star formation was triggered across the central
regions of the galaxy. We have also modelled the nuclear UV to mid-infrared
spectral energy distribution (SED) of NGC5253 and found that the infrared part
is well modelled with a highly obscured (A_V= 17mag) young starburst with a
stellar mass consistent with our photometric estimates for C1 and C2. The SED
model predicts a moderately bright polycyclic aromatic hydrocarbon (PAH)
feature at 3.3micron that is not detected in our nuclear L-band spectrum.
NGC5253's low metallicity and a top-heavy IMF likely combine to suppress the
3.3micron PAH emission that is commonly seen in more massive starburst systems.


title: The Origin and Properties of Intracluster Stars in a Rich Cluster

abstract:
  We use a multi million particle N-body + SPH simulation to follow the
formation of a rich galaxy cluster in a Lambda+CDM cosmology, with the goal of
understanding the origin and properties of intracluster stars. The simulation
includes gas cooling, star formation, the effects of a uniform UVB and feedback
from supernovae. Halos that host galaxies as faint as M_R = -19.0 are resolved
by this simulation, which includes 85% of the total galaxy luminosity in a rich
cluster. We find that the accumulation of intracluster light (ICL) is an
ongoing process, linked to infall and stripping events. The unbound star
fraction increases with time and is 20% at z = 0, consistent with observations
of galaxy clusters. The surface brightness profile of the cD shows an excess
compared to a de Vaucouleur profile near 200 kpc, which is also consistent with
observations. Both massive and small galaxies contribute substantially to the
formation of the ICL, with stars stripped preferentially from the outer parts
of their stellar distributions. Simulated observations of planetary nebulae
(PNe) show significant substructure in velocity space. Despite this, individual
intracluster PNe might be useful mass tracers if more than 5 fields at a range
of radii have measured line-of-sight velocities, where an accurate mass
calculation depends more on the number of fields than the number of PNe
measured per field. However, the orbits of IC stars are more anisotropic than
those of galaxies or dark matter, which leads to a systematic underestimate of
cluster mass relative to that calculated with galaxies, if not accounted for in
dynamical models. Overall, the properties of ICL formed in a hierarchical
scenario are in good agreement with current observations. (Abridged)


title: Black Hole Growth & the M_BH--Bulge Relations

abstract:
  We present the black hole mass--bulge velocity dispersion relation for a
complete sample of 75 soft X-ray selected AGNs. We find that the AGNs with
highest accretion rates relative to Eddington lie below the \mbh--\sig\
relation of broad line Seyfert 1s, confirming the Mathur et al (2001) result.
The statistical result is robust and not due to any systematic measurement
error. This has important consequences towards our understanding of black hole
formation and growth: black holes grow by accretion in well formed bulges. As
they grow, they get closer to the \mbh--\sig relation for normal galaxies. The
accretion is highest in the beginning and dwindles as time goes by. Our result
does not support theories of the \mbh--\sig relation in which the black hole
mass is a constant fraction of the bulge mass/ velocity dispersion {\it at all
times} or those in which bulge growth is controlled by AGN feedback.


title: Dark Energy with w>-4/3

abstract:
  Acceleration of the universe might be driven by a continuous elastic medium
-- elastic dark energy (Bucher and Spergel 1999). Elastic dark energy can
stably support equations of state with pressure to energy ratio w > -4/3.
Stable expansion with w<-1 combined with an assumption of ``reheating of
elastic energy'' leads to exotic possibilities such as Expanding Cyclic
Universe -- an ever-expanding universe with periodically repeating inflationary
epochs.


title:
Morphology and Evolution in Galaxy Clusters I: Simulated Clusters in the
  Adiabatic limit and with Radiative Cooling

abstract:
  We have studied morphological evolution in clusters simulated in the
adiabatic limit and with radiative cooling. Cluster morphology in the redshift
range, $0 < z < 0.5$, is quantified by multiplicity and ellipticity. In terms
of ellipticity, our result indicates slow evolution in cluster shapes compared
to those observed in the X-ray and optical wavelengths. The result is
consistent with Floor, Melott & Motl (2003). In terms of multiplicity, however,
the result indicate relatively stronger evolution (compared to ellipticity but
still weaker than observation) in the structure of simulated clusters
suggesting that for comparative studies of simulation and observation,
sub-structure measures are more sensitive than the shape measures. We highlight
a few possibilities responsible for the discrepancy in the shape evolution of
simulated and real clusters.


title: The profiles of the 3 to 12 $\mu$m PAH features

abstract:
  We present spectra of the 3.3 $\mu$m and 11.2 $\mu$m PAH features of a large
number of (extra-) galactic sources, obtained with ISO-SWS. Clear variations
are present in the profiles of these features. The sources are classified
independently based on the 3.3 and 11.2 $\mu$m feature profiles and peak
positions. Correlations between these classes and those based on the 6--9
$\mu$m features (Peeters et al. 2002) are found. Also, these classifications
depend on the type of object. The observed pronounced contrast in the spectral
variations for the CH modes (3.3 and 11.2 $\mu$m bands) versus the CC modes
(6.2, 7.7 and 8.6 $\mu$m bands) is striking : the peak wavelengths of the
features attributed to CC modes vary by $\sim$15--80 cm$^{-1}$, while for the
CH modes the variations are $\sim$4--6.5 cm$^{-1}$. We summarize existing
laboratory data and theoretical calculations of PAH molecules and complexes. In
contrast to the 6.2 and 7.7 $\mu$m components which are attributed to PAH
cations, the 3.3 $\mu$m feature appears to originate in neutral and/or
negatively charged PAHs. We attribute the variations in peak position and
profile of these features to the composition of the PAH family. The variations
in FWHM of the 3.3 $\mu$m feature remains an enigma while those of the 11.2
$\mu$m can be explained by anharmonicity and molecular structure. The possible
origin of the observed contrast in profile variations between the CH modes and
the CC modes is highlighted.


title:
Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin
  Parameters of Black Holes

abstract:
  Can we determine a spin parameter of a black hole by observation of a black
hole shadow in an accretion disk? In order to answer this question, we make a
qualitative analysis and a quantitative analysis of a shape and a position of a
black hole shadow casted by a rotating black hole on an optically thick
accretion disk and its dependence on an angular momentum of a black hole. We
have found black hole shadows with a quite similar size and a shape for largely
different black hole spin parameters and a same black hole mass. Thus, it is
practically difficult to determine a spin parameter of a black hole from a size
and a shape of a black hole shadow in an accretion disk. We newly introduce a
bisector axis of a black hole shadow named a shadow axis. For a rotating black
hole a shape and a position of a black hole shadow are not symmetric with
respect to a rotation axis of a black hole shadow. So, in this case the minimum
interval between a mass center of a black hole and a shadow axis is finite. An
extent of this minimum interval is roughly proportional to a spin parameter of
a black hole for a fixed inclination angle between a rotation axis of a black
hole and a direction of an observer. In order to measure a spin parameter of a
black hole, if a shadow axis is determined observationally, it is crucially
important to determine a position of a mass center of a black hole in a region
of a black hole shadow.


title: (Two) Open Questions in Stellar Nuclear Physics

abstract:
  No doubt, among the most exciting discoveries of the third millennium thus
far are {\bf Oscillations of Massive Neutrinos} and {\bf Dark Energy} that
leads to an accelerated expansion of the Universe. Accordingly, Nuclear Physics
is presented with two extraordinary challenges: the need for precise (5% or
better) prediction of solar neutrino fluxes within the Standard Solar Model,
and the need for an accurate (5% or better) understanding of stellar evolution
and in particular of Type Ia super nova that are used as cosmological standard
candle. In contrast, much confusion is found in the field with contradicting
data and strong statements of accuracy that can not be supported by current
data. We discuss an experimental program to address these challenges and
disagreements.


title: Calibrated stellar models for metal-poor population

abstract:
  We extend to lower metallicities recent evolutionary computations devoted to
Magellanic Clouds stars, presenting and discussing new stellar models with
Z=0.0002, 0.0004, 0.0006, 0.001 and suitable assumptions about the original He
content. As in the previous paper, evolutionary results are compared with
observational data to properly calibrate the assumptions about the efficiency
of the surface convection. On this basis, we follow the evolution of stellar
models in the mass range 0.6 to 11Mo from the Main Sequence (MS) to the C
ignition or the onset of thermal pulses in the advanced Asymptotic Giant Branch
(AGB) phase, presenting cluster isochrones covering the range of ages from 20
Myr to 20 Gyr. Selected predictions constraining the cluster ages are
discussed, presenting a calibration of the difference in magnitude between the
luminous MS termination and the He burning giants in terms of the cluster age.
Both evolutionary tracks and isochrones are available at the URL
http://astro.df.unipi.it/SAA/PEL/Z0.html. Data files are also available at the
CDS.


title: Properties of Spiral and Elliptical Galaxy Progenitors at z > 1

abstract:
  We present the results of a Hubble Space Telescope and ground-based optical
and near-infrared study to identify progenitors of spirals and ellipticals at z
> 1. We identify these systems through photometric and spectroscopic redshifts,
deep K-band imaging, stellar mass measurements, and high resolution imaging.
The major modes of galaxy formation, including major mergers, minor mergers,
and accretion of intergalactic gas, and their relative contributions towards
building up the stellar masses of galaxies, can now be directly measured using
these data.


title:
Spatial and velocity coincidence of 4765- and 1720-MHz OH masers in two
  star-forming regions Cep A and W75N

abstract:
  We present the first maps of 4765-MHz OH masers in two star-forming regions
Cepheus A and W75N, made with Multi-Element Radio Linked Interferometer
Network. In Cep A the emission has an arc-like structure of size 40 mas with a
clear velocity gradient, and lies at the edge of H II region 3b Over a period
of 8 weeks the maser diminished in intensity by a factor of 7 but its structure
remained stable. This structure coincides with a newly mapped 1720-MHz maser in
Cep A within the positional error, and matches it in velocity. The 1720-MHz
line exhibits Zeeman splitting that corresponds to a magnetic field strength of
-17.3 mG. In W75N the excited 4765-MHz OH maser has a linear structure of size
45 mas with a well defined velocity gradient, and lies at the edge of H II
region VLA 1. This structure coincides in position and velocity with the
1720-MHz masers. We conclude that in both sources the 4765-MHz emission
coexists with 1720-MHz emission in the same volume of gas. In such a case the
physical conditions in these regions are tightly constrained by the
maser-pumping models.


title: Broad band X-ray spectra of short bursts from SGR 1900+14

abstract:
  We report on the X-ray spectral properties of 10 short bursts from SGR1900+14
observed with the Narrow Field Instruments onboard BeppoSAX in the hours
following the intermediate flare of 2001 April 18. Burst durations are
typically shorter than 1 s, and often show significant temporal structure on
time scales as short as $\sim$10 ms. Burst spectra from the MECS and PDS
instruments were fit across an energy range from 1.5 to above 100 keV. We fit
several spectral models and assumed Nh values smaller than 5$\times 10^{22}$
cm$^{-2}$, as derived from observations in the persistent emission. Our results
show that the widely used optically thin thermal bremsstrahlung law provides
acceptable spectral fits for energies higher than 15 keV, but severely
overestimated the flux at lower energies. Similar behavior had been observed
several years ago in short bursts from SGR 1806-20, suggesting that the
rollover of the spectrum at low energies is a universal property of this class
of sources. Alternative spectral models - such as two blackbodies or a cut-off
power law - provide significantly better fits to the broad band spectral data,
and show that all the ten bursts have spectra consistent with the same spectral
shape.


title: An embedded circumnuclear disk in Mrk 273

abstract:
  Radio observations using very long baseline interferometry (VLBI) and the
Westerbork interferometer have been carried out to study the hydroxyl Megamaser
emission in Mrk~273 at different spatial resolutions. Line and continuum
observations were carried out by the European VLBI network (EVN) at 1.6 GHz and
display a number of distinct structural components in the central arcsec^2
region. The observed continuum emission shows three prominent regions with both
flat and steep spectral indexes. The hydroxyl (OH) emission detected by the EVN
measurements accounts for only 12 percent of the total OH emission in Mrk 273,
but it does show the same dominant 1667 MHz line emission components as the
WSRT observations. The spatial distribution of the maser emission provides a
high resolution view of the molecular environment in the nuclear region. The OH
emission has only been detected toward a distinct radio source in the northern
nucleus with a spatial extent of 108 pc. The OH emission is only partially
superposed on the radio continuum and is associated with the near-infrared
emission source. The low pump efficiency of the maser and the OH main-line
ratio suggest that this emission originates in an optically thin and
unsaturated maser environment with a complex pumping scheme that cannot be
explained by radiative infrared pumping with a single dust temperature. The
specific line emission pattern and the line-of-sight velocities indicate the
organized structure of an edge-on disk/TORUS with a Keplerian rotation
surrounding a central object with a binding mass of (1.39+-0.16)x10^9 M_sun.


title:
Identifying a black hole X-ray transient in M31 with XMM-Newton and
  Chandra

abstract:
  Stochastic variability in two out of four XMM-Newton observations of XMMU
J004303+4115 along with its power spectra and X-ray luminosities suggest a
low-mass X-ray binary (LMXB) with a black hole primary. However, Chandra
observations resolve the object into two point sources. We use data from 35
Chandra observations to analyse the contributions of each source, and attribute
the variability to CXOM31 J004303.2+411528 (known as r2-3), which varies in
intensity by a factor of ~100 between observations. We assume that the power
density spectra of LMXBs are governed by the luminosity, and that the
transition between types of power density spectra occurs at some critical
luminosity in Eddington units, l_c, that applies to all LMXBs. We use results
from these XMM-Newton observations and past results from the available
literature to estimate this transition luminosity, and find that all results
are consistent with l_c ~0.1 in the 0.3--10 keV band. CXOM31 J004303.2+411528
exhibits a low accretion rate power density spectrum at a 0.3--10 keV
luminosity of (5.3+/-0.6)x10^{37} erg/s. Known stellar mass black holes have
masses of 4--15 M_{\odot}; hence our observations of CXOM31 J004303.2+411528
are consistent with l_c ~0.1 if it has a black hole primary.


title:
The nuclear ring in the unbarred galaxy NGC 278: result of a minor
  merger?

abstract:
  We present fully sampled high angular resolution two-dimensional kinematics
in the H alpha spectral line, optical and near-infrared imaging, as well as 21
cm atomic hydrogen data of the spiral galaxy NGC 278. This is a small
non-barred galaxy, which has a bright star forming inner region of about 2 kpc
in diameter, reminiscent of nuclear rings seen mainly in barred galaxies. The H
alpha kinematics show a disturbed velocity field, which may be partly the
result of spiral density wave streaming motions. The 21 cm data trace the
atomic hydrogen well outside the optical disk. The HI is not abundant but
clearly shows disturbed morphology and kinematics. We postulate that the
current structure of NGC 278 is a result of a recent interaction with a small
gas-rich galaxy, which is now dispersed into the outer disk of NGC 278.
Non-axisymmetries set up in the disk by this minor merger may well be the cause
of the intense star formation in the inner region, which can be interpreted as
a rare example of a nuclear ring in a non-barred galaxy. Rather than being
induced by a bar, this nuclear ring would then be the direct result of an
interaction event in the recent history of the galaxy.


title:
The equilibrium state of the dense electron-nuclear plasma in the
  self-gravitational field. The stellar mass distribution and stellar magnetic
  fields

abstract:
  The equilibrium of dense plasma in a self-gravitation is considered. The
obtained results radically distinguish from the point of view which is commonly
accepted in the astrophysical society. It is important that all these results
were obtained without any disputable speculative assumptions. They were
obtained on the standard physical base by standard formal methods. The novelty
of the obtained results is based on a rejection of the oversimplified ideal gas
approximation which is usually accepted for a star interior description and on
a taking into consideration the electron-nuclear plasma features. It was shown
that there is the minimum for plasma energy at a density and a temperature
which determines the equilibrium state of plasma in the self-gravitation at
zero gradient of the general parameters of plasma. This effect plays an
important role for astrophysics. It enables to explain the mechanism of the
star magnetic field generation and to make a prediction for the spectrum of
star masses with a quite satisfactory agreement for the observation data.


title:
Neutrinos from extragalactic cosmic ray interactions in the far infrared
  background

abstract:
  Extragalactic background of high energy neutrinos arising from the
interactions of cosmic ray protons with far-infrared extragalactic background
radiation is calculated. The main assumption is that the cosmic ray spectrum at
energies higher than $10^8 GeV$ has extragalactic origin and, therefore, is
proton dominated. All calculations are performed with taking into account the
possible cosmological evolution of extragalactic sources of cosmic ray protons
as well as infrared-luminous galaxies.


title: Multiwavelength Observation of WIMP Annihilation

abstract:
  The annihilation of neutralino dark matter may result in observable signals
in different wavelength. In the present paper we will discuss the effect of
neutralino annihilation in the halo of our Galaxy and in its center. According
to high resolution cold dark matter simulations, large virialized halos are
formed through the constant merging of smaller halos appeared at previous
times. At each epoch, dark matter halos have then a clumpy component which is
made of these merging subhalos. The annihilation of dark matter in these
clumps, always present in the halo of our Galaxy, may be responsible for
appreciable fluxes of $\gamma$-rays, potentially detectable. We find that,
depending on the fundamental parameters of the clump density profile and on the
distribution of clumps in the Galactic halo, the contribution to the diffuse
$\gamma$-ray background from clumps could be used to obtain constraints on the
neutralino properties such as mass and annihilation cross section. On the other
hand the annihilation of neutralino dark matter in the galactic center may
result in radio signals. At the galactic center, infact, the accretion flow
onto the central black hole sustains strong magnetic fields that can induce
synchrotron emission, in the radio wavelength, by electrons and positrons
generated in neutralino annihilations during advection onto the black hole. We
find that the observed emission from the galactic center is consistent with
neutralinos following a Navarro Frenk and White density profile at the galactic
center while it is inconsistent with the presence of a spike density profile,
supposed to be generated by the formation history of the central black hole.


title: First determination of the dynamical mass of a binary L dwarf

abstract:
  We present here the results of astrometric, photometric and spectroscopic
observations leading to the determination of the orbit and dynamical masses of
the binary L dwarf 2MASSW J0746425+2000321. High angular resolution
observations spread over almost 4 years and obtained with the Hubble Space
Telescope (HST), the ESO Very Large Telescope (VLT), and a the W. M. Keck
Observatory (Keck) allow us to cover 36% of the period, corresponding to 60% of
the orbit, and, for the first time, to derive a precise estimate of the total
and individual masses of such a late-type object. We find an orbital period of
3850.9$^{+904}_{-767}$ days. The corresponding total mass is
0.146$^{+0.016}_{-0.006}$ M$_{\sun}$, with uncertainties depending on the
distance. Spatially resolved low resolution optical (550--1025 nm) spectra have
been obtained with HST/STIS, allowing us to measure the spectral types of the
two components (L0$\pm$0.5 for the primary and L1.5$\pm$0.5 for the secondary).
We also present precise photometry of the individual components measured on the
high angular resolution images obtained with HST/ACS and WFPC2 (visible),
VLT/NACO (J, H and Ks bands) and Keck I (Ks) band). These spectral and
photometric measurements enable us to estimate their effective temperatures and
mass ratio, and to place the object accurately in a H--R diagram. The binary
system is most likely formed by a primary with a mass of 0.085$\pm$0.010
M$_{\sun}$ and a secondary with a mass of 0.066$\pm$0.006 M$_{\sun}$, thus
clearly substellar, for an age of approximately 300$\pm$150 Myr. H$\alpha$
variability indicates chromospheric and/or magnetic activity.


title: The gas content of peculiar galaxies: strongly interacting systems

abstract:
  A study of the gas content in 1038 interacting galaxies, essentially selected
from Arp, Arp and Madore, Vorontsov-Velyaminov catalogues and some of the
published literature, is presented here. The data on the interstellar medium
have been extracted from a number of sources in the literature and compared
with a sample of 1916 normal galaxies. The mean values for each of the
different ISM tracers (FIR, 21 cm, CO lines, X-ray) have been estimated by
means of survival analysis techniques, in order to take into account the
presence of upper limits. From the data it appears that interacting galaxies
have a higher gas content than normal ones. Galaxies classified as ellipticals
have both a dust and gas content one order of magnitude higher than normal.
Spirals have in most part a normal dust and HI content but an higher molecular
gas mass. The X-ray luminosity also appears higher than that of normal galaxies
of same morphological type, both including or excluding AGNs. We considered the
alternative possibilities that the molecular gas excess may derive from the
existence of tidal torques which produce gas infall from the surrounding
regions or from a different metallicity which affects the X conversion factor
between the observed CO line luminosity and the H$_2$ calculated mass.
According to our tests, it appears that interacting galaxies possess a higher
molecular mass than normal galaxies but with a similar star formation
efficiency.


title: Black Hole Induced Ejections

abstract:
  Black Holes generate a particular kind of environments dominated by an
accretion flow which concentrates a magnetic field. The interplay of gravity
and magnetism creates this paradoxical situation where relativistic ejection is
allowed and consequently high energy phenomena take place. Therefore Black
Holes, which are very likely at the origin of powerfull astrophysical phenomena
such as AGNs, micro- quasars and GRBs where relativistic ejections are
observed, are at the heart of high energy astrophysics. The combination of
General Relativity and Magneto-HydroDynamics (MHD) makes theory difficult;
however great pionneers opened beautiful tracks in the seventies and left
important problems to be solved for the next decades. These lectures will
present the status of these issues. They have a tutorial aspect together with
critical review aspect and contain also some new issues. Most of these lectures
has been presented at the "School on Black Hole in the Universe" at Cargese, in
May 2003.


title:
Second Epoch Global VLBI Observations of Compact Radio Sources in the
  M82 Starburst Galaxy

abstract:
  We have presented the results of a second epoch of global Very Long Baseline
Interferometry observations, taken on 23 February 2001 at a wavelength of 18
cm, of the central kiloparsec of the nearby starburst galaxy Messier 82. These
observations were aimed at studying the structural and flux evolution of some
of the compact radio sources in the central region that have been identified as
supernova remnants. The objects 41.95+575 and 43.31+592 have been studied,
expansion velocities of 2500 +/- 1200 km/s and 7350 +/- 2100 km/s respectively
have been derived. Flux densities of 31.1 +/- 0.3 mJy and 17.4 +/- 0.3 mJy have
been measured for the two objects. These results are consistent with
measurements and predictions from previous epochs.


title:
The Hubble constant from gravitational lens CLASS B0218+357 using the
  Advanced Camera for Surveys

abstract:
  We present deep optical observations of the gravitational lens system CLASS
B0218+357, from which we derive an estimate of the Hubble constant. Extensive
radio observations have reduced the degeneracies between Hubble's constant and
the mass model in this lens to one involving only the position of the
radio-quiet lensing galaxy relative to the lensed images. B0218+357 has an
image separation of only 334 mas, so optical observations have previously been
unable to resolve the lens galaxy from the bright lensed images. Using the new
Advanced Camera for Surveys installed on the Hubble Space Telescope, we have
measured the separation between the lens galaxy centre and the brightest image.
The position found, and hence our estimate of Hubble's constant, depends on our
approach to the spiral arms in B0218+357. If the most prominent arms are left
unmasked, we find a value for Hubble's constant of 70+/-5 km/s /Mpc (95%
confidence). If the spiral arms are masked out, we find a value of 61+/-7 km/s
/Mpc (95% confidence).


title: XMM-Newton observations of three high redshift radio galaxies

abstract:
  We present results on the physical states of three high-redshift powerful
radio galaxies (3C 292 at z=0.7, 3C 184 at z=1, and 3C322 at z=1.7). They were
obtained by combining radio measurements with X-ray measurements from
XMM-Newton that separate spectrally and/or spatially radio-related and hot-gas
X-ray emission. Originally observed as part of a programme to trace clusters of
galaxies at high redshift, none of the sources is found to lie in a rich
X-ray-emitting environment similar to those of some powerful radio galaxies at
low redshift, although the estimated gas pressures are sufficient to confine
the radio lobes. The weak gas emission is a particularly interesting result for
3C 184, where a gravitational arc is seen, suggesting the presence of a very
massive cluster. Here Chandra data complement the XMM-Newton measurements in
spatially separating X-ray extended emission from that associated with the
nucleus and rather small radio source. 3C 292 is the source for which the
X-ray-emitting gas is measured with the greatest accuracy, and its temperature
of 2 keV and luminosity of 6.5E43 erg/s are both characteristic of a poor
cluster. This source allows the most accurate measurement of inverse-Compton
X-ray emission associated with the radio lobes. In all structures where the
magnetic-field strength can be estimated through combining measurements of
radio-synchrotron and inverse-Compton-X-ray emission, the field strengths are
consistent with sources being in a state of minimum total energy.


title:
Simulating star formation in molecular cores II. The effects of
  different levels of turbulence

abstract:
  (Abridged) We explore, by means of a large ensemble of SPH simulations, how
the level of turbulence affects the collapse and fragmentation of a
star-forming core. All our simulated cores have the same, except that we vary
(a) the initial level of turbulence (as measured by the ratio of turbulent to
gravitational energy, $\alpha_{\rm turb} \equiv U_{\rm turb}/|\Omega| = 0,
0.01, 0.025, 0.05, 0.10 {\rm and} 0.25$) and (b), for fixed $\alpha_{\rm
turb}$, the details of the initial turbulent velocity field (so as to obtain
good statistics).
  A low level of turbulence ($\alpha_{\rm turb} \sim 0.05$) suffices to produce
multiple systems. As $\alpha_{\rm turb}$ is increased, the number of objects
formed and the companion frequency both increase. The mass function is bimodal,
with a flat low-mass segment representing single objects ejected from the core
before they can accrete much, and a Gaussian high-mass segment representing
objects which because they remain in the core grow by accretion and tend to
pair up in multiple systems.


title:
Cosmological parameter estimation with large scale structure and
  supernovae data

abstract:
  Most cosmological parameter estimations are based on the same set of
observations and are therefore not independent. Here, we test the consistency
of parameter estimations using a combination of large-scale structure and
supernovae data, without cosmic microwave background (CMB) data. We combine
observations from the IRAS 1.2 Jy and Las Campanas redshift surveys, galaxy
peculiar velocities and measurements of type Ia supernovae to obtain
h=0.57_{-0.14}^{+0.15}, Omega_m=0.28+/-0.05 and sigma_8=0.87_{-0.05}^{+0.04} in
agreement with the constraints from observations of the CMB anisotropies by the
WMAP satellite. We also compare results from different subsets of data in order
to investigate the effect of priors and residual errors in the data. We find
that some parameters are consistently well constrained whereas others are
consistently ill-determined, or even yield poorly consistent results, thereby
illustrating the importance of priors and data contributions.


title:
An intense soft-excess and evidence for light bending in the luminous
  narrow-line quasar PHL 1092

abstract:
  The narrow-line quasar PHL 1092 was observed by XMM-Newton at two epochs
separated by nearly thirty months. Timing analyses confirm the extreme
variability observed during previous X-ray missions. A measurement of the
radiative efficiency is in excess of what is expected from a Schwarzschild
black hole. In addition to the rapid X-ray variability, the short UV light
curves (< 4 hours) obtained with the Optical Monitor may also show
fluctuations, albeit at much lower amplitude than the X-rays. In general, the
extreme variability is impressive considering that the broad-band (0.4-10 keV
rest-frame) luminosity of the source is ~10^45 erg/s. During at least one of
the observations, the X-ray and UV light curves show common trends, although
given the short duration of the OM observations, and low significance of the UV
light curves it is difficult to comment on the importance of this possible
correlation. Interestingly, the high-energy photons (> 2 keV) do not appear
highly variable. The X-ray spectrum resembles that of many narrow-line Seyfert
1 type galaxies: an intense soft-excess modelled with a multi-colour disc
blackbody, a power-law component, and an absorption line at ~1.4 keV. The ~1.4
keV feature is curious given that it was not detected in previous observations,
and its presence could be related to the strength of the soft-excess. Of
further interest is curvature in the spectrum above ~2 keV which can be
described by a strong reflection component. The strong reflection component,
lack of high-energy temporal variability, and extreme radiative efficiency
measurements can be understood if we consider gravitational light bending
effects close to a maximally rotating black hole.


title: Phaseless VLBI mapping of compact extragalactic radio sources

abstract:
  The problem of phaseless aperture synthesis is of current interest in
phase-unstable VLBI with a small number of elements when either the use of
closure phases is not possible (a two-element interferometer) or their quality
and number are not enough for acceptable image reconstruction by standard
adaptive calibration methods. Therefore, we discuss the problem of unique image
reconstruction only from the spectrum magnitude of a source. We suggest an
efficient method for phaseless VLBI mapping of compact extragalactic radio
sources. This method is based on the reconstruction of the spectrum magnitude
for a source on the entire UV plane from the measured visibility magnitude on a
limited set of points and the reconstruction of the sought-for image of the
source by Fienup's method from the spectrum magnitude reconstructed at the
first stage. We present the results of our mapping of the extragalactic radio
source 2200 +420 using astrometric and geodetic observations on a global VLBI
array. Particular attention is given to studying the capabilities of a
two-element interferometer in connection with the putting into operation of a
Russian-made radio interferometer based on Quasar RT-32 radio telescopes.


title: The Sample of Gamma-ray Bursts Observed With SPI-ACS

abstract:
  The SPI anticoincidence shield consists of 91 BGO crystals and is operated as
a nearly omnidirectional gamma-ray burst detector above ~75 keV. Since the
start of the mission 269 gamma-ray burst candidates have been detected. 110
bursts have been confirmed with the instruments included in the 3rd
Interplanetary Network. Here we present a preliminary statistical analysis of
the SPI-ACS sample of gamma-ray bursts and gamma-ray burst candidates; in
particular we discuss the duration distribution of the bursts. A prominent
population of short burst candidates (duration <200ms) is found which is
discovered to be strongly contaminated by cosmic-ray nuclei interacting in the
detectors.


title: Confronting the Superbubble Model with X-ray Observations of 30 Dor C

abstract:
  We present an analysis of XMM-Newton observations of the superbubble 30 Dor C
and compare the results with the predictions from the standard wind-blown
bubble model. We find that the observed X-ray spectra cannot be fitted
satisfactorily with the model alone and that there is evidence for nonthermal
X-ray emission, which is particularly important at > 4 keV. The total
unabsorbed 0.1-10 keV luminosities of the eastern and western parts of the
bubble are ~3 10^36 erg/s and ~5 10^36 erg/s, respectively. The unabsorbed
0.1-10 keV luminosity of the bubble model is 4 10^36 erg/s and so the power-law
component contributes between 1/3 and 1/2 to the total unabsorbed luminosity in
this energy band. The nature of the hard nonthermal emission is not clear,
although recent supernovae in the bubble may be responsible. We expect that
about one or two core-collapse supernovae could have occured and are required
to explain the enrichment of the hot gas, as evidenced by the overabundance of
alpha-elements by a factor of 3, compared to the mean value of 0.5 solar for
the interstellar medium in the Large Magellanic Cloud. As in previous studies
of various superbubbles, the amount of energy currently present in 30 Dor C is
significantly less than the expected energy input from the enclosed massive
stars over their lifetime. We speculate that a substantial fraction of the
input energy may be radiated in far-infrared by dust grains, which are mixed
with the hot gas because of the thermal conduction and/or dynamic mixing.


title:
Compton Echoes from Gamma-Ray Bursts: Unveiling Misaligned Jets in
  Nearby Type Ib/c Supernovae

abstract:
  There is now compelling evidence of a link between long-duration gamma-ray
bursts (GRBs) and Type Ib/c supernovae (SNe). These core-collapse explosions
are conjectured to radiate an anisotropic, beamed component associated with a
decelerating, relativistic outflow and an unbeamed, isotropic component
associated with the slowly expanding stellar debris. The anisotropic emission
remains at a very low level until the Doppler cone of the beam intersects the
observer's line of sight, making off-axis GRB jets directly detectable only at
long wavelengths and late times. Circumstellar material, however, will Compton
scatter the prompt gamma-ray and afterglow radiation flux and give rise to a
reflection echo. We show that the Compton echo of a misaligned GRB carries an
X-ray luminosity that may exceed by many orders of magnitude that produced by
the underlying subrelativistic SN during the first few weeks. Bright scattering
echoes may therefore provide a means for detecting a population of misaligned
GRBs associated with nearby Type Ib/c SNe and yield crucial information on the
environment surrounding a massive star at the time of its death. The question
of whether the interpretation of GRB980425 as an ordinary GRB observed off-axis
is consistent with the lack of an X-ray echo is addressed, along with the
constraints derived on the possible existence of misaligned GRB jets in
SN1993J, SN1994I, SN1999em, and SN2002ap.


title: The Mass of the MACHO-LMC-5 Lens Star

abstract:
  We combine the available astrometric and photometric data for the 1993
microlensing event MACHO-LMC-5 to measure the mass of the lens, M=0.097 +/-
0.016 Msun. This is the most precise direct mass measurement of a single star
other than the Sun. In principle, the measurement error could be reduced as low
as 10% by improving the trig parallax measurement using, for example, the Space
Interferometry Mission. Further improvements might be possible by rereducing
the original photometric lightcurve using image subtraction or by obtaining
new, higher-precision baseline photometry of the source. We show that the
current data strongly limit scenarios in which the lens is a dark (i.e.,
brown-dwarf) companion to the observed M dwarf rather than being the M dwarf
itself. These results set the stage for a confrontation between mass estimates
of the M dwarf obtained from spectroscopic and photometric measurements and a
mass measurement derived directly from the star's gravitational influence. This
would be the first such confrontation for any isolated star other than the Sun.


title:
Extragalactic Ultracompact HII Regions: Probing the Birth Environments
  of Super Star Clusters

abstract:
  In recent years, a number of extragalactic massive star clusters that are
still deeply embedded in their birth material have been discovered. These
objects represent the youngest stage of massive star cluster evolution yet
observed, and the most massive and dense of these may be proto globular
clusters. Their properties appear to be similar to those of ultracompact HII
regions in the Galaxy, but scaled up in total mass and luminosity. In many
cases, these clusters are only visible at mid-IR to radio wavelengths, and they
have typically been detected as ``inverted'' spectrum radio sources. However,
the set of existing observations is anemic, and our current physical model for
these natal clusters in simplistic. This article will overview what we think we
know about these objects based on existing observations and outline some of the
most significant gaps in our current understanding.


title: Implications of Quasar Black Hole Masses at High Redshifts

abstract:
  We investigated a sample of 15 luminous high-redshift quasars (3.3 < z < 5.1)
to measure the mass of their super-massive black holes (SMBH) and compare, for
the first time, results based on CIV, MgII, and Hbeta emission lines at
high-redshifts. Assuming gravitationally bound orbits as dominant broad-line
region gas motion, we determine black hole masses in the range of M_bh = 2
times 10^8 M_sun up to M_bh = 4 times 10^10 M_sun. While the black hole mass
estimates based on CIV and Hbeta agree well, MgII typically indicates a factor
of $\sim 5 \times$ lower SMBH masses. A flatter slope of the Hbeta radius -
luminosity relation, a possibly steeper slope of the MgII radius - luminosity
relation, and a slightly larger radius of the MgII BLR than for Hbeta could
relax the discrepancy. In spite of these uncertainties, the CIV, MgII, and
Hbeta emission lines consistently indicate super-massive black hole masses of
several times 10^9 M_sun at redshifts up to z = 5.1. Assuming logarithmic
growth by spherical accretion with a mass to energy conversion efficiency of
epsilon = 0.1 and an Eddington ratio L_bol / L_edd calculated for each quasar
individually, we estimate black hole growth-times of the order of several ~100
Myr which are smaller than the age of the universe at the corresponding
redshift. Assuming high-mass seed black holes (M_bh^seed = 10^3 to 10^5 M_sun)
the SMBHs in the z = 3.5 quasars began to grow at redshifts z > 4, while for
the quasars with z > 4.5 they started at z = 6 to 10. These estimated time
scales for forming SMBHs at high redshifts, together with previous studies
indicating high quasar metallicities, suggest that the main SMBH growth phase
occurs roughly contemporaneously with a period of violent and extensive star
formation in proto-galactic nuclei.


title: Altair: The Brightest Delta Scuti Star

abstract:
  We present an analysis of observations of the bright star Altair (alpha Aql)
obtained using the star camera on the Wide-Field Infrared Explorer (WIRE)
satellite. Although Altair lies within the delta Scuti instability strip,
previous observations have not revealed the presence of oscillations. However,
the WIRE observations show Altair to be a low-amplitude (Delta m < 1 ppt) delta
Scuti star with at least 7 modes present.


title:
Probing the Evolution of the Galaxy Interaction/Merger Rate Using
  Collisional Ring Galaxies

abstract:
  We present the results from our program to determine the evolution of the
galaxy interaction/merger rate with redshift using the unique star-forming
characteristics of collisional ring galaxies. We have identified 25 distant
collisional ring galaxy candidates (CRGCs) in a total of 162 deep Hubble Space
Telescope Wide Field/Planetary Camera-2 images obtained from the HST Archives.
Based on measured and estimated redshifts, these 25 CRGCs all lie in the
redshift interval of 0.1 < z < 1. Using the local collisional ring galaxy
volume density and the new ``standard'' cosmology, we find that in order to
account for the number of identified CRGCs in our surveyed fields, the galaxy
interaction/merger rate, parameterized as (1 + z)^m, must increase steeply with
redshift.We determine a minimum value of m = 5.2 $\pm$ 0.7, though m could be
as high as 7 or 8. We can rule out a non-evolving (m = 0) and weakly evolving
(m = 1-2) galaxy interaction/merger rate at greater than the 4 sigma level of
confidence.


title:
Rotation of Early B-type Stars in the Large Magellanic Cloud - The role
  of evolution and metallicity

abstract:
  I present measurements of the projected rotational velocities of a sample of
100 early B-type main-sequence stars in the Large Magellanic Cloud. This is the
first extragalactic study of the distribution of stellar rotational velocities.
The sample is drawn from two sources: a sample derived from the vicinity of the
main-sequence turnoff of young clusters (ages 1-3x10^7yrs), and a sample from
the general field. I find the cluster population exhibits significantly more
rapid rotation than that seen in the field. I have drawn analogous Galactic
cluster and field samples from the literature. Comparison of these samples
reveals the same effect. I propose the observed difference between cluster and
field populations can be explained by a scenario of evolutionary enhancement of
the surface angular momentum over the main-sequence lifetime. A comparison is
made between the cluster and field populations of the LMC and the Galaxy in
order to explore the effects of metallicity. This shows that the LMC stars are
more rapid rotators than their Galactic counterparts.


title:
It's EZ to Evolve ZAMS Stars: A Program Derived from Eggleton's Stellar
  Evolution Code

abstract:
  "Evolve ZAMS", "EZ" for short, is derived from Peter Eggleton's stellar
evolution program. The core of EZ is a stripped down, rewritten version of a
subset of Eggleton's code, specialized to handle single star evolution from the
zero-age main sequence until forced to stop by an event such as a helium flash
or a crystallizing core. The procedure and data interfaces to the program are
designed to be easy to use while still providing a wide range of function. EZ
is written in Fortran 95 following current programming practices and can be
downloaded from http://theory.kitp.ucsb.edu/~paxton/.


title:
Radio pulsars as progenitors of AXPs and SGRs: magnetic field evolution
  through pulsar glitches

abstract:
  Glitches are common phenomena in pulsars. After each glitch, there is usually
a permanent increase in the pulsar's spin-down rate. Therefore a pulsar's
present spin-down rate may be much higher than its initial value. Thus the
characteristic age of a pulsar based on its present spin-down rate and period
may be shorter than a pulsar's age. At the same time, the permanent increase of
its spin-down rate implies that the pulsar's surface magnetic field is
increased after each glitch. Consequently after many glitches some radio
pulsars may evolve into AXPs and SGRs, i.e., strongly magnetized and slowly
rotating neutron stars.


title: Seismology of the Accreting White Dwarf in GW Lib

abstract:
  We present a first analysis of the g-mode oscillation spectrum for the white
dwarf (WD) primary of GW Lib, a faint cataclysmic variable (CV). Stable
periodicities have been observed from this WD for a number of years, but their
interpretation as stellar pulsations has been hampered by a lack of theoretical
models appropriate to an accreting WD. Using the results of Townsley and
Bildsten, we construct accreting models for the observed effective temperature
and approximate mass of the WD in GW Lib. We compute g-mode frequencies for a
range of accreted layer masses, Macc, and long term accretion rates, <Mdot>. If
we assume that the observed oscillations are from l=1 g-modes, then the
observed periods are matched when M ~= 1.02 Msun, Macc ~= 0.31 x 10^-4 Msun and
<Mdot> ~= 7.3 x 10^-11 Msun/yr. Much more sensitive observations are needed to
discover more modes, after which we will be able to more accurately measure
these parameters and constrain or measure the WD's rotation rate.


title: A Comprehensive Catalogue of Variable Stars in the field of 47 Tucanae

abstract:
  We present the results of a comprehensive search for stellar variability in
the globular cluster 47 Tucanae. Using the Mount Stromlo 40-inch (1m) telescope
at Siding Spring Observatory and a combined V+R filter, we have detected 100
variable stars across a 52$\times52'$ field centered on the cluster. Here we
present the V+R lightcurves and preliminary investigations of the detected
variables, which comprise 28 Eclipsing Binaries (21 contact binaries and 7
detached systems), 45 RR Lyrae stars (41 of which belong to the SMC and four
seemingly to the Galactic Halo), and 20 K-giant Long Period Variables (LPVs).
We also detected four $\delta$ Scuti stars, one TypeI Cepheid, and one TypeII
Cepheid. One variable appears to be a dust-enshrouded SMC star with a short
period pulsation. Of these 100 variables, 69 are new discoveries. Our eclipsing
binary sample indicates a radial segregation in period, and includes two
binaries that are seemingly orbited by low-luminosity stellar companions. One
RR Lyrae star shows a Blahzko effect with remarkable regularity.


title:
The XMM-Newton/2dF survey - V. the radio properties of the X-ray
  population

abstract:
  In this paper we cross-correlate the FIRST 1.4GHz radio survey with a wide
field (~ 1.6deg^2) shallow [f(0.5-8keV) ~ 1e-14erg/s/cm^2] XMM-Newton survey.
We find 12 X-ray/radio matches representing 4% of the X-ray selected sample.
Most of them are found to be associated with AGNs (total of 9) on the basis of
the observed optical spectra (3), radio morphology (2) or X-ray/optical
properties (4), while one radio source is identified with an X-ray selected
cluster. We also find two sources associated with low redshift galaxies with
narrow emission line optical spectra, X-ray luminosity L(0.5-8keV) ~ 1e41erg/s,
radio luminosity density L(1.4GHz) ~ 5e22W/Hz and logf_X/f_{opt} ~ -2
suggesting `normal' star-forming galaxies. We argue that radio surveys combined
with X-ray sample could provide a powerful tool for identifying X-ray selected
`normal' galaxies powered by stellar processes. Finally, radio loud and quiet
systems in the present sample have mean X-ray spectral properties consistent
with Gamma ~ 1.9.


title: The INTEGRAL view of the Soft Gamma-ray Repeater SGR 1806-20

abstract:
  We present the results obtained by INTEGRAL on the Soft-Gamma Ray Repeater
SGR 1806-20. In particular we report on the temporal and spectral properties of
the bursts detected during a moderately active period of the source in
September and October 2003 and on the search for quiescent emission.


title: Linking Gas Fractions to Bimodalities in Galaxy Properties

abstract:
  Galaxies over four decades in stellar mass are shown to obey a strong
correlation between u-K colors and atomic-gas-to-stellar mass ratios (G/S),
using stellar mass-to-light ratios derived from optical colors. The correlation
holds for G/S ranging from nearly 10:1 to 1:100 for a sample obtained by
merging the SDSS DR2, 2MASS, and HYPERLEDA HI catalogs. This result implies
that u-K colors can be calibrated to provide ``photometric gas fractions'' for
statistical applications. Here this technique is applied to a sample of ~35,000
SDSS-2MASS galaxies to examine the relationship of gas fractions to observed
bimodalities in galaxy properties as a function of color and stellar mass. The
recently identified transition in galaxy properties at stellar masses
\~2-3x10^10 Msun corresponds to a shift in gas richness, dividing low-mass
late-type galaxies with G/S ~ 1:1 from high-mass galaxies with
intermediate-to-low G/S. Early-type galaxies below the transition mass also
show elevated G/S, consistent with formation scenarios involving mergers of
low-mass gas-rich systems and/or cold-mode gas accretion.


title: Globular Clusters and Horizontal Branch

abstract:
  An analysis of available Galactic globular cluster data on metallicity, ages,
the distribution of stars on the horizontal branch and the distribution of the
periods of RR0 Lyr variables showed that: 1. The latter two characteristics can
be used for determining the Oosterhoff type. 2. The metallicities of the
observed OoI and OoII clusters overlap in a narrow interval
-1.65$<$[Fe/H]$<$1.52. 3. The OoII clusters are characterized by R-B$<$0, a
statistically significant relation (r=0.97) between the relative number of
B(BS) and V(VS) stars on the horizontal branch. 4. The OoI clusters divide into
two groups: R-B$<$0 and R-B$>$0 with a relation between B and R (r=0.90). The
former clusters do not show a relation between VS and RS stars and the latter a
relation between VS and BS stars on the horizontal branch. 5. The oldest
clusters are characterized by BS close to 1 and the youngest by R close to 1.


title:
A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey III: Discovery
  of Five Additional Quasars

abstract:
  We present the discovery of five new quasars at z>5.7, selected from the
multicolor imaging data of the Sloan Digital Sky Survey (SDSS). Three of them,
at redshifts 5.93, 6.07, and 6.22, were selected from ~1700 deg^2 of new SDSS
Main Survey imaging in the Northern Galactic Cap. An additional quasar, at
redshift 5.85, was discovered by coadding the data obtained in the Fall
Equatorial Stripe in the SDSS Southern Survey Region. The fifth object, at
redshift 5.80, is selected from a non-standard SDSS scan in the Southern
Galactic Cap outside the Main Survey area. The spectrum of SDSS
J162331.81+311200.5 (z=6.22) shows a complete Gunn-Peterson trough at z_abs >
5.95, similar to the troughs detected in other three z>6.2 quasars known. We
present a composite spectrum of the z>5.7 quasars discovered in the SDSS to
date. The average emission line and continuum properties of z~6 quasars exhibit
no significant evolution compared to those at low redshift. Using a complete
sample of nine z>5.7 quasars, we find that the density of quasars with M_1450 <
-26.7 at z~6 is (6+/-2) x 10^-10 per Mpc^3 consistent with our previous
estimates. The luminosity distribution of the sample is fit with a power law
luminosity function Psi(L) ~ L^(-3.2+/-0.7), somewhat steeper than but
consistent with our previous estimates.


title: Temperature and Entropy Fields of Baryonic Gas in the Universe

abstract:
  (Abridged)The temperature (T) and entropy (S) fields of baryonic gas/IGM are
analyzed using simulation samples by a cosmological hydro/N-body code. We show
that in the nonlinear regime the dynamical similarity between the IGM and dark
matter will be broken by strong shocks. The heating and entropy production by
the shocks breaks the IGM into multiple phases. The mean entropy, or the
cosmological entropy floor, is found to be more than 100 h^(-1/3) keV cm^2 in
all regions when z < 1. At redshift z ~ 2 - 3, high-entropy gas (S > 50
h^(-1/3) keV cm^2) mostly resides in areas on scales larger than 1 h^(-1) Mpc
and with density $\rho_{dm}>10^2$. Therefore, gravitational shocks are an
effective preheating mechanism of the IGM, and probably enough to provide the
entropy excess of clusters and groups if the epoch of the gas falling in
cluster cores is not earlier than z ~ 2 - 3. On the other hand, at redshifts z
< 4, there is always a more than 90% volume of the low dark matter mass density
regions filled by the IGM with T < 10^4.5 K. Therefore, the multiphased
character and non-Gaussianity of the IGM field would explain the
high-temperature and high-entropy gas observed in groups and clusters.


title: VERA Observation of the W49N H2O Maser Outburst in 2003 October

abstract:
  We report on a strong outburst of the W49N H2O maser observed with VERA.
Single-dish monitoring with VERA 20 m telescopes detected a strong outburst of
the maser feature at V_LSR = -30.7 km/s in 2003 October. The outburst had a
duration of ~100 days and a peak intensity of 7.9 x 10^4 Jy, being one of the
strongest outbursts in W49N observed so far. VLBI observations with the VERA
array were also carried out near to the maximum phase of the outburst, and the
outburst spot was identified in the VLBI map. While the map was in good
agreement with previous studies, showing three major concentrations of maser
spots, we found a newly formed arc-like structure in the central maser
concentration, which may be a shock front powered by a forming star or a star
cluster. The outburst spot was found to be located on the arc-like structure,
indicating a possible connection of the present outburst to a shock phenomenon.


title: Quenched millimetre emission from Cygnus X-1 in a soft X-ray state

abstract:
  We present millimetre wavelength observations of the black hole candidate
X-ray binary Cygnus X-1 which indicate a suppression, or quenching, of the
emission as the source switches to a softer X-ray state. Combining the data
with those for another black hole candidate, XTE J1118+480, we demonstrate that
the millimetre emission shows the same coupling to X-rays as the radio
emission, although with a much stronger sensitivity to spectral shape. We
therefore confirm the association of the millimetre emission with the jets in
low/hard state black hole candidate X-ray binaries.


title:
Bending instability in galaxies: the stellar disk thickness and the mass
  of spheroidal component

abstract:
  We present results of numerical N-body simulations of a galactic stellar disk
embedded into a spherical dark halo. The non-linear dynamics of bending
instabilities developing in the disk is studied. The bending modes,
axisymmetric and not, are considered as main factors increasing the disk
thickness. The relation between the disk vertical scale height and the
halo+bulge-to-disk mass ratio is inferred. The method of estimation of the
spherical-to-disk mass ratio for edge-on spiral galaxies based on this relation
is studied and applied to constrain the spherical subsystem mass and the mass
of dark halos (M_h/M_d) in seven edge-on galaxies. The values of M_h/M_d are of
order 1 for our galaxies.


title: Gravitational lensing magnification without multiple imaging

abstract:
  Gravitational lensing can amplify the apparent brightness of distant sources.
Images that are highly magnified are often part of multiply-imaged systems, but
we consider the possibility of having large magnifications without additional
detectable images. In rare but non-negligible situations, lensing can produce a
singly highly magnified image; this phenomenon is mainly associated with
massive cluster-scale halos (>~1e13.5 Msun). Alternatively, lensing can produce
multiply-imaged systems in which the extra images are either unresolved or too
faint to be detectable. This phenomenon is dominated by galaxies and lower-mass
halos (<~1e12 Msun), and is very sensitive to the inner density profile of the
halos. Although we study the general problem, we customize our calculations to
four quasars at redshift z~6 in the Sloan Digital Sky Survey (SDSS), for which
Richards et al. (2004) have ruled out the presence of extra images down to an
image splitting of 0.3" and a flux ratio of f=0.01. We predict that 9-29% of
all z~6 quasars that are magnified by a factor of mu>10 would lack detectable
extra images, with 5-10% being true singly-imaged systems. The maximum of 29%
is reached only in the unlikely event that all low-mass (<~1e10 Msun) halos
have highly concentrated (isothermal) profiles. In more realistic models where
dwarf halos have flatter (NFW) inner profiles, the maximum probability is ~10%.
We conclude that the probability that all four SDSS quasars are magnified by a
factor of 10 is <~1e-4. The only escape from this conclusion is if there are
many (>10) multiply-imaged z~6 quasars in the SDSS database that have not yet
been identified, which seems unlikely. In other words, lensing cannot explain
the brightnesses of the z~6 quasars, and models that invoke lensing to avoid
having billion-Msun black holes in the young universe are not viable.


title: How are AGN Found?

abstract:
  We discuss the very different methods in each wavelength band for selecting
and finding Active Galactic Nuclei (AGN). We briefly review the history of the
different techniques for finding AGN and compare and contrast the advantages
and difficulties of selection in different wavelength bands. We stress the
strong selection effects in each wavelength band and the difficulty of defining
complete samples. Of all the techniques presently used, we conclude that
selection in the hard X-ray band via imaging and spectroscopy is the most
complete and allows the best estimate of the number and evolution of active
galaxies. However, all of the techniques have difficulties at low luminosities
where emission due to stellar processes can have similar sizes and
luminosities.


title: An investigation of the absolute circular polarization in radio pulsars

abstract:
  In most pulsars, the circularly polarized component, Stokes $V$, is weak in
the average pulse profiles. By forming the average profile of $|V|$ from single
pulses we can distinguish between pulsars where $V$ is weak in the individual
pulses and those where large $V$ of variable handedness is observed from one
pulse to the other. We show how $|V|$ profiles depend on the signal-to-noise
ratio of $V$ in the single pulses and demonstrate that it is possible to
simulate the observed, broad distributions of $V$ by assuming a model where
$|V|$ is distributed around a mean value and the handedness of $V$ is permitted
to change randomly. The $|V|$ enhanced profiles of 13 pulsars are shown, 5
observed at 1.41 GHz and 8 observed at 4.85 GHz, to complement the set in
Karastergiou et al. (2003b). It is argued that the degree of circular
polarization in the single pulses is related to the orthogonal polarization
mode phenomenon and not to the classification of the pulse components as cone
or core.


title:
A multi-wavelength search for a counterpart of the unidentified
  gamma-ray source 3EG J2020+4017 (2CG078+2)

abstract:
  In search of the counterpart to the brightest unidentified gamma-ray source
3EG J2020+4017 we report on new X-ray and radio observations of the gamma-Cygni
field with the Chandra X-ray Observatory and with the Green Bank Telescope. We
also report on reanalysis of archival ROSAT data. With Chandra it became
possible for the first time to measure the position of the putative gamma-ray
counterpart RX J2020.2+4026 with sub-arcsec accuracy and to deduce its X-ray
spectral characteristics. These observations demonstrate that RX J2020.2+4026
is associated with a K field star and therefore is unlikely to be the
counterpart of the bright gamma-ray source 2CG078+2 in the SNR G78.2+2.1 as had
been previously suggested. The Chandra observation detected 37 additional X-ray
sources which were correlated with catalogs of optical and infrared data.
Subsequent GBT radio observations covered the complete 99% EGRET likelihood
contour of 3EG J2020+4017 with a sensitivity limit of L_820 ~ 0.1 mJy kpc^2
which is lower than most of the recent deep radio search limits. If there is a
pulsar operating in 3EG J2020+4017 this sensitivity limit suggests that the
pulsar either does not produce significant amounts of radio emission or that
its geometry is such that the radio beam does not intersect with the line of
sight. Finally, reanalysis of archival ROSAT data leads to a flux upper limit
of f_x < 1.8 x 10^-13 erg s^-1 cm^-2 for a putative point-like X-ray source
located within the 68% confidence contour of 3EG J2020+4017. Adopting the SNR
age of 5400 yrs and assuming a spin-down to X-ray energy conversion factor of
10^-4 this upper limit constrains the parameters of a putative neutron star as
a counterpart for 3EG J2020+4017 to be P >= 160 (d/1.5 kpc)^-1 ms, P_dot >= 5 x
10^-13 (d/1.5 kpc)^-1 s s^-1 and B_perp >= 9 x 10^12 (d/1.5 kpc)^-1 G.


title:
Gravitational lensing in a concordance LCDM universe: The importance of
  secondary matter along the line of sight

abstract:
  To date, in almost all strong gravitational lensing analyses for modeling
giant arc systems and multiple quasar images, it has been assumed that all the
deflecting matter is concentrated in one lens plane at a certain distance - the
thin lens approximation. However, in a few observed cases, lenses at more than
one redshift have been identified as contributing to the image splitting.
  Here we report on a quantitative investigation of the importance and
frequency of significant multiple lensing agents. We use multi-lens plane
simulations to evaluate how frequently two or more lens planes combined are
essential for multiple imaging, as compared with the cases where a single lens
plane alone provides enough focusing to be supercritical.
  We find that the fraction of cases for which more than one lens plane
contributes significantly to a multi-image lensing situation is a strong
function of source redshift. For sources at redshift unity, 95% of lenses
involve only a single mass concentration, but for a more typical scenario with,
e.g., a source at a redshift of z_s = 3.8, as many as 38% of the strongly
lensed quasars/arcs occur because of a significant matter contribution from one
or more ADDITIONAL lens planes. In the 30% to 40% of cases when additional
planes make a significant contribution, the surface mass density of the primary
lens will be overestimated by about 15% to 20%, if the additional contributions
are not recognized.


title:
Are the sungrazing comets the inner source of pickup ions and energetic
  neutral atoms?

abstract:
  We present arguments that at least part of the inner source of pickup ions in
the solar wind might be the material released by sungrazing comets. Based on a
statistical analysis of sungrazing comets detected over almost eight years of
LASCO operation (1996 -- September 09 2004) an overwhelming majority of the
observed sungrazers belong to the Kreutz group of comets, follows tightly
clumped orbits and break up at $\sim 40 - 4$ solar radii in a well defined
region of space. The material released from these comets could be (after
ionization) an important portion of the inner source of pickup ions (PUIs), as
the local mass flux of the inner source and cometary PUIs seem comparable. We
indicate time intervals during the year when the cometary PUIs could be
observed from a spacecraft on the Earth's orbit (from the end of July until the
end of the year) and show three time intervals when they should be observable
by Ulysses (from its launch time until the end of 1990, from the end of
November 1994 until mid-May 1995 and from February 2001 until the end of July,
2001). We argue that the PUIs from the inner source should include both singly
and doubly charged ions and that this cometary hypothesis alleviates some
difficulties (in particular, the issue of hydrogen deficit) in the
interpretation of the inner source as solar wind neutralized on dust grains
close to the Sun.


title: Acoustic causality in relativistic shells

abstract:
  The motion of sound waves propagating in the perfect fluid with inhomogeneous
background flow is effectively described as a massless scalar field on a curved
space-time. This effective geometry is characterized by the acoustic metric,
which depends on the background flow, and null geodesics on the geometry
express the acoustic causal structure. Therefore by the effective geometry we
can easily study the causality on the flows. In this paper, we consider a
spherically symmetric, relativistic outflow and present the maximal causally
connected region for a super-sonic flow. When Lorentz factor of the radial
velocity of the flow is constant or obeys power-law with respect to the radial
coordinate r, we can solve it analytically. As a result we show that in the
constant case the maximum angle is proportional to inverse of Lorentz factor
and logarithmically increases with respect to r, in contrast, accelerative
expansions in power-law case make this angle bounded.


title: Deep Dredge-up in Intermediate-Mass TP-AGB Stars

abstract:
  We present results of the evolution of AGB stars of 3M_sol and 5M_sol with
solar metallicity calculated with the Eggleton stellar evolution code (STARS),
which has a fully implicit and simultaneous method for solving for the stellar
structure, convective mixing and nuclear burning. We introduce the concept of a
viscous mesh in order to improve the numerical stability of the calculations.
For the 5M_sol star, we evolve through 25 thermal pulses and their associated
third dredge-up events. We obtain a maximum helium luminosity of 1.7x10^9 L_sol
and significantly deep dredge-up after the second pulse. Strong hot-bottom
burning is observed after the 5th pulse. The 3M_sol model is evolved through 20
thermal pulse events and we find third dredge-up after the 7th pulse. During
the 14th pulse sufficient carbon has been brought to the surface to produce a
carbon star. We find that dredge-up and the transformation into a carbon star
occur at significantly smaller core masses (0.584M_sol and 0.608M_sol,
respectively) than in previous calculations for 3M_sol.


title:
Supernova light curve models for the bump in the Optical Counterpart of
  X-Ray Flash 030723

abstract:
  XRF 030723 is the first X-ray flash (XRF) to show in its optical light curve
(LC) a bump that has been interpreted as the signature of a supernova (SN).
After subtracting the afterglow component from the observed optical LC of the
XRF counterpart, the properties of the putative SN are constrained by means of
synthetic LCs of core-collapse SNe. For the redshift range $z \sim 0.3$ -- 1,
all possible models require a rather small mass of synthesized \Nifs, i.e.
$M$(\Nifs) $\sim$ 0.01 -- 0.3 $\Msun$. The models used to describe the
energetic SNe Ic associated with gamma-ray bursts (SNe 1998bw and 2003dh) are
too massive for the observed LC. If the relation between ejected \Nifs mass and
total ejecta mass established from models of various Type Ic SNe also holds for
the putative SN in XRF 030723, the ejecta mass is constrained to be $\sim$ 1 --
3 $\Msun$ and the kinetic energy $\lsim 1\times 10^{52}$ erg. This corresponds
to a progenitor with $15\Msun \lesssim M_{\rm MS}\lesssim 25\Msun$. The SN
therefore appears to have properties intermediate between a normal SN Ic like
SN 1994I and a more energetic object like SN 2002ap.


title:
Log-parabolic spectra and particle acceleration in blazars - II: The
  BeppoSAX wide band X-ray spectra of Mkn 501

abstract:
  We present the results of a spectral and temporal study of the complete set
of BeppoSAX NFI (11) and WFC (71) observations of the BL Lac object Mkn 501.
The WFC 2-28 keV data, reported here for the first time, were collected over a
period of about five years, from September 1996 to October 2001. These
observations, although not evenly distributed, show that Mkn 501, after going
through a very active phase from spring 1997 to early 1999, remained in a low
brightness state until late 2001. The data from the LECS, MECS and PDS
instruments, covering the wide energy interval 0.1-150 keV, have been used to
study in detail the spectral variability of the source. We show that the X-ray
energy distribution of Mkn 501 is well described by a log-parabolic law in all
luminosity states. This model allowed us to obtain good estimates of the SED
synchrotron peak energy and of its associated power. The strong spectral
variability observed, consisting of strictly correlated changes between the
synchrotron peak energy and bolometric flux, suggests that the main physical
changes are not only due to variations of the maximum Lorentz factor of the
emitting particles but that other quantities must be varying as well. During
the 1997 flare the high energy part of the spectrum of Mkn 501 shows evidence
of an excess above the best fit log-parabolic law suggesting the existence of a
second emission component that may be responsible for most of the observed
variability.


title: A Chandra Observation of a TW Hydrae Association Brown Dwarf

abstract:
  We present Chandra observations of the young brown dwarf 2MASSW
J1207334-393254, which is a probable member of the TW Hya association. Although
this substellar object has strong H alpha emission, it has no detected X Ray
flux in a fifty kilosecond ACIS-S observation. We place a conservative upper
limit of 1.2 x 10^{26} erg/sec on its X-ray luminosity. We compare our M8
target to the similar mass object TWA 5B, which has weaker H alpha emission but
strong X-ray emission. We argue our results are consistent with the notion that
2MASSW J1207334-393254 is interacting with a disk.


title:
Center-to-Limb Variation of Solar Line Profiles as a Test of NLTE Line
  Formation Calculations

abstract:
  We present new observations of the center-to-limb variation of spectral lines
in the quiet Sun. Our long-slit spectra are corrected for scattered light,
which amounts to 4-8 % of the continuum intensity, by comparison with a Fourier
transform spectrum of the disk center. We examine the effect of inelastic
collisions with neutral hydrogen in NLTE line formation calculations of the
oxygen infrared triplet, and the Na I 6160.8 A line. Adopting a classical
one-dimensional theoretical model atmosphere, we find that the sodium
transition, formed in higher layers, is much more effectively thermalized by
hydrogen collisions than the high-excitation oxygen lines. This result appears
as a simple consequence of the decrease of the ratio NH/Ne with depth in the
solar photosphere. The center-to-limb variation of the selected lines is
studied both under LTE and NLTE conditions. In the NLTE analysis, inelastic
collisions with hydrogen atoms are considered with a simple approximation or
neglected, in an attempt to test the validity of such approximation. For the
sodium line studied, the best agreement between theory and observation happens
when NLTE is considered and inelastic collisions with hydrogen are neglected in
the rate equations. The analysis of the oxygen triplet benefits from a very
detailed calculation using an LTE three-dimensional model atmosphere and NLTE
line formation. The chi**2 statistics favors including hydrogen collisions with
the approximation adopted, but the oxygen abundance derived in that case is
significantly higher than the value derived from OH infrared transitions.


title: The local surface density of disc matter mapped by Hipparcos

abstract:
  We determine the surface density of matter in the disc of the Galaxy at the
solar position using K giant stars. The local space density and luminosity
function of the giants is determined using parallaxes from the Hipparcos
satellite; for more distant giants, observed in a cone at the South Galactic
Pole, distances are determined using intermediate band DDO photometry (which
has been calibrated to the Hipparcos absolute magnitudes). From this sample, we
determine the gravitational potential vertically of the local Galactic disc, by
comparing the number of giant stars observed in the cone with the number
expected for various models of the matter distribution in the disc. We derive
an estimate of the dynamical disc mass surface density of 56 +/- 6 solar masses
/pc^2, which may be compared to an estimate of 53 solar masses/pc^2 in visible
matter. For all gravitating matter (disc + dark halo) we find the total density
within 1.1 kpc of the disc midplane to be 74 +/- 6 solar masses/pc^2. As has
been found by a number of studies, including our own, we find no compelling
evidence for significant amounts of dark matter in the disc.


title:
The very bright SCUBA galaxy count: looking for SCUBA galaxies with the
  Mexican Hat Wavelet

abstract:
  We present the results of a search for bright high-redshift galaxies in two
large SCUBA scan-maps of Galactic regions. A Mexican Hat Wavelet technique was
used to locate point sources in these maps, which suffer high foreground
contamination as well as typical scan-map noise signatures. A catalogue of
point source objects was selected and observed again in the submillimetre
continuum, and in HCO+ (3->2) at zero redshift to rule out Galactic sources. No
extragalactic sources were found. Simulations show that the survey was
sensitive to sources with fluxes > 50 mJy, depending on the local background.
These simulations result in upper limits on the 850-micron counts of SCUBA
galaxies of 53 per square degree at 50 mJy and 2.9 per square degree at 100
mJy.


title: Gravity of Cosmological Perturbations in the CMB

abstract:
  First, we establish which measures of large-scale perturbations are least
afflicted by gauge artifacts and directly map the apparent evolution of
inhomogeneities to local interactions of cosmological species. Considering
nonlinear and linear perturbations of phase-space distribution, radiation
intensity and arbitrary species' density, we require that: (i) the dynamics of
perturbations defined by these measures is determined by observables within the
local Hubble volume; (ii) the measures are practically applicable on
microscopic scales and in an unperturbed geometry retain their microscopic
meaning on all scales. We prove that all measures of linear overdensity that
satisfy (i) and (ii) coincide in the superhorizon limit. Their dynamical
equations are simpler than the traditional ones, have a nonsingular
superhorizon limit and explicit Cauchy form. Then we show that, contrary to the
popular view, the perturbations of the cosmic microwave background (CMB) in the
radiation era are not resonantly boosted self-gravitationally during horizon
entry. (Consequently, the CMB signatures of uncoupled species which may be
abundant in the radiation era, e.g. neutrinos or early quintessence, are mild;
albeit non-degenerate and robust to cosmic variance.) On the other hand, dark
matter perturbations in the matter era gravitationally suppress large-angle CMB
anisotropy by an order of magnitude stronger than presently believed. If cold
dark matter were the only dominant component then, for adiabatic perturbations,
the CMB temperature power spectrum C_l would be suppressed 25-fold.


title:
Partial Covering Interpretation of the X-Ray Spectrum of the NLS1 1H
  0707-495

abstract:
  The X-ray spectrum of 1H 0707-495 obtained with XMM-Newton showing a deep
flux drop at ~7 keV (Boller et al. 2002) is studied based on the partial
covering concept. The previously inferred extreme iron overabundance can be
reduced down to ~3x solar if the hard component gradually steepens at high
energies. The spectral shape supports that 1H 0707-495 is an AGN analogue of
the galactic black-hole binaries in the soft state. Interpreting the soft
excess as the emission from an optically-thick disk, the minimum black hole
mass M is estimated to be 2 x 10^6 solar masses from the intrinsic luminosity
corrected for partial covering. Based on the slim disk model, the observed disk
temperature implies that the luminosity is close to the Eddington limit. The
rapid and large flux variations with little change in the spectral shape can
also be explained, if not all, as due to changes in the partial covering
fraction. Partial covering may account for the large variability
characteristics of NLS1.


title:
Long-term spectral changes in the partial-covering candidate NLS1 1H
  0707-495

abstract:
  We compare two XMM-Newton observations of the Narrow-Line Seyfert 1 galaxy 1H
0707-495 separated by two years, and discuss the results in terms of the
partial-covering phenomenon. The second longer observation once again displays
a sharp (< 200 eV) spectral drop above 7 keV; however, in contrast to the first
observation, the edge depth and energy have changed significantly. In addition
to changes in the edge parameters, the high-energy spectrum appears steeper.
The changes in the high-energy continuum can be adequately explained in terms
of a partial-covering absorber outflowing from the central region. The
low-energy spectrum also shows significant long-term spectral variability,
including: a substantial increase in the disc temperature; detection of a ~0.9
keV emission feature; and the presence of warm absorption that was also
detected during the ASCA mission, but not seen during the first XMM-Newton
observation. The large increase in disc temperature, and more modest rise in
luminosity, can be understood if we consider the slim-disc model for 1H
0707-495. In addition, the higher disc luminosity could be the driving force
behind the outflow scenario and the re-appearance of a warm medium during the
second XMM-Newton observation.


title: X-ray reflection in the NLS1 1H 0707-495

abstract:
  We apply a reflection-dominated model to the second XMM-Newton observation of
the Narrow Line Seyfert 1 galaxy 1H 0707-495. As in the first XMM-Newton
observation a sharp spectral drop is detected with energy that has shifted from
7 keV to 7.5 keV in two years. The drop is interpreted in terms of
relativistically blurred ionised reflection from the accretion disc, while the
energy shift can be accounted for by changes in the ionisation state and, more
importantly, emissivity profile on the disc. A flatter emissivity profile
during the second higher flux observation reduces gravitational redshift
effects, therefore shifting the edge to higher energy. Remarkably, ionised disc
reflection and the associated power law continuum provide a reasonable
description of the broadband spectrum, including the soft excess. Considering
both observations, the spectral variability in 1H 0707-495 appears to be due to
the interplay between these two spectral components. The reflection component
in the second observation is significantly less variable than the power law.
Changes of the emissivity profile, spectral shape and variability properties
(such as the rms spectrum) within the two observations are all consistent with
a recently proposed model in which relativistic effects in the very inner
regions of the nucleus play a major role.


title:
A population of extreme mid-to-near-infrared sources: obscured AGN and
  dusty starbursts

abstract:
  We present a sample of mid-infrared detected sources from the European Large
Area ISO Survey (ELAIS) regions characterised by strong mid-IR radiation with
faint near-IR and optical counterparts. These extreme mid-to-near-IR objects
(EMNOs) are defined here by a flux ratio of f_15um / f_2.2um > 25. This
population is not obvious in deeper small area ISO surveys, though it produces
more than 20% of the observed cosmic IR background radiation (CIRB) at 15um
above 1 mJy. Near-future large area deep mid-IR surveys with the Spitzer Space
Telescope, however, are bound to uncover large amounts of these objects, which
we argue to most likely be obscured AGN, based on SED shapes and X-ray data.
Very strong dusty starbursts at z>1 may also have high mid-to-near-IR flux
ratios, but using the MIR/NIR and FIR/MIR ratios these may be separated. Most
of our EMNOs appear to be ULIRGs, half are also extremely red objects (ERO). A
curious case of a low redshift, less luminous object with a very young stellar
population is also found. We predict that the simple broad band selection
method makes EMNOs a useful window into high-redshift obscured nuclear activity
and its sought after relation to star-formation, in a similar way that EROs
have been used to define samples of high-redshift early type galaxies.


title: Type Ia Supernovae: An Asymmetric Deflagration Model

abstract:
  We present the first high-resolution three-dimensional simulations of the
deflagration phase of Type Ia supernovae that treat the entire massive white
dwarf. We report the results of simulations in which ignition of the nuclear
burning occurs slightly off-center. The subsequent evolution of the nuclear
burning is surprisingly asymmetric with a growing bubble of hot ash rapidly
rising to the stellar surface. Upon reaching the surface, the mass of burned
material is $\approx 0.075 M_\sun$ and the kinetic energy is $4.3 \times
10^{49}$ ergs. The velocity of the top of the rising bubble approaches 8000 km
s$^{-1}$. The amount of the asymmetry found in the model offers a natural
explanation for the observed diversity in Type Ia supernovae. Our study
strongly disfavors the classic central-ignition pure deflagration scenario by
showing that the result is highly sensitive to details of the initial
conditions.


title: Type Ia Supernova Explosion: Gravitationally Confined Detonation

abstract:
  We present a new mechanism for Type Ia supernova explosions in massive white
dwarfs. The proposed scenario follows from relaxing the assumption of symmetry
in the model and involves a detonation created in an unconfined environment.
The explosion begins with an essentially central ignition of stellar material
initiating a deflagration. This deflagration results in the formation of a
buoyantly-driven bubble of hot material that reaches the stellar surface at
supersonic speeds. The bubble breakout forms a strong pressure wave that
laterally accelerates fuel-rich outer stellar layers. This material, confined
by gravity to the white dwarf, races along the stellar surface and is focused
at the location opposite to the point of the bubble breakout. These streams of
nuclear fuel carry enough mass and energy to trigger a detonation just above
the stellar surface. The flow conditions at that moment support a detonation
that will incinerate the white dwarf and result in an energetic explosion. The
stellar expansion following the deflagration redistributes stellar mass in a
way that ensures production of intermediate mass and iron group elements
consistent with observations. The ejecta will have a strongly layered structure
with a mild amount of asymmetry following from the early deflagration phase.
This asymmetry, combined with the amount of stellar expansion determined by
details of the evolution (principally the energetics of deflagration, timing of
detonation, and structure of the progenitor), can be expected to create a
family of mildly diverse Type Ia supernova explosions.


title:
Dynamical Friction of Galactic Center Star Clusters with an
  Intermediate-Mass Black Hole

abstract:
  Numerical simulations of the dynamical friction suffered by a Galactic center
star cluster harboring an intermediate-mass black hole (IMBH) have been
performed. Gerhard has suggested that dynamical friction, which causes a
cluster to lose orbital energy and spiral in toward the Galactic center, may
explain the presence of a cluster of very young stars in the central parsec,
where star formation might be prohibitively difficult because of strong tidal
forces. However, numerical simulations by Kim & Morris showed that this is only
possible if the cluster initially has an extremely dense core. Hansen &
Milosavljevic recently suggested that the presence of an IMBH in the cluster
core might stabilize the core against tidal disruption during the inspiral
through dynamical friction, and thus might easily deliver young stars down to
the central parsec. We find that the presence of an IMBH does lower the minimum
initial core density required to transport young stars down to the central
parsec, but this is possible only when the mass of the IMBH is at least ~10% of
the total cluster mass. This fraction is significantly higher than that
estimated by Portegies Zwart & McMillan with numerical simulations of IMBH
formation by successive merging of stars in the cluster core, so it does not
appear that a realistic IMBH can help transport young stars into the central
parsec.


title:
A Mushroom-shaped Structure from the Impact of a Cloud with the Galactic
  Disk

abstract:
  We propose that the mushroom-shaped structure of the Galactic worm GW
123.4--1.5 is created by a cloud collision with the Galactic gas disk. A
hydrodynamic simulation shows that a mushroom-shaped structure is created after
the cloud crosses the Galactic midplane. The lifetime of the mushroom-shaped
structure is of order the dynamical time scale of the disk, \sim 10^7 years. We
find that the velocities across the cap of the mushroom-shaped structure in the
simulation are consistent with the observed values. The simulation also
predicts a structure on the opposite side of the Galactic plane which is
created by the Kelvin-Helmholtz instability after the cloud passes through the
disk.


title: Vela X at 31 GHz

abstract:
  We present observations of the Vela X region at 31 GHz using the Cosmic
Background Imager (CBI). We find a strong compact radio source (5.9'x4.1',
FWHM) about the Vela pulsar, which we associate with the Vela pulsar wind
nebula (PWN) recently discovered at lower radio-frequencies. The CBI's 4'
resolution for a 45' field of view allows the PWN to be studied in the
large-scale context of Vela X. Filamentary structure in Vela X, which stands
out in lower frequency maps, is very low-level at 31 GHz. By combining the 10
CBI channels, which cover 26-36 GHz, and 8.4 GHz archive data, we study the
spectral energy distribution (SED) of the PWN and the brightest filaments. Our
results show that the spectral index alpha (F_{nu} propto nu^alpha) of the PWN
is flat, or even marginally positive, with a value of
alpha_{8.4}^{31}=0.10+-0.06, while the Vela X filamentary structure has a
negative spectral index of alpha_{8.4}^{31}=-0.28+-0.09. The SED inhomogeneity
observed in Vela X suggests different excitation processes between the PWN and
the filaments. We investigate whether the PWN's flat spectrum is a consequence
of variability or truly reflects the SED of the object. The peak of the PWN at
31 GHz is 80''+-20'' south-west of the peak at 8.4 GHz. This shift is confirmed
by comparing the 31 GHz CBI image with higher resolution 5 GHz Australia
Telescope Compact Array observations, and is likely to be due to SED variations
within the PWN. We also investigate the nature of the Vela X filamentary
structure.


title: The Solar Galactic Environment

abstract:
  Combined heliosphere-astronomical data and models enrich our understanding
both of effects the solar galactic environment might have on the inner
heliosphere, and of interstellar clouds. Present data suggest that FeII/DI
increases toward the upwind direction of the cluster of interstellar clouds
(CLIC) flowing past the Sun. Cloud kinematics and abundances suggest an origin
related to a supershell around the Scorpius-Centaurus Association. The solar
space trajectory indicates the Sun entered the CLIC gas relatively recently.