title:
Chemical enrichment of the complex hot ISM of the Antennae galaxies: I.
  Spatial and spectral analysis of the diffuse X-ray emission

abstract:
  We present an analysis of the properties of the hot interstellar medium (ISM)
in the merging pair of galaxies known as The Antennae (NGC 4038/39), performed
using the deep, coadded ~411 ks Chandra ACIS-S data set. These deep X-ray
observations and Chandra's high angular resolution allow us to investigate the
properties of the hot ISM with unprecedented spatial and spectral resolution.
Through a spatially resolved spectral analysis, we find a variety of
temperatures (from 0.2 to 0.7 keV) and Nh (from Galactic to 2x10^21 cm^-2).
Metal abundances for Ne, Mg, Si, and Fe vary dramatically throughout the ISM
from sub-solar values (~0.2) up to several times solar.


title:
Relativistic Shocks: Particle Acceleration and Magnetic Field
  Generation, and Emission

abstract:
  Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas.
Plasma waves and their associated instabilities (e.g.,Buneman, Weibel and other
two-stream instabilities) created in collisionless shocks are responsible for
particle (electron, positron, and ion) acceleration. Using a 3-D relativistic
electromagnetic particle (REMP) code, we have investigated particle
acceleration associated with a relativistic jet front propagating into an
ambient plasma with and without initial magnetic fields. Simulations show that
the Weibel instability created in the collisionless shock front accelerates jet
and ambient particles both perpendicular and parallel to the jet propagation
direction. The non-linear fluctuation amplitudes of densities, currents,
electric, and magnetic fields in the electron-positron shock are larger than
those found in the electron-ion shock at the same simulation time. This comes
from the fact that both electrons and positrons contribute to generation of the
Weibel instability. The simulation results show that the Weibel instability is
responsible for generating and amplifying nonuniform, small-scale (mainly
transverse) magnetic fields which contribute to the electron's (positron's)
transverse deflection behind the jet head. This small scale magnetic field
structure is appropriate to the generation of ``jitter'' radiation from
deflected electrons (positrons) as opposed to synchrotron radiation.


title: The Efficiency of Using Accretion Power of Kerr Black Holes

abstract:
  The efficiency of a rapidly spinning Kerr black hole to turn accretion power
into observable power can attain 32 percent for the photon emission from the
disk, as is well known, following the work of Novikov-Page-Thorne. But many
accretion disks are now understood to be underluminous ($L<L_{Edd}$), while
still putting large amounts of energy into the jet. In this case, the apparent
efficiency of jets driven by the innermost accretion disk of a highly rotating
Kerr black hole ($a_*=0.999999$) can reach 96 percent.


title: SDSS Data Management and Photometric Quality Assessment

abstract:
  We summarize the Sloan Digital Sky Survey data acquisition and processing
steps, and describe runQA, a pipeline designed for automated data quality
assessment. In particular, we show how the position of the stellar locus in
color-color diagrams can be used to estimate the accuracy of photometric
zeropoint calibration to better than 0.01 mag in 0.03 deg2 patches. Using this
method, we estimate that typical photometric zeropoint calibration errors for
SDSS imaging data are not larger than ~0.01 mag in the g, r, and i bands, 0.02
mag in the z band, and 0.03 mag in the u band (root-mean-scatter for zeropoint
offsets).


title: The enigmatic B[e] star Hen 2-90 -- an interacting binary?

abstract:
  We present the enigmatic galactic unclassified B[e] star Hen 2-90. Its
optical spectrum is discussed and analysed in terms of the forbidden emission
lines coming from a non-spherical wind. The evolutionary phase of Hen 2-90 is
discussed. We raise the question whether an interacting binary nature seems to
be a possible solution to account for all observed characteristics.


title: Neutron Star Crustal Interface Waves

abstract:
  The eigenfrequencies of nonradial oscillations are a powerful probe of a
star's interior structure. This is especially true when there exist
discontinuities such as at the neutron star (NS) ocean/crust boundary, as first
noted by McDermott, Van Horn & Hansen. The interface mode associated with this
boundary has subsequently been neglected in studies of stellar nonradial
oscillations. We revisit this mode, investigating its properties both
analytically and numerically for a simple NS envelope model. We find that it
acts like a shallow surface ocean wave, but with a large radial displacement at
the ocean/crust boundary due to flexing of the crust with shear modulus $\mu\ll
P$, the pressure. This displacement lowers the mode's frequency by a factor of
$\sim(\mu/P)^{1/2}\sim0.1$ in comparison to a shallow surface wave frequency on
a hard surface. The interface mode may be excited on accreting or bursting NSs
and future work on nonradial oscillations should consider this mode. Our work
also implies an additional mode on massive and/or cold white dwarfs with
crystalline cores, which may have a frequency between the f-mode and g-modes,
an otherwise empty part of the frequency domain.


title:
Changes in the structure of the accretion disc of V2051 Ophiuchi through
  the outburst cycle

abstract:
  We present the results of the analysis of light curves of V2051 Oph through
an outburst with eclipse mapping techniques.


title:
Surface Magnetic Field Distributions of the White Dwarfs PG 1015+014 and
  HE 1045-0908

abstract:
  We have applied the method of Zeeman tomography to analyze the surface
magnetic field structures of the white dwarfs PG 1015+014 and HE 1045-0908 from
spin-phase resolved flux and circular polarization spectra obtained with FORS1
at the ESO VLT. We find for both objects field topologies that deviate
significantly from centred dipoles. For HE 1045-0908, the frequency
distribution of magnetic field strengths is sharply peaked at 16 MG for all
rotational phases covered by our data but extends to field strengths at least
five times this value. In the case of PG 1015+014 there are significant
contributions to the frequency distribution in the range from 50 to 90 MG with
the maximum near 70 MG. The detailed shape of the frequency distribution is
strongly variable with respect to the rotational phase.


title: Observations of Outflows in Cataclysmic Variables

abstract:
  Outflows in the form of fast winds from the accretion disk appear in nearly
all high accretion rate cataclysmic variables (CVs), both novalikes (NLs) and
dwarf novae in outburst (DN). The primary signatures of CV winds are broad,
blueshifted absorption features and P Cygni profiles that appear in the ionized
metal lines of lower inclination systems and the broad emission lines that
appear in eclipsing systems. Much progress has been made in our understanding
of the structure and behavior of CV outflows based on data obtained with X-ray,
EUV, and UV telescopes and the kinematical models developed to fit the
observations. Our current picture of CV outflows is that they are bipolar,
rotating winds driven off the accretion disk primarily by radiative line
driving from disk, boundary layer, and white dwarf radiation. Other mechanical
forces may play a role in the formation of CV winds. The winds are highly
turbulent and show complex vertical and azimuthal structure. Future work will
focus on determining the physical, thermal and ionization structure of the
winds and probing the mechanisms that govern wind formation and behavior.


title: FUSE Observations of Active Binaries

abstract:
  FUSE observations have been instrumental in advancing our understanding of
the physical properties and behavior of active binary systems, including
cataclysmic variables (CVs) and X-ray binaries (XRBs). FUSE data have allowed
observers to study: accretion disks, magnetically-channeled accretion flow, and
white dwarf accretors, and how these respond to accretion fluctuations and disk
outbursts; the role of binary evolution in determining system properties; the
vertical and azimuthal structure in disks and disk winds; and what the
variations in active binary properties reveal about accretion physics in
compact systems. Results of FUSE observations of active binaries are reviewed
here.


title:
A search for clusters at high redshift - III. Candidate H-alpha emitters
  and EROs in the PKS 1138-262 proto-cluster at z=2.16

abstract:
  In this paper we present deep VLT multi wavelength imaging observations of
the field around the radio galaxy PKS 1138-262 aimed at detecting and studying
a (potential) proto-cluster centered at this radio source. PKS 1138-262 is a
massive galaxy at z=2.16, located in a dense environment as indicated by
optical, X-ray and radio observations. We had already found an over-density of
Ly-alpha emitting galaxies in this field, consistent with a proto-cluster
structure associated with the radio galaxy. In addition, we find 40 candidate
H-alpha emitters that have nominal rest frame equivalent width > 25 Angstrom
within 1.8 Mpc and 2000 km/s of the radio galaxy. Furthermore, we find 44
objects with I - K > 4.3. This number of extremely red objects (EROs) is about
twice the number found in blank field ERO surveys, suggesting that some EROs in
this field are part of the proto-cluster. The density of H-alpha emitters and
extremely red objects increases towards the radio galaxy, indicating a physical
association. From comparisons with other K band, ERO, H-alpha and Ly-alpha
surveys, we conclude that PKS 1138-262 is located in a density peak which will
evolve into a cluster of galaxies.


title:
A search for clusters at high redshift - IV. Spectroscopy of H-alpha
  emitters in a proto-cluster at z=2.16

abstract:
  Radio galaxy PKS 1138-262 is a massive galaxy at z=2.16, located in a dense
environment. We have found an overdensity of Ly-alpha emitting galaxies in this
field, consistent with a proto-cluster structure associated with the radio
galaxy. Recently, we have discovered forty candidate H-alpha emitters by their
excess near infrared narrow band flux. Here, we present infrared spectroscopy
of nine of the brightest candidate H-alpha emitters. All these candidates show
an emission line at the expected wavelength. The identification of three of
these lines with H-alpha is confirmed by accompanying [NII] emission. The
spectra of the other candidates are consistent with H-alpha emission at z~2.15,
one being a QSO as indicated by the broadness of its emission line. The
velocity dispersion of the emitters (360 km/s) is significantly smaller than
that of the narrow band filter used for their selection (1600 km/s). We
therefore conclude that the emitters are associated with the radio galaxy. The
star formation rates (SFRs) deduced from the H-alpha flux are in the range 6-44
M_solar/yr and the SFR density observed is 5-10 times higher than in the HDF-N
at z=2.23. The properties of the narrow emission lines indicate that the
emitters are powered by star formation and contain very young (< 100 Myr)
stellar populations with moderately high metallicities.


title:
High redshift radio quiet quasars - exploring the parameter space of
  accretion models. Part I: hot semi-spherical flow

abstract:
  Two families of models are currently considered to describe an accretion flow
onto black holes and production of the observed X-ray radiation: (1) a standard
cold accretion disk with a hot corona above it and (2) an outer truncated
accretion disk with a hot semispherical inner flow. We compute spectra in the
scenario with a hot inner flow surrounded by a truncated accretion disk covered
by a hot corona and test the results on a sample of high redshift (z > 4)
quasars observed with Chandra. We find that in order to reproduce the ratio of
optical to X-ray fluxes (the $\alpha_{\rm ox}$ parameter), the optical depth of
the Comptonizing plasma has to be rather low ($\tau = 0.02 - 0.15 in the corona
above the disk, and $\tau = 0.15 - 0.70 in the hot inner flow). This, together
with the observed X-ray photon indices, implies either a high temperature in a
thermal plasma ($kT_{\rm e} = 90 - 500 keV), or a nonthermal electron
distribution in the plasma. We put an upper limit on the disk truncation
radius, $r_{\rm tr} \leq 40 R_{\rm S}$. The modeled accretion rate is high,
$\dot{m} > 0.2 Eddington rate, which may suggest that high-z radio quiet
quasars are analogs of X-ray binaries in their high or very high state.


title:
Mrk 421 and 501 above 60 GeV: the Influence of CELESTE's Energy Scale on
  the Study of Flares and Spectra

abstract:
  The CELESTE atmospheric Cherenkov detector ran until June 2004. It has
detected several gamma-ray flares of Mrk 421 since 1999. The new data analysis
provides better background rejection. We compare our light curves with X-ray
data. We significantly improved our understanding of the atmosphere, and of the
optical throughput of the detector. This will allow a spectral measurement for
Mrk 421 with smaller uncertainties and a more sensitive search for a signal
from Mrk 501.


title:
High redshift radio quiet quasars -- exploring parameter space of
  accretion models. Part II: patchy corona model

abstract:
  We modeled the spectral energy distribution (SED) of high redshift radio
quiet quasars (high-z RQQs). We computed spectra in a patchy corona geometry
where an accretion disk extends to the last stable orbit and the Comptonizing
active regions (hot clouds) are distributed above the disk. We explored the
model parameter space to find theoretical parameters that give spectra with the
optical/UV luminosity, the X-ray loudness, and the X-ray photon index
compatible with those of high-z RQQs observed with Chandra. We found that a
range of solutions is possible, from high-$kT_{\rm e}$ low-$\tau$ to
low-$kT_{\rm e}$ high-$\tau$ models. The solutions require low level of energy
dissipation in the hot clouds and low disk covering factor. The modeled mass is
of the order of $10^{10}$ Solar masses and the accretion rate is $\dot{M} >
0.2$ Eddington rate. We compare our results to those obtained previously for
hot inner flow geometry.


title:
Evolutionary population synthesis: models, analysis of the ingredients
  and application to high-z galaxies

abstract:
  Evolutionary population synthesis models for a wide range of metallicities,
ages, star formation histories, and Horizontal Branch morphologies, including
blue morphologies at high metallicity, are computed. The energetics of the post
Main Sequence evolutionary phases are evaluated with the fuel consumption
theorem. The impact on the models of the stellar evolutionary tracks is
assessed. We find modest differences in synthetic broad-band colours as induced
by the use of different tracks in our code (e.g. d(V-K) ~ 0.08 mag; d(B-V) ~
0.03 mag). These differences are smaller than the scatter among other models in
the literature, even when the latter adopt the same evolutionary tracks. The
models are calibrated with globular cluster data from the Milky Way for old
ages, and the Magellanic Clouds plus the merger remnant galaxy NGC 7252, for
ages of ~ 0.1 - 2 Gyr, in a large wavelength range from U to K. Particular
emphasis is put on the contribution from the Thermally-Pulsing Asymptotic Giant
Branch phase. We show that this phase is crucial for the modelling of young
stellar populations by the comparison with observed spectral energy
distributions of Magellanic Clouds clusters, which are characterised by high
fluxes both blueward and redward the V-band. We find that the combination of
the near-IR spectral indices C2 and H2O can be used to determine the
metallicity of ~ 1 Gyr stellar populations. We re-analyze the spectral energy
distributions of some of the high-z galaxies (2.4 < z < 2.9) observed with the
Spitzer Space Telescope by Yan et al. (2004). Their high rest-frame near-IR
fluxes are reproduced very well with the models including Thermally-Pulsing
Asymptotic Giant Branch stars for ages in the range 0.6-1.5 Gyr, suggesting
formation redshifts around z ~ 3-6.


title: Composition of the Innermost Core Collapse Supernova Ejecta

abstract:
  With presently known input physics and computer simulations in 1D, a
self-consistent treatment of core collapse supernovae does not yet lead to
successful explosions, while 2D models show some promise. Thus, there are
strong indications that the delayed neutrino mechanism works combined with a
multi-D convection treatment for unstable layers. On the other hand there is a
need to provide correct nucleosynthesis abundances for the progressing field of
galactic evolution and observations of low metallicity stars. The innermost
ejecta is directly affected by the explosion mechanism, i.e. most strongly the
yields of Fe-group nuclei for which an induced piston or thermal bomb treatment
will not provide the correct yields because the effect of neutrino interactions
is not included. We apply parameterized variations to the neutrino scattering
cross sections and alternatively, parameterized variations are applied to the
neutrino absorption cross sections on nucleons in the ``gain region''. We find
that both measures lead to similar results, causing explosions and a Ye>0.5 in
the innermost ejected layers, due to the combined effect of a short weak
interaction time scale and a negligible electron degeneracy, unveiling the
proton-neutron mass difference. We include all weak interactions (electron and
positron capture, beta-decay, neutrino and antineutrino capture on nuclei, and
neutrino and antineutrino capture on nucleons) and present first
nucleosynthesis results for these innermost ejected layers to discuss how they
improve predictions for Fe-group nuclei. The proton-rich environment results in
enhanced abundances of 45Sc, 49Ti, and 64Zn as requested by chemical evolution
studies and observations of low metallicity stars as well as appreciable
production of nuclei in the mass range up to A=80.


title: The epochs of early-type galaxy formation as a function of environment

abstract:
  The aim of this paper is to set constraints of the epochs of early-type
galaxy formation through the 'archaeology' of the stellar populations in local
galaxies. Using our models of absorption line indices that account for variable
abundance ratios, we derive the stellar population parameters of 124 early-type
galaxies in high and low density environments. We find that all three
parameters age, metallicity, and alpha/Fe ratio are correlated with velocity
dispersion. We further find evidence for an influence of the environment on the
stellar population properties. Massive early-type galaxies in low-density
environments appear on average ~2 Gyrs younger and slightly more metal-rich
than their counterparts in high density environments. No offsets in the
alpha/Fe ratios, instead, are detected. We translate the derived ages and
alpha/Fe ratios into star formation histories. We show that most star formation
activity in early-type galaxies is expected to have happened between redshifts
3 and 5 in high density and between redshifts 1 and 2 in low density
environments. We conclude that at least 50 per cent of the total stellar mass
density must have already formed at z 1, in good agreement with observational
estimates of the total stellar mass density as a function of redshift. Our
results suggest that significant mass growth in the early-type galaxy
population below z 1 must be restricted to less massive objects, and a
significant increase of the stellar mass density between redshifts 1 and 2
should be present caused mainly by the field galaxy population. The results of
this paper further imply vigorous star formation episodes in massive objects at
z 2-5 and the presence of evolved ellipticals around z 1, both observationally
identified as SCUBA galaxies and EROs.


title:
Photoionization models of roundish galactic planetary nebulae in the
  thick disk

abstract:
  We present the result of photo-ionizing modelling of the three planetary
nebulae (PNe) A 20, A 15 and MeWe 1-3. All three objects are roughly roundish,
highly excited and have a high galactic $z$. The PNe displayed low densities in
the shell, but relatively dense halos. A low metallicity and a relative high
electron temperature were found. Comparisons with radio observations confirmed
the obtained properties. The objects are very likely originating from thick
disk stellar progenitors. The distances found investigating the PNe shells are
somewhat lower than those derived spectroscopically with the central stars in
the past.


title: Radio emission from WR140

abstract:
  Milliarcsecond resolution Very Long Baseline Array (VLBA) observations of the
archetype WR+O star colliding-wind binary (CWB) system WR140 have been obtained
at 23 epochs between orbital phases 0.74 to 0.97. The emission in the
wind-collision region (WCR) is resolved as a bow-shaped arc which rotates as
the orbital phase progresses. This rotation provides for the first time the
inclination of the orbit (122+/-5 degrees), the longitude of the ascending node
(353+/-3 degrees), and the orbit semi-major axis (9.0+/-0.5 mas). The implied
distance is 1.85+/-0.16 kpc, which requires the O star to be a supergiant, and
leads to a wind-momentum ratio of 0.22. Quasi-simultaneous Very Large Array
(VLA) observations show the synchrotron spectra evolve dramatically through the
orbital phases observed, exhibiting both optically thin and optically thick
emission. The optically thin emission maintains a spectral index of -0.5, as
expected from diffusive shock acceleration.


title:
PHOTZIP: A Lossy FITS Image Compression Algorithm that Protects
  User-Defined Levels of Photometric Integrity

abstract:
  A lossy compression algorithm is presented for astronomical images that
protects photometric integrity for detected point sources at a user-defined
level of statistical tolerance. PHOTZIP works by modeling, smoothing, and then
compressing the astronomical background behind self-detected point sources,
while completely preserving values in and around those sources. The algorithm
also guaranties a maximum absolute difference (in terms of $\sigma$) between
each compressed and original background pixel, allowing users to control
quality and lossiness. For present purposes, PHOTZIP has been tailored to FITS
format and is freely available over the web. PHOTOZIP has been tested over a
broad range of astronomical imagery and is in routine use by the Night Sky Live
(NSL) project for compression of all-sky FITS images. Compression factors
depend on source densities, but for the canonical NSL implementation, a PHOTZIP
(and subsequently GZIP or BZIP2) compressed file is typically 20% of its
uncompressed size.


title:
Inferring coronal structure using X-ray spectra: A Chandra study of AB
  Dor

abstract:
  The Chandra X-ray observatory monitored the single cool star, AB Doradus,
continuously for a period lasting 88ksec (1.98 Prot) in 2002 December with the
LETG/HRC-S. The X-ray lightcurve shows significant rotational modulation. It
can be represented as having a flat level of emission superimposed with bright
flaring regions that appear at the same phases in both rotation cycles.
Phase-binned OVIII line profiles show centroid shifts that also repeat in
consecutive rotation cycles. These Doppler shifts trace a roughly sinusoidal
pattern with a a semi-amplitude of 30 +/-10km/s. By taking both the lightcurve
and spectral diagnostics into account along with constraints on the rotational
broadening of line profiles (provided by archival Chandra HETG FeXVII line
profiles) we can construct a simple model of the X-ray corona. The corona can
be described as having two components, one component is homogeneously
distributed, extending less than 1.75R*; and the other consists of at least two
compact emitting regions near the stellar surface. These compact regions
account for 16% of the X-ray emission and are likely to be located less than
0.4R* above the stellar surface.


title: The solar chemical composition

abstract:
  We review our current knowledge of the solar chemical composition as
determined from photospheric absorption lines. In particular we describe the
recent significant revisions of the solar abundances as a result of the
application of a time-dependent, 3D hydrodynamical model of the solar
atmosphere instead of 1D hydrostatic models. This has decreased the metal
content in the solar convection zone by almost a factor of two compared with
the widely used compilation by Anders & Grevesse (1989). While resolving a
number of long-standings problems, the new 3D-based element abundances also
pose serious challenges, most notably for helioseismology.


title:
A general relativistic approach to the Navarro-Frenk-White (NFW)
  galactic halos

abstract:
  In order to study their interplay with large scale cosmic evolution and with
relativistic effects, such as gravitational lenses, quintessence sources or
gravitational waves, we construct a post-Newtonian fluid framework for the
"Navarro-Frenk-White'' (NFW) models of galactic halos that follow from N-body
numerical simulations. Since these simulations are unable to resolve regions
very near the halo center, the extrapolation of the fitting formula leads to a
spherically averaged "universal'' density profile that diverges at the origin.
We remove this inconvenient feature by replacing a small central region of the
NFW halo with an interior Schwarzschild solution with constant density,
continuously matched to the remaining NFW spacetime. A model of a single halo,
as an isolated object with finite mass, follows by smoothly matching the NFW
spacetime to a Schwarzschild vacuum exterior along the virial radius, the
physical "cut-off'' customarily imposed, as the mass associated with NFW
profiles diverges asymptotically. Numerical simulations assume weakly
interacting collisionless particles, hence we suggest that NFW halos
approximately satisfy an "ideal gas'' type of equation of state, where
mass-density is the dominant rest--mass contribution to matter--energy, with
the internal energy contribution associated with an anisotropic kinetic
pressure. We show that, outside the central core, this pressure and the mass
density roughly satisfy a polytropic relation. Since stellar polytropes are the
equilibrium configurations in Tsallis' non-extensive formalism of Statistical
Mechanics, we argue that NFW halos might provide a rough empirical estimate of
the free parameter $q$ of Tsallis' formalism.


title:
Eclipse mapping of the stream and disk flickering components in V2051
  Oph

abstract:
  We report on the investigation of the spatial distribution of the flickering
sources in the dwarf nova V2051 Oph with eclipse mapping techniques.
Low-frequency flickering originates in the gas stream and is related to the
mass transfer process, whereas high-frequency flickering arises in the
accretion disk and is probably connected to magneto-hydrodynamic turbulence.


title:
Cosmic Microwave Background Fluctuation Amplitude from Dark Energy
  De-Coherence

abstract:
  Standard cosmology connects the scale generated at late times by the
cosmological constant with that generated in early times by the energy
dynamics. Assuming dark energy de-coherence occurs during early times when the
scale parameter expansion rate is no longer supra-luminal specifies a class of
cosmological models in which the cosmic microwave background fluctuation
amplitude at last scattering is approximately $10^{-5}$.


title: Correlated X-ray and Optical Variability in X-ray Binaries

abstract:
  It has long been known that X-ray and optical/UV variability in active X-ray
binaries is sometimes correlated. The expectation has been that this arises
from rapid reprocessing of X-rays into longer wavelength photons, and hence
that the lags between the bandpasses can be used to reconstruct an echo-map of
the binary, revealing the geometry and spatial scale of reprocessing sites. I
will review how this can be done, what can be learned, and what progress has
been made with real data. In addition, an interesting twist to the story has
emerged in the form of correlated variability that does not seem associated
with reprocessing. This extends to very short timescales, includes
quasi-periodic behavior, and may be associated with optical synchrotron
emission from a jet. Finally, contrary to expectations we have recently
discovered that similar correlations are seen even in an ostensibly `quiescent'
object allowing similar analyses of reprocessing effects.


title: A Toy Model for Gamma-Ray Bursts in Type Ib/C Supernovae

abstract:
  A toy model for gamma-ray burst-supernovae (GRB-SN) is discussed by
considering the coexistence of baryon poor outflows from black holes (BHs) and
a powerful spin-connection to surrounding disk, giving rise to consistent
calorimetry as described by van Putten (2001a) in a variant of the
Blandford-Znajek process (BZ, 1977). In this model the half-opening angle of
the magnetic flux tube on the horizon is determined by the mapping relation
between the angular coordinate on the BH horizon and the radial coordinate on
the surrounding accretion disk. The GRB is powered by the baryon poor outflows
in the BZ process, and the associated SN is powered by very small fraction of
the spin energy transferred from the BH to the disk in the magnetic coupling
(MC) process. The timescale of the GRB is fitted by the duration of the open
magnetic flux on the horizon. It turns out that the data of several GRB-SNe are
well fitted with our model.


title:
The Stellar Populations in the Central Parsecs of Galactic Bulges
  Central Stellar Populations

abstract:
  We present Hubble Space Telescope blue spectra at intermediate spectral
resolution for the nuclei of 23 nearby disk galaxies. These objects were
selected to have nebular emission in their nuclei, and span a range of
emission-line classifications as well as Hubble types. In this paper we focus
on the stellar population as revealed by the continuum spectral energy
distribution measured within the central 0."13 (~8pc) of these galaxies. The
data were modeled with linear combinations of single-age stellar population
synthesis models. The large majority (~80%) of the surveyed nuclei have spectra
whose features are consistent with a predominantly old (>5x10^9 yr) stellar
population. Approximately 25% of these nuclei show evidence of a component with
age younger than 1 Gyr, with the incidence of these stars related to the
nebular classification. Successful model fits imply an average reddening
corresponding to A_V~0.4 mag and stellar metallicity of (1--2.5) Z_sun. We
discuss the implications of these results for the understanding of star
formation history in the environment of quiescent and active supermassive black
holes. Our findings reinforce the picture wherein Seyfert nuclei and the
majority of low-ionization nuclear emission-line regions (LINERs) are
predominantly accretion-powered, and suggest that much of the central star
formation in Hii nuclei is actually circumnuclear.


title: Did the Universe loiter at high redshifts ?

abstract:
  We show that loitering at high redshifts ($z \gsim 6$) can easily arise in
braneworld models of dark energy which, in addition to being spatially flat,
also accelerate at late times. Loitering is characterized by the fact that the
Hubble parameter dips in value over a narrow redshift range which we shall
refer to as the `loitering epoch'. During loitering, density perturbations are
expected to grow rapidly. In addition, since the expansion of the universe
slows down, its age near loitering dramatically increases. An early epoch of
loitering is expected to boost the formation of high redshift gravitationally
bound systems such as $10^9 M_\odot$ black holes at $z \sim 6$ and lower-mass
black holes and/or Population III stars at $z > 10$, whose existence could be
problematic within the LCDM scenario. Loitering models also help to reduce the
redshift of reionization from its currently (high) value of $z_{\rm reion}
\simeq 17$ in LCDM cosmology, thus alleviating a significant source of tension
between observations of the high-redshift universe and theoretical model
building. Currently a loitering universe accelerates with an effective equation
of state $w < -1$ thus mimicking phantom dark energy. Unlike phantom, however,
the late-time expansion of the universe in our model is singularity free, and a
universe that loitered in the past will approach a LCDM model asymptotically in
the distant future.


title: Outflows of neutral (and ionized) gas in radio galaxies

abstract:
  Outflows up to 1500 km/s of atomic neutral hydrogen are detected in a growing
number of radio galaxies. Outflows with similar velocities are also detected in
ionized gas, suggesting a common origin for the extreme kinematics of these two
phases of the gas. The high detection rate ofsuch outflows in young (or
restarted) radio sources appears to be related to the existence of a dense ISM
around these objects. Such a dense ISM can have important consequences for the
evolution of the radio source and the galaxy as a whole. Here we summarize the
recent results obtained and the characteristics derived so far for these
outflows. We also discuss possible mechanisms (e.g. interaction between the
radio plasma and the ISM and adiabatically expanding broad emission lines
clouds) that can be at the origin of these phenomena.


title: HS2331+3905: The cataclysmic variable that has it all

abstract:
  We report detailed follow-up observations of the cataclysmic variable
HS2331+3905, identified as an emission-line object in the Hamburg Quasar
Survey. An orbital period of 81.08min is unambiguously determined from the
detection of eclipses in the light curves of HS2331+3905. A second photometric
period is consistently detected at P~83.38min, ~2.8% longer than the orbital
period, which we tentatively relate to the presence of permanent superhumps.
High time resolution photometry exhibits short-timescale variability on time
scales of 5-6min which we interpret as non-radial white dwarf pulsations, as
well as a coherent signal at 1.12min, which is likely to be the white dwarf
spin period. A large-amplitude quasi-sinusoidal radial velocity modulation of
the Balmer and Helium lines with a period ~3.5h is persistently detected
throughout three seasons of time-resolved spectroscopy. However, this
spectroscopic period, which is in no way related to the orbital period, is not
strictly coherent but drifts in period and/or phase on time scales of a few
days. Modeling the far-ultraviolet to infrared spectral energy distribution of
HS2331+3905, we determine a white dwarf temperature of Teff=10500K (assuming
Mwd=0.6Msun), close to the ZZ Ceti instability strip of single white dwarfs.
The spectral model implies a distance of d=90+-15pc, and a low value for the
distance is supported by the large proper motion of the system, mu=0.14"/yr.
The non-detection of molecular bands and the low J, H, and K fluxes of
HS2331+3905 make this object a very likely candidate for a brown-dwarf donor.


title: An hydrodynamic shear instability in stratified disks

abstract:
  We discuss the possibility that astrophysical accretion disks are dynamically
unstable to non-axisymmetric disturbances with characteristic scales much
smaller than the vertical scale height. The instability is studied using three
methods: one based on the energy integral, which allows the determination of a
sufficient condition of stability, one using a WKB approach, which allows the
determination of the necessary and sufficient condition for instability and a
last one by numerical solution. This linear instability occurs in any inviscid
stably stratified differential rotating fluid for rigid, stress-free or
periodic boundary conditions, provided the angular velocity $\Omega$ decreases
outwards with radius $r$. At not too small stratification, its growth rate is a
fraction of $\Omega$. The influence of viscous dissipation and thermal
diffusivity on the instability is studied numerically, with emphasis on the
case when $d \ln \Omega / d \ln r =-3/2$ (Keplerian case). Strong
stratification and large diffusivity are found to have a stabilizing effect.
The corresponding critical stratification and Reynolds number for the onset of
the instability in a typical disk are derived. We propose that the spontaneous
generation of these linear modes is the source of turbulence in disks,
especially in weakly ionized disks.


title: The Exploration of the Unknown

abstract:
  The Square Kilometre Array is conceived as a telescope which will both test
fundamental physical laws and transform our current picture of the Universe.
However, the scientific challenges outlined in this book are today's
problems--will they still be the outstanding problems that will confront
astronomers in the period 2020 to 2050 and beyond, when the SKA will be in its
most productive years? If history is any example, the excitement of the SKA
will not be in the old questions which are answered, but the new questions that
will be raised by the new types of observations it will permit. The SKA is a
tool for as-yet-unborn users and there is an onus on its designers to allow for
the exploration of the unknown. We outline a philosophy for the design and
operation of the SKA that can lead the radio astronomers in the 21st century to
add to the many discoveries of new phenomena made by radio astronomers in the
20th century.


title:
A possible third component in the L dwarf binary system DENIS-P
  J020529.0-115925 discovered with the Hubble Space Telescope

abstract:
  We present results showing that the multiple system DENIS-P J020529.0-115925
is likely to be a triple system of brown dwarfs. The secondary of this
previously known binary system shows a clear elongation on six images obtained
at six different epochs. Significant residuals remain after PSF subtraction on
these images, characteristic of multiplicity, and indicating that the secondary
is probably a double itself. Dual-PSF fitting shows that the shape of the
secondary is consistent with that of a binary system. These measurements show
that the probability that DENIS-P J020529.0-115925 is a triple system is very
high. The photometric and spectroscopic properties of the system are consistent
with the presence of three components with spectral types L5, L8 and T0.


title: Third Dredge-up in Low Mass Stars: Solving the LMC Carbon Star Mystery

abstract:
  A long standing problem with asymptotic giant branch (AGB) star models has
been their inability to produce the low-luminosity carbon stars in the Large
and Small Magellanic Clouds. Dredge-up must begin earlier and extend deeper. We
find this for the first time in our models of LMC metallicity. Such features
are not found in our models of SMC metallicity. The fully implicit and
simultaneous stellar evolution code STARS has been used to calculate the
evolution of AGB stars with metallicities of Z=0.008 and Z=0.004, corresponding
to the observed metallicities of the Large and Small Magellanic Clouds,
respecitively. Third dredge-up occurs in stars of 1Msol and above and carbon
stars were found for models between 1Msol and 3Msol. We use the detailed models
as input physics for a population synthesis code and generate carbon star
luminosity functions. We now find that we are able to reproduce the carbon star
luminosity function of the LMC without any manipulation of our models. The SMC
carbon star luminosity function still cannot be produced from our detailed
models unless the minimum core mass for third dredge-up is reduced by 0.06Msol.


title:
The structure of elliptical galaxies in the Virgo cluster. Results from
  the INT Wide Field Survey

abstract:
  We report on a complete CCD imaging survey of 226 elliptical galaxies in the
North-East quadrant of the Virgo cluster, representative of the properties of
giant and dwarf elliptical galaxies in this cluster. We fit their radial light
profiles with the Sersic r^(1/n) model of light distribution. We confirm the
result of Graham & Guzman (2003) that the apparent dichotomy between E and dE
galaxies in the luminosity-<mu>_e plane no longer appears when other structural
parameters are considered and can be entirely attributed to the onset of "core"
galaxies at B_T sim -20.5 mag. When "core" galaxies are not considered, E and
dE form a unique family with n linearly increasing with the luminosity. For 90
galaxies we analyze the B-I color indices, both in the nuclear and in the outer
regions. Both indices are bluer toward fainter luminosities. We find also that
the outer color gradients do not show any significant correlation with the
luminosity. The scatter in all color indicators increases significantly toward
lower luminosities, e.g. galaxies fainter than B_T sim -15 have a B-I spread
0.5 mag.


title: Resolved Molecular Gas in a Quasar Host Galaxy at Redshift z=6.42

abstract:
  We present high-resolution VLA observations of the molecular gas in the host
galaxy of the highest redshift quasar currently known, SDSS J1148+5251
(z=6.42). Our VLA data of the CO(3-2) emission have a maximum resolution of
0.17'' x 0.13'' (~1 kpc), and enable us to resolve the molecular gas emission
both spatially and in velocity. The molecular gas in J1148+5251 is extended to
a radius of 2.5 kpc, and the central region shows 2 peaks, separated by 0.3''
(1.7 kpc). These peaks account for about half of the total emission, while the
remainder is more extended. Each of these unresolved peaks contains a molecular
gas mass of ~5 x 10^9 M_sun (similar to the total mass found in nearby ULIRGS)
and has an intrinsic brightness temperature of ~35 K (averaged over the 1
kpc-sized beam), comparable to what is found in nearby starburst centers.
Assuming that the molecular gas is gravitationally bound, we estimate a
dynamical mass of ~4.5 x 10^10 M_sun within a radius of 2.5 kpc (~5.5 x 10^10
M_sun if corrected for a derived inclination of i~65 deg.). This dynamical mass
estimate leaves little room for matter other than the detected molecular gas,
and in particular the data are inconsistent with a ~10^12 M_sun stellar bulge
which would be predicted based on the M_BH-sigma_bulge relation. This finding
may indicate that black holes form prior to the assembly of the stellar bulges
and that the dark matter halos are less massive than predicted based on the
black hole/bulge mass relationship.


title: The mass of the sdB primary of the binary HS 2333+3927

abstract:
  Short period sdB binaries with cool companions are crucial to understand
pre-CV evolution, because they will evolve into cataclysmic variables, when the
sdB will have left the extended horizontal branch. Recently we discovered the
sixth such system, HS 2333+3927, consisting of an sdB star and an M dwarf
(period: 0.172 d) with a very strong reflection effect, but no eclipses. The
reflection is stronger than in any of the other similar systems which renders a
quantitative spectral analysis very difficult because the Balmer line profiles
may be disturbed by the reflected light. A spectroscopic analysis results in
Teff = 36500 K, log g = 5.70, and log (n_He/n_H) = -2.15. Mass-radius relations
were derived from the results of the analysis of light and radial-velocity
curves. Comparison with the mass-radius relation derived from the surface
gravity of the sdB star favours a rather low mass of 0.38 Msun for the primary.
The mass of the companion is 0.29 M_sun. HS 2333+3927 is the only known sdB+dM
system with a period above the CV period gap.


title: Linear Accelerating Superluminal Motion Model

abstract:
  Accelerating superluminal motions were detected recently by multi-epoch Very
Long Baseline Interferometry (VLBI) observations. Here, a Linear Accelerating
Superluminal Motion (LASM) model is proposed to interpret the observed
phenomena. The model provides a direct and accurate way to estimate the viewing
angle of a relativistic jet. It also predicts that both Doppler boosting and
deboosting effects may take place in an accelerating forward jet. The LASM
model is applied to the data of the quasar 3C 273, and the initial velocity,
acceleration and viewing angle of its three components are derived through
model fits. The variations of the viewing angle suggest that a supermassive
black hole binary system may exist in the center of 3C273. The gap between the
inner and outer jet in some radio loud AGNs my be explained in terms of Doppler
deboosting effects when the components accelerate to ultra-relativistic speed.


title: Joint VLBA/VLTI Observations of the Mira Variable S Orionis

abstract:
  We present the first coordinated VLBA/VLTI measurements of the stellar
diameter and circumstellar atmosphere of a Mira variable star. Observations of
the v=1, J=1-0 (43.1 GHz) and v=2, J=1-0 (42.8 GHz) SiO maser emission toward
the Mira variable S Ori were conducted using the VLBA. Coordinated
near-infrared K-band measurements of the stellar diameter were performed using
VLTI/VINCI closely spaced in time to the VLBA observations. Analysis of the SiO
maser data recorded at a visual variability phase 0.73 show the average
distance of the masers from the center of the distribution to be 9.4 mas for
the v=1 masers and 8.8 mas for the v=2 masers. The velocity structure of the
SiO masers appears to be random with no significant indication of global
expansion/infall or rotation. The determined near-infrared, K-band, uniform
disk (UD) diameters decreased from ~10.5 mas at phase 0.80 to ~10.2 mas at
phase 0.95. For the epoch of our VLBA measurements, an extrapolated UD diameter
of Theta_{UD}^K=10.8 +/- 0.3 mas was obtained, corresponding to a linear radius
R_{UD}^K = 2.3 +/- 0.5 AU or 490 +/- 115 solar radii. Our coordinated VLBA/VLTI
measurements show that the masers lie relatively close to the stellar
photosphere at a distance of ~2 photospheric radii, consistent with model
estimates. This result is virtually free of the usual uncertainty inherent in
comparing observations of variable stars widely separated in time and stellar
phase.


title:
Observational signatures of an electromagnetic overcritical
  gravitational collapse

abstract:
  We present theoretical predictions for the spectral, temporal and intensity
signatures of the electromagnetic radiation emitted during the process of the
gravitational collapse of a stellar core to a black hole, during which
electromagnetic field strengths rise over the critical value for $e^+e^-$ pair
creation. The last phases of this gravitational collapse are studied, leading
to the formation of a black hole with a subcritical electromagnetic field,
likely with zero charge, and an outgoing pulse of initially optically thick
$e^+e^-$-photon plasma. Such a pulse reaches transparency at Lorentz gamma
factors of $10^2$--$10^4$. We find a clear signature in the outgoing
electromagnetic signal, drifting from a soft to a hard spectrum, on very
precise time-scales and with a very specific intensity modulation. The
relevance of these theoretical results for the understanding of short gamma-ray
bursts is outlined.


title: Magnetorotational supernovae

abstract:
  We present the results of 2D simulations of the magnetorotational model of a
supernova explosion. After the core collapse the core consists of rapidly a
rotating proto-neutron star and a differentially rotating envelope. The
toroidal part of the magnetic energy generated by the differential rotation
grows linearly with time at the initial stage of the evolution of the magnetic
field. The linear growth of the toroidal magnetic field is terminated by the
development of magnetohydrodynamic instability, leading to drastic acceleration
in the growth of magnetic energy. At the moment when the magnetic pressure
becomes comparable with the gas pressure at the periphery of the proto-neutron
star $\sim 10-15$km from the star centre the MHD compression wave appears and
goes through the envelope of the collapsed iron core. It transforms soon to the
fast MHD shock and produces a supernova explosion. Our simulations give the
energy of the explosion $0.6\cdot 10^{51}$ ergs. The amount of the mass ejected
by the explosion is $\sim 0.14M_\odot$. The implicit numerical method, based on
the Lagrangian triangular grid of variable structure, was used for the
simulations.


title: Detecting Primordial Stars

abstract:
  We discuss the expected properties of the first stellar generations in the
Universe. We find that it is possible to discern truly primordial populations
from the next generation of stars by measuring the metallicity of high-z star
forming objects. The very low background of the future James Webb Space
Telescope (JWST) will enable it to image and study first-light sources at very
high redshifts, whereas its relatively small collecting area limits its
capability in obtaining spectra of z~10-15 first-light sources to either the
bright end of their luminosity function or to strongly lensed sources. With a
suitable investment of observing time JWST will be able to detect individual
Population III supernovae, thus identifying the very first stars that formed in
the Universe.


title: Deep ALTAIR + NIRI Imaging of the Disk and Bulge of M31

abstract:
  Deep J, H, and K' images, recorded with the ALTAIR adaptive optics system and
NIRI imager on Gemini North, are used to probe the stellar content of the disk
and bulge of the Local Group galaxy M31. With FWHM near 0.08 arcsec in K, these
are the highest angular resolution near-infrared images yet obtained of this
galaxy. Four fields that sample M31 at galactocentric radii of 62, 9, 4, and 2
arcmin were observed. The RGB-tip occurs between K = 17.0 and 17.2, and the
color of the RGB in the field closest to the center of M31 is consistent with
that of NGC 6528. After accounting for random photometric errors, the upper RGB
in each field has a width on the (K, J-K) CMD that is consistent with a +/- 0.5
dex dispersion in [Fe/H], in rough agreement with what is seen in other disk
and spheroid fields in M31. A population of very bright red stars, which we
identify as C stars, are seen in the three fields that are closest to the
center of M31. The spatial distribution of these objects suggests that they are
well mixed throughout this part of M31, and so likely did not form in a compact
region near the galactic nucleus, but more probably formed in the inner disk.
We speculate that these C stars may be the most luminous members of the
intermediate age population that has been detected previously in studies of the
integrated spectrum of the central regions of M31.


title:
X-ray Reflection from Inhomogeneous Accretion Disks: II. Emission Line
  Variability and Implications for Reverberation Mapping

abstract:
  One of the principal scientific objectives of the upcoming Constellation-X
mission is to attempt to map the inner regions of accretion disks around black
holes in Seyfert galaxies by reverberation mapping of the Fe K fluorescence
line. This area of the disk is likely radiation pressure dominated and subject
to various dynamical instabilities. Here, we show that density inhomogeneities
in the disk atmosphere resulting from the photon bubble instability (PBI) can
cause rapid changes in the X-ray reflection features, even when the
illuminating flux is constant. Using a simulation of the development of the
PBI, we find that, for the disk parameters chosen, the Fe K and O VIII Ly\alpha
lines vary on timescales as short as a few hundredths of an orbital time. In
response to the changes in accretion disk structure, the Fe K equivalent width
(EW) shows variations as large as ~100 eV. The magnitude and direction
(positive or negative) of the changes depends on the ionization state of the
atmosphere. The largest changes are found when the disk is moderately ionized.
The O VIII EW varies by tens of eV, as well as exhibiting plenty of rapid,
low-amplitude changes. This effect provides a natural explanation for some
observed instances of short timescale Fe K variability which was uncorrelated
with the continuum (e.g., Mrk 841). New predictions for Fe K reverberation
mapping should be made which include the effects of this accretion disk driven
line variability and a variable ionization state. Reflection spectra averaged
over the evolution of the instability are well fit by constant density models
in the 2-10 keV region.


title: High-Velocity Clouds in M 83 and M 51

abstract:
  Various scenarios have been proposed to explain the origin of the Galactic
high-velocity clouds, predicting different distances and implying widely
varying properties for the Galaxy's gaseous halo. To eliminate the difficulties
of studying the Galactic halo from within, we have embarked on a program to
study anomalous neutral gas in external galaxies, and here we present the
results for two nearby, face-on spiral galaxies, M 83 and M 51. Significant
amounts of anomalous-velocity HI are detected in deep VLA 21-cm observations,
including an extended, slowly rotating disk and several discrete HI clouds. Our
detection algorithm reaches a limiting HI source mass of 7x10^5 solar masses,
and it allows for detailed statistical analysis of the false detection rate. We
use this to place limits on the HVC mass distributions in these galaxies and
the Milky Way; if the HVC populations are similar, then the Galactocentric HVC
distances must be less than about 25 kpc.


title: The Third Data Release of the Sloan Digital Sky Survey

abstract:
  This paper describes the Third Data Release of the Sloan Digital Sky Survey
(SDSS). This release, containing data taken up through June 2003, includes
imaging data in five bands over 5282 deg^2, photometric and astrometric
catalogs of the 141 million objects detected in these imaging data, and spectra
of 528,640 objects selected over 4188 deg^2. The pipelines analyzing both
images and spectroscopy are unchanged from those used in our Second Data
Release.


title: Clusters in the Luminous Giant HII Regions in M101

abstract:
  (Abridged) We have obtained HST WFPC2 observations of three very luminous but
morphologically different giant HII regions (GHRs) in M101, NGC5461, NGC5462,
and NGC5471, in order to study cluster formation in GHRs. The measured (M_F547M
- M_F675W) colors and M_F547M magnitudes are used to determine the ages and
masses of the cluster candidates with M_F547M <= -9.0. NGC5461 is dominated by
a very luminous core, and has been suggested to host a super-star cluster
(SSC). Our observations show that it contains three R136-class clusters
superposed on a bright stellar background in a small region. This tight group
of clusters may dynamically evolve into an SSC in the future, and may appear
unresolved and be identified as an SSC at large distances, but at present
NGC5461 has no SSCs. NGC5462 has loosely distributed HII regions and clusters
without a prominent core. It has the largest number of cluster candidates among
the three GHRs, but most of them are faint and older than 10 Myr. NGC5471 has
multiple bright HII regions, and contains a large number of faint clusters
younger than 5 Myr. Two of the clusters in NGC5471 are older than R136, but
just as luminous; they may be the most massive clusters in the three GHRs. The
fraction of stars formed in massive clusters is estimated from the clusters'
contribution to the total stellar continuum emission and a comparison of the
ionizing power of the clusters to the ionizing requirement of the associated
HII regions. Both estimates show that <~ 50% of massive stars are formed in
massive clusters. The cluster luminosity functions (CLFs) of the three GHRs
show different slopes. NGC5462 has the steepest CLF and the most loosely
distributed interstellar gas, qualitatively consistent with the hypothesis that
massive clusters are formed in high-pressure interstellar environments.


title: Propagation of Cosmic Rays and Diffuse Galactic Gamma Rays

abstract:
  This paper presents an introduction to the astrophysics of cosmic rays and
diffuse gamma rays and discusses some of the puzzles that have emerged recently
due to more precise data and improved propagation models: the excesses in
Galactic diffuse gamma-ray emission, secondary antiprotons and positrons, and
the flatter than expected gradient of cosmic rays in the Galaxy. These also
involve the dark matter, a challenge to modern physics, through its indirect
searches in cosmic rays. Though the final solutions are yet to be found, I
discuss some ideas and results obtained mostly with the numerical propagation
model GALPROP. A fleet of spacecraft and balloon experiments targeting these
specific issues is set to lift off in a few years, imparting a feeling of
optimism that a new era of exciting discoveries is just around the corner. A
complete and comprehensive discussion of all the recent results is not
attempted here due to the space limitations.


title:
Total Mass of Ordinary Chondrite Matter Originally Present in the Solar
  System

abstract:
  Recently, I reported the discovery of a new fundamental relationship of the
major elements (Fe, Mg, Si) of chondrites that admits the possibility that
ordinary chondrite meteorites are derived from two components, a relatively
oxidized and undifferentiated, primitive component and a somewhat
differentiated, planetary component, with oxidation state like the highly
reduced enstatite chondrites, which I suggested was identical to Mercury's
complement of lost elements. Subsequently, on the basis of that relationship, I
derived expressions, as a function of the mass of planet Mercury and the mass
of its core, to estimate the mass of Mercury's lost elements, the mass of
Mercury's alloy and rock protoplanetary core, and the mass of Mercury's gaseous
protoplanet. Here, on the basis of the supposition that Mercury's complement of
lost elements is in fact identical to the planetary component of ordinary
chondrite formation, I estimate, as a function of Mercury's core mass, the
total mass of ordinary chondrite matter originally present in the Solar System.
Although Mercury's mass is well known, its core mass is not, being widely
believed to be in the range of 70 to 80 percent of the planet mass. For a core
mass of 75 percent, the calculated total mass of ordinary chondrite matter
originally present in the Solar System amounts to 1.83E24 kg, about 5.5 times
the mass of Mercury. That amount of mass is insufficient in itself to form a
planet as massive as the Earth, but may have contributed significantly to the
formation of Mars, as well as adding to the veneer of other planets, including
the Earth. Presently, only about 0.1 percent of that mass remains in the
asteroid belt.


title: TeV Emission from the Galactic Center Black-Hole Plerion

abstract:
  The HESS collaboration recently reported highly significant detection of TeV
gamma-rays coincident with Sgr A*. In the context of other Galactic Center (GC)
observations, this points to the following scenario: In the extreme
advection-dominated accretion flow (ADAF) regime of the GC black hole (BH),
synchrotron radio/sub-mm emission of 100 MeV electrons emanates from an
inefficiently radiating turbulent magnetized corona within 20 Schwarzschild
radii of the GCBH. These electrons are accelerated through second-order Fermi
processes by MHD turbulence. Closer to the innermost stable orbit of the ADAF,
instabilities and shocks within the flow inject power-law electrons through
first-order Fermi acceleration to make synchrotron X-ray flares observed with
Chandra, XMM, and INTEGRAL. A subrelativistic MHD wind subtending a 1sr cone
with power > 10^{37} erg/s is driven by the ADAF from the vicinity of the GCBH.
As in pulsar powered plerions, electrons are accelerated at the wind
termination shock, at > 10^{16.5} cm from the GCBH, and Compton-scatter the
ADAF and the far infra-red (FIR) dust radiation to TeV energies. The
synchrotron radiation of these electrons forms the quiescent X-ray source
resolved by Chandra. The radio counterpart of this TeV/X-ray plerion, formed
when the injected electrons cool on timescales 10^4 yrs, could explain the
origin of nonthermal radio emission in the pc-scale bar of the radio nebula Sgr
A West.


title:
Photometric Identification of the low-Mass Population of Orion OB1b I:
  The sigma Ori Cluster

abstract:
  We report an optical photometric survey of 0.89 sq. degrees of the Orion OB1b
association centered on sigma Ori. This region includes most of the sigma Ori
cluster, the highest density region within Orion OB1b. We have developed a
statistical procedure to identify the young, low-mass pre-main sequence
population of the association. We estimate that the cluster has ~160 members in
the mass range (0.2<M<1Msun). The cluster has a radius of ~3.5 pc and an
estimated age of 2.5+/-0.3 Myr. We estimate that the total mass of the cluster
is 225+/-30 Msun. This mass is similar to the estimated mass of the ~0.5 Myr
old cluster NGC 2024. NGC 2024 and sigma Ori appear to be a well matched pair
of clusters, except for the ~2 Myr difference in their ages.


title:
Phase transitions to spin-triplet ferromagnetic superconductivity in
  neutron stars

abstract:
  Effects of the anisotropy of Cooper pairs in spin-triplet ferromagnetic
superconductors are investigated on the basis of the Ginzburg-Landau theory. A
special attention is paid to the triggering of the superconducting state by the
ferromagnetic order. The ground states of these superconductors are outlined
and discussed. The idea about a possible coexistence of ferromagnetism and
spin-triplet superconductivity in neutron stars is introduced.


title:
Mapping Large-Scale Gaseous Outflows in Ultraluminous Galaxies with Keck
  II ESI Spectra: Variations in Outflow Velocity with Galactic Mass

abstract:
  Measurements of interstellar absorption lines in 18 ultraluminous infrared
galaxies (ULIGs) have been combined with published data, in order to reassess
the dependence of galactic outflow speeds on starburst luminosity and galactic
mass. The Doppler shifts reveal outflows of relatively cool gas at $330 \pm
100$km/s. The outflow speeds increase with the star formation rate (SFR) as
roughly $v \propto SFR^{0.35}$. This result is surprising since, in the
traditional model for starburst-driven winds, these relatively cool gas clouds
are accelerated by the ram pressure of a hot, supernova-heated wind that
exhibits weak (if any) \x temperature variation with increasing galactic mass.
The lack of evidence for much hotter winds is partly a sensitivity issue; but
the outflow velocities in ultraluminous starbursts actually are consistent with
acceleration by the tepid wind, indicating a hotter component is unlikely to
dominate the momentum flux. The \nad velocities in the dwarf starburst winds do
not reach the terminal velocity of a hot wind at the measured temperature of kT
~0.73 keV. A dynamically-motivated explanation is that the dwarf starburst
winds simply lack enough momentum to accelerate the clouds to the velocity of
the hot wind. Among the subsample of starbursts with well- constrained
dynamical masses, the terminal outflow velocities approach the galactic escape
velocity. If this relation, which is similar to that observed for stellar
winds, arises from radiation pressure on dust and gas limiting the maximum
luminosity of a starburst, then feedback will be stronger in massive galaxies
than previously thought helping shape the high-mass end of the galaxy
luminosity function.


title:
The bottom magnetic field and magnetosphere evolution of neutron star in
  low mass X-ray binary

abstract:
  The accretion induced neutron star magnetic field evolution is studied
through considering the accretion flow to drag the field lines aside and dilute
the polar field strength, and as a result the equatorial field strength
increases and is buried inside the crust. The main conclusions of model are as
follows: (i) the polar field decays with increasing the accreted mass; (ii) The
bottom magnetic field strength of about $10^8$ G can occur when neutron star
magnetosphere radius approaches the star radius, which depends on the accretion
rate as $\mdot^{1/2}$; (iii) The neutron star magnetosphere radius decreases
with accretion until it reaches the star radius, and its evolution is little
influenced by the initial field and the accretion rate after accreting $\sim
0.01 \ms$, which implies that the magnetosphere radii of neutron stars in LMXBs
would be homogeneous for Z sources and Atoll sources if they accreted the
comparable masses. As an extension, the physics effects of the possible strong
magnetic zone in the X-ray neutron stars and recycled pulsars are discussed.
Moreover, The strong magnetic fields in the binary pulsars PSR 1831-00 and PSR
1718-19 after accreting about half solar mass in the binary accretion phase,
$8.7\times10^{10}$ G and $1.28\times10^{12}$ G, respectively, can be explained
through considering the incomplete frozen flow in the polar zone. As a model's
expectation, the existence of the low magnetic field ($\sim 3\times 10^{7}$ G)
neutron stars or millisecond pulsars is suggested.


title:
Accretion disks around Black Holes with Advection and Optical Depth
  Transition

abstract:
  We consider the effects of advection and radial gradients of pressure and
radial drift velocity on the structure of accretion disks around black holes
with proper description of optically thick/thin transitions. We concentrated
our efforts on the models with large accretion rate. Contrary to disk models
neglecting advection, we find that continuous solutions extending from the
outer disk regions to the inner edge exist for all accretion rates we have
considered. We show that the sonic point moves outward with increasing
accretion rate, and that in the innermost disk region advection acts as a
heating process that may even dominate over dissipative heating. Despite the
importance of advection on it's structure, the disk remains geometrically thin.
Global solutions of advective accretion disks, which describe continuously the
transition between optically thick outer region and optically thin inner region
are constructed and analyzed.


title: Truncation of stellar disks in galaxies at z~1

abstract:
  We report here the first evidence for stellar disk truncation at high
redshift, based on surface photometry of a sample of 16 high redshift (0.6 < z
< 1.0) disk galaxies from the GOODS HST/ACS data. The radial profiles are best
fit by a double exponential profile. This result agrees with the profile of
disks in local galaxies. The cosmological surface brightness dimming at this
redshift range only allows us to detect galaxies with spatially ``early''
truncation, R_br/h_in <= 3.5. Six galaxies show the radial double exponential
structure, with an average value of R_br/h_in ~ 1.8. Such ``early'' truncated
galaxies are missing in local samples so far. This result opens the ground for
observing directly disk evolution through the study of the truncation radius as
a function of redshift.


title:
HST-STIS Spatially Resolved Spectroscopy and Coronagraphic Imaging of
  the TW Hydrae Circumstellar Disk

abstract:
  We present the first spatially resolved spectrum of scattered light from the
TW Hydrae protoplanetary disk. This nearly face-on disk is optically thick,
surrounding a classical T Tauri star in the nearby 10 Myr old TW Hya
association. The spectrum was taken with the HST-STIS CCD, providing resolution
R ~ 360 over the wavelength range 5250 - 10300 A. Spatially resolved
spectroscopy of circumstellar disks is difficult due to the high contrast ratio
between the bright star and faint disk. Our novel observations provide optical
spectra of scattered light from the disk between 40 AU and 155 AU from the
star. The scattered light has the same color as the star (gray scattering) at
all radii, except the innermost region. This likely indicates that the
scattering dust grains are larger than about 1 micron all the way out to large
radii. From the spectroscopic data, we also obtained radial profiles of the
integrated disk brightness at two position angles, over almost the same region
as previously observed in HST-WFPC2 and NICMOS coronagraphic images (35 AU to
173 AU from the star). The profiles have the same shape as the earlier ones,
but show a small azimuthal asymmetry in the disk not previously noted. Our STIS
broad-band coronagraphic images of TW Hya confirm the reality of this
asymmetry, and show that the disk surface brightness interior to 140 AU has a
sinusoidal dependence on azimuthal angle. The maximum brightness occurs at a
position angle of 233.6 +/- 5.7 degrees East of North. This might be caused by
the combination of forward-scattering and an increase in inclination in the
inner region of the disk, suggesting that the TW Hya disk has a warp like that
seen in the Beta Pictoris debris disk.


title: Study of the Bipolar Nebula IRAS 19312+1950. II. Circumstellar Chemistry

abstract:
  The bipolar nebula, IRAS 19312+1950, is a unique SiO maser source exhibiting
both properties as young and evolved objects. To clarify the nature of this
object, we made molecular line observations with the Nobeyama 45-m radio
telescope. We detected emission from O-bearing (HCO^+, SiO, SO, and SO_2), C-
and N-bearing molecules (CN, CS, HCN, HNC, NH_3, N_2H^+, HC_3N, H_2CS, and
CH_3OH), and their isotopic species (C^17O, ^13C^18O, and C^34S). Line profiles
consist of a weak broad (Dv 30 km/s) and/or a strong narrow (DV< 5 km/s)
components, depending on molecular species. Strong time variations of H_2O and
SiO masers were also observed. Numerical modeling of the envelope with the
LVG-code results in a good fit of the model with a mass loss rate of 2.6 10^-4
M_sun/yr to the observed intensities for the broad-component lines. On the
other hand, non-O-bearing molecules, which have only the narrow profiles, were
found to have abundances typical to those in cool dust clouds. No isotopic
enrichment was found, indicating little evidence of the narrow cool component
being an ejecta of the central AGB star or a possible companion. These facts
compelled us to conclude that IRAS 19312+1950 is an exotic mass-losing evolved
star embedded in a low-mass (~20 M_sun) dark cloud.


title:
The lens and source of the optical Einstein ring gravitational lens ER
  0047-2808

abstract:
  (Abridged) We perform a detailed analysis of the optical gravitational lens
ER 0047-2808 imaged with WFPC2 on the Hubble Space Telescope. Using software
specifically designed for the analysis of resolved gravitational lens systems,
we focus on how the image alone can constrain the mass distribution in the lens
galaxy. We find the data are of sufficient quality to strongly constrain the
lens model with no a priori assumptions about the source. Using a variety of
mass models, we find statistically acceptable results for elliptical
isothermal-like models with an Einstein radius of 1.17''. An elliptical
power-law model (Sigma \propto R^-beta) for the surface mass density favours a
slope slightly steeper than isothermal with beta = 1.08 +/- 0.03. Other models
including a constant M/L, pure NFW halo and (surprisingly) an isothermal sphere
with external shear are ruled out by the data. We find the galaxy light profile
can only be fit with a Sersic plus point source model. The resulting total
M/L_B contained within the images is 4.7 h_65 +/-0.3. In addition, we find the
luminous matter is aligned with the total mass distribution within a few
degrees. The source, reconstructed by the software, is revealed to have two
bright regions, with an unresolved component inside the caustic and a resolved
component straddling a fold caustic. The angular size of the entire source is
approx. 0.1'' and its (unlensed) Lyman-alpha flux is 3 x 10^-17 erg/s/cm^2.


title:
Molecular gas structure around an AGN with nuclear starburst: 3-D
  Non-LTE calculations of CO lines

abstract:
  We have performed three-dimensional, non-LTE radiative transfer calculations
for 12CO and 13CO lines, applying them to our high-resolution hydrodynamic
models of the `torus' around a SMBH in an active galactic nucleus. The
hydrodynamic simulations reveal inhomogeneous and turbulent gas structure on a
sub-pc scale in a circum-nuclear starburst region. Thick disks interlaced with
filaments, clumps and holes are naturally formed due to the interplay among
energy feedback from supernovae, self-gravity of the gas, galactic rotation,
and radiative cooling. The intensity maps of the molecular lines for the
circum-nuclear disks show a clumpy structure reflecting the intrinsic
inhomogeneity and turbulent motion of the gas disk. The fine structure of the
`torus' could be resolved in the nearby active galaxies using ALMA. We also
found that the X-factor is not uniformly distributed in the central 100 pc
region. The X-factor derived for 12CO(J=1-0) intensity depends strongly on the
intensity, whereas the X for 12CO(3-2) is nearly constant over two orders of
magnitude of the intensity. The suggested conversion factor for the molecular
gas mass is X_CO (3-2) ~ 0.27 x 10^{20} cm^{-2} (K km s^{-1})^{-1}.


title:
XMM observations of the high-redshift quasar RXJ1028.6-0844 at z=4.276:
  soft X-ray spectral flattening

abstract:
  We present results from a new XMM-Newton observation of the high-redshift
quasar RXJ1028.6-0844 at a redshift of 4.276. The soft X-ray spectral
flattening, as reported by a study with ASCA previously (Yuan et al. 2000, ApJ
545, 625), is confirmed to be present, however, with reduced column density
when modelled by absorption. The inferred column density for absorption
intrinsic to the quasar is 2.1(+0.4-0.3)x10^22 (cm^-2) for cold matter, and
higher for ionised gas. The spectral flattening shows remarkable similarity
with those of two similar objects, GB1428+4217 (Worsley et al. 2004, MNRAS 350,
L67) and PMNJ0525-3343 (Worsley et al. 2004, MNRAS 350, 207). The results
improve upon those obtained from a previous short-exposure observation for
RXJ1028.6-0844 with XMM-Newton (Grupe et al. 2004, AJ 127, 1). A comparative
study of the two XMM-Newton observations reveals a change in the power-law
photon index from Gamma ~1.3 to 1.5 on timescales of about one year. A
tentative excess emission feature in the rest-frame 5-10keV band is suggested,
which is similar to that marginally suggested for GB1428+4217.


title: Local Structures as revealed by HIPASS

abstract:
  The HI Parkes All-Sky Survey (HIPASS) gives an unprecedented view of the
local large-scale structures in the southern sky. I will review the results
from the HIPASS Bright Galaxy Catalog (BGC, Koribalski et al. 2004) and the
first version of the deep catalog (HICAT, Meyer et al. 2004) with particular
emphasis on galaxy structures across the Zone of Avoidance. Some previously
hardly noticed galaxy groups stand out quite distinctively in the HI sky
distribution and several large-scale structures are seen for the first time.
Because HI surveys preferentially detect late-type spiral and dwarf galaxies,
their distribution is less clustered than that of optically selected galaxies.
HI surveys also significantly enhance the connectivity of large-scale filaments
by filling in gaps populated by gas-rich galaxies.


title: Looking for outflows from brown dwarfs

abstract:
  First evidences of IR excess and disk mass accretion (strong H$\alpha$
emission) around brown dwarfs seem to indicate the existence of circumstellar
disks around these sub-stellar objects. Nothing is known at the present time
about outflows which potentially might be launched from brown dwarfs, although
jets are typically associated with the accretion in standard T Tauri star
disks. In this paper we calculate the H$\alpha$ emission of internal working
surfaces produced by a radiative jet in a neutral and in a photoionized
environment as a function of the jet parameters (the ejection velocity $v_j$,
shock velocity $v_s$, mass loss rate ${\dot M}$ and radius $r_j$ of the jet)
and we provide estimates of the H$\alpha$ luminosity for the parameters of
``standard'' Herbig-Haro (HH) jets from T Tauri stars and for the parameters
expected for jets from BDs. Interestingly, we find that while the mass loss
rates associated with jets from BDs are found to be two orders of magnitude
lower than the mass loss rates associated with ``standard'' HH jets (from T
Tauri stars), their velocities are likely to be similar. Based on our
calculations, we discuss the conditions in which jets from BDs can be detected
and we conclude that the H$\alpha$ luminosities of internal working surfaces of
jets from BDs in a photoionized environment should have only one order of
magnitude lower than the H$\alpha$ luminosities of T Tauri jets in a neutral
environment.


title: Chaotic Phenomena in Astrophysics and Cosmology

abstract:
  Chaos as typical property of non-linear systems has revealed its crucial role
in various problems of astrophysics and cosmology. The problems discussed at
these lectures include planetary dynamics, galactic dynamics, reconstruction of
the substructure of clusters of galaxies, instability in Wheeler-DeWitt
superspace. The choice of the problems aimed to show also the diversity of
approaches and mathematical tools, which include the geometric criterion
(Ricci) of relative instability in many dimensional systems, the estimation of
Kolmogorov-Sinai entropy, the hyperbolicity in pseudo-Riemannian spaces, etc.


title:
On the Soft Excess in the X-ray Spectrum of Cir X-1: Revisitation of the
  Distance to Cir X-1

abstract:
  We report on a 300 ks BeppoSAX (0.12-200 keV) observation of Circinus X-1
(Cir X-1) at phases between 0.62 and 0.84 and on a 90 ks BeppoSAX observation
of Cir X--1 at phases 0.11-0.16. Using the canonical model adopted until now to
fit the energy spectrum of this source large residuals appear below 1 keV.
These are well fitted using an equivalent hydrogen column of $0.66 \times
10^{22}$ cm$^{-2}$, adding absorption edges of O VII, O VIII and Ne IX in the
spectra extracted from the observation at phases 0.62-0.84 and adding
absorption edges of O VII, O VIII, Mg XI and Mg XII and absorption lines of O
VIII and Mg XII in the spectra extracted from the observation at phases
0.11-0.16. During the observation at phases 0.62--0.84 the electron density
associated to the ionized matter is $\sim 10^{13}$ cm$^{-3}$ remaining quit
constant going away from the compact object. During the observation at phases
0.11-0.16 the electron density profile varies along the distance going from
$\sim 6 \times 10^{13}$ cm$^{-3}$ at $\sim 10^{11}$ cm to $\sim 9 \times
10^{10}$ cm$^{-3}$ at $\sim 10^{13}$ cm. The equivalent hydrogen column towards
Cir X-1 is thre times lower than the value obtained from previous models. This
low value would imply that Cir X-1 is at a distance of 4.1 kpc.


title: Variable G and $\Lambda$: scalar-tensor versus RG-improved cosmology

abstract:
  We study the consequences due to time varying $G$ and $\Lambda$ in
scalar-tensor theories of gravity for cosmology, inspired by the modifications
introduced by the Renormalization Group (RG) equations in the Quantum Einstein
Gravity. We assume a power-law scale factor in presence contemporarily of both
the scalar field and the matter components of the cosmic fluid, and analyze a
special case and its generalization, also showing the possibility of a phantom
cosmology. In both such situations we find a negative kinetic term for the
scalar field $Q$ and, possibly, an equation-of-state parameter $w_Q<-1$. A
violation of dominant energy condition (DEC) for $Q$ is also possible in both
of them; but, while in the first special case the $Q$-energy density then
remains positive, in the second one we find it negative.


title: The exceptional X-ray variability of the dwarf Seyfert nucleus NGC 4395

abstract:
  An analysis of the X-ray variability of the low luminosity Seyfert nucleus
NGC 4395, based on a long XMM-Newton observation, is presented. The power
spectrum shows a clear break from a flat spectrum (alpha ~ 1) to a steeper
spectrum (alpha ~ 2) at a frequency f_br = 0.5 - 3.0 * 10^-3 Hz, comparable to
the highest characteristic frequency found previously in a Seyfert galaxy. This
extends the measured M_BH-f_br values to lower M_BH than previous studies of
Seyfert galaxies, and is consistent with an inverse scaling of variability
frequency with black hole mass. The variations observed are among the most
violent seen in an AGN to date, with the fractional rms amplitude (F_var)
exceeding 100 per cent in the softest band. The amplitude of the variations
seems intrinsically higher in NGC 4395 than most other Seyferts, even after
accounting for the differences in characteristic frequencies. The origin of
this difference is not clear, but it is unlikely to be a high accretion rate
(L/L_Edd < 20 per cent for NGC 4395). The variations clearly follow the linear
rms-flux relation, further supporting the idea that this is a ubiquitous
characteristics of accreting black holes. The variations are highly coherent
between different energy bands with any frequency-dependent time delay limited
to <1 per cent.


title: Photometric Variability in the Faint Sky Variability Survey

abstract:
  The Faint Sky Variability Survey (FSVS) is aimed at finding photometric
and/or astrometric variable objects between 16th and 24th mag on time-scales
between tens of minutes and years with photometric precisions ranging from 3
millimag to 0.2 mag. An area of 23 deg$^2$, located at mid and high Galactic
latitudes, was covered using the Wide Field Camera (WFC) on the 2.5-m Isaac
Newton Telescope (INT) on La Palma. Here we present some preliminary results on
the variability of sources in the FSVS.


title: Subdwarf B Binaries from the Edinburgh--Cape Survey

abstract:
  We present the first results of a campaign to obtain orbital solutions of
subdwarf B (sdB) stars from the Edinburgh-Cape survey. We have obtained blue
spectra of 35 sdBs, 20 of which have been observed in more than two epochs. 15
out of the 35 are certain binaries with a few other objects showing radial
velocity variations with small amplitude, possibly long period sdB binaries. We
have secured the orbital parameters for 2 of the 15 systems and narrowed down
the orbits of another one to a small range of periods. These preliminary
results only use data taken up to December 2003.


title:
High Resolution X-ray Spectroscopy of Pre-Main-Sequence Stars: TWA 5 and
  PZ Tel

abstract:
  We report on the analysis of high resolution X-ray spectra of two
pre-main-sequence stars: TWA 5 (observed with XMM-Newton) and PZ Telescopii
(observed with Chandra/HETGS). TWA 5 is a classical T Tauri star in the TW
Hydrae association while PZ Tel is a rapidly rotating weak-lined T Tauri star
in the beta-Pictoris moving group. For both stars we have reconstructed the
emission measure distribution and derived the coronal abundances to check for
possible patterns of the abundances related to the first ionization potential
of the various elements. We have also derived estimates of the plasma density
from the analysis of the He-like triplets. We compare the characteristics of
our targets with those of other pre-main sequence stars previously analyzed by
other authors: TW Hya, HD 98800 and HD 283572. Our findings suggest that X-ray
emission from classical T Tauri and weak-lined T Tauri stars is produced in all
cases by magnetically-heated coronae, except for TW Hya which has unique plasma
temperatures and densities. Moreover we derive that TWA 5 has the same peculiar
Ne/Fe abundance ratio as TW Hya.


title: Quark clusters in quark stars and possible astrophysical implications

abstract:
  A quark-cluster state, rather than the color-super-conductivity state, may
appear in matter with low-temperature but high density, since the phase
transition of chiral symmetry broken and that of color-confinement could not
occur imultaneously. Such quark clusters might be stable in strange quark
matter. Quark stars would have temperatures to be low enough to freeze by
residual color interaction between the clusters, and become then solid ones.The
charge numbers and the sizes of quark clusters, as well as the residual
interactions in-between are investigated. The solid state properties of quark
stars are constrained by observations.


title:
Particle Acceleration, Magnetic Field Generation, and Emission in
  Relativistic Shocks

abstract:
  Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas.
Plasma waves and their associated instabilities (e.g., Buneman, Weibel and
other two-stream instabilities) created in collisionless shocks are responsible
for particle (electron, positron, and ion) acceleration. Using a 3-D
relativistic electromagnetic particle (REMP) code, we have investigated
particle acceleration associated with a relativistic jet front propagating into
an ambient plasma. We find small differences in the results for no ambient and
modest ambient magnetic fields. Simulations show that the Weibel instability
created in the collisionless shock front accelerates jet and ambient particles
both perpendicular and parallel to the jet propagation direction. The small
scale magnetic field structure generated by the Weibel instability is
appropriate to the generation of ``jitter'' radiation from deflected electrons
(positrons) as opposed to synchrotron radiation. The jitter radiation resulting
from small scale magnetic field structures may be important for understanding
the complex time structure and spectral evolution observed in gamma-ray bursts
or other astrophysical sources containing relativistic jets and relativistic
collisionless shocks.


title: Very Light Jets II: Bipolar large scale simulations in King atmospheres

abstract:
  Hydrodynamic jets, underdense with respect to their environment by a factor
of up to 10,000, were computed in axisymmetry as well as in 3D. They finally
reached a size of up to 220 jet radii, corresponding to a 100 kpc sized radio
galaxy. The simulations are "bipolar", involving both jets. These are injected
into a King type density profile with small stochastic density variations. The
back-reaction of the cocoons on the beams in the center produces armlength
asymmetries of a few percent, with the longer jets on the side with the higher
average density. Two distinguishable bow shock phases were observed: an inner
elliptical part, and a later cylindrical, cigar-like phase, which is known from
previous simulations. The sideways motion of the inner elliptical bow shock
part is shown to follow the law of motion for spherical blast waves also in the
late phase, where the aspect ratio is high, with good accuracy. X-ray emission
maps are calculated and the two bow shock phases are shown to appear as rings
and elongated or elliptical regions, depending on the viewing angle. Such
structures are observed in the X-ray data of several radio galaxies (e.g. in
Abell 2052 and Hercules A), the best example being Cygnus A. In this case, an
elliptical bow shock is infered from the observations, a jet power of 10^47
erg/s is derived, and the Lorentz factor can be limited to Gamma>10. Based on
the simulation results and the comparison to the observations, the emission
line gas producing the alignment effect in radio galaxies at high redshift is
suggested to be cooled gas entrained over the cocoon boundary.


title:
Constraining dark energy models using the lookback time to galaxy
  clusters and the age of the universe

abstract:
  An impressive amount of different astrophysical data converges towards the
picture of a spatially flat universe undergoing a today phase of accelerated
expansion. The nature of the dark energy dominating the energy content of the
universe is still unknown and a lot of different scenarios are viable
candidates to explain cosmic acceleration. Most of the methods employed to test
these cosmological models are essentially based on distance measurements to a
particular class of objects. A different method, based on the lookback time to
galaxy clusters and the age of the universe, is used here. In particular, we
constrain the characterizing parameters of three classes of dark energy
cosmological models to see whether they are in agreement with this kind of
data, based on time measurements rather than distance observations.


title: Shear acceleration in relativistic astrophysical jets

abstract:
  We consider the acceleration of energetic particles by a velocity shear in
the relativistic background flow containing scattering centers. Three possible
acceleration sites for astrophysical jets are identified: (1) gradual velocity
shear parallel to the jet axis, such as a velocity profile decreasing linearly
outward with radial coordinate, (2) gradual velocity shear perpendicular to the
jet axis, such as intrinsic jet rotation, and (3) non-gradual/discontinuous,
longitudinal velocity shear at the jet-side boundary. We determine the
characteristic acceleration timescales, specify the conditions for efficient
acceleration and discuss observational features with respect to each process.
In particular, it is shown that in the case of (2) the higher energy emission
is expected to be concentrated closer to the jet axis, while in the case of (1)
and (3) the higher energy particles are likely to be located near the edges of
the jet, thus possibly leading to some form of limb-brightening.


title: Intrinsic Absorption in NGC 7469

abstract:
  We present results from a coordinated FUSE, HST/STIS and Chandra campaign to
study intrinsic UV and X-ray absorption in the outflow of the Seyfert 1 galaxy
NGC 7469. Previous non-simultaneous observations of this outflow found two
distinct UV absorption components, one of which likely corresponds to the X-ray
absorber. The FUSE data reveal that the O VI absorption in this component has
strengthened over time, as the continuum flux decreased. We use measured H I, N
V, C IV, and O VI column densities to model self-consistently the
photoionization state of the absorbers. We confirm the physical picture of the
outflow in which the low velocity component is a highly ionized, high density
absorber located near the broad emission line region, while the high velocity
component is of lower density and resides farther from the central engine.


title:
An Unbiased Far Ultraviolet Survey of Magellanic Cloud Supernova
  Remnants

abstract:
  We have undertaken a FUSE survey of Magellanic Cloud supernova remnants,
looking primarily for O VI and C III emission lines. Work in earlier cycles
with FUSE indicates that optical and/or X-ray characteristics of supernova
remnants are not always good predictors of the objects that will be bright and
detectable in the UV. The goal of our survey is to test this concept by
obtaining spectra of a random sample of Magellanic Cloud remnants with a broad
range of radio, optical, and X-ray properties. Previously observed objects and
remnants with known high extinction (or known high column densities) are the
only objects eliminated from consideration. To date, we have clearly detected O
VI emission from 12 of the 33 objects observed, with weak or marginal
detections possible in a handful more.


title: Obscured accreting black holes at high redshift

abstract:
  A significant fraction of the accreting black holes powering high redshift
AGN are obscured by large columns of dust and gas. For this reason, luminous
type 2 quasars can be efficiently discovered combining hard X-ray and
near-infrared observations. We will briefly discuss the most recent results.


title:
Evidence for Superhumps in the Radio Light Curve of Algol and a New
  Model for Magnetic Activity in Algol Systems

abstract:
  Extensive radio data of two Algol systems and two RS CVn binaries were
re-analyzed. We found evidence for a new periodicity that we interpret as a
superhump in Algol, in which it may have been expected according to its
semi-detached nature and low binary mass ratio. This is the first detection of
the superhump phenomenon in the radio and the first observation of superhumps
in Algol systems. According to our result, the accretion disk in Algol
precesses in spite of its non-Keplerian nature and therefore this phenomenon is
not restricted to the classical Keplerian disks in compact binaries.We propose
that in Algol systems with short orbital periods, the disk is magnetically
active as well as the secondary star. The magnetic field in the disk originates
from amplification of the seed field in the magnetized material transferred
from the secondary. The disk and stellar fields interact with each other, with
reconnection of the field lines causing flares and particle acceleration.
Relativistic particles are trapped in the field and directed toward the polar
regions of the secondary star because of the dipole structure of its magnetic
field. Our proposed model for the magnetic activity in Algol systems provides a
simple explanation to the observed properties of Algol in the radio
wavelengths, and to the presence of quiescent gyrosynchrotron emission near the
polar region of the secondary star, where electrons are difficult to be
confined if the field lines are open as in normal single magnetic stars. We
propose that the superhump variation in the radio is generated by enhanced
reconnection when the elongated side of the elliptic disk is the closest to the
cool star. This leads to flares and enhancement in particle acceleration and is
manifested as stronger gyrosynchrotron radiation.


title: Direct simulations of helical Hall-MHD turbulence and dynamo action

abstract:
  Direct numerical simulations of turbulent Hall dynamos are presented. The
evolution of an initially weak and small scale magnetic field in a system
maintained in a stationary turbulent regime by a stirring force at a
macroscopic scale is studied to explore the conditions for exponential growth
of the magnetic energy. Scaling of the dynamo efficiency with the Reynolds
numbers is studied, and the resulting total energy spectra are found to be
compatible with a Kolmogorov type law. A faster growth of large scale magnetic
fields is observed at intermediate intensities of the Hall effect.


title: SN 1987A: The Unusual Explosion of a Normal Type II Supernova

abstract:
  I review the unwrapping story the SN 1987A explosion event, and the main
discoveries associated with it. I will show that, although this supernova is
somewhat peculiar, the study of SN 1987A has clarified quite a number of
important aspects of the nature and the properties of supernovae in general.


title: Waves, Coriolis force and the dynamo effect

abstract:
  Dynamo activity caused by waves in a rotating magneto-plasma is investigated.
In astrophysical environments such as accretion disks and at sufficiently small
spatial scales, the Hall effect is likely to play an important role. It is
shown that a combination of the Coriolis force and Hall effect can produce a
finite $\alpha$-effect by generating net helicity in the small scales. The
shear/ion-cyclotron normal mode of the Hall plasma is the dominant contributor
to the dynamo action for short scale motions.


title:
The mechanism of Swing Absorption of fast magnetosonic waves in
  inhomogeneous media

abstract:
  The recently suggested swing interaction between fast magnetosonic and
Alfv\'en waves (2002) is generalized to inhomogeneous media. We show that the
fast magnetosonic waves propagating across an applied non-uniform magnetic
field can parametrically amplify the Alfv\'en waves propagating along the field
through the periodical variation of the Alfv\'en speed. The resonant Alfv\'en
waves have half the frequency and the perpendicular velocity polarization of
the fast waves. The wavelengths of the resonant waves have different values
across the magnetic field, due to the inhomogeneity in the Alfv\'en speed.
Therefore, if the medium is bounded along the magnetic field, then the
harmonics of the Alfv\'en waves, which satisfy the condition for onset of a
standing pattern, have stronger growth rates. In these regions the fast
magnetosonic waves can be strongly 'absorbed', their energy going in
transversal Alfv\'en waves. We refer to this phenomenon as 'Swing Absorption'.
This mechanism can be of importance in various astrophysical situations.


title:
Fireballs, Flares and Flickering: A Semi-analytic, LTE, Explosive Model
  from Accretion Disks to Supernovae

abstract:
  We derive simple analytic expressions for the continuum lightcurves and
spectra of flaring and flickering events that occur over a wide range of
astrophysical systems. We compare these results to data taken from the
cataclysmic variable SS Cygni and also with SN 1987A, deriving physical
parameters for the material involved. Fits to the data indicate a nearly
time-independent photospheric temperature arising from the strong temperature
dependence of opacity when hydrogen is partially ionized.


title: Is the solar corona nonmodally self-heated?

abstract:
  Recently it was pointed out that nonmodally (transiently and/or
adiabatically) pre-amplified waves in shear flows, undergoing subsequent
viscous damping, can ultimately heat the ambient flow. The key ingredient of
this process is the ability of waves to grow, by extracting energy from the
spatially inhomogeneous mean flow. In this paper we examine this mechanism in
the context of the solar coronal plasma flows. "Self-heating" (SH) processes
are examined when both viscous damping and magnetic resistivity are at work. We
show that if the plasma viscosity is in the favorable range of values the
asymptotic SH rate in these flows can be quite substantial.


title: CMB and foregrounds in WMAP first year data

abstract:
  We perform a blind multi-component analysis of the WMAP 1 year foreground
cleaned maps using SMICA (Spectral Matching Independent Component Analysis). We
provide a new estimate of the CMB power spectrum as well as the amplitude of
the CMB anisotropies across frequency channels. We show that the CMB
anisotropies are compatible with temperature fluctuations as expected from the
standard paradigm. The analysis also allows us to identify and separate a weak
residual galactic emission present significantly in the Q-band outside of the
Kp2 mask limits, and mainly concentrated at low galactic latitudes. We produce
a map of this residual component by Wiener filtering using estimated
parameters. The level of contamination of CMB data by this component is
compatible with the WMAP team estimation of foreground residual contamination.
In addition, the multi-component analysis allows us to estimate jointly the
power spectrum of unresolved point source emission.