title: Mid-infrared imaging of NGC1068 with VISIR at the VLT

abstract:
  High resolution mid-infrared (MIR) images of the central region of NGC1068
have been obtained with VISIR, the multi-mode MIR instrument recently installed
at the ESO/VLT on Paranal. A map of the emission at 12.8mic with increased
sensitivity over the central 8"x 8" area is discussed. It shows a central core
(unresolved along the E-W direction) and an extended emission which draws a
spiral pattern similar to that observed on near-infrared images. Patches of MIR
emission can be detected up to a distance of 4" from the core. The deconvolved
12.8mic map is fully consistent with previous high-resolution MIR observations.
It highlights the structure of the extended emission, already seen on the
un-deconvolved image, and allows to identify a set of mid-infrared sources: 7
in the NE quadrant and 5 in the SW quadrant. The MIR emission map is compared
with those obtained at comparable angular resolution in the near-infrared and
in the [OIII] line emission. The very good correlation between the VISIR map
and the HST optical map supports the idea that the MIR emission not associated
with the torus arises from dust associated with the narrow line region clouds.
The N-S extension of the MIR core (0.44") is then probably simply due to the
mixing of the MIR emission from the dusty torus and the MIR emission from NLR
cloud B, located only 0.1" to the North.


title: Is the island universe model consistent with observations?

abstract:
  We study the island universe model, in which initially the universe is in a
cosmological constant sea, then the local quantum fluctuations violating the
null energy condition create the islands of matter, some of which might
corresponds to our observable universe. We examine the possibility that the
island universe model is regarded as an alternative scenario of the origin of
observable universe.


title: The K-band spectrum of the Cataclysmic Variable RXJ 0502.8+1624 (Tau 4)

abstract:
  We present the K-band spectrum of the cataclysmic variable RXJ 0502.8+1624
(Tau 4). The spectrum shows a broad, smooth hump, with no absorption lines from
the secondary star visible. This result indicates that the infrared light of
this system is dominated by cyclotron emission, and, in combination with the
optical spectrum and X-ray properties, suggests that Tau 4 is a polar-type
cataclysmic variable (CV).
  The system was chosen for study because the broadband JHK colours of Tau 4
are consistent with an L-type dwarf, suggesting that this system might harbour
an elusive sub-stellar secondary star. The result presented here, along with
the recent discovery of cyclotron emission in the cataclysmic variable EF Eri,
suggests that care must be taken when using the broadband JHK colours of CVs
when targeting searches for sub-stellar secondary stars


title:
HD 172189: An eclipsing and spectroscopic binary with a Delta Sct-ttype
  pulsating component in an open cluster

abstract:
  We present a study based on more than 2500 uvby-measurements collected on HD
172189, a new eclipsing binary system with a Delta Sct-type pulsating component
that belongs to the open cluster IC 4756. The great interest of this object
lies in that three important characteristics coexist: cluster membership,
binarity and pulsation. Its binarity and the Delta Sct-type pulsations of one
component were detected in the course of several Stromgren photometric
campaigns. The frequency analysis of all the uvby out-of-eclipse data reveals a
clear frequency of 19.5974 c/d as well as the existence of other high values in
the range 18-20 c/d. We have also carried out a first evaluation of the binary
parameters and determined a value of 5.702 d for the orbital period. An
additional potential interest of HD 172189 resides in its location in the field
of view of the COROT mission and, therefore, this star is an excellent
candidate for becoming a target for asteroseismology.


title: A non-main-sequence secondary in SY Cancri

abstract:
  Simultaneous spectroscopic and photometric observations of the Z Cam type
dwarf nova SY Cancri were used to obtain absolute flux calibrations. A
comparison of the photometric calibration with a wide slit spectrophotometric
calibration showed that either method is equally satisfactory. A radial
velocity study of the secondary star, made using the far red NaI doublet,
yielded a mass ratio q = 0.68; this is very different from the value of 1.13
quoted in the literature. Using the new lower mass ratio, and constraining the
mass of the white dwarf to be within reasonable limits, then leads to a mass
for the secondary star that is substantially less than would be expected for
its orbital period if it satisfied a main-sequence mass-radius relationship. We
find a spectral type of M0 that is consistent with that expected for a
main-sequence star of the low mass we have found. However, in order to fill its
Roche lobe, the secondary must be significantly larger than a main sequence
star of that mass and spectral type. The secondary is definitely not a normal
main-sequence star.


title: Dynamics of assisted quintessence

abstract:
  We explore the dynamics of assisted quintessence, where more than one scalar
field is present with the same potential. For potentials with tracking
solutions, the fields naturally approach the same values; in the context of
inflation this leads to the assisted inflation phenomenon where several fields
can cooperate to drive a period of inflation though none is able to
individually. For exponential potentials, we study the fixed points and their
stability confirming results already in the literature, and then carry out a
numerical analysis to show how assisted quintessence is realized. For inverse
power-law potentials, we find by contrast that there is no assisted behaviour;
indeed those are the unique (monotonic) potentials where several fields
together behave just as a single field in the same potential. More generally,
we provide an algorithm for generating a single-field potential giving
equivalent dynamics to multi-field assisted quintessence.


title:
Infrared Surface Brightness Distances to Cepheids: a comparison of
  Bayesian and linear-bisector calculations

abstract:
  We have compared the results of Bayesian statistical calculations and
linear-bisector calculations for obtaining Cepheid distances and radii by the
infrared surface brightness method. We analyzed a set of 38 Cepheids using a
Bayesian Markov Chain Monte Carlo method that had been recently studied with a
linear-bisector method. The distances obtained by the two techniques agree to
1.5 \pm 0.6% with the Bayesian distances being larger. The radii agree to 1.1%
\pm 0.7% with the Bayesian determinations again being larger. We interpret this
result as demonstrating that the two methods yield the same distances and
radii. This implies that the short distance to the LMC found in recent
linear-bisector studies of Cepheids is not caused by deficiencies in the
mathematical treatment. However, the computed uncertainties in distance and
radius for our dataset are larger in the Bayesian calculation by factors of
1.4-6.7. We give reasons to favor the Bayesian computations of the
uncertainties. The larger uncertainties can have a significant impact upon
interpretation of Cepheid distances and radii obtained from the infrared
surface brightness method.


title:
Photon-axion conversion as a mechanism for supernova dimming: Limits
  from CMB spectral distortion

abstract:
  Axion-photon conversion induced by intergalactic magnetic fields has been
proposed as an explanation for the dimming of distant supernovae of type Ia SNe
Ia) without cosmic acceleration. The effect depends on the intergalactic
electron density $n_e$ as well as the $B$-field strength and domain size. We
show that for $n_e\alt 10^{-9} {\rm cm}^{-3}$ the same mechanism would cause
excessive spectral distortion of the cosmic microwave background (CMB). This
small-$n_e$ parameter region had been left open by the most restrictive
previous constraints based on the dispersion of quasar (QSO) spectra. The
combination of CMB and QSO limits suggests that the photon-axion conversion
mechanism can only play a subleading role for SN Ia dimming. A combined
analysis of all the observables affected by the photon-axion oscillations would
be required to give a final verdict on the viability of this model.


title: Young, Jupiter-Mass Objects in Ophiuchus

abstract:
  We have used 3.5 to 8 micron data from the Cores to Disks (c2d) Legacy survey
and our own deep IJHKs images of a 0.5 square degree portion of the c2d fields
in Ophiuchus to produce a sample of candidate young objects with probable
masses between 1 and 10 Jupiter masses. The availability of photometry over
whole range where these objects emit allows us to discriminate between young,
extremely low-mass candidates and more massive foreground and background
objects and means our survey will have fewer false positives than existing
near-IR surveys. The sensitive inventory of a star forming cloud from the red
to the mid-IR will allow us to constrain the IMF for these non-clustered star
formation regions to well below the deuterium burning limit. For stars with
fluxes in the broad gap between the 2MASS limits and our limits, our data will
provide information about the photospheres. We will use the Spitzer results in
combination with current disk models to learn about the presence and nature of
circumstellar disks around young brown dwarfs.


title: Radio Quiet AGN

abstract:
  Active Galactic Nuclei are powered by accretion onto massive black holes.
Although radio-quiet objects are not as spectacular sources of very high energy
photons as radio-loud ones this class of objects also represents a challenge
for modeling high energy processes close to a black hole. Both a hot optically
thin plasma and a cooler optically thick accretion disk are usually thought to
be present in the vicinity of a black hole although the details of the
accretion flow are still under discussion. The role of the disk seems to
decrease with a drop in the Eddington ratio: in sources like quasars and Narrow
Line Seyfert 1 galaxies disk flow dominates while in Seyfert galaxies the disk
retreats, and in sources like LINERS or Sgr A* a disk is most likely absent.
Shocks and reconnections are possibly taking place in an inner hot flow and in
the magnetic corona above the cold disk. Uncollimated outflow is also present
and it may carry significant fraction of available mass and energy.


title: End-effects in rapidly rotating cylindrical Taylor-Couette flow

abstract:
  We present numerical simulations of the flow in a rapidly rotating
cylindrical annulus. We show that at the rotation rates relevant to the
magneto-rotational instability, the flow is strongly constrained by the
Taylor-Proudman theorem. As a result, it is controlled almost entirely by the
end-plates. We then consider two possible options for minimizing these
end-effects, namely (i) simply taking a very long cylinder, and (ii) splitting
the end-plates into a series of differentially rotating rings. Regarding option
(i), we show that the cylinder would have to be hundreds of times as long as it
is wide before end-effects become unimportant in the interior. Since this is
clearly not feasible, we turn to option (ii), and show that in order to obtain
a smooth angular velocity profile, the end-plates would have to be split into
around ten rings. If the end-plates are split into fewer rings, perhaps 3-5,
the angular velocity profile will not be smooth, but will instead consist of a
series of Stewartson layers at the boundaries from one ring to the next. We
suggest therefore that the instabilities one obtains in this system will be the
familiar Kelvin-Helmholtz instabilities of these Stewartson layers, rather than
the magneto-rotational instability. At best, one might hope to obtain the MRI
superimposed on these Kelvin-Helmholtz modes. Any subsequent interpretation of
results is thus likely to be quite complicated.


title:
A Chandra HETGS Spectral Study of the Iron K Bandpass in MCG-6-30-15: A
  Narrow View of the Broad Iron Line

abstract:
  We present a high resolution X-ray spectrum of the iron K bandpass in
MCG-6-30-15 based on a 522 ksec observation with Chandra's High Energy
Transmission Grating Spectrometer. The Chandra spectrum is consistent with the
presence of a relativistically broadened, highly redshifted iron K alpha
emission line with a similar profile to previous observations. A number of
narrow features are detected above 2 keV, including a narrow Fe K alpha
emission line and narrow absorption lines from H- and He-like Fe, H-like S and
H-like Si. This absorption is well described by a photoionized plasma with a
column density log N_H = 23.2 and an ionization parameter log xi = 3.6,
assuming the iron abundance has the Solar value and a velocity dispersion
parameter b = 100 km/s. Applying this absorption model to a high fidelity
XMM-Newton EPIC-pn spectrum we find that a broad iron line is still required
with emission extending to within 1.9 gravitational radii of the black hole. If
the iron line comes from an accretion disk truncated at the innermost stable
circular orbit, this indicates that the black hole must be spinning rapidly
with a>0.95. Ionized absorption models attempting to explain the 3-6 keV
spectral curvature without strong gravity predict absorption lines in the
6.4-6.6 keV range that are inconsistent with the Chandra spectrum. The H- and
He-like iron absorption lines in the Chandra spectrum are blueshifted by 2.0
(+0.7/-0.9) x 10^3 km/s compared to the source frame, and may originate in a
high velocity, high ionization component of the warm absorber outflow. This
high ionization component may dominate the energy budget of the outflow, and
account for a significant fraction of the outflowing mass. (Abstract
truncated).


title:
Spectroscopic Survey of the Galaxy with Gaia II. The expected science
  yield from the Radial Velocity Spectrometer

abstract:
  The Gaia mission is designed as a Galaxy explorer, and will measure
simultaneously, in a survey mode, the five or six phase space parameters of all
stars brighter than 20th magnitude, as well as providing a description of their
astrophysical characteristics. These measurements are obtained by combining an
astrometric instrument with micro-arcsecond capabilities, a photometric system
giving the magnitudes and colours in 15 bands and a medium resolution
spectrograph named the Radial Velocity Spectrometer (RVS). The latter
instrument will produce spectra in the 848 to 874 nm wavelength range, with a
resolving power R = 11 500, from which radial velocities, rotational
velocities, atmospheric parameters and abundances can be derived. A companion
paper (Katz et al. 2004) presents the characteristics of the RVS and its
performance. This paper details the outstanding scientific impact of this
important part of the Gaia satellite on some key open questions in present day
astrophysics. The unbiased and simultaneous acquisition of multi-epoch radial
velocities and individual abundances of key elements in parallel with the
astrometric parameters is essential for the determination of the dynamical
state and formation history of our Galaxy. Moreover, for stars brighter than
V=15, the resolving power of the RVS will give information about most of the
effects which influence the position of a star in the Hertzsprung-Russell
diagram, placing unprecedented constraints on the age, internal structure and
evolution of stars of all types. Finally, the RVS multi-epoch observations are
ideally suited to the identification, classification and characterisation of
the many types of double, multiple and variable stars.


title:
Interstellar 12C/13C ratios through CH+ ll 3957,4232 absorption in local
  clouds: incomplete mixing in the ISM

abstract:
  The 12C/13C isotope ratio is a tracer of stellar yields and the efficiency of
mixing in the ISM. 12CH+/13CH+ is not affected by interstellar chemistry, and
is the most secure way of measuring 12C/13C in the diffuse ISM. R= 12C/13C is
90 in the solar system. Previous measurements of 12CH+ ll3957.7,4232.3 and
13CH+ ll3958.2,4232.0 absorption toward nearby stars indicate some variations
in 12C/13C, with values ranging from 40 to 90 suggesting inefficient mixing.
Except for the cloud toward zeta Oph, these R values are strongly affected by
noise. With UVES on the VLT we have improved on the previous interstellar
12C/13C measurements. The weighted 12C/13C ratio in the local ISM is 78.27 +-
1.83, while the weighted dispersion of our measurements is 12.7, giving a 6.9
sigma scatter. Thus we report on a 6.9 sigma detection of 16.2%
root-mean-square variations in the carbon isotopic ratio on scales of ~100 pc:
R= 74.7 +- 2.3 in the zetaOph cloud, while R = 88.6 +- 3.0 toward HD152235 in
the Lupus clouds, R = 62.2 +- 5.3 towards HD110432 in the Coalsack, and R =
98.9 +- 10.1 toward HD170740. The observed variations in 13C/12C are the first
significant detection of chemical heterogeneity in the local ISM.


title: Optical and Infrared Signatures of ULX's

abstract:
  We have constructed a model to describe the optical emission from
ultra-luminous X-ray sources (ULXs). We assume a binary model with a black hole
accreting matter from a Roche lobe filling companion star. We consider the
effects of radiative transport and radiative equilibrium in the irradiated
surfaces of both the star and a thin accretion disk. We have developed this
model as a tool with which to positively identify the optical counterparts of
ULXs, and subsequently derive parameters such as the black hole mass and the
luminosity class and spectral type of the counterpart. We examine the
dependence of the optical emission on these and other variables. We extend our
model to examine the magnitude variation at infrared wavelengths, and we find
that observations at these wavelengths may have more diagnostic power than in
the optical. We apply our model to existing HST observations of the candidates
for the optical counterpart of ULX X-7 in NGC 4559. All candidates could be
consistent with an irradiated star alone, but we find that a number of them are
too faint to fit with an irradiated star and disk together. Were one of these
the optical counterpart to X-7, it would display a significant temporal
variation.


title: Comparisons of an Evolutionary Chemical Model with Other Models

abstract:
  We compare an evolutionary chemical model with simple empirical models of the
abundance and with static chemical models. We focus on the prediction of
molecular line profiles that are commonly observed in low mass star forming
cores. We show that empirical models can be used to constrain evaporation radii
and infall radii using lines of some species. Species with more complex
abundance profiles are not well represented by the empirical models. Static
chemical models produce abundance profiles different from those obtained from
an evolutionary calculation because static models do not account for the flow
of matter inward from the outer regions. The resulting profiles of lines used
to probe infall may differ substantially.


title: A Brighter Past: Galaxy Luminosity Function At High Redshifts

abstract:
  Using the conditional luminosity function -- the luminosity distribution of
galaxies in a dark matter halo as a function of the halo mass -- we present an
empirical model to describe the redshift evolution of the rest B-band galaxy
luminosity function (LF). The model is compared to measured LFs out to a
redshift of 3.5, including LFs of galaxy types separated to red and blue
galaxies. The increase in the number density of luminous galaxies, at the
bright-end of the LF, can be explained as due to a brightening of the
luminosity of galaxies present in dark matter halo centers, relative to the
luminosity of central galaxies in similar mass halos today. The lack of strong
evolution in the faint-end of the LF, however, argues against a model involving
pure luminosity evolution at all halo mass scales. The increase in luminosity
at the bright-end compensates the rapid decline in the number density of
massive halos as the redshift is increased. The decline in group to
cluster-mass dark matter halos out to a redshift of ~ 2 is not important as the
central galaxy luminosity flattens at halo masses around 10^13 M_sun At
redshifts ~ 2 to 3, however, the density of bright galaxies begins to decrease
due to the rapid decline in the number density of dark matter halos at mass
scales around and below 10^13 M_sun. We compare our predictions to the UV LF of
galaxies at redshifts 3 to 6 and the galaxy clustering bias measurements at
redshifts ~ 3, and use our models to establish the dark matter halo mass scales
of galaxies observed at high redshifts. In general, to explain high-redshift
LFs, galaxies in dark matter halos around 10^12 M_sun must increase in
luminosity by a factor of ~ 4 to 6 between today and redshift of 6.


title:
A VLT study of metal-rich extragalactic H II regions. I. Observations
  and empirical abundances

abstract:
  We have obtained spectroscopic observations from 3600 Angstrom to 9200
Angstrom with FORS at the Very Large Telescope for approximately 70 H II
regions located in the spiral galaxies NGC 1232, NGC 1365, NGC 2903, NGC 2997
and NGC 5236. These data are part of a project aiming at measuring the chemical
abundances and characterizing the massive stellar content of metal-rich
extragalactic H II regions. In this paper we describe our dataset, and present
emission line fluxes for the whole sample. In 32 H II regions we measure at
least one of the following auroral lines: [S II]4072, [N II]5755, [S III]6312
and [O II]7325. From these we derive electron temperatures, as well as oxygen,
nitrogen and sulphur abundances, using classical empirical methods (both
so-called "Te-based methods" and "strong line methods"). Under the assumption
that the temperature gradient does not introduce severe biases, we find that
the most metal-rich nebulae with detected auroral lines are found at
12+log(O/H)~8.9, i.e. about 60% larger than the adopted solar value. However,
classical abundance determinations in metal-rich H II regions may be severely
biased and must be tested with realistic photoionization models. The
spectroscopic observations presented in this paper will serve as a homogeneous
and high-quality database for such purpose.


title: The Complex Wind Torus and Jets of PSR B1706-44

abstract:
  We report on Chandra ACIS imaging of the pulsar wind nebula (PWN) of the
young Vela-like PSR B1706-44, which shows the now common pattern of an
equatorial wind and polar jets. The structure is particularly rich, showing a
relativistically boosted termination shock, jets with strong confinement, a
surrounding radio/X-ray PWN and evidence for a quasi-static `bubble nebula'.
The structures trace the pulsar spin geometry and illuminate its possible
relation to SNR G343.1-2.3. We also obtain improved estimates of the pulsar
flux and nebular spectrum, constraining the system age and energetics.


title: A CO Survey of Young Planetary Nebulae

abstract:
  We report the results of a sensitive survey of young planetary nebulae in the
CO J=2-1 line that significantly increases the available data on warm, dense,
molecular gas in the early phases of planetary nebula formation. The
observations were made using the IRAM 30 m telescope with the 3 by 3 pixel
Heterodyne Receiver Array (HERA). The array provides an effective means of
discriminating the CO emission of planetary nebulae in the galactic plane from
contaminating emission of interstellar clouds along the line of sight. 110
planetary nebulae were observed in the survey and 40 were detected. The results
increase the number of young planetary nebulae with known CO emission by
approximately a factor of two. The CO spectra yield radial velocities for the
detected nebulae, about half of which have uncertain or no velocity
measurements at optical wavelengths. The CO profiles range from parabolic to
double-peaked, tracing the evolution of structure in the molecular gas. The
line widths are significantly larger than on the Asymptotic Giant Branch, and
many of the lines show extended wings, which probably result from the effects
on the envelopes of high velocity jets.


title: Cosmology with a Variable Chaplygin Gas

abstract:
  We consider a new generalized Chaplygin gas model that includes the original
Chaplygin gas model as a special case. In such a model the generalized
Chaplygin gas evolves as from dust to quiessence or phantom. We show that the
background evolution for the model is equivalent to that for a coupled dark
energy model with dark matter. The constraints from the current type Ia
supernova data favour a phantom-like Chaplygin gas model.


title:
QPOs and firehose instabilities in neutron star magnetospheres in
  accreting systems

abstract:
  We show that the interaction of an accretion disk with the magnetosphere of a
neutron star can excite resonant shear Alfven waves with Hz-kHz frequencies in
a region of enhanced density gradients. This is the the region where accretion
material flows along the magnetic field lines in the magnetosphere. We argue
that due to the pressure anisotropy produced by the plasma flow, firehose
instabilities are likely to occur. Furthermore, for a dipolar field topology,
we show that a new instability develops due to both magnetic field curvature
and the plasma flow.


title: Fitting Non-Minimally Coupled Scalar Models to Gold SnIa Dataset

abstract:
  Non-minimally coupled theories of special potentials are analyzed
numerically. Such theories yield equations of state $\omega<-1$ and
oscillations of the cosmological expansion, which are favored by the recent
analysis of observations. Fitting these theories to the Gold SnIa dataset, we
obtain results comparable with other models. A potential of the form
$V(\phi)=V_0e^{a_1\phi^2}$ yields $\chi^2_{min}=170.127$. Similar results are
obtained for potentials of the form $V(\phi)=V_0+a_1\phi^n$.


title:
GRAPE-SPH Chemodynamical Simulation of Elliptical Galaxies II: Scaling
  Relations and the Fundamental Plane

abstract:
  We simulate the formation and chemodynamical evolution of 128 elliptical
galaxies using a GRAPE-SPH code that includes various physical processes that
are associated with the formation of stellar systems: radiative cooling, star
formation, feedback from Type II and Ia supernovae and stellar winds, and
chemical enrichment. We find that the star formation timescale controls when
and where stars form in the contracting gas cloud, determines the effective
radius at given mass, and is constrained by observation to be ten times longer
than the local dynamical timescale. We succeed in reproducing the observed
global scaling relations under our CDM-based scenario, e.g., the Faber-Jackson
relation, the Kormendy relation, and the fundamental plane. An intrinsic
scatter exists along the fundamental plane, and the origin of this scatter lies
in differences in merging history. Galaxies that undergo major merger events
tend to have larger effective radii and fainter surface brightnesses, which
result in larger masses, smaller surface brightnesses, and larger mass-to-light
ratios. We can also reproduce the observed colour-magnitude and
mass-metallicity relations, although the scatter is larger than observed. The
scatter arises because feedback is not very effective and star formation does
not terminate completely in our simulations. ~25% of accreted baryons are blown
away in the simulations, independent of the assumed star formation timescale
and initial mass function. Most heavy elements end up locked into stars in the
galaxy. The ejected metal fraction depends only on the star formation
timescale, and is ~2% even to rapid star formation.


title:
Discovery and Monitoring of the likely IR Counterpart of SGR 1806-20
  during the 2004 gamma-ray burst-active state

abstract:
  The sky region including the Chandra position of SGR 1806-20 was monitored in
the IR band during 2004, following its increased high energy bursting activity.
Observations were performed using NAOS-CONICA, the adaptive optics IR camera
mounted on Yepun VLT, which provided images of unprecedented quality (FWHM
better than 0.1"). After the 2004 December 27th giant flare, the source
position has been nailed by VLA observations of its radio counterpart, reducing
the positional uncertainty to 0.04". Using IR data from our monitoring
campaign, we discovered the likely IR counterpart to SGR 1806-20 based on
positional coincidence with the Chandra and VLA uncertainty regions and flux
variability of a factor of about 2 correlated with that at higher energies. We
compare our findings with other isolated neutron star classes thought to be
related, at some level, with SGRs.


title: AGN-driven convection in galaxy-cluster plasmas

abstract:
  This paper describes how active galactic nuclei can heat galaxy-cluster
plasmas by driving convection in the intracluster medium. A model is proposed
in which a central supermassive black hole accretes intracluster plasma at the
Bondi rate and powers a radio source. The central radio source produces cosmic
rays, which mix into the thermal plasma. The cosmic-ray luminosity is
proportional to the mass accretion rate. The cosmic-ray pressure gradient
drives convection, which causes plasma heating. It is assumed that plasma
heating balances radiative cooling. The plasma heating rate is self-regulating
because the Bondi accretion rate is a decreasing function of the specific
entropy near the cluster center; if heating exceeds cooling, then the central
entropy increases, the Bondi rate and cosmic-ray luminosity decrease, and the
convective heating rate is reduced. This paper focuses on the role of
intracluster magnetic fields, which affect convection by causing heat and
cosmic rays to diffuse primarily along magnetic field lines. A new stability
criterion is derived for convection in a thermal-plasma/cosmic-ray fluid, and
equations for the average fluid properties in a convective cluster are obtained
with the use of a nonlocal two-fluid mixing length theory. Numerical solutions
of the model equations compare reasonably well with observations without
requiring fine tuning of the model parameters.


title: Regularized energy-dependent solar flare hard x-ray spectral index

abstract:
  The deduction from solar flare X-ray photon spectroscopic data of the energy
dependent model-independent spectral index is considered as an inverse problem.
Using the well developed regularization approach we analyze the energy
dependency of spectral index for a high resolution energy spectrum provided by
Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The regularization
technique produces much smoother derivatives while avoiding additional errors
typical of finite differences. It is shown that observations imply a spectral
index varying significantly with energy, in a way that also varies with time as
the flare progresses. The implications of these findings are discussed in the
solar flare context.


title: Discovery of Non-radial pulsations in PQ Andromedae

abstract:
  We have detected pulsations in time-series photometry of the WZ Sge dwarf
nova PQ And. The strongest peak in the power spectrum occurs at a period of
10.5 minutes. Similar periods have been observed in other WZ Sge systems and
are attributed to ZZ Ceti type non-radial pulsations. There is no indication in
the photometry of an approximately 1.7 hour orbital period as reported in
previous spectroscopic observations.


title:
Relation between the 16O(alpha,gamma)20Ne reaction and its reverse
  20Ne(gamma,alpha)16O reaction in stars and in the laboratory

abstract:
  The astrophysical reaction rates of the 16O(a,g)20Ne capture reaction and its
inverse 20Ne(g,a)16O photodisintegration reaction are given by the sum of
several narrow resonances and a small direct capture contribution at low
temperatures. Although the thermal population of low lying excited states in
16O and 20Ne is extremely small, the first excited state in 20Ne plays a
non-negligible role for the photodisintegration rate. Consequences for
experiments with so-called quasi-thermal photon energy distributions are
discussed.


title:
Supernova Neutrino-Effects on R-Process Nucleosynthesis in Black Hole
  Formation

abstract:
  Stars with a wide range of masses provide a variety of production sites for
intermediate-to-heavy mass elements. Very massive stars with mass $\geq 8
M_{\odot}$ culminate their evolution by supernova explosions which are presumed
to be the most viable candidate astrophysical sites of r-process
nucleosynthesis. If the models for the supernova r-process are correct, then
nucleosynthesis results could also pose a significant constraint on the remnant
of supernova explosions, $i.e.$ neutron star or black hole. In the case of very
massive core collapse, a remnant stellar black hole is thought to be formed.
Intense neutrino flux from the neutronized core and the neutrino sphere might
suddenly cease during the Kelvin-Helmholtz cooling phase because of the black
hole formation. It is interesting to explore observable consequences of such a
neutrino flux truncation. Arguments have recently been given in the literature
that even the neutrino mass may be determined from the time delay of deformed
neutrino energy spectrum after the cease of neutrino ejection (neutrino cutoff
effect). Here, we study the expected theoretical response of the r-process
nucleosynthesis to the neutrino cutoff effect in order to look for another
independent signature of this phenomenon. We found a sensitive response of the
r-process yield if the neutrino cutoff occurs after the critical time when the
expanding materials in the neutrino-driven wind drop out of the Nuclear
Statistical Equilibrium (NSE). The r-process nucleosynthesis yields change
maximally if the cutoff occurs during the r-process. Using this result,
connected with future detection of the time-variation of SN neutrino spectrum,
we are able to identify when the black hole formation occurs in the course of
SN collapse.


title:
On the Afterglow and Host Galaxy of GRB021004: A Comprehensive Study
  with the Hubble Space Telescope

abstract:
  (Abridged) We report on HST observations of the late-time afterglow and host
galaxy of GRB021004 (z=2.33). Although this GRB is one of the best observed so
far, there is substantial disagreement between different interpretations of
data sets on this burst in the literature. We have observed the field of
GRB021004 with the HST at multiple epochs from 3 days until almost 10 months
after the burst. With STIS spectroscopy we cover the spectral region 600-1700AA
in the restframe. From the limit on the flux recovery bluewards of the
Lyman-limit we constrain the HI column density to be above 1x10^18 cm-2 Based
on ACS and NICMOS imaging we find that the afterglow evolved achromatically
within the errors. The color changes observed by other authors during the first
four days must be related to a stochastic phenomenon superimposed on an
afterglow component with a constant spectral shape. This achromaticity implies
that the cooling break has remained on the blue side of the optical part of the
spectrum for at least two weeks after the burst. The optical-to-X-ray slope is
consistent with being the same at 1.4 and 52.4 days after the burst. This
indicates that the cooling frequency is constant and hence, according to
fireball models, that the circumburst medium has a constant density profile.
The late-time slope of the lightcurve is in the range alpha_2 = 1.8-1.9, and is
inconsistent with a single power-law. This could be due to a late-time
flattening caused by the transition to non-relativistic expansion or due to
excess emission (a lightcurve `bump') 7 days after burst. The host is a
starburst galaxy with no evidence for dust and with strong Ly-alpha emission.
The afterglow was located very close (~100 pc) to the center of the host
suggesting that the progenitor was associated with a circumnuclear starburst.


title:
The radial velocity dispersion profile of the Galactic halo:
  Constraining the density profile of the dark halo of the Milky Way

abstract:
  We have compiled a new sample of 240 halo objects with accurate distance and
radial velocity measurements, including globular clusters, satellite galaxies,
field blue horizontal branch stars and red giant stars from the Spaghetti
survey. The new data lead to a significant increase in the number of known
objects for Galactocentric radii beyond 50 kpc, which allows a reliable
determination of the radial velocity dispersion profile out to very large
distances. The radial velocity dispersion shows an almost constant value of 120
km/s out to 30 kpc and then continuously declines down to 50 km/s at about 120
kpc. This fall-off puts important constraints on the density profile and total
mass of the dark matter halo of the Milky Way. For a constant velocity
anisotropy, the isothermal profile is ruled out, while both a dark halo
following a truncated flat model of mass $1.2^{+1.8}_{-0.5}\times 10^{12}$
M_sun and an NFW profile of mass $0.8^{+1.2}_{-0.2}\times 10^{12}$ M_sun and
c=18 are consistent with the data. The significant increase in the number of
tracers combined with the large extent of the region probed by these has
allowed a more precise determination of the Milky Way mass in comparison to
previous works. We also show how different assumptions for the velocity
anisotropy affect the performance of the mass models.


title:
A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the
  smallest galactic scales

abstract:
  We present the results of a kinematic survey of the dwarf spheroidal
satellite of M31, And-IX, which appears to be the lowest surface brightness and
also the faintest galaxy (M_V = -8.3) found to date. Using Keck/DEIMOS
spectroscopic data, we have measured its velocity relative to M31, its velocity
dispersion, and its metallicity. It exhibits a significant velocity dispersion
sigma_v = 6.8+3.0-2.0km/s, which coupled with the low luminosity implies a very
high mass to V-band light ratio, M/L ~ 93+120-50msun/lsun (M/L > 17msun/lsun at
99% confidence). Unless strong tidal forces have perturbed this system, this
smallest of galaxies is a highly dark matter dominated system.


title: A compact binary merger model for the short, hard GRB 050509b

abstract:
  The first X-ray afterglow for a short (~30 ms), hard gamma-ray burst was
detected by Swift on 9 May 2005 (GRB 050509b). No optical or radio counterpart
was identified in follow-up observations. The tentative association of the GRB
with a nearby giant elliptical galaxy at redshift z=0.2248 would imply a total
energy release E(gamma, isotropic) ~3 x 10**48 erg, and that the progenitor had
traveled several tens of kpc from its point of origin, in agreement with
expectations linking these events to the final merger of compact binaries
driven by gravitational wave emission. We model the dynamical merger of such a
system and the time-dependent evolution of the accretion tori thus created. The
resulting energetics, variability, and expected durations are consistent with
GRB 050509b originating from the tidal disruption of a neutron star by a
stellar mass black hole, or of the merger of two neutron stars followed by
prompt gravitational collapse of the massive remnant. We discuss how the
available gamma-ray and X-ray data provide a probe for the nature of the
relativistic ejecta and the surrounding medium.


title:
Transport and mixing in the radiation zones of rotating stars II.
  Axisymmetric magnetic field

abstract:
  The purpose of this paper is to improve the modeling of the mixing of
chemical elements that occurs in stellar radiation zones. In addition to the
classical rotational mixing considered in our previous paper, which results of
the combined action of the thermally-driven meridional circulation and of the
turbulence generated by the shear of differential rotation, we include here the
effect of an axisymmetric magnetic field in a self-consistent way. We treat the
advection of the field by the meridional circulation, its Ohmic diffusion, and
the production of its toroidal component through the shear of differential
rotation. The Lorentz force is assumed not to exceed the centrifugal force; it
acts on the baroclinic balance and therefore on the meridional flow, and it has
a strong impact on the transport of angular momentum. All variables and
governing equations are expanded in spherical or spherical vectorial functions,
to arbitrary order: this yields a system of partial differential equations in
time and in the radial coordinate, which is ready to be implemented in a
stellar structure code.


title:
Evaluating Gaia performances on eclipsing binaries. IV. Orbits and
  stellar parameters for SV Cam, BS Dra and HP Dra

abstract:
  This is the fourth in a series of papers that aim both to provide reasonable
orbits for a number of eclipsing binaries and to evaluate the expected
performance of Gaia of these objects and the accuracy that is achievable in the
determination of such fundamental stellar parameters as mass and radius. In
this paper, we attempt to derive the orbits and physical parameters for three
eclipsing binaries in the mid-F to mid-G spectral range. As for previous
papers, only the Hp, Vt, Bt photometry from the Hipparcos/Tycho mission and
ground-based radial velocities from spectroscopy in the region 8480-8740 A are
used in the analyses. These data sets simulate the photometric and
spectroscopic data that are expected to be obtained by Gaia, the approved ESA
Cornerstone mission to be launched in 2011. The systems targeted in this paper
are SV Cam, BS Dra and HP Dra. SV Cam and BS Dra have been studied previously,
allowing comparisons of the derived parameters with those from full scale and
devoted ground-based investigations. HP Dra has no published orbital solution.
SV Cam has a beta Lyrae type light curve and the others have Algol-like light
curves. SV Cam has the complication of light curve anomalies, usually
attributed to spots; BS Dra has non-solar metallicity, and HP Dra appears to
have a small eccentricity and a sizeable time derivative in the argument of the
periastron. Thus all three provide interesting and different test cases.


title: Type Ia supernova diversity in three-dimensional models

abstract:
  The use of type Ia supernovae as distance indicators for cosmology has
initiated a search for theoretical arguments supporting the empirical
calibration methods applied. To this end, as a first step, a sound
understanding of the origin of the observed diversity in type Ia supernova
properties is needed. Here we present a first systematic study of effects
resulting from changing some physical parameters of three-dimensional
deflagration models of thermonuclear supernovae. In our study we vary the
progenitor's carbon-to-oxygen ratio and its central density prior to ignition
because both properties are not well determined by stellar evolution theory and
they may change from supernova to supernova. Next we compute for these
explosion models the nucleosynthesis yields in a post-processing step. This, in
addition, allows us to study variations in the progenitor's metallicity by
means of different $^{22}$Ne mass fractions in the initial composition. We find
that the progenitor's carbon-to-oxygen ratio and its central density affect the
energy release of the models and thus the expansion velocity of the supernova.
Moreover, we find that changing the metallicity and the central density changes
the production of radioactive $^{56}$Ni and thus affects the luminosity. In
contrast, the carbon-to-oxygen ratio has little effect on the $^{56}$Ni
production. Implications of the found variations of the explosion energy and
the produced $^{56}$Ni mass for the type Ia supernova diversity are discussed.


title:
The near-IR Surface Brightness Method applied to six Cepheids in the
  young LMC cluster NGC1866

abstract:
  We present new near-IR light curves for six Cepheids in the young blue LMC
cluster NGC1866 as well as high precision radial velocity curves for ten
Cepheids in NGC1866 and two in NGC2031. For the six Cepheids in NGC1866 with
new J and K light curves we determine distances and absolute magnitudes by
applying the near-IR surface brightness method. We find that the formal error
estimates on the derived distances are underestimated by about a factor of two.
We find excellent agreement between the absolute magnitudes for the low
metallicity LMC Cepheids with the Period-Luminosity (P-L) relation determined
by the near-IR surface brightness (ISB) method for Galactic Cepheids suggesting
that the slope of the P-L relations for low metallicity and solar metallicity
samples could be very similar in contrast to other recent findings. Still there
appears to be significant disagreement between the observed slopes of the OGLE
based apparent P-L relations in the LMC and the slopes derived from ISB
analysis of Galactic Cepheids, and by inference for Magellanic Cloud Cepheids,
indicating a possible intrinsic problem with the ISB method itself. Resolving
this problem could reaffirm the P-L relation as the prime distance indicator
applicable as well to metallicities significantly different from the LMC value.


title:
The nature of Composite Seyfert/Star-forming galaxies revealed by X-ray
  observations

abstract:
  This paper presents new Chandra and BeppoSAX observations aimed at
investigating the optical/X-ray mismatch in the enigmatic class of the
Composite galaxies, discovered by a cross-correlation of IRAS and ROSAT all sky
survey catalogues. These galaxies have been classified as star-forming objects
on the basis of their optical spectra, while the detection of weak broad wings
in the H(alpha) emission in a few of them and their high X-ray luminosity in
the ROSAT band indicated the presence of an active nucleus. The analysis of
Chandra observations for 4 Composites has revealed nuclear point-like sources,
with a typical AGN spectrum (Gamma = 1.7-1.9) and little intrinsic absorption.
A strong flux variability has been observed on different time scales, in
particular most of the sources were brighter at the ROSAT epoch. Although of
relative low luminosity for the AGN class (L(2-10 keV) = 3-60 x 10^{41} erg/s),
the active nucleus is nevertheless dominant in the X-ray domain. At other
wavelengths it appears to be overwhelmed by the starburst and/or host galaxy
light, yielding the Composite classification for these objects.


title:
Galactic Gradients, Postbiological Evolution and the Apparent Failure of
  SETI

abstract:
  Motivated by recent developments impacting our view of Fermi's paradox
(absence of extraterrestrials and their manifestations from our past light
cone), we suggest a reassessment of the problem itself, as well as of
strategies employed by SETI projects so far. The need for such reevaluation is
fueled not only by the failure of searches thus far, but also by great advances
recently made in astrophysics, astrobiology, computer science and future
studies, which have remained largely ignored in SETI practice. As an example of
the new approach, we consider the effects of the observed metallicity and
temperature gradients in the Milky Way on the spatial distribution of
hypothetical advanced extraterrestrial intelligent communities. While,
obviously, properties of such communities and their sociological and
technological preferences are entirely unknown, we assume that (1) they operate
in agreement with the known laws of physics, and (2) that at some point they
typically become motivated by a meta-principle embodying the central role of
information-processing; a prototype of the latter is the recently suggested
Intelligence Principle of Steven J. Dick. There are specific conclusions of
practical interest to be drawn from coupling of these reasonable assumptions
with the astrophysical and astrochemical structure of the Galaxy. In
particular, we suggest that the outer regions of the Galactic disk are most
likely locations for advanced SETI targets, and that intelligent communities
will tend to migrate outward through the Galaxy as their capacities of
information-processing increase, for both thermodynamical and astrochemical
reasons. This can also be regarded as a possible generalization of the Galactic
Habitable Zone, concept currently much investigated in astrobiology.


title: The excitation of water in the S140 photon dominated region

abstract:
  We consider the excitation of water in the Photon Dominated Region (PDR).
With the use of a three-dimensional escape probability method we compute the
level populations of ortho- and para-H_2O up to 350 K (i.e., 8 levels), as well
as line intensities for various transitions. Homogeneous and inhomogeneous
models are presented with densities of 10^4-10^5 cm^{-3} and the differences
between the resulting intensities are displayed. Density, temperature, and
abundance distributions inside the cloud are computed with the use of a
self-consistent physi-chemical (in)homogeneous model in order to reproduce the
line intensities observed with SWAS, and to make predictions for various lines
that HIFI will probe in the future. Line intensities vary from 10^{-13} erg
cm^{-2} s^{-1} sr^{-1} to a few times 10^{-6} erg cm^{-2} s^{-1} sr^{-1}. We
can reproduce the intensity for the 1_{10}-1_{01} line observed by the SWAS
satellite. It is found that the 2_{12}-1_{01} line is the strongest, whereas
the 3_{12}-2_{21} line is the weakest, in all the models. It is found that the
1_{10}-1_{01} line probes the total column, while higher excitation lines probe
the higher density gas (e.g., clumps).


title:
The Shear TEsting Programme 1: Weak lensing analysis of simulated
  ground-based observations

abstract:
  The Shear TEsting Programme, STEP, is a collaborative project to improve the
accuracy and reliability of all weak lensing measurements in preparation for
the next generation of wide-field surveys. In this first STEP paper we present
the results of a blind analysis of simulated ground-based observations of
relatively simple galaxy morphologies. The most successful methods are shown to
achieve percent level accuracy. From the cosmic shear pipelines that have been
used to constrain cosmology, we find weak lensing shear measured to an accuracy
that is within the statistical errors of current weak lensing analyses, with
shear measurements accurate to better than 7%. The dominant source of
measurement error is shown to arise from calibration uncertainties where the
measured shear is over or under-estimated by a constant multiplicative factor.
This is of concern as calibration errors cannot be detected through standard
diagnostic tests. The measured calibration errors appear to result from stellar
contamination, false object detection, the shear measurement method itself,
selection bias and/or the use of biased weights. Additive systematics (false
detections of shear) resulting from residual point-spread function anisotropy
are, in most cases, reduced to below an equivalent shear of 0.001, an order of
magnitude below cosmic shear distortions on the scales probed by current
surveys.
  Our results provide a snapshot view of the accuracy of current ground-based
weak lensing methods and a benchmark upon which we can improve. To this end we
provide descriptions of each method tested and include details of the eight
different implementations of the commonly used Kaiser, Squires and Broadhurst
(1995) method (KSB+) to aid the improvement of future KSB+ analyses.


title: DDO 43: A Prototypical Dwarf Irregular Galaxy?

abstract:
  We present sensitive and high resolution 21 cm observations of the dwarf
irregular (dIm) galaxy DDO 43, in conjunction with optical broad and narrow
band images in U, B, V, and Halpha. The observations are used to examine the
relationship between its HI morphology and kinematics to past and present star
formation. Optically, it is a small (R_25 = 990 pc), faint (M_B of -14.0) Im
with a slightly boxy shape. In HI, DDO 43 has an extended (R_HI/R_Ho = 2.8) gas
envelope. There is a high density ridge associated with the optical body of the
galaxy, containing several higher density knots and lower density holes. The
largest hole is ~850x530 pc. No expansion is detected, so it must be relatively
old. The largest and potentially oldest (7-70 Myr) of the six identified star
clusters is located at the western edge of the hole. Four of the other clusters
are located near high density peaks. There are several HII regions, most of
which are associated with peaks in the HI surface density. The overall star
formation rate is average for its type. In many ways, DDO 43 is a very typical
dwarf irregular galaxy. Its HI morphology is consistent with a history of
episodes of localized star ormation that create holes and shells in the ISM,
some of which can overlap. These features are located within the area of
solid-body rotation in the galaxy; the lack of shear in these small systems
allows such structures to persist for long periods of time.


title: Ultra-Low Amplitude Cepheids in the Large Magellanic Cloud

abstract:
  The MACHO variables of LMC Field 77 that lie in the vicinity of the Cepheid
instability strip are reexamined. Among the 144 variables that we identify as
Cepheids we find 14 that have Fourier amplitudes <0.05 mag in the MACHO red
band, of which 7 have an amplitude <0.006 mag : we dub the latter group of
stars ultra-low amplitude (ULA) Cepheids. The variability of these objects is
verified by a comparison of the MACHO red with the MACHO blue lightcurves and
with those of the corresponding OGLE LMC stars. The occurrence of ULA Cepheids
is in agreement with theory. We have also discovered 2 low amplitude variables
whose periods are about a factor of 5--6 smaller than those of F Cepheids of
equal apparent magnitude. We suggest that these objects are Cepheids undergoing
pulsations in a surface mode and that they belong to a novel class of Strange
Cepheids (or Surface Mode Cepheids) whose existence was predicted by Buchler et
al. (1997).


title: On quasar host galaxies as tests of non-cosmological redshifts

abstract:
  Despite a general consensus in the astronomical community that all quasars
are located at the distances implied by their redshifts, a number of
observations still challenge this interpretation, possibly indicating that some
subpopulation of quasars may harbour significant redshift components not
related to the expansion of the universe. It has been suggested that these
objects may have been ejected from local galaxies and are likely to evolve into
new galaxies themselves. Here, a test of such exotic scenarios is proposed,
based on the spectral energy distribution of the galaxies hosting quasars with
suspected ejection origin. Provided that the time scales over which the ejected
objects manifest themselves as quasars is short, one would in the framework of
ejection scenarios expect to find either no quasar host galaxy, a pseudo-host
consisting of gas ionized by the quasar, or a host galaxy consisting of young
stars only. It is argued that the spectral energy distributions corresponding
to the latter two options should differ significantly from those of most quasar
host galaxies detected at low redshift so far, thus providing a potential test
of the claimed existence of ejected quasars. A minimal implementation of this
test, involving optical and near-IR broadband photometry, is suggested.


title: Mass Flows in Cometary UCHII Regions

abstract:
  High spectral and spatial resolution, mid-infrared fine structure line
observations toward two ultracompact HII (UCHII) regions (G29.96 -0.02 and Mon
R2) allow us to study the structure and kinematics of cometary UCHII regions.
In our earlier study of Mon R2, we showed that highly organized mass motions
accounted for most of the velocity structure in that UCHII region. In this
work, we show that the kinematics in both Mon R2 and G29.96 are consistent with
motion along an approximately paraboloidal shell. We model the velocity
structure seen in our mapping data and test the stellar wind bow shock model
for such paraboloidal like flows. The observations and the simulation indicate
that the ram pressures of the stellar wind and ambient interstellar medium
cause the accumulated mass in the bow shock to flow along the surface of the
shock. A relaxation code reproduces the mass flow's velocity structure as
derived by the analytical solution. It further predicts that the pressure
gradient along the flow can accelerate ionized gas to a speed higher than that
of the moving star. In the original bow shock model, the star speed relative to
the ambient medium was considered to be the exit speed of ionized gas in the
shell.


title:
A Study of Edge-On Galaxies with the Hubble Space Telescope's Advanced
  Camera for Surveys. II. Vertical distribution of the resolved stellar
  population

abstract:
  We analyze the vertical distribution of the resolved stellar populations in
six low-mass, edge-on, spiral galaxies observed with the Hubble Space Telescope
Advanced Camera for Surveys. In each galaxy we find evidence for an extraplanar
stellar component extending up to 15 scale heights (3.5 kpc) above the plane.
We analyze the vertical distribution as a function of stellar age by tracking
changes in the color-magnitude diagram. The young stellar component (<10^8 yrs)
is found to have a scale height larger than the young component in the Milky
Way, suggesting that stars in these low mass galaxies form in a thicker disk.
We also find that the scale height of a stellar population increases with age,
with young main sequence stars, intermediate age asymptotic giant branch stars,
and old red giant branch stars having succesively larger scale heights in each
galaxy. This systematic trend indicates that disk heating must play some role
in producing the extraplanar stars. We constrain the rate of disk heating using
the observed trend between scale height and stellar age, and find that the
observed heating rates are dramatically smaller than in the Milky Way. The
color distributions of the red giant branch stars well above the midplane
indicate that the extended stellar components we see are moderately metal-poor,
with peak metallicities around [Fe/H]=-1 and with little or no metallicity
gradient with height. The lack of metallicity gradient can be explained if a
majority of extraplanar RGB stars were formed at early times and are not
dominated by a younger heated population. Our observations suggest that, like
the Milky Way, low-mass disk galaxies also have multiple stellar components. In
its structure, mean metallicity and old age, the RGB component in these
galaxies seems analagous to the Milky Way thick disk. [ABRIDGED]


title:
Luminosity-dependent evolution of soft X-ray selected AGN: New Chandra
  and XMM-Newton surveys

abstract:
  We present new results on the cosmological evolution of unabsorbed (type-1)
active galactic nuclei (AGN) selected in the soft (0.5-2 keV) X-ray band. From
a variety of ROSAT, XMM-Newton and Chandra surveys we selected a total of ~1000
AGN with an unprecedented spectroscopic and photometric optical/NIR
identification completeness. For the first time we are able to derive reliable
space densities for low-luminosity (Seyfert-type) X-ray sources at cosmological
redshifts. The evolutionary behaviour of AGN shows a strong dependence on X-ray
luminosity: while the space density of high-luminosity AGN reaches a peak
around z~2, similar to that of optically selected QSO, the space density of
low-luminosity AGNs peaks at redshifts below z=1. This confirms previous ROSAT
findings of a luminosity-dependent density evolution. Using a rigorous
treatment of the optical identification completeness we are able to show that
the space density of AGN with X-ray luminosities L_x < 10^45 erg s^-1 declines
significantly towards high redshifts.


title:
Investigating ionized disc models of the variable narrow-line Seyfert 1
  PG 1404+226

abstract:
  We investigate the use of relativistically blurred photoionized disc models
on an XMM-Newton observation of the Narrow Line Seyfert 1 galaxy PG 1404+226.
The model is designed to reproduce the radiation from the inner accretion disc
around a Kerr black hole, and is more successful at fitting the spectrum than
models based on a thermal soft excess. The source varies strongly over the
course of the observation, and the disc model works over all observed flux
states. We conclude that it is a useful tool in the study of certain quasars.


title: Flux Modulation from Non-Axisymmetric Stuctures in Accretion Discs

abstract:
  Non-axisymmetric accretion discs can lead to flux variability. Here we
provide an analytic framework for modeling non-axisymmetric structures like
hotspots and spiral waves and their influence on observed timing measurements.
The presently unexplained Low-frequency Quasi-Periodic Oscillations (LFQPO),
observed in X-ray binaries and cataclysmic variables, could be the result of
such discs. Our framework serves as a guide to quantify the properties that
non-axisymmetric structures produced by nonlinear accretion disc models must
have in order to explain observed features such as LFQPOs. The results from our
microquasar appliations also provide analogous predictions for X-ray modulation
in active galactic nuclei. The formalism and physical interpration is of
practical use for generic non-axisymmetric accretion disc systems.


title:
Dynamical evolution of neutrino--cooled accretion disks: detailed
  microphysics, lepton-driven convection, and global energetics

abstract:
  We present a detailed, two dimensional numerical study of the microphysical
conditions and dynamical evolution of accretion disks around black holes when
neutrino emission is the main source of cooling. Such structures are likely to
form after the gravitational collapse of massive rotating stellar cores, or the
coalescence of two compact objects in a binary (e.g., the Hulse--Taylor
system). The physical composition is determined self consistently by
considering two regimes: neutrino--opaque and neutrino--transparent, with a
detailed equation of state which takes into account neutronization, nuclear
statistical equilibrium of a gas of free nucleons and alpha particles,
blackbody radiation and a relativistic Fermi gas of arbitrary degeneracy.
Various neutrino emission processes are considered, with electron/positron
capture onto free nucleons providing the dominant contribution to the cooling
rate. We find that important temporal and spatial scales, related to the
optically thin/optically thick transition are present in the disk, and manifest
themselves clearly in the energy output in neutrinos. This transition produces
an inversion of the lepton gradient in the innermost regions of the flow which
drives convective motions, and affects the density and disk scale height radial
profiles. The electron fraction remains low in the region close to the black
hole, and if preserved in an outflow, could give rise to heavy element
nucleosynthesis. Our specific initial conditions arise from the binary merger
context, and so we explore the implications of our results for the production
of gamma ray bursts.


title:
UBVR and HST mid-UV and near-IR surface photometry and radial color
  gradients of late-type, irregular, and peculiar galaxies

abstract:
  We introduce a dataset of 142 mostly late-type spiral, irregular, and
peculiar (interacting or merging) nearby galaxies observed in UBVR at the
Vatican Advanced Technology Telescope (VATT), and present an analysis of their
radial color gradients. We confirm that nearby elliptical and early- to
mid-type spiral galaxies show either no or only small color gradients, becoming
slightly bluer with radius. In contrast, we find that late-type spiral,
irregular, peculiar, and merging galaxies become on average redder with
increasing distance from the center. The scatter in radial color gradient
trends increases toward later Hubble type. As a preliminary analysis of a
larger data-set obtained with the Hubble Space Telescope (HST), we also analyze
the color gradients of six nearby galaxies observed with NICMOS in the near-IR
(H) and with WFPC2 in the mid-UV (F300W) and red (F814W). We discuss the
possible implication of these results on galaxy formation and compare our
nearby galaxy color gradients to those at high redshift. We present examples of
images and UBVR radial surface brightness and color profiles, and of the tables
of measurements; the full atlas and tables are published in the electronic
edition only.


title: GRB 050509B: Constraints on short gamma-ray burst models

abstract:
  We have obtained deep optical images with the Very Large Telescope at ESO of
the first well-localized short-duration gamma-ray burst, GRB 050509B. From V
and R imaging, initiated ~2 days after the GRB trigger and lasting up to three
weeks, we detect no variable object inside the small Swift/XRT X-ray error
circle down to 2sigma limits of V = 26.5 and R = 25.1. The X-ray error circle
includes a giant elliptical galaxy at z = 0.225, which has been proposed as the
likely host of this GRB. Our limits indicate that if the GRB originated at z =
0.225, any supernova-like event accompanying the GRB would have to be over 100
times fainter than normal Type Ia SNe or Type Ic hypernovae, 5 times fainter
than the faintest known Ia or Ic SNe, and fainter than the faintest known Type
II SNe. Moreover, we use the optical limits to constrain the energetics of the
GRB outflow. Simple models indicate that, unless the intrinsic energy in the
outflow from GRB 050509B was << 10^51 erg, there was very little radioactive
material with efficient decay timescales for generating a large luminosity.
These limits strongly constrain progenitor models for this short GRB.


title: Superstellar clusters and their impact on their host galaxies

abstract:
  We review the properties of young superstellar clusters and the impact that
their evolution has in their host galaxies. In particular we look at the two
different star-forming feedback modes: positive and negative feedback. The
development of strong isotropic winds emanating from massive clusters, capable
of disrupting the remains of the parental cloud as well as causing the
large-scale restructuring of the surrounding ISM, has usually been taken as a
negative feedback agent. Here we show the impact that radiative cooling has on
the resultant outflows and then, as an extreme example, we infer from the
observations of M82 the detailed inner structure of supergalactic winds and
define through numerical simulations the ingredients required to match such
structures.We also show how when radiative cooling becomes significant within
the star cluster volume itself (~ 30% of the deposited energy), the force of
gravity takes over and drives in situ all the matter deposited by winds and
supernovae into several generations of star formation. A situation in which the
mass deposition rate from the star cluster instead of causing a wind as in the
adiabatic solution, turns into a positive feedback star-forming mode equal to
the star formation rate.


title:
Radial distribution and strong lensing statistics of satellite galaxies
  and substructure using high resolution LCDM hydrodynamical simulations

abstract:
  We analyse the number density and radial distribution of substructures and
satellite galaxies using cosmological simulations that follow the gas dynamics
of a baryonic component, including shock heating, radiative cooling and star
formation within the hierarchical concordance LCDM model. We find that the
dissipation of the baryons greatly enhances the survival of subhaloes,
expecially in the galaxy core, resulting in a radial distribution of satellite
galaxies that closely follows the overall mass distribution in the inner part
of the halo. Hydrodynamical simulations are necessary to resolve the adiabatic
contraction and dense cores of galaxies, resulting in a total number of
satellites a factor of two larger than found in pure dark matter simulation, in
good agreement with the observed spatial distribution of satellite galaxies
within galaxies and clusters. Convergence tests show that the cored
distribution found by previous authors in pure N-body simulations was due to
physical overmerging of dark matter only structures.
  We proceed to use a ray-shooting technique in order to study the impact of
these additional substructures on the number of violations of the cusp caustic
magnification relation. We develop a new approach to try to disentangle the
effect of substructures from the intrinsic discreteness of N-Body simulations.
Even with the increased number of substructures in the centres of galaxies, we
are not able to reproduce the observed high numbers of discrepancies observed
in the flux ratios of multiply lensed quasars.


title:
Cosmic gamma-ray background from Type Ia supernovae revisited: Evidence
  for missing gamma-rays at MeV

abstract:
  The observed cosmic gamma-ray background at ~ MeV has often been attributed
to Type Ia supernovae (SNIa). Since SNIa is close to a standard candle, one can
calculate the gamma-ray intensity of SNIa integrated over redshifts fairly
accurately, once the evolution of the SNIa rate is known. The latest SNIa rate
measured at z < ~1.6 (Dahlen et al. 2004) indicates that the previous
calculations of the gamma-ray background consistently overestimated the SNIa
rate. With the new rate, we find that the SNIa contribution is an order of
magnitude smaller than observed, and thus new population(s) of sources should
be invoked.


title:
High Resolution Spectroscopy of X-ray Quasars: Searching for the X-ray
  Absorption from the Warm-Hot Intergalactic Medium

abstract:
  We present a survey of six low to moderate redshift quasars with Chandra and
XMM-Newton. The primary goal is to search for the narrow X-ray absorption lines
produced by highly ionized metals in the Warm-Hot Intergalactic Medium. All the
X-ray spectra can be fitted by a power law with neutral hydrogen absorption
method. The residuals that may caused by additional emission mechanisms or
calibration uncertainties are taken account by polynomial in order to search
for narrow absorption features. No real absorption line is detected at above
3-sigma level in all the spectra. We discuss the implications of the lack of
absorption lines for our understanding of the baryon content of the universe
and metallicity of the intergalactic medium (IGM). We find that the
non-detection of X-ray absorption lines indicates that the metal abundance of
the IGM should be smaller than ~0.3 solar abundance. We also discuss
implications of the non-detection of any local (z ~ 0) X-ray absorption
associated with the ISM, Galactic halo or local group, such as has been seen
along several other lines of sight (LOS). By comparing a pair of LOSs we
estimate a lower limit on the hydrogen number density for the (z ~ 0) 3C 273
absorber of n_H >= 4e-3 cm^-3.


title: GZK Photons as Ultra High Energy Cosmic Rays

abstract:
  We calculate the flux of "GZK-photons", namely the flux of Ultra High Energy
Cosmic Rays (UHECR) consisting of photons produced by extragalactic nucleons
through the resonant photoproduction of pions, the so called GZK effect. We We
calculate the flux of "GZK-photons", namely the flux of Ultra High Energy
Cosmic Rays (UHECR) consisting of photons produced by extragalactic nucleons
through the resonant photoproduction of pions, the so called GZK effect. We
show that, for primary nucleons, the GZK photon fraction of the total UHECR
flux is between $10^{-4}$ and $10^{-2}$ above $10^{19}$ eV and up to the order
of 0.1 above $10^{20}$ eV. The GZK photon flux depends on the assumed UHECR
spectrum, slope of the nucleon flux at the source, distribution of sources and
intervening backgrounds. Detection of this photon flux would open the way for
UHECR gamma-ray astronomy. Detection of a larger photon flux would imply the
emission of photons at the source or new physics. We compare the photon
fractions expected for GZK photons and the minimal predicted by Top-Down
models. We find that the photon fraction above $10^{19}$ eV is a crucial test
for Top-Down models.


title: Neutrino Processes in Strong Magnetic Fields

abstract:
  The processes of electron neutrino capture on neutron and electron
anti-neutrino capture on proton, and their reverse processes provide the
dominant mechanisms for heating and cooling the material below the stalled
shock in a core-collapse supernova. We summarize the major effects of strong
magnetic fields on the rates of the above reactions and illustrate these
effects with a simple supernova model. Due to parity violation of weak
interaction the heating rates are asymmetric even for a uniform magnetic field.
The cooling rates are also asymmetric for nonuniform fields. The most dramatic
effect of strong magnetic fields of 10^16 G is suppression of the cooling rates
by changing the equations of state through the phase space of electrons and
positrons.


title: Bright X-ray Flares in Gamma-Ray Burst Afterglows

abstract:
  Gamma-ray burst (GRB) afterglows have provided important clues to the nature
of these massive explosive events, providing direct information on the nearby
environment and indirect information on the central engine that powers the
burst. We report the discovery of two bright X-ray flares in GRB afterglows,
including a giant flare comparable in total energy to the burst itself, each
peaking minutes after the burst. These strong, rapid X-ray flares imply that
the central engines of the bursts have long periods of activity, with strong
internal shocks continuing for hundreds of seconds after the gamma-ray emission
has ended.


title:
Self-Sustained Ionization and Vanishing Dead Zones in Protoplanetary
  Disks

abstract:
  We analyze the ionization state of the magnetohydrodynamically turbulent
protoplanetary disks and propose a new mechanism of sustaining ionization.
First, we show that in the quasi-steady state of turbulence driven by
magnetorotational instability in a typical protoplanetary disk with dust
grains, the amount of energy dissipation should be sufficient for providing the
ionization energy that is required for activating magnetorotational
instability. Second, we show that in the disk with dust grains the energetic
electrons that compose electric currents in weakly ionized gas can provide
collisional ionization, depending on the actual saturation state of
magnetorotational turbulence. On the other hand, we show that in the
protoplanetary disks with the reduced effect of dust grains, the turbulent
motion can homogenize the ionization degree, leading to the activation of
magnetorotational instability even in the absence of other ionization
processes. The results in this Letter indicate that most of the regions in
protoplanetary disks remain magnetically active, and we thus require a change
in the theoretical modeling of planet formation.


title: Where Are The M Dwarf Disks Older Than 10 Million Years?

abstract:
  We present 11.7-micron observations of nine late-type dwarfs obtained at the
Keck I 10-meter telescope in December 2002 and April 2003. Our targets were
selected for their youth or apparent IRAS 12-micron excess. For all nine
sources, excess infrared emission is not detected. We find that stellar wind
drag can dominate the circumstellar grain removal and plausibly explain the
dearth of M Dwarf systems older than 10 Myr with currently detected infrared
excesses. We predict M dwarfs possess fractional infrared excess on the order
of L_{IR}/L_{*}\sim10^{-6} and this may be detectable with future efforts.


title:
X-ray outburst of 4U 0115+634 and ROTSE Observations of its Optical
  Counterpart V635 Cas

abstract:
  ROTSE IIId (The Robotic Optical Transient Experiment) observations of X-ray
binary system 4U 0115+634/V635 Cas obtained during 2004 June and 2005 January
make possible, for the first time, to study the correlation between optical and
type II X-ray outbursts. The X-ray outburst sharply enhanced after periastron
passage where the optical brightness was reduced by 0.3 magnitude for a few
days. We interpret the sharp reduction of optical brightness as a sign of mass
ejection from the outer parts of the disc of the Be star. After this sharp
decrease, the optical brightness healed and reached the pre X-ray outburst
level. Afterwards, gradual decrease of the optical brightness followed a
minimum then a gradual increase started again. Qualitatively, change of optical
lightcurve suggests a precession of the Be star disc around a few hundred days.
We also investigate the periodic signatures from the archival RXTE-ASM (Rossi
X-ray Timing Explorer - All Sky Monitor) light curve covering a time span of
$\sim 9$ years. We find significant orbital modulation in the ASM light curve
during the type I X-ray outburst.


title:
Bright X-ray flares in Orion young stars from COUP: evidence for
  star-disk magnetic fields?

abstract:
  We have analyzed a number of intense X-ray flares observed in the Chandra
Orion Ultradeep Project (COUP), a 13 days observation of the Orion Nebula
Cluster (ONC). Analysis of the flare decay allows to determine the size, peak
density and magnetic field of the flaring structure. A total of 32 events (the
most powerful 1% of COUP flares), have sufficient statistics for the analysis.
A broad range of decay times (from 10 to 400 ks) are present in the sample.
Peak flare temperatures are often very high, with half of the flares in the
sample showing temperatures in excess of 100 MK. Significant sustained heating
is present in the majority of the flares. The magnetic structures which are
found, are in a number of cases very long, with semi-lengths up to 10^12 cm,
implying the presence of magnetic fields of hundreds of G extending to
comparable distance from the stellar photosphere. These very large sizes for
the flaring structures ($ >> R_*) are not found in more evolved stars, where,
almost invariably, the same type of analysis results in structures with L <=
R_*. As the majority of young stars in the ONC are surrounded by disks, we
speculate that the large magnetic structures which confine the flaring plasma
are actually the same type of structures which channel the plasma in the
magnetospheric accretion paradigm, connecting the star's photosphere with the
accretion disk.


title: The Dwarf Nova PQ Andromedae

abstract:
  We report a photometric study of the WZ Sagittae-type dwarf nova PQ
Andromedae. The light curve shows strong (0.05 mag full amplitude) signals with
periods of 1263(1) and 634(1) s, and a likely double-humped signal with
P=80.6(2) min. We interpret the first two as nonradial pulsation periods of the
underlying white dwarf, and the last as the orbital period of the underlying
binary. We estimate a distance of 150(50) pc from proper motions and the two
standard candles available: the white dwarf and the dwarf-nova outburst. At
this distance, the K magnitude implies that the secondary is probably fainter
than any star on the main sequence -- indicating a mass below the Kumar limit
at 0.075 M_sol. PQ And may be another "period bouncer", where evolution now
drives the binary out to longer period.


title: Realistic arrival time distribution from an isotropic light source

abstract:
  The event reconstruction in high energy neutrino telescopes is based on the
expression of the time delay distribution of the detected photons propagating
to some distance from their emission point through a uniform and scattering
medium.
  Considering a realistic detector with a finite time resolution, we derive an
expression for the probability density function of the time delay of detected
photons. The asymptotic properties of this function as well as its
corresponding cumulative probability distribution are calculated and discussed.


title:
Parker-Jeans Instability of Gaseous Disks Including the Effect of Cosmic
  Rays

abstract:
  We use linear analysis to examine the effect of cosmic rays (CRs) on the
Parker-Jeans instability of magnetized self-gravitating gaseous disks. We adopt
a slab equilibrium model in which the gravity (including self-gravity) is
perpendicular to the mid-plane, the magnetic field lies along the slab. CR is
described as a fluid and only along magnetic field lines diffusion is
considered. The linearised equations are solved numerically. The system is
susceptible to Parker-Jeans instability. In general the system is less unstable
when the CR diffusion coefficient is smaller (i.e., the coupling between the
CRs and plasma is stronger). The system is also less unstable if CR pressure is
larger. This is a reminiscence of the fact that Jeans instability and Parker
instability are less unstable when the gas pressure is larger (or temperature
is higher). Moreover, for large CR diffusion coefficient (or small CR
pressure), perturbations parallel to the magnetic field are more unstable than
those perpendicular to it. The other governing factor on the growth rate of the
perturbations in different directions is the thickness of the disk or the
strength of the external pressure on the disk. In fact, this is the determining
factor in some parameter regimes.


title:
Spectral energy distribution of the metagalactic ionizing radiation
  field from QSO absorption spectra

abstract:
  A computational procedure is presented to estimate the spectral shape of the
ionizing background between 1 and 10 Ryd by analyzing optically thin absorption
systems in the spectra of high redshift quasars. The procedure is based on the
response surface methodology from the theory of experimental design. The shape
of the recovered UV background at z~3 shows a significant intensity decrease
between 3 and 4 Ryd compared to the metagalactic spectrum of Haardt & Madau
(1996). This decrease is interpreted as produced by HeII Gunn-Peterson effect.
There are no features indicating a contribution from galaxies to the UV
background which is therefore dominated by QSOs at z~3.


title: A Reverse-Shock Model for the Early Afterglow of GRB 050525A

abstract:
  The prompt localization of gamma-ray burst (GRB) 050525A by {\em Swift}
allowed the rapid follow-up of the afterglow. The observations revealed that
the optical afterglow had a major rebrightening starting at $\sim 0.01$ days
and ending at $\sim 0.03$ days, which was followed by an initial power-law
decay. Here we show that this early emission feature can be interpreted as the
reverse shock emission superposed by the forward shock emission in an
interstellar medium environment. By fitting the observed data, we further
constrain some parameters of the standard fireball-shock model: the initial
Lorentz factor of the ejecta $\gamma_0>120$, the magnetic energy fraction
$\epsilon_B>4\times10^{-6}$, and the medium density $n<2 {\rm cm^{-3}}$. These
limits are consistent with those from the other very-early optical afterglows
observed so far. In principle, a wind environment for GRB 050525A is
disfavored.


title:
The effect of wavefront corrugations on fringe motion in an astronomical
  interferometer with spatial filters

abstract:
  Numerical simulations of atmospheric turbulence and AO wavefront correction
are performed to investigate the timescale for fringe motion in optical
interferometers with spatial filters. These simulations focus especially on
partial AO correction, where only a finite number of Zernike modes are
compensated. The fringe motion is found to depend strongly on both the aperture
diameter and the level of AO correction used. In all of the simulations the
coherence timescale for interference fringes is found to decrease dramatically
when the Strehl ratio provided by the AO correction is <~30%. For AO systems
which give perfect compensation of a limited number of Zernike modes, the
aperture size which gives the optimum signal for fringe phase tracking is
calculated. For AO systems which provide noisy compensation of Zernike modes
(but are perfectly piston-neutral), the noise properties of the AO system
determine the coherence timescale of the fringes when the Strehl ratio is
<~30%.


title: Resonant absorption in dissipative flux tubes

abstract:
  We study the resonant absorption of MHD waves in magnetized flux tubes with a
radial density inhomogeneity. Within the approximation that resistive and
viscous processes are operative in thin layers surrounding the singularities of
the MHD equations, we give the full spectrum of the eigenfrequencies and
damping rates of the MHD quasi modes of the tube. Both surface and body modes
are analyzed. \keywords{Sun -- corona: magnetohydrodynamics (MHD) -- Sun:
magnetic fields -- Sun: oscillations


title:
Upper limits on gravitational waves emission in association with the Dec
  27 2004 giant flare of SGR1806-20

abstract:
  At the time when the giant flare of SGR1806-20 occurred, the AURIGA "bar" gw
detector was on the air with a noise performance close to stationary gaussian.
This allows to set relevant upper limits, at a number of frequencies in the
vicinities of 900 Hz, on the amplitude of the damped gw wave trains, which,
according to current models, could have been emitted, due to the excitation of
normal modes of the star associated with the peak in X-rays luminosity.


title:
Infrared Emission from Intracluster Dust Grains and Constraints on Dust
  Properties

abstract:
  For 117 clusters of galaxies, we explore the detectability of intracluster
dust grains by current and future infrared facilities, taking into account both
collisional heating and sputtering of grains by ambient plasma. If the dust
grains are injected into the intergalactic space with the amount and size
comparable to the Galactic values, the dust-to-gas ratio is typically $10^{-6}$
and the mean dust temperature is $\sim 30$ K near the cluster center. The
predicted infrared intensities lie marginally above the detection thresholds
for Spitzer Space Telescope, ASTRO-F, Herschel and SPICA missions. For some
nearby clusters such as Perseus, A3571, A2319, A3112 and A2204, good detections
of intracluster dust signal are expected in the 70 $\mu$m band. Given rather
tight constraints on the dust temperature from observed electron density and
temperature, the dust mass can be inferred directly from the infrared
observations. Further constraints on the size distribution will be obtained
once multi-band data are available. They will definitely provide a powerful
probe of the dust injection processes and dust-gas interactions in the
intergalactic space.


title: Theoretical HDO emission from low-mass protostellar envelopes

abstract:
  We present theoretical predictions of the rotational line emission of
deuterated water in low-mass protostar collapsing envelopes. The model accounts
for the density and temperature structure of the envelope, according the
inside-out collapse framework. The deuterated water abundance profile is
approximated by a step function, with a low value in the cold outer envelope
and a higher value in the inner envelope where the grain mantles evaporate. The
two abundances are the two main parameters of the modeling, along with the
temperature at which the mantles evaporate. We report line flux predictions for
a 30 and 5 L$_\odot$ source luminosity respectively. We show that ground based
observations are capable to constrain the three parameters of the model in the
case of bright low-mass protostars (L$>$10 L$_{\odot}$), and that no space
based observations, like for example HSO observations, are required in this
case. On the contrary, we show that the study of low-luminosity sources (L$<$10
L$_{\odot}$), assuming the same HDO abundance profile, requires too much
integration time to be carried out either with available ground-based
telescopes or with the HIFI instrument on board HSO. For these sources, only
the large interferometer ALMA will allow to constrain the HDO abundance.


title: Carbon Abundances in the Galactic Thin and Thick Disks

abstract:
  Although carbon is, together with oxygen and nitrogen, one of the most
important elements in the study of galactic chemical evolution its production
sites are still poorly known and have been much debated (see e.g. Gustafsson et
al. 1999; Chiappini et al. 2003). To trace the origin and evolution of carbon
we have determined carbon abundances from the forbidden [C I] line at 8727 A
and made comparisons to oxygen abundances from the forbidden [O I] line at 6300
A in a sample of 51 nearby F and G dwarf stars. These data and the fact that
the forbidden [C I] and [O I] lines are very robust abundance indicators (they
are essentially insensitive to deviations from LTE and uncertainties in the
stellar parameters, see, e.g., Gustafsson et al. 1999; Asplund et al. 2005)
enable us to very accurately measure the C/O ratio as well as individual C and
O abundances. Our first results indicate that the time-scale for the main
source that contribute to the carbon enrichment of the interstellar medium
operate on the same time-scale as those that contribute to the iron enrichment
(and can possibly be AGB stars...)


title: The chemistry of high-mass star formation

abstract:
  This paper reviews the chemistry of star-forming regions, with an emphasis on
the formation of high-mass stars. We first outline the basic molecular
processes in dense clouds, their implementation in chemical models, and
techniques to measure molecular abundances. Then, recent observational,
theoretical and laboratory developments are reviewed on the subjects of hot
molecular cores, cosmic-ray ionization, depletion and deuteration, and oxygen
chemistry. The paper concludes with a summary of outstanding problems and
future opportunities.


title: Jupiter's Obliquity and a Long-lived Circumplanetary Disk

abstract:
  It has been claimed (Canup and Ward 2002; Ward 2003) that a long-lived
massive (compared to the mass of the Galilean satellites) circumplanetary gas
disk is inconsistent with Jupiter's low obliquity. Such a constraint could be
downplayed on the basis that it deals with a single observation. Here we argue
that this argument is flawed because it assumes a solar system much like that
of the present day with the one exception of a circumjovian disk which is then
allowed to dissipate on a long timescale (10^6-10^7 yrs). Given that the
sequence of events in solar-system history that fit known constraints is
non-unique, we choose for the sake of clarity of exposition the orbital
architecture framework of Tsiganis et al. (2005), in which Jupiter and Saturn
were once in closer, less inclined orbits than they are at present, and show
that Jupiter's low obliquity is consistent with the SEMM (solids-enhanced
minimum mass) satellite formation model of Mosqueira and Estrada (2003a,b).


title:
Rotational Widths for Use in the Tully-Fisher Relation. I. Long-slit
  Spectroscopic Data

abstract:
  We present new long-slit Halpha spectroscopy for 403 non-interacting spiral
galaxies, obtained at the Palomar Observatory 5 m Hale telescope, which is used
to derive well-sampled optical rotation curves. Because many of the galaxies
show optical emission features which are significantly extended along the
spectrograph slit, a technique was devised to separate and subtract the night
sky lines from the galaxy emission. We exploit a functional fit to the rotation
curve to identify its center of symmetry; this method minimizes the asymmetry
in the final, folded rotation curve. We derive rotational widths using both
velocity histograms and the Polyex model fit. The final rotational width is
measured at a radius containing 83% of the total light as derived from I-band
images. In addition to presenting the new data, we use a large sample of 742
galaxies for which both optical long-slit and radio HI line spectroscopy are
available to investigate the relation between the HI content of the disks and
the extent of their rotation curves. Our results show that the correlation
between those quantities, which is well-established in the case of HI-poor
galaxies in clusters, is present also in HI-normal objects: for a given optical
size, star formation can be traced further out in the disks of galaxies with
larger HI mass.


title: The Near-UV Pulse Profile and Spectrum of the Pulsar PSR B0656+14

abstract:
  We have observed the middle-aged pulsar PSR B0656+14 with the prism and the
NUV MAMA detector of the Space Telescope Imaging Spectrograph (STIS) to measure
the pulsar spectrum and periodic pulsations in the near-ultraviolet (NUV). The
pulsations are clearly detected, double-peaked and very similar to the optical
pulse profile. The NUV pulsed fraction is 70 +/- 12%. The spectral slope of the
dereddened phase-integrated spectrum in the 1800 - 3200 A range is 0.35 +/- 0.5
which together with the high pulse fraction indicates a non-thermal origin for
the NUV emission. The total flux in the range 1700-3400 A is estimated to be
3.4 +/- 0.3e-15 erg/s/cm2 when corrected for E(B-V)=0.03. At a distance of 288
pc this corresponds to a luminosity 3.4e28 erg/s assuming isotropy of the
emission. We compare the NUV pulse profile with observations from radio to
gamma-rays. The first NUV sub-pulse is in phase with the gamma-ray pulse
marginally detected with the EGRET, while the second NUV sub-pulse is similar
both in shape and in phase with the non- thermal pulse in hard X-rays. This
indicates a single origin of the non-thermal emission in the optical-NUV and in
the X-rays. This is also supported by the observed NUV spectral slope, which is
compatible with a blackbody plus power-law fit extended from the X-ray range,
but dominated by the power-law component in most of the NUV range.


title:
Red-sequence galaxies with young stars and dust: The cluster Abell
  901/902 seen with COMBO-17

abstract:
  We report the discovery of a rich component of dusty star-forming galaxies
contaminating the red-sequence in the supercluster system comprising Abell
901a, 901b and A902 at redshift ~0.17. These galaxies do not fit into the
colour-density relation, because their preferred habitat is different from that
of regular red-sequence galaxies, which are typically dust-poor, old and
passively evolving. The dusty red galaxies prefer the medium-density outskirts
of clusters while being rare in both the low-density field and the high-density
cluster cores. This new result is based on the information content in the
medium-band photometry of the COMBO-17 survey. The photo-z accuracy of the ~800
brightest cluster galaxies is <0.01 and of the order of the velocity dispersion
of the cluster. This enables us to select a rich and clean cluster sample, in
which we can trace age-sensitive and dust-sensitive spectral features
independently with the detailed medium-band SED data. We find the red colour of
the dusty galaxies to be a result of dust extinction combined with relatively
old stellar ages. We speculate that the dusty red galaxies could either be a
product of minor mergers between established old red cluster galaxies with
infalling blue field galaxies, or mark a period in the internal transformation
of blue field galaxies into red cluster galaxies, which is triggered by the
environmental influences experienced during cluster infall.


title:
Stochastic Electron Acceleration During the NIR and X-ray Flares in
  Sagittarius A*

abstract:
  Recent near-IR (NIR) and X-ray observations of Sagittarius A*'s spectrum have
yielded several strong constraints on the transient energization mechanism,
justifying a re-examination of the stochastic acceleration model proposed
previously for these events. We here demonstrate that the new results are fully
consistent with the acceleration of electrons via the transit-time damping
process. But more importantly, these new NIR and X-ray flares now can constrain
the source size, the gas density, the magnetic field, and the wave energy
density in the turbulent plasma. Future simultaneous multi-wavelength
observations with good spectral information will, in addition, allow us to
study their temporal evolution, which will eventually lead to an accurate
determination of the behavior of the plasma just minutes prior to its
absorption by the black hole.


title:
Nearby stars from the LSPM-north Proper Motion Catalog. I. Main Sequence
  Dwarfs and Giants Within 33 Parsecs of the Sun

abstract:
  A list of 4,131 dwarfs, subgiants, and giants located, or suspected to be
located, within 33 parsecs of the Sun is presented. All the stars are drawn
from the new LSPM-north catalog of 61,976 stars with annual proper motions
larger than 0.15''/yr$. Trigonometric parallax measurements are found in the
literature for 1,676 of the stars in the sample; photometric and spectroscopic
distance moduli are found for another 783 objects. The remaining 1,672 objects
are reported here as nearby star candidates for the first time. Photometric
distance moduli are calculated for the new stars based on the (M_V,V-J)
relationship, calibrated with the subsample of stars which have trigonometric
parallaxes. The list of new candidates includes 539 stars which are suspected
to be within 25 parsecs of the Sun, including 63 stars estimated to be within
only 15 parsecs. The current completeness of the census of nearby stars in the
northern sky is discussed in light of the new candidates presented here. It is
estimated that 32% (18%) of nuclear burning stars within 33 parsecs (25
parsecs) of the Sun remain to be located. The missing systems are expected to
have proper motions below the 0.15''/yr limit of the LSPM catalog.


title: Unstable quasi g-modes in rotating main-sequence stars

abstract:
  This paper studies the oscillatory stability of uniformly rotating
main-sequence stars of mass 3-8 M_sun by solving the linearized non-adiabatic,
non-radial oscillation equations with a forcing term and searching for resonant
response to a complex forcing frequency. By using the traditional approximation
the solution of the forced oscillation equations becomes separable, whereby the
energy equation is made separable by approximation. It is found that the
kappa-mechanism in rotating B-stars can destabilize not only gravity- or
pressure modes, but also a branch of low frequency retrograde (in corotating
frame) oscillations in between the retrograde g-modes and toroidal r-modes.
These unstable quasi g-modes (or `q-modes') hardly exhibit rotational
confinement to the equatorial regions of the star, while the oscillations are
always prograde in the observer's frame, all in contrast to g-modes. The
unstable q-modes occur in a few narrow period bands (defined by their azimuthal
index m), and seem to fit the oscillation spectra observed in SPB stars rather
well. The unstable q-mode oscillation spectrum of a very rapidly rotating 8
M_sun star appears similar to that of the well studied Be-star mu Cen. The
unstable q-modes thus seem far better in explaining the observed oscillation
spectra in SPB-stars and Be-stars than normal g-modes.