title: Radio behavior of four southern non-thermal O-type stars

abstract:
  We have conducted high resolution continuum observations at 1.4 and 2.4 GHz
with the Australia Telescope Compact Array, towards the four southern Of stars:
CD-47 4551, HD 93129A, HD 124314,and HD 150136. All stars have been detected at
the two frequencies. HD 93129A - the only O2 I star catalogued so far, and in a
double system -, has also been observed at 17.8 and 24.5 GHz. Its radio
spectrum, complemented with previous observations at higher frequencies, is
analyzed here. The interpretation yields the estimate of its mass loss rate,
and a non-thermal spectral index of radiation coming from a putative colliding
wind region. The synchrotron and corresponding inverse Compton luminosities are
derived.


title:
Magnetospheric Birefringence Induces Unique Polarization Signatures in
  Neutron-Star Spectra

abstract:
  We study the propagation of polarization light through the magnetosphere of
neutron stars. At intermediate frequencies (the optical through the infrared),
both the birefringence induced by the plasma and by quantumelectrodynamics
influence the observation polarization of radiation from the surface of the
neutron star. Because these two processes compete in this regime, we find that
polarization observations can constrain the properties of the neutron-star
magnetosphere, specifically the total charge density. We calculate both the
phase-resolved and the phase-averaged polarization signatures induced by
magnetospheric birefringence.


title: Orbital solutions to the HD160691 (mu Arae) Doppler signal

abstract:
  We perform a dynamical analysis of the recently updated set of the radial
velocity (RV) measurements of the HD160691 (mu Arae). The kinematic,
2-Keplerian model of the measurements leads to the best-fit solution in which
the eccentricity of the outer planet is about 0.7 and its semi-major axis is
about 4AU. The parameters of the inner planet are well determined. The
eccentricity is about 0.3 and the semi-major axis is about 1.65AU. The best
2-Keplerian model leads to a catastrophically unstable configuration, self
disrupting in less than 20,000yr. To derive dynamically stable configurations
which are simultaneously consistent with the RV data, we use the so called GAMP
(Genetic Algorithm with MEGNO Penalty). Using this method, we derive meaningful
limits on the parameters of the outer planet which provide a stable behavior of
the system. The best-fit solutions are located in a shallow valley of Chi^2, in
the (a_c,e_c)-plane, extending over 2AU (for the formal 1sigma confidence
interval of the best fit). We find two equally good best-fit solutions leading
to the qualitatively different orbital configurations. One of them corresponds
to the center of the 5:1 mean motion resonance (MMR) and the second one
describes a configuration between the 6:1 and 17:2MMRs. The mu Arae system can
be found in the zone confined to other low-order MMRs of the type p:1 with p>5.
Our results support the classification of the mu Arae as a hierarchical
planetary system, dynamically similar to other known multi-planet systems
around HD12661 and HD169830. The results of the GAMP on the extended data set
are fully consistent with our previous conclusions concerning a much shorter
observational window.


title: Type I Migration in a Non-Isothermal Protoplanetary Disk

abstract:
  We calculate rates of Type I migration of protoplanets in a non-isothermal
three-dimensional protoplanetary disk, building upon planet-disk models
developed in previous work. We find that including the vertical thickness of
the disk results in a decrease in the Type I migration rate by a factor of ~2
from a two-dimensional disk. The vertical temperature variation has only a
modest effect on migration rates since the torques at the midplane are weighted
heavily both because the density and the perturbing potential are maximized at
the midplane. However, temperature perturbations resulting from shadowing and
illumination at the disk's surface can decrease the migration rate by up to
another factor of 2 for planets at the gap-opening threshold at distances where
viscous heating is minimal. This would help to resolve the timescale mismatch
between the standard core-accretion scenario for planet formation and the
survival of planets, and could help explain some of the rich diversity of
planetary systems already observed.


title: A review of rapid X-ray variability in X-ray binaries

abstract:
  A comprehensive review of aperiodic rapid X-ray variability (QPO and noise)
in X-ray binaries with neutron stars and black holes.


title:
A new measurement of the altitude dependence of the atmospheric muon
  intensity

abstract:
  We present a new measurement of atmospheric muons made during an ascent of
the High Energy Antimatter Telescope balloon experiment. The muon charge ratio
mu+/mu- as a function of atmospheric depth in the momentum interval 0.3-0.9
GeV/c is presented. The differential mu- intensities in the 0.3-50 GeV/c range
and for atmospheric depths between 4-960 g/cm^2 are also presented. We compare
these results with other measurements and model predictions. We find that our
charge ratio is ~1.1 for all atmospheric depths and is consistent, within
errors, with other measurements and the model predictions. We find that our
measured mu- intensities are also consistent with other measurements, and with
the model predictions, except at shallow atmospheric depths.


title:
Formation of GEMS from shock-accelerated crystalline dust in
  superbubbles

abstract:
  Interplanetary dust particles (IDPs) contain enigmatic sub-micron components
called GEMS (Glass with Embedded Metal and Sulfides). The compositions and
structures of GEMS indicate that they have been processed by exposure to ion-
izing radiation but details of the actual irradiation environment(s) have
remained elusive. Here we propose a mechanism and astrophysical site for GEMS
formation that explains for the first time the following key properties of
GEMS; they are stoichiometrically enriched in oxygen and systematically deple-
ted in S, Mg, Ca and Fe (relative to solar abundances), most have normal
(solar) oxygen isotopic compositions, they exhibit a strikingly narrow size
distribution (0.1-0.5 $\mu$m diameter), and some of them contain ``relict''
crystals within their glass matrices. We show that these properties are incon-
sistent with amorphization by particles accelerated by diffusive shock accel-
eration. Instead, we propose that GEMS are formed from crystalline grains that
condense in outflows from massive stars in OB associations, are accelerated in
encounters with frequent supernova shocks inside the associated superbubble,
and are implanted with atoms from the hot gas in the SB interior. We thus rev-
erse the usual roles of target and projectile. Rather than being bombarded at
rest by energetic ions, grains are accelerated and bombarded by a nearly mono-
velocity beam of atoms as viewed in their rest frame. Meyer, Drury and Ellison
have proposed that galactic cosmic rays originate from ions sputtered from such
accelerated dust grains. We suggest that GEMS are surviving members of a pop-
ulation of fast grains that constitute the long-sought source material for gal-
actic cosmic rays. Thus, representatives of the GCR source material may have
been awaiting discovery in cosmic dust labs for the last thirty years.


title: CLASS B2108+213: A new wide separation gravitational lens system

abstract:
  We present observations of CLASS B2108+213, the widest separation
gravitational lens system discovered by the Cosmic Lens All-Sky Survey. Radio
imaging using the VLA at 8.46 GHz and MERLIN at 5 GHz shows two compact
components separated by 4.56 arcsec with a faint third component in between
which we believe is emission from a lensing galaxy. 5-GHz VLBA observations
reveal milliarcsecond-scale structure in the two lensed images that is
consistent with gravitational lensing. Optical emission from the two lensed
images and two lensing galaxies within the Einstein radius is detected in
Hubble Space Telescope imaging. Furthermore, an optical gravitational arc,
associated with the strongest lensed component, has been detected. Surrounding
the system are a number of faint galaxies which may help explain the wide image
separation. A plausible mass distribution model for CLASS B2108+213 is also
presented.


title:
Ozone Abundance in a Nitrogen-Carbon Dioxide Dominated Terrestrial
  Paleoatmosphere

abstract:
  We compute the ozone distribution for a model terrestrial paleoatmosphere in
which the present oxygen abundance is largely replaced by carbon dioxide, which
we argue is a reasonable working assumption. In principle, the presence of
carbon dioxide might supplement the ozone shield as compared with models based
on nitrogen without high carbon dioxide abundance so that early life need not
have been as UV-resistant as often assumed. An extrasolar planet with a
high-CO2 atmosphere might contain enough O3 to be a source of false positive
biomarkers. We find that the globally averaged O3 column density can be the
same, or nearly four times higher (depending upon the O2 partial pressure) when
CO2 is used in place of N2 as the replacement component for lowered O2 in a
1-atm terrestrial planet with solar radiation. The effect is important for
making quantitative deductions from future data, but does not invalidate the
use of O3 as a biomarker for free oxygen. These results make prospects for
detection of extrasolar planetary O3 absorption somewhat better than before.

categories: astro-ph physics.ao-ph physics.geo-ph physics.space-ph


title: Inclination Effects and Beaming in Black Hole X-ray Binaries

abstract:
  We investigate the dependence of observational properties of black hole X-ray
binaries on the inclination angle i of their orbits. We find the following: (1)
Transient black hole binaries show no trend in their quiescent X-ray
luminosities as a function of i, suggesting that the radiation is not
significantly beamed. This is consistent with emission from an accretion disk.
If the X-rays are from a jet, then the Lorentz factor gamma of the jet is less
than 1.24 at the 90% confidence level. (2) The X-ray binary 4U1543-47 with i of
order 21 degrees has a surprisingly strong fluorescent iron line in the high
soft state. Quantifying an earlier argument by Park et al. (2004), we conclude
that if the continuum X-ray emission in this source is from a jet, then gamma <
1.04. (3) None of the known binaries has cos i < 0.25 or i > 75 degrees. This
fact, plus the lack of eclipses among the 20 black hole binaries in our sample,
strongly suggests at the 99.5% confidence level that systems with large
inclination angles are hidden from view. The obscuration could be the result of
disk flaring, as suggested by Milgrom (1978) for neutron star X-ray binaries.
(4) Transient black hole binaries with i ~ 70-75 degrees have significantly
more complex X-ray light curves than systems with i < 65 degrees. This may be
the result of variable obscuration and/or variable height above the disk of the
radiating gas.


title: Note on the generalized Hansen and Laplace coefficients

abstract:
  Recently, Breiter et al (2004) reported the computation of Hansen
coefficients $X_k^{\gamma,m}$ for non integer values of $\gamma$. In fact, the
Hansen coefficients are closely related to the Laplace $b_{s}^{(m)}$, and
generalized Laplace coefficients $b_{s,r}^{(m)}$ (Laskar and Robutel, 1995)
that do not require $s,r$ to be integers. In particular, the coefficients
$X_0^{\g,m}$ have very simple expressions in terms of the usual Laplace
coefficients $b_{\g+2}^{(m)}$, and all their properties derive easily from the
known properties of the Laplace coefficients.


title:
Extended Neutral Gas Around z ~ 0.5 Galaxies: Properties of Damped Lya
  Absorbing Galaxies

abstract:
  I review current results from searching for galaxies giving rise to damped
Lya absorbers (DLAs) at z<1. Using 14 confirmed DLA galaxies, I further show
that intermediate-redshift galaxies possess large HI envelope out to 24-30
h^{-1} kpc radius. The photometric and spectral properties of these galaxies
confirm that DLA galaxies are drawn from the typical field population, and not
from a separate population of low surface brightness or dwarf galaxies.
Comparisons of the ISM abundances of the DLA galaxies and the metallicities of
the absorbers at large galactic radii suggest that some DLAs originate in the
relatively unevolved outskirts of galactic disks.


title:
Cosmic Ray Energy Spectra and Mass Composition at the Knee - Recent
  Results from KASCADE -

abstract:
  Recent results from the KASCADE experiment on measurements of cosmic rays in
the energy range of the knee are presented. Emphasis is placed on energy
spectra of individual mass groups as obtained from an two-dimensional unfolding
applied to the reconstructed electron and truncated muon numbers of each
individual EAS. The data show a knee-like structure in the energy spectra of
light primaries (p, He, C) and an increasing dominance of heavy ones (A > 20)
towards higher energies. This basic result is robust against uncertainties of
the applied interaction models QGSJET and SIBYLL which are used in the shower
simulations to analyse the data. Slight differences observed between
experimental data and EAS simulations provide important clues for further
improvements of the interaction models. The data are complemented by new limits
on global anisotropies in the arrival directions of CRs and by upper limits on
point sources. Astrophysical implications for discriminating models of maximum
acceleration energy vs galactic diffusion/drift models of the knee are
discussed based on this data.


title:
A Deep Search with HST for Late Time Supernova Signatures in the Hosts
  of XRF 011030 and XRF 020427

abstract:
  X-ray Flashes (XRFs) are, like Gamma-Ray Bursts (GRBs), thought to signal the
collapse of massive stars in distant galaxies. Many models posit that the
isotropic equivalent energies of XRFs are lower than those for GRBs, such that
they are visible from a reduced range of distances when compared with GRBs.
Here we present the results of two epoch Hubble Space Telescope imaging of two
XRFs. These images taken approximately 45 and 200 days post burst reveal no
evidence for an associated supernova in either case. Supernovae such as SN
1998bw would have been visible out to z ~1.5 in each case, while fainter
supernovae such as SN 2002ap would have been visible to z ~ 1. If the XRFs lie
at such large distances, their energies would not fit the observed correlation
between the GRB peak energy and isotropic energy release, in which soft bursts
are less energetic. We conclude that, should these XRFs reside at low redshifts
($z<0.6$), either their line of sight is heavily extinguished, or they are
associated with extremely faint supernovae, or, unlike GRBs, these XRFs do not
have temporally coincident supernovae.


title: The importance of 15O(a,g)19Ne to X-ray bursts and superbursts

abstract:
  One of the two breakout reactions from the hot CNOcycle is 15O(a,g)19Ne,
which at low temperatures depends strongly on the resonance strength of the
4.033 MeV state in 19Ne. An experimental upper limit has been placed on its
strength, but the lower limit on the resonance strength and thereby the
astrophysical reaction rate is unconstrained experimentally. However, this
breakout reaction is crucial to the thermonuclear runaway which causes type I
X-ray bursts on accreting neutron stars. In this paper we exploit astronomical
observations in an attempt to constrain the relevant nuclear physics and deduce
a lower limit on the reaction rate. Our sensitivity study implies that if the
rate were sufficiently small, accreting material would burn stably without
bursts. The existence of type I X-ray bursts and superbursts consequently
suggests a lower limit on the 15O(a,g)19Ne reaction rate at low temperatures.


title:
Observational Evidence for Small-Scale Mixture of Weak and Strong Fields
  in the Quiet Sun

abstract:
  Three different maps of the quiet Sun, observed with the Advanced Stokes
Polarimeter (ASP) and the Diffraction-Limited Stokes Polarimeter (DLSP), show
evidence of strong ($\simeq$1700 G) and weak ($<$500 G) fields coexisting
within the resolution element both at network and internetwork locations. The
angular resolution of the observations is of 1\arcsec (ASP) and 0.\arcsec6
(DLSP), respectively. Even at the higher DLSP resolution, a significant
fraction of the network magnetic patches harbor a mixture of strong and weak
fields. Internetwork elements that exhibit kG fields when analyzed with a
single-component atmosphere are also shown to harbor considerable amounts of
weak fields. Only those patches for which a single-component analysis yields
weak fields do not show this mixture of field strengths. Finally, there is a
larger fractional area of weak fields in the convective upflows than in the
downflows.


title:
Polarimetric Calibration of Large-Aperture Telescopes II: The
  sub-aperture method

abstract:
  A new method for absolute polarimetric calibration of large telescopes is
presented. The proposed method is highly accurate and is based on the
calibration of a small sub-aperture, which is then extended to the full system
by means of actual observations of an astronomical source. The calibration
procedure is described in detail along with numerical simulations that explore
its robustness and accuracy. The advantages and disadvantages of this technique
with respect to other possible alternatives are discussed.


title:
Polarimetric Calibration of Large-Aperture Telescopes I: The
  Beam-Expansion Method

abstract:
  This paper describes a concept for the high-accuracy absolute calibration of
the instrumental polarization introduced by the primary mirror of a
large-aperture telescope. This procedure requires a small aperture with
polarization calibration optics (e.g., mounted on the dome) followed by a lens
that opens the beam to illuminate the entire surface of the mirror. The Jones
matrix corresponding to this calibration setup (with a diverging incident beam)
is related to that of the normal observing setup (with a collimated incident
beam) by an approximate correction term. Numerical models of parabolic on-axis
and off-axis mirrors with surface imperfections are used to explore its
accuracy.


title:
Feature Extraction Techniques for the Analysis of Spectral Polarization
  Profiles

abstract:
  This paper introduces a novel feature extraction technique for the analysis
of spectral line Stokes profiles. The procedure is based on the use of an
auto-associative artificial neural network containing non-linear hidden layers.
The neural network extracts a small subset of parameters from the profiles
(features), from which it is then able to reconstruct the original profile.
This new approach is compared to two other procedures that have been proposed
in previous works, namely principal component analysis and Hermitian function
expansions. Depending on the target application, each one of these three
techniques has some advantages and disadvantages, which are discussed here.


title:
Physical Properties of Spicules from Simultaneous Spectro-Polarimetric
  Observations of He I and Ca II Lines

abstract:
  We present full Stokes observations from SPINOR in the \ion{Ca}{2} infrared
triplet and the \ion{He}{1} multiplet at 1083 nm from which some properties of
spicules have been derived. There are important advantages in multi-line
observations, particularly from different elements. We find that the
orientation of the plane of polarization is very different for the Ca and He
lines, which provides the first direct model-independent evidence for magnetic
fields in spicules. Our data shows that the Ca and He lines have almost
identical widths. Since the Ca atom is 10 times heavier than He, we are able to
conclude that most of the broadening is non-thermal ($\simeq$16 km s$^{-1}$)
and to set an upper limit of 13 kK to the spicular temperatures. The bisectors
of the lines span a velocity range of over 15 km s$^{-1}$ for the He line and
30 km s$^{-1}$ for the Ca ones. The vertical gradient of line-of-sight
velocities is also very different for both elements. We obtain 2.8 km s$^{-1}$
Mm$^{-1}$ from He versus 6.4 km s$^{-1}$ Mm$^{-1}$ from Ca. These properties,
and others from similar observations, should be taken into account in future
physical models of spicules.


title:
Strategies for Spectral Profile Inversion using Artificial Neural
  Networks

abstract:
  This paper explores three different strategies for the inversion of spectral
lines (and their Stokes profiles) using artificial neural networks. It is shown
that a straightforward approach in which the network is trained with synthetic
spectra from a simplified model leads to considerable errors in the inversion
of real observations. This problem can be overcome in at least two different
ways that are studied here in detail. The first method makes use of an
additional pre-processing auto-associative neural network to project the
observed profile into the theoretical model subspace. The second method
considers a suitable regularization of the neural network used for the
inversion. These new techniques are shown to be robust and reliable when
applied to the inversion of both synthetic and observed data, with errors
typically below $\sim$100 G.


title: Shocks in the Quiet Solar Photosphere: A Rather Common Occurrence

abstract:
  We present observations of the quiet solar photosphere in the \ion{Fe}{1}
lines at 6302 \AA where at least four different spatial locations exhibit
upwards-directed supersonic flows. These upflows can only be detected in the
circular polarization profiles as a double-peaked structure in the blue lobe of
both \ion{Fe}{1} lines. We have detected cases of either magnetic polarity in
the data. The polarization signals associated with the upflows are very weak,
which is probably why they had not been seen before in this type of
observations. We propose that the observed flows are the signature of aborted
convective collapse, similar to the case reported by \citeN{BRRHC+01}. Our data
indicates that this phenomenon occurs frequently in the quiet Sun, which means
that many magnetic elements (although the fraction is still unknown) are
destroyed even before they are formed completely. The spectral signatures of
supersonic upflows reported here are probably present in most
spectro-polarimetric observations of sufficient signal-to-noise and spatial
resolution.


title: Why the Model of a Hydrogen-Filled Sun Is Obsolete

abstract:
  Isotope analyses on meteorites, planets, lunar samples, the solar wind, and
solar flares show that heterogeneous debris of a supernova (SN) that exploded
here 5 Gy ago formed the solar system. The Sun formed on the collapsed SN core.
Iron meteorites and the iron cores of the terrestrial planets formed out of
iron-rich material surrounding the SN core. Giant gaseous planets formed out of
the light-weight elements in the outer SN layers. Mass separation enriches
light elements like H and He at the solar surface, but the bulk Sun consists
almost entirely of the same seven, even-numbered elements that comprise 99% of
ordinary meteorites - iron (Fe), oxygen (O), nickel (Ni), silicon (Si),
magnesium (Mg), sulfur (S) and calcium (Ca).


title: Ion acceleration processes at reforming collisionless shocks

abstract:
  The identification of pre-acceleration mechanisms for cosmic ray ions in
supernova remnant shocks is an important problem in astrophysics. Recent
particle-in-cell (PIC) shock simulations have shown that inclusion of the full
electron kinetics yields non-time-stationary solutions, in contrast to previous
hybrid (kinetic ions, fluid electrons) simulations. Here, by running a PIC code
at high phase space resolution, ion acceleration mechanisms associated with the
time dependence of a supercritical collisionless perpendicular shock are
examined. In particular the components of $\int \mathbf{F} \cdot \mathbf{v} dt$
are analysed along trajectories for ions that reach both high and low energies.
Selection mechanisms for the ions that reach high energies are also examined.
In contrast to quasi-stationary shock solutions, the suprathermal protons are
selected from the background population on the basis of the time at which they
arrive at the shock, and thus are generated in bursts.


title: Magnetic fields in Herbig Ae stars

abstract:
  Herbig Ae stars are young A-type stars in the pre-main sequence evolutionary
phase with masses of ~1.5-3 M_o. They show rather intense surface activity
(Dunkin et al. 1997) and infrared excess related to the presence of
circumstellar disks. Because of their youth, primordial magnetic fields
inherited from the parent molecular cloud may be expected, but no direct
evidence for the presence of magnetic fields on their surface, except in one
case (Donati et al. 1997), has been found until now. Here we report
observations of optical circular polarization with FORS 1 at the VLT in the
three Herbig Ae stars HD 139614, HD 144432 and HD 144668. A definite
longitudinal magnetic field at 4.8 sigma level, <B_z>=-450+-93 G, has been
detected in the Herbig Ae star HD 139614. This is the largest magnetic field
ever diagnosed for a Herbig Ae star. A hint of a weak magnetic field is found
in the other two Herbig Ae stars, HD 144432 and HD 144668, for which magnetic
fields are measured at the ~1.6 sigma and ~2.5 sigma level respectively.
Further, we report the presence of circular polarization signatures in the Ca
II K line in the V Stokes spectra of HD 139614 and HD 144432, which appear
unresolved at the low spectral resolution achievable with FORS 1. We suggest
that models involving accretion of matter from the disk to the star along a
global stellar magnetic field of a specific geometry can account for the
observed Zeeman signatures.


title:
High Resolution Observations of the Near-Infrared Emission from NGC 6822
  Hubble V

abstract:
  We observed Hubble V, the brightest HII region complex in the dwarf irregular
galaxy NGC 6822, at near-infrared (1.8--2.4 um) wavelengths using the Cooled
Grating Spectrometer 4 (CGS4) at the United Kingdom Infra-Red Telescope
(UKIRT). The line emission maps of Hubble V show the typical structure of a
photo-dissociation region (PDR) where an ionized core, traced by compact He I
emission (2.0587 um) and Br_gamma emission (2.1661 um), is surrounded by an
outer layer traced by molecular hydrogen (H_2) emission. The measured line
ratios of H_2 2-1 S(1) (2.2477 um) / 1-0 S(1) (2.1218 um) from 0.2 to 0.6 and
the un-shifted and un-resolved line profiles suggest that the H_2 emission
originates purely from a PDR. By comparing the H_2 results with a PDR model, we
conclude that Hubble V includes dense (10^{4.5} cm^{-3}) and warm PDRs. In this
environment, most of the H_2 molecules are excited by far-UV photons (with a
field strength of 10^{2-4} times that of the average interstellar field),
although collisional processes de-excite H_2 and contribute significantly to
the excitation of the first vibrational level. We expect that Hubble V is in
the early stage of molecular cloud dissolution.


title: A Simplified Model of the Formation of Structures in Dark Matter

abstract:
  The collapse of a rotating 3-axis ellipsoid is approximated by a system of
ordinary differential equations. Violent relaxation, mass and angular momentum
losses are taken into account phenomenologically. The formation of the
equilibrium configuration and different types of instability are investigated.


title: Remarks on astrophysical origin of the knee in cosmic ray spectrum

abstract:
  All astrophysical explanations of the knee in cosmic ray spectrum accept the
hypothesis of its existence {\it a priori} without any doubt. But, there exist
experimental evidences against this hypothesis. Experimental data on the knee
in various secondary cosmic ray components obtained by KASCADE array as well as
by many other arrays reveal the existence of the knee
($\Delta\gamma\approx0.4\div0.5$) in electromagnetic component (e and $\gamma$
including Cherenkov light) and the absence of it or a very small knee
($\Delta\gamma\approx0.1\div0.2$) in muonic and hadronic components. But, one
could expect the inverse relationship in case of the astrophysical knee origin.
A brief review of experimental data concerning this problem is given.


title: The Dependence of Differential Rotation on Temperature and Rotation

abstract:
  We use Doppler imaging techniques to determine the dependence of starspot
rotation rates on latitude in an homogeneous sample of young, rapidly-rotating
solar analogues. A solar-like differential rotation law is used, where the
rotation depends on sin$^2$($\theta$), where $\theta$ is the stellar latitude.
By including this term in the image reconstruction process, using starspots as
tracers, we are able to determine the magnitude of the shear over more than one
rotation cycle. We also consider results from matched filter starspot tracking
techniques, where individual starspot rotation rates are determined. In
addition we have re-analysed published results and present a new measurement
for the K3 dwarf, Speedy Mic.
  A total of 10 stars of spectral type G2 - M2 are considered. We find a trend
towards decreasing surface differential rotation with decreasing effective
temperature. The implied approach to solid body rotation with increasing
relative convection zone depth implies that the dynamo mechanism operating in
low-mass stars may be substantially different from that in the Sun.


title: Motivation and Initial Results from SPINOR in the Near Infrared

abstract:
  SPINOR is a new spectro-polarimeter that will serve as a facility instrument
for the Dunn Solar Telescope at the National Solar Observatory. This instrument
is capable of achromatic operation over a very broad range of wavelengths, from
$\sim$400 up to 1600 nm, allowing for the simultaneous observation of several
visible and infrared spectral regions with full Stokes polarimetry. Another key
feature of the design is its flexibility to observe virtually any combination
of spectral lines, limited only by practical considerations (e.g., the number
of detectors available, space on the optical bench, etc). SPINOR is scheduled
for commissioning by the end of 2005. In this paper we report on the current
status of the project and present actual observations of active regions in the
Ca II infrared triplet and the He I multiplet at 1083 nm.


title:
The OH (1720 MHz) Supernova Remnant Masers in W28: MERLIN and VLBA
  Polarization Observations

abstract:
  Full-polarization MERLIN and VLBA observations of the 1720 MHz maser emission
from the OH molecule in the supernova remnant W28 are presented. Zeeman
splitting (|B| \approx 0.75 mG) has been directly resolved between right- and
left-circularly polarized spectra for the first time. Linear-polarization
position angles and circular-polarization Zeeman splitting observed in the
maser emission permit interpretation of a comprehensive picture of the magnetic
field at the supernova/molecular cloud interface marked by the masers. We find
the post-SNR-shock magnetic field to be well-ordered over the ~1 pc covered by
the maser region (compared with the approximately 30-pc diameter of the entire
SNR) and well-aligned with the shock front that is traced by synchrotron
radiation and molecular emission. Based on MERLIN data having a resolution of
200 mas and VLBA data with a resolution of 15 mas, the masers are measured to
have deconvolved angular sizes of 90 to 350 mas (225 to 875 AU) with compact
cores 20 mas (50 AU) in size, consistent with theoretical expectation and
previous observations.


title:
Simulation of Coherent Synchrotron Radiation Emission from Rotating
  Relativistic Electron Layers

abstract:
  The electromagnetic radiation of a rotating relativistic electron layers is
studied numerically using particle-in-cell simulation. The results of the
simulation confirm all relevant scaling properties predicted by theoretical
models. These models may turn out to be important for the understanding of the
coherent synchrotron radiation (CSR) instability that may occur in systems as
diverse as particle accelerators radio pulsars.


title:
Contrasting the chemical evolution of the Milky Way and Andromeda
  galaxies

abstract:
  The chemical evolution history of a galaxy hides clues about how it formed
and has been changing through time. We have studied the chemical evolution
history of the Milky Way (MW) and Andromeda (M31) to find which are common
features in the chemical evolution of disc galaxies as well as which are
galaxy-dependent. We use a semi-analytic multi-zone chemical evolution model.
Such models have succeeded in explaining the mean trends of the observed
chemical properties in these two Local Group spiral galaxies with similar mass
and morphology. Our results suggest that while the evolution of the MW and M31
shares general similarities, differences in the formation history are required
to explain the observations in detail. In particular, we found that the
observed higher metallicity in the M31 halo can be explained by either a) a
higher halo star formation efficiency or b) a larger reservoir of infalling
halo gas with a longer halo formation phase. These two different pictures would
lead to a) a higher [O/Fe] at low metallicities or b) younger stellar
populations in the M31 halo, respectively. Both pictures result in a more
massive stellar halo in M31, which suggests a possible correlation between the
halo metallicity and its stellar mass.


title: On the origin of fluorine in the Milky Way

abstract:
  The main astrophysical factories of fluorine (19F) are thought to be Type II
supernovae, Wolf-Rayet stars, and the asymptotic giant branch (AGB) of
intermediate mass stars. We present a model for the chemical evolution of
fluorine in the Milky Way using a semi-analytic multi-zone chemical evolution
model. For the first time, we demonstrate quantitatively the impact of fluorine
nucleosynthesis in Wolf-Rayet and AGB stars. The inclusion of these latter two
fluorine production sites provides a possible solution to the long-standing
discrepancy between model predictions and the fluorine abundances observed in
Milky Way giants. Finally, fluorine is discussed as a possible probe of the
role of supernovae and intermediate mass stars in the chemical evolution
history of the globular cluster omega Centauri.


title:
Probing non-Gaussian features in the HI distribution at the epoch of
  reionization

abstract:
  The HI distribution at the epoch of reionization (EOR) is largely determined
by the sizes and distribution of the ionized regions. In the scenario where the
ionized regions have comoving sizes of the order of a few Mpc, the large scale
statistical properties of the HI distribution are dominated by the Poisson
noise of the discrete ionized regions, and it is highly non-Gaussian. We
investigate the possibility of probing reionization by studying these
non-Gaussian features using future radio interferometric observations of
redshifted 21 cm HI radiation. We develop a formalism relating correlations
between the visibilities measured at three different baselines and frequencies
to the bispectrum of HI fluctuations. For visibilities at the same frequency,
this signal is found to be of the same order as the two visibility correlation
which probes the HI power spectrum. For visibilities at different frequencies,
we find that the correlations decay within a frequency difference of ~1 MHz.
This implies that it is, in principle, straightforward to extract this HI
signal from various contaminants which are believed to have a continuum spectra
and are expected to be correlated even at large frequency separations.


title:
Molecular Evolution in Collapsing Prestellar Cores III: Contraction of A
  Bonnor-Ebert Sphere

abstract:
  The gravitational collapse of a spherical cloud core is investigated by
numerical calculations. The initial conditions of the core lie close to the
critical Bonnor-Ebert sphere with a central density of \sim 10^4 cm^{-3} in one
model (alpha=1.1), while gravity overwhelms pressure in the other (alpha=4.0),
where alpha is the internal gravity-to-pressure ratio. The alpha=1.1 model
shows reasonable agreement with the observed velocity field in prestellar
cores. Molecular distributions in cores are calculated by solving a chemical
reaction network that includes both gas-phase and grain-surface reactions. When
the central density of the core reaches 10^5 cm^{-3}, carbon-bearing species
are significantly depleted in the central region of the alpha=1.1 model, while
the depletion is only marginal in the other model. The two different approaches
encompass the observed variations of molecular distributions in different
prestellar cores, suggesting that molecular distributions can be probes of
contraction or accumulation time scales of cores. The central enhancement of
the NH3/N2H+ ratio, which is observed in some prestellar cores, can be
reproduced under certain conditions by adopting recently measured branching
fractions for N2H+ recombination. Various molecular species, such as CH3OH and
CO2, are produced by grain-surface reactions. The ice composition depends
sensitively on the assumed temperature. Multi-deuterated species are included
in our most recent gas-grain chemical network. The deuterated isotopomers of
H3+ are useful as probes of the central regions of evolved cores, in which
gas-phase species with heavy elements are strongly depleted. At 10 K, our model
can reproduce the observed abundance ratio of ND3/NH3, but underestimates the
isotopic ratios of deuterated to normal methanol.


title: Mass and angular momentum loss during RLOF in Algols

abstract:
  We present a set of evolutionary computations for binaries with a B-type
primary at birth. Some liberal computations including loss of mass and angular
momentum during binary evolution are added to an extensive grid of conservative
calculations. Our computations are compared statistically to the observed
distributions of orbital periods and mass ratios of Algols. Conservative Roche
Lobe Over Flow (RLOF) reproduces the observed distribution of orbital periods
decently but fails to explain the observed mass ratios in the range 0.4-1. In
order to obtain a better fit the binaries have to lose a significant amount of
matter, without transferring too much angular momentum.


title:
Local models of stellar convection II: Rotation dependence of the mixing
  length relations

abstract:
  We study the mixing length concept in comparison to three-dimensional
numerical calculations of convection with rotation. In a limited range, the
velocity and temperature fluctuations are linearly proportional to the
superadiabaticity, as predicted by the mixing length concept and in accordance
with published results. The effects of rotation are investigated by varying the
Coriolis number, Co = 2 Omega tau, from zero to roughly ten, and by calculating
models at different latitudes. We find that \alpha decreases monotonically as a
function of the Coriolis number. This can be explained by the decreased spatial
scale of convection and the diminished efficiency of the convective energy
transport, the latter of which leads to a large increase of the
superadibaticity, \delta = \nabla - \nabla_ad as function of Co. Applying a
decreased mixing length parameter in a solar model yields very small
differences in comparison to the standard model within the convection zone. The
main difference is the reduction of the overshooting depth, and thus the depth
of the convection zone, when a non-local version of the mixing length concept
is used. Reduction of \alpha by a factor of roughly 2.5 is sufficient to
reconcile the difference between the model and helioseismic results. The
numerical results indicate reduction of \alpha by this order of magnitude.


title:
Enhanced mass transfer during dwarf nova outbursts by irradiation of the
  secondary?

abstract:
  One of the remaining issues in the problems of dwarf novae is whether or not
enhanced mass transfer due to irradiation of the secondary stars could occur
during outbursts. In a previous paper (Osaki and Meyer 2003), we presented a
theoretical analysis that shows no appreciable enhancement of the mass outflow
rate. This conclusion is challenged by Smak (2004) who claims that equations
used in our analysis were incorrect and that in systems with short orbital
periods substantial enhancement could occur. In this letter, we examine the
origin of such divergent conclusions. We show that Smak's solutions are
unacceptable from the standpoint of the equation of continuity and that our
analysis is an appropriate one to treat this problem.


title: Local models of stellar convection III: The Strouhal number

abstract:
  Aims: The Strouhal number (St), which is a nondimensional measure of the
correlation time, is determined from numerical models of convection. The
Strouhal number arises in the mean-field theories of angular momentum transport
and magnetic field generation, where its value determines the validity of
certain widely used approximations, such as the first order smoothing
(hereafter FOSA). More specifically, the relevant transport coefficients can be
calculated by means of a cumulative series expansion if St < St_crit \approx 1.
Methods: We define the Strouhal number as the ratio of the correlation and
turnover times, which we determine separately, the former from the
autocorrelation of velocity, and the latter by following test particles
embedded in the flow. Results: We find that the Strouhal numbers are,
generally, of the order of 0.1 to 0.4 which is close to the critical value
above which deviations from FOSA become significant. Increasing the rotational
influence tends to shorten both timescales in such a manner that St decreases.
However, we do not find a clear trend as function of the Rayleigh number for
the parameter range explored in the present study.


title: Estimates of the Strouhal number from numerical models of convection

abstract:
  We determine the Strouhal number (hereafter St), which is essentially a
nondimensional measure of the correlation time, from numerical calculations of
convection. We use two independent methods to estimate St. Firstly, we apply
the minimal tau-approximation (MTA) on the equation of the time derivative of
the Reynolds stress. A relaxation time is obtained from which St can be
estimated by normalising with a typical turnover time. Secondly, we calculate
the correlation and turnover times separately, the former from the
autocorrelation of velocity and the latter by following test particles embedded
in the flow. We find that the Strouhal number is in general of the order of 0.1
to 1, i.e. rather large in comparison to the typical assumption in the
mean-field theories that St << 1. However, there is a clear decreasing trend as
function of the Rayleigh number and increasing rotation. Furthermore, for the
present range of parameters the decrease of St does not show signs of
saturation, indicating that in stellar convection zones, where the Rayleigh
numbers are much larger, the Strouhal number may indeed be significantly
smaller.


title: FUSE observations of the HeII Lyman alpha forest towards HS1700+6416

abstract:
  We present FUSE observations of the HeII Lyman alpha forest in the redshift
range 2.3 < z < 2.7 towards HS1700+6416. Between October 2002 and February
2003, the brightness of the QSO increased by a factor 2. Therefore, with an
exposure time of 203 ks during orbital night, the quality of the resulting
spectrum is comparable to the HE2347-4342 data. This second line of sight with
a resolved HeII Lyman alpha forest reveals a similar variation of several
orders of magnitude of the column density ratio eta = N(HeII)/N(HI) and
confirms the results of previous studies. The well-known metal line spectrum of
HS1700+6416 permits to examine the influence of metal line absorption on the
HeII column densities.


title: The Obscured X-ray Background and Evolution of AGN

abstract:
  The X-ray Background has been resolved in the 0.5-5keV band and found to
consist mostly of both unabsorbed and absorbed AGN with column densities <1e23.
This contrasts with the local AGN population where the column density range
extends to Compton-thick objects and beyond (>1e24). Stacking analysis of the
integrated emission of sources detected by XMM-Newton in the Lockman Hole, and
by Chandra in the CDF-N and S reveals that the resolved fraction of the X-ray
Background drops above 6keV and is about 50% above 8keV. The missing flux has
the spectrum of highly absorbed AGN, making it likely that the range of column
density at redshift one is similar to that locally, and that many AGN are as
yet undetected in well-studied fields.


title: Broadband Observations of the Transient X-ray Pulsar SAX J2103.5+4545

abstract:
  We investigated the optical, X-ray, and gamma-ray variability of the pulsar
SAX J2103.5+4545. Our timing and spectral analyses of the X-ray and gamma-ray
emissions from the source using RXTE and INTEGRAL data show that the shape of
its spectrum in the energy range 3 -- 100 keV is virtually independent of its
intensity and the orbital phase. Based on XMM-Newton data, we accurately (5
arcsec) localized the object and determined the optical counterpart in the
binary. We placed upper limits on the variability of the latter in the R band
and the H-alpha line on time scales of the orbital and pulse periods,
respectively.


title:
Constraints on Dark Matter interactions from structure formation:
  Damping lengths

abstract:
  (Shortened) Weakly Interacting Massive Particles are often said to be the
best Dark Matter candidates. Studies have shown however that rather large Dark
Matter-photon or Dark Matter-baryon interactions could be allowed by cosmology.
Here we address the question of the role of the Dark Matter interactions in
more detail to determine at which extent Dark Matter has to be necessarily
weakly interacting. To this purpose, we compute the collisional damping (and
free-streaming) lengths of generic interacting Dark Matter candidates and
compare them to the scale of the smallest primordial structures known to exist
in the Universe. We obtain necessary conditions that any candidate must
satisfy. We point out the existence of new Dark Matter scenarios and exhibit
new damping regimes. For example, an interacting candidate may bear a similar
damping than that of collisionless Warm Dark Matter particles. The main
difference is due to the Dark Matter coupling to interacting (or even
freely-propagating) species. Our approach yields a general classification of
Dark Matter candidates which extends the definitions of the usual Cold, Warm
and Hot Dark Matter scenarios when interactions, weak or strong, are
considered.


title:
Relationship between X-ray and ultraviolet emission of flares from dMe
  stars observed by XMM-Newton

abstract:
  We present simultaneous ultraviolet and X-ray observations of the dMe-type
flaring stars AT Mic, AU Mic, EV Lac, UV Cet and YZ CMi obtained with the
XMM-Newton observatory. During 40 hours of simultaneous observation we identify
13 flares which occurred in both wave bands. For the first time, a correlation
between X-ray and ultraviolet flux for stellar flares has been observed. We
find power-law relationships between these two wavelength bands for the flare
luminosity increase, as well as for flare energies, with power-law exponents
between 1 and 2. We also observe a correlation between the ultraviolet flare
energy and the X-ray luminosity increase, which is in agreement with the
Neupert effect and demonstrates that chromospheric evaporation is taking place.


title: The Effect of Type Ibc Contamination in Cosmological Supernova Samples

abstract:
  We explore the effect of contamination of intermediate redshift Type Ia
supernova samples by Type Ibc supernovae. Simulating observed samples of Ia and
mixed Ibc/Ia populations at a range of redshifts for an underlying cosmological
concordance model (\Omega_{m}=0.27, \Omega_{\Lambda}=0.73), we find that even
small contamination levels, 2-5% may bias the derived \Omega_{\Lambda} and
\Omega_{m} towards larger values. We thus emphasize the need for clean samples
of Type Ia SNe for accurate measurements of the cosmological parameters. We
also simulate a SN sample similar to the fiducial SNAP detected distribution
(Kim et al. 2004), but include Ibc contamination. For this distribution we
illustrate the effect of Ibc contamination on the distance modulus vs. redshift
diagram for low and high precision measurements.


title: The Supernova Legacy Survey

abstract:
  Type Ia supernovae (SNe Ia) currently provide the most direct evidence for an
accelerating Universe and for the existence of an unknown "dark energy" driving
this expansion. The 5-year Supernova Legacy Survey (SNLS;
http://cfht.hawaii.edu/SNLS/) will deliver ~1000 SN Ia detections with
well-sampled g'r'i'z' light curves. Using this definitive dataset, we will
obtain a precise measurement of the cosmological parameters (Omega_m,
Omega_lambda); our goal is to determine the cosmological equation of state
parameter "w" to a statistical precision of +/-0.07, testing theories for the
origin of the universal acceleration. In this proceeding, we summarise the
progress made during the first full year of the survey operation.


title: SNLS: Overview and High-z Spectroscopy

abstract:
  The Supernova Legacy Survey (SNLS; http://cfht.hawaii.edu/SNLS) will discover
and obtain g'r'i'z' lightcurves for more than 700 spectroscopically confirmed
SNe Ia (0.3<z<0.9) to differentiate between competing models for Dark Energy.
We fit the multicolor lightcurves of the candidates to determine which are
likely SNe Ia and send them for follow-up spectroscopy to the Keck, VLT, and
Gemini telescopes. Here we show the results from Gemini, where we send most of
our highest redshift (0.6<z<0.9) targets.


title: LO Peg in 1998: Starspot patterns and differential rotation

abstract:
  We present Doppler images of the young K5V - K7V rapid rotator LO Peg from
seven nights of continuous spectroscopy obtained in 1998 from July 04 to July
10. The images reveal the presence of a strong polar cap with appendages
extending to mid-latitudes, but no starspots are seen below 15\degr. We briefly
discuss the distribution of spots in light of recent flux transport simulations
which are able to reproduce the observed latitude dependence.
  With the full timeseries of spectra, of which 314 are useful, many phases are
observed three times over the seven nights of observations. Using starspots as
tracers of a solar-like latitudinal differential rotation in our image
reconstructions, we find that the equatorial regions complete one more rotation
than the polar regions every {181 $\pm$ 35} d. LO Peg is the second coolest
star for which such a measurement has been made using indirect imaging methods.
The degree of latitudinal shear is less than that seen in G and early K dwarfs,
suggesting a trend in which differential rotation decreases with stellar mass
in (pre-)main sequence objects.


title: Which Globular Clusters contain Intermediate-mass Black Holes?

abstract:
  It has been assumed that intermediate-mass black holes (IMBHs) in globular
clusters can only reside in the most centrally concentrated clusters, with a
so-called `core-collapsed' density profile. While this would be a natural
guess, it is in fact wrong. We have followed the evolution of star clusters
containing IMBHs with masses between 125 \le M_{BH} \le 1000 M_{\odot} through
detailed N-body simulations, and we find that a cluster with an IMBH, in
projection, appears to have a relatively large `core' with surface brightness
only slightly rising toward the center. This makes it highly unlikely that any
of `core-collapsed' clusters will harbor an IMBH. On the contrary, the places
to look for an IMBH are those clusters that can be fitted well by
medium-concentration King models.
  The velocity dispersion of the visible stars in a globular cluster with an
IMBH is nearly constant well inside the apparent core radius. For a cluster of
mass M_C containing an IMBH of mass M_{BH}, the influence of the IMBH becomes
significant only at a fraction 2.5 M_{BH}/M_C of the half-mass radius, deep
within the core, where it will affect only a small number of stars. In
conclusion, observational detection of an IMBH may be possible, but will be
challenging.


title:
Probing the Surfaces of Interstellar Dust Grains: The Adsorption of CO
  at Bare Grain Surfaces

abstract:
  A solid-state feature was detected at around 2175 cm-1 towards 30 embedded
young stellar objects in spectra obtained using the ESO VLT-ISAAC. We present
results from laboratory studies of CO adsorbed at the surface of Zeolite
wafers, where absorption bands were detected at 2177 and 2168 cm-1
(corresponding to CO chemisorbed at the Zeolite surface), and 2130 cm-1
(corresponding to CO physisorbed at the Zeolite surface), providing an
excellent match to the observational data. We propose that the main carrier of
the 2175-band is CO chemisorbed at bare surfaces of dust grains in the
interstellar medium. This result provides the first direct evidence that
gas-surface interactions do not have to result in the formation of ice mantles
on interstellar dust. The strength of the 2175-band is estimated to be ~ 4 x
10-19 cm molecule-1. The abundance of CO adsorbed at bare grain surfaces ranges
from 0.06 to 0.16 relative to H2O ice, which is, at most, half of the abundance
(relative to H2O ice) of CO residing in H2O-dominated ice environments. These
findings imply that interstellar grains have a large (catalytically-active)
surface area, providing a refuge for interstellar species. Consequently the
potential exists for heterogeneous chemistry to occur involving CO molecules in
unique surface chemistry pathways not currently considered in gas-grain models
of the interstellar medium.


title: Astronomical Site Ranking Based on Tropospheric Wind Statistics

abstract:
  We present comprehensive and reliable statistics of high altitude wind speeds
and the tropospheric flows at the location of five important astronomical
observatories. Statistical analysis exclusively of high altitude winds point to
La Palma as the most suitable site for adaptive optics, with a mean value of
22.13 m/s at the 200 mbar pressure level. La Silla is at the bottom of the
ranking, with the largest average value 200 mbar wind speed(33.35 m/s). We have
found a clear annual periodicity of high altitude winds for the five sites in
study. We have also explored the connection of high to low altitude atmospheric
winds as a first approach of the linear relationship between the average
velocity of the turbulence and high altitude winds (Sarazin & Tokovinin 2001).
We may conclude that high and low altitude winds show good linear relationships
at the five selected sites. The highest correlation coefficients correspond to
Paranal and San Pedro Martir, while La Palma and La Silla show similar high to
low altitude wind connection. Mauna Kea shows the smallest degree of
correlation, which suggests a weaker linear relationship. Our results support
the idea of high altitude winds as a parameter for rank astronomical sites in
terms of their suitability for adaptive optics, although we have no evidence
for adopting the same linear coefficient at different sites. The final value of
this linear coefficient at a particular site could drastically change the
interpretation of high altitude wind speeds as a direct parameter for site
characterization.


title:
Magnetospheric Radio Emission from Extrasolar Giant Planets: The Role of
  the Host Stars

abstract:
  We present a new analysis of the expected magnetospheric radio emission from
extrasolar giant planets for a distance limited sample of the nearest known
extrasolar planets. Using recent results on the correlation between stellar
X-ray flux and mass-loss rates from nearby stars, we estimate the expected
mass-loss rates of the host stars of extrasolar planets that lie within 20pc of
the Earth. We find that some of the host stars have mass-loss rates that are
more than 100 times that of the Sun, and given the expected dependence of the
planetary magnetospheric radio flux on stellar wind properties this has a very
substantial effect. Using these results and extrapolations of the likely
magnetic properties of the extrasolar planets we infer their likely radio
properties.
  We compile a list of the most promising radio targets, and conclude that the
planets orbiting Tau Bootes, Gliese 86, Upsilon Andromeda and HD1237 (as well
as HD179949) are the most promising candidates, with expected flux levels that
should be detectable in the near future with upcoming telescope arrays. The
expected emission peak from these candidate radio emitting planets is typically
\~40-50 MHz. We also discuss a range of observational considerations for
detecting extrasolar giant planets.


title:
Near-arcsecond resolution observations of the hot corino of the solar
  type protostar IRAS 16293-2422

abstract:
  Complex organic molecules have previously been discovered in solar type
protostars, raising the questions of where and how they form in the envelope.
Possible formation mechanisms include grain mantle evaporation, interaction of
the outflow with its surroundings or the impact of UV/X-rays inside the
cavities. In this Letter we present the first interferometric observations of
two complex molecules, CH3CN and HCOOCH3, towards the solar type protostar
IRAS16293-2422. The images show that the emission originates from two compact
regions centered on the two components of the binary system. We discuss how
these results favor the grain mantle evaporation scenario and we investigate
the implications of these observations for the chemical composition and
physical and dynamical state of the two components.


title: Abundances and Depletions of Interstellar Oxygen

abstract:
  We report on the abundance of interstellar neutral oxygen (OI) for 26
sightlines, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE),
the International Spectroscopic Explorer (IUE), and the Hubble Space Telescope
(HST). OI column densities are derived by measuring the equivalent widths of
several ultraviolet absorption lines, and subsequently fitting those to a curve
of growth. We consider both our general sample of 26 sightlines and a more
restrictive sample of 10 sightlines that utilize HST data for a measurement of
the weak 1355 angstrom line of oxygen, and are thus better constrained due to
our sampling of all three sections of the curve of growth. The column densities
of our HST sample show ratios of O/H that agree with the current best solar
value if dust is considered, with the possible exception of one sightline (HD
37903). We note some very limited evidence in the HST sample for trends of
increasing depletion with respect to the ratio of total to selective extinction
and the molecular fraction of hydrogen, but the trends are not conclusive.
Unlike a recent result from Cartledge et al. (2004), we do not see evidence for
increasing depletion with respect to the average volume density of hydrogen,
but our HST sample contains only two points more dense than the critical
density determined in that paper. The column densities of our more general
sample show some scatter in O/H, but most agree with the solar value to within
errors. We discuss these results in the context of establishing the best method
for determining interstellar abundances, the unresolved question of the best
value for O/H in the interstellar medium (ISM), the O/H ratios observed in
Galactic stars, and the depletion of gas-phase oxygen onto dust grains.


title: Color bimodality: Implications for galaxy evolution

abstract:
  We use a sample of 69726 galaxies from the SDSS to study the variation of the
bimodal color-magnitude (CM) distribution with environment. Dividing the galaxy
population by environment (Sigma_5) and luminosity (-23<M_r<-17), the u-r color
functions are modeled using double-Gaussian functions. This enables a
deconvolution of the CM distributions into two populations: red and blue
sequences. The changes with increasing environmental density can be separated
into two effects: a large increase in the fraction of galaxies in the red
distribution, and a small color shift in the CM relations of each distribution.
The average color shifts are 0.05+-0.01 and 0.11+-0.02 for the red and blue
distributions, respectively, over a factor of 100 in projected neighbor
density. The red fraction varies between about 0% and 70% for low-luminosity
galaxies and between about 50% and 90% for high-luminosity galaxies. This
difference is also shown by the variation of the luminosity functions with
environment. We demonstrate that the effects of environment and luminosity can
be unified. A combined quantity, Sigma_mod = Sigma_5/Mpc^{-2} + L_r/L_{-20.2},
predicts the fraction of red galaxies, which may be related to the probability
of transformation events. Our results are consistent with major interactions
(mergers and/or harassment) causing galaxies to transform from the blue to the
red distribution. We discuss this and other implications for galaxy evolution
from earlier results and model the effect of slow transformations on the color
functions.


title:
Spherical Infall in G10.6-0.4: Accretion Through an Ultracompact HII
  Region

abstract:
  We present high resolution (0.''12 x 0.''079) observations of the
ultracompact HII region G10.6-0.4 in 23 GHz radio continuum and the NH3(3,3)
line. Our data show that the infall in the molecular material is largely
spherical, and does not flatten into a molecular disk at radii as small as 0.03
pc. The spherical infall in the molecular gas matches in location and velocity
the infall seen in the ionized gas. We use a non-detection to place a stringent
upper limit on the mass of an expanding molecular shell associated with
pressure driven expansion of the HII region. These data support a scenario in
which the molecular accretion flow passes through an ionization front and
becomes an ionized accretion flow onto one or more main sequence stars, not the
classical pressure-driven expansion scenario. In the continuum emission we see
evidence for externally ionized clumps of molecular gas, and cavities evacuated
by an outflow from the central source.


title:
Extragalactic source contributions to arcminute-scale Cosmic Microwave
  Background anisotropies

abstract:
  The possible contributions of the various classes of extragalactic sources
(including, in addition to the canonical radio sources, GHz Peaked Spectrum
sources, advection-dominated sources, starburst galaxies, high-redshift
proto-spheroidal galaxies) to the arcminute scale fluctuations measured by the
CBI, BIMA, and ACBAR experiments are discussed. At 30 GHz, fluctuations due to
radio sources undetected by ancillary low-frequency surveys may be higher than
estimated by the CBI and BIMA groups. High-redshift dusty galaxies, whose
fluctuations may be strongly enhanced by the effect of clustering, could
contribute to the BIMA excess signal, and dominate at 150 GHz (the ACBAR
frequency). Moreover, in the present data situation, the dust emission of these
high-redshift sources set an unavoidable limit to the detection of primordial
CMB anisotropies at high multipoles, even at frequencies as low as $\simeq 30$
GHz. It is concluded that the possibility that the excess power at high
multipoles is dominated by unsubtracted extragalactic sources cannot be ruled
out. On the other hand, there is room for a contribution from the
Sunyaev-Zeldovich effect within clusters of galaxies, with a density
fluctuation amplitude parameter $\sigma_8$ consistent with the values preferred
by current data.


title:
XMM-Newton observations of UW CrB -- detection of X-ray bursts and
  evidence for accretion disc evolution

abstract:
  UW CrB (MS1603+2600) is a peculiar short period X-ray binary that exhibits
extraordinary optical behaviour. The optical light curve shape of the system
changes drastically from night to night, without any changes in overall
brightness. Here we report X-ray observations of UW CrB obtained with {\it
XMM-Newton}. We find evidence for several X-ray bursts confirming a neutron
star primary. This considerably strengthens the case that UW CrB is an
Accretion Disc Corona (ADC) system located at a distance of at least 5--7 kpc,
  (3--5 kpc above the galactic plane). The X-ray and optical monitor
(UV+optical) light curves show remarkable shape variation from one observing
run to another, which we suggest are due to large scale variations in the
accretion disc shape resulting from a warp which periodically obscures the
optical and soft X-ray emission. This is also supported by the changes in
phase-resolved X-ray spectra.


title: A Biography of the Magnetic Field of a Neutron Star

abstract:
  After some post-natal cooling, a spinning, magnetized, canonical neutron-star
(NS) has a core of superconducting protons, superfluid neutrons, and degenerate
extreme relativistic electrons, all surrounded by a thin highly conducting
solid crust. The quantum fluids are threaded by a dense array of quantized
vortex-lines which can interact strongly with a denser and much less uniform
one of quantizedmagnetic flux-tubes. The physics of such a core predicts the
evolution of a NS'ssurface magnetic field and related phenomena as the star's
spin changes. Predictions include changes in NS magnetic dipole moments,
anomolously small polar caps in millesecond pulsars, properties of two
different families of spin-period "glitches", and spin-down ages much greater
than true ages for some pulsars. Quantitative model-based estimates for all of
these are given. None are in conflict with observations.


title:
Absorption-Line Spectroscopy of Planetary Nebulae with FUSE: Probing the
  Molecular, Atomic, and Ionized Gas

abstract:
  The central stars of planetary nebulae (PNe) are natural targets for FUSE due
to their UV brightness. The FUSE spectra of many PNe show absorption features
due to circumstellar material in species ranging from H_2 and neutrals in the
photodissociation region (PDR) to ions resident in the H II region. We report
results from a program designed to search for nebular components in the H_2
Lyman and Werner resonance lines that are responsible for the fluorescent
excitation of H_2 in strong FUV radiation fields. Our failure to detect H_2 in
absorption in several PNe with strong near-infrared H_2 emission indicates that
the molecular material has an asymmetrical or clumpy distribution. We also
detect enrichments in the s-process product Ge, find that Fe is not depleted
into dust along at least one line of sight through a PN, and show that
starlight fluorescence can affect the populations of the excited fine-structure
levels of O I.


title: Type Ia Supernovae and Cosmology

abstract:
  I discuss the use of Type Ia supernovae (SNe Ia) for cosmological distance
determinations. Low-redshift SNe Ia (z < 0.1) demonstrate that the Hubble
expansion is linear with H_0 = 72 +/- 8 km/s/Mpc, and that the properties of
dust in other galaxies are generally similar to those of dust in the Milky Way.
The measured luminosity distances of SNe Ia as a function of redshift have
shown that the expansion of the Universe is currently accelerating, probably
due to the presence of repulsive dark energy such as Einstein's cosmological
constant (Lambda). From about 200 SNe Ia, we find that Omega_Lambda - 1.4
Omega_M = 0.35 +/- 0.14. Combining our data with other results, we find a best
fit for Omega_M and Omega_Lambda of 0.28 and 0.72, respectively. A number of
possible systematic effects (dust, supernova evolution) thus far do not seem to
eliminate the need for Omega_Lambda > 0. Recently, analyses of SNe Ia at z =
1.0-1.7 provide further support for current acceleration, and give tentative
evidence for an early epoch of deceleration. The dynamical age of the Universe
is estimated to be 13.1 +/- 1.5 Gyr. According to the most recent data sets,
the SN Ia rate at z > 1 is several times greater than that at low redshifts,
presumably because of higher star formation rates long ago. Moreover, the
typical delay time from progenitor star formation to SNIa explosion appears to
be substantial, ~3 Gyr. Current projects include the measurement of a few
hundred SNe Ia at z = 0.2-0.8 to more accurately determine the
equation-of-state parameter of the dark energy, w = P/(\rho c^2), whose value
is now constrained by SNe Ia to be in the range -1.48 < w < -0.72 at 95%
confidence.


title:
The tidal disruption rate in dense galactic cusps containing a
  supermassive binary black hole

abstract:
  We consider the problem of tidal disruption of stars in the centre of a
galaxy containing a supermassive binary black hole with unequal masses. We
assume that over the separation distance between the black holes the
gravitational potential is dominated by the more massive black hole. Also, we
assume that the number density of stars is concentric with the primary black
hole and has a power law cusp.We show that the bulk of stars with a small
angular-momentum component normal to the black hole binary orbit can reach a
small value of total angular momentum through secular evolution in the
gravitational field of the binary, and hence they can be tidally disrupted.
This effect is analogous to the so-called Kozai effect (Kozai, 1962, Lidov,
1961,1962) well known in celestial mechanics. We develop an analytical theory
of secular evolution of the stellar orbits and calculate the rate of tidal
disruption. We confront our analytical theory with a simple numerical model and
find very good agreement.
  Our results show that for primary black-hole mass \sim
10^{6}-10^{7}M_{\odot}, the black- hole mass ratio q > 10^{-2}, cusp size \sim
1pc, the tidal disruption rate can be as large as \sim 10^{-2}-1M_{\odot}/yr.
This is at least 10^{2}-10^{4} times larger than estimated for the case of a
single supermassive black hole. The duration of the phase of enhanced tidal
disruption is determined by the dynamical friction time scale, and it is rather
short: \sim 10^{5}yr. The dependence of the tidal disruption rate on the mass
ratio, as well as on the size of the cusp, is also discussed.


title:
The Closest View of a Dwarf Galaxy: New Evidence on the Nature of the
  Canis Major over-density

abstract:
  We present a first deep colour-magnitude diagram of the putative central
region (0.5 deg x 0.5 deg) of the Canis Major stellar over-density
(l,b)=(240,-8) found by Martin et al. (2004), which has been proposed as the
remnant of a dwarf satellite accreted onto the Milky Way on a near-equatorial
orbit. We find a narrow (in apparent magnitude) main-sequence, extending 6
magnitudes below the turn-off to our limiting magnitude of B ~ 24.5 mag. This
main sequence has very high constrast (>3) with respect to the thin/thick
disk/halo background; its narrowness at brighter magnitudes clearly implies the
presence of a distinct and possibly still bound stellar system. We derived the
line-of-sight size (r_{1/2}) of this system based on the B-band width of the
lower main sequence, obtaining 0.94 +/- 0.18 (random) +/- 0.18 (systematic)
kpc. That size matches a model prediction for the main body of the parent
galaxy of the Monoceros tidal stream. The high density contrast and limited
spatial extent in the radial direction are very hard to reconcile with the
alternative explanation put forward to explain the Canis Major
stellar-overdensity: a flared or warped Galactic disk viewed in projection
(Momamy et al. 2004). We also derived a central surface brightness of mu_{V,0}=
23.3 +/- 0.1 mag arcsec^{-2} and an absolute magnitude of M_{V}=-14.5 +/- 0.1
mag. These values place the Canis Major object in the category of dwarf galaxy
in the the L_{V}--size and M_V - mu_{V} planes for such objects. However, like
the Sagittarius dwarf, it is an outlier in the[Fe/H] -M_V plane in the sense
that it is too metal rich for its estimated absolute magnitude. This suggests
that the main mechanism driving its recent and current star formation history
(possibly tidal stripping) is different to that of isolated dwarfs.


title: Towards a Precision Cosmology from Starburst Galaxies at z>2

abstract:
  This work investigates the use of a well-known empirical correlation between
the velocity dispersion, metallicity, and luminosity in H beta of nearby HII
galaxies to measure the distances to HII-like starburst galaxies at high
redshifts. This correlation is applied to a sample of 15 starburst galaxies
with redshifts between z=2.17 and z=3.39 to constrain Omega_m, using data
available from the literature. A best-fit value of Omega_m = 0.21 +0.30 -0.12
in a Lambda-dominated universe and of Omega_m = 0.11 +0.37 -0.19 in an open
universe is obtained. A detailed analysis of systematic errors, their causes,
and their effects on the values derived for the distance moduli and Omega_m is
carried out. A discussion of how future work will improve constraints on
Omega_m by reducing the errors is also presented.


title: Stability of Homogeneous Extra Dimensions

abstract:
  In order not to be in conflict with observations it is crucial that extra
dimensions, if they exist, are stable. It is shown that in the context of
homogeneous extra dimensions, this can easily be achieved during both (4D)
radiation and vacuum energy dominated eras of the cosmological evolution.
During matter domination, however, there is no such possibility even for a very
general class of stabilization mechanisms. Even if extra dimensions could be
stabilized during matter domination, it is argued that they are generically
time-varying during any transition period, such as the one from radiation to
matter domination.


title: The Lens Redshift and Group Environment for HE 0435-1223

abstract:
  The redshift of the galaxy lensing HE 0435-1223 is 0.4546 +/- 0.0002, based
on observations obtained with the Low Dispersion Survey Spectrograph 2 (LDSS2)
on the Magellan Consortium's 6.5 m Clay telescope. HST/ACS observations of the
system also reveal a spiral-rich group of 10 galaxies within 40" of the
elliptical lensing galaxy. The redshifts for two of these galaxies were
measured to be in the foreground (at z=0.419) with respect to the lens, thus at
least some of the nearby galaxies are not part of the same physical group as
the lensing galaxy. Mass models of the system (assuming same-plane deflectors)
that take the local group environment into account do better at explaining the
observed emission-line flux ratios (which are presumably unaffected by
microlensing) than single halo models, but the match is still not perfect. In
particular, component A (a minimum of the light travel time) is observed to be
0.20 mag brighter than predicted and component C (also a minimum image) is
observed to be 0.16 mag fainter than predicted. Mass models for the system
predict an A-D time delay of either 15.8 or 17.6 days (Ho = 72 km/s/Mpc)
depending on the details of the local galaxy environment.


title: Gamma-ray constraints on the infrared background excess

abstract:
  Motivated by the idea that the recently detected near-infrared (1.2-4 micron)
excess over the contribution of known galaxies is due to redshifted light from
the first cosmic stars (Salvaterra & Ferrara 2003), we have used the effect
caused by photon-photon absorption on gamma-ray spectra of blazars to put
constraints on extragalactic background light (EBL) from the optical to the
far-IR bands. Our analysis is mainly based on the blazar H 1426+428, for which
we assume a power-law unabsorbed spectrum. We find that an EBL model with no
excess over known galaxies in the near-infrared background (NIRB) is in
agreement with all the considered blazars; however, it implies a very peculiar
intrinsic spectrum for H 1426+428. Additional data on the blazars 1ES1101-232,
H 2356-309 and PKS 2155-304 exclude the existence of a strong NIRB excess
consistent with Kelsall's model of zodiacal light subtraction (ZL); the
COBE/DIRBE measurements, after Wright's model ZL subtraction, represent a firm
NIRB upper limit. The constraints on the optical EBL are weaker, due to the
fact that predictions from different optical EBL models are often comparable to
the experimental errors. In the mid-infrared the SPITZER measurement at 24
micron gives a good fit for all the considered blazars.


title:
The X-ray Afterglow of Dark GRB 970815: A Common Origin for GRBs and
  XRFs?

abstract:
  GRB 970815 was a well-localized gamma-ray burst (GRB) detected by the All-Sky
Monitor (ASM) on the Rossi X-Ray Timing Explorer (RXTE) for which no afterglow
was identified despite follow-up ASCA and ROSAT pointings and optical imaging
to limiting magnitude R>23. While an X-ray source, AX/RX J1606.8+8130, was
detected just outside the ASM error box, it was never associated with the GRB
because it was not clearly fading and because no optical afterglow was ever
found. We recently obtained an upper limit for this source with Chandra that is
at least factor of 100 fainter than the ASCA detection. We also made deep
optical observations of the AX/RX J1606.8+8130 position, which is blank to
limits V>25.2 and I>24.0. In view of these extreme limits we conclude that
AX/RX J1606.8+8130 was indeed the afterglow of GRB 970815, which corresponds to
an optically "dark" GRB. AX/RX J1606.8+8130 can therefore be ruled out as the
counterpart of the persistent EGRET source 3EG J1621+8203. The early light
curves from BATSE and the RXTE ASM show spectral softening between multiple
peaks of prompt emission. We propose that GRB 970815 might be a case in which
the properties of an X-ray flash (XRF) and a "normal" GRB coincide in a single
event.


title:
Diffractive Interaction and Scaling Violation in pp->pi^0 Interaction
  and GeV Excess in Galactic Diffuse Gamma-Ray Spectrum of EGRET

abstract:
  We present here a new calculation of the gamma-ray spectrum from pp->pi^0 in
the Galactic ridge environment. The calculation includes the diffractive pp
interaction and incorporates the Feynman scaling violation for the first time.
Galactic diffuse gamma-rays come, predominantly, from pi^0->gamma gamma in the
sub-GeV to multi-GeV range. Hunter et al. found, however, an excess in the GeV
range ("GeV Excess") in the EGRET Galactic diffuse spectrum above the
prediction based on experimental pp->pi^0 cross-sections and the Feynman
scaling hypothesis. We show, in this work, that the diffractive process makes
the gamma-ray spectrum harder than the incident proton spectrum by ~0.05 in
power-law index, and, that the scaling violation produces 30-80% more pi^0 than
the scaling model for incident proton energies above 100GeV. Combination of the
two can explain about a half of the "GeV Excess" with the local cosmic proton
(power-law index ~2.7). The excess can be fully explained if the proton
spectral index in the Galactic ridge is a little harder (~0.2 in power-law
index) than the local spectrum. Given also in the paper is that the diffractive
process enhances e^+ over e^- and the scaling violation gives 50-100% higher
p-bar yield than without the violation, both in the multi-GeV range.


title:
Joint modeling of the probability distribution and power spectrum of the
  Lya forest: comparison with observations at z=3

abstract:
  We presents results of joint modeling of the probability distribution
function (PDF) and the one-dimensional power spectrum (PS) of the Lya forest
flux decrement. The sensitivity of these statistical measures to the shape and
amplitude of the linear matter power spectrum is investigated using two
variants of the LCDM cosmology. In the first model, the linear power spectrum
has a scale-invariant spectral index, whereas in the second, it has a negative
running index (RSI). We generate mock catalogs of QSO spectra, and compare
their statistical properties to those of the observations at z=3. We perform a
joint fit of the power spectrum and PDF. A scale-invariant model with
\sigma_8=0.9 matches well the data if the mean IGM temperature is T\leq 15000K.
For higher temperature, it tends to overestimate the flux power spectrum over
scales k < 0.01s/km. The discrepancy is less severe when the PS alone is
fitted. However, models matching the PS alone do not yield a good fit to the
PDF. A joint analysis of the flux PS and PDF tightens the constraints on the
model parameters and reduces systematic biases. The RSI model is consistent
with the observed PS and PDF only if the temperature is T\geq 20000K. The best
fit models reproduce the slope and normalisation of the column density
distribution, irrespective of the shape and amplitude of the linear power
spectrum. They are also consistent with the observed line-width distribution
given the large uncertainties. Our joint analysis suggests that \sigma_8 is
likely to be in the range 0.7 - 0.9 for a temperature 10000K<T<20000K and a
reasonable reionization history.


title: HDO abundance in the envelope of the solar-type protostar IRAS16293-2422

abstract:
  We present IRAM 30m and JCMT observations of HDO lines towards the solar-type
protostar IRAS 16293-2422. Five HDO transitions have been detected on-source,
and two were unfruitfully searched for towards a bright spot of the outflow of
IRAS 16293-2422. We interpret the data by means of the Ceccarelli, Hollenbach
and Tielens (1996) model, and derive the HDO abundance in the warm inner and
cold outer parts of the envelope. The emission is well explained by a jump
model, with an inner abundance of 1e-7 and an outer abundance lower than 1e-9
(3 sigma). This result is in favor of HDO enhancement due to ice evaporation
from the grains in theinner envelope. The deuteration ratio HDO/H2O is found to
be f_in=3% and f_out < 0.2% (3 sigma) in the inner and outer envelope
respectively and therefore, the fractionation also undergoes a jump in the
inner part of the envelope. These results are consistent with the formation of
water in the gas phase during the cold prestellar core phase and storage of the
molecules on the grains, but do not explain why observations of H2O ices
consistently derive a H2O ice abundance of several 1e-5 to 1e-4, some two
orders of magnitude larger than the gas phase abundance of water in the hot
core around IRAS 16293-2422.


title:
Sloan Digital Sky Survey Quasars in the SWIRE ELAIS N1 Field: Properties
  and Spectral Energy Distributions

abstract:
  We present a mid-infrared analysis of 35 quasars with spectroscopic redshifts
selected from the Spitzer Wide-area InfraRed Extragalactic Survey (SWIRE). We
discuss their optical and mid-infrared (MIR) colors, and show that these
quasars occupy well defined regions in MIR color-color space. We examine the
issue of type-I AGN candidate selection in detail and propose new selection
methods based on mid-IR colors. The available multi-band data allows us to
construct two new, well-sampled quasar templates, covering wavelengths from the
ultraviolet to the MIR.


title: Cosmological bounds on the equation of state of dark matter

abstract:
  In this exploratory study, we investigate the bounds on the equation of state
of dark matter. Modeling dark matter as a fluid component, we take into account
both positive and negative fixed equations of state. Using CMB, supernovae Ia
and large scale structure data we find constraints on the equation of state in
a modified LambdaCDM cosmology. We obtain -1.50 x 10^{-6} < w_{dm} < 1.13 x
10^{-6} if the dark matter produces no entropy and -8.78 x 10^{-3}< w_{dm} <
1.86 x 10^{-3} if the adiabatic sound speed vanishes, both at 3 sigma
confidence level.


title: The HeII Lyman alpha forest: evaluation of simulated data

abstract:
  Using an artificial HI Lyman alpha spectrum we simulate the corresponding
HeII forest with fixed values of eta and a Doppler parameter consisting of a
thermal and a turbulent part. In addition metal lines with line strengths and
line density as expected in the case of HS 1700+6416 are superimposed.
FUSE-like noise is added. The analysis of the simulated spectra in terms of
Doppler profiles recovers the input eta = N(HeII)/N(HI) with a scatter by a
factor of 10. About 10 % have significantly lower eta-values for various
reasons. The majority of the extremely high eta-values (up to 1000) are
evidently caused by metal lines. We conclude that part of the scatter in eta of
previous analyses of the HeII forest in HE 2347-4342 can be regarded as an
artifact. However, we confirm that the correlation between small column
densities (in voids) and high eta-values is not a methodical artifact and
appears to be a true phenomenon.


title: Radio Detections of Ultraluminous X-ray Sources

abstract:
  We present some results from an archival VLA study of ultraluminous X-ray
source s (ULXs). These unresolved non-nuclear X-ray sources have luminosities
(L_X >= 1 0^39 ergs/sec) which may require somewhat exotic explanations, such
as intermedi ate mass black holes or super-Eddington accretion. Radio emission
is a powerful way to investigate such sources, through radio morphology and the
implications m ade by source energy and lifetimes derived from the radio. The
three galaxies we present here suggest that no single model explains all ULXs,
yet there is growi ng evidence that some ULXs are powered by intermediate mass
black holes.


title:
At what particle energy do extragalactic cosmic rays start to
  predominate?

abstract:
  We have argued [J. Szabelski et al. (2002)] that the well-known `ankle' in
the cosmic ray energy spectrum, at logE (eV) ~ 18.7-19.0, marks the transition
from mainly Galactic sources at lower energies to mainly extragalactic above.
Recently, however, there have been claims for lower transitional energies,
specifically from logE (eV) ~ 17.0 [G. Thompson et al. (2004)] via 17.2-17.8
[V.S. Berezinsky et al. (2004)] to 18.0 [A.M. Hillas (2004)]. In our model the
ankle arises naturally from the sum of simple power law-spectra with slopes
differing by ~ 1.8; from differential slope -3.8 for Galactic particles (near
logE = 19) to ~ -2.0 for extragalactic sources. In the other models, on the
other hand, the ankle is intrinsic to the extragalactic component alone, and
arises from the shape of the rate of energy loss versus energy for the
(assumed) protons interacting with the cosmic microwave background (CMB).
  Our detailed analysis of the world's data on the ultra-high energy spectrum
shows that taken together, or separately, the resulting mean sharpness of the
ankle (second difference of the log(intensity*E^3) with respect to logE) is
consistent with our `mixed' model. For explanation in terms of extragalactic
particles alone, however, the ankle will be at the wrong energy - for
reasonable production models and of insufficient magnitude if, as seems likely,
there is still a significant fraction of heavy nuclei at the ankle energy.


title: Calibration Observations of Fomalhaut with the VLTI

abstract:
  An investigation of the stability of the transfer function of the European
Southern Observatory's Very Large Telescope Interferometer has been carried out
through observations of Fomalhaut over a wide range in hour angle. No
significant variation in the transfer function was found for the zenith angle
range 5-70 degrees. The projected baseline varied between 139.7 m and 49.8 m
during the observations and, as an integral part of the determination of the
transfer function, a new accurate limb-darkened angular diameter for Fomalhaut
has been established. This has led to improved values for the emergent flux,
effective temperature, radius and luminosity.


title:
A High Galactic Latitude HI 21cm-line Absorption Survey using the GMRT:
  I. Observations and Spectra

abstract:
  We have used the Giant Meterwave Radio Telescope (GMRT) to measure the
Galactic HI 21-cm line absorption towards 102 extragalactic radio continuum
sources, located at high (|b| >15deg.) Galactic latitudes. The Declination
coverage of the present survey is Decl. ~ -45deg.. With a mean rms optical
depth of ~0.003, this is the most sensitive Galactic HI 21-cm line absorption
survey to date. To supplement the absorption data, we have extracted the HI
21-cm line emission profiles towards these 102 lines of sight from the Leiden
Dwingeloo Survey of Galactic neutral hydrogen. We have carried out a Gaussian
fitting analysis to identify the discrete absorption and emission components in
these profiles. In this paper, we present the spectra and the components. A
subsequent paper will discuss the interpretation of these results.


title:
A High Galactic Latitude HI 21cm-line Absorption Survey using the GMRT:
  II. Results and Interpretation

abstract:
  We have carried out a sensitive high-latitude (|b| > 15deg.) HI 21cm-line
absorption survey towards 102 sources using the GMRT. With a 3-sigma detection
limit in optical depth of ~0.01, this is the most sensitive HI absorption
survey. We detected 126 absorption features most of which also have
corresponding HI emission features in the Leiden Dwingeloo Survey of Galactic
neutral Hydrogen. The histogram of random velocities of the absorption features
is well-fit by two Gaussians centered at V(lsr) ~ 0 km/s with velocity
dispersions of 7.6 +/- 0.3 km/s and 21 +/- 4 km/s respectively. About 20% of
the HI absorption features form the larger velocity dispersion component. The
HI absorption features forming the narrow Gaussian have a mean optical depth of
0.20 +/- 0.19, a mean HI column density of (1.46 +/- 1.03) X 10^{20} cm^{-2},
and a mean spin temperature of 121 +/- 69 K. These HI concentrations can be
identified with the standard HI clouds in the cold neutral medium of the
Galaxy. The HI absorption features forming the wider Gaussian have a mean
optical depth of 0.04 +/- 0.02, a mean HI column density of (4.3 +/- 3.4) X
10^{19} cm^{-2}, and a mean spin temperature of 125 +/- 82 K. The HI column
densities of these fast clouds decrease with their increasing random
velocities. These fast clouds can be identified with a population of clouds
detected so far only in optical absorption and in HI emission lines with a
similar velocity dispersion. This population of fast clouds is likely to be in
the lower Galactic Halo.


title: Lead abundance in the uranium star CS 31082-001

abstract:
  In a previous paper we were able to measure the abundance of uranium and
thorium in the very-metal poor halo giant BPS CS 31082-001, but only obtained
an upper limit for the abundance of lead (Pb). We have got from ESO 17 hours of
additional exposure on this star in order to secure a detection of the minimum
amount of lead expected to be present in CS 31082-001, the amount arising from
the decay of the original content of Th and U in the star. We report here this
successful detection. We find an LTE abundance log(Pb/H)+12=-0.55 \pm 0.15 dex,
one dex below the upper limits given by other authors for the similar stars CS
22892-052 and BD +17d3248, also enhanced in r-process elements. From the
observed present abundances of Th and U in the star, the expected amount of Pb
produced by the decay of 232Th, and 238U alone, over 12-15 Gyr is -0.73\pm 0.17
dex. The decay of 235U is more difficult to estimate, but is probably slightly
below the contribution of 238U, making the contribution of the 3 actinides only
slightly below, or even equal to, the measured abundance. The contribution from
the decay of 234U has was not included, for lack of published data. In this
sense our determination is a lower limit to the contribution of actinides to
lead production. We comment this result, and we note that if a NLTE analysis,
not yet possible, doubles our observed abundance, the decay of the 3 actinides
will still represent 50 per cent of the total lead, a proportion higher than
the values considered so far in the literature.


title: Inflation: Where Do We Stand?

abstract:
  In this short review, the predictions of inflation are presented and compared
to the most recent measurements of the Cosmic Microwave Background (CMB)
anisotropy. It is argued that inflation is compatible with these observations
but that these ones are not yet accurate enough to probe the details of the
scenario.


title:
Observations of Massive Star Forming Regions with Water Masers:
  Mid-Infrared Imaging

abstract:
  We present here a mid-infrared imaging survey of 26 sites of water maser
emission. Observations were obtained at the InfraRed Telescope Facility 3-m
telescope with the University of Florida mid-infrared imager/spectrometer
OSCIR, and the JPL mid-infrared camera MIRLIN. The main purpose of the survey
was to explore the relationship between water masers and the massive star
formation process. It is generally believed that water masers predominantly
trace outflows and embedded massive stellar objects, but may also exist in
circumstellar disks around young stars. We investigate each of these
possibilities in light of our mid-infrared imaging. We find that mid-infrared
emission seems to be more closely associated with water and OH maser emission
than cm radio continuum emission from UC HII regions. We also find from the
sample of sources in our survey that, like groups of methanol masers, both
water and OH masers have a proclivity for grouping into linear or elongated
distributions. We conclude that the vast majority of linearly distributed
masers are not tracing circumstellar disks, but outflows and shocks instead.


title:
Markov-chain reconstruction of the 2dF Galaxy Redshift Survey real-space
  power spectrum

abstract:
  The real-space power spectrum of L* galaxies measured from the 2dF Galaxy
Redshift Survey (2dFGRS) is presented. Markov-Chain Monte-Carlo (MCMC) sampling
was used to fit radial and angular modes resulting from a Spherical Harmonics
decomposition of the 2dFGRS overdensity field (described in Percival et al.
2004) with 16 real-space power spectrum values and linear redshift-space
distortion parameter \beta(L*,0). The recovered marginalised band-powers are
compared to previous estimates of galaxy power spectra. Additionally, we
provide a simple model for the 17 dimensional likelihood hyper-surface in order
to allow the likelihood to be quickly estimated given a set of model
band-powers and \beta(L*,0). The likelihood surface is not well approximated by
a multi-variate Gaussian distribution with model-independent covariances.
Instead, a model is presented in which the distribution of each band-power has
a Gaussian distribution in a combination of the band-power and its logarithm.
The relative contribution of each component was determined by fitting the MCMC
output. Using these distributions, we demonstrate how the likelihood of a given
cosmological model can be quickly and accurately estimated, and use a simple
set of models to compare estimated likelihoods with likelihoods calculated
using the full Spherical Harmonics procedure. All of the data are made
publically available (from http://www.roe.ac.uk/~wjp/, enabling the Spherical
Harmonics decomposition of the 2dFGRS of Percival et al. (2004) to be easily
used as a cosmological constraint.


title: Sub-mm detection of a high redshift Type 2 QSO

abstract:
  We report on the first SCUBA detection of a Type 2 QSO at z=3.660 in the
Chandra Deep Field South. This source is X-ray absorbed, shows only narrow
emission lines in the optical spectrum and is detected in the sub-mm: it is the
ideal candidate in an evolution scheme for AGN (e.g. Fabian (1999); Page et al.
(2004)) of an early phase corresponding to the main growth of the host galaxy
and formation of the central black hole. The overall photometry (from the radio
to the X-ray energy band) of this source is well reproduced by the spectral
energy distribution (SED) of NGC 6240, while it is incompatible with the
spectrum of a Type 1 QSO (3C273) or a starburst galaxy (Arp 220). Its sub-mm
(850 \mu m) to X-ray (2 keV) spectral slope (alpha_SX) is close to the
predicted value for a Compton-thick AGN in which only 1% of the nuclear
emission emerges through scattering. Using the observed flux at 850 \mu m we
have derived a SFR=550--680 M$_odot/yr and an estimate of the dust mass,
M$_dust=4.2 10^8 M_odot


title:
Random-Walk Statistics and the Spherical Harmonic Representation of CMB
  Maps

abstract:
  We investigate the properties of the (complex) coefficients obtained in a
spherical harmonic representation of temperature maps of the cosmic microwave
background (CMB). We study the effect of the coefficient phase only, as well as
the combined effects of phase and amplitude. The method used to check for
anomalies is to construct a ``random walk'' trajectory in the complex plane
where the step length and direction are given by the amplitude and phase
(respectively) of the harmonic coefficient. If the fluctuations comprise a
homogeneous and isotropic Gaussian random field on the sky, the path so
obtained should be a classical ``Rayleigh flight'' with very well known
statistical properties. We illustrate the use of this random-walk
representation by using the net walk length as a test statistic, and apply the
method to the coefficients obtained from a Wilkinson Microwave Anisotropy Probe
(WMAP) preliminary sky temperature map.


title: Dynamics of Extended Objects: the Einstein-Hilbert Drop

abstract:
  The Einstein-Hilbert worldspace action is used to investigate the dynamics of
extended object. In the Robertson-Walker worldspace, this is seen to introduce
a pressureless density which could contribute to dark matter. Such pressureless
energy density, present from the very beginning, should have enormous
consequences on large scale structure formation in the early Universe.
Generalizing the idea to complexified internal co-ordinates, it becomes
possible to gauge the action with U(1) symmetry. A trivial solution of this
theory is Einstein's general relativity and source free Maxwell theory.
Generally, the equations of motion of the gauge fields are Maxwell equations
with source terms that include these fields themselves. The internal
co-ordinates, under vacuum domination with negative pressure, obey an EOM that
is a hyperbolic wave equation of a charged scalar field that interacts with the
gauge fields and gravity in a disperso-conductive medium ; under matter
domination with positive pressure however, it is an elliptic potential
equation. Since the hyperbolic to elliptic transition can be made by
introducing imaginary time, this result supports the view that time is actually
complex, becoming Minkowskian in vacuum and Euclidean in matter. A
supersymmetric version of the action can also be immediately written down.