title:
The Optical/Near-Infrared Light Curves of SN 2002ap for the First 1.5
  Years after Discovery

abstract:
  Late-time BVRIJHK photometry of the peculiar Type Ic SN 2002ap, taken between
2002 June 12 and 2003 August 29 with the MAGNUM telescope, is presented. The
light curve decline rate is derived in each band and the color evolution is
studied through comparison with nebular spectra and with SN 1998bw. Using the
photometry, the OIR bolometric light curve is built, extending from before
light maximum to day 580 after explosion. The light curve has a late-time shape
strikingly similar to that of the hypernova SN 1998bw. The decline rate changes
from 0.018 mag/day between day 130 and 230 to 0.014 mag/day between day 270 and
580. To reproduce the late-time light curve, a dense core must be added to the
1-D hypernova model that best fits the early-time observations, bringing the
ejecta mass from 2.5 Msun to 3 Msun without much change in the kinetic energy,
which is 4 times 10^51 ergs. This is similar to the case of other hypernovae
and suggests asymmetry. A large H-band bump developed in the spectral energy
distribution after about day 300, probably caused by strong [Si I] 1.646 micron
and 1.608 micron emissions. The near-infrared flux contribution increased
simultaneously from <30% to >50% at day 580. The near-infrared light curves
were compared with those of other Type Ib/c supernovae, among which SN 1983I
seems similar to SN 2002ap both in the near-infrared and in the optical.


title: Mid infrared properties of distant infrared luminous galaxies

abstract:
  We present evidence that the mid infrared (MIR) is a good tracer of the total
infrared luminosity, L(IR), and star formation rate (SFR), of galaxies up to z
1.3. We use deep MIR images from the Infrared Space Observatory (ISO) and the
Spitzer Space Telescope in the Northern field of the Great Observatories
Origins Deep Survey (GOODS-N) together with VLA radio data to compute three
independant estimates of L(IR). The L(IR,MIR) derived from the observed 15
and/or 24 um flux densities using a library of template SEDs, and L(IR,radio),
derived from the radio (1.4 and/or 8.5 GHz) using the radio-far infrared
correlation, agree with a 1-sigma dispersion of 40 %. We use the k-correction
as a tool to probe different parts of the MIR spectral energy distribution
(SED) of galaxies as a function of their redshift and find that on average
distant galaxies present MIR SEDs very similar to local ones. However, in the
redshift range z= 0.4-1.2, L(IR,24um) is in better agreement with L(IR,radio)
than L(IR,15 um) by 20 %, suggesting that the warm dust continuum is a better
tracer of the SFR than the broad emission features due to polycyclic aromatic
hydrocarbons (PAHs). We find marginal evidence for an evolution with redshift
of the MIR SEDs: two thirds of the distant galaxies exhibit rest-frame MIR
colors (L(12 um)/L(7 um) and L(10 um)/L(15 um) luminosity ratios) below the
median value measured for local galaxies. Possible explanations are examined
but these results are not sufficient to constrain the physics of the emitting
regions. We compare three commonly used SED libraries which reproduce the
color-luminosity correlations of local galaxies with our data and discuss
possible refinements to the relative intensities of PAHs, warm dust continuum
and silicate absorption.


title:
IRS Spectra of Solar-Type Stars: \break A Search for Asteroid Belt
  Analogs

abstract:
  We report the results of a spectroscopic search for debris disks surrounding
41 nearby solar type stars, including 8 planet-bearing stars, using the {\it
Spitzer Space Telescope}. With accurate relative photometry using the Infrared
Spectrometer (IRS) between 7-34 $\micron$ we are able to look for excesses as
small as $\sim$2% of photospheric levels with particular sensitivity to weak
spectral features. For stars with no excess, the $3\sigma$ upper limit in a
band at 30-34 $\mu$m corresponds to $\sim$ 75 times the brightness of our
zodiacal dust cloud. Comparable limits at 8.5-13 $\mu$m correspond to $\sim$
1,400 times the brightness of our zodiacal dust cloud. These limits correspond
to material located within the $<$1 to $\sim$5 AU region that, in our solar
system, originates from debris associated with the asteroid belt. We find
excess emission longward of $\sim$25 $\mu$m from five stars of which four also
show excess emission at 70 $\mu$m. This emitting dust must be located around
5-10 AU. One star has 70 micron emission but no IRS excess. In this case, the
emitting region must begin outside 10 AU; this star has a known radial velocity
planet. Only two stars of the five show emission shortward of 25 $\micron$
where spectral features reveal the presence of a population of small, hot dust
grains emitting in the 7-20 $\mu$m band. The data presented here strengthen the
results of previous studies to show that excesses at 25 $\micron$ and shorter
are rare: only 1 star out of 40 stars older than 1 Gyr or $\sim 2.5$% shows an
excess. Asteroid belts 10-30 times more massive than our own appear are rare
among mature, solar-type stars.


title: IRS Spectra of Solar-Type Stars: A Search for Asteroid Belt Analogs


title: Comparative Planetology and the Search for Life Beyond the Solar System

abstract:
  The study of planets beyond the solar system and the search for other
habitable planets and life is just beginning. Ground-based (radial velocity and
transits) and space-based surveys (transits and astrometry) will identify
planets spanning a wide range of size and orbital location, from Earth-sized
objects within 1 AU to giant planets beyond 5 AU, orbiting stars as near as a
few parsec and as far as a kiloparsec. After this initial reconnaissance, the
next generation of space observatories will directly detect photons from
planets in the habitable zones of nearby stars. The synergistic combination of
measurements of mass from astrometry and radial velocity, of radius and
composition from transits, and the wealth of information from the direct
detection of visible and mid-IR photons will create a rich field of comparative
planetology. Information on proto-planetary and debris disks will complete our
understanding of the evolution of habitable environments from the earliest
stages of planet-formation through to the transport into the inner solar system
of the volatiles necessary for life.
  The suite of missions necessary to carry out the search for nearby, habitable
planets and life requires a ``Great Observatories'' program for planet finding
(SIM PlanetQuest, Terrestrial Planet Finder-Coronagraph, and Terrestrial Planet
Finder-Interferometer/Darwin), analogous to the highly successful ``Great
Observatories Program'' for astrophysics. With these new Great Observatories,
plus the James Webb Space Telescope, we will extend planetology far beyond the
solar system, and possibly even begin the new field of comparative evolutionary
biology with the discovery of life itself in different astronomical settings.


title: Theoretical Isochrones with Extinction in the K Band. II. J - K versus K

abstract:
  We calculate theoretical isochrones in a consistent way for five filter pairs
near the J and K band atmospheric windows (J-K, J-K', J-Ks, F110W-F205W, and
F110W-F222M) using the Padova stellar evolutionary models of Girardi et al. We
present magnitude transformations between various K-band filters as a function
of color. Isochrones with extinction of up to 6 mag in the K band are also
presented. As found for the filter pairs composed of H & K band filters, we
find that the reddened isochrones of different filter pairs behave as if they
follow different extinction laws, and that the extinction curves of Hubble
Space Telescope NICMOS filter pairs in the color-magnitude diagram are
considerably nonlinear. Because of these problems, extinction values estimated
with NICMOS filters can be in error by up to 1.3 mag. Our calculation suggests
that the extinction law implied by the observations of Rieke et al for
wavelengths between the J and K bands is better described by a power-law
function with an exponent of 1.66 instead of 1.59, which is commonly used with
an assumption that the transmission functions of J and K filters are Dirac
delta functions.


title:
Reconstruction of Five-dimensional Bounce cosmological Models From
  Deceleration Factor

abstract:
  In this paper, we consider a class of five-dimensional Ricci-flat vacuum
solutions, which contain two arbitrary functions $\mu(t)$ and $\nu(t)$. It is
shown that $\mu(t)$ can be rewritten as a new arbitrary function $f(z)$ in
terms of redshift $z$ and the $f(z)$ can be determined by choosing particular
deceleration parameters $q(z)$ which gives early deceleration and late time
acceleration. In this way, the $5D$ cosmological model can be reconstructed and
the evolution of the universe can be determined.


title: Elemental abundances as a function of kinematics in the Milky Way's disk

abstract:
  We present the results of our investigation of three samples kinematically
representative of the thin and thick disks and the Hercules stream using the
catalogue of Soubiran & Girard (2005). We have observed abundance trends and
age distribution of each component. Our results show that the two disks are
chemically well separated, they overlap greatly in metallicity and both show
parallel decreasing trends of alpha elements with increasing metallicity, in
the interval -0.80 < [Fe/H] < -0.30. The thick disk is clearly older than the
thin disk with a tentative evidence of an Age-Metallicity Relation over 2-3 Gyr
and a hiatus in star formation before the formation of the thin disk. In order
to improve the statistics on the disk's abundance trends, we have developed an
automatic code, TGMET{\Large\alpha}; to determine (Teff, logg, [Fe/H],
[\alpha/Fe]) for thousands of stellar spectra available in spectroscopic
archives. We have assessed the performances of the algorithm for 350 spectra of
stars being part of the abundance catalogue.


title: Time delay of SBS 0909+532

abstract:
  The time delays between the components of a lensed quasar are basic tools to
analyze the expansion of the Universe and the structure of the main lens galaxy
halo. In this paper, we focus on the variability and time delay of the double
system SBS 0909+532A,B as well as the time behaviour of the field stars. We use
VR optical observations of SBS 0909+532A,B and the field stars in 2003. The
frames were taken at Calar Alto, Maidanak and Wise observatories, and the VR
light curves of the field stars and quasar components are derived from aperture
and point-spread function fitting methods. We measure the R-band time delay of
the system from the chi-square and dispersion techniques and 1000 synthetic
light curves based on the observed records. One nearby field star (SBS
0909+532c) is found to be variable, and the other two nearby field stars are
non-variable sources. With respect to the quasar components, the R-band records
seem more reliable and are more densely populated than the V-band ones. The
observed R-band fluctuations permit a pre-conditioned measurement of the time
delay. From the chi-square minimization, if we assume that the quasar emission
is observed first in B and afterwards in A (in agreement with basic
observations of the system and the corresponding predictions), we obtain a
delay of - 45 (+ 1)/(- 11) days (95% confidence interval). The dispersion
technique leads to a similar delay range. A by-product of the analysis is the
determination of a totally corrected flux ratio in the R band (corrected by the
time delay and the contamination due to the galaxy light). Our 95% measurement
of this ratio (0.575 +/- 0.014 mag) is in excellent agreement with previous
results from contaminated fluxes at the same time of observation.


title: Radio Linear and Circular Polarization from M81*

abstract:
  We present results from archival Very Large Array (VLA) data and new VLA
observations to investigate the long term behavior of the circular polarization
of M81*, the nuclear radio source in the nearby galaxy M81. We also used the
Berkeley-Illinois-Maryland Association (BIMA) array to observe M81* at 86 and
230 GHz. M81* is unpolarized in the linear sense at a frequency as high as 86
GHz and shows variable circular polarization at a frequency as high as 15 GHz.
The spectrum of the fractional circular polarization is inverted in most of our
observations. The sign of circular polarization is constant over frequency and
time. The absence of linear polarization sets a lower limit to the accretion
rate of $10^{-7} M_\odot y^{-1}$. The polarization properties are strikingly
similar to the properties of Sgr A*, the central radio source in the Milky Way.
This supports the hypothesis that M81* is a scaled up version of Sgr A*. On the
other hand, the broad band total intensity spectrum declines towards milimeter
wavelengths which differs from previous observations of M81* and also from Sgr
A*.


title: Three component model of cosmic ray spectra from 10 GeV to 100 PeV

abstract:
  A model to describe cosmic ray spectra in the energy region from 10 GeV to
100 PeV is suggested based on the assumption that Galactic cosmic ray flux is a
mixture of fluxes accelerated by shocks from nova and supernova of different
types. We analyze recent experimental data on cosmic ray spectra obtained in
direct measurements above the atmosphere and data obtained with ground
Extensive Air Shower arrays. The model of the three classes of cosmic ray
sources is consistent with direct experimental data on cosmic ray elemental
spectra and gives a smooth transition from the all particle spectrum measured
in the direct experiments to the all particle spectrum measured with EAS.


title:
The Hamburg/ESO R-process Enhanced Star survey (HERES) III. HE 0338-3945
  and the formation of the r+s stars

abstract:
  We have derived abundances of 33 elements and upper limits for 6 additional
elements for the metal-poor ([Fe/H] = -2.42) turn-off star HE 0338-3945 from
high-quality VLT-UVES spectra. The star is heavily enriched, by about a factor
of 100 relative to iron and the Sun, in the heavy s-elements (Ba, La, ..). It
is also heavily enriched in Eu, which is generally considered an r-element, and
in other similar elements. It is less enriched, by about a factor of 10, in the
lighter s-elements (Sr, Y and Zr). C is also strongly enhanced and, to a
somewhat lesser degree, N and O. These abundance estimates are subject to
severe uncertainties due to NLTE and thermal inhomogeneities which are not
taken into detailed consideration. However, an interesting result, which is
most probably robust in spite of these uncertainties, emerges: the abundances
derived for this star are very similar to those of other stars with an overall
enhancement of all elements beyond the iron peak.
  We have defined criteria for this class of stars, r+s stars, and discuss nine
different scenarios to explain their origin. None of these explanations is
found to be entirely convincing. The most plausible hypotheses involve a binary
system in which the primary component goes through its giant branch and
asymptotic giant branch phases and produces CNO and s-elements which are dumped
onto the observed star. Whether the r-element Eu is produced by supernovae
before the star was formed (perhaps triggering the formation of a low-mass
binary), by a companion as it explodes as a supernova (possibly triggered by
mass transfer), or whether it is possibly produced in a high-neutron-density
version of the s-process is still unclear. Several suggestions are made on how
to clarify this situation.


title:
Spectroscopic Identification of Cool White Dwarfs in the Solar
  Neighbourhood

abstract:
  The New Luyten Two-Tenths catalog contains a large number of high-proper
motion white dwarf candidates that remain to be spectroscopically confirmed. We
present new spectroscopic observations as well as SDSS archival spectra of 49
white dwarf candidates which have been selected from the revised NLTT catalog
of Salim & Gould 2003. Out of these, 34 are cool DA white dwarfs with
temperatures ranging from approximately 5000 K up to 11690 K, and 11 are DC
white dwarfs with temperatures ranging from 4300 K (NLTT 18555) up to 11000 K.
Three of the DA white dwarfs also display abundances of heavy elements (NLTT
3915, NLTT 44986 and NLTT 43806) and one is a cool magnetic white dwarf (NLTT
44447) with an estimated magnetic field strength of 1.3 MG. We also present a
new cool DQ white dwarf (NLTT 31347) with an estimated temperature of 6250 K.
We supplement our sample with SDSS ugriz photometry for a fraction of the newly
identified white dwarfs. A kinematical study of this sample of white dwarfs,
characterized by proper motions ranging from 0.136 to 0.611 arcsec per yr
suggest that they belong to the thin disk population.


title: Modified Newtonian Dynamics, an Introductory Review

abstract:
  By the time, in 1937, the Swiss astronomer Zwicky measured the velocity
dispersion of the Coma cluster of galaxies, astronomers somehow got acquainted
with the idea that the universe is filled by some kind of dark matter. After
almost a century of investigations, we have learned two things about dark
matter, (i) it has to be non-baryonic -- that is, made of something new that
interact with normal matter only by gravitation-- and, (ii) that its effects
are observed in stellar systems when and only when their internal acceleration
of gravity falls below a fix value a0=1.2x10-8 cm s-2. This systematic, more
than anything else, tells us we might be facing a failure of the law of gravity
in the weak field limit rather then the effects of dark matter. Thus, in an
attempt to avoid the need for dark matter, the Modified Newtonian Dynamics.
MOND posits a breakdown of Newton's law of gravity (or inertia) below a0, after
which the dependence with distance became linear. Despite many attempts, MOND
resisted stubbornly to be falsified as an alternative to dark matter and
succeeds in explaining the properties of an impressively large number of
objects without invoking the presence of non-baryonic dark matter. In this
paper, I will review the basics of MOND and its ability to explain observations
without the need of dark matter.


title: Linear perturbative theory of the discrete cosmological N-body problem

abstract:
  We present a perturbative treatment of the evolution under their mutual
self-gravity of particles displaced off an infinite perfect lattice, both for a
static space and for a homogeneously expanding space as in cosmological N-body
simulations. The treatment, analogous to that of perturbations to a crystal in
solid state physics, can be seen as a discrete (i.e. particle) generalization
of the perturbative solution in the Lagrangian formalism of a self-gravitating
fluid. Working to linear order, we show explicitly that this fluid evolution is
recovered in the limit that the initial perturbations are restricted to modes
of wavelength much larger than the lattice spacing. The full spectrum of
eigenvalues of the simple cubic lattice contains both oscillatory modes and
unstable modes which grow slightly faster than in the fluid limit. A detailed
comparison of our perturbative treatment, at linear order, with full numerical
simulations is presented, for two very different classes of initial
perturbation spectra. We find that the range of validity is similar to that of
the perturbative fluid approximation (i.e. up to close to ``shell-crossing''),
but that the accuracy in tracing the evolution is superior. The formalism
provides a powerful tool to systematically calculate discreteness effects at
early times in cosmological N-body simulations.


title: Simulation of Shock Waves by Smoothed Particle Hydrodynamics

abstract:
  Isothermal and adiabatic shocks, which are produced from fast expansion of
the gas, is simulated with smoothed particle hydrodynamics (SPH). The results
are compared with the analytic solutions. The algorithm of the program is
explained and the package, which is written in Fortran, is presented in the
appendix of this paper. It is possible to change (to complete) the program for
a wide variety of applications ranging from astrophysics to fluid mechanics.


title:
Nongaussian and nonscale-invariant perturbations from tachyonic
  preheating in hybrid inflation

abstract:
  We show that in hybrid inflation it is possible to generate large
second-order perturbations in the cosmic microwave background due to the
instability of the tachyonic field during preheating. We carefully calculate
this effect from the tachyon contribution to the gauge-invariant curvature
perturbation, clarifying some confusion in the literature concerning nonlocal
terms in the tachyon curvature perturbation; we show explicitly that such terms
are absent. We quantitatively compute the nongaussianity generated by the
tachyon field during the preheating phase and translate the experimental
constraints on the nonlinearity parameter f_{NL} into constraints on the
parameters of the model. We also show that nonscale-invariant second-order
perturbations from the tachyon field can become larger than the
inflaton-generated first-order perturbations, leading to stronger constraints
than those coming from nongaussianity. The width of the excluded region in
terms of the logarithm of the dimensionless coupling g, grows linearly with the
log of the ratio of the Planck mass to the tachyon VEV, \log(M_p/v); hence very
large regions are ruled out if the inflationary scale v is small. We apply
these results to string-theoretic brane-antibrane inflation, and find a
stringent upper bound on the string coupling, g_s < 10^{-4.5}.


title: Opening angles, Lorentz factors and confinement of X-ray binary jets

abstract:
  We present a collation of the available data on the opening angles of jets in
X-ray binaries, which in most cases are small (less than 10 degrees). Under the
assumption of no confinement, we calculate the Lorentz factors required to
produce such small opening angles via the transverse relativistic Doppler
effect. The derived Lorentz factors, which are in most cases lower limits, are
found to be large, with a mean greater than 10, comparable to those estimated
for AGN and much higher than the commonly-assumed values for X-ray binaries of
2 to 5. Jet power constraints do not in most cases rule out such high Lorentz
factors. The upper limits on the opening angles show no evidence for smaller
Lorentz factors in the steady jets of Cygnus X-1 and GRS 1915+105. In those
sources in which deceleration has been observed (notably XTE J1550-564 and
Cygnus X-3), some confinement of the jets must be occurring, and we briefly
discuss possible confinement mechanisms. It is however possible that all the
jets could be confined, in which case the requirement for high bulk Lorentz
factors can be relaxed.


title: Stokes Inversion Techniques: Recent Advances and New Challenges

abstract:
  Inversion techniques (ITs) allow us to infer the magnetic, dynamic, and
thermal properties of the solar atmosphere from polarization line profiles. In
recent years, major progress has come from the application of ITs to
state-of-the-art observations. This paper summarizes the main results achieved
both in the photosphere and in the chromosphere. It also discusses the
challenges facing ITs in the near future. Understanding the limitations of
spectral lines, implementing more complex atmospheric models, and devising
efficient strategies of data analysis for upcoming ground-based and space-borne
instruments, are among the most important issues that need to be addressed. It
is argued that proper interpretations of diffraction-limited Stokes profiles
will not be possible without accounting for gradients of the atmospheric
parameters along the line of sight. The feasibility of determining gradients in
real time from space-borne observations is examined.


title: Simulating large-scale structure formation with magnetic fields

abstract:
  In the past, different works based on numerical simulations have been
presented to explain magnetic fields (MFs) in the large scale structure and
within galaxy clusters. In this review, I will summarize the main findings
obtained by different authors and - even if many details are still unclear - I
will try to construct a consistent picture of our interpretation of large-scale
magnetic fields based on numerical effort. I will also sketch how this is
related to our understanding of radio emission and summarize some arguments
where our theoretical understanding has to be improved to match the
observations.


title:
Spitzer Reveals Hidden Quasar Nuclei in Some Powerful FR II Radio
  Galaxies

abstract:
  We present a Spitzer mid-infrared survey of 42 Fanaroff-Riley class II radio
galaxies and quasars from the 3CRR catalog at redshift z<1. All of the quasars
and 45+/-12% of the narrow-line radio galaxies have a mid-IR luminosity of
nuLnu(15 micron) > 8E43 erg/s, indicating strong thermal emission from hot dust
in the active galactic nucleus. Our results demonstrate the power of Spitzer to
unveil dust-obscured quasars. The ratio of mid-IR luminous narrow-line radio
galaxies to quasars indicates a mean dust covering fraction of 0.56+/-0.15,
assuming relatively isotropic emission. We analyze Spitzer spectra of the 14
mid-IR luminous narrow-line radio galaxies thought to host hidden quasar
nuclei. Dust temperatures of 210-660 K are estimated from single-temperature
blackbody fits to the low and high-frequency ends of the mid-IR bump. Most of
the mid-IR luminous radio galaxies have a 9.7 micron silicate absorption trough
with optical depth <0.2, attributed to dust in a molecular torus. Forbidden
emission lines from high-ionization oxygen, neon, and sulfur indicate a source
of far-UV photons in the hidden nucleus. However, we find that the other
55+/-13% of narrow-line FR II radio galaxies are weak at 15 micron, contrary to
single-population unification schemes. Most of these galaxies are also weak at
30 micron. Mid-IR weak radio galaxies may constitute a separate population of
nonthermal, jet-dominated sources with low accretion power


title: Rapid Formation of Gas Giant Planets around M Dwarf Stars

abstract:
  Extrasolar planet surveys have begun to detect gas giant planets in orbit
around M dwarf stars. While the frequency of gas giant planets around M dwarfs
so far appears to be lower than that around G dwarfs, it is clearly not zero.
Previous work has shown that the core accretion mechanism does not seem to be
able to form gas giant planets around M dwarfs, because the time required for
core formation scales with the orbital period, which lengthens for lower mass
stars, resulting in failed (gas-poor) cores unless the gaseous protoplanetary
disk survives for > 10 Myr. Disk instability, on the other hand, is rapid
enough (~ 1000 yrs) that it should be able to form gas giant protoplanets
around even low mass stars well before the gaseous disk disappears. A new suite
of three dimensional radiative, gravitational hydrodynamical models is
presented that calculates the evolution of initially marginally gravitationally
unstable disks with masses of 0.021 to 0.065 solar masses orbiting around stars
with masses of 0.1 and 0.5 solar masses, respectively. The models show that gas
giant planets are indeed likely to form by the disk instability mechanism in
orbit around M dwarf stars, the opposite of the prediction for formation by the
core accretion mechanism. This difference offers another observational test for
discriminating between these two theoretical end members for giant planet
formation. Ongoing and future extrasolar planet searches around M dwarfs by
spectroscopy, microlensing, photometry, and astrometry offer the opportunity to
help decide between the dominance of the two mechanisms.


title:
Radio Observations and Spectrum of the SNR G127.1+0.5 and its Central
  Source 0125+628

abstract:
  We present new images of the Supernova Remnant (SNR) G127.1+0.5 (R5), based
on the 408 MHz and 1420 MHz continuum emission and the HI-line emission data of
the Canadian Galactic Plane Survey (CGPS). The radio spectrum of the central
compact source (0125+628) is analyzed in the range 178 MHz - 8.7 GHz,
indicating a flat spectrum with synchrotron self-absorption below 800 MHz. The
SNR's flux density at 408 MHz is 17.1$\pm$1.7 Jy and at 1420 MHz is
10.0$\pm$0.8 Jy, corrected for flux densities from compact sources within the
SNR. The SNR's integrated flux density based spectral index
(S$_{\nu}$$\propto$$\nu$$^{-\alpha}$) is 0.43$\pm$0.10. The respective T-T plot
spectral index (derived from the relative size of brightness temperature
variations between two frequencies, see text for details) is 0.46$\pm$0.01.
There is no evidence at 1$\sigma$ for spatial variations in spectral index
within G127.1+0.5. In particular, we compared the northern shell, southern
shell and central diffuse region. HI observations show structures associated
with the SNR in the radial velocity range of -12 to -16 km$/$s, suggesting
G127.1+0.5's distance is 1.15 kpc. The estimated Sedov age is 2 - 3
$\times$$10^{4}$ yr.


title:
First scattered light images of debris disks around HD 53143 and HD
  139664

abstract:
  We present the first scattered light images of debris disks around a K star
(HD 53143) and an F star (HD 139664) using the coronagraphic mode of the
Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST). With
ages 0.3 - 1 Gyr, these are among the oldest optically detected debris disks.
HD 53143, viewed ~45 degrees from edge-on, does not show radial variation in
disk structure and has width >55 AU. HD 139664 is seen close to edge-on and has
belt-like morphology with a dust peak 83 AU from the star and a distinct outer
boundary at 109 AU. We discuss evidence for significant diversity in the radial
architecture of debris disks that appears unconnected to stellar spectral type
or age. HD 139664 and possibly the solar system belong in a category of narrow
belts 20-30 AU wide. HD 53143 represents a class of wide disk architecture with
characteristic width >50 AU.


title: Dark matter: A phenomenological existence proof

abstract:
  The non-Keplerian galactic rotational curves and the gravitational lensing
data strongly indicate a significant dark matter component in the universe.
Moreover, these data can be combined to deduce the equation of state of dark
matter. Yet, the existence of dark matter has been challenged following the
tradition of critical scientific spirit. In the process, the theory of general
relativity itself has been questioned and various modified theories of
gravitation have been proposed. Within the framework of the Einsteinian general
relativity, here I make the observation that if the universe is described by a
spatially flat Friedmann-Robertson-Walker cosmology with Einsteinian
cosmological constant then the resulting cosmology predicts a significant dark
matter component in the universe. The phenomenologically motivated existence
proof refrains from invoking the data on galactic rotational curves and
gravitational lensing, but uses as input the age of the universe as deciphered
from studies on globular clusters.


title:
An extensive study of dynamical friction in dwarf galaxies: the role of
  stars, dark matter, halo profiles and MOND

abstract:
  We investigate the in-spiraling timescales of globular clusters in dwarf
spheroidal (dSph) and dwarf elliptical (dE) galaxies, due to dynamical
friction. We address the problem of these timescales having been variously
estimated in the literature as much shorter than a Hubble time. Using
self-consistent two-component (dark matter and stars) models, we explore
mechanisms which may yield extended dynamical friction timescales in such
systems in order to explain why dwarf galaxies often show globular cluster
systems. As a general rule, dark matter and stars both give a comparable
contribution to the dynamical drag. By exploring various possibilities for
their gravitational make-up, it is shown that these studies help constrain the
parameters of the dark matter haloes in these galaxies, as well as to test
alternatives to dark matter. Under the assumption of a dark haloes having a
constant density core, dynamical friction timescales are naturally extended
upwards of a Hubble time. Cuspy dark haloes yield timescales $\lesssim$ 4.5
Gyr, for any dark halo parameters in accordance with observations of stellar
line-of-sight velocity dispersion in dwarf spheroidal galaxies. We find that
under the hypothesis of MOND dynamics, due to the enhanced dynamical drag of
the stars, the dynamical friction timescales would be extremely short. Taking
the well-measured structural parameters of the Fornax dSph and its globular
cluster system as a case study, we conclude that requiring dynamical friction
timescales comparable to the Hubble time strongly favours dark haloes with a
central core.


title:
A Further Study of the Luminosity-Dependent Cyclotron Resonance Energies
  of the Binary X-ray Pulsar 4U0115+63 with RXTE

abstract:
  The present paper reports on the RXTE observations of the binary X-ray pulsar
4U0115+63, covering an outburst in 1999 March-April with 44 pointings. The 3-30
keV PCA spectra and the 15-50 keV HEXTE spectra were analyzed jointly for the
cyclotron resonance features. When the 3-50 keV luminosity at an assumed
distance of 7 kpc was in the range (5-13)x10^{37} erg s^{-1}, harmonic double
cyclotron features were observed in absorption at ~11 and ~22 keV, as was
measured previously during typical outbursts. As the luminosity decreased below
\~5x10^{37} erg s^{-1}, the second resonance disappeared, and the fundamental
resonance energy gradually increased, up to $\sim$16 keV at 0.16x10^{37} erg
s^{-1}. These results reconfirm the report by Mihara et al. (2004) using Ginga,
who observed a single absorption at ~16 keV in a minor (~10^{37} erg s^{-1})
outburst of this object. The luminosity-dependent cyclotron resonance energy
may be understood as a result of a decrease in the accretion column height, in
response to a decrease in the mass accretion rate.


title:
Atmospheric Turbulence Compensation with Laser Phase Shifting
  Interferometry

abstract:
  Laser guide stars with adaptive optics allow astronomical image correction in
the absence of a natural guide star. Single guide star systems with a star
created in the earth's sodium layer can be used to correct the wavefront in the
near infrared spectral regime for 8-m class telescopes. For possible future
telescopes of larger sizes, or for correction at shorter wavelengths, the use
of a single guide star is ultimately limited by focal anisoplanatism that
arises from the finite height of the guide star. To overcome this limitation we
propose to overlap coherently pulsed laser beams that are expanded over the
full aperture of the telescope, traveling upwards along the same path which
light from the astronomical object travels downwards. Imaging the scattered
light from the resultant interference pattern with a camera gated to a certain
height above the telescope, and using phase shifting interferometry we have
found a method to retrieve the local wavefront gradients. By sensing the
backscattered light from two different heights, one can fully remove the cone
effect, which can otherwise be a serious handicap to the use of laser guide
stars at shorter wavelengths or on larger telescopes. Using two laser beams
multiconjugate correction is possible, resulting in larger corrected fields.
With a proper choice of laser, wavefront correction could be expanded to the
visible regime and, due to the lack of a cone effect, the method is applicable
to any size of telescope. Finally the position of the laser spot could be
imaged from the side of the main telescope against a bright background star to
retrieve tip-tilt information, which would greatly improve the sky coverage of
the system.


title:
A Bayesian analysis of regularised source inversions in gravitational
  lensing

abstract:
  Strong gravitational lens systems with extended sources are of special
interest because they provide additional constraints on the models of the lens
systems. To use a gravitational lens system for measuring the Hubble constant,
one would need to determine the lens potential and the source intensity
distribution simultaneously. A linear inversion method to reconstruct a
pixellated source brightness distribution of a given lens potential model was
introduced by Warren & Dye. In the inversion process, a regularisation on the
source intensity is often needed to ensure a successful inversion with a
faithful resulting source. In this paper, we use Bayesian analysis to determine
the optimal regularisation constant (strength of regularisation) of a given
form of regularisation and to objectively choose the optimal form of
regularisation given a selection of regularisations. We consider and compare
quantitatively three different forms of regularisation previously described in
the literature for source inversions in gravitational lensing: zeroth-order,
gradient and curvature. We use simulated data with the exact lens potential to
demonstrate the method. We find that the preferred form of regularisation
depends on the nature of the source distribution.


title: The true nature of CSL-1

abstract:
  On January 12 2006, the Hubble Space Telescope observed the peculiar double
extragalactic object CSL-1, suspected to be the result of gravitational lensing
by a cosmic string. The high resolution image shows that the object is actually
a pair of interacting giant elliptical galaxies. In spite of the weird
similarities of the energy and light distributions and of the radial velocities
of the two components, CSL-1 is not the lensing of an elliptical galaxy by a
cosmic string.


title:
SN 1987A After 18 Years: Mid-Infrared GEMINI and SPITZER Observations of
  the Remnant

abstract:
  We present high resolution 11.7 and 18.3um mid-IR images of SN 1987A obtained
on day 6526 with T-ReCS attached to the Gemini telescope. The 11.7um flux has
increased significantly since our last observations on day 6067. The images
clearly show that all the emission arises from the equatorial ring (ER).
Spectra obtained with Spitzer, on day 6184 with MIPS at 24um, on day 6130 with
IRAC in the 3.6-8um region, and on day 6190 with IRS in the 12-37um region show
that the emission consists of thermal emission from silicate dust that
condensed out in the red giant wind of the progenitor star. The dust
temperature is ~166K, and the emitting dust mass is ~2.6 x 10-6 Msun. Lines of
[Ne II]12.82um and [Ne III]15.56um are clearly present, as well as a weak [Si
II]34.8um line. We also detect two lines near 26um which we tentatively ascribe
to [Fe II]25.99um and [O IV]25.91um. Comparison of the Gemini 11.7um image with
X-ray images from Chandra, UV-optical images from HST, and radio synchrotron
images obtained by the ATCA show generally good correlation of the images
across all wavelengths. Because of the limited resolution of the mid-IR images
we cannot uniquely determine the location or heating mechanism of the dust
giving rise to the emission. The dust could be collisionally heated by the
X-ray emitting plasma, providing a unique diagnostic of plasma conditions.
Alternatively, the dust could be radiatively heated in the dense UV-optical
knots that are overrun by the advancing supernova blast wave. In either case
the dust-to-gas mass ratio in the circumstellar medium around the supernova is
significantly lower than that in the general ISM of the LMC, suggesting either
a low condensation efficiency in the wind of the progenitor star, or the
efficient destruction of the dust by the SN blast wave.


title: Magnetic helicity in primordial and dynamo scenarios of galaxies

abstract:
  Some common properties of helical magnetic fields in decaying and driven
turbulence are discussed. These include mainly the inverse cascade that
produces fields on progressively larger scales. Magnetic helicity also
restricts the evolution of the large scale field: the field decays less rapidly
than a non-helical field, but it also saturates more slowly, i.e. on a
resistive time scale if there are no magnetic helicity fluxes. The former
effect is utilized in primordial field scenarios, while the latter is important
for successfully explaining astrophysical dynamos that saturate faster than
resistively. Dynamo action is argued to be important not only in the galactic
dynamo, but also in accretion discs in active galactic nuclei and around
protostars, both of which contribute to producing a strong enough seed magnetic
field. Although primordial magnetic fields may be too weak to compete with
these astrophysical mechanisms, such fields could perhaps still be important in
producing polarization effects in the cosmic background radiation.


title:
Distant early-type galaxies: tracers of the galaxy mass assembly
  evolution

abstract:
  We review the most recent observational results on the formation and
evolution of early-type galaxies and their mass assembly by focusing on: the
existence, properties and role of distant old, massive, passive systems to z~2,
the stellar mass function evolution, the ``downsizing'' scenario, and the
high-z precursors of massive early-type galaxies.


title: Rotating massive stars @ very low Z: high C and N production

abstract:
  Two series of models and their yields are presented in this paper. The first
series consists of 20 Mo models with varying initial metallicity (solar down to
$Z=10^{-8}$) and rotation (Vini=0-600 km/s). The second one consists of models
with an initial metallicity of $Z=10^{-8}$, masses between 20 and 85 Mo and
average rotation velocities at these metallicities (Vini=600-800 km/s). The
most interesting models are the models with $Z=10^{-8}$ ([Fe/H]=~-6.6). In the
course of helium burning, carbon and oxygen are mixed into the hydrogen burning
shell. This boosts the importance of the shell and causes a reduction of the
size of the CO core. Later in the evolution, the hydrogen shell deepens and
produces large amount of primary nitrogen. For the most massive models (M>~60
Mo), significant mass loss occurs during the red supergiant stage. This mass
loss is due to the surface enrichment in CNO elements via rotational and
convective mixing.
  The yields of the fast rotating 20 Mo models can best reproduce (within our
study) the observed abundances at the surface of extremely metal poor (EMP)
stars. The wind of the massive models can reproduce the CNO abundances of the
carbon--rich UMPs, in particular for the most metal poor star known to date,
HE1327-2326.


title:
A localised subgrid scale model for fluid dynamical simulations in
  astrophysics I: Theory and numerical tests

abstract:
  We present a one-equation subgrid scale model that evolves the turbulence
energy corresponding to unresolved velocity fluctuations in large eddy
simulations. The model is derived in the context of the Germano consistent
decomposition of the hydrodynamical equations. The eddy-viscosity closure for
the rate of energy transfer from resolved toward subgrid scales is localised by
means of a dynamical procedure for the computation of the closure parameter.
Therefore, the subgrid scale model applies to arbitrary flow geometry and
evolution. For the treatment of microscopic viscous dissipation a
semi-statistical approach is used, and the gradient-diffusion hypothesis is
adopted for turbulent transport. A priori tests of the localised eddy-viscosity
closure and the gradient-diffusion closure are made by analysing data from
direct numerical simulations. As an a posteriori testing case, the large eddy
simulation of thermonuclear combustion in forced isotropic turbulence is
discussed. We intend the formulation of the subgrid scale model in this paper
as a basis for more advanced applications in numerical simulations of complex
astrophysical phenomena involving turbulence.


title:
A localised subgrid scale model for fluid dynamical simulations in
  astrophysics II: Application to type Ia supernovae

abstract:
  The dynamics of the explosive burning process is highly sensitive to the
flame speed model in numerical simulations of type Ia supernovae. Based upon
the hypothesis that the effective flame speed is determined by the unresolved
turbulent velocity fluctuations, we employ a new subgrid scale model which
includes a localised treatment of the energy transfer through the turbulence
cascade in combination with semi-statistical closures for the dissipation and
non-local transport of turbulence energy. In addition, subgrid scale buoyancy
effects are included. In the limit of negligible energy transfer and transport,
the dynamical model reduces to the Sharp-Wheeler relation. According to our
findings, the Sharp-Wheeler relation is insuffcient to account for the
complicated turbulent dynamics of flames in thermonuclear supernovae. The
application of a co-moving grid technique enables us to achieve very high
spatial resolution in the burning region. Turbulence is produced mostly at the
flame surface and in the interior ash regions. Consequently, there is a
pronounced anisotropy in the vicinity of the flame fronts. The localised
subgrid scale model predicts significantly enhanced energy generation and less
unburnt carbon and oxygen at low velocities compared to earlier simulations.


title: PopII 1/2 stars: very high N14 and low O16 yields

abstract:
  Nine 20 Mo models were computed with metallicities ranging from solar,
through $Z=10^{-5}$ ([Fe/H]=~-3.1) down to $Z=10^{-8}$ ([Fe/H]=~-6.1) and with
initial rotational velocities between 0 and 600 km/s to study the impact of
initial metallicity and rotational velocity. The very large amounts of N14
observed (~0.03 Mo) are only produced at $Z=10^{-8}$ (PopII 1/2). The strong
dependence of the N14 yields on rotation and other parameters like the initial
mass and metallicity may explain the large scatter in the observations of N14
abundance. The metallicity trends are best reproduced by the models with
Omega_ini/Omega_c=~0.75, which is slightly above the mean observed value for OB
solar metallicity stars. Indeed, in the model with Vini=600 km/s at
$Z=10^{-8}$, the O16 yield is reduced due to strong mixing. This allows in
particular to reproduce the upturn for C/O and a slightly decreasing [C/Fe],
which are observed below [Fe/H]=~-3.


title: Stellar evolution of massive stars at very low metallicities

abstract:
  Recently, measurements of abundances in extremely metal poor (EMP) stars have
brought new constraints on stellar evolution models. In an attempt to explain
the origin of the abundances observed, we computed pre--supernova evolution
models, explosion models and the related nucleosynthesis. In this paper, we
start by presenting the pre-SN models of rotating single stars with
metallicities ranging from solar metallicity down to almost metal free. We then
review key processes in core-collapse and bounce, before we integrate them in a
simplistic parameterization for 3D MHD models, which are well underway and
allow one to follow the evolution of the magnetic fields during collapse and
bounce. Finally, we present explosive nucleosynthesis results including
neutrino interactions with matter, which are calculated using the outputs of
the explosion models.
  The main results of the pre-SN models are the following. First, primary
nitrogen is produced in large amount in models with an initial metallicity
$Z=10^{-8}$. Second, at the same metallicity of $Z=10^{-8}$ and for models with
an initial mass larger than about 60 Mo, rotating models may experience heavy
mass loss (up to more than half of the initial mass of the star). The chemical
composition of these winds can qualitatively reproduce the abundance patterns
observed at the surface of carbon-rich EMP stars. Explosive nucleosynthesis
including neutrino-matter interactions produce improved abundances for iron
group elements, in particular for scandium and zinc. It also opens the way to a
new neutrino and proton rich process ($\nu$p-process) able to contribute to the
nucleosynthesis of elements with A > 64. (Abridged)


title:
Spectral states of the X-ray binary IGR J17091--3624 observed by
  INTEGRAL and RXTE

abstract:
  IGR J17091-3624 was discovered in 2003 April by INTEGRAL/IBIS during its
Galactic Centre Deep Exposure programme. The source was initially detectable
only in the 40--100 keV range, but after two days was also detected in the
15-40 keV range. Its flux had by then increased to 40 mCrab and 25 mCrab in the
15-40 keV and 40-100 keV bands respectively. RXTE observed the source
simultaneously on 2003 April 20, with an effective exposure of 2 ksec. We
report here the spectral and temporal evolution of the source, which shows a
transition between the hard and soft states. We analyse in detail the
RXTE/INTEGRAL Comptonised spectrum of the hard state as well as the JEM-X
detection of a blackbody component during the source softening. Even though the
source spectral behaviour and time variability show a similarity with the
outburst of the black-hole candidate IGR J17464-3213 (= H1743-322), observed by
INTEGRAL in 2003, the nature of its compact object (BH vs. NS) remains
controversial.


title: Post-AGB stars as testbeds of nucleosynthesis in AGB stars

abstract:
  We construct a data base of 125 post-AGB objects (including R CrB and extreme
helium stars) with published photospheric parameters (effective temperature and
gravity) and chemical composition. We estimate the masses of the post-AGB stars
by comparing their position in the (log Teff, log g) plane with theoretical
evolutionary tracks of different masses. We construct various diagrams, with
the aim of finding clues to AGB nucleosynthesis. This is the first time that a
large sample of post-AGB stars has been used in a systematic way for such a
purpose and we argue that, in several respects, post-AGB stars should be more
powerful than planetary nebulae to test AGB nucleosynthesis. Our main findings
are that: the vast majority of objects which do not show evidence of N
production from primary C have a low stellar mass (M* < 0.56 Msun); there is no
evidence that objects which did not experience 3rd dredge-up have a different
stellar mass distribution than objects that did; there is clear evidence that
3rd dredge-up is more efficient at low metallicity. The sample of known
post-AGB stars is likely to increase significantly in the near future thanks to
the ASTRO-F and follow-up observations, making these objects even more
promising as testbeds for AGB nucleosynthesis.


title: Evolution of field spiral galaxies up to redshifts z=1

abstract:
  We have gained VLT/FORS spectra and HST/ACS images of a sample of 220 distant
field spiral galaxies. Spatially resolved rotation curves were extracted and
fitted with synthetic velocity fields that take into account all geometric and
observational effects, like blurring due to the slit width and seeing
influence. The maximum rotation velocity Vmax could be determined for 124
galaxies that cover the redshift range 0.1<z<1.0. The luminosity-rotation
velocity distribution of this sample is offset from the Tully-Fisher relation
(TFR) of local low-mass spirals, whereas the distant high-mass spirals are
compatible with the local TFR. We show that the slope of the local and the
intermediate-z TFR would be in compliance if its scatter decreased by more than
a factor of 3 between z~0.5 and z~0. On the other hand, the distant
low-luminosity disks have much lower stellar M/L ratios than their local
counterparts, while high-luminosity disks barely evolved in M/L over the
covered redshift range. This could be the manifestation of the "downsizing"
effect, i.e. the succesive shift of the peak of star formation from high-mass
to low-mass galaxies towards lower redshifts. This trend might be canceled out
in the TF diagram due to the simultaneous evolution of multiple parameters. We
also estimate the ratios between stellar and total masses, finding that these
remained constant since z=1, as would be expected in the context of
hierarchically growing structure. (Abridged)


title:
ESO-VLT optical spectroscopy of BL Lac objects: II. New redshifts,
  featureless objects and classification assessments

abstract:
  We report on ESO Very Large Telescope optical spectroscopy of 42 BL Lacertae
objects of unknown redshift. Nuclear emission lines were observed in 12
objects, while for another six we detected absorption features due to their
host galaxy. The new high S/N spectra therefore allow us to measure the
redshift of 18 sources. Five of the observed objects were reclassified either
as stars or quasars, and one is of uncertain nature. For the remaining 18 the
optical spectra appear without intrinsic features in spite of our ability to
measure rather faint (EW nearly 0.1 Angstrom) spectral lines. For the latter
sources a lower limit to the redshift was set exploiting the very fact that the
absorption lines of the host galaxy are undetected on the observed spectra.


title: Gamma Ray Bursts as Cosmological Probes

abstract:
  We discuss the prospects of using Gamma Ray Bursts (GRBs) as high-redshift
distance estimators, and consider their use in the study of two dark energy
models, the Generalized Chaplygin Gas (GCG), a model for the unification of
dark energy and dark matter, and the XCDM model, a model where a generic dark
energy fluid like component is described by the equation of state, $p= \omega
\rho$. Given that the GRBs range of redshifts is rather high, it turns out that
they are not very sensitive to the dark energy component, being however, fairly
good estimators of the amount of dark matter in the Universe.


title: X-rays from HH210 in the Orion nebula

abstract:
  We report the detection during the Chandra Orion Ultradeep Project (COUP) of
two soft, constant, and faint X-ray sources associated with the Herbig-Haro
object HH210. HH210 is located at the tip of the NNE finger of the emission
line system bursting out of the BN-KL complex, northwest of the Trapezium
cluster in the OMC-1 molecular cloud. Using a recent Halpha image obtained with
the ACS imager on board HST, and taking into account the known proper motions
of HH210 emission knots, we show that the position of the brightest X-ray
source, COUP703, coincides with the emission knot 154-040a of HH210, which is
the emission knot of HH210 having the highest tangential velocity (425 km/s).
The second X-ray source, COUP704, is located on the complicated emission tail
of HH210 close to an emission line filament and has no obvious optical/infrared
counterpart. Spectral fitting indicates for both sources a plasma temperature
of ~0.8 MK and absorption-corrected X-ray luminosities of about 1E30 erg/s
(0.5-2.0 keV). These X-ray sources are well explained by a model invoking a
fast-moving, radiative bow shock in a neutral medium with a density of ~12000
cm^{-3}. The X-ray detection of COUP704 therefore reveals, in the complicated
HH210 region, an energetic shock not yet identified at other wavelengths.


title:
Stellar kinematics for the central spheroid in the Polar Disk Galaxy
  NGC4650A

abstract:
  We have obtained high angular resolution, high signal-to-noise spectra of the
Calcium triplet absorption lines on the photometric axes of the stellar
spheroid in the polar disk galaxy NGC4650A. Along the major axis, the observed
rotation and velocity dispersion measurements show the presence of a
kinematically decoupled nucleus, and a flat velocity dispersion profile. The
minor axis kinematics is determined for the first time: along this direction
some rotation is measured, and the velocity dispersion is nearly constant and
slightly increases at larger distances from the center. The new high resolution
kinematic data suggest that the stellar component in NGC4650A resembles a
nearly-exponential oblate spheroid supported by rotation. The main implications
of these results on the previous mass models for NGC4650A are discussed.
Moreover, the new kinematic data set constraints on current models for the
formation scenarios of Polar Ring Galaxies (PRGs), supporting a slow accretion
rather then a secondary strong dissipative event.


title: Galactic Bulge Microlensing Optical Depth from EROS-2

abstract:
  We present a new EROS-2 measurement of the microlensing optical depth toward
the Galactic Bulge. Light curves of $5.6\times 10^{6}$ clump-giant stars
distributed over $66 \deg^2$ of the Bulge were monitored during seven Bulge
seasons. 120 events were found with apparent amplifications greater than 1.6
and Einstein radius crossing times in the range $5 {\rm d}<t_\e <400 {\rm d}$.
This is the largest existing sample of clump-giant events and the first to
include northern Galactic fields. In the Galactic latitude range
$1.4\degr<|b|<7.0\degr$, we find $\tau/10^{-6}=(1.62 \pm 0.23)\exp[-a(|b|-3
{\rm deg})]$ with $a=(0.43 \pm0.16)\deg^{-1}$. These results are in good
agreement with our previous measurement, with recent measurements of the MACHO
and OGLE-II groups, and with predictions of Bulge models.


title: The possible source of the UHECR observed in AGASA Experiment

abstract:
  In this paper the results of AGASA experiment is discussed. It is argued that
the UHECR radiation is composed of long lived particles with mass, where is the
proton mass. Keywords: UHECR; Modified Lorentz transformation; New particles.
PACS: 96.50.S, 96.50sb, 13.85Tp


title: SDSSJ212531.92-010745.9 - the first definite PG1159 close binary system

abstract:
  The archival spectrum of SDSSJ212531.92-010745.9 shows not only the typical
signature of a PG1159 star, but also indicates the presence of a companion. Our
aim was the proof of the binary nature ofthis object and the determination of
its orbital period.We performed time-series photometry of
SDSSJ212531.92-010745.9. We observed the object during 10 nights, spread over
one month, with the Tuebingen 80cm and the Goettingen 50cm telescopes. We
fitted the observed light curve with a sine and simulated the light curve of
this system with the nightfall program. Furthermore, we compared the spectrum
of SDSSJ212531.92-010745.9 with NLTE models, the results of which also
constrain the light curve solution. An orbital period of 6.95616(33)h with an
amplitude of 0.354(3)mag is derived from our observations. A pulsation period
could not be detected. For the PG1159 star we found, as preliminary results
from comparison with our NLTE models, Teff about 90000K, log g about 7.60, and
the abundance ratio C/He = 0.05 by number fraction. For the companion we
obtained with a mean radius of 0.4 +/- 0.1 Rsol, a mass of 0.4 +/- 0.1 Msol,
and a temperature of 8200K on the irradiated side, good agreement between the
observed light curve and the nightfall simulation, but we do not regard those
values as final.


title: The non-perturbative regime of cosmic structure formation

abstract:
  This paper focusses on the barely understood gap between the weakly nonlinear
regime of structure formation and the onset of the virialized regime. While the
former is accessed through perturbative calculations and the latter through
virialization conditions incorporating dynamical stresses that arise in
collisionless self-gravitating systems due to velocity dispersion forces, the
addressed regime can only be understood through non-perturbative models. We
here present an exact Lagrangian integral that provides a tool to access this
regime. We derive a transport equation for the peculiar-gravitational field
strength and integrate it along comoving trajectories of fluid elements. The
so-obtained integral provides an exact expression that solves the longitudinal
gravitational field equation in general. We argue that this integral provides a
powerful approximation beyond the Lagrangian perturbative regime, and discuss
its relation to known approximations, among them Lagrangian perturbation
solutions including the Zel'dovich approximation and approximations for
adhesive gravitational clustering, including the adhesion approximation.
Furthermore, we propose an iteration scheme for a systematic analytical and
numerical construction of trajectory fields. The integral may also be employed
to improve inverse reconstruction techniques.


title: Big-Bang nucleosynthesis (Particle Data Group mini-review)

abstract:
  A critical review is given of the current status of cosmological
nucleosynthesis. In the framework of the Standard Model with 3 types of
relativistic neutrinos, the baryon-to-photon ratio, $\eta$, corresponding to
the inferred primordial abundances of deuterium and helium-4 is consistent with
the independent determination of $\eta$ from WMAP observations of anisotropies
in the cosmic microwave background. However the primordial abundance of
lithium-7 inferred from observations is significantly below its expected value.
Taking systematic uncertainties in the abundance estimates into account, there
is overall concordance in the range $\eta = (4.7 - 6.5) x 10^{-10}$ @ 95% c.l.
(corresponding to a cosmological baryon density $\Omega_B h^2$ = 0.017 -
0.024). The D and He-4 abundances, together with the CMB determination of
$\eta$, provide the bound $N_\nu = 3.24 \pm 1.2$ @ 95% c.l. on the effective
number of neutrino species. Other constraints on new physics are discussed
briefly.


title: A Physical Orbit for the High Proper Motion Binary HD 9939

abstract:
  We report spectroscopic and interferometric observations of the high-proper
motion double-lined binary system HD 9939, with an orbital period of
approximately 25 days. By combining our radial-velocity and visibility
measurements we estimate the system physical orbit and derive dynamical masses
for the components of $M_A = 1.072 \pm 0.014$ M$_{\sun}$ and $M_B = 0.8383 \pm
0.0081$ M$_{\sun}$; fractional errors of 1.3% and 1.0%, respectively. We also
determine a system distance of $42.23 \pm 0.21$ pc, corresponding to an orbital
parallax of $\pi_{\rm orb} = 23.68 \pm 0.12$ mas. The system distance and the
estimated brightness difference between the stars in $V$, $H$, and $K$ yield
component absolute magnitudes in these bands. By spectroscopic analysis and
spectral energy distribution modeling we also estimate the component effective
temperatures and luminosities as $T_{\rm eff}^A = 5050 \pm 100$ K and $T_{\rm
eff}^B = 4950 \pm 200$ K and $L_A$ = 2.451 $\pm$ 0.041 $L_{\sun}$ and $L_B$ =
0.424 $\pm$ 0.023 $L_{\sun}$.
  Both our spectral analysis and comparison with stellar models suggest that HD
9939 has elemental abundances near solar values. Further, comparison with
stellar models suggests the HD 9939 primary has evolved off the main sequence
and appears to be traversing the Hertzsprung gap as it approaches the red giant
phase of its evolution. Our measurements of the primary properties provide new
empirical constraints on stellar models during this particularly dynamic
evolutionary phase. That HD 9939 is currently in a relatively short-lived
evolutionary state allows us to estimate the system age as 9.12 $\pm$ 0.25 Gyr.
In turn the age and abundance of the system place a potentially interesting, if
anecdotal, constraint on star formation in the galactic disk.


title:
Searching for links between magnetic fields and stellar evolution. I. A
  survey of magnetic fields in open cluster A- and B-type stars with FORS1

abstract:
  About 5% of upper main sequence stars are permeated by a strong magnetic
field, the origin of which is still matter of debate.
  With this work we provide observational material to study how magnetic fields
change with the evolution of stars on the main sequence, and to constrain
theory explaining the presence of magnetic fields in A and B-type stars.
  Using FORS1 in spectropolarimetric mode at the ESO VLT, we have carried out a
survey of magnetic fields in early-type stars belonging to open clusters and
associations of various ages.
  We have measured the magnetic field of 235 early-type stars with a typical
uncertainty of about 100 G. In our sample, 97 stars are Ap or Bp stars. For
these targets, the median error bar of our field measurements was about 80 G. A
field has been detected in about 41 of these stars, 37 of which were not
previously known as magnetic stars. For the 138 normal A and B-type stars, the
median error bar was 136 G, and no field was detected in any of them.


title: Stable Models of superacceleration

abstract:
  We discuss an instability in a large class of models where dark energy is
coupled to matter. In these models the mass of the scalar field is much larger
than the expansion rate of the Universe. We find models in which this
instability is absent, and show that these models generically predict an
apparent equation of state for dark energy smaller than -1, i.e.,
superacceleration. These models have no acausal behavior or ghosts.


title: Tertiary companions to close spectroscopic binaries

abstract:
  We have surveyed a sample of 165 solar-type spectroscopic binaries (SB) with
periods from 1 to 30 days for higher-order multiplicity. 62 targets have been
observed with the NACO adaptive optics system and 13 new physical tertiary
companions were detected. Another 12 new wide companions (5 still tentative)
were retrieved from the 2MASS sky survey. Our binaries belong to 161 stellar
systems; of these 64 are triple, 11 quadruple and 7 quintuple. After correction
for incomplete detection, the fraction of SBs with additional companions is 63%
+- 5%. We find that this fraction is a strong function of the SB period P,
reaching 96% for P<3d and dropping to 36% for P>12d. Period distributions of
SBs with and without tertiaries are significantly different, but their mass
ratio distributions are identical. New statistical data on the multiplicity of
close SBs indicate that their periods and mass ratios were established very
early, but periods of SBs within triples were further shortened by angular
momentum exchange with companions.


title:
A Modified Higher Order Godunov's Scheme for Stiff Source Conservative
  Hydrodynamics

abstract:
  Hyperbolic conservation laws with stiff source terms appear in the study of a
variety of physical systems. Early work showed that the use of formally
second-order accurate semi-implicit methods could lead to a substantial loss of
accuracy, due to inconsistencies between the flux calculation without sources
and the limiting equilibrium behavior of the gas. In this paper we present an
efficient second order accurate scheme to treat stiff source terms within the
framework of higher order Godunov's methods. We employ Duhamel's formula to
devise a modified predictor step which accounts for the effects of stiff source
terms on the conservative fluxes and recovers the correct isothermal behavior
in the limit of an infinite cooling/reaction rate. Source term effects on the
conservative quantities are fully accounted for by means of a one-step, second
order accurate semi-implicit corrector scheme based on the deferred correction
method of Dutt et. al. We demostrate the accurate, stable and convergent
results of the proposed method through a set of benchmark problems for a
variety of stiffness conditions and source types.


title: A Full Loss Cone For Triaxial Galaxies

abstract:
  Stars and compact objects that plunge toward a black hole are either 1)
captured, emitting gravitational waves as the orbit decays, 2) tidally
disrupted, leaving a disc of baryonic material, 3) scattered to a large radius,
where they may thereafter avoid encounters with the black hole or 4) swallowed
whole, contributing to black hole growth. These processes occur on a dynamical
time, which implies that for a static spherically symmetric stellar system, the
loss cone is quickly emptied. However, most elliptical galaxies and spiral
bulges are thought to be triaxial in shape. The centrophilic orbits comprising
the backbone of a triaxial galaxy have been suggested as one way to keep the
loss cone around a supermassive black hole filled with stars, stellar remnants,
and intermediate mass black holes. We investigate the evolution of the loss
cone population in a triaxial galaxy model with high resolution N-body
simulations. We find that enough regular orbits flow through angular momentum
space to maintain a full loss cone for a Hubble time. This increases the
astrophysical capture rate by several orders of magnitude. In the Milky Way,
for example, we find that the white dwarf capture rate can be as high as
$10^{-5}$ per year, 100 times larger than previous estimates based on spherical
models for the bulge.


title: The Parallax and Proper Motion of PSR J0030+0451

abstract:
  We report the parallax and proper motion of millisecond pulsar J0030+0451,
one of thirteen known isolated millisecond pulsars in the disk of the Galaxy.
We obtained more than 6 years of monthly data from the 305 m Arecibo telescope
at 430 MHz and 1410 MHz. We measure the parallax of PSR J0030+0451 to be 3.3
+/- 0.9 mas, corresponding to a distance of 300 +/- 90 pc. The Cordes and Lazio
(2002) model of galactic electron distribution yields a dispersion measure
derived distance of 317 pc which agrees with our measurement. We place the
pulsar's transverse space velocity in the range of 8 to 17 km/s, making this
pulsar one of the slowest known. We perform a brief census of velocities of
isolated versus binary millisecond pulsars. We find the velocities of the two
populations are indistinguishable. However, the scale height of the binary
population is twice that of the isolated population and the luminosity
functions of the two populations are different. We suggest that the scale
height difference may be an artifact of the luminosity difference.


title: The Small-Scale Environment of Quasars

abstract:
  Where do quasars reside? Are quasars located in environments similar to those
of typical L* galaxies, and, if not, how do they differ? An answer to this
question will help shed light on the triggering process of quasar activity. We
use the Sloan Digital Sky Survey to study the environment of quasars and
compare it directly with the environment of galaxies. We find that quasars (M_i
< -22, z < 0.4) are located in higher local overdensity regions than are
typical L* galaxies. The enhanced environment around quasars is a local
phenomenon; the overdensity relative to that around L* galaxies is strongest
within 100 kpc of the quasars. In this region, the overdensity is a factor of
1.4 larger than around L* galaxies. The overdensity declines monotonically with
scale to nearly unity at ~1 Mpc, where quasars inhabit environments comparable
to those of L* galaxies. The small-scale density enhancement depends on quasar
luminosity, but only at the brightest end: the most luminous quasars reside in
higher local overdensity regions than do fainter quasars. The mean overdensity
around the brightest quasars (M_i < -23.3) is nearly three times larger than
around L* galaxies while the density around dimmer quasars (M_i = -22.0 to
-23.3) is ~1.4 times that of L* galaxies. By ~0.5 Mpc, the dependence on quasar
luminosity is no longer significant. The overdensity on all scales is
independent of redshift to z = 0.4. The results suggest a picture in which
quasars typically reside in L* galaxies, but have a local excess of neighbors
within ~0.1 - 0.5 Mpc; this local density excess likely contributes to the
triggering of quasar activity through mergers and other interactions.


title: Microlensing of the Lensed Quasar SDSS0924+0219

abstract:
  We analyze V, I and H band HST images and two seasons of R-band monitoring
data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that
image D is a point-source image of the quasar at the center of its host galaxy.
We can easily track the host galaxy of the quasar close to image D because
microlensing has provided a natural coronograph that suppresses the flux of the
quasar image by roughly an order of magnitude. We observe low amplitude,
uncorrelated variability between the four quasar images due to microlensing,
but no correlated variations that could be used to measure a time delay. Monte
Carlo models of the microlensing variability provide estimates of the mean
stellar mass in the lens galaxy (0.02 Msun < M < 1.0 Msun), the accretion disk
size (the disk temperature is 5 x 10^4 K at 3.0 x 10^14 cm < rs < 1.4 x 10^15
cm), and the black hole mass (2.0 x 10^7 Msun < MBH \eta_{0.1}^{-1/2}
(L/LE)^{1/2} < 3.3 x 10^8 Msun), all at 68% confidence. The black hole mass
estimate based on microlensing is consistent with an estimate of MBH = 7.3 +-
2.4 x 10^7 Msun from the MgII emission line width. If we extrapolate the
best-fitting light curve models into the future, we expect the the flux of
images A and B to remain relatively stable and images C and D to brighten. In
particular, we estimate that image D has a roughly 12% probability of
brightening by a factor of two during the next year and a 45% probability of
brightening by an order of magnitude over the next decade.


title: Multiple stars: designation, catalogues, statistics

abstract:
  Discussion of the designation of multiple-star components leads to a
conclusion that, apart from components, we need to designate systems and
centers-of-mass. The hierarchy is coded then by simple links to parent. This
system is adopted in the multiple star catalogue, now available on-line. A
short review of multiple-star statistics is given: the frequency of different
multiplicities in the field, periods of spectroscopic sub-systems, relative
orbit orientation, empirical stability criterion, and period-period diagram
with its possible connection to formation of multiple stars.


title:
Bulk viscosity of a gas of neutrinos and coupled scalar particles, in
  the era of recombination

abstract:
  Bulk viscosity may serve to damp sound waves in a system of neutrinos coupled
to very light scalar particles, in the era after normal neutrino decoupling but
before recombination. We calculate the bulk viscosity parameter in a minimal
scheme involving the coupling of the two systems. We add some remarks on the
bulk viscosity of a system of fully ionized hydrogen plus photons.


title:
Explaining the Color Distributions of Globular Cluster Systems in
  Elliptical Galaxies

abstract:
  The colors of globular clusters in most of large elliptical galaxies are
bimodal. This is generally taken as evidence for the presence of two cluster
subpopulations that have different geneses. However, here we find that, because
of the non-linear nature of the metallicity-to-color transformation, a coeval
group of old clusters with a unimodal metallicity spread can exhibit color
bimodality. The models of cluster colors indicate that the horizontal-branch
stars are the main drivers behind the empirical non-linearity. We show that the
scenario gives simple and cohesive explanations for all the key observations,
and could simplify theories of elliptical galaxy formation.


title:
Model Atmospheres for Irradiated Giant Stars: Implications for the
  Galactic Center

abstract:
  Irradiation of a stellar atmosphere by an external source (e.g. an AGN)
changes its structure and therefore its spectrum. Using a state-of-the-art
stellar atmosphere code, we calculate the infrared spectra of such irradiated
and transformed stars. We show that the original spectrum of the star, which is
dominated by molecular bands, changes dramatically when irradiated even by a
low-luminosity AGN ($L_{\rm X} = 10^{33}$ erg s$^{-1}$), becoming dominated by
atomic lines in absorption. We study the changes in the spectrum of low-mass
carbon- and oxygen-rich giant stars as they are irradiated by a modest AGN,
similar to the one at the Galactic center (GC). The resulting spectra are
similar to those of the faintest S-cluster stars observed in the GC. The
spectrum of a star irradiated by a much brighter AGN, like that powered by a
tidally disrupted star, is very different from that of any star currently
observed near the GC. For the first time we have discovered that the structure
of the atmosphere of an irradiated giant changes dramatically and induces a
double inversion layer. We show that irradiation at the current level can
explain the observed trend of CO band intensities decreasing as a function of
increasing proximity to Sg $A^{*}$. This may indicate that (contrary to
previous claims) there is no paucity of old giants in the GC, which coexist
simultaneously with young massive stars.


title: GRB Host Studies (GHostS)

abstract:
  The GRB Host Studies (GHostS) is a public archive collecting observed
quantities of GRB host galaxies. At this time (January 2006) it contains
information on 32 GRB hosts, i.e. about half of the total number of GRBs with
known redshift. Here we present some preliminary statistical analysis of the
sample, e.g. the total stellar mass, metallicity and star formation rate for
the hosts. We found that these are generally low-mass objects, with 79% having
M_*<10^10 M_sun. The total stellar mass and the metallicity for a subsample of
7 hosts at 0.4<z<1 are consistent with the mass-metallicity relation recently
found for normal star-forming galaxies in the same redshift interval. At least
56% of the total sample are bursty galaxies: their growth time-scale (the time
required to form the observed stellar mass assuming that the observed SFR is
constant over the entire life of the galaxy) is shorter than 400 Myr.


title:
Comparison of 13CO Line and Far-Infrared Continuum Emission as a
  Diagnostic of Dust and Molecular Gas Physical Conditions: I. Motivation and
  Modeling

abstract:
  Determining temperatures in molecular clouds from ratios of CO rotational
lines or from ratios of continuum emission in different wavelength bands
suffers from reduced temperature sensitivity in the high-temperature limit. In
theory, the ratio of far-IR, submillimeter, or millimeter continuum to that of
a 13CO (or C18O) rotational line can place reliable upper limits on the
temperature of the dust and molecular gas. Consequently, far-infrared continuum
data from the {\it COBE}/{\it DIRBE} instrument and Nagoya 4-m $\cOone$
spectral line data were used to plot 240$\um$/13CO J=1-0 intensity ratios
against 140$\um$/240$\um$ dust color temperatures, allowing us to constrain the
multiparsec-scale physical conditions in the Orion$ $A and B molecular clouds.
  The best-fitting models to the Orion clouds consist of two components: a
component near the surface of the clouds that is heated primarily by a very
large-scale (i.e. $\sim 1 $kpc) interstellar radiation field and a component
deeper within the clouds. The former has a fixed temperature and the latter has
a range of temperatures that varies from one sightline to another. The models
require a dust-gas temperature difference of 0$\pm 2 $K and suggest that 40-50%
of the Orion clouds are in the form of dust and gas with temperatures between 3
and 10$ $K. These results have a number implications that are discussed in
detail in later papers. These include stronger dust-gas thermal coupling and
higher Galactic-scale molecular gas temperatures than are usually accepted, an
improved explanation for the N(H$_2$)/I(CO) conversion factor, and ruling out
one dust grain alignment mechanism.


title:
A Braking Index for the Young, High-Magnetic-Field, Rotation-Powered
  Pulsar in Kes 75

abstract:
  We present the first phase-coherent measurement of a braking index for the
young, energetic rotation-powered pulsar PSR J1846-0258. This 324 ms pulsar is
located at the center of the supernova remnant Kes 75 and has a characteristic
age of tau_c = 723 years, a spin-down energy of 8.3x10^{36}erg/s, and inferred
magnetic field of 4.9x10^{13} G. Two independent phase-coherent timing
solutions are derived which together span 5.5 yr of data obtained with the
Rossi X-ray Timing Explorer. In addition, a partially phase-coherent timing
analysis confirms the fully phase-coherent result. The measured value of the
braking index, n=2.65+/-0.01, is significantly less than 3, the value expected
from magnetic dipole radiation, implying another physical process must
contribute to the pulsar's rotational evolution. Assuming the braking index has
been constant since birth, we place an upper limit on the spin-down age of
J1846-0258 of 884 yr, the smallest age estimate of any rotation-powered pulsar.


title:
Gemini/GMOS Spectra of Globular Clusters in the Virgo Giant Elliptical
  NGC 4649

abstract:
  NGC 4649 (M60) is one of a handful of giant Virgo ellipticals. We have
obtained Gemini/GMOS spectra for 38 GCs associated with this galaxy. Applying
the multi-index chi^2 minimisation technique of Proctor & Sansom (2002) with
the single stellar population models of Thomas, Maraston & Korn (2004) we
derive ages, metallicities and alpha-element abundance ratios. We find several
young (2--3 Gyr old) super-solar metallicity GCs, while the majority are old
(>10 Gyrs), spanning a range of metallicities from solar to [Z/H]=-2. At least
two of these young GCs are at large projected radii of 17-20 kpc. The galaxy
itself shows no obvious signs of a recent starburst, interaction or merger. A
trend of decreasing alpha-element ratio with increasing metallicity is found.


title: Occurrence Frequency of CO Outflows in Massive Protostellar Candidates

abstract:
  We mapped 12 massive protostellar candidates in the CO J=2-1 line, which in
combination with Zhang et al. (2005) completes an unbiased survey of outflows
for all 48 sources with l>50^o in a sample of 101 massive protostellar
candidates. We detected outflows in 10 sources, implying 88% occurrence
frequency of outflows for the 48 sources. This supports the conclusion of
previous studies that bipolar outflows are an integral component in the
formation process of massive stars. The vast majority of the observed outflows
are much more massive (>10~Mo) and energetic (>100~Mo~km/s) than outflows from
low-mass protostars. They also have large mass outflow rates
(>2x10^{-4}~Mo/yr), suggesting large (~1x10^{-4}~Mo/yr) accretion rates
sufficient to overcome radiation pressure of the central massive protostars. We
compared the frequency distribution of collimation factors of 40 massive
outflows including those of this study with that of 36 low-mass outflows from
the literature, and found NO significant difference between the two. All these
results are consistent with the suggestion that massive stars form through
accretion as do low-mass stars but with much higher accretion rates.


title: Polarimetry with NICMOS

abstract:
  NICMOS cameras 1 and 2 each carry a set of three polarizing elements to
provide high sensitivity observations of linearly polarized light. The
polarizers are bandpass limited and provide diffraction-limited imaging in
camera 1 at 0.8 - 1.3um, and in camera 2 at 1.9-2.1um. The NICMOS design
specified the intra-camera primary axis angles of the polarizers to be
differentially offset by 120 degree, and with identical polarizing efficiency
and transmittance. While this ideal concept was not strictly achieved, accurate
polarimetry in both cameras, over their full (11" and ~19.2" square) fields of
view was enabled through ground and on-orbit calibration of the as-built and
HST-integrated systems. The Cycle 7 & 7N calibration program enabled and
demonstrated excellent imaging polarimetric performance with uncertainties in
measured polarization fractions <=1%. After the installation of the NICMOS
Cooling System (NCS), the polarimetric calibration was re-established in Cycle
11, resulting in systemic performance comparable to (or better than) Cycle 7 &
7N. The NCS era NICMOS performance inspired the development of an earlier
conceived, but non-implemented, observing mode combining high contrast
coronagraphic imaging and polarimetry in camera 2. We successfully executed a
program to calibrate and commission the "Coronagraphic Polarimetry'' mode in
NICMOS in Cycle 13, and the mode was made available for GO use in Cycle 14. We
discuss the data reduction and calibration of direct and coronagraphic NICMOS
polarimetry. Importantly, NICMOS coronagraphic polarimetry provides unique
access to polarized light near bright targets over a range of spatial scales
intermediate between direct polarimetry and ground-based (coronagraphic)
polarimetry using adaptive optics.


title: Water Ice on the Satellite of Kuiper Belt Object 2003 EL61

abstract:
  We have obtained a near infrared spectrum of the brightest satellite of the
large Kuiper Belt Object, 2003 EL61. The spectrum has absorption features at
1.5 and 2.0 microns, indicating that water ice is present on the surface. We
find that the satellite's absorption lines are much deeper than water ice
features typically found on Kuiper Belt Objects. We argue that the unusual
spectrum indicates that the satellite was likely formed by impact and not by
capture.


title:
A multiwavelength study of the massive star forming region IRAS
  06055+2039 (RAFGL 5179)

abstract:
  We present a multiwavelength study of the massive star forming region
associated with IRAS 06055+2039 which reveals an interesting scenario of this
complex where regions are at different stages of evolution of star formation.
Narrow band near-infrared (NIR) observations were carried out with UKIRT-UFTI
in molecular hydrogen and Br$\gamma$ lines to trace the shocked and ionized
gases respectively. We have used 2MASS $J H K_{s}$ data to study the nature of
the embedded cluster associated with IRAS 06055+2039. We obtain a power-law
slope of 0.43$\pm$0.09 for the $K_{s}$-band Luminosity Function (KLF) which is
in good agreement with other young embedded clusters. We estimate an age of 2
-- 3 Myr for this cluster. The radio emission from the ionized gas has been
mapped at 610 and 1280 MHz using the Giant Metrewave Radio Telescope (GMRT),
India. Apart from the diffuse emission, the high resolution 1280 MHz map also
shows the presence of several discrete sources which possibly represent high
density clumps. The morphology of shocked molecular hydrogen forms an arc
towards the N-E of the central IRAS point source and envelopes the radio
emission. Submillimetre emission using JCMT-SCUBA show the presence of a dense
cloud core which is probably at an earlier evolutionary stage compared to the
ionized region with shocked molecular gas lying in between the two. Emission
from warm dust and the Unidentified Infrared Bands (UIBs) have been estimated
using the mid-infrared (8 -- 21 $\mu$m) data from the MSX survey. From the
submillimetre emission at 450 and 850 $\mu$m the total mass of the cloud is
estimated to be $\sim$ 7000 -- 9000 $\rm M_{\odot}$.


title: A Universe with both acceleration and deceleration

abstract:
  A model for the universe with both acceleration and deceleration is given.
The model incorporates an initial acceleration, then a deceleration as has been
observed by Schaefer in respect of gamma ray bursts, a second phase of
acceleration that would explain the observations by Perlmutter et.al. on
supernovae, and a second phase of deceleration in the future.


title:
AMS02 Ecal gamma trigger performance measured at the October 2004 CERN
  test beam

abstract:
  Test beam data collected in October 2004 at CERN PS to validate the AMS02
Ecal Intermediate Board (EIB) are analyzed. After describing the experimental
setup and the event samples, results concerning noise measurement, trigger
efficiency and threshold accuracy are presented. They demonstrate that the EIB
fulfils the physics requirements. Therefore the analog part of the trigger is
validated, and hardware choices are also made towards the final device.


title: Cosmological constraints from galaxy clustering

abstract:
  In this manuscript I review the mathematics and physics that underpins recent
work using the clustering of galaxies to derive cosmological model constraints.
I start by describing the basic concepts, and gradually move on to some of the
complexities involved in analysing galaxy redshift surveys, focusing on the 2dF
Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky survey (SDSS).
Difficulties within such an analysis, particularly dealing with redshift space
distortions and galaxy bias are highlighted. I then describe current
observations of the CMB fluctuation power spectrum, and consider the importance
of measurements of the clustering of galaxies in light of recent experiments.
Finally, I provide an example joint analysis of the latest CMB and large-scale
structure data, leading to a set of parameter constraints.


title:
Dwarf nova oscillations and quasi-periodic oscillations in cataclysmic
  variables -- V. Results from an extensive survey

abstract:
  We present observations of dwarf nova oscillations (DNOs), longer period
dwarf nova oscillations (lpDNOs), and quasi-periodic oscillations (QPOs) in 13
cataclysmic variable stars (CVs). In the six systems WW Cet, BP CrA, BR Lup, HP
Nor, AG Hya, and V1193 Ori, rapid, quasi-coherent oscillations are detected for
the first time. For the remainder of the systems discussed we have observed
more classes of oscillations, in addition to the rapid oscillations they were
already known to display, or previously unknown aspects of the behaviour of
oscillations. The period of a QPO in RU Peg is seen to change by 84% over ten
nights of the decline from outburst--the largest evolution of a QPO period
observed to date. A period-luminosity relation similar to the relation that has
long been known to apply to DNOs is found for lpDNOs in X Leo; this is the
first clear case of lpDNO frequency scaling with accretion luminosity. WX Hyi
and V893 Sco are added to the small list of dwarf novae that have shown
oscillations in quiescence.


title: Black hole spin in GRS 1915+105

abstract:
  Microquasars are galactic black hole binary systems with radio jets which can
sometimes be spatially resolved to show superluminal motion. The first and best
known of this class of objects is GRS 1915+105, the brightest accreting source
in our Galaxy. There is persistent speculation that strong jet emission could
be linked to black hole spin. If so, the high spin should also be evident in
accretion disc spectra. We search the RXTE archive to find disc-dominated X-ray
spectra from this object, as these are the only ones which can give reliable
spin determinations by this method. Finding these is complicated by the rapid,
unique limit cycle variability, but we are able to identify such spectra by
going to the shortest possible time resolution (16 s). We fit them with a
simple multicolour disc blackbody diskbb, and with the best current model which
include full radiative transfer as well as relativistic effects bhspec. Both
these models show that the spin is intermediate, neither zero nor maximal.
bhspec, the most physical model, gives a value for the dimensionless spin of a*
\~ 0.7 for a distance of 12.5 kpc and inclination of 66 deg. This, together
with the range of spins 0.1 < a* < 0.8 derived using this method for other
black holes, suggests that jet emission is probably fundamentally powered by
gravity rather than spin, and implies that high-to-maximal spin is not a
pre-requisite for powerful relativistic jets.


title: The NICMOS Polarimetric Calibration

abstract:
  The value of accurately knowing the absolute calibration of the polarizing
elements in the Near Infrared Camera and Multi-Object Spectrometer (NICMOS)
becomes especially important when conducting studies which require measuring
degrees of polarization of close to 1% in the near infrared. We present a
comprehensive study of all previously observed polarimetric standards using the
NIC2 camera on NICMOS. Considering both pre- and post-NICMOS Cooling System
observations we find variations in the polarimetry consistent with the effects
of sub-pixel mis-alignments and the point spread function. We also measure
non-zero results from unpolarized standards indicating an instrumental
polarization of p ~ 1.2%, theta ~ 88degrees. The lack of polarized and
unpolarized standard stars with which to perform a comprehensive calibration
study means we cannot be confident that the current calibration will be
effective for a number of recent large NICMOS GO programs. Further observations
of polarimetric standards are needed in order to fully characterize the
behavior of NICMOS at around p=1%.


title: Collapse of Positronium and Vacuum Instability

abstract:
  A hypercritical value for the magnetic field is determined, which provides
the full compensation of the positronium rest mass by the binding energy in the
maximum symmetry state and disappearance of the energy gap separating the
electron-positron system from the vacuum. The compensation becomes possible
owing to the falling to the center phenomenon. The structure of the vacuum is
described in terms of strongly localized states of tightly mutually bound (or
confined) pairs. Their delocalization for still higher magnetic field, capable
of screening its further growth, is discussed.


title:
Optical Structure and Proper-Motion Age of the Oxygen-rich Supernova
  Remnant 1E 0102-7219 in the Small Magellanic Cloud

abstract:
  We present new optical emission-line images of the young SNR 1E 0102-7219
(E0102) in the SMC obtained with the HST Advanced Camera for Surveys (ACS).
E0102 is a member of the oxygen-rich class of SNRs showing strong oxygen, neon
, and other metal-line emissions in its optical and X-ray spectra, and an
absence of H and He. The progenitor of E0102 may have been a Wolf-Rayet star
that underwent considerable mass loss prior to exploding as a Type Ib/c or
IIL/b SN. The ejecta in this SNR are fast-moving (V > 1000 km/s) and emit as
they are compressed and heated in the reverse shock. In 2003, we obtained
optical [O III], H-alpha, and continuum images with the ACS Wide Field Camera.
The [O III] image captures the full velocity range of the ejecta, and shows
considerable high-velocity emission projected in the middle of the SNR that was
Doppler-shifted out of the narrow F502N bandpass of a previous Wide Field and
Planetary Camera 2 image from 1995. Using these two epochs separated by ~8.5
years, we measure the transverse expansion of the ejecta around the outer rim
in this SNR for the first time at visible wavelengths. From proper-motion
measurements of 12 ejecta filaments, we estimate a mean expansion velocity for
the bright ejecta of ~2000 km/s and an inferred kinematic age for the SNR of
\~2050 +/- 600 years. The age we derive from HST data is about twice that
inferred by Hughes et al.(2000) from X-ray data, though our 1-sigma error bars
overlap. Our proper-motion age is consistent with an independent optical
kinematic age derived by Eriksen et al.(2003) using spatially resolved [O III]
radial-velocity data. We derive an expansion center that lies very close to
X-ray and radio hotspots, which could indicate the presence of a compact
remnant (neutron star or black hole).


title: Early Dark Energy Cosmologies

abstract:
  We propose a novel parameterization of the dark energy density. It is
particularly well suited to describe a non-negligible contribution of dark
energy at early times and contains only three parameters, which are all
physically meaningful: the fractional dark energy density today, the equation
of state today and the fractional dark energy density at early times. As we
parameterize Omega_d(a) directly instead of the equation of state, we can give
analytic expressions for the Hubble parameter, the conformal horizon today and
at last scattering, the sound horizon at last scattering, the acoustic scale as
well as the luminosity distance. For an equation of state today w_0 < -1, our
model crosses the cosmological constant boundary. We perform numerical studies
to constrain the parameters of our model by using Cosmic Microwave Background,
Large Scale Structure and Supernovae Ia data. At 95% confidence, we find that
the fractional dark energy density at early times Omega_early < 0.06. This
bound tightens considerably to Omega_early < 0.04 when the latest Boomerang
data is included. We find that both the gold sample of Riess et. al. and the
SNLS data by Astier et. al. when combined with CMB and LSS data mildly prefer
w_0 < -1, but are well compatible with a cosmological constant.


title: Evidence for VHE Gamma-ray Emission from the Distant BL Lac PG 1553+113

abstract:
  The high-frequency peaked BL Lac PG 1553+113 was observed in 2005 with the
H.E.S.S. stereoscopic array of imaging atmospheric-Cherenkov telescopes in
Namibia. Using the H.E.S.S. standard analysis, an excess was measured at the
4.0 sigma level in these observations (7.6 hours live time). Three alternative,
lower-threshold analyses yield >5 sigma excesses. The observed integral flux
above 200 GeV is (4.8 +/- 1.3_{stat} +/- 1.0_{syst}) x10^{-12} cm^{-2} s^{-1},
and shows no evidence for variability. The measured energy spectrum is
characterized by a very soft power law (photon index of Gamma=4.0 +/- 0.6).
Although the redshift of PG 1553+113 is unknown, there are strong indications
that it is greater than z=0.25 and possibly larger than z=0.78. The observed
spectrum is interpreted in the context of VHE gamma-ray absorption by the
Extragalactic Background Light, and is used to place an upper limit on the
redshift of z<0.74.


title:
VLT spectroscopy and non-LTE modeling of the C/O-dominated accretion
  disks in two ultracompact X-ray binaries

abstract:
  We present new medium-resolution high-S/N optical spectra of the ultracompact
low-mass X-ray binaries 4U0614+091 and 4U1626-67, taken with the ESO Very Large
Telescope. They are pure emission line spectra and the lines are identified as
due to C II-IV and O II-III Line identification is corroborated by first
results from modeling the disk spectra with detailed non-LTE radiation transfer
calculations. Hydrogen and helium lines are lacking in the observed spectra.
Our models confirm the deficiency of H and He in the disks. The lack of neon
lines suggests an Ne abundance of less than about 10 percent (by mass),
however, this result is uncertain due to possible shortcomings in the model
atom. These findings suggest that the donor stars are eroded cores of C/O white
dwarfs with no excessive neon overabundance. This would contradict earlier
claims of Ne enrichment concluded from X-ray observations of circumbinary
material, which was explained by crystallization and fractionation of the white
dwarf core.


title:
Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope
  Imaging. IV: Measurement for Sculptor

abstract:
  This article presents a measurement of the proper motion of the Sculptor
dwarf spheroidal galaxy determined from images taken with the Hubble Space
Telescope using the Space Telescope Imaging Spectrograph in the imaging mode.