title: Near-Infrared water lines in V838 Monocerotis

abstract:
  V838 Monocerotis had an intriguing, nova-like outburst in January 2002 which
has subsequently led to several studies of the object. It is now recognized
that the outburst of V838 Mon and its evolution are different from that of a
classical nova or other classes of well-known eruptive variables. V838 Mon,
along with two other objects that have analogous properties, appears to
comprise a new class of eruptive variables. There are limited infrared studies
of V838 Mon. Here, we present near-infrared H band (1.5 - 1.75micron) spectra
of V838 Mon from late 2002 to the end of 2004. The principal, new result from
our work is the detection of several, rotation-vibration lines of water in the
H band spectra. The observed water lines have been modeled to first establish
that they are indeed due to water. Subsequently the temperature and column
densities of the absorbing material, from where the water absorption features
originate, are derived. From our analysis, we find that the water features
arise from a cool ~750-900 K region around V838 Mon which appears to be
gradually cooling with time.


title: The $\Omega_{DE}-\Omega_{M}$ Plane in Dark Energy Cosmology

abstract:
  The dark energy cosmology with the equation of state $w=constant$ is
considered in this paper. The $\Omega_{DE}-\Omega_{M}$ plane has been used to
study the present state and expansion history of the universe. Through the
mathematical analysis, we give the theoretical constraint of cosmological
parameters. Together with some observations such as the transition redshift
from deceleration to acceleration, more precise constraint on cosmological
parameters can be acquired.


title:
The fingerprint of binary intermediate mass black holes in globular
  clusters: supra-thermal stars and angular momentum alignment

abstract:
  We explore the signatures that a binary intermediate mass black hole (IMBH)
imprints on the velocity and on the angular momentum of globular cluster stars.
Simulating 3-body encounters between a star and a binary IMBH, we find that the
binary IMBH generates a family of few hundreds of stars (~100-300) which remain
bound to the globular cluster (GC) and have velocity significantly higher than
the dispersion velocity. For this reason we term them ''supra-thermal'' stars.
We also notice that, after the interaction, a considerable fraction (55-70%) of
stars tend to align their orbital angular momentum with the angular momentum of
the binary IMBH, introducing an anisotropy in the angular momentum distribution
of cluster stars. We simulate the dynamical evolution of these supra-thermal
stars before thermalization, and find that these stars tend to cluster at a
distance of few core radii from the GC center. We conclude that the
detectability of such signatures appears problematic with present telescopes.


title: Debris Disk Radiative Transfer Simulation Tool (DDS)

abstract:
  A WWW interface for the simulation of spectral energy distributions of
optically thin dust configurations with an embedded radiative source is
presented. The density distribution, radiative source, and dust parameters can
be selected either from an internal database or defined by the user. This tool
is optimized for studying circumstellar debris disks where large grains are
expected to determine the far-infrared through millimeter dust reemission
spectral energy distribution. The tool is available at
http://aida28.mpia-hd.mpg.de/~swolf/dds


title: Early-time Spitzer observations of the type II-Plateau supernova, 2004dj

abstract:
  We present mid-infrared observations with the Spitzer Space Telescope of the
nearby type II-P supernova, SN 2004dj, at epochs of 89 to 129 days. We have
obtained the first mid-IR spectra of any supernova apart from SN 1987A. A
prominent [NiII] 6.64 micron line is observed, from which we deduce that the
mass of stable nickel must be at least 2.2e10(-4) Msun. We also observe the red
wing of the CO-fundamental band. We relate our findings to possible progenitors
and favour an evolved star, most likely a red supergiant, with a probable
initial mass between ~10 and 15 Msun.


title: Grain Evolution across the Shocks in the L1448-mm Outflow

abstract:
  The recent detection of shock-precursors toward the very young L1448-mm
outflow offers us the possibility to study the grain chemistry during the first
stages of the shock evolution, constraining the molecules ejected from grains
and the species formed in gas phase. Observations of key molecules in the grain
chemistry such as SiO, CH3OH, SO, CS, H2S, OCS, and SO2 toward this outflow are
presented. The line profiles and the derived abundances show three distinct
velocity regimes that trace the shock evolution: the preshock, the
shock-precursor and the postshock gas. The SiO, CH3OH, SO, and CS abundances
are enhanced with respect to the quiescent gas by 1 order of magnitude in the
shock-precursor component, and by 3 orders of magnitude in the postshock gas.
The derived SiO and CH3OH abundances are consistent with the recent ejection of
these molecules from grains. Since H2S is only enhanced in the shock-precursor
component, and OCS and SO2 are undetected, SO and CS are the most abundant
sulfur-bearing species in the grain mantles of L1448-mm. The ejection of mainly
SO and CS rather than H2S or OCS from grains, suggests that the sulfur
chemistry will depend on the chemical "history" of the grain mantles in
outflows and hot cores.


title:
Deep Echelle Spectrophotometry of S 311, a galactic H II Region Outside
  the Solar Circle

abstract:
  We present echelle spectrophotometry of the Galactic H II region S 311. The
data have been taken with the Very Large Telescope UVES echelle spectrograph in
the 3100 to 10400 angstroms range. We have measured the intensities of 263
emission lines, 178 are permitted lines of H0, D0 (deuterium), He0, C0, C+, N0,
N+, O0, O+, S+, Si0, Si+, Ar0 and Fe0; some of them are produced by
recombination and others mainly by fluorescence. Physical conditions have been
derived using different continuum and line intensity ratios. We have derived
He+, C++ and O++ ionic abundances from pure recombination lines as well as
abundances from collisionally excited lines for a large number of ions of
different elements. We have obtained consistent estimations of t2 applying
different methods. We have found that the temperature fluctuations paradigm is
consistent with the t2(He I) vs. t2(H I) relation for H II regions, in contrast
with what has been found for planetary nebulae. We report the detection of
deuterium Balmer lines up to D6 in the blue wings of the hydrogen lines, which
excitation mechanism seems to be continuum fluorescence.


title:
Non-Gaussianity of Large-Scale Cosmic Microwave Background Anisotropies
  beyond Perturbation Theory

abstract:
  We compute the fully non-linear Cosmic Microwave Background (CMB)
anisotropies on scales larger than the horizon at last-scattering in terms of
only the curvature perturbation, providing a generalization of the linear
Sachs-Wolfe effect at any order in perturbation theory. We show how to compute
the n-point connected correlation functions of the large-scale CMB anisotropies
for generic primordial seeds provided by standard slow-roll inflation as well
as the curvaton and other scenarios for the generation of cosmological
perturbations. As an application of our formalism, we compute the three- and
four-point connected correlation functions whose detection in future CMB
experiments might be used to assess the level of primordial non-Gaussianity,
giving the theoretical predictions for the parameters of quadratic and cubic
non-linearities f_NL and g_NL.


title:
Extinction properties of the X-ray bright/optically faint afterglow of
  GRB 020405

abstract:
  We present an optical-to-X-ray spectral analysis of the afterglow of GRB
020405. The optical spectral energy distribution not corrected for the
extragalactic extinction is significantly below the X-ray extrapolation of the
single powerlaw spectral model suggested by multiwavelength studies. We
investigate whether considerable extinction could explain the observed spectral
``mismatch'' by testing several types of extinction curves. For the first time
we test extinction curves computed with time-dependent numerical simulations of
dust grains destruction by the burst radiation. We find that an extinction law
weakly depen dent on wavelength can reconcile the unabsorbed optical and X-ray
data with the expected synchrotron spectrum. A gray extinction law can be
provided by a dust grain size distribution biased toward large grains.


title: Propagation of UHECRs

abstract:
  In this general introduction to Ultra High Energy Cosmic Rays (UHECRs) we
discuss the propagation of UHE protons and the GZK feature that is expected
approaching $10^{20}\eV$ for homogeneously distributed sources. We also briefly
present the effects of the propagation on other particles that can play the
role of UHECRs. With the help of numerical simulations for the propgation of
UHECRs, we show that the GZK feature cannot be accurately determined with the
small sample of events with energies $\sim10^{20}\eV$ detected thus far by the
largest two experiments, AGASA and HiRes.


title: Red clump distances to the inner Galactic structures

abstract:
  The least well known structure of the Galaxy is its central region, because
of the high extinction, the crowding and the confusion between disk and bulge
sources along the line of sight. We show how the structure of the inner Galaxy
and the dust distribution can be strongly constrained by using red clump stars
as distance indicator. The results of this method applied on the deep
near-infrared survey of the inner Galactic bulge made with the Cambridge
Infrared Survey Instrument (CIRSI) are presented.


title: An HLLC Riemann Solver for Relativistic Flows: I. Hydrodynamics

abstract:
  We present an extension of the HLLC approximate Riemann solver by Toro,
Spruce and Speares to the relativistic equations of fluid dynamics. The solver
retains the simplicity of the original two-wave formulation proposed by Harten,
Lax and van Leer (HLL) but it restores the missing contact wave in the solution
of the Riemann problem. The resulting numerical scheme is computationally
efficient, robust and positively conservative. The performance of the new
solver is evaluated through numerical testing in one and two dimensions.


title: Constraints on the Progenitor Systems of Type Ia Supernovae

abstract:
  UVOIR bolometric light curves provide valuable insight into the nature of
type Ia supernovae. We present an analysis of sixteen well-observed SNe Ia.
Constraints are placed on several global parameters concerning the progenitor
system, explosion mechanism and subsequent radiation transport. By fitting a
radioactive decay energy deposition function to the quasi-exponential phase (50
to 100 days after maximum light), it is found that the ejected mass varies by
at least a factor of two. This result suggests that a sub-Chandrasekhar mass
model could be responsible for the progenitor system of some type Ia
supernovae. We find that the range in the amount of synthesized (56)Ni
indicates a significant variation in the burning mechanism. In order to explain
a factor of ten range in the observed bolometric luminosity more detailed
modeling of the explosion mechanism is required.


title:
An Analysis of the Shapes of Ultraviolet Extinction Curves. IV.
  Extinction without Standards

abstract:
  We present a new method for deriving UV-through-IR extinction curves, based
on the use of stellar atmosphere models to provide estimates of the intrinsic
(i.e., unreddened) stellar spectral energy distributions (SEDs), rather than
unreddened (or lightly reddened) standard stars. We show that this
``extinction-without-standards'' technique greatly increases the accuracy of
the derived extinction curves and allows realistic estimations of the
uncertainties. An additional benefit of the technique is that it simultaneously
determines the fundamental properties of the reddened stars themselves, making
the procedure valuable for both stellar and interstellar studies. We
demonstrate how the extinction-without-standards curves make it possible to: 1)
study the uniformity of extinction in localized spatial regions with
unprecedented precision; 2) determine the relationships between different
aspects of curve morphology; 3) produce high quality extinction curves from low
color excess sightlines; and 4) derive reliable extinction curves for mid-late
B stars, thereby increasing spatial coverage and allowing the study of
extinction in open clusters and associations dominated by such stars. The
application of this technique to the available database of UV-through-IR SEDs,
and to future observations, will provide valuable constraints on the nature of
interstellar grains and on the processes which modify them, and will enhance
our ability to remove the multi-wavelength effects of extinction from
astronomical energy distributions.


title: Compact Stars for Undergraduates

abstract:
  We report on an undergraduate student project initiated in the summer
semester of 2004 with the aim to establish equations of state for white dwarfs
and neutron stars for computing mass-radius relations as well as corresponding
maximum masses. First, white dwarfs are described by a Fermi gas model of
degenerate electrons and neutrons and effects from general relativity are
examined. For neutron star matter, the influence of a finite fraction of
protons and electrons and of strong nucleon-nucleon interactions are studied.
The nucleon--nucleon interactions are introduced within a Hartree-Fock scheme
using a Skyrme-type interaction. Finally, masses and radii of neutron stars are
computed for given central pressure.


title: Parsec-scale X-ray Flows in High-mass Star-forming Regions

abstract:
  The Chandra X-ray Observatory is providing remarkable new views of massive
star-forming regions, revealing all stages in the life cycle of high-mass stars
and their effects on their surroundings. We present a Chandra tour of several
high-mass star-forming regions, highlighting physical processes that
characterize the life of a cluster of high-mass stars, from deeply-embedded
cores too young to have established an HII region to superbubbles so large that
they shape our views of galaxies. Along the way we see that X-ray observations
reveal hundreds of stellar sources powering great HII region complexes,
suffused by both hard and soft diffuse X-ray structures caused by fast O-star
winds thermalized in wind-wind collisions or by termination shocks against the
surrounding media. Finally, we examine the effects of the deaths of high-mass
stars that remained close to their birthplaces, exploding as supernovae within
the superbubbles that these clusters created. We present new X-ray results on
W51 IRS2E and 30 Doradus and we introduce new data on Trumpler 14 in Carina and
the W3 HII region complexes W3 Main and W3(OH).


title:
A Coherent Timing Solution for the Nearby Isolated Neutron Star RX
  J0720.4-3125

abstract:
  We present the results of a dedicated effort to measure the spin-down rate of
the nearby isolated neutron star RX J0720.4-3125. Comparing arrival times of
the 8.39-sec pulsations for data from Chandra we derive an unambiguous timing
solution for RX J0720.4-3125 that is accurate to <0.1 cycles over >5 years.
Adding data from XMM and ROSAT, the final solution yields
Pdot=(6.98+/-0.02)x10^(-14) s/s; for dipole spin-down, this implies a
characteristic age of 2 Myr and a magnetic field strength of 2.4e13 G. The
phase residuals are somewhat larger than those for purely regular spin-down,
but do not show conclusive evidence for higher-order terms or a glitch. From
our timing solution as well as recent X-ray spectroscopy, we concur with recent
suggestions that RX J0720.4-3125 is most likely an off-beam radio pulsar with a
moderately high magnetic field.


title: Spectral Synthesis of SDSS Galaxies

abstract:
  We investigate the power of spectral synthesis as a mean to estimate physical
properties of galaxies. Spectral synthesis is nothing more than the
decomposition of an observed spectrum in terms of a superposition of a base of
simple stellar populations of various ages and metallicities (here from Bruzual
& Charlot 2003), producing as output the star-formation and chemical histories
of a galaxy, its extinction and velocity dispersion. We discuss the reliability
of this approach and apply it to a volume limited sample of 50362 galaxies from
the SDSS Data Release 2, producing a catalog of stellar population properties.
A comparison with recent estimates of both observed and physical properties of
these galaxies obtained by other groups shows good qualitative and quantitative
agreement, despite substantial differences in the method of analysis. The
confidence in the method is further strengthened by several empirical and
astrophysically reasonable correlations between synthesis results and
independent quantities. For instance, we report the existence of strong
correlations between stellar and nebular metallicites, stellar and nebular
extinctions, mean stellar age and equivalent width of Halpha and 4000 \AA
break, and between stellar mass and velocity dispersion. We also present
preliminary results of an analysis of a magnitude-limited sample which clearly
reveals that the bimodality of galaxy populations is present in the parameters
computed in the synthesis. Our results are also consistent with the
"down-sizing" scenario of galaxy formation and evolution. Finally, we point out
one of the major problems facing spectral synthesis of early-type systems: the
spectral base adopted here is based on solar-scaled evolutionary tracks whose
abundance pattern may not be appropriate for this type of galaxy.


title: ISO's Contribution to the Study of Clusters of Galaxies

abstract:
  Starting with nearby galaxy clusters like Virgo and Coma, and continuing out
to the furthest galaxy clusters for which ISO results have yet been published
($z=0.56$), we discuss the development of knowledge of the infrared and
associated physical properties of galaxy clusters from early IRAS observations,
through the "ISO-era" to the present, in order to explore the status of ISO's
contribution to this field. Relevant IRAS and ISO programmes are reviewed,
addressing both the cluster galaxies and the still-very-limited evidence for an
infrared-emitting intra-cluster medium. ISO made important advances in
knowledge of both nearby and distant galaxy clusters, such as the discovery of
a major cold dust component in Virgo and Coma cluster galaxies, the elaboration
of the correlation between dust emission and Hubble-type, and the detection of
numerous Luminous Infrared Galaxies (LIRGs) in several distant clusters. These
and consequent achievements are underlined and described. We recall that, due
to observing time constraints, ISO's coverage of higher-redshift galaxy
clusters to the depths required to detect and study statistically significant
samples of cluster galaxies over a range of morphological types could not be
comprehensive and systematic, and such systematic coverage of distant clusters
will be an important achievement of the Spitzer Observatory.


title: Direct detection of the inflationary gravitational wave background

abstract:
  Inflation generically predicts a stochastic background of gravitational waves
over a broad range of frequencies, from those accessible with cosmic microwave
background (CMB) measurements, to those accessible directly with
gravitational-wave detectors, like NASA's Big-Bang Observer (BBO) or Japan's
Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO), both currently
under study. Here we investigate the detectability of the inflationary
gravitational-wave background at BBO/DECIGO frequencies. To do so, we survey a
range of slow-roll inflationary models consistent with constraints from the CMB
and large-scale structure (LSS). We go beyond the usual assumption of power-law
power spectra, which may break down given the 16 orders of magnitude in
frequency between the CMB and direct detection, and solve instead the
inflationary dynamics for four classes of inflaton potentials. Direct detection
is possible in a variety of inflationary models, although probably not in any
in which the gravitational-wave signal does not appear in the CMB polarization.
However, direct detection by BBO/DECIGO can help discriminate between
inflationary models that have the same slow-roll parameters at CMB/LSS scales.


title:
The Rise of Dwarfs and the Fall of Giants: Galaxy Formation Feedback
  Signatures in the Halo Satellite Luminosity Function

abstract:
  The observed luminosity function (LF) of satellite galaxies shows several
interesting features that require a better understanding of gas-thermodynamic
processes and feedback effects related to reionization and galaxy formation. In
galaxy clusters, the abundance of dwarf galaxies is in good agreement with the
expectation based on the subhalo mass function, whereas in galaxy groups, the
relatively small abundance of dwarfs conflicts with theoretical expectations.
In all halo systems, there is a dip in the abundance of galaxies with
luminosities in the range ~ 2x10^8 L_sun to 10^10 L_sun, corresponding to
subhalo mass scales between ~ 5x10^10 M_sun to few times 10^11 M_sun.
Photoionization from reionization has been used to explain statistics of the
dwarf population, with larger systems forming prior to, and smaller systems
forming subsequent to, reionization. The observed dip in the LF is an imprint
of small dwarf galaxies (<2x10^8 L_sun) that formed prior to reionization. The
galactic winds powered by supernovae in these dwarf galaxies propagate energy
and metals to large distances such that the intergalactic medium is uniformly
enriched to a level of 10^-3 zsun, as observed in the low-redshift Ly-alpha
forest. The associated energy related to this metallicity raises the
intergalactic medium temperature and the Jeans mass to a range 10^10-10^11
M_sun at z ~ 3.4-6.0. Because the epoch of nonlinearity for halos in this mass
range is at z > 3.4-4.4, their gas content, hence star formation, is greatly
suppressed on average and leads to a dip in the observed LF at $z=0$. Larger
halos (M > 10^11 M_sun), becoming nonlinear at z < 3.4-4.4, have masses topping
the Jeans mass, where subhalo mass function based LF is again in agreement with
observations.


title:
Star Formation Histories of Nearby Elliptical Galaxies: I. Volume
  Limited Sample

abstract:
  This work presents high $S/N$ spectroscopic observations of a representative
sample of nearby elliptical galaxies. These observations provide a strong test
of models for the formation of elliptical galaxies and their star formation
histories. Combining these data with the Gonzalez (1993) data set, a volume
limited sample of 45 galaxies has been defined. Results are in agreement with
previous studies: the existence of the metallicity hyper-plane and the Z-plane
of Trager et al. (2000) is confirmed, and the distribution is clearly due to
physical variations in stellar population parameters and not measurement
uncertainty. Trends between stellar population parameters and galaxy structural
parameters suggest that angular momentum may determine the chemical abundance
of a galaxy at a given mass.


title:
Dry Mergers in GEMS: The Dynamical Evolution of Massive Early-Type
  Galaxies

abstract:
  We have used the 28'x 28' HST image mosaic from the GEMS (Galaxy Evolution
from Morphology and SEDs) survey in conjunction with the COMBO-17 photometric
redshift survey to constrain the incidence of major mergers between
spheroid-dominated galaxies with little cold gas (dry mergers) since z = 0.7. A
set of N-body merger simulations was used to explore the morphological
signatures of such interactions: they are recognizable either as < 5kpc
separation close pairs or because of broad, low surface brightness tidal
features and asymmetries. Data with the depth and resolution of GEMS are
sensitive to dry mergers between galaxies with M_V < -20.5 for z < 0.7; dry
mergers at higher redshifts are not easily recovered in single-orbit HST
imaging. Six dry mergers (12 galaxies) with luminosity ratios between 1:1 and
4:1 were found from a sample of 379 red early-type galaxies with M_V < -20.5
and 0.1 < z < 0.7. The simulations suggest that the morphological signatures of
dry merging are visible for ~250Myr and we use this timescale to convert the
observed merger incidence into a rate. On this basis we find that present day
spheroidal galaxies with M_V < -20.5 on average have undergone between 0.5 and
2 major dry mergers since z ~ 0.7. We have compared this result with the
predictions of a Cold Dark Matter based semi-analytic galaxy formation model.
The model reproduces the observed declining major merger fraction of bright
galaxies and the space density of luminous early-type galaxies reasonably well.
The predicted dry merger fraction is consistent with our observational result.
Hence, hierarchical models predict and observations now show that major dry
mergers are an important driver of the evolution of massive early-type galaxies
in recent epochs.


title:
Astrometric Microlensing Constraints on a Massive Body in the Outer
  Solar System with Gaia

abstract:
  A body in Solar orbit beyond the Kuiper belt exhibits an annual parallax that
exceeds its apparent proper motion by up to many orders of magnitude. Apparent
motion of this body along the parallactic ellipse will deflect the angular
position of background stars due to astrometric microlensing ("induced
parallax"). By synoptically sampling the astrometric position of background
stars over the entire sky, constraints on the existence (and basic properties)
of a massive nearby body may be inferred. With a simple simulation, we estimate
the signal-to-noise for detecting such a body -- as function of mass,
heliocentric distance, and ecliptic latitude -- using the anticipated
sensitivity and temporal cadences from Gaia (launch 2011). A Jupiter-mass
(M_Jup) object at 2000 AU is detectable by Gaia over the whole sky above
5-sigma, with even stronger constraints if it lies near the ecliptic plane.
Hypotheses for the mass (~3M_Jup), distance (~20,000 AU) and location of the
proposed perturber ("Planet X") which gives rise to long-period comets may be
testable.


title:
The theory of canonical perturbations applied to attitude dynamics and
  to the Earth rotation. Osculating and nonosculating Andoyer variables

abstract:
  The Hamiltonian theory of Earth rotation, known as the Kinoshita-Souchay
theory, operates with nonosculating Andoyer elements. This situation parallels
a similar phenomenon that often happens (but seldom gets noticed) in orbital
dynamics, when the standard Lagrange-type or Delaunay-type planetary equations
unexpectedly render nonosculating orbital elements. In orbital mechanics,
osculation loss happens when a velocity-dependent perturbation is plugged into
the standard planetary equations. In attitude mechanics, osculation is lost
when an angular-velocity-dependent disturbance is plugged in the standard
dynamical equations for the Andoyer elements. We encounter exactly this
situation in the theory of Earth rotation, because this theory contains an
angular-velocity-dependent perturbation (the switch from an inertial frame to
that associated with the precessing ecliptic of date).
  While the osculation loss does not influence the predictions for the figure
axis of the planet, it considerably alters the predictions for the
instantaneous spin-axis' orientation. We explore this issue in great detail.


title:
The Low Excitation Planetary Nebulae HuDo 1 and HuBi 1 and their [WC10]
  Central Stars

abstract:
  Low- and high-resolution spectra of the planetary nebulae HuDo 1 and HuBi 1,
around [WC-late] stars, are analyzed. The objects belong to the galactic disk,
with heliocentric radial velocities of -12 km/s (HuDo 1) and 57 km/s (HuBi 1).
  C(Hbeta) reddening values are of 2.04 for HuDo 1 and 1.22 for HuBi 1. Plasma
line ratios are used to estimate physical conditions and abundances. We find
log (O/H)+12 = 8.43 and 8.57, and N/O = 0.2 and 0.1 for HuDo 1 and HuBi 1
respectively. HuBi 1 is the only PN excited by a very late [WC] star showing
intense nebular HeI recombination lines. From the stellar lines we derive a [WC
10] type for both stars, although HuBi 1 central star should be slightly hotter
for providing a large amount of He^0 ionizing photons. Nebular and stellar
parameters of HuDo 1 and HuBi 1 are compared with those of other [WC 10]
objects, concluding that the stars of HuDo 1 and HuBi 1 should be intrinsically
fainter. In particular HuBi 1 seems a low-density evolved nebula around a
low-mass slowly-evolving star.


title: The Vertical Structure of Stars in Edge-on Galaxies

abstract:
  We present a summary of our recent work on the vertical distribution of the
resolved stellar populations in six low mass, edge-on, spiral galaxies observed
with the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS). In each
galaxy we find evidence for an extraplanar stellar component extending up to 15
scale heights (~3.5 kpc) above the plane. We analyze the vertical distribution
as a function of stellar age by tracking changes in the color-magnitude
diagram. The young stellar component (< 10^8 yrs) is found to have a scale
height larger than the young component in the Milky Way, suggesting that stars
in these low mass galaxies form in a thicker disk. We also find that the scale
height of a stellar population increases with age, with young main sequence
stars, intermediate age asymptotic giant branch stars, and old red giant branch
stars having succesively larger scale heights in each galaxy. The color
distributions of the red giant branch (RGB) stars well above the midplane
indicate that the extended stellar components we see are moderately metal-poor,
with peak metallicities of [Fe/H] ~ -1 and with little or no metallicity
gradient with height. The lack of metallicity gradient can be explained if a
majority of extraplanar RGB stars were formed at early times and are not
dominated by a younger heated population. Our observations suggest that, like
the Milky Way, low mass disk galaxies also have multiple stellar components. We
examine our results in light of disk heating and merger scenarios and conclude
that both mechanisms likely played a role in forming the disks of our sample
galaxies.


title: Star Formation Histories of Local Group Dwarf Galaxies

abstract:
  We report preliminary results of a project to homogeneously measure star
formation histories for the majority of Local Group dwarf galaxies, based on
archival WFPC2 observations. For the dwarf spheroidal and elliptical galaxies,
we find that the more luminous systems all show extended star formation
episodes, while the less luminous systems typically formed most of their stars
over ten Gyr ago. Irregular galaxies show no comparable trend. We find that a
galaxy's classification as an irregular or spheroidal is entirely explained by
its star formation within the past Gyr or less. Several elliptical/spheroidal
systems actively formed stars within the past two Gyr, and would have been
indistinguishable from present-day irregulars if observed two Gyr ago.


title:
Radio-quiet neutron star 1E 1207.4-5209: a possible strong
  Gravitational-wave source

abstract:
  There are four puzzles on 1E 1207.4-5209: (1) the characteristic age of the
pulsar is much higher than the estimated age of the supernova remnant; (2) the
magnetic field inferred from spin-down is significantly different from the
value obtained from the cyclotron absorption lines; (3) the spinning down of
the pulsar is non-monotonic; (4) the magnitude of the frequency's first
derivative varies significantly and its sign is also variable. The third puzzle
can be explained by a wide binary system, with orbital period from 0.2 to 6 yr.
This letter proposes that all four puzzles can be explained naturally by an
ultra-compact binary with orbital period of between 0.5 and 3.3 min. With the
shortest orbital period and a close distance of 2 kpc, the characteristic
amplitude of gravitational waves is $h\sim3\times10^{-21}$. It would be an
excellent source of gravitational-wave detectors such as the Laser
Interferometer Space Antenna.


title: How far do they go? The outer structure of dark matter halos

abstract:
  We study the density profiles of collapsed galaxy-size dark matter halos with
masses 1e11-5e12 Msun focusing mostly on the halo outer regions from the formal
virial radius Rvir up to 5-7Rvir. We find that isolated halos in this mass
range extend well beyond Rvir exhibiting all properties of virialized objects
up to 2-3Rvir: relatively smooth density profiles and no systematic infall
velocities. The dark matter halos in this mass range do not grow as one naively
may expect through a steady accretion of satellites, i.e., on average there is
no mass infall. This is strikingly different from more massive halos, which
have large infall velocities outside of the virial radius. We provide accurate
fit for the density profile of these galaxy-size halos. For a wide range
(0.01-2)Rvir of radii the halo density profiles are fit with the approximation
rho=rho_s exp(-2n[x^{1/n}-1])+rho_m, where x=r/r_s, rho_m is the mean matter
density of the Universe, and the index n is in the range n=6-7.5. These
profiles do not show a sudden change of behavior beyond the virial radius. For
larger radii we combine the statistics of the initial fluctuations with the
spherical collapse model to obtain predictions for the mean and most probable
density profiles for halos of several masses. The model give excellent results
beyond 2-3 formal virial radii.


title:
Imaging Bright Spots in the Accretion Flow Near the Black Hole Horizon
  of Sgr A*

abstract:
  Images from the vicinity of the black hole horizon at the Galactic centre
(Sgr A*) could be obtained in the near future with a Very Large Baseline Array
of sub-millimetre telescopes. The recently observed short-term infrared and
X-ray variability of the emission from Sgr A* implies that the accretion flow
near the black hole is clumpy or unsteady. We calculate the appearance of a
compact emission region (bright spot) in a circular orbit around a spinning
black hole as a function of orbital radius and orientation. We find that the
mass and spin of the black hole can be extracted from their generic signatures
on the spot image as well as on the lightcurves of its observed flux and
polarisation. The strong-field distortion remains noticeable even when the spot
image is smoothed over the expected ~20 microarcsecond resolution of future
sub-millimetre observations.


title:
Formation and Evolution of Planetary Systems: Cold Outer Disks
  Associated with Sun-like stars

abstract:
  We present the discovery of debris systems around three solar mass stars
based upon observations performed with the Spitzer Space Telescope as part of a
Legacy Science Program, ``the Formation and Evolution of Planetary Systems''
(FEPS). We also confirm the presence of debris around two other stars. All the
stars exhibit infrared emission in excess of the expected photospheres in the
70 micron band, but are consistent with photospheric emission at <= 33 micron.
This restricts the maximum temperature of debris in equilibrium with the
stellar radiation to T < 70 K. We find that these sources are relatively old in
the FEPS sample, in the age range 0.7 - 3 Gyr. Based on models of the spectral
energy distributions, we suggest that these debris systems represent materials
generated by collisions of planetesimal belts. We speculate on the nature of
these systems through comparisons to our own Kuiper Belt, and on the likely
planet(s) responsible for stirring the system and ultimately releasing dust
through collisions. We further report observations of a nearby star HD 13974 (d
=11 pc) that is indistinguishable from a bare photosphere at both 24 micron and
70 micron. The observations place strong upper limits on the presence of any
cold dust in this nearby system (L_IR/L_* < 10^{-5.2}).


title:
IRAS 16293-2422: proper motions, jet precession, the hot core, and the
  unambiguous detection of infall

abstract:
  We present observations of IRAS 16293-2422 using the Submillimeter Array
(SMA) at 300 GHz, and the Very Large Array (VLA) at frequencies from 1.5 to 43
GHz. This source was already known to be a binary system with components A and
B separated by ~5". The new SMA data now separate source A into two submm
continuum components, denoted Aa and Ab. The strongest of these, Aa, peaks
between the cm radio sources A1 and A2. Archival VLA data show proper motion of
sources A and B of 17 mas/yr, associated with motion of the rho Ophiuchi cloud.
We also find relative motion between A1 and A2 which excludes the possibility
that they are gravitationally bound. A2 remains stationary relative to source
B, and we identify it as the protostar driving the NE-SW CO outflow. A1 is
shock-ionized gas where a precessing jet interacts with dense gas. This jet
probably drives the E-W CO outflow. The origin of this jet must be located
close to A2, and may be the submm source Aa. Thus source A is now shown to
comprise three components within 1". Source B, however, is single, exhibits
optically-thick dust emission even at 8 GHz, has a high luminosity, and yet
shows no sign of outflow, indicating it is probably very young.
  The SMA spectrum of IRAS 16293-2422 reports the first astronomical
identification of many lines at 300 and 310 GHz. The species detected are
typical of hot cores, and are mainly associated with source A. We suggest the
shock at A1 may explain the enhanced abundances measured, especially of
sulphur-bearing molecules. We use the high brightness temperature of the submm
dust emission from source B to demonstrate the unambiguous detection of infall
by observing redshifted SO (7_7-6_6) absorption against the dust disk.


title:
Luminosity and mass limits for the progenitor of the type Ic supernova
  2004gt in NGC 4038

abstract:
  We report our attempts to locate the progenitor of the type Ic SN 2004gt in
NGC 4038. We use high resolution HST ACS images of SN 2004gt and have compared
them with deep pre-explosion HST WFPC2 F336W, F439W, F555W and F814W images. We
identify the SN location on the pre-explosion frames with an accuracy of 5mas.
We show that the progenitor is below the detection thresholds of all the
pre-explosion images. These detection limits are used to place luminosity and
mass limits on the progenitor, by comparing them with stellar evolution tracks
on the Hertzsprung-Russell diagram. The progenitor of SN 2004gt seems to be
restricted to a low-luminosity high-temperature star, either a single WC star
with initial mass $>40M_{\odot}$ or a low mass star in a binary. The
pre-explosion data cannot distinguish between the two scenarios.


title: Hard X-ray diffuse emission from the Galactic Center seen by INTEGRAL

abstract:
  We study the hard X-ray (20-100 keV) variability of the Galactic Center (GC)
and of the nearby sources on the time scale of 1000 s. We find that 3 of the 6
hard X-ray sources detected by INTEGRAL within the central 1 degree of the
Galaxy are not variable on this time scale: the GC itself (the source IGR
J1745.6-2901) as well as the source 1E 1743.1-2843 and the molecular cloud Sgr
B2. We put an upper limit of 5 x 10^{-12} erg/(cm^2 sec) (in 20 to 60 keV band)
on the variable emission form the supermassive black hole (the source Sgr A*)
which powers the activity of the GC(although we can not exclude the possibility
of rare stronger flares). The non-variable 20-100 keV emission from the GC
turns out to be the high-energy non-thermal tail of the diffuse hard ``8 keV''
component of emission from Sgr A region. Combining the XMM-Newton and INTEGRAL
data we find that the size of the extended hard X-ray emission region is about
20 pc. The only physical mechanism of production of diffuse non-thermal hard
X-ray flux, which does not contradict the multi-wavelength data on the GC, is
the synchrotron emission from electrons of energies 10-100 TeV.


title:
Pulse-phase spectroscopy of SMC X-1 with Chandra and XMM-Newton:
  reprocessing by a precessing disk?

abstract:
  We present pulse-phase X-ray spectroscopy of the high-mass X-ray pulsar SMC
X-1 from five different epochs, using Chandra X-ray Observatory ACIS-S and
XMM-Newton EPIC-pn data. The X-ray spectrum consistently shows two distinct
components, a hard power law and a soft blackbody with kT_BB ~ 0.18 keV. For
all five epochs the hard component shows a simple double-peaked pulse shape,
and also a variation in the power law slope, which becomes harder at maximum
flux and softer at minimum flux. For the soft component, the pulse profile
changes between epochs, in both shape and phase relative to the power law
pulses. The soft component is likely produced by reprocessing of the hard X-ray
pulsar beam by the inner accretion disk. We use a model of a twisted inner
disk, illuminated by the rotating X-ray pulsar beam, to simulate pulsations in
the soft component due to this reprocessing. We find that for some disk and
beam geometries, precession of an illuminated accretion disk can roughly
reproduce the observed long-term changes in the soft pulse profiles.


title:
Collapse and Fragmentation of Rotating Magnetized Clouds. I. Magnetic
  Flux - Spin Relation

abstract:
  We discuss evolution of the magnetic flux density and angular velocity in a
molecular cloud core, on the basis of three-dimensional numerical simulations,
in which a rotating magnetized cloud fragments and collapses to form a very
dense optically thick core of > 5 times 10 ^10 cm^-3 . As the density increases
towards the formation of the optically thick core, the magnetic flux density
and angular velocity converge towards a single relationship between the two
quantities. If the core is magnetically dominated its magnetic flux density
approaches 1.5 (n/5 times 10^10 cm^-3)^1/2 mG, while if the core is
rotationally dominated the angular velocity approaches 2.57 times 10^-3, (n/5
times 10^10 cm^-3)^1/2 yr^-1, where n is the density of the gas. We also find
that the ratio of the angular velocity to the magnetic flux density remains
nearly constant until the density exceeds 5 times 10^10 cm^-3. Fragmentation of
the very dense core and emergence of outflows from fragments are shown in the
subsequent paper.


title:
Collapse and Fragmentation of Rotating Magnetized Clouds. II. Binary
  Formation and Fragmentation of First Cores

abstract:
  Subsequent to Paper I, the evolution and fragmentation of a rotating
magnetized cloud are studied with use of three-dimensional MHD nested-grid
simulations. After the isothermal runaway collapse, an adiabatic gas forms a
protostellar first core at the center of the cloud. When the isothermal gas is
stable for fragmentation in a contracting disk, the adiabatic core often breaks
into several fragments. Conditions for fragmentation and binary formation are
studied. All the cores which show fragmentations are geometrically thin, as the
diameter-to-thickness ratio is larger than 3. Two patterns of fragmentation are
found. (1) When a thin disk is supported by centrifugal force, the disk
fragments through a ring configuration (ring fragmentation). This is realized
in a fast rotating adiabatic core as Omega >0.2 tau_ff^-1, where Omega and
tau_ff represent the angular rotation speed and the free-fall time of the core,
respectively. (2) On the other hand, the disk is deformed to an elongated bar
in the isothermal stage for a strongly magnetized or rapidly rotating cloud.
The bar breaks into 2 - 4 fragments (bar fragmentation). Even if a disk is
thin, the disk dominated by the magnetic force or thermal pressure is stable
and forms a single compact body. In either ring or bar fragmentation mode, the
fragments contract and a pair of outflows are ejected from the vicinities of
the compact cores. The orbital angular momentum is larger than the spin angular
momentum in the ring fragmentation. On the other hand, fragments often quickly
merge in the bar fragmentation, since the orbital angular momentum is smaller
than the spin angular momentum in this case. Comparison with observations is
also shown.


title:
Cosmic shear as a tool for precision cosmology: minimising intrinsic
  galaxy alignment-lensing interference

abstract:
  Cosmic shear leads to a correlation of the observed ellipticities of
galaxies, an effect which is used to place constraints on cosmological
parameters, and to explore the evolution of dark matter and dark energy in the
universe. However, a possible systematic contaminant of the lensing signal is
intrinsic galaxy alignment, with a correlation length of a few Mpc. Hirata &
Seljak (2004) have recently demonstrated that for some models of intrinsic
distortions, there may also be a cross-correlation between the intrinsic and
lensing signals, which may dominate the intrinsic signal, and suppress the
lensing power spectrum by several tens of percent. Unlike the pure intrinsic
signal, this new term cannot be accounted for by neglecting or down-weighting
pairs of galaxies which are physically close. Extending the correlation
function tomography method of King & Schneider (2003) we illustrate how the
impact of both intrinsic and cross-correlations can be significantly reduced,
in the context of surveys with photometric redshift information. For a
ground-based cosmic shear survey of ~100 sq. degrees with photometric
redshifts, even in the presence of systematic contaminants at the level
considered here, cosmological models degenerate in the Omega_m-sigma_8 plane
can be distinguished well in excess of the 3-sigma level.


title: A Search for Untriggered GRB Afterglows with ROTSE-III

abstract:
  We present the results of a search for untriggered gamma-ray burst (GRB)
afterglows with the Robotic Optical Transient Search Experiment-III (ROTSE-III)
telescope array. This search covers observations from September 2003 to March
2005. We have an effective coverage of 1.74 deg^2 yr for rapidly fading
transients that remain brighter than ~ 17.5 magnitude for more than 30 minutes.
This search is the first large area survey to be able to detect typical
untriggered GRB afterglows. Our background rate is very low and purely
astrophysical. We have found 4 previously unknown cataclysmic variables (CVs)
and 1 new flare star. We have not detected any candidate afterglow events or
other unidentified transients. We can place an upper limit on the rate of
fading optical transients with quiescent counterparts dimmer than ~ 20th
magnitude at a rate of less than 1.9 deg^-2 yr-1 with 95% confidence. This
places limits on the optical characteristics of off-axis (orphan) GRB
afterglows. As a byproduct of this search, we have an effective ~ 52 deg^2 yr
of coverage for very slowly decaying transients, such as CVs. This implies an
overall rate of outbursts from high galactic latitude CVs of 0.1 deg^2 yr^-1.


title: Chandra Observations of Shock Kinematics in Supernova Remnant 1987A

abstract:
  We report the first results from deep X-ray observations of the SNR 1987A
with the Chandra LETG. Temperatures inferred from line ratios range from 0.1 -
2 keV and increase with ionization potential. Expansion velocities inferred
from X-ray line profiles range from 300 - 1700 km/s, much less than the
velocities inferred from the radial expansion of the radio and X-ray images. We
can account for these observations with a scenario in which the X-rays are
emitted by shocks produced where the supernova blast wave strikes dense
protrusions of the inner circumstellar ring, which are also responsible for the
optical hot spots.


title:
Spectral state transitions in low-mass X-ray binaries - the effect of
  hard and soft irradiation

abstract:
  In neutron star and black hole X-ray binaries the transitions between the two
spectral states, hard and soft, signals the change between accretion via a hot
advection-dominated flow(ADAF) and disk accretion. In a few cases the hard/soft
transition were observed during the rise to the nova outburst, mostly only the
soft/hard transition during the luminosity decrease. Surprisingly the
luminosities at the second transition is always lower by a factor of 3 to 5. A
model for this hysteresis was presented in a preceding paper: It was shown that
this switch in the accretion mode at different mass accretion rates and
therefore different luminosities is caused by the different amount of Compton
cooling or heating of the accretion disk corona as it is irradiated by hard or
soft radiation from the central light source, respectively. We now give
detailed results on the dependence on hardness of this radiation and on
radiation efficiency. We further discuss the influence of the inclination and a
possible warping of the disk on the observed hysteresis.


title:
Thermal Dust Emission from Proplyds, Unresolved Disks, and Shocks in the
  Orion Nebula

abstract:
  We present a new 11.7 micron mosaic image of the Orion nebula obtained with
T-ReCS on Gemini South. The map includes the BN/KL region, the Trapezium, and
OMC-1 South. Excluding BN/KL, we detect 91 point sources, with 27 known
proplyds and over 30 ``naked'' stars showing no extended structure in HST
images. Within the region we surveyed, 80 percent of known proplyds show
detectable emission, almost 40 percent of naked stars are detected at 11.7
micron, and the fraction of all visible sources with IR excess emission is
roughly 50 percent. Thermal dust emission from stars with no extended structure
in HST images means that they have dust disks comparable to the size of our
solar system. Proplyds and stars with IR excess show a clear anti-correlation
in their spatial distribution, with proplyds clustered close to theta1C, and
other infrared sources found farther away. We suspect that the clustered
proplyds trace the youngest 0.5 Myr age group associated with the Trapezium,
while the more uniformly-distributed sources trace the older 1-2 Myr population
of the ONC. This suggests that small disks persist for a few Myr in irradiated
environments, and hints that hierarchical sub-clustering has been important.
Within 30 arcsec of theta1C, all proplyds are detected at 11.7 micron. The star
theta1D is associated with the most prominent mid-IR dust arc in the nebula. We
propose that this arc is the consequence of theta1D being the closest member of
the Trapezium to the background cloud. Finally, we detect dust emission from HH
jets in Orion, including HH202, HH529, HH513, and HH514. This is the first
detection of mid-IR continuum emission from dust in the body of a collimated HH
jet or bow shock.


title:
Nitrogen-deficient and iron-rich associated absorbers with oversolar
  metallicities towards the quasar HE0141-3932

abstract:
  HE0141-3932 (zem=1.80) is a bright blue radio-quite quasar which reveals an
emission line spectrum with an unusually weak Ly-alpha line. In addition, large
redshift differences (Delta z=0.05) are observed between high ionization and
low ionization emission lines. Absorption systems identified at z=1.78, 1.71,
and 1.68 show mild oversolar metallicities (Z ~= 1-2Zsolar) and can be
attributed to the associated gas clouds ejected from the circumnuclear region.
The joint analysis of the emission and absorption lines leads to the conclusion
that this quasar is seen almost pole-on. Its apparent luminosity may be Doppler
boosted by ~10 times. The absorbing gas shows high abundance of Fe, Mg, and Al
([Fe, Mg, Al/C] ~= 0.15+/-0.10) along with underabundance of N ([N/C]<=-0.5).
This abundance pattern is at variance with current chemical evolution models of
QSOs predicting [N/C]>0 and [Fe/C]<0 at Z ~ Zsolar. Full details of this work
are given in Reimers et al. (2005).


title:
EGRET Excess of Galactic Gamma Rays as Signal of Dark Matter
  Annihilation

abstract:
  The EGRET excess in the diffuse galactic gamma ray data above 1 GeV shows all
features expected from Dark Matter WIMP Annihilation: a)it is present and has
the same spectrum in all sky directions, not just in the galactic plane. b) The
intensity of the excess shows the $1/r^2$ profile expected for a flat rotation
curve outside the galactic disc with additionally an interesting substructure
in the disc in the form of a doughnut shaped ring at 14 kpc from the centre of
the galaxy. At this radius a ring of stars indicates the probable infall of a
dwarf galaxy, which can explain the increase in DM density.
  From the spectral shape of the excess the WIMP mass is estimated to be
between 50 and 100 GeV, while from the intensity the halo profile is
reconstructed. Given the mass and intensity of the WIMPs the mass of the ring
can be calculated, which is shown to explain the peculiar change of slope in
the rotation curve at about 11 kpc. These results are model independent in the
sense that only the known shapes of signal and background were fitted with free
normalization factors, thus being independent of the model dependent flux
caluclations. The statistical significance is more than 10 sigma in comparison
with a fit of the conventional galactic model to the EGRET data. These signals
of Dark Matter Annihilation are compatible with Supersymmetry including all
electroweak constraints. The statistical significance combined with all
features mentioned above provide an intriguing hint that the EGRET excess is
indeed a signal from Dark Matter Annihilation.


title: GRB environment properties through X and optical afterglow observations

abstract:
  We present the spectral analysis of 14 gamma-ray bursts (GRB) X-ray
afterglows in order to investigate the properties of interstellar matter (ISM)
along the line of sight of GRB. We carried out a simultaneous analysis of the
NIR-optical and X-band for those afterglows with an optical counterpart too, in
order to evaluate and strongly constrain the absorption effect on the spectral
energy distribution due to dust extinction from GRB environment. We evaluated
the equivalent hydrogen column density Nh from X-ray spectroscopy and rest
frame visual extinction Av by assuming different type of ISM composition and
dust grain size distribution. From our analysis we obtained a distribution of
the GRB rest frame consistent with the one expected if GRB were embedded in a
Galactic-like molecular cloud. Moreover, values of the visual extinction
estimated from the simultaneous analysis of NIR-to-X band favour an environment
where small dust grain are destroyed by the interaction with the X-ray and UV
photons from GRB.


title: Can a dust dominated universe have accelerated expansion?

abstract:
  Recently, there has been suggestions that the apparent accelerated expansion
of the universe is due not to a cosmological constant, but rather to
inhomogeneities in the distribution of matter. In this work, we investigate a
specific class of inhomogeneous models that can be solved analytically, namely
the dust-dominated Lemaitre-Tolman-Bondi universe models. We show that they do
not permit accelerated cosmic expansion.


title:
Wave attractors and the asymptotic dissipation rate of tidal
  disturbances

abstract:
  Linear waves in bounded inviscid fluids do not generally form normal modes
with regular eigenfunctions. Examples are provided by inertial waves in a
rotating fluid contained in a spherical annulus, and internal gravity waves in
a stratified fluid contained in a tank with a non-rectangular cross-section.
For wave frequencies in the ranges of interest, the inviscid linearized
equations are spatially hyperbolic and their characteristic rays are typically
focused on to wave attractors. When these systems experience periodic forcing,
for example of tidal origin, the response of the fluid can become localized in
the neighbourhood of a wave attractor. In this paper I define a prototypical
problem of this form and construct analytically the long-term response to a
periodic body force in the asymptotic limit of small viscosity. The vorticity
of the fluid is localized in a detached shear layer close to the wave attractor
in such a way that the total rate of dissipation of energy is asymptotically
independent of the viscosity. I further demonstrate that the same asymptotic
dissipation rate is obtained if a non-viscous damping force is substituted for
the Navier-Stokes viscosity. I discuss the application of these results to the
problem of tidal forcing in giant planets and stars, where the excitation and
dissipation of inertial waves may make a dominant, or at least important,
contribution to the orbital and spin evolution.


title: Towards an Empirical Determination of the ZZ Ceti Instability Strip

abstract:
  We present atmospheric parameters for a large sample of DA white dwarfs that
are known to be photometrically constant. For each star, we determine the
effective temperature and surface gravity by comparing high signal-to-noise
ratio optical spectra to the predictions of detailed model atmosphere
calculations. We also report the successful prediction and detection of
photometric variability in G232-38 based on similar Teff and log g
determinations. The atmospheric parameters derived for this sample of constant
stars as well as those for the known sample of bright ZZ Ceti stars (now
boosted to a total of 39) have been obtained in a highly homogeneous way. We
combine them to study the empirical red and blue edges as well as the purity of
the ZZ Ceti instability strip. We find that the red edge is rather well
constrained whereas there exists a rather large range of possibilities for the
slope of the blue edge. Furthermore, the ZZ Ceti instability strip that results
from our analysis contains no nonvariable white dwarfs. Our sample of constant
stars is part of a much broader spectroscopic survey of bright (V < 17) DA
white dwarfs, which we have recently undertaken. We also present here some
preliminary results of this survey. Finally, we revisit the analysis by Mukadam
et al. of the variable and nonvariable DA stars uncovered as part of the Sloan
Digital Sky Survey. Their erroneous conclusion of an instability strip
containing several nonvariable stars is traced back to the low signal-to-noise
ratio spectroscopic observations used in that survey.


title:
Separating C-stars from Dust in the Central Region of the Seyfert 2
  Galaxy NGC 1241

abstract:
  The Sy 2 galaxy NGC 1241 presents a 1.5 kpc large circumnuclear ring of star
formation (CNR) embracing a small bar plus leading arms. Those structures are P
alpha emitters, but barely seen in H alpha. It presents also stellar trailing
arms inside the CNR. GEMINI and HST imagery allow the construction of high
resolution (V-H) and (J-K_s) color maps as well as a (J-K_s) vs. K
color-magnitude diagram (CMD) of this complex region. The CNR is heavily
obscured in V, but a fairly transparent window appears in the direction of the
nucleus. Nonetheless, the nucleus presents a (J-K_s) color that is redder than
the CNR. The CNR is composed of extremely young HII regions still enshrouded in
their dust cocoons. However, the nuclear (J-K_s) color can not be explained in
this manner. Therefore, we propose the contribution of C-Stars as the most
feasible mechanism for explaining the colors. If the nuclear stellar population
is comparable to that of the LMC bar, 500 C-stars and 25000 AGB O-rich stars
inside 50 pc may reproduce the observed colors. C-Stars release enriched
material to the nuclear environment, probably fueling the central engine of
this Sy 2 galaxy during the lifetime of stars with masses between 2 M_sun <
M_C-star < 6 M_sun (C-star phase). The ejected material that remains trapped in
the central potential might also explain the systematically observed increased
strength of the optical CN-bands in Sy 2 galaxies and is consistent with the
significant contribution of intermediate age stars to the optical continuum of
low luminosity AGNs.


title:
Prompt and afterglow early X-ray phases in the comoving frame. Evidence
  for Universal properties?

abstract:
  We analyze the Swift XRT light curves and spectra of the gamma-ray bursts
(GRBs) for which the redshift has been measured. The sample consists of seven
GRBs. The soft X-ray light curves of all these GRBs are separated into at least
two morphological classes: 1) those starting off with a very steep light curve
decay and 2) those showing a rather mild initial decay. This initial decay is
followed by a flattening and by a further steepening. During these transitions
the soft X-ray spectrum of these GRBs remains constant within the observational
errors (except for one case, GRB050319). For the first time we are able to
exploit the early light curve of GRB afterglows in the comoving frame. Besides
the temporal and spectral behavior we find that the energy of the afterglow
emitted in the (rest frame) time interval 20-200 s and 1300-12600 s after the
trigger correlates with the mean energy of the prompt emission, hinting at a
close link between the two. Averaging over the bursts that have a rather well
sampled light curve and starting immediately after the prompt phase, the energy
emitted in the soft X-rays is about 3% of the energy emitted during the prompt
phase, except for GRB050315, where the soft X-ray emission is as high as 14% of
the prompt emission.


title:
Radiative effects by high-z UV radiation background: Implications for
  the future CMB polarization measurements

abstract:
  We investigate the role of the radiative effects for the temporal evolution
of the reionization fraction by using cosmological Smooth Particle
Hydrodynamics (SPH) simulations. We find that the increase of photo-ionization
and photo-heating rates due to optical depth effects results in a significantly
contribute to the heating of the IGM before and during the reionization. The
main effect of the UV radiation spectrum on the temporal evolution of the
ionization fraction is given by the value of the reionization redshift and the
redshift interval, in which the reionization is completed. We evaluate the
effects of the UV radiation background on the CMB angular power spectrum taking
into account different temporal evolutions of the ionization fraction. We show
that through E-mode CMB polarization power spectrum measurements, the Planck
experiment will have the sensitivity to distinguish between different
reionization histories even when they imply the same optical depth to electron
scattering and degenerated temperature anisotropy power spectra.


title: Where are the X-ray QPOs in active galaxies?

abstract:
  In this paper we address the question of whether existing X-ray observations
of Seyfert galaxies are sufficiently sensitive to detect quasi-periodic
oscillations (QPOs) similar to those observed in the X-ray variations of
Galactic Black Holes (GBHs). We use data from XMM-Newton and simulated data
based on the best RXTE long-term monitoring light curves, to show that if X-ray
QPOs are present in Seyfert X-ray light curves - with similar shapes and
strengths to those observed in GBHs, but at lower frequencies commensurate with
their larger black hole masses - they would be exceedingly difficult to detect.
Our results offer a simple explanation for the present lack of QPO detections
in Seyferts. We discuss the improvements in telescope size and monitoring
patterns needed to make QPO detections feasible. The most efficient type of
future observatory for searching for X-ray QPOs in AGN is an X-ray All-Sky
Monitor (ASM). A sufficiently sensitive ASM would be ideally suited to
detecting low frequency QPOs in nearby AGN. The detection of AGN QPOs would
strengthen the AGN-GBH connection and could serve as powerful diagnostics of
the black hole mass, and the structure of the X-ray emitting region in AGN.


title: Detecting X-ray QPOs in Active Galaxies

abstract:
  Since EXOSAT produced the first good quality X-ray light curves of Seyfert
galaxies there have been several claims of quasi-periodic oscillations (QPOs).
None of these have withstood repeated analyses and observations. We review some
problems concerning the detection of QPOs.


title: From Hubble diagrams to scale factors

abstract:
  We present a lower bound on the radius of the universe today $a_0$ and a
monotonicity constraint on the Hubble diagram. Our theoretical input is
Einstein's kinematics and maximally symmetric universes. Present supernova data
yield $a_0 > 1.2\cdot 10^{26}$ m. A first attempt to quantify the monotonicity
constraint is described. We do not see any indication of non-monotonicity.


title:
The age of the Galactic thin disk from Th/Eu nucleocosmochronology III.
  Extended sample

abstract:
  The first determination of the age of the Galactic thin disk from Th/Eu
nucleocosmochronology was accomplished by us in Papers I and II. The present
work aimed at reducing the age uncertainty by expanding the stellar sample with
the inclusion of seven new objects - an increase by 37%. A set of [Th/Eu]
abundance ratios was determined from spectral synthesis and merged with the
results from Paper I. Abundances for the new, extended sample were analyzed
with the aid of a Galactic disk chemical evolution (GDCE) model developed by us
is Paper II. The result was averaged with an estimate obtained in Paper II from
a conjunction of literature data and our GDCE model, providing our final,
adopted disk age T_G = (8.8 +/- 1.7) Gyr with a reduction of 0.1 Gyr (6%) in
the uncertainty. This value is compatible with the most up-to-date white dwarf
age determinations (<~ 10 Gyr). Considering that the halo is currently presumed
to be (13.5 +/- 0.7) Gyr old, our result prompts groups developing Galactic
formation models to include an hiatus of (4.7 +/- 1.8) Gyr between the
formation of halo and disk.


title: FADC Pulse Reconstruction Using a Digital Filter for the MAGIC Telescope

abstract:
  Presently, the MAGIC telescope uses a 300 MHz FADC system to sample the
transmitted and shaped signals from the captured Cherenkov light of air
showers. We describe a method of Digital Filtering of the FADC samples to
extract the charge and the arrival time of the signal: Since the pulse shape is
dominated by the electronic pulse shaper, a numerical fit can be applied to the
FADC samples taking the noise autocorrelation into account. The achievable
performance of the digital filter is presented and compared to other signal
reconstruction algorithms.


title: Two New Milky Way Companions

abstract:
  We discuss the detection limits and current status of a uniform survey of
SDSS I for ultra-faint Milky Way dwarf galaxies. We present the properties of
two new, low surface brightness Milky Way companions discovered as a result of
this survey. One of these companions is the Ursa Major dwarf, the newest dwarf
spheroidal companion to the Milky Way and the lowest luminosity galaxy yet
known. Ursa Major is about 100 kpc away and is similar to Sextans, but with
roughly an order of magnitude fewer stars. The other companion, SDSSJ1049+5103,
lies $\sim$ 50 kpc away. Its stellar distribution suggests that it may be
undergoing tidal stripping. This companion is extremely faint (M$_V$ $\sim$ -3)
but has a large half-light size for its luminosity. It is therefore unclear
whether it is a globular cluster or a dwarf galaxy.


title:
Theoretical Color-Magnitude Diagrams and the Star Forming Histories of
  Interacting Open Multi-population Model Galaxies: Bursts and Busts

abstract:
  This note presents theoretical color-magnitude diagrams (CMDs) and
metallicity evolution for Galactic multi-population models coupled to stellar
evolution models for systems undergoing stripping and re-accretion of ambient
material, called ``open'' systems in our recent studies (Valle, Galli, and
Shore, 2005, A&A, 435, 551). We show that the observables for such systems, in
particular those related to the recovered star formation as a function of time,
are ambiguous -- systems with non-monotonic star formation rates can appear as
either bursting systems or galaxies with a hiatus in the star formation.


title:
Infrared luminosity functions from the Chandra Deep Field South : the
  Spitzer view on the history of dusty star formation at 0<z<1

abstract:
  We analyze a sample of ~2600 MIPS/Spitzer 24mic sources brighter than ~80muJy
and located in the Chandra Deep Field South to characterize the evolution of
the comoving infrared (IR) energy density of the Universe up to z~1. Using
published ancillary optical data we first obtain a nearly complete redshift
determination for the 24mic objects associated with R<24 counterparts at z<1.
We find that the 24mic population at 0.5<z<1 is dominated by ``Luminous
Infrared Galaxies'' (i.e., 10^11 L_sol < L_IR < 10^12 L_sol), the counterparts
of which appear to be also luminous at optical wavelengths and tend to be more
massive than the majority of optically-selected galaxies. We finally derive
15mic and total IR luminosity functions (LFs) up to z~1. In agreement with the
previous results from ISO and SCUBA and as expected from the MIPS source number
counts, we find very strong evolution of the contribution of the IR-selected
population with lookback time. Pure evolution in density is firmly excluded by
the data, but we find considerable degeneracy between strict evolution in
luminosity and a combination of increases in both density and luminosity (L*_IR
prop. to (1+z)^{3.2_{-0.2}^{+0.7}}, Phi*_IR prop. to
(1+z)^{0.7_{-0.6}^{+0.2}}). Our results imply that the comoving IR energy
density of the Universe evolves as (1+z)^(3.9+/-0.4) up to z~1 and that
galaxies luminous in the infrared (i.e., L_IR > 10^11 L_IR) are responsible for
70+/-15% of this energy density at z~1. Taking into account the contribution of
the UV luminosity evolving as (1+z)^~2.5, we infer that these IR-luminous
sources dominate the star-forming activity beyond z~0.7. The uncertainties
affecting these conclusions are largely dominated by the errors in the
k-corrections used to convert 24mic fluxes into luminosities.


title: A "UV+IR" history of star formation at 0<z<1

abstract:
  The combination of both contributions from the observed UV emission and the
absorbed radiations reprocessed in the infrared represents the ideal approach
to constrain the activity of massive star formation in galaxies. Using recent
results from GALEX and Spitzer, we compare the evolutions of the UV and IR
energy densities with redshift as well as their contributions to the star
formation history at 0<z<1. We find that the comoving IR luminosity is
characterized by a much faster evolution than seen in the UV. Our results also
indicate that ~70% of the star-forming activity at z~1 is produced by the
so-called IR-luminous sources (L_IR > 10^11 L_sol).


title:
Inter-occurrence Times in the Bak-Tang-Wiesenfeld Sandpile Model: A
  Comparison with the Turbulent Statistics of Solar Flares

abstract:
  A sequence of bursts observed in an intermittent time series may be caused by
a single avalanche, even though these bursts appear as distinct events when
noise and/or instrument resolution impose a detection threshold. In the
Bak-Tang-Wiesenfeld sandpile, the statistics of quiet times between bursts
switches from Poissonian to scale invariant on raising the threshold for
detecting instantaneous activity, since each zero-threshold avalanche breaks
into a hierarchy of correlated bursts. Calibrating the model with the time
resolution of GOES data, qualitative agreement with the inter-occurrence time
statistics of solar flares at different intensity thresholds is found.


title:
STEREO ARRAY of 30 m Imaging Atmospheric Cherenkov Telescopes: A
  Next-Generation Detector for Ground-Based High Energy Gamma-ray Astronomy

abstract:
  The construction of the H.E.S.S. (High Energy Stereoscopic System), a
superior system of four 12 m imaging atmospheric Cherenkov telescopes, has been
completed recently in the Namib desert close to Windhoek, at 1800 m above sea
level. This new generation of ground-based gamma-ray detectors has an energy
threshold of about 100 GeV in observations at zenith and a sensitivity of about
1% Crab flux for a point-like gamma-ray source. Such high sensitivity was
achieved due to 0.1 degree angular resolution, as well as, severe cosmic ray
background rejection acquired from multi-fold imaging of individual atmospheric
showers. In addition H.E.S.S. has a rather good energy resolution of 15%.
H.E.S.S. has been taking routine observations of the gamma-ray sources since
December 2003. The outstanding physics results achieved with H.E.S.S. already
in a first year of its exploitation strongly encourage further development of
imaging atmospheric Cherenkov technique for high-quality gamma-ray
observations, which is basically driven by father reduction of the energy
threshold of a forthcoming major future gamma-ray detector. Here we are dealing
with such a detector. Basic results on performance and sensitivity for a single
stand-alone 30 m imaging atmospheric Cherenkov telescope, as well as for a
system of two and five telescopes, are discussed here.


title:
Correlations from Galactic foregrounds in the 1-year Wilkinson Microwave
  Anisotropy Probe WMAP data

abstract:
  We study a specific correlation in spherical harmonic multipole domain for
cosmic microwave background (CMB) analysis. This group of correlation between
\Delta l=4n, n=1,2... is caused by symmetric signal in the Galactic coordinate
system. An estimator targeting such correlation therefore helps remove the
localized bright point-like sources in the Galactic plane and the strong
diffused component down to the CMB level. We use 3 toy models to illustrate the
significance of these correlations and apply this estimator on some derived CMB
maps with foreground residuals. In addition, we show that our proposed
estimator significantly damp the phase correlations caused by Galactic
foregrounds. This investigation provides the understanding of mode correlations
caused by Galactic foregrounds, which is useful for paving the way for
foreground cleaning methods for the CMB.


title: Tracing Galaxy Formation with Stellar Halos I: Methods

abstract:
  If the favored hierarchical cosmological model is correct, then the Milky Way
system should have accreted ~100-200 luminous satellite galaxies in the past
\~12 Gyr. We model this process using a hybrid semi-analytic plus N-body
approach which distinguishes explicitly between the evolution of light and dark
matter in accreted satellites. This distinction is essential to our ability to
produce a realistic stellar halo, with mass and density profile much like that
of our own Galaxy, and a surviving satellite population that matches the
observed number counts and structural parameter distributions of the satellite
galaxies of the Milky Way. Our model stellar halos have density profiles which
typically drop off with radius faster than those of the dark matter. They are
assembled from the inside out, with the majority of mass (~80%) coming from the
\~15 most massive accretion events. The satellites that contribute to the
stellar halo have median accretion times of ~9 Gyr in the past, while surviving
satellite systems have median accretion times of ~5 Gyr in the past. This
implies that stars associated with the inner halo should be quite different
chemically from stars in surviving satellites and also from stars in the outer
halo or those liberated in recent disruption events. We briefly discuss the
expected spatial structure and phase space structure for halos formed in this
manner. Searches for this type of structure offer a direct test of whether
cosmology is indeed hierarchical on small scales.


title: Obliquity Tides on Hot Jupiters

abstract:
  Obliquity tides are a potentially important source of heat for extrasolar
planets on close-in orbits. Although tidal dissipation will usually reduce the
obliquity to zero, a nonzero obliquity can persist if the planet is in a
Cassini state, a resonance between spin precession and orbital precession.
Obliquity tides might be the cause of the anomalously large size of the
transiting planet HD 209458b.


title: A unified model for black hole X-ray binary jets ?

abstract:
  We have recently put forward a 'unified' semi-empirical model for the
coupling between accretion and jet production in galactic black hole X-ray
binaries (published in MNRAS, 2004). In this paper we summarise this model and
briefly discuss relevant considerations which have arisen since its
publication.


title: Evidence for Spectropolarimetric Diversity in Type Ia Supernovae

abstract:
  We present single-epoch, post-maximum spectropolarimetry of four Type Ia
supernovae (SNe Ia) that span a range of spectral and photometric properties:
SN 2002bf and SN 2004dt exhibit unusually high-velocity (HV) absorption lines.
SN 1997dt is probably somewhat subluminous, and SN 2003du is slightly
overluminous. We detect polarization modulations across strong lines in all
four objects, demonstrating that all are intrinsically polarized. However, the
nature and degree of the polarization varies considerably. Including all SNe Ia
studied thus far, the following order emerges in terms of increasing strength
of line-polarization features: ordinary/overluminous < subluminous < HV SNe Ia,
with the strength of the line-polarization features increasing from 0.2% in the
slightly overluminous SN 2003du to 2% in both of the HV SNe Ia in our study.
The most convincing explanation for the line polarization of all objects is
partial obscuration of the photosphere by clumps of intermediate-mass elements
(IMEs) forged in the explosion; the polarization characteristics of the HV SNe
Ia in particular effectively rule out a simple ellipsoidal asphericity as the
root cause of their line polarization. That SNe Ia are separable into different
groups based on their spectropolarimetric characteristics may help narrow down
progenitor possibilities and/or explosion physics. In particular, the recently
proposed gravitationally confined detonation model may provide an attractive
explanation for many of the observed polarization characteristics of HV SNe Ia.


title:
The Brightest Point X-Ray Sources in Elliptical Galaxies and the Mass
  Spectrum of Accreting Black Holes

abstract:
  We propose that the shape of the upper-end X-ray luminosity function observed
in elliptical galaxies for point sources is a footprint of the black-hole (BH)
mass spectrum among old X-ray transients formed in the galaxies. We show that
this underlying BH mass spectrum is modified by a weighting factor that is
related to the transient duty cycle and it generally depends on the BH mass and
XRB donor type (main-sequence, red-giant, or white-dwarf donors). A duty cycle
that depends on the binary mass-transfer rate relative to the critical rate for
transient behavior is most probably favored. We also find that the derived BH
mass spectrum slope depends on the strength of angular momentum loss due to
magnetic braking for main-sequence donors. More specifically, we find that, for
``standard'' magnetic braking, BH XRBs with red-giant donors dominate the
upper-end XLF; for weaker magnetic braking prescriptions main-sequence donors
are found to be dominant. In both cases the BH mass spectrum has a differential
slope of ~2.5 and an upper BH mass cut-off at ~20 Msun is needed to understand
the very brightest of the BH XRBs in elliptical galaxies. We expect that our
result will help to constrain binary population synthesis models and the
adopted relations between black holes and the masses of their progenitors.


title:
A high angular-resolution search for the progenitor of the type Ic
  Supernova 2004gt

abstract:
  We report the results of a high-spatial-resoltion search for the progenitor
of type Ic supernova SN 2004gt, using the newly commissioned Keck laser-guide
star adaptive optics system (LGSAO) along with archival Hubble Space Telescope
data. This is the deepest search yet performed for the progenitor of any type
Ib/c event in a wide wavelength range stretching from the far UV to the near
IR. We determine that the progenitor of SN 2004gt was most likely less luminous
than M_V=-5.5 and M_B=-6.5 magnitudes. The massive stars exploding as
hydrogen-deficient core-collapse supernovae (SNe) should have lost their outer
hydrogen envelopes prior to their explosion, either through winds -- such stars
are identified within our Galaxy as Wolf-Rayet (W-R) stars -- or to a binary
companion. The luminosity limits we set rule out more than half of the known
galactic W-R stars as possible progenitors of this event. In particular, they
imply that a W-R progenitor should have been among the more-evolved (highly
stripped, less luminous) of these stars, a concrete constraint on its
evolutionary state just prior to core collapse. The possibility of a less
luminous, lower-mass binary progenitor cannot be constrained. This study
demonstrates the power of LGS observations in furthering our understanding of
core collapse, and the physics powering supernovae, GRBs and XRFs.


title:
Spitzer detections of new dust components in the outflow of the Red
  Rectangle

abstract:
  We present Spitzer high spectral resolution IRS spectroscopy of three
positions in the carbon-rich outflow of post-AGB star HD 44179, better known as
the Red Rectangle. Surprisingly, the spectra show some strong unknown
mid-infrared resonances, in the 13-20 micron range. The shape and position of
these resonances varies with position in the nebula, and are not correlated
with the PAH features. We conclude these features are due to oxygen-rich
minerals, located in a region which is believed to be predominantly
carbon-rich. We provide possible explanations for the presence of oxygen-rich
dust in the carbon-rich outflows. Simple Mg-Fe-oxides are suggested as carriers
of these unidentified features.


title:
Investigating the Nature of the Dust Emission around Massive Protostar
  NGC 7538 IRS 1: Circumstellar Disk and Outflow?

abstract:
  We have obtained high resolution mid-infrared images of the high mass
protostar NGC 7538 IRS 1 using Michelle on Gemini North and find that the
circumstellar dust associated with this source is extended on both large and
small scales. The large-scale mid-infrared emission is asymmetric about the
peak of IRS 1, being more extended to the northwest than the southeast. The
position angle of the mid-infrared emission is similar to the position angle of
the linearly distributed methanol masers at this location which are thought to
trace a circumstellar disk. However, this position angle is also very similar
to that of the CO outflow in this region which appears to be centered on IRS 1.
We suggest that the large-scale extended mid-infrared emission is coming from
dust heated on the walls of the outflow cavities near the source. IRS 1 is also
elongated in the mid-infrared on a smaller scale, and this elongation is near
PERPENDICULAR to the axis of the CO outflow (and the linearly distributed
methanol masers). Because of its orientation with respect to the outflow and
its estimated size (R_disk~450AU at 11.7um), we propose that the small-scale
elongation seen in the mid-infrared is a circumstellar disk that may be
collimating the outflow from IRS 1.


title: Imaging of the Radio Remnant of SN 1987A at 12 mm Wavelength

abstract:
  Observations of the radio remnant of Supernova 1987A using the Australia
Telescope Compact Array in the 12-mm band on 2003 July 31 (day 6002.7 after the
explosion) give the first fully resolved radio image of the supernova remnant.
The diffraction-limited image has a resolution of about 0.45 arcsec, a factor
of two better than that of the 3-cm images previously obtained. There is
excellent agreement between the 12-mm image and a contemporaneous
super-resolved 3-cm image. Super-resolution of the 12-mm image gives a further
factor of two improvement in resolution, to 0.25 arcsec, albeit with limited
dynamic range. While the spatial distributions of the radio and X-ray emission
are broadly similar, there are significant differences in detail with no
correspondence in the regions of brightest emission. The 12-mm image is well
modelled by a thick equatorial ring inclined at 43 deg to the line of sight.
This, together with the common east-west asymmetry and the relatively steady
increase in the radio flux density, suggests that the reverse shock is the main
site for generation of the radio emission.


title: Evaluation of cosmic ray rejection algorithms on single-shot exposures

abstract:
  To maximise data output from single-shot astronomical images, the rejection
of cosmic rays is important. We present the results of a benchmark trial
comparing various cosmic ray rejection algorithms. The procedures assess
relative performances and characteristics of the processes in cosmic ray
detection, rates of false detections of true objects and the quality of image
cleaning and reconstruction. The cosmic ray rejection algorithms developed by
Rhoads (2000), van Dokkum (2001), Pych (2004) and the IRAF task xzap by
Dickinson are tested using both simulated and real data. It is found that
detection efficiency is independent of the density of cosmic rays in an image,
being more strongly affected by the density of real objects in the field. As
expected, spurious detections and alterations to real data in the cleaning
process are also significantly increased by high object densities. We find the
Rhoads' linear filtering method to produce the best performance in detection of
cosmic ray events, however, the popular van Dokkum algorithm exhibits the
highest overall performance in terms of detection and cleaning.


title: Prospects in space-based Gamma-Ray Astronomy

abstract:
  With the unequalled INTEGRAL observatory, ESA has provided a unique tool to
the astronomical community that has made Europe the world leader in the field
of gamma-ray astronomy. INTEGRAL provides an unprecedented survey of the soft
gamma-ray sky, revealing hundreds of sources of different kinds, new classes of
objects, extraordinary views of antimatter annihilation in our Galaxy, and
fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the
longly awaited global overview over the soft gamma-ray sky, there is a growing
need to perform deeper, more focused investigations of gamma-ray sources,
comparable to the step that has been taken in X-rays by going from the ROSAT
survey satellite to the more focused XMM-Newton observatory. Technological
advances in the past years in the domain of gamma-ray focusing using Laue
diffraction techniques have paved the way towards a future European gamma-ray
mission, that will outreach past missions by large factors in sensitivity and
angular resolution. Such a future Gamma-Ray Imager will allow to study particle
acceleration processes and explosion physics in unprecedented depth, providing
essential clues on the intimate nature of the most violent and most energetic
processes in the Universe.


title:
Evidence for Evolution or Bias in Host Extinctions of Type 1a Supernovae
  at High Redshift

abstract:
  Type 1a supernova magnitudes conventionally include an additive parameter
called the extinction coefficient. We find that the extinction coefficients of
a popular ``gold'' set are well correlated with the deviation of magnitudes
from Hubble diagrams. If the effect is due to bias, extinctions have been
overestimated, which makes supernovas appear more dim. The statistical
significance of the extinction-acceleration correlation has a random chance
probability of less than one in a million. The hypothesis that extinction
coefficients should be corrected empirically provides greatly improved fits to
both accelerating and non-accelerating models, with the independent feature of
eliminating any significant correlation of residuals.


title: Length of inflation and WMAP data in the case of power-law inflation

abstract:
  The effect of the length of inflation on the power spectra of scalar and
tensor perturbations is estimated using the power-law inflation model with a
scale factor of a(t) = t^q. Considering various pre-inflation models with
radiation-dominated or matter-dominated periods before inflation in combination
with two matching conditions, the power spectrum of curvature perturbations at
large scales is calculated. Comparison of the derived angular power spectrum
with the Wilkinson Microwave Anisotropy Probe (WMAP) data reveals a possibility
that the WMAP can be explained by the finite length of inflation model if the
length of inflation is near 60 e-folds and q>200.


title:
Optical-Near Infrared Color Gradients of Elliptical Galaxies and Their
  Environmental Dependence

abstract:
  We have studied the environmental effect on optical-NIR color gradients of
273 nearby elliptical galaxies. Color gradient is a good tool to study the
evolutionary history of elliptical galaxies, since the steepness of the color
gradient reflects merging history of early types. When an elliptical galaxy
goes through many merging events, the color gradient can be get less steep or
reversed due to mixing of stars. One simple way to measure color gradient is to
compare half-light radii in different bands. We have compared the optical and
near infrared half-light radii of 273 early-type galaxies from Pahre(1999). Not
surprisingly, we find that r$_{e}$(V)s (half-light radii measured in V-band)
are in general larger than r$_{e}$(K)s (half-light radii measured in K-band).
However, when divided into different environments, we find that elliptical
galaxies in the denser environment have gentler color gradients than those in
the less dense environment. Our finding suggests that elliptical galaxies in
the dense environment have undergone many merging events and the mixing of
stars through the merging have created the gentle color gradients.


title: The Chemical Composition of Local Group Dwarf Spheroidals

abstract:
  I will review the progress of VLT spectroscopy of large numbers of individual
stars in nearby dwarf spheroidal galaxies. This spectroscopy has allowed us to
obtain detailed insights into the chemical and dynamical properties of the
resolved stellar population in these nearby systems.


title: Soft coincidence in late acceleration

abstract:
  We study the coincidence problem of late cosmic acceleration by assuming that
the present ratio between dark matter and dark energy is a slowly varying
function of the scale factor. As dark energy component we consider two
different candidates, first a quintessence scalar field, and then a tachyon
field. In either cases analytical solutions for the scale factor, the field and
the potential are derived. Both models show a good fit to the recent
magnitude-redshift supernovae data. However, the likelihood contours disfavor
the tachyon field model as it seems to prefer a excessively high value for the
matter component.


title: A continuous Flaring- to Normal-branch transition in Sco X-1

abstract:
  We report the first resolved rapid transition from a Flaring Branch
Oscillation to a Normal Branch Oscillation in the RXTE data of the Z source Sco
X-1. The transition took place on a time scale of ~100 seconds and was clearly
associated to the Normal Branch-Flaring Branch vertex in the color-color
diagram. We discuss the results in the context of the possible association of
the Normal Branch Oscillation with other oscillations known both in
Neutron-Star and Black-Hole systems, concentrating on the similarities with the
narrow 4-6 Hz oscillations observed at high flux in Black-Hole Candidates.


title:
Distant Field BHB Stars III: Identification of a probable outer halo
  stream at Galactocentric distance r = 70 kpc

abstract:
  We present VLT-FORS1 spectra of a sample of 34 faint 20.0 < g* < 21.1 A-type
stars selected from the Sloan Digital Sky Survey Early Data Release, with the
goal of measuring the velocity dispersion of blue horizontal branch (BHB) stars
in the remote Galactic halo, R~80kpc. We show that colour selection with 1.08 <
u*-g* < 1.40 and -0.2 < g*-r* < -0.04 minimises contamination of the sample by
less luminous blue stragglers. In classifying the stars we confine our
attention to the 20 stars with spectra of signal-to-noise ratio > 15 per
Angstrom. Classification produces a sample of eight BHB stars at distances
65-102 kpc from the Sun (mean 80 kpc), which represents the most distant sample
of Galactic stars with measured radial velocities. The dispersion of the
measured radial component of the velocity with respect to the centre of the
Galaxy is 58+-15km/s. This value is anomalously low in comparison with measured
values for stars at smaller distances, as well as for satellites at similar
distances. Seeking an explanation for the low measured velocity dispersion,
further analysis reveals that six of the eight remote BHB stars are plausibly
associated with a single orbit. Three previously known outer halo carbon stars
also appear to belong to this stream. The velocity dispersion of all nine stars
relative to the orbit is only 15+-4 km/s. Further observations along the orbit
are required to trace the full extent of this structure on the sky.


title: A resolved outflow of matter from a Brown Dwarf

abstract:
  The birth of stars involves not only accretion but also, counter-intuitively,
the expulsion of matter in the form of highly supersonic outflows. Although
this phenomenon has been seen in young stars, a fundamental question is whether
it also occurs amongst newborn brown dwarfs: these are the so-called 'failed
stars', with masses between stars and planets, that never manage to reach
temperatures high enough for normal hydrogen fusion to occur. Recently,
evidence for accretion in young brown dwarfs has mounted, and their spectra
show lines that are suggestive of outflows. Here we report spectro-astrometric
data that spatially resolve an outflow from a brown dwarf. The outflow's
characteristics appear similar to, but on a smaller scale than, outflows from
normal young stars. This result suggests that the outflow mechanism is
universal, and perhaps relevant even to the formation of planets.


title: A very extended reionization epoch ?

abstract:
  The recent observations of cross temperature-polarization power spectra of
the Cosmic Microwave Background (CMB) made by the WMAP satellite are in better
agreement with a high value of the Thomson scattering optical depth \tau
\approx 0.17. This value is close to \tau = 0.3, which is taken as the upper
limit in the parameter extraction analysis made by the WMAP team. However,
models with \tau \sim 0.3 provide a good fit to current CMB data and are not
significantly excluded when combined with Large Scale Structure data. By making
use of a self-consistent reionization model, we verify the astrophysical
feasibility of models with \tau \sim 0.3. It turns out that current data on
various observations related to the thermal and ionization history of the
intergalactic medium are not able to rule out \tau \sim 0.3. The possibility of
a very extended reionization epoch can significantly undermine the WMAP
constraints on crucial cosmological parameters such as the Hubble constant, the
spectral index of primordial fluctuations and the amplitude of dark matter
clustering.


title:
Curious Variables Experiment (CURVE). CCD Photometry of Dwarf Nova V660
  Herculis

abstract:
  We report extensive photometry of the dwarf nova V660 Herculis. During our
campaign, lasting from August 2003 to November 2004, we recorded one bright
eruption which turned out to be a superoutburst lasting about 15 days and
having amplitude of ~4.5 mag. Clear superhumps with a mean period of Psh =
0.080924(18) days were present during all nights of the superoutburst. The
period of the superhumps was not stable and in the interval covered by our
observations it decreased with a rate of -4.0(1.4) * 10^{-5}.
  Basing on our data and the known orbital period of the binary (Thorstensen
and Fenton 2003) we calculate the period excess of 3.4 +/- 0.1%, which is
typical for an SU UMa star at this orbital period. This value indicates that
the mass ratio of the system is q=0.154.


title: SMC: Stellar Populations through deep CMDs

abstract:
  We present deep color-magnitud diagrams (CMDs) reaching the oldest
main-sequence turnoffs for 12 fields in the SMC. The {\it B}-band and {\it
R}-band observations were performed using the 100-inch Ir\'en\'ee du Pont
telescope at Las Campanas Observatory, Chile, during four different campaigns
(2001-2004). Our fields cover a wide range of galactocentric distance ranging
from $\sim1\deg$ to $\sim4\deg$ from the center of the galaxy and are located a
different position angles. Photometry was carried out using DAOPHOT
II/ALLSTAR/ALLFRAME. Teramo isochrones have been overlapped. All our
unprecedented deep ground-based CMDs reach the old MS turnoffs with very good
photometric accuracy. They clearly show stellar population gradients as a
function of both galactocentric distance and position angle. The most
conspicuous difference involves the young population (age$<$1 Gyr): the young
MS is much more populated on the eastern fields, located on the SMC wing area,
than on the western fields located at similar galactocentric radius. In
addition, the main stellar population gets progresively older on average as we
go to larger galactocentric radius.


title:
A Detailed Study of Molecular Clouds toward the TeV Gamma-Ray SNR
  G347.3-0.5

abstract:
  We present a detailed study of molecular gas toward the supernovae remnant
G347.3-0.5 (J1713.7-3946) obtained with the 4m mm/sub-mm telescope NANTEN .
This study has revealed that several intensity peaks and the overall
distribution of the molecular gas with radial velocities from -12 km s-1 to -3
km s-1 show a remarkably good correlation with the X-ray features, strongly
supporting the kinematic distance ~ 1 kpc derived by Fukui et al. (2003), as
opposed to 6 kpc previously claimed. In addition, we show that absorption of
X-rays is caused by local molecular gas at softer X-ray bands. Subsequent
measurements of the CO(J=3-2) made with the ASTE 10 m and CSO 10.4 m telescopes
toward the molecular intensity peaks have revealed higher excitation
conditions, most likely higher temperatures above ~ 30 K as compared to that of
the typical gas in low mass dark clouds. This is most likely caused by enhanced
heating by the high energy events in the SNR, where possible mechanisms include
heating by X-rays, gamma-rays, and/or cosmic ray protons, although we admit
additional radiative heating by young protostars embedded may be working as
well. In one of the CO peaks, we have confirmed the presence of broad molecular
wings of ~ 20 km s-1 velocity extent in the CO(J=3-2) transition. The SNR
evolution is well explained as the free expansion phase based on the distance
of 1 kpc.