title: Homogeneous and isotropic big rips?

abstract:
  We investigate the way big rips are approached in a fully inhomogeneous
description of the space-time geometry. If the pressure and energy densities
are connected by a (supernegative) barotropic index, the spatial gradients and
the anisotropic expansion decay as the big rip is approached. This behaviour is
contrasted with the usual big-bang singularities. A similar analysis is
performed in the case of sudden (quiescent) singularities and it is argued that
the spatial gradients may well be non-negligible in the vicinity of pressure
singularities.


title:
A search for very high energy gamma-ray emission from the starburst
  galaxy NGC 253 with H.E.S.S

abstract:
  We present the result of 28 hours of observations of the nearby starburst
galaxy NGC 253 with the H.E.S.S. detector in 2003. We find no evidence for very
high energy gamma-ray emission from this object. Gamma-ray emission above 400
GeV from NGC 253 had been reported by the CANGAROO collaboration in 2002. From
the H.E.S.S. data we derive upper limits on the flux above 300 GeV of 1.9 *
10^-12 photons cm^-2 s^-1 for a point-like source and 6.3 * 10^-12 photons
cm^-2 s^-1 for a source of radius 0.5 degrees as reported by CANGAROO, both at
a confidence level of 99%. These upper limits are inconsistent with the
spectrum reported by CANGAROO. The expected very high energy gamma-ray emission
from this object is discussed in the framework of a galactic wind propagation
model.


title:
Superhumps in Cataclysmic Binaries. XXV. q_crit, epsilon(q), and
  Mass-Radius

abstract:
  We report on successes and failures in searching for positive superhumps in
cataclysmic variables, and show the superhumping fraction as a function of
orbital period. Basically, all short-period systems do, all long-period systems
don't, and a 50% success rate is found at P_orb=3.1+-0.2 hr. We can use this to
measure the critical mass ratio for the creation of superhumps. With a
mass-radius relation appropriate for cataclysmic variables, and an assumed mean
white-dwarf mass of 0.75 M_sol, we find a mass ratio q_crit=0.35+-0.02.
  We also report superhump studies of several stars of independently known mass
ratio: OU Virginis, XZ Eridani, UU Aquarii, and KV UMa (= XTE J1118+480). The
latter two are of special interest, because they represent the most extreme
mass ratios for which accurate superhump measurements have been made. We use
these to improve the epsilon(q) calibration, by which we can infer the elusive
q from the easy-to-measure epsilon (the fractional period excess of P_superhump
over P_orb). This relation allows mass and radius estimates for the secondary
star in any CV showing superhumps. The consequent mass-radius law shows an
apparent discontinuity in radius near 0.2 M_sol, as predicted by the disrupted
magnetic braking model for the 2.1-2.7 hour period gap. This is effectively the
"empirical main sequence" for CV secondaries.


title: Interpreting Cosmological Vacuum Decay

abstract:
  The cosmological vacuum decay scenario recently proposed by Wang and Meng
\cite{wm} is rediscussed. From thermodynamic arguments it is found that the
$\epsilon$ parameter quantifying the vacuum decay rate must be positive in the
presence of particle creation. If there is no particle creation, the proper
mass of Cold Dark Matter (CDM) particles is necessarily a time dependent
quantity, scaling as $m(t) = m_o a(t)^{\epsilon}$. By considering the presence
of baryons in the cosmological scenario, it is also shown that their dynamic
effect is to alter the transition redshift $z_*$ (the redshift at which the
Universe switches from decelerating to accelerating expansion), predicting
values of $z_*$ compatible with current estimates based on type Ia supernova.
In order to constrain the $\Omega_m - \epsilon$ plane, a joint statistical
analysis involving the current supernovae observations, gas mass fraction
measurements in galaxy clusters and CMB data is performed. At 95% c.l. it is
found that the vacuum decay rate parameter lies on the interval $\epsilon =
0.11 \pm 0.12$). The possibility of a vacuum decay into photons is also
analyzed. In this case, the energy density of the radiation fluid scales as
$\rho_r = \rho_{ro}a^{-4 + \epsilon}$, and its temperature evolution law obeys
$T(t) = T_oa(t)^{\epsilon/4 - 1}$.


title: Lyman alpha emission from local starburst galaxies and high-z objects

abstract:
  We review the history and the current status of the understanding of the
processes that regulate Lyman alpha emission from star-forming galaxies. We
present some of the most recent results of our study to image local starburst
galaxies in the Lyman alpha emission line using the Advanced Camera for Surveys
on the Hubble Space Telescope. Particular attention is dedicated to our study
of the low-metallicity, dust-poor Blue Compact Galaxy ESO338-IG04. We discuss
some of our local observational results with reference to the interpretation of
results of high-redshift Lyman alpha surveys and recent simulations of the
detection properties of high-z Lyman alpha emitting objects performed by our
group.


title: Mass Estimates for Some of the Binary Lenses in OGLE III Database

abstract:
  We model binary microlensing events OGLE 2003-BLG-170, 267, and 291. Source
angular sizes are measured for the events 267 and 291. Model fits to the light
curves give parallaxes for the events 267 and 291, and relative source sizes
for 170 and 267. Selfconsistency arguments provide extra limits on the models
of the event 291. As a result we obtain likelihood estimate of the lens mass
for the event 170, mass measurement based on angular size and parallax for 267,
and narrow limits on mass in the case of 291. Brown dwarfs are most likely
candidates for some of the lens components. The influence of the binary lens
rotation and the Earth parallax may be important but hard to distinguish when
modeling relatively short lasting binary lens events.


title: Effects of line-blocking on the non-LTE Fe I spectral line formation

abstract:
  The effects of background line opacity (line-blocking) in statistical
equilibrium calculations for Fe in late-type stellar atmospheres have been
investigated using an extensive and up-to-date model atom with radiative data
primarily from the IRON Project. The background metal line opacities have been
computed using data from the MARCS stellar model atmospheres.
  While accounting for this line opacity is important at solar metallicity, the
differences between calculations including and excluding line-blocking at low
metallicity are insignificant for the non-local thermodynamic equilibrium
(non-LTE) abundance corrections for Fe I lines. The line-blocking has no impact
on the non-LTE effects of Fe II lines. The dominant uncertainty in Fe non-LTE
calculations for metal-poor stars is still the treatment of the inelastic H I
collisions, which have here been included using scaling factors to the
classical Drawin formalism, and whether or not thermalisation of the high Fe I
levels to Fe II ground state should be enforced. Without such thermalisation,
the Fe I non-LTE abundance corrections are substantial in metal-poor stars:
about 0.3 dex with efficient (i.e. Drawin-like) H I collisions and about 0.5
dex without. Without both thermalisation and H I collisions, even Fe II lines
show significant non-LTE effects in such stars.


title:
The orbit of the close spectroscopic binary epsilon Lupi and the
  intrinsic variability of its early B-type components

abstract:
  We subjected 106 new high-resolution spectra of the double-lined
spectroscopic close binary epsilon Lupi, obtained in a time-span of 17 days
from two different observatories, to a detailed study of orbital and intrinsic
variations. We derived accurate values of the orbital parameters. We refined
the sidereal orbital period to 4.55970 days and the eccentricity to e=0.277. By
adding old radial velocities, we discovered the presence of apsidal motion with
a period of the rotation of apses of about 430 years. Such a value agrees with
theoretical expectations. Additional data is needed to confirm and refine this
value. Our dataset did not allow us to derive the orbit of the third body,
which is known to orbit the close system in approximately 64 years. We present
the secondary of epsilon Lupi as a new beta Cephei variable, while the primary
is a beta Cephei suspect. A first detailed analysis of line-profile variations
of both primary and secondary led to detection of one pulsation frequency near
10.36 c/d in the variability of the secondary, while no clear periodicity was
found in the primary, although low-amplitude periodicities are still suspected.
The limited accuracy and extent of our dataset did not allow any further
analysis, such as mode-identification.


title:
Molecular Hydrogen in Orion as Observed by the Far Ultraviolet
  Spectroscopic Explorer

abstract:
  Diffuse far-ultraviolet stellar emission scattered by dust grains has been
observed in a region near the Orion Nebula. In addition to the scattered
stellar continuum, emission and absorption features produced by molecular
hydrogen have been identified. In this Letter, we present an analysis of this
absorption and fluorescent emission from molecular hydrogen in Orion. We model
the spectra obtained with the Far Ultraviolet Spectroscopic Explorer using
optical depth templates and a fluorescent emission code. These results are
surprising because previous studies have found little ultraviolet absorption
from H_2 in this region, and the emission is coming from a seemingly empty part
of the nebula. We find that the emission fills in the observed absorption lines
where the two overlap. These data support the claim that fluorescent excitation
by ultraviolet photons is the primary mechanism producing the near-infrared
emission spectrum observed in the outer regions of the Orion Nebula.


title: Resolving the Hard X-ray Emission of GX 5-1 with INTEGRAL

abstract:
  We present the study of one year of INTEGRAL data on the neutron star low
mass X-ray binary GX 5-1. Thanks to the excellent angular resolution and
sensitivity of INTEGRAL, we are able to obtain a high quality spectrum of GX
5-1 from ~5 keV to ~100 keV, for the first time without contamination from the
nearby black hole candidate GRS 1758-258 above 20 keV. During our observations,
GX 5-1 is mostly found in the horizontal and normal branch of its hardness
intensity diagram. A clear hard X-ray emission is observed above ~30 keV which
exceeds the exponential cut-off spectrum expected from lower energies. This
spectral flattening may have the same origin of the hard components observed in
other Z sources as it shares the property of being characteristic to the
horizontal branch. The hard excess is explained by introducing Compton
up-scattering of soft photons from the neutron star surface due to a thin hot
plasma expected in the boundary layer. The spectral changes of GX 5-1 downward
along the "Z" pattern in the hardness intensity diagram can be well described
in terms of monotonical decrease of the neutron star surface temperature. This
may be a consequence of the gradual expansion of the boundary layer as the mass
accretion rate increases.


title:
The FLASH Thick Target Experiment: Direct Measurement of Air
  Fluorescence Yield in Electromagnetic Showers

abstract:
  A key assumption in the reconstruction of extensive air showers using the air
fluorescence technique is the hypothesis that fluorescence is proportional to
energy deposition at all depths in the shower. This ansatz, along with the
supposition that particle distribution and energy loss can be well modeled by
modern shower simulation software, must be thoroughly verified in order to
validate the air fluorescence technique. We report here the results of the
first direct measurement of air fluorescence yield as a function of shower
depth, as performed in the thick-target phase of the FLASH (FLuorescence in Air
from SHowers) experimental program at the SLAC Final-Focus Test Beam facility.
We compare observed fluorescence light yields as a function of shower depth to
concurrently measured charged particle yields, to the predictions of the EGS
and GEANT software packages, and to empirical energy-loss models. We also
examine the extent to which the relative yield versus shower depth is
independent of wavelength within the fluorescence spectrum.


title:
The Importance of Interactions for Mass Loss from Satellite Galaxies in
  Cold Dark Matter Haloes

abstract:
  We investigate the importance of interactions between dark matter
substructures for the mass loss they suffer whilst orbiting within a sample of
high resolution galaxy cluster mass Cold Dark Matter haloes formed in
cosmological N-body simulations. We have defined a quantitative measure that
gauges the degree to which interactions are responsible for mass loss from
substructures. This measure indicates that interactions are more prominent in
younger systems when compared to older more relaxed systems. We show that this
is due to the increased number of encounters a satellite experiences and a
higher mass fraction in satellites. This is in spite of the uniformity in the
distributions of relative distances and velocities of encounters between
substructures within the different host systems in our sample. Using a simple
model to relate the net force felt by a single satellite to the mass loss it
suffers, we show that interactions with other satellites account for ~30% of
the total mass loss experienced over its lifetime. The relation between the age
of the host and the importance of interactions increases the scatter about this
mean value from ~25% for the oldest to ~45% for the youngest system we have
studied. We conclude that satellite interactions play a vital role in the
evolution of substructure in dark matter halos and that a significant fraction
of the tidally stripped material can be attributed to these interactions.


title:
Testing the "Dark-Energy"-Dominated Cosmology via the Solar-System
  Experiments

abstract:
  The effect of "dark energy" (i.e. the Lambda-term in Einstein equations) is
sought for at the interplanetary scales by comparing the rates of secular
increase in the lunar orbit obtained by two different ways: (1) measured
immediately by the laser ranging and (2) estimated independently from the
deceleration of the Earth's proper rotation. The first quantity involves both
the well-known effect of geophysical tides and the Kottler effect of
Lambda-term (i.e. a kind of the "local" Hubble expansion), while the second
quantity is associated only with the tidal influence. The difference between
them, 2.2 +/- 0.3 cm/yr, can be attributed just to the local Hubble expansion
with rate H_0^(loc) = 56 +/- 8 km/s/Mpc. Assuming that Hubble expansion is
formed locally only by the uniformly distributed dark energy (Lambda-term),
while globally also by a clumped substance (for the most part, the cold dark
matter), the total (large-scale) Hubble constant should be H_0 = 65 +/- 9
km/s/Mpc. This is in reasonable agreement both with the commonly-accepted WMAP
result, H_0 = 71 +/- 3.5 km/s/Mpc, and with the data on supernovae Ia
distribution. The above coincidence can serve as one more argument in favor of
the dark energy.


title:
Effect of strong magnetic field on surface electric field of strange
  stars

abstract:
  We made a detailed study of the properties of the electron layer near the
quark surface of strange stars with strong ($\sim 10^{14}-10^{17}$G) magnetic
fields. The electrostatic potential and the electric field at the quark surface
were calculated as functions of the magnetic field intensity of bare strange
stars. Using an ultrastrong ($B\geq 2.5\times10^{16}$G) magnetic field, we
found that the distribution of electrons becomes an exponential function of
radial distance, which is quite different in a magnetic field-free case. We
also calculated the variation in gap width between the strange core and the
normal nuclear crust for strange stars, which is due to magnetic field effect.


title: Magnetohydrodynamics in full general relativity: Formulation and tests

abstract:
  A new implementation for magnetohydrodynamics (MHD) simulations in full
general relativity (involving dynamical spacetimes) is presented. In our
implementation, Einstein's evolution equations are evolved by a BSSN formalism,
MHD equations by a high-resolution central scheme, and induction equation by a
constraint transport method. We perform numerical simulations for standard test
problems in relativistic MHD, including special relativistic magnetized shocks,
general relativistic magnetized Bondi flow in stationary spacetime, and a
longterm evolution for self-gravitating system composed of a neutron star and a
magnetized disk in full general relativity. In the final test, we illustrate
that our implementation can follow winding-up of the magnetic field lines of
magnetized and differentially rotating accretion disks around a compact object
until saturation, after which magnetically driven wind and angular momentum
transport inside the disk turn on.


title:
Steps towards a solution of the FS Aurigae puzzle. I. Multicolour
  high-speed photometry with ULTRACAM

abstract:
  We present the analysis of high-speed photometric observations of FS Aur
taken with the 4.2-m William Herschel Telescope and the high-speed camera
ULTRACAM in late 2003. These observations were intended to determine whether
there was any evidence of photometric variability with a period in the range
50-100 seconds. The discovery of such variations would help to explain
existence, in FS Aur, of the very coherent photometric period of 205.5 min that
exceeds the spectroscopic period by 2.4 times. Such a discrepancy in the
photometric and spectroscopic periods is an unusual for a low mass binary
system that is unambiguously identified as a Cataclysmic Variable. Using
various methods, including wavelet-analysis, we found that with exception of
the 205.5-minute periodicity, the main characteristic of variability of FS Aur
is usual flickering and Quasi-Periodic Oscillations. However, we detected
variability with a period of ~101 and/or ~105 sec, seen for a short time every
half of the orbital period. These oscillations may be associated with the spin
period of the white dwarf, not ruling out the possibility that we are observing
a precessing rapidly rotating white dwarf in FS Aur.


title: ALMA and Cosmology

abstract:
  ALMA is a privileged instrument to tackle high redshift galaxies, due to the
negative K-correction in the millimeter domain. Many dusty star-forming
galaxies, invisible in the optical or NIR, will be detected easily through the
peak of their emission in the FIR redshifted in the submm between z=10 and z=5.
Their mass and dynamics will be determined through the CO lines, together with
the efficiency of star formation. Normal intervening galaxies at all z will be
studied through absorption lines in front of quasars, exploring the dense tail
of the column density spectrum. CMB anisotropies could be detected at the
arcsecond scale, the secondary effects (SZ, Vishniak-Ostriker) could test the
re-ionization and the nature of dark energy. The detection of the SZ effect on
a few arcsec scales will allow to map in detail clusters and proto-clusters.


title:
Force-Free Magnetohydrodynamic Waves: Non-Linear Interactions and
  Effects of Strong Gravity

abstract:
  The propagation and non-linear interactions of magnetohydrodynamic waves are
considered in the force-free limit, where the inertia of the conducting matter
which enforces the MHD condition E.B = 0 can be neglected in comparison with
the inertia of the electromagnetic field. By extending the analysis beyond the
WKB approximation, we are able to study the non-linearities induced by a
gravitational field. We treat the perturbed electromagnetic field as a fluid of
infinite conductivity. We calculate the scattering of a torsional (Alfven) wave
by a gravitational potential, and demonstrate a nonlinear coupling with a
compressive (fast) wave which is second order in the amplitude of the Alfven
wave. In a cylindrically symmetric spacetime with slow rotation, the coupling
is second order in g_{t\phi} and first order in the amplitude of the wave. We
also give a fresh analysis of the non-linear interactions between compressive
and torsional waves in Minkowski space, with a focus on the relative strengths
of their three- and four-mode interactions. In contrast with non-relativistic
magnetofluids, the effects of compression are always present. In the case of
colliding fast waves, a net displacement of the field lines across (at least)
one of the colliding wavepackets is shown to have a strong effect on the
outgoing waveform, and to have a qualitatively different interpretation than
was previously suggested for colliding Alfven waves. Finally, we show how
spacetime curvature modifies the collision between two torsional waves, in both
the weak- and strong-field regimes.


title:
Deceleration of a Relativistic, Photon-Rich Shell: End of
  Preacceleration, Damping of MHD Turbulence, and the Emission Mechanism of
  Gamma-Ray Bursts

abstract:
  (Abridged) We consider the interaction of a relativistically-moving shell,
composed of thermal photons, a reversing magnetic field and a small admixture
of charged particles, with a dense Wolf-Rayet wind. A thin outer layer of
Wolf-Rayet material is entrained by the jet head; it cools and becomes
Rayleigh-Taylor unstable, thereby providing an additional source of inertia and
variability. Pair creation in the wind material, and the associated
pre-acceleration, defines a characteristic radiative compactness at the point
where the reverse shock has completed its passage back through the shell. We
argue that the prompt gamma-ray emission is triggered by this external braking,
at an optical depth ~1 to electron scattering. Torsional waves, excited by the
forced reconnection of the reversing magnetic field, carry a fluctuating
current, and are damped at high frequencies by the electrostatic acceleration
of electrons and positrons. We show that inverse Compton radiation by the
accelerated charges is stronger than their synchrotron emission, and is beamed
along the magnetic field. Thermal radiation that is advected out from the base
of the jet cools the particles. The observed relation between peak energy and
isotropic luminosity is reproduced if the blackbody seeds are generated in a
relativistic jet core that is subject to Kelvin-Helmholtz instabilities with
the Wolf-Rayet envelope. This relation is predicted to soften to E_peak ~
L_iso^{1/4} below an isotropic luminosity L_iso ~ 3x10^{50} ergs/s. The
duration of spikes in the inverse-Compton emission is narrower at higher
frequencies, in agreement with the observed relation. The transition from
prompt gamma-ray emission to afterglow can be explained by the termination of
the thermal X-ray seed and the onset of synchrotron-self-Compton emission.


title: Search for Pulsed VHE gamma-ray Emission from Young Pulsars with H.E.S.S

abstract:
  Pulsars are commonly regarded as highly magnetized neutron stars, rotating up
to several hundred times per second. Over 1,500 radio pulsars have been found
so far, about 70 of which are X-ray pulsars, but only a handful have been
observed in gamma rays. This high-energy emission is believed to be produced by
the electrons accelerated to TeV energies in the pulsar magnetosphere,
resulting in cascades of secondary particles. The H.E.S.S. experiment is a
system of four imaging atmospheric Cherenkov telescopes in Namibia, which is
sensitive to gamma rays above 100 GeV. Three young pulsars, Crab, Vela, and PSR
B1706-44 have been observed with H.E.S.S. The results of the search for pulsed
emission for these targets, and the constraints on the theories of pulsed very
high energy gamma-ray emission, are summarized here.


title: Time Domain Studies of X-ray Shot Noise in Cygnus X-1

abstract:
  We investigate the variability of Cygnus X-1 in the context of shot moise
models, and employ a peak detection algorithm to select individual shots. For a
long observation of the low, hard state, the distribution of time intervals
between shots is found to be consistent with a purely random process, contrary
to previous claims in the literature. The detected shots are fit to several
model templates and found to have a broad range of shapes. The fitted shots
have a distribution of timescales from below 10 milliseconds to above 1 second.
The coherence of the cross spectrum of light curves of these data in different
energy bands is also studied. The observed high coherence implies that the
transfer function between low and high energy variability is uniform. The
uniformity of the tranfer function implies that the observed distribution of
shot widths cannot have been acquired through Compton scattering. Our results
in combination with other results in the literature suggest that shot
luminosities are correlated with one another. We discuss how our experimental
methodology relates to non-linear models of variability.


title: Non-leptonic Weak Interaction in Magnetized Quark matter

abstract:
  We investigated the non-leptonic weak interaction in magnetic field.
  We discussed an improvement of previous method to analytical work out the
rate for weak field case.Our result easily goes over to field-free limit.Then
we calculated the reaction rate in strong magnetic field where the charged
particles are confined to the lowest Landau level. A strong magnetic field
strongly suppressed the rate,which will be foreseen to affect viscous dynamics
in SQM .We also derived a few approximation formulae under given conditions
that can be conveniently applied.


title:
X-ray Emission from Wind Blown Bubbles. III. ASCA SIS Observations of
  NGC6888

abstract:
  We present ASCA SIS observations of the wind-blown bubble NGC6888. Owing to
the higher sensitivity of the SIS for higher energy photons compared to the
ROSAT PSPC, we are able to detect a T ~ 8x10^6 K plasma component in addition
to the T ~ 1.3x10^6 K component previously detected in PSPC observations. No
significant temperature variations are detected within NGC6888. Garcia-Segura &
Mac Low's (1995) analytical models of WR bubbles constrained by the observed
size, expansion velocity, and mass of the nebular shell under-predict the
stellar wind luminosity, and cannot reproduce simultaneously the observed X-ray
luminosity, spectrum, surface brightness profile, and SIS count rate of
NGC6888's bubble interior. The agreement between observations and expectations
from models can be improved if one or more of the following ad hoc assumptions
are made: (1) the stellar wind luminosity was weaker in the past, (2) the
bubble is at a special evolutionary stage and the nebular shell has recently
been decelerated to 1/2 of its previous expansion velocity, and (3) the heat
conduction between the hot interior and the cool nebular shell is suppressed.
Chandra and XMM-Newton observations with high spatial resolution and high
sensitivity are needed to determine accurately the physical conditions
NGC6888's interior hot gas for critical comparisons with bubble models.


title:
Probing The Dust-To-Gas Ratio of z > 0 Galaxies Through Gravitational
  Lenses

abstract:
  We report the detection of differential gas column densities in three
gravitational lenses, MG0414+0534, HE1104-1805, and PKS1830-211. Combined with
the previous differential column density measurements in B1600+434 and
Q2237+0305 and the differential extinction measurements of these lenses, we
probe the dust-to-gas ratio of a small sample of cosmologically distant normal
galaxies. We obtain an average dust-to-gas ratio of E(B-V)/NH =(1.4\pm0.5) e-22
mag cm^2/atoms with an estimated intrinsic dispersion in the ratio of ~40%.
This average dust-to-gas ratio is consistent with the average Galactic value of
1.7e-22 mag cm^2/atoms and the estimated intrinsic dispersion is also
consistent with the 30% observed in the Galaxy.


title:
Light-Element Reaction Flow and the Conditions for r-Process
  Nucleosynthesis

abstract:
  We deduce new constraints on the entropy per baryon ($s/k$), dynamical
timescale ($\tau_{dyn}$), and electron fraction ($Y_{e}$) consistent with heavy
element nucleosynthesis in the r-process. We show that the previously neglected
reaction flow throu gh the reaction sequence \atg (n,$\gamma$)\Li~
significantly enhances the production of seed nuclei. We analyze the r-process
nucleosynthesis in the context of a schematic exponential wi nd model. We show
that fewer neutrons per seed nucleus implies that the entropy per baryon
required for successful r-process nucleosynthesis must be more than a factor of
two higher than previous estimates. This places new constraints on dynamical mo
dels for the r-process.


title:
Identification of the Red Supergiant Progenitor of Supernova 2005cs: Do
  the Progenitors of Type II-P Supernovae Have Low Mass?

abstract:
  The stars that end their lives as supernovae (SNe) have been directly
observed in only a handful of cases, due mainly to the extreme difficulty in
identifying them in images obtained prior to the SN explosions. Here we report
the identification of the progenitor for the recent Type II-plateau
(core-collapse) SN 2005cs in pre-explosion archival images of the Whirlpool
Galaxy (M51) obtained with the Hubble Space Telescope (HST) Advanced Camera for
Surveys (ACS). From high-quality ground-based images of the SN from the
Canada-France-Hawaii Telescope, we precisely determine the position of the SN
and are able to isolate the SN progenitor to within 0".04 in the HST/ACS
optical images. We further pinpoint the SN location to within 0".005 from
HST/ACS ultraviolet images of the SN, confirming our progenitor identification.
  From photometry of the SN progenitor obtained with the pre-SN ACS images, and
also limits to its brightness in pre-SN HST/NICMOS images, we infer that the
progenitor is a red supergiant star of spectral type K0--M3, with initial mass
7--9 Msun. We also discuss the implications of the SN 2005cs progenitor
identification and its mass estimate. There is an emerging trend that the most
common Type II-plateau SNe originate from low-mass supergiants 8--15 Msun.


title: High energy neutrinos from fast spinning magnetars

abstract:
  Fast spinning magnetars are discussed as strong sources of high energy
neutrinos. Pulsars may be born with a short rotation period of milliseconds
with the magnetic field amplified through dynamo processes up to $\sim
10^{15}-10^{16} \rm G$. As such millisecond magnetars (MSMs) have an enormous
spin-down power $\sim 10^{50} {\rm erg} {\rm s}^{-1}$, they can be potentially
a strong, extragalactic high-energy neutrino source. Specifically, acceleration
of ions and subsequent photomeson production within the MSM magnetosphere are
considered. As in normal pulsars, particle acceleration leads to
electron-positron pair cascades that constrains the acceleration efficiency.
The limit on the neutrino power as a fraction of the spin-down power is
calculated. It is shown that neutrinos produced in the inner magnetosphere have
characteristic energy about a few $\times100$ GeV due to the constraint of
cooling of charged pions through inverse Compton scattering. TeV neutrinos may
be produced in the outer magnetosphere where ions can be accelerated to much
higher energies and the pion cooling is less severe than in the inner
magnetosphere. High energy neutrinos can also be produced from interactions
between ultra-high energy protons accelerated in the magnetosphere and a
diffuse thermal radiation from the ejecta or from the interaction region
between the MSM wind and remnant shell. The detectability of neutrinos in the
early spin-down phase by the current available and planned neutrino detectors
is discussed.


title:
GALEX Observations of an Energetic Ultraviolet Flare on the dM4e Star GJ
  3685A

abstract:
  The Galaxy Evolution Explorer (GALEX) satellite has obtained high time
resolution ultraviolet photometry during a large flare on the M4 dwarf star GJ
3685A. Simultaneous NUV (1750 - 2800A) and FUV (1350 - 1750A) time-tagged
photometry with time resolution better than 0.1 s shows that the overall
brightness in the FUV band increased by a factor of 1000 in 200 s. Under the
assumption that the NUV emission is mostly due to a stellar continuum, and that
the FUV flux is shared equally between emission lines and continuum, then there
is evidence for two distinct flare components for this event. The first flare
type is characterized by an exponential increase in flux with little or no
increase in temperature. The other involves rapid increases in both temperature
and flux. While the decay time for the first flare component may be several
hours, the second flare event decayed over less than 1 minute, suggesting that
there was little or no confinement of the heated plasma.


title:
Correspondence Between $5D$ Ricci-Flat Cosmological Models and
  Quintessence Dark Energy Models

abstract:
  We study the accelerating expansion and the induced dark energy of the $5D$
Ricci-flat universe which is characterized by having a big bounce as opposed to
a big bang. We show that the arbitrary function $\mu(t)$ contained in the $5D$
solutions can be rewritten in terms of the redshift $z$ as a new arbitrary
function $f(z)$, and we find that there is a correspondence between this $f(z)$
and the potential $V(\phi)$ of the 4D quintessence models. Using this
correspondence, the arbitrary function $f(z)$ and the $5D$ solution could be
specified for a given form of the potential $V(\phi)$.


title: AMBER : a near infrared focal instrument for the VLTI

abstract:
  AMBER is the General User near-infrared focal instrument of the Very Large
Telescope interferometer. Its specifications are based on three key programs on
Young Stellar Objects, Active Galactic Nuclei central regions, masses and
spectra of hot Extra Solar Planets. It has an imaging capacity because it
combines up to three beams and very high accuracy measurement are expected from
the spatial filtering of beams by single mode fibers and the comparison of
measurements made simultaneously in different spectral channels.


title: Dark Matter Haloes and Rotation Curves via Brans-Dicke Theory

abstract:
  In the present work, the Brans-Dicke (BD) theory of gravity is taken as a
possible theory of k-essence. Then starting with the (already known)
Brans-Dicke-Schwarzschild solution which can represent the gravitationally
bound static configurations of the BD scalar k-essence, issues like whether
these configurations can reproduce the observed properties of galactic dark
matter haloes have been addressed. It has been realized that indeed the BD
scalar k-essence can cluster into dark matter halo-like objects with flattened
rotation curves while exhibiting a dark energy-like negative pressure on larger
scales.


title: Chemical composition of Galactic OB stars II. The fast rotator Z Oph

abstract:
  Z Oph, HD149757, is an O9.5 Vnn star with a very high projected rotational
velocity (vsini >= 340 km\s). It is also a classical runaway star due to its
high proper motion. We perform a quantitative analysis of its optical spectrum
in order to measure important observables of the star such as its mass,
effective temperature, luminosity and He, C, N, and O abundances. Comparing
these observed values to those predicted by the rotating evolutionary models of
the Geneva group we find that none of the two sets of models is capable of
reproducing the characteristics of the star. Nevertheless, due to its runaway
nature, the reason for this discrepancy may be that the star is not the result
of the evolution of a single object, but the product of the evolution of a
close binary system.


title:
Studies of Systematic Uncertainties in the HiRes-II Measurement of the
  UHECR Spectrum

abstract:
  We present studies of systematic uncertainties in the measurement of the
ultra-high energy cosmic ray (UHECR) spectrum with the FADC detector of the
High Resolution Fly's Eye experiment (HiRes-II). One source of uncertainties
lies in the simulation of the energy dependent aperture of the air fluorescence
detector. We study the impact of changes in the energy spectrum and composition
that are used as input to the aperture simulation. We also compare aperture
estimates for two different hadronic interaction models - QGSJet and SIBYLL.
Systematic uncertainties may further be introduced by the modeling of the
aerosol component of the atmosphere. We have repeated the HiRes-II monocular
analysis using an atmospheric database with hourly entries instead of our
measurement of the average aerosol content. We will discuss changes in
reconstructed energies and in the resulting spectrum.


title:
Upper limit on the primary photon fraction from the Pierre Auger
  Observatory

abstract:
  Based on observations of the depth of shower maximum performed with the
hybrid detector of the Auger Observatory, an upper limit on the cosmic-ray
photon fraction of 26% (at 95% confidence level) is derived for primary
energies above 10^19 eV. Additional observables recorded with the surface
detector array, available for a sub-set of the data sample, support the
conclusion that a photon origin of the observed events is not favoured.


title: Molecular Gas in NUclei of GAlaxies (NUGA) III. The warped LINER NGC3718

abstract:
  We present the first interferometric observations of CO(1-0) and CO(2-1) line
emission from the warped LINER NGC3718, obtained with the IRAM PdBI. This L1.9
galaxy has a prominent dust lane and on kpc scales, a strongly warped atomic
and molecular gas disk. The molecular gas is closely associated with the dust
lane across the nucleus and its kinematic center is consistent with the mm
continuum AGN. A comparison of our interferometric mosaic data, which fully
cover the ~9kpc warped disk, with a previously obtained IRAM 30m single dish
CO(1-0) map shows that the molecular gas distribution in the disk is heavily
resolved by the PdBI map. After applying a short-spacing correction with the
IRAM 30m data, we find in total six main source components within the dust
lane: one associated with the nucleus, four symmetrically positioned on either
side at galactocentric distances of about 1.3kpc and 4.0kpc from the center,
and a sixth on the western side at ~3kpc with only a very weak eastern
counterpart. In the framework of a kinematic model using tilted rings, we
interpret the five symmetric source components as locations of strong orbital
crowding. We further find indications that the warp appears not only on kpc
scales, but continues down to 250pc. Besides the sixth feature on the western
side, the lower flux of the eastern components compared to the western ones
indicates an intrinsic large scale asymmetry in NGC3718 that cannot be
explained by the warp. Indications for a small scale asymmetry are also seen in
the central 600pc. These asymmetries might be evidence for a tidal interaction
with a companion galaxy (large scales) and gas accretion onto the nucleus
(small scales). Our study of NGC3718 is part of the NUGA project that aims at
investigating the different processes of gas accretion onto AGN.


title: Phosphorus in the Diffuse Interstellar Medium

abstract:
  We present FUSE and HST/STIS measurements of the PII column density toward
Galactic stars. We analyzed PII through the profile fitting of the unsaturated
$\lambda$1125 and $\lambda$1533 lines and derived column densities integrated
along the sightlines as well as in individual resolved components. We find that
phosphorus is not depleted along those sightlines sampling the diffuse neutral
gas. We also investigate the correlation existing between PII and OI column
densities and find that there is no differential depletion between these two
specie. Furthermore, the ratio N(PII)/N(OI) is consistent with the solar P/O
value, implying that PII and OI coexist in the same gaseous phase and are
likely to evolve in parallel since the time they are produced in stars. We
argue that phosphorus, as traced by PII, is an excellent neutral oxygen tracer
in various physical environments, except when ionization corrections are a
significant issue. Hence, PII lines (observable with FUSE, HST/STIS, or with
VLT/UVES for the QSO sightlines) reveal particularly useful as a proxy for OI
lines when these are saturated or blended.


title:
Optical Camera with high temporal resolution to search for transients in
  the wide field

abstract:
  The wide field optical camera with high temporal resolution for the
continuous monitoring of the sky in order to catch the initial stages of GRBs
is described.


title: Relativistic Models of Galaxies

abstract:
  A special form of the isotropic metric in cylindrical coordinates is used to
construct what may be interpreted as the General Relativistic versions of some
wellknown potential-density pairs used in Newtonian gravity to model
three-dimensional distributions of matter in galaxies. The components of the
energy-momentum tensor are calculated for the first two Miyamoto-Nagai
potentials and a particular potential due to Satoh. The three potentials yield
distributions of matter in which all tensions are pressures and all energy
conditions are satisfied for certain ranges of the free parameters. A few
non-planar geodesic orbits are computed for one of the potentials and compared
with the Newtonian case. Rotation is also incorporated to the models and the
effects of the source rotation on the rotation profile are calculated as first
order corrections by using an approximate form of the Kerr metric in isotropic
coordinates.


title:
FAVOR (FAst Variability Optical Registration) -- A Two-telescope Complex
  for Detection and Investigation of Short Optical Transients

abstract:
  An astronomical complex intended to detect optical transients (OTs) in a wide
field and follow them up with high time resolution investigation is described.


title: XMM-Newton 13H Deep field - I. X-ray sources

abstract:
  We present the results of a deep X-ray survey conducted with XMM-Newton,
centred on the UK ROSAT 13H deep field area. This region covers 0.18 deg^2 and
is the first of two areas covered with XMM-Newton as part of an extensive
multi-wavelength survey designed to study the nature and evolution of the faint
X-ray source population. We have produced detailed Monte-Carlo simulations to
obtain a quantitative characterisation of the source detection procedure and to
assess the reliability of the resultant sourcelist. We use the simulations to
establish a likelihood threshold above which we expect less than 7 (3%) of our
sources to be spurious. We present the final catalogue of 225 sources. Within
the central 9 arcmin, 68 per cent of source positions are accurate to 2 arcsec,
making optical follow-up relatively straightforward. We construct the N(>S)
relation in four energy bands: 0.2-0.5 keV, 0.5-2 keV, 2-5 keV and 5-10 keV. In
all but our highest energy band we find that the source counts can be
represented by a double powerlaw with a bright end slope consistent with the
Euclidean case and a break around 10^-14 cgs. Below this flux the counts
exhibit a flattening. Our source counts reach densities of 700, 1300, 900 and
300 deg^-2 at fluxes of 4.1x10^-16, 4.5x10^-16, 1.1x10^-15 and 5.3x10^-15 cgs
in the 0.2-0.5, 0.5-2, 2-5 and 5-10 keV energy bands respectively. We have
compared our source counts with those in the two Chandra deep fields and
Lockman hole and find our source counts to be amongst the highest of these
fields in all energy bands. We resolve >51% (>50%) of the X-ray background
emission in the 1-2 keV (2-5 keV) energy bands.


title: The X-ray spectra of accreting Kerr black holes

abstract:
  The relativistic broad iron lines seen in the X-ray spectra of several active
galaxies and Galactic black hole systems are reviewed. Most such objects
require emission from within the innermost stable orbit of a non-rotating black
hole, suggesting that the black holes are rapidly spinning Kerr holes. We
discuss the soft excess, the broad iron line and the Compton hump
characteristic of reflection from partially ionized gas and show that they may
be a common ingredient in the X-ray spectra of many radiatively-efficient,
accreting black holes. Strong gravitational bending of the radiation close to a
Kerr black hole can explain the otherwise puzzling spectral variability seen in
some objects. The Narrow Line Seyfert 1 galaxies may be among the most extreme
objects yet seen.


title: The Burst Alert Telescope (BAT) on the Swift MIDEX Mission

abstract:
  The Burst Alert Telescope (BAT) is one of 3 instruments on the Swift MIDEX
spacecraft to study gamma-ray bursts (GRBs). The BAT first detects the GRB and
localizes the burst direction to an accuracy of 1-4 arcmin within 20 sec after
the start of the event. The GRB trigger initiates an autonomous spacecraft slew
to point the two narrow field-of-view (FOV) instruments at the burst location
within 20-70 sec so to make follow-up x-ray and optical observations. The BAT
is a wide-FOV, coded-aperture instrument with a CdZnTe detector plane. The
detector plane is composed of 32,768 pieces of CdZnTe (4x4x2mm), and the
coded-aperture mask is composed of approximately 52,000 pieces of lead
(5x5x1mm) with a 1-m separation between mask and detector plane. The BAT
operates over the 15-150 keV energy range with approximately 7 keV resolution,
a sensitivity of approximately 10E-8 erg*cm^-2*s^-1, and a 1.4 sr (half-coded)
FOV. We expect to detect >100 GRBs/yr for a 2-year mission. The BAT also
performs an all-sky hard x-ray survey with a sensitivity of approximately 2
mCrab (systematic limit) and it serves as a hard x-ray transient monitor.


title:
Broad-band electromagnetic radiation from microquasars interacting with
  ISM

abstract:
  Microquasars (MQs) are galactic objects with relativistic jets that
constitute a source population which can be responsible for production of a
non-negligible fraction of the observed galactic cosmic rays. These
relativistic protons, associated with the termination of the jet, interact with
the interstellar medium and, at certain surrounding conditions, may lead to
production of detectable fluxes of high-energy and very high-energy gamma-rays.
This radiation is accompanied by the broad-band emission of secondary electrons
from decays of $\pi^\pm$-mesons produced through synchrotron, bremstrahlung and
inverse Compton process. The features of broad-band emission initiated by
proton-proton (pp) interactions in such a scenario is discussed in the context
of the strategy of search for counterparts of high-energy and very high-energy
gamma-ray sources in the galactic plane.


title: Orbital X-Ray Variability of the Microquasar LS 5039

abstract:
  The properties of the orbit and the donor star in the high mass X-ray binary
microquasar LS 5039 indicate that accretion processes should mainly occur via a
radiatively driven wind. In such a scenario, significant X-ray variability
would be expected due to the eccentricity of the orbit. The source has been
observed at X-rays by several missions, although with a poor coverage that
prevents to reach any conclusion about orbital variability. Therefore, we
conducted RossiXTE observations of the microquasar system LS 5039 covering a
full orbital period of 4 days. Individual observations are well fitted with an
absorbed power-law plus a Gaussian at 6.7 keV, to account for iron line
emission that is probably a diffuse background feature. In addition, we have
taken into account that the continuum is also affected by significant diffuse
background contamination. Our results show moderate power-law flux variations
on timescales of days, as well as the presence of miniflares on shorter
timescales. The new orbital ephemeris of the system recently obtained by
Casares et al. have allowed us to show, for the first time, that an increase of
emission is seen close to the periastron passage, as expected in an accretion
scenario. Moreover, the detected orbital variability is a factor of ~4 smaller
than the one expected by using a simple wind accretion model, and we suggest
that an accretion disk around the compact object could be responsible for this
discrepancy. On the other hand, significant changes in the photon index are
also observed clearly anti-correlated with the flux variations. We interpret
the overall X-ray spectral characteristics of LS 5039 in the context of X-ray
radiation produced by inverse Compton and/or synchrotron processes in the jet
of this microquasar.


title: The Swift Ultra-Violet/Optical Telescope

abstract:
  The UV/Optical Telescope (UVOT) is one of three instruments flying aboard the
Swift Gamma-ray Observatory. It is designed to capture the early (approximately
1 minute) UV and optical photons from the afterglow of gamma-ray bursts in the
170-600 nm band as well as long term observations of these afterglows. This is
accomplished through the use of UV and optical broadband filters and grisms.
The UVOT has a modified Ritchey-Chretien design with micro-channel plate
intensified charged-coupled device detectors that record the arrival time of
individual photons and provide sub-arcsecond positioning of sources. We discuss
some of the science to be pursued by the UVOT and the overall design of the
instrument.


title:
Correlation of the estimated arrival time of the relativistic solar ions
  at 1 AU and start of ground level enhancement (GLE)

abstract:
  We are investigated possible correlations between the calculated arrival
times of the first relativistic ions at Earth and GLE start times registered by
surface monitors. The analysis is based on the arrival times and energies of
the first solar ions, registered by the Solar Isotope Spectrometer (SIS) on
board of the ACE satellite, and protons, registered by GOES satellites. We
consider both cases when the interplanetary propagation of the first high
energy ions is essentially scatter-free and the diffusion of high energy ions
during propagation in the interplanetary magnetic field. We extrapolate the
time-velocity and time-rigidity relationships to calculate the expected arrival
times of the relativistic ions that are energetic enough to enter the
atmosphere at the Aragats geographical location and produce secondary fluxes
that reach the monitors.


title: The formation of DA white dwarfs with thin hydrogen envelopes

abstract:
  We study the formation and evolution of DA white dwarfs, the progenitors of
which have experienced a late thermal pulse (LTP) shortly after the departure
from the thermally pulsing AGB. To this end, we compute the complete evolution
of an initially 2.7 Mo star all the way from the zero-age main sequence to the
white dwarf stage. We find that most of the original H-rich material of the
post-AGB remnant is burnt during the post-LTP evolution, with the result that,
at entering its white dwarf cooling track, the remaining H envelope becomes
10^-6 Mo in agreement with asteroseismological inferences for some ZZ Ceti
stars.


title:
A Moving Cluster Distance to the Exoplanet 2M1207 B in the TW Hya
  Association

abstract:
  A candidate extrasolar planet companion to the young brown dwarf 2MASSW
J1207334-393254 (2M1207) was recently discovered by Chauvin et al. They find
that 2M1207 B's temperature and luminosity are consistent with being a young,
\~5 M_Jupiter planet. The 2M1207 system is purported to be a member of the TW
Hya association (TWA), and situated ~70 pc away. Using a revised space motion
vector for TWA, and improved proper motion for 2M1207, I use the moving cluster
method to estimate the distance to the 2M1207 system and other TWA members. The
derived distance for 2M1207 (53+-6 pc) forces the brown dwarf and planet to be
half as luminous as previously thought. The inferred masses for 2M 1207 A and B
decrease to ~21 M_Jup and ~3-4 M_Jup, respectively, with the mass of B being
well below the observed tip of the planetary mass function and the theoretical
deuterium-burning limit. After removing probable Lower Centaurus-Crux (LCC)
members from the TWA sample, as well as the probable non-member TWA 22, the
remaining TWA members are found to have distances of 49 +- 3(s.e.m.) +-
12(1sigma) pc, and an internal 1D velocity dispersion of 0.8(+0.3,-0.2) km/s.
There is weak evidence that the TWA is expanding, and the data are consistent
with a lower limit on the expansion age of 10 Myr (95% confidence).


title:
A Hubble Space Telescope Snapshot Survey of Dynamically Close Galaxy
  Pairs in the CNOC2 Redshift Survey

abstract:
  We compare the structural properties of two classes of galaxies at
intermediate redshift: those in dynamically close galaxy pairs, and those which
are isolated. Both samples are selected from the CNOC2 Redshift Survey, and
have redshifts in the range 0.1 < z <0.6. Hubble Space Telescope WFPC2 images
were acquired as part of a snapshot survey, and were used to measure bulge
fraction and asymmetry for these galaxies. We find that paired and isolated
galaxies have identical distributions of bulge fractions. Conversely, we find
that paired galaxies are much more likely to be asymmetric (R_T+R_A >= 0.13)
than isolated galaxies. Assuming that half of these pairs are unlikely to be
close enough to merge, we estimate that 40% +/- 11% of merging galaxies are
asymmetric, compared with 9% +/- 3% of isolated galaxies. The difference is
even more striking for strongly asymmetric (R_T+R_A >= 0.16) galaxies: 25% +/-
8% for merging galaxies versus 1% +/- 1% for isolated galaxies. We find that
strongly asymmetric paired galaxies are very blue, with rest-frame B-R colors
close to 0.80, compared with a mean (B-R)_0 of 1.24 for all paired galaxies. In
addition, asymmetric galaxies in pairs have strong [OII]3727 emission lines. We
conclude that close to half of the galaxy pairs in our sample are in the
process of merging, and that most of these mergers are accompanied by triggered
star formation.


title:
The Optical - Infrared Colors of CORALS QSOs: Searching for Dust
  Reddening Associated With High Redshift Damped Lyman Alpha Systems

abstract:
  The presence of dust in quasar absorbers, such as damped Lyman alpha (DLA)
systems, may cause the background QSO to appear reddened. We investigate the
extent of this potential reddening by comparing the optical-to-infrared (IR)
colors of QSOs with and without intervening absorbers. Our QSO sample is based
on the Complete Optical and Radio Absorption Line System (CORALS) survey of
Ellison et al (2001). We have obtained near-simultaneous B and K band
magnitudes for subset of the CORALS sample and supplemented our observations
with further measurements published in the literature. To account for
redshift-related color changes, the B-K colors are normalized using the Sloan
Digital Sky Survey (SDSS) QSO composite. The mean normalized B-K color of the
DLA sub-sample is +0.12, whereas the mean for the no-DLA sample is -0.10; both
distributions have RMS scatters ~0.5. Neither a student's T-test nor a KS test
indicate that there is any significant difference between the two color
distributions. Based on simulations which redden the colors of QSOs with
intervening DLAs, we determine a reddening limit which corresponds to E(B-V) <
0.04 (SMC-like extinction) at 99% confidence (3 sigma), assuming that E(B-V) is
the same for all DLAs. Finally, we do not find any general correlation between
absorber properties (such as [Fe/Zn] or neutral hydrogen column density) and
B-K color. One of these two QSOs shows evidence for strong associated
absorption from X-ray observations, an alternative explanation for its very red
color. We conclude that the presence of intervening galaxies causes a minimal
reddening of the background QSO.


title:
The Wendelstein Calar Alto Pixellensing Project (WeCAPP): The M31
  Variable Star Catalogue

abstract:
  In this paper we present the WeCAPP variable star catalogue towards the bulge
of M31. The observations of the WeCAPP microlensing survey (optical R and I
bands) during three years (2000-2003) result in a database with unprecedented
time coverage for an extragalactic variable star study. We detect 23781
variable sources in a 16.1' x 16.6' field centered on the nucleus of M31. The
catalogue of variable stars contains the positions, the periods and the
variations in the R and I bands. We classify the variables according to their
position in the R-band period-amplitude plane. Three groups can be
distinguished; while the first two groups can be mainly associated with
Cepheid-like variables (population I Cepheids in group I, type II Cepheids and
RV Tauri stars in group II), the third one consists of Long Period Variables
(LPVs). We detect 37 RV Tauri stars and 11 RV Tauri candidates which is one of
the largest collections of this class of stars to date. The classification
scheme is supported by Fourier decomposition of the light curves. Our data
shows a correlation of the low-order Fourier coefficients Phi_21 with Phi_31
for classical Cepheids, as well for type II Cepheids and RV Tauri stars.
Correlating our sample of variable stars with the X-ray based catalogues of
Kaaret (2002) and Kong et al. (2002) results in 23 and 31 coincidences, 8 of
which are M31 globular clusters. The number density of detected variables is
clearly not symmetric, which has to be included in the calculations of the
expected microlensing event rate towards M31. This asymmetry is due to the
enhanced extinction in the spiral arms superimposed on the bulge of M31 which
reduces the number of sources to about 60%, if compared to areas of equivalent
bulge brightness (without enhanced extinction being present).


title: The Mass of a Millisecond Pulsar

abstract:
  We report on nearly two years of timing observations of the low-mass binary
millisecond pulsar, PSR J1909-3744 with the Caltech-Parkes-Swinburne Recorder
II (CPSR2), a new instrument that gives unprecedented timing precision. Daily
observations give a weighted rms residual of 74 ns, indicating an extremely low
level of systematic error. We have greatly improved upon the previous parallax
and proper motion measurements of PSR J1909-3744, yielding a distance of
$1.14^{+0.04}_{-0.03}$ kpc and transverse velocity of $(200^{+7}_{-6})$ km
s$^{-1}$. The system's orbital eccentricity is just 1.35(12)$\times10^{-7}$,
the smallest yet recorded. Since their discovery, the masses of the rapidly
rotating millisecond pulsars have remained a mystery, with the recycling
hypothesis arguing for heavy objects, and the accretion-induced collapse of a
white dwarf more consistent with neutron stars less than the Chandrashkar
limit. Fortuitously, PSR J1909-3744 is an edge-on system, and our data have
allowed the measurement of the range and shape of the Shapiro delay to high
accuracy, giving the first precise determination of a millisecond pulsar mass
to date, $m_p = (1.438 \pm 0.024) M_\odot$. The mass of PSR J1909-3744 is at
the upper edge of the range observed in mildly recycled pulsars in double
neutron star systems, consistent with the the recycling hypothesis. It appears
that the production of millisecond pulsars is possible with the accretion of
less than $0.2 M_\odot$.


title:
Long-Term Evolution of Supernova Remnants in Magnetized Interstellar
  Medium

abstract:
  The evolution of supernova remnants (SNRs) is studied, with particular
attention to the effect of magnetic fields with axisymmetric two-dimensional
magnetohydrodynamical simulations. The evolution of magnetic SNRs is the same
as non-magnetic ones in the adiabatic Sedov stage. After a thin shell is
formed, the shell is driven by the pressure of the hot interior gas (bubble).
Evolution in the pressure-driven snow-plow phase is much affected by the
magnetic field. The shell sweeping the magnetic field lines thickens owing to
the magnetic pressure force. After $5\times 10^5{\rm yr}$ - $2\times 10^6{\rm
yr}$, the inner boundary of the thick shell begins to contract. This compresses
the hot bubble radially and maintains its thermal pressure. Thus, the bubble
forms a prolate spheroidal shape and becomes thinner and thinner, since it
expands in a direction parallel to the magnetic field for $B_0 \gtrsim 3\mu
{\rm G}$. Finally, the bubble contracts. The porosity of the hot low-density
gas in ISM is reduced, taking the effect of the magnetic field into account.


title:
Atmosphere, Interior, and Evolution of the Metal-Rich Transiting Planet
  HD 149026b

abstract:
  We investigate the atmosphere and interior of the new transiting planet HD
149026b, which appears to be very rich in heavy elements. We first compute
model atmospheres at metallicities ranging from solar to ten times solar, and
show how for cases with high metallicity or inefficient redistribution of
energy from the day side, the planet may develop a hot stratosphere due to
absorption of stellar flux by TiO and VO. The spectra predicted by these models
are very different than cooler atmosphere models without stratospheres. The
spectral effects are potentially detectable with the Spitzer Space Telescope.
In addition the models with hot stratospheres lead to a large limb brightening,
rather than darkening. We compare the atmosphere of HD 149026b to other
well-known transiting planets, including the recently discovered HD 189733b,
which we show have planet-to-star flux ratios twice that of HD 209458 and
TrES-1. The methane abundance in the atmosphere of HD 189733b is a sensitive
indicator of atmospheric temperature and metallicity and can be constrained
with Spitzer IRAC observations. We then turn to interior studies of HD 149026b
and use a grid of self-consistent model atmospheres and high-pressure equations
of state for all components to compute thermal evolution models of the planet.
We estimate that the mass of heavy elements within the planet is in the range
of 60 to 93 M_earth. Finally, we discuss trends in the radii of transiting
planets with metallicity in light of this new member of the class.


title:
Mid-Infrared Spectra of Classical AGN Observed with the Spitzer Space
  Telescope

abstract:
  Full low resolution (65<R<130) and high resolution (R~600) spectra between 5
microns and 37 microns obtained with the Infrared Spectrograph (IRS) on the
Spitzer Space Telescope are presented for eight classical active galactic
nuclei (AGN) which have been extensively studied previously. Spectra of these
AGN are presented as comparison standards for the many objects, including
sources at high redshift, which are being observed spectroscopically in the
mid-infrared for the first time using the IRS. The AGN are NGC4151, Markarian
3, I Zwicky 1, NGC 1275, Centaurus A, NGC 7469, Markarian 231, and NGC 3079.
These sources are used to demonstrate the range of infrared spectra encountered
in objects which have widely different classification criteria at other
wavelengths but which unquestionably contain AGN. Overall spectral
characteristics - including continuum shape, nebular emission lines, silicate
absorption and emission features, and PAH emission features - are considered to
understand how spectral classifications based on mid-infrared spectra relate to
those previously derived from optical spectra. The AGN are also compared to the
same parameters for starburst galaxies such as NGC 7714 and the compact, low
metallicity starburst SBS 0335-052 previously observed with the IRS. Results
confirm the much lower strengths of PAH emission features in AGN, but there are
no spectral parameters in this sample which unambiguously distinguish AGN and
starbursts based only on the slopes of the continuous spectra.


title:
Keck Deep Fields. I. Observations, Reductions, and the Selection of
  Faint Star-Forming Galaxies at Redshifts z~4, 3, and 2

abstract:
  We introduce a very deep, R_lim~27, multicolor imaging survey of very faint
star-forming galaxies at z~4, z~3, z~2.2, and z~1.7. This survey, carried out
on the Keck I telescope, uses the very same UGRI filter system that is employed
by the Steidel team to select galaxies at these redshifts, and thus allows us
to construct identically-selected, but much fainter, samples. However, our
survey reaches ~1.5 mag deeper than the work of Steidel and his group, letting
us probe substantially below the characteristic luminosity L* and thus study
the properties and redshift evolution of the faint component of the high-z
galaxy population. The survey covers 169 square arcminutes in three spatially
independent patches on the sky and -- to R<~27 -- contains 427 GRI-selected z~4
LBGs, 1481 UGR-selected z~3 LBGs, 2417 UGR-selected z~2.2 star-forming
galaxies, and 2043 UGR-selected z~1.7 star-forming galaxies. In this paper, the
first in a series, we introduce the survey, describe our observing and data
reduction strategies, and outline the selection of our z~4, z~3, z~2.2, and
z~1.7 samples.


title: Ensemble Characteristics of the ZZ Ceti stars

abstract:
  We present the observed pulsation spectra of all known non-interacting ZZ
Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) and examine
changes in their pulsation properties across the instability strip. We confirm
the well established trend of increasing pulsation period with decreasing
effective temperature across the ZZ Ceti instability strip. We do not find a
dramatic order of magnitude increase in the number of observed independent
modes in ZZ Ceti stars, traversing from the hot to the cool edge of the
instability strip; we find that the cool DAVs have one more mode on average
compared to the hot DAVs. We confirm the initial increase in pulsation
amplitude at the blue edge, and find strong evidence of a decline in amplitude
prior to the red edge. We present the first observational evidence that ZZ Ceti
stars lose pulsation energy just before pulsations shut down at the empirical
red edge of the instability strip.


title: Exploring Dark Energy with SNAP

abstract:
  The accelerating expansion of the Universe is one of the most surprising and
potentially profound discoveries of modern cosmology. Measuring the
acceleration well enough to meaningfully constrain interesting physical models
requires improvements an order of magnitude beyond on-going and near-term
experiments. The Supernova/Acceleration Probe (SNAP) has been conceived as a
powerful yet simple experiment to use Type Ia supernovae and weak gravitational
lensing to reach this level of accuracy. As fundamentally different causes for
the acceleration map into very small differences in observational parameters
for all relevant cosmological methods, control of systematics is especially
important and so has been built into the SNAP mission design from the very
beginning.


title:
Star Formation in NGC5194 (M51a): The Panchromatic View from GALEX to
  Spitzer

abstract:
  (Abridged) Far ultraviolet to far infrared images of the nearby galaxy
NGC5194, from Spitzer, GALEX, Hubble Space Telescope and ground--based data,
are used to investigate local and global star formation, and the impact of dust
extinction in HII-emitting knots. In the IR/UV-UV color plane, the NGC5194 HII
knots show the same trend observed for normal star-forming galaxies, having a
much larger dispersion than starburst galaxies. We identify the dispersion as
due to the UV emission predominantly tracing the evolved, non-ionizing stellar
population, up to ages 50-100 Myr. While in starbursts the UV light traces the
current SFR, in NGC5194 it traces a combination of current and recent-past SFR.
Unlike the UV emission, the monochromatic 24 micron luminosity is an accurate
local SFR tracer for the HII knots in NGC5194; this suggests that the 24 micron
emission carriers are mainly heated by the young, ionizing stars. However,
preliminary results show that the ratio of the 24 micron emission to the SFR
varies by a factor of a few from galaxy to galaxy. While also correlated with
star formation, the 8 micron emission is not directly proportional to the
number of ionizing photons. This confirms earlier suggestions that the carriers
of the 8 micron emission are heated by more than one mechanism.


title: The Current Flows in Pulsar Magnetospheres

abstract:
  The global structure of the current flows in pulsar magnetospheres is
investigated, with rough calculations of the elements in the magnetospheric
circuit. It is emphasized that the potential of critical field lines is the
same as that of interstellar medium, and that the pulsars whose rotation axes
and magnetic dipole axes are parallel should be positively charged, in order to
close the pulsar's current flows. The statistical relation between the radio
luminosity and pulsar's electric charge (or the spindown power) may hint that
the millisecond pulsars could be low-mass bare strange stars.


title:
First Ultraviolet Spectrum of a Brown Dwarf: Evidence for H_2
  Fluorescence and Accretion

abstract:
  We analyze an HST/STIS ultraviolet spectrum of the young brown dwarf 2MASSW
J1207334-393254, a member of the ten million-year old TW Hya Association that
has a planetary-mass companion. We detect and identify numerous emission lines.
CIV and other ions are seen that arise in hot gas. We identify a series of
lines with Lyman-pumped H_2 molecular lines, indicating that cool gas is also
present. Overall, this substellar object shows many of the same characteristics
as classical T Tauri stars. We interpret our results as direct evidence of
accretion from a circumstellar gas disk, consistent with previous claims. The
lack of SiIV emission from the accreting gas indicates that silicon has been
depleted into grains.


title: On constructing horizontal branch models

abstract:
  We investigate different methods used to construct (zero-age) horizontal
branch models and compare the resulting horizontal branch evolution with that
of models resulting from the calculation of the complete stellar evolution from
the main sequence and through the core helium flash. We show that the
approximate methods may lead to small, but discernible effects, but that some
methods, which are as simple, reproduce the complete evolution very well.


title:
CHANDRA reveals galaxy cluster with the most massive nearby cooling
  core, RXCJ1504.1-0248

abstract:
  A CHANDRA follow-up observation of an X-ray luminous galaxy cluster with a
compact appearance, RXCJ1504.1-0248 discovered in our REFLEX Cluster Survey,
reveals an object with one of the most prominent cluster cooling cores. With a
core radius of ~30 kpc smaller than the cooling radius with ~140 kpc more than
70% of the high X-ray luminosity of Lbol = 4.3 10e45 erg s-1 of this cluster is
radiated inside the cooling radius. A simple modeling of the X-ray morphology
of the cluster leads to a formal mass deposition rate within the classical
cooling flow model of 1500 - 1900 Msun yr-1 (for h=0.7), and 2300 - 3000 Msun
yr-1 (for h=0.5). The center of the cluster is marked by a giant elliptical
galaxy which is also a known radio source. Thus it is very likely that we
observe one of the interaction systems where the central cluster AGN is heating
the cooling core region in a self-regulated way to prevent a massive cooling of
the gas, similar to several such cases studied in detail in more nearby
clusters. The interest raised by this system is then due to the high power
recycled in RXCJ1504-0248 over cooling time scales which is about one order of
magnitude higher than what occurs in the studied, nearby cooling core clusters.
The cluster is also found to be very massive, with a global X-ray temperature
of about 10.5 keV and a total mass of about 1.7 10e15 Msun inside 3 Mpc.


title: Metal Abundances in the ICM as a Diagnostics of the Cluster History

abstract:
  Galaxy clusters with a dense cooling core exhibit a central increase in the
metallicity of the intracluster medium. Recent XMM-Newton studies with detailed
results on the relative abundances of several heavy elements show that the high
central abundances are mostly due to the contribution from supernovae type Ia.
The dominant source is the stellar population of the central cluster galaxy.
With this identification of the origin of heavy elements and the observed rates
of SN Ia in elliptical galaxies, the central abundance peak can be used as a
diagnostic for the history of the cluster core region. We find for four nearby
cooling core clusters that the enrichment times for the central peaks are
larger than 6 - 10 Gyrs even for a higher SN Ia rate in the past. This points
to an old age and a relatively quiet history of these cluster core regions. A
detailed analysis of the element abundance ratios provides evidence that the SN
Ia yields in the central cluster galaxies are more rich in intermediate mass
elements, like Si and S, compared to the SN Ia models used to explain the heavy
element enrichment in our Galaxy.


title: Deuterium depletion and magnesium enhancement in the local disc

abstract:
  The local disc deuter is known to be depleted in comparison to the local
bubble. We show, that the same lines of sight that are depleted in deuter, are
enhanced in magnesium. Heavier elements - Si and Fe do not show any difference
in the abundance between the local disc and the local bubble. This observation
implicates that astration is responsible for both deuter depletion and
magnesium enhancement.


title: The SDSS-XMM Quasar Sample: First Results

abstract:
  We have searched in the XMM-Newton public archive for quasars in the Sloan
Digital Sky Survey (SDSS) First Data Release (DR1), and found 55 lying in the
field of a XMM-Newton observation with exposure times >20 ksec (as of August,
2004). The 35 quasars which yielded good X-ray spectra span redshifts from 0.5
to 2.5. The large collecting area of XMM-Newton allows us to investigate the
dependence of the X-ray spectra of quasars on luminosity, redshift and optical
colors. We find: (1) no evolution of X-ray slope Gamma with either redshift or
luminosity; (2) no correlation between Gamma or absorbing column density and
the optical to X-ray ratio, alpha_{OX}; (4) no relation between alpha_{OX} and
optical colors. The two latter results suggest that obscuration is not the
dominant cause of the spread in X-ray slope or optical color. We find four
unusual quasars, 10% of the sample: three are absorbed (N_H>10^{22} cm^{-2}),
of which one has high luminosity (1.5x10$^{44} erg/s); the fourth has
Gamma=0.6+-0.2, far flatter than the typical value of 1.8-2.0, and a strong
emission line (EW=1.2+-$0.4 keV) which, if Fe-K, implies a redshift of ~1.4.


title:
The supermassive black hole in Centaurus A: a benchmark for gas
  kinematical measurements

abstract:
  We present new HST/STIS observations of Centaurus A. [SIII] 9533A was used to
study the kinematics in the nuclear region with a 0.1" spatial resolution. The
STIS data and the VLT/ISAAC spectra by Marconi et al. (2001) provide
independent and consistent measures of the BH mass, which are in agreement with
our previous estimate based on the ISAAC data alone: MBH=(1.1+/-0.1) 10^8 Msun
for a disk inclination of i=25deg or or MBH=(6.5+/-0.7) 10^7 Msun for i=35deg,
the largest i value allowed by the data. We find that the choice of the
intrinsic surface brightness distribution, a crucial element in the modeling,
has no effects on MBH but has a large impact on the gas velocity dispersion. A
mismatch between the observed and model velocity dispersion is not necessarily
an indication of non-circular motions or kinematically hot gas, but is as
easily due to an inaccurate computation arising from too course a model grid,
or the adoption of an intrinsic brightness distribution which is too smooth.
The observed velocity dispersion, line profiles and the higher order moments in
the Hermite expansion, h_3 and h_4, are consistent with emission from a
rotating disk. Results from gas kinematical estimate are in good agreement with
a recent stellar dynamical estimate of MBH. The BH mass in Centaurus A agrees
with the correlation with infrared luminosity and mass of the host spheroid but
is not in disagreement with the stellar velocity dispersion if one takes into
account the intrinsic scatter of the MBH-sigma correlation. Finally, using HST
data we can constrain the size of any cluster of dark objects alternative to a
BH to r<0.035" (~0.6pc). Thus Centaurus A ranks among the best cases for
supermassive Black Holes in galactic nuclei. (ABRIDGED)


title: A compact starburst ring traced by clumpy OH megamaser emission

abstract:
  We model the OH megamaser emission from the luminous infrared galaxy IIIZw35
as arising from a narrow rotating starburst ring of radius 22 pc enclosing a
mass of 7 x 10^6 Msun. We show how both the compact and apparently diffuse
maser emission from this ring can arise from a single phase of unsaturated
maser clouds amplifying background radio continuum. The masing clouds are
estimated to have a diameter of <0.7 pc and internal velocity dispersion of
about 20 km/s. We find that the clouds are neither self-gravitating nor
pressure confined but are freely expanding. Their dispersal lifetimes may set
the vertical thickness of the ring. For an estimated internal density of 3 x
10^3 cm^-3, cloud masses are of order 24 Msun. The observed spectral features
and velocity gradients indicate that the clouds must be outflowing and escaping
the nucleus. The cloud mass outflow rate is estimated to be 0.8 Msun/yr, while
the star formation rate is about 19 Msun/yr. Associated ionised gas, possibly
generated from dissipated clouds, provides free-free absorption along the
source axis, explaining the observed East-West asymmetries. We show that the
clumpiness of a maser medium can have a dramatic effect on what is observed
even in a relatively low gain OH megamaser. Specifically, in IIIZw35 our clumpy
maser model naturally explains the large line to continuum ratios, the large
1667MHz:1665MHz line ratios and the wide velocity dispersions seen in the
compact maser spots. Other astrophysical masers showing both compact and
apparently diffuse emission might be explained by similar clumpy structures.


title: Cosmological black holes as voids progenitors. I. Simulations

abstract:
  Cosmological black holes (CBH), i.e. black holes with masses larger than
$10^{14} solar masses, have been proposed as possible progenitors of galaxy
voids (Stornaiolo 2002). The presence of a CBH in the central regions of a void
should induce significant gravitational lensing effects and in this paper we
discuss such gravitational signatures using simulated data. These signatures
may be summarized as follows: i) a blind spot in the projected position of the
CBH where no objects can be detected; ii) an excess of faint secondary images;
iii) an excess of double images having a characteristic angular separation. All
these signatures are shown to be detectable in future deep surveys.


title: Dark energy exponential potential models as curvature quintessence

abstract:
  It has been recently shown that, under some general conditions, it is always
possible to find a fourth order gravity theory capable of reproducing the same
dynamics of a given dark energy model. Here, we discuss this approach for a
dark energy model with a scalar field evolving under the action of an
exponential potential. In absence of matter, such a potential can be recovered
from a fourth order theory via a conformal transformation. Including the matter
term, the function f(R) entering the generalized gravity Lagrangian can be
reconstructed according to the dark energy model.


title: Heavy Element Production in Inhomogeneous Big Bang Nucleosynthesis

abstract:
  We present a new astrophysical site of the big bang nucleosynthesis (BBN)
that are very peculiar compared with the standard BBN. Some models of the
baryogenesis suggest that very high baryon density regions were formed in the
early universe. On the other hand, recent observations suggest that heavy
elements already exist in high red-shifts and the origin of these elements
become a big puzzle. Motivated by these, we investigate BBN in very high baryon
density regions. BBN proceeds in proton-rich environment, which is known to be
like the p-process. However, by taking very heavy nuclei into account, we find
that BBN proceeds through both the p-process and the r-process simultaneously.
P-nuclei such as 92Mo, 94Mo, 96Ru, 98Ru whose origin is not well known are also
synthesized.


title: TeV Gamma-Ray Observations of the Perseus Galaxy Cluster

abstract:
  We report on observations of the Perseus cluster of galaxies using the 10 m
Whipple $\gamma$-ray telescope during the 2004-2005 observing season. We apply
a two dimensional analysis technique to allow us to scrutinize the cluster for
TeV emission. In this contribution we will first calculate flux upper limits on
TeV gamma-ray sources within the cluster. Second, we derive an upper limit on
the extended cluster emission. We then compare the flux upper limits with the
EGRET upper limit at 100 MeV and theoretical models.


title: Observations of AGN with the First VERITAS Telescope

abstract:
  The first VERITAS (Very Energetic Radiation Imaging Telescope Array System)
telescope has been in operation at the basecamp of the Whipple Observatory
since January 2005. Here we present initial observations of AGN made using this
telescope. Although this is engineering data, significant detections of
Markarian 421 and Markarian 501 have been achieved.


title:
Chemical Evolution in Hierarchical Models Of Cosmic Structure I:
  Constraints on the Early Stellar Initial Mass Function

abstract:
  I present a new Galactic chemical evolution model motivated by and grounded
in the hierarchical theory of galaxy formation, as expressed by a halo merger
history of the Galaxy. This model accurately reproduces the "metallicity
distribution function" (MDF) for Population II stars residing today in the
Galactic halo. The observed MDF and the apparent absence of true Population III
stars from the halo strongly imply that there is some critical metallicity,
Z_crit <~ 10^-4 Z_sun, below which low-mass star formation is inhibited, and
perhaps impossible. The observed constraints from the halo MDF, relative metal
abundances from Galactic halo stars, and the ionizing photon budget needed to
reionize the IGM together imply a stellar IMF that is peaked in the range of
massive stars that experience core-collapse supernovae, with mean mass <M> = 8
- 42 Msun. This mass range is similar to the masses predicted by models of
primordial star formation that account for formation feedback. The model also
implies that metal-poor halo stars below [Fe/H] <~ -3 had only 1 - 10
metal-free stars as their supernova precursors, such that the relative
abundances in these halo stars exhibit IMF-weighted averages over the intrinsic
yields of the first supernovae. This paper is the first part of a long term
project to connect the high-redshift in situ indicators of early star formation
with the low-z, old remnants of the first stars.


title: The Effect of Thermal Conduction on the Virgo Cluster

abstract:
  Thermal conduction has been suggested as a possible mechanism by which
sufficient energy is supplied to the central regions of galaxy clusters to
balance the effect of radiative cooling. Here we present the results of a
simulated, high-resolution, 3-d Virgo cluster for different values of thermal
conductivity (1, 1/10, 1/100, 0 times the full Spitzer value). Starting from an
initially isothermal cluster atmosphere we allow the cluster to evolve freely
over timescales of roughly $ 1.3-4.7 \times 10^{9} $ yrs. Our results show that
thermal conductivity at the Spitzer value can increase the central ICM
radiative cooling time by a factor of roughly 3.6. In addition, for larger
values of thermal conductvity the simulated temperature and density profiles
match the observations significantly better than for the lower values. However,
no physically meaningful value of thermal conductivity was able to postpone the
cooling catastrophe (characterised by a rapid increase in the central density)
for longer than a fraction of the Hubble time nor explain the absence of a
strong cooling flow in the Virgo cluster today. We also calculate the effective
adiabatic index of the cluster gas for both simulation and observational data
and compare the values with theoretical expectations. Using this method it
appears that the Virgo cluster is being heated in the cluster centre by a
mechanism other than thermal conductivity. Based on this and our simulations it
is also likely that the thermal conductvity is suppressed by a factor of at
least 10 and probably more. Thus, we suggest that thermal conductvity, if
present at all, has the effect of slowing down the evolution of the ICM, by
radiative cooling, but only by a factor of a few.


title: A New Technique for Probing Convection in Pulsating White Dwarf Stars

abstract:
  In this paper we demonstrate how pulsating white dwarfs can be used as an
astrophysical laboratory for empirically constraining convection in these
stars. We do this using a technique for fitting observed non-sinusoidal light
curves, which allows us to recover the thermal response timescale of the
convection zone (its "depth") as well as how this timescale changes as a
function of effective temperature. We also obtain constraints on mode
identifications for the pulsation modes, allowing us to use asteroseismology to
study the interior structure of these stars. Aspects of this approach may have
relevance for other classes of pulsators, including the Cepheids and RR Lyrae
stars.


title: Monte Carlo Studies of the first VERITAS telescope

abstract:
  The Very High Energy Radiation Telescope Array (VERITAS) is a system of four
imaging Cherenkov telescopes currently under construction at Kitt Peak,
Arizona, USA. The first telescope has been in operation at the Mt. Hopkins
basecamp since January 2005. We present here detailed Monte Carlo simulations
of the telescope response to extensive air showers. The energy threshold for
this stand-alone telescope is calculated to be 150 GeV at trigger level, the
gamma-ray trigger rate is 22 gamma's/min. Image parameter distributions, and
the quality of gamma-hadron discrimination are calculated and show good
agreement with distributions from observations of background cosmic rays and
high-energy gamma-rays from the Crab Nebula and Markarian 421. The energy
spectrum of the Crab is reconstructed as $(3.26\pm0.9)\cdot 10^{-7}\cdot
E^{-(2.6\pm 0.3)}$ m$^{-2}$s$^{-1}$TeV$^{-1}$.


title:
Search for Cygnus Arm Diffuse TeV Gamma Ray Emission with the Whipple
  10m Telescope

abstract:
  The Whipple 10 meter atmospheric Cherenkov telescope has made observations of
the region known as the Cygnus arm. This region has been recently reported by
the Milagro experiment to contain a diffuse TeV gamma-ray source centered at
RA=308 and Dec=42. We report upper limits (using the Whipple 10 m telescope)
obtained during the Fall 2004 observing season centered on RA=310 and
Dec=42.65.


title: Spectral Monitoring of Mrk 421 during 2004

abstract:
  Daily monitoring of Mrk 421 in the X-ray and TeV bands during the first half
of 2004 showed rapid flaring events above an elevated base flux level,
culminating from March to May 2004 at an average flux level matching the
highest detected flux state in 2001. Here we summarise the daily X-ray spectral
variability observed with the RXTE-PCA instrument. We also explore the X-ray
and TeV gamma-ray connection from near simultaneous data obtained using the
Whipple 10m Cherenkov imaging telescope.


title: Search for TeV Radiation from Selected Local Group Galaxies

abstract:
  Some candidate dark matter particles, such as neutralinos in supersymmetry,
would annihilate producing GeV/TeV gamma rays. We report on recent observations
of two dwarf spheroid galaxies, Draco, Ursa Minor, the compact elliptical
galaxy M32, and the spiral galaxy M33 with the Whipple 10m gamma-ray telescope.
No significant signal was found, and we derived upper limits for the gamma-ray
flux from each object. We discuss our astrophysical selection criteria for
these galaxies in the context of an indirect search for dark matter and the
implications of these flux upper limits on the density of neutralinos.


title: Calibration of VERITAS Telescope 1 via Muons

abstract:
  Cherenkov light from cosmic-ray muons is a significant source of background
for the Imaging Atmospheric Cherenkov Technique. However, muon events are also
valuable as a diagnostic tool because they produce distinctive ring images, and
the expected amount of Cherenkov light per unit arclength can be accurately
calculated. We report on a comparison of real and simulated muon events in
VERITAS Telescope 1, using this comparison to validate the detector model and
to determine the light collection efficiency of the telescope.


title: Exploiting VERITAS Timing Information

abstract:
  The 499 pixel photomultiplier cameras of the VERITAS gamma ray telescopes are
instrumented with 500MHz sampling Flash ADCs. This paper describes a
preliminary investigation of the best methods by which to exploit this
information so as to optimize the signal-to-noise ratio for the detection of
Cherenkov light pulses. The FADCs also provide unprecedented resolution for the
study of the timing characteristics of Cherenkov images of cosmic-ray and
gamma-ray air showers. This capability is discussed, together with the
implications for gamma-hadron separation.


title: Status and Performance of the First VERITAS telescope

abstract:
  The first of the four atmospheric Cherenkov telescopes of the VERITAS array
has been in operation at the Mt. Hopkins base camp since January 2005. The
telescope has met all specifications. We present here a description of the
technical performance, including calibration details and a summary of a
preliminary analysis of Crab Nebula observations. The construction status of
the complete VERITAS array is also discussed.


title:
XMM-Newton study of the two-dimensional structure of the REFLEX-DXL
  galaxy clusters

abstract:
  We carry out a two-dimensional study of temperature, entropy and pressure
distributions in a nearly volume-limited subsample of REFLEX clusters at
redshift 0.3, the REFLEX-DXL. We use the observations gained by XMM-Newton,
which cover the central 1-2 x r500. We define the substructure in both entropy
and pressure as a deviation from the mean profile of the sample. The
non-parametric locally weighted regression suggests a broken power law
approximation to the entropy profile with inner and outer slopes of 0.78 and
0.52, respectively, and a break at 0.5r500. The characterization of the
pressure profile is more complex, requiring three power laws, with slopes -0.64
at r<0.3r500, -2.47 at r>0.5r500 and a slope of -1.50 in between. An analysis
of the substructure in the pressure and entropy maps reveals somewhat larger
fluctuations around the mean pressure profile compared to the entropy.
Typically, pressure fluctuations are found on the 30% level, while the entropy
fluctuations are at the 20% level (r.m.s.). We compare the cumulative
distribution of the substructure level in the REFLEX-DXL sample with the
results of numerical simulation and by means of KS test show that they are in
agreement. A discussion of the origin of the substructure is provided on
individual cluster basis.


title: Multiplicity at the Stellar/Substellar Boundary in Upper Scorpius

abstract:
  We present the results of a high-resolution imaging survey of 12 brown dwarfs
and very low mass stars in the closest (~145 pc) young (~5 Myr) OB association,
Upper Scorpius. We obtained images with the Advanced Camera for Surveys/High
Resolution Camera on HST through the F555W (V), F775W (i'), and F850LP (z')
filters. This survey discovered three new binary systems, including one
marginally resolved pair with a projected separation of only 4.9 AU, resulting
in an observed binary fraction of 25+/-14% at separations >4 AU. After
correcting for detection biases assuming a uniform distribution of mass ratios
for q>0.6, the estimated binary fraction is 33+/-17%. The binary fraction is
consistent with that inferred for higher-mass stars in Upper Sco, but the
separation and mass ratio distributions appear to be different. All three
low-mass binary systems in Upper Sco are tight (<18 AU) and of similar mass
(q>0.6), consistent with expectations based on previous multiplicity studies of
brown dwarfs and very low mass stars in the field and in open clusters. The
implication is that the distinct separation and mass ratio distributions of
low-mass systems are set in the formation process or at very young ages, rather
than by dynamical disruption of wide systems at ages >5 Myr. Finally, we
combine the survey detection limits with the models of Burrows et al. (1997) to
show that there are no planets or very low-mass brown dwarfs with masses >10
M_J at projected separations >20 AU, or masses >5 M_J at projected separations
>40 AU orbiting any of the low-mass (0.04-0.10 M_sun) objects in our sample.


title:
The Lensed Arc Production Efficiency of Galaxy Clusters: A Comparison of
  Matched Observed and Simulated Samples

abstract:
  We compare the statistical properties of giant gravitationally lensed arcs
produced in matched simulated and observed cluster samples. The observed sample
consists of 10 X-ray selected clusters at redshifts z ~ 0.2 imaged with HST by
Smith et al. The simulated dataset is produced by lensing the Hubble Deep
Field, which serves as a background source image, with 150 realizations
(different projections and shifts) of five simulated z = 0.2 clusters from a
LambdaCDM N-body simulation. The real and simulated clusters have similar
masses, the real photometric redshift is used for each background source, and
all the observational effects influencing arc detection in the real dataset,
including light from cluster galaxies, are simulated in the artificial dataset.
We develop, and apply to both datasets, an objective automatic arc-finding
algorithm. We find consistent arc statistics in the real and in the simulated
sample, with an average of ~ 1 detected giant (length to width ratio >= 10) arc
per cluster and ~ 0.2 giant luminous (R<22.3 mag) arc per cluster. Thus, taking
into account a realistic source population and observational effects, the
clusters predicted by LambdaCDM have the same arc-production efficiency as the
observed clusters. If, as suggested by other studies, there is a discrepancy
between the predicted and the observed total number of arcs on the sky, it must
be the result of differences between the redshift dependent cluster mass
functions, and not due to differences in the lensing efficiency of the most
massive clusters.


title: Inflationary predictions for scalar and tensor fluctuations reconsidered

abstract:
  We reconsider the predictions of inflation for the spectral index of scalar
(energy density) fluctuations (n_s) and the tensor/scalar ratio (r) using a
discrete, model-independent measure of the degree of fine-tuning required to
obtain a given combination of (n_s, r). We find that, except for cases with
numerous unnecessary degrees of fine-tuning, n_s is less than 0.98, measurably
different from exact Harrison-Zel'dovich. Furthermore, if n_s \gtrsim 0.95, in
accord with current measurements, the tensor/scalar ratio satisfies r \gtrsim
10^{-2}, a range that should be detectable in proposed cosmic microwave
background polarization experiments and direct gravitational wave searches.


title: The Type Ia Supernova Rate

abstract:
  We explore the idea that the Type Ia supernovae (SNe Ia) rate consists of two
components: a prompt piece that is proportional to the star formation rate
(SFR) and an extended piece that is proportional to the total stellar mass. We
fit the parameters of this model to the local observations of Mannucci and
collaborators and then study its impact on three important problems. On cosmic
scales, the model reproduces the observed SNe Ia rate density below z=1, and
predicts that it will track the measured SFR density at higher redshift,
reaching a value of 1-3.5 X 10^-4 per yr per Mpc^3 at z=2. In galaxy clusters,
a large prompt contribution helps explain the iron content of the intracluster
medium. Within the Galaxy, the model reproduces the observed stellar [O/Fe]
abundance ratios if we allow a short (approximately 0.7 Gyr) delay in the
prompt component. Ongoing medium-redshift SN surveys will yield more accurate
parameters for our model


title:
Dark Energy and Cosmic Sound: w(z) Surveys with the Gemini/Subaru
  Wide-Field Multi-Object Spectrograph

abstract:
  This white paper gives an overview of the proposed Gemini/Subaru Wide-Field
Multi-Object Spectrograph (WFMOS) and the proposed redshift surveys of 2.6
million galaxies with 0.5<z<3.3 over 2000 deg^2 of sky. These surveys will
probe the baryonic acoustic oscillations in the galaxy power spectrum with
unprecedented precision and over a range of redshifts and deliver dark energy
w(z) constraints an order of magnitude better than current limits. We discuss
the requirements on precursor observations and on calibrations, the systematics
in the method and the quantitative precision obtainaible in distance-redshift
and expansion-rate-redshift measurements which feed in to the w(z) precision.
We also outline the technological and scientific strengths and risks which
might be associated with the project and the relationship of WFMOS to other
baryon oscillation experiments.


title: Seeing the Nature of the Accelerating Physics: It's a SNAP

abstract:
  For true insight into the nature of dark energy, measurements of the
precision and accuracy of the Supernova/Acceleration Probe (SNAP) are required.
Precursor or scaled-down experiments are unavoidably limited, even for
distinguishing the cosmological constant. This white paper presents an overview
of the necessity for SNAP and the role of precursor experiments; accompanying
white papers detail the supernovae and weak lensing parts of the experiment.


title:
Supernova Acceleration Probe: Studying Dark Energy with Type Ia
  Supernovae

abstract:
  The Supernova Acceleration Probe (SNAP) will use Type Ia supernovae (SNe Ia)
as distance indicators to measure the effect of dark energy on the expansion
history of the Universe. (SNAP's weak-lensing program is described in a
companion White Paper.) The experiment exploits supernova distance measurements
up to their fundamental systematic limit; strict requirements on the monitoring
of each supernova's properties lead to the need for a space-based mission.
Results from pre-SNAP experiments, which characterize fundamental SN Ia
properties, will be used to optimize the SNAP observing strategy to yield data,
which minimize both systematic and statistical uncertainties. SNAP has achieved
technological readiness and the collaboration is poised to begin construction.