title:
A search for the optical and near-infrared counterpart of the accreting
  millisecond X-ray pulsar XTE J1751-305

abstract:
  We have obtained optical and near-infrared images of the field of the
accreting millisecond X-ray pulsar XTE J1751-305. There are no stars in the
0.7'' error circle (0.7'' is the overall uncertainty arising from tying the
optical and X-ray images and from the intrinsic uncertainty in the Chandra
X-ray astrometric solution). We derive limiting magnitudes for the counterpart
of R>23.1, I>21.6, Z>20.6, J>19.6, K>19.2. We compare these upper limits with
the magnitudes one would expect for simple models for the possible donor stars
and the accretion disk subject to the reddening observed in X-rays for XTE
J1751-305 and when put at the distance of the Galactic Centre (8.5 kpc). We
conclude that our non-detection does not constrain any of the models for the
accretion disk or possible donor stars. Deep, near-infrared images obtained
during quiescence will, however, constrain possible models for the donor stars
in this ultra-compact system.


title: Red and Reddened Quasars in the Sloan Digital Sky Survey

abstract:
  We investigate the continuum and emission line properties of 4576 SDSS
quasars as a function of their optical/UV SEDs. The optical/UV color
distribution of our sample is roughly Gaussian, but with a red tail; we
distinguish between 1) intrinsically blue (optically flat) quasars, 2)
intrinsically red (optically steep) quasars, and 3) the 273 (6%) of our quasars
whose continua are inconsistent with a single power-law and appear redder due
to SMC-like dust reddening rather than synchrotron emission. The color
distribution suggests that the population of moderately dust reddened
broad-line quasars is smaller than that of unobscured quasars, but we estimate
that a further 10% of the luminous quasar population is missing from the SDSS
sample because of dust extinction with E(B-V)<0.5. We also investigate the
emission and absorption line properties of these quasars as a function of color
with regard to Boroson & Green type eigenvectors. Intrinsically red (optically
steep) quasars tend to have narrower Balmer lines and weaker CIV, CIII], HeII
and 3000A bump emission as compared with bluer (optically flatter) quasars. The
change in strength of the 3000A bump appears to be dominated by the Balmer
continuum and not by FeII emission. The dust reddened quasars have even
narrower Balmer lines and weaker 3000A bumps, in addition to having
considerably larger equivalent widths of [OII] and [OIII] emission. The
fraction of broad absorption line quasars (BALQSOs) increases from ~3.4% for
the bluest quasars to perhaps as large as 20% for the dust reddened quasars,
but the intrinsic color distribution is affected by dust reddening. (abridged)


title: A Tale of Two Mergers: Searching for Strangeness in Compact Stars

abstract:
  We contrast the evolution of gravitational binary mergers for the two cases
of a black hole and a normal neutron star, and a black hole and a self-bound
strange quark matter star. In both cases inspiral continues until the Roche
limit is reached, at which point it is expected that stable mass transfer to
the balck hole ensues. Whereas a neutron star would then outspiral, the strange
quark matter star barely moves out at all. Eventually, the strange quark star
loses all its mass to the black hole, as compared to the neutron star whose
outspiral continues until stable mass transfer terminates and inspiral resumes.
These scenarios result in distinctly different gravitational wave signatures.


title:
A XMM-Newton observation of Nova LMC 1995, a bright supersoft X-ray
  source

abstract:
  Nova LMC 1995, previously detected during 1995-1998 with ROSAT, was observed
again as a luminous supersoft X-ray source with XMM-Newton in December of 2000.
This nova offers the possibility to observe the spectrum of a hot white dwarf,
burning hydrogen in a shell and not obscured by a wind or by nebular emission
like in other supersoft X-ray sources. Notwithstanding uncertainties in the
calibration of the EPIC instruments at E<0.5 keV, using atmospheric models in
Local Thermonuclear Equilibrium we derived T(eff)=400,000-450,000 K, L(bol)=2.3
x 110(-14) 0(37) erg cm(-2) s(-1) and we verified that the C abundance is not
significantly enhanced. The RGS spectra do not show emission lines of a wind or
nebula, but the white dwarf absorption lines cannot be resolved. The upper
limit to the flux in the 0.6-10 keV range is 10(-14) erg cm(-2) s(-1). There is
no rapid or large variability in the light curve, but we find a peak at 5.25
hours in the power spectrum.


title:
Observation of TeV Gamma Rays from the Crab Nebula with Milagro Using a
  New Background Rejection Technique

abstract:
  The recent advances in TeV gamma-ray astronomy are largely the result of the
ability to differentiate between extensive air showers generated by gamma rays
and hadronic cosmic rays. Air Cherenkov telescopes have developed and perfected
the "imaging" technique over the past several decades. However until now no
background rejection method has been successfully used in an air shower array
to detect a source of TeV gamma rays. We report on a method to differentiate
hadronic air showers from electromagnetic air showers in the Milagro gamma ray
observatory, based on the ability to detect the energetic particles in an
extensive air shower. The technique is used to detect TeV emission from the
Crab nebula. The flux from the Crab is estimated to be 2.68(+-0.42stat +-
1.4sys) x10^{-7} (E/1TeV)^{-2.59} m^{-2} s^{-1} TeV^{-1}, where the spectral
index is assumed to be as given by the HEGRA collaboration.


title: XMM-Newton Observations of Two BAL QSOs: Q1246-057 and SBS1542+541

abstract:
  We report on the results of XMM-Newton observations of two Broad Absorption
Line Quasars (BAL QSOs), Q1246-057 and SBS 1542+541. Unprecedented sensitivity
of XMM allows spectral analysis of these X-ray weak sources. The X-ray spectral
data of these sources can be fitted by a power-law with alpha_X=1.0-1.2 and
either a partially covering absorber or an ionized absorber model. Rest frame
UV spectroscopy together with polarimetry favors the model with a partially
covering absorber with column density a few times 10^22 cm^-2 and a covering
fraction of about 0.80. After correcting for absorption, the X-ray loudness of
these BAL QSOs appears to be similar to other, unabsorbed quasars. The mystery
of X-ray weakness of BAL QSOs appears to be all but solved, with strong
absorption being the primary reason. With the available X-ray data, however,
the issue of whether BAL QSOs represent highly accreting/ younger population of
quasars remains unsettled.


title: Dark Matter at Boulby Mine

abstract:
  The Boulby Dark Matter Collaboration (BDMC) is running a WIMP Dark Matter
research programme in the underground laboratory of Boulby Mine. The two axes
of the programme are based on (1) liquid Xenon (LXe) as the WIMP target and (2)
directional detection in low pressure gas detectors. ZEPLIN-1 is a 3.1kg of LXe
scintillation detector with a background discrimination based on Pulse Shape
Analysis. A new limit from a preliminary analysis is presented. Further
generation setups with improved background discrimination tools (as the
ionisation is also recorded) are in construction. ZEPLIN-2 and ZEPLIN-3, are
predicted to be sensitive to rate of 0.1-0.01 events/kg/day within 2 years of
data, with fiducial masses of 30kg and 6kg, respectively. These are important
steps towards the design of a tonne-scale LXe Dark Matter detector array. The
DRIFT programme relies on discrimination by tracking and directionnal
detection. This enables the measurement of any sidereal modulation, as the
earth's rotation changes the flux angle of Galactic WIMPs. A low pressure
1m$^3$ chamber (DRIFT-1) is currently taking data underground. A setup for a
bigger volume with increased spatial resolution (enabling the pressure, and
hence the target mass to be increase) is in the designing process.


title:
Spectroscopic Constraints on the Surface Magnetic Field of the Accreting
  Neutron Star EXO 0748-676

abstract:
  Gravitationally redshifted absorption lines of Fe XXVI, Fe XXV, and O VIII
were inferred recently in the X-ray spectrum of the bursting neutron star EXO
0748-676. We place an upper limit on the stellar magnetic field based on the
iron lines. The oxygen absorption feature shows a multiple component profile
that is consistent with Zeeman splitting in a magnetic field of ~(1-2)x10^9
gauss, and for which the corresponding Zeeman components of the iron lines are
expected to be blended together. In other systems, a field strength >5x10^{10}
gauss could induce a blueshift of the line centroids that would counteract
gravitational redshift and complicate the derivation of constraints on the
equation of state of the neutron star.


title: The ESI/KeckII Damped Lya Abundance Database

abstract:
  This paper presents chemical abundance measurements for 37 damped Lya systems
at z>2.5 observed with the Echellette Spectrograph and Imager on the KeckII
telescope. We measure the HI column densities of these damped systems through
Voigt profile fits to their Lya profiles and we implement the apparent optical
depth method to determine ionic column densities. Figures and tables of all
relevant data are presented. A full analysis of the chemical enrichment history
described by these observations will be presented in a future paper. This
dataset is also valuable for efficiently planning future echelle observations
and for rough abundance pattern analyses. We aim to make this entire data set
public within three years of this publication.


title:
New Damped Lya Metallicities from ESI Spectroscopy of Five Palomar Sky
  Survey Quasars

abstract:
  This paper presents chemical abundance measurements for 12 new z>3 damped Lya
systems discovered toward five quasars from the Palomar Sky Survey. We
determine HI column densities from profile fits to the observed damped Lya
profiles and measure ionic column densities and limits for all observed
metal-line transitions. This dataset, acquired with the Echellette Spectrograph
and Imager on the KeckII telescope, adds to the rapidly growing database of
damped Lya abundances. It will impact studies of chemical evolution in the
early universe and help identify candidates for detailed follow-up observations
with echelle spectrographs. We report the discovery of the first quasar
sightline with four cosmologically distinct damped Lya systems.


title:
The Age-Metallicity Relation of the Universe in Neutral Gas: The First
  100 Damped Lya Systems

abstract:
  We present accurate metallicity measurements for 121 damped Lya systems at
0.5<z<5 including ~50 new measurements from our recently published Echellette
Spectrograph and Imager surveys. This dataset is analysed to determine the
age-metallicity relation of neutral gas in the universe. Contrary to previous
datasets this sample shows statistically significant evolution in the mean
metallicity. The best linear fit rate to metallicity vs. redshift is -0.26 +/-
0.07 dex corresponding to approximately a factor of 2 every Gyr at z=3. The DLA
continue to maintain a floor in metallicity of ~1/700 solar independent of
observational effects. This metallicity threshold limits the prevalence of
primordial gas in high redshift galaxies and stresses the correspondence
between damped systems and star formation (i.e. galaxy formation). This floor
is significantly offset from the metallicity of the Lya forest and therefore we
consider it to be more related to active star formation within these galaxies
than scenarios of enrichment in the very early universe. Finally, we comment on
an apparent 'missing metals problem': the mean metallicity of the damped
systems is ~10x lower than the value expected from their observed star
formation history. This problem is evident in current theoretical treatments of
chemical evolution and galaxy formation; it may indicate a serious flaw in our
understanding of the interplay between star formation and metal production.


title:
The Optical Gravitational Lensing Experiment. Catalog of stellar proper
  motions in the OGLE-II Galactic bulge fields

abstract:
  We present a proper motion (\mu) catalogue of 5,080,236 stars in 49 Optical
Gravitational Lensing Experiment II (OGLE-II) Galactic bulge (GB) fields,
covering a range of -11 deg. <l< 11 deg. and -6 deg. <b<3 deg., the total area
close to 11 square degrees. The proper motion measurements are based on 138 -
555 I-band images taken during four observing seasons: 1997-2000. The catalogue
stars are in the magnitude range 11 < I < 18 mag. In particular, the catalogue
includes Red Clump Giants (RCGs) and Red Giants in the GB, and main sequence
stars in the Galactic disc. The proper motions up to \mu = 500 mas/yr were
measured with the mean accuracy of 0.8-3.5 mas/yr, depending on the brightness
of a star. This catalogue may be useful for studying the kinematic of stars in
the GB and the Galactic disk.


title:
An HST/WFPC2 Survey for Brown Dwarf Binaries in the alpha Per and the
  Pleiades Open Clusters

abstract:
  We present the results of a high-resolution imaging survey for brown dwarf
(BD) binaries in two open clusters. The observations were carried out with
WFPC2 onboard HST. Our sample consists of 8 BD candidates in the alpha Per
cluster and 25 BD candidates in the Pleiades. We have resolved 4 binaries in
the Pleiades with separations in the range 0".094--0".058, corresponding to
projected separations between 11.7~AU and 7.2~AU. No binaries were found among
the alpha Per targets. Three of the binaries have proper motions consistent
with cluster membership in the Pleiades cluster, and for one of them we report
the detection of Halpha in emission and LiI absorption obtained from
Keck~II/ESI spectroscopy. One of the binaries does not have a proper motion
consistent with Pleiades membership. We estimate that BD binaries wider than
12~AU are less frequent than 9% in the alphaPer and Pleiades clusters. This is
consistent with an extension to substellar masses of a trend observed among
stellar binaries: the maximum semimajor axis of binary systems decreases with
decreasing primary mass. We find a binary frequency of 2 binaries over 13 BDs
with confirmed proper motion membership in the Pleiades, corresponding to a
binary fraction of 15%(1 sigma error bar +15%/-5%). These binaries are limited
to the separation range 7-12~AU and their mass ratios are larger than 0.7. The
relatively high binary frequency (>10%), the bias to separations smaller than
about 15 AU and the trend to high mass ratios (q>0.7) are fundamental
properties of BDs. Current theories of BD formation do not appear to provide a
good description of all these properties.


title:
Binary and Multiple Star Formation in Magnetic Clouds: Bar Growth and
  Fragmentation

abstract:
  We study the non-axisymmetric evolution of magnetized clouds, using a 2D MHD
code based on the physically motivated thin-disk approximation. We found that
such clouds become unstable to non-axisymmetric perturbations after the
supercritical cores are formed due to ambipolar diffusion. We show that for a
wide range of initial cloud parameters, the $m=2$ mode grows nonlinearly into a
bar during the isothermal collapse after the supercritical core formation. The
supercritical core can break up into fragments during or after the isothermal
phase of cloud evolution. The outcome of fragmentation depends on the initial
cloud conditions, such as the magnetic field strength, rotation rate, amount of
cloud mass and mass distribution. It is classified into three different types:
(1) separate core formation, (2) bar fragmentation, and (3) disk fragmentation.
These three types of fragmentation loosely correspond to the empirical
classification of embedded binary and multiple systems of Looney, Mundy, &
Welch, based on millimeter dust continuum observations. The well-studied
starless core, L1544, appears to belong to the bar fragmentation type. We
expect it to produce a highly elongated, opaque bar at the center in the
future, which should break up into fragments of initial masses in the
substellar regime.


title:
Evidence for a Significant Intermediate-Age Population in the M31 Halo
  from Main Sequence Photometry

abstract:
  We present a color-magnitude diagram (CMD) for a minor-axis field in the halo
of the Andromeda galaxy (M31), 51 arcmin (11 kpc) from the nucleus. These
observations, taken with the Advanced Camera for Surveys (ACS) on the Hubble
Space Telescope, are the deepest optical images yet obtained, attaining 50%
completeness at V = 30.7 mag. The CMD, constructed from approximately 300,000
stars, reaches more than 1.5 mag fainter than the old main-sequence turnoff.
Our analysis is based on direct comparisons to ACS observations of four
globular clusters through the same filters, as well as chi-squared fitting to a
finely-spaced grid of calibrated stellar-population models. We find that the
M31 halo contains a major (approximately 30% by mass) intermediate-age (6-8
Gyr) metal-rich ([Fe/H] > -0.5) population, as well as a significant
globular-cluster age (11-13.5 Gyr) metal-poor population. These findings
support the idea that galaxy mergers played an important role in the formation
of the M31 halo.


title:
A search for Low Surface Brightness galaxies in the near-infrared III.
  Nancay HI line observation

abstract:
  A total of 334 Low Surface Brightness galaxies detected in the 2MASS all-sky
near-infrared survey have been observed in the 21 cm HI line using the Nancay
telescope. All have a K_s-band mean central surface brightness, measured within
a 5 arcsec radius, fainter than 18 mag/arcsec^2 and a K_s-band isophotal radius
at the 20 mag/arcsec^2 level larger than 20 arcsec. We present global HI line
parameters for the 171 clearly detected objects and the 23 marginal detections,
as well as upper limits for the undetected objects. The 171 clear detections
comprise 50 previously uncatalogued objects and 41 objects with a PGC entry
only.


title:
Bulk viscosity of strange quark matter in density-dependent quark mass
  model and dissipation of r-modes in strange stars

abstract:
  We study the bulk viscosity of strange quark matter(SQM) in density dependent
quark mass model(DDQM) under the background of self-consistent thermodynamics.
The correct formulae, with which the viscosity can be evaluated, are derived.
We also find that the viscosity in DDQM can be higher by 2 to 3 orders of
magnitude than MIT bag model. We calculate the damping time scales due to
viscosity coupled to r-modes. The numerical results show the time scale can't
be shorter than $10^{-1}$s.


title: Optical Spectra of the Type Ia Supernova 1998aq

abstract:
  We present 29 optical spectra of the normal Type Ia SN 1998aq, ranging from 9
days before to 241 days after the time of maximum brightness. This
spectroscopic data set, together with photometric data presented elsewhere,
makes SN 1998aq one of the best observed Type Ia supernova at optical
wavelengths. We use the parameterized supernova synthetic-spectrum code SYNOW
to study line identifications in the early photospheric-phase spectra. The
results include evidence for lines of singly ionized carbon, at ejection
velocities as low as 11,000 km/sec. Implications for explosion models are
discussed.


title: The self-gravitating gas in the presence of dark energy

abstract:
  The non-relativistic self-gravitating gas in thermal equilibrium in the
presence of a positive cosmological constant Lambda (dark energy) is
investigated. The dark energy introduces a force pushing outward all particles
with strength proportional to their distance to the center of mass.We consider
the statistical mechanics of the self-gravitating gas of N particles in a
volume V at thermal equilibrium in the presence of Lambda. It is shown that the
thermodynamic limit exists and is described by the mean field equations
provided N, V -> inf with N/V^{1/3} fixed and Lambda V^{2/3} fixed. That is,
Lambda -> 0 for N, V -> inf. The case of Lambda fixed and N, V -> inf is solved
too. We solve numerically the mean field equation for spherical symmetry
obtaining an isothermal sphere for Lambda>0. The particle distribution turns to
flatten compared with the Lambda = 0 case.Moreover, the particle density
increases with the distance when the cosmological constant dominates. There is
a bordering case with uniform density.The density contrast between the center
and the boundary is significatively reduced. In addition, the critical point
associated to the collapse (Jeans') phase transition is pushed towards higher
values of N/[T V^{1/3}] by the presence of Lambda > 0.The nature and the
behaviour near the critical points is not affected by the presence of Lambda>0.


title:
X-Ray Observation on the Monoceros R2 Star-Forming Region with the
  Chandra ACIS-I Array

abstract:
  We report on the results of the Chandra observation on the central region of
the Monoceros R2 cloud (Mon R2), a high-mass star-forming region (SFR). With a
deep exposure of 100 ks, we detected 368 X-ray sources, 80% of which were
identified with the NIR counterparts. We systematically analyzed the spectra
and time variability of most of the X-ray emitting sources and provided a
comprehensive X-ray source catalog for the first time. Using the J-, H-, and
K-band magnitudes of the NIR counterparts, we estimated the evolutionary phase
(classical T Tauri stars and weak-lined T Tauri stars) and the mass of the
X-ray emitting sources, and analyzed the X-ray properties as a function of the
age and mass. We found a marginal hint that classical T Tauri stars have a
slightly higher temperature (2.4 keV) than that of weak-lined T Tauri stars
(2.0 keV). A significant fraction of the high- and intermediate-mass sources
have a time variability and high plasma temperatures (2.7 keV). We performed
the same analysis for other SFRs, the Orion Nebula Cluster and Orion Molecular
Cloud-2/3, and obtained similar results to Mon R2. This supports the earlier
results of this observation obtained by Kohno et al. (2002, ApJ, 567, 423) and
Preibisch et al. (2002, A&A, 392, 945) that high- and intermediate- mass young
stellar objects emit X-rays via magnetic activity. We also found a significant
difference in the spatial distribution between X-ray and NIR sources.


title: Anomalous Absorption in Cyclic C$_3$H Radical

abstract:
  Yamamoto et al. (1987) reported the first detection of $c$-C$_3$H radical in
{TMC-1} through its transition $2_{1 2} \to 1_{1 1}$ at 91.5 GHz. Mangum and
Wootten (1990) detected $c$-C$_3$H through the transition $1_{1 0} \to 1_{1 1}$
at 14.8 GHz in 12 additional galactic objects. The column density of $c$-C$_3$H
in the objects was estimated to be about one order of magnitude lower than that
of the C$_3$H$_2$ which is ubiquitous in the galactic objects. The most
probable production mechanism of both the C$_3$H and C$_3$H$_2$ in dark clouds
is a common dissociation reaction of C$_3$H$_3^+$ ion (Adams & Smith, 1987).
Although the $c$-C$_3$H is 0.8 eV less stable than its isomer $l$-C$_3$H,
finding of comparable column densities of both the isomers in {TMC-1} supports
the idea of comparable formation of both the $c$-C$_3$H and $l$-C$_3$H in the
cosmic objects. Existence of a metaisomer in interstellar condition is a well
known phenomenon in astronomy.
  We propose that $c$-C$_3$H may be identified through the transition $3_{3 1}
\to 3_{3 0}$ at 3.4 GHz in absorption against the cosmic 2.7 K background in
dense cosmic objects when no strong source is present in the background. When
there is some strong source in the background of the object, peak of the
absorption line decreases with the increase of the strength of the background
source. However, at low densities, the intensity is found to increase. Hence,
in low density regions, a background source can help in detection of the line.
This absorption line may play an important role for identification of
$c$-C$_3$H in a large number of cosmic objects. Similar absorption features are
found for $c$-C$_3$D radical also.


title:
The primary cosmic ray composition between 10**15 and 10**16 eV from
  Extensive Air Showers electromagnetic and TeV muon data

abstract:
  The cosmic ray primary composition in the energy range between 10**15 and
10**16 eV, i.e., around the "knee" of the primary spectrum, has been studied
through the combined measurements of the EAS-TOP air shower array (2005 m
a.s.l., 10**5 m**2 collecting area) and the MACRO underground detector (963 m
a.s.l., 3100 m w.e. of minimum rock overburden, 920 m**2 effective area) at the
National Gran Sasso Laboratories. The used observables are the air shower size
(Ne) measured by EAS-TOP and the muon number (Nmu) recorded by MACRO. The two
detectors are separated on average by 1200 m of rock, and located at a
respective zenith angle of about 30 degrees. The energy threshold at the
surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons
are produced in the early stages of the shower development and in a kinematic
region quite different from the one relevant for the usual Nmu-Ne studies. The
measurement leads to a primary composition becoming heavier at the knee of the
primary spectrum, the knee itself resulting from the steepening of the spectrum
of a primary light component (p, He). The result confirms the ones reported
from the observation of the low energy muons at the surface (typically in the
GeV energy range), showing that the conclusions do not depend on the production
region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET)
provides consistent composition results from data related to secondaries
produced in a rapidity region exceeding the central one. Such an evolution of
the composition in the knee region supports the "standard" galactic
acceleration/propagation models that imply rigidity dependent breaks of the
different components, and therefore breaks occurring at lower energies in the
spectra of the light nuclei.


title: Do Bulges of Early- and Late-type Spirals Have Different Morphology?

abstract:
  We study HST/NICMOS H-band images of bulges of two equal-sized samples of
early- (T(RC3) < 4) and late-type spiral (mainly Sbc-Sc) galaxies matched in
outer disk axis ratio. We find that bulges of late-type spirals are more
elongated than their counterparts in early-type spirals. Using a KS-test we
find that the two distributions are different at the 98.4% confidence level. We
conclude that the two data sets are different, i.e. late-type galaxies have a
broader ellipticity distribution and contain more elongated features in the
inner regions. We discuss the possibility that these would correspond to bars
at a later evolutionary stage, i.e. secularly evolved bars. Consequent
implications are raised, and we discuss relevant questions regarding the
formation and structure of bulges. Are bulges of early-type and late-type
spirals different? Are their formation scenarios different? Can we talk about
bulges in the same way for different types of galaxies?


title:
3-point temperature anisotropies in WMAP: Limits on CMB
  non-Gaussianities and non-linearities

abstract:
  We present a study of the 3-pt angular correlation function w_3= <delta_1
delta_2 delta_3> of (adimensional) temperature anisotropies measured by the
Wilkinson Microwave Anisotropy Probe (WMAP). Results can be normalized to the
2-point function w_2 = <delta_1 delta_2> in terms of the hierarchical: q_3 ~
w_3/w_2^2 or dimensionless: d_3 ~ w_2/w_2^{3/2}$ amplitudes. Strongly
non-Gaussian models are generically expected to show d_3 > 1 or q_3 > 10^3 d_3.
Unfortunately, this is comparable to the cosmic variance on large angular
scales. For Gaussian primordial models, q_3 gives a direct measure of the
non-linear corrections to temperature anisotropies in the sky: delta = delta_L
+ f_{NLT} (delta_L^2 - <delta_L^2>) with f_{NLT} = q_3/2 for the leading order
term in w_2^2. We find good agreement with the Gaussian hypothesis d_3 ~ 0
within the cosmic variance of LCDM simulations (with or without a low
quadrupole). The strongest constraints on q_3 come from scales smaller than 1
degree. We find q_3 =19 +/-141 for (pseudo) collapsed configurations and an
average of q_3 = 336 +/-218 for non-collapsed triangles. The corresponding
non-linear coupling parameter, f_{NL}, for curvature perturbations Phi, in the
Sachs-Wolfe (SW) regime is: f_{NL}^{SW} = q_3/6, while on degree scales, the
extra power in acoustic oscillations produces f_{NL} ~ q_3/30 in the LCM model.
Errors are dominated by cosmic variance, but for the first time they begin to
be small enough to constrain the leading order non-linear effects with coupling
of order unity.


title: The faint supernova remnant G 34.7-0.4 (W44)

abstract:
  Flux calibrated images of the known supernova remnant G 34.7-0.4 in basic
optical emission lines are presented. The low ionization images show a
relatively flat flux distribution. The diffuse and patchy morphology of the
detected optical emission may indicate the presence of turbulent magnetic
fields. Typical observed Halpha+[N II] fluxes are ~8 x 10^{-17} erg s^{-1}
cm^{-2} arcsec^{-2}, while the [S II] fluxes are lower around 4 x 10^{-17} erg
s^{-1} cm^{-2} arcsec^{-2}. Emission in the medium ionization line of [O III]
5007 A is not detected within our sensitivity limits, probably due to the heavy
extinction towards the remnant. The long-slit spectra reveal strong [S II] and
[N II] emission relative to Halpha and moderate [O I] 6300 A emission. Shock
velocities in the range of 110-150 km/s and low electron densities are
estimated. Archival MSX infrared data show emission in the south and west areas
of the remnant matching rather well the optical and radio emission.


title: A BeppoSAX observation of MKN6

abstract:
  We have used the BeppoSAX satellite to study the broad band (0.5-100 keV)
X-ray spectrum of the Seyfert 1.5 galaxy MKN6. The source is characterized by a
power law of Gamma=1.7 [+0.08, -0.07] and there is no strong evidence for
either a reflection bump or a high energy cut-off. We have detected a narrow
iron line at 6.4 keV (rest frame) with an equivalent width of 98 [+33, -35] eV.
MKN6 also exhibits strong and complex absorption. At least two components (NH_1
=1.34 [+0.4,-0.4] x 10^(22) cm^(-2) and NH_2 = 4.18 [+2.2, -1.3] x 10^(22)
cm^(-2)) are present and they both partially cover the source with covering
fractions of ~90% and ~50% respectively. Comparison with a previous ASCA
observation indicates that in both absorbing columns the NH is variable over a
2 year timescale, while the covering fractions are constant over the same
amount of time. The state of each absorber is cold or mildly photoionized. The
Broad Line Region (BLR) is suggested as the possible location for this complex
absorption.


title:
Visual orbit for the low-mass binary Gliese 22 AC from speckle
  interferometry

abstract:
  Based on 14 data points obtained with near-infrared speckle interferometry
and covering an almost entire revolution, we present a first visual orbit for
the low-mass binary system Gliese 22 AC. The quality of the orbit is largely
improved with respect to previous astrometric solutions. The dynamical system
mass is 0.592 +- 0.065 solar masses, where the largest part of the error is due
to the Hipparcos parallax. A comparison of this dynamical mass with
mass-luminosity relations on the lower main sequence and theoretical
evolutionary models for low-mass objects shows that both probably underestimate
the masses of M dwarfs. A mass estimate for the companion Gliese 22 C indicates
that this object is a very low-mass star with a mass close to the hydrogen
burning mass limit.


title:
A Compact X-ray Source and Possible X-ray Jets within the Planetary
  Nebula Menzel 3

abstract:
  We report the discovery, by the Chandra X-ray Observatory, of X-ray emission
from the bipolar planetary nebula Menzel 3. In Chandra CCD imaging, Mz 3
displays hot (3-6x10^6 K) gas within its twin, coaxial bubbles of optical
nebulosity, as well as a compact X-ray source at the position of its central
star(s). The brightest diffuse X-ray emission lies along the polar axis of the
optical nebula, suggesting a jet-like configuration. The observed combination
of an X-ray-emitting point source and possible X-ray jet(s) is consistent with
models in which accretion disks and, potentially, magnetic fields shape bipolar
planetary nebulae via the generation of fast, collimated outflows.


title: Radio Emission From EAS - Coherent Geosynchrotron Radiation

abstract:
  Extensive air showers (EAS) have been known for over 30 years to emit pulses
of radio emission at frequencies from a few to a few hundred MHz, an effect
that offers great opportunities for the study of EAS with the next generation
of "software radio interferometers" such as LOFAR and LOPES. The details of the
emission mechanism, however, remain rather uncertain to date. Following past
suggestions that the bulk of the emission is of geomagnetic origin, we model
the radio pulses as "coherent geosynchrotron radiation" arising from the
deflection of electrons and positrons in the earth's magnetic field. We
analytically develop our model in a step-by-step procedure to disentangle the
coherence effects arising from different scales present in the shower structure
and infer which shower characteristics govern the frequency spectrum and radial
dependence of the emission. The effect is unavoidable and our predictions are
in good agreement with the available experimental data within their large
margins of error.


title: The First Supernova Explosions in the Universe

abstract:
  We investigate the supernova explosions that end the lives of massive
Population III stars in low-mass minihalos (M~10^6 M_sun) at redshifts z~20.
Employing the smoothed particle hydrodynamics method, we carry out numerical
simulations in a cosmological set-up of pair-instability supernovae with
explosion energies of E_SN=10^51 and 10^53 ergs. We find that the more
energetic explosion leads to the complete disruption of the gas in the
minihalo, whereas the lower explosion energy leaves much of the halo intact.
The higher energy supernova expels > 90% of the stellar metals into a region ~1
kpc across over a timescale of 3-5 Myr. Due to this burst-like initial star
formation episode, a large fraction of the universe could have been endowed
with a metallicity floor, Z_min>10^-4 Z_sun, already at z>15.


title:
Cosmic Microwave Background and Supernova Constraints on Quintessence:
  Concordance Regions and Target Models

abstract:
  We perform a detailed comparison of the Wilkinson Microwave Anisotropy Probe
(WMAP) measurements of the cosmic microwave background (CMB) temperature and
polarization anisotropy with the predictions of quintessence cosmological
models of dark energy. We consider a wide range of quintessence models,
including: a constant equation-of-state; a simply-parametrized, time-evolving
equation-of-state; a class of models of early quintessence; scalar fields with
an inverse-power law potential. We also provide a joint fit to the CBI and
ACBAR CMB data, and the type 1a supernovae. Using these select constraints we
identify viable, target models for further analysis.


title:
A Scheme to Unify Low-Power Accreting Black Holes - Jet-Dominated
  Accretion Flows and the Radio/X-Ray Correlation

abstract:
  We explore the evolution in power of black holes of all masses, and their
associated jets, within the scheme of an accretion rate-dependent state
transition. Below a critical value of the accretion rate all systems are
assumed to undergo a transition to a state where the dominant accretion mode is
optically thin and radiatively inefficient. In these significantly
sub-Eddington systems, the spectral energy distribution is predicted to be
dominated by non-thermal emission from a relativistic jet whereas
near-Eddington black holes will be dominated instead by emission from the
accretion disk. Reasonable candidates for such a sub-Eddington state include
X-ray binaries in the hard and quiescent states, the Galactic Center (Sgr A*),
LINERs, FR I radio galaxies, and a large fraction of BL Lac objects. Standard
jet physics predicts non-linear scaling between the optically thick (radio) and
optically thin (optical or X-ray) emission of these systems, which has been
confirmed recently in X-ray binaries. We show that this scaling relation is
also a function of black hole mass and only slightly of the relativistic
Doppler factor. Taking the scaling into account we show that indeed hard and
quiescent state X-ray binaries, LINERs, FR I radio galaxies, and BL Lacs can be
unified and fall on a common radio/X-ray correlation. This suggests that jet
domination is an important stage in the luminosity evolution of accreting black
hole systems.


title: The GZK Feature in the Spectrum of UHECRs: What is it Telling Us?

abstract:
  We developed a numerical simulation of the propagation of UHECR in the Cosmic
Microwave Background (CMB) and we used it to determine the significance of the
GZK feature in the spectrum of UHECR measured by AGASA and HiRes. We find that
these two experiments are best fit by two different injection spectra in the
region below 10^20 eV and that the error bars around the GZK feature are
dominated by fluctuations which leave a determination of the GZK feature not
attainable at present. In addition the comparison of the spectra of AGASA and
HiRes suggests the presence of about a 30% systematic errors in the relative
energy determination of the two experiments. Correcting for these systematics,
the two experiments are brought in agreement at energies below 10^20 eV and, in
this region, are best fit by an injection spectrum with spectral index 2.5-2.6.
In the high energy region (above 10^20 eV) the two experiments maintain their
disagreement, but only at the 2sigma level. Our results clearly show the need
for much larger experiments such as Auger, EUSO, and OWL, that can increase the
number of detected events by one or two orders of magnitude.


title: The Search for Extrasolar Earth-like planets

abstract:
  The search for extrasolar Earth-like planets is underway. Over 100 extrasolar
giant planets are known to orbit nearby sun-like stars, including several in
multiple-planet systems. These planetary systems are stepping stones for the
search for Earth-like planets; the technology development, observational
strategies, and science results can all be applied to Earth-like planets. Stars
much less massive than the sun the most common stars in our Galaxy are being
monitored for the gravitational influence of Earth-like planets. Although
Earth-like planets orbiting sun-like stars are much more difficult to detect,
space missions are being built to detect them indirectly due to their effects
on the parent star and to quantify fundamental factors such as terrestrial
planet frequency, size distribution, and mass distribution. Extremely ambitious
space programs are being developed to directly detect Earth-like planets
orbiting sun-like stars, and must tackle the immense technological challenge of
blocking out the light of the parent star, which is brighter than the planet by
six to ten orders of magnitude. Direct detection of radiation from the planet
is necessary for the definitive goal of the search for Earth-like planets: the
study of atmospheric spectral signatures for signs of severe disequilibrium
chemistry that could be indicative of biological activity. In addition to
technological development, a growing flurry of scientific activity has begun
to: understand terrestrial planet formation and terrestrial planet frequency;
model terrestrial-like planet atmospheres and evolution; articulate the
biological signatures of our own Earth; and even to study Earth as an
extrasolar planet by observation and analysis of the spatially unresolved
Earth.


title:
The Significance of the Sodium Detection in the Extrasolar Planet
  HD209458b Atmosphere

abstract:
  The Hubble Space Telescope (HST) detection of an extrasolar planet atmosphere
in 2001 was a landmark step forward for the characterization of extrasolar
planets. HST detected the trace element sodium, via the neutral atomic
resonance doublet at 593 nm, in the transiting extrasolar giant planet
HD209458b. In this paper I discuss the significance of this first ever
extrasolar planet atmosphere detection. I explain how the sodium measurement
can be used as a constraint on HD209458b atmosphere models and review recent
interpretations of the lower-than-expected sodium line strength.


title:
HST Snaphot Study of Variable Stars in Globular Clusters: Inner Region
  of NGC 6441

abstract:
  [Abridged] We present the results of a Hubble Space Telescope snapshot
program to survey the inner region of the globular cluster NGC 6441 for its
variable stars. A total of 57 variable stars was found including 38 RR Lyrae
stars, 6 Population II Cepheids, and 12 long period variables. Of the RR Lyrae
stars observed in this survey, 26 are pulsating in the fundamental mode with a
mean period of 0.753d and 12 are first-overtone mode pulsators with a mean
period of 0.365d. These values match up very well with those found in
ground-based surveys. Combining all the available data for NGC 6441, we find
mean periods of 0.759d and 0.375d for the RRab and RRc stars, respectively. We
also find that the RR Lyrae in this survey are located in the same regions of a
period-amplitude diagram as those found in ground-based surveys. Although NGC
6441 is a metal-rich globular cluster, its RR Lyrae more closely resemble those
in Oosterhoff type II globular clusters. However, even compared to typical
Oosterhoff type II systems, the mean period of its RRab stars is unusually
long. We also derived I-band period-luminosity relations for the RR Lyrae
stars. Of the six Population II Cepheids, five are of W Virginis type and one
is a BL Herculis variable stars. This makes NGC 6441, along with NGC 6388, the
most metal-rich globular cluster known to contain these types of variable
stars. Another variable, V118, may also be a Population II Cepheid given its
long period and its separation in magnitude from the RR Lyrae stars. We argue
that there does not appear to be a change in the period-luminosity relation
slope between the BL Herculis and W Virginis stars, but that a change of slope
does occur when the RV Tauri stars are added to the period-luminosity relation.


title: A triple nucleus in the Brightest Cluster Galaxy in Abell 193

abstract:
  We present a ground-based near-infrared K-band image and an HST/WFPC2 image
of the brightest cluster galaxy in Abell 193 (IC 1695). This object was
selected as the central cluster galaxy using X-ray information. Both images
reveal a triple nucleus structure. Previously, this galaxy was thought to have
only 2 nuclei. We present colours and magnitudes and a colour plot of the three
nuclei. The nuclear structure and colours of the nuclei in this galaxy suggest
that a merger may have taken place in its recent history.


title:
Self Calibration in Cluster Studies of Dark Energy: Combining the
  Cluster Redshift Distribution, the Power Spectrum and Mass Measurements

abstract:
  We examine the prospects for measuring the dark energy equation of state
parameter w within the context of any uncertain redshift evolution of galaxy
cluster structure (building on Majumdar and Mohr, 2003) and show that including
the redshift averaged cluster power spectrum, P_cl(k), and direct mass
measurements of 100 clusters helps tremendously in reducing cosmological
parameter uncertainties. Specifically, we show that when combining the redshift
distribution and the power spectrum information for a particular X-ray survey
(DUET) and two SZE surveys (SPT & Planck), the constraints on the dark energy
equation of state w can be improved by roughly a factor of 4. Because surveys
designed to study the redshift distribution of clusters will have all the
information necessary to construct P_cl(k), the benefit of adding P_cl(k) in
reducing uncertainties comes at no additional observational cost. Combining
detailed mass studies of 100 clusters with the redshift distribution improves
the parameter uncertainties by a factor of 3-5. The data required for these
detailed mass measurements-- assumed to have 1sigma uncertainties of 30-- are
accumulating in the the XMM-Newton and Chandra archives. The best constraints
are obtained when one combines both the power spectrum constraints and mass
measurements with the cluster redshift distribution; when using the survey to
extract the parameters and evolution of the mass--observable relations, we
estimate the uncertainties on w of ~4% to 6%. These parameter constraints are
obtained from self-calibrating cluster surveys alone. In combination with CMB
or distance measurements that have different parameter degeneracies, cluster
studies of dark energy will provide enhanced constraints and allow for
cross--checks of systematics.


title: On the Spatial Correlations of Lyman Break Galaxies

abstract:
  Motivated by the observed discrepancy between the strong spatial correlations
of Lyman break galaxies (LBGs) and their velocity dispersions, we consider a
theoretical model in which these starbursting galaxies are associated with dark
matter halos that experience appreciable infall of material. We show using
numerical simulation that selecting halos that substantially increase in mass
within a fixed time interval introduces a ``temporal bias'' which boosts their
clustering above that of the underlying population. If time intervals
consistent with the observed LBGs star formation rates of 50 solar masses per
year are chosen, then spatial correlations are enhanced by up to a factor of
two. These values roughly correspond to the geometrical bias of objects three
times as massive. Thus, it is clear that temporal biasing must be taken into
account when interpreting the properties of Lyman break galaxies.


title:
Effects of the dissolution of low-concentration globular clusters on the
  evolution of globular cluster systems

abstract:
  We investigate the role of dissolution of low-concentration clusters due to
mass loss through stellar evolution on the evolution of the properties of
globular cluster systems (GCSs) in elliptical galaxies. Our simulations show
that, for an initial mass-concentration relationship based on that inferred
from Galactic globular clusters, dissolution of low-concentration clusters
leads to the disruption of a large number of clusters. A power-law initial
globular cluster system mass function (GCMF) similar to that observed in young
cluster systems in merging galaxies is transformed by this dissolution into a
bell-shaped GCMF with a mean mass similar to that of old GCSs for all the
galaxies investigated. Two-body relaxation and dynamical friction, which are
also included in our simulations, subsequently lead to an additional
significant evolution and disruption of the population of clusters. As shown
previously, when these processes act on a bell-shaped GCMF with a mean mass
similar to that of old GCS, they do not significantly alter the value of the
mean mass. The final GCMFs are bell-shaped with similar peaks at different
radii within galaxies and between different galaxies, in agreement with current
observations.


title: Gauge Symmetry of the N-body Problem in the Hamilton-Jacobi Approach

abstract:
  In most books the Delaunay and Lagrange equations for the orbital elements
are derived by the Hamilton-Jacobi method: one begins with the 2-body Hamilton
equations, performs a canonical transformation to the orbital elements, and
obtains the Delaunay system. A standard trick is then used to generalise the
approach to the N-body case. We re-examine this step and demonstrate that it
contains an implicit condition which restricts the dynamics to a
9(N-1)-dimensional submanifold of the 12(N-1)-dimensional space spanned by the
elements and their time derivatives. The tacit condition is equivalent to the
so-called Lagrange constraint. It is the condition of the orbital elements
being osculating, i.e., of the instantaneous ellipse (or hyperbola) being
always tangential to the physical velocity. Imposure of any condition different
from the Lagrange constraint (but compatible with the equations of motion) is
legitimate and will not alter the physical trajectory or velocity (though will
alter the mathematical form of the planetary equations).
  This freedom of nomination of the supplementary constraint reveals a
gauge-type internal symmetry of the celestial-mechanics equations and has
consequences for the stability of numerical integrators. Another important
aspect of this freedom is that any gauge different from that of Lagrange makes
the Delaunay system non-canonical. In a more general setting, when the
disturbance depends not only upon positions but also upon velocities, there is
a "generalised Lagrange gauge" wherein the Delaunay system is symplectic. This
gauge renders orbital elements that are osculating in the phase space. It
coincides with the regular Lagrange gauge when the perturbation is
velocity-independent.

categories: astro-ph math-ph math.MP nlin.CD physics.hist-ph


title:
Ultra-Luminous X-ray Source Populations in Normal Galaxies: a
  Preliminary Survey with Chandra

abstract:
  We present results of a Chandra survey of the ultra-luminous X-ray sources
(ULX) in 13 normal galaxies, in which we combine source detection with X-ray
flux measurement. 22 ULX were detected, i.e. with L_x > 1 x 10^{39} erg s^{-1}
(L_10), and 39 other sources were detected with L_x > 5 x 10^{38} erg s^{-1}
(L_5). We also use radial intensity profiles to remove extended sources from
the sample. The majority of sources are not extended, which for a typical
distance constrains the emission region size to less than 50 pc. X-ray
colour-colour diagrams and spectral fitting results were examined for
indicators of the ULX nature. In the case of the brighter sources, spectral
fitting generally requires two-component models. In only a few cases do
colour-colour diagrams or spectral fitting provide evidence of black hole
nature. We find no evidence of a correlation with stellar mass, however there
is a strong correlation with star formation as indicated by the 60 micron flux
as found in previous studies.


title: Measuring Stellar Limb Darkening by Gravitational Microlensing

abstract:
  Observations of microlensing transit events can be used to measure the limb
darkening of the lensed star. We discuss the advantages and drawbacks of
several microlensing light curve inversion methods. The method of choice in
this work is inversion by means of decomposition of the stellar surface
brightness profile. We construct an ideal basis by principal component analysis
of brightness profiles obtained from model atmosphere calculations. Limb
darkening approximations using such a basis are superior to those using
standard power-law limb darkening laws. We perform a full analysis of simulated
single-lens microlensing transit events including a detailed error analysis of
the method. In realistic events with a low impact parameter the brightness
profile of the source can be recovered with a relative accuracy of 2% from the
center of the source disk to 0.9 of the disk radius. We show that in the
particular case of the observed MACHO Alert 95-30 event the intrinsic complex
variability of the lensed red giant hinders efforts to recover its surface
features.


title: An Initial Survey of White Dwarfs in the Sloan Digital Sky Survey

abstract:
  An initial assessment is made of white dwarf and hot subdwarf stars observed
in the Sloan Digital Sky Survey. In a small area of sky (190 square degrees),
observed much like the full survey will be, 269 white dwarfs and 56 hot
subdwarfs are identified spectroscopically where only 44 white dwarfs and 5 hot
subdwarfs were known previously. Most are ordinary DA (hydrogen atmosphere) and
DB (helium) types. In addition, in the full survey to date, a number of WDs
have been found with uncommon spectral types. Among these are blue DQ stars
displaying lines of atomic carbon; red DQ stars showing molecular bands of C_2
with a wide variety of strengths; DZ stars where Ca and occasionally Mg, Na,
and/or Fe lines are detected; and magnetic WDs with a wide range of magnetic
field strengths in DA, DB, DQ, and (probably) DZ spectral types. Photometry
alone allows identification of stars hotter than 12000 K, and the density of
these stars for 15<g<20 is found to be ~2.2 deg^{-2} at Galactic latitudes
29-62 deg. Spectra are obtained for roughly half of these hot stars. The
spectra show that, for 15<g<17, 40% of hot stars are WDs and the fraction of
WDs rises to ~90% at g=20. The remainder are hot sdB and sdO stars.


title:
VLT Echelle Spectrophotometry of the Planetary Nebula NGC 5307 and
  Temperature Variations

abstract:
  Echelle spectrophotometry of the planetary nebula NGC 5307 is presented. The
data consists of VLT UVES observations in the 3100 to 10360 A range. Electron
temperatures and densities have been determined using different line intensity
ratios. We determine the H, He, C, and O abundances based on recombination
lines, these abundances are almost independent of the temperature structure of
the nebula. We also determine the N, O, Ne, S, Cl, and Ar abundances based on
collisionally excited lines, the ratios of these abundances relative to that of
H depend strongly on the temperature structure of the nebula. From the
OII/[OIII] ratio we find a t^2 = 0.056+-0.005. The chemical composition of NGC
5307 is compared with those of the Sun and the Orion nebula. From the study of
the relative intensities of the OII recombination lines of multiplet 1 in this
and other nebulae it isfound that for electron densities smaller than about
5000 cm-3 collisional redistribution is not complete, this effect has to be
taken into account to derive the O abundances for those cases in which not all
the lines of the multiplet are observed. From the 4649 OII versus N_e$(ClIII)
diagram we find a critical electron density of 1325 cm-3 for collisional
redistribution of the OII lines of multiplet 1. Also based on this diagram we
argue that the OII and the [OIII] lines originate in the same regions. We also
find that the radial velocities and the FWHM of the OII and [OIII] lines in NGC
5307 are similar supporting the previous result. These two results imply that
for NGC 5307 and probably for many other gaseous nebulae chemical
inhomogeneities are not responsible for the large temperature fluctuations
observed.


title:
A Possible Bifurcation in Atmospheres of Strongly Irradiated Stars and
  Planets

abstract:
  We show that under certain circumstances the differences between the
absorption mean and Planck mean opacities can lead to multiple solutions for an
LTE atmospheric structure. Since the absorption and Planck mean opacities are
not expected to differ significantly in the usual case of radiative
equilibrium, non-irradiated atmospheres, the most interesting situations where
the effect may play a role are strongly irradiated stars and planets, and also
possibly structures where there is a significant deposition of mechanical
energy, such as stellar chromospheres and accretion disks. We have presented an
illustrative example of a strongly irradiated giant planet where the
bifurcation effect is predicted to occur for a certain range of distances from
the star.


title: HST Paschen alpha and 1.9 micron imaging of Sgr A West

abstract:
  We present HST/NICMOS images at 0.2" resolution of the HI Paschen Alpha (PaA)
emission line in a 70" x 90" region of the Galactic center centered on the
non-thermal radio source Sgr A*. The majority of the emission arises from
ionized gas in the mini-spiral in the central parsec. PaA emission is also seen
from 26 stellar sources, presumably early-type stars with mass-loss winds. The
new data reveal significant small-scale structure (<1"~0.04pc) in the ionized
gas of the mini-spiral; low surface brightness emission features are also seen
for the first time. Extinction, estimated from the ratio of observed PaA
emission to 6-cm continuum emission, varies from 20 to 50 mag with a median
Av=31.1 mag, in excellent agreement with earlier estimates for the stellar
sources and indepedent measurements derived using H92alpha recombination line
data. Large increases in extinction are seen along the periphery of the ionized
gas, suggesting that the ionized gas is partially extincted by dust in the
molecular clouds at the outside of the ionized regions. The small-scale,
filamentary structures in the ionized gas have a free thermal expansion time of
only ~ 3000 yrs; either magnetic fields or mass-loss winds from the hot
emission line stars may contain the ionized filaments. For both the ionized gas
and the stellar continuum, the centroids of the emission remain within ~+/- 1"
from a radius of 2" out to 40", providing further evidence that Sgr A* is
indeed at or extremely close to the dynamical center of the Galactic nucleus
stellar distribution. The 1.9 micron surface brightness increases inwards to
0.9" and then decreases or levels off closer to Sgr A*, possibly indicating the
core radius of the central stellar distribution or depletion of the late-type
stars by stellar collisions near the central black hole.


title:
An Estimate Of The Primary Mass Of Cosmic Rays At $10^{18}$ eV As
  Inferred From Volcano Ranch Data

abstract:
  Accurate measurements of the lateral distribution of extensive air showers
produced by cosmic rays of energy greater than $10^{17}$ eV were made in the
1970s by Linsley. At the time, the state of knowledge about the best hadronic
interaction model to use to describe such data prevented conclusions about the
cosmic ray mass from being drawn. We have used a modern model, {\sc qgsjet98},
to infer the primary mass from these data, using the very careful records left
by Linsley. We find that at a median energy of $10^{18}$ eV, the data are well
described by an iron-dominated composition (88 $\pm$ 6(stat) $\pm$ 18 (syst))%.
We discuss the systematic errors in this estimate that arise from model
uncertainties and from the range of energies used in the work of Linsley. These
data are used with the permission of the late John Linsley to whom this work is
dedicated.


title:
Relativistic stars with poloidal and toroidal magnetic fields and
  meridional flow

abstract:
  We investigate stationary axisymmetric configurations of magnetized stars in
the framework of general relativistic ideal magnetohydrodynamics. Our
relativistic stellar model incorporates a toroidal magnetic field and
meridional flow in addition to a poloidal magnetic field for the first time.
The magnetic field and meridional flow are treated as perturbations, but no
other approximation is made. We find that the stellar shape can be prolate
rather than oblate when a toroidal field exists. We also find that, for fixed
baryonic mass and total magnetic helicity, more spherical the star is, lower
the energy it has. Further, we find two new types of the frame dragging effect
which differ from the standard one in a rotating star or Kerr geometry. They
may violate the reflection symmetry about the equatorial plane.


title:
Searching for a Long Cosmic String Through the Gravitational Lensing
  Effect

abstract:
  It has been suggested that cosmic strings produced at a phase transition in
the early universe can be the origin of the extremely high energy cosmic rays
(EHCR) observed by AGASA above 10^20 eV.
  Superheavy cosmic strings with linear mass density of 10^22 g/cm can be
indirectly observed through the gravitational lensing effect the distant
galaxies. The lensing effect by a long straight object can be characterized by
a line of double galaxies or quasars with angular separation of about 5 arcsec.
We have searched for aligned double objects from the archived data taken by the
Subaru Prime Focus Camera (Suprime-Cam). The Suprime-Cam has a great advantage
in observing the wide field of view (30x30 arcmin^2) with high sensitivity
(R<26 400s exposure), so it is suitable for this research.
  In this paper, we describe the result of simulation study for developing the
method of searching the objects lensed by cosmic strings, and present the
observational result obtained by this method.


title: RXTE Observations of A2256

abstract:
  The cluster of galaxies A2256 was observed by the PCA and HEXTE experiments
aboard the RXTE satellite during the period July 2001 - January 2002, for a
total of 343 ks and 88 ks, respectively. Most of the emission is thermal, but
the data analysis yields evidence for two components in the spectrum. Based on
statistical likelihood alone, the secondary component can be either thermal or
power-law. Inclusion in the analysis of data from ASCA measurements leads to a
more definite need for a second component.Joint analysis of the combined
RXTE-ASCA data sets yields $kT_1 = 7.9^{+0.5}_{-0.2}$ and $kT_2 =
1.5^{+1.0}_{-0.4}$, when the second component is also thermal, and $kT =
7.7^{+0.3}_{-0.4}$ and $\alpha = 2.2^{+0.9}_{-0.3}$, if the second component is
fit by a power-law with (photon) index $\alpha$; all errors are at 90%
confidence. Given the observed extended regions of radio emission in A2256, it
is reasonable to interpret the deduced power-law secondary emission as due to
Compton scattering of the radio producing relativistic electrons by the cosmic
microwave background radiation. If so, then the {\it effective, mean
volume-averaged} value of the magnetic field in the central 1$^{o}$ region of
the cluster -- which contains both the `halo' and `relic' radio sources -- is
$B \sim 0.2^{+1.0}_{-0.1}$ $\mu G$.


title: The post-AGB evolution of AGB mass loss variations

abstract:
  We present new numerical hydrodynamical modelling of the evolution of
Asymptotic Giant Branch (AGB) mass loss fluctuations during the
post-AGB/Planetary Nebula phase. These models show that after ionization, the
observable effects of the mass loss fluctuations disappear in a few thousand
years, consistent with the fact that only few PNe have been found to be
surrounded by `rings'. We derive the observational characteristics of these
rings, and compare them to reported observations of the rings around NGC 6543,
finding a good match of emission properties and line shapes. We predict small
variations in the observable electron temperatures.


title:
Modeling of the Lyman gamma satellites in FUSE spectra of DA white
  dwarfs

abstract:
  We present new theoretical calculations of the line profile of Lyman gamma
that include transitions in which a photon is absorbed by a neutral hydrogen
atom while it interacts with a proton. Models show that two absorption features
located near 992 A and 996 A are due to H-H^+ collisions. These quasi-molecular
satellites are similar to those that were identified in the wings of Lyman
alpha and Lyman beta lines of hydrogen-rich white dwarfs. We compute synthetic
spectra that take account of these new theoretical profiles and compare them to
the spectra of four DA white dwarfs that were observed with FUSE. The models
predict the absorption features that are observed in the wing of Lyman gamma
near 995 A, and confirm that these features are quasi-molecular satellites.


title: Cosmological perturbations and the reionization epoch

abstract:
  We investigate the dependence of the epoch of reionization on the properties
of cosmological perturbations, in the context of cosmologies permitted by WMAP.
We compute the redshift of reionization using a simple model based on the
Press-Schechter approximation. For a power-law initial spectrum we estimate
that reionization is likely to occur at a redshift $z_{reion} = 17^{+10}_{-7}$,
consistent with the WMAP determination based on the temperature-polarization
cross power spectrum. We estimate the delay in reionization if there is a
negative running of the spectral index, as weakly indicated by WMAP. We then
investigate the dependence of the reionization redshift on the nature of the
initial perturbations. We consider chi-squared probability distribution
functions with various degrees of freedom, motivated both by non-standard
inflationary scenarios and by defect models. We find that in these models
reionization is likely occur much earlier, and to be a slower process, than in
the case of initial gaussian fluctuations. We also consider a hybrid model in
which cosmic strings make an important contribution to the seed fluctuations on
scales relevant for reionization. We find that in order for that model to agree
with the latest WMAP results, the string contribution to the matter power
spectrum on the standard $8 h^{-1} Mpc$ scale is likely to be at most at the
level of one percent, which imposes tight constraints on the value of the
string mass per unit length.


title:
Abundances for metal-poor stars with accurate parallaxes II.
  alpha-elements in the halo

abstract:
  Abundances for alpha-elements and Fe in about 150 field subdwarfs and early
subgiants with accurate parallaxes and kinematic data are used to discuss the
run of abundance ratios in metal-poor stars in the solar neighborhood. Based on
kinematics, we separated stars into two populations: the first one has a
positive velocity of rotation around the galactic center, and it is likely to
be related to the dissipational collapse of the galaxy; the second one has
either negligible or negative rotational velocity, and it is likely related to
an accretion component. The two populations show a large overlap in
metallicity. However, they show distinct chemical properties. For the first
population we found that there are close correlations (with small scatters
around) of the rotational velocity with metallicity and with the Fe/alpha
abundance ratio: this might be a signature of a not very fast collapse of the
progenitor clouds, with enough time for a significant contribution by SNe Ia,
although this result needs to be confirmed by a 3-D/non-LTE study. On the other
side, the second population exhibits a larger scatter in both the above
mentioned relations, and on average, a larger Fe/alpha ratio at a given
metallicity, suggesting a larger scatter in ages. We argue that the lack of
stars with moderate rotational velocities and high Fe/alpha abundance ratios is
due to the short merging time for protogalactic clouds with prograde motion,
while the presence of a group of counter-rotating stars with this
characteristics indicates a much longer typical lifetimes for protogalactic
fragments having such a motion. Finally, we found that perigalactic distances
correlate with the Fe/alpha abundance ratios better than the apogalactic
distances.


title: X/gamma-ray measurements of the faint GRB 020321

abstract:
  GRB 020321 is a faint GRB that received wide follow-up attention in X-rays
(BeppoSAX/NFI, Chandra/ACIS-S, XMM-Newton), radio (ATCA) and optical (ESO,
HST). We identify a weak X-ray afterglow by a combined study of the Chandra and
XMM-Newton observations. Its decay index of 1.2 is typical for GRB afterglows.
Inside the 4"-accurate error box there is a weak optical counterpart candidate
with a much shallower decay index.


title: A fourth component in the young multiple system V 773 Tau

abstract:
  I report on a new component in the pre-main sequence multiple system V 773
Tauri. This second visual companion, V 773 Tau C, with a projected separation
of about 0."2 has been detected using speckle interferometry in the
near-infrared. Repeated observations from 1996 to 2002 show significant orbital
motion and thus confirm the character of the new companion as a gravitationally
bound star. Together with the two components of the spectroscopic binary V 773
Tau A and the previously known visual companion V 773 Tau B, the V 773 Tau
system appears as a young "mini-cluster" of four T Tauri stars within a sphere
of a radius less than 100 AU. V 773 Tau, A, B and C form a triple system that
is not hierarchic, but is apparently stable despite of this. The brightness of
V 773 Tau C has probably increased over the last years, which may explain its
non-detection in previous binary surveys.


title: Long and faint GRBs in archival BeppoSAX-WFC data

abstract:
  In an ongoing effort to search for X-ray transients on diverse time scales in
the data archive of the BeppoSAX Wide Field Cameras we have identified four
GRBs that are long (between 540 and at least 2550 s) and faint (with 3 events
having peak fluxes below 7X10^-9 erg/s/cm2 in 2-10 keV). Three of the events
were covered and detected by BATSE, suggesting that there may be a substantial
number of bursts still hidden in the BATSE database. A spectral analysis of the
three events shows that, although soft, they are not typical X-ray flashes. The
fourth event (not covered by BATSE) is within 3' coincident with a double-lobed
radio galaxy. The chance probability is estimated at 0.001. If real, the
association would be remarkable.


title: The cluster of galaxies Abell 376

abstract:
  We present a dynamical analysis of the galaxy cluster Abell 376 based on a
set of 73 velocities, most of them measured at Pic du Midi and Haute-Provence
observatories and completed with data from the literature. Data on individual
galaxies are presented and the accuracy of the determined velocities is
discussed as well as some properties of the cluster. We obtained an improved
mean redshift value z=0.0478^{+0.005}_{-0.006} and velocity dispersion
sigma=852^{+120}_{-76}km/s. Our analysis indicates that inside a radius of
900h_{70}^{-1}kpc (15 arcmin) the cluster is well relaxed without any
remarkable feature and the X-ray emission traces fairly well the galaxy
distribution. A possible substructure is seen at 20 arcmin from the centre
towards the Southwest direction, but is not confirmed by the velocity field.
This SW clump is, however, kinematically bound to the main structure of Abell
376. A dense condensation of galaxies is detected at 46 arcmin (projected
distance 2.6h_{70}^{-1}Mpc) from the centre towards the Northwest and analysis
of the apparent luminosity distribution of its galaxies suggests that this
clump is part of the large scale structure of Abell 376. X-ray spectroscopic
analysis of ASCA data resulted in a temperature kT = 4.3+/-0.4 keV and metal
abundance Z = 0.32+/-0.08 Z_solar. The velocity dispersion corresponding to
this temperature using the T_X-sigma scaling relation is in agreement with the
measured galaxies velocities.


title:
Correlations and Charge Composition of UHECR without Knowledge of
  Galactic Magnetic Field

abstract:
  We develop a formalism which allows to study correlations of charged UHECR
with potential sources without using any Galactic Magnetic Field (GMF) model.
The method is free of subjective chose of parameters on which the significance
of correlations depends strongly. We show that correlations of the AGASA
dataset with BL Lacs (found previously after reconstruction of particle
trajectories in a specific GMF) are present intrinsically and can be detected
without reference to a particular model of magnetic field.


title: Cosmological model with macroscopic spin fluid

abstract:
  We consider a Friedmann-Robertson-Walker cosmological model with some exotic
perfect fluid with spin known as the Weyssenhoff fluid. The possibility that
the dark energy may be described in part by the Weyssenhoff fluid is discussed.
The observational constraint coming from supernovae type Ia observations is
established. This result indicates that, whereas the cosmological constant is
still needed to explain current observations, the model with spin fluid is
admissible. For high redshifts $z > 1$ the differences between the model with
spin fluid and the cold dark matter model with a cosmological constant become
detectable observationally for the flat case with $\Omega_{\text{m},0}=0.3$.
  From the maximum likelihood method we obtain the value of
$\Omega_{\text{s},0} = 0.004 \pm 0.016$. This gives us the limit
$\Omega_{\text{s},0} > -0.012$ at the $1\sigma$ level. While the model with
``brane effects'' is preferred by the supernovae Ia data, the model with spin
fluid is statistically admissible. For comparison, the limit on the spin fluid
coming from cosmic microwave background anisotropies is also obtained. The
uncertainties in the location of a first peak give the interval $-1.4 \times
10^{-10} < \Omega_{\text{s},0} < -10^{-10}$. From big bang nucleosynthesis we
obtain the strongest limit $\Omega_{\text{s},0} \gtrsim -10^{-20}$. The
interconnection between the model considered and brane models is also pointed
out.


title: Extending emission line Doppler tomography ; mapping modulated line flux

abstract:
  Emission line Doppler tomography is a powerful tool that resolves the
accretion flow in binaries on micro-arcsecond scales using time-resolved
spectroscopy. I present an extension to Doppler tomography that relaxes one of
its fundamental axioms and permits the mapping of time-dependent emission
sources. Significant variability on the orbital period is a common
characteristic of the emission sources that are observed in the accretion flows
of cataclysmic variables and X-ray binaries. Modulation Doppler tomography maps
sources varying harmonically as a function of the orbital period through the
simultaneous reconstruction of three Doppler tomograms. One image describes the
average flux distribution like in standard tomography, while the two additional
images describe the variable component in terms of its sine and cosine
amplitudes. I describe the implementation of such an extension in the form of
the maximum entropy based fitting code MODMAP. Test reconstructions of
synthetic data illustrate that the technique is robust and well constrained.
Artifact free reconstructions of complex emission distributions can be achieved
under a wide range of signal to noise levels. An application of the technique
is illustrated by mapping the orbital modulations of the asymmetric accretion
disc emission in the dwarf nova IP Pegasi.


title: The line-of-sight warp of the spiral galaxy ESO 123-G23

abstract:
  We present 3-D modelling of the distribution and kinematics of the neutral
hydrogen in the spiral galaxy ESO 123-G23. The optical appearance of this
galaxy is an almost perfectly edge-on disk, while the neutral hydrogen is found
to extend vertically out to about 15 kpc on either side of the galactic plane.
The HI layer and the major features of the HI data cube can be successfully
explained by a model dominated by a strong (about 30 degrees) line-of-sight
warp. Other models were tried, including a flare model and a two-component
model, but they clearly do not reproduce the data. This is the first
unambiguous detection of a galactic warp that has the maximum deviation from
the central plane almost along the line-of-sight. No evidence for the presence
of any companion galaxy is found in the HI data cube. Line-of-sight warps in
edge-on galaxies are probably frequent, but escape detection as they are too
weak. Moreover they may easily be mistaken as flares or 'thick disks'. A 3-D
modelling of the HI layer as the one presented here is needed in order to
distinguish between these possibilities.


title:
Secondary antiproton flux induced by cosmic ray interactions with the
  atmosphere

abstract:
  The atmospheric secondary antiproton flux is studied for detection altitudes
extending from sea level up to about 3 earth radii, by means of a 3-dimensional
Monte-Carlo simulation, successfully applied previously on other satellite and
balloon data. The calculated antiproton flux at mountain altitude is found in
fair agreement with the recent BESS measurements. The flux at balloon altitude
is also in agreement with calculations performed in previous studies and used
for the analysis of balloon data. The flux at sea level is found to be
significant. The antineutron flux is also evaluated. The antiproton flux is
prospectively explored at large distance from earth up to around 2 10$^4$ km.
The results are discussed in the context of the forthcoming measurements by
large acceptance experiments.


title: The value of the equation of state of dark energy

abstract:
  From recent CMB and Large Scale Structure observations the value of the
equation of state of dark energy, assuming it to be constant in time, is
constrained to be -1.3<w<-0.7 at the 95% confidence level: consistent with dark
energy being a classical vacuum term. Here we describe two novel and
independent methods, sensitive to different systematics, that give the same
value for w and similar confidence regions. This suggests that systematics are
not an issue in current determinations of w. The first method yields a
measurement of $w$ that relies on the minimum number of model-dependent
parameters; the second method is a non-parametric measurement of the time
dependence of w(z). We also present a method to statistically determine the
edge of a distribution.


title:
Secondary proton flux induced by cosmic ray interactions with the
  atmosphere

abstract:
  The atmospheric secondary proton flux is studied for altitudes extending from
sea level up to the top of atmosphere by means of a 3-dimensional Monte-Carlo
simulation procedure successfully used previously to account for flux
measurements of protons, light nuclei, and electrons-positrons below the
geomagnetic cutoff (satellite data), and of muons and antiprotons (balloon
data). The calculated flux are compared with the experimental measurements from
sea level uo to high float ballon altitudes. The agreement between data and
simulation results are very good at all altitudes, including the lowest ones,
where the calculations become extremely sensitive to the proton production
cross section. The results are discussed in this context. The calculations are
extended to the study of quasi trapped particles above the atmosphere to about
5 Earth radii, for prospective purpose.


title: Young Stars and Outflows in the globule IC1396W

abstract:
  We have observed the IC1396W globule in a narrow band filter centred on the
1-0 S(1) line of molecular hydrogen and in the J, H, K' broad-band filters.
Three molecular hydrogen outflows could be identified by means of H2 emission.
The projected axes of the flows are parallel to each other. By means of the NIR
images and IRAS/ISOPHOT data we could identify the driving sources of all
outflows, the possible Class0 source IRAS21246+5743 and two red objects
(Class1/2). NIR photometry reveals an embedded cluster of young stars in the
globule, coinciding with FIR emission. Other young stars in the field are more
or less clustered in several small groups, an indication that star formation
takes place at different positions at the same time in such small globules.


title:
Discovery of unusual pulsations in the cool, evolved Am stars HD 98851
  and HD 102480

abstract:
  The chemically peculiar (CP) stars HD 98851 and HD 102480 have been
discovered to be unusual pulsators during the ``Naini Tal Cape Survey''
programme to search for pulsational variability in CP stars. Time series
photometric and spectroscopic observations of these newly discovered stars are
reported here. Fourier analyses of the time series photometry reveal that HD
98851 is pulsating mainly with frequencies 0.208 mHz and 0.103 mHz, and HD
102480 is pulsating with frequencies 0.107 mHz, 0.156 mHz and 0.198 mHz. The
frequency identifications are all subject to 1 d$^{-1}$ cycle count
ambiguities. We have matched the observed low resolution spectra of HD 98851
and HD 102480 in the range 3500-7400 \AA with theoretical synthetic spectra
using Kurucz models with solar metallicity and a micro-turbulent velocity 2 km
s$^{-1}$. These yield $T_{eff}=7000\pm250$ K, log $g=3.5 \pm 0.5$ for HD 98851
and $T_{eff} = 6750 \pm 250$ K, log $g = 3.0 \pm 0.5$ for HD 102480. We
determined the equivalent H-line spectral class of these stars to be F1 IV and
F3 III/IV, respectively. A comparison of the location of HD 98851 and HD 102480
in the HR diagram with theoretical stellar evolutionary tracks indicates that
both stars are about 1-Gyr-old, 2-$M_{\odot}$ stars that lie towards the red
edge of the $\delta$ Sct instability strip. We conclude that HD 98851 and HD
102480 are cool, evolved Am pulsators. The light curves of these pulsating
stars have alternating high and low amplitudes, nearly harmonic (or
sub-harmonic) period ratios, high pulsational overtones and Am spectral types.
This is unusual for both Am and $\delta$ Sct pulsators, making these stars
interesting objects.


title: Mapping Observations of DNC and HN^13C in Dark Cloud Cores

abstract:
  We present results of mapping observations of the DNC, HN^13C, and H^13CO^+
lines (J=1-0) toward 4 nearby dark cloud cores, TMC-1, L1512, L1544, and L63,
along with observations of the DNC and HN^13C lines (J=2-1) toward selected
positions. By use of statistical equilibrium calculations based on the LVG
model, the H_2 densities are derived to be (1.4-5.5)*10^5 cm^-3, and the
[DNC]/[HN^13C] ratios are derived to be 1.25-5.44 with a typical uncertainty by
a factor of 2. The observed [DNC]/[HNC] ratios range from 0.02 to 0.09,
assuming the [^12C]/[^13C] ratio of 60. Distributions of DNC and HN^13C are
generally similar to each other, whereas the distribution of H^13CO^+ is more
extended than those of DNC and HN^13C, indicating that they reside in an inner
part of the cores than HCO^+. The [DNC]/[HN^13C] ratio is rather constant
within each core, although a small systematic gradients are observed in TMC-1
and L63. Particularly, no such systematic gradient is found in L1512 and L1544,
where a significant effect of depletion of molecules is reported toward the
central part of the cores. This suggests that the [DNC]/[HNC] ratio would not
be very sensitive to depletion factor, unlike the [DCO^+]/[HCO^+] ratio. On the
other hand, the core to core variation of the [DNC]/[HNC] ratio, which range an
order of magnitude, is more remarkable than the variation within each core.
These results are interpreted qualitatively by a combination of three competing
time-dependent processes; gas-phase deuterium fractionation, depletion of
molecules onto grain surface, and dynamical evolution of a core.


title: Magnetic helicity evolution in a periodic domain with imposed field

abstract:
  In helical hydromagnetic turbulence with an imposed magnetic field (which is
constant in space and time) the magnetic helicity of the field within a
periodic domain is no longer an invariant of the ideal equations.
Alternatively, there is a generalized magnetic helicity that is an invariant of
the ideal equations. It is shown that this quantity is not gauge invariant and
that it can therefore not be used in practice. Instead, the evolution equation
of the magnetic helicity of the field describing the deviation from the imposed
field is shown to be a useful tool. It is demonstrated that this tool can
determine steady state quenching of the alpha-effect. A simple three-scale
model is derived to describe the evolution of the magnetic helicity and to
predict its sign as a function of the imposed field strength. The results of
the model agree favorably with simulations.


title: How magnetic helicity ejection helps large scale dynamos

abstract:
  There is mounting evidence that the ejection of magnetic helicity from the
solar surface is important for the solar dynamo. Observations suggest that in
the northern hemisphere the magnetic helicity flux is negative. We propose that
this magnetic helicity flux is mostly due to small scale magnetic fields; in
contrast to the more systematic large scale field of the 11 year cycle, whose
helicity flux may be of opposite sign, and may be excluded from the
observational interpretation. Using idealized simulations of MHD turbulence as
well as a simple two-scale model, we show that shedding small scale (helical)
field has two important effects. (i) The strength of the large scale field
reaches the observed levels. (ii) The evolution of the large scale field
proceeds on time scales shorter than the resistive time scale, as would
otherwise be enforced by magnetic helicity conservation. In other words, the
losses ensure that the solar dynamo is always in the near-kinematic regime.
This requires, however, that the ratio of small scale to large scale losses
cannot be too small, for otherwise the large scale field in the near-kinematic
regime will not reach the observed values.


title: SWIRE: The SIRTF Wide-area InfraRed Extragalactic Survey

abstract:
  The SIRTF Wide-area InfraRed Extragalactic survey (SWIRE), the largest SIRTF
Legacy program, is a wide-area, imaging survey to trace the evolution of dusty,
star-forming galaxies, evolved stellar populations, and AGN as a function of
environment, from redshifts z~3 to the current epoch. SWIRE will survey 7
high-latitude fields, totaling 60 - 65 sq. deg. in all 7 SIRTF bands: IRAC 3.6,
4.5, 5.6, 8 microns and MIPS 24, 70, 160 microns. The Legacy Extragalactic
Catalog may contain in excess of 2 million IR-selected galaxies, dominated by
(1) ~150,000 luminous infrared galaxies (LIRGs: L{FIR}>10^11 L_sun), ~7000 of
these with z>2; (2) 1 million early-type galaxies, ~10,000 with z>2; and (3)
\~20,000 classical AGN, plus significantly more dust-obscured QSO/AGN among the
LIRGs. SWIRE will provide an unprecedented view of the evolution of galaxies,
structure, and AGN. The key scientific goals of SWIRE are: (1) to determine the
evolution of actively star-forming and passively evolving galaxies in order to
understand the history of galaxy formation in the context of cosmic structure
formation; (2) to determine the evolution of the spatial distribution and
clustering of evolved galaxies, starbursts and AGN in the key redshift range,
0.5<z<3, over which much of cosmic evolution has occurred; (3) to determine the
evolutionary relationship between ``normal galaxies'' and AGN, and the
contribution of AGN accretion energy vs stellar nucleosynthesis to the cosmic
backgrounds. SWIRE's large area is important to create statistically
significant population samples over enough volume cells that we can resolve the
star formation history as a function of epoch and environment The large volume
is also optimised for finding rare objects.


title:
On the relative frequencies of core-collapse supernovae sub-types: the
  role of progenitor metallicity

abstract:
  We show that the observed ratio of the subtypes Ib,c and II core-collapse
supernovae depends on the metallicity of the host galaxy, as expected on
theoretical grounds. However, the observed relation differs considerably from
expectations based on non-rotating models of single stars with mass loss. We
argue that the predictions of recent models with rotation offer a much better
agreement with observations, at least for progenitor stars with solar
metallicity; calculations of models with higher and lower metallicities are
required in order to substantiate these conclusions. We also suggest that
systematic surveys of core collapse supernovae up to redshift of 1 with the
SNAP satellite would allow to probe the effect of metallicity on supernovae
properties during the past history of the universe.


title:
Polarization of the prompt gamma-ray emission from the gamma-ray burst
  of 6 December 2002

abstract:
  Observations of the afterglows of gamma-ray bursts (GRBs) have revealed that
they lie at cosmological distances, and so correspond to the release of an
enormous amount of energy. The nature of the central engine that powers these
events and the prompt gamma-ray emission mechanism itself remain enigmatic
because, once a relativistic fireball is created, the physics of the afterglow
is insensitive to the nature of the progenitor. Here we report the discovery of
linear polarization in the prompt gamma-ray emission from GRB021206, which
indicates that it is synchrotron emission from relativistic electrons in a
strong magnetic field. The polarization is at the theoretical maximum, which
requires a uniform, large-scale magnetic field over the gamma-ray emission
region. A large-scale magnetic field constrains possible progenitors to those
either having or producing organized fields. We suggest that the large magnetic
energy densities in the progenitor environment (comparable to the kinetic
energy densities of the fireball), combined with the large-scale structure of
the field, indicate that magnetic fields drive the GRB explosion.


title:
Lyman Break Galaxies at Redshift z~3: Survey Description and Full Data
  Set

abstract:
  We present the basic data for a large ground-based spectroscopic survey for
z~3 ``Lyman break galaxies'' (LBGs), photometrically selected using rest-UV
colors from very deep images in 17 high Galactic latitude fields. The total
survey covers an area of 0.38 square degrees, and includes 2347
photometrically-selected candidate LBGs to an apparent R_{AB} magnitude limit
of 25.5. Approximately half of these objects have been observed
spectroscopically using the Keck telescopes, yielding 940 redshifts with <z>
=2.96 +/- 0.29. We discuss the images, photometry, target selection, and the
spectroscopic program in some detail, and present catalogs of the photometric
and spectroscopic data, made available in electronic form. We discuss the
general utility of conducting nearly-volume-limited redshift surveys in
prescribed redshift intervals using judicious application of photometric
pre-selection.


title: Radio Imaging of GRB Jets in Nearby Supernovae

abstract:
  We calculate the time evolution of the flux, apparent size, and image
centroid motion of gamma-ray burst (GRB) radio jets, and show that they can be
resolved by the VLBA at distances of hundreds of Mpc. We find that GRB 030329
which showed spectroscopic evidence for an associated Type Ic supernova (SN) at
a distance of $\approx$ 800 Mpc might just be resolvable by VLBA after several
months. The prospects are much better for jets that are oriented sideways in
similar SNe with no GRB counterpart; in particular, the motion of the flux
centroid in such jets can be detected by VLBA up to $z\sim 1$ even when the jet
cannot be resolved. If most GRBs are accompanied by a Type Ib/c SN, then there
should be a few SN/GRB jets per year within a distance $\lesssim$ 200 Mpc, and
most of them would be oriented sideways with no gamma-ray or X-ray precursor.
Detection of these jets can be used to calibrate the fraction of all core
collapse SNe that produce relativistic outflows and determine the local GRB
rate. Overall, the rate of Type Ib/c SNe that do not produce a GRB at all, but
rather make relativistic radio jets with an initial Lorentz factor of a few,
may be larger by up to 2 orders of magnitude than the rate of those that
produce GRBs.


title: A New Globular Cluster Metallicity Scale Based on the Abundance of FeII

abstract:
  When using Fe as a surrogate for ``metallicity'', the metallicity is best
represented by the dominant species of Fe. Accordingly, we have derived a new
globular cluster metallicity scale based on the equivalent widths of FeII lines
measured from high resolution spectra of giant stars. The scale is primarily
based on the results of analyses by the Lick-Texas group of 149 stars in 11
clusters, supplemented by other high resolution studies in five additional
clusters. We also derive ab initio the true distance moduli for M3, M5, M13,
M15, and M92 as a means of setting stellar surface gravities. We find that
[Fe/H]II is correlated linearly with W', the reduced strength of the
near-infrared CaII triplet defined by Rutledge et al (1997), although the
correlation coefficients depend on the stellar atmosphere model employed. In
addition to the 66 globular cluster metallicity estimates presented in a recent
PASP review, we present here an additional 39 globular cluster metallicity
estimates based on transformations from Q39, the photometric index defined by
Zinn (1980).


title:
Halo model prediction of the cosmic magnification statistics: the full
  non-linear contribution

abstract:
  The lensing magnification effect due to large-scale structure is
statistically measurable by correlation of size fluctuations in distant galaxy
images as well as by the QSO-galaxy cross-correlation. We use the halo model
formulation of Takada & Jain (2003) to compute these magnification-induced
correlations without employing the weak lensing approximation, mu=1+2kappa. Our
predictions thus include the full contribution from non-linear magnification
that is due to lensing halos. We compare the model prediction with ray-tracing
simulations and find excellent agreement over a range of angular scales
(0.'5<theta<30').
  The non-linear magnification contribution enhances the amplitude of the
magnification correlation relative to the weak lensing approximation, and the
non-linear correction is more significant on smaller angular scales and for
sources at higher redshifts. The enhancement amounts to 10-25% on arcminite
scales for the QSO-galaxy cross-correlation, even after inclusion of a
realistic model of galaxy clustering within the host halo. Therefore, it is
necessary to account for the non-linear contribution in theoretical models in
order to make an unbiased, cosmological interpretation of the precise
measurements expected from forthcoming massive surveys.


title: The Redshift Distribution of Flat-Spectrum Radio Sources

abstract:
  The redshift distribution of flat-spectrum radio sources with 5 GHz flux
densities S>5 mJy is a key component in using current radio lens surveys to
probe the cosmological model. We have constructed the first flat-spectrum radio
sample in the flux density range 3-20 mJy. Our new sample has 33 sources; we
have determined the redshifts of 14 of these (42% complete). The low mean
redshift, <z>~0.75, of our faintest sample needs to be confirmed by further
observations to improve the sample completeness. We also increased the redshift
completeness of several surveys of brighter flat-spectrum sources. While the
mean redshift, <z>~1.1 of flat-spectrum samples fainter than 1 Jy is nearly
constant, the fraction of the sources identifiable as quasars steadily drops
from ~80% to ~10% as the flux density of the sources decreases.


title: An X-Ray Pulsar in the Oxygen-Rich Supernova Remnant G292.0+1.8

abstract:
  We report the discovery of pulsed X-ray emission from the compact object CXOU
J112439.1-591620 within the supernova remnant (SNR) G292.0+1.8 using the High
Resolution Camera on the Chandra X-ray Observatory. The X-ray period
(P=0.13530915 s) is consistent with extrapolation of the radio pulse period of
PSR J1124-5916 for a spindown rate of dP/dt=7.6E-13 s/s. The X-ray pulse is
single peaked and broad with a FWHM width of 0.23P (83 degrees). The
pulse-averaged X-ray spectral properties of the pulsar are well described by a
featureless power law model with an absorbing column density, N_H= 3.1E21
atoms/cm^2; photon index, gamma = 1.6; and unabsorbed 0.3-10 keV band
luminosity, L_X = 7.2E32 erg/s. We plausibly identify the location of the
pulsar's termination shock. Pressure balance between the pulsar wind and the
larger synchrotron nebula, as well as lifetime issues for the X-ray-emitting
electrons, argues for a particle- dominated PWN that is far from the minimum
energy condition. Upper limits on the surface temperature of the neutron star
are at, or slightly below, values expected from ``standard'' cooling curves.
There is no optical counterpart to the new pulsar; its optical luminosity is at
least a factor of 5 below that of the Crab pulsar.


title: Ultraviolet Spectra of CV Accretion Disks with Non-Steady T(r) Laws

abstract:
  An extensive grid of synthetic mid- and far-ultraviolet spectra for accretion
disks in cataclysmic variables has been presented by Wade and Hubeny (1998). In
those models, the disk was assumed to be in steady-state, that is T_eff(r) is
specified completely by the mass M_WD and radius R_WD of the accreting white
dwarf star and the mass transfer rate M_dot which is constant throughout the
disk. In these models, T_eff(r) is proportional to r^{-3/4} except as modified
by a cutoff term near the white dwarf.
  Actual disks may vary from the steady-state prescription for T_eff(r),
however, e.g. owing to outburst cycles in dwarf novae M_dot not constant with
radius) or irradiation (in which case T_eff in the outer disk is raised above
T_steady). To show how the spectra of such disks might differ from the steady
case, we present a study of the ultraviolet (UV) spectra of models in which
power-law temperature profiles T_eff(r) is proportional to r^{-gamma} with
gamma < 3/4 are specified. Otherwise, the construction of the models is the
same as in the Wade & Hubeny grid, to allow comparison. We discuss both the UV
spectral energy distributions and the appearance of the UV line spectra. We
also briefly discuss the eclipse light curves of the non-standard models.
Comparison of these models with UV observations of novalike variables suggests
that better agreement may be possible with such modified T_eff(r) profiles.


title:
2MASS Studies of Differential Reddening Across Three Massive Globular
  Clusters

abstract:
  J, H, and K_S band data from the Two Micron All-Sky Survey (2MASS) are used
to study the effects of differential reddening across the three massive
Galactic globular clusters Omega Centauri, NGC 6388, and NGC 6441. Evidence is
found that variable extinction may produce false detections of tidal tails
around Omega Centauri. We also investigate what appears to be relatively strong
differential reddening towards NGC 6388 and NGC 6441, and find that
differential extinction may be exaggerating the need for a metallicity spread
to explain the width of the red giant branches for these two clusters. Finally,
we consider the implications of these results for the connection between
unusual, multipopulation globular clusters and the cores of dwarf spheroidal
galaxies (dSph).