title: Gamma-Ray Bursts from quark stars

abstract:
  Long gamma-ray bursts (GRBs) are believed to be related to the explosion of
type Ic supernovae, which have been stripped of their hydrogen and helium
envelopes. There appear to be two types of these explosions: those which are
approximately spherical (GRB980425/1998bw), and which are associated with weak
bursts, and the classical GRBs which generate ultrarelativistic jets
(GRB030329/SN2003dh). If this bimodality is real Swift will provide a clear
evidence for it.
  We propose that classical powerful GRBs, which generate ultrarelativistic
outflows, are a result of a formation of quark stars. Quark stars may provide
an additional energy for the explosion of SN Ic, but far more important is a
creation of a surface which acts as a membrane which cannot be penetrated by
baryons. A surface of a quark star allows only ultrarelativistic matter to
escape: photons, neutrinos, electron -- positron pairs and magnetic fields. The
formation of a quark star follows the initial core collapse in several minutes.
Possible evidence for this time delay is provided by BATSE precursors to GRBs,
as analyzed by Lazzati (2005).


title: Intrinsic Curvature in the X-ray Spectra of BL Lacertae Objects

abstract:
  We report results from {\it XMM-Newton} observations of thirteen X-ray bright
BL Lacertae objects, selected from the {\it Einstein} Slew Survey sample. The
survey was designed to look for evidence of departures of the X-ray spectra
from a simple power law shape (i.e., curvature and/or line features), and to
find objects worthy of deeper study. Our data are generally well fit by
power-law models, with three cases having hard ($\Gamma<2; dN/dE \propto
E^{-\Gamma}$) spectra that indicate synchrotron peaks at $E \gsim 5$ keV.
Previous data had suggested a presence of absorption features in the X-ray
spectra of some BL Lacs. In contrast, none of these spectra show convincing
examples of line features, either in absorption or emission, suggesting that
such features are rare amongst BL Lacs, or, more likely, artifacts caused by
instrumental effects. We find significant evidence for intrinsic curvature
(steepening by $d\Gamma / d({\rm log} E) = 0.4 \pm 0.15$) in fourteen of the
seventeen X-ray spectra. This cannot be explained satisfactorily via excess
absorption, since the curvature is essentially constant from $0.5-6$ keV, an
observation which is inconsistent with the modest amounts of absorption that
would be required. We use the {\it XMM-Newton} Optical Monitor data with
concurrent radio monitoring to derive broadband spectral energy distributions
and peak frequency estimates. From these we examine models of synchrotron
emission and model the spectral curvature we see as the result of episodic
particle acceleration.


title: The Lens Galaxy In PG1115+080 is an Ellipse

abstract:
  We use the structure of the Einstein ring image of the quasar host galaxy in
the four-image quasar lens PG1115+080 to determine the angular structure of the
gravitational potential of the lens galaxy. We find that it is well described
as an ellipsoid and that the best fit non-ellipsoidal models are consistent
with the ellipsoidal model. We find upper limits on the standard parameters for
the m=3 and m=4 deviations from an ellipse of <0.035 and <0.064, respectively.
We also find that the position of the center of mass is consistent with the
center of light, with an upper limit of 0.005 arcsec on the offset between
them. Neither the ellipsoidal nor the non-ellipsoidal models can reproduce the
observed image flux ratios while simultaneously maintaining a reasonable fit to
the Einstein ring, so the anomalous flux ratio of the A_1 and A_2 quasar images
must be due to substructure in the gravitational potential such as compact
satellite galaxies or stellar microlenses rather than odd angular structure in
the lens galaxy.


title: Afterglow Observations Shed New Light on the Nature of X-ray Flashes

abstract:
  X-ray flashes (XRFs) and X-ray rich gamma-ray bursts (XRGRBs) share many
observational characteristics with long duration GRBs, but the reason for which
their prompt emission peaks at lower photon energies, $E_p$, is still under
debate. Although many different models have been invoked in order to explain
the lower $E_p$ values, their implications for the afterglow emission were not
considered in most cases, mainly because observations of XRF afterglows have
become available only recently. Here we examine the predictions of the various
XRF models for the afterglow emission, and test them against the observations
of XRF 030723 and XRGRB 041006, the events with the best monitored afterglow
light curves in their respective class. We show that most existing XRF models
are hard to reconcile with the observed afterglow light curves, which are very
flat at early times. Such light curves are, however, naturally produced by a
roughly uniform jet with relatively sharp edges that is viewed off-axis (i.e.
from outside of the jet aperture). This type of model self consistently
accommodates both the observed prompt emission and the afterglow light curves
of XRGRB 041006 and XRF 030723, implying viewing angles $\theta_{obs}$ from the
jet axis of $(\theta_{obs}-\theta_0)\sim 0.15\theta_0$ and $\sim \theta_0$,
respectively, where $\theta_0\sim 3$ deg is the jet half-opening angle. This
suggests that GRBs, XRGRBs and XRFs are intrinsically similar relativistic jets
viewed from different angles, corresponding to $\gamma(\theta_{obs}-\theta_0)$
of less than 1, between 1 and a few, and more than a few, respectively, where
$\gamma$ is the Lorentz factor. Future observations with Swift could help test
this unification scheme in which GRBs, XRGRBs and XRFs share the same basic
physics and differ only by their orientation relative to our line of sight.


title: Fast identification of transits from light-curves

abstract:
  We present an algorithm that allows fast and efficient detection of transits,
including planetary transits, from light-curves. The method is based on
building an ensemble of fiducial models and compressing the data using the
MOPED algorithm. We describe the method and demonstrate its efficiency by
finding planet-like transits in simulated Pan-STARRS light-curves. We show that
that our method is independent of the size of the search space of transit
parameters. In large sets of light-curves, we achieve speed up factors of order
of $10^{8}$ times over the full $\chi2$ search. We discuss how the algorithm
can be used in forthcoming large surveys like Pan-STARRS and LSST and how it
may be optimized for future space missions like Kepler and COROT where most of
the processing must be done on board.


title:
The Molecular ISM of Dwarf Galaxies on Kiloparsec Scales: A New Survey
  for CO in Northern, IRAS-detected Dwarf Galaxies

abstract:
  We present a new survey for CO in dwarf galaxies using the Kitt Peak 12m
telescope. We observed the central regions of 121 northern dwarfs with IRAS
detections and no known CO emission. We detect CO in 28 of these galaxies and
marginally detect another 16, increasing by about 50% the number of such
galaxies known to have significant CO emission. The galaxies we detect are
comparable in mass to the LMC, although somewhat brighter in CO and fainter in
the FIR. Within dwarfs, we find that the CO luminosity, L_CO, is most strongly
correlated with the K-band and the far infrared luminosities. There are also
strong correlations with the radio continuum and B-band luminosities, and
linear diameter. We suggest that L_CO and L_K correlate well because the
stellar component of a galaxy dominates the midplane gravitational field and
thus sets the pressure of the atomic gas, which controls the formation of H_2
from HI. We compare our sample with more massive galaxies and find that dwarfs
and large galaxies obey the same relationship between CO and the 1.4 GHz radio
continuum (RC) surface brightness. This relationship is well described by a
Schmidt Law with Sigma_RC proportional to Sigma_CO^1.3. Therefore, dwarf
galaxies and large spirals exhibit the same relationship between molecular gas
and star formation rate (SFR). We find that this result is robust to moderate
changes in the RC-to-SFR and CO-to-H_2 conversion factors. Our data appear to
be inconsistent with large (order of magnitude) variations in the CO-to-H_2
conversion factor in the star forming molecular gas. [abridged]


title: Evidence for TeV Gamma-Ray Emission from the Galactic Plane

abstract:
  Gamma-ray emission from a narrow band at the Galactic equator has previously
been detected up to 30 GeV. We report evidence for a TeV gamma-ray signal from
the Galactic plane by Milagro, a large field of view water Cherenkov detector
for extensive air showers. An excess with a significance of 4.5 standard
deviations has been observed from the region of Galactic longitude between 40
and 100 deg and latitude |b| < 5 deg. Under the assumption of a simple power
law spectrum, with no cutoff, in the EGRET-Milagro energy range, the measured
integral flux is phi(>3.5TeV) = (6.4 +/- 1.4 +/- 2.1) 10^{-11} cm^{-2}s^{-1}
str^{-1}. This flux is consistent with an extrapolation of the EGRET spectrum
between 1 and 30 GeV in this Galactic region.


title: Population III and the Near-Infrared Background Excess

abstract:
  We make a critical assessment of models that attribute the recently detected
near-infrared background ``excess'' (NIRBE) to the redshifted light from
Population III objects. To supply the required 25 keV/baryon at redshift 9, Pop
III massive stars must form with an efficiency exceeding 30% in all
``minihalos'' with virial temperatures above a few hundred kelvins: to avoid
excessive metal pollution, most of the baryons once in Pop III stars must end
up in intermediate-mass black holes (IMBHs). Gas accretion onto such IMBHs must
either be inhibited or lead to early miniquasars with steep UV/X-ray spectra,
in order not to overproduce the present-day unresolved soft X-ray background.
In the latter case (NIRBE dominated by "X-ray quiet miniquasars"), the total
mass density of IMBHs at redshift 9 must be >50 times higher than the mass
density of supermassive black holes observed today in the nuclei of galaxies. A
stellar-dominated NIRBE is less economical energetically: more than 5% of all
baryons in the universe must be processed into Population III stars. We survey
various aspects of the Population III hypothesis for the NIRBE, and show that
the ionizing photon budget required to account for the NIRBE is much larger
than that required to explain the high electron scattering optical depth
measured by the WMAP satellite.


title:
The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary
  Systems

abstract:
  We investigate the relationship between age and chromospheric activity for
139 M dwarf stars in wide binary systems with white dwarf companions. The age
of each system is determined from the cooling age of its white dwarf component.
The current limit for activity-age relations found for M dwarfs in open
clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for
the exploration of this relationship at ages older than 4 Gyr. The general
trend of stars remaining active for a longer time at later spectral type is
confirmed. However, our larger sample and greater age range reveals additional
complexity in assigning age based on activity alone. We find that M dwarfs in
wide binaries older than 4 Gyr depart from the log-linear relation for clusters
and are found to have activity at magnitudes, colors and masses which are
brighter, bluer and more massive than predicted by the cluster relation. In
addition to our activity-age results, we present the measured radial velocities
and complete space motions for 161 white dwarf stars in wide binaries.


title: Intergalactic HI Clouds

abstract:
  Neutral intergalactic clouds are so greatly out numbered by galaxies that
their integral HI content is negligible in comparison to that contained in
optically luminous galaxies. In fact, no HI cloud that is not associated with a
galaxy or grouping of galaxies has yet been identified. This points to a causal
relationship that relies on gravitational potentials that bind galaxies also
being responsible for confining HI clouds to sufficient density that they can
become self-shielding to the ionizing background radiation. Unconfined clouds
of low density become ionized, but confined clouds find themselves vulnerable
to instability and collapse, leading to star formation.


title: A dwarf galaxy with a giant HI disk

abstract:
  We present Giant Meterwave Radio Telescope (GMRT) HI 21cm images of a nearby
dwarf irregular galaxy NGC 3741 (M_B ~ -13.13 mag) which show it to have a gas
disk that extends to ~ 8.3 times its Holmberg radius. This makes it probably
the most extended gas disk known. Our observations allow us to derive the
rotation curve (which is flat in the outer regions) out to ~ 38 optical scale
lengths. NGC 3741 has a dynamical mass to light ratio of ~ 107 and is one of
the ``darkest'' irregular galaxies known. However, the bulk of the baryonic
mass in NGC 3741 is in the form of gas and the ratio of the dynamic mass to the
baryonic mass (~ 8), falls within the range that is typical for galaxies. Thus
the dark matter halo of NGC 3741 has acquired its fair share of baryons, but
for some reason, these baryons have been unable to collapse to form stars. A
comparison of NGC 3741's dark halo properties with those of a sample of
galaxies with well measured rotation curves suggests that if one has to
reconcile the observations with the expectation that low mass galaxies suffer
fractionally greater baryon loss then baryon loss from halos occurs in such a
way that, in the net, the remaining baryons occupy a fractionally smaller
volume of the total halo.


title: Nebular abundances of southern symbiotic stars

abstract:
  We have calculated relative elemental abundances for a sample of 43 symbiotic
stars. Helium abundances and the relative elemental abundances N/O, Ne/O, Ar/O
were derived from new spectra collected in the optical range through low
dispersion spectroscopy. The He ionic abundances were derived taking into
account self-absorption effects in Balmer lines. We found that the symbiotic
stars in the galactic bulge have heavy element abundances showing the same wide
distribution as other bulge objects. In the galactic disk, the symbiotic stars
follow the abundance gradient as derived from different kinds of objects.


title: Polarization of L Dwarfs by Dust Scattering

abstract:
  The degree of polarization in L dwarfs of spectral types L0 to L6 resulting
from dust scattering in a rotation-induced oblate photosphere is calculated.
Assuming that forsterite is the main condensate, the atmospheric dust
distribution is derived for different spectral types based on a chemical
equilibrium model. The degree of polarization at optical is then calculated
using a single scattering model. The expected linear polarization at optical is
found to peak at around spectral type L1. For a fixed rotational velocity, the
degree of polarization decreases from hotter to cooler objects. However, with
the increase in mean grain size, the degree of linear polarization reduces
significantly. We fit the recently observed linear polarimetric data of L
dwarfs and find that single dust scattering model coupled with the chemical
equilibrium models of condensates is consistent with the observational results.


title: Overview of Technical Approaches to RFI Mitigation

abstract:
  This overview provides an interface between lines of thought on rfi
mitigation in the fields of radio astronomy and signal processing. The goal is
to explore the commonality of different approaches to help researchers in both
fields interpret each others' concepts and jargon. The paper elaborates on the
astronomers' concept of gain closure relations and how they may be used in a
"self-calibrating" system of rfi cancellation. Further discussion of the eigen
decomposition method in terms of rfi power and antenna gains introduces
adaptive nulling and rfi cancellation through matrix partitioning. While
multipath scattering appears at first glance to be fatal to methods of rfi
cancellation, its effect is easily incorporated in frequency dependent gain
coefficients under many circumstances.


title: The stellar populations of the bluest low surface brightness galaxies

abstract:
  Using optical/near-IR broadband photometry together with Halpha emission line
data, we attempt to constrain the star formation histories, ages, total stellar
masses and stellar mass-to-light ratios for a sample of extremely blue low
surface brightness galaxies. We find that, under standard assumptions about the
stellar initial mass function, the Halpha equivalent widths of these objects
appear inconsistent with recently suggested scenarios including constant or
increasing star formation rates over cosmological time scales. In a critical
assessment of the prospects of obtaining ages from integrated broadband
photometry, we conclude that even with near-IR data, the ages are poorly
constrained and that current observations cannot rule out the possibility that
these objects formed as recently as 1-2 Gyr ago. Methods which could
potentially improve the age estimates are discussed. The stellar masses of
these galaxies are inferred to lie below 10^10 solar masses. This, in
combination with low ages, could constitute a problem for current hierarchical
models of galaxy formation, which predict objects of this mass to form
predominantly early in the history of the universe. The possibility to use the
ages of the bluest low surface brightness galaxies as a test of such models is
demonstrated.


title: A Dark Hydrogen Cloud in the Virgo Cluster

abstract:
  VIRGOHI21 is an HI source detected in the Virgo Cluster survey of Davies et
al. (2004) which has a neutral hydrogen mass of 10^8 M_solar and a velocity
width of Delta V_20 = 220 km/s. From the Tully-Fisher relation, a galaxy with
this velocity width would be expected to be 12th magnitude or brighter; however
deep CCD imaging has failed to turn up a counterpart down to a
surface-brightness level of 27.5 B mag/sq. arcsec. The HI observations show
that it is extended over at least 16 kpc which, if the system is bound, gives
it a minimum dynamical mass of ~10^11 M_solar and a mass to light ratio of
M_dyn/L_B > 500 M_solar/L_solar. If it is tidal debris then the putative
parents have vanished; the remaining viable explanation is that VIRGOHI21 is a
dark halo that does not contain the expected bright galaxy. This object was
found because of the low column density limit of our survey, a limit much lower
than that achieved by all-sky surveys such as HIPASS. Further such sensitive
surveys might turn up a significant number of the dark matter halos predicted
by Dark Matter models.


title: On the mass distribution of neutron stars in HMXBs

abstract:
  We present the results of a monitoring campaign of three eclipsing high-mass
X-ray binaries (HMXBs: SMC X-1, LMC X-4 and Cen X-3). High-resolution VLT/UVES
spectra are used to measure the radial velocities of these systems with high
accuracy. We show that the subsequent mass determination of the neutron stars
in these systems is significantly improved and discuss the implications of this
result.


title: Massive Stars and their Compact Remnants in High-mass X-ray Binaries

abstract:
  In a high-mass X-ray binary (HMXB) a massive star interacts with a
neutron-star or black-hole companion in various ways. The gravitational
interaction enables the measurement of fundamental parameters such as the mass
of both binary components, providing important constraints on the evolutionary
history of the system, the equation of state of matter at supra-nuclear
density, and the supernova mechanism. The stellar wind of the massive star is
intercepted by the strong gravitational field of the compact companion, giving
rise to the production of X-rays. The X-rays increase the degree of ionization
in a small to very extended region of the surrounding stellar wind, depending
on the X-ray luminosity. This has observable consequences for the structure and
dynamics of the accretion flow. In this paper we concentrate on the fundamental
paramaters of the most massive HMXBs, i.e. those with an OB supergiant
companion, including some systems exhibiting relativistic jets
(``microquasars'').


title: GEOTAIL observation of the SGR1806-20 Giant Flare: The first 600 ms

abstract:
  On December 27, 2004, plasma particle detectors on the GEOTAIL spacecraft
detected an extremely strong signal of hard X-ray photons from the giant flare
of SGR1806-20, a magnetar candidate. While practically all gamma-ray detectors
on any satellites were saturated during the first ~500 ms interval after the
onset, one of the particle detectors on GEOTAIL was not saturated and provided
unique measurements of the hard X-ray intensity and the profile for the first
600 ms interval with 5.48 ms time resolution. After ~50 ms from the initial
rapid onset, the peak photon flux (integrated above ~50 keV) reached the order
of 10^7 photons sec^{-1} cm^{-2}. Assuming a blackbody spectrum with kT=175
keV, we estimate the peak energy flux to be 21 erg sec^{-1} cm^{-2} and the
fluence (for 0-600 ms) to be 2.4 erg cm^{-2}. The implied energy release
comparable to the magnetic energy stored in a magnetar (~10^{47} erg) suggests
an extremely efficient energy release mechanism.


title:
On the nature of bulges in general and of box/peanut bulges in
  particular. Input from $N$-body simulations

abstract:
  Objects designated as bulges in disc galaxies do not form a homogeneous
class. I distinguish three types. The classical bulges, whose properties are
similar to those of ellipticals and which form by collapse or merging. Boxy and
peanut bulges, which are seen in near edge-on galaxies and which are in fact
just a part of the bar seen edge-on. Finally disc-like bulges, which result
from the inflow of (mainly) gas to the center-most parts, and subsequent star
formation. I make a detailed comparison of the properties of boxy and peanut
bulges with those of $N$-body bars seen edge-on and answer previously voiced
objections about the links between the two. I also present and analyse
simulations where a boxy /peanut feature is present at the same time as a
classical spheroidal bulge and compare them with observations. Finally, I
propose a nomenclature that can help distinguish between the three types of
bulges and avoid considerable confusion.


title:
The complete set of ASCA X-ray observations of non-magnetic cataclysmic
  variables

abstract:
  We present the complete set of thirty four ASCA observations of non-magnetic
cataclysmic variables. Timing analysis reveals large X-ray flux variations in
dwarf novae in outburst (Z Cam, SS Cyg and SU UMa) and orbital modulation in
high inclination systems (including OY Car, HT Cas, U Gem, T Leo). We also
found episodes of unusually low accretion rate during quiescence (VW Hyi and SS
Cyg). Spectral analysis reveals broad temperature distributions in individual
systems, with emission weighted to lower temperatures in dwarf novae in
outburst. Absorption in excess of interstellar values is required in dwarf
novae in outburst, but not in quiescence. We also find evidence for sub-solar
abundances and X-ray reflection in the brightest systems. LS Peg, V426 Oph and
EI UMa have X-ray spectra that are distinct from the rest of the sample and all
three exhibit candidate X-ray periodicities. We argue that they should be
reclassified as intermediate polars. In the case of V345 Pav we found that the
X-ray source had been previously misidentified.


title: Adhesive Gravitational Clustering

abstract:
  The notion of `adhesion' has been advanced for the phenomenon of
stabilization of large-scale structure emerging from gravitational instability
of a cold medium. Recently, the physical origin of adhesion has been
identified: a systematic derivation of the equations of motion for the density
and the velocity fields leads naturally to the key equation of the `adhesion
approximation' - however, under a set of strongly simplifying assumptions. In
this work, we provide an evaluation of the current status of adhesive
gravitational clustering and a clear explanation of the assumptions involved.
Furthermore, we propose systematic generalizations with the aim to relax some
of the simplifying assumptions. We start from the general Newtonian evolution
equations for self-gravitating particles on an expanding Friedmann background
and recover the popular `dust model' (pressureless fluid), which breaks down
after the formation of density singularities; then we investigate, in a unified
framework, two other models which, under the restrictions referred to above,
lead to the `adhesion approximation'. We apply the Eulerian and Lagrangian
perturbative expansions to these new models and, finally, we discuss some
non-perturbative results that may serve as starting points for workable
approximations of non-linear structure formation in the multi-stream regime. In
particular, we propose a new approximation that includes, in limiting cases,
the standard `adhesion model' and the Eulerian as well as Lagrangian
first-order approximations.


title:
Deep Photometry of GRB 041006 Afterglow: Hypernova Bump at Redshift
  z=0.716

abstract:
  We present deep optical photometry of the afterglow of gamma-ray burst (GRB)
041006 and its associated hypernova obtained over 65 days after detection (55
R-band epochs on 10 different nights). Our early data (t<4 days) joined with
published GCN data indicates a steepening decay, approaching F_nu ~t^{-0.6} at
early times (<<1 day) and F_nu ~t^{-1.3} at late times. The break at
t_b=0.16+-0.04 days is the earliest reported jet break among all GRB
afterglows. During our first night, we obtained 39 exposures spanning 2.15
hours from 0.62 to 0.71 days after the burst that reveal a smooth afterglow,
with an rms deviation of 0.024 mag from the local power-law fit, consistent
with photometric errors. After t~4 days, the decay slows considerably, and the
light curve remains approximately flat at R~24 mag for a month before decaying
by another magnitude to reach R~25 mag two months after the burst. This
``bump'' is well-fitted by a k-corrected light curve of SN1998bw, but only if
stretched by a factor of 1.38 in time. In comparison with the other GRB-related
SNe bumps, GRB 041006 stakes out new parameter space for GRB/SNe, with a very
bright and significantly stretched late-time SN light curve. Within a small
sample of fairly well observed GRB/SN bumps, we see a hint of a possible
correlation between their peak luminosity and their ``stretch factor'', broadly
similar to the well-studied Phillips relation for the type Ia supernovae.


title: Giant flare of SGR 1806-20 from a relativistic jet

abstract:
  Japanese magnetospheric explorer GEOTAIL recorded a detailed light curve
during the initial 600 msec of a giant flare from SGR 1806-20 on December 27,
2004. We show that the observed light curve is well explained by an emission
from relativistically expanding fireballs, like those of gamma-ray bursts
(GRBs). Especially, the observed rapid fading after 500msec suggests that
ejecta is collimated in a jet. We derive an upper limit on the jet opening
half-angle of 0.2 radian that is as narrow as those of GRBs.


title:
The FUSE Spectrum of the Planetary Nebula SwSt 1: Evidence for
  Inhomogeneities in the Gas and Dust

abstract:
  [Abridged] We present Far Ultraviolet Spectroscopic Explorer (FUSE)
observations of the young, compact planetary nebula (PN) SwSt 1 along the line
of sight to its central star HD 167362. We detect circumstellar absorption
lines from several species against the continuum of the central star. The
physical parameters of the nebula derived from the FUSE data differ
significantly from those found from emission lines. We derive an electron
density n_e = 8800^{+4800}_{-2400} cm^{-3} from the column density ratio of the
excited S III fine structure levels, which is at least a factor of 3 lower than
all prior estimates. The gaseous iron abundance derived from the UV lines is
quite high ([Fe/S] = -0.35+/-0.12), which implies that iron is not
significantly depleted into dust. In contrast, optical and near-infrared
emission lines indicate that Fe is more strongly depleted: [Fe/H] =
-1.64+/-0.24 and [Fe/S] = -1.15+/-0.33. We do not detect nebular H_2
absorption, to a limit N(H_2) < 7\times10^14 cm^{-2}, at least four orders of
magnitude lower than the column density estimated from infrared H_2 emission
lines. Taken together, the lack of H_2 absorption, low n_e, and high gaseous Fe
abundance derived from the FUSE spectrum provide strong evidence that dense
structures (which can shield molecules and dust from the destructive effects of
energetic stellar photons) are not present along the line of sight to the
central star. On the other hand, there is substantial evidence for dust,
molecular material, and dense gas elsewhere in SwSt 1. Therefore, we conclude
that the nebula must have an inhomogeneous structure.


title:
Further evidence for a merger in Abell 2218 from an XMM-Newton
  observation

abstract:
  (Abridged) The galaxy cluster Abell 2218, at z=0.171, is well-known for the
discrepancy between mass estimates derived from X-ray and strong lensing
analyses. With the present XMM observation, we trace the gas density and
temperature profiles out to a radius of ~ 1400 h_70^-1 kpc (approximately the
virial radius of the cluster). The surface brightness profile is well fitted
over three orders of magnitude with a beta model, with a core radius of 0.'95
and \beta=0.63. The projected temperature profile declines steeply with radius
(by ~50%), and is well described by a polytrope with parameters t_0=8.09 keV
and \gamma=1.15. The temperature map shows a pronounced peak in the central
arcminute, with an increase of a factor of two (from ~5 to ~10 keV). The mass
profile, calculated assuming hydrostatic equilibrium and spherical symmetry, is
best fitted with a King approximation to an isothermal sphere, implying a dark
matter distribution with a central core, in contrast with the cusped cores
found in more obviously relaxed clusters. The X-ray mass is two times less than
the strong lensing mass at r ~ 80 h_50^-1 kpc, although the agreement between
X-ray and weak lensing mass measurements at larger radius (r ~ 400 h_50^-1 kpc)
is slightly better. While the X-ray total mass estimates can vary by 30%
depending on the mass model, all measurements are lower than the corresponding
total mass from optical measurements. Given the X-ray results indicating
disturbance of the intracluster gas, leading to a likely violation of the
assumption of hydrostatic equilibrium, and the observed substructure in the
optical, suggesting a line-of-sight merger, it is unlikely that the different
mass estimates of this cluster can be reconciled, at least with standard
modelling assumptions.


title: A changing inner radius in the accretion disc of Q0056-363?

abstract:
  Q0056-363 is the most powerful X-ray quasar known to exhibit a broad, likely
relativistic iron line (Porquet & Reeves 2003). It has been observed twice by
XMM-$Newton$, three and half years apart (July 2000 and December 2003). In the
second observation, the UV and soft X-ray fluxes were fainter, the hard X-ray
power law flatter, and the iron line equivalent width (EW) smaller than in the
2000 observation. These variations can all be explained, at least
qualitatively, if the disc is truncated in the second observation. We report
also on the possible detection of a transient, redshifted iron absorption line
during the 2003 observation.


title: Astrophysical constraints from gamma-ray spectroscopy

abstract:
  Gamma-ray lines from cosmic sources provide unique isotopic information,
since they originate from energy level transitions in the atomic nucleus.
Gamma-ray telescopes explored this astronomical window in the past three
decades, detecting radioactive isotopes that have been ejected in interstellar
space by cosmic nucleosynthesis events and nuclei that have been excited
through collisions with energetic particles. Short-lived radioactivities have
been detected in a couple of supernovae (56Co and 57Co in SN1987A, 44Ti in Cas
A), the diffuse glow of long-lived 26Al has been mapped along the entire plane
of the Galaxy, several excited nuclei have been detected in solar flares, and,
last but not least, positron annihilation has been observed in the inner Galaxy
since the 70ies. Recent imaging and line shape measurements of e-/e+
annihilation emission from the Galactic bulge can hardly be accounted for by
conventional sources of positrons; recent 26Al emission and line width
measurement from the inner Galaxy and from the Cygnus region can constrain the
properties of the interstellar medium; a diffuse 60Fe gamma-ray line emission
appears rather weak, in view of current theoretical predictions. Recent
Galactic core-collapse supernovae are studied through 44Ti radioactivity, but,
apart from Cas A, no other source has been found. The characteristic signature
of 22Na-line emission from a nearby O-Ne-Mg novae is expected to be measured
during INTEGRAL's lifetime.


title: On the volatile enrichments and composition of Jupiter

abstract:
  Using the clathrate hydrates trapping theory, we discuss the enrichments in
volatiles in the atmosphere of Jupiter measured by the \textit{Galileo} probe
in the framework of new extended core-accretion planet formation models
including migration and disk evolution. We construct a self-consistent model in
which the volatile content of planetesimals accreted during the formation of
Jupiter is calculated from the thermodynamical evolution of the disk. Assuming
CO2:CO:CH4 = 30:10:1 (ratios compatible with ISM measurements), we show that we
can explain the enrichments in volatiles in a way compatible with the recent
constraints set from internal structure modeling on the total amount of heavy
elements present in the planet.


title: Swift XRT and VLT Observations of the Afterglow of GRB 041223

abstract:
  The Swift Gamma-Ray Burst Explorer, launched on 2004 November 20, is a
multiwavelength, autonomous, rapid-slewing observatory for gamma-ray burst
(GRB) astronomy. On 2004 December 23, during the activation phase of the
mission, the Swift X-Ray Telescope (XRT) was pointed at a burst discovered
earlier that day by the Swift Burst Alert Telescope. A fading, uncataloged
X-ray source was discovered by the XRT and was observed over a period of about
3 hours, beginning 4.6 hours after the burst. The X-ray detection triggered a
VLT observation of the optical/NIR counterpart, located about 1.1 arcseconds
from the XRT position. The X-ray counterpart faded rapidly, with a power law
index of -1.72 +/- 0.20. The average unabsorbed X-ray flux 4.6-7.9 hours after
the burst was 6.5 x 10^{-12} erg cm^{-2} s^{-1} in the 0.5-10 keV band, for a
power-law spectrum of photon index 2.02 +/- 0.13 with Galactic absorption. The
NIR counterpart was observed at three epochs between 16 and 87 hours after the
burst, and faded with a power-law index of -1.14 +/- 0.08 with a
reddening-corrected SED power-law slope of -0.40 +/- 0.03. We find that the
X-ray and NIR data are consistent with a two-component jet in a wind medium,
with an early jet break in the narrow component and an underlying electron
index of 1.8-2.0.


title:
Global Dynamical Evolution of the ISM in Star Forming Galaxies - I. High
  Resolution 3D HD and MHD Simulations: Effect of the Magnetic Field

abstract:
  In star forming disk galaxies, matter circulation between stars and the
interstellar gas, and, in particular the energy input by random and clustered
supernova explosions, determine the dynamical and chemical evolution of the
ISM, and hence of the galaxy as a whole. Using a 3D MHD code with adaptive mesh
refinement developed for this purpose, we have investigated the r\^ole of
magnetized matter circulation between the gaseous disk and the surrounding
galactic halo. Special emphasis has been put on the effect of the magnetic
field with respect to the volume and mass fractions of the different ISM
``phases'', the relative importance of ram, thermal and magnetic pressures, and
whether the field can prevent matter transport from the disk into the halo. The
simulations were performed on a grid with an area of 1 kpc$^{2}$, centered on
the solar circle, extending $\pm 10$ kpc perpendicular to the galactic disk
with a resolution as high as 1.25 pc. The simulations were run for a time scale
of 400 Myr, sufficiently long to avoid memory effects of the initial setup, and
to allow for a global dynamical equilibrium to be reached in case of a constant
energy input rate. (...) We find that in general gas transport into the halo in
3D is not prevented by an initial disk parallel magnetic field, but only
delayed initially, for as long as it is needed to punch holes into the thick
magnetized gas disk. The mean volume filling factor of the hot phase in the
disk is similar in HD and MHD (the latter with a total field strength of 4.4
$\mu$G) runs, amounting to $\sim 17-21%$ for the Galactic supernova rate.


title:
Inflationary Cosmology: Exploring the Universe from the Smallest to the
  Largest Scales

abstract:
  Understanding the behavior of the universe at large depends critically on
insights about the smallest units of matter and their fundamental interactions.
Inflationary cosmology is a highly successful framework for exploring these
interconnections between particle physics and gravitation. Inflation makes
several predictions about the present state of the universe -- such as its
overall shape, large-scale smoothness, and smaller-scale structure -- which are
being tested to unprecedented accuracy by a new generation of astronomical
measurements. The agreement between these predictions and the latest
observations is extremely promising. Meanwhile, physicists are busy trying to
understand inflation's ultimate implications for the nature of matter, energy,
and spacetime.


title:
An exceptionally bright flare from SGR1806-20 and the origins of
  short-duration gamma-ray bursts

abstract:
  Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous
short-duration (about 0.1 s) bursts of hard X-rays during sporadic active
periods. They are thought to be magnetars: strongly magnetized neutron stars
with emissions powered by the dissipation of magnetic energy. Here we report
the detection of a long (380 s) giant flare from SGR 1806-20, which was much
more luminous than any previous transient event observed in our Galaxy. (In the
first 0.2 s, the flare released as much energy as the Sun radiates in a quarter
of a million years.) Its power can be explained by a catastrophic instability
involving global crust failure and magnetic reconnection on a magnetar, with
possible large-scale untwisting of magnetic field lines outside the star. From
a great distance this event would appear to be a short-duration, hard-spectrum
cosmic gamma-ray burst. At least a significant fraction of the mysterious
short-duration gamma-ray bursts therefore may come from extragalactic
magnetars.


title:
CMB observations from the CBI and VSA: A comparison of coincident maps
  and parameter estimation methods

abstract:
  We present coincident observations of the Cosmic Microwave Background (CMB)
from the Very Small Array (VSA) and Cosmic Background Imager (CBI) telescopes.
The consistency of the full datasets is tested in the map plane and the Fourier
plane, prior to the usual compression of CMB data into flat bandpowers. Of the
three mosaics observed by each group, two are found to be in excellent
agreement. In the third mosaic, there is a 2 sigma discrepancy between the
correlation of the data and the level expected from Monte Carlo simulations.
This is shown to be consistent with increased phase calibration errors on VSA
data during summer observations. We also consider the parameter estimation
method of each group. The key difference is the use of the variance window
function in place of the bandpower window function, an approximation used by
the VSA group. A re-evaluation of the VSA parameter estimates, using bandpower
windows, shows that the two methods yield consistent results.


title:
Particle acceleration, magnetic field generation, and emission in
  relativistic pair jets

abstract:
  Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas.
Plasma waves and their associated instabilities (e.g., Buneman, Weibel and
other two-stream instabilities) created in collisionless shocks are responsible
for particle (electron, positron, and ion) acceleration. Using a 3-D
relativistic electromagnetic particle (REMP) code, we have investigated
particle acceleration associated with a relativistic jet front propagating into
an ambient plasma. We find that the growth times of Weibel instability are
proportional to the Lorentz factors of jets. Simulations show that the Weibel
instability created in the collisionless shock front accelerates jet and
ambient particles both perpendicular and parallel to the jet propagation
direction.


title:
The Strengths of Near-Infrared Absorption Features Relevant to
  Interstellar and Planetary Ices

abstract:
  The abundances of ices in planetary environments have historically been
obtained through measurements of near-infrared absorption features (lambda =
1.0-2.5 microns), and near-IR transmission measurements of materials present in
the interstellar medium are becoming more common. For transmission
measurements, the band strength (or absorption intensity) of an absorption
feature must be known in order to determine the column density of an ice
component. In the experiments presented here, we have measured the band
strengths of the near-IR absorption features for several molecules relevant to
the study of interstellar icy grain mantles and icy planetary bodies: CO
(carbon monoxide), CO2 (carbon dioxide), C3O2 (carbon suboxide), CH4 (methane),
H2O (water), CH3OH (methanol), and NH3 (ammonia). During a vacuum deposition,
the sizes of the near-IR features were correlated with that of a studied mid-IR
feature whose strength is well known from previous ice studies. These data may
be used to determine ice abundances from observed near-IR spectra of
interstellar and planetary materials or to predict the sizes of near-IR
features in spectral searches for these molecules in astrophysical
environments.


title: Magnetospheric Eclipses in the Binary Pulsar J0737-3039

abstract:
  (Abridged) In the binary radio pulsar system J0737-3039, the faster pulsar A
is eclipsed once per orbit. We construct a simple geometric model which
successfully reproduces the eclipse light curves, based on the idea that the
radio pulses are attenuated by synchrotron absorption on the closed magnetic
field lines of pulsar B. The model explains most of the properties of the
eclipse: its asymmetric form, the nearly frequency-independent duration, and
the modulation of the brightness of pulsar A at both once and twice the
rotation frequency of pulsar B in different parts of the eclipse. This detailed
agreement confirms the dipolar structure of the star's poloidal magnetic field.
The model makes clear predictions for the degree of linear polarization of the
transmitted radiation.
  The weak frequency dependence of the eclipse duration implies that the
absorbing plasma is relativistic, with a density much larger than the
corotation charge density. Such hot, dense plasma can be effectively stored in
the outer magnetosphere, where cyclotron cooling is slow. The gradual loss of
particles inward through the cooling radius is compensated by an upward flux
driven by a fluctuating component of the current, and by the pumping of
magnetic helicity on the closed field lines. The trapped particles are heated
to relativistic energies by the damping of magnetospheric turbulence and, at a
slower rate, by the absorption of the radio emission of the companion pulsar.


title:
One-Up On L1: Can X-rays Provide Longer Advanced Warning of Solar Wind
  Flux Enhancements Than Upstream Monitors?

abstract:
  Observations of strong solar wind proton flux correlations with ROSAT X-ray
rates along with high spectral resolution Chandra observations of X-rays from
the dark Moon show that soft X-ray emission mirrors the behavior of the solar
wind. In this paper, based on an analysis of an X-ray event observed by
XMM-Newton resulting from charge exchange of high charge state solar wind ions
and contemporaneous neutral solar wind data, we argue that X-ray observations
may be able to provide reliable advance warning, perhaps by as much as half a
day, of dramatic increases in solar wind flux at Earth. Like neutral atom
imaging, this provides the capability to monitor the solar wind remotely rather
than in-situ.


title:
The Intermediate-band Dropout Method: A New Method to Search for
  High-Redshift Galaxies

abstract:
  We propose a new method to search for high-redshift galaxies that is based on
an intermediate-band dropout technique rather than the usual broad-band dropout
one. In this method, we use an intermediate-band filter whose central
wavelength is longer than 7000 \AA. This new method makes it possible to
distinguish both very late-type stars such as L and T dwarfs and dusty galaxies
at intermediate redshift from real high-$z$ Lyman break galaxies. The reason
for this is that such interlopers do not show strong intermediate-band
depression although they have very red broad-band colors that are indicative of
Lyman break galaxies. Applying our new method to imaging data sets obtained
with the Suprime-Cam on the Subaru Telescope, we find a new sample of Lyman
break galaxies at $z \simeq 5$.


title:
Lifting the Iron Curtain : Toward an Understanding of the Iron Stars XX
  Oph and AS 325

abstract:
  We present new optical, near infrared, and archival ultraviolet observations
of XX Ophiuchi and AS 325, two proposed iron stars. These unusual stars have
optical spectra dominated by emission lines arising from hydrogen as well as
ionized metals such as iron, chromium, and titanium. Both stars have been
classified as iron stars and a number of exotic models have been presented for
their origin. Using two years of moderately high resolution optical
spectroscopy, the first high signal-to-noise K-band spectroscopy of these
sources (which reveals stellar photospheric absorption lines), and new
near-infrared interferometric observations, we confirm that both systems are
composed of two stars, likely binaries, containing a hot Be star with an
evolved late-type secondary. The hydrogen emission features arise in the hot
wind from the Be star while the corresponding P-Cygni absorption lines are
produced from dense material in the expanding, radiation driven, wind around
each system. The optical FeII emission lines are pumped by ultraviolet FeII
absorption lines through fluorescence. Contrary to some claims in the
literature, the spectral features of XX Oph and AS 325 are quite similar,
evidence that they are comparable systems. We examine the variability of the
spectral morphology and radial velocity motions of both sources. We also study
the variability of XX Oph during a major photometric event and find that the
spectral nature of the system varies during the event. A comparison of the
velocity of the absorption line components in our new spectra with those in the
literature show that the structure of the stellar wind from XX Oph has changed
since the system was observed in 1951.


title: Polarisation profiles of southern pulsars at 3.1 GHz

abstract:
  We present polarisation profiles for 48 southern pulsars observed with the
new 10-cm receiver at the Parkes telescope. We have exploited the low system
temperature and high bandwidth of the receiver to obtain profiles which have
good signal to noise for most of our sample at this relatively high frequency.
Although, as expected, a number of profiles are less linearly polarised at 3.1
GHz than at lower frequencies, we identify some pulsars and particular
components of profiles in other pulsars which have increased linear
polarisation at this frequency. We discuss the dependence of linear
polarisation with frequency in the context of a model in which emission
consists of the superposition of two, orthogonally polarised modes. We show
that a simple model, in which the orthogonal modes have different spectral
indices, can explain many of the observed properties of the frequency evolution
of both the linear polarisation and the total power, such as the high degree of
linear polarisation seen at all frequencies in some high spin-down, young
pulsars. Nearly all the position angle profiles show deviations from the
rotating vector model; this appears to be a general feature of high-frequency
polarisation observations.


title:
Gamma-Rays from Large Scale Structure Formation and the Warm-Hot
  Intergalactic Medium: Cosmic Baryometry with Gamma-Rays

abstract:
  It is shown that inverse Compton gamma-rays from electrons accelerated in
large scale structure formation shocks can be crucially affected by
non-gravitational effects such as radiative cooling and galaxy formation, with
corresponding uncertainties by an order of magnitude in either the gamma-ray
source counts or the extragalactic background contribution. However, this also
implies that such gamma-rays may in the near future provide us with valuable
information about the fraction of cosmic baryons in different forms,
particularly the warm-hot intergalactic medium where the majority of the
baryons in the universe are believed to reside. We address this problem in a
simple way through semi-analytic modeling of structure formation shocks which
self-consistently treats merger and accretion shocks.


title: Modelling the UV to sub-mm SED of Starburst Galaxies

abstract:
  This paper reviews the theoretical modelling of starburst galaxies with
particular emphasis on the importance of the gas-phase physics in determining
the form of the continuum SED and the emission line spectrum. Both line and
continuum diagnostics have been used as star formation indicators. Here, we
examine from the point of view of the theory how reliable each of these
indicators may be, and to what physics of the galaxy they are sensitive, with
the aim of decreasing the errors associated with measuring the star formation
history of the universe.


title:
Different Characteristics of the Bright Branches of the Globular
  Clusters M3 and M13

abstract:
  We carried out wide-field BVI CCD photometric observations of the GCs M3 and
M13 using the BOAO 1.8 m telescope equipped with a 2K CCD. We present CMDs of
M3 and M13. We have found AGB bumps at V = 14.85 for M3 at V = 14.25 for M13.
It is found that AGB stars in M3 are more concentrated near the bump, while
those in M13 are scattered along the AGB sequence. We identified the RGB bump
of M3 at V = 15.50 and that of M13 at V = 14.80. We have estimated the ratios R
and R2 for M3 and M13 and found that of R for M3 is larger than that for M13
while R2's for M3 and M13 are similar when only normal HB stars are used in R
and R2 for M13. However, we found that R's for M3 and M13 are similar while R2
for M3 is larger than that for M13 when all the HB stars are included in R and
R2 for M13. We have compared the observed RGB LFs of M3 and M13 with the
theoretical RGB LF of Bergbusch & VandenBerg at the same radial distances from
the cluster centers as used in R and R2 for M3 and M13. We found "extra stars"
belonging to M13 in the comparison of the observed RGB LF of M13 and the
theoretical RGB LF of Bergbusch & VandenBerg. In the original definition of R
of Buzzoni et al., N(HB) corresponds to the lifetime of HB stars in the RR
Lyrae instability strip at log T_eff = 3.85. So, the smaller R value resulting
for M13 compared with that for M3 in the case where only normal HB stars are
included in R and R2 for M13 may be partially caused by "extra stars", and the
similar R's for M3 and M13 in the case where the all HB stars are included in R
and R2 for M13 may be caused by "extra stars" in the upper RGB of M13. If
"extra stars" in the upper RGB of M13 are caused by an effective "deep mixing"
these facts support the contention that an effective "deep mixing" could lead
to different HB morphologies between M3 and M13 and subsequent sequences.


title:
Stochastic Acceleration of $^3$He and $^4$He in Solar Flares by Parallel
  Propagating Plasma Waves: General Results

abstract:
  We study the acceleration in solar flares of $^3$He and $^4$He from a thermal
background by parallel propagating plasma waves with a general broken power-law
spectrum that takes into account the turbulence generation processes at large
scales and the thermal damping effects at small scales. The exact dispersion
relation for a cold plasma is used to describe the relevant wave modes. Because
low-energy $\alpha$-particles only interact with small scale waves in the
$^4$He-cyclotron branch, where the wave frequencies are below the
$\alpha$-particle gyro-frequency, their pitch angle averaged acceleration time
is at least one order of magnitude longer than that of $^3$He ions, which
mostly resonate with relatively higher frequency waves in the proton-cyclotron
(PC) branch. The $\alpha$-particle acceleration rate starts to approach that of
$^3$He beyond a few tens of keV nucleon$^{-1}$, where $\alpha$-particles can
also interact with long wavelength waves in the PC branch. However, the $^4$He
acceleration rate is always smaller than that of $^3$He. Consequently, the
acceleration of $^4$He is suppressed significantly at low energies, and the
spectrum of the accelerated $\alpha$-particles is always softer than that of
$^3$He. The model gives reasonable account of the observed low-energy $^3$He
and $^4$He fluxes and spectra in the impulsive solar energetic particle events
observed with the {\it Advanced Composition Explorer}. We explore the model
parameter space to show how observations may be used to constrain the model.


title:
3D ISM-Shock Spectral Emission: X-ray models for Radio Galaxy SED
  Modeling

abstract:
  Galaxies form out of small fluctuations in a smoothly expanding Universe.
However, the initial gravitational collapse phase is accompanied by the
formation of supermassive black holes and clusters of massive stars. Black
holes and star clusters generate powerful outflows in the form of jets and
superwinds that interact with still infalling gas, possibly regulating the
galaxy formation process, initiating new sites of star formation, and carrying
chemically enriched gas to the intergalactic medium. Unfortunately, beyond this
qualitative description our detailed theoretical understanding is poor.
  New results from 3D simulations of a GPS/CSS galaxy, with gravitational
potentials included, shed some new light on the jet driven outflow process in
particular. New code capabilites to predict detailed X-ray spectra from
multi-dimensional time-dependent dynamics simulations of Galaxy Feedback, and
will be useful for future interpretation of X-ray and radio SEDs of forming
galaxies.


title: Possible Explanation to Low CMB Quadrupole

abstract:
  The universe might experience many cycles with different vacua. The slow-roll
inflation may be preceded by kinetic-dominated contraction occurring in
"adjacent" vacua during some cycles. In this report we briefly show this
phenomenon may lead to a cutoff of primordial power spectrum. Thus in some
sense the CMB at large angular scale might encode the information of other
vacua.


title: On the Possibility of Combustion of Neutrons into Strange Quark Matter

abstract:
  It is shown that a conversion of neurons into strange quark matter in neutron
stars is possible by means of a combustion process with a well-defined front.
Conditions for the realization of a specific combustion mode, whether
deflagration, detonation, or fast combustion, are discussed for several forms
of the equations of state of neutron and strange matters.


title:
Acceleration of Plasma Flows in the Solar Atmosphere Due to Magnetofluid
  Coupling - Simulation and Analysis

abstract:
  Within the framework of a two-fluid description possible pathways for the
generation of fast flows (dynamical as well as steady) in the lower solar
atmosphere is established. It is shown that a primary plasma flow (locally
sub-Alfv\'enic) is accelerated when interacting with emerging/ambient
arcade--like closed field structures. The acceleration implies a conversion of
thermal and field energies to kinetic energy of the flow. The time-scale for
creating reasonably fast flows ($\gtrsim 100$ km/s) is dictated by the initial
ion skin depth while the amplification of the flow depends on local $\beta $.
It is shown, for the first time, that distances over which the flows become
"fast" are $\sim 0.01 R_s$ from the interaction surface; later the fast flow
localizes (with dimensions $\lesssim 0.05 R_S$) in the upper central region of
the original arcade. For fixed initial temperature the final speed ($\gtrsim
500 km/s$) of the accelerated flow, and the modification of the field structure
are independent of the time-duration (life-time) of the initial flow. In the
presence of dissipation, these flows are likely to play a fundamental role in
the heating of the finely structured Solar atmosphere.


title:
Energy Extraction from a Kerr Black Hole - An Ultimate Power Source in
  the Universe?

abstract:
  It is widely believed that some classes of high-energy transients may be
powered by the rotational energy of a rapidly spinning black hole. The energy
extraction mechanism commonly discussed involves macroscopic magnetic fields
that are produced by currents flowing in a disk or torus surrounding the black
hole. In spite of large efforts that have led to impressive progress in our
understanding of the physics of magnetized flows in Kerr geometry, several
important issues remain unresolved: the nature of the load in the
Blandford-Znajeck model, the causality and stability of a force-free
magnetosphere, global current closure, and the role of boundary conditions on
the channels through which the extracted energy is released. This chapter
provides an account of recent work that addresses some of those open questions.


title:
The Murmur of the Sleeping Black Hole: Detection of Nuclear Ultraviolet
  Variability in LINER Galaxies

abstract:
  LINER nuclei, which are present in many nearby galactic bulges, may be the
manifestation of low-rate or low-radiative-efficiency accretion onto
supermassive central black holes. However, it has been unclear whether the
compact UV nuclear sources present in many LINERs are clusters of massive
stars, rather than being directly related to the accretion process. We have
used HST to monitor the UV variability of a sample of 17 galaxies with LINER
nuclei and compact nuclear UV sources. Fifteen of the 17 galaxies were observed
more than once, with two to five epochs per galaxy, spanning up to a year. We
detect significant variability in most of the sample, with peak-to-peak
amplitudes from a few percent to 50%. In most cases, correlated variations are
seen in two independent bands (F250W and F330W). Comparison to previous UV
measurements indicates, for many objects, long-term variations by factors of a
few over decade timescales. Variability is detected in LINERs with and without
detected compact radio cores, in LINERs that have broad H-alpha wings detected
in their optical spectra (``LINER 1's''), and in those that do not (``LINER
2s''). This variability demonstrates the existence of a non-stellar component
in the UV continuum of all types, and sets a lower limit to the luminosity of
this component. We note a trend in the UV color (F250W/F330W) with spectral
type - LINER 1s tend to be bluer than LINER 2s. This trend may indicate a link
between the shape of the nonstellar continuum and the presence or the
visibility of a broad-line region. In one target, the post-starburst galaxy NGC
4736, we detect variability in a previously noted UV source that is offset by
2.5" (60 pc in projection) from the nucleus. This may be the nearest example of
a binary active nucleus, and of the process leading to black hole merging.


title:
Mixed-phase induced core-quakes and the changes in neutron star
  parameters

abstract:
  We present approximate formulae describing the changes in neutron star
parameters caused by the first-order phase transition to an ``exotic'' state
(pion or kaon condensate, quark matter) resulting in formation of a mixed-phase
core. The analytical formulae for the changes in radius, moment of inertia and
the amount of energy released during the core-quake are derived using the
theory of linear response of stellar structure to the core transformation.
Numerical coefficients in these formulae are obtained for two realistic EOSs of
dense matter. The problem of nucleation of the exotic phase as well as possible
astrophysical scenarios leading to a core-quake phenomenon is also discussed.


title: A QED Model for Non-thermal Emission from SGRs and AXPs

abstract:
  Previously, we showed that, owing to effects arising from quantum
electrodynamics (QED), magnetohydrodynamic fast modes of sufficient strength
will break down to form electron-positron pairs while traversing the
magnetospheres of strongly magnetised neutron stars. The bulk of the energy of
the fast mode fuels the development of an electron-positron fireball. However,
a small, but potentially observable, fraction of the energy ($\sim 10^{33}$
ergs) can generate a non-thermal distribution of electrons and positrons far
from the star. In this paper, we examine the cooling and radiative output of
these particles. We also investigate the properties of non-thermal emission in
the absence of a fireball to understand the breakdown of fast modes that do not
yield an optically thick pair plasma. This quiescent, non-thermal radiation
associated with fast mode breakdown may account for the recently observed
non-thermal emission from several anomalous X-ray pulsars and soft-gamma
repeaters.


title:
On the Interpretation of High Velocity White Dwarfs as Members of the
  Galactic Halo

abstract:
  A detailed analysis of 32 of the 38 halo white dwarf candidates identified by
Oppenheimer et al. is presented, based on model atmosphere fits to observed
energy distributions built from optical BVRI and infrared JHK CCD photometry.
Effective temperatures and atmospheric compositions are determined for all
objects, as well as masses and cooling ages when trigonometric parallax
measurements are available. This sample is combined with that of other halo
white dwarf candidates and disk white dwarfs to study the nature of these
objects in terms of reduced proper motion diagrams, tangential velocities, and
stellar ages. We reaffirm the conclusions of an earlier analysis based on
photographic magnitudes of the same sample that total stellar ages must be
derived in order to associate a white dwarf with the old halo population, and
that this can only be accomplished through precise mass and distance
determinations.


title:
The High-Energy Polarization-Limiting Radius of Neutron Star
  Magnetospheres II -- Magnetized Hydrogen Atmospheres

abstract:
  In the presence of strong magnetic fields, the vacuum becomes a birefringent
medium. We show that this QED effect couples the direction of the polarization
of photons leaving the NS surface, to the direction of the magnetic field along
the ray's path. We analyze the consequences that this effect has on aligning
the polarization vectors to generate large net polarizations, while considering
thermal radiation originating from a thermal hydrogen atmosphere. Counter to
previous predictions, we show that the thermal radiation should be highly
polarized even in the optical. When detected, this polarization will be the
first demonstration of vacuum birefringence. It could be used as a tool to
prove the high magnetic field nature of AXPs and it could also be used to
constrain physical NS parameters, such as $R/M$, to which the net polarization
is sensitive.


title:
High Resolution Gratings Spectroscopy of GRBs 030382 and 041006 with
  Chandra LETGS

abstract:
  We present high resolution X-ray spectroscopy of two recent GRB afterglows
observed with the Low Energy Transmission Gratings on Chandra. The afterglows
to GRBs 030328 and 041006 are detected beginning 15.33 and 16.8 hours after
each burst, respectively, and are observed to fade in time during each ~90 ksec
observation. We fit for the continuum emission in each full data set and for
the data sliced into half and quarter time sections. For both afterglows, the
continuum emission is well described by an absorbed power-law model, and the
model parameters describing the absorption and spectral slope do not appear to
evolve in time. We perform a careful search for deviations from the model
continua for the full and time-sliced data and find no evidence for significant
(>~3sigma) narrow emission/absorption lines or edges. The lack of detections
implies that line emission--if it is a general feature in GRB X-ray
afterglows--occurs early (t~0.3 days in the source frame) and/or is short-lived
(dt<~10 ksec). We also comment on synchrotron fireball models for the X-ray and
optical data.


title: The analysis of magnetic field measurements of T Tau

abstract:
  It is shown that the existence of hot accretion spots at the surface of T Tau
practically has no effect on the accuracy of estimation of its magnetic field
strength at photospheric level.
  We also found that one can interpret results of T Tau's photospheric magnetic
field strength measurements carried out via different methods in the frame of
the following alternative: 1) if T Tau's inclination angle $i\le 10^\circ,$
then magnetic field of the star may be dipolar with the angle between
rotational and magnetic axes is near $85^\circ;$ 2) if it will be found (e.g.
from interferometric observations) that $i>10^\circ,$ then magnetic field of T
Tau is essentially non-dipolar or/and non-stationary.


title:
Large Magellanic Cloud Microlensing Optical Depth with Imperfect Event
  Selection

abstract:
  I present a new analysis of the MACHO Project 5.7 year Large Magellanic Cloud
(LMC) microlensing data set that incorporates the effects of contamination of
the microlensing event sample by variable stars. Photometric monitoring of
MACHO LMC microlensing event candidates by the EROS and OGLE groups has
revealed that one of these events is likely to be a variable star, while
additional data has confirmed that many of the other events are very likely to
be microlensing. This additional data on the nature of the MACHO microlensing
candidates is incorporated into a simple likelihood analysis to derive a
probability distribution for the number of MACHO microlens candidates that are
true microlensing events. This analysis shows that 10-12 of the 13 events that
passed the MACHO selection criteria are likely to be microlensing events, with
the other 1-3 being variable stars. This likelihood analysis is also used to
show that the main conclusions of the MACHO LMC analysis are unchanged by the
variable star contamination. The microlensing optical depth toward the LMC is =
1.0 +/- 0.3 * 10^{-7}. If this is due to microlensing by known stellar
populations, plus an additional population of lens objects in the Galactic
halo, then the new halo population would account for 16% of the mass of a
standard Galactic halo. The MACHO detection exceeds the expected background of
2 events expected from ordinary stars in standard models of the Milky Way and
LMC at the 99.98% confidence level. The background prediction is increased to 3
events if maximal disk models are assumed for both the MilkyWay and LMC, but
this model fails to account for the full signal seen by MACHO at the 99.8%
confidence level.


title: Non-LTE Spectra of Accretion Disks Around Intermediate-Mass Black Holes

abstract:
  We have calculated the structures and the emergent spectra of stationary,
geometrically thin accretion disks around 100 and 1000 M_sun black holes in
both the Schwarzschild and extreme Kerr metrics. Equations of radiative
transfer, hydrostatic equilibrium, energy balance, ionization equilibrium, and
statistical equilibrium are solved simultaneously and consistently. The six
most astrophysically abundant elements (H, He, C, N, O, and Fe) are included,
as well as energy transfer by Comptonization. The observed spectrum as a
function of viewing angle is computed incorporating all general relativistic
effects. We find that, in contrast with the predictions of the commonly-used
multi-color disk (MCD) model, opacity associated with photoionization of heavy
elements can significantly alter the spectrum near its peak. These ionization
edges can create spectral breaks visible in the spectra of slowly-spinning
black holes viewed from almost all angles and in the spectra of
rapidly-spinning black holes seen approximately pole-on. For fixed mass and
accretion rate relative to Eddington, both the black hole spin and the viewing
angle can significantly shift the observed peak energy of the spectrum,
particularly for rapid spin viewed obliquely or edge-on. We present a detailed
test of the approximations made in various forms of the MCD model. Linear
limb-darkening is confirmed to be a reasonable approximation for the integrated
flux, but not for many specific frequencies of interest.


title: Construction of Special Solutions for Nonintegrable Systems

abstract:
  The Painleve test is very useful to construct not only the Laurent series
solutions of systems of nonlinear ordinary differential equations but also the
elliptic and trigonometric ones. The standard methods for constructing the
elliptic solutions consist of two independent steps: transformation of a
nonlinear polynomial differential equation into a nonlinear algebraic system
and a search for solutions of the obtained system. It has been demonstrated by
the example of the generalized Henon-Heiles system that the use of the Laurent
series solutions of the initial differential equation assists to solve the
obtained algebraic system. This procedure has been automatized and generalized
on some type of multivalued solutions. To find solutions of the initial
differential equation in the form of the Laurent or Puiseux series we use the
Painleve test. This test can also assist to solve the inverse problem: to find
the form of a polynomial potential, which corresponds to the required type of
solutions. We consider the five-dimensional gravitational model with a scalar
field to demonstrate this.


title: The star formation history of the LSB Galaxy UGC 5889

abstract:
  We present HST photometry of the LSB galaxy UGC 5889 and derive its recent
star formation history. In the last 200 Myr the star formation proceeded in
modest bursts at a rate of the order of e-2 to e-3 solar masses masses per
year, with periods of extremely low SFR or even quiescence. The rate derived
from the present study for the last 20 Myr is in agreement with the Halpha
emission from the galaxy. The presence of a consistent population older than
200 Myr is suggested by the data. However, observational errors and
completeness correction prevent any firm conclusion on the oldest age. The
total mass of stars is of the order of 5.5e7 solas masses. Even if the recent
episodes of star formation have heated the gas and carved a hole in the disk,
blow-away of the gas is unlikely to occur.


title:
Hubble Space Telescope NICMOS Imaging of W3 IRS 5: A Trapezium in the
  Making?

abstract:
  We present Hubble Space Telescope NICMOS imaging of W3 IRS 5, a binary
high-mass protostar. In addition to the two protostars, NICMOS images taken in
the F222M and F160W filters show three new 2.22 micron sources with very red
colors; these sources fall within a region 5600 AU in diameter, and are
coincident with a 100 solar mass dense molecular clump. Two additional point
sources are found within 0.4'' (800 AU) of one of the high-mass protostars;
these may be stellar companions or unresolved emission knots from an outflow.
We propose that these sources constitute a nascent Trapezium system in the
center of the W3 IRS 5 cluster containing as many as five proto OB stars. This
would be the first identification of a Trapezium still deeply embedded in its
natal gas.


title:
Radio astronomical probes of cosmic reionization and the first luminous
  sources: probing the 'twilight zone'

abstract:
  The epoch of reionization (EoR) corresponds to a 'cosmic phase transition',
when the neutral intergalactic medium (IGM) becomes ionized by the first stars
and/or AGN. While the discoveries of Gunn-Peterson (GP) absorption troughs in
the spectra of the highest redshift QSOs, and large scale polarization of the
CMB, have set the first hard constraints on the EoR, the redshift and process
of reionization, and the nature of the first luminous objects, remain two of
the paramount questions in cosmic structure formation. Moreover, the GP effect
is such that observations of objects during this epoch will be difficult at
wavelengths shorter than about 1 micron. Hence, cosmic reionization, and the
formation of the first luminous objects, occurs in a 'twilight zone',
observable only at radio through near-IR wavelengths. In this talk I explore
studies of the EoR at meter through submillimeter wavelengths. I present recent
observations of the dust, molecular gas, and star formation activity in the
host galaxies of the highest redshift QSOs. These results have interesting
implications on the timescale for metal and dust enrichment, on the possibility
of co-eval formation of SMBHs and galaxies, and on the process of reionization.
I then discuss future capabilities of low frequency radio astronomy to study
the neutral IGM via the HI 21cm line, including imaging and power spectral
analyses of large scale structure in emission, and absorption studies toward
the first radio loud sources. I conclude with a summary of the VLA-VHF system
to study cosmic Stromgren spheres associated with the highest redshift SDSS
QSOs in the HI 21cm line at 190 MHz.


title: Can a Gravitational Lens Magnify Gravity? A Possible Solar System Test

abstract:
  Can a gravitational lens magnify gravity? Leading theories of gravity likely
indicate "no", but the possibility might be testable by using our Sun as a
gravitational lens and carefully aligning a satellite past the minimum
transparent focal distance of about 25 AU. Here the magnitude of a maximal
effect is estimated and found potentially observable.


title: Stochastic approaches to inflation model building

abstract:
  While inflation gives an appealing explanation of observed cosmological data,
there are a wide range of different inflation models, providing differing
predictions for the initial perturbations. Typically models are motivated
either by fundamental physics considerations or by simplicity. An alternative
is to generate large numbers of models via a random generation process, such as
the flow equations approach. The flow equations approach is known to predict a
definite structure to the observational predictions. In this paper, we first
demonstrate a more efficient implementation of the flow equations exploiting an
analytic solution found by Liddle (2003). We then consider alternative
stochastic methods of generating large numbers of inflation models, with the
aim of testing whether the structures generated by the flow equations are
robust. We find that while typically there remains some concentration of points
in the observable plane under the different methods, there is significant
variation in the predictions amongst the methods considered.


title: XMM-Newton and Gemini Observations of Eight RASSCALS Galaxy Groups

abstract:
  We study the distribution of gas pressure and entropy in eight groups of
galaxies belonging to the ROSAT All-Sky Survey / Center for Astrophysics Loose
Systems (RASSCALS). We use archival and proprietary XMM-Newton observations,
supplementing the X-ray data with redshifts derived from the literature; we
also list 127 new redshifts measured with the Gemini North telescope. The
groups show remarkable self-similarity in their azimuthally averaged entropy
and temperature profiles. The entropy increases with radius; the behavior of
the entropy profiles is consistent with an increasing broken power law with
inner and outer slope 0.92+0.04-0.05 and 0.42+0.05-0.04 (68% confidence),
respectively. There is no evidence of a central, isentropic core, and the
entropy distribution in most of the groups is flatter at large radii than in
the inner region, challenging earlier reports as well as theoretical models
predicting large isentropic cores or asymptotic slopes of 1.1 at large radii.
The pressure profiles are consistent with a self-similar decreasing broken
power law in radius; the inner and outer slopes are -0.78+0.04-0.03 and
-1.7+0.1-0.3, respectively. The results suggest that the larger scatter in the
entropy distribution reflects the varied gasdynamical histories of the groups;
the regularity and self-similarity of the pressure profiles is a sign of a
similarity in the underlying dark matter distributions.


title:
Microlensing optical depth toward the Galactic Bulge using bright
  sources from OGLE-II

abstract:
  We present a measurement of the microlensing optical depth toward the
Galactic Bulge based on 4 years of the OGLE-II survey using Red Clump Giant
(RCG). Using 32 events we find tau=2.55_{-0.46}^{+0.57}* 10^{-6} at
(l,b)=(1.16, -2.75). Taking into account the measured gradient along the
Galactic latitude b, tau = [ (4.48+/- 2.37) + (0.78+/- 0.84)* b]* 10^{-6}, this
value is consistent with previous measurements using RCG sources and recent
theoretical predictions. We determine the microlensing parameters and select
events using a model light curve with the flux blending. We find that ~38% of
the OGLE-II events which appear to have RCG sources are actually due to much
fainter stars blended with a bright companion. We show explicitly that model
fits without blending result in similar tau estimates through partial
cancellation of contributions from higher detection efficiency, underestimated
time-scales and larger number of selected events. This approach, however, leads
to biased time-scale distributions and event rates. Consequently, microlensing
studies should carefully consider source confusion effects even for bright
stars.


title:
Can Enhanced Diffusion Improve Helioseismic Agreement for Solar Models
  with Revised Abundances?

abstract:
  Recent solar photospheric abundance analyses (Asplund et al. 2004, 2005;
Lodders 2003) have revised downward the C, N, O, Ne, and Ar abundances by 0.15
to 0.2 dex compared to previous determinations of Grevesse & Sauval (1998).
With these revisions, the photospheric Z/X decreases to 0.0165 (0.0177
Lodders), and Z to ~0.0122 (0.0133 Lodders). A number of papers report that
solar models evolved with standard opacities and diffusion treatment using
these new abundances give poor agreement with helioseismic inferences. Here we
explore evolved solar models with varying diffusion treatments to reduce the
photospheric abundances while keeping the interior abundances about the same as
earlier standard models. While enhanced diffusion improves agreement with some
helioseismic constraints compared to a solar model evolved with the new
abundances using nominal input physics, the required increases in thermal
diffusion rates are unphysically large, and none of the variations tried
restores the good agreement attained using the earlier abundances. A
combination of modest opacity increases, diffusion enhancements, and abundance
increases near the level of the uncertainties, while somewhat contrived,
remains the most physically plausible means to restore agreement with
helioseismology. The case for enhanced diffusion would be improved if the
inferred convection-zone helium abundance could be reduced; we recommend
reconsidering this derivation in light of new equations of state with modified
abundances and other improvements. We also recommend considering, as a last
resort, diluting the convection zone, which contains only 2.5% of the sun's
mass, by accretion of material depleted in these more volatile elements C, N,
O, Ne, & Ar after the sun arrived on the main sequence.


title:
Quiescent Radio Emission from Southern Late-type M Dwarfs and a
  Spectacular Radio Flare from the M8 Dwarf DENIS 1048-3956

abstract:
  We report the results of a radio monitoring program conducted at the
Australia Telescope Compact Array to search for quiescent and flaring emission
from seven nearby Southern late-type M and L dwarfs. Two late-type M dwarfs,
the M7 V LHS 3003 and the M8 V DENIS 1048-3956, were detected in quiescent
emission at 4.80 GHz. The observed emission is consistent with optically thin
gyrosynchrotron emission from mildly relativistic (~1-10 keV) electrons with
source densities n_e <~ 10^9 cm^-3 in B >~ 10 G magnetic fields. DENIS
1048-3956 was also detected in two spectacular, short-lived flares, one at 4.80
GHz (peak f_nu = 6.0+/-0.8 mJy) and one at 8.64 GHz (peak f_nu = 29.6+/-1.0
mJy) approximately 10 minutes later. The high brightness temperature (T_B >~
10^13 K), short emission period (~4-5 minutes), high circular polarization
(~100%), and apparently narrow spectral bandwidth of these events imply a
coherent emission process in a region of high electron density (n_e ~
10^11-10^12 cm^-3) and magnetic field strength (B ~ 1 kG). If the two flare
events are related, the apparent frequency drift in the emission suggests that
the emitting source either moved into regions of higher electron or magnetic
flux density; or was compressed, e.g., by twisting field lines or gas motions.
The quiescent fluxes from the radio-emitting M dwarfs violate the Gudel-Benz
empirical radio/X-ray relations, confirming a trend previously noted by Berger
et al. (abridged)


title:
Discovery of an extended halo of metal-poor stars in the Andromeda
  spiral galaxy

abstract:
  Understanding galaxy formation involves look-back and fossil-record studies
of distant and nearby galaxies, respectively. Debris trails in our Galaxy's
spheroidal halo of old stars provide evidence of "bottom-up" formation via
tidal disruption/merging of dwarf satellite galaxies, but it is difficult to
study our Galaxy's large-scale structure from within. Studies of our
neighbouring Andromeda galaxy have concluded that its spheroid contains
chemically enriched ("metal-rich") stars out to a radius of 30 kiloparsecs with
an exponential r^1/4 fall-off in density thereby resembling a galactic "bulge".
Were Andromeda's true halo to be found, our detailed yet global view of its
stellar dynamics, substructure, chemical abundance, and age distribution would
directly constrain hierarchical halo formation models. We report here on the
discovery of a hitherto elusive halo of metal-poor Andromeda stars, distinct
from its bulge, with a power-law brightness profile extending beyond r = 160
kiloparsecs. This is 3 - 5 times larger than any previously mapped Andromeda
spheroidal/disk component. Together, the Galactic and Andromeda halos span >1/3
of the distance between them, suggesting that stars occupy a substantial volume
fraction of our Local Group, and possibly most galaxy groups.


title: Interactions of Jets with Inhomogeneous Cloudy Media

abstract:
  We present two-dimensional slab-jet simulations of jets in inhomogeneous
media consisting of a tenuous hot medium populated with a small filling factor
by warm, dense clouds. The simulations are relevant to the structure and
dynamics of sources such as Gigahertz Peak Spectrum and Compact Steep Spectrum
radio galaxies, High Redshift Radio Galaxies and radio galaxies in cooling
flows. The jets are disrupted to a degree depending upon the filling factor of
the clouds. With a small filling factor, the jet retains some forward momentum
but also forms a halo or bubble around the source. At larger filling factors
channels are formed in the cloud distribution through which the jet plasma
flows and a hierarchical structure consisting of nested lobes and an outer
enclosing bubble results. We suggest that the CSS quasar 3C48 is an example of
a low filling factor jet - interstellar medium interaction whilst M87 may be an
example of the higher filling factor type of interaction. Jet disruption occurs
primarily as a result of Kelvin-Helmholtz instabilities driven by turbulence in
the radio cocoon not through direct jet-cloud interactions, although there are
some examples of these. In all radio galaxies whose morphology may be the
result of jet interactions with an inhomogeneous interstellar medium we expect
that the dense clouds will be optically observable as a result of radiative
shocks driven by the pressure of the radio cocoon. We also expect that the
radio galaxies will possess faint haloes of radio emitting material well beyond
the observable jet structure.


title:
Frequency and time profiles of metric wave isolated Type I solar noise
  storm bursts at high spectral and temporal resolution

abstract:
  Type I noise storms constitute a sizeable faction of the active-Sun radio
emission component. Observations of isolated instances of such bursts, in the
swept-frequency-mode at metric wavelengths, have remained sparse, with several
unfilled regions in the frequency coverage. Dynamic spectra of the burst
radiation, in the 30 - 130 MHz band, obtained from the recently commissioned
digital High Resolution Spectrograph (HRS) at the Gauribidanur Radio
Observatory, on account of the superior frequency and time resolution, have
unravelled in explicit detail the temporal and spectral profiles of isolated
bursts. Apart from presenting details on their fundamental emission features,
the time and frequency profile symmetry, with reference to custom-specific
Gaussian distributions, has been chosen as the nodal criterion to statistically
explain the state of the source regions in the vicinity of magnetic
reconnections, the latent excitation agent that contributes to plasma wave
energetics, and the quenching phenomenon that causes damping of the burst
emission.


title: Photometric observations of Grid Giant Star Survey candidates

abstract:
  We compare variability of radial velocity (RV) and brightness for a sample of
red giants which were selected as candidates for the Grid Giant Star Survey
(GGSS). The purpose of the survey is to select astrometrically stable stars as
a reference frame for the future Space Interferometry Mission. We incorporate
photometric data taken by ROTSE-I and being taken by ROTSE-III robotic
telescopes. Typically 2/3 of all GGSS stars to the north of DEC=-35 were
observed 76 and 8 times by ROTSE-I and III respectively in white-light filters.
It is shown that photometric stability at the 0.02 mag level cannot be used for
a pre-selection of RV-stable stars, and the most important tool remains
high-resolution spectroscopy. We deeply thank the ROTSE collaboration providing
us observing time at the ROTSE-IIIb telescope. We gratefully acknowledge NASA
grant NRA-99-04-OSS-058.


title: A case for nucleosynthesis in slowly evolving models

abstract:
  We present a case for Cosmological Nucleosynthesis in an FRW universe in
which the scale factor expands linearly with time: $a(t) \sim t$. It is
demonstrated that adequate amount of $^4He$ requires a baryon density that
saturates mass bounds from galactic clusters. There is a collataral metallicity
production that is quite close to the lowest metallicity observed in metal poor
Pop II stars and clouds. On the other hand, sites for incipient low metallicity
(Pop II) starformation can support environments conducive to Deuterium
production up to levels observed in the universe. A profile of a revised
``Standard Cosmology'' is outlined.


title:
Time Evolution of Relativistic Force-Free Fields Connecting a Neutron
  Star and its Disk

abstract:
  We study the magnetic interaction between a neutron star and its disk by
solving the time-dependent relativistic force-free equations. At the initial
state, we assume that the dipole magnetic field of the neutron star connects
the neutron star and its equatorial disk, which deeply enters into the
magnetosphere of the neutron star. Magnetic fields are assumed to be frozen to
the star and the disk. The rotation of the neutron star and the disk is imposed
as boundary conditions. We apply Harten-Lax-van Leer (HLL) method to simulate
the evolution of the star-disk system. We carry out simulations for (1) a disk
inside the corotation radius, in which the disk rotates faster than the star,
and (2) a disk outside the corotation radius, in which the neutron star rotates
faster than the disk. Numerical results indicate that for both models, the
magnetic field lines connecting the disk and the star inflate as they are
twisted by the differential rotation between the disk and the star. When the
twist angle exceeds pi radian, the magnetic field lines expand with speed close
to the light speed. This mechanism can be the origin of relativistic outflows
observed in binaries containing a neutron star.


title: In-situ Particle Acceleration in Collisionless Shocks

abstract:
  The outflows from gamma ray bursts, active galactic nuclei and relativistic
jets in general interact with the surrounding media through collisionless
shocks. With three dimensional relativistic particle-in-cell simulations we
investigate such shocks. The results from these experiments show that
small--scale magnetic filaments with strengths of up to percents of
equipartition are generated and that electrons are accelerated to power law
distributions N(E)~E^{-p} in the vicinity of the filaments through a new
acceleration mechanism. The acceleration is locally confined, instantaneous and
differs from recursive acceleration processes such as Fermi acceleration. We
find that the proposed acceleration mechanism competes with thermalization and
becomes important at high Lorentz factors.


title:
Method of determining cosmological parameter ranges with samples of
  candles with an intrinsic distribution

abstract:
  In this paper, the effect of the intrinsic distribution of cosmological
candles is investigated. We find that, in the case of a narrow distribution,
the deviation of the observed modulus of sources from the expected central
value could be estimated within a ceratin range. We thus introduce a lower and
upper limits of $\chi ^{2}$, $\chi_{\min}^{2}$ and $ \chi_{\max}^{2}$, to
estimate cosmological parameters by applying the conventional minimizing $\chi
^{2}$ method. We apply this method to a gamma-ray burst (GRB) sample as well as
to a combined sample including this GRB sample and an SN Ia sample. Our
analysis shows that: a) in the case of assuming an intrinsic distribution of
candles of the GRB sample, the effect of the distribution is obvious and should
not be neglected; b) taking into account this effect would lead to a poorer
constraint of the cosmological parameter ranges. The analysis suggests that in
the attempt of constraining the cosmological model with current GRB samples,
the results tend to be worse than what previously thought if the mentioned
intrinsic distribution does exist.


title: An Exact Equilibrium Model of an Unbound Stellar System in a Tidal Field

abstract:
  Star clusters and dwarf galaxies gradually dissolve as they move in the
potential of their host galaxy. Once their density falls below a certain
critical density (which is comparable with the background density of the
galaxy) it is often assumed that their evolution is completed. In fact the
remnant of such a system forms a distribution of stars which are unbound to
each other and which move on similar orbits in their host potential. With this
motivation we study the evolution of an idealised unbound system and follow its
expansion and dissolution in the tidal field of a model galaxy. Initially the
stars are uniformly distributed (with a density below the critical density)
within an ellipsoidal volume. The system itself travels on a circular orbit
within a galaxy modelled as an isothermal sphere. The initial velocities of the
stars are chosen by assuming that they move on (three-dimensional) epicycles
with guiding centre at the centre of the ellipsoid, though the usual epicyclic
theory is altered to account for the self-gravity of the system. This is
believed to be the first exact equilibrium model of a stellar system in a tidal
field. Our main task is to study the stability of such configurations and the
time-scale of their dissolution, as a function of the initial density and size
of the ellipsoid. If the time of dissolution is measured by an increase of the
half-mass radius of 50 %, we find that systems of low density (about 1 % of the
background density) and small radius (50 pc on an orbit of radius 10 kpc) can
survive for about 20 galactic orbits. For small systems we show that the
lifetime is approximately proportional to the inverse square root of the
density.


title:
Wavelet transform and diffusion equations: applications to the
  processing of the "Cassini" spacecraft observations

abstract:
  We show that continuous transform with the complex Morlet wavelet is easily
performed if we replace the integration of the fast-oscillation function by the
solution of the diffusion differential equations. The most important advantage
of this approach is that the initial data can be represented by non-uniform
sample of an arbitrary node number. We apply the proposed method to the
processing of the image of the Saturn A-ring obtained from the Cassini
spacecraft. Also we have got via the wavelet transform using PDE, the local
correlation coefficient of the signal and the harmonic function.


title:
A search for hot massive extrasolar planets around nearby young stars
  with the adaptive optics system NACO

abstract:
  We report on a survey devoted for the search of exo-planets around young and
nearby stars carried out with NACO at the VLT. The detection limit for 28 among
the best available targets vs. the angular separation from the star is
presented. The non-detection of any planetary mass companion in our survey is
used to derive, for the first time, the frequency of the upper limit of the
projected separation planet-stars. In particular, we find that in 50 % of
cases, no 5 MJ planet (or more massive) has been detected at projected
separations larger than 14 AU and no 10 MJ planet (or more massive) has been
detected at projected separations larger than 8.5 AU. In 100 % of cases, these
values increase to 36 AU and 65 AU respectively. The excellent sensitivity
reached by our study leads to a much lower upper limit of the projected
planet-star separation compared with previous studies. For example, for the
Beta Pictoris group, (~ 12 Myr), we did not detect any 10 MJ planet at
distances larger than 15 AU. A previous study carried out with 4 m class
telescopes put an upper limit for 10 MJ planets at ~ 60 AU. For our closest
target (V 2306 Oph - d = 4.3 pc) it is shown that it would be possible to
detect a 10 MJ planet at a minimum projected separation from the star of 1 AU
and a 5 MJ planet at a minimum projected separation of 3.7 AU. Our results are
discussed with respect to mechanisms explaining planet formation and migration
and to forthcoming observational strategies and future planet finder
observations from the ground.


title: Detection of cosmic neutrino clustering by cosmic ray spectra

abstract:
  We propose a method to investigate the scenario that cosmic relic neutrinos
are highly clustered around stars and galaxies, or dark-matter clusters, rather
than uniformly distributed in the universe. Such a scenario can be detected or
constrained by the interaction of high energy cosmic ray protons and nuclei
with the cosmic neutrinos. There should be observable signature in the energy
spectra of cosmic ray protons and nuclei for a neutrino clustering factor
beyond $10^{13}$. We provide a relation on the signature onset positions
between proton and nuclei spectra, and discuss possible support from existing
experiments. It is also suggested that the relative abundance of cosmic ray
nuclei may detect or constrain the cosmic neutrinos with smaller clustering.


title: The Three-Dimensional Circumstellar Environment of SN 1987A

abstract:
  We present the detailed construction and analysis of the most complete map to
date of the circumstellar environment around SN 1987A, using ground and
space-based imaging from the past 16 years. PSF-matched difference-imaging
analyses of data from 1988 through 1997 reveal material between 1 and 28 ly
from the SN. Careful analyses allows the reconstruction of the probable
circumstellar environment, revealing a richly-structured bipolar nebula. An
outer, double-lobed ``Peanut,'' which is believed to be the contact
discontinuity between red supergiant and main sequence winds, is a prolate
shell extending 28 ly along the poles and 11 ly near the equator. Napoleon's
Hat, previously believed to be an independent structure, is the waist of this
Peanut, which is pinched to a radius of 6 ly. Interior to this is a cylindrical
hourglass, 1 ly in radius and 4 ly long, which connects to the Peanut by a
thick equatorial disk. The nebulae are inclined 41\degr south and 8\degr east
of the line of sight, slightly elliptical in cross section, and marginally
offset west of the SN. From the hourglass to the large, bipolar lobes, echo
fluxes suggest that the gas density drops from 1--3 cm^{-3} to >0.03 cm^{-3},
while the maximum dust-grain size increases from ~0.2 micron to 2 micron, and
the Si:C dust ratio decreases. The nebulae have a total mass of ~1.7 Msun. The
geometry of the three rings is studied, suggesting the northern and southern
rings are located 1.3 and 1.0 ly from the SN, while the equatorial ring is
elliptical (b/a < 0.98), and spatially offset in the same direction as the
hourglass.


title: Spectral Indications of Density Variability in the Corona of AD Leonis

abstract:
  Direct comparison of high-resolution X-ray spectra of the active dMe star AD
Leo, observed three times with Chandra, shows variability of key
density-sensitive lines, possibly due to flaring activity. In particular, a
significant long-duration enhancement of the coronal density is indicated by
the Ne IX and Si XIII He-like triplets, and possibly also by density-sensitive
Fe XXI line ratios.


title: Atmospheric Neutrino Fluxes

abstract:
  Starting with an historical review, I summarize the status of calculations of
the flux of atmospheric neutrinos and how they compare to measurements.