title: Monte Carlo radiative transfer in SPH density fields

abstract:
  We combine a Monte Carlo radiative transfer code with an SPH code, so that --
assuming thermal equilibrium -- we can calculate dust-temperature fields,
spectral energy distributions, and isophotal maps, for the individual
time-frames generated by an SPH simulation. On large scales, the radiative
transfer cells (RT cells) are borrowed from the tree structure built by the SPH
code, and are chosen so that their size -- and hence the resolution of the
calculated temperature field -- is comparable with the resolution of the
density field. We refer collectively to these cubic RT cells as the 'global
grid'. The code is tested and found to treat externally illuminated dust
configurations very well. However, when there are embedded discrete sources,
i.e. stars, these produce very steep local temperature gradients which can only
be modelled properly if -- in the immediate vicinity of, and centred on, each
embedded star -- we supplement the global grid with a 'star grid' of closely
spaced concentric RT cells.


title:
Possible Dark Matter Signals from Antiprotons, Positrons, X-rays and
  Gamma-rays

abstract:
  A number of signals involving charged cosmic rays and high-energy photons
have been interpreted as being due to annihilating dark matter. This article
provides an overview of the experimental evidence and discusses in particular
detections of antiprotons and positrons in the cosmic radiation, the diffuse
gamma-ray emission between 10 MeV and 100 GeV from the Milky Way, and the 511
keV annihilation radiation and the flux of very high-energy photons (>100 GeV)
from the Galactic Centre.


title: How to identify the youngest protostars

abstract:
  We study the transition from a prestellar core to a Class 0 protostar, using
SPH to simulate the dynamical evolution, and a Monte Carlo radiative transfer
code to generate the SED and isophotal maps. For a prestellar core illuminated
by the standard interstellar radiation field, the luminosity is low and the SED
peaks at ~190 micron. Once a protostar has formed, the luminosity rises (due to
a growing contribution from accretion onto the protostar) and the peak of the
SED shifts to shorter wavelengths (~80-100 micron). However, by the end of the
Class 0 phase, the accretion rate is falling, the luminosity has decreased, and
the peak of the SED shifts back towards longer wavelengths (90-150 micron). In
our simulations, the density of material around the protostar remains
sufficiently high well into the Class 0 phase that the protostar only becomes
visible in the NIR if it is displaced from the centre dynamically. Raw submm/mm
maps of Class 0 protostars tend to be much more centrally condensed than those
of prestellar cores. However, when convolved with a typical telescope beam, the
difference in central concentration is less marked, although the Class 0
protostars appear more circular. Our results suggest that, if a core is deemed
to be prestellar on the basis of having no associated IRAS source, no cm radio
emission, and no outflow, but it has a circular appearance and an SED which
peaks at wavelengths below ~170 micron, it may well contain a very young Class
0 protostar.


title: Blank Field Sources in the ROSAT HRI Brera Multiscale Wavelet catalog

abstract:
  The search for Blank Field Sources (BFS), i.e. X-ray sources without optical
counterparts, paves the way to the identification of unusual objects in the
X-ray sky. Here we present four BFS detected in the Brera Multiscale Wavelet
catalog of ROSAT HRI observations. This sample has been selected on the basis
of source brightness, distance from possible counterparts at other wavelengths,
point-like shape and good estimate of the X-ray flux (f_X). The observed f_X
and the limiting magnitude of the optical catalogs fix a lower limit for our
BFS on f_X/f_opt~40. This value puts them well beyond 90% threshold for usual
source classes once HRI energy band and proper spectral shape are taken into
account, leaving room for speculation on their nature. Three BFS show also
evidence of a transient behaviour.


title:
VLT K-band spectroscopy of massive stars deeply embedded in IRAS sources
  with UCHII colours

abstract:
  We have obtained high resolution (R = 10,000) K-band spectra of candidate
young massive stars deeply embedded in (ultra-) compact HII regions (UCHIIs).
In these clusters, three types of objects are identified. The first type (38
objects) consists of ``naked'' OB stars whose K-band spectra are dominated by
photospheric emission. We classify the K-band spectra of the OB-type cluster
members using near-infrared classification criteria. The spectral
classification provides an important constraint on the distance to the embedded
cluster. The ionising power of the population thus derived is compared to the
information obtained from the infrared and radio flux of these sources. In most
cases these two different determinations of the ionising flux are consistent,
from which we conclude that we have identified the ionising star(s) in about
50% of the embedded clusters. The second type (7 objects) are point sources
associated with UCHII radio emission, that exhibit nebular emission lines in
the near-infrared. Six of the objects in this group produce HeI emission
indicative of an embedded O-type star. These objects are more embedded than the
OB stars and probably do not dominate the infrared flux as measured by IRAS.
The third type (20 objects) is characterised by broad (100--200 km/s) Brgamma
emission and no photospheric absorption profiles. Bik et al (2005) show that
these objects are massive YSO candidates surrounded by dense circumstellar
disks.


title: Open issues in gamma-ray bursts: polarimetry and dark GRBs

abstract:
  We review some open problems in the physics of afterglows, namely their
polarization properties and the existence of dark/faint bursts. Polarization
studies yield precious insights in the physical structure and dynamical
evolution of GRB jets, revealing their magnetization properties and their
energy profile. Polarimetric observations of GRB 020813 already allowed to
exclude a homogeneous jet for this event. We then present observations of
faint/dark bursts, showing that some of them may be obscured by dust, while
others are possibly just intrinsically dim.


title:
The Physical Natures of Class I and Flat-Spectrum Protostellar
  Photospheres: A Near-Infrared Spectroscopic Study

abstract:
  We present high resolution (R = 18,000), high signal-to-noise, 2 micron
spectra of 52 infrared-selected Class I and flat-spectrum young stellar objects
in the Taurus-Auriga, $\rho$ Ophiuchi, Serpens, Perseus, and Corona Australis
dark clouds. We detect key absorption lines in 41 objects and fit synthetic
spectra generated from pre-main sequence models to deduce the effective
temperatures, surface gravities, near-infrared veilings, rotation velocities,
and radial velocities of each of these 41 sources. We find these objects to
span ranges in effective temperature, surface gravity, and stellar luminosity
which appear similar to those of late spectral-type Class II sources and
classical T-Tauri stars. We determine that the mean 2 micron veiling of Class I
and flat-spectrum objects is significantly higher than that of Class II objects
in the same region where both types of objects are extensively observed ($\rho$
Oph). We find a significant fraction of our protostellar sample also exhibits
emission lines. Twenty-three objects show H$_2$ emission, usually indicative of
the presence of energetic outflows. Thirty-four sources show HI Br $\gamma$
emission and a number of these exhibit profile asymmetries consistent with
in-fall. Eight sources show significant $\Delta v = 2$ CO emission suggestive
of emission from a circumstellar disk. Overall, these observations indicate
that Class I and flat-spectrum objects are self-embedded protostars undergoing
significant mass accretion, although the objects appear to span a broad range
of mass accretion activity.


title: Winds, B-Fields, and Magnetotails of Pulsars

abstract:
  We investigate the emission of rotating magnetized neutron stars due to the
acceleration and radiation of particles in the relativistic wind and in the
magnetotail of the star. We consider that the charged particles are accelerated
by driven collisionless reconnection. Outside of the light cylinder, the star's
rotation acts to wind up the magnetic field to form a predominantly azimuthal,
slowly decreasing with distance, magnetic field of opposite polarity on either
side of the equatorial plane normal to the star's rotation axis. The magnetic
field annihilates across the equatorial plane with the magnetic energy going to
accelerate the charged particles to relativistic energies. For a typical
supersonically moving pulsar, the star's wind extends outward to the standoff
distance with the interstellar medium. At larger distances, the power output of
pulsar's wind $\dot{E}_w$ of electromagnetic field and relativistic particles
is {\it redirected and collimated into the magnetotail} of the star. In the
magnetotail it is proposed that equipartition is reached between the magnetic
energy and the relativistic particle energy. For such conditions, synchrotron
radiation from the magnetotails may be a significant fraction of $\dot{E}_w$
for high velocity pulsars. An equation is derived for the radius of the
magnetotail $r_m(z^\prime)$ as a function of distance $z^\prime$ from the star.
For large distances $z^\prime$, of the order of the distance travelled by the
star, we argue that the magnetotail has a `trumpet' shape owing to the slowing
down of the magnetotail flow.


title:
The Evolution of the Optical and Near-Infrared Galaxy Luminosity
  Functions and Luminosity Densities to z~2

abstract:
  Using Hubble Space Telescope and ground-based U through K- band photometry
from the Great Observatories Origins Deep Survey (GOODS), we measure the
evolution of the luminosity function and luminosity density in the rest-frame
optical (UBR) to z ~ 2, bridging the poorly explored ``redshift desert''
between z~1 and z~2. We also use deep near-infrared observations to measure the
evolution in the rest-frame J-band to z~1. Compared to local measurements from
the SDSS, we find a brightening of the characteristic magnitude, (M*), by ~2.1,
\~0.8 and ~0.7 mag between z=0.1 and z=1.9, in U, B, and R bands, respectively.
The evolution of M* in the J-band is in the opposite sense, showing a dimming
between redshifts z=0.4 and z=0.9. This is consistent with a scenario in which
the mean star formation rate in galaxies was higher in the past, while the mean
stellar mass was lower, in qualitative agreement with hierarchical galaxy
formation models. We find that the shape of the luminosity function is strongly
dependent on spectral type and that there is strong evolution with redshift in
the relative contribution from the different spectral types to the luminosity
density.
  We find good agreement in the luminosity function derived from an R-selected
and a K-selected sample at z~1, suggesting that optically selected surveys of
similar depth (R < 24) are not missing a significant fraction of objects at
this redshift relative to a near-infrared-selected sample. We compare the
rest-frame B-band luminosity functions from z~0--2 with the predictions of a
semi-analytic hierarchical model of galaxy formation, and find qualitatively
good agreement. In particular, the model predicts at least as many optically
luminous galaxies at z~1--2 as are implied by our observations.


title: Confinement of supernova explosions in a collapsing cloud

abstract:
  We analyze the confining effect of cloud collapse on an expanding supernova
shockfront. We solve the differential equation for the forces on the shockfront
due to ram pressure, supernova energy, and gravity. We find that the expansion
of the shockfront is slowed and in fact reversed by the collapsing cloud.
Including radiative losses and a potential time lag between supernova explosion
and cloud collapse shows that the expansion is reversed at smaller distances as
compared to the non-radiative case. We also consider the case of multiple
supernova explosions at the center of a collapsing cloud. For instance, if we
scale our self-similar solution to a single supernova of energy 10^51 ergs
occurring when a cloud of initial density 10^2 H/cm^3 has collapsed by 50%, we
find that the shockfront is confined to ~15 pc in ~1 Myrs. Our calculations are
pertinent to the observed unusually compact non-thermal radio emission in blue
compact dwarf galaxies (BCDs). More generally, we demonstrate the potential of
a collapsing cloud to confine supernovae, thereby explaining how dwarf galaxies
would exist beyond their first generation of star formation.


title: Multi-phase High-Velocity Clouds toward HE 0226-4110 and PG 0953+414

abstract:
  We study the physical conditions, elemental abundances, and kinematics of the
high-velocity clouds (HVCs) along the sight lines toward active galaxies
HE0226-4110 and PG0953+414 using Hubble Space Telescope Imaging Spectrograph
and Far Ultraviolet Spectroscopic Explorer data. Our observations reveal
multiple components of HVC absorption in lines of HI, CII, CIII, CIV, OVI,
SiII, SiIII, and SiIV in both directions. We investigate whether
photoionization by the extragalactic background radiation or by escaping Milky
Way radiation can explain the observed ionization pattern. We find that
photoionization is a good explanation for the CII, CIII, SiII, and SiIII
features, but not for the OVI or CIV associated with the HVCs, suggesting that
two principal phases exist: a warm (T~10^4K), photoionized phase and a hotter
(T=1-3x10^5K), collisionally-ionized phase. The warm HVCs toward HE0226-4110
have high levels of ionization (97-99%), and metallicities ([Z/H] between -0.9
and -0.4) close to those in the Magellanic Stream, which lies eleven degrees
away on the sky at similar velocities. These HVCs have thermal pressures that
would place them close to equilibrium in a fully ionized 10^6 K Galactic corona
with n_H=4-9x10^{-5}cm^{-3} at 50 kpc. A mini-survey of the hot, collisionally
ionized HVC components seen here and in five other sight lines finds that in
11/12 cases, the high ions have kinematics and ionic ratios that are consistent
with an origin in conductive interfaces. However, the broad absorption wing on
the OVI profile toward PG0953+414 is not completely explained by the interface
scenario, and may be tracing the outflow of hot gas into the Milky Way halo as
part of a Galactic fountain or wind.


title: AGN Unification and the X-ray Background

abstract:
  Active Galactic Nuclei (AGN) unification, which implies a large number of
obscured AGN, can explain the optical, infrared and X-ray content of deep
multiwavelength surveys. Here, we show that the same model also successfully
explains the spectral shape and intensity of the X-ray background. The simplest
possible unified model assumes a constant ratio of obscured to unobscured AGN,
independent of redshift or luminosity. With almost no free parameters, the
predicted X-ray background agrees remarkably well with observations. Both the
observed properties of deep AGN samples and the X-ray background can be
explained by the same model without invoking different evolution for obscured
and unobscured AGN. Recent observational evidence shows that the ratio of
obscured to unobscured AGN may depend on luminosity. An AGN unification model
that allows for such a dependence also fits the X-ray background spectrum, and
the predicted numbers counts in the 2-10 keV X-ray band are in good agreement
with observations. We present predictions for the source counts in hard X-rays
(10-100 keV), which indicate that future missions like the Black Hole Finder
will observe thousands of heavily obscured AGN.


title:
NOAO Fundamental Plane Survey -- II. Age and Metallicity along the Red
  Sequence

abstract:
  We present spectroscopic linestrength data for 4097 red-sequence galaxies in
93 low-redshift galaxy clusters, and use these to investigate variations in
average stellar populations as a function of galaxy mass. Our analysis includes
an improved treatment of nebular emission contamination, which affects ~10% of
the sample galaxies. Using the stellar population models of D. Thomas and
collaborators, we simultaneously fit twelve observed linestrength-sigma
relations in terms of common underlying trends of age, [Z/H] (total
metallicity) and a/Fe (alpha-element enhancement). We find that the observed
linestrength-sigma relations can be explained only if higher-mass red-sequence
galaxies are, on average, older, more metal rich, and more alpha-enhanced than
lower-mass galaxies. Quantitatively, the scaling relations are
age=sigma^(0.59+/-0.13), Z/H=sigma^(0.53+/-0.08) and a/Fe=sigma^(0.31+/-0.06),
where the errors reflect the range obtained using different subsets of indices.
We conclude that although the stars in giant red galaxies in clusters formed
early, most of the galaxies at the faint end joined the red sequence only at
recent epochs. This "down-sizing" trend is in good qualitative agreement with
observations of the red sequence at higher redshifts, but is not predicted by
semi-analytic models of galaxy formation.


title: Rapid Dissipation of Primordial Gas from the AU Microscopii Debris Disk

abstract:
  The disk around AU Microscopii, an M1 star in the Beta Pictoris Moving Group,
is extraordinarily well-suited for comparison to the Beta Pic debris disk (type
A5V). We use far-UV absorption spectroscopy of AU Mic to probe its edge-on disk
for small amounts of molecular hydrogen, the primary constituent of gas giant
planets. Our conservative upper limit on the line-of-sight H_2 column density
is 1.7 x 10^{19} cm^{-2}, which is 18.5 times lower than the limit obtained
from non-detection of sub-mm CO emission (Liu et al. 2004). In addition, there
is a hint of H_2 absorption at a column density an order of magnitude or more
below our upper limit. The H_2-to-dust ratio in the AU Mic disk is < 6:1,
similar to that in the Beta Pic disk. This shows that the primordial gas has
largely been dissipated in less than about 12 Myr for both disks, despite their
very different stellar masses and luminosities. It is extremely difficult to
form a giant planet around AU Mic with current core-accretion scenarios in such
a short time.


title:
Observational Signature of Tidal Disruption of a Star by a Massive Black
  Hole

abstract:
  We have modeled the time-variable profiles of the Balmer alpha emission from
the nonaxisymmetric disk and debris tail created in the tidal disruption of a
solar-type star by a million solar mass black hole. Two tidal disruption events
were simulated using a three dimensional relativistic smoothed particle
hydrodynamic code to describe the early evolution of the debris during the
first 50-90 days. We have calculated the physical conditions and radiative
processes in the debris using the photoionization code CLOUDY. We model the
emission-line profiles in the period immediately after the accretion rate onto
the black hole becomes significant. We find that the line profiles at these
very early stages of the evolution of the postdisruption debris do not resemble
the double-peaked profiles expected from a rotating disk, since the debris has
not yet settled into such a stable structure. As a result of the uneven
distribution of the debris and the existence of a ``tidal tail'' (the stream of
returning debris), the line profiles depend sensitively on the orientation of
the tail relative to the line of sight. Moreover, the predicted line profiles
vary on fairly short time scales (of order hours to days). Given the accretion
rate onto the black hole we also model the Balmer alpha light curve from the
debris.


title: The cooling of shock-compressed primordial gas

abstract:
  We find that at redshifts z > 10, HD line cooling allows strongly-shocked
primordial gas to cool to the temperature of the cosmic microwave background
(CMB). This temperature is the minimum value attainable via radiative cooling.
Provided that the abundance of HD, normalized to the total number density,
exceeds a critical level of ~ 10^{-8}, the CMB temperature floor is reached in
a time which is short compared to the Hubble time. We estimate the
characteristic masses of stars formed out of shocked primordial gas in the wake
of the first supernovae, and resulting from the mergers of dark matter haloes
during hierarchical structure formation to be ~ 10 M_{solar}. In addition, we
show that cooling by HD enables the primordial gas in relic H II regions to
cool to temperatures considerably lower than those reached via H_2 cooling
alone. We confirm that HD cooling is unimportant in cases where the primordial
gas does not go through an ionized phase, as in the formation process of the
very first stars in z ~ 20 minihaloes of mass ~ 10^{6} M_{solar}.


title: The Progenitor of Supernova 2004dj in a Star Cluster

abstract:
  The progenitor of type II-plateau supernova (SN) 2004dj is identified with a
supergiant in a compact star cluster known as "Sandage Star 96" (S96) in the
nearby spiral galaxy NGC 2403, which was fortuitously imaged as part of the
Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey from Feb 1995
to Dec 2003 prior to SN 2004dj. The superior photometry of BATC images for S96,
taken with 14 intermediate-band filters covering 3000-10000\AA, unambiguously
establishes the star cluster nature of S96 with an age of $\sim 20$Myr, a
reddening of $\hbox{E}(B-V)\sim 0.35$ mag and a total mass of $\sim
96,000$M$_{\odot}$. The compact star cluster nature of S96 is also consistent
with the lack of light variations in the past decade. The SN progenitor is
estimated to have a main-sequence mass of $\sim$12M$_{\odot}$. The comparison
of our intermediate-band data of S96 with the post-outburst photometry obtained
as the SN has significantly dimmed, may hopefully conclusively establish the
nature of the progenitor.


title:
Homeoidally striated density profiles: sequences of virial equilibrium
  configurations with constant anisotropy parameters

abstract:
  The formulation of the tensor virial equations is generalized to unrelaxed
configurations, where virial equilibrium does not coincide with dynamical (or
hydrostatic) equilibrium. Further investigation is devoted to special classes
of homeoidally striated ellipsoids, defined as homeoidally striated, Jacobi
ellipsoids. In particular, virial equilibrium configurations with constant
anisotropy parameters are studied with more detail, including both flattened
and elongated, triaxial configurations, and the determination of the related
bifurcation points. The explicit expression of different rotation parameters is
also determined. An application is made to dark matter haloes hosting giant,
galaxies, with regard to assigned initial and final configuration, following
and generalizing to many respects a procedure conceived by Thuan & Gott (1975).
The dependence of the limiting axis ratios, below which no configuration is
allowed for the sequence under consideration, on the change in mass, total
energy, and angular momentum, during the evolution, is illustrated in some
representative situations. The dependence of axis ratios and rotation
parameters on an additional parameter, related to the initial conditions of the
density perturbation, is analysed in connection with a few special cases.
Within the range of Peebles (1969) rotation parameter, inferred from
high-resolution numerical simulations, the shape of dark matter haloes is
mainly decided by the amount of anisotropy in residual velocity distribution.
On the other hand, the contribution of rotation has only a minor effect on the
meridional plane, and no effect on the equatorial plane, as bifurcation points
occur for larger values of Peebles (1969) rotation parameter. To this respect,
dark matter haloes are found to resemble giant elliptical galaxies.


title: Family ties: abundances in Terzan 7, a Sgr dSph globular cluster

abstract:
  We study the chemical composition of 5 giant stars in the globular cluster
Terzan 7 associated with the Sagittarius dwarf spheroidal galaxy (Sgr dSph),
based on high resolution UVES-VLT spectra. We confirm the metallicity found by
previous high resolution investigations: [Fe/H] ~ -0.6. We also show that this
cluster displays the same low alpha-element to iron ratio found in Sgr dSph
field stars of similar metallicity, as well as the same low Ni/Fe ratio. These
chemical signatures are characteristic of the Sgr dSph system, and appear to be
shared both by the globular cluster Pal 12, which was most likely stripped from
Sgr by tidal interaction, and by Pal 5, which may also have belonged in the
past to the Sgr dSph system. Intriguingly even globular cluster Ruprecht 106,
although not associated to Sgr, displays similar characteristics.


title: On virialization with dark energy

abstract:
  We review the inclusion of dark energy into the formalism of spherical
collapse, and the virialization of a two-component system, made of matter and
dark energy. We compare two approaches in previous studies. The first assumes
that only the matter component virializes, e.g. as in the case of a classic
cosmological constant. The second approach allows the full system to virialize
as a whole. We show that the two approaches give fundamentally different
results for the final state of the system. This might be a signature
discriminating between the classic cosmological constant which cannot virialize
and a dynamical dark energy mimicking a cosmological constant. This signature
is independent of the measured value of the equation of state. An additional
issue which we address is energy non-conservation of the system, which
originates from the homogeneity assumption for the dark energy. We propose a
way to take this energy loss into account.


title:
The FWHM of local pulses and the corresponding power-law index of
  gamma-ray burst FRED pulses

abstract:
  The FWHM of gamma-ray burst (GRB) pulses is known to be related with energy
by a power-law. We wonder if the power-law index $\alpha$ is related with the
corresponding local pulse width $FWHM_0$. Seven FRED (fast rise and exponential
decay) pulse GRBs are employed to study this issue, where six of them were
interpreted recently by the relativistic curvature effect (the Doppler effect
of fireballs) and the corresponding local pulses were intensely studied. A
regression analysis shows an anti-correlation between $log \alpha$ and $log
FWHM_0$ with a slope of $-0.37\pm0.13$. This suggests that, for the class of
the GRB pulses which are consequences of the curvature effect, the difference
of the local pulse width might lead to the variation of the power law index,
where the smaller the width the larger the value of $\alpha$. Since the number
of sources employed in this analysis is small, our result is only a preliminary
one which needs to be confirmed by larger samples.


title: Low-energy quantum gravity leads to another picture of the universe

abstract:
  If gravitons are super-strong interacting particles and the low-temperature
graviton background exists, the basic cosmological conjecture about the
Dopplerian nature of redshifts may be false: a full magnitude of cosmological
redshift would be caused by interactions of photons with gravitons.
Non-forehead collisions with gravitons will lead to a very specific additional
relaxation of any photonic flux that gives a possibility of another
interpretation of supernovae 1a data - without any kinematics. These facts may
implicate a necessity to change the standard cosmological paradigm. Some
features of a new paradigm are discussed. In a frame of this model, every
observer has two different cosmological horizons. One of them is defined by
maximum existing temperatures of remote sources - by big enough distances, all
of them will be masked with the CMB radiation. Another, and much smaller, one
depends on their maximum luminosity - the luminosity distance increases with a
redshift much quickly than the geometrical one.
  If the considered quantum mechanism of classical gravity is realized in the
nature, then an existence of black holes contradicts to the equivalence
principle. In this approach, the two fundamental constants - Hubble's and
Newton's ones - should be connected between themselves. The theoretical value
of the Hubble constant is computed. Also, every massive body would be
decelerated due to collisions with gravitons that may be connected with the
Pioneer 10 anomaly.


title: A Statistical Solar Flare Forecast Method

abstract:
  A Bayesian approach to solar flare prediction has been developed, which uses
only the event statistics of flares already observed. The method is simple,
objective, and makes few ad hoc assumptions. It is argued that this approach
should be used to provide a baseline prediction for certain space weather
purposes, upon which other methods, incorporating additional information, can
improve. A practical implementation of the method for whole-Sun prediction of
Geostationary Observational Environment Satellite (GOES) events is described in
detail, and is demonstrated for 4 November 2003, the day of the largest
recorded GOES flare. A test of the method is described based on the historical
record of GOES events (1975-2003), and a detailed comparison is made with US
National Oceanic and Atmospheric Administration (NOAA) predictions for
1987-2003. Although the NOAA forecasts incorporate a variety of other
information, the present method out-performs the NOAA method in predicting mean
numbers of event days, for both M-X and X events. Skill scores and other
measures show that the present method is slightly less accurate at predicting
M-X events than the NOAA method, but substantially more accurate at predicting
X events, which are important contributors to space weather.


title:
Deciphering the cosmic star formation history and the Nature of Type Ia
  Supernovae by Future Supernova Surveys

abstract:
  We investigate the prospects of future supernova searches to get meaningful
constraints about the cosmic star formation history (CSFH) and the delay time
of type Ia supernovae from star formation (tau_{Ia}), based only on supernova
data. Here we parameterize the CSFH by two parameters, alpha and beta that are
the evolutionary indices (proportional to (1+z)^{alpha, beta}) at z <~ 1 and >~
1, respectively, and quantitatively examined how well the three parameters
(alpha, beta, and tau_{Ia}) can be constrained in ongoing and future supernova
surveys. We found that the type classification of detected supernovae down to
the magnitude of I_{AB} ~ 27 is essential, to get useful constraint on beta.
The parameter tau_{Ia} can also be constrained within an accuracy of ~ 1--2
Gyr, without knowing alpha that is somewhat degenerate with tau_{Ia}. This
might be potentially achieved by ground-based surveys but depending on the
still highly uncertain type-classification by imaging data. More reliable
classification will be achieved by the SNAP mission. The supernova counts at a
magnitude level of I_{AB} or K_{AB} ~ 30 will allow us to break degeneracies
between alpha and tau_{Ia} and independently constrain all the three
parameters, even without knowing supernova types. This can be achieved by the
SNAP and JWST missions, having different strength of larger statistics and
reach to higher redshifts, respectively. The dependence of observable
quantities on survey time intervals is also quantitatively calculated and
discussed.


title: Planned Dark Matter searches with the MAGIC Telescope

abstract:
  The MAGIC 17m-diameter Imaging Air Cherenkov Telescope (IACT) has been
commissioned beginning of 2005. The telescope has been designed to achieve the
lower detection energy threshold ever obtained with an IACT, about 50 GeV. A
new window in gamma-ray astronomy is being opened with great impact for
exciting new physics and new discoveries. Among the targets of MAGIC is the
indirect detection of Dark Matter (DM). We have considered different DM halo
models of high DM density objects like the center of the Milky Way, its closest
satellites and nearby galaxies (M31,M87). For each object, detection limits are
computed for different DM halo models in a mSUGRA scenario for supersymmetric
neutralino annihilation $\gamma$-ray production. Advantages and drawbacks of
these objects and plans for future observations are discussed.


title:
NGC 146: A young open cluster with a Herbig Be star and intermediate
  mass pre-main sequence stars

abstract:
  We present UBV CCD photometry and low-resolution spectra of stars in the
field of the young open cluster NGC 146. UBV photometry of 434 stars were used
to estimate the E(B$-$V) reddening of 0.55 $\pm$ 0.04 mag and BV photometry of
976 stars were used to estimate a distance modulus of (m$-$M)$_0$ = 12.7
$\pm$0.2 mag, corresponding to a distance of 3470$^{+335}_{-305}$ pc. We
estimated 10 -- 16 Myr as the turn-off age for the upper main sequence of the
cluster using isochrones and synthetic colour magnitude diagrams. We identified
two B type stars with H$_\alpha$ in emission and located on the MS using
slit-less spectra. A higher resolution spectrum of the brighter Be star
indicated the presence of a number of emission lines, with some lines showing
the signature of gas infall. This star was found to be located in the region of
Herbig Ae/Be stars in the (J$-$H) vs (H$-$K) colour-colour diagram. Thus, we
identify this star as a Herbig Be star. On the other hand, 54 stars were found
to show near infrared excess, of which 17 were found to be located in the
region of Herbig Ae/Be stars and 18 stars were found to be located in the
region of Be stars in the NIR colour-colour diagram. Thus NGC 146 is a young
cluster with a large number of intermediate mass pre-main sequence stars. The
turn-on age of the cluster is found to be $\sim$ 3 Myr. Though NGC 146 shows an
older turn off, the bulk of stars in this cluster seems to belong to the
younger population of 3 Myr.


title: Host Galaxies of the High-redshift AGNs in the GOODS Fields

abstract:
  The star-formation rates and the stellar masses of the host galaxies of AGNs
at high-redshifts are keys to understanding the evolution of the relation
between the mass of the spheroidal component of a galaxy and the mass of its
central black hole. We investigate the host galaxies of 31 AGNs with
spectroscopic redshifts between 2 and 4 found in the deep Chandra surveys of
the GOODS fields with the ACS images. The sample can be divided into 17
``extended'' AGNs and 14 ``compact'' AGNs based on the concentration parameter
defined as the difference between the aperture magnitudes with 0.07" and 0.25"
diameter. We derive upper limits of the UV luminosities of the host galaxies of
the ``compact'' AGN sample, and upper and lower limits of the UV luminosities
of the host galaxies of the ``extended'' AGN sample.These limits are consistent
with the knee of the luminosity function of the Lyman Break Galaxies (LBGs) at
z=3, suggesting moderate star-formation rates, less than 40 Msolar/yr, in the
host galaxies of the AGNs at 2<z_sp<4 without correcting the dust extinction.
By combining the limits of the UV luminosities with the observed K-band
magnitudes for the ``extended'' AGNs, we derive the upper and lower limits of
the stellar masses of their host galaxies. The derived upper limits on the
stellar masses range from 10^10 Msolar to 10^12 Msolar. The upper limits imply
that the Mbulge-MBH relation of the high-redshift AGNs is different from that
of the galaxies in the nearby universe or the average Eddington ratio of the
high-redshift AGNs is higher than that of low-redshift AGNs with
lower-luminosity.


title: Black Hole Shadows of Charged Spinning Black Holes

abstract:
  We propose a method for measuring the black hole charge by imaging a black
hole shadow in a galactic center by future interferometers. Even when the black
hole is uncharged, it is possible to confirm the charge neutrality by this
method. We first derive the analytic formulae of the black hole shadow in an
optically thin medium around a charged spinning black hole, and then
investigate how contours of the black hole shadow depend on the spin and the
charge of the black hole for several inclination angles between the rotation
axis of the black hole and the observer. This method only assumes stationary
black hole and general relativity. By fitting the formula of the contours of
the shadow to the observed image of the shadow, in addition to the black hole
charge, one can also determine the black hole spin and the inclination angle
without any degeneracy among the charge, the spin, and the inclination angle
unless the inclination angle is null.


title:
Aten-Alinda orbital evolution: the example of possible interacting
  orbits

abstract:
  Minor planets 887 Alinda and 2062 Aten are typical near Earth asteroids
(NEA). Our previous researches show their possible origin in catastrophic
collision near Earth orbit. It is determine the target of present research --
to investigate interactions between these objects in more details. Orbits m.p.
887 and 2062 are crossed near pericenter and apocenter accordingly. So possible
interval of the interaction of these objects is repeated through the
significant time interval and has relatively small duration. On the strength of
several reasons, orbits of fragments of the disastrous collision can have no an
exact intersection. Besides, when integrating on the greater gap in the past
increases a role of the uncertainty of initial values of elements of orbits.
These factors determine a probabilistic nature of the result as well as need of
modeling of the disastrous process. However, on the strength of the specific
spatial location of orbits, result has highly determined numeric expression -
in the suggestion on the possible interaction m. p. 887 and 2062, this event
has occurred about 1400 years ago. The possible participation some other near
Earth minor objects, include Quadrantides meteoric stream, in described
disastrous event is discussed.


title:
Explicit computation of shear three-point correlation functions: the
  one-halo model case

abstract:
  We present a method for calculating explicit expressions of the shear
three-point function for various cosmological models. The method is applied
here to the one-halo model in case of power law density profiles for which
results are detailed. The three-point functions are found to reproduce to a
large extent patterns in the shear correlations obtained in numerical
simulations and may serve as a guideline to implement optimized methods for
detecting the shear three-point function. In principle, the general method
presented here can also be applied for other models of matter correlation.


title:
Identification of the optical counterparts of high-mass X-ray binaries
  through optical photometry and spectroscopy

abstract:
  We present the results of our search for optical counterparts to high-mass
X-ray transient sources discovered by various X-ray missions. We obtained CCD
images of the X-ray fields through BVR and Halpha filters in order to identify
early-type stars in the R-Halpha versus B-V colour-colour diagram. We also
obtained medium-resolution spectroscopy of the candidates in order to confirm
the presence of H\alpha emission and perform spectral classification. We report
on the discovery of the optical counterparts to two X-ray sources: XTE
J1858+034 and IGR J01363+6610, and the follow-up observations of another two,
newly identified by our group: SAX J2103.5+4545 and GRO J2058+42. For another
source, IGR J00370+6122, we present the first detailed optical spectral
analysis. The optical photometry and spectroscopy reveal B-type companions in
all five sources; GRO J2058+42, SAX J2103.5+4545 and IGR J01363+6610 are
positively identified with Be/X-ray binaries, IGR J00370+6122 with a supergiant
X-ray binary, while the nature of XTE J1858+034 is uncertain. We also study the
relationship between the optical and X-ray emission during quiescent states.


title: The Globular Cluster System of NGC 1399 IV. Some noteworthy objects

abstract:
  We present 8 bright globular clusters and/or objects of less familiar nature
which we found in the course of scrutinizing the globular cluster system of NGC
1399. These objects are morphologically striking, either by their sizes or by
other structural properties. Some of them may be candidates for stripped dwarf
galaxy nuclei, emphasizing the possible role of accretion in the NGC 1399
cluster system. They are all highly interesting targets for further deep
spectroscopy or HST-imaging. Since these objects have been found within an area
of only 42 arcmin**2, we expect many more still to be detected in a full census
of the NGC 1399 cluster system.


title:
Polynomial Approximants for the Calculation of Polarization Profiles in
  the \ion{He}{1} 10830 \AA Multiplet

abstract:
  The \ion{He}{1} multiplet at 10830 \AA is formed in the incomplete
Paschen-Back regime for typical conditions found in solar and stellar
atmospheres. The positions and strengths of the various components that form
the Zeeman structure of this multiplet in the Paschen-Back regime are
approximated here by polynomials. The fitting errors are smaller than
$\sim10^{-2}$ m\AA in the component positions and $\sim10^{-3}$ in the relative
strengths. The approximant polynomials allow for a very fast implementation of
the incomplete Paschen-Back regime in numerical codes for the synthesis and
inversion of polarization profiles in this important multiplet.


title:
An Artificial Neural Network Approach to the Solution of Molecular
  Chemical Equilibrium

abstract:
  A novel approach is presented for the solution of instantaneous chemical
equilibrium problems. The chemical equilibrium can be considered, due to its
intrinsically local character, as a mapping of the three-dimensional parameter
space spanned by the temperature, hydrogen density and electron density into
many one-dimensional spaces representing the number density of each species. We
take advantage of the ability of artificial neural networks to approximate
non-linear functions and construct neural networks for the fast and efficient
solution of the chemical equilibrium problem in typical stellar atmosphere
physical conditions. The neural network approach has the advantage of providing
an analytic function, which can be rapidly evaluated. The networks are trained
with a learning set (that covers the entire parameter space) until a relative
error below 1% is reached. It has been verified that the networks are not
overtrained by using an additional verification set. The networks are then
applied to a snapshot of realistic three-dimensional convection simulations of
the solar atmosphere showing good generalization properties.


title: IRAC Observations of Taurus Pre-Main Sequence Stars

abstract:
  We present infrared photometry obtained with the IRAC camera on the Spitzer
Space Telescope of a sample of 82 pre-main sequence stars and brown dwarfs in
the Taurus star-forming region. We find a clear separation in some IRAC
color-color diagrams between objects with and without disks. A few
``transition'' objects are noted, which correspond to systems in which the
inner disk has been evacuated of small dust. Separating pure disk systems from
objects with remnant protostellar envelopes is more difficult at IRAC
wavelengths, especially for objects with infall at low rates and large angular
momenta. Our results generally confirm the IRAC color classification scheme
used in previous papers by Allen et al. and Megeath et al. to distinguish
between protostars, T Tauri stars with disks, and young stars without (inner)
disks. The observed IRAC colors are in good agreement with recent improved disk
models, and in general accord with models for protostellar envelopes derived
from analyzing a larger wavelength region. We also comment on a few Taurus
objects of special interest. Our results should be useful for interpreting IRAC
results in other, less well-studied star-forming regions.


title: Acceleration of weakly collisional solar-type winds

abstract:
  One of the basic properties of the solar wind, that is the high speed of the
fast wind, is still not satisfactorily explained. This is mainly due to the
theoretical difficulty of treating weakly collisional plasmas. The fluid
approach implies that the medium is collision dominated and that the particle
velocity distributions are close to Maxwellians. However the electron velocity
distributions observed in the solar wind depart significantly from Maxwellians.
Recent kinetic collisionless models (called exospheric) using velocity
distributions with a suprathermal tail have been able to reproduce the high
speeds of the fast solar wind. In this letter we present new developments of
these models by generalizing them over a large range of corona conditions. We
also present new results obtained by numerical simulations that include
collisions. Both approaches calculate the heat flux self-consistently without
any assumption on the energy transport. We show that both approaches - the
exospheric and the collisional one - yield a similar variation of the wind
speed with the basic parameters of the problem; both produce a fast wind speed
if the coronal electron distribution has a suprathermal tail. This suggests
that exospheric models contain the necessary ingredients for the powering of a
transonic stellar wind, including the fast solar one.


title:
A Multi-wavelength View of the TeV Blazar Markarian 421: Correlated
  Variability, Flaring, and Spectral Evolution

abstract:
  We report results from a multi-wavelength monitoring campaign on Mrk 421 over
the period of 2003-2004. The source was observed simultaneously at TeV and
X-ray energies, with supporting observations frequently carried out at optical
and radio wavelengths. The large amount of simultaneous data has allowed us to
examine the variability of Mrk 421 in detail. The variabilities are generally
correlated between the X-ray and gamma-ray bands, although the correlation
appears to be fairly loose. The light curves show the presence of flares with
varying amplitudes on a wide range of timescales both at X-ray and TeV
energies. Of particular interest is the presence of TeV flares that have no
coincident counterparts at longer wavelengths, because the phenomenon seems
difficult to understand in the context of the proposed emission models for TeV
blazars. We have also found that the TeV flux reached its peak days before the
X-ray flux during a giant flare in 2004. Such a difference in the development
of the flare presents a further challenge to the emission models. Mrk 421
varied much less at optical and radio wavelengths. Surprisingly, the normalized
variability amplitude in optical seems to be comparable to that in radio,
perhaps suggesting the presence of different populations of emitting electrons
in the jet. The spectral energy distribution (SED) of Mrk 421 is seen to vary
with flux, with the two characteristic peaks moving toward higher energies at
higher fluxes. We have failed to fit the measured SEDs with a one-zone SSC
model; introducing additional zones greatly improves the fits. We have derived
constraints on the physical properties of the X-ray/gamma-ray flaring regions
from the observed variability (and SED) of the source. The implications of the
results are discussed. (Abridged)


title: Late-time Inhomogeneity and Acceleration Without Dark Energy

abstract:
  The inhomogeneous distribution of matter in the non-linear regime of
galaxies, clusters of galaxies and voids is described by an exact, spherically
symmetric inhomogeneous solution of Einstein's gravitational field equations,
corresponding to an under-dense void. The solution becomes the homogeneous and
isotropic Einstein-de Sitter solution for a red shift $z > 10-20$, which
describes the matter dominated CMB data with small inhomogeneities
$\delta\rho/\rho\sim 10^{-5}$. A spatial volume averaging of physical
quantities is introduced and the averaged time evolution expansion parameter
$\theta$ in the Raychoudhuri equation can give rise in the late-time universe
to a volume averaged deceleration parameter $<q>$ that is negative for a
positive matter density. This allows for a region of accelerated expansion
which does not require a negative pressure dark energy or a cosmological
constant. A negative deceleration parameter can be derived by this volume
averaging procedure from the Lema\^{i}tre-Tolman-Bondi open void solution,
which describes the late-time non-linear regime associated with galaxies and
under-dense voids and solves the ``coincidence'' problem.


title: Spin-Dependent Cyclotron Decay Rates in Strong Magnetic Fields

abstract:
  Cyclotron decay and absorption rates have been well studied in the
literature, focusing primarily on spectral, angular and polarization
dependence. Astrophysical applications usually do not require retention of
information on the electron spin state, and these are normally averaged in
obtaining the requisite rates. In magnetic fields, higher order quantum
processes such as Compton scattering become resonant at the cyclotron frequency
and its harmonics, with the resonances being formally divergent. Such
divergences are usually eliminated by accounting for the finite lifetimes of
excited Landau states. This practice requires the use of spin-dependent
cyclotron rates in order to obtain accurate determinations of process rates
very near cyclotronic resonances, the phase space domain most relevant for
certain applications to pulsar models. This paper develops previous results in
the literature to obtain compact analytic expressions for cyclotron decay
rates/widths in terms of a series of Legendre functions of the second kind;
these expressions can be expediently used in astrophysical models. The rates
are derived using two popular eigenstate formalisms, namely that due to Sokolov
and Ternov, and that due to Johnson and Lippmann. These constitute two sets of
eigenfunctions of the Dirac equation that diagonalize different operators, and
accordingly yield different spin-dependent cyclotron rates. This paper
illustrates the attractive Lorentz transformation characteristics of the
Sokolov and Ternov formulation, which is another reason why it is preferable
when electron spin information must be explicitly retained.


title:
The Century Survey Galactic Halo Project II: Global Properties and the
  Luminosity Function of Field Blue Horizontal Branch Stars

abstract:
  We discuss a 175 deg^2 spectroscopic survey for blue horizontal branch (BHB)
stars in the Galactic halo. We use the Two Micron All Sky Survey (2MASS) and
the Sloan Digital Sky Survey (SDSS) to select BHB candidates, and find that the
2MASS and SDSS color-selection is 38% and 50% efficient, respectively, for BHB
stars. Our samples include one likely run-away B7 star 6 kpc below the Galactic
plane. The global properties of the BHB samples are consistent with membership
in the halo population: the median metallicity is [Fe/H]=-1.7, the velocity
dispersion is 108 km/s, and the mean Galactic rotation of the BHB stars
3<|z|<15 kpc is -4 +- 30 km/s. We discuss the theoretical basis of the Preston,
Shectman & Beers M_V-color relation for BHB stars, and conclude that intrinsic
shape of the BHB M_V-color relation results from the physics of stars on the
horizontal branch. We calculate the luminosity function for the field BHB star
samples using the Efstathiou, Ellis, & Peterson maximum-likelihood method which
is unbiased by density variations. The field BHB luminosity function exhibits a
steep rise at bright luminosities, a peak between 0.8 < M_V < 1.0, and a tail
at faint luminosities. We compare the field BHB luminosity functions with the
luminosity functions derived from sixteen different globular cluster BHBs.
Kolmogorov-Smirnov tests suggest that field BHB stars and BHB stars in globular
clusters share a common distribution of luminosities, with the exception of
globular clusters with extended BHBs.


title:
Smoothing Supernova Data to Reconstruct the Expansion History of the
  Universe and its Age

abstract:
  We propose a non-parametric method of smoothing supernova data over redshift
using a Gaussian kernel in order to reconstruct important cosmological
quantities including H(z) and w(z) in a model independent manner. This method
is shown to be successful in discriminating between different models of dark
energy when the quality of data is commensurate with that expected from the
future SuperNova Acceleration Probe (SNAP). We find that the Hubble parameter
is especially well-determined and useful for this purpose. The look back time
of the universe may also be determined to a very high degree of accuracy (\lleq
0.2 %) in this method. By refining the method, it is also possible to obtain
reasonable bounds on the equation of state of dark energy. We explore a new
diagnostic of dark energy-- the `w-probe'-- which can be calculated from the
first derivative of the data. We find that this diagnostic is reconstructed
extremely accurately for different reconstruction methods even if \Omega_m is
marginalized over. The w-probe can be used to successfully distinguish between
$\Lambda$CDM and other models of dark energy to a high degree of accuracy.


title: How many dark energy parameters?

abstract:
  For exploring the physics behind the accelerating universe a crucial question
is how much we can learn about the dynamics through next generation
cosmological experiments. For example, in defining the dark energy behavior
through an effective equation of state, how many parameters can we
realistically expect to tightly constrain? Through both general and specific
examples (including new parametrizations and principal component analysis) we
argue that the answer is 42 - no, wait, two. Cosmological parameter analyses
involving a measure of the equation of state value at some epoch (e.g. w_0) and
a measure of the change in equation of state (e.g. w') are therefore realistic
in projecting dark energy parameter constraints. More elaborate
parametrizations could have some uses (e.g. testing for bias or comparison with
model features), but do not lead to accurately measured dark energy parameters.


title:
Fourier Transform Spectroscopy of the submillimetre continuum emission
  from hot molecular cores

abstract:
  We have used a Fourier Transform Spectrometer on the James Clerk Maxwell
Telescope to study the submillimetre continuum emission from dust in three hot
molecular cores (HMC). The spectral index beta of the dust emission for these
sources has been determined solely within the 30 GHz wide 350 GHz (850 micron)
passband to an accuracy comparable to those determined through multi-wavelength
observations. We find an average beta = 1.6, in agreement with spectral indices
determined from previous submillimetre observations of these sources and with
those determined for HMC in general. The largest single source of uncertainty
in these results is the variability of the atmosphere at 350 GHz, and with
better sky subtraction techniques we show that the dust spectral index can
clearly be determined within one passband to high accuracy with a submillimetre
FTS. Using an imaging FTS on SCUBA-2, the next generation wide-field
submillimetre camera currently under development to replace SCUBA at the JCMT
in 2006, we calculate that at 350 GHz it will be possible to determine beta to
+/- 0.1 for sources as faint as 400 mJy/beam and to +/- 0.3 for sources as
faint as 140 mJy/beam.


title:
Unusual Pulsed X-ray Emission from the Young, High Magnetic Field Pulsar
  PSR J1119-6127

abstract:
  We present XMM-Newton observations of the radio pulsar PSR J1119-6127, which
has an inferred age of 1,700 yr and surface dipole magnetic field strength of
4.1x10^13 G. We report the first detection of pulsed X-ray emission from PSR
J1119-6127. In the 0.5--2.0 keV range, the pulse profile shows a narrow peak
with a very high pulsed fraction of (74 +/- 14)%. In the 2.0--10.0 keV range,
the upper limit for the pulsed fraction is 28% (99% confidence). The pulsed
emission is well described by a thermal blackbody model with a temperature of
T^{\infty} = 2.4^{+0.3}_{-0.2}x10^6 K and emitting radius of 3.4^{+1.8}_{-0.3}
km (at a distance of 8.4 kpc). Atmospheric models result in problematic
estimates for the distance/emitting area. PSR J1119-6127 is now the radio
pulsar with smallest characteristic age from which thermal X-ray emission has
been detected. The combined temporal and spectral characteristics of this
emission are unlike those of other radio pulsars detected at X-ray energies and
challenge current models of thermal emission from neutron stars.


title: Burst Neutrinos from Nitrogen Flash

abstract:
  Neutrinos give a novel probe to explore deep interior of astrophysical
objects, which otherwise is not accessible with optical observations; among
notable examples are solar and supernova neutrinos. We show that there is a new
class of strong neutrino emission from helium burning, N + alpha --> 18F gamma
followed by beta decay 18F --> 18O + e+ + nu_e, that gives a maximum neutrino
luminosity of 10^8 times the solar bolometric luminosity at the helium-core
flash of a 1 M_sun star, whereas the flash is not observable by optical means.
This means that the neutrino flux, of average energy of 0.382 MeV, will be 10%
the solar CNO neutrino flux on Earth if the star is located at 10pc.


title: The UV, Optical, and IR Properties of SDSS Sources Detected by GALEX

abstract:
  We discuss the UV, optical, and IR properties of the SDSS sources detected by
GALEX as part of its All-sky Imaging Survey Early Release Observations.
Virtually all of the GALEX sources in the overlap region are detected by SDSS.
GALEX sources represent ~2.5% of all SDSS sources within these fields and about
half are optically unresolved. Most unresolved GALEX/SDSS sources are bright
blue turn-off thick disk stars and are typically detected only in the GALEX
near-UV band. The remaining unresolved sources include low-redshift quasars,
white dwarfs, and white dwarf/M dwarf pairs, and these dominate the optically
unresolved sources detected in both GALEX bands.
  Almost all the resolved SDSS sources detected by GALEX are fainter than the
SDSS 'main' spectroscopic limit. These sources have colors consistent with
those of blue (spiral) galaxies (u-r<2.2), and most are detected in both GALEX
bands. Measurements of their UV colors allow much more accurate and robust
estimates of star-formation history than are possible using only SDSS data.
Indeed, galaxies with the most recent (<20 Myr) star formation can be robustly
selected from the GALEX data by requiring that they be brighter in the far-UV
than in the near-UV band. However, older starburst galaxies have UV colors
similar to AGN, and thus cannot be selected unambiguously on the basis of GALEX
fluxes alone.
  With the aid of 2MASS data, we construct and discuss median 10 band
UV-optical-IR spectral energy distributions for turn-off stars, hot white
dwarfs, low-redshift quasars, and spiral and elliptical galaxies. We point out
the high degree of correlation between the UV color and the contribution of the
UV flux to the UV-optical-IR flux of galaxies detected by GALEX.


title: Recent results from the Milagro TeV gamma-ray observatory

abstract:
  Milagro is a gamma-ray observatory employing a water Cherenkov detector to
observe extensive air showers produced by high-energy particles impacting in
the Earth's atmosphere. We discuss the first detection of TeV gamma-rays from
the Galactic plane and report the detection of an extended TeV source
coincident with the EGRET source 3EG J0520+2556, and the observation of TeV
emission from the Cygnus region of our Galaxy. We also summarize the status of
our search for Very High Energy (VHE) emission from satellite-triggered Gamma
Ray Bursts (GRBs) and discuss plans for the next generation water Cherenkov
detector.


title: RAPTOR observations of the early optical afterglow from GRB 050319

abstract:
  The RAPid Telescopes for Optical Response (RAPTOR) system at Los Alamos
National Laboratory observed GRB 050319 starting 25.4 seconds after gamma-ray
emission triggered the Burst Alert Telescope (BAT) on-board the Swift
satellite. Our well sampled light curve of the early optical afterglow is
composed of 32 points (derived from 70 exposures) that measure the flux decay
during the first hour after the GRB. The GRB 050319 light curve measured by
RAPTOR can be described as a relatively gradual flux decline (power-law index
alpha = -0.37) with a transition, at about 400 s after the GRB, to a faster
flux decay (alpha = -0.91). The addition of other available measurements to the
RAPTOR light curve suggests that another emission component emerged after 10^4
s. We hypothesize that the early afterglow emission is powered by extended
energy injection or delayed reverse shock emission followed by the emergence of
forward shock emission.


title:
Scalar Field Models: From the Pioneer Anomaly to Astrophysical
  Constraints

abstract:
  In this work we study how scalar fields may affect solar observables, and use
the constraint on the Sun's central temperature to extract bounds on the
parameters of relevant models. Also, a scalar field driven by a suitable
potential is shown to produce an anomalous acceleration similar to the one
found in the Pioneer anomaly.


title:
On the temperature profile of radiatively efficient geometrically thin
  disks in black hole binaries with the ASCA GIS

abstract:
  X-ray spectra of black hole binaries(BHBs) in the high/soft state were
studied comprehensively by using ASCA GIS data, and partially RXTE PCA data. A
mathematical disk model was applied to several BHBs to see if the observed
accretion disk temperature profile was consistent with that expected from the
standard accretion disk model. This model is called p-free disk, and assumes
that the spectrum is composed of multi-temperature blackbody emission of which
the local temperature T(r) at radius r is given by T(r) ~ r^-p with p being a
positive free parameter. The standard disk roughly requires p~3/4, while a
small deviation is expected depending on the inner boundary conditions, general
relativistic effects and disk vertical structures.Our sample objects included
LMC X-1, LMC X-3, XTE J2012+381, and GRO J1655-40. During the ASCA
observations, these BHBs showed characteristics of the standard high/soft
state. Under the standard modeling of high-state black hole binaries, the
sources show Tin=0.76-1.17keV, the disk fraction to the total 0.7-10keV flux of
54-98%, and Nh=(0.7--12)E21/cm^2. The best-fit p-values were found in 0.6-0.8,
and the standard value of p=3/4 was accepted for all the sources.The obtained
p-values are also compared with those expected for the standard accretion disk
in the Schwarzschild metric, and they were consistent with those expected from
the standard accretion disk.


title: Implications of the Curvaton on Inflationary Cosmology

abstract:
  We study implications of the curvaton, a late-decaying light scalar field, on
inflationary cosmology, paying particular attentions to modifications of
observable quantities such as the scalar spectral index of the primordial power
spectrum and the tensor-to-scalar ratio. We consider this issue from a general
viewpoint and discuss how the observable quantities are affected by the
existence of the curvaton. It is shown that the modification owing to the
curvaton depends on class of inflation models. We also study the effects of the
curvaton on inflation models generated by the inflationary flow equation.


title: The sub-DLA toward HE0001-2340: galaxy formation at z=2

abstract:
  We present a detailed analysis of chemical abundances in a sub-damped Ly
alpha absorber (sub-DLA) at z=2.187 towards the quasar HE0001-2340 (z_em=2.28)
using VLT/UVES data. This sub-DLA system consists of at least 25 individual
subcomponents spanning a restframe velocity range of ~400 km/s. Detected
species include CII, CIV, NI, NII, OI, MgII, AlII, AlIII, SiII, SiIV, PII,
FeII, and possibly DI. For the dominating neutral gas component at v=+13 km/s
we derive an oxygen abundance of [O/H]=-1.81. With its extremely low nitrogen
content ([N/H]<-3.3 and [N/O]<-1.5) the absorber exhibits a classic massive
star abundance pattern. The low [N/O] value is consistent with the idea that
primary nitrogen production by the very first stars have enriched the
intergalactic gas to a level of [N/O] ~ -1.5. Peculiar abundances are found in
the outermost blue components, where we observe significant overabundances of
phosphorus ([P/C] ~ +1.5), silicon ([Si/C] ~ +0.6), and aluminum ([Al/C] ~
+0.5). Our study suggests that the sight line passes through the gaseous
environment of one or more stellar clusters that locally enriched their
interstellar neighbourhood by supernova ejecta generating the observed
abundance anomalies. The large velocity spread of the entire absorption system
points to a merger that triggers the formation of these clusters. We thus may
be observing a young galaxy at z ~ 2 that currently forms out of a merger event
(abstract truncated).


title: The near-IR luminosity-metallicity relation of dwarf irregular galaxies

abstract:
  We report on the recent developments of our long-term investigation of the
near-IR luminosity-metallicity relation for dwarf irregular galaxies in nearby
groups. A very well-defined relation is emerging from our observational
database, and a preliminary discussion of its implications is given.


title:
Detection of a classical Delta Scuti star in the new eclipsing binary
  system HIP 7666

abstract:
  HIP 7666 is a variable star newly discovered during the Hipparcos mission and
classified as of unknown type (ESA 1997). During 23 nights between July 2000
and November 2000, over 2300 CCD observations in the V band were obtained from
Hostalets de Pierola and Monegrillo observatories in Spain. These data show
that the new variable is a detached eclipsing binary system with an orbital
period of 2.37229 days. In addition, one of the components undergoes very
short-period oscillations with a main pulsation frequency of 24.46 or 25.47
c/d. HIP 7666 is therefore a new member of the presently very few known
detached eclipsing binary systems with a Delta Scuti type component.


title: The Local Group Census: searching for PNe in IC 1613, WLM and GR8

abstract:
  In the framework of the Local Group Census (LGC), a survey of the Local Group
(LG) galaxies above Dec=$-30^\circ$, which is aimed at surveying their
populations with strong emission lines, we have searched for planetary nebulae
(PNe) in the low-metallicity dwarf irregular galaxies IC1613, WLM, GR8. Two new
candidate PNe have been found in IC1613, one in WLM and none in GR8. The
observations presented in this paper, together with the previous results from
the LGC, represent the first step in the study of the PN population in
low-metallicity, dwarf irregular galaxies of the Local Group. They will be
followed by deep spectroscopy to confirm their nature and to study their
physical-chemical properties. We used the observed number of PNe in each LG
galaxy to estimate a lower limit to the mass of the intermediate-age population
which was compared to the Star Formation Rate (SFR) of LG dwarf galaxies. These
results are in agreement with those from accurate star formation history (SFH)
analysis for these small galaxy systems.


title: Asphericity and clumpiness in the winds of Luminous Blue Variables

abstract:
  We present the first systematic spectropolarimetric study of Luminous Blue
Variables (LBVs) in the Galaxy and the Magellanic Clouds, in order to
investigate the geometries of their winds. We find that at least half of our
sample show changes in polarization across the strong H$\alpha$ emission line,
indicating that the light from the stars is intrinsically polarized and
therefore that asphericity already exists at the base of the wind. Multi-epoch
spectropolarimetry on four targets reveals variability in their intrinsic
polarization. Three of these, AG Car, HR Car and P Cyg, show a position angle
(PA) of polarization which appears random with time. Such behaviour can be
explained by the presence of strong wind-inhomogeneities, or `clumps' within
the wind. Only one star, R 127, shows variability at a constant PA, and hence
evidence for axi-symmetry as well as clumpiness. However, if viewed at low
inclination, and at limited temporal sampling, such a wind would produce a
seemingly random polarization of the type observed in the other three stars.
Time-resolved spectropolarimetric monitoring of LBVs is therefore required to
determine if LBV winds are axi-symmetric in general.
  The high fraction of LBVs ($>$ 50%) showing intrinsic polarization is to be
compared with the lower $\sim$ 20-25 % for similar studies of their
evolutionary neighbours, O supergiants and Wolf-Rayet stars. We anticipate that
this higher incidence is due to the lower effective gravities of the LBVs,
coupled with their variable temperatures within the bi-stability jump regime.
This is also consistent with the higher incidence of wind asphericity that we
find in LBVs with strong H$\alpha$ emission and recent (last $\sim$ 10 years)
strong variability.


title:
Spitzer Observations of CO2 Ice Towards Field Stars in the Taurus
  Molecular Cloud

abstract:
  We present the first Spitzer Infrared Spectrograph observations of the 15.2
micron bending mode of CO2 ice towards field stars behind a quiescent dark
cloud. CO2 ice is detected towards 2 field stars (Elias 16, Elias 3) and a
single protostar (HL Tau) with anabundance of ~15-20% relative to water ice.
CO2 ice is not detected towards the source with lowest extinction in our
sample, Tamura 17 (A_V = 3.9m). A comparison of the Elias 16 spectrum with
laboratory data demonstrates that the majority of CO2 ice is embedded in a
polar H2O-rich ice component, with ~15% of CO2 residing in an apolar H2O-poor
mantle. This is the first detection of apolar CO2 towards a field star. We find
that the CO2 extinction threshold is A_V = 4m +/- 1m, comparable to the
threshold for water ice, but significantly less than the threshold for CO ice,
the likely precursor of CO2. Our results confirm CO2 ice forms in tandem with
H2O ice along quiescent lines of sight. This argues for CO2 ice formation via a
mechanism similar to that responsible for H2O ice formation, viz. simple
catalytic reactions on grain surfaces.


title:
Detectable neutrino fluxes due to enhanced cosmic ray densities in the
  Galactic Center region

abstract:
  We examine in detail the detectability of a signal of diffuse high energy
neutrinos produced in the Milky Way by the interaction of cosmic rays (CRs)
with the interstellar medium (ISM). We show that highly inhomogeneous galactic
CR densities arise naturally from large scale drift effects and the
inhomogeneous distribution of CR sources. In particular, the CR density in the
Galactic Center region (where the ISM density is maximal) could be an order of
magnitude larger than the local CR density. Hence, the expected diffuse flux of
neutrinos from the Galactic Center region becomes enhanced and could be
detected at energies above $\sim 10^4$ GeV in a km$^3$-size neutrino telescope
within 10 years of operation. The galactic anisotropy, which is the main
signature of this flux, allows to discriminate this signal from other possible
extraterrestrial diffuse fluxes of high energy neutrinos.


title: A helium spread among the main sequence stars in NGC 2808

abstract:
  We studied the color distribution of the main sequence of the Globular
Cluster NGC 2808, based on new deep HST-WFPC2 photometry of a field in the
uncrowded outskirts of the cluster. The color distribution of main sequence
stars is wider than expected for a single stellar population, given our
(carefully determined) measurement errors. About 20% of the sample stars are
much bluer than expected and are most plausibly explained as a population
having a much larger helium abundance than the bulk of the main sequence. We
estimate that the helium mass fraction of these stars is Y ~ 0.4. NGC 2808 may
have suffered self-enrichment, with different stellar populations born from the
ejecta of the intermediate mass asymptotic giant branch (AGB) stars of the
first generation. In addition to the Y=0.40 stars, roughly 30% of the stars
should have Y distributed between 0.26-0.29 while 50% have primordial Y, to
explain also the peculiar horizontal branch morphology. Three main stages of
star formation are identified, the first with primordial helium content Y ~
0.24, the second one born from the winds of the most massive AGBs of the first
stellar generation (6-7msun), having Y ~ 0.4, and a third one born from the
matter ejected from less massive AGBs (~ 3.5-4.5msun) with Y ~ 0.26-0.29. For a
long hiatus of time (several 10^7yr) between the second and third generation,
star formation might have been inhibited by the explosion of late Supernovae II
deriving from binary evolution.


title:
Subaru Super Deep Field with Adaptive Optics I. Observations and First
  Implications

abstract:
  We present a deep $K^{\prime}$-band (2.12$\mu$m) imaging of 1\arcmin\
$\times$ 1\arcmin Subaru Super Deep Field (SSDF) taken with the Subaru adaptive
optics (AO) system. Total integration time of 26.8 hours results in the
limiting magnitude of $K^{\prime} \sim 24.7$ (5$\sigma$, 0\farcs2 aperture) for
point sources and $K^{\prime} \sim 23.5$ (5$\sigma$, 0\farcs6 aperture) for
galaxies, which is the deepest limit ever achieved in the $K^{\prime}$ band.
The average stellar FWHM of the co-added image is 0\farcs18. Based on the
photometric measurements of detected galaxies, we obtained the differential
galaxy number counts, for the first time, down to $K^{\prime} \sim 25$, which
is more than 0.5 mag deeper than the previous data. We found that the number
count slope $d\log N/dm$ is about 0.15 at $22 < K^{\prime} < 25$, which is
flatter than the previous data. Therefore, detected galaxies in the SSDF have
only negligible contribution to the near-infrared extragalactic background
light (EBL), and the discrepancy claimed so far between the diffuse EBL
measurements and the estimated EBL from galaxy count integration has become
more serious . The size distribution of detected galaxies was obtained down to
the area size of less than 0.1 arcsec$^2$, which is less than a half of the
previous data in the $K^{\prime}$ band. We compared the observed size-magnitude
relation with a simple pure luminosity evolution model allowing for intrinsic
size evolution, and found that a model with no size evolution gives the best
fit to the data. It implies that the surface brightness of galaxies at high
redshift is not much different from that expected from the size-luminosity
relation of present-day galaxies.


title:
INTEGRAL and XMM-Newton observations of the low-luminosity and X-ray
  rich burst GRB 040223

abstract:
  GRB 040223 was observed by INTEGRAL and XMM-Newton. GRB 040223 has a peak
flux of (1.6+/-0.13) x10^-8 ergs cm^-2 s^-1, a fluence of (4.4+/-0.4)x10^-7
ergs cm^-2 and a steep photon power law index of -2.3+/-0.2, in the energy
range 20-200 keV. The steep spectrum implies it is an x- ray rich GRB with
emission up to 200 keV and E_peak < 20 keV. If E_peak is < 10 keV, it would
qualify as an x-ray flash with high energy emission. The x-ray data has a
spectral index beta_x = -1.7+/-0.2, a temporal decay of t^(-0.75+/-0.25) and a
large column density of (1.8 x 10^22) cm^-2. The luminosity-lag relationship
was used to obtain a redshift (z = 0.1+0.04-0.02). The isotropic energy
radiated in gamma-rays and x-ray luminosity after 10 hours are factors of 1000
and 100 less than classical GRBs. GRB 040223 is consistent with the
extrapolation of the Amati relation into the region that includes XRF 030723
and XRF 020903.


title:
The dM4.5e star G124-62 and its binary L dwarf companion DENIS-P
  J1441-0945: Common proper motion, distance, age, and masses

abstract:
  We present astrometric and photometric measurements of the field binary L1
dwarf DENIS-P J1441-0945. Analysis of archival HST images and photometric
parallax measurements give a distance of 34+/-7 pc and a proper motion close to
that of the nearby high proper motion star G124-62. Comparison of SuperCOSMOS
and 2MASS images confirms that these objects form a common proper motion pair,
while spectroscopy of G124-62 shows it to be a dM4.5e star. The kinematics show
that this system is a member of the Hyades supercluster. The resulting age
constraints for the system are 500--800 Myr and the mass of each component of
DENIS-P J1441-0945 is 0.072 (+0.010/-0.018) M_sun.


title:
On the role of injection in kinetic approaches to nonlinear particle
  acceleration at non-relativistic shock waves

abstract:
  The dynamical reaction of the particles accelerated at a shock front by the
first order Fermi process can be determined within kinetic models that account
for both the hydrodynamics of the shocked fluid and the transport of the
accelerated particles. These models predict the appearance of multiple
solutions, all physically allowed. We discuss here the role of injection in
selecting the real solution, in the framework of a simple phenomenological
recipe, which is a variation of what is sometimes referred to as thermal
leakage. In this context we show that multiple solutions basically disappear
and when they are present they are limited to rather peculiar values of the
parameters. We also provide a quantitative calculation of the efficiency of
particle acceleration at cosmic ray modified shocks and we identify the
fraction of energy which is advected downstream and that of particles escaping
the system from upstream infinity at the maximum momentum. The consequences of
efficient particle acceleration for shock heating are also discussed.


title:
The binary period and outburst behaviour of the SMC X-ray binary pulsar
  system SXP504

abstract:
  A probable binary period has been detected in the optical counterpart to the
X-ray source CXOU J005455.6-724510 = RX J0054.9-7245 = AXJ0054.8-7244 = SXP504
in the Small Magellanic Cloud. This source was detected by Chandra on 04 Jul
2002 and subsequently observed by XMM-Newton on 18 Dec 2003. The source is
coincident with an Optical Gravitational Lensing (OGLE) object in the
lightcurves of which several optical outburst peaks are visible at ~ 268 day
intervals. Timing analysis shows a period of 268.6 +/- 0.1 days at > 99%
significance. Archival Rossi X-ray Timing Explorer (RXTE) data for the 504s
pulse-period has revealed detections which correspond closely with predicted or
actual peaks in the optical data. The relationship between this orbital period
and the pulse period of 504s is within the normal variance found in the Corbet
diagram.


title: Discovery of CH and OH in the -513 km s-1 Ejecta of Eta Carinae

abstract:
  The very massive star, Eta Carinae, is enshrouded in an unusual complex of
stellar ejecta, which is highly depleted in C and O, and enriched in He and N.
This circumstellar gas gives rise to distinct absorption components
corresponding to at least 20 different velocities along the line-of-sight. The
velocity component at -513 kms-1 exhibits very low ionization with
predominantly neutral species of iron-peak elements. Our statistical
equilibrium/photoionization modeling indicates that the low temperature (T =
760 K) and high density (n_H=10^7 cm^-3) of the -513 kms-1 component is
conducive to molecule formation including those with the elements C and O.
Examination of echelle spectra obtained with the Space Telescope Imaging
Spectrograph (STIS) aboard the confirms the model's predictions. The molecules,
H_2, CH, and most likely OH, have been identified in the -513 kms-1 absorption
spectrum. This paper presents the analysis of the HST/STIS spectra with the
deduced column densities for CH, OH and C I, and upper limit for CO. It is
quite extraordinary to see molecular species in a cool environment at such a
high velocity. The sharp molecular and ionic absorptions in this extensively
CNO- processed material offers us a unique environment for studying the
chemistry, dust formation processes, and nucleosynthesis in the ejected layers
of a highly evolved massive star.


title:
The Filamentary Large Scale Structure around the z = 2.16 Radio Galaxy
  PKS 1138-262

abstract:
  PKS 1138-262 is a massive radio galaxy at z = 2.16 surrounded by
overdensities of Lya emitters, Ha emitters, EROs and X-ray emitters. Numerous
lines of evidence exist that it is located in a forming cluster. We report on
Keck spectroscopy of candidate members of this protocluster, including nine of
the 18 X-ray sources detected by Pentericci et al. (2002) in this field. Two of
these X-ray sources (not counting PKS 1138-262 itself) were previously
confirmed to be members of the protocluster; we have discovered that an
additional two (both AGN) are members of a filamentary structure, at least 3.5
Mpc in projection, aligned with the radio jet axis, the 150 kpc-sized
emission-line halo, and the extended X-ray emission around the radio galaxy.
Three of the nine X-ray sources observed are lower redshift AGN, and three are
M-dwarf stars.


title:
Spectroscopic Confirmation of Multiple Red Galaxy-Galaxy Mergers in
  MS1054-03 (z=0.83)

abstract:
  We present follow-up spectroscopy of the galaxy cluster MS1054-03 (z=0.83)
confirming that at least six of the nine merging galaxy pairs identified by van
Dokkum et al. (1999) are indeed bound systems: they have projected separations
of R_s<10 kpc and relative line-of sight velocities of dv<165 km/s. For the
remaining three pairs, we were unable to obtain redshifts of both constituent
galaxies. To identify a more objective sample of merging systems, we select
bound red galaxy pairs (R_s<=30 kpc, dv<=300 km/s) from our sample of 121
confirmed cluster members: galaxies in bound red pairs make up 15.7+/-3.6% of
the cluster population. The (B-K_s) color-magnitude diagram shows that the pair
galaxies are as red as the E/S0 members and have a homogeneous stellar
population. The red pair galaxies span a large range in luminosity and internal
velocity dispersion to include some of the brightest, most massive members
(L>L*, sigma>200 km/s); these bound galaxy pairs must evolve into E/S0 members
by z~0.7. These results combined with MS1054's high merger fraction and
reservoir of likely future mergers indicates that most, if not all, of its
early-type members evolved from (passive) galaxy-galaxy mergers at z<~1.


title:
Difficulty of detecting minihalos via $\gamma$-rays from dark matter
  annihilation

abstract:
  Analytical calculations and recent numerical experiments have shown that a
sizable of the mass in our Galaxy is in a form of clumpy, virialized
substructures that, according to \cite{dms:05}, can be as light as $10^{-6}
\msun$. In this work we estimate the gamma-rays flux expected from dark matter
annihilation occurring within these minihalos, under the hypothesis that the
bulk of dark matter is composed by neutralinos. We generate mock sky maps
showing the angular distribution of the expected gamma-ray signal. We compare
them with the sensitivities of satellite-borne experiments such as GLAST and
find that a possible detection of minihalos is indeed very challenging.


title:
Faraday Rotation Measure Gradients from a Helical Magnetic Field in 3C
  273

abstract:
  Using high frequency (12-22 GHz) VLBA observations we confirm the existence
of a Faraday rotation measure gradient of ~ 500 rad/m^2/mas transverse to the
jet axis in the quasar 3C 273. The gradient is seen in two epochs spaced
roughly six months apart. This stable transverse rotation measure gradient is
expected if a helical magnetic field wraps around the jet. The overall order to
the magnetic field in the inner projected 40 parsecs is consistent with a
helical field. However, we find an unexpected increase in fractional
polarization along the edges of the source, contrary to expectations. This high
fractional polarization rules out internal Faraday rotation, but is not readily
explained by a helical field. After correcting for the rotation measure, the
intrinsic magnetic field direction in the jet of 3C 273 changes from parallel
to nearly perpendicular to the projected jet motion at two locations. If a
helical magnetic field causes the observed rotation measure gradient then the
synchrotron emitting electrons must be separate from the helical field region.
The presence or absence of transverse rotation measure gradients in other
sources is also discussed.


title: Polarization of 21cm Radiation from the Epoch of Reionization

abstract:
  We consider the polarization of 21cm line radiation from the epoch of
reionization due to both intrinsically polarized emission and secondary
mechanisms. We argue that Thomson scattering of the 21cm quadrupole by the
reionized universe is likely to produce the largest effect. The 21cm quadrupole
is sourced by baryonic density fluctuations and the fluctuations in the
ionization fraction due to discrete \ion{H}{2} regions. Since Thomson
scattering produces only E-type polarization and is achromatic, its unique
fingerprint can in principle be separated from foregrounds associated with
polarized synchrotron emission which should not be correlated with the cosmic
signal. We estimate that Poisson fluctuations of \ion{H}{2} regions at the end
of reionization ($z_R \sim 6$--20) produce a brightness
temperature-polarization cross-correlation signal of $\sim 0.1 - 0.3 {mK}$ on
angular scales of tens of arcminutes. This cross-correlation signal is within
the instrument sensitivities of the future {\it Square Kilometer Array} (SKA)
and close to the sensitivities of the forthcoming {\it Mileura Widefield Array}
(MWA) and {\it Low Frequency Array} (LOFAR).


title: Comparative Planetary Atmospheres: Models of TrES-1 and HD209458b

abstract:
  We present new self-consistent atmosphere models for transiting planets
TrES-1 and HD209458b. The planets were recently observed with the Spitzer Space
Telescope in bands centered on 4.5 and 8.0 $\mu$m, for TrES-1, and 24 $\mu$m,
for HD209458b. We find that standard solar metallicity models fit the
observations for HD209458b. For TrES-1, which has an T_eff ~300 K cooler, we
find that models with a metallicity 3-5 times enhanced over solar abundances
can match the 1$\sigma$ error bar at 4.5 $\mu$m and 2$\sigma$ at 8.0$\mu$m.
Models with solar abundances that included energy deposition into the
stratosphere give fluxes that fall within the 2$\sigma$ error bars in both
bands. The best-fit models for both planets assume that reradiation of absorbed
stellar flux occurs over the entire planet. For all models of both planets we
predict planet/star flux ratios in other Spitzer bandpasses.


title:
Long-Term Radio Modulation in Sagittarius A* from Spin-Induced Disk
  Precession

abstract:
  There is some evidence, though yet unconfirmed, that Sagittarius A*--the
supermassive black hole at the Galactic center--emits its radio waves modulated
with a ~100-day period. What is intriguing about this apparent
quasi-periodicity is that, though the amplitude of the modulation increases
with decreasing wavelength (from 3.6 to 1.3 cm), the quasi-period itself does
not seem to depend on the frequency of the radiation. It is difficult to
imagine how a binary companion, were that the cause of this modulation, could
have escaped detection until now. Instead, it has been suggested that the
spin-induced precession of a disk surrounding a slowly rotating black hole
could have the right period to account for this behavior. In this paper, we
examine how Sagittarius A*'s light curve could be modulated by this mechanism.
We demonstrate that the partial occultation of a nonthermal halo by a compact,
radio-opaque disk does indeed produce the observed frequency-dependent
amplitude. This appears to be in line with other observational arguments
suggesting that Sagittarius A*'s mm/sub-mm spectrum is produced by a ~10
Schwarzschild-radius disk, whereas its cm-waves originate from a nonthermal
particle distribution in a halo extending out to over 20 Schwarzschild radii.
Interestingly, this model suggests that the observed period corresponds to half
the precession period and that a non-axisymmetric disk could produce a second
period roughly twice as long as the first.


title: Large-Scale Velocity Structures in the Horologium-Reticulum Supercluster

abstract:
  We present 547 optical redshifts obtained for galaxies in the region of the
Horologium-Reticulum Supercluster (HRS) using the 6dF multi-fiber spectrograph
on the UK Schmidt Telescope at the Anglo Australian Observatory. The HRS covers
an area of more than 12deg x 12deg on the sky centered at approximately RA =
03h19m, DEC = -50deg 02amin. Our 6dF observations concentrate upon the
inter-cluster regions of the HRS, from which we describe four primary results.
First, the HRS spans at least the redshift range from 17,000 to 22,500 km s^-1.
Second, the overdensity of galaxies in the inter-cluster regions of the HRS in
this redshift range is estimated to be 2.4, or del rho/ rho ~ 1.4. Third, we
find a systematic trend of increasing redshift along a Southeast-Northwest
(SE-NW) spatial axis in the HRS, in that the mean redshift of HRS members
increases by more than 1500 km s^-1 from SE to NW over a 12 deg region. Fourth,
the HRS is bi-modal in redshift with a separation of ~ 2500 km s^-1 (35 Mpc)
between the higher and lower redshift peaks. This fact is particularly evident
if the above spatial-redshift trend is fitted and removed. In short, the HRS
appears to consist of two components in redshift space, each one exhibiting a
similar systematic spatial-redshift trend along a SE-NW axis. Lastly, we
compare these results from the HRS with the Shapley supercluster and find
similar properties and large-scale features.


title:
SDSS J124058.03-015919.2: A new AM CVn star with a 37-minute orbital
  period

abstract:
  We present high time resolution VLT spectroscopy of SDSS J124058.03-015919.2,
a new helium-transferring binary star identified in the Sloan Digital Sky
Survey. We measure an orbital period of 37.355+/-0.002 minutes, confirming the
AM CVn nature of the system. From the velocity amplitudes of the accretor and
the accretion stream--disc impact, we derive a mass ratio q=0.039+/-0.010. Our
spectral coverage extends from 3700A--9500A and shows the presence of helium,
nitrogen, silicon and iron in the accretion disc, plus the redshifted,
low-velocity "central spikes" in the helium lines, known from the low-state AM
CVn stars GP Com and CE 315. Doppler tomography of the helium and silicon
emission lines reveals an unusual pattern of two bright emission sites in the
tomograms, instead of the usual one emission site identified with the impact of
the mass stream into the accretion disc. One of the two is preferred as the
conventional stream--disc impact point in velocity space, at the 3-sigma
confidence level. We speculate briefly on the origin of the second.


title: Properties of Central Caustics in Planetary Microlensing

abstract:
  To maximize the number of planet detections, current microlensing follow-up
observations are focusing on high-magnification events which have a higher
chance of being perturbed by central caustics. In this paper, we investigate
the properties of central caustics and the perturbations induced by them. We
derive analytic expressions of the location, size, and shape of the central
caustic as a function of the star-planet separation, $s$, and the planet/star
mass ratio, $q$, under the planetary perturbative approximation and compare the
results with those based on numerical computations. While it has been known
that the size of the planetary caustic is \propto \sqrt{q}, we find from this
work that the dependence of the size of the central caustic on $q$ is linear,
i.e., \propto q, implying that the central caustic shrinks much more rapidly
with the decrease of $q$ compared to the planetary caustic. The central-caustic
size depends also on the star-planet separation. If the size of the caustic is
defined as the separation between the two cusps on the star-planet axis
(horizontal width), we find that the dependence of the central-caustic size on
the separation is \propto (s+1/s). While the size of the central caustic
depends both on $s$ and q, its shape defined as the vertical/horizontal width
ratio, R_c, is solely dependent on the planetary separation and we derive an
analytic relation between R_c and s. Due to the smaller size of the central
caustic combined with much more rapid decrease of its size with the decrease of
q, the effect of finite source size on the perturbation induced by the central
caustic is much more severe than the effect on the perturbation induced by the
planetary caustic. Abridged.


title:
The Effect of Gravity Between Particles on the Shape and Resonant
  Structure of Planetary Rings

abstract:
  The resonance perturbation of planetary ring by distant satellite is
considered. The gravity interaction between rings particles is taken into
account. The gravitation interaction between particles in rings can change
shape of non-circular rings, so it is differ from keplerian ellipse. The shift
between simple mean motion resonances and parametric resonance zones is
detected. This shift depends on ring properties.


title:
The location of the broad HI absorption in 3C305: clear evidence for a
  jet-accelerated neutral outflow

abstract:
  We present high-spatial resolution 21-cm HI VLA observations of the radio
galaxy 3C305 (z=0.041). These new high-resolution data show that the ~1000 km/s
broad HI absorption, earlier detected in low-resolution WSRT observations, is
occurring against the bright, eastern radio lobe, about 1.6 kpc from the
nucleus. We use new optical spectra taken with the WHT to make a detailed
comparison of the kinematics of the neutral hydrogen with that of the ionised
gas. The striking similarity between the complex kinematics of the two gas
phases suggests that both the ionised gas and the neutral gas are part of the
same outflow. Earlier studies of the ionised gas had already found evidence for
a strong interaction between the radio jet and the interstellar medium at the
location of the eastern radio lobe. Our results show that the fast outflow
produced by this interaction also contains a component of neutral atomic
hydrogen. The most likely interpretation is that the radio jet ionises the ISM
and accelerates it to the high outflow velocities observed. Our observations
demonstrate that, following this strong jet-cloud interaction, not all gas
clouds are destroyed and that part of the gas can cool and become neutral. The
mass outflow rate measured in 3C~305 is comparable, although at the lower end
of the distribution, to that found in Ultra-Luminous IR galaxies. This suggests
that AGN-driven outflows, and in particular jet-driven outflows, can have a
similar impact on the evolution of a galaxy as starburst-driven superwinds.


title:
Are radio galaxies and quiescent galaxies different? Results from the
  analysis of HST brightness profiles

abstract:
  We present a study of the optical brightness profiles of early type galaxies,
using a number of samples of radio galaxies and optically selected elliptical
galaxies. For the radio galaxy samples--B2 of Fanaroff-Riley type I and 3C of
Fanaroff-Riley type II-- we determined a number of parameters that describe a
"Nuker-law" profile, which were compared with those already known for the
optically selected objects. We find that radio active galaxies are always of
the "core" type (i.e. an inner Nuker law slope gamma < 0.3). However, there are
core-type galaxies which harbor no significant radio source and which are
indistinguishable from the radio active galaxies. We do not find any radio
detected galaxy with a power law profile (gamma > 0.5). This difference is not
due to any effect with absolute magnitude, since in a region of overlap in
magnitude the dichotomy between radio active and radio quiescent galaxies
remains. We speculate that core-type objects represent the galaxies that have
been, are, or may become, radio active at some stage in their lives; active and
non-active core-type galaxies are therefore identical in all respects except
their eventual radio-activity: on HST scales we do not find any relationship
between boxiness and radio-activity. There is a fundamental plane, defined by
the parameters of the core (break radius r_b and break brightness mu_b), which
is seen in the strong correlation between r_b and mu_b. The break radius is
also linearly proportional to the optical Luminosity in the $I$ band. Moreover,
for the few galaxies with an independently measured black hole mass, the break
radius turns out to be tightly correlated with M_{BH}. The black hole mass
correlates even better with the combination of fundamental plane parameters r_b
and mu_b, which represents the central velocity dispersion.


title:
Modeling the Jovian subnebula: I - Thermodynamical conditions and
  migration of proto-satellites

abstract:
  We have developed an evolutionary turbulent model of the Jovian subnebula
consistent with the extended core accretion formation models of Jupiter
described by Alibert et al. (2005b) and derived from Alibert et al.
(2004,2005a). This model takes into account the vertical structure of the
subnebula, as well as the evolution of the surface density as given by an
$\alpha$-disk model and is used to calculate the thermodynamical conditions in
the subdisk, for different values of the viscosity parameter. We show that the
Jovian subnebula evolves in two different phases during its lifetime. In the
first phase, the subnebula is fed through its outer edge by the solar nebula as
long as it has not been dissipated. In the second phase, the solar nebula has
disappeared and the Jovian subdisk expands and gradually clears with time as
Jupiter accretes the remaining material. We also demonstrate that early
generations of satellites formed during the beginning of the first phase of the
subnebula cannot survive in this environment and fall onto the proto-Jupiter.
As a result, these bodies may contribute to the enrichment of Jupiter in heavy
elements. Moreover, migration calculations in the Jovian subnebula allow us to
follow the evolution of the ices/rocks ratios in the proto-satellites as a
function of their migration pathways. By a tempting to reproduce the distance
distribution of the Galilean satellites, as well as their ices/rocks ratios, we
obtain some constraints on the viscosity parameter of the Jovian subnebula.