title: The Outward Radial Offset of Neptune Ring Arcs

abstract:
  The designation of the customary restricted three-body disturbing potential
$\Phi$ as the perturbation Hamiltonian is believed to be the cause of Neptune
ring arcs' radial offset between theories and observations. To identify the
appropriate perturbation Hamiltonian, the energy integral in the fixed frame of
a restricted three-body system, consisting of the central, primary, and test
bodies, is reconsidered. It is shown that the perturbation energy includes the
disturbing potential $\Phi$ and the potential arising from the angular momentum
terms of the test body. Both potentials happen to be singular as the test body
goes to infinity contradicting to the perturbation nature. These two potentials
can be combined to an energy relevant disturbing potential $\Phi^{*}=\beta\Phi$
which is regular at infinity because of the cancellation of the singularities.
For circular orbits of the primary, the energy equation is conservative, and
$\Phi^{*}$ is identified as the perturbation Hamiltonian. Applying this result
to evaluate the backgrund effect of Triton to the arc-Galatea system of
Neptune, it is shown that there is a small difference
$\Delta\Phi=(\Phi^{*}-\Phi)$ which amounts to an outward radial offset of the
corotation location of Galatea by 0.3 Km. The mismatch between the pattern
speed of Galatea's corotation potential and the mean motion velocity of the
arcs could be resolved by considering the finite mass of Fraternite. However,
by using $\Phi^{*}$, Galatea's eccentricity could be reassessed in terms of the
mass of Fraternite.


title:
Metal Abundances in a Damped Lyman-alpha System Along Two Lines of Sight
  at z=0.93

abstract:
  We study metal abundances in the z=0.9313 damped Lya system observed in the
two lines-of-sight, A and B, toward the gravitationally-lensed double QSO
HE0512-3329. Spatially resolved STIS spectra constrain the neutral-gas column
density to be LogN(HI)=20.5 in both Aand B. UVES spectra (spectral resolution
FWHM=9.8 km/s) show, in contrast, significant line-of-sight differences in the
column densities of MnII and FeII; these are not due to observational
systematics. We find that [Mn/H]=-1.44 and [Fe/H]=-1.52 in damped Lya system A,
while [Mn/H]=-0.98 and [Fe/H]>-1.32, and possibly as high as [Fe/H] approx. -1
in damped Lya system B. A careful assessment of possible systematic errors
leads us to conclude that these transverse differences are significant at a 5
sigma level or greater. Although nucleosynthesis effects may also be at play,
we favor differential dust-depletion as the main mechanism producing the
observed abundance gradient. The transverse separation is 5 kpc at the redshift
of the absorber, which is also likely to be the lensing galaxy. The derived
abundances therefore probe two opposite sides of a single galaxy hosting both
damped Lya systems. This is the first time firm abundance constraints have been
obtained for a single damped system probed by two lines-of-sight. The
significance of this finding for the cosmic evolution of metals is discussed.


title: Radiation Pressure Supported Starburst Disks and AGN Fueling

abstract:
  We consider the structure of marginally Toomre-stable starburst disks under
the assumption that radiation pressure on dust grains provides the dominant
vertical support against gravity. This is particularly appropriate when the
disk is optically thick to its own IR radiation, as in the central regions of
ULIRGs. Because the disk radiates at its Eddington limit, the Schmidt-law for
star formation changes in the optically-thick limit, with the star formation
rate per unit area scaling as Sigma_g/kappa, where Sigma_g is the gas surface
density and kappa is the mean opacity. We show that optically thick starburst
disks have a characteristic flux and dust effective temperature of F ~ 10^{13}
L_sun/kpc^2 and T_eff ~ 90K, respectively. We compare our predictions with
observations and find good agreement. We extend our model from many-hundred
parsec scales to sub-parsec scales and address the problem of fueling AGN. We
assume that angular momentum transport proceeds via global torques rather than
a local viscosity. We account for the radial depletion of gas due to star
formation and find a strong bifurcation between two classes of disk models: (1)
solutions with a starburst on large scales that consumes all of the gas with
little fueling of a central AGN and (2) models with an outer large-scale
starburst accompanied by a more compact starburst on 1-10 pc scales and a
bright central AGN. The luminosity of the latter models is in many cases
dominated by the AGN. We show that the vertical thickness of the starburst disk
on pc scales can approach h ~ r, perhaps accounting for the nuclear obscuration
in some Type 2 AGN. We also argue that the disk of young stars in the Galactic
Center may be the remnant of such a compact nuclear starburst.


title: INTEGRAL observations of V0332+53 in outburst

abstract:
  We present the analysis of a 100ksec Integral(3-100kev) observation of the
transient X-ray pulsar V0332+53 inoutburst. The source is pulsating at
P=4.3751+/-0.0002s with a clear double pulse from 6 kev to 60 kev. The average
flux was ~550mCrab between 20 kev and 60 kev. We modeled the broad band
continuum from 5 kev to 100 kev with a power-law modified by an exponential cut
off. We observe three cyclotron lines: the fundamental line at 24.9+/-0.1 kev,
the first harmonic at 50.5+/-0.1 kev as well as the second harmonic
at71.7+/-0.8 kev, thus confirming the discovery of the harmonic lines by Coburn
et al. (2005) in RXTE data.


title:
Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis
  Star Forming Core

abstract:
  With the XMM-Newton and Chandra observatories, we detected two extremely
embedded X-ray sources in the R Corona Australis (R CrA) star forming core,
near IRS 7. These sources, designated as XB and XA, have X-ray absorption
columns of ~3e23 cm-2 equivalent to AV ~180 mag. They are associated with the
VLA centimeter radio sources 10E and 10W, respectively. XA is the counterpart
of the near-infrared source IRS 7, whereas XB has no K-band counterpart above
19.4 mag. This indicates that XB is younger than typical Class I protostars,
probably a Class 0 protostar or in an intermediate phase between Class 0 and
Class I. The X-ray luminosity of XB varied between 29<log LX <31.2 ergs s-1 on
timescales of 3-30 months. XB also showed a monotonic increase in X-ray
brightness by a factor of two in 30 ksec during an XMM-Newton observation. The
XMM-Newton spectra indicate emission from a hot plasma with kT ~3-4 keV and
also show fluorescent emission from cold iron. Though the X-ray spectrum from
XB is similar to flare spectra from Class I protostars in luminosity and
temperature, the light curve does not resemble the lightcurves of magnetically
generated X-ray flares because the variability timescale of XB is too long and
because variations in X-ray count rate were not accompanied by variations in
spectral hardness. The short-term variation of XB may be caused by the partial
blocking of the X-ray plasma, while the month-long flux enhancement may be
driven by mass accretion.


title: Gamma-Ray Observations of a Giant Flare from The Magnetar SGR 1806-20

abstract:
  Magnetars comprise two classes of rotating neutron stars (Soft Gamma
Repeaters (SGRs) and Anomalous X-ray Pulsars), whose X-ray emission is powered
by an ultrastrong magnetic field, B ~ 10^15 G. Occasionally SGRs enter into
active episodes producing many short X-ray bursts; extremely rarely (about once
per 50 years per source), SGRs emit a giant flare, an event with total energy
at least 1000 times higher than their typical bursts. Here we report that, on
2004 December 27, SGR 1806-20 emitted the brightest extra-solar transient event
ever recorded, even surpassing the full moon brightness for 0.2 seconds. The
total (isotropic) flare energy is 2x10^46 erg, 100 times higher than the only
two previous events, making this flare a once in a century event. This colossal
energy release likely occurred during a catastrophic reconfiguration of the
magnetar's magnetic field. Such an event would have resembled a short, hard
Gamma Ray Burst (GRB) if it had occurred within 40 Mpc, suggesting that
extragalactic SGR flares may indeed form a subclass of GRBs.


title: A Radio Study of the Mouse, G359.23--0.82

abstract:
  The recent detection of a young pulsar powering ``the Mouse'', G359.23--0.82,
as well as detailed imaging of surrounding nebular X-ray emission, have
motivated us to investigate the structural details and polarization
characteristics of the radio emission from this axisymmetric source with a
supersonic bow shock. Using polarization data at 3.6 and 6cm, we find that the
magnetic field wraps around the bow shock structure near the apex of the
system, but downnstream runs parallel to the inferred direction of the pulsar's
motion. The rotation measure (RM) distribution of the Mouse also suggests that
the low degree of polarization combined with a high RM ahead of the pulsar
result from internal plasma within the bowshock region. In addition, using
sub-arcsecond radio image of the Mouse, we identify modulations in the
brightness distribution of the Mouse that may be associated with the unshocked
pulsar wind behind the pulsar. Lastly, we discuss the relationship between the
Mouse and its neighboring shell-type supernova remnant G359.1--0.5 and argue
that these two sources could potentially have the same origin.


title:
Spectroscopic Studies of Very Metal-Poor Stars with the Subaru High
  Dispersion Spectrograph. III. Light Neutron-Capture Elements

abstract:
  Elemental abundance measurements have been obtained for a sample of 18 very
metal-poor stars using spectra obtained with the Subaru Telescope High
Dispersion Spectrograph. Seventeen stars, among which 16 are newly analyzed in
the present work, were selected from candidate metal-poor stars identified in
the HK survey of Beers and colleagues. The metallicity range covered by our
sample is -3.1 ~< [Fe/H] ~< -2.4. The abundances of carbon, alpha-elements, and
iron-peak elements determined for these stars confirm the trends found by
previous work. One exception is the large over-abundance of Mg, Al and Sc found
in BS16934--002, a giant with [Fe/H] = -2.8. By combining our new results with
those of previous studies, we investigate the distribution of neutron-capture
elements in very metal-poor stars, focusing on the production of the light
neutron-capture elements (e.g., Sr, Y, and Zr).


title: Constraints on the solid dark universe model

abstract:
  If the dark energy is modelled as a relativistic elastic solid then the
standard CDM and $\Lambda$CDM models, as well as lattice configurations of
cosmic strings or domain walls, are points in the two-dimensional parameter
space $(w,c_{\rm s}^2)$. We present a detailed analysis of the best fitting
cosmological parameters in this model using data from a range of observations.
We find that the $\chi^2$ is improved by $\sim 10$ by including the two
parameters and that the $w=-1$ $\Lambda$CDM model is only the best fit to the
data when a large number of different datasets are included. Using CMB
observations alone we find that $w=-0.38\pm 0.16 $ and with the addition of
Large-Scale Structure data $w=-0.62\pm 0.15 $ and $\log c_{\rm s}=-0.77\pm
0.28$. We conclude that the models based on topological defects provide a good
fit to the current data, although $\Lambda$CDM cannot be ruled out.


title:
HST and UKIRT imaging observations of z~1 6C radio galaxies - II. Galaxy
  morphologies and the alignment effect

abstract:
  (abridged) Powerful radio galaxies often display enhanced optical/UV emission
regions, elongated and aligned with the radio jet axis. The aim of this series
of papers is to separately investigate the effects of radio power and redshift
on the alignment effect, together with other radio galaxy properties. In this
second paper, we present a deeper analysis of the morphological properties of
these systems, including both the host galaxies and their surrounding aligned
emission. The host galaxies of our 6C subsample are well described as de
Vaucouleurs ellipticals, with typical scale sizes of ~10kpc. This is comparable
to the host galaxies of low-z radio sources of similar powers, and also the
more powerful 3CR sources at the same redshift. The contribution of nuclear
point source emission is also comparable, regardless of radio power. The 6C
alignment effect is remarkably similar to that seen around more powerful 3CR
sources at the same redshift in terms of extent and degree of alignment with
the radio source axis, although it is generally less luminous. The bright,
knotty features observed in the case of the z~1 3CR sources are far less
frequent in our 6C subsample; neither do we observe such strong evidence for
evolution in the strength of the alignment effect with radio source size/age.
However, we do find a very strong link between the most extreme alignment
effects and emission line region properties indicative of shocks, regardless of
source size/age or power. In general, the 6C alignment effect is still
considerably stronger than that seen around lower redshift galaxies of similar
radio powers. (abridged)


title: Mass loss from red giants in the Magellanic Clouds

abstract:
  The Magellanic Clouds provide the ideal laboratory for the study of mass loss
and molecule and dust formation in red giants as a function of luminosity and
metal abundance. I present some recent observational work.


title: Dark Matter and Dark Energy from a single scalar field and CMB data

abstract:
  Axions are likely to be the Dark Matter (DM) that cosmological data require.
They arise in the Peccei Quinn solution of the strong CP problem. In a previous
work we showed that their model has a simple and natural generalization which
yields also Dark Energy (DE), in fair proportions, without tuning any
parameter: DM and DE arise from a single scalar field and are weakly coupled in
the present era. In this paper we extend the analysis of this dual-axion
cosmology and fit it to WMAP data, by using a Markov chain technique. We find
that LCDM, dynamical DE with a SUGRA potential, DE with a SUGRA potential and a
constant DE-DM coupling, as well as the dual-axion model with a SUGRA
potential, fit data with a similar accuracy. The best-fit parameters are
however fairly different, although consistency is mostly recovered at the
2-sigma level. A peculiarity of the dual-axion model with SUGRA potential is to
cause more stringent constraints on most parameters and to favor high values of
the Hubble parameter.


title: The IRAC galaxy correlation functions from SWIRE

abstract:
  We present an analysis of large-scale structure from the Spitzer Wide-area
Infrared Extragalactic legacy survey, SWIRE. The two-point angular correlation
functions were computed for galaxies detected in the 3.6-micron IRAC band, on
angular scales up to a degree. Significant evolution in the clustering
amplitude was detected, as the median redshift of the samples increases from
z=0.2 to 0.6. The galaxy clustering in the GALICS semi-analytic models was
compared with the observed correlation functions and found to disagree with the
data at faint flux limits.


title: The element abundance FIP effect in the quiet Sun

abstract:
  The Mg/Ne abundance ratio in the quiet Sun is measured in both network and
supergranule cell centre regions through EUV spectra from the Coronal
Diagnostic Spectrometer on SOHO. Twenty four sets of data over the period 1996
March to 1998 June (corresponding to solar minimum) are studied. Emission lines
of the sequences Ne IV-VII and Mg V-VIII are simultaneously analysed by
comparing with theoretical emissivities from the CHIANTI database to yield the
Mg/Ne abundance and emission measure over the temperature region 5.0 < logT <
6.1. The average enhancements over the photospheric Mg/Ne abundance are found
to be 1.25 +/- 0.10 (network) and 1.66 +/- 0.23 (cell centres), significantly
lower than the typical 4-5 enhancements found in the slow solar wind. This
result implies that only a small fraction of the quiet Sun connects into the
solar wind. The quiet Sun spectra are also utilised to determine the coronal
density and temperature, leading to average values of 2.6^+0.5_-0.4 x 10^8
cm^-3 and log (T/K)=5.95 +/- 0.02. No significant trend with the rise in solar
activity during 1996--98 is found for any of the derived quantities, implying
that quiet Sun regions show little dependence on the solar cycle.


title:
Effect of component separation on the temperature distribution of the
  CMB

abstract:
  We present a study of the effect of component separation on the recovered
cosmic microwave background (CMB) temperature distribution, considering
Gaussian and non-Gaussian input CMB maps. First, we extract the CMB component
from simulated Planck data (in small patches of the sky) using the maximum
entropy method (MEM), Wiener filter (WF) and a method based on the subtraction
of foreground templates plus a linear combination of frequency channels (LCFC).
We then apply a wavelet-based method to study the Gaussianity of the recovered
CMB and compare it with the same analysis for the input map. When the original
CMB map is Gaussian (and assuming that point sources have been removed), we
find that none of the methods introduce non-Gaussianity (NG) in the CMB
reconstruction. On the contrary, if the input CMB map is non-Gaussian, all the
studied methods produce a reconstructed CMB with lower detections of NG than
the original map. This effect is mainly due to the presence of instrumental
noise. In this case, MEM tends to produce slightly higher non-Gaussian
detections in the reconstructed map than WF whereas the detections are lower
for the LCFC. We have also studied the effect of point sources in the MEM
reconstruction. If no attempt to remove point sources is performed, they
clearly contaminate the CMB reconstruction, introducing spurious NG. When the
brightest point sources are removed from the data using the Mexican Hat
Wavelet, the Gaussian character of the CMB is preserved. However, when
analysing larger regions of the sky, the variance of our estimators will be
appreciably reduced and, in this case, we expect the point source residuals to
introduce spurious NG in the CMB. Thus, a careful subtraction (or masking) of
point source emission is crucial when studying the Gaussianity of the CMB.


title: A Survey for Planetary Transits in the Field of NGC 7789

abstract:
  We present results from 30 nights of observations of the open cluster NGC
7789 with the WFC camera on the INT telescope in La Palma. From ~900 epochs, we
obtained lightcurves and Sloan r-i colours for ~33000 stars, with ~2400 stars
with better than 1% precision. We expected to detect ~2 transiting hot Jupiter
planets if 1% of stars host such a companion and that a typical hot Jupiter
radius is ~1.2RJ. We find 24 transit candidates, 14 of which we can assign a
period. We rule out the transiting planet model for 21 of these candidates
using various robust arguments. For 2 candidates we are unable to decide on
their nature, although it seems most likely that they are eclipsing binaries as
well. We have one candidate exhibiting a single eclipse for which we derive a
radius of 1.81+0.09-0.00RJ. Three candidates remain that require follow-up
observations in order to determine their nature.


title: Radial Velocity Studies of Close Binary Stars.X

abstract:
  Radial-velocity measurements and sine-curve fits to the orbital velocity
variations are presented for the ninth set of ten close binary systems: V395
And, HS Aqr, V449 Aur, FP Boo, SW Lac, KS Peg, IW Per, V592 Per, TU UMi, FO
Vir. The first three are very close, possibly detached, early-type binaries and
all three require further investigation. Particularly interesting is V395 And
whose spectral type is as early as B7/8 for a 0.685 day orbit binary. KS Peg
and IW Per are single-line binaries, with the former probably hosting a very
low mass star. We have detected a low-mass secondary in an important
semi-detached system FO Vir at q=0.125+/-0.005. The contact binary FP Boo is
also a very small mass-ratio system, q=0.106+/-0.005. The other contact
binaries in this group are V592 Per, TU UMi and the well known SW Lac. V592 Per
and TU UMi have bright tertiary companions; for these binaries, and for V395
And, we used a novel technique of the broadening functions arranged into a
2-dimensional image in phase. The case of TU UMi turned out intractable even
using this approach and we have not been able to derive a firm radial velocity
orbit for this binary. Three systems of this group were observed
spectroscopically before: HS Aqr, SW Lac, KS Peg.


title: Instabilities of Galactic Disks in the Presence of Star Formation

abstract:
  We discuss the stability of galactic disks in which the energy of
interstellar clouds is gained in encounters with expanding supernova remnants
and lost in inelastic collisions. Energy gain and loss processes introduce a
phase difference between the pressure and density perturbations, making disks
unstable on small scales for several recipes of star formation. This is in
contrast to the standard stability analysis in which small scale perturbations
are stabilized by pressure. In the limit of small scales the dispersion
relation for the growth rate reduces to that of thermal instabilities in a
fluid without gravity. If instabilities lead to star formation, then our
results imply a secondary mode of star formation which operates on small scales
and feeds on the existence of a primary mode on intermediate scales. This may
be interpreted as a positive feedback. Further, the standard stability
criterion on intermediate scales is significantly modified.


title: Polarized Diffuse Emission at 2.3 GHz in a High Galactic Latitude Area

abstract:
  Polarized diffuse emission observations at 2.3 GHz in a high Galactic
latitude area are presented. The 2\degr X 2\degr field, centred in
(\alpha=5^h,\delta=-49\degr), is located in the region observed by the
BOOMERanG experiment. Our observations has been carried out with the Parkes
Radio telescope and represent the highest frequency detection done to date in
low emission areas. Because of a weaker Faraday rotation action, the high
frequency allows an estimate of the Galactic synchrotron contamination of the
Cosmic Microwave Background Polarization (CMBP) that is more reliable than that
done at 1.4 GHz. We find that the angular power spectra of the E- and B-modes
have slopes of \beta_E = -1.46 +/- 0.14 and \beta_B = -1.87 +/- 0.22,
indicating a flattening with respect to 1.4 GHz. Extrapolated up to 32 GHz, the
E-mode spectrum is about 3 orders of magnitude lower than that of the CMBP,
allowing a clean detection even at this frequency. The best improvement
concerns the B-mode, for which our single-dish observations provide the first
estimate of the contamination on angular scales close to the CMBP peak (about 2
degrees). We find that the CMBP B-mode should be stronger than synchrotron
contamination at 90 GHz for models with T/S > 0.01. This low level could move
down to 60-70 GHz the optimal window for CMBP measures.


title:
Effect of entrainment on stress and pulsar glitches in neutron star
  crust

abstract:
  The build up of the stress whose relaxation is presumed to account for pulsar
frequency glitches can be attributed to various mechanisms, of which the most
efficient involve differential rotation of the neutron superfluid in the inner
layers of the (magnetically braked) solid crust of a rotating neutron star. In
such a case it is usually supposed that the stress is attributable to pinning
of superfluid vortices to crust nuclei, but it has been suggested that, even if
the pinning effect is too weak, a comparably large stress might still arise
just from the deficit of centrifugal buoyancy in the slowed down crust. The
present work is a re-examination that investigates the way such processes may
be affected by considerations that were overlooked in the previous work --
notably uncertainties about the ``effective'' masses that have to be attributed
to the ``free'' superfluid neutrons to allow for their entrainment by the ionic
crust material. Though restricted to a Newtonian formulation, this analysis
distinguishes more carefully than has been usual between true velocities, which
are contravariantly vectorial, and so called ``superfluid velocities'' that are
proportional to momenta, which are essentially covectorial, a technicality that
is important when more than one independent current is involved. The results
include a Proudman type theorem to the effect that the superfluid angular
velocity must be constant on slightly deformed Taylor cylinders in the force
free case, and it is shown how to construct a pair of integral constants of the
motion that determine the solution for the pinned case assuming beta
equilibrium.


title: QSO Narrow [OIII] Line Width and Host Galaxy Luminosity

abstract:
  Galaxy bulge luminosity L, black hole mass (Mbh), and stellar velocity
dispersion (sigma_*) increase together in a way suggesting a close evolutionary
relationship. Measurements of the Mbh-sigma_* relationship as a function of
cosmic time may shed light on the origin of this relationship. Direct
measurements of sigma_* at high redshift are difficult, and the width of the
narrow emission lines of AGN has been proposed as a surrogate. We investigate
the utility of using sigma_[OIII] for sigma_* by examining host galaxy
magnitudes and [OIII] line widths for low redshift QSOs. For radio-quiet QSOs,
sigma_[OIII] is consistent in the mean with the value of sigma_* predicted by
the Faber-Jackson relation. For our limited range of host luminosity, scatter
obscures the expected increase of sigma_[OIII] with host luminosity. However,
for a sample of AGN covering a wide range of measured or inferred sigma_*,
there is a clear increase of sigma_[OIII] with sigma_*. Radio-loud QSOs on
average have sigma_* smaller by ~0.1 dex than radio-quiet QSOs of similar host
luminsotiy, at least for luminosities typical of PG QSOs. Star formation rates
in our low redshift QSOs are smaller than required to maintain the typical
observed ratio of bulge mass to black hole mass.


title:
Simulation of a population of isolated neutron stars evolving through
  the emission of gravitational waves

abstract:
  We study, via a Monte Carlo simulation, a population of isolated asymmetric
neutron stars where the magnitude of the magnetic field is low enough so that
the dynamical evolution is dominated by the emission of gravitational waves. A
starting population, with age uniformly distributed back to 100 Myr (or 500
Myr) and endowed with a birth kick velocity, is evolved in the Galactic
gravitational potential to the present time. In describing the initial spatial
distribution, the Gould Belt, with an enhanced neutron star formation rate, is
taken into account. Different models for the initial period distribution are
considered. The star ellipticity, measuring the amount of deformation, is drawn
from an exponential distribution. We estimate the detectability of the emitted
gravitational signals by the first and planned second generation of
interferometric detectors. Results are parametrized by the fraction of the
whole galactic neutron star population made of this kind of sources. Some
possible mechanisms, which would make possible the existence of such a
population, are discussed. A comparison of the gravitational spin-down with the
braking due to a possible interaction of the neutron star with the interstellar
medium is also presented.


title: Magnetic fields in neutron stars: A theoretical perspective

abstract:
  We present our view of the main physical ingredients determining the
evolution of neutron star magnetic fields. This includes the basic properties
of neutron star matter, possible scenarios for the origin of the magnetic
field, constraints and mechanisms for its evolution, and a discussion of our
recent work on the Hall drift.


title:
The Configuration of Fraternite-Egalite2-Egalite1 in the Neptune Ring
  Arcs System

abstract:
  By considering the finite mass of Fraternite, although small, it is shown
that there are two time averaged stationary points in its neighborhood due to
the reaction of the test body to the fields of Neptune, Galatea, and
Fraternite. These two locations measuring 11.7 and 13.8 degrees from the center
of Fraternite could correspond to the locations of Egalite 2 and Egalite 1.
This model accounts for the 10 degree span of Fraternite and estimates its mass
at $m_{f}=6.4\times 10^{16}$ Kg. The eccentricities of Egalite 2 and Egalite 1
are believed to be about $e=5\times 10^{-4}$.


title: Afterglow emission from pair-loaded blast waves in gamma-ray bursts

abstract:
  The MeV radiation front of gamma-ray bursts creates copious e+- pairs as it
propagates through an ambient medium. The created pairs enrich the leptonic
component of the medium by a large factor at distances R < R_load ~ 10^{16} cm
from the burst center. The following blast wave sweeps up the pair-rich medium
and then emits the observed afterglow radiation. We find that the afterglow has
a "memory" of e+- loading outside R_load. The e+- pairs remain in the swept-up
material and slowly cool down by emitting synchrotron radiation. They are
likely to dominate the blast-wave emission in IR, optical, and UV bands during
the first minutes of the observed afterglow. The expected e+- radiation is
described by a simple formula, which is derived analytically and checked by
numerical integration of synchrotron emission over the blast material; a
suitable Lagrangian formalism is developed for such calculations. The main
signature of e+- radiation is its flat ("white") spectrum in a broad range of
frequencies from IR to UV and possibly soft X-rays. This radiation can be
detected by Swift satellite, which would enable new observational tests for the
explosion physics.


title: X-ray Outburst in Mira A

abstract:
  We report here the Chandra ACIS-S detection of a bright soft X-ray transient
in the Mira AB interacting symbiotic-like binary. We resolved the system for
the first time in the X-rays. Using Chandra and HST images we determined that
the unprecedented outburst is likely associated with the cool AGB star (Mira
A), the prototype of Mira-type variables. X-rays have never before been
detected from an AGB star, and the recent activity signals that the system is
undergoing dramatic changes. The total X-ray luminosity of the system is
several times higher than the luminosity estimated using previous XMM and ROSAT
observations. The outburst may be caused by a giant flare in Mira A associated
with a mass ejection or a jet, and may have long term consequences on the
system.


title: Detection of Ne VIII in the Low-Redshift Warm-Hot IGM

abstract:
  High resolution FUSE and STIS observations of the bright QSO HE 0226-4110
(zem = 0.495) reveal the presence of a multi-phase absorption line system at
zabs(O VI) = 0.20701 containing absorption from H I (Ly alpha to Ly theta), C
III, O III, O IV, O VI, N III, Ne VIII, Si III, S VI and possibly S V. Single
component fits to the Ne VIII and O VI absorption doublets yield logN(Ne VIII)
= 13.89+/-0.11 and logN(O VI) = 14.37+/-0.03. The Ne VIII and O VI doublets are
detected at 3.9 sigma and 16 sigma significance levels, respectively. This
represents the first detection of intergalactic Ne VIII, a diagnostic of gas
with temperature in the range from 5x10(5) to 1x10(6) K. The O VI and Ne VIII
are not likely created in a low density medium photoionized solely by the
extragalactic background at z = 0.2 since the required path length of ~11 Mpc
implies the Hubble flow absorption line broadening would be ~10 times greater
than the observed line widths. A collisional ionization origin is therefore
more likely. Assuming [Ne/H] and [O/H] = -0.5, the value N(Ne VIII)/N(O VI) =
0.33+/-0.10 is consistent with gas in collisional ionization equilibrium near
T=5.4x10(5) K with logN(H)= 19.9 and N(H)/N(H I) = 1.7x10(6). The observations
support the basic idea that a substantial fraction of the baryonic matter at
low redshift exists in hot very highly ionized gaseous structures.


title: A powerful bursting radio source towards the Galactic Centre

abstract:
  Transient astronomical sources are typically powered by compact objects and
usually signify highly explosive or dynamic events. While radio astronomy has
an impressive record of obtaining high time resolution observations, usually it
is achieved in quite narrow fields-of-view. Consequently, the dynamic radio sky
is poorly sampled, in contrast to the situation in the X- and gamma-ray bands
in which wide-field instruments routinely detect transient sources. Here we
report a new transient source, GCRT J1745-3009, detected in 2002 during a
moderately wide-field radio transient monitoring program of the Galactic center
(GC) region at 0.33 GHz. The characteristics of its bursts are unlike those
known for any other class of radio transient. If located in or near the GC, its
brightness temperature (~10^16 K) and the implied energy density within GCRT
J1745-3009 vastly exceeds that observed in most other classes of radio
astronomical sources, and is consistent with coherent emission processes rarely
observed. We conclude that GCRT J1745-3009 is the first member of a new class
of radio transient sources, the first of possibly many new classes to be
identified through current and upcoming radio surveys.


title: On the Spectrum of Magnetohydrodynamic Turbulence

abstract:
  We propose a phenomenological model for incompressible magnetohydrodynamic
turbulence. We argue that nonlinear-wave interaction weakens as the energy
cascade proceeds to small scales, however, the anisotropy of fluctuations along
the large-scale magnetic field increases, which makes turbulence strong at all
scales. To explain the weakening of the interaction, we propose that
small-scale fluctuations of the velocity and magnetic fields become
increasingly dynamically aligned as their scale decreases, so that turbulent
eddies become locally anisotropic in the plane perpendicular to the large-scale
magnetic field. In the limit of weak anisotropy, that is, weak large-scale
magnetic field, our model reproduces the Goldreich-Sridhar spectrum, while the
limit of strong anisotropy, that is, strong large-scale magnetic field,
corresponds to the Iroshnikov-Kraichnan scaling of the spectrum. This is in
good agreement with recent numerical results.

categories: astro-ph nlin.CD physics.flu-dyn physics.plasm-ph


title: An upper limit to [C II] emission in a z ~= 5 galaxy

abstract:
  Low-ionization-state far-infrared (FIR) emission lines may be useful
diagnostics of star-formation activity in young galaxies, and at high redshift
may be detectable from the ground. In practice, however, very little is known
concerning how strong such line emission might be in the early Universe. We
attempted to detect the 158 micron [C II] line from a lensed galaxy at z =
4.926 using the Caltech Submillimeter Observatory. This source is an ordinary
galaxy, in the sense that it shows high but not extreme star formation, but
lensing makes it visible. Our analysis includes a careful consideration of the
calibrations and weighting of the individual scans. We find only modest
improvement over the simpler reduction methods, however, and the final spectrum
remains dominated by systematic baseline ripple effects. We obtain a 95 per
cent confidence upper limit of 33 mJy for a 200 km/s full width at half maximum
line, corresponding to an unlensed luminosity of 1x10^9 L_sun for a standard
cosmology. Combining this with a marginal detection of the continuum emission
using the James Clerk Maxwell Telescope, we derive an upper limit of 0.4 per
cent for the ratio of L_CII/L_FIR in this object.


title: An interferometric CO survey of luminous submm galaxies

abstract:
  In this paper we present results from an IRAM Plateau de Bure millimetre-wave
Interferometer (PdBI) survey for CO emission towards radio-detected
submillimetre galaxies (SMGs) with known optical and near-infrared
spectroscopic redshifts. Five sources in the redshift range z~1-3.5 were
detected, nearly doubling the number of SMGs detected in CO. We summarise the
properties of all 12 CO-detected SMGs, as well as 6 sources not detected in CO
by our survey, and use this sample to explore the bulk physical properties of
the SMG population as a whole. The median CO line luminosity of the SMGs is
<L_CO> = (3.8 +- 2.0) x 10^10 K km/s pc^2. Using a CO-to-H_2 conversion factor
appropriate for starburst galaxies, this corresponds to a molecular gas mass
<M(H_2)> = (3.0 +- 1.6) x 10^10 Msun within a ~2kpc radius, about four times
greater than the most luminous local ultraluminous infrared galaxies (ULIRGs)
but comparable to that of the most extreme high-redshift radio galaxies and
QSOs. The median CO fwhm linewidth is broad, <fwhm> = 780 +- 320 km/s, and the
SMGs often have double peaked line profiles, indicative of either a merger or a
disk. From their median gas reservoirs (~3 x 10^10 Msun) and star-formation
rates (>700 Msun/yr) we estimate a lower limit on the typical gas-depletion
time scale of >40Myr in SMGs. This is marginally below the typical age expected
for the starbursts in SMGs, and suggests that negative feedback processes may
play an important role in prolonging the gas consumption time scale. We find a
statistically-significant correlation between the far-infrared and CO
luminosities of the SMGs which extends the observed correlation for local
ULIRGs to higher luminosities and higher redshifts. [ABRIDGED]


title:
Infrared Properties of AGN in the GOODS Fields: AGN in Stellar Dominated
  High-z Galaxies

abstract:
  We present analysis of spectral energy distributions (SEDs) from mid-infrared
through X-ray of a sample of 420 hard X-ray selected, z-band and Spitzer/IRAC
detected active galactic nuclei (AGN) and AGN candidates from the GOODS
multiwavelength survey. We fit local empirical SED templates of both normal and
active galaxies to the rest-frame luminosities calculated from spectroscopic
(where available) and photometric redshifts. The majority of the optically
stellar-dominated (with early-type galaxy fits) sources are moderately luminous
(L_X,2-10 keV ~ 10^43 erg/s) hard X-ray sources with high X-ray hardness ratios
(HR > 0.2), high MIR luminosities and red MIR colors in excess of a typical
stellar dominated elliptical galaxy. These sources likely harbor heavily
obscured (though Compton-thin) AGN. The observed ratio of obscured to
unobscured AGN has an integrated mean of ~3.4:1 but declines with increasing
redshift. This effect has been explained by Treister et al. (2004) as an
observational bias triggered by the lack of spectroscopic redshifts at R > 24
which are predominantly higher redshift obscured sources.


title: Infrared Number Counts of AGN in the GOODS Fields

abstract:
  Using the known numbers and evolution of unobscured AGN, and assuming that
there is a large number of corresponding obscured AGN -- as expected if AGN
unification is correct -- we predict the infrared number counts of AGN. These
agree well with the observed GOODS Spitzer data at 3.6, 8 and 24 $\mu$m,
provided that the dust content of the obscuring torus is $\sim 2$x less than
assumed. This strongly supports the AGN unification picture, and implies a
large population of infrared bright obscured AGN at all redshifts and
luminosities.


title: The Geometric Distance and Proper Motion of the Triangulum Galaxy (M33)

abstract:
  We measured the angular rotation and proper motion of the Triangulum Galaxy
(M33) with the Very Long Baseline Array by observing two H2O masers on opposite
sides of the galaxy. By comparing the angular rotation rate with the
inclination and rotation speed, we obtained a distance of 730 +/- 168
kiloparsecs. This distance is consistent with the most recent Cepheid distance
measurement. M33 is moving with a velocity of 190 +/- 59 km/s relative to the
Milky Way. These measurements promise a new method to determine dynamical
models for the Local Group and the mass and dark matter halos of M31, M33 and
the Milky Way.


title:
Hyperfine splitting of [Al VI]3.66um and the Al isotopic ratio in
  NGC6302

abstract:
  The core of planetary nebula NGC 6302 is filled with high-excitation
photoionised gas at low expansion velocities. It represents a unique
astrophysical situation in which to search for hyperfine structure (HFS) in
coronal emission lines from highly ionised species. HFS is otherwise blended by
thermal or velocity broadening. Spectra containing [AlVI]~3.66um 3P2-3P1,
obtained with Phoenix on Gemini-South at resolving powers of up to 75000,
resolve the line into five hyperfine components separated by 20 to 60km/s due
to the coupling of the I=5/2 nuclear spin of 27Al with the total electronic
angular momentum J. 26Al has a different nuclear spin of I=5, and a different
HFS, which allows us to place a 3sigma upper limit on the 26Al/27Al abundance
ratio of 1/33. We measure the HFS magnetic-dipole coupling constants for
[AlVI], and provide the first estimates of the electric-quadrupole HFS coupling
constants obtained through astronomical observations of an atomic transition.


title: Magnetic Fields in Gamma-Ray Bursts: A Short Review

abstract:
  Magnetic fields play a crucial role in the physics of Gamma-Ray Bursts
(GRBs). Strong observational evidence indicates that the observed afterglow and
most likely the prompt emission arise from synchrotron emission. It is possible
that Poynting flux plays an important or even dominant role in the relativistic
outflow from the inner engine, but like in other astronomical relativistic jets
this suggestion is controversial. Finally, it is likely that magnetic fields
larger than $10^{15}$ G occur within GRBs' inner engines and contribute to the
acceleration and collimation of the relativistic jets. I review here the GRB
fireball model and discuss the role that magnetic fields play in its various
components. I suggest that the early afterglow, that reflects the initial
interaction of the relativistic jet with its surrounding matter is the best
available tool to explore the nature of relativistic outflow in astronomical
relativistic jets.


title:
Spatially Resolved Low Frequency VLA observations of the Supernova
  Remnant 3C 391

abstract:
  We present VLA images of the supernova remnant (SNR) 3C~391 at 74, 330, and
1465 MHz. This remnant has been known for some time to exhibit a turnover in
its integrated radio continuum spectrum at frequencies < 100 MHz, indicative of
free-free absorption from thermal ionized gas along the line of sight. For the
first time, our data reveal the spatially resolved morphology of the low
frequency free-free absorption with a resolution of ~70 arcsec. Contrary to the
expectation that such absorption arises from unrelated low density HII regions
(or their envelopes) along the line of sight, these data suggest that in this
case the absorbing medium is directly linked to the SNR itself. 3C~391 has been
shown in a number of recent papers to be interacting with a molecular cloud.
Indeed, it exhibits a number of signposts of SNR/molecular cloud shocks
including OH (1720 MHz) masers and broad molecular emission lines. Comparison
of the regions of strongest 74 MHz absorption with existing X-ray, IR, and
molecular data suggests that the free-free absorption originates from the
SNR/molecular cloud shock boundaries due to ionized gas created from the
passage of a J-type shock with a speed of ~100 km/s. This makes only the second
SNR for which such (extrinsic) spatially resolved absorption has been measured,
and the only one for which the absorption is thought to arise from a
SNR/molecular cloud interface region.


title:
Spatially Resolved Spectroscopy of the E+A Galaxies in the z=0.32
  Cluster AC114

abstract:
  We present spatially resolved intermediate resolution spectroscopy of a
sample of twelve E+A galaxies in the z=0.32 rich galaxy cluster AC 114,
obtained with the FLAMES multi-integral field unit system on the European
Southern Observatory's VLT. Previous integrated spectroscopy of all these
galaxies by Couch & Sharples (1987) had shown them to have strong Balmer line
absorption and an absence of [OII 3727] emission -- the defining
characteristics of the``E+A'' spectral signature, indicative of an abrupt halt
to a recent episode of quite vigorous star formation. We have used our spectral
data to determine the radial variation in the strength of Hdelta absorption in
these galaxies and hence map out the distribution of this recently formed
stellar population. Such information provides important clues as to what
physical event might have been responsible for this quite dramatic change in
star formation activity in these galaxies' recent past. We find a diversity of
behaviour amongst these galaxies in terms of the radial variation in Hdelta
absorption: Four galaxies show little Hdelta absorption across their entire
extent; it would appear they were misidentified as E+A galaxies in the earlier
integrated spectroscopic studies. The remainder show strong Hdelta absorption,
with a gradient that is either negative (Hdelta equivalent width decreasing
with radius), flat, or positive. By comparing with numerical simulations we
suggest that the first of these different types of radial behaviour provides
evidence for a merger/interaction origin, whereas the latter two types of
behaviour are more consistent with the truncation of star formation in normal
disk galaxies. It would seem therefore that more than one physical mechanism is
responsible for E+A formation in the same environment.


title:
Multi-wavelength carbon recombination line observations with the VLA
  toward an UCHII region in W48: Physical properties and kinematics of neutral
  material

abstract:
  Using the Very Large Array (VLA) the C76$\alpha$ and C53$\alpha$
recombination lines (RLs) have been detected toward the ultra-compact \HII\
region (UCHII region) G35.20$-$1.74. We also obtained upper limits to the
carbon RLs at 6 cm (C110$\alpha$ & C111$\alpha$) and 3.6 cm (C92$\alpha$)
wavelengths with the VLA. In addition, continuum images of the W48A complex
(which includes G35.20$-$1.74) are made with angular resolutions in the range
14\arcsec to 2\arcsec. Modeling the multi-wavelength line and continuum data
has provided the physical properties of the UCHII region and the
photodissociation region (PDR) responsible for the carbon RL emission. The gas
pressure in the PDR, estimated using the derived physical properties, is at
least four times larger than that in the UCHII region. The dominance of
stimulated emission of carbon RLs near 2 cm, as implied by our models, is used
to study the relative motion of the PDR with respect to the molecular cloud and
ionized gas. Our results from the kinematical study are consistent with a
pressure-confined UCHII region with the ionizing star moving with respect to
the molecular cloud. However, based on the existing data, other models to
explain the extended lifetime and morphology of UCHII regions cannot be ruled
out.


title:
Reconstruction of the One-point Distribution of Convergence from Weak
  Lensing by Large-scale Structure

abstract:
  Weak lensing measurements are starting to provide statistical maps of the
distribution of matter in the universe that are increasingly precise and
complementary to cosmic microwave background maps. The probability distribution
(PDF) provides a powerful tool to test non-Gausian features in the convergence
field and to discriminate the different cosmological models. In this letter, we
present a new PDF space Wiener filter approach to reconstruct the probability
density function of the convergence from the noisy convergence field. We find
that for parameters comparable to the CFHT legacy survey, the averaged PDF of
the convergence in a 3 degree field can be reconstructed with an uncertainty of
about 10%, even though the pointwise PDF is noise dominated.


title: TASI Lectures on AstroParticle Physics

abstract:
  Selected topics in Astroparticle Physics including the CMB, dark matter, BBN,
and the variations of fundamental couplings are discussed.


title:
One-armed spiral structure of accretion discs induced by a
  phase-dependent mass transfer in Be/X-ray binaries

abstract:
  We study non-axisymmetric structure of accretion discs in Be/X-ray binaries,
performing three dimensional Smoothed Particle Hydrodynamics simulations for a
coplanar system with a short period and a moderate eccentricity. We find that
ram pressure due to the phase-dependent mass transfer from the Be-star disc
excites a one-armed, trailing spiral structure in the accretion disc around the
neutron star. The spiral wave is transient; it is excited around the periastron
passage, when the material is transferred from the Be disc, and is gradually
damped afterwards. The disc changes its morphology from circular to eccentric
with the development of the spiral wave, and then from eccentric to circular
with the decay of the wave during one orbital period. It turns out that the
inward propagation of the spiral wave significantly enhances the mass-accretion
rate onto the neutron star. Thus, the detection of an X-ray luminosity peak
corresponding to the peak in enhanced mass-accretion rate provides
circumstantial evidence that an accretion disc is present in Be/X-ray binaries.


title: A Field Programmable Gate Array Spectrometer for Radio Astronomy

abstract:
  We describe the technological concept and the first-light results of a
1024-channel spectrometer based on field programmable gate array (FPGA)
hardware. This spectrometer is the prototype for the seven beam L-band receiver
to be installed at the Effelsberg 100-m telescope in autumn 2005. Using
"of-the-shelf" hardware and software products, we designed and constructed an
extremely flexible Fast-Fourier-Transform (FFT) spectrometer with unprecedented
sensitivity and dynamic range, which can be considered prototypical for
spectrometer development in future radio astronomy.


title:
Modeling optical properties of cosmic dust grains using a distribution
  of hollow spheres

abstract:
  In this paper we study the combined effects of size and shape of small solid
state particles on the absorption, emission and scattering characteristics. We
use the statistical approach to calculate these optical properties. In this
approach the average optical properties of an ensemble of particles in random
orientation are represented by the average optical properties of an ensemble of
simple shapes. The validity of this approach is studied in detail for a uniform
distribution of hollow spheres where the fractional volume of the central
inclusion is varied. We apply the results to two different areas of interest,
i) infrared spectroscopy and ii) polarization of scattered light. The effects
of particle size and shape on the optical characteristics are discussed. We
compare the results using the distribution of hollow spheres with those
obtained by using randomly oriented spheroids. Also we compare the results with
observations and laboratory measurements. The distribution of hollow spheres is
very successful in reproducing laboratory measurements of the scattering angle
distribution of the degree of linear polarization for incident unpolarized
light of randomly oriented irregular quartz particles. Furthermore, we show
that we are able to derive the size distribution of dust grains by fitting the
measured degree of linear polarization using computational result for hollow
spheres. It is shown that the distribution of hollow spheres is a powerful tool
for studying light scattering, absorption and emission by cosmic dust grains
and in particular when large numbers of particle parameters need to be
considered since the computational demand of the distribution of hollow spheres
is small.


title:
On the stellar populations in NGC 185 and NGC 205, and the nuclear star
  cluster in NGC 205 from Hubble Space Telescope observations

abstract:
  [Abridged] We present a first detailed analysis of resolved stellar
populations in the dwarf galaxies NGC 185 and NGC 205 based on archival V- and
I-band WFPC2 pointings. For NGC 185 we deduce that star formation was probably
still active about 4 x 10^8 yr ago. Key abundance-related results are: (1) We
identify ancient stars with [Fe/H] <~ -1.5 dex by a well-defined horizontal
branch (HB). (2) We find a prominent RGB/ faint-AGB clump/ bump- like feature
with the same mean V-band magnitude as the HB, within uncertainties; from a
comparison with theory, ancient stars have [Fe/H] ~ -1.5 dex, with a higher
abundance level for intermediate-age stars. (3) From colour information we
infer that the median [Fe/H] > -1.11 +/- 0.08 dex for ancient stars. For NGC
205, we record (m-M)o = 24.76 +/- 0.1 mag, based on the RGB I-band tip
magnitude method. We find that stars were probably still forming less than 3 x
10^8 yr ago, which is compatible with star formation triggered by an
interaction with M31. Key abundance-related results are: (1) The RGB/ faint-AGB
is significantly skewed to redder values than that of a control field in the
outskirts of M31; it probably results from a relatively narrow metallicity and
or age range for a significant fraction of the dwarf's stars. (2) For ancient
stars we infer from colour information that the median [Fe/H] > -1.06+/-0.04
dex. We briefly compare the stellar populations of NGC 205, NGC 185 and NGC
147.
  Finally, we find an apparent blue excess in the outer region of the nuclear
star cluster in NGC 205. It is as compact as a typical galactic globular
cluster, but is quite bright (10^6 L_solar,R); and by matching its blue colour
with models, its stellar population is young, up to a few times 10^8 yr old.


title: New H2O masers in Seyfert and FIR bright galaxies

abstract:
  Extragalactic water vapor masers with 50, 1000, 1, and 230 solar (isotropic)
luminosities were detected toward Mrk1066 (UGC2456), Mrk34, NGC3556 and Arp299,
respectively. The interacting system Arp299 appears to show two maser hotspots
separated by 20 arcsec. A statistical analysis of 53 extragalactic H2O sources
indicates (1) that the correlation between IRAS Point Source and H2O
luminosities, established for individual star forming regions in the galactic
disk, also holds for AGN dominated megamaser galaxies, (2) that maser
luminosities are not correlated with 60/100 micron color temperatures and (3)
that only a small fraction of the luminous megamasers detectable with 100-m
sized telescopes have so far been identified. The slope of the H2O luminosity
function, -1.5, indicates that the number of detectable masers is almost
independent of their luminosity. If the LF is not steepening at very high maser
luminosities, H2O megamasers at significant redshifts should be detectable with
present day state-of-the-art facilities.


title: The Mass Spectrum of X-Ray Binaries

abstract:
  This review summarizes the observational constraints on the mass spectrum of
compact objects in X-ray binaries. We currently have 20 X-ray binaries with
confirmed black holes, based on dynamical information (i.e. mass in excess of 3
Msun). In two cases, V404 Cyg and GRS 1915+105, the black hole mass exceeds the
maximum predicted by current Type Ib supernovae models and challenges black
hole formation scenarios. The great majority of black hole binaries are members
of the class of X-ray Transients, where long periods of quiescence enable
spectroscopic studies of the faint donor stars. On the other hand, neutron star
binaries are mostly found in persistent binaries, where reprocessed light from
the accretion disc overwhelms the companion star and precludes mass estimates.
New results, based on the detection of optical fluorescent lines from the donor
star and X-ray burst oscillations, provide the best prospects for mass
constraints of neutron stars in persistent X-ray binaries.


title:
Coupled Quintessence in a Power-Law Case and the Cosmic Coincidence
  Problem

abstract:
  The problem of the cosmic coincidence is a longstanding puzzle. This
conundrum may be solved by introducing a coupling between the two dark sectors.
In this Letter, we study a coupled quintessence scenario in which the scalar
field evolves in a power law potential and the mass of dark matter particles
depends on a power law function of $\phi$. It is shown that this scenario has a
stable attractor solution and can thus provide a natural solution to the cosmic
coincidence problem.


title: Echo Tomography of Sco X-1 using Bowen Fluorescence Lines

abstract:
  We present preliminary results of a simultaneous X-ray/optical campaign of
the prototypical LMXB Sco X-1 at 1-10 Hz time resolution. Lightcurves of the
high excitation Bowen/HeII emission lines were obtained through narrow
interference filters with ULTRACAM, and these were cross-correlated with X-ray
lightcurves. We find evidence for correlated variability, in particular when
Sco X-1 enters the Flaring Branch. The Bowen/HeII lightcurves lag the X-ray
lightcurves with a light travel time which is consistent with reprocessing in
the companion star.


title: Stochastic Particle Acceleration in Parallel Relativistic Shocks

abstract:
  We present results of test-particle simulations on both the first- and the
second-order Fermi acceleration for relativistic parallel shock waves. Our
studies suggest that the role of the second-order mechanism in the turbulent
downstream of a relativistic shock may have been underestimated in the past,
and that the stochastic mechanism may have significant effects on the form of
the particle spectra and its time evolution.


title: Statefinder diagnostic for coupled quintessence

abstract:
  The problem of the cosmic coincidence is a longstanding puzzle. This
conundrum may be solved by introducing a coupling between the two dark sectors.
In this Letter, we study two cases of the coupled quintessence scenario. $(a)$
Assume that the mass of dark matter particles depends exponentially on the
scalar field associated to dark energy and meanwhile the scalar field evolves
in an exponential potential; $(b)$ Assume that the mass of dark matter
particles depends on a power law function of the scalar field and meanwhile the
scalar field evolves in a power law potential. Since the dynamics of this
system is dominated by an attractor solution, the mass of dark matter particles
is forced to change with time as to ensure that the ratio between the energy
densities of dark matter and dark energy becomes a constant at late times, and
one thus solve the cosmic coincidence problem naturally. We perform a
statefinder diagnostic to both cases of this coupled quintessence scenario. It
is shown that the evolving trajectory of this scenario in the $s-r$ diagram is
quite different from those of other dark energy models.


title: The Herbig Ae star HD 163296 in X-rays

abstract:
  Chandra X-ray imaging spectroscopy of the nearby Herbig Ae star HD 163296 at
100 AU angular resolution is reported. A point-like, soft (kT~0.5 keV),
emission-line source is detected at the location of the star with an X-ray
luminosity of 4.0e29 erg/s. In addition, faint emission along the direction of
a previously-detected Ly-alpha-emitting jet and Herbig-Haro outflow may be
present. The relatively low luminosity, lack of a hard spectral component, and
absence of strong X-ray variability in HD 163296 can be explained as
originating from optically-thin shock-heated gas accreting onto the stellar
surface along magnetic field lines. This would require a (dipole) magnetic
field strength at the surface of HD 163296 of at least ~100 G and perhaps as
high as several kG. HD 163296 joins the T Tauri star TW Hya in being the only
examples known to date of pre-main-sequence stars whose quiescent X-ray
emission appears to be completely dominated by accretion.


title: Photometric and Obscurational Completeness

abstract:
  We report a method that uses "completeness" to estimate the number of
exrasolar planets discovered by an observing program with a direct-imaging
instrument. We develop a completeness function for Earth-like planets on
"habitable" orbits for an instrument with a central field obscuration, uniform
sensitivity in an annular detection zone, and limiting sensitivity that is
expressed as a "delta magnitude" with respect to the star, determined by
systematic effects (given adequate exposure time). We demonstrate our method of
estimation by applying it to our understanding of the coronagraphic version of
the Terrestrial Planet Finder (TPF-C) mission as of October 2004. We establish
an initial relationship between the size, quality, and stability of the
instrument's optics and its ability to meet mission science requirements. We
provide options for increasing the fidelity and versatility of the models on
which our method is based, and we discuss how the method could be extended to
model the TPF-C mission as a whole, to verify that its design can meet the
science requirements.


title: Thermal and non-thermal energies in solar flares

abstract:
  The energy of the thermal flare plasma and the kinetic energy of the
non-thermal electrons in 14 hard X-ray peaks from 9 medium-sized solar flares
have been determined from RHESSI observations. The emissions have been
carefully separated in the spectrum. The turnover or cutoff in the low-energy
distribution of electrons has been studied by simulation and fitting, yielding
a reliable lower limit to the non-thermal energy. It remains the largest
contribution to the error budget. Other effects, such as albedo, non-uniform
target ionization, hot target, and cross-sections on the spectrum have been
studied. The errors of the thermal energy are about equally as large. They are
due to the estimate of the flare volume, the assumption of the filling factor,
and energy losses. Within a flare, the non-thermal/thermal ratio increases with
accumulation time, as expected from loss of thermal energy due to radiative
cooling or heat conduction. Our analysis suggests that the thermal and
non-thermal energies are of the same magnitude. This surprising result may be
interpreted by an efficient conversion of non-thermal energy to hot flare
plasma.


title:
Multiwavelength Spectral Models for SNR G347.3-0.5 from Non-Linear Shock
  Acceleration

abstract:
  The remnant G347.3-0.5 exhibits strong shell emission in the radio and X-ray
bands, and has a purported detection in the TeV gamma-ray band by the
CANGAROO-II telescope. The CANGAROO results were touted as evidence for the
production of cosmic ray ions, a claim that has proven controversial due to
constraining fluxes associated with a proximate unidentified EGRET source 3EG
J1714-3857. HESS has now seen this source in the TeV band. The complex
environment of the remnant renders modeling of its broadband spectrum sensitive
to assumptions concerning the nature and parameters of the circumremnant
medium. This paper explores a sampling of reasonable possibilities for
multiwavelength spectral predictions from this source, using a non-linear model
of diffusive particle acceleration at the shocked shell. The magnetic field
strength, shell size and degree of particle cross-field diffusion act as
variables to which the radio to X-ray to gamma-ray signal is sensitive. The
modeling of the extant data constrains these variables, and the potential
impact of the recent HESS detection on such parameters is addressed. Putative
pion decay signals in hard gamma-rays resulting from hadronic interactions in
dense molecular clouds are briefly discussed; the requisite suppression of the
GeV component needed to accommodate the 3EG J1714-3857 EGRET data provides
potential bounds on the diffusive distance from the shell to the proximate
clouds.


title: An Atlas of Warm AGN and Starbursts from the IRAS Deep Fields

abstract:
  We present 180 AGN candidates based on color selection from the IRAS
slow-scan deep observations, with color criteria broadened from the initial
Point-Source Catalog samples to include similar objects with redshifts up to
z=1 and allowing for two-band detections. Spectroscopic identifications have
been obtained for 80 (44%); some additional ones are secure based on radio
detections or optical morphology, although yet unobserved spectroscopically.
These spectroscopic identifications include 13 Sy 1 galaxies, 17 Sy 2 Seyferts,
29 starbursts, 7 LINER systems, and 13 emission-line galaxies so heavily
reddened as to remain of ambiguous classification. The optical magnitudes range
from R=12.0-20.5; counts suggest that incompleteness is important fainter than
R=15.5. Redshifts extend to z=0.51, with a significant part of the sample at
z>0.2. The sample includes slightly more AGN than star-forming systems among
those where the spectra contain enough diagnostic feature to make the
distinction. The active nuclei include several broad-line objects with strong
Fe II emission, and composite objects with the absorption-line signatures of
fading starbursts. These AGN with warm far-IR colors have little overlap with
the "red AGN" identified with 2MASS; only a single Sy 1 was detected by 2MASS
with J-K > 2. Some reliable IRAS detections have either very faint optical
counterparts or only absorption-line galaxies, potentially being deeply
obscured AGN. The IRAS detections include a newly identified symbiotic star,
and several possible examples of the "Vega phenomenon", including dwarfs as
cool as type K. Appendices detail these candidate stars, and the
optical-identification content of a particularly deep set of high-latitude IRAS
scans (probing the limits of optical identification from IRAS data alone).


title:
How To Distinguish Neutron Star and Black Hole X-ray Binaries? Spectral
  index and Quasi-Periodic Oscillation Frequency Correlation

abstract:
  Recent studies have revealed strong correlations between 1-10 Hz frequencies
of quasiperiodic oscillations (QPOs) and the spectral power law index of
several Black Hole (BH) candidate sources when seen in the low/hard state, the
steep power-law (soft) state, and in transition between these states. In the
soft state these index-QPO frequency correlations show a saturation of the
photon index about 2.7 at high values of the low frequency. This saturation
effect was previously identified as a black hole signature. In this paper we
argue that this saturation does not occur, at least for one neutron star (NS)
source 4U 1728-34, for which the index monotonically increases with the low
frequency to the values of 6 and higher. We base this conclusion on our
analysis about 1.5 Msec of RXTE archival data for 4U 1728-34. We reveal the
spectral evolution of the Comptonized blackbody spectra when the source
transitions from the hard to soft states. The hard state spectrum is a typical
thermal Comptonization spectrum of the soft photons which originate in the disk
and the NS outer photospheric layers. The hard state photon index is about 2.
The soft state spectrum consists of two blackbody components which are only
slightly Comptonized. Thus we can claim (as expected from theory) that in NS
sources thermal equilibrium is established for the soft state. To the contrary
in BH sources, the equilibrium is never established due to the presence of the
BH horizon. The emergent BH spectrum, even in the high/soft state, has a power
law component. We also show that the presence of Fe K_alpha emission-line
strengths, QPOs, and the link between them does not depend on radio flux in 4U
1728-34.


title:
Modelling of aspherical nebulae. I. A quick pseudo-3D photoionization
  code

abstract:
  We describe a pseudo-3D photoionization code, NEBU_3D and its associated
visualization tool, VIS_NEB3D, which are able to easily and rapidly treat a
wide variety of nebular geometries, by combining models obtained with a 1D
photoionization code. The only requirement for the code to work is that the
ionization source is uniqu e and not extended. It is applicable as long as the
diffuse ionizing radiation f ield is not dominant and strongly inhomogeneous.
As examples of the capabilities of these new tools, we consider two very differ
ent theoretical cases. One is that of a high excitation planetary nebula that
ha s an ellipsoidal shape with two polar density knots. The other one is that
of a blister HII region, for which we have also constructed a spherical model
(the sp herical impostor) which has exactly the same Hbeta surface brightness
distrib ution as the blister model and the same ionizing star. These two
examples warn against preconceived ideas when interpreting spectroscop ic and
imaging data of HII regions and planetary nebulae. The tools NEBU_3D and
VIS_NEB3D, which will be made publicly available in the future, should
facilitat e the performance of numerical experiments, to yield a better
understanding of t he physics of aspherical ionized nebulae.


title: Direct determination of the spiral pattern rotation speed of the Galaxy

abstract:
  The rotation velocity of the spiral pattern of the Galaxy is determined by
direct observation of the birthplaces of open clusters of stars in the galactic
disk as a function of their age. Our measurement does not depend on any
specific model of the spiral structure, like the existence of a given number of
spiral arms, or the presence of a bar in the central regions. This study became
possible due to the recent completion of a large database on open clusters by
our group. The birthplaces of the clusters are determined by two methods, one
that assumes that the orbits are circular, and the other by integrating the
orbits in the Galactic potential for a time equal to the age of the clusters.
We selected in the database a sample of 212 clusters for which proper motions,
radial velocities, distances and ages are available, or of 612 clusters that
have ages and distances available. We tested different assumptions concerning
the rotation curve and the radius $R_0$ of the solar orbit. Our results confirm
that a dominant fraction of the open clusters are formed in spiral arms, and
that the spiral arms rotate like a rigid body, as predicted by the classical
theory of spiral waves. We find that the corotation radius $R_c$ is close to
the solar galactic orbit ($R_c/R_0 = 1.08 \pm 0.08$). This proximity has many
potentially interesting consequences, like a better preservation of life on the
Earth, and a new understanding of the history of star formation in the solar
neighborhood, and of the evolution of the abundance of elements in the galactic
disk.


title:
Measuring High Moments of Galaxy Angular Distribution in the First Look
  Survey using Infrared Array Camera

abstract:
  We present the results of using three methods, the probability distribution
function, the Renyi information, and the multi-fractals, to measure the high
moments of galaxy angular distribution in the Infrared Array Camera data of the
Spitzer First Look Survey. This is the first time that Renyi information is
explicitly used to describe the large-scale galaxy spatial distribution, and
our galaxy samples are also the first of the kind in their wavelengths and
sensitivities.


title:
Spectrum of Very High Energy Gamma-Rays from the blazar 1ES1959+650
  during Flaring Activity in 2002

abstract:
  The blazar 1ES 1959+650 was observed in a flaring state with the Whipple 10 m
Imaging Atmospheric Cherenkov Telescope during May of 2002. A spectral analysis
has been carried out on the data from that time period and the resulting very
high energy gamma-ray spectrum ($E \geq 316$ GeV) can be well fit by a
power-law of differential spectral index \alpha = 2.78 +/- 0.12_{stat.} +/-
0.21_{sys.}. On June 4th 2002, the source flared dramatically in the gamma-ray
range without any coincident increase in the X-ray emission, providing the
first unambiguous example of an `orphan' gamma-ray flare from a blazar. The
gamma-ray spectrum for these data can also be described by a simple power-law
fit with \alpha = 2.82 +/- 0.15_{stat.} +/- 0.30_{sys.}. There is no compelling
evidence for spectral variability, or for any cut-off to the spectrum.


title:
The uBVI Photometric System. I. Motivation, Implementation, and
  Calibration

abstract:
  This paper describes the design principles for a CCD-based photometric system
that is highly optimized for ground-based measurement of the size of the Balmer
jump in stellar energy distributions. It is shown that, among ultraviolet
filters in common use, the Thuan-Gunn u filter is the most efficient for this
purpose. This filter is combined with the standard Johnson-Kron-Cousins B, V,
and I bandpasses to constitute the uBVI photometric system.
  Model stellar atmospheres are used to calibrate color-color diagrams for the
uBVI system in terms of the fundamental stellar parameters of effective
temperature, surface gravity, and metallicity. The u-B index is very sensitive
to log g, but also to [Fe/H]. It is shown that an analog of the Str\"omgren c_1
index, defined as (u-B)-(B-V), is much less metallicity dependent, but still
sensitive to log g. The effect of interstellar reddening on u-B is determined
through synthetic photometric calculations, and practical advice is given on
dealing with flat fields, atmospheric extinction, the red leak in the u filter,
and photometric reductions.
  The uBVI system offers a wide range of applicability in detecting stars of
high luminosity in both young (yellow supergiants) and old (post-AGB stars)
populations, using stars of both types as standard candles to measure
extragalactic distances with high efficiency, and in exploring the horizontal
branch in globular clusters. In many stellar applications, it can profitably
replace the classical uBVI system.
  Paper II in this series will present a network of well-calibrated standard
stars for the uBVI system.


title: The uBVI Photometric System. II. Standard Stars

abstract:
  Paper I of this series described the design of a CCD-based photometric system
that is optimized for ground-based measurements of the size of the Balmer
discontinuity in stellar spectra. This "uBVI" system combines the Thuan-Gunn u
filter with the standard Johnson-Kron-Cousins BVI filters, and it can be used
to discover luminous yellow supergiants in extragalactic systems and
post-asymptotic-giant-branch stars in globular clusters and galactic halos. In
the present paper we use uBVI observations obtained on 54 nights with 0.9-m
telescopes at Kitt Peak and Cerro Tololo to construct a catalog of standardized
u magnitudes for standard stars taken from the 1992 catalog of Landolt. We
describe the selection of our 14 Landolt fields, and give details of the
photometric reductions, including red-leak and extinction corrections,
transformation of all of the observations onto a common magnitude system, and
establishment of the photometric zero point. We present a catalog of u
magnitudes of 103 stars suitable for use as standards. We show that data
obtained with other telescopes can be transformed to our standard system with
better than 1% accuracy.


title:
266 E+A Galaxies Selected from the Sloan Digital Sky Survey Data Release
  2: The Origin of E+A Galaxies

abstract:
  E+A galaxies are characterized as a galaxy with strong Balmer absorption
lines but without any [OII] nor H$\alpha$ emission lines. The existence of
strong Balmer absorption lines indicates that E+A galaxies have experienced
starburst within recent one Gyr. However, the lack of [OII] and H$\alpha$
emission lines indicates that E+A galaxies do not have any on-going star
formation. Therefore, E+A galaxies are interpreted as a post-starburst galaxy.
For many years, however, it has been a mystery why E+A galaxies started
starburst and why they quenched the star formation abruptly.
  Using one of the largest samples of 266 E+A galaxies carefully selected from
the Sloan Digital Sky Survey Data Release 2, we have investigated the
environment of E+A galaxies from 50 kpc to 8 Mpc scale, i.e., from a typical
distance to satellite galaxies to the scale of large scale structures. We found
that E+A galaxies have excess of local galaxy density only at a scale of $<100$
kpc (with a two $\sigma$ significance), but not at the cluster scale ($\sim$1.5
Mpc) nor in the scale of large scale structure ($\sim$8 Mpc). These results
indicate that E+A galaxies are not created by the physical mechanisms
associated with galaxy clusters or the large scale structure, but are likely to
be created by the dynamical interaction with closely accompanying galaxies at a
$<$100 kpc scale. The claim is also supported by the morphology of E+A
galaxies. We have found that almost all E+A galaxies have a bright compact
core, and that $\sim$30% of E+A galaxies have dynamically disturbed signatures
or the tidal tails, being quite suggestive of morphological appearance of
merger/interaction remnants.


title:
Velocity Dispersion of 335 Galaxy Clusters Selected from the Sloan
  Digital Sky Survey: Statistical Evidence for Dynamical Interaction, and
  Against Ram-Pressure Stripping

abstract:
  There has been plenty of observational evidence of cluster galaxy evolution.
However, it has been difficult to identify the origin of the cluster galaxy
evolution. Here we show that gravitational interaction/friction between
galaxies is the statistically dominant physical mechanism responsible for the
cluster galaxy evolution, and that the well-favored ram-pressure stripping by
the cluster gas is not statistically driving the cluster galaxy evolution.
  We have constructed the largest composite cluster with 14548 member galaxies
out of 335 clusters with ~>300 km/s carefully selected from the SDSS. By
measuring velocity dispersions of various subsamples of galaxies in this
composite cluster, we found that bright cluster galaxies (Mz<-23) have
significantly smaller velocity dispersion than faint galaxies (Mz>-23). We
interpret this as direct evidence of the dynamical interaction/friction between
cluster galaxies, where massive galaxies lose their velocity through the energy
equipartition during the dynamical interaction/friction with less massive
galaxies. We also found that star-forming late-type galaxies have a larger
velocity dispersion than passive late-type galaxies. This is inconsistent with
the ram-pressure stripping model; since the ram-pressure is proportional to
sigma v^2 (i.e., stronger for galaxies with high velocity), the ram-pressure
stripping cannot explain the observed trends of passive (evolved) galaxies
having low velocity rather than high velocity. On the other hand, the result is
again consistent with the dynamical galaxy-galaxy interaction/friction, where
more evolved (passive) galaxies lose their velocity through dynamical
interaction/friction.


title:
Evidence for Companion-Induced Secular Changes in the Turbulent Disk of
  a Be Star in the LMC MACHO Database

abstract:
  The light curve of a blue variable in the MACHO LMC database (FTS ID
78.5979.72) appeared nearly unvarying for ~4 years (quasi-flat segment) but
then rapidly changed to become periodic with noisy minima for the remaining 4
years (periodic segment); there are no antecedent indications of a gradual
approach to this change. Lomb Periodogram analyses indicate the presence of two
distinct periods of ~61 days and 8 days in both the quasi-flat and the periodic
segments. Minima of the periodic segment cover at least 50% of the orbital
period and contain spikes of light with the 8-day period; maxima do not show
this short period. The system typically shows maxima to be redder than minima.
The most recent OGLE-III light curve shows only a 30-day periodicity. The
variable's V and R magnitudes and color are those of a Be star, and recent sets
of near infrared spectra four days apart, secured during the time of the
OGLE-III data, show H-alpha emission near and at a maximum, confirming its Be
star characteristics. The model that best fits the photometric behavior
consists of a thin ring-like circumstellar disk of low mass with four obscuring
sectors orbiting the central B star in unison at the 61-day period. The central
star peers through the three equi- spaced separations between the four sectors
producing the 8-day period. The remainder of the disk contains hydrogen in
emission making maxima appear redder. A companion star of lower mass in an
inclined and highly eccentric orbit produces an impulsive perturbation near its
periastron to change the disk's orientation, changing eclipses from partial to
complete within ~ 10 days.


title: The Chandra X-Ray Observatory: Five Years of Operation

abstract:
  The Chandra X-ray Observatory is the X-ray component of NASA's Great
Observatory Program and has been operating successfully for over five years. We
present here brief overview of the technical performance and some of the
remarkable discoveries.


title:
On the deficit of calculated muon flux at sea level for energies $>100$
  GeV

abstract:
  In this paper we discuss the problem, why the use of the direct data on
primary nuclei spectra together with the modern hadronic interaction models
leads to significant deficit of computed vertical muon flux at sea level for
energies $>100$ GeV. We suggest, that to find out the source of this
inconsistency it is necessary to perform an analysis of sensitivity of emulsion
chamber data to variations of hadron-nucleus interaction characteristics. Such
analysis will give more ground for discussion of adequacy of the up-to-date
interaction models and of mutual compatibility of primary nuclei spectra,
obtained in direct and EAS experiments.


title:
The Deepest Supernova Search is Realized in the Hubble Ultra Deep Field
  Survey

abstract:
  The Hubble Ultra Deep Field Survey has not only provided the deepest optical
and near infrared views of universe, but has enabled a search for the most
distant supernovae to z~2.2. We have found four supernovae by searching spans
of integrations of the Ultra Deep Field and the Ultra Deep Field Parallels
taken with the Hubble Space Telescope paired with the Advanced Camera for
Surveys and the Near Infrared Multi Object Spectrometer. Interestingly, none of
these supernovae were at z>1.4, despite the substantially increased sensitivity
per unit area to such objects over the Great Observatories Origins Deep Survey.
We present the optical photometric data for the four supernovae. We also show
that the low frequency of Type Ia supernovae observed at z>1.4 is statistically
consistent with current estimates of the global star formation history combined
with the non-trivial assembly time of SN Ia progenitors.


title: The Star Formation Rate-Density Relationship at Redshift Three

abstract:
  We study the star formation rate (SFR) as a function of environment for UV
selected Lyman break galaxies (LBGs) at redshift three. From deep UBVI KPNO
4-m/MOSAIC images, covering a total of 0.90 deg^2, we select 334 LBGs in slices
100 Mpc (co-moving) deep spanning the redshift range 2.9<z<3.4 based on
Bayesian photometric redshifts that include the I magnitude as a prior. The
slice width (100 Mpc) corresponds to the photometric redshift accuracy
(\Delta_z\sim 0.15).
  We used mock catalogs from the GIF2 cosmological simulations to show that
this redshift resolution is sufficient to statistically differentiate the high
density regions from the low density regions using $\Sigma_5$, the projected
density to the 5th nearest neighbor. These mock catalogs have a redshift depth
of 100 Mpc, similar to our slice width.
  The large area of the MOSAIC images, 40x40 Mpc (co-moving) per field, allows
us to measure the SFR from the dust-corrected UV continuum as a function of
$\Sigma_5$. In contrast to low-redshift galaxies, we find that the SFR (or UV
luminosity) of LBGs at z=3 shows no detectable dependence on environment over 2
orders of magnitude in density.
  To test the significance of our result, we use Monte Carlo simulations (from
the mock catalogs) and the same projected density estimators we applied to our
data. We find that we can reject the steep z=0 SFR-density at the 5-$\sigma$
level. We conclude that the SFR-density at z=3 must be at least 3.6 times
flatter than it is locally, i.e. the SFR of LBGs is significantly less
dependent on environment than the SFR of local star-forming galaxies. We find
that the rest-frame UV colors are also independent of environment.


title: The alpha-effect and current helicity for fast sheared rotators

abstract:
  We explore the alpha-effect and the small-scale current helicity, for the
case of weakly compressible magnetically driven turbulence that is subjected to
the differential rotation. No restriction is applied to the amplitude of
angular velocity, i.e., the derivations presented are valid for an arbitrary
Coriolis number, though the differential rotation itself is assumed to be weak.
The expressions obtained are used to explore the possible distributions of
alpha-effect and current helicity in convection zones (CZ) of the solar-type
stars. The implications of the obtained results to the mean-field dynamo models
are discussed.


title:
Optical spectroscopy of X-Mega targets in the Carina Nebula - V. The
  spectroscopic binary HD93161A and its visual companion HD93161B

abstract:
  We present the analysis of an extensive set of high resolution spectroscopic
observations of HD93161, a visual binary with a separation of 2 arcsec. HD93161
A is a spectroscopic binary, with both components clearly detected throughout
the orbit. The primary star is most probably of spectral type O8V, while the
secondary is likely an O9V. We obtain the first orbital solution for this
system, characterized by a period of 8.566\pm0.004 days. The minimum masses of
the primary and secondary stars are 22.2\pm0.6 M_sol and 17.0\pm0.4 M_sol
respectively. These values are quite large, suggesting a high inclination of
the orbit. The second object, HD93161 B, displays an O6.5V((f)) spectral type
and is thus slightly hotter than its neighbour. This star is at first sight
single but presents radial velocity variations. We finally study HD93161 in the
X-ray domain. No significant variability is detected. The X-ray spectrum is
well described by a 2T model with kT_1~0.3keV and kT_2~0.7keV. The X-ray
luminosity is rather moderate, without any large emission excess imputable to a
wind interaction.


title:
Using radio emission to detect isolated and quiescent accreting black
  holes

abstract:
  We discuss the implications of new relations between black holes' masses,
X-ray luminosities and radio luminosities, as well as the properties of the
next generation of radio telescopes, for the goal of finding isolated accreting
black holes. Because accreting black holes have radio-to-X-ray flux ratios that
increase with decreasing luminosity in Eddington units, and because deep
surveys over large fields of view should be possible with planned
instrumentation such as LOFAR, radio surveys should be significantly more
efficient than X-ray surveys for finding these objects.


title:
Ages, metallicities and $\alpha$-element enhancement for galaxies in
  Hickson compact groups

abstract:
  Central velocity dispersions and eight line-strength Lick indices have been
determined from 1.3${\rm \AA}$ resolution long-slit spectra of 16 elliptical
galaxies in Hickson compact groups. These data were used to determine galaxy
properties (ages, metallicities and $\alpha$-element enhancements) and allowed
a comparison with the parameters determined for a sample of galaxies in lower
density environments, studied by Gonz\'alez (1993). The stellar population
parameters were derived by comparison to single stellar population models of
Thomas et al. (2003) and to a new set of SSP models for the indices Mg$_2$,
Fe5270 and Fe5335 based on synthetic spetra. These models, based on an update
version of the fitting functions presented in Barbuy et al. (2003), are fully
described here. Our main results are: (1) the two samples have similar mean
values for the metallicities and [$\alpha$/Fe] ratios, (2) the majority of the
galaxies in compact groups seem to be old (median age of 14 Gyr for eight
galaxies for which ages could be derived), in agreement with recent work by
Proctor et al. (2004). These findings support two possible scenarios: compact
groups are either young systems whose members have recently assembled and had
not enough time to experience any merging yet or, instead, they are old systems
that have avoided merging since their time of formation.


title: The dark energy-dominated Universe

abstract:
  In this paper we investigate the epochs in which the Universe started
accelerating and when it began to become dark energy-dominated (i.e., the
dynamics of the expansion of the Universe dominated by the dark energy). We
provide analytic expressions to calculate the redshifts of these epochs as a
function of density parameters. Moreover, we review and discuss cosmological
models with a dark energy component, which can have an interesting
characteristic, namely, they never stop accelerating. This holds even if the
Universe is at present time either flat, open, or closed. If the dark energy is
the cosmological constant the Universe will eventually end up undergoing an
exponentially expansion phase, and the total density parameter converging to
$\Omega=1$. This is exactly what is considered in inflationary scenario to
generate the initial conditions for the big bang. One can then argue that the
Universe begun with an inflationary phase and will end up with another
inflationary phase. Thus, it follows that in both the early and the late
Universe $\Omega \to 1$. We also discuss the above issues in the context of the
XCDM parametrization.


title:
MCG-6-30-15: Long Timescale X-Ray Variability, Black Hole Mass and AGN
  High States

abstract:
  We present a detailed study of the long-timescale X-ray variability of the
Narrow Line Seyfert 1 (NLS1) Galaxy MCG-6-30-15, based on 8 years of frequent
observations with the Rossi X-ray Timing Explorer. Combined with short
timescale XMM-Newton observations, we derive the powerspectral density (PSD)
covering 6 decades from ~10^{-8} to ~10^{-2} Hz. As with NGC4051, another NLS1,
the PSD of MCG-6-30-15 is a close analogue of the PSD of a Galactic Black Hole
X-ray binary system (GBH) in a `high' rather than a `low' state. Like high
state GBHs, its PSD is better fitted by a smoothly bending rather than sharply
breaking powerlaw model and the break frequency is 7.6^{+10}_{-3} x 10^{-5} Hz.
Assuming linear scaling of break frequency with mass, we estimate the black
hole (BH) mass in MCG-6-30-15 to be ~2.9^{+1.8}_{-1.6} X 10^{6} solar masses.
We also derive the BH mass using a variety of new optical observations and find
a value between 3.6 and 6 x 10^{6} solar masses, consistent with the mass
derived from the PSD. Combining these data with revised reverberation masses
for other AGN we update the BH mass/break timescale diagram. The observations
are consistent with NLS1s having shorter break timescales, for a given mass,
than broad line AGN, probably reflecting a higher accretion rate. However the
data are also consistent with all of the X-ray bright AGN being high state
objects. This result may simply be a selection effect, based on their selection
from X-ray all sky catalogues, and their consequent typically high X-ray/radio
ratios, which indicate high state systems.


title:
Solid state components of varying compositions in the outflow of the Red
  Rectangle

abstract:
  We present high resolution Spitzer spectroscopy of several pointings in the
outflow of the Red Rectangle. Besides the resonances due to the C-rich PAHs,
the spectra show a wealth of new emission bands, in particular in the 13-19.5
micron range. We argue that these bands are due to solid state components, and
show that simple oxides of a varying composition show a good match to the data.
The presence of these O-rich species in the supposedly C-rich outflow is
unexplained.


title:
Passively Evolving Early-type Galaxies at 1.4<z<2.5 in the Hubble Ultra
  Deep Field

abstract:
  We report on a complete sample of 7 luminous early-type galaxies in the
Hubble Ultra Deep Field (UDF) with spectroscopic redshifts between 1.39 and
2.47 and to K<23 AB. Using the BzK selection criterion we have pre-selected a
set of objects over the UDF which fulfill the photometric conditions for being
passively evolving galaxies at z>1.4. Low-resolution spectra of these objects
have been extracted from the HST+ACS grism data taken over the UDF by the
GRAPES project. Redshift for the 7 galaxies have been identified based on the
UV feature at rest frame 2640<lambda<2850 AA. This feature is mainly due to a
combination of FeII, MgI and MgII absorptions which are characteristic of
stellar populations dominated by stars older than about 0.5 Gyr. The redshift
identification and the passively evolving nature of these galaxies is further
supported by the photometric redshifts and by the overall spectral energy
distribution (SED), with the ultradeep HST+ACS/NICMOS imaging revealing compact
morphologies typical of elliptical/early-type galaxies. From the SED we derive
stellar masses of 10^{11}Msun or larger and ages of about 1 Gyr. Their space
density at < z >=1.7 appears to be roughly a factor of 2--3 smaller than that
of their local counterparts, further supporting the notion that such massive
and old galaxies are already ubiquitous at early cosmic times. Much smaller
effective radii are derived for some of the objects compared to local massive
ellipticals, which may be due to morphological K corrections, evolution, or the
presence of a central point-like source. Nuclear activity is indeed present in
a subset of the galaxies, as revealed by them being hard X-ray sources, hinting
to AGN activity having played a role in discontinuing star formation.


title: Elliptic CMB Sky

abstract:
  The ellipticity of the anisotropy spots of the Cosmic Microwave Background
measured by the Wilkinson Microwave Anisotropy Probe (WMAP) has been studied.
We find an average ellipticity of about 2, confirming with a far larger
statistics similar results found first for the COBE-DMR CMB maps, and then for
the BOOMERanG CMB maps. There are no preferred directions for the obliquity of
the anisotropy spots. The average ellipticity is independent of temperature
threshold and is present on scales both smaller and larger than the horizon at
the last scattering. The measured ellipticity characteristics are consistent
with being the effect of geodesics mixing occurring in an hyperbolic Universe,
and can mark the emergence of CMB ellipticity as a new observable constant
describing the Universe. There is no way of simulating this effect. Therefore
we cannot exclude that the observed behavior of the measured ellipticity can
result from a trivial topology in the popular flat $\Lambda$-CDM model, or from
a non-trivial topology.


title: Testing MOND with VirgoHI21

abstract:
  The 'dark galaxy' VIRGOHI21 seems to be composed of an unusually high
proportion of darkmatter and is situated in a strong external gravitational
field. As such it offers a rare test for theories of modified dynamics. If the
system is bound then its dynamics are inconsistent with those predicted by
theMOND theory.


title: Spatially resolved PAH emission in the inner disks of Herbig Ae/Be stars

abstract:
  We present adaptive optics high angular resolution ($\sim0.1\arcsec$)
spectroscopic observations in the 3 \um region of eight well known Herbig Ae/Be
stars with circumstellar disks. We detect the aromatic emission feature at 3.3
\um for four out of six of our objects with flared disks (HD 169142, HD 97048,
HD 100453, HD 100546), some weaker additional features at 3.4 and 3.46 $\mu$m
and nanodiamond features at 3.43 and 3.53 \um in two of our flared object (HD
100546 and HD 97048 respectively). We also detect hydrogen recombination line
at 3.74 \um in practically all objects. The emission in the polycyclic aromatic
hydrocarbons (PAHs) feature at 3.3 \um, additional and nanodiamond features in
the 3.4-3.5 \um region is, for the first time, spatially resolved in all the
sources where the features are detected. The full-width at half-maximum sizes
that we derive are typical of emission arising in a circumstellar disk. On the
other hand, the continuum emission is unresolved, with the exception of HD
97048 where it is marginally resolved. We compare the observed spatial
distribution of the 3.3 $\mu$m PAH feature and the adjacent continuum to the
predictions of a disk model that includes transiently heated small grains and
PAHs in addition to large grains in thermal equilibrium \cite[]{habart2004a}.
The model predicts that, as observed, the 3.3 $\mu$m PAH emission feature is
significantly broader than that of the adjacent continuum and that about 50% of
its integrated intensity comes from a radius $R<$ 30 AU. We find that the
predicted brightness profiles reproduce very well the observed ones. This
proves beyond doubt that the energetic 3.3 $\mu$m PAH emission feature takes
its origin in the inner disk regions.


title:
Initial conditions to cosmological N-body simulations, or how to run an
  ensemble of simulations

abstract:
  The conventional method of generating initial conditions for cosmological
N-body simulations introduces a significant error in the real-space statistical
properties of the particles. More specifically, the finite box size leads to a
significant underestimate of sigma_8, the correlation function, and nonlinear
effects. I implement a method of generating initial conditions for N-body
simulations that accurately models the real-space statistical properties, such
as the mass variance in spheres and the correlation function. The method
requires running ensembles of simulations because the power in the DC mode is
no longer assumed to be zero. For moderately sized boxes, I demonstrate that
the new method corrects the underestimate in the mass variance in spheres and
the shape of the correlation function. I also argue that subtracting Poisson
noise from the power spectrum is a dangerous practice. Code to generate initial
conditions to second order in Lagrangian perturbation theory with the new
method is available at http://www.astro.princeton.edu/~esirko/ic .


title: Analysis of DA White Dwarfs from the McCook & Sion Catalog

abstract:
  The Sloan Digital Sky Survey has already doubled the number of
spectroscopically identified white dwarfs. However, there remains a wealth of
white dwarfs in the McCook & Sion catalog for which little or nothing is known.
We have thus undertaken a spectroscopic survey of all Northern hemisphere DA
white dwarfs from this catalog in order to (1) confirm the spectroscopic
classification, and (2) provide measurements of Teff and log g for each star.
As part of this project, we have also secured spectroscopic data for all DA
stars with high-speed photometric measurements available, in order to study the
purity of the ZZ Ceti instability strip, which has recently been challenged,
once again.