title: The Circumnuclear Star-forming Activities along the Hubble Sequence

abstract:
  In order to study the circumnuclear star-forming activity along the Hubble
sequence, we cross-correlate the Sloan Digital Sky Survey Data Release 2 (SDSS
DR2) with the Third Reference Catalog of Bright Galaxies (RC3) to derive a
large sample of 1015 galaxies with both morphological and spectral information.
Among these, 385 sources are classified as star-forming galaxies and the SDSS
fibre covered the circumnuclear regions (0.2 $-$ 2.0 kpc). By using the
spectral synthesis method to remove the contribution from the underlying old
stellar population, we measure the emission lines fluxes accurately which are
then used to estimate the star formation rates(SFRs). Our main findings are
that: (1) Early-type spirals show much larger H$\alpha$ luminosities and hence
higher SFRs, they also suffer more extinctions than late-type ones. The
equivalent widths (EWs) of H$\alpha$ emission lines show the similar trend,
however, the very late types (Sdm $\sim$ Irr) do have large fractions of high
EWs. (2) We confirm that D$_n(4000)$ has strong correlation with the strengthes
of metallic absorption lines (such as CN band, G band and Mg Ib). Both these
lines and the Balmer absorption lines show interesting variations between Sbc
to Sd type galaxies. (3) The bar structure tightly relates with the enhanced
star forming activity, this effect is even more significant in the early-type
spirals. But we should note that the bar structure is not a necessary or
sufficient condition for galaxies to harbor circumnuclear star formations.


title: Type Ia Supernova Spectral Line Ratios as Luminosity Indicators

abstract:
  Type Ia supernovae have played a crucial role in the discovery of the dark
energy, via the measurement of their light curves and the determination of the
peak brightness via fitting templates to the observed lightcurve shape. Two
spectroscopic indicators are also known to be well correlated with peak
luminosity. Since the spectroscopic luminosity indicators are obtained directly
from observed spectra, they will have different systematic errors than do
measurements using photometry. Additionally, these spectroscopic indicators may
be useful for studies of effects of evolution or age of the SNe Ia progenitor
population. We present several new variants of such spectroscopic indicators
which are easy to automate and which minimize the effects of noise. We show
that these spectroscopic indicators can be measured by proposed JDEM missions
such as SNAP and JEDI.


title: Keck Interferometer Observations of FU Orionis Objects

abstract:
  We present new K-band long baseline interferometer observations of three
young stellar objects of the FU Orionis class, V1057 Cyg, V1515 Cyg and Z
CMa-SE, obtained at the Keck Interferometer during its commissioning science
period. The interferometer clearly resolves the source of near-infrared
emission in all three objects. Using simple geometrical models we derive size
scales (0.5-4.5 AU) for this emission. All three objects appear significantly
more resolved than expected from simple models of accretion disks tuned to fit
the broadband optical and infrared spectro-photometry. We explore variations in
the key parameters that are able to lower the predicted visibility amplitudes
to the measured levels, and conclude that accretion disks alone do not
reproduce the spectral energy distributions and K-band visibilities
simultaneously. We conclude that either disk models are inadequate to describe
the near-infrared emission, or additional source components are needed. We
hypothesize that large scale emission (10s of AU) in the interferometer field
of view is responsible for the surprisingly low visibilities. This emission may
arise in scattering by large envelopes believed to surround these objects.


title:
Acceptances for Space-Based and Ground-Based Fluorescence Detectors, and
  Inference of the Neutrino-Nucleon Cross-Section above 10^19 eV

abstract:
  Detection of ultra-high energy neutrinos will be useful for unraveling the
dynamics of the most violent sources in the cosmos and for revealing the
neutrino cross-section at extreme energy. Above ~ 10^20 eV, neutrinos may well
be the only cosmic primariies. Thus, it is important to know the acceptances
(event rate/flux) of proposed air-shower experiments for detecting
``horizontal'' neutrino events initiated in our atmosphere, and
``Earth-skimming'' events initiated in the Earth's surface rock or ocean. We
calculate these acceptances for fluorescence detectors, both space-based as
with the EUSO and OWL proposals, and ground-based, as with Auger, HiRes and
Telescope Array. The neutrino cross-section sigma_nuN is not measured at
energies above 5.2 x 10^13 eV. Although QCD extrapolations offer motivated
guesses for sigma_nuN, new physics could intervene to provide a surprise.
Therefore, we present the acceptances of horizontal (HAS) and upgoing (UAS) air
showers as a function of sigma_nuN over the interesting range 10^(-34) to
10^(-30) cm^2. The dependences of acceptances on neutrino energy,
shower-threshold energy, shower length and column density, and cloud layers are
also studied. For UAS, we present acceptances for events over land (rock), and
over the ocean (water). The latter are larger by about an order of magnitude,
thus favoring space-based detectors. We revisit the idea of Kusenko and Weiler
to infer sigma_nuN at E_nu ~ 10^20 eV from the ratio of HAS-to-UAS events, and
find favorable results. Our calculation is mostly analytic. Included in the UAS
calculation are realistic energy-losses for taus, and Earth-curvature effects.


title: What Can Gamma Ray Bursts Teach Us About Dark Energy?

abstract:
  It has been suggested that Gamma Ray Bursts (GRB) may enable the expansion
rate of our Universe to be measured out to very high redshifts ($z \gsim 5$)
just as type Ia supernovae have done at $z \sim$1--1.5. We explore this
possibility here, and find that GRB have the potential to detect dark energy at
high statistical significance, but they are unlikely to be competitive with
future supernovae missions, such as SNAP, in measuring the properties of the
dark energy. The exception to this conclusion is if there is appreciable dark
energy at early times, in which case the information from GRB's will provide an
excellent complement to the $z\sim 1$ information from supernovae.


title:
The DEEP2 Galaxy Redshift Survey: Clustering of Galaxies as a Function
  of Luminosity at z=1

abstract:
  We measure the clustering of DEEP2 galaxies at z=1 as a function of
luminosity on scales 0.1 Mpc/h to 20 Mpc/h. Drawing from a parent catalog of
25,000 galaxies at 0.7<z<1.3 in the full DEEP2 survey, we create volume-limited
samples having upper luminosity limits between M_B=-19 and M_B=-20.5, roughly
0.2-1 L^* at z=1. We find that brighter galaxies are more strongly clustered
than fainter galaxies and that the slope of the correlation function does not
depend on luminosity for L<L^*. The brightest galaxies, with L>L^*, have a
steeper slope. The clustering scale-length, r_0, varies from 3.69 +/-0.14 for
the faintest sample to 4.43 +/-0.14 for the brightest sample. The relative bias
of galaxies as a function of L/L^* is steeper than the relation found locally
for SDSS galaxies (Zehavi et al. 2005) over the luminosity range that we
sample. The absolute bias of galaxies at z=1 is scale-dependent on scales r_p<1
Mpc/h, and rises most significantly on small scales for the brightest samples.
For a concordance cosmology, the large-scale bias varies from 1.26 +/-0.04 to
1.54 +/-0.05 as a function of luminosity and implies that DEEP2 galaxies reside
in dark matter halos with a minimum mass of ~1-3 10^12 h^-1 M_sun.


title: Modeling Luminosity-Dependent Galaxy Clustering Through Cosmic Time

abstract:
  We employ high-resolution dissipationless simulations of the concordance LCDM
cosmology to model the observed luminosity dependence and evolution of galaxy
clustering through most of the age of the universe, from z~5 to z~0. We use a
simple, non-parametric model which monotonically relates galaxy luminosities to
the maximum circular velocity of dark matter halos (V_max) by preserving the
observed galaxy luminosity function in order to match the halos in simulations
with observed galaxies. The novel feature of the model is the use of the
maximum circular velocity at the time of accretion, V_max,acc, for subhalos,
the halos located within virial regions of larger halos. We argue that for
subhalos in dissipationless simulations, V_max,acc reflects the luminosity and
stellar mass of the associated galaxies better than the circular velocity at
the epoch of observation, V_max,now. The simulations and our model L-V_max
relation predict the shape, amplitude, and luminosity dependence of the
two-point correlation function in excellent agreement with the observed galaxy
clustering in the SDSS data at z~0 and in the DEEP2 samples at z~1 over the
entire probed range of projected separations, 0.1<r_p/(Mpc/h)<10.0. In
particular, the small-scale upturn of the correlation function from the
power-law form in the SDSS and DEEP2 luminosity-selected samples is reproduced
very well. At z~3-5, our predictions also match the observed shape and
amplitude of the angular two-point correlation function of Lyman-break galaxies
(LBGs) on both large and small scales, including the small-scale upturn.


title: Formation of early-type galaxies from cosmological initial conditions

abstract:
  We describe high resolution Smoothed Particle Hydrodynamics (SPH) simulations
of three approximately $M_*$ field galaxies starting from \LCDM initial
conditions. The simulations are made intentionally simple, and include
photoionization, cooling of the intergalactic medium, and star formation but
not feedback from AGN or supernovae. All of the galaxies undergo an initial
burst of star formation at $z \approx 5$, accompanied by the formation of a
bubble of heated gas. Two out of three galaxies show early-type properties at
present whereas only one of them experienced a major merger. Heating from
shocks and -PdV work dominates over cooling so that for most of the gas the
temperature is an increasing function of time. By $z \approx 1$ a significant
fraction of the final stellar mass is in place and the spectral energy
distribution resembles those of observed massive red galaxies. The galaxies
have grown from $z=1 \to 0$ on average by 25% in mass and in size by gas poor
(dry) stellar mergers. By the present day, the simulated galaxies are old
($\approx 10 {\rm Gyrs}$), kinematically hot stellar systems surrounded by hot
gaseous haloes. Stars dominate the mass of the galaxies up to $\approx 4$
effective radii ($\approx 10$ kpc). Kinematic and most photometric properties
are in good agreement with those of observed elliptical galaxies. The galaxy
with a major merger develops a counter-rotating core. Our simulations show that
realistic intermediate mass giant elliptical galaxies with plausible formation
histories can be formed from \LCDM initial conditions even without requiring
recent major mergers or feedback from supernovae or AGN.


title: The Transparency of the Universe Limited by Ly-alpha Clouds

abstract:
  The brightnesses of supernovae are commonly understood to indicate that
cosmological expansion is accelerating due to dark energy. However the entire
discussion presumes a perfectly transparent universe because no effects of
reddening associated with the interstellar extinction law are seen. We note
that with two kinds of dark matter (baryonic and non-baryonic) strongly
dominating the known mass of the universe, it is seriously premature to assume
that these dark matter components have not reduced the transmission of the
universe for cosmological sources.
  We show that the long-known $Lyman-\alpha$ clouds, if nucleated by the
population of baryonic dark matter primordial planetoids indicated by quasar
microlensing, would act as spherical lenses and achromatically fade
cosmologically distant sources. We attempt to estimate the amount of this
cosmological fading, but ultimately the calculation is limited by lack of a
satisfactory model for the tenuous outer parts of a primordial planetoid. We
also consider the effects of such cosmological fading on the light of quasars.


title: Polarimetry of Li-rich giants

abstract:
  Protoplanetary nebulae typically present non-spherical envelopes. The origin
of such geometry is still controversial. There are indications that it may be
carried over from an earlier phase of stellar evolution, such as the AGB phase.
But how early in the star's evolution does the non-spherical envelope appear?
Li-rich giants show dusty circumstellar envelopes that can help answer that
question. We study a sample of fourteen Li-rich giants using optical
polarimetry in order to detect non-spherical envelopes around them. We used the
IAGPOL imaging polarimeter to obtain optical linear polarization measurements
in V band. Foreground polarization was estimated using the field stars in each
CCD frame. After foreground polarization was removed, seven objects presented
low intrinsic polarization (0.19 - 0.34)% and two (V859 Aql and GCSS 557)
showed high intrinsic polarization values (0.87 - 1.16)%. This intrinsic
polarization suggests that Li-rich giants present a non-spherical distribution
of circumstellar dust. The intrinsic polarization level is probably related to
the viewing angle of the envelope, with higher levels indicating objects viewed
closer to edge-on. The correlation of the observed polarization with optical
color excess gives additional support to the circumstellar origin of the
intrinsic polarization in Li-rich giants. The intrinsic polarization correlates
even better with the IRAS 25 microns far infrared emission. Analysis of
spectral energy distributions for the sample show dust temperatures for the
envelopes tend to be between 190 and 260 K. We suggest that dust scattering is
indeed responsible for the optical intrinsic polarization in Li-rich giants.
Our findings indicate that non-spherical envelopes may appear as early as the
red giant phase of stellar evolution.


title: The Nature of Weak MgII Absorbing Structures

abstract:
  We consider geometries and possible physical models for weak low ionization
absorbers based on the relative incidence of low and high ionization absorption
systems. We found a total of 16 metal-line systems, with low and/or high
ionization absorption detected in our survey of weak low ionization absorption
systems from the archive of HST/STIS data. The weak low ionization absorbers
trace an abundant population of metal-enriched regions (close to solar
metallicity). Generally, models show that these systems have a ~10pc region of
higher density gas and a ~1kpc region of lower density phase of higher
ionization absorption. We compare absorption systems detected in low and/or
high ionization gas and find the following: 1) All but 1 of the 10 weak low
ionization systems have a related high ionization phase. In 3 cases the high
ionization gas has only a single component, kinematically centered on the low
ionization absorption, and in the other 6 cases there are additional high
ionization components offset in velocity. The system, toward quasar 3C 273, do
not have a high ionization cloud; 2) There are just 6 systems with only a high
ionization phase as compared to the 9 systems with both low and high ionization
phases; 3) The high ionization absorption in weak low ionization systems is, on
average, stronger than in systems with only high ionization absorption; 4) The
kinematic structure of the high ionization in weak low ionization systems is
similar to that in high ionization only systems. We find that filamentary and
sheetlike geometries are favored, due to the relatively small observed
cross-section of high ionization only systems. Although low ionization
absorbers are not closely associated with luminous galaxies, they arise in
their immediate environments within the cosmic web.


title:
SDSS J0806+2006 and SDSS J1353+1138: Two New Gravitationally Lensed
  Quasars from the Sloan Digital Sky Survey

abstract:
  We report the discoveries of two, two-image gravitationally lensed quasars
selected from the Sloan Digital Sky Survey: SDSS J0806+2006 at z_s=1.540 and
SDSS J1353+1138 at z_s=1.629 with image separations of 1.40" and 1.41"
respectively. Spectroscopic and optical/near-infrared imaging follow-up
observations show that the quasar images have identical redshifts and possess
extended objects between the images that are likely to be lens galaxies at
z_l~0.6 in SDSS J0806+2006 and z_l~0.3 in SDSS J1353+1138. The field of SDSS
J0806+2006 contains several nearby galaxies that may significantly perturb the
system, and SDSS J1353+1138 has an extra component near its Einstein ring that
is probably a foreground star. Simple mass models with reasonable parameters
reproduce the quasar positions and fluxes of both systems.


title: Evolution of the X-Ray Jets from 4U 1755--33

abstract:
  We report on new X-ray observations of the large-scale jets recently
discovered in X-rays from the black hole candidate 4U 1755-33. Our observations
in 2004 show that the jets found in 2001 are still present in X-rays. However,
sensitive radio observations in 2004 failed to detect the jets. We suggest that
synchrotron radiation is a viable emission mechanism for the jets and that
thermal bremsstrahlung and inverse-Compton emission are unlikely on energetic
grounds. In the synchrotron interpretation, the production of X-rays requires
acceleration of electrons up to ~ 60 TeV, the jet power is ~ 4x10^35 erg s^-1,
and the radio non-detection requires a spectral index alpha > -0.65 (S_\nu
\propto \nu^\alpha) which is similar to the indexes found in lobes surrounding
some other compact objects. We find an upper limit on the flux of 4U 1755-33 in
quiescence of 5x10^-16 erg cm^-2 s^-1 in the 0.3-8 keV band.


title:
Capture of a Red Giant by the Black Hole Sagittarius A* as a Possible
  Origin for the TeV Gamma Rays from the Galactic Center

abstract:
  Non-thermal TeV $\gamma$-ray emission within a multiparsec has been observed
from the center region of our Galaxy. We argue that these $\gamma$-rays are the
result of transient activity of the massive black hole Sgr A$^*$ that resides
at the Galactic Center. Several thousand years ago, the black hole may have
experienced an active phase by capturing a red giant star and forming an
accretion disk, temporarily behaving like an active galactic nucleus. A
powerful jet, which contains plenty of high speed protons, was launched during
the process. These runaway protons interact with the dense ambient medium,
producing TeV $\gamma$-ray emission through the $\pi^0$-decay process. We show
that the total energy deposited in this way is large enough to account for
observations. The diffusion length of protons is also consistent with the
observed size of the TeV source.


title: Gas Pixel Detectors for X-ray Polarimetry applications

abstract:
  We discuss a new class of Micro Pattern Gas Detectors, the Gas Pixel Detector
(GPD), in which a complete integration between the gas amplification structure
and the read-out electronics has been reached. An Application-Specific
Integrated Circuit (ASIC) built in deep sub-micron technology has been
developed to realize a monolithic device that is, at the same time, the
pixelized charge collecting electrode and the amplifying, shaping and charge
measuring front-end electronics. The CMOS chip has the top metal layer
patterned in a matrix of 80 micron pitch hexagonal pixels, each of them
directly connected to the underneath electronics chain which has been realized
in the remaining five layers of the 0.35 micron VLSI technology. Results from
tests of a first prototype of such detector with 2k pixels and a full scale
version with 22k pixels are presented. The application of this device for
Astronomical X-Ray Polarimetry is discussed. The experimental detector response
to polarized and unpolarized X-ray radiation is shown. Results from a full
MonteCarlo simulation for two astronomical sources, the Crab Nebula and the
Hercules X1, are also reported.


title: On the properties of fractal cloud complexes

abstract:
  We study the physical properties derived from interstellar cloud complexes
having a fractal structure. We first generate fractal clouds with a given
fractal dimension and associate each clump with a maximum in the resulting
density field. Then, we discuss the effect that different criteria for clump
selection has on the derived global properties. We calculate the masses, sizes
and average densities of the clumps as a function of the fractal dimension
(D_f) and the fraction of the total mass in the form of clumps (epsilon). In
general, clump mass does not fulfill a simple power law with size of the type
M_cl ~ (R_cl)**(gamma), instead the power changes, from gamma ~ 3 at small
sizes to gamma<3 at larger sizes. The number of clumps per logarithmic mass
interval can be fitted to a power law N_cl ~ (M_cl)**(-alpha_M) in the range of
relatively large masses, and the corresponding size distribution is N_cl ~
(R_cl)**(-alpha_R) at large sizes. When all the mass is forming clumps
(epsilon=1) we obtain that as D_f increases from 2 to 3 alpha_M increases from
~0.3 to ~0.6 and alpha_R increases from ~1.0 to ~2.1. Comparison with
observations suggests that D_f ~ 2.6 is roughly consistent with the average
properties of the ISM. On the other hand, as the fraction of mass in clumps
decreases (epsilon<1) alpha_M increases and alpha_R decreases. When only ~10%
of the complex mass is in the form of dense clumps we obtain alpha_M ~ 1.2 for
D_f=2.6 (not very different from the Salpeter value 1.35), suggesting this a
likely link between the stellar initial mass function and the internal
structure of molecular cloud complexes.


title:
Boxy/peanut "bulges": comparing the structure of galaxies with the
  underlying families of periodic orbits

abstract:
  The vertical profiles of disc galaxies are built by the material trapped
around stable periodic orbits, which form their "skeletons". According to this,
the knowledge of the stability of the main families of periodic orbits in
appropriate 3D models, can predict possible morphologies for edge-on disc
galaxies. In a pilot survey we compare the orbital structures which lead to the
appearance of "peanuts" and "X"-like features with the edge-on profiles of
three disc galaxies (IC 2531, NGC 4013 and UGC 2048). The subtraction from the
images of a model representing the axisymmetric component of the galaxies
reveals the contribution of the non-axisymmetric terms. We find a direct
correspondence between the orbital profiles of 3D bars in models and the
observed main morphological features of the residuals. We also apply a simple
unsharp masking technique in order to study the sharpest features of the
images. Our basic conclusion is that the morphology of the boxy "bulges" of
these galaxies can be explained by considering disc material trapped around
stable 3D periodic orbits. In most models these building-blocks periodic orbits
are bifurcated from the planar central family of a non-axisymmetric component,
usually a bar, at low order vertical resonances. In such a case the boxy
"bulges" are parts of bars seen edge-on. For the three galaxies we study the
families associated with the "peanut" or "X"-shape morphology are most probably
bifurcations at the vertical 2/1 or 4/1 resonance.


title:
Extrasolar Planets with AMBER/VLTI, What can we expect from current
  performances ?

abstract:
  We present the current performances of the AMBER / VLTI instrument in terms
of differential observables (differential phase and differential visibility)
and show that we are already able to reach a sufficient precision for very low
mass companions spectroscopy and mass characterization. We perform some
extrapolations with the knowledge of the current limitations of the instrument
facility. We show that with the current setup of the AMBER instrument, we can
already reach $3\sigma = 10^{-3}$ radians and have the potential to some low
mass companions characterization (Brown dwarves or hypothetical very hot Extra
Solar Giant Planets). With some upgrades of the VLTI infrastructure,
improvements of the instrument calibration and improvements of the observing
strategy, we will be able to reach $3\sigma = 10^{-4}$ radians and will have
the potential to perform Extra Solar Giant Planets spectroscopy and mass
characterization.


title:
A New Multidimensional Relativistic Hydrodynamics code based on
  Semidiscrete Central and WENO schemes

abstract:
  We have proposed a new High Resolution Shock Capturing (HRSC) scheme for
Special Relativistic Hydrodynamics (SRHD) based on the semidiscrete central
Godunov-type schemes and a modified Weighted Essentially Non-oscillatory (WENO)
data reconstruction algorithm. This is the first application of the
semidiscrete central schemes with high order WENO data reconstruction to the
SRHD equations. This method does not use a Riemann solver for flux computations
and a number of one and two dimensional benchmark tests show that the algorithm
is robust and comparable in accuracy to other SRHD codes.


title:
Resolution requirements for simulating gravitational fragmentation using
  SPH

abstract:
  Jeans showed analytically that, in an infinite uniform-density isothermal
gas, plane-wave perturbations collapse to dense sheets if their wavelength,
$\lambda$, satisfies $\lambda > \lambda_{_{\rm JEANS}} = (\pi a^2 / G
\rho_{_0})^{1/2}$ (where $a$ is the isothermal sound speed and $\rho_{_0}$ is
the unperturbed density); in contrast, perturbations with smaller $\lambda$
oscillate about the uniform density state. Here we show that Smoothed Particle
Hydrodynamics reproduces these results well, even when the diameters of the SPH
particles are twice the wavelength of the perturbation. Our simulations are
performed in 3-D with initially settled (i.e. non-crystalline) distributions of
particles. Therefore there exists the seed noise for artificial fragmentation,
but it does not occur. We conclude that, although there may be -- as with any
numerical scheme -- `skeletons in the SPH cupboard', a propensity to fragment
artificially is evidently not one of them.


title:
Very Efficient Methods for Multilevel Radiative Transfer in Atomic and
  Molecular Lines

abstract:
  The development of fast numerical methods for multilevel radiative transfer
(RT) applications often leads to important breakthroughs in astrophysics,
because they allow the investigation of problems that could not be properly
tackled using the methods previously available. Probably, the most familiar
example is the so-called Multilevel Accelerated $\Lambda$-Iteration (MALI)
technique of Rybicki & Hummer for the case of a local approximate operator,
which is based on Jacobi iteration. However, there are superior
operator-splitting methods, based on Gauss-Seidel (GS) and Successive
Overrelaxation (SOR) iteration, which provide a dramatic increase in the speed
with which non-LTE multilevel transfer problems can be solved in one, two and
three-dimensional geometries. Such RT methods, which were introduced by
Trujillo Bueno & Fabiani Bendicho ten years ago, are the main subject of the
first part of this paper. We show in some detail how they can be applied for
solving multilevel RT problems in spherical geometry, for both atomic and
molecular line transitions. The second part of the article addresses the issue
of the calculation of the molecular number densities when the approximation of
instantaneous chemical equilibrium turns out to be inadequate, which happens to
be the case whenever the dynamical time scales of the astrophysical plasma
under consideration are much shorter than the time needed by the molecules to
form.


title: XMM-Newton observations of X-ray emission from Jupiter

abstract:
  We present the results of two XMM-Newton observations of Jupiter carried out
in 2003 for 100 and 250 ks (or 3 and 7 planet rotations) respectively. X-ray
images from the EPIC CCD cameras show prominent emission from the auroral
regions in the 0.2 - 2.0 keV band: the spectra are well modelled by a
combination of emission lines, including most prominently those of highly
ionised oxygen (OVII and OVIII). In addition, and for the first time,
XMM-Newton reveals the presence in both aurorae of a higher energy component (3
- 7 keV) which is well described by an electron bremsstrahlung spectrum. This
component is found to be variable in flux and spectral shape during the Nov.
2003 observation, which corresponded to an extended period of intense solar
activity. Emission from the equatorial regions of Jupiter's disk is also
observed, with a spectrum consistent with that of solar X-rays scattered in the
planet's upper atmosphere. Jupiter's X-rays are spectrally resolved with the
RGS which clearly separates the prominent OVII contribution of the aurorae from
the OVIII, FeXVII and MgXI lines, originating in the low-latitude disk regions
of the planet.


title: The radio properties of the cD galaxy of Abell 2390

abstract:
  We present multi-frequency, multi-epoch radio imaging of the complex radio
source B2151+174 in the core of the cluster, Abell 2390 (z~0.23). From new and
literature data we conclude that the FRII-powerful radio source is the
combination of a compact, core-dominated `medium-symmetric object' (MSO) with a
more extended, steeper spectrum mini-halo. B2151+174 is unusual in a number of
important aspects: i) it is one of the most compact and flat spectrum sources
in a cluster core known; ii) it shows a complex, compact twin-jet structure in
a north-south orientation; iii) the orientation of the jets is 45deg misaligned
with apparent structure (ionization cones and dust disk) of the host galaxy on
larger scales. Since the twin-jet of the MSO has its northern half with an
apparent `twist', it might be that precession of the central supermassive black
hole explains this misalignement.
  B2151+174 may be an example of the early stage (10^3-10^4 yrs duration) of a
`bubble' being blown into the ICM where the plasma has yet to expand.


title:
The Effect of the Transit of Venus on ACRIM's Total Solar Irradiance
  Measurements: Implications for Transit Studies of Extrasolar Planets

abstract:
  We used the 8 June 2004 transit of Venus (ToV) as a surrogate to test
observing methods, strategies and techniques that are being contemplated for
future space missions to detect and characterize extrasolar terrestrial planets
(ETPs) as they transit their host stars, notably NASA's Kepler mission planned
for 2008. As an analog to "Kepler-like" photometric transit observations, we
obtained (spatially unresolved) radiometric observations with the ACRIM 3
instrument on ACRIMSAT to follow the effect of the ToV on the total solar
irradiance (TSI). Contemporaneous high-resolution broadband imagery with NASA's
TRACE spacecraft provided, directly, measures of the stellar (solar)
astrophysical noise that can intrinsically limit such transit observations.
During the ~ 5.5 h transit, the planet's angular diameter was approximately
1/32 the solar diameter, thus covering ~ 0.1 of the stellar surface. With our
ACRIM 3 data, we measure temporal changes in TSI with a 1 sigma per sample
(unbinned) uncertainty of approximately 100 mW m^-2 (0.007%). A diminution in
TSI of ~ 1.4 W m^-2 (~ 0.1%, closely corresponding to the geometrically
occulted area of the photosphere) was measured at mid-transit compared with a
mean pre/post transit TSI of ~ 1365.9 W m^-2. These observations serve as a
surrogate to future photometric observations of ETPs such as Kepler will
deliver. Detailed analysis of the ToV, a rare event within our own solar
system, with time-resolved radiometry augmented with high-resolution imagery
provides a useful analogue for investigating the detectability and
characterization of ETPs from observations that are anticipated in the near
future.


title: SiO J=5--4 in the HH211 Protostellar Jet Imaged with the SMA

abstract:
  We have mapped the SiO J=5-4 line at 217GHz from the HH211 molecular outflow
with the Submillimeter Array (SMA). The high resolution map (1.6''x0.9'') shows
that the SiO J=5-4 emission comes from the central narrow jet along the outflow
axis with a width of ~0.8'' (~250 AU) FWHM. The SiO jet consists of a chain of
knots separated by 3-4'' (~1000 AU) and most of the SiO knots have counterparts
in shocked H_2 emission seen in a new, deep VLT near-infrared image of the
outflow. A new, innermost pair of knots are discovered at just +/-2'' from the
central star. The line ratio between the SiO J=5-4 data and upper limits from
the SiO J=1-0 data of Chandler & Richer (2001) suggests that these knots have a
temperature in excess of 300-500 K and a density of (0.5-1) x10^7 cm^{-3}. The
radial velocity measured for these knots is ~30 km/s, comparable to the maximum
velocity seen in the entire jet. The high temperature, high density, and
velocity structure observed in this pair of SiO knots suggest that they are
closely related to the primary jet launched close to the protostar.


title:
Infrared Spectroscopy of Symbiotic Stars. IV. V2116 Ophiuchi/GX 1+4, The
  Neutron Star Symbiotic

abstract:
  We have computed, based on 17 infrared radial velocities, the first set of
orbital elements for the M giant in the symbiotic binary V2116 Ophiuchi. The
giant's companion is a neutron star, the bright X-ray source GX 1+4. We find an
orbital period of 1161 days by far the longest of any known X-ray binary. The
orbit has a modest eccentricity of 0.10 with an orbital circularization time of
less than 10^6 years. The large mass function of the orbit significantly
restricts the mass of the M giant. Adopting a neutron-star mass of 1.35M(Sun),
the maximum mass of the M giant is 1.22M(Sun), making it the less massive star.
Derived abundances indicate a slightly subsolar metallicity. Carbon and
nitrogen are in the expected ratio resulting from the red-giant first dredge-up
phase. The lack of O-17 suggests that the M-giant has a mass less than
1.3M(Sun), consistent with our maximum mass. The red giant radius is 103R(Sun),
much smaller than the estimated Roche lobe radius. Thus, the mass loss of the
red giant is via a stellar wind. Although the M giant companion to the neutron
star has a mass similar to the late-type star in low-mass X-ray binaries, its
near-solar abundances and apparent runaway velocity are not fully consistent
with the properties of this class of stars.


title: The Multiple System HD 27638

abstract:
  We report spectroscopic observations of HD 27638B, the secondary in a visual
binary in which the physically associated primary (separation approximately 19
arcsec) is a B9V star. The secondary shows strong Li 6708 absorption suggesting
youth, and has attracted attention in the past as a candidate post-T Tauri star
although this has subsequently been ruled out. It was previously known to be a
double-lined spectroscopic binary (F8+G6) with a period of 17.6 days, and to
show velocity residuals indicating a more distant massive third companion with
a period of at least 8 years. Based on our radial velocity measurements
covering more than two cycles of the outer orbit, along with other
measurements, we derive an accurate triple orbital solution giving an outer
period of 9.447 +/- 0.017 yr. The third object is more massive than either of
the other two components of HD 27638B, but is not apparent in the spectra. We
derive absolute visual magnitudes and effective temperatures for the three
visible stars in HD 27638. Isochrone fitting based on those properties gives an
age of 200 +/- 50 Myr for the system. We infer also an inclination angle of
about 53.3 degrees for the inner orbit of HD 27638B. We detect a near-infrared
excess in HD 27638B which we attribute to the third star being a close binary
composed of late-type stars. This explains its large mass and lack of a visible
signature. Modeling of this excess allows us to infer not only the masses of
the components of the unseen companion, but also the inclination angle of the
outer orbit (approximately 73 deg). The HD 27638 system is thus at least
quintuple.


title: Massive stars in sub-parsec rings around galactic centers

abstract:
  We consider the structure of self-gravitating marginally stable accretion
disks in galactic centers in which a small fraction of the disk mass has been
converted into proto-stars. We find that proto-stars accrete gaseous disk
matter at prodigious rates. Mainly due to the stellar accretion luminosity, the
disk heats up and geometrically thickens, shutting off further disk
fragmentation. The existing proto-stars however continue to gain mass by gas
accretion. As a results, the initial mass function for disk-born stars at
distances R ~ 0.03-3 parsec from the super-massive black hole should be
top-heavy. The effect is most pronounced at around R ~ 0.1 parsec. We suggest
that this result explains observations of rings of young massive stars in our
Galaxy and in M31, and predict that more of such rings will be discovered.


title: Origin and Dynamical Evolution of Comets and their Reservoirs

abstract:
  This text was originally written to accompany a series of lectures that I
gave at the `35th Saas-Fee advanced course' in Switzerland and at the Institute
for Astronomy of the University of Hawaii. It reviews my current understanding
of the dynamics of comets and of the origin and primordial sculpting of their
reservoirs. It starts discussing the structure of the Kuiper belt and the
current dynamics of Kuiper belt objects, including scattered disk objects. Then
it discusses the dynamical evolution of Jupiter family comets from the
trans-Neptunian region, and of long period comets from the Oort cloud. The
formation of the Oort cloud is then reviewed, as well as the primordial
sculpting of the Kuiper belt. Finally, these issues are revisited in the light
of a new model of giant planets evolution that has been developed to explain
the origin of the late heavy bombardment of the terrestrial planets.


title: A MERLIN Observation of PSR B1951+32 and its associated Plerion

abstract:
  In an investigative 16 hour L band observation using the MERLIN radio
interferometric array, we have resolved both the pulsar PSR B1951+32 and
structure within the flat spectral radio continuum region, believed to be the
synchrotron nebula associated with the interaction of the pulsar and its `host'
supernova remnant CTB 80. The extended structure we see, significant at $\sim$
4.5 $\sigma$, is of dimensions 2.5" $\times$ 0.75", and suggests a sharp bow
shaped arc of shocked emission, which is correlated with similar structure
observed in lower resolution radio maps and X-ray images. Using this MERLIN
data as a new astrometric reference for other multiwavelength data we can place
the pulsar at one edge of the HST reported optical synchrotron knot, ruling out
previous suggested optical counterparts, and allowing an elementary analysis of
the optical synchrotron emission which appears to trail the pulsar. The latter
is possibly a consequence of pulsar wind replenishment, and we suggest that the
knot is a result of magnetohydrodynamic (MHD) instabilities. These being so, it
suggests a dynamical nature to the optical knot, which will require high
resolution optical observations to confirm.


title:
Multiplicity of very low-mass objects in the Upper Scorpius OB
  association: a possible wide binary population

abstract:
  We report the initial results of a VLT/NACO high spatial resolution imaging
survey for multiple systems among 58 M-type members of the nearby Upper
Scorpius OB association. Nine pairs with separations below 100 have been
resolved. Their small angular separations and the similarity in the brightness
of the components (DMagK <1 for all of them), indicate there is a reasonable
likelihood several of them are true binaries rather than chance projections.
Follow-up imaging observations with WHT/LIRIS of the two widest binaries
confirm that their near-infrared colours are consistent with physical very low
mass binaries. For one of these two binaries, WHT/LIRIS spectra of each
component were obtained. We find that the two components have similar M6-M7
spectral types and signatures of low-gravity, as expected for a young brown
dwarf binary in this association. Our preliminary results indicate a possible
population of very low-mass binaries with semimajor axis in the range 100 AU
150 AU, which has not been seen in the Pleiades open cluster. If these
candidates are confirmed (one is confirmed by this work), these results would
indicate that the binary properties of very low-mass stars and brown dwarfs may
depend on the environment where they form.


title:
On the Dissociation Equilibrium of H2 in Very Cool, Helium-Rich White
  Dwarf Atmospheres

abstract:
  We investigate the dissociation equilibrium of $\rm H_2$ in very cool,
helium-rich white dwarf atmospheres. We present the solution of the non-ideal
chemical equilibrium for the dissociation of molecular hydrogen in a medium of
dense helium. We find that at the photosphere of cool white dwarfs of $T_{\rm
eff}\rm=4000 K$, the non-ideality results in an increase of the mole fraction
of molecular hydrogen by up to a factor of $\sim 10$, compared to the
equilibrium value for the ideal gas. This increases the $\rm H_{2}-He$ CIA
opacity by an order of magnitude and will affect the determination of the
abundance of hydrogen in very cool, helium-rich white dwarfs.


title: Bright X-ray Transients in M31: 2004 July XMM-Newton Observations

abstract:
  We present the results of X-ray observations of four bright transients
sources detected in the July 2004 XMM-Newton observations of the central bulge
of M31. Two X-ray sources, XMMU J004315.5+412440 and XMMU J004144.7+411110,
were discovered for the first time. Two other sources, CXOM31 J004309.9+412332
and CXOM31 J004241.8+411635, were previously detected by Chandra. The
properties of the sources suggest their identification with accreting binary
systems in M31. The X-ray spectra and variability of two sources, XMMU
J004144.7+411110 and CXOM31 J004241.8+411635, are similar to that of the
Galactic black hole transients, making them a good black hole candidates. The
X-ray source XMMU J004315.5+412440 demonstrates a dramatic decline of the X-ray
flux on a time scale of three days, and a remarkable flaring behavior on a
short time scales. The X-ray data on XMMU J004315.5+412440 and CXOM31
J004309.9+412332 suggest that they can be either black hole or neutron star
systems. Combining the results of 2000-2004 XMM observations of M31, we
estimate a total rate of the bright transient outbursts in the central region
of M31 to be 6-12 per year, in agreement with previous studies.


title:
Simple, Accurate, Approximate Orbits in the Logarithmic and a Range of
  Power-Law Galactic Potentials

abstract:
  Curves in a family derived from powers of the polar coordinate formula for
ellipses are found to provide good fits to bound orbits in a range of power-law
potentials. This range includes the well-known $1/r$ (Keplerian) and
logarithmic potentials. These approximate orbits, called p-ellipses, retain
some of the basic geometric properties of ellipses. They satisfy and generalize
Newton's apsidal precession formula, which is one of the reasons for their
surprising accuracy. Because of their simplicity the p-ellipses make very
useful tools for studying trends among power-law potentials, and especially the
occurence of closed orbits. The occurence of closed or nearly closed orbits in
different potentials highlights the possibility of period resonances between
precessing, eccentric orbits and circular orbits, or between the precession
period of multi-lobed closed orbits and satellite periods. These orbits and
their resonances promise to help illuminate a number of problems in galaxy and
accretion disk dynamics.


title:
Constraints on Fundamental Cosmological Parameters with Upcoming
  Redshifted 21 cm Observations

abstract:
  Constraints on cosmological parameters from upcoming measurements with the
Mileura Widefield Array-Low Frequency Demonstrator (MWA-LFD) of the redshifted
21 cm power spectrum are forecast assuming a flat LCDM cosmology and that the
reionization of neutral hydrogen in the intergalactic medium occurs below a
redshift of z=8. We find that observations with the MWA-LFD cannot constrain
the underlying cosmology in this scenario. In principle, a similar experiment
with a 10-fold increase in collecting area could provide useful constraints on
the slope of the inflationary power spectrum, n_s, and the running of the
spectral index, alpha_s, but these constraints are subject to the caveat that
even a small reionization contribution could be confused with the cosmological
signal. In addition to the redshifted 21 cm signal, we include two nuisance
components in our analysis related to the systematics and astrophysical
foregrounds present in low-frequency radio observations. These components are
found to be well separated from the signal and contribute little uncertainty
(<30%) to the measured values of the cosmological model parameters.


title:
Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch
  of Reionization

abstract:
  A number of radio interferometers are currently being planned or constructed
to observe 21 cm emission from reionization. Not only will such measurements
provide a detailed view of that epoch, but, since the 21 cm emission also
traces the distribution of matter in the Universe, this signal can be used to
constrain cosmological parameters at 6 < z < 20. The sensitivity of an
interferometer to the cosmological information in the signal may depend on how
precisely the angular dependence of the 21 cm 3-D power spectrum can be
measured. Utilizing an analytic model for reionization, we quantify all the
effects that break the spherical symmetry of the 3-D 21 cm power spectrum and
produce physically motivated predictions for this power spectrum. We find that
upcoming observatories will be sensitive to the 21 cm signal over a wide range
of scales, from larger than 100 to as small as 1 comoving Mpc. We consider
three methods to measure cosmological parameters from the signal: (1) direct
fitting of the density power spectrum to the signal, (2) using only the
velocity field fluctuations in the signal, (3) looking at the signal at large
enough scales such that all fluctuations trace the density field. With the
foremost method, the first generation of 21 cm observations should moderately
improve existing constraints on cosmological parameters for certain
low-redshift reionization scenarios, and a two year observation with the second
generation interferometer MWA5000 can improve constraints on Omega_w, Omega_m
h^2, Omega_b h^2, Omega_nu, n_s, and alpha_s. If the Universe is substantially
ionized by z = 12 or if spin temperature fluctuations are important, we show
that it will be difficult to place competitive constraints on cosmological
parameters with any of the considered methods.


title: The MHD collapsar model for GRBs: an inflow produces an outflow

abstract:
  We present our recent results from numerical simulations of a magnetized flow
in the vicinity of a black hole in the context of the collapsar model for GRBs.
The simulations show that after an initial transient, the flow settles into a
complex convolution of several distinct, time-dependent flow components
including an accretion torus, its corona and outflow, an inflow and an outflow
in the polar funnel. We focus on studying the nature and connection between
these components, in particular between the inflows and related outflows. We
find that rotational and MHD effects launch, accelerate, and sustain the
outflows. We also find that an outflow can be formed even when the collapsing
envelope has initially a very weak magnetic field and a very small angular
momentum. Our main conclusion is that even for a relatively weak initial
magnetic field and a slow rotation, a gravitational collapse of a stellar
envelope can lead to formation of a very strong and very fast jet.


title: Constraints on Cosmic Neutrino Fluxes from the ANITA Experiment

abstract:
  We report new limits on cosmic neutrino fluxes from the test flight of the
Antarctic Impulsive Transient Antenna (ANITA) experiment, which completed an
18.4 day flight of a prototype long-duration balloon payload, called
ANITA-lite, in early 2004. We search for impulsive events that could be
associated with ultra-high energy neutrino interactions in the ice, and derive
limits that constrain several models for ultra-high energy neutrino fluxes. We
rule out the long-standing Z-burst model as the source for the ultra-high
energy cosmic rays.


title:
The Youngest Stellar clusters Clusters associated with massive
  protostellar candidates

abstract:
  We report on the identification of 54 embedded clusters around 217 massive
protostellar candidates of which 34 clusters are new detections. The embedded
clusters are identified as stellar surface density enhancements in the 2 $\mu$m
All Sky Survey (2MASS) data. Because the clusters are all associated with
massive stars in their earliest evolutionary stage, the clusters should also be
in an early stage of evolution. Thus the properties of these clusters should
reflect properties associated with their formation rather than their evolution.
For each cluster, we estimate the mass, the morphological type, the photometry
and extinction. The clusters in our study, by their association with massive
protostars and massive outflows, reinstate the notion that massive stars begin
to form after the first generation of low mass stars have completed their
accretion phase. Further, the observed high gas densities and accretion rates
at the centers of these clusters is consistent with the hypothesis that high
mass stars form by continuing accretion onto low mass stars.


title:
Temperature Fluctuations of the Cosmic Microwave Background Radiation: A
  Case of Nonextensivity?

abstract:
  Temperature maps of the Cosmic Microwave Background (CMB) radiation, as those
obtained by the Wilkinson Microwave Anisotropy Probe (WMAP), provide one of the
most precise data sets to test fundamental hypotheses of modern cosmology. One
of these issues is related to the statistical properties of the CMB temperature
fluctuations, which would have been produced by Gaussian random density
fluctuations when matter and radiation were in thermal equilibrium in the early
Universe. We analysed here the WMAP data and found that the distribution of the
CMB temperature fluctuations P^{CMB}(Delta T) can be quite well fitted by the
anomalous temperature distribution emerging within nonextensive statistical
mechanics. This theory is based on the nonextensive entropy S_q = k (1 - \int
dx [P_q(x)]^q) /(q-1), with the Boltzmann-Gibbs expression as the limit case q
-> 1. For the frequencies investigated (\nu= 40.7, 60.8, and 93.5 GHz), we
found that P^{CMB}(Delta T) is well described by P_q(Delta T) \propto 1/[1 +
(q-1) B(\nu) (Delta T)^2]^{1/(q-1)}, with q = 1.055 \pm 0.002, which exclude,
at the 99% confidence level, exact Gaussian temperature distributions
P^{Gauss}(Delta T) \propto e^{- B(\nu) Delta T^2}, corresponding to the q -> 1
limit, to properly represent the CMB temperature fluctuations measured by WMAP.


title:
Subaru IR Echelle Spectroscopy of Herbig-Haro Driving Sources I. H_2 and
  [Fe II] Emission

abstract:
  We present infrared echelle spectroscopy of three Herbig-Haro (HH) driving
sources (SVS 13, B5-IRS 1 and HH 34 IRS) using Subaru-IRCS. The large diameter
of the telescope and wide spectral coverage of the spectrograph allowed us to
detect several H_2 and [Fe II] lines in the H- and K-bands. These include H_2
lines arising from v=1-3 and J=1-11, and [Fe II] lines with upper level
energies of E/k=1.1-2.7x10^4 K. For all objects the outflow is found to have
two velocity components: (1) a high-velocity (-70 to -130 km s^-1) component
(HVC), seen in [Fe II] or H_2 emission and associated with a collimated jet;
and (2) a low-velocity (-10 to -30 km s^-1) component (LVC), which is seen in
H_2 emission only and is spatially more compact. Such a kinematic structure
resembles optical forbidden emission line outflows associated with classical T
Tauri stars, whereas the presence of H_2 emission reflects the low-excitation
nature of the outflowing gas close to these protostars. The observed H_2 flux
ratios indicate a temperature of 2-3x10^3 K, and a gas density of 10^5 cm^-3 or
more, supporting shocks as the heating mechanism. B5-IRS 1 exhibits faint
extended emission associated with the H_2-LVC, in which the radial velocity
slowly increases with distance from the protostar (by ~20 km s^-1 at ~500 AU).
This is explained as warm molecular gas entrained by an unseen wide-angled
wind. The [Fe II] flux ratios indicate electron densities to be ~10^4 cm^-3 or
greater, similar to forbidden line outflows associated with classical T Tauri
stars. Finally the kinematic structure of the [Fe II] emission associated with
the base of the B5-IRS 1 and HH 34 IRS outflows is shown to support disk-wind
models.


title: Linear Thermal Instability and Fluctuations in Molecular Clouds

abstract:
  Evidence of small-scale condensations in the magnetic molecular clouds has
been accumulating over the past decades through radio and optical/ultraviolet
observations. The origin and shape of these small-scale condensations is a
disputable issue. Nejad-Asghar & Ghanbari (2004 hereafter NG) have recently
studied the effect of the linear thermal instability on the formation of
fluctuations in molecular clouds. The authors inferred that under certain
conditions (e.g., depending on expansion or contraction of the background)
thermal instability and ambipolar diffusion can produce spherical, oblate, or
prolate condensations.


title: On the Spectral Lags of the Short Gamma-Ray Bursts

abstract:
  We present a detail analysis on the spectral lags of the short gamma-ray
bursts (GRBs) and compare them with that of the long GRBs by using the
CGRO/BATSE GRB Catalog. Our results are as follows. (1)The spectral lag
distribution of the short GRBs is significantly different from that of the long
GRBs. Excluding the statistical fluctuation effect, a proportion of ~17% of the
short GRBs have a negative spectral lag, i.e., the hard photons being lag
behind the soft photons. We do not find any peculiar features from their light
curves to distinguish these bursts from those with a positive spectral lag. We
argue that a more physical mechanism dominated the hard lag may be hid behind
the morphological features of the light curves. This should be a great
challenge to the current GRB models. We notice that this proportion is
consistent with the proportion of short GRBs correlated with nearby galaxies
newly discovered by Tanvir et al., although it is unclear if these short GRBs
are indeed associated with the sources originated at low redshift. (2)While the
spectral lags of the long GRBs are strongly correlated with the pulse
durations, they are not for the short GRBs. However, the ratios of the spectral
lag to the pulse duration for the short and long GRBs normally distributed at
0.023 and 0.046, respectively, with the sample width, indicating that the
curvature effect alone could not explain the difference of the spectral lags
between the two types of GRBs. The hydrodynamic timescales of the outflows and
the radiative processes at work in GRBs might also play an important role as
suggested by Daigne and Mochkovitch.


title:
On the Collapsar Model of Long Gamma-Ray Bursts: Constraints from Cosmic
  Metallicity Evolution

abstract:
  We explore the consequences of new observational and theoretical evidence
that long gamma-ray bursts prefer low metallicity environments. Using recently
derived mass-metallicity correlations and the mass function from SDSS studies,
and adopting an average cosmic metallicity evolution from \citet{kewley2005}
and \citet{savaglio2005} we derive expressions for the the relative number of
massive stars formed below a given fraction of solar metallicity, $\epsilon$,
as function of redshift. We demonstrate that about 1/10th of all stars form
with $\epsilon < 0.1$. Therefore, a picture where the majority of GRBs form
with $\epsilon < 0.1$ is not inconsistent with an empirical global SN/GRB ratio
of 1/1000. It implies that (1) GRB's peak at a significantly higher redshift
than supernovae; (2) massive star evolution at low metallicity may be
qualitatively different and; (3) the larger the low-metallicity bias of GRBs
the less likely binary evolution channels can be significant GRB producers.


title:
Dust sedimentation and self-sustained Kelvin-Helmholtz turbulence in
  protoplanetary disk mid-planes. I. Radially symmetric simulations

abstract:
  We perform numerical simulations of the Kelvin-Helmholtz instability in the
mid-plane of a protoplanetary disk. A two-dimensional corotating slice in the
azimuthal--vertical plane of the disk is considered where we include the
Coriolis force and the radial advection of the Keplerian rotation flow. Dust
grains, treated as individual particles, move under the influence of friction
with the gas, while the gas is treated as a compressible fluid. The friction
force from the dust grains on the gas leads to a vertical shear in the gas
rotation velocity. As the particles settle around the mid-plane due to gravity,
the shear increases, and eventually the flow becomes unstable to the
Kelvin-Helmholtz instability. The Kelvin-Helmholtz turbulence saturates when
the vertical settling of the dust is balanced by the turbulent diffusion away
from the mid-plane. The azimuthally averaged state of the self-sustained
Kelvin-Helmholtz turbulence is found to have a constant Richardson number in
the region around the mid-plane where the dust-to-gas ratio is significant.
Nevertheless the dust density has a strong non-axisymmetric component. We
identify a powerful clumping mechanism, caused by the dependence of the
rotation velocity of the dust grains on the dust-to-gas ratio, as the source of
the non-axisymmetry. Our simulations confirm recent findings that the critical
Richardson number for Kelvin-Helmholtz instability is around unity or larger,
rather than the classical value of 1/4


title:
An Atlas of K-line Spectra for Cool Magnetic CP Stars: The Wing-Nib
  Anomaly (WNA)

abstract:
  We present a short atlas illustrating the unusual Ca {\sc ii} K-line profiles
in upper main sequence stars with anomalous abundances. Slopes of the profiles
for 10 cool, magnetic chemically peculiar (CP) stars change abruptly at the
very core, forming a deep "nib." The nibs show the same or nearly the same
radial velocity as the other atomic lines. The near wings are generally more
shallow than in normal stars. In three magnetic CP stars, the K-lines are too
weak to show this shape, though the nibs themselves are arguably present. The
Ca {\sc ii} H-lines also show deep nibs, but the profiles are complicated by
the nearby, strong H$\epsilon$ absorption. The K-line structure is nearly
unchanged with phase in $\beta$ CrB and $\alpha$ Cir. Calculations, including
NLTE, show that other possibilities in addition to chemical stratification may
yield nib-like cores.


title:
Study of Fe K-alpha lines in Non-magnetic Cataclysmic Variables using
  Chandra HEG data

abstract:
  Results from a study of Fe K-alpha emission lines for a sample of six
non-magnetic Cataclysmic Variables (CVs) using the high resolution X-ray data
from the Chandra High Energy Transmission Grating (HETG) are presented. Two of
the sources, SS Cyg and U Gem are observed in both quiescent and outburst
states whereas V603 Aql, V426 Oph, WX Hyi and SU UMa are observed only in
quiescence. The fluorescent Fe line is prominent in V603 Aql, V426 Oph and SS
Cyg during quiescence indicating the presence of a conspicuous reflection
component in these sources. The observed equivalent width of the fluorescent Fe
line is consistent with reflection from a white dwarf surface that subtends 2pi
solid angle at the X-ray source. During the outburst in SS Cyg, the fluorescent
line is red-shifted by about 2300 km/s. The Fe XXV triplet at 6.7 keV is found
to be dominant in all sources. The value of the G-ratio derived from the Fe XXV
triplet indicates that the plasma is in collisional ionization equilibrium
during the quiescent state. The Fe XXV line is significantly broadened in U Gem
and SS Cyg during the outbursts compared to quiescence, indicating the presence
of a high velocity material near the white dwarf during the outburst. The ratio
of Fe XXVI/XXV indicates a higher ionization temperature during quiescence than
in outburst in U Gem and SS Cyg.


title:
High Energy Neutrino Emission and Neutrino Background from Gamma-Ray
  Bursts in the Internal Shock Model

abstract:
  High energy neutrino emission from GRBs is discussed. In this paper, by using
the simulation kit GEANT4, we calculate proton cooling efficiency including
pion-multiplicity and proton-inelasticity in photomeson production. First, we
estimate the maximum energy of accelerated protons in GRBs. Using the obtained
results, neutrino flux from one burst and a diffuse neutrino background are
evaluated quantitatively. We also take account of cooling processes of pion and
muon, which are crucial for resulting neutrino spectra. We confirm the validity
of analytic approximate treatments on GRB fiducial parameter sets, but also
find that the effects of multiplicity and high-inelasticity can be important on
both proton cooling and resulting spectra in some cases. Finally, assuming that
the GRB rate traces the star formation rate, we obtain a diffuse neutrino
background spectrum from GRBs for specific parameter sets. We introduce the
nonthermal baryon-loading factor, rather than assume that GRBs are main sources
of UHECRs. We find that the obtained neutrino background can be comparable with
the prediction of Waxman & Bahcall, although our ground in estimation is
different from theirs. In this paper, we study on various parameters since
there are many parameters in the model. The detection of high energy neutrinos
from GRBs will be one of the strong evidences that protons are accelerated to
very high energy in GRBs. Furthermore, the observations of a neutrino
background has a possibility not only to test the internal shock model of GRBs
but also to give us information about parameters in the model and whether GRBs
are sources of UHECRs or not.


title: The Big Bang Problems: Anisotropy of z <= 6 Redshifts

abstract:
  The three-dimensional space distribution of 48921 quasars and 16113 Seyfert
galaxies with redshifts z <= 6 is investigated. The global anisotropy caused by
the shift of the observer place by \simeq 50 Mpc from a center of their
symmetry (supposed center of the Metagalaxy) to the side of the vector with
equatorial coordinates \alpha \simeq 13 degrees and \delta \simeq 70 degrees
has been found in the placement of these objects. In the opposite direction
there exists the extensive region where the progressive decrease of redshifts
up to a minimum (near \alpha \simeq 193 degrees, \delta \simeq -70 degrees) is
observed. The influence of gravitational potential and possible rotation of the
Metagalaxy on the anisotropy of redshifts of the cosmological objects has been
considered.


title:
Correlations of near-infrared, optical and X-ray luminosity for
  early-type galaxies

abstract:
  The relation between X-ray luminosity and near-infrared luminosity for
early-type galaxies has been examined. Near-infrared (NIR) luminosities should
provide a superior measure of stellar mass compared to optical luminosities
used in previous studies, especially if there is significant star-formation or
dust present in the galaxies. However, we show that the X-ray-NIR relations are
remarkably consistent with the X-ray-optical relations. This indicates that the
large scatter of the relations is dominated by scatter in the X-ray properties
of early-type galaxies, and is consistent with early-types consisting of old,
quiescent stellar populations.
  We have investigated scatter in terms of environment, surface brightness
profile, Mg2, H_beta, H_gamma line strength indices, spectroscopic age, and
nuclear H_alpha emission. We found that galaxies with high Mg2 index, low
H_beta and H_gamma indices or a `core' profile have a large scatter in Lx,
whereas galaxies with low Mg2, high H_beta and H_gamma indices or `power-law'
profiles, generally have Lx<10^41 erg/s. There is no clear trend in the scatter
with environment or nuclear H_alpha emission.


title: Cluster Formation in Protostellar Outflow-Driven Turbulence

abstract:
  Most, perhaps all, stars go through a phase of vigorous outflow during
formation. We examine, through 3D MHD simulation, the effects of protostellar
outflows on cluster formation. We find that the initial turbulence in the
cluster-forming region is quickly replaced by motions generated by outflows.
The protostellar outflow-driven turbulence (``protostellar turbulence'' for
short) can keep the region close to a virial equilibrium long after the initial
turbulence has decayed away. We argue that there exist two types of turbulence
in star-forming clouds: a primordial (or ``interstellar'') turbulence and a
protostellar turbulence, with the former transformed into the latter mostly in
embedded clusters such as NGC 1333. Since the majority of stars are thought to
form in clusters, an implication is that the stellar initial mass function is
determined to a large extent by the stars themselves, through outflows which
individually limit the mass accretion onto forming stars and collectively shape
the environments (density structure and velocity field) in which most cluster
members form. We speculate that massive cluster-forming clumps supported by
protostellar turbulence gradually evolve towards a highly centrally condensed
``pivotal'' state, culminating in rapid formation of massive stars in the
densest part through accretion.


title:
Constraining the Cosmological Parameters and Transition Redshift with
  Gamma-Ray Bursts and Supernovae

abstract:
  A new method of measuring cosmology with gamma-ray bursts(GRBs) has been
proposed by Liang and Zhang recently. In this method, only observable
quantities including the rest frame peak energy of the \nu F_\nu spectrum
(E'_p), the isotropic energy of GRB (E_{\gamma,iso}), and the break time of the
optical afterglow light curves in the rest frame (t'_b) are used. By
considering this method we constrain the cosmological parameters and the
redshift at which the universe expanded from the deceleration to acceleration
phase. We add five recently-detected GRBs to the sample and derive E_{\gamma,
iso}/10^{52} ergs=(0.93\pm 0.25)\times (E'_p/100 keV)^{1.91\pm 0.32}\times
(t'_b/day)^{-0.93\pm 0.38} for a flat cosmology with \Omega_M=0.28 and H_0=71.0
km s^{-1} Mpc^{-1}. This relation is independent of the medium density around
bursts and the efficiency of conversion of the explosion energy to gamma-ray
energy that are difficult to measure. We regard the E_{\gamma,iso}(E'_p, t'_b)
relationship as a standard candle and find 0.05<\Omega_M<0.48 and
\Omega_\Lambda<1.15 (at the 1\sigma confidence level). In a flat universe with
the cosmological constant we obtain 0.25<\Omega_M <0.46 and
0.54<\Omega_\Lambda<0.78 at the 1\sigma confidence level. The transition
redshift is z_T=0.69_{-0.12}^{+0.11}. Combining 20 GRBs and 157 type Ia
supernovae, we find \Omega_M=0.29 \pm0.03 for a flat universe and the
transition redshift is z_T=0.61_{-0.05}^{+0.06}, which is slightly larger than
the value found by considering SNe Ia alone. In particular, We also discuss
several dark-energy models in which the equation of state w(z) is arameterized
and investigate constraints on the cosmological parameters in detail.


title:
Fine-Structure FeII and SiII Absorption in the Spectrum of GRB 051111:
  Implications for the Burst Environment

abstract:
  We present an analysis of fine-structure transitions of FeII and SiII
detected in a high-resolution optical spectrum of the afterglow of GRB 051111
(z=1.54948). The fine-structure absorption features arising from FeII* to
FeII****, as well as SiII*, are confined to a narrow velocity structure
extending over +/-30 km/s, which we interpret as the burst local environment,
most likely a star forming region. We investigate two scenarios for the
excitation of the fine-structure levels by collisions with electrons and
radiative pumping by an infra-red or ultra-violet radiation field produced by
intense star formation in the GRB environment, or by the GRB afterglow itself.
We find that the conditions required for collisional excitation of FeII
fine-structure states cannot be easily reconciled with the relatively weak
SiII* absorption. Radiative pumping by either IR or UV emission requires >10^3
massive hot OB stars within a compact star-forming region a few pc in size, and
in the case of IR pumping a large dust content. On the other hand, it is
possible that the GRB itself provides the source of IR and/or UV radiation, in
which case we estimate that the excitation takes place at a distance of ~10-20
pc from the burst. Detailed radiative transfer calculations are required in
order to verify that excitation of the low-ionization fine-structure states is
possible given the intense UV flux from the burst. Still, it is clear that GRB
absorption spectroscopy can provide direct information on the mode and
conditions of star formation at high redshift.


title:
The Impact of Box Size on the Properties of Dark Matter Haloes in
  Cosmological Simulations

abstract:
  We investigate the impact finite simulation box size has on the structural
and kinematic properties of Cold Dark Matter haloes forming in cosmological
simulations. Our approach involves generating a single realisation of the
initial power spectrum of density perturbations and studying how truncation of
this power spectrum on scales larger than L_cut affects the structure of dark
matter haloes at z=0. In particular, we have examined the cases of L_cut =
f_cut L_box with f_cut=1 (i.e. no truncation), 1/2, 1/3 and 1/4. In common with
previous studies, we find that the suppression of long wavelength perturbations
reduces the strength of clustering, as measured by a suppression of the 2-point
correlation function xi(r), and reduces the numbers of the most massive haloes,
as reflected in the depletion of the high mass end of the mass function n(M).
Interestingly, we find that truncation has little impact on the internal
properties of haloes. The masses of high mass haloes decrease in a systematic
manner as L_cut is reduced, but the distribution of concentrations is
unaffected. On the other hand, the median spin parameter is ~50% lower in runs
with f_cut<1. We argue that this is an imprint of the linear growth phase of
the halo's angular momentum by tidal torquing, and that the absence of any
measurable trend in concentration and the weak trend observed in halo shape
reflect the importance of virialisation and complex mass accretion histories
for these quantities. These results are of interest for studies that require
high mass resolution and statistical samples of simulated haloes, such as
simulations of the population of first stars. Our analysis shows that
large-scale tidal fields have relatively little effect on the internal
properties of Cold Dark Matter haloes and hence may be ignored in such studies.


title: Comments on an Expanding Universe

abstract:
  Various results are obtained for a Friedmann-Robertson-Walker cosmology. We
derive an exact equation that determines Hubble's law, clarify issues
concerning the speeds of faraway objects and uncover a "tail-light angle
effect" for distant luminous sources. The latter leads to a small, previously
unnoticed correction to the parallax distance formula.


title: MAGIC observations of very high energy gamma-rays from HESS J1813-178

abstract:
  Recently, the HESS collaboration has reported the detection of gamma-ray
emission above a few hundred GeV from eight new sources located close to the
Galactic Plane. The source HESS J1813-178 has sparked particular interest, as
subsequent radio observations imply an association with SNR G12.82-0.02.
Triggered by the detection in VHE gamma-rays, a positionally coincident source
has also been found in INTEGRAL and ASCA data. In this Letter we present MAGIC
observations of HESS J1813-178, resulting in the detection of a differential
gamma-ray flux consistent with a hard-slope power law, described as dN/(dA dt
dE) = (3.3+/-0.5)*10^{-12} (E/TeV)^{-2.1+/-0.2} cm^(-2)s^(-1)TeV^(-1). We
briefly discuss the observational technique used, the procedure implemented for
the data analysis, and put this detection in the perspective of multifrequency
observations.


title:
Multi-periodic variations in the last 104 years light curve of the
  symbiotic star BF Cyg

abstract:
  We analyse a light curve of the symbiotic star BF Cyg, covering 114 years of
its photometric history. The star had a major outburst around the year 1894.
Since then the mean optical brightness of the system is in steady decline,
reaching only in the last few years its pre-outburst value. Superposed on this
general decline are some 6 less intense outbursts of 1-2 magnitude and duration
of 2000-5000 days. We find a cycle of ~6376 days, or possibly twice this
period, in the occurrence of these outbursts. We suggest that the origin of the
system outbursts is in some magnetic cycle in the outer layers of the giant
star of the system, akin to the less intense ~8000 days magnetic cycle of our
Sun. We further find, that in addition to its well known binary period of 757.3
days, BF Cyg possesses also another photometric period of 798.8 days. This
could be the rotation period of the giant star of the system. If it is, the
beat period of these two periodicities, 14580 days, is the rotation period of a
tidal wave on the surface of the giant. A 4th period of 4436 days, the beat
period of the 14580 and the 6376 cycles is possibly also present in the LC. We
predict that BF Cyg will be at the peak of its next outburst around the month
of May in the year 2007. The newly discovered 798.8 days period explains the
disappearance of the orbital modulation at some epochs in the light curve. The
757.3 oscillations will be damped again around the year 2013.


title:
Correlated X-ray spectral and timing variability of the Be/X-ray binary
  V0332+53/BQ Cam during a type II outburst

abstract:
  We have used INTEGRAL & RXTE data to investigate the timing properties of the
source in correlation with its spectral states as defined by different
positions in the colour-colour diagram. The source shows two distinct branches
in the colour-colour diagram that resemble those of the Z sources. The hard
branch (similar to the horizontal branch of Z sources) is characterised by a
low-amplitude change of the hard colour compared to the change in the soft
colour. In the soft branch (analogue to the normal branch) the amplitude of
variability of the hard colour is about three times larger than that of the
soft colour. As the count rate decreases the source moves up gradually through
the soft to the hard branch. The aperiodic variability (excluding the pulse
noise) consists of band-limited noise (represented by three broad Lorentzian
components) and two QPOs at 0.05 Hz and 0.22 Hz. The strength of the lower
frequency QPO increases as the source approaches the hard branch (similar to
HBOs in Z sources). The higher frequency QPO reaches maximum significance when
the source is in the middle of the branch (like NBOs). We have performed the
first measurements of phase lags in the band limited noise below 8 Hz in an
accreting X-ray pulsar and found that soft lags dominate at high frequencies.
Above the pulse frequency (0.23 Hz), the amplitude of the lag increases as the
X-ray flux increases. The Z topology appears to be a signature of the neutron
star binaries as it is present in all types of neutron-star binaries (Z, atoll
and, as we show here, in accreting pulsars as well). However, the motion along
this track, the time scales through the different branches of the diagram and
the aperiodic variability associated with portions of the Z track differ for
each subclass of neutron-star binary.


title: Deep 1.4-GHz observations of diffuse polarized emission

abstract:
  Polarized diffuse emission observations at 1.4-GHz in a high Galactic
latitude area of the northern Celestial hemisphere are presented. The 3.2 X 3.2
deg^2 field, centred at RA = 10h 58m, Dec = +42deg 18' (B1950), has Galactic
coordinates l~172deg, b~+63deg and is located in the region selected as
northern target of the BaR-SPOrt experiment. Observations have been performed
with the Effelsberg 100-m telescope. We find that the angular power spectra of
the E- and B-modes have slopes of beta_E = -1.79 +/- 0.13 and beta_B = -1.74
+/- 0.12, respectively. Because of the very high Galactic latitude and the
smooth emission, a weak Faraday rotation action is expected, which allows both
a fair extrapolation to Cosmic Microwave Background Polarization (CMBP)
frequencies and an estimate of the contamination by Galactic synchrotron
emission. We extrapolate the E-mode spectrum up to 32-GHz and confirm the
possibility to safely detect the CMBP E-mode signal in the Ka band found in
another low emission region (Carretti et al. 2005b). Extrapolated up to 90-GHz,
the Galactic synchrotron B-mode looks to compete with the cosmic signal only
for models with a tensor-to-scalar perturbation power ratio T/S < 0.001, which
is even lower than the T/S value of 0.01 found to be accessible in the only
other high Galactic latitude area investigated to date. This suggests that
values as low as T/S = 0.01 might be accessed at high Galactic latitudes. Such
low emission values can allow a significant red-shift of the best frequency to
detect the CMBP B-mode, also reducing the contamination by Galactic dust, and
opening interesting perspectives to investigate Inflation models.


title:
Most precise single redshift bound to the variability of the
  fine-structure constant

abstract:
  Verification of theoretical predictions of an oscillating behavior of the
fine-structure constant, alpha, with cosmic time requires high precision
measurements at individual redshifts, while in earlier studies the mean Delta
alpha/alpha values averaged over wide redshift intervals were usually reported.
This requirement can be met via the Single Ion Differential alpha Measurement
(SIDAM) procedure. We apply SIDAM to the FeII lines associated with the damped
Ly-alpha system observed at z=1.15 in the spectrum of HE0515-4414. The weighted
mean calculated on base of carefully selected 34 FeII pairs is <Delta
alpha/alpha>=(-0.07+/-0.84)10^{-6}. The precision of this estimate represents
the absolute improvement with respect to what has been done in the measurements
of Delta alpha/alpha.


title: Understanding the Radio Variability of Sgr A*

abstract:
  We determine the characteristics of the 7mm to 20cm wavelength radio
variability in Sgr A* on time scales from days to three decades. The amplitude
of the intensity modulation is between 30 and 39% at all wavelengths. Analysis
of uniformly sampled data with proper accounting of the sampling errors
associated with the lightcurves shows that Sgr A* exhibits no 57- or 106-day
quasi-periodic oscillations, contrary to previous claims. The cause of the
variability is investigated by examining a number of plausible scintillation
models, enabling those variations which could be attributed to interstellar
scintillation to be isolated from those that must be intrinsic to the source.
Thin-screen scattering models do not account for the variability amplitude on
most time scales. However, models in which the scattering region is extended
out to a radius of 50-500pc from the Galactic Center account well for the broad
characteristics of the variability on >4-day time scales. The ~ 10% variability
on <4-day time scales at 0.7-3cm appears to be intrinsic to the source. The
degree of scintillation variability expected at millimeter wavelengths depends
sensitively on the intrinsic source size; the variations, if due to
scintillation, would require an intrinsic source size smaller than that
expected.


title:
A multisite photometric campaign on the Pre-Main-Sequence delta Scuti
  pulsator IP Per

abstract:
  We present the results of a photometric multisite campaign on the $\delta$
Scuti Pre-Main-Sequence star IP Per. Nine telescopes have been involved in the
observations, with a total of about 190 hours of observations over 38 nights.
Present data confirms the multiperiodic nature of this star and leads to the
identification of at least nine pulsational frequencies. Comparison with the
predictions of linear non-adiabatic radial pulsation models allowed us to
identify only five of the nine observed frequencies, and to constrain the
position of IP Per in the HR diagram. The latter is in good agreement with the
empirical determination of the stellar parameters obtained by Miroshnichenko et
al. (2001). An initial interpretation of the observed frequencies using the
Aarhus non-radial pulsation code suggests that three frequencies could be
associated with non-radial ($l$=2) modes. Finally, we present new evolutionary
and pulsation models at lower metallicity (Z=0.008) to take into account the
possibility that IP Per is metal deficient, as indicated by Miroshnichenko et
al. (2001).


title:
Oxygen abundances in metal-poor subgiants as determined from [O I], O I
  and OH lines

abstract:
  The debate on the oxygen abundances of metal-poor stars has its origin in
contradictory results obtained using different abundance indicators. To achieve
a better understanding of the problem we have acquired high quality spectra
with the Ultraviolet and Visual Echelle Spectrograph at VLT, with a
signal-to-noise of the order of 100 in the near ultraviolet and 500 in the
optical and near infrared wavelength range. Three different oxygen abundance
indicators, OH ultraviolet lines around 310.0 nm, the [OI] line at 630.03 nm
and the OI lines at 777.1-5 nm were observed in the spectra of 13 metal-poor
subgiants with -3.0<=[Fe/H]<=-1.5. Oxygen abundances were obtained from the
analysis of these indicators which was carried out assuming local thermodynamic
equilibrium and plane-parallel model atmospheres. Abundances derived from OI
were corrected for departures from local thermodynamic equilibrium. Stellar
parameters were computed using Teff-vs-color calibrations based on the infrared
flux method and Balmer line profiles, Hipparcos parallaxes and FeII lines.
[O/Fe] values derived from the forbidden line at 630.03 nm are consistent with
an oxygen/iron ratio that varies linearly with [Fe/H] as
[O/Fe]}=-0.09(+/-0.08)[Fe/H]+0.36(+/-0.15). Values based on the OI triplet are
on average 0.19+/-0.22 dex(s.d.) higher than the values based on the forbidden
line while the agreement between OH ultraviolet lines and the forbidden line is
much better with a mean difference of the order of -0.09+/-0.25 dex(s.d.). In
general, our results follow the same trend as previously published results with
the exception of the ones based on OH ultraviolet lines. In that case our
results lie below the values which gave rise to the oxygen abundance debate for
metal-poor stars.


title:
Ultraviolet Radiation Constraints around the Circumstellar Habitable
  Zones

abstract:
  Ultraviolet radiation is known to inhibit photosynthesis, induce DNA
destruction and cause damage to a wide variety of proteins and lipids. In
particular, UV radiation between 200-300 nm becomes energetically very damaging
to most of the terrestrial biological systems. On the other hand, UV radiation
is usually considered one of the most important energy source on the primitive
Earth for the synthesis of many biochemical compounds and, therefore, essential
for several biogenesis processes. In this work, we use these properties of the
UV radiation to define the bounderies of an ultraviolet habitable zone. We also
analyze the evolution of the UV habitable zone during the main sequence stage
of the star. We apply these criteria to study the UV habitable zone for those
extrasolar planetary systems that were observed by the International
Ultraviolet Explorer (IUE). We analyze the possibility that extrasolar planets
and moons could be suitable for life, according to the UV constrains presented
in this work and other accepted criteria of habitability (liquid water, orbital
stability, etc.).


title: Gas Flow Across Gaps in Protoplanetary Disks

abstract:
  We analyze the gas accretion flow through a planet-produced gap in a
protoplanetary disk. We adopt the alpha disk model and ignore effects of
planetary migration. We develop a semi-analytic, one-dimensional model that
accounts for the effects of the planet as a mass sink and also carry out
two-dimensional hydrodynamical simulations of a planet embedded in a disk. The
predictions of the mass flow rate through the gap based on the semi-analytic
model generally agree with the hydrodynamical simulations at the 25% level.
Through these models, we are able to explore steady state disk structures and
over large spatial ranges. The presence of an accreting Jupiter-mass planet
significantly lowers the density of the disk within a region of several times
the planet's orbital radius. The mass flow rate across the gap (and onto the
central star) is typically 10% to 25% of the mass accretion rate outside the
orbit of the planet, for planet-to-star mass ratios that range from 5e-5 to
1e-3.


title: Li and Be depletion in metal-poor subgiants

abstract:
  A sample of metal-poor subgiants has been observed with the UVES spectrograph
at the Very Large Telescope and abundances of Li and Be have been determined.
Typical signal-to-noise per spectral bin values for the co-added spectra are of
the order of 500 for the Li I line (670.78 nm) and 100 for the Be II doublet
lines (313.04 nm). The spectral analysis of the observations was carried out
using the Uppsala suite of codes and MARCS (1D-LTE) model atmospheres with
stellar parameters from photometry, parallaxes, isochrones and Fe II lines.
Abundance estimates of the light elements were corrected for departures from
local thermodynamic equilibrium in the line formation. Effective temperatures
and Li abundances seem to be correlated and Be abundances correlate with [O/H].
Standard models predict Li and Be abundances approximately one order of
magnitude lower than main-sequence values which is in general agreement with
the observations. On average, our observed depletions seem to be 0.1 dex
smaller and between 0.2 and 0.4 dex larger (depending on which reference is
taken) than those predicted for Li and Be, respectively. This is not surprising
since the initial Li abundance, as derived from main-sequence stars on the
Spite plateau, may be systematically in error by 0.1 dex or more, and
uncertainties in the spectrum normalisation and continuum drawing may affect
our Be abundances systematically.


title:
Abundances of Vanadium and Bromine in 3 Cen A: Additional Odd-Z
  Anomalies

abstract:
  We report abundance excesses of 1.2 and 2.6 dex, respectively, for vanadium
and bromine in the hot, peculiar star 3 Cen A. Abundances for these two odd-Z
elements have not been previously reported for this star. Taken with previous
work, they strengthen the case of the origin of the abundance peculiarities by
diffusion.


title:
Optical/near-infrared colours of early-type galaxies and constraints on
  their star formation histories

abstract:
  (abridged) We introduce and discuss the properties of a theoretical
(B-K)-(J-K) integrated colour diagram for single-age, single-metallicity
stellar populations. This combination of integrated colours is able to largely
disentangle the well known age-metallicity degeneracy when the age of the
population is greater than ~300 Myr. We discuss in detail the effect on this
colour-colour diagram of alpha-enhanced metal abundance ratios, the presence of
blue horizontal branch stars unaccounted for in the theoretical calibration,
and of statistical colour fluctuations in low mass stellar systems. In the case
of populations with multiple stellar generations, the luminosity-weighted mean
age obtained from this diagram is shown to be heavily biased towards the
youngest stellar components. We apply this method to several datasets for which
optical and near-IR photometry are available in the literature. For the two
Local Group dwarf galaxies NGC185 and NGC6822, the mean ages derived from the
integrated colours are consistent with the star formation histories inferred
independently from photometric observations of their resolved stellar
populations. A sample of bright field and Virgo cluster elliptical galaxies is
found to exhibit a range of luminosity-weighted mean ages from 3 to 14 Gyr,
with a mean of 8 Gyr, independent of environment, and mean metallicities at or
just above the solar value. Colour gradients are found in all of the galaxies
studied, in the sense that central regions are redder. Aperture data for five
Virgo early-type dwarf galaxies show that these galaxies appear to be shifted
to lower mean metallicities and lower mean ages (range 1 to 6 Gyr) than their
higher luminosity counterparts.


title: Fine structure in the phase space distribution of nearby subdwarfs

abstract:
  We analysed the fine structure of the phase space distribution function of
nearby subdwarfs using data extracted from various catalogues. Applying a new
search strategy based on Dekker's theory of galactic orbits, we found four
overdensely populated regions in phase space. Three of them were correlated
with previously known star streams: the Hyades-Pleiades and Hercules streams in
the thin disk of the Milky Way and the Arcturus stream in the thick disk. In
addition we find evidence for another stream in the thick disk, which resembles
closely the Arcturus stream and probably has the same extragalactic origin.


title:
The luminosity function of young star clusters: implications for the
  maximum mass and luminosity of clusters

abstract:
  We introduce a method to relate a possible truncation of the star cluster
mass function at the high mass end to the shape of the cluster luminosity
function (LF). We compare the observed LFs of five galaxies containing young
star clusters with synthetic cluster population models with varying initial
conditions. The LF of the SMC, the LMC and NGC 5236 are characterized by a
power-law behavior NdL~L^-a dL, with a mean exponent of <a> = 2.0 +/- 0.2. This
can be explained by a cluster population formed with a constant cluster
formation rate, in which the maximum cluster mass per logarithmic age bin is
determined by the size-of-sample effect and therefore increases with
log(age/yr). The LFs of NGC 6946 and M51 are better described by a double
power-law distribution or a Schechter function. When a cluster population has a
mass function that is truncated below the limit given by the size-of-sample
effect, the total LF shows a bend at the magnitude of the maximum mass, with
the age of the oldest cluster in the population, typically a few Gyr due to
disruption. For NGC 6946 and M51 this implies a maximum mass of M_max = 5*10^5
M_sun. Faint-ward of the bend the LF has the same slope as the underlying
initial cluster mass function and bright-ward of the bend it is steeper. This
behavior can be well explained by our population model. We compare our results
with the only other galaxy for which a bend in the LF has been observed, the
``Antennae'' galaxies (NGC 4038/4039). There the bend occurs brighter than in
NGC 6946 and M51, corresponding to a maximum cluster mass of M_max = 2*10^6
M_sun (abridged).


title:
Observational evidence for a truncation of the star cluster initial mass
  function at the high mass end

abstract:
  We present the luminosity function (LF) of star clusters in M51 based on
HST/ACS observations taken as part of the Hubble Heritage project. The clusters
are selected based on their size and with the resulting 5990 clusters we
present one of the largest cluster samples of a single galaxy. We find that the
LF can be approximated with a double power-law distribution with a break around
M_V = -8.9. On the bright side the index of the power-law distribution is
steeper (a = 2.75) than on the faint-side (a = 1.93), similar to what was found
earlier for the ``Antennae'' galaxies. The location of the bend, however,
occurs about 1.6 mag fainter in M51. We confront the observed LF with the model
for the evolution of integrated properties of cluster populations of Gieles et
al., which predicts that a truncated cluster initial mass function would result
in a bend in, and a double power-law behaviour of, the integrated LF. The
combination of the large field-of view and the high star cluster formation rate
of M51 make it possible to detect such a bend in the LF. Hence, we conclude
that there exists a fundamental upper limit to the mass of star clusters in
M51. Assuming a power-law cluster initial mass function with exponentional
cut-off of the form NdM ~ M^-b * exp(-M/M_C)dM, we find that M_C = 10^5 M_sun.
A direct comparison with the LF of the ``Antennae'' suggests that there M_C =
4*10^5 M_sun.


title:
Modeling the ortho-to-para abundance ratio of cyclic C3H2 in cold dense
  cores

abstract:
  We report a detailed attempt to model the ortho-to-para abundance ratio of
c-C3H2 so as to reproduce observed values in the cores of the well-known source
TMC-1. According to observations, the ortho-to-para ratios vary, within large
uncertainties, from a low of near unity to a high of approximately three
depending on the core. We used the osu.2003 network of gas-phase chemical
reactions augmented by reactions that specifically consider the formation,
depletion, and interconversion of the ortho and para forms of the c-C3H2 and
its precursor ion c-C3H3+. We investigated the sensitivity of the calculated
ortho-to-para ratio for c-C3H2 to a large number of factors. For the less
evolved cores C, CP, and D, we had no difficulty reproducing the observed
ortho-to-para ratios of 1-2.


title: The ignition of thermonuclear flames in Type Ia supernovae

abstract:
  In the framework of the Chandrasekhar-mass deflagration model for Type Ia
supernovae (SNe Ia), a persisting free parameter is the initial morphology of
the flame front, which is linked to the ignition process in the progenitor
white dwarf. Previous analytical models indicate that the thermal runaway is
driven by temperature perturbations (''bubbles'') that develop in the white
dwarf's convective core. In order to probe the conditions at ignition
(diameters, temperatures and evolutionary timescales), we have performed
hydrodynamical 2D simulations of buoyant bubbles in white dwarf interiors. Our
results show that fragmentation occurring during the bubble rise affects the
outcome of the bubble evolution. Possible implications for the ignition process
of SNe Ia are discussed.


title: Complexes of stars and complexes of star clusters

abstract:
  Most star complexes are in fact complexes of stars, clusters and gas clouds;
term "star complexes" was introduced as general one disregarding the
preferential content of a complex. Generally the high rate of star formation in
a complex is accompanied by the high number of bound clusters, including
massive ones, what was explained by the high gas pressure in such regions.
However, there are also complexes, where clusters seems to be more numerous in
relation to stars than in a common complex. The high rate of clusters - but not
isolated stars - formation seems to be typical for many isolated bursts of star
formation, but deficit of stars might be still explained by the observational
selection. The latter cannot, however, explain the complexes or the dwarf
galaxies, where the high formation rate of only stars is observed. The
possibility of the very fast dissolution of parental clusters just in such
regions should itself be explained. Some difference in the physical conditions
(turbulence parameters ?) within the initial gas supercloud might be a reason
for the high or low stars/clusters number ratio in a complex.


title: Complexes of clusters and complexes of stars


title: UHECR Particle Spectra from Crypton Decays

abstract:
  We calculate the spectra of ultra-high-energy cosmic rays (UHECRs) in an
explicit top-down model based on the decays of metastable neutral `crypton'
states in a flipped SU(5) string model. For each of the eight specific
10th-order superpotential operators that might dominate crypton decays, we
calculate the spectra of both protons and photons, using a code incorporating
supersymmetric evolution of the injected spectra. For all the decay operators,
the total UHECR spectra are compatible with the available data. Also, the
fractions of photons are compatible with all the published upper limits, but
may be detectable in future experiments.


title:
Late-type galaxies observed with SAURON. Two-dimensional stellar and
  emission-line kinematics of 18 spirals

abstract:
  We present the stellar and gas kinematics of a sample of 18 nearby late-type
spiral galaxies (Hubble types ranging from Sb to Sd), observed with the
integral-field spectrograph SAURON at the 4.2-m William Herschel Telescope.
SAURON covers the spectral range 4800-5380 A, allowing us to measure the Hbeta,
Fe, Mgb absorption features and the emission in the Hbeta line and the [OIII],
and [NI] doublets over a 33x41 arcsec field of view. The maps cover the nuclear
region of these late-type galaxies and in all cases include the entire bulge.
In many cases the stellar kinematics suggests the presence of a cold inner
region, as visible from a central drop in the stellar velocity dispersion. The
ionised gas is almost ubiquitous and behaves in a complicated fashion: the gas
velocity fields often display more features than the stellar ones, including
wiggles in the zero-velocity lines, irregular distributions, ring-like
structures. The line ratio [OIII]/Hbeta often takes on low values over most of
the field, probably indicating a wide-spread star formation.