title:
Are stellar coronae optically thin in X-rays? - A systematic
  investigation of opacity effects

abstract:
  The relevance of resonant scattering (absorption by photo-excitation and
re-emission out of the line of sight) in the solar corona has always been
discussed controversially. Ratios of emission lines from identical ions but
different oscillator strengths are tracers for damping of resonance lines due
to possible resonant scattering. We present an analysis of a large sample of 44
stellar spectra obtained with all gratings on board Chandra and XMM-Newton and
systematically measure line ratios of FeXVII lines at 15.27A and 16.78A lines
to the resonance line at 15.03A as well as the He-like f/r ratio of OVII and
NeIX. The same ratios obtained from optically thin plasma atomic databases such
as MEKAL, Chianti, and APEC are found to be discrepant, however, we find no
convincing proof for resonance line scattering. Optical depths are basically
identical for all kinds of stellar coronae and we conclude that identical
optical depths are more probable when effects from resonant scattering are
generally negligible. The 15.27/15.03A ratio shows a regular trend suggesting
blending of the 15.27A line by a cooler Fe line, possibly FeXVI. The He-like
f/r ratios for O and Ne show no indication for significant damping of the
resonance lines. We mainly attribute deviations from the atomic databases to
still uncertain emissivities which do not agree well with laboratory
measurements and which come out with differing results when accounting for one
or the other side effect.


title:
13C isotope effects on infrared bands of quenched carbonaceous composite
  (QCC)

abstract:
  We investigate carbon isotope effects on the infrared bands of a laboratory
analogue of carbonaceous dust, the quenched carbonaceous composite (QCC),
synthesized from a plasma gas of methane with various 12C/13C ratios. Peak
shifts to longer wavelengths due to the substitution of 12C by 13C are clearly
observed in several absorption bands. The shifts are almost linearly
proportional to the 13C fraction. New features associated with 13C are not
seen, indicating that the infrared bands in the QCC are not very localized
vibration modes but come from vibrations associated with rather large carbon
structures. An appreciable peak shift is detected in the 6.2 micron band, which
is attributed to a carbon-carbon vibration. A peak shift in an out-of-plane
bending mode of aromatic C--H at 11.4 micron is also observed, while only a
small shift is detected in the 3.3 micron band, which arises from a C--H
stretching mode. The present experiment suggests that peak shifts in the
unidentified infrared (UIR) bands, particularly in the 6.2 micron band, should
be detectable in celestial objects with low 12C/13C ratios (< 10). The isotopic
shifts seen in the QCC are discussed in relation to the variations in the UIR
band peaks observed in post-asymptotic giant branch stars and planetary
nebulae. The observed peak shift pattern of the UIR bands is qualitatively in
agreement with the isotopic shifts in the QCC except for the 7.7 micron band
complex although the observed shifts in the UIR bands are larger than those
inferred from derived isotope ratios for individual objects. The present
investigation suggests that part of the observed variations in the UIR band
peaks may come from the isotopic effects.


title: Radio and submillimetre observations of wind structure in zeta Pup

abstract:
  We present radio and submillimetre observations of the O4I(n)f star zeta Pup,
and discuss structure in the outer region of its wind (~ 10-100 R*). The
properties of bremsstrahlung, the dominant emission process at these
wavelengths, make it sensitive to structure and allow us to study how the
amount of structure changes in the wind by comparing the fluxes at different
wavelengths. To look for variability, we acquired 3.6 and 6 cm observations
with the Australia Telescope Compact Array (ATCA). We supplemented these with
archive observations from the NRAO Very Large Array (VLA). We did not find
variability at more than the +- 20 % level. The long integration time does
allow an accurate determination of the fluxes at 3.6 and 6 cm. Converting these
fluxes into a mass loss rate, we find Mdot = 3.5 x 10^{-6} Msun/yr. This value
confirms the significant discrepancy with the mass loss rate derived from the
Halpha profile, making zeta Pup an exception to the usually good agreement
between Halpha and radio mass loss rates. We also observed zeta Pup at 850 mum
with the James Clerk Maxwell Telescope (JCMT) and at 20 cm with the VLA. A
smooth wind model shows that the millimetre fluxes are too high compared to the
radio fluxes. While recombination of helium in the outer wind cannot be
discounted as an explanation, the wealth of evidence for structure strongly
suggests this as the explanation for the discrepancy. Model calculations show
that the structure needs to be present in the inner ~ 70 R* of the wind, but
that it decays significantly, or maybe even disappears, beyond that radius.


title: The Inflationary Energy Scale in Braneworld Cosmology

abstract:
  Upper bounds on the energy scale at the end of inflation in the
Randall-Sundrum type II braneworld scenario are derived. The analysis is made
exact by introducing new parameters that represent extensions of the Hubble
flow parameters. Only very weak assumptions about the form of the inflaton
potential are made. In the high energy and slow roll regime the bounds depend
on the amplitude of gravitational waves produced during inflation and become
stronger as this amplitude increases.


title: Cosmic Ray Antiprotons from Relic Neutralinos in a Diffusion Model

abstract:
  We use the constraints on the diffusion parameters as obtained with stable
nuclei to calculate the cosmic antiproton flux from annihilating relic
neutralinos. We discuss the relevance of each characteristic parameter,
describing our two dimension diffusion model, on the flux of antiprotons
produced in the dark halo of our Galaxy. We estimate a two orders of magnitude
uncertainty on the flux due to the unknowledge of the propagation parameters. A
conservative and systematic evaluation of the flux in the supersymmetric
parameter space is done in order to exclude configurations providing a total
(secondary plus primary) flux in excess with observations. We also study the
effect on the flux induced by modifications in the distribution of cold dark
matter in the Galaxy.


title: Stable and Radioactive Nuclei in a Diffusion Model

abstract:
  We present the results on the source spectrum function for primary nuclei in
galactic cosmic rays, where two distinct energy dependences are used for the
source spectra. We discuss the evolution of the goodness of fit to B/C data
with the propagation parameters and also show that the results are not much
affected by a different choice for the diffusion scheme. We apply the
constraints on the diffusion scheme as derived from stable nuclei to calculate
the propagation of beta-radioactive isotopes. The diffusion model is refined to
properly take into account the effect of a local bubble in the interstellar
medium. Our calculations are compared to existing data, which prefer the local
bubble description instead of the homogeneus scheme.


title: Extended X-ray emission around 4C 41.17 at z=3.8

abstract:
  We present sensitive, high-resolution, X-ray imaging from Chandra of the
high-redshift radio galaxy 4C 41.17 (z=3.8). Our 150-ks Chandra exposure
detects strong X-ray emission from a point source coincident with the nucleus
of the radio galaxy. In addition we identify extended X-ray emission with a
luminosity ~1e45 erg/s covering a 100kpc (15'') diameter region around the
radio galaxy. The extended X-ray emission follows the general distribution of
radio emission in the radio lobes of this source, and the distribution of a
giant Lyman-alpha emission line halo, while the spectrum of the X-ray emission
is non-thermal and has a power law index consistent with that of the radio
synchrotron. We conclude that the X-ray emission is most likely Inverse-Compton
scattering of far-infrared photons from a relativistic electron population
probably associated with past and current activity from the central object.
Assuming an equipartition magnetic field the CMB energy density at z=3.8 can
only account for at most 40% of the Inverse-Compton emission. Published
submillimeter maps of 4C 41.17 have detected an apparently extended and
extremely luminous far-infrared emission around the radio galaxy. We
demonstrate that this photon component and its spatial distribution, in
combination with the CMB can reproduce the observed X-ray luminosity. We
propose that photo-ionization by these Inverse-Compton X-ray photons plays a
significant role in this system, and provides a new physical feedback mechanism
to preferentially affect the gas within the most massive halos at high
redshift. This is the highest redshift example of extended X-ray emission
around a radio galaxy currently known. (Abridged)


title: A numerical code to study the variability of Blazar emission

abstract:
  We present a numerical code, written in C, which can be used to simulate or
to analyze the emission of Blazars over the entire electromagnetic spectrum.
Our code can reproduce the following features: synchrotron emission, inverse
Compton emission (Thomson Klein-Nishina regime) external Compton emission,
accretion disk variability using a Cellular Automata algorithm, temporal
evolution of the emitting plasma energy distribution, flaring phenomena, light
curves in the rest and in the observer frame (taking account for time crossing
effects). In this paper we will show mainly the accretion disk simulation, and
the implications in the External Compton scenario.


title:
Luminosity Functions of Young Clusters: Modeling the Substellar Mass
  Regime

abstract:
  We predict near-infrared luminosity functions of young (5 Myr to 1 Gyr) star
clusters by combining evolutionary models of very low-mass ($1 M_J$ to $0.15
M_{\odot}$) dwarfs with empirical bolometric corrections. We identify several
characteristic features in our results. These can be attributed to three
causes: (1) deuterium burning in the most massive substellar objects; (2)
methane absorption in bodies with $T_{eff}$ less than 1300 K, the temperature
of the L/T transition; and (3) the formation of dust clouds and the rainout of
dust at roughly the same effective temperature as methane formation. Accurate
reconstruction of the substellar mass function from luminosity function
observations requires that these phenomena are taken into account. At present,
few observational studies extend to sufficient sensitivities to allow detection
of these effects. However, the luminosity function of the young open cluster IC
2391 shows a clear peak at $M_I \sim 14$ which we attribute to the result of
deuterium burning in substellar objects. The location of this feature is a
strong function of age, and we estimate an age of 35 Myr for IC 2391. This is
significantly younger than the 53 Myr derived from the location of the lithium
depletion boundary but agrees with the main sequence turnoff age. We consider
the implications of this result and our multi-band luminosity functions for
future observational studies. All predicted luminosity function features are,
or will be, accessible to observations using new wide-field IR imagers and the
Space Infrared Telescope Facility.


title: CHANDRA Observations of X-ray Jet Structure on kpc to Mpc Scales

abstract:
  With its exquisite spatial resolution of better than 0.5 arcsecond, the
Chandra observatory is uniquely capable of resolving and studying the spatial
structure of extragalactic X-ray jets on scales of a few to a few hundred
kilo-parsec. Our analyses of four recent Chandra images of quasar jets
interpret the X-ray emission as inverse Compton scattering of high energy
electrons on the cosmic microwave background. We infer that these jets are in
bulk relativistic motion, carrying kinetic powers upwards of 10^46 ergs/s to
distances of hundreds of kpc, with very high efficiency.


title:
Detection of Magnesium-Rich Ejecta in the Middle-Aged Supernova Remnant
  N49B

abstract:
  The middle-aged supernova remnant (SNR) N49B in the Large Magellanic Cloud
has been observed with the {\it Chandra X-Ray Observatory}. The superb angular
resolution of {\it Chandra} resolves the complex structure of X-ray emitting
filaments across the SNR. All observed features are soft ($E <$ 3 keV) and we
find no evidence for either point-like or extended hard emission within the
SNR. Spectral lines from O, Ne, Mg, Si, S, and Fe are present. Equivalent width
images for the detected elemental species and spatially-resolved spectral
analysis reveal the presence of Mg-rich ejecta within the SNR. We find no such
enrichment in O or Ne, which may reflect details of the nucleosynthesis process
or the heating and cooling of the ejecta as it evolved. The bright
circumferential filaments are emission from the shocked dense interstellar
medium (ISM). We detect faint diffuse X-ray emission that extends beyond the
X-ray bright filaments toward the west and southeast. These features appear to
be the blast wave shock front expanding into lower density portions of the ISM
seen in projection. We set an upper limit of $\sim$$2\times 10^{33}$ ergs
s$^{-1}$ on the 0.5 $-$ 5 keV band X-ray luminosity of any embedded compact
object.


title:
Cosmological constraints on Chaplygin gas dark energy from galaxy
  clusters X-ray and supernova data

abstract:
  The recent observational evidences for the present accelerated stage of the
Universe have stimulated renewed interest for alternative cosmologies. In
general, such models contain an unknown negative-pressure dark component that
explains the supernova results and reconciles the inflationary flatness
prediction ($\Omega_{\rm{T}} = 1$) and the cosmic microwave background
measurements with the dynamical estimates of the quantity of matter in the
Universe ($\Omega_{\rm{m}} \simeq 0.3 \pm 0.1$). In this paper we study some
observational consequences of a dark energy candidate, the so-called
generalized Chaplygin gas which is characterized by an equation of state $p_{C}
= -A/\rho_{C}^{\alpha}$, where $A$ and $\alpha$ are positive constants. We
investigate the prospects for constraining the equation of state of this dark
energy component by combining Chandra observations of the X-ray luminosity of
galaxy clusters, independent measurements of the baryonic matter density, the
latest measurements of the Hubble parameter as given by the HST Key Project and
data of the Supernova Cosmology Project. We show that very stringent
constraints on the model parameters can be obtained from this combination of
observational data.


title: Decay Properties of K-Vacancy States in Fe X-Fe XVII

abstract:
  We report extensive calculations of the decay properties of fine-structure
K-vacancy levels in Fe X-Fe XVII. A large set of level energies, wavelengths,
radiative and Auger rates, and fluorescence yields has been computed using
three different standard atomic codes, namely Cowan's HFR, AUTOSTRUCTURE and
the Breit-Pauli R-matrix package. This multi-code approach is used to the study
the effects of core relaxation, configuration interaction and the Breit
interaction, and enables the estimate of statistical accuracy ratings. The
K-alpha and KLL Auger widths have been found to be nearly independent of both
the outer-electron configuration and electron occupancy keeping a constant
ratio of 1.53+/-0.06. By comparing with previous theoretical and measured
wavelengths, the accuracy of the present set is determined to be within 2 mA.
Also, the good agreement found between the different radiative and Auger data
sets that have been computed allow us to propose with confidence an accuracy
rating of 20% for the line fluorescence yields greater than 0.01. Emission and
absorption spectral features are predicted finding good correlation with
measurements in both laboratory and astrophysical plasmas.


title: Modeling of iron K lines: radiative and Auger decay data for Fe II-Fe IX

abstract:
  A detailed analysis of the radiative and Auger de-excitation channels of
K-shell vacancy states in Fe II-Fe IX has been carried out. Level energies,
wavelengths, A-values, Auger rates and fluorescence yields have been calculated
for the lowest fine-structure levels populated by photoionization of the ground
state of the parent ion. Different branching ratios, namely
K-alpha_2/K-alpha_1, K-beta/K-alpha, KLM/KLL, KMM/KLL, and the total K-shell
fluorescence yields, omega_K, obtained in the present work have been compared
with other theoretical data and solid-state measurements, finding good general
agreement with the latter. The K-alpha_2/K-alpha_1 ratio is found to be
sensitive to the excitation mechanism. From these comparisons it has been
possible to estimate an accuracy of ~10% for the present transition
probabilities.


title:
The Most Probable Cause for the High Gamma-Ray Polarization in GRB
  021206

abstract:
  The exciting detection of a very high degree of linear polarization,
$P=(80\pm 20)%$, in the prompt gamma-ray emission of GRB 021206, supports
synchrotron emission as being the dominant radiation mechanism. There were also
claims that this implies a magnetic field ordered on large scales within the
ejecta, that must therefore be produced at the source, which in turn was used
as an argument in favor magnetic fields playing an active role in the
production of GRB jets. However, an alternative explanation was suggested which
also works with a magnetic field that is generated in the internal shocks and
does not originate at the source: a very narrow jet, of opening angle
$\theta_j\sim 1/\gamma$, where $\gamma\gtrsim 100$ is the Lorentz factor during
the GRB, viewed at $\theta_j<\theta_{obs}\lesssim\theta_j+1/\gamma$. We
calculate $P$ for these two scenarios, and find that it is significantly easier
to produce $P\gtrsim 50%$ with an ordered field. More specifically, we obtain
$P\sim(43-61)%$ for an ordered transverse magnetic field, $B_{ord}$, whereas a
random field within the plane of the shock, $B_\perp$, produces
$P\lesssim(38-54)%$ for a single pulse in the GRB light curve, but the
integrated emission over many pulses (as measured in GRB 021206) is a factor of
$\sim 2$ lower. A magnetic field normal to the shock front, $B_\parallel$,
produces $P\sim(35-62)%$ for the emission integrated over many pulses. However,
polarization measurements from GRB afterglows suggest a more isotropic
shock-produced field configuration that would reduce $P$ by a factor $\sim
2-3$. Therefore, an ordered magnetic field, $B_{ord}$, that originates at the
source, can produce the observed polarization most naturally, while
$B_\parallel$ is less likely, and $B_\perp$ is the least likely of the above.


title: Orbital structure in oscillating galactic potentials

abstract:
  This paper focuses on symmetric potentials subjected to periodic driving.
Four unperturbed potentials V_0(r) were considered, namely the Plummer
potential and Dehnen potentials with \gamma=0.0, 0.5, and 1.0, each subjected
to a time-dependence of the form V(r,t)=V_0(r)(1+m_0\sin(\omega t)). In each
case, the orbits divide clearly into regular and chaotic, distinctions which
appear absolute. In particular, transitions from regularity to chaos are
seemingly impossible. Over finite time intervals, chaotic orbits subdivide into
what can be termed `sticky' chaotic orbits, which exhibit no large scale
secular changes in energy and remain trapped in the phase space region where
they started; and `wildly chaotic' orbits, which do exhibit systematic drifts
in energy as the orbits diffuse to inhabit different phase space regions. This
latter distinction is not absolute, apparently corresponding instead to orbits
penetrating a `leaky' phase space barrier. The three different orbit types can
be identified simply in terms of the frequencies for which their Fourier
spectra have the most power. An examination of the statistical properties of
orbit ensembles as a function of driving frequency \omega allows one to
identify the specific resonances that determine orbital structure. Attention
focuses also on how, for fixed amplitude m_0, such quantities as the mean
energy shift, the relative measure of chaotic orbits, and the mean value of the
largest Lyapunov exponent vary with driving frequency \omega and how, for fixed
\omega, the same quantities depend on m_0.


title:
A scheme to deal accurately and efficiently with complex angular masks
  in galaxy surveys

abstract:
  This paper presents a scheme to deal accurately and efficiently with complex
angular masks, such as occur typically in galaxy surveys. An angular mask is
taken to be an arbitrary union of arbitrarily weighted angular regions bounded
by arbitrary numbers of edges. The restrictions on the mask are (i) that each
edge must be part of some circle on the sphere (but not necessarily a great
circle), and (ii) that the weight within each subregion of the mask must be
constant. The scheme works by resolving a mask into disjoint polygons, convex
angular regions bounded by arbitrary numbers of edges. The polygons may be
regarded as the `pixels' of a mask, with the feature that the pixels are
allowed to take a rather general shape, rather than following some predefined
regular pattern. Among other things, the scheme includes facilities to compute
the spherical harmonics of the angular mask, and Data-Random <DR> and
Random-Random <RR> angular integrals. A software package mangle which
implements this scheme, along with complete software documentation, is
available at http://casa.colorado.edu/~ajsh/mangle/ .


title:
Stellar Populations in NGC 4038/39 (The Antennae): Exploring A Galaxy
  Merger Pixel-by-Pixel

abstract:
  We present deep, photometrically calibrated BVRJHK images of the nearby
interacting galaxy pair NGC 4038/39 (``The Antennae''). Color maps of the
images are derived, and those using the B, V, and K-bands are analyzed with
techniques developed for examining the colors of stars. From these data we
derive pixel-by-pixel maps of the distributions of stellar populations and dust
extinction for the galaxies. Analysis of the stellar population map reveals two
distinct episodes of recent star formation: one currently in progress and a
second that occurred ~600 Myr ago. A roughly 15 Gyr-old population is found
which traces the old disks of the galaxies and the bulge of NGC 4038. The
models used successfully reproduce the locations of clusters, and the ages we
derive are consistent with those found from previous Hubble Space Telescope
observations of individual star clusters. We also find 5 luminous ``super star
clusters'' in our K-band images that do not appear in the B or V-band images.
These clusters are located in the overlap region between the two galaxies, and
are hidden by dust with visual extinctions of A_V ~> 3 mag. The techniques we
describe in this paper should be generally applicable to the study of stellar
populations in galaxies for which detailed spatial resolution with Hubble is
not possible.


title:
The Multiphase Intracluster Medium in Galaxy Groups Probed by the Lyman
  Alpha Forest

abstract:
  The case is made that the intracluster medium (ICM) in spiral-rich galaxy
groups today probably has undergone much slower evolution than that in
elliptical-rich groups and clusters. The environments of proto-clusters and
proto-groups at z > 2 are likely similar to spiral-rich group environments at
lower redshift. Therefore, like the ICM in spiral-rich groups today, the ICM in
proto-groups and proto-clusters at z > 2 is predicted to be significantly
multiphased. The QSO Lyman alpha forest in the vicinity of galaxies is an
effective probe of the ICM at a wide range of redshift. Two recent observations
of Lyman alpha absorption around galaxies by Adelberger et al. and by
Pascarelle et al are reconciled, and it is shown that observations support the
multiphase ICM scenario. Galaxy redshifts must be very accurate for such
studies to succeed. This scenario can also explain the lower metallicity and
lower hot gas fraction in groups.


title: The structure of halos in Self-Interacting Cold Dark Matter models

abstract:
  High-resolution numerical simulations were performed to study the structure
and substructure of Milky Way- and cluster-sized halos in a LCDM cosmology with
self-interacting (SI) dark particles, where the particle cross section,
+AFw-sig, is assumed constant or inversely proportional to the relative
velocity. We conclude that the cuspy halo problem at galaxy scales of the LCDM
cosmogony can be solved in the latter case. In this case, the inner density of
galaxy-cluster halos is only slightly affected by the SI, resulting in
agreement with observational constraints. At the same time, the subhalo
population in galaxy and cluster SI-CDM halos remains roughly similar to that
seen on collisionless CDM halos.


title: Viscosity-Driven Winds from Magnetized Accretion Disks

abstract:
  We present an analytic model in which an inefficiently radiating accretion
disk drives upward wind from its surfaces. The accretion process is controlled
simultaneously by a global magnetic field penetrating the disk and by a
viscosity of the accreting plasma. It is shown that energy is transported
radially outward within the accreting flow, associated with the viscous
angular-momentum transport in the same direction, and that this addition of
energy from the inner part to the disk part makes the latter possible to drive
an upward wind. The parameter that specifies the strength of a wind is
determined uniquely in terms of a naturally introduced viscosity parameter.


title: Inter-Network magnetic fields observed with sub-arcsec resolution

abstract:
  We analyze a time sequence of Inter-Network (IN) magnetograms observed at the
solar disk center. Speckle reconstruction techniques provide a good spatial
resolution (0.5" cutoff frequency) yet maintaining a fair sensitivity (some
20G). Patches with signal above noise cover 60% of the observed area, most of
which corresponds to intergranular lanes. The large surface covered by signal
renders a mean unsigned magnetic flux density between 17G and 21G (1G \equiv
1Mx cm$^{-2}$). The difference depends on the spectral line used to generate
the magnetograms (Fe I 6302 or Fe I 6301). Such systematic difference can be
understood if the magnetic structures producing the polarization have intrinsic
field strengths exceeding 1 kG, and consequently, occupying only a very small
fraction of the surface (some 2%). We observe both, magnetic signals changing
in time scales smaller than 1 min, and a persistent pattern lasting longer than
the duration of the sequence (17 min). The pattern resembles a network with a
spatial scale between 5 and 10 arcsec, which we identify as the
mesogranulation. The strong dependence of the polarization signals on spatial
resolution and sensitivity suggests that much quiet Sun magnetic flux still
remains undetected.


title: Massive circumstellar envelope around type IIn supernova SN 1995G

abstract:
  We model the interaction of the supernova SN 1995G with a dense circumstellar
(CS) gas in a thin shell approximation. A model fit of the observed bolometric
light curve combined with data on the supernova expansion velocity provides an
estimate of the density of the CS shell, its mass ($\approx 1 M_{\odot}$), and
age ($\approx 8$ years). It is shown that the derived CS gas density does not
depend on the assumed mass of the supernova ejecta. This results from the high
CS density, which ensures that the forward shock wave is essentially radiative.
The derived CS density is consistent with the H$\alpha$ luminosity and with the
presence of the apparent effect of Thomson scattering in the red wing of this
line. The mass of the CS envelope together with its expansion velocity
indicates that the CS envelope was ejected as a result of violent energy
release ($\sim 6\times10^{48}$ erg) eight years before the supernova outburst.


title: Chandra observation of the core of the galaxy cluster AWM7

abstract:
  We present results from a Chandra observation of the core region of the
nearby X-ray bright galaxy cluster AWM7. There are blob-like substructures,
which are seen in the energy band 2--10 keV, within 10 kpc (20'') of the cD
galaxy NGC1129, and the brightest sub-peak has a spatial extent more than 4
kpc. We also notice that the central soft X-ray peak is slightly offset from
the optical center by 1 kpc. These structures have no correlated features in
optical, infrared, or radio band. Energy spectrum of the hard sub-peak
indicates a temperature higher than 3 keV with a metallicity less than 0.3
solar, or a power-law spectrum with photon index 1.2. A hardness ratio map and
a narrow Fe-K band image jointly indicate two Fe-rich blobs symmetrically
located around the cD galaxy, with the direction perpendicular to the sub-peak
direction. In larger scales (r<60 kpc), the temperature gradually drops from 4
keV to 2 keV toward the cluster center and the metal abundance rises steeply to
a peak of 1.5 solar at r=7 kpc. These results indicate that a dynamical process
is going on in the central region of AWM7, which probably creates heated gas
blobs and drives metal injection.


title: A Role of the Boundary Shear Layer in Modeling of Large Scale Jets

abstract:
  We discuss a role of the boundary shear layer of large scale jets for their
observed multiwavelength emission. We consider a simple mechanism of a
turbulent particle acceleration acting within such regions as an alternative
mechanism with respect to the standard approaches involving internal shocks in
the jet. We show, that under simple assumptions the boundary layer acceleration
can provide very high energy electrons possibly generating the X-ray emission
observed by Chandra from some large scale jets in powerful radiogalaxies.


title: VHE gamma-rays From Extragalactic Large Scale Jets

abstract:
  We discuss production of very high energy (VHE) gamma-rays in large scale
extragalactic jets of FR I sources. Based on recent optical and X-ray
observations of these objects we evaluate their VHE emission in a framework of
one electron population model. We consider possibility for detection of the
predicted radiation, which could provide important constraints on the jet
structure and some hardly known large scale jet parameters.


title:
First Look XMM-Newton EPIC Observations of the Prototypical Starburst
  Galaxy M82

abstract:
  We present initial XMM-Newton EPIC observations of the prototypical starburst
galaxy M82. The superwind is seen to extend continuously from the starburst
region to the X-ray emission associated with the Halpha 'cap'. We also find
evidence for a ridge feature, probably associated with the superwind
interacting with an HI streamer. Narrow band images, centred on individual
X-ray lines, show differences in morphology, with higher energy lines being
less spatially extended, and a systematic shift with energy in the region of
peak emission. Spectral fits with two thermal and one power-law component
provide a good fit to the spectra of the nuclear and inner wind regions,
indicating a multiphase superwind. We discuss the implications of these
observations on our understanding of superwinds.


title:
Observational properties of visual binaries as modelled using a
  synthetic catalogue, I: For visual apparent magnitudes $m_v < 15$

abstract:
  A simulated binary star catalogue is created that represents the full sky
distribution of stars, excluding those with galactic latitude $|b|<10\degr$,
down to $m_v < 15$. The catalogue is compatible with observed magnitude and
number distributions of the HST Guide Star Catalog. The simulated catalogue is
analyzed for observational properties of visual binary stars, both in a general
context without taking any observational constraints into account, and using
different observability criteria that model the observational capability of the
astrometric DIVA satellite. It is shown that several observational bias effects
should be taken into account when final output catalogues are analyzed. The
results indicate that $\Delta m_v$ distribution peaks at $\Delta m_v \approx 7$
and to maximize the number of binary detections with large mass ratios, the
magnitude threshold should be set as high as possible. This is especially
important if low mass $M<0.2 M_{\sun}$ secondaries are studied. The predicted
number of optical pairs is calculated and for large magnitude differences close
to the galactic plane and toward the galactic center it may be difficult to
discriminate between a red companion and a low-mass foreground/background star
for distant double stars for which no parallax measurements are available.
Using optimal detection procedures for optical double stars it is estimated
that, depending on the assumed double star distributions, 60%-70% of all the
visual binary stars in the catalogue with separations
$0.0625\arcsec<\theta<3.5\arcsec$, $m_{v}(\mathrm{secondary})<22$, and $\Delta
m<10$ could be observed during the DIVA or similar missions.


title: Chandra LETGS and XMM-Newton observations of NGC 4593

abstract:
  In this paper, we analyze spectra of the Seyfert 1 galaxy NGC 4593 obtained
with the Chandra Low Energy Transmission Grating Spectrometer (LETGS), the
Reflection Grating Spectrometer (RGS) and the European Photon Imaging Camera's
(EPIC) onboard of XMM-Newton. The two observations were separated by ~7 months.
In the LETGS spectrum we detect a highly ionized warm absorber corresponding to
an ionization state of 400x10^{-9} W m, visible as a depression at 10-18 \AA.
This depression is formed by multiple weak Fe and Ne lines. A much smaller
column density was found for the lowly ionized warm absorber, corresponding to
xi = 3x10^{-9} W m. However, an intermediate ionization warm absorber is not
detected. For the RGS data the ionization state is hard to constrain. The EPIC
results show a narrow Fe Kalpha line.


title:
Kinetic equilibrium of iron in the atmospheres of cool stars III. The
  ionization equilibrium of selected reference stars

abstract:
  Non-LTE line formation calculations of Fe I are performed for a small number
of reference stars to investigate and quantify the efficiency of neutral
hydrogen collisions. Using the atomic model that was described in previous
publications, the final discrimination with respect to hydrogen collisions is
based on the condition that the surface gravities as determined by the Fe I/Fe
II ionization equilibria are in agreement with their astrometric counterparts
obtained from HIPPARCOS parallaxes. Depending on the choice of the hydrogen
collision scaling factor S_H, we find deviations from LTE in Fe I ranging from
0.00 (S_H = infinity) to 0.46 dex (S_H = 0 for HD140283) in the logarithmic
abundances while Fe II follows LTE.
  With the exception of Procyon, for which a mild temperature correction is
needed to fulfil the ionization balance, excellent consistency is obtained for
the metal-poor reference stars if Balmer profile temperatures are combined with
S_H = 3. The correct choice of collisional damping parameters ("van-der-Waals"
constants) is found to be generally more important for these little evolved
metal-poor stars than considering departures from LTE. For the Sun the
calibrated value for S_H leads to average Fe I non-LTE corrections of 0.02 dex
and a mean abundance from Fe I lines of log epsilon(Fe) = 7.49 \pm 0.08.
  We confront the deduced stellar parameters with comparable spectroscopic
analyses by other authors which also rely on the iron ionization equilibrium as
a gravity indicator. On the basis of the HIPPARCOS astrometry our results are
shown to be an order of magnitude more precise than published data sets, both
in terms of offset and star-to-star scatter.


title: The Narrow Line Region of Ark 564

abstract:
  The continuum and emission-line spectrum of the narrow-line Seyfert 1 galaxy
Ark 564 is used to investigate, for the first time, the physical conditions and
structure of its narrow line region (NLR). For this purpose, composite models,
accounting for the coupled effect of photoionization and shocks, are employed.
The emission-line spectrum of Ark 564, which ranges from the ultraviolet to the
near-infrared, shows a rich forbidden line spectrum. Strong emphasis is given
to the study of the coronal line region. The diversity of physical conditions
deduced from the observations requires multi-cloud models to reproduce the
observed lines and continuum. We find that a combination of high velocity (Vs =
1500 km/s) shock-dominated clouds as well as low velocity (Vs = 150 km/s)
radiation-dominated clouds explains the coronal lines, while the optical
low-ionization lines are mainly explained by shock-dominated clouds. The
results for Ark 564 are compared with those obtained for other Seyfert galaxies
previously analyzed such as NGC 5252, Circinus, NGC 4051 and NGC 4151. The
model results for the ultraviolet and optical permitted lines suggest that the
broad line region may contribute up to 80%, depending on the emission-line,
being of about 30% for Hbeta. The consistency of the multi-cloud model is
checked by comparing the predicted and observed continuum, from radio to X-ray,
and indicate that the dust-to-gas ratio in the clouds varies from 10^{-15} to
10^{-12}.


title:
VLT surface photometry and isophotal analysis of early-type dwarf
  galaxies in the Virgo cluster

abstract:
  We have carried out surface photometry and an isophotal analysis for a sample
of 25 early-type dwarf (dE and dS0) galaxies in the Virgo cluster based on CCD
images taken at the VLT with FORS1 and FORS2. For each galaxy we present $B$
and $R$-band surface brightness profiles, as well as the radial colour ($B-R$)
profile. We give total apparent $BR$ magnitudes, effective radii, effective
surface brightnesses and total colour indices. The light profiles have been
fitted with S\'ersic models and the corresponding parameters are compared to
the ones for other classes of objects. The observed profiles of the brightest
cluster dwarfs show significant deviations from a simple S\'ersic model,
indicating that there is more inner structure than just a nucleus. In addition,
we find a relation between the effective surface brightness, at a given
luminosity, and the strength of the offset of the galaxy's nucleus with respect
to the center of the isophotes. Dwarfs with large nuclear offsets also tend to
have stronger isophotal twists. In sum, our findings suggest the presence of
substructure in most, and preferentially in the less compact, bright early-type
dwarfs. The physical (dynamical) meaning of this has yet to be explored.
(abridged)


title: Flare stars in the TW Hydrae association: The HIP 57269 system

abstract:
  We discuss a new member candidate of the TW Hydrae association (TWA) among
the stars of the Gershberg et al. (1999) flare star catalog. TWA is one of the
closest known associations of young stars at about 60 pc. Three supposedly
young flare stars are located in the same region of the sky as TWA. One of them
(HIP 57269) shows strong Lithium absorption with spectral type K1/K2V and a
high level of chromospheric and coronal activity. It is located at a distance
of 48.7\pm6.3 pc in common with the five TWA members observed with Hipparcos
(46.7 to 103.9 pc). HIP 57268 A has a wide companion C which also shows Lithium
absorption at 6707\AA and which has common proper motion with HIP 57269, as
well as a close companion resolved visually by Tycho. HIP 57269A&C lie above
the main sequence and are clearly pre-main-sequence stars. The UVW-space
velocity is more consistent with the star system being a Pleiades super cluster
member. The two other flare stars in the TWA sky region do not show Lithium at
all and are, hence, unrelated.


title: A Soft X-ray Component in the Abell 754 Cluster

abstract:
  We have analyzed the Chandra, BeppoSax, and ROSAT observations of Abell 754
and report evidence of a soft, diffuse X-ray component. The emission is peaked
in the cluster center and is detected out to 8' from the X-ray center. Fitting
a thermal model to the combined BeppoSax and PSPC spectra show excess emission
below 1 keV in the PSPC and above 100 keV in the BeppoSax PDS. The source 26W20
is in the field of view of the PDS. The addition of a powerlaw with the
spectral parameters measured by Silverman et al. (1998) for 26W20 successfully
models the hard component in the PDS. The remaining excess soft emission can be
modeled by either a low temperature, 0.75 - 1.03 keV component, or by a
powerlaw with a steep spectral index, 2.3. Addition of a second thermal
component model provides a much better fit to the data than does the addition
of a non-thermal component. The Chandra temperature map does not show any
region cooler than 6.9 keV within the region where the cool component was
detected. Simulations of the emission from embedded groups were performed and
compared with the Chandra temperature map which show groups are a plausible
source of ~1 keV emission. The cool component is centrally peaked in the
cluster and the gas density and temperature are relatively high arguing against
the WHIM as the source of the X-ray emission. X-ray emission from elliptical
galaxies is not high enough to provide the total cool component luminosity,
7.0x10^43 ergs s^-1. The peak of the cool component is located between the low
frequency radio halos arguing against a non-thermal interpretation for the
emission. We conclude that emission from embedded groups is the most likely
origin of the cool component in Abell 754.


title:
The Difference Between Clusters and Groups: A Journey from Cluster Cores
  to their Outskirts and Beyond

abstract:
  In this review, we take the reader on a journey. We start by looking at the
properties of galaxies in the cores of rich clusters. We have focused on the
overall picture: star formation in clusters is strongly suppressed relative to
field galaxies at the same redshift. We will argue that the increasing activity
and blue populations of clusters with redshift results from a greater level of
activity in field galaxies rather than a change in the transformation imposed
by the cluster environment. With this in mind, we travel out from the cluster
focussing firstly on the properties of galaxies in the outskirts of clusters
and then on galaxies in isolated groups. At low redshift, we are able to
efficiently probe these environments using the Sloan and 2DF redshift surveys.
These allow an accurate comparison of galaxy star formation rates in different
regions. The current results show a strong suppression of star formation above
a critical threshold in local density. The threshold seems similar regardless
of the overall mass of the system. At low redshift at least, only galaxies in
close, isolated pairs have their star formation rate boosted above the global
average. At higher redshift, work on constructing homogeneous catalogues of
galaxies in groups and in the infall regions of clusters is still at an early
stage. In the final section, we draw these strands together, summarising what
we can deduce about the mechanisms that transform star forming field galaxies
into their quiescent cluster counter-parts. We discuss what we can learn about
the impact of environment on the global star formation history of the universe.


title: CMB Anisotropies in the Presence of Extra Dimensions

abstract:
  We discuss the effect of the time evolution of extra dimensions on CMB
anisotropies and large-scale structure formation. We study the impact of scalar
fields in a low-energy effective description of a general class of brane world
models on the temperature anisotropy power spectrum. We show that when the
coupling between these scalar fields and matter evolves over cosmological
timescales, current observations of the CMB anisotropies can constrain
primordial values of the fields in a manner complementary to local, late-time
tests of gravity. We also present the effect of these fields on the
polarization anisotropy spectra and the growth of large-scale structure,
showing that future CMB observations will constrain theories of the Universe
involving extra dimensions even further.


title: Probing TeV gravity with extensive air-showers

abstract:
  Particle collisions with center-of-mass energy larger than the fundamental
gravitational scale can generate non perturbative gravitational objects such as
black holes and branes. In models with large extra dimensions, the fundamental
gravitational scale may be around a TeV, making it possible for next generation
particle colliders and ultra-high energy cosmic rays to produce such non
perturbative gravitational objects. The decay of TeV gravitational objects is
significantly different from standard model processes such that probes of these
new ideas are within reach. We study the differences between standard model and
TeV gravity interactions in extensive air showers (EAS) generated by ultra-high
energy cosmic neutrinos. We show that discriminating TeV gravity from standard
model interactions is generally difficult, but not impossible given a few
unique signatures.


title: A New Estimate of the Extragalactic Gamma-Ray Background from EGRET Data

abstract:
  We use the GALPROP model for cosmic-ray (CR) propagation to obtain our best
prediction of the Galactic component of gamma rays, and show that away from the
Galactic plane it gives an accurate prediction of the observed EGRET
intensities. On this basis we re-evaluate the isotropic extragalactic gamma-ray
background (EGRB). We find that for some energies previous work underestimated
the Galactic contribution and hence overestimated the background. Our new EGRB
spectrum shows a positive curvature similar to that expected for models of the
extragalactic emission based on the blazar population.


title: Evaluation of Models for Diffuse Continuum Gamma Rays in EGRET Range

abstract:
  The GALPROP model for cosmic-ray (CR) propagation produces explicit
predictions for the angular distribution of Galactic diffuse gamma rays. We
compare our current models with EGRET spectra for various regions of the sky.
This allows a critical test of alternative hypotheses for the observed GeV
excess. We show that a population of hard-spectrum gamma-ray sources cannot be
solely responsible for the excess since it also appears at high latitudes; on
the other hand a hard CR electron spectrum model cannot explain the gamma-ray
excess in the inner Galaxy. Hence some combination of these explanations is
suggested.


title:
A very energetic supernova associated with the gamma-ray burst of 29
  March 2003

abstract:
  Over the past five years evidence has mounted that long-duration (> 2 s)
gamma-ray bursts (GRBs)--the most brilliant of all astronomical
explosions--signal the collapse of massive stars in our Universe. This evidence
was originally based on the probable association of one unusual GRB with a
supernova, but now includes the association of GRBs with regions of massive
star formation in distant galaxies, the appearance of supernova-like 'bumps' in
the optical afterglow light curves of several bursts and lines of freshly
synthesized elements in the spectra of a few X-ray afterglows. These
observations support, but do not yet conclusively demonstrate, the idea that
long-duration GRBs are associated with the deaths of massive stars, presumably
arising from core collapse. Here we report evidence that a very energetic
supernova (a hypernova) was temporally and spatially coincident with a GRB at
redshift z = 0.1685. The timing of the supernova indicates that it exploded
within a few days of the GRB, strongly suggesting that core-collapse events can
give rise to GRBs, thereby favouring the 'collapsar' model.


title:
The Star-Forming Dwarf Galaxy Populations of two z ~ 0.4 Clusters:
  MS1512.4+3647 and Abell 851

abstract:
  We present the results of a deep narrow-band [OII] 3727 \AA emission-line
search for faint ($g <$ 27), star-forming galaxies in the field of the $z=0.37$
MS1512.4+3647 cluster. We find no evidence for an over-density of emission-line
sources relative to the field at $z \sim$ 0.4 (Hogg et al. 1998), and therefore
conclude that the MS1512.4+3647 sample is dominated by field [OII]
emission-line galaxies which lie along the $\sim$ 180 Mpc line of sight
immediately in front and behind the cluster. This is surprising, given that the
previously surveyed $z=0.41$ cluster Abell 851 has 3-4 times the field
emission-line galaxy density (Martin et al. 2000). We find that the
MS1512.4+3647 sample is deficient in galaxies with intermediate colors (1.0 $<
g-i <$ 2.0) and implied star-formation exponential decay timescales $\tau \sim$
100 Myr - 1 Gyr that dominate the Abell 851 emission-line galaxy population.
Instead, the majority of [OII] emission-line galaxies surrounding the
MS1512.4+3647 cluster are blue ($g-i \leq 1.0$) and forming stars in bursts
with $\tau < $ 100 Myr. In both samples, galaxies with the shortest
star-formation timescales are preferentially among the faintest star-forming
objects. Their i luminosities are consistent with young stellar populations
$\sim 10^8 - 10^9 \Msun$, although an additional factor of ten in stellar mass
could be hiding in underlying old stellar populations. We discuss the
implications for the star-formation histories of dwarf galaxies in the field
and rich clusters.


title: Propagation of Light Elements in the Galaxy

abstract:
  The origin and evolution of isotopes of the lightest elements H2, He3, Li,
Be, B in the universe is a key problem in such fields as astrophysics of CR,
Galactic evolution, non-thermal nucleosynthesis, and cosmological studies. One
of the major sources of these species is spallation by CR nuclei in the
interstellar medium. On the other hand, it is the B/C ratio in CR and Be10
abundance which are used to fix the propagation parameters and thus the
spallation rate. We study the production and Galactic propagation of isotopes
of elements Z<6 using the numerical propagation code GALPROP and updated
production cross sections.


title: Constraints from ISO Data on the Velocity Law and Clumpiness of WR 136

abstract:
  Observations with the Infrared Space Observatory (ISO) SWS spectrometer are
used to constrain the velocity law and wind clumping of the well-studied
Wolf-Rayet (WR) star WR 136 (HD 192163) (WN6). Because the free-free continuum
opacity in WR winds increases steadily with wavelength in the IR, each point in
the continuous spectrum may be regarded as forming in a pseudo-photosphere of
larger radius for longer wavelength. Using this idea in combination with an
analysis of the Doppler-broadened widths of several \ion{He}{2} recombination
lines, we can derive information about the velocity law and clumpiness of the
stellar wind of WR 136. Adopting a $\beta$-law distribution for the outflow
velocity law, we compute the continuous energy distribution and line profiles.
Interestingly,the continuum data are found to constrain the wind to have fairly
low clumping values for the IR-forming region.


title: Ballooning Modes in Thin Accretion Disks: Limits for their Excitation

abstract:
  The conditions that limit the possible excitation of ideal MHD axisymmetric
ballooning modes in thin accretion disks are discussed. As shown earlier by
Coppi and Coppi (2001), these modes are well-localized in the vertical
direction but have characteristic oscillatory and non-localized profiles in the
radial direction. A necessary condition for their excitation is that the
magnetic energy be considerably lower than the thermal energy. Even when this
is satisfied, there remains the problem of identifying the possible physical
factors which can make the considered modes radially localized. The general
solution of the normal mode equation describing the modes is given, showing
that it is characterized by a discrete spectrum of eigensolutions. The growth
rates are reduced and have a different scaling relative to those of the
"long-cylinder" modes, commonly known as the Magneto Rotational Instability,
that have been previously studied.


title:
Multicolor Photometry of the Galaxies in Abell 2255 by the BATC and SDSS
  Surveys

abstract:
  We present our optical multicolor photometry for the nearby cluster of
galaxies Abell 2255 with 13 intermediate filters in the BATC system. The
spectral energy distributions (SEDs) in the optical band for more than 7000
sources are achieved down to V ~ 20 in a field of 58' x 58' centered on this
rich cluster. Abell 2255 has been recently observed by the SDSS. A method of
combining the SDSS photometric data in five broad bands and the BATC SEDs is
then explored. The application of the technique of photometric redshift shows
that the combined SEDs with higher resolution could lead to a more accurate
estimate of photometric redshift. Based on 214 spectroscopically confirmed
member galaxies, the bimodality and large dispersion in the velocity
distribution indicate that Abell 2255 is an unrelaxed system. A tight
color-magnitude correlation for 188 known early-type cluster galaxies is found.
After an exclusion of 254 extragalactic sources with known redshifts, the
combined SEDs for 2522 galaxies allow a further membership selection by the
photometric redshift technique and color-magnitude correlation. As a result,
313 galaxies with their photometric redshifts between 0.068 and 0.090 are
selected as new cluster members. The combined SEDs and estimated redshifts for
previously known and newly-selected member galaxies are cataloged. On the basis
of the enlarged sample of member galaxies, the spatial distribution, localized
velocity structure, color-magnitude relation, and luminosity function of
cluster galaxies are discussed. The reverse peculiar velocities are found for
two satellite subclusters located on opposite sides of the central
concentration, which supports an ongoing merger in Abell 2255.


title:
The Stellar-Dynamical Search for Supermassive Black Holes in Galactic
  Nuclei

abstract:
  The robustness of stellar-dynamical black hole (BH) mass measurements is
illustrated using 7 galaxies that have results from independent groups. Derived
masses have remained constant to a factor of about 2 as spatial resolution has
improved by factors of 2 - 330 and as the analysis has improved from spherical,
isotropic models to axisymmetric, three-integral models. This gives us
confidence that the masses are reliable and that the galaxies do not indulge in
a wide variety of perverse orbital structures. Constraints on BH alternatives
are also improving. In M31, Hubble Space Telescope (HST) spectroscopy shows
that the central massive dark object (MDO) is in a tiny cluster of blue stars
embedded in the P2 nucleus of the galaxy. The MDO must be less than about 0.06
arcsec in radius. M31 becomes the third galaxy in which dark clusters of brown
dwarf stars or stellar remnants can be excluded. In our Galaxy, observations of
almost-complete stellar orbits show that the MDO radius is less than about
0.0006 pc. Among BH alternatives, this excludes even neutrino balls. Therefore,
measurements of central dark masses and the conclusion that these are BHs have
both stood the test of time. Confidence in the BH paradigm for active galactic
nuclei is correspondingly high. Compared to the radius of the BH sphere of
influence, BHs are discovered at similar spatial resolution with HST as in
ground-based work. The reason is that HST is used to observe more distant
galaxies. Large, unbiased samples are accessible. As a result, HST has
revolutionized the study of BH demographics.


title:
Reconstruction of lensing from the cosmic microwave background
  polarization

abstract:
  Gravitational lensing of the cosmic microwave background (CMB) polarization
field has been recognized as a potentially valuable probe of the cosmological
density field. We apply likelihood-based techniques to the problem of lensing
of CMB polarization and show that if the B-mode polarization is mapped, then
likelihood-based techniques allow significantly better lensing reconstruction
than is possible using the previous quadratic estimator approach. With this
method the ultimate limit to lensing reconstruction is not set by the lensed
CMB power spectrum. Second-order corrections are known to produce a curl
component of the lensing deflection field that cannot be described by a
potential; we show that this does not significantly affect the reconstruction
at noise levels greater than 0.25 microK arcmin. The reduction of the mean
squared error in the lensing reconstruction relative to the quadratic method
can be as much as a factor of two at noise levels of 1.4 microK arcmin to a
factor of ten at 0.25 microK arcmin, depending on the angular scale of
interest.


title: Accretion-Induced Collimated Fast Wind Model for Eta Carinae

abstract:
  I propose a scenario to account for the fast polar outflow detected to be
blown by Eta Carinae in 2000. The scenario accounts also for the lack of this
flow in 1998 and 1999. The scenario is based on the binary nature of Eta
Carinae. The collision of the winds blown by the two stars, in particular near
periastron passages, slows down about 5 per cent of the wind blown by Eta
Carinae, i.e., the massive primary star, such that it stays bound to the
system. I assume that most of this mass is accreted back through the equator by
Eta Carinae during apastron passage, when its orbital velocity is much lower.
The mass accretion rate of this backflowing material may become about 25 per
cent of the wind's mass loss rate near apastron passages. If the backflowing
matter has enough specific angular momentum it can form an accretion disk and
may lead to the formation of a polar collimated fast wind (CFW) on top of the
stellar wind.


title:
RR Lyrae stars in Galactic globular clusters. II. A theoretical approach
  to variables in M3

abstract:
  We present predicted relations connecting pulsational and evolutionary
parameters, as based on a wide set of convective pulsating models of RR Lyrae
stars with Z=0.001, Y=0.24 and mass and luminosity suitable for the ``old''
(age $>$ 8 Gyr) variables observed in globular clusters. The relations are
collated with sound constraints on the mass of pulsators, as inferred from
up-to-date evolutionary models of horizontal branch stars, in order to provide
a self-consistent theoretical framework for the analysis of observed variables.
The theoretical predictions are tested through a detailed comparison with
measurements of RR Lyrae stars in the globular cluster M3. We show that the
predicted relations satisfy a variety of observed data, thus providing a
"pulsational" route to the determination of accurate distances to RR Lyrae-rich
globular clusters with intermediate metal content. We discuss the effect of
different physical inputs in evolutionary computations, as well as of different
bolometric corrections adopted to convert bolometric luminosity into absolute
magnitude. We show that the constraints inferred by pulsation theory support
the large value of the mixing-length parameter adopted to fit observed RGB,
but, at the same time, they would yield that the luminosity of updated HB
models is too bright. Such discrepancy is significantly reduced if element
diffusion is properly taken into account.


title:
Recombining WMAP: constraints on ionizing and resonance radiation at
  recombination

abstract:
  We place new constraints on sources of ionizing and resonance radiation at
the epoch of the recombination process using the recent CMB temperature and
polarization spectra coming from WMAP. We find that non-standard recombination
scenarios are still consistent with the current data. In light of this we study
the impact that such models can have on the determination of several
cosmological parameters. In particular, the constraints on curvature and baryon
density appear to be weakly affected by a modified recombination scheme.
However, it may affect the current WMAP constraints on inflationary parameters
like the spectral index and its running. Physically motivated models, like
those based on primordial black hole or super heavy dark matter decay, are able
to provide a good fit to the current data. Future observations in both
temperature and polarization will be needed to more stringently test these
models.


title: Magellanic Cloud Star Clusters as Simple Stellar Populations

abstract:
  Integrated spectra have been obtained of 31 star clusters in the Magellanic
Clouds (MC) and of 4 Galactic globular clusters. The spectra cover the
wavelength range 3500 -- 4700 Angstroms at a resolution of 3.2 Angstroms FWHM.
The MC clusters primarily cover the age range <10^8 -- 3 Gyr, and hence are
well-suited to an empirical study of aging post-starburst stellar populations.
An age-dating method is presented that relies on two spectral absorption
feature indices, H\delta/Fe I 4045 and Ca II, as well as an index measuring the
strength of the Balmer discontinuity. We compare the behavior of the spectral
indices in the observed integrated spectra of the MC clusters to that of
indices generated from theoretical evolutionary synthesis models of varying age
and metal-abundance. The synthesis models are based on those of Worthey (1994,
ApJS, 95, 107), when coupled with the combination of an empirical library of
stellar spectra (Jones 1999, PhD thesis, University of North Carolina) for the
cooler stars and synthetic spectra, generated from Kurucz model atmospheres,
for the hotters stars. Overall, we find good agreement between the ages of the
MC clusters derived from our integrated spectra (and the evolutionary synthesis
modelling of the spectral indices) and ages derived from analyses of the
cluster color-magnitude diagrams, as found in the literature. Hence the
principal conclusion of this study is that ages of young stellar populations
can be reliably measured from modelling of their integrated spectra.


title: Smoothed Particle Magnetohydrodynamics (some shocking results...)

abstract:
  There have been some issues in the past in attempts to simulate magnetic
fields using the Smoothed Particle Hydrodynamics (SPH) method. SPH is well
suited to star formation problems because of its Lagrangian nature. We present
new, stable and conservative methods for magnetohydrodynamics (MHD) in SPH and
present numerical tests on both waves and shocks in one dimension to show that
it gives robust and accurate results.


title: Polarization of GRB via scattering off a relativistic sheath

abstract:
  GRB fireballs could be ensheathed by a relativistic, baryon-enriched outflow
that would in selected directions scatter a polarized beam of gamma rays. The
strong polarization recently announced by RHESSI is attainable by the
scattering mechanism, though not most of the time. The scattering mechanism,
when acting in addition to the synchrotron mechanism, could circumvent some of
the predictions implied by a purely synchrotron origin for the polarization.
The time profile of the scattered component could differ from that of the
primary gamma rays.


title: Radiation from hot bare strange stars

abstract:
  We present the results of numerical simulations of stationary, spherically
outflowing, pair winds, with total luminosities of L=10^{35}- 10^{42} ergs/s.
These results have direct relevance to the emission from hot, bare, strange
stars, which are thought to be powerful sources of electron-positron pairs
created by the Coulomb barrier at the quark surface. The spectra of emergent
photons and pairs are calculated. For L > 2x10^{35} erg/s, photons dominate the
emerging emission. As L increases from 10^{35} to 10^{42} ergs/s, the mean
photon energy decreases from ~ 400-500 keV to 40 keV, while the spectrum
changes in shape from a wide annihilation line to being nearly blackbody with a
high energy (> 100 keV) tail. Such a correlation of the photon spectrum with
the luminosity, together with the fact that super-Eddington luminosities can be
achieved, might be a good observational signature of hot, bare, strange stars.


title: Nature and Environment of Very Luminous Galaxies

abstract:
  The most luminous galaxies in the blue passband have a larger correlation
amplitude than L* galaxies. They do not appear to be preferentially located in
rich clusters or groups, but a significant fraction of them seem to be in
systems which include fainter members.We present an analysis of fields centered
on 18 Very Luminous Galaxies (MB < -21) selected from the Southern Sky Redshift
Survey 2, based on new observations and public data of the 2dF Galaxy Redshift
Survey; we present also additional data on a CfA VLG and on Arp 127. We find
that all the selected VLGs are physically associated to fainter companions.
Moreover, there is a relation between the VLG morphology (early or late) and
the dynamical properties of the system, which reflects the morphology-density
relation. 6 out of the 18 SSRS2 VLGs are early type galaxies: 2 are in the
center of rich Abell clusters with velocity dispersion sigma ~600 km/s, and the
other 4 are in poor clusters or groups with sigma ~300. The VLG extracted from
the CfA catalog is also an elliptical in a Zwicky cluster. The remaining 2/3 of
the sample are late-type VLGs, generally found in poorer systems with a larger
spread in velocity dispersion, from ~100 up to ~750 km/s. The low velocity
dispersion, late-type VLG dominated systems appear to be the analogous of our
own Local Group. The possibile association of VLG systems to dark matter halos
with mass comparable to rich groups or clusters, as suggested by the comparable
correlation amplitude, would imply significant differences in the galaxy
formation process. This work also shows that observing fields around VLGs
represents an effective way of identifying galaxy systems which are not
selected through other traditional techniques.


title: A Study of the Ground Level Event of April 15, 2001 with GRAND

abstract:
  Project GRAND, a proportional wire chamber array, is used to examine the
increased counting rate of single muons during the solar Ground Level Event
(GLE) of April 15, 2001. Data are presented and compared to our background
rates and to that of neutron monitor stations. This GLE is seen with a
statistical significance of 6.1 sigma.


title: The Evolution of Inverse Power Law Quintessence at Low Redshift

abstract:
  Quintessence models based on a scalar field, phi, with an inverse power law
potential display simple tracking behavior at early times, when the
quintessence energy density, rho_phi, is sub-dominant. At late times, when
rho_phi becomes comparable to the matter density, the evolution of phi diverges
from its scaling behavior. We calculate the first order departure of phi from
its tracker solution at low redshift. Our results for the evolution of phi,
rho_phi, Omega_phi, and w are suprisingly accurate even down to z=0. We find
that w and Omega_phi are related linearly to first order. We also derive a
semi-analytic expression for w(z) which is accurate to within a few percent.
Our analytic techniques are potentially applicable to any quintessence model in
which the quintessence component comes to dominate at late times.


title:
Limits on the WIMP-Nucleon Coupling Coefficients from Dark Matter Search
  Experiment with NaF Bolometer

abstract:
  We have performed the underground dark matter search experiment with a sodium
fl uoride (NaF) bolometer array from 2002 through 2003 at Kamioka Observatory
(2700 m.w.e.). The bolometer array consists of eight NaF absorbers with a total
mass of 176 g, and sensitive NTD germanium thermistors glued to each of them.
This experiment aims for the direct detection of weakly interacting massive
part icles (WIMPs) via spin-dependent interaction. With an exposure of 3.38 kg
days, we derived the limits on the WIMP-n ucleon coupling coefficients, a_p and
a_n. These limits confirmed and tightened those derived from our previous
results wit h the lithium fluoride (LiF) bolometer. Our results excluded the
parameter space complementary to the results obtained b y NaI detectors of
UKDMC experiment.


title:
Dissipation of Hydromagnetic Waves on Energetic Particles: Impact on
  Interstellar Turbulence and Cosmic Ray Transport

abstract:
  The diffusion of galactic cosmic rays (CR) is considered. It is anticipated
that the nonlinear MHD cascade sets the power-law spectrum of turbulence from
the principle scale 100 pc to much smaller scales. We found that the
dissipation of waves due to the resonant interaction with energetic particles
may terminate the cascade at less than 1.e13 cm. The shape of CR diffusion
coefficient that was found may explain the observed peaks of secondary to
primary nuclei ratios at a few GeV/n.


title: Evaluation of Production Cross Sections of Li, Be, B in CR

abstract:
  Accurate evaluation of production cross sections of light elements is
important for models of CR propagation, galactic chemical evolution, and
cosmological studies. However, experimental spallation cross section data are
scarce and often unavailable to CR community while semi-empirical systematics
are frequently wrong by a significant factor. We use all available data from
LANL nuclear database together with modern nuclear codes to produce evaluated
production cross sections of isotopes of Li, Be, B suitable for astrophysical
applications.


title: Antiprotons in CR: What Do They Tell Us?

abstract:
  Recent measurements of the CR antiproton flux have been shown to pose a
problem for conventional propagation models. In particular, models consistent
with secondary/primary nuclei ratio in CR produce too few antiprotons, while
matching the ratio and the antiproton flux requires ad hoc assumptions. This
may indicate an additional local CR component or new phenomena in CR
propagation in the Galaxy. We discuss several possibilities which may cause
this problem.


title:
On the Detectability of Gamma Rays from Clusters of Galaxies: Mergers
  versus Secondary Infall

abstract:
  Particle acceleration in clusters of galaxies is expected to take place at
both merger and accretion shocks. The electron component may be energized to
energies of several TeV, and upscatter a small fraction of the photons in the
cosmic microwave background up to gamma ray energies. We address here the issue
of the detectability of the gamma radiation generated either in merger events
or during the accretion of matter onto cluster potential wells. The predictions
are specialized to the cases of GLAST and AGILE, for which a few tens of
clusters are expected to be detected, and to Cherenkov telescopes, for which
however the perspectives do not appear to be optimistic.


title: Search for Sub-TeV Gamma Rays Coincident with BATSE Gamma Ray Bursts

abstract:
  Project GRAND is a 100m x 100m air shower array of proportional wire chambers
(PWCs). There are 64 stations each with eight 1.29 m^2 PWC planes arranged in
four orthogonal pairs placed vertically above one another to geometrically
measure the angles of charged secondaries. A steel plate above the bottom pair
of PWCs differentiates muons (which pass undeflected through the steel) from
non-penetrating particles. FLUKA Monte Carlo studies show that a TeV gamma ray
striking the atmosphere at normal incidence produces 0.23 muons which reach
ground level where their angles and identities are measured. Thus,
paradoxically, secondary muons are used as a signature for gamma ray primaries.
The data are examined for possible angular and time coincidences with eight
gamma ray bursts (GRBs) detected by BATSE. Seven of the GRBs were selected
because of their good acceptance by GRAND and high BATSE Fluence. The eighth
GRB was added due to its possible coincident detection by Milagrito. For each
of the eight candidate GRBs, the number of excess counts during the BATSE T90
time interval and within plus or minus five degrees of BATSE's direction was
obtained. The highest statistical significance reported in this paper (2.7
sigma) is for the event that was predicted to be the most likely to be observed
(GRB 971110).


title: A Proportional Wire Chamber Array: GRAND's Status

abstract:
  Project GRAND is a 100m x 100m air shower array of position sensitive
proportional wire chambers (PWCs) located at 41.7 degrees North and 86.2
degrees West at an elevation of 220m above sea level. Its convenient location
adjacent to the campus of the University of Notre Dame makes it a good training
ground for students. There are 64 stations each with eight 1.29 m^2 PWCs. The
geometry of the stations allows for the angles of charged secondaries to be
determined to within 0.26 degrees in each of two orthogonal planes; muons are
differentiated from electrons and hadrons by means of a steel plate. Two
triggers are run simultaneously: a multiple hit coincidence trigger, rich in
extensive air showers, and a single track trigger, rich in secondary muon
tracks. The former trigger is sensitive to primary energies greater than ~100
TeV, the latter to energies greater than ~10 GeV.


title:
Spatial Variation of the Fine-Structure Parameter and the Cosmic
  Microwave Background

abstract:
  We study the effects on cosmic microwave background (CMB) temperature and
polarization anisotropies of spatial fluctuations of the fine-structure
parameter between causally disconnected regions of the Universe at the time of
recombination. Analogous to weak gravitational lensing, in addition to
modifying the mean power spectra and inducing a curl component (B mode) to the
polarization, spatial fluctuations of the fine-structure parameter induce
higher-order (non-Gaussian) temperature and polarization correlations in the
CMB. We calculate these effects for the general case of arbitrary correlation
between temperature fluctuations and fine-structure parameter fluctuations, and
show the results for a model where these two types of fluctuations are
uncorrelated. The formalism we present here may also be applied to other
modifications of recombination physics that do not significantly alter the
evolution of the dominant density perturbations. We discuss the constraints on
the effective Lagrangian for variable fine-structure parameter necessary to
realize this scenario.


title:
Kinematic Masses of Super Star Clusters in M82 from High-Resolution
  Near-Infrared Spectroscopy

abstract:
  Using high-resolution (R~22,000) near-infrared (1.51 -- 1.75 microns) spectra
from Keck Observatory, we measure the kinematic masses of two super star
clusters in M82. Cross-correlation of the spectra with template spectra of cool
evolved stars gives stellar velocity dispersions of sigma_r=15.9 +/- 0.8 km/s
for MGG-9 and sigma_r=11.4 +/- 0.8 km/s for MGG-11. The cluster spectra are
dominated by the light of red supergiants, and correlate most closely with
template supergiants of spectral types M0 and M4.5. We fit King models to the
observed profiles of the clusters in archival HST/NICMOS images to measure the
half-light radii. Applying the virial theorem, we determine masses of 1.5 +/-
0.3 x 10^6 M_sun for MGG-9 and 3.5 +/- 0.7 x 10^5 M_sun for MGG-11. Population
synthesis modelling suggests that MGG-9 is consistent with a standard initial
mass function, whereas MGG-11 appears to be deficient in low-mass stars
relative to a standard IMF. There is, however, evidence of mass segregation in
the clusters, in which case the virial mass estimates would represent lower
limits.


title: Bar-Induced Evolution of Dark Matter Cusps

abstract:
  The evolution of a stellar bar transforms not only the galactic disk, but
also the host dark matter halo. We present high resolution, fully
self-consistent N-body simulations that clearly demonstrate that dark matter
halo central density cusps flatten as the bar torques the halo. This effect is
independent of the bar formation mode and occurs even for rather short bars.
The halo and bar evolution is mediated by resonant interactions between orbits
in the halo and the bar pattern speed, as predicted by linear Hamiltonian
perturbation theory. The bar lengthens and slows as it loses angular momentum,
a process that occurs even in rather warm disks. We demonstrate that the bar
and halo response can be critically underestimated for experiments that are
unable to resolve the relevant resonant dynamics; this occurs when the phase
space in the resonant region is under sampled or plagued by noise.


title:
Chandra observations of the X-ray luminous star-forming galaxy merger
  Arp~299

abstract:
  We report results of a Chandra observation of the X-ray luminous star-forming
galaxy Arp299 (NGC3690/IC694). We detect 18 discrete X-ray sources with
luminosities above ~10^39 erg\s (0.5-8.0 keV band), which contribute ~40% of
the total galactic emission in this band. The remaining emission is associated
with a diffuse component spatially coincident with regions of widespread
star-formation. We detect X-ray emission from both nuclei. One of the discrete
sources within the complex nuclear region of NGC 3690 is found to have a very
hard spectrum and therefore we associate it with the origin of the AGN-like
spectrum that has also been detected at high X-ray energies using Beppo-SAX.


title: Cassiopeia A and its Clumpy Presupernova Wind

abstract:
  The observed shock wave positions and expansion in Cas A can be interpreted
in a model of supernova interaction with a freely expanding stellar wind with a
mass loss rate of ~3e-5 Msun/yr for a wind velocity of 10 km/s. The wind was
probably still being lost at the time of the supernova, which may have been of
Type IIn or IIb. The wind may play a role in the formation of very fast knots
observed in Cas A. In this model, the quasi-stationary flocculi (QSFs)
represent clumps in the wind, with a density contrast of several 1000 compared
to the smooth wind. The outer, unshocked clumpy wind is photoionized by
radiation from the supernova, and is observed as a patchy HII region around Cas
A. This gas has a lower density than the QSFs and is heated by nonradiative
shocks driven by the blast wave. Denser clumps have recombined and are observed
as HI compact absorption features towards Cas A.


title:
HST/NICMOS Observations of the Embedded Cluster in NGC 2024: Constraints
  on the IMF and Binary Fraction

abstract:
  We present an analysis of NICMOS observations of the embedded cluster
associated with NGC 2024. An analysis of the cluster color-magnitude diagram
(CMD) using the models of D'Antona & Mazzitelli (1997) and Baraffe et al.
(1998) indicates that the ratio of intermediate mass (1.0 to 10.0 M_sun) to low
mass (0.1 to 1.0 M_sun) stars is consistent with the stellar initial mass
function (IMF) for the field. In addition to the CMD analysis, we present
results on the multiplicity of stars in the region. Three companions (in a
sample of 95 potential primaries) were found, with angular separations between
0".4 and 1".0, translating to a projected linear separation of 184 AU to 460 AU
for an estimated distance of 460 pc. The completeness of binary detections is
assessed using recovery fractions calculated by a series of tests using
artificially generated companions to potential primaries in the data frames. We
find that the binary fraction in NGC 2024 is consistent with that of Duquennoy
& Mayor (1991) for solar neighborhood stars over the range of separations and
companion masses appropriate for our survey.


title:
On non-linear hydrodynamic instability and enhanced transport in
  differentially rotating flows

abstract:
  In this paper we argue that differential rotation can possibly sustain
hydrodynamic turbulence in the absence of magnetic field. We explain why the
non-linearities of the hydrodynamic equations (i.e. turbulent diffusion) should
not be neglected, either as a simplifying approximation or based on boundary
counditions. The consequences of lifting this hypothesis are studied for the
flow stability and the enhanced turbulent transport. We develop a simple
general model for the energetics of turbulent fluctuations in differentially
rotating flows. By taking into account the non-linearities of the equations of
motions, we give constraints on the mean flow properties for the possible
development of shear instability. The results from recent laboratory
experiments on rotating flows show -- in agreement with the model -- that the
pertinent parameter for stability appears to be the Rossby number Ro. The
laboratory experiments seem to be compatible with Ro<-1/2 and Ro > 1 in the
inviscid or high rotation rates limit. Our results, taken in the inviscid
limit, are coherent with the classical linear stability analysis, in the sense
that the critical perturbation equals zero on the marginal linear stability
curve. We also propose a prescription for turbulent viscosity which generalize
the beta-prescription derived in Richard & Zahn 1999.


title: On the alignment of T Tauri stars with the local magnetic field

abstract:
  Magnetic field is believed to play an important role in the collapse of a
molecular cloud. In particular, due to the properties of magnetic forces,
collapse should be easier along magnetic field lines, as supported by the
large-scale sheet-like structure of the Taurus giant molecular cloud for
instance. Here we investigate whether such a prefered orientation for collapse
is present at a much smaller scale, that of individual objects. We use recent
high-angular resolution images of T Tauri stars located in the Taurus
star-forming region to find the orientation of the symmetry axis of each
star+jet+disk system and compare it to that of the local magnetic field. We
find that i) the orientations of the symmetry axis of T Tauri stars are not
random with respect to the magnetic field, and ii) that young stars that are
associated to a jet or an outflow are oriented very differently from those
which do not have a detected outflow. We present some implications of this
puzzling new result.


title: The Coronae of AR Lac

abstract:
  We observed the coronally active eclipsing binary, AR Lac, with the High
Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five
orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV
spectra and photometry were also obtained with the Extreme Ultraviolet
Explorer. Significant variability in both X-ray and EUV fluxes were observed,
dominated by at least one X-ray flare and one EUV flare. We saw no evidence of
primary or secondary eclipses. X-ray flux modulation was largest at high
temperature, indicative of flare heating of coronal plasma. Line widths
interpreted in terms of Doppler broadening suggest that both binary stellar
components are active. From line fluxes obtained from total integrated spectra,
we have modeled the emission measure and abundance distributions. A strong
maximum was found in the differential emission measure, characterized by peaks
at log T = 6.9 and 7.4, together with a weak but significant cooler maximum
near log T=6.2, and a moderately strong hot tail from log T= 7.6-8.2. Coronal
abundances have a broad distribution and show no simple correlation with first
ionization potential. While the resulting model spectrum generally agrees very
well with the observed spectrum, there are some significant discrepancies,
especially among the many Fe L-lines. Both the emission measure and abundance
distributions are qualitatively similar to prior determinations from other
X-ray and ultraviolet spectra, indicating some long-term stability in the
overall coronal structure.


abstract:
  The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the full sky in
five frequency bands between 23 and 94 GHz. The primary goal of the mission is
to produce high-fidelity, all-sky, polarization-sensitive maps that can be used
to study the cosmic microwave background. Systematic errors in the maps are
constrained to new levels: using all-sky data, aspects of the anisotropy may
confidently be probed to sub-microKelvin levels. We give a brief description of
the instrument and an overview of the first results from an analysis of maps
made with one year of data. The highlights are (1) the flat Lambda-CDM model
fits the data remarkably well, whereas an Einstein-de Sitter model does not;
(2) we see evidence of the birth of the first generation of stars at z ~ 20;
(3) when the WMAP data are combined and compared with other cosmological
probes, a cosmic consistency emerges: multiple different lines of inquiry lead
to the same results.


title:
Minor-axis velocity gradients in spirals and the case of inner polar
  disks

abstract:
  We measured the ionized-gas and stellar kinematics along the major and minor
axis of a sample of 10 early-type spirals. Much to our surprise we found a
remarkable gas velocity gradient along the minor axis of 8 of them. According
to the kinematic features observed in their ionized-gas velocity fields, we
divide our sample galaxies in three classes of objects. (i) NGC 4984, NGC 7213,
and NGC 7377 show an overall velocity curve along the minor axis without
zero-velocity points, out to the last measured radius, which is interpreted as
due to the warped structure of the gaseous disk. (ii) NGC 3885, NGC 4224, and
NGC 4586 are characterized by a velocity gradient along both major and minor
axis, although non-zero velocities along the minor axis are confined to the
central regions. Such gas kinematics have been explained as being due to
non-circular motions induced by a triaxial potential. (iii) NGC 2855 and NGC
7049 show a change of slope of the velocity gradient measured along the major
axis (which is shallower in the center and steeper away from the nucleus), as
well as non-zero gas velocities in the central regions of the minor axis. This
has been attributed to the presence of a kinematically-decoupled gaseous
component in orthogonal rotation with respect to the galaxy disk, namely an
inner polar disk. The case and origin of inner polar disks are discussed and
the list of their host galaxies is presented.


title:
Interferometric Observations of the Cosmic Microwave Background
  Radiation

abstract:
  Radio interferometers are well suited to studies of both total intensity and
polarized intensity fluctuations of the cosmic microwave background radiation,
and they have been used successfully in measurements of both the primary and
secondary anisotropy. Recent observations with the Cosmic Background Imager
operating in the Chilean Andes, the Degree Angular Scale Interferometer
operating at the South Pole, and the Very Small Array operating in Tenerife
have probed the primary anisotropy over a wide range of angular scales. The
advantages of interferometers for microwave background observations of both
total intensity and polarized radiation are discussed, and the cosmological
results from these three instruments are presented. The results show that,
subject to a reasonable value for the Hubble constant, which is degenerate with
the geometry in closed models, the geometry of the Universe is flat to high
precision (~5%) and the primordial fluctuation spectrum is very close to the
scale-invariant Harrison-Zel'dovich spectrum. Both of these findings are
concordant with inflationary predictions. The results also show that the
baryonic matter content is consistent with that found from primordial
nucleosynthesis, while the cold dark matter component can account for no more
than ~40% of the energy density of the Universe. It is a requirement of these
observations, therefore, that ~60% of the energy content of the Universe is not
related to matter, either baryonic or nonbaryonic. This dark energy component
of the energy density is attributed to a nonzero cosmological constant.


title: Exploring the sub-eV neutrino mass range with supernova neutrinos

abstract:
  A new method to study the effects of neutrino masses on a supernova neutrino
signal is proposed. The method relies exclusively on the analysis of the full
statistics of neutrino events, it is independent of astrophysical assumptions,
and does not require the observation of any additional phenomenon to trace
possible delays in the neutrino arrival times. The sensitivity of the method to
the sub-eV neutrino mass range, defined as the capability of disentangling at
95% c.l. the case $m_\nu=1$eV from $m_\nu=0$, is tested by analyzing a set of
synthetic neutrino samples modeled according to the signal that could be
detected at SuperKamiokande. For a supernova at the Galactic center success is
achieved in more than 50% of the cases. It is argued that a future Galactic
supernova yielding several thousands of inverse $\beta$ decays might provide
enough information to explore a neutrino mass range somewhat below 1 eV.


title:
Formation time distribution of dark matter haloes: theories versus
  N-body simulations

abstract:
  This paper uses numerical simulations to test the formation time distribution
of dark matter haloes predicted by the analytic excursion set approaches. The
formation time distribution is closely linked to the conditional mass function
and this test is therefore an indirect probe of this distribution. The
excursion set models tested are the extended Press-Schechter (EPS) model, the
ellipsoidal collapse (EC) model, and the non-spherical collapse boundary (NCB)
model. Three sets of simulations (6 realizations) have been used to investigate
the halo formation time distribution for halo masses ranging from dwarf-galaxy
like haloes ($M=10^{-3} M_*$, where $M_*$ is the characteristic non-linear mass
scale) to massive haloes of $M=8.7 M_*$. None of the models can match the
simulation results at both high and low redshift. In particular, dark matter
haloes formed generally earlier in our simulations than predicted by the EPS
model. This discrepancy might help explain why semi-analytic models of galaxy
formation, based on EPS merger trees, under-predict the number of high redshift
galaxies compared with recent observations.


title: A preference for a non-zero neutrino mass from cosmological data

abstract:
  We present results from the analysis of cosmic microwave background (CMB),
large scale structure (galaxy redshift survey) and X-ray galaxy cluster (baryon
fraction and X-ray luminosity function) data, assuming a geometrically flat
cosmological model and allowing for tensor components and a non-negligible
neutrino mass. From a combined analysis of all data, assuming three degenerate
neutrinos species, we measure a contribution of neutrinos to the energy density
of the universe, Omega_nu h^2=0.0059^{+0.0033}_{-0.0027} (68 per cent
confidence limits), with zero falling on the 99 per cent confidence limit. This
corresponds to ~4 per cent of the total mass density of the Universe and
implies a species-summed neutrino mass \sum_i m_i =0.56^{+0.30}_{-0.26} eV, or
m_nu~0.2 eV per neutrino. We examine possible sources of systematic uncertainty
in the results. Combining the CMB, large scale structure and cluster baryon
fraction data, we measure an amplitude of mass fluctuations on 8h^{-1} Mpc
scales of sigma_8=0.74^{+0.12}_{-0.07}, which is consistent with measurements
based on the X-ray luminosity function and other studies of the number density
and evolution of galaxy clusters. This value is lower than that obtained when
fixing a negligible neutrino mass (sigma_8=0.86^{+0.08}_{-0.07}). The
combination of CMB, large scale structure and cluster baryon fraction data also
leads to remarkably tight constraints on the Hubble constant,
H_0=68.4^{+2.0}_{-1.4} km/s/Mpc, mean matter density, Omega_m =0.31\pm0.02 and
physical baryon density, Omega_b h^2=0.024\pm0.001, of the Universe.


title:
Theory of the Mercury's spin-orbit motion and analysis of its main
  librations

abstract:
  The upcoming space missions, MESSENGER and BepiColombo with onboard
instrumentation capable of measuring the rotational parameters stimulate the
objective to reach an accurate theory of the rotational motion of Mercury. For
obtaining the real motion of Mercury, we have used our relativistic BJV model
of solar system integration including the coupled spin-orbit motion of the
Moon. We have extended this model by generalizing the spin-orbit couplings to
the terrestrial planets, notably Mercury. The updated model is called SONYR
(acronym of Spin-Orbit N-BodY Relativistic model). The SONYR model giving an
accurate solution of the spin-orbit motion of Mercury permits to analyze the
different families of the Hermean rotational librations. The spin-orbit motion
of Mercury is characterized by two proper frequencies (namely 15.847 and 1066
years) and its 3:2 resonance presents a second synchronism which can be
understood as a spin-orbit secular resonance (278 898 years). By using the
SONYR model, we find a new determination of the mean obliquity, namely 1.6
arcminutes. Besides, we identify in the Hermean librations the impact of the
uncertainty of the greatest principal moment of inertia (\cmr2) on the
obliquity and on the libration in longitude (2.3 mas and 0.45 as respectively
for an increase of 1% on the \cmr2 value). These determinations prove to be
suitable for providing constraints on the internal structure of Mercury.


title:
Detection of low Eu abundances in extremely metal-poor stars and the
  origin of r-process elements

abstract:
  We report abundance analyses of three extremely metal-poor stars with [Fe/H]
$\lesssim -3$, using the Subaru High Dispersion Spectrograph (HDS). All are
found to have sub-solar values of [Eu/Fe]. Comparison with our chemical
evolution model of the Galactic halo implies the dominant source of Eu to be
the low-mass end of the supernova mass range. Future studies of stars with low
Eu abundances will be important to determine the r-process site.


title:
Accretion disk wind in the AGN broad-line region: Spectroscopically
  resolved line profile variations in Mrk110

abstract:
  Detailed line profile variability studies of the narrow line Seyfert 1 galaxy
Mrk110 are presented. We obtained the spectra in a variability campaign carried
out with the 9.2m Hobby-Eberly Telescope at McDonald Observatory. The
integrated Balmer and Helium (HeI,II) emission lines are delayed by 3 to 33
light days to the optical continuum variations respectively. The outer wings of
the line profiles respond much faster to continuum variations than the central
regions. The comparison of the observed profile variations with model
calculations of different velocity fields indicates an accretion disk structure
of the broad line emitting region in Mrk110. Comparing the velocity-delay maps
of the different emission lines among each other a clear radial stratification
in the BLR can be recognized. Furthermore, delays of the red line wings are
slightly shorter than those of the blue wings. This indicates an accretion disk
wind in the BLR of Mrk110. We determine a central black hole mass of M =
$1.8\cdot10^{7} M_{\odot}$. Because of the poorly known inclination angle of
the accretion disk this is a lower limit only.


title:
Galaxy Types in the Sloan Digital Sky Survey Using Supervised Artificial
  Neural Networks

abstract:
  Supervised artificial neural networks are used to predict useful properties
of galaxies in the Sloan Digital Sky Survey, in this instance morphological
classifications, spectral types and redshifts. By giving the trained networks
unseen data, it is found that correlations between predicted and actual
properties are around 0.9 with rms errors of order ten per cent. Thus, given a
representative training set, these properties may be reliably estimated for
galaxies in the survey for which there are no spectra and without human
intervention.


title:
Optical and near-infrared photometry of the Type Ia Supernova 2000E in
  NGC 6951

abstract:
  We present optical and near-infrared photometry, along with optical spectra,
of the Type Ia supernova SN 2000E in the spiral galaxy NGC 6951. It was
discovered by the staff of the Teramo Observatory during the monitoring of the
SN 1999el. The observations span a time interval of 234 days in the optical and
134 days in the near-infrared (starting 16 days and 7 days before maximum B
light, respectively). Optical spectra are available from 6 days before maximum
B light to 122 days after it. SN 2000E exhibits a Dm15(B) = 0.94, thus being
classifiable as a slow-declining Type Ia SN and showing the distinctive
features of such a class of objects. Spectroscopically, SN 2000E appears as a
normal Type Ia SN, like SN 1990N. We could constrain reddening [E(B-V) ~0.5
mag] and distance (mu0 ~32.14 mag) using a number of different methods. The
bolometric luminosity curve of SN 2000E, allows a determination of the Ni56
mass amounting to 0.9Msun.


title: Intranight optical variability of Blazars

abstract:
  We present results of a multi-epoch intra-night optical monitoring of eleven
blazars consisting of six BL Lac objects and five radio core-dominated quasars
(CDQs). These densely sampled and sensitive R-band CCD observations, carried
out from November 1998 through May 2002 during a total of 47 nights with an
average of 6.5 hours/night, have enabled us to detect variability amplitudes as
low as $\sim 1%$ on intra-night time scales. A distinction is found for the
first time between the intra-night optical variability (INOV) properties of the
these two classes of relativistically beamed radio-loud AGNs. BL Lacs are found
to show a duty cycle (DC) of INOV of $\sim$60%, in contrast to CDQs, which show
a much smaller INOV DC of $\sim$20%, the difference being attributable mainly
to the weakly polarized CDQs. On longer time scales (i.e., between a week to a
few years) variability is seen from all the CDQs and BL Lacs in our sample. The
results reported here form part of our long-term programme to understand the
intra-night optical variability characteristics of the four main classes of
luminous AGNs, i.e., radio-quiet quasars (RQQs) and radio lobe-dominated
quasars (LDQs), as well as CDQs and BL Lac objects.