title:
An integral equation approach to time-dependent kinematic dynamos in
  finite domains

abstract:
  The homogeneous dynamo effect is at the root of cosmic magnetic field
generation. With only a very few exceptions, the numerical treatment of
homogeneous dynamos is carried out in the framework of the differential
equation approach. The present paper tries to facilitate the use of integral
equations in dynamo research. Apart from the pedagogical value to illustrate
dynamo action within the well-known picture of Biot-Savart's law, the integral
equation approach has a number of practical advantages. The first advantage is
its proven numerical robustness and stability. The second and perhaps most
important advantage is its applicability to dynamos in arbitrary geometries.
The third advantage is its intimate connection to inverse problems relevant not
only for dynamos but also for technical applications of magnetohydrodynamics.
The paper provides the first general formulation and application of the
integral equation approach to time-dependent kinematic dynamos in finite
domains. For the spherically symmetric alpha^2 dynamo model it is shown how the
general formulation is reduced to a coupled system of two radial integral
equations for the defining scalars of the poloidal and the toroidal field
components. The integral equation formulation for spherical dynamos with
general velocity fields is also derived. Two numerical examples, the alpha^2
dynamo model with radially varying alpha, and the Bullard-Gellman model
illustrate the equivalence of the approach with the usual differential equation
method.


title:
Intranight optical variability of radio-quiet and radio lobe dominated
  quasars

abstract:
  We present results of a programme of multi-epoch, intra-night optical
monitoring of a sample of non-blazar type AGN, which includes seven radio-quiet
QSOs (RQQs) and an equal number of radio-loud, lobe-dominated quasars (LDQs),
covering a redshift range from about 0.2 to 2.0. These two sets of optically
bright and intrinsically luminous QSOs are well matched in the redshift-optical
luminosity ($z - M_B$) plane. Our CCD monitoring covered a total of 61 nights
with an average of 6.1 hours of densely sampled monitoring of just a single QSO
per night, thereby achieving a typical detection threshold of $\sim 1$%
variation over the night. Unambiguous detection of intra-night
variability(INOV) amplitudes in the range 1$-$3% on day-like or shorter time
scales were thus made for both RQQs and LDQs. Based on these clear detections
of INOV, we estimate duty cycles of 17% and 9% for RQQs and LDQs, respectively;
inclusion of the two cases of probable variations of LDQs would raise the duty
cycle to 15% for LDQs. The similarity in the duty cycle and amplitude of INOV
for the RQQs and LDQs suggests, firstly, that the radio loudness alone does not
guarantee an enhanced INOV in QSOs and,secondly, that as in LDQs, relativistic
jets may also be present in RQQs. We argue that, as compared to BL Lacs, the
conspicuously milder, rarer and possibly slower INOV of RQQs and LDQs, can in
fact be readily understood in terms of their having optical synchrotron jets
which are modestly misaligned from us,but are otherwise intrinsically as
relativistic and active as the jets in BL Lacs.


title: Optical variability properties of high luminosity AGN classes

abstract:
  We present the results of a comparative study of the intra-night optical
variability (INOV) characteristics of radio-loud and radio-quiet quasars, which
involves a systematic intra-night optical monitoring of seven sets of high
luminosity AGNs covering the redshift range {\it z} $\simeq 0.2$ to {\it z}
$\simeq 2.2$. The sample, matched in the optical luminosity -- redshift (M$_B$
-- z) plane, consists of seven radio-quiet quasars (RQQs), eight radio
lobe-dominated quasars (LDQs), six radio core-dominated quasars (CDQs) and five
BL Lac objects (BLs). Systematic CCD observations, aided by a careful data
analysis procedure, have allowed us to detect INOV with amplitudes as low as
1%. Present observations cover a total of 113 nights (720 hours) with only a
single quasar monitored as continuously as possible on a night. Considering
cases of only unambiguous detections of INOV we have estimated duty cycles
(DCs) of 17%, 12%, 20% and 72% respectively for RQQs, LDQs, CDQs, and BLs. The
low amplitude and low DC of INOV shown by RQQs compared to BLs can be
understood in terms of their having optical synchrotron jets which are modestly
misdirected from us. From our fairly extensive dataset, no unambiguous general
trend of a correlation between the INOV amplitude and the apparent optical
brightness of the quasar is noticed.


title:
Structure in the early afterglow lightcurve of the gamma-ray burst of 29
  March 2003

abstract:
  Gamma-ray bursts (GRBs) are energetic explosions that for 0.01--100 s are the
brightest gamma-ray sources in the sky. Observations of the early evolution of
afterglows we expected to provide clues about the nature of the bursts, but
their rapid fading has hampered such studies; some recent rapid localizations
of bursts have improved the situation. Here we report on an early detection of
the very bright afterglow of the burst of 29 March 2003 (GRB030329). Our data
show that, even early in the aferglow phase, the light curve shows unexpectedly
complicated structures superimposed on the fading background.


title: A New Procedure for the Photometric Parallax Estimation

abstract:
  We present a new procedure for photometric parallax estimation. The data for
1236 stars provide calibrations between the absolute magnitude offset from the
Hyades main-sequence and the UV-excess for different (B-V)o colour-index
intervals, i.e.: (0.3 0.4), (0.4 0.5), (0.5 0.6), (0.6 0.7), (0.7 0.8), (0.8
0.9), (0.9 1.0), and (1.0 1.1). The mean difference between the original and
estimated absolute magnitudes and the corresponding standard deviation are
rather small, +0.0002 and +/-0.0613 mag. The procedure has been adapted to the
Sloan photometry by means of colour equations and applied to a set of
artificial stars with different metallicity. The comparison of the absolute
magnitudes estimated by the new procedure and the canonical one indicates that
a single colour-magnitude diagram does not supply reliable absolute magnitudes
for stars with large range of metallicity.


title: Photometric variability of a young, low-mass brown dwarf

abstract:
  We report differential I-band and J-band photometry of S Ori 45, a cool
(M8.5), young (1-8 Myr) brown dwarf of the sigma Orionis cluster with a likely
mass estimated at around 20 times the mass of Jupiter. We detect variability
(amplitudes ranging from 34 to 81 mmag) and observe a modulation at a period of
2.5-3.6 h in both optical and near-infrared light curves. The most recent
optical data set, however, presents a modulation at the very short period of
46.4+/-1.5 min, which remains a mystery. The origin of the 2.5-3.6 h modulation
is analized in terms of various scenarios: inhomogeneous features (dust clouds
or magnetically induced dark spots) co-rotating with the object's surface, and
presence of an unseen very low-mass companion that is steadily transferring
mass to the primary. Because of the very young age of the object and its
persistent strong Halpha emission, the possible presence of an accreting disk
is also discussed. If the period of a few hours is related to rotation, our
results suggest that sigma Orionis low-mass brown dwarfs are rotating faster
than more massive cluster brown dwarfs at a rate consistent with their
theoretically inferred masses and radii, implying that all of these objects
have undergone similar angular momentum evolution.


title:
Disks around the Young Stars TW Hya and HD 100546 Imaged at 3.4
  Millimeters with the Australia Telescope Compact Array

abstract:
  We present observations of the young stars TW Hya and HD 100546 made with the
Australia Telescope Compact Array at 89 GHz with $\sim2''$ resolution and
$\sim3$ mJy continuum sensitivity. Compact thermal dust continuum emission is
detected from disks surrounding both stars. HD 100546 also shows hints of
extended emission, presumably a residual protostellar envelope, which is also
visible in scattered light at optical wavelengths. For TW Hya, HCO$^+$ J=1--0
line emission from the circumstellar disk is detected and spatially resolved.
The observed size and intensity are in good agreement with model calculations
based on an irradiated disk with substantial depletions derived previously from
single dish observations of higher-J HCO$^+$ transitions.


title: The X-ray spectrum of the black hole candidate GX339-4 in a low state

abstract:
  We report on four observations of the black hole candidate GX 339-4 collected
in the spectral range 0.4-140 keV with the BeppoSAX satellite during 1997. All
our spectra are typical of a black hole candidate in its low-hard state, i.e.
are dominated by the hard tail of the emission from the corona. Although the
direct emission from the accretion disk in the soft X-ray range is weak,
spectra are well described only with models that take into consideration the
Compton reflection of hard X-rays from the corona onto the surface of an
accretion disk of non negligible extent.


title: Late B-type stars and their candidate companions resolved with Chandra

abstract:
  We present the first results from a series of Chandra observations carried
out with the aim to examine the origin of X-ray emission in main-sequence late
B-type stars. We use high spatial resolution X-ray observations to enlighten
the prevalent speculation that previously unknown late-type or low-mass
companion stars are the sites of the X-ray emission, instead of the B-type
primaries. Here we present the results for HD1685, HD113703, HD123445,
HD133880, and HD169978. Adaptive optics observations have recently revealed at
least one faint object near each of these B-type stars (at separation of 1-6").
Four of the new infrared objects show infrared colors and magnitudes typical
for low-mass pre-main sequence stars, and are likely true companions to the
10-50 Myr old B-type stars. These multiple systems are now resolved for the
first time in X-ray light.


title: New Light on Dark Matter

abstract:
  Dark matter, proposed decades ago as a speculative component of the universe,
is now known to be the vital ingredient in the cosmos, eight times more
abundant than ordinary matter, one quarter of the total energy density and the
component which has controlled the growth of structure in the universe. Its
nature remains a mystery, but, assuming it is comprised of weakly interacting
sub-atomic particles, is consistent with large scale cosmic structure. However,
recent analyses of structure on galactic and sub-galactic scales have suggested
discrepancies and stimulated numerous alternative proposals. We discuss how
studies of the density, demography, history and environment of smaller scale
structures may distinguish among these possibilities and shed new light on the
nature of dark matter.


title:
On the Ly-alpha emission from gamma-ray burst host galaxies: evidence
  for low metallicities

abstract:
  We report on the results of a search for Ly-alpha emission from the host
galaxy of the z=2.140 GRB 011211 and other galaxies in its surrounding field.
We detect Ly-alpha emission from the host as well as from six other galaxies in
the field. The restframe equivalent width of the Ly-alpha line from the GRB
011211 host is about 21 AA. This is the fifth detection of Ly-alpha emission
out of five possible detections from GRB host galaxies, strongly indicating
that GRB hosts, at least at high redshifts, are Ly-alpha emitters. This is
intriguing as only about 25% of the Lyman-Break selected galaxies at similar
redshifts have Ly-alpha emission lines with restframe equivalent width larger
than 20 AA. Possible explanations are i) a preference for GRB progenitors to be
metal-poor as expected in the collapsar model, ii) an optical afterglow
selection bias against dusty hosts, and iii) a higher fraction of Ly-alpha
emitters at the faint end of the luminosity function for high-z galaxies. Of
these, the current evidence seems to favour i).


title:
The Host Galaxies of Narrow-Line Seyfert 1s: Evidence for Bar-Driven
  Fueling

abstract:
  We present a study of the host-galaxy morphologies of narrow- and broad-line
Seyfert 1 galaxies (NLS1s and BLS1s) based on broad-band optical images from
the Hubble Space Telescope archives. We find that large-scale stellar bars,
starting at ~1 kpc from the nucleus, are much more common in NLS1s than BLS1s.
Furthermore, the fraction of NLS1 spirals that have bars increases with
decreasing full-width at half-maximum (FWHM) of the broad component of H-beta.
These results suggest a link between the large-scale bars, which can support
high fueling rates to the inner kpc, and the high mass-accretion rates
associated with the supermassive black holes in NLS1s.


title:
Molecular Counterparts of Ultracompact HII Regions with Extended
  Envelopes

abstract:
  We carried out 13CO J=1-0, CS, and C34S J=2-1 and J=3-2 line observations of
molecular clouds associated with 16 ultracompact (UC) HII regions with extended
envelopes. The molecular clouds are the ones that give birth to rich stellar
clusters and/or very massive (O7-O4) stars. Our data show that the clouds are
very clumpy and of irregular morphology. They usually have much larger masses,
velocity dispersions, and fractions of dense gas than molecular clouds that
form early B or late O stars. This is compatible with earlier findings that
more massive stars form in more massive cores. 13CO cores are in general
associated with compact HII regions regardless of the presence of UC HII
regions therein. In contrast, CS cores are preferentially associated with
compact HII regions that contain UC HII regions. As with the fact that the
compact HII regions containing UC HII regions are more compact than those not
associated with UC HII regions, these indicate that the former may be in an
earlier evolutionary phase than the latter. The diffuse extended envelopes of
HII regions often develop in the direction of decreasing molecular gas density.
Based on detailed comparison of molecular line data with radio continuum and
recombination line data, the extended ionized envelopes are likely the results
of champagne flows in at least 10 sources in our sample. Together these results
appear to support a published suggestion that the extended emission around UC
HII regions can be naturally understood by combining the champagne flow model
with the hierarchical structure of molecular clouds. We discuss the implication
of our results for the blister model of HII regions.


title: RXTE observations of X-ray transients IGRJ17091-3624 and IGRJ18539+072

abstract:
  We present results of analysis of observations of two transient sources IGR
J17091-3624 and IGR J18539+0727 in April 2003 with RXTE observatory. Obtained
energy spectra of sources, and also power spectra of their flux variations give
us a possibility to classify them as X-ray binary systems in low/hard spectral
state. Parameters of power spectrum of IGR J18539+0727 indicates that this
source is a black hole candidate.


title: A Possible New Population of Sources with Extreme X-Ray / Optical Ratios

abstract:
  We describe a possible new class of X-ray sources that have robust detections
in ultra-deep Chandra data, yet have no detections at all in our deep
multi-band GOODS Hubble Space Telescope (HST) ACS images, which represent the
highest quality optical imaging obtained to date on these fields. These extreme
X-ray / Optical ratio sources ("EXO"s) have values of Fx/Fopt at least an order
of magnitude above those generally found for other AGN, even those that are
harbored by reddened hosts. We thus infer two possible scenarios: (1) if these
sources lie at redshifts z < 6, then their hosts need to be exceedingly
underluminous, or more reddened, compared with other known sources; (2) if
these sources lie above z ~ 6-7, such that even their Lyman-alpha emission is
redshifted out of the bandpass of our ACS z(850) filter, then their optical and
X-ray fluxes can be accounted for in terms of relatively normal L* hosts and
moderate-luminosity AGN.


title: Recent Results from the RICE Experiment at the South Pole

abstract:
  We present a compilation of recent results, submitted to the 2003
International Cosmic Ray Conference (Tsukuba, Japan). These include: a) Revised
Monte Carlo estimates of the radiofrequency signals produced by electromagnetic
showers in ice, b) an updated search for ultra-high energy (UHE) neutrinos
based on detection of radio-wavelength Cherenkov radiation; such radiation
results from neutrino-induced electromagnetic showers in cold Polar ice, and c)
An in situ measurement of the index of refraction through the South Polar firn.


title: Lyman$\alpha$ Emitters beyond Redshift 5:The Dawn of Galaxy Formation

abstract:
  The 8m class telescopes in the ground-based optical astronomy together with
help from the ultra-sharp eye of the Hubble Space Telescope have enabled us to
observe forming galaxies beyond redshift $z=5$. In particular, more than twenty
Ly$\alpha$-emitting galaxies have already been found at $z > 5$. These findings
provide us with useful hints to investigate how galaxies formed and then
evolved in the early universe. Further, detailed analysis of Ly$\alpha$
emission line profiles are useful in exploring the nature of the intergalactic
medium because the trailing edge of cosmic reionization could be close to $z
\sim 6$ -- 7, at which forming galaxies have been found recently. We also
discuss the importance of superwinds from forming galaxies at high redshift,
which has an intimate relationship between galaxies and the intergalactic
medium. We then give a review of early cosmic star formation history based on
recent progress in searching for Ly$\alpha$-emitting young galaxies beyond
redshift 5.


title:
Enhancement of the helium resonance lines in the solar atmosphere by
  suprathermal electron excitation II: non-Maxwellian electron distributions

abstract:
  In solar EUV spectra the He I and He II resonance lines show unusual
behaviour and have anomalously high intensities compared with other transition
region lines. The formation of the helium resonance lines is investigated
through extensive non-LTE radiative transfer calculations. The model
atmospheres of Vernazza, Avrett & Loeser are found to provide reasonable
matches to the helium resonance line intensities but significantly
over-estimate the intensities of other transition region lines. New model
atmospheres have been developed from emission measure distributions derived by
Macpherson & Jordan, which are consistent with SOHO observations of transition
region lines other than those of helium. These models fail to reproduce the
observed helium resonance line intensities by significant factors. The
possibility that non-Maxwellian electron distributions in the transition region
might lead to increased collisional excitation rates in the helium lines is
studied. Collisional excitation and ionization rates are re-computed for
distribution functions with power law suprathermal tails which may form by the
transport of fast electrons from high temperature regions. Enhancements of the
helium resonance line intensities are found, but many of the predictions of the
models regarding line ratios are inconsistent with observations. These results
suggest that any such departures from Maxwellian electron distributions are not
responsible for the helium resonance line intensities.


title: Highlights from XMM-Newton

abstract:
  The launch of the Chandra (NASA) and XMM-Newton (ESA) X-ray observatories in
1999 has revolutionized our view of the Universe, by providing astrophysical
information about many classes of sources with unprecedent detail. The high
throughput of XMM-Newton makes it the ideal instrument to provide low to
moderate resolution spectroscopy of faint and extended sources. After 3 years
of operations, XMM-Newton has observed many types of astronomical sources and
delivered very interesting results in many areas. In this review, we highlight
a few points where the contribution of XMM-Newton has significantly furthered
our knowledge of the energetic Universe.


title:
Nucleosynthesis in Black-Hole-Forming Supernovae and Abundance Patterns
  of Extremely Metal-Poor Stars

abstract:
  Stars more massive than $\sim$ 20 - 25 \ms form a black hole at the end of
their evolution. Stars with non-rotating black holes are likely to collapse
"quietly" ejecting a small amount of heavy elements (Faint supernovae). In
contrast, stars with rotating black holes are likely to give rise to very
energetic supernovae (Hypernovae). We present distinct nucleosynthesis features
of these two types of "black-hole-forming" supernovae. Nucleosynthesis in
Hypernovae is characterized by larger abundance ratios (Zn,Co,V,Ti)/Fe and
smaller (Mn,Cr)/Fe than normal supernovae, which can explain the observed trend
of these ratios in extremely metal-poor stars. Nucleosynthesis in Faint
supernovae is characterized by a large amount of fall-back. We show that the
abundance pattern of the recently discovered most Fe-poor star, HE0107-5240,
and other extremely metal-poor carbon-rich stars are in good accord with those
of black-hole-forming supernovae, but not pair-instability supernovae. This
suggests that black-hole-forming supernovae made important contributions to the
early Galactic (and cosmic) chemical evolution. Finally we discuss the nature
of First (Pop III) Stars.


title: Constraining superheavy dark matter model of UHECR with SUGAR data

abstract:
  Models which associate the origin of the ultra-high energy cosmic rays
(UHECR) with decays of relic superheavy particles predict the anisotropy of
UHECR flux toward the Galactic center. We use the existing SUGAR data, which
covered the Galactic center best so far, to look for such a signal and limit
the fraction of UHECR produced by this mechanism. The absence of anisotropy
toward the Galactic center in the SUGAR data implies at 95% confidence level
that the fraction of SHDM-related cosmic rays should be less than 20% at
$E>1\times10^{19}$ eV and less than 50% at $E>4\times10^{19}$ eV.


title:
Compact Groups in the UZC galaxy sample: II. Connections between
  morphology, luminosity and large-scale density

abstract:
  The nature of Compact Groups (CGs) is investigated by comparing the
luminosities and morphologies of CG galaxies, CG Neighbours and Isolated
galaxies. CGs turn out to include more early type galaxies than Isolated
galaxies and fewer low-luminosity galaxies. The 33 CGs with a dominant E/S0 and
the 30 CGs with a dominant spiral have similar LF parameters. Spiral dominated
CGs have fewer galaxies at high and low luminosity in comparison with their
Neighbours, while E-S0 dominated CGs seem to lack only faint galaxies when
compared to their Neighbours. Ellipticals which are the dominant galaxy of a CG
are also brighter than all their Neighbours, while this holds true for only
half of the dominant spirals and S0s. Relations linking the number of
Neighbours of dominant E-S0s to the luminosity of E-S0s and to the difference
between the first and the second ranked CG members do suggest a link between
the formation of bright early-type galaxies and the presence of a group-like
potential. No similar relations are found for dominant spirals. These tentative
results are compatible with the assumption that CG dominant Ellipticals are
anomalous galaxies whose formation might have been a secondary outcome during
the process of groups formation.


title: Is there a Dichotomy in the Radio Loudness Distribution of Quasars?

abstract:
  We present a new approach to tackle the issue of radio loudness in quasars.
We constrain a (simple) prescription for the intrinsic distribution of
radio-to-optical ratios by comparing properties of Monte Carlo simulated
samples with those of observed optically selected quasars. We find strong
evidence for a dependence of the radio luminosity on the optical one, even
though with a large scatter. The dependence of the fraction of radio loud
quasars on apparent and absolute optical magnitudes results in a selection
effect related to the radio and optical limits of current surveys. The
intrinsic distribution of the radio-to-optical ratios shows a peak at
$R^*_{1.4} \sim 0.3$, with only $\simlt 5$ per cent of objects being included
in a high $R^*_{1.4}$ tail which identifies the radio loud regime. No lack or
deficit of sources -- but only a steep transition region -- is present between
the radio loud and radio quiet populations at any $R^*_{1.4}$. We briefly
discuss possible origins for this behaviour (e.g. absence of jets in radio
quiet sources, large range of radiative radio efficiency, different life-times
for the accretion and jet ejection phenomena, ...).


title:
Large-scale curvature perturbations with spatial and time variations of
  the inflaton decay rate

abstract:
  We present a gauge-invariant formalism to study the evolution of the
curvature and entropy perturbations in the case in which spatial and time
variations of the inflaton decay rate into ordinary matter are present. During
the reheating stage after inflation curvature perturbations can vary with time
on super-horizon scales sourced by a a gauge-invariant inflaton decay rate
perturbation. We show that the latter is a function not only of the spatial
variations of the decay rate generated during inflation, as envisaged in a
recently proposed scenario, but also of the time variation of the inflaton
decay rate during reheating. If only the second source is present, the final
curvature perturbation at the end of the reheating stage is proportional to the
curvature perturbation at the beginning of reheating with a coefficient of
proportionality which can be either smaller or larger than unity depending upon
the underlying physics governing the time variation of the inflaton decay rate.
As a consequence, we show that the standard consistency relation between the
amplitude of curvature perturbations, the amplitude of tensor perturbations and
the tensor spectral index of one-single field models of inflation is violated
and there is the possibility that the tensor-to-curvature amplitude ratio is
larger than in the standard case.


title:
Explosive Nucleosynthesis Associated with Formation of Jet-induced GRBs
  in Massive Stars

abstract:
  We perform 2-dimensional relativistic hydrodynamical simulations in the
context of collapsar model. Calculations of explosive nucleosynthesis are also
accomplished. We investigate the influence of the structure of the progenitor
and energy deposition rate on the resulting explosive nucleosynthesis, assuming
that 56Ni is mainly synthesized in the jet launched by the neutrino heating. We
show the amount of 56Ni is very sensitive to the energy deposition rate. Thus
we conclude that it is quite natural not to detect an underlying supernova in
some X-ray afterglows as in GRB 010921. We also point out the possibility that
the relative abundance of the elements with intermediate mass number such as Si
and S in the X-ray afterglow of GRB 011211 may be naturally explained if the
energy deposition rate at the central engine is relatively long because little
amount of 56Ni should be synthesized under such an environment. If this
discussion is true, there should be correlation between the line features in
the X-ray afterglow and duration of the GRB. It should be noted that the
duration of GRB 011211 is 270 seconds, making it the longest burst ever
observed by Beppo-SAX although it suffers from the effect of red-shift
(z_host=2.14), which supports our conclusion. Our results also suggest that the
type I collapsar model in which the energy deposition rate is relatively low
(\dot{E} \sim 10^{51} erg/s) might have difficulty in reproducing the observed
amount of 56Ni in a hypernova such as SN 1998bw. This means that the mechanism
of the central engine of a hypernova accompanying GRB may be constrained by the
discussion of explosive nucleosynthesis.


title:
High Resolution Calculations of Merging Neutron Stars III: Gamma-Ray
  Bursts

abstract:
  Recent three dimensional, high-resolution simulations of neutron star
coalescences are analysed to assess whether short gamma-ray bursts (GRBs) could
originate from such encounters. The two most popular modes of energy extraction
-- namely the annihilation of $\nu\bar{\nu}$ and magnetohydrodynamic processes-
are explored in order to investigate their viability in launching GRBs. We find
that $\nu\bar{\nu}$ annihilation can provide the necessary stresses to drive a
highly relativistic expansion. But unless the outflow is beamed into less than
one percent of the solid angle this mechanism may fail to explain the apparent
isotropized energies implied for short GRBs at cosmological distances. We argue
that the energetic, neutrino-driven wind that accompanies the merger event will
have enough pressure to provide adequate collimation to the
$\nu\bar{\nu}$-annihilation-driven jet, thereby comfortably satisfying
constraints on event rate and apparent luminosity. We also assess magnetic
mechanisms to transform the available energy into a GRB. If the central object
does not collapse immediately into a black hole it will be convective and it is
expected to act as an effective large scale dynamo amplifying the seed magnetic
fields to a few times $10^{17}$ G within a small fraction of a second. The
associated spindown time scale is 0.2 s, coinciding with the typical duration
of a short GRB. The efficiencies of the various assessed magnetic processes are
high enough to produce isotropized luminosities in excess of $10^{52}$ ergs/s
even without beaming.


title:
Ringing effects reduction by improved deconvolution algorithm
  Application to A370 CFHT image of gravitational arcs

abstract:
  We develop a self-consistent automatic procedure to restore informations from
astronomical observations. It relies on both a new deconvolution algorithm
called LBCA (Lower Bound Constraint Algorithm) and the use of the Wiener
filter. In order to explore its scientific potential for strong and weak
gravitational lensing, we process a CFHT image of the galaxies cluster Abell
370 which exhibits spectacular strong gravitational lensing effects. A high
quality restoration is here of particular interest to map the dark matter
within the cluster. We show that the LBCA turns out specially efficient to
reduce ringing effects introduced by classical deconvolution algorithms in
images with a high background. The method allows us to make a blind detection
of the radial arc and to recover morphological properties similar to
thoseobserved from HST data. We also show that the Wiener filter is suitable to
stop the iterative process before noise amplification, using only the
unrestored data.


title:
Star formation and Asymmetry in the spiral arms of M51-- Variable star
  formation caused by more than one spiral density wave

abstract:
  In the inner 3kpc of M51 we find that logarithmic spirals provide good fits
to the peak intensities in molecular gas observed by BIMA in the CO (J=1-0)
emission line along the spiral arms. However, we measure significant
asymmetries between the location and density of the arms observed on one side
of the galaxy compared to those on the opposite side. Between a radius of 1 and
2.2 kpc the gas distribution traced in CO is lopsided with densities twice as
large in one arm compared to the opposite one. In the same region, the spiral
arms are offset by 20 degrees from the position of the arm on the opposite side
of the galaxy after a rotation of 180 degrees. We use the ratio of CO emission
to that in the Pa alpha hydrogen recombination line to estimate the efficiency
of star formation along each arm. Except for a narrow region at about 2kpc
where star formation is surprisingly inefficient, the gas depletion time is
approximately 200 million years despite large variations in the molecular gas
density in the arms.
  We account for the deviations from two armed bi-symmetric structure with a
simple model that includes an additional three-armed spiral density wave. This
model accounts for the angular offset between the arm on one side compared to
its opposite, the lopsided distribution in molecular gas, and inter-arm star
formation to the north east of the galaxy nucleus. Since the star formation
efficiency is unaffected by the variations in gas density, and the variations
in gas density can be accounted for by the presence of an additional
three-armed density wave, we suggest that the star formation rate is variable,
and is highest where and when the maxima of the two spiral density waves
coincide or constructively add.


title: A Synoptic X-ray Study of M31 with the Chandra-HRC

abstract:
  We have obtained 17 epochs of Chandra High Resolution Camera (HRC) snapshot
images, each covering most of the M31 disk. The data cover a total baseline of
2.5 years and contain a mean effective exposure of 17 ks. We have measured the
mean fluxes and long-term lightcurves for 166 objects detected in these data.
At least 25% of the sources show significant variability. The cumulative
luminosity function (CLF) of the disk sources is well-fit by a power-law with a
slope comparable to those observed in typical elliptical galaxies. The CLF of
the bulge is a broken power law similar to measurements made by previous
surveys. We note several sources in the southwestern disk with L_X > 10^{37}
erg/s . We cross-correlate all of our sources with published optical and radio
catalogs, as well as new optical data, finding counterpart candidates for 55
sources. In addition, 17 sources are likely X-ray transients. We analyze
follow-up HST WFPC2 data of two X-ray transients, finding F336W (U-band
equivalent) counterparts. In both cases, the counterparts are variable. In one
case, the optical counterpart is transient with F336W = 22.3 +/- 0.1 mag. The
X-ray and optical properties of this object are consistent with a ~10 solar
mass black hole X-ray nova with an orbital period of ~20 days. In the other
case, the optical counterpart varies between F336W = 20.82 +/- 0.06 mag and
F336W = 21.11 +/- 0.02 mag. Ground-based and HST observations show this object
is bright (V = 18.8 +/- 0.1) and slightly extended. Finally, the frequency of
bright X-ray transients in the M31 bulge suggests that the ratio of neutron
star to black hole primaries in low-mass X-ray binaries (NS/BH) is ~1.


title: The Evolution of Protoplanetary Disk Edges

abstract:
  We investigate gap formation in gaseous protostellar disks by a planet in a
circular orbit in the limit of low disk viscosity. This regime may be
appropriate to an aging disk after the epoch of planet formation. We find that
the distance of planet to the gap outer boundary can be between the location of
the $m=2$ and $m=1$ outer Lindblad resonances. This distance is weakly
dependent upon both the planet's mass and disk viscosity. We find that the
evolution of the disk edge takes place on two timescales. The first timescale
is set by the spiral density waves driven by the planet. The second timescale
depends on the viscosity of the disk. The disk approaches a state where the
outward angular momentum flux caused by the disk viscosity is balanced by the
dissipation of spiral density waves which are driven at the Lindblad
resonances. This occurs inefficiently however because of the extremely low gas
density near the planet. We find that the distance between the planet and the
peak density at the disk outer edge is only weakly dependent on the viscosity
and planet mass, however the ratio of the gas density near the planet to that
in the disk (or the slope of density along the disk edge) is strongly dependent
upon both quantities. We find that the disk density profile along the edge
scales approximately with disk viscosity divided by the square of the planet
mass. We account for this behavior with a simple scenario in which the
dissipation of angular momentum from the spiral density waves is balanced
against diffusion in the steep edge of the disk.


title:
Discovery of a Clustered Quasar Pair at z ~ 5: Biased Peaks in Early
  Structure Formation

abstract:
  We report a discovery of a quasar at z = 4.96 +- 0.03 within a few Mpc of the
quasar SDSS 0338+0021 at z = 5.02 +- 0.02. The newly found quasar has the SDSS
i and z magnitudes of ~ 21.2, and an estimated absolute magnitude M_B ~ -25.2.
The projected separation on the sky is 196 arcsec, and the redshift difference
Delta z = 0.063 +- 0.008. The probability of finding this quasar pair by chance
in the absence of clustering in this particular volume is ~ 10^-4 to 10^-3. We
conclude that the two objects probably mark a large-scale structure, possibly a
protocluster, at z ~ 5. This is the most distant such structure currently
known. Our search in the field of 13 other QSOs at z >~ 4.8 so far has not
resulted in any detections of comparable luminous QSO pairs, and it is thus not
yet clear how representative is this structure at z ~ 5. However, along with
the other evidence for clustering of quasars and young galaxies at somewhat
lower redshifts, the observations are at least qualitatively consistent with a
strong biasing of the first luminous and massive objects, in agreement with
general predictions of theoretical models. More extensive searches for
clustered quasars and luminous galaxies at these redshifts will provide
valuable empirical constraints for our understanding of early galaxy and
structure formation.


title:
Coronae & Outflows from Helical Dynamos, Compatibility with the MRI, and
  Application to Protostellar Disks

abstract:
  Magnetically mediated disk outflows are a leading paradigm to explain winds
and jets in a variety of astrophysical sources, but where do the fields come
from? Since accretion of mean magnetic flux may be disfavored in a thin
turbulent disk, and only fields generated with sufficiently large scale can
escape before being shredded by turbulence, in situ field production is
desirable. Nonlinear helical inverse dynamo theory can provide the desired
fields for coronae and outflows. We discuss the implications for contemporary
protostellar disks, where the MRI (magneto-rotational instability) can drive
turbulence in the inner regions, and primordial protostellar disks, where
gravitational instability drives the turbulence. We emphasize that helical
dynamos are compatible with the magneto-rotational instability, and clarify the
relationship between the two.


title:
The Spectrum of Integrated Millimeter Flux of the Magellanic Clouds and
  30-Doradus from TopHat and DIRBE Data

abstract:
  We present measurements of the integrated flux relative to the local
background of the Large and Small Magellanic Clouds and the region 30-Doradus
(the Tarantula Nebula) in the LMC in four frequency bands centered at 245, 400,
460, and 630 GHz, based on observations made with the TopHat telescope. We
combine these observations with the corresponding measurements for the DIRBE
bands 8, 9, and 10 to cover the frequency range 245 - 3000 GHz (100 - 1220
micrometers) for these objects. We present spectra for all three objects and
fit these spectra to a single-component greybody emission model and report
best-fit dust temperatures, optical depths, and emissivity power-law indices,
and we compare these results with other measurements in these regions and
elsewhere. Using published dust grain opacities, we estimate the mass of the
measured dust component in the three regions.


title:
Red variables in the OGLE-II database. I. Pulsations and
  period-luminosity relations below the tip of the Red Giant Branch of the LMC

abstract:
  We present period-luminosity relations for more than 23,000 red giants in the
Large Magellanic Cloud observed by the OGLE-II microlensing project. The OGLE
period values were combined with the 2MASS single-epoch JHK photometric data.
For the brighter stars we find agreement with previous results (four different
sequences corresponding to different modes of pulsation in AGB stars). We also
discovered two distinct and well-separated sequences below the tip of the Red
Giant Branch. They consist of almost 10,000 short-period (15 d <P< 50 d),
low-amplitude (A_I<0.04 mag) red variable stars, for which we propose that a
significant fraction is likely to be on the Red Giant Branch, showing radial
pulsations in the second and third overtone modes. The excitation mechanism
could be either Mira-like pulsation or solar-like oscillations driven by
convection.


title: Alfven Waves in Disks, Outflows and Jets

abstract:
  Observations of young stellar objects, such as classical T Tauri stars
(CTTSs), show evidence of accretion disks (ADs), outflows and jets. It is shown
that Alfven waves (AWs) are important in all of these phenomena. AWs can be
created by turbulence in the AD and magnetosphere of a CTTS. Jets, stellar
outflows, and the heating of the central regions of ADs may be due to the
damping of AWs. Our recent investigations of the heating of the AD and the
magnetosphere by AWs as well as of the structures produced in outflows from ADs
initiated by turbulent AWs, are discussed. We comment on the possible
importance of AWs in resolving the energy and angular momentum problems of
CTTSs.


title:
Fe XXV and Fe XXVI Diagnostics of the Black Hole and Accretion Disk in
  Active Galaxies: Chandra Time-Resolved Spectroscopy of NGC 7314

abstract:
  We report the detection of Fe XXV and Fe XXVI $K\alpha$ emission lines from a
Chandra HETGS observation of the Seyfert~1 galaxy NGC 7314, made simultaneously
with RXTE. The lines are redshifted (cz ~ 1500 km/s) relative to the systemic
velocity and unresolved. We argue that the lines originate in a near face-on
(<7 degrees) disk having a radial line emissivity flatter than r^-2. Line
emission from ionization states of Fe in the range ~Fe I up to Fe XXVI is
observed. The ionization balance of Fe responds to continuum variations on
timescales less than 12.5 ks, supporting an origin of the lines close to the
X-ray source. We present additional, detailed diagnostics from this rich data
set. These results identify NGC 7314 as a key source to study in the future if
we are to pursue reverberation mapping of space-time near black-hole event
horizons. This is because it is first necessary to understand the ionization
structure of accretion disks and the relation between the X-ray continuum and
Fe K line emission. However, we also describe how our results are suggestive of
a means of measuring black-hole spin without a knowledge of the relation
between the continuum and line emission. Finally, these data emphasize that one
{\it can} study strong gravity with narrow (as opposed to very broad) disk
lines. In fact narrow lines offer higher precision, given sufficient energy
resolution.


title: Extreme blazars

abstract:
  TeV emission can be a common characteristic of low power blazars. This is in
line with the sequence of blazars relating the observed bolometric luminosity
with their overall spectral energy distribution. Detecting new TeV blazars,
possibly at different redshifts, is important for studying the particle
acceleration process operating in the jet, and it is even more important for
studying the far infrared-optical background. Recent studies of low power BL
Lacs suggest that the particle acceleration mechanism may be a two-step
process, analogous to what is invoked to explain the spectra of gamma-ray
bursts. I will briefly discuss these findings, together with a simple scheme
for selecting good TeV candidates and I will briefly comment on the very fast
TeV and X-ray variability observed in BL Lacs.


title: Gravitational Radiation from Axisymmetric Rotational Core Collapse

abstract:
  We have done a series of two-dimensional hydrodynamic simulations of the
rotational collapse of a supernova core in axisymmetry. We have employed a
realistic equation of state (EOS) and taken into account electron captures and
neutrino transport by the so-called leakage scheme. It is an important progress
to apply the realistic EOS coupled with the microphysics to 2-D simulations for
computing gravitational radiation in rotational core collapse.
  We have used the quadrupole formula to calculate the amplitudes and the
waveforms of gravitational wave assuming the Newtonian gravity. From these
computations, we have extended the conventional category of the gravitational
waveforms. Our results have shown that the peak amplitudes of gravitational
wave are mostly within the sensitivity range of the laser interferometers such
as TAMA and first
  LIGO for a source at a distance of 10 kpc. Furthermore we have found that the
amplitudes of the second peaks are within the detection limit of first LIGO for
the source and first pointed out the importance of the detections, since they
will give us the information as to the angular momentum distribution of evolved
massive stars.


title: The Statistical Significance of the Low CMB Mulitipoles

abstract:
  The Wilkinson Microwave Anisotropy Probe (WMAP) has measured lower amplitudes
for the temperature quadrupole and octopole anisotropies than expected in the
best fitting (concordance) Lambda-dominated cold dark matter cosmology. Some
authors have argued that this discrepancy may require new physics. Yet the
statistical significance of this result is not clear. Some authors have applied
frequentist arguments and claim that the discrepancy would occur by chance
about 1 time in 700 if the concordance model is correct. Other authors have
used Bayesian arguments to claim that the data show marginal evidence for new
physics. I investigate these confusing and apparently conflicting claims using
a frequentist analysis and a simplified Bayesian analysis. I conclude that the
WMAP results are consistent with the concordance Lambda CDM model.


title:
The Arecibo 430-MHz Intermediate Galactic Latitude Survey: Discovery of
  Nine Radio Pulsars

abstract:
  We have used the Arecibo Radio Telescope to search for millisecond pulsars in
two intermediate Galactic latitude regions (7 deg < | b | < 20 deg) accessible
to this telescope. For these latitudes the useful millisecond pulsar search
volume achieved by Arecibo's 430-MHz beam is predicted to be maximal. Searching
a total of 130 square degrees, we have discovered nine new pulsars and detected
four previously known objects. We compare the results of this survey with those
of other 430-MHz surveys carried out at Arecibo and of an intermediate latitude
survey made at Parkes that included part of our search area; the latter
independently found two of the nine pulsars we have discovered.
  At least six of our discoveries are isolated pulsars with ages between 5 and
300 Myr; one of these, PSR J1819+1305, exhibits very marked and periodic
nulling. We have also found a recycled pulsar, PSR J2016+1948. With a
rotational period of 65 ms, this is a member of a binary system with a 635-day
orbital period. We discuss some of the the properties of this system in detail,
and indicate its potential to provide a test of the Strong Equivalence
Principle. This pulsar and PSR J0407+16, a similar system now being timed at
Arecibo, are by far the best systems known for such a test.


title:
Supernova Neutrino Spectrum with Matter and Spin Flavor Precession
  Effects

abstract:
  We consider Majorana neutrino conversions inside supernovae by taking into
account both flavor mixing and the neutrino magnetic moment. We study the
adiabaticity of various possible transitions between the neutrino states for
both normal and inverted hierarchy within the various solar neutrino problem
solutions. From the final mass spectrum within diffrent scenarios, we infer the
consequences of the various conversion effects on the neutronization peak, the
nature of final spectra, and the possible Earth matter effect on the final
fluxes. This enable us to check the sensibility of the SN neutrino flux on
magnetic moment interaction, and narrow down possible scenarios which depend
on: the mass spectrum normal or inverted, the solution of the solar neutrino
problem; and the value of MuxB.


title: Can Microlensing Explain the Long-Term Optical Variability of Quasars?

abstract:
  Although controversial, the scenario of microlensing as the dominant
mechanism for the long-term optical variability of quasars does provide a
natural explanation for both the statistical symmetry, achromaticity and lack
of cosmological time dilation in quasar light curves. Here, we investigate to
what extent dark matter populations of compact objects allowed in the currently
favored Omega_M=0.3, Omega_Lambda=0.7 cosmology really can explain the
quantitative statistical features of the observed variability. We find that
microlensing reasonably well reproduces the average structure function of
quasars, but fails to explain both the high fraction of objects with amplitudes
higher than 0.35 magnitudes and the mean amplitudes observed at redshifts below
one. Even though microlensing may still contribute to the long-term optical
variability at some level, another significant mechanism must also be involved.
This severely complicates the task of using light-curve statistics from quasars
which are not multiply imaged to isolate properties of any cosmologically
significant population of compact objects which may in fact be present.


title: The termination shock in a striped pulsar wind

abstract:
  The origin of radio emission from plerions is considered. Recent observations
suggest that radio emitting electrons are presently accelerated rather than
having been injected at early stages of the plerion evolution. The observed
flat spectra without a low frequency cutoff imply an acceleration mechanism
that raises the average particle energy by few orders of magnitude but leaves
most of the particles at the energy less than about few hundred MeV. It is
suggested that annihilation of the alternating magnetic field at the pulsar
wind termination shock provides the necessary mechanism. Toroidal stripes of
opposite magnetic polarity are formed in the wind emanated from an obliquely
rotating pulsar magnetosphere (the striped wind). At the termination shock, the
flow is compressed and the magnetic field annihilates by driven reconnection.
Jump conditions are obtained for the shock in a striped wind. It is shown that
postshock MHD parameters of the flow are the same as if the energy of
alternating field has already been converted into the plasma energy upstream
the shock. Therefore the available estimates of the ratio of the Poynting flux
to the matter energy flux, $\sigma$, should be attributed not to the total
upstream Poynting flux but only to that associated with the average magnetic
field. A simple model for the particle acceleration in the shocked striped wind
is presented.


title: Arp 299: a second merging system with two active nuclei?

abstract:
  Recent BeppoSAX observations of Arp 299, a powerful far-IR merging starburst
system composed of IC 694 and NGC 3690, clearly unveiled for the first time in
this system the presence of a strongly absorbed active galactic nucleus (AGN).
However the system was not spatially resolved by BeppoSAX. Here we present the
analysis of archival Chandra and (for the first time) XMM-Newton observations,
which allow us to disentangle the X-ray emission of the two galaxies. The
detection of a strong 6.4 keV line in NGC 3690 clearly demonstrates the
existence of an AGN in this galaxy, while the presence of a strong 6.7 keV
Fe-Kalpha line in the spectrum of IC 694 suggests that also this nucleus might
harbor an AGN. This would be the second discovery of two AGNs in a merging
system after NGC 6240.


title:
Decaying Superheavy Dark Matter and Subgalactic Structure of the
  Universe

abstract:
  The collisionless cold dark matter (CCDM) model predicts overly dense cores
in dark matter halos and overly abundant subhalos. We show that the idea that
CDM are decaying superheavy particles which produce ultra-high energy cosmic
rays with energies beyond the Greisen-Zatsepin-Kuzmin cutoff may simultaneously
solve the problem of subgalactic structure formation in CCDM model. In
particular, the Kuzmin-Rubakov's decaying superheavy CDM model may give an
explanation to the smallness of the cosmological constant and a new thought to
the CDM experimental search.


title: Is Cosmic Speed-Up Due to New Gravitational Physics?

abstract:
  We show that cosmic acceleration can arise due to very tiny corrections to
the usual gravitational action of General Relativity of the form $R^n$, with
$n<0$. This eliminates the need for dark energy, though it does not address the
cosmological constant problem. Since a modification to the Einstein-Hilbert
action of the form $R^n$, with $n>0$, can lead to early-time inflation, our
proposal provides a unified and purely gravitational origin for the early and
late time accelerating phases of the Universe.


title: Observational evidence for supermassive black hole binaries

abstract:
  Coalescing massive black hole binaries are powerful emitters of gravitational
waves, in the LISA sensitivity range for masses M_BH ~ 10^{4-7} M_sun.
According to hierarchical galaxy merger models, binary black holes should form
frequently, and should be common in the cores of galaxies. The presence of
massive black hole binaries has been invoked to explain a number of class
properties of different types of galaxies, and in triggering various forms of
activity. The search for such binary black holes is therefore of great interest
for key topics in astrophysics ranging from galaxy formation to activity in
galaxies.
  A number of phenomena were attributed to the presence of supermassive binary
black holes, including X-shaped radio galaxies and double-double radio
galaxies, helical radio-jets, periodicities in the lightcurves of blazars,
(double-horned emission-line profiles), binary galaxies with radio-jet cores,
binary quasars, and the X-ray active binary black hole at the center of the
galaxy NGC 6240. Here, I review the observational evidence for the presence of
supermassive binary black holes in galaxies, and the scenarios which have been
discussed to explain these observations.


title:
Supersoft X-ray Sources in M31: I. A Chandra Survey and an Extension to
  Quasisoft Sources

abstract:
  We report on very soft X-ray sources (VSSs) in M31. In a survey which was
most sensitive to soft sources in four 8'x8' regions covered by Chandra's
ACIS-S S3 CCD, we find 33 VSSs that appear to belong to M31. Fifteen VSSs have
spectral characteristics mirroring the supersoft X-ray sources studied in the
Magellanic Cloud and Milky Way ($k T_{eff} \leq 100$ eV); we therefore call
these ``classical'' supersoft sources, or simply supersoft sources (SSSs).
Eighteen VSSs may either have small (< 10%) hard components, or slightly higher
effective temperatures (but still < 350 eV). We refer to these VSSs as
quasisoft sources (QSSs). While hot white dwarf models may apply to SSSs, the
effective temperatures of QSSs are too high, unless, e.g., the radiation
emanates from only a small portion of surface. Two of the SSSs were first
detected and identified as such through ROSAT observations. One SSS and one QSS
may be identified with symbiotics, and 2 SSSs with supernova remnants. Both
SSSs and QSSs in the disk are found near star-forming regions, possibly
indicating that they are young. VSSs in the outer disk and halo are likely to
be old systems; in these regions, there are more QSSs than SSSs, which is
opposite to what is found in fields closer to the galaxy center. The largest
density of bright VSSs is in the bulge; some of the bulge sources are close
enough to the nucleus to be remnants of the tidal disruption of a giant by the
massive central black hole. By using Chandra data in combination with ROSAT and
XMM observations, we find most VSSs to be highly variable, fading from or
brightening toward detectability on time scales of months. There is evidence
for VSSs with low luminosities ($\sim 10^{36}$ erg s$^{-1}$).


title:
X-ray Point Sources in the Sombrero Galaxy: Supersoft sources, the
  globular cluster/LMXB connection, and an overview

abstract:
  We report on the population of point sources discovered during an 18.5 ksec
Chandra ACIS-S observation of the Sombrero Galaxy. We present the luminosity
function, the spectra of the 6 brightest sources, consider correlations with
globular clusters (GCs) and with planetary nebulae (PNe), and study the
galaxy's population of SSSs. We detected 122 sources, 22 of them are identified
as luminous supersoft X-ray sources (SSSs). There is an over density of SSSs
within 1.5 kpc of the nucleus, which is itself the brightest X-ray source. SSSs
are also found in the disk and halo, with 1 SSS in a globular cluster (GC).
Several sources in Sombrero's halo are good candidates for SSS models in which
the accretor is a nuclear-burning white dwarf. In total, 32 X-ray sources are
associated with GCs. The majority of sources with luminosity > 1e38 erg/s are
in GCs. These results for M104, an Sa galaxy, are similar to what has been
found for elliptical galaxies and for the late-type spiral M31. We find that
those optically bright GCs with X-ray sources house only the brightest X-ray
sources. We find that, in common with other galaxies, there appears to be a
positive connection between young (metal-rich) GCs and X-ray sources, but that
the brightest X-ray sources are equally likely to be in metal-poor GCs. We
propose a model which can explain the trends seen in the data sets from the
Sombrero and other galaxies. Thermal-time scale mass transfer can occur in some
of the the younger clusters in which the turn-off mass is slightly greater than
$0.8 M_\odot$; multiplicity may play a role in some of the most massive
clusters; accretion from giant stars may be the dominant mechanism in some
older, less massive and less centrally concentrated clusters.


title: The Case for a Low Extragalactic Gamma-ray Background

abstract:
  Measurements of the diffuse extragalactic gamma-ray background (EGRB) are
complicated by a strong Galactic foreground. Estimates of the EGRB flux and
spectrum, obtained by modeling the Galactic emission, have produced a variety
of (sometimes conflicting) results. The latest analysis of the EGRET data found
an isotropic flux I_x=1.45+-0.05 above 100 MeV, in units of 10^-5 s^-1 cm^-2
sr^-1. We analyze the EGRET data in search for robust constraints on the EGRB
flux, finding the gamma-ray sky strongly dominated by Galactic foreground even
at high latitudes, with no conclusive evidence for an additional isotropic
component. The gamma-ray intensity measured towards the Galactic poles is
similar to or lower than previous estimates of I_x. The high latitude profile
of the gamma-ray data is disk-like for 40<|b[deg]|<70, and even steeper for
|b|>70; overall it exhibits strong Galactic features and is well fit by a
simple Galactic model. Based on the |b|>40 data we find that I_x<0.5 at a 99%
confidence level, with evidence for a much lower flux. We show that
correlations with Galactic tracers, previously used to identify the Galactic
foreground and estimate I_x, are not satisfactory; the results depend on the
tracers used and on the part of the sky examined, because the Galactic emission
is not linear in the Galactic tracers and exhibits spectral variations across
the sky. The low EGRB flux favored by our analysis places stringent limits on
extragalactic scenarios involving gamma-ray emission, such as radiation from
blazars, intergalactic shocks and production of ultra-high energy cosmic rays
and neutrinos. We suggest methods by which future gamma-ray missions such as
GLAST and AGILE could indirectly identify the EGRB.


title: Magnetic fields in cosmology

abstract:
  Different mechanisms which may possibly explain existence of magnetic fields
on astronomically large scales are described. A recently suggested model of
magnetic fields generation slightly before hydrogen recombination is discussed
in more detail.


title:
The Optical Gravitational Lensing Experiment. Additional Planetary and
  Low-Luminosity Object Transits from the OGLE 2001 and 2002 Observational
  Campaigns

abstract:
  The photometric data collected by OGLE-III during the 2001 and 2002
observational campaigns aiming at detection of planetary or low-luminosity
object transits were corrected for small scale systematic effects using the
data pipeline by Kruszewski and Semeniuk and searched again for low amplitude
transits. Sixteen new objects with small transiting companions, additional to
previously found samples, were discovered. Most of them are small amplitude
cases which remained undetected in the original data.
  Several new objects seem to be very promising candidates for systems
containing substellar objects: extrasolar planets or brown dwarfs. Those
include OGLE-TR-122, OGLE-TR-125, OGLE-TR-130, OGLE-TR-131 and a few others.
Those objects are particularly worth spectroscopic follow-up observations for
radial velocity measurements and mass determination. With well known
photometric orbit only a few RV measurements should allow to confirm their
actual status.
  All photometric data of presented objects are available to the astronomical
community from the OGLE Internet archive.


title: Flux-limited strong gravitational lensing and dark energy

abstract:
  In the standard flat cosmological constant ($\Lambda$) cold dark matter (CDM)
cosmology, a model of two populations of lens halos for strong gravitational
lensing can reproduce the results of the Jodrell-Bank VLA Astrometric Survey
(JVAS) and the Cosmic Lens All-Sky Survey (CLASS) radio survey. In such a
model, lensing probabilities are sensitive to three parameters: the
concentration parameter $c_1$, the cooling mass scale $M_\mathrm{c}$ and the
value of the CDM power spectrum normalization parameter $\sigma_8$. The value
ranges of these parameters are constrained by various observations. However, we
found that predicted lensing probabilities are also quite sensitive to the flux
density (brightness) ratio $q_{\mathrm{r}}$ of the multiple lensing images,
which has been, in fact, a very important selection criterion of a sample in
any lensing survey experiments. We re-examine the above mentioned model by
considering the flux ratio and galactic central Super Massive Black Holes
(SMBHs), in flat, low-density cosmological models with different cosmic
equations of state $\omega$, and find that the predicted lensing probabilities
without considering $q_{\mathrm{r}}$ are over-estimated. A low value of
$q_\mathrm{r}$ can be compensated by raising the cooling mass scale
$M_\mathrm{c}$ in fitting the predicted lensing probabilities to JVAS/CLASS
observations. In order to determine the cosmic equation of state $\omega$, the
uncertainty in $M_\mathrm{c}$ must be resolved. The effects of SMBHs cannot be
detected by strong gravitational lensing method when $q_{\mathrm{r}}\leq 10$.


title: On the formation of star clusters in the merger NGC 6240

abstract:
  We identified star clusters in archived HST/WFPC2 images of the merger and
ultra-luminous infrared galaxy NGC 6240, with the aim of investigating whether
star cluster properties (luminosity, age and mass) in such an extreme
environment differ from those of clusters in less luminous starburst galaxies.
We found 54 star clusters in all of the F450W, F547M and F814W exposures, of
which 41 are located in the main body of NGC 6240 and 13 in the galactic tails.
Given that only two colours are available to derive two independent variables
(cluster reddening and age), we adopted an ad hoc procedure to statistically
derive cluster parameters under the assumption that the cluster metallicity is
LMC-like. The colours of each cluster are fitted to STARBURST99 models of fixed
mass and variable ages and reddenings. All cluster reddening and age solutions
with Chi squared < 1 are considered to be consistent with the data. Masses are
derived by scaling the luminosity of the models with best-fit Chi squared < 1
by the observed V luminosity, after correction for reddening and distance. We
infer that the most probable age of the observed clusters is (5 - 13) Myr and
their most probable mass is about (1 - 2)e05 solar masses. Comparison with star
clusters in starburst galaxies seems to point to more massive clusters being
formed in more massive galaxies and gas-rich mergers, while the overall cluster
mass distribution might be relatively independent of the details of the
associated starburst where dense, massive clusters preferentially form.


title:
Determination of the gas-to-dust ratio in nearby dense clouds using
  X-ray absorption measurements

abstract:
  We present a comparison of the gas and dust properties of the dense
interstellar matter in six nearby star-forming regions (d<500 pc): rho Oph, Cha
I, R CrA, IC 348, NGC 1333, and Orion. We measure from Chandra and XMM-Newton
observations the X-ray absorption toward pre-main sequence stars (PMS) without
accretion disks (i.e., Class III sources) to obtain the total hydrogen column
density N_{H,X}. For these sources we take from the literature the
corresponding dust extinction in the near-infrared, A_J, or when unavailable we
derive it from SED fitting using the available DENIS, 2MASS, ISOCAM and other
data. We then compare N_{H,X} and A_J for each object, up to unprecedently high
extinction. For the rho Oph dark cloud with a relatively large sample of 20
bona-fide Class III sources, we probe the extinction up to A_J <~ 14 (A_V <~
45), and find a best-fit linear relation N_{H,X}/A_J = 5.6 (+/- 0.4)x10^{21}
cm^{-2} mag^{-1}, adopting standard ISM abundances. The other regions reveal a
large dispersion in the N_{H,X}/A_J ratio for each source but for lack of
adequate IR data these studies remain limited to moderate extinctions (A_J <~
1.5 or A_V <~5). For rho Oph, the N_{H,X}/A_J ratio is significantly lower (>~2
sigma) than the galactic value, derived using the standard extinction curve
(R_V = 3.1). This result is consistent with the recent downwards revision of
the metallicity of the Sun and stars in the solar vicinity. We find that the
rho Oph dense cloud has the same metallicity than the local ISM when assuming
that the galactic gas-to-dust ratio remains unchanged. The difference between
galactic and local values of the gas-to-dust ratio can thus be attributed
entirely to a difference in metallicity.


title: A Concordant "Freely Coasting Cosmology"

abstract:
  A strictly linear evolution of the cosmological scale factor is surprisingly
an excellent fit to a host of cosmological observations. Any model that can
support such a coasting presents itself as a falsifiable model as far as
classical cosmological tests are concerned. Such evolution is known to be
comfortably concordant with the Hubble diagram as deduced from data of recent
supernovae 1a and high redshift objects, it passes constraints arising from the
age and gravitational lensing statistics and clears basic constraints on
nucleosynthesis. Such an evolution exhibits distinguishable and verifiable
features for the recombination era. This article discusses the concordance of
such an evolution in relation to minimal requirements for large scale structure
formation and cosmic microwave background anisotropy along with the overall
viability of such models.
  While these results should be of interest for a host of alternative gravity
models that support a linear coasting, we conjecture that a linear evolution
would emerge naturally either from General Relativity itself or from a General
Relativistic theory of a non-minimally coupled scalar field theory.


title:
FUSE observations of H2 around the Herbig AeBe stars HD 100546 and HD
  163296

abstract:
  We present the analysis of FUSE observations of two Herbig AeBe stars known
to harbor young circumstellar disks: HD 100546 and HD 163296. In both cases we
detect absorption lines from warm and dense H2. The thermalization of the
rotational levels up to J~4 allows evaluation of the temperature, density and
typical size of the absorbing layer. These quantities are consistent with
absorption of the light of the central star by a thin layer of a circumstellar
disk seen at an intermediate inclination.


title: Are Two z~6 Quasars Gravitationally Lensed ?

abstract:
  Several high-z (z > 5.7) quasars have been found in the course of Sloan
Digital Sky Survey. The presence of such very high-z quasars is expected to
give constraints on early structure formation. On one hand, it is suggested
that these most luminous objects at high redshift are biased toward the highly
magnified objects by gravitational lensing. To clarify the effect of
gravitational lensing on the high-z quasars, we began the imaging survey of
intervening lensing galaxies. Indeed our previous optical image showed that
SDSSp J104433.04+012502.2 at z=5.74 is gravitationally magnified by a factor 2.
In this paper, we report our new optical imaging of other two high-z quasars,
SDSSp J103027.10+052455.0 at z=6.28 and SDSSp J130608.26+035626.3 at z=5.99.
Since we find neither intervening galaxy nor counter image with i^{\prime} <
25.4-25.8 around each quasar, we conclude that they are not strongly magnified
regardless that a lens galaxy is dusty.


title: Theoretical X-ray Line Profiles from Colliding Wind Binaries

abstract:
  We present theoretical X-ray line profiles from a range of model colliding
wind systems. In particular, we investigate the effects of varying the stellar
mass-loss rates, the wind speeds, and the viewing orientation. We find that a
wide range of theoretical line profile shapes is possible, varying with orbital
inclination and phase. At or near conjunction, the lines have approximately
Gaussian profiles, with small widths (HWHM ~ 0.1 v_\infty) and definite blue-
or redshifts (depending on whether the star with the weaker wind is in front or
behind). When the system is viewed at quadrature, the lines are generally much
broader (HWHM ~ v_\infty), flat-topped and unshifted. Local absorption can have
a major effect on the observed profiles - in systems with mass-loss rates of a
few times 10^{-6} Msol/yr the lower energy lines (E <~ 1 kev) are particularly
affected. This generally results in blueward-skewed profiles, especially when
the system is viewed through the dense wind of the primary. The orbital
variation of the line widths and shifts is reduced in a low inclination binary.
The extreme case is a binary with i = 0 degrees, for which we would expect no
line profile variation.


title: Viscosity in spherically symmetric accretion

abstract:
  The influence of viscosity on the flow behaviour in spherically symmetric
accretion, has been studied here. The governing equation chosen has been the
Navier-Stokes equation. It has been found that at least for the transonic
solution, viscosity acts as a mechanism that detracts from the effectiveness of
gravity. This has been conjectured to set up a limiting scale of length for
gravity to bring about accretion, and the physical interpretation of such a
length-scale has been compared with the conventional understanding of the
so-called "accretion radius" for spherically symmetric accretion. For a
perturbative presence of viscosity, it has also been pointed out that the
critical points for inflows and outflows are not identical, which is a
consequence of the fact that under the Navier-Stokes prescription, there is a
breakdown of the invariance of the stationary inflow and outflow solutions --
an invariance that holds good under inviscid conditions. For inflows, the
critical point gets shifted deeper within the gravitational potential well.
Finally, a linear stability analysis of the stationary inflow solutions, under
the influence of a perturbation that is in the nature of a standing wave, has
indicated that the presence of viscosity induces greater stability in the
system, than has been seen for the case of inviscid spherically symmetric
inflows.


title: High resolution simulations of nonhelical MHD turbulence

abstract:
  According to the kinematic theory of nonhelical dynamo action the magnetic
energy spectrum increases with wavenumber and peaks at the resistive cutoff
wavenumber. It has previously been argued that even in the dynamical case the
magnetic energy peaks at the resistive scale. Using high resolution simulations
(up to 1024^3 meshpoints) with no large scale imposed field we show that the
magnetic energy peaks at a wavenumber that is independent of the magnetic
Reynolds number and about 5 times larger than the forcing wavenumber.
Throughout the inertial range the spectral magnetic energy exceeds the kinetic
energy by a factor of 2 to 3. Both spectra are approximately parallel. The
total energy spectrum seems to be close to k^{-3/2}, but there is a strong
bottleneck effect and it is suggested that the asymptotic spectrum is instead
k^{-5/3}. This is supported by the value of the second order structure function
exponent that is found to be zeta_2=0.70, suggesting a k^{-1.70} spectrum. The
third order structure function scaling exponent is very close to unity, in
agreement with Goldreich-Sridhar theory.
  Adding an imposed field tends to suppress the small scale magnetic field. We
find that at large scales the magnetic power spectrum follows then a k^{-1}
slope. When the strength of the imposed field is of the same order as the
dynamo generated field, we find almost equipartition between the magnetic and
kinetic power spectra.


title:
Precise measurement of cross section of 3He(3He,2p)4He by using He-3
  doubly charged beam

abstract:
  The fusion cross section of 3He(3He,2p)4He at a center of mass energy of 30
to 50 keV has been measured by using helium-3 doubly ionized beam at a
low-energy high current accelerator facility, OCEAN. Free from molecular
interference in the beam, the measurement determines the astrophysical S-factor
with better statistical and systematical errors than previous data. By using
singly and doubly charged helium-3 ions the facility envisages to provide the
data from high energy to Gamow energy regions.


title:
Simultaneous single-pulse observations of radio pulsars - IV. Flux
  density spectra of individual pulses

abstract:
  In this paper we demonstrate that a large, unexplored reservoir of
information about pulsar emission exists, that is directly linked to the
radiating particles and their radiation process: We present a study of flux
density measurements of individual pulses simultaneously observed at four
different frequencies. Correcting for effects caused by the interstellar
medium, we derive intrinsic flux density spectra of individual radio pulses
observed at several frequencies for the first time. Pulsar B0329+54 was
observed at 238, 626, 1412 and 4850 MHz, while observations of PSR B1133+16
were made at 341, 626, 1412 and 4850 MHz. We derive intrinsic pulse-to-pulse
modulation indices which show a minimum around 1 GHz. Correlations between the
flux densities of different frequency pairs worsen as the frequency separation
widens and also tend to be worse for outer profile components. The single pulse
spectra of PSR B0329+54 resemble the spectra of the integrated profile.
However, the spectral index distributions for the single pulses of PSR B1133+16
show significant deviations from a Gaussian. This asymmetry is caused by very
strong pulses with flux densities exceeding the mean value by more than a
factor of ten. These strong pulses occur preferentially at the trailing edge of
the leading component and appear to be broadband in most cases. Their
properties are similar to those of so-called giant pulses, suggesting that
these phenomena are related.


title: Pulsars with the SKA

abstract:
  As for other areas in modern astronomy, the SKA will revolutionize the field
of pulsar astrophysics. Not only will new science be possible by the shear
number of pulsars discovered, but also by the unique timing precision
achievable with the SKA. The combination of both will not simply mean a
continuation of the successes already achieved by using pulsars as fundamental
tools of physics but the SKA will provide a new quality of science.


title:
Deep Hubble Space Telescope Imaging of IC 1613 II. The Star Formation
  History

abstract:
  We present deep HST WFPC2 imaging of the Local Group dwarf irregular galaxy
IC 1613. The photometry is the deepest to date for an isolated dwarf irregular
galaxy. The resulting color-magnitude diagram (CMD) is analyzed using three
different methods to derive a star formation history (SFH). All three find an
enhanced star formation rate (SFR), from 3 to 6 Gyr ago, and similar
age-metallicity relationships (AMR). A comparison of the newly observed outer
field with an earlier studied central field of IC 1613 shows that the SFR in
the outer field has been significantly depressed during the last Gyr. This
implies that the optical scale length of the galaxy has been decreasing with
time and that comparison of galaxies at intermediate redshift with present day
galaxies should take this effect into account. We find strong similarities
between IC 1613 and the more distant Milky Way dSph companions in that all are
dominated by star formation at intermediate ages. In particular, the SFH and
AMR for IC 1613 and Leo I are indistinguishable. This implies that dIrr
galaxies cannot be distinguished from dSphs by their intermediate age stellar
populations. This type of a SFH may also be evidence for slower or suppressed
early star formation in dwarf galaxies due to photoionization after the
reionization of the universe by background radiation. Assuming that IC 1613 is
typical of a dIrr evolving in isolation, since most of the star formation
occurs at intermediate ages, these dwarf systems cannot be responsible for the
fast chemical enrichment of the IGM which is seen at high redshift. There is no
evidence for any large amplitude bursts of star formation in IC 1613, and we
find it highly unlikely that analogs of IC 1613 have contributed to the excess
of faint blue galaxies in existing galaxy redshift surveys.


title: RV survey for planets of brown dwarfs and very low-mass stars in ChaI

abstract:
  We have carried out a radial velocity (RV) search for planets and brown dwarf
companions to very young (1-10Myr) brown dwarfs and very low-mass stars in the
ChaI star forming region. This survey has been carried out with the
high-resolution Echelle spectrograph UVES at the VLT. It is sensitive down to
Jupiter mass planets.
  Out of the twelve monitored very low-mass stars and brown dwarfs, ten have
constant RVs in the presented RV survey. This hints at a small multiplicity
fraction of the studied population of brown dwarfs and very low-mass stars in
ChaI at small separations. Upper limits for the mass Msini of possible
companions have been estimated to range between 0.1 and 1.5 Jupiter masses.
However, two very low-mass stars in ChaI show significant RV variations. The
nature of these variations is still unclear. If caused by orbiting objects the
recorded variability amplitudes would correspond to planets of the order of a
few Jupiter masses.
  Furthermore, as a by-product of the RV survey for companions, we have studied
the kinematics of the brown dwarfs in ChaI. Precise kinematic studies of young
brown dwarfs are interesting in the context of the question if brown dwarfs are
formed by the recently proposed ejection scenario. We have found that the RV
dispersion of brown dwarfs in ChaI is only 2.2 km\s giving a first empirical
upper limit for possible ejection velocities.


title: Extinction by grey dust in the intergalactic medium

abstract:
  Condensation in the outer regions of decaying supernovae is an efficient
source of dust with grain size up to 1 micron. The largest grains leave the
parent galaxy, thus forming "grey" intergalactic dust, which can explain the
observed dimming of light from distant supernovae without invoking cosmic
acceleration


title: Toward a Self Consistent Model of the Ionized Absorber in NGC 3783

abstract:
  We present a detailed model for the ionized absorbing gas evident in the 900
ksec Chandra HETGS spectrum of NGC 3783. The analysis was carried out with
PHASE a new tool designed to model X-ray and UV absorption features in ionized
plasmas. The 0.5-10 keV intrinsic continuum of the source is well represented
by a single power law (Gamma=1.53) and a soft black-body component (kT=10 keV).
The spectrum contains over 100 features, which are well fit by PHASE with just
six free parameters. The model consists of a simple two phase absorber with
difference of 35 in the ionization parameter and difference of 4 in the column
density of the phases. The two absorption components turned out to be in
pressure equilibrium, and are consistent with a single outflow (750 kms-1) an a
single turbulent velocity (300 km s-1), and with solar elemental abundances.
The main features of the low ionization phase are an Fe M-shell unresolved
transition array (UTA) and the OVII lines. The OVII features, usualy identified
with the OVIII and a warm absorber, are instead produced in a cooler medium
also producing OVI lines. The UTA sets tight constraints on the ionization
degree of the absorbers, making the model more reliable. The high ionization
phase is required by the OVII and the Fe L-shell lines, and there is evidence
for an even more ionized component in the spectrum. A continuous range of
ionization parameters is disfavored by the fits, particularly to the UTA. The
low ionizaton phase can be decomposed into three subcomponents based on the
outflow velocity, FWHM, and H column densities found for three out of the four
UV absorbers detected in NGC 3783. However, the ionization parametes are
systematically smaller in our model than derived from UV data, indicating a
lower degree of ionization.


title: The stellar content of OMC 2/3

abstract:
  We have revisited the stellar content of OMC 2 and OMC 3 by means of MIR
imaging and NIR photometry; in addition, we have extended the existing (sub)mm
maps by a huge 1200 micron map obtained with SIMBA showing new sources and
filamentary features for the first time at that wavelength. The MIR data reveal
43 new sources at N and Q which are partly associated with dense condensations
at millimetre wavelengths. Six close binary sources could be resolved at
locations where existing (sub)mm maps only show single emission peaks; three of
them are classified as early (B-type) systems, one of them is compatible with
type K while the remaining two seem to be T Tauri stars. Furthermore, the MIR
images indicate the existence of separate circumstellar discs in the K-binary
system. NIR colour-colour and colour-magnitude diagrams obtained from 2MASS
data are examined to explore the physical properties of the sources and to
derive the distribution of J luminosities. There is a clear decrease in
luminosity and thus in stellar mass when going from South to North. Likewise,
there is an anti-correlation between Class I and II objects in both regions:
while OMC 2 contains twice as much Class II objects compared to Class I, the
situation is reversed in OMC 3.


title:
Pulsar PSR B0656+14, the Monogem Ring, and the Origin of the `Knee' in
  the Primary Cosmic Ray Spectrum

abstract:
  The Monogem ring is a bright, diffuse, 25-degree-diameter supernova remnant
easily visible in soft X-ray images of the sky. Projected within the ring is a
young radio pulsar, PSR B0656+14. An association between the remnant and pulsar
has been considered, but was seemingly ruled out by the direction and magnitude
of the pulsar proper motion and by a distance estimate that placed the pulsar
twice as far from Earth as the remnant. Here we show that in fact the pulsar
was born very close to the center of the expanding remnant, both in distance
and projection. The inferred pulsar and remnant ages are in good agreement. The
conclusion that the pulsar and remnant were born in the same supernova
explosion is nearly inescapable. The remnant distance and age are in remarkable
concordance with the predictions of a model for the primary cosmic ray energy
spectrum in which the `knee' feature is produced by a single dominant source.


title: Chemical Evolution of Dwarf Spheroidal and Blue Compact Galaxies

abstract:
  We studied the chemical evolution of Dwarf Spheroidal (dSph) and Blue Compact
Galaxies (BCGs) by means of comparison between the predictions of chemical
evolution models and several observed abundance ratios. Detailed models with up
to date nucleosynthesis taking into account the role played by supernovae of
different types (II, Ia) were developed for both types of galaxies allowing us
to follow the evolution of several chemical elements. The models are specified
by the prescriptions of the star formation (SF) and galactic wind efficiencies
chosen to reproduce the main features of these galaxies. We also investigated a
possible connection in the evolution of dSph and BCGs and compared the
predictions of the models to the abundance ratios observed in Damped Lyman
alpha Systems (DLAs). The main conclusions are: i) the observed distribution of
[alpha/Fe] vs. [Fe/H] in dSph is mainly a result of the SF rate coupled with
the wind efficiency; ii) a low SF efficiency and a high wind efficiency are
required to reproduce the observational data for dSph; iii) the low gas content
of these galaxies is the result of the combined action of gas consumption by SF
and gas removal by galactic winds; iv) the BCGs abundance ratios are reproduced
by models with 2 to 7 bursts of SF with low efficiencies ; v) the low values of
N/O observed in BCGs are the natural result of a bursting SF; vi) a connection
between dSph and BCGs in an unified evolutionary scenario is unlikely; vii) the
models for the dSph and BCGs imply different formation scenarios for the DLAs;
viii) a suitable amount of primary N produced in massive stars can be perhaps
an explanation for the low plateau in the [N/$\alpha$] distribution observed in
DLAs, if real.


title:
Kinematics of Ten Early-Type Galaxies from HST and Ground-Based
  Spectroscopy

abstract:
  We present stellar kinematics for a sample of 10 early-type galaxies observed
using the STIS aboard the Hubble Space Telescope, and the Modular Spectrograph
on the MDM Observatory 2.4-m telescope. The spectra are used to derive
line-of-sight velocity distributions (LOSVDs) of the stars using a Maximum
Penalized Likelihood method. We use Gauss-Hermite polynomials to parameterize
the LOSVDs and find predominantly negative h4 values (boxy distributions) in
the central regions of our galaxies. One galaxy, NGC 4697, has significantly
positive central h4 (high tail weight). The majority of galaxies have a central
velocity dispersion excess in the STIS kinematics over ground-based velocity
dispersions. The galaxies with the strongest rotational support, as quantified
with v_MAX/sigma_STIS, have the smallest dispersion excess at STIS resolution.
The best-fitting, general, axisymmetric dynamical models (described in a
companion paper) require black holes in all cases, with masses ranging from
10^6.5 to 10^9.3 Msun. We replot these updated masses on the BH/sigma relation,
and show that the fit to only these 10 galaxies has a slope consistent with the
fits to larger samples. The greatest outlier is NGC 2778, a dwarf elliptical
with relatively poorly constrained black hole mass. The two best candidates for
pseudobulges, NGC 3384 and 7457, do not deviate significantly from the
established relation between black hole and sigma. Neither do the three
galaxies which show the most evidence of a recent merger, NGC 3608, 4473, and
4697.


title: Gravitational lensing as a probe of structure

abstract:
  Gravitational lensing has become one of the most interesting tools to study
the mass distribution in the Universe. Since gravitational light deflection is
independent of the nature and state of the matter, it is ideally suited to
investigate the distribution of all (and thus also of dark) matter in the
Universe. Lensing results have now become available over a wide range of
scales, from the search for MACHOs in the Galactic halo, to the mass
distribution in galaxies and clusters of galaxies, and the statistical
properties of the large-scale matter distribution in the Universe. Here, after
introducing the concepts of strong and weak lensing, several applications are
outlined, from strong lensing by galaxies, to strong and weak lensing by
clusters and the lensing properties of the large-scale structure.


title:
Effects of Strong Magnetic Fields in Neutron Star and Gravitational Wave
  Emission

abstract:
  I review in this work the properties of nuclear and quark matter equation of
state under the influence of a strong magnetic field. We analyse the results
when they are applied to compact stars description. Finally, we describe the
emission of gravitational wave from a compact star that goes over a phase
transition.


title:
Interpretation of the Helix Planetary Nebula using Hydro-Gravitational
  Theory

abstract:
  Wide angle Hubble Space Telescope (HST/ACS) images of the Helix Planetary
Nebula (NGC 7293) are interpreted using the hydro-gravitational theory (HGT) of
Gibson 1996-2000 that predicts the baryonic dark matter and interstellar medium
(ISM) consists of Mars-mass primordial-fog-particle (PFP) frozen H-He planets.
The new ACS images confirm and extend the O'Dell and Handron 1996 WFPC2 images
showing thousands of cometary globules, which we suggest are cocoons of PFP and
Jupiter frozen-gas-planets evaporated by powerful beamed radiation from the hot
central white dwarf and its companion. The atmosphere mass of the largest
cometary globules is ~ 3x10^{25} kg with spacing ~ 10^{14} m, supporting the
prediction of HGT that the mass density of the ISM in Galaxy star forming
regions should match the large baryonic primordial value at the time of first
structure formation (10^{12} s or 30,000 years), with \rho ~ (3-1)x 10^{-17} kg
m^{-3}.


title: The Structure of High Strehl Ratio Point-Spread Functions

abstract:
  We describe the symmetries present in the point-spread function (PSF) of an
optical system either located in space or corrected by an adaptive o to Strehl
ratios of about 70% and higher. We present a formalism for expanding the PSF to
arbitrary order in terms of powers of the Fourier transform of the residual
phase error, over an arbitrarily shaped and apodized entrance aperture. For
traditional unapodized apertures at high Strehl ratios, bright speckles pinned
to the bright Airy rings are part of an antisymmetric perturbation of the
perfect PSF, arising from the term that is first order in the residual phase
error. There are two symmetric second degree terms. One is negative at the
center, and, like the first order term, is modulated by the perfect image's
field strength -- it reduces to the Marechal approximation at the center of the
PSF. The other is non-negative everywhere, zero at the image center, and can be
responsible for an extended halo -- which limits the dynamic range of faint
companion detection in the darkest portions of the image. In regimes where one
or the other term dominates the speckles in an image, the symmetry of the
dominant term can be exploited to reduce the effect of those speckles,
potentially by an order of magnitude or more. We demonstrate the effects of
both secondary obscuration and pupil apodization on the structure of residual
speckles, and discuss how these symmetries can be exploited by appropriate
telescope and instrument design, observing strategies, and filter bandwidths to
improve the dynamic range of high dynamic range AO and space-based
observations. Finally, we show that our analysis is relevant to high dynamic
range coronagraphy.


title:
Metallicity of the intergalactic medium using pixel statistics. II. The
  distribution of metals as traced by C IV

abstract:
  (Modified) We measure the distribution of carbon in the intergalactic medium
as a function of redshift z and overdensity delta. Using a hydrodynamical
simulation to link the H I absorption to the density and temperature of the
absorbing gas, and a model for the UV background radiation, we convert ratios
of C IV to H I pixel optical depths into carbon abundances. A careful analysis
of 19 high-quality quasar absorption spectra reveals that the carbon abundance
is spatially highly inhomogeneous and is well-described by a lognormal
distribution for fixed delta and z. Using data in the range log(delta) = -0.5 -
1.8 and z = 1.8 - 4.1, and a renormalized version of the Haardt & Madau (2001)
model for the UV background radiation from galaxies and quasars, we measure a
median metallicity of [C/H] = -3.47 + 0.08(z-3) + 0.65[log(delta)-0.5] and a
lognormal scatter of sigma([C/H]) = 0.76 + 0.02(z-3) - 0.23[log(delta)-0.5].
Thus, we find significant trends with overdensity, but no evidence for
evolution. These measurements imply that gas in this density range accounts for
a cosmic carbon abundance of [C/H] = -2.80 +/- 0.13 (Omega_C = 2e-7), with no
evidence for evolution. The dominant source of systematic error is the spectral
shape of the UV background, with harder spectra yielding higher carbon
abundances. While the systematic errors due to uncertainties in the spectral
hardness may exceed the quoted statistical errors for delta < 10, we stress
that UV backgrounds that differ significantly from our fiducial model give
unphysical results. The measured lognormal scatter is strictly independent of
the spectral shape, provided the background radiation is uniform. We also
present measurements of the C III/C IV ratio (which rule out collisional
ionization) and of the evolution of the effective Lyman-alpha optical depth.


title: Near Infrared Spectra of Type Ia Supernovae

abstract:
  We report near infrared (NIR) spectroscopic observations of twelve
``Branch-normal'' Type Ia supernovae (SNe Ia) which cover the wavelength region
from 0.8-2.5 microns. Our sample more than doubles the number of SNe Ia with
published NIR spectra within three weeks of maximum light. The epochs of
observation range from thirteen days before maximum light to eighteen days
after maximum light. A detailed model for a Type Ia supernovae is used to
identify spectral features. The Doppler shifts of lines are measured to obtain
the velocity and, thus, the radial distribution of elements.
  The NIR is an extremely useful tool to probe the chemical structure in the
layers of SNe Ia ejecta. This wavelength region is optimal for examining
certain products of the SNe Ia explosion that may be blended or obscured in
other spectral regions. We identify spectral features from MgII, CaII, SiII,
FeII, CoII, NiII and possibly MnII. We find no indications for hydrogen, helium
or carbon in the spectra. The spectral features reveal important clues about
the physical characteristics of SNe Ia. We use the features to derive upper
limits for the amount of unburned matter, to identify the transition regions
from explosive carbon to oxygen burning and from partial to complete silicon
burning, and to estimate the level of mixing during and after the explosion.


title:
The X-ray and extreme-ultraviolet flux evolution of SS Cygni throughout
  outburst

abstract:
  We present the most complete multiwavelength coverage of any dwarf nova
outburst: simultaneous optical, Extreme Ultraviolet Explorer, and Rossi X-ray
Timing Explorer observations of SS Cygni throughout a narrow asymmetric
outburst. Our data show that the high-energy outburst begins in the X-ray
waveband 0.9--1.4d after the beginning of the optical rise and 0.6d before the
extreme-ultraviolet rise. The X-ray flux drops suddenly, immediately before the
extreme-ultraviolet flux rise, supporting the view that both components arise
in the boundary layer between the accretion disc and white dwarf surface. The
early rise of the X-ray flux shows the propagation time of the outburst heating
wave may have been previously overestimated.
  The transitions between X-ray and extreme-ultraviolet dominated emission are
accompanied by intense variability in the X-ray flux, with timescales of
minutes. As detailed by Mauche & Robinson, dwarf nova oscillations are detected
throughout the extreme-ultraviolet outburst, but we find they are absent from
the X-ray lightcurve.
  X-ray and extreme-ultraviolet luminosities imply accretion rates of 3e15g/s
in quiescence, 1e16g/s when the boundary layer becomes optically thick, and
\~1e18g/s at the peak of the outburst. The quiescent accretion rate is two and
a half orders of magnitude higher than predicted by the standard disc
instability model, and we suggest this may be because the inner accretion disc
in SS Cyg is in a permanent outburst state.


title: Branch, Spur, and Feather Formation in Spiral Galaxies

abstract:
  We use hydrodynamical simulations to investigate the response of
geometrically thin, self-gravitating, singular isothermal disks of gas to
imposed rigidly rotating spiral potentials. By minimizing reflection-induced
feedback from boundaries, and by restricting our attention to models where the
swing parameter $X \sim 10$, we minimize the swing amplification of global
normal modes even in models where Toomre's $Q_g \sim 1-2$ in the gas disk. We
perform two classes of simulations: short-term ones over a few galactic
revolutions where the background spiral forcing is large, and long-term ones
over many galactic revolutions where the spiral forcing is considerably
smaller. In both classes of simulations, the initial response of the gas disk
is smooth and mimics the driving spiral field. At late times, many of the
models evince substructure akin to the so-called branches, spurs, and feathers
observed in real spiral galaxies. We comment on the parts played respectively
by ultraharmonic resonances, reflection off internal features produced by
nonlinear dredging, and local, transient, gravitational instabilites within
spiral arms in the generation of such features. Our simulations reinforce the
idea that spiral structure in the gaseous component becomes increasingly
flocculent and disordered with the passage of time, even when the background
population of old disk stars is a grand-design spiral. We speculate that truly
chaotic behavior arises when many overlapping ultraharmonic resonances develop
in reaction to an imposed spiral forcing that has itself a nonlinear, yet
smooth, wave profile.