title: Simulations of Adaptive Optics with a Laser Guide Star for SINFONI

abstract:
  The SINFONI instrument for ESO's VLT combines integral field spectroscopy and
adaptive optics (AO). We discuss detailed simulations of the adaptive optics
module. These simulations are aimed at assessing the AO module performance,
specifically for operations with extended sources and a laser guide star.
Simulated point spread function (PSF) images will be used to support scientific
preparations and the development of an exposure time calculator, while
simulated wavefront sensor measurements will be used to study PSF
reconstruction methods. We explain how the adaptive optics simulations work,
focusing on the realistic modelling of the laser guide star for a curvature
wavefront sensor. The predicted performance of the AO module is discussed,
resulting in recommendations for the operation of the SINFONI AO module at the
telescope.


title:
A thorough study of the intriguing X-ray emission from the Cartwheel
  ring

abstract:
  We present the results from the high resolution Chandra observation of the
Cartwheel galaxy. Many individual sources are resolved in the image, mostly
associated with the outer ring. All detected sources have a very high X-ray
luminosity ($\geq 10^{39}$ erg s$^{-1}$)that classifies them as Ultra Luminous
X-ray sources (ULX). The brightest of them is possibly the most luminous
individual non-nuclear source observed so far, with L$_X \sim 10^{41}$ erg
s$^{-1}$ (at D=122 Mpc). The spatial extent of this source is consistent with a
point source at the Chandra resolution. The luminosity function of individual
X-ray sources extends about an order of magnitude higher than previously
reported in other galaxies. We discuss this in the context of the "universal"
luminosity function for High Mass X-ray Binaries and we derive a Star Formation
Rate higher than in other starburst galaxies studied so far. A diffuse
component, associated with hot gas, is present. However, deeper observations
that we will obtain with XMM-Newton are needed to constrain its properties.


title:
Rotation curves of spiral galaxies: Influence of magnetic fields and
  energy flows

abstract:
  Physical mechanisms that can influence rotation curves of spiral galaxies are
discussed. For dark matter studies, possible contributions due to magnetic
fields and non-Newtonian gravitational accelerations should be carefully
accounted for. We point out that magnetic fields are particularly important in
outermost parts of the disk. In the framework of general relativity the
physical reason of an enhanced gravity in spiral galaxies depends on the
assumed metric. The additional gravity is provided for Schwarzschild metric by
nonluminous mass, whereas for Vaidya metric [1] by emission of radiative
energy. In the latter case the non-Newtonian acceleration displays 1/r
behaviour. Also matter flows contribute to non-Newtonian gravity.


title:
X-ray variability during the quiescent state of the neutron-star X-ray
  transient in the globular cluster NGC 6440

abstract:
  The globular cluster NGC 6440 is known to harbor a bright neutron-star X-ray
transient. We observed the globular cluster with Chandra on two occasions when
the bright transient was in its quiescent state in July 2000 and June 2003
(both observations were made nearly 2 years after the end of their preceding
outbursts). The quiescent spectrum during the first observation is well
represented by a two component model (a neutron-star atmosphere model plus a
power-law component which dominates at energies above 2 keV). During the second
observation (which was roughly of equal duration to the first observation) we
found that the power-law component could no longer be detected. Our spectral
fits indicate that the effective temperature of the neutron-star surface was
consistent between the two observations. We conclude that the effect of the
change in power-law component caused the 0.5-10 keV flux to be a factor of ~2
lower during the second observation compared to the first observation. We
discuss plausible explanations for the variations, including variable residual
accretion onto the neutron star magnetosphere or some variation in the
interaction of the pulsar wind with the matter still outflowing from the
companion star.


title: Outflows from Luminous YSOs: An Infrared Polarimetric Study

abstract:
  e present Near Infrared imaging polarimetry of three regions of massive star
formation, G$192.16 - 3.82$, Cepheus A, and W42. In W42 we have discovered a
new bipolar nebula located at the far side of the HII region behind the visible
cluster of exciting stars. The axis of this new nebula is aligned with the
magnetic field threading the entire cluster region. Polarization in the bipolar
outflow nebulosity associated with G192.16 is consistent with a single
illuminating source, too faint to be detected at $2 \micron$. Polarization in
the reflection nebulosity associated with Ceph A requires more than one
illuminating source, although HW2 is clearly dominant. In all three objects,
the magnetic field in the outflow at distances greater than $\sim 0.2$ pc is
radial. In G192.16 the magnetic field geometry closer than $\sim 0.2$ pc to the
embedded star appears chaotic. For G192.16 the outflow is not aligned with the
surrounding magnetic field, which lies in the galactic plane. In Ceph A, the
outflow axis could be interpreted as being aligned with the galactic plane, but
the magnetic field threading the region is not. Only in the case of W42 is the
magnetic field threading the HII region aligned with the mean field in the
surrounding galactic plane.


title: Gamma-Ray Emission From Be/X-Ray Binaries

abstract:
  Be/X-ray binaries are systems formed by a massive Be star and a magnetized
neutron star, usually in an eccentric orbit. The Be star has strong equatorial
winds occasionally forming a circumstellar disk. When the neutron star
intersects the disk the accretion rate dramatically increases and a transient
accretion disk can be formed around the compact object. This disk can last
longer than a single orbit in the case of major outbursts. If the disk rotates
faster than the neutron star, the Cheng-Ruderman mechanism can produce a
current of relativistic protons that would impact onto the disk surface,
producing gamma-rays from neutral pion decays and initiating electromagnetic
cascades inside the disk. In this paper we present calculations of the
evolution of the disk parameters during both major and minor X-ray events, and
we discuss the generation of gamma-ray emission at different energies within a
variety of models that include both screened and unscreened disks.


title:
X-ray binaries and their descendants: binary radio pulsars; evidence for
  three classes of neutron stars?

abstract:
  An important recent discovery by Pfahl et al. (2002) is that there are two
classes of Be X-ray binaries: one with orbits of small eccentricity (<0.25), in
which the neutron stars received hardly any kick velocity at birth and a class
with substantial orbital eccentricities, in which the neutron stars received a
kick velocity of order 100 km/s at birth. Also many of the double neutron stars
(5 out of 7) have a low orbital eccentricity (0.09 to 0.27), which indicates
that their second-born neutron stars received hardly any velocity kick at
birth. These second-born neutron stars tend to have low masses (1.25 to 1.35
Msun). It is proposed that the low-mass, low-kick neutron stars are formed by
the electron capture of degenerate O-Ne-Mg cores of stars with initial masses
below about 12-14 Msun, while the high-kick neutron stars originated from the
photo-disintegration collapse of the iron cores of stars which started out with
masses larger than this limit. The latter group may be further subdivided into
two classes of different mass.


title:
Probing Dark Energy with Supernovae : a concordant or a convergent
  model?

abstract:
  We present a revised interpretation of recent analysis of supernovae data. We
evaluate the effect of the priors on the extraction of the dark energy equation
of state. We find that the conclusions depend strongly on the $\Omega_M$ prior
value and on its uncertainty, and show that a biased fitting procedure applied
on non concordant simulated data can converge to the "concordance model".
Relaxing the prior on $\Omega_M$ points to other sets of solutions, which are
not excluded by observational data.


title: The XMM-Newton View of the Broad-Line Radio Galaxy 3C 120

abstract:
  We present the results of a 127 ks XMM-Newton observation of the broad-line
radio galaxy 3C 120 performed simultaneously with RXTE. The time-averaged
spectrum is Seyfert-like, with a reflection amplitude R ~ 0.5, and a neutral Fe
K line with equivalent width ~53 eV. The line is slightly broadened with a
FWHM$\approx 10^4$ km s$^{-1}$. This is consistent with arising from an
accretion disc radius of $\ga 75$ $GM/c^2$ at an inclination angle of ~10
degrees, consistent with the limit of < 14 degree derived from the radio jets.
At low energies the spectrum requires excess absorption above the Galactic
value and a soft excess which is best fit with a bremsstrahlung model
(kT=0.3-0.4 keV). The total luminosity in the bremsstrahlung component is just
under half of the total hard X-ray luminosity. Weak O VII and O VIII edges are
detected with high precision, suggesting the presence of a warm absorber
component. A two-component ionized disc model, with a very highly ionized
reflector presumably arising from very close to the black hole, is only a small
improvement over a truncated disc model. The strength of the soft X-ray
emission features produced by the distant neutral reflector are overpredicted
in our solar abundance model, implying that the heavy metal abundance in 3C 120
is subsolar. The total count-rate declined by 20 per cent over the course of
the long observation, while small-scale rapid variability was present at the
level of a few percent. A possible increase in the Fe K line flux, significant
at the 90 per cent level, was identified at ~80 ks in the observation. The
total unabsorbed luminosity of 3C 120 implies that it is accreting close to its
Eddington rate, consistent with a model of an ionized thick disc. A connection
between accretion disc thickness and radio jet production is discussed.


title: Identifying variable gamma-ray sources through radio observations

abstract:
  We present preliminary results of a campaign undertaken with different radio
interferometers to observe a sample of the most variable unidentified EGRET
sources. We expect to detect which of the possible counterparts of the
gamma-ray sources (any of the radio emitters in the field) varies in time with
similar timescales as the gamma-ray variation. If the gamma-rays are produced
in a jet-like source, as we have modelled theoretically, synchrotron emission
is also expected at radio wavelengths. Such radio emission should appear
variable in time and correlated with the gamma-ray variability.


title:
New membership determination and proper motions of NGC 1817. Parametric
  and non-parametric approach

abstract:
  We have calculated proper motions and re-evaluated the membership
probabilities of 810 stars in the area of two NGC objects, NGC 1817 and NGC
1807. We have obtained absolute proper motions from 25 plates in the reference
system of the Tycho-2 Catalogue. The plates have a maximum epoch difference of
81 years; and they were taken with the double astrograph at Zo-Se station of
Shanghai Observatory, which has an aperture of 40 cm and a plate scale of 30
arcsec/mm. The average proper motion precision is 1.55 mas/yr. These proper
motions are used to determine the membership probabilities of stars in the
region, based on there being only one very extended physical cluster: NGC 1817.
With that aim, we have applied and compared parametric and non-parametric
approaches to cluster/field segregation. We have obtained a list of 169
probable member stars.


title: uvby-Hbeta CCD Photometry of NGC 1817 and NGC 1807

abstract:
  We have investigated the area of two NGC entries, NGC 1817 and NGC 1807, with
deep CCD photometry in the uvby-Hbeta intermediate-band system. The photometric
analysis of a selected sample of stars of the open cluster NGC 1817 yields a
reddening value of E(b-y)= 0.19$\pm$0.05, a distance modulus of V0-MV=
10.9$\pm$0.6, a metallicity of [Fe/H]= -0.34$\pm$0.26 and an age of log t =
9.05$\pm$0.05. Our measurements allow us to confirm that NGC 1807 is not a
physical cluster.


title:
Design and imaging performance of achromatic diffractive/refractive
  X-ray and Gamma-ray Fresnel lenses

abstract:
  Achromatic combinations of a diffractive Phase Fresnel Lens and a refractive
correcting element have been proposed for X-ray and gamma-ray astronomy and for
microlithography, but considerations of absorption often dictate that the
refractive component be given a stepped profile, resulting in a double Fresnel
lens. The imaging performance of corrected Fresnel lenses, with and without
`stepping' is investigated and the trade-off between resolution and useful
bandwidth in different circumstances is discussed. Provided the focal ratio is
large, correction lenses made of low atomic number materials can be used with
X-rays in the range approximately 10--100 keV without stepping. The use of
stepping extends the possibility of correction to higher aperture systems, to
energies as low as a few kilo electron volts and to gamma-rays of $\sim$ mega
electron volt energy.


title: Timescale Analysis of Spectral Lags

abstract:
  A technique for timescale analysis of spectral lags performed directly in the
time domain is developed. Simulation studies are made to compare the time
domain technique with the Fourier frequency analysis for spectral time lags.
The time domain technique is applied to studying rapid variabilities of X-ray
binaries and $\gamma$-ray bursts. The results indicate that in comparison with
the Fourier analysis the timescale analysis technique is more powerful for the
study of spectral lags in rapid variabilities on short time scales and short
duration flaring phenomena.


title: Evolution of Massive Stars Up to the End of Central Oxygen Burning

abstract:
  We present a detailed study of the evolution of massive stars of masses 15,
20, 25 and 30 $\msun$ assuming solar-like initial chemical composition. The
stellar sequences were evolved through the advanced burning phases up to the
end of core oxygen burning. We present a careful analysis of the physical
characteristics of the stellar models. In particular, we investigate the effect
of the still unsettled reaction $^{12}$C($\alpha$,$\gamma$)$^{16}$O on the
advanced evolution by using recent compilations of this rate. We find that this
rate has a significant impact on the evolution not only during the core helium
burning phase, but also during the late burning phases, especially the shell
carbon-burning. We have also considered the effect of different treatment of
convective instability based on the Ledoux criterion in regions of varying
molecular weight gradient during the hydrogen and helium burning phases. We
compare our results with other investigations whenever available. Finally, our
present study constitutes the basis of analyzing the nucleosynthesis processes
in massive stars. In particular we will present a detail analysis of the {\it
s}-process in a forthcoming paper.


title:
The Globular Cluster Systems of Five Nearby Spiral Galaxies: New
  Insights from Hubble Space Telescope Imaging

abstract:
  We use available multifilter Hubble Space Telescope (HST) WFPC2 imaging of
five (M81, M83, NGC 6946, M101, and M51) low inclination, nearby spiral
galaxies to study ancient star cluster populations. M81 globular clusters (GC)
have an intrinsic color distribution which is very similar to those in the
Milky Way and M31, with ~40% of the clusters having colors expected for a
metal-rich population. On the other hand, the GC system in M51 appears almost
exclusively blue and metal poor. This lack of metal-rich GCs associated with
the M51 bulge indicates that the bulge formation history of this Sbc galaxy may
have differed significantly from that of our own. Ancient clusters in M101, and
possibly in NGC 6946, appear to have luminosity distributions which continue to
rise to our detection limit (M_V ~ -6.0), well beyond the expected turnover
(M_V ~ -7.4) in the luminosity function. This is reminiscent of the situation
in M33, a Local Group galaxy of similar Hubble type. The faint ancient cluster
candidates in M101 and NGC 6946 have colors and radii similar to their more
luminous counterparts, and we suggest that these are either intermediate age
(3-9 Gyr) disk clusters or the low mass end of the original GC population. If
the faint, excess GC candidates are excluded, we find that the specific
frequency (S_N) of ancient clusters formed in later-type spirals is roughly
constant, with S_N=0.5 +- 0.2. By combining the results of this study with
literature values for other systems, we find that the total GC specific
frequencies in spirals appear to correlate best with Hubble type and
bulge/total ratio, rather than with galaxy luminosity or galaxy mass
(abridged).


title: Microquasars and gamma-ray sources

abstract:
  Microquasars are X-ray binary systems with non-thermal radio emission
originated in jet-like features. They are attractive sites for gamma-ray
production, since relativistic particles in the jet should traverse locally
strong both photon and matter fields. In this review we discuss whether some of
the unidentified gamma-ray sources detected by the EGRET instrument of the
Compton Gamma-Ray Observatory might be associated with microquasars. Relevant
models for gamma-ray emission in such binaries are described and prospects for
the detection of microquasars with instruments of new generation are briefly
evaluated.


title: Gamma Ray Bursts as Probes of Quantum Gravity

abstract:
  Gamma ray bursts (GRBs) are short and intense pulses of $\gamma$-rays
arriving from random directions in the sky. Several years ago Amelino-Camelia
et al. pointed out that a comparison of time of arrival of photons at different
energies from a GRB could be used to measure (or obtain a limit on) possible
deviations from a constant speed of light at high photons energies. I review
here our current understanding of GRBs and reconsider the possibility of
performing these observations.


title: The Galaxy Structure-Redshift Relationship

abstract:
  There exists a gradual, but persistent, evolutionary effect in the galaxy
population such that galaxy structure and morphology change with redshift. This
galaxy structure-redshift relationship is such that an increasingly large
fraction of all bright and massive galaxies at redshifts 2 < z < 3 are
morphologically peculiar at wavelengths from rest-frame ultraviolet to
rest-frame optical. There are however examples of morphologically selected
spirals and ellipticals at all redshifts up to z ~ 3. At lower redshift, the
bright galaxy population smoothly transforms into normal ellipticals and
spirals. The rate of this transformation strongly depends on redshift, with the
swiftest evolution occurring between 1 < z < 2. This review characterizes the
galaxy structure-redshift relationship, discusses its various physical causes,
and how these are revealing the mechanisms responsible for galaxy formation.


title: FORTIS: Pathfinder to the Lyman Continuum

abstract:
  Shull et al. (1999) have asserted that the contribution of stars, relative to
quasars, to the metagalactic background radiation that ionizes most of the
baryons in the universe remains almost completely unknown at all epochs. The
potential to directly quantify this contribution at low redshift has recently
become possible with the identification by GALEX of large numbers of sparsely
distributed faint ultraviolet galaxies. Neither STIS nor FUSE nor GALEX have
the ability to efficiently survey these sparse fields and directly measure the
Lyman continuum radiation that may leak into the low redshift (z < 0.4)
intergalactic medium. We present here a design for a new type of far
ultraviolet spectrograph, one that is more sensitive, covers wider fields, and
can provide spectra and images of a large number of objects simultaneously,
called the Far-ultraviolet Off Rowland-circle Telescope for Imaging and
Spectroscopy (FORTIS). We intend to use a sounding rocket flight to validate
the new instrument with a simple long-slit observation of the starburst
populations in the galaxy M83. If however, the long-slit were replaced with
microshutter array, this design could isolate the chains of blue galaxies found
by GALEX over an ~30' diameter field-of-view and directly address the Lyman
continuum problem in a long duration orbital mission. Thus, our development of
the sounding rocket instrument is a pathfinder to a new wide field
spectroscopic technology for enabling the potential discovery of the long
hypothesized but elusive Lyman continuum radiation that is thought to leak from
low redshift galaxies and contribute to the ionization of the universe.


title:
Discovery of a Primitive Damped Lyman alpha Absorber Near an X-ray
  Bright Galaxy Group in the Virgo Cluster

abstract:
  We present a new UV echelle spectrum of PG1216+069, obtained with HST+STIS,
which reveals damped Lya (DLA) absorption as well as O I, C II, Si II, and Fe
II absorption lines at z(abs) = 0.00632 near the NGC4261 group. The absorber
shows no evidence of highly-ionized gas, which places constraints on "warm-hot"
missing baryons in the NGC4261 group. The well-developed damping wings of the
Lya line tightly constrain the H I column density; we find log N(H I) =
19.32+/-0.03. The metallicity of this sub-DLA is remarkably low, [O/H] =
-1.60^{+0.09}_{-0.11}, which is comparable to many analogous high-redshift
systems, and the iron abundance indicates that this absorber contains little or
no dust. Nitrogen is underabundant; we detect neither N I or N II, and we show
that this is not due to ionization effects but rather indicates that [N/O] <
-0.28 (3sigma). Despite the proximity to NGC4261 group, there are no bright
galaxies close to the sight line at the absorption redshift. The nearest known
galaxy is a sub-L* galaxy with a projected distance rho = 86 kpc; the closest
L* galaxy is NGC4260 at rho = 246 kpc. The low metallicity and [N/O] indicate
that this low-z sub-DLA is a relatively primitive gas cloud. We consider the
nature and origin of the sub-DLA, and we find several possibilities. The
properties of the sub-DLA are similar to those of the interstellar media in
blue compact dwarf galaxies and are also reminiscent of Milky Way HVCs. Or, the
object could simply be a small dark-matter halo, self-enriched by a small
amount of internal star formation but mostly undisturbed since its initial
formation. In this case, the small halo would likely be an ancient building
block of galaxy formation that formed before the epoch of reionization.


title:
Surface Hydrogen Modeling of Super Soft X-ray Sources: Are They
  Supernova Ia Progenitors?

abstract:
  Nova explosions occur on the white dwarf (WD) component of a Cataclysmic
Variable stellar system which is accreting matter lost by a companion. A Type
Ia supernova explosion is thought to result when a WD, in a similar binary
configuration, grows in mass to the Chandrasekhar Limit. Here, we present
calculations of accretion of Solar matter, at a variety of mass accretion
rates, onto hot ($2.3 \times 10^{5}$K), luminous (30L$_\odot$), massive
(1.25M$_\odot$, 1.35M$_\odot$) Carbon-Oxygen WDs. In contrast to our nova
simulations where the WD has a low initial luminosity and a thermonuclear
runaway (TNR) occurs and ejects material, these simulations do not eject
material (or only a small fraction of the accreted material) and the WD grows
in mass. A hydrogen TNR does not occur because hydrogen fuses to helium in the
surface layers, and we call this process Surface Hydrogen Burning (SHB). As the
helium layer grows in mass, it gradually fuses either to carbon and oxygen or
to more massive nuclei depending on the WD mass and mass accretion rate. If
such a WD were to explode in a SN Ia event, therefore, it would show neither
hydrogen nor helium in its spectrum as is observed. Moreover, the luminosities
and effective temperatures of our simulations agree with the observations of
some of the Super Soft X-ray Binary Sources and, therefore, our results
strengthen previous speculation that some of them (CAL 83 and CAL 87 for
example) are probably progenitors of SN Ia explosions. Finally, we have
achieved SHB for values of the mass accretion rate that almost span the
observed values of the Cataclysmic Variables.


title:
Total Opacity of Local Group Galaxies and Large Scale Structure behind
  the Galactic Bulge

abstract:
  Recently, we have developed and calibrated the Synthetic Field Method to
derive total extinction through disk galaxies. The method is based on the
number counts and colors of distant background field galaxies that can be seen
through the foreground object. Here, we investigate how large (10-m) and very
large (20 to 30-m), diffraction-limited, optical and infrared telescopes in
space would improve the detection of background galaxies behind Local Group
objects, including the Galactic bulge. We find that, besides and perhaps more
important than telescope size, a well-behaved, well-characterized PSF would
facilitate in general the detection of faint objects in crowded fields, and
greatly benefit several other important research areas, like the search for
extrasolar planets, the study of quasar hosts and, most relevant for this
meeting, the surveying of nearby large scale structure in the Zone of
Avoidance, in particular behind the Galactic bulge.


title:
The Chemical Composition of Alpha Centauri A: Strong Lines and the ABO
  Theory of Collisional Line Broadening

abstract:
  The mean abundances of Mg, Si, Ca, Ti, Cr and Fe based on both strong and
weak lines of Alpha Centauri A are determined by matching the observed line
profiles with those synthesized from stellar atmospheric models and comparing
these results with a similar analysis for the Sun. There is good agreement
between the abundances from strong and weak lines.
  Strong lines should generally be an excellent indicator of abundance and far
easier to measure than the weak lines normally used. Until the development of
the Anstee, Barklem and O'Mara theory for collisional line broadening, the
uncertainty in the value of the damping constant prevented strong lines being
used for abundance determinations other than in close differential analyses.
  We found that Alpha Centauri A has a mean overabundance of 0.12+/-0.06 dex
compared to solar mean abundances. This result agrees remarkably well with
previous studies that did not use strong lines or the Anstee, Barklem and
O'Mara theory for collisional line broadening. Our result support the
conclusion that reliable abundances can be derived from strong lines provided
this new theory for line broadening is used to calculate the van der Waal's
damping.


title:
Near-infrared and Millimeter Constraints on the Nuclear Energy Source of
  the Infrared Luminous Galaxy NGC 4418

abstract:
  We present near-infrared and millimeter investigations of the nucleus of the
infrared luminous galaxy NGC 4418, which previous observations suggest
possesses a powerful buried AGN. We found the following main results: (1) The
infrared K-band spectrum shows CO absorption features at 2.3-2.4 micron owing
to stars and very strong H2 emission lines. The luminosity ratios of H2
emission lines are suggestive of a thermal origin, and the equivalent width of
the H2 1-0 S(1) line is the second largest observed to date in an external
galaxy, after the well-studied strong H2-emitting galaxy NGC 6240. (2) The
infrared L-band spectrum shows a clear polycyclic aromatic hydrocarbon (PAH)
emission feature at 3.3 micron, which is usually found in star-forming
galaxies. The estimated star-formation luminosity from the observed PAH
emission can account for only a small fraction of the infrared luminosity. (3)
Millimeter interferometric observations of the nucleus reveal a high HCN (1-0)
to HCO+ (1-0) luminosity ratio of 1.8, as has been previously found in pure
AGNs. (4) The measurements of HCN (1-0) luminosity using a single-dish
millimeter telescope show that the HCN (1-0) to infrared luminosity ratio is
slightly larger than the average, but within the scattered range, for other
infrared luminous galaxies. All of these results can be explained by the
scenario in which, in addition to energetically-insignificant, weakly-obscured
star-formation at the surface of the nucleus, a powerful X-ray emitting AGN
deeply buried in dust and high density molecular gas is present.


title: Shot cutoff timescales in different spectral states of Cygnus X-1

abstract:
  We investigate the shot cutoff timescale evolutions during different spectral
states in the black hole binary Cygnus X-1 with the recently proposed w
spectral analysis technique. For low energy shots, their cutoff timescale
decreases from the low state to intermediate state, and to high state
monotonically. However in the high energy range, where shots are believed to be
reprocessed in the hot corona, timescales are almost the same for different
spectral states. A linear correlation is found between the energy spectrum
photon index and the shot cutoff timescale at low energies. Both narrow and
broad iron Kalpha lines are distinguished from timing analysis, providing
dynamical evidence that broad and narrow iron lines originate respectively at
small and large radii of the accretion disk. Possible mechanisms for state
transitions and accretion flow geometry in accreting stellar mass black holes
are discussed.


title:
The nature of premaximum halts of classical nova outbursts: V723
  Cassiopeiae and V463 Scuti

abstract:
  We present a new interpretation of long premaximum halts of nova outbursts.
For V723 Cas (Nova Cas 1995) and V463 Sct (Nova Sct 2000), we have reproduced
light curves, excluding the brightness maxima, starting from the long
premaximum halt through the late decay phase of the outbursts using a
steady-state optically thick wind model. When the hydrogen-rich envelope of the
white dwarf (WD) is massive enough, the star expands to \sim 100 R_\sun or over
and its surface temperature decreases to below 7000 K. At this supergiant
mimicry stage, the changes in both the photospheric radius and the temperature
are small against the large increase in the envelope mass. These changes cause
a saturation in visual magnitude that lasts a long time before it begins to
decline. This saturation is known as the premaximum halt of a classical nova
outburst. The visual magnitude during the saturation is close to the bolometric
magnitude, which is an upper limit for a given WD mass. Since the WD masses are
estimated to be 0.59 M_\sun for V723 Cas and 1.1 M_\sun for V463 Sct by fitting
the decline rate of nova light curves, we can determine the absolute magnitude
of premaximum halts. It is a refined Eddington luminosity. Thus, the premaximum
halt of a nova works as a standard candle.


title:
XMM-Newton observation of the Seyfert 1.8 ESO 113-G010: discovery of a
  highly redshifted iron line at 5.4 keV

abstract:
  We present a spectral analysis of the Seyfert 1.8 ESO 113-G010 observed with
XMM-Newton for 4 ks. The spectrum shows a soft excess below 0.7 keV and more
interestingly a narrow emission Gaussian line at 5.4 keV (in its rest-frame),
most probably originating from a redshifted iron Kalpha line. No significant
line at or above 6.4 keV is found contrary to other objects showing redshifted
lines, ruling out a strong blue-wing to the line profile. The line is detected
at 99% confidence, from performing Monte Carlo simulations which fully account
for the range of energies where a narrow iron line is likely to occur. The
energy of the line could indicate emission from relativistic (0.17 - 0.23 c)
ejected matter moving away from the observer, as proposed for Mrk 766 by Turner
et al. (2004). Alternatively, the emission from a narrow annulus at the surface
of the accretion disk is unlikely due to the very small inclination angle (i.e.
less than 10 deg) required to explain the narrow, redshifted line in this
intermediate Seyfert galaxy. However emission from a small, localized hot-spot
on the disk, occurring within a fraction of a complete disk orbit, could also
explain the redshifted line. This scenario would be directly testable in a
longer observation, as one would see significant variations in the energy and
intensity of the line within an orbital timescale.


title: Molecular and ionized gas in the tidal tail in Stephan's Quintet

abstract:
  We have mapped with the IRAM interferometer at Plateau de Bure (PdBI) the
12CO emission towards intergalactic star forming regions located in the tidal
tail stemming from NGC7319, in the Stephan's Quintet compact group of galaxies.
The 13CO emission of the same region was observed with the IRAM 30m telescope
and optical spectroscopy of several HII regions in the area were obtained with
the Calar Alto 3.5m telescope. We recovered with the interferometer about 50%
of the CO(1-0) total emission that had been earlier measured with single dish
observations. We find two main areas of CO emission: (i) an elongated region
towards the area known as SQ B where a Tidal Dwarf Galaxy could currently be
forming (ii) a barely resolved area at the tip of the optical tidal arm. Both
regions follow dust lanes visible on HST images and their CO peak coincides
spatially exactly with the maximum of the Halpha line emission. In SQ B, there
is furthermore very good kinematical agreement between the CO, Halpha and HI
components. We conclude from these coincidences that the gaseous matter found
in quantities in the area is physically associated to the optical tidal tail
and thus that the intergalactic atomic hydrogen there was expelled from
NGC7319. Furthermore, the relatively high oxygen abundances (about solar)
estimated from the optical spectra of the HII regions imply that the gas
feeding the star formation originated from the inner regions of the parent
galaxy. In SQ B, we derive from different tracers a star formation rate of 0.5
\msun/yr. The inferred molecular gas consumption time of 0.5 Gyr lies in the
range of values found for spiral and starburst galaxies. On the other hand, the
ratio of 12CO/13CO>25 is much higher than the values found in disks of spiral
galaxies. A relatively low opacity for the 12CO gas is the most likely reason.


title: Excitation of low-frequency QPOs in black-hole accretion

abstract:
  We study possible mechanisms of excitation of quasiperiodic oscillations in
the accretion flow of black hole accreters in their hard spectral states, in
the context of the `truncated disk' model. Quasi-spherical oscillations of the
inner ion-supported accretion flow (ISAF) can be excited by the interaction of
this hot flow with the cool disk extending outward from it. The fundamental
mode of (p-mode) oscillation is most easily excited, and has a frequency near
the Kepler frequency at the inner edge of the cool disk. The strongest
excitation mechanism is a feedback loop involving cooling of the ISAF by soft
photons from the cool disk and heating of the cool disk by the ISAF, while
synchrotron emission can be a relatively strong damping effect. Growth times
are computed by detailed Comptonization calculations of the interaction of an
idealized ISAF with a cool disk. Typical growth times as short as a few
dynamical times are found, while amplitudes can be as large as 10%.


title: Status and First Results of the MAGIC Telescope

abstract:
  The 17 m MAGIC Cherenkov telescope for gamma ray astronomy between 30 and 300
GeV started operations in its final configuration in October 2003 and is
currently well into its calibration phase. Here I report on its present status
and its first gamma ray source detections.


title: How special is the Solar System?

abstract:
  Most mechanisms proposed for the formation of planets are modified versions
of the mechanism proposed for the solar system. Here we argue that, in terms of
those planetary systems which have been observed, the case for the solar system
being a typical planetary system has yet to be established. We consider the
possibility that most observed planetary systems have been formed in some quite
different way. If so, it may be that none of the observed planetary systems is
likely to harbour an earth-like planet.


title: Overdensity of X-Ray sources near 3C 295: a candidate filament

abstract:
  We present a statistical analysis of the Chandra observation of the source
field around the 3C 295 galaxy cluster (z=0.46) aimed at the search for
clustering of X-ray sources. Three different methods of analysis, namely a chip
by chip logN-logS, a two dimensional Kolmogorov-Smirnov test, and the angular
correlation function (ACF) show a strong overdensity of sources in the
North-East of the field. In particular, the ACF shows a clear signal on scales
of 0.5 - 5 arcmin. This correlation angle is > 2 times higher than that of a
sample of 8 ACIS-I field at the 2.5 sigma confidence level. If this overdensity
is spatially associated to the cluster, we are observing a 'filament' of the
large scale structure of the Universe. We discuss some first results that seem
to indicate such an association.


title: Superluminal apparent motions in distant radio sources

abstract:
  We derive the prediction of the standard model of superluminal radio sources
for the apparent transverse velocity of a radio source located at redshift z.
The apparent velocity of the source is reduced by a factor of 1 + z compared to
that of a similar nearby source. The cause of this reduction is recession of
the distant source due to the expansion of the universe. The apparent velocity
of a source can be estimated from its redshift and proper motion using the
values of the Hubble constant and the mean densities of different energy
components in the universe. We derive an expression for the velocity valid for
the currently favored cosmological model: a flat universe with a nonzero
cosmological constant.


title:
ISO observations of the Galactic center Interstellar Medium: neutral gas
  and dust

abstract:
  The 500 central pc of the Galaxy (hereafter GC) exhibit a widespread gas
component with a kinetic temperature of 100-200 K. The bulk of this gas is not
associated to the well-known thermal radio continuum or far infrared sources
like Sgr A or Sgr B. How this gas is heated has been a longstanding problem.
With the aim of studying the thermal balance of the neutral gas and dust in the
GC, we have observed 18 molecular clouds located at projected distances far
from thermal continuum sources with the Infrared Space Observatory (ISO). In
this paper we present observations of several fine structure lines and the full
continuum spectra of the dust between 40 and 190 microns. A warm dust component
with a temperature between 27 and 42 K is needed to fit the spectra. We have
compared the gas and the dust emission with the predictions from J-type and
C-type shocks and photodissociation region (PDRs) models. We conclude that the
dust and the fine structure lines observations are best explained by a PDR with
a density of 10$^3$ cm^-3 and an incident far-ultraviolet field 10$^3$ times
higher than the local interstellar radiation field. PDRs can naturally explain
the discrepancy between the gas and the dust temperatures. However, these PDRs
can only account for 10-30% of the total H2 column density with a temperature
of ~ 150 K. We discuss other possible heating mechanisms (short version).


title: Hamiltonian Cosmological Dynamics of General Relativity

abstract:
  The Hamiltonian approach to General Relativity is developed similarly to the
Wheeler-DeWitt Hamiltonian cosmology, where the cosmological scale factor is
treated as a time-like dynamic variable and its canonical momentum is
considered as an evolution generator in the field space of events with the
postulate about a physical vacuum as a state with the minimal eigenvalue of
this generator.
  The cosmological scale factor is extracted from the Hamiltonian General
Relativity without double counting of the spatial metric determinant in
contrast to the standard cosmological perturbation theory. The Friedmann-like
equations in the exact theory are derived. A new version of cosmological
perturbation theory keeps the form of the Newton interactions in an early
Universe. We show how the considered Hamiltonian approach to GR can solve the
topical problems of modern cosmology and quantum theory of gravitation.
cosmology and quantum theory of gravitation.


title: Exploring the X-ray Sky with the XMM-Newton Bright Serendipitous Survey

abstract:
  ABRIDGED. We present "The XMM-Newton Bright Serendipitous Survey", two
flux-limited samples with flux limit fx ~7E-14 cgs in the 0.5-4.5 keV (BSS) and
4.5-7.5 keV (HBSS) energy band, respectively. After discussing the survey
strategy, we present the basic data on a complete sample of 400 X-ray sources
derived from the analysis of 237 XMM-Newton fields. The survey covers an area
of 28.10 (25.17 for the HBSS) sq. deg. Up to now ~71% (~90%) of the sources
have been spectroscopically identified making the BSS (HBSS) the sample with
the highest number of identified XMM-Newton sources published so far. We find
that: a) the optical counterpart in the majority (~90%) of cases has a
magnitude brighter than the POSS II limit; b) the majority of the objects
identified so far are broad line AGN. No obvious trend of the source spectra
(as deduced from the Hardness Ratios analysis) as a function of the count rate
is seen and the average spectra of the "extragalactic" population corresponds
to an X-ray energy spectral index of ~0.8 (~0.64) for the BSS (HBSS) sample.
About 13% (40%) of the sources are described by an energy spectral index
flatter than that of the CXB. We measure a surface density of optically type 1
and type 2 AGN of 1.63+/-0.25 deg-2 and 0.83+/-0.18$ deg-2, respectively;
optically type 2 AGN represent 34+/-9% of the total AGN population. Finally, we
find a clear separation, in the hardness ratio diagram and in the (hardness
ratio) vs. (X-ray to optical flux ratio) diagram, between "coronal emitting"
stars and extragalactic sources.


title:
Multiple protostellar systems. I. A deep near infrared survey of Taurus
  and Ophiuchus protostellar objects

abstract:
  (Abridged) We performed a deep infrared imaging survey of 63 embedded young
stellar objects (YSOs) located in the Taurus and Ophiuchus clouds to search for
companions. The sample includes Class I and flat infrared spectrum protostellar
objects. We find 17 companions physically bound to 15 YSOs with angular
separations in the range 0.8-10" (110-1400 AU) and derive a companion star
fraction of 23+/-9 % and 29+/-7 % for embedded YSOs in Taurus and Ophiuchus,
respectively. In spite of different properties of the clouds and especially of
the prestellar cores, the fraction of wide companions, 27+/-6 % for the
combined sample, is identical in the two star-forming regions. This suggests
that the frequency and properties of wide multiple protostellar systems are not
very sensitive to specific initial conditions. Comparing the companion star
fraction of the youngest YSOs still surrounded by extended envelopes to that of
more evolved YSOs, we find evidence for a possible evolution of the fraction of
wide multiple systems, which seems to decrease by a factor of about 2 on a
timescale of about 10^5 yr. Somewhat contrary to model predictions, we do not
find evidence for a sub-clustering of embedded sources at this stage on a scale
of a few 100 AU that could be related to the formation of small-N protostellar
clusters. Possible interpretations for this discrepancy are discussed.


title: Unusual glitch behaviours of two young pulsars

abstract:
  In this paper we report unusual glitches in two young pulsars, PSR J1825-0935
(B1822-09) and PSR J1835-1106. For PSR J1825-0935, a slow glitch characterised
by a temporary decrease in the slowdown rate occurred between 2000 December 31
to 2001 December 6. This event resulted in a permanent increase in frequency
with fractional size $\Delta\nu/\nu\sim31.2(2)\times10^{-9}$, however little
effect remained in slowdown rate. The glitch in PSR J1835-1106 occurred
abruptly in November 2001 (MJD 52220\pm3) with
$\Delta\nu/\nu\sim14.6(4)\times10^{-9}$ and little or no change in the
slow-down rate. A significant change in $\ddot\nu$ apparently occurred at the
glitch with $\ddot\nu$ having opposite sign for the pre- and post-glitch data.


title: Active Galaxies and Cluster Gas

abstract:
  Two lines of evidence indicate that active galaxies, principally radio
galaxies, have heated the diffuse hot gas in clusters. The first is the general
need for additional heating to explain the steepness of the X-ray
luminosity--temperature relation in clusters, the second is to solve the
cooling flow problem in cluster cores. The inner core of many clusters is
radiating energy as X-rays on a timescale much shorter than its likely age.
Although the temperature in this region drops by a factor of about 3 from that
of the surrounding gas, little evidence is found for gas much cooler than that.
Some form of heating appears to be taking place, probably by energy transported
outward from the central accreting black hole or radio source. How that energy
heats the gas depends on poorly understood transport properties (conductivity
and viscosity) of the intracluster medium. Viscous heating is discussed as a
possibility. Such heating processes have consequences for the truncation of the
luminosity function of massive galaxies.


title:
Period Color and Amplitude Color relations for MACHO project LMC RR
  Lyraes

abstract:
  In this paper, we analyze period color and amplitude color relations at
minimum, mean and maximum $V$ band light for 6391 RRab stars in the Large
Magellanic Cloud obtained by the MACHO project. Specifically, we find that
color and amplitude are nearly independent of period at minimum light but that
there exists a definite relation between period and color and amplitude and
color at maximum light. These two properties are easily explained by the
application of the Stefan Boltzmann law and the interaction of the photosphere
and hydrogen ionization front at minimum light. When we examine the slope of
the period color relation as a function of phase, we find that the slope varies
significantly with phase and is small for a wide range of phases around minimum
light. This suggests that another factor that needs to be considered when
trying to understand RR Lyrae observed properties is their behavior at
different phases during a pulsation cycle.


title: The IC133 Water Vapor Maser in the Galaxy M33: A Geometric Distance

abstract:
  We report on the results of a 14 year long VLBI study of proper motions in
the IC133 H2O maser source in the galaxy M33. The method of Ordered Motion
Parallax was used to model the 3-dimensional structure and dynamics of IC133
and obtain a distance estimate, 800 +/- 180 kpc. Our technique for determining
the distance to M33 is independent of calibrations common to other distance
indicators, such as Cepheid Period-Luminosity relations, and therefore provides
an important check for previous distance determinations.


title: Hot Baryons in Supercluster Filaments

abstract:
  Most of the baryons in the local universe are ``missing'' in that they are
not in galaxies or in the previously detected gaseous phases. These missing
baryons are predicted to be in a moderately hot phase, 10^5-10^7 K, largely in
the form of giant cosmic filaments that connect the denser virialized clusters
and groups of galaxies. Models show that the highest covering fraction of such
filaments occurs in superclusters. To determine whether such filaments exist,
we have begun a project to search for UV absorption against AGNs projected
behind possible supercluster filaments. Using data from the HST and FUSE
archives along with new observations, we have detected UV absorption within
about 1300 km/s of seven supercluster sightlines out of a sample of eight. The
likelihood of such detections being generated by chance is less than 10^-4.


title: Core Formation in Galactic Nuclei Due to Recoiling Black Holes

abstract:
  Anisotropic gravitational radiation from a coalescing black hole binary can
impart a recoil velocity of up to several hundred km/s to the remnant black
hole. We examine the effects of recoiling massive black holes on their host
stellar bulges, both for holes that escape their host and those that return to
the galactic center via dynamical friction. We show that removal of a black
hole via radiation recoil generally results in a rapidly-formed central core in
the stellar system, with the effect being largest when the hole stays bound to
the bulge and the recoil velocity is comparable to the bulge velocity
dispersion. Black hole recoil therefore provides a mechanism for producing
cores in some early type galaxies, but it is expected to be most efficient in
faint ellipticals that are known to have steep density profiles. We argue that
these results may hint at a significant role for gas in facilitating the
coalescence of binary black holes in faint (power-law) early-type galaxies.


title: Looking for an extra dimension with tomographic cosmic shear

abstract:
  The cosmic acceleration was discovered in one of the brane-based models. We
are interested in discriminating this model from the dark energy by tomographic
cosmic shear. Growth factors are different in the two models when one adjusts
parameters to get nearly identical H(z). The two models could be distinguished
with independent determinations of both geometrical factors and the growth
factor. We introduce new parameterizations to separate the influence of
geometry and the influence of growth on cosmic shear maps. We find that future
observations will be able to distinguish between both models.


title:
X-ray Surveys and Wide-Field Optical/Near-Infrared Imaging with the
  Joint Dark Energy Mission

abstract:
  I briefly describe a few important scientific issues that could be addressed
effectively via the combination of data from JDEM and X-ray missions. The
topics covered are largely focused on active galactic nuclei (AGN) and include
(1) the selection of AGN via X-ray emission and optical variability, (2)
nuclear outbursts in galaxies due to transient fueling of their supermassive
black holes, (3) moderate-luminosity AGN at high redshift (z > 4) found via
application of "dropout" techniques to X-ray sources, and (4) the host-galaxy
morphologies of X-ray selected AGN. I also describe the substantial challenges
to obtaining wide-field X-ray data with sufficient sensitivity to complement
JDEM properly.


title:
An Optical and X-ray Examination of Two Radio Supernova Remnant
  Candidates in 30 Doradus

abstract:
  The giant HII region 30 Doradus is known for its violent internal motions and
bright diffuse X-ray emission, suggesting the existence of supernova remnants
(SNRs), but no nonthermal radio emission has been detected. Recently, Lazendic
et al. compared the H-alpha/H-beta and radio/H-alpha ratios and suggested two
small radio sources to be nonthermal and thus SNR candidates; however, no
optical or X-ray counterparts were detected. We have used high-resolution
optical images and high-dispersion spectra to examine the morphological,
spectral, and kinematic properties of these two SNR candidates, and still find
no optical evidence supporting their identification as SNRs. We have also
determined the X-ray luminosities of these SNR candidates, and find them 1-3
orders of magnitude lower than those commonly seen in young SNRs. High
extinction can obscure optical and X-ray signatures of an SNR, but would
prohibit the use of a high radio/H-alpha ratio to identify nonthermal radio
emission. We suggest that the SNR candidate MCRX J053831.8-690620 is associated
with a young star forming region; while the radio emission originates from the
obscured star forming region, the observed optical emission is dominated by the
foreground. We suggest that the SNR candidate MCRX J053838.8-690730 is
associated with a dust/molecular cloud, which obscures some optical emission
but not the radio emission.


title: The Role of Pressure in GMC Formation

abstract:
  We examine the hypothesis that hydrostatic pressure alone determines the
ratio of atomic to molecular gas averaged over a particular radius in disk
galaxies. The hypothesis implies that the transition radius, the location where
the ratio is unity, should always occur at the same value of stellar surface
density in all galaxies. We examine data for 28 galaxies and find that the
stellar surface density at the transition radius is indeed constant to 40% at a
value of 120 M_sun/pc^2. If the hypothesis can be confirmed at all radii within
a large range of galaxy types and metallicities, combining it with the observed
constancy of the star formation rate with H_2 surface density may enable a
physically motivated star formation prescription with wide applicability.


title: Candidates of z ~ 5.5--7 Galaxies in the HST Ultra Deep Field

abstract:
  We report results from our $z\simeq 5.5$--7 galaxy search in the HST Ultra
Deep Field (UDF). Using the 400-orbit of ACS data, we found 108 plausible
$5.5\leq z\leq 6.5$ (or $z\simeq 6$ for short) candidates to
$m_{AB}(z_{850})=30.0$ mag. The contamination to the sample, either due to
image artifacts or known types of astronomical objects, is likely negligible.
The inferred surface densities of $z\simeq 6$ galaxies are consistent with our
earlier predictions from $m_{AB}(z_{850})=26.5$ to 28.5 mag. After correcting
for detection incompleteness, the counts of $z\simeq 6$ candidates to
$m_{AB}(z_{850})=29.2$ mag suggests that the faint-end slope of the galaxy
luminosity function (LF) at this redshift is likely between $\alpha=-1.8$ and
-1.9, which is sufficient to account for the entire Lyman photon budget
necessary to complete the reionization of the universe at $z\simeq 6$. We also
searched for $z\simeq 6.5$--7 candidates using the UDF NICMOS data, and have
found four candidates to $J_{110}=27.2$ mag. However, the infrared colors of
three candidates cannot be easily explained by galaxies in this redshift range.
We tentatively derive an upper limit to the cumulative surface density of
galaxies at $z\simeq 7$ of 0.36 per arcmin$^2$ to $J_{110}=26.6$ mag, which
suggest a noticeable drop in the LF amplitude from $z\simeq 6$ to $z\simeq 7$.


title: Neutrinos from microquasars

abstract:
  The jets of microquasars with high-mass stellar companions are exposed to the
dense matter field of the stellar wind as well as to the photon densities found
in the surrounding medium. Photopion and proton-proton interactions could then
lead to copious production of neutrinos. In this work, we analyze the hadronic
microquasar model, particularly in what concerns to the neutrino production.
Limits to this kind of models using data from AMANDA-II are established. New
constraints are also imposed upon specific microquasar models based on
photopion processes. These are very restrictive particularly for the case of
SS433, a microquasar for which the presence of accelerated hadrons has been
already inferred from iron X-ray line observations.


title: On Bode's law

abstract:
  In a planetary or satellite system, idealized as n small bodies in initially
coplanar, concentric orbits around a large central body, obeying Newtonian
point-particle mechanics, resonant perturbations will cause dynamical evolution
of the orbital radii except under highly specific mutual relationships, here
derived analytically.


title:
Irregular Magnetic Fields and the Far-Infrared Polarimetry of Dust
  Emission from Interstellar Clouds

abstract:
  (abridged) The polarized thermal radiation at far infrared and submillimeter
wavelengths from dust grains in interstellar clouds with irregular magnetic
fields is simulated. We show that the polarization properties of quiescent
clouds and of star-forming regions are consistent with Kolmogorov-like
turbulent magnetic fields that are comparable in magnitude to the uniform
component of the magnetic fields. If the beam size is much smaller than the
correlation length $L_{\rm corr}$ of the fields, the calculated percentage
polarization $p$ decreases to an asymptotic value when the number of
correlation lengths $N_{\rm corr}$ through the cloud exceeds a few tens. For
these values of $N_{\rm corr}$, the dispersion in the position angles
$\sigma_\alpha$ is still appreciable--decreasing to only about $20^{\circ}$.
However, when the finite size of a telescope beam is taken into account, the
asymptotic value of $p$ is reached for fewer correlation lengths (smaller
$N_{\rm corr}$) due to averaging over the beam; $\sigma_\alpha$ becames much
smaller and consistent with the observational data. The smoothing of the
polarization properties due to the combined effect of the thickness of the
cloud and the finite size of the beam can be described by a single variable
which we designate as the generalized number of correlation lengths. In
addition, we study various factors that may contribute to the decrease in the
linear polarization percentage with increasing intensity that is observed at
submillimeter and far infrared wavelengths in many, though not in all, dark
clouds (the "polarization hole" effect).


title: Constraining $\Omega_M$ and Dark Energy with Gamma-Ray Bursts

abstract:
  An $E_{\gamma,{\rm jet}}\propto {E'_p}^{1.5}$ relationship with a small
scatter for current $\gamma$-ray burst (GRB) data was recently reported, where
$E_{\gamma,{\rm jet}}$ is the beaming-corrected $\gamma$-ray energy and $E'_p$
is the $\nu F_\nu$ peak energy in the local observer frame. By considering this
relationship for a sample of 12 GRBs with known redshift, peak energy, and
break time of afterglow light curves, we constrain the mass density of the
universe and the nature of dark energy. We find that the mass density
$\Omega_M=0.35\pm^{0.15}_{0.15}$ (at the $1\sigma$ confident level) for a flat
universe with a cosmological constant, and the $w$ parameter of an assumed
static dark-energy equation of state $w=-0.84\pm^{0.57}_{0.83}$ ($1\sigma$).
Our results are consistent with those from type Ia supernovae. A larger sample
established by the upcoming {\em Swift} satellite is expected to provide
further constraints.


title:
A super massive black hole binary in 3C66B: future observational
  perspectives

abstract:
  Supermassive black hole binaries (SMBHBs) may exist in the centers of
galaxies and active galactic nuclei (AGN) and are expected to be fairly common
in the Universe as a consequence of merging processes between galaxies. The
existence of SMBHBs can be probed by looking for double nuclei in galaxy
centers or, more easily, detecting periodic behavior in the observed radio
light curves. In a recent paper, Sudou et al. \cite{sudou2003} announced the
first direct observation of an SMBHB. Using VLBI observations they found that
the unresolved radio core of the radio galaxy 3C66B shows a well defined
elliptical motion with a period of $1.05\pm 0.03$ yrs, implying the presence of
a couple of massive black holes in the center of the galaxy. In the present
paper we study the astrophysical implications of the existence of such an SMBHB
in 3C66B. In particular we focus on the information that can be obtained from
detecting a signal periodicity either in the $X$-ray and/or $\gamma$-ray light
curves as a consequence of the motion of the black holes. These observations
could be used to extract further information on the physical parameters of the
SMBHB and partially solve the system parameter degeneracy. The detection of the
gravitational wave spectrum emitted by such system may be used to completely
determine the physical parameters of the binary system.


title: Modeling the faint radio population: the nanoJy radio sky

abstract:
  The apparent change in the composition of the parent optical objects of radio
sources around 1 mJy (at 1.4 GHz) is now well established, although there is
still some debate about the relative importance of classical radio galaxies and
star-forming galaxies at sub-mJy levels (see e.g. Gruppioni et al. 1999;
Prandoni et al. 2001b). It is clear, however, that at microJy levels
star-forming galaxies are dominant (see Fomalont et al. 1997; Haarsma et al.
2000). Does this mean that SKA will basically tell us more about the history of
star formation than about the space density (and its cosmological evolution) of
active galactic nuclei? Using current best estimates of luminosity functions
(and their evolution) of various classes of objects, we show that the
increasing dominance of star-forming galaxies below 1 mJy is a natural
consequence of the different luminosity functions, but that this does not at
all mean that star-forming galaxies do necessarily dominate at all sub-mJy flux
levels and all redshifts.


title: Pulsar Magnetosphere : A General Relativistic Treatment

abstract:
  A fully general relativistic description of the pulsar magnetosphere is
provided. To be more concrete, a study of the pulsar magnetosphere is performed
in the context of general relativistic magnetohydrodynamics (MHD) employing the
so-called Grad-Shafranov approach. Not surprisingly, the resulting
Grad-Shafranov equations and all the other related general relativistic MHD
equations turn out to take essentially the same structures as those for the
(rotating) black hole magnetosphere. Other different natures between the two
cases including the structure of singular surfaces of MHD flows in each
magnetosphere are essentially encoded in the different spacetime (metric)
contents. In this way, the pulsar and the black hole magnetospheres can be
described in an unified fashion. Particularly, the direction of poloidal
currents circulating in the neutron star magnetosphere turns out to be the same
as that of currents circulating in the black hole magnetosphere which, in turn,
leads to the pulsar and the black hole spin-downs via the ``magnetic braking''.


title: Why the astrophysical Black Hole Candidates are not rotating black holes

abstract:
  It is believed that the basic component of the central engine of quasars,
micro-quasars, and energetic Gamma Ray Bursts are the rotating or the Kerr
Black Holes (BH)[1]. But by using a generic property[2-4] of the metric
components of a stationary axisymmertic rotating metric in its standard form},
namely, g_phi \phi = sin^2 theta g_theta theta, where phi is the azimuth angle
and theta is the polar angle measured from the axis of symmetry, we have found
the unexpected and surprising result that (i) in order to have a mass of a Kerr
BH m ge 0, it is necessary that its rotation parameter a=0 and if one insists
for an a ge 0, one must have m le 0! Thus if the suspected Black Hole
candidates with m >0 are really rotating they cannot be BHs at all which is in
agreement with some detailed analysis of recent observations[5-8]. However, if
it is assumed that such objects are strictly non-rotating, they could be
non-rotating Schwarzschild BHs (a=0) with m ge 0 if we ignore the physical
difficulties associated with the existence of such objects. This result calls
for new theoretical efforts to understand a vast range of astrophysical
phenomenon. If one derives the Kerr Metric in a straightforward manner by using
the Backlund transformation, it is seen that a=m sin phi. This relationship
confirms that a=m=0 for Kerr BHs.


title:
Has the black hole in XTE J1118+480 experienced an asymmetric natal
  kick?

abstract:
  We explore the origin of the Galactic high latitude black hole X-ray binary
XTE J1118+480, and in particular its birth location and the magnitude of the
kick received by the black hole upon formation in the supernova explosion. We
constrain the age of the companion to the black hole using stellar evolution
calculations between 2 Gyr and 5 Gyr, making an origin in a globular cluster
unlikely. We therefore argue that the system was born in the Galactic disk and
the supernova propelled it in its current high latitude orbit. Given the
current estimates on its distance, proper motion and radial velocity, we
back-trace the orbit of XTE J1118+480 in the Galactic potential to infer the
peculiar velocity of the system at different disk crossings over the last 5
Gyr. Taking into account the uncertainties on the velocity components, we infer
an average peculiar velocity of 183 \pm 31 km/s. The maximum velocity which the
binary can acquire by symmetric supernova mass loss is about 100 km/s, which is
2.7 sigma away from the mean of the peculiar velocity distribution. We
therefore argue that an additional asymmetric kick velocity is required. By
considering the orientation of the system relative to the plane of the sky, we
derive a 95% probability for a non null component of the kick perpendicular to
the orbital plane of the binary. The distribution of perpendicular velocities
is skewed to lower velocities with an average of 93^{+55}_{-60} km/s.


title: A New Astrophysical "Triptych": GRB030329/SN2003dh/URCA-2

abstract:
  We analyze the data of the Gamma-Ray Burst/Supernova GRB030329/SN2003dh
system obtained by HETE-2 (GCN [1]), R-XTE (GCN [2]), XMM (Tiengo et al. [3])
and VLT (Hjorth et al. [4]) within our theory (Ruffini et al. [5] and
references therein) for GRB030329. By fitting the only three free parameters of
the EMBH theory, we obtain the luminosity in fixed energy bands for the prompt
emission and the afterglow (see Fig.1). Since the Gamma-Ray Burst (GRB)
analysis is consistent with a spherically symmetric expansion, the energy of
GRB030329 is E = 2.1 * 10^{52} erg, namely ~ 2 * 10^3 times larger than the
Supernova energy. We conclude that either the GRB is triggering an
induced-supernova event or both the GRB and the Supernova are triggered by the
same relativistic process. In no way the GRB can be originated from the
supernova. We also evidence that the XMM observations (Tiengo et al. [3]), much
like in the system GRB980425/SN1998bw (Ruffini et al. [6], Pian et al. [7]),
are not part of the GRB afterglow, as interpreted in the literature (Tiengo et
al. [3]), but are associated to the Supernova phenomenon. A dedicated campaign
of observations is needed to confirm the nature of this XMM source as a newly
born neutron star cooling by generalized URCA processes.


title:
Stochastic Fermi Acceleration of sub-Relativistic Electrons and Its Role
  in Impulsive Solar Flares

abstract:
  We reexamine stochastic Fermi acceleration (STFA) in the low energy
(Newtonian) regime in the context of solar flares. The particle energization
rate depends a dispersive term and a coherent gain term. The energy dependence
of pitch angle scattering is important for determining the electron energy
spectrum. For scattering by whistler wave turbulence, STFA produces a
quasi-thermal spectrum. A second well-constrained scattering mechanism is
needed for STFA to match the observed 10-100keV non-thermal spectrum. We
suggest that STFA most plausibly acts as phase one of a two phase particle
acceleration engine in impulsive flares: STFA can match the thermal spectrum
below 10kev, and possibly the power law spectrum between 10 and 100keV, given
the proper pitch angle scattering. However, a second phase, such as shock
acceleration at loop tops, is likely required to match the spectrum above the
observed knee at 100keV. Understanding this knee, if it survives further
observations, is tricky.


title: Gauge-Invariant Temperature Anisotropies and Primordial Non-Gaussianity

abstract:
  We provide the gauge-invariant expression for large-scale cosmic microwave
background temperature fluctuations at second-order in perturbation theory. It
enables to unambiguously define the nonlinearity parameter f_NL which is used
by experimental collaborations to pin down the level of Non-Gaussianity in the
temperature fluctuations. Furthermore, it contains a primordial term encoding
all the information about the Non-Gaussianity generated at primordial epochs
and about the mechanism which gave rise to cosmological perturbations, thus
neatly disentangling the primordial contribution to Non-Gaussianity from the
one caused by the post-inflationary evolution.


title:
Chemically inhomogeneous photoionization modelling of the planetary
  nebula SMC N87

abstract:
  We present results from dual-abundance photoionization modelling of the
planetary nebula SMC N87 (SMC-SMP 27). The models succesfully resolve the
observed discrepancy between the heavy-element abundances derived
semiempirically from the optical recombination lines and the collisionally
excited lines, incorporating a H-poor gaseous component in the main body of the
PN. The mass of the H-poor plasma is only about 1 per cent of the total PN
ionized mass and its electron temperature is 6300 K. The average heavy element
abundances in the PN approximate those returned by the ICF method using the
collisionally excited lines (for t^2 = 0), while the He abundance is less than
the one found empirically. The C/O ratio in the H-depleted component is smaller
than in the normal metallicity gas, in contrast to stellar nucleosynthetic
models which predict the opposite for processed material ejected from an
evolved PN nucleus.


title: Two New X-ray/Optical/Radio Supernova Remnants in M31

abstract:
  We compare a deep (37 ks) Chandra ACIS-S image of the M31 bulge to Local
Group Survey narrow-band optical data and Very Large Array (VLA) radio data of
the same region. Our precisely registered images reveal two new optical shells
with X-ray counterparts. These shells have sizes, [S II]/H-alpha flux ratios,
and X-ray spectral properties typical of supernova remnants (SNRs) with ages of
9$^{+3}_{-4}$ and 17$^{+6}_{-9}$ kyr. Analysis of complementary VLA data
reveals the radio counterparts, further confirming that they are SNRs. We
discuss and compare the properties and morphologies of these SNRs at the
different wavelengths.


title: Primordial constraint on the spatial dependence of the Newton constant

abstract:
  A Nordtvedt effect at cosmological scales affects the acoustic oscillations
imprinted in the cosmic microwave background. The gravitational baryonic mass
density of the universe is inferred at the first peak scale from WMAP data. The
independent determination of the inertial baryonic mass density through the
measurement of the deuterium abundance in the framework of standard big bang
nucleosynthesis leads to a new constraint on a possible violation of the strong
equivalence principle at the recombination time.


title: Extended Molecular Gas in the Nearby Starburst Galaxy Maffei 2

abstract:
  We present a 9'x9' fully-sampled map of the CO J=1-0 emission in the nearby
starburst galaxy Maffei 2 obtained at the Five College Radio Astronomy
Observatory. The map reveals previously known strong CO emission in the central
starburst region as well as an extended asymmetric distribution with bright CO
lines at the ends of the bar and in a feature at the north-east edge of the
molecular disk. This northern feature, proposed previously to be an interacting
companion galaxy, could be a dwarf irregular galaxy, although the CO data are
also consistent with the feature being simply an extension of one of the spiral
arms. We estimate the total molecular gas mass of Maffei 2 to be (1.4-1.7)x10^9
Mo or ~3-4% of its dynamical mass. Adopting the recently determined lower value
for the CO-to-H2 conversion factor in the central region, our data lead to the
surprising result that the largest concentrations of molecular gas in Maffei 2
lie at the bar ends and in the putative dwarf companion rather than in the
central starburst. A gravitational stability analysis reveals that the extended
disk of Maffei 2 lies above the critical density for star formation; however,
whether the central region is also gravitationally unstable depends both on the
details of the rotation curve and the precise value of the CO-to-H2 conversion
factor in this region.


title:
Viscous Flows and Conditions for Existence of Shocks in Relativistic
  Magnetic Hydrodynamics

abstract:
  We present a criterion for a shock wave existence in relativistic magnetic
hydrodynamics with an arbitrary (possibly non-convex) equation of state. The
criterion has the form of algebraic inequality that involves equation of state
of the fluid; it singles out the physical solutions and it can be easily
checked for any discontinuity satisfying concervation laws. The method of proof
uses introduction of small viscosity into the coupled set of equations of
motion of ideal relativistic fluid with infinite conductivity and Maxwell
equations.


title: Radio Continuum Emission in Polar-Ring Galaxies

abstract:
  We have used the Very Large Array aperture synthesis telescope to conduct a
radio continuum survey of polar-ring galaxies, at 20cm and 6cm. Forty objects
were observed at 20cm with 5" resolution. Twenty (50%) of the program sources
were detected at 20cm, down to our 5-sigma limit of 0.5 mJy/beam. This
detection rate is similar to those in surveys with comparable sensitivity for
early-type galaxies without polar rings. Sixteen of the objects we detected at
20cm were also observed at 6cm. We show radio continuum maps for the five
objects in our sample that have noticeably extended emission. Our spatial
resolution was sufficient to distinguish between emission originating in the
host galaxy from that in the polar ring. The radio morphology of the extended
sources, as well as the radio to far-infrared flux ratio and the radio spectral
indices of our detected sources, indicate that star formation, not nuclear
activity, is the dominant source of the radio continuum emission in polar-ring
galaxies. However, the implied star-formation rates are modest, and only one of
our sample galaxies will consume its supply of cool gas within 500 Myr.


title: Black hole growth by accretion

abstract:
  We show that black holes grow substantially by accretion at close to
Eddington rates. Using a complete sample of soft X-ray selected AGNs,
  Grupe & Mathur (2004) have shown that narrow line Seyfert 1 galaxies, as a
class, lie below the M_BH-sigma relation of normal galaxies. Some NLS1s,
however, lie on or close to the M_BH-sigma relation. Here we show that not all
NLS1s accrete at close to Eddington rates: those with low {L/L_{Eddington}} are
close to the M_BH-sigma relation, and those with high {L/L_{Eddington}} are
far. With various tests in this paper, we argue that black holes grow in mass
substantially in their high-accretion phase and approach the M_BH-sigma
relation over time. The mass growth in a low accretion phase, as in BLS1s and
also in some NLS1s, appears to be insignificant. Any theoretical model
attempting to explain the M_BH-sigma relation will have to explain the above
observations.


title:
On an Analytical Framework for Voids: Their abundances, density profiles
  and local mass functions

abstract:
  We present a general analytical procedure for computing the number density of
voids with radius above a given value within the context of gravitational
formation of the large scale structure of the universe out of Gaussian initial
conditions. To this end we develop an accurate (under generally satisfied
conditions) extension of unconditional mass function to constrained
environments, which allowes us both to obtain the number density of collapsed
objects of certain mass at any distance from the center of the void, and to
derive the number density of voids defined by those collapsed objects. We have
made detailed calculations for the spherically averaged mass density and halo
number density profiles for individual voids. We also present a formal
expression for the number density of voids defined by galaxies of a given type
and luminosity. This expression contains the probability for a collapsed object
of certain mass to host a galaxy of that type and luminosity as a function of
the environmental density. We propose a procedure to infer this function, which
may provide useful clues as to the galaxy formation process, from the observed
void densities.


title: Celestial position of the companion of PSR J1740-5340

abstract:
  We present optical astrometry of archival ground and space based imaging of
the companion to PSR J1740-5340. The optical position of the companion is
significantly offset from the timing position of the pulsar. We briefly
investigate the effects of this inconsistency on other timing parameters and
compare our position with an improved position of PSR J1740-5340 from recent,
preliminary, timing results.


title:
Correlation between Hard X-ray Peak Flux and Soft X-ray Peak Flux in the
  Outburst Rise of Low Mass X-ray Binaries

abstract:
  We have analyzed {\it Rossi} X-ray timing explorer (RXTE) pointed
observations of the outbursts of black hole and neutron star soft X-ray
transients in which an initial low/hard state or `island' state, followed by a
transition to a softer state, was observed. In three sources, the black hole
transient XTE J1550-564, the neutron star transient Aquila X-1 and a
quasi-persistent neutron star low mass X-ray binary (LMXB) 4U 1705-44, two such
outbursts were found. We find that the flux of the soft X-ray peak, which lags
the hard X-ray peak by a few days to several weeks, scales with the flux of the
hard X-ray peak. We conclude that we are able to predict the soft X-ray
outburst peak flux based on the `preceding' hard X-ray peak flux, implying an
early set up of the outbursts. We also find that the X-ray luminosity
corresponding to the peak of the hard X-ray flux, which corresponds to the
X-ray luminosity of the start of the hard-to-soft state transition, varies by a
factor of about 2. If the accretion geometry early in the outburst rise is
composed of two flows (e.g. a hot sub-Keplerian halo flow and a Keplerian disk
flow, or an outflow and a Keplerian disk flow), the correlation indicates that
the two flows are initially related, probably due to processes in the outer
part of the accretion disk. We discuss constraints on a single flow model and a
disk-jet model from these observations.


title:
Australia Telescope Compact Array Survey of Candidate Ultra-Compact and
  Buried HII Regions in the Magellanic Clouds

abstract:
  We present a systematic survey for ultracompact HII (UCHII) regions in the
Magellanic Clouds. Understanding the physics of massive star formation (MSF) is
a critical astrophysical problem. The study of MSF began in our galaxy with
surveys of UCHII regions, but before now this has not been done for other
galaxies. We selected candidates based on their Infrared Astronomical Satellite
(IRAS) colors and imaged them at 3 and 6 cm with the Australia Telescope
Compact Array (ATCA). Nearly all of the observed regions contain compact radio
sources consistent with thermal emission. Many of the sources are related to
optically visible HII regions, and often the radio emission traces the youngest
and densest part of the HII region. The luminosity function and number
distribution of Lyman continuum fluxes of the compact radio sources are
consistent with standard stellar and cluster initial mass functions. This type
of systematic assessment of IRAS diagnostics is important for interpreting
Spitzer Space Telescope data, which will probe similar physical scales in
nearby galaxies as IRAS did in the Magellanic Clouds.


title: On the Nature of the Heat Source for Damped Lya Systems

abstract:
  We investigate the heat source of the neutral gas comprising DLAs. Unlike the
Lya forest, where the extragalactic background radiation field ionizes and
heats the gas, we find that grain photoelectric heating by the FUV background
is not sufficient to balance the C II 158um cooling rate inferred from DLAs. In
these systems, a local energy source is required. We show that in the case of
the z=1.919 DLA toward Q2206-19, the local source is FUV emission from the
associated galaxy found by Moller et al (2002): the mean intensity inferred
from photometry is in good agreement with the intensity Jnu required to explain
the cooling rate. The FUV mean intensity predicted for a cold neutral medium
(CNM) model, Jnu=(1.7+2.7-1.0)x10^(-18) cgs (95% c.l.), is the largest expected
from our CII* study of 45 DLAs. This may explain why this is the only confirmed
DLA yet detected in emission at z>1.9. We argue that in most DLAs with detected
CII* absorption, Jnu is between 10^{-19} and 10^{-18} and heats the gas which
is a CNM. By contrast, in most DLAs with upper limits on CII* absorption the
gas is a warm neutral medium (WNM). Surprisingly, the upper limits are
compatible with the same range of Jnu values suggesting the majority of DLAs
are heated by radiation fields generated by a limited range of star formation
rates per unit H I area, between 10^{-3} and 10^{-2} Msol/kpc^2. We also show
that CII* absorption is unlikely to arise in gas that is ionized.


title:
A close binary nucleus in the most oxygen-poor planetary nebula PN G
  135.9+55.9

abstract:
  We report FUSE and new deep optical spectroscopic observations of PN G
135.9+55.9, the most oxygen-poor planetary nebula located in the Galactic halo.
These observations allow us to estimate the gravity of the central star by
fitting the profile of the observed H I absorption lines with NLTE model
atmospheres. Our best fit implies that the central star is still in a pre-white
dwarf stage. We also find large variability of the radial velocities of the
absorption component of the Balmer lines on a timescale of hours. This is
direct evidence that the nucleus of PN G 135.9+55.9 is a close binary. The
large semi-amplitude of the radial velocity variations and the probably short
period suggest a massive compact companion, likely a white dwarf. Although our
orbital solutions are very preliminary, they indicate that the total mass of
the system probably exceeds the Chandrasekhar limit. If confirmed, this would
make this binary the potential progenitor of a type Ia supernova.


title: Observations of the Diffuse FUV Background with FUSE

abstract:
  We have used observations taken under the FUSE S405/S505 channel realignment
program to explore the diffuse FUV (1000 - 1200 \AA) radiation field. Of the 71
independent locations in that program, we have observed a diffuse signal in 32,
ranging in brightness from 1600 photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$ \AA$^{-1}$
to a maximum of $2.9 \times 10^5$ photons cm$^{-2}$ s$^{-1}$ sr$^{-1}$
\AA$^{-1} in Orion. The FUSE data confirm that the diffuse FUV sky is patchy
with regions of intense emission, usually near bright stars, but also with dark
regions, even at low Galactic latitudes. We find a weak correlation between the
FUV flux and the 100 micron ratio but with wide variations, perhaps due to
differences in the local radiation field.


title:
Quantitative Morphological Analysis of the HDF--North and HDF-South. I.
  Early- and Late-type Luminosity-Size Relations of galaxies out to z~1

abstract:
  Based on drizzled F606W and F814W images, we present quantitative structural
parameters in the V-band rest-frame for all galaxies with z<1 and
I_814(AB)<24.5 mag in the Hubble Deep Fields North and South. Our structural
parameters are based on a two-component surface brightness distribution using a
Sersic bulge and an exponential disc. Detailed simulations and comparisons with
previous work are presented. The luminosity-size distribution of early-type
galaxies is consistent with the hypothesis that their structural properties
were already in place by z~1 and have evolved passively since then; early-type
galaxies were ~1.35(+-0.1) mag brighter in rest-frame V-band luminosity at
z~0.7 than now. Compared to present day late-type galaxies, those at z~0.7 with
L_V>0.2x10^{10} h^{-2} L_sun show a moderate decrease (~30(+-10)%) in size (or
interpreted differently, a decrease of ~0.77(+-0.30) mag in the central surface
brightness) at a given luminosity. Finally, we make a comparison of our results
with the infall and hierarchical models.


title:
FUSE Observation of the Non-Radiative Collisionless Shock in the Remnant
  of SN1006

abstract:
  The appearance of the young supernova remnant SN1006 is dominated by emission
from non-radiative shocks in the NE and NW regions. At X-ray energies the
northeast shock exhibits predominantly nonthermal synchrotron emission, while
the northwest shock exhibits a thermal spectrum. We present far ultraviolet
spectra of the northeast (NE) and northwest (NW) portions of SN 1006 acquired
with the Far Ultraviolet Spectroscopic Explorer (FUSE). We have detected
emission lines of O VI (1032, 1038 A) and broad Ly-beta (1025 A) in the NW
filament, but detect no emission lines in the NE region. We observed in the NW
an O VI intensity of measured an O VI line width of 2100 km s-1 at a position
where the H-alpha width was measured to be 2290 km s-1(Ghavamian et al. 2002).
This implies less than mass proportional heating of the ions. Using the ratio
of intensities, I(NW)/I(NE) ~ n(NW)/n(NE), the density ratio of the two regions
is found to be >4, a value that is with the uncertainties of the ratio of 2.5
measured by Long et al. (2003). The derived O VI kinetic temperature is
compared to previous estimates of electron, proton, and ion temperatures in the
remnant to study the relative heating efficiency of various species at the
shock front. The degree of postshock temperature equilibration may be crucial
to particle acceleration since the temperature of each species determines the
number of high speed particles available for injection into an acceleration
process that could produce Galactic cosmic rays.


title: Spheroidal galactic halos and mirror dark matter

abstract:
  Mirror matter has been proposed as a dark matter candidate. It has several
very attractive features, including automatic stability and darkness, the
ability to mimic the broad features of cold dark matter while in the linear
density perturbation regime, and consistency with all direct dark matter search
experiments, both negative (e.g. CDMS II) and positive (DAMA). In this paper we
consider an important unsolved problem: Are there plausible reasons to explain
why most of the mirror matter in spiral galaxies exists in the form of gaseous
{\it spheroidal} galactic halos around ordinary matter {\it disks}? We compute
an order-of-magnitude estimate that the mirror photon luminosity of a typical
spiral galaxy today is around $10^{44}$ erg/s. Interestingly, this rate of
energy loss is similar to the power supplied by ordinary supernova explosions.
We discuss circumstances under which supernova power can be used to heat the
gaseous part of the mirror matter halo and hence prevent its collapse to a
disk. The {\it macro}scopic ordinary-mirror asymmetry plays a fundamental role
in our analysis.


abstract:
  We present XMM-Newton observations of the eclipsing polar EP Dra which cover
nearly 3 binary orbital cycles. The X-ray and UV data show evidence for a
prominent dip before the eclipse which is due to the accretion stream obscuring
the accretion region. The dip ingress is rapid in hard X-rays suggesting there
is a highly collimated core of absorption. We find that a different level of
absorption column density is required to match the observed count rates in
different energy bands. We propose that this is due to the fact that different
absorption components should be used to model the reprocessed X-rays, the
shocked X-ray component and the UV emission and explore the affect that this
has on the resulting fits to the spectrum. Further, there is evidence that
absorption starts to obscure the softer X-rays shortly after the onset of the
bright phase. This suggests that material is threaded by an unusually wide
range of magnetic field lines, consistent with the suggestion of Bridge et al.
We find that the period is slightly greater than that determined by Schwope &
Mengel.


title:
Beryllium in turnoff stars of NGC6397: early Galaxy spallation,
  cosmochronology and cluster formation

abstract:
  We present the first detection of beryllium in two turnoff stars of the old,
metal-poor globular cluster NGC 6397. The beryllium lines are clearly detected
and we determine a mean beryllium abundance of log(Be/H)=-12.35 +/- 0.2. The
beryllium abundance is very similar to that of field stars of similar Fe
content. We interpret the beryllium abundance observed as the result of primary
spallation of cosmic rays acting on a Galactic scale, showing that beryllium
can be used as a powerful cosmochronometer for the first stellar generations.
With this method, we estimate that the cluster formed 0.2-0.3 Gyr after the
onset of star formation in the Galaxy, in excellent agreement with the age
derived from main sequence fitting. From the same spectra we also find low O
(noticeably different for the two stars) and high N abundances, suggesting that
the original gas was enriched in CNO processed material. Our beryllium results,
together with the N, O, and Li abundances, provide insights on the formation of
this globular cluster, showing that any CNO processing of the gas must have
occurred in the protocluster cloud before the formation of the stars we observe
now. We encounter, however, difficulties in giving a fully consistent picture
of the cluster formation, able to explain the complex overall abundance
pattern.


title: The Compact Group of Galaxies HCG 31 is in an early phase of merging

abstract:
  We have obtained high spectral resolution (R = 45900) Fabry-Perot velocity
maps of the Hickson Compact Group HCG 31 in order to revisit the important
problem of the merger nature of the central object A+C and to derive the
internal kinematics of the candidate tidal dwarf galaxies in this group. Our
main findings are: (1) double kinematic components are present throughout the
main body of A+C, which strongly suggests that this complex is an ongoing
merger (2) regions $A2$ and E, to the east and south of complex A+C, present
rotation patterns with velocity amplitudes of $\sim 25 km s^{-1}$ and they
counterrotate with respect to A+C, (3) region F, which was previously thought
to be the best example of a tidal dwarf galaxy in HCG 31, presents no rotation
and negligible internal velocity dispersion, as is also the case for region
$A1$. HCG 31 presents an undergoing merger in its center (A+C) and it is likely
that it has suffered additional perturbations due to interactions with the
nearby galaxies B, G and Q.


title: Powerful gravitational-wave bursts from supernova neutrino oscillations

abstract:
  During supernova core collapse and bounce resonant active-to-active, as well
as active-to-sterile, neutrino ($\nu$) oscillations can take place. Over this
phase weak magnetism increases antineutrino mean free paths, and thus its
luminosity. Because oscillations feed mass-energy into the target $\nu$
species, the large mass-squared difference between $\nu$ states implies a huge
amount of power to be given off as gravitational waves (GWs) due to the
universal {\it spin-rotation} and the spin-magnetic coupling driven $\nu$
anisotropic flow, which is coherent over the oscillation length. The spacetime
strain produced is about two orders of magnitude larger than those from $\nu$
difussion or neutron star matter anisotropies. GWs observatories as LIGO,
VIRGO, GEO-600, TAMA-300, etc., can search for these bursts far out to the
VIRGO cluster of galaxies.


title: Detection of the Sgr A* activity at 3.8 and 4.8 microns with NACO

abstract:
  L'-band (lambda=3.8 microns) and M'-band (lambda=4.8 microns) observations of
the Galactic Center region, performed in 2003 at VLT (ESO) with the adaptive
optics imager NACO, have lead to the detection of an infrared counterpart of
the radio source Sgr A* at both wavelengths. The measured fluxes confirm that
the Sgr A* infrared spectrum is dominated by the synchrotron emission of
nonthermal electrons. The infrared counterpart exhibits no significant short
term variability but demonstrates flux variations on daily and yearly scales.
The observed emission arises away from the position of the dynamical center of
the S2 orbit and would then not originate from the closest regions of the black
hole.


title: The helium abundances in HgMn and normal stars

abstract:
  The parameter-free model of diffusion in the atmospheres of HgMn stars
(Michaud 1986; Michaud et al 1979) predicts that helium should sink below the
He II ionization zone in order that diffusion of other elements may take place,
and that all HgMn stars should have deficits of helium in their photospheres,
with a minimum deficit of 0.3 dex. In this study, the Smith & Dworetsky (1993)
sample of HgMn stars and normal comparison stars is examined, and the helium
abundances determined by spectrum synthesis using echelle spectra taken at Lick
Observatory and the AAT. The prediction is confirmed; all HgMn stars are
deficient in He by as much as 1.5 dex. Also, two HgMn stars, HR7361 and HR7664,
show clear evidence of helium stratification.


title: Gravitational Wave asteroseismology revisited

abstract:
  The frequencies and damping times of the non radial oscillations of neutron
stars are computed for a set of recently proposed equations of state (EOS)
which describe matter at supranuclear densites. These EOS are obtained within
two different approaches, the nonrelativistic nuclear many-body theory and the
relativistic mean field theory, that model hadronic interactions in different
ways leading to different composition and dynamics. Being the non radial
oscillations associated to the emission of gravitational waves, we fit the
eigenfrequencies of the fundamental mode and of the first pressure and
gravitational-wave mode (polar and axial) with appropriate functions of the
mass and radius of the star, comparing the fits, when available, with those
obtained by Andersson and Kokkotas in 1998. We show that the identification in
the spectrum of a detected gravitational signal of a sharp pulse corresponding
to the excitation of the fundamental mode or of the first p-mode, combined with
the knowledge of the mass of the star - the only observable on which we may
have reliable information - would allow to gain interesting information on the
composition of the inner core. We further discuss the detectability of these
signals by gravitational detectors.


title: The diffusive instability of kaon condensate in neutron star matter

abstract:
  The beta equilibrated dense matter with kaon condensate is analyzed with
respect to extended stability conditions including charge fluctuations. This
kind of the diffusive instability, appeared to be common property in the kaon
condensation case. Results for three different nuclear models are presented.


title: Relativistic Shocks and Ultra High Energy Cosmic Ray Origin

abstract:
  The current status of the theory of particle acceleration at relativistic
shocks is presented, and a few possible scenarios for ultra-high-energy cosmic
ray production at such shocks are briefly discussed.


title: Bose-Einstein Condensation, Dark Matter and Acoustic Peaks

abstract:
  Scalar mediated interactions among baryons extend well above the Compton
wavelength, when they are embedded in a Bose-Einstein condensate composed of
the mediating particles. Indeed, this non-trivial environment results in an
infinite-ranged interaction. We show that if the Dark Matter of the Universe is
composed of such a condensate, the imprints of an interaction between baryonic
and Dark Matter could be manifest as anomalies in the peak structure of the
Cosmic Microwave Background.


title: Bar-halo Friction in Galaxies I: Scaling Laws

abstract:
  It has been known for some time that rotating bars in galaxies slow due to
dynamical friction against the halo. However, recent attempts to use this
process to place constraints on the dark matter density in galaxies and
possibly also to drive dark matter out of the center have been challenged. This
paper uses simplified numerical experiments to clarify several aspects of the
friction mechanism. I explicitly demonstrate the Chandrasekhar scaling of the
friction force with bar mass, halo density, and halo velocity dispersion. I
present direct evidence that exchanges between the bar and halo orbits at major
resonances are responsible for friction and study both individual orbits and
the net changes at these resonances. I also show that friction alters the phase
space density of particles in the vicinity of a major resonance, which is the
reason the magnitude of the friction force depends on the prior evolution. I
demonstrate that bar slow down can be captured correctly in simulations having
modest spatial resolution and practicable numbers of particles. Subsequent
papers in this series delineate the dark matter density that can be tolerated
in halos of different density profiles.


title:
Composite Accretion Disk and White Dwarf Photosphere Analyses of the
  FUSE and HST Observations of EY Cygni

abstract:
  We explore the origin of FUSE and HST STIS far UV spectra of the dwarf nova,
EY Cyg, during its quiescence using \emph{combined} high gravity photosphere
and accretion disk models as well as model accretion belts. The best-fitting
single temperature white dwarf model to the FUSE plus HST STIS spectrum of EY
Cygni has T$_{eff} = 24,000$K, log $g = 9.0$, with an Si abundance of 0.1 x
solar and C abundance of 0.2 x solar but the distance is only 301 pc. The
best-fitting composite model consists of white dwarf with T$_{eff} = 22,000$K,
log $g = 9$, plus an accretion belt with T$_{belt} = 36,000$K covering 27% of
the white dwarf surface with V$_{belt} sin i = 2000$ km/s. The accretion belt
contributes 63% of the FUV light and the cooler white dwarf latitudes
contribute 37%. This fit yields a distance of 351 pc which is within 100 pc of
our adopted distance of 450 pc. EY Cyg has very weak C {\sc iv} emission and
very strong N {\sc v} emission, which is atypical of the majority of dwarf
novae in quiescence. We also conducted a morphological study of the
surroundings of EY Cyg using direct imaging in narrow nebular filters from
ground-based telescopes. We report the possible detection of nebular material^M
associated with EY Cygni. Possible origins of the apparently large N {\scv}/C
{\sc iv} emission ratio are discussed in the context of nova explosions,
contamination of the secondary star and accretion of nova abundance-enriched
matter back to the white dwarf via the accretion disk or as a descendant of a
precursor binary that survived thermal timescale mass transfer. The scenario
involving pollution of the secondary by past novae may be supported by the
possible presence of a nova remnant-like nebula around EY Cyg.