title: The faint counterparts of MAMBO mm sources near the NTT Deep Field

abstract:
  We discuss identifications for 18 sources from our MAMBO 1.2mm survey of the
region surrounding the NTT Deep Field. We have obtained accurate positions from
Very Large Array 1.4GHz interferometry and in a few cases IRAM mm
interferometry, and have also made deep BVRIzJK imaging at ESO. We find
thirteen 1.2mm sources associated with optical/near-infrared objects in the
magnitude range K=19.0 to 22.5, while five are blank fields at K>22. The median
redshift of the radio-identified mm sources is ~2.6 from the radio/mm
estimator, and the median optical/near-infrared photometric redshifts for the
objects with counterparts ~2.1. This suggests that those radio-identified mm
sources without optical/near-infrared counterparts tend to lie at higher
redshifts than those with optical/near-infrared counterparts. Compared to
published identifications of objects from 850micron surveys of similar depth,
the median K and I magnitudes of our counterparts are roughly two magnitudes
fainter and the dispersion of I-K colors is less. Real differences in the
median redshifts, residual mis-identifications with bright objects, cosmic
variance, and small number statistics are likely to contribute to this
significant difference, which also affects redshift measurement strategies. We
discuss basic properties of the near-infrared/(sub)mm/radio spectral energy
distributions of our galaxies and of interferometrically identified submm
sources from the literature. From a comparison with submm objects with
CO-confirmed spectroscopic redshifts we argue that roughly two thirds of the
(sub)mm galaxies are at z>~2.5. This fraction is probably larger when including
sources without radio counterparts. (abridged)


title:
Ejection of the inner accretion disk in GRS 1915+105: the magnetic
  rubber-band effect

abstract:
  We examine theoretically the behaviour of the inner accretion disk in GRS
1915+105 when soft X-ray dips are present in the X-ray light curve. We assume
the presence of a radial shock in the accretion disk, as in some of the Two
Component Advective Flow (TCAF) solutions. We discuss the behaviour of the flux
tubes inside a TCAF (which we name Magnetized TCAF or MTCAF model for brevity)
and compare various competing forces on the flux tubes. In this MTCAF model, we
find that the magnetic tension is the strongest force in a hot plasma of
temperature $\gsim 10^{10}$K and as a result, magnetic flux tubes entering in
this region collapse catastrophically, thereby occasionally evacuating the
inner disk. We postulate that this magnetic `rubber-band' effect induced
evacuated disk matter produces the blobby components of outflows and IR/radio
jets. We derive the size of the post-shock region by equating the time scale of
the Quasi-Periodic Oscillations to the infall time of accreting matter in the
post-shock region and found the shock location to be $\sim 45-66 r_g$. We
calculate the transition radius $r_{tr}$, where the Keplerian disk deviates
into a sub-Keplerian flow, to be $\sim 320r_g$. Based on the derived X-ray
spectral parameters, we calculate the mass of this region to be $\sim10^{18}$g.
We conclude that during the X-ray dips the matter in the post-shock region,
which manifests itself as the thermal-Compton component in the X-ray spectrum,
is ejected, along with some sub-Keplerian matter in the pre-shock region.


title:
Helical jets in blazars. Interpretation of the multifrequency long-term
  variability of AO 0235+16

abstract:
  The long-term variability of the multiwavelength blazar emission can be
interpreted in terms of orientation variations of a helical, inhomogeneous,
non-thermally emitting jet, possibly caused by the orbital motion of the parent
black hole in a binary system (Villata & Raiteri 1999). The helical-jet model
is here applied to explain the quasi-periodic radio-optical light curves and
the broad-band spectral energy distributions (SEDs) of the BL Lac object AO
0235+16. Through a suitable choice of the model parameters, the helix rotation
can well account for the periodicity of the main radio and optical outbursts
and for the corresponding SED variability, while the interspersed minor radio
events could be interpreted as due either to some local distortions of the
helical structure or to other phenomena contributing to the source emission. In
particular, the probable existence of flow instabilities provides a viable
interpretation for the non-periodic features.


title: Collapse and expansion in the bright-rimmed cloud SFO 11NE

abstract:
  We report the results of a search for the double-peaked blue-skewed infall
signature in the bright-rimmed cloud core SFO 11NE SMM1. Observations of the
optically thick HCO$^{+}$ and optically thin H$^{13}$CO$^{+}$ J=3--2 lines
reveal that there is indeed a characteristic double-peaked line profile, but
skewed to the red rather than the blue. Modelling of the dust continuum
emission and line profiles show that the motions within SFO 11NE SMM1 are
consistent with a collapsing central core surrounded by an expanding outer
envelope. We show that the collapse is occurring at a similar rate to that
expected onto a single solar-mass protostar and is unlikely to represent the
large-scale collapse of gas onto the infrared cluster seen at the heart of SFO
11NE SMM1. The outer envelope is expanding at a much greater rate than that
expected for a photoevaporated flow from the cloud surface. The modelled
expansion is consistent with the bulk cloud re-expansion phase predicted by
radiative-driven implosion models of cometary clouds.


title:
Model Dependence of Transonic Properties of Accretion Flows Around Black
  Holes

abstract:
  We analytically study how the behaviour of accretion flows changes when the
flow model is varied. We study the transonic properties of the conical flow, a
flow of constant height and a flow in vertical equilibrium and show that all
these models are basically identical provided the polytropic constant is
suitably changed from one model to another. We show that this behaviour is
extendible even when standing shocks are produced in the flow. The parameter
space where shocks are produced remain roughly identical in all these models
when the same transformation among the polytropic indices is used. We present
applications of these findings.


title: E.A.Milne and the Universes of Newton and Relativistic Cosmology

abstract:
  Here the 1930's work of Milne on the relationship between the universes of
relativistic cosmology and those which follow from Newtonian theory is
reviewed. The extension to the case of non-zero pressure is considered also. In
each case, any assumptions made are noted and the thermodynamic implications of
these are explored in the final section.


title: Computation of outflow rates from accretion disks around black holes

abstract:
  We self-consistently estimate the outflow rate from the accretion rates of an
accretion disk around a black hole in which both the Keplerian and the
sub-Keplerian matter flows simultaneously. While Keplerian matter supplies
soft-photons, hot sub-Keplerian matter supplies thermal electrons. The
temperature of the hot electrons is decided by the degree of inverse
Comptonization of the soft photons. If we consider only thermally-driven flows
from the centrifugal pressure-supported boundary layer around a black hole, we
find that when the thermal electrons are cooled down, either because of the
absence of the boundary layer (low compression ratio), or when the surface of
the boundary layer is formed very far away, the outflow rate is negligible. For
an intermediate size of this boundary layer the outflow rate is maximal. Since
the temperature of the thermal electrons also decides the spectral state of a
black hole, we predict that the outflow rate should be directly related to the
spectral state.


title: Molecular Gas Chemistry in AGN I. The IRAM Survey of NGC1068

abstract:
  There is observational evidence that nuclear winds and X-rays can heavily
influence the physical conditions and chemical abundances of molecular gas in
the circumnuclear disks (CND) of Active Galactic Nuclei (AGN). In this paper we
probe the chemical status of molecular gas in the CND of NGC1068, a
prototypical Seyfert 2 galaxy. Precedent claims that the chemistry of molecular
gas in the nucleus of NGC1068 is abnormal by galactic standards were based on
the high HCN/CO luminosity ratio measured in the CND. Results from new
observations obtained in this survey have served to derive abundances of
molecular species such as SiO, CN, HCO+, HOC+, H13CO+ and HCO. These estimates
are complemented by a re-evaluation of molecular abundances for HCN, CS and CO,
based on previously published single-dish and interferometer observations of
NGC1068. We report on the first detection of SiO emission in the CND of
NGC1068. The estimated large abundance of SiO in the CND, X(SiO)~5-10x10^{-9},
cannot be attributed to shocks related to star formation, as there is little
evidence of a recent starburst in the nucleus of NGC1068. Alternatively, we
propose that silicon chemistry is driven by intense X-ray processing of
molecular gas. We also report on the first extragalactic detection of the
reactive ion HOC+. Most remarkably, the estimated HCO+/HOC+ abundance ratio in
the nucleus of NGC1068, ~30-80, is the smallest ever measured in molecular gas.
The abundances derived for all molecules that have been the subject of this
survey are compared with the predictions of models invoking either
oxygen-depletion or X-ray chemistry in molecular gas. Our conclusions favour an
overall scenario where the CND of NGC1068 has become a giant X-ray Dominated
Region (XDR).


title:
The effect of cooling on time dependent behaviour of accretion flows
  around black holes

abstract:
  We present the results of several numerical simulations of two dimensional
axi-symmetric accretion flows around black holes using Smoothed Particle
Hydrodynamics (SPH) in the presence of cooling effects. We consider both
stellar black holes and super-massive black holes. We observe that due to {\it
both radial and vertical oscillation} of shock waves in the accretion flow, the
luminosity and average thermal energy content of the inner disk exhibit very
interesting behaviour. When power density spectra are taken, quasi-periodic
variabilities are seen at a few Hz and also occasionally at hundreds of Hz for
stellar black holes. For super-massive black holes, the time scale of the
oscillations ranges from hours to weeks. The power density spectra have a flat
top behavior with average {\it rms} amplitude of a few percent and a broken
power-law behavior. The break frequency is generally found to be close to the
frequency where the shock oscillates.


title: Properties of the linearly polarized radiation from PSR B0950+08

abstract:
  Measurements of average pulse profiles made with a single linear polarization
over the range 41-112 MHz are presented for PSR B0950+08. We show that the
observed variable structure of the pulse profiles is a result of Faraday
sinusoidal modulation of the pulse intensity with frequency. The rotation
measure corresponding to this effect, RM = 4 rad/m^2, is about 3 times greater
than the tabulated value of RM = 1.35 rad/m^2.


title: Symbiotic Stars in the Magellanic Clouds

abstract:
  Orbital periods and other parameters of symbiotic binaries in the LMC and SMC
are presented and discussed. In particular, the symbiotic stars in the MCs are
compared with those in the Milky Way.


title:
Possible Photometric Evidence of Ejection of Bullet Like Features in the
  Relativistic Jet source SS433

abstract:
  SS433 is well-known for its precessing twin jets having optical bullets
inferred through {\it spectroscopic} observation of $H_\alpha$ lines. Recently,
Chakrabarti et al. (2002) described processes which may be operating in
accretion disk of SS433 to produce these bullets. In a recent multi-wavelength
campaign, we find sharp rise in intensity in time-scales of few minutes in
X-rays, IR and radio waves through {\it photometric} studies. We interpret them
to be possible evidence of ejection of bullet-like features from accretion
disks.


title: Properties of Accretion Shock Waves in Viscous Flows Around Black Holes

abstract:
  Accretion flows having low angular momentum and low viscosity can have
standing shock waves. These shocks arise due to the presence of multiple sonic
points in the flow. We study the region of the parameter space in which
multiple sonic points occur in viscous flows in the absence of cooling. We also
separate the parameter space in regions allowing steady shocks and oscillating
shocks. We quantify the nature of two critical viscosities which separate the
flow topologies. A post-shock region being hotter, it emits harder X-rays and
oscillating shocks cause oscillating X-ray intensities giving rise to
quasi-periodic oscillations. We show that with the increase in viscosity
parameter, the shock always moves closer to the black hole. This implies an
enhancement of the quasi-periodic oscillation frequency as viscosity is
increased


title: Study of Accretion Processes on Black Holes: Fifty Years of Developments

abstract:
  Fifty years ago, in 1952, the first significant paper on accretion flows was
written by Bondi. The subject has grown exponentially since then. In fact,
today many of the satellites engaged in space physics research look for
signatures of accretion processes in whatever objects are studied. In this
review, I will touch upon the significant developments in these years in this
subject, emphasizing mainly on accretion onto black holes. Since winds and
accretions are generally studied under similar framework, some references of
the winds/outflows studies will also be made.


title: Massive molecular outflows at high spatial resolution

abstract:
  We present high-spatial resolution Plateau de Bure Interferometer CO(2-1) and
SiO(2-1) observations of one intermediate-mass and one high-mass star-forming
region. The intermediate-mass region IRAS20293+3952 exhibits four molecular
outflows, one being as collimated as the highly collimated jet-like outflows
observed in low-mass star formation sources. Furthermore, comparing the data
with additional infrared H2 and cm observations we see indications that the
nearby ultracompact HII region triggers a shock wave interacting with the
outflow. The high-mass region IRAS19217+1651 exhibits a bipolar outflow as well
and the region is dominated by the central driving source. Adding two more
sources from the literature, we compare position-velocity diagrams of the
intermediate- to high-mass sources with previous studies in the low-mass
regime. We find similar kinematic signatures, some sources can be explained by
jet-driven outflows whereas other are better constrained by wind-driven models.
The data also allow to estimate accretion rates varying from a few times
10^{-5}Msun/yr for the intermediate-mass sources to a few times 10^{-4}Msun/yr
for the high-mass source, consistent with models explaining star formation of
all masses via accretion processes.


title:
Revealing stellar brightness profiles by means of microlensing fold
  caustics

abstract:
  With a handful of measurements of limb-darkening coefficients, galactic
microlensing has already proven to be a powerful technique for studying
atmospheres of distant stars. Survey campaigns such as OGLE-III are capable of
providing ~ 10 suitable target stars per year that undergo microlensing events
involving passages over the caustic created by a binary lens which last from a
few hours to a few days and allow to resolve the stellar atmosphere by frequent
broadband photometry. For a caustic exit lasting 12 h and a photometric
precision of 1.5%, a moderate sampling interval of 30 min (corresponding to ~
25-30 data points) is sufficient for providing a reliable measurement of the
linear limb-darkening coefficient Gamma with an uncertainty of ~ 8% which
reduces to ~ 3% for a reduced sampling interval of 6 min for the surroundings
of the end of the caustic exit. While some additional points over the remaining
parts of the lightcurve are highly valuable, a denser sampling in these regions
provides little improvements. Unless a high-precision measurement is desired,
limb-darkening coefficients for several filters can be obtained or observing
time can be spent on other targets during the same night. The adoption of an
inappropriate stellar intensity profile yields characteristic systematics in
the model residuals which can be distinguished from those arising from effects
causing an acceleration between source and caustic which are however unlikely
to affect the lightcurve significantly for most events, although a free
acceleration parameter blurs the limb-darkening measurement if the passage
duration cannot be accurately determined.


title: Is T Leonis a superoutbursting intermediate polar?

abstract:
  We present an XMM-Newton analysis of the cataclysmic variable T Leo. The
X-ray light curve shows sinusoidal variation on a period P_x equal to
0.89^{+0.14}_{-0.10} times the previously spectroscopically determined orbital
period. Furthermore, we find a signal in the power spectrum at 414 sec that
could be attributed to the spin period of the white dwarf. If true, T Leo would
be the first confirmed superoutbursting intermediate polar IP). The spin
profile is double-peaked with a peak separation of about 1/3 spin phases. This
appears to be a typical feature for IPs with a small magnetic field and fast
white dwarf rotation. An alternative explanation is that the 414 sec signal is
a Quasi-periodic Oscillation (QPO) that is caused by mass transfer variation
from the secondary, a bright region (``blob'') rotating in the disc at a radius
of approximately ~9 Rwd or - more likely - a travelling wave close to the inner
disc edge of a dwarf nova with a low field white dwarf. The XMM-Newton RGS
spectra reveal double peaked emission for the O VIII Ly alpha line. Scenarios
in the IP and dwarf nova model are discussed (an emitting ring in the disc,
bright X-ray spot on disc edge, or emitting accretion funnels), but the
intermediate polar model is favoured. Supported is this idea by the finding
that only the red peak appears to be shifted and the `blue' peak is compatible
with the rest wavelength. The red peak thus is caused by emission from the
northern accretion spot when it faces the observer. Instead, the peak at the
rest wavelength is caused when the southern accretion funnel is visible just on
the lower edge of the white dwarf - with the velocity of the accreting material
being perpendicular to the line of sight.


title: Galaxy groups in the 2dFGRS: the luminous content of the groups

abstract:
  The 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue of ~29000
objects is used to study the luminous content of galaxy systems of various
sizes. Mock galaxy catalogues constructed from cosmological simulations are
used to gauge the accuracy with which intrinsic group properties can be
recovered. A Schechter function is found to be a reasonable fit to the galaxy
luminosity functions in groups of different mass in the real data. The
characteristic luminosity L* is larger for more massive groups. However, the
mock data show that the shape of the recovered luminosity function is expected
to differ from the true shape, and this must be allowed for when interpreting
the data. The variation of halo mass-to-light ratio with group size is studied
in both these wavebands. A robust trend of increasing M/L with increasing group
luminosity is found in the 2PIGG data. From groups with L_bj=10^{10}Lsol to
those 100 times more luminous, the typical bj-band M/L increases by a factor of
5, whereas the rf-band M/L grows by a factor of 3.5. These trends agree well
with the simulations, which also predict a minimum M/L on a scale corresponding
to the Local Group. Our data indicate that if such a minimum exists, then it
must occur at L<~10^{10}Lsol, below the range accurately probed by the 2PIGG
catalogue. According to the mock data, the bj M/Ls of the largest groups are
expected to be approximately 1.1 times the global value. Assuming that this
correction applies to the real data yields an estimate of Omega_m=0.26+/-0.03
(statistical).


title:
Galaxy groups in the 2dFGRS: the group-finding algorithm and the 2PIGG
  catalogue

abstract:
  The construction of a catalogue of galaxy groups from the 2-degree Field
Galaxy Redshift Survey (2dFGRS) is described. Groups are identified by means of
a friends-of-friends percolation algorithm which has been thoroughly tested on
mock versions of the 2dFGRS generated from cosmological N-body simulations. The
tests suggest that the algorithm groups all galaxies that it should be
grouping, with an additional 40% of interlopers. About 55% of the ~190000
galaxies considered are placed into groups containing at least two members of
which ~29000 are found. Of these, ~7000 contain at least four galaxies, and
these groups have a median redshift of 0.11 and a median velocity dispersion of
260km/s. This 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue
represents the largest available homogeneous sample of galaxy groups. It is
publicly available on the WWW.


title:
2-10 keV luminosity of high-mass binaries as a gauge of ongoing
  star-formation rate

abstract:
  Based on recent work on spectral decomposition of the emission of
star-forming galaxies, we assess whether the integrated 2-10 keV emission from
high-mass X-ray binaries (HMXBs), L_{2-10}^{HMXB}, can be used as a reliable
estimator of ongoing star formation rate (SFR). Using a sample of 46 local (z <
0.1) star forming galaxies, and spectral modeling of ASCA, BeppoSAX, and
XMM-Newton data, we demonstrate the existence of a linear SFR-L_{2-10}^{HMXB}
relation which holds over ~5 decades in X-ray luminosity and SFR. The total
2-10 keV luminosity is not a precise SFR indicator because at low SFR (i.e., in
normal and moderately-starbursting galaxies) it is substantially affected by
the emission of low-mass X-ray binaries, which do not trace the current SFR due
to their long evolution lifetimes, while at very high SFR (i.e., for very
luminous FIR-selected galaxies) it is frequently affected by the presence of
strongly obscured AGNs. The availability of purely SB-powered galaxies - whose
2-10 keV emission is mainly due to HMXBs - allows us to properly calibrate the
SFR-L_{2-10}^{HMXB} relation. The SFR-L_{2-10}^{HMXB} relation holds also for
distant (z ~ 1) galaxies in the Hubble Deep Field North sample, for which we
lack spectral information, but whose SFR can be estimated from deep radio data.
If confirmed by more detailed observations, it may be possible to use the
deduced relation to identify distant galaxies that are X-ray overluminous for
their (independently estimated) SFR, and are therefore likely to hide strongly
absorbed AGNs.


title:
Searching for Planets in the Hyades V: Limits on Planet Detection in the
  Presence of Stellar Activity

abstract:
  We present the results of a radial velocity survey of a sample of Hyades
stars, and discuss the effects of stellar activity on radial velocity
measurements. The level of radial velocity scatter due to rotational modulation
of stellar surface features for the Hyades is in agreement with the predictions
of Saar & Donahue (1997)- the maximum radial velocity rms of up to ~50 m/s,
with an average rms of ~16 m/s. In this sample of 94 stars, we find 1 new
binary, 2 stars with linear trends indicative of binary companions, and no
close-in giant planets. We discuss the limits on extrasolar planet detection in
the Hyades and the constraints imposed on radial velocity surveys of young
stars.


title:
Possible Limits on Photon Propagation from Quantum Gravity and
  Space-time Foam

abstract:
  Many quantum gravity theories imply that the vacuum is filled with virtual
black holes. This paper explores the process in which high energy photons
interact with virtual black holes and decay into gravitons and photons of lower
energy. The effect requires violation (or modification) of Lorentz invariance
and implies that high energy photons cannot propagate over arbitrarily large
distances. For the standard Planck mass and the likely form for the interaction
cross section, this quantum foam limit becomes $\dist < 450$ Mpc $(\egam/10^7
{\rm GeV})^{-5}$. For quantum gravity theories that posit a lower Planck scale,
the interaction rate is larger and the limit is stronger. This paper uses
extant observations of gamma rays from cosmological sources to constrain this
process for varying values of the Planck mass and a range of forms for the
interaction cross sections.


title: Trouble for cluster parameter estimation from blind SZ surveys?

abstract:
  (Abriged version) The Sunyaev-Zel'dovich (SZ) effect of galaxy clusters is a
tool to measure three quantities: Compton parameter, electron temperature, and
cluster peculiar velocity. However, a major problem is non-removed
contamination by astrophysical sources that emit in the SZ frequencies. This
includes interstellar dust emission, infra-red (IR) galaxies, and radio sources
in addition to primary Cosmic Microwave Background (CMB) anisotropies. The
three former contaminations induce systematic shifts in the three SZ
parameters. In this study, we carefully estimated, both for a large beam
experiment (namely Planck Surveyor) and a small beam experiment (ACT-like), the
systematic errors that result if a fraction of the expected levels of emission
from dust, IR galaxies, and radio sources remains non-removed. ...


title:
T-ReCS and Michelle: The Mid-Infrared Spectroscopic Capabilities of the
  Gemini Observatory

abstract:
  Gemini Observatory's northern and southern telescopes are both presently
being outfitted with facility mid-infrared imagers/spectrometers. This will
allow observers the unique opportunity to apply to one observatory for all-sky
spectroscopic access in the mid-infrared with the light gathering power of
8-meter telescopes. Gemini South has recently commissioned the Thermal-Region
Camera and Spectrograph (T-ReCS) and is now available to perform queue
observations for the community. T-ReCS is capable of low-resolution long-slit
spectroscopy of R~100 near 10 and 20 um, and medium-resolution long-slit
spectroscopy of R~1000 near 10 um. Gemini North is presently commissioning
Michelle, which will be capable of low-, medium-, and high-resolution long-slit
spectroscopy of R~200, 1000, and 3000, respectively, near 10 um, as well as
low-resolution long-slit spectroscopy of R~200 near 20 um. Michelle can also
perform echelle spectroscopy of R~30000 at 10 and 20 um. The low-, medium-, and
high-resolution spectroscopic modes of Michelle will be available to the public
for the fall semester of 2004, and the echelle mode is expected to be available
in 2005.


title: Molecular gas in high redshift QSOs

abstract:
  We review cm and mm observations of thermal molecular line emission from high
redshift QSOs. These observations reveal the massive gas reservoirs (10^{10} to
10^{11} M_sun) required to fuel star formation at high rates. We discuss
evidence for active star formation in QSO host galaxies, and we show that these
high redshift, FIR-luminous QSOs follow the non-linear trend of increasing
L_{FIR}/L'(CO) with increasing L_{FIR}. We conclude with a brief discussion of
the recent CO detection of the most distant QSO at z=6.42, and its implications
for cosmic reionization.


title: A binary system of tailed radio galaxies

abstract:
  We present a detailed study of a binary system of tailed radio galaxies
which, along with 3C75, is the only such binary known to exist. The binary is
located in a region of low galaxy density at the periphery of a poor cluster
Abell S345, but lies close to the massive Horologium Reticulum supercluster.
The radio sources have bent tail morphologies and show considerable meandering
and wiggling along the jets, which are collimated throughout their lengths.
This work presents observations of the large-scale-structure environment of the
binary tailed radio sources with a view to examining the influence of
large-scale flows on the morphology and dynamics of the associated radio tails.
We argue that the orbital motions of the host galaxies together with tidal
accelerations toward the supercluster have resulted in the complex structure
seen in these radio tails.


title: Warm-Hot Intergalactic Medium in the Sculptor Supercluster

abstract:
  We have analyzed the soft X-ray emission in a wide area of the Sculptor
supercluster by using overlapping ROSAT PSPC pointings. After subtraction of
the point sources we have found evidence for extended, diffuse soft X-ray
emission. We have investigated the nature of such extended emission through the
cross-correlation with the density of galaxies as inferred from the Muenster
Redshift Survey. In particular we have analyzed the correlation as a function
of the temperature of the X-ray emitting gas. We have found a significant
correlation of the galaxy distribution only with the softest X-ray emission
(0.1--0.3 keV) and only for gas temperatures kT < 0.5 keV. We have excluded
that this soft X-ray diffuse emission, and its correlation with the galaxy
distribution, is significantly contributed by unresolved AGN, group of galaxies
or individual galaxies. The most likely explanation is that the soft, diffuse
X-ray emission is tracing Warm-Hot Intergalactic Medium, with temperatures
below 0.5 keV, associated with the large-scale structures in the Sculptor
supercluster.


title: The galaxy density environment of gamma-ray burst host galaxies

abstract:
  We analyze cross-correlation functions between Gamma-Ray Burst (GRB) hosts
and surrounding galaxies. We have used data obtained with the Very Large
Telescope at Cerro Paranal (Chile), as well as public Hubble Space Telescope
data. Our results indicate that Gamma-Ray Burst host galaxies do not reside in
high galaxy density environments. Moreover, the host-galaxy cross-correlations
show a relatively low amplitude. Our results are in agreement with the
cross-correlation function between star-forming galaxies and surrounding
objects in the HDF-N.


title: The 2dF Galaxy Redshift Survey: The clustering of galaxy groups

abstract:
  We measure the clustering of galaxy groups in the 2dFGRS Percolation-Inferred
Galaxy Group (2PIGG) catalogue. The 2PIGG sample has 29,000 groups with at
least two members. The clustering amplitude of the full 2PIGG catalogue is
weaker than that of 2dFGRS galaxies, in agreement with theoretical predictions.
We have subdivided the 2PIGG catalogue into samples that span a factor of 25 in
median total luminosity. Our correlation function measurements span an
unprecedented range of clustering strengths, connecting the regimes probed by
groups fainter than L* galaxies and rich clusters. There is a steady increase
in clustering strength with group luminosity; the most luminous groups are ten
times more strongly clustered than the full 2PIGG catalogue. We demonstrate
that the 2PIGG results are in very good agreement with the clustering of groups
expected in the LCDM model.


title:
An Instrument to Measure the Temperature of the Cosmic Microwave
  Background Radiation at Centimeter Wavelengths

abstract:
  The Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission
(ARCADE) is a balloon-borne instrument to measure the temperature of the cosmic
microwave background at centimeter wavelengths. ARCADE uses narrow-band
cryogenic radiometers to compare the sky to an external full-aperture
calibrator. To minimize potential sources of systematic error, ARCADE uses a
novel open-aperture design which maintains the antennas and calibrator at
temperatures near 3 K at the mouth of an open bucket Dewar, without windows or
other warm objects between the antennas and the sky. We discuss the design and
performance of the ARCADE instrument from its 2001 and 2003 flights.


title: The Temperature of the CMB at 10 GHz

abstract:
  We report the results of an effort to measure the low frequency portion of
the spectrum of the Cosmic Microwave Background Radiation (CMB), using a
balloon-borne instrument called ARCADE (Absolute Radiometer for Cosmology,
Astrophysics, and Diffuse Emission). These measurements are to search for
deviations from a thermal spectrum that are expected to exist in the CMB due to
various processes in the early universe. The radiometric temperature was
measured at 10 and 30 GHz using a cryogenic open-aperture instrument with no
emissive windows. An external blackbody calibrator provides an in situ
reference. A linear model is used to compare the radiometer output to a set of
thermometers on the instrument. The unmodeled residuals are less than 50 mK
peak-to-peak with a weighted RMS of 6 mK. Small corrections are made for the
residual emission from the flight train, atmosphere, and foreground Galactic
emission. The measured radiometric temperature of the CMB is 2.721 +/- 0.010 K
at 10 GHz and 2.694 +/- 0.032 K at 30 GHz.


title:
Design and Calibration of a Cryogenic Blackbody Calibrator at Centimeter
  Wavelengths

abstract:
  We describe the design and calibration of an external cryogenic blackbody
calibrator used for the first two flights of the Absolute Radiometer for
Cosmology, Astrophysics, and Diffuse Emission (ARCADE) instrument. The
calibrator consists of a microwave absorber weakly coupled to a superfluid
liquid helium bath. Half-wave corrugations viewed 30 deg off axis reduce the
return loss below -35 dB. Ruthenium oxide resistive thermometers embedded
within the absorber monitor the temperature across the face of the calibrator.
The thermal calibration transfers the calibration of a reference thermometer to
the flight thermometers using the flight thermometer readout system. Data taken
near the superfluid transition in 8 independent calibrations 4 years apart
agree within 0.3 mK, providing an independent verification of the thermometer
calibration at temperatures near that of the cosmic microwave background.


title:
A Chandra view of the normal S0 galaxy NGC 1332: I. An unbroken, steep
  power law luminosity function for the LMXB population

abstract:
  Chandra ACIS-S3 observations of the S0 galaxy NGC 1332 resolve much of the
emission into 73 point-sources, of which 37 lie within the D_25 isophote. The
unresolved emission is discussed in two companion papers. The source luminosity
function (XLF) shows the break seen in other early-type galaxies at
\~2x10^{38}ergs/s. After correcting for detection incompleteness due to source
confusion and contamination from diffuse emission, the break vanishes and the
data are well-described as a single power law. This casts further doubt on
there being a ``universal'' XLF break in such galaxies dividing neutron-star
and black-hole systems. The slope of the differential XLF (dN/dL),
beta=2.7+/-0.5, is marginally (~2.5 sigma) steeper than has been found for
analogous fits of other early-type galaxies but resembles what is generally
seen at high luminosities. Two of the sources within D_25 are ULX, although
neither have L_X>2x 10^{39} ergs/s. The absence of very luminous ULX in
early-type galaxies suggests a break in the XLF slope at ~1-2x 10^{39} ergs/s,
but we cannot constrain it in NGC 1332. The sources have a spatial distribution
consistent with the optical light and display a range of properties expected
for a LMXB population. The spectra of the individual sources, as well as the
composite source spectra, agree with observations of other early-type galaxies,
although a small number of highly-absorbed sources are seen. Two sources have
very soft spectra, two show strong variability and one source shows evidence of
an extended radial profile. We do not detect a central source in NGC 1332, but
we find a faint (L_X=2+/-1 x 10^{38} ergs/s) point-source coincident with the
centre of the companion dwarf galaxy NGC 1331. (Abridged)


title: Chromospheric CaII Emission in Nearby F, G, K, and M stars

abstract:
  We present chromospheric CaII activity measurements, rotation periods and
ages for ~1200 F-, G-, K-, and M- type main-sequence stars from ~18,000
archival spectra taken at Keck and Lick Observatories as a part of the
California and Carnegie Planet Search Project. We have calibrated our
chromospheric S values against the Mount Wilson chromospheric activity data.
  From these measurements we have calculated median activity levels and derived
R'HK, stellar ages, and rotation periods for 1228 stars, ~1000 of which have no
previously published S values. We also present precise time series of activity
measurements for these stars.


title: A new search for features in the primordial power spectrum

abstract:
  We develop a new approach toward a high resolution non-parametric
reconstruction of the primordial power spectrum using WMAP cosmic microwave
background temperature anisotropies that we confront with SDSS large-scale
structure data in the range k~0.01-0.1 h/Mpc. We utilise the standard LambdaCDM
cosmological model but we allow the baryon fraction to vary. In particular, for
the concordance baryon fraction, we compare indications of a possible feature
at k~0.05 h/Mpc in WMAP data with suggestions of similar features in large
scale structure surveys.


title:
An observational signature of evolved oceans on extra-solar terrestrial
  planets

abstract:
  The increase in luminosity with time of a main sequence star eventually can
lead to substantial evaporation of the oceans on an orbiting terrestrial
planet. Subsequently, the gas phase water in the planet's upper atmosphere can
be photodissociated by stellar ultraviolet and the resulting atomic hydrogen
then may be lost in a wind. This gaseous envelope may pass in front of the host
star and produce tansient, detectable ultraviolet absorption in the Lyman lines
in systems older than 1 Gyr.


title: Oxygen Overabundance in the Extremely Iron-Poor Star CS29498-043

abstract:
  An abundance analysis for the carbon-enhanced, extremely iron-poor ([Fe/H]
-3.5) star CS29498-043 has been obtained using new high-resolution, high
signal-to-noise spectra from the Subaru Telescope. The [O I] forbidden line at
6300A and the O I triplet feature at 7771-7776A are both clearly detected. The
overabundance of oxygen is significant ([O/Fe]>2). In addition, Na, Co, and Ni
abundances have been newly measured. The abundance pattern from C to Ni of this
object is quite similar to that of CS 22949--037, another extremely metal-poor
star with large excesses of C, N, O, and the alpha-elements. The abundance
patterns of these two stars suggest the existence of supernovae progenitors
that ejected relatively little material fromtheir iron cores during the very
early era of nucleosynthesis in the Galaxy. Themetallicity in these objects,
when one includes the elements C, N, and O in the tally of total metals, is not
as low as in the most metal-poor stars, suggesting the existence of quite
different formation processes for these iron-deficient objects than pertain to
the bulk of other metal-deficient stars.


title: Which acceleration process for UHE-Cosmic Rays in Gamma Ray Bursts ?

abstract:
  In this paper, we have made an accurate investigation of proton acceleration
in GRBs and we have predicted a possible signature of cosmic rays, in a
sufficiently baryon-loaded fireball, via GeV $\gamma$-ray emission produced by
$\pi^{0}$-meson decay. If two ungrounded assumptions are removed, namely,
Bohm's scaling and a slow magnetic field decrease, the usual Fermi processes
are unable to generate ultra high energy cosmic rays (UHECRs) in GRBs. We
propose to develop another scenario of relativistic Fermi acceleration in the
internal shock stage. We present the results of a realistic Monte-Carlo
simulation of a multi-front acceleration which clearly shows the possible
generation of UHECR. The amount of energy converted into UHECRs turns out to be
a sizeable fraction of the magnetic energy.


title: Gamma-Ray All-Sky Imaging with the Burst and Transient Source Experiment

abstract:
  The BATSE mission aboard CGRO monitored the whole sky in the 20 keV - 1 MeV
energy band continuously from April 1991 until June 2000. Although BATSE had
very poor intrinsic angular resolution, the data can be used to survey the
entire soft gamma-ray sky with < 1 degree angular resolution and ~ 1 mCrab
sensitivity by using the Earth occultation method. This method determines flux
by measuring the step in the count rate profile in each BATSE detector as a
source rises above or sets below the Earth's limb. A maximum likelihood imaging
technique can then be used to build up all-sky maps from the images of the
Earth's limb produced by occulting sources. However, since the Earth seen from
BATSE has a radius of ~ 70 degrees, the limb images that intersect at the
positions of bright point sources have a significant effect over the area of
the all-sky map. A method for performing image cleaning on likelihood data has
also been developed and is used to effectively remove artefacts from the
all-sky maps. This paper describes the 'LIMBO' imaging technique and presents
preliminary all-sky maps of 25 - 160 keV emission, the first to be made since
the HEAO1-A4 mission of 1978-79.


title: Neutralino Annihilation at the Galactic Center Revisited

abstract:
  The annihilation of neutralino dark matter in the Galactic Center (GC) may
result in radio signals that can be used to detect or constrain the dark matter
halo density profile or dark matter particle properties. At the Galactic
Center, the accretion flow onto the central Black Hole (BH) sustains strong
magnetic fields that can induce synchrotron emission by electrons and positrons
generated in neutralino annihilations during advection onto the BH. Here we
reanalyze the radiative processes relevant for the neutralino annihilation
signal at the GC, with realistic assumptions about the accretion flow and its
magnetic properties. We find that neglecting these effects, as done in previous
papers, leads to the incorrent electron and photon spectra. We find that the
magnetic fields associated with the flow are significantly stronger than
previously estimated. We derive the appropriate equilibrium distribution of
electrons and positron and the resulting radiation, considering adiabatic
compression in the accretion flow, inverse Compton scattering off synchrotron
photons (synchrotron self-Compton scattering), and synchrotron self-absorption
of the emitted radiation. We derive the signal for a Navarro-Frenk-White (NFW)
dark matter halo profile and a NFW profile with a dark matter spike due to the
central BH. We find that the observed radio emission from the GC is
inconsistent with the scenario in which a spiky distribution of neutralinos is
present. We discuss several important differences between our calculations and
those previously presented in the literature.


title:
Is HE0107-5240 A Primordial Star? -- The Characteristics of Extremely
  Metal-Poor Carbon-Rich Stars --

abstract:
  We discuss the origin of HE0107-5240 which is the most metal poor star yet
observed ([Fe/H] = -5.3). Its discovery has an important bearing on the
question of the observability of "first generation" stars. In common with other
metal-poor stars (-4 < [Fe/H] < -2.5), HE0107-5240 shows a peculiar abundance
pattern (CNO rich, moderate Na rich). We elaborate the binary scenario on the
basis of the evolution and nucleosynthesis of extremely metal-poor, low-mass
model stars and discuss the possibility of discriminating this scenario from
others. In our picture, iron peak elements arise in surface layers of the
component stars by accretion of gas from the polluted primordial cloud. To
explain the observed C, N, O, and Na enhancements as well as 12C/13C ratio, we
suppose that the currently observed star accreted matter from a AGB companion.
To estimate the abundances in the matter transferred in the binary, we rely on
the results of computations of model stars constructed with up-to-date input
physics. Nucleosynthesis in the helium flash convection with hydrogen injected
is followed, allowing us to discuss the abundances of s-process elements, in
addition to explaining the origin of the observed O and Na enrichments. From
the observed abundances, we conclude that HE0107-5240 has evolved from a wide
binary with a primary of initial mass, 1.2 ~ 3 Msun. We estimated the present
binary separation of ~ 34 AU and period of ~ 150 years. We also conclude that
the abundance distribution of the heavy s-process elements, may hold the key to
understand the origin of HE0107-5240. An enhancement of [Pb/Fe] = 1 ~ 2 should
be observed. If the enhancement of s-process elements is not detected,
HE0107-5240 may be a first generation secondary in a binary system with a
primary of mass less than 2.5 Msun.


title: Time Lags of Z Source GX 5-1

abstract:
  We investigated the time lags and the evolution of the cross spectra of Z
source GX~5-1, observed by the Rossi X-ray Timing Explorer (RXTE), when it is
in the horizontal branch oscillations. We showed that the time lags of 3
horizontal branch oscillations are related to the position on the hardness
intensity diagram. All of the three QPOs were shown to have hard time lags.
However on the cross spectra, one is in a `dip', one in a `bump', the other has
no so obvious characteristic. The time lags of two of the QPOs decrease with
QPO's frequency, while the other has a trend increasing with its frequency.
Moreover, in the normal branch, we found no significant time lags in the
present observational data.


title: Evolutionary design of photometric systems and its application to Gaia

abstract:
  Designing a photometric system to best fulfil a set of scientific goals is a
complex task, demanding a compromise between conflicting requirements and
subject to various constraints. A specific example is the determination of
stellar astrophysical parameters (APs) - effective temperature, metallicity
etc. - across a wide range of stellar types. I present a novel approach to this
problem which makes minimal assumptions about the required filter system. By
considering a filter system as a set of free parameters it may be designed by
optimizing some figure-of-merit (FoM) with respect to these parameters. In the
example considered, the FoM is a measure of how well the filter system can
`separate' stars with different APs. This separation is vectorial in nature, in
the sense that the local directions of AP variance are preferably mutually
orthogonal to avoid AP degeneracy. The optimization is carried out with an
evolutionary algorithm, which uses principles of evolutionary biology to search
the parameter space. This model, HFD (Heuristic Filter Design), is applied to
the design of photometric systems for the Gaia space astrometry mission. The
optimized systems show a number of interesting features, not least the
persistence of broad, overlapping filters. These HFD systems perform as least
as well as other proposed systems for Gaia, although inadequacies remain in
all. The principles underlying HFD are quite generic and may be applied to
filter design for numerous other projects, such as the search for specific
types of objects or photometric redshift determination.


title:
Relative Frequencies of Blue Stragglers in Galactic Globular Clusters:
  Constraints for the Formation Mechanisms

abstract:
  We discuss the main properties of the Galactic globular cluster (GC) blue
straggler stars (BSS), as inferred from our new catalog containing nearly 3000
BSS. The catalog has been extracted from the photometrically homogeneous V vs.
(B-V) color-magnitude diagrams (CMD) of 56 GCs, based on WFPC2 images of their
central cores. In our analysis we used consistent relative distances based on
the same photometry and calibration. The number of BSS has been normalized to
obtain relative frequencies (F_{BSS}) and specific densities (N_S) using
different stellar populations extracted from the CMD. The cluster F_{BSS} is
significantly smaller than the relative frequency of field BSS. We find a
significant anti-correlation between the BSS relative frequency in a cluster
and its total absolute luminosity (mass). There is no statistically significant
trend between the BSS frequency and the expected collision rate. F_{BSS} does
not depend on other cluster parameters, apart from a mild dependence on the
central density. PCC clusters act like normal clusters as far as the BSS
frequency is concerned. We also show that the BSS luminosity function for the
most luminous clusters is significantly different, with a brighter peak and
extending to brighter luminosities than in the less luminous clusters. These
results imply that the efficiency of BSS production mechanisms and their
relative importance vary with the cluster mass.


title:
On the origin of the HI holes in the interstellar medium of dwarf
  irregular galaxies

abstract:
  We suggest that large HI holes observed in the interstellar medium (ISM) of
galaxies such as the Large Magellanic Cloud (LMC) and Holmberg II (Ho II, DDO
50, UGC 4305) can form as the combined result of turbulence coupled to thermal
and gravitational instabilities. We investigate this problem with three
dimensional hydrodynamical simulations, taking into account cooling and heating
processes and the action of the self-gravity of the gas. We construct an
algorithm for radiative transfer to post-process the simulated data and build
emission maps in the 21 cm neutral hydrogen line. With this approach, we are
able to reproduce the structure of the shells and holes as observed in regions
of the ISM, where no stellar activity is detected. In order to quantify the
comparison of our synthetic maps to the observations, we calculate the physical
scale-autocorrelation length relation (L-L_{cr} relation) both on the synthetic
HI maps and the HI map of Ho II. The L-L_{cr} relation shows a linear increase
of the autocorrelation length with the physical scale up to the scale of energy
injection and flattens for larger scales. The comparison of the L-L_{cr}
relation between the observations and the synthetic maps suggests that
turbulence is driven in the ISM of Ho II on large scales (~ 6 kpc). The slope
of the L-L_{cr} relation in the linear regime in Ho II is better reproduced by
models where turbulence is coupled with a weak efficiency cooling of the gas.
These results demonstrate the importance of the interplay between turbulence
and the thermodynamics of the gas for structure formation in the ISM. Our
analysis can be used to determine the scale on which kinetic energy is injected
in the ISM of dwarf irregular galaxies, and to derive, in a first
approximation, the cooling rate of the gas.


title:
The ubiquitous nature of the Horizontal Branch second U-jump: A link
  with the Blue Hook scenario?

abstract:
  In a previous paper we reported on a discontinuity in the extreme horizontal
branch (EHB) of the Galactic globular cluster NGC6752, which we called the
second U-jump. This feature was attributed to a combination of post zero-age
horizontal branch evolution and diffusion effects. In this follow-up study we
analyze other EHB clusters and show that the second U-jump is a common feature
among EHB clusters reaching T_{eff}\ge 23,000K, and that its onset in different
clusters converges around T_{eff}\sim 21,000\pm3,000K. We also present
near-ultraviolet diagrams of \omega Cen and NGC2808, the only two objects with
spectroscopically confirmed ``blue hook'' stars (T_{eff}\ge 35,000K). We
confirm predictions of a photometric discontinuity separating late from
early-helium flashers. Moreover, we present empirical evidence that the second
U-jump population might be mainly composed by early-helium flashers. Lastly, we
revisit the discussion on the ubiquitous nature of the gaps and jumps so far
identified in the blue HB tails, suggesting a possible discrete nature of the
distribution in temperature of the HB stars.


title: In situ acceleration in the galactic center arc

abstract:
  For the nonthermal radio emission of the Galactic Center Arc in situ electron
acceleration is imperative. The observed radio spectrum can be modeled by a
transport equation for the relativistic electrons which includes particle
acceleration by electric fields, momentum diffusion via scattering by
magnetohydrodynamical turbulence and energy losses by synchrotron radiation.
The accelerating electric fields can be regarded as a natural consequence of
multiple reconnection events, caused by the interaction between a molecular
cloud and the Arc region. The radio spectrum and even the recently detected 150
GHz emission, explicitely originating from the interaction regions of a
molecular cloud with the magnetized Arc, can be explained in terms of
quasi-monoenergetically distributed relativistic electrons with a typical
energy of about 10 GeV accelerated in stochastically distributed magnetic
reconnection zones.


title: Can a simple instrument measure polarization in gamma-ray bursts?

abstract:
  The recent claim of a high degree of linear polarization in the prompt
gamma-ray burst (GRB) emission of GRB 021206 might have important implications
for the underlying mechanism ultimately responsible for the GRB radiation.
While the claim itself remains controversial, a full characterization of the
GRB polarization has become a scientific imperative. A review of past and
present polarimetry missions motivates a set of guidelines for future dedicated
GRB polarization experiments. It is also argued that polarization in GRBs could
be measured by a relatively simple instrument using readily available
technology.


title: Structure of Stars and Nuclei

abstract:
  The properties of dense hadronic and quark matter and its relation to compact
stars are discussed. In a bottom-up approach one starts with nuclear and
hypernuclear physics at low density and extrapolates hadronic matter to large
densities. The matching to the quark matter phase is performed in a top-down
approach starting at asymptotically large densities. Implications for the
mass-radius relation of compact stars and the existence of a new family of
solutions will be outlined.


title: Analytic Solutions for the Evolution of Radiative Supernova Remnants

abstract:
  We present the general analytic solution for the evolution of radiative
supernova remnants in a uniform interstellar medium, under thin-shell
approximation. This approximation is shown to be very accurate approach to this
task. For a given set of parameters, our solution closely matches the results
of numerical models, showing a transient in which the deceleration parameter
reaches a maximum value of 0.33, followed by a slow convergence to the
asymptotic value 2/7. Oort (1951) and McKee and Ostriker (1977) analytic
solutions are discussed, as special cases of the general solution we have
found.


title:
Study of the properties and spectral energy distributions of the Herbig
  AeBe stars HD 34282 and HD 141569

abstract:
  We present a study of the stellar parameters, distances and spectral energy
distributions (SEDs) of HD 34282 and HD 141569, two pre-main sequence Herbig
AeBe stars. Both objects have been reported to show `anomalous positions' in
the HR diagram in the sense that they appear below the main sequence. A
significant result of this work is that both stars are metal-deficient. The
{\it Hipparcos} distance of HD 34282 is very uncertain and the current study
places the star at the expected evolutionary position in the HR diagram, i.e.
as a PMS star. The distance for HD 141569 found in this work matches the {\it
Hipparcos} distance, and the problem of its anomalous position is solved as a
result of the low metallicity of the object: using the right metallicity
tracks, the star is in the PMS region. The SEDs are constructed using data
covering ultraviolet to millimetre wavelengths. Physical, non-parametric
models, have been applied in order to extract some properties of the disks
surrounding the stars. The disk around HD 34282 is accreting actively, it is
massive and presents large grains in the mid-plane and small grains in the
surface. HD 141569 has a very low mass disk, which is in an intermediate stage
towards a debris-type disk.


title:
Radio detections of the neutron star X-ray binaries 4U 1820-30 and Ser
  X-1 in soft X-ray states

abstract:
  We present the analysis of simultaneous X-ray (RXTE) and radio (VLA)
observations of two atoll-type neutron star X-ray binaries: 4U 1820-30 and Ser
X-1. Both sources were steadily in the soft (banana) X-ray state during the
observations. We have detected the radio counterpart of 4U 1820-30 at 4.86 GHz
and 8.46 GHz at a flux density of ~0.1 mJy. This radio source is positionally
coincident with the radio pulsar PSR 1820-30A. However, the pulsar's radio
emission falls rapidly with frequency (proportional to \nu^(-3)) and we argue
that the X-ray binary's radio emission is dominant above ~2 GHz. Supporting
this interpretation, comparison with previous observations reveals variability
at the higher radio frequencies that is likely to be due to the X-ray binary.
We have detected for the first time the radio counterpart of Ser X-1 at 8.46
GHz, also at a flux density of ~0.1 mJy. The position of the radio counterpart
has allowed us to unambiguously identify its optical counterpart. We briefly
discuss similarities and differences between the disc-jet coupling in neutron
star and black hole X-ray binaries. In particular, we draw attention to the
fact that, contrary to other states, neutron star X-ray binaries seem to be
more radio loud than persistent black hole candidates when the emission is
'quenched' in the soft state.


title:
On the Insignificance of Photochemical Hydrocarbon Aerosols in the
  Atmospheres of Close-in Extrasolar Giant Planets

abstract:
  The close-in extrasolar giant planets (CEGPs) reside in irradiated
environments much more intense than that of the giant planets in our solar
system. The high UV irradiance strongly influences their photochemistry and the
general current view believed that this high UV flux will greatly enhance
photochemical production of hydrocarbon aerosols. In this letter, we
investigate hydrocarbon aerosol formation in the atmospheres of CEGPs. We find
that the abundances of hydrocarbons in the atmospheres of CEGPs are
significantly less than that of Jupiter except for models in which the CH$_4$
abundance is unreasonably high (as high as CO) for the hot (effective
temperatures $\gtrsim 1000$ K) atmospheres. Moreover, the hydrocarbons will be
condensed out to form aerosols only when the temperature-pressure profiles of
the species intersect with the saturation profiles--a case almost certainly not
realized in the hot CEGPs atmospheres. Hence our models show that photochemical
hydrocarbon aerosols are insignificant in the atmospheres of CEGPs. In
contrast, Jupiter and Saturn have a much higher abundance of hydrocarbon
aerosols in their atmospheres which are responsible for strong absorption
shortward of 600 nm. Thus the insignificance of photochemical hydrocarbon
aerosols in the atmospheres of CEGPs rules out one class of models with low
albedos and featureless spectra shortward of 600 nm.


title: Wavelets and WMAP non-Gaussianity

abstract:
  We study the statistical properties of the 1st year WMAP data on different
scales using the spherical mexican hat wavelet transform. Consistent with the
results of Vielva et al. (2003) we find a deviation from Gaussianity in the
form of kurtosis of wavelet coefficients on $3-4^\circ$ scales in the southern
Galactic hemisphere. This paper extends the work of Vielva et al. as follows.
We find that the non-Gaussian signal shows up more strongly in the form of a
larger than expected number of cold pixels and also in the form of scale-scale
correlations amongst wavelet coefficients. We establish the robustness of the
non-Gaussian signal under more wide-ranging assumptions regarding the Galactic
mask applied to the data and the noise statistics. This signal is unlikely to
be due to the usual quadratic term parametrized by the non-linearity parameter
$f_{NL}$. We use the skewness of the spherical mexican hat wavelet coefficients
to constrain $f_{NL}$ with the 1st year WMAP data. Our results constrain
$f_{NL}$ to be $50\pm 80$ at 68% confidence, and less than 280 at 99%
confidence.


title:
Reflection spectra from an accretion disc illuminated by a neutron star
  X-ray burst

abstract:
  Recent time-resolved X-ray spectra of a neutron star undergoing a superburst
revealed an Fe K line and edge consistent with reprocessing from the
surrounding accretion disc. Here, we present models of X-ray reflection from a
constant density slab illuminated by a blackbody, the spectrum emitted by a
neutron star burst. The calculations predict a prominent Fe K line and a rich
soft X-ray line spectrum which is superimposed on a strong free-free continuum.
The lines slowly vanish as the ionization parameter of the slab is increased,
but the free-free continuum remains dominant at energiesless than 1 keV. The
reflection spectrum has a quasi-blackbody shape only at energies greater than 3
keV. If the incident blackbody is added to the reflection spectrum, the Fe K
equivalent width varies between 100 and 300 eV depending on the ionization
parameter and the temperature, kT, of the blackbody. The equivalent width is
correlated with kT, and therefore we predict a strong Fe K line when an X-ray
burst is at its brightest (if iron is not too ionized or the reflection
amplitude too small). Extending the study of reflection features in the spectra
of superbursts to lower energies would provide further constraints on the
accretion flow. If the Fe K line or other features are relativistically
broadened then they can determine the system inclination angle (which leads to
the neutron star mass), and, if the mass is known, a lower-limit to the
mass/radius ratio of the star.


title:
Probing the Early Stages of Low-Mass Star Formation in LDN 1689N: Dust
  and Water in IRAS 16293-2422A, B, and E

abstract:
  We present deep images of dust continuum emission at 450, 800, and 850 micron
of the dark cloud LDN 1689N which harbors the low-mass young stellar objects
(YSOs) IRAS 16293-2422A and B (I16293A and I16293B) and the cold prestellar
object I16293E. Toward the positions of I16293A and E we also obtained spectra
of CO-isotopomers and deep submillimeter observations of chemically related
molecules with high critical densities. To I16293A we report the detection of
the HDO 1_01 - 0_00 and H2O 1_10 - 1_01 ground-state transitions as broad
self-reversed emission profiles with narrow absorption, and a tentative
detection of H2D+ 1_10 - 1_11. To I16293E we detect weak emission of
subthermally excited HDO 1_01 - 0_00. Based on this set of submillimeter
continuum and line data we model the envelopes around I16293A and E. The
density and velocity structure of I16293A is fit by an inside-out collapse
model, yielding a sound speed of a=0.7 km/s, an age of t=(0.6--2.5)e4 yr, and a
mass of 6.1 Msun. The density in the envelope of I16293E is fit by a radial
power law with index -1.0+/-0.2, a mass of 4.4 Msun, and a constant temperature
of 16K. These respective models are used to study the chemistry of the
envelopes of these pre- and protostellar objects.
  The [HDO]/[H2O] abundance ratio in the warm inner envelope of I16293A of a
few times 1e-4 is comparable to that measured in comets. This supports the idea
that the [HDO]/[H2O] ratio is determined in the cold prestellar core phase and
conserved throughout the formation process of low-mass stars and planets.


title: Particle Acceleration in Multiple Dissipation Regions

abstract:
  The sharp magnetic discontinuities which naturally appear in solar magnetic
flux tubes driven by turbulent photospheric motions are associated with intense
currents. \citet{Par83} proposed that these currents can become unstable to a
variety of microscopic processes, with the net result of dramatically enhanced
resistivity and heating (nanoflares). The electric fields associated with such
``hot spots'' are also expected to enhance particle acceleration. We test this
hypothesis by exact relativistic orbit simulations in strong random phase
magnetohydrodynamic (MHD) turbulence which is forming localized super-Dreicer
Ohm electric fields ($E_\Omega/E_D$ = $10^2 ... 10^5$) occurring in 2..15 % of
the volume. It is found that these fields indeed yield a large amplification of
acceleration of electrons and ions, and can effectively overcome the injection
problem. We suggest in this article that nanoflare heating will be associated
with sporadic particle acceleration.


title: High-Wavenumber Finite Differences and Turbulence Simulations

abstract:
  We introduce a fluid dynamics algorithm that performs with nearly spectral
accuracy, but uses finite-differences instead of FFTs to compute gradients and
thus executes 10 times faster. The finite differencing is not based on a
high-order polynomial fit. The polynomial scheme has supurb accuracy for
low-wavenumber gradients but fails at high wavenumbers. We instead use a scheme
tuned to enhance high-wavenumber accuracy at the expense of low wavenumbers,
although the loss of low-wavenumber accuracy is negligibly slight. A tuned
gradient is capable of capturing all wavenumbers up to 80 percent of the
Nyquist limit with an error of no worse than 1 percent. The fact that gradients
are based on finite differences enables diverse geometries to be considered and
eliminates the parallel communications bottleneck.


title:
The Nature of the Companion to the Eclipsing Overtone Cepheid MACHO
  81.8997.87

abstract:
  The lightcurve of the Large Magellanic Cloud (LMC) variable star MACHO
81.8997.87 shows evidence for photometric variations due to both stellar
pulsation, with a 2.035 day period, and eclipsing behavior, with an 800.4 day
period. The primary star of the system has been identified as a first-overtone
Cepheid but the nature of the secondary star has not been determined. Here we
present multicolor BVI photometry of a primary eclipse of the system and fit a
model to the complete lightcurve to produce an updated set of elements. These
results are combined with 2MASS JHK photometry to give further insight into the
identity of the companion star. We find that the companion is most consistent
with a late-K or an early-M giant but also that there are a number of problems
with this interpretation. The prospects for future observations of this system
are also discussed.


title:
A Hint of Poincar\'e Dodecahedral Topology in the WMAP First Year Sky
  Map

abstract:
  Luminet et al. (2003) suggested that WMAP data are better matched by a
Poincar\'e dodecahedral FLRW model of global geometry, rather than by an
infinite flat model. The analysis by Cornish et al. (2003) for angular radii
25-90 degrees failed to support this. Here, a matched circles analysis
specifically designed to detect dodecahedral patterns of matched circles is
performed over angular radii in the range 1-40 degrees on the one-year WMAP ILC
map, using a correlation statistic and an rms difference statistic. Extreme
value distributions of these statistics are calculated for left-handed and
right-handed 36 degree `screw motions' (Clifford translations) when matching
circles and for a zero (unphysical) rotation. The most correlated circles
appear for circle radii of 11\pm1 degrees, for the left-handed screw motion,
but not for the right-handed one, nor for the zero rotation. The favoured six
dodecahedral face centres in galactic coordinates are (l,b)= (252, +65), (51,
+51), (144,+38), (207,+10), (271,+3), (332,+25) and their opposites. The six
pairs of circles_independently_ each favour a circle angular radius of 11\pm1
degrees. Whether or not these six circle pairs centred on dodecahedral faces
match via a 36 degree rotation only due to unexpected statistical properties of
the WMAP ILC map, or whether they match due to global geometry, it is clear
that the WMAP ILC map has some unusual statistical properties which mimic a
potentially interesting cosmological signal. The software for reading the WMAP
data and for carrying out this analysis are released under the GNU General
Public License.


title: Addendum to "Superimposed Oscillations in the WMAP Data?"

abstract:
  We elaborate further on the possibility that the inflationary primordial
power spectrum contains superimposed oscillations. We study various effects
which could influence the calculation of the multipole moments in this case. We
also present the theoretical predictions for two other cosmological
observables, the matter power spectrum and the EE polarization channel.


title: Physical-chemical modeling of the low-mass protostar IRAS 16293-2422

abstract:
  We present detailed gas-phase chemical models for the envelope of the
low-mass star-forming region IRAS 16293-2422. By considering both time- and
space-dependent chemistry, these models are used to study both the physical
structure proposed by Schoier et al. (2002), as well as the chemical evolution
of this region. A new feature of our study is the use of a detailed,
self-consistent radiative transfer model to translate the model abundances into
line strengths and compare them directly with observations of a total of 76
transitions for 18 chemical species, and their isotopes. The model can
reproduce many of the line strengths observed within 50%. The best fit is for
times in the range of 3e3 - 3e4 yrs, and requires only minor modifications to
our model for the high-mass star-forming region AFGL 2591. The ionization rate
for the source may be higher than previously expected -- either due to an
enhanced cosmic-ray ionization rate, or, more probably, to the presence of
X-ray induced ionization from the center. A significant fraction of the CO is
found to desorb in the temperature range of 15-40 K; below this temperature,
\~90% or more of the CO is frozen out. The inability of the model to explain
the HCS+, C2H, and OCS abundances suggests the importance of further laboratory
studies of basic reaction rates. Finally, predictions of the abundances and
spatial distributions of other species which could be observed by future
facilities (e.g., Herschel-HIFI, SOFIA, millimeter arrays) are provided.


title: Stars, Star Clusters, and Dust in NGC 3077

abstract:
  Images obtained with the CFHTIR camera on the Canada-France-Hawaii Telescope
are used to investigate the near-infrared photometric properties of the
star-forming M81 group galaxy NGC 3077. The spectral-energy distribution (SED)
of the near-infrared light within 10 arcsec of the nucleus is consistent with
the 2um light being dominated by hot young (log(t_{yr}) < 6.8) stars reddened
by A_V = 3 - 4, with A_V < 8 mag in some regions. A population like that near
the center of NGC 205 likely contributes only a modest fraction of the light
near 2um. A number of candidate star clusters are detected in and around NGC
3077. The specific frequency of globular clusters falls within the range
measured in nearby dEs. The candidate young clusters have photometric masses
that are similar to those of compact young clusters in other active
star-forming systems, and SEDs consistent with ages log(t_{yr}) < 6.6. Based on
the masses and ages of the young clusters, it is estimated that the star
formation rate in NGC 3077 was at least 0.25 - 0.50 solar masses per year
during the past few million years.


title:
A study of some current methods of analysing observations of star
  forming regions

abstract:
  We present an evaluative study of some current methods utilized in the
analysis of infrared (IR) observatinons of star-forming regions. A series of
self-consistent radiative transfer models are constructed, with the outputs
analysed using these methods to infer source properties such as dust
temperature, mass, opacity function, and density distribution. Any
discrepancies between the inferred and model quantities can be attributed to
the analysis methods. The range of validity of most methods is smaller than
expected, due to two effects: (1) limited applicability of the Rayleigh-Jeans
limit except to very long wavelengths, and (2) significant errors in the
isothermal approximation, even when temperature variations are less than 2 K
over 90% of the region. Still, an accurate mean dust temperature can be found
using a modified Wien's law. This temperature can yield dust masses to within
10-25% -- much better than masses inferred from the integrated luminosity.
Using long wavelengths (greater than 1000 - 2000 microns), the opacity index
can be determined from the far-IR spectrum to within 20%. Fitting the spectrum
yields better results. The desnity distribution can be somewhat constrained by
fitting the surface brightness, for well-resolved sources. Better results are
found by fitting the flux spectrum with detailed models.


title:
A Multi-Wavelength Perspective of Flares on HR 1099: Four Years of
  Coordinated Campaigns

abstract:
  We report on four years of multiple wavelength observations of the RS CVn
system V711 Tau (HR 1099) from 1993, 1994, 1996, and 1998. This combination of
radio, ultraviolet, extreme ultraviolet, and X-ray observations allows us to
view, in the most comprehensive manner currently possible, the coronal and
upper atmospheric variability of this active binary system. We report on the
changing activity state of the system as recorded in the EUV and radio across
the four years of the observations, and study the high energy variability using
an assemblage of X-ray telescopes. (Longer abstract in paper).


title:
Dynamics of the circumstellar gas in the Herbig Ae stars BF Orionis, SV
  Cephei, WW Vulpeculae and XY Persei

abstract:
  We present high resolution (lambda / Delta_lambda = 49000) echelle spectra of
the intermediate mass, pre-main sequence stars BF Ori, SV Cep, WW Wul and XY
Per. The spectra cover the range 3800-5900 angstroms and monitor the stars on
time scales of months and days. All spectra show a large number of Balmer and
metallic lines with variable blueshifted and redshifted absorption features
superimposed to the photospheric stellar spectra. Synthetic Kurucz models are
used to estimate rotational velocities, effective temperatures and gravities of
the stars. The best photospheric models are subtracted from each observed
spectrum to determine the variable absorption features due to the circumstellar
gas; those features are characterized in terms of their velocity, v, dispersion
velocity, Delta v, and residual absorption, R_max. The absorption components
detected in each spectrum can be grouped by their similar radial velocities and
are interpreted as the signature of the dynamical evolution of gaseous clumps
with, in most cases, solar-like chemical composition. This infalling and
outflowing gas has similar properties to the circumstellar gas observed in UX
Ori, emphasizing the need for detailed theoretical models, probably in the
framework of the magnetospheric accretion scenario, to understand the complex
environment in Herbig Ae (HAe) stars. WW Vul is unusual because, in addition to
infalling and outflowing gas with properties similar to those observed in the
other stars, it shows also transient absorption features in metallic lines with
no obvious counterparts in the hydrogen lines. This could, in principle,
suggest the presence of CS gas clouds with enhanced metallicity around WW Vul.
The existence of such a metal-rich gas component, however, needs to be
confirmed by further observations and a more quantitative analysis.


title:
Laser Guide Star Adaptive Optics Imaging Polarimetry of Herbig Ae/Be
  Stars

abstract:
  We have used laser guide star adaptive optics and a near-infrared
dual-channel imaging polarimeter to observe light scattered in the
circumstellar environment of Herbig Ae/Be stars on scales of 100-300 AU. We
discover a strongly polarized, biconical nebula 10 arcseconds in diameter (6000
AU) around the star LkHa 198, and also observe a polarized jet-like feature
associated with the deeply embedded source LkHa 198-IR. The star LkHa 233
presents a narrow, unpolarized dark lane consistent with an optically thick
circumstellar disk blocking our direct view of the star. These data show that
the lower-mass T Tauri and intermediate mass Herbig Ae/Be stars share a common
evolutionary sequence.


title: Palomar-QUEST: A case study in designing sky surveys in the VO era

abstract:
  The advent of wide-area multicolour synoptic sky surveys is leading to data
sets unprecedented in size, complexity and data throughput. VO technology
offers a way to exploit these to the full but requires changes in design
philosophy. The Palomar-QUEST survey is a major new survey being undertaken by
Caltech, Yale, JPL and Indiana University to repeatedly observe 1/3 of the sky
(~15000 sq. deg. between -27 < Dec <27 in seven passbands. Utilising the
48-inch Oschin Schmidt Telescope at the Palomar Observatory with the 112-CCD
QUEST camera covering the full 4 x 4 sq. deg. field of view, it will generate
\~1TB of data per month. In this paper, we review the design of QUEST as a VO
resource, a federated data set and an exemplar of VO standards.


title:
Multiwavelength Properties of the X-ray Sources in the Groth-Westphal
  Strip Field

abstract:
  We summarize the multiwavelength properties of X-ray sources detected in the
80 ks XMM-Newton observation of the Groth-Westphal Strip. We find 23 XMM-Newton
sources within the WFPC2 fields. Ten spectroscopic redshifts are available from
the DEEP and CFRS projects and 4 of these show broad Mg II emission (type 1
AGNs). Two of those without any broad lines, nevertheless, have [NeV] emission
which is an unambiguous signature of AGN activity, one of which is a
narrow-line Seyfert 1 and the other a type 2 AGN. We have made near-infrared
(NIR) spectroscopic observations using the Subaru OHS/CISCO spectrometer for
five of the X-ray sources for which we found no indication of an AGN activity
in the optical spectrum. We have detected H-alpha+[NII] emission in four of
them. A broad H-alpha component and/or a large [NII]/H-alpha ratio is seen,
suggestive of AGN activity. Nineteen sources have been detected in the Ks band
and four of these are extremely red objects (I814-Ks>4). The optical
counterparts for the majority of the X-ray sources are bulge-dominated with
colors consistent with evolving elliptical galaxies, with starburst/AGN
contamination. Assuming that the known local relations among the bulge
luminosity,central velocity dispersion, and the mass of the central blackhole
hold at about z=1, the AGN bolometric luminosity to Eddington luminosity ratio
ranges from 0.3% to 10%. (abridged)


title:
Cosmological Density Distribution Function from the Ellipsoidal Collapse
  Model in Real Space

abstract:
  We calculate the one-point probability distribution function (PDF) for cosmic
density in non-linear regime of the gravitational evolution. Under the local
approximation that the evolution of cosmic fluid fields can be characterized by
the Lagrangian local dynamics with finite degrees of freedom, the analytic
expressions of PDF are derived taking account of the smoothing effect. The
validity and the usefulness of the local approximation are then discussed
comparing those results with N-body simulations in a Gaussian initial
condition. Adopting the ellipsoidal collapse model (ECM) and the spherical
collapse model (SCM) as Lagrangian local dynamics, we found that the PDFs from
the local approximation excellently match the simulation results in the case of
the cold dark matter initial spectrum.
  As for the scale-free initial spectra given by $P(k)\propto k^n$,
  N-body result suffers from spurious numerical effects, which prevent us to
give a detailed comparison.
  Nevertheless, at the quality of N-body data, the model predictions based on
the ECM and the SCM quantitatively agree with N-body results in cases with
spectral index n<0.
  For the index n>=0, choice of the Lagrangian local dynamics becomes crucial
for an accurate prediction and a more delicate modeling is required, however,
we find that the model prediction based on the ECM provides a better
approximation to the N-body results of cumulants and PDFs.


title: M31 Globular Cluster X-ray Sources: XMM-Newton and Chandra results

abstract:
  (Abridged) We present the results of M31 globular cluster (GC) X-ray source
survey, based on the data of XMM-Newton and Chandra observations covering ~6100
sq.arcmin of M31. We detected 43 X-ray sources coincident with globular cluster
candidates from optical surveys. The estimated isotropic X-ray luminosities of
GC sources lie between ~10e35 and ~10e39 erg/s in the 0.3 - 10 keV energy band.
The spectral properties and variability of M31 GC X-ray sources are consistent
with that derived for the LMXBs in the bulges of M31 and Milky Way. We found
that ~80% of the M31 GC sources with multiple flux measurements available show
significant variability on a time scales from days to years. The X-ray
luminosity function of GC sources is found to be significantly different from
that of the point sources in the bulge and disk of M31 and that of the Galactic
GC X-ray sources. GC sources make dominant contribution to the bright source
counts in the areas of M31 covered by the survey: ~40% of the total number of
sources with luminosities above 10e37 ergs/s reside in GCs with fraction of GC
sources rising to 67-90% for the luminosities above 10e38 ergs/s. The
contribution of the GC sources to the total number of bright sources found in
M31 is much higher than in the Milky Way galaxy, but surprisingly close to that
of the early-type galaxies. The brightest M31 GC sources tend to reside at
large galactocentric distances outside the central bulge. We found that
globular clusters hosting bright X-ray sources are optically brighter and more
metal rich than the rest of M31 globular clusters. The brightest sources with
luminosities above ~10e38 ergs/s show tendency to reside in more metal poor
clusters.


title:
Effects of Helium Phase Separation on the Evolution of Extrasolar Giant
  Planets

abstract:
  We build on recent new evolutionary models of Jupiter and Saturn and here
extend our calculations to investigate the evolution of extrasolar giant
planets of mass 0.15 to 3.0 M_J. Our inhomogeneous thermal history models show
that the possible phase separation of helium from liquid metallic hydrogen in
the deep interiors of these planets can lead to luminosities ~2 times greater
than have been predicted by homogeneous models. For our chosen phase diagram
this phase separation will begin to affect the planets' evolution at ~700 Myr
for a 0.15 M_J object and ~10 Gyr for a 3.0 M_J object. We show how phase
separation affects the luminosity, effective temperature, radii, and
atmospheric helium mass fraction as a function of age for planets of various
masses, with and without heavy element cores, and with and without the effect
of modest stellar irradiation. This phase separation process will likely not
affect giant planets within a few AU of their parent star, as these planets
will cool to their equilibrium temperatures, determined by stellar heating,
before the onset of phase separation. We discuss the detectability of these
objects and the likelihood that the energy provided by helium phase separation
can change the timescales for formation and settling of ammonia clouds by
several Gyr. We discuss how correctly incorporating stellar irradiation into
giant planet atmosphere and albedo modeling may lead to a consistent
evolutionary history for Jupiter and Saturn.


title:
Two long-period X-ray pulsars detected in the SMC field around XTE
  J0055-727

abstract:
  An XMM-Newton target of opportunity observation of the field around the
transient 18.37 s pulsar XTE J0055-727 in the Small Magellanic Cloud (SMC)
revealed two bright, long-period X-ray pulsars in the EPIC data. A new pulsar,
XMMU J005517.9-723853, with a pulse period of 701.7 +/- 0.8 s was discovered
and 500.0 +/- 0.2 s pulsations were detected from XMMU J005455.4-724512 (= CXOU
J005455.6-724510), confirming the period found in Chandra data. We derive X-ray
positions of RA = 00h5455.88s, Dec = -72d45m10.5s and RA = 00h55m18.44s, Dec =
-72d38m51.8s (J2000.0) with an uncertainty of 0.2'' utilizing optical
identification with OGLE stars. For both objects, the optical brightness and
colours and the X-ray spectra are consistent with Be/X-ray binary systems in
the SMC.


title:
The formation of massive black holes through collision runaway in dense
  young star clusters

abstract:
  A luminous X-ray source is associated with a cluster (MGG-11) of young stars
\~200pc from the center of the starburst galaxy M82. The properties of the
X-ray source are best explained by a black hole with a mass of at least
350Msun, which is intermediate between stellar-mass and supermassive black
holes. A nearby but somewhat more massive star cluster (MGG-9) shows no
evidence of such an intermediate mass black hole, raising the issue of just
what physical characteristics of the clusters can account for this difference.
Here we report numerical simulations of the evolution and the motions of stars
within the clusters, where stars are allowed to mergers with each other. We
find that for MGG-11 dynamical friction leads to the massive stars sinking
rapidly to the center of the cluster to participate in a runaway collision,
thereby producing a star of 800-3000Msun, which ultimately collapses to an
black hole of intermediate mass. No such runaway occurs in the cluster MGG-9
because the larger cluster radius leads to a mass-segregation timescale a
factor of five longer than for MGG-11.


title: XMM-Newton observations of the giant HII region N11 in the LMC

abstract:
  Using the sensitive XMM-Newton observatory, we have observed the giant HII
region N11 in the LMC for \sim30 ks. We have detected several large areas of
soft diffuse X-ray emission along with 37 point sources. One of the most
interesting results is the possible association of a faint X-ray source with
BSDL 188, a small extended object of uncertain nature. The OB associations in
the field-of-view (LH9, LH10 and LH13) are all detected with XMM-Newton, but
they appear very different from one another. [...] (for complete abstract, see
paper) Finally, our XMM-Newton observation included simultaneous observations
with the OM camera that provide us with unique UV photometry of more than 6000
sources and enable the discovery of the UV emission from the SNR N11L.


title: CO bands in V4334 Sgr (Sakurai's Object): the 12C/13C ratio

abstract:
  We present the results of our analysis of a high resolution (R ~ 30000)
infrared spectrum of V4334 Sgr (Sakurai's Object) around the first overtone CO
bands, obtained in 1998 July. The 12CO and 13CO bands are well-resolved, and we
compute synthetic hydrogen-deficient model atmosphere spectra to determine the
12C/13C ratio. We find 12C/13C ~ 4 +/-1, consistent with the interpretation of
V4334 Sgr as an object that has undergone a very late thermal pulse.


title: Explosive yields of massive stars from Z=0 to Z=Zsun

abstract:
  We present a new and homogeneous set of explosive yields for masses 13, 15,
20, 25, 30 and 35 Msun and metallicities Z=0, 10^{- 6}, 10^{- 4}, 10^{- 3},
6x10^{- 3}, 2x10^{-2}. A wide network extending up to Mo has been used in all
the computation. We show that at low metallicities (Z<10^{- 4}) the final
yields do not depend significantly on the initial chemical composition of the
models so that a scaled solar distribution may be safely assumed at all
metallicities. Moreover, no elements above Zn are produced by any mass in the
grid up to a metallicity ~10^{-3}. These yields are available for any choice of
the mass cut upon request.


title: The Richness-Shape Relation of the 2dFGRS Groups

abstract:
  We estimate the group shape of the recently compiled Pecolation-Inferred
Galaxy Group (2PIGG) catalogue. Using a set of integral equations we invert the
projected distribution of group axial ratios and recover the corresponding
intrinsic distribution under the assumption that groups are pure spheroids. In
agreement with the analysis of the UZC-SSRS2 group sample (Plionis, Basilakos &
Tovmassian 2004) we find that groups are extremely elongated prolate-like
systems. We also find an interesting trend between shape and group richness
with poorer groups being significantly flatter than richer ones.


title: Exploring NLS1 through the physical properties of their hosts

abstract:
  In this work we aim at addressing the still open question about the nature of
Narrow-Line Seyfert 1 (NLS1) galaxies: are they really active nuclei with lower
mass Black-Holes (BHs) than Seyfert 1 (S1) and quasars? Our approach is based
on the recently discovered physical connections between nuclear supermassive
BHs and their hosting spheroids (spiral bulges or ellipticals). In particular
we compare BH masses of NLS1s and S1s analyzing the properties of their hosts
by means of spectroscopic and photometric data in the optical wavelength
domain. We find that NLS1s fill the low BH mass and bulge luminosity values of
the BH mass - bulge magnitude relation, a result strongly suggesting that NLS1s
are active nuclei where less massive BHs are hosted by less massive bulges. The
correlation is good with a relatively small scatter fitting simultaneously
NLS1s, S1s and quasars. On the other hand, NLS1s seem to share the same stellar
velocity dispersion range of S1s in the BH mass - stellar velocity dispersion
relation, indicating that NLS1s have a smaller BH/bulge mass ratio than S1s.
These two conflicting results support in any case the idea that NLS1s could be
young S1s. Finally we do not confirm the significantly non linear BH--bulge
relation claimed by some authors.


title: A Hard X-ray View of Accreting X-ray Binary Pulsars

abstract:
  The study of the hard (E>10 keV) energy spectra of X-ray binary pulsars can
give a wealth of information on the physical processes that occur close to the
neutron star surface. Extreme matter regimes are probed, and precious
information on how matter and radiation behave and interact in critical
conditions can be obtained. We will give an overview on the most recent results
obtained by RXTE and BeppoSAX on this class of objects, in order to pass the
baton onto just launched experiments, like INTEGRAL, or soon to be launched,
like AGILE and ASTRO-E2.


title:
An X-ray investigation of the NGC 346 field in the SMC (3): XMM-Newton
  data

abstract:
  We present new XMM-Newton results on the field around the NGC346 star cluster
in the SMC. This continues and extends previously published work on Chandra
observations of the same field. The two XMM-Newton observations were obtained,
respectively, six months before and six months after the previously published
Chandra data. Of the 51 X-ray sources detected with XMM-Newton, 29 were already
detected with Chandra. Comparing the properties of these X-ray sources in each
of our three datasets has enabled us to investigate their variability on times
scales of a year. Changes in the flux levels and/or spectral properties were
observed for 21 of these sources. In addition, we discovered long-term
variations in the X-ray properties of the peculiar system HD5980, a luminous
blue variable star, that is likely to be a colliding wind binary system, which
displayed the largest luminosity during the first XMM-Newton observation.


title:
The contribution of halo red giant mass loss to the high-velocity gas
  falling onto the Milky Way disk

abstract:
  The origin of gas falling from the halo toward the disk of the Milky Way is
still largely unclear. Here the amount of gas shed by the (older) halo red
giants is estimated. The distribution of red giants (RGs) in the halo is not
known but that of a subset of stars in the post RG phase, the sdB stars of the
horizontal-branch (HB), is. Using the mid-plane density and $z$-distribution of
sdB stars, the ratio of sdB stars to all HB stars, and the RG mass loss, the
infall due to total mass lost by all halo RG stars at $z>1$ kpc is calculated.
For the extended halo component $\dot{M}_{\rm halo RGs} \simeq 1.4 \cdot
10^{-5}$ \msun kpc$^{-2}$ yr$^{-1}$ while the thick disk component RGs
contribute $\dot{M}_{\rm thick disk RGs} \simeq 5.4 \cdot 10^{-5}$ \msun
kpc$^{-2}$ yr$^{-1}$, each with an uncertainty of a factor 4. The total rate of
infall due to RG mass-loss is $\dot{M}_{{\rm RGs at\}z>1 {\rm kpc}} \simeq 7
\cdot 10^{-5}$ \msun kpc$^{-2}$ yr$^{-1}$, a sizeable fraction of the equally
uncertain observed rate of infall of material. Since most of the RG stars in
the extended halo are old, their mass loss is predominantly metal-poor, while
that of the disk RGs is more metal-rich. The galactic fountain flow provides
additional metal-rich infall and small galaxies being accreted contribute to
the infall of gas as well.


title:
Implications for the formation of star clusters from extra-galactic
  star-formation rates

abstract:
  Observations indicate that young massive star clusters in spiral and dwarf
galaxies follow a relation between luminosity of the brightest young cluster
and the star-formation rate (SFR) of the host galaxy, in the sense that higher
SFRs lead to the formation of brighter clusters. Assuming that the empirical
relation between maximum cluster luminosity and SFR reflects an underlying
similar relation between maximum cluster mass (M_ecl,max) and SFR, we compare
the resulting SFR(M_ecl,max) relation with different theoretical models. The
empirical correlation is found to suggest that individual star clusters form on
a free-fall time-scale with their pre-cluster molecular-cloud-core radii
typically being a few pc independent of mass. The cloud cores contract by
factors of 5 to 10 while building-up the embedded cluster. A theoretical
SFR(M_ecl,max) relation in very good agreement with the empirical correlation
is obtained if the cluster mass function of a young population has a Salpeter
exponent beta approx. 2.35 and if this cluster population forms within a
characteristic time-scale of a few-10 Myr. This short time-scale can be
understood if the inter-stellar medium is pressurised thus precipitating rapid
local fragmentation and collapse on a galactic scale. Such triggered star
formation on a galactic scale is observed to occur in interacting galaxies.
With a global SFR of 3-5 Msol/yr the Milky Way appears to lie on the empirical
SFR(M_ecl,max) relation, given the recent detections of very young clusters
with masses near 10^5 Msol in the Galactic disk. The observed properties of the
stellar population of very massive young clusters suggests that there may exist
a fundamental maximum cluster mass, 10^6 < M_ecl,max*/Msol < 10^7.


title: Buoyant radio-lobes in a viscous intracluster medium

abstract:
  (Abridged) Ideal hydrodynamic models of the intracluster medium (ICM) in the
core regions of galaxy clusters fail to explain both the observed temperature
structure of this gas, and the observed morphology of radio-galaxy/ICM
interactions. It has recently been suggested that, even in the presence of
reasonable magnetic fields, thermal conduction in the ICM may be crucial for
reproducing the temperature floor seen in many systems. If this is indeed
correct, it raises the possibility that other transport processes may be
important. With this motivation, we present a numerical investigation of the
buoyant evolution of AGN-blown cavities in ICM that has a non-negligible shear
viscosity. We use the ZEUS-MP code to follow the 3-d evolution of an initially
static, hot bubble in a beta-model ICM atmosphere with varying degrees of shear
viscosity. With no explicit viscosity, it is found that the combined action of
Rayleigh-Taylor and Kelvin-Helmholtz instabilities shred the ICM cavity and one
does not reproduce the intact and detached ``ghost cavities'' observed in
systems such as Perseus-A. On the other hand, even a modest level of shear
viscosity can be important in quenching the fluid instabilities and maintaining
the integrity of the bubble. In particular, we show that the morphology of the
NW ghost cavity found in Perseus-A can be reproduced, as can the flow pattern
inferred from the morphology of H-alpha filaments. Finally, we discuss the
possible relevance of ICM viscosity to the fact that many of the active ICM
cavities are not bounded by strong shocks.


title:
The Physical Properties and Effective Temperature Scale of O-type Stars
  as a Function of Metallicity. I. A Sample of 20 Stars in the Magellanic
  Clouds

abstract:
  We have obtained HST and ground-based observations of a sample of 20 O-type
stars in the LMC and SMC, including six of the hottest massive stars known
(subtypes O2-3) in the R136 cluster. In general, these data include (a) the HST
UV spectra in order to measure the terminal velocities of the stellar winds,
(b) high signal-to-noise, blue-optical data where the primary temperature- and
gravity-sensitive photospheric lines are found, and (c) nebular-free H-alpha
profiles, which provide the mass-loss rates. The line-blanketed non-LTE
atmosphere code FASTWIND was then used to determine the physical parameters of
this sample of stars. We find good agreement between the synthetic line
profiles for the hydrogen, He I, and He II lines in the majority of the stars
we analyzed; the three exceptions show evidence of being incipiently resolved
spectroscopic binaries or otherwise spectral composites. One such system is
apparently an O3 V+O3 V eclipsing binary, and a follow-up radial velocity study
is planned to obtain Keplerian masses. Although we did not use them to
constrain the fits, good agreement is also found for the He I $\lambda 3187$
and He II $\lambda 3203$ lines in the near-UV, which we plan to exploit in
future studies. Our effective temperatures are compared to those recently
obtained by Repolust, Puls & Herrero for a sample of Galactic stars using the
same techniques. We find that the Magellanic Cloud sample is
3,000-4,000$^\circ$K hotter than their Galactic counterparts for the early
through mid-O's. These higher temperatures are the consequence of a decreased
importance of wind emission, wind blanketing, and metal-line blanketing at
lower metallicities.


title: X-ray Measurement of Dark Matter "Temperature" in Abell 1795

abstract:
  We present a method from an X-ray observation of a galaxy cluster to measure
the radial profile of the dark matter velocity dispersion, sigma_DM, and to
compare the dark matter ``temperature'' defined as mu m_p sigma_DM**2 / k_B
with the gas temperature. The method is applied to the XMM-Newton observation
of Abell 1795. The ratio between the specific energy of the dark matter and
that of the intracluster medium (ICM), which can be defined as beta_DM in
analogy with beta_spec, is found to be less than unity everywhere ranging
\~0.3-0.8. In other words, the ICM temperature is higher than the dark matter
``temperature'', even in the central region where the radiative cooling time is
short. A beta_DM value smaller than unity can most naturally be explained by
heating of the ICM. The excess energy of ICM is estimated to be ~1-3 keV per
particle.