title: A study of the two northern open clusters NGC 1582 and NGC 1663

abstract:
  We present CCD $UBV(I)_C$ observations obtained in the field of the
previously unstudied northern open clusters NGC 1582 and NGC 1663. For the
former, we also provide high-resolution spectra of the brightest stars and
complement our data with Two-Micron All-Sky-Survey (2MASS) near-infrared
photometry and with astrometric data from the Tycho-2 catalog. From the
analysis of all these data, we argue that NGC 1582 is a very poor, quite large
and heavily contaminated open cluster. It turns out to have a reddening
$E_{B-V} = 0.35 \pm 0.03$, to be situated $1100 \pm 100$ pc from the Sun and to
have an age of $300 \pm 100$ Myr. On the other hand, we were not able to
unambiguously clarify the nature of NGC 1663. By assuming it is a real cluster
and from the analysis of its photometric diagrams, we found a color excess
value $E_{B-V} = 0.20$, an intermediate age value ($\sim 2000$ Myr) and a
distance of about 700 pc. The distribution of the stars in the region however
suggests we are probably facing an open cluster remnant. As an additional
result, we obtained aperture photometry of three previously unclassified
galaxies placed in the field of NGC 1663 and performed a preliminary
morphological classification of them.


title: Large disk-like galaxies at high redshift

abstract:
  Using deep near-infrared imaging of the Hubble Deep Field South with ISAAC on
the Very Large Telescope we find 6 large disk-like galaxies at redshifts z =
1.4-3.0. The galaxies, selected in K_s (2.2 micron), are regular and
surprisingly large in the near-infrared (rest-frame optical), with face-on
effective radii r_e = 0.65"-0.9" or 5.0-7.5 h_70^-1 kpc in a Lambda-CDM
cosmology, comparable to the Milky Way. The surface brightness profiles are
consistent with an exponential law over 2-3 effective radii. The WFPC2
morphologies in Hubble Space Telescope imaging (rest-frame UV) are irregular
and show complex aggregates of star-forming regions ~2" (~15 h_70^-1 kpc)
across, symmetrically distributed around the K_s-band centers. The spectral
energy distributions show clear breaks in the rest-frame optical. The breaks
are strongest in the central regions of the galaxies, and can be identified as
the age-sensitive Balmer/4000 Angstrom break. The most straightforward
interpretation is that these galaxies are large disk galaxies; deep NIR data
are indispensable for this classification. The candidate disks constitute 50%
of galaxies with L_V > 6 x 10^10 h_70^-2 L_sun at z = 1.4-3.0. This discovery
was not expected on the basis of previously studied samples. In particular, the
Hubble Deep Field North is deficient in large galaxies with the morphologies
and profiles we report here.


title: Three-Dimensional Statistics of Radio Polarimetry

abstract:
  The measurement of radio polarization may be regarded as a three-dimensional
statistical problem because the large photon densities at radio wavelengths
allow the simultaneous detection of the three Stokes parameters which
completely describe the radiation's polarization. The statistical nature of the
problem arises from the fluctuating instrumental noise, and possibly from
fluctuations in the radiation's polarization. A statistical model is used to
derive the general, three-dimensional statistics that govern radio polarization
measurements. The statistics are derived for specific cases of source-intrinsic
polarization, with an emphasis on the orthogonal polarization modes in pulsar
radio emission. The statistics are similar to those commonly found in other
fields of the physical, biological, and Earth sciences. Given the highly
variable linear and circular polarization of pulsar radio emission, an
understanding of the three-dimensional statistics may be an essential
prequisite to a thorough interpretation of pulsar polarization data.


title:
Captures of stars by a massive black hole: Investigations in numerical
  stellar dynamics

abstract:
  Among the astrophysical systems targeted by LISA, stars on relativistic
orbits around massive black holes (MBHs) are particularly promising sources.
Unfortunately, the prediction for the number and characteristics of such
sources suffers from many uncertainties. Stellar dynamical Monte Carlo
simulations of the evolution of galactic nucleus models allow more realistic
estimates of these quantities. The computations presented here strongly suggest
that the closest such extreme mass-ratio binary to be detected by LISA could be
a low-mass MS star (MSS) orbiting the MBH at the center of our Milky Way. Only
compact stars contribute to the expected detections from other galaxies because
MSSs are disrupted by tidal forces too early.


title: PSR J1847-0130: A Radio Pulsar with Magnetar Spin Characteristics

abstract:
  We report the discovery of PSR J1847-0130, a radio pulsar with a 6.7-s spin
period, in the Parkes multibeam survey of the Galactic plane. The slowdown rate
for the pulsar, 1.3x10^{-12} s/s, is high and implies a surface dipole magnetic
field strength of 9.4x10^{13} G. This inferred dipolar magnetic field strength
is the highest by far among all known radio pulsars and over twice the
``quantum critical field'' above which some models predict radio emission
should not occur. The inferred dipolar magnetic field strength and period of
this pulsar are in the same range as those of the anomalous X-ray pulsars,
which have been identified as being "magnetars" whose luminous X-ray emission
is powered by their large magnetic fields. We have examined archival ASCA data
and place an upper limit on the X-ray luminosity of J1847-0130 which is lower
than the luminosities of all but one AXP. The properties of this pulsar prove
that inferred dipolar magnetic field strength and period cannot alone be
responsible for the unusual high-energy properties of the magnetars and creates
new challenges for understanding the possible relationship between these two
manifestations of young neutron stars.


title:
The late stages of evolution of helium star-neutron star binaries and
  the formation of double neutron star systems

abstract:
  With a view to understanding the formation of double neutron-stars (DNS), we
investigate the late stages of evolution of helium stars with masses of 2.8 -
6.4 Msun in binary systems with a 1.4 Msun neutron-star companion. We found
that mass transfer from 2.8 - 3.3 Msun helium stars and from 3.3 - 3.8 Msun in
very close orbits (P_orb > 0.25d) will end up in a common-envelope (CE) and
spiral-in phase due to the development of a convective helium envelope. If the
neutron star has sufficient time to complete the spiraling-in process before
the core collapses, the system will produce very tight DNSs (P_orb ~ 0.01d)
with a merger timescale of the order of 1 Myr or less. These systems would have
important consequences for the detection rate of GWR and for the understanding
of GRB progenitors. On the other hand, if the time left until the explosion is
shorter than the orbital-decay timescale, the system will undergo a SN
explosion during the CE phase. Helium stars with masses 3.3 - 3.8 Msun in wider
orbits (P_orb > 0.25d) and those more massive than 3.8 Msun do not go through
CE evolution. The remnants of these massive helium stars are DNSs with periods
in the range of 0.1 - 1 d. This suggests that this range of mass includes the
progenitors of the galactic DNSs with close orbits (B1913+16 and B1534+12). A
minimum kick velocity of 70 km/s and 0 km/s (for B1913+16 and B1534+12,
respectively) must have been imparted at the birth of the pulsar's companion.
The DNSs with wider orbits (J1518+4904 and probably J1811-1736) are produced
from helium star-neutron star binaries which avoid RLOF, with the helium star
more massive than 2.5 Msun. For these systems the minimum kick velocities are
50 km/s and 10 km/s (for J1518+4904 and J1811-1736, respectively).


title: Molecular outflows in the young open cluster IC348

abstract:
  We present a wide-field survey of the young open cluster IC348 for molecular
H2 outflows. Outflow activity is only found at its south-western limit, where a
new subcluster of embedded sources is in an early phase of its formation. If
the IC348 cluster had been built up by such subclusters forming at different
times, this could explain the large age-spread that Herbig (1998) found for the
IC348 member stars. In addition to several compact groups of H2 knots, our
survey reveals a large north-south oriented outflow, and we identify the newly
discovered far-infrared and mm-object IC348MMS as its source. New deep images
in the 1-0 S(1) line of molecular hydrogen trace the HH211 jet and counterjet
as highly-collimated chains of knots, resembling the interferometric CO and SiO
jets. This jet system appears rotated counter-clockwise by about 3 degrees with
respect to the prominent H2 bow shocks. Furthermore, we resolve HH211-mm as a
double point-like source in the mm-continuum.


title: Quasar Elemental Abundances and Host Galaxy Evolution

abstract:
  High redshift quasars mark the locations where massive galaxies are rapidly
being assembled and forming stars. There is growing evidence that quasar
environments are metal-rich out to redshifts of at least five. The gas-phase
metallicities are typically solar to several times solar, based on independent
analyses of quasar broad emission lines and intrinsic narrow absorption lines.
These results suggest that massive galaxies (e.g., galactic nuclei) experience
substantial star formation before the central quasar becomes observable. The
extent and epoch of this star formation (nominally at redshifts z > 2, but
sometimes at z > 5) are consistent with observations of old metal-rich stars in
present-day galactic nuclei/spheroids, and with standard models of galactic
chemical evolution. There is further tantalizing (but very tentative) evidence,
based on FeII/MgII broad emission line ratios, that the star formation usually
begins >0.3 Gyr before the onset of visible quasar activity. For the highest
redshift quasars, at z ~ 4.5 to ~6, this result suggests that the first major
star formation began at redshifts >6 to >10, respectively.


title: Dynamo action in turbulent flows

abstract:
  We present results from numerical simulations of nonlinear MHD dynamo action
produced by three-dimensional flows that become turbulent for high values of
the fluid Reynolds number. The magnitude of the forcing function driving the
flow is allowed to evolve with time in such way as to maintain an approximately
constant velocity amplitude (and average kinetic energy) when the flow becomes
hydrodynamically unstable. It is found that the saturation level of the dynamo
increases with the fluid Reynolds number (at constant magnetic Prandtl number),
and that the average growth rate approaches an asymptotic value for high fluid
Reynolds number. The generation and destruction of magnetic field is examined
during the laminar and turbulent phase of the flow and it is found that in the
neighborhood of strong magnetic "flux cigars" Joule dissipation is balanced by
the work done against the Lorentz force, while the steady increase of magnetic
energy occurs mainly through work done in the weak part of the magnetic field.


title: Probing the core and envelope structure of DBV white dwarfs

abstract:
  We investigate the global pulsation properties of DBV white dwarf models that
include both the double-layered envelope structure expected from time-dependent
diffusion calculations, as well as a non-uniform C/O core expected from prior
nuclear burning. We compare these models to otherwise identical models
containing a pure C core to determine whether the addition of core structure
leads to any significant improvement. Our double-layered envelope model fit to
GD 358 that includes an adjustable C/O core is significantly better than our
pure C core fit (7sigma improvement). We find a comparable improvement from
fits to a second DBV star, CBS 114, though the values of the derived parameters
may be more difficult to reconcile with stellar evolution theory. We find that
our models are systematically cooler by 1,900 K relative to the similar models
of Fontaine & Brassard (2002). Although a fit to their model reproduces the
mass and envelope structure almost exactly, we are unable to reproduce the
absolute quality of their fit to GD 358. Differences between the constitutive
physics employed by the two models may account for both the temperature offset
and the period residuals.


title:
The Transition between Nonorthogonal Polarization Modes in PSR B2016+28
  at 1404 MHz

abstract:
  Polarization observations of the radio emission from PSR B2016+28 at 1404 MHz
reveal properties that are consistent with two, very different, interpretations
of the pulsar's viewing geometry. The pulsar's average polarization properties
show a rapid change in position angle (PA) near the pulse center, suggesting
that the observer's sightline nearly intersects the star's magnetic pole. But
single pulse, polarization observations of the pulsar show nearly orthogonal
modes of polarization following relatively flat and parallel PA trajectories
across the pulse, suggesting that the sightline is far from the pole.
Additionally, PA histograms reveal a "modal connecting bridge", of unknown
origin, joining the modal PA trajectories over much of the pulse and following
the rapid PA change shown in the average data. The nonorthogonality of
polarization modes is incorporated in a statistical model of radio polarization
to account for the deviations from mode orthogonality that are observed in the
pulsar. The model is used to interpret the rapid PA change and modal connecting
bridge as a longitudinally-resolved transition between modes of nonorthogonal
polarization. Thus, the modal PA trajectories are argued to reflect the
pulsar's true viewing geometry. This interpretation is consistent with the
pulsar's morphological classification, preserves the Radhakrishnan & Cooke
model of pulsar radio emission, and avoids the complication that the modal
connecting bridge might be produced by some other emission mechanism. The
statistical model's ability to simulate the rich variety of polarization
properties observed in the emission lends additional support to the model's
applicability and its underlying assumption that the polarization modes occur
simultaneously.


title:
The near-synchronous polar V1432 Aql (RX J1940.1-1025): Accretion
  geometry and synchronization time scale

abstract:
  The magnetic Cataclysmic Variable (mCV) V1432 Aql (RX 1940.1-1025) belongs to
the four-member subclass of near-synchronous polars with a slight
non-synchronism (<2 %) between the spin period of the white dwarf and the
binary period. In these systems the accretion geometry changes periodically
with phase of the beat cycle. We present the application of a dipole accretion
model for near-synchronous systems developed by Geckeler & Staubert (1997a) to
extended optical and X-ray data. We detect a significant secular change of the
white dwarf spin period in V1432 Aql of dP_spin/dt = -5.4 (+3.7/-3.2) 10-9 s/s
from the optical data set alone. This corresponds to a synchronization time
scale tau_sync = 199 (+441/-75) yr, comparable to the time scale of 170 yr for
V1500 Cyg. The synchronization time scale in V1432 Aql is in excellent
agreement with the theoretical prediction from the dominating magnetic torque
in near-synchronous systems. We also present period analyses of optical CCD
photometry and RXTE X-ray data, which argue against the existence of a 4000 s
period and an interpretation of V1432 Aql as an intermediate polar. The dipole
accretion model also allows to constrain the relevant parameters of the
accretion geometry in this system: the optical data allow an estimate of the
dimensionless parameter (R_t0'/R_wd)1/2 sin(beta) = 3.6 (+2.7/-1.1), with a
lower limit for the threading radius of R_t0' > 10 R_wd (68% confidence).


title: Measuring the Hubble Constant with the Sunyaev-Zel'dovich Effect

abstract:
  Combined with X-ray imaging and spectral data, observations of the
Sunyaev-Zel'dovich effect (SZE) can be used to determine direct distances to
galaxy clusters. These distances are independent of the extragalactic distance
ladder and do not rely on clusters being standard candles or rulers.
Observations of the SZE have progressed from upper limits to high
signal-to-noise ratio detections and imaging of the SZE. SZE/X-ray determined
distances to galaxy clusters are beginning to trace out the theoretical
angular-diameter distance relation. The current ensemble of 41 SZE/X-ray
distances to galaxy clusters imply a Hubble constant of H_0~ 61 +/- 3 +/- 18 km
s-1 Mpc-1, where the uncertainties are statistical followed by systematic at
68% confidence. With a sample of high-redshift galaxy clusters, SZE/X-ray
distances can be used to measure the geometry of the Universe.


title: The need for a second black hole at the Galactic center

abstract:
  Deep infra-red observations and long-term monitoring programs have provided
dynamical evidence for a supermassive black hole of mass 3.e6 solar masses
associated with the radio source Sagitarrius A* at the center of our Galaxy.
The brightest stars orbiting within 0.1 parsecs of the black hole appear to be
young, massive main sequence stars, n spite of an environment near the black
hole that is hostile to star formation. We discuss mechanisms by which stars
born outside the central parsec can sink towards the black hole and conclude
that the drag coming from plausible stellar populations does not operate on the
short timescales required by the stellar ages. We propose that these stars were
dragged in by a second black hole of mass of 1.e3-1.e4 solar masses, which
would be classified as an intermediate-mass black hole. We discuss the
implications for the stellar populations and the kinematics in the Galactic
center. Finally we note that continued astrometric monitoring of the central
radio source offers the prospect for a direct detection of such objects.


title: An AST/RO Survey of CO(4-3) in ultracompact HII regions

abstract:
  The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) has
been used to observe 78 of the IRAS point sources identified by Bronfman et al.
(1996) as likely ultracompact HII regions. Results for the CO(4-3) line at
461.041GHz are presented. The 74 sources detected are bright and in many cases
compact, making them potentially suitable as pointing calibrators for single
dish submillimeter telescopes.


title:
Finding cool subdwarfs using a V-J reduced proper-motion diagram:
  Stellar parameters for 91 candidates

abstract:
  We present the results of a search for cool subdwarfs for which our
candidates were drawn from a V-J reduced proper-motion diagram constructed by
Salim & Gould (2002). Kinematic (U, V, and W) and self-consistent stellar
parameters (Teff, log g, [Fe/H], and V_t) are derived for 91 candidate
subdwarfs based on high resolution spectra. The observed stars span 3900K <
Teff < 6200K and -2.63 < [Fe/H] < 0.25 including only 3 giants (log g < 4.0).
Of the sample, 77 stars have MgH lines present in their spectra. With more than
56% of our candidate subdwarfs having [Fe/H] < -1.5, we show that the V-J
reduced proper-motion diagram readily identifies metal-poor stars.


title:
A comparison of DA white dwarf temperatures and gravities from FUSE
  Lyman line and ground-based Balmer line observations

abstract:
  Observation of the strengths and profiles of the hydrogen Balmer absorption
series is an established technique for determining the effective temperature
and surface gravity of hot H-rich white dwarf stars. In principle, the Lyman
series lines should be equally useful but, lying in the far-UV, are only
accessible from space. Nevertheless, there are situations (for example, where
the optical white dwarf spectrum is highly contaminated by the presence of a
companion) in which use of the Lyman series may be essential. Therefore, it is
important to establish whether or not the Lyman lines provide an equally valid
means of measurement. We have already made a first attempt to study this
problem, comparing Lyman line measurements from a variety of far-UV instruments
with ground-based Balmer line studies. Within the measurement uncertainties we
found the results from each line series to be broadly in agreement. However, we
noted a number of potential systematic effects that could bias either
measurement. With the availability of the FUSE data archive and observations
from our own Guest Observer programmes, we now have an opportunity of examining
the use of the Lyman series in more detail from observations of 16 DA white
dwarfs. The new results partially reproduce the earlier study, showing that
Balmer and Lyman line determined temperatures are in good agreement up to
\~50000K. However, above this value there is an increasing systematic
difference between the Lyman and Balmer line results, the former yielding the
higher temperature.


title:
Variation of dispersion measure: evidence of geodetic precession of
  binary pulsars

abstract:
  Variations of dispersion measure (DM) have been observed in some binary
pulsars, which can not be well explained by the propagation effects, such as
turbulence of the interstellar media (ISM) between the Earth and the pulsar.
This paper provides an alternative interpretation of the phenomena, the
geodetic precession of the orbit plane of a binary pulsar system. The dynamic
model can naturally avoid the difficulties of propagation explanations.
Moreover the additional time delay represented by the DM variation of two
binary pulsars can be fitted numerically, through which some interesting
parameters of the binary pulsar system, i.e., the moment of inertia of pulsars
can be obtained, $I_1=(2.0\pm0.6)\times 10^{45}$g cm$^{2}$. The elimination of
the additional time delay by the dynamic effect means that ISM between the
these pulsars and the Earth might also be stable, like some other binary
pulsars.


title: Colour ratios of pulsation amplitudes in red giants

abstract:
  We have analysed the three-colour photometry of 34 pulsating red giants that
was published by Percy, Wilson and Henry (2001). As is common with
semiregulars, many of these stars have long secondary periods (LSPs) of several
years, in addition to the usual shorter-period pulsations. We measured
pulsation amplitudes in VRI and found that both the V/R and V/I amplitude
ratios in most stars are systematically lower for the LSPs that for the shorter
periods. These results must be taken into account by any theory that attempts
to explain LSPs.


title:
Theoretical Modeling of the Thermal State of Accreting White Dwarfs
  Undergoing Classical Novae

abstract:
  White dwarfs experience a thermal renaissance when they receive mass from a
stellar companion in a binary. For accretion rates < 10^-8 Msun/yr, the freshly
accumulated hydrogen/helium envelope ignites in a thermally unstable manner
that results in a classical novae (CN) outburst and ejection of material. We
have undertaken a theoretical study of the impact of the accumulating envelope
on the thermal state of the underlying white dwarf (WD). This has allowed us to
find the equilibrium WD core temperatures (T_c), the classical nova ignition
masses (M_ign) and the thermal luminosities for WDs accreting at rates of
10^-11 - 10^-8 Msun/yr. These accretion rates are most appropriate to WDs in
cataclysmic variables (CVs) of P_orb <~ 7 hr, many of which accrete
sporadically as dwarf novae. We have included ^3He in the accreted material at
levels appropriate for CVs and find that it significantly modifies the CN
ignition mass. We compare our results with several others from the CN
literature and find that the inclusion of ^3He leads to lower M_ign for <Mdot>
>~ 10^-10 Msun/yr, and that for <Mdot> below this the particular author's
assumption concerning T_c, which we calculate consistently, is a determining
factor. Initial comparisons of our CN ignition masses with measured ejected
masses find reasonable agreement and point to ejection of material comparable
to that accreted.


title:
A study of dark matter halos and gas properties in clusters of galaxies
  from ROSAT data

abstract:
  Self-gravitating systems such as elliptical galaxies appear to have a
constant integrated specific entropy and obey a scaling law relating their
potential energy to their mass. These properties can be interpreted as due to
the physical processes involved in the formation and evolution of these
structures. Dark matter halos obtained through numerical simulations have also
been found to obey a scaling law relating their potential energy to their mass
with the same slope as for ellipticals, and very close to the expected value
predicted by theory. Since the X-ray gas in clusters is weakly dissipative, we
test here the hypothesis that it verifies similar properties. Comparable
properties for the dark matter component are also investigated. With this aim,
we have analyzed ROSAT-PSPC images of 24 clusters, and fit a S\'ersic law to
their X-ray surface brightness profiles. We found that: 1) the S\'ersic law
parameters (intensity, shape and scale) describing the X-ray gas emission are
correlated two by two, with a strong correlation between the shape and scale
parameters; 2) the hot gas in all these clusters roughly has the same
integrated specific entropy, although a second order correlation between this
integrated specific entropy and both the gas mass and the dynamical mass is
observed; 3) a scaling law links the cluster potential energy to its total
mass, with the same slope as that derived for elliptical galaxies and for dark
matter halo simulations. Comparable relations are obtained for the dark matter
component. All these correlations are probably the consequence of the formation
and evolution processes undergone by clusters of galaxies.


title: Galactic cannibalism in the galaxy cluster C0337-2522 at z=0.59

abstract:
  According to the galactic cannibalism model, cD galaxies are formed in the
center of galaxy clusters by merging of massive galaxies and accretion of
smaller stellar systems: however, observational examples of the initial phases
of this process are lacking. We have identified a strong candidate for this
early stage of cD galaxy formation: a group of five elliptical galaxies in the
core of the X-ray cluster C0337-2522 at redshift z=0.59. With the aid of
numerical simulations, in which the galaxies are represented by N-body systems,
we study their dynamical evolution up to z=0; the cluster dark matter
distribution is also described as a N-body system. We find that a multiple
merging event in the considered group of galaxies will take place before z=0
and that the merger remnant preserves the Fundamental Plane and the
Faber-Jackson relations, while its behavior with respect to the Mbh-sigma
relation is quite sensitive to the details of black hole merging [abridged].


title:
Magnetic coupling of a rotating black hole with its surrounding
  accretion disk

abstract:
  Effects of magnetic coupling (MC) of a rotating black hole (BH) with its
surrounding accretion disk are discussed in detail in the following aspects:
(i) The mapping relation between the angular coordinate on the BH horizon and
the radial coordinate on the disk is modified based on a more reasonable
configuration of magnetic field, and a condition for coexistence of the
Blandford-Znajek (BZ) and the MC process is derived. (ii) The transfer
direction of energy and angular momentum in MC process is described
equivalently by the co-rotation radius and by the flow of electromagnetic
angular momentum and redshifted energy, where the latter is based on an
assumption that the theory of BH magnetosphere is applicable to both the BZ and
MC processes. (iii) The profile of the current on the BH horizon and that of
the current density flowing from the magnetosphere onto the horizon are given
in terms of the angular coordinate of the horizon. It is shown that the current
on the BH horizon varies with the latitude of the horizon and is not continuous
at the angular boundary between the open and closed magnetic field lines. (iv)
The MC effects on disk radiation are discussed, and a very steep emissivity is
produced by MC process, which is consistent with the recent XMM-Newton
observation of the nearby bright Seyfert 1 galaxy MCG-6-30-15 by a variety of
parameters of the BH-disk system.


title: WR bubbles and HeII emission

abstract:
  We present the very first high quality images of the HeII 4686 emission in
three high excitation nebulae of the Magellanic Clouds. A fourth high
excitation nebula, situated around the WR star BAT99-2, was analysed in a
previous letter. Using VLT FORS data, we investigate the morphology of the ring
nebulae around the early-type WN stars BAT99-49 & AB7. We derive the total HeII
fluxes for each object and compare them with the most recent theoretical WR
models. Using Halpha, [OIII] and HeI 5876 images along with long-slit
spectroscopy, we investigate the physical properties of these ring nebulae and
find only moderate chemical enrichment. We also surveyed seven other LMC WR
stars but we failed to detect any HeII emission but note that the nebula around
BAT99-11 shows a N/O ratio and an oxygen abundance slightly lower than the LMC
values, while the nebula around BAT99-134 presents moderate chemical enrichment
similar to the one seen near BAT99-2, 49 and AB7. The third high excitation
nebula presented in this paper, N44C, does not harbor stars hotter than mid-O
main sequence stars. It was suggested to be a fossil X-ray nebula ionized but
our observations of N44C reveal no substantial changes in the excitation
compared to previous results reported in the literature.


title:
Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic
  Variables: III. A New Kind of Dwarf Nova Oscillation, and Further Examples of
  the Similarities to X-Ray Binaries

abstract:
  We present measurements of the periods of Dwarf Nova Oscillations (DNOs) and
Quasi-Periodic Oscillations (QPOs) in Cataclysmic Variable stars (CVs), many
culled from published literature, but also others newly observed (in VZ Pyx, CR
Boo, OY Car, Z Cha, AQ Eri, TU Men, HX Peg, CN Ori, V893 Sco, WX Hyi and
EC2117-54). These provide data for 26 systems. We show that in general P_QPO ~
15 P_DNO and that the correlation for CVs extends by three orders of magnitude
lower in frequency the similar relationship found for X-Ray binaries. In
addition, we have found that there is a second type of DNO, previously
overlooked, which have periods ~ 4 times those of the regular DNOs (As well as
those mined from publications, we have observed them in VW Hyi, OY Car, AQ Eri,
V803 Cen, CR Boo, VZ Pyx, HX Peg and EC2117-54). Often both types of DNO
coexist. Unlike the standard DNOs, the periods of the new type, which we refer
to as longer period DNOs (lpDNOs), are relatively insensitive to accretion
luminosity and can even appear in quiescence of dwarf novae. We interpret them
as magnetically channelled accretion onto the differentially rotating main body
of the white dwarf primary, rather than onto a rapidly slipping equatorial belt
as in the case of the standard DNOs. This is supported by published
measurements of v sin(i) for some of the primaries. Some similarities of the
DNOs, lpDNOs and QPOs in CVs to the three types of QPO in X-Ray binaries (burst
pulsation, high and low frequency QPOs) are noted.


title:
High Angular Resolution, Sensitive CS J=2-1 and J=3-2 Imaging of the
  Protostar L1551 NE: Evidence for Outflow-Triggered Star Formation ?

abstract:
  High angular resolution and sensitive aperture synthesis observations of CS
($J=2-1$) and CS ($J=3-2$) emissions toward L1551 NE, the second brightest
protostar in the Taurus Molecular Cloud, made with the Nobeyama Millimeter
Array are presented. L1551 NE is categorized as a class 0 object deeply
embedded in the red-shifted outflow lobe of L1551 IRS 5. Previous studies of
the L1551 NE region in CS emission revealed the presence of shell-like
components open toward L1551 IRS 5, which seem to trace low-velocity shocks in
the swept-up shell driven by the outflow from L1551 IRS 5. In this study,
significant CS emission around L1551 NE was detected at the eastern tip of the
swept-up shell from $V_{\rm{lsr}}$ = 5.3 km s$^{-1}$ to 10.1 km s$^{-1}$, and
the total mass of the dense gas is estimated to be 0.18 $\pm$ 0.02 $M_\odot$.
Additionally, the following new structures were successfully revealed: a
compact disklike component with a size of $\approx$ 1000 AU just at L1551 NE,
an arc-shaped structure around L1551 NE, open toward L1551 NE, with a size of
$\sim 5000$ AU, i.e., a bow shock, and a distinct velocity gradient of the
dense gas, i.e., deceleration along the outflow axis of L1551 IRS 5. These
features suggest that the CS emission traces the post-shocked region where the
dense gas associated with L1551 NE and the swept-up shell of the outflow from
L1551 IRS 5 interact. Since the age of L1551 NE is comparable to the timescale
of the interaction, it is plausible that the formation of L1551 NE was induced
by the outflow impact. The compact structure of L1551 NE with a tiny envelope
was also revealed, suggesting that the outer envelope of L1551 NE has been
blown off by the outflow from L1551 IRS 5.


title:
Timing Detection of Eclipsing Binary Planets and Transiting Extrasolar
  Moons

abstract:
  We investigate the improved detection of extrasolar planets around eclipsing
binaries using eclipse minima timing, and extrasolar moons around transiting
planets using transit timing, offered by the upcoming COROT (ESA, 2005), Kepler
(NASA, 2007), and Eddington (ESA 2008) spacecraft missions. Hundreds of
circum-binary planets should be discovered, and a thorough survey of moons
around transiting planets will be accomplished by these missions.


title: Giant Arc Statistics In Concordance With A Concordance LCDM Universe

abstract:
  The frequency of giant arcs - highly distorted and strongly gravitationally
lensed background galaxies - is a powerful test for cosmological models.
Previous comparisons of arc statistics for the currently favored concordance
cosmological model (a flat lambda-dominated universe) with observations have
shown an apparently large discrepancy. We present here new ray-shooting
results, based on a high resolution (1024^3 particles in a 320 Mpc/h box)
large-scale structure simulation normalized to the WMAP observations. We follow
light rays through a pseudo-3D matter distribution approximated by up to 38
lens planes, and evaluate the occurrence of arcs for various source redshifts.
We find that the frequency of strongly lensed background sources is a steep
function of source redshift: the optical depth for giant arcs increases by a
factor of five when the background sources are moved from redshift z_s = 1.0 to
z_s = 1.5. This is a consequence of a moderate decrease of the critical surface
mass density for lensing, combined with the very steep cluster mass function at
the high mass end. Our results are consistent with those of Bartelmann et al.
(1998) if we - as they did - restrict all sources to be exactly at z_s = 1. But
if we allow for a more realistic distribution of source redshifts extending to
or beyond z_s > 1.5, the apparent discrepancy vanishes: the frequency of arcs
is increased by about a factor of ten as compared to previous estimates, and
results in roughly one arc per 20 square degrees over the sky. This prediction
for an LCDM model is then in good agreement with the observed frequency of
arcs. Hence we consider the ``missing arc'' problem for a concordance LCDM
cosmology to be solved.


title: A model for the cross section of a turbulent, radiative jet or wake

abstract:
  We present an analytical model for the cross section of a turbulent,
radiative jet or wake. This model is appropriate for modeling HH jets, or
"wakes" left behind by "astrophysical bullets". Even though the model is very
simple, it has the benign property of only having four free parameters (the
outer radius of the beam, the axial velocity, the velocity at the edge of the
beam, and the turbulent velocity width), which can be derived by fitting the
radial velocity and line width cross sections of an observed outflow. We
illustrate how to do such fits using previously published spectroscopic data of
the HH 110 jet.


title: Influence of Black Holes on Stellar Orbits

abstract:
  We review the current state of dynamical modeling for galaxies in terms of
being able to measure both the central black hole mass and stellar orbital
structure. Both of these must be known adequately to measure either property.
The current set of dynamical models do provide accurate estimates of the black
hole mass and the stellar orbital distribution. Generally, these models are
able to measure the black hole mass to about 20%--30% accuracy given present
observations, and the stellar orbital structure to about 20% accuracy in the
radial to tangential dispersions. The stellar orbital structure of the stars
near the galaxy center show strong tangential velocity anisotropy for most
galaxies studied. Theoretical models that best match this trend are black hole
binary/merger models. There is also a strong correlation between black hole
mass and the contribution of radial motion at large radii. This correlation may
be an important aspect of galaxy evolution.


title: The 2001 April Burst Activation of SGR 1900+14: X-ray afterglow emission

abstract:
  After nearly two years of quiescence, the soft gamma-ray repeater SGR 1900+14
again became burst-active on April 18 2001, when it emitted a large flare,
preceded by few weak and soft short bursts. After having detected the X and
gamma prompt emission of the flare, BeppoSAX pointed its narrow field X-ray
telescopes to the source in less than 8 hours. In this paper we present an
analysis of the data from this and from a subsequent BeppoSAX observation, as
well as from a set of RossiXTE observations. Our data show the detection of an
X-ray afterglow from the source, most likely related to the large hard X-ray
flare. In fact, the persistent flux from the source, in 2-10 keV, was initially
found at a level $\sim$5 times higher than the usual value. Assuming an
underlying persistent (constant) emission, the decay of the excess flux can be
reasonably well described by a t$^{-0.9}$ law. A temporal feature - a
$\sim$half a day long bump - is observed in the decay light curve approximately
one day after the burst onset. This feature is unprecedented in SGR afterglows.
We discuss our results in the context of previous observations of this source
and derive implications for the physics of these objects.


title:
The 2001 April Burst Activation of SGR 1900+14: Pulse Properties and
  Torque

abstract:
  We report on observations of SGR 1900+14 made with the Rossi X-ray Timing
Explorer (RXTE) and BeppoSAX during the April 2001 burst activation of the
source. Using these data, we measure the spindown torque on the star and
confirm earlier findings that the torque and burst activity are not directly
correlated. We compare the X-ray pulse profile to the gamma-ray profile during
the April 18 intermediate flare and show that (i) their shapes are similar and
(ii) the gamma-ray profile aligns closely in phase with the X-ray pulsations.
The good phase alignment of the gamma-ray and X-ray profiles suggests that
there was no rapid spindown following this flare of the magnitude inferred for
the August 27 giant flare. We discuss how these observations further constrain
magnetic field reconfiguration models for the large flares of SGRs.


title: NGC 6738: not a real open cluster

abstract:
  A photometric, astrometric and spectroscopic investigation of the poorly
studied open cluster NGC 6738 has been performed in order to ascertain its real
nature. NGC 6738 is definitely not a physical stellar ensemble: photometry does
not show a defined mean sequence, proper motions and radial velocities are
randomly distributed, spectro-photometric parallaxes range between 10 and 1600
pc, and the apparent luminosity function is identical to that of the
surrounding field. NGC 6738 therefore appears to be an apparent concentration
of a few bright stars projected on patchy background absorption.


title: Probing the circumstellar structure of pre-main sequence stars

abstract:
  We present Halpha spectropolarimetry of a large sample of pre-main sequence
(PMS) stars of low and intermediate mass, and argue that the technique is a
powerful tool in studying the circumstellar geometry around these objects. For
the intermediate mass (2 -- 15 Msun) Herbig Ae/Be stars we find that 16 out of
23 show a line effect, which immediately implies that flattening is common
among these objects. Furthermore, we find a significant difference in Halpha
spectropolarimetry behaviour between the Herbig Be and Ae groups. For the
Herbig Be stars, the concept of an electron scattering disc is shown to be a
useful concept to explain the depolarizations seen in this spectral range. At
lower masses, more complex Halpha polarimetry behaviour starts to appear. The
concept of a compact source of Halpha emission that is formed close to the
stellar surface, for instance by hot spots due to magnetospheric accretion, is
postulated as a working hypothesis to qualitatively explain the Halpha
spectropolarimetry behaviour around Herbig Ae and lower mass (M < 2 Msun) T
Tauri stars. The striking resemblance in spectropolarimetric behaviour between
the T Tauri star RY Tau and the Herbig Ae stars suggests a common origin of the
polarized line photons, and hints that low and higher mass pre-main sequence
stars may have more in common than had hitherto been suspected.


title:
Resolved polarization changes across Halpha in the classical T Tauri
  star RY Tau

abstract:
  We present linear Halpha spectropolarimetry of the classical T Tauri star RY
Tau. A change in the polarization percentage and position angle across Halpha
is detected, which suggests that line photons are scattered in a rotating disc.
We derive the position angle from the slope of the loop in the (Q,U) diagram
and find it to be 146 +/- 3 degrees. This is perpendicular to the position
angle of the disc of 48 +/- 5 degrees as deduced from submillimeter imaging by
Koerner & Sargent (1995). This finding is consistent, as scattering off the
imaged millimeter disc is expected to yield a polarization signature in a
direction that is rotated by 90 degrees from this disc. The observed
spectropolarimetric behaviour of RY Tau is reminiscent of that seen in a large
group of Herbig Ae stars, suggesting a common circumstellar origin of the
polarized photons.


title: Self-Similar Models for the Mass Profiles of Early-type Lens Galaxies

abstract:
  We introduce a self-similar mass model for early-type galaxies, and constrain
it using the aperture mass-radius relations determined from the geometries of
22 gravitational lenses. The model consists of two components: a concentrated
component which traces the light distribution, and a more extended power-law
component (rho propto r^-n) which represents the dark matter. We find that lens
galaxies have total mass profiles which are nearly isothermal, or slightly
steeper, on the several-kiloparsec radial scale spanned by the lensed images.
In the limit of a single-component, power-law radial profile, the model implies
n=2.07+/-0.13, consistent with isothermal (n=2). Models in which mass traces
light are excluded at >99 percent confidence. An n=1 cusp (such as the
Navarro-Frenk-White profile) requires a projected dark matter mass fraction of
f_cdm = 0.22+/-0.10 inside 2 effective radii. These are the best statistical
constraints yet obtained on the mass profiles of lenses, and provide clear
evidence for a small but non-zero dark matter mass fraction in the inner
regions of early-type galaxies. In addition, we derive the first strong lensing
constraint on the relation between stellar mass-to-light ratio (Upsilon) and
galaxy luminosity (L): Upsilon propto L^[0.14 (+0.16)(-0.12)], which is
consistent with the relation suggested by the fundamental plane. Finally, we
apply our self-similar mass models to current problems regarding the
interpretation of time delays and flux ratio anomalies in gravitational lens
systems.


title:
The effect of imperfect corrections of PSF anisotropy on cosmic shear
  measurements

abstract:
  Current measurements of the weak lensing signal induced by large scale
structure provide useful constraints on a range of cosmological parameters.
However, the ultimate succes of this technique depends on the accuracy with
which one can correct for the effect of the Point Spread Function (PSF). In
this paper we examine the accuracy of the PSF anisotropy correction using
images of fields with a large number of stars. The ellipticity correlation
function of the residuals is studied to quantify the effect of imperfect
corrections for PSF anisotropy on cosmic shear studies. These imperfections
occur on the chip scale and consequently the systematic signal decreases
rapidly with increasing angular scale. Separation of the signal into ``E''
(curl-free) and ``B'' (curl) components can help to identify the presence of
residual systematics, but in general, the amplitude of the ``B''-mode is
different from that of the ``E''-mode. The study of fields with many stars can
be beneficial in finding a proper description of the variation of PSF
anisotropy, and consequently help to significantly improve the accuracy with
which the cosmic shear signal can be measured. We show that with such an
approach it is feasible that the accuracy of future cosmic shear studies is
limited by the statistical noise introduced by the intrinsic shapes of the
sources. In particular, the prospects for accurate measurements of the cosmic
shear signal on scales larger than ~10 arcminutes are excellent.


title:
On resonance line profiles predicted by radiation driven disk wind
  models

abstract:
  We report on resonance line profiles predicted by radiation driven disk wind
models which extend radially one order of magnitude farther out than our
previous models. Our main result is that the inclusion of a disk wind at larger
radii changes qualitatively and quantitatively the line profiles predicted by
the models. Our new models predict line absorption that is significantly
stronger than those predicted by old models. Some of the previous line profiles
exhibit a doubled-humped structure near the line center which is now replaced
by a more plausible single, blueshifted minimum. We emphasize that the
improvements in the shape as well as the strength of the absorption were
achieved without changing the gross properties of the wind. In particular, our
new models do not predict a higher mass-loss rate than the previous models. The
main changes in the line profiles are due to the fact that the ratio between
the rotational velocity and poloidal velocity of the wind decreases downstream.
The new line profiles reproduce well the line absorption of the nova-like
variable, IX~Vel, and promise to reproduce observations of other cataclysmic
variables. This success of the radiation driven disk wind model provides an
important link between outflows in OB stars and outflows in active galactic
nuclei.


title: Winds in R Coronae Borealis Stars

abstract:
  We present new spectroscopic observations of the He I $\lambda$10830 line in
R Coronae Borealis (RCB) stars which provide the first strong evidence that
most, if not all, RCB stars have winds. It has long been suggested that when
dust forms around an RCB star, radiation pressure accelerates the dust away
from the star, dragging the gas along with it. The new spectra show that nine
of the ten stars observed have P-Cygni or asymmetric blue-shifted profiles in
the He I $\lambda$10830 line. In all cases, the He I line indicates a mass
outflow - with a range of intensity and velocity. Around the RCB stars, it is
likely that this state is populated by collisional excitation rather than
photoionization/recombination. The line profiles have been modeled with an SEI
code to derive the optical depth and the velocity field of the helium gas. The
results show that the typical RCB wind has a steep acceleration with a terminal
velocity of \Vinf = 200-350 \kms and a column density of N $\sim10^{12}$
cm$^{-2}$ in the He I $\lambda$10830 line. There is a possible relationship
between the lightcurve of an RCB star and its He I $\lambda$10830 profile.
Stars which have gone hundreds of days with no dust-formation episodes tend to
have weaker He I features. The unusual RCB star, V854 Cen, does not follow this
trend, showing little or no He I absorption despite high mass-loss activity.
The He I $\lambda$10830 line in R CrB itself, which has been observed at four
epochs between 1978 and 2001, seems to show a P-Cygni or asymmetric
blue-shifted profile at all times whether it is in decline or at maximum light.


title:
Nucleosynthesis of Light and Heavy Elements in Baryon-Rich Outflows
  Associated with Gamma-Ray Bursts

abstract:
  Gamma-ray bursts (GRBs) must originate from low baryon load,
ultrarelativistic outflows; however, slower, more baryon-rich outflows (BROs)
should also arise in connection with GRBs as ``circum-jet winds'' and/or
``failed GRBs''. We study the possibility of nucleosynthesis within such BROs
by conducting detailed reaction network calculations in the framework of the
fireball model, showing that they can be interesting sites for synthesis of
heavy neutron capture elements, as well as of light elements such as deuterium.
These products may be observable in the companion stars of black hole binary
systems or in extremely metal-poor stars, offering an interesting probe of
conditions in the central engine.


title: Multiple outflows in IRAS 19410+2336

abstract:
  PdBI high-spatial resolution CO observations combined with near-infrared H2
data disentangle at least 7 (maybe even 9) molecular outflows in the massive
star-forming region IRAS19410+2336. Position-velocity diagrams of the outflows
reveal Hubble-like relationships similar to outflows driven by low-mass
objects. Estimated accretion rates are of the order 10^-4 Msun/yr, sufficiently
high to overcome the radiation pressure and form massive stars via
disk-mediated accretion processes. The single-dish large-scale mm continuum
cores fragment into several compact condensations at the higher spatial
resolution of the PdBI which is expected due to the clustering in massive star
formation. While single-dish data give a simplified picture of the source,
sufficiently high spatial resolution resolves the structures into outflows
resembling those of low-mass star-forming cores. We interpret this as further
support for the hypothesis that massive stars do form via disk-accretion
processes similar to low-mass stars.


title:
Arc Statistics in Triaxial Dark Matter Halos: Testing the Collisionless
  Cold Dark Matter Paradigm

abstract:
  Statistics of lensed arcs in clusters of galaxies serve as a powerful probe
of both the non-sphericity and the inner slope of dark matter halos. We develop
a semi-analytic method to compute the number of arcs in triaxial dark matter
halos. This combines the lensing cross section from the Monte Carlo ray-tracing
simulations, and the probability distribution function (PDF) of the axis ratios
evaluated from cosmological N-body simulations. This approach enables one to
incorporate both asymmetries in the projected mass density and elongations
along the line-of-sight analytically, for the first time in cosmological lensed
arc statistics. As expected, triaxial dark matter halos significantly increase
the number of arcs relative to spherical models; the difference amounts to more
than one order of magnitude while the value of enhancement depends on the
specific properties of density profiles. Then we compare our theoretical
predictions with the observed number of arcs from 38 X-ray selected clusters.
In contrast to the previous claims, our triaxial dark matter halos with inner
density profile \rho \propto r^{-1.5} in a Lambda-dominated cold dark matter
(CDM) universe reproduces well the observation. Since both the central mass
concentration and triaxial axis ratios (minor to major axis ratio ~0.5)
required to account for the observed data are consistent with cosmological
N-body simulations, our result may be interpreted to lend strong support for
the collisionless CDM paradigm at the mass scale of clusters.


title:
Orbital Motion in the Radio Galaxy 3C 66B: Evidence for a Supermassive
  Black Hole Binary

abstract:
  Supermassive black hole binaries may exist in the centers of active galactic
nuclei like quasars and radio galaxies and mergers between galaxies may result
in the formation of supermassive binaries during the course of galactic
evolution. Using the very-long-baseline interferometer, we imaged the radio
galaxy 3C 66B at radio frequencies and found that the unresolved radio core of
3C 66B shows well-defined elliptical motions with a period of 1.05 +/- 0.03
years, which provides a direct detection of a supermassive black hole binary.


title: The 6dF Galaxy Survey

abstract:
  The 6dF Galaxy Survey (6dFGS) is a spectroscopic survey of the entire
southern sky with $|b|>10\deg$, based on the 2MASS near infrared galaxy
catalog. It is conducted with the 6dF multi-fiber spectrograph attached to the
1.2-m UK Schmidt Telescope. The survey will produce redshifts for some 170,000
galaxies, and peculiar velocities for about 15,000 and is expected to be
complete by June 2005.


title: Galaxy Bias in Quintessence Cosmological Models

abstract:
  We derive the evolution of the linear bias factor, $b(z)$, in cosmological
models driven by an exotic fluid with an equation of state: $p_{x}=w\rho_{x}$,
where $-1\le w<0$ (quintessence). Our aim is to put constrains on different
cosmological and biasing models by combining the recent observational
clustering results of optical ({\em 2dF}) galaxies (Hawkings et al.) with those
predicted by the models. We find that our bias model when fitted to the {\em
2dF} clustering results predicts different bias evolution for different values
of $w$. The models that provide the weak biasing ($b_{\circ} \sim 1.1$) of
optical galaxies found in many recent observational studies are flat,
$\Omega_{\rm m}=0.3$ with $w\le -0.9$. These models however, predict a weak
redshift evolution of $b(z)$, not corroborated by N-body simulations.


title: A Direct Measurement of Major Galaxy Mergers at z < 3

abstract:
  This paper presents direct evidence for hierarchical galaxy assembly out to
redshifts z ~ 3. We identify major mergers using the model-independent CAS
(concentration, asymmetry, clumpiness) physical morphological system on
galaxies detected, and photometrically selected, in the WFPC2 and NICMOS Hubble
Deep Field North. We specifically use the asymmetric distributions of
rest-frame optical light measured through the asymmetry parameter (A) to
determine the fraction of galaxies undergoing major mergers as a function of
redshift (z), stellar mass (M_{*}), and absolute magnitude (M_{B}). We find
that the fraction of galaxies consistent with undergoing a major merger
increases with redshift for all galaxies, but most significantly, at 5 - 10
sigma confidence, for the most luminous and massive systems. The highest merger
fractions we find are 40% - 50% for galaxies with M_{B} < -21, or M_{*} > 10^10
M_0 at z > 2.5, i.e., objects identified as Lyman-break galaxies. We model the
merger fraction evolution in the form: f x (1+z)^m, finding m values ~4-6 for
the most luminous and massive galaxies. We use these merger fractions combined
with merger time scales calculated from N-body simulations to derive galaxy
merger rates to z ~ 3. We also use stellar masses of HDF-N galaxies to
determine the mass accretion rate of field galaxies involved in major mergers,
and how this changes with redshift. We further find that the fraction of
stellar mass density in galaxies involved in major mergers increases with
redshift. By comparing merger fractions predicted in Cold Dark Matter
semi-analytic models with our results there is a reasonably good agreement for
the largest and brightest systems, although there are more low-mass galaxy
mergers at lower redshifts than what these models predict. (abridged)


title:
Spectroscopic Binary Orbits from Photoelectric Radial Velocities --
  Paper 171: HD 152028 and Hde 284195 (GK Draconis and V1094 Tauri)

abstract:
  The two stars that form the subject of this paper are both short-period
double- lined eclipsing binaries having non-circular orbits despite their short
periods. Although the HD type of HD 152028 is G0, the integrated spectral type
of the system must actually be much earlier: the B-V colour index is only about
0.37 mag and the parallax indicates an integrated absolute magnitude as bright
as +1.4 mag. A published photometric investigation suggests that the primary
star exhibits delta Scuti pulsations, with a period of 0.1138 days. That period
is not present in the radial velocities, but we have identified a comparable
periodicity in the initially excessive residuals (sigma of the order of 2 km/s)
in the radial velocities of the primary star: there is an asymmetrical
pulsational velocity curve with a semi-amplitude of about 3 km/s and a period
of 0.1178 days. HDE 284195 was not observed by Hipparcos, but its HDE type of
G0 is in reasonable agreement with its colour and the nature of its
radial-velocity traces. The rotations of both stars appear to be
pseudo-synchronized to the orbit. The orbital inclinations are not formally
determined but they must be very high,however and there is specific evidence
that the inclination of HD 152028 is very close to 90 degrees,so it is
permissible to assume that the masses are scarcely above the minimum values,
which in the case of HD 152028 are 1.78 and 1.42 solar mass and in that of HDE
284195 are 1.10 and 1.01 solar mass, with uncertainties below 1%.(ABRIDGED)


title:
6C radio galaxies at z~1: The influence of radio power on the alignment
  effect

abstract:
  Powerful radio galaxies often display enhanced optical/UV continuum emission
and extended emission line regions, elongated and aligned with the radio jet
axis. The expansion of the radio source strongly affects the gas clouds in the
surrounding IGM, and the kinematic and ionization properties of the extended
emission line regions display considerable variation over the lifetime of
individual sources, as well as with cosmic epoch. We present the results of
deep rest-frame UV and optical imaging and UV spectroscopy of high redshift 6C
radio galaxies. The interdependence of the host galaxy and radio source
properties are discussed, considering: (i) the relative contribution of shocks
associated with the expanding radio source to the observed emission line gas
kinematics, and their effect on the ionization state of the gas; (ii) the
similarities and differences between the morphologies of the host galaxies and
aligned emission for a range of radio source powers; and (iii) the influence of
radio power on the strength of the observed alignment effect.


title: A relativistic jet in the radio-quiet quasar PG1407+263

abstract:
  We present the results of a multi-epoch radio monitoring campaign measuring
the milliarcsecond structure of the jet in the radio-quiet quasar PG1407+263.
This is the highest-sensitivity, highest-resolution multi-year study of a
distant active galaxy. The observations are naturally explained in terms of a
beamed relativistic jet, some of whose fluctuations in flux density can be
ascribed to interaction with the narrow-line region of the quasar. The optical
properties of PG1407+263, in particular the low equivalent widths of the
emission lines, may be related to the fact that we are viewing this quasar
almost pole-on, giving us a direct view into its broad-line region.


title:
The under-explored radio-loudness of quasars and the possibility of
  radio-source--environment interactions

abstract:
  I demonstrate that radio observations in the literature to date of
optically-selected quasars are largely inadequate to reveal the full extent of
their jet-activity. I discuss a recent example of an optically-powerful quasar,
which is radio-quiet according to all the standard classifications, which
Blundell & Rawlings discovered to have a >100 kpc jet, and show that other than
being the first FRI quasar to be identified, there is no reason to presume it
is exceptional. I also discuss a possible new probe of accounting for the
interactions of radio sources with their environments. This tool could help to
avoid over-estimating magnetic fields strengths within cluster gas. I briefly
describe recent analyses by Rudnick & Blundell which confront claims in the
literature of cluster gas B-fields > 10 micro-G.


title: Shock emission in the bipolar post-AGB star IRAS 16594-4656

abstract:
  In this paper we study the near-infrared emission spectrum of IRAS
16594-4656, a bipolar post-AGB star with spectral type B7 and no observed
ionization. Using optical and near-infrared photometry we determined the total
extinction towards this object to be A_V=7.5 +/- 0.4 mag and derived a distance
of 2.2 +/- 0.4 kpc, assuming a luminosity of 10^4 L_sol. The near-infrared
spectrum shows strong H_2 emission lines and some typical metastable shock
excited lines such as [Fe II] 1.257 & 1.644 micron. We determined the
rotational and vibrational excitation temperatures, as well as the
ortho-to-para ratio of the molecular hydrogen. Based on these we argue that the
H_2 emission is mainly collisionally excited. Line ratios indicate that the H_2
emission originates in a +/- 25 km/s C-type shock. On the other hand, the
metastable lines, and especially the [Fe II] emission lines, indicate the
presence of a +/- 75 km/s J-type shock. Hence we postulate that the H_2
emission originates where the stellar wind (with an observed terminal velocity
of +/- 126 km/s) is funneled through an equatorial density enhancement,
impinging almost tangentially upon the circumstellar material. The [Fe II]
emission either occurs along the walls of the bipolar lobes where the
transverse shock velocity would be higher, or could originate much closer to
the central star in shocks in the post-AGB wind itself, or possibly even an
accretion disk. Further high resolution near-infrared spectra are currently
being obtained to confirm the proposed geometry and kinematics.


title:
A serendipitous survey for galaxy clusters by the XMM-Newton Survey
  Science Center

abstract:
  We describe the initial results of a programme to detect and identify
extended X-ray sources found serendipitously in XMM-Newton observations. We
have analysed 186 EPIC-PN images at high galactic latitude with a limiting flux
of $1\times 10^{-14}$ \ergcms and found 62 cluster candidates. Thanks to the
enhanced sensitivity of the XMM-Newton telescopes, the new clusters found in
this pilot study are on the average fainter, more compact, and more distant
than those found in previous X-ray surveys. At our survey limit the surface
density of clusters is about 5 deg$^{-2}$. We also present the first results of
an optical follow-up programme aiming at the redshift measurement of a large
sample of clusters. The results of this pilot study give a first glimpse on the
potential of serendipitous cluster science with XMM-Newton based on real data.
The largest, yet to be fulfilled promise is the identification of a large
number of high-redshift clusters for cosmological studies up to $z=1$ or 1.5.


title: Explaining UXOR variability with self-shadowed disks

abstract:
  In this Letter we propose a new view on UX Orionis type variability. The idea
is based on the earlier proposal by various authors that UXORs are
nearly-edge-on disks in which hydrodynamic fluctuations could cause clumps of
dust and gas to cross the line of sight. However, because the standard disk
models have a flaring geometry, it is mostly the outer regions of the disk that
obscure the star. The time scales for such obscuration events would be too long
to match the observed time scales of weeks to months. Recent 2-D
self-consistent models of Herbig Ae/Be protoplanetary disks (Dullemond et al.
2002,2003 henceforth D02/DD03), however, have indicated that for Herbig Ae/Be
star disks there exists, in addition to the usual flared disks, also a new
class of disks: those that are fully self-shadowed. Only their puffed-up inner
rim (at the dust evaporation radius) is directly irradiated by the star, while
the disk at larger radius resides in the shadow of the rim. For these disks
there exist inclinations at which the line of sight towards the star skims the
upper parts of the puffed-up inner rim, while passing high over the surface of
outer disk regions. Small hydrodynamic fluctuations in the puffed-up inner rim
could then be held responsible for the extinction events seen in UXORs. If this
idea is correct, it makes a prediction for the shape of the SEDs of these
stars. It was shown by D02/DD03 that flared disks have a strong far-IR excess
and can be classified as `group I' (in the classification of Meeus et al.
2001), while self-shadowed disks have a relatively weak far-IR excess and are
classified as `group II'. Our model therefore predicts that UXORs belong to the
`group II' sources. We show that this correlation is indeed found within a
sample of 86 Herbig Ae/Be stars.


title: Radiative Transfer in Prestellar Cores: A Monte Carlo Approach

abstract:
  We use our Monte Carlo radiative transfer code to study non-embedded
prestellar cores and cores that are embedded at the centre of a molecular
cloud. Our study indicates that the temperature inside embedded cores is lower
than in isolated non-embedded cores, and generally less than 12 K, even when
the cores are surrounded by an ambient cloud of small visual extinction (Av~5).
Our study shows that the best wavelength region to observe embedded cores is
between 400 and 500 microns, where the core is quite distinct from the
background. We also predict that very sensitive observations (~1-3 MJy/sr) at
170-200 microns can be used to estimate how deeply a core is embedded in its
parent molecular cloud. Finally, we present preliminary results of asymmetric
models of non-embedded cores.


title:
Temperature gradients in XMM-Newton observed REFLEX-DXL galaxy clusters
  at z~0.3

abstract:
  We present XMM-Newton results on the temperature profiles of a volume-limited
sample of galaxy clusters at redshifts z~0.3, selected from the REFLEX survey
(REFLEX-DXL sample). In the spectral analysis, where only the energies above 1
keV were considered, we obtained consistent results on the temperature derived
from the EPN, EMOS1 and EMOS2 data. Useful temperature measurements could be
performed out to radii with overdensity 500 (r500) for all nine clusters. We
discovered a diversity in the temperature gradients at the outer cluster radii
with examples of both flat and strongly decreasing profiles. Using the total
mass and the gas mass profiles for the cluster RXCJ0307.0-2840 we demonstrate
that the errors on the mass estimates for the REFLEX-DXL clusters are within
25% up to r500.


title: XTE J0111.2-7317 : a nebula-embedded X-ray binary in the SMC

abstract:
  The observed characteristics of the nebulosity surrounding the SMC High Mass
X-ray Binary XTE J0111.2-7317 are examined in the context of three possible
nebular types: SNR, bowshock and HII region. Observational evidence is
presented which appears to support the interpretation that the nebulosity
surrounding XTE J0111.2-7317 is an HII region. The source therefore appears to
be a normal SMC Be X-ray binary (BeXRB) embedded in a locally enhanced ISM
which it has photoionised to create an HII region. This is supported by
observations of the X-ray outburst seen with BATSE and RXTE in 1998-1999. It
exhibited characteristics typical of a giant or type II outburst in a BeXRB
including large spin-up rates, Lx~10E38 erg/sq.cm-s, and a correlation between
spin-up rate and pulsed flux. However, the temporal profile of the outburst was
unusual, consisting of two similar intensity peaks, with the first peak of
shorter duration than the second.


title:
The Lower Limit for Masses of Progenitors of Supernova Remnants and
  Radio Pulsars

abstract:
  We examined correlations between young radio pulsars (PSRs), Supernova
remnants (SNRs) which have different surface brightness values and young star
formation regions (SFRs). Angular correlation of PSRs with SFRs is reliable up
to 4 kpc and considerably strong up to 3 kpc from the Sun. On average this
correlation is stronger for Galactic anticenter directions compared to Galactic
central directions. Angular correlation of SNRs with SFRs is weaker and depends
on the surface brightness of the SNR. Spatial correlation of PSRs with SFRs is
also stronger than spatial correlation of SNRs with SFRs. Dim SNRs show weak
spatial correlation with SFRs. These investigations and analysis of various
data show that the lower limit for masses of progenitors of PSRs is about 9
M$_{\odot}$ and of SNRs (or supernovae) is about 7 M$_{\odot}$.


title: Neutrinos and gravitational waves from cosmological gamma-ray bursts

abstract:
  Cosmological gamma ray bursts are very likely powerful sources of high energy
neutrinos and gravitational waves. The aim of this paper is to review and
update the current predictions about the intensity of emission in this two
forms to be expected from GRB's. In particular a revised calculation of the
neutrino emission by photohadronic interaction at the internal shock is
obtained by numerical integration, including both the resonant and the
hadronization channels. The detectability of gravitational waves from
individual bursts could be difficult for presently planned detectors if the
GRB's are beamed, but it is possible, as we have proposed in a paper two years
ago, that the incoherent superimposition of small amplitude pulse trains of
GW's impinging on the detector, could be detected as an excess of noise in the
full VIRGO detector, integrating over a time of the order of one year.


title:
On the Determination of Ejecta Structure and Explosion Asymmetry from
  the X-ray Knots of Cassiopeia A

abstract:
  We present a detailed analysis of Chandra X-ray spectra from individual
ejecta knots in the supernova remnant Cassiopeia A. The spectra are fitted to
give the electron temperature and (single) ionization age. These quantities are
compared with the predictions of self similar hydrodynamic models incorporating
time dependent ionization and radiation losses, and Coulomb electron-ion
equilibration behind the reverse shock, for a variety of different ejecta
density profiles described by a uniform density core and a power law envelope.
We find that the ejecta close to the "jet" region in the NE, but not actually
in the jet itself, have a systematically shallower outer envelope than ejecta
elsewhere in the remnant, and we interpret this as being due to more energy of
the initial explosion being directed in this polar direction as opposed to
equatorially. The degree of asymmetry we infer is at the low end of that
generally modelled in asymmetric core-collapse simulations, and may possibly be
used to rule out highly asymmetric explosion models.


title: Where was the Iron Synthesized in Cassiopeia A?

abstract:
  We investigate the properties of Fe-rich knots on the east limb of the
Cassiopeia A supernova remnant using observations with Chandra/ACIS and
analysis methods developed in a companion paper. We use the fitted ionization
age and electron temperature of the knots to constrain the ejecta density
profile and the Lagrangian mass coordinates of the knots. Fe-rich knots which
also have strong emission from Si, S, Ar, and Ca are clustered around mass
coordinates q~0.35-0.4 in the shocked ejecta; for ejecta mass 2M_sun, this
places the knots 0.7-0.8 M_sun out from the center (or 2-2.1 M_sun, allowing
for a 1.3 M_sun compact object). We also find an Fe clump that is evidently
devoid of line emission from lower mass elements, as would be expected if it
were the product of alpha-rich freeze out; the mass coordinate of this clump is
similar to those of the other Fe knots.


title:
Fragmentation of a Molecular Cloud Core versus Fragmentation of the
  Massive Protoplanetary Disk in the Main Accretion Phase

abstract:
  The fragmentation of molecular cloud cores a factor of 1.1 denser than the
critical Bonnor-Ebert sphere is examined though three-dimensional numerical
simulations. A nested grid is employed to resolve fine structure down to 1 AU
while following the entire structure of the molecular cloud core of radius 0.14
pc. A total of 225 models are shown to survey the effects of initial rotation
speed, rotation law, and amplitude of bar mode perturbation. The simulations
show that the cloud fragments whenever the cloud rotates sufficiently slowly to
allow collapse but fast enough to form a disk before first-core formation. The
latter condition is equivalent to $\Omega_0 t_{\rm ff} \gtrsim 0.05$, where
$\Omega_0$ and $t_{\rm ff}$ denote the initial central angular velocity and the
freefall time measured from the central density, respectively. Fragmentation is
classified into six types: disk-bar, ring-bar, satellite, bar, ring, and
dumbbell types according to the morphology of collapse and fragmentation. When
the outward decrease in initial angular velocity is more steep, the cloud
deforms from spherical at an early stage. The cloud deforms into a ring only
when the bar mode m = 2 perturbation is very minor. The ring fragments into two
or three fragments via ring-bar type fragmentation and into at least three
fragments via ring type fragmentation. When the bar mode is significant, the
cloud fragments into two fragments via either bar or dumbbell type
fragmentation. These fragments eventually merge due to their low angular
momenta, after which several new fragments form around the merged fragment via
satellite type fragmentation.


title: On non-gaussianities in single-field inflation

abstract:
  We study the impact of higher dimension operators in the inflaton Lagrangian
on the non-gaussianity of the scalar spectrum. These terms can strongly enhance
the effect without spoiling slow-roll, though it is difficult to exceed f_NL ~
1, because the scale which suppresses the operators cannot be too low, if we
want the effective field theory description to make sense. In particular we
explicitly calculate the 3-point function given by an higher derivative
interaction of the form (\nabla\phi)^4, which is expected to give the most
important contribution. The angular dependence of the result turns out to be
quite different from the minimal case without higher dimension operators.


title:
The Technical Performance of the HEGRA System of Imaging Air Cherenkov
  Telescopes

abstract:
  Between early 1997 and late 2002, the HEGRA collaboration operated a
stereoscopic system of 4 (later 5) imaging atmospheric Cherenkov telescopes. In
this paper we present the calibration schemes which were developed for the
system, and report on the performance of the detector over the years. In
general, the telescope system was very well understood, regarding both the
absolute calibration and the slight changes in performance over the years. The
system had an energy threshold of 500 GeV for observations at zenith and under
optimum detector conditions. With the corresponding calibration schemes, a
systematic accuracy of 15 percent on the absolute energy scale has been
achieved. The continuous sensitivity monitoring provided a relative accuracy of
a few percent, and showed that the threshold did not exceed 600 GeV throughout
the entire operation time. The readout electronics and the imaging quality of
the dishes were well monitored and stable. The absolute pointing had an
accuracy of at least 25 arcsec; this number was guaranteed throughout the whole
lifetime of the experiment.


title: Status of the Search for Supersymmetric Dark Matter

abstract:
  We assume the supersymmetric model for dark matter in the universe and our
galaxy, and direct methods to distinguish these kinds of dark matter are
described. We then focus on the current and future experiment search for
SUSY-WIMPS. Theoretical models suggest that a new generation of at least one
ton detectors may be required to observe this form of dark matter. We
concentrate on Liquid Xenon detectors because they can be scaled to large mass.


title: XMM-NEWTON Reveals the Quasar Outflow in PG 1115+080

abstract:
  We report on an observation of the Broad Absorption Line (BAL) quasar PG
1115+080 performed with the XMM-Newton observatory. Spectral analysis reveals
the second case of a relativistic X-ray absorbing outflow in a BAL quasar. The
first case was revealed in a recent observation of APM 08279+5255 with the
Chandra X-ray Observatory. The spectrum of PG1115+080 indicates the presence of
complex low-energy absorption in the 0.2-0.6 keV observed energy band and
high-energy absorption in the 2-5 keV observed energy band. The high-energy
absorption is best modeled by two Gaussian absorption lines with rest-frame
energies of 7.4 keV and 9.5 keV. Assuming that these two lines are produced by
resonant absorption due to Fe xxv Kalpha, we infer that the X-ray absorbers are
outflowing with velocities of ~0.10c and ~0.34c, respectively. We have detected
significant variability of the energies and widths of the X-ray BALs in PG
1115+080 and APM 08279+5255 over timescales of 19 and 1.8 weeks (proper-time),
respectively. The BAL variability observed from APM 08279+5255 supports our
earlier conclusion that these absorbers are most likely launched at relatively
small radii of ~ 10^(16)(M_BH/M_8)^(1/2)cm. A comparison of the ionization
properties and column densities of the low-energy and high-energy absorbers
indicates that these absorbers are likely distinct; however, higher spectral
resolution is needed to confirm this result. Finally, we comment on prospects
for constraining the kinematic and ionization properties of these X-ray BALs
with the next generation of X-ray observatories.


title: Supernova Remnant Crossing a Density Jump: A Thin Shell Model

abstract:
  The environments of supernova explosion are often inhomogeneous and there may
be jumps in their density structure. We have developed a semi-analytic model
under the thin-shell approximation for supernova remnants that evolve crossing
a density jump in the ambient medium. The generic evolutionary relations are
presented for the blast wave after impacting on a cavity wall, which may be
produced by the energetic stellar wind from the supernova progenitor. The
relations can also be extended to the case that the blast waves break out from
a dense cloud if different density contrast is used. This model is applied to
N132D, a well-known cavity-born supernova remnant whose evolution has not yet
been quantitively estimated in a cavity scenario due to lack of model formulae,
and self-consistent physical parameters are obtained.


title: Why are the K dwarfs in the Pleiades so Blue?

abstract:
  The K dwarfs in the Pleiades fall nearly one half magnitude below a main
sequence isochrone when plotted in a color-magnitude diagram utilizing V
magnitude as the luminosity index and B-V as the color index. This peculiarity
has been known for forty years but has gone unexplained and mostly ignored.
When compared to Praesepe members, the Pleiades K dwarfs again are subluminous
(or blue) in a color-magnitude diagram using B-V as the color index. However,
using V-I as the color index, stars in the two clusters are coincident to M_V ~
10; using V-K as the color index, Pleiades late K and M stars fall above the
main sequence locus defined by Praesepe members. We believe that the anomalous
spectral energy distributions for the Pleiades K dwarfs, as compared to older
clusters, are a consequence of rapid stellar rotation and may be primarily due
to spottedness. If so, the required areal filling factor for the cool component
has to be very large (=> 50%). Weak-lined T Tauri stars have similar color
anomalies, and we suspect this is a common feature of all very young K dwarfs
(sp. type > K3). The peculiar spectral energy distribution needs to be
considered in deriving accurate pre-main sequence isochrone-fitting ages for
clusters like the Pleiades since the age derived will depend on the temperature
index used.


title: Red Galaxy Clustering in the NOAO Deep Wide-Field Survey

abstract:
  We have measured the clustering of z<0.9 red galaxies and constrained models
of the evolution of large-scale structure using the initial 1.2 sq. degree data
release of the NOAO Deep Wide-Field Survey (NDWFS). The area and BwRI passbands
of the NDWFS allow samples of >1000 galaxies to be selected as a function of
spectral type, absolute magnitude, and photometric redshift. Spectral synthesis
models can be used to predict the colors and luminosities of a galaxy
population as a function of redshift. We have used PEGASE2 models, with
exponentially declining star formation rates, to estimate the observed colors
and luminosity evolution of galaxies and to connect, as an evolutionary
sequence, related populations of galaxies at different redshifts. A red galaxy
sample, with present-day rest-frame Vega colors of Bw-R>1.44, was chosen to
allow comparisons with the 2dF Galaxy Redshift Survey and Sloan Digital Sky
Survey. We find the spatial clustering of red galaxies to be a strong function
of luminosity, with r0 increasing from 4.4+/-0.4 Mpc/h at M_R=-20 to 11.2+/-1.0
Mpc/h at M_R=-22. Clustering evolution measurements using samples where the
rest-frame selection criteria vary with redshift, including all deep
single-band magnitude limited samples, are biased due to the correlation of
clustering with rest-frame color and luminosity. The clustering of M_R=-21,
Bw-R>1.44 galaxies exhibits no significant evolution over the redshift range
observed with r0= 6.3+/-0.5 Mpc/h in comoving coordinates. This is consistent
with recent LCDM models where the bias of L* galaxies undergoes rapid evolution
and r0 evolves very slowly at z<2.


title:
Chandra Discovery of an X-ray jet and Extended X-ray Structure in z=0.63
  quasar, B2 0738+313

abstract:
  We have made a 30 ksec Chandra observation of the redshift z=0.63 GPS quasar
B2 0738+313. We detected X-ray emission from the core and have discovered a 200
kpc (projected on the sky) X-ray jet. The X-ray jet is narrow and curves,
following the extended radio structure to the south of the quasar, and ending
with a hot spot at the southernmost part of the radio lobe. The jet has a knot
at ~13 arcsec away from the core. The knot emission is consistent with the
X-rays being created by the inverse Compton scattering of the cosmic microwave
background (CMB) photons and requires jet bulk Lorentz factors of a few
(Gamma_{bulk} ~ 5-7). We discuss the emission mechanisms that may be
responsible for the jet emission. We present new VLA data of the core and jet,
and discuss the relation between the extended radio and X-ray emission.
Extended emission observed in several GPS sources has been interpreted as a
signature of the source past activity, while the GPS source is young and newly
expanded. We argue that B2~0738+313 may be an example of a new class of radio
sources similar to the FRII radio galaxies in their high jet bulk velocities,
but with the powerful GPS-like nucleus.
  B2 0738+313 also has two damped Lyman-alpha systems along the line of sight,
at z_{abs} = 0.0912 and 0.2212. We discuss the possible connection between the
X-ray absorption (7.2+/-0.9 e20 cm(-2)) detected in the ACIS spectrum and these
two intervening absorbers. We also investigate an extended structure within the
central 10 arcsec of the core in the relation to structure seen in the optical.


title: Stellar Orbits Around the Galactic Center Black Hole

abstract:
  We present new proper motion measurements and simultaneous orbital solutions
for three newly identified (S0-16, S0-19, and S0-20) and four previously known
(S0-1, S0-2, S0-4, and S0-5) stars at the Galactic Center. This analysis
pinpoints the Galaxy's central dark mass to within +-1 milli-arcsec and, for
the first time from orbital dynamics, limits its proper motion to 1.5+-0.5
mas/y, which is consistent with our derivation of the position of Sgr A* in the
infrared reference frame (+-10 mas). The estimated central dark mass from
orbital motions is 3.7 (+-0.2) x 10^6 (Ro/8kpc)^3 Mo; this is a more direct
measure of mass than those obtained from velocity dispersion measurements,
which are as much as a factor of two smaller. The smallest closest approach is
achieved by S0-16, which confines the mass to within a radius of a mere 45 AU
and increases the inferred dark mass density by four orders of magnitude
compared to earlier analyses based on velocity and acceleration vectors, making
the Milky Way the strongest existing case by far for a supermassive black hole
at the center of any normal type galaxy. The stellar orbital properties suggest
that the distributions of eccentricities and angular momentum vector and
apoapse directions are consistent with those of an isotropic system. Therefore
many of the mechanisms proposed for the formation of young stars in the
vicinity of a supermassive black hole, such as formation from a pre-existing
disk, are unlikely solutions for the Sgr A* cluster stars. Unfortunately, all
existing alternative theories are also somewhat problematic. Understanding the
apparent youth of stars in the Sgr A* cluster, as well as the more distant He I
emission line stars, has now become one of the major outstanding issues in the
study of the Galactic Center.


title:
Rhombic Cell Analysis - A New Way of Probing the Large-Scale Structure
  of the Universe. I. General Considerations

abstract:
  A new way of probing the large-scale structure of the universe is proposed.
Space is partitioned into cells the shape of rhombic dodecahedron. The cells
are labelled ``filled'' or ``empty'' according as they contain galaxies or not.
The cell size is so chosen as to have nearly equal numbers of filled and empty
cells for the given galaxy sample. Two observables on each cell are definable:
the number of its {\em like} neighbors, $n_1$, and a two-suffixed topological
type $\tau$, the suffixes being the numbers of its like and unlike {\em
neighbor-groups}. The frequency distributions of $n_1$ and $\tau$ in the
observed set of filled (empty) cells are then considered as indicators of the
morphology of the set. The method is applied to the CfA catalogue of galaxies
as an illustration. Despite its limited size the data offers evidence 1) that
the empty cells are more strongly clustered than the filled cells, and 2) that
the filled cells, but not the empty cells, have a tendency of occurring in
sheets. Further directions of development both in theory and application are
indicated.


title: WMAP First Year Results

abstract:
  The Wilkinson Microwave Anisotropy Probe (WMAP) science team has released
results from the first year of operation at the Earth-Sun L2 Lagrange point.
The maps are consistent with previous observations but have much better
sensitivity and angular resolution than the COBE DMR maps, and much better
calibration accuracy and sky coverage than ground-based and balloon-borne
experiments. The angular power spectra from these ground-based and
balloon-borne experiments are consistent within their systematic and
statistical uncertainties with the WMAP results. WMAP detected the large
angular-scale correlation between the temperature and polarization anisotropies
of the CMB caused by electron scattering since the Universe became reionized
after the "Dark Ages", giving a value for the electron scattering optical depth
of 0.17+/-0.04. The simplest Lambda-CDM model with n=1 and Omega_tot=1 provides
an adequate fit to the WMAP data and gives parameters which are consistent with
determinations of the Hubble constant and observations of the accelerating
Universe using supernovae. The time-ordered data, maps, and power spectra from
WMAP can be found at http://lambda.gsfc.nasa.gov along with 13 papers by the
WMAP science team describing the results in detail.


title:
Simulating a dual-recycled gravitational wave interferometer with
  realistically imperfect optics

abstract:
  We simulate the performance of a gravitational wave interferometer in the
Dual Recycling (DR) configuration, as will be used for systems like
Advanced-LIGO. Our grid-based simulation program models complex interferometric
detectors with realistic optical deformations (e.g., fine-scale mirror surface
roughness). Broadband and Tuned DR are modeled here; the results are also
applied qualitatively to Resonant Sideband Extraction (RSE). Several beneficial
properties anticipated for DR detectors are investigated: signal response
tuning and narrowbanding, power loss reduction, and the reclamation of lost
power as useful light for signal detection. It is shown that these benefits
would be limited by large scattering losses in large (multi-kilometer) systems.
Furthermore, losses may be resonantly enhanced (particularly for RSE), if the
interferometer's modal resonance conditions are not well chosen. We therefore
make two principal recommendations for DR/RSE interferometers: the DR/RSE
cavity must be modally nondegenerate; and fabricated mirror surfaces and
coatings must be as smooth as is practically feasible.


title: Status and Perspectives of Direct Dark Matter Searches

abstract:
  Supersymmetric particles represent the best motivated candidates to fill the
Dark Matter gap, and are actively hunted by a number of competing experiments.
Discriminating experiments are testing for the first time SUSY models
compatible with accelerator constraints. These experiments contradict the 60
GeV WIMP candidate reported by the DAMA experiment. The sensitivities of direct
and indirect detection techniques for both present experiments and future
projects are compared.


title:
Production of the High Energy-Momentum Spectra of Quasars 3C 279 and 3C
  273 Using the Penrose Mechanism

abstract:
  Theoretical and numerical (Monte Carlo) N-particle computer model simulations
show that Penrose Compton scattering (PCS) near the event horizon and Penrose
pair production (PPP) at or near the photon orbit, in the ergosphere of a
supermassive rotating black hole, can generate the necessary energy-momentum
spectra to explain the origin of the mysterious fluxes of ultrarelativistic
electrons, inferred from observations to emerge from the cores of Quasars 3C
279 and 3C 273, and other active galactic nuclei (AGNs). Particles from an
accretion disk surrounding the black hole fall into the ergosphere and scatter
off particles that are in trapped or bound unstable orbits. The Penrose
mechanism allows rotational energy of a Kerr black hole, and energy-momentum
produced by its strong gravitational field, to be extracted by scattered
particles escaping from the ergosphere to infinity. The results of these model
calculations show that the Penrose mechanism is capable of producing the
observed high energy particles (~GeV) emitted by quasars and other AGNs. This
mechanism can extract hard X-ray/gamma-ray photons from PCS of initially
infalling low energy UV/soft X-ray photons by target orbiting electrons in the
ergosphere. The PPP allows the escape of relativistic e-e+ pairs--produced by
infalling low energy photons interacting with highly blueshifted target photons
at the photon orbit. Moreover, and importantly, the emission of scattered
particles by this mechanism naturally produces relativistic jets collimated
about the polar axis, and in most cases one-sided or asymmetrical, agreeing
with observations of AGNs. In these fully relativistic calculations, the
energy-momentum four vectors (or four-momenta) of the scattered particles are
obtained.(ABRIDGED)


title: Expected sensitivity of ARGO-YBJ to detect point gamma-ray sources

abstract:
  ARGO-YBJ is a full coverage air shower detector currently under construction
at the Yangbajing Laboratory (4300 m a.s.l., Tibet, China). First data obtained
with a subset of the apparatus will be available in summer 2003 while the full
detector operation is expected in 2005. One of the main aims of ARGO-YBJ is the
observation of gamma-ray sources, at an energy threshold of a few hundreds GeV.
In this paper we present the expected sensitivity to detect point gamma ray
sources, with particular attention to the Crab Nebula. According to our
simulations a Crab-like signal could be detected in one year of operation with
a statistical significance of 10 standard deviations, without any gamma/hadron
discrimination.


title: First hours of the GRB 030329 optical afterglow

abstract:
  We present the first results of the observations of the extremely bright
optical afterglow of gamma-ray burst (GRB) 030329 with the 1.5m Russian-Turkish
telescope RTT150 (TUBITAK National Observatory, Bakyrlytepe, Turkey). RTT150
was one of the first 1.5m-class telescopes pointed to the afterglow.
Observations were started approximately 6 hours after the burst. During the
first 5 hours of our observations the afterglow faded exactly as a power law
with index -1.19+-0.01 in each of the BVRI Bessel filters. After that, in all
BVRI filters simultaneously we observe a steepening of the power law light
curve. The power law decay index smoothly approaches the value ~= -1.9,
observed by other observatories later. This power law break occurs at t-t_0
=0.57 days and lasts for +-0.1 days. We observe no variability above the
gradual fading with the upper limits 10--1% on time scales 0.1--1000s. Spectral
flux distribution in four BVRI filters corresponds to the power law spectrum
with spectral index \alpha=0.66+-0.01. The change of the power law decay index
in the end of our observations can be interpreted as a signature of collimated
ultrarelativistic jet. The afterglow flux distribution in radio, optical and
x-rays is consistent with synchrotron spectrum. We continue our observations of
this unique object with RTT150.


title:
The puzzling dynamical status of the core of the globular cluster NGC
  6752

abstract:
  We have used high resolution WFPC2-HST and ground based Wide Field images to
determine the center of gravity and construct an extended radial density and
brightness profile of the cluster NGC 6752 including, for the first time,
detailed star counts in the very inner region. The barycenter of the 9
innermost X-ray sources detected by Chandra is located only 1.9" off the new
center of gravity. Both the density and the brightness profile of the central
region are best fitted by a double King model, suggesting that NGC 6752 is
experiencing a post-core collapse "bounce". Taking advantage from our new
optical data, we discuss the puzzling nature of the accelerations displayed by
the innermost millisecond pulsars detected in this cluster. We discuss two
possible origins to the accelerations: 1) the overall cluster gravitational
potential which would require a central projected mass to light ratio of order
6-7 and the existence of a few thousand solar masses of low-luminosity matter
within the inner 0.08 pc of NGC6752; 2) the existence of a local perturber(s)
of the pulsar dynamics, such as a recently proposed binary black hole of
intermediate (100-$200 Msun) mass.


title: The X-ray nebula around the Seyfert 2 galaxy NGC4388

abstract:
  We report on X-ray emission from the Seyfert 2 galaxy NGC4388 observed with
the Chandra X-ray Observatory. A hard X-ray peak is found at the position of
the active nucleus suggested by optical and radio observations. Extended soft
X-ray emission correlates well with the ionization cone found in optical line
emission. A large soft X-ray extension is found up to 16 kpc to the north of
the galaxy. Photoionized gas with low ionization parameters (xi<3) appears to
be the likely explanation of this emission. The same ionized gas clouds could
be responsible for the optical [OIII] emission. Fe K line emission from cold
material is found to be extended by a few kpc.


title:
Molecular Gas in NUclei of GAlaxies (NUGA) I.The counter-rotating LINER
  NGC4826

abstract:
  We present new high-resolution observations of the nucleus of the
counter-rotating LINER NGC4826, made in the J=1-0 and J=2-1 lines of 12CO with
the IRAM Plateau de Bure mm-interferometer(PdBI).The CO maps, which achieve
0.8''(16pc) resolution in the 2-1 line, fully resolve an inner molecular gas
disk which is truncated at an outer radius of 700pc. The total molecular gas
mass is distributed in a lopsided nuclear disk of 40pc radius and two one-arm
spirals, which develop at different radii in the disk. The distribution and
kinematics of molecular gas in the inner 1kpc of NGC4826 show the prevalence of
different types of m=1 perturbations in the gas. Although dominated by
rotation, the gas kinematics are perturbed by streaming motions related to the
m=1 instabilities. The non-circular motions associated with the inner m=1
perturbations agree qualitatively with the pattern expected for a trailing wave
developed outside corotation ('fast' wave). In contrast, the streaming motions
in the outer m=1 spiral are better explained by a 'slow' wave. A paradoxical
consequence is that the inner m=1 perturbations would not favour AGN feeding.
An independent confirmation that the AGN is not being generously fueled at
present is found in the low values of the gravitational torques exerted by the
stellar potential for R<530pc. The distribution of star formation in the disk
of NGC4826 is also strongly asymmetrical. Massive star formation is still
vigorous, fed by the significant molecular gas reservoir at R<700pc. There is
supporting evidence for a recent large mass inflow episode in NGC4826.
  These observations have been made in the context of the NUclei of GAlaxies
(NUGA) project, aimed at the study of the different mechanisms for gas fueling
of AGN.


title:
The identification of HCN and HNC in Carbon Stars: Model Atmospheres,
  Synthetic Spectra and Fits to Observations in the 2.7-4.0 micron Region

abstract:
  Model carbon star atmospheres and synthetic spectra have been calculated
using the recent HCN/HNC vibration rotation linelist of Harris et al. (2002)
ApJ, 578, 657. The calculations are repeated using only HCN lines and show that
HNC has a significant effect upon the temperature, density and optical depth of
a stellar atmosphere.
  We fit synthetic spectra in the 2.7-4.0 micron region to observed ISO spectra
of the carbon stars WZ Cas and TX Psc obtained by Aoki et al. (1998), A&A, 340,
222. These fits allow us to identify absorption by HNC in the spectrum of WZ
Cas at 2.8-2.9 microns, and to determine new independent estimates of effective
temperature and log(Nc)/log(No). The findings reported here indicate that
absorption by both HCN and HNC is needed to fully explain the observed stellar
spectra and represent the first identification of HNC in a star. Q branch
absorption by the HCN $\Delta v_2=1$, $\Delta v_3=1$ and $\Delta v_1=1$,
$\Delta v_2=-1$ bands at 3.55 and 3.86 microns respectively, are identified in
the spectrum of WZ Cas.