title: A Taylor-Couette Dynamo

abstract:
  Recent experiments have shown that it is possible to study a fundamental
astrophysical process such as dynamo action in controlled laboratory conditions
using simple MHD flows. In this paper we explore the possibility that
Taylor-Couette flow, already proposed as a model of the magneto-rotational
instability of accretion discs, can sustain generation of magnetic field.
Firstly, by solving the kinematic dynamo problem, we identify the region of
parameter space where the magnetic field's growth rate is higher. Secondly, by
solving simultaneously the coupled nonlinear equations which govern velocity
field and magnetic field, we find a self-consistent nonlinearly saturated
dynamo.


title:
The Infrared Emission of Circumstellar Envelopes, Dark Silhouettes and
  Photoionized Disks in HII Regions

abstract:
  We model the IR Spectral Energy Distribution of circumstellar disks embedded
in a HII region and photoevaporated by the external UV radiation. The model
applies to the photoevaporated disks (proplyds) in Orion Nebula. First we
calculate the IR emission of a PMS star surrounded by a dusty globule that is
immersed within an HII region. The globule is assumed to be spherical,
homogeneous, optically thin in the IR and photoevaporated according to the
Dyson (1968) model. Second, we consider the IR emission of a disk directly
exposed to the nebular environment. The disk is passive and treated according
to the Chiang and Goldreich (1997) model. We improve over the CG97 treatment by
tracing the propagation of the various radiative fluxes through the disk
superheated atmosphere. Since the opposite disk sides receive different amounts
of radiation, the flaring angle and the surface temperature distributions are
different, resulting in well distinguished SEDs for the two disk faces.
Finally, we combine the globule and disk models to estimate the IR emission of
proplyds. The energy input from the central star and the nebular environment
increase the disk flaring angle, and therefore also the amount of stellar
radiation intercepted by the disk. The relative intensity of the disk vs.
envelope emission varies with the tilt angle relative to the directions of
th1Ori-C, and of the Earth. We explore the dependence of the SEDs upon the tilt
angle with respect to the Earth, the distance from th1Ori-C, the size on the
envelope, the inner disk radius and the temperature of the central star. The
resulting SEDs are characterized by a broad peak of emission at 30-60micron,
and are in general significantly different from those of isolated disks in
low-mass star forming regions like Taurus-Auriga.


title:
Structure Function Scaling in the Taurus and Perseus Molecular Cloud
  Complexes

abstract:
  We compute the structure function scaling of the integrated intensity images
of two J=1-0 13CO maps of Taurus and Perseus. The scaling exponents of the
structure functions follow the velocity scaling of supersonic turbulence,
suggesting that turbulence plays an important role in the fragmentation of cold
interstellar clouds. The data also allows to verify the validity of the two
basic assumptions of the hierarchical symmetry model, originally proposed for
the derivation of the velocity structure function scaling. This shows that the
same hierarchical symmetry holds for the projected density field of cold
interstellar clouds.


title:
Illuminating the darkness: More evidence from faint-star proper-motions
  for a cool and warm component to the local dark matter in the Galaxy

abstract:
  We present new evidence, based on faint HST proper-motions, for a bi-modal
kinematic population of old white dwarfs, representative of the Thick-Disk and
Halo of our Galaxy. This evidence supports the idea of a massive Halo comprised
of faint and old white dwarfs, along with an extant population of Thick-Disk
white dwarfs. We show how most of the required dark matter in the solar
vicinity can be accounted for by the remnants from these two components
together.


title: Two massive star-forming regions at early evolutionary stages

abstract:
  We report sensitive ATCA radio-continuum observations toward IRAS 15596-5301
and 16272-4837, two luminous objects (> 2x10^4 Lsun) thought to represent
massive star-forming regions in early stages of evolution (due to previously
undetected radio emission at the 1-sigma level of 2 mJy per beam). Also
reported are 1.2-millimeter continuum and a series of molecular-line
observations made with the SEST telescope. For IRAS 15596-5301, the
observations reveal the presence of three distinct compact radio-continuum
sources associated with a dense molecular core. We suggest that this core
contains a cluster of B stars which are exciting compact HII regions that are
in pressure equilibrium with the dense molecular surroundings. No radio
continuum emission was detected from IRAS 16272-4837 (3-sigma limit of 0.2
mJy). However, a dense molecular core has been detected. The high luminosity
and lack of radio emission from this massive core suggests that it hosts an
embedded young massive protostar that is still undergoing an intense accretion
phase. This scenario is supported by the observed characteristics of the line
profiles and the presence of a bipolar outflow detected from observations of
the SiO emission. We suggest that IRAS 16272-4837 is a bona fide massive star-
forming region in a very early evolutionary stage, being the precursor of an
ultra compact HII region.


title:
The correlation of line strength with luminosity and redshift from
  composite QSO spectra

abstract:
  We have generated a series of composite QSO spectra using over 22000
individual low resolution (~8A) QSO spectra obtained from the 2dF
(18.25<bj<20.85) and 6dF (16<bj<18.25) QSO Redshift Surveys. The large size of
the catalogue has enabled us to construct composite spectra in narrow redshift
(dz=0.25) and absolute magnitude (dMb=0.5) bins. The median number of QSOs in
each composite is ~200, yielding typical S/N of ~100. For a given redshift
interval, the composite spectra cover a factor of over 25 in luminosity. Using
the composite spectra we have measured the equivalent widths (EWs) of the major
broad and narrow emission lines, and the CaII K absorption feature due to the
host galaxy of the AGN. Assuming a fixed host galaxy spectral energy
distribution (SED), the correlation between CaII K EW and luminosity implies
Lgal proportional to Lqso**{0.42+-0.05}. We find strong anti-correlations with
luminosity for the EWs of [OII] and [NeV]. These provide hints to the general
fading of the NLR in high luminosity sources which we attribute to the NLR
dimensions becoming larger than the host galaxy. If average AGN host galaxies
have SEDs similar to average galaxies, then the observed narrow [OII] emission
could be solely due to the host galaxy at low luminosities (M_B~-20). We
measure highly significant Baldwin effects for most broad emission lines (CIV,
CIII], MgII, Hbeta, Hgamma) and show that they are predominantly due to
correlations with luminosity, not redshift. We find that the Hbeta and Hgamma
Balmer lines show an inverse Baldwin effect and are positively correlated with
luminosity, unlike the broad UV lines. We postulate that this previously
unknown effect is due to a luminosity dependent change in the the ratio of disk
to non-disk continuum components (abridged).


title:
Trans-Planckian Particle Creation in Cosmology and Ultra-High Energy
  Cosmic Rays

abstract:
  We consider observational constraints on creation of particles induced by
hypothetical trans-Planckian effects during the current stage of the Universe
expansion. We show that compatibility with the diffuse gamma-ray background
measured by the EGRET experiment strongly restricts this creation. In
particular, it rules out the possibility to detect signatures of such short
distance effects in anisotropies of the cosmic microwave background radiation.
On the other hand, a possibility that some part of the ultra-high energy cosmic
rays originates from new trans-Planckian physics remains open.


title:
The effect of disk magnetic fields on the truncation of geometrically
  thin disks in AGN

abstract:
  We suggest that magnetic fields in the accretion disks of AGN reach into the
coronae above and have a profound effect on the mass flow rate in the corona.
This strongly affects the location where the accretion flow changes from a
geometrically thin disk to a pure vertically extended coronal or
advection-dominated accretion flow (ADAF). We show that this can explain the
different disk truncation radii in elliptical galaxies and low luminosity AGN
with about the same mass flow rate, a discrepancy pointed out by Quataert et
al. (1999). Without disk magnetic activity the disk truncation is expected to
be uniquely related to the mass flow rate (Meyer et al. 2000b). Whether dynamo
action occurs depends on whether the electrical conductivity measured by a
magnetic Reynolds number surpasses a critical value (Gammie and Menou 1998).In
elliptical galaxies the disk is self-gravitating at the radii where the
truncation should occur. It is plausible that instead of a cool disk a ``layer
of clouds'' may form (Shlosman et al. 1990, Gammie 2001) for which no dynamo
action is expected. For low luminosity AGN the magnetic Reynolds number is well
above critical. Simple model calculations show that magnetic fields in the
underlying disks reduce the strength of the coronal flow and shift the
truncation radius significantly inward.


title:
Stellar Parameters of Wolf-Rayet Stars from Far-UV to Mid-IR
  Observations

abstract:
  Recent results for Galactic and Magellanic Cloud Wolf-Rayet stars are
summarised based on line blanketed, clumped model atmospheres together with UV,
optical and IR spectroscopy. The trend towards earlier WN and WC spectral types
with decreasing metallicity is explained via the sensitivity of classification
diagnostics to abundance/wind density, such that WR mass-loss rates are
metallicity dependent. Pre-supernovae masses for WC stars are determined, in
reasonable agreement with CO-cores of recent Type-Ic SN.


title: Boundary layer, accretion disk and X-ray variability in luminous LMXBs

abstract:
  Using Fourier frequency resolved X-ray spectroscopy we study short term
spectral variability in luminous LMXBs. With RXTE/PCA observations of
4U1608--52 and GX340+0 on the horizontal/normal branch of the color-intensity
diagram we show that aperiodic and quasiperiodic variability on ~ sec-msec time
scales is caused primarily by variations of the luminosity of the boundary
layer. The emission of the accretion disk is less variable on these time scales
and its power density spectrum follows Pdisk(f) ~ 1/f law, contributing to
observed flux variation at low frequencies and low energies only. The kHz QPOs
have the same origin as variability at lower frequencies, i.e. independent of
the nature of the "clock", the actual luminosity modulation takes place on the
neutron star surface,
  The boundary layer spectrum remains nearly constant in the course of the
luminosity variations and is represented to certain accuracy by the Fourier
frequency resolved spectrum. In the considered range Mdot ~ (0.1-1)Mdot_Edd it
depends weakly on the global mass accretion rate and in the limit Mdot ~
Mdot_Edd is close to Wien spectrum with kT ~ 2.4 keV (in the distant observer's
frame). The spectrum of the accretion disk emission is significantly softer and
in the 3--20 keV range is reasonably well described by a relativistic disk
model with a mass accretion rate consistent with the value inferred from the
observed X-ray flux.


title: Jets, winds and bursts from coalescing neutron stars

abstract:
  Recent high-resolution calculations of neutron star coalescences are used to
investigate whether nu bar{nu} annihilation can provide sufficient energy to
power gamma-ray bursts, especially those belonging to the short duration
category. Late time slices of the simulations, where the neutrino emission has
reached a maximum, stationary level are analyzed to address this question. We
find that nu bar{nu} annihilation can provide the necessary driving stresses
that lead to relativistic jet expansion. Maximum Lorentz factors of the order
of 15 are found along the binary rotation axis, but larger values are expected
to arise from higher numerical resolution. Yet the accompanying neutrino-driven
wind must be absent from the axis when the burst occurs or prohibitive baryon
loading may occur. We argue that even under the most favorable conditions, nu
bar{nu} annihilation is unlikely to power a burst in excess of ~ 10^{48} erg.
Unless the emission is beamed into less than one percent of the solid angle,
which we argue is improbable if it is collimated by gas pressure, this may fail
to satisfy the apparent isotropic energies inferred at cosmological distances.
This mechanism may nonetheless drive a precursor fireball, thereby evacuating a
cavity into which a later magnetic driven jet could expand. A large range of
time delays between the merger and the black hole formation are to be expected.
If the magnetic driven jet occurs after the black hole has formed, a time span
as long as weeks could pass between the neutrino powered precursor and the
magnetic driven GRB.


title:
Detection of doubly-deuterated methanol in the solar-type protostar
  IRAS16293-2422

abstract:
  We report the first detection of doubly-deuterated methanol (CHD2OH), as well
as firm detections of the two singly-deuterated isotopomers of methanol (CH2DOH
and CH3OD), towards the solar-type protostar IRAS16293-2422. From the present
multifrequency observations, we derive the following abundance ratios:
[CHD2OH]/[CH3OH] = 0.2 +/- 0.1, [CH2DOH]/[CH3OH] = 0.9 +/- 0.3, [CH3OD]/[CH3OH]
= 0.04 +/- 0.02. The total abundance of the deuterated forms of methanol is
greater than that of its normal hydrogenated counterpart in the circumstellar
material of IRAS16293-2422, a circumstance not previously encountered.
Formaldehyde, which is thought to be the chemical precursor of methanol,
possesses a much lower fraction of deuterated isotopomers (~ 20%) with respect
to the main isotopic form in IRAS16293-2422. The observed fractionation of
methanol and formaldehyde provides a severe challenge to both gas-phase and
grain-surface models of deuteration. Two examples of the latter model are
roughly in agreement with our observations of CHD2OH and CH2DOH if the
accreting gas has a large (0.2-0.3) atomic D/H ratio. However, no gas-phase
model predicts such a high atomic D/H ratio, and hence some key ingredient
seems to be missing.


title: Variable gamma-ray emission from microblazars

abstract:
  We propose a model for gamma-ray emitting microblazars based on the Compton
interaction of a relativistic electron-positron plasma, ejected in a jet
feature, with the UV-photon field provided by a high-mass stellar companion.
Taking into account the gravitational effects of the star upon the accretion
disk, we predict a jet precession which results in a variable, periodic,
high-energy gamma-ray source. The specific case of Cygnus X-1 is briefly
discussed.


title:
Thermal Pressures in Neutral Clouds inside the Local Bubble, as
  Determined from C I Fine-Structure Excitations

abstract:
  High-resolution spectra covering absorption features from interstellar C I
were recorded for four early-type stars with spectrographs on HST, in a program
to measure the fine-structure excitation of this atom within neutral clouds
inside or near the edge of the Local Bubble, a volume of hot (T ~ 10^6 K) gas
that emits soft x-rays and extends out to about 100 pc away from the Sun. The
excited levels of C I are populated by collisions, and the ratio of excited
atoms to those in the ground level give a measure of the local thermal
pressure. Absorptions from the two lowest levels of C I were detected toward
alpha Del and delta Cyg, while only marginal indications of excited C I were
obtained for gamma Ori, and lambda Lup. Along with temperature limits derived
by other means, the C I fine-structure populations indicate that for the clouds
in front of gamma Ori, delta Cyg and alpha Del, 10^3 < p/k < 10^4 cm^{-3}K at
about the +-1 sigma confidence level in each case. The results for lambda Lup
are not as well constrained, but still consistent with the other three stars.
The results indicate that the thermal pressures are below generally accepted
estimates p/k > 10^4 cm^{-3}K for the Local Bubble, based on the strength of
x-ray and EUV emission from the hot gas. This inequality of pressure for these
neutral clouds and their surroundings duplicates a condition that exists for
the local, partly-ionized cloud that surrounds the Sun. An appendix in the
paper describes a direct method for determining and eliminating small spectral
artifacts arising from variations of detector sensitivity with position.


title: A New Feature Along the Extended Blue Horizontal Branch of NGC 6752

abstract:
  In this letter we report on the detection of a new feature in the complex
structure of the horizontal branch (HB) of the Galactic globular cluster NGC
6752. In the U vs. (U-V) plane, the HB shows a discontinuity (``jump'') at U-V
~= -1.0 (corresponding T_e ~ 23,000 K). This ``second U-jump'' adds to the
u-jump identified by Grundahl et al. (1999) in a dozen of clusters at T_e ~
11,500 K. We show that this new discontinuity might be due to the combination
of post zero age HB evolution and diffusion effects. We identify 11 AGB-manque
stars. The comparison between post-HB star counts and evolutionary lifetimes,
as predicted by canonical stellar models, shows good agreement, at variance
with similar estimates for NGC 6752 available in the literature.


title: Non linear predictions from linear theories in models with Dark Energy

abstract:
  We study the cluster mass function and its evolution in different models with
Dark Energy arising from a self--interacting scalar field, with Ratra-Peebles
and SUGRA potentials. Computations are based on a Press & Schechter
approximation. The mass functions we obtain are compared with results holding
for open models or models with Dark Energy due to a cosmological constant.
Evolution results, in the Dark Energy cases, closely approach open models.


title:
On the Dynamical Overstability of Radiative Blast Waves: The Atomic
  Physics of Shock Stability

abstract:
  Atomic physics calculations of radiative cooling are used to calculate
criteria for the overstability of radiating shocks. Our calculations explain
the measurement of shock overstability by Grun et al. and explain why the
overstability was not observed in other experiments. The methodology described
here can be especially useful in astrophysical situations where the relevant
properties leading to an overstability can be measured spectroscopically, but
the effective adiabatic index is harder to determine.


title: On the baryometric status of He3

abstract:
  Recent observations by Bania et al. (2002) measure He3 versus oxygen in
Galactic HII regions, finding that He3/H is within a factor of 2 of the solar
abundance for [O/H] > -0.6. These results are consistent with a flat behavior
in this metallicity range, tempting one to deduce from these observations a
primordial value for the He3 abundance, which could join D and Li7 as an
indicator of the cosmic baryon density. However, using the same data, we show
that it is not possible to obtain a strong constraint on the baryon density
range. This is due to (i) the intrinsically weak sensitivity of the primordial
He3 abundance to the baryon density; (ii) the limited range in metallicity of
the sample; (iii) the intrinsic scatter in the data; and (iv) our limited
understanding of the chemical and stellar evolution of this isotope.
Consequently, the He3 observations correspond to an extended range of
baryon-to-photon ratio, eta = (2.2 - 6.5) x 10^{-10}, which diminishes the role
of He3 as a precision baryometer. On the other hand, once the baryon-to-photon
ratio is determined by the CMB, D/H, or Li7/H, the primordial value of He3/H
can be inferred. Henceforth new observations of Galactic He3, can in principle
greatly improve our understanding of stellar and/or chemical evolution and
reconcile the observations of the HII regions and those of the planetary
nebulae.


title:
Return mapping of phases and the analysis of the gravitational
  clustering hierarchy

abstract:
  In the standard paradigm for cosmological structure formation, clustering
develops from initially random-phase (Gaussian) density fluctuations in the
early Universe by a process of gravitational instability. The later, non-linear
stages of this process involve Fourier mode-mode interactions that result in a
complex pattern of non-random phases. We present a novel mapping technique that
reveals mode coupling induced by this form of nonlinear interaction and allows
it to be quantified statistically. The phase mapping technique circumvents the
difficulty of the circular characteristic of phi_k and illustrates the
statistical significance of phase difference at the same time. This generalized
method on phases allows us to detect weak coupling of phases on any Delta k
scales.


title: On the Abundance of Holmium in the Sun

abstract:
  The abundance of holmium (Z = 67) in the Sun remains uncertain. The
photospheric abundance, based on lines of Ho II, has been reported as +0.26 +/-
0.16 (on the usual scale where log(H) = 12.00), while the meteoretic value is
+0.51 +/- 0.02. Cowan code calculations have been undertaken to improve the
partition function for this ion by including important contributions from
unobserved levels arising from the (4f^{11}6p + 4f^{10}(5d + 6s)^{2}) group.
Based on 6994 computed energy levels, the partition function for Ho II is 67.41
for a temperature of 6000 K. This is approximately 1.5 times larger than the
value derived from the 49 published levels. The new partition function alone
leads to an increase in the solar abundance of Ho to log(Ho) = +0.43. This is
within 0.08 dex of the meteoretic abundance. Support for this result has been
obtained through LTE spectrum synthesis calculations of a previously
unidentified weak line at 3416.38 A in the solar spectrum. Attributing the
feature to Ho II, the observations may be fitted with log(Ho) = +0.53. This
calculation assumes log(gf) = 0.25 and is uncertain by at least 0.1 dex.


title:
AST/RO Observations of CO J=7-6 and J=4-3 Emission toward the Galactic
  Center Region

abstract:
  We present position-velocity strip maps of the Galactic Center region in the
CO J=7-6 and J=4-3 transitions observed with the Antarctic Submillimeter
Telescope and Remote Observatory (AST/RO) located at Amundsen-Scott South Pole
Station. Emission from the two rotational transitions of 12^CO was mapped at
b=0 deg for 3.5 deg > l > -1.5 deg, on a 1' grid with a FWHM beamsize of 58''
at 806 GHz and 105'' at 461 GHz. Previous observations of CO J=4-3 (Martin et
al., in preparation) and CI (Ojha et al. 2001) emission from this region show
that these lines are distributed in a manner similar to CO J=1-0 (Stark et al.
1987); the (CO J=4-3)/(CO J=1-0) line ratio map is almost featureless across
the entire Galactic Center region. In contrast, the CO J=7-6 emission from the
Galactic Center is strongly peaked toward the Sgr A and Sgr B molecular
complexes. A Large Velocity Gradient (LVG) analysis shows that aside from the
two special regions Sgr A and Sgr B, the photon-dominated regions within a few
hundred parsecs of the Galactic Center are remarkably uniform in mean density
and kinetic temperature at n = 2500 to 4000 cm^{-3} and T=30 to 45K. The (CO
J=7-6)/(CO J=4-3) line temperature ratios near Sgr B are a factor of two higher
than those observed in the nuclear region of the starburst galaxy M82 (Mao et
al. 2000), while the CO(J=7-6)/CO(J=4-3) line temperature ratios around Sgr A
are similar to M82. The line ratio on large scales from the Galactic Center
region is an order of magnitude less than that from M82.


title:
The identification of the optical/IR counterpart of the 15.8-s transient
  X-ray pulsar XTE J1946+274

abstract:
  We report on the discovery of the optical/IR counterpart of the 15.8s
transient X-ray pulsar XTE J1946+274. We re-analysed archival BeppoSAX
observations of XTE J1946+274, obtaining a new refined position (a circle with
22" radius at 90% confidence level). Based on this new position we carried out
optical and infra-red (IR) follow-up observations. Within the new error circle
we found a relatively optical faint (B=18.6) IR bright (H=12.1) early type
reddened star (V--R=1.6). The optical spectra show strong H-alpha and H-beta
emission lines. The IR photometric observations of the field confirm the
presence of an IR excess for the H-alpha--emitting star (K=11.6, J--H=0.6)
which is likely surrounded by a circumstellar envelope. Spectroscopic and
photometric data indicate a B0--1V--IVe spectral-type star located at a
distance of 8--10kpc and confirm the Be-star/X-ray binary nature of XTE
J1946+274.


title: K-Band Red Clump Distances to the LMC Clusters Hodge 4 and NGC 1651

abstract:
  We present near-infrared color-magnitude diagrams for the LMC star clusters
Hodge 4 and NGC 1651 revealing the helium burning red clump stars for the first
time in the JK passbands. From these diagrams, which extend to K~19, and
existing optical CMDs that reveal the clusters' main sequence turnoffs, we
determine the following cluster parameters. For Hodge 4, we estimate a
metallicity of [Fe/H] = -0.17 +/- 0.04, an age of 1.7 +/- 0.3 Gyr, and a red
clump absolute magnitude of Mk(RC) = -1.64 +/- 0.17. Along with an adopted
reddening of E(J-K) = 0.03 +/- 0.01 based on the Burstein & Heiles and Schlegel
et al. reddening maps, we find a distance of (m-M)o = 18.52 +/- 0.17 for Hodge
4. In the case of NGC 1651, we derive [Fe/H] = -0.07 +/- 0.10, an age of 1.8
+/- 0.3 Gyr, Mk(RC) = -1.56 +/- 0.12, E(J-K) = 0.06 +/- 0.01, and (m-M)o =18.55
+/- 0.12, all measured in the same manner as for Hodge 4. Based on these two
clusters, we calculate a mean LMC distance of (m-M)o = 18.54 +/- 0.10.


title:
Conditions for Steady Gravitational Radiation from Accreting Neutron
  Stars

abstract:
  The gravitational-wave and accretion driven evolution of the angular
velocity, core temperature, and (small) amplitude of an r-mode of neutron stars
in low mass X-ray binaries and similar systems is investigated. The conditions
required for evolution to a stable equilibrium state (with gravitational wave
flux proportional to average X-ray flux) are determined. In keeping with
conclusions derived from observations of neutron star cooling, the core
neutrons are taken to be normal while the core protons and hyperons and the
crust neutrons are taken to be singlet superfluids. The dominant sources of
damping are then hyperon bulk viscosity (if much of the core is at least 2--3
times nuclear density) and (e-e and n-n) shear (and possibly magnetic)
viscosity within the core--crust boundary layer. It is found that a stable
equilibrium state can be reached if the superfluid transition temperature of
the hyperons is sufficiently small ($\lesssim 2\times 10^9$ K), allowing the
gravitational radiation from Sco X-1 and several other neutron stars in
low-mass X-ray binaries to be potentially detectable by the second generation
LIGO (and VIRGO) arrays.


title:
Evidence for a Mid-Atomic-Number Atmosphere in the Neutron Star
  1E1207.4-5209

abstract:
  Recently Sanwal et al. (2002) reported the first clear detection of
absorption features in an isolated neutron star, 1E1207.4-5209. Remarkably
their spectral modeling demonstrates that the atmosphere cannot be Hydrogen.
They speculated that the neutron star atmosphere is indicative of ionized
Helium in an ultra-strong (~1.5x10^{14} G) magnetic field. We have applied our
recently developed atomic model (Mori & Hailey 2002) for strongly-magnetized
neutron star atmospheres to this problem. We find that this model, along with
some simp le atomic physics arguments, severely constrains the possible
composition of the atmosphere. In particular we find that the absorption
features are naturally associated with He-like Oxygen or Neon in a magnetic
field of ~10^{12} G, comparable to the magnetic field derived from the spin
parameters of the neutron star. This interpretation is consistent with the
relative line strengths and widths and is robust. Our model predicts possible
substructure in the spectral features, which has now been reported by
XMM-Newton (Mereghetti et al. 2002). However we show the Mereghetti et al.
claim that the atmosphere is Iron or some comparable high-Z element at ~
10^{12} G is easily ruled out by the Chandra and XMM-Newton data.


title:
Probing the Reionization History of the Universe using the Cosmic
  Microwave Background Polarization

abstract:
  The recent discovery of a Gunn--Peterson (GP) trough in the spectrum of the
redshift 6.28 SDSS quasar has raised the tantalizing possibility that we have
detected the reionization of the universe. However, a neutral fraction (of
hydrogen) as small as 0.1% is sufficient to cause the GP trough, hence its
detection alone cannot rule out reionization at a much earlier epoch. The
Cosmic Microwave Background (CMB) polarization anisotropy offers an alternative
way to explore the dark age of the universe. We show that for most models
constrained by the current CMB data and by the discovery of a GP trough
(showing that reionization occurred at z > 6.3), MAP can detect the
reionization signature in the polarization power spectrum. The expected 1-sigma
error on the measurement of the electron optical depth is around 0.03 with a
weak dependence on the value of that optical depth. Such a constraint on the
optical depth will allow MAP to achieve a 1-sigma error on the amplitude of the
primordial power spectrum of 6%. MAP with two years (Planck with one year) of
observation can distinguish a model with 50% (6%) partial ionization between
redshifts of 6.3 and 20 from a model in which hydrogen was completely neutral
at redshifts greater than 6.3. Planck will be able to distinguish between
different reionization histories even when they imply the same optical depth to
electron scattering for the CMB photons.


title: PN-Carbon Yields and the Chemical Evolution of the Galactic Disk

abstract:
  Two sets of observational carbon stellar yields for low-and-intermediate mass
stars are computed based on planetary nebula abundances derived from C II
lambda 4267 and C III lambda lambda 1906 + 1909 lines, respectively. These
observational yields are assumed in chemical evolution models for the solar
vicinity and the Galactic disk. C/O values observed in stars of the solar
vicinity and Galactic H II regions are compared with those predicted by
chemical evolution models for the Galaxy. I conclude that the C yields derived
from permitted lines are in better agreement with the observational constraints
than those derived from forbidden lines.


title: Proposed gravitational wave background from black hole-torus systems

abstract:
  Cosmological gamma-ray bursts may be powered by rotating black holes with
contemporaneous emission of gravitational radiation from a surrounding torus.
We calculate the resulting stochastic background radiation assuming strong
cosmological evolution and a uniform black hole mass distribution of M=
(4--14)M_odot. The predicted spectral flux density corresponds to a peak
spectral closure density of (1--2) times 10^{-7}, and has comparable
contributions at 450 Hz times kappa and over 300--450 Hz times kappa from
nearby and distant sources, respectively, where kappa refers to an uncertainty
factor of order unity in the radius of the torus. For two optimized advanced
LIGO-type detectors the proposed gravitational wave background could be
detectable within a year of integration.


title: Correlated radial velocity and X-ray variations in HD 154791/4U 1700+24

abstract:
  We present evidence for approximately 400-d variations in the radial velocity
of HD 154791 (V934 Her), the suggested optical counterpart of 4U 1700+24. The
variations are correlated with the previously reported approximately 400 d
variations in the X-ray flux of 4U 1700+24, which supports the association of
these two objects, as well as the identification of this system as the second
known X-ray binary in which a neutron star accretes from the wind of a red
giant. The HD 154791 radial velocity variations can be fit with an eccentric
orbit with period 404 +/- 3 d, amplitude K=0.75 +/- 0.12 km/s and eccentricity
e=0.26 +/- 0.15. There are also indications of variations on longer time scales
>~ 2000 d. We have re-examined all available ASM data following an unusually
large X-ray outburst in 1997-98, and confirm that the 1-d averaged 2-10 keV
X-ray flux from 4U 1700+24 is modulated with a period of 400 +/- 20 d. The mean
profile of the persistent X-ray variations was approximately sinusoidal, with
an amplitude of 0.108 +/- 0.012 ASM count/s (corresponding to 31% rms). The
epoch of X-ray maximum was approximately 40 d after the time of periastron
according to the eccentric orbital fit. If the 400 d oscillations from HD
154791/4U 1700+24 are due to orbital motion, then the system parameters are
probably close to those of the only other neutron-star symbiotic-like binary,
GX 1+4. We discuss the similarities and differences between these two systems.


title: Onset of Convectionon a Pre-Runaway White Dwarf

abstract:
  Observed novae abundances and explosion energies estimated from observations
indicate that there must be significant mixing of the heavier material of the
white dwarf (C+O) into the lighter accreted material (H+He). Accordingly, nova
models must incorporate a mechanism that will dredge up the heavier white dwarf
material, and fluid motions from an early convection phase is one proposed
mechanism.
  We present results from two-dimensional simulations of classical nova
precursor models that demonstrate the beginning of a convective phase during
the `simmering' of a Nova precursor. We use a new hydrostatic equilibrium
hydrodynamics module recently developed for the adaptive-mesh code FLASH. The
two-dimensional models are based on the one-dimensional models of Ami Glasner,
and were evolved with FLASH from a pre-convective state to the onset of
convection.


title: r-Process Abundance Universality and Actinide Cosmochronology

abstract:
  We review recent observational and theoretical results concerning the
presence of actinide nuclei on the surfaces of old halo stars and their use as
an age determinant. We present model calculations which show that the observed
universality of abundances for 56 < Z < 75 elements in these stars does not
imply a unique astrophysical site for the r-process. Neither does it imply a
universality of abundances of nuclei outside of this range. In particular, we
show that a variety of astrophysical $r$-process models can be constructed
which reproduce the same observed universal r-process curve for 56 < Z < 75
nuclei, yet have vastly different abundances for Z >= 75 and possibly Z <= 56
as well. This introduces an uncertainty into the use of the Th/Eu chronometer
as a means to estimate the ages of the metal deficient stars. We do find,
however, that the U/Th ratio is a robust chronometer. This is because the
initial production ratio of U to Th is almost independent of the astrophysical
nucleosynthesis environment. The largest remaining uncertainties in the U/Th
initial production ratio are due to the input nuclear physics models.


title: The Host Galaxies of Radio-Loud AGN: The Black Hole--Galaxy Connection

abstract:
  We have studied the host galaxies of a sample of radio-loud AGN spanning more
than four decades in the energy output of the nucleus. The core sample includes
40 low-power sources (BL Lac objects) and 22 high-power sources (radio-loud
quasars) spanning the redshift range z~0.15 to z~0.5, all imaged with the high
spatial resolution of HST. All of the sources are found to lie in luminous
elliptical galaxies, which follow the Kormendy relation for normal ellipticals.
A very shallow trend is detected between nuclear brightness (corrected for
beaming) and host galaxy luminosity. Black hole masses are estimated for the
entire sample, using both the bulge luminosity--black hole mass and the
velocity dispersion--black hole mass relations for local galaxies. The latter
involves a new method, using the host galaxy morphological parameters, mu_e and
r_e, to infer the velocity dispersion, sigma, via the fundamental plane
correlation. Both methods indicate that the entire sample of radio-loud AGN are
powered by very massive central black holes, with M_{black hole} ~ 10^8 to
10^10 M_{sun}$. Eddington ratios range from L/L_{Eddington} ~ 2 x 10^-4 to ~1,
with the high- power sources having higher Eddington ratios than the low-power
sources. Overall, radio-loud AGN appear to span a very large range in accretion
efficiency, which is all but independent of the mass of the host galaxy.


title:
X-ray and gamma-ray spectra and variability of the black-hole candidate
  GX 339-4

abstract:
  We analyse five observations of the X-ray binary GX 339-4 by the soft
gamma-ray OSSE detector on board CGRO simultaneous with either Ginga or RXTE
observations. The source was bright during four of them, with the luminosity of
L ~ 10^{37} erg/s and the spectrum typical for hard states of accreting black
holes, and it was in an off state during the fifth one, with L ~ 10^{35} erg/s.
Our broad-band spectral fits show the mean electron energy of electrons in the
Comptonizing plasma decreasing with increasing luminosity within the hard
(bright) state. For the observation with the best statistics at soft
gamma-rays, approximately 1/4 of energy in the Comptonizing plasma is probably
carried by non-thermal electrons. Then, considering the efficiency of
Comptonized hybrid synchrotron emission allows us to obtain an upper limit on
the strength of the magnetic field in the X-ray source. Furthermore, this
synchrotron emission is capable of producing the optical spectrum observed in
an optically-high state of GX 339-4. In the off state, the hard X-ray spectrum
is consistent with being dominated by bremsstrahlung. The unusually strong Fe K
alpha line observed by the PCA during that state is found not to be intrinsic
to the source but to originate mostly in the Galactic diffuse emission.


title: A Chandra Spectroscopic Survey of Persistent Black Hole Candidates

abstract:
  We present results from observations of persistent black hole candidates with
the High Energy Transmission Gratings aboard the Chandra X-ray Observatory. The
sources include LMC X-1, LMC X-3, GRS 1758-258, and Cyg X-1. Along with the
published results on 1E1740.7-2942, we have completed a high-resolution
spectroscopic survey of such systems. The observed X-ray spectra of LMC X-1 and
LMC X-3 show no prominent discrete features, while absorption edges (Mg K and
Si K) are detected in the spectrum of GRS 1758-258. The edges are likely to be
of interstellar origin. In most cases, the X-ray continuum can be described
well by models that are often adopted in low-resolution studies of black hole
candidates: a multi-temperature disk spectrum plus a Comptonization component.
However, the relative contribution of the two components varies greatly among
different sources. For instance, only the disk component is present for LMC X-1
and GRS 1758-258, while the Comptonized component is required for other
sources. We discuss general issues related to obtaining disk parameters from
modeling X-ray continuum.


title:
Measuring Cluster Peculiar Velocities and Temperatures at cm and mm
  Wavelengths

abstract:
  We present a detailed investigation of issues related to the measurement of
peculiar velocities and temperatures using Sunyaev-Zel'dovich (SZ) effects. We
estimate the accuracy to which peculiar velocities and gas temperatures of
distant galaxy clusters could be measured. With uK sensitivity on arcminute
scales at several frequencies it will be possible to measure peculiar
velocities to an accuracy of about 130 km/s and gas temperatures to better than
1 keV. The limiting factor for the accuracy of the measured peculiar velocity
is the presence of bulk motions within the galaxy cluster, even for apparently
relaxed clusters. The accuracy of the temperature is mainly limited by noise.
These results are independent of redshift. Such constraints can best be
achieved with only three frequencies: one in the Rayleigh-Jeans region (<40
GHz), one near 150 GHz, and the third at 300 GHz or higher. Measurements at the
null of the thermal SZ effect are of marginal utility, other than as a
foreground/background monitor.


title:
A Study of the Type II-Plateau Supernova 1999gi, and the Distance to its
  Host Galaxy, NGC 3184

abstract:
  We present optical spectra and photometry sampling the first six months after
discovery of supernova (SN) 1999gi in NGC 3184. SN 1999gi is shown to be a Type
II-plateau event with a photometric plateau lasting until about 100 days after
discovery. The reddening values resulting from five independent techniques are
all consistent with an upper bound of E(B-V) < 0.45 mag established by
comparing the early-time color of SN 1999gi with that of an infinitely hot
blackbody, and yield a probable reddening of E(B-V) = 0.21 +/- 0.09 mag. Using
the expanding photosphere method (EPM), we derive a distance to SN 1999gi of
11.1^{+2.0}_{-1.8} Mpc and an explosion date of 1999 December
5.8^{+3.0}_{-3.1}, or 4.1^{+3.0}_{-3.1} days prior to discovery. This distance
is consistent with a recent Tully-Fisher distance derived to NGC 3184 (D ~
11.59 Mpc), but is somewhat closer than the Cepheid distances derived to two
galaxies that have generally been assumed to be members of a small group
containing NGC 3184 (NGC 3319, D = 13.30 +/- 0.55 Mpc, and NGC 3198, D = 13.80
+/- 0.51 Mpc).
  We reconsider the upper mass limit (9^{+3}_{-2} M_{sun}) recently placed on
the progenitor star of SN 1999gi by Smartt et al. (2001, 2002) in light of
these results. Following the same procedures, but using the new data presented
here, we arrive at a less restrictive upper mass limit of 15^{+5}_{-3} M_{sun}
for the progenitor. The increased upper limit results mainly from the larger
distance derived through the EPM than was assumed by the Smartt et al.
analyses, which relied on less precise (and less recent) distance measurements
to NGC 3184.


title: The Compact Central Object in the Supernova Remnant G266.2-1.2

abstract:
  We observed the compact central object CXOU J085201.4--461753 in the
supernova remnant G266.2--1.2 (RX J0852.0--4622) with the Chandra ACIS detector
in timing mode. The spectrum of this object can be described by a blackbody
model with the temperature kT=404 eV and radius of the emitting region R=0.28
km, at a distance of 1 kpc. Power-law and thermal plasma models do not fit the
source spectrum. The spectrum shows a marginally significant feature at 1.68
keV. Search for periodicity yields two candidate periods, about 301 ms and 33
ms, both significant at a 2.1 sigma level; the corresponding pulsed fractions
are 13% and 9%, respectively. We find no evidence for long-term variability of
the source flux, nor do we find extended emission around the central object. We
suggest that CXOU J085201.4--461753 is similar to CXOU J232327.9+584842, the
central source of the supernova remnant Cas A. It could be either a neutron
star with a low or regular magnetic field, slowly accreting from a fossil disk,
or, more likely, an isolated neutron star with a superstrong magnetic field. In
either case, a conservative upper limit on surface temperature of a 10 km
radius neutron star is about 90 eV, which suggests accelerated cooling for a
reasonable age of a few thousand years.


title: X-ray Detection of the Inner Jet in the Radio Galaxy M84

abstract:
  During the course of an investigation of the interaction of the radio galaxy
M84 and its ambient cluster gas, we found excess X-ray emission aligned with
the northern radio jet. The emission extends from the X-ray core of the host
galaxy as a weak bridge and then brightens to a local peak coincident with the
first detectable radio knot at approx. 2.5" from the core. The second radio
knot at 3.3" is brighter in both radio and X-rays. The X-ray jet terminates
3.9" from the core. Although all the evidence suggests that Doppler favoritism
augments the emission of the northern jet, it is unlikely that the excess X-ray
emission is produced by inverse Compton emission. We find many similarities
between the M84 X-ray jet and recent jet detections from Chandra data of low
luminosity radio galaxies. For most of these current detections synchrotron
emission is the favored explanation for the observed X-rays.


title:
Microlensing optical depth towards the Galactic bulge from MOA
  observations during 2000 with Difference Image Analysis

abstract:
  We analyze the data of the gravitational microlensing survey carried out by
by the MOA group during 2000 towards the Galactic Bulge (GB). Our observations
are designed to detect efficiently high magnification events with faint source
stars and short timescale events, by increasing the the sampling rate up to 6
times per night and using Difference Image Analysis (DIA). We detect 28
microlensing candidates in 12 GB fields corresponding to 16 deg^2. We use Monte
Carlo simulations to estimate our microlensing event detection efficiency,
where we construct the I-band extinction map of our GB fields in order to find
dereddened magnitudes. We find a systematic bias and large uncertainty in the
measured value of the timescale $t_{\rm Eout}$ in our simulations. They are
associated with blending and unresolved sources, and are allowed for in our
measurements. We compute an optical depth tau = 2.59_{-0.64}^{+0.84} \times
10^{-6} towards the GB for events with timescales 0.3<t_E<200 days. We consider
disk-disk lensing, and obtain an optical depth tau_{bulge} =
3.36_{-0.81}^{+1.11} \times 10^{-6}[0.77/(1-f_{disk})] for the bulge component
assuming a 23% stellar contribution from disk stars. These observed optical
depths are consistent with previous measurements by the MACHO and OGLE groups,
and still higher than those predicted by existing Galactic models. We present
the timescale distribution of the observed events, and find there are no
significant short events of a few days, in spite of our high detection
efficiency for short timescale events down to t_E = 0.3 days. We find that half
of all our detected events have high magnification (>10). These events are
useful for studies of extra-solar planets.


title: HST NICMOS Images of the HH 7/11 Outflow in NGC1333

abstract:
  We present near infrared images in H2 at 2.12um of the HH 7/11 outflow and
its driving source SVS 13 taken with HST NICMOS 2 camera, as well as archival
Ha and [SII] optical images obtained with the WFPC2 camera. The NICMOS high
angular resolution observations confirm the nature of a small scale jet arising
from SVS 13, and resolve a structure in the HH 7 working surface that could
correspond to Mach disk H2 emission. The H2 jet has a length of 430 AU (at a
distance of 350 pc), an aspect ratio of 2.2 and morphologically resembles the
well known DG Tau optical micro-jet. The kinematical age of the jet (approx. 10
yr) coincides with the time since the last outburst from SVS 13. If we
interpret the observed H2 flux density with molecular shock models of 20-30
km/s, then the jet has a density as high as 1.e+5 cc. The presence of this
small jet warns that contamination by H2 emission from an outflow in studies
searching for H2 in circumstellar disks is possible. At the working surface,
the smooth H2 morphology of the HH 7 bowshock indicates that the magnetic field
is strong, playing a major role in stabilizing this structure. The H2 flux
density of the Mach disk, when compared with that of the bowshock, suggests
that its emission is produced by molecular shocks of less than 20 km/s. The
WFPC2 optical images display several of the global features already inferred
from groundbased observations, like the filamentary structure in HH 8 and HH
10, which suggests a strong interaction of the outflow with its cavity. The H2
jet is not detected in {SII] or Ha, however, there is a small clump at approx.
5'' NE of SVS 13 that could be depicting the presence either of a different
outburst event or the north edge of the outflow cavity.


title: Delayed Flashes from Counter Jets of Gamma Ray Bursts

abstract:
  If X-ray flashes are due to the forward jet emissions from gamma ray bursts
(GRBs) observed with large viewing angles, we show that a prompt emission from
a counter jet should be observed as a delayed flash in the UV or optical band
several hours to a day after the X-ray flash. Ultraviolet and Optical Telescope
on Swift can observe the delayed flashes within ~13 Mpc, so that (double-sided)
jets of GRBs may be directly confirmed. Since the event rate of delayed flashes
detected by Swift may be as small as 6*10^{-5}events/yr, we require more
sensitive detectors in future experiments.


title:
An Aligned Stream of Low-Metallicity Clusters in the Halo of the Milky
  Way

abstract:
  One of the long-standing problems in modern astronomy is the curious division
of Galactic globular clusters, the "Oosterhoff dichotomy," according to the
properties of their RR Lyrae stars. Here, we find that most of the
lowest-metallicity ([Fe/H]<-2.0) clusters, which are essential to an
understanding of this phenomenon, display a planar alignment in the outer halo.
This alignment, combined with evidence from kinematics and stellar population,
indicates a captured origin from a satellite galaxy. We show that, together
with the horizontal-branch evolutionary effect, the factor producing the
dichotomy could be a small time-gap between the cluster-formation epochs in the
Milky Way and the satellite. The results oppose the traditional view that the
metal-poorest clusters represent the indigenous and oldest population of the
Galaxy.


title: Do Neutron Star Gravitational Waves Carry Superfluid Imprints?

abstract:
  Isolated neutron stars undergoing non-radial oscillations are expected to
emit gravitational waves in the kilohertz frequency range. To date, radio
astronomers have located about 1,300 pulsars, and can estimate that there are
about 2 times 10^8 neutron stars in the galaxy. Many of these are surely old
and cold enough that their interiors will contain matter in the superfluid or
superconducting state. In fact, the so-called glitch phenomenon in pulsars (a
sudden spin-up of the pulsar's crust) is best described by assuming the
presence of superfluid neutrons and superconducting protons in the inner crusts
and cores of the pulsars. Recently there has been much progress on modelling
the dynamics of superfluid neutron stars in both the Newtonian and general
relativistic regimes. We will discuss some of the main results of this recent
work, perhaps the most important being that superfluidity should affect the
gravitational waves from neutron stars (emitted, for instance, during a glitch)
by modifying both the rotational properties of the background star and the
modes of oscillation of the perturbed configuration. Finally, we present an
analysis of the so-called zero-frequency subspace (i.e. the space of
time-independent perturbations) and determine that it is spanned by two sets of
polar (or spheroidal) and two sets of axial (or toroidal) degenerate
perturbations for the general relativistic system. As in the Newtonian case,
the polar perturbations are the g-modes which are missing from the pulsation
spectrum of a non-rotating configuration, and the axial perturbations should
lead to two sets of r-modes when the degeneracy of the frequencies is broken by
having the background rotate.


title: Beaming Effects in Gamma-Ray Bursts

abstract:
  Based on a refined generic dynamical model, we investigate afterglows from
jetted gamma-ray burst (GRB) remnants numerically. In the relativistic phase,
the light curve break could marginally be seen. However, an obvious break does
exist at the transition from the relativistic phase to the non-relativistic
phase, which typically occurs at time 10 to 30 days. It is very interesting
that the break is affected by many parameters, especially by the electron
energy fraction (xi_e), and the magnetic energy fraction (xi_B^2). Implication
of orphan afterglow surveys on GRB beaming is investigated. The possible
existence of a kind of cylindrical jets is also discussed.


title: Short term X-ray rms variability of Cyg X-1

abstract:
  A linear dependence of the amplitude of broadband noise variability on flux
for GBHC and AGN has been recently shown by Uttley & McHardy (2001). We present
the long term evolution of this rms-flux-relation for Cyg X-1 as monitored from
1998-2002 with RXTE. We confirm the linear relationship in the hard state and
analyze the evolution of the correlation for the period of 1996-2002. In the
intermediate and the soft state, we find considerable deviations from the
otherwise linear relationship. A possible explanation for the rms-flux-relation
is a superposition of local mass accretion rate variations.


title:
NSV 10934: an Unusual ROSAT-Selected Dwarf Nova: An Analogous Object to
  HT Cam?

abstract:
  NSV 10934 was discovered as a large-amplitude suspected variable star of
unknown classification. We noticed that the object is identified with a bright
ROSAT X-ray source (1RXS J184050.3-834305). Systematic monitoring of this
object by the VSNET team revealed four outbursts between 2001 and 2002,
confirming the dwarf nova-type nature of NSV 10934. The outbursts were
characterized by a rapid fading (1.5 mag within 0.90 d) toward the end of the
outbursts. Combined with the strong and relatively hard X-ray detection, this
outburst behavior suggests that the object may be related to the recently
discovered intermediate polar, HT Cam (astro-ph/0206184).


title: Reflection Symmetry of Cusps in Gravitational Lensing

abstract:
  Criticality in graviational microlensing is an everyday issue because that is
what generates microlensing signals which may be of photon-challenged compact
objects such as black holes or planetary systems ET calls home. The criticality
of these quasi-analytic lenses is intrinsically quadratic, and the critical
curve behaves as a mirror generating two mirror images along the image line
(parallel +/- E_-) at the same distances from the critical curve in the
opposite sides.
  At the (pre)cusps where the caustic curve "reflects" and develops cusps,
however, "would-be" two pairs of quadratic images "superpose" to produce three
mirror images because of the degenerate criticality. The critical curve behaves
as a parabolic mirror, and the image inside the parabola is indeed a superposed
image having the sum of the magnifications of the other two that are outside
the parabola. All three images lie on a parabolic image curve shaped by a
property (nabla J) of the (pre)cusp, and two distances of the system determine
the position of the image curve and positions of the three images on the image
curve. The triplet images satisfy sum J^{-1} = 0, and the function sum J^{-1}
is discontinuous at a caustic crossing where a pair of quadratic images
disappear into a critical point. The reflection symmetry of the image curve is
a manifestation of the symmetry of the cusp which is also respected by a trio
of parabolic curves that are tangnet at the (pre)cusp and define the image
domains. The symmetry is guaranteed when J_{+-} vanishes or can be ignored, and
the cusps on the lens axis of the binary lenses are strongly symmetric having
J_{+-} = 0 because of the global reflection symmetry of the binary lenses.
"E_{+/-}-algebra" is laid out for users' convenience.


title:
Multi-wavelength study of the nebula associated with the galactic LBV
  candidate HD 168625

abstract:
  We present high resolution HST imaging of the nebula associated with the
galactic LBV candidate HD 168625, together with ISO imaging and AAT echelle
spectroscopy. The overall nebular morphology is elliptical with the major axis
at PA ~ 120 deg. The dimensions of the nebula are 12'' x 16''.7 at Halpha and
15''.5 x 23''.5 at 4 micron. In the HST Halpha image, the nebula is resolved
into a complex structure of filaments and arcs of different brightness. The
asymmetry is lost in the HST continuum image where the nebula appears more
diffuse and richer in filaments and clumps with the shape of cometary tails. At
11.3 micron the nebular emission peaks in two diametrically opposite lobes,
placed on the nebula boundaries and along its major axis. A very faint loop is
also visible at optical wavelengths, north and south of the shell. We suggest
that the nebula is an ellipsoid with projected sizes of 14'' and 9'' (0.19 pc x
0.12 pc) along the RA and DEC directions, respectively. This ellipsoid is
expanding at 19 km/s and is dynamically as old as ~ 4800 yrs; it probably
interacts with the stellar wind and the loop so that PAH emission is detected
from its caps, i.e. the lobes seen in the ISO images. The chemistry of the loop
suggests that it is composed of un-processed material, probably from the local
interstellar medium swept by the stellar wind.


title:
Two jets from the Orion (M42) `proplyds' - kinematics, morphologies and
  origins

abstract:
  A spatially unresolved velocity feature, with an approaching radial velocity
of ~100 km/s with respect to the systemic radial velocity, in a
position-velocity array of [O III] 5007 line profiles is identified as the
kinematical counterpart of a jet from the proplyd LV 5 (158-323) in the core of
the Orion Nebula. The only candidate in HST imagery for this jet appears to be
a displaced, ionized knot. Also an elongated jet projects from the proplyd GMR
15 (161-307). Its receding radial velocity difference appears at ~80 km/s in
the same position-velocity array.
  A `standard' model for jets from young, low mass stars invokes an
accelerating, continuous flow outwards with an opening angle of a few degrees.
Here an alternative explanation is suggested which may apply to some, if not
all, of the proplyd jets. In this, a `bullet' of dense material is ejected
which ploughs through dense circumstellar ambient gas. The decelerating tail of
material ablated from the bullet's surface would be indistinguishable from a
continuously emitted jet in current observations.


title: The iron Kalpha Compton Shoulder in transmitted and reflected spectra

abstract:
  We calculate the Equivalent Widht of the Core and the centroid energy and
relative flux of the 1st order Compton Shoulder of the iron Kalpha emission
line from neutral matter. The calculations are performed with Monte Carlo
simulations. We explore a large range of column densities for both transmitted
and reflected spectra, and study the dependence on the iron abundance. The
Compton Shoulder is now becoming observable in many objects thanks to the
improved sensitivity and/or energy resolution of XMM-Newton and Chandra
satellites, and the present work aims to provide a tool to derive informations
on the geometry and element abundances of the line emitting matter from Compton
Shoulder measurements.


title: The Search for Matter with Gravitational Lensing

abstract:
  Gravitational lensing is a powerful tool to detect compact matter on very
different mass scales. Of particular importance is the fact that lensing is
sensitive to both luminous and dark matter alike. Depending on the mass scale,
all lensing effects are used in the search for matter: offset in position,
image distortion, magnification, and multiple images. Gravitational lens
detections cover three main mass ranges: roughly stellar mass, galaxy mass and
galaxy cluster mass scales, i.e. well known classes of objects. Various
searches based on different techniques explored the frequency of compact
objects over more than 15 orders of magnitude, so far mostly providing null
results in mass ranges different from the ones just mentioned. Combined, the
lensing results offer some interesting limits on the cosmological frequency of
compact objects in the mass interval 10^{-3} <= M/M_odot <= 10^{15},
unfortunately still with some gaps in between. In the near future, further
studies along these lines promise to fill the gaps and to push the limits
further down, or they might even detect new object classes.


title: On the thickness of a mildly relativistic collisional shock wave

abstract:
  We consider an imperfect relativistic fluid which develops a shock wave and
discuss its structure and thickness, taking into account the effects of
viscosity and heat conduction in the form of sound absorption. The junction
conditions and the non linear equations describing the evolution of the shock
are derived with the corresponding Newtonian limit discussed in detail. As
happens in the non relativistic regime, the thickness is inversely proportional
to the discontinuity in the pressure, but new terms of purely relativistic
origin are present. Particularizing for a polytropic gas, it is found that the
pure viscous relativistic shock is thicker than its nonrelativistic
counterpart, while the opposite holds for pure heat conduction.


title:
Detection of the BL Lac object 1ES1426+428 in the Very High Energy
  gamma-ray band by the CAT Telescope from 1998-2000

abstract:
  The BL Lac Object 1ES 1426+428, at a red-shift of z=0.129, has been monitored
by the CAT telescope from February 1998 to June 2000. The accumulation of 26
hours of observations shows a gamma-ray signal of 321 events above 250 GeV at
5.2 standard deviations, determined using data analysis cuts adapted to a weak,
steep-spectrum source. The source emission has an average flux of Phi_diff(400
GeV) = 6.73 +/- 1.27stat +/- 1.45syst x 10^-11 /cm^-2/s/TeV, and a very steep
spectrum, with a differential spectral index of gamma = -3.60 +/- 0.57 which
can be refined to gamma = -3.66 +/- 0.41 using a higher flux data subset. If,
as expected from its broad-band properties, the Very High Energy emission is
hard at the source, these observations support a strong absorption effect of
gamma-rays by the Intergalactic Infrared field.


title: Three aspects of red giant studies in the Magellanic Clouds

abstract:
  There are three important aspects concerning the study of the red giant and
in particular of the asymptotic giant branch (AGB) stars in the Magellanic
Clouds. These are: the surface distribution, the luminosity function and the
variability. The spatial distribution of AGB stars is an efficient tool to
study the structure of the galaxies and their metalicity by analysing the ratio
between carbon- and oxygen-rich AGB stars. The shape of the luminosity function
carries informations about the star formation rate in the Clouds and it can be
mathematically related to their history. Most AGB stars vary their magnitude in
a few to several hundred years time; the one epoch DENIS magnitudes for both
Large and Small Magellanic Cloud AGB stars outline the same relations as a
function of period.


title:
A New X-Ray Flare from the Galactic Nucleus Detected with the XMM-Newton
  Photon Imaging Cameras

abstract:
  Sgr A*, the compact radio source, believed to be the counterpart of the
massive black hole at the galactic nucleus, was observed to undergo rapid and
intense flaring activity in X-rays with Chandra in October 2000. We report here
the detection with XMM-Newton EPIC cameras of the early phase of a similar
X-ray flare from this source, which occurred on September 4, 2001. The source
2-10 keV luminosity increased by a factor about 20 to reach a level of 4
10^{34} erg s^{-1} in a time interval of about 900 s, just before the end of
the observation. The data indicate that the source spectrum was hard during the
flare. This XMM-Newton observation confirms the results obtained by Chandra and
suggests that, in Sgr A*, rapid and intense X-ray flaring is not a rare event.
This can constrain the emission mechanism models proposed for this source, and
also implies that the crucial multiwavelength observation programs planned to
explore the behaviour of the radio/sub-mm and hard X-ray/gamma-ray emissions
during the X-ray flares, have a good chance of success.


title:
ISO-SWS calibration and the accurate modelling of cool-star atmospheres
  - II. General results

abstract:
  The fine calibration of the ISO-SWS detectors (Infrared Space Observatory -
Short Wavelength Spectrometer) has proven to be a delicate problem. We
therefore present a detailed spectroscopic study in the 2.38 -- 12 micron
wavelength range of a sample of 16 A0 -- M2 stars used for the calibration of
ISO-SWS. By investigating the discrepancies between the ISO-SWS data of these
sources, the theoretical predictions of their spectra, the high-resolution
FTS-KP (Kitt Peak) spectrum of Alpha Boo and the solar FTS-ATMOS (Atmospheric
Trace Molecule Spectroscopy) spectrum, both calibration problems and problems
in computing the theoretical models and the synthetic spectra are revealed. The
underlying reasons for these problems are sought for and the impact on the
further calibration of ISO-SWS and on the theoretical modelling is discussed
extensively.


title:
The ELAIS Deep X-ray Survey I: Chandra Source Catalogue and First
  Results

abstract:
  We present an analysis of two deep (75 ks) Chandra observations of the
European Large Area ISO Survey (ELAIS) fields N1 and N2 as the first results
from the ELAIS deep X-ray survey. This survey is being conducted in well
studied regions with extensive multi-wavelength coverage. Here we present the
Chandra source catalogues along with an analysis of source counts, hardness
ratios and optical classifications. A total of 233 X-ray point sources are
detected in addition to 2 soft extended sources, which are found to be
associated with galaxy clusters. An over-density of sources is found in N1 with
30% more sources than N2, which we attribute to large-scale structure. A
similar variance is seen between other deep Chandra surveys. The source count
statistics reveal an increasing fraction of hard sources at fainter fluxes. The
number of galaxy-like counterparts also increases dramatically towards fainter
fluxes, consistent with the emergence of a large population of obscured
sources.


title:
Gravitational Settling of ^{22}Ne in Liquid White Dwarf
  Interiors--Cooling and Seismological Effects

abstract:
  We assess the impact of the trace element ^{22}Ne on the cooling and
seismology of a liquid C/O white dwarf (WD). Due to this elements' neutron
excess, it sinks towards the interior as the liquid WD cools. The subsequent
gravitational energy released slows the cooling of the WD by 0.25--1.6 Gyrs by
the time it has completely crystallized, depending on the WD mass and the
adopted sedimentation rate. The effects will make massive WDs or those in metal
rich clusters (such as NGC 6791) appear younger than their true age. Our
diffusion calculations show that the ^{22}Ne mass fraction in the crystallized
core actually increases outwards. The stability of this configuration has not
yet been determined. In the liquid state, the settled ^{22}Ne enhances the
internal buoyancy of the interior and changes the periods of the high radial
order g-modes by approximately 1%. Though a small adjustment, this level of
change far exceeds the accuracy of the period measurements. A full assessment
and comparison of mode frequencies for specific WDs should help constrain the
still uncertain ^{22}Ne diffusion coefficient for the liquid interior.


title: State Transitions in Black Hole Candidates

abstract:
  As described in the review by Marek Abramowicz (these proceedings), accretion
theory is at something of a crossroads. Many theoretical descriptions of
observations have centered on the ``hydrodynamic'' approach of the ``standard''
Shakura & Sunyaev alpha-disk; however, recent MHD simulations of
(non-radiative) accretion flow have called into question the validity of this
approach. There has been a great deal of optimism that these simulations give
direct insight into current observations as similar phenomena appear in both;
e.g., jets, rapid high-amplitude fluctuations, etc. In comparison to real data
from black hole candidates (BHC), however, these similarities are in many ways
only superficial. In some aspects, simple theories agree with the observations
quite well. The observed rapid variability is much more highly structured than
found in simulations, and shows interesting correlations with spectra that have
been interpreted in terms of simple models. On the other hand, debates have
arisen over even the most basic phenomenological issues concerning, e.g., the
geometry and dominant radiation mechanisms of the accretion flow. In this
article I present my views of those observational properties of BHC states that
most urgently need to be addressed, and I briefly discuss some of the models
currently being debated.


title: Advective Accretion Disks and Related Problems Including Magnetic Fields

abstract:
  Accretion disk theory was first developed as a theory with the local heat
balance, where the whole energy produced by a viscous heating was emitted to
the sides of the disk.
  One of the most important new invention of this theory was the
phenomenological treatment of the turbulent viscosity, known the `` alpha''
prescription, where the (r phi) component of the stress tensor was approximated
by (alpha p) with a unknown constant alpha.
  This prescription played the role in the accretion disk theory as well
important as the mixing-length theory of convection for stellar evolution.
Sources of turbulence in the accretion disk are discussed, including
hydrodynamical turbulence, convection and magnetic field role. In parallel to
the optically thick geometrically thin accretion disk models, a new branch of
the optically thin accretion disk models was discovered, with a larger
thickness for the same total luminosity. The choice between these solutions
should be done of the base of a stability analysis.
  The ideas underlying the necessity to include advection into the accretion
disk theory are presented and first models with advection are reviewed.
  The present status of the solution for a low-luminous optically thin
accretion disk model with advection is discussed and the limits for an
advection dominated accretion flows (ADAF) imposed by the presence of magnetic
field are analysed. Related problems of mass ejection from accretion disks and
jet formation are discussed.


title: Detection of Molecular Hydrogen Orbiting a "Naked" T Tauri Star

abstract:
  Astronomers have established that for a few million years newborn stars
possess disks of orbiting gas and dust. Such disks, which are likely sites of
planet formation, appear to disappear once these stars reach ages of 5-10 times
10^6 yr; yet, >= 10^7 yr is thought necessary for giant planet formation. If
disks dissipate in less time than is needed for giant planet formation, such
planets may be rare and those known around nearby stars would be anomalies.
Herein, we report the discovery of H_2 gas orbiting a weak-lined T Tauri star
heretofore presumed nearly devoid of circumstellar material. We estimate that a
significant amount of H_2 persists in the gas phase, but only a tiny fraction
of this mass emits in the near-infrared. We propose that this star possesses an
evolved disk that has escaped detection thus far because much of the dust has
coagulated into planetesimals. This discovery suggests that the theory that
disks are largely absent around such stars should be reconsidered. The
widespread presence of such disks would indicate that planetesimals can form
quickly and giant planet formation can proceed to completion before the gas in
circumstellar disks disperses.


title: WSO/UV: World Space Observatory/Ultraviolet

abstract:
  We summarize the capabilities of the World Space Observatory (UV) Project
(WSO/UV). An example of the importance of this project (with a planned launch
date of 2007/8) for the study of Classical Novae is given.


title: Density profiles of dark matter halos with anisotropic velocity tensors

abstract:
  We present density profiles, that are solutions of the spherical Jeans
equation, derived under the following two assumptions: (i) the coarse grained
phase-density follows a power-law of radius, rho/(sigma^3) proportional to
r^{-alpha}, and (ii) the velocity anisotropy parameter is given by the relation
beta_a(r) = beta_1 + 2 beta_2 {(r/r_*)/(1+(r/r_*)^2)} where beta_1, beta_2 are
parameters and r_* equals twice the virial radius, r_{vir}, of the system.
These assumptions are well motivated by the results of N-body simulations.
Density profiles have increasing logarithmic slopes gamma, defined by gamma = -
{(d ln rho)/(d ln r)}. The values of gamma at r = 10^{-2.5}r_{vir}, a distance
where the systems could be resolved by large N-body simulations, lie in the
range 1. - 1.6. These inner values of gamma increase for increasing beta_1 and
for increasing concentration of the system. On the other hand, slopes at r =
r_{vir} lie in the range 2.42 - 3.82. A model density profile that fits well
the results at radial distances between 10^{-3}r_{vir} and r_{vir} and connects
kinematic and structural characteristics of spherical systems is described.


title:
Implications of Ultrahigh Energy Air Showers for Physics and
  Astrophysics

abstract:
  The primary ultrahigh energy particles which produce giant extensive air
showers in the Earth's atmosphere present an intriguing mystery from two points
of view: (1) How are these particles produced with such astounding energies,
eight orders of magnitude higher than those produced by the best man-made
terrestrial accelerators? (2) Since they are most likely extragalactic in
origin, how do they reach us from extragalactic distances without suffering the
severe losses expected from interactions with the 2.7 K thermal cosmic
background photons -- the so-called GZK effect? The answers to these questions
may involve new physics: violations of special relativity, grand unification
theories, and quantum gravity theories involving large extra dimensions. They
may involve new astrophysical sources, "zevatrons". Or some heretofore totally
unknown physics or astrophysics may hold the answer. I will discuss here the
mysteries involving the production and extragalactic propagation of ultrahigh
energy cosmic rays and some suggested possible solutions.


title:
The Size of the Extragalactic Source J1801-231 and the Association of
  Pulsar PSR B1758-23 with the Supernova Remnant W28

abstract:
  We have used the NRAO Very Large Array (VLA) in conjunction with the Very
Long Baseline Array (VLBA) Pie Town antenna as a real-time interferometer
system to measure the size of the extragalactic source J1801-231 as a function
of frequency from 1285 to 4885 MHz. These observations were made in an attempt
to determine the effect interstellar scattering has on the observed sizes of OH
(1720 MHz) masers in the nearby (d=2.5 kpc) supernova remnant W28. The
observations clearly show that J1801-231 displays angular broadening due to
turbulence in the Galaxy's interstellar medium. The minimum distance of the
nearby (two arcminutes from J1801-231) pulsar PSR B1758-23 is constrained to be
9.4 +/- 2.4 kpc. This value is based on both the measured size of 220 mas for
J1801-231 at 1715 MHz and the temporal broadening of the pulsar. A single thin
scattering screen along the line of sight to the W28 OH(1720 MHz) masers must
be at 4.7 +/- 1.2 kpc for this minimum pulsar distance. The screen may be
placed closer to the Earth, but for reasonable values of the pulsar distance
(i.e., the pulsar is within the Galaxy), this choice leads to a negligible
scattering contribution to the sizes of the masers. Thus the OH(1720 MHz)
masers, at a distance of 2.5 +/- 0.7 kpc, are unaffected by interstellar
scattering, and the measured maser sizes must be intrinsic. Our measured upper
limits to the size of the pulsar itself are consistent with the distance
estimates to the pulsar and the scattering screen.


title:
Gravitational lensing by the truncated isothermal sphere model for
  cosmological halos. I. Individual lens properties

abstract:
  The gravitational lensing properties of cosmological halos depend upon the
mass distribution within each halo. The description of halos as nonsingular,
truncated isothermal spheres, a particular solution of the isothermal Lane-
Emden equation (suitably modified for Lambda non equal 0), has proved to be a
useful approximation for the halos which form from realistic initial conditions
in a CDM universe. We derive here the basic lensing properties of such halos,
including the image separation, magnification, shear, and time-delay. We also
provide analytical expressions for the critical curves and caustics. We show
how the scale-free results we derive yield scale-dependent lensing properties
which depend upon the cosmological background universe and the mass and
collapse redshift of the lensing halos, according to the truncated isothermal
sphere (TIS) model of CDM halos derived elsewhere. We briefly describe the
application of these results to the currently-favored Lambda-CDM universe.


title: Type Ia supernovae and the formation history of early-type galaxies

abstract:
  Using the standard prescription for the rates of supernovae type II and type
Ia, we compare the predictions of a simple model of star formation in galaxies
with the observed radial gradients of abundance ratios in a sample of
early-type galaxies to infer the relative contribution of each type of
supernova. The data suggests a correlation between the fractional contribution
of Type Ia to the chemical enrichment of the stellar populations (1-xi) and
central velocity dispersion of order 1-xi ~ -0.16log sigma_0+0.40, so that the
type Ia contribution in stars ranges from a negligible amount in massive
galaxies up to 10% in low-mass systems. Our model is parametrized by a star
formation timescale (t_SF) which controls the duration of the starburst. A
correlation with galaxy radius as a power law (t_SF ~ r^beta) translates into a
radial gradient of the abundance ratios. The data implies a wide range of
formation scenarios for a simple model that fixes the luminosity profile,
ranging from inside-out (beta=2), to outside-in formation (beta=-1), as is
consistent with numerical simulations of elliptical galaxy formation. An
alternative scenario that links t_SF to the dynamical timescale favours
inside-out formation over a smaller range. In both cases, massive galaxies are
predicted to have undergone a more extended period of star formation in the
outer regions with respect to their low-mass counterparts.


title: CMB-Normalized Predictions for Sunyaev-Zel'dovich effect fluctuations

abstract:
  We predict the level of small-scale anisotropy in the cosmic microwave
background (CMB) due to the Sunyaev--Zel'dovich (SZ) effect for the ensemble of
cosmological models that are consistent with current measurements of
large-scale CMB anisotropy. We argue that the recently reported detections of
the small-scale (arcminutes) CMB anisotropy are only marginally consistent with
being the SZ effect when cosmological models are calibrated to the existing
primary CMB data on large scales. The discrepancy is at more than 2-2.5 sigma,
and is mainly due to a lower sigma_8 <0.8 favored by the primary CMB and a
higher sigma_8 > 1 favored by the SZ effect. A degeneracy between the optical
depth to Thomson scattering and the CMB-derived value of sigma_8 suggests that
the discrepancy is reduced if the universe was reionized very early, at a
redshift of about 25.


title:
3D MHD Modeling of the Gaseous Structure of the Galaxy: Setup and
  Initial Results

abstract:
  We show the initial results of our 3D MHD simulations of the flow of the
Galactic atmosphere as it responds to a spiral perturbation in the potential.
In our standard case, as the gas approaches the arm, there is a downward
converging flow that terminates in a complex of shocks just ahead of the
midplane density peak. The density maximum slants forward at high z, preceeded
by a similarly leaning shock. The latter diverts the flow upward and over the
arm, as in a hydraulic jump. Behind the gaseous arm, the flow falls again,
generating further secondary shocks as it approaches the lower z material.
Structures similar to the high z part of the gaseous arms are found in the
interarm region of our two-armed case, while broken arms and low column density
bridges are present in the four-armed case.
  We present three examples of what can be learned from these models.


title:
Analytical Expressions for Spiral Arm Gravitational Potential and
  Density

abstract:
  When modeling the three-dimensional hydrodynamics of interstellar material
rotating in a galactic gravitational potential, it is useful to have an
analytic expression for gravitational perturbations due to stellar spiral arms.
We present such an expression for which changes in the assumed characteristics
of the arms can be made easily and the sensitivity of the hydrodynamics to
those characteristics examined. This analytic expression also makes it easy to
rotate the force field at the pattern angular velocity with little overhead on
the calculations.


title:
ISO-SWS calibration and the accurate modelling of cool-star atmospheres
  - III. A0 to G2 stars

abstract:
  Vega, Sirius, Beta Leo, Alpha Car and Alpha Cen A belong to a sample of
twenty stellar sources used for the calibration of the detectors of the
Short-Wavelength Spectrometer on board the Infrared Space Observatory
(ISO-SWS). While general problems with the calibration and with the theoretical
modelling of these stars are reported in Decin et al. (2002), each of these
stars is discussed individually in this paper. As demonstrated in Decin et al.
(2002), it is not possible to deduce the effective temperature, the gravity and
the chemical composition from the ISO-SWS spectra of these stars. But since
ISO-SWS is absolutely calibrated, the angular diameter of these stellar sources
can be deduced from their ISO-SWS spectra, which consequently yields the
stellar radius (R), the gravity-inferred mass (M) and the luminosity (L) for
these stars. These deduced parameters are confronted with other published
values and the goodness-of-fit between observed ISO-SWS data and the
corresponding synthetic spectrum is discussed.


title:
Cosmic Ray Diffusion from the Galactic Spiral Arms, Iron Meteorites, and
  a possible climatic connection?

abstract:
  We construct a Galactic cosmic ray (CR) diffusion model while considering
that CR sources reside predominantly in the Galactic spiral arms. We find that
the CR flux (CRF) reaching the solar system should periodically increase each
crossing of a Galactic spiral arm. We search for this signal in the CR exposure
age record of Iron meteorites and confirm this prediction. We then check the
hypothesis that climate, and in particular the temperature, is affected by the
CRF to the extent that glaciations can be induced or completely hindered by
possible climatic variations. We find that although the geological evidence for
the occurrence of IAEs in the past Eon is not unequivocal, it appears to have a
nontrivial correlation with the spiral arm crossings--agreeing in period and
phase. Thus, a better timing study of glaciations could either confirm this
result as an explanation to the occurrence of IAEs or refute a CRF climatic
connection.


title: Pair Creation in the Pulsar Magnetosphere

abstract:
  We present numerical simulations of the electron-positron plasma creation
process in a simple neutron star magnetosphere. We have developed a set of
cascade `kernels', which represent the endpoint of the pair cascades resulting
from monoenergetic photon seeds. We explore two popular models by convolving
these kernels with the seed photon distributions produced by curvature
radiation and by inverse Compton scattering. We find that the pair plasma in
either case is well-described in its rest frame by a relativistic Maxwellian
distribution with temperature near mc^2/k_B. We present cascade multiplicities
and efficiencies for a range of seed particle energies and stellar magnetic
fields. We find that the efficiencies and multiplicities of pair creation are
often lower than has been assumed in previous work.


title: Classical Novae as Super-Eddington Objects

abstract:
  Several of the inconsistencies plaguing the field of novae are resolved once
we consider novae to be steady state super-Eddington objects. In particular, we
show that the super-Eddington shell burning state is a natural consequence of
the equations of stellar structure, and that the predicted mass loss in the
super-Eddington state agrees with nova observations. We also find that the
transition phase of novae can be naturally explained as "stagnating" winds.


title:
Sco X-1 and Cyg X-1: Determination of Strength and Structure of Magnetic
  Field in the Nearest Environment of Accreting Compact Stars

abstract:
  We estimated the magnetic field strength of compact stars in X-ray binaries
Sco X-1 and Cyg X-1, via various methods of determination of magnetic fields.
For Sco X-1 we used three independent methods. One of them is based on the
correct account of the Faraday rotation of polarization plane in the process of
electron scattering of X-rays from accreting neutron stars. Numerical
calculations are made with use of first X-rays polarimetric data presented by
Long et al. (1979). Other original method of determing the magnetic field
developed by Titarchuk at al. (2001) is based on observed quasi-periodic
oscillations (QPO) frequencies in X-ray binaries that can be considered as
magnetoacoustic oscillations of boundary layer near a neutron star. The optical
polarimetric data obtained in 70-th have been also used for estimation of
magnetic field of the neutron star in Sco X-1 and of nearest environment around
the black hole in Cyg X-1.


title: Gravity-driven Turbulence in Galactic Disks

abstract:
  High-resolution, 2-D hydrodynamical simulations with a large dynamic range
are performed to study the turbulent nature of the interstellar medium (ISM) in
galactic disks. The simulations are global, where the self-gravity of the ISM,
realistic radiative cooling, and galactic rotation are taken into account. In
the analysis undertaken here, feedback processes from stellar energy source are
omitted. We find that the velocity field of the disk in a non-linear phase
shows a steady power-law energy spectrum over three-orders of magnitude in wave
number. This implies that the random velocity field can be modeled as
fully-developed, stationary turbulence. Gravitational and thermal instabilities
under the influence of galactic rotation contribute to form the turbulent
velocity field. The Toomre effective Q value, in the non-linear phase, ranges
over a wide range, and gravitationally stable and unstable regions are
distributed patchily in the disk. These results suggest that large-scale
galactic rotation coupled with the self-gravity of the gas can be the ultimate
energy sources that maintain the turbulence in the local ISM. We find that our
models of turbulent rotating disks are consistent with the velocity dispersion
of an extended HI disk in the dwarf galaxy, NGC 2915, where there is no
prominent active star formation. Numerical simulations show that the stellar
bar in NGC 2915 enhances the velocity dispersion, and it also drives spiral
arms as observed in the HI disk.


title:
What Can We Learn from the Infrared Spectral Energy Distributions of
  Dust Disks?

abstract:
  The spectral energy distributions (SEDs) of dust disks are widely used to
infer dust properties (compositions and sizes) and disk structures (dust
spatial distributions) which might be indicative of the presence or absence of
planets or smaller bodies like asteroids and comets in the disk. Based on
modelling of the SED of HR 4796A, a young main-sequence star with the largest
fractional infrared (IR) emission, we show that the SED alone is not a good
discriminator of dust size, spatial distribution (and composition if no
spectroscopic data are available). A combination of SED, mid-IR spectroscopy,
and coronagraphic near-IR imaging of scattered starlight and mid-IR imaging of
dust thermal emission provides a better understanding of these properties.


title:
A New Orbital Ephemeris and Reinterpretation of Spectroscopic Data for
  the Supersoft X-ray Binary RX J0513.9-6951

abstract:
  We have analyzed nearly eight years of MACHO optical photometry of the
supersoft X-ray binary RX J0513.9-6951 and derived a revised orbital period and
ephemeris. Previously published velocities are reinterpreted using the new
ephemeris. We show that the spectroscopic characteristics of the system depend
strongly on whether the system is in a high or low optical state. We also
discuss the properties of the source's high/low optical states and its
long-term light curve. Evidence for a 83.3-day periodicity in the photometry is
presented.


title:
Scale-free equilibria of self-gravitating gaseous disks with flat
  rotation curves

abstract:
  We introduce exact analytical solutions of the steady-state hydrodynamic
equations of scale-free, self-gravitating gaseous disks with flat rotation
curves. We express the velocity field in terms of a stream function and obtain
a third-order ordinary differential equation (ODE) for the angular part of the
stream function. We present the closed-form solutions of the obtained ODE and
construct hydrodynamical counterparts of the power-law and elliptic disks, for
which self-consistent stellar dynamical models are known. We show that the
kinematics of the Large Magellanic Cloud can well be explained by our findings
for scale-free elliptic disks.


title:
Do High Frequency QPOs Depend on Phase of Low Frequency QPOs in XTE
  J1550-564 ?

abstract:
  We have studied the dependence of the high frequency Quasi-periodic
Oscillation (QPO) (~284 Hz) on the phase of the low frequency QPO (~6 Hz) in
the black hole X-ray binary XTE J1550-564 in the observations of the Rossi
X-ray Timing Explorer (RXTE) performed on MJD 51241. By selecting the local
maxima and the local minima in the light curve on the 6 Hz QPO time scale, we
have found the corresponding high frequency QPO frequencies are consistent
within 1.5 sigma. However, the average central QPO frequency of the maxima and
the minima is about 2.0 sigma lower than the average high frequency QPO
frequency obtained in the entire observation. This marginally suggests that the
high frequency QPOs probably varies in frequency on short time scales. We
briefly discuss these results and their consequences.


title: The atoll source 4U 1608-52 is not a Z source

abstract:
  We have studied the spectral and timing behaviour of the atoll source 4U
1608-52. We find that the timing behaviour of 4U 1608-52 is almost identical to
that of the atoll sources 4U 0614+09 and 4U 1728-34. Recently Muno, Remillard &
Chakrabarty (2002) and Gierlinski & Done (2002) suggested that the atoll
sources trace out similar three-branch patterns as the Z sources. The timing
behaviour is not consistent with the idea that 4U 1608-52 traces out a
three-branched Z shape in the color-color diagram along which the timing
properties vary gradually.


title:
Radio-Emission from Cosmic Ray Air-Showers - A Theoretical Perspective
  for LOPES

abstract:
  High-energy cosmic ray air-showers have been known for over 30 years to emit
strong radio pulses in the regime between a few and several 100 MHz (Allan
1971). To date, however, a thorough analysis of the emission mechanisms has not
yet been conducted. Adopting a simplified shower geometry and electron-positron
energy distribution, we calculate theoretical pulse spectra in the scheme of
synchrotron emission from highly relativistic electron-positron pairs gyrating
in the Earth's magnetic field. These calculations will play an important role
for the calibration of observational data of radio-emission from cosmic ray
air-showers acquired with LOPES and later LOFAR and SKA.


title: 3-D Kinematics of Water Masers in the W51A Region

abstract:
  We report proper motion measurements of water masers in the massive-star
forming region W51A and the analyses of the 3-D kinematics of the masers in
three maser clusters of W51A (W51 North, Main, and South). In W~51 North, we
found a clear expanding flow that has an expansion velocity of ~70 km/s and
indicates deceleration. The originating point of the flow coincides within 0.1
as with a silicon-monoxide maser source near the HII region W~51d. In W51 Main,
no systematic motion was found in the whole velocity range (158 km/s =< V(lsr)
=< -58 km/s) although a stream motion was reported previously in a limited
range of the Doppler velocity (54 km/s =< V(lsr) =< 68 kms). Multiple driving
sources of outflows are thought to explain the kinematics of W51 Main. In W51
South, an expansion motion like a bipolar flow was marginally visible. Analyses
based on diagonalization of the variance-covariance matrix of maser velocity
vectors demonstrate that the maser kinematics in W51 North and Main are
significantly tri-axially asymmetric. We estimated a distance to W51 North to
be 6.1 +/- 1.3 kpc on the basis of the model fitting method adopting a radially
expanding flow.


title:
Evolution of a low frequency QPO during the 2000 outburst of XTE
  J1550-564

abstract:
  We follow the evolution of a low frequency QPO during the 2000 outburst of
the microquasar XTE J1550-564, which was found to be present in the PCA energy
range (2-65 keV) in 19 of 43 observations. The frequency of the QPO varies from
0.1 Hz to 6 Hz, and appears to follow the evolution of the soft
  X-ray flux. If we assume the soft X-rays represent the behavior of an
accretion disk, the relation indicates that this low frequency QPO is linked to
the accretion disk. We show that the non-trivial relation between the QPO
frequency and the soft flux may be as expected from the Accretion Ejection
  Instability (AEI), when the disk approaches its last stable orbit.
Furthermore, the energy dependence of the QPO may indicate the presence of a
hot spot rotating in the disk as predicted by the AEI.


title:
An XMM-Newton observation of Ton S180: Constraints on the continuum
  emission in ultrasoft Seyfert galaxies

abstract:
  We present an XMM-Newton observation of the bright, narrow-line, ultrasoft
Seyfert 1 galaxy Ton S180. The 0.3-10 keV X-ray spectrum is steep and curved,
showing a steep slope above 2.5 keV (Gamma ~ 2.3) and a smooth, featureless
excess of emission at lower energies. The spectrum can be adequately
parameterised using a simple double power-law model. The source is strongly
variable over the course of the observation but shows only weak spectral
variability, with the fractional variability amplitude remaining approximately
constant over more than a decade in energy. The curved continuum shape and weak
spectral variability are discussed in terms of various physical models for the
soft X-ray excess emission, including reflection off the surface of an ionised
accretion disc, inverse-Compton scattering of soft disc photons by thermal
electrons, and Comptonisation by electrons with a hybrid thermal/non-thermal
distribution. We emphasise the possibility that the strong soft excess may be
produced by dissipation of accretion energy in the hot, upper atmosphere of the
putative accretion disc.


title: FUV Spectroscopy of the Supersoft X-ray Binary RX J0513.9-6951

abstract:
  We have obtained spectroscopy with the Far Ultraviolet Spectroscopic Explorer
(FUSE) of the supersoft X-ray binary RX J0513.9-6951 over a complete binary
orbital cycle. The spectra show a hot continuum with extremely broad O VI
emission and weak Lyman absorptions. He II emission is weak and narrow, while N
III and C III emissions are undetected, although lines from these ions are
prominent at optical wavelengths. The broad O VI emission and Lyman absorption
show radial velocity curves that are approximately antiphased and have
semiamplitudes of ~117 +- 40 and 54 +- 10 km/s, respectively. Narrow emissions
from He II and O VI show small velocity variations with phasing different from
the broad O VI, but consistent with the optical line peaks. We also measure
considerable changes in the FUV continuum and O VI emission line flux. We
discuss the possible causes of the measured variations and a tentative binary
interpretation.


title:
A discrete ordinates method of radiative transfer in one-dimensional
  spherical geometry

abstract:
  A new set of discrete ordinates is proposed for one-dimensional radiative
transfer in spheres with central symmetry. The set is structured with
un-normalized circular functions. This resulted in a conservative and closed
set of discrete ordinates equations that need not starter intensity: N
equations with N unknowns. The angular derivative of the transfer equation is
represented by a set of angular parameters that are calculated directly and
without recursion from the abscissas and weights of the quadrature and without
the constraint of asymptotic conditions. An analytic solution is obtained in
infinite homogeneous and heterogeneous cold media for monochromatic radiation.
Graphical and tabulated data validate the proposed set of discrete ordinates at
all radial positions ranging from 10^(-7) to 10^7 within round-off errors


title:
ISO-SWS calibration and the accurate modelling of cool-star atmospheres
  - IV. G9 to M2 stars

abstract:
  presented. The 2.38 -- 4.08 micron wavelength-range of band 1 of ISO-SWS
(Short-Wavelength Spectrometers on board of the Infrared Space Observatory) in
which many different molecules -- with their own dependence on each of the
stellar parameters -- are absorbing, enables us to estimate the effective
temperature, the gravity, the microturbulence, the metallicity, the
CNO-abundances, the 12C/13C-ratio and the angular diameter from the ISO-SWS
data. Using the Hipparcos' parallax, the radius, luminosity and
gravity-inferred mass are derived. The stellar parameters obtained are in good
agreement with other published values, though also some discrepancies with
values deduced by other authors are noted. For a few stars (Delta Dra, Xi Dra,
Alpha Tuc, H Sco and Alpha Cet) some parameters -- e.g. the CNO-abundances --
are derived for the first time. By examining the correspondence between
different ISO-SWS observations of the same object and between the ISO-SWS data
and the corresponding synthetic spectrum, it is shown that the relative
accuracy of ISO-SWS in band 1 (2.38 -- 4.0 micron) is better than 2% for these
high-flux sources. The high level of correspondence between observations and
theoretical predictions, together with a confrontation of the estimated
Teff(ISO) value with Teff-values derived from colours -- which demonstrates the
consistency between V-K, BC(K), Teff and the angular diameter derived from
optical or IR data -- proves that both the used MARCS models to derive the
stellar quantities and the flux calibration of the ISO-SWS detectors have
reached a high level of reliability.