title:
The Origin of Radio Haloes and Non-thermal Emission in Clusters of
  Galaxies

abstract:
  We study the origin of the non-thermal emission from the intracluster medium,
including the excess hard X-ray emission and cluster-wide radio haloes, through
fitting two representative models to the Coma cluster. If the synchrotron
emitting relativistic electrons are accelerated in situ from the vast pool of
thermal electrons, then a quasi-stationary solution of the kinetic equation
with particle acceleration through turbulence at high energies (>200 keV)
naturally produces a population of supra-thermal electrons responsible for the
excess hard X-ray emission through bremsstrahlung. Inverse Compton scattering
is negligible at hard X-ray energies in this case. The radio halo flux density
constrains the magnetic field strength to a value close to that of
equipartition ~1 uG. Alternatively, if the relativistic electrons are injected
from numerous localised `external' sources then the hard X-rays are best
explained by inverse Compton scattering from GeV electrons, and little of the
hard X-radiation has a bremsstrahlung origin. In this case, the magnetic field
strength is constrained to ~0.1-0.2 uG. Both models assume that the non-thermal
emissions are generated by a single electron spectrum, so that only two free
parameters, well constrained by the observed hard X-ray and radio halo spectra,
are needed in either case. Measurements of the cluster magnetic field will
distinguish between the models.


title: Surface brightness measurements for APM galaxies

abstract:
  This paper considers some simple surface brightness (SB) estimates for
galaxies in the Automated Plate Measuring Machine (APM) catalogue in order to
derive homogeneous SB data for a very large sample of faint galaxies. The
isophotal magnitude and area are used to estimate the central surface
brightness and total magnitude based on the assumption of an exponential SB
profile. The surface brightness measurements are corrected for field effects on
each UK Schmidt plate and the zero-point of each plate is adjusted to give a
uniform sample of SB and total magnitude estimates over the whole survey.
Results are obtained for 2.4 million galaxies with blue photographic magnitudes
brighter than b_J = 20.5 covering 4300 deg^2 in the region of the south
galactic cap. Almost all galaxies in our sample have central surface brightness
in the range 20 to 24 b_J mag per arcsec^2. The SB measurements we obtain are
compared to previous SB measurements and we find an acceptable level of error
of +/- 0.2 b_J mag per arcsec^2. The distribution of SB profiles is considered
for different galaxy morphologies for the bright APM galaxies. We find that
early-type galaxies have more centrally concentrated profiles.


title: Small-Scale Cosmic Microwave Background Polarization from Reionization

abstract:
  We discuss fluctuations in the cosmic microwave background (CMB) polarization
due to scattering from reionized gas at low redshifts. Polarization is produced
by re-scattering of the primordial temperature anisotropy quadrupole and of the
kinematic quadrupole that arises from gas motion transverse to the line of
sight. We show that both effects produce equal E- and B-parity polarization,
and are, in general, several orders of magnitude below the dominant
polarization contributions at the last scattering surface to E-modes or the
gravitational-lensing contribution to B-modes at intermediate redshifts. These
effects are also several orders of magnitude below the B polarization due to
lensing even after subtraction with higher-order correlations, and are thus too
small to constitute a background for searches for the polarization signature of
inflationary gravitational waves.


title: Exploring the Expansion History of the Universe

abstract:
  Exploring the recent expansion history of the universe promises insights into
the cosmological model, the nature of dark energy, and potentially clues to
high energy physics theories and gravitation. We examine the extent to which
precision distance-redshift observations can map out the history, including the
acceleration-deceleration transition, and the components and equations of state
of the energy density. We consider the ability to distinguish between various
dynamical scalar field models for the dark energy, as well as higher dimension
and alternate gravity theories. Finally, we present a new, advantageous
parametrization for the study of dark energy.


title:
The Spectrum of the FeLoBAL Quasar FBQS 1214+2803: A
  Resonance-Scattering Interpretation

abstract:
  The usual interpetation of the spectrum of a BAL QSO is that a broad-band
continuum from the central engine plus broad emission lines from a surrounding
region (the BELR) emerges from near the center of the QSO, and broad absorption
lines are superimposed in a separate outlying region (the BALR). For FBQS
1214+2803, designated as an FeLoBAL QSO because its spectrum contains numerous
absorption features from excited states of Fe II, we explore an alternative
interpretation based on resonance scattering. In this model line emission and
absorption occur in the same line-forming region (the LFR). A
resonance-scattering synthetic spectrum computed with the supernova
synthetic-spectrum code SYNOW fits the spectrum of FBQS 1214+2802 rather well,
so the resonance-scattering model merits further study. Some implications of
the model and its possible applicability to other QSOs are briefly discussed.


title:
On-axis spatially resolved spectroscopy of low redshift quasar host
  galaxies: HE 1503+0228 at z=0.135

abstract:
  We present the first result of a comprehensive spectroscopic study of quasar
host galaxies. On-axis, spatially resolved spectra of low redshift quasars have
been obtained with FORS1, mounted on the 8.2m ESO Very Large Telescope, Antu.
The spectra are spatially deconvolved using a spectroscopic version of the
``MCS deconvolution algorithm''. The algorithm decomposes two dimensional
spectra into the individual spectra of the central point-like nucleus and of
its host galaxy. Applied to HE1503+0228, at z=0.135 (M_B=-23.0), it provides us
with the spectrum of the host galaxy between 3600A, and 8500A, (rest-frame), at
a mean resolving power of 700. The data allow us to measure several of the
important Lick indices. The stellar populations and gas ionization state of the
host galaxy of HE1503+0228, are very similar to the ones measured for normal
non-AGN galaxies. Dynamical information is also available for the gas and
stellar components of the galaxy. Using deconvolution and a deprojection
algorithm, velocity curves are derived for emission lines, from the center up
to 4arcsec, away from the nucleus of the galaxy. Fitting a simple
three-components mass model (point mass, spherical halo of dark matter, disk)
to the position-velocity diagram, we infer a mass of M(r<1kpc) = (2.0 +- 0.3)
10^{10} solar mass within the central kiloparsec of the galaxy, and a mass
integrated over 10 kpc of M(r<10kpc) = (1.9 +- 0.3) 10^{11} solar mass, with an
additional 10% error due to the uncertainty on the inclination of the galaxy.
This, in combination with the analysis of the stellar populations indicates
that the host galaxy of HE1503+0228, is a normal spiral galaxy.


title: Magnification effects as measures of large-scale structure

abstract:
  The magnification effects of clustered matter produce variations in the image
sizes and number density of galaxies across the sky. This paper advocates the
use of these effects in wide field surveys to map large-scale structure and the
profiles of galaxy and cluster sized halos. The magnitude of the size variation
as a function of angular scale is computed and the signal-to-noise is estimated
for different survey parameters. Forthcoming surveys, especially well designed
space-based imaging surveys, will have high signal-to-noise on scales of about
0.1 arcminute to several degrees. Thus the clustering of matter could be
measured on spatial scales of about 50 Kpc to 100 Mpc. The signal-to-noise is
dominated by sample variance rather than shot-noise due to the finite number
density of galaxies, hence the accuracy of the measurements will be limited
primarily by survey area, sampling strategy and possible systematics. Methods
based on magnification are compared with the use of shape distortions and the
contrasts and complementarities are discussed. Future work needed to plan
survey strategy and interpret measurements based on magnification is outlined.


title:
Discovery of Enhanced Germanium Abundances in Planetary Nebulae with
  FUSE

abstract:
  We report the discovery of Ge III $\lambda$1088.46 in the planetary nebulae
(PNe) SwSt 1, BD+30$^{\rm o}$3639, NGC 3132, and IC 4593, observed with the Far
Ultraviolet Spectroscopic Explorer. This is the first astronomical detection of
this line and the first measurement of Ge (Z = 32) in PNe. We estimate Ge
abundances using S and Fe as reference elements, for a range of assumptions
about gas-phase depletions. The results indicate that Ge, which is synthesized
in the initial steps of the s-process and therefore can be self-enriched in
PNe, is enhanced by factors of > 3-10. The strongest evidence for enrichment is
seen for PNe with Wolf-Rayet central stars, which are likely to contain heavily
processed material.


title:
Accretion of low angular momentum material onto black holes: 2D
  hydrodynamical inviscid case

abstract:
  We report on the first phase of our study of slightly rotating accretion
flows onto black holes. We consider inviscid accretion flows with a spherically
symmetric density distribution at the outer boundary, but with spherical
symmetry broken by the introduction of a small, latitude-dependent angular
momentum. We study accretion flows by means of numerical 2D, axisymmetric,
hydrodynamical simulations. Our main result is that the properties of the
accretion flow do not depend as much on the outer boundary conditions (i.e.,
the amount as well as distribution of the angular momentum) as on the geometry
of the non-accreting matter. The material that has too much angular momentum to
be accreted forms a thick torus near the equator. Consequently, the geometry of
the polar region, where material is accreted (the funnel), and the mass
accretion rate through it are constrained by the size and shape of the torus.
Our results show one way in which the mass accretion rate of slightly rotating
gas can be significantly reduced compared to the accretion of non-rotating gas
(i.e., the Bondi rate), and set the stage for calculations that will take into
account the transport of angular momentum and energy.


title: Evidence for Solar-like Oscillations in Arcturus (Alpha Boo)

abstract:
  Observations of the red giant Arcturus (Alpha Boo) obtained with the star
tracker on the Wide Field Infrared Explorer (WIRE) satellite during a baseline
of 19 successive days in 2000 July-August are analysed. The power spectrum has
a significant excess of power at low-frequencies. The highest peak is at about
4.1 micro-Hz, which is in agreement with the ground-based radial velocity and
photometry study of Belmonte et al. (1990a; 1990b). The variability of Arcturus
can be explained by sound waves, but it is not clear whether these are coherent
p-mode oscillations.


title:
From Massive Protostars to a Giant HII Region: Submillimeter Imaging of
  the Galactic Mini-starburst W43

abstract:
  We have carried out a submillimeter continuum and spectroscopic study of the
W43 main complex, a massive star-forming region, which harbors a giant HII
region. The maps reveal a filamentary structure containing ~50 fragments with
masses of 40-4000 Msun and typical diameters of 0.25 pc. Their large sizes,
large non-thermal velocities (Dv ~ 5 km/s), and high densities (n_H2 ~ 10^6
cm^-3) suggest that they are protoclusters and excellent sites to form massive
stars. Follow-up observations are necessary, but we have already identified
three protoclusters to be very good candidates for containing very young
massive protostars. The starburst cluster, that excites the giant HII region
has a large impact on the molecular complex. However, it remains unclear if
this first episode of star formation is triggering the formation of new massive
stars, through ionization shocks crossing the closeby molecular clouds. W43 is
thus an ideal laboratory to investigate massive star formation from the
protostellar phase to that of giant HII regions. Moreover, the very active
star-forming complex W43 may be considered a Galactic mini-starburst region
that could be used as a miniature model of starburst galaxies.


title: Masses, Accretion Rates and Inclinations of AGNs

abstract:
  We assume that the gravitational instability of standard thin accretion disks
leads to the Broad Line Regions (BLRs), the B band luminosity comes from
standard thin disk and the motion of BLRs is virial. The central black hole
masses, the accretion rates and the disk inclinations to the line of sight for
17 Seyfert 1 galaxies and 17 Palomar-Green (PG) quasars have been calculated.
Our results are sensitive to $\alpha$ parameter of the standard $\alpha$ disk.
With the same values of $\alpha$ ($\alpha=1$), calculated central black hole
masses for 17 Seyfert 1 galaxies are consistent with that from Kaspi et al.
(2000) while that for 17 PG quasars are larger than that from Kaspi et al.
(2000) by almost 2 orders of magnitude. Inclinations of 17 Seyfert 1 galaxies
are about 6 times larger than that of 17 PG quasars. These inclinations, with a
mean value of $32^{o}$ for 17 Seyfert 1 galaxies that agrees well with the
result obtained by fitting the iron $K\alpha$ lines of Seyfert 1 galaxies
observed with ASCA (Nandra et al. 1997) and the result obtained by Wu & Han
(2001), provide further support for the orientation-dependent unification
scheme of active galactic nuclei. There is a relation between the FWHM of
H$\beta$ and the inclination, namely the inclination is smaller in AGNs with
smaller FWHM of H$\beta$. The effect of inclinations in narrow line Seyfert 1
galaxies (NLS1s) should be considered when one studies the physics of NLS1s.
(abbreviated)


title:
Searching for the Signature of the Magnetic Fields at the Base of the
  Solar Convection Zone with Solar-Cycle Variations of p-Mode Travel Time

abstract:
  We study the solar-cycle variations of solar p-mode travel time for different
wave packets to probe the magnetic fields at the base of the solar convection
zone. We select the wave packets which return to the same spatial point after
traveling around the Sun with integral number of bounces. The change in
one-bounce travel time at solar maximum relative to minimum is approximately
the same for all wave packets studied except a wave packet whose lower turning
point is located at the base of the convection zone. This particular wave
packet has an additional decrease in travel time at solar maximum relative to
other wave packets. The magnitude of the additional decrease in travel time for
this particular wave packet increases with solar activity. This additional
decrease in travel time might be caused by the magnetic field perturbation and
sound speed perturbation at the base of the convection zone. With the
assumption that this additional decrease is caused only by the magnetic field
perturbation at the base of the convection zone, the field strength is
estimated to be about a 4-7x10^5 gauss at solar maximum if the filling factor
is unity. We also discuss the problem of this interpretation.


title: The peculiar variable V838 Mon

abstract:
  V838 Mon underwent, after a first nova-like outburst in January and a usual
decline, a second outburst after one month, and a third weak one again a month
later. Moreover a very small increase of the temperature at the beginning of
April gives us a hint on a physical process with a period of one month. We
obtained a BVRIc time sequence and modelled the photometric behaviour of the
object. This leads us to the conclusion that the interstellar foreground
extinction has to be 0.6 < E(B-V) < 0.8 and that the quasi-photosphere had
persistently unusually low temperatures for nova-like systems. The photometry
was used to follow the dramatic changes of the expansion. While the appearing
10 micron excess can be well described by the heating of material ejected
during this event, the IRAS emission near the location of the progenitor,
originates most likely from dust, which were formed during the previous
evolution of the object. Assuming that the light echoes are coming from
circumstellar material, the distance is 640 to 680 pc - smaller than the 790 pc
given in Munari et al. (2002). In our opinion V838 Mon and V4332 Sgr are
manifestations of a new class of eruptive variables. We do not count M31 RV to
this class.


title: Does Betelgeuse have a magnetic field?

abstract:
  Recent numerical simulations by Freytag et al. of the outer convection
envelope of the cool super-giant Betelgeuse, have shown that the fluctuations
in the star's apparent luminosity may be caused by giant cell convection. These
simulations bring forth the possibility of addressing another question; namely
whether stars such as Betelgeuse may harbor magnetic activity. Taking the
detailed numerical simulations of the star at face value, we have applied a
kinematic dynamo analysis, to study whether the flow field of the super-giant
may be able to amplify a weak seed magnetic field. We do indeed find a positive
exponential growth rate of the magnetic energy. The possible Betelgeusian
dynamo may be characterized as belonging to the class of so-called ``local
small-scale dynamos'' (i.e. dynamos where rotation is not dominant), but this
is a less meaningful designation in the case of Betelgeuse, since the field is
both global and large-scale.


title: New Problems for the Formation of Disk Galaxies

abstract:
  The standard picture for the formation of disk galaxies has come to face a
number of problems related to angular momentum. Numerical simulations produce
disks that are too small, and analytical models predict too much low angular
momentum compared to observations. In addition, angular momentum distributions
of proto-galaxies in numerical simulations reveal large mass fractions with
negative specific angular momentum, which implies that the gas cannot conserve
its detailed distribution of specific angular momentum when cooling to form the
disk. This crumples one of the main pillars of our standard picture, and
indicates that a new spin on the angular momentum acquisition of disk galaxies
may be required.


title:
Lithium abundances in the atmospheres of SLR C--giants WZ Cas and WX Cyg
  from resonance and subordinate Li I lines

abstract:
  Lithium abundances in the atmospheres of the super Li-rich C-giants WZ Cas
and WX Cyg are derived by the spectral synthesis technique {\bf using} the Li I
resonance line at \lambda 670.8 nm and {\bf three subordinate} lines at
\lambda\lambda 812.6, 610.4 and 497.2 nm. The differences between the Li
abundances derived from the \lambda 670.8 nm line and the \lambda\lambda 497.2,
812.6 nm lines do not exceed $\pm$ 0.5 dex. The lithium line at \la610.4 nm
provides typically lower abundances than the resonance line (by $\approx$ 1
dex). The mean LTE and NLTE Li abundances from three Li I lines (excluding
\la610.4 nm) are 4.7, 4.9 for WZ Cas, and 4.6, 4.8 for WX Cyg, respectively.


title: Auger : A Large Air Shower Array and Neutrino Telescope

abstract:
  Detection of Ultra High Energy Neutrinos (UHEN), with energy above 0.l EeV
(10**18 eV) is one of the most exciting challenges of high energy astrophysics
and particle physics. In this article we show that the Auger Observatories,
built to study ultra high energy cosmic rays, are one of the most sensitive
neutrino telescopes that will be available in the next decade. Furthermore, we
point out that the Waxman-Bahcall upper bound for high energy neutrino fluxes
below 1 EeV turns into a lower bound above a few EeV. In this framework and
given the experimental evidences for nu_mu <--> nu_tau oscillations with large
mixing, we conclude that observation of Tau UHEN in the southern Auger
Observatory should most certainly occur within the next five years.


title: The origin of the rebrightening in soft X-ray transient outbursts

abstract:
  We present a model of an outburst of the soft X-ray transient A0620-003. A
two-dimensional time-dependent smoothed particle hydrodynamics scheme is used
to simulate the evolution of the accretion disc through a complete outburst.
The scheme includes the full tidal potential of the binary and a simple
treatment of the thermal-viscous disc instability.
  In the case where the mass accretion rate onto the primary determines the
fraction of the disc that can be kept in a hot, high viscosity state by the
resulting X-ray emission, we find that the shape of the X-ray light curve is
ultimately determined by the relative sizes of the irradiated and unirradiated
parts of the disc and the growth time-scale of the tidal instability.
  The model accounts for the rebrightening that has been observed in the light
curves of A0620-003 and several other transients. The primary maximum and
subsequent decline are due to the accretion of gas within the irradiated
portion of the disc, while the secondary maximum is caused by the accretion of
gas in the outer part of the disc that is initially shadowed from the central
X-rays, but subject to tidal forces. We propose that tidal effects at the disc
edge can be sufficient to drive accretion on a time-scale shorter than that
expected for a standard alpha-viscosity disc.
  The final decay is subsequently controlled by the gradual retreat of the
irradiated portion of the disc. If the entire disc is kept in the
high-viscosity state by the irradiation, no rebrightening is possible.


title: Alternatives to Quintessence Model Building

abstract:
  We discuss the issue of toy model building for the dark energy component of
the universe. Specifically, we consider two generic toy models recently
proposed as alternatives to quintessence models, known as Cardassian expansion
and the Chaplygin gas. We show that the former is enteriely equivalent to a
class of quintessence models. We determine the observational constraints on the
latter, coming from recent supernovae results and from the shape of the matter
power spectrum. As expected, these restrict the model to a behaviour that
closely matches that of a standard cosmological constant $\Lambda$.


title:
The Frequency Content of the VIRGO/SoHO Lightcurves: Implications for
  Planetary Transit Detection from Space

abstract:
  Stellar micro-variability poses a serious threat to the capacities of
space-based planet-finding missions such as Kepler or Eddington. The solar
lightcurves obtained by the VIRGO PMO6 and SPM instruments on board SoHO from
1996 to 2001 have been studied in order to follow variability changes through
the activity cycle. In all datasets, active regions-induced variability, below
2 microHz, is closely correlated to the BBSO Ca II K-line index. The PMO6
(total irradiance) data shows evidence for a meso-granulation component around
tau = 8x10^3 s, while all narrow-band SPM datasets (red, green and blue) show
super-granulation (tau = 5x10^4 s) but no meso-granulation. Both actvity and
granulation related components have significantly smaller amplitudes in the red
than in the blue channel. These results, coupled with available stellar data,
allow us to generate simulated lightcurves with enhanced variability as a
testbed for pre-processing and detection methods, and influence the case for
using colour information in this kind of mission.


title:
The Kinematics and Physical Conditions of the Ionized Gas in Markarian
  509. I. Chandra High-Energy Grating Spectroscopy

abstract:
  We observed the Seyfert 1 galaxy Mrk 509 simultaneously with Chandra/HETG,
HST/STIS and RXTE. We measure strong absorption lines from He-like Ne and Mg,
and from H-like N, O, and Ne. The lines are unresolved except for Ne Lya and Ne
IX(r). The absorption-line profiles are blueshifted by ~200 km/s with respect
to the systemic velocity of Mrk 509, and there is a hint of another component
near systemic. The soft X-ray spectrum can be described in remarkable detail
with a simple, single-zone photoionized absorber with a column density of 2.06
(+0.39,-0.45) x 10^21 cm^-2 and an ionization parameter of log{xi} = 1.76
(+0.13,-0.14) (or log{U}=0.27). The UV data, on the other hand, can easily
detect eight kinematic components, covering roughly the same velocities as the
X-ray absorption profiles. Even though the X-ray and UV absorbers share the
same velocity space, the UV absorbers have a much smaller column density and
ionization state. We show that models of the X-ray data do not predict
significant UV absorption and are therefore consistent with the UV data. The UV
absorbers could be embedded in the X-ray absorber, as a multiphase medium.
Finally, we do not detect any soft X-ray emission lines.


title: Small-area molecular clouds without shielding

abstract:
  Using the IRAM 30m telescope two molecular structures have been detected
which cover very small areas, FWHM<1'. The clouds have velocities of v_lsr~5kms
and linewidth of dv~0.8km/s; thus they belong most likely to the Milky Way.
Applying standard conversion factors one finds that even at the upper distance
limit of 2200pc the structures are low mass objects
(M=(1-6)x10^{-4}(d/100pc)^2Msun) which are not gravitationally virialized. HI
21cm line data towards the clouds show no prominent HI clouds. The total HI
column densities for both structures are below N(HI)<2.1x10^{20}cm^{-2},
corresponding to A_V<0.2mag, assuming a standard gas-to-dust ratio. IRAS
100micron data towards the structures show also only low emission, consistent
with low extinction. Unless there is unseen cold dust associated with the
structures this shielding is too low for the structures to survive the
interstellar radiation field for a long time. The detection of 2 such
structures in a rather limited sample of observations suggests that they could
be a rather common feature in the interstellar medium, however, so far not
recognized as such due to the weakness of their lines and their small extent.


title: The Multi-Band Magnification Bias for Gravitational Lenses

abstract:
  We present a generalization of the concept of magnification bias for
gravitationally-lensed quasars, in which the quasars are selected by flux in
more than one wavelength band. To illustrate the principle, we consider the
case of two-band selection, in which the fluxes in the two bands are
uncorrelated, perfectly correlated, or correlated with scatter. For
uncorrelated fluxes, we show that the previously-held result - that the bias is
the product of the single-band biases - is generally false. We demonstrate some
important properties of the multi-band magnification bias using model
luminosity functions inspired by observed correlations among X-ray, optical,
infrared and radio fluxes of quasars. In particular, the bias need not be an
increasing function of each flux, and the bias can be extremely large for
non-linear correlations. The latter fact may account for the high lensing rates
found in some X-ray/optical and infrared/radio selected samples.


title: Interpolation and smoothing

abstract:
  Smoothing is omnipresent in astronomy, because almost always measurements
performed at discrete positions in the sky need to be interpolated into a
smooth map for subsequent analysis. Still, the statistical properties of
different interpolation techniques are very poorly known. In this paper, we
consider the general problem of interpolating discrete data whose location
measurements are distributed on the sky according to a known density
distribution (with or without clustering). We derive expressions for the
expectation value and for the covariance of the smoothed map for many
interpolation techniques, and obtain a general method that can be used to
obtain these quantities for any linear smoothing. Moreover, we show that few
basic properties of smoothing procedures have important consequences on the
statistical properties of the smoothed map. Our analysis allows one to obtain
the statistical properties of an arbitrary interpolation procedure, and thus to
optimally choose the technique that is most suitable for one's needs.


title: PSR B1951+32 and PSR J0537-6910 - where are the optical counterparts?

abstract:
  There remain several definitive gamma-ray pulsars that are as yet undetected
in the optical regime. A classic case is the pulsar PSR B1951+32, associated
with the complex CTB 80 SNR. Previous ground based high speed 2-d optical
studies have ruled out candidates to m_V ~ 24. Hester (2000) has reported an
analysis of archival HST/WFPC2 observations of the CTB 80 complex which suggest
a compact synchrotron nebula coincident with the pulsar's radio position.
Performing a similar analysis, we have identified a possible optical
counterpart within this synchrotron nebula at m_V ~ 25.5, and another optical
counterpart candidate nearby at m_V ~ 24.2.
  PSR J0537-6910 is a young (canonical age ~ 5000 years), 16ms pulsar in the
LMC. We report a search for optical pulsations from the region around the X-ray
position. We see no obvious candidate exhibiting optical pulsations at the
X-ray period, with a 3 sigma upper limit of m_V ~ 23.6. We have also examined
recent Chandra results (Wang et al. 2001) and show that their X-ray-Optical
astrometry is in error by about 7''.


title:
Molecular gas in spiral galaxies: a new warm phase at large
  galactocentric distances?

abstract:
  There is now strong evidence suggesting that the 12CO J = 1-0 transition,
widely used to trace H2 gas, significantly underestimates its mass in
metal-poor regions. In spiral disks such regions are found in large
galactocentric distances where we show that any unaccounted H2 gas phase is
likely to be diffuse (~5-20 cm^-3) and warmer (T(kin) ~ 50-100 K) than the cool
(T(kin) ~ 15-20 K) CO-luminous one. Moreover we find that a high value of the
H2 formation rate on grains, suggested by recent observational work, can
compensate for the reduction of the available grain surface in the metal-poor
part of typical galactic disks and thus enhance this CO-poor H2 component which
may be contributing significantly to the mass and pressure of spiral disks
beyond their optical radius.


title: Natural Limits for Currents in Charge Separated Pulsar Magnetospheres

abstract:
  Rough estimates and upper limits on current and particle densities form the
basis of most of the canonical pulsar models. Whereas the surface of the
rotating neutron star is capable of supplying sufficient charges to provide a
current that, given the polar cap potential, could easily fuel the observed
energy loss processes, observational and theoretical constraints provide strict
upper limits to the charge densities. The space charge of a current consisting
solely of particles having only one sign creates a compensating potential that
will make the maximum current dependent on potential and distance. In the
non-relativistic case this fact is expressed in the familiar Child-Langmuir
law. Its relativistic generalization and subsequent application to the inner
pulsar magnetosphere provides clear limits on the strength and radial extension
of charged currents originating on the polar cap. Violent Pierce-type
oscillations set in, if one attempts to inject more current than the space
charge limit into a given volume. These considerations apply wherever there is
a significant amount of charged current flow, in particular in the gap regions.
There they can be used to derive limits on the size of such gaps and their
stability.


title: Bias in Absolute Magnitude Determination from Parallaxes

abstract:
  Relations are given for the correction of bias when mean absolute magnitudes
are derived by the method of reduced parallaxes. The bias in the case of the
derivation of the absolute magnitudes of individual objects is also considered.


title:
The Effects of Mergers on the Formation of Disc-Bulge Systems in
  Hierarchical Clustering Scenarios

abstract:
  We study the effects of mergers on the structural properties of disc-like
systems by using Smooth Particle Hydrodynamical (SPH) numerical simulations in
hierarchical clustering scenarios. In order to assess the effects of mergers on
the mass distributions we performed a bulge-disc decomposition of the projected
surface density of the systems at different stages of the merger process. We
assumed an exponential law for the disc component and the S\'ersic law for the
bulges. We found that simulated objects at $z=0$ have bulge profiles with shape
parameters $n\approx 1$, consistent with observational results of spiral
galaxies. The complete sample of simulated objects at $z=0$ and $z>0$ shows
that $n$ takes values in the range $n\approx 0.4 - 4$. We found that secular
evolution tends to produce exponential bulge profiles, while the fusion of
baryonic cores tends to increase the $n$ value and helps to generate the
correlation between $B/D$ and $n$. We found no dependence on the relative mass
of the colliding objects. Our results suggest that mergers, through secular
evolution and fusions, could produce the transformation of galactic objects
along the Hubble sequence by driving a morphological loop that might also
depend on the properties of the central galactic potential wells, which are
also affected by mergers.


title: Emission Mechanisms in High Energy Pulsars: From Gamma Rays to Infrared

abstract:
  We present a model for the gamma-ray emission of pulsars in terms of
curvature radiation by highly relativistic particles. It is shown that the
injection of power-law primary particles from an outer gap and subsequent
cooling by curvature radiation losses reproduces the high energy spectrum and
the luminosity of pulsars. As a result a spectral break is to be expected at a
photon energy of $\sim 1\thinspace{\rm GeV}$. This value does not depend on the
surface magnetic field strength or on the period of the neutron star, but only
involves a geometric factor. The predicted change of the spectral index by 1
explains in particular the spectral shape of PSR B1706--44. We find that
according to this model the luminosity of pulsars in the high energy band
varies according to $L_{\gamma}\propto B_0/P^{5/3}$, which is in good agreement
with the observations.
  A model for the infrared, optical and soft X-ray emission of pulsar is also
presented. It is based on anisotropic synchrotron emission by relativistic
particles in an outer gap scenario with a single energy distribution
$N(\gamma)\propto \gamma^{-2}$. It is shown that this synchrotron model is able
to reproduce the spectral shape between the infrared and soft X-rays and also
the corresponding luminosities for the Crab pulsar. In particular, the long
standing problem of the rapid spectral decline towards infrared frequencies is
understandable as emission at very small pitch angles from low energy particles
with $\gamma\ga 10$. It is also shown that the scaling of the synchrotron model
explains the observed correlation between the X-ray luminosity and the
spin-down luminosity of the neutron star $L_{\rm x} \sim 10^{-3} {\dot E}$.


title: Fluctuations in the CMB Induced by Cosmic Strings: Methods and Formalism

abstract:
  We present methods to compute maps of CMB fluctuations from high resolution
cosmic string networks using a full Boltzmann code, on both large and small
angular scales. The accuracy and efficency of these methods are discussed.


title:
Molecular Gas and Nuclear Activity in Ultraluminous Infrared Galaxies
  with Double Nuclei

abstract:
  High-resolution CO(1-0) observations of five ultraluminous infrared galaxies
(ULIGs: L_IR [8-1000um] >~ 10^12 L_sun) with double nuclei are analyzed. These
sources constitute a complete subset of local ULIGs expected to be in an
intermediate stage of merging and selected with projected nuclear separations
of 2.0-5.4 (3-5 kpc) so they could be resolved with the Owens Valley Radio
Observatory Millimeter Array. The observed pairs include two mergers with cool
far-infrared colors (25um to 60um flux density ratio f_25um/f_60um < 0.2) from
the Infrared Astronomical Satellite (IRAS) Bright Galaxy Sample (IRAS
12112+0305 and IRAS 14348-1447) and three mergers with warm infrared dust
temperatures f_25um/f_60um >~ 0.2) selected from the IRAS Warm Galaxy Sample
(IRAS 08572+3915, IRAS 13451+1232 = PKS 1345+12, and IRAS 13536+1836 = Mrk
463). These ULIGs are further distinguished by the presence of pairs of active
nuclei; among the ten nuclei, nine have Seyfert or LINER classifications and
one is unclassified. Molecular gas is detected only on the redder, more
radio-luminous nucleus of the warm objects, whereas both nuclei of the cool
ULIGs are detected in CO. The inferred molecular gas masses for the detected
nuclei are 0.1-1.2x10^10 M_sun, and the undetected nuclei have molecular gas
masses at least 1.2--2.8 times less than that of their CO-luminous companions.
Upper limits on the extent of the CO emitting regions of each detected nucleus
range from 2--4 kpc, which is about 3-6 times smaller than the average
effective CO diameter of nearby spiral galaxies...


title: A New Kinetic Equation for Compton Scattering

abstract:
  A kinetic equation for Compton scattering is given that differs from the
Kompaneets equation in several significant ways. By using an inverse
differential operator this equation allows treatment of problems for which the
radiation field varies rapidly on the scale of the width of the Compton kernel.
This inverse operator method describes, among other effects, the thermal
Doppler broadening of spectral lines and continuum edges, and automatically
incorporates the process of Compton heating/cooling. It is well adapted for
inclusion into a numerical iterative solution of radiative transfer problems.
The equivalent kernel of the new method is shown to be a positive function and
with reasonable accuracy near the intitial frequency, unlike the Kompaneets
kernel, which is singular and not wholly positive. It is shown that iterates of
the inverse operator kernel can be easily calculated numerically, and a simple
summation formula over these iterates is derived that can be efficiently used
to compute Comptonized spectra. It is shown that the new method can be used for
initial value and other problems with no more numerical effort than the
Kompaneets equation, and that it more correctly describes the solution over
times comparable to the mean scattering time.


title:
X-ray Spectroscopy of the Accreting Millisecond Pulsar XTE J0929-314 in
  Outburst

abstract:
  We present the high-resolution spectrum of the accretion-powered millisecond
pulsar XTE J0929-314 during its 2002 outburst, measured using the Low Energy
Transmission Grating Spectrometer onboard the Chandra X-ray Observatory. The
1.5-25.3 A (0.5-8.3 keV) Chandra spectrum is well fit by a power-law +
blackbody model with photon index Gamma=1.55+/-0.03, blackbody temperature
kT_bb=0.65+/-0.03 keV, and blackbody normalization R_bb,km/d_10kpc=7.6+/-0.8.
No emission or absorption features are found in the high-resolution spectrum,
with a 3 sigma equivalent width upper limit of <0.007 A at 1.5 A and <0.12 A at
24 A. The neutral absorption edge depths are consistent with the estimated
interstellar absorption along the line of sight to the source. We found no
orbital modulation of the 2-10 keV X-ray flux, to a 3 sigma upper limit of
1.1%, which implies an upper limit on the binary inclination angle of i<85deg
for a Roche-lobe-filling companion. We also present the broadband spectrum
measured over the course of the outburst by the Rossi X-ray Timing Explorer.
The XTE spectrum of XTE J0929-314 is also well fit with a power-law + blackbody
model, with average values of Gamma=1.76+/-0.03, kT_bb=0.66+/-0.06 keV, and
R_bb,km/d_10kpc=5.9+/-1.3 in the 2-50 keV energy range. The blackbody flux
remained constant over the course of the outburst, while the power-law flux was
strongly correlated to the (decreasing) flux of the source. We find that the
difference in power-law photon indices measured from Chandra and XTE spectra
can be explained by a change in the power-law photon index at low energies.


title:
Exploring the cosmic dark ages with the next generation of space and
  ground-based facilities

abstract:
  This paper reviews our current understanding of the process of re-ionization
of the Universe, focusing especially on those models where re-ionization is
caused by UV radiation from massive stars. After reviewing the expected
properties of stars at zero metallicity, I discuss the properties of primordial
HII regions and their observability.


title: A new two-pole accretion polar: RX J1846.9+5538

abstract:
  We report the discovery of a new, bright (V = 17 mag) AM Her system as the
optical counterpart of the soft ROSAT All-Sky-Survey source RX J1846.9+5538 (=
1RXS J184659.4+553834). Optical photometric and spectroscopic follow-up
observations reveal a single period of 128.7 min, consistent with a high degree
of spin-orbit synchronization, and a low polar field strength ($B<20$ MG) of
the primary accretion region. The system was observed in optical intermediate
and high states that differ by about 1 mag. These brightness variations were
accompanied by a correlated change of the optical light curve, which we
interpret as a switch between one- and two-pole accretion. This explanation is
also supported by the X-ray light curves, which at two different epochs display
emission from two equally bright accretion regions separated by 160 degrees.
Both spots possess distinct spectral X-ray properties as seen from the X-ray
hardness ratio, where the secondary accretion region appears significantly
softer, thus probably indicating a higher field strength compared to the
primary region. In all ROSAT pointings a deep dip is present during the primary
flux maxima, very likely caused by absorption in one of the accretion streams.


title: Flare Heating in Stellar Coronae

abstract:
  We investigate the contribution of very weak flares to the coronal luminosity
of low-mass active stars. We analyze EUVE/DS events data from FK Aqr, V1054
Oph, and AD Leo and conclude that in all these cases the coronal emission is
dominated by flares to such an extent that in some cases the entire emission
may be ascribed to flare heating. We have developed a new method to directly
model for the first time stochastically produced flare emission, including
undetectable flares, and their effects on the observed photon arrival times. We
find that the index of the power-law distribution of flare energies (dN/dE ~
E^{-alpha}) is 2.6+-0.34, 2.74+-0.35, and 2.03-2.32 for FK Aqr, V1054 Oph, and
AD Leo respectively. We also find that the flare component accounts for a large
fraction (generally >50 percent) of the total flux.


title: A Model for the Formation and Evolution of Cosmological Halos

abstract:
  Adaptive SPH and N-body simulations were carried out to study the collapse
and evolution of dark matter halos that result from the gravitational
instability and fragmentation of cosmological pancakes. Such halos resemble
those formed by hierarchical clustering in a CDM universe and serve as a
convenient test-bed model for studying halo dynamics. Our halos are in
approximate virial equilibrium and roughly isothermal, as in CDM simulations.
Their density profiles agree quite well with the fit to N-body results for CDM
halos by Navarro, Frenk, & White (NFW). This test-bed model enables us to study
the evolution of individual halos. The masses of our halos evolve in three
stages: an initial collapse, continuous infall, and a final stage in which
infall tapers off as a result of finite mass supply. In the continuous infall
stage, halo mass grows at the rate expected for self-similar spherical infall,
with M(a) proportional to the scale factor a. After the end of initial collapse
at a=a_0, the concentration parameter grows linearly with a, c(a)~4a/a_0. The
virial ratio 2T/|W| just after virialization is about 1.35, as predicted by the
truncated isothermal sphere model and consistent with the value expected for a
virialized halo in which mass infall contributes an effective surface pressure.
Thereafter, the virial ratio evolves towards the value expected for an isolated
halo, 2T/|W|~1. This mass accretion history and evolution of concentration
parameter are very similar to those reported recently in N-body simulations of
CDM. We therefore conclude that the fundamental properties of halo formation
and evolution are generic to the formation of cosmological halos by
gravitational instability and are not limited to hierarchical collapse
scenarios or even to Gaussian-random-noise initial conditions.


title:
Deep spectroscopy of z~1 6C radio galaxies - I. The effects of radio
  power and size on the properties of the emission line gas

abstract:
  (abridged) The results of deep long-slit optical spectroscopy for a sample of
8 6C radio galaxies at z~1 are presented. Emission line ratios are derived for
emission lines with rest-frame wavelengths of 1500 - 4500Ang, and the kinematic
propertiess of the emission line gas are derived from an analysis of the 2-d
structure of thee [OII]3727 Ang emission line at ~5Ang spectral resolution. In
general, the 6C spectra display many characteristics similar to those of more
powerful 3CR sources at the same redshifts. The emission line region gas
kinematics are more extreme for the smaller radio sources in the sample, which
often display distorted velocity profiles. The ionization state of the emission
line region also varies with radio size: the spectra of large radio sources
(>120kpc) are consistent with photoionization by an obscured AGN, whilst
smaller (<120kpc) sources typically exist in a lower ionization state and have
spectra which are better explained by additional ionization due to shocks
associated with the expanding radio source. The kinematic and ionization
properties of the 6C radio galaxies are clearly linked. As for the 3CR sources,
smaller radio sources also typically possess more extensive emission line
regions, with enhanced emission line luminosities. It is clear that the best
interpretation of the spectra of radio sources requires a combination of
ionization mechanisms.


title:
Deep spectroscopy of z~1 6C radio galaxies - II. Breaking the
  redshift-radio power degeneracy

abstract:
  The results of a spectroscopic analysis of 3CR and 6C radio galaxies at
redshift z~1 are contrasted with the properties of lower redshift radio
galaxies, chosen to be matched in radio luminosity to the 6C sources studied at
z~1, thus enabling the P-z degeneracy to be broken. Partial rank correlations
and principal component analysis have been used to determine which of z and P
are the critical parameters underlying the observed variation of the ionization
state andd kinematics of the emission line gas. [OII]/H-beta is shown to be a
useful ionization mechanism diagnostic. Statistical analysis of the data shows
that the ionization state of the emission line gas is strongly correlated with
radio power, once the effects of other parameters are removed. No dependence of
ionization state on z is observed, implying that the ionization state of the
emission line gas is solely a function of the AGN properties rather than the
hostt galaxy and/or environment. Statistical analysis of the kinematic
properties of the emission line gas shows that these are strongly correlated
independently withh both P and z. The correlation with redshift is the stronger
of the two, suggesting that host galaxy composition or environment may play a
role in producing the less extreme gas kinematics observed in the emission line
regions of low redshift galaxies. For both the ionization and kinematic
properties of thee galaxies, the independent correlations observed with radio
size are strongest. Radio source age is a determining factor for the extended
emission line regions.


title:
The evolution of radio galaxy emission line regions: Breaking the P-z
  degeneracy

abstract:
  The ionization and kinematic properties of the emission line regions of three
subsamples of 6C and 3CR radio galaxies have been compared. The degeneracy
between redshift and radio power is broken, and the relative importance of
radio power (P), radio size (D) and redshift (z) for the emission line region
properties is determined.


title:
Star Formation in Emission-Line Galaxies Between Redshifts of 0.8 and
  1.6

abstract:
  Optical spectra of 14 emission-line galaxies representative of the 1999
NICMOS parallel grism Ha survey of McCarthy et al. are presented. Of the 14, 9
have emission lines confirming the redshifts found in the grism survey. The
higher resolution of our optical spectra improves the redshift accuracy by a
factor of 5. The [O II]/Ha values of our sample are found to be more than two
times lower than expected from Jansen et al. This [O II]/Ha ratio discrepancy
is most likely explained by additional reddening in our Ha-selected sample [on
average, as much as an extra E(B-V) = 0.6], as well as to a possible stronger
dependence of the [O II]/Ha ratio on galaxy luminosity than is found in local
galaxies. The result is that star formation rates (SFRs) calculated from [O
II]3727 emission, uncorrected for extinction, are found to be on average 4 +/-
2 times lower than the SFRs calculated from Ha emission. Classification of
emission-line galaxies as starburst or Seyfert galaxies based on comparison of
the ratios [O II]/Hb and [Ne III]3869/Hb is discussed. New Seyfert 1
diagnostics using the Ha line luminosity, H-band absolute magnitude, and Ha
equivalent widths are also presented. One galaxy is classified as a Seyfert 1
based on its broad emission lines, implying a comoving number density for
Seyfert 1s of 2.5{+5.9, -2.1} times 10^{-5} Mpc^{-3}. This commoving number
density is a factor of 2.4{+5.5,-2.0} times higher than estimated by other
surveys.


title: Radial Flow of Dust Particles in Accretion Disks

abstract:
  We study the radial migration of dust particles in accreting protostellar
disks analogous to the primordial solar nebula. This study takes account of the
two dimensional (radial and normal) structure of the disk gas, including the
effects of the variation in the gas velocity as a function of distance from the
midplane. It is shown that the dust component of disks accretes slower than the
gas component. At high altitude from the disk midplane, the gas rotates faster
than particles because of the inward pressure gradient force, and its drag
force causes particles to move outward in the radial direction. Viscous torque
induces the gas within a scale height from the disk midplane to flow outward,
carrying small (size < 100 micron at 10 AU) particles with it. Only particles
at intermediate altitude or with sufficiently large sizes (> 1 mm at 10 AU)
move inward. When the particles' radial velocities are averaged over the entire
vertical direction, particles have a net inward flux. At large distances from
the central star, particles migrate inward with a velocity much faster than the
gas accretion velocity. However, their inward velocity is reduced below that of
the gas in the inner regions of the disk. The rate of velocity decrease is a
function of the particles' size. While larger particles retain fast accretion
velocity until they approach closer to the star, 10 micron particles have
slower velocity than the gas in the most part of the disk (r < 100 AU). This
differential migration of particles causes the size fractionation. Dust disks
composed mostly of small particles (size < 10 micron) accrete slower than gas
disks, resulting in the increase in the dust-gas ratio during the gas accretion
phase.


title: The Large-scale Bipolar Wind in the Galactic Center

abstract:
  During a 9-month campaign (1996--1997), the Midcourse Space Experiment (MSX)
satellite mapped the Galactic Plane at mid-infrared wavelengths (4.3--21.3um).
Here we report evidence for a spectacular limb- brightened, bipolar structure
at the Galactic Center extending more than a degree (170 pc at 8.0 kpc) on
either side of the plane. The 8.3um emission shows a tight correlation with the
3, 6 and 11 cm continuum structure over the same scales. Dense gas and dust are
being entrained in a large-scale bipolar wind powered by a central starburst.
The inferred energy injection at the source is ~10^54/kappa erg for which
\kappa is the covering fraction of the dusty shell (kappa <= 0.1).
  There is observational evidence for a galactic wind on much larger scales,
presumably from the same central source which produced the bipolar shell seen
by MSX. Sofue has argued that the North Polar Spur -- a thermal x-ray/radio
loop which extends from the Galactic Plane to b = +80 deg -- was powered by a
nuclear explosion (1-30 x 10^55 erg) roughly 15 Myr ago. We demonstrate that an
open-ended bipolar wind (~10^55 erg), when viewed in near-field projection,
provides the most natural explanation for the observed loop structure. The
ROSAT 1.5 keV diffuse x-ray map over the inner 45 deg provides compelling
evidence for this interpretation. Since the faint bipolar emission would be
very difficult to detect beyond the Galaxy, the phenomenon of large-scale
galactic winds may be far more common than has been observed to date.


title: Star Formation in Space and Time: Taurus-Auriga

abstract:
  To understand the formation of stellar groups, one must first document
carefully the birth pattern within real clusters and associations. In this
study of Taurus-Auriga, we combine pre-main-sequence ages from our own
evolutionary tracks with stellar positions from observational surveys. Aided by
the extensive, millimeter data on the molecular clouds, we develop a picture of
the region's history. Star formation began, at a relatively low level and in a
spatially diffuse manner, at least 10 Myr in the past. Within the last few
million years, new stars have been produced at an accelerating rate, almost
exclusively within a confined group of striated cloud filaments. The gas both
inside and around the filaments appears to be in force balance. Thus, the
appearance of the filaments is due to global, quasi-static contraction of the
parent cloud material. Gravity drives this contraction and shock dissipation
mediates it, but the internal motion of the gas does not appear to be
turbulent. The accelerating nature of recent star formation means that the
condensation of cloud cores is a threshold phenomenon, requiring a minimum
background density. Other, nearby cloud regions, including Lupus and
Chamaeleon, contain some locales that have attained this density, and others
that have not. In the latter, we find extensive and sometimes massive molecular
gas that is still devoid of young stars.


title: Compton Heated Outflow from CDAFs

abstract:
  Convection-dominated accretion flows (CDAF) are expected to have a shallower
density profile and a higher radiation efficiency as compared to
advection-dominated accretion flows (ADAF). Both solutions have been developed
to account for the observed properties of the low luminosity, high temperature
X-ray sources believed to involve accretion onto massive black holes.
Self-similar CDAFs also have steeper poloidal density gradients and
temperatures close to the virial temperature. All these characteristics make
CDAFs more capable of producing polar outflows driven by Compton heating as
compared to other classical accretion disks. We investigate the conditions for
producing such outflows in CDAFs and look for the mass accretion rate, or,
equally, the luminosity of CDAFs for which such outflows will exist. When the
electron temperature saturates around 10^11 K at the inner region, polar
outflows are probable for 8x10^-7 <~ L/L_E <~ 4x10^-5, where L_E is the
Eddington luminosity. Outflows are well collimated with small opening angles.
The luminosity range for which outflow solutions exist is narrower for lower
electron temperature flows and disappears completely for electron temperature
<~ 6x10^9 K. When the magnetic field is present, we find that outflows are
possible if the magnetic field is less than from 10% to 1% of the equipartition
field. We also find that outflows are more likely to be produced when the
viscosity parameter alpha is small. The tendency for jet-like collimated
outflows for these solutions is presumably astrophysically relevant given the
high frequency of jets from AGNs.


title:
Galactic Environment of the Sun and Stars: Interstellar and
  Interplanetary Material

abstract:
  Interstellar material surrounding an extrasolar planetary system interacts
with the stellar wind to form the stellar astrosphere, and regulates the
properties of the interplanetary medium and cosmic ray fluxes throughout the
system. Advanced life and civilization developed on Earth during the time
interval when the Sun was immersed in the vacuum of the Local Bubble and the
heliosphere was large, and probably devoid of most anomalous and galactic
cosmic rays. The Sun entered an outflow of diffuse cloud material from the
Sco-Cen Association within the past several thousand years. By analogy with the
Sun and solar system, the Galactic environment of an extrasolar planetary
system must be a key component in understanding the distribution of systems
with stable interplanetary environments, and inner planets which are shielded
by stellar winds from interstellar matter (ISM), such as might be expected for
stable planetary climates.


title: The Characteristics of (Normal) Pulsars

abstract:
  Pulsars have now been studied for 34 years. We know of the existence of some
1500 objects at radio frequencies. Many of the characteristics of pulsars such
as pulsar period, period derivative, spectrum, polarization, etc., have been
catalogued for many objects. Still we do not know the details of the pulsar
emission mechanism. The present review will give an up-to-date description of
the characteristics of (normal, slow) radio pulsars. Millisecond pulsars will
be dealt with by M. Kramer (this volume).


title:
Interpretation of Pioneer 10 Lyman alpha based on heliospheric interface
  models: methodology and first results

abstract:
  The Very Local Interstellar Medium (VLISM) neutral hydrogen and proton
densities are still not precisely known even after three decades of deep space
research and the existence of the EUV and other diagnostic data obtained by
Pioneer 10/11, Voyager 1/2 and other spacecraft. The EUV data interpretation,
in particular, has suffered because of inadequate neutral hydrogen-plasma
models, difficulty of calculating the multiply scattered Lyman alpha glow and
calibration uncertainties. Recently, all these difficulties have been
significantly reduced. In the present work we have used the latest state of the
art supersonic VLISM neutral hydrogen-plasma and Monte Carlo radiative transfer
model, incorporating neutral density, temperature, and velocity variations,
actual solar line shape, realistic redistribution function, Doppler and
aberration effects. This work presents the methodology of the radiative
transfer code and the first results of the comparison of the model predictions
with the Pioneer 10 data. Monte Carlo radiative transfer calculations were
carried out for five neutral hydrogen- plasma models and compared with Pioneer
data. The first results are quite encouraging. We found that the VLISM
ionization ratio is between 0.2 and 0.5 and that the VLISM neutral hydrogen
density is less than 0.25 cm^{-3}. The present calculation suggests that the
Pioneer 10 photometer derived intensities (Rayleighs) need to be increased by a
factor of 2. If this model- derived calibration is used then the difference
between Pioneer 10 and Voyager 2 intensity values is reduced to about 2.2. The
model, neutral hydrogen density = 0.15 cm${-3} and proton density = 0.07
cm^{-3}, is found to best fit the Pioneer 10 data.


title:
The peculiar millisecond pulsars in the globular clusters NGC 6397 and
  NGC 6752

abstract:
  The millisecond pulsars discovered in globular clusters are diagnostic tools
for studying the dynamics of the clusters, the intracluster ionized gas and the
evolution of the binaries embedded in the cluster. In the first two years of a
search at 1.4 GHz in progress at the Parkes radio telescope 12 new millisecond
pulsars have been discovered in 6 globular clusters in which no pulsars were
previously known. The scientific fall-back of these discoveries is here
discussed for the case of two globular clusters: NGC 6397 and NGC 6752.


title: Models of the Solar Wind Interaction with Local Interstellar Cloud

abstract:
  This paper reviews the theoretical approaches and existing models of the
solar wind interaction with the Local Interstellar Cloud (LIC). Models
discussed take into account the multi-component nature of the solar wind and
local interstellar medium. Basic results of the modeling and their possible
applications to interpretation of space experiments are summarized. Open
questions of global modeling of the solar wind/LIC interaction and future
perspectives are discussed.


title: Emission altitude in radio pulsars

abstract:
  This paper presents a method of estimation of emission altitudes using
observational data - precise measurements of pulse profile widths at low
intensity level. The analysis of emission altitudes obtained using this method
for a large number of pulsars gives constraints that should be useful for
theory of coherent pulsar emission. It seems that radio emission originates at
altitudes of about few percent of the light cylinder and that they depend on
frequency, pulsar period and period derivative.


title: Evolution of large-scale perturbations in quintessence models

abstract:
  We carry out a comprehensive study of the dynamics of large-scale
perturbations in quintessence scenarios. We model the contents of the Universe
by a perfect fluid with equation of state w_f and a scalar field Q with
potential V(Q). We are able to reduce the perturbation equations to a system of
four first-order equations. During each of the five main regimes of
quintessence field behaviour, these equations have constant coefficients,
enabling analytic solution of the perturbation evolution by eigenvector
decomposition. We determine these solutions and discuss their main properties.


title: Neutron Stars, Pulsars and Supernova Remnants: concluding remarks

abstract:
  Concluding Remarks of the 270.WE-Heraeus Seminar on Neutron Stars, Pulsars
and Supernova Remnants.


title:
On the Field-Aligned Particle Acceleration in the presence of
  Electron-Positron Pairs

abstract:
  We study self-consistency for the pulsar polar cap model. In general, there
will remain an unscreened electric field at the pair production front (PPF). We
have derived the condition of electric field screening by pairs in the presence
of returning particles. A previous belief that pairs with a density higher than
the Goldreich-Julian density immediately screen out the electric field beyond
PPF is unjustified. Pairs have little contribution on screening the electric
field, and the geometrical screening is the only known way of getting a finite
potential drop.


title: Stability of rotating spherical stellar systems

abstract:
  The stability of rotating isotropic spherical stellar systems is investigated
by using N-body simulations. Four spherical models with realistic density
profiles are studied: one of them fits the luminosity profile of globular
clusters, while the remaining three models provide good approximations to the
surface brightness of elliptical galaxies. The phase-space distribution
function f(E) of each one of these non-rotating models satisfies the sufficient
condition for stability df/dE < 0. Different amounts of rotation are introduced
in these models by changing the sign of the z-component of the angular momentum
for a given fraction of the particles. Numerical simulations show that all
these rotating models are stable to both radial and non-radial perturbations,
irrespective of their degree of rotation. These results suggest that rotating
isotropic spherical models with realistic density profiles might generally be
stable. Furthermore, they show that spherical stellar systems can rotate very
rapidly without becoming oblate.


title: Coherent Radio Emission from Pulsars

abstract:
  Generation of the pulsar radio emission from plasma waves excited by the
two-stream instability is considered. Special attention is given to propagation
effects.


title: Neutrino physics from cosmological observations

abstract:
  We review the current status of neutrino cosmology, focusing mainly on the
question of the absolute values of neutrino masses and the possibility of a
cosmological neutrino lepton asymmetry.


title: A current circuit model of pulsar radio emission

abstract:
  We present the outline of a new model for the coherent radio emission of
pulsars that succeeds in reproducing the energetics and brightness temperatures
of the observed radio emission from the observationally deduced distances of
50-100 pulsar radii above the neutron star in a narrow region.
  The restrictions imposed by energy conservation, plasma dynamics of the
coherent radiation process and propagation effects are used to apply the action
of a plasma process like coherent inverse Compton scattering (CICS) (see
Benford, 1992). In accordance with our findings (Kunzl et al. 1998a) this
process requires Lorentz factors of about 10 which are lower than in most other
radio emission models. This implies that no significant pair production can
take place near the surface and we expect charge densities close to the
Goldreich-Julian value (Goldreich & Julian (1969)).
  To fulfill the energetic and electrodynamic constraints the model requires
constant re-acceleration in dissipation regions which can be interpreted as a
voltage drop similar to that in a resistive current circuit built of a battery,
connecting copper wires and a resistive load.
  Using the emission heights for PSR 0329+54 published by Mitra and Rankin
(2002) and the spectral data from Malofeev et al. (1994) we find that a
constant depth of the dissipation region of about 2 r_NS can account for the
observed luminosities and spectral behavior.
  The extremely high peak fluxes in the substructures of single pulses can be
explained by beaming effects as discussed in Kunzl et al. (1998b).


title: From Pulsar Spin to Pulsar Wind: The Spectral Connection?

abstract:
  We present preliminary results from a systematic spectral study of pulsars
and their wind nebulae using the Chandra X-Ray Observatory. The superb spatial
resolution of Chandra allows us to differentiate the compact object's spectrum
from that of its surrounding nebulae. Specifically, for six Crab-like pulsars,
we compare spectral fits of the averaged pulsar wind nebulae (PWN) emission to
that of the central core using an absorbed power-law model. These results
suggest an empirical relationship between the bulk averaged photon indices for
the PWNe and the pulsar cores; Gamma_{PWN} = 0.8 times Gamma_{Core} + 0.8. The
photon indices of PWNe are found to fall in the range of 1.3 < Gamma_{PWN} <
2.3. We propose that the morphological and spectral characteristics of the
pulsars observed herein seem to indicate consistent emission mechanisms common
to all young pulsars. We point out that the previous spectral results obtained
for most X-ray pulsars are likely contaminated by PWN emission.


title: Towards a consistent model for Neutron-Star Sources

abstract:
  We are still far from understanding how pulsars pulse, how neutron stars are
born, what neutron stars can emit, and in which way they do this. In this short
communication, I list 18 alternatives -- several of them old, a few of them new
-- which are handled differently by different authors but all of which are
crucial for a model of neutron stars to be viable.


title: Reviewing Pulsar Spectra

abstract:
  Problems solved? Pulsar research must be considered - 35 years after the
detection of pulsars - a mature science, where the basic questions have been
raised and discussed. One would hope that many if not all generic and important
problems have found some kind of answer and that scientific work can
concentrate now on specific details requiring more in depth investigation. We
know, however, that this picture is not true. Even well studied areas did in
the past not always lead to a general accepted model and some were investigated
at the beginning with enthusiasm but left behind.
  This paper will concentrate on one narrow topic, pulsar radio spectra. It is
the attempt to work out, what features are now generally accepted, but also
what features are still in discussion after so many years of pulsar research.
In this sense the paper will enlighten in a personal view those aspects which
are still under discussion.


title: New Limits on Gravitational Radiation using Pulsars

abstract:
  We calculate a new gravitational wave background limit using timing residuals
from PSRs J1713+0747, B1855+09, and B1937+21. The new limit is based on 17
years of continuous data pieced together from 3 different observing projects: 2
at the Arecibo Observatory and 1 at the 140ft Green Bank Telescope. This
project represents the earliest results from the `Pulsar Timing Array' which
will soon be able detect the stochastic background from early massive black
hole mergers.


title: Solar-like oscillations in Delta Scuti stars

abstract:
  Model computations of Delta Scuti stars, located in the vicinity of the red
edge of the classical instability strip, suggest amplitudes of solar-like
oscillations larger than in cooler models located outside the instability
strip. Solar-like amplitudes in our Delta Scuti models are found to be large
enough to be detectable with ground-based instruments provided they can be
distinguished from the opacity-driven large-amplitude pulsations. There would
be advantages in observing simultaneously opacity-driven and stochastically
excited modes in the same star. We anticipate their possible detection in the
context of the planned asteroseismic space missions, such as the French mission
COROT (COnvection ROtation and planetary Transits). We propose known Delta
Scuti stars as potential candidates for the target selection of these upcoming
space missions.


title: The Free Electron Maser in Pulsar Magnetospheres

abstract:
  We present the numerical simulations of coherent inverse Compton scattering
(CICS) in a highly magnetized plasma process by means of a full three
dimensional particle in cell code (PIC), which is mass and energy conservative.
We used the parameters of a pulsar magnetosphere where CICS is one of the most
promising models for the generation of the observed highly coherent radio
emission. First we show details of the onset and time evolution of strong
Langmuir turbulence driven by a relativistic electron beam penetrating a
strongly magnetized background plasma. The Langmuir turbulence acts as
self-generated wiggler fields which bunch the beam electrons thereby inducing
strong coherent emission of the bunches at frequency gamma^2 times the plasma
frequency. The emitted power is about 10 GW in a few nanoseconds. This
radiation is interpreted in terms of inverse Compton scattering on nonlinear
density fluctuations. CICS is the longitudinal version of a laboratory free
electron laser and is applicable in strongly magnetized plasmas like pulsars.


title:
Chasing the second gamma-ray bright isolated neutron star: 3EG
  J1835+5918/RX J1836.2+5925

abstract:
  The EGRET telescope aboard NASAs Compton GRO has repeatedly detected 3EG
J1835+5918, a bright and steady source of high-energy gamma-ray emission with
no identification suggested until recently. The long absence of any likely
counterpart for a bright gamma-ray source located 25 degrees off the Galactic
plane initiated several attempts of deep observations at other wavelengths. We
report on counterparts in X-rays on a basis of a 60 ksec ROSAT HRI image. In
order to conclude on the plausibility of the X-ray counterparts, we reanalyzed
data from EGRET at energies above 100 MeV and above 1 GeV, including data up to
CGRO observation cycle 7. The gamma-ray source location represents the latest
and probably the final positional assessment based on EGRET data. The X-ray
counterparts were studied during follow-up optical identification campaigns,
leaving only one object to be likely associated with the gamma-ray source 3EG
J1835+5918. This object, RX J1836.2+5925, has the characteristics of an
isolated neutron star and possibly of a radio-quiet pulsar.


title: Tsunami Inflation: Selfconsistent Quantum Dynamics

abstract:
  The physics during the inflationary stage of the universe is of quantum
nature involving extremely high energy densities. Moreover, it is out of
equilibrium on a fastly expanding dynamical geometry. We complement here the
1999 Chalonge Lectures on out of equilibrium fields in self-consistent
inflationary dynamics [astro-ph/0006446] investigating inflation driven by the
evolution of highly excited quantum states. These states are characterized by a
non-perturbatively large number of quanta in a band of momenta and with zero or
nonzero expectation value of the inflaton scalar field. They represent the
situation in which initially a non-perturbatively large energy density is
localized in a band of high energy quantum modes and are coined tsunami-waves.
The self- consistent evolution of this quantum state and the scale factor is
studied analytically and numerically. It is shown that the time evolution of
these quantum states lead to two consecutive stages of inflation under
conditions that are the quantum analogue of slow-roll. The evolution of the
scale factor during the first stage has new features that are characteristic of
the quantum state. During this initial stage the quantum fluctuations in the
highly excited band build up an effective homogeneous condensate with a
non-perturbatively large amplitude as a consequence of the large number of
quanta.The second stage of inflation is similar to the usual classical chaotic
scenario but driven by this effective condensate.The excited quantum modes are
superhorizon in the first stage and do not affect the power spectrum of scalar
perturbations.Thus, this tsunami quantum state provides a field theoretical
justification for chaotic scenarios driven by a classical homogeneous scalar
field of large amplitude.


title:
Characterizing the dynamic properties of the solar turbulence with 3-D
  simulations: Consequences in terms of p-mode excitation

abstract:
  A 3D simulation of the upper part of the solar convective zone is used to
derive constraints about the averaged and dynamic properties of solar turbulent
convection. Theses constraints are then used to compute the acoustic energy
supply rate P(nu) injected into the solar radial oscillations according to the
theoretical expression in Samadi & Goupil (2001). The result is compared with
solar seismic data. Assuming, as it is usually done, a gaussian model for the
frequency (nu) component chi_k(nu) of the model of turbulence, it is found that
the computed P(nu) is underestimated compared with the solar seismic data by a
factor ~ 2.5. A frequency analysis of the solar simulation shows that the
gaussian model indeed does not correctly model chi_k(nu) in the frequency range
where the acoustic energy injected into the solar p-modes is important (nu ~ 2
- 4 mHz). One must consider an additional non-gaussian component for chi_k(nu)
to reproduce its behavior. Computed values of P obtained with this non-gaussian
component reproduce better the solar seismic observations. This non-gaussian
component leads to a Reynolds stress contribution of the same order than the
one arising from the advection of the turbulent fluctuations of entropy by the
turbulent motions.


title: The far-ultraviolet emission of early-type galaxies

abstract:
  We have assembled a UV-flux selected sample of 82 early-type galaxies and
collected additional information at other wavelengths. These data confirm a
large spread of the UV-V color in the range 2 to 5. The spread in UV-V is
accompanied by a spread in B-V that is mainly attributed to the range of
morphological types and luminosities. A large fraction of the objects have red
colors, UV-V = 4 +-0.4, corresponding to a weak UV-upturn as observed with IUE.
If the current interpretation for the UV emission from early-type galaxies is
applicable to our sample, the PAGB (Post-Asymptotic Giant Branch) tracks are
the most common evolution path for the low-mass stars responsible for the UV
emission. A small number of very blue (UV-V < 1.4) objects have been found that
can be reasonably interpreted as harbouring some low level of star formation.
In contrast with a previous sample based on IUE observations, no correlation is
found between the UV-V color and the Mg_2 spectral line index; possible
explanations are reviewed. The potential of a more extended UV survey like
GALEX is briefly presented.


title: Why study pulsars optically?

abstract:
  Observations of the five confirmed optical pulsars indicate that the peak
emission scales according to the magnetic field strength at the light cylinder.
To the accuracy that such low number allows we show that this gives further
confirmation that a straightforward synchrotron model such as Pacini & Salvati
(1987) still has validity. The derived relationships indicates that the
emission mechanism is common across all of the pulsars and towards the edge of
the light cylinder. In the future observations should include near and far
infra red work to determine the long wave self absorption cut-off and
polarization observations of all pulsars to restrict (to first order) emission
zone geometry.


title:
Migration and Accretion of Protoplanets in 2D and 3D Global
  Hydrodynamical Simulations

abstract:
  Planet evolution is tightly connected to the dynamics of both distant and
close disk material. Hence, an appropriate description of disk-planet
interaction requires global and high resolution computations, which we
accomplish by applying a Nested-Grid method. Through simulations in two and
three dimensions, we investigate how migration and accretion are affected by
long and short range interactions. For small mass objects, 3D models provide
longer growth and migration time scales than 2D ones do, whereas time lengths
are comparable for large mass planets.


title: First detection of the RGB-bump in the Sagittarius dSph

abstract:
  We present V, I photometry of the Sagittarius Dwarf Spheroidal galaxy (Sgr)
for a region of ~ 1^{circ} times 1^{circ}, centered on the globular cluster M
54. This catalog is the largest database of stars (~500,000) ever obtained for
this galaxy. The wide area covered allows us to measure for the first time the
position of the RGB-bump, a feature that has been identified in most Galactic
globular clusters and only recently in a few galaxies of the Local Group. The
presence of a single-peaked bump in the RGB differential Luminosity Function
confirms that there is a dominant population in Sgr (Pop A).
  The photometric properties of the Pop A RGB and the position of the RGB bump
have been used to constrain the range of possible ages and metallicities of
this population. The most likely solution lies in the range -0.6 < [M/H] <=
-0.4 and 4 Gyr <= age <= 8 Gyr.


title: Hard X-ray emission from a young massive star-forming cluster

abstract:
  We report the detection of hard X-ray emission (>2 keV) from a number of
point sources associated with the very young massive star-forming region IRAS
19410+2336. The X-ray emission is detected from several sources located around
the central and most deeply embedded mm continuum source, which remains
undetected in the X-ray regime. All X-ray sources have K-band counterparts, and
those likely belonging to the evolving massive cluster show near-infrared
colors in the 2MASS data indicative of pre-main-sequence stages. The X-ray
luminosities around 10^{31} erg/s are at the upper end of luminosities known
for low-mass pre-main-sequence sources, and mass estimates based on the
infrared data indicate that at least some of the X-ray detected sources are
intermediate-mass objects. Therefore, we conclude that the X-ray emission is
due to intermediate-mass pre-main-sequence Herbig Ae/Be stars or their
precursors. The emission process is possibly due to magnetic star-disk
interaction as proposed for their low-mass counterparts.


title:
Energy transport, overshoot, and mixing in the atmospheres of very cool
  stars

abstract:
  We constructed hydrodynamical model atmospheres for mid M-type main-, as well
as pre-main-sequence objects. Despite the complex chemistry encountered in such
cool atmospheres a reasonably accurate representation of the radiative transfer
is possible. The detailed treatment of the interplay between radiation and
convection in the hydrodynamical models allows to study processes usually not
accessible within the framework conventional model atmospheres. In particular,
we determined the efficiency of the convective energy transport, and the
efficiency of mixing by convective overshoot. The convective transport
efficiency expressed in terms of an equivalent mixing-length parameter amounts
to values around ~2 in the optically thick, and ~2.8 in the optically thin
regime. The thermal structure of the formally convectively stable layers is
little affected by convective overshoot and wave heating, i.e. stays close to
radiative equilibrium. Mixing by convective overshoot shows an exponential
decline with geometrical distance from the Schwarzschild stability boundary.
The scale height of the decline varies with gravitational acceleration roughly
as g^(-1/2), with 0.5 pressure scale heights at log(g)=5.0.


title: Numerical simulations of surface convection in a late M-dwarf

abstract:
  Based on detailed 2D and 3D numerical radiation-hydrodynamics (RHD)
simulations of time-dependent compressible convection, we have studied the
dynamics and thermal structure of the convective surface layers of a
prototypical late-type M-dwarf (Teff~2800K log(g)=5.0, solar chemical
composition). The RHD models predict stellar granulation qualitatively similar
to the familiar solar pattern. Quantitatively, the granular cells show a
convective turn-over time scale of ~100s, and a horizontal scale of 80km; the
relative intensity contrast of the granular pattern amounts to 1.1%, and
root-mean-square vertical velocities reach 240m/s at maximum. Deviations from
radiative equilibrium in the higher, formally convectively stable atmospheric
layers are found to be insignificant allowing a reliable modeling of the
atmosphere with 1D standard model atmospheres. A mixing-length parameter of
alpha=2.1 provides the best representation of the average thermal structure of
the RHD model atmosphere while alternative values are found when fitting the
asymptotic entropy encountered in deeper layers of the stellar envelope
alpha=1.5, or when matching the vertical velocity field alpha=3.5. The close
correspondence between RHD and standard model atmospheres implies that
presently existing discrepancies between observed and predicted stellar colors
in the M-dwarf regime cannot be traced back to an inadequate treatment of
convection in the 1D standard models. The RHD models predict a modest extension
of the convectively mixed region beyond the formal Schwarzschild stability
boundary which provides hints for the distribution of dust grains in cooler
(brown dwarf) atmospheres.


title: A Low Noise Thermometer Readout for Ruthenium Oxide Resistors

abstract:
  The thermometer and thermal control system, for the Absolute Radiometer for
Cosmology, Astrophysics, and Diffuse Emission (ARCADE) experiment, is
described, including the design, testing, and results from the first flight of
ARCADE. The noise is equivalent to about 1 Omega or 0.15 mK in a second for the
RuO_2 resistive thermometers at 2.7 K. The average power dissipation in each
thermometer is 1 nW. The control system can take full advantage of the
thermometers to maintain stable temperatures. Systematic effects are still
under investigation, but the measured precision and accuracy are sufficient to
allow measurement of the cosmic background spectrum.
  Journal-ref: Review of Scientific Instruments Vol 73 #10 (Oct 2002)


title: On the Stability of Particles in Extrasolar Planetary Systems

abstract:
  In this paper, we present preliminary results on the stability of massless
particles in two and three-planet systems. The results of our study may be used
to address questions concerning the stability of terrestrial planets in these
systems and also the trapping of particles in resonances with the planets. The
possibility of the existence of islands of stability and/or instability at
different regions in multi-body systems and their probable correspondence to
certain resonances are also discussed.


title: The Compton-thick AGN in the GPS radio source OQ+208

abstract:
  We report in this paper the ASCA discovery of the first radio-loud Active
Galactic Nucleus (AGN) covered by a Compton-thick X-ray absorber, in the
GigaHertz Peaked Spectrum (GPS) radio source OQ+208. It represents one of the
few available direct measurements of dense matter in the nuclear environment of
this class of sources, which may provide the confining medium to the
radio-emitting region if GPS sources are indeed "frustrated" classical radio
doubles. The perspective of future studies with XEUS are discussed.


title:
Dynamical Evolution of Solids Subject to the Drag Force and the
  Self-Gravity of an Inhomogeneous and Marginally- Gravitationally Unstable
  Disk

abstract:
  The results of an extensive numerical study of the orbital dynamics of small
bodies ranging from micron-sized dust grains to 1 km objects subject to gas
drag and also the gravitational attraction of a non-uniform gaseous nebula are
presented. The results indicate that it is possible for small bodies to migrate
rapidly toward the locations of the maxima of the gas density where the
probabilities of collisions and coagulations are enhanced.


title:
ROSAT X-ray Spectral Properties of Nearby Young Associations: TW Hydrae,
  Tucana-Horologium, and the beta Pic Moving Group

abstract:
  We present archival ROSAT data for three recently identified, nearby (D<70
pc), young (~10-40 Myr) stellar associations: the TW Hydrae Association, the
Tucana-Horologium Association, and the beta Pic Moving Group. The distributions
of ROSAT X-ray hardness ratios (HR1, HR2) for these three groups, whose
membership is dominated by low-mass, weak-lined T Tauri stars, are tightly
clustered and very similar to one another. The value of HR1 for TW Hya itself
-- the only bona fide classical T Tauri star in any of the nearby groups -- is
clearly anomalous among these nearby young stars. We compare the hardness ratio
distributions of stars in the three nearby groups with those of T Tauri stars,
the Hyades, and main sequence dwarfs in the field. This comparison demonstrates
that the X-ray spectra of F through M stars soften with age, and that F and G
stars evolve more rapidly in X-ray spectral hardness than do K and M stars. It
is as yet unclear whether this trend can be attributed to age-dependent changes
in the intrinsic X-ray spectra of stars of type F and later, to a decrease in
the column density of circumstellar gas (e.g., in residual protoplanetary
disks), or to the diminishing contributions of star-disk interactions to X-ray
emission. Regardless, these results demonstrate that analysis of archival ROSAT
X-ray spectral data can help both to identify nearby, young associations and to
ascertain the X-ray emission properties of members of known associations.


title:
The "Supercritical Pile" Model for GRB: Getting the nu F_{nu} peak at 1
  MeV

abstract:
  We propose that the internal energy of the GRB blast waves, thought to be
stored in the form of relativistic protons co-moving with the blast wave, is
converted explosively (i.e. on light crossing time scales) into relativistic
electrons of the same Lorentz factor, which are responsible for the production
of observed prompt gamma-ray emission of the burst. This conversion is the
result of the combined effects of the reflection of photons produced within the
flow by upstream located matter, their re-interception by the blast wave and
their eventual conversion into e^+e^--pairs in interactions with the
relativistic protons of the blast wave (via the p gamma --> p e^+e^- reaction).
This entire procedure is contingent on two conditions on the relativistic
protons: a kinematic one imposed by the threshold of the p gamma --> e^+e^-
reaction and a dynamic one related to the column density of the post shock
matter to the same process. This latter condition is in essence identical to
that of the criticality of a nuclear pile, hence the terminology. It is argued
that the properties of relativistic blast waves operating under these
conditions are consistent with GRB phenomenology, including the recently found
correlation between quiescence periods and subsequent flare fluence.
Furthermore, it is shown that, when operating near threshold, the resulting GRB
spectrum produces its peak luminosity at an energy (in the lab frame) E ~=
m_ec^2, thereby providing an answer to this outstanding question of GRBs.


title: The Far-Infrared Background Correlation with CMB Lensing

abstract:
  The intervening large--scale structure distorts cosmic microwave background
(CMB) anisotropies via gravitational lensing. The same large--scale structure,
traced by dusty star--forming galaxies, also induces anisotropies in the
far--infrared background (FIRB). We investigate the resulting inter--dependence
of the FIRB and CMB with a halo model for the FIRB. In particular, we calculate
the cross--correlation between the lensing potential and the FIRB. The lensing
potential can be quadratically estimated from CMB temperature and/or
polarization maps. We show that the cross--correlation can be measured with
high signal--to--noise with data from the Planck Surveyor. We discuss how such
a measurement can be used to understand the nature of FIRB sources and their
relation to the distribution of dark matter.


title:
Large-scale Vortices in Protoplanetary Disks: On the observability of
  possible early stages of planet formation

abstract:
  We investigate the possibility of mapping large-scale anti-cyclonic vortices,
resulting from a global baroclinic instability, as pre-cursors of planet
formation in proto-planetary disks with the planned Atacama Large Millimeter
Array (ALMA). On the basis of three-dimensional radiative transfer simulations,
images of a hydrodynamically calculated disk are derived which provide the
basis for the simulation of ALMA. We find that ALMA will be able to trace the
theoretically predicted large-scale anti-cyclonic vortex and will therefore
allow testing of existing models of this very early stage of planet formation
in circumstellar disks.


title:
A variational formalism for tidal excitation: non-rotating, homentropic
  stars

abstract:
  We present a variational formalism for describing the dynamical evolution of
an oscillating star with a point-mass companion in the linear, non-relativistic
regime. This includes both the excitation of normal modes and the back-reaction
of the modes on the orbit. The general formalism for arbitrary fluid
configurations is presented, and then specialized to a homentropic potential
flow. Our formalism explicitly identifies and conserves both energy and angular
momentum. We also consider corrections to the orbit up to 7/2 post-Newtonian
order.


title:
First Interferometric Observations of Molecular Gas in a Polar Ring: The
  Helix Galaxy NGC 2685

abstract:
  We have detected four Giant Molecular cloud Associations (GMAs) (sizes <
6.6'' ~ 430 pc) in the western and eastern region of the polar ring in NGC2685
(the Helix galaxy) using the Owens Valley Radio Observatory (OVRO) millimeter
interferometer. Emission from molecular gas is found close to the brightest
Halpha and HI peaks in the polar ring and is confirmed by new IRAM 30m single
dish observations. The CO and HI line velocities are very similar, providing
additional kinematic confirmation that the CO emission emerges from the polar
ring. For the first time, the total molecular mass within a polar ring is
determined (M_H2~(8-11)x10^6 M_sol, using the standard Galactic conversion
factor). We detect about M_H2~4.4x10^6 M_sol in the nuclear region with the
single dish. Our upper limit derived from the interferometric data is lower
(M_H2<0.7x10^6 M_sol) suggesting that the molecular gas is distributed in an
extended (< 1.3 kpc) diffuse disk. These new values are an order of magnitude
lower than in previous reports. The total amount of molecular gas and the
atomic gas content of the polar ring are consistent with formation due to
accretion of a small gas-rich object, such as a dwarf irregular. The properties
of the NGC2685 system suggest that the polar ring and the host galaxy have been
in a stable configuration for a considerable time (few Gyr). The second (outer)
HI ring within the disk of NGC2685 is very likely at the outer Lindblad
resonance (OLR) of the ~ 11 kpc long stellar bar.


title: Brown Dwarfs as Ejected Stellar Embryos: Observational Perspectives

abstract:
  We discuss a scenario in which brown dwarfs are formed like stars, except
that their full collapse phases are interrupted through dynamical interactions
in small multiple systems, leading to the ejection of the lightest member. This
disintegration is a stochastic process, often resulting in the expulsion of
newborn low mass stars, but when it occurs early enough the ejected stellar
embryo will be a substellar object. This process may be so common at early ages
that a large fraction of the ubiquitous brown dwarfs could have formed in this
manner. Detailed gas dynamical simulations are required in order to better
understand the details of the decay of small newborn multiple systems. We
discuss the observational consequences of the ejection hypothesis, noting
especially the importance of binaries with brown dwarf components as an
observational test. Finally, we note that brown dwarfs that have recently been
ejected may be so disturbed, by infall from the collapsing core and also by
heavy accretion from perturbed circumstellar disks, that traditional spectral
and luminosity criteria may fail to identify their substellar nature.


title: Nova V1974 Cygni - results of the 1997 campaign

abstract:
  This report analyzes the I-band CCD photometry of Nova V1974 Cygni from the
1997 observational season. The analysis shows that both short-term modulations
with periods 0.0813 and 0.085 days are still present in the light curve of the
star. We confirmed the stability of the shorter period which is interpreted as
the orbital period of the binary system. Its value, determined using the O-C
residuals, is P_{orb}=0.08125873(23) days = 117.0126(3) min. The longer period,
which appeared in the light curve in 1994, was decreasing until the beginning
of 1995 but then started to increase quite rapidly. In October 1996 the value
of the period was 122.67\pm0.02 min. Until the next observing run the period
significantly decreased. Its value, determined from our observations performed
in July 1997, was 121.87\pm0.12 min. This means that the rate of change of the
period in 1996-1997 was as high as $\dot P \approx 10^{-6}$. Such a rapid
change of the period requires a large amount of rotational kinetic energy, if
we assume that a 122-min periodicity is the rotation period of a white dwarf.
Thus the more probable explanation is the hypothesis is that the longer period
including a superhump period is caused by the precession of an accretion disc
surrounding a white dwarf primary.


title:
X-ray Evidence for Supermassive Black Holes at the Centers of Nearby
  Galaxies

abstract:
  We first present a short overview of X-ray probes of the black hole region of
active galaxies (AGN) and then concentrate on the X-ray search for supermassive
black holes (SMBHs) in optically non-active galaxies.
  The first part focuses on recent results from the X-ray observatories Chandra
and XMM-Newton which detected a wealth of new spectral features which originate
in the nuclear region of AGN.
  In the last few years, giant-amplitude, non-recurrent X-ray flares have been
observed from several non-active galaxies. All of them share similar
properties, namely: extreme X-ray softness in outburst, huge peak luminosity
(up to ~10^{44} erg/s), and the absence of optical signs of Seyfert activity.
Tidal disruption of a star by a supermassive black hole is the favored
explanation of these unusual events. The second part provides a review of the
initial X-ray observations, follow-up studies,and the relevant aspects of tidal
disruption models studied in the literature.


title:
Magnetic Reconnection Triggered by the Parker Instability in the Galaxy:
  Two-Dimensional Numerical Magnetohydrodynamic Simulations and Application to
  the Origin of X-Ray Gas in the Galactic Halo

abstract:
  We propose the Galactic flare model for the origin of the X-ray gas in the
Galactic halo. For this purpose, we examine the magnetic reconnection triggered
by Parker instability (magnetic buoyancy instability), by performing the
two-dimensional resistive numerical magnetohydrodynamic simulations. As a
result of numerical simulations, the system evolves as following phases: Parker
instability occurs in the Galactic disk. In the nonlinear phase of Parker
instability, the magnetic loop inflates from the Galactic disk into the
Galactic halo, and collides with the anti-parallel magnetic field, so that the
current sheets are created in the Galactic halo. The tearing instability
occurs, and creates the plasmoids (magnetic islands). Just after the plasmoid
ejection, further current-sheet thinning occurs in the sheet, and the anomalous
resistivity sets in. Petschek reconnection starts, and heats the gas quickly in
the Galactic halo. It also creates the slow and fast shock regions in the
Galactic halo. The magnetic field ($B\sim 3 \mu$G), for example, can heat the
gas ($n\sim 10^{-3}$ cm$^{-3}$) to temperature of $\sim 10^6$ K via the
reconnection in the Galactic halo. The gas is accelerated to Alfv\'en velocity
($\sim 300$ km s$^{-1}$). Such high velocity jets are the evidence of the
Galactic flare model we present in this paper, if the Doppler shift of the
bipolar jet is detected in the Galactic halo. Full size figures are available
at http://www.kwasan.kyoto-u.ac.jp/~tanuma/study/ApJ2002/ApJ2002.html