title: Gamma-Ray Bursts and Cosmic Radiation Backgrounds

abstract:
  GRBs contribute to the evolving cosmic radiation field. We discuss the
contribution of GRBs to the high-energy background, and the effect of pair
creation off low-energy photons on their observable TeV spectrum.


title:
Long-Term X-Ray Variabilities of the Seyfert Galaxy MCG-2-58-22 :
  Secular Flux Decrease and Flares

abstract:
  We have studied the long-term X-ray light curve (2$-$10 keV) of the luminous
Seyfert 1 galaxy MCG-2-58-22 by compiling data, from various X-ray satellites,
which together cover more than 20 years. We have found two distinct types of
time variations in the light curve. One is a gradual and secular decrease of
the X-ray flux, and the other is the episodic increase of X-ray flux (or flare)
by a factor of 2$-$4 compared with the level expected from the secular
variation. We detected 3 such flares in total; a representative duration for
the flares is $\sim $2 years, with intervening quiescent intervals lasting
$\sim 6-8$ years. We discuss a few possible origins for these variabilities.
Though a standard disk instability theory may explain the displayed time
variability in the X-ray light curve, the subsequent accretions of stellar
debris, from a tidal disruption event caused by a supermassive black hole in
MCG-2-58-22, cannot be ruled out as an alternative explanation.


title: A Gamma-Ray Burst Bibliography, 1973-2001

abstract:
  On the average, 1.5 new publications on cosmic gamma-ray bursts enter the
literature every day. The total number now exceeds 5300. I describe here a
relatively complete bibliography which is on the web, and which can be made
available electronically in various formats.


title: Observations of the unusual counterpart to the X-ray pulsar AX J0051-733

abstract:
  We report optical and IR observations of the ASCA X-ray pulsar system AX
J0051-733. The relationship between the X-ray source and possible optical
counterparts is discussed. Long term optical data from over 7 years are
presented which reveal both a 1.4d modulation and an unusually rapid change in
this possible binary period. Various models are discussed.


title: Crystalline silicate dust around evolved stars I. The sample stars

abstract:
  This is the first paper in a series of three where we present the first
comprehensive inventory of solid state emission bands observed in a sample of
17 oxygen-rich circumstellar dust shells surrounding evolved stars. The data
were taken with the Short and Long Wavelength Spectrographs on board of the
Infrared Space Observatory (ISO) and cover the 2.4 to 195 micron wavelength
range. The spectra show the presence of broad 10 and 18 micron bands that can
be attributed to amorphous silicates. In addition, at least 49 narrow bands are
found whose position and width indicate they can be attributed to crystalline
silicates. Almost all of these bands were not known before ISO. We have
measured the peak positions, widths and strengths of the individual, continuum
subtracted bands. Based on these measurements, we were able to order the
spectra in sequence of decreasing crystalline silicate band strength. We found
that the strength of the emission bands correlates with the geometry of the
circumstellar shell, as derived from direct imaging or inferred from the shape
of the spectral energy distribution. This naturally divides the sample into
objects that show a disk-like geometry (strong crystalline silicate bands), and
objects whose dust shell is characteristic of an outflow (weak crystalline
silicate bands). All stars with the 33.6 micron forsterite band stronger than
20 percent over continuum are disk sources. We define spectral regions (called
complexes) where a concentration of emission bands is evident, at 10, 18, 23,
28, 33, 40 and 60 micron. We derive average shapes for these complexes and
compare these to the individual band shapes of the programme stars.


title:
Crystalline silicate dust around evolved stars II. The crystalline
  silicate complexes

abstract:
  This is the second paper in a series of three in which we present an
exhaustive inventory of the 49 solid state emission bands observed in a sample
of 17 oxygen-rich dust shells surrounding evolved stars. Most of these emission
bands are concentrated in well defined spectral regions (called complexes). We
define 7 of these complexes; the 10, 18, 23, 28, 33, 40 and 60 micron complex.
We derive average properties of the individual bands. Comparison with
laboratory data suggests that both olivines (Mg(2x)Fe(2-2x)SiO(4)) and
pyroxenes (Mg(x)Fe(1-x)SiO(3)) are present, with x close to 1, i.e. the
minerals are very Mg-rich and Fe-poor. This composition is similar to that seen
in disks surrounding young stars and in the solar system comet Hale-Bopp. A
significant fraction of the emission bands cannot be identified with either
olivines or pyroxenes. Possible other materials that may be the carriers of
these unidentified bands are briefly discussed. There is a natural division
into objects that show a disk-like geometry (strong crystalline silicate
bands), and objects whose dust shell is characteristic of an outflow (weak
crystalline silicate bands). In particular, stars with the 33.5 micron olivine
band stronger than about 20 percent over continuum are invariably disk sources.
Likewise, the 60 micron region is dominated by crystalline silicates in the
disk sources, while it is dominated by crystalline H(2)O ice in the outflow
sources. We show that the disk and outflow sources have significant differences
in the shape of the emission bands. This difference must be related to the
composition or grain shapes of the dust particles. The incredible richness of
the crystalline silicate spectra observed by ISO allows detailed studies of the
mineralogy of these dust shells, and is the origin and history of the dust.


title:
Crystalline silicate dust around evolved stars III. A correlations study
  of crystalline silicate features

abstract:
  We have carried out a quantitative trend analysis of the crystalline
silicates observed in the ISO spectra of a sample of 14 stars with different
evolutionary backgrounds. We have modeled the spectra using a simple dust
radiative transfer model and have correlated the results with other known
parameters. We confirm the abundance difference of the crystalline silicates in
disk and in outflow sources, as found by Molster et al. (1999, Nature 401,
563). We found some indication that the enstatite over forsterite abundance
ratio differs, it is slightly higher in the outflow sources with respect to the
disk sources. It is clear that more data is required to fully test this
hypothesis. We show that the 69.0 micron feature, attributed to forsterite, may
be a very suitable temperature indicator. We found that the enstatite is more
abundant than forsterite in almost all sources. The temperature of the
enstatite grains is about equal to that of the forsterite grains in the disk
sources but slightly lower in the outflow sources. Crystalline silicates are on
average colder than amorphous silicates. This may be due to the difference in
Fe content of both materials. Finally we find an indication that the ratio of
ortho to clino enstatite, which is about 1:1 in disk sources, shifts towards
ortho enstatite in the high luminosity (outflow) sources.


title: Formation of Double Rings Around Evolved Stars

abstract:
  I propose a scenario for the formation of double-ring systems, as observed in
some planetary nebulae and in the outer rings of SN 1987A. In this scenario,
two jets, one jet on each side of the equatorial plane, expand into a thin,
dense shell. Such a flow is expected in binary systems where the mass-losing
primary undergoes an impulsive mass loss episode which forms a thin, dense
shell. I assume that a small fraction of that mass is accreted onto a companion
which blows the jets. Each jet accelerates shell's material it hits sideways,
forming a higher density ring. Using several simplifying assumptions, I derive
an expression for the radius of the ring, which depends relatively weakly on
the jets and impulsive mass loss episode properties. This shows that such a
scenario is feasible. If there are several such impulsive mass loss episodes,
more double rings will be formed, as observed in the planetary nebulae MyCn 18
(the Hourglass nebula). Because of the binary interaction and orbital motion,
the double-ring system is displaced from the symmetry axis of the main nebula,
as observed.


title:
BL Lacertae: complex spectral variability and rapid synchrotron flare
  detected with BeppoSAX

abstract:
  We report on two BeppoSAX observations of BL Lac (2200+420) performed
respectively in June and December 1999, as part of a ToO program to monitor
blazars in high states of activity. During both runs the source has been
detected up to 100 keV, but it showed quite different spectra: in June it was
concave with a very hard component above 5-6 keV (alpha_1 ~ 1.6; alpha_2 ~
0.15); in December it was well fitted by a single power law (alpha ~ 0.6).
During the first BeppoSAX observation BL Lac showed an astonishing variability
episode: the 0.3 - 2 keV flux doubled in ~ 20 minutes, while the flux above 4
keV was almost constant. This frequency-dependent event is one of the shortest
ever recordered for BL Lac objects and places lower limits on the dimension and
the magnetic field of the emitting region and on the energy of the synchrotron
radiating electrons. A similar but less extreme behaviour is detected also in
optical light curves, that display non-simultaneous, smaller fluctuations of ~
20% in 20 min. We fit the spectral energy distributions with a homogeneous,
one-zone model to constrain the emission region in a very simple but effective
SSC + external Compton scenario, highlightning the importance of the location
of the emitting region with respect to the Broad Line Region and the relative
spectral shape dependence. We compare our data with historical radio to
gamma-ray Spectral Energy Distributions.


title: Thermal metastabilities in the solar core

abstract:
  Linear stability analysis indicates that solar core is thermally stable for
infinitesimal internal perturbations. For the first time, thermal
metastabilities are found in the solar core when outer perturbations with
significant amplitude are present. The obtained results show that hot bubbles
generated by outer perturbations may travel a significant distance in the body
of the Sun. These deep-origin hot bubbles have mass, energy, and chemical
composition that may be related to solar flares. The results obtained may have
remarkable relations to activity cycles in planets like Jupiter and also in
extrasolar planetary systems.


title: V407 Vul: a direct impact accretor

abstract:
  V407 Vul (= RXJ1914.4+2457) shows pulsations in X-ray flux on a period of 9.5
minutes, which have been ascribed to accretion onto a magnetic white dwarf,
with the X-ray pulses seen as the accreting pole moves into and out of view.
The X-ray flux drops to zero between pulses, and no other periods are seen,
suggesting that V407 Vul is a type of system known as a ``polar'' in which the
white dwarf has a strong enough field to lock to the orbit of its companion. If
so, then V407 Vul has the shortest orbital period known for any binary star.
However, unlike other polars, V407 Vul shows neither polarization nor line
emission. In this paper we propose that V407 Vul is the first example of a new
type of X-ray emitting binary in which the mass transfer stream directly hits a
non-magnetic white dwarf as a result of the very compact orbit. Our model
naturally explains the X-ray and optical pulsations, as well as the absence of
polarization and line emission. We show that direct impact will occur for
plausible masses of the accreting star and its companion, e.g. M1 ~ 0.5, M2 ~
0.1 Msun. In our model V407 Vul retains its status as the binary star with the
shortest known orbital period, and is therefore a strong source of
low-frequency gravitational waves. V407 Vul is representative of an early phase
of the evolution of the AM CVn class of binary stars and will evolve into the
normal disc-accretion phase on a timescale of 10^6 to 10^7 yr. The existence of
V407 Vul supports the double-degenerate route for the formation of AM CVn
stars.


title:
Theory of synchrotron radiation: I. Coherent emission from ensembles of
  particles

abstract:
  Synchrotron emission of relativistic particles in magnetic fields is a
process of paramount importance in astrophysics. Although known for over thirty
years, there are still aspects of this radiative process that have received
little attention, mainly because they appear only in extreme conditions. In the
present paper, we first provide a general introduction to synchrotron emission,
using a formalism that represents a generalization of the standard
calculations. The use of this formalism allows us to discuss situations in
which charged particles can radiate coherently, with special attention for the
cases in which the production occurs in the form of a bunch of particles
created in a pulse of very short duration. We calculate the spectra of the
radiation for both monoenergetic particles and distributions of particles with
different Lorentz factors. For both cases we study the conditions for the
coherent effects to appear, and demonstrate that in the limit of incoherent
emission we reobtain the well known results.


title: Detection of FeO towards SgrB2

abstract:
  We have observed the J=5-4 ground state transition of FeO at a frequency of
153 GHz towards a selection of galactic sources.
  Towards the galactic center source SgrB2, we see weak absorption at
approximately the velocity of other features towards this source (62 km
s$^{-1}$ LSR).
  Towards other sources, the results were negative as they were also for
MgOH(3-2) and FeC(6-5). We tentatively conclude that the absorption seen toward
SgrB2 is due to FeO in the hot ($\sim $ 500 K) relatively low density absorbing
gas known to be present in this line of sight.
  This is the first (albeit tentative) detection of FeO or any iron--containing
molecule in the interstellar gas. Assuming the observed absorption to be due to
FeO, we estimate [FeO]/[SiO] to be of order or less than 0.002 and
[FeO]/[H$_{2}$] of order $3 10^{-11}$. This is compatible with our negative
results in other sources.
  Our results suggest that the iron liberated from grains in the shocks
associated with SgrB2 remains atomic and is not processed into molecular form.


title:
Theory of synchrotron radiation: II. Backreaction in ensembles of
  particles

abstract:
  The standard calculations of the synchrotron emission from charged particles
in magnetic fields does not apply when the energy losses of the particles are
so severe that their energy is appreciably degraded during one Larmor rotation.
In these conditions, the intensity and spectrum of the emitted radiation depend
on the observation time $T_{obs}$: the standard result is recovered only in the
limit $T_{obs}\ll T_{loss}$, where $T_{loss}$ is the time for synchrotron
losses. In this case the effects of the radiation backreaction cannot be
detected by the observer. We calculate the emitted power of the radiation in
the most general case, naturally including both the cases in which the
backreaction is relevant and the standard case, where the usual result is
recovered. Finally we propose several scenarios of astrophysical interest in
which the effects of the backreaction cannot and should not be ignored.


title: Emission of Positron Annihilation Line Radiation by Clusters of Galaxies

abstract:
  Clusters of galaxies are enriched with positrons from jets of active galactic
nuclei (AGNs) or from the interaction of cosmic rays with the intracluster gas.
We follow the cooling of these positrons and show that their eventual
annihilation with cluster electrons yields a narrow annihilation line. Unlike
annihilation in the interstellar medium of galaxies, the line produced in
clusters is not smeared by three-photon decay of positronium, because
positronium formation is suppressed at the high (>~ 1 keV) temperature of the
cluster electrons. We show that if AGN jets are composed of e^+e^- pairs, then
the annihilation line from rich clusters within a distance of 100 Mpc might be
detectable with future space missions, such as INTEGRAL or EXIST.


title:
Implications of a solar-system population of massive 4th generation
  neutrinos for underground searches of monochromatic neutrino-annihilation
  signals

abstract:
  It has been recently pointed out that any primary galactic population of
Weakly Interacting Massive Particles (WIMP) generates, through collisions with
solar matter, a secondary population of ``slow'' WIMPs trapped in the inner
solar system. We show that taking into account this ``slow'' solar-system
population dramatically enhances the possibility to probe the existence of
stable massive neutrinos (of a 4th generation) in underground neutrino
experiments. Our work suggests that a reanalysis of existing underground
neutrino data should be able to bring extremely tight constraints on the
possible existence of a stable massive 4th neutrino.


title:
The Ionization of the Emission Line Gas in Nearby Powerful Radio
  Galaxies

abstract:
  In this article I review the dominant physical mechanisms in the extended
emission line regions (EELR) of powerful radio galaxies at low redshifts and,
in particular, the balance between jet-induced shocks and AGN photoionization.
I consider the evidence for jet-induced shocks based on morphological,
kinematical and ionization (diagnostic diagram) information. Although each of
these three types of information separately provides some evidence for the
effects of jet-induced shocks, this evidence is often ambiguous. The major
advance in recent years has been to combine morphological, kinematical and
diagnostic diagram approaches. In this way it has been possible to show that
jet-induced shocks dominate the ionization and acceleration of the EELR along
the radio axes of many powerful radio galaxies. However, AGN photoionization is
likely to remain the dominant mechanism in the nuclear regions of radio
galaxies in which the radio sources extend well beyond the emission line
regions.


title: New Approach to Sgr A* Problem

abstract:
  The hypothesis that radiation of Sgr A* is caused by accretion onto a
supermassive compact object without the events horizon is studied. The main
equations of the accretion and a relativistic equation of the trasfer radiation
are obtained. The synchrotron spectrum in the vicinity of the maximum is
considered.


title:
The Environment and Nature of the Class I Protostar Elias 29: Molecular
  Gas Observations and the Location of Ices

abstract:
  A (sub-)millimeter line and continuum study of the class I protostar Elias 29
in the Rho Ophiuchi molecular cloud is presented, whose goals are to understand
the nature of this source, and to locate the ices that are abundantly present
along this line of sight. Within 15-60" beams, several different components
contribute to the line emission. Two different foreground clouds are detected,
an envelope/disk system and a dense ridge of HCO+ rich material. The latter two
components are spatially separated in millimeter interferometer maps. We
analyze the envelope/disk system by using inside-out collapse and flared disk
models. The disk is in a relatively face-on orientation (<60 degrees), which
explains many of the remarkable observational features of Elias 29, such as its
flat SED, its brightness in the near infrared, the extended components found in
speckle interferometry observations, and its high velocity molecular outflow.
It cannot account for the ices seen along the line of sight, however. A small
fraction of the ices is present in a (remnant) envelope of mass 0.12-0.33 Msun,
but most of the ices (~70%) are present in cool (T<40 K) quiescent foreground
clouds. This explains the observed absence of thermally processed ices
(crystallized H2O) toward Elias 29. Nevertheless, the temperatures could be
sufficiently high to account for the low abundance of apolar (CO, N2, O2) ices.
This work shows that it is crucial to obtain spectrally and spatially resolved
information from single-dish and interferometric molecular gas observations in
order to determine the nature of protostars and to interpret infrared ISO
satellite observations of ices and silicates along a pencil beam.


title: Accretion during the merger of supermassive black holes

abstract:
  We study the evolution of disk accretion during the merger of supermassive
black hole binaries in galactic nuclei. In hierarchical galaxy formation
models, the most common binaries are likely to arise from minor galactic
mergers, and have unequal mass black holes. Once such a binary becomes embedded
in an accretion disk at a separation of the order of 0.1 pc, the merger
proceeds in two distinct phases. During the first phase, the loss of orbital
angular momentum to the gaseous disk shrinks the binary on a timescale of ~10
Myr. The accretion rate onto the primary black hole is not increased, and can
be substantially reduced, during this disk-driven migration. At smaller
separations, gravitational radiation becomes the dominant angular momentum loss
process, and any gas trapped inside the orbit of the secondary is driven
inwards by the inspiralling black hole. The implied accretion rate just prior
to coalescence exceeds the Eddington limit, so the final merger is likely to
occur within a common envelope formed from the disrupted inner disk, and be
accompanied by high velocity (~10,000 km/s) outflows.


title: The FUV spectrum of TW Hya. I. Observations of H$_2$ Fluorescence

abstract:
  We observed the classical T Tauri star TW Hya with \textit{HST}/STIS using
the E140M grating, from 1150--1700 \AA, with the E230M grating, from 2200--2900
\AA, and with \FUSE from 900--1180 \AA. Emission in 143 Lyman-band H$_2$ lines
representing 19 progressions dominates the spectral region from 1250--1650 \AA.
The total H$_2$ emission line flux is $1.94 \times 10^{-12}$ erg cm$^{-2}$
s$^{-1}$, which corresponds to $1.90\times10^{-4}$ $L_\odot$ at TW Hya's
distance of 56 pc. A broad stellar \Lya line photoexcites the H$_2$ from
excited rovibrational levels of the ground electronic state to excited
electronic states. The \ion{C}{2} 1335 \AA doublet, \ion{C}{3} 1175 \AA\
multiplet, and \ion{C}{4} 1550 \AA doublet also electronically excite H$_2$.
The velocity shift of the H$_2$ lines is consistent with the photospheric
radial velocity of TW Hya, and the emission is not spatially extended beyond
the $0\farcs05$ resolution of \textit{HST}. The H$_2$ lines have an intrinsic
FWHM of $11.91\pm0.16$ \kms. One H$_2$ line is significantly weaker than
predicted by this model because of \ion{C}{2} wind absorption. We also do not
observe any H$_2$ absorption against the stellar \Lya profile. From these
results, we conclude that the H$_2$ emission is more consistent with an origin
in a disk rather than in an outflow or circumstellar shell. We also analyze the
hot accretion-region lines (e.g., \ion{C}{4}, \ion{Si}{4}, \ion{O}{6}) of TW
Hya, which are formed at the accretion shock, and discuss some reasons why Si
lines appear significantly weaker than other TR region lines.


title:
Migration of giant planets in a time-dependent planetesimal accretion
  disc

abstract:
  In this paper, we further develop the model for the migration of planets
introduced in Del Popolo et al. (2001). We first model the protoplanetary
nebula as a time-dependent accretion disc and find self-similar solutions to
the equations of the accretion disc that give to us explicit formulas for the
spatial structure and the temporal evolution of the nebula. These equations are
then used to obtain the migration rate of the planet in the planetesimal disc
and to study how the migration rate depends on the disc mass, on its time
evolution and on some values of the dimensionless viscosity parameter alpha. We
find that planets that are embedded in planetesimal discs, having total mass of
10^{-4}-0.1 M_{\odot}, can migrate inward a large distance for low values of
alpha (e.g., alpha \simeq 10^{-3}-10^{-2}) and/or large disc mass and can
survive only if the inner disc is truncated or because of tidal interaction
with the star. Orbits with larger $a$ are obtained for smaller value of the
disc mass and/or for larger values of alpha. This model may explain several
orbital features of the recently discovered giant planets orbiting nearby
stars.


title: Prompt Emission and Early Afterglows of Gamma-Ray Bursts

abstract:
  Observations and models of GRBs are reviewed with an emphasis on the early
phase of the burst. Recent revision of the early afterglow model is described.


title: Off-Axis Afterglow Emission from Jetted Gamma-Ray Bursts

abstract:
  We calculate Gamma-Ray Burst afterglow light-curves from a relativistic jet
of initial opening angle theta_0, as seen by observers at a wide range of
viewing angles, theta_obs, from the jet axis. We describe three increasingly
more realistic models and compare the resulting light-curves. An observer at
theta_obs < theta_0 should see a light curve very similar to that for an
on-axis observer. An observer at theta_obs > theta_0 should see a rising light
curve at early times, the flux peaking when the jet Lorentz factor sim
1/theta_obs. After this time the flux is not very different from that seen by
an on-axis observer. A strong linear polarization (<40%) may occur near the
peak in the light curve, and slowly decay with time. We show that if GRB jets
have a universal energy, then orphan afterglows associated with off-axis jets
should be seen up to a constant theta_obs, therefore the detection rate of
orphan afterglows would be proportional to the true GRB rate. We also discuss
the proposed connection between supernova 1998bw and GRB 980425.


title: New UBVRI colour distributions in E-type galaxies I.The data

abstract:
  New colour distributions have been derived from wide field UBVRI frames for
36 northern bright elliptical galaxies and a few lenticulars. The classical
linear representations of colours against log r were derived, with some
improvements in the accuracy of the zero point colours and of the gradients.
The radial range of signicant measurements was enlarged both towards the
galaxian center and towards the outskirts of each object. Thus, the "central
colours", integrated within a radius of 3", and the "outermost colours"
averaged near the mu_V = 24 surface brightness, could also be obtained. Some
typical deviations of colour profiles from linearity are described.
Colour-colour relations of interest are presented. Very tight correlations are
found between the U-V colour and the Mg2 line-index, measured either at the
galaxian center or at the effective radius.


title: The Smallest Mass Ratio Young Star Spectroscopic Binaries

abstract:
  Using high resolution near-infrared spectroscopy with the Keck telescope, we
have detected the radial velocity signatures of the cool secondary components
in four optically identified pre-main-sequence, single-lined spectroscopic
binaries. All are weak-lined T Tauri stars with well-defined center of mass
velocities. The mass ratio for one young binary, NTTS 160905-1859, is M2/M1 =
0.18+/-0.01, the smallest yet measured dynamically for a pre-main-sequence
spectroscopic binary. These new results demonstrate the power of infrared
spectroscopy for the dynamical identification of cool secondaries. Visible
light spectroscopy, to date, has not revealed any pre-main-sequence secondary
stars with masses <0.5 M_sun, while two of the young systems reported here are
in that range. We compare our targets with a compilation of the published young
double-lined spectroscopic binaries and discuss our unique contribution to this
sample.


title: Hot Bubbles in Cooling Flow Clusters

abstract:
  As more cooling flow clusters of galaxies with central radio sources are
observed with the Chandra and XMM-Newton X-ray Observatories, more examples of
"bubbles" (low-emission regions in the X-ray coincident with radio emission)
are being found. These bubbles are surrounded by bright shells of X-ray
emission, and no evidence of current strong shocks has yet been found. Using an
analytic approach and some simplifying assumptions, we derive expressions
relating the size and location of a bubble, as well as the density contrast
between the bubble and the ambient medium, with the shock history of the
bubble. These can be applied straightforwardly to new observations. We find
that existing observations are consistent with a mild shock occurring in the
past, and with the bulk of the cool material in the X-ray shells being cooled
at the cluster center and then pushed outward by the radio source. Strong
shocks are ruled out unless they occurred more than 1 Gyr ago. We also discuss
Rayleigh-Taylor instabilities as well as the case of a bubble expanding into an
older bubble produced from a previous cycle of radio activity.


title:
The Nature of the faint far-infrared extragalactic source population:
  Optical/NIR and radio follow-up observations of ISOPHOT deep-field sources
  using Keck, Subaru, and VLA telescopes

abstract:
  We report on optical and near-infrared (NIR) follow-up spectroscopy of faint
far-infrared (FIR) sources found in our deep FIR survey by Kawara et al.


title: Trans-Magnetosonic Accretion in a Black Hole Magnetosphere

abstract:
  We present the critical conditions for hot trans-fast magnetohydrodynamical
(MHD) flows in a stationary and axisymmetric black-hole magnetosphere. To
accrete onto the black hole, the MHD flow injected from a plasma source with
low velocity must pass through the fast magnetosonic point after passing
through the ``inner'' or ``outer'' Alfven point. We find that a trans-fast MHD
accretion solution related to the inner Alfven point is invalid when the
hydrodynamical effects on the MHD flow dominate at the magnetosonic point,
while the other accretion solution related to the outer Alfven point is invalid
when the total angular momentum of the MHD flow is seriously large. When both
regimes of the accretion solutions are valid in the black hole magnetosphere,
we can expect the transition between the two regimes. The variety of these
solutions would be important in many highly energetic astrophysical situations.


title: The Bulk of the Cosmic Infrared Background Resolved by ISOCAM

abstract:
  We have computed the 15 microns integrated galaxy light produced by ISOCAM
galaxies above a sensitivity limit of 50 microJy. It sets a lower limit to the
15 microns extragalactic background light of (2.4+/-0.5) nW/m^2/Hz. The
redshift distribution of the ISOCAM galaxies is inferred from the
spectroscopically complete sample of galaxies in the Hubble Deep Field North
(HDFN). We demonstrate that mid (MIR) and far (FIR) infrared luminosities
correlate for local star forming galaxies and that this correlation is
consistent with the radio-FIR one up to z ~ 1. From these correlations, about
75 % of the ISOCAM galaxies are found to belong to the class of luminous
infrared galaxies (L[IR] >= 10^11 Lsol), with star formation rates of the order
of ~ 100 Msol/yr. The cross-correlation with the deepest X-ray surveys from the
Chandra and XMM-Newton observatories in the HDFN and Lockman Hole respectively,
indicates that at most 20 % of the 15 microns integrated galaxy light is due to
active galactic nuclei (AGNs) unless a large population of AGNs was missed by
Chandra and XMM-Newton. The contribution of ISOCAM galaxies to the peak of the
cosmic infrared background (CIRB) at 140 microns was computed from the MIR-FIR
correlations for star forming galaxies and from the spectral energy
distribution of the Seyfert 2, NGC 1068, for AGNs. We find that the galaxies
unveiled by ISOCAM surveys are responsible for the bulk of the CIRB, i.e
(16+/-5) nW/m^2/Hz as compared to the (25+/-7) nW/m^2/Hz measured with the COBE
satellite, with less than 10 % due to AGNs. Since the CIRB contains most of the
light radiated over the history of star formation in the universe, this means
that a large fraction of present-day stars must have formed during a dusty
starburst event similar to those revealed by ISOCAM.


title:
Dynamical evolution driven by bars and interactions : Input from
  numerical simulations

abstract:
  We discuss the evolution of a disc galaxy due to the formation of a bar and,
subsequently, a peanut. After the formation stage there is still considerable
evolution, albeit slower. In purely stellar cases the pattern speed of the bar
decreases with time, while its amplitude grows. However, if a considerable
gaseous component is present in the disc, the pattern speed may increase with
time, while the bar strength may decrease. In some cases the gas can be brought
sufficiently close to the center to create a strong central concentration,
which, in turn, may modify the properties of the bar.
  More violent evolution can take place during interactions, so that some disc
substructures can be either formed or destroyed in a time scale which is small
compared to a Hubble time. These include spirals, bars, bridges, tails, rings,
thick discs and bulges. In some cases interactions may lead to mergings. We
briefly review comparisons of the properties of merger remnants with those of
elliptical galaxies, both for the case of pairwise mergings and the case of
multiple mergings.


title: Dust emission and star formation toward a redshift 5.5 QSO

abstract:
  We report observations of the low-luminosity z = 5.50 quasar RD
J030117+002025 (RD0301 hereafter) at 250 GHz (1.20mm) using the Max-Planck
Millimeter Bolometer (MAMBO) array at the IRAM 30-meter telescope. The quasar
was detected with a 1.2mm flux density of 0.87 +-0.20 mJy. The lack of
detectable 1.4 GHz radio emission indicates that the millimeter emission is of
thermal nature, making RD0301 the most distant dust-emission source known. When
matching a 50K grey body thermal far-infrared (FIR) spectrum to the observed
millimeter flux we imply a FIR luminosity ~4x10^12 L_sun, which is comparable
to the quasar's optical luminosity. If the FIR luminosity arises from massive
star formation, the implied star formation rate would be ~600 M_sun/yr,
comparable to that of the starburst galaxies which dominate the average star
formation and FIR emission in the early Universe. The FIR luminosity of RD0301
is close to the average of that found in optically far more luminous
high-redshift quasars. The comparably high millimeter to optical brightness
ratio of RD0301 is further evidence for that there is no strong correlation
between the optical and millimeter brightness of high-redshift quasars,
supporting the idea that in high-redshift quasars the dust is not heated by the
AGN, but by starbursts.


title: Resolving the Spin Crisis: Mergers and Feedback

abstract:
  We model in simple terms the angular momentum (J) problem of galaxy formation
in CDM, and identify the key elements of a scenario that can solve it. The
buildup of J is modeled via dynamical friction and tidal stripping in mergers.
This reveals how over-cooling in incoming halos leads to transfer of J from
baryons to dark matter (DM), in conflict with observations. By incorporating a
simple recipe of supernova feedback, we match the observed J distribution in
disks. Gas removal from small incoming halos, which make the low-J component of
the product, eliminates the low-J baryons. Partial heating and puffing-up of
the gas in larger incoming halos, combined with tidal stripping, reduces the J
loss of baryons. This implies a higher baryonic spin for lower mass halos. The
observed low baryonic fraction in dwarf galaxies is used to calibrate the
characteristic velocity associated with supernova feedback, yielding v_fb sim
100 km/s, within the range of theoretical expectations. The model then
reproduces the observed distribution of spin parameter among dwarf and bright
galaxies, as well as the J distribution inside these galaxies. This suggests
that the model captures the main features of a full scenario for resolving the
spin crisis.


title: On the X-ray emission of the low-mass galaxy groups

abstract:
  It is shown that the low-mass groups obey the $L_{x}\sim\sigma_v^{4}$ law
deduced for galaxy clusters. The impression of the more shallow slope of the
$L_x-\sigma_{v}$ correlation for groups is created not by enhanced X-ray
emission, but by underestimation of the radial velocity dispersion of some
groups.


title: AGB Stars: Summary and Warning

abstract:
  The Asymptotic Giant Branch (AGB) phase is very short but its importance is
seen in its nucleosynthesis. A revolution in stellar modelling has taken place
in the last 20 years, inspired jointly by this rich nucleosynthesis and partly
by new data. For example, the isotopic data coming from pre-solar grains (see
this volume) forces theorists to include species that were previously ignored,
species which are energetically of no importance (i.e. they play no role in
determining the stellar structure) but which can be used to constrain the
models. Nucleosynthesis is now important as a tracer of temperature and mixing,
and not simply a by-product of energy generation. But along with these advances
come more quantitative demands. It is now increasingly important to know what
is known well and what is less sure. This is the goal of this paper.


title:
An attempt to model globular cluster red-giant abundance anomalies with
  a simulated hydrogen shell instability

abstract:
  It has been suggested that the anomalous Na, Mg and Al observed in Globular
Cluster Red Giant stars could be the result of a thermally unstable hydrogen
shell. Currently accepted reaction rates indicate that temperatures of
approximately 70-75 million K are required to produce the observed enhancements
in Na and Al along with depletions in Mg.
  The work presented here attempts to model the H shell instability by a simple
mechanism of altering the energy production in the region of the H shell. We
show that even extreme cases only give rise to small intermittent temperature
increases that have minimal affect on the surface abundances. Full evolutionary
modelling incorporating this technique simply accelerates the evolution of the
RGB phase producing the same surface abundances as other models but at an
earlier time. We conclude that, unless hydrogen shell instabilities manifest
themselves quite differently, they are unlikely to lead to the required
temperatures and alternative explanations of the abundance anomalies are more
promising.


title: On the dark energy clustering properties

abstract:
  We highlight a viable mechanism leading to the formation of dark energy
structures on sub-horizon cosmological scales, starting from linear
perturbations in scalar-tensor cosmologies. We show that the coupling of the
dark energy scalar field, or Quintessence, to the Ricci scalar induces a
"dragging" of its density perturbations through the general relativistic
gravitational potentials. We discuss, in particular, how this process forces
dark energy to behave as a pressureless component if the cosmic evolution is
dominated by non-relativistic matter. This property is also analyzed in terms
of the effective sound speed of the dark energy, which correspondingly
approaches the behavior of the dominant cosmological component, being
effectively vanishing after matter-radiation equality. To illustrate this
effect, we consider Extended Quintessence scenarios involving a quadratic
coupling between the field and the Ricci scalar. We show that Quintessence
density perturbations reach non-linearity at scales and redshifts relevant for
the structure formation process, respecting all the existing constraints on
scalar-tensor theories of Gravity. This study opens new perspectives on the
standard picture of structure formation in dark energy cosmologies, since the
Quintessence field itself, if non-minimally coupled to Gravity, may undergo
clustering processes, eventually forming density perturbations exiting from the
linear regime. A non-linear approach is then required to further investigate
the evolution of these structures, and in particular their role in the dark
haloes surrounding galaxies and clusters.


title:
Probing quintessence: reconstruction and parameter estimation from
  supernovae

abstract:
  We explore the prospects for using future supernova observations to probe the
dark energy. We focus on quintessence, an evolving scalar field that has been
suggested as a candidate for the dark energy. After simulating the observations
that would be expected from the proposed SuperNova / Acceleration Probe
satellite (SNAP), we investigate two methods for extracting information about
quintessence from such data. First, by expanding the quintessence equation of
state as w_Q(z) = w_Q(0)-alpha*ln(1+z), to fit the data, it is possible to
reconstruct the quintessence potential for a wide range of smoothly varying
potentials. Second, it will be possible, to test the basic properties of the
dark energy by constraining the parameters Omega_Q, w_Q and alpha. We show that
it may be possible, for example, to distinguish between quintessence and the
cosmological constant in this way. Further, when supernova data are combined
with other planned cosmological observations, the precision of reconstructions
and parameter constraints is significantly improved, allowing a wider range of
dark energy models to be distinguished.


title:
A Statistical Analysis of The Extrasolar Planets and The Low-Mass
  Secondaries

abstract:
  We show that the astrometric Hipparcos data of the stars hosting planet
candidates are not accurate enough to yield statistically significant orbits.
Therefore, the recent suggestion, based on the analysis of the Hipparcos data,
that the orbits of the sample of planet candidates are not randomly oriented in
space, is not supported by the data. Assuming random orientation, we derive the
mass distribution of the planet candidates and show that it is flat in log M,
up to about 10 Jupiter masses. Furthermore, the mass distribution of the planet
candidates is well separated from the mass distribution of the low-mass
companions by the 'brown-dwarf desert'. This indicates that we have here two
distinct populations, one which we identify as the giant planets and the other
as stellar secondaries. We compare the period and eccentricity distributions of
the two populations and find them surprisingly similar. The period
distributions between 10 and 1650 days are flat in log period, indicating a
scale-free formation mechanism in both populations. We further show that the
eccentricity distributions are similar - both have a density distribution peak
at about 0.2-0.4, with some small differences on both ends of the eccentricity
range. We present a toy model to mimic both distributions. We found a
significant paucity of massive giant planets with short orbital periods. The
low frequency of planets is noticeable for masses larger than about 1 Jupiter
Mass and periods shorter than 30 days. We point out how, in principle, one can
account for this paucity.


title: Mid-IR Observations of Mass Loss in Elliptical Galaxies

abstract:
  Early-type galaxies exhibit thermal and molecular resonance emission from
dust that is shed and heated through stellar mass loss as a subset of the
population moves through the AGB phase of evolution. Because this emission can
give direct insight into stellar evolution in addition to galactic stellar mass
loss and ISM injection rates, we conducted a program to search for this
signature emission with CAM on ISO. We obtained 6-15 micron imaging
observations in six narrow bands for nine elliptical galaxies; every galaxy is
detected in every band. For wavelengths shorter than 9 microns, the spectra are
well matched by a blackbody, originating from the K and M stars that dominate
the integrated light of elliptical galaxies. However, at wavelengths between 9
and 15 microns, the galaxies display excess emission relative to the stellar
photospheric radiation. Additional data taken with the fine resolution circular
variable filter on one source clearly shows broad emission from 9 to 15
microns, peaking around 10 microns. This result is consistent with the known,
broad silicate feature at 9.7 microns, originating in the circumstellar
envelopes of AGB stars. This emission is compared with studies of Galactic and
LMC AGB stars to derive cumulative mass loss rates. In general, these mass loss
rates agree with the expected ~0.8 solar masses per year value predicted by
stellar evolutionary models. Both the photospheric and circumstellar envelope
emission follow a de Vaucouleurs' R^{1/4} law, supporting the conclusion that
the mid-infrared excess emission originates in the stellar component of the
galaxies and acts as a tracer of AGB mass loss and mass injection into the ISM.


title: Kilohertz QPO Frequency Anti-Correlated with mHz QPO Flux in 4U 1608-52

abstract:
  We analysed {\it Rossi X-ray Timing Explorer} (RXTE) data of the low-mass
X-ray binary and atoll source 4U 1608-52 obtained on March 3, 1996 in which the
source simultaneously showed a strong single kilohertz quasi-periodic
oscillation (QPO) around 840 Hz, and a 7.5 mHz QPO detected at energies below 5
keV. We find that the frequency of the kHz QPO is approximately anti-correlated
with the 2--5 keV X-ray count rate associated with the mHz QPO. The average kHz
QPO frequency varies by about 0.6 Hz (0.07%) during a mHz QPO cycle over which
the average 2--5 keV count rate varies by about 60 c/s (4%). This is opposite
to the frequency-count rate correlation observed in the same data on longer
time scales and hence constitutes the first example of a sign reversal in the
frequency-flux correlation related to the origin of the flux. Such a sign
reversal is predicted by the radiative disk truncation model for the case where
the flux variations originate on the neutron star but are not due to disk
accretion rate fluctuations. The results support the nuclear burning
interpretation of the mHz QPO, and the interpretation of the kHz QPO frequency
as an indicator of the orbital frequency at the inner edge of the accretion
disk. The varying radiative stresses on the inner disk exerted by the flux due
to the quasi-periodic nuclear burning lead to changes in the inner disk radius
and hence to the observed anti-correlation between kHz QPO frequency and X-ray
count rate. There is a time lag of about ten seconds of the X-ray count rate
relative to the kHz QPO frequency in terms of the anti-correlation we found
between these two quantities, which could be caused by the propagation of the
nuclear burning front on the neutron star away from the equatorial region.


title:
Calibration of the distance scale from galactic Cepheids: I Calibration
  based on the GFG sample

abstract:
  New estimates of the distances of 36 nearby galaxies are presented based on
accurate distances of galactic Cepheids obtained by Gieren, Fouque and Gomez
(1998) from the geometrical Barnes-Evans method.
  The concept of 'sosie' is applied to extend the distance determination to
extragalactic Cepheids without assuming the linearity of the PL relation. Doing
so, the distance moduli are obtained in a straightforward way.
  The correction for extinction is made using two photometric bands (V and I)
according to the principles introduced by Freedman and Madore (1990). Finally,
the statistical bias due to the incompleteness of the sample is corrected
according to the precepts introduced by Teerikorpi (1987) without introducing
any free parameters (except the distance modulus itself in an iterative
scheme).
  The final distance moduli depend on the adopted extinction ratio {R_V}/{R_I}
and on the limiting apparent magnitude of the sample. A comparison with the
distance moduli recently published by the Hubble Space Telescope Key Project
(HSTKP) team reveals a fair agreement when the same ratio {R_V}/{R_I} is used
but shows a small discrepancy at large distance.
  In order to bypass the uncertainty due to the metallicity effect it is
suggested to consider only galaxies having nearly the same metallicity as the
calibrating Cepheids (i.e. Solar metallicity). The internal uncertainty of the
distances is about 0.1 magnitude but the total uncertainty may reach 0.3
magnitude.


title: Accretion of gas by globular cluster stars

abstract:
  Some recent observations of the abundances of s-process, r-process, and alpha
elements in metal-poor stars have led to a new scenario for their formation.
According to this scenario, these stars were born in a globular cluster and
accreted the s-process enriched gas expelled by cluster stars of higher-mass,
thereby modifying their surface abundances. Later on, these polluted stars
evaporated from the globular cluster to constitute an important fraction of the
current halo population. In addition, there are now many direct observations of
abundance anomalies not only in globular cluster giant stars but also in
subgiant and main-sequence stars. Accretion provides again a plausible
explanation for (at least some of) these peculiarities. Here we investigate
further the efficiency of the accretion scenario. We find that in concentrated
clusters with large escape velocities, accretion is very efficient and can
indeed lead to major modifications of the stellar surface abundances.


title: Gamma Ray Bursts from the First Stars: Neutrino Signals

abstract:
  If the first (PopIII) stars were very massive, their final fate is to
collapse into very massive black holes. Once a proto-black hole has formed into
the stellar core, accretion continues through a disk. It is widely accepted,
although not confirmed, that magnetic fields drive an energetic jet which
produces a burst of TeV neutrinos by photon-meson interaction, and eventually
breaks out of the stellar envelope appearing as a Gamma Ray Burst (GRB). Based
on recent numerical simulations and neutrino emission models, we predict the
expected neutrino diffuse flux from these PopIII GRBs and compare it with the
capabilities of present and planned detectors as AMANDA and IceCube. If beamed
into 1% of the sky, we find that the rate of PopIII GRBs is $\le 4 \times 10^6$
yr$^{-1}$. High energy neutrinos from PopIII GRBs could dominate the overall
flux in two energy bands [$10^4 - 10^5$] GeV and [$10^5 - 10^6$] GeV of
neutrino telescopes. The enhanced sensitivities of forthcoming detectors in the
high-energy band (AMANDA-II, IceCube) will provide a fundamental insight on the
characteristic explosion energies of PopIII GRBs and will constitute a unique
probe of the the Initial Mass Function (IMF) of the first stars and of the
redshift $z_f$ marking the metallicity-driven transition from a top-heavy to a
normal IMF. The current upper limit set by AMANDA-B10 implies that such
transition must have occurred not later than $z_f =9.2$ for the most plausible
jet energies. Based on such results, we speculate that PopIII GRBs, if not
chocked, could be associated with a new class of events detected by BeppoSax,
the Fast X-ray Transient (FXTs), which are bright X-ray sources, with peak
energies in the 2-10 keV band and durations between 10-200 s.


title:
Distribution of EAS arrival times according to data of the EAS-1000
  prototype array

abstract:
  We have analysed arrival times of extensive air showers (EAS) registered with
the EAS-1000 prototype array during the period from August, 1997 till February,
1999. Our analysis has revealed that though the vast majority of samples of
consecutive time intervals between EAS arrival times obey the exponential
distribution, there are sequences of showers that have another distribution and
thus violate the homogeneity hypothesis. The search for correlation between
such events and clusters of showers and events with big delays between arrival
times was also carried out.


title: The Gravitational Lens CFRS03.1077

abstract:
  An exquisite gravitational arc with a radius of 2.1" has been discovered
around the z = 0.938 field elliptical galaxy CFRS03.1077 during HST
observations of Canada-France Redshift Survey (CFRS) fields. Spectroscopic
observations of the arc show that the redshift of the resolved lensed galaxy is
z = 2.941. This gravitational lens-source system is well-fitted using the
position angle and ellipticity derived from the visible matter distribution and
an isothermal mass profile with a mass corresponding to sigma =387+-5 km/s.
Surprisingly, given the evidence for passive evolution of elliptical galaxies,
this is in good agreement with an estimate based on the fundamental plane for z
= 0 ellipticals. This, perhaps, indicates that this galaxy has not shared in
the significant evolution observed for average elliptical galaxies at z ~ 1. A
second elliptical galaxy with similar luminosity from the CFRS survey, CFRS
14.1311 at z=0.807, is also a lens but in this case the lens model gives a much
smaller mass-to-light ratio, i.e., it appears to confirm the expected
evolution. This suggests that this pair of field elliptical galaxies may have
very different evolutionary histories, a significant result if confirmed.
Clearly, CFRS03.1077 demonstrates that these "Einstein rings" are powerful
probes of high redshift galaxies.


title: The gradient of diffuse gamma-ray emission in the Galaxy

abstract:
  We show that the well-known discrepancy between the radial dependence of the
Galactic cosmic ray (CR) nucleon distribution, as inferred most recently from
EGRET observations of diffuse gamma-rays above 100 MeV, and of the most likely
CR source distribution (supernova remnants, pulsars) can be explained purely by
PROPAGATION effects. Contrary to previous claims, we demonstrate that this is
possible, if the dynamical coupling between the escaping CRs and thermal plasma
is taken into account, and thus a self-consistent GALACTIC WIND calculation is
carried out. Given a dependence of the CR source distribution on Galactocentric
radius, r, our numerical wind solutions show that the CR outflow velocity,
V(r,z) depends both on r, and on vertical distance, z, at reference level z_C.
The latter is defined as the transition boundary from diffusion to advection
dominated CR transport and is therefore also a function of r. In fact, the CR
escape time averaged over particle energies decreases with increasing CR source
strength. Such an increase is counteracted by a reduced average CR residence
time in the gas disk. Therfore pronounced peaks in the radial source
distribution result in mild radial gamma-ray gradients at GeV energies, as it
has been observed. This effect is enhanced by anisotropic diffusion, assuming
different radial and vertical diffusion coefficients. We have calculated 2D
analytic solutions of the stationary diffusion-advection equation, including
anisotropic diffusion, for a given CR source distribution and a realistic
outflow velocity field V(r,z), inferred from self-consistent numerical Galactic
Wind simulations. At TeV energies the gamma-rays from the sources are expected
to dominate the observed "diffuse" flux from the disk. Its observation should
allow an empirical test of the theory presented.


title:
Efficiency of Electron-Positron Pair Productionby Neutrino Flux from
  Accretion Disk of a Kerr Black Hole

abstract:
  Dominant processes of neutrino production and neutrino-induced \ep-pair
production are examined in the model of a disk hyper-accreting onto a Kerr
black hole. The efficiency of plasma production by a neutrino flux from the
disk, obtained for the both cases of presence and absence of a magnetic field,
is found to be no more than several tenths of percent and, therefore, not
enough for the origin of cosmological gamma-ray bursts.


title:
Magnetic Fields in Star-Forming Molecular Clouds III. Submillimeter
  Polarimetry of Intermediate Mass Cores and Filaments in Orion B

abstract:
  Using the imaging polarimeter for the Submillimeter Common User Bolometric
Array at the James Clerk Maxwell Telescope, we have detected polarized thermal
emission at 850 micron from dust toward three star-forming core systems in the
Orion B molecular cloud: NGC 2071, NGC 2024 and LBS 23N (HH 24). The
polarization patterns are not indicative of those expected for magnetic fields
dominated by a single field direction, and all exhibit diminished polarization
percentages toward the highest intensity peaks. NGC 2024 has the most organized
polarization pattern which is centered consistently along the length of a chain
of 7 far-infrared sources. We have modeled NGC 2024 using a helical field
geometry threading a curved filament and also as a magnetic field swept up by
the ionization front of the expanding HII region. In the latter case, the field
is bent by the dense ridge, which accounts for both the polarization pattern
and existing measurements of the line-of-sight field strength toward the
northern cores FIR 1 to FIR 4. The direction of the net magnetic field
direction within NGC 2071 is perpendicular to the dominant outflow in that
region. Despite evidence that line contamination exists in the 850 micron
continuum, the levels of polarization measured indicate that the polarized
emission is dominated by dust.


title:
Magnetic Fields in Star-Forming Molecular Clouds IV. Polarimetry of the
  Filamentary NGC 2068 Cloud in Orion B

abstract:
  We present submillimeter polarimetry at 850 micron toward the filamentary
star-forming region associated with the reflection nebulosity NGC 2068 in Orion
B. These data were obtained using the James Clerk Maxwell Telescope's SCUBA
polarimeter. The polarization pattern observed is not consistent with that
expected for a field geometry defined by a single mean field direction. There
are three distinct distributions of polarization angle, which could represent
regions of differing inclination and/or field geometry within the filamentary
gas. In general, the polarization pattern does not correlate with the
underlying total dust emission. The presence of varying inclinations against
the plane of the sky is consistent with the comparison of the 850 micron
continuum emission to the optical emission from the Palomar Optical Sky Survey,
which shows that the western dust emission lies in the foreground of the
optical nebula while the eastern dust emission originates in the background.
Percentage polarizations are high, particularly toward the north-east region of
the cloud. The mean polarization percentage in the region is 5.0% with a
standard deviation of 3.1%. Depolarization toward high intensities is
identified in all parts of the filament.


title:
Recent CHANDRA and XMM observations of two very different galaxy
  clusters: RBS797 and CL 0939+4713

abstract:
  RBS797 and CL 0939+4713 are two intermediate red-shift clusters
($z=0.35-0.41$). They have very different morphologies but both show
surprisingly interesting structures. RBS797 looks relaxed, with an almost
circular morphology; a CHANDRA observation of this cluster has revealed two
deep depressions in the X-ray emission near the core. CL 0939+4713 has instead
an irregular morphology with evident substructures which seem to be in the
process of merging.


title: HETE-II and the Interplanetary Network

abstract:
  The FREGATE experiment aboard HETE-II has been successfully integrated into
the Third Interplanetary Network (IPN) of gamma-ray burst detectors. We show
how HETE's timing has been verified in flight, and discuss what HETE can do for
the IPN and vice-versa.


title:
A FUSE Survey of Interstellar O VI Absorption in the Small Magellanic
  Cloud

abstract:
  We present the results of a FUSE survey of O VI 1031.93 Angstrom and 1037.62
Angstrom absorption toward 18 OB stars in the Small Magellanic Cloud (SMC). We
detect O VI along every sight line. The average value of the O VI column
density in the SMC is log <N(O VI)>=14.53. This value is 1.7 times higher than
the average value for the Milky Way halo (perpendicular to the Galactic plane)
of log N_perp(O VI)=14.29 found by FUSE, even though the SMC has much lower
metallicity than the Galaxy. The column density in the SMC is higher along
sight lines that lie close to star-forming regions, in particular NGC 346 in
the northern part of the SMC. The standard deviation of the column densities
for sight lines outside of NGC 346 is +/- 27%, somewhat lower than the
deviation seen in the Milky Way halo. The lowest O VI column densities, log N(O
VI)~14.3, occur in the central region and in the southeastern ``Wing'' of the
galaxy. Even these low column densities are as high as the Milky Way average,
establishing the presence of a substantial, extended component of coronal gas
in the SMC. The O VI absorption is always shifted to higher velocities than the
main component of lower ionization gas. The O VI line widths are broader than
expected for pure thermal broadening. We discuss several mechanisms that may be
able to explain the observed properties of the hot gas, including supershells,
a galactic fountain, and the infall of gas previously stripped from the SMC by
tidal interactions with the Milky Way and the Large Magellanic Cloud. If a
fountain produces the hot gas, the mass flux per unit surface area is ~0.02
M_sun/yr/kpc2.


title: Dark halo properties from rotation curves

abstract:
  We study a large set of high spatial resolution optical rotation curves of
galaxies with the goal of determining the model parameters for a disk embedded
within a CDM halo that we model either with a NFW profile or pseudo-isothermal
profile. We show that parameter degeneracies present in lower resolution data
are lifted at these higher resolutions. 34% of the galaxies do not have a
meaningful fit when using the NFW profile and 32% when using the
pseudoisothermal profile, however only 14% do not have a meaningful fit in
either model. In both models we find correlations between the disk baryon
fraction $f_d$ and the spin parameter of the halo $\lambda'$, between $f_d$ and
the dark halo mass $M_{200}$, and between $M_{200}$ and the concentration
parameter $c$. We show that the distribution of the concentration parameters
$c$, for a NFW halo, is in good agreement with CDM predictions; no significant
galaxy population is found with very low values of $c$. The overall
distribution of $\lambda'$ is in good agreement with theoretical predictions
from hierarchical tidal torque theory. The whole sample is also well fitted by
a pseudo-isothermal dark halo with a core, but the size of the core is rather
small (for 70% of the sample the core size is less than 2 kpc). Thus we
conclude that the profile of dark matter is steep ($r^{-1}$ or steeper) down to
this radius; large dark matter cores (and therefore very low dark matter
central densities) seem to be excluded. LSBs tend to have higher values of
$\lambda'$ for a given $f_d$ and lower values of $c$ for a given mass than
HSBs. In an appendix we give some useful formula for pseudo-isothermal profile
halos and discuss in detail the issue of parameter degeneracies.


title:
The Kinematic Connection Between QSO-Absorbing Gas and Galaxies at
  Intermediate Redshift

abstract:
  We present complementary data on 5 intermediate redshift (0.44 < z < 0.66)
MgII absorbing galaxies, combining high spatial resolution imaging from HST,
high--resolution QSO spectroscopy from Keck/HIRES, and galaxy kinematics from
intermediate resolution spectroscopy using Keck/LRIS. These data allow a direct
comparison of the kinematics of gas at large galactocentric impact parameters
with the galaxy kinematics obtained from the faint galaxy spectroscopy. All 5
galaxies appear to be relatively normal spirals, with measured rotation curves
yielding circular velocities in the range 100 < v_c < 260 km/s. We find that in
4 of the 5 cases examined, the velocities of all of the Mg II absorption
components lie entirely to one side of the galaxy systemic redshift. These
observations are consistent with rotation being dominant for the absorbing gas
kinematics; however, the total range of velocities observed is inconsistent
with simple disk rotation in every case. Simple kinematic models that
simultaneously explain both the systemic offset of the absorbing material
relative to the galaxy redshifts, and the total velocity width spanned by the
absorption, require either extremely thick rotating gas layers, rotation
velocities that vary with height above the extrapolation of the galactic plane,
or both. In any case, our small sample suggests that rotating ``halo'' gas is a
common feature of intermediate redshift spiral galaxies, and that the kinematic
signature of rotation dominates over radial infall or outflow even for gas well
away from the galactic plane. We discuss possible explanations for this
behavior, and compare our observations to possible local analogs.


title:
Measuring Galaxy Disk Mass with the SparsePak Integral Field Unit on
  WIYN

abstract:
  We present first results from commissioning data of the SparsePak Integral
Field Unit on the WIYN telescope. SparsePak is a bundle of 82 fibers, each 5
arcsec in diameter and arranged in a sparsely filled, 76x77 arcsec hexagonal
grid. NGC 3982, a nearly face-on, blue and very high surface brightness galaxy,
was mapped in three spectral regions; around 5130A (MgI), 6680A (H-alpha) and
8660A (CaII-triplet) with FWHM spectral resolutions of 24, 16 and 37 km/s
respectively. At 3.5 disk scale lengths, the spectra of 18 fibers were averaged
after deprojection of the rotation curve. Stellar velocity dispersions were
determined in the CaII region by convolving the spectrum of a K0.5-III template
star with a Gaussian of varying FWHM and finding the best match to the
azimuthally avaraged galaxy spectra. A radial mass surface density profile has
been derived for a variety of scale heights assuming an isothermal vertical
density profile. At two disk scale lengths, the mass surface density of N3982
is ~3 times higher than that of the Milky Way in the solar neighborhood.
Surprisingly, the stellar rotation curve of this compact and high surface
brightness galaxy is substantially sub-maximum.


title: Convective Wavelength Shifts in the Spectra of Late-Type Stars

abstract:
  We present ultra-high resolution spectra for a set of nearby F-G-K stars on,
or close to, the main sequence. The wavelength shifts of stellar lines relative
to their laboratory wavelengths are measured for more than a thousand Fe I
lines per star, finding a clear correlation with line depth. The observed
patterns are interpreted as convective blue-shifts that become more prominent
for weaker lines, which are formed in deeper atmospheric layers. A
morphological sequence with spectral type or effective temperature is apparent.
Two K giant stars have also been studied. The velocity span between weak and
strong lines for these stars is larger than for the dwarfs and subgiants of
similar spectral types. Our results show that convective wavelength shifts may
seriously compromise the accuracy of absolute spectroscopic radial velocities,
but that an empirical correction may be applied to measured velocities.


title:
The Dynamics of the Merging Galaxy Cluster System A2256: Evidence for a
  New Subcluster

abstract:
  We present 236 new radial velocities of galaxies in the cluster A2256
measured with the WIYN Hydra multi-object spectrograph. Combined with the
previous work of Fabricant, Kent, and Kurtz (1989), we have velocities for a
total of 319 galaxies of which 277 are cluster members. In addition to the new
radial velocities, we present a 3x3 image mosaic in the R band of the central
19'x19' region of A2256, from which we obtained photometry for 861 galaxies.
These data provide strong evidence for a merger event between two groups. In
addition, we present evidence for the presence of a third group, on the outer
reaches of the system, that is just now beginning to merge with the system.


title: Planetary Nebulae in the Scheme of Binary Evolution

abstract:
  In this review I present the binary model for the shaping of planetary
nebulae (PNe) as I view it, in the context of historical evolution of other
models for the shaping of PNe over more than 30 years. In describing the binary
model, I concentrate on works published since the last IAU meeting on PNe. I
think stellar companions are behind the shaping of bipolar PNe, i.e., having
two lobes with an equatorial waist between them, and extreme elliptical PNe,
e.g., having a dense equatorial ring, but no lobes. The question of whether a
planet is required to spin the progenitor in order to form a moderate
elliptical PN, or whether a single stars can form moderate elliptical PNe, I
consider to be an open question.


title: Spatial Distribution of Dust Grains within H II Regions

abstract:
  We discuss the dust distribution within photoionized regions. Assuming a
geometry with a central dust cavity, which is strongly suggested by the
literature, we can estimate the cavity's radius from the ratio of the infrared
and radio fluxes by using a simple transfer model of Lyman continuum photons.
We apply the method to a sample of the Galactic H {\sc ii} regions. The
estimated typical radius of the dust cavity of the Galactic compact H {\sc ii}
regions is about 30% of the Str{\"o}mgren radius. Taking account of
uncertainties both of the observational data and the model, we can reject a
dust distribution lacking a central cavity. Therefore, the dust cavity model is
supported independently of the previous works. We discuss the formation
mechanism of such a dust cavity and its detectability by present and future
infrared facilities.


title: V893 Sco Is Not an ER UMa-Type Star

abstract:
  V893 Sco is a recently rediscovered bright eclipsing dwarf nova below the
period gap. Most recently, Mason et al. (2001) proposed an idea that V893 Sco
is an ER UMa-type dwarf nova. From the analysis of our CCD observations and
reports to VSNET, we show that V893 Sco bears no similar characters with ER UMa
stars. We propose that the arguments in Mason et al. (2001), including the
evolutionary status of ER UMa star as inferred from the observation of V893
Sco, need to be reconsidered.


title: Simulations of pulsar wind formation

abstract:
  We present initial results of the first self-consistent numerical model of
the outer magnetosphere of a pulsar. By using the relativistic
``particle-in-cell'' method with special boundary conditions to represent
plasma dynamics in 3D, we are able to follow magnetospheric plasma through the
light cylinder into the wind zone for arbitrary magnetic inclination angles.
For aligned rotators we confirm the ``disk-dome'' charge-separated structure of
the magnetosphere and find that this configuration is unstable to a 3D
nonaxisymmetric diocotron instability. This instability allows plasma to move
across the field lines and approach the corotating Goldreich-Julian solution
within several rotation periods. For oblique rotators formation of the spiral
``striped wind'' in the equatorial direction is demonstrated and the
acceleration of the wind and its magnetization is discussed. We find that the
wind properties vary with stellar latitude; however, whether injection
conditions at the pulsar are responsible for the observed jet-equator geometry
of Crab and Vela is currently under investigation. We also comment on the
electrodynamics of the simulated magnetospheres, their current closure, and
future simulations.


title:
The Properties of Satellite Galaxies in External Systems. I. Morphology
  and Structural Parameters

abstract:
  We present the first results of an ongoing project to study the
morphological, kinematical, dynamical, and chemical properties of satellite
galaxies of external giant spiral galaxies. The sample of objects has been
selected from the catalogue by Zaritsky et al. (1997). The paper analyzes the
morphology and structural parameters of a subsample of 60 such objects. The
satellites span a great variety of morphologies and surface brightness
profiles. About two thirds of the sample are spirals and irregulars, the
remaining third being early-types. Some cases showing interaction between pairs
of satellites are presented and briefly discussed.


title: Average Quasar Spectra in the Context of Eigenvector 1

abstract:
  [LaTeX removed] Recent work has shown that it is possible to systematize
quasar spectral diversity in a parameter space called ``Eigenvector 1'' (E1).
We present median AGN spectra for fixed regions of the E1 (optical) parameter
space (FWHM(H-beta) vs. equivalent width ratio RFE=W(FeII4570)/W(H-beta).
Comparison of the median spectra for different regions show considerable
differences. We suggest that an E1-driven approach to median/average spectra
emphasizes significant differences between AGN, and offers more insights into
AGN physics and dynamics than a single population median/average derived from a
large and heterogeneous sample of sources. We find that the H-beta broad
component line profile changes in shape along the E1 sequence both in average
centroid shift and asymmetry. While objects with FWHM(H-beta)< 4000 km/s are
well fitted by a Lorentz function, AGN with FWHM(H-beta)> 4000 km/s are well
fitted if two broad line components are used: a broad (the "classical" broad
line component) and a very broad/redshifted component.


title:
A new, cleaner colour-magnitude diagram for the metal-rich globular
  cluster NGC 6528 - Velocity dispersion in the Bulge, age and proper motion of
  NGC 6528

abstract:
  Using two epochs of HST/WFPC2 images of the metal-rich globular cluster NGC
6528 we derive the proper motions of the stars and use them to separate the
stars belonging to NGC 6528 from those of the Galactic bulge. The stellar
sequences in theresulting colour-magnitude diagram for the cluster are
significantly better determined than in previously published data. From
comparison of the colour-magnitude diagram with the fiducial line for NGC 6553
from Zoccali et al. (2001) we conclude that the two globular clusters have the
same age. Further, using alpha-enhanced stellar isochrones, NGC 6528 is found
to have an age of 11+-2 Gyr. This fitting of isochrones also give that the
cluster is 7.2 kpc away from us. From the measured velocities both the proper
motion of the cluster and the velocity dispersion in the Galactic bulge are
found. NGC 6528 is found to have a proper motion relative to the Galactic bulge
of mu_l=0.006 and mu_b=0.044 arcsec per century. Using stars with 14<V_555<19
(i.e. the red giant branch and horizontal branch) we find, for the Galactic
bulge, sigma_l= 0.33+-0.03 and sigma_{b}= 0.25+-0.02 arcsec per century. This
give sigma_l/sigma_b=1.32+-0.16, consistent both with previous proper motion
studies of K giants in the Galactic bulge as well as with predictions by models
of the kinematics of bulge stars.


title:
The K20 survey. II. The Different Spatial Clustering of z~1 Old and
  Dusty Star-Forming EROs

abstract:
  We compare the 3D clustering of old passively-evolving and dusty star-forming
z~1 EROs from the K20 survey. With detailed simulations of clustering, the
comoving correlation length of dusty star-forming EROs is constrained to be
less than r_0~2.5 Mpc/h. In contrast, the old EROs are much more positively
correlated, with 5.5<~r_0/(Mpc/h)<~16, consistent with previous claims for z~1
field early-type galaxies based on analyses of ERO angular clustering. The low
level of clustering of dusty star-forming EROs does not support these to be
major mergers building up an elliptical galaxy, or typical counterparts of
SCUBA sources, but it is instead consistent with the weak clustering of high
redshift blue galaxies and of luminous local IRAS galaxies. Current
hierarchical merging models can explain the large r_0 for z~1 field early-type
galaxies, but fail in matching their high number density and overall old ages.


title: First SIMBA observations toward CH3OH masers

abstract:
  We report SIMBA 1.2 mm dust continuum observations of the environments of
eight methanol maser sources, all discovered during spatially fully-sampled,
untargeted surveys of the galactic plane. We summarise our search for possible
associations of the masers with IR sources (IRAS and MSX) and find that it is
not always possible to make definite associations. A preliminary
characterisation of the IR sources found in the maser neighbourhood is given
according their position in the [60-25] -- [25-12] colour-colour diagram.


title: On the circularly polarized optical emission from AE Aquarii

abstract:
  The reported nightly mean value of the circular polarization of optical
emission observed from the close binary system AE Aqr is 0.06% (+-) 0.01%. We
discuss a possibility that the observed polarized radiation is emitted mainly
by the white dwarf or its vicinity. We demonstrate that this hypothesis is
rather unlikely since the contribution of the white dwarf to the optical
radiation of the system is too small. This indicates that the polarimetric data
on AE Aqr cannot be used for the evaluation of the surface magnetic field
strength of the white dwarf in this system.


title: Spectral atlas of dwarf novae in outburst

abstract:
  Up to now, only a very small number of dwarf novae have been studied during
their outburst state (~30 per cent in the Northern hemisphere). In this paper
we present the first comprehensive atlas of outburst spectra of dwarf novae. We
study possible correlations between the emission and absorption lines seen in
the spectra and some fundamental parameters of the binaries. We find that out
of the 48 spectra presented, 12 systems apart from IP Peg show strong HeII in
emission: SS Aur, HL CMa, TU Crt, EM Cyg, SS Cyg, EX Dra, U Gem, HX Peg, GK
Per, KT Per, V893 Sco, IY UMa, and 7 others less prominently: FO And, V542 Cyg,
BI Ori, TY Psc, VZ Pyx, ER UMa, and SS UMi. We conclude that these systems are
good targets for finding spiral structure in their accretion discs during
outburst if models of Smak (2001) and Ogilvie (2001) are correct. This is
confirmed by the fact that hints of spiral asymmetries have already been found
in the discs of SS Cyg, EX Dra and U Gem.


title: Searching for spiral shocks

abstract:
  Spiral shocks in cataclysmic variables (CVs) are the result of tidal
interactions of the mass donor star with the accretion disc. Their study is
fundamental for our understanding of angular momentum transfer in discs. In our
quest to learn how widespread amongst binaries spiral shocks are, and how their
presence depends upon orbital period and mass ratio (as they are created by
direct interaction with the donor star), we have obtained spectra of a large
sample of CVs during their high-mass-transfer states. We find that 24 out of
the 63 systems observed are candidates for containing spiral shocks. 5 out of
those 24 CVs have been confirmed as showing shocks in the disc during outburst.


title: Strange star candidates

abstract:
  In this talk we discuss possible signatures for the existence of strange
quark matter stars (strange stars).


title: A Semi-analytic Model of Halo Dynamics

abstract:
  We have developed a new semi-analytic model for the formation and evolution
of structure on galaxy, group and cluster scales. The model combines merger
trees with a detailed, spatially resolved description of the dynamical
evolution of halo substructure. It reproduces the results of numerical
simulations of mergers and halo formation at a fraction of the computational
expense. We use this model to study the formation of the dwarf galaxies in the
Local Group and the structural components of the Milky Way. We find that
reionization can explain the scarcity of Local Group dwarfs, although the
reionization epoch is constrained to be high -- z_ri >= 12. We also find that
disk disruption at recent times is rare, such that many galactic disks have an
old, thin component.


title:
Keck Absorption-Line Spectroscopy of Galactic Winds in Ultraluminous
  Infrared Galaxies

abstract:
  In this paper, we present moderately-high resolution (~65 km/s) spectroscopy,
acquired with ESI on Keck II, of 11 ultraluminous infrared galaxies at z < 0.3
from the IRAS 1 Jy sample. The targets were chosen as good candidates to host
galaxy-scale outflows, and most have infrared luminosities dominated by star
formation. We use a chi-squared minimization to fit one- to three-component
profiles to the NaI D interstellar absorption doublet in each object. Assuming
that gas blueshifted by more than 70 km/s relative to the systemic velocity of
the host is outflowing, we detect outflows in 73% of these objects. We adopt a
simple model of a mass-conserving free wind to infer mass outflow rates in the
range (dM/dt)_tot(H) = 13-133 M_sun/yr for galaxies hosting a wind. These
values of (dM/dt)_tot, normalized to the corresponding global star formation
rates inferred from infrared luminosities, are in the range eta = (dM/dt)_tot /
SFR = 0.1-0.7. This is on average a factor of only 10 less than eta from recent
measurements of nearby dwarfs, edge-on spirals, and lower-luminosity infrared
galaxies. Within our sample, we conclude that eta has no dependence on the mass
of the host (parameterized by host galaxy kinematics and absolute R- and
K'-band magnitudes). We also attempt to estimate the average escape fraction
<f_esc> = Sum(dM/dt_esc^i) / Sum(dM/dt_tot^i) and ``ejection efficiency''
<delta> = Sum(dM/dt_esc^i) / Sum(SFR^i) for our sample, which we find to be
\~0.4-0.5 and ~0.1, respectively. The complex absorption-line properties of Mrk
231, an ultraluminous infrared galaxy which is optically classified as a
Seyfert 1, are discussed separately in an appendix.


title:
New Evolutionary Synthesis code. An application to the irregular galaxy
  NGC 1560

abstract:
  We have developed a new evolutionary synthesis code, which incorporates the
output from chemical evolution models. We compare results of this new code with
other published codes, and we apply it to the irregular galaxy NGC 1560 using
sophisticated chemical evolution models. The code makes important contributions
in two areas: a) the building of synthetic populations with time-dependent star
formation rates and stellar populations of different metallicities; b) the
extension of the set of stellar tracks from the Geneva group by adding the AGB
phases for $m_i/M_\odot \geq 0.8$ as well as the very low mass stars. Our code
predicts spectra, broad band colors, and Lick indices by using a spectra
library, which cover a more complete grid of stellar parameters. The
application of the code with the chemical models to the galaxy NGC 1560
constrain the star formation age for its stellar population around 10.0 Gy.


title:
Extinction with 2MASS: star counts and reddening toward the North
  America and the Pelican Nebulae

abstract:
  We propose a general method for mapping the extinction in dense molecular
clouds using 2MASS near-infrared data. The technique is based on the
simultaneous utilization of star counts and colors. These two techniques
provide independent estimations of the extinction and each method reacts
differently to foreground star contamination and to star clustering. We take
advantage of both methods to build a large scale extinction map (2.5 x 2.5
degrees) of the North America-Pelican nebulae complex. With Ks star counts and
H-Ks color analysis the visual extinction is mapped up to 35 mag. Regions with
visual extinction greater than 20 mag account for less than 3% of the total
mass of the cloud. Color is generally a better estimator for the extinction
than star counts. Nine star clusters are identified in the area, seven of which
were previously unknown.


title: The Current Performance of the Third Interplanetary Network

abstract:
  The 3rd Interplanetary Network (IPN) has been operating since April 2001 with
two distant spacecraft, Ulysses and Mars Odyssey, and numerous near-Earth
spacecraft, such as BeppoSAX, Wind, and HETE-II. Mars Odyssey is presently in
orbit about Mars, and the network has detected approximately 30 cosmic, SGR,
and solar bursts. We discuss the results obtained to date and use them to
predict the future performance of the network.


title: The Sunyaev Zel'dovich effect: simulation and observation

abstract:
  The Sunyaev Zel'dovich effect (SZ effect) is a complete probe of ionized
baryons, the majority of which are likely hiding in the intergalactic medium.
We ran a $512^3$ $\Lambda$CDM simulation using a moving mesh hydro code to
compute the statistics of the thermal and kinetic SZ effect such as the power
spectra and measures of non-Gaussianity. The thermal SZ power spectrum has a
very broad peak at multipole $l\sim 2000-10^4$ with temperature fluctuations
$\Delta T \sim 15\mu$K. The power spectrum is consistent with available
observations and suggests a high $\sigma_8\simeq 1.0$ and a possible role of
non-gravitational heating. The non-Gaussianity is significant and increases the
cosmic variance of the power spectrum by a factor of $\sim 5$ for $l<6000$.
  We explore optimal driftscan survey strategies for the AMIBA CMB
interferometer and their dependence on cosmology. For SZ power spectrum
estimation, we find that the optimal sky coverage for a 1000 hours of
integration time is several hundred square degrees. One achieves an accuracy
better than 40% in the SZ measurement of power spectrum and an accuracy better
than 20% in the cross correlation with Sloan galaxies for $2000<l<5000$. For
cluster searches, the optimal scan rate is around 280 hours per square degree
with a cluster detection rate 1 every 7 hours, allowing for a false positive
rate of 20% and better than 30% accuracy in the cluster SZ distribution
function measurement.


title: Dark Matter Spikes and Annihilation Radiation from the Galactic Center

abstract:
  The annihilation rate of weakly interacting cold dark matter particles at the
galactic center could be greatly enhanced by the growth of a density spike
around the central supermassive black hole (SBH). Here we discuss the effects
of hierarchical mergers on the central spike. Mergers between halos containing
SBHs lead to the formation of SBH binaries which transfer energy to the dark
matter particles, lowering their density. The predicted flux of annihiliation
photons from the galactic center is several orders of magnitude smaller than in
models that ignore the effects of SBHs and mergers. Measurement of the
annihilation radiation could in principle be used to constrain the merger
history of the galaxy.


title:
Difference Image Analysis of the OGLE-II Bulge Data. III. Catalog of
  200,000 Candidate Variable Stars

abstract:
  We present the first edition of a catalog of variable stars from OGLE-II
Galactic Bulge data covering 3 years: 1997-1999. Typically 200-300 I band data
points are available in 49 fields between -11 and 11 degrees in galactic
longitude, totaling roughly 11 square degrees in sky coverage. Photometry was
obtained using the Difference Image Analysis (DIA) software and tied to the
OGLE data base with the DoPhot package. The present version of the catalog
comprises 221,801 light curves. In this preliminary work the level of
contamination by spurious detections is still about 10%. Parts of the catalog
have only crude calibration, insufficient for distance determinations. The
next, fully calibrated, edition will include the data collected in year 2000.
The data is accessible via FTP. Due to the data volume, we also distribute DAT
tapes upon request.


title: A search for giant pulses in Vela-like pulsars

abstract:
  We have carried out a survey for `giant pulses' in 6 young, Vela-like
pulsars. In no cases did we find single pulses with flux densities more than 10
times the mean flux density. However, in PSR B1706-44 we have detected giant
micro-pulses very similar to those seen in the Vela pulsar. In PSR B1706-44
these giant micro-pulses appear on the trailing edge of the profile and have an
intrinsic width of ~1 ms. The cumulative probability distribution of their
intensities is best described by a power-law. If the power-law continues to
higher intensities, then 3.7x10^6 rotations are required to obtain a pulse with
20 times the mean pulse flux. This number is similar to the giant pulse rate in
PSR B1937+21 and PSR B1821-24 but significantly higher than that for the Crab.


title:
Discovery of a z=4.93, X-ray selected quasar by the Chandra
  Multiwavelength Project (ChamP)

abstract:
  We present X-ray and optical observations of CXOMP J213945.0-234655, a high
redshift (z=4.93) quasar discovered through the Chandra Multiwavelength Project
(ChaMP). This object is the most distant X-ray selected quasar published, with
an X-ray luminosity of L(X)=5.9x10^44 erg/s (measured in the 0.3-2.5 keV band
and corrected for Galactic absorption). CXOMP J213945.0-234655 is a g' dropout
object (>26.2), with r'=22.87 and i'=21.36. The rest-frame X-ray to optical
flux ratio is similar to quasars at lower redshifts and slightly X-ray bright
relative to z>4 optically-selected quasars observed with Chandra. The ChaMP is
beginning to acquire significant numbers of high redshift quasars to
investigate the unobscured X-ray luminosity function out to z~5.


title:
Atmospheres and Spectra of Strongly Magnetized Neutron Stars II: Effect
  of Vacuum Polarization

abstract:
  We study the effect of vacuum polarization on the atmosphere structure and
radiation spectra of neutron stars with surface magnetic fields B=10^14-10^15
G, as appropriate for magnetars. Vacuum polarization modifies the dielectric
property of the medium and gives rise to a resonance feature in the opacity;
this feature is narrow and occurs at a photon energy that depends on the plasma
density. Vacuum polarization can also induce resonant conversion of photon
modes via a mechanism analogous to the MSW mechanism for neutrino oscillation.
We construct atmosphere models in radiative equilibrium with an effective
temperature of a few \times 10^6 K by solving the full radiative transfer
equations for both polarization modes in a fully ionized hydrogen plasma. We
discuss the subtleties in treating the vacuum polarization effects in the
atmosphere models and present approximate solutions to the radiative transfer
problem which bracket the true answer. We show from both analytic
considerations and numerical calculations that vacuum polarization produces a
broad depression in the X-ray flux at high energies (a few keV \la E \la a few
tens of keV) as compared to models without vacuum polarization; this arises
from the density dependence of the vacuum resonance feature and the large
density gradient present in the atmosphere. Thus the vacuum polarization effect
softens the high energy tail of the thermal spectrum, although the atmospheric
emission is still harder than the blackbody spectrum because of the non-grey
opacities. We also show that the depression of continuum flux strongly
suppresses the equivalent width of the ion cyclotron line and therefore makes
the line more difficult to observe.


title:
Bias Properties of Extragalactic Distance Indicators.XI. Methods to
  Correct for Observational Selection Bias for RR Lyrae Absolute Magnitudes
  from Trigonometric Parallaxes Expected from the FAME Astrometric Satellite

abstract:
  Please note that this abstract has been shortened from that found in the
paper. A brief history is given of the development of the correction for
observation selection bias inherent in the calibration of absolute magnitudes
using trigonometric parallaxes. As a tutorial to gain an intuitive
understanding of several complicated trigonometric bias problems, we study a
toy bias model of a parallax catalog which incorporates assumed parallax
measuring errors of various severities. The two effects of bias errors on the
derived absolute magnitudes are (1) the Lutz-Kelker correction itself that
depends on the fractional parallax error and the spatial distribution, and (2)
a Malmquist-like `incompleteness' correction of opposite sign due to various
apparent magnitude cut-offs as they are progressively imposed on the catalog.
The simulations involve 3 million stars spread with varying density
distributions in a volume bounded by a radius of 50,000 pc. A fixed absolute
magnitude of M_V = +0.6 is used to imitate RR Lyrae variables in the mean. The
bias is demonstrated for various assumed spatial densities and parallax error
models, including one that is projected for the FAME satellite. The effects of
imposing magnit ude limits and limits on the `observer's' error are displayed.
We contrast the method of calculating mean absolute magnitude directly from the
parallaxes where bias corrections are mandatory, with an inverse method using
maximum likelihood which is free of the Lutz-Kelker bias, although a Malmquist
bias is present. We discuss the level of accuracy that can be expected in a
calibration of RR Lyrae absolute magnitudes from the FAME data over the
metallicity range of [Fe/H] from 0 to -2, given the known frequency of the
local RR Lyraes closer than 1.5 kpc.


title: A Search for Variability in the Active T dwarf 2MASS 1237+6526

abstract:
  We present spectroscopic and imaging observations of the active T dwarf 2MASS
1237+6526, intended to investigate the emission mechanism of this cool brown
dwarf. The H$\alpha$ emission line first detected in 1999 July appears to be
persistent over 1.6 years, with no significant variation from
$\log_{10}(L_{H{\alpha}}$/L$_{bol}$) = $-$4.3, ruling out flaring as a possible
source. The relatively high level of emission in this object appears to be
unique amongst observed late-L and T dwarfs. One of our spectra shows an
apparent velocity shift in the H$\alpha$ line, which could be indicative of an
accretion hot spot in orbit around the brown dwarf; further confirmation of
this shift is required. J-band monitoring observations fail to detect any
significant variability (e.g., eclipsing events) at the $\pm$0.025 mag level
over periods of up to 2.5 hours, and there appears to be no statistical
evidence of variability for periods of up to 14 hours. These limits constrain
the mass of a hypothetical interacting secondary to M$_2$ $\lesssim$ 20
M$_{Jup}$ for inclinations $i$ $\gtrsim$ 60$\degr$. While our observations do
not explicitly rule out the binary hypothesis for this object, it does suggest
that other mechanisms, such as youthful accretion, may be responsible.


title:
Coronal--Temporal Correlations in GX339-4: Hysteresis, Possible
  Reflection Changes, and Implications for ADAFs

abstract:
  We present spectral fits and timing analysis of Rossi X-ray Timing Explorer
observations of GX339-4. These observations were carried out over a span of
more than two years and encompassed both the soft/high and hard/low states.
Hysteresis in the soft state/hard state transition is observed. The hard state
exhibits a possible anti-correlation between coronal compactness (i.e.,
spectral hardness) and the covering fraction of cold, reflecting material. The
correlation between `reflection fraction' and soft X-ray flux, however, appears
to be more universal. Furthermore, low flux, hard state observations - taken
over a decline into quiescence- show that the Fe line, independent of
`reflection fraction', remains broad and at a roughly constant equivalent
width, counter to expectations from ADAF models. All power spectral densities
(PSD) of the hard state X-ray lightcurves are describable as the sum of just a
few broad, quasi-periodic features with frequencies that roughly scale as
coronal compactness to the -3/2 power. Similar to observations of Cyg X-1, time
lags between soft and hard variability anti-correlate with coronal compactness.
A stronger correlation is seen between the time lags and the `reflection
fraction'.


title:
PSR J1124-5916: discovery of a young, energetic pulsar in the supernova
  remnant G292.0+1.8

abstract:
  We report the discovery with the Parkes radio telescope of a pulsar
associated with the ~ 1700 yr-old oxygen-rich composite supernova remnant
G292.0+1.8. PSR J1124-5916 has period 135 ms and period derivative 7.4e-13,
implying characteristic age 2900 yr, spin-down luminosity 1.2e37 erg/s, and
surface magnetic field strength 1.0e13 G. Association between the pulsar and
the synchrotron nebula previously identified with Chandra within this supernova
remnant is confirmed by the subsequent detection of X-ray pulsations by Hughes
et al. The pulsar's flux density at 1400 MHz is very small, S ~ 0.08 mJy, but
the radio luminosity of Sd^2 ~ 2 mJy kpc^2 is not especially so, although it is
one order of magnitude smaller than that of the least luminous young pulsar
previously known. This discovery suggests that very deep radio searches should
be done for pulsations from pulsar wind nebulae in which the central pulsed
source is yet to be detected and possibly other more exotic neutron stars.


title: Smooth maps from clumpy data: Covariance analysis

abstract:
  Interpolation techniques play a central role in Astronomy, where one often
needs to smooth irregularly sampled data into a smooth map. In a previous
article (Lombardi & Schneider 2001), we have considered a widely used smoothing
technique and we have evaluated the expectation value of the smoothed map under
a number of natural hypotheses. Here we proceed further on this analysis and
consider the variance of the smoothed map, represented by a two-point
correlation function. We show that two main sources of noise contribute to the
total error budget and we show several interesting properties of these two
noise terms. The expressions obtained are also specialized to the limiting
cases of low and high densities of measurements. A number of examples are used
to show in practice some of the results obtained.


title: Cooling flows in clusters of galaxies

abstract:
  The gas temperature in the cores of many clusters of galaxies drops inward by
about a factor of three or more within the central 100kpc radius. The radiative
cooling time drops over the same region from 5 or more Gyr down to about 10^8
yr. Although it would seem that cooling has taken place, XMM and Chandra
spectra show no evidence for strong mass cooling rates of gas below 1-2 keV.
Chandra images show holes coincident with radio lobes and cold fronts
indicating that the core regions are complex. The observational situation is
reviewed here and ways in which continued cooling may be hidden are discussed,
togther with the implications for any heat source which balances radiative
cooling.