title: The Modified Weighted Slab Technique: Models and Results

abstract:
  In an attempt to understand the source and propagation of galactic cosmic
rays we have employed the Modified Weighted Slab technique along with recent
values of the relevant cross sections to compute primary to secondary ratios
including B/C and Sub-Fe/Fe for different galactic propagation models. The
models that we have considered are the disk-halo diffusion model, the dynamical
halo wind model, the turbulent diffusion model and a model with minimal
reacceleration. The modified weighted slab technique will be briefly discussed
and a more detailed description of the models will be given. We will also
discuss the impact that the various models have on the problem of anisotropy at
high energy and discuss what properties of a particular model bear on this
issue.


title: Accretion column disruption in GX 1+4

abstract:
  Daily observations of the binary X-ray pulsar GX 1+4 were made with the Rossi
X-ray Timing Explorer (RXTE) satellite between 1997 May 16-20 as part of a
four-month monitoring program. On May 17 the sharp dips normally observed in
the lightcurve were all but absent, resulting in a pulse fraction f_p approx.
0.5 instead of the more typical value of approx. 0.8 measured before and after.
Also observed was a dramatic hardening of the 2-40 keV phase-averaged spectrum.
The power-law photon index was 1.16 +/- 0.02, whereas values of 1.6-2.0 are
more typical. In terms of a Comptonization continuum component, the optical
depth for scattering was tau approx 19, with 4-6 the usual range for RXTE
spectra (Galloway 2000). Pulse-phase spectrosopy indicates that tau is
decreased relative to the phase-averaged value around the primary minimum,
where an increase is normally observed. The reduced depth of the dip is
interpreted as disruption of the accretion column, and the accompanying
spectral variation suggests a substantially different accretion regime than is
usual for this source.


title:
Hierarchical galaxy formation and substructure in the Galaxy's stellar
  halo

abstract:
  We develop an explicit model for the formation of the stellar halo from
tidally disrupted, accreted dwarf satellites in the cold dark matter (CDM)
framework, focusing on predictions testable with the Sloan Digital Sky Survey
(SDSS) and other wide-field surveys. Subhalo accretion and orbital evolution
are calculated using a semi-analytic approach within the Press-Schechter
formalism. Motivated by our previous work, we assume that low-mass subhalos (v
< 30 km/s) can form significant populations of stars only if they accreted a
substantial fraction of their mass before the epoch of reionization. With this
assumption, the model reproduces the observed velocity function of galactic
satellites in the Local Group, solving the ``dwarf satellite problem'' without
modifying the popular LCDM cosmology. The disrupted satellites yield a stellar
distribution with a total mass and radial density profile consistent with those
observed for the Milky Way stellar halo. Most significantly, the model predicts
the presence of many large-scale, coherent substructures in the outer halo.
These substructures are remnants of individual, tidally disrupted dwarf
satellite galaxies. Substructure is more pronounced at large galactocentric
radii because of the smaller number density of tidal streams and the longer
orbital times. This model provides a natural explanation for the coherent
structures in the outer stellar halo found in the SDSS commissioning data, and
it predicts that many more such structures should be found as the survey covers
more of the sky. The detection (or non-detection) and characterization of such
structures could eventually test variants of the CDM scenario, especially those
that aim to solve the dwarf satellite problem by enhancing satellite
disruption.


title:
On the origin of the Trojan asteroids: Effects of Jupiter's mass
  accretion and radial migration

abstract:
  We present analytic and numerical results which illustrate the effects of
Jupiter's accretion of nebular gas and the planet's radial migration on its
Trojan companions. Initially, we approximate the system by the planar circular
restricted three-body problem and assume small Trojan libration amplitudes.
Employing an adiabatic invariant calculation, we show that Jupiter's
thirty-fold growth from a $10 M_\oplus$ core to its present mass causes the
libration amplitudes of Trojan asteroids to shrink by a factor of about 2.5 to
$\sim 40%$ of their original size. The calculation also shows that Jupiter's
radial migration has comparatively little effect on the Trojans; inward
migration from 6.2 to 5.2 AU causes an increase in Trojan libration amplitudes
of $\sim4%$. In each case, the area enclosed by small tadpole orbits, if made
dimensionless by using Jupiter's semimajor axis, is approximately conserved.
Similar adiabatic invariant calculations for inclined and eccentric Trojans
show that Jupiter's mass growth leaves the asteroid's eccentricities and
inclinations essentially unchanged, while one AU of inward migration causes an
increase in both of these quantities by $\sim 4%$. Numerical integrations
confirm and extend these analytic results. We demonstrate that our predictions
remain valid for Trojans with small libration amplitudes even when the
asteroids have low, but


title:
Limitations in using luminosity distance to determine the equation of
  state of the universe

abstract:
  Supernova searches have been been suggested as a method for determining
precisely the current value and time variation of the equation of state, $w$,
of the dark energy component responsible for the accelerated expansion of the
Universe. We show that the method is fundamentally limited by the fact that
luminosity dista nce depends on $w$ through a multiple integral relation that
smears out information about $w$ and its time variatio n. The effect degrades
the resolution of $w$ that can be obtained from current d ata.


title: The Low-Mass Stars in Starburst Clusters

abstract:
  If star formation depends strongly on the global properties of the
environment in which they form, the slope of the IMF as well as the upper and
lower mass cut-offs would be expected to vary significantly between violent
starbursts and more quiescent star forming regions. To test this hypothesis we
observed the stellar content of the two closest massive star forming regions,
30Doradus and NGC3603 with HST/NICMOS and VLT/ISAAC. Our observations are the
most sensitive observations made to date of dense starburst cores, allowing us
to investigate its low-mass stellar population with unprecedented quality. The
NIR luminosity function of 30Doradus shows no evidence for a truncation down to
at least 1 M_o, its stellar core R136 is populated in low-mass stars to at
least 2 M_o and NGC3603, which is very similar to R136, down to 0.1 M_o. Our
observations clearly show that low-mass stars do form in massive starbursts.


title:
Time-Delay Effect on the cOsmic Background Radiation by Static
  Gravitational Potential of Clusters

abstract:
  We present a quantitative analysis of the time-delay effect on the cosmic
background radiation (CBR) by static gravitational potential of galaxy
clusters. This is primarily motivated by growing observational evidence that
clusters have essentially experienced no-evolution since redshift $z\approx1$,
indicating that the contribution of a time-dependent potential to CBR
anisotropy discussed in literature could be rather small for the
dynamically-relaxed clusters. Using the softened isothermal sphere model and
the universal density profile for the mass distribution of rich clusters, we
calculate the CBR anisotropy by the time-delay effect and compare it with those
generated by the thermal and kinematic S-Z effects as well as by the transverse
motion of clusters. While it is unlikely that the time-delay effect is
detectable in the current S-Z measurement because of its small amplitude of
$10^{-6}$-$10^{-7}$ and its achromaticity, it nevertheless leads to an
uncertainty of $\sim10%$ in the measurement of the kinematic S-Z effect of
clusters. Future cosmological application of the peculiar velocity of clusters
to be measured through the S-Z effect should therefore take this uncertainty
into account.


title: Science with SIRTF - Some Examples

abstract:
  The Space InfraRed Telescope Facility (SIRTF) is a space-borne,
cryogenically-cooled infrared observatory capable of studying objects ranging
from our Solar System to the distant reaches of the Universe. SIRTF is the
final element in NASA's Great Observatories Program, and an important component
of its Origins Program. The intent of this paper is to summarize the most
important parameters of the observatory and its scientific instruments and to
present three typical examples of scientific areas where SIRTF will have a
significant impact. These examples of ``nearby'' targets -- brown dwarf
surveys, protostellar disks, and massive young clusters -- have been selected
in regard to the main topics of this conference.


title:
Spectrum and proper motion of a brown dwarf companion of the T Tauri
  star CoD-33 7795

abstract:
  We present optical and infrared spectra as well as the proper motion of an
H=12 mag object 2" off the ~5 mag brighter spectroscopic binary star CoD-33
7795 (=TWA-5), a member of the TW Hya association of T Tauri stars at ~55 pc.
It was suggested as companion candidate by Lowrance et al. (1999) and Webb et
al. (1999), but neither a spectrum nor the proper motion of the faint object
were available before. Our spectra taken with FORS2 and ISAAC at the ESO-VLT
reveal that the companion candidate has spectral type M8.5 to M9. It shows
strong H-alpha emission and weak Na I absorption, both indicative of a young
age. The faint object is clearly detected and resolved in our optical and
infrared images, with a FWHM of 0.18" in the FORS2 image. The faint object's
proper motion, based on two year epoch difference, is consistent with the
proper motion of CoD-33 7795 by 5 Gaussian sigma significance. From three
different theoretical pre-main sequence models, we estimate the companion mass
to be between ~15 and 40 M_jup, assuming the distance and age of the primary. A
slight offset between the VLT and HST images with an epoch difference of two
years can be interpreted as orbital motion. The probability for chance
alignment of such a late-type object that close to CoD-33 7795 with the correct
proper motion is below 7e-9. Hence, the faint object is physically associated
with CoD-33 7795, the 4th brown dwarf companion around a normal star confirmed
by both spectrum and proper motion, the first around a pre-main sequence star.


title: SN 1984A and Delayed Detonation Models of Type Ia Supernovae

abstract:
  SN 1984A shows unusually large expansion velocities in lines from freshly
synthesized material, relative to typical Type Ia Supernovae (SNe Ia). SN 1984A
is an example of a group of SNe Ia which have very large blue-shifts of the
P-Cygni features, but otherwise normal spectra. We have modeled several early
spectra of SN 1984A with the multi-purpose NLTE model atmosphere and spectrum
synthesis code, PHOENIX. We have used as input two delayed detonation models:
CS15DD3 (Iwamoto et al. 1999) and DD21c (Hoeflich, Wheeler & Thielemann 1998).
These models show line expansion velocities which are larger than that for a
typical deflagration model like W7, which we have previously shown to fit the
spectra of normal SNe Ia quite well. We find these delayed detonation models to
be reasonable approximations to large absorption feature blue-shift SNe Ia,
like SN 1984A. Higher densities of newly synthesized intermediate mass elements
at higher velocities, v > 15,000 km/s, are found in delayed detonation models
than in deflagration models. We find that this increase in density at high
velocities is responsible for the larger blue-shifts in the synthetic spectra.
We show that the variations in line width in observed SNe Ia are likely due to
density variations in the outer, high-velocity layers of their atmospheres.


title:
Observing the Unobservable: Coronal Line Data from NLS1s as a Test of
  EUV Continuum Models

abstract:
  We have measured coronal line emission for a sample of 19 Narrow-Line
Seyfert~1 galaxies. Kinematic analysis shows that the Coronal Line Region (CLR)
consists of gas in a decelerating outflow.
  We intend to use these data as a test of the EUV emission of NLS1s. By
comparison with photoionization modelling for a number of power-law + black
body spectra, we plan to deduce the most likely EUV continua for these objects
as well as explore physical conditions in the CLR.


title:
Star Formation Efficiency in the Central 1 kpc Region of Early-Type
  Spiral Galaxies

abstract:
  It has been reported recently that there are some early-type spiral (Sa--Sab)
galaxies having evident star-forming regions which concentrate in their own
central 1-kpc. In such central region, is the mechanism of the star formation
distinct from that in disks of spiral galaxies? To reveal this, we estimate the
star formation efficiency (SFE) in this central 1-kpc star-forming region of
some early-type spiral galaxies, taking account of the condition for this 1-kpc
region to be self-gravitating. Using two indicators of present star formation
rate (H$\alpha$ and infrared luminosity), we estimate the SFE to be a few
percents. This is equivalent to the observational SFE in the disks of late-type
spiral (Sb--) galaxies. This coincidence may support the universality of the
mean SFE of spiral galaxies reported in the recent studies. That is, we find no
evidence of distinct mechanism of the star formation in the central 1-kpc
region of early-type galaxies. Also, we examine the structure of the central
star-forming region, and discuss a method for estimating the mass of
star-forming regions.


title:
Direct imaging search for planetary companions next to young nearby
  stars

abstract:
  We report first results from our ground-based infrared imaging search for
sub-stellar companions (brown dwarfs and giant planets) of young (up to 100
Myrs) nearby (up to 75 pc) stars, where companions should be well separated
from the central stars and still relatively bright due to ongoing accretion
and/or contraction. Among our targets are all members of the TW Hya
association, as well as other binary and single young stars either discovered
recently among ROSAT sources (some of which as yet unpublished) or known
before. Our observations are performed mainly with SOFI and SHARP at the ESO
3.5m NTT on La Silla and with ISAAC at the ESO 8.2m Antu (VLT-UT1) on Cerro
Paranal, all in the H- and K-bands. We present direct imaging data and H-band
spectroscopy of a faint object detected next to TWA-7 which, if at the same age
and distance as the central star, could be an object with only a few Jupiter
masses. Our spectrum shows, though, that it is a background K-dwarf.


title: What is the Cosmic-Ray luminosity of our Galaxy?

abstract:
  The total cosmic-ray luminosity of the Galaxy is an important constraint on
models of cosmic-ray generation. The diffuse high energy $\gamma$-ray and
radio-synchrotron emissions of the Milky Way are used to derive this
luminosity. The result is almost two orders of magnitude larger than the
standard estimate, based on the observed isotopic abundances of cosmic ray
nuclides. We discuss the plausible interpretation of this discrepancy and the
possible origin of such a relatively large luminosity.


title:
Massive Star Forming Regions: from diagnostic tools to derived
  properties

abstract:
  The current state-of-the-art of multi-wavelength diagnostic tools
(evolutionary synthesis, photoionisation models) for massive star forming
regions (HII regions, starbursts, etc.) and some of their input physics
(especially model atmospheres) is reviewed. Analysis of stellar populations
based on integrated spectra from both stellar features and nebular emission
lines from the UV to IR are summarised. We stress the importance of "template"
studies at various scales (from individual stars to well studied galaxies) and
various wavelengths, to understand the processes operating in massive star
forming regions and to reliably derive their properties.


title: First search for gravitational wave bursts with a network of detectors

abstract:
  We report the initial results from a search for bursts of gravitational
radiation by a network of five cryogenic resonant detectors during 1997 and
1998. This is the first significant search with more than two detectors
observing simultaneously. No gravitational wave burst was detected. The false
alarm rate was lower than 1 per 10^4 years when three or more detectors were
operating simultaneously. The typical threshold was H ~ 4 10^-21 Hz^-1 on the
Fourier component at ~ 10^3 Hz of the gravitational wave strain amplitude. New
upper limits for amplitude and rate of g.w. bursts have been set.


title:
The Contribution of Field OB Stars to the Ionization of the Diffuse
  Ionized Gas in M33

abstract:
  (Abridged) We present a study of the ionizing stars associated with the
diffuse ionized gas (DIG) and HII regions in the nearby spiral galaxy M33. We
compare our Schmidt H-alpha image to the far-ultraviolet (FUV, 1520A) image
from the Ultraviolet Imaging Telescope (UIT). The H-alpha/FUV ratio is higher
in HII regions than in the DIG, suggesting an older population of ionizing
stars in the DIG. When compared to models of evolving stellar populations, the
N(Lyc)/FUV ratio in HII regions is consistent with a young burst, while the DIG
ratio resembles an older burst population, or a steady state population built
up by constant star formation. The UIT data is complimented with archival FUV
and optical images of a small portion of the disk of M33 obtained with WFPC2 on
HST. Using the HST FUV and optical photometry, we assign spectral types to the
stars observed in DIG and HII regions. The photometry indicates that ionizing
stars are present in the DIG. We compare the predicted ionizing flux with the
amount required to produce the observed H-alpha emission, and find that field
OB stars in the HST images can account for 40% +/- 12% of the ionization of the
DIG, while the stars in HII regions can provide 107% +/- 26% of the H-alpha
luminosity of the HII regions. We do not find any correlation between leakage
of ionizing photons and H-alpha luminosity for the HII regions in these HST
fields. If stellar photons alone are responsible for ionizing the DIG, the
current results are consistent with no or few ionizing photons escaping from
the galaxy.


title: The Vela Pulsar and its Synchrotron Nebula

abstract:
  (Abridged) We present high-resolution Chandra X-ray observations of PSR
B0833-45, the 89 ms pulsar associated with the Vela supernova remnant. We have
acquired two observations separated by one month to search for changes in the
pulsar and its environment following an extreme glitch in its rotation
frequency. We find a well-resolved nebula with a toroidal morphology remarkably
similar to that observed in the Crab Nebula, along with an axial Crab-like jet.
Between the two observations the flux from the pulsar is found to be steady to
within 0.75%; the 3 sigma limit on the fractional increase in the pulsar's
X-ray flux is < ~10^-5 of the inferred glitch energy. We use this limit to
constrain parameters of glitch models and neutron star structure. We do find a
significant increase in the flux of the nebula's outer arc; if associated with
the glitch, the inferred propagation velocity is > 0.7c, similar to that seen
in the brightening of the Crab Nebula wisps. We propose an explanation for the
X-ray structure of the Vela synchrotron nebula based on a model originally
developed for the Crab Nebula. In a departure from the Crab model, the
magnetization parameter "sigma" of the Vela pulsar wind is allowed to be of
order unity; this is consistent with the simplest MHD transport of magnetic
field from the pulsar to the nebula, where B < 4 X 10^-4 G. We review effects
that may enhance the probability of alignment between the spin axis and space
velocity of a pulsar, and speculate that short-period, slowly moving pulsars
are just the ones best-suited to producing synchrotron nebulae with such
aligned structures.


title: Prospects for the Lensing of Supernovae

abstract:
  Observations of high redshift type Ia supernovae (SNe) will enable us to
probe the structure of galaxy halos and the composition of dark matter. The
future prospects for this field are briefly discussed here. First the ability
of SN observations to differentiate between dark matter made of macroscopic
compact objects and dark matter made of microscopic particles is reviewed. Then
a new method for probing the structure of galaxy halos and galaxy cluster halos
is described. This method utilizes the correlations between foreground galaxy
light and supernova brightnesses to substantially decrease possible systematic
errors. The technique may be particularly useful for measuring the size of dark
matter halos, a measurement to which the galaxy--galaxy lensing is not well
suited, and the level of substructure in galaxy halos, a problematic prediction
of the cold dark matter model. The required observations of hundreds of SNe at
z ~ 1 are already being proposed for the purposes of cosmological parameter
estimation.


title: Quasar Variability in the Framework of Poissonian Models

abstract:
  In this paper we review the basic Poissonian formulation of quasar
variability, using it as a mathematical tool to extract relevant parameters
such as the energy, rate and lifetimes of the flares through the analysis of
observed light curves. It is shown that in this very general framework the well
established anti-correlation between variability amplitude and wavelength can
only be understood as an effect of an underlying spectral component which
remains stable on long time-scales, and is redder than the variable component.
The formalism is applied to the B and R light curves of 42 PG quasars collected
by the Wise Observatory group. Variability indices for these data are obtained
with a Structure Function analysis. The mean number of living flares is
constrained to be in the range between 5 and 100, while their rates are found
to be of order 1--100 per yr. Monochromatic optical flare energies of
10^{46-48} erg/A and life-times of 0.5 to 3 yr are derived. Lower limits of
typically 25% are established for the contribution of a non-variable component
in the R band. The substantial diversity in these properties among quasars
invalidates simple versions of the Poissonian model in which flare energies,
lifetimes and the background contribution are treated as universal invariants.
The good correlation between the EW(H_beta) and the long term variability
amplitude is interpreted in a scenario where only the variable component
participates in the ionization of the line emitting gas. This idea is
consistent with the observed trends of the variability amplitude with lambda,
EW(HeII) and the X-ray to optical spectral index (abridged).


title: Frequency decomposition of astrometric signature of planetary systems

abstract:
  We present theoretical analysis of the astrometric searches for extrasolar
planets with the Space Interferometry Mission (SIM). Particularly, we derive a
model for the future measurements with SIM and discuss the problem of reliable
estimation of orbital elements of planets. For this purpose we propose a new
method of data analysis and present a numerical test of its application on
simulated SIM astrometric measurements of $\upsilon$ Andromedae planetary
system. We demonstrate that our approach allows successfull determination of
its orbital elements.


title:
Chemical Abundances in our Galaxy and Other Galaxies Derived from H II
  Regions

abstract:
  We discuss the accuracy of the abundance determinations of H II regions in
our Galaxy and other galaxies. We focus on the main observational constraints
derived from abundance determinations that have implications for models of
galactic chemical evolution: a) the helium to hydrogen abundance ratio, He/H;
b) the oxygen to hydrogen abundance ratio, O/H; c) the carbon to oxygen
abundance ratio, C/O; d) the helium to oxygen and helium to heavy elements
abundance ratios, Delta Y/ Delta O and Delta Y/ Delta Z; and e) the primordial
helium abundance, Yp.


title: Faint Radio Sources and Star Formation History

abstract:
  The centimeter-wave luminosity of local radio galaxies correlates well with
their star formation rate. We extend this correlation to surveys of
high-redshift radio sources to estimate the global star formation history. The
star formation rate found from radio observations needs no correction for dust
obscuration, unlike the values calculated from optical and ultraviolet data.
Three deep radio surveys have provided catalogs of sources with nearly complete
optical identifications and nearly 60% complete spectroscopic redshifts: the
Hubble Deep Field and Flanking Fields at 12h+62d, the SSA13 field at 13h+42d,
and the V15 field at 14h+52d. We use the redshift distribution of these radio
sources to constrain the evolution of their luminosity function. The epoch
dependent luminosity function is then used to estimate the evolving global star
formation density. At redshifts less than one, our calculated star formation
rates are significantly larger than even the dust-corrected optically-selected
star formation rates; however, we confirm the rapid rise from z=0 to z=1 seen
in those surveys.


title: Extreme Galactic-Winds and Starburst in IR Mergers and IR QSOs

abstract:
  We report -as a part of a long-term study of mergers and IR QSOs- detailed
spectroscopic evidences for outflow (OF) and/or Wolf Rayet features in: (i) low
velocity OF in the ongoing mergers NGC 4038/39 and IRAS 23128-5919; (ii)
extreme velocity OF (EVOF) in the QSOs IRAS 01003-2238 and IRAS 13218+0552;
(iii) OF and EVOF in a complete sample of ultra-luminous IR galaxies/QSOs ("The
IRAS 1 Jy MKO-KPNO Survey", of 118 objects). We found EVOF in IRAS 11119+3257,
14394+5332, 15130+1958 and 15462-0450. The OF components detected in these
objects were mainly associated to starburst processes: i.e., to galactic-winds
generated in multiple type II SN explosions and massive stars. The EVOF were
detected in objects with strong starburst plus obscured IR QSOs; which suggest
that interaction of both processes could generate EVOF. In addition, we analyze
the presence of Wolf Rayet features in the large sample of Bright PG-QSOs
(Boroson and Green 1992), and nearby mergers and galactic-wind galaxies. We
found clear WR features in the Fe II QSOs (type I): PG 1244+026, 1444+407,
1448+273, 1535+547; and in the IR merger Arp 220. HST archive images of IR+BAL
QSOs show in practically all of these objects "arc or shell" features probably
associated to galactic-winds (i.e., to multiple type II SN explosions) and/or
merger processes. Finally, we discuss the presence of extreme starburst and
galactic wind as a possible evolutive link between IR merger and IR QSOs; where
the relation between mergers and extreme starburst (with powerful
galactic-winds) plays in important role, in the evolution of galaxies.


title: Recent results by the MOA group on gravitational microlensing

abstract:
  Recent work by the MOA gravitational microlensing group is briefly described,
including (i) the current observing strategy, (ii) use of a high-speed parallel
computer for analysis of results by inverse ray shooting, (iii) analysis of the
light curve of event OGLE-2000-BUL12 in terms of extra-solar planets, and (iv)
the MOA alert system using difference imaging.


title: Molecular Gas in Galaxies

abstract:
  Knowledge of the molecular component of the ISM is fundamental to understand
star formation. The H2 component appears to dominate the gas mass in the inner
parts of galaxies, while the HI component dominates in the outer parts.
Observation of the CO and other lines in normal and starburst galaxies have
questioned the CO-to-H2 conversion factor, and detection of CO in dwarfs have
shown how sensitive the conversion f actor is to metallicity. Our knowledge has
made great progress in recent years, because of sensitivity and spatial
resolution improvements. Large-scale CO maps of nearby galaxies are now
available, which extend our knowledge on global properties, radial gradients,
and spiral structure of the molecular ISM. Millimetric interferometers reveal
high velocity gradients in galaxy nuclei, and formation of embedded structures,
like bars within bars. Galaxy interactions are very effective to enhance gas
concentrations and trigger starbursts. Nuclear disks or rings are frequently
observed, that concentrate the star formation activity. Since the density of
starbursting galaxies is strongly increasing with redshift, the CO lines and
the mm dust emission are a privileged tool to follow evolution of galaxies and
observe the ISM dynamics at high redshift: they could give an answer about the
debated question of the star-formation history, since many massive remote
starbursts could be dust-enshrouded.


title:
The ISO-LWS map of the Serpens cloud core: I. The SEDs of the IR/SMM
  sources

abstract:
  ISO-LWS mapping observations of the Serpens molecular cloud core are
presented. The spectral range is 50 - 200 micron and the map size is 8' X 8'.
These observations suffer from severe source confusion at FIR wavelengths and
we employ a Maximum Likelihood Method for the spectro-spatial deconvolution.
The strong and fairly isolated source SMM1 FIRS1 presented a test case, whose
modelled spectral energy distribution (SED), within observational errors, is
identical to the observed one. The model results for the other infrared and
submillimetre sources are therefore likely to represent their correct SEDs.
Simulations demonstrating the reliability and potential of the developed method
support this view. For the majority of sources the peak of the SEDs is found
within the spectral range of the LWS and derived temperatures are generally
higher (>30K) than have been found by earlier deconvolution attempts using IRAS
data. SMM sizes are found to be only a few arcsec in diameter. In addition, the
SMMs are generally optically thick even at LWS wavelengths. Self-consistent
radiative transfer calculations indicates that the SMMs are optically thick out
to even longer wavelengths. Models were calculated for five sources, for which
sufficient data were available, viz. SMM 1, 2, 3, 4 and 9. These models are
optically thick out to millimetre wavelengths (wavelength of unit optical depth
900 to 1400 micron). Envelope masses for these SMMs are in the range 2-6 Msun,
which is of course considerably more massive than estimates based on the
optically thin assumption. The luminosities are in the range 10-70 Lsun,
suggesting the formation of low-mass to intermediate mass stars, so that the
existence of such massive envelopes argues for extreme youth of the SMMs in the
Serpens cloud core.


title: The jet and circumburst stellar wind of GRB 980519

abstract:
  We present extensive multi-colour (UBVR_CI_C) photometry of the optical
afterglow of GRB 980519. Upon discovery, 8.3 hours after the burst, the source
was decaying as a power law, (t-t_GRB)^alpha, with a rapid decay rate alpha_1 =
- 1.73+-0.04. About 13 hours after the burst a steepening of the light-curve to
alpha_2 = -2.22+-0.04 was observed. Within the framework of current afterglow
models, we argue that the rapid initial decline, the `break' in the light
curve, and the spectral properties of the afterglow are best interpreted as
being due to a collimated ultra-relativistic jet of fixed opening angle
expanding into an inhomogeneous medium. In this scenario, we find that the
circumburst medium has a density structure that goes as r^(-2.05+-0.22). This
is characteristic of a preexisting wind expelled from a massive star. A
possible physical scenario is that the progenitor star collapsed to form a
black hole (i.e., a `collapsar'), producing the observed burst and afterglow.
However, the supernova signature expected in the light curve in such a scenario
is not detected. This either implies that the redshift of GRB980519 is greater
than 1.5 or that supernovae accompanying GRBs are not standard candles.


title:
One Hundred Years of Observations of the Be Star HDE 245770 (the X-ray
  Binary A0535+26/V725 Tau): The End of an Active Phase

abstract:
  UBV observations of the X-ray binary system A0535+26/V725 Tau at the Crimean
Station of the Sternberg Astronomical Institute in 1980-1998 are presented.
Based on our and published data, we analyze the photometric history of the star
from 1898.


title: Galaxies in the infrared

abstract:
  The mid infrared spectra of the starbursts show the 9.7$\mu m$ silicate
absorption feature and strong mid infrared emission bands centered at 6.2, 7.7,
and 11.3 $\mu$m. Illustrative models of the {\it active} galaxies are
presented: As the starbursts are most likely confined to the central region of
the galaxy the radiative transfer in the nucleus is solved under the assumption
of spherical symmetry. The distribution of stars and dust are adjusted until
the complete infrared spectrum of the galaxies are modeled. The dust is
described as a mixture of large grains, very small grains and PAH, which are
undergoing temperature fluctuations. Although the galactic nuclei are deeply
hidden in the dust its global structure can be estimated by the simple
calculations presented. ISOPHOT samples of eleven {\it active} galaxies and
seven {\it inactive} spirals are presented. The far infrared and submillimeter
spectrum of the {\it active} galaxies can be described by a single modified
black--body at a color temperature of $31.5 \pm 2.8$ K. This leads to a ratio
of infrared luminosity to gas mass, $L_{\rm IR}/M_{\rm gas}$, of $\sim 90$
L$_\odot$/ M$_\odot$. In contrast, the spectral energy distributions of {\it
inactive} spirals require, apart from warm dust of $31.8 \pm 2.8$ K, an
additional very cold component of at most $12.9\pm 1.7$ K. This implies a
$L_{\rm IR}/M_{\rm gas}$ ratio of $\sim 3$ L$_\odot$/ M$_\odot$ for the {\it
inactive} spirals, a factor $\sim 30$ lower than for the {\it active} galaxies.
The detection of such cold dust can be predicted by radiative transfer models.


title: The filament of ionized gas in the outskirt of M87

abstract:
  We report on the filament of ionized gas found at the NE periphery of M87,
the second brightest elliptical galaxy in the Virgo cluster. The object lies at
3.16 arcmin (15.7 kpc) projected distance of the nucleus of M87, and it
coincides in position with the Eastern radio lobe of M87. Long slit
spectroscopy confirmed the gaseus nature of this object, showing Hbeta, [OIII],
[OI], [NII], Halpha and [SII] lines, without any underlying continuum. The
redshift of the object, V = 1170+-25 km/s, agrees with the velocity of M87
itself (V = 1280 km/s), and with the bulk of the ionized material found near
the center of M87. The Halpha flux of this filament corresponds to 1 % of the
ionized material in M87. The radio-optical coincidence together with the
spectral characteristics suggest that the filament is ionized by a shock.


title:
Moderate resolution near-infrared spectroscopy of cool stars: a new
  K-band library

abstract:
  I present an atlas of near-infrared K-band spectra of 31 late-type giants and
supergiants, and two carbon stars. The spectra were obtained at resolving
powers of 830 and 2000, and have a signal-to-noise ratio of 100 or higher.
These data are complemented with results from similar existing libraries in
both K- and H-band, and are used to identify various tools useful for stellar
population studies at moderate resolution. I focus on several of the most
prominent absorption features and (1) investigate the effects of spectral
resolution on measurements of their equivalent width (EW), (2) examine the
variations with stellar parameters of the EWs, and (3) construct composite
indices as indicators of stellar parameters and of the contribution from excess
continuum sources commonly found in star-forming and AGN galaxies. Among the
features considered, the CO (2,0) and CO (6,3) bandheads together with the SiI
1.59 micron feature, first proposed by Oliva, Origlia, and coworkers,
constitute the best diagnostic set for stellar spectral classification and for
constraining the excess continuum emission. The CaI 2.26 micron and MgI 2.28
micron features offer alternatives in the K-band to the CO (6,3) bandhead and
SiI feature.


title: Time Lags in Low Mass X-ray Binaries

abstract:
  Using RXTE/PCA data, we have studied the time lag (TL) properties of a sample
of four accreting neutron stars (NSs), namely 1E1724-3045, GS1826-238,
4U1705-44 and 4U1728-34. The aim of the study is to identify the spectral and
timing state(s) in which TLs are detected. Along this work, we have discovered
TLs between the 7-40 keV hard and 2-7 keV soft photons from 4U1728-34 with
amplitudes similar to those seen in 4U1705-44 (i.e. 2 ms at 5 Hz). We show that
the TLs are only seen in the low states of those sources, but that within the
so-called ``island'' spectral state, some sources display TLs whereas some do
not. On the other hand, we have found that TLs are detected when the associated
Power Density Spectrum (PDS) shows excess power at high frequencies (above 1
Hz).


title:
Relation between $\gamma$-rays and emission lines for the $\gamma$-ray
  loud blazars

abstract:
  The relation between the $\gamma$-ray and the emission line luminosities for
a sample of 36 $\gamma$-ray loud blazars is investigated; an apparent
correlation between them, $L_{\gamma} \propto L_{Line}^{0.69\pm0.11}$, with a
correlation coefficient $r=0.741$ and a chance probability of $p =
1.9\times10^{-6}$, is found. It is found, however, that there is no intrinsic
correlation between them: the apparent correlation is due to the redshift
dependence in a flux-limited sample. Thus no evidence is found to support the
argument that the up-scattered soft photons are from the broad emission lines.
Our analysis does not conflict with the SSC model. The disk-jet symbiosis and
radio/$\gamma$-ray correlation found in the literature are also discussed. The
radio/$\gamma$-ray correlation may be an apparent correlation caused by the
boosting effect since both bands are strongly beamed.


title:
Probing Dense Matter in the cores of AGN: Observations with RXTE and
  ASCA

abstract:
  Preliminary results from an X-ray spectral study of Seyfert 1 galaxies with
ASCA and RXTE are presented. From an analysis of X-ray reprocessing features of
Compton reflection and Fe K-alpha fluorescence, it is found that iron line
strength is not necessarily a good predictor of the amount of reflection. The
variability properties of Fe K-alpha and reflection do not necessarily scale
together and substantial decoupling of the behavior of the reprocessed flux
with respect to continuum variability is common. Such trends suggest the
presence of multiple and/or complex regions of dense matter in AGN cores and
that standard accretion disk models drastically oversimplify reality.


title:
Parameter Estimation in Astronomy with Poisson-Distributed Data. II. The
  Modified Chi-Square-Gamma Statistic

abstract:
  I investigate the use of Pearson's chi-square statistic, the Maximum
Likelihood Ratio statistic for Poisson distributions, and the chi-square-gamma
statistic (Mighell 1999, ApJ, 518, 380) for the determination of the
goodness-of-fit between theoretical models and low-count Poisson-distributed
data. I demonstrate that these statistics should not be used to determine the
goodness-of-fit with data values of 10 or less. I modify the chi-square-gamma
statistic for the purpose of improving its goodness-of-fit performance. I
demonstrate that the modified chi-square-gamma statistic performs (nearly) like
an ideal chi-square statistic for the determination of goodness-of-fit with
low-count data. On average, for correct (true) models, the mean value of
modified chi-square-gamma statistic is equal to the number of degrees of
freedom (nu) and its variance is 2*nu --- like the chi-square distribution for
nu degrees of freedom. Probabilities for modified chi-square-gamma
goodness-of-fit values can be calculated with the incomplete gamma function. I
give a practical demonstration showing how the modified chi-square-gamma
statistic can be used in experimental astrophysics by analyzing simulated X-ray
observations of a weak point source (signal-to-noise ratio of 5.2; 40 photons
spread over 317 pixels) on a noisy background (0.06 photons per pixel).
Accurate estimates (95% confidence intervals/limits) of the location and
intensity of the X-ray point source are determined.


title:
10^20 eV Cosmic-Ray and Particle Physics with Kilometer-Scale Neutrino
  Telelscopes

abstract:
  We show that a kilometer-scale neutrino observatory, though optimized for TeV
to PeV energy, is sensitive to the neutrinos associated with super-EeV sources.
These include super-heavy relics, neutrinos associated with the Greisen cutoff,
and topological defects which are remnant cosmic structures associated with
phase transitions in grand unified gauge theories. It is a misconception that
new instruments optimized to EeV energy are required to do this important
science. Because kilometer-scale neutrino telescopes can reject atmospheric
backgrounds by establishing the very high energy of the signal events, they
have sensitivity over the full solid angle, including the horizon where most of
the signal is concentrated. This is important because up-going neutrino-induced
muons, routinely considered in previous calculations, are absorbed by the
Earth.


title: Substellar Companions to Nearby Stars from NICMOS Surveys

abstract:
  A coronagraphic imaging survey of 65 nearby stars was conducted using the
Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space
Telescope by the Instrument Definition Team. Using these guaranteed time
observations we searched for very low mass stellar and substellar (extra-solar
giant planet and brown dwarf) companions to young main sequence and late M
dwarf stars. Nineteen additional stars, similarly observed in our circumstellar
disk program, were also examined for evidence of companions. We discuss the
large depth and dynamic range of these surveys which have given rise to several
putative and confirmed detections. Using follow-up spectrographic observations
obtained with the Space Telescope Imaging Spectrograph (STIS) we have begun to
characterize the physical nature of the objects found in the companion search
program.


title: NICMOS Imaging of Candidate Extra-Solar Planetary Systems

abstract:
  The connection between the formation and growth of planetesimals into larger
bodies and the circumstellar debris disks around young and nascent stars from
which they arise has been the subject of continual speculation, discussion and
inquiry, since the original scenario for such evolution was first expanded upon
by Laplace (1796) following the general proposition by Kant (1755). NICMOS
coronagraphy has enabled both the direct imaging of such circumstellar disks
seen in scattered light about more mature stars (other than b Pictoris)
exhibiting morphologically resolved spatial features, and the detection of
substellar companions (brown dwarfs and extra-solar giant planets) with masses
extending into the Jovian domain for recently formed objects (< a few x 107
years). Exploiting this capability, approximately 18% of the NICMOS IDTs
observing time on HST was dedicated to addressing fundamental questions
relating to the origins of extra-solar systems while exploring the Environments
of Nearby Stars under the umbrella of our EONS project.


title: Fragmentation and Star Formation in Turbulent Cores

abstract:
  We examine the conditions under which binary and multiple stars may form out
of turbulent molecular cloud cores using high resolution 3-D, adaptive mesh
refinement (AMR) hydrodynamics (Truelove et al., 1997, 1998; Klein, 1999). We
argue that previous conclusions on the conditions for cloud fragmentation have
limited applicability, since they did not allow for the nonlinear density and
velocity perturbations that are ubiquitous in molecular cloud cores. Over the
past year, we have begun to simulate the evolution of marginally stable,
turbulent cores. These models have radii, masses, density contrasts, turbulent
linewidths, and projected velocity gradients consistent with observations of
low-mass molecular cloud cores. Our models are evolved in time under
self-gravitational hydrodynamics with AMR using a barotropic equation of state
that models the transition from an isothermal to an adiabatic equation of
state. We examine several properties of the resulting protostellar fragments
and discuss the qualitative nature of the fragmentation process in realistic
cloud cores: the transition from single to binary and multiple stars; the
formation of misaligned binary systems; and the role played by filament
formation in the formation of stars.


title: Cosmology from Maxima-1, Boomerang and COBE/DMR CMB Observations

abstract:
  Recent results from BOOMERANG-98 and MAXIMA-1, taken together with COBE-DMR,
provide consistent and high signal-to-noise measurements of the CMB power
spectrum at spherical harmonic multipole bands over $2<\ell\lta800$. Analysis
of the combined data yields 68% (95%) confidence limits on the total density,
$\Omega_{\rm {tot}}\simeq 1.11 \pm 0.07 (^{+0.13}_{-0.12})$, the baryon
density, $\Omega_b h^2\simeq 0.032^{+0.005}_{-0.004} (^{+0.009}_{-0.008})$, and
the scalar spectral tilt, $n_s\simeq1.01^{+0.09}_{-0.07} (^{+0.17}_{-0.14})$.
These data are consistent with inflationary initial conditions for structure
formation. Taken together with other cosmological observations, they imply the
existence of both non-baryonic dark matter and dark energy in the universe.


title:
CO and Near-Infrared Observations of High-Redshift Submillimeter
  Galaxies

abstract:
  I discuss our ongoing Owens Valley Millimeter Array observations and Keck
near-infrared wavelength observations of the high-redshift sub-mm population of
galaxies. These observations are important for our understanding of the distant
universe since the sub-mm population accounts for a large fraction of the
extragalactic background at mm/sub-mm wavelengths and contributes significantly
to the total amount of star-formation and AGN activity at high redshift. The CO
data suggest that the sub-mm galaxies are analogous to the gas-rich
ultraluminous systems found in the local universe. Initial near-infrared data
show that many of the sub-mm galaxies are faint-red sources which are
undetected at ultraviolet/optical wavelengths. These results highlight the
importance that future sensitive mm-wavelength instruments, such as the LMT and
ALMA, will have on our understanding of the early evolution and formation of
galaxies.


title: Improved timing formula for the PSR B1257+12 planetary system

abstract:
  We present a new analysis of the dynamics of the planetary system around the
pulsar B1257+12. A semi-analytical theory of perturbation between
terrestrial-mass planets B and C is developed and applied to improve
multi-orbit timing formula for this object. We use numerical simulations of the
pulse arrival times for PSR B1257+12 to demonstrate that our new timing model
can serve as a toll to determine the masses of the two planets.


title: Mass Loss from Globular Clusters

abstract:
  We consider both observational and theoretical issues related to dynamical
mass loss from the old globular star clusters of the Galaxy. On the
observational side the evidence includes tidal tails and extratidal extensions,
kinematic effects, effects on the mass function, and influences on the
statistical properties of surviving objects. Even for isolated clusters, the
theoretical issues are not fully understood. The effects of a steady tide (i.e.
for a cluster in a circular orbit) include the imposition of a tidal boundary,
and lowering of the escape energy. Less familiar, however, are the effects of
induced mass loss. Even the definition of an ``escaper'' is not
straightforward. When mass loss is driven by relaxation, as in N-body models,
the rate of loss of mass does not scale in a simple way with the relaxation
time. Reasons for this include the very long time scales on which stars escape
even with energies above the escape threshold. For the realistic case of
unsteady tides it is still unclear under what circumstances mass loss is
dominated by relaxation or tidal heating.


title: The plasma-solid transition:two simple examples

abstract:
  Using a simple criterion proposed by Kirzhnitz,we have discussed the
plasma-solid transition in two simple model cases: the Fermi-Dirac and Bose
Einstein gas.Some possibilities of astrophysical applications of our results
are also indicated.


title:
The multiphase nature of the intra-cluster medium of some clusters of
  galaxies

abstract:
  The discovery of EUV and soft X-ray excess emission in clusters of galaxies
(the cluster soft-excess phenomenon) challenged the notion of the hot ($\sim
10^{7-8}$ K) gas as the only dominant thermal component of the intracluster
medium (ICM). The spatial analysis of ROSAT PSPC 1/4 keV images presented here
reveals compelling evidence for substantial amounts of cold gas (HI) in the ICM
of the Coma and Virgo clusters. This finding bolsters the original
interpretation of the soft excess as emission from a `warm' ($\sim 10^6$ K) gas
and points to the scenario of a multiphase ICM where the hot component
co-exists with gases at sub-Virial temperatures (the `warm' and `cold' phases).


title: Dissipative Collapse of a Spherical Cluster of Gas Clouds

abstract:
  With a view to understand the galaxy/star formation scenario, we investigate
the dissipative collapse of a spherical cluster of gas clouds with an isotropic
velocity distribution. The time scale for collapse to one tenth radius is
studied as a function of the collision time in the system. The scalar virial
equation is used to investigate the evolution of the size of the cluster. This
is supplemented with an evolution equation for the random kinetic energy. The
above system is numerically solved and the results analyzed. For large values
of the collision time we find that the time scale for collapse is proportional
to the collision time as expected. However for large values of the dissipation,
i.e. for small collision times, the collapse time shows a nonlinear dependence
on the collision time.


title:
Cosmological Density Perturbations in two fluid models on spin dominated
  inflation and the stability of Friedmann metric

abstract:
  A spinning fluid embedded in a space section flat Friedmann model is used to
compute the cosmological density perturbation of the model.The spinning fluid
obeys the Einstein-Cartan field equations while the Friedmann embedded model is
assumed to obey the general the Friedmann equation in General Relativity.It is
shown that at the early epochs of the Universe the spin-torsion contribution to
the density perturbation on the matter phase dominates over the radiation
perturbation.On the other hand at the present epochs of the Universe the
spin-torsion contribution is more efficient in the matter
perturbation.Stability of the Friedmann solution in Einstein-Cartan cosmology
is also discussed.


title: On the cosmological distance and redshift between any two objects

abstract:
  We discuss the problem of how to calculate the distance between two
cosmological objects given their redshifts and angular separation on the sky.
Although of a fundamental nature, this problem and its solution seem to lack a
detailed description in the literature. We present a new variant of its
solution and quantitatively assess the most commonly used approximation.


title:
A framework for perturbations and stability of differentially rotating
  stars

abstract:
  The paper provides a new framework for the description of linearized
adiabatic lagrangian perturbations and stability of differentially rotating
newtonian stars. In doing so it overcomes problems in a previous framework by
Dyson and Schutz and provides the basis of a rigorous analysis of the stability
of such stars. For this the governing equation of the oscillations is written
as a first order system in time. From that system the generator of time
evolution is read off and a Hilbert space is given where it generates a
strongly continuous group. As a consequence the governing equation has a
well-posed initial value problem. The spectrum of the generator relevant for
stability considerations is shown to be equal to the spectrum of an operator
polynomial whose coefficients can be read off from the governing equation.
Finally, we give for the first time sufficient criteria for stability in the
form of inequalities for the coefficients of the polynomial. These show that a
negative canonical energy of the star does not necessarily indicate
instability. It is still unclear whether these criteria are strong enough to
prove stability for realistic stars.


title:
Population effects on the Red Giant Clump absolute magnitude, and
  distance determinations to nearby galaxies

abstract:
  (Abridged) The red giant clump has been recently argued to be a reliable
distance indicator for the galaxies in the Local Group. We re-address the
problem of the systematic magnitude differences (DeltaM_I) between the local
clump revealed by Hipparcos, and the clump stars observed in distant galaxies.
First, we present tables and equations with the theoretically-predicted clump
M_I as a function of age and metallicity, that allow the computation of
DeltaM_I for any given galaxy model. We then explain in some detail what
determines the distribution of masses, ages, and metallicities of clump stars
in a galaxy. We point out that in galaxies with recent/ongoing star formation,
the age distribution of clump stars is strongly biased toward younger (1-3 Gyr)
ages, and hence toward higher metallicities. Obviously, this does not happen in
galaxies with predominantly old stellar populations. We construct a model for
the local clump that is shown to produce distributions of metallicities,
colours, and magnitudes, similar to those derived from spectroscopic and
Hipparcos data. Bulge, Magellanic Clouds, and Carina dSph models are used to
analyse the values of DeltaM_I for these systems. We show how the clump-RR
Lyrae data is well reproduced by the models. However, despite this, the models
indicate that the linear DeltaM_I vs. [Fe/H] relations that have been derived
from the data are not general. Finally, we provide revised clump distances to
the Bulge, Magellanic Clouds, and Carina dSph. The largest DeltaM_I values are
found for the Magellanic Clouds and Carina dSph, which turn out to be located
at distance moduli 0.2-0.3 mag longer than indicated by works which ignore
population effects. The Galactic Bulge, instead, may be slightly closer (0.1
mag) than indicated by previous works based on the red clump.


title:
Induced Scattering and Two-Photon Absorption of Alfven Waves with
  Arbitrary Propagation Angles

abstract:
  The equation for temporary evolution of spectral energy of collisionless
Alfven waves is derived in framework of weak turbulence theory. The main
nonlinear processes for such conditions are induced scattering and two quantum
absorption of Alfven waves by thermal ions. The equation for velocity
distribution of thermal particles is derived that describes diffusion in
momentum space due to this nonlinear processes. Comparison is done with the
results of another authors. Results obtained are qualitatively differ from the
ones obtained for the case of Alfven waves propagation along mean magnetic
field.


title:
Discovery of hard X-ray emission from Type II bursts of the Rapid
  Burster

abstract:
  We report on results of BeppoSAX Target Of Opportunity (TOO) observations of
the source MXB 1730-335, also called the Rapid Burster (RB), made during its
outburst of February-March 1998. We monitored the evolution of the spectral
properties of the RB from the outburst decay to quiescence. During the first
TOO, the X-ray light curve of the RB showed many Type II bursts and its
broadband (1-100 keV) spectrum was acceptably fit with a two blackbody plus
power law model. Moreover, to our knowledge, this is the first time that this
source is detected beyond 30 keV.


title: Pre-Orion Cores in the Trifid Nebula

abstract:
  The Trifid nebula is a young HII region undergoing a burst of star formation.
In this article, we report on far-infrared and millimeter continuum and line
observations of several massive and bright protostellar sources in the vicinity
of the exciting star fo the nebula, just behind the ionization front. These
objects are probably young protostars (Class 0) and are associated with very
massive cores (M ~ 8-90 Msol) powering young energetic outflows. Analysis of
the far-infrared emission in the 45-200 micron range from ISO/LWS data shows
that they are embedded in cold dense material. Inspection of their physical
properties suggest that they are similar to the dust protostellar cores
observed in Orion, although at an earlier evolutionary "Pre-Orion" stage. The
cores are embedded in a compressed layer of dense gas. Based on comparison with
the models, we find that the cores could have formed from the fragmentation of
the layer and that the birth of the protostars was triggered by the expansion
of the Trifid nebula.


title: Dual-Frequency VSOP Observations of AO 0235+164

abstract:
  AO 0235+164 is a very compact, flat spectrum radio source identified as a BL
Lac object at a redshift of z=0.94. It is one of the most violently variable
extragalactic objects at both optical and radio wavelengths. The radio
structure of the source revealed by various ground-based VLBI observations is
dominated by a nearly unresolved compact component at almost all available
frequencies.
  Dual-frequency space VLBI observations of AO 0235+164 were made with the VSOP
mission in January-February 1999. The array of the Japanese HALCA satellite and
co-observing ground radio telescopes in Australia, Japan, China and South
Africa allowed us to study AO 0235+164 with an unprecedented angular resolution
at frequencies of 1.6 and 5 GHz. We report on the sub-milliarcsecond structural
properties of the source. The 5-GHz observations led to an estimate of T_B >
5.8 x 10^{13} K for the rest-frame brightness temperature of the core, which is
the highest value measured with VSOP to date.


title:
A simluated TCDM cosmology cluster catalogue: the NFW profile and the
  temperature-mass scaling relations

abstract:
  We have extracted over 400 clusters, covering more than 2 decades in mass,
from three simulations of the TCDM cosmology. This represents the largest,
uniform catalogue of simulated clusters ever produced. The clusters exhibit a
wide variety of density-profiles. Only a minority are well-fit in their outer
regions by the widely used density profile of Navarro, Frenk & White (1977).
Others have steeper outer density profiles, show sharp breaks in their density
profiles, or have significant substructure. If we force a fit to the NFW
profile, then the best-fit concentrations decline with increasing mass, but
this is driven primarily by an increase in substructure as one moves to higher
masses. The measured temperature-mass relations for properties measured within
a sphere enclosing a fixed overdensity all follow the self-similar form,
T\propto M^{2/3}, however the normalisation is lower than in observed clusters.
The temperature-mass relations for properties measured within a fixed physical
radius are significantly steeper then this. Both can be accurately predicted
using the NFW model.


title: Distribution of Cold dust in Orion A and B

abstract:
  Large scale far-infrared (FIR) observations of the Orion complex at 205 and
138 micron are presented with an aim of studying the distribution of cold (< 25
K) dust. The maps in these FIR bands extend over approximately 3600 sq. arcmin
and cover regions around OMC-1, 2, 3 in Orion A and NGC 2023 and NGC 2024 in
Orion B. Some limited regions have also been mapped at 57 micron. A total of 15
sources in Orion A and 14 in Orion B (south) have been identified from our FIR
maps. Dust temperature distribution in both Orion A and Orion B (south) have
been determined reliably using the maps at 205 & 138 micron obtained from
simultaneous observations using almost identical beams (1.6 dia). These
temperatures have been used to generate map of the optical depth at 150 micron,
for the Orion B region. The coldest source detected is in OMC-3 and has a
temperature of about 15 K. The diffuse FIR emission in the different
sub-regions is found to vary between 25% to 50% of the total FIR emission from
that sub-region.


title: X-ray emission from young stars in the Tucanae association

abstract:
  We report on X-ray emission from members of the recently discovered Tucanae
association, a group of stars with youth signatures and similar space motion.
The Tucanae association is the nearest known region of recent star formation
(at 45 pc) far from molecular clouds. We have made use of the ROSAT Data
Archive, and searched for X-rays from Tucanae stars in both ROSAT All-Sky
Survey (RASS) and pointed observations. The RASS detection rate for the Tucanae
members is 59%. We compare the X-ray luminosity function of the Tucanae
association to that of other star forming regions and young star clusters. Both
the X-ray luminosity function and the strong variability observed in the X-ray
lightcurves suggest that the examined stars are young, on the order of 10-30
Myrs.


title: HeII Recombination Lines From the First Luminous Objects

abstract:
  The hardness of the ionizing continuum from the first sources of UV radiation
plays a crucial role in the reionization of the intergalactic medium (IGM).
While usual stellar populations have soft spectra, mini-quasars or metal-free
stars with high effective temperatures may emit hard photons, capable of doubly
ionizing helium and increasing the IGM temperature. Absorption within the
source and in the intervening IGM will render the ionizing continuum of
high-redshift sources inaccessible to direct observation. Here we show that
HeII recombination lines from the first luminous objects are potentially
detectable by the Next Generation Space Telescope. Together with measurements
of the hydrogen Balmer alpha emission line, this detection can be used to infer
the ratio of HeII to HI ionizing photons. A measurement of this ratio would
shed light on the nature and emission mechanism of the first luminous sources,
with important astrophysical consequences for the reheating and reionization of
the IGM.


title: Cosmological magnetic fields

abstract:
  Magnetic fields are observed not only in stars, but in galaxies, clusters,
and even high redshift Lyman-alpha systems. In principle, these fields could
play an important role in structure formation and also affect the anisotropies
in the cosmic microwave background radiation (CMB). The study of cosmological
magnetic fields aims not only to quantify these effects on large-scale
structure and the CMB, but also to answer one of the outstanding puzzles of
modern cosmology: when and how do magnetic fields originate? They are either
primordial, i.e. created before the onset of structure formation, or they are
generated during the process of structure formation itself.


title: Extracting Energy from Black Hole through Transition Region

abstract:
  A new scenario for extracting energy from a Kerr black hole is proposed. With
magnetic field lines connecting plasma particles inside the ergosphere with
remote loads, the frame dragging twists the field lines so that energy and
angular momentum are extracted from the plasma particles. If the magnetic field
is strong enough, the energy extracted from the particles can be so large that
the particles have negative energy as they fall into the black hole. So
effectively the energy is extracted from the black hole.
  The particles inside the ergosphere can be continuously replenished with
accretion from a disk surrounding the black hole, so a transition region with
sufficient amount of plasma is formed between the black hole's horizon and the
inner edge of the disk. Thus the energy can be continuously extracted from the
black hole through the transition region. This may be the most efficient way
for extracting energy from a Kerr black hole: in principle almost all of the
rotational energy (up to $\approx 29%$ of the total energy of the black hole)
can be extracted.


title:
Gravitational Lens Statistics for Generalized NFW Profiles: Parameter
  Degeneracy and Implications for Self-Interacting Cold Dark Matter

abstract:
  Strong lensing is a powerful probe of the distribution of matter in the cores
of clusters of galaxies. Recent studies suggest that the cold dark matter model
predicts cores that are denser than those observed in galaxies, groups and
clusters. One possible resolution of the discrepancy is that the dark matter
has strong interactions (SIDM), which leads to lower central densities. A
generalized form of the Navarro, Frenk and White profile (Zhao profile) may be
used to describe these halos. In this paper we examine gravitational lensing
statistics for this class of model. The optical depth to multiple imaging is a
very sensitive function of the profile parameters in the range of interest for
SIDM halos around clusters of galaxies. Less concentrated profiles, which
result from larger self-interaction cross-sections, can produce many fewer
lensed pairs. Lensing statistics provide a powerful test for SIDM. More
realistic and observationally oriented calculations remain to be done, however
larger self-interaction cross-sections may well be ruled out by the very
existence of strong lenses on galaxy cluster scales. The inclusion of centrally
dominant cluster galaxies should boost the cross-section to multiple imaging.
However our preliminary calculations suggest that the additional multiple
imaging rate is small with respect to the differences in multiple imaging rate
for different halo profiles. In future statistical studies, it will be
important to properly account for the scatter among halo profiles since the
optical depth to multiple imaging is dominated by the most concentrated members
of a cluster population.


title:
Stellar orbits in triaxial clusters around black holes in galactic
  nuclei

abstract:
  We investigate the orbital structure of a model triaxial star cluster,
centered around a supermassive black hole (BH), appropriate to galactic nuclei.
Sridhar and Touma (1999) proved that the presence of the BH enforces some
regularity in the dynamics within the radius of influence of the BH. We employ
their averaging method to reduce the degrees of freedom from three to two.
Numerical orbit integrations, together with Poincar\'e surfaces of section
allow us to draw a global portrait of the orbital structure; in our
calculations we employ a model cluster potential that is triaxial and harmonic.
The averaged dynamics of the axisymmetric case is integrable, and we present a
detailed comparison of orbits in oblate and prolate axisymmetric potentials.
Both cases support resonant orbits with fixed values of eccentricity,
inclination, and periapse, whose lines of nodes rotates steadily. We then
systematically explore significantly triaxial potentials, possessing small
oblateness, or prolateness. Resonant orbits and their families are studied both
numerically, and through secular perturbation theory. Chaos appears to be
suppressed for all the cases we studied, and we obtain effective third
integrals. Some of the orbits appear to reinforce the shape of the potential;
we provide phase space, as well as real space portraits of these orbits. A
particularly promising resonant orbit exists in highly prolate, triaxial
potentials.


title: Iron K line emission in AGN: observations

abstract:
  Iron K-alpha lines are key diagnostics of the central regions of AGN. Their
profiles indicate that they are formed deep in the potential well of the
central black hole, where extreme broadening and red shift occur. The profiles
are most easily reproducible in an accretion disk: the lack of significant
emission blue-ward of the rest energy is difficult produce in other geometries.
In one source an apparent (and perhaps variable) absorption feature in the red
wing of the line may represent rare evidence for inflow onto the black hole.
Sample analysis has defined the mean properties, showing a strong concentration
of the emission in the central regions and face-on accretion disks, at least in
Seyfert 1 galaxies. Surprising results have been obtained from examination of
the line variability. Strong profile changes may be accounted for by changes in
the illumination pattern of the central, relativistic part of the disk. In at
least the case of MCG-6-30-15, there is evidence for emission from within 6
R_g, possibly indicating a spinning black hole. Developing an understanding of
these complex changes has the potential to reveal the geometry and kinematics
of the inner few gravitational radii around extragalactic black holes.


title:
The Frequency of Polarized Broad Emission Lines in Type 2 Seyfert
  Galaxies

abstract:
  We have discovered polarized broad emission lines in five type 2 Seyfert
galaxies (NGC 424, NGC 591, NGC 2273, NGC 3081, and NGC 4507), establishing
that these objects are type 1 Seyferts obscured by dense circumnuclear
material. The galaxies are part of a distance-limited sample of 31 Seyfert 2s,
for which spectropolarimetric observations are now complete. Combined with
published reports, our results indicate that at least 11 of the galaxies in
this sample, or > 35%, possess hidden broad-line regions. This represents the
first reliable estimate of the frequency of polarized broad emission lines in
type 2 Seyferts, which has important implications for the general applicability
of Seyfert unification models.


title: Face-on Dust Disks in Galaxies with Optical Jets

abstract:
  The presence of optical synchrotron jets in radio galaxies is relatively
rare. Here, we show that of the nearest five FR-I 3CR radio galaxies showing
optical jets, {\it four} show evidence for almost circular, presumably face-on,
dust disks. This is strong support for the two-fold idea that (\romannumeral1)
jets emerge close to perpendicular to inner gas disks and (\romannumeral2)
optical non-thermal synchrotron emission is seen only when the jet points
towards the observer. The implied critical angle to the line-of-sight is
approximately 30 - $40^{\circ}$, i.e. if the angle of the jet to the
line-of-sight is less than about $40^{\circ}$ we see an optical jet. The
corresponding relativisitic $\gamma$ factor is $\approx 1.5$ which is
consistent with current observations of jet proper motion that show a range up
to $\gamma \sim 6$ for M87. The relatively low speeds implied by $\gamma
\approx 1.5$ may be due to a global deceleration of the jet as in unified
theories, or else to stratification within the jet. Unresolved nuclei are
common in the optical. Their luminosities are also consistent with the beaming
concept when compared to inclination inferred from the dust lanes. The disk
sizes are typically several hundred parsecs, to kiloparsec size. The galaxy
with an optical jet that does not show a face-on disk, M87, instead has more
complex radial dust and ionized gas filaments.


title: Emission-Line Properties of the Optical Filaments of NGC 1275

abstract:
  Extended nebular filaments are seen at optical wavelengths in NGC 1275, the
central galaxy in the Perseus cluster. The agents responsible for the
excitation of these filaments remain poorly understood. In this paper we
investigate possible mechanisms for powering the filaments, using measurements
from an extensive spectroscopic data set acquired at the Lick Observatory 3-m
Shane telescope. The results show that the filaments are in an extremely low
ionization and excitation state. The high signal-to-noise ratio of the spectra
allows us to measure or place sensitive upper limits on weak but important
diagnostic lines. We compare the observed line intensity ratios to the
predictions of various ionization models, including photoionization by an
active galactic nucleus, shock heating, stellar photoionization, and
photoionization by the intracluster medium. We also investigate possible roles
for cluster extreme-ultraviolet emission, and filtering of cluster soft X-ray
emission by an ionized screen, in the energetics of the filaments. None of
these mechanisms provides an entirely satisfactory explanation for the physical
state of the nebulae. Heating and ionization by reconnection of the
intracluster magnetic field remains a potentially viable alternative, which
merits further investigation through Faraday rotation studies.


title: Characterising the Primordial Cosmic Perturbations

abstract:
  The most general homogeneous and isotropic statistical ensemble of linear
scalar perturbations which are regular at early times, in a universe with only
photons, baryons, neutrinos, and a cold dark matter (CDM) component, is
described by a 5x5 symmetric matrix-valued generalization of the power
spectrum. This description is complete if the perturbations are Gaussian, and
even in the non-Gaussian case describes all observables quadratic in the small
perturbations. The matrix valued power spectrum describes the auto- and
cross-correlations of the adiabatic, baryon isocurvature, CDM isocurvature,
neutrino density isocurvature, and neutrino velocity isocurvature modes. In
this paper we examine the prospects for constraining or discovering
isocurvature modes using forthcoming MAP and PLANCK measurements of the cosmic
microwave background (CMB) anisotropy. We also consider the degradation in
estimates of the cosmological parameters resulting from the inclusion of these
modes. In the case of MAP measurements of the temperature alone, the
degradation is drastic. When isocurvature modes are admitted, uncertainties in
the amplitudes of the mode auto-- and cross--correlations, and in the
cosmological parameters, become of order one. With the inclusion of
polarisation (at an optimistic sensitivity) the situation improves for the
cosmological parameters but the isocurvature modes are still only weakly
constrained. Measurements with PLANCK's estimated errors are far more
constraining, especially so with the inclusion of polarisation. If PLANCK
operates as planned the amplitudes of isocurvature modes will be constrained to
less than ten per cent of the adiabatic mode and simultaneously key
cosmological parameters will be estimated to a few per cent or better.


title:
Seeing Galaxies Through Thick and Thin: II. Direct Measures of
  Extinction in Spiral Disks Through Spectroscopy of Overlapping Galaxies

abstract:
  We use slit spectroscopy of overlapping pairs of galaxies to directly
determine the extinction in disks of foreground spiral galaxies. The Doppler
shifts of pair members are determined via cross-correlation and their relative
correlation amplitudes are used to separate their contributions to the combined
spectra in regions of overlap. This spectroscopic approach is less subject to
stringent symmetry constraints than our previous purely photometric analyses.
Extinctions of foreground members were obtained for 6 of the candidates in our
sample of 18 mostly spiral/spiral pairs, when the signal to noise and velocity
difference were suitable. In agreement with our previous imaging results, we
find that the extinction in interarm regions is very modest, typically A_B=0.1
mag (corrected to face on), while spiral arms exhibit higher extinctions of 0.3
mag.


title:
Public Release of N-body simulation and related data by the Virgo
  consortium

abstract:
  We are making available on the WWW a selection of the archived data from
N-body simulations carried out by the Virgo consortium and related groups. This
currently includes: (i) time-slice, lightcone and cluster data from the two
$10^9$-particle Hubble volume simulations described by Evrard 1998; (ii)
time-slice data from simulations of 4 different cold dark matter cosmological
models with $256^3$ particles analysed by Jenkins et al 1998; (iii) Dark halo
catalogs, merger trees and galaxy catalogs from the GIF project described by
Kauffmann et al 1999. Basic software is supplied to read the data. The data can
be accessed from: http://www.mpa-garching.mpg.de/Virgo/data_download.html


title: Order and Chaos in the Local Disc Stellar Kinematics

abstract:
  The effects of the Galactic bar on the velocity distribution of old disc
stars in the Solar neighbourhood are investigated using high-resolution 2D test
particle simulations. A detailed orbital analysis reveals that the structure of
the U-V distribution in these simulations is closely related to the phase-space
extent of regular and chaotic orbits. At low angular momentum and for a
sufficiently strong bar, stars mainly follow chaotic orbits which may cross the
corotation radius and the U-V contours follow lines of constant Jacobi's
integral except near the regions occupied by weakly populated eccentric regular
orbits. These properties can naturally account for the observed outward motion
of the local high asymmetric drift stars.


title:
Self-Consistent Response of a Galactic Disk to an Elliptical
  Perturbation Halo Potential

abstract:
  We calculate the self-consistent response of an axisymmetric galactic disk
perturbed by an elliptical halo potential of harmonic number m = 2, and obtain
the net disk ellipticity. Such a potential is commonly expected to arise due to
a galactic tidal encounter and also during the galaxy formation process. The
self-gravitational potential corresponding to the self-consistent,
non-axisymmetric density response of the disk is obtained by inversion of
Poisson equation for a thin disk. This response potential is shown to oppose
the perturbation potential, because physically the disk self-gravity resists
the imposed potential. This results in a reduction in the net ellipticity of
the perturbation halo potential in the disk plane. The reduction factor
denoting this decrease is independent of the strength of the perturbation
potential, and has a typical minimum value of 0.75 - 0.9 for a wide range of
galaxy parameters. The reduction is negligible at all radii for higher
harmonics (m > or = 3) of the halo potential. (abridged).


title: Discovery of Non-Thermal X-Rays from the Shell of RCW86

abstract:
  We report the ASCA (Advanced Satellite for Cosmology and Astrophysics)
results of RCW 86, a shell-like supernova remnant (SNR). The bright region in
the X-ray band traces the radio clumpy shell, although details of the structure
are different. The X-ray spectrum from each part of the shell can not be fitted
to a thin thermal plasma model, but requires, at least three components: a low
temperature plasma of 0.3 keV, high temperature plasma of > several keV, and a
power-law component with a photon index = 3. The abundances of O, Ne, Mg and Si
are significantly higher than that of Fe, indicating that RCW 86 is a type II
SNR. The absorption column of 3e21 H cm^-2 indicates the distance to the SNR to
be several kpc. The power-law component can be interpreted to be synchrotron
radiation of high energy electrons. Assuming energy density equipartition
between the magnetic field and the electrons, and using the radio and X-ray
spectra, we argue that high energy electrons are accelerated up to 20 TeV. The
acceleration efficiency is, however, different from shell to shell.


title:
Power Spectrum of the density of cold atomic gas in the Galaxy towards
  Cas A and Cygnus A

abstract:
  We have obtained the power spectral description of the density and opacity
fluctuations of the cold HI gas in the Galaxy towards Cas A, and Cygnus A. We
have employed a method of deconvolution, based on CLEAN, to estimate the true
power spectrum of optical depth of cold HI gas from the observed distribution,
taking into account the finite extent of the background source and the
incomplete sampling of optical depth over the extent of the source. We
investigate the nature of the underlying spectrum of density fluctuations in
the cold HI gas which would be consistent with that of the observed HI optical
depth fluctuations. These power spectra for the Perseus arm towards Cas A, and
for the Outer arm towards Cygnus A have a slope of 2.75 +/- 0.25 (3sigma
error). The slope in the case of the Local arm towards Cygnus A is 2.5, and is
significantly shallower in comparison. The linear scales probed here range from
0.01 to 3 pc. We discuss the implications of our results, the non-Kolmogorov
nature of the spectrum, and the observed HI opacity variations on small
transverse scales.


title:
Optimizing the angular resolution of the HEGRA telescope system to study
  the emission region of VHE gamma rays in the Crab Nebula

abstract:
  The HEGRA system of imaging atmospheric Cherenkov telescopes provides for
specially selected classes of events an angular resolution of better than 3'.
By comparing the measured angular distribution of TeV gamma rays from the Crab
Nebula with the distribution expected on the basis of Monte Carlo simulations,
and with measurements of gamma rays from the point source Mrk 501, we conclude
that the rms size of the VHE gamma-ray emission region in the Crab Nebula is
less than 1.5'.


title: Weak Weak Lensing: How Accurately Can Small Shears be Measured?

abstract:
  Now that weak lensing signals on the order of a percent are actively being
searched for (cosmic shear, galaxy-galaxy lensing, large radii in clusters...)
it is important to investigate how accurately weak shears can be determined.
Many systematic effects are present, and need to be understood. I show that the
Kaiser et al. technique can leave residual systematic errors at the percent
level (through imperfect PSF anisotropy correction), and present an alternative
technique which is able to recover shears a factor of ten weaker.


title:
The correlation between black hole mass and bulge velocity dispersion in
  hierarchical galaxy formation models

abstract:
  Recent work has demonstrated that there is a tight correlation between the
mass of a black hole and the velocity dispersion of the bulge of its host
galaxy. We show that the model of Kauffmann & Haehnelt, in which bulges and
supermassive black holes both form during major mergers, produces a correlation
between M_bh and sigma with slope and scatter comparable to the observed
relation. In the model, the M_bh - sigma relation is significantly tighter than
the correlation between black hole mass and bulge luminosity or the correlation
between bulge luminosity and velocity dispersion. There are two reasons for
this: i) the gas masses of bulge progenitors depend on the velocity dispersion
but not on the formation epoch of the bulge, whereas the stellar masses of the
progenitors depend on both; ii) mergers between galaxies move black holes along
the observed M_bh - sigma relation, even at late times when the galaxies are
gas-poor and black holes grow mainly by merging of pre-existing black holes. We
conclude that the small scatter in the observed M_bh - sigma relation is
consistent with a picture in which bulges and black holes form over a wide
range in redshift.


title: Daemon detection experiment

abstract:
  A month-long observation of two horizontal ZnS(Ag) scintillating screens, 1
m^2 in area and located one above the other a certain distance apart, revealed
about 10 correlated signals, whose time shift corresponds to an average
velocity of only ~10-15 km/s. We assign the origin of these signals to the
negative daemons, i.e. electrically charged Planckian particles, which
supposedly form a part of the DM in the Galactic disk and were captured into
the near-Earth orbits. The estimated flux of daemons is >=10^-4 m^-2 s^-1. The
key part in the detection of daemons is played apparently by two processes: (i)
the daemon shedding the captured heavy nucleus in a few tens of mks as a result
of a relatively rapid decay of the daemon-containing nucleons, and (ii)
emission of numerous Auger electrons and nuclear particles occurring in the
next capture or recapture of a (heavier) nucleus by the daemon.


title:
Electron Positron Annihilation Radiation from SgrA East at the Galactic
  Center

abstract:
  Maps of the Galactic electron-positron annihilation radiation show evidence
for three distinct and significant features: (1) a central bulge source, (2)
emission in the Galactic plane, and (3) an enhancement of emission at positive
latitudes above the Galactic Center. In this paper, we explore the possibility
that Sgr A East, a very prominent radio structure surrounding the Galactic
nucleus, may be a significant contributer to the central bulge feature. The
motivation for doing so stems from a recently proposed link between this radio
object and the EGRET gamma-ray source 2EG J1746-2852. If this association is
correct, then Sgr A East is also expected to be a source of copious positron
production. The results presented here show that indeed Sgr A East must have
produced a numerically significant population of positrons, but also that most
of them have not yet had sufficient time to thermalize and annihilate. As such,
Sgr A East by itself does not appear to be the dominant current source of
annihilation radiation, but it will be when the positrons have cooled
sufficiently and they have become thermalized. This raises the interesting
possibility that the bulge component may be due to the relics of earlier
explosive events like the one that produced Sgr A East.


title: A Broadband X-Ray Study of the Supernova Remnant 3C 397

abstract:
  We present an X-ray study of the radio bright supernova remnant (SNR) 3C 397
with ROSAT, ASCA, and RXTE. A central X-ray spot seen with the ROSAT
High-Resolution Imager hints at the presence of a pulsar-powered component, and
gives this SNR a composite X-ray morphology. Combined ROSAT and ASCA imaging
show that the remnant is highly asymmetric, with its hard X-ray emission
peaking at the western lobe. The spectrum of 3C 397 is heavily absorbed, and
dominated by thermal emission with emission lines evident from Mg, Si, S, Ar
and Fe. Single-component models fail to describe the spectrum, and at least two
components are required. We use a set of non-equilibrium ionization (NEI)
models (Borkowski et al. in preparation). The temperatures from the soft and
hard components are 0.2 keV and 1.6 keV respectively. The corresponding
ionization time-scales $n_0 t$ ($n_0$ being the pre-shock hydrogen density) are
6 $\times 10^{12}$ cm$^{-3}$ s and 6 $\times$ 10$^{10}$ cm$^{-3}$ s,
respectively. The spectrum obtained with the Proportional Counter Array (PCA)
of RXTE is contaminated by emission from the Galactic ridge, with only $\sim$
15% of the count rate originating from 3C 397 in the 5-15 keV range. The PCA
spectrum allowed us to confirm the thermal nature of the hard X-ray emission. A
third component originating from a pulsar-driven component is possible, but the
contamination of the source signal by the Galactic ridge did not allow us to
find pulsations from any hidden pulsar. We discuss the X-ray spectrum in the
light of two scenarios: a young ejecta-dominated remnant of a core-collapse SN,
and a middle-aged SNR expanding in a dense ISM. Spatially resolved spectroscopy
(with CHANDRA and XMM) is needed to differentiate between the two scenarios,
and address the nature of the mysterious radio-quiet X-ray hot spot.


title: Looking into Pulsar Magnetospheres

abstract:
  Diffractive and refractive magnetospheric scintillations may allow a direct
testing of the plasma inside the light cylinder. Unusual electrodynamics of the
strongly magnetized electron-positron plasma allow separation of the
magnetospheric and interstellar scattering.
  The most distinctive feature of the magnetospheric scintillations is their
independence on frequency. Diffractive scattering due to small scale
inhomogeneities produce a scattering angle that may be as large as 0.1 radians,
and a typical decorrelation time of $10^{-8}$ seconds.
  Refractive scattering due to large scale inhomogeneities is also possible,
with a typical angle of $10^{-3}$ radians and a correlation time of the order
of $10^{-4}$ seconds. Some of the magnetospheric propagation effects may have
already been observed.


title: The emission nebula associated with V1974 Cyg: a unique object?

abstract:
  Through a program of narrow band imaging, we have observed the changing
structure of the H alpha emission line around Nova Cyg 1992 (V1974 Cyg) at
regular intervals from 1996 to 1999. Between 1994 and 1996, the nebular
boundary advanced to the southwest at nearly the speed of light, implying that
the nebula was created by an expanding wave of radiation originating in the
explosion interacting with surrounding material. The expansion speed dropped to
0.35c during 1996-1999. We have taken spectra of the nebula in 1998 and 1999.
Only Balmer lines are detected, no He I, [OIII], [OII], [NII], or [SII]. There
is also no trace of the high excitation nova lines (He II, NeV, etc). These
spectra show that the nebula is NOT a reflection nebula, a conventional HII
region, or a shock involving motions of the gas. The integrated H alpha
luminosity of the nebula between 1996 and 1999 is in the range =~1.3-2.2 x
10(35) erg s(-1). The density is poorly determined, but is probably very large
(10(4) cm(-3)) in order to explain the brightest region of the nebula. The
dynamical timescale is about a year and the recombination timescale of the same
order. Bright patches are observed to fade in these times. The energy required
to ionize the nebula is the bolometric luminosity of the nova for 30 days,
smaller than the time during which the temperature of the nova photosphere was
in the right range to produce the ionizing photons. We have also undertaken
sensitive surveys of H alpha nebulae around recent novae but find no evidence
of other such nebulae, so this type of object must be rare.


title: New Constraints on inflation from the Cosmic Microwave Background

abstract:
  The recent data from the Boomerang and MAXIMA-1 balloon flights have marked
the beginning of the precision era of Cosmic Microwave Background anisotropy
(CMB) measurements. We investigate the observational constraints from the
current CMB anisotropy measurements on the simplest inflation models,
characterized by a single scalar field $\phi$, in the parameter space
consisting of scalar spectral index $n_S$ and tensor/scalar ratio $r$. If we
include constraints on the baryon density from big bang nucleosynthesis (BBN),
we show that the favored inflationary models have negligible tensor amplitude
and a ``red'' tilt, with a best fit of $n_S \simeq 0.93$, which is consistent
with the simplest ``small-field'' inflation models, but rules out large-field
models at the $1\sigma$ level. Without including BBN constraints, a broader
range of models are consistent with the data. The best fit (assuming negligible
reionization) is a scale-invariant spectrum, $n_S \simeq 1$, which includes
large-field and hybrid scenarios. Large-field models (such as chaotic and
power-law inflation) with tilt $n_S < 0.9$ are strongly disfavored in all
cases.


title:
X-ray emission from the galactic center region Supernova Remnant
  G0.9+0.1

abstract:
  We report the results of a BeppoSAX observation of the composite supernova
remnant G0.9+0.1, located in the Galactic Center region. This new observation,
in which the core of G0.9+0.1 is observed on-axis, confirms our previous
results obtained from a pointing in which the supernova remnant was
serendipitously observed at a large off-axis angle. The better quality of the
new data allows us to confirm the non-thermal nature of the X-ray source
coincident with the central plerion, to significantly improve the estimate of
its spectral parameters, to put more stringent upper limits on the presence of
coherent pulsations (in the range of periods from 4ms to ~ 4\times10^4 s), to
obtain marginal evidence of the possible extended nature of the X-ray plerion
and to put a better upper limit on the 2--10 keV X-ray emission from the 8'
diameter radio shell (L$_{\rm S}<3.4\times 10^{34} {\rm d}_{10}^{2}$ erg
s^{-1}). The X-ray spectrum is best fit with a power-law model with a photon
index \Gamma ~ 2, N_{\rm H} ~ 10^{23} \hcm and a 2-10 keV luminosity of
7.5\times 10^{34} {\rm d}_{10}^{2} erg s^{-1}. The broad band (radio-X-ray)
properties of the composite supernova remnant G0.9+0.1 are indicative of the
likely presence of a young (~ 2,700 yr) neutron star in its central radio core.


title: The BeppoSAX view of the Galactic Center region

abstract:
  The Galactic Center Region has been surveyed in 1997-1998 with the Narrow
Field Instruments on-board the BeppoSAX satellite (2-10keV energy range). The
X-ray emission from SgrA*, the putative supermassive black hole at the center
of our Galaxy, has been measured and its spectrum studied, together with the
X-ray emission from several bright X-ray sources, LMXBs containing neutron
stars and black holes located within the region ($|l|<2\deg)\times(|b|<1\deg$).
New point-like X-ray sources have also been discovered. The results on the
diffuse emission coming from the SgrA Complex are summarized here: it displays
a two-temperature thermal spectrum (kT1~0.6keV and kT2~8keV) and an
energy-dependent morphology, with the hard emission (5-10 keV) elongated along
the galactic plane and the soft one (2-5 keV) spatially correlated with the
radio halo of SgrAEast. The results of the study of the diffuse X-ray emission
from other three fields in the Galactic Center Region containing the giant
molecular clouds SgrB2, SgrC and SgrD are reported for the first time. The
diffuse emission from the direction of these three molecular clouds shows a
double temperature nature as well, with a prominent iron line at \~6.7keV, the
intensity and equivalent width of which depends on the galactic longitude.
Moreover, the SgrB2 spectrum shows an intense 6.4keV line of fluorescent
origin. While the hard component of the Galactic Center diffuse emission
displays a similar temperature with respect to the Galactic Ridge, the low
temperature plasma is significantly softer. This may be due to a net
contribution produced from the accretion of material onto old isolated neutron
stars located inside the giant molecular clouds.


title:
HST observations of FR I radiogalaxies: what do they tell us about the
  BL Lac - FR I unification scheme?

abstract:
  We explore the viability of the unification of BL Lacs and FR I radio
galaxies by comparing the core emission of radio galaxies with those of BL
Lacs, taking advantage of the newly measured optical nuclear luminosity of FR I
sources. The spectral properties of complete samples are studied in the
radio-optical luminosity plane: we calculate the predicted luminosity of BL
Lacs when observed off-axis, in the frame of a simple one-zone model. We find
that the bulk Lorentz factors required in order to account for the observed
luminosities are significantly smaller than those implied by other, both
observational and theoretical, considerations. In order to reconcile these
results with the unification scheme, velocity structures in the jet are
suggested, where a fast spine is surrounded by a slower layer.


title: Hard X-ray Emission and the Ionizing Source in LINERs

abstract:
  We report X-ray fluxes in the 2--10 keV band from LINERs (low-ionization
nuclear emission-line regions) and low-luminosity Seyfert galaxies obtained
with the ASCA satellite. Observed X-ray luminosities are in the range between
4e39 and 5e41 ergs/s, which are significantly smaller than that of the
``classical'' low-luminosity Seyfert 1 galaxy NGC 4051. We found that X-ray
luminosities in 2--10 keV of LINERs with broad Halpha emission in their optical
spectra (LINER 1s) are proportional to their Halpha luminosities. This
correlation strongly supports the hypothesis that the dominant ionizing source
in LINER 1s is photoionization by hard photons from low-luminosity AGNs. On the
other hand, the X-ray luminosities of most LINERs without broad Halpha emission
(LINER 2s) in our sample are lower than LINER 1s at a given Halpha luminosity.
The observed X-ray luminosities in these objects are insufficient to power
their Halpha luminosities, suggesting that their primary ionizing source is
other than an AGN, or that an AGN, if present, is obscured even at energies
above 2 keV.


title: Phase Dependent Spectroscopy of Mira Variable Stars

abstract:
  Spectroscopic measurements of Mira variable stars, as a function of phase,
probe the stellar atmospheres and underlying pulsation mechanisms. For example,
measuring variations in TiO, VO, and ZrO with phase can be used to help
determine whether these molecular species are produced in an extended region
above the layers where Balmer line emission occurs or below this shocked
region. Using the same methods, the Balmer-line increment, where the strongest
Balmer line at phase zero is H-delta and not H-alpha can be measured and
explanations tested, along with another peculiarity, the absence of the
H-epsilon line in the spectra of Miras when other Balmer lines are strong. We
present new spectra covering the spectral range from 6200 Angstroms to 9000
Angstroms of 20 Mira variables. A relationship between variations in the CaII
IR triplet and H-alpha as a function of phase support the hypothesis that
H-epsilon's observational characteristics result from an interaction of
H-epsilon photons with the CaII H line. New periods and epochs of variability
are also presented for each star.


title: Mid-infrared interferometry on spectral lines: I. Instrumentation

abstract:
  The U. C. Berkeley Infrared Spatial Interferometer has been outfitted with a
filterbank system to allow interferometric observations of mid-infrared
spectral lines with very high spectral resolution (R ~ 10^5). This paper
describes the design, implementation, and performance of the matched 32-channel
filterbank modules, and new spectral line observations of Mars and IRC+10216
are used to demonstrate their scientific capability. In addition, observing
strategies are discussed for accurate calibration of fringe visibilities in
spectral lines, despite strong atmospheric fluctuations encountered in the
infrared.