title: Coherent neutrino radiation in supernovae at two loops

abstract:
  We develop a neutrino transport theory, in terms of the real-time
non-equilibrium Green's functions, which is applicable to physical conditions
arbitrary far from thermal equilibrium. We compute the coherent neutrino
radiation in cores of supernovae by evaluating the two-particle-two-hole
(2p-2h) polarization function with dressed propagators. The propagator dressing
is carried out in the particle-particle channel to all orders in the
interaction. We show that at two loops there are two distinct sources of
coherence effects in the bremsstrahlung. One is the generically off-shell
intermediate state propagation, which leads to the Landau-Pomeranchuk-Migdal
type suppression of radiation. We extend previous perturbative results,
obtained in the leading order in quasiparticle width, by deriving the exact
non-perturbative expression. A new contribution due to off-shell finial/initial
baryon states is treated in the leading order in the quasiparticle width. The
latter contribution corresponds to processes of higher order than second order
in the virial expansion in the number of quasiparticles. At 2p-2h level, the
time component of the polarization tensor for the vector transitions vanishes
identically in the soft neutrino limit. Vector current thereby is conserved.
The contraction of the neutral axial vector current with tensor interaction
among the baryons leads to a non-vanishing contribution to the bremsstrahlung
rate. These rates are evaluated numerically for finite temperature pure neutron
matter at and above the nuclear saturation density.


title:
BeppoSAX spectrum of GRB971214: evidence of a substantial energy output
  during afterglow

abstract:
  We report the X/gamma-ray spectrum of GRB971214 and of its afterglow. The
afterglow was measured few hours after the main event and for an elapsed time
of more than two days. The measure of this GRB and afterglow is relevant due to
its extreme, cosmological distance (z=3.42). The prompt event shows a hard
photon spectrum, consistent with a broken power law with photon indices
Gamma_X~0.1 below ~20 keV and Gamma_g~1.3 above 60 keV. The afterglow spectrum,
measured with the MECS and LECS BeppoSAX telescopes, is consistent with a power
law with spectral photon index Gamma=1.6. Within the statistical accuracy of
our measure no spectral evolution is detected during the observation of the
afterglow. When integrated during the time span covered by BeppoSAX
observations, the power in the afterglow emission, even with very conservative
assumptions, is at least comparable with the power in the main event. The
IR-to-X rays broad band spectrum is also presented, collecting data from the
literature and adding them to the BeppoSAX measure. It shows that the
predictions from synchrotron emission models is qualitatively confirmed. The
BeppoSAX measurement of the X and gamma ray spectrum of this GRB/afterglow is
discussed in the framework of current theoretical models.


title:
Atomic data from the Iron Project.XLIII. Transition probabilities for Fe
  V

abstract:
  An extensive set of dipole-allowed, intercombination, and forbidden
transition probabilities for Fe V is presented. The Breit-Pauli R-matrix (BPRM)
method is used to calculate 1.46 x 10^6 oscillator strengths for the allowed
and intercombination E1 transitions among 3,865 fine-structure levels dominated
by configuration complexes with n <= 10 and l <= 9. These data are complemented
by an atomic structure configuration interaction (CI) calculation using the
SUPERSTRUCTURE program for 362 relativistic quadrupole (E2) and magnetic dipole
(M1) transitions among 65 low-lying levels dominated by the 3d^4 and 3d^ 4s
configurations. Procedures have been developed for the identification of the
large number of fine-structure levels and transitions obtained through the BPRM
calculations. The target ion Fe VI is represented by an eigenfunction expansion
of 19 fine-structure levels of 3d^3 and a set of correlation configurations. Fe
V bound levels are obtained with angular and spin symmetries SL\pi and J\pi of
the (e + Fe VI) system such that 2S+1 = 5,3,1, L <= 10, J <= 8 of even and odd
parities. The completeness of the calculated dataset is verified in terms of
all possible bound levels belonging to relevant LS terms and transitions in
correspondence with the LS terms. The fine-structure averaged relativistic
values are compared with previous Opacity Project LS coupling data and other
works. The 362 forbidden transition probabilities considerably extend the
available data for the E2 and M1 transtions, and are in good agreement with
those computed by Garstang for the 3d^4 transitions.


title:
Formation of Disk Galaxies: On the Angular Momentum Problem, the
  Tully-Fisher Relation and Magnetohydrodynamics

abstract:
  Two ways of possibly solving the angular momentum problem plaguing cold dark
matter (CDM) ab initio simulations of disk galaxy formation are discussed: 1)
Stellar feedback processes and 2) Warm dark matter (WDM) rather than CDM.
  In relation to the chemical evolution of disk galaxies our simulations
indicate that in case 1) the first generation of disk stars formed in disk
galaxies like the Milky Way should have an abundance about two dex below solar,
in fairly good agreement with the lowest observed abundance of the metal-weak
tail of the Galactic thick disk. For the second case no such statements can be
made without further assumptions about the star-formation history of the
galaxies.
  We find that the I-band Tully-Fisher relation can be matched by WDM disk
galaxy formation simulations provided (M/L_I) is about 0.8 for disk galaxies,
which Sommer-Larsen & Dolgov (1999) argue is a reasonable value.
  Finally it is discussed how the magnetic field strengths observed in galactic
disks can be obtained through disk galaxy formation, as an alternative to the
conventional dynamo hypothesis.


title: Neutron Star Structure and the Equation of State

abstract:
  The structure of neutron stars is considered from theoretical and
observational perspectives. We demonstrate an important aspect of neutron star
structure: the neutron star radius is primarily determined by the behavior of
the pressure of matter in the vicinity of nuclear matter equilibrium density.
In the event that extreme softening does not occur at these densities, the
radius is virtually independent of the mass and is determined by the magnitude
of the pressure. For equations of state with extreme softening, or those that
are self-bound, the radius is more sensitive to the mass. Our results show that
in the absence of extreme softening, a measurement of the radius of a neutron
star more accurate than about 1 km will usefully constrain the equation of
state. We also show that the pressure near nuclear matter density is primarily
a function of the density dependence of the nuclear symmetry energy, while the
nuclear incompressibility and skewness parameters play secondary roles.
  In addition, we show that the moment of inertia and the binding energy of
neutron stars, for a large class of equations of state, are nearly universal
functions of the star's compactness. These features can be understood by
considering two analytic, yet realistic, solutions of Einstein's equations,
due, respectively, to Buchdahl and Tolman. We deduce useful approximations for
the fraction of the moment of inertia residing in the crust, which is a
function of the stellar compactness and, in addition, the presssure at the
core-crust interface.


title:
The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables
  Determined from Cluster Turn-offs. I. Results from 19 OB Associations in the
  Magellanic Clouds

abstract:
  We combine new CCD UBV photometry and spectroscopy with that from the
literature to investigate 19 Magellanic Cloud OB associations that contain
Wolf-Rayet (WR) and other types of evolved massive stars. Our spectroscopy
reveals a wealth of newly identified interesting objects, including early
O-type supergiants, a high mass double-lined binary in the SMC, and, in the
LMC, a newly confirmed LBV (R 85), a newly discovered WR star (Sk-69 194), and
a newly found luminous B[e] star (LH85-10). We use the data to evaluate the
extent that each association is coeval, and for the ones with little age
spread, determine the turn-off masses of the unevolved stars, as a means of
finding the progenitor masses of LBVs and WRs. Our data is also used to find
the (minimum) bolometric corrections that apply to these evolved objects. We
find that WRs in the SMC come from only the highest mass stars (>70Mo), while
in the LMC the WNEs come from a wide range of masses---possibly all stars with
masses >30Mo pass though a WNE stage at LMC metallicities. In both the SMC and
LMC the WCs appear to come from the same mass range as do the WNs, a finding
that has important implications for interpreting the WC/WN ratio among Local
Group galaxies. LBVs appear to come from the very highest mass stars. The
Ofpe/WN9 stars, sometimes implicated in the "LBV phenonomon" come from very
modest mass stars, 25-35Mo, suggesting a different origin for their
variability. The BCs of WRs are considerably more negative than those of O-type
stars, with BC(WNE)=-6.0 mag and BC(WC4)=-5.5mag; more modest values are found
for the Ofpe/WN9 stars (-2 to -4 mag). These findings are consistent with
recent analysis done with Hillier's "standard model".


title:
The SCUBA Local Universe Galaxy Survey I: First Measurements of the
  Submillimetre Luminosity and Dust Mass Functions

abstract:
  We have used SCUBA to observe a complete sample of 104 galaxies selected at
60 microns from the IRAS BGS and we present here the 850 micron measurements.
Fitting the 60,100 and 850 micron fluxes with a single temperature dust model
gives the sample mean temperature T=36 K and beta = 1.3. We do not rule out the
possibility of dust which is colder than this, if a 20 K component was present
then our dust masses would increase by factor 1.5-3. We present the first
measurements of the luminosity and dust mass functions, which were well fitted
by Schechter functions (unlike those 60 microns). We have correlated many
global galaxy properties with the submillimetre and find that there is a
tendancy for less optically luminous galaxies to contain warmer dust and have
greater star formation efficiencies (cf. Young 1999). The average gas-to-dust
ratio for the sample is 581 +/- 43 (using both atomic and molecular hydrogen),
significantly higher than the Galactic value of 160. We believe this
discrepancy is due to a cold dust component at T < 20 K. There is a suprisingly
tight correlation between dust mass and the mass of molecular hydrogen as
estimated from CO measurements, with an intrinsic scatter of ~50%.


title: Problems encountered in the Hipparcos variable stars analysis

abstract:
  Among the 17 volumes of results from the Hipparcos space mission, two are
dedicated to variable stars. These two volumes arose from the work of two
groups, one at the Geneva Observatory and one at RGO (Royal Greenwich
Observatory), on the 13 million photometric measurements produced by the
satellite for 118204 stars.
  The analysis of photometric time series permitted us to identify several
instrumental and mathematical problems: overestimation of the precision,
offsets in the zero-points depending on the field of view, mispointing effects,
image superpositions, trends in the magnitudes, binarity effects (spurious
periods and amplitudes) and time-sampling effects. In this article we summarize
some of the problems encountered by the Geneva group.


title: The Schweizer-Middleditch star revisited

abstract:
  We have re-observed and re-analysed the optical spectrum of the
Schweizer-Middleditch star, a hot subdwarf which lies along almost the same
line-of-sight as the centre of the historic SN1006 supernova remnant (SNR).
Although this object is itself unlikely to be the remnant of the star which
exploded in 1006AD, Wellstein et al. (1999) have demonstrated that it could be
the remnant of the donor star in a pre-supernova Type Ia interacting binary, if
it possesses an unusually low mass. We show that, if it had a mass of 0.1-0.2
Msun, the SM star would lie at the same distance (~800pc) as the SNR as
estimated by Willingale et al. (1995). However, most distance estimates to
SN1006 are much larger than this, and there are other convincing arguments to
suggest that the SM star lies behind this SNR. Assuming the canonical subdwarf
mass of 0.5 Msun, we constrain the distance of the SM star as 1050 pc<d<2100
pc. This places the upper limit on the distance of SN1006 at 2.1 kpc.


title:
High-resolution spectroscopy of V854 Cen in decline - Absorption and
  emission lines of C_2 molecules

abstract:
  High-resolution optical spectra of the R Coronae Borealis (RBC) star V854
Centauri in the early stages of a decline show, in addition to the features
reported for other RCBs in decline, narrow absorption lines from the C_2
Phillips system. The low rotational temperature, T_rot = 1150K, of the C_2
ground electronic state suggests the cold gas is associated with the developing
shroud of carbon dust. These absorption lines were not seen at a fainter
magnitude on the rise from minimum light nor at maximum light. This is the
first detection of cold gas around a RCB star.


title:
Large-Scale Sunyaev-Zel'dovich Effect: Measuring Statistical Properties
  with Multifrequency Maps

abstract:
  We study the prospects for extracting detailed statistical properties of the
Sunyaev-Zel'dovich (SZ) effect associated with large scale structure using
upcoming multifrequency CMB experiments. The greatest obstacle to detecting the
large-angle signal is the confusion noise provided by the primary anisotropies
themselves, and to a lesser degree galactic and extragalactic foregrounds. We
employ multifrequency subtraction techniques and the latest foregrounds models
to determine the detection threshold for the Boomerang, MAP (several microK)
and Planck CMB (sub microK) experiments. Calibrating a simplified biased-tracer
model of the gas pressure off recent hydrodynamic simulations, we estimate the
SZ power spectrum, skewness and bispectrum through analytic scalings and N-body
simulations of the dark matter. We show that the Planck satellite should be
able to measure the SZ effect with sufficient precision to determine its power
spectrum and higher order correlations, e.g. the skewness and bispectrum.
Planck should also be able to detect the cross correlation between the SZ and
gravitational lensing effect in the CMB. Detection of these effects will help
determine the properties of the as yet undetected gas, including the manner in
which the gas pressure traces the dark matter.


title: One-Line Redshifts and Searches for High-Redshift Lyman-Alpha Emission

abstract:
  We report the serendipitous discovery of two objects close in projection with
fairly strong emission lines at long wavelength (~9190 A). One (A) seems not to
be hosted by any galaxy brighter than V(555)=27.5, or I(814)=26.7 (Vega-based
3-sigma limits in 1.0 arcsec diameter apertures), while the other line is
associated with a faint (I(814)~24.4) red galaxy (B) offset by 2.7 arcsec and 7
A spectrally. Both lines are broad (FWHM 700 km/s), extended spatially, and
have high equivalent widths (W(A,obs)>1225 A, 95% confidence limit;
W(B,obs)~150 A). No secondary spectral features are detected for galaxy A. Blue
continuum and the marginal detection of a second weak line in the spectrum of
galaxy B is consistent with [OII] (the strong line) and MgII (the weak line) at
z=1.466. By association, galaxy A is likely at z=1.464, implying a rest-frame
equivalent width of the [OII] emission line in excess of 600 A and a projected
separation of 30 kpc for the galaxy pair. Conventional wisdom states that
isolated emission lines with rest-frame equivalent widths larger than ~200 A
are almost exclusively Lyman-alpha. This moderate-redshift discovery therefore
compromises recent claims of high-redshift Lyman-alpha emitters for which other
criteria (i.e., line profile, associated continuum decrements) are not
reported. We discuss observational tests to distinguish Lyman-alpha emitters at
high redshift from foreground systems.


title:
Projected bispectrum in spherical harmonics and its application to
  angular galaxy catalogues

abstract:
  We present a theoretical and exact analysis of the bispectrum of projected
galaxy catalogues. The result can be generalized to evaluate the projection in
spherical harmonics of any 3D bispectrum and therefore has applications to
cosmic microwave background and gravitational lensing studies. By expanding the
2D distribution of galaxies on the sky in spherical harmonics, we show how the
3-point function of the coefficients can be used in principle to determine the
bias parameter of the galaxy sample. If this can be achieved, it would allow a
lifting of the degeneracy between the bias and the matter density parameter of
the Universe which occurs in linear analysis of 3D galaxy catalogues. In
previous papers we have shown how a similar analysis can be done in three
dimensions, and we show here, through an error analysis and by implementing the
method on a simulated projected catalogue, that ongoing three-dimensional
galaxy redshift surveys (even with all the additional uncertainties introduced
by partial sky coverage, redshift-space distortions and smaller numbers) will
do far better than all-sky projected catalogues with similar selection
function.


title:
A Serendipitous Search for High-Redshift Lyman alpha Emission: Two
  Primeval Galaxy Candidates at z~3

abstract:
  In the course of our ongoing search for serendipitous high-redshift Lyman
alpha (LyA) Emissionin deep archival Keck spectra, we discovered two very high
equivalent width (W_{obs} ~ 450A, 2-sigma) LyA emission line candidates at z ~3
in a moderate dispersion (R~1200) spectrogram. Both lines have low velocity
dispersions (sigma_v ~ 60 km/s) and deconvolved radii r ~ 1 kpc (h = 0.5). We
argue that the lines are LyA, and are powered by stellar ionization. The
surface density of robust, high equivalent width LyA candidates is estimated to
be ~3 \pm 2 per arcmin^2 per unit redshift at z ~ 3, consistent with the
estimate of Cowie etal (1998). The LyA emission line source characteristics are
consistent with the galaxies undergoing their first burst of star formation,
ie, with being primeval. Source sizes and velocity dispersions are comparable
to the theoretical primeval galaxy model of Lin and Murray (1992) based on the
inside-out, self-similar collapse of an isothermal sphere. In this model, star
formation among field galaxies is a protracted process. Galaxies are thought to
be able to display high equivalent widths for only the first few x 10 Myr. This
time is short in relation to the difference in look back times between z=3 and
z=4, and implies that a substantial fraction of strong line-emitting galaxies
at z=3 were formed at redshifts z < 4. We discuss the significance of
high-equivalent width LyA-emitting galaxies in terms of the emerging picture of
the environment, and the specific characteristics of primeval galaxy formation
at high redshift.


title: The RR Lyrae U Com as a test for nonlinear pulsation models

abstract:
  We use high precision multiband photometric data of the first overtone RR
Lyrae U Com to investigate the predictive capability of full amplitude,
nonlinear, convective hydrodynamical models. The main outcome of this
investigation is that theoretical predictions properly account for the
luminosity variations along a full pulsation cycle. Moreover, we find that this
approach, due to the strong dependence of this observable and of the pulsation
period on stellar parameters, supply tight constraints on stellar mass,
effective temperature, and distance modulus. Pulsational estimates of these
parameters appear in good agreement with empirical ones. Finally, the
occurrence of a well-defined bump just before the luminosity maximum gave the
unique opportunity to calibrate the turbulent convection model adopted for
handling the coupling between pulsation and convection.


title: Gamma-Ray Bursts, Cosmic-Rays and Neutrinos

abstract:
  The gamma-ray burst (GRB) model for production of ultra-high-energy
cosmic-rays (UHECRs) is based on the hypothesis that GRBs arise from the
dissipation of the kinetic energy of relativistic fireballs at cosmological
distances. Recent GRB afterglow observations support the validity of this
hypothesis and provide quantitative support for the model. The inferred
physical fireball parameters imply that protons may be accelerated to >10^20
eV, and the inferred GRB energy generation rate is similar to that required to
account for the observed flux of UHECRs.
  Strong suppression of UHECR flux is expected in this model above 10^19.7 eV,
due to proton interaction with CMB photons. Strong deviations from model flux
derived under the assumption of uniform source distribution is expected above
10^20 eV, due to source clustering. The flux above 10^20.5 eV is expected to be
dominated by few, narrow spectrum sources. While model predictions can not be
tested (with high confidence level) at present, the predicted signatures should
be observed with the planned Auger and Telescope-Array UHECR detectors.
  A natural consequence of the GRB model of UHECR production is the conversion
of a large fraction, ~10%, of the fireball energy to accompanying burst of
\~10^14 eV and ~10^18 eV neutrinos. A km^2 neutrino detector would observe
several tens of events per year correlated with GRBs, and test for neutrino
properties (e.g. flavor oscillations, for which upward moving tau's would be a
unique signature, and coupling to gravity) with an accuracy many orders of
magnitude better than is currently possible.


title: The Elusive Active Nucleus of NGC 4945

abstract:
  We present new HST NICMOS observations of NGC 4945, a starburst galaxy
hosting a highly obscured active nucleus that is one of the brightest
extragalactic sources at 100 keV. The HST data are complemented with ground
based [FeII] line and mid--IR observations. A 100pc-scale starburst ring is
detected in Pa alpha, while H_2 traces the walls of a super bubble opened by
supernova-driven winds. The conically shaped cavity is particularly prominent
in Pa alpha equivalent width and in the Pa alpha/H_2 ratio. Continuum images
are heavily affected by dust extinction and the nucleus of the galaxy is
located in a highly reddened region with an elongated, disk-like morphology. No
manifestation of the active nucleus is found, neither a strong point source nor
dilution in CO stellar features, which are expected tracers of AGN activity.
Even if no AGN traces are detected in the near-IR, with the currently available
data it is still not possible to establish whether the bolometric luminosity of
the object is powered by the AGN or by the starburst: we demonstrate that the
two scenarios constitute equally viable alternatives. However, the absence of
any signature other than in the hard X-rays implies that, in both scenarios,
the AGN is non-standard: if it dominates, it must be obscured in all
directions, conversely, if the starburst dominates, the AGN must lack UV
photons with respect to X-rays. An important conclusion is that powerful AGNs
can be hidden even at mid-infrared wavelengths and, therefore, the nature of
luminous dusty galaxies cannot be always characterized by long-wavelength data
alone but must be complemented with sensitive hard X-ray observations.


title: A Model of Supernovae Feedback in Galaxy Formation

abstract:
  A model of supernovae feedback during disc galaxy formation is developed. The
model incorporates infall of cooling gas from a halo and outflow of hot gas
from a multiphase interstellar medium and a self-regulated model for star
formation. Hot gas is created by thermal evaporation of cold gas clouds in
supernovae remnants, and criteria are derived to estimate the characteristic
temperature and density of the hot component and hence the net mass outflow
rate. A number of refinements of the model are investigated, including a simple
model of a galactic fountain, the response of the cold component to the
pressure of the hot gas, pressure induced star formation and chemical
evolution. The main conclusion of this paper is that low rates of star
formation can expel a large fraction of the gas from a dwarf galaxy. Effective
feedback can therefore take place in a quiescent mode and does not require
strong bursts of star formation. Consequences for galaxy formation and damped
Ly alpha systems are discussed.


title: IZ Photometry of L dwarfs and the implications for brown dwarf surevys

abstract:
  The I-Z colour has been recently shown to be a good temperature indicator for
M dwarfs. We present the first IZ photometry of a small sample of L dwarfs
ranging in spectral type from L0.5V to L6.0V. We find that the I-Z colour is
not a good temperature indicator for objects between L1V and L5V, such objects
having colours that overlap with mid M dwarfs. We attribute this to the
reduction in the strength of the TiO and VO bands in the L dwarfs which are the
dominant opacity source in the I band for late M dwarfs. Beyond L5V, I-Z
appears to be a reasonable indicator. This has important implications for the
planning of optical surveys for cool objects in clusters and the field. For
example I-Z will cease to be a good method of discriminating brown dwarfs in
the Pleiades below around 0.04 Msolar, and at around 0.075 Msolar in the Hyades
and Praesepe.


title: Constraining reionization using the thermal history of the baryons

abstract:
  The thermal evolution of the intergalactic medium (IGM) depends on the
reionization history of the universe. Numerical simulations indicate that the
low density IGM, which is responsible for the low column density Ly-alpha
forest, follows a well defined temperature-density relation. This results in a
cut-off in the distribution of line widths as a function of column density. We
use hydrodynamic simulations to calibrate the relation between the cut-off and
the temperature-density relation and apply this relation to Keck spectra
spanning a redshift range z=2-4.5. We find that the temperature peaks at z~3
and interpret this as evidence for reheating due to the reionization of helium.


title: Big Bang Nucleosynthesis updated with the NACRE Compilation

abstract:
  We update the Big Bang Nucleosynthesis calculations on the basis of the
recent NACRE compilation. The average values of the calculated abundances of
light nuclei do not differ significantly from that obtained using the previous
Fowler's compilation.
  ${^7}Li$ is slightly depressed at high baryon to photon ratio $\eta$.
  The main uncertainty concerns the $D(p,\gamma){^3}He$ reaction rate affecting
the synthesis of ${^7}Li$ (via the ${^3}He(\alpha,\gamma){^7}Be(e\nu){^7}Li$)
at rather high baryonic density. On the left part of the lithium valley the
uncertainty is strongly reduced due to the improvement of the measurement of
the $T(\alpha,\gamma)^{7}Li$ reaction rate.
  We use lithium-7 as the main baryometer, since, though much efforts have been
devoted to the determination of Deuterium in absorbing clouds in the line of
sight of remote quasars, the statistics is very poor compared to the long
series of lithium measurements.
  Taking into account the lithium constraints, two possible baryonic density
ranges emerge,
  $\eta_{10}= 1.4 - 1.9$ and $\eta_{10} = 3.3 - 5.1$.
  The Be and B abundances produced in the big bang are orders of magnitudes
lower, and spallation of fast carbon and oxygen is probably their unique
source, in the early Galaxy.


title: CMB Anisotropies and the Determination of Cosmological Parameters

abstract:
  I review the basic theory of the cosmic microwave background anisotropies in
adiabatic cold dark matter cosmologies. The latest observational results on the
CMB power spectrum are consistent with the simplest inflationary models and
indicate that the Universe is close to spatially flat with a nearly scale
invariant fluctuation spectrum. We are also beginning to see interesting
constraints on the density of CDM, with a best fit value of omega_c = Omega_c
h^2 of about 0.1. The CMB constraints, when combined with observations of
distant Type Ia supernovae, are converging on a Lambda-dominated Universe with
Omega_m approx 0.3 and Omega_Lambda approx 0.7.


title: Modelling galaxy clustering at high redshift

abstract:
  Most phenomenological galaxy formation models show a discrepancy between the
predicted Tully-Fisher relation and the luminosity function. We show that this
is mainly due to overmerging of galaxy haloes, which is inherent in both the
Press-Schechter formalism and dissipationless N-body simulations. This
overmerging problem be circumvented by including a specific galaxy halo
formation recipe into an otherwise standard N-body code. Resolving the
overmerging also allows us to include models for chemical evolution and
starbursts, which improves the match to observational data and renders the
modelling more realistic. We use high-redshift clustering data to try and
distinguish models which predict similar results at low redshifts for different
sets of parameters.


title: Ionizing Radiation in Smoothed Particle Hydrodynamics

abstract:
  A new method for the inclusion of ionizing radiation from uniform radiation
fields into 3D Smoothed Particle Hydrodynamics (SPHI) simulations is presented.
We calculate the optical depth for the Lyman continuum radiation from the
source towards the SPHI particles by ray-tracing integration. The
time-dependent ionization rate equation is then solved locally for the
particles within the ionizing radiation field. Using test calculations, we
explore the numerical behaviour of the code with respect to the implementation
of the time-dependent ionization rate equation. We also test the coupling of
the heating caused by the ionization to the hydrodynamical part of the SPHI
code.


title:
Very High-Energy Gamma-Ray Observations of PSR B1509-58 with the
  CANGAROO 3.8m Telescope

abstract:
  The gamma-ray pulsar PSR B1509-58 and its surrounding nebulae have been
observed with the CANGAROO 3.8m imaging atmospheric Cherenkov telescope. The
observations were performed from 1996 to 1998 in Woomera, South Australia,
under different instrumental conditions with estimated threshold energies of
4.5 TeV (1996), 1.9 TeV (1997) and 2.5 TeV (1998) at zenith angles of ~30 deg.
Although no strong evidence of the gamma-ray emission was found, the lowest
energy threshold data of 1997 showed a marginal excess of gamma-ray--like
events at the 4.1 sigma significance level. The corresponding gamma-ray flux is
calculated to be (2.9 +/- 0.7) * 10^{-12}cm^{-2}s^{-1} above 1.9 TeV. The
observations of 1996 and 1998 yielded only upper limits (99.5% confidence
level) of 1.9 * 10^{-12}cm^{-2}s^{-1} above 4.5 TeV and 2.0 *
10^{-12}cm^{-2}s^{-1} above 2.5 TeV, respectively. Assuming that the 1997
excess is due to Very High-Energy (VHE) gamma-ray emission from the pulsar
nebula, our result, when combined with the X-ray observations, leads to a value
of the magnetic field strength ~5 micro G. This is consistent with the
equipartition value previously estimated in the X-ray nebula surrounding the
pulsar. No significant periodicity at the 150ms pulsar period has been found in
any of the three years' data. The flux upper limits set from our observations
are one order of magnitude below previously reported detections of pulsed TeV
emission.


title: Not enough stellar Mass Machos in the Galactic Halo

abstract:
  We combine new results from the search for microlensing towards the Large
Magellanic Cloud (LMC) by EROS2 (Experience de Recherche d'Objets Sombres) with
limits previously reported by EROS1 and EROS2 towards both Magellanic Clouds.
The derived upper limit on the abundance of stellar mass MACHOs rules out such
objects as an important component of the Galactic halo if their mass is smaller
than 1 solar mass.


title: Decay of proton into Planck neutrino in the theory of gravity

abstract:
  It is considered gravitational interaction within the framework of the Newton
theory and the quantum field theory. It is introduced the Planck neutrino
$\nu_{Pl}$. Gravitational interaction of the fields $\psi\psi$ includes
short-range interaction $\psi\nu_{Pl}$ and long-range interaction
$\nu_{Pl}\nu_{Pl}$. Gravitational radiation can be identified with the Planck
neutrino. The theory predicts the decay of proton into Planck neutrino. It is
assumed that the Planck mass built from three fundamental constants $\hbar$,
$c$ and $G$ is fixed in all the inertial frames. This leads to that the
lifetime of proton relative to the decay into Planck neutrino decreases with
the Lorentz factor as $\sim \gamma^{-5}$. Such a dependence of the lifetime of
proton on the Lorentz factor yields a cut-off in the EHECRs spectrum. It is
shown that the first "knee" in the EHECRs spectrum $E\sim 3\times 10^{15}$ eV
corresponds to the lifetime of proton equal to the lifetime of the universe,
the second "knee" $E\sim 10^{17}-10^{18}$ eV corresponds to the lifetime of
proton equal to the thickness of our galactic disc. The EHECRs with the
energies $E>3 \times 10^{18}$ eV can be identified with the Planck neutrinos.


title: Multiwavelength observations of Mkn 501 during the 1997 high state

abstract:
  During the observation period 1997, the nearby Blazar Mkn 501 showed
extremely strong emission and high variability. We examine multiwavelength
aspects of this event using radio, optical, soft and hard X-ray and TeV data.
We concentrate on the medium-timescale variability of the broadband spectra,
averaged over weekly intervals.
  We confirm the previously found correlation between soft and hard X-ray
emission and the emission at TeV energies, while the source shows only minor
variability at radio and optical wavelengths. The non-linear correlation
between hard X-ray and TeV fluxes is consistent with a simple analytic estimate
based on an SSC model in which Klein-Nishina effects are important for the
highest-energy electrons in the jet, and flux variations are caused by
variations of the electron density and/or the spectral index of the electron
injection spectrum.
  The time-averaged spectra are fitted with a Synchrotron Self-Compton (SSC)
dominated leptonic jet model, using the full Klein-Nishina cross section and
following the self-consistent evolution of relativistic particles along the
jet, accounting for gamma-gamma absorption and pair production within the
source as well as due to the intergalactic infrared background radiation. The
contribution from external inverse-Compton scattering is tightly constrained by
the low maximum EGRET flux and found to be negligible at TeV energies. We find
that high levels of the X-ray and TeV fluxes can be explained by a hardening of
the energy spectra of electrons injected at the base of the jet, in remarkable
contrast to the trend found for gamma-ray flares of the flat-spectrum radio
quasar PKS 0528+134.


title:
Theory of pixel lensing towards M31 I: the density contribution and mass
  of MACHOs

abstract:
  POINT-AGAPE is an Anglo-French collaboration which is employing the Isaac
Newton Telescope (INT) to conduct a pixel-lensing survey towards M31. In this
paper we investigate what we can learn from pixel-lensing observables about the
MACHO mass and fractional contribution in M31 and the Galaxy for the case of
spherically-symmetric near-isothermal haloes. We employ detailed pixel-lensing
simulations which include many of the factors which affect the observables. For
a maximum MACHO halo we predict an event rate in V of up to 100 per season for
M31 and 40 per season for the Galaxy. However, the Einstein radius crossing
time is generally not measurable and the observed full-width half-maximum
duration provides only a weak tracer of lens mass. Nonetheless, we find that
the near-far asymmetry in the spatial distribution of M31 MACHOs provides
significant information on their mass and density contribution. We present a
likelihood estimator for measuring the fractional contribution and mass of both
M31 and Galaxy MACHOs which permits an unbiased determination to be made of
MACHO parameters, even from data-sets strongly contaminated by variable stars.
If M31 does not have a significant population of MACHOs in the mass range
0.001-1 Solar masses strong limits will result from the first season of INT
observations. Simulations based on currently favoured density and mass values
indicate that, after three seasons, the M31 MACHO parameters should be
constrained to within a factor four uncertainty in halo fraction and an order
of magnitude uncertainty in mass (90% confidence). Interesting constraints on
Galaxy MACHOs may also be possible. For a campaign lasting ten years,
comparable to the lifetime of current LMC surveys, reliable estimates of MACHO
parameters in both galaxies should be possible. (Abridged)


title:
Neural networks and separation of Cosmic Microwave Background and
  astrophysical signals in sky maps

abstract:
  The Independent Component Analysis (ICA) algorithm is implemented as a neural
network for separating signals of different origin in astrophysical sky maps.
Due to its self-organizing capability, it works without prior assumptions on
the signals, neither on their frequency scaling, nor on the signal maps
themselves; instead, it learns directly from the input data how to separate the
physical components, making use of their statistical independence. To test the
capabilities of this approach, we apply the ICA algorithm on sky patches, taken
from simulations and observations, at the microwave frequencies, that are going
to be deeply explored in a few years on the whole sky, by the Microwave
Anisotropy Probe (MAP) and by the {\sc Planck} Surveyor Satellite. The maps are
at the frequencies of the Low Frequency Instrument (LFI) aboard the {\sc
Planck} satellite (30, 44, 70 and 100 GHz), and contain simulated astrophysical
radio sources, Cosmic Microwave Background (CMB) radiation, and Galactic
diffuse emissions from thermal dust and synchrotron. We show that the ICA
algorithm is able to recover each signal, with precision going from 10% for the
Galactic components to percent for CMB; radio sources are almost completely
recovered down to a flux limit corresponding to $0.7\sigma_{CMB}$, where
$\sigma_{CMB}$ is the rms level of CMB fluctuations. The signal recovering
possesses equal quality on all the scales larger then the pixel size. In
addition, we show that the frequency scalings of the input signals can be
partially inferred from the ICA outputs, at the percent precision for the
dominant components, radio sources and CMB.


title: Dithering Strategies for Efficient Self-Calibration of Imaging Arrays

abstract:
  With high sensitivity imaging arrays, accurate calibration is essential to
achieve the limits of detection of space observatories. One can simultaneously
extract information about the scene being observed and the calibration
properties of the detector and imaging system from redundant dithered images of
a scene. There are large differences in the effectiveness of dithering
strategies for allowing the separation of detector properties from sky
brightness measurements. In this paper, we quantify these differences by
developing a figure of merit (FOM) for dithering procedures based on their
usefulness for allowing calibration on all spatial scales. The figure of merit
measures how well the gain characteristics of the detector are encoded in the
measurements, and is independent of the techniques used to analyze the data.
Patterns similar to the antenna arrangements of radio interferometers with good
u-v plane coverage, are found to have good figures of merit. We present
patterns for both deep surveys of limited sky areas and for shallow surveys. By
choosing a strategy that encodes the calibration in the observations in an
easily extractable way, we enhance our ability to calibrate our detector
systems and to reach the ultimate limits of sensitivity which are required to
achieve the promise of many missions.


title:
The elusive structure of the diffuse molecular gas: shocks or vortices
  in compressible turbulence?

abstract:
  The cold diffuse interstellar medium must harbor pockets of hot gas to
produce the large observed abundances of molecular species, the formation of
which require much more energy than available in the bulk of its volume. These
hot spots have so far escaped direct detection but observations and modeling
severely constrain their phase-space structure i.e. they must have a small
volume filling factor (a few %), surface filling factors larger than unity with
large fluctuations about average and comparable velocity structure in ``pencil
beams'' and ``large beams''. The dissipation of the non-thermal energy of
supersonic turbulence occurs in bursts, either in shocks or in the regions of
large shear at the boundary of coherent vortices. These two processes are
susceptible to generate localized hot regions in the cold medium. Yet, it is of
interest to determine which of them, if any, dominates the dissipation of
turbulence in the cold interstellar medium. In this paper, we analyze the
spatial and kinematic properties of two subsets of hydrodynamical compressible
turbulence: the regions of largest negative divergence and those of largest
vorticity and confront them with the observational constraints. We find that
these two subsets fulfill the constraints equally well. A similar analysis
should be conducted in the future on simulations of MHD turbulence.


title: Calibrating Array Detectors

abstract:
  The development of sensitive large format imaging arrays for the infrared
promises to provide revolutionary capabilities for space astronomy. For
example, the Infrared Array Camera (IRAC) on SIRTF will use four 256 x 256
arrays to provide background limited high spatial resolution images of the sky
in the 3 to 8 micron spectral region. In order to reach the performance limits
possible with this generation of sensitive detectors, calibration procedures
must be developed so that uncertainties in detector calibration will always be
dominated by photon statistics from the dark sky as a major system noise
source. In the near infrared, where the faint extragalactic sky is observed
through the scattered and reemitted zodiacal light from our solar system,
calibration is particularly important. Faint sources must be detected on this
brighter local foreground.
  We present a procedure for calibrating imaging systems and analyzing such
data. In our approach, by proper choice of observing strategy, information
about detector parameters is encoded in the sky measurements. Proper analysis
allows us to simultaneously solve for sky brightness and detector parameters,
and provides accurate formal error estimates.
  This approach allows us to extract the calibration from the observations
themselves; little or no additional information is necessary to allow full
interpretation of the data. Further, this approach allows refinement and
verification of detector parameters during the mission, and thus does not
depend on a priori knowledge of the system or ground calibration for
interpretation of images.


title:
Cooling curves and initial models for low-mass white dwarfs (<0.25 Msun)
  with helium core

abstract:
  We present a detailed calculation of the evolution of low-mass ($<
0.25~M_\odot $) helium white dwarfs. These white dwarfs (the optical companions
to binary millisecond pulsars) are formed via long-term, low-mass binary
evolution. After detachment from the Roche lobe, the hot helium cores have a
rather thick hydrogen layer with mass between 0.01 to 0.06$~M_\odot $. Due to
mixing between the core and outer envelope, the surface hydrogen content is 0.5
to 0.35, depending on the initial value of the heavy element (Z) and the
initial secondary mass. We found that the majority of our computed models
experience one or two hydrogen shell flashes. We found that the mass of the
helium dwarf in which the hydrogen shell flash occurs depends on the chemical
composition. The minimum helium white dwarf mass in which a hydrogen flash
takes place is 0.213$~M_\odot $ (Z=0.003), 0.198$~M_\odot $ (Z=0.01),
0.192$~M_\odot $ (Z=0.02) or 0.183$~M_\odot $ (Z=0.03). The duration of the
flashes (independent of chemical composition) is between few $\times 10^6 $
years to few $\times 10^7 $ years. In several flashes the white dwarf radius
will increase so much that it forces the model to fill its Roche lobe again.
Our calculations show that cooling history of the helium white dwarf depends
dramatically on the thickness of the hydrogen layer. We show that the
transition from a cooling white dwarf with a temporary stable hydrogen-burning
shell to a cooling white dwarf in which almost all residual hydrogen is lost in
a few thermal flashes (via Roche-lobe overflow) occurs between
0.183-0.213$~M_\odot $ (depending on the heavy element value).


title:
Structural and Photometric Classification of Galaxies - I. Calibration
  Based on a Nearby Galaxy Sample

abstract:
  In this paper we define an observationally robust, multi-parameter space for
the classification of nearby and distant galaxies. The parameters include
luminosity, color, and the image-structure parameters: size, image
concentration, asymmetry, and surface brightness. Based on an initial
calibration of this parameter space using the ``normal'' Hubble-types surveyed
by Frei et al. (1996), we find that only a subset of the parameters provide
useful classification boundaries for this sample. Interestingly, this subset
does not include distance-dependent scale parameters, such as size or
luminosity. The essential ingredient is the combination of a spectral index
(e.g., color) with parameters of image structure and scale: concentration,
asymmetry, and surface-brightness. We refer to the image structure parameters
(concentration and asymmetry) as indices of ``form.'' We define a preliminary
classification based on spectral index, form, and surface-brightness (a scale)
that successfully separates normal galaxies into three classes. We
intentionally identify these classes with the familiar labels of Early,
Intermediate, and Late. This classification, or others based on the above four
parameters can be used reliably to define comparable samples over a broad range
in redshift. The size and luminosity distribution of such samples will not be
biased by this selection process except through astrophysical correlations
between spectral index, form, and surface-brightness.


title: Interactions as a Driver of Galaxy Evolution

abstract:
  Gravitational interactions and mergers are shaping and reshaping galaxies
throughout the observable universe. While observations of interacting galaxies
at low redshifts yield detailed information about the processes at work,
observations at high redshifts suggest that interactions and mergers were much
more frequent in the past. Major mergers of nearby disk galaxies form remnants
that share many properties with ellipticals and are, in essence, present-day
protoellipticals. There is also tantalizing evidence that minor mergers of
companions may help build bulges in disk galaxies. Gas plays a crucial role in
such interactions. Because of its dissipative nature, it tends to get crunched
into molecular form, turning into fuel for starbursts and active nuclei.
Besides the evidence for ongoing interactions, signatures of past interactions
and mergers in galaxies abound: tidal tails and ripples, counterrotating disks
and bulges, polar rings, systems of young globular clusters, and aging
starbursts. Galaxy formation and transformation clearly is a prolonged process
occurring to the present time. Overall, the currently available observational
evidence points towards Hubble's morphological sequence being mainly a sequence
of decreasing merger damage.


title: Optical Observations of Type II Supernovae

abstract:
  I present an overview of optical observations (mostly spectra) of Type II
supernovae. SNe II are defined by the presence of hydrogen, and exhibit a very
wide variety of properties. SNe II-L tend to show evidence of late-time
interaction with circumstellar material. SNe IIn are distinguished by
relatively narrow emission lines with little or no P-Cygni absorption component
and (quite often) slowly declining light curves; they probably have unusually
dense circumstellar gas with which the ejecta interact. Some SNe IIn, however,
might not be genuine SNe, but rather are super-outbursts of luminous blue
variables. The progenitors of SNe IIb contain only a low-mass skin of hydrogen;
their spectra gradually evolve to resemble those of SNe Ib. Limited
spectropolarimetry thus far indicates large asymmetries in the ejecta of SNe
IIn, but much smaller ones in SNe II-P. There is intriguing, but still
inconclusive, evidence that some peculiar SNe IIn might be associated with
gamma-ray bursts. SNe II-P are useful for cosmological distance determinations
with the Expanding Photosphere Method, which is independent of the Cepheid
distance scale.


title:
Hard X-Ray Spectra of Broad-Line Radio Galaxies from the Rossi X-Ray
  Timing Explorer

abstract:
  We present the results of hard-X-ray observations of four broad-line radio
galaxies (BLRGs) with the Rossi X-Ray Timing Explorer (RXTE). The original
motivation behind the observations was to search for systematic differences
between the BLRGs and their radio-quiet counterparts, the Seyfert galaxies. We
do, indeed, find that the Fe K-alpha lines and Compton "reflection" components,
which are hallmarks of the X-ray spectra of Seyferts galaxies, are weaker in
BLRGs by about a factor of 2. This observational result is in agreement with
the conclusions of other recent studies of these objects. We examine several
possible explanations for this systematic difference, including beaming of the
primary X-rays away from the accretion disk, a low iron abundance, a small
solid angle subtended by the disk to the primary X-ray source, and dilution of
the observed spectrum by beamed X-rays from the jet. We find that a small solid
angle subtended by the disk to the primary X-ray source is a viable and
appealing explanation, while all others suffer from drawbacks. We interpret
this as an indication of a difference in the inner accretion disk structure
between Seyfert galaxies and BLRGs, namely that the inner accretion disks of
BLRGs have the form of an ion-supported torus or an advection-dominated
accretion flow, which irradiates the geometrically thin outer disk.


title:
Spatially resolved Spectro-photometry of M81: Age, Metallicity and
  Reddening Maps

abstract:
  In this paper, we present a multi-color photometric study of the nearby
spiral galaxy M81, using images obtained with the Beijing Astronomical
Observatory 60/90 cm Schmidt Telescope in 13 intermediate-band filters from
3800 to 10000{\AA}. The observations cover the whole area of M81 with a total
integration of 51 hours from February 1995 to February 1997. This provides a
multi-color map of M81 in pixels of $1\arcsec.7 \times 1\arcsec.7$. Using
theoretical stellar population synthesis models, we demonstrate that some BATC
colors and color indices can be used to disentangle the age and metallicity
effect. We compare in detail the observed properties of M81 with the
predictions from population synthesis models and quantify the relative chemical
abundance, age and reddening distributions for different components of M81. We
find that the metallicity of M81 is about $Z=0.03$ with no significant
difference over the whole galaxy. In contrast, an age gradient is found between
stellar populations of the central regions and of the bulge and disk regions of
M81: the stellar population in its central regions is older than 8 Gyr while
the disk stars are considerably younger, $\sim 2$ Gyr. We also give the
reddening distribution in M81. Some dust lanes are found in the galaxy bulge
region and the reddening in the outer disk is higher than that in the central
regions.


title: On PSR1913+16

abstract:
  There are reference frames for which both stars of binary radio-pulsar
PSR1913+16 are at rest. As a consequence, PSR1913+16 does not emit gravity
waves. (If the accelerated bodies should send out a gravitational radiation,
they would represent a class of physically privileged systems. But this is
forbidden by general relativity.)


title:
Extended Quintessence: imprints on the cosmic microwave background
  spectra

abstract:
  We describe the observable features of the recently proposed Extended
Quintessence scenarios on the Cosmic Microwave Background (CMB) anisotropy
spectra. In this class of models a scalar field $\phi$, assumed to provide most
of the cosmic energy density today, is non-minimally coupled to the Ricci
curvature scalar $R$. We implement the linear theory of cosmological
perturbations in scalar tensor gravitational theories to compute CMB
temperature and polarization spectra. All the interesting spectral features are
affected: on sub-degree angular scales, the acoustic peaks change both in
amplitude and position; on larger scales the low redshift dynamics enhances the
Integrated Sachs Wolfe effect. These results show how the future CMB
experiments could give information on the vacuum energy as well as on the
structure of the gravitational Lagrangian term.


title:
On the universality of the spectrum of cosmic rays accelerated at highly
  relativistic shocks

abstract: A small error was corrected.


title:
Systematic effects in the interpretations of Cluster X-ray Temperature
  functions

abstract:
  The formation and evolution of clusters of galaxies are sensitive to the
underlying cosmological model. Constraints on cosmological parameters of cold
dark matter models have been derived from mass, temperature and luminosity
functions of clusters. We study the importance of including cluster formation
history and a correction for collapsed fraction of objects in determining the
cluster X-ray temperature function. We find that both effects are important. We
compare temperature functions obtained by using a power law approximation for
the mass variance normalized to X-ray clusters to those obtained by using a
COBE normalized full CDM treatment. We conclude that the temperature function
could be a powerful test on the average density of the Universe if we could
find the correct way of interpreting the data.


title:
Contributions to the Power Spectrum of Cosmic Microwave Background from
  Fluctuations Caused by Clusters of Galaxies

abstract:
  We estimate the contributions to the cosmic microwave background radiation
(CMBR) power spectrum from the static and kinematic Sunyaev-Zel'dovich (SZ)
effects, and from the moving cluster of galaxies (MCG) effect. We conclude, in
agreement with other studies, that at sufficiently small scales secondary
fluctuations caused by clusters provide important contributions to the CMBR. At
$\ell \gtrsim 3000$, these secondary fluctuations become important relative to
lensed primordial fluctuations. Gravitational lensing at small angular scales
has been proposed as a way to break the ``geometric degeneracy'' in determining
fundamental cosmological parameters. We show that this method requires the
separation of the static SZ effect, but the kinematic SZ effect and the MCG
effect are less important. The power spectrum of secondary fluctuations caused
by clusters of galaxies, if separated from the spectrum of lensed primordial
fluctuations, might provide an independent constraint on several important
cosmological parameters.


title:
Detection of X-ray pulsations from the Be/X-ray transient A 0535+26
  during a disc loss phase of the primary

abstract:
  Using the RossiXTE experiment, we detect weak X-ray emission from the
recurrent Be/X-ray transient A 0535+26 at a time when the optical counterpart
V725 Tau displayed H-alpha in absorption, indicating the absence of a
circumstellar disc. The X-ray radiation is strongly modulated at the 103.5-s
pulse period of the neutron star, confirming that it originates from A 0535+26.
The source is weaker than in previous quiescence detections by two orders of
magnitude and should be in the centrifugal inhibition regime. We show that the
X-ray luminosity cannot be due to accretion on to the magnetosphere of the
neutron star. Therefore this detection represents a new state of the accreting
pulsar. We speculate that the X-ray emission can be due to some matter leaking
through the magnetospheric barrier or thermal radiation from the neutron star
surface due to crustal heating. The observed luminosity is probably compatible
with recent predictions of thermal radiation from X-ray transients in
quiescence. The detection of the X-ray source in the inhibition regime implies
a reduced density in the outflow from the Be companion during its disc-less
phase.


title:
Jupiter's hydrocarbons observed with ISO-SWS: vertical profiles of C2H6
  and C2H2, detection of CH3C2H

abstract:
  We have analysed the ISO-SWS spectrum of Jupiter in the 12-16 micron range,
where several hydrocarbons exhibit rovibrational bands. Using temperature
information from the methane and hydrogen emissions, we derive the mixing
ratios (q) of acetylene and ethane at two independent pressure levels. For
acetylene, we find $q=(8.9^{+1.1}_{-0.6})\times10^{-7}$ at 0.3 mbar and
$q=(1.1^{+0.2}_{-0.1})\times10^{-7}$ at 4 mbar, giving a slope $-d\ln q / d\ln
P=0.8\pm0.1$, while for ethane $q=(1.0\pm0.2)\times10^{-5}$ at 1 mbar and
$q=(2.6^{+0.5}_{-0.6})\times10^{-6}$ at 10 mbar, giving $-d\ln q / d\ln
P=0.6\pm0.2$. The ethane slope is consistent with the predictions of Gladstone
et al. (1996), but that predicted for acetylene is larger than we observe. This
disagreement is best explained by an overestimation of the acetylene production
rate compared to that of ethane in the Gladstone et al. (1996) model.
  At 15.8 micron, methylacetylene is detected for the first time at low jovian
latitudes, and a stratospheric column density of $(1.5\pm0.4)\times10^{15}$
molecule.cm-2 is inferred. We also derive an upper limit for the diacetylene
column density of $7\times10^{13}$ molecule.cm-2.


title: Hidden source of high-energy neutrinos in collapsing galactic nucleus

abstract:
  We propose the model of a short-lived very powerful source of high energy
neutrinos. It is formed as a result of the dynamical evolution of a galactic
nucleus prior to its collapse into a massive black hole and formation of
high-luminosity AGN. This stage can be referred to as ``pre-AGN''. A dense
central stellar cluster in the galactic nucleus on the late stage of evolution
consists of compact stars (neutron stars and stellar mass black holes). This
cluster is sunk deep into massive gas envelope produced by destructive
collisions of a primary stellar population. Frequent collisions of neutron
stars in a central stellar cluster are accompanied by the generation of
ultrarelativistic fireballs and shock waves. These repeating fireballs result
in a formation of the expanding rarefied cavity inside the envelope. The
charged particles are effectively accelerated in the cavity and, due to
pp-collisions in the gas envelope, they produce high energy neutrinos. All high
energy particles, except neutrinos, are absorbed in the thick envelope.
Duration of this pre-AGN phase is about 10 yr, the number of the sources can be
\~ 10 per cosmological horizon. High energy neutrino signal can be detected by
underground neutrino telescope with effective area ~1 km^2.


title: Mining for Metals in the Lyman Alpha Forest

abstract:
  In order to ascertain the extent of metal enrichment in the Ly alpha forest,
we have analysed a very high S/N spectrum of the z = 3.625 QSO Q1422+231. We
find that in high column density Ly alpha clouds, the power law column density
distribution function of C IV continues down to log N(C IV) = 11.7. In
addition, by analysing pixel-by-pixel optical depths we show that there are
considerably more metals in the Ly alpha forest than are currently directly
detectable.


title: New gamma Doradus Stars from the Hipparcos Mission and Geneva Photometry

abstract:
  A search for new gamma Dor stars was undertaken using the Hipparcos periodic
variable star catalogue and the Geneva photometric database, leading to a list
of 40 new candidates. We started a monitoring of the candidates which suited
the observational window with the CORALIE spectrograph at the Swiss Euler
Telescope for establishing a robust list of new gamma Dor stars and studying
line profile variations. We here present our long-term program.


title: Gas and dust in NGC 7469: sub-mm imaging and CO J=3-2

abstract:
  We present sensitive sub-mm imaging of the Seyfert 1 galaxy NGC 7469 at 850
$\mu $m and 450 $\mu $m with the Submillimetre Common User Bolometer Array
(SCUBA) on the James Clerk Maxwell Telescope (JCMT) and ^{12}CO J=3-2 line
observations of its central starbursting region. The global dust spectrum, as
constrained by the new set of sub-mm data and available 1.30 mm and IRAS 100
$\mu $m, 60 $\mu $m data reveals a dominant warm dust component with a
temperature of $\rm T_{\rm d} \sim 35$ K and a global molecular gas-to-dust
ratio $\rm M(H_2)/M_{\rm d}\sim 600$. Such high values are typical for
IR-bright spirals and in order to reconcile them with the significantly lower
ratio of ~ 100 obtained for the Milky Way a cold dust reservoir, inconspicuous
at FIR wavelengths, is usually postulated. We present evidence that, rather
than unaccounted cold dust mass, this high ratio suggests an overestimate of
$\rm M(H_2)$ from its associated ^{12}CO J=1-0 line luminosity by a factor of ~
5 when a Milky Way value for this conversion is used in starburst nuclei
environments.


title: Low Frequency Radio Pulses from Gamma-Ray Bursts?

abstract:
  Gamma-ray bursts, if they are generated in the process of interaction between
relativistic strongly magnetized winds and an ambient medium, may be
accompanied by very short pulses of low-frequency radio emission. The bulk of
this emission is expected to be at the frequencies of $\sim 0.1-1$ MHz and
cannot be observed. However, the high-frequency tail of the low-frequency radio
emission may reach a few ten MHz and be detected, especially if the strength of
the magnetic field of the wind is extremely high.


title:
Optical, near-infrared and hard X-ray observations of SAXJ1353.9+1820: a
  red quasar

abstract:
  We present the results of a follow-up ASCA observation and multicolour
optical and near-infrared photometry carried out at the 3.5-m Italian National
Telescope Galileo of SAXJ1353.9+1820. This object, serendipitously discovered
by BeppoSAX in the 5-10 keV band, has been spectroscopically identified as a
red quasar at z=0.217. The combined X-ray and optical-infrared data reveal the
presence of a moderately luminous X-ray source (~ 10^{44} erg s^{-1}) obscured
by a column density of the order of 10^{22} cm^{-2} in a otherwise optically
passive early-type galaxy. The implications for the nature of red quasars and
their possible contribution to the hard X-ray background are briefly outlined.


title:
Use of DPOSS data to study globular cluster halos: an application to M
  92

abstract:
  We exploited the large areal coverage offered by the DPOSS to analyze the
outermost regions of the galactic globular cluster M 92. Two independent
photometric reduction programs (SKICAT and DAOPHOT) were used to construct a
color-magnitude diagram and a surface density profile for this cluster, based
on J- and F-band DPOSS plates. A strong similarity has been found in the
performance of the two programs in the low--crowded outermost cluster regions.
After removing the background contribution, we obtained the cluster outer
surface density profile down to a surface brightness magnitude of mu_V ~ 31
mag/sq.arcsec and matched it with the inner profile of Trager et al. 1995. The
profile shapes match very well: since our data are uncalibrated, the shift in
magnitude between the profiles has been also used to calibrate our profile. The
analysis shows that the cluster has an extra tidal halo extending out to ~ 30
arcmin from the cluster center at a 3 sigma level over the background noise.
This halo is revealed to be almost circular.


title:
Geometric Gaussianity and Non-Gaussianity in the Cosmic Microwave
  Background

abstract:
  In this paper, Gaussianity of eigenmodes and non-Gaussianity in the Cosmic
Microwave Background (CMB) temperature fluctuations in two smallest compact
hyperbolic (CH) models are investigated. First, it is numerically found that
the expansion coefficients of low-lying eigenmodes on the two CH manifolds
behave as if they are Gaussian random numbers at almost all the places. Next,
non-Gaussianity of the temperature fluctuations in the (l,m) space in these
models is studied. Assuming that the initial fluctuations are Gaussian, the
real expansion coefficients b_{l m} of the temperature fluctuations in the sky
are found to be distinctively non-Gaussian. In particular, the cosmic variances
are found to be much larger than that for Gaussian models. On the other hand,
the anisotropic structure is vastly erased if one averages the fluctuations at
a number of different observing points because of the Gaussian
pseudo-randomness of the eigenmodes. Thus the dominant contribution to the
two-point correlation functions comes from the isotropic terms described by the
angular power spectra C_l. Finally, topological quantities: the total length
and the genus of isotemperature contours are investigated. The variances of
total length and genus at high and low threshold levels are found to be
considerably larger than that of Gaussian models while the means almost agree
with them.


title: Silicate emission in Orion

abstract:
  We present mid-infrared spectro-imagery and high-resolution spectroscopy of
the Orion bar and of a region in the Orion nebula. These observations have been
obtained in the Guaranteed Time with the Circular Variable Filters of the ISO
camera (CAM-CVF) and with the Short Wavelength Spectrometer (SWS), on board the
European Infrared Space Observatory (ISO). Our data shows emission from
amorphous silicate grains from the entire HII region and around the isolated
O9.5V star Theta2 Ori A. The observed spectra can be reproduced by a mixture of
interstellar silicate and carbon grains heated by the radiation of the hot
stars present in the region. Crystalline silicates are also observed in the
Orion nebula and suspected around Theta2 Ori A. They are probably of
interstellar origin. The ionization structure and the distribution of the
carriers of the Aromatic Infrared Bands (AIBs) are briefly discussed on the
basis of the ISO observations.


title: FIRBACK Source Counts and Cosmological Implications

abstract:
  FIRBACK is a one of the deepest surveys performed at 170 microns with ISOPHOT
onboard ISO, and is aimed at the study of cosmic far infrared background
sources. About 300 galaxies are detected in an area of four square degrees, and
source counts present a strong slope of 2.2 on an integral "logN-logS" plot,
which cannot be due to cosmological evolution if no K-correction is present.
The resolved sources account for less than 10% of the Cosmic Infrared
Background at 170 microns. In order to understand the nature of the sources
contributing to the CIB, and to explain deep source counts at other
wavelengths, we have developed a phenomenological model, which constrains in a
simple way the luminosity function evolution with redshift, and fits all the
existing deep source counts from the mid-infrared to the submillimetre range.
Images, materials and papers available on the FIRBACK web:
http://wwwfirback.ias.u-psud.fr wwwfirback.ias.u-psud.fr


title:
The extragalactic background and its fluctuations in the far-infrared
  wavelengths

abstract:
  A Cosmic Far-InfraRed Background (CFIRB) has long been predicted that would
traces the intial phases of galaxy formation. It has been first detected by
Puget et al.(1996) using COBE data and has been later confirmed by several
recent studies (Fixsen et al. 1998, Hauser et al. 1998, Lagache et al. 1999).
We will present a new determination of the CFIRB that uses for the first time,
in addition to COBE data, two independent gas tracers: the HI survey of
Leiden/Dwingeloo (hartmann, 1998) and the WHAM H$_{\alpha}$ survey (Reynolds et
al 1998). We will see that the CFIRB above 100 micron is now very well
constrained. The next step is to see if we can detect its fluctuations. To
search for the CFIRB fluctuations, we have used the FIRBACK observations.
FIRBACK is a deep cosmological survey conducted at 170 micron with ISOPHOT
(Dole et al., 2000). We show that the emission of unresolved extra-galactic
sources clearly dominates, at arcminute scales, the background fluctuations in
the lowest galactic emission regions. This is the first detection of the CFIRB
fluctuations.


title: High Velocity Star Formation in the LMC

abstract:
  Light-echo measurements show that SN1987A is 425 pc behind the LMC disk. It
is continuing to move away from the disk at $18 \kms$. Thus, it has been
suggested that SN1987A was ejected from the LMC disk. However, SN1987A is a
member of a star cluster, so this entire cluster would have to have been
ejected from the disk. We show that the cluster was formed in the LMC disk,
with a velocity perpendicular to the disk of about $50 \kms$. Such high
velocity formation of a star cluster is unusual, having no known counterpart in
the Milky Way.


title: Black-Hole Transients and the Eddington Limit

abstract:
  I show that the Eddington limit implies a critical orbital period P_crit(BH)
= 2d beyond which black-hole LMXBs cannot appear as persistent systems. The
unusual behaviour of GRO J1655-40 may result from its location close to this
critical period.


title: Secondary caustics in close multiple lenses

abstract:
  We investigate the caustic structure of a lens composed by a discrete number
of point-masses, having mutual distances smaller than the Einstein radius of
the total mass of the system. Along with the main critical curve, it is known
that the lens map is characterized by secondary critical curves producing small
caustics far from the lens system. By exploiting perturbative methods, we
derive the number, the position, the shape, the cusps and the area of these
caustics for an arbitrary number of close multiple lenses. Very interesting
geometries are created in some particular cases. Finally we review the binary
lens case where our formulae assume a simple form.


title:
Evidence for Pressure Driven Flows and Turbulent Dissipation in the
  Serpens NW Protocluster

abstract:
  We have mapped the dense gas distribution and dynamics in the NW region of
the Serpens molecular cloud in the CS(2-1) and N2H+(1-0) lines and 3 mm
continuum using the FCRAO telescope and BIMA interferometer. 7 continuum
sources are found. The N2H+ spectra are optically thin and fits to the 7
hyperfine components are used to determine the distribution of velocity
dispersion. 8 cores, 2 with continuum sources, 6 without, lie at a local
linewidth minimum and optical depth maximum. The CS spectra are optically thick
and generally self-absorbed over the full 0.2 pc extent of the map. We use the
line wings to trace outflows around at least 3, and possibly 4, of the
continuum sources, and the asymmetry in the self-absorption as a diagnostic of
relative motions between core centers and envelopes. The quiescent regions with
low N2H+ linewidth tend to have more asymmetric CS spectra than the spectra
around the continuum sources indicating higher infall speeds. These regions
have typical sizes ~5000 AU, linewidths ~0.5 km/s, and infall speeds ~0.05
km/s. The correlation of CS asymmetry with N2H+ velocity dispersion suggests
that the inward flows of material that build up pre-protostellar cores are
driven at least partly by a pressure gradient rather than by gravity alone. We
discuss a scenario for core formation and eventual star forming collapse
through the dissipation of turbulence.


title: HST/NICMOS Imaging of the Planetary Nebula Hubble 12

abstract:
  Images of Hubble 12 were obtained with the HST/NICMOS instrument in the
F110W, F164N, and F166N filters of NIC1, and the F160W, F187N, F190N, F212N,
F215N filters of NIC2. The images show the structure of the inner ``torus'' and
lobes much clearer than previous ground-based images. In particular, the [Fe
II] lobes are clearly resolved and shown to be distinct from the molecular
hydrogen emission structures. Apparent changes in the inner ionized and neutral
bipolar shell implies periodic mass loss or changes in stellar wind shape or
direction. The molecular hydrogen in the ``eye'' is radiatively excited and
shows a complex morphology that suggests that several mass ejection events are
responsible for producing this structure. The position angle of the molecular
hydrogen and [Fe II] lobes differ, indicating a possible precession of the
ejection axis.


title: Evolution and surface abundances of red giants experiencing deep mixing

abstract:
  We have calculated the evolution of low metallicity red giant stars under the
assumption of deep mixing between the convective envelope and the hydrogen
burning shell. We find that the extent of the observed abundance anomalies, and
in particular the universal O-Na anticorrelation, can be totally explained by
mixing which does not lead to significant helium enrichment of the envelope. On
the other hand, models with extremely deep mixing and strong helium enrichment
predict anomalies of sodium and oxygen, which are much larger than the observed
ones. This latter result depends solely on the nucleosynthesis inside the
hydrogen burning shell, but not on the details of the mixing descriptions.
These, however, influence the evolution of surface abundances with brightness,
which we compare with the limited observational material available. Our models
allow, nevertheless, to infer details on the depth and speed of the mixing
process in several clusters. Models with strong helium enrichment evolve to
high luminosities and show an increased mass loss. However, under peculiar
assumptions, red giants reach very high luminosities even without extreme
helium mixing. Due to the consequently increased mass loss, such models could
be candidates for blue horizontal branch stars, and, at the same time, would be
consistent with the observed abundance anomalies.


title: The shock waves in decaying supersonic turbulence

abstract:
  We here analyse numerical simulations of supersonic, hypersonic and
magnetohydrodynamic turbulence that is free to decay. Our goals are to
understand the dynamics of the decay and the characteristic properties of the
shock waves produced. This will be useful for interpretation of observations of
both motions in molecular clouds and sources of non-thermal radiation.
  We find that decaying hypersonic turbulence possesses an exponential tail of
fast shocks and an exponential decay in time, i.e. the number of shocks is
proportional to t exp (-ktv) for shock velocity jump v and mean initial
wavenumber k. In contrast to the velocity gradients, the velocity Probability
Distribution Function remains Gaussian with a more complex decay law.
  The energy is dissipated not by fast shocks but by a large number of low Mach
number shocks. The power loss peaks near a low-speed turn-over in an
exponential distribution. An analytical extension of the mapping closure
technique is able to predict the basic decay features. Our analytic description
of the distribution of shock strengths should prove useful for direct modeling
of observable emission. We note that an exponential distribution of shocks such
as we find will, in general, generate very low excitation shock signatures.


title:
The Globular Cluster Systems in the Coma Ellipticals. III: The Unique
  Case of IC 4051

abstract:
  Using archival \hst WFPC2 data, we derive the metallicity distribution,
luminosity function, and spatial structure of the globular cluster system
around IC 4051, a giant E galaxy on the outskirts of the Coma cluster core. The
metallicity distribution derived from the (V-I) colors has a mean [Fe/H] =
-0.3, a near-complete lack of metal-poor clusters, and only a small metallicity
gradient with radius; it may, however, have two roughly equal metallicity
subcomponents, centered at [Fe/H] ~ 0.0 and -1.0. The luminosity distribution
(GCLF) has the Gaussian-like form observed in all other giant E galaxies, with
a peak (turnover) at V = 27.8, consistent with a Coma distance of 100 Mpc. The
radial profiles of both the GCS and the halo light show an unusually steep
falloff which may indicate that the halo of this galaxy has been tidally
truncated. Lastly, the specific frequency of the GCS is remarkably large: we
find S_N = 11 +- 2, resembling the central cD-type galaxies even though IC 4051
is not a cD or brightest cluster elliptical. A formation model consistent with
most of the observations would be that this galaxy was subjected to removal of
a large fraction of its protogalactic gas shortly after its main phase of
globular cluster formation, probably by its first passage through the Coma
core. Since then, no significant additions due to accretions or mergers have
taken place.


title:
On the Role of Dust Particles in Decoupling of Plasma from Magnetic
  Field in Laboratory and Space

abstract:
  The objective of this paper is to apply the recent achievements in
understanding of the non-MHD effects in plasma (acquired both in laboratory
experiments, as well as in theory), to the interstellar phenomena. Applied to
the space plasma, these effects can significantly change the picture of plasma
dynamics. Charged dust particles are always present in the interstellar medium
and can easily remain not magnetized, even when the plasma electrons and ions
are strongly magnetized. In such a medium, the magnetic field can propagate
with the super-Alfven velocity. This breaks the local "frozen-in" law for the
magnetic field, which can significantly affect the gravitational collapse
phenomena, the space plasma turbulence spectrum, magnetic dynamo and the rate
of the Fermi acceleration of cosmic rays.


title: Studying the Pulsation of Mira Variables in the Ultraviolet

abstract:
  We present results from an empirical study of the Mg II h & k emission lines
of selected Mira variable stars, using spectra from the International
Ultraviolet Explorer (IUE). The stars all exhibit similar Mg II behavior during
the course of their pulsation cycles. The Mg II flux always peaks after optical
maximum near pulsation phase 0.2-0.5, although the Mg II flux can vary greatly
from one cycle to the next. The lines are highly blueshifted, with the
magnitude of the blueshift decreasing with phase. The widths of the Mg II lines
are also phase-dependent, decreasing from about 70 km/s to 40 km/s between
phase 0.2 and 0.6. We also study other UV emission lines apparent in the IUE
spectra, most of them Fe II lines. These lines are much narrower and not nearly
as blueshifted as the Mg II lines. They exhibit the same phase-dependent flux
behavior as Mg II, but they do not show similar velocity or width variations.


title: The Power Spectrum of Rich Clusters on Near Gigaparsec Scales

abstract:
  Recently, there have been numerous analyses of the redshift space power
spectrum of rich clusters of galaxies. Some of these analyses indicate a "bump"
in the Abell/ACO cluster power spectrum around k= 0.05hMpc^-1. Such a feature
in the power spectrum excludes most standard formation models and indicates
possible periodicity in the distribution of large-scale structure. However, the
data used in detecting this peak include clusters with estimated redshifts
and/or clusters outside of Abell's (1958) statistical sample, i.e. R=0
clusters. Here, we present estimations of the redshift-space power spectrum for
a newly expanded sample of 637 R >= 1 Abell/ACO clusters which has a constant
number density to z = 0.10 in the Southern Hemisphere and a nearly constant
number density to z = 0.14 in the Northern Hemisphere. The volume sampled,
\~10^8h^{-3}Mpc^{3}, is large enough to accurately calculate the power per mode
to scales approaching 10^3h^{-1}Mpc. We find the shape of the power spectrum is
is a power-law on scales 0.02 <= k <= 0.10hMpc^{-1}, with enhanced power over
less rare clusters, such as APM clusters. The slope of this power-law is n=
-1.4. The power spectrum is essentially featureless, although we do see a dip
near $k = 0.04h$Mpc$^{-1}$ which cannot be considered statistically significant
based on this data alone. We do not detect a narrow peak at $k \sim
0.05h$Mpc$^{-1}$ and there is no evidence for a turn-over in the power spectrum
as has been previously reported. We compare the shape of the Abell/ACO rich
cluster power spectrum to various linear models.


title: Primordial Nucleosynthesis For The New Millennium

abstract:
  The physics of the standard hot big bang cosmology ensures that the early
Universe was a primordial nuclear reactor, synthesizing the light nuclides (D,
3He, 4He, and 7Li) in the first 20 minutes of its evolution. After an overview
of nucleosynthesis in the standard model (SBBN), the primordial abundance
yields will be presented, followed by a status report (intended to stimulate
further discussion during this symposium) on the progress along the road from
observational data to inferred primordial abundances. Theory will be confronted
with observations to assess the consistency of SBBN and to constrain cosmology
and particle physics. Some of the issues/problems key to SBBN in the new
millenium will be highlighted, along with a wish list to challenge theorists
and observers alike.


title:
A Sample of 669 Ultra Steep Spectrum Radio Sources to Find High Redshift
  Radio Galaxies

abstract:
  Since radio sources with Ultra Steep Spectra (USS; alpha <~ -1.30; S ~
nu^alpha) are efficient tracers of high redshift radio galaxies (HzRGs), we
have defined three samples of such USS sources using the recently completed
WENSS, TEXAS, MRC, NVSS and PMN radio-surveys. Our combined sample contains 669
sources with S_1400 > 10 mJy and covers virtually the entire sky outside the
Galactic plane (|b|>15). For our 2 largest samples, covering declination > -35,
we selected only sources with angular sizes Theta < 1'. For 410 sources, we
present radio-maps with 0.3" to ~5" resolution from VLA and ATCA observations
or from the FIRST survey, which allows the optical identification of these
radio sources. We find that the spectral index distribution of 143,000 sources
from the WENSS and NVSS consists of a steep spectrum galaxy and a flat spectrum
quasar population, with the relative contribution of flat spectrum sources
doubling from S_1400 >0.1 Jy to S_1400 >2.5 Jy. The identification fraction of
our USS sources on the POSS (R <~ 20) is as low as 15%, independent of spectral
index alpha < -1.30. We further show that 85% of the USS sources that can be
identified with an X-ray source are probably contained in galaxy clusters, and
that alpha < -1.6 sources are excellent Galactic pulsar candidates, because the
percentage of these sources is four times higher in the Galactic plane. Our
sample has been constructed to start an intensive campaign to obtain a large
sample of high redshift objects (z>3) that is selected in a way that does not
suffer from dust extinction or any other optical bias [abridged].


title: X-ray variability and prediction of TeV emission in the HBL 1ES1101-232

abstract:
  1ES1101-232 is a bright BL Lac of the High frequency peak class. We present
here the results of two BeppoSAX observations in which the source has shown a
variation of about 30% in flux with a corresponding spectral variability. We
interpret the overall spectral energy distribution in terms of an homogeneous
SSC model and, by using also the TeV upper limit from a short Mark 6 pointing,
derive constraints on the physical parameters of the source, in particular on
the magnetic field strength. The overall Spectral Energy Distribution makes
1ES1101-232 a very promising candidate for TeV detection.


title: Water Masers Diagnosing Postshocked Conditions in W49N

abstract:
  We present spectroscopic results of 146 water maser outbursts in W49 N,
obtained with the Metsahovi radio telescope at 22 GHz. Combining this data with
Gwinn's VLBI results, we were able to fix the free parameters in the shock
model of Hollenbach and McKee and the maser model of Elitzur, Hollenbach, and
McKee. This enabled a straightforward determination of some 20 shock and maser
parameters, among others, the kinetic temperature, postshock density, water
density, water abundance, preshock and postshock magnetic field strengths as
well as the inclination of the mean field with respect to the line of sight. A
step-by-step presentation of our diagnostic method is given and the relation
between observations and model parameters is discussed. One uniquely powerful
outburst feature, referred to as the "big flare feature", showed also the
narrowest linewidth. Observations indicate that the velocity of this feature
lies in the plane of the sky, whereas preshock and postshock magnetic fields
are directed nearly along the line of sight. Consequently, Alfvenic wave
fluctuations along the line of sight, and linewidth, are minimal, and a very
high aspect ratio is achieved. Furthermore, the big flare feature stands out
through its low space velocity, higher temperature (480 K), and larger preshock
magnetic field strength (8.2 mG).


title:
Rotational modes of non-isentropic stars and the gravitational radiation
  driven instability

abstract:
  We investigate the properties of r-mode and inertial mode of slowly rotating,
non-isentropic, Newtonian stars, by taking account of the effects of the
Coriolis force and the centrifugal force. For the non-isentropic models we
consider only two cases, that is, the models with the stable fluid
stratification in the whole interior and the models that are fully convective.
For simplicity we call these two kinds of models "radiative" and "convective"
models in this paper. For both cases, we assume the deviation of the models
from isentropic structure is small. Examining the dissipation timescales due to
the gravitational radiation and several viscous processes for the polytropic
neutron star models, we find that the gravitational radiation driven
instability of the r-modes remains strong even in the non-isentropic models.
Calculating the rotational modes of the radiative models as functions of the
angular rotation frequency $\Omega$, we find that the inertial modes are
strongly modified by the buoyant force at small $\Omega$, where the buoyant
force as a dominant restoring force becomes comparable with or stronger than
the Coriolis force. Because of this property we obtain the mode sequences in
which the inertial modes at large $\Omega$ are identified as g-modes or the
r-modes with l=|m| at small $\Omega$. We also note that as $\Omega$ increases
from $\Omega=0$ the retrograde g-modes become retrograde inertial modes, which
are unstable against the gravitational radiation reaction.


title: Sachs-Wolfe effect in space-times with torsion

abstract:
  Cartan torsion contribution to Sachs-Wolfe effect in the inflationary phase
of the Universe is discussed.From the COBE data of the microwave anisotropy is
possible to compute the spin-density in the Universe as $10^{16}$ mks units.The
spin-density fluctuations at the hadron era is shown to coincide with the
anisotropy temperature fluctuations.


title: Spirals and the size of the disk in EX Dra

abstract:
  Observations at high spectral and temporal resolution are presented of the
dwarf nova EX Dra in outburst. The disk seen in the He I line reconstructed by
Doppler tomography shows a clear two-armed spiral pattern pointing to spiral
shocks in the disk. The Balmer and He II maps also give evidence for the
presence of spirals. The eclipse as seen in the red continuum indicates a disk
radius of 0.31 times the orbital separation, which might be large enough to
explain the observed spiral shocks through excitation by the tidal field of the
secondary. The eclipse in the Balmer line profiles, well resolved in our
observations, indicates a somewhat smaller disk size (0.25). We discuss the
possibility that this is related to an optical depth effect in the lines.


title:
Design optimization of MACHe3, a project of superfuid He3 detector for
  direct Dark Matter search

abstract:
  MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for
direct Dark Matter (DM) search. A cell of superfluid He3 has been developed and
the idea of using a large number of such cells in a high granularity detector
is proposed. This paper presents, after a brief description of the superfluid
He3 cell, the simulation of the response of different matrix configurations
allowing to define an optimum design as a function of the number of cells and
the volume of each cell. The background rejection, for several configurations,
is presented both for neutrons and gamma-rays of various kinetic energies.


title: The frequency content of Delta Sct stars as determined by photometry

abstract:
  The results obtained by means of the photometric approach to the study of
Delta Sct stars are extensively discussed. The different frequency contents of
the three best candidates for asteroseismological studies (FG Vir, 4 CVn and XX
Pyx) are presented and compared; the importance of the amplitude variations and
of the combination terms is emphasized. The analysis of other multiperiodic
variables shows how a large variety of nonradial modes are excited; in some
cases, modifications of the power spectrum can be observed over a few years and
new modes can be seen to grow. Among monoperiodic pulsators, constant as well
as variable amplitudes can be observed. The difficulty of identifying an
oscillation yielding quantum numbers is emphasized; the possibilities offered
by $\delta$ Sct stars belonging to binary systems and open clusters are
discussed. In this respect, combining the photometric and the spectroscopic
approaches could lead to a solution. A comparison is also made between low- and
high-amplitude pulsators, finding similarities. The use of a reliable
Period-Luminosity-Colour relationships toward the shortest periods can greatly
help mode identification in the galactic stars; moreover, it could provide an
independent verification of extragalactic distances.


title: On dust-correlated Galactic emission in the Tenerife data

abstract:
  Recently correlation analyses between Galactic dust emission templates and a
number of CMB data sets have led to differing claims on the origin of the
Galactic contamination at low frequencies. de Oliviera-Costa {\em et al} (1999)
have presented work based on Tenerife data supporting the spinning dust
hypothesis. Since the frequency coverage of these data is ideal to discriminate
spectrally between spinning dust and free-free emission, we used the latest
version of the Tenerife data, which have lower systematic uncertainty, to study
the correlation in more detail. We found however that the evidence in favor of
spinning dust originates from a small region at low Galactic latitude where the
significance of the correlation itself is low and is compromised by systematic
effects in the Galactic plane signal. The rest of the region was found to be
uncorrelated. Regions that correlate with higher significance tend to have a
steeper spectrum, as is expected for free-free emission. Averaging over all
correlated regions yields dust-correlation coefficients of $180\pm47$ and
$123\pm16$ $\mu$K /MJy sr$^{-1}$ at 10 and 15 GHz respectively.
  These numbers however have large systematic uncertainties that we have
identified and care should be taken when comparing with results from other
experiments. We do find evidence for synchrotron emission with spectral index
steepening from radio to microwave frequencies, but we cannot make conclusive
claims about the origin of the dust-correlated component based on the spectral
index estimates. Data with higher sensitivity are required to decide about the
significance of the dust-correlation at high Galactic latitudes and other
Galactic templates, in particular H$_\alpha$ maps, will be necessary for
constraining its origin.


title: Flash-Heating of Circumstellar Clouds by Gamma Ray Bursts

abstract:
  The blast-wave model for gamma-ray bursts (GRBs) has been called into
question by observations of spectra from GRBs that are harder than can be
produced through optically thin synchrotron emission. If GRBs originate from
the collapse of massive stars, then circumstellar clouds near burst sources
will be illuminated by intense gamma radiation, and the electrons in these
clouds will be rapidly scattered to energies as large as several hundred keV.
Low-energy photons that subsequently pass through the hot plasma will be
scattered to higher energies, hardening the intrisic spectrum. This effect
resolves the "line-of-death" objection to the synchrotron shock model.
Illuminated clouds near GRBs will form relativistic plasmas containing large
numbers of electron-positron pairs that can be detected within ~ 1-2 days of
the explosion before expanding and dissipating. Localized regions of pair
annihilation radiation in the Galaxy would reveal past GRB explosions.


title: The Origin of Cosmic Magnetic Fields

abstract:
  In this talk, I review a number of particle-physics models that lead to the
creation of magnetic fields in the early universe and address the complex
problem of evolving such primordial magnetic fields into the fields observed
today. Implications for future observations of the Cosmic Microwave Background
(CMB) are discussed. Focussing on first-order phase transitions in the early
universe, I describe how magnetic fields arise in the collision of expanding
true-vacuum bubbles both in Abelian and non-Abelian gauge theories.


title: Collisional versus Collisionless Dark Matter

abstract:
  We compare the structure and substructure of dark matter halos in model
universes dominated by collisional, strongly self interacting dark matter
(SIDM) and collisionless, weakly interacting dark matter (CDM). While SIDM
virialised halos are more nearly spherical than CDM halos, they can be
rotationally flattened by as much as 20% in their inner regions. Substructure
halos suffer ram-pressure truncation and drag which are more rapid and severe
than their gravitational counterparts tidal stripping and dynamical friction.
Lensing constraints on the size of galactic halos in clusters are a factor of
two smaller than predicted by gravitational stripping, and the recent detection
of tidal streams of stars escaping from the satellite galaxy Carina suggests
that its tidal radius is close to its optical radius of a few hundred parsecs
--- an order of magnitude smaller than predicted by CDM models but consistent
with SIDM. The orbits of SIDM satellites suffer significant velocity bias
$\sigma_{SIDM}/\sigma_{CDM}=0.85$ and are more circular than CDM,
$\beta_{SIDM}} \approx 0.5$, in agreement with the inferred orbits of the
Galaxy's satellites. In the limit of a short mean free path, SIDM halos have
singular isothermal density profiles, thus in its simplest incarnation SIDM is
inconsistent with galactic rotation curves.


title: Formation and evolution of disk galaxies within cold dark matter halos

abstract:
  We present results of extensive model calculations of disk galaxy evolution
within an hierarchical inside-out formation scenario. We first compare
properties of the dark halos identified in a cosmological N-body simulation
with predictions of a seminumerical method based on an extended collapse model
and find a good agreement. We also study the properties of the halos in
dependence on their environment. We then describe detailed modelling of the
formation and evolution of disks within the growing isolated cold dark matter
halos and predictions for the main properties, correlations and evolutionary
features of normal disk galaxies. The possible shortcomings of the scenario are
discussed.


title: The Mass-To-Light Function: Antibias and Omega_m

abstract:
  We use large-scale cosmological simulations to estimate the mass-to-light
ratio of galaxy systems as a function of scale, and compare the results with
observations of galaxies, groups, clusters, and superclusters of galaxies. We
find remarkably good agreement between observations and simulations.
Specifically, we find that the simulated mass-to-light ratio increases with
scale on small scales and flattens to a constant value on large scales, as
suggested by observations. We find that while mass typically follows light on
large scales, high overdensity regions --- such as rich clusters and
superclusters of galaxies --- exhibit higher M/L_B values than average, while
low density regions exhibit lower M/L_B values; high density regions are thus
antibiased in M/L_B, with mass more strongly concentrated than blue light. This
is true despite the fact that the galaxy mass density is unbiased or positively
biased relative to the total mass density in these regions. The M/L_B antibias
is likely due to the relatively old age of the high density regions, where
light has declined significantly since their early formation time, especially
in the blue band which traces recent star formation. Comparing the simulated
results with observations, we place a powerful constraint on the mass density
of the universe; using, for the first time, the entire observed mass-to-light
function, from galaxies to superclusters, we find Omega =0.16+/-0.05.


title:
On the origin of the color Tully-Fisher and color-magnitude relations of
  disk galaxies

abstract:
  We propose and show that the dependence of the internal face-on dust
absorption upon B-band luminosity reported by Wang & Heckman (1996) for a
sample of late-type galaxies may explain the empirical color-magnitude and
color Tully-Fisher relations of disk galaxies. Thus, in order to explain these
relations, it is not necessary to evoke star formation and gas infall
efficiencies dependent on the mass of the galaxy system. After applying the
Wang & Heckman's luminosity-dependent extinction to hierarchical inside-out
galaxy formation and evolution models where the star formation and gas infall
efficiencies do not significantly depend on mass, we succesfully predict the
observed Tully-Fisher relations in the H and B bands as well as the
color-magnitude relation.


title: Gamma-Ray Bursts via the Neutrino Emission from Heated Neutron Stars

abstract:
  A model is proposed for gamma-ray bursts based upon a neutrino burst of about
10^52 ergs lasting a few seconds above a heated collapsing neutron star. This
type of thermal neutrino burst is suggested by relativistic hydrodynamic
studies of the compression, heating, and collapse of close binary neutron stars
as they approach their last stable orbit, but may arise from other sources as
well. We present a hydrodynamic simulation of the formation and evolution of
the pair plasma associated with such a neutrino burst. This pair plasma leads
to the production of ~10^51 - 10^52 ergs in gamma-rays with spectral and
temporal properties consistent with observed gamma-ray bursts.