Astrophysics
We present spectral analysis of ASCA data of 17 elliptical and 3 lenticular galaxies most of which have high L_x/L_B. Single-temperature models (MEKAL and Raymond-Smith) give unacceptable fits (chi^2_red > 1.5) in most cases and, in…
Natural (such as lunar) occultations have long been used to study sources on small angular scales, while coronographs have been used to study high contrast sources. We propose launching the Improved Resolution and Image Selection (IRIS)…
We present the results of realistic end-to-end simulations of observations of nearby stars with the proposed global astrometry mission GAIA, recently recommended within the context of ESA's Horizon 2000 Plus long-term scientific program. We…
We present a parsec-scale image of the OH maser in the nucleus of the active galaxy IIIZw35, made using the Very Long Baseline Array at a wavelength of 18 cm. We detected two distinct components, with a projected separation of 50 pc (for…
We report the detection of the H_2O molecule in absorption at a redshift z = 0.68466 in front of the gravitationally lensed quasar B0218+357. We detect the fundamental transition of ortho-water at 556.93 GHz (redshifted to 330.59 GHz). The…
Based on the large number of elliptical planetary nebulae I argue that about 55 per cent of all progenitors of planetary nebulae have planets around them. The planets spin up the stars when the later evolve along the red giant branch or…
We have studied head-on collisions between equal-mass, mildly supersonic (Mach number 1.5) HI clouds, in a standard Two-phase ISM (T_cl = 74 K, n_cl = 22 cm^-3, \chi = 100). We explore the role of various factors, including the radiative…
We present a deep color-magnitude diagram in the VI passbands of the globular cluster M54, a member of the Sagittarius dwarf galaxy. The data extend below the cluster's main sequence turn-off, allowing us to estimate the cluster's age. We…
Rapid UBVRI photometry of this ultracompact LMXB pulsar has detected 7.67 s optical pulsations in all five bands. The optical pulsations, which are at the same frequency as the X-ray pulsations, are understood as reprocessing of pulsed…
We review current cosmological constraints on the axion. We describe the basic mechanisms by which axions are created in the early universe, focussing on the standard thermal scenario where the dominant process is through axion radiation by…
We present the results of a search for emission-line galaxies (ELGs) towards nearby voids, based on a sample selected on the HQS (Hamburg Quasar Survey) - III-aJ objective-prism plates. The survey was based on the presence of emission-lines…
(Abridged) We examine the theoretical relationship between Omega_0 and substructure in galaxy clusters which are formed by the collapse of high density peaks in a gaussian random field. The radial mass distributions of the clusters are…
We study the influence of the various parameters of scenarios of large-scale structure formation on properties of galaxy clusters, and investigate which cluster properties are most sensitive to these parameters. We present a set of large…
The largest underground neutrino observatory, Super-Kamiokande, located near Kamioka, Japan has been collecting data since April 1996. It is located at a depth of roughly 2.7 kmwe in a zinc mine under a mountain, and has an effective area…
We study the auto-correlation function of CMB polarization anisotropies and their cross correlation with temperature fluctuations as probe of the causal structure of the universe. Because polarization is generated at the last scattering…
Comparing Big Bang Nucleosynthesis predictions with the light element abundances inferred from observational data, we can obtain the strong constraints on some neutrino properties, e.g. number of neutrino species, mass, lifetime. Recently…
Several recent measurements have been made of the angular correlation function $w(\theta,m)$ of faint galaxies in deep surveys (e.g., Hubble Deep Field, HDF). Are the measured correlations indicative of gravitational growth of primordial…
We investigate the pulsational properties of RSG models --- which we evolve from ZAMS masses in the range 10 to $20 \Msun$ --- by means of linear and non-linear calculations. We find period and growth rate of the dominant fundamental mode…
(Abridged) The ESO Slice Project (ESP) is a galaxy redshift survey we have completed as an ESO Key-Project over ~23 square degrees, in a region near the South Galactic Pole. The survey is nearly complete to the limiting magnitude b_J=19.4…
In this paper, we review the current theory of very low mass stars model atmospheres including the coolest known M~dwarfs, M~subdwarfs, and brown dwarfs, i.e. T$_{eff} \leq 5,000 $K and $-2.0 \le [M/H] \le +0.0$. We discuss ongoing efforts…