Search Publications
Absolute magnitudes of carbon stars from HIPPARCOS parallaxes
Eglitis, I.; Alksnis, A.; Balklavs, A. +1 more
Hipparcos trigonometric parallaxes and photometric data for about 40 bright carbon stars have been analysed. Individual absolute visual and bolometric magnitudes, normal color indices (B-V)_0, absorption values and distance moduli were determined. By comparison with stellar evolutionary tracks for initial mass 1<= M/M_⊙<=4 it is found that t…
The mass of (1) Ceres from its gravitational perturbations on the orbits of 9 asteroids
Viateau, B.; Rapaport, M.
The mass of (1) Ceres is about half of the total mass of the main asteroid belt, and its long-term perturbations on the orbits of many solar system objects are important. For this reason, a very good knowledge of this mass is necessary. Although many determinations of the mass of Ceres have been made until now, the uncertainty remaining on its val…
Detection of short-term variations in Mira-type variables from HIPPARCOS photometry
de Laverny, P.; Mignard, F.; Mennessier, M. O. +1 more
The Hipparcos photometric observations carried out over 37 months have been investigated in detail for ~ 250 Miras. This leads to an unexpected by-product of the mission that we already suspected from ESOC real-time reductions: the first detection from space of photometric short-term brightness variations in Mira-type variables. Altogether, 51 eve…
Diffuse ionized gas toward beta Canis Majoris
Gry, Cecile; Dupin, Olivier
This paper presents the study of the interstellar medium toward beta CMa, a disk sight-line known for its low neutral gas density. This study uses high and medium resolution HST-GHRS spectra including lines from the following species: H i, D i, N i, O i, S ii, S iii, Si ii, Si iii, Si iv, Al ii, Al iii, Fe ii, Mg i, Mg ii, Mn ii, C ii and C iv. Th…
Detection of further UV-bright high-redshift QSOs
Reimers, D.; Hagen, H. -J.; Rodriguez-Pascual, P. +1 more
We present successful UV observations with IUE of several newly discovered high-redshift QSOs from the Hamburg QSO Surveys. In addition to three previously discovered QSOs three new objects have been found to have lines of sight transparent to wavelengths as short as 1200 { Angstroms}: HS 0747+4259 (z = 1.9, V = 15.8); HS 1147+6556 (z = 2.21, V = …
Resonance scattering of Lyman alpha from interstellar hydrogen
Brasken, Mats; Kyrola, Erkki
We derive a set of new line-of-sight (LOS) integrals and phase functions for the resonance scattering of unpolarized Lyman alpha light in the optically thin medium limit. To explicitly show the approximations done, and to indicate the range of validity of previously published formulas, we start by treating the general theory of resonance scatterin…
High resolution spectroscopy of symbiotic stars. IV. BX Monocerotis: orbital and stellar parameters
Schmutz, W.; Nussbaumer, H.; Shore, S. N. +4 more
We investigate the orbit and the components of the symbiotic BX Mon system with new high resolution spectroscopy, IUE spectra, published photographic magnitudes, and brightness estimates from the RASNZ. We review the available photometry and deduce a new binary period of 1401 days. We also find evidence in the IUE data that BX Mon is an eclipsing …
Abundance analysis of the lambda Bootis stars HD 192640, HD 183324, and HD 84123
Heiter, U.; Paunzen, E.; Weiss, W. W. +2 more
The classification of lambda Bootis stars based on photometric indices or low resolution spectra is not sufficient for a final decision concerning a membership to this group. A detailed spectroscopic investigation is necessary to rule out stars with similar classification spectra but different abundance patterns. Therefore a program on abundance a…
General relativistic satellite astrometry. I. A non-perturbative approach to data reduction
Lattanzi, M. G.; Vecchiato, A.; de Felice, F. +1 more
A general relativistic scenario is utilized to build a non-perturbative model, in Schwarzschild metric, for the representation of observed angles among star pairs. This model is then applied to an end-to-end simulation of the GAIA satellite, a concept for global astrometry within the 2000+ scientific program of the European Space Agency. GAIA is e…
Heating and acceleration of minor ions in the solar wind
McKenzie, J. F.; Czechowski, A.; Axford, W. I. +1 more
We make use of the results of a one-ion model of McKenzie et al. (1997) to obtain the critical solution describing the acceleration of a two-ion solar wind. The model includes preferential heating of the heavy ion species and the temperature anisotropy expected if the heating is predominantly due to ion-cyclotron damping. The relationship of the m…