Search Publications
The HIPPARCOS Catalogue
Grewing, M.; Arenou, F.; Lindegren, L. +17 more
The principal observational characteristics of the Hipparcos Catalogue, and a summary of its main astrometric and photometric properties, are presented. Median astrometric standard errors (in position, parallax, and annual proper motion) are in the range 0.7-0.9 milliarcsec (mas) for stars brighter than 9 mag at the catalogue epoch (J1991.25). The…
Notes on the convection in the ATLAS9 model atmospheres.
Castelli, F.; Gratton, R. G.; Kurucz, R. L.
The mixing-length theory for the convection, as it is used in the ATLAS9 code (Kurucz, 1993a), is summarized and discussed. We investigated the effect of the modification called ``approximate overshooting'' on the model structure of the Sun and of stars with T_eff_ included between 4000K and 8500K, logg included between 2.5 and 4.5, and metallicit…
The nature of intermediate-redshift damped Lyα absorbers.
Deharveng, J. M.; Bergeron, J.; Le Brun, V. +1 more
We present HST/WFPC2 high-spatial resolution images in the R and B bands of the close environment of the sightlines to seven quasars which spectra show either a damped Lyα absorption line, 21cm absorption, or a very strong MgII/FeII absorption system at intermediate redshifts (0.4<=z<=1). Objects down to about 0.3", or 2.0kpc at z=0.6 (H_0_=…
Evolutionary models for metal-poor low-mass stars. Lower main sequence of globular clusters and halo field stars
Hauschildt, P. H.; Allard, F.; Baraffe, I. +1 more
We have performed evolutionary calculations of very-low-mass stars from 0.08 to 0.8 M_sunl for different metallicites from [M/H]= -2.0 to -1.0 and we have tabulated the mechanical, thermal and photometric characteristics of these models. The calculations include the most recent interior physics and improved non-grey atmosphere models. The models r…
Line-blanketed model atmospheres for R Coronae Borealis stars and hydrogen-deficient carbon stars.
Eriksson, K.; Gustafsson, B.; Asplund, M. +1 more
We have constructed line-blanketed model atmospheres for the hydrogen-deficient and carbon-rich R Coronae Borealis (RCrB) stars, as well as for the similar hydrogen-deficient carbon (HdC) stars and the cool extreme helium (EHe) stars. Improved continuum opacities have been used together with realistic line absorption data for atomic and molecular …
HIPPARCOS data on Herbig Ae/Be stars: an evolutionary scenario.
Waters, L. B. F. M.; Catala, C.; The, P. S. +4 more
Fundamental astrophysical parameters (distance, temperature, luminosity, mass, age) of a sample of 10 Herbig Ae/Be candidates and 3 non-emission line A and B stars in star forming regions were computed combining Hipparcos parallaxes with data from literature. All genuine Herbig stars in our sample are located between the birthline and the zero-age…
SN IA light curves and radioactive decay
Turatto, M.; Cappellaro, E.; Benetti, S. +4 more
The absolute V light curves of 5 SNe Ia, selected to represent the known range of absolute luminosities at maximum for this class of objects, are presented. Comparison of the long term luminosity evolution shows that the differences seen at maximum persist, and actually increase with time, reinforcing the notion that intrinsic differences do exist…
Microvariability survey with the Hubble Space Telescope Fine Guidance Sensors. Exploring the instrumental properties
Kuschnig, R.; Weiss, W. W.; Gruber, R. +2 more
The suitability of the Hubble Space Telescope (HST) Fine Guidance Sensors (FGS) for a magnitude limited survey of microvariability among guide stars is investigated. The linearity, relative sensitivity, and dead-time constants of the three FGSs are determined, and the photon noise limitation of the FGS photometry is confirmed. The noise spectrum i…
Infrared spectroscopy of interstellar apolar ice analogs
van Dishoeck, E. F.; Tielens, A. G. G. M.; Boogert, A. C. A. +2 more
Apolar ices have been observed in several regions in dense clouds and are likely dominated by molecules such as CO, CO_2 and the infrared inactive molecules O_2 and N_2. Interstellar solid CO has been well characterized by ground-based high resolution measurements. Recent ISO results showed the ubiquitous presence of abundant CO_2 ice and the pres…
Optical-IUE observations of the gamma-ray loud BL Lacertae object S5 0716+714: data and interpretation.
Maraschi, L.; Ghisellini, G.; Pian, E. +14 more
We monitored the BL Lac object S5 0716+714 in the optical band during the period November 1994 - April 1995, which includes the time of a γ-ray observation by the Energetic Gamma Ray Experiment Telescope (EGRET) on February 14-28, 1995. The light curves in the R and B bands show fast fluctuations superimposed on longer timescale variations. The co…