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HIPPARCOS subdwarfs and globular cluster ages: the distance and age of M 92
Pont, F.; Turon, C.; Mayor, M. +1 more
A new determination of the distance and age of the old globular cluster M 92 (NGC 6341) is obtained from a consideration of a set of more than 500 subdwarf candidates with Hipparcos parallaxes. Precise [Fe/H] values are derived for most stars using the equivalent width of the Coravel cross-correlation function. We examine at some length the biases…
Towards a fundamental calibration of stellar parameters of A, F, G, K dwarfs and giants
di Benedetto, G. P.
I report on the implementation of the empirical surface brightness technique using the near-infrared Johnson broadband { (V-K)} colour as suitable sampling observable aimed at providing accurate effective temperatures of 537 dwarfs and giants of A-F-G-K spectral-type selected for a flux calibration of the Infrared Space Observatory (ISO). The surf…
Quiet Sun EUV transient brightenings and turbulence. A panoramic view by EIT on board SOHO
Berghmans, D.; Clette, F.; Moses, D.
Since January 1996, the Extreme-Ultraviolet Imaging Telescope (EIT, onboard SOHO) has produced unique image sequences covering a wide field of view with a high temporal resolution, in the He Ii transition region line and in several Fe coronal emission lines. Using two sequences acquired with cadences of the order of one minute and with durations r…
Asteroids as far-infrared photometric standards for ISOPHOT
Mueller, T. G.; Lagerros, J. S. V.
Asteroids are used as far-IR calibrators for the imaging photopolarimeter ISOPHOT on board the Infrared Space Observatory ISO. For the 10 selected objects we compiled a large uniform database of 678 individual observations, ranging from 7-2 000 microns. Applying a new thermophysical model to the observations we derived thermal properties of the se…
Study of an unbiased sample of B stars observed with Hipparcos: the discovery of a large amount of new slowly pulsating B stars
Eyer, L.; Aerts, C.; Grenon, M. +2 more
We present a classification of 267 new variable B-type stars discovered by Hipparcos. We have used two different classification schemes and they both result in only a few new beta Cephei stars, a huge number of new slowly pulsating B stars, quite some supergiants with alpha Cyg-type variations and variable CP stars, and further some new periodic B…
Evidence for water vapor in Titan's atmosphere from ISO/SWS data
de Graauw, Th.; Kessler, M. F.; Lellouch, E. +6 more
The infrared spectrum of Titan around 40 mu m was recorded in the grating mode of the Short Wavelength Spectrometer (SWS) of ISO, with a resolving power of about 1900. Two emission features appear at 43.9 and 39.4 mu m, where pure rotational water lines are expected. Line strengths are about 8 times the 1sigma statistical noise level. The H_2O ver…
Laboratory identification of the 4.62mu M solid state absorption band in the ISO-SWS spectrum of RAFGL 7009S
Heras, A. M.; Dartois, E.; Demyk, K. +3 more
We focus on the problem of the assignment of the ``XCN'' solid state feature observed in the spectra of numerous protostellar objects. This feature, located at 4.62µm has been tentatively identified with the molecular ion OCN(-) . New laboratory experiments have been performed in order to confirm this identification. OCN(-) is produced by UV…
ISO deep far-infrared survey in the ``Lockman Hole''. A search for obscured objects at high redshift. I. Observations
Sanders, D. B.; Kawara, K.; Taniguchi, Y. +11 more
Two 44arcmin x 44arcmin fields in the Lockman Hole were mapped at 95 mu m and 175 mu m using ISOPHOT. A simple program code combined with PIA works well to correct for drift in the detector responsivity. The number density of 175 mu m sources is 3-10 times higher than expected from the no-evolution model. Based on observations with ISO, an ESA pro…
Investigation of the variability of bright Be stars using HIPPARCOS photometry
Floquet, M.; Hubert, A. M.
The high accuracy and the homogeneity of Hipparcos data for bright stars have allowed us to quantify the degree of variability of Be stars. This degree has been found to be highly dependent on the temperature of the star. Rapid variability is the main feature of the 86% of early Be and less than 20% of late Be stars taking into account the limit o…
Spectral analyses of PG 1159 star: constraints on the GW Virginis pulsations from HST observations
Dreizler, S.; Heber, U.
We present the results of a quantitative analysis of UV and optical spectra of nine PG 0122+200ls, very hot hydrogen-deficient [pre-] white dwarfs, by means of line blanketed NLTE model atmospheres. Four programme stars constitute the GW Vir variables, a class of non-radial g-mode pulsators. Precise effective temperatures, carbon, nitrogen and oxy…