Hipparcos red stars in the HpV_T2 and systems ^*,**

¹ Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
² Universities Space Research Association, Division of Astronomy and Space Physics, 300 D Street SW, Washington, D.C. 20024, USA
³ U.S. Naval Observatory, 3450 Massachusetts Ave., NW, Washington D.C. 20392-5420, USA
⁴ Sternberg Astronomical Institute and Isaac Newton Institute of Chile, Moscow Branch, 13 Universitetskij Prosp., Moscow 119992, Russia
⁵ Institute of Astronomy, Russian Academy of Sciences, 48 Pyatnitskaya Str., Moscow 119017, Russia
⁶ School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, Scotland KY16 9SS
⁷ Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, 1180 Vienna, Austria
⁸ Vilnius University Observatory, Ciurlionio 29, Vilnius 2009, Lithuania

Corresponding author: D. Pourbaix, pourbaix@astro.ulb.ac.be

Received: 20 September 2002
Accepted: 28 October 2002

Abstract

For Hipparcos M, S, and C spectral type stars, we provide calibrated instantaneous (epoch) Cousins color indices using newly derived HpV_T2 photometry. Three new sets of ground-based Cousins data have been obtained for more than 170 carbon and red M giants. These datasets in combination with the published sources of photometry served to obtain the calibration curves linking Hipparcos/Tycho with the Cousins index. In total, 321 carbon stars and 4464 M- and S-type stars have new indices. The standard error of the mean is about 0.1 mag or better down to although it deteriorates rapidly at fainter magnitudes. These indices can be used to verify the published Hipparcos color indices. Thus, we have identified a handful of new cases where, instead of the real target, a random field star has been observed. A considerable fraction of the DMSA/C and DMSA/V solutions for red stars appear not to be warranted. Most likely such spurious solutions may originate from usage of a heavily biased color in the astrometric processing.