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Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| Observations and elements of the eclipsing binary FO Hydra
Photometric observations in the UBV system are presented for theeclipsing binary FO Hydra (FO Hya). An analysis of the observed times ofminimum light yields revised elements, with the times of primary minimagiven by Min I (JD)=244 4717.7658+0.469 5571E. The light curve of FO Hyais shown to have the defining characteristics of the beta Lyrae class ofeclipsing binaries. The differential corrections program of Wilson &Devinney was used to model the light curve of FO Hya. A solution basedon the assumption of an overcontact system is shown to provide anexcellent fit to the light curves obtained with V, B and U filters. Acomparison with two similar systems suggests that FO Hya is an evolvedcontact binary system.
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