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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
| Radial velocities of giant M stars near the ecliptic
A search dedicated to the identification of new, dwarf and cold starsclose to the Sun has allowed us to measure the radial velocities of aset of stars of late spectral type. The stars selected were M-type starspresent in the Hipparcos Input Catalogue located in a strip of+/-20° around the Ecliptic and observables from La Silla. Our inalset contains 22 M-type stars whose radial velocities Vr havebeen measured with an accuracy of ~ 0.5 km s-1 during asingle observing run. From their velocities, parallaxes and magnitudeswe deduce that all the stars observed are red giants, with spacevelocities relative to the Sun mostly lower than 100 km s-1.Based on observations collected at the CAT telescope, European SouthernObservatory, La Silla, Chile.
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