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Description
For Hipparcos M, S, and C spectral type stars, we provide calibrated instantaneous (epoch) Cousins V-I color indices using newly derived HpV_T2_ photometry. Three new sets of ground-based Cousins VI data have been obtained for more than 170 carbon and red M giants, observed at SAAO in 1984 and 1987 (table1), at Siding Spring Observatory in 2002 (table2), and with the Automatic Photoelectric Telescopes located at Fairborn Observatory from 1996 (table3). These datasets in combination with the published sources of VI photometry served to obtain the calibration curves linking Hipparcos/Tycho Hp-V_T2_ with the Cousins V-I index. In total, 321 carbon stars and 4464 M- and S-type stars have new V-I indices. The standard error of the mean V-I is about 0.1mag or better down to Hp~9 although it deteriorates rapidly at fainter magnitudes. These V-I indices can be used to verify the published Hipparcos V-I 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.
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