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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
| Differential UBV photometry of the short-period eclipsing binaries RW Dor, EZ Hya and V701 CEN
Photometric UBV differential observations of three short-periodeclipsing binaries (RW Dor, EZ Hya, and V701 Cen) are presented. Newtimes of minimum light and improved linear ephemerides are given.Analysis of the trends of the differential color curves show that RW Dorcannot be considered a normal W UMa system, since its d(B-V) at minimais redder than at maxima. The curves for EZ Hya do not show remarkablevariations, while V701 Cen shows a d(B-V) higher at primary minimum thatat maxima.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | נחש מים |
| התרוממות ימנית: | 09h29m17.20s |
| סירוב: | -13°44'12.5" |
| גודל גלוי: | 7.157 |
| מרחק: | 709.22 פארסק |
| תנועה נכונה: | -11.7 |
| תנועה נכונה: | 4.1 |
| B-T magnitude: | 9.321 |
| V-T magnitude: | 7.336 |
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