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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
| Photometry of symbiotic stars. X. EG And, Z And, BF Cyg, CH Cyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir
We present new photometric observations of EG And, Z And, BF Cyg, CHCyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir made in the standardJohnson UBVR system. The current issue summarizes observations of theseobjects to 2001 December. The main results can be summarized as follows:EG And: A periodic double-wave variation in all bands as a function ofthe orbital phase was confirmed. A maximum of the light changes wasobserved in U (Delta U ~ 0.5 mag). Z And: Our observations cover anactive phase, which peaked around 8.4 in U at the beginning of 2000December. Consequently, a gradual decrease in the star's brightness hasbeen observed. BF Cyg: A periodic wave-like variation in the opticalcontinuum reflects a quiescent phase of this star. A complex light curve(LC) profile was observed. CH Cyg: The recent episode of activity endedin Spring 2000. We determined the position of an eclipse in the outerbinary at JD 2451426 +/- 3. Recent observations indicate a slow increasein the star's brightness. V1329 Cyg: Observations were made around amaximum at 2001.2. AG Dra: Our measurements from the Autumn of 2001revealed a new eruption, which peaked at ~JD 2452217. RW Hya: The lightminimum in our mean visual LC precedes the time of the spectroscopicconjunction of the giant in the binary. AX Per: A periodic wave-likevariation was observed. Our recent observations revealed a secondaryminimum at the orbital phase 0.5, seen best in the V and B bands. IVVir: The LC displays a double-wave throughout the orbital cycle.
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