A&A 404, 631-636 (2003)
Effect of chromospheric activity on the mean colours of late-type stars
II. Is ( B-V)0 also affected?P. J. Amado
Instituto de Astrofísica de Andalucía-CSIC, Camino Bajo de Huétor 24, PO Box 3004, 18080 Granada, Spain
(Received 28 October 2002 / Accepted 21 March 2003)
We confirm the existence of an "excess" in the mean dereddened ( U-B)0 colour of active single-lined spectroscopic giants over quiescent stars of the same spectral type and find evidence for this "excess" in ( B-V)0, although at a lower scale, when plotted against ( R-I)0. This result suggests that the use of ( B-V)0 calibrations to determine fundamental parameters or spectral types for late-type active stars should be taken with caution. Since magnetic activity is definitely involved, these and similar calibrations using ( U-B)0 and/or ( B-V)0 should not be used for the study of late-type young clusters' members or late-type pre-main sequence stars without some consideration. Instead, near-infrared colours like ( R-I)0 should be better temperature indicators for these stars.
Key words: stars: activity -- stars: fundamental parameters -- stars: late-type
© ESO 2003