EDP Sciences
Free access
Volume 404, Number 2, June III 2003
Page(s) 631 - 636
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030494

A&A 404, 631-636 (2003)
DOI: 10.1051/0004-6361:20030494

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

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