UBVRIJHK light curves of four active binaries of the RS CVn class are presented together with coordinated spectrophotometric observations in the near infrared (1.4-2.5 μm). Low amplitude time variations in the optical filters are clearly present. They are interpreted as effects of dark spots partially covering the stellar surface. However, the whole spectral distributions (from U to K) of three out of four studied systems (with the exception of TY Pyx) cannot be simply explained by a combination of stellar spectra and of spot-related photospheric perturbations. Moreover, at least in two cases, the data clearly show infrared excesses that cannot be simply explained by classification errors, and seem to require the presence of circumstellar matter. A preliminary analysis suggests that, at least in two systems, thermal radiation from a thin dust shell is likely to explain the data.
A search for non-stellar contributions to the optical and near-IR flux of RS CVn binaries
BUSSO, Maurizio Maria;
1987
Abstract
UBVRIJHK light curves of four active binaries of the RS CVn class are presented together with coordinated spectrophotometric observations in the near infrared (1.4-2.5 μm). Low amplitude time variations in the optical filters are clearly present. They are interpreted as effects of dark spots partially covering the stellar surface. However, the whole spectral distributions (from U to K) of three out of four studied systems (with the exception of TY Pyx) cannot be simply explained by a combination of stellar spectra and of spot-related photospheric perturbations. Moreover, at least in two cases, the data clearly show infrared excesses that cannot be simply explained by classification errors, and seem to require the presence of circumstellar matter. A preliminary analysis suggests that, at least in two systems, thermal radiation from a thin dust shell is likely to explain the data.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
