A Halpha lighthouse on II Peg .
Abstract
Observations extended over four consecutive rotations of II Peg, one of the most luminous members of the magnetically active binary RS CVn systems, reveal a cusp-like shape of the Halpha emission line flux versus orbital phase. The flux peak corresponds to the conjuction phase of the system, with the primary at the back. Such a behavior is repeated over the four observed rotations and it is therefore interpreted as due to chromospheric rotational modulation rather than to a long-term flare. Contemporaneous V-band photometric observations confirm the presence of a spotted photospheric area close to the chromospheric active region. The longitude corresponding to the direction of the secondary, together with the opposite one, is known to be a preferential site for the formation and emersion of active region in some RS CVn systems, characterized by large photospheric spots and chromospheric plages. The observed Halpha emission is therefore consistent with the presence of an extended active region with a longitude corresponding to the direction of the secondary. Furthermore, the cusp-like behavior of the observed flux versus time suggests an extension in height of the chromospheric active region with a consequent increase of the Halpha optical depth in the direction of the secondary star.
- Publication:
-
Memorie della Societa Astronomica Italiana Supplementi
- Pub Date:
- 2006
- Bibcode:
- 2006MSAIS...9..250L
- Keywords:
-
- Stars: activity;
- Stars: binaries: spectroscopic;
- Stars: chromospheres;
- Stars: individual: II Peg;
- Stars: rotation;
- Stars: late-type