A major optical flare on the recently discovered X-ray active dMe star G 102-21
I. Pagano 1,
R. Ventura 1,
M. Rodonò 1, 2,
G. Peres 3 and
G. Micela 3
Received 2 December 1994 / Accepted 6 July 1996
During the course of UBV photoelectric measurements made at the Catania Astrophysical Observatory we have observed an unusually intense optical flare on the nearby M dwarf G 102-21, the optical counterpart of a strong X-ray source recently detected by ROSAT.
The amplitude of the magnitude increase ( mag) and the total energy release in the UBV bands ( erg) put this event among the strongest flares ever detected on UV Ceti-type stars. The U-B and B-V colours of the flare emission did not significantly change during most of the flare development. While the B-V is quite a typical colour for stellar flares, the U-B is much bluer when compared with typical values given in literature. This unusually strong ultraviolet component of the flare emission, together with the very fast flare decay, suggest a possible flare site close to the limb. We find that the observed amount of flare energy could be explained by the fast release of energy stored in a magnetic filament located in between the two G 102-21 stellar components, with a surface magnetic field 3600 G.
The characteristics of the quiescent optical emission are also discussed.
Key words: stars: activity stars: flare stars: G 102-21 X-rays: stars
Send offprint requests to: I. Pagano, email@example.com
© European Southern Observatory (ESO) 1997
Online publication: July 8, 1998