(Presented at the: 192nd Meeting of the AAS June 7-11 1998)
We report the detection of a long-duration optical flare in the recenltly discovered, X-ray selected, chromospherically binary 2RE~J0743+224. The high resolution echelle spectroscopic observations taken in 12-21th January 1998 exhibit a dramatic increase in the chromospheric emissions (H\alpha and Ca~{\sc ii} IRT lines) that we interpret as a flare based on: the temporal evolution of the event, the broad component observed in the H\alpha line profile, the detection of the He~{\sc i} D_{3} in emission and a filled-in He~{\sc i} 6678ÅP>During these obsevations we detect a Li~{\sc i} 6708Å\ line enhancement which is clearly related with the temporal evolution of the flare. The maximum Li~{\sc i} enhancement occurs just after the maximum chromospheric emission observed in the flare. A significant increase of the ^6Li/^7Li isotopic ratio is also detected. For all this we suggest that this Li~{\sc i} enhancement is produced by spallation reactions during the flare. This is the first time that such Li~{\sc i} enhancement associate with a stellar flare is reported, and probably the long-duration of this flare is a key factor for this detection. A large fraction of the stellar surface seem to be covered by starspots during the event, as we deduce for the analysis of the TiO 7055Å\ band, thus taken into account the Li~{\sc i} is very temperature sensitive, we can not discard that this Li~{\sc i} variations was related the presence of starspots. However, the correlation with the temporal evolution of the flare, the no detection of changes in the other photospheric absorption lines, and the large changes observed in the core of the Li~{\sc i}, as predict the models, argue in favour of the hipothesis that the Li~{\sc i} is produced during the flare.
Presentation type: display
Category: Stellar Evolution, Atmospheres, Intrinsic Variable Stars
Submitter: Lawrence W. Ramsey
Correspondent email address: dmg@astro.psu.edu
Correspondent phone: 814 865 0150
Correspondent address: The Pennsylvania State University, Department of Astronomy and Astrophysics, 525 Davey Laboratory, University Park, PA 16802
Supplemental email: dmg@astrax.fis.ucm.es
Supplemental URL: http://www.ucm.es/info/Astrof/rej0743.html