Magnetic Activity in Stellar Merger Products

We study the expected X-ray luminosity of stellar merger products several years after merger. The X-ray emission is assumed to result from magnetic activity. The extended envelope of the merger product possesses a large convective region and it is expected to rotate fast. The rotation and convection might give rise to an efficient dynamo operation, therefore we expect strong magnetic activity. Using well known relations connecting magnetic activity and X-ray luminosity in other types of magnetically active stars, we estimate that the strong X-ray luminosity will start several years after merger, will reach a maximum of Lx ∼ 3×10 30 erg s, and will slowly decline on a time scale of ∼ 100 yr. We predict that X-ray emission from V838 Mon which erupted in 2002 will be detected in 2008 with 20 hours of observation. Subject headings: stars: supergiants − stars: main sequence − stars: binary − stars: individual: V838 Mon − stars: magnetic activity − stars: merger