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 L-x similar to 3 x 10(30) erg s(-1), and will slowly decline on a time-scale of similar to 100 yr. We predict that X-ray emission from V838 Mon which erupted in 2002 will be detected in 2008 with 20 h of observation.