The mysterious X-ray emission and optical flash of Zeta Lyrae

Zeta Lyrae is a nearby (d47 pc) bright (V4.1) star which has shown an strongoptical flash and which shows strong Xray emission. The system is asinglelined spectroscopic binary. While ordinarily, these properties could allbe explained by coronal activity from either the primary or the secondary, theprimary here is an A star, and the secondary is both unseen, and has a mass ofat least 0.8 solar masses. The source is not detected in the radio down to about40 microJy (about 20 times below the flux density expected for a stellar massblack hole at this Xray luminosity). We propose XMM observations to test ideasfor the origin of the Xray emission and hopefully to explain the optical flashas well. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]