A Large X-Ray Outburst in Mira A

Abstract

We report here the Chandra ACIS-S detection of a bright soft X-ray transient in the Mira AB interacting symbiotic-like binary. We resolved the system for the first time in the X-rays. Using Chandra and HST images we determined that the unprecedented outburst is likely associated with the cool AGB star (Mira A), the prototype of Mira-type variables. X-rays have never before been detected from an AGB star, and the recent activity signals that the system is undergoing dramatic changes. The total X-ray luminosity of the system is several times higher than the luminosity estimated using previous XMM and ROSAT observations. The outburst may be caused by a giant flare in Mira A associated with a mass ejection or a jet, and may have long term consequences on the system.