Discovery of a bright radio transient in M?82: a new radio supernova?

摘要

In this Letter, we report the discovery of a new bright radio transient in82. Using the Very Large Array, we observed the nuclear region of M82 atseveral epochs at 22GHz and detected a new bright radio source in thisgalaxy's central region. We find a flux density for this flaring sourcethat is times larger than the upper limits determined in previous observations. The flare must havestarted between 2007 October29 and 2008 March24. Over the past year,the flux density of this new source has decreased from 100mJy to11mJy. The lightcurve (based on only three data points) can befitted better with an exponential decay than with a power law. Based onthe current data we cannot identify the nature of this transientsource. However, a new radio supernova seems to be the most naturalexplanation. With its flux density of more than 100mJy, it is at least 1.5times brighter than SN1993J in M81 at the peak of itslightcurve at 22GHz. Key words: stars: supernovae: general - radio continuum: general - galaxies: individual: M82