Speaker: Brian Metzger, Columbia University & CCA Flatiron Institute
Abstract: "Novae" - thermonuclear outbursts from white dwarfs accreting from a binary star companion - have been observed since antiquity as "guest stars" to our ancestors. Despite their storied place in the history of Astronomy, our understanding of the physical processes that give rise to novae and their emission remains strikingly incomplete. Nothing illustrates this better than the unexpected discovery by NASA's Fermi satellite that GeV gamma-ray emission is common if not ubiquitous from novae. These gamma-rays are likely produced by relativistic ions accelerated at shock waves produced in the nova ejecta. I will review our understanding of the multi-wavelength picture of novae, and describe how these transients can be used testbeds for studying relativistic particle acceleration at non-relativistic shocks in the novel "radiative" regime (in which the post-shock gas radiates ~100% of the its thermal/non-thermal energy). Lessons gleaned from novae can be applied to other shock-powered transients, which are candidate high-energy neutrino sources for IceCube. Time permitting, I will describe implications of the recent H.E.S.S. and MAGIC discovery of TeV gamma-rays from the recurrent nova RS Oph.