Speaker: Navin Sridhar (Columbia University)
Applications of hyper-accreting sources to common envelope mergers, fast radio bursts, and high energy neutrinos.
Roche lobe overflow from a donor star onto a compact object binary companion can evolve to a phase of unstable runaway mass transfer, eventually culminating in a common-envelope event. The highly super-Eddington accretion rates achieved during this brief phase are accompanied by intense mass loss in disk winds, analogous to but even more extreme than ultraluminous X-ray sources in the nearby universe. This expanding outflow will inflate a compact and energetic bubble of plasma into the circumbinary medium ("hypernebula"). Embedded within this hypernebula are relativistic electrons heated at the termination shock of the winds from the inner accretion flow. I will present a time-dependent model for the synchrotron radio emission and other observable multimessenger properties of such hypernebulae such as high energy neutrino emission. If episodic, relativistic jets are sources of repeating fast radio bursts (as recently proposed in Sridhar+21b), such hypernebulae could generate persistent radio emission and contribute large and time-variable rotation measure to the bursts, consistent with observations. Hypernebulae can be discovered independently of an FRB association in radio surveys, such as VLASS, as off-nuclear point sources whose fluxes can evolve significantly on timescales as short as years, possibly presaging energetic transients from common-envelope mergers.
