Zoltan Haiman (Columbia U.)

Title: Electromagnetic Counterparts to Supermassive Black Hole Mergers

Abstract: I will review ideas that may be useful in identifying electromagnetic (EM) counterparts to supermassive black hole (SMBH) binaries detected by LISA. In particular, any detectable EM emission is likely to be time-variable, which should aid in this identification. I will discuss four possibilities for such variable emission: (i) a roughly periodic signal due to the orbital motion prior to coalescence, (ii) a transient pre-cursor caused by the gas trapped inside the binary's orbit, and a transient "after-glow" produced by (iii) post-merger gas accretion and (iv) by merger-induced shocks in the circumbinary disk. I will discuss whether these time-variable EM signatures may be detectable, and how they can help in identifying a unique counterpart, even with the relatively poor sky localization provided by LISA. I will also highlight the extra science that will be enabled if an EM counterpart is found, such as constraints on SMBH accretion physics, cosmology, and gravitational physics.



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