Date : 1/4 (Wed) [15:00 - 17:00] @ F313
Speaker: Dr. Shigeo Kimura (Penn State University)
Title : Electromagnetic radiations from binary black holes
Abstract: We study electromagnetic radiations from gnewbornh binary black holes (BBHs) and gmergingh BBHs. The detection of gravitational waves reveals existence of BBHs, and it is becoming important to investigate electromagnetic radiations from BBHs. A powerful electromagnetic radiations are possible when BBHs are born or merging, because black holes (BHs) can accrete a large amount of material. According to binary evolution scenarios, a BBH is born from a binary consisting of a primary black hole (BH) and a secondary evolved star. When the secondary collapses to a BH, a fraction of its outer layer is ejected. The primary BH accretes the ejected material and produces a powerful outflow. This outflow injects energy to the ejected material. This results in a sub-energetic supernova of kinetic energy ~10^{49} ergs and bolometric luminosity ~10^{42} erg/s. After this event, an accretion disk is formed around the primary BH, which leads to an electromagnetic radiation in the merging phase. When this disk becomes neutral due to radiative cooling, the disk becomes a gdeadh disk where the angular momentum transport is inefficient. This dead disk remains around the BH for a long time. When the binary separation becomes sufficiently small, the tidal torque from the companion heats up and ionizes the dead disk, restarting accretion onto the BH many years before the merger. The mass accretion induced by the tidal torque increases as the separation decreases, and a relativistic jet could be launched before the merger. The electromagnetic radiation from the jet can be detectable if the merger events happen within 10 M pc.

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