NBIA Colloquium "The Origin of Cosmic Fireworks" by Tsvi Piran – Niels Bohr Institute - University of Copenhagen

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NBIA Colloquium "The Origin of Cosmic Fireworks" by Tsvi Piran

Speaker:  Tsvi Piran (Hebrew University, Jerusaem)

Title: The Origin of Cosmic Fireworks

Abstract: Among the most interesting fireworks observed on the sky are the brightest (gamma ray bursts GRBs), the least known (neutron star mergers), and the recently observed puzzling tidal disruption events. After a general introduction, I will present new results on GRB progenitors that, on the one hand, demonstrate the existence of a new group of objects (low-luminosity GRBs) and, on the other hand, provide the first direct observational evidence for the Collapsar mechanism. I examine the links between these conclusions and short GRBs that are expected to arise from neutron star mergers and I predict the existence of long-lasting flares from merger events. These could help identify gravitational radiation emission from merger events, increasing the effective sensitivity of gravitational radiation detectors by a large factor.  I examine the puzzling Swift events J1644 and J2058, and explain why they were observed in non-thermal X-rays and not in the expected thermal UV. I also demonstrate surprising (theoretical) links between the three unrelated classes of objects.