NBIA Colloquium by Tsvi Piran – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2012 > NBIAColPiran30032012

NBIA Colloquium by Tsvi Piran

The Origin of Cosmic Fireworks

Tsvi Piran

(Hebrew University)

 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.

Refreshments will be available in the NBIA lounge after the