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Tsvi Piran

PI (Black Holes)

I am a professor in the Racah Institute of Physics at the Hebrew University. My past and current research interests include numerous relativistic astrophysical phenomena focusing on black holes and neutron stars and range from purely theoretical to the interpretation of observations. 


I suggested that binary neutron star mergers, in addition to being sources of gravitational radiation, produce Gamma-ray bursts, a prediction that was confirmed dramatically in 2017 with the first LIGO detection of a nearby neutron star merger. Using this association, I have shown that they can be the major sources of r-process nucleosynthesis. Later on, I suggested that neutron star mergers’ ejecta will produce a long-lasting afterglow. Again, this observation was also confirmed by the observations of GW 2017. Currently, I am puzzled by the effect of GRB jets on Macronova observations and by the possibility of observing the gravitational radiation produced by jet acceleration. 


I have explored the possibility of the collisional Penrose process in rotating black hole ergospheres as a way to extract energy from the black hole. I have worked on the stability of accretion disks and on the polarization pattern that arises from disk accretion in cases where the central black hole is rotating.  The satellite IXPE is now exploring such signatures. More recently my work focuses on Gamma Ray Bursts and in particular on particle acceleration, magnetic field amplification, and the resulting high-energy radiation.  This study is particularly interesting in the context of relativistic jets that arise in these and other systems involving black holes.  


In addition to carrying out research funded by the Simons collaboration, my current research is funded by an Advanced ERC grant MultiJets.

Five recent relevant references

Sari, R., Piran, T. and Narayan, R., 1998, "Spectra and light curves of Gamma-Ray Burst Afterglows", ApJL, 497, 17

Nakar, E., and Piran T., 2011, "Detectable radio flares following gravitational waves from mergers of binary neutron stars"

Nature 478, 82, 2011

Eichler, D., Livio, M.,  Piran, T., and Schramm, D., 1989, "Nucleosynthesis, neutrino bursts and γ-rays from coalescing neutron stars" Nature, 340, 126

Derishev, E., and Piran, T., 2016, "Particle acceleration, magnetization and radiation in relativistic shocks" MNRAS, 460, 2036

 Derishev, E., and Piran, T., 2019, "The Physical Conditions of the Afterglow Implied by MAGIC’s Sub-TeV Observations of GRB 190114C"ApJL, 880, 27


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