On the observation of supernovae in the late phases of Gamma-Ray Bursts
Student No.:100
Time:Thu 16:30-17:30, Aug.9
Instructor:Remo Ruffini  
Place:Cheng Yu-Tung Lecture Hall, Tsinghua University (清华大学理科楼郑裕彤讲堂)
Starting Date:2018-8-9
Ending Date:2018-8-9

Speaker: Remo Ruffini [Director of ICRANet]

Gamma-Ray Bursts:
The cosmic objects with the largest electromagnetic luminosity in the Universe are the Gamma-Ray Bursts (GRBs). In a finite time lasting less than 100s, the luminosity of such a single object equals the summed one of all the hundred billions of billions stars of the Universe. There are two main GRB families: the long GRBs, lasting more than 2s, and the short GRBs, lasting less than 2s. For a few decades, all GRBs were considered to originate from the formation of a standard isolated black hole with an ultrarelativistic jetted emission.

The single supernova evolution:
The understanding of single supernovae still presents some outstanding problems, in the attempt to explain the supernova ejecta only in terms of fermions fulfilling beta equilibrium undergiong gravitational collapse. What is clear is that, in the early phases of the gravitational collapse of the neutron star, a very rich process of nuclear burning occurs, leading to the formation of a core made by Nichel and Cobalt.

The cosmic matrix:
In all cases of long GRBs, the trigger originates in a supernova event occurring in a tight binary system composed of an evolved FeCO core and a companion neutron star. The further evolution of the system depends on the separation of the binary components. As a function of this separation, the hypercritical accretion of the supernova ejecta onto the companion neutron star may lead to the formation of a more massive neutron star or of a black hole: an authentic "cosmic matrix". The most striking results is that the optical emission of the supernova, peaking after 15 days, appears to be quite universal, independent of the different properties of the previous GRB phases.

Remo Ruffini received his doctorate at Sapienza in Rome in 1967. He taught in Hamburg, at Princeton University and the Institute for Advanced Study, in Japan, Australia and CBPF (Brazil). He is the coauthor of 722 scientific publications and 13 books, some of his major results: boson stars, “Introducing the Black Hole” with J.A. Wheeler, and the limiting critical mass of neutron stars. He identified the first black hole in our Galaxy using UHURU satellite data with Giacconi (Nobel recipient 2002), and received the Cressy Morrison Award (1973). Returning to Sapienza (1978), he promoted a Rome-Stanford collaboration on gravitational wave detectors. With European, US and Chinese institutions he established the International Center for Relativistic Astrophysics (ICRA) and later ICRANet in Italy, Armenia, France and Brazil (2005). He developed an understanding of gamma ray bursts, confirmed by the largest telescopes on Earth and from space: from their discovery in 1973, to their cosmological origin in 1997, to determining seven different GRBs families and their conceptual understanding, in 2018. This has enabled GRBs, the largest explosions in the Universe, to be used to enlighten our comprehension of our Universe.