Accretion onto black hole in collapsing stars

Black holes are formed as the end product of stellar evolution. The objects known before from electromagnetic observations, are not heavier than about 20 Solar masses. These found recently, by detecting their mergers and gravitational wave emission, are as massive as 60-80 Solar mass. At birth, some of the black holes must be very rapidly spinning, to be able to power the ultra-fast jets of plasma, which give a gamma ray burst signal. The process responsible for jet launching is called accretion and in the GRB engines it is a very violent event. Nevertheless, some of the black holes may be born without formation of a disk/jet engine, and then the star will collapse without an electromagnetic transient.
In this talk, I will present some of the recent works of the astrophysics group at CFT PAN related to the collapsars and GRB jets modeling.