Copenhagen Physicists Add a Neutrino Effect to Models of How Massive Stars Die

Two physicists at the Niels Bohr Institute in Copenhagen report that letting neutrinos switch from one type to another as they stream out of a dying star changes which stars explode and which collapse straight into black holes. Mariam Gogilashvili and Irene Tamborra reached that result in simulations of 195 collapsing stars, published as a Letter in Physical Review D on Sept. 22.

The authors describe the relative rate of neutron stars and black holes produced by collapsing massive stars as highly uncertain. Nothing in the work was observed. The collapses are computer models, and the neutrino switching is handled by what the authors call a schematic treatment.

The Letter covers stars from 9 to 120 times the mass of the Sun. The authors report that including the flavor switching reshapes which of those stars are able to explode, that the effect is strongest between 16 and 30 solar masses, and that it also shifts the range of masses of the neutron star or black hole left behind.

Gogilashvili and Tamborra call the effect neutrino flavor conversion, and they say it eases long-standing mismatches between theory and observation: the red-supergiant problem and the supernova-rate problem. They also say it brings theoretical expectations closer to the lightest neutron stars astronomers have measured.

Their conclusion is that the effect belongs in any model used to predict how many neutron stars and how many black holes massive stars leave behind.