Supernova explosions, black holes and the spectrum of cosmic rays

Peter Biermann


Since 1934 (Baade & Zwicky), the view has prevailed that Super-Nova (SN) explosions produce the very energetic particles known since 1912 as Cosmic Rays (CRs; Hess). Up to about 3 × 10¹⁸ eV they are believed to arise from Galactic sources, such a massive star explosions. For many years now it has been observed that the explosions of massive stars into their own winds demonstrate a surprising commonality: The magnetic field is about 1 Gauß at 10¹⁶ cm, and decreases as r^-1 following the Parker law (1958) out to about 10¹⁹ cm; the Super-Nova shock front advances at about 0.1 c; putting in numbers this requires a piston, probably clumps of heavy elements such as Co, Ni, Fe, as observed in γ-ray lines from nuclear decay. All of these stars also make black holes (BH) in the explosion; while massive stars rotate relatively fast, probably due to their binary character, the resulting black holes - with 20 observed by LIGO/VIRGO - all show negligible spin. The ubiquity of these numbers readily explains why CRs have a well defined spectrum with a kink down and a turn-off at higher energy, despite arising probably from many explosions. However, how making a BH with an observed mass range from about 7.5 Solar masses to over 50 Solar masses can give rise to such an observed commonality is an open question. I will discuss some ingredients for a possible solution. Whatever the final answer we will learn more about black holes.