Discovery of a recombining plasma from the SNR HB 21

Our paper titled “Discovery of recombining plasma from the faintest GeV SNR HB 21 and a possible scenario of the cosmic ray escaping from SNR shocks” has been accepted for publication in PASJ.

Hiromasa Suzuki et al. revealed for the first time that a thermal plasma in the soft GeV gamma-ray SNR HB 21 had been suffered from rapid cooling very long time ago (~170 kyr), and is still on the way of recombination to the collisional ionization equilibrium. Furthermore, by comparing published data of 9 similar SNRs, the authors discovered a clue of a positive correlation between the elapsed time from the rapid cooling and the degree of escape of accelerated particles from SNRs. This result can be crucial for understanding escaping processes of Galactic cosmic rays from SNRs.