A Galactic Type Ia Supernova (SNIa) could go entirely unnoticed to us due to the large optical and near-IR extinction in the MilkyWay plane, low radio and X-ray luminosities, and a weak neutrino signal. But the recent SN2014J confirms that Type Ia supernovae emit nuclear gamma-ray lines, from the 56Ni !56 Co !56 Fe radioactive decay. The lines last for weeks, and span from 158 keV to 2.6 MeV, squarely within the Fermi Gamma-ray Burst Monitor (GBM) energy range. The MilkyWay is optically thin to gamma rays and GBM has continuous and nearly all-sky coverage, therefore the GBM is ideal to serve as a Galactic SNIa monitor and alarm. To illustrate the GBM capabilities, we use a simple model for SNIa gamma-ray emission and transfer to estimate MeV light curves and spectra. Our work is constrained and calibrated by SN2014J MeV data, which suggest - 10% of the 56Ni is in an optically thin belt surrounding the rest of the initially opaque ejecta. We estimate that the supernova signal emerges as distinct from the GBM background within the first days after the explosion in the SN2014J belt model. Therefore if a Galactic SNIa were to explode, GBM could confirm and sound the alarm possibly even on the first day of the explosion, and localize the SNIa to within -1 degree, using the Earth occultation technique.
|Original language||English (US)|
|Journal||Proceedings of Science|
|State||Published - Jan 1 2015|
|Event||34th International Cosmic Ray Conference, ICRC 2015 - The Hague, Netherlands|
Duration: Jul 30 2015 → Aug 6 2015
ASJC Scopus subject areas