LAT Gamma-ray spectra of RS Oph 2021 nova

In this system, unlike classical novae from cataclysmic binaries, the ejecta from the white dwarf form shocks when interacting with the dense circumstellar wind environment of the red giant companion. We find the LAT spectra from 50MeV to ~20-23GeV, the highest-energy photons detected in some subintervals, are consistent with {pi}0-decay emission from shocks in the ejecta as proposed by Tatischeff & Hernanz for its previous 2006 outburst.

The LAT light curve displayed a fast rise to its peak >0.1 GeV flux of ~6x10^-6^ph/cm^2^/s beginning on day 0.745 after its optically constrained eruption epoch of 2021 August 8.50. The peak lasted for ~1day and exhibited a power-law decline up to the final LAT detection on day 45. We analyze the data on shorter timescales at early times and found evidence of an approximate doubling of emission over ~200minutes at day 2.2, possibly indicating a localized shock-acceleration event.