Evidence for Gamma-Ray Pulsations from the Classical Nova ASASSN-16ma

Abstract

Abstract I report here a new result extracted from the Fermi Large Area Telescope observation of the classical nova ASASSN-16ma that exhibits coherent γ-ray pulsations at 544.84(7) s during its outburst in 2016. Considering the number of independent trials, the significance of the evidence is 4.0σ, equivalent to a false-alarm probability of 5.9 × 10−5. The periodicity was steady during the 4 days of its appearance, indicating its origin as the spinning signal of the white dwarf. Given that the optical and γ-ray light curves of some shock-powered γ-ray novae have been recently shown to be closely correlated to each other, the γ-ray pulsation phenomenon likely implies an existence of associated optical pulsations, which would provide detailed ephemerides for these extreme white dwarf binaries for further investigations in the near future.