X-ray and gamma-ray study for 2023 nova eruption of V1716 Sco (2406.19233v2)

Abstract: We report the results of X-ray and gamma-ray analyses of the classical-nova V1716 Sco using data taken by \verb|Swift|, \verb|NICER|, \verb|NuSTAR| and \verb|Fermi|-LAT. We confirm gamma-ray emission at a significant level exceeding 8~$\sigma$ in the one-day bin immediately following the optical eruption. The gamma-ray emission, with a Test Statistic value more than four, persists for approximately 40 days. The X-ray emission being concurrent with the gamma-ray emission is described by the optically thin thermal plasma emission and it is likely dominated by the emission from the gas heated up by the shock. This X-ray component acquires the flux peak at approximately 20 days after the eruption and the observed X-ray emission enters super soft state (SSS) about 45 days after the eruption. The gamma-ray and X-ray emission properties of V1716 Sco are similar to those of other classical novae. Unlike other classical nova, the X-ray emission initially resolved by the \verb|Swift| occurs earlier, during a period when the gamma-ray emission is still at a detectable flux level by \verb|Fermi|-LAT observations. Using the X-ray emission properties observed before the SSS phase, we interpret that the nova produces initial slow and less dense outflow, which is eventually overtaken by the fast and dense outflow that causes the main outburst, and the X-ray emission is powered by the forward shock that propagates in the slow outflow. During the SSS, the \verb|NICER| data reveal a quasi-periodic oscillation with a observed period of $\sim 79$~seconds with a possible temporal variation, and indicates the temporal variation of the emission region on the white dwarf's surface.