Hydrodynamic evolution and detectability of nova remnants in the Galactic centre

ABSTRACT Thousands of X-ray sources have been detected in the Galactic centre (GC), most believed to be cataclysmic variables (CVs). As a potential probe of the old stellar population, in particular CVs, the existence and detectability of novae in the GC remain elusive, due to the prohibitive extinction towards the GC and their relatively low occurrence rate. Nova remnants evolving in the characteristic hot ($T\sim {10^{6}~\rm K}$) and dense ($n_e\sim {10~\rm cm^{-3}}$) interstellar medium in the GC may shed light on recent novae and provide useful insight on the GC ecosystem. In this work, we perform hydrodynamical simulations of putative nova remnants in the GC environment and calculate their time-dependent multiwavelength emission to estimate the detectability. Among 79 models sampling the nova parameter space (primarily ejecta mass and velocity), 6, 44, and 51 modelled nova remnants are detectable at their X-ray, radio, and Paschen-$\alpha$ (Paα) maximum, respectively, for existing Chandra, Very Large Array, and Hubble Space Telescope observations of the GC. The predicted peak luminosities are $\sim 10^{32}$, $\sim 10^{31}$, and $\sim 10^{36}~\rm erg~s^{-1}$ in these three bands and the detectable window ranges from weeks to notably hundred years. By specifying a CV population of the nuclear star cluster, we estimate the probability of detecting at least one remnant to be 20 per cent, 8 per cent, and 18 per cent in X-rays, radio, and Pa$\alpha$. The nova remnant would be best resolved in the X-ray band. Our study highlights the potential for detecting nova remnants through further observations, leveraging James Web Space Telescope and the potentially forthcoming Advanced X-ray Imaging Satellite and Square Kilometer Array.