2021MNRAS.502.4658T

We present the analysis of XMM-Newton European Photon Imaging Camera (EPIC) observations of the nova shell IPHASX J210204.7+471015. We detect X-ray emission from the progenitor binary star with properties that resemble those of underluminous intermediate polars such as DQ Herculis (DQ Her): an X-ray-emitting plasma with temperature of T_X = (6.4 ± 3.1) x 10⁶ K, a non-thermal X-ray component, and an estimated X-ray luminosity of L_X = 10³⁰ erg s^–1. Time series analyses unveil the presence of two periods, the dominant with a period of 2.9 ± 0.2 h, which might be attributed to the spin of the white dwarf, and a secondary of 4.5 ± 0.6 h that is in line with the orbital period of the binary system derived from optical observations. We do not detect extended X-ray emission as in other nova shells probably due to its relatively old age (130-170 yr) or to its asymmetric disrupted morphology that is suggestive of explosion scenarios different to the symmetric ones assumed in available numerical simulations of nova explosions.