The first resolved and detected classical nova shell in X-rays in comparison with the rosat detections of hard X-ray emission from classical nova in outburst Original Research Article

We present the ROSAT High Resolution Imager (HRI) data of the first resolved and detected classical nova shell in the X-ray wavelengths: The shell of Nova Persei (1901). We find that the shell is composed of knots and has an elliptical shape. The surface brightness is about 703.4±54.5 counts arcmin−2. We estimate that the spectrum is of thermal origin with a luminosity of ∼ 8.0×1031 erg s−1 and an X-ray temperature of ∼ 2.0×106 K in the 0.1–2.4 keV energy range. The knots are most likely a result of fragmentation and condensation in the post-shock region. This detection sheds some light into one of the most poorly understood stages of classical nova evolution.