1999ApJ...518L.111B

We present the ROSAT High-Resolution Imager 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 X-ray nebula is composed of knots/clumps and has an elliptical shape with a total count rate of about 0.01±0.001 counts.s^–1. We estimate that the spectrum is of thermal origin with a luminosity of ∼8.0x10³¹ ergs.s^–1 and an X-ray temperature of ∼2.0x10⁶ K in the 0.1-2.4 keV energy range. The knots/clumps are a result of fragmentation and condensation in the postshock region. The estimated electron density in the knots/clumps is about 10.0 cm^–3≤n_e≤70.0 cm^–3. We suggest that the detected X-ray nebula could also be the reverse shock zone. This detection sheds light into one of the most poorly understood stages of the classical nova evolution.