XMM-Newton EPIC and OM observation of Nova Centauri 1986 (V842 Cen)

Abstract

We report the results from the temporal and spectral analysis of an XMM–Newton observation of Nova Centauri 1986 (V842 Cen). We detect a period at 3.51 ± 0.4 h in the EPIC data and at 4.0 ± 0.8 h in the Optical Monitor (OM) data. The X-ray spectrum is consistent with the emission from an absorbed thin thermal plasma with a temperature distribution given by an isobaric cooling flow. The maximum temperature of the cooling flow model is kTmax = 43+23 −12 keV. Such a high temperature can be reached in a shocked region and, given the periodicity detected, most likely arises in a magnetically channelled accretion flow characteristic of intermediate polars. The pulsed fraction of the 3.51-h modulation decreases with energy as observed in the X-ray light curves of magnetic cataclysmic variables, possibly due either to occultation of the accretion column by the white dwarf body or phase-dependent to absorption. We do not find the 57-s white dwarf spin period, with a pulse amplitude of 4 mmag, reported by Woudt et al. in either the OM data, which are sensitive to pulse amplitudes 0.03 mag, or the EPIC data, sensitive to pulse fractions p 14 ± 2 per cent.