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


E-mail: gjmluna@iafe.uba.ar


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 inline image 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.