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

TL;DR

This study analyzes XMM-Newton observations of Nova Centauri 1986, revealing a periodicity likely linked to a magnetically-channelled accretion flow and characterizing its X-ray spectrum with a high-temperature plasma model.

Contribution

First detailed X-ray spectral and timing analysis of Nova Centauri 1986 using XMM-Newton data, identifying a significant periodicity and plasma temperature.

Findings

Detected a 3.51-hour period in X-ray data.

X-ray spectrum fits an absorbed thin thermal plasma model.

Maximum plasma temperature around 43 keV.

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$\pm$0.4 h in the EPIC data and at 4.0$\pm$0.8 h in the 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 $kT_{max}=43_{-12}^{+23}$ 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 CVs, 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. (2009) either in the Optical Monitor (OM) data, which are sensitive to pulse amplitudes $\gtrsim$ 0.03 magnitudes, or the EPIC data, sensitive to pulse fractions $p \gtrsim$ 14 $\pm$2%.