57 second oscillations in Nova Centauri 1986 (V842 Cen)

TL;DR

This study reveals that Nova Centauri 1986 hosts the fastest rotating white dwarf among intermediate polars, with a 57-second modulation, and identifies multiple periodic signals indicating complex accretion dynamics.

Contribution

The paper provides the first detailed timing analysis of V842 Cen, establishing it as the fastest rotating white dwarf in an intermediate polar and characterizing its multi-periodic signals.

Findings

Detected 57-second white dwarf rotation period.

Identified sidebands indicating reprocessing at 3.94-hour orbital period.

Observed low X-ray luminosity compared to similar systems.

Abstract

High speed photometry in 2008 shows that the light curve of V842 Cen possesses a coherent modulation at 56.825 s, with sidebands at 56.598 s and 57.054 s. These have appeared since this nova remnant was observed in 2000 and 2002. We deduce that the dominant signal is the rotation period of the white dwarf primary and the sidebands are caused by reprocessing from a surface moving with an orbital period of 3.94 h. Thus V842 Cen is an intermediate polar (IP) of the DQ Herculis subclass, is the fastest rotating white dwarf among the IPs and is the third fastest known in a cataclysmic variable. As in other IPs we see no dwarf nova oscillations, but there are often quasi-periodic oscillations in the range 350 - 1500 s. There is a strong brightness modulation with a period of 3.78 h, which we attribute to negative superhumps, and there is an even stronger signal at 2.886 h which is of unknown origin but is probably a further example of that seen in GW Lib and some other systems. We used the Swift satellite to observe V842 Cen in the ultra-violet and in X-rays, although no periodic modulation was detected in the short observations. The X-ray luminosity of this object appears to be much lower than that of other IPs in which the accretion region is directly visible.