Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic Variables - VIII. VW Hyi in outburst observed with the Southern African Large Telescope

TL;DR

This study provides high-resolution observations of Dwarf Nova Oscillations and Quasi-Periodic Oscillations in VW Hyi during outburst, revealing a new 13.39 s modulation and insights into their interaction and evolution.

Contribution

It presents unprecedented detail of DNOs, discovers a new 13.39 s modulation, and interprets these oscillations within a magnetically controlled accretion flow model.

Findings

Detection of a new 13.39 s modulation in DNOs.

DNO fundamental period does not exceed ~ 90 s.

Rare late outburst DNOs observed, supporting the model.

Abstract

We analyse four light curves obtained at high time resolution (~ 0.1 s) with the 11-m Southern African Large Telescope, at the ends of two normal outbursts and one superoutburst of the dwarf nova VW Hyi. All of these contain at least some Dwarf Nova Oscillations (DNOs), which, when at their highest amplitudes, are seen in unprecedented detail. In addition to the expected DNOs with periods > 20 s we find a previously unknown modulation at 13.39 s, but none at shorter periods. The various DNOs and their interaction with the longer period Quasi-periodic Oscillations are interpreted in terms of the model of magnetically controlled flow from an accretion disc proposed earlier in this series of papers. Our observations include rare DNOs very late in outburst; we find that the fundamental period does not increase beyond ~ 90 s, which is the same value that the independent ``longer period DNOs'' converge on.