Multi-wavelength quasi-periodic pulsations in a stellar superflare

TL;DR

This study reports the first simultaneous multi-wavelength detection of quasi-periodic pulsations in a stellar superflare, revealing insights into oscillatory processes affecting both thermal and non-thermal emissions in stellar flares.

Contribution

It provides the first analysis of stellar flare oscillations in both X-ray and white light simultaneously, linking QPP parameters to electric current oscillations in the flare loop.

Findings

QPP periods are approximately 1.5 hours in X-rays and 3 hours in white light.

QPP in X-ray and white light are well correlated.

Results support the LCR-contour model of flare loops in stellar superflares.

Abstract

We present the first multi-wavelength simultaneous detection of QPP in a superflare (more than a thousand times stronger than known solar flares) on a cool star, in soft X-rays (SXR, with XMM-Newton) and white light (WL, with Kepler). It allowed for the first-ever analysis of oscillatory processes in a stellar flare simultaneously in thermal and non-thermal emissions, conventionally considered to come from the corona and chromosphere of the star, respectively. The observed QPP have periods $1.5 \pm 0.15$ hours (SXR) and $3 \pm 0.6$ hours (WL), and correlate well with each other. The unique relationship between the observed parameters of QPP in SXR and WL allowed us to link them with oscillations of the electric current in the flare loop, which directly affect the dynamics of non-thermal electrons and indirectly (via Ohmic heating) the thermal plasma. These findings could be considered in favour of the equivalent LCR-contour model of a flare loop, at least in the extreme conditions of a stellar superflare.