Doubling of minute-long quasi-periodic pulsations from super-flares on a low-mass star

Doyle, J. Gerry; Irawati, Puji; Kolotkov, Dmitrii Y.; Ramsay, Gavin; Nhalil, Nived Vilangot; Dhillon, Vik S.; Marsh, Tom R.; Yadav, Ram Kesh
Referencia bibliográfica

Monthly Notices of the Royal Astronomical Society

Fecha de publicación:
8
2022
Número de autores
8
Número de autores del IAC
1
Número de citas
4
Número de citas referidas
4
Descripción
Using the ULTRASPEC instrument mounted on the 2.4-m Thai National Telescope, we observed two large flares, each with a total energy close to 1034 erg with sub-second cadence. A combination of a wavelet analysis, a Fourier transform plus an empirical mode decomposition, reveals quasi-periodic pulsations (QPPs) that exhibit an apparent doubling of the oscillation period. Both events showed oscillations of a few minutes over a interval of several minutes, and despite the availability of sub-second cadence, there was no evidence of sub-minute oscillations. The doubling of the QPP periods and shorter lifetime of shorter-period QPP modes strongly favour resonant dynamics of magnetohydrodynamic waves in a coronal loop. We estimate loop lengths to be 0.2-0.7 R⋆, in agreement with a typical length of solar coronal loops. These observations presents rare and compelling evidence for the presence of compact plasma loops in a stellar corona.