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

ABSTRACT 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-periodi...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2022-07, Vol.514 (4), p.5178-5182
Main Authors: Doyle, J Gerry, Irawati, Puji, Kolotkov, Dmitrii Y, Ramsay, Gavin, Nhalil, Nived Vilangot, Dhillon, Vik S, Marsh, Tom R, Yadav, Ram Kesh
Format: Article
Language:English
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Summary:ABSTRACT 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.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stac1695