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-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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2022
- DOI:
- 10.1093/mnras/stac1695
- arXiv:
- arXiv:2206.08070
- Bibcode:
- 2022MNRAS.514.5178D
- Keywords:
-
- stars: activity;
- stars: flare;
- stars: late-type;
- stars: low-mass;
- stars: oscillations;
- stars: rotation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- doi:10.1093/mnras/stac1695