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Oscillations in stellar superflares
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Balona, L. A., Broomhall, Anne-Marie, Kosovichev, A., Nakariakov, V. M., Pugh, Chloe E. and Van Doorsselaere, Tom (2015) Oscillations in stellar superflares. Monthly Notices of the Royal Astronomical Society, 450 (1). pp. 956-966. doi:10.1093/mnras/stv661
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WRAP_9877890-px-140416-1504.01491v1.pdf - Accepted Version - Requires a PDF viewer. Download (3065Kb) | Preview |
Official URL: http://dx.doi.org/10.1093/mnras/stv661
Abstract
Two different mechanisms may act to induce quasi-periodic pulsations (QPP) in whole-disc observations of stellar flares. One mechanism may be magnetohydromagnetic forces and other processes acting on flare loops as seen in the Sun. The other mechanism may be forced local acoustic oscillations due to the high-energy particle impulse generated by the flare (known as ‘sunquakes’ in the Sun). We analyse short-cadence Kepler data of 257 flares in 75 stars to search for QPP in the flare decay branch or post-flare oscillations which may be attributed to either of these two mechanisms. About 18 per cent of stellar flares show a distinct bump in the flare decay branch of unknown origin. The bump does not seem to be a highly damped global oscillation because the periods of the bumps derived from wavelet analysis do not correlate with any stellar parameter. We detected damped oscillations covering several cycles (QPP), in seven flares on five stars. The periods of these oscillations also do not correlate with any stellar parameter, suggesting that these may be a due to flare loop oscillations. We searched for forced global oscillations which might result after a strong flare. To this end, we investigated the behaviour of the amplitudes of solar-like oscillations in eight stars before and after a flare. However, no clear amplitude change could be detected. We also analysed the amplitudes of the self-excited pulsations in two δ Scuti stars and one γ Doradus star before and after a flare. Again, no clear amplitude changes were found. Our conclusions are that a new process needs to be found to explain the high incidence of bumps in stellar flare light curves, that flare loop oscillations may have been detected in a few stars and that no conclusive evidence exists as yet for flare induced global acoustic oscillations (starquakes).
| Item Type: | Journal Article | ||||||||
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| Subjects: | Q Science > QB Astronomy | ||||||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
| Library of Congress Subject Headings (LCSH): | Flare stars | ||||||||
| Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||
| Publisher: | Oxford University Press | ||||||||
| ISSN: | 0035-8711 | ||||||||
| Official Date: | 11 June 2015 | ||||||||
| Dates: |
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| Volume: | 450 | ||||||||
| Number: | 1 | ||||||||
| Number of Pages: | 11 | ||||||||
| Page Range: | pp. 956-966 | ||||||||
| DOI: | 10.1093/mnras/stv661 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Access rights to Published version: | Restricted or Subscription Access | ||||||||
| Funder: | United States. National Aeronautics and Space Administration (NASA), National Research Foundation (South Africa) (NRF), European Research Council (ERC), Science and Technology Facilities Council (Great Britain) (STFC), University of Warwick. Institute of Advanced Study (IAS) | ||||||||
| Grant number: | NAS5- 26555 (NASA), NNX09AF08G (NASA), 321141 (ERC), ST/L000733/1 (STFC), NNX14AB68G (NASA) |
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