Namekata, Kosuke and Maehara, Hiroyuki and Honda, Satoshi and Notsu, Yuta and Okamoto, Soshi and Takahashi, Jun and Takayama, Masaki and Ohshima, Tomohito and Saito, Tomoki and Katoh, Noriyuki and Tozuka, Miyako and Murata, Katsuhiro L. and Ogawa, Futa and Niwano, Masafumi and Adachi, Ryo and Oeda, Motoki and Shiraishi, Kazuki and Isogai, Keisuke and Nogami, Daisaku and Shibata, Kazunari (2022) Discovery of a Long-duration Superflare on a Young Solar-type Star EK Draconis with Nearly Similar Time Evolution for Hα and White-light Emissions. The Astrophysical Journal Letters, 926 (1). L5. ISSN 2041-8205
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Abstract
Young solar-type stars are known to show frequent "superflares," which may severely influence the habitable worlds on young planets via intense radiation and coronal mass ejections. Here we report an optical spectroscopic and photometric observation of a long-duration superflare on the young solar-type star EK Draconis (50–120 Myr age) with the Seimei telescope and Transiting Exoplanet Survey Satellite. The flare energy 2.6 × 1034 erg and white-light flare duration 2.2 hr are much larger than those of the largest solar flares, and this is the largest superflare on a solar-type star ever detected by optical spectroscopy. The Hα emission profile shows no significant line asymmetry, meaning no signature of a filament eruption, unlike the only previous detection of a superflare on this star. Also, it did not show significant line broadening, indicating that the nonthermal heating at the flare footpoints is not essential or that the footpoints are behind the limb. The time evolution and duration of the Hα flare are surprisingly almost the same as those of the white-light flare, which is different from general M-dwarf (super-)flares and solar flares. This unexpected time evolution may suggest that different radiation mechanisms than general solar flares are predominant, such as: (1) radiation from (off-limb) flare loops and (2) re-radiation via radiative back-warming, in both of which the cooling timescales of flare loops could determine the timescales of Hα and white light.
Item Type: | Article |
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Subjects: | Middle Asian Archive > Physics and Astronomy |
Depositing User: | Managing Editor |
Date Deposited: | 29 Apr 2023 07:00 |
Last Modified: | 19 Jul 2025 03:44 |
URI: | http://peerreview.go2articles.com/id/eprint/379 |