A Superflare on YZ Canis Minoris Observed by Seimei Telescope and TESS: Red Asymmetry of Hα Emission Associated with White-Light Emission |
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Keiichi Namizaki Submitted: 2023-02-13 00:19
Active M-type stars are known to often produce superflares on the surface. Radiation from stellar (super-)flares is important for the exoplanet habitability, but the mechanisms are not well understood. In this paper, we report simultaneous optical spectroscopic and photometric observations of a stellar superflare on an active M dwarf YZ CMi with the 3.8-m Seimei telescope and the Transiting Exoplanet Survey Satellite. The flare bolometric energy was 1.3+1.6-0.6 × 1034 erg and Hα energy was 3.0+0.1-0.1 × 1032 erg. The Hα emission line profile showed red asymmetry throughout the flare with a duration of 4.6-5.1 hrs. The velocity of the red asymmetry was 〜 200-500 km s-1 and line width of Hα was broadened up to 34 ±14 Å. The redshifted velocity and line width of Hα line decayed more rapidly than the equivalent width, and their time evolutions are correlated with that of the white-light emission. This indicates a possibility that the white light, Hα red asymmetry, and Hα line broadening originate from nearly the same site, i.e., the dense chromospheric condensation region heated by non-thermal electrons. On the other hand, the flux ratio of the redshifted excess components to the central components is enhanced one hour after the flare onset. This may be due to the change of the main source of the red asymmetry to the post-flare loops in the later phase of the flare.
Authors: Keiichi Namizaki, Kosuke Namekata, Hiroyuki Maehara, Yuta Notsu, Satoshi Honda, Daisaku Nogami, Kazunari Shibata
Projects: None
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Publication Status: Accepted for publication in The Astrophysical Journal
Last Modified: 2023-02-14 04:00
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