Simultaneous photometry and spectroscopy of superflares on M- and K-type stars

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04032
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 16010:Astronomy-related
• Research Institution: National Astronomical Observatory of Japan
• Principal Investigator: Maehara Hiroyuki 国立天文台, ハワイ観測所, 助教 (40456851)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 恒星フレア / 恒星黒点 / コロナ質量放出

Outline of Final Research Achievements

In this study, we performed simultaneous photometry and spectroscopy of M and K-type stars using TESS and Seimei 3.8-m telescope to observe the rotational modulations and flares. Using the long-term photometric and spectroscopic data of an active M-dwarf, we found that the area of starspots and H-alpha flux increase as the flare frequency increases. In addition, we succeeded in observing several superflares on M-, K-, G-type stars and RS CVn binaries. Furthermore, we found that some flares showed ``blue-asymmetries'' in the H-alpha line, which are thought to be caused by the prominence/filament eruptions. The estimated masses of the erupted materials are consistent with the empirical relation between the flare energy and CME mass on the Sun.

Free Research Field

恒星物理学

Academic Significance and Societal Importance of the Research Achievements

本研究により明らかになった恒星フレアのエネルギーとフレアに伴うプラズマ噴出現象の質量、速度の関係は、恒星におけるフレアが恒星の周りを周回する惑星の大気にどのような影響を与えるのか、特にハビタブルゾーン内の惑星において生命居住可能な環境を維持することが可能かどうか、を評価する上で重要な基礎データとなる。さらに、太陽において現在知られているよりも規模の大きなスーパーフレアが発生した場合、それに伴うCMEによって現代社会に最大でどのくらいの被害が生じうるのかを見積もるうえでも本研究で得られた知見が役立つと考えられる。