On the correlation between starspot activity and superflares on solar-type stars

• Project/Area Number: 17K05400
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Astronomy
• Research Institution: National Astronomical Observatory of Japan (2018-2019); Kyoto University (2017)
• Principal Investigator: Maehara Hiroyuki 国立天文台, ハワイ観測所, 助教 (40456851)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000); Fiscal Year 2019: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2017: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
• Keywords: 太陽型星 / 黒点 / フレア / 晩期型星 / 恒星黒点 / 光学赤外線天文学

Outline of Final Research Achievements

We studied the occurrence frequency and lifetime of large starspots which can produce "superflares" on solar-type stars by using photometric data by Kepler space telescope and ground-based long-term observations. We found that the size distribution of large starspots on solar-type stars as a function of the area of starspots shows the power-law distribution. Our results suggest that the size distribution of starspots on solar-type stars and that of sunspots lie on the same power-law line. We also analyzed the lifetime of starspots on solar-type stars from the rotational brightness modulations and found that larger starspots tend to have longer lifetime. The lifetime of large starspots on solar-type stars is consistent with that predicted from the lifetime-area relation for sunspots. Our findings imply that both sunspots and larger starspots on solar-type stars are caused by the same physical mechanisms.

Academic Significance and Societal Importance of the Research Achievements

本研究で得られた研究結果から、スーパーフレアを起こしうる巨大黒点の発生頻度や寿命を初めて明らかにすることができ、それらが従来の太陽観測から知られていた黒点の発生頻度と面積の関係や、寿命と面積の関係の延長線上にのることが明らかとなった。このことは、スーパーフレアを起こすような巨大黒点と太陽で見られる黒点は、同じメカニズムで生成・発展・消滅することを示唆する。さらに、太陽でもスーパーフレアを起こすような巨大黒点が発生しうることを示唆しており、本研究の結果は太陽でのスーパーフレアに伴う巨大磁気嵐等の地球上の文明社会への影響やそのリスク評価にとっても重要である。

Research Products

• [Int'l Joint Research] University of Washington/NASA/University of Colorado(米国)
• [Int'l Joint Research] University of Washington/NASA/University of Colorad(米国)
• [Int'l Joint Research] University of Washington/NASA/University of Colorad(米国)
• [Journal Article] Temporal Evolution of Spatially Resolved Individual Star Spots on a Planet-hosting Solar-type Star: Kepler-17 (2020)
  • Author(s): Namekata Kosuke、Davenport James R. A.、Morris Brett M.、Hawley Suzanne L.、Maehara Hiroyuki、Notsu Yuta、Toriumi Shin、Ikuta Kai、Notsu Shota、Honda Satoshi、Nogami Daisaku、Shibata Kazunari
  • Journal Title: The Astrophysical Journal Volume: 891 Issue: 2 Pages: 103-103
  • DOI: 10.3847/1538-4357/ab7384
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars??Results Using APO 3.5 m Telescope Spectroscopic Observations and Gaia-DR2 Data (2019)
  • Author(s): Notsu Yuta、Maehara Hiroyuki、Honda Satoshi、Hawley Suzanne L.、Davenport James R. A.、Namekata Kosuke、Notsu Shota、Ikuta Kai、Nogami Daisaku、Shibata Kazunari
  • Journal Title: The Astrophysical Journal Volume: 876 Issue: 1 Pages: 58-96
  • DOI: 10.3847/1538-4357/ab14e6
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Impact of Stellar Superflares on Planetary Habitability (2019)
  • Author(s): Yamashiki Yosuke A.、Maehara Hiroyuki、Airapetian Vladimir、Notsu Yuta、Sato Tatsuhiko、Notsu Shota、Kuroki Ryusuke、Murashima Keiya、Sato Hiroaki、Namekata Kosuke、Sasaki Takanori、Scott Thomas B.、Bando Hina、Nashimoto Subaru、Takagi Fuka、Ling Cassandra、Nogami Daisaku、Shibata Kazunari
  • Journal Title: The Astrophysical Journal Volume: 881 Issue: 2 Pages: 114-114
  • DOI: 10.3847/1538-4357/ab2a71
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Lifetimes and Emergence/Decay Rates of Star Spots on Solar-type Stars Estimated by Kepler Data in Comparison with Those of Sunspots (2019)
  • Author(s): Namekata, Kosuke; Maehara, Hiroyuki; Notsu, Yuta; Toriumi, Shin; Hayakawa, Hisashi; Ikuta, Kai; Notsu, Shota; Honda, Satoshi; Nogami, Daisaku; Shibata, Kazunari
  • Journal Title: The Astrophysical Journal Volume: 871 Issue: 2 Pages: 187-187
  • DOI: 10.3847/1538-4357/aaf471
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Time resolved spectroscopic observations of an M-dwarf flare star EV Lac during a flare (2018)
  • Author(s): Honda, Satoshi; Notsu, Yuta; Namekata, Kosuke; Notsu, Shota; Maehara, Hiroyuki; Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari
  • Journal Title: Publications of the Astronomical Society of Japan Volume: - Issue: 4 Pages: 62-62
  • DOI: 10.1093/pasj/psy055
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] On the nature of long-period dwarf novae with rare and low-amplitude outbursts (2018)
  • Author(s): Kimura, Mariko; Kato, Taichi; Maehara, Hiroyuki; et al.
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 70 Issue: 4 Pages: 1-17
  • DOI: 10.1093/pasj/psy073
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Starspot activity and superflares on solar-type stars (2017)
  • Author(s): Maehara, H., Notsu, Y., Notsu, S., Namekata, K., Honda, S., Ishii, T., T., Nogami, D., and Shibata, K.
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 印刷中 Issue: 3 Pages: 41-41
  • DOI: 10.1093/pasj/psx013
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars (2017)
  • Author(s): Namekata, K., Sakaue, T., Watanabe, K., Asai, A., Maehara, H., Notsu, Y., Notsu, S., Honda, S., Ishii, T. T., Ikuta, K., Nogami, D., Shibata, K.
  • Journal Title: The Astrophysical Journal Volume: 851 Issue: 2 Pages: 91-91
  • DOI: 10.3847/1538-4357/aa9b34
  • Peer Reviewed
• [Presentation] 中小口径望遠鏡とTESSの連携によるフレア星 EV Lac の測光分光同時観測 (2020)
  • Author(s): 前原裕之
  • Organizer: 日本天文学会2020年春季年会
• [Presentation] Statistical properties of starspots on late-type main sequence stars and their correlation with flare activity (2019)
  • Author(s): Maehara Hiroyuki
  • Organizer: 2019 Astrobiology Conference
  • Int'l Joint Research
• [Presentation] Simultaneous Photometry and Spectroscopy of an Active M dwarf YZ Canis Minoris with TESS and OISTER (2019)
  • Author(s): Maehara Hiroyuki
  • Organizer: TESS Science Conference I
  • Int'l Joint Research
• [Presentation] 光赤外線大学間連携とTESSによるフレア星YZ CMiの測光分光同時観測 (2019)
  • Author(s): 前原裕之
  • Organizer: 日本天文学会2019年秋季年会
• [Presentation] G, K, M型星の恒星黒点の統計的性質とフレア活動性との関係 (2019)
  • Author(s): 前原裕之
  • Organizer: 日本天文学会2019年春季年会
• [Presentation] Starspots on late-type stars and their correlation with flare activity (2018)
  • Author(s): Maehara, Hiroyuki; Notsu, Yuta; Namekata, Kousuke; Ikuta, Kai; Notsu, Shota; Honda, Satoshi; Nogami, Daisaku; Shibata, Kazunari
  • Organizer: 20th Cambridge Workshop: Cool Stars, Stellar Systems, and the Sun
  • Int'l Joint Research
• [Presentation] Statistical properties of starspots on solar-type stars and their correlation with flare activity (2018)
  • Author(s): Maehara, Hiroyuki
  • Organizer: IAU Focus Meeting FM9: Solar Irradiance: Physics-Based Advances
  • Int'l Joint Research
• [Presentation] Superflares and starspot activity on solar-type stars (2018)
  • Author(s): Maehara, Hiroyuki
  • Organizer: ISEE workshop on Extreme Solar Events
  • Int'l Joint Research / Invited
• [Presentation] Superflares on solar-type stars (2018)
  • Author(s): Maehara, H.
  • Organizer: Asteroseismology and its impact on other branches of astronomy
  • Int'l Joint Research / Invited
• [Presentation] G,K,M型星におけるスーパーフレアのエネルギーと継続時間の関係 (2018)
  • Author(s): 前原裕之
  • Organizer: 日本天文学会2018年春季年会
• [Presentation] Starspot activity and superflares on solar-type stars (2017)
  • Author(s): Maehara, H.
  • Organizer: Kepler & K2 Science Conference IV
  • Int'l Joint Research
• [Presentation] Starspot activity and superflares on solar-type stars (2017)
  • Author(s): Maehara, H.
  • Organizer: JpGU-AGU Joint Meeting 2017
  • Int'l Joint Research
• [Book] Extreme Solar Particle Storms The hostile Sun (2019)
  • Author(s): Miyake F., Usoskin I., Poluianov S., Baroni M., Cliver E., Dyer C., Ebihara Y., Feinberg A., Hayakawa H., Jull., Kovaltsov G., Kusano K., Maehara H., Mekhaldi F., Mitsuma Y., Muscheler R., Oinonen M., Sokoloff D., Rozanov E., Sukhodolov T., Wacker L., Wang F., Willis D.
  • Total Pages: 276
  • Publisher: IOP Publishing
  • ISBN: 9780750322300
• [Remarks] 生命が居住可能な惑星にスーパーフレアが与える影響
  • URL: https://www.nao.ac.jp/news/science/2019/20190716-kyoto.html