Observational Studies of Solar-type Stars toward an Universal Understanding of Solar and Stellar Magnetic Activity

• Project/Area Number: 18J20048
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Astronomy
• Research Institution: Kyoto University
• Principal Investigator: 行方 宏介 京都大学, 理学研究科, 特別研究員(DC1)
• Project Period (FY): 2018-04-25 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥3,100,000 (Direct Cost: ¥3,100,000); Fiscal Year 2020: ¥1,000,000 (Direct Cost: ¥1,000,000); Fiscal Year 2019: ¥1,000,000 (Direct Cost: ¥1,000,000); Fiscal Year 2018: ¥1,100,000 (Direct Cost: ¥1,100,000)
• Keywords: 恒星 / 太陽 / 黒点 / フレア / Kepler衛星 / せいめい望遠鏡 / TESS衛星 / スーパーフレア / 巨大黒点 / 太陽型星 / 分光観測 / 測光観測 / ケプラー衛星

Outline of Annual Research Achievements

恒星フレア・恒星黒点のデータ収集を行い、飛騨天文台SMART望遠鏡SDDIで観測された太陽フレア・フィラメント噴出のSun-as-a-star解析も行い、恒星フレアと比較する研究も行った。具体的には、京都大学3.8m望遠鏡の低分散分光器で、スーパーフレアを起こす星を数週間に渡り分光観測し、スーパーフレアの放射スペクトルを得る研究を行った。本年度は、特に活動度が高いM型フレア星の観測だけでなく、太陽型星EK Draでの観測も行う予定である。TESS衛星やSwift衛星との同時観測を行った。この際、東京工業大学所有の岡山188cm望遠鏡の観測時間を科研費で購入し、高分散分光観測も行った。これにより、太陽型星におけるスーパーフレアの可視光分光観測データを世界で初めて検出することに成功した。それだけでなく、スーパーフレアに伴うスペクトルの変化から、大量の質量噴出が発生し、惑星間空間に放出されていることを、太陽型星で世界で初めて検出した。また、M型星におけるフレアにおいても、質量噴出を示唆するような青方偏移するバルマー線成分を検出した。これらを、太陽フレアと比較することにより、これらの他の恒星での極端現象は単に太陽での小規模な現象をスケール倍した描像と相違ないということが発見された。これらから、若く活動的な太陽型星やM型星では、質量噴出と言った形で惑星間空間に影響を与えている可能性を示唆することができた。この結果は、太陽で発生しうるスーパーフレアの模型として考えることもでき、宇宙に進出しつつある人類文明にとっても重要な観測的示唆を得た。これらの成果を論文としてまとめ、現在国際学会誌に投稿中である。また、昨年の研究成果をまとめ、国際学会雑誌PASJにて出版し、多数の新聞・ウェブ記事にて報道された。さらに、前年度に引き続き、国内・国際学会で研究成果を積極的に発表も行った。

Research Progress Status

令和2年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和2年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] NASA/コロラド大学(米国)
• [Int'l Joint Research] ワシントン大学(米国)
• [Journal Article] Statistical Properties of Superflares on Solar-type Stars: Results Using All of the Kepler Primary Mission Data (2021)
  • Author(s): Okamoto Soshi、Notsu Yuta、Maehara Hiroyuki、Namekata Kosuke、Honda Satoshi、Ikuta Kai、Nogami Daisaku、Shibata Kazunari
  • Journal Title: The Astrophysical Journal Volume: 906 Issue: 2 Pages: 72-72
  • DOI: 10.3847/1538-4357/abc8f5
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Time-resolved spectroscopy and photometry of M dwarf flare star YZ Canis Minoris with OISTER and TESS: Blue asymmetry in the Hα line during the non-white light flare (2021)
  • Author(s): Maehara Hiroyuki、Notsu Yuta、Namekata Kousuke、Honda Satoshi、Kowalski Adam F、Katoh Noriyuki、Ohshima Tomohito、Iida Kota、Oeda Motoki、Murata Katsuhiro L、Yamanaka Masayuki、Takagi Kengo、Sasada Mahito、Akitaya Hiroshi、Ikuta Kai、Okamoto Soshi、Nogami Daisaku、Shibata Kazunari
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 73 Issue: 1 Pages: 44-65
  • DOI: 10.1093/pasj/psaa098
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with the Seimei Telescope, SCAT, NICER, and OISTER (2020)
  • Author(s): Namekata, Kosuke et al.
  • Journal Title: Publications of the Astronomical Society of Japan Volume: 72 Issue: 4 Pages: 4-15
  • DOI: 10.1093/pasj/psaa051
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Starspot Mapping with Adaptive Parallel Tempering. I. Implementation of Computational Code (2020)
  • Author(s): Ikuta Kai、Maehara Hiroyuki、Notsu Yuta、Namekata Kosuke、Kato Taichi、Notsu Shota、Okamoto Soshi、Honda Satoshi、Nogami Daisaku、Shibata Kazunari
  • Journal Title: The Astrophysical Journal Volume: 902 Issue: 1 Pages: 73-73
  • DOI: 10.3847/1538-4357/abae5f
  • Peer Reviewed
• [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] 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] 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] 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] The extreme space weather event in September 1909 (2018)
  • Author(s): Hayakawa Hisashi、Ebihara Yusuke、Cliver Edward W、Hattori Kentaro、Toriumi Shin、Love Jeffrey J、Umemura Norio、Namekata Kosuke、Sakaue Takahito、Takahashi Takuya、Shibata Kazunari
  • Journal Title: Monthly Notices of the Royal Astronomical Society Volume: 484 Issue: 3 Pages: 4083-4099
  • DOI: 10.1093/mnras/sty3196
  • 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
• [Presentation] 太陽型星EK Draの長時間スーパーフレアのHα線分光・可視測光観測 (2021)
  • Author(s): 行方宏介
  • Organizer: 日本天文学会 2021年春季年会
• [Presentation] First detection of stellar mass ejection from a superflare on a solar-type star (2021)
  • Author(s): Kosuke Namekata
  • Organizer: COSPAR 43rd Scientific Assembly
  • Int'l Joint Research
• [Presentation] Detection of mass ejection from a superflare on a solar-type star (2021)
  • Author(s): Kosuke Namekata
  • Organizer: Cool Stars 20.5
  • Int'l Joint Research
• [Presentation] 太陽型星のスーパーフレアに伴うHα線放射・プラズマ噴出現象の世界初検出 (2020)
  • Author(s): 行方宏介
  • Organizer: 日本天文学会 2020年秋季年会
• [Presentation] Lifetimes and emergence/decay rates of star spots on solar-type stars estimated by Kepler data in comparison with those of sunspots (2020)
  • Author(s): Namekata, K.; Shibata, K.; Maehara, H.; Notsu, Y.; Nogami, D.; Toriumi, S.; Davenport, J.; Hawley, S.; Morris, B.
  • Organizer: American Astronomical Society meeting #235
  • Int'l Joint Research
• [Presentation] 恒星フレアの多波長モニタ観測~OISTERとTESS/NICERの連携~ (2020)
  • Author(s): 行方宏介
  • Organizer: 日本天文学会 2020年春季年会
  • Invited
• [Presentation] Namekata, Kosuke; Maehara, H.; Davenport, J.; Morris, B.; Hawley, S.; Notsu, Y.; Toriumi, S.; Hayakawa, H.; Honda, S.; Notsu, S.; Ikuta, K.; Nogami, D.; Shibata, K. (2019)
  • Author(s): Lifetimes and emergence/decay rates of star spots on solar-type stars estimated by Kepler data in comparison with those of sunspots
  • Organizer: Solar Atmospheric and Interplanetary Environment (SHINE 2019)
  • Int'l Joint Research
• [Presentation] せいめい望遠鏡の初期観測成果：M型星AD Leoの恒星フレアの連続分光 (2019)
  • Author(s): 行方宏介
  • Organizer: 日本天文学会 2019年秋季年会
• [Presentation] 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): Kosuke Namekata
  • Organizer: Kepler & K2 Science Conference V
  • Int'l Joint Research
• [Presentation] 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): Kosuke Namekata
  • Organizer: Flux Emergence Workshop
  • Int'l Joint Research
• [Presentation] 惑星トランジットを用いた、空間分解された恒星黒点の面積の時間変化の推定 (2019)
  • Author(s): 行方宏介
  • Organizer: 日本天文学会 2019年春季年会
• [Presentation] Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars (2018)
  • Author(s): Kosuke Namekata
  • Organizer: COSPAR 2018 42th Assembly
  • Int'l Joint Research
• [Presentation] Lifetime, Emerging and Decay Rates of Starspots on Solar-type Stars Estimated by Kepler Data and Comparisons with Sunspots (2018)
  • Author(s): Kosuke Namekata
  • Organizer: COOL STARS 20
  • Int'l Joint Research
• [Presentation] Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars (2018)
  • Author(s): Kosuke Namekata
  • Organizer: Hinode-12 Meeting
  • Int'l Joint Research
• [Remarks] Kosuke Namekata's HP
  • URL: https://www.kwasan.kyoto-u.ac.jp/~namekata/
• [Remarks] 京大せいめい望遠鏡でスーパーフレアの検出に成功 －生命居住可能な惑星への影響の理解に向けて－
  • URL: https://www.kyoto-u.ac.jp/ja/research-news/2020-07-10-1
• [Remarks] 京大せいめい望遠鏡でスーパーフレアの検出に成功 －生命居住可能な惑星への影響の理解に向けて－
  • URL: https://www.nao.ac.jp/news/science/2020/20200710-okayama.html
• [Remarks] 研究成果：せいめい望遠鏡でスーパーフレアの検出に成功
  • URL: https://www.kwasan.kyoto-u.ac.jp/general/facilities/okayama/2020/07/10/superflare-adleo/