重力マイクロレンズ法による惑星存在率の銀河系内分布及び主星質量依存性の推定

• Project/Area Number: 18J00897
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Astronomy
• Research Institution: The University of Tokyo
• Principal Investigator: 越本 直季 東京大学, 理学系研究科, 特別研究員(PD)
• Project Period (FY): 2018-04-25 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000); Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
• Keywords: 重力マイクロレンズ / 太陽系外惑星 / 天の川銀河 / 銀河系バルジ / 初期質量関数

Outline of Annual Research Achievements

本研究課題は重力マイクロレンズ法により、雪線以遠の惑星存在率が、主星の質量や銀河系内の場所にどう依存するか初めて解明することを目的とする。本年度は(i) 最新の観測データに合うように銀河系の星のモデルをアップデートし、(ii) それを用いることで、上記目的の一つである、惑星存在率の銀河系内の位置依存性を初めて測定した。
(i)について述べる。本研究では、銀河系の星の質量・数密度・速度のモデル分布（＝銀河モデル）から予想されるマイクロレンズのパラメーターの分布と、実際に観測された分布を比較することで、惑星存在率の主星質量や銀河系内の場所への依存性を測定する。本手法による測定結果は用いる銀河モデルに依存する一方で、従来マイクロレンズの研究に用いられてきた銀河モデルは、過度に単純化されたもので、例えば、超高精度位置天文衛星Gaiaによる星の速度分散の測定結果等の最新のデータとの矛盾点が多かった。そこで私は、最新の観測データと一致するような新たな銀河モデルを開発した(Koshimoto et al. 2021, submitted)。モデルの開発を通して、太陽から遠く離れた銀河系バルジの星の質量関数を、褐色矮星質量から太陽質量以上までの広い質量範囲で初めて同時に測定し、また、バルジ領域のダークマター質量は従来考えられていたよりも重い可能性を示した。
次に、(ii) について述べる。(i)で開発した銀河モデルを用いて計算したマイクロレンズのパラメーターの分布と、28個の惑星イベントに対して観測された同じパラメーターの分布を比較することにより、円盤領域の星は、バルジ領域の星に比べて、0.7 - 2.9 倍惑星を持ちやすいと推定した。これは、惑星存在率の銀河系内の位置依存性の世界初の測定結果である。現在、論文を準備している。

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 Goddard Space Flight Center/Ohio State University/NASA JPL(米国)
• [Int'l Joint Research] Massey University/The University of Auckland/Canterbury University(ニュージーランド)
• [Int'l Joint Research] Institut d’Astrophysique de Paris(フランス)
• [Int'l Joint Research] University of Tasmania(オーストラリア)
• [Int'l Joint Research] NASA Goddard Space Flight Center/Ohio State University/NASA JPL(米国)
• [Int'l Joint Research] Massey University/The University of Auckland/Canterbury University(ニュージーランド)
• [Int'l Joint Research] Institut d’Astrophysique de Paris(フランス)
• [Int'l Joint Research] University of Tasmania(オーストラリア)
• [Int'l Joint Research] Goddard Space Flight Center/University of Maryland(米国)
• [Int'l Joint Research] Sorbonne Universits(フランス)
• [Int'l Joint Research] University of Tasmania(オーストラリア)
• [Journal Article] Revealing Short-period Exoplanets and Brown Dwarfs in the Galactic Bulge Using the Microlensing Xallarap Effect with the Nancy Grace Roman Space Telescope (2021)
  • Author(s): Miyazaki Shota、Johnson Samson A.、Sumi Takahiro、Penny Matthew T.、Koshimoto Naoki、Yamawaki Tsubasa
  • Journal Title: The Astronomical Journal Volume: 161 Issue: 2 Pages: 84-84
  • DOI: 10.3847/1538-3881/abcec2
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] MOA-2009-BLG-319Lb: A Sub-Saturn Planet inside the Predicted Mass Desert (2021)
  • Author(s): Terry Sean K.、Bhattacharya Aparna、Bennett David P.、Beaulieu Jean-Philippe、Koshimoto Naoki、Blackman Joshua W.、Bond Ian A.、Cole Andrew A.、Henderson Calen B.、Lu Jessica R.、Marquette Jean Baptiste、Ranc Cl?ment、Vandorou Aikaterini
  • Journal Title: The Astronomical Journal Volume: 161 Issue: 2 Pages: 54-54
  • DOI: 10.3847/1538-3881/abcc60
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Evidence of Systematic Errors in Spitzer Microlens Parallax Measurements (2020)
  • Author(s): Koshimoto Naoki、Bennett David P.
  • Journal Title: The Astronomical Journal Volume: 160 Issue: 4 Pages: 177-177
  • DOI: 10.3847/1538-3881/abaf4e
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Revisiting MOA 2013-BLG-220L: A Solar-type Star with a Cold Super-Jupiter Companion (2020)
  • Author(s): Vandorou Aikaterini、Bennett David P.、Beaulieu Jean-Philippe、Alard Christophe、Blackman Joshua W.、Cole Andrew A.、Bhattacharya Aparna、Bond Ian A.、Koshimoto Naoki、Marquette Jean-Baptiste
  • Journal Title: The Astronomical Journal Volume: 160 Issue: 3 Pages: 121-121
  • DOI: 10.3847/1538-3881/aba2d3
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] OGLE-2017-BLG-0406: Spitzer Microlens Parallax Reveals Saturn-mass Planet Orbiting M-dwarf Host in the Inner Galactic Disk (2020)
  • Author(s): Hirao Yuki、Bennett David P.、Ryu Yoon-Hyun、 et al.
  • Journal Title: The Astronomical Journal Volume: 160 Issue: 2 Pages: 74-74
  • DOI: 10.3847/1538-3881/ab9ac3
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] A Gas Giant Planet in the OGLE-2006-BLG-284L Stellar Binary System (2020)
  • Author(s): Bennett David P.、Udalski Andrzej、Bond Ian A. et al.
  • Journal Title: The Astronomical Journal Volume: 160 Issue: 2 Pages: 72-72
  • DOI: 10.3847/1538-3881/ab9cb9
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Bayesian Approach for Determining Microlens System Properties with High-angular-resolution Follow-up Imaging (2020)
  • Author(s): Koshimoto Naoki、Bennett David P.、Suzuki Daisuke
  • Journal Title: The Astronomical Journal Volume: 159 Issue: 6 Pages: 268-268
  • DOI: 10.3847/1538-3881/ab8adf
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] A Wide-orbit Exoplanet OGLE-2012-BLG-0838Lb (2020)
  • Author(s): Poleski R.、Suzuki Daisuke、et al.
  • Journal Title: The Astronomical Journal Volume: 159 Issue: 6 Pages: 261-261
  • DOI: 10.3847/1538-3881/ab8a49
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Confirmation of the Stellar Binary Microlensing Event, Macho 97-BLG-28 (2020)
  • Author(s): Blackman J. W.、Beaulieu J.-P.、Cole A. A.、Vandorou A.、Koshimoto N.、Bachelet E.、Batista V.、Bhattacharya A.、Bennett D. P.
  • Journal Title: The Astrophysical Journal Volume: 890 Issue: 1 Pages: 87-87
  • DOI: 10.3847/1538-4357/ab68da
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] OGLE-2013-BLG-0911Lb: A Secondary on the Brown-dwarf Planet Boundary around an M Dwarf (2020)
  • Author(s): Miyazaki Shota、et al.
  • Journal Title: The Astronomical Journal Volume: 159 Issue: 2 Pages: 76-76
  • DOI: 10.3847/1538-3881/ab64de
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Keck Observations Confirm a Super-Jupiter Planet Orbiting M Dwarf OGLE-2005-BLG-071L (2020)
  • Author(s): Bennett David P.、Bhattacharya Aparna、Beaulieu Jean-Philippe、Blackman Joshua W.、Vandorou Aikaterini、Terry Sean K.、Cole Andrew A.、Henderson Calen B.、Koshimoto Naoki、Lu Jessica R.、Baptiste Marquette Jean、Ranc Cl?ment、Udalski Andrzej
  • Journal Title: The Astronomical Journal Volume: 159 Issue: 2 Pages: 68-68
  • DOI: 10.3847/1538-3881/ab6212
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] MOA-bin-29b: A Microlensing Gas-giant Planet Orbiting a Low-mass Host Star (2019)
  • Author(s): Kondo Iona、et al.
  • Journal Title: The Astronomical Journal Volume: 158 Issue: 6 Pages: 224-224
  • DOI: 10.3847/1538-3881/ab4e9e
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] OGLE-2015-BLG-1649Lb: A Gas Giant Planet around a Low-mass Dwarf (2019)
  • Author(s): Nagakane M.、et al.
  • Journal Title: The Astronomical Journal Volume: 158 Issue: 5 Pages: 212-212
  • DOI: 10.3847/1538-3881/ab4881
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Kojima-1Lb Is a Mildly Cold Neptune around the Brightest Microlensing Host Star (2019)
  • Author(s): Fukui A.、Suzuki D.、Koshimoto N.、Bachelet E.、Vanmunster T.、Storey D.、Maehara H.、Yanagisawa K.、Yamada T.、Yonehara A.、Hirano T.、et al.
  • Journal Title: The Astronomical Journal Volume: 158 Issue: 5 Pages: 206-206
  • DOI: 10.3847/1538-3881/ab487f
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] A Likely Detection of a Two-planet System in a Low-magnification Microlensing Event (2018)
  • Author(s): Suzuki D.他
  • Journal Title: The Astronomical Journal Volume: 155 Issue: 6 Pages: 263-263
  • DOI: 10.3847/1538-3881/aabd7a
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] A Planetary Microlensing Event with an Unusually Red Source Star: MOA-2011-BLG-291 (2018)
  • Author(s): Bennett David P.他
  • Journal Title: The Astronomical Journal Volume: 156 Issue: 3 Pages: 113-113
  • DOI: 10.3847/1538-3881/aad59c
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] MOA-2015-BLG-337: A Planetary System with a Low-mass Brown Dwarf/Planetary Boundary Host, or a Brown Dwarf Binary (2018)
  • Author(s): Miyazaki S.他
  • Journal Title: The Astronomical Journal Volume: 156 Issue: 3 Pages: 136-136
  • DOI: 10.3847/1538-3881/aad5ee
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] WFIRST Exoplanet Mass-measurement Method Finds a Planetary Mass of 39 +/- 8 M_Earth for OGLE-2012-BLG-0950Lb (2018)
  • Author(s): Bhattacharya, A., Beaulieu, J.-P., Bennett, D. P., et al.
  • Journal Title: The Astronomical Journal Volume: 156 Issue: 6 Pages: 289-289
  • DOI: 10.3847/1538-3881/aaed46
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Microlensing Results Challenge the Core Accretion Runaway Growth Scenario for Gas Giants (2018)
  • Author(s): Suzuki, D., Bennett, D. P., Ida, S., et al.
  • Journal Title: The Astrophysical Journal Volume: 869 Issue: 2 Pages: L34-L34
  • DOI: 10.3847/2041-8213/aaf577
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Comparison of microlensing planet distribution with a Galactic model (2021)
  • Author(s): Naoki Koshimoto
  • Organizer: 237th AAS Meeting
  • Int'l Joint Research
• [Presentation] 重力マイクロレンズ法による惑星系の銀河系内分布測定 (2021)
  • Author(s): 越本直季
  • Organizer: 日本天文学会春季年会
• [Presentation] Comparison of microlensing planet distribution with a Galactic model (2020)
  • Author(s): Naoki Koshimoto
  • Organizer: Exoplanet Demographics
  • Int'l Joint Research
• [Presentation] Comparison of microlensing planet distribution with Galactic model (2020)
  • Author(s): Naoki Koshimoto
  • Organizer: Exoplanets III
  • Int'l Joint Research
• [Presentation] Galactic distribution of planets studied by microlensing (2019)
  • Author(s): Naoki Koshimoto
  • Organizer: WFIRST Science Jamboree
  • Int'l Joint Research
• [Presentation] Evidence of systematic errors in Spitzer 2015 parallax measurements (2019)
  • Author(s): Naoki Koshimoto
  • Organizer: 23rd International Microlensing Conference
  • Int'l Joint Research
• [Presentation] 重力マイクロレンズ現象による太陽系外惑星探査 (2018)
  • Author(s): 越本直季
  • Organizer: アストロバイオロジー分野間連携セミナー
• [Presentation] MOAおよびPRIMEによるマイクロレンズ法を用いた系外惑星探査 (2018)
  • Author(s): 越本直季
  • Organizer: 新学術領域研究「新しい星形成理論によるパラダイムシフト：銀河系におけるハビタブル惑星開拓史の解明」キックオフミーティング
• [Presentation] 連星を考慮した質量関数及びその重力マイクロレンズのレンズ星の質量推定値への影響 (2018)
  • Author(s): 越本直季
  • Organizer: 日本天文学会2018年秋季年会
• [Remarks] アマチュア天文家が発見した最近傍の重力レンズ系外惑星
  • URL: https://www.s.u-tokyo.ac.jp/ja/press/2019/6605/