論文 / 著書情報
Article / Book Information
題目(和文)
Title(English)

Multi-wavelength study of long-term activities of galactic Be/X-raybinaries

著者(和文)

庭野聖史

Author(English)

Masafumi Niwano

出典(和文)

学位:博士(理学),学位授与機関:東京工業大学,
報告番号:甲第12641号,
授与年月日:2024年3月26日,
学位の種別:課程博士,
審査員:谷津 陽一,堂谷 忠靖,松原 英雄,宗宮 健太郎,関澤 一之

Citation(English)

Degree:Doctor (Science),
Conferring organization: Tokyo Institute of Technology,
Report number:甲第12641号,
Conferred date:2024/3/26,
Degree Type:Course doctor,Examiner:,,,,

学位種別(和文)

博士論文

Category(English)

Doctoral Thesis

種別(和文)論文要旨

Type(English)

Summary

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（博士課程）Doctoral Program論 文 要 旨ＴＨＥＳＩＳ ＳＵＭＭＡＲＹ

系・コース：
Department of, Graduate major in

物理学
物理学

学生氏名：
Student’s Name

庭野 聖史系コース

申請学位（専攻分野）：

博士

Academic Degree Requested

Doctor of

審査員主査：
Chief Examiner

（理学）
谷津 陽一

要旨（英文 800 語程度）
Thesis Summary （approx.800 English Words ）A Be star is an early-type massive star with a circumstellar disk, and a Be/X-ray binary (BeXB) isa binary system composed of a Be star and a compact star. Be stars and BeXBs are important not only
for their interesting phenomena related to their disks but also in terms of binary evolution,
gravitational wave astronomy, and cosmology. However, many aspects of the physics remain unknown,such as the mechanisms of disk formation and the two types of outbursts in BeXBs. One way toinvestigate the activity of massive stars is to study periodic flux oscillations in the amplitudeof less than a few percent and on the time scale of hours to days caused by their rotation andpulsation. Study of such flux variations has been difficult due to limitation of ground-based
observations, but Transiting Exoplanet Survey Satellite (TESS), which brings high-accuracy and highcadence continuous optical photometric data of all-sky sources, has enabled comprehensive
investigation of Be star activities in BeXBs.
The purpose of this study is to constrain the relationship between Be star activities and thecircumstellar disk in BeXBs. Therefore, we investigated long-term variations of flux periodicity
and multi-wavelength luminosity using TESS data and multi-wavelength long-term light curves for 17
galactic BeXBs. As a result, we confirmed long-term optical and near-infrared (OIR) variations
originating from circumstellar disks for all targets with available OIR light curves, and fivesources exhibited giant outbursts. In addition, we found anti-correlations between the infraredexcess and the amplitude of flux oscillations for the five giant outbursters, which appears tocontradict the conventional idea that non-radial pulsation contributes to the growth of thecircumstellar disk. After examining multiple scenarios to explain these results, we conclude that
there should be a genuine inverse correlation between the pulsation amplitude and the disk growth,and pulsations may not contribute to the mass ejection. We proposed a scenario in which internal
temperature changes of the Be star cause a transition between a pulsation active state and a massejection active state. For a more rigorous discussion, more frequent and multi-wavelength
observations of flux periodicity are required.

備考 : 論文要旨は、和文 2000 字と英文 300 語を 1 部ずつ提出するか、もしくは英文 800 語を 1 部提出してください。
Note : Thesis Summary should be submitted in either a copy of 2000 Japanese Characters and 300 Words (Engｌish) or 1copy of 800
Words (English).
注意：論文要旨は、東工大リサーチリポジトリ（T2R2）にてインターネット公表されますので、公表可能な範囲の内容で作成してください。
Attention: Thesis Summary will be published on Tokyo Tech Research Repository Website (T2R2).