オブ・ランナウェイ・スターの起源 OBランナウェイ・スターの起源

Michiko S Fujii¹, Simon Portegies Zwart

¹Leiden Observatory, Leiden University, 2300 RA Leiden, Netherlands.

Science (New York, N.Y.)

|November 19, 2011

まとめ

天文学者は,高速の大量恒星の謎を解明しました. 若い星団の重力相互作用は,これらの"逃げ出した星"を放出し,天の川におけるそれらの存在と特徴を説明します.

科学分野:

天体物理学天体物理学
星の動力学星の動力学
銀河系天文学銀河系天文学

背景:

銀河系にある大質量の恒星の約20%は,数十年もの間説明がつかない現象である異常な高速を誇示しています.
これらの高速の恒星は,OB Runawaysとして知られており,恒星の進化と銀河のダイナミクスを理解する上で大きな課題となっています.

研究の目的:

銀河系における高速の大量恒星の起源を調査する.
これらの脱走星の観測された特性を説明するモデルを提案し,検証する.

主な方法:

若い星群の密集した環境の中で,単一の星と二重星系間の重力相互作用をシミュレートします.
星群の崩壊段階 (≤100万年) 中の二重星体の形成と放出のダイナミクスを分析する.

主要な成果:

提案されたモデルは,OBランナーウェイの主要な特徴を,その高い速度と若い恒星群との関連を含め,成功裏に複製しています.
このモデルは,R136やWesterlund 2のような星団の近くで観測された非常に巨大な脱走星 (≥100太陽質量) の存在を説明しています.
銀河系における脱走星の観測された割合と分布は,大質量の恒星が主に密集した低質量星団 (5,000〜10,000 M) で形成されていると仮定すると再現されます.

結論:

若くて密集した恒星群の内部での強い重力相互作用は,巨大な恒星を高速で放出する主なメカニズムです.
脱走星の特徴は,恒星群の形成の初期条件,特に巨大な恒星が誕生する群の典型的な質量と密度に関する重要な制約を提供します.

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