低質量恒星の重元素合成の温度と年代順
P Neyskens1, S Van Eck1, A Jorissen1
1Institut d'Astronomie et d'Astrophysique, Université libre de Bruxelles (ULB), CP 226, 1050 Bruxelles, Belgium.
Nature
|January 9, 2015
まとめ
この研究では,進化した恒星のゆっくりとした中性子捕獲プロセス (sプロセス) の温度を決定し,炭素13を主要な中性子源として支持しました. この発見は,星における重元素合成の時間スケールも提供している.
科学分野:
- 核天体物理学 核天体物理学とは
- 恒星の進化について
- 宇宙化学 (コスモケミストリー)
背景:
- 重元素は,中性子捕獲 (sプロセス) を通して星の中で合成されます.
- s-プロセスには,炭素13とネオン22という2つの中性子源が提案されている.
- 以前のモデルは炭素13を好んでいたが,隕石のデータはネオン22.2を示唆していた.
研究 の 目的:
- 進化した低質量巨星におけるsプロセスの温度を直接決定するために.
- 重元素の合成に責任を負う支配的な中性子源を特定する.
- s-プロセス核合成の時間スケールを設定する.
主な方法:
- 進化した低質量巨星におけるジルコニウムとニオビウムの豊富さの分析.
- 放射性ペアであるジルコニウム-93/ニオビウム-93とテクネチウム-99/ルテニウム-99をクロノメーターとして利用する.
- 恒星の進化モデルに頼らずに,sプロセスの温度を独立に決定する.
主要な成果:
- 導出されたsプロセスの温度は,中性子源として炭素13を直接サポートします.
- この研究は,s-プロセスの開始のための100万年から300万年の時間スケールを提供しています.
- 恒星の進化モデルと隕石の同位体比の不一致を調和させる.
結論:
- 炭素13は,低質量恒星のsプロセスの主要な中性子源として確認されています.
- この発見は,重元素核合成と恒星の化学濃縮に関する重要な洞察を提供します.
- 確立された時間スケールは,銀河化学進化の歴史を理解するのに役立ちます.
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