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GRB 120308Aの安定した有秩序な磁場からの高度に偏光した光
C G Mundell1, D Kopač, D M Arnold
1Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK.
Nature
|December 6, 2013
まとめ
ガンマ線爆発後の高分極化は,安定した磁場を持つ磁気ジェットを示唆している. この発見は,ジェット内の大規模な磁場が爆発を生き延び,プラズマの不安定性を排除するモデルを支持する.
科学分野:
- 天体物理学 天体物理学
- 高エネルギー天体物理学
- プラズマ物理学のプラズマ物理学
背景:
- ガンマ線爆発 (GRB) は,強力な宇宙爆発です.
- 後発光は,周辺物質と衝突したGRBエジェクトの衝撃によって生成されます.
- リバースショックの光の偏振は,GRBジェットの磁場の性質を明らかにすることができます.
研究 の 目的:
- GRBの初期の後光からの光の偏振を調査する.
- GRBジェット構造と磁場振る舞いの競合するモデルをテストするために.
- GRBジェットが地球規模に秩序付けられた磁場を持っているかどうかを判断する.
主な方法:
- スウィフト GRB 120308Aの光学偏振が,ガンマ線で検出されてから4分後に観測されました.
- その後の10分間,極化レベルと位置の角度を測定した.
- GRBジェットの磁場の性質を推論するために,極化データを分析した.
主要な成果:
- すぐ後の光の中で高線形極化 (P=28%,16%に減少) が検出されました.
- 最小の変動 (≤15度) を伴う安定した偏極位置の角度が観測されました.
- これらの極化特性は,プラズマの不安定性によって生成されるランダムな磁場と矛盾しています.
結論:
- GRBには,大規模で均一な磁場を持つ磁気化されたバリオンジェットが特徴です.
- これらのオーダーされた磁場は,最初のGRB爆発の後に長期間持続することができます.
- この発見は,GRBジェットのアドベクト,オーダーされた磁場モデルを裏付けている.
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