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Title: 紊流混合對快中子捕獲過程(r-process)核合成的影響
Effect of turbulence mixing on R-process nucleosynthesis
Authors: 陳樂仁
Chen, Le-Ren
Contributors: 吳孟儒

Meng-Ru Wu
Jhih-Kai Yang
Shang-Fan Lee

Chen, Le-Ren
Keywords: 快過程核合成
r-process nucleosynthesis
neutron stars mergers(NSM)
short gamma-ray burst(sGRB)
Date: 2021
Issue Date: 2021-09-03
Abstract: 2017 年 8 月雙中子星合併 (BNSM) 事件 GW170817 的重力波和電磁輻射的觀測,不僅標誌著重力波多信使天文學的開始,也提供了不少的證據——證實雙中子星合併是由快中子補獲過程 (r-process 或 快過程) 的不穩定核衰變,來為短γ射線暴 (sGRB) 和千新星提供能量。



The detection of the gravitational wave and electromagnetic emissions from the binary neutron star merger (BNSM) event GW170817 in August 2017 not only marked the beginning of the gravitational-wave multi-messenger astronomy, but also provided evidence that BNSMs are the sources of the short gamma-ray bursts (sGRB) and kilonovae -- transients powered by the decay of unstable nuclei synthesis by the rapid neutron-capture process (r-process).

Recent studies suggested that mechanisms such as the sGRB jet penetrating the BNSM ejecta may result in large-scale turbulence inside the ejecta. Such turbulence can possibly cause composition mixing of different fluid components inside the ejecta, which might have different nucleosynthesis conditions. If the mixing caused by the turbulence happens during r-process, it may affect the resulting r-process yield predictions when compared to cases without mixing.

In this thesis, we use a simple two-fluid toy-model to study the impact of a potential composition mixing on the r-process nucleosynthesis outcome in BNSM events. We find that not only mixing itself will alter the final result, but also the time that mixing happen will make the result have different shape.

In particular, we find that if mixings happen when one of fluids is within the r-process while the other one has finished its r-process, mixing effect leads to sudden increase of free neutrons in the latter. Thus, it can help re-start the r-process in the fluid wherein the r-process had ceased. This allows the whole system to produce overall heavier nuclei when compared to the direct average of two unmixed fluids.
On the other hand, if mixings occur when both fluids are still within the r-process, then mixing let both fluids exchange their remaining free neutrons, make high $Y_e$ fluid get more free neutron to r-process, and low $Y_e$ fluid get lesser free neutron to r-process, where $Y_e\equiv n_e/n_b$, and $n_e$ ($n_b$) is the electron (baryon) number density. This will cause both fluids' final abundance distribution getting close toward each other, and it pretty similar to take a partial initial $Y_e$ averaging at begin of mixing system.
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Description: 碩士
Source URI:
Data Type: thesis
Appears in Collections:[應用物理研究所 ] 學位論文

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