arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2009.03571astro-ph.SRastro-ph.GA
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小麦哲伦星云中逃逸的OB星:动力学与超新星抛射

Runaway OB Stars in the Small Magellanic Cloud: Dynamical Versus Supernova Ejections

J. Dorigo Jones, M. S. Oey, K. Paggeot, N. Castro, M. Moe

摘要:

逃逸的OB星通过两种机制从它们的母星团中弹射出来,这两种机制都涉及多颗恒星:动力学弹射情景(DES)和双星超新星情景(BSS)。我们约束的相对贡献,这两个弹射机制在小麦哲伦云(SMC)使用的数据为304场OB星的空间完整,失控和孤立的O型星光谱调查的SMC(RIOTS 4)。我们获得恒星质量和投影旋转速度$v_r\sin i $的样品使用RIOTS 4光谱,并使用横向速度$v_{\rm loc}$从$\it{Gaia}$ DR 2自行。运动学分析的群众,$v_r\sin i $,非紧凑型双星,高质量的X射线双星,和Oe/Be星在很大程度上支持DES和BSS人口的统计特性的预测。我们发现,动力学喷射占主导地位的超新星喷射的一个因素的$\sim 2-3$在SMC,我们的研究结果表明,DES逃逸和二进制喷射的频率很高。被视为BSS失控的对象还包括由SN踢重新加速的二进制文件的两步喷射。我们发现,两步离家出走可能占主导地位的BSS失控人口。我们的研究结果进一步表明,任何贡献,从$\it{in-situ}$领域OB星的形成是小的。最后,我们的数据强烈支持后质量转移模型的起源经典的Oe/Be星,提供了一个简单的解释双峰的$v_r\sin i $分布和高,近临界,Oe/Be旋转速度。Oe/Be星与BSS预测的密切对应意味着发射线盘是长寿命的。

英文摘要:

Runaway OB stars are ejected from their parent clusters via two mechanisms, both involving multiple stars: the dynamical ejection scenario (DES) and the binary supernova scenario (BSS). We constrain the relative contributions from these two ejection mechanisms in the Small Magellanic Cloud (SMC) using data for 304 field OB stars from the spatially complete, Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4). We obtain stellar masses and projected rotational velocities $v_r\sin i $ for the sample using RIOTS4 spectra, and use transverse velocities $v_{\rm loc}$ from $\it{Gaia}$ DR2 proper motions. Kinematic analyses of the masses, $v_r\sin i $, non-compact binaries, high-mass X-ray binaries, and Oe/Be stars largely support predictions for the statistical properties of the DES and BSS populations. We find that dynamical ejections dominate over supernova ejections by a factor of $\sim 2-3$ in the SMC, and our results suggest a high frequency of DES runaways and binary ejections. Objects seen as BSS runaways also include two-step ejections of binaries that are reaccelerated by SN kicks. We find that two-step runaways likely dominate the BSS runaway population. Our results further imply that any contribution from $\it{in-situ}$ field OB star formation is small. Finally, our data strongly support the post-mass-transfer model for the origin of classical Oe/Be stars, providing a simple explanation for the bimodality in the $v_r\sin i $ distribution and high, near-critical, Oe/Be rotation velocities. The close correspondence of Oe/Be stars with BSS predictions implies that the emission-line disks are long-lived.

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