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The possible disappearance of a massive star in the low-metallicity galaxy PHL 293B
Monthly Notices of the Royal Astronomical Society ( IF 4.7 ) Pub Date : 2020-06-30 , DOI: 10.1093/mnras/staa1629
Andrew P Allan 1 , Jose H Groh 1 , Andrea Mehner 2 , Nathan Smith 3 , Ioana Boian 1 , Eoin J Farrell 1 , Jennifer E Andrews 3
Affiliation  

We investigate a suspected very massive star in one of the most metal-poor dwarf galaxies, PHL~293B. Excitingly, we find the sudden disappearance of the stellar signatures from our 2019 spectra, in particular the broad H lines with P~Cygni profiles that have been associated with a massive luminous blue variable (LBV) star. Such features are absent from our spectra obtained in 2019 with the ESPRESSO and X-shooter instruments of the ESO's VLT. We compute radiative transfer models using CMFGEN that fit the observed spectrum of the LBV and are consistent with ground-based and archival Hubble Space Telescope photometry. Our models show that during 2001--2011 the LBV had a luminosity $L_* = 2.5-3.5 \times 10^6 ~L_{\odot}$, a mass-loss rate $\dot{M} = 0.005-0.020 ~M_{\odot}$~yr$^{-1}$, a wind velocity of 1000~km~s$^{-1}$, and effective and stellar temperatures of $T_\mathrm{eff} = 6000-6800$~K and $T_\mathrm{*}=9500-15000$~K. These stellar properties indicate an eruptive state. We consider two main hypotheses for the absence of the broad emission components from the spectra obtained since 2011. One possibility is that we are seeing the end of an LBV eruption of a surviving star, with a mild drop in luminosity, a shift to hotter effective temperatures, and some dust obscuration. Alternatively, the LBV could have collapsed to a massive black hole without the production of a bright supernova.

中文翻译:

低金属度星系PHL 293B中一颗大质量恒星可能消失

我们在最缺乏金属的矮星系 PHL~293B 中调查了一颗疑似质量非常大的恒星。令人兴奋的是,我们发现 2019 年光谱中的恒星特征突然消失了,特别是与大质量明亮蓝色变星 (LBV) 相关的带有 P~Cygni 剖面的宽 H 线。我们在 2019 年使用 ESO 的 VLT 的 ESPRESSO 和 X-shooter 仪器获得的光谱中没有这些特征。我们使用 CMFGEN 计算辐射传输模型,该模型适合 LBV 的观测光谱,并且与基于地面和存档的哈勃太空望远镜光度测量一致。我们的模型表明,在 2001--2011 年期间,LBV 的光度 $L_* = 2.5-3.5 \times 10^6 ~L_{\odot}$,质量损失率 $\dot{M} = 0.005-0.020 ~ M_{\odot}$~yr$^{-1}$,风速1000~km~s$^{-1}$,$T_\mathrm{eff} = 6000-6800$~K 和 $T_\mathrm{*}=9500-15000$~K 的有效和恒星温度。这些恒星特性表明处于喷发状态。对于自 2011 年以来获得的光谱中不存在宽发射分量,我们考虑了两个主要假设。一种可能性是我们正在看到一颗幸存恒星的 LBV 喷发结束,光度略有下降,转向更热的有效温度和一些灰尘遮蔽。或者,LBV 可能已经坍缩成一个巨大的黑洞,而不会产生明亮的超新星。一种可能性是,我们正在看到一颗幸存恒星的 LBV 喷发结束,光度略有下降,有效温度转移到更高的温度,以及一些尘埃被遮蔽。或者,LBV 可能已经坍缩成一个巨大的黑洞,而不会产生明亮的超新星。一种可能性是,我们正在看到一颗幸存恒星的 LBV 喷发结束,光度略有下降,有效温度转移到更高的温度,以及一些尘埃被遮蔽。或者,LBV 可能已经坍缩成一个巨大的黑洞,而不会产生明亮的超新星。
更新日期:2020-06-30
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