On the Possibility of Stellar Lenses in the Black Hole Candidate Microlensing Events MACHO-96-BLG-5 and MACHO-98-BLG-6
On the Possibility of Stellar Lenses in the Black Hole Candidate Microlensing Events MACHO-96-BLG-5 and MACHO-98-BLG-6
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DOI：
10.3847/1538-4357/abee83
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
F. Abdurrahman;Haynes Stephens;Jessica R. Lu
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文献类型：
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作者：
F. Abdurrahman;Haynes Stephens;Jessica R. Lu
虽然银河系中可能有大量的恒星质量黑洞（N = 108-109），但迄今为止只发现了20个，都是在吸积双星系统中。引力微透镜是一种被提出来寻找孤立的黑洞的技术，这些黑洞还没有被探测到。两个特殊的微透镜事件，分别是1996年和1998年在透镜-源最小角距附近观测到的M90 -1996-BLG-5（M96-B5）和M90 -1998-BLG-6（M98-B6），它们具有很长的爱因斯坦穿越时间（>300天），将透镜确定为候选黑洞。20年过去了，因为这些事件的时间透镜源最近的办法，表明如果透镜和源都是发光的，如果他们的相对自行是足够大的，这两个组件应该是空间可分辨的。在这项工作中，我们试图消除这些事件的恒星透镜的可能性：（1）使用凯克近红外自适应光学图像搜索一个潜在的现在解决，发光的透镜，和（2）检查多波段测光的来源，以寻找通量的贡献，从一个潜在的未解决，发光的透镜。我们将来自NIRC 2图像的联合收割机检测限与光变曲线数据相结合，以排除所有非BH透镜，使M96-B5的透镜-源相对自行大于0.81 mas yr−1，M98-B6的透镜-源相对自行大于2.48 mas yr−1。此外，我们使用WFPC 2宽带图像，以消除恒星透镜在任何自行的可能性。我们提出了我们的各种分析所允许的非BH的可能性的范围很窄。最后，我们建议未来的观察，以限制剩余的参数空间，通过在这项工作中开发的方法。
Although stellar-mass black holes (BHs) are likely to be abundant in the Milky Way (N = 108–109), only 20 have been detected to date, all in accreting binary systems. Gravitational microlensing is a proposed technique to search for isolated BHs, which have not yet been detected. Two specific microlensing events, MACHO-1996-BLG-5 (M96-B5) and MACHO-1998-BLG-6 (M98-B6), initially observed near the lens-source minimum angular separation in 1996 and 1998, respectively, have long Einstein crossing times (>300 days), identifying the lenses as candidate black holes. Twenty years have elapsed since the time of lens-source closest approach for each of these events, indicating that if the lens and source are both luminous, and if their relative proper motion is sufficiently large, the two components should be spatially resolvable. In this work, we attempt to eliminate the possibility of a stellar lens for these events by: (1) using Keck near-infrared adaptive optics images to search for a potentially now-resolved, luminous lens, and (2) examining multi-band photometry of the source to search for flux contributions from a potentially unresolved, luminous lens. We combine detection limits from NIRC2 images with light-curve data to eliminate all non-BH lenses for relative lens-source proper motions above 0.81 mas yr−1 for M96-B5, and 2.48 mas yr−1 for M98-B6. Furthermore, we use WFPC2 broad-band images to eliminate the possibility of stellar lenses at any proper motion. We present the narrow range of non-BH possibilities permitted by our varied analyses. Finally, we suggest future observations to constrain the remaining parameter space via the methods developed in this work.