A Brown Dwarf Microlens Candidate from the Second Phase of the Optical Gravitational Lensing Experiment
A Brown Dwarf Microlens Candidate from the Second Phase of the Optical Gravitational Lensing Experiment
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光学引力透镜实验第二阶段的候选褐矮星微透镜
DOI：
10.1086/373985
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
P. Woźniak
中科院分区：
文献类型：
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作者：
Martin C. Smith;S. Mao;P. Woźniak
我们描述了光学引力透镜实验第二阶段的微透镜事件的独特质量测定。事件 sc26_2218 非常明亮（基线星等 I = 15.10），似乎同时表现出视差和有限源效应。视差效应使我们能够确定观察者平面上的投影爱因斯坦半径 (E ≈ 3.8 AU)，而有限源效应使我们能够确定角源尺寸与角爱因斯坦半径的比率。由于恒星的角大小可以使用其颜色和星等来估计，因此我们可以确定爱因斯坦角半径 θE ≈ 0.1 mas。通过结合 E 和 θE，我们可以确定透镜质量 M ≈ 0.050M☉，与源距离无关。因此，该透镜体是一颗褐矮星候选者，距离约为 6.5 kpc。然而，“视差”特征很弱，因此我们不能完全忽视这些特征源自光源的二元旋转（这将阻止对透镜质量的任何估计）而不是视差的可能性。然而，这可以通过未来的光谱观测来测试。这一事件凸显了对明亮微透镜事件进行密集监测的科学回报，因为视差和有限源效应由于其高信噪比而可以更容易地识别。
We describe a unique mass determination for a microlensing event from the second phase of the Optical Gravitational Lensing Experiment. The event, sc26_2218, which is very bright (baseline magnitude I = 15.10), appears to exhibit both parallax and finite-source effects. The parallax effect allows us to determine the projected Einstein radius on the observer plane (E ≈ 3.8 AU), while the finite-source effect allows us to determine the ratio of the angular source size and the angular Einstein radius. As the angular size of the star can be estimated using its color and magnitude, we can hence determine the angular Einstein radius θE ≈ 0.1 mas. By combining E and θE, we can determine the lens mass M ≈ 0.050M☉, independent of the source distance. The lens is therefore a brown dwarf candidate, located at a distance of ~6.5 kpc. However, the "parallax" signature is weak, and so we cannot completely discount the possibility that these signatures originate from binary rotation of the source (which would prevent any estimate of the lens mass) rather than parallax. However, this can be tested by future spectroscopic observations. This event highlights the scientific returns for intense monitoring of bright microlensing events, since the parallax and finite-source effects can be more easily identified because of their high signal-to-noise ratios.