THE EXTREME MICROLENSING EVENT OGLE-2007-BLG-224: TERRESTRIAL PARALLAX OBSERVATION OF A THICK-DISK BROWN DWARF
THE EXTREME MICROLENSING EVENT OGLE-2007-BLG-224: TERRESTRIAL PARALLAX OBSERVATION OF A THICK-DISK BROWN DWARF
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DOI：
10.1088/0004-637x/698/2/l147
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发表时间：
2009-04
期刊：
影响因子：
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通讯作者：
A. Gould;A. Gould;A. Udalski;B. Monard;K. Horne;S. Dong;N. Miyake;K. Sahu;David P. Bennett;Ł. Wyrzykowski;I. Soszyński;M. Szymański;M. Kubiak;G. Pietrzyński;G. Pietrzyński;O. Szewczyk;K. Ulaczyk;William H. Allen;G. Christie;D. Depoy;B. Gaudi;C. Han;C.‐U. Lee;J. Mccormick;T. Natusch;B.-G. Park;R. Pogge;A. Allan;M. Bode;D. Bramich;M. Burgdorf;Martin Dominik;Martin Dominik;S. Fraser;E. Kerins;C. Mottram;C. Snodgrass;I. A. Steele;R. Street;Y. Tsapras;F. Abe;I. Bond;C. Botzler;A. Fukui;K. Furusawa;J. Hearnshaw;Y. Itow;K. Kamiya;P. Kilmartin;A. Korpela;W. Lin;C. Ling;K. Masuda;Y. Matsubara;Yasushi Muraki;M. Nagaya;K. Ohnishi;Teppei Okumura;Y. Perrott;N. Rattenbury;T. Saito;T. Sako;L. Skuljan;D. Sullivan;T. Sumi;W. Sweatman;P. Tristram;P. Yock;M. Albrow;J. Beaulieu;J. Beaulieu;C. Coutures;H. Calitz;J. Caldwell;P. Fouqué;R. Martin;A. Williams
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文献类型：
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作者：
A. Gould;A. Gould;A. Udalski;B. Monard;K. Horne;S. Dong;N. Miyake;K. Sahu;David P. Bennett;Ł. Wyrzykowski;I. Soszyński;M. Szymański;M. Kubiak;G. Pietrzyński;G. Pietrzyński;O. Szewczyk;K. Ulaczyk;William H. Allen;G. Christie;D. Depoy;B. Gaudi;C. Han;C.‐U. Lee;J. Mccormick;T. Natusch;B.-G. Park;R. Pogge;A. Allan;M. Bode;D. Bramich;M. Burgdorf;Martin Dominik;Martin Dominik;S. Fraser;E. Kerins;C. Mottram;C. Snodgrass;I. A. Steele;R. Street;Y. Tsapras;F. Abe;I. Bond;C. Botzler;A. Fukui;K. Furusawa;J. Hearnshaw;Y. Itow;K. Kamiya;P. Kilmartin;A. Korpela;W. Lin;C. Ling;K. Masuda;Y. Matsubara;Yasushi Muraki;M. Nagaya;K. Ohnishi;Teppei Okumura;Y. Perrott;N. Rattenbury;T. Saito;T. Sako;L. Skuljan;D. Sullivan;T. Sumi;W. Sweatman;P. Tristram;P. Yock;M. Albrow;J. Beaulieu;J. Beaulieu;C. Coutures;H. Calitz;J. Caldwell;P. Fouqué;R. Martin;A. Williams
视差是测量天体距离的最基本技术。尽管地球视差是由喜帕恰斯（约公元前 140 年）在 2000 多年前开创的，用于测量到月球的距离，但地球的基线非常小，因此地球视差通常只能应用于太阳系中的物体。然而，存在一类极端的引力微透镜事件，其中地球视差的影响可以很容易地被检测到，因此可以测量透镜的距离、质量和横向速度。在这里，我们报告了对第一个此类极端微透镜事件 OGLE-2007-BLG-224 的观测，从中我们推断透镜是质量为 M = 0.056 ± 0.004 M☉ 的褐矮星，距离为 525 ± 40 pc，横向速度为 113 ± 21 km s−1。速度将透镜置于厚盘中，使其成为迄今为止检测到的质量最低的厚盘棕矮星。后续观测可能使人们能够观察到褐矮星本身发出的光，从而成为这些天体演化模型的重要约束，并有可能为了解亚恒星天体打开一扇新窗口。在这次事件中检测到厚盘棕矮星的先验概率较低，与其他观测的额外证据相结合，表明古老的亚恒星天体可能比之前假设的更常见。
Parallax is the most fundamental technique for measuring distances to astronomical objects. Although terrestrial parallax was pioneered over 2000 years ago by Hipparchus (ca. 140 B.C.E.) to measure the distance to the Moon, the baseline of the Earth is so small that terrestrial parallax can generally only be applied to objects in the Solar System. However, there exists a class of extreme gravitational microlensing events in which the effects of terrestrial parallax can be readily detected and so permit the measurement of the distance, mass, and transverse velocity of the lens. Here we report observations of the first such extreme microlensing event OGLE-2007-BLG-224, from which we infer that the lens is a brown dwarf of mass M = 0.056 ± 0.004 M☉, with a distance of 525 ± 40 pc and a transverse velocity of 113 ± 21 km s−1. The velocity places the lens in the thick disk, making this the lowest-mass thick-disk brown dwarf detected so far. Follow-up observations may allow one to observe the light from the brown dwarf itself, thus serving as an important constraint for evolutionary models of these objects and potentially opening a new window on substellar objects. The low a priori probability of detecting a thick-disk brown dwarf in this event, when combined with additional evidence from other observations, suggests that old substellar objects may be more common than previously assumed.