A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192
A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192
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DOI：
10.1086/589940
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发表时间：
2008-05
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通讯作者：
D. Bennett;I. Bond;A. Udalski;T. Sumi;F. Abe;A. Fukui;K. Furusawa;J. Hearnshaw;S. Holderness;Y. Itow;K. Kamiya;A. Korpela;P. Kilmartin;W. Lin;C. Ling;K. Masuda;Y. Matsubara;N. Miyake;Y. Muraki;M. Nagaya;Teppei Okumura;K. Ohnishi;Y. Perrott;N. Rattenbury;T. Sako;T. Saito;S. Sato;L. Skuljan;D. Sullivan;W. Sweatman;P. Tristram;P. Yock;M. Kubiak;M. Szymański;G. Pietrzyński;I. Soszyński;O. Szewczyk;Ł. Wyrzykowski;K. Ulaczyk;V. Batista;J. Beaulieu;S. Brillant;A. Cassan;P. Fouqué;P. Kervella;D. Kubas;J. Marquette
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作者：
D. Bennett;I. Bond;A. Udalski;T. Sumi;F. Abe;A. Fukui;K. Furusawa;J. Hearnshaw;S. Holderness;Y. Itow;K. Kamiya;A. Korpela;P. Kilmartin;W. Lin;C. Ling;K. Masuda;Y. Matsubara;N. Miyake;Y. Muraki;M. Nagaya;Teppei Okumura;K. Ohnishi;Y. Perrott;N. Rattenbury;T. Sako;T. Saito;S. Sato;L. Skuljan;D. Sullivan;W. Sweatman;P. Tristram;P. Yock;M. Kubiak;M. Szymański;G. Pietrzyński;I. Soszyński;O. Szewczyk;Ł. Wyrzykowski;K. Ulaczyk;V. Batista;J. Beaulieu;S. Brillant;A. Cassan;P. Fouqué;P. Kervella;D. Kubas;J. Marquette
我们报道了在微透镜事件MOA-2007-BLG-192中探测到一颗质量比为q ~ 2 × 10−4的系外行星。最合适的微透镜模型显示了微透镜视差和有限源效应，这些可以结合起来得到主恒星的透镜质量为M = 0.060+ 0.028−0.021 M☉，行星的透镜质量为M = 3.3+ 4.9−1.6 M⊕。然而，对行星偏差的观测覆盖是稀疏和不完整的，并且在没有测量源星颜色的情况下估计了源的半径。因此，质量比和有限源测量的2 σ极限很弱。然而，微透镜视差信号明显倾向于一个次恒星质量的行星宿主，并且光曲线中有限源效应的测量支持了这一结论。用甚大望远镜（VLT） NACO仪器拍摄的自适应光学图像与一颗透镜星一致，该透镜星要么是褐矮星，要么是主序星底部的一颗恒星。后续的VLT和/或哈勃太空望远镜（HST）观测将要么确认主恒星是一颗褐矮星，要么探测到低质量透镜星，并精确确定其质量。无论哪种情况，透镜星MOA-2007-BLG-192L是已知质量最低的伴星，而行星MOA-2007-BLG-192Lb可能是迄今为止发现的质量最低的系外行星，除了质量最低的脉冲星行星。
We report the detection of an extrasolar planet of mass ratio q ∼ 2 × 10−4 in microlensing event MOA-2007-BLG-192. The best-fit microlensing model shows both the microlensing parallax and finite source effects, and these can be combined to obtain the lens masses of M = 0.060+ 0.028−0.021 M☉ for the primary and m = 3.3+ 4.9−1.6 M⊕ for the planet. However, the observational coverage of the planetary deviation is sparse and incomplete, and the radius of the source was estimated without the benefit of a source star color measurement. As a result, the 2 σ limits on the mass ratio and finite source measurements are weak. Nevertheless, the microlensing parallax signal clearly favors a substellar mass planetary host, and the measurement of finite source effects in the light curve supports this conclusion. Adaptive optics images taken with the Very Large Telescope (VLT) NACO instrument are consistent with a lens star that is either a brown dwarf or a star at the bottom of the main sequence. Follow-up VLT and/or Hubble Space Telescope (HST) observations will either confirm that the primary is a brown dwarf or detect the low-mass lens star and enable a precise determination of its mass. In either case, the lens star, MOA-2007-BLG-192L, is the lowest mass primary known to have a companion with a planetary mass ratio, and the planet, MOA-2007-BLG-192Lb, is probably the lowest mass exoplanet found to date, aside from the lowest mass pulsar planet.