文章基本信息

标题：Spectroscopic characterisation of microlensing events - Towards a new interpretation of OGLE-2011-BLG-0417
其他标题：Towards a new interpretation of OGLE-2011-BLG-0417⋆⋆⋆
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作者：A. Santerne ; A. Santerne ; J.-P. Beaulieu 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2016
卷号：595
页码：1-8
DOI：10.1051/0004-6361/201527710
语种：English
出版社：EDP Sciences
摘要：The microlensing event OGLE-2011-BLG-0417 is an exceptionally bright lens binary that was predicted to present radial velocity variation at the level of several km s-1. Pioneer radial velocity follow-up observations with the UVES spectrograph at the ESO−VLT of this system clearly ruled out the large radial velocity variation, leaving a discrepancy between the observation and the prediction. In this paper, we further characterise the microlensing system by analysing its spectral energy distribution (SED) derived using the UVES spectrum and new observations with the ARCoIRIS (CTIO) near-infrared spectrograph and the Keck adaptive optics instrument NIRC2 in the J, H, and Ks-bands. We determine the mass and distance of the stars independently from the microlensing modelling. We find that the SED is compatible with a giant star in the Galactic bulge and a foreground star with a mass of 0.94 ± 0.09 M⊙ at a distance of 1.07 ± 0.24 kpc. We find that this foreground star is likely the lens. Its parameters are not compatible with the ones previously reported in the literature (0.52 ± 0.04 M⊙ at 0.95 ± 0.06 kpc), based on the microlensing light curve. A thoughtful re-analysis of the microlensing event is mandatory to fully understand the reason of this new discrepancy. More importantly, this paper demonstrates that spectroscopic follow-up observations of microlensing events are possible and provide independent constraints on the parameters of the lens and source stars, hence breaking some degeneracies in the analysis. UV-to-NIR low-resolution spectrographs like X-shooter (ESO−VLT) could substantially contribute to this follow-up efforts, with magnitude limits above all microlensing events detected so far.
关键词：techniques: spectroscopic;techniques: high angular resolution;stars: individual: OGLE-2011-BLG-0417