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标题：Twenty years of photometric microlensing events predicted by Gaia DR2
其他标题：Potential planet-hosting lenses within 100 pc⋆
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作者：Alexander J. Mustill ; Melvyn B. Davies ; Lennart Lindegren 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：617
DOI：10.1051/0004-6361/201833527
语种：English
出版社：EDP Sciences
摘要：Context.GaiaData Release 2 (DR2) offers unparalleled precision on stars’ parallaxes and proper motions. This allows the prediction of microlensing events for which the lens stars (and any planets they possess) are nearby and may be well studied and characterised.Aims.We identify a number of potential microlensing events that will occur before the year 2035.5, 20 years from theGaiaDR2 reference epoch.Methods.We queryGaiaDR2 for potential lenses within 100 pc, extract parallaxes and proper motions of the lenses and background sources, and identify potential lensing events. We estimate the lens masses from Priam effective temperatures and use these to calculate peak magnifications and the size of the Einstein radii relative to the lens stars’ habitable zones.Results.We identify seven future events with a probability >10% of an alignment within one Einstein radius. Of particular interest is DR2 5918299904067162240 (WISE J175839.20–583931.6), magnitudeG= 14.9, which will lens aG= 13.9 background star in early 2030, with a median 23% net magnification. Other pairs are typically fainter, hampering characterisation of the lens (if the lens is faint) or the ability to accurately measure the magnification (if the source is much fainter than the lens). Of timely interest is DR2 4116504399886241792 (2MASS J17392440–2327071), which will lens a background star in July 2020, albeit with weak net magnification (0.03%). Median magnifications for the other five high-probability events range from 0.3% to 5.3%. The Einstein radii for these lenses are one to ten times the radius of the habitable zone, allowing these lensing events to pick out cold planets around the ice line, and filling a gap between transit and current microlensing detections of planets around very low-mass stars.Conclusions.We provide a catalogue of the predicted events to aid future characterisation efforts. Current limitations include a lack of many high-proper-motion objects inGaiaDR2 and often large uncertainties on the proper motions of the background sources (or only two-parameter solutions). Both of these deficiencies will be rectified withGaiaDR3 in 2020. Further characterisation of the lenses is also warranted to better constrain their masses and predict the photometric magnifications.
关键词：engravitational lensing: microastrometryplanets and satellites: detection