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Revisiting MOA 2013-BLG-220L: a solar-type star with a cold super-Jupiter companion

Vandorou, A, Bennett, DP, Beaulieu, J-P, Alard, C, Blackman, JW ORCID: 0000-0001-5860-1157, Cole, AA ORCID: 0000-0003-0303-3855, Bhattacharya, A, Bond, IA, Koshimoto, N and Marquette, J-B 2020 , 'Revisiting MOA 2013-BLG-220L: a solar-type star with a cold super-Jupiter companion' , Astronomical Journal, vol. 160, no. 3 , pp. 1-8 , doi: 10.3847/1538-3881/aba2d3.

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We present the analysis of high-resolution images of MOA-2013-BLG-220, taken with the Keck adaptive optics system six years after the initial observation, identifying the lens as a solar-type star hosting a super-Jupiter-mass planet. The masses of planets and host stars discovered by microlensing are often not determined from light-curve data, while the star–planet mass ratio and projected separation in units of Einstein ring radius are well measured. High-resolution follow-up observations after the lensing event is complete can resolve the source and lens. This allows direct measurements of flux, and the amplitude and direction of proper motion, giving strong constraints on the system parameters. Due to the high relative proper motion, μrel,Geo = 12.62 ± 0.11 mas yr-1, the source and lens were resolved in 2019, with a separation of 77.1 ± 0.5 mas. Thus, we constrain the lens flux to KKeck,lens = 17.92 ± 0.02. By combining constraints from the model and Keck flux, we find the lens mass to be ML = 0.88 ± 0.05 M⊙ at DL = 6.72 ± 0.59 kpc. With a mass ratio of q = (3.00 ± 0.03) x 10-3 the planet’s mass is determined to be MP = 2.74 ± 0.17 MJ at a separation of r⊥ = 3.03 ± 0.27 au. The lens mass is much higher than the prediction made by Bayesian analysis that assumes all stars have an equal probability to host a planet of the measured mass ratio, and suggests that planets with mass ratios of a few times 10-3 are more common orbiting massive stars. This demonstrates the importance of high-resolution follow-up observations for testing theories like these.

Item Type: Article
Authors/Creators:Vandorou, A and Bennett, DP and Beaulieu, J-P and Alard, C and Blackman, JW and Cole, AA and Bhattacharya, A and Bond, IA and Koshimoto, N and Marquette, J-B
Keywords: exoplanets; gravitational microlensing; proper motions
Journal or Publication Title: Astronomical Journal
Publisher: Univ Chicago Press
ISSN: 0004-6256
DOI / ID Number: 10.3847/1538-3881/aba2d3
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© 2020. The American Astronomical Society

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