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Abstract

We report an analysis of the planetary microlensing event OGLE-2018-BLG-1185, which was observed by a large number of ground-based telescopes and by the Spitzer Space Telescope. The ground-based light curve indicates a low planet–host star mass ratio of q = (6.9 ± 0.2) × 10−5, which is near the peak of the wide-orbit exoplanet mass-ratio distribution. We estimate the host star and planet masses with a Bayesian analysis using the measured angular Einstein radius under the assumption that stars of all masses have an equal probability of hosting the planet. The flux variation observed by Spitzer is marginal, but still places a constraint on the microlens parallax. Imposing a conservative constraint that this flux variation should be ΔfSpz < 4 instrumental flux units yields a host mass of ${M}_{\mathrm{host}}={0.37}_{-0.21}^{+0.35}\ {M}_{\odot }$ and a planet mass of ${m}_{{\rm{p}}}={8.4}_{-4.7}^{+7.9}\ {M}_{\oplus }$. A Bayesian analysis including the full parallax constraint from Spitzer suggests smaller host star and planet masses of ${M}_{\mathrm{host}}={0.091}_{-0.018}^{+0.064}\ {M}_{\odot }$ and ${m}_{{\rm{p}}}={2.1}_{-0.4}^{+1.5}\ {M}_{\oplus }$, respectively. Future high-resolution imaging observations with the Hubble Space Telescope or Extremely Large Telescope could distinguish between these two scenarios and help reveal the planetary system properties in more detail.

Item Type: Article
Additional Information: The final version of this article and all relevant information related to it, including copyrights, can be found online at; https://iopscience.iop.org/article/10.3847/1538-3881/ac00ba
Subjects: Q Science > Q Science (General)
Q Science > QB Astronomy
Q Science > QB Astronomy > QB460 Astrophysics
Q Science > QB Astronomy > QB600 Planets. Planetology
Q Science > QC Physics
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Related URLs:
Depositing User: Symplectic
Date Deposited: 16 Sep 2021 10:08
Last Modified: 16 Sep 2021 10:08
URI: https://eprints.keele.ac.uk/id/eprint/10021

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