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Toward a Galactic Distribution of Planets. I. Methodology and Planet Sensitivities of the 2015 High-cadence Spitzer Microlens Sample

Zhu, Wei and Calchi Novati, S. and Beichman, C. and Carey, S. (2017) Toward a Galactic Distribution of Planets. I. Methodology and Planet Sensitivities of the 2015 High-cadence Spitzer Microlens Sample. Astronomical Journal, 154 (5). Art. No. 210. ISSN 1538-3881. doi:10.3847/1538-3881/aa8ef1.

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We analyze an ensemble of microlensing events from the 2015 Spitzer microlensing campaign, all of which were densely monitored by ground-based high-cadence survey teams. The simultaneous observations from Spitzer and the ground yield measurements of the microlensing parallax vector π_E, from which compact constraints on the microlens properties are derived, including ≾25% uncertainties on the lens mass and distance. With the current sample, we demonstrate that the majority of microlenses are indeed in the mass range of M dwarfs. The planet sensitivities of all 41 events in the sample are calculated, from which we provide constraints on the planet distribution function. In particular, assuming a planet distribution function that is uniform in log q, where q is the planet-to-star mass ratio, we find a 95% upper limit on the fraction of stars that host typical microlensing planets of 49%, which is consistent with previous studies. Based on this planet-free sample, we develop the methodology to statistically study the Galactic distribution of planets using microlensing parallax measurements. Under the assumption that the planet distributions are the same in the bulge as in the disk, we predict that ~1/3 of all planet detections from the microlensing campaigns with Spitzer should be in the bulge. This prediction will be tested with a much larger sample, and deviations from it can be used to constrain the abundance of planets in the bulge relative to the disk.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Zhu, Wei0000-0003-4027-4711
Calchi Novati, S.0000-0002-7669-1069
Beichman, C.0000-0002-5627-5471
Carey, S.0000-0002-0221-6871
Additional Information:© 2017 The American Astronomical Society. Received 2017 January 5; revised 2017 September 19; accepted 2017 September 19; published 2017 November 6. Work by W.Z. and A.G. was supported by NSF grant AST-1516842. Work by A.G. was also supported by JPL grant 1500811. Work by C.H. was supported by the Creative Research Initiative Program (2009-0081561) of the National Research Foundation of Korea. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to A.U. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This research has made use of the KMTNet system operated by KASI, and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Research Foundation of Korea2009-0081561
National Science Centre (Poland)2014/14/A/ST9/00121
Subject Keywords:gravitational lensing: micro – methods: statistical – planetary systems – planets and satellites: dynamical evolution and stability
Issue or Number:5
Record Number:CaltechAUTHORS:20171106-103226482
Persistent URL:
Official Citation:Wei Zhu et al 2017 AJ 154 210
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82978
Deposited By: Tony Diaz
Deposited On:06 Nov 2017 18:44
Last Modified:15 Nov 2021 19:54

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