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MOA-2009-BLG-319Lb: A Sub-Saturn Planet inside the Predicted Mass Desert

Terry, Sean K. and Bhattacharya, Aparna and Bennett, David P. and Beaulieu, Jean-Philippe and Koshimoto, Naoki and Blackman, Joshua W. and Bond, Ian A. and Cole, Andrew A. and Henderson, Calen B. and Lu, Jessica R. and Marquette, Jean Baptiste and Ranc, Clément and Vandorou, Aikaterini (2021) MOA-2009-BLG-319Lb: A Sub-Saturn Planet inside the Predicted Mass Desert. Astronomical Journal, 161 (2). Art. No. 54. ISSN 1538-3881. doi:10.3847/1538-3881/abcc60.

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We present an adaptive optics (AO) analysis of images from the Keck II telescope NIRC2 instrument of the planetary microlensing event MOA-2009-BLG-319. The ~10 yr baseline between the event and the Keck observations allows the planetary host star to be detected at a separation of 66.5 ± 1.7 mas from the source star, consistent with the light-curve model prediction. The combination of the host star brightness and light-curve parameters yields host star and planet masses of M_(host) = 0.524 ± 0.048 M_⊙ and m_p = 67.3 ± 6.2 M_⊕ at a distance of D_L = 7.1 ± 0.7 kpc. The star−planet projected separation is 2.03 ± 0.21 au. The planet-to-star mass ratio of this system, q = (3.857 ± 0.029) × 10⁻⁴, places it in the predicted "planet desert" at 10⁻⁴ < q < 4 × 10⁻⁴ according to the runaway gas accretion scenario of the core accretion theory. Seven of the 30 planets in the Suzuki et al. sample fall in this mass ratio range, and this is the third with a measured host mass. All three of these host stars have masses of 0.5 ≤ M_(host)/M_⊙ ≤ 0.7, which implies that this predicted mass ratio gap is filled with planets that have host stars within a factor of two of 1 M_⊙. This suggests that runaway gas accretion does not play a major role in determining giant planet masses for stars somewhat less massive than the Sun. Our analysis has been accomplished with a modified DAOPHOT code that has been designed to measure the brightness and positions of closely blended stars. This will aid in the development of the primary method that the Nancy Grace Roman Space Telescope mission will use to determine the masses of microlens planets and their hosts.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Terry, Sean K.0000-0002-5029-3257
Bennett, David P.0000-0001-8043-8413
Beaulieu, Jean-Philippe0000-0003-0014-3354
Koshimoto, Naoki0000-0003-2302-9562
Blackman, Joshua W.0000-0001-5860-1157
Cole, Andrew A.0000-0003-0303-3855
Henderson, Calen B.0000-0001-8877-9060
Lu, Jessica R.0000-0001-9611-0009
Ranc, Clément0000-0003-2388-4534
Vandorou, Aikaterini0000-0002-9881-4760
Additional Information:© 2021. The American Astronomical Society. Received 2020 September 15; revised 2020 November 10; accepted 2020 November 16; published 2021 January 6. The authors thank Dr. Peter Stetson for advice on modifications to the DAOPHOT-II software. We also thank the anonymous referee for constructive comments that led to a stronger manuscript. This work was performed in part under contract with the Center for Research and Exploration in Space Sciences and Technologies (CRESST-II). The Keck observations were supported by a NASA Keck PI Data Award, 80NSSC18K0793, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. D.P.B., A.B., and C.R. were supported by NASA through grant NASA-80NSSC18K0274. This work was supported by the University of Tasmania through the UTAS Foundation and the endowed Warren Chair in Astronomy and the ANR COLD-WORLDS (ANR-18-CE31-0002). Work by N.K. is supported by JSPS KAKENHI grant No. JP18J00897. This research was also supported in part by the Australian government through the Australian Research Council Discovery Program (project No. 200101909) grant awarded to Cole and Beaulieu. This work made use of data from the Astro Data Lab at NSF's OIR Lab, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation. Some of this research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under the Exoplanet Exploration Program. Software: DAOPHOT-II (Stetson 1987), DAOPHOT-MCMC (this work), gnuplot, Matplotlib (Hunter 2007), Numpy (Oliphant 2006).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
University of TasmaniaUNSPECIFIED
Agence Nationale pour la Recherche (ANR)ANR-18-CE31-0002
Japan Society for the Promotion of Science (JSPS)JP18J00897
Australian Research Council200101909
Subject Keywords:Exoplanets ; Gravitational microlensing ; Computational methods
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanets (498); Gravitational microlensing (672); Computational methods (1965)
Record Number:CaltechAUTHORS:20210112-151232135
Persistent URL:
Official Citation:Sean K. Terry et al 2021 AJ 161 54
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107447
Deposited By: George Porter
Deposited On:13 Jan 2021 16:16
Last Modified:16 Nov 2021 19:03

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