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OGLE-2015-BLG-1670Lb: A Cold Neptune beyond the Snow Line in the Provisional WFIRST Microlensing Survey Field

Ranc, Clement and Shvartzvald, Yossi (2019) OGLE-2015-BLG-1670Lb: A Cold Neptune beyond the Snow Line in the Provisional WFIRST Microlensing Survey Field. Astronomical Journal, 157 (6). Art. No. 232. ISSN 1538-3881.

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We present the analysis of the microlensing event OGLE-2015-BLG-1670, detected in a high-extinction field very close to the Galactic plane. Due to the dust extinction along the line of sight, this event was too faint to be detected before it reached the peak of magnification. The microlensing light-curve models indicate a high-magnification event with a maximum of A_(max) ≳ 200, very sensitive to planetary deviations. An anomaly in the light curve has been densely observed by the microlensing surveys MOA, KMTNet, and OGLE. From the light-curve modeling, we find a planetary anomaly characterized by a planet-to-host mass ratio, q = (1.00^(+0.18)_(-0.16) x 10^(-4), at the peak recently identified in the mass-ratio function of microlensing planets. Thus, this event is interesting to include in future statistical studies about planet demography. We have explored the possible degeneracies and find two competing planetary models resulting from the s ↔ 1/s degeneracy. However, because the projected separation is very close to s = 1, the physical implications for the planet for the two solutions are quite similar, except for the value of s. By combining the light-curve parameters with a Galactic model, we have estimated the planet mass M_2 = 17.9^(+9.6)_(-8.8) M⊕ and the lens distance D_L = 6.7^(+1.0)_(-1.3) kpc, corresponding to a Neptune-mass planet close to the Galactic bulge. Such events with a low absolute latitude (|b| ≈ 1.°1) are subject to both high extinction and more uncertain source distances, two factors that may affect the mass measurements in the provisional Wide Field Infrared Survey Telescope fields. More events are needed to investigate the potential trade-off between the higher lensing rate and the difficulty in measuring masses in these low-latitude fields.

Item Type:Article
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URLURL TypeDescription Paper
Ranc, Clement0000-0003-2388-4534
Shvartzvald, Yossi0000-0003-1525-5041
Alternate Title:A Cold Neptune Beyond the Snow Line in the Provisional WFIRST Field
Additional Information:© 2019 The American Astronomical Society. Received 2018 September 26; revised 2019 March 4; accepted 2019 March 26; published 2019 May 20. C.R. is grateful to M. T. Penny for providing him with the footprints of the provisional baseline WFIRST-WFI fields from Penny et al. (2019). This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI), and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. The MOA project is supported by JSPS KAKENHI grant Nos. JSPS24253004, JSPS26247023, JSPS23340064, JSPS15H00781, JP16H06287, and JP17H02871. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121, to A.U. The work by C.R. was supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by USRA through a contract with NASA. D.P.B., A.B., and C.R. were supported by NASA through grant NASA-80NSSC18K0274. Work by C.H. was supported by grant 2017R1A4A1015178 of the National Research Foundation of Korea. Work by A.G. was supported by AST-1516842 from the US NSF. A.G. received support from the European Research Council under the European Union's Seventh Framework Programme (FP 7) ERC Grant Agreement No. [321035]. I.G.S. and A.G. were supported by JPL grant 1500811. Software: Astropy (The Astropy Collaboration et al. 2018), GetDist (Lewis & Bridle 2002), Matplotlib (Hunter 2007), MuLAn (C. Ranc & A. Cassan 2018, in preparation), NumPy (Ph 2015), SciPy (Jones et al. 2001).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)JSPS24253004
Japan Society for the Promotion of Science (JSPS)JSPS26247023
Japan Society for the Promotion of Science (JSPS)JSPS23340064
Japan Society for the Promotion of Science (JSPS)JSPS15H00781
Japan Society for the Promotion of Science (JSPS)JP16H06287
Japan Society for the Promotion of Science (JSPS)JP17H02871
National Science Centre (Poland)MAESTRO 2014/14/A/ST9/00121
NASA Postdoctoral ProgramUNSPECIFIED
National Research Foundation of Korea2017R1A4A1015178
European Research Council (ERC)321035
Subject Keywords:gravitational lensing: micro – planets and satellites: detection
Issue or Number:6
Record Number:CaltechAUTHORS:20190521-082215129
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Official Citation:Clément Ranc et al 2019 AJ 157 232
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95624
Deposited By: Tony Diaz
Deposited On:21 May 2019 17:32
Last Modified:03 Oct 2019 21:15

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