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OGLE-2015-BLG-0479LA,B: Binary Gravitational Microlens Characterized by Simultaneous Ground-based and Space-based Observations

Han, C. and Beichman, C. and Calchi Novati, S. and Carey, S. (2016) OGLE-2015-BLG-0479LA,B: Binary Gravitational Microlens Characterized by Simultaneous Ground-based and Space-based Observations. Astrophysical Journal, 828 (1). Art. No. 53. ISSN 0004-637X.

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We present a combined analysis of the observations of the gravitational microlensing event OGLE-2015-BLG-0479 taken both from the ground and by the Spitzer Space Telescope. The light curves seen from the ground and from space exhibit a time offset of ~13 days between the caustic spikes, indicating that the relative lens-source positions seen from the two places are displaced by parallax effects. From modeling the light curves, we measure the space-based microlens parallax. Combined with the angular Einstein radius measured by analyzing the caustic crossings, we determine the mass and distance of the lens. We find that the lens is a binary composed of two G-type stars with masses of ~1.0 M⊙ and ~0.9 M⊙ located at a distance of ~3 kpc. In addition, we are able to constrain the complete orbital parameters of the lens thanks to the precise measurement of the microlens parallax derived from the joint analysis. In contrast to the binary event OGLE-2014-BLG-1050, which was also observed by Spitzer, we find that the interpretation of OGLE-2015-BLG-0479 does not suffer from the degeneracy between (±, ±) and (±, ∓) solutions, confirming that the four-fold parallax degeneracy in single-lens events collapses into the two-fold degeneracy for the general case of binary-lens events. The location of the blend in the color–magnitude diagram is consistent with the lens properties, suggesting that the blend is the lens itself. The blend is bright enough for spectroscopy and thus this possibility can be checked from future follow-up observations.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Beichman, C.0000-0002-5627-5471
Calchi Novati, S.0000-0002-7669-1069
Carey, S.0000-0002-0221-6871
Additional Information:© 2016 The American Astronomical Society. Received 2016 April 2; revised 2016 June 29; accepted 2016 June 30; published 2016 August 29. Work by C. Han was supported by the Creative Research Initiative Program (2009-0081561) of 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. The OGLE Team thanks Profs. M. Kubiak and G. Pietrzyński, former members of the OGLE team, for their contribution to the collection of the OGLE photometric data over the past years. Work by A.G. was supported by JPL grant 1500811. Work by J.C.Y. was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. Work by C.B.H. and Y.S. was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by Universities Space Research Association through a contract with NASA. The Spitzer Team thanks Christopher S. Kochanek for graciously trading us his allocated observing time on the CTIO 1.3 m during the Spitzer campaign. We acknowledge the high-speed internet service (KREONET) provided by Korea Institute of Science and Technology Information (KISTI).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Research Foundation of KoreaUNSPECIFIED
National Science Centre (Poland)MAESTRO 2014/14/A/ST9/00121
Subject Keywords:binaries: general – gravitational lensing: micro
Issue or Number:1
Record Number:CaltechAUTHORS:20160831-082551535
Persistent URL:
Official Citation:C. Han et al 2016 ApJ 828 53
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70051
Deposited By: Tony Diaz
Deposited On:31 Aug 2016 16:41
Last Modified:24 Feb 2020 10:30

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