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A new type of ambiguity in the planet and binary interpretations of central perturbations of high-magnification gravitational microlensing events

Choi, J.-Y.; Shin, I.-G.; Han, C.; Udalski, A.; Sumi, T.; Gould, A.; Bozza, V.; Dominik, M.; Fouqué, P.; Horne, K.; Szymański, M. K.; Kubiak, M.; Soszyński, I.; Pietrzyński, G.; Poleski, R.; Ulaczyk, K.; Pietrukowicz, P.; Kozłowski, S.; Skowron, J.; Wyrzykowski, Ł.; Abe, F.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Chote, P.; Freeman, M.; Fukui, A.; Furusawa, K.; Itow, Y.; Kobara, S.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Ohmori, K.; Ohnishi, K.; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Suzuki, D.; Suzuki, K.; Sweatman, W. L.; Takino, S.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; Bramich, D. M.; Snodgrass, C.; Steele, I. A.; Street, R. A.; Tsapras, Y.; Alsubai, K. A.; Browne, P.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Dreizler, S.; Fang, X.-S.; Grundahl, F.; Gu, C.-H.; Hardis, S.; Harpsøe, K.; Hinse, T. C.; Hornstrup, A.; Hundertmark, M.; Jessen-Hansen, J.; Jørgensen, U. G.; Kains, N.; Kerins, E.; Liebig, C.; Lund, M.; Lunkkvist, M.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Skottfelt, J.; Southworth, J.; Surdej, J.; Tregloan-Reed, J.; Wambsganss, J.; Wertz, O.; Almeida, L. A.; Batista, V.; Christie, G.; DePoy, D. L.; Dong, Subo; Gaudi, B. S.; Henderson, C.; Jablonski, F.; Lee, C.-U.; McCormick, J.; McGregor, D.; Moorhouse, D.; Natusch, T.; Ngan, H.; Pogge, R. W.; Tan, T.-G.; Thornley, G.; Yee, J. C.; Albrow, M. D.; Bachelet, E.; Beaulieu, J.-P.; Brillant, S.; Cassan, A.; Cole, A. A.; Corrales, E.; Coutures, C.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Greenhill, J.; Kubas, D.; Marquette, J.-B.; Menzies, J. W.; Sahu, K. C. and Zub, M. (2012). A new type of ambiguity in the planet and binary interpretations of central perturbations of high-magnification gravitational microlensing events. Astrophysical Journal, 756(1), article no. 48.

DOI (Digital Object Identifier) Link: https://doi.org/10.1088/0004-637X/756/1/48
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Abstract

High-magnification microlensing events provide an important channel to detect planets. Perturbations near the peak of a high-magnification event can be produced either by a planet or a binary companion. It is known that central perturbations induced by both types of companions can be generally distinguished due to the essentially different magnification pattern around caustics. In this paper, we present a case of central perturbations for which it is difficult to distinguish the planetary and binary interpretations. The peak of a lensing light curve affected by this perturbation appears to be blunt and flat. For a planetary case, this perturbation occurs when the source trajectory passes the negative perturbation region behind the back end of an arrowhead-shaped central caustic. For a binary case, a similar perturbation occurs for a source trajectory passing through the negative perturbation region between two cusps of an astroid-shaped caustic. We demonstrate the degeneracy for two high-magnification events of OGLE-2011-BLG-0526 and OGLE-2011-BLG-0950/MOA-2011-BLG-336. For OGLE-2011-BLG-0526, the χ2 difference between the planetary and binary model is ~3, implying that the degeneracy is very severe. For OGLE-2011-BLG-0950/MOA-2011-BLG-336, the stellar binary model is formally excluded with Δχ2 ~ 105 and the planetary model is preferred. However, it is difficult to claim a planet discovery because systematic residuals of data from the planetary model are larger than the difference between the planetary and binary models. Considering that two events observed during a single season suffer from such a degeneracy, it is expected that central perturbations experiencing this type of degeneracy is common.

Item Type: Journal Item
Copyright Holders: 2012 The American Astronomical Society.
ISSN: 1538-4357
Extra Information: 9 pp.
Keywords: galaxies; galactic bulge; gravitational lensing
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Centre for Electronic Imaging (CEI)
Space
Item ID: 43059
Depositing User: Colin Snodgrass
Date Deposited: 29 May 2015 09:27
Last Modified: 07 Dec 2018 10:31
URI: http://oro.open.ac.uk/id/eprint/43059
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