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

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Choi, J-Y and Shin, I-G and Han, C and Udalski, A and Sumi, T and Gould, A and Bozza, V and Dominik, M and Fouque, P and Horne, K and Szymanski, MK and Kubiak, M and Soszynski, I and Pietrzynski, G and Poleski, R and Ulaczyk, K and Pietrukowicz, P and Kozlowski, S and Skowron, J and Wyrzykowski, L and Abe, F and Bennett, DP and Bond, IA and Botzler, CS and Chote, P and Freeman, M and Fukui, A and Furusawa, K and Itow, Y and Kobara, S and Ling, CH and Masuda, K and Matsubara, Y and Miyake, N and Muraki, Y and Ohmori, K and Ohnishi, K and Rattenbury, NJ and Saito, T and Sullivan, DJ and Suzuki, D and Suzuki, K and Sweatman, WL and Takino, S and Tristram, PJ and Wada, K and Yock, PCM and Bramich, DM and Snodgrass, C and Steele, IA and Street, RA and Tsapras, Y and Alsubai, KA and Browne, P and Burgdorf, MJ and Calchi Novati, S and Dodds, P and Dreizler, S and Fang, X-S and Grundahl, F and Gu, C-H and Hardis, S and Harpsoe, K and Hinse, TC and Hornstrup, A and Hundertmark, M and Jessen-Hansen, J and Jorgensen, UG and Kains, N and Kerins, E and Liebig, C and Lund, M and Lunkkvist, M and Mancini, L and Mathiasen, M and Penny, MT and Rahvar, S and Ricci, D and Scarpetta, G and Skottfelt, J and Southworth, J and Surdej, J and Tregloan-Reed, J and Wambsganss, J and Wertz, O and Almeida, LA and Batista, V and Christie, G and Depoy, DL and Dong, S and Gaudi, BS and Henderson, C and Jablonski, F and Lee, C-U and McCormick, J and McGregor, D and Moorhouse, D and Natusch, T and Ngan, H and Pogge, RW and Tan, T-G and Thornley, G and Yee, JC and Albrow, MD and Bachelet, E and Beaulieu, J-P and Brillant, S and Cassan, A and Cole, AA and Corrales, E and Coutures, C and Dieters, S and Dominis Prester, D and Donatowicz, J and Greenhill, J and Kubas, D and Marquette, J-B and Menzies, JW and Sahu, KC and Zub, M, 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 48. ISSN 0004-637X (2012) [Refereed Article]

Copyright Statement

Copyright 2012 The American Astronomical Society

DOI: doi:10.1088/0004-637X/756/1/48

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 χ 2 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 &Deltaχ2 ~ 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 Details

Item Type:Refereed Article
Keywords:Galaxy, bulge, gravitational lensing, micro
Research Division:Physical Sciences
Research Group:Astronomical and Space Sciences
Research Field:Stellar Astronomy and Planetary Systems
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Physical Sciences
Author:Cole, AA (Dr Andrew Cole)
Author:Dieters, S (Dr Stefan Dieters)
Author:Greenhill, J (Dr John Greenhill)
ID Code:82641
Year Published:2012
Web of Science® Times Cited:9
Deposited By:Mathematics and Physics
Deposited On:2013-02-12
Last Modified:2017-11-06
Downloads:0

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