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Moa-2010-BLG-073L: An M-dwarf with a substellar companion at the planet/brown dwarf boundary


Street, RA and Choi, J-Y and Tsapras, Y and Han, C and Furusawa, K and Hundertmark, M and Gould, A and Sumi, T and Bond, IA and Wouters, D and Zellem, R and Udalski, A and Snodgrass, C and Horne, K and Dominik, M and Browne, P and Kains, N and Bramich, DM and Bajek, D and Steele, IA and Ipatov, S and Abe, F and Bennett, DP and Botzler, CS and Chote, P and Freeman, M and Fukui, A and Harris, P and Itow, Y and Ling, CH and Masuda, K and Matsubara, Y and Miyake, N and Muraki, Y and Nagayama, T and Nishimaya, S and Ohnishi, K and Rattenbury, N and Saito, T and Sullivan, DJ and Suzuki, D and Sweatman, WL and Tristram, PJ and Wada, K and Yock, PCM and Szymanski, MK and Kubiak, M and Pietrzynski, G and Soszynski, I and Poleski, R and Ulaczyk, K and Wyrzykowski, L and Yee, J and Dong, S and Shin, I-G and Lee, C-U and Skowron, J and Andrade De Almeida, L and DePoy, DL and Gaudi, BS and Hung, L-W and Jablonski, F and Kaspi, S and Klein, N and Hwang, K-H and Koo, J-R and Maoz, D and Munoz, JA and Pogge, RW and Polishhook, D and Shporer, A and McCormick, J and Christie, G and Natusch, T and Allen, B and Drummond, J and Moorhouse, D and Thornley, G and Knowler, M and Bos, M and Bolt, G and Beaulieu, J-P and Albrow, MD and Batista, V and Brillant, S and Caldwell, JAR and Cassan, A and Cole, A and Corrales, E and Coutures, C and Dieters, S and Dominis Prester, D and Donatowicz, J and Fouque, P and Bachelet, E and Greenhill, J and Kane, SR and Kubas, D and Marquette, J-B and Martin, R and Menzies, J and Pollard, KR and Sahu, KC and Wambsganss, J and Williams, A and Zub, M and Alsubai, KA and Bozza, V and Burgdorf, MJ and Calchi Novati, S and Dodds, P and Dreizler, S and Finet, F and Gerner, T and Hardis, S and Harpsoe, K and Hessman, F and Hinse, TC and Jorgensen, UG and Kerins, E and Liebig, C and Mancini, L and Mathiasen, M and Penny, MT and Proft, S and Rahvar, S and Ricci, D and Scarpetta, G and Schafer, S and Schonebeck, F and Southworth, J and Surdej, J, Moa-2010-BLG-073L: An M-dwarf with a substellar companion at the planet/brown dwarf boundary, Astrophysical Journal, 763, (1) Article 67. ISSN 0004-637X (2013) [Refereed Article]

Copyright Statement

Copyright 2013 The American Astronomical Society

DOI: doi:10.1088/0004-637X/763/1/67


We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010 March 18. This event was remarkable because the source was previously known to be photometrically variable. Analyzing the pre-event source light curve, we demonstrate that it is an irregular variable over timescales >200 days. Its dereddened color, (V – I)S,0, is 1.221 ± 0.051 mag, and from our lens model we derive a source radius of 14.7 ± 1.3 R, suggesting that it is a red giant star. We initially explored a number of purely microlensing models for the event but found a residual gradient in the data taken prior to and after the event. This is likely to be due to the variability of the source rather than part of the lensing event, so we incorporated a slope parameter in our model in order to derive the true parameters of the lensing system. We find that the lensing system has a mass ratio of q = 0.0654 ± 0.0006. The Einstein crossing time of the event, tE = 44.3 ± 0.1 days, was sufficiently long that the light curve exhibited parallax effects. In addition, the source trajectory relative to the large caustic structure allowed the orbital motion of the lens system to be detected. Combining the parallax with the Einstein radius, we were able to derive the distance to the lens, DL  = 2.8 ± 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with ML,1 = 0.16 ± 0.03 M, while the companion has ML, 2 = 11.0 ± 2.0 MJ, putting it in the boundary zone between planets and brown dwarfs.

Item Details

Item Type:Refereed Article
Keywords:brown dwarfs – gravitational lensing: micro – planetary systems – planets and satellites: formation – planets and satellites: general – techniques: photometric
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Stellar astronomy and planetary systems
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Cole, A (Professor Andrew Cole)
UTAS Author:Dieters, S (Dr Stefan Dieters)
UTAS Author:Greenhill, J (Dr John Greenhill)
ID Code:84202
Year Published:2013
Web of Science® Times Cited:29
Deposited By:Mathematics and Physics
Deposited On:2013-04-30
Last Modified:2017-11-06

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