A possible binary system of a stellar remnant in the high-magnification gravitational microlensing event OGLE-2007-BLG-514

Miyake, N.; Udalski, A.; Sumi, T.; Bennett, D. P.; Dong, S.; Street, R. A.; Greenhill, J.; Bond, I. A.; Gould, A.; Kubiak, M.; Szymański, M. K.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Wyrzykowski, L.; Abe, F.; Fukui, A.; Furusawa, K.; Holderness, S.; Itow, Y.; Korpela, A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagayama, T.; Ohnishi, K.; Rattenbury, N.; Saito, To.; Sako, T.; Sullivan, D. J.; Sweatman, W. L.; Tristram, P. J.; Yock, P. C. M.; Allen, W.; Christie, G. W.; DePoy, D. L.; Gaudi, B. S.; Han, C.; Lee, C.-U.; McCormick, J.; Monard, B.; Natusch, T.; Park, B.-G.; Pogge, R. W.; Allan, A.; Bode, M.; Bramich, D. M.; Clay, N.; Dominik, M.; Horne, K. D.; Kains, N.; Mottram, C.; Snodgrass, C.; Steele, I.; Tsapras, Y.; Albrow, M. D.; Batista, V.; Beaulieu, J. P.; Brillant, S.; Burgdorf, M.; Caldwell, J. A. R.; Cassan, A.; Cole, A.; Cook, K. H.; Coutures, Ch.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Jorgensen, U. G.; Kane, S.; Kubas, D.; Marquette, J. B.; Martin, R.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Wambsganss, J.; Williams, A. and Zub, M. (2012). A possible binary system of a stellar remnant in the high-magnification gravitational microlensing event OGLE-2007-BLG-514. Astrophysical Journal, 752(2), article no. 82.

DOI: https://doi.org/10.1088/0004-637X/752/2/82

Abstract

We report the extremely high-magnification (A > 1000) binary microlensing event OGLE-2007-BLG-514. We obtained good coverage around the double peak structure in the light curve via follow-up observations from different observatories. The binary lens model that includes the effects of parallax (known orbital motion of the Earth) and orbital motion of the lens yields a binary lens mass ratio of q = 0.321 ± 0.007 and a projected separation of s = 0.072 ± 0.001 in units of the Einstein radius. The parallax parameters allow us to determine the lens distance DL = 3.11 ± 0.39 kpc and total mass ML = 1.40 ± 0.18 M☉; this leads to the primary and secondary components having masses of M1 = 1.06 ± 0.13 M☉ and M2 = 0.34 ± 0.04 M☉, respectively. The parallax model indicates that the binary lens system is likely constructed by the main-sequence stars. On the other hand, we used a Bayesian analysis to estimate probability distributions by the model that includes the effects of xallarap (possible orbital motion of the source around a companion) and parallax (q = 0.270 ± 0.005, s = 0.083 ± 0.001). The primary component of the binary lens is relatively massive, with M1 = 0.9+4.6–0.3 M☉ and it is at a distance of DL = 2.6+3.8–0.9 kpc. Given the secure mass ratio measurement, the companion mass is therefore M2 = 0.2+1.2–0.1 M☉. The xallarap model implies that the primary lens is likely a stellar remnant, such as a white dwarf, a neutron star, or a black hole.

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