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First Space‐Based Microlens Parallax Measurement:SpitzerObservations of OGLE‐2005‐SMC‐001
Author(s) -
Subo Dong,
A. Udalski,
Andrew Gould,
W. T. Reach,
G. W. Christie,
Andrew F. Boden,
D. P. Bennett,
G. G. Fazio,
K. Griest,
M. K. Szymański,
M. Kubiak,
I. Soszyński,
G. Pietrzyński,
O. Szewczyk,
Ł. Wyrzykowski,
K. Ulaczyk,
Tadeusz Więckowski,
B. Paczyński,
D. L. DePoy,
Richard W. Pogge,
George W. Preston,
I. B. Thompson,
B. M. Patten
Publication year - 2007
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/518536
Subject(s) - parallax , halo , physics , microlens , small magellanic cloud , astrophysics , lens (geology) , population , gravitational microlensing , caustic (mathematics) , interferometry , astronomy , optics , stars , galaxy , demography , sociology , mathematical physics
We combine Spitzer and ground-based observations to measure the microlensparallax of OGLE-2005-SMC-001, the first such space-based determination sinceS. Refsdal proposed the idea in 1966. The parallax measurement yields aprojected velocity \tilde v ~ 230 km/s, the typical value expected for halolenses, but an order of magnitude smaller than would be expected for lenseslying in the Small Magellanic Cloud (SMC) itself. The lens is a weak (i.e.,non-caustic-crossing) binary, which complicates the analysis considerably butultimately contributes additional constraints. Using a test proposed by Assefet al. (2006), which makes use only of kinematic information about differentpopulations but does not make any assumptions about their respective massfunctions, we find that the likelihood ratio is L_halo/L_SMC = 20. Hence, halolenses are strongly favored but SMC lenses are not definitively ruled out.Similar Spitzer observations of additional lenses toward the Magellanic Cloudswould clarify the nature of the lens population. The Space InterferometryMission could make even more constraining measurements.Comment: ApJ, in press. Text and figures are updated to match the journal versio

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