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1999ApJ...518...44A - Astrophys. J., 518, 44-49 (1999/June-2)
Discovery and characterization of a caustic crossing microlensing event in the Small Magellanic Cloud.
ALCOCK C., ALLSMAN R.A., ALVES D., AXELROD T.S., BECKER A.C., BENNETT D.P., COOK K.H., DRAKE A.J., FREEMAN K.C., GRIEST K., KING L.J., LEHNER M.J., MARSHALL S.L., MINNITI D., PETERSON B.A., PRATT M.R., QUINN P.J., RHIE S.H., RODGERS A.W., STETSON P.B., STUBBS C.W., SUTHERLAND W., TOMANEY A. and VANDEHEI T.
Abstract (from CDS):
Frequent coverage of the evolving light curve allowed an accurate prediction for the date of the source crossing out of the lens caustic structure. The caustic crossing temporal width, along with the angular size of the source star, measures the proper motion of the lens with respect to the source and thus allows an estimate of the location of the lens. Lenses located in the Galactic halo would have a velocity projected to the SMC of v{d4}∼1500 km.s–1, while an SMC lens would typically have v{d4}∼60 km.s–1. The event light curve allows us to obtain a unique fit to the parameters of the binary lens and to estimate the proper motion of the lensing system.
We have performed a joint fit to the MACHO/GMAN data presented here, including recent EROS data of this event from (ref???)Afonso and collaborators. These joint data are sufficient to constrain the time t* for the lens to move an angle equal to the source angular radius: t*=0.116±0.010 days. We estimate a radius for the lensed source of R*=1.1±0.1 R☉ from its unblended color and magnitude. This yields a projected velocity of v{d4}=76±10 km.s–1. Only 0.12% of halo lenses would be expected to have a v{d4} value at least as small as this, while 38% of SMC lenses would be expected to have v{d4} as large as this. This implies that the lensing system is more likely to reside in the SMC than in the Galactic halo. Similar observations of future Magellanic Cloud microlensing events will help to determine the contribution of MACHOS to the Galaxy's dark halo.
Abstract Copyright: ∼
Journal keyword(s): Cosmology: Dark Matter - Cosmology: Gravitational Lensing - Galaxies: Magellanic Clouds - Stars: Low-Mass, Brown Dwarfs
Simbad objects: 6
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