First Detection of a Gravitational Microlensing Candidate toward the Small Magellanic Cloud

We report the first discovery of a gravitational microlensing candidate toward a new population of source stars, the Small Magellanic Cloud (SMC). The candidate event's light curve shows no variation for 3 yr before an upward excursion lasting ~217 days that peaks around 1997 January 11 at a magnification of ~2.1. Microlensing events toward the Large Magellanic Cloud and the Galactic bulge have allowed important conclusions to be reached on the stellar and dark matter content of the Milky Way. The SMC gives a new line of sight through the Milky Way and is expected to prove useful in determining the flattening of the Galactic halo.

[1]  L. Vigroux,et al.  Evidence for gravitational microlensing by dark objects in the Galactic halo , 1993, Nature.

[2]  M. J. Lehner,et al.  The MACHO Project LMC Microlensing Results from the First Two Years and the Nature of the Galactic Dark Halo , 1996 .

[3]  J. Caldwell,et al.  The geometry and distance of the Magellanic Clouds from Cepheid variables , 1986 .

[4]  J. Frieman,et al.  Can MACHOs probe the shape of the galaxy halo , 1993, astro-ph/9312043.

[5]  B. Peterson,et al.  Real-Time Detection and Multisite Observations of Gravitational Microlensing , 1996 .

[6]  P. J. Quinn,et al.  Possible gravitational microlensing of a star in the Large Magellanic Cloud , 1993, Nature.

[7]  Austin B. Tomaney,et al.  Results from a Survey of Gravitational Microlensing toward M31 , 1996, astro-ph/9610065.

[8]  Christopher W. Stubbs,et al.  The macho project first-year large magellanic cloud results: The microlensing rate and the nature of the galactic dark halo , 1996 .

[9]  A. Gould,et al.  MACHOs in a Flattened Halo , 1993, astro-ph/9304023.

[10]  B. Madore,et al.  Distance Moduli and Structure of the Magellanic Clouds from Near-Infrared Photometry of Classical Cepheids , 1987 .

[11]  M. J. Lehner,et al.  The MACHO Project: Limits on Planetary Mass Dark Matter in the Galactic Halo from Gravitational Microlensing , 1996, astro-ph/9604176.

[12]  Bohdan Paczynski,et al.  Gravitational microlensing by the galactic halo , 1986 .

[13]  B. Paczynski,et al.  The Optical Gravitational Lensing Experiment. The Optical Depth to Gravitational Microlensing in the Direction of the Galactic Bulge , 1994 .

[14]  Austin B. Tomaney,et al.  Expanding the Realm of Microlensing Surveys with Difference Image Photometry , 1996 .

[15]  D. Mathewson,et al.  The structure of the Small Magellanic Cloud , 1986 .

[16]  M. J. Lehner,et al.  The Macho Project: 45 Candidate Microlensing Events from the First Year Galactic Bulge Data , 1997 .

[17]  Bohdan Paczynski,et al.  Gravitational Microlensing in the Local Group , 1996 .