The Feasibility of Obtaining Finite Source Sizes from MACHOType Microlensing Light Curves
Abstract
Recent discussion of the effects of finite source size on highmagnification microlensing events due to MACHOs motivates a study of the feasibility of observing such effects and extracting the source radius. Simulated observations are generated by adding Gaussian error to points sampled on theoretical microlensing light curves for a limbdarkened, extended source. These simulated data sets are fitted in an attempt to see how well the fits extract the radius of the source. The source size can be fitted with reasonable accuracy only if the impact parameter of the event, p, is less than the stellar radius, R_{*}. It is possible to distinguish ``crossing'' events, ones where p < R_{*}, from ``noncrossing'' events if the light curve is well sampled around the peak and photometric error is smalli.e., >=3 observations while the lens transits the disk of the source, and σ_{phot} < 0.08 mag. These requirements are just within the reach of current observational programs; the use of an earlywarning system and multiple observing sites should increase the likelihood that R_{*} can be fitted. The programs used to simulate and fit data can be obtained via anonymous ftp.
 Publication:

The Astrophysical Journal
 Pub Date:
 January 1997
 DOI:
 10.1086/303502
 arXiv:
 arXiv:astroph/9608096
 Bibcode:
 1997ApJ...475...43P
 Keywords:

 Cosmology: Gravitational Lensing;
 Stars: LowMass;
 Brown Dwarfs;
 Astrophysics
 EPrint:
 10 pages with 3 figures, LaTex, uses aaspp.sty, will appear in 20 January 1997 ApJ Letters