A Study into the Feasibility of Obtaining Finite Source Sizes From MACHO-type Microlensing Light Curves

Abstract

Recent discussion of the effects of finite source size on high magnification microlensing events due to MACHOs motivates a study into 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 limb darkened, 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, $R_{\star }$. It is possible to distinguish ``crossing'' events, ones where $p<R_{\star }$, from ``non--crossing'' events if the light curve is well sampled around the peak and photometric error is small --- i.e.~$\ge 3$ observations while the lens transits the disk of the source, and ${\sigma }_{phot}<0.08\mathrm{mag}$. These requirements are just within the reach of current observational programs; the use of an early-warning system and multiple observing sites should increase the likelihood that $R_{\star }$ can be fitted. The programs used to simulate and fit data can be obtained via anonymous {\tt ftp}.

10 pages with 3 figures, LaTex, uses aaspp.sty, will appear in 20 January 1997 ApJ Letters

References in corpus (5)

• Possible Gravitational Microlensing of a Star in the Large Magellanic Cloud
• First Observation of Parallax in a Gravitational Microlensing Event
• Finite Source Sizes and the Information Content of MACHO-Type Lens Search Light Curves
• The Optical Depth to Gravitational Microlensing in the Direction of the Galactic Bulge
• The Optical Gravitational Lensing Experiment. the Early Warning System

Cited by in corpus (13)

• MACHO Alert 95-30 : First Real-Time Observation of Extended Source Effects in Gravitational Microlensing
• The 1995 Pilot Campaign of PLANET: Searching for Microlensing Anomalies through Precise, Rapid, Round-the-Clock Monitoring
• Limb-Darkening of a K Giant in the Galactic Bulge: PLANET Photometry of MACHO 97-BLG-28
• A New Channel for the Detection of Planetary Systems Through Microlensing: I. Isolated Events Due to Planet Lenses
• Optical Gravitational Lensing Experiment. OGLE 2000-BUL-43: A Spectacular Ongoing Parallax Microlensing Event. Difference Image Analysis
• Astrometric Properties of Gravitational Binary-Microlens Events and Their Applications
• The microlensing signatures of starspots
• Detection of Stellar Spots from the Observations of Caustic-Crossing Binary-Lens Gravitational Microlensing Events
• The polarisation signature from microlensing of circumstellar envelopes in caustic crossing events
• Constraining the Location of Microlensing Objects by using the Finite Source Effect in EAGLE events
• Distribution of Caustic-Crossing Intervals for Galactic Binary-Lens Microlensing Events
• Constraining the Location of Microlensing Objects towards the LMC through Parallax Measurement in EAGLE Observations
• On the Intrinsic Bias in detecting Caustic Crossings between Galactic Halo and Self-lensing Events in the Magellanic Clouds