Abstract
We present PLANET observations of OGLE-1999-BUL-23, a binary-lens microlensing event toward the Galactic bulge. PLANET observations in the I and V bands cover the event from just before the first caustic crossing until the end of the event. In particular, a densely sampled second caustic crossing enables us to derive the linear limb-darkening coefficients of the source star : and c(V) = 0.786(-0.078)(+0.080) c(I) = 0.632(-0.037)(+0.047). Combined analysis of the light curve and the color-magnitude diagram suggests that the source star is a G/K subgiant in the Galactic bulge (T-eff similar or equal to 4800 K). The resulting linear limb-darkening coefficient of the source is consistent with theoretical predictions, although it is likely that nonlinearity of the stellar surface brightness profile complicates the interpretation, especially for the I band. The global light curve fit to the data indicates that the event is due to a binary lens of a mass ratio q similar or equal to 0.39 and a projected separation d similar or equal to 2.42. The lens/source relative proper motion is (22.8 +/- 1.5) km s(-1) kpc(-1), typical of bulge/bulge or bulge/disk events.
Original language | English |
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Pages (from-to) | 759-769 |
Number of pages | 11 |
Journal | Astrophysical Journal |
Volume | 549 |
Issue number | 2 |
DOIs | |
Publication status | Published - 10 Mar 2001 |
Keywords
- binaries : general
- gravitational lensing
- stars : atmospheres
- stars : fundamental parameters
- GRAVITATIONAL LENSING EXPERIMENT
- LIGHT CURVES
- MODEL ATMOSPHERES
- PROPER MOTIONS
- STELLAR
- PHOTOMETRY
- COEFFICIENTS
- MACHOS
- WINDOW
- GIANT