PLANET Observations of Microlensing Event OGLE-1999-BUL-23: Limb-darkening Measurement of the Source Star Academic Article uri icon


  • 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: cv = 0.786+0.080-0.078 and cI = 0.632+0.047-0.037. 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 (Teff 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 0.39 and a projected separation d 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.

published proceedings

  • The Astrophysical Journal

author list (cited authors)

  • Albrow, M. D., An, J., Beaulieu, J., Caldwell, J., DePoy, D. L., Dominik, M., ... Williams, A.

citation count

  • 65

complete list of authors

  • Albrow, MD||An, J||Beaulieu, J‐P||Caldwell, JAR||DePoy, DL||Dominik, M||Gaudi, BS||Gould, A||Greenhill, J||Hill, K||Kane, S||Martin, R||Menzies, J||Pogge, RW||Pollard, KR||Sackett, PD||Sahu, KC||Vermaak, P||Watson, R||Williams, A

publication date

  • March 2001