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

M D Albrow, J An, J-P Beaulieu, J A R Caldwell, D L DePoy, Martin Dominik, B S Gaudi, A Gould, J Greenhill, K Hill, S Kane, R Martin, J Menzies, R W Pogge, K R Pollard, P D Sackett, K C Sahu, P Vermaak, R Watson, A WilliamsPLANET Collaboration

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)

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 languageEnglish
Pages (from-to)759-769
Number of pages11
JournalAstrophysical Journal
Volume549
Issue number2
DOIs
Publication statusPublished - 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

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