Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published July 2010 | Published
Journal Article Open

OGLE 2008–BLG–290: an accurate measurement of the limb darkening of a galactic bulge K Giant spatially resolved by microlensing

Abstract

Context. Not only is gravitational microlensing a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event. Aims. In high-magnification events, the lens caustic may cross over the source disk, which allows determination of the angular size of the source and measurement of its limb darkening. Methods. When such extended-source effects appear close to maximum magnification, the resulting light curve differs from the characteristic Paczyński point-source curve. The exact shape of the light curve close to the peak depends on the limb darkening of the source. Dense photometric coverage permits measurement of the respective limb-darkening coefficients. Results. In the case of the microlensing event OGLE 2008-BLG-290, the K giant source star reached a peak magnification at about 100. Thirteen different telescopes have covered this event in eight different photometric bands. Subsequent light-curve analysis yielded measurements of linear limb-darkening coefficients of the source in six photometric bands. The best-measured coefficients lead to an estimate of the source effective temperature of about 4700^(+100)_(-200) K. However, the photometric estimate from colour-magnitude diagrams favours a cooler temperature of 4200 ± 100 K. Conclusions. Because the limb-darkening measurements, at least in the CTIO/SMARTS2 V_S- and I_S-bands, are among the most accurate obtained, the above disagreement needs to be understood. A solution is proposed, which may apply to previous events where such a discrepancy also appeared.

Additional Information

© 2010 ESO. Received 13 January 2010; Accepted 5 May 2010; Published online 02 September 2010. We express our gratitude to ESO for a two months invitation at Santiago headquarters, Chile, where part of this work was achieved. We are very grateful to the observatories that support our science (Bronberg, Canopus, CTIO, ESO, IRSF, LCOGT, Liverpool, LOAO, MOA, OGLE, Perth, SAAO, Skinakas) via the generous allocation of time that makes this work possible. The operation of Canopus Observatory is in part supported by a financial contribution from David Warren. The OGLE project is partially supported by the Polish MNiSW grant N20303032/4275 to AU. Allocation of the Holmes grant from the French Agence Nationale de la Recherche has been indispensable to finance observing trips and meeting travels, and is gratefully acknowledged here. D.H. was supported by Czech Science Foundation grant GACR 205/07/0824 and by the Czech Ministry of Education project MSM0021620860. C.H. was supported by the grant 2009-0081561 of National Research Foundation of Korea. T.C.H. was financed for his astronomical research at the Armagh Observatory by the Department for Culture, Arts and Leisure, Northern Ireland, UK. D.R. and J.S. acknowledge support from the Communauté française de Belgique – Actions de recherche concertées – Académie universitaire Wallonie-Europe. The Dark Cosmology Centre is funded by the Danish National Research Council. P.F. wishes to thank Noriyuki Matsunaga for discussions about the interplay between adopted distance and derived extinction, David Nataf for measuring the red giant clump in the recently released OGLE-III photometric catalogue, and Etienne Bachelet for checking the whole chain from extinction to source size using a refined method. We are grateful to the anonymous referee for constructive comments that helped us improve the manuscript. This publication makes use of data products from the 2MASS project, as well as the SIMBAD database, Aladin and Vizier catalogue operation tools (CDS Strasbourg, France). The Two Micron All Sky Survey is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

Attached Files

Published - Fouque2010p12366Astron_Astrophys.pdf

Files

Fouque2010p12366Astron_Astrophys.pdf
Files (1.1 MB)
Name Size Download all
md5:9bb96c105f6f190b1f90cd702be41874
1.1 MB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 21, 2023