. (2010) OGLE 2008–BLG–290 : an accurate measurement of the limb darkening of a galactic bulge K giant spatially resolved by microlensing. Astronomy & Astrophysics, Vol.518 (No.A51). ISSN 0004-6361

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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 Paczy´nski 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 Vs- and Is-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.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Microlensing (Astrophysics), Caustics (Optics), Giant stars, Stars -- Temperature, Galactic bulges
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	July 2010
Volume:	Vol.518
Number:	No.A51
Identification Number:	10.1051/0004-6361/201014053
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Poland. Ministerstwo Nauki i Szkolnictwa Wyższego [Ministry of Science and Higher Education] (MNiSW), France. Agence nationale de la recherche (ANR), Grantová agentura České republiky [Grant Agency of the Czech Republic] (GACR), Czech Republic. Ministerstvo školství, mládeže a tělovýchovy [Ministry of Education, Youth, and Sport], National Research Foundation of Korea (NRF), Northern Ireland. Dept. of Culture, Arts & Leisure, Communauté française de Belgique. Action de Recherche Concertée, Danmarks Grundforskningsfond [Danish National Research Foundation], National Science Foundation (U.S.) (NSF)
Grant number:	N20303032/4275 (MNiSW), 205/07/0824 (GACR), MSM0021620860 (MSMT), 2009-0081561 (NRF),
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URI:	http://wrap.warwick.ac.uk/id/eprint/3412

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