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Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlensed H line


Cassan, A and Beaulieu, JP and Brillant, S and Coutures, C and Dominik, M and Donatowicz, J and Jorgensen, UG and Kubas, D and Albrow, MD and Caldwell, JAR and Fouque, P and Greenhill, JG and Hill, KM and Horne, K and Kane, S and Martin, R and Menzies, J and Pollard, KR and Sahu, KC and Vinter, C and Wambsganss, J and Watson, RD and Williams, A and Fendt, C and Hauschildt, P and Heinmueller, J and Marquette, JB and Thurl, C, Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlensed Ha line, Astronomy & Astrophysics, 419, (1) pp. L1-L4. ISSN 0004-6361 (2004) [Refereed Article]

DOI: doi:10.1051/0004-6361:20040112


We discuss high-resolution, time-resolved spectra of the caustic exit of the binary microlensing event OGLE 2002-BLG-069 obtained with UVES on the VLT. The source star is a G5III giant in the Galactic Bulge. During such events, the source star is highly magnified, and a strong differential magnification around the caustic resolves its surface. Using an appropriate model stellar atmosphere generated by the PHOENIX v2.6 code we obtain a model light curve for the caustic exit and compare it with a dense set of photometric observations obtained by the PLANET microlensing follow up network. We further compare predicted variations in the Hα equivalent width with those measured from our spectra. While the model and observations agree in the gross features, there are discrepancies suggesting shortcomings in the model, particularly for the Hα line core, where we have detected amplified emission from the stellar chromosphere after the source star's trailing limb exited the caustic. This achievement became possible by the provision of the very efficient OGLE-III Early Warning System, a network of small telescopes capable of nearly-continuous round-the-clock photometric monitoring, on-line data reduction, daily near-real-time modelling in order to predict caustic crossing parameters, and a fast and efficient response of a 8 m class telescope to a "Target-of- Opportunity" observation request.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Greenhill, JG (Dr John Greenhill)
UTAS Author:Hill, KM (Dr Kym Hill)
UTAS Author:Watson, RD (Dr Bob Watson)
ID Code:31079
Year Published:2004
Web of Science® Times Cited:27
Deposited By:Physics
Deposited On:2004-08-01
Last Modified:2005-06-06

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