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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
OGLE 2004-BLG-254: A K3 III Galactic bulge giant spatially resolved by a single microlens
Astronomy and Astrophysics, Volume 460, No. 1, Year 2006
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Description
Aims. We present an analysis of OGLE 2004-BLG-254, a high-magnification (Ao ≃ 60) and relatively short duration (Ao ≃ 13.2 days) microlensing event in which the source star, a Bulge K-giant, has been spatially resolved by a point-like lens. We seek to determine the lens and source distance, and provide a measurement of the linear limb-darkening coefficients of the source star in the I and R bands. We discuss the derived values of the latter and compare them to the classical theoretical laws, and furthermore examine the cases of already published microlensed GK-giants limb-darkening measurements. Methods. We have obtained dense photometric coverage of the event light curve with OGLE and PLANET telescopes, as well as a high signal-to-noise ratio spectrum taken while the source was still magnified by A ∼ 20, using the UVES/VLT spectrograph. We have performed a modelling of the light curve, including finite source and parallax effects, and have combined spectroscopic and photometric analysis to infer the source distance. A Galactic model for the mass and velocity distribution of the stars has been used to estimate the lens distance. Results. From the spectrum analysis and calibrated color-magnitude of the event target, we found that the source was a K3 III Bulge giant, situated at the far end of the Bulge. From modelling the light curve, we have derived an angular size of the Einstein ring θE ≃ 114 μas, and a relative lens-source proper motion μ = θE/tE ≃ 3.1 mas/yr. We could also measure the angular size of the source, θ*, ≃ 4.5 μas, whereas given the short duration of the event, no significant constraint could be obtained from parallax effects. A Galactic model based on the modelling of the light curve then provides us with an estimate of the lens distance, mass and velocity as DL ≃ 9.6 kpc, M ≃ 0.11 M⊙ and v ≃ 145 km s-1 (at the lens distance) respectively. Our dense coverage of this event allows us to measure limb darkening of the source star in the I and R bands. We also compare previous measurements of linear limb-darkening coefficients involving GK-giant stars with predictions from ATLAS atmosphere models. We discuss the case of K-giants and find a disagreement between limb-darkening measurements and model predictions, which may be caused by the inadequacy of the linear limb-darkening law. © ESO 2006.
Authors & Co-Authors
Cassan, Arnaud
Germany, Heidelberg
Astronomisches Rechen-institut
France, Paris
Institut D’astrophysique de Paris
Beaulieu, Jean Philippe H.
France, Paris
Institut D’astrophysique de Paris
Fouqué, Pascal
France, Toulouse
Observatoire Midi-pyrénées
Brillant, Stéphanie
Chile, Santiago
European Southern Observatory Santiago
Dominik, Martin
United Kingdom, St Andrews
University of st Andrews
Greenhill, John G.
Australia, Hobart
University of Tasmania
Heyrovský, D.
Czech Republic, Prague
Charles University
Hörne, Keith D.
United Kingdom, St Andrews
University of st Andrews
Jörgensen, Uffe Gråe
Denmark, Copenhagen
Niels Bohr Institutet
Kubas, Daniel
Chile, Santiago
European Southern Observatory Santiago
Stempels, H. C.
United Kingdom, St Andrews
University of st Andrews
Vinter, C.
Denmark, Copenhagen
Niels Bohr Institutet
Albrow, Michael D.
New Zealand, Christchurch
University of Canterbury
Bennett, David P.
United States, Notre Dame
University of Notre Dame
Caldwell, John A.R.
United States, Baltimore
Space Telescope Science Institute
United States, Austin
University of Texas System
Calitz, J. J.
South Africa, Bloemfontein
University of the Free State
Cook, Kem H.
United States, Livermore
Lawrence Livermore National Laboratory
Coutures, Christian
France, Gif-sur-yvette
Cea Saclay
Dominis, D.
Germany, Potsdam
Leibniz Institute for Astrophysics Potsdam
Donatowicz, J.
Austria, Vienna
Technische Universität Wien
Hill, Kym M.
Australia, Hobart
University of Tasmania
Hoffman, Matie J.H.
South Africa, Bloemfontein
University of the Free State
Kane, Stephen R.
United States, Gainesville
University of Florida
Marquette, Jean Baptiste
France, Paris
Institut D’astrophysique de Paris
Martin, Ralph
Australia, Bickley
Perth Observatory
Meintjes, Pieter J.
South Africa, Bloemfontein
University of the Free State
Menzies, John W.
South Africa, Cape Town
South African Astronomical Observatory
Miller, V. R.
New Zealand, Christchurch
University of Canterbury
Pollard, Karen R.
New Zealand, Christchurch
University of Canterbury
Sahu, Kailash C.
United States, Baltimore
Space Telescope Science Institute
Wambsganss, Joachim
Germany, Heidelberg
Astronomisches Rechen-institut
Williams, Andrew J.
Australia, Bickley
Perth Observatory
Udalski, Andrzej
Poland, Warsaw
University of Warsaw
Szymánski, Michał K.
Poland, Warsaw
University of Warsaw
Kubiak, Marcin
Poland, Warsaw
University of Warsaw
Pietrzýnski, Grzegorz
Poland, Warsaw
University of Warsaw
Chile, Biobio
Universidad de Concepcion
Soszyński, Igor
Poland, Warsaw
University of Warsaw
Chile, Biobio
Universidad de Concepcion
Zebruń, Karol
Poland, Warsaw
University of Warsaw
Szewczyk, Olaf
Poland, Warsaw
University of Warsaw
Wyrzykowski, Łukasz
Poland, Warsaw
University of Warsaw
United Kingdom, Manchester
The University of Manchester
Statistics
Citations: 40
Authors: 40
Affiliations: 23
Identifiers
Doi:
10.1051/0004-6361:20054414
ISSN:
00046361
e-ISSN:
14320746
Research Areas
Health System And Policy