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Pregled bibliografske jedinice broj: 288123


Autori: Cassan, A.; Beaulieu, J.-P.; Fouqué, P.; Brillant, S.; Dominik, M.; Greenhill, J.; Heyrovský, D.; Horne, K.; Jørgensen, U. G.; Kubas, D.; Stempels, H. C.; Vinter, C.; Albrow, M. D.; Bennett, D.; Caldwell, J. A. R.; Calitz, J. J.; Cook, K.; Coutures, C.; Dominis, Dijana; Donatowicz, J.; Hill, K.; Hoffman, M.; Kane, S.; Marquette, J.-B.; Martin, R.; Meintjes, P.; Menzies, J.; Miller, V. R.; Pollard, K. R.; Sahu, K. C.; Wambsganss, J.; Williams, A.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Żebruń, K.; Szewczyk, O.; Wyrzykowski, Ł.
Naslov: OGLE 2004-BLG-254: a K3 III Galactic bulge giant spatially resolved by a single microlens
Izvornik: Astronomy and Astrophysics (0004-6361) 460 (2006), 1; 277-288
Vrsta rada: članak
Ključne riječi: gravitational lensing; techniques: high angular resolution; stars: atmospheres; stars:; individual: OGLE 2004-BLG-254
We present an analysis of OGLE 2004-BLG-254, a high-magnification (Â &simeq ; 60) and relatively short duration (t_E&simeq ; 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 θ _E&simeq ; 114 μ as, and a relative lens-source proper motion μ = θ _E/t_E&simeq ; 3.1 mas/yr. We could also measure the angular size of the source, θ _*&simeq ; 4.5 μ as, 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 D_L&simeq ; 9.6 kpc, M&simeq ; 0.11 Mȯ and v &simeq ; 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.
Izvorni jezik: ENG
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Kategorija: Znanstveni
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Broj citata:
DOI: 10.1051/0004-6361:20054414
URL cjelovitog teksta:
Google Scholar: OGLE 2004-BLG-254: a K3 III Galactic bulge giant spatially resolved by a single microlens

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