High‐Precision Limb‐Darkening Measurement of a K3 Giant Using Microlensing

Fields, Dale L.; Albrow, M. D.; An, J.; Beaulieu, J. P.; Caldwell, J. A. R.; Depoy, D. L.; Dominik, M.; Gaudi, B. Scott; Gould, Andrew; Greenhill, J.; Hill, K.; Jørgensen, U. G.; Kane, Stephen R.; Martin, R.; Menzies, John; Pogge, Richard W.; Pollard, K. R.; Sackett, Penny D.; Sahu, Kailash C.; Vermaak, P.; Watson, R.; Williams, A.; Glicenstein, J. F.; Hauschildt, P. H.

doi:10.1086/378196

Cited by 77 publications

(66 citation statements)

References 21 publications

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“…Article published by EDP Sciences and available at http://www.aanda.org or http://dx.doi.org/10.1051/0004-6361:20040112 giants and sub-giants (Fields et al 2003 and references therein) and a main sequence star (Abe et al 2003). A new generation of stellar atmosphere models (Orosz & Hauschildt 2000) have revealed limb-darkening laws that are significantly different from the traditional analytic ones (Bryce et al 2002;Claret & Hauschildt 2003).…”

Section: Letter To the Editormentioning

confidence: 99%

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

Cassan

Beaulieu

Brillant

et al. 2004

A&A

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Abstract. 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.

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Section: Letter To the Editormentioning

confidence: 99%

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

Cassan

Beaulieu

Brillant

et al. 2004

A&A

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“…An et al (2002) and Fields et al (2003) constrained non-linear limb-darkening relations from microlensing observations of a K3 giant and compared them to model stellar atmospheres. They found significant disagreement between the observed and predicted limb-darkening relation.…”

Section: Introductionmentioning

confidence: 99%

Spherically-symmetric model stellar atmospheres and limb darkening

Neilson

Lester

2013

A&A

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Model stellar atmospheres are fundamental tools for understanding stellar observations from interferometry, microlensing, eclipsing binaries and planetary transits. However, the calculations also include assumptions, such as the geometry of the model. We use intensity profiles computed for both plane-parallel and spherically symmetric model atmospheres to determine fitting coefficients in the BVRIHK, CoRot and Kepler wavebands for limb darkening using several different fitting laws, for gravity-darkening and for interferometric angular diameter corrections. Comparing predicted variables for each geometry, we find that the spherically symmetric model geometry leads to different predictions for surface gravities log g < 3. In particular, the most commonly used limb-darkening laws produce poor fits to the intensity profiles of spherically symmetric model atmospheres, which indicates the need for more sophisticated laws. Angular diameter corrections for spherically symmetric models range from 0.67 to 1, compared to the much smaller range from 0.95 to 1 for plane-parallel models.

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“…fit model intensity profiles to interferometric observations from Wittkowski et al (2004) and predicted similar fundamental parameters as those authors. Also, Neilson & Lester (2011) predicted limb-darkening coefficients for a specific limb-darkening law from spherical models, compared them to results for microlensing observations from Fields et al (2003), and found better agreement than the authors did using plane-parallel models and spherical models that had intensity profiles clipped to remove the extended limb.…”

Section: Stellar Atmosphere Code and Limb-darkening Lawsmentioning

confidence: 99%

Comparison of Limb-Darkening Laws from Plane-Parallel and Spherically-Symmetric Model Stellar Atmospheres

Neilson

2011

Proc. IAU

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Abstract. Limb-darkening is a fundamental constraint for modeling eclipsing binary and planetary transit light curves. As observations, for example from Kepler, CoRot, and Most, become more precise then a greater understanding of limb-darkening is necessary. However, limbdarkening is typically modeled as simple parameterizations fit to plane-parallel model stellar atmospheres that ignores stellar atmospheric extension. In this work, I compute linear, quadratic and four-parameter limb-darkening laws from grids of plane-parallel and spherically-symmetric model stellar atmospheres in a temperature and gravity range representing stars evolving on the Red Giant branch. The limb-darkening relations for each geometry are compared and are found to fit plane-parallel models much better than the spherically-symmetric models. Assuming that limb-darkening from spherically-symmetry model atmospheres are more physically representative of actual stellar limb-darkening than plane-parallel models, then these limb-darkening laws will not fit the limb of a stellar disk leading to errors in a light curve fit. This error will increase with a star's atmospheric extension.

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High‐Precision Limb‐Darkening Measurement of a K3 Giant Using Microlensing

Cited by 77 publications

References 21 publications

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

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

Spherically-symmetric model stellar atmospheres and limb darkening

Comparison of Limb-Darkening Laws from Plane-Parallel and Spherically-Symmetric Model Stellar Atmospheres

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