SCO LDC Calculator

Computes Quadratic (u1, u2), Power-2 (g, h) and Four-Parameter nonlinear (a1–a4) limb-darkening coefficients for exoplanet transit light-curve fits, by trilinear interpolation of published Claret tables in Teff, log(g), and [Fe/H].

Inputs

Results

g
—
h
—
Filter—
Model—
Method—
Source—

I(μ) / I(1) = 1 − g·(1 − μh)

Mullen, E. H., Conti, D. M., Collins, K. A. 2026, “SCO-LDC: A Web Calculator for Quadratic Limb-darkening Coefficients by Trilinear Interpolation of Claret Grids”, Research Notes of the AAS, Vol. 10, No. 6. DOI: 10.3847/2515-5172/ae7e67. Published by the American Astronomical Society.

Methodology

Quadratic limb-darkening coefficients are derived by trilinear interpolation of published tables in Teff, log(g), and [Fe/H]. For Johnson–Cousins, Sloan/SDSS, Strömgren, Kepler, CoRoT, and Spitzer filters, coefficients are from Claret & Bloemen (2011) using ATLAS9 plane-parallel models. For TESS, coefficients are from Claret (2018) using PHOENIX-COND spherical models at solar metallicity. For the CBB filter, coefficients are from Claret, Mullen & Gary (2022) RNAAS, using ATLAS9 plane-parallel models. For the CHEOPS filter, coefficients are from Claret (2021, RNAAS 5, 13), using ATLAS9 plane-parallel models.

Power-2 coefficients are similarly derived for Johnson–Cousins, Sloan/SDSS, Strömgren, Gaia, Kepler, and TESS filters, with coefficients from Claret & Southworth (2022, A&A 664, A128) using ATLAS9 plane-parallel models and from Claret & Southworth (2023, A&A 674, A63) using PHOENIX-COND spherical models at solar metallicity. For the CHEOPS filter, coefficients are from Claret & Southworth (2023) using PHOENIX-COND models (solar metallicity only).

Four-parameter nonlinear coefficients (a1–a4) are derived by the same trilinear interpolation. For Johnson–Cousins, Sloan/SDSS, Strömgren, and Kepler filters, ATLAS9 plane-parallel coefficients are from Claret & Bloemen (2011) and PHOENIX-COND spherical coefficients at solar metallicity are from Claret & Southworth (2023, A&A 674, A63). For the Gaia (GBP, G, GRP), TESS, and CHEOPS filters, coefficients are from Claret & Southworth (2023) using PHOENIX-COND models (solar metallicity only). For the CoRoT and Spitzer IRAC filters, coefficients are from Claret & Bloemen (2011) using ATLAS9 plane-parallel and PHOENIX models.

Microturbulent velocity is fixed at ξ = 2.0 km/s. The LSM fitting method is used throughout. No extrapolation is performed beyond grid boundaries. A REST API is available and is documented here.

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