jaxoplanet.experimental.limb_dark_poly_coeffs

Functions

calc_poly_coeffs(→ jaxtyping.Array)

Calculate the polynomial coefficients for a limb-darkening intensity profile.

Module Contents

jaxoplanet.experimental.limb_dark_poly_coeffs.calc_poly_coeffs(mu: jaxtyping.Array, intensity_profile: jaxtyping.Array, poly_degree: int = 10) → jaxtyping.Array

Calculate the polynomial coefficients for a limb-darkening intensity profile.

As jaxoplanet uses an arbitrary polynomial limb-darkening law (see Agol et al. (2020) <https://arxiv.org/pdf/1908.03222>), this function may be useful for users wanting to use non-polynomial limb-darkening laws within the jaxoplanet framework. Given a limb-darkening profile, this function will fit the profile with a polynomial of a user-specified order/degree and return the least-squares polynomial coefficients. These coefficients can then be passed as the u parameter when using the light_curve objects.

The intensity profile should be relatively densely evaluated as otherwise the polynomial approximation may be non-monotonic.

Parameters:

• mu (Array) – An array of values between 0 and 1 indicating the locations where the limb-darkening intensity profile was evaluated. mu is the cosine of the angle between the line of sight and the emergent intensity and is 1 at the center of the star and 0 at the limb.

• intensity_profile (Array) – A stellar limb-darkening intensity profile. We assume the profile is normalized so that it’s value is 1 at the center of the star.

• poly_degree (int) – The degree/order of the polynomial. Setting this to 1 would fit with a straight line, 2 would fit with a quadratic, and so on. We set the default to a relatively high value of 10.

Returns:

An array containing the polynomial coefficients that can be passed to the light_curve objects. The size of this array will be equal to the poly_degree value, and the ordering of the coefficients corresponds to the lowest order to the highest order of the polynomial.