transit_light_curve

luas.exoplanet.transit_fns.transit_light_curve(par, t)

Uses the package jaxoplanet to calculate transit light curves using JAX assuming quadratic limb darkening and a simple circular orbit.

Note

If using this function then make sure to cite jaxoplanet separately as it is an independent package from luas.

This particular function will only compute a single transit light curve but JAX’s vmap function can be used to calculate the transit light curve of multiple wavelength bands at once.

It assumes that the central transit time T0, period P, semi-major axis to stellar ratio a/R* = a and impact parameter b are size-1 arrays as this makes it easier to implement with vmap and PyMC. Feel free to vary this however, for example it can easily be modified to fit for T0 separately for each light curve.

>>> from luas.exoplanet import transit_light_curve
>>> import jax.numpy as jnp
>>> par = {
>>> ... "T0":0.*jnp.ones(1),     # Central transit time (days)
>>> ... "P":3.4*jnp.ones(1),     # Period (days)
>>> ... "a":8.2*jnp.ones(1),     # Semi-major axis to stellar ratio (aka a/R*)
>>> ... "rho":0.1,               # Radius ratio (aka Rp/R* or rho)
>>> ... "b":0.5*jnp.ones(1),     # Impact parameter
>>> ... # Uses standard quadratic limb darkening parameterisation:
>>> ... # I(r) = 1 − u1(1 − mu) − u2(1 − mu)^2
>>> ... "u1":0.5,                # First quadratic limb darkening coefficient
>>> ... "u2":0.1,                # Second quadratic limb darkening coefficient
>>> ... "Foot":1.,               # Baseline flux out of transit
>>> ... "Tgrad":0.               # Gradient in baseline flux (hrs^-1)
>>> }
>>> t = jnp.linspace(-0.1, 0.1, 100)
>>> flux = transit_light_curve(par, t)

Parameters:

• par (PyTree) – The transit parameters stored in a PyTree/dictionary (see example above).

• t (JAXArray) – Array of times to calculate the light curve at.

Returns:

Array of flux values for each time input.

Return type:

JAXArray