Fast starspot rotational modulation light curves in Python 3.

fleck is a pure Python software package for simulating rotational modulation of stars due to starspots, which we use to overcome the degeneracies and determine starspot coverages accurately for a sample of young stars. fleck simulates starspots as circular dark regions on the surfaces of rotating stars, accounting for foreshortening towards the limb, and limb darkening.

The user supplies the latitudes, longitudes and radii of spots, and the stellar inclinations from which each star is viewed, and fleck takes advantage of efficient array broadcasting with numpy to return approximate light curves. For example, the present algorithm can compute rotational modulation curves sampled at ten points throughout the rotation of each star for one million stars, with two unique spots each, all viewed at unique inclinations, in about 10 seconds on a 2.5 GHz Intel Core i7 processor. This rapid computation of light curves en masse makes it possible to measure starspot distributions with Approximate Bayesian Computation, for example.