API

catwoman has two main classes: TransitModel and TransitParams.

class catwoman.TransitParams

Object to store the physical parameters of the transit.

Parameters:
  • t0 (float) – Time of inferior conjunction.
  • t_secondary (float, optional) – Time of secondary eclipse center.
  • per (float) – Orbital period.
  • rp (float) – Planet radius 1 (in stellar radii).
  • rp2 (float) – Planet radius 2 (in stellar radii)
  • a (float) – Semi-major axis (in stellar radii).
  • inc (float) – Orbital inclination (in degrees).
  • ecc (float) – Orbital eccentricity.
  • w (float) – Argument of periapse (in degrees)
  • u (array_like) – List of limb darkening coefficients.
  • limb_dark (str) – Limb darkening model (choice of “nonlinear”, “quadratic”, “exponential”, “logarithmic”, “squareroot”, “linear”, “uniform”, “power2”, or “custom”).
  • fp (float, optional) – Planet-to-star flux ratio (for secondary eclipse models).
  • phi (float) – Rotation angle of planet, relative to horizontal (in degrees)

Note

  • Units for the orbital period and ephemeris can be anything as long as they are consistent (e.g. both in days).
Example: 
>>> import catwoman
>>> params = catwoman.TransitParams()
>>> params.t0 = 0.                              #time of inferior conjunction
>>> params.per = 1.                             #orbital period 
>>> params.rp = 0.1                             #planet radius 1 (in units of stellar radii)
>>> params.rp2 = 0.1005                         #planet radius 2 (in units of stellar radii)
>>> params.a = 15.                              #semi-major axis (in units of stellar radii)
>>> params.inc = 87.                            #orbital inclination (in degrees)       
>>> params.ecc = 0.                             #eccentricity   
>>> params.w = 90.                              #longitude of periastron (in degrees) 
>>> params.u = [0.1, 0.3]                       #limb darkening coefficients
>>> params.limb_dark = "quadratic"              #limb darkening model
>>> params.phi = 90.                            #rotation angle of planet
class catwoman.TransitModel(params, t, max_err=1.0, nthreads=1, fac=None, transittype='primary', supersample_factor=1, exp_time=0.0)

Class for generating model asymmetric transit light curves.

Parameters:
  • params (a TransitParams instance) – A TransitParams object containing the physical parameters of the transit
  • t (ndarray) – Array of times at which to calculate the model.
  • max_err (float, optional) – Error tolerance/truncation error (in parts per million) for the model.
  • fac (float, optional) – Scale factor for integration step size
  • supersample_factor (integer, optional) – Number of points subdividing exposure
  • exp_time (double, optional) – Exposure time (in same units as t)
Example: 
>>> model = catwoman.TransitModel(params, t, max_err = 1.0)
calc_err(plot=False)

Calculate maximum error for a specific transit light curve calculation.

Parameters:plot (bool) – If True, plots the error in the light curve model against the separation of centres, d.
Returns:Truncation error (in parts per million)
Return type:float
light_curve(params)

Calculates and returns a model asymmetric light curve.

Parameters:params (A TransitParams instance) – Transit parameters
Returns:Relative flux
Return type:ndarray
Example: 
>>> flux = model.light_curve(params)