BATMAN & SPIDERMAN: Saving the World One Exoplanet Light Curve at a Time talk about two open-source Python package for modeling transits, eclipses, and phase curves of exoplanets we have some extraordinarly precise light curves coming from JWST and we want to be prepared to model them. community resource – we don’t all need to write our own codes! Laura Kreidberg Junior Fellow, Harvard Society of Fellows Enabling Transiting Exoplanets with JWST, 7/11/17

BATMAN: Bad-Ass Transit Model cAlculatioN Python package for transit modeling (Kreidberg 2015, PASP, 127, 1161) determines planet position based on orbital parameters calculates drop in stellar flux for any radially symmetric stellar limb darkening law first: BATMAN BATMAN does two things: calculate planets position calculates how much stellar flux the planet blocks, based on where it is. can do this for any radially symmetric stellar limb darkening law

Calculating Planet Position input parameters: period, time of inferior conjunction, longitude of periastron, inclination, a/Rs, eccentricity solves Kepler’s equation with the Newton-Raphson method outputs separation of centers in the plane of the sky this is the easy part! Murray & Correia, 2011, Exoplanets (ed. Seager)

Why is modeling transits hard? limb darkening!

Limb Darkening Laws Espinoza & Jordàn 2015 uniform, linear, quadratic, square-root, logarithmic, exponential, nonlinear, power2… some have analytic transit solutions, others must be solved numerically (Mandel & Agol 2002)

Limb Darkening Matters imperfect limb darkening law can significantly bias transit depths, and stellar models may be wrong (Espinoza & Jordàn 2015) stellar photospheres may contain same species as planetary atmospheres (e.g. H2O, Kreidberg et al. 2014) Water absorption features in the limb darkening coefficients for GJ 1214 designed BATMAN to be as flexible as possible in how it treats limb darkening Kreidberg et al. 2014 Nature, 505, 69

BATMAN numeric integration scheme In addition to the standard analytic LD laws, BATMAN can also handle any radially symmetric LD parameterization Kreidberg 2015, PASP

Users can specify the error tolerance: 1 ppm

BATMAN specs in active development on github installs with pip (https://github.com/lkreidberg/batman) installs with pip written in Python with C extensions now compatible with GPUs! (thanks Michael Zhang) handles any radially symmetric limb darkening law, supersampling, simple eclipses speed: ~1e5 models/min at 10 ppm precision (on my ancient laptop)

SPIDERMAN: [backronym pending) Python package for eclipse mapping and phase curves for any planet brightness distribution (Louden & Kreidberg, in prep) as you can see, SAVING the world is SERIOUS business

SPIDERMAN integration scheme planet figures c/o Tom Louden

SPIDERMAN integration scheme figures c/o Tom Louden

SPIDERMAN integration scheme can calculate area of triangles and area between chord and circle perimeter figures c/o Tom Louden

Brightness Models Zhang & Showman 2017 offset hotspot physically motivated analytic model radiative/advective timescale nightside temperature day/night temperature contrast offset hotspot spot parameterized by: latitude & longitude size temperature Other models: two temperature, Lambertian, spherical harmonics, forward model (from GCM) Stellar brightness model: blackbody or Phoenix

input: temperature or brightness model for the planet output: planet-to-star flux ratio at any orbital phase GCM temperature map for WASP-43b (Vivien Parmentier) Infrared phase curves for a range of pressures figures c/o Tom Louden

Eclipse Mapping zoom in on secondary eclipse (simulated MIRI observations from PandExo) deviation from a uniform dayside brightness model figures c/o Tom Louden

SPIDERMAN specs in active development on github (https://github.com/tomlouden/SPIDERMAN) written in Python with C extensions speed: fast enough for MCMC brightness models: Zhang & Showman, hot spot, Lambertian, spherical harmonics, forward stellar models: blackbody or Phoenix check back for a paper very soon!

Conclusion Check out BATMAN and SPIDERMAN https://github.com/lkreidberg/batman https://github.com/tomlouden/SPIDERMAN Open-source development is awesome – your contributions are welcome! great thing about open source – the whole community can work to make the best possible models and it’s the opposite of a black box community has really improved the package because it’s open source, you can see inner workings and not have black box