JWST Spectroscopy of transiting planets Drake Deming University of Maryland at College Park K2 Science Conference, November 5, 2015

In the early days of transiting planets, we were interested in what JWST could detect Deming et al Now we need to optimize the total science return

JWST has more than a dozen spectroscopic modes: Beichman et al. 2014

MIRI has multiple filters for secondary eclipse

Can use for transit or secondary eclipse spectroscopy NIRSpec

The observational problem: For a given planet, what's the best combination of secondary eclipse photometry / spectroscopy + transit spectroscopy, in what wavelength bands, at what spectral resolving power, to: 1. Determine the atmospheric temperature structure 2. Measure the abundances of major molecular constituents 3. Define the properties of clouds...and do it with the least amount of observing time AND: 4. Be open to seredipitous detections

Approach: Generate simulated JWST spectra based on model planets and JWST sensitivity - TESS planets from Sullivan et al. Do retrievals (via MCMC) on the simulated observations Limitations: 1. currently using the same models for retrievals as for observations 2. photon and background-limited 3. JWST parameters are still preliminary 4. So far, just eclipse, not transit 5....and clear atmospheres A similar but more mature effort is by Tom Greene et al. (2015)

Atmospheric modeling Gray radiative & hydrostatic equilibrium atmospheres Molecular abundances in thermal equilibrium Synthetic spectra at high resolution, 1 to 20 microns 66 million water lines >> 500 million (Barber & Tennyson) 361,000 methane lines >> 9.8 billion (Yurchenko & Tennyson) 114,000 CO lines Voigt line profiles at sub-Doppler resolution Validate vs. Burrows & Fortney

MIRI photometry

Example for TESS-579: Rp = 2.4 Re Tp = 958K K2V host star AU orbit CH 4 NIRSpec G395H range

[M/H]=-1.0 solar abundance one eclipse

Temperature vs. abundance degeneracy NIRSpec G395H + MIRI 12.8  m

NIRSpec G395H + MIRI 12.8  m

Summary Even in the best case, there will be degeneracies unless JWST observations are very carefully planned JWST is a spectroscopic machine, but we may still need its eclipse photometry to break degeneracies and measure temperature