E xoplanetary atmospheres at high spectral resolution with SPICA/SMI

1. Exoplanetary atmospheres at high spectral resolution with SPICA/SMI A. Sozzetti1, A.S. Bonomo1, R. Claudi2, P. Giacobbe1, G. Guilluy1, S. Ligori1, G. Micela3 1INAF- Osservatorio Astrofisico di Torino, Pino Torinese (TO), Italy 2INAF – Osservatorio Astronomico di Padova, Padova, Italy 3INAF - Osservatorio Astronomico di Palermo, Palermo, Italy

2. 25 Years of Exoplanet Discoveries • Thousands of planets found • Amazing diversity (hot Jupiters, warm Super Earths and Neptunes, cold Super Jupiters…) • Most systems unlike the Solar System • Earth-mass/size objects very common around low-mass stars • Planetary atmospheres: some spectacular successes, but we have just started

3. Atmospheres: What can you study at what λ? Madhusudhan 2019 Key processes active in exoplanetary atmospheres

4. Atmospheric Composition: Fossil evidence of planet formation location and migration Madhusudhan 2019 Madhusudhan et al. 2016 Determining abundances (e.g., CO, H2O, CH4, CO2, NH3, C2H2) for close-in planets over a wide range of wavelengths allows to derive abundance ratios (e.g. O/H, C/H, C/O), thereby constraining planetary formation conditions and subsequent orbital evolution

5. Transiting Exoplanet atmospheres Tinetti et al. 2013 Deming et al. 2019 A Rosetta Stone for planetary formation and evolution processes!

6. Close-in Planets: Where do we stand? Madhusudhan 2019

7. Successes of low-res spectroscopy • Continuum of clear to cloudy atmospheres • Clear: strong Alkali and H20 absorption, larger radii in the NIR • Hazy, cloudy: strong Rayleigh scattering slope, narrow Alkali lines, H20 absorption more or less obscured Hardly any spectroscopy beyond 3 μm Sing et al. 2016

8. Atmospheres at high spectral resolution • * At R > 20,000 molecular bands are resolved in a dense forest of individual lines • * Strong Doppler effects due to orbital motion of the planet (up to >150 km/s). • Moving planet lines are distinguished from stationary telluric + stellar lines • Molecules are detected by cross-correlation with libraries of synthetic spectra • High-cadence time-series critical to disentangle the planetary motion

9. GIANO @ TNG • - Transmission spectroscopy of H2O at 0.95-2.45 μm • for HD189733b (Brogi, Giacobbe, Guilluy et al. 2018) • Emission spectroscopy of H2O and for the first time CH4for HD102195b(Guilluy, Sozzetti, Brogi et al. 2019) • Same SNR (> 5) of the CRIRES@VLT detections.

10. Low-res vs. High-res Spectroscopy Brogi et al. 2018 Birkby 2019 GIANO LRS+HRS: High Complementarity!

11. ARIEL (LRS) Warm Neptune Hot Jupiter Warm sub.Neptune Hot super Earth Tinetti et al. 2018

12. JWST (LRS+MRS) Greene et al. 2016 Batalha et al. 2018 MIRI appears unlikely to provide robust constraints on the atmospheric composition of warm sub-Neptunes and temperate terrestrial planets.

13. Mid-Infrared: SPICA/SMI is competitive SMI/HRS Madhusudhan 2019 Degeneracies between abundances and other atmospheric properties (clouds, hazes) can only be resolved with high-precision spectra over a long spectral baseline, from visible to infrared, and with multiple molecular features (most of all for temperate terrestrials!)

14. SNR Considerations - JWST Deming et al. 2019 SNR for water vapor absorption of known small planets and anticipated TESS planet discoveries, vs. planetary radius. These calculationsapply to observations using JWST for 10 hr per planet (only a relatively few planets will be observed).

15. SMI Transmission spectroscopy: A Simple Exercise • Use NASA’s Planetary Spectrum Generator • Adopt an ideal (photon-noise limited) SPICA/SMI • 1 transit time-series observations of HD189733b, GJ1214b, and TRAPPIST-1e, with • basic hydrostatic equilibrium atmospheric properties (no clouds) • Simple SNR calculation for detection of absoprtion from the strongest molecules • in the 12-18 micron range (proportional to sqrt(Nlines)) • - HD189733b (hot Jupiter): SNR of order 200 • GJ124b (warm sub-Neptune): SNR of order 50 • TRAPPIST-1e (temperate Earth-type): SNR of order 10

16. Summary • The study of exoplanetary atmospheres provides fundamental insights on the • formation and evolutionary paths of extrasolar planetary systems • High-resolution spectroscopy (HRS) is becoming a key observational channel for • investigating atmospheric chemistry, physics, and dynamics. Key is being able to access • simultaneously a large wavelenght range • The mid-infrared window accessible ONLY with SPICA/SMI at HRS can potentially • provide crucial elements of complementarity (via tranmission and emission spectroscopy) • with and resolve elements of ambiguities or limitations inherent to the space-based ARIEL • and JWST LRS&MRS observations (occurring before SPICA flies). It will also provide access • to a sample of close-in non-transiting system • Naturally, to move further quantitatively, this will require better studies of the SPICA/SMI • potential given a realistic instrument performance (stability, background limits, etc.), time-series • observations capabilities, and overall identification of the interest for using SPICA observing • time for exoplanet atmospheres science