Looking above the cloud deck of GJ 3470b Spandan Dash1, Matteo Brogi1,2 and Siddharth Gandhi3 1. Department of Physics, University of Warwick, Coventry, UK, CV47AL 2. Department of Physics, University of Turin, 1-10125 Torino, Italy 3. Leiden Observatory, Leiden University, Neils Bohrweg 2, 2333 CA, The Netherlands INTRODUCTION METHODOLOGY RESULTS and DISCUSSION REFERENCES GJ 3470b Properties • Neptune sized but slightly less massive (14 ME < 17.2 ME for Neptune) [4] • P = 3.88 days, Transit time = 1.918 hours [4] • Eccentric orbit – values of e vary quite a lot in literature – can go from slightly eccentric 0.017 to quite eccentric 0.114! [4] • Orbits an M-dwarf [4] but in a polar orbit [5] • Equilibrium temperature 600 K – Hence, warm Neptune – with evidence of clouds [1]. H2O detection but CH4 depletion[1] Fall due to Mie scattering? [1] High Resolution spectroscopy can look above a higher layer of clouds which proves difficult for low res! Figure reproduced from [2]. Figure reproduced from [1]. Spectra (time) Wavelength (pixel) Order 3D flux cuboid for each night Best fit H2O model to low resolution data Model Selection on a grid • ‘Goodness’ of a night is determined by whether we can detect 1x of an artificial exoplanet signal injected into the data. Possible using both nights of CARMENES by processing data between the ingress and egress phases. • Our best fit model to low res observations using just H2O and a cloud cover at 10-2.3 bar shows a detection (>5σ for Panel (e)) by combining both nights of observations with 1 times the best fit model injected in them. • In comparison, raw observations show no direct detection (Panel (f)) and prominent telluric contamination away from the exoplanet position. • Repeating the previous analysis for a grid of models will provide an estimate of how well a group of models are selected against the entire grid. Performing this on an isothermal grid with varying H2O abundances and cloud deck pressures results in both nights (Panels (e) and (f)) giving mostly consistent plots in terms of parameter selection. Combining nights strengthens the choice of selection to a strip of degenerate models, not all of which are in line with the finding in [1]. Combining 2 nights of observations with CARMENES does not show any direct detection of H2O above the cloud deck in the atmosphere of GJ 3470b. However, more good nights are necessary to conclude anything definite. A strong residual telluric feature also suggests the need for more aggressive detrending. Model Selection on an isothermal grid with varying H2O abundances and cloud deck pressures suggests a preference for a set of degenerate models with similar variances from the continuum which is wider than the finding from low resolution HST+Spitzer data. However, the grid assumed is not the same as previous studies and a more accurate grid of models with possible inclusion of two other molecules (CH4 and NH3) can be a potential solution to this non-conformity. This is currently being investigated. [1] Benneke, B., Knutson, H.A., Lothringer, J. et al. A sub-Neptune exoplanet with a low-metallicity methane-depleted atmosphere and Mie-scattering clouds. Nat Astron 3, 813–821 (2019). https://doi.org/10.1038/s41550-019-0800-5 [2] Siddharth Gandhi, Matteo Brogi, Rebecca K Webb, Seeing above the clouds with high-resolution spectroscopy, Monthly Notices of the Royal Astronomical Society, Volume 498, Issue 1, October 2020, Pages 194–204, https://doi.org/10.1093/mnras/staa2424 [3] Matteo Brogi and Michael R. Line 2019 AJ 157 114, https://doi.org/10.3847/1538-3881/aaffd3 [4] NASA Exoplanet Archive: https://exoplanetarchive.ipac.caltech.edu/overview/gj%203470b [5] Stefànsson, Guđmundur, et al. "The Warm Neptune GJ 3470b Has a Polar Orbit." The Astrophysical Journal Letters 931.2 (2022): L15 The figure above shows that detection of molecules with high res spectroscopy becomes much easier even at high cloud decks because the cores of molecular lines at high res