ARES IV: Probing the Atmospheres of the Two Warm Small Planets HD 106315c and HD 3167c with the HST/WFC3 Camera*
Gloria Guilluy, Amélie Gressier, Sam Wright, Alexandre Santerne, Adam Yassin Jaziri, Billy Edwards, Quentin Changeat, Darius Modirrousta-Galian, Nour Skaf, Ahmed Al-Refaie, Robin Baeyens, Michelle Fabienne Bieger, Doriann Blain, Flavien Kiefer, Mario Morvan, Lorenzo V. Mugnai, William Pluriel, Mathilde Poveda, Tiziano Zingales, Niall Whiteford, Kai Hou Yip, Benjamin Charnay, Jérémy Leconte, Pierre Drossart, Alessandro Sozzetti, Emmanuel Marcq, Angelos Tsiaras, Olivia Venot, Ingo Waldmann, Jean-Philippe Beaulieu
Abstract
Abstract We present an atmospheric characterization study of two medium-sized planets bracketing the radius of Neptune: HD 106315c ( R P = 4.98 ± 0.23 R ⊕ ) and HD 3167c ( R ⊕ ). We analyze spatially scanned spectroscopic observations obtained with the G141 grism (1.125–1.650 μ m) of the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. We use the publicly available Iraclis pipeline and TauREx3 atmospheric retrieval code and detect water vapor in the atmosphere of both planets, with an abundance of (∼5.68 σ ) and (∼3.17 σ ) for HD 106315c and HD 3167c, respectively. The transmission spectrum of HD 106315c also shows possible evidence of ammonia absorption ( , even if it is not significant), while carbon dioxide absorption features may be present in the atmosphere of HD 3167c in the ∼1.1–1.6 μ m wavelength range ( , ∼3.28 σ ). However, the CO 2 detection appears significant, and it must be considered carefully and put into perspective. Indeed, CO 2 presence is not explained by 1D equilibrium chemistry models, and it could be due to possible systematics. The additional contributions of clouds, CO, and CH 4 are discussed. HD 106315c and HD 3167c will be interesting targets for upcoming telescopes such as the James Webb Space Telescope and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey.