The First Near-infrared Transmission Spectrum of HIP 41378 f, A Low-mass Temperate Jovian World in a Multiplanet System
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We present a near-infrared transmission spectrum of the long-period (P = 542 days), temperate (T eq = 294 K) giant planet HIP 41378 f obtained with the Wide-Field Camera 3 instrument aboard the Hubble Space Telescope (HST). With a measured mass of 12 ± 3 M ⊕ and a radius of 9.2 ± 0.1 R ⊕, HIP 41378 f has an extremely low bulk density (0.09 ± 0.02 g cm-3). We measure the transit depth with a median precision of 84 ppm in 30 spectrophotometric channels with uniformly sized widths of 0.018 μm. Within this level of precision, the spectrum shows no evidence of absorption from gaseous molecular features between 1.1 and 1.7 μm. Comparing the observed transmission spectrum to a suite of 1D radiative-convective-thermochemical-equilibrium forward models, we rule out clear, low-metallicity atmospheres and find that the data prefer high-metallicity atmospheres or models with an additional opacity source, such as high-altitude hazes and/or circumplanetary rings. We explore the ringed scenario for HIP 41378 f further by jointly fitting the K2 and HST light curves to constrain the properties of putative rings. We also assess the possibility of distinguishing between hazy, ringed, and high-metallicity scenarios at longer wavelengths with the James Webb Space Telescope. HIP 41378 f provides a rare opportunity to probe the atmospheric composition of a cool giant planet spanning the gap in temperature, orbital separation, and stellar irradiation between the solar system giants, directly imaged planets, and the highly irradiated hot Jupiters traditionally studied via transit spectroscopy.
| Originalsprog | Engelsk |
|---|---|
| Artikelnummer | L5 |
| Tidsskrift | Astrophysical Journal Letters |
| Vol/bind | 927 |
| Antal sider | 9 |
| ISSN | 2041-8205 |
| DOI | |
| Status | Udgivet - 2022 |
Bibliografisk note
Funding Information:
We thank the anonymous referee for their insightful comments. We appreciate the painstaking work of the HST technical staff including Patrica Royle and Nikolay Nikolov in scheduling this long sequence of observations. This paper makes use of observations from the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. These observations are associated with HST-GO program 16267 (PI: Dressing), and the analysis was supported by grant HST-GO-16267. M.K.A. is grateful to Johanna Teske and Anjali Piette for useful discussions. C.D.D. gratefully acknowledges additional support from the David & Lucile Packard Foundation (grant No. 2019–69648) and helpful conversations with Christina Hedges. K.O. was supported by JSPS Overseas Research Fellowship. N.S., S.B., and B.A. acknowledge the support by FCT (Fundaçao para a Ciência e a Tecnologia) through national funds and by FEDER through COMPETE2020—Programa Operacional Competitividade e Internacionalização by these grants: UID/FIS/04434/2019; UIDB/04434/2020; UIDP/04434/2020; PTDC/FISAST/32113/2017 & POCI-01-0145-FEDER-032113; PTDC/FISAST/28953/2017 & POCI-01-0145-FEDER-028953. V.A. acknowledges the support from FCT through Investigador contract nr. IF/00650/2015/CP1273/CT0001. J.L.-B. acknowledges financial support received from “la Caixa” Foundation (ID 100010434) and from the European Unions Horizon 2020 research and innovation program under the Marie Slodowska-Curie grant agreement No. 847648, with fellowship code LCF/BQ/PI20/11760023. This research has also been partly funded by the Spanish State Research Agency (AEI) Project No. ESP2017-87676-C5-1-R and No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu”- Centro de Astrobiología (INTA-CSIC).
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
ID: 300907435