Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 µ m Kristin Sotzen, Kevin Stevenson, David Sing, Brian Kilpatrick, Hannah Wakeford, Joseph Filippazzo, Nikole Lewis, Sarah Hörst, Mercedes López-Morales, Gregory Henry, et al. To cite this version: Kristin Sotzen, Kevin Stevenson, David Sing, Brian Kilpatrick, Hannah Wakeford, et al.. Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 µ m. Astronomical Journal, American Astronomical Society, 2020, 159 (1), pp.5. 10.3847/1538-3881/ab5442. hal-03038422 HAL Id: hal-03038422 https://hal.archives-ouvertes.fr/hal-03038422 Submitted on 3 Dec 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Draft version November 7, 2019 Typeset using LATEX twocolumn style in AASTeX62 Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 µm Kristin S. Sotzen,1, 2 Kevin B. Stevenson,3, 4 David K. Sing,1 Brian M. Kilpatrick,4 Hannah R. Wakeford,4 Joseph C. Filippazzo,4 Nikole K. Lewis,5 Sarah M. Horst,¨ 1, 4 Mercedes Lopez-Morales,´ 6 Gregory W. Henry,7 Lars A. Buchhave,8 David Ehrenreich,9 Jonathan D. Fraine,10 Antonio Garc´ıa Munoz,~ 11 Rahul Jayaraman,12 Panayotis Lavvas,13 Alain Lecavelier des Etangs,14 Mark S. Marley,15 Nikolay Nikolov,1 Alexander D. Rathcke,8 and Jorge Sanz-Forcada16 1Johns Hopkins University, 3400 N. Charles St, Baltimore, MD 21218, USA 2 JHU Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723, USA 3 JHU Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA 4Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218, USA 5Department of Astronomy and Carl Sagan Institute, Cornell University, 122 Sciences Drive, Ithaca, NY 14853, USA 6Center for Astrophysics j Harvard & Smithsonian, 60 Garden St, Cambridge, Cambridge, MA 02138, USA 7Center for Excellence in Information Systems, Tennessee State University, Nashville, TN 37209, USA 8DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 328, DK-2800 Kgs. Lyngby, Denmark 9Observatoire de lUniversit´ede Gen`eve, 51 chemin des Maillettes, 1290 Sauverny, Switzerland 10Space Science Institute, 4750 Walnut St #205, Boulder, CO 80301, USA 11Zentrum f¨urAstronomie und Astrophysik, Technische Universit¨atBerlin, EW 801, Hardenbergstrasse 36, D-10623 Berlin, Germany 12Brown University, Department of Physics, Box 1843, Providence, RI 02904, USA 13Groupe de Spectrom´etrieMoleculaire et Atmosph´erique,Universit´ede Reims Champagne Ardenne, Reims, France 14Institut d'astrophysique de Paris, UMR7095 CNRS, Sorbonne Universit´e,98bis Boulevard Arago, 75014 Paris, France 15NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA 16Centro de Astrobiolog´ıa(CSIC-INTA), E-28692 Villanueva de la Ca~nada,Madrid, Spain (Received 3 September 2019; Revised 31 October 2019; Accepted 3 November 2019) ABSTRACT As part of the PanCET program, we have conducted a spectroscopic study of WASP-79b, an inflated hot Jupiter orbiting an F-type star in Eridanus with a period of 3.66 days. Building on the original WASP and TRAPPIST photometry of Smalley et al.(2012), we examine HST/WFC3 (1.125 - 1.650 µm), Magellan/LDSS-3C (0.6 - 1 µm) data, and Spitzer data (3.6 and 4.5 µm). Using data from all three instruments, we constrain the water abundance to be {2.20 ≤ log(H2O) ≤ {1.55. We present these results along with the results of an atmospheric retrieval analysis, which favor inclusion of FeH and H- in the atmospheric model. We also provide an updated ephemeris based on the Smalley, HST/WFC3, LDSS-3C, Spitzer, and TESS transit times. With the detectable water feature and its occupation of the clear/cloudy transition region of the temperature/gravity phase space, WASP-79b is a target of interest for the approved JWST Director's Discretionary Early Release Science (DD ERS) program, with ERS observations planned to be the first to execute in Cycle 1. Transiting exoplanets have been approved for 78.1 hours of data collection, and with the delay in the JWST launch, WASP-79b is now arXiv:1911.02051v1 [astro-ph.EP] 5 Nov 2019 a target for the Panchromatic Transmission program. This program will observe WASP-79b for 42 hours in 4 different instrument modes, providing substantially more data by which to investigate this hot Jupiter. Keywords: methods | observational: atmospheres | planets and satellies: individual | WASP-79b 1. INTRODUCTION Corresponding author: Kristin Showalter Sotzen Based on studies of planets and moons within the solar [email protected], [email protected] system and spectral analyses of exoplanets, a persistent atmosphere is generally accompanied by clouds and/or 2 hazes. Recent studies of hot Jupiters have revealed that estimate of approximately one MJup and such a large ra- many of the exoplanets observed in transmission have dius estimate, WASP-79b's density is comparatively low, cloudy or hazy properties, with their spectra dominated implying that its atmosphere is extended. In addition, by strong optical Rayleigh and/or Mie scattering from the host star WASP-79 is a bright, quiet F-type star with high-altitude aerosol particles (e.g., Sing et al.(2016); consistent stellar activity, with variation in the baseline Stevenson et al.(2016a); Wakeford & Sing(2016); Lav- stellar flux within 0.1% (Section 2.3.4). vas & Koskinen(2017)). Clouds and hazes in exoplan- WASP-79b has a Teq ∼1800 K and a log g between 2.67 etary atmospheres can have a significant impact on the and 2.85 (Smalley et al. 2012), placing this planet in a detectable spectra for these worlds. In the optical range, transition region of the temperature/gravity phase space. small particles produce scattering that leads to steep On one side of this transition region, planets have been slopes that progressively become shallower as the parti- found to have muted water features due to clouds and cle radius increases (see e.g., Lavvas & Koskinen(2017)). hazes, while on the other side, planets have been found This scattering effectively dampens any features from the to have strong measured water features, implying clearer deeper atmosphere, including pressure-broadened alkali atmospheres (Stevenson 2016). Being in this transition Na and K lines, and can mute or obscure expected water region, WASP-79b provided an opportunity to further absorption features in the near-infrared (see e.g., Wake- study this relationship between temperature, gravity, and ford & Sing(2016)). the presence of atmospheric clouds and/or hazes. These The majority of current exoplanet spectra are con- studies are important for predictions of atmospheric fea- structed from wavelengths in the optical and near- ture obscuration, which inform target selection and ob- infrared wavelengths, revealing information on the por- servations for telescopes like the Hubble Space Telescope tion of transmission spectra for aerosols where only scat- (HST). tering features are seen. When interpreting these ob- Additionally, with its broad observing windows (Bean servations, the slope of spectra in the optical regime is et al. 2018), WASP-79b presented an excellent candidate proportional to the temperature of the atmosphere and for a transmission spectroscopy study as well as a poten- can be indicative of specific species when small grain sizes tial Early Release Science (ERS) candidate for the James are considered (Wakeford & Sing 2016). Additionally, ab- Webb Space Telescope (JWST). It was therefore sched- sorption features in the near- and mid-infrared spectra uled for follow-up observations using HST, the Magellan can be identified as the vibrational modes of the major Large Dispersion Survey Spectrograph 3 (LDSS3), and bond pairs in certain potential condensates, providing the Spitzer Space Telescope to determine its value as a composition information (Wakeford & Sing 2016). candidate for JWST observation, with broad wavelength The survey analysis performed by Sing et al.(2016) coverage to evaluate its value as an ERS candidate. of ten hot Jupiters found that planets with predomi- In Sections 2.1, 2.2, 2.3, and 2.4, we describe obser- nantly clear atmospheres show prominent alkali and H2O vations, analysis methods, and results from TESS, HST, absorption, with infrared radii values commensurate or LDSS3, and Spitzer respectively. In Section3, we dis- higher than the optical altitudes, while heavily hazy and cuss the atmospheric retrieval analysis and expectations cloudy planets have strong optical scattering slopes, nar- for JWST observations, and in Section4, we present our row alkali lines, and H2O absorption that is partially or conclusions. completely obscured. Like many transiting exoplanets found using ground- 2. OBSERVATIONS based surveys, WASP-79b is a hot Jupiter with an ex- 2.1. TESS Data tended atmosphere. Discovered in 2012 by Smalley et The Transiting Exoplanet Survey Satellite (TESS) ob- al using photometry from the WASP-South and TRAP- served 12 transits of WASP-79b in January and February PIST telescopes, it was found to have a planetary mass of 2019. TESS provides data in the 0.6 - 1.0 µm band, of 0.90 ± 0.08 M and a large radius estimate, ranging Jup and the TESS light curve contains data covering 12 tran- from 1.7 ± 0.11 R using a main-sequence mass-radius Jup sits in Sectors 4 and 5. We fit the TESS WASP-79b constraint on the Markov Chain Monte Carlo (MCMC) 2-minute cadence transits using the Presearch Data Con- process, to 2.1 ± 0.14 R using a non-main sequence Jup ditioning (PDC) light curve, which has been corrected for constraint (Smalley et al.