Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 μm

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(H 2 O) ≤ -1.55. We present these results along with the results of an atmospheric retrieval analysis, which favor inclusion of FeH and Hin 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 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.

ARES. II. Characterizing the Hot Jupiters WASP-127 b, WASP-79 b, and WASP-62b with the Hubble Space Telescope*

“…Their retrieval results indicates the presence of H 2 O, Na, and FeH. Our retrieved water abundance is consistent with that from Sotzen et al (2020): (−2.20<log(H 2 O)<−1.55).…”

“…We do not detect signatures of CH 4 , CO, or CO 2 . The retrieved temperature of ∼1000 K is lower than the calculated equilibrium temperature for this type of planet; this was also found in Sotzen et al (2020) and is discussed further in Section 4. (Figures 8 and 9).…”

“…In our retrievals without FeH as an opacity source, our solution is driven to low temperatures; Sotzen et al (2020) encountered a similar predicament when attempting to fit a chemical equilibrium model to the data. Here, by adding FeH as a retrieval parameter, our recovered temperature increases to…”

On The Compatibility of Ground-based and Space-based Data: WASP-96 b, An Example

“…observations from NASA Infrared Telescope Facility (IRTF)/ SpeX instrument and WFC3 observations on HD 189733b, many others followed similar trends (e.g., Bean et al 2013;Mancini et al 2013;Stevenson et al 2016;Sotzen et al 2020). While these data sets could be compatible, there is no guarantee and this should not be taken for granted.…”

Transmission Spectroscopy for the Warm Sub-Neptune HD 3167c: Evidence for Molecular Absorption and a Possible High-metallicity Atmosphere

“…The Hubble Space Telescope (HST) has proven a productive facility for characterizing the atmospheres of transiting exoplanets. Observational studies released since 2019 alone include Arcangeli et al (2019), Benneke et al (2019aBenneke et al ( , 2019b, Chachan et al (2019), dos Santos et al (2019), Mikal-Evans et al (2019, Sing et al (2019), Spake et al (2019), Guo et al (2020), Wong et al (2020), Alam et al (2020), Fu et al (2020), Wakeford et al (2020), Carter et al (2020), Bruno et al (2020), Sotzen et al (2020), Carone et al (2020), Kreidberg et al (2020), and Colón et al (2020). Transmission spectroscopy measurements, made during primary transit, allow the composition of the day-night terminator atmosphere to be probed, while at other phases in the orbit when the irradiated dayside hemisphere is visible, the planetary emission can be constrained (for overviews, see Deming & Seager 2017;Deming et al 2019).…”