TESS Revisits WASP-12: Updated Orbital Decay Rate and Constraints on Atmospheric Variability

Abstract

After observing WASP-12 in the second year of the primary mission, the Transiting Exoplanet Survey Satellite (TESS) revisited the system in late 2021 during its extended mission. In this paper, we incorporate the new TESS photometry into a reanalysis of the transits, secondary eclipses, and phase curve. We also present a new K s -band occultation observation of WASP-12b obtained with the Palomar/Wide-field Infrared Camera instrument. The latest TESS photometry spans three consecutive months, quadrupling the total length of the TESS WASP-12 light curve and extending the overall time baseline by almost two years. Based on the full set of available transit and occultation timings, we find that the orbital period is shrinking at a rate of −29.81 ± 0.94 ms yr−1. The additional data also increase the measurement precision of the transit depth, orbital parameters, and phase-curve amplitudes. We obtain a secondary eclipse depth of 466 ± 35 ppm, a 2σ upper limit on the nightside brightness of 70 ppm, and a marginal 6.°2 ± 2.°8 eastward offset between the dayside hotspot and the substellar point. The voluminous TESS data set allows us to assess the level of atmospheric variability on timescales of days, months, and years. We do not detect any statistically significant modulations in the secondary eclipse depth or day–night brightness contrast. Likewise, our measured K s -band occultation depth of 2810 ± 390 ppm is consistent with most ∼2.2 μm observations in the literature.

Evidence of Long-term Period Variations in the Exoplanet Transit Database (ETD)

“…Thus, comparing only UTC times that span multiple years may introduce an artificial drift in the transit times that could mimic a true variation in the HJ's orbit. The ETD includes long-term observations of WASP-12 b, which serves as a critical reference due to its comprehensive study in the literature (Maciejewski et al 2016;Patra et al 2017;Yee et al 2019;Turner et al 2020;Wong et al 2022). It is thus reassuring that the WASP-12 b results from this study are in agreement with literature values, showing a highly significant decay (Table A9).…”

Twinkle: a small satellite spectroscopy mission for the next phase of exoplanet science

“…Work is ongoing to identify further targets of interest for this science case. Furthermore, Twinkle data could be utilised to search for orbital decay or precession, [28][29][30] for which a long baseline is again critical. With Spitzer no longer operating, CHEOPS only providing visible data, and HST or JWST time unlikely to be granted purely for this science case, Twinkle's infrared spectrometer will be unique in its ability to provide measurements of the timing of secondary eclipses which will be useful in distinguishing between decay and precession models.…”

“…With Spitzer no longer operating, CHEOPS only providing visible data, and HST or JWST time unlikely to be granted purely for this science case, Twinkle's infrared spectrometer will be unique in its ability to provide measurements of the timing of secondary eclipses which will be useful in distinguishing between decay and precession models. 29,30 Figure 5. Twinkle can view targets that are within 40 • of the ecliptic plane.…”

Revisiting the Transit Timing Variations in the TrES-3 and Qatar-1 Systems with TESS Data

“…Patra et al (2017) confirmed this, but suspected the possibility of apsidal precession. Recent timing analyses performed by Yee et al (2020), Turner et al (2021), and Wong et al (2022), including data from TESS and from the literature, provide strong evidence of orbital decay for WASP-12b. The WASP-12 system is currently the only system in which orbital decay has been confirmed directly through transit observations.…”

“…In order to address these issues, the Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2014), which launched in 2018, is valuable, because it is not only discovering new extrasolar planets, but also following up the transits of previously known hot Jupiters. Combining ground-based transit data with the high-precision 2 minute cadence transit data provided by TESS is extremely helpful for refining the estimates of system parameters (e.g., Cortés-Zuleta et al 2020;Ikwut-Ukwa et al 2020;Szabó et al 2020;Southworth et al 2022), exploring the existence of additional planets (e.g., Huang et al 2018;Garai et al 2020;Teske et al 2020), and searching for the possibility of long-term trends due to orbital decay, apsidal precession, the Applegate mechanism (Applegate 1992), and line-of-sight acceleration phenomena in hot-Jupiter systems (e.g., Watson & Marsh 2010;Bouma et al 2019;Southworth et al 2019;Bouma et al 2020;Yee et al 2020;Battley et al 2021;Turner et al 2021Turner et al , 2022Wong et al 2022). In the context of orbital decay studies, Maciejewski et al (2016) first reported an orbital decay rate of −25.60 ± 4.0 ms yr −1 for the hot Jupiter WASP-12b, using transit data spanning a decade.…”