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Evidence for a Nonzero Eccentricity Superpuff Exoplanet WASP-107 b Using JWST Occultation Observation

Yunke Wu, Zixin Zhang, Xinyue Ma, Zhangliang Chen, Wenqin Wang, Shang-Fei Liu, Cong Yu, DiChang Chen, Bo Ma

TL;DR

The paper addresses constraining the eccentricity of WASP-107 b, a low-density super-puff whose inflated radius raises questions about internal heating and migration. It employs a joint analysis of primary transits, secondary eclipse data from JWST, transit timings from HST and TESS, and radial velocity measurements to derive a precise orbital solution. The results yield an eccentricity of $e = 0.09 \pm 0.02$, a mass of $0.096 \pm 0.005 \, M_J$, and a period of $5.721487 \pm 0.000001$ days, with a $99.7\%$ lower limit of $e \approx 0.04$, supporting a scenario in which WASP-107 b is in the final stage of high-eccentricity migration and that tidal dissipation could contribute to the radius inflation. These measurements establish the dynamical status of this planet and inform models of its formation, tidal evolution, and energy budget needed to sustain its inflated radius.

Abstract

WASP-107~b is an extremely low-density super-puff exoplanet whose inflated radius and evidence of strong internal heating make it a key target for understanding planetary structure and evolution. Its orbital eccentricity is a critical parameter for testing mechanisms such as tidal heating and high-eccentricity migration, yet previous measurements have remained inconclusive. Due to the large radial velocity jitter caused by stellar activity, and the presence of at least one additional planet in the system, previous radial velocity measurements could not robustly determine the eccentricity of WASP-107~b. Here we combine the new JWST secondary eclipse data with transit timing data from HST, TESS, and JWST to measure the eccentricity of WASP-107~b. Our joint analysis shows that WASP-107~b has an eccentricity of $0.09\pm0.02$, a mass of $0.096\pm0.005 \, M_J$, and an orbital period of $5.721487\pm0.000001$~days. We find the $99.7\%$ lower limit of the eccentricity is about 0.04. These new measurements are consistent with the scenario in which WASP-107~b is in the final stage of high-eccentricity migration. Preliminary estimate shows that eccentricity-driven tidal dissipation can provide a significant contribution to the energy required to sustain the observed radius inflation of WASP-107~b. Our results establish the dynamical status of one of the most intriguing low-density exoplanets known, and offer new insights into its formation and evolution history.

Evidence for a Nonzero Eccentricity Superpuff Exoplanet WASP-107 b Using JWST Occultation Observation

TL;DR

The paper addresses constraining the eccentricity of WASP-107 b, a low-density super-puff whose inflated radius raises questions about internal heating and migration. It employs a joint analysis of primary transits, secondary eclipse data from JWST, transit timings from HST and TESS, and radial velocity measurements to derive a precise orbital solution. The results yield an eccentricity of , a mass of , and a period of days, with a lower limit of , supporting a scenario in which WASP-107 b is in the final stage of high-eccentricity migration and that tidal dissipation could contribute to the radius inflation. These measurements establish the dynamical status of this planet and inform models of its formation, tidal evolution, and energy budget needed to sustain its inflated radius.

Abstract

WASP-107~b is an extremely low-density super-puff exoplanet whose inflated radius and evidence of strong internal heating make it a key target for understanding planetary structure and evolution. Its orbital eccentricity is a critical parameter for testing mechanisms such as tidal heating and high-eccentricity migration, yet previous measurements have remained inconclusive. Due to the large radial velocity jitter caused by stellar activity, and the presence of at least one additional planet in the system, previous radial velocity measurements could not robustly determine the eccentricity of WASP-107~b. Here we combine the new JWST secondary eclipse data with transit timing data from HST, TESS, and JWST to measure the eccentricity of WASP-107~b. Our joint analysis shows that WASP-107~b has an eccentricity of , a mass of , and an orbital period of ~days. We find the lower limit of the eccentricity is about 0.04. These new measurements are consistent with the scenario in which WASP-107~b is in the final stage of high-eccentricity migration. Preliminary estimate shows that eccentricity-driven tidal dissipation can provide a significant contribution to the energy required to sustain the observed radius inflation of WASP-107~b. Our results establish the dynamical status of one of the most intriguing low-density exoplanets known, and offer new insights into its formation and evolution history.
Paper Structure (2 sections, 1 figure)

This paper contains 2 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Data and Observation

Figures (1)

  • Figure 1: Reduced light curves and transit model fitting results of WASP-107 b. Left panels show relative flux light curves, while right panels display corresponding residuals. Data are presented with vertical offsets for clarity: JWST (top), TESS (middle), and HST (bottom), each labeled by observation ID and instrument. For JWST and TESS, un-filled blue points show unbinned data and solid blue points show 50-point binned data. For HST, solid blue points represent unbinned normalized detrended data. Black lines indicate best-fitting transit models.