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WASP-121b Secondary Eclipses Revisited Using TESS Observation


We present the detection and characterization of the ultrahot Jupiter WASP-121b (\({{R}_{p}} \simeq 1.865{\kern 1pt} {{R}_{J}}\), \({{M}_{p}} \simeq 1.184{\kern 1pt} {{M}_{J}}\)) around F6 spectral type star (\(V{{ = 10.4}^{m}}\)) using observations from the Transiting Exoplanet Survey Satellite (TESS). The host star is located \(270.0 \pm 90.0\) pc away with a radius of \((1.45 \pm 0.03){\kern 1pt} {{R}_{ \odot }}\) and a mass of \((1.35 \pm 0.06){\kern 1pt} {{M}_{ \odot }}\). We study the publicly available data collected by the TESS in sector 7. We apply Gaussian processes (GPs) to model the systematic noise and the Markov Chain Monte Carlo (MCMC) method to fit it to the data. After removing the instrumental systematic noise, we reliably detect the secondary eclipse with a depth of \(486_{{ - 25}}^{{ + 24}}\) parts-per-million (ppm) and planet-to-star radius ratio, \(p = 0.1237_{{ - 0.0002}}^{{ + 0.0001}}\). The transit ephemeris of WASP-121b is updated using the MCMC method. Finally, to complement our study, we use updated ephemeris to investigate transit time variations (TTVs) for WASP-121b. We observe small variations from the constant-period models in our transit time data.

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NASA’s Science Mission Directorate funds the TESS mission. Our work is based on data collected by this mission, available at Mikulski Archive for Space Telescopes (MAST). Special thanks to Mahmoudreza Oshagh, who helped with useful suggestions that greatly improved the paper, and fruitful discussions on the topics covered in this paper.

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Correspondence to Mohammad Eftekhar.

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Eftekhar, M. WASP-121b Secondary Eclipses Revisited Using TESS Observation. Astron. Rep. 66, 606–615 (2022).

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  • planetary systems
  • stars, individual, WASP-121
  • techniques: photometric methods, data analysis