TESS observations of the WASP-121 b phase curve

Tansu Daylan, Maximilian N. Günther, Thomas Mikal-Evans, David K. Sing, Ian Wong, Avi Shporer, Prajwal Niraula, Julien De Wit, Daniel D.B. Koll, Vivien Parmentier, Tara Fetherolf, Stephen R. Kane, George R. Ricker, Roland Vanderspek, S. Seager, Joshua N. Winn, Jon M. Jenkins, Douglas A. Caldwell, David Charbonneau, Christopher E. HenzeMartin Paegert, Stephen Rinehart, Mark Rose, Lizhou Sha, Elisa Quintana, Jesus Noel Villasenor

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


We study the red-optical photometry of the ultrahot Jupiter WASP-121 b as observed by the Transiting Exoplanet Survey Satellite (TESS) and model its atmosphere through a radiative transfer simulation. Given its short orbital period of ∼1.275 days, inflated state, and bright host star, WASP-121 b is exceptionally favorable for detailed atmospheric characterization. Toward this purpose, we use allesfitter to characterize its full red-optical phase curve, including the planetary phase modulation and secondary eclipse. We measure the day- and nightside brightness temperatures in the TESS passband as 3012-+4240 and 2022-+602254 K, respectively, and do not find a statistically significant phase shift between the brightest and substellar points. This is consistent with inefficient heat recirculation on the planet. We then perform an atmospheric retrieval analysis to infer the dayside atmospheric properties of WASP-121 b, such as its bulk composition, albedo, and heat recirculation. We confirm the temperature inversion in the atmosphere and suggest H-, TiO, and VO as potential causes of the inversion, absorbing heat at optical wavelengths at low pressures. Future Hubble Space Telescope and James Webb Space Telescope observations of WASP-121 b will benefit from its first full phase curve measured by TESS.

Original languageEnglish (US)
Article number131
JournalAstronomical Journal
Issue number3
StatePublished - Mar 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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