An Ultra-Hot Neptune in the Neptune desert

James S. Jenkins, Matías R. Díaz, Nicolás T. Kurtovic, Néstor Espinoza, Jose I. Vines, Pablo A. Peña Rojas, Rafael Brahm, Pascal Torres, Pía Cortés-Zuleta, Maritza G. Soto, Eric D. Lopez, George W. King, Peter J. Wheatley, Joshua N. Winn, David R. Ciardi, George Ricker, Roland Vanderspek, David W. Latham, Sara Seager, Jon M. JenkinsCharles A. Beichman, Allyson Bieryla, Christopher J. Burke, Jessie L. Christiansen, Christopher E. Henze, Todd C. Klaus, Sean McCauliff, Mayuko Mori, Norio Narita, Taku Nishiumi, Motohide Tamura, Jerome Pitogo de Leon, Samuel N. Quinn, Jesus Noel Villaseñor, Michael Vezie, Jack J. Lissauer, Karen A. Collins, Kevin I. Collins, Giovanni Isopi, Franco Mallia, Andrea Ercolino, Cristobal Petrovich, Andrés Jordán, Jack S. Acton, David J. Armstrong, Daniel Bayliss, François Bouchy, Claudia~Belardi, Edward M. Bryant, Matthew R. Burleigh, Juan Cabrera, Sarah L. Casewell, Alexander Chaushev, Benjamin F. Cooke, Philipp Eigmüller, Anders Erikson, Emma Foxell, Boris T. Gänsicke, Samuel Gill, Edward Gillen, Maximilian N. Günther, Michael R. Goad, Matthew J. Hooton, James A. G. Jackman, Tom Louden, James McCormac, Maximiliano Moyano, Louise D. Nielsen, Don Pollacco, Didier Queloz, Heike Rauer, Liam Raynard, Alexis M. S. Smith, Rosanna H. Tilbrook, Ruth Titz-Weider, Oliver Turner, Stéphane Udry, Simon R. Walker, Christopher A. Watson, Richard G. West, Enric Palle, Carl Ziegler, Nicholas Law, Andrew W. Mann

Research output: Contribution to journalArticle

Abstract

About one out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultra-short-period planet (Sanchis-ojeda et al. 2014; Winn et al. 2018). All of the previously known ultra-short-period planets are either hot Jupiters, with sizes above 10 Earth radii (Re), or apparently rocky planets smaller than 2 Re. Such lack of planets of intermediate size (the "hot Neptune desert") has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here, we report the discovery of an ultra-short-period planet with a radius of 4.6 Re and a mass of 29 Me, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite (Ricker et al. 2015) revealed transits of the bright Sun-like star LTT9779, every 0.79 days. The planet's mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0^(+2.7)_(-2.9)% of the total mass. With an equilibrium temperature around 2000 K, it is unclear how this "ultra-hot Neptune" managed to retain such an envelope. Follow-up observations of the planet's atmosphere to better understand its origin and physical nature will be facilitated by the star's brightness (Vmag=9.8).
Original languageEnglish
JournalNature Astronomy
DOIs
Publication statusPublished - 21 Sep 2020

Bibliographical note

26 pages, 10 figures, 3 tables. Published in Nature Astronomy (21/09/2020)

Keywords

  • astro-ph.EP
  • astro-ph.SR

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    Jenkins, J. S., Díaz, M. R., Kurtovic, N. T., Espinoza, N., Vines, J. I., Rojas, P. A. P., Brahm, R., Torres, P., Cortés-Zuleta, P., Soto, M. G., Lopez, E. D., King, G. W., Wheatley, P. J., Winn, J. N., Ciardi, D. R., Ricker, G., Vanderspek, R., Latham, D. W., Seager, S., ... Mann, A. W. (2020). An Ultra-Hot Neptune in the Neptune desert. Nature Astronomy. https://doi.org/10.1038/s41550-020-1142-z