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arXiv · 1809.00678

NGTS-4b: A sub-Neptune Transiting in the Desert

Richard G. West·Edward Gillen·Daniel Bayliss·Matthew R. Burleigh·Laetitia Delrez·Maximilian N. Günther·Simon T. Hodgkin·James A. G. Jackman·James S. Jenkins·George King·James McCormac·Louise D. Nielsen·Liam Raynard·Alexis M. S. Smith·Maritza Soto·Oliver Turner·Peter J. Wheatley·Yaseen Almleaky·David J. Armstrong·Claudia Belardi·François Bouchy·Joshua T. Briegal·Artem Burdanov·Juan Cabrera·Sarah L. Casewel·Alexander Chaushev·Bruno Chazelas·Paul Chote·Benjamin F. Cooke·Szilard Csizmadia·Elsa Ducrot·Philipp Eigmüller·Anders Erikson·Emma Foxell·Boris T. Gänsicke·Michaël Gillon·Michael R. Goad·Emmanuël Jehin·Gregory Lambert·Emma S. Longstaff·Tom Louden·Maximiliano Moyano·Catriona Murray·Don Pollacco·Didier Queloz·Heike Rauer·Sandrine Sohy·Samantha J. Thompson·Stéphane Udry·Simon. R. Walker·Christopher A. Watson
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Abstract

We report the discovery of NGTS-4b, a sub-Neptune-sized planet transiting a 13th magnitude K-dwarf in a 1.34d orbit. NGTS-4b has a mass M=$20.6\pm3.0$M_E and radius R=$3.18\pm0.26$R_E, which places it well within the so-called "Neptunian Desert". The mean density of the planet ($3.45\pm0.95$g/cm^3) is consistent with a composition of 100% H$_2$O or a rocky core with a volatile envelope. NGTS-4b is likely to suffer significant mass loss due to relatively strong EUV/X-ray irradiation. Its survival in the Neptunian desert may be due to an unusually high core mass, or it may have avoided the most intense X-ray irradiation by migrating after the initial activity of its host star had subsided. With a transit depth of $0.13\pm0.02$%, NGTS-4b represents the shallowest transiting system ever discovered from the ground, and is the smallest planet discovered in a wide-field ground-based photometric survey.

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Richard G. West, Edward Gillen, Daniel Bayliss, Matthew R. Burleigh, Laetitia Delrez, Maximilian N. Günther, Simon T. Hodgkin, James A. G. Jackman, James S. Jenkins, George King, James McCormac, Louise D. Nielsen, Liam Raynard, Alexis M. S. Smith, Maritza Soto, Oliver Turner, Peter J. Wheatley, Yaseen Almleaky, David J. Armstrong, Claudia Belardi, François Bouchy, Joshua T. Briegal, Artem Burdanov, Juan Cabrera, Sarah L. Casewel, Alexander Chaushev, Bruno Chazelas, Paul Chote, Benjamin F. Cooke, Szilard Csizmadia, Elsa Ducrot, Philipp Eigmüller, Anders Erikson, Emma Foxell, Boris T. Gänsicke, Michaël Gillon, Michael R. Goad, Emmanuël Jehin, Gregory Lambert, Emma S. Longstaff, Tom Louden, Maximiliano Moyano, Catriona Murray, Don Pollacco, Didier Queloz, Heike Rauer, Sandrine Sohy, Samantha J. Thompson, Stéphane Udry, Simon. R. Walker, Christopher A. Watson. 2018-09-03. NGTS-4b: A sub-Neptune Transiting in the Desert. https://doi.org/10.1093/mnras%2Fstz1084

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