The CARMENES search for exoplanets around M dwarfs
Authors: Dreizler S. , Crossfield I. J. M. , Kossakowski D. , Plavchan P. , Jeffers S. V. , Kemmer J. , Luque R. , Espinoza N. , Pallé E. , Stassun K. , Matthews E. , Cale B. , Caballero J. A. , Schlecker M. , Lillo-Box J. , Zechmeister M. , Lalitha S. , Reiners A. , Soubkiou A. , Bitsch B. , Zapatero Osorio M. R. , Chaturvedi P. , Hatzes A. P. , Ricker G. , Vanderspek R. , Latham D. W. , Seager S. , Winn J. , Jenkins J. M. , Aceituno J. , Amado P. J. , Barkaoui K. , Barbieri M. , Batalha N. M. , Bauer F. F. , Benneke B. , Benkhaldoun Z. , Beichman C. , Berberian J. , Burt J. , Butler R. P. , Caldwell D. A. , Chintada A. , Chontos A. , Christiansen J. L. , Ciardi D. R. , Cifuentes C. , Collins K. A. , Collins K. I. , Combs D. , Cortés-Contreras M. , Crane J. D. , Daylan T. , Dragomir D. , Esparza-Borges E. , Evans P. , Feng F. , Flowers E. E. , Fukui A. , Fulton B. , Furlan E. , Gaidos E. , Geneser C. , Giacalone S. , Gillon M. , Gonzales E. , Gorjian V. , Hellier C. , Hidalgo D. , Howard A. W. , Howell S. , Huber D. , Isaacson H. , Jehin E. , Jensen E. L. N. , Kaminski A. , Kane S. R. , Kawauchi K. , Kielkopf J. F. , Klahr H. , Kosiarek M. R. , Kreidberg L. , Kürster M. , Lafarga M. , Livingston J. , Louie D. , Mann A. , Madrigal-Aguado A. , Matson R. A. , Mocnik T. , Morales J. C. , Muirhead P. S. , Murgas F. , Nandakumar S. , Narita N. , Nowak G. , Oshagh M. , Parviainen H. , Passegger V. M. , Pollacco D. , Pozuelos F. J. , Quirrenbach A. , Reefe M. , Ribas I. , Robertson P. , Rodríguez-López C. , Rose M. E. , Roy A. , Schweitzer A. , Schlieder J. , Shectman S. , Tanner A. , Şenavcı H. V. , Teske J. , Twicken J. D. , Villasenor J. , Wang S. X. , Weiss L. M. , Wittrock J. , Yılmaz M. , Zohrabi F. 
Published: November 2020

We report the discovery of a Neptune-like planet (LP 714-47 b, P = 4.05204 d, mb = 30.8 ± 1.5M⊕, Rb = 4.7 ± 0.3 R⊕) located in the “hot Neptune desert”. Confirmation of the TESS Object of Interest (TOI 442.01) was achieved with radial-velocity follow-up using CARMENES, ESPRESSO, HIRES, iSHELL, and PFS, as well as from photometric data using TESS, Spitzer, and ground-based photometry from MuSCAT2, TRAPPIST-South, MONET-South, the George Mason University telescope, the Las Cumbres Observatory Global Telescope network, the El Sauce telescope, the TÜBİTAK National Observatory, the University of Louisville Manner Telescope, and WASP-South. We also present high-spatial resolution adaptive optics imaging with the Gemini Near-Infrared Imager. The low uncertainties in the mass and radius determination place LP 714-47 b among physically well-characterised planets, allowing for a meaningful comparison with planet structure models. The host star LP 714-47 is a slowly rotating early M dwarf (Teff = 3950 ± 51 K) with a mass of 0.59 ± 0.02M⊙ and a radius of 0.58 ± 0.02R⊙. From long-term photometric monitoring and spectroscopic activity indicators, we determine a stellar rotation period of about 33 d. The stellar activity is also manifested as correlated noise in the radial-velocity data. In the power spectrum of the radial-velocity data, we detect a second signal with a period of 16 days in addition to the four-day signal of the planet. This could be shown to be a harmonic of the stellar rotation period or the signal of a second planet. It may be possible to tell the difference once more TESS data and radial-velocity data are obtained.