A transiting, temperate mini-Neptune orbiting the M dwarf TOI-1759 unveiled by TESS
Creators: name: Espinoza, Néstor
name: Pallé, Enric
name: Kemmer, Jonas
name: Luque, Rafael
name: Caballero, José A.
name: Cifuentes, Carlos
name: Herrero, Enrique
name: Béjar, Víctor J. Sánchez
name: Stock, Stephan
name: Molaverdikhani, Karan
name: Morello, Giuseppe
name: Kossakowski, Diana
name: Schlecker, Martin
name: Amado, Pedro J.
name: Bluhm, Paz
name: Cortés-Contreras, Miriam
name: Henning, Thomas
name: Kreidberg, Laura
name: Kürster, Martin
name: Lafarga, Marina
name: Lodieu, Nicolas
name: Morales, Juan Carlos
name: Oshagh, Mahmoudreza
name: Passegger, Vera M.
name: Pavlov, Alexey
name: Quirrenbach, Andreas
name: Reffert, Sabine
name: Reiners, Ansgar
name: Ribas, Ignasi
name: Rodríguez, Eloy
name: López, Cristina Rodríguez
name: Schweitzer, Andreas
name: Trifonov, Trifon
name: Chaturvedi, Priyanka
name: Dreizler, Stefan
name: Jeffers, Sandra V.
name: Kaminski, Adrian
name: López-González, María José
name: Lillo-Box, Jorge
name: Montes, David
name: Nowak, Grzegorz
name: Pedraz, Santos
name: Vanaverbeke, Siegfried
name: Osorio, Maria R. Zapatero
name: Zechmeister, Mathias
name: Collins, Karen A.
name: Girardin, Eric
name: Guerra, Pere
name: Naves, Ramon
name: Crossfield, Ian J. M.
name: Matthews, Elisabeth C.
name: Howell, Steve B.
name: Ciardi, David R.
name: Gonzales, Erica
name: Matson, Rachel A.
name: Beichman, Charles A.
name: Schlieder, Joshua E.
name: Barclay, Thomas
name: Vezie, Michael
name: Villaseñor, Jesus Noel
name: Daylan, Tansu
name: Mireies, Ismael
name: Dragomir, Diana
name: Twicken, Joseph D.
name: Jenkins, Jon
name: Winn, Joshua N.
name: Latham, David
name: Ricker, George
name: Seager, Sara
Publisher: name: arXiv
Year: 2022
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the discovery and characterization of TOI-1759~b, a temperate (400 K) sub-Neptune-sized exoplanet orbiting the M~dwarf TOI-1759 (TIC 408636441). TOI-1759 b was observed by TESS to transit on sectors 16, 17 and 24, with only one transit observed per sector, creating an ambiguity on the orbital period of the planet candidate. Ground-based photometric observations, combined with radial-velocity measurements obtained with the CARMENES spectrograph, confirm an actual period of $18.85019 \pm 0.00014$ d. A joint analysis of all available photometry and radial velocities reveal a radius of $3.17 \pm 0.10\,R_\oplus$ and a mass of $10.8 \pm 1.5\,M_\oplus$. Combining this with the stellar properties derived for TOI-1759 ($R_\star = 0.597 \pm 0.015\,R_\odot$; $M_\star = 0.606 \pm 0.020\,M_\odot$; $T_{\textrm{eff}} = 4065 \pm 51$ K), we compute a transmission spectroscopic metric (TSM) value of over 80 for the planet, making it a good target for transmission spectroscopy studies. TOI-1759 b is among the top five temperate, small exoplanets ($T_\textrm{eq} &lt; 500$ K, $R_p &lt; 4 \,R_\oplus$) with the highest TSM discovered to date. Two additional signals with periods of 80 d and $&gt;$ 200 d seem to be present in our radial velocities. While our data suggest both could arise from stellar activity, the later signal's source and periodicity are hard to pinpoint given the $\sim 200$ d baseline of our radial-velocity campaign with CARMENES. Longer baseline radial-velocity campaigns should be performed in order to unveil the true nature of this long period signal.
description: 22 pages, 10 figures, 7 tables. AJ in press