<i>TESS</i> and <i>CHEOPS</i> discover two warm sub-Neptunes transiting the bright K-dwarf HD 15906

Tuson, A.; Queloz, D.; Osborn, H.; Wilson, T. G.; Hooton, Matthew J.; Beck, M.; Lendl, M.; Olofsson, G.; Fortier, A.; Bonfanti, A.; Brandeker, Alexis; Buchhave, Lars A.; Cameron, A. Collier; Ciardi, David R.; Collins, Karen A.; Gandolfi, D.; Garai, Z.; Giacalone, Steven; Silva, João Gomes da; Howell, Steve B.; Patel, Jayshil A.; Persson, C. M.; Serrano, L. M.; Sousa, S. G.; Ulmer-Moll, S.; Vanderburg, Andrew; Ziegler, Carl; Alibert, Yann; Alonso, R.; Anglada, Guillem; Bárczy, T.; Navascués, D. Barrado y; Barros, S. C. C.; Baumjohann, W.; Beck, T.; Benz, W.; Billot, N.; Bonfils, X.; Borsato, L.; Broeg, C.; Cabrera, J.; Charnoz, Sébastien; Conti, Dennis M.; Csizmadia, Szilárd; Cubillos, Patricio; Davies, Melvyn B.; Deleuil, M.; Delrez, Laetitia; Demangeon, O.; Demory, Brice-Olivier; Dragomir, Diana; Dressing, Courtney D.; Ehrenreich, D.; Erikson, A.; Essack, Zahra; Farinato, Jacopo; Fossati, L.; Fridlund, M.; Furlan, Elise; Gill, Holden; Gillon, M.; Gnilka, Crystal L.; Gonzales, Erica J.; Güdel, M.; Günther, Maximilian N.; Hoyer, S.; Isaak, K. G.; Jenkins, Jon M.; Kiss, L. L.; Laskar, Jacques; Latham, David W.; Law, Nicholas M.; Étangs, A. Lecavelier des; Curto, G. Lo; Lovis, C.; Luque, R.; Magrin, Demetrio; Mann, Andrew W.; Maxted, P. F. L.; Mayor, M.; McDermott, Scott; Mečina, M.; Mordasini, Christoph; Mortier, A.; Nascimbeni, V.; Ottensamer, R.; Pagano, I.; Πάλλη, Ε.; Peter, G.; Piotto, G.; Pollacco, D.; Pritchard, T. A.; Ragazzoni, Roberto; Rando, N.; Ratti, F.; Rauer, H.; Ribas, I.; Ricker, G.; Rieder, Martin; Santos, N. C.; Savel, Arjun B.; Scandariato, G.; Schwarz, Richard P.; Seager, Sara; Ségransan, D.; Shporer, Avi; Simon, A. E.; Smith, A. M. S.; Steller, M.; Stockdale, Chris; Szabó, Gy. M.; Thomas, Nicolas; Torres, Guillermo; Tronsgaard, R.; Udry, S.; Ulmer, B.; Grootel, Valérie Van; Vanderspek, R.; Venturini, Julia; Walton, N. A.; Winn, Joshua N.; Wohler, Bill

doi:10.1093/mnras/stad1369

Cited by 10 publications

(1 citation statement)

References 165 publications

(178 reference statements)

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“…We demonstrated how CHEOPS can be used to followup TESS duotransits to expand the sample of long-period planets. Through the CHEOPS GTO Duos program, we have contributed to the discovery of 6 planets with orbital periods longer than 20 d, radii smaller than 5 R ⊕ , and host stars brighter than G = 12 mag (Osborn et al, 2022(Osborn et al, , 2023Tuson et al, 2023;Ulmer-Moll et al, 2023;Garai et al, 2023). There are only ∼ 18 other planets confirmed by TESS in this parameter space, illustrating the power of the TESS and CHEOPS synergy for the discovery of small, long-period planets transiting bright stars.…”

Section: Discussionmentioning

confidence: 99%

Confirming long-period transiting exoplanets with TESS and CHEOPS. The case of HD 22946 d

Garai,

Osborn,

Tuson

et al. 2024

caosp

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Due to the limited observing duration of the Transiting Exoplanet Survey Satellite (TESS) primary mission, which observed the majority of the near-ecliptic sectors for only 27 days, planets on long periods produce only single transits. However, thanks to its extended mission, TESS re-observed the same fields 2 years later, and in many cases was able to re-detect a second transit. These duotransit cases require follow-up in order to uncover the true orbital period due to the gap, which causes a set of aliases. The Characterising Exoplanet Satellite (CHEOPS) space observatory can be used to follow-up duotransit targets and to determine their true orbital periods and other characteristics. We investigated the HD 22946 planetary system with a similar aim. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d to be 47.42489 ± 0.00011 d, and derived precise radii of the planets in the system. Planet d, as a warm sub-Neptune, is very interesting because there are only a few similar confirmed exoplanets to date.

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Section: Discussionmentioning

confidence: 99%

Confirming long-period transiting exoplanets with TESS and CHEOPS. The case of HD 22946 d

Garai,

Osborn,

Tuson

et al. 2024

caosp

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A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067

Luque,

Osborn,

Leleu

et al. 2023

Nature

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TOI-5678b: A 48-day transiting Neptune-mass planet characterized with CHEOPS and HARPS

Ulmer-Moll,

Osborn,

Tuson

et al. 2023

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Context. A large sample of long-period giant planets has been discovered thanks to long-term radial velocity surveys, but only a few dozen of these planets have a precise radius measurement. Transiting gas giants are crucial targets for the study of atmospheric composition across a wide range of equilibrium temperatures and, more importantly, for shedding light on the formation and evolution of planetary systems. Indeed, compared to hot Jupiters, the atmospheric properties and orbital parameters of cooler gas giants are unaltered by intense stellar irradiation and tidal effects. Aims. We aim to identify long-period planets in the Transiting Exoplanet Survey Satellite (TESS) data as single or duo-transit events. Our goal is to solve the orbital periods of TESS duo-transit candidates with the use of additional space-based photometric observations and to collect follow-up spectroscopic observations in order to confirm the planetary nature and measure the mass of the candidates. Methods. We use the CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability period aliases in order to discard or confirm a transit event at a given period. Once a period is confirmed, we jointly model the TESS and CHEOPS light curves along with the radial velocity datasets to measure the orbital parameters of the system and obtain precise mass and radius measurements. Results. We report the discovery of a long-period transiting Neptune-mass planet orbiting the G7-type star TOI-5678. Our spectroscopic analysis shows that TOI-5678 is a star with a solar metallicity. The TESS light curve of TOI-5678 presents two transit events separated by almost two years. In addition, CHEOPS observed the target as part of its Guaranteed Time Observation program. After four non-detections corresponding to possible periods, CHEOPS detected a transit event matching a unique period alias. Follow-up radial velocity observations were carried out with the ground-based high-resolution spectrographs CORALIE and HARPS. Joint modeling reveals that TOI-5678 hosts a 47.73 day period planet, and we measure an orbital eccentricity consistent with zero at 2σ. The planet TOI-5678 b has a mass of 20 ± 4 Earth masses (M⊕) and a radius of 4.91 ± 0.08 R⊕ Using interior structure modeling, we find that TOI-5678 b is composed of a low-mass core surrounded by a large H/He layer with a mass of 3.2±1.7−1.3 M⊕. Conclusions. TOI-5678 b is part of a growing sample of well-characterized transiting gas giants receiving moderate amounts of stellar insolation (11 S⊕). Precise density measurement gives us insight into their interior composition, and the objects orbiting bright stars are suitable targets to study the atmospheric composition of cooler gas giants.

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TESS and CHEOPS discover two warm sub-Neptunes transiting the bright K-dwarf HD 15906

Cited by 10 publications

References 165 publications

Confirming long-period transiting exoplanets with TESS and CHEOPS. The case of HD 22946 d

Confirming long-period transiting exoplanets with TESS and CHEOPS. The case of HD 22946 d

A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067

TOI-5678b: A 48-day transiting Neptune-mass planet characterized with CHEOPS and HARPS

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