The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary*

Carleo, I.; Gandolfi, D.; Barragán, Oscar; Livingston, John H.; Persson, C. M.; Lam, K. W. F.; Vidotto, A. A.; Lund, Michael B.; D’Angelo, Carolina Villarreal; Collins, Karen A.; Fossati, L.; Howard, Andrew W.; Kubyshkina, Daria; Brahm, R.; Oklopčić, Antonija; Mollière, P.; Redfield, Seth; Serrano, L. M.; Dai, Fei; Fridlund, M.; Borsa, F.; Korth, J.; Esposito, M.; Díaz, Matías R.; Nielsen, L. D.; Hellier, C.; Mathur, S.; Deeg, H. J.; Hatzes, A. P.; Benatti, S.; Rodler, F.; Alarcon, Javier; Spina, L.; Santos, A. R. G.; Georgieva, Iskra; García, Rafael A.; González-Cuesta, L.; Ricker, G.; Vanderspek, R.; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Albrecht, S.; Batalha, Natalie M.; Beard, Corey; Boyd, Patricia T.; Bouchy, F.; Burt, Jennifer; Butler, R. Paul; Cabrera, J.; Chontos, Ashley; Ciardi, David R.; Cochran, William D.; Collins, Kevin I.; Crane, Jeffrey D.; Crossfield, Ian J. M.; Csizmadia, Szilárd; Dragomir, Diana; Dressing, Courtney D.; Eigmüller, Philipp; Endl, Michael; Erikson, A.; Espinoza, N.; Fausnaugh, Michael; Feng, Fabo; Flowers, Erin; Fulton, Benjamin J.; Gonzales, Erica J.; Grieves, Nolan; Grziwa, S.; Guenther, E. W.; Guerrero, Natalia; Henning, Thomas; Hidalgo, D.; Hirano, Teruyuki; Hjorth, María; Huber, Daniel; Isaacson, Howard; Jones, M. I.; Jordán, Andrés; Kabáth, P.; Kane, Stephen R.; Knudstrup, Emil; Polanski, Alex S.; Luque, R.; Mireles, Ismael; Narita, Norio; Nespral, D.; Niraula, Prajwal; Nowak, G.; Πάλλη, Ε.; Pätzold, M.; Petigura, Erik A.; Prieto-Arranz, J.; Rauer, H.; Robertson, Paul; Rose, Mark; Roy, Arpita; Sarkis, P.; Schlieder, Joshua E.; Ségransan, D.; Shectman, Stephen; Skarka, Marek; Smith, A. M. S.; Smith, Jeffrey C.; Stassun, Keivan G.; Teske, Johanna; Twicken, Joseph D.; Eylen, Vincent Van; Wang, Sharon; Weiss, Lauren M.; Wyttenbach, A.

doi:10.3847/1538-3881/aba124

Cited by 23 publications

(21 citation statements)

References 160 publications

(118 reference statements)

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“…On the other hand, this can be done for essentially any type of stellar rotator, as stellar history does not affect the estimate on the initial atmospheric mass fraction of TOI-421 c much (as well as varying the initial mass of the planet within the range cor-responding to the measured mass uncertainty of TOI-421 c). This is consistent with the estimates made in Carleo et al (2020) with the simpler model (not accounting consistently for the thermal evolution of a planet), but with a more thorough probabilistic approach.…”

Section: Toi-421 B and C And Their Pastsupporting

confidence: 88%

“…In the present study, we model the evolution of planetary atmospheres in two systems of very similar configuration, but very different ages, the 9-Gyr old TOI-421 (Carleo et al 2020) and the 50-Myr old TOI-942 (Carleo et al 2021). These two host-stars have similar masses of about 0.85 M⊙ and close spectral types (G9 and K2.5V) and each of them hosts two sub-Neptune-like planets at similar close-in orbits about 0.05 and 0.1 AU, where the evolution of their atmospheres is to a large extent controlled by atmospheric mass loss driven by stellar irradiation.…”

Section: Introductionmentioning

confidence: 99%

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Atmospheric mass loss and stellar wind effects in young and old systems – II. Is TOI-942 the past of TOI-421 system?

Kubyshkina

Vidotto

D’Angelo

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The two planetary systems TOI-942 and TOI-421 share many similar characteristics, apart from their ages (50 Myr and 9 Gyr). Each of the stars hosts two sub-Neptune-like planets at similar orbits and in similar mass ranges. In this paper, we aim to investigate whether the similarity of the host stars and configuration of the planetary systems can be taken as proof that the two systems were formed and evolved in a similar way. In paper I of this series, we performed a comparative study of these two systems using 3D modeling of atmospheric escape and its interaction with the stellar wind, for the four planets. We demonstrated that though the strong wind of the young star has a crucial effect on observable signatures, its effect on the atmospheric mass loss is minor in the evolutionary context. Here, we use atmosphere evolution models to track the evolution of planets in the younger system TOI-942 and also to constrain the past of the TOI-421 system. We demonstrate that despite all the similarities, the two planetary systems are on two very different evolutionary pathways. The inner planet in the younger system, TOI-942, will likely lose all of its atmosphere and become a super-Earth-like planet, while the outer planet will become a typical sub-Neptune. Concerning the older system, TOI-421, our evolution modeling suggests that they must have started their evolution with very substantial envelopes, which can be a hint of formation beyond the snow line.

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Section: Toi-421 B and C And Their Pastsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Atmospheric mass loss and stellar wind effects in young and old systems – II. Is TOI-942 the past of TOI-421 system?

Kubyshkina

Vidotto

D’Angelo

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…The observations revealed a faint companion to the southeast, K2-288B, that likely hosts the exoplanet. (C) K-band observations of TOI-421 (Carleo et al, 2020). (D) Br-γ observations of GJ 3473 (TOI-488).…”

Section: Resultsmentioning

confidence: 99%

“…The HRI observations of TESS targets are also beginning to validate and characterize systems around brighter, closer stars. This includes the TOI-421 system, three planets orbiting a bright G dwarf (Carleo et al, 2020); GJ 3473 (TOI-488), a nearby M dwarf hosting a hot, transiting, Earth-size planet (Kemmer et al, 2020), and TOI-503, a short period brown dwarf transiting an A type star (Šubjak et al, 2020).…”

Section: Hri In Planet Validationmentioning

confidence: 99%

Follow-Up and Validation of K2 and TESS Planetary Systems With Keck NIRC2 Adaptive Optics Imaging

Schlieder

Gonzales

Ciardi

et al. 2021

Front. Astron. Space Sci.

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High resolution imaging (HRI) is a critical part of the transiting exoplanet follow-up and validation process. HRI allows previously unresolved stellar companions and background blends to be resolved, vetting false positive signals and improving the radii measurements of true planets. Through a multi-semester Keck NIRC2 adaptive optics imaging program, we have pursued HRI of K2 and TESS candidate planet host systems to provide the transiting exoplanet community with necessary data for system validation and characterization. Here we present a summary of our ongoing program that includes an up to date list of targets observed, a description of the observations and data reduction, and a discussion of planetary systems validated by the community using these data. This observing program has been key in NASA's K2 and TESS missions reaching their goals of identifying new exoplanets ideal for continued follow-up observations to measure their masses and investigate their atmospheres. Once processed, all observations presented here are available as calibrated images and resulting contrast curves through the Exoplanet Follow-up Observing Program (ExoFOP) website. We encourage members of the exoplanet community to use these data products in their ongoing planetary system validation and characterization efforts.

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“…mini-Neptunes such as TOI-421 c (Carleo et al 2020), as well as planets which follow a more linear track from rocky super-earths to Neptunes dominated by gaseous envelopes, such as the two inner planets orbiting ν 2 Lupi (Kane et al 2020) and TOI-735 (Cloutier et al 2020;Nowak et al 2020).…”

mentioning

confidence: 99%

A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113

Osborn

Adibekyan

Collins

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We report the discovery of HD 110113 b (TOI-755.01), a transiting mini-Neptune exoplanet on a 2.5-day orbit around the solar-analogue HD 110113 (Teff= 5730K). Using TESS photometry and HARPS radial velocities gathered by the NCORES program, we find HD 110113 b has a radius of 2.05 ± 0.12 R⊕ and a mass of 4.55 ± 0.62 M⊕. The resulting density of $2.90^{+0.75}_{-0.59}$ g cm−3 is significantly lower than would be expected from a pure-rock world; therefore, HD 110113 b must be a mini-Neptune with a significant volatile atmosphere. The high incident flux places it within the so-called radius valley; however, HD 110113 b was able to hold on to a substantial (0.1-1 per cent) H-He atmosphere over its ∼4Gyr lifetime. Through a novel simultaneous Gaussian process fit to multiple activity indicators, we were also able to fit for the strong stellar rotation signal with period 20.8 ± 1.2 d from the RVs and confirm an additional non-transiting planet, HD 110113 c, which has a mass of 10.5 ± 1.2 M⊕ and a period of $6.744^{+0.008}_{-0.009}$ d.

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The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary*

Cited by 23 publications

References 160 publications

Atmospheric mass loss and stellar wind effects in young and old systems – II. Is TOI-942 the past of TOI-421 system?

Atmospheric mass loss and stellar wind effects in young and old systems – II. Is TOI-942 the past of TOI-421 system?

Follow-Up and Validation of K2 and TESS Planetary Systems With Keck NIRC2 Adaptive Optics Imaging

A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113

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