2024A&A...685A...5P

Query : 2024A&A...685A...5P

2024A&A...685A...5P - Astronomy and Astrophysics, volume 685A5 (2024/5-1)

Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815.

PSARIDI A., OSBORN H., BOUCHY F., LENDL M., PARC L., BILLOT N., BROEG C., SOUSA S.G., ADIBEKYAN V., ATTIA O., BONFANTI A., CHAKRABORTY H., COLLINS K.A., DAVOULT J., DELGADO-MENA E., GRIEVES N., GUILLOT T., HEITZMANN A., HELLED R., HELLIER C., JENKINS J.M., KNIERIM H., KRENN A., LISSAUER J.J., LUQUE R., RAPETTI D., SANTOS N.C., SUAREZ O., VENTURINI J., WILKIN F.P., WILSON T.G., WINN J.N., ZIEGLER C., ZINGALES T., ALIBERT Y., BRANDEKER A., EGGER J.A., GANDOLFI D., HOOTON M.J., TUSON A., ULMER-MOLL S., ABE L., ALLART R., ALONSO R., ANDERSON D.R., ESCUDE G.A., BARCZY T., BARRADO D., BARROS S.C.C., BAUMJOHANN W., BECK M., BECK T., BENZ W., BONFILS X., BORSATO L., BOURRIER V., CIARDI D.R., CAMERON A.C., CHARNOZ S., COINTEPAS M., CSIZMADIA S., CUBILLOS P., LO CURTO G., DAVIES M.B., DAYLAN T., DELEUIL M., DELINE A., DELREZ L., DEMANGEON O.D.S., DEMORY B.-O., DORN C., DUMUSQUE X., EHRENREICH D., ERIKSON A., LECAVELIER DES ETANGS A., DE MIGUEL D., FORTIER A., FOSSATI L., FRENSCH Y.G.C., FRIDLUND M., GILLON M., GUDEL M., GUNTHER M.N., HAGELBERG J., HELLING C., HOYER S., ISAAK K.G., KISS L.L., LAM K.W.F., LASKAR J., LAVIE B., LOVIS C., MAGRIN D., MARAFATTO L., MAXTED P., McDERMOTT S., MEKARNIA D., MORDASINI C., MURGAS F., NASCIMBENI V., NIELSEN L.D., OLOFSSON G., OTTENSAMER R., PAGANO I., PALLE E., PETER G., PIOTTO G., POLLACCO D., QUELOZ D., RAGAZZONI R., RAMOS D., RANDO N., RAUER H., REIMERS C., RIBAS I., SEAGER S., SEGRANSAN D., SCANDARIATO G., SIMON A.E., SMITH A.M.S., STALPORT M., STELLER M., SZABO G., THOMAS N., PRITCHARD T.A., UDRY S., CORRAL VAN DAMME C., VAN GROOTEL V., VILLAVER E., WALTER I., WALTON N., WATKINS C.N. and WEST R.G.

Abstract (from CDS):

We present the discovery and characterization of two warm mini-Neptunes transiting the K3V star TOI-815 in a K-M binary system. Analysis of its spectra and rotation period reveal the star to be young, with an age of 200–200+400 Myr. TOI-8l5b has a 11.2-day period and a radius of 2.94 ± 0.05 R⊕ with transits observed by TESS, CHEOPS, ASTEP, and LCOGT. The outer planet, TOI-8l5c, has a radius of 2.62 ± 0.10 R⊕, based on observations of three nonconsecutive transits with TESS; targeted CHEOPS photometry and radial velocity follow-up with ESPRESSO were required to confirm the 35-day period. ESPRESSO confirmed the planetary nature of both planets and measured masses of 7.6 ± 1.5 M⊕ (ρP = 1.64–0.31+0.33 g cm–3) and 23.5 ± 2.4 M⊕ (ρP = 7.2–1.0+1.1 g cm–3), respectively. Thus, the planets have very different masses, which is unusual for compact multi-planet systems. Moreover, our statistical analysis of mini-Neptunes orbiting FGK stars suggests that weakly irradiated planets tend to have higher bulk densities compared to those undergoing strong irradiation. This could be ascribed to their cooler atmospheres, which are more compressed and denser. Internal structure modeling of TOI-815b suggests it likely has a H-He atmosphere that constitutes a few percent of the total planet mass, or higher if the planet is assumed to have no water. In contrast, the measured mass and radius of TOI-815c can be explained without invoking any atmosphere, challenging planetary formation theories. Finally, we infer from our measurements that the star is viewed close to pole-on, which implies a spin-orbit misalignment at the 3σ level. This emphasizes the peculiarity of the system's orbital architecture, and probably hints at an eventful dynamical history.

Abstract Copyright: © The Authors 2024

Journal keyword(s): techniques: photometric - techniques: radial velocities - planets and satellites: composition - planets and satellites: detection - planets and satellites: formation - stars: individual: TOI-815

VizieR on-line data: <Available at CDS (J/A+A/685/A5): lcs1.dat lcs2.dat lcs3.dat lcs4.dat rvs.dat>

Simbad objects: 18

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Number of rows : 18
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NGC 1039 OpC 02 42 09.1 +42 44 02           ~ 467 0
2 HD 21749b Pl 03 26 59.2226447548 -63 29 56.762928961           ~ 49 0
3 Cl Melotte 25 OpC 04 30 27.4 +16 46 43           ~ 3309 0
4 NGC 2168 OpC 06 09 07.5 +24 20 15           ~ 604 0
5 NGC 2548 OpC 08 13 34.0 -05 43 11           ~ 227 0
6 NGC 2632 OpC 08 39 58.4 +19 36 33           ~ 1733 0
7 UCAC3 93-101439 PM* 10 23 29.0380670448 -43 50 00.259820160       12.70 11.12 ~ 5 0
8 CD-43 6219b Pl 10 23 29.2522978464 -43 50 05.841369096           ~ 4 0
9 CD-43 6219c Pl 10 23 29.2522978464 -43 50 05.841369096           ~ 3 0
10 CD-43 6219 * 10 23 29.2522978464 -43 50 05.841369096   11.15 10.22     ~ 19 0
11 HD 119130b Pl 13 41 30.3033490344 -09 56 45.879437004           ~ 26 0
12 NGC 6475 OpC 17 53 44.1 -34 49 36           ~ 413 0
13 Kepler-25b Pl 19 06 33.2141354736 +39 29 16.358725104           ~ 75 1
14 Kepler-411b Pl 19 10 25.3469947368 +49 31 23.712634632           ~ 59 0
15 Kepler-107b Pl 19 48 06.7734610824 +48 12 30.964175676           ~ 44 0
16 Kepler-107c Pl 19 48 06.7734610824 +48 12 30.964175676           ~ 75 0
17 Kepler-107 Er* 19 48 06.7734610824 +48 12 30.964175676   13.330 12.639 12.448   ~ 116 0
18 Kepler-18c Pl 19 52 19.0688312520 +44 44 46.807928916           ~ 87 1

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