The young HD 73583 (TOI-560) planetary system: Two 10-M_⊕ mini-Neptunes transiting a 500-Myr-old, bright, and active K dwarf

O. Barragán , D. J. Armstrong , D. Gandolfi , I. Carleo , A. A. Vidotto , C. Villarreal d'Angelo , A. Oklopčić , H. Isaacson , D. Oddo , M. Fridlund , S. G. Sousa , C. M. Persson , C. Hellier , S. Howell , A. Howard , S. Redfield , N. Eisner , I. Y. Georgieva , D. Dragomir , D. Bayliss , L. D. Nielsen , B. Klein , S. Aigrain , M. Zhang , J. Teske , J. D. Twicken , J. Jenkins , M. Esposito , V. van Eylen , F. Rodler , V. Adibekyan , J. Alarcon , D. R. Anderson , J. M. Akana Murphy , D. Barrado , S. C. C. Barros , B. Benneke , F. Bouchy , E. M. Bryant , R. P. Butler , J. Burt , J. Cabrera , S. Casewell , P. Chaturvedi , R. Cloutier , W. D. Cochran , J. Crane , I. Crossfield , N. Crouzet , K. I. Collins , F. Dai , H. J. Deeg , A. Deline , O. D. S. Demangeon , X. Dumusque , P. Figueira , E. Furlan , C. Gnilka , M. R. Goad , E. Goffo , F. Gutiérrez-Canales , A. Hadjigeorghiou , Z. Hartman , A. P. Hatzes , M. Harris , B. Henderson , T. Hirano , S. Hojjatpanah (1) , S. Hoyer (1) , P. Kabáth , J. Korth , J. Lillo-Box , R. Luque , M. Marmier , T. Močnik , A. Muresan , F. Murgas , E. Nagel , H. L. M. Osborne , A. Osborn , H. P. Osborn , E. Palle , G. R. Ricker , R. A. Rubenzahl , C. Stockdale , N. C. Santos , N. Scott , R. P. Schwarz , S. Shectman , M. Raimbault , S. Seager , D. Ségransan , L. M. Serrano , M. Skarka , A. M. S. Smith , J. Šubjak , T. G. Tan , S. Udry , C. Watson , P. J. Wheatley , R. West , J. N. Winn , S. X. Wang , A. Wolfgang , C. Ziegler

1 LAM - Laboratoire d'Astrophysique de Marseille

We present the discovery and characterisation of two transiting planets observed by TESS in the light curves of the young and bright (V = 9.67) star HD73583 (TOI-560). We perform an intensive spectroscopic and photometric space- and ground-based follow-up in order to confirm and characterise the system. We found that HD73583 is a young (~500 Myr) active star with a rotational period of 12.08 ± 0.11 d, and a mass and radius of 0.73 ± 0.02 M_⊙ and 0.65 ± 0.02 R_⊙, respectively. HD 73583 b (P_b =$6.3980420 _{ - 0.0000062 } ^ { + 0.0000067 }$ d) has a mass and radius of $10.2 _{ - 3.1 } ^ { + 3.4 }$ M_⊕ and 2.79 ± 0.10 R_⊕, respectively, that gives a density of $2.58 _{ - 0.81 } ^ { + 0.95 }$ g cm^-3. HD 73583 c (P_c=$18.87974 _{ - 0.00074 } ^ { + 0.00086 }$ d) has a mass and radius of $9.7 _{ - 1.7 } ^ { + 1.8 }$ M_⊕ and $2.39 _{ - 0.09 } ^ { + 0.10 }$ R_⊕, respectively, this translates to a density of $3.88 _{ - 0.80 } ^ { + 0.91 }$ g cm^-3. Both planets are consistent with worlds made of a solid core surrounded by a volatile envelope. Because of their youth and host star brightness, they both are excellent candidates to perform transmission spectroscopy studies. We expect on-going atmospheric mass-loss for both planets caused by stellar irradiation. We estimate that the detection of evaporating signatures on H and He would be challenging, but doable with present and future instruments.

Keywords: Astrophysics - Solar and Stellar Astrophysics; Planets and satellites: individual: HD 73583 (TOI-560); Stars: activity; Techniques: photometric; Techniques: radial velocities; Astrophysics - Earth and Planetary Astrophysics

Domains: Sciences of the Universe [physics]

O. Barragán, D. J. Armstrong, D. Gandolfi, I. Carleo, A. A. Vidotto, et al.. The young HD 73583 (TOI-560) planetary system: Two 10-M_⊕ mini-Neptunes transiting a 500-Myr-old, bright, and active K dwarf. Monthly Notices of the Royal Astronomical Society, 2022, ⟨10.1093/mnras/stac638⟩. ⟨insu-03667449⟩