The young HD 73583 (TOI-560) planetary system: Two 10-M$_\oplus$ mini-Neptunes transiting a 500-Myr-old, bright, and active K dwarf

• Main Authors: Armstrong, D. J, Gandolfi, D, Carleo, I, Vidotto, A. A, D'Angelo, C. Villarreal, Oklopčić, A, Isaacson, H, Oddo, D, Collins, K, Fridlund, M, Sousa, S. G, Persson, C. M, Hellier, C, Howell, S, Howard, A, Redfield, S, Georgieva, I. Y, Dragomir, D, Bayliss, D, Nielsen, L. D, Klein, B, Aigrain, S, Zhang, M, Teske, J, Twicken, J D, Jenkins, J, Esposito, M, Van Eylen, V, Rodler, F, Adibekyan, V, Alarcon, J, Anderson, D. R, Murphy, J. M. Akana, Barrado, D, Barros, S. C. C, Benneke, B, Bouchy, F, Bryant, E. M, Butler, P, Burt, J, Casewell, S, Chaturvedi, P, Cloutier, R, Cochran, W. D, Crane, J, Crossfield, I, Crouzet, N, Collins, K. I, Dai, F, Deeg, H. J, Deline, A, Demangeon, O. D. S, Dumusque, X, Figueira, P, Furlan, E, Gnilka, C, Goad, M. R, Goffo, E, Gutiérrez-Canales, F, Hadjigeorghiou, A, Hartman, Z, Hatzes, A. P, Harris, M, Henderson, B, Hirano, T, Hojjatpanah, S, Hoyer, S, Kabáth, P, Korth, J, Lillo-Box, J, Luque, R, Močnik, T, Muresan, A, Murgas, F, Nagel, E, Osborne, H. L. M, Osborn, A, Osborn, H. P, Palle, E, Raimbault, M, Ricker, G. R, Rubenzahl, R A, Stockdale, C, Santos, N. C, Scott, N, Schwarz, R. P, Seager, S, Ségransan, D, Serrano, L. M, Skarka, M, Smith, A. M. S, Šubjak, J, Tan, T. G, Udry, S, Watson, C, Wheatley, P. J, West, R, Wang, S. X, Wolfgang, A, Ziegler, C
• Format: Journal Article
• Language: English
• Published: 25-10-2021
• Subjects: Physics - Earth and Planetary Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.2110.13069

We present the discovery and characterisation of two transiting planets
observed by \textit{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 ($\sim 500$~Myr) active star with a
rotational period of $12.08 \pm 0.11 $\,d, and a mass and radius of $ 0.73 \pm
0.02 M_\odot$ and $0.65 \pm 0.02 R_\odot$, respectively. HD73583 b
($P_b=6.3980420 _{ - 0.0000062 }^{+0.0000067}$ d) has a mass and radius of
$10.2 _{-3.1}^{+3.4} M_\oplus$ and$2.79 \pm 0.10 R_\oplus$, respectively, that
gives a density of $2.58 _{-0.81}^{ 0.95} {\rm g\,cm^{-3}}$. HD73583 c ($P_c=
18.87974 _{-0.00074 }^{+0.00086}$) has a mass and radius of $9.7_{-1.7} ^
{+1.8} M_\oplus$ and $2.39_{-0.09}^{+0.10} R_\oplus$, respectively, this
translates to a density of $3.88 _{-0.80}^{+0.91} {\rm g\,cm^{-3}}$. 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 ongoing 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.