Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N, and TESS

• DOI: 10.1093/mnras/stac199
• Publication Date: 2022-01-25T20:14:10Z
• Authors: G Lacedelli; T G Wilson; L Malavolta; M J Hooton; A Collier Cameron; Y Alibert; A Mortier; A Bonfanti; R D Haywood; S Hoyer; G Piotto; A Bekkelien; A M Vanderburg; W Benz; X Dumusque; A Deline; M López-Morales; L Borsato; K Rice; L Fossati; D W Latham; A Brandeker; E Poretti; S G Sousa; A Sozzetti; S Salmon; C J Burke; V Van Grootel; M M Fausnaugh; V Adibekyan; C X Huang; H P Osborn; A J Mustill; E Pallé; V Bourrier; V Nascimbeni; R Alonso; G Anglada; T Bárczy; D Barrado y Navas...; S C C Barros; W Baumjohann; M Beck; T Beck; N Billot; X Bonfils; C Broeg; L A Buchhave; J Cabrera; S Charnoz; R Cosentino; Sz Csizmadia; M B Davies; M Deleuil; L Delrez; O Demangeon; B -O Demory; D Ehrenreich; A Erikson; E Esparza-Borges; H G Florén; A Fortier; M Fridlund; D Futyan; D Gandolfi; A Ghedina; M Gillon; M Güdel; P Guterman; A Harutyunyan; K Heng; K G Isaak; J M Jenkins; L Kiss; J Laskar; A Lecavelier des ...; M Lendl; C Lovis; D Magrin; L Marafatto; A F Martinez Fior...; P F L Maxted; M Mayor; G Micela; E Molinari; F Murgas; N Narita; G Olofsson; R Ottensamer; I Pagano; A Pasetti; M Pedani; F A Pepe; G Peter; D F Phillips; D Pollacco; D Queloz; R Ragazzoni; N Rando; F Ratti; H Rauer; I Ribas; N C Santos; D Sasselov; G Scandariato; S Seager; D Ségransan; L M Serrano; A E Simon; A M S Smith; M Steinberger; M Steller; Gy Szabó; N Thomas; J D Twicken; S Udry; N Walton; J N Winn
• Keywords: 103003 Astronomie; Planets and satellites: interiors; stars: individual: TOI-561 (TIC 377064495. Gaia EDR3 3850421005290172416); Astrophysics / csillagászat; 01 natural sciences; 7. Clean energy; techniques: photometric; QB460; techniques: radial velocities; QB Astronomy; techniques: photometric – techniques: radial velocities – planets and satellites: fundamental parameters – planetsand satellites: interiors – stars: individual: TOI-561 (TIC 377064495; individual; 103004 Astrophysics; QA; planets and satellites: fundamental parameters; QC; Gaia EDR3 3850421005290172416; QB; Earth and Planetary Astrophysics (astro-ph.EP); [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; 520 Astronomy; 103004 Astrophysik; 16. Peace & justice; 520; Planets and satellites: fundamental parameters; planets and satellites: interiors; techniques photometric; planets and satellites fundamental parameters; Techniques: radial velocities; stars; stars: individual: TOI-561 (TIC 377064495; individual: TOI-561 (TIC 377064495 [Stars]; fundamental parameters [Planets and satellites]; TOI-561 TIC 377064495; FOS: Physical sciences; 103003 Astronomy; techniques radial velocities; 0103 physical sciences; Stars: individual: TOI-561 (TIC 377064495; Gaia EDR3 3850421005290172416); techniques: photometric; techniques: radial velocities; planets and satellites: fundamental parameters; planets and satellites: interiors; stars: individual: TOI-561 (TIC 377064495, Gaia EDR3 3850421005290172416); QB600; MCC; radial velocities [Techniques]; stars: individual: TOI-561 (TIC 377064495, Gaia EDR3 3850421005290172416); planets and satellites interiors; photometric [Techniques]; DAS; 620 Engineering; interiors [Planets and satellites]; QC Physics; asztrofizika; [SDU]Sciences of the Universe [physics]; 13. Climate action; MCP; astro-ph.EP; Techniques: photometric; Astrophysics - Earth and Planetary Astrophysics

We present a precise characterization of the TOI-561 planetary system obtained by combining previously published data with TESS and CHEOPS photometry, new set $62$ HARPS-N radial velocities (RVs). Our joint analysis confirms presence four transiting planets, namely b ($P = 0.45$ d, $R 1.42$ R$_\oplus$, $M 2.0$ M$_\oplus$), c 10.78$ 2.91$ 5.4$ d 25.7$ 2.82$ 13.2$ M$_\oplus$) e 77$ 2.55$ 12.6$ M$_\oplus$). Moreover, we identify an additional, long-period signal ($>450$ d) in RVs, which could be due to either external companion or stellar magnetic activity. The masses radii for planets allowed us conduct interior structure atmospheric escape modelling. is confirmed lowest density ($ρ_{\rm b} 3.8 \pm 0.5$ g cm$^{-3}$) ultra-short period (USP) planet known date, low metallicity host star makes it consistent general bulk density-stellar trend. According our modelling, has basically no gas envelope, certain amount water. In contrast, c, likely retained H/He addition possibly large water layer. inferred compositions suggest different evolutionary paths, having experienced significant loss, showing content original one. uniqueness USP planet, e, complex architecture make this appealing target follow-up studies.