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

Lacedelli, G. and Wilson, T. G. and Malavolta, L. and Hooton, M. J. and Cameron, A. Collier and Alibert, Y. and Mortier, A. and Bonfanti, A. and Haywood, R. D. and Hoyer, S. and Piotto, G. and Bekkelien, A. and Vanderburg, A. M. and Benz, W. and Dumusque, X. and Deline, A. and Lopez-Morales, M. and Borsato, L. and Rice, K. and Fossati, L. and Latham, D. W. and Brandeker, A. and Poretti, E. and Sousa, S. G. and Sozzetti, A. and Salmon, S. and Burke, C. J. and Van Grootel, V. and Fausnaugh, M. M. and Adibekyan, V. and Huang, C. X. ORCID: https://orcid.org/0000-0003-0918-7484 and Osborn, H. P. and Mustill, A. J. and Palle, E. and Bourrier, V. and Nascimbeni, V. and Alonso, R. and Anglada, G. and Barczy, T. and Barrado y Navascues, D. and Barros, S. C. C. and Baumjohann, W. and Beck, M. and Beck, T. and Billot, N. and Bonfils, X. and Broeg, C. and Buchhave, L. A. and Cabrera, J. and Charnoz, S. and Cosentino, R. and Csizmadia, Sz and Davies, M. B. and Deleuil, M. and Delrez, L. and Demangeon, O. and Demory, B. -O. and Ehrenreich, D. and Erikson, A. and Esparza-Borges, E. and Floren, H. G. and Fortier, A. and Fridlund, M. and Futyan, D. and Gandolfi, D. and Ghedina, A. and Gillon, M. and Gudel, M. and Guterman, P. and Harutyunyan, A. and Heng, K. and Isaak, K. G. and Jenkins, J. M. and Kiss, L. and Laskar, J. and des Etangs, A. Lecavelier and Lendl, M. and Lovis, C. and Magrin, D. and Marafatto, L. and Martinez Fiorenzano, A. F. and Maxted, P. F. L. and Mayor, M. and Micela, G. and Molinari, E. and Murgas, F. and Narita, N. and Olofsson, G. and Ottensamer, R. and Pagano, I. and Pasetti, A. and Pedani, M. and Pepe, F. A. and Peter, G. and Phillips, D. F. and Pollacco, D. and Queloz, D. and Ragazzoni, R. and Rando, N. and Ratti, F. and Rauer, H. and Ribas, I. and Santos, N. C. and Sasselov, D. and Scandariato, G. and Seager, S. and Segransan, D. and Serrano, L. M. and Simon, A. E. and Smith, A. M. S. and Steinberger, M. and Steller, M. and Szabo, Gy and Thomas, N. and Twicken, J. D. and Udry, S. and Walton, N. and Winn, J. N. (2022) Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N, and TESS. Monthly Notices of the Royal Astronomical Society, 511 (3). pp. 4551-4571. ISSN 0035-8711

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Abstract

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


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Date Deposited: 04 Apr 2022 03:54
Last Modified: 09 Jun 2022 03:30
Uncontrolled Keywords: techniques: photometric – techniques: radial velocities – planets and satellites: fundamental parameters – planets and satellites: interiors – stars: individual: TOI-561 (TIC 377064495, Gaia EDR3 3850421005290172416); Astrophysics - Earth and Planetary Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Identification Number or DOI: https://doi.org/10.1093/mnras/stac199
URI: http://eprints.usq.edu.au/id/eprint/47397

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