Exoplanets & Exomoons

Precise Characterisation Of HD 15337 With CHEOPS: A Laboratory For Planet Formation And Evolution

By Keith Cowing
Status Report
March 26, 2024
Filed under , , , , , , , , ,
Precise Characterisation Of HD 15337 With CHEOPS: A Laboratory For Planet Formation And Evolution
Phase-folded light curves from TESS (upper panels) and CHEOPS (lower panels) measurements. The best-fit model of the transit is plotted in black for HD 15337 b (left) and HD 15337 c (right). The bottom panels for each instrument show the residuals of the best-fit model. We over-plot the binned light curves and residuals with 20-min bins. — astro-ph.EP

We aim to constrain the internal structure and composition of HD 15337 b and c, two short-period planets situated on opposite sides of the radius valley, using new transit photometry and radial velocity data.

We acquire 6 new transit visits with the CHaracterising ExOPlanet Satellite (CHEOPS) and 32 new radial velocity measurements from the High Accuracy Radial Velocity Planet Searcher (HARPS) to improve the accuracy of the mass and radius estimates for both planets.

We reanalyse light curves from TESS sectors 3 and 4 and analyse new data from sector 30, correcting for long-term stellar activity. Subsequently, we perform a joint fit of the TESS and CHEOPS light curves, and all available RV data from HARPS and the Planet Finder Spectrograph (PFS).

Our model fits the planetary signals, the stellar activity signal and the instrumental decorrelation model for the CHEOPS data simultaneously. The stellar activity was modelled using a Gaussian-process regression on both the RV and activity indicators.

We finally employ a Bayesian retrieval code to determine the internal composition and structure of the planets. We derive updated and highly precise parameters for the HD 15337 system. Our improved precision on the planetary parameters makes HD 15337 b one of the most precisely characterised rocky exoplanets, with radius and mass measurements achieving a precision better than 2\% and 7\%, respectively.

We are able to improve the precision of the radius measurement of HD 15337 c to 3\%. Our results imply that the composition of HD 15337 b is predominantly rocky, while HD 15337 c exhibits a gas envelope with a mass of at least 0.01 M.Our results lay the groundwork for future studies, which can further unravel the atmospheric evolution of these exoplanets and give new insights into their composition and formation history and the causes behind the radius gap.

N. M. Rosário, O. D. S. Demangeon, S. C. C. Barros, D. Gandolfi, J. A. Egger, L. M. Serrano, H. P. Osborn, M. Beck, W. Benz, H.-G. Florén, P. Guterman, T. G. Wilson, Y. Alibert, L. Fossati, M. J. Hooton, L. Delrez, N. C. Santos, S. G. Sousa, A. Bonfanti, S. Salmon, V. Adibekyan, A. Nigioni, J. Venturini, R. Alonso, G. Anglada, J. Asquier, T. Bárczy, D. Barrado Navascues, O. Barragán, W. Baumjohann, T. Beck, N. Billot, F. Biondi, X. Bonfils, L. Borsato, A. Brandeker, C. Broeg, V. Cessa, S. Charnoz, A. Collier Cameron, Sz. Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, A. Deline, B.-O. Demory, D. Ehrenreich, A. Erikson, M. Esposito, A. Fortier, M. Fridlund, M. Gillon, M. Güdel, M. N. Günther, Ch. Helling, S. Hoyer, K. G. Isaak, L. L. Kiss, K. W. F. Lam, J. Laskar, A. Lecavelier des Etangs, M. Lendl, A. Luntzer, D. Magrin, P. F. L. Maxted, C. Mordasini, V. Nascimbeni, G. Olofsson, H. L. M. Osborne, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, G. Scandariato, D. Ségransan, A. E. Simon, A. M. S. Smith, M. Stalport, Gy. M. Szabó, N. Thomas, S. Udry, V. Van Eylen, V. Van Grootel, E. Villaver, I. Walter, N. A. Walton

Comments: 17 pages, including appendix
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2403.16621 [astro-ph.EP] (or arXiv:2403.16621v1 [astro-ph.EP] for this version)
Submission history
From: Nuno Rosário
[v1] Mon, 25 Mar 2024 11:06:25 UTC (11,270 KB)
Astrobiology, Astrochemistry,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻