TESS and CHEOPS Discover Two Warm Sub-Neptunes Transiting the Bright K-dwarf HD 15906
Abstract
We report the discovery of two warm sub-Neptunes transiting the bright (G = 9.5 mag) K-dwarf HD 15906 (TOI 461, TIC 4646810). This star was observed by the Transiting Exoplanet Survey Satellite (TESS) in sectors 4 and 31, revealing two small transiting planets. The inner planet, HD 15906 b, was detected with an unambiguous period but the outer planet, HD 15906 c, showed only two transits separated by 734 days, leading to 36 possible values of its period. We performed follow-up observations with the CHaracterising ExOPlanet Satellite (CHEOPS) to confirm the true period of HD 15906 c and improve the radius precision of the two planets. From TESS, CHEOPS and additional ground-based photometry, we find that HD 15906 b has a radius of 2.24 0.08 R and a period of 10.924709 0.000032 days, whilst HD 15906 c has a radius of 2.93 R and a period of 21.583298 days. Assuming zero bond albedo and full day-night heat redistribution, the inner and outer planet have equilibrium temperatures of 668 13 K and 532 10 K, respectively. The HD 15906 system has become one of only six multiplanet systems with two warm ( 700 K) sub-Neptune sized planets transiting a bright star (G 10 mag). It is an excellent target for detailed characterisation studies to constrain the composition of sub-Neptune planets and test theories of planet formation and evolution.
Cite
@article{arxiv.2306.04511,
title = {TESS and CHEOPS Discover Two Warm Sub-Neptunes Transiting the Bright K-dwarf HD 15906},
author = {Amy Tuson and Didier Queloz and Hugh P. Osborn and Thomas G. Wilson and Matthew J. Hooton and Mathias Beck and Monika Lendl and Göran Olofsson and Andrea Fortier and Andrea Bonfanti and Alexis Brandeker and Lars A. Buchhave and Andrew Collier Cameron and David R. Ciardi and Karen A. Collins and Davide Gandolfi and Zoltan Garai and Steven Giacalone and João Gomes da Silva and Steve B. Howell and Jayshil A. Patel and Carina M. Persson and Luisa M. Serrano and Sérgio G. Sousa and Solène Ulmer-Moll and Andrew Vanderburg and Carl Ziegler and Yann Alibert and Roi Alonso and Guillem Anglada and Tamas Bárczy and David Barrado Navascues and Susana C. C. Barros and Wolfgang Baumjohann and Thomas Beck and Willy Benz and Nicolas Billot and Xavier Bonfils and Luca Borsato and Christopher Broeg and Juan Cabrera and Sébastien Charnoz and Dennis M. Conti and Szilard Csizmadia and Patricio E. Cubillos and Melvyn B. Davies and Magali Deleuil and Laetitia Delrez and Olivier D. S. Demangeon and Brice-Olivier Demory and Diana Dragomir and Courtney D. Dressing and David Ehrenreich and Anders Erikson and Zahra Essack and Jacopo Farinato and Luca Fossati and Malcolm Fridlund and Elise Furlan and Holden Gill and Michaël Gillon and Crystal L. Gnilka and Erica Gonzales and Manuel Güdel and Maximilian N. Günther and Sergio Hoyer and Kate G. Isaak and Jon M. Jenkins and Laszlo L. Kiss and Jacques Laskar and David W. Latham and Nicholas Law and Alain Lecavelier des Etangs and Gaspare Lo Curto and Christophe Lovis and Rafael Luque and Demetrio Magrin and Andrew W. Mann and Pierre F. L. Maxted and Michel Mayor and Scott McDermott and Marko Mecina and Christoph Mordasini and Annelies Mortier and Valerio Nascimbeni and Roland Ottensamer and Isabella Pagano and Enric Pallé and Gisbert Peter and Giampaolo Piotto and Don Pollacco and Tyler Pritchard and Roberto Ragazzoni and Nicola Rando and Francesco Ratti and Heike Rauer and Ignasi Ribas and George R. Ricker and Martin Rieder and Nuno C. Santos and Arjun B. Savel and Gaetano Scandariato and Richard P. Schwarz and Sara Seager and Damien Ségransan and Avi Shporer and Attila E. Simon and Alexis M. S. Smith and Manfred Steller and Chris Stockdale and Gyula M. Szabó and Nicolas Thomas and Guillermo Torres and René Tronsgaard and Stéphane Udry and Bernd Ulmer and Valérie Van Grootel and Roland Vanderspek and Julia Venturini and Nicholas A. Walton and Joshua N. Winn and Bill Wohler},
journal= {arXiv preprint arXiv:2306.04511},
year = {2023}
}
Comments
30 pages, 20 figures, 11 tables (including appendix). Published in MNRAS