Wolf 327b: A new member of the pack of ultra-short-period super-Earths around M dwarfs

April 2024 • 2024A&A...684A..83M

Authors • Murgas, F. • Pallé, E. • Orell-Miquel, J. • Carleo, I. • Peña-Moñino, L. • Pérez-Torres, M. • Watkins, C. N. • Jeffers, S. V. • Azzaro, M. • Barkaoui, K. • Belinski, A. A. • Caballero, J. A. • Charbonneau, D. • Cheryasov, D. V. • Ciardi, D. R. • Collins, K. A. • Cortés-Contreras, M. • de Leon, J. • Duque-Arribas, C. • Enoc, G. • Esparza-Borges, E. • Fukui, A. • Geraldía-González, S. • Gilbert, E. A. • Hatzes, A. P. • Hayashi, Y. • Henning, Th. • Herrero, E. • Jenkins, J. M. • Lillo-Box, J. • Lodieu, N. • Lund, M. B. • Luque, R. • Montes, D. • Nagel, E. • Narita, N. • Parviainen, H. • Polanski, A. S. • Reffert, S. • Schlecker, M. • Schöfer, P. • Schwarz, R. P. • Schweitzer, A. • Seager, S. • Stassun, K. G. • Tabernero, H. M. • Terada, Y. • Twicken, J. D. • Vanaverbeke, S. • Winn, J. N. • Zambelli, R. • Amado, P. J. • Quirrenbach, A. • Reiners, A. • Ribas, I.

Abstract • Planets with orbital periods shorter than 1 day are rare and have formation histories that are not completely understood. Small (R_p < 2 R_⊕) ultra-short-period (USP) planets are highly irradiated, probably have rocky compositions with high bulk densities, and are often found in multi-planet systems. Additionally, USP planets found around small stars are excellent candidates for characterization using present-day instrumentation. Of the current full sample of approximately 5500 confirmed exoplanets, only 130 are USP planets and around 40 have mass and radius measurements. Wolf 327 (TOI-5747) is an M dwarf (R_* = 0.406 ± 0.015 R_☉, M_* = 0.405 ± 0.019 M_☉, T_eff = 3542 ± 70 K, and V = 13 mag) located at a distance d = 28.5 pc. NASA's planet hunter satellite, TESS, detected transits in this star with a period of 0.573 day (13.7 h) and with a transit depth of 818 ppm. Ground-based follow-up photometry, high resolution imaging, and radial velocity (RV) measurements taken with the CARMENES spectrograph confirm the presence of this new USP planet. Wolf 327b is a super-Earth with a radius of R_p = 1.24 ± 0.06 R_⊕ and a mass of M_p = 2.53 ± 0.46 M_⊕, yielding a bulk density of 7.24 ± 1.66 g cm^‒3 and thus suggesting a rocky composition. Owing to its close proximity to its host star (a = 0.01 au), Wolf 327b has an equilibrium temperature of 996 ± 22 K. This planet has a mass and radius similar to K2-229b, a planet with an inferred Mercury-like internal composition. Planet interior models suggest that Wolf 327b has a large iron core, a small rocky mantle, and a negligible (if any) H/He atmosphere.

Radial velocity measurement table is available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/684/A83

Links

• PREPRINT http://arxiv.org/abs/2401.12150
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202348813/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202348813
• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2024A%26A...684A..83M
• PDF https://www.aanda.org/10.1051/0004-6361/202348813/pdf
• DATA https://irsa.ipac.caltech.edu/bibdata/2024/M/2024A&A...684A..83M.html