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

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

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Planets with orbital periods shorter than 1 day are rare and have formation histories that are not completely understood. Small (Rp < 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, Teff = 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 Rp = 1.24 ± 0.06 R and a mass of Mp = 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.

Original languageEnglish (US)
Article numberA83
JournalAstronomy and Astrophysics
StatePublished - Apr 1 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planets and satellites: detection
  • planets and satellites: terrestrial planets
  • stars: individual: Wolf 327
  • stars: late-type
  • techniques: photometric
  • techniques: radial velocities


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