Discovery and mass measurement of the hot, transiting, Earth-sized planet, GJ 3929 b

J. Kemmer, S. Dreizler, D. Kossakowski, S. Stock, A. Quirrenbach, J. A. Caballero, P. J. Amado, K. A. Collins, N. Espinoza, E. Herrero, J. M. Jenkins, D. W. Latham, J. Lillo-Box, N. Narita, E. Pallé, A. Reiners, I. Ribas, G. Ricker, E. Rodríguez, S. SeagerR. Vanderspek, R. Wells, J. Winn, F. J. Aceituno, V. J.S. Béjar, T. Barclay, P. Bluhm, P. Chaturvedi, C. Cifuentes, K. I. Collins, M. Cortés-Contreras, B. O. Demory, M. M. Fausnaugh, A. Fukui, Y. Gómez Maqueo Chew, D. Galadí-Enríquez, T. Gan, M. Gillon, A. Golovin, A. P. Hatzes, Th Henning, C. Huang, S. V. Jeffers, A. Kaminski, M. Kunimoto, M. Kürster, M. J. López-González, M. Lafarga, R. Luque, J. McCormac, K. Molaverdikhani, D. Montes, J. C. Morales, V. M. Passegger, S. Reffert, L. Sabin, P. Schöfer, N. Schanche, M. Schlecker, U. Schroffenegger, R. P. Schwarz, A. Schweitzer, A. Sota, P. Tenenbaum, T. Trifonov, S. Vanaverbeke, M. Zechmeister

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


We report the discovery of GJ 3929 b, a hot Earth-sized planet orbiting the nearby M3.5 V dwarf star, GJ 3929 (G 180-18, TOI-2013). Joint modelling of photometric observations from TESS sectors 24 and 25 together with 73 spectroscopic observations from CARMENES and follow-up transit observations from SAINT-EX, LCOGT, and OSN yields a planet radius of Rb = 1.150 ± 0.040 R⊕, a mass of Mb = 1.21 ± 0.42 M⊕, and an orbital period of Pb = 2.6162745 ± 0.0000030 d. The resulting density of ρb = 4.4 ± 1.6 g cm-3 is compatible with the Earth's mean density of about 5.5 g cm-3. Due to the apparent brightness of the host star (J = 8.7 mag) and its small size, GJ 3929 b is a promising target for atmospheric characterisation with the JWST. Additionally, the radial velocity data show evidence for another planet candidate with P[c] = 14.303 ± 0.035 d, which is likely unrelated to the stellar rotation period, Prot = 122 ± 13 d, which we determined from archival HATNet and ASAS-SN photometry combined with newly obtained TJO data.

Original languageEnglish (US)
Article numberA17
JournalAstronomy and Astrophysics
StatePublished - Mar 1 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Planetary systems
  • Planets and satellites: Detection
  • Stars: Individual: GJ 3929
  • Stars: Late-type
  • Techniques: Photometric
  • Techniques: Radial velocities


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