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, Karen A. Collins, N. Espinoza, E. Herrero, Jon M. Jenkins, David W. Latham, J. Lillo-Box, Norio Narita, E. Pallé, A. Reiners, I. Ribas, G. Ricker, E. Rodrı́guez, S. Seager, R. Vanderspek, Robert D. Wells, Joshua N. Winn, F. J. Aceituno, V. J. S. Béjar, Thomas Barclay, P. Bluhm, P. Chaturvedi, C. Cifuentes, Kevin I. Collins, M. Cortés‐Contreras, Brice-Olivier Demory, Michael Fausnaugh, Akihiko Fukui, Y. Gómez Maqueo Chew, D. Galadí-Enríquez, Tianjun Gan, M. Gillon, Alex Golovin, A. P. Hatzes, Th. Henning, Chelsea X. Huang, S. V. Jeffers, A. Kaminski, M. Kunimoto, M. Kürster, M. J. López‐González, M. Lafarga, R. Luque, J. McCormac, Karan Molaverdikhani, D. Montes, J. C. Morales, V. M. Passegger, S. Reffert, L. Sabin, P. Schöfer, N. Schanche, Martin Schlecker, U. Schroffenegger, Richard P. Schwarz, A. Schweitzer, A. Sota, P. Tenenbaum, Trifon Trifonov, S. Vanaverbeke, M. Zechmeister
Abstract
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 R b = 1.150 ± 0.040 R ⊕ , a mass of M b = 1.21 ± 0.42 M ⊕ , and an orbital period of P b = 2.6162745 ± 0.0000030 d . The resulting density of ρ b = 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, P rot = 122 ± 13 d, which we determined from archival HATNet and ASAS-SN photometry combined with newly obtained TJO data.