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

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 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.

A detailed analysis of the Gl 486 planetary system

“…In case of ∆ ln Z < 1.0, one must keep the simplest model with the smallest N par . In previous works on CARMENES RV follow-up of transiting planets detected by TESS, even more conservative criteria of ∆ ln Z > 2.5 or 5.0 for decisive difference between models has been used (Kossakowski et al 2021;González-Álvarez et al 2022;Kemmer et al 2022). Such conservative criteria in Bayesian analyses applied to exoplanets can be traced back to previous works (e.g., Gregory 2005;Feroz et al 2011).…”

“…Besides, we added by hand the uncertainties in stellar mass for the hosts of 23 planets, including the seven planets in the TRAPPIST-1 system, since they are incorrectly rounded when downloaded. Additionally, we incorporated four planets not yet included in the Exoplanet Archive: GJ 3929 b (Kemmer et al 2022), TOI-1759 b (Espinoza et al 2022), and TOI-1238b and TOI-1238c (González-Álvarez et al 2022. In total, the sample contains 651 confirmed transiting exoplanets with mass and radius determination, displayed in Fig.…”

GJ 3929: High-precision Photometric and Doppler Characterization of an Exo-Venus and Its Hot, Mini-Neptune-mass Companion

“…As outlined in Kemmer et al (2022), high air mass caused the CTIO observations to exhibit higher scatter. In fact, both transits on 2021 April 10 exhibit much higher scatter (rms CTIO = 3300 ppm; rms MCD = 2200 ppm) than on 2021 April 15 (rms gp = 1010 ppm; rms ip = 850 ppm; rms rp = 910 ppm; rms zs = 920 ppm).…”

“…Our team began follow-up observations using RV instruments and high-contrast imaging shortly after this announcement, with the intent to confirm the planetary nature of this system and refine the planetary parameters of the transiting candidate. Kemmer et al (2022) recently published an analysis of the system, placing constraints on its planetary parameters and validating its planetary nature, as well as discovering a second, nontransiting planet candidate during their analysis. Kemmer et al (2022) were unable to precisely constrain the mass of the transiting planet (K/σ = 2.88), however, possibly due to the unanticipated existence of planet c.…”

“…Kemmer et al (2022) recently published an analysis of the system, placing constraints on its planetary parameters and validating its planetary nature, as well as discovering a second, nontransiting planet candidate during their analysis. Kemmer et al (2022) were unable to precisely constrain the mass of the transiting planet (K/σ = 2.88), however, possibly due to the unanticipated existence of planet c.…”