GJ 3929
Observation data
Epoch J2000      Equinox J2000
Constellation Corona Borealis[note 1]
Right ascension 15h 58m 18.8s[1]
Declination +35° 24′ 24.3″[1]
Apparent magnitude (V) 12.67[2]
Characteristics
Spectral type M3.5V[1]
Astrometry
Radial velocity (Rv)10.14[2] km/s
Proper motion (μ) RA: −143.277±0.066 mas/yr[2]
Dec.: 318.219±0.082 mas/yr[2]
Parallax (π)63.1727 ± 0.038 mas[1]
Distance51.58±0.02 ly
(15.822±0.006 pc)[3]
Absolute magnitude (MV)11
Details[3]
Mass0.313+0.027
−0.022 M☉
Radius0.32±0.01 R☉
Luminosity0.0109+0.0005
−0.0004 L☉
Surface gravity (log g)4.89±0.05 cgs
Temperature3,384±88 K
Metallicity [Fe/H]−0.02±0.12 dex
Rotation122±13 d[4]
Rotational velocity (v sin i)<2 km/s
Age2.2 – 11.2[note 2] Gyr
Other designations
TOI-2013, TIC 188589164, 2MASS J15581883+3524236, Gaia DR3 1372215976327300480,[3] G 180-18[5]
Database references
SIMBADdata

GJ 3929, also known as Gliese 3929 and TOI-2013, is a red dwarf star located 51.6 light-years from Earth, in the constellation Corona Borealis.[5][note 3] With an apparent magnitude of 12,[5] it is not visible to the naked eye. In 2022, two exoplanets were detected orbiting the star.[4]

Characteristics

GJ 3929 is a red dwarf of spectral type M3.5V, having a radius of 0.32±0.01 R☉, a mass of 0.313+0.027
−0.022 M☉ and a temperature of 3384±88 K.[6] With an apparent magnitude of 12.7,[2] it cannot be visible with the naked eye, neither with a small telescope.[5] It has no companion stars.[4] The age of GJ 3929 is estimated at 2.2 to 12.2 billion years.[3]

The star is located in the northern hemisphere, approximately 50 light years from Earth,[5] in the direction of the constellation Corona Borealis.[lower-alpha 1] Its closest neighbor is the red dwarf G 179–57, located at a distance of 3.9 light years.[5]

Nearest stars to GJ 3929[5]
Name Distance (light-years)
G 179-57 3.9
LP 224-38 5.2
Ross 640 5.6
Rho Coronae Borealis 5.9
Gliese 611 5.9

Planetary system

In 2022, two exoplanets were detected orbiting around GJ 3929.[4] The innermost, GJ 3929 b, is a rocky planet just 9% larger than Earth, while the outermost, GJ 3929 c, is a sub-Neptune with 5.7 times the mass of Earth.[3] Both planets orbit below the star's habitable zone.[6]

The GJ 3929 planetary system[3]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 1.75±0.45 M🜨 0.0252±0.0005 2.616 0 (fixed) 88.442°±0.008° 1.09±0.04 R🜨
c >5.71±0.94 M🜨 0.081±0.002 15.04±0.03 0 (fixed) — —

GJ 3929 b

The innermost planet, GJ 3929 b (TOI-2013 b), is an Earth-sized planet discovered by the transit method.[4] Orbiting its star at a distance of 0.0252 astronomical units (3,770,000 km), the planet is located in its star's Venus zone, and completes a revolution every 2 days and 15 hours.[3] The planet's equilibrium temperature is calculated at 568 K (295 °C), and it receives a planetary insolation 17 times greater than what the Earth receives from the Sun.[3]

The planet's mass is calculated at 1.75±0.45 M🜨 according to photometric observations using the NEID spectrometer.[3] Observations using the ARCTIC imager, plus photometry from TESS and LCOGT, constrained the planet's radius to 1.09±0.04 R🜨.[3] This radius makes GJ 3929 b very similar to Earth in terms of size.

Due to the apparent brightness of the host star, and its small size, GJ 3929 b is an excellent planet for atmospheric study with the James Webb Space Telescope.[3][4]

It was discovered by a team of astronomers led by Jonas Kemmer.[7] They reported an planetary transit signal in the host star's light curve.[7] Subsequent observations, mainly with the CARMENES spectrograph, revealed that this transit signal is an orbiting exoplanet.[7][4]

GJ 3929 c

The outermost planet, GJ 3929 c (TOI-2013 c) is a Sub-Neptune discovered using the radial velocity method.[4] It orbits its star at a distance of 0.081 astronomical units (12,100,000 km), 3 times further away than GJ 3929 b, but still below GJ 3929's habitable zone,[6] completing an orbit every 15 days.[3]

Its minimum mass is 5.71±0.94 M🜨, while its radius is unknown.[3] Estimates using mass-radius relationship derive a radius of 2.26 R🜨.[3] Its equilibrium temperature is calculated at 317 K (44 °C), and it receives a planetary insolation 68% greater than what the Earth receives from the Sun.[3]

GJ 3929 c was first identified in radial velocity data, which indicated the existence of another planet besides GJ 3929 b.[4][8] Initially, it was just an exoplanet candidate, but it was later confirmed by a team led by Corey Beard.[3][8] Because its orbital period (15 days) is far from its star's rotation period (122 days), it is unlikely that the radial velocity signal is actually an artifact of its parent star's activity and rotation.[4]

See also

Notes and references

  1. 1 2 3 4 5 6 7 "G 180-18". SIMBAD. Retrieved January 4, 2023.
  2. 1 2 3 4 5 "GJ 3929 | NASA Exoplanet Archive". exoplanetarchive.ipac.caltech.edu. Retrieved 2024-01-03.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Beard, Corey; Robertson, Paul; Kanodia, Shubham; Lubin, Jack; Cañas, Caleb I.; Gupta, Arvind F.; Holcomb, Rae; Jones, Sinclaire; Libby-Roberts, Jessica E.; Lin, Andrea S. J.; Mahadevan, Suvrath; Stefánsson, Guðmundur; Bender, Chad F.; Blake, Cullen H.; Cochran, William D. (2022-09-01). "GJ 3929: High Precision Photometric and Doppler Characterization of an Exo-Venus and its Hot, Mini-Neptune-mass Companion". The Astrophysical Journal. 936 (1): 55. arXiv:2207.10672. Bibcode:2022ApJ...936...55B. doi:10.3847/1538-4357/ac8480. ISSN 0004-637X.
  4. 1 2 3 4 5 6 7 8 9 10 Kemmer, J.; Dreizler, S.; Kossakowski, D.; Stock, S.; Quirrenbach, A.; Caballero, J. A.; Amado, P. J.; Collins, K. A.; Espinoza, N.; Herrero, E.; Jenkins, J. M.; Latham, D. W.; Lillo-Box, J.; Narita, N.; Pallé, E. (2022-03-01). "Discovery and mass measurement of the hot, transiting, Earth-sized planet, GJ 3929 b". Astronomy & Astrophysics. 659: A17. arXiv:2202.00970. Bibcode:2022A&A...659A..17K. doi:10.1051/0004-6361/202142653. ISSN 0004-6361.
  5. 1 2 3 4 5 6 7 "★ Gliese 3929". Stellar Catalog. Retrieved 2024-01-01.
  6. 1 2 3 "Open Exoplanet Catalogue - GJ 3929 b". www.openexoplanetcatalogue.com. Retrieved 2024-01-02.
  7. 1 2 3 "Hot Earth-sized exoplanet detected with TESS". phys.org. Retrieved 2024-01-04.
  8. 1 2 Cassese, Ben (2022-12-09). "Dotting the i's, Crossing the t's: Follow-Up of an Exo-Venus". AAS Nova. Retrieved 2024-01-04.
  1. ↑ Obtained with a right ascension of 15h 58m 18.8s and a declination of +35° 24′ 24.3″[1] on this website.
  1. ↑ Obtained with a right ascension of 15h 58m 18.8s and a declination of +35° 24′ 24.3″[1] on this website.
  2. ↑ The quoted value of 7.1+4.1
    −4.9     has very high margins of error.
  3. ↑ Obtained with a right ascension of 15h 58m 18.8s and a declination of +35° 24′ 24.3″[1] on this website.
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