GJ 3512

GJ 3512 is a nearby star in the northern circumpolar constellation of Ursa Major. It is invisible to the naked eye but can be observed using a telescope, having an apparent visual magnitude of +15.05.[2] The star is located at a distance of 31 light years from the Sun based on parallax.[1] It has a high proper motion,[7] traversing the celestial sphere at the rate of 1.311″ yr−1.[9] The measurement of the star's radial velocity is poorly constrained, but it appears to be drifting further away at a rate of ~8 km/s.[4]

GJ 3512
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 08h 41m 20.1289s[1]
Declination +59° 29′ 50.445″[1]
Apparent magnitude (V) +15.05[2]
Characteristics
Evolutionary stage Main sequence
Spectral type dM5.5[3]
Astrometry
Radial velocity (Rv)+8±4[4] km/s
Proper motion (μ) RA: −260.421[1] mas/yr
Dec.: −1,279.613[1] mas/yr
Parallax (π)105.3856 ± 0.0944[1] mas
Distance30.95 ± 0.03 ly
(9.489 ± 0.008 pc)
Details[3]
Mass0.1254±0.0031 M☉
Radius0.1636±0.0023 R☉
Luminosity0.001574±0.000018 L☉
Surface gravity (log g)5.240±0.044 cgs
Temperature3,081±51 K
Metallicity [Fe/H]−0.07±0.16 dex
Rotation87±5 d[5]
Rotational velocity (v sin i)2.0[6] km/s
Age3–8[7] Gyr
Other designations
G 234-45, LHS 252, 2MASS J08412013+5929505[8]
Database references
SIMBADdata

The stellar classification of GJ 3512 is dM5.5,[3] which determines this to be a small red dwarf star that is generating energy through core hydrogen fusion. It displays a moderate amount of magnetic activity with a Sun-like cycle lasting 14 years. A low-level variability lasting ~87 d matches the approximate rotation period.[5] The star has 12.5% of the mass of the Sun and 16% of the Sun's radius. It is radiating 1.6% of the luminosity of the Sun from its photosphere at an effective temperature of 3,081 K.[3]

A gas giant planet in eccentric orbit around GJ 3512 was discovered in 2019 utilizing a radial velocity method. The star's mass is only 250 times that of the gas giant, calling into question traditional models of planetary formation.[10][7] If the star was born in an open cluster, this planet may instead have formed around a higher mass star then been swapped into this system during an interaction.[11] The eccentric orbit of this object may have been caused by the ejection of another exoplanet from the system.[7] A second gas giant planet on wider, circular orbit is suspected.[5]

The GJ 3512 planetary system[5]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥0.463±0.023 MJ 0.338+0.008
−0.0084		 203.59±0.14 0.4356±0.0052 — —
c (unconfirmed) 0.20±0.01 MJ 1.292±0.003 1,599.6+1.1
−0.8		 0.0183±0.0001 — —

See also

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Weis, Edward W. (1996). "Photometry of Stars with Large Proper Motion". The Astronomical Journal. 112: 2300. Bibcode:1996AJ....112.2300W. doi:10.1086/118183.
  3. Schweitzer, A.; et al. (May 2019). "The CARMENES search for exoplanets around M dwarfs. Different roads to radii and masses of the target stars". Astronomy & Astrophysics. 625: 16. arXiv:1904.03231. Bibcode:2019A&A...625A..68S. doi:10.1051/0004-6361/201834965. A68.
  4. Newton, Elisabeth R.; et al. (2014). "Near-infrared Metallicities, Radial Velocities, and Spectral Types for 447 Nearby M Dwarfs". The Astronomical Journal. 147 (1): 20. arXiv:1310.1087. Bibcode:2014AJ....147...20N. doi:10.1088/0004-6256/147/1/20. S2CID 26818462.
  5. Lopez-Santiago, J.; et al. (2020). "A likely magnetic activity cycle for the exoplanet host M dwarf GJ 3512". The Astronomical Journal. 160 (6): 273. arXiv:2010.07715. doi:10.3847/1538-3881/abc171.
  6. Reiners, A.; et al. (2018). "The CARMENES search for exoplanets around M dwarfs. High-resolution optical and near-infrared spectroscopy of 324 survey stars". Astronomy and Astrophysics. 612: A49. arXiv:1711.06576. Bibcode:2018A&A...612A..49R. doi:10.1051/0004-6361/201732054. S2CID 62818673.
  7. Morales, J. C.; et al. (2019). "A giant exoplanet orbiting a very-low-mass star challenges planet formation models". Science. 365 (6460): 1441–1445. arXiv:1909.12174. Bibcode:2019Sci...365.1441M. doi:10.1126/science.aax3198. PMID 31604272. S2CID 202888425.
  8. "G 234-45". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-18.
  9. Lépine, Sébastien; Shara, Michael M. (March 2005). "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)". The Astronomical Journal. 129 (3): 1483–1522. arXiv:astro-ph/0412070. Bibcode:2005AJ....129.1483L. doi:10.1086/427854. S2CID 2603568.
  10. Choi, Charles Q. "Surprise! Giant Planet Found Circling Tiny Red Dwarf Star". Space.com. Retrieved 26 September 2019.
  11. Wang, Yi-Han; et al. (March 2020). "Giant Planet Swaps during Close Stellar Encounters". The Astrophysical Journal Letters. 891 (1): 6. arXiv:2002.08366. Bibcode:2020ApJ...891L..14W. doi:10.3847/2041-8213/ab77d0. L14.
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