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HD 204313 is a star with two and possibly three exoplanetary companions in the southern constellation of Capricornus. With an apparent magnitude of 7.99, it is an eighth magnitude star that is too faint to be readily visible to the naked eye. The star is located at a distance of 157 light years from the Sun based on parallax measurements, but it is drifting closer with a radial velocity of −10 km/s.

This is an ordinary G-type main-sequence star with a stellar classification of G5V, which indicates it is generating energy through hydrogen fusion at its core. It is an estimated four billion years old, chromospherically extremely quiet, and is spinning with a projected rotational velocity of just 0.8 km/s. The star has a slightly larger mass and radius compared to the Sun. It is radiating 118% of the luminosity of the Sun from its photosphere at an effective temperature of 5,783 K.

Planetary system

This star was in observation by the CORALIE radial velocity planet-search program since the year 2000. In August 2009, a superjovian planetary companion was announced. Two years later, a hot Neptune HD 204313 c on a 35-day orbit was announced, followed by a third Jupiter-like planet candidate HD 204313 d on a 2800-day orbit, which was announced in 2012. Assuming that planet d exists, planets b & d are apparently orbiting close to a 7:5 mean motion resonance, which may be stabilizing their periods.

A 2015 study independently confirmed the first two discoveries, but did not detect any significant signal at the claimed period of planet d. Another study in 2022 agreed with these results, in addition to finding a new planet or brown dwarf, designated HD 204313 e to differentiate it from the dubious candidate. The inclination and true mass of planets b & e were measured via astrometry.

See also

• HD 147018
• HD 171238
• List of extrasolar planets

References

1. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
3. ^ Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H
4. ^ Bonfanti, A.; Ortolani, S.; Nascimbeni, V. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: 14. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692. A5.
5. ^ Costa Silva, A. R.; et al. (February 2020). "Chemical abundances of 1111 FGK stars from the HARPS-GTO planet search sample. III. Sulfur". Astronomy & Astrophysics. 634: 10. arXiv:1912.08659. Bibcode:2020A&A...634A.136C. doi:10.1051/0004-6361/201936523. S2CID 209405391. A136.
6. "HD 204313". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-10-16.
7. Robertson, Paul; et al. (July 2012), "A Second Giant Planet in 3:2 Mean-motion Resonance in the HD 204313 System", The Astrophysical Journal, 754 (1): 9, arXiv:1205.3689, Bibcode:2012ApJ...754...50R, doi:10.1088/0004-637X/754/1/50, S2CID 118630310, 50.
8. Ségransan, D.; et al. (2010). "The CORALIE survey for southern extrasolar planets. XVI. Discovery of a planetary system around HD 147018 and of two long period and massive planets orbiting HD 171238 and HD 204313". Astronomy and Astrophysics. 511: A45. arXiv:0908.1479. Bibcode:2010A&A...511A..45S. doi:10.1051/0004-6361/200912136. S2CID 8864844.
9. Mayor, M.; et al. (September 2011), "The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets", eprint, arXiv:1109.2497, Bibcode:2011arXiv1109.2497M
10. Robertson, Paul; et al. (2012). "A Second Giant Planet in 3:2 Mean-motion Resonance in the HD 204313 System". The Astrophysical Journal. 754 (1): 50. arXiv:1205.3689. Bibcode:2012ApJ...754...50R. doi:10.1088/0004-637X/754/1/50. S2CID 118630310.
11. Petit, A. C.; et al. (November 2017), "AMD-stability in the presence of first-order mean motion resonances", Astronomy & Astrophysics, 607: 17, arXiv:1705.06756, Bibcode:2017A&A...607A..35P, doi:10.1051/0004-6361/201731196, S2CID 55740532, A35.
12. ^ Díaz, R. F.; et al. (2016). "The HARPS search for southern extra-solar planets. XXXVIII. Bayesian re-analysis of three systems. New super-Earths, unconfirmed signals, and magnetic cycles". Astronomy and Astrophysics. 585. A134. arXiv:1510.06446. Bibcode:2016A&A...585A.134D. doi:10.1051/0004-6361/201526729. S2CID 118531921.
13. ^ Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.

v t e Constellation of Capricornus
Capricornus in Chinese astronomy List of stars in Capricornus
Stars	Bayer α (Prima Giedi) α (Algedi) β (Dabih) β γ (Nashira) δ (Deneb Algedi) ε ζ η θ ι κ λ μ ν (Alshat) ξ ξ ο ο π ρ σ τ τ υ φ χ ψ ω Flamsteed 3 4 17 19 20 21 24 (A) 27 29 30 31 33 35 36 (b) 37 41 42 44 45 46 (c) 47 (c) 50 Variable R HR 7722 7845 7898 HD 197027 202206 204313 Other HATS-3 LP 816-60
Exoplanets HD 192310 b c HD 202206 c HD 204313 b HD 202772 Ab PSO J318.5−22
Star clusters Messier 30 Palomar 12
Galaxies	NGC 6907 7016 7019 7030 7035 7035A 7073 Other IC 1337 PKS 2126-158
Galaxy clusters HCG 87
Category

• G-type main-sequence stars
• Planetary systems with two confirmed planets
• Capricornus
• 2MASS objects
• Durchmusterung objects
• Henry Draper Catalogue objects
• Hipparcos objects