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HD 203473 is a star in the equatorial constellation Equuleus. With an apparent magnitude of 8.23, it’s only visible by using an amateur telescope. The star is located at a distance of 237 light years based on its parallax shift but is drifting closer at a high rate of 61.7 km/s. As of 2014, no stellar companions have been detected around the star.

HD 203473 is an ordinary G-type main-sequence star with 82% the mass of the Sun, but is 48% larger than the latter. This star is over luminous and hot for its class, with it radiating at 2.31 the luminosity of the Sun and an effective temperature of 5,847 K. HD 203473 has different age estimates, either being 5 or 8 billion years old. The higher luminosity and low projected rotational velocity of 1 km/s favors the older age estimate. Like many planetary hosts, HD 203473 has an enhanced metallicity, with an iron abundance 1.51 times that of the Sun.

Companion

In 2018, the N2K project discovered an object, initially thought to be a planet, orbiting the star via Doppler spectroscopy. Due to the detection method, its inclination and true mass were initially unknown. In 2022, the inclination and true mass of this companion were measured via astrometry, revealing it to be 96 M_J and thus either a massive brown dwarf or low-mass star. The companion's orbital period was also found to be twice as long as originally thought.

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. (2012-05-01). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 119257644.
3. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 05: 0. Bibcode:1999MSS...C05....0H.
4. ^ Brewer, John M.; Fischer, Debra A.; Valenti, Jeff A.; Piskunov, Nikolai (2016-08-01). "Spectral Properties of Cool Stars: Extended Abundance Analysis of 1,617 Planet-search Stars". The Astrophysical Journal Supplement Series. 225 (2): 32. arXiv:1606.07929. Bibcode:2016ApJS..225...32B. doi:10.3847/0067-0049/225/2/32. ISSN 0067-0049. S2CID 118507965.
5. ^ 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.
6. ^ Nordström, B.; Mayor, M.; Andersen, J.; Holmberg, J.; Pont, F.; Jørgensen, B. R.; Olsen, E. H.; Udry, S.; Mowlavi, N. (2004-05-01). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ~14 000 F and G dwarfs". Astronomy and Astrophysics. 418: 989–1019. arXiv:astro-ph/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. ISSN 0004-6361. S2CID 11027621.
7. Tokovinin, Andrei (2014-04-01). "From Binaries to Multiples. I. Data on F and G Dwarfs within 67 pc of the Sun". The Astronomical Journal. 147 (4): 86. arXiv:1401.6825. Bibcode:2014AJ....147...86T. doi:10.1088/0004-6256/147/4/86. ISSN 0004-6256. S2CID 53965918.
8. Ment, Kristo; Fischer, Debra A.; Bakos, Gaspar; Howard, Andrew W.; Isaacson, Howard (2018-11-01). "Radial Velocities from the N2K Project: Six New Cold Gas Giant Planets Orbiting HD 55696, HD 98736, HD 148164, HD 203473, and HD 211810". The Astronomical Journal. 156 (5): 213. arXiv:1809.01228. Bibcode:2018AJ....156..213M. doi:10.3847/1538-3881/aae1f5. ISSN 0004-6256. S2CID 119243619.
9. ^ 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 Equuleus
Equuleus in Chinese astronomy List of stars in Equuleus
Stars	Bayer α (Kitalpha) β γ δ ε ζ λ Flamsteed 4 6 9 Variable R U SY HR 8038 8067 8090 8095 8149 8191 HD 200779 200964 201585 202908 203473 Other HAT-P-65 WASP-90
Exoplanets MASCARA-1b
Galaxies	NGC 7015 7040 7046
Category

• Astronomy
• Stars
• Spaceflight
• Outer space
• Solar System

• Equuleus
• G-type main-sequence stars
• Hipparcos objects
• Henry Draper Catalogue objects
• Planetary systems with one confirmed planet
• Durchmusterung objects