Epoch J2000.0 Equinox J2000.0
|Right ascension||13h 34m 02.5394s|
|Declination||+53° 43′ 42.6984″|
|Apparent magnitude (V)||8.06|
|B−V color index||0.699±0.012|
|Radial velocity (Rv)||−29.07±0.24 km/s|
|Proper motion (μ)|| RA: −85.877±0.052 mas/yr |
Dec.: −78.913±0.038 mas/yr
|Parallax (π)||10.8102 ± 0.0275 mas|
|Distance||301.7 ± 0.8 ly |
(92.5 ± 0.2 pc)
|Absolute magnitude (MV)||3.32|
|Surface gravity (log g)||3.93±0.02 cgs|
|Metallicity [Fe/H]||0.16 dex|
|Rotational velocity (v sin i)||7.0 km/s|
HD 118203 is a star located in the northern circumpolar constellation of Ursa Major. It has the proper name Liesma, which means flame, and it is the name of a character from the Latvian poem Staburags un Liesma (Staburags and Liesma). The name was selected in the NameExoWorlds campaign by Latvia, during the 100th anniversary of the IAU.
The apparent visual magnitude of HD 118203 is 8.06, which means it is invisible to the naked eye but it can be seen using binoculars or a telescope. Based on parallax measurements, it is located at a distance of 302 light years from the Sun. The star is drifting closer with a radial velocity of −29 km/s. Based on its position and space velocity this is most likely (97% chance) an older thin disk star. An exoplanet has been detected in a close orbit around the star.
The spectrum of this star matches a K-type dwarf with a class of K0. Its absolute magnitude of 3.32 is too high for a K-type main-sequence star, indicating that it has begun to evolve on the subdwarf stage. This is confirmed by the surface gravity, which is too low for a typical dwarf star of this class. It has a low level of chromospheric activity, which means a low level of radial velocity jitter for planet detection purposes. The star has 1.23 times the mass of the Sun and double the Sun's radius. It is around 5.4 billion years old and is spinning with a projected rotational velocity of 7.0 km/s. HD 118203 is radiating 3.8 times the luminosity of the Sun from its photosphere at an effective temperature of 5,741 K.
In 2006, a hot Jupiter candidate was reported in an eccentric orbit around this star. It was discovered using the radial velocity method based on observation of high-metallicity stars begun in 2004. In 2020, it was found that this is a transiting planet, which allowed the mass and radius of the body to be determined. This exoplanet has more than double the mass of Jupiter and a 13% greater radius. The fact that the parent star is among the brighter known planet hosts (as of 2020) makes it an interesting object for further study.
(in order from star)
- 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.
- Luck, R. Earle (January 2017). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal. 153 (1): 19. arXiv:1611.02897. Bibcode:2017AJ....153...21L. doi:10.3847/1538-3881/153/1/21. S2CID 119511744. 21.
- 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.
- Bonfanti, A.; et al. (2015). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: A5. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692.
- "HD 118203". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-13.
- "Approved names". NameExoworlds. Retrieved 2020-01-02.
- "International Astronomical Union | IAU". www.iau.org. Retrieved 2020-01-02.
- Pepper, Joshua; et al. (2020). "TESS Reveals HD 118203 b to be a Transiting Planet". The Astronomical Journal. 159 (6): 243. arXiv:1911.05150. Bibcode:2020AJ....159..243P. doi:10.3847/1538-3881/ab84f2. S2CID 207930540.
- da Silva, R.; et al. (2006). "Elodie metallicity-biased search for transiting Hot Jupiters I. Two Hot Jupiters orbiting the slightly evolved stars HD118203 and HD149143". Astronomy and Astrophysics. 446 (2): 717–722. arXiv:astro-ph/0510048. Bibcode:2006A&A...446..717D. doi:10.1051/0004-6361:20054116. S2CID 18907493.