HD 104985

HD 104985, formally named Tonatiuh (/toʊnəˈtiːuː/),[7][8] is a solitary[9] star with a exoplanetary companion in the northern constellation of Camelopardalis. The companion is designated HD 104985 b and named Meztli (/ˈmɛstli/). This star has an apparent visual magnitude of 5.78[2] and thus is dimly visible to the naked eye under favorable seeing conditions. It is located at a distance of approximately 329 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −20 km/s.[1]

HD 104985 / Tonatiuh
Observation data
Epoch J2000      Equinox J2000
Constellation Camelopardalis
Right ascension 12h 05m 15.11770s[1]
Declination +76° 54′ 20.6385″[1]
Apparent magnitude (V) 5.78[2]
Characteristics
Evolutionary stage Horizontal branch[3]
Spectral type G8.5IIIb[4]
B−V color index 1.029±0.005[2]
Astrometry
Radial velocity (Rv)−20.20±0.16[1] km/s
Proper motion (μ) RA: 147.071[1] mas/yr
Dec.: –92.204[1] mas/yr
Parallax (π)9.9146 ± 0.0706 mas[1]
Distance329 ± 2 ly
(100.9 ± 0.7 pc)
Absolute magnitude (MV)0.85[2]
Details[5]
Mass1.22±0.05 M☉
Radius10.64±0.29 R☉
Luminosity51±1[6] L☉
Surface gravity (log g)2.43±0.06 cgs
Temperature4,685±15 K
Metallicity [Fe/H]−0.36±0.02 dex
Age4.39±0.54 Gyr
Other designations
Tonatiuh, BD+77° 461, FK5 451, GC 16514, HD 104985, HIP 58952, HR 4609, SAO 7500, NLTT 29548[3]
Database references
SIMBADdata
Extrasolar Planets
Encyclopaedia		data

The stellar classification of this star is G8.5IIIb,[4] indicating this is an evolved giant star that has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It is located in the red clump region of the HR diagram, suggesting it is on the horizontal branch and generating energy through core helium fusion.[10] The star is approximately 4.4 billion years old with 1.2 times the mass of the Sun and has expanded to 10.6 times the Sun's radius.[5] It is radiating 51[6] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,730 K.[5]

In 2003, radial velocity measurements made by the Okayama Planet Search Program led to the announcement of an exoplanetary companion.[11] It is orbiting at a distance of 0.95 AU (142 Gm) with a period of 199.5 days with an eccentricity (ovalness) of 0.09. Since the inclination of the exoplanet's orbital plane is unknown, only a lower bound on its mass can be determined. It has at least 8.3 times the mass of Jupiter.[10]

Naming

HD 104985 is the star's entry in the Henry Draper Catalogue. Following its discovery in 2003[12] the planet was designated HD 104985 b. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.[13] The process involved public nomination and voting for the new names.[14] In December 2015, the IAU announced the winning names were Tonatiuh for this star and Meztli for its planet.[15]

The winning names were those submitted by the Sociedad Astronomica Urania of Morelos, Mexico. 'Tonatiuh' was the Aztec god of the Sun; 'Meztli' was the Aztec goddess of the Moon.[16]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[17] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[18] the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.[7]

The HD 104985 planetary system[10]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (Meztli) >8.3 MJ 0.95 199.505 ± 0.085 0.090 ± 0.009 — —

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. 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. "HD 104985". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-09-29.
  4. Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  5. Maldonado, J.; Villaver, E. (April 2016). "Evolved stars and the origin of abundance trends in planet hosts". Astronomy & Astrophysics. 588: 11. arXiv:1602.00835. Bibcode:2016A&A...588A..98M. doi:10.1051/0004-6361/201527883. S2CID 119212009. A98.
  6. Bonfanti, A.; et al. (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.
  7. "IAU Catalog of Star Names". Retrieved 28 July 2016.
  8. For the pronunciation of a bilingual English–Spanish speaker, see Duncan Tonatiuh: Audio Name Pronunciation
  9. Eggleton, Peter; Tokovinin, A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  10. Sato, Bun'ei; et al. (2008). "Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Delphini, ξ Aquilae and HD 81688". Publications of the Astronomical Society of Japan. 60 (3): 539–550. arXiv:0802.2590. Bibcode:2008PASJ...60..539S. doi:10.1093/pasj/60.3.539. S2CID 18806627.
  11. Sato, Bun'ei; Ando, Hiroyasu; Kambe, Eiji; Takeda, Yoichi; Izumiura, Hideyuki; Masuda, Seiji; Watanabe, Etsuji; Noguchi, Kunio; Wada, Setsuko; Okada, Norio; Koyano, Hisashi; Maehara, Hideo; Norimoto, Yuji; Okada, Takafumi; Shimizu, Yasuhiro; Uraguchi, Fumihiro; Yanagisawa, Kenshi; Yoshida, Michitoshi (November 2003). "A Planetary Companion to the G-Type Giant Star HD 104985". The Astrophysical Journal. 597 (2): L157–L160. Bibcode:2003ApJ...597L.157S. doi:10.1086/379967.
  12. Sato, Bun'ei; et al. (2003). "A Planetary Companion to the G-Type Giant Star HD 104985". The Astrophysical Journal Letters. 597 (2): L157–L160. Bibcode:2003ApJ...597L.157S. doi:10.1086/379967.
  13. "NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars". IAU.org. 9 July 2014.
  14. "NameExoWorlds The Process". Archived from the original on 2015-08-15. Retrieved 2015-09-05.
  15. "Final Results of NameExoWorlds Public Vote Released". International Astronomical Union. 15 December 2015.
  16. "NameExoWorlds The Approved Names". Archived from the original on 2018-02-01. Retrieved 2015-12-31.
  17. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  18. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
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