G Doradus

G Doradus (HD 37297; HR 1917; 28 G. Doradus) is a spectroscopic binary located in the southern constellation Dorado, the dolphinfish. It has an apparent magnitude of 5.34,[2] making it faintly visible to the naked eye under ideal conditions. The system is located relatively close at a distance of 234 light-years based on Gaia DR3 parallax measurements but it is receding with a heliocentric radial velocity of approximately 9.8 km/s.[5] At its current distance, G Doradus' brightness is diminished by a quarter of a magnitude due to interstellar extinction[16] and it has an absolute magnitude of +1.08.[6] The bayer designation "G Doradus" was not assigned by Benjamin Gould or Lacaille. It merely arose due to the designation assigned by Gould; 28 G. Doradus.

G Doradus
Location of G Doradus on the map (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Dorado
Right ascension 05h 32m 59.56572s[1]
Declination −64° 13′ 39.0537″[1]
Apparent magnitude (V) 5.34±0.01[2]
Characteristics
Spectral type G8/K0 III[3]
U−B color index +0.85[4]
B−V color index +1.04[4]
Astrometry
Radial velocity (Rv)9.8±2.8[5] km/s
Proper motion (μ) RA: +45.741 mas/yr[1]
Dec.: −3.051 mas/yr[1]
Parallax (π)13.9330 ± 0.2335 mas[1]
Distance234 ± 4 ly
(72 ± 1 pc)
Absolute magnitude (MV)+1.08[6]
Orbit[7]
Period (P)180.8757 d
Semi-major axis (a)0.320 AU
Eccentricity (e)0.509±0.010
Inclination (i)52.2±5.2[8]°
Longitude of the node (Ω)45.4±6.6[8]°
Periastron epoch (T)2,423,108.42±0.65 JD
Argument of periastron (ω)
(secondary)		332.93±1.61°
Semi-amplitude (K1)
(primary)		22.36±0.35 km/s
Details
A
Mass3.47[9] M☉
Radius10.5+0.1
−0.2[1] R☉
Luminosity48.4+1.6
−1.5[1] L☉
Surface gravity (log g)2.61[10] cgs
Temperature4819±123[11] K
Metallicity [Fe/H]−0.20[12] dex
Rotational velocity (v sin i)<1.0[13] km/s
Age556+153
−188[1] Myr
B
Mass1.87[9] M☉
Other designations
G Dor, 28 G. Doradus[14], CPD−64°456, FK5 2418, GC 6927, HD 37297, HIP 26001, HR 1917, SAO 249309, TIC 149304313[15]
Database references
SIMBADdata

The visible component has a stellar classification of G8/K0 III,[3] indicating that it is an evolved star with the characteristics of a G8 and K0 giant star. It has 3.47 times the mass of the Sun[9] but at the age of 556 million years, it has expanded to 10.5 times the radius of the Sun.[1] It radiates 48.4 times the luminosity of the Sun[1] from its enlarged photosphere at an effective temperature of 4,819 K,[11] giving it an orangish-yellow hue when viewed in the night sky. G Doradus is slightly metal deficient with an iron abundance of [Fe/H] = −0.20[12] and it spins too slowly for its projected rotational velocity to be measured accurately.[13]

G Doradus is a single-lined spectroscopic binary; the components – which have a separation of 0.32 AU – take 181 days to circle each other in an elliptical orbit, but the orbit is not well constrained.[7] Although only the primary can be observed in the spectrum, the masses of both components can be determined. Krachieva et al. (1980) derives a mass of 1.87 M☉ for the companion,[9] which might be an A-type star.

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. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361. S2CID 17128864.
  3. Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars: Declinations −90° to −53°. Vol. 1. Bibcode:1975mcts.book.....H.
  4. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
  5. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
  6. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  7. Lunt, Joseph (1924). "On the orbits of the seven spectroscopic-binary stars : ί Gruis, θ1 Crucis, 28 Doradus, α Phoenicis, β Doradus, W Velorum, ρ Tucanae". Annals of the Cape Observatory. 10: 7. Bibcode:1924AnCap..10....7L.
  8. Jancart, S.; Jorissen, A.; Babusiaux, C.; Pourbaix, D. (September 30, 2005). "Astrometric orbits of SB9 stars". Astronomy & Astrophysics. EDP Sciences. 442 (1): 365–380. arXiv:astro-ph/0507695. Bibcode:2005A&A...442..365J. doi:10.1051/0004-6361:20053003. ISSN 0004-6361. S2CID 55637839.
  9. Kraicheva, Z.; Popova, E.; Tutukov, A.; Yungelson, L. (July 1980). "Catalogue of physical parameters of spectroscopic binary stars". Bull. Inf. Centre Données Stellaires. 19: 71. Bibcode:1980BICDS..19...71K. S2CID 118298938.
  10. Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. eISSN 1432-0746. ISSN 0004-6361. S2CID 131780028.
  11. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
  12. Eggen, Olin J. (January 1989). "Large and Kinematically Unbiased Samples of G- and K-Type Stars. III. Evolved Young Disk Stars in the Bright Star Sample". Publications of the Astronomical Society of the Pacific. 101: 54. Bibcode:1989PASP..101...54E. doi:10.1086/132404. eISSN 1538-3873. ISSN 0004-6280. S2CID 122928361.
  13. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars *". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.
  14. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
  15. "* G Dor". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 11, 2023.
  16. Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711. S2CID 118879856.
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