Astronomy:Delta Arae

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Short description: Star in the constellation Ara
Delta Arae
δ Arae (circled) in the Ara Constellation
Observation data
Equinox J2000.0]] (ICRS)
Constellation Ara
Right ascension  17h 31m 05.91272s[1]
Declination −60° 41′ 01.8522″[1]
Apparent magnitude (V) 3.62[2]
Characteristics
Spectral type B8 Vn[3] + G8 V[4]
U−B color index −0.31[2]
B−V color index −0.10[2]
Astrometry
Radial velocity (Rv)+10[5] km/s
Proper motion (μ) RA: −54.01[1][1] mas/yr
Dec.: −99.25[1] mas/yr
Parallax (π)16.48 ± 0.34[1] mas
Distance198 ± 4 ly
(61 ± 1 pc)
Absolute magnitude (MV)−0.31[6]
Orbit[7]
PrimaryA
CompanionB
Period (P)2.46697±0.00500 yr
Semi-major axis (a)52.0±0.2 mas
Eccentricity (e)0.7380±0.0264
Inclination (i)90.32±0.97°
Longitude of the node (Ω)127.13±0.91°
Argument of periastron (ω)
(secondary)		347.80±1.05°
Details
δ Ara A
Mass3.44±0.01[7] M☉
Radius3.12±0.15[8] R☉
Luminosity214[6] L☉
Surface gravity (log g)3.81±0.06[8] cgs
Temperature12,549[7] K
Rotational velocity (v sin i)255[9] km/s
Age125[10] Myr
δ Ara B
Mass2.03±0.01[7] M☉
Temperature9,161[7] K
Other designations
δ Ara, CPD−60°6842, FK5 648, GC 23681, HD 158094, HIP 85727, HR 6500, SAO 253945, PPM 362756, WDS J17311-6041A[11]
Database references
SIMBADdata

Delta Arae is a binary star[7] in the southern constellation Ara. Its name is a Bayer designation that is Latinized from δ Arae, and abbreviated Delta Ara or δ Ara. This system has an apparent visual magnitude of 3.62[2] and is visible to the naked eye as a point of light. Based upon an annual parallax of 16.48 mas, it is about 198 light-years (61 parsecs) distant from the Earth.[1]

Characteristics

This is an astrometric binary system, identified using data from the Gaia spacecraft. The components have an orbital period of about 2.47 years and a high orbital eccentricity of 0.7380. The orbit is nearly edge-on relative to Earth.[7]

The brighter component is an intermediate-mass B-type main sequence star with a stellar classification of B8 Vn.[3] The 'n' suffix indicates the absorption lines are spread out broadly because the star is spinning rapidly. It has a projected rotational velocity of 255 km/s, resulting in an equatorial bulge with a radius 13% larger than the polar radius.[9] The star has 3.44 times the mass[7] and 3.1 times the radius of the Sun.[8] It is radiating 214 times the luminosity of the Sun from its photosphere[6] at an effective temperature of 12,549 K.[7]

The secondary is 1.27 times fainter than the primary at Gaia's G-band, it has 2.03 times the mass of the Sun and an effective temperature of 9,161 K.[7]

There is a magnitude 9.5 companion G-type main sequence star that may (17% chance) form a gravitationally bpund system with Delta Arae.[4] A 12th magnitude optical companion is located 47.4 arcseconds away along a position angle of 313°.[10]

Etymology

Delta Arae was known as 龜三 (meaning: "the 3rd (star) of Guī") in traditional Chinese astronomy.[12][13]

Allen erroneously called both Delta and Zeta Arae "Tseen Yin" (天陰).[14] He probably confused the constellation "Ara" with "Ari", as 天陰 is actually in Aries.[12][13]

See also

  • Ara (Chinese astronomy)
  • Aries (Chinese astronomy)

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series 34: 1–49, Bibcode: 1978A&AS...34....1N. 
  3. ↑ 3.0 3.1 Houk, Nancy (1979), "Michigan catalogue of two-dimensional spectral types for the HD stars", Ann Arbor: Dept. Of Astronomy (Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan) 1, Bibcode: 1978mcts.book.....H. 
  4. ↑ 4.0 4.1 Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement 192 (1): 2, doi:10.1088/0067-0049/192/1/2, Bibcode: 2011ApJS..192....2S. 
  5. ↑ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, 30, University of Toronto: International Astronomical Union, pp. 57, Bibcode: 1967IAUS...30...57E. 
  6. ↑ 6.0 6.1 6.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 Pérez-Couto, X.; Docobo, J. Á.; Campo, P. P. (2024-01-29), "Methodology for obtaining the relative orbit and individual masses of Gaia astrometric binaries" (in en), Astronomy & Astrophysics 682: A12, doi:10.1051/0004-6361/202348125, ISSN 0004-6361, Bibcode: 2024A&A...682A..12P. 
  8. ↑ 8.0 8.1 8.2 Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal 129 (3): 1642–1662, doi:10.1086/427855, Bibcode: 2005AJ....129.1642F. 
  9. ↑ 9.0 9.1 van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review 20 (1): 51, doi:10.1007/s00159-012-0051-2, Bibcode: 2012A&ARv..20...51V. 
  10. ↑ 10.0 10.1 Ehrenreich, D. et al. (November 2010), "Deep infrared imaging of close companions to austral A- and F-type stars", Astronomy and Astrophysics 523: A73, doi:10.1051/0004-6361/201014763, Bibcode: 2010A&A...523A..73E. 
  11. ↑ "del Ara". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=del+Ara. 
  12. ↑ 12.0 12.1 Chevalier, S., and Tsuchihashi, P., (1911): "Catalogue d'Étoiles fixes, observés a Pekin sous l'Empereur Kien Long (Qianlong (Chien-Lung)), XVIIIe siecle", Annales de l'Observatoire Astronomique de Zô-Sé.
  13. ↑ 13.0 13.1 伊世同 (Yi Shi Tong) (1981): 『中西対照恒星図表』科学出版社.(in Chinese)
  14. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc., p. 64, ISBN 0-486-21079-0, https://archive.org/details/bub_gb_5xQuAAAAIAAJ/page/n86, retrieved 2025-04-25. 

Further reading

  • 大崎正次 (1987): 「中国の星座・星名の同定一覧表」『中国の星座の歴史』 雄山閣出版, pp. 312, 328.(in Japanese)



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