Zeta Boötis

Zeta Boötis, Latinized from ζ Boötis, is a binary star system in the constellation of Boötes. They have the Flamsteed designation 30 Boötis; Zeta Boötis is the Bayer designation. This system is visible to the naked eye with a combined apparent magnitude of +3.78.[2] The individual magnitudes differ slightly, with component A having a magnitude of 4.46 and component B at the slightly dimmer magnitude 4.55.[3] It is located at a distance of approximately 180 light years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −9 km/s.[6]

ζ Boötis
Location of ζ Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 41m 08.95158s[1]
Declination +13° 43′ 41.8967″[1]
Apparent magnitude (V) 3.78[2](4.46 + 4.55)[3]
Characteristics
Spectral type A2III + A2III[4]
A1V[5]
U−B color index +0.05[2]
B−V color index +0.05[2]
Astrometry
Radial velocity (Rv)−8.5±0.6[6] km/s
Proper motion (μ) RA: +51.95[1] mas/yr
Dec.: -11.08[1] mas/yr
Parallax (π)18.07 ± 1.24[1] mas
Distance180 ± 10 ly
(55 ± 4 pc)
Absolute magnitude (MV)+0.13[7]
Orbit[8]
CompanionB
Period (P)45,460±62 d
Semi-major axis (a)2.3±1.7″
Eccentricity (e)0.9977±0.0034
Inclination (i)102.3±9.2°
Longitude of the node (Ω)8.2±2.6°
Periastron epoch (T)2,460,183.5±57 JD
Argument of periastron (ω)
(secondary)		262.9±5.9°
Details
Luminosity81[7] L☉
Other designations
ζ Boo, 30 Boötis, BD+14° 2770, GC 19777, HIP 71795, SAO 101145, ADS 9343, CCDM 14411+1344, WDS J14411+1344[9]
A: HD 129247, HR 5478[10]
B: HD 129246, HR 5477[11]
Database references
SIMBADdata

The duplicity of this star was discovered by English astronomer William Herschel in 1796, and their changing positions have been tracked from 1823 onward.[12] They complete an orbit roughly every 124.5 years (45,460 days). The orbit of this pair has a very high eccentricity of 0.9977, bringing the stars within 0.3 AU at their closest approach. The next close approach will occur during August 2023.[8]

In 1976, T. W. Edwards found a stellar classification of A2III for both components, suggesting they may be evolved A-type giant stars. Helmut A. Abt reported a class of A2V in 1981, which matches an A-type main-sequence star.[13] Abt and Nidia Morrell updated the classification to A1V in 1995.[5] Considering the extreme nature of their orbit, it is unlikely that any companion exoplanets could have stable orbits around either star.[14]

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
  2. 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. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  4. Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal, 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879.
  5. Abt, Helmut A.; Morrell, Nidia I. (July 1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", Astrophysical Journal Supplement, 99: 135, Bibcode:1995ApJS...99..135A, doi:10.1086/192182.
  6. Gontcharov, G. A. (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, S2CID 119231169.
  7. 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.
  8. Muterspaugh, Matthew W.; et al. (December 2010), "The Phases Differential Astrometry Data Archive. II. Updated Binary Star Orbits and a Long Period Eclipsing Binary", The Astronomical Journal, 140 (6): 1623–1630, arXiv:1010.4043, Bibcode:2010AJ....140.1623M, doi:10.1088/0004-6256/140/6/1623.
  9. "zet Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-31.
  10. "zet Boo A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-31.
  11. "zet Boo B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-31.
  12. Wierzbiński, St. (1956), "Orbites des étoiles doubles", Acta Astronomica, 6: 82, Bibcode:1956AcA.....6...82W.
  13. Abt, H. A. (1981), "Visual multiples. VII. MK classifications", The Astrophysical Journal Supplement Series, 45: 437, Bibcode:1981ApJS...45..437A, doi:10.1086/190719.
  14. Muterspaugh, Matthew W.; et al. (December 2010), "The Phases Differential Astrometry Data Archive. III. Limits to Tertiary Companions", The Astronomical Journal, 140 (6): 1631–1645, arXiv:1010.4044, Bibcode:2010AJ....140.1631M, doi:10.1088/0004-6256/140/6/1631.
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