Zeta Sagittae

Zeta Sagittae


Location of ζ Sagittae (circled)

Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagitta
Right ascension 19h 48m 58.65978s[1]
Declination +19° 08′ 31.3516″[1]
Apparent magnitude (V) +5.00[2] (5.64 + 6.04 + 9.01)[3]
Characteristics
Spectral type A3 Vnn[4] (A1 V + A3 V)[5]
U−B color index +0.06[2]
B−V color index +0.10[2]
Astrometry
Proper motion (μ) RA: +17.63[1] mas/yr
Dec.: +26.27[1] mas/yr
Parallax (π)12.79 ± 0.67[1] mas
Distance260 ± 10 ly
(78 ± 4 pc)
Orbit[6]
Period (P)8487.9±4.9 d
Semi-major axis (a)0.13605±0.00044″
Eccentricity (e)0.7948±0.0019
Inclination (i)132.33±0.41°
Longitude of the node (Ω)340.97±0.68°
Periastron epoch (T)44199.6 ± 5.9 HMJD
Argument of periastron (ω)
(secondary)		355.3±1.0°
Details
ζ Sge A
Mass1.80[7] M☉
Radius1.7[8] R☉
Luminosity46[9] L☉
Surface gravity (log g)3.89[7] cgs
Temperature8,422±286[7] K
Rotational velocity (v sin i)240[10] km/s
Age347[7] Myr
Other designations
ζ Sge, 8 Sge, BD+19° 4229, GC 27431, HD 187362, HIP 97496, HR 7546, SAO 105298, PPM 137034, ADS 12973, WDS J19490+1909AB[11]
Database references
SIMBADdata

Zeta Sagittae (ζ Sagittae) is triple star[3] system in the northern constellation of Sagitta. It is visible to the naked eye, having a combined apparent visual magnitude of +5.00.[2] Based upon an annual parallax shift of 12.79 mas,[1] the distance to this star is approximately 260 light years.

The inner pair is a visual binary system consisting of two A-type main-sequence stars with an orbital period of 23.2 years (8,487.9 d), a semimajor axis of 0.136 arc seconds, and an eccentricity of 0.79.[6] The primary, component A, has a visual magnitude of 5.64[3] with a stellar classification of A3 Vnn,[4] where the 'nn' suffix indicates "nebulous" lines due to rotation. It is spinning rapidly with a projected rotational velocity of 240 km/s. This is giving the star an oblate shape with an equatorial bulge that is 14% larger than the polar radius.[10]

The secondary member, component B, is a magnitude 6.04 star, while the more distant component C is magnitude 9.01 and lies at an angular separation of 8.330 arc seconds from the other two.[3]

Naming

In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of ζ Sagittae, α Sagittae, β Sagittae, δ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, ζ Sagittae itself is known as 左旗四 (Zuǒ Qí sì, English: the Fourth Star of Left Flag.)[12]

References

  1. 1 2 3 4 5 6 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752 Freely accessible, doi:10.1051/0004-6361:20078357.
  2. 1 2 3 4 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. 1 2 3 4 Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, Bibcode:2008MNRAS.389..869E, arXiv:0806.2878 Freely accessible, doi:10.1111/j.1365-2966.2008.13596.x.
  4. 1 2 Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  5. ↑ Christy, James W.; Walker, R. L., Jr. (October 1969), "MK Classification of 142 Visual Binaries", Publications of the Astronomical Society of the Pacific, 81 (482): 643, Bibcode:1969PASP...81..643C, doi:10.1086/128831.
  6. 1 2 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, Bibcode:2010AJ....140.1623M, arXiv:1010.4043 Freely accessible, doi:10.1088/0004-6256/140/6/1623.
  7. 1 2 3 4 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, Bibcode:2015ApJ...804..146D, arXiv:1501.03154 Freely accessible, doi:10.1088/0004-637X/804/2/146.
  8. ↑ Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, Bibcode:2001A&A...367..521P, arXiv:astro-ph/0012289 Freely accessible, doi:10.1051/0004-6361:20000451.
  9. ↑ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, Bibcode:2012MNRAS.427..343M, arXiv:1208.2037 Freely accessible, doi:10.1111/j.1365-2966.2012.21873.x.
  10. 1 2 Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20: 51, Bibcode:2012A&ARv..20...51V, arXiv:1204.2572 Freely accessible, doi:10.1007/s00159-012-0051-2.
  11. ↑ "zet Sge". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-11.
  12. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 3 日
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