Zeta¹ Lyrae

Zeta¹ Lyrae, Latinized from ζ¹ Lyrae, is a binary star in the northern constellation of Lyra. Based upon an annual parallax shift of 20.89 mas as seen from Earth,[1] the pair are located about 156 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of 4.37.[2]

ζ¹ Lyrae

Location of ζ Lyrae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Lyra
Right ascension	18^h 44^m 46.35735^s[1]
Declination	+37° 36′ 18.4171″[1]
Apparent magnitude (V)	4.37[2]
Characteristics
Spectral type	kA5hF0mF2[3]
U−B color index	+0.17[2]
B−V color index	+0.18[2]
Astrometry
Proper motion (μ)	RA: +29.04[1] mas/yr Dec.: +27.03[1] mas/yr
Parallax (π)	20.89 ± 0.17[1] mas
Distance	156 ± 1 ly (47.9 ± 0.4 pc)
Absolute magnitude (MV)	+0.94[4]
Orbit[5]
Period (P)	4.3 d
Eccentricity (e)	0.01
Periastron epoch (T)	2440000.723 JD
Argument of periastron (ω) (secondary)	0.00°
Semi-amplitude (K1) (primary)	51.6 km/s
Details
Mass	2.36[6] M☉
Radius	2.5[7] R☉
Luminosity	31[8] L☉
Surface gravity (log g)	3.7±0.1[9] cgs
Temperature	7914±112[9] K
Metallicity [Fe/H]	0.38±0.06[9] dex
Rotational velocity (v sin i)	47[10] km/s
Age	500[6] Myr
Other designations
ζ^1 Lyr, 6 Lyr, BD+37° 3222, HD 173648, HIP 91971, HR 7056, SAO 67321.[11]
Database references
SIMBAD	data

Observational history

The stars Zeta1 and Zeta2 Lyrae photographed with an amateur telescope by David Chifiriuc. The visual separation between the two stars is 43.7″ (in 2020).

ζ¹ Lyrae was discovered to be a spectroscopic binary by William Wallace Campbell and Heber Doust Curtis in 1905 from photographic plates taken at the Lick Observatory between 1902 and 1904.[12] The first orbit was calculated by Frank Craig Jordan of Allegheny Observatory in 1910 with results in good agreement with the most recent orbit.[13]

Binary system

This is a single-lined spectroscopic binary system with an orbital period of 4.3 days and a nearly circular orbit with an eccentricity of 0.01.[5] The primary, component A, is an Am star with a stellar classification of kA5hF0mF2. This complex notation indicates that the spectral type determined solely from the calcium K line would be A5, the spectral type determined from other metallic lines would be F2, and the type determined from hydrogen lines would be F0.[3]

Variability

ζ¹ Lyrae appears to be slightly variable, with a frequency of 0.65256 cycles per day and an amplitude of 0.0032 in magnitude.[14] The star has an estimated 2.36[6] times the mass of the Sun and around 2.5[7] times the Sun's radius. The position of this system is associated with an X-ray source with a luminosity of 571.6×10²⁰ W.[15]

References

1. van Leeuwen, F. (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. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
3. Abt, Helmut A.; Morrell, Nidia I. (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.
4. 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.
5. Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004), "S_B⁹: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
6. De Rosa, R. J.; et al. (2013), "The VAST Survey - III. The multiplicity of A-type stars within 75 pc", Monthly Notices of the Royal Astronomical Society, 437 (2): 1216, arXiv:1311.7141, Bibcode:2014MNRAS.437.1216D, doi:10.1093/mnras/stt1932.
7. Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (3rd ed.), 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
8. McDonald, I.; et al. (2012). "Fundamental Parameters and Infrared Excesses of Hipparcos Stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–57. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x.
9. Prugniel, Ph.; et al. (2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769.
10. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393 (3): 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943.
11. "* zet01 Lyr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-03-17.
12. Campbell, W. W.; Curtis, H. D. (1905). "A list of nine stars whose radial velocities vary". The Astrophysical Journal. 21: 189. Bibcode:1905ApJ....21..185C. doi:10.1086/141200.
13. Jordan, Frank Craig (1910). "The orbit of ζ¹ Lyrae". Publications of the Allegheny Observatory of the University of Pittsburgh. 1 (17): 115–118. Bibcode:1910PAllO...1..115J.
14. Koen, Chris; Eyer, Laurent (2002), "New periodic variables from the Hipparcos epoch photometry", Monthly Notices of the Royal Astronomical Society, 331: 45, arXiv:astro-ph/0112194, Bibcode:2002MNRAS.331...45K, doi:10.1046/j.1365-8711.2002.05150.x.
15. Schröder, C.; Schmitt, J. H. M. M. (November 2007), "X-ray emission from A-type stars", Astronomy and Astrophysics, 475 (2): 677–684, Bibcode:2007A&A...475..677S, doi:10.1051/0004-6361:20077429.