Zeta2 Lyrae

Zeta2 Lyrae is a single,[10] white-hued star in the northern constellation of Lyra. It is a dim star that is just visible to the naked eye with an apparent visual magnitude of 5.74[2] An annual parallax shift of 20.97 mas as seen from Earth provides a distance estimate of about 156 light years from the Sun. It is moving closer to the Sun with a radial velocity of −25 km/s.[4]

For other stars with this Bayer designation, see ζ Lyrae.
Zeta2 Lyrae
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension  18h 44m 48.20367s[1]
Declination +37° 35′ 40.6162″[1]
Apparent magnitude (V) 5.74[2]
Characteristics
Spectral type F0 IVn[3]
U−B color index +0.06[2]
B−V color index +0.29[2]
Astrometry
Radial velocity (Rv)−25.0±3.7[4] km/s
Proper motion (μ) RA: +18.70±0.21[1] mas/yr
Dec.: +20.98±0.29[1] mas/yr
Parallax (π)20.97 ± 0.24[1] mas
Distance156 ± 2 ly
(47.7 ± 0.5 pc)
Absolute magnitude (MV)+2.34[5]
Details
Mass1.74[6] M☉
Luminosity9[7] L☉
Surface gravity (log g)3.94[6] cgs
Temperature7,000[7] K
Rotational velocity (v sin i)212[8] km/s
Age1.223[6] Gyr
Other designations
ζ2 Lyr, 7 Lyr, BD+37° 3223, GC 25678, HD 173649, HIP 91973, HR 7057, SAO 67324, WDS J18448+3736D[9]
Database references
SIMBADdata

This star has a stellar classification of F0 IVn,[3] suggesting it is an F-type subgiant star that is evolving away from the main sequence as its supply of hydrogen at the core has been consumed. The n suffix indicates "nebulous" lines caused by its rotation. It is spinning rapidly with a projected rotational velocity of 212 km/s.[8] This is giving the star an oblate shape with an equatorial bulge that is an estimated 29% larger than the polar radius.[11] The star is radiating approximately 9 times the Sun's luminosity from the photosphere at an effective temperature of 7,000 K.[7] It has 1.7[6] times the mass of the Sun and is about 1.2[6] billion years old.

It is a suspected variable.[9]

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. Deutschman, W. A.; et al. (February 1976), "The galactic distribution of interstellar absorption as determined from the Celescope catalog of ultraviolet stellar observations and a new catalogue of UBV, Hbeta photoelectric observations", Astrophysical Journal Supplement Series, 30: 97–225, Bibcode:1976ApJS...30...97D, doi:10.1086/190359.
  3. 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
  4. Kharchenko, N. V.; et al. (2007), "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations", Astronomische Nachrichten, 328 (9): 889–896, arXiv:0705.0878, Bibcode:2007AN....328..889K, doi:10.1002/asna.200710776.
  5. 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.
  6. 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. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. Vizier catalog entry
  7. 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.
  8. Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  9. "zet02 Lyr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 25 July 2015.
  10. De Rosa, R. J.; et al. (2014). "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.
  11. Belle, G. T. (2012). "Interferometric observations of rapidly rotating stars". The Astronomy and Astrophysics Review. 20: 51. arXiv:1204.2572. Bibcode:2012A&ARv..20...51V. doi:10.1007/s00159-012-0051-2.
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