Psi2 Draconis

Psi2 Draconis is a solitary[9] giant star in the northern circumpolar constellation of Draco, also designated 34 Draconis. It lies just over a degree east of the brighter Psi1 Draconis.[10] Psi2 Draconis has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.45.[2] It is located at a distance of 940 light-years (287 parsecs) from the Sun based on parallax, but is drifting closer with a radial velocity of −2 km/s.[5]

For other stars with this Bayer designation, see ψ Draconis.
Psi2 Draconis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 17h 55m 11.15296s[1]
Declination +72° 00′ 18.4470″[1]
Apparent magnitude (V) 5.45[2]
Characteristics
Spectral type F2 III+[3] or F3 II-III[4]
U−B color index +0.15[2]
B−V color index +0.30[2]
Astrometry
Radial velocity (Rv)−2.0[5] km/s
Proper motion (μ) RA: +8.545[1] mas/yr
Dec.: −2.133[1] mas/yr
Parallax (π)3.4888 ± 0.0832[1] mas
Distance930 ± 20 ly
(287 ± 7 pc)
Absolute magnitude (MV)−2.12±0.14[6]
Details[5]
Mass2.02 M☉
Radius14.70+0.64
−0.34[1] R☉
Luminosity448±13[1] L☉
Surface gravity (log g)2.32 cgs
Temperature6925+83
−152[1] K
Metallicity [Fe/H]−1.29 dex
Rotational velocity (v sin i)50[7] km/s
Age800 Myr
Other designations
ψ2 Dra, 34 Dra, BD+72° 818, FK5 3429, HD 164613, HIP 87728, HR 6725, SAO 8961[8]
Database references
SIMBADdata

According to R. O. Gray and associates (2001), the stellar classification of Psi2 Draconis is F2III+;[3] a star that has used up its core hydrogen, cooled, and expanded away from the main sequence. A. P. Cowley and W. P. Bidelman (1979) found a similar class of F3 II-III, with the comment that the spectrum showed "many weak lines".[4] Based on the abundance of iron, the metallicity of this star is much lower than in the Sun. It is about 800[5] million years old and is spinning with a projected rotational velocity of 50 km/s.[7] The star has double[5] the mass of the Sun but has expanded to 15[1] times the Sun's radius. It is radiating 448[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 6,925 K.[1]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Oja, T. (April 1983), "UBV photometry of FK4 and FK4 supplement stars", Astronomy and Astrophysics Supplement Series, 52: 1311–34, Bibcode:1983A&AS...52..131O.
  3. Gray, R. O.; et al. (April 2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal, 121 (4): 2148–2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
  4. Cowley, A. P.; Bidelman, W. P. (February 1979), "MK spectral types for some F and G stars", Publications of the Astronomical Society of the Pacific, 91: 83–86, Bibcode:1979PASP...91...83C, doi:10.1086/130446.
  5. Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276.
  6. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191.
  7. Danziger, I. J.; Faber, S. M. (May 1972), "Rotation of evolving A and F stars", Astronomy and Astrophysics, 18: 428, Bibcode:1972A&A....18..428D.
  8. "psi02 Dra -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-05-29.
  9. 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  10. Sinnott, Roger W.; Perryman, Michael A. C. (1997), Millennium Star Atlas, 3, Sky Publishing Corporation and the European Space Agency, p. 1054, ISBN 0-933346-84-0.
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