Tau Draconis, Latinized from τ Draconis, is an astrometric binary[9] star system in the northern circumpolar constellation of Draco. The star is faintly visible to the naked eye, having an apparent visual magnitude of 4.45.[2] Based upon an annual parallax shift of 22.28 mas as measured from Earth,[1] it is located around 146 light years from the Sun. Its proper motion is propelling it across the sky at the rate of 0.176 arc seconds per year.[10]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Draco |
| Right ascension | 19h 15m 33.05868s[1] |
| Declination | +73° 21′ 19.6769″[1] |
| Apparent magnitude (V) | 4.45[2] |
| Characteristics | |
| Spectral type | K2 III:[3] |
| U−B color index | +1.45[2] |
| B−V color index | +1.25[2] |
| Astrometry | |
| Radial velocity (Rv) | −33.70[3] km/s |
| Proper motion (μ) | RA: −115.29[1] mas/yr Dec.: +103.23[1] mas/yr |
| Parallax (π) | 22.28 ± 0.50 mas[1] |
| Distance | 146 ± 3 ly (45 ± 1 pc) |
| Absolute magnitude (MV) | +1.19[4] |
| Details | |
| Mass | 1.25[3] M☉ |
| Luminosity | 48[3] L☉ |
| Surface gravity (log g) | 2.00[5] cgs |
| Temperature | 4,413±77[3] K |
| Metallicity [Fe/H] | 0.17±0.06[6] dex |
| Rotational velocity (v sin i) | 8[7] km/s |
| Age | 6.48[3] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a K-type giant star with a stellar classification of K2 III:,[3] where the semi-colon indicates some uncertainty about its spectral value. It is considered metal-rich[6] star and is past the first dredge-up phase of its post-main sequence evolution, although it shows under-abundances of carbon and oxygen in its spectrum.[5] The star has 1.25[3] times the mass of the Sun and is an estimated 6.48[3] billion years old. It is radiating 48[3] times the solar luminosity from its enlarged photosphere at an effective temperature of 4,413 K.[3]
References
edit- ^ a b c d e f 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, S2CID 18759600.
- ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
- ^ a b c d e f g h i j k Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
- ^ 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, S2CID 119257644.
- ^ a b Mishenina, T. V.; et al. (October 1995), "Chemical composition of five giants with positive CN-indices.", Astronomy and Astrophysics Supplement, 113: 333, Bibcode:1995A&AS..113..333M.
- ^ a b Taylor, B. J. (February 2002), "A statistical search for supermetallicity in F, G and K stars", Monthly Notices of the Royal Astronomical Society, 329 (4): 839–847, Bibcode:2002MNRAS.329..839T, doi:10.1046/j.1365-8711.2002.05046.x.
- ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B.
- ^ "tau Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-05-30.
{{cite web}}: CS1 maint: postscript (link) - ^ 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. S2CID 14878976.
- ^ Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854, S2CID 2603568.