Tau Coronae Borealis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 16h 08m 58.30151s[1] |
| Declination | +36° 29′ 27.3740″[1] |
| Apparent magnitude (V) | 4.76[2] (4.89 + 13.2)[3] |
| Characteristics | |
| Spectral type | K0 III-IV[4] |
| U−B color index | +0.86[2] |
| B−V color index | +1.01[2] |
| Astrometry | |
| Radial velocity (Rv) | −21.02±0.33[5] km/s |
| Proper motion (μ) | RA: −37.02[1] mas/yr Dec.: +340.44[1] mas/yr |
| Parallax (π) | 27.95 ± 1.24[1] mas |
| Distance | 117 ± 5 ly (36 ± 2 pc) |
| Absolute magnitude (MV) | +2.03[6] |
| Details[5] | |
| Radius | 6 R☉ |
| Luminosity | 16.2 L☉ |
| Surface gravity (log g) | 3.1 cgs |
| Temperature | 4,742 K |
| Metallicity [Fe/H] | −0.20 dex |
| Rotational velocity (v sin i) | 1.7 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Tau Coronae Borealis, Latinized from τ Coronae Borealis, is a probable astrometric binary[3] star system in the northern constellation of Corona Borealis. It is visible to the naked eye with a combined apparent visual magnitude of 4.76.[2] As of 2014, the pair had an angular separation of 2.20 arc seconds along a position angle of 186°.[8] Based upon an annual parallax shift of 27.95 mas as seen from Earth,[1] it is located about 117 light years from the Sun. At that distance, the visual magnitude of the system is diminished by an extinction factor of 0.04 due to interstellar dust.[9]
The brighter component is a magnitude 4.89[3] K-type star with a stellar classification of K0 III-IV,[4] having a spectrum that shows mixed traits of a evolved subgiant and giant star. It is catalogued as a red clump giant, which would indicate it is generating energy through helium fusion at its core.[10] The star has expanded to six times the Sun's radius and is radiating 16 times the solar luminosity from its photosphere at an effective temperature of 4,742 K.[5] The secondary companion is a magnitude 13.2 star.[8]
References
- 1 2 3 4 5 6 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.
- 1 2 3 4 Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
- 1 2 3 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.
- 1 2 Eggen, O. J. (1962), "Space-velocity vectors for 3483 stars with proper motion and radial velocity", Royal Observatory Bulletin, 51, Bibcode:1962RGOB...51...79E.
- 1 2 3 Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
- ↑ 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.
- ↑ "tau CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-04-30.
- 1 2 Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
- ↑ Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272.
- ↑ Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278.