Tau Coronae Borealis, Latinized from τ Coronae Borealis, is a possible astrometric and spectroscopic binary star system in the northern constellation of Corona Borealis. It is visible to the naked eye with an apparent visual magnitude of 4.76.
| 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 | K1 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 mas[1] |
| 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 CrB has a visible companion of visual magnitude 13.2 and they have been treated as a common proper motion pair.[8] As of 2014, the pair had an angular separation of 2.20 arc seconds along a position angle of 186°.[8] It has also been described as a spectroscopic binary, but there is no confirmation of this.[9] Due to an abnormal space motion, it has also been described as an astrometric binary although there is no orbit.[3]
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.[10]
The primary component is a magnitude 4.89[3] K-type star with a stellar classification of K1 III-IV, having a spectrum that shows mixed traits of an 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.[11] 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]
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 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.
- ^ a b c 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.
- ^ Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
- ^ a b c 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, S2CID 119257644.
- ^ "tau CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-04-30.
{{cite web}}: CS1 maint: postscript (link) - ^ a b Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
- ^ Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
- ^ 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, S2CID 17804304.
- ^ 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, S2CID 16673121.
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