Tau Ursae Majoris (τ UMa) is the Bayer designation for a binary star in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye, having an apparent visual magnitude of 4.66.[2] With an annual parallax shift of 25.82 mas,[1] it is located about 126 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.19 due to interstellar dust.[9]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 09h 10m 55.06553s[1] |
| Declination | +63° 30′ 49.0553″[1] |
| Apparent magnitude (V) | 4.66[2] |
| Characteristics | |
| Spectral type | kA5hF0mF5 II[3] |
| U−B color index | +0.14[2] |
| B−V color index | +0.35[2] |
| Astrometry | |
| Radial velocity (Rv) | −9.80±0.30[4] km/s |
| Proper motion (μ) | RA: +102.37[1] mas/yr Dec.: −63.55[1] mas/yr |
| Parallax (π) | 25.82 ± 0.54 mas[1] |
| Distance | 126 ± 3 ly (38.7 ± 0.8 pc) |
| Absolute magnitude (MV) | +1.73[5] |
| Orbit[6] | |
| Period (P) | 1,062.4 d |
| Eccentricity (e) | 0.48 |
| Periastron epoch (T) | 2425721.6 JD |
| Argument of periastron (ω) (secondary) | 349.4° |
| Semi-amplitude (K1) (primary) | 3.9 km/s |
| Details | |
| τ UMa A | |
| Mass | 1.8±0.1[7] M☉ |
| Luminosity | 16[8] L☉ |
| Surface gravity (log g) | 3.86±0.43[9] cgs |
| Temperature | 7,343±100[9] K |
| Metallicity [Fe/H] | +0.57±0.15[9] dex |
| Rotational velocity (v sin i) | 21[10] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a single-lined spectroscopic binary star system with an orbital period of 2.9 years and an eccentricity of 0.48.[6] The primary member, component A, is an evolved bright giant with a stellar classification of kA5hF0mF5 II.[3] This notation indicates the star's spectrum shows the calcium K lines of an A5 star, the hydrogen lines of an F0 star, and the metallic lines of an F5 star.[12] It is an evolved Am star of the ρ Puppis type, a class of evolved stars showing the Am chemical peculiarities.[13] It is located in the instability strip of the Hertzsprung–Russell diagram but is not thought to be variable.[7]
Naming
editWith φ, h, υ, θ, e, and f, it composed the Arabic asterism Sarīr Banāt al-Na'sh, the Throne of the daughters of Na'sh, and Al-Haud, the Pond.[14] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al-Haud were the title for seven stars : f as Alhaud I, this star (τ) as Alhaud II, e as Alhaud III, h as Alhaud IV, θ as Alhaud V, υ as Alhaud VI and φ as Alhaud VII .[15]
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 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
- ^ a b Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
- ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
- ^ 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 Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
- ^ a b Burkhart, C.; et al. (January 2005), "The field Am and ρ Puppis-like stars: Lithium and heavier elements", Astronomy and Astrophysics, 429 (3): 1043–1049, Bibcode:2005A&A...429.1043B, doi:10.1051/0004-6361:20040467.
- ^ 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, S2CID 118665352.
- ^ a b c d Koleva, M.; Vazdekis, A. (February 2012), "Stellar population models in the UV. I. Characterisation of the New Generation Stellar Library", Astronomy & Astrophysics, 538: A143, arXiv:1111.5449, Bibcode:2012A&A...538A.143K, doi:10.1051/0004-6361/201118065, S2CID 53999614.
- ^ Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763.
- ^ "tau UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-25.
{{cite web}}: CS1 maint: postscript (link) - ^ Gray, Richard O.; Corbally, J. (2009), Stellar Spectral Classification, Princeton University Press, p. 178, ISBN 978-0691125114.
- ^ Zaremba, D. (1979), "On the determination of the stellar chemical composition. I - Tau UMa", Acta Astronomica, 29 (4): 573–586, Bibcode:1979AcA....29..573Z.
- ^ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 442.
- ^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.