Theta Ursae Minoris, Latinized from θ Ursae Minoris, is a suspected binary star system that is visible to the naked eye in the northern circumpolar constellation of Ursa Minor. It is roughly 860 light years from Earth with an apparent visual magnitude of 5.0.[2] The system is moving closer to the Sun with a radial velocity of −25 km/s.[5]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 15h 31m 25.05417s[1] |
| Declination | +77° 20′ 57.6199″[1] |
| Apparent magnitude (V) | 4.982[2] |
| Characteristics | |
| Spectral type | K5-III CN0.5[3] |
| B−V color index | +1.553[2] |
| Variable type | suspected[4] |
| Astrometry | |
| Radial velocity (Rv) | −25.3±0.5[5] km/s |
| Proper motion (μ) | RA: −47.55±0.37[1] mas/yr Dec.: +5.33±0.43[1] mas/yr |
| Parallax (π) | 3.81 ± 0.37 mas[1] |
| Distance | 860 ± 80 ly (260 ± 30 pc) |
| Absolute magnitude (MV) | −2.04[6] |
| Details | |
| Radius | 96[7] R☉ |
| Luminosity | 1,618[8] L☉ |
| Surface gravity (log g) | 1.44±0.23[9] cgs |
| Temperature | 3,962±36[9] K |
| Metallicity [Fe/H] | +0.18±0.06[9] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a probable spectroscopic binary with two roughly equal components. [11] The spectrum matches a stellar classification of K5-III CN0.5,[3] which would normally indicate an evolved, orange-hued giant star of type K that has a mild overabundance of cyanogen in the outer atmosphere. The estimated diameter is around 96 times that of the Sun,[7] and it is radiating approximately 1,618[8] times the Sun's luminosity from an expanded photosphere at an effective temperature of 3,962 K.[9]
Photometry from the Hipparcos satellite mission shows that θ Ursae Minoris varies in brightness by a few hundredths of a magnitude. It is listed as NSV 20342 in the New Catalogue of Suspected Variable Stars.[12]
References
edit- ^ a b c d e van Leeuwen, F. (November 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 Høg, E.; et al. (2000). "Tycho Star Catalogs: The 2.5 Million Brightest Stars". The Tycho-2 catalogue of the 2.5 million brightest stars. Vol. 355. pp. L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862. ISBN 0-333-75088-8.
{{cite book}}:|journal=ignored (help) - ^ a b Keenan, P. C.; McNeil, R. 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.
- ^ Perryman, M. A. C.; et al. (1997). "The Hipparcos Catalogue". Astronomy & Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
- ^ a b 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.
- ^ Schiavon, Ricardo P. (July 2007), "Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations", The Astrophysical Journal Supplement Series, 171 (1): 146–205, arXiv:astro-ph/0611464, Bibcode:2007ApJS..171..146S, doi:10.1086/511753, S2CID 13946698.
- ^ a b McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017-10-01), "Fundamental parameters and infrared excesses of Tycho-Gaia stars", Monthly Notices of the Royal Astronomical Society, 471 (1): 770–791, arXiv:1706.02208, doi:10.1093/mnras/stx1433, ISSN 0035-8711 theta UMi' database entry at VizieR.
- ^ a b 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 Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: 25, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769, S2CID 54940439, A165.
- ^ "* tet UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 June 2014.
- ^ 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.
- ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.