Sigma Boötis

Sigma Boötis, its name Latinized from σ Boötis, is a single[15][16] star in the northern constellation of Boötes. It has a yellow-white hue and is visible to the naked eye with an apparent visual magnitude of 4.46.[2] Located to the southeast of Rho Boötis, the dwarf Sigma may at first appear as a naked-eye double, but the angular proximity with Rho is merely line-of-sight. Sigma Boötis is located at a distance of 51.1 light years from the Sun based on parallax.[1] The star has a relatively high proper motion and is traversing the sky at the rate of 0.230″ yr−1.[17]

σ Boötis
Location of σ Boötes (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 34m 40.81718s[1]
Declination +29° 44′ 42.4637″[1]
Apparent magnitude (V) 4.46[2]
Characteristics
Spectral type F4VkF2mF1[3]
U−B color index −0.084[2]
B−V color index +0.366[2]
Variable type Suspected[4]
Astrometry
Radial velocity (Rv)+0.37±0.09[5] km/s
Proper motion (μ) RA: +188.762[1] mas/yr
Dec.: +131.222[1] mas/yr
Parallax (π)63.8633 ± 0.2303[1] mas
Distance51.1 ± 0.2 ly
(15.66 ± 0.06 pc)
Absolute magnitude (MV)3.52[6]
Details
Mass1.48 M☉[7]
1.18[8] M☉
Radius1.431±0.023[9] R☉
Luminosity3.461±0.042[9] L☉
Surface gravity (log g)4.30[6] cgs
Temperature6,594±55[9] K
Metallicity [Fe/H]−0.24[10] dex
Rotational velocity (v sin i)7.32[11] km/s
Age1.7 Gyr[12]
2.42 Gyr[8]
3.1[13] Gyr
Other designations
σ Boo, 28 Boötis, BD+30°2536, GC 19659, GJ 557, HD 128167, HIP 71284, HR 5447, SAO 83416, CCDM 14347+2945[14]
Database references
SIMBADdata

The stellar classification of Sigma Boötis is F4VkF2mF1.[3] This notation is used for so-called "metal-weak" stars, Am stars with absorption lines of some metals weaker than expected in comparison with other spectral features. The 'F4V', indicating an F-type main-sequence star, is derived from the hydrogen spectral lines and the shape of the metallic lines, the 'kF2' meaning it has the Calcium K line strength of an F2 star and 'mF1' showing it has the metallic line strength of an F1 star.[18] It is around twice as luminous as a comparable zero age main sequence star, which may indicate it is near the end of its main sequence lifetime.[13]

Sigma Boötis is a solar-type star but is larger and more massive than the Sun. It has an estimated age of around two[12] to three[13] billion years and is spinning with a projected rotational velocity of 7 km/s.[11] There is some evidence of variation in radial velocity as well as rotational modulation of active latitudes.[13] Even though the outer convective zone of the star only occupies a few percent of the stellar radius, a surface magnetic field has been detected with a strength of 1.4±0.4 Gauss.[19] The star is radiating 3.5[9] times the luminosity of the Sun from its photosphere at an effective temperature of 6,594 K.[9] It appears to be a source for X-ray emission.[20]

Infrared surveys with the Spitzer and Herschel space telescopes failed to detect an infrared excess around this star at wavelengths up to 160 μm. However, the HOSTS Survey with the Large Binocular Telescope reported a detection of an excess in the far infrared, indicating the presence of exozodiacal dust near the habitable zone of the star.[21]

Chinese name

In Chinese, 梗河 (Gěng Hé), meaning Celestial Lance, refers to an asterism consisting of σ Boötis, ε Boötis and ρ Boötis.[22] Consequently, the Chinese name for σ Boötis itself is 梗河二 (Gěng Hé èr, English: the Second Star of Celestial Lance.)[23]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Elliott, J. E. (October 1974), "Study of delta Scuti variables" (PDF), Astronomical Journal, 79: 1082–1090, Bibcode:1974AJ.....79.1082E, doi:10.1086/111657, hdl:2152/34447.
  3. Gray, R. O.; et al. (April 2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal, 121 (4): 2148–2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
  4. Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  5. Nidever, David L.; et al. (August 2002), "Radial Velocities for 889 Late-Type Stars", The Astrophysical Journal Supplement Series, 141 (2): 503–522, arXiv:astro-ph/0112477, Bibcode:2002ApJS..141..503N, doi:10.1086/340570, S2CID 51814894.
  6. Paunzen, E.; et al. (July 2014), "Investigating the possible connection between λ Bootis stars and intermediate Population II type stars", Astronomy & Astrophysics, 567: 8, arXiv:1406.3936, Bibcode:2014A&A...567A..67P, doi:10.1051/0004-6361/201423817, S2CID 56332289, A67.
  7. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
  8. Luck, R. Earle (March 2018), "Abundances in the Local Region. III. Southern F, G, and K Dwarfs", The Astronomical Journal, 155 (3): 31, Bibcode:2018AJ....155..111L, doi:10.3847/1538-3881/aaa9b5, 111.
  9. Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101, S2CID 18993744. See Table 10.
  10. Bensby, T.; et al. (2014), "Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the solar neighbourhood", Astronomy & Astrophysics, 562 (A71): 28, arXiv:1309.2631, Bibcode:2014A&A...562A..71B, doi:10.1051/0004-6361/201322631, S2CID 118786105.
  11. Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics, 520: A79, arXiv:1002.4391, Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725, S2CID 43455849.
  12. Decin, G.; et al. (November 2003), "Age Dependence of the Vega Phenomenon: Observations", The Astrophysical Journal, 598 (1): 636–644, arXiv:astro-ph/0308294, Bibcode:2003ApJ...598..636D, doi:10.1086/378800, S2CID 16751327.
  13. Rachford, Brian L.; Foight, Dillon R. (June 2009), "Chromospheric Variability in Early F-Type Stars", The Astrophysical Journal, 698 (1): 786–802, arXiv:0904.1620, Bibcode:2009ApJ...698..786R, doi:10.1088/0004-637X/698/1/786.
  14. "sig Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-26.
  15. 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.
  16. Rodriguez, David R; et al. (2015), "Stellar multiplicity and debris discs: An unbiased sample", Monthly Notices of the Royal Astronomical Society, 449 (3): 3160, arXiv:1503.01320, Bibcode:2015MNRAS.449.3160R, doi:10.1093/mnras/stv483, S2CID 119237891.
  17. 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.
  18. Gray, Richard O.; Corbally, Christopher (2009), Stellar Spectral Classification, Princeton University Press, Bibcode:2009ssc..book.....G.
  19. Seach, J. M.; et al. (June 2020), "A magnetic snapshot survey of F-type stars", Monthly Notices of the Royal Astronomical Society, 494 (4): 5682–5703, Bibcode:2020MNRAS.494.5682S, doi:10.1093/mnras/staa1107.
  20. Haakonsen, Christian Bernt; Rutledge, Robert E. (September 2009), "XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources", The Astrophysical Journal Supplement, 184 (1): 138–151, arXiv:0910.3229, Bibcode:2009ApJS..184..138H, doi:10.1088/0067-0049/184/1/138.
  21. Ertel, S.; et al. (May 2018), "The HOSTS Survey—Exozodiacal Dust Measurements for 30 Stars", The Astronomical Journal, 155 (5): 19, arXiv:1803.11265, Bibcode:2018AJ....155..194E, doi:10.3847/1538-3881/aab717, S2CID 52227431, 194.
  22. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  23. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 29 日
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