Astronomy:Sigma Boötis

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σ Boötis
Boötes IAU.svg
Red circle.svg
Location of σ Boötes (circled)
Observation data
Equinox J2000.0]] (ICRS)
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

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]

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]

Nomenclature

Sigma Boötis is known by several different names, including σ Boo, 28 Boötis, BD+30°2536, GC 19659, GJ 557, HD 128167, HIP 71284, HR 5447, SAO 83416, and CCDM 14347+2945.[14]

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. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Elliott, J. E. (October 1974), "Study of delta Scuti variables", Astronomical Journal 79: 1082–1090, doi:10.1086/111657, Bibcode: 1974AJ.....79.1082E, https://repositories.lib.utexas.edu/bitstream/2152/34447/1/studydeltascutivariables.pdf. 
  3. ↑ 3.0 3.1 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, doi:10.1086/319956, Bibcode: 2001AJ....121.2148G. 
  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, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  5. ↑ Nidever, David L. et al. (August 2002), "Radial Velocities for 889 Late-Type Stars", The Astrophysical Journal Supplement Series 141 (2): 503–522, doi:10.1086/340570, Bibcode: 2002ApJS..141..503N. 
  6. ↑ 6.0 6.1 Paunzen, E. et al. (July 2014), "Investigating the possible connection between λ Bootis stars and intermediate Population II type stars", Astronomy & Astrophysics 567: 8, doi:10.1051/0004-6361/201423817, A67, Bibcode: 2014A&A...567A..67P. 
  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, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D. 
  8. ↑ 8.0 8.1 Luck, R. Earle (March 2018), "Abundances in the Local Region. III. Southern F, G, and K Dwarfs", The Astronomical Journal 155 (3): 31, doi:10.3847/1538-3881/aaa9b5, 111, Bibcode: 2018AJ....155..111L. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 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, doi:10.1088/0004-637X/746/1/101, Bibcode: 2012ApJ...746..101B. . 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, doi:10.1051/0004-6361/201322631, Bibcode: 2014A&A...562A..71B. 
  11. ↑ 11.0 11.1 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, doi:10.1051/0004-6361/200913725, Bibcode: 2010A&A...520A..79M. 
  12. ↑ 12.0 12.1 Decin, G. et al. (November 2003), "Age Dependence of the Vega Phenomenon: Observations", The Astrophysical Journal 598 (1): 636–644, doi:10.1086/378800, Bibcode: 2003ApJ...598..636D. 
  13. ↑ 13.0 13.1 13.2 13.3 Rachford, Brian L.; Foight, Dillon R. (June 2009), "Chromospheric Variability in Early F-Type Stars", The Astrophysical Journal 698 (1): 786–802, doi:10.1088/0004-637X/698/1/786, Bibcode: 2009ApJ...698..786R. 
  14. ↑ 14.0 14.1 "sig Boo". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=sig+Boo. 
  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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  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, doi:10.1093/mnras/stv483, Bibcode: 2015MNRAS.449.3160R. 
  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, doi:10.1086/427854, Bibcode: 2005AJ....129.1483L. 
  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, doi:10.1093/mnras/staa1107, Bibcode: 2020MNRAS.494.5682S. 
  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, doi:10.1088/0067-0049/184/1/138, Bibcode: 2009ApJS..184..138H. 
  21. ↑ Ertel, S. et al. (May 2018), "The HOSTS Survey—Exozodiacal Dust Measurements for 30 Stars", The Astronomical Journal 155 (5): 19, doi:10.3847/1538-3881/aab717, 194, Bibcode: 2018AJ....155..194E. 
  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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