Astronomy:Beta Boötis

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Short description: Star in the constellation Boötes
Beta Boötis
A star chart showing the position of β Boötis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Boötes
Right ascension  15h 01m 56.7623s[1]
Declination +40° 23′ 26.047″[1]
Apparent magnitude (V) 3.488[2]
Characteristics
Evolutionary stage Yellow giant
Spectral type G8IIIa Fe-0.5[3]
U−B color index +0.75[2]
B−V color index +0.94[2]
Variable type Flare star[4]
Astrometry
Radial velocity (Rv)−18.35±0.21[5] km/s
Proper motion (μ) RA: −40.708[1] mas/yr
Dec.: −30.168[1] mas/yr
Parallax (π)13.878 ± 0.131[1] mas
Distance235 ± 2 ly
(72.1 ± 0.7 pc)
Absolute magnitude (MV)−0.70[6]
Details
Mass3.23±0.07[7] M☉
Radius18.44±0.19[8] R☉
Luminosity188±10[8] L☉
Surface gravity (log g)2.45±0.03[7] cgs
Temperature4,997[9] K
Metallicity [Fe/H]–0.086[9] dex
Rotation200±10[4] days
Rotational velocity (v sin i)4.1±1.0[4] km/s
Age320±20[7] Myr
Other designations
Nakkar, Nekkar, Merez, Meres, Merets, Beta Boo, β Boo, 42 Boötis, BD+40°2840, FK5 555, GC 20226, HD 133208, HIP 73555, HR 5602, SAO 45337[10]
Database references
SIMBADdata

Beta Boötis is a star in the northern constellation of Boötes. Its name is a Bayer designation that is Latinized from β Boötis, and abbreviated Beta Boo or β Boo. The star has the official name Nekkar, pronounced /ˈnɛkɑːr/, which is derived from an Arabic name for 'the Herdsman'.[11] It has an apparent visual magnitude of 3.5,[2] making it visible to the naked eye and one of the brighter members of the constellation. In the modern constellation, it marks the head of Boötes the herdsman.[12] Based upon parallax measurements obtained by the Gaia spacecraft, this star is approximately 235 light-years (72 parsecs) from the Sun.[1] It is drawing closer to the Sun with a radial velocity of −18 km/s.[5] The magnitude of the star is reduced by 0.06 from extinction caused by intervening gas and dust.[6]

Nomenclature

β Boötis (Latinised to Beta Boötis) is the star's Bayer designation.

It bore the traditional name Nekkar or Nakkar derived from the Arabic name for the constellation: Al Baḳḳār 'the Herdsman'.[12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalogue and standardize proper names for stars. The WGSN approved the name Nekkar for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[11]

Properties

This star had its angular diameter measured using interferometric observations by the Navy Precision Optical Interferometer. The angular diameter, together with the star's distance, yield a radius 18 times the radius of the Sun.[8] Beta Boötis is 3.2 times more massive than the Sun. At the estimated age of 320 million years,[7] it has evolved into a giant star with a stellar classification of G8 IIIa Fe-0.5. In this notation, the a indicating a slightly higher luminosity class than a typical giant and the Fe-05 indicating slightly weak spectral lines of iron.[3] The star is radiating around 188[8] times as much luminosity as the Sun from its outer envelope at an effective temperature of 5,000 K.[9] This heat gives it the yellow-hued glow of a G-type star. It has an estimated rotation period of about 200 days and the pole is inclined 28° ± 6° to the plane of the sky.[4]

In 1993, the ROSAT satellite was used to observe an X-ray flare on Beta Boötis, which released an estimated 1.7 × 1032 erg. This was the first such observation for a low-activity star of this type. The flare may be explained by an as yet unobserved M-type dwarf companion star.[14] Beta Boötis is a mild barium star, which is evidence for a white dwarf companion.[15]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Fernie, J. D. (May 1983). "New UBVRI photometry for 900 supergiants". Astrophysical Journal Supplement Series 52: 7–22. doi:10.1086/190856. Bibcode: 1983ApJS...52....7F. 
  3. ↑ 3.0 3.1 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. doi:10.1086/191373. Bibcode: 1989ApJS...71..245K. 
  4. ↑ 4.0 4.1 4.2 4.3 König, B. et al. (January 2006). "Spectral synthesis analysis and radial velocity study of the northern F-, G- and K-type flare stars". Monthly Notices of the Royal Astronomical Society 365 (3): 1050–1056. doi:10.1111/j.1365-2966.2005.09796.x. Bibcode: 2006MNRAS.365.1050K. 
  5. ↑ 5.0 5.1 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. doi:10.1088/0004-6256/135/1/209. Bibcode: 2008AJ....135..209M. 
  6. ↑ 6.0 6.1 Takeda, Yoichi et al. (August 2008). "Stellar parameters and elemental abundances of late-G giants". Publications of the Astronomical Society of Japan 60 (4): 781–802. doi:10.1093/pasj/60.4.781. Bibcode: 2008PASJ...60..781T. 
  7. ↑ 7.0 7.1 7.2 7.3 Jofré, E. et al. (2015-02-01). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy and Astrophysics 574: A50. doi:10.1051/0004-6361/201424474. ISSN 0004-6361. Bibcode: 2015A&A...574A..50J.  Beta Boötis' database entry at VizieR.
  8. ↑ 8.0 8.1 8.2 8.3 Baines, Ellyn K. et al. (2018). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal 155 (1): 30. doi:10.3847/1538-3881/aa9d8b. Bibcode: 2018AJ....155...30B. .
  9. ↑ 9.0 9.1 9.2 Gray, David F.; Kaur, Taranpreet (2019-09-01). "A Recipe for Finding Stellar Radii, Temperatures, Surface Gravities, Metallicities, and Masses Using Spectral Lines". The Astrophysical Journal 882 (2): 148. doi:10.3847/1538-4357/ab2fce. ISSN 0004-637X. Bibcode: 2019ApJ...882..148G. 
  10. ↑ "bet Boo". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=bet+Boo. 
  11. ↑ 11.0 11.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  12. ↑ 12.0 12.1 Allen, Richard Hinckley (1899). Star-names and their meanings. G. E. Stechert. p. 103. https://books.google.com/books?id=5xQuAAAAIAAJ&pg=RA103. Retrieved 2011-11-28. 
  13. ↑ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  14. ↑ Huensch, M.; Reimers, D. (April 1995). "Detection of an X-ray flare on the low-activity G 8 III-type giant β Boo". Astronomy and Astrophysics 296: 509–513. Bibcode: 1995A&A...296..509H. 
  15. ↑ Böhm-Vitense, Erika et al. (April 2000). "Do All BA II Stars Have White Dwarf Companions?". The Astrophysical Journal 533 (2): 969–983. doi:10.1086/308678. Bibcode: 2000ApJ...533..969B. 



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