Beta Boötis
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Boötes |
| Right ascension | 15h 01m 56.7623s[1] |
| Declination | +40° 23′ 26.0469″[1] |
| Apparent magnitude (V) | 3.488[2] |
| Characteristics | |
| Evolutionary stage | Yellow giant |
| Spectral type | G8IIIa[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[5] km/s |
| Proper motion (μ) | RA: –40.708 mas/yr[1] Dec.: –30.168 mas/yr[1] |
| Parallax (π) | 13.878 ± 0.131 mas[1] |
| Distance | 235 ± 2 ly (72.1 ± 0.7 pc) |
| Absolute magnitude (MV) | –0.70[6] |
| Details | |
| Mass | 3.4 ± 0.2[4] M☉ |
| Radius | 17.68[7] R☉ |
| Luminosity | 170[5]–194[6] L☉ |
| Surface gravity (log g) | 2.2[7] cgs |
| Temperature | 4,997[7] K |
| Metallicity [Fe/H] | –0.086[7] dex |
| Rotation | 200 ± 10[4] days |
| Rotational velocity (v sin i) | 4.10 ± 1.0[4] km/s |
| Age | 240[4]–251[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Beta Boötis, Latinized from β Boötis, and also named Nekkar /ˈnɛkɑːr/,[8] is a star in the northern constellation of Boötes. It has an apparent visual magnitude of 3.5,[2] making it one of the brighter members of the constellation. In the modern constellation, it marks the head of Boötis the herdsman.[9] Based upon parallax measurements obtained by the Gaia spacecraft, this star is approximately 235 light-years (72 parsecs) from the Sun.[1] The magnitude of the star is reduced by 0.06 from extinction caused by intervening gas and dust.[6]
Nomenclature[edit]
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'.[9] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[10] 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.[8]
Properties[edit]
An angular diameter measurement of 1.226 mas places Nekkar's radius at 17.7 R☉.[7] (König et al. (2006) give it 3.4 solar masses,[4] while Tetzlaff et al. (2011) list a higher estimated mass of 5.0 ± 1.5[11] solar masses and Takeda et al. (2008) show it as 3.24[6] solar masses.) At the estimated age of 240–251 million years, it has evolved into a giant star with a stellar classification of G8 IIIa.[3] The star is radiating around 170[5]–194[6] times as much luminosity as the Sun from its outer envelope at an effective temperature of 5,000 K.[7] 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 line of sight from the Earth.[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.[12]
References[edit]
- ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d Fernie, J. D. (May 1983), "New UBVRI photometry for 900 supergiants", Astrophysical Journal Supplement Series, 52: 7–22, Bibcode:1983ApJS...52....7F, doi:10.1086/190856
- ^ a b c "bet Boo -- Flare Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-11-28
- ^ a b c d e f g 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, arXiv:astro-ph/0511232, Bibcode:2006MNRAS.365.1050K, doi:10.1111/j.1365-2966.2005.09796.x, S2CID 16676999
- ^ a b c 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, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
- ^ a b c d e f Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke (August 2008), "Stellar parameters and elemental abundances of late-G giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781, S2CID 16258166
- ^ a b c d e f 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. Bibcode:2019ApJ...882..148G. doi:10.3847/1538-4357/ab2fce. ISSN 0004-637X.
- ^ a b "Naming Stars". IAU.org. Retrieved 7 March 2018.
- ^ a b Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 103, retrieved 2011-11-28
- ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
- ^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873
- ^ 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
