Pi Boötis

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Pi Boötis
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 40m 43.56087s[1]
Declination +16° 25′ 05.8863″[1]
Apparent magnitude (V) 4.5038[1] (4.893 + 5.761)[2]
Spectral type B9 IIIp (MnHgSi) + A6 V[3]
U−B color index −0.31[4]
B−V color index −0.03[4]
R−I color index −0.02
Radial velocity (Rv) −1.1±0.8[5] km/s
Proper motion (μ) RA: +11.44[1] mas/yr
Dec.: +9.47[1] mas/yr
Parallax (π) 10.67 ± 1.35[1] mas
Distance approx. 310 ly
(approx. 90 pc)
Absolute magnitude (MV) –0.39[6]
π1 Boo
Mass 3.49±0.14 M
Radius 3.2±0.4 R
Luminosity 214 L
Surface gravity (log g) 3.99±0.18[7] cgs
Temperature 12,052±456[7] K
Metallicity [Fe/H] +0.18±0.17[7] dex
Rotational velocity (v sin i) 14.0[8] km/s
Other designations
π Boo, 29 Boötis, BD+17° 2768, HIP 71762, ADS 9338[9]
π1 Boötis: HD 129174, HR 5475, SAO 101138
π2 Boötis: HD 129175, HR 5476, SAO 101139
Database references
Database references
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

Pi Boötis, Latinized from π Boötis, is a probable triple star[10] system in the northern constellation of Boötes. It is visible to the naked eye with a combined apparent visual magnitude of 4.50.[1] Based upon an annual parallax shift of 10.67[1] mas as seen from Earth, it is located roughly 310 light years from the Sun.

The brighter primary, component π1 Boötis, has a visual magnitude of 4.89[2] and a stellar classification of B9 IIIp (MnHgSi),[3] which suggests it is an evolved blue-white hued B-type giant star. It is a chemically peculiar star of the HgMn type,[8] with a spectrum that displays anomalous overabundances of mercury, manganese, and silicon.[3] This component is most likely a single-lined spectroscopic binary with an unknown companion.[10] Its magnitude 5.76[2] visible companion, π2 Boötis, is a white-hued A-type main-sequence star with a class of A6 V.[3] As of 2010, the pair were separated by 5.537±0.003 arcseconds on the sky along a position angle of 110.5°±0.5°. This corresponds to a projected separation of 538.6±47.7 AU. The odds that is a mere chance alignment is 0.85%.[10]

Pi Boötis has the Chinese traditional star name 左攝提二 (Zuǒ shè tí èr)


  1. ^ a b c d e f g h van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Høg, E.; et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, 355: L27, Bibcode:2000A&A...355L..27H, doi:10.1888/0333750888/2862. 
  3. ^ a b c d Abt, H. A.; Cardona, O. (January 1, 1984), "The nature of the visual companions of Ap and Am stars", Astrophysical Journal, Part 1, 276: 266−269, Bibcode:1984ApJ...276..266A, doi:10.1086/161610. 
  4. ^ a b Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N. 
  5. ^ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053Freely accessible, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065. 
  6. ^ a b North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics, 334: 181–187, arXiv:astro-ph/9802286Freely accessible, Bibcode:1998A&A...334..181N. 
  7. ^ a b c Prugniel, P.; et al. (2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952Freely accessible, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769. 
  8. ^ a b Ghazaryan, S.; Alecian, G. (August 2016), "Statistical analysis from recent abundance determinations in HgMn stars", Monthly Notices of the Royal Astronomical Society, 460 (2): 1912−1922, Bibcode:2016MNRAS.460.1912G, doi:10.1093/mnras/stw911 
  9. ^ "pi Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-10-18. 
  10. ^ a b c Schöller, M.; et al. (November 2010), "Multiplicity of late-type B stars with HgMn peculiarity", Astronomy and Astrophysics, 522: 12, Bibcode:2010A&A...522A..85S, doi:10.1051/0004-6361/201014246, A85 

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