Pi Boötis

Pi Boötis is a candidate triple star^[13] system in the northern constellation of Boötes. Its name is a Bayer designation that is Latinized from π Boötis, and abbreviated Pi Boo or π Boo. This system is visible to the naked eye as a point of light with a combined apparent visual magnitude of 4.50.^[14] Based upon an annual parallax shift of 10.67 mas^[2] as seen from Earth, it is located roughly 316 light years from the Sun.

Pi Boötis

Observation data Epoch J2000      Equinox J2000
Constellation	Boötes[1]
Right ascension	14h 40m 43.559s[2]
Declination	+16° 25′ 05.98″[2]
Apparent magnitude (V)	4.49[1] (4.893 + 5.761)[3]
Characteristics
Spectral type	B9 IIIp (MnHgSi) + A6 V[4]
U−B color index	−0.31[5]
B−V color index	−0.002±0.010[1]
R−I color index	−0.02[citation needed]
Astrometry
Radial velocity (Rv)	−1.1±0.8[6] km/s
Proper motion (μ)	RA: +13.922 mas/yr[2] Dec.: +15.566 mas/yr[2]
Parallax (π)	10.3357±0.1199 mas[2]
Distance	316 ± 4 ly (97 ± 1 pc)
Absolute magnitude (MV)	–0.39[7]
Details
π1 Boo
Mass	3.49±0.14[7] M☉
Radius	3.2±0.4[7] R☉
Luminosity	214[7] L☉
Surface gravity (log g)	3.99±0.18[8] cgs
Temperature	12,052±456[8] K
Metallicity [Fe/H]	+0.18±0.17[8] dex
Rotational velocity (v sin i)	14.0[9] km/s
π2 Boo
Surface gravity (log g)	3.60±0.01[10] cgs
Temperature	7504+21 −17[10] K
Metallicity [Fe/H]	0.580[10] dex
Rotational velocity (v sin i)	144[11] km/s
Other designations
π Boo, 29 Boötis, BD+17°2768, HIP 71762, ADS 9338[12]
π1 Boötis: HD 129174, HR 5475, SAO 101138
π2 Boötis: HD 129175, HR 5476, SAO 101139
Database references
π1 Boo
SIMBAD	data
π1 Boo
SIMBAD	data
Data sources:
Hipparcos Catalogue, CCDM (2002), Bright Star Catalogue (5th rev. ed.)

The brighter primary, component π¹ Boötis, has a visual magnitude of 4.89^[3] and a stellar classification of B9 IIIp (MnHgSi),^[4] which suggests it is an evolved blue-white hued B-type giant star. It is a chemically peculiar star of the HgMn type,^[9] with a spectrum that displays anomalous overabundances of mercury, manganese, and silicon.^[4] This component is most likely a single-lined spectroscopic binary with an unknown companion.^[13]

Its magnitude 5.76^[3] visible companion, π² Boötis, is a white-hued A-type main-sequence star with a class of A6 V.^[4] It is spinning rapidly with a projected rotational velocity of 144 km/s.^[11] 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%.^[13]

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