Pi Boötis
Star in the constellation Boötes
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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.
 | |
| 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 | |
| SIMBAD | π1 Boo |
| π2 Boo | |
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).