Phi Boötis
Star in the constellation of Boötes
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Phi Boötis is a single,[9] yellow-hued star in the northern constellation of Boötes. Its name is a Bayer designation that is Latinized from φ Boötis, and abbreviated Phi Boo or φ Boo. This star is dimly visible to the naked eye with an apparent visual magnitude of +5.24.[2] Based upon an annual parallax shift of 18.58 mas as seen from the Earth,[1] it is located 176 light-years (54 pc) from the Sun. At that distance, the visual magnitude is diminished by an extinction of 0.09 due to interstellar dust.[6] It is moving closer to the Sun with a radial velocity of −10.6 km/s.[5]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Boötes |
| Right ascension | 15h 37m 49.598s[1] |
| Declination | +40° 21′ 12.36″[1] |
| Apparent magnitude (V) | +5.24[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | G7 III-IV Fe-2[4] |
| U−B color index | +0.53[2] |
| B−V color index | +0.88[2] |
| Astrometry | |
| Radial velocity (Rv) | −10.62±0.30[5] km/s |
| Proper motion (μ) | RA: +61.380 mas/yr[1] Dec.: +59.791 mas/yr[1] |
| Parallax (π) | 18.5752±0.0555 mas[1] |
| Distance | 175.6 ± 0.5 ly (53.8 ± 0.2 pc) |
| Absolute magnitude (MV) | +1.67[6] |
| Details | |
| Mass | 1.43[6] M☉ |
| Radius | 5[5] R☉ |
| Luminosity | 17[5] L☉ |
| Surface gravity (log g) | 2.82±0.14[7] cgs |
| Temperature | 4,945±57[7] K |
| Metallicity [Fe/H] | −0.51±0.06[7] dex |
| Rotational velocity (v sin i) | 0.0[5] km/s |
| Age | 3.16[6] Gyr |
| Other designations | |
| φ Boo, 54 Boötis, BD+40°2907, FK5 580, GC 21032, HD 139641, HIP 76534, HR 5823, SAO 45643[8] | |
| Database references | |
| SIMBAD | data |
The stellar classification of Phi Boötis is G7 III-IV Fe-2,[4] which would suggest it is an evolving G-type star that shows spectral traits of both a subgiant and a giant star. However, Alves (2000) has it listed as a member of the so-called "red clump", indicating that it is an aging giant star that is generating energy through helium fusion at its core.[3] The 'Fe-2' suffix notation in its class means that it displays a significant underabundance of iron in its spectrum. Around three billion years old,[6] Phi Boötis has an estimated 1.43[6] times the mass of the Sun and 5[5] times the Sun's radius. It is radiating 17[5] times the Sun's luminosity from its enlarged photosphere at an effective temperature of about 4,945 K.[7]