71 Aquilae
Binary star system in the constellation Aquila
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71 Aquilae (abbreviated 71 Aql) is a binary star in the equatorial constellation of Aquila. 71 Aquilae is its Flamsteed designation though it also bears the Bayer designation l Aquilae. The apparent visual magnitude of the system is 4.33,[2] making it bright enough to be viewed by the naked eye. It has an annual parallax shift of 9.67 mas,[1] which equates to a physical distance of 340 light-years (100 parsecs) from Earth, give or take a 30 light-year margin of error. At this distance, the brightness of the system is diminished by 0.065 in visual magnitude from extinction caused by interstellar gas and dust.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 20h 38m 20.28206s[1] |
| Declination | −01° 06′ 18.4311″[1] |
| Apparent magnitude (V) | 4.33[2] |
| Characteristics | |
| Spectral type | G7.5 IIIa[3] |
| U−B color index | +0.68[2] |
| B−V color index | +0.96[2] |
| R−I color index | 0.46 |
| Astrometry | |
| Radial velocity (Rv) | −5.6[4] km/s |
| Proper motion (μ) | RA: +14.84[1] mas/yr Dec.: −16.45[1] mas/yr |
| Parallax (π) | 9.67±0.75 mas[1] |
| Distance | 340 ± 30 ly (103 ± 8 pc) |
| Absolute magnitude (MV) | −1.03[5] |
| Orbit[6] | |
| Period (P) | 205.2 days |
| Semi-major axis (a) | 3.82±0.81 mas |
| Eccentricity (e) | 0.000 |
| Inclination (i) | 147.70±5.90° |
| Longitude of the node (Ω) | 314.00±1.30° |
| Periastron epoch (T) | 2423358.0 HJD |
| Argument of periastron (ω) (secondary) | 0.00° |
| Details | |
| primary | |
| Mass | 3.6[7] M☉ |
| Radius | 16.7[8] R☉ |
| Luminosity | 162[8] L☉ |
| Surface gravity (log g) | 2.77[8] cgs |
| Temperature | 5,046[8] K |
| Metallicity [Fe/H] | −0.03[8] dex |
| Rotational velocity (v sin i) | 10[9] km/s |
| Age | 347[10] Myr |
| secondary | |
| Mass | 0.88[7] M☉ |
| Other designations | |
| BD−01 4016, HD 196574, HIP 101847, HR 7884, SAO 144649.[11] | |
| Database references | |
| SIMBAD | data |
This is a spectroscopic binary system where the presence of an orbiting companion is revealed by shifts in the spectral lines caused by the Doppler effect. The primary component is a giant star with a stellar classification of G7.5 IIIa and is listed as a standard star for that class.[3] The secondary is following a circular orbit with a period of 205.2 days.[6]