71 Aquilae

"l Aquilae" redirects here. Not to be confused with Lambda Aquilae. For the commune in Italy, see L'Aquila.

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]

71 Aquilae

Location of 71 Aquilae (circled)
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]