4 Aquilae

4 Aquilae, abbreviated 4 Aql, is a single,^[9] white-hued star in the equatorial constellation of Aquila. 4 Aquilae is the Flamsteed designation. It has an apparent visual magnitude of 5.02,^[2] making it a faint star visible to the naked eye. The distance to 4 Aql can be estimated from its annual parallax shift of 6.7 mas,^[1] yielding an estimated range of around 480 light years. It is moving closer to the Earth with a heliocentric radial velocity of −13 km/s.^[4]

4 Aquilae

Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	18h 44m 49.93813s[1]
Declination	+02° 03′ 36.1381″[1]
Apparent magnitude (V)	5.02[2]
Characteristics
Spectral type	B9 V[3]
B−V color index	−0.055±0.016[2]
Astrometry
Radial velocity (Rv)	−13.0±4.2[4] km/s
Proper motion (μ)	RA: +9.347[1] mas/yr Dec.: −14.719[1] mas/yr
Parallax (π)	6.7299±0.2433 mas[1]
Distance	480 ± 20 ly (149 ± 5 pc)
Absolute magnitude (MV)	−0.75[2]
Details
Mass	3.60±0.06[5] M☉
Radius	3.00[6] R☉
Luminosity	294+20.4 −20.9[5] L☉
Surface gravity (log g)	3.46±0.10[7] cgs
Temperature	10,965+50 −51[5] K
Rotational velocity (v sin i)	259[5] km/s
Other designations
4 Aql, AG+02 2306, BD+01°3766, GC 25652, HD 173370, HIP 91975, HR 7040, SAO 123879[8]
Database references
SIMBAD	data

This is a B-type main-sequence star with a stellar classification of B9 V.^[3] It was classed as a Be star by Arne Sletteback in 1982, indicating it has ionized circumstellar gas.^[6] The star is spinning rapidly, showing a projected rotational velocity of 259 km/s,^[5] and is being viewed almost equator-on.^[7] It has 3.6^[5] times the mass of the Sun and 3^[6] times the Sun's radius. The star is radiating 294^[5] times the Sun's luminosity from its photosphere at an effective temperature of 10,965 K.^[5]