QS Aquilae is a triple or quadruple star system consisting of an eclipsing binary in a 2.5 day orbit around which a third star orbits in 77 years.[3] There is some indication that there is a fourth component with a period of roughly 18 years.[5] It is located in the constellation Aquila and is barely visible to the naked eye.

QS Aquilae

A visual band light curve for QS Aquilae. Adapted from Zasche et al. (2017)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	19h 41m 05.528s[2]
Declination	+13° 48′ 56.45″[2]
Apparent magnitude (V)	5.988
Characteristics
Spectral type	B5V
U−B color index	−0.52
B−V color index	−0.08
Variable type	Eclipsing binary[3]
Astrometry
Radial velocity (Rv)	−14.2 ± 2 km/s
Proper motion (μ)	RA: −0.04 ± 0.60[2] mas/yr Dec.: −11.47 ± 0.43[2] mas/yr
Parallax (π)	0.49 ± 0.62 mas[2]
Orbit[3]
Primary	QS Aquilae AB (eclipsing pair)
Companion	QS Aquilae C
Period (P)	77.0±4.3 yr
Semi-major axis (a)	0.111±0.045″
Eccentricity (e)	0.947±0.038
Inclination (i)	61.2±3.6°
Longitude of the node (Ω)	144.5±5.1°
Periastron epoch (T)	1962.3±2.3
Argument of periastron (ω) (secondary)	336.8±4.7°
Orbit[3]
Primary	QS Aquilae A
Companion	QS Aquilae B
Period (P)	2.5132987±0.0000075 d
Semi-major axis (a)	13.78±0.11 R⊙
Inclination (i)	83.6±1.3°
Semi-amplitude (K1) (primary)	73.98±0.33 km/s
Semi-amplitude (K2) (secondary)	201.76±2.09 km/s
Other designations
KUI 93, QS Aql, BD+13° 4098, HD 185936, HIP 96840, HR 7486, WDS J19411+1349, 2MASS J19410553+1348565[4]
Database references
SIMBAD	data

References

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