Chi Aquilae

χ Aquilae
Diagram showing star positions and boundaries of the Aquila constellation and its surroundings
Location of χ Aquilae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 42m 34.00828s[1]
Declination +11° 49′ 35.7023″[1]
Apparent magnitude (V) 5.292[2] (5.80/6.68)[3]
Characteristics
Spectral type G2 Ib-II + B5 V[3]
U−B color index +0.01[4]
B−V color index +0.56[4]
Astrometry
Radial velocity (Rv)−19.2[2] km/s
Proper motion (μ) RA: 1.75[1] mas/yr
Dec.: −10.11[1] mas/yr
Parallax (π)3.82 ± 0.51 mas[1]
Distanceapprox. 900 ly
(approx. 260 pc)
Absolute magnitude (MV)−1.53 (−2.1 + −1)[5]
Details
Luminosity420[6] L☉
Temperature5,545[6] K
Rotational velocity (v sin i)3.6[7] km/s
Other designations
47 Aquilae, ADS 12808, BD+11 3955, HD 186203, HIP 96957, HR 7497, SAO 105168
Database references
SIMBADdata

Chi Aquilae (χ Aql, χ Aquilae) is the Bayer designation for a binary star[3] in the equatorial constellation of Aquila, the eagle. This system is bright enough to be seen with the naked eye at a combined visual magnitude of +5.29.[2] Based upon parallax measurements made during the Hipparcos mission, Chi Aquilae is at a distance of approximately 900 light-years (280 parsecs) from Earth.[1]

The two components of χ Aquilae can be separated in the spectrum and their relative brightness has been measured, but their other properties are uncertain. The cool component is a G2 bright giant or supergiant and is visually brighter than the hot component, so it is treated as the primary. The hot component is a late B- or A-type star, presumed to be a main-sequence star.[5][3]

The observed spectrum of the primary star is G2 Ib, a yellow supergiant. It is calculated to have an absolute magnitude of −2.1. The secondary is observed to have a spectral type of B5.5 and is expected to be a main-sequence star with an absolute magnitude of −1. However, the brightness difference between a G2 supergiant and a B5.5 dwarf is expected to be larger. It is unclear whether the primary is not a supergiant or the secondary is brighter than a main-sequence star.[5]

As of 2004, the secondary is located at an angular separation of 0.418 arcseconds along a position angle of 76.7° from the primary.[8] The separation and position angle are both decreasing.[9]

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