Chi Aquilae
Binary star system in the constellation Aquila
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Chi Aquilae is a binary star[3] system in the equatorial constellation of Aquila, the eagle. Its name is a Bayer designation that is Latinized from χ Aquilae, and abbreviated Chi Aql or χ Aql. This system is bright enough to be seen with the naked eye at a combined apparent 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]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| 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) | −17.37±0.38[5] km/s |
| Proper motion (μ) | RA: 1.75 mas/yr[1] Dec.: −10.11 mas/yr[1] |
| Parallax (π) | 3.82±0.51 mas[1] |
| Distance | approx. 900 ly (approx. 260 pc) |
| Absolute magnitude (MV) | −1.53 (−2.1 + −1)[6] |
| Details | |
| Luminosity | 420[7] L☉ |
| Temperature | 5,545[7] K |
| Metallicity [Fe/H] | −0.39±0.10[8] dex |
| Rotational velocity (v sin i) | 3.6[9] km/s |
| Other designations | |
| χ Aql, χ Aquilae, 47 Aquilae, BD+11 3955, HD 186203, HIP 96957, HR 7497, SAO 105168, ADS 12808[10] | |
| Database references | |
| SIMBAD | data |
The two components of χ Aquilae can be separated by spectrum and their relative brightness has been measured, but their other properties are uncertain. The cooler component displays an intermediate spectra between a G2 bright giant and a supergiant, and is visually brighter than the hot component, so it is treated as the primary. The hot component has a stellar classification of B5.5V, matching a B-type main-sequence star.[6][3][11]
The absolute magnitude of the primary is −2.1, while that of the secondary is −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.[6] 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.[12] The separation and position angle are both decreasing.[13]