Location of 18 Aquilae (circled) | |
Observation data Epoch J2000 Equinox J2000 | |
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Constellation | Aquila |
Right ascension | 19h06m 58.60289s[1] |
Declination | +11° 04′ 16.4173″[1] |
Apparent magnitude (V) | 5.072 |
Characteristics | |
Spectral type | B8 III[2] |
U−B color index | −0.44[3] |
B−V color index | −0.08[3] |
Variable type | Eclipsing[4] |
Astrometry | |
Radial velocity (Rv) | −18.6[5] km/s |
Proper motion (μ) | RA: −0.89[1] mas/yr Dec.: −32.11[1] mas/yr |
Parallax (π) | 6.43 ± 0.79 mas[1] |
Distance | approx. 510 ly (approx. 160 pc) |
Orbit[6] | |
Primary | A |
Companion | B |
Period (P) | 205.16 yr |
Semi-major axis (a) | 0.399″ |
Eccentricity (e) | 0.23 |
Inclination (i) | 134.3° |
Orbit[6] | |
Primary | Aa |
Companion | Ab |
Period (P) | 1.3023 d |
Semi-amplitude (K1) (primary) | 27.6 km/s |
Details | |
Aa | |
Mass | 5.6[6] M☉ |
Luminosity | 4,875[7] L☉ |
Rotational velocity (v sin i) | 50[2] km/s |
Ab | |
Mass | 0.38[6] M☉ |
Luminosity | 12.7[7] L☉ |
B | |
Mass | 3.49[6] M☉ |
Other designations | |
Y Aquilae, 18 Aql, BD+10 3787, FK5 3525, HD 178125, HIP 93867, HR 7248, SAO 104488[8] | |
Database references | |
SIMBAD | data |
18 Aquilae (abbreviated 18 Aql) is a triple star[9] system in the constellationofAquila. 18 Aquilae is the Flamsteed designation; it also bears the variable star designation Y Aquilae. It has an apparent visual magnitude of 5.07. The distance to this system can be estimated from the annual parallax shift of 6.43 mas, yielding a value of around 510 light-years (160 parsecs) away from Earth.
The inner pair of stars in this system form a spectroscopic binary with a combined magnitude of 5.44 and an orbital period of 1.302 days. The primary component is a giant star with a stellar classification of B8 III.[2] Because the orbital plane is inclined near the line of sight, two form an eclipsing binary system. The eclipse of the primary component causes a 0.04 drop in magnitude, while the eclipse of the secondary results in a decrease of 0.03.[11] At an angular separation of 0.310 arcseconds is the magnitude 6.39 tertiary component.[9] This system has a high peculiar velocityof29.7 ± 3.9 km/s relative to the neighboring stars.[12]
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