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]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
3. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
4. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
5. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
6. Silaj, J.; et al. (November 2014), "The Hα Profiles of Be Shell Stars", The Astrophysical Journal, 795 (1): 12, Bibcode:2014ApJ...795...82S, doi:10.1088/0004-637X/795/1/82, S2CID 120167606, 82.
7. Lefever, K.; et al. (June 2010), "Spectroscopic determination of the fundamental parameters of 66 B-type stars in the field-of-view of the CoRoT satellite", Astronomy and Astrophysics, 515: A74, arXiv:0910.2851, Bibcode:2010A&A...515A..74L, doi:10.1051/0004-6361/200911956, S2CID 54028925.
8. "4 Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 27, 2018.
9. Chini, R.; et al. (2012), "A spectroscopic survey on the multiplicity of high-mass stars", Monthly Notices of the Royal Astronomical Society, 424 (3): 1925–1929, arXiv:1205.5238, Bibcode:2012MNRAS.424.1925C, doi:10.1111/j.1365-2966.2012.21317.x, S2CID 119120749.