71 Aquilae

"l Aquilae" redirects here. Not to be confused with Lambda Aquilae or L'Aquila.

71 Aquilae (abbreviated 71 Aql) is a binary star in the equatorial constellation of Aquila. 71 Aquilae is its Flamsteed designation though it also bears the Bayer designation l Aquilae. The apparent visual magnitude of the system is 4.33,^[2] making it bright enough to be viewed by the naked eye. It has an annual parallax shift of 9.67 mas,^[1] which equates to a physical distance of 340 light-years (100 parsecs) from Earth, give or take a 30 light-year margin of error. At this distance, the brightness of the system is diminished by 0.065 in visual magnitude from extinction caused by interstellar gas and dust.^[5]

71 Aquilae

Location of 71 Aquilae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	20h 38m 20.28206s[1]
Declination	−01° 06′ 18.4311″[1]
Apparent magnitude (V)	4.33[2]
Characteristics
Spectral type	G8 III[3]
U−B color index	+0.68[2]
B−V color index	+0.96[2]
R−I color index	0.46
Astrometry
Radial velocity (Rv)	-5.6[4] km/s
Proper motion (μ)	RA: +14.84[1] mas/yr Dec.: -16.45[1] mas/yr
Parallax (π)	9.67 ± 0.75 mas[1]
Distance	340 ± 30 ly (103 ± 8 pc)
Absolute magnitude (MV)	–1.03[5]
Orbit[6]
Period (P)	205.2 days
Semi-major axis (a)	3.82 ± 0.81 mas
Eccentricity (e)	0.000
Inclination (i)	147.70° ± 5.90°
Longitude of the node (Ω)	314.00 ± 1.30°
Periastron epoch (T)	2423358.0 HJD
Argument of periastron (ω) (secondary)	0.00°
Details
Surface gravity (log g)	2.87[7] cgs
Temperature	5,060[7] K
Metallicity [Fe/H]	–0.13[7] dex
Rotational velocity (v sin i)	10[8] km/s
Other designations
BD-01 4016, HD 196574, HIP 101847, HR 7884, SAO 144649.[9]
Database references
SIMBAD	data

This is a spectroscopic binary system where the presence of an orbiting companion is revealed by shifts in the spectral lines caused by the Doppler effect. The primary component is a giant star with a stellar classification of G8 III.^[3] The secondary is following a circular orbit with a period of 205.2 days.^[6]

References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
3. Herbig, George H.; Spalding, John F. Jr. (January 1955), "Axial Rotation and Line Broadening in Stars of Spectral Types F0-K5", Astrophysical Journal, 121: 118, Bibcode:1955ApJ...121..118H, doi:10.1086/145969.
4. Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
5. Ryon, Jenna; Shetrone, Matthew D.; Smith, Graeme H. (August 2009), "Comparing the Ca ii H and K Emission Lines in Red Giant Stars", Publications of the Astronomical Society of the Pacific, 121 (882): 842–856, arXiv:0907.3346, Bibcode:2009PASP..121..842R, doi:10.1086/605456, S2CID 17821279.
6. Jancart, S.; et al. (October 2005), "Astrometric orbits of SB^9 stars", Astronomy and Astrophysics, 442 (1): 365–380, arXiv:astro-ph/0507695, Bibcode:2005A&A...442..365J, doi:10.1051/0004-6361:20053003, S2CID 15123997.
7. McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
8. Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B.
9. "* l Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-23.