26 Aquilae
Diagram showing star positions and boundaries of the Aquila constellation and its surroundings
Location of 26 Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 20m 32.90437s[1]
Declination –05° 24′ 56.7440″[1]
Apparent magnitude (V) 5.00[2]
Characteristics
Spectral type G8 III-IV[3]
U−B color index +0.634[2]
B−V color index +0.936[2]
R−I color index 0.5
Astrometry
Radial velocity (Rv)−16.91±1.93[4] km/s
Proper motion (μ) RA: +113.13[1] mas/yr
Dec.: +46.20 [1] mas/yr
Parallax (π)21.15 ± 0.39 mas[1]
Distance154 ± 3 ly
(47.3 ± 0.9 pc)
Orbit[4]
Period (P)266.544 days
Eccentricity (e)0.833
Semi-amplitude (K1)
(primary)		29.86 km/s
Details
26 Aquilae A
Mass3.2+0.2
−0.2[5] M☉
Radius6[4] R☉
Luminosity21[4] L☉
Surface gravity (log g)3.2[4] cgs
Temperature4940[5] K
Metallicity [Fe/H]–0.21[4] dex
Rotational velocity (v sin i)1.3[4] km/s
26 Aquilae B
Mass1.4±0.05[5] M☉
Other designations
f Aquilae, BD–05° 4936, FK5 3544, HD 181391, HIP 95066, HR 7333, SAO 143286.[6]
Database references
SIMBADdata

26 Aquilae (abbreviated 26 Aql) is a binary star system in the equatorial constellation of Aquila. 26 Aquilae is its Flamsteed designation though it also bears the Bayer designation f Aquilae. It has an apparent visual magnitude of 5.00,[2] which means it is faintly visible to the naked eye. As the Earth orbits the Sun, this star system undergoes a parallax shift of 21.15 mas.[1] This means it is located at a distance of approximately 154 light-years (47 parsecs) from Earth, give or take a three-light-year margin of error.

This is a single-lined spectroscopic binary system, meaning that the presence of an orbiting companion is revealed through shifts in the spectrum of the primary star. The pair orbit each other with a period of 266.544 days at a high eccentricity of 0.833.[4] Little is known about this companion, although its mass can be estimated as 140% of the Sun's.

The primary component has a stellar classification of G8 III-IV.[3] The luminosity class of III-IV indicates the spectrum resembles that of a star part way between the subgiant and giant stages of its evolution. It has more than three[5] times the mass of the Sun and six[4] times the Sun's radius. It is radiating 21[4] times as much luminosity as the Sun from this enlarged outer envelope at an effective temperature of 4,940 K.[5] At this heat, the star glows with the characteristic yellow hue of a G-type star.[7]

References

  1. 1 2 3 4 5 6 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. 1 2 3 4 Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants.", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
  3. 1 2 Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  4. 1 2 3 4 5 6 7 8 9 10 Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  5. 1 2 3 4 5 Pourbaix, D.; Boffin, H. M. J. (February 2003), "Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries. II. Systems with a giant component", Astronomy and Astrophysics, 398 (3): 1163–1177, arXiv:astro-ph/0211483, Bibcode:2003A&A...398.1163P, doi:10.1051/0004-6361:20021736, S2CID 12361870.
  6. ↑ "f Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-22.{{cite web}}: CS1 maint: postscript (link)
  7. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16
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