27 Aquilae

27 Aquilae (abbreviated 27 Aql) is a star in the equatorial constellation of Aquila. 27 Aquilae is its Flamsteed designation though it also bears the Bayer designation d Aquilae. It has an apparent visual magnitude of 5.49,[2] which is faintly visible to the naked eye. Based upon parallax measurements made during the Hipparcos mission, this star is at a distance of 440 light-years (130 parsecs) from Earth, give or take a 20 light-year margin of error.[1] At this distance, the brightness of the star is diminished from extinction caused by interstellar gas and dust.[5]

27 Aquilae
Location of 27 Aquilae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Aquila
Right ascension 19h 20m 35.68321s[1]
Declination −00° 53′ 31.8067″[1]
Apparent magnitude (V) 5.49[2]
Characteristics
Spectral type B9 III[3]
U−B color index −0.23[2]
B−V color index −0.04[2]
Astrometry
Radial velocity (Rv)−27[4] km/s
Proper motion (μ) RA: 5.42[1] mas/yr
Dec.: 2.83[1] mas/yr
Parallax (π)7.45 ± 0.28 mas[1]
Distance440 ± 20 ly
(134 ± 5 pc)
Absolute bolometric
magnitude (Mbol)		2.04–2.27[5]
Details
Surface gravity (log g)3.61 ± 0.50[6] cgs
Temperature11,500[6] K
Rotational velocity (v sin i)55[7] km/s
Other designations
BD−01° 3716, GC 26673, HD 181440, HIP 95073, HR 7336, PPM 180629, SAO 143292.[8]
Database references
SIMBADdata

The spectrum of 27 Aquilae fits a stellar classification of B9 III,[3] with the luminosity class of III typically indicating this is an evolved giant star. As it lies within the field of view of the CoRoT satellite,[6] close observation have been made of its luminosity. The star shows a multiperiodic variability with at least six pulsation frequencies discovered.[9] It has a high rate of rotation with a projected rotational velocity of 55 km/s.[7] The outer atmosphere is radiating energy into space at an effective temperature of around 11,500 K,[6] giving it the blue-white hue of a B-type star.

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. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  4. Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. van Belle, G. T.; et al. (May 2008), "The Palomar Testbed Interferometer Calibrator Catalog", The Astrophysical Journal Supplement Series, 176 (1): 276–292, arXiv:0711.4194, Bibcode:2008ApJS..176..276V, doi:10.1086/526548, S2CID 10713221.{{citation}}: CS1 maint: multiple names: authors list (link)
  6. 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.
  7. Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  8. "d Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-21.
  9. Degroote, P.; et al. (December 2011), "CoRoT's view on variable B8/9 stars: spots versus pulsations. Evidence for differential rotation in HD 174648", Astronomy & Astrophysics, 536: A82, arXiv:1110.5601, Bibcode:2011A&A...536A..82D, doi:10.1051/0004-6361/201116802, S2CID 54570565.
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