26 Vulpeculae

26 Vulpeculae is a close binary star[5] system in the northern constellation of Vulpecula,[9] around 644 light years away from the Sun.[1] It is a challenge to view with the naked eye, having an apparent visual magnitude of 6.40.[2] The star is moving closer to the Earth with a heliocentric radial velocity of −63 km/s,[4] and is expected to come within 225 light-years in around 2.6 million years.[2]

26 Vulpeculae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Vulpecula
Right ascension 20h 36m 08.3399s[1]
Declination +25° 52′ 57.5615″[1]
Apparent magnitude (V) 6.40[2]
Characteristics
Spectral type A5 III[3]
B−V color index 0.158±0.005[2]
Astrometry
Radial velocity (Rv)−63.4±2.3[4] km/s
Proper motion (μ) RA: +26.010[1] mas/yr
Dec.: +12.189[1] mas/yr
Parallax (π)5.0684 ± 0.0346[1] mas
Distance644 ± 4 ly
(197 ± 1 pc)
Absolute magnitude (MV)−0.04[2]
Orbit[5]
Period (P)11.088 d
Eccentricity (e)0.28
Periastron epoch (T)2,426,492.6090 JD
Argument of periastron (ω)
(secondary)		50.1°
Semi-amplitude (K1)
(primary)		58.7 km/s
Details
Radius4.6[6] R☉
Luminosity79.75[7] L☉
Temperature7,888[7] K
Rotational velocity (v sin i)15[8] km/s
Other designations
26 Vul, BD+25°4299, HD 196362, HIP 101641, HR 7874, SAO 88884[9]
Database references
SIMBADdata

This is a single-lined spectroscopic binary with an orbital period of 11 days and an eccentricity of 0.28.[5] The visible component is a suspected chemically peculiar star[10] with a stellar classification of A5 III,[3] suggesting this is an evolved giant star. It has about 4.6[6] times the Sun's radius and is radiating 80 times the Sun's luminosity from its photosphere at an effective temperature of 7,888 K.[7]

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. Gaia DR2 record for this source at VizieR.
  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.
  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. Gontcharov, G. A. (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.
  5. Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  6. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  7. McDonald, I.; et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–357, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  8. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393 (3): 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943.
  9. "26 Vul". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-17.
  10. Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
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