16 Vulpeculae

16 Vulpeculae is a binary star system in the northern constellation Vulpecula.[1] It has a combined apparent visual magnitude of 5.787,[2] which is near the lower limit of visibility to the naked eye. Based upon an annual parallax shift of 14.71±0.50[1] as seen from Earth's orbit, it is located about 222 light years away. The system is moving closer to the Sun with a heliocentric radial velocity of about −37 km/s.[6] It will make its closest approach in about 0.9 million years, coming within 155 light-years (47.42 pc).[10]

16 Vulpeculae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Vulpecula
Right ascension  20h 02m 01.43152s[1]
Declination +24° 56′ 16.9534″[1]
Apparent magnitude (V) 5.787[2] 5.93 + 6.22[3]
Characteristics
Spectral type F2 III[4]
U−B color index +0.10[5]
B−V color index +0.37[5]
Astrometry
Radial velocity (Rv)−37.00±3.7[6] km/s
Proper motion (μ) RA: 89.31[1] mas/yr
Dec.: 69.44[1] mas/yr
Parallax (π)14.71 ± 0.50[1] mas
Distance222 ± 8 ly
(68 ± 2 pc)
Absolute magnitude (MV)2.47[7]
Orbit[8]
Period (P)1201 yr
Semi-major axis (a)2.687″
Eccentricity (e)0.932
Inclination (i)79.0°
Longitude of the node (Ω)84.5°
Periastron epoch (T)B 1863.7
Argument of periastron (ω)
(secondary)		276.5°
Details
16 Vul A
Mass1.34[9] M☉
Luminosity31.13[10] L☉
Surface gravity (log g)3.76±0.14[9] cgs
Temperature6,888±234[9] K
Metallicity [Fe/H]0.17[11] dex
Rotational velocity (v sin i)136.1±6.8[7] km/s
Age742[9] Myr
Other designations
16 Vul, BD+24° 3977, HD 190004, HIP 98636, HR 7657, SAO 88098[12]
Database references
SIMBADdata

The pair orbit each other with an estimated period of 1,201 years and an orbital eccentricity of 0.932.[8] The magnitude 5.93 primary, component A, displays a stellar classification of F2III,[12] matching an aging F-type giant star. This star is spinning rapidly with a projected rotational velocity of 136 km/s.[7] This is giving the star an oblate shape with an equatorial bulge that is an estimated 21% larger than the polar radius.[13] It is 742[9] million years old with 1.34[9] times the mass of the Sun. The star is radiating 31[10] times the Sun's luminosity from its photosphere at an effective temperature of about 6,888 K.[9]

References
  1. van Leeuwen, F.; et al. (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.
  2. Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
  3. 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.
  4. Cowley, Anne; Fraquelli, Dorothy (1974), "MK Spectral Types for Some Bright F Stars", Publications of the Astronomical Society of the Pacific, 86 (509): 70, Bibcode:1974PASP...86...70C, doi:10.1086/129562
  5. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. Holmberg, J.; et al. (2007), "The Geneva-Copenhagen survey of the Solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk", Astronomy & Astrophysics, 475 (2): 519–537, arXiv:0707.1891, Bibcode:2007A&A...475..519H, doi:10.1051/0004-6361:20077221.
  7. Ammler-von Eiff, M.; Reiners, A. (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724.
  8. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 24 August 2017.
  9. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  10. 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.
  11. Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276.
  12. "* 16 Vul". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 August 2017.
  13. Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2.


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