Nu2 Sagittarii

Nu2 Sagittarii (ν2 Sagittarii) is a binary star[8] system in the zodiac constellation of Sagittarius. It is faintly visible to the naked eye, having an apparent visual magnitude of +4.98;[2] it is 0.16 degree north of the ecliptic. The annual parallax shift of 11.91 mas as seen from Earth,[1] indicates this system is roughly 270 light years from the Sun. Nu2 Sagittarii has a high peculiar velocity of 86.0+11.6
−14.4 km/s and is most likely a runaway star system.[3]

For other stars with this Bayer designation, see ν Sagittarii.
Nu2 Sagittarii
Diagram showing star positions and boundaries of the Sagittarius constellation and its surroundings
Location of ν2 Sagittarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 18h 55m 07.14098s[1]
Declination −22° 40′ 16.8185″[1]
Apparent magnitude (V) +4.98[2]
Characteristics
Spectral type K1 Ib–II[3]
B−V color index +1.32[2]
Astrometry
Radial velocity (Rv)−109.6[2] km/s
Proper motion (μ) RA: −109.04[1] mas/yr
Dec.: −35.25[1] mas/yr
Parallax (π)11.91 ± 0.52 mas[1]
Distance270 ± 10 ly
(84 ± 4 pc)
Absolute magnitude (MV)+0.38[4]
Details
ν2 Sgr A
Mass1.44[2] M☉
Radius85[5] R☉
Luminosity120[2] L☉
Surface gravity (log g)1.03[6] cgs
Temperature4,244±57[2] K
Metallicity [Fe/H]−0.13[6] dex
Age4.52[2] Gyr
Other designations
ν2 Sgr, 35 Sgr, BD−22° 4915, HD 175190, HIP 92845, HR 7120, SAO 187445[7]
Database references
SIMBADdata

The spectrum of the primary component displays a stellar classification of K1 Ib–II,[3] indicating this is a K-type star with a mixed luminosity class of an evolved bright giant/supergiant star. It is a mild barium star, showing an enhanced abundance of s-process elements in its outer atmosphere. This material was most likely acquired during a previous mass transfer from its now white dwarf companion.[9] The primary has an estimated 1.4[2] times the mass of the Sun and has expanded to 85[5] times the Sun's radius.

References
  1. van Leeuwen, F. (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. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114.
  3. Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  4. 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, S2CID 119257644.
  5. Pasinetti Fracassini, L. E.; et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy & Astrophysics (3rd ed.), 367: 521–24, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  6. Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247, S2CID 118362423.
  7. "nu02 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-06.
  8. 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.
  9. Gomez, A. E.; et al. (1997), "Absolute magnitudes and kinematics of barium stars", Astronomy and Astrophysics, 319: 881, Bibcode:1997A&A...319..881G.
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