Kappa2 Sagittarii

Kappa2 Sagittarii (κ2 Sagittarii) is a binary star[3] system in the zodiac constellation of Sagittarius. It is visible to the naked eye with a combined apparent visual magnitude of +5.64.[2] Based upon an annual parallax shift of 10.47 mas as seen from Earth,[1] this system is located around 310 light years from the Sun. They are receding with a radial velocity of +2.6 km/s.[6]

For other stars with this Bayer designation, see κ Sagittarii.
Kappa2 Sagittarii
Location of κ2 Sagittarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 20h 23m 53.17666s[1]
Declination −42° 25′ 22.3376″[1]
Apparent magnitude (V) +5.64[2] (6.04 + 7.12)[3]
Characteristics
Spectral type A5 V[4] (A1 + A6)[5]
U−B color index +0.099[2]
B−V color index +0.192[2]
Astrometry
Radial velocity (Rv)+2.6[6] km/s
Proper motion (μ) RA: −13.07[1] mas/yr
Dec.: +13.64[1] mas/yr
Parallax (π)10.47 ± 0.50[1] mas
Distance310 ± 10 ly
(96 ± 5 pc)
Absolute magnitude (MV)1.03/2.35[5]
Orbit[7]
Period (P)700 yr
Semi-major axis (a)2.032″
Eccentricity (e)0.401
Inclination (i)80°
Longitude of the node (Ω)40.7°
Periastron epoch (T)1912.00
Argument of periastron (ω)
(secondary)		177.3°
Details
κ2 Sgr A
Mass1.85[8] M☉
Luminosity38[9] L☉
Surface gravity (log g)4.03[8] cgs
Temperature7,990±272[8] K
Age833[8] Myr
Other designations
κ2 Sgr, CD−42° 14847, HD 193807, HIP 100591, HR 7787, SAO 230184, WDS J20239-4225[10]
Database references
SIMBADdata

This is a visual binary system with the components orbiting each other over a period of roughly 700 years, having an eccentricity of 0.4 and a semimajor axis of 2 arc seconds.[7] The pair have a combined spectral type that matches an A-type main sequence star with a stellar classification of A5 V.[4] The individual components are of estimated types A1 and A6.[5] The primary member, component A, is a magnitude 6.04[3] star with 1.85[8] times the mass of the Sun. It is radiating 38[9] times the Sun's luminosity from its photosphere at an effective temperature of about 7,990 K.[8] The companion, component B, is visual magnitude 7.12.[3]

There are two visual companions: component C is a magnitude 14.3 star at an angular separation of 18.6 arc seconds along a position angle of 266°, as of 2000; component D is magnitude 14.0 with a separation of 29.8 arc seconds along a position angle of 219°, also as of 2000.[11]

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. Cousins, A. W. J. (1983), "UBV photometry of E region standard stars of intermediate brightness", South African Astronomical Observatory Circular, 7 (7): 36–46, Bibcode:1983SAAOC...7...36C.
  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, S2CID 14878976.
  4. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  5. Cvetkovic, Z.; Ninkovic, S. (2010), "On the Component Masses of Visual Binaries", Serbian Astronomical Journal, 180 (180): 71–80, Bibcode:2010SerAJ.180...71C, doi:10.2298/SAJ1080071C.
  6. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), The Revision of the General Catalogue of Radial Velocities, 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E
  7. Seymour, Diana M.; et al. (February 2002), "Binary Star Orbits. II. Preliminary First Orbits for 117 Systems", The Astronomical Journal, 123 (2): 1023–1038, Bibcode:2002AJ....123.1023S, doi:10.1086/338441.
  8. 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, S2CID 33401607.
  9. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  10. "kappa02 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-06.
  11. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22.
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