Eta Lupi

η Lupi, often Latinised as Eta Lupi, is a probable triple star[4][12] system in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 3.41.[2] Based upon an annual parallax shift of 27.80[1] mas as seen from Earth, it is located around 136 parsecs (440 ly) distant from the Sun. It is a member of the Upper Centaurus Lupus subgroup of the nearby Sco OB2 association.[13]

η Lupi
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Lupus
Right ascension  16h 00m 07.32786s[1]
Declination −38° 23′ 48.1513″[1]
Apparent magnitude (V) 3.41[2] (3.37 + 7.50 + 10.85)[3]
Characteristics
Spectral type B2 IV + A5 Vp + F5 V[4]
U−B color index −0.83[2]
B−V color index −0.22[2]
Astrometry
Radial velocity (Rv)+1.00±3.80[5] km/s
Proper motion (μ) RA: −16.96[1] mas/yr
Dec.: −27.83[1] mas/yr
Parallax (π)7.38 ± 0.18[1] mas
Distance440 ± 10 ly
(136 ± 3 pc)
Absolute magnitude (MV)−2.24[6]
Details
η Lup A
Mass7.0±0.2[7] M☉
Radius6.7[8] R☉
Luminosity1,729[9] L☉
Temperature14,668[9] K
Rotational velocity (v sin i)242[10] km/s
Age39.8±9.2[7] Myr
Other designations
η Lup, CD−38° 10797, HD 143118, HIP 78384, HR 5948, SAO 207208.[11]
Database references
SIMBADdata

The inner pair in this triple system has an estimated orbital period of around 27,000 years.[12] As of 2013, they had an angular separation of 15.0 arc seconds along a position angle of 19°.[3] The primary star, component A, is an evolving A-type subgiant star with a stellar classification of B2 IV.[4] It has used up the supply of hydrogen at its core and has begun to expand off the main-sequence.

The secondary, component B, is a chemically peculiar A-type main sequence star with a class of A5 Vp[4] and an estimated mass 2.10 times that of the Sun.[12] The outer member, component C, has an orbital period of around half a million years.[12] As of 2007, it had an angular separation of 115.8 arc seconds along a position angle of 248° from the primary.[3] It is an F-type main sequence star with a classification of F5 V and an estimated 1.29 times the Sun's mass.[12]

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.
  2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22
  4. 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.
  5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  6. 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.
  7. 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.
  8. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (3rd ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  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.
  10. Uesugi, Akira; Fukuda, Ichiro (1970), "Catalogue of rotational velocities of the stars", Contributions from the Institute of Astrophysics and Kwasan Observatory, University of Kyoto, Bibcode:1970crvs.book.....U
  11. "eta Lup -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-03-03.
  12. Tokovinin, A. (2008), "Comparative statistics and origin of triple and quadruple stars", Monthly Notices of the Royal Astronomical Society, 389 (2): 925, arXiv:0806.3263, Bibcode:2008MNRAS.389..925T, doi:10.1111/j.1365-2966.2008.13613.x.
  13. Kouwenhoven, M. B. N.; et al. (October 2007), "The primordial binary population. II. Recovering the binary population for intermediate mass stars in Scorpius OB2", Astronomy and Astrophysics, 474 (1): 77–104, arXiv:0707.2746, Bibcode:2007A&A...474...77K, doi:10.1051/0004-6361:20077719.
  • Kaler, James B. (June 24, 2011), "Eta Lupi", Stars, University of Illinois, retrieved 2017-03-04.
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