Astronomy:KT Lupi

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Short description: Visual binary star system in the constellation of Lupus
KT Lupi
Location of KT Lupi (circled in red)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Lupus
Right ascension  15h 35m 53.24806s[1]
Declination −44° 57′ 30.1982″[1]
Apparent magnitude (V) 4.55[2] (4.66 + 6.62)[3]
Characteristics
Spectral type B3 V + B6 V[4]
B−V color index −0.175±0.003[2]
Variable type Be[5]
Astrometry
Radial velocity (Rv)+6.5±2.8[6] km/s
Proper motion (μ) RA: −20.53[1] mas/yr
Dec.: −21.23[1] mas/yr
Parallax (π)7.62 ± 0.43[1] mas
Distance430 ± 20 ly
(131 ± 7 pc)
Absolute magnitude (MV)−1.03[2]
Details
KT Lup A
Mass5.9±0.1[7] M☉
Radius3.00±0.06[8] R☉
Luminosity794+791
−396[9] L☉
Surface gravity (log g)3.50±0.04[8] cgs
Temperature18,400±184[8] K
Rotational velocity (v sin i)30±0.6[8] km/s
Age21.0±10.6[7] Myr
KT Lup B
Mass2.79[10] M☉
Other designations
d Lup, KT Lup, CD−44°10239, HD 138769, HIP 76371, HR 5781, SAO 225950, WDS J15359-4457AB[11]
Database references
SIMBADdata

KT Lupi is a visual binary star[4] system in the constellation Lupus. It is visible to the naked eye with a combined apparent visual magnitude of 4.55.[2] As of 1983, the pair had an angular separation of 2.19″±0.03″.[9] Based upon an annual parallax shift of 7.6 mas[1] as seen from Earth's orbit, it is located 430 light-years from the Sun. The system is moving further from the Earth with a heliocentric radial velocity of +6.5 km/s.[6] It is a member of the Upper Centaurus-Lupus sub-group of the Scorpius–Centaurus association.[4]

A light curve for KT Lupi, plotted from Hipparcos data [12]

The primary, component A, is a variable Be star,[5] with the variation being modulated by rotation.[13] It is visual magnitude 4.66[3] with a stellar classification of B3 V,[4] matching a B-type main-sequence star. Hiltner et al. (1969) gave a class of B3 IVp,[14] which is still used in some studies.[7][8][9] It is a helium-weak chemically peculiar star showing an enhanced silicon patch near the equator and a silicon-weak region close to the pole.[9] The star is about 21 million years old with nearly six[7] times the mass of the Sun and three times the Sun's radius.[8] It is radiating roughly 794[9] times the Sun's luminosity from its photosphere at an effective temperature of 18,400 K.[8]

The secondary companion, component B, is of magnitude 6.62[3] with a class of B6 V.[4] It has 2.79 times the Sun's mass.[10]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  3. ↑ 3.0 3.1 3.2 Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Chen, Christine H. et al. (September 2012), "A Spitzer MIPS Study of 2.5-2.0 M⊙ Stars in Scorpius–Centaurus", The Astrophysical Journal 756 (2): 24, doi:10.1088/0004-637X/756/2/133, 133, Bibcode: 2012ApJ...756..133C. 
  5. ↑ 5.0 5.1 Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports 61 (1): 80, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  6. ↑ 6.0 6.1 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, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  7. ↑ 7.0 7.1 7.2 7.3 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, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T. 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 Arcos, C. et al. (March 2018), "Stellar parameters and H α line profile variability of Be stars in the BeSOS survey", Monthly Notices of the Royal Astronomical Society 474 (4): 5287–5299, doi:10.1093/mnras/stx3075, Bibcode: 2018MNRAS.474.5287A. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 Briquet, M. et al. (January 2007), "Discovery of magnetic fields in three He variable Bp stars with He and Si spots", Astronomische Nachrichten 328 (1): 41–45, doi:10.1002/asna.200610702, Bibcode: 2007AN....328...41B. 
  10. ↑ 10.0 10.1 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, doi:10.1051/0004-6361:20077719, Bibcode: 2007A&A...474...77K. 
  11. ↑ "KT Lup". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=KT+Lup. 
  12. ↑ "Hipparcos Tools Interactive Data Access". ESA. https://www.cosmos.esa.int/web/hipparcos/interactive-data-access. 
  13. ↑ Briquet, M. et al. (January 2004), "He and Si surface inhomogeneities of four Bp variable stars", Astronomy and Astrophysics 413: 273–283, doi:10.1051/0004-6361:20031450, Bibcode: 2004A&A...413..273B 
  14. ↑ Hiltner, W. A. et al. (July 1969), "MK Spectral Types for Bright Southern OB Stars", Astrophysical Journal 157: 313, doi:10.1086/150069, Bibcode: 1969ApJ...157..313H 



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