HD 134687

HD 134687 (e Lupi) is a binary star system in the southern constellation Lupus. It is visible to the naked eye with an apparent visual magnitude of 4.81.[2] The distance to HD 134687 can be estimated from its annual parallax shift of 7.6 mas,[1] yielding a separation of roughly 730 light years. It is a member of the ~11 million year old Upper Centaurus Lupus subgroup of the Scorpius–Centaurus Association, the closest OB association to the Sun.[11]

This article is about e Lupi. It is not to be confused with ε Lupi.
HD 134687
Observation data
Epoch J2000      Equinox J2000
Constellation Lupus
Right ascension 15h 12m 49.58802s[1]
Declination −44° 30′ 01.4867″[1]
Apparent magnitude (V) 4.81[2]
Characteristics
Spectral type B3 IV/V[3]
B−V color index −0.177±0.011[4]
Astrometry
Radial velocity (Rv)+13.5±7.4[5] km/s
Proper motion (μ) RA: −22.015[1] mas/yr
Dec.: −22.164[1] mas/yr
Parallax (π)7.6373 ± 0.9664[1] mas
Distanceapprox. 430 ly
(approx. 130 pc)
Absolute magnitude (MV)−1.11[4]
Orbit[6]
Period (P)0.901407 d
Eccentricity (e)≤ 0.03
Periastron epoch (T)0.366
Details
e Lup A
Mass6.0±0.1[7] M☉
Radius7.1[8] R☉
Luminosity (bolometric)997[2] L☉
Temperature17,100[2] K
Rotational velocity (v sin i)13[9] km/s
Age20.3±4.8 Myr
Other designations
e Lup, CD−44° 9932, HD 134687, HIP 74449, HR 5651, SAO 225539[10]
Database references
SIMBADdata

This is a single-lined spectroscopic binary star system. The pair have a nearly circular orbit with an eccentricity of at or below 0.03 and a period of 0.901407 days (21.6338 h). The primary has an a sin i value of 2.735×105 km, which only gives a lower bound for the semimajor axis a since the orbital inclination i to the line of sight is unknown.[6] The system is a source for X-ray emission.[12]

The visible component has a stellar classification of B3 IV/V,[3] matching a B-type star showing a spectrum with mixed traits of a main sequence and a subgiant star. It is 20 million years old with a projected rotational velocity of 13 km/s.[9] The star has 6.0[7] times the mass of the Sun and 7.1[8] times the Sun's radius. It is radiating 997[2] times the Sun's luminosity from its photosphere at an effective temperature of 17,100 K.[2]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
  3. 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.
  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.
  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. Buscombe, W.; Kennedy, P. M. (August 1962), "Two B-Type Spectroscopic Binaries", Publications of the Astronomical Society of the Pacific, 74 (439): 323, Bibcode:1962PASP...74..323B, doi:10.1086/127818
  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 (Third ed.), 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  9. Wolff, S. C.; Strom, S. E.; Dror, D.; Venn, K. (2007), "Rotational Velocities for B0-B3 Stars in Seven Young Clusters: Further Study of the Relationship between Rotation Speed and Density in Star-Forming Regions", The Astronomical Journal, 133 (3): 1092–1103, arXiv:astro-ph/0702133, Bibcode:2007AJ....133.1092W, doi:10.1086/511002.
  10. "HD 134687". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-22.
  11. 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, arXiv:1207.3415, Bibcode:2012ApJ...756..133C, doi:10.1088/0004-637X/756/2/133, 133.
  12. Berghoefer, T. W.; Schmitt, J. H. M. M.; Cassinelli, J. P. (September 1996), "The ROSAT all-sky survey catalogue of optically bright OB-type stars", Astronomy and Astrophysics Supplement, 118: 481–494, Bibcode:1996A&AS..118..481B.
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