Delta Librae

Delta Librae, Latinized from δ Librae, is a variable star in the constellation Libra. It has the traditional name Zuben Elakribi, a variant of the traditional name of Gamma Librae.[10] With μ Vir it forms one of the Akkadian lunar mansions Mulu-izi[11] (meaning "Man-of-fire"[12]).

δ Librae
Observation data
Epoch J2000      Equinox J2000
Constellation Libra
Right ascension 15h 00m 58.35013s[1]
Declination −08° 31′ 08.2063″[1]
Apparent magnitude (V) 4.93[2]
Characteristics
Spectral type B9.5V[3]
U−B color index –0.10[4]
B−V color index +0.00[4]
Variable type Eclipsing binary of Algol type (EA/SD)[5]
Astrometry
Radial velocity (Rv)−38.7±2[6] km/s
Proper motion (μ) RA: -63.46[1] mas/yr
Dec.: -4.76[1] mas/yr
Parallax (π)11.11 ± 0.60[1] mas
Distance290 ± 20 ly
(90 ± 5 pc)
Absolute magnitude (MV)+0.15[7]
Orbit[8]
Period (P)2.3274 d
Eccentricity (e)0.07
Semi-amplitude (K1)
(primary)		76.6 km/s
Semi-amplitude (K2)
(secondary)		218.7 km/s
Details
δ Lib A
Mass4.9±0.2[8] M☉
Radius3.94[9] R☉
Luminosity86[7] L☉
Temperature8800[9] K
Age0.5[9] Gyr
δ Lib B
Mass1.7±0.2[8] M☉
Other designations
δ Lib, Zuben Elakribi, 19 Librae, BD–07° 3938, HD 132742, HIP 73473, HR 5586, SAO 140270
Database references
SIMBADdata

δ Lib is approximately 300 light years from the Earth and the primary, component A, belongs to the spectral class B9.5V, indicating it is a B-type main-sequence star. It is visible to the naked eye with an apparent visual magnitude of 4.93[2] and is moving closer to the Sun with a radial velocity of −39 km/s.[6] This is an Algol-like eclipsing binary star system, with a period of 2.3274 days and an eccentricity of 0.07.[8] Its apparent magnitude varies from 4.91m to 5.9m.[13] The secondary is filling its roche lobe and there is evidence of large-scale mass transfer in the past, with the star being more evolved than the primary.[8]

Along with λ Tau, it was one of the first stars on which rotational line broadening[14] was observed, by Frank Schlesinger in 1911.

References
  1. van Leeuwen, F.; et al. (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. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
  4. Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
  5. "Del Lib". The International Variable Star Index. AAVSO – American Association of Variable Star Observers. Retrieved 27 September 2017.
  6. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
  7. 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.
  8. Tomkin, J. (April 1978), "Secondaries of eclipsing binaries. I. Detection of the secondary of Delta Librae", Astrophysical Journal, 221: 608–615, Bibcode:1978ApJ...221..608T, doi:10.1086/156064.
  9. Rhee, Joseph H.; Song, Inseok; Zuckerman, B.; McElwain, Michael (2007). "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs". The Astrophysical Journal. 660 (2): 1556–1571. arXiv:astro-ph/0609555. Bibcode:2007ApJ...660.1556R. doi:10.1086/509912. S2CID 11879505.
  10. Bečvář, A., Atlas Coeli II Atlas Coeli II- Catalog, Ceskoslovenské Akademie Ved, Praha,1959.
  11. Allen, R. H. (1963). Star Names: Their Lore and Meaning (rep. ed.). New York, NY: Dover Publications Inc. pp. 277, 473.
  12. Brown Jr., R., (1891). "Remarks on the Euphratean Astronomical Names of the Signs of the Zodiac", Proceedings of the Society of Biblical Archaeology, vo. 13, p. 194.
  13. Samus, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869, retrieved 2018-01-07.
  14. Schlesinger, F. (1909), "Rotation of Stars about their Axes", Monthly Notices of the Royal Astronomical Society, 71 (9): 719, Bibcode:1911MNRAS..71..719S, doi:10.1093/mnras/71.9.719.
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