# Epsilon Lupi

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Multiple star system

ε Lupi Location of ε Lupi (circled) Observation data Epoch J2000.0 Equinox J2000.0 Constellation Lupus Right ascension 15h 22m 40.86826s[1] Declination −44° 41′ 22.6146″[1] Apparent magnitude (V) 3.41[2] Characteristics Spectral type B2 IV-V[3] U−B color index −0.778[2] B−V color index −0.195[2] Astrometry Radial velocity (Rv) +7.9[4] km/s Proper motion (μ) RA: −22.86[1] mas/yr Dec.: −18.87[1] mas/yr Parallax (π) 6.37±0.70 mas[1] Distance approx. 510 ly (approx. 160 pc) Absolute magnitude (MV) −2.55[5] Orbit[6] Primary Aa Name Ab Period (P) 4.559646 days Semi-major axis (a) 31.5+2.5 −2.3 R☉ Eccentricity (e) 0.2806+0.0059 −0.0047 Inclination (i) 18.8+1.6 −1.4° Periastron epoch (T) 2,452,790.33[3] Argument of periastron (ω) (primary) 335.7+4.8 −4.5° Semi-amplitude (K1) (primary) 53.8[3] km/s Semi-amplitude (K2) (secondary) 64.7[3] km/s Details[6] ε Lup Aa Mass 11.0+2.9 −2.2 M☉ Radius 4.64+0.37 −0.48 R☉ Luminosity (bolometric) 3,407+658 −567 L☉ Surface gravity (log g) 3.89 ± 0.17[3] cgs Temperature 20,500 K Rotational velocity (v sin i) 133[3] km/s ε Lup Ab Mass 9.2+2.4 −1.9 M☉ Radius 4.83+0.42 −0.46 R☉ Luminosity 2,197+489 −399 L☉ Temperature 18,000 K Other designations ε Lup, CPD−44°7342, HD 136504, HIP 75264, HR 5708, SAO 225712[7] Database references SIMBAD data

**Epsilon Lupi**, [Latinized](/source/Latinisation_of_names) from **ε Lup**, is a multiple [star system](/source/Star_system) in the southern [constellation](/source/Constellation) of [Lupus](/source/Lupus_(constellation)). At an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 3.41, Epsilon Lupi can be readily viewed from the southern hemisphere with [sufficiently dark skies](/source/Bortle_Dark-Sky_Scale). It is the [fifth-brightest star](/source/List_of_stars_in_Lupus) or star system in the constellation.[2] [Parallax](/source/Parallax) measurements give a distance to this system of roughly 510 [light-years](/source/Light-year) (160 [parsecs](/source/Parsec)).[1]

This system is what astronomers term a double-lined [spectroscopic binary](/source/Spectroscopic_binary). When the [spectrum](/source/Spectrum) is examined, the [absorption line](/source/Absorption_line) features of both stars can be viewed. As a result of the [Doppler effect](/source/Doppler_effect), these lines shift back and forth in frequency as the two stars orbit around each other. This allows some of their [orbital elements](/source/Orbital_elements) to be deduced, even though the individual stars have not been resolved with a telescope. The pair share a close, elliptical orbit with a [period](/source/Orbital_period) of 4.55970 days. The [orbital eccentricity](/source/Orbital_eccentricity) is 0.277,[3] which means that at the separation at closest approach, or [periapsis](/source/Periapsis), is only 57% of the distance at their greatest separation, or [apoapsis](/source/Apoapsis).[8] There is a third, more distant companion at an [angular separation](/source/Angular_separation) of around 1 [arcsecond](/source/Arcsecond) that may be orbiting the pair with a period of about 64 years.[3]

The pair that share the close orbit, Epsilon Lupi Aa and Epsilon Lupi Ab, have estimated masses of 13.24 and 11.46 times the [mass of the Sun](/source/Solar_mass), respectively. The more distant component, Epsilon Lupi B, has a mass of about 7.64 times the Sun. The combined [stellar classification](/source/Stellar_classification) of the system is B2 IV-V, while the individual components may have spectral classes of B3 IV, B3 V, and A5 V, in order of decreasing mass. The inner A-a pair appear to have their rate of spin synchronized with their orbit, so that the same face of each star always faces its partner. The secondary, Epsilon Lupi a, shows regular variation in luminosity of the type that occurs with [Beta Cephei variables](/source/Beta_Cephei_variable), at a periodicity of 10.36 cycles per day.[3]

This star system is a probable member of the [Scorpius–Centaurus association](/source/Scorpius%E2%80%93Centaurus_association), a [moving group](/source/Moving_group) of stars that originated together and share a similar trajectory through space.[2]

## References

1. ^ [***a***](#cite_ref-aaa474_2_653_1-0) [***b***](#cite_ref-aaa474_2_653_1-1) [***c***](#cite_ref-aaa474_2_653_1-2) [***d***](#cite_ref-aaa474_2_653_1-3) [***e***](#cite_ref-aaa474_2_653_1-4) [***f***](#cite_ref-aaa474_2_653_1-5) van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", *Astronomy and Astrophysics*, **474** (2): 653–664, [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752), [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357), [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600)

1. ^ [***a***](#cite_ref-apjs15_459_2-0) [***b***](#cite_ref-apjs15_459_2-1) [***c***](#cite_ref-apjs15_459_2-2) [***d***](#cite_ref-apjs15_459_2-3) [***e***](#cite_ref-apjs15_459_2-4) Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", *Astrophysical Journal Supplement*, **15**: 459, [Bibcode](/source/Bibcode_(identifier)):[1968ApJS...15..459G](https://ui.adsabs.harvard.edu/abs/1968ApJS...15..459G), [doi](/source/Doi_(identifier)):[10.1086/190168](https://doi.org/10.1086%2F190168)

1. ^ [***a***](#cite_ref-aaa440_1_249_3-0) [***b***](#cite_ref-aaa440_1_249_3-1) [***c***](#cite_ref-aaa440_1_249_3-2) [***d***](#cite_ref-aaa440_1_249_3-3) [***e***](#cite_ref-aaa440_1_249_3-4) [***f***](#cite_ref-aaa440_1_249_3-5) [***g***](#cite_ref-aaa440_1_249_3-6) [***h***](#cite_ref-aaa440_1_249_3-7) [***i***](#cite_ref-aaa440_1_249_3-8) Uytterhoeven, K.; et al. (September 2005), "The orbit of the close spectroscopic binary epsilon Lup and the intrinsic variability of its early B-type components", *Astronomy and Astrophysics*, **440** (1): 249–260, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0507376](https://arxiv.org/abs/astro-ph/0507376), [Bibcode](/source/Bibcode_(identifier)):[2005A&A...440..249U](https://ui.adsabs.harvard.edu/abs/2005A&A...440..249U), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20053009](https://doi.org/10.1051%2F0004-6361%3A20053009), [S2CID](/source/S2CID_(identifier)) [16644667](https://api.semanticscholar.org/CorpusID:16644667)

1. **[^](#cite_ref-rgcrv_4-0)** Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). *Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30*. *Determination of Radial Velocities and Their Applications*. Vol. 30. University of Toronto: [International Astronomical Union](/source/International_Astronomical_Union). p. 57. [Bibcode](/source/Bibcode_(identifier)):[1967IAUS...30...57E](https://ui.adsabs.harvard.edu/abs/1967IAUS...30...57E).

1. **[^](#cite_ref-Anderson2012_5-0)** Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *Astronomy Letters*, **38** (5): 331, [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971), [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A), [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015), [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. ^ [***a***](#cite_ref-Pablo2019_6-0) [***b***](#cite_ref-Pablo2019_6-1) Pablo, H.; Shultz, M.; Fuller, J.; Wade, G. A.; Paunzen, E.; Mathis, S.; Le Bouquin, J. -B.; Pigulski, A.; Handler, G.; Alecian, E.; Kuschnig, R.; Moffat, A. F. J.; Neiner, C.; Popowicz, A.; Rucinski, S. (2019-09-01). ["ɛ Lupi: measuring the heartbeat of a doubly magnetic massive binary with BRITE Constellation"](https://doi.org/10.1093%2Fmnras%2Fstz1661). *Monthly Notices of the Royal Astronomical Society*. **488** (1): 64–77. [arXiv](/source/ArXiv_(identifier)):[1906.09251](https://arxiv.org/abs/1906.09251). [Bibcode](/source/Bibcode_(identifier)):[2019MNRAS.488...64P](https://ui.adsabs.harvard.edu/abs/2019MNRAS.488...64P). [doi](/source/Doi_(identifier)):[10.1093/mnras/stz1661](https://doi.org/10.1093%2Fmnras%2Fstz1661). [ISSN](/source/ISSN_(identifier)) [0035-8711](https://search.worldcat.org/issn/0035-8711).

1. **[^](#cite_ref-SIMBAD_7-0)** ["gam Sgr -- Variable Star"](http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Epsilon+Lupi), *SIMBAD*, [Centre de Données astronomiques de Strasbourg](/source/Centre_de_Donn%C3%A9es_astronomiques_de_Strasbourg), retrieved 2012-01-08

1. **[^](#cite_ref-ratio_8-0)** The ratio of the periapsis (rp) to the apoapsis (ra) is given by: 1. r p r a = 1 − e 1 + e = 0.723 1.277 = 0.566 {\displaystyle {{r_{p}} \over {r_{a}}}={{1-e} \over {1+e}}={{0.723} \over {1.277}}=0.566} where *e* is the ellipticity.

v t e Constellation of Lupus List of stars in Lupus Lupus in Chinese astronomy Stars Bayer α (Uridim) β γ δ ε ζ η θ ι κ λ μ ν1 ν2 ξ ο π ρ σ τ1 τ2 υ φ1 φ2 χ ψ1 ψ2 ω Flamsteed 1 (i) 2 (f) Variable RU EX GG GQ HR II IL IM KT (d) V407 V462 HR 5362 5364 5401 5651 (e) 5724 (k) 5825 (g) 5943 5967 HD 134004 135344 136164 141943 142527 143811 Other Gliese 588 HIP 70849 Lupus-TR-3 SSSPM J1549−3544 WASP-132 Exoplanets GQ Lupi b HIP 70849 b Lupus-TR-3b WASP-178b Star clusters NGC 5749 NGC 5822 NGC 5824 NGC 5927 NGC 5986 Nebulae IC 4406 NGC 5882 Galaxies IC 4444 NGC 5530 NGC 5643 Astronomical events SN 1006 Category

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Adapted from the Wikipedia article [Epsilon Lupi](https://en.wikipedia.org/wiki/Epsilon_Lupi) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Epsilon_Lupi?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.