# Sigma Lupi

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B-type main-sequence star

Sigma Lupi Location of σ Lupi (circled in red) Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Lupus Right ascension 14h 32m 37.05667s[1] Declination −50° 27′ 25.7746″[1] Apparent magnitude (V) 4.416[2] Characteristics Spectral type B1/B2 V[2] U−B color index −0.84[3] B−V color index −0.19[3] Variable type Uncertain,[4][5] SX Arietis variable Astrometry Radial velocity (Rv) −1.5±2.7[6] km/s Proper motion (μ) RA: −29.26[1] mas/yr Dec.: −15.72[1] mas/yr Parallax (π) 5.67±0.19 mas[1] Distance 580 ± 20 ly (176 ± 6 pc) Absolute magnitude (MV) −1.79[7] Details[2] Mass 9.0±0.5 M☉ Radius 4.8±0.5 R☉ Luminosity 5,754 L☉ Surface gravity (log g) 4.02±0.10 cgs Temperature 23,000±550 K Rotation 3.01938±0.00022 d Rotational velocity (v sin i) 68±6 km/s Age 13.4 Myr Other designations σ Lup, CD−49°8831, HD 127381, HIP 71121, HR 5425, SAO 241781[8] Database references SIMBAD data

**Sigma Lupi**, [Latinized](/source/Latinisation_of_names) from **σ Lupi**, is a [star](/source/Star) in the southern [constellation](/source/Constellation) of [Lupus](/source/Lupus_(constellation)). It is visible to the [naked eye](/source/Naked_eye) with an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 4.4.[2] Based upon an annual [parallax shift](/source/Stellar_parallax) of 5.67 [mas](/source/Milliarcsecond) as seen from Earth,[1] it is located about 580 [light years](/source/Light_year) from the [Sun](/source/Sun). It is a member of the Upper Centaurus–Lupus subgroup of the nearby [Sco OB2](/source/Sco_OB2) association.[9] D. vander Linden and Christiaan L. Sterken discovered that the star is a [variable star](/source/Variable_star), based on data obtained in 1984, and announced their discovery in 1987.[10]

A [light curve](/source/Light_curve) for Sigma Lupi, plotted from *[TESS](/source/Transiting_Exoplanet_Survey_Satellite)* data[11]

This is a [B-type main sequence star](/source/B-type_main_sequence_star) with a [stellar classification](/source/Stellar_classification) of B1/B2 V. Sigma Lupi is a [Helium strong star](/source/Helium_star) with an enhanced abundance nitrogen and an underabundance of carbon.[2] Jerzykiewicz and Sterken (1992) showed a small amplitude variability with a period of 3.02 days. This suggests it is a close binary system forming a [rotating ellipsoidal variable](/source/Rotating_ellipsoidal_variable), although other causes such as [rotational modulation](/source/Rotational_modulation) can not be ruled out.[4] There is a higher frequency photometric variability with a rate of 10.93482 per day and an amplitude of 0.0031 in visual magnitude,[5] but the cause of this is unknown.[2]

At an age of just 13.4 million years, Sigma Lupi is spinning with a [projected rotational velocity](/source/Projected_rotational_velocity) of 68 km/s giving it a rotation period of 3.02 days. A [magnetic field](/source/Stellar_magnetic_field) has been detected with a polar field strength of around 500 [G](/source/Gauss_(unit)), which is varying longitudinally with an amplitude of around 100 G. The star has an estimated nine times the [mass of the Sun](/source/Solar_mass) and 4.8 times the [Sun's radius](/source/Solar_radius). It is radiating 5,754 times the [solar luminosity](/source/Solar_luminosity) from its [outer atmosphere](/source/Stellar_atmosphere) at an [effective temperature](/source/Effective_temperature) of around 23,000 K.[2]

## References

1. ^ [***a***](#cite_ref-vanLeeuwen2007_1-0) [***b***](#cite_ref-vanLeeuwen2007_1-1) [***c***](#cite_ref-vanLeeuwen2007_1-2) [***d***](#cite_ref-vanLeeuwen2007_1-3) [***e***](#cite_ref-vanLeeuwen2007_1-4) [***f***](#cite_ref-vanLeeuwen2007_1-5) van Leeuwen, F. (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-Henrichs2012_2-0) [***b***](#cite_ref-Henrichs2012_2-1) [***c***](#cite_ref-Henrichs2012_2-2) [***d***](#cite_ref-Henrichs2012_2-3) [***e***](#cite_ref-Henrichs2012_2-4) [***f***](#cite_ref-Henrichs2012_2-5) [***g***](#cite_ref-Henrichs2012_2-6) Henrichs, H. F.; et al. (September 2012), "Discovery of a magnetic field in the early B-type star σ Lupi", *Astronomy & Astrophysics*, **545**: 10, [arXiv](/source/ArXiv_(identifier)):[1208.4627](https://arxiv.org/abs/1208.4627), [Bibcode](/source/Bibcode_(identifier)):[2012A&A...545A.119H](https://ui.adsabs.harvard.edu/abs/2012A&A...545A.119H), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201219632](https://doi.org/10.1051%2F0004-6361%2F201219632), [S2CID](/source/S2CID_(identifier)) [54184191](https://api.semanticscholar.org/CorpusID:54184191), A119.

1. ^ [***a***](#cite_ref-Johnson1966_3-0) [***b***](#cite_ref-Johnson1966_3-1) Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", *Communications of the Lunar and Planetary Laboratory*, **4** (99): 99, [Bibcode](/source/Bibcode_(identifier)):[1966CoLPL...4...99J](https://ui.adsabs.harvard.edu/abs/1966CoLPL...4...99J).

1. ^ [***a***](#cite_ref-Jerzykiewicz1992_4-0) [***b***](#cite_ref-Jerzykiewicz1992_4-1) Jerzykiewicz, M.; Sterken, C. (August 1992), "Three periodic variables of early B spectral type", *Astronomy and Astrophysics*, **261** (2): 477–481, [Bibcode](/source/Bibcode_(identifier)):[1992A&A...261..477J](https://ui.adsabs.harvard.edu/abs/1992A&A...261..477J).

1. ^ [***a***](#cite_ref-koen2002_5-0) [***b***](#cite_ref-koen2002_5-1) Koen, Chris; Eyer, Laurent (2002), "New periodic variables from the Hipparcos epoch photometry", *Monthly Notices of the Royal Astronomical Society*, **331** (1): 45–59, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0112194](https://arxiv.org/abs/astro-ph/0112194), [Bibcode](/source/Bibcode_(identifier)):[2002MNRAS.331...45K](https://ui.adsabs.harvard.edu/abs/2002MNRAS.331...45K), [doi](/source/Doi_(identifier)):[10.1046/j.1365-8711.2002.05150.x](https://doi.org/10.1046%2Fj.1365-8711.2002.05150.x), [S2CID](/source/S2CID_(identifier)) [10505995](https://api.semanticscholar.org/CorpusID:10505995).

1. **[^](#cite_ref-deBruijne2012_6-0)** 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](/source/ArXiv_(identifier)):[1208.3048](https://arxiv.org/abs/1208.3048), [Bibcode](/source/Bibcode_(identifier)):[2012A&A...546A..61D](https://ui.adsabs.harvard.edu/abs/2012A&A...546A..61D), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201219219](https://doi.org/10.1051%2F0004-6361%2F201219219), [S2CID](/source/S2CID_(identifier)) [59451347](https://api.semanticscholar.org/CorpusID:59451347), A61.

1. **[^](#cite_ref-Anderson2012_7-0)** 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. **[^](#cite_ref-SIMBAD_8-0)** ["sig Lup -- Ellipsoidal variable Star"](https://simbad.u-strasbg.fr/simbad/sim-id?Ident=sig+Lup), *SIMBAD Astronomical Database*, Centre de Données astronomiques de Strasbourg, retrieved 2017-03-10.

1. **[^](#cite_ref-Hoogerwerf2000_9-0)** Hoogerwerf, Ronnie (March 2000), "OB association members in the ACT and TRC catalogues", *Monthly Notices of the Royal Astronomical Society*, **313** (1): 43–65, [Bibcode](/source/Bibcode_(identifier)):[2000MNRAS.313...43H](https://ui.adsabs.harvard.edu/abs/2000MNRAS.313...43H), [doi](/source/Doi_(identifier)):[10.1046/j.1365-8711.2000.03192.x](https://doi.org/10.1046%2Fj.1365-8711.2000.03192.x).

1. **[^](#cite_ref-Linden1987_10-0)** vander Linden, D.; Sterken, C. (May 1987). ["UVBY photometry of southern B- and A stars"](https://articles.adsabs.harvard.edu/pdf/1987A%26AS...69..157V). *Astronomy and Astrophysics, Suppl. Ser*. **69**: 157–169. [Bibcode](/source/Bibcode_(identifier)):[1987A&AS...69..157V](https://ui.adsabs.harvard.edu/abs/1987A&AS...69..157V). Retrieved 27 December 2024.

1. **[^](#cite_ref-MAST_11-0)** [*MAST: Barbara A. Mikulski Archive for Space Telescopes*](https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html), Space Telescope Science Institute, retrieved 26 September 2022.

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 [Sigma Lupi](https://en.wikipedia.org/wiki/Sigma_Lupi) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Sigma_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.