Epsilon Normae

Epsilon Normae, Latinised from ε Normae, is a blue-white hued triple star^[3] system in the southern constellation of Norma. It has an apparent visual magnitude of 4.47,^[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 6.15 mas as seen from Earth,^[1] the system is located around 530 light years distant from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.21 due to interstellar dust.^[5]

Epsilon Normae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Norma
Right ascension	16h 27m 11.03611s[1]
Declination	−47° 33′ 17.2226″[1]
Apparent magnitude (V)	4.47[2]
Characteristics
Spectral type	B4 V + B4 V + B9 V[3]
U−B color index	−0.54[2]
B−V color index	−0.07[2]
Astrometry
Radial velocity (Rv)	−12.5±2.7[4] km/s
Proper motion (μ)	RA: −13.68±0.27[1] mas/yr Dec.: −19.89±0.20[1] mas/yr
Parallax (π)	6.15 ± 0.28 mas[1]
Distance	530 ± 20 ly (163 ± 7 pc)
Absolute magnitude (MV)	0.06[5]
Orbit[6]
Period (P)	3.2617 d
Eccentricity (e)	0.13
Periastron epoch (T)	2438825.9310 JD
Argument of periastron (ω) (secondary)	271.5°
Semi-amplitude (K1) (primary)	122.5 km/s
Semi-amplitude (K2) (secondary)	132.9 km/s
Details
Mass	6.4±0.2[7] M☉
Luminosity	474[8] L☉
Temperature	10,888[8] K
Age	50.1±14.0[7] Myr
Other designations
ε Nor, CD−47° 10765, HD 147971, HIP 80582, HR 6115, SAO 226773, WDS J16272-4733A[9]
Database references
SIMBAD	data

The inner pair form a double-lined spectroscopic binary^[10] system with an orbital period of 3.26 days and an eccentricity of 0.13.^[6] Both stars appear to be similar B-type main-sequence stars with stellar classifications of B4 V.^[3] The third component has an angular separation of 22.8 arc seconds from the inner pair, and most likely is a smaller B-type main sequence star of spectral type B9V.^[3] The system is relatively young, with an estimated age of around 50 million years.^[7]

References

1. van Leeuwen, F. (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. Johnson, H. L. (1966), "UBVRIJKL Photometry of the Bright Stars", Communications of the Lunar and Planetary Laboratory, 4: 99, Bibcode:1966CoLPL...4...99J.
3. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
4. 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, S2CID 59451347, A61.
5. Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID 119108982.
6. Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
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, S2CID 118629873.
8. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
9. "eps Nor". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-12.{{cite web}}: CS1 maint: postscript (link)
10. Chini, R.; et al. (2012), "A spectroscopic survey on the multiplicity of high-mass stars", Monthly Notices of the Royal Astronomical Society, 424 (3): 1925, arXiv:1205.5238, Bibcode:2012MNRAS.424.1925C, doi:10.1111/j.1365-2966.2012.21317.x, S2CID 119120749.