Epsilon Normae

Epsilon Normae, Latinised from ε Normae, is a blue-white hued triple star^[5] 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.^[7]

Epsilon Normae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Norma
A
Right ascension	16h 27m 11.03611s[1]
Declination	−47° 33′ 17.2226″[1]
Apparent magnitude (V)	4.47[2]
B
Right ascension	16h 27m 10.06643s[3]
Declination	−47° 32′ 56.6763″[3]
Apparent magnitude (V)	6.13[4]
Characteristics
Spectral type	B4 V + B4 V + B9 V[5]
U−B color index	−0.54[2]
B−V color index	−0.07[2]
Astrometry
A
Radial velocity (Rv)	−12.5±2.7[6] 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[7]
B
Radial velocity (Rv)	−6.67±0.83[3] km/s
Proper motion (μ)	RA: −10.393[3] mas/yr Dec.: −20.277[3] mas/yr
Parallax (π)	5.4467±0.0299 mas[3]
Distance	599 ± 3 ly (184 ± 1 pc)
Orbit[8]
Primary	Aa
Companion	Ab
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
Aa
Mass	7.7[9] M☉
Ab
Mass	4.5[9] M☉
B
Mass	2.3[9] M☉
Radius	2.4[3] R☉
Luminosity	74[3] L☉
Surface gravity (log g)	4.00[3] cgs
Temperature	11,104[3] K
Other designations
ε Nor, CD−47°10765, HD 147971, HIP 80582, HR 6115, SAO 226773, WDS J16272-4733A[10]
B: HD 147970, HIP 80579[11]
Database references
SIMBAD	data
	B

The inner pair form a double-lined spectroscopic binary^[12] system with an orbital period of 3.26 days and an eccentricity of 0.13.^[8] Both stars appear to be similar B-type main-sequence stars with stellar classifications of B4 V.^[5]

The third component, at an angular separation of 22.8 arc seconds from the inner pair, is HD 147970. It is most likely is a smaller B-type main sequence star of spectral type B9V.^[5]