Epsilon Monocerotis

ε Monocerotis

Location of ε Monocerotis (circled red)
Observation data Epoch J2000      Equinox
Constellation	Monoceros
ε Mon A
Right ascension	06h 23m 46.08471s[1]
Declination	4° 35′ 34.3153″[1]
Apparent magnitude (V)	4.39[2]
ε Mon B
Right ascension	06h 23m 46.48292s[1]
Declination	4° 35′ 45.2307″[1]
Apparent magnitude (V)	6.72[2]
Characteristics
ε Mon A
Spectral type	class = A5 IV[3]
U−B color index	+0.14[4]
B−V color index	+0.20[4]
ε Mon B
Spectral type	F5 V[3]
U−B color index	−0.05[5]
B−V color index	+0.45[5]
Astrometry
ε Mon A
Radial velocity (Rv)	+13.10[6] km/s
Proper motion (μ)	RA: −22.06[1] mas/yr Dec.: +10.91[1] mas/yr
Parallax (π)	26.67 ± 0.90 mas[1]
Distance	122 ± 4 ly (37 ± 1 pc)
Absolute magnitude (MV)	1.52[2]
ε Mon B
Radial velocity (Rv)	+12.40[6] km/s
Proper motion (μ)	RA: −21.86[1] mas/yr Dec.: +11.35[1] mas/yr
Parallax (π)	26.95 ± 0.99 mas[1]
Distance	121 ± 4 ly (37 ± 1 pc)
Absolute magnitude (MV)	+3.88[2]
Details
ε Mon A
Mass	2.04[7] M☉
Radius	2.5[8] R☉
Luminosity	25[7] L☉
Surface gravity (log g)	3.95[9] cgs
Temperature	7,923[9] K
Metallicity [Fe/H]	−0.11[10] dex
Rotational velocity (v sin i)	149[7] km/s
ε Mon B
Mass	1.16[8] M☉
Radius	1.1[8] R☉
Luminosity	2.39[2] L☉
Surface gravity (log g)	3.95[9] cgs
Temperature	7,923[9] K
Rotational velocity (v sin i)	25[3] km/s
Other designations
ε Mon, 8 Monocerotis, CCDM J06237+0436, WDS J06238+0436
ε Mon A: BD+04° 1236, FK5 244, GC 8240, HD 44769, HIP 30419, HR 2298, SAO 113810
ε Mon B: BD+04° 1237, FK5 244, GC 8241, HD 44770, HIP 30422, HR 2299, SAO 113811
Database references
SIMBAD	data
SIMBAD	data

ε Monocerotis, Latinised as Epsilon Monocerotis, is the Bayer designation of a binary star system in the equatorial constellation Monoceros. Its location is a guide for sky navigation toward the Rosette Nebula.^[11]

The white-hued primary component has a stellar classification of A5 IV,^[3] suggesting it is an aging subgiant star. Its apparent magnitude is 4.39^[2] and it is approximately 122 light years away based on parallax.^[1] It is reportedly a spectroscopic binary with a period around 331 days.^[12]

The B component, at a separation of around 12.3",^[12] is a yellow-white hued F-type main-sequence star of class F5 V^[3] and an apparent magnitude of 6.72.^[2]