13 Monocerotis

13 Monocerotis (13 Mon) is a class A0 Ib (white supergiant) star in the constellation Monoceros. Its apparent magnitude is 4.5 and it is approximately 780 parsecs (2,500 ly) away.

13 Monocerotis

Location of 13 Monocerotis (circled red)
Observation data Epoch J2000      Equinox J2000
Constellation	Monoceros
Right ascension	06h 32m 54.22948s[1]
Declination	07° 19′ 58.6942″[1]
Apparent magnitude (V)	4.498[2]
Characteristics
Spectral type	A0 Ib[2]
U−B color index	−0.217[2]
B−V color index	+0.007[2]
Variable type	suspected[3]
Astrometry
Radial velocity (Rv)	+11.80[4] km/s
Proper motion (μ)	RA: -0.20[1] mas/yr Dec.: -3.48[1] mas/yr
Parallax (π)	0.83±0.46 mas[1]
Distance	780[5] pc
Absolute magnitude (MV)	−4.80[6]
Details
Mass	12.0[7] M☉
Radius	34[6] R☉
Surface gravity (log g)	2.15[2] cgs
Temperature	10,000[2] K
Metallicity [Fe/H]	−0.18[8] dex
Rotational velocity (v sin i)	0[2] km/s
Age	16[7] Myr
Other designations
BD+07 1337, FK5 1174, GC 8506, HIP 31216, HR 2385, HD 46300, NSV 16904, SAO 114034
Database references
SIMBAD	data

13 Mon lies within the Monoceros OB1 stellar association,^[6] halfway between the Rosette Nebula and NGC 2264, at a distance of about 780 parsecs.^[5] It is surrounded by a small reflection nebula listed as Van den Bergh 81 (VdB 81).^[9]

13 Monocerotis has been used as a standard star for the A0 Ib spectral class.^[10]

Extended photometry of 13 Monocerotis from 1997 to 2000 shows irregular variation of up to 0.04 magnitudes and also a slight trend to become fainter over the period.^[11] All the bright A0 - A5 supergiants analysed using Hipparcos satellite data were found to be variable, but 13 Mon was the least variable.^[12]