FN Canis Majoris

FN Canis Majoris is a binary star^[4] system in the southern constellation Canis Major, near the northern constellation border with Monoceros. It is dimly visible to the naked eye with a combined apparent visual magnitude of 5.41.^[3] The system is located at a distance of approximately 3,000 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +31 km/s.^[3] It is a runaway star associated with the Sh 2-296 nebula in the CMa OB1 association, and has a conspicuous bow-shock feature.^[6]

FN Canis Majoris

A light curve for FN Canis Majoris from Hipparcos data. Adapted from Rivinius et al. (2011)[1]
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Canis Major
Right ascension	07h 06m 40.76672s[2]
Declination	−11° 17′ 38.4396″[2]
Apparent magnitude (V)	5.41[3] (5.69 + 7.04)[4]
Characteristics
Spectral type	B0 III/IV[5] or B2 Ia/ab[6]
B−V color index	0.033±0.004[3]
Astrometry
Radial velocity (Rv)	+31.0±4.2[3] km/s
Proper motion (μ)	RA: −3.14±0.72[2] mas/yr Dec.: +3.32±0.55[2] mas/yr
Parallax (π)	1.07±0.61 mas[2]
Distance	approx. 3,000 ly (approx. 900 pc)
Details
Mass	19.23±1.85,[7] 24.0±0.1,[8] 35.5±4.6[9] M☉
Luminosity (bolometric)	122,079,[7] 690,000[9] L☉
Surface gravity (log g)	3.59±0.11[9] cgs
Temperature	26,850,[7] 33,600±1,840[9] K
Rotational velocity (v sin i)	100±9[9] km/s
Age	6.0±0.1[8] Myr
Other designations
FN CMa, BD−11°1790, GC 9389, HD 53974, HIP 34301, HR 2678, SAO 152394, WDS J07067-1118[10]
Database references
SIMBAD	data

The brighter component is a visual magnitude 5.69^[4] B-type star that has been assigned various stellar classification from B0 III/IV^[5] to B2 Ia/ab,^[6] suggesting it is an evolved state. In 1967, Graham Hill announced his discovery that the star, then known as HD 53974, is a variable star.^[11] It was given its variable star designation, FN Canis Majoris, in 1970.^[12] In the past it was classified as a Beta Cephei type variable star^[11] with an apparent magnitude that was measured varying between +5.38 and +5.42 over a period of 36.7 hours,^[13] but is no longer considered to be one.^[14] This is a massive star with estimates ranging from 19^[7] to 36^[9] times the mass of the Sun, and luminosity estimates of 122,079^[7] to 690,000^[9] times the Sun's luminosity. The magnitude 7.04^[4] companion is located at an angular separation of 0.60″ from the primary at a position angle of 111°, as of 2003.^[15]