19 Monocerotis is a single,[12] variable star[4] in the equatorial constellation of Monoceros, located approximately 1,220 light years away from the Sun based on parallax.[1] It has the variable star designation V637 Monocerotis, while 19 Monocerotis is the Flamsteed designation. This object is visible to the naked eye as a faint, blue-white hued star with a baseline apparent visual magnitude of 5.00.[2] It is receding from the Earth with a heliocentric radial velocity of +25 km/s.[5]

19 Monocerotis

Location of 19 Monocerotis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Monoceros
Right ascension	07h 02m 54.77667s[1]
Declination	−04° 14′ 21.2377″[1]
Apparent magnitude (V)	5.00[2]
Characteristics
Spectral type	B1V[3]
U−B color index	−0.93[2]
B−V color index	−0.20[2]
Variable type	β Cep[4]
Astrometry
Radial velocity (Rv)	+24.80[5] km/s
Proper motion (μ)	RA: −5.05[1] mas/yr Dec.: +2.24[1] mas/yr
Parallax (π)	2.68 ± 0.22 mas[1]
Distance	1,220 ± 100 ly (370 ± 30 pc)
Absolute magnitude (MV)	−2.85[6]
Details
Mass	12.3[7] M☉
Radius	9±3[8] R☉
Luminosity	4,817[6] L☉
Surface gravity (log g)	3.662[9] cgs
Temperature	25,400[10] K
Rotational velocity (v sin i)	274±3[8] km/s
Other designations
19 Mon, V637 Mon, BD−04°1788, FK5 2547, GC 9293, HD 52918, HIP 33971, HR 2648, SAO 134106[11]
Database references
SIMBAD	data

This massive, B-type main-sequence star has a stellar classification of B1 V.[3] It is a Beta Cephei variable, ranging from 5.01 to 4.96 magnitude with a period of 0.19 days.[4] Closer examination shows there are three frequencies present, consisting of 5.22994, 0.17017, and 4.88956 cycles per day.[8] At one point it was thought to be a marginal Be star, but this was not confirmed.[8] The star is spinning rapidly with a projected rotational velocity of 274 km/s.[8] It has 12.3[7] times the mass of the Sun and is radiating 4,817[6] times the Sun's luminosity from its photosphere at an effective temperature of 25,400 K.[10]

References