HD 37756

Location of HD 37756 (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Orion[1]
Right ascension	05h 40m 50.71498s[2]
Declination	−01° 07′ 43.6366″[2]
Apparent magnitude (V)	4.95[1]
Characteristics
primary
Spectral type	B2IV-V[3] or B3V[4]
U−B color index	−0.83[5]
B−V color index	−0.21[5]
secondary
Spectral type	B1[6]
Astrometry
Radial velocity (Rv)	+26.10[7] km/s
Proper motion (μ)	RA: −1.50[2] mas/yr Dec.: −0.84[2] mas/yr
Parallax (π)	3.63±0.37 mas[2]
Distance	approx. 900 ly (approx. 280 pc)
Absolute magnitude (MV)	−2.74[1]
Orbit[8]
Period (P)	27.154925 d
Eccentricity (e)	0.739±0.007
Periastron epoch (T)	2,447,886.076±0.065 HJD
Argument of periastron (ω) (secondary)	81.4±2.4°
Semi-amplitude (K1) (primary)	84.7±1.1 km/s
Details
A
Mass	13.0[6] M☉
B
Mass	8.3[6] M☉
Other designations
NSV 2556, BD−01°1004, GC 7091, HD 37756, HIP 26736, HR 1952, SAO 132445[9]
Database references
SIMBAD	data

HD 37756 is a binary star system in the equatorial constellation of Orion, positioned less than a degree to the north of the bright star Alnitak.^[10] It has a blue-white hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.95.^[1] The system is located at a distance of approximately 900 light-years from the Sun based on parallax,^[2] and is drifting further away with a radial velocity of +26 km/s.^[7] It is a member of the OB1b subgroup of the Orion OB1 association.^[11]

The binary nature of this system was identified by E. B. Frost in 1906.^[12] It is a double-lined spectroscopic binary with an orbital period of 27.15 days and a high eccentricity of 0.74.^[8] The spectrum matches a massive B-type main-sequence star with a stellar classification of B3V.^[4] The secondary is luminous enough to interfere with measurements of the primary spectrum.^[12] It is a suspected Beta Cephei variable with a period of 0.37968 days and an amplitude of 0.03 magnitude in the B band of the UBV photometric system.^[13] The system is a candidate eclipsing binary with a minimum dip of 0.04 in visual magnitude during each orbit.^[14]

References