HD 37756
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. It has a blue-white hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.95. The system is located at a distance of approximately 900 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +26 km/s. It is a member of the OB1b subgroup of the Orion OB1 association.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 40m 50.71498s |
| Declination | −01° 07′ 43.6366″ |
| Apparent magnitude (V) | 4.95 |
| Characteristics | |
| primary | |
| Spectral type | B2IV-V or B3V |
| U−B color index | −0.83 |
| B−V color index | −0.21 |
| secondary | |
| Spectral type | B1 |
| Astrometry | |
| Radial velocity (Rv) | +26.10 km/s |
| Proper motion (μ) | RA: −1.50 mas/yr Dec.: −0.84 mas/yr |
| Parallax (π) | 3.63 ± 0.37 mas |
| Distance | approx. 900 ly (approx. 280 pc) |
| Absolute magnitude (MV) | −2.74 |
| Orbit | |
| Period (P) | 27.154925 d |
| Eccentricity (e) | 0.739±0.007 |
| Periastron epoch (T) | 2447886.076±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 | 8.6±0.2 M☉ |
| Radius | 5.3 R☉ |
| Luminosity | 4,830 L☉ |
| Surface gravity (log g) | 3.84 cgs |
| Temperature | 21,150 K |
| Metallicity [Fe/H] | +0.01 dex |
| Rotational velocity (v sin i) | 75 km/s |
| Age | 18.0±3.2 Myr |
| B | |
| Mass | 8.3 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The binary nature of this system was identified by E. B. Frost in 1904. It is a double-lined spectroscopic binary with an orbital period of 27.15 days and a high eccentricity of 0.74. The spectrum matches a massive B-type main-sequence star with a stellar classification of B3V. The secondary is luminous enough to interfere with measurements of the primary spectrum. It is a suspected Cepheid variable with a period of 0.37968 days and an amplitude of 0.03 magnitude in the B band of the UBV photometric system. The system is a candidate eclipsing binary with a minimum dip of 0.04 in visual magnitude during each orbit.