27 Canis Majoris
Binary star system in the constellation Canis Major
From Wikipedia, the free encyclopedia
27 Canis Majoris is a binary star[3] system in the northern constellation of Canis Major,[10] located approximately 1,700 light years away from the Sun.[1] It has the variable star designation EW Canis Majoris;[2] 27 Canis Majoris is the Flamsteed designation. This system is visible to the naked eye as a 4th-magnitude,[2] blue-white hued star. It is moving away from the Earth with a heliocentric radial velocity of 16 km/s.[5]
  | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 14m 15.21192s[1] |
| Declination | −26° 21′ 09.0312″[1] |
| Apparent magnitude (V) | +4.62 – 4.82[2] (+4.92 + 5.39)[3] |
| Characteristics | |
| Spectral type | B3 IIIpe[4] |
| B−V color index | −0.17±0.16[5] |
| Variable type | γ Cas + β Cep:[2] |
| Astrometry | |
| Radial velocity (Rv) | 16.3±3.6[5] km/s |
| Proper motion (μ) | RA: −6.91[1] mas/yr Dec.: +3.17[1] mas/yr |
| Parallax (π) | 1.88±0.32 mas[1] |
| Distance | approx. 1,700 ly (approx. 530 pc) |
| Absolute magnitude (MV) | −4.13[5] |
| Orbit[6] | |
| Period (P) | 118.54±11.14 yr |
| Semi-major axis (a) | 0.178±0.012″ |
| Eccentricity (e) | 0.747±0.094 |
| Inclination (i) | 80.2±1.0° |
| Longitude of the node (Ω) | 131.3±3.0° |
| Periastron epoch (T) | 1,971.01±0.74 |
| Argument of periastron (ω) (secondary) | 85.0±3.6° |
| Details | |
| 27 CMa A | |
| Mass | 12.5±2.5[7] M☉ |
| Luminosity (bolometric) | 15,610[8] L☉ |
| Surface gravity (log g) | 3.514[9] cgs |
| Temperature | 21,061[9] K |
| Rotational velocity (v sin i) | 290[9] km/s |
| Age | 0.1±0.1[7] Myr |
| Other designations | |
| 27 CMa, EW Canis Majoris, CD−26°4057, GC 9608, HD 56014, HIP 34981, HR 2745, SAO 173264, CCDM J07143-2621, WDS J07143-2621[10] | |
| Database references | |
| SIMBAD | data |
The pair of stars in this system were first resolved by W. S. Finsen in 1953, and the split has been widening since that time.[13] The system has an orbital period of around 119 years with an eccentricity of 0.7 and a semimajor axis of 0.178″.[6] The magnitude 4.92[3] primary, designated component A, is a Be star with a stellar classification of B3 IIIpe.[4] It is spinning rapidly with a projected rotational velocity of 290 km/s, compared to a critical velocity of 389 km/s.[9] The star appears to be a Beta Cephei variable[14] with a pulsation period of 0.0919 days and an amplitude of 0.0080 in magnitude.[15]
The magnitude 5.39[3] secondary, component B, is classified as a Gamma Cassiopeiae type variable star. Due to its variable nature, the brightness of the system varies from magnitude +4.42 to +4.82.[2]