Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Canis Major |
Right ascension | 06h 54m 13.04410s [1] |
Declination | −23° 55′ 42.0150″ [1] |
Apparent magnitude (V) | 6.91 [2] 6.71 to 6.95 [3] |
Characteristics | |
Spectral type | WN4-s [4] |
U−B color index | −0.89 [2] |
B−V color index | −0.28 [2] |
Variable type | UGZ? [3] |
Astrometry | |
Proper motion (μ) |
RA: −4.431±0.057
[5]
mas/
yr Dec.: 2.884±0.092 [5] mas/ yr |
Parallax (π) | 0.4119 ± 0.0503 mas [5] |
Distance | 4,900
ly (1,500 [6] pc) |
Absolute magnitude (MV) | −5.33 [4] |
Orbit [7] | |
Period (P) | 3.63 d |
Semi-major axis (a) | 0.13 au |
Eccentricity (e) | 0.10 |
Inclination (i) | 74° |
Details | |
WR | |
Mass | 23 [4] M☉ |
Radius | 3.25 [4] R☉ |
Luminosity (bolometric) | 620,000 [4] L☉ |
Temperature | 89,100 [4] K |
companion | |
Mass | 1.5 [7] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
EZ Canis Majoris (abbreviated to EZ CMa, also designated as WR 6) is binary system in the constellation of Canis Major. The primary is a Wolf-Rayet star and it is one of the ten brightest Wolf-Rayet stars, brighter than apparent magnitude 7. [8]
EZ CMa has an apparent visual magnitude which varies between 6.71 and 6.95 over a period of 3.766 days, along with changes in the spectrum. [9] It has been proposed that it could be a binary star, with a neutron star as companion that would complete an orbit around the Wolf-Rayet with that period, being the cause of those variations. The General Catalogue of Variable Stars lists it as a possible cataclysmic variable on this basis. It has been argued that the companion does not exist and spectral variations are caused by activity on the star's surface. [9]
Observations of the light variations over a four-month period from late 2015 to early 2016 confirmed the clear 3.76 d variations. This was interpreted as a 3.66 d orbital period with rapid apsidal precession completing a full rotation in about 100 days. The orbit is inclined at around 60–74 degrees and there are two eclipses during each orbit. [7]
The spectral type of WN4 indicates an extremely hot star, and this leads to a very high luminosity, mostly emitted as ultraviolet radiation. The spectrum shows a star entirely devoid of hydrogen at the surface. [4]
EZ CMa is surrounded by a faint bubble nebula, a small HII region blown by stellar winds up to 1,700 km/s and ionised by the intense UV radiation. This is catalogued as Sharpless Sh2-308, or just S308. [6] It is likely to be a member of the very scattered open cluster Collinder 121, found around the orange supergiant ο1 CMa.
Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Canis Major |
Right ascension | 06h 54m 13.04410s [1] |
Declination | −23° 55′ 42.0150″ [1] |
Apparent magnitude (V) | 6.91 [2] 6.71 to 6.95 [3] |
Characteristics | |
Spectral type | WN4-s [4] |
U−B color index | −0.89 [2] |
B−V color index | −0.28 [2] |
Variable type | UGZ? [3] |
Astrometry | |
Proper motion (μ) |
RA: −4.431±0.057
[5]
mas/
yr Dec.: 2.884±0.092 [5] mas/ yr |
Parallax (π) | 0.4119 ± 0.0503 mas [5] |
Distance | 4,900
ly (1,500 [6] pc) |
Absolute magnitude (MV) | −5.33 [4] |
Orbit [7] | |
Period (P) | 3.63 d |
Semi-major axis (a) | 0.13 au |
Eccentricity (e) | 0.10 |
Inclination (i) | 74° |
Details | |
WR | |
Mass | 23 [4] M☉ |
Radius | 3.25 [4] R☉ |
Luminosity (bolometric) | 620,000 [4] L☉ |
Temperature | 89,100 [4] K |
companion | |
Mass | 1.5 [7] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
EZ Canis Majoris (abbreviated to EZ CMa, also designated as WR 6) is binary system in the constellation of Canis Major. The primary is a Wolf-Rayet star and it is one of the ten brightest Wolf-Rayet stars, brighter than apparent magnitude 7. [8]
EZ CMa has an apparent visual magnitude which varies between 6.71 and 6.95 over a period of 3.766 days, along with changes in the spectrum. [9] It has been proposed that it could be a binary star, with a neutron star as companion that would complete an orbit around the Wolf-Rayet with that period, being the cause of those variations. The General Catalogue of Variable Stars lists it as a possible cataclysmic variable on this basis. It has been argued that the companion does not exist and spectral variations are caused by activity on the star's surface. [9]
Observations of the light variations over a four-month period from late 2015 to early 2016 confirmed the clear 3.76 d variations. This was interpreted as a 3.66 d orbital period with rapid apsidal precession completing a full rotation in about 100 days. The orbit is inclined at around 60–74 degrees and there are two eclipses during each orbit. [7]
The spectral type of WN4 indicates an extremely hot star, and this leads to a very high luminosity, mostly emitted as ultraviolet radiation. The spectrum shows a star entirely devoid of hydrogen at the surface. [4]
EZ CMa is surrounded by a faint bubble nebula, a small HII region blown by stellar winds up to 1,700 km/s and ionised by the intense UV radiation. This is catalogued as Sharpless Sh2-308, or just S308. [6] It is likely to be a member of the very scattered open cluster Collinder 121, found around the orange supergiant ο1 CMa.