EZ Canis Majoris

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EZ Canis Majoris
Canis Major constellation map.svg
Red circle.svg
Location of EZ CMa (circled)
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
EZ  CMa, ALS  98, CD−23°4553, CEL  1426, Collinder  121 4, CPD−23°1588, GC  9061, HD  50896, Hen  3-20, HIP  33165, HR  2583, LBN  1052, MR  6, PPM  251223, SAO  172546, SH  2-308, TYC  6522-3270-1, WR  6
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]

Contents

Binary system

Detail of one edge of the bubble blown by EZ CMa. EZ CMa is off frame to the left (east). Sh2-308.jpg
Detail of one edge of the bubble blown by EZ CMa. EZ CMa is off frame to the left (east).

L. W. Ross announced his discovery that the star's brightness varies, in 1961. [9] 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. [10] 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. [10]

A light curve for EZ Canis Majoris, plotted from TESS data EZCMaLightCurve.png
A light curve for EZ Canis Majoris, plotted from TESS data

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]

Wolf Rayet star and nebula

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.

Related Research Articles

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Omicron<sup>1</sup> Canis Majoris Variable star in the constellation Canis Major

Omicron1 Canis Majoris is a red supergiant star in the constellation Canis Major. It is also a variable star.

<span class="mw-page-title-main">Y Carinae</span> Star in the constellation Carina

Y Carinae is a Classical Cepheid variable, a type of variable star, in the constellation Carina. Its apparent magnitude varies from 7.53 to 8.48.

<span class="mw-page-title-main">1 Vulpeculae</span> Star in the constellation Vulpecula

1 Vulpeculae is a class B4IV star in the constellation Vulpecula. Its apparent magnitude is 4.77 and it is approximately 780 light years away based on parallax.

<span class="mw-page-title-main">WR 136</span> Star in the constellation of Cygnus

WR 136 is a Wolf–Rayet star located in the constellation Cygnus. It is in the center of the Crescent Nebula. Its age is estimated to be around 4.7 million years and it is nearing the end of its life. Within a few hundred thousand years, it is expected to explode as a supernova.

<span class="mw-page-title-main">WR 46</span> Star in the constellation Crux

WR 46 is a Wolf-Rayet star in the constellation of the Southern Cross of apparent magnitude +10.8. It is located at 55 arcmin north of Theta2 Crucis. The star is a member of the distant stellar association Cru OB4, and is around 2,900 parsecs or 9,300 light years from the Solar System.

<span class="mw-page-title-main">WR 24</span> Wolf-Rayet star in the constellation Carina

WR 24 is a Wolf-Rayet star in the constellation Carina. It is one of the most luminous stars known. At the edge of naked eye visibility it is also one of the brightest Wolf Rayet stars in the sky.

<span class="mw-page-title-main">WR 148</span> Binary star in the constellation of Cygnus

WR 148 is a spectroscopic binary in the constellation Cygnus. The primary star is a Wolf–Rayet star and one of the most luminous stars known. The secondary has been suspected of being a stellar-mass black hole but may be a class O main sequence star.

<span class="mw-page-title-main">Sigma Ophiuchi</span> Star in the constellation Ophiuchus

Sigma Ophiuchi, Latinized from σ Ophiuchi, is a single, orange-hued star in the equatorial constellation Ophiuchus. Its apparent visual magnitude is 4.31, which is bright enough to be faintly visible to the naked eye. The annual parallax shift of 3.62 mas as seen from Earth provides a distance estimate of roughly 900 light years. It is moving closer to the Sun with a radial velocity of −28 km/s.

<span class="mw-page-title-main">QZ Puppis</span> Star in the constellation Puppis

QZ Puppis is a class B2.5V star in the constellation Puppis. Its apparent magnitude is 4.5 and it is approximately 650 light years away based on parallax.

<span class="mw-page-title-main">WR 134</span> Star in the constellation of Cygnus

WR 134 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus, surrounded by a faint bubble nebula blown by the intense radiation and fast wind from the star. It is five times the radius of the sun, but due to a temperature over 63,000 K it is 400,000 times as luminous as the Sun.

EQ Pegasi is a nearby binary system of two red dwarfs. Both components are flare stars, with spectral types of M4Ve and M6Ve respectively, and a current separation between the components of 5.8 arcseconds. The system is at a distance of 20.4 light-years, and is 950 million years old. The primary star is orbited by one known exoplanet.

<span class="mw-page-title-main">WR 20a</span> Star in the constellation Carina

WR 20a is an eclipsing binary star belonging to or recently ejected from the young, massive cluster Westerlund 2. It was discovered in 2004 to be one of the most massive binary systems known, for which the masses of the components have been accurately measured.

<span class="mw-page-title-main">CD Crucis</span> Eclipsing binary star system in the constellation Crux

CD Crucis, also known as HD 311884, is an eclipsing binary star system in the constellation Crux. It is around 14,000 light years away near the faint open cluster Hogg 15. The binary contains a Wolf–Rayet star and is also known as WR 47.

<span class="mw-page-title-main">WR 30a</span> Binary star in the constellation Carina

WR 30a is a massive spectroscopic binary in the Milky Way galaxy, in the constellation Carina. The primary is an extremely rare star on the WO oxygen sequence and the secondary a massive class O star. It appears near the Carina Nebula but is much further away.

<span class="mw-page-title-main">S Cassiopeiae</span> Star in the constellation Cassiopeia

S Cassiopeiae is a Mira variable and S-type star in the constellation Cassiopeia. It is an unusually cool star, rapidly losing mass and surrounded by dense gas and dust producing masers.

<span class="mw-page-title-main">WR 137</span> Star in the constellation of Cygnus

WR 137 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus.

<span class="mw-page-title-main">WR 9</span> Spectroscopic binary star system in the constellation Puppis

WR 9 is a spectroscopic binary in the constellation Puppis consisting of a Wolf-Rayet star and a class O star. It is around 12,000 light years away.

<span class="mw-page-title-main">HD 151932</span> Star in the constellation of Scorpius

HD 151932, also known as WR 78, is a Wolf-Rayet star located in the constellation Scorpius, close to the galactic plane. Its distance is around 1,300 parsecs away from the Earth. Despite being a blue-colored Wolf-Rayet star, it is extremely reddened by interstellar extinction, so its apparent magnitude is brighter for longer-wavelength passbands. HD 151932 lies about 22 west of the open cluster NGC 6231, the center of the OB association Scorpius OB1; it is not clear whether it is a part of the association or not. With an apparent magnitude of about 6.5, it is one of the few Wolf-Rayet stars that can be seen with the naked eye.

References

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  2. 1 2 3 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  3. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S.
  4. 1 2 3 4 5 6 7 Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy & Astrophysics. A57: 625. arXiv: 1904.04687 . Bibcode:2019A&A...625A..57H. doi:10.1051/0004-6361/201834850. S2CID   104292503.
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