UW Canis Majoris

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UW Canis Majoris
Location of UW CMa (circled)
Observation data
J2000.0      Equinox
Constellation Canis Major
Right ascension 07h 18m 40.37894s[1]
Declination −24° 33′ 31.3182″[1]
Apparent magnitude (V) 4.95[2] (4.82 - 5.33[3])
Characteristics
Spectral type O7.5-8Iabf + O9.7Ib[4]
U−B color index −1.00[2]
B−V color index −0.15[2]
Variable type Beta Lyrae[3]
Distance
approx. 3,800 ly
(approx. 1,200 pc)
Absolute magnitude (MV)−6.1[6]
Longitude of the node
(Ω)		3.3-4.5°
Details
UW CMa A
Mass11-44 M☉
Radius12-20[7] R☉
Luminosity170,000-450,000[7] L☉
Temperature33,750[7] K
UW CMa B
Mass17-33[7] M☉
Radius14-17[7] R☉
Luminosity240,000-330,000[7] L☉
Temperature33,300-33,700[7] K
SAO 173444, GC
 9734
Database references
SIMBADdata
NGC 2362 with UW CMa at the top (north) of the frame

UW Canis Majoris is a star in the constellation Canis Major. It is classified as a Beta Lyrae eclipsing contact binary and given the variable star designation UW Canis Majoris. Its brightness varies from magnitude +4.84 to +5.33 with a period of 4.39 days.[8] Bode had initially labelled it as Tau2 Canis Majoris, but this designation had been dropped by Gould and subsequent authors.[9]

A light curve for UW Canis Majoris from Hipparcos data, adapted from Antokhina et al. (2011)[7]

UW Canis Majoris A is a rare

luminosity 200,000 times that of the Sun as opposed to the secondary's 63,000 times. However the secondary is the more massive star at 19 Solar masses (M☉) compared to the primary's 16 M☉.[4]

However, a more recent photometric analysis finds several configurations of mass and luminosity ratios that match the observed data.[7]

Parallax measurements showed it to be approximately 3,000

mas,[1] corresponding to a distance of around 3,800 light years. It is thought to be a distant member of NGC 2362 which would place it about 5,000 light years and more closely match its expected luminosity. The contradiction between the different distance results is still a subject of research.[6]

UW Canis Majoris is part of the giant

Sh2-310 and it along with Tau Canis Majoris[11] which is the brightest member of NGC 2362,[12] HD 58011,[11] and VY Canis Majoris[13] are thought to be are thought to be probable sources of ionization of gases in Sh2-310.[11]

References

  1. ^
    S2CID 244398875
    . Gaia DR3 record for this source at VizieR.
  2. ^
    Bibcode:2002yCat.2237....0D
    .
  3. ^
    Bibcode:2009yCat....102025S
    .
  4. ^
    doi:10.1086/173822
    .
  5. S2CID 119387088
    .
  6. ^
    doi:10.1046/j.1365-8711.2000.03170.x
    .
  7. ^
    S2CID 118460690
    .
  8. JSTOR 40677088
    .
  9. ISBN 978-0-939923-78-6
    .
  10. S2CID 18759600
    .
  11. ^
    ISSN 0004-637X
    .
  12. ISSN 0004-6256
    .
  13. ISSN 0004-637X
    .
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