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Gamma Cassiopeiae




name=Gamma Cassiopeiae }}
  Epoch J2000
  Ra 00<sup>h</sup> 56<sup>m</sup> 425<sup>s</sup>
  Dec +60&deg 43&prime 00&Prime
  Appmag V 215


  Class B05 IVe
  B-v -015
  U-b -108


  Radial V -7
  Prop Mo Ra 2565
  Prop Mo Dec -382
  Parallax 532
  P Error 056
  Dist Ly 613
  Dist Pc 188


  Mass 15
  Radius
  Luminosity 70,000
  Temperature 25,000
  Metal
  Rotation >300 km/sec





Gamma Cassiopeiae (γ Cas / γ Cassiopeiae) is an eruptive Variable Star , whose brightness changes irregularly between +2.20 mag and +3.40 mag. Although it is a fairly bright star, it has no traditional Arabic or Latin name. In Chinese , however, it has the name ''Tsih'', meaning "the whip". It is located at the center of the distinctive "W" shape that forms the Cassiopeia Constellation .

The apparent magnitude of this star was +2.2 mag in 1937, +3.4 mag in 1940, +2.9 mag in 1949, +2.7 mag in 1965 and now it is +2.15 mag. Normally a gamma (γ) designation is assigned to the third-brightest star within a particular Constellation . At maximum intensity though, Gamma Cassiopeiae outshines both the alpha ( Schedir , magnitude 2.25) and beta ( Caph , magnitude 2.3) stars in Cassiopeia .

This is a rapidly spinning star that bulges outward along the equator. When combined with the high luminosity, the result is mass loss that forms a disk around the star. The emissions and brightness variations are apparently caused by this disk.

Gamma Cassiopeiae is also a bright source of X-ray s, and is a Spectroscopic Binary . The companion has an orbital period of 203.59 days with an Eccentricity (e) of 0.26. The mass of the companion is believed to be similar to our own Sun (Harmanec et al. 2000). The X-ray emission could be explained if the companion were a dense object with a high surface gravity, such as a White Dwarf or a Neutron Star . The escaping gas from Gamma Cassiopeiae could accrete on the surface of the companion, transforming gravitational potential into thermal energy.

This is also a visual double star system, with the designation of ADS782AB.


REFERENCES

  • P. Harmanec, P. ''et al'', "Binary Nature and Orbital Elements of Gamma Cas", 2000, ''Astronomy and Astrophysics'', 364, L85.



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