[vsnet-chat 1145] EX Hya ephemeris

[Taichi Kato <tkato>]

(Re: vsnet-chat 1140)

W. S. G. Walker wrote:

> Bill Allen and I have been CCD monitoring EX Hydrae along with other DN
> during
> the last few months. The eclipse events measured (20 to 30) are close to
> the predicted times. However the 67 minute cycle which is visible as a
> sinusoidal wave with an amplitude of ~0.5 to 0.7 magnitudes is rather
> different to the GCVS ephemeris - which dates back to 1979 - and we'd be
> interested in any more recent information on this. 

  In IBVS 3724, C. Hellier and L. N. Sproats give the following ephemerides:

  TDB_eclipse = 2437699.94179 + 0.068233846 E
   (with a sinusoidal term of 0.00028 d)

  TDB_67_max = 2437699.8914(5) + 0.046546504(9) E - 7.9(4)x10^-13 E^2
  (spin maximum)

  Please note the time is expressed in TDB.

Regards,
Taichi Kato

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