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Session 46 - Variable Stars - Late Type.
Display session, Thursday, January 08
The seventh magnitude star VY Pyx was recently suggested to possibly be a Type II Cepheid. We present the first optical slit spectra of this object, and derive estimates of its log g and effective temperature. The spectra show some evidence of enhanced metallicity. We have derived the Fourier parameters of its light curve, which, along with other arguments, strongly suggest that it is a Type II Cepheid which is an overtone pulsator. However, various criteria give inconsistent indications as to whether it is pulsating in the first or second overtone. By a few measures, it falls outside the parameter plane regions of both the first and second overtone pulsators. Further, while VY Pyx meets a classical definition of s-Cepheids, its Fourier parameters place it apart from other s-Cepheids in the comparison plots used.
Program listing for Thursday