Observations of epsilon Cep from Two Sites

Summary

Epsilon Cep (HR 8494, V=4.19, F0IV, v sin i = 86 km/s) is a bright, rapidly rotating, multi-periodic Delta Scuti star which has thus far received only limited attention. Photometric observations have been acquired and analyzed on a few occasions (e.g., Breger (1969), Fesen (1973), Lopez de Coca et al. (1979), Percy (1979), and Seeds and Price (1983)). These studies show evidence for multiperiodicity in terms of amplitude variations and suggest a principle pulsation period of about 0.042 days. There is also evidence for a second period at 0.068 days and these two identifications agree with the values expected for the second overtone and fundamental radial modes of oscillation. In addition, radial velocity variations consistent with the 0.042-day period but with a rather large amplitude have been measured by Gray (1970) and evidence for line-profile variations with similar periods (but owing to high-degree modes) have been reported by Kennelly and Walker (1991) and Baade et al. (1993).

In September 1994, an intensive investigation of epsilon Cep was carried out with spectroscopic observations from Mt Hopkins Observatory (with the AFOE) and from the Dominion Astrophysical Observatory. Using a new Doppler Deconvolution technique to model the broadening function of each spectrum in the time series, very high quality representation of the star's line profile variations was obtained.

The above figure was derived from the AFOE observations of epsilon Cep and shows the residual pattern of line-profile variations after subtracting the mean profile. In the simpler case of a single mode, the number of bumps in the profiles would be related to the degree of oscillation, but for epsilon Cep, the complex pattern is indicative of multiperiodic oscillations with periods between 0.03 and 0.07 cycles per day. Unfortunately, problems resulting from the presense of the daily gaps in this data has made the isolation of individual frequencies extremely difficult. Final results are still in preparation.

References

  1. Baade, D., Bardelli, S., Beaulieu, J.Ph., and Vogel, S. 1993, A&A 269, 195
  2. Breger, M. 1966, ApJ 146, 958
  3. Fesen, R.A. 1973, PASP 85, 732
  4. Gray, D.F. 1970, PASP 83, 103
  5. Kennelly, E.J. and Walker, G.A.H. 1991, CFHT Inform. Bull. No 25, p. 17
  6. Lopez de Coca, P., Costa, V., Rolland, A., and Walker, E.N. 1979, A&AS 36, 61
  7. Percy, J.R. 1977, MNRAS 181, 647
  8. Seeds, M.A. and Price, C.W. 1983, IBVS 2278
____________________________________________
Edward J. Kennelly (kennelly@hao.ucar.edu)
Last modified: Thu May 1 17:41:12 1997