Pulsation of the Lambda Bootis star HD 210111
  CONTEXT. The Lambda Bootis stars are a small spectroscopic subgroup of Population I A-type stars and show significant underabundances of metals. Many are Delta Scuti pulsators.   AIMS. HD 210111 was selected for a detailed multisite pulsation study to determine whether its pulsation properties differ from those of normal A stars.   METHODS. 262 hours of high-precision photometry were obtained at the SAAO and SSO observatories.   RESULTS. 13 statistically significant pulsation frequencies were detected with very small photometric amplitudes from 1 to 7 millimag in the visual. A comparison with earlier 1994 measurements indicates a small increase in amplitude. As a byproduct, one of the comparison stars, HD 210571, was discovered to be a millimag variable with a frequency of 1.235 c/d and is probably a new Gamma Doradus variable. The observed wide range of excited frequencies from 12 to 30 c/d in HD 210111 can be explained with both the single- and double-star hypothesis. HD 210111 is in a similar evolutionary status to FG Vir, which also shows a wide range of excited frequencies with a similar frequency spacing near 4 c/d. This is interpreted as successive radial orders of the excited nonradial modes. In the double-star hypothesis previously evoked for HD 210111, the low and the high frequencies originate in different stars: here HD 210111 would resemble Theta^2 Tau.   CONCLUSIONS. The pulsation of the Lambda Bootis star HD 210111 does not differ from that of normal Delta Scuti stars. 
M. Breger, P. Beck, P. Lenz, L. Schmitzberger, E. Guggenberger, R. R.   Shobbrook