Pulsation of the Lambda Bootis star HD 210111

¹ Institut für Astronomie der Universität Wien, Türkenschanzstr. 17, 1180 Wien, Austria e-mail: michel.breger@univie.ac.at
² Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT, Australia e-mail: rshob@tpg.com.au

Received: 19 April 2006
Accepted: 12 May 2006

Abstract

Context.The λ Bootis stars are a small spectroscopic subgroup of Population I A-type stars and show significant underabundances of metals. Many are δ 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 h 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 cd^-1 and is probably a new γ Doradus variable. The observed wide range of excited frequencies from 12 to 30 cd^-1 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 cd^-1. 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  Tau.

Conclusions.The pulsation of the λ Bootis star HD 210111 does not differ from that of normal δ Scuti stars.