On the roAp star status of  Coronae Borealis

¹ Centre for Astrophysics, University of Central Lancashire, Preston PR1 2HE, UK e-mail: dwkurtz@uclan.ac.uk
² INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy e-mail: fleone@ct.astro.it

Received: 15 September 2005
Accepted: 1 August 2006

Abstract

β CrB is one of the best-studied of the magnetic Ap stars. Three independent investigations have suggested that this star is pulsating with a period of either 6.1 min, 11.5 min or 16.2 min, making this a rapidly oscillating Ap star. The presence of pulsations in β CrB has important implications for the understanding of pulsation driving and damping in roAp stars, and each study has called for additional observations to confirm the suggested pulsations. New high time resolution, high spectral resolution, high signal-to-noise spectra of β CrB obtained with the high resolution spectrograph SARG on the 3.55-m Telescopio Nazionale Galileo are unable to confirm any of the suggested periods. There is no indication of any variability with a period near 6.1 min. Studies of Fe i lines suggest that the 11.5-min period is spurious. Studies of Ce ii lines do not find the 16.2-min period suggested for one Ce ii line, but are not precise enough to test the finding of 16.2-min oscillations for a large section of spectrum, hence the case for the 16.2-min period is still good. An extensive investigation of β CrB is needed to resolve the issue.