The Hvar survey for roAp stars: II. Final results (Research Note)

TL;DR

This survey aimed to find new rapidly oscillating Ap stars using CCD photometry but detected none, highlighting the need for combined spectroscopic and photometric approaches to identify pulsationally unstable stars.

Contribution

The study provides new CCD photometric data for 21 roAp candidates and establishes upper limits for pulsations, contributing to the understanding of pulsation detection limits in these stars.

Findings

No new roAp stars detected in the sample.

Upper limits for pulsations are comparable to previous studies.

Emphasizes the need for spectroscopic data to improve target selection.

Abstract

The 60 known rapidly oscillating Ap (roAp) stars are excellent laboratories to test pulsation models in the presence of stellar magnetic fields. Our survey is dedicated to search for new group members in the Northern Hemisphere. We attempt to increase the number of known chemically peculiar stars that are known to be pulsationally unstable. About 40 h of new CCD photometric data of 21 roAp candidates, observed at the 1m Austrian-Croatian Telescope (Hvar Observatory) are presented. We carefully analysed these to search for pulsations in the frequency range of up to 10mHz. No new roAp star was detected among the observed targets. The distribution of the upper limits for roAp-like variations is similar to that of previoius similar efforts using photomultipliers and comparable telescope sizes. In addition to photometric observations, we need to consolidate spectroscopic information to select suitable targets.