The Nainital-Cape Survey

IV. A search for pulsational variability in 108 chemically peculiar stars^⋆

¹ Aryabhatta Research Institute of Observational Sciences, Manora peak, 263129 Nainital, India
e-mail: santosh@aries.res.in
² SpaceLab, Department of Electrical Engineering, University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa
³ South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa
⁴ Department of Physics, Christ University, Hosur Road, 560029 Bangalore, Karnataka, India
⁵ School of Studies in Physics and Astrophysics, Pt Ravishankar Shukla University, 492 010 Raipur, India
⁶ Department of Physics, University of the North-West, Private Bag X2046, 2735 Mmabatho, South Africa
⁷ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, PR China

Received: 25 August 2015
Accepted: 7 March 2016

Abstract

Context. The Nainital-Cape Survey is a dedicated ongoing survey program to search for and study pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution.

Aims. The main aims of this survey are to find new pulsating Ap and Am stars in the northern and southern hemisphere and to perform asteroseismic studies of these new pulsators.

Methods. The survey is conducted using high-speed photometry. The candidate stars were selected on the basis of having Strömgren photometric indices similar to those of known pulsating CP stars.

Results. Over the last decade a total of 337 candidate pulsating CP stars were observed for the Nainital-Cape Survey, making it one of the longest ground-based surveys for pulsation in CP stars in terms of time span and sample size. The previous papers of this series presented seven new pulsating variables and 229 null results. In this paper we present the light curves, frequency spectra and various astrophysical parameters of the 108 additional CP stars observed since the last reported results. We also tabulated the basic physical parameters of the known roAp stars. As a part of establishing the detection limits in the Nainital-Cape Survey, we investigated the scintillation noise level at the two observing sites used in this survey, Sutherland and Nainital, by comparing the combined frequency spectra stars observed from each location. Our analysis shows that both the sites permit the detection of variations of the order of 0.6 milli-magnitude (mmag) in the frequency range 1–4 mHz, Sutherland is on average marginally better.