The Nainital-Cape Survey -- II:Report for pulsation in five chemically peculiar A-type stars and presentation of 140 null results

TL;DR

This survey investigated pulsations in chemically peculiar A-type stars, discovering three new variables and confirming null results for 140 stars, thereby enhancing understanding of stellar variability in this class.

Contribution

The paper reports the discovery of three new pulsating chemically peculiar A-type stars and provides a large set of null results, improving the data on stellar variability in these stars.

Findings

HD 113878 pulsates with a 2.31 hr period.

HD 118660 shows multi-periodic variability near 1 hr.

HD 207561 exhibits probable 6 min pulsations.

Abstract

To search photometric variability in chemically peculiar A type stars in the northern hemisphere. High-speed photometric observations of Ap and Am star candidates have been carried out from ARIES (Manora Peak, Nainital) using a three-channel fast photometer attached to the ARIES 104-cm Sampurnanand telescope. This paper presents three new variables: HD 113878, HD 118660 and HD 207561. During the time span of the survey (1999 December to 2004 January) pulsations of the $\delta$ Sct type were also found for the two evolved Am stars HD 102480 and HD 98851, as reported in Joshi et al. (2002, 2003). Additionally, we present 140 null results of the survey for this time span. The star HD 113878 pulsates with a period of 2.31 hr, which is typical of $\delta$ Sct stars. HD 118660 exhibits multi-periodic variability with a prominent period of nearly 1 hr. These periods need to be investigated and make HD 118660 a particularly interesting target for further observations. For HD 207561, a star classified as Am, a probable pulsation with a period of 6 min was found in the light curves obtained on two consecutive nights. Both HD 102480 and HD 98851 exhibit unusual alternating high and low amplitude maxima, with a period ratio of 2:1. The analysis of the null results confirms the photometric quality of the Nainital