HD 12098 – A new northern hemisphere roAp star

Abstract

We present the analysis of 65 hours of high speed photometric observations of HD 12098 taken from State Observatory, Naini Tal and Gurushikhar Observatory, Mt. Abu on sixteen nights spanning from November 1999 to November 2000. HD 12098 is the first rapidly oscillating Ap star discovered from the “Naini Tal-Cape survey for northern hemisphere roAp stars”. It is the 32nd in the complete list. HD 12098 exhibits one predominant mode of oscillation at ν₁ = 2.1738 mHz. The second-most significant frequency in our data is at ν₂ = 2.1641 mHz with a 1 cycle/day alias ambiguity. We argue that ν₂ is a rotational sidelobe of ν₁ , rather than an independent pulsation mode. Evidence for the presence of two other frequencies at 2.1807 and 2.3056 mHz is also presented.