New β Cep pulsators discovered with K2 space photometry

Abstract

We present the discovery of three new β Cep pulsators, three new pulsators with frequency groupings, and frequency patterns in a B3Ib star, all of which show pulsations with frequencies as high as about 17 d−1, with K2 space mission photometry. Based on a Fourier analysis and iterative pre-whitening, we present a classification and evaluate the potential for asteroseismic modelling. We include the lists of pulsation frequencies for three new β Cep pulsators, CD-28 12286, CD-27 10876, LS 3978, and additional pulsation mode frequencies for the known β Cep pulsator HD 164741. In addition, we characterize the regular frequency spacing found in the new pulsator HD 169173, and discuss its origin. We place the newly discovered variables in a colour-magnitude diagram using parallaxes from Gaia DR2 (second data release), showcasing their approximate location in the massive star domain. The identified frequency lists of these multiperiodic pulsators are a good starting point for future forward seismic modelling, after identification of at least one pulsation frequency from high-resolution time-series spectroscopy and/or multicolour photometry.