The hot Gamma-Doradus and Maia stars

Abstract

The hot ${\hat{I}}^3$~Doradus stars have multiple low frequencies characteristic of ${\hat{I}}^3$~Dor or SPB variables, but are located between the red edge of the SPB and the blue edge of the ${\hat{I}}^3$~Dor instability strips where all low-frequency modes are stable in current models of these stars. Though $\hat{I}´$~Sct stars also have low frequencies, there is no sign of high frequencies in hot ${\hat{I}}^3$~Dor stars. We obtained spectra to refine the locations of some of these stars in the H-R diagram and conclude that these are, indeed, anomalous pulsating stars. The Maia variables have multiple high frequencies characteristic of ${\hat{I}}^2$~Cep and $\hat{I}´$~Sct stars, but lie between the red edge of the ${\hat{I}}^2$~Cep and the blue edge of the $\hat{I}´$~Sct instability strips. We compile a list of all Maia candidates and obtain spectra of two of these stars. Again, it seems likely that these are anomalous pulsating stars which are currently not understood.

10 pages, 8 figures, 2016, MNRAS, 460, 1318