β Cephei variables¶
The β Cephei variables are early B-type stars that, like the slowly-pulsating B-type (SPB) stars, are unstable to pulsation because of an opacity bump caused by iron-group elements. Unlike the SPB stars, the pulsations are low-order pressure modes, like the δ Scuti variables but with a different driving mechanism. Many are multiperiodic and all have frequencies higher than about 3 cycles per day.