Pulsation among TESS A and B stars and the Maia variables

Classification of over 50 000 TESS stars in sectors 1-18 has resulted in the detection of 766 pulsating main-sequence B stars as well as over 5000 delta Scuti, 2300 gamma Doradus, and 114 roAp candidates. Whereas it has been assumed that high-frequency pulsations among B-type mainsequence stars are confined to the early B-type beta Cephei stars, the observations indicate that high frequencies are to be found over the whole B-star range, eventually merging with delta Scuti stars. The cool B stars pulsating in high frequencies are called Maia variables. It is shown that Maia variables are not rapidly rotating and thus cannot be beta Cephei pulsators that appear to have lower temperatures due to gravity darkening. In the region where beta Cephei variables are found, the proportion of pulsating stars is larger and amplitudes are higher and a considerable fraction pulsate in a single mode and low rotation rate. There is no distinct region of slowly pulsating B stars (SPB stars). Stars pulsating solely in low frequencies are found among all B stars. At most, only one-third of B stars appear to pulsate. These results, as well as the fact that a large fraction of A and B stars show rotational modulation, indicate a need for a revision of current ideas regarding stars with radiative envelopes.