Pulsation among TESS A and B stars and the Maia variables

Abstract

Classification of over 50000 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. It is found that a distinct group of $\beta$ Cephei stars, defined as B stars with frequencies greater than 2.5 d${}^{-1}$ and predicted by models, does not exist. Instead, 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 the Maia variables. It is shown that Maia variables are not rapidly-rotating $\beta$ Cephei or SPB stars. 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 SPB instability region. Stars pulsating sole 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.

arXiv comment9 pages, 7 figures, 3 tables

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