The Rotation Properties of δ Sct and γ Dor Stars

Based on the LAMOST spectroscopy and TESS time-series photometry, we have obtained a main-sequence star sample of delta Scuti and gamma Doradus stars. The sample includes 1534 delta Sct stars, 367 gamma Dor stars, 1703 delta Sct divided by gamma Dor stars, 270 gamma Dor divided by delta Sct stars, along with 105 "dsct candidates" and 32 "gdor candidates". After correcting for projection effects, we derived the equatorial rotational velocity distribution for delta Sct and gamma Dor stars and compared it with that of normal stars. The rotational velocity distributions of delta Sct and gamma Dor stars are extremely similar, with the only difference potentially due to the rotational variable stars that have not been completely removed. In contrast, the rotational velocity distribution of normal stars is more dispersed compared to pulsating stars. Additionally, the peak rotational velocity of the pulsating stars is about 10 km s-1 higher than that of normal stars. Unlike the normal stars, which show a monotonic increase in peak velocity with mass between 1.8 and 2.5 M circle dot, the rotational velocity distribution of delta Sct stars does not exhibit a strong mass dependence. We also found that normal stars accelerate during the late main-sequence evolutionary phase, while delta Sct stars decelerate. Furthermore, there may still be unclassified stars with diverse rotational properties in the normal star sample compared to the delta Sct stars, which is likely to be an important contributor to the broader dispersion observed in its rotational velocity distribution. The photometric amplitude in delta Sct stars is modulated with rotational velocity, with high-amplitude stars typically rotating slowly and low-amplitude stars showing a broad distribution of rotational velocities.