SIMBAD references

δ Scuti stars are hot, rapid rotators and a poorly understood class of pulsators. Asteroseismology provides the only means with which to probe their interior dynamics. However, their complex and unexplained oscillation patterns restrict analyses to only a small fraction with interpretable pulsations. Here, we identify 5381 δ Scuti stars from 63 sectors of TESS observations, of which 300 had interpretable oscillations, with 24 showing rotational splittings. We inferred compositions and ages (τ) for the 300 stars, finding them in near-zero-age-main-sequence (ZAMS) states, and measured the mean envelope rotation rates (〈f_rot〉) for 24 of them. Analyzing their age-dependent rotation, we found that these stars essentially exhibit weak to no spin-down while evolving past the ZAMS across a narrow time span during which they show regular pulsations. A quantitative fit to their spin evolution results in a trend f_rot(d^–1) ∝ (τ/Gyr)^-0.048 ± 0.016^, much slower than the spin-down of cooler late-type stars due to magnetic braking (Skumanich's law: f_rot(d^–1) ∝ (τ/Gyr)^–0.5). Based on stellar evolution calculations, we show that this weak spin-down is consistent with the gradual increase in the moment of inertia.