Asteroseismology M4 study with K2 data

We find an integrated RGB mass-loss of {Delta}M_avg_ = 0.17 +/- 0.01 M_{Sun}_, equivalent to a Reimers' mass-loss coefficient of {eta}_R_ = 0.39. Our results for initial mass, horizontal branch mass, {eta}_R_, and integrated RGB mass-loss show remarkable agreement with previous studies, but with higher precision using asteroseismology. We also report the first detections of solar- like oscillations in early asymptotic giant branch (EAGB) stars in GCs.

We find an average mass of M_avg,EAGB_ = 0.54 +/- 0.01 M_{Sun}_, significantly lower than predicted by models. This suggests larger-than-expected mass-loss on the horizontal branch. Alternatively, it could indicate unknown systematics in the scaling relations for the EAGB.

We discover a tentative mass bimodality in the RGB sample, possibly due to the multiple populations. In our red horizontal branch sample, we find a mass distribution consistent with a single value. We emphasize the importance of seismic studies of GCs since they could potentially resolve major uncertainties in stellar theory.