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Through the McDonald Observatory M Dwarf Planet Search, we have acquirednearly 3,000 high-resolution spectra of 93 late-type (K5-M5) stars over morethan a decade using HET/HRS. This sample provides a unique opportunity toinvestigate the occurrence of long-term stellar activity cycles for low-massstars. In this paper, we examine the stellar activity of our targets asreflected in the H-alpha feature. We have identified periodic signals for 6stars, with periods ranging from days to more than 10 years, and find long-termtrends for 7 others. Stellar cycles with P > 1 year are present for at least 5%of our targets. Additionally, we present an analysis of the time-averagedactivity levels of our sample, and search for correlations with other stellarproperties. In particular, we find that more massive, earlier type (M0-M2)stars tend to be more active than later type dwarfs. Furthermore,high-metallicity stars tend to be more active at a given stellar mass. We alsoevaluate H-alpha variability as a tracer of activity-induced radial velocity(RV) variation. For the M dwarf GJ 1170, H-alpha variation reveals stellaractivity patterns matching those seen in the RVs, mimicking the signal of agiant planet, and we find evidence that the previously identified stellaractivity cycle of GJ 581 may be responsible for the recently retracted planet f(Vogt et al. 2012) in that system. In general, though, we find that H-alpha isnot frequently correlated with RV at the precision (typically 6-7 m/s) of ourmeasurements.

H-alpha Activity of Old M Dwarfs: Stellar Cycles and Mean Activity Levels For 93 Low-Mass Stars in the Solar Neighborhood