Speaker
Description
Volume-complete samples are key to characterizing stellar populations. We have set out to constrain the activity and rotation rates of all 150 early-M dwarf stars from the `10pc sample in the era of Gaia' (from Reyle et al. 2021). Hereby, we uncover the full spread that such stars can exhibit, which we find to span three orders of magnitude both in X-ray brightness and rotation period.
At the extremes, we have identified a superflare on AD Leo, that was shown to be 10 000 times more energetic than a typical solar flare, and a star with no persistent X-ray emission, consistent with the properties of a solar coronal hole. To calibrate the M dwarf X-ray activity on our Sun, we use the Sun-as-an-Xray-star approach, which transforms solar Yohkoh observations to stellar-like data.
Our study makes use of a dedicated deep XMM-Newton survey complementing archival X-ray data and the recent eROSITA half-sky surveys, as well as newly determined TESS rotation periods combined with published rotation data. We find the majority of 10pc M dwarfs to be low-activity and slowly rotating stars, in contrast to flux-limited samples of M dwarfs where the majority are `saturated'. This underlines the importance of volume-limited studies for our understanding of biases in larger but incomplete samples.
