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arXiv · 2209.13107

Spatially Dependent Photometric Activity of M dwarfs in the Solar Cylinder

Seo-Won Chang·Christian Wolf·Christopher A. Onken
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Abstract

We study the relationship between Galactic location ($R, Z$) and photometric activity for 3.6 million M dwarf stars within 1 kpc of the Sun. For this purpose, we identify 906 unique flare events as a proxy for magnetic activity from the SkyMapper Southern Survey DR3. We adopt vertical distance $|Z|$ from the Galactic disc as a proxy for age and confirm a strong trend of flaring fraction decreasing with growing stellar age. Among M dwarfs within 50 pc of the Sun, we find a flaring fraction of 1-in-1,500, independent of spectral type from M2 to M7, suggesting that these stars are all in a flare-saturated young evolutionary stage. We find a hint of a kink in the slope of the overall flare fraction near 100 pc from the plane, where a steep decline begins; this slope change is visible for mid-type M dwarfs (M3--M5), suggesting it is not an artefact of mixing spectral type. Together with SDSS H$α$ emission, this trend is additional evidence that the activity fraction of M dwarfs depends on Galactic height and activity lifetime. While there is a hint of flattening of the overall activity fraction above $|Z|\approx$ 500 pc, our data do not constrain this further. Within $\sim$500 pc distance from the Sun, we find no sign of radial disk gradients in flare activity, which may only be revealed by samples covering a larger radial range.

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Seo-Won Chang, Christian Wolf, Christopher A. Onken. 2022-09-27. Spatially Dependent Photometric Activity of M dwarfs in the Solar Cylinder. https://doi.org/10.1093/mnras%2Fstac2788

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