More Rapidly Rotating PMS M Dwarfs with Light Curves Suggestive of Orbiting Clouds of Material

TL;DR

This study identifies and analyzes rapidly rotating mid-to-late M dwarf stars with complex light curves suggestive of orbiting clouds of material, expanding understanding of their variability in star-forming regions.

Contribution

The paper reports the discovery of additional M dwarf stars with scallop-shell light curves, providing detailed analysis and physical characteristics to explore their unique variability mechanisms.

Findings

Identified 8 new probable members with similar light curves

Shared periods and spectral types across different star-forming regions

Detailed characterization of their physical properties

Abstract

In a previous paper, using data from K2 Campaign 2, we identified 11 very low mass members of the $\rho$ Oph and Upper Scorpius star-forming region as having periodic photometric variability and phased light curves showing multiple scallops or undulations. All the stars with the "scallop-shell" light curve morphology are mid-to-late M dwarfs without evidence of active accretion, and with photometric periods generally $<$1 day. Their phased light curves have too much structure to be attributed to non-axisymmetrically distributed photospheric spots and rotational modulation. We have now identified an additional eight probable members of the same star-forming region plus three stars in the Taurus star-forming region with this same light curve morphology and sharing the same period and spectral type range as the previous group. We describe the light curves of these new stars in detail and present their general physical characteristics. We also examine the properties of the overall set of stars in order to identify common features that might help elucidate the causes of their photometric variability.