Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle
Abstract
New sets of young M dwarfs with complex, sharp-peaked, and strictly periodic photometric modulations have recently been discovered with Kepler/K2 (scallop shells) and TESS (complex rotators). All are part of star-forming associations, are distinct from other variable stars, and likely belong to a unified class. Suggested hypotheses include star spots, accreting dust disks, co-rotating clouds of material, magnetically constrained material, spots and misaligned disks, and pulsations. Here, we provide a comprehensive overview and add new observational constraints with TESS and SPECULOOS Southern Observatory (SSO) photometry. We scrutinize all hypotheses from three new angles: (1) we investigate each scenario's occurrence rates via young star catalogs; (2) we study the features' longevity using over one year of combined data; and (3) we probe the expected color dependency with multi-color photometry. In this process, we also revisit the stellar parameters accounting for activity effects, study stellar flares as activity indicators over year-long time scales, and develop toy models to simulate typical morphologies. We rule out most hypotheses, and only (i) co-rotating material clouds and (ii) spots and misaligned disks remain feasible - with caveats. For (i), co-rotating dust might not be stable enough, while co-rotating gas alone likely cannot cause percentage-scale features; and (ii) would require misaligned disks around most young M dwarfs. We thus suggest a unified hypothesis, a superposition of large-amplitude spot modulations and sharp transits of co-rotating gas clouds. While the complex rotators' mystery remains, these new observations add valuable pieces to the puzzle going forward.
Keywords
Cite
@article{arxiv.2008.11681,
title = {Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle},
author = {Maximilian N. Günther and David A. Berardo and Elsa Ducrot and Catriona A. Murray and Keivan G. Stassun and Katalin Olah and L. G. Bouma and Saul Rappaport and Joshua N. Winn and Adina D. Feinstein and Elisabeth C. Matthews and Daniel Sebastian and Benjamin V. Rackham and Bálint Seli and Amaury H. M. J. Triaud and Edward Gillen and Alan M. Levine and Brice-Olivier Demory and Michaël Gillon and Didier Queloz and George Ricker and Roland K. Vanderspek and Sara Seager and David W. Latham and Jon M. Jenkins and C. E. Brasseur and Knicole D. Colón and Tansu Daylan and Laetitia Delrez and Michael Fausnaugh and Lionel J. Garcia and Rahul Jayaraman and Emmanuel Jehin and Martti H. Kristiansen and J. M. Diederik Kruijssen and Peter Philmann Pedersen and Francisco J. Pozuelos and Joseph E. Rodriguez and Bill Wohler and Zhuchang Zhan},
journal= {arXiv preprint arXiv:2008.11681},
year = {2022}
}
Comments
Accepted in The Astronomical Journal, 23 pages, 14 figures, 2 tables. This is the authors' version of the manuscript