TY - JOUR
T1 - Complex modulation of rapidly rotating young M dwarfs
T2 - adding pieces to the puzzle
AU - Günther, Maximilian N.
AU - Berardo, David A.
AU - Ducrot, Elsa
AU - Murray, Catriona A.
AU - Stassun, Keivan G.
AU - Olah, Katalin
AU - Bouma, L. G.
AU - Rappaport, Saul
AU - Winn, Joshua N.
AU - Feinstein, Adina D.
AU - Matthews, Elisabeth C.
AU - Sebastian, Daniel
AU - Rackham, Benjamin V.
AU - Seli, Bálint
AU - Triaud, Amaury H. M. J.
AU - Gillen, Edward
AU - Levine, Alan M.
AU - Demory, Brice-Olivier
AU - Gillon, Michaël
AU - Queloz, Didier
AU - Ricker, George
AU - Vanderspek, Roland K.
AU - Seager, Sara
AU - Latham, David W.
AU - Jenkins, Jon M.
AU - Brasseur, C. E.
AU - Colón, Knicole D.
AU - Daylan, Tansu
AU - Delrez, Laetitia
AU - Fausnaugh, Michael
AU - Garcia, Lionel J.
AU - Jayaraman, Rahul
AU - Jehin, Emmanuel
AU - Kristiansen, Martti H.
AU - Kruijssen, J. M. Diederik
AU - Pedersen, Peter Philmann
AU - Pozuelos, Francisco J.
AU - Rodriguez, Joseph E.
AU - Wohler, Bill
AU - Zhan, Zhuchang
PY - 2022/4
Y1 - 2022/4
N2 - 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.
AB - 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.
KW - M dwarf stars
KW - Periodic variable stars
KW - Pre-main sequence stars
KW - Starspots
KW - Stellar activity
KW - Stellar flares
KW - Stellar rotation
KW - T Tauri stars
KW - Variable stars
KW - astro-ph.EP
KW - astro-ph.SR
UR - http://www.scopus.com/inward/record.url?scp=85126081983&partnerID=8YFLogxK
U2 - 10.3847/1538-3881/ac503c
DO - 10.3847/1538-3881/ac503c
M3 - Article
SN - 0004-6256
VL - 163
JO - The Astronomical Journal
JF - The Astronomical Journal
IS - 4
M1 - 144
ER -