{lambda} Orionis PMS stars with Gaia & SPOTS

For the Class II population, we use a Gaia G-RP dereddening method, minimizing systematics from disks, accretion, and other physics associated with youth. The cluster age is systematically different in models incorporating the structural impact of starspots or magnetic fields than in nonmagnetic models. Our mean ages range from 2-3Myr (nonmagnetic models) to 3.9+/-0.2Myr in the SPOTS model (f=0.34).

We find that star-by-star dereddening methods distinguishing between pre-main-sequence classes provide a smaller age spread than techniques using a uniform extinction, and we infer a minimum age spread of 0.19dex and a typical age spread of 0.35dex after modeling age distributions convolved with observed errors. This suggests that the {lambda} Ori cluster may have a long star formation timescale and that spotted stellar models significantly change age estimates for young clusters.