³ÉÈË´óƬ

Young stars accrete material from their surrounding disks. Simulations predict that matter accretes via the stellar magnetic field lines, leaving a hot spot with a density gradient. We present observational evidence of this density gradient utilizing a comprehensive, coordinated multi-epoch multi-wavelength observing campaign. UV and optical light curves of GM Aur display periodicity, but do not peak at the same time. The offset peaks are due to a hot spot with a density gradient; different density regions of the hot spot emit at distinct wavelengths and have separate physical locations leading to periodic, offset peaks in the UV and optical as the hot spot rotates along with the star. These observations confirm theoretical predictions and demonstrate the insights gained from coordinated multi-epoch multi-wavelength observations.