086507

Red giants like Arcturus occupy a region in the X-ray Hertzsprung-Russell Diagram openParHRDclosePar known as the coronal graveyard. The physical cause for the sharp decline of X-ray emission beyond a so-called dividing line that separates X-ray emitting yellow giants from X-ray dark red giants is comma despite decades of research comma not finally answered. The recent X-ray detection of Arcturus with Chandra HRC-I motivates our request to obtain spectral information with XMM-Newton EPIC spectroscopy. An 80 ks exposure is sufficient to detect large absorbing column densities that may be expected if severe obscuration by layers above the giant.s corona cause the decrease in their observed X-ray luminosity.