X-ray emission from Ae/Be Herbig stars due to disc-stellar magnetosphere interaction

We reanalyse archival X-ray data of 16 Ae/Be Herbig stars obtained by the XMM-Newton and Chandra satellites. Stellar X-ray spectra in the energy range 0.2-8 keV were fitted with the use of APEC and MEKAL hot plasma emission models, and with models with an additional power-law component. We find that for Herbig stars, the dependence of the unabsorbed X-ray luminosity on stellar mass and radius, L_X ∝ R^αM^β with α ≈ 3 and β ≈ 2, is similar to that for T Tauri stars. The independently determined accretion rates, rotation periods, and the surface magnetic fields follow a tight correlation predicted by the standard magnetospheric accretion theory. We suggest that X-ray emission from Herbig stars is powered by magnetic reconnection events in the tenuous corona at the disc-magnetosphere boundary.