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High-resolution ground-based images of the T Tauri star LkCa 15 have revealedmultiple companions that are thought to comprise a formative planetary system.The candidate protoplanets orbit at distances ~15 - 20 AU within thedust-depleted inner region of the circumstellar disk. Because of its young age(1 - 4 Myr), LkCa 15 provides a benchmark system for testing planet-formationmodels. We detected LkCa 15 as a bright X-ray source in a short 10 ks Chandraobservation in 2009. We report here new results obtained from a deeper 37 ksXMM-Newton observation in 2014. The new data provide better sampling in thetime domain and improved sensitivity at low energies below 1 keV. Spectral fitswith thermal emission models require at least two temperature components atkT_cool ~ 0.4 keV and kT_hot ~ 2.2 keV. The value of kT_hot is about a factorof two less than inferred from Chandra, suggesting that the hot-componenttemperature is variable. The best-fit absorption column density is in goodagreement with that expected from optical extinction estimates A_v = 1.3 - 1.7mag. The intrinsic X-ray luminosity is L_x(0.2 - 10 keV) = 3e30 ergs/s.Estimates of the X-ray heating rate of the inner disk and protoplanets aresensitive to the assumed disk gas surface density for which recent ALMAobservations give estimates Sigma_0(gas) ~ 100 g/cm^2 at 1 AU from the star. Atsuch densities, X-ray heating is confined mainly to the upper disk layers andX-ray penetration through the disk midplane to the protoplanets at r ~ 15 - 20AU is negligible.

XMM-Newton X-ray Observations of LkCa 15: A T Tauri Star With a Formative Planetary System