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We use X-ray and infrared observations to study the properties of threeclasses of young stars in the Carina Nebula: intermediate-mass (2--5~M$_\odot$)pre-main sequence stars (IMPS; i.e. intermediate-mass T Tauri stars), late-Band A stars on the zero-age main sequence (AB), and lower-mass T Tauri stars(TTS). We divide our sources among these three sub-classifications and furtheridentify disk-bearing young stellar objects versus diskless sources with nodetectable infrared (IR) excess emission using IR (1--8 $\mu$m) spectral energydistribution modeling. We then perform X-ray spectral fitting to determine thehydrogen absorbing column density ($N_{\rm H}$), absorption-corrected X-rayluminosity ($L_{\rm X}$), and coronal plasma temperature ($kT$) for eachsource. We find that the X-ray spectra of both IMPS and TTS are characterizedby similar $kT$ and $N_{\rm H}$, and on average $L_{\rm X}$/$L_{\rm bol}\sim4\times10^{-4}$. IMPS are systematically more luminous in X-rays (by$\sim$0.3 dex) than all other sub-classifications, with median $L_{\rm X} =2.5\times10^{31}$ erg s$^{-1}$, while AB stars of similar masses have X-rayemission consistent with TTS companions. These lines of evidence converge on amagneto-coronal flaring source for IMPS X-ray emission, a scaled-up version ofthe TTS emission mechanism. IMPS therefore provide powerful probes ofisochronal ages for the first $\sim$10 Myr in the evolution of a massivestellar population, because their intrinsic, coronal X-ray emission decaysrapidly after they commence evolving along radiative tracks. We suggest thatthe most luminous (in both X-rays and IR) IMPS could be used to place empiricalconstraints on the location of the intermediate-mass stellar birth line.

Characterizing the X-ray Emission of Intermediate-Mass Pre-Main-Sequence Stars