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

Probabilistic H-R Diagrams (pHRD) and X-ray spectral results for sources in the IMPS Paper (abstract below). phrds.zip (uncompressed size ~ 30 MB): Contains flip through PS (postscript) of the pHRDs for each source. The PS are separated by disk status (disky/diskless) and IR classification (AB, IMPS, TTS, and Unc). MIR names are used. XRay_spectra_and_lightcurves.zip (uncompressed size ~50 MB): Contains PS of binned best X-ray spectral fit (binned for display purposes), sequenced light curve, and stacked light curve for each source. X-ray names are used. spectra.ps: A compilation of the binned X-ray spectral fits for our entire sample as a flip through PS Paper Abstract: We use X-ray and infrared observations to study the properties of three classes of young stars in the Carina Nebula: intermediate-mass \edit1{(2--5~M$_\odot$)} pre-main sequence stars (IMPS\edit1{; i.e. intermediate-mass T Tauri stars}), late-B and 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 further identify disk-bearing young stellar objects versus diskless sources with no detectable infrared (IR) excess emission using IR (1--8 $\mu$m) spectral energy distribution modeling. We then perform X-ray spectral fitting to determine the hydrogen absorbing column density ($N_{\rm H}$), absorption-corrected X-ray luminosity ($L_{\rm X}$), and coronal plasma temperature ($kT$) for each source. We find that the X-ray spectra of both IMPS and TTS are characterized by 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-ray emission consistent with TTS companions. These lines of evidence converge on a magneto-coronal flaring source for IMPS X-ray emission, a scaled-up version of the TTS emission mechanism. IMPS therefore provide powerful probes of isochronal ages for the first $\sim$10 Myr in the evolution of a massive stellar population, because their intrinsic, coronal X-ray emission decays rapidly after they commence evolving along radiative tracks. We suggest that the most luminous (in both X-rays and IR) IMPS could be used to place empirical constraints on the location of the intermediate-mass stellar birth line.