X-Ray Emission of the γ-ray-loud Young Radio Galaxy NGC 3894

The radio source 1146+596 is hosted by an elliptical/S0 galaxy NGC 3894, with a low-luminosity active nucleus. The radio structure is compact, suggesting a very young age of the jets in the system. Recently, the source has been confirmed as a high-energy (HE, $>0.1$ GeV) $\gamma$-ray emitter, in the most recent accumulation of the {\it Fermi} Large Area Telescope (LAT) data. Here we report on the analysis of the archival {\it Chandra} X-ray Observatory data for the central part of the galaxy, consisting of a single 40 ksec-long exposure. We have found that the core spectrum is best fitted by a combination of an ionized thermal plasma with the temperature of $\simeq 0.8$ keV, and a moderately absorbed power-law component (photon index $\Gamma \simeq 1.4\pm 0.4$, hydrogen column density $N_{\rm H}/10^{22}$ cm$^{-2}$ $\simeq 2.4\pm 0.7$). We have also detected the iron K$\alpha$ line at $\simeq 6.47\pm 0.07$ keV, with a large equivalent width of EW $\simeq 1$ keV. Based on the simulations of the {\it Chandra}'s Point Spread Function (PSF), we have concluded that, while the soft thermal component is extended on the scale of the galaxy host, the hard X-ray emission within the narrow photon energy range 6.0--7.0 keV originates within the unresolved core (effectively the central $<5^{\prime\prime}\simeq 1.2$ kpc radius). The line is therefore indicative of the X-ray reflection from a cold neutral gas in the central regions of NGC 3894. We discuss the implications of our findings in the context of the X-ray Baldwin effect, and the overall energetic of the system. We note that NGC 3894 becomes the first HE $\gamma$-ray source with the detected K$\alpha$ iron line.