SIMBAD references

Compact Symmetric Objects (CSOs) are a distinct category of jetted active galactic nuclei whose high-energy emission is not well understood. We examined the X-ray characteristics of 17 bona fide CSOs using observations from Chandra, XMM-Newton, and NuSTAR. Among the sources with XMM-Newton observations, we found two sources, J0713+4349 and J1326+3154 to show clear evidence of variations in the soft (0.3-2 keV), the hard (2-10 keV), and the total energy (0.3-10 keV) bands with the normalized excess variance (F$_{\mathrm{ var}}$) as large as 1.17$\pm$0.27. Also, the F$_{\mathrm{ var}}$ is found to be larger in the hard band relative to the soft band for J1326+3154. From the analysis of the hardness ratio (HR) with count rate, we found both sources to show a harder when brighter (HWB) trend. Similarly, in the Chandra observations, we found one source, J0131+5545, to show flux variations in the total energy band (0.5-7 keV). We discuss possible reasons for about 82 per cent of the CSOs being non-variable. From spectral analysis, carried out in a homogeneous manner, we found the existence of obscured as well as unobscured CSOs. Three CSOs, J0111+3906, J1407+2827, and J2022+6136, were found to have the intrinsic neutral hydrogen column density N$_{\rm H,z} \gt 10^{23}$ cm$^{-2}$, consistent with earlier analyses. For the majority of the CSOs, the observed hard X-ray emission is expected to be dominated by their mildly relativistic jet emission. For the sources, J0713+4349, J1347+1217, J1407+2827, J1511+0518, and J2022+6136, the confirmed detection of Fe K $\alpha$ emission line suggests a significant contribution from the disc/corona. Our results point to diverse X-ray characteristics of CSOs.