nuclear physics - How in Cesium 137 spectroscopy Barium X-rays being detected?

Iv been looking at gamma ray spectroscopy of late for a project that I am currently researching and going to be doing in the lab, but what I cannot seem to figure is how the barium x-rays are being shown in the spectrum?

Looking at the decay scheme and comparing it to a c137 spectrograph I cant see how the x-ray photons are being generated. My only reasoning is that there is some sort of characteristic x-ray being formed from during the transition gamma photo being ejected during the decay.

Answer

Beta decay changes $Z$ which may produce a hole in the K shell ("shake-up"). That hole then decays. But that is then the K-shell of the progeny nucleus: barium.

Edit: probably more important: the metastable state of $^{137}$Ba decays by internal conversion in which a K electron was emitted.

https://www.ld-didactic.de/software/524221en/Content/Appendix/Cs137.htm

Indeed, when one washes out the barium product, the spectrum of the eluate looks the same.