Long-term Spectral Variability of the Ultra-luminous X-ray source Holmberg IX X--1

V. Jithesh, Ranjeev Misra, Zhongxiang Wang

We investigate the long-term spectral variability in the ultra-luminous X-ray source Holmberg IX X--1. By analyzing the data from eight {\it Suzaku} and 13 {\it XMM-Newton} observa…