A Systematic Study on Energy Dependence of Quasi-Periodic Oscillation   Frequency in GRS 1915+105
  Systematically studying all the RXTE/PCA observations for GRS 1915+105 before November 2010, we have discovered three additional patterns in the relation between Quasi-Periodic Oscillation (QPO) frequency and photon energy, extending earlier outcomes reported by Qu et al. (2010). We have confirmed that as QPO frequency increases, the relation evolves from the negative correlation to positive one. The newly discovered patterns provide new constraints on the QPO models. 
Shu-Ping Yan, Jin-Lu Qu, Guo-Qiang Ding, Peng Han, Li-Ming Song,   Hong-Xing Yin, Cheng-Min Zhang, Shu Zhang and Jian-Min Wang
astro-ph.HE