Phase-Resolved Timing Analysis of GRS 1915+105 in Its ρ State

Abstract: We made a phase-resolved timing analysis of GRS 1915+105 in its {\rho} state and obtained detailed {\rho} cycle evolutions of the frequency, the amplitude and the coherence of low-frequency quasi-periodic oscillation (LFQPO). We combined our timing results with the spectral study by Neilsen et al. to perform an elaborate comparison analysis. Our analyses show that the LFQPO frequency does not scale with the inner disk radius, but it is related to the spectral index, indicating a possible correlation between the LFQPOs and the corona. The LFQPO amplitude spectrum and other results are naturally explained by tying the LFQPO to the corona. The similarities of the spectra of variability parameters between the LFQPO from {\rho} state and those from more steady states indicate that the LFQPOs of GRS 1915+105 in very different states seem to share the same origin.