SIMBAD references

We present results from the analysis of X-ray power density spectra and coherence when GRS 1915+105 is in soft states. We use three data sets that belong to µ, φ, and δ classes as found in the work of Belloni et al. We find that the power density spectra appear to be complex, with several features between 0.01 and 10 Hz. The coherence deviates from unity above a characteristic frequency. We discuss our results from different models. The corona size in the sphere-disk model implied by this break frequency is on the order of 10⁴GM/c², which is unphysical. Our results are more consistent with the prediction of the model of a planar corona sustained by magnetic flares, in which the characteristic frequency is associated with the longest timescale of an individual flare, which is about 8 s.