The Narrow-line Seyfert 1 galaxy NGC 4051 is known to exhibit significant X-ray spectral/flux variations and have a number of emission/absorption features .
X-ray observations have revealed that these absorption features are blueshifted , which indicates that NGC 4051 has warm absorber outflow .
In order to constrain physical parameters of the warm absorber outflow , we analyze the archival data with the longest exposure taken by XMM-Newton in 2009 .
We calculate the root-mean-square ( RMS ) spectra with the grating spectral resolution for the first time .
The RMS spectra have a sharp peak and several dips , which can be explained by variable absorption features and non-variable emission lines ; a lower-ionized warm absorber ( WA1 : \log \xi = 1.5 , v = -650 \mathrm { km s } ^ { -1 } ) shows large variability , whereas higher-ionized warm absorbers ( WA2 : \log \xi = 2.5 , v = -4100 \mathrm { km s } ^ { -1 } , WA3 : \log \xi = 3.4 , v = -6100 \mathrm { km s } ^ { -1 } ) show little variability .
WA1 shows the maximum variability at a timescale of \sim 10 ^ { 4 } s , suggesting that the absorber locates at \sim 10 ^ { 3 } times of the Schwarzschild radius .
The depth of the absorption features due to WA1 and the observed soft X-ray flux are anti-correlated in several observational sequences , which can be explained by variation of partial covering fraction of the double-layer blobs that are composed of the Compton-thick core and the ionized layer ( = WA1 ) .
WA2 and WA3 show little variability and presumably extend uniformly in the line of sight .
The present result shows that NGC 4051 has two types of the warm absorber outflows ; the static , high-ionized and extended line-driven disk winds , and the variable , low-ionized and clumpy double-layer blobs .