We present the results of six Suzaku observations of the recurrent black hole transient 4U 1630 - 472 during its decline from outburst from February 8 to March 23 in 2006 .
All observations show the typical high/soft state spectral shape in the 2–50 keV band , roughly described by an optically thick disk spectrum in the soft energy band plus a weak power-law tail that becomes dominant only above \sim 20 keV .
The disk temperature decreases from 1.4 keV to 1.2 keV as the flux decreases by a factor 2 , consistent with a constant radius as expected for disk-dominated spectra .
All the observations reveal significant absorption lines from highly ionized ( H-like and He-like ) iron K \alpha at 7.0 keV and 6.7 keV .
The brightest datasets also show significant but weaker absorption structures between 7.8 keV and 8.2 keV , which we identify as a blend of iron K \beta and nickel K \alpha absorption lines .
The energies of these absorption lines suggest a blue shift with an outflow velocity of \sim 1000 ~ { } { km~ { } s ^ { -1 } } .
The H–like iron K \alpha equivalent width remains approximately constant at \sim 30 eV over all the observations , while that of the He–like K \alpha line increases from 7 eV to 20 eV .
Thus the ionization state of the material decreases , as expected from the decline in flux .
We fit the profiles with Voigt functions ( curve of growth ) to derive absorbing columns , then use these together with detailed photo-ionization calculations to derive physical parameters of the absorbing material .
The data then constrain the velocity dispersion of the absorber to 200– 2000 ~ { } { km~ { } s ^ { -1 } } , and the size of the plasma as \sim 10 ^ { 10 } ~ { } { cm } assuming a source distance of 10 kpc .