A 0.4-20 mu m spectroscopic study of the clumped wind of WR 147

We present a detailed spectroscopic study of the WN8(h)+B0.5 V binary syste m WR 147 using a non-LTE model that incorporates advances in line blanketin g and allows for clumping in the wind. Ground-based optical and near-infrar ed observations, and high-resolution spectra obtained with the ISO Short wa velength Spectrometer are combined for this study. Previously derived inter stellar extinction values of EB-V similar or equal to 4.1 mag at R-V simila r or equal to 2.7 are confirmed here. The distance to WR 147 is revised sli ghtly upwards to 650 pc, based on Galactic and LMC WN8-9 calibrators in the It band. An infrared extinction curve for this sightline reveals absorptio n bands at 9.7 and 18 mu m that are stronger than expected for the average ISM, but the nature and location of the intervening material is unknown. He line profiles of the WN8 star exhibit clear evidence for clumping in the wind. We find that a volume filling factor f of 0.1 yields line profile wh ich match observations (emphasizing the electron scattering wings), though values of f in the range of 0.04 to 0.25 are reasonable. This leads to a ma ss-loss rate range of (1.5-3.7)x 10(-5) M., yr(-1), substantially lower tha n derived ft om optical or radio observations under assumptions of homogene ity. Additionally including the effects of line-blanketing, the wind perfor mance factor, M upsilon(infinity)/(L-* /c), is reduced to similar to 2.5. Hydrogen is severely depleted, but present at 9% by mass. Observations of t he [Ca IV] 3.21 mu m, [S IV] 10.51 mu m, and [Ne III] 15.56 mu m fine struc ture lines, from which we measure a terminal wind velocity of similar to 95 0 kms(-1), allow us to place constraints on the surface abundances of these elements. In all cases we find good agreement with cosmic abundances (adju sted to a hydrogen-poor environment) and thus with evolutionary predictions for WN stars.