Paper: The dense core OPH D seen in extinction by ISOCAM Volume: 132, Star Formation with the Infrared Space Observatory (ISO) Page: 220 Authors: Abergel, A.; Bernard, J. P.; Boulanger, F.; Desert, F. X.; Lagache, G.; Puget, J. L.; Reach, W. T.; Falgarone, E.; Nordh, L.; Olofsson, G.; Andre, P.; Bacmann, A.; Ristorcelli, I. Abstract: We present a detailed analysis of the dense core Oph D which is one of the most spectacular prestellar cores revealed in extinction by ISOCAM in the rho Ophiuchi main cloud (Abergel et al. 1996). Conducted in the two filters LW2 (5-8.5 microns) and LW3 (12-18 microns), the observations confirm the wavelength dependence of the extinction curve for standard graphite-silicate dust grains. Opacity maps are obtained with an unprecedented angular resolution (6 arc sec) and sensitivity. We deduce new estimates of the total mass of the core: MTOT= 7.3-13.9 and 8.4-10.8 M_{\odot} for the LW2 and LW3 filters respectively. The density structure of the core edge which has the steepest IR brightness gradient is modeled with a simple spherical geometry. The density profiles strongly depart from a r^{-2} sphere due to a central flattening of the internal regions (typically for r < 0.02 pc). Using the over-simplified picture of a core embedded in an external cloud with a constant density fixed to 10^4 H cm^{-3}, we reach the conclusion that the external parts of the profiles are steeper than a r^{-2} law. However r^{-2} density profiles are also compatible with the data since the density outside the core is actually poorly constrained.