## 6. The method of mass momentsFor the moments of the -distribution for several events, one obtains following RJM where yields for the case , , and for the average mass (in units of ) as One sees that the moments of the mass spectrum can be extracted from the moments of the time-scale distribution if the spatial distribution of the mass density and the velocity distribution is given (RJM). For the moments of the mass spectrum one gets This gives for which yields so that For , one obtains since , which is the same value as obtained for the expectation value of the lens mass for as derived above, if one considers a single observed event. © European Southern Observatory (ESO) 1998 Online publication: January 27, 1998 |