. XMM-Newton Science Analysis System . specadd (specadd-1.14) [xmmsas_20050815_1803-6.5.0] . Meta Index . It creates a multiple X-ray spectrum FITS file either by stacking or putting together two single spectrum files or by stacking a single spectrum on top of an existing multiple spectrum file. Instruments/Modes . Use . Description . Parameters . Errors . Input Files . Output Files . Algorithm . Comments . Future developments . Bibliography . Index . XMM-Newton SOC/SSC -- 2005-08-15