Measuring the mass of the white dwarf in the symbiotic binary RT Cru

The extraordinary symbiotic binary RT Cru, which hosts a massive (>1.25 solarmasses) white dwarf (WD) and thus is a serious candidate to be a SNIaprogenitor, is currently in a new optical/hard Xray bright state; the previousone was detected in 2012 in optical photometry and with Swift/BAT. At that timethe accretion rate onto the WD increased, but did not reach the value where theaccretion disk boundary layer transitions to the optically thick regime. Wepropose to observe RTvirgulCru with XMM and NuSTAR during the current maximum anevent that is unlikely to repeat within the next ten years in order to fullycharacterize the 0.380 keV spectrum during the maximum, allowing us to measurethe shock temperature and thus the WD mass and the accretion rate through the boundary layer. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]