Constraints of age, distance and progenitor of the supernova remnant RX J0852.0-4622/GRO J0852-4642

The discovery of the nearest young supernova rem- nant RX J0852.0-4622 / GRO J0852-4642 in the Galaxy by ROSAT and COMPTEL has been reported recently. Age and distance are determined to 680 years and 200 pc by the X- ray diameter and the -ray line flux of radioactive 44 Ti. Here we discuss the implications of the X-ray spectra and of the fact that 1.8 MeV -ray line emission from the decay of 26 Al has been measured from the Vela region with a certain fraction possibly associated with the new SNR. We estimate an uncertainty of the age of 100 yrs for a fixed yield of 44 Ti. The highest values of 44 Ti yield provided by current supernova explosion models give worst case upper limits of 1100 yrs for the age and of 500 pc for the distance. Also the unknown ionization stage of 44 Ti adds to the uncertainty of age and distance which is at most another 35% on top. Both the energy balance compiled for the remnant and yield predictions for 44 Ti and 26 Al by supernova models favour a core-collapse event. Two point sources have been found in the vicinity of the explosion center, either one of these might be the neutron star left by the supernova. If there is a neutron star the X-ray count rates of the two point sources provide an upper limit of the blackbody surface temperature, which is very unlikely to exceed 310 5 K. The supernova might have been observed some 700 150 yrs ago, but based on the data of SN 1181, e.g., there is a realistic chance that it has been missed if the supernova was sub-luminous.