Serendipitous isolated neutron star candidates from the 4XMM-DR9 catalogue

The large number of radioquiet thermally emitting isolated neutron stars (INSs)in our local volume suggests that they belong to a formerly neglected componentof the overall population. At fainter fluxes, source confusion and contaminationfrom other classes of Xray emitters hamper the identification of new membersdue to the large positional and spectral errors. In preparation for the fullsensitivity of the eROSITA AllSky Survey, the use of serendipitous data fromXMMNewton proves an excellent opportunity to test search algorithms anddiscover new INSs. We propose to investigate newly selected candidates from the4XMMDR9 catalogue with the immediate goals to improve spectral determinationand source localisation for future followup studies. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]