Neutron Stars From Young Nearby Associations: The Origin of RX J1605.3+3249

Many neutron stars (NSs) and runaway stars apparently come from the same regions on the sky. This suggests that they share the same birth places, namely associations and clusters of young massive stars. To identify NS birth places, we attempt to find NS-runaway pairs that could be former companions that were disrupted in a supernova (SN). The remains of recent (<fewMyr) nearby (<150pc) SNe should still be identifiable by observing the emission of rare radioisotopes such as ²⁶Al and ⁶⁰Fe that can also be used as additional indicators to confirm a possible SN event. We investigated the origin of the isolated NS RX J1605.3+3249 and found that it was probably born ~100pc far from Earth 0.45Myr ago in the extended Corona Australis or Octans associations, or in Sco OB4 ~1kpc 3.5Myr ago. A SN in Octans is supported by the identification of one to two possible former companions - the runaway stars HIP 68228 and HIP 89394 - as well as the appearance of a feature in the γ-ray emission from ²⁶Al decay at the predicted SN place. Both, the progenitor masses estimated by comparison with theoretical ²⁶Al yields as well as derived from the life-time of the progenitor star, are found to be ~11M_solar.