Constraints on the kinetic energy of type-Ic supernova explosion from young PSR J1906 + 0746 in a double neutron star candidate*

Abstract

So far among the nineteen pairs of detected double neutron star (DNS) systems, it is a usual fact that the first-born recycled pulsar is detected, however the youngest DNS system PSR J1906+0746, with the characteristic age of 113 kyr, is one of the three detected DNS as a non-recycled and second-born NS, which is believed to be formed by an electron capture or a low energy ultra-stripped iron core-collapse supernova (SN) explosion. The SN remnant around PSR J1906+0746 is too dim to be observed by optical telescopes, then its X-ray flux limit has been given by Chandra. A reference pulsar PSR J1509-5850 with the young characteristic age of 154 kyr was chosen as an object of comparison, which has an SN remnant observed by Chandra and is believed to be formed by iron core SN explosion. We impose a restriction on the maximum kinetic energy of electron-capture(EC) SN explosion that induces the formation of PSR J1906+0746. The estimated result is (4-8)×10⁵⁰ erg, which is consistent with that of the published simulations of the EC process, i.e., a lower value than that of the conventional iron core SN explosion of (1-2)×10⁵¹ erg. As suggested, EC process for NS formation is pertained to the subluminous Type Ic SN by the helium star with ONeMg core, thus for the first time we derived the kinetic energy of EC SN explosion of DNS, which may be reconciled with the recent observation of Type Ic SN 2014ft with kinetic energy of 2×10⁵⁰ erg.