Two bright X-ray transients were reported from the Chandra Deep Field South ( CDF-S ) archival data , namely CDF-S XT1 and XT2 .
Whereas the nature of the former is not identified , the latter was suggested as an excellent candidate for a rapidly spinning magnetar born from a binary neutron star ( BNS ) merger .
Here we propose a unified model to interpret both transients within the framework of the BNS merger magnetar model .
According to our picture , CDF-S XT2 is observed from the ‘ ‘ free zone ’ ’ where the magnetar spindown powered X-ray emission escapes freely , whereas CDF-S XT1 originates from the ‘ ‘ trapped zone ’ ’ where the X-ray emission is initially blocked by the dynamical ejecta and becomes transparent after the ejecta is pushed to a distance where Thomson optical depth drops below unity .
We fit the magnetar model to the light curves of both transients and derived consistent parameters for the two events , with magnetic field , initial spin period and X-ray emission efficiency being ( B _ { p } = 10 ^ { 16 } G , P _ { i } = 1.2 ms , \eta = 0.001 ) and ( B _ { p } = 10 ^ { 15.8 } G , P _ { i } = 4.4 ms , \eta = 0.001 ) for XT1 and XT2 , respectively .
The ‘ ‘ isotropic equivalent ’ ’ ejecta mass of XT1 is M _ { ej } \sim 10 ^ { -3 } M _ { \odot } , while it is not constrained for XT2 .
Our results suggest that more extreme magnetar parameters are required to have XT1 detected from the trapped zone .
The model parameters for both events are generally consistent with those derived from SGRB X-ray plateau observations .
The host-galaxy properties of both transients are also consistent with those of SGRBs .
The event rate densities of both XT1 and XT2 are consistent with that of BNS mergers .