Evidence for 1.01 s pulsations of the Central Compact Object in the supernova remnant RCW 103 with ASCA, XMM-Newton, and NuSTAR

Abstract The neutron-star X-ray source 1E 161348–5055, associated with the supernova remnant RCW 103, exhibits clear intensity variations with a period of 6.67 h. To clarify the nature of this object and its long periodicity, detailed timing studies were applied to its archival X-ray data, taken with ASCA (in 1993), XMM-Newton (in 2001, 2005, and 2016), and NuSTAR (2016 and 2017). It was assumed that the 6.67 h period arises due to the beat between the rotation and free precession periods of the star that is slightly aspherical. By removing timing perturbations to be caused by this long periodicity, the six data sets consistently yielded evidence for pulsations at periods of $P\approx 1.01$ s, to be interpreted as the objects’ spin period, although the optimum energy range differed among the data sets. The measured six periods accurately line up on a linear spin-down trend of $\dot{P} = 1.097 \times 10^{-12}~{\rm s~s}^{-1}$. The object is implied to have a characteristic age of 14.7 kyr, a spin-down luminosity of $4.2\times 10^{34}$ erg s$^{-1}$, which is insufficient to power the X-ray luminosity, a dipole magnetic field of ${\sim }4.6\times 10^{13}$ G, and a toroidal field of ${\sim }7 \times 10^{15}$ G. Its similarity and dissimilarity to magnetars are discussed. An emission geometry, which crudely explain these results, is presented.