2016ApJ...817..129B

PSR B0656+14 is a middle-aged pulsar with a characteristic age τ_c = 110 kyr and spin-down power {dot}E = 3.8 x 10³⁴ erg/s. Using Chandra data, we searched for a pulsar wind nebula (PWN). We found evidence of an extended emission in a 3".5-15" annulus around the pulsar, with a luminosity L_0.5^ext - 8 keV_ ∼ 8 x 10²⁸ erg/s (at the distance of 288 pc), which is a fraction of ∼0.05 of the nonthermal pulsar luminosity. If the extended emission is mostly due to a PWN, its X-ray effiency, n_pwn = L_0.5^ext - 8 keV/{dot}E ∼ 2 x 10^–6, is lower than those of most other known PWNe, but similar to that of the middle-aged Geminga pulsar. The small radial extent and nearly round shape of the putative PWN can be expained if the pulsar is receding (or approaching) in the direction close to the line of sight. The very soft spectrum of the extended emission (Τ ∼ 8) is much softer than those of typical PWNe; this could be explained by contribution from a faint dust scattering halo, which may dominate in the outer part of the extended emission. Interstellar Medium