A Chandra search for the pulsar wind nebula around PSR B1055-52

The nearby, middle-aged PSR B1055-52 has many properties in common with the Geminga pulsar. Motivated by the Geminga's enigmatic and prominent pulsar wind nebula (PWN), we searched for extended emission around PSR B1055-52 with Chandra ACIS. For an energy range 0.3-1 keV, we found a flux enhancement in a annulus around the pulsar. There is a slight asymmetry in the emission close, , to the pulsar. The excess emission has a luminosity of about 10²⁹ erg s^-1 in an energy range 0.3-8 keV for a distance of 350 pc. Overall, the faint extended emission around is consistent with a PWN of an aligned rotator moving away from us along the line of sight with supersonic velocity, but a contribution from a dust scattering halo cannot be excluded. Comparing the properties of other nearby, middle-aged pulsars, we suggest that the geometry - the orientations of rotation axis, magnetic field axis, and the sight-line - is the deciding factor for a pulsar to show a prominent PWN. We also report on an flux decrease of PSR B1055-52 between the 2000 XMM-Newton and our 2012 Chandra observation. We tentatively attribute this flux decrease to a cross-calibration problem, but further investigations of the pulsar are required to exclude actual intrinsic flux changes.