PSR J0636+5128: A Heated Companion in a Tight Orbit

Abstract: We present an analysis of archival Gemini g', r', K and Keck H, K_s imaging of this nearby short period binary (P_B=95.8min) 2.87ms pulsar. The heated companion is clearly detected. Direct pulsar heating provides an acceptable model at the revised >700pc parallax distance. The relatively shallow light curve modulation prefers an inclination i<40deg; this high latitude view provides a likely explanation for the lack of radio signatures of wind dispersion or eclipse. It also explains the low minimum companion mass and, possibly, the faintness of the source in X- and gamma-rays.