Presentation #110.04 in the session “Stellar/Compact (Poster)”.
We report on a search for X-ray pulsations from the original black widow pulsar PSR B1957+20 using 300 ks of NICER observations from 2017 and 2020. We folded the NICER data in the 0.3-10 keV range using a contemporaneous radio timing ephemeris for the 1.6 ms pulsar derived from 9 years of observations with the Nançay Radio Telescope. No X-ray pulsations were detected. We discuss the implications of our non-detection in the context of a previously reported 4-sigma detection of 0.5-4.5 keV X-ray pulsations from a XMM-Newton observation in 2004 with a pulsed fraction of ~30 percent. We will also discuss a search for spectral variability at different orbital phases, corresponding to emission from the intrabinary shock and non-shock regions.