Phase resolved spectrum of the Crab pulsar from NICER

M. Vivekanand

Published 2021-02-09Version 1

context{ The high energy emission regions of rotation powered pulsars are studied using folded light curves (FLCs) and phase resolved spectra (PRS).} aims{ This work uses the NICER observatory to obtain the highest resolution FLC and PRS of the Crab pulsar at soft X-ray energies.} methods{ NICER has accumulated about 347 kilo seconds of data on the Crab pulsar. The data are processed using the standard analysis pipeline. Stringent filtering is done for spectral analysis. The individual detectors are calibrated in terms of long time light curve (LTLC), raw spectrum and deadtime. The arrival times of the photons are referred to the solar system's barycenter, and the rotation frequency nu and its time derivative nu_dot are used to derive the rotation phase of each photon.} results{ The LTLCs, raw spectra and deadtimes of the individual detectors are statistically similar; the latter two show no evolution with epoch; detector deadtime is independent of photon energy. The deadtime for the Crab pulsar, taking into account the two types of deadtime, is only about 7% to 8% larger than that obtained using the cleaned events. Detector 00 behaves slightly differently from the rest, but can be used for spectral work. The PRS of the two peaks of the crab pulsar are obtained at a resolution of better than 1/512 in rotation phase. The FLC very close to the first peak rises slowly and falls faster, opposite in behavior to that seen further away from the peak. The spectral index of the PRS is almost constant very close to the first peak.} conclusions{ The high resolution FLC and PRS of the first peak of the Crab pulsar provide important constraints for the formation of caustics in the emission zone.}