The Effects of Instrumental Deadtime on NICER Timing Products

TL;DR

This paper investigates how instrumental deadtime affects NICER's timing measurements of X-ray sources, finding that existing correction methods remain effective at typical count rates and no additional corrections are needed.

Contribution

It provides an analysis of deadtime effects on NICER timing data and confirms the adequacy of current correction techniques for high-precision X-ray timing.

Findings

No significant deadtime effects across NICER detectors.

Existing deadtime correction methods are sufficient.

Deadtime does not significantly bias Fourier timing products at typical count rates.

Abstract

The X-ray Timing Instrument as part of the Neutron Star Interior Composition Explorer has the potential to examine the time-domain properties of compact objects in regimes not explored by previous timing instruments, due to its combination of high effective area and timing resolution. We consider the effects of instrumental deadtime at a range of effective countrates in a series of observations of the X-ray binary GX 339-4 to determine what effect deadtime has on photometric and Fourier frequency-domain products. We find that there are no significant inconsistencies across the functional detectors in the instrument, and that in the regimes where instrumental deadtime is a limiting factor on observations that previous approaches to dealing with deadtime, as applied to RXTE and other detectors, are still appropriate, and that performing deadtime corrections to lightcurves before creating Fourier products are not necessary at the count rates considered in our analysis.