On Calibrations using the Crab Nebula and Models of the Nebular X-ray Emission

TL;DR

This paper evaluates the use of the Crab Nebula as a calibration standard for X-ray instruments, highlighting the need for response function refinements and comparing theoretical models of nebular X-ray emission.

Contribution

It analyzes the impact of intrinsic spectral deviations on calibration accuracy and distinguishes between two models of the nebular X-ray spectrum.

Findings

Refinement needed for two instrument response functions.

Discrimination between two theoretical spectral models.

Implications for calibration using the Crab Nebula.

Abstract

Motivated by a paper (Kirsch et al. 2005) on possible use of the Crab Nebula as a standard candle for calibrating X-ray response functions, we examine consequences of intrinsic departures from a single (absorbed) power law upon such calibrations. We limit our analyses to three more modern X-ray instruments-the ROSAT/PSPC, the RXTE/PCA, and the XMM-Newton/EPIC-pn (burst mode). The results indicate a need to refine two of the three response functions studied. We are also able to distinguish between two current theoretical models for the system spectrum.