Intrinsic spectra of the AXPs

Abstract

Using direct measurements of photo-electric absorption edges, I derive the intrinsic spectra for the Anomalous X-ray Pulsars. In the past, the hydrogen column density, NH had been found by fitting the X-ray spectra with a variety of simple continuum models. Since different models fit equally well, with different values of NH, little is learned about the true column density or intrinsic spectra. Here, I measure the column densities in a model-independent way, and thus derive intrinsic spectra without first assuming what those spectra ought to look like. Particularly for the brightest source, 4U 0142+61, the column density can be determined accurately, and is a factor of 1.4 smaller that the typically NH quoted. With this new value, the new intrinsic spectrum can be investigated anew, and shows a slight hint of a feature around 13 A.