X-Ray Observations of X2127+119/AC 211 in the Metal-poor Globular Cluster M15: An X-Ray Measure of Metallicity?

摘要

We present results from observations of the 17.1 hr low-mass X-ray binary X2127+119 (AC 211) in M15 obtained with the broadband X-ray telescope (BBXRT) in 1990 December and observations obtained with the solid state spectrometer (SSS) together with the monitor proportional counter (MPC) on the Einstein Observatory in 1978 and 1979. The continuum can be well described with the two-component model of a blackbody (kT 1 keV) and a power law that was found to fit the EXOSAT medium-energy data. Short- term variability observed by the SSS and MPC was related to changes in the intensities of both components in this description. The SSS and MPC observed factor of 10 differences in column density in observations separated by a few binary orbits. These observations confirm correlations between the steepness of the spectrum and the column density, and column density with phase.