Bowen fluorescence in Scorpius X-1

Abstract

The first measurements of O III Bowen fluorescence lines in the near-ultraviolet spectra of the X-ray binary system Scorpius X-1 are presented. The flux-calibrated spectra from the atmospheric limit to 1 micron also reveal the nitrogen Bowen lines near-4640 A, the Balmer and Paschen series of hydrogen, the Paschen and Brackett series of He II, and numerous lines from Fe II and He I, among others. All of these lines probably arise in emission-line regions photoionized by X-rays produced near the neutron star surface. The observed line intensities are used to estimate explicitly the roles of the O1 and O3 channels of the Bowen cascades, as well as the possible importance of charge transfer between H I and O IV.