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[45.04] HETG Observations of Zeta Puppis

J.P. Cassinelli, N.A. Miller (Univ. of Wisconsin-Madison), J.J. MacFarlane (Prism Computational Sciences)

We present recent HETG observations of \zeta Puppis (O4f). These observations are among the first to show Doppler-broadened X-ray emission lines coming from the expanding wind. The star \zeta Pup has long been a touchstone for hot star X-ray studies, dating back to its use in the successful prediction of early-type stellar wind X-ray emission and its subsequent confirmation by Einstein. The much higher resolution attainable using grating spectroscopy on Chandra (\delta v \approx 500 km/s) clearly shows resolved emission lines from ions ranging from helium-like silicon to hydrogen- and helium-like magnesium, neon, and oxygen. Many of the iron lines which are present are attributable to Fe XVII. A first attempt at fitting the line profiles using an 10⁷ K shell of gas expanding at 1000 km/s fits the data reasonably well, a result which can be compared with the terminal velocity of 2660 km/s. A multi-temperature, multi-shell model is required for detailed fitting. As another indicator of the location of the X-ray emitting regions, we have analyzed the Forbidden, Intercombination, and Resonance (FIR) line complexes of helium-like ions, a sensitive density diagnostic. The derived density is then compared to the range of densities throughout the wind. We would like to thank NASA for support of this project under grant NAG5-9226.