Presentation #100.06 in the session “Stellar/Compact I (Oral)”.
The O supergiant ζ Puppis is the prototype single, non-magnetic, early O star with a strong radiation-driven wind. The X-ray emission in this star is produced via shock-heating of the wind, the bulk of which is moderately optically thick to soft X-ray emission. Two observing campaigns with the Chandra HETGS, eighteen years apart, showed an unexpected change in the star’s X-ray spectral properties, which are naturally interpreted as a ~40 percent increase in the wind mass-loss rate. We initially identified this unexpected change in the wind properties via an increase in the asymmetry of the spectrally resolved X-ray emission line profiles, and now we have also confirmed changes in the broadband X-ray spectra that are consistent with a mass-loss rate increase.