Observed epochal variations in X-ray lines from the O Supergiant $\zeta$ Puppis do not require substantial changes in the wind mass flux

Abstract

We fit the high resolution \textit{Chandra} X-ray spectra of the O supergiant $\zeta$ Puppis using the variable boundary condition (VBC) line model to test the stability of its mass-loss rate between two epochs of observation: 2000 March and 2018 July -- 2019 August. At issue is whether the observed variations are induced by global changes in the cool (unshocked) wind itself or are isolated to the local pockets of hot gas (i.e., changes in the frequency and location of the shocks). Evidence in the literature favored the possibility of a 40 per cent increase in the mass flux of the entire stellar wind, based on X-ray reabsorption from a line-deshadowing-instability-inspired parameterization, whereas our fit parameters are consistent with a constant mass flux with a change in the velocity variations that determine the locations where shocks form. Our results suggest the shocks in the more recent data are formed at somewhat larger radii, mimicking the enhanced blueshifts and increased line fluxes interpreted in the previous analysis as being due to increases in both the X-ray generation and reabsorption from an overall stronger wind.

18 pages, 13 figures, 4 tables

References in corpus (8)

• The XMM-Newton serendipitous survey IX. The fourth XMM-Newton serendipitous source catalogue
• Bright OB stars in the Galaxy - III. Constraints on the radial stratification of the clumping factor in hot star winds from a combined Halpha, IR and radio analysis
• Towards a unified view of inhomogeneous stellar winds in isolated supergiant stars and supergiant high mass X-ray binaries
• BRITE-Constellation high-precision time-dependent photometry of the early-O-type supergiant $\zeta$ Puppis unveils the photospheric drivers of its small- and large-scale wind structures
• Time-series photometry of the O4 I(n)fp star zeta Puppis
• The distance, rotation, and physical parameters of zeta Pup
• Correlated X-ray and optical variability in the O-type supergiant zeta Puppis
• Testing the Reliability of X-rays as a Tool for Constraining Mass-loss Rates of Hot Stars

Cited by in corpus (2)

• Deriving X-ray Line Profiles for Massive-Star Winds from Momentum-Conserving Dynamical Working Surface Solutions
• Methods to Test the Source of the Extreme Gas Motions in WS 35