Cohen, David H. and Leutenegger, Maurice A. and Wollman, Emma E. and Zsargó, Janos and Hillier, D. John and Townsend, Richard H. D. and Owocki, Stanley P. (2010) A mass-loss rate determination for ζ Puppis from the quantitative analysis of X-ray emission-line profiles. Monthly Notices of the Royal Astronomical Society, 405 (4). pp. 2391-2405. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20100720-091209033
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We fit every emission line in the high-resolution Chandra grating spectrum of ζ Pup with an empirical line profile model that accounts for the effects of Doppler broadening and attenuation by the bulk wind. For each of 16 lines or line complexes that can be reliably measured, we determine a best-fitting fiducial optical depth, τ_∗ ≡ κM/4πR_∗v_∞, and place confidence limits on this parameter. These 16 lines include seven that have not previously been reported on in the literature. The extended wavelength range of these lines allows us to infer, for the first time, a clear increase in τ_∗ with line wavelength, as expected from the wavelength increase of bound–free absorption opacity. The small overall values of τ ∗, reflected in the rather modest asymmetry in the line profiles, can moreover all be fitted simultaneously by simply assuming a moderate mass-loss rate of 3.5 ± 0.3 × 10^(−6)M_⊙ yr^(−1), without any need to invoke porosity effects in the wind. The quoted uncertainty is statistical, but the largest source of uncertainty in the derived mass-loss rate is due to the uncertainty in the elemental abundances of ζ Pup, which affects the continuum opacity of the wind, and which we estimate to be a factor of 2. Even so, the mass-loss rate we find is significantly below the most recent smooth-wind Hα mass-loss rate determinations for ζ Pup, but is in line with newer determinations that account for small-scale wind clumping. If ζ Pup is representative of other massive stars, these results will have important implications for stellar and Galactic evolution.
|Additional Information:||© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 March 1. Received 2010 February 28; in original form 2009 February 27. Support for this work was provided by NASA through Chandra award number AR7-8002X to Swarthmore College and award number TM6-7003X to the University of Pittsburgh, issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. EEW was supported by a Lotte Lazarsfeld Bailyn Summer Research Fellowship from the Provost’s Office at Swarthmore College. MAL also acknowledges support from the Provost’s office of Swarthmore College. RHDT, SPO and DHC acknowledge support from NASA LTSA grant NNG05GC36G and JZ and DJH acknowledge support from STScI grant HST-AR- 10693.02. The authors also thank Marc Gagné, Alex Fullerton, Yaël Nazé and Joachim Puls for careful reading of the manuscript, advice and many useful suggestions. And we thank the referee for additional useful suggestions, especially about porosity and its effect on the wavelength dependence of the wind opacity.|
|Subject Keywords:||radiative transfer; stars: early-type; stars: individual: zeta Pup; stars: mass-loss; stars: winds, outflows; X-rays: stars|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||05 Aug 2010 18:41|
|Last Modified:||26 Dec 2012 12:15|
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