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Measuring mass-loss rates and constraining shock physics using X-ray line profiles of O stars from the Chandra archive

Cohen, David H. and Wollman, Emma E. and Leutenegger, Maurice A. and Sundqvist, Jon O. and Fullerton, Alex W. and Zsargó, Janos and Owocki, Stanley P. (2014) Measuring mass-loss rates and constraining shock physics using X-ray line profiles of O stars from the Chandra archive. Monthly Notices of the Royal Astronomical Society, 439 (1). pp. 908-923. ISSN 0035-8711. https://resolver.caltech.edu/CaltechAUTHORS:20140424-155206867

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Abstract

We quantitatively investigate the extent of wind absorption signatures in the X-ray grating spectra of all non-magnetic, effectively single O stars in the Chandra archive via line profile fitting. Under the usual assumption of a spherically symmetric wind with embedded shocks, we confirm previous claims that some objects show little or no wind absorption. However, many other objects do show asymmetric and blueshifted line profiles, indicative of wind absorption. For these stars, we are able to derive wind mass-loss rates from the ensemble of line profiles, and find values lower by an average factor of 3 than those predicted by current theoretical models, and consistent with Hα if clumping factors of fcl ≈ 20 are assumed. The same profile fitting indicates an onset radius of X-rays typically at r ≈ 1.5R*, and terminal velocities for the X-ray emitting wind component that are consistent with that of the bulk wind. We explore the likelihood that the stars in the sample that do not show significant wind absorption signatures in their line profiles have at least some X-ray emission that arises from colliding wind shocks with a close binary companion. The one clear exception is ζ Oph, a weak-wind star that appears to simply have a very low mass-loss rate. We also reanalyse the results from the canonical O supergiant ζ Pup, using a solar-metallicity wind opacity model and find M^˙=1.8×10−6 M_ ⊙yr^−1, consistent with recent multiwavelength determinations.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1093/mnras/stu008DOIArticle
http://mnras.oxfordjournals.org/content/439/1/908PublisherArticle
http://arxiv.org/abs/1401.7995arXivDiscussion Paper
ORCID:
AuthorORCID
Wollman, Emma E.0000-0002-5474-3745
Additional Information:© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 January 3; Received 2014 January 2; in original form 2013 July 21. Support for this work was provided by the National Aeronautics and Space Administration through the ADAP award NNX11AD26G and Chandra award numbers TM3-14001B and AR2-13001A to Swarthmore College and award number TM6-7003X to University of Pittsburgh. EEW was supported by a Lotte Lazarsfeld Bailyn Summer Research Fellowship from the Provost’s Office at Swarthmore College. JOS and SPO acknowledge support from NASA award ATP NNX11AC40G to the University of Delaware and JOS also acknowledges support from DFG grant Pu117/8-1. Special thanks to Véronique Petit for her careful reading of the manuscript and her numerous helpful suggestions.
Funders:
Funding AgencyGrant Number
NASANNX11AD26G
NASATM3-14001B
NASAAR2-13001A
NASATM6-7003X
Swarthmore CollegeUNSPECIFIED
NASANNX11AC40G
Deutsche Forschungsgemeinschaft (DFG)Pu117/8-1
Subject Keywords:stars: early-type; stars: mass-loss; stars: winds, outflows; X-rays: stars
Issue or Number:1
Record Number:CaltechAUTHORS:20140424-155206867
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140424-155206867
Official Citation:Cohen, D. H., Wollman, E. E., Leutenegger, M. A., Sundqvist, J. O., Fullerton, A. W., Zsargó, J., & Owocki, S. P. (2014). Measuring mass-loss rates and constraining shock physics using X-ray line profiles of O stars from the Chandra archive. Monthly Notices of the Royal Astronomical Society, 439(1), 908-923. doi: 10.1093/mnras/stu008
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45201
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:24 Apr 2014 23:33
Last Modified:03 Oct 2019 06:28

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