Conditions in the WR 140 wind-collision region revealed by the 1.083-μ m He i line profile

Author:

Williams Peredur M1ORCID,Varricatt Watson P2,Chené André-Nicolas3ORCID,Corcoran Michael F45,Gull Ted R6ORCID,Hamaguchi Kenji47,Moffat Anthony F J8,Pollock Andrew M T9,Richardson Noel D10ORCID,Russell Christopher M P11,Sander Andreas A C12ORCID,Stevens Ian R13,Weigelt Gerd14

Affiliation:

1. Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK

2. Institute for Astronomy, UKIRT Observatory, 640 North A'ohoku Place, Hilo, HI 96720, USA

3. Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96720, USA

4. CRESST II and X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, MD 20771, USA

5. Department of Physics, Institute for Astrophysics and Computational Sciences, The Catholic University of America, Washington, DC 20064, USA

6. Astrophysics Science Division, NASA/GSFC, Greenbelt, MD 20771, USA

7. Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA

8. Département de physique and Centre de Recherche en Astrophysique du Québec (CRAQ), Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7, Canada

9. Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK

10. Department of Physics, Embry-Riddle Aeronautical University, Prescott, AZ 86301, USA

11. Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA

12. Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK

13. School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

14. Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn, Germany

Abstract

ABSTRACT We present spectroscopy of the P Cygni profile of the 1.083-$\mu$m He i line in the WC7+O5 colliding-wind binary (CWB) WR 140 (HD 193793), observed in 2008, before its periastron passage in 2009, and in 2016–2017, spanning the subsequent periastron passage. Both absorption and emission components showed strong variations. The variation of the absorption component as the O5 star was occulted by the wind-collision region (WCR) sets a tight constraint on its geometry. While the sightline to the O5 star traversed the WCR, the strength and breadth of the absorption component varied significantly on time-scales of days. An emission subpeak was observed on all our profiles. The variation of its radial velocity with orbital phase was shown to be consistent with formation in the WCR as it swung round the stars in their orbit. Modelling the profile gives a measure of the extent of the subpeak-forming region. In the phase range 0.93–0.99, the flux in the subpeak increased steadily, approximately inversely proportionally to the stellar separation, indicating that the shocked gas in the WCR where the line was formed was adiabatic. After periastron, the subpeak flux was anomalously strong and varied rapidly, suggesting formation in clumps downstream in the WCR. For most of the time, its flux exceeded the 2–10-keV X-ray emission, showing it to be a significant coolant of the shocked wind.

Funder

Science and Technology Facilities Council

NASA

National Science Foundation

NSERC

Publisher

Oxford University Press (OUP)

Subject

Space and Planetary Science,Astronomy and Astrophysics

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