Abstract
Wolf-Rayet (WR) 140 is the archetypal periodic dust-forming colliding-wind binary that hosts a carbon-rich WR (WC) star and an O-star companion with an orbital period of 7.93 yr and an orbital eccentricity of 0.9. Throughout the past few decades, multiple dust-formation episodes from WR 140 have been observed that are linked to the binary orbit and occur near the time of periastron passage. Given its predictable dust-formation episodes, WR 140 presents an ideal astrophysical laboratory to investigate the formation and evolution of dust in the hostile environment around a massive binary system. In this paper, we present near- and mid-infrared (IR) spectroscopic and imaging observations of WR 140 with Subaru/SCExAO+CHARIS, Keck/NIRC2+PyWFS, and Subaru/Cooled Mid-Infrared Camera and Spectrograph taken between 2020 June and September that resolve the circumstellar dust emission linked to its most recent dust-formation episode in 2016 December. Our spectral energy distribution analysis of WR 140's resolved circumstellar dust emission reveals the presence of a hot (T d ∼ 1000 K) near-IR dust component that is co-spatial with the previously known and cooler (T d ∼ 500 K) mid-IR dust component composed of 300-500 Å sized dust grains. We attribute the hot near-IR dust emission to the presence of nano-sized (nanodust) grains and suggest they were formed from grain-grain collisions or the rotational disruption of the larger grain size population by radiative torques in the strong radiation field from the central binary. Lastly, we speculate on the astrophysical implications of nanodust formation around colliding-wind WC binaries, which may present an early source of carbonaceous nanodust in the interstellar medium.
| Original language | English (US) |
|---|---|
| Article number | 89 |
| Journal | Astrophysical Journal |
| Volume | 951 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jul 1 2023 |
Funding
R.M.L. thanks Thiem Hoang for the insightful discussions on grain disruption and the RATD mechanism. R.M.L. also thanks T. Fujiyoshi, the Subaru Observatory staff, and the Keck Observatory staff for supporting our observations of WR 140. We also thank the anonymous referee for their valuable feedback on our analysis an interpretation. The work of R.M.L. is supported by NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. R.M.L. acknowledges the Japan Aerospace Exploration Agency\u2019s International Top Young Fellowship (ITYF). A.A.C.S. is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) in the form of an Emmy Noether Research Group (grant No. SA4064/1-1, PI Sander) and acknowledges additional support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)\u2014Project-ID 138713538\u2014SFB 881 (\u201CThe Milky Way System,\u201D subproject P04). A.F.J.M. is grateful for financial aid from NSERC (Canada). IE acknowledges support from Grant-in-Aid for JSPS Fellows (grant No. 21J13200). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The development of SCExAO was supported by the Japan Society for the Promotion of Science (Grant-in-Aid for Research #23340051, #26220704, #23103002, #19H00703 & #19H00695), the Astrobiology Center of the National Institutes of Natural Sciences, Japan, the Mt Cuba Foundation, and the director's contingency fund at Subaru Telescope.
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science