Revisiting the Impact of Dust Production from Carbon-rich Wolf–Rayet Binaries

Year: 2020

DOI: 10.3847/1538-4357/ab9cb5

We present a dust spectral energy distribution (SED) and binary stellar population analysis revisiting the dust production rates (DPRs) in the winds of carbon-rich Wolf–Rayet (WC) binaries and their impact on galactic dust budgets. DustEM SED models of 19 Galactic WC "dustars" reveal DPRs of Ṁ_d ~ 10⁻¹⁰-10⁻⁶ M_⊙ yr⁻¹ and carbon dust condensation fractions, χ C , between 0.002% and 40%. A large (0.1–1.0 μm) dust grain size composition is favored for efficient dustars where χ_C ≳ 1%. Results for dustars with known orbital periods verify a power-law relation between χ_C , orbital period, WC mass-loss rate, and wind velocity consistent with predictions from theoretical models of dust formation in colliding-wind binaries. We incorporated dust production into Binary Population and Spectral Synthesis (BPASS) models to analyze dust production rates from WC dustars, asymptotic giant branch stars (AGBs), red supergiants (RSGs), and core-collapse supernovae (SNe). BPASS models assuming constant star formation (SF) and a coeval 10⁶ M_⊙ stellar population were performed at low, Large Magellanic Cloud (LMC)–like, and solar metallicities (Z = 0.001, 0.008, and 0.020). Both constant SF and coeval models indicate that SNe are net dust destroyers at all metallicities. Constant SF models at LMC-like metallicities show that AGB stars slightly outproduce WC binaries and RSGs by factors of 2–3, whereas at solar metallicities WC binaries are the dominant source of dust for ~60 Myr until the onset of AGBs, which match the dust input of WC binaries. Coeval population models show that, for "bursty" SF, AGB stars dominate dust production at late times (t ≳ 70 Myr).