# # Program information file # PROGRAM_ID 2022B043 PROGRAM_TITLE IRTF Observations of Large-scale Wind Structure and Mass-loss in Wolf-Rayet Stars PROGRAM_INV1 Melissa Butner PROGRAM_INV2 Richard Ignace PROGRAM_INV3 J. Allyn Smith PROGRAM_INV4 Christiana Erba PROGRAM_INV5 Nicole St. Louis PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG Massive stars strongly influence their environment due to their powerful UV-ionizing radiation fields, their extreme mass loss, and their critical role in the production of metals. This is especially true for Wolf-Rayet stars, with mass-loss rates exceeding those of other O-type stars by an order of magnitude. However, mass-loss rate estimates for these stars are uncertain, due to the intrinsically structured nature of their wind outflows [clumping]. Organized structures such as co-rotating interaction regions [CIRs] are also observed in massive star winds, adding to the challenges faced in characterizing these winds. This proposal seeks to examine how CIRs affect long-wavelength [IR/radio] emissions by monitoring WR 134 [which hosts a detected CIR] and WR 136 [which shows distinct signatures of a spherically symmetric wind]. Time series IR data in key wind lines [e.g., He I 1.083 micron], continuum [SpeX waveband], and forbidden lines [Ca IV 3.21 micron], will trace the CIR's presence and influence on the variable long-wavelength emission. A comparison of the data from WR 134 and WR 136 will reveal the coherence of the CIR structure at large radii, since WR 136 is not expected to show any corresponding structure. We will apply existing models to SpeX data to distinguish between the influence of organized and stochastic structure on wind diagnostics. An improved understanding of the influence of CIRs will enable our ability to decode with confidence the important information contained within the stellar wind. PROGRAM_ABSTRACT_END