The CHARA Science Meeting 2021 The First Dynamical Mass Determination of a Nitrogen-rich Wolf– Rayet Star Using a Combined Visual and Spectroscopic Orbit Noel Richardson, Laura Lee, et al. Embry-Riddle Aeronautical University 1 The CHARA Science Meeting 2021 What is a Wolf-Rayet star? • Classical WR stars are H-free, evolved massive stars. They have extremely high effective temperatures and strong stellar winds. WR124, HST Sana et al. (2012) 2 The CHARA Science Meeting 2021 Previous Interferometry of WR stars • Due to the rarity of these objects, only a few have been observed. • Large distances – not much to resolve for most WR stars • Binaries are main focus with current instrumentation 3 The CHARA Science Meeting 2021 Gamma2 Vel • WC8 + O7.5III • P = 78.53 d • e = 0.33 • Lamberts et al. 2017 + RiChardson et al. 2017 • M_O = 28.4 Msun • M_WR = 9 Msun 4 The CHARA Science Meeting 2021 WR140 – Monnier et al. (2011); Thomas, Richardson et al. (submitted) • WC7pd + O5.5fC • P = 7.93 years • e = 0.8993 • M_O = 29.3 Msun • M_WR = 10.3 Msun 5 The CHARA Science Meeting 2021 WR137, WR138 – resolved with CHARA (Richardson et al. 2016) • WR 137 • WC7 + O • P = 13 yr • Dust formation at periastron • WR 138 • WN + O • P – unknown, possibly ~4 yr? • CLIMB observations resolved the binaries – began a long-term NOAO NOIR Lab program for orbits. • Upgraded MIRC-X made the program finally take off! 6 The CHARA Science Meeting 2021 WR 133 - background • WN5o + O9I • Known SB2 orbit with P=133 d, but relatively understudied. • member of NGC 6871 • Inclination at least 115deg from polarimetric analysis 7 The CHARA Science Meeting 2021 CHARA observations and the new paper 8 The CHARA Science Meeting 2021 Archive of DAO Spectra 1.2 1.1 2452838.8 1.0 0.9 2449145.8 0.8 NORMALIZED FLUX 0.7 5200 5400 5600 5800 6000 WAVELENGTH (ANGSTROMS) 1.2 He II O III He I 1.0 0.8 NORMALIZED FLUX 0.6 -2000 -1000 0 1000 -400 -200 0 200 400 -400 -200 0 200 400 RADIAL VELOCITY (km s-1) 9 The CHARA Science Meeting 2021 CHARA 10 The CHARA Science Meeting 2021 Orbital Elements/Masses • P = 112.78 d • e = 0.36 • d = 1.73 kpc • a = 0.79 mas = 292 Rsun • M_O = 18.1 Msun • M_WR = 8.2 Msun 11 The CHARA Science Meeting 2021 Comparisons with Theoretical models Best models indiCate a speCtroscopiC mass of 14 Msun, ~2-3 sigma from measured mass! 12 The CHARA Science Meeting 2021 If you need supporting spectroscopy for CHARA observations… We have a small telesCope and an eshel (R~10,000) speCtrograph that Covers the ~4500-6800A range. We have up to 300 Clear nights per year, and my students and I will gladly help with Coverage. Early results show that we Can aCCurately measure an SB2 with a half hour exposure and a stellar contrast of 13.