The curious case of WR 148

Melissa Munoz ( Université de Montréal )

WR 148 (WN8h) is a single lined spectroscopic binary with an established period of 4.3174d suspected to harbour either a low mass B star or a black hole. We obtained two nights of spectra from the Keck Observatory at both quadratures complemented with several other spectra from l'Observatoire du Mont-Megantque in the summers of 2014 and 2015. The high resolution and high signal-to-noise Keck spectra reveal the long time hidden companion's absorption lines. Moving in anti-phase to the WR emission lines at similar amplitudes, the mass ratio appears to be in the order of unity. Considering an orbital inclination of ~67 degrees, derived from previous polarimetry observations, its total mass would be a mere 2-3 Msol; an unprecedented result for a thought to be massive binary. We apply the shift and add technique to disentangle the spectra and obtain a companion spectra compatible with an O4 spectral type. Assuming a typical for a O4V type, we obtain a new orbital inclination of ~20 degrees. Thus, WR 148 is indeed a massive binary system.