Discovery of a 310 Day Period from the Enshrouded Massive System NaSt1 (WR 122)

Abstract We present optical and infrared (IR) light curves of NaSt1, also known as Wolf–Rayet 122, with observations from Palomar Gattini-IR (PGIR), the Zwicky Transient Facility (ZTF), Katzman Automatic Imaging Telescope, Asteroid Terrestrial-impact Last Alert System, All-Sky Automated Survey for Supernovae (ASAS-SN). identify a P = 309.7 ± 0.7 day photometric period IR that reveal periodic, sinusoidal variability between 2014 July 2021 July. historical taken 1983 1989 May, which show consistent present-day curves. In past, NaSt1 was brighter in J band larger amplitudes than PGIR values, suggesting exhibits on longer (≳decade) timescales. Sinusoidal fits to recent amplitude NaSt1's differs at various wavelengths significant phase offsets 17.0 2.5 ZTF r interpret 310 orbital an enshrouded massive binary. suggest may arise variations line-of-sight depth toward circumstellar optical/IR-emitting regions throughout its orbit due colliding-wind dust formation. speculate past mass transfer have been triggered by Roche-lobe overflow (RLOF) during eruptive Ofpe/WN9 star. Lastly, we argue is no undergoing RLOF transfer.