  At the moment, there are two neutron star X-ray binaries with massive red
supergiants as donors. De et al. (2023) proposed that the system SWIFT
J0850.8-4219 contains a neutron star at the propeller stage. We study this
possibility by applying various models of propeller spin-down. We demonstrate
that the duration of the propeller stage is very sensitive to the regime of
rotational losses. Only in the case of a relatively slow propeller model
proposed by Davies and Pringle (1981), the duration of the propeller is long
enough to provide a significant probability to observe the system at this
stage. Future determination of the system parameters (orbital and spin periods,
magnetic field of the compact object, etc.) will allow putting strong
constraints on the propeller behavior.
