2017ApJ...834..209L

We report the results of the monitoring campaign of the transient X-ray pulsar SMC X-2 performed with the Swift/XRT telescope over the period of 2015 September-2016 January during the Type II outburst. During this event, the bolometric luminosity of the source ranged from ≃10³⁹ down to several x10³⁴ erg s^–1. Moreover, we discovered its dramatic drop by a factor of more than 100 below the limiting value of L_lim≃4×10³⁶ erg s^–1, which can be interpreted as a transition to the propeller regime. These measurements make SMC X-2 the sixth pulsating X-ray source where such a transition is observed and allow us to estimate the magnetic field of the neutron star in the system B ≃ 3 x 10¹² G, which is in agreement with independent results of the spectral analysis.