Establish definitive link SO/Spin

Background: In supergiant High-Mass X-ray Binaries (sgHMXBs), phenomena such as pulse period changes (torque reversals) and periodic variations in X-ray luminosity (superorbital modulations) are observed. Understanding the mechanism linking these phenomena is an ongoing research challenge.

Question / Future Work: The paper notes that while a possible link between superorbital modulations and pulse period changes has been suggested for 4U 1538–52 and 2S 0114+650, continued long-term monitoring of these and other systems are required to establish a definitive link between the two phenomena. Additionally, the difficulty in disentangling short-term variability from long-term variations in spectral parameters associated with the underlying mechanism remains. A forthcoming study using long-term Swift-BAT monitoring is planned to further investigate the disentangling of short-term versus long-term spectral variations. Furthermore, regular monitoring of these sources with current and future instruments like eXTP is needed to further understand the connection between superorbital modulations and pulse period changes.