Observational characteristics of supermassive stars

Stars with masses greater than 1000 times the mass of the Sun are still hypothetical and are candidate polluters to explain the chemical signatures observed in globular cluster member stars. A scenario has been suggested that forms these supermassive stars (SMS) in the centre of young massive clusters via collisions of stars. This project first investigates, if such stars can have gaseous accretion discs and makes predictions for water maser lines that may be observed from such systems. The student will investigate this with 3D hydrodynamics simulations building on previous 2D simulations that they did in the preceding MSc project. A candidate maser system has been identified in the nearby galaxy NGC 253 and the predictions will be compared to observations of that system. Stellar merger remnants have recently been identified to have very high magnetic field strengths. A significant fraction of O-stars in the Milky Way show evidence for this. As SMS would be a collision product as well, they would be expected to have high magnetic field strengths. Hence their strong winds would be highly magnetised. This will produced strongly magnetised bubbles, and since many massive stars would be expected to form close to the SMS, a superbubble when the individual bubbles have merged. In the second part of this project, superbubbles from magnetised massive stars will be modelled with 3D hydrodynamics simulations. The resulting radio synchrotron emission will be compared to superbubbles with known radio emission, like the non-thermal bubble in IC10 and predictions will be made how magnetic massive and supermassive stars change the radio emission of superbubbles.