Eesha Das Gupta

In 2020, Emma Beasor and collaborators provided a novel mass loss prescription for Red Supergiant (RSG) stars in terms of their initial masses, in addition to their luminosities. Their paper reported lower rates for these stars than previously thought, implying significant consequences for their evolutionary history and compact object fate. However, things get complicated if binary interactions are brought into the mix. Binary stars can gain or lose mass and can change evolutionary tracks on the HR diagram, taking on paths not expected of their single star counterparts. HR Diagram evolutionary paths are very much dictated by initial mass. So what happens when a lower mass loss rate that depends on initial mass, is introduced to the system? What does that mean for the compact objects these stars would form? Does that impact mergers and would it be of importance for something like LIGO - a detector well suited for measuring gravitational waves for compact object mergers? I'm using COSMIC,a binary population synthesis code, to investigate this by modifying the mass loss prescription for Red Supergiant stars. Stay tuned for a paper!

With recent advances in the field of observational asteroseismology, we are getting pretty good at measuring the internal rotation of stars. But our models are yet to catch up. The solar core, for instance, is rotating slower than what models can reproduce. This implies that the angular momentum transport inside the Sun is more efficient than what our current models imply. The nonlinear nature of the problem itself makes a complete 3D model of the problem computationally expensive, and therefore near impossible. However, reducing dimensionality means compromising on facets of the problem that could be crucial to understanding internal rotation within stars. Given that, the best we can do is come up with prescriptions that can closely reproduce observations, despite being approximations of the ongoing physics.
In their 2006 paper, Menou and Le Mer proposed a dispersion relation approach to implementing Magneto-rotational Instability or MRI - a double diffusive instability that is very well modelled in astrophysical disks - for the interior of the early Sun. I'm trying to translate their MRI recipe to MESA - a one-dimensional stellar evolution code. Magnetic fields transport angular momentum on scales larger than simply hydrodynamic instabilities and Menou and Le Mer 2006 found that MRI modes may have existed in a young sun. I'm working on extending their work and hope to explore a parameter space on the HR Diagram to chart the effects of MRI on core rotation rates.