Simulating magnetized white dwarfs by time evolution: Chandrasekhar limit and beyond

Over the last few decades, there has been considerable interest in the violation of the sacred ”Chandrasekhar” mass limit of white dwarfs (WDs). This is particularly so due to several observational evidences for peculiar over-luminous type Ia supernovae (e.g. SNLS-03D3bb), whose power could be explained by super-Chandrasekhar WD progenitors only. Our group has been actively working on the theoretical possibility of these objects for more than a decade. Some of the proposed underlying physics responsible for such a super-Chandrasekhar WD are the effects of magnetic field, modified gravity, non-commutative spacetime etc. In this talk, we will explore the possibility of super-Chandrasekhar WDs through the presence of the star’s magnetic field. The field greatly contributes to the existence of these massive WDs, both through classical and quantum effects. We explore in detail the time-dependent simulation for the evolution of the magnetized main sequence (MS) stars to magnetized WDs using the Cambridge Stellar evolution code: STARS. In order to do so, we have appropriately modified the said code by introducing magnetic effect and cooling. We investigate further the possible existence of stable, massive, super-Chandrasekhar WDs by exploring the classical effects of magnetic fields on the structure of the MS stars, the evolution of the star on the HR diagram and, finally, WDs. We investigate the stability of magnetic WDs, both below and above the Chandrasekhar limit. We obtain the possibility of existence of super-Chandrasekhar WDs and new mass limit(s), depending on the magnetic field geometry, mass accretion from its companion and cooling rates. This has far reaching implications.