Modified Einstein's gravity to probe the sub- and super-Chandrasekhar limiting mass white dwarfs: a new perspective to unify under- and over-luminous type Ia supernovae

Type Ia supernovae (SNeIa), used as one of the standard candles in astrophysics, are believed to form when the mass of the white dwarf approaches Chandrasekhar mass limit. However, observations in last few decades detected some peculiar SNeIa, which are predicted to be originating from white dwarfs of mass much less than the Chandrasekhar mass limit or much higher than it. Although the unification of these two sub-classes of SNeIa was attempted earlier by our group, in this work, we, for the first time, explain this phenomenon in terms of just one property of the white dwarf which is its central density. Thereby we do not vary the fundamental parameters of the underlying gravity model in the contrary to the earlier attempt. We effectively consider higher order corrections to the Starobinsky-$f(R)$ gravity model to reveal the unification. We show that the limiting mass of a white dwarf is $\sim M_\odot$ for central density $\rho_c \sim 1.4\times10^8$ g/cc, while it is $\sim 2.8M_\odot$ for $\rho_c \sim1.6\times 10^{10}$ g/cc under the same model parameters. We further confirm that these models are viable with respect to the solar system test. This perhaps enlightens very strongly the long standing puzzle lying with the predicted variation of progenitor mass in SNeIa.