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

TL;DR

This paper modifies Einstein's gravity to explain the full range of white dwarf masses leading to Type Ia supernovae, unifying under- and over-luminous events through a single property, the central density, without changing fundamental gravity parameters.

Contribution

It introduces higher order corrections to $f(R)$ gravity to unify sub- and super-Chandrasekhar white dwarf masses based solely on central density variations.

Findings

White dwarf mass limits vary with central density under modified gravity.

Models are consistent with solar system tests.

Unified explanation for diverse Type Ia supernovae progenitors.

Abstract

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.