Suppression of luminosity and mass-radius relation of highly magnetized white dwarfs

TL;DR

This study investigates how luminosity and strong magnetic fields influence the structure and mass limits of white dwarfs, revealing the potential existence of faint, super-Chandrasekhar white dwarfs with high magnetic fields.

Contribution

It presents a self-consistent model incorporating magnetic fields and luminosity effects, showing the possibility of highly magnetized, low-luminosity super-Chandrasekhar white dwarfs.

Findings

Super-Chandrasekhar white dwarfs can exist at high magnetic fields (~10^{14} G).

Luminosity affects the mass-radius relation, especially for large-radius white dwarfs.

Faint, highly magnetized white dwarfs may be observationally hidden.

Abstract

We explore the luminosity L of magnetized white dwarfs and its effect on the mass-radius relation. We self-consistently obtain the interface between the electron degenerate gas dominated inner core and the outer ideal gas surface layer or envelope by incorporating both the components of gas throughout the model white dwarf. This is obtained by solving the set of magnetostatic equilibrium, photon diffusion and mass conservation equations in the Newtonian framework, for different sets of luminosity and magnetic field. We appropriately use magnetic opacity, instead of Kramer's opacity, wherever required. We show that the Chandrasekhar-limit is retained, even at high luminosity upto about 10^{-2} solar luminosity but without magnetic field, if the temperature is set constant inside the interface. However there is an increased mass for large-radius white dwarfs, an effect of photon diffusion. Nevertheless, in the presence of strong magnetic fields, with central strength of about 10^{14} G, super-Chandrasekhar white dwarfs, with masses of about 1.9 solar mass, are obtained even when the temperature inside the interface is kept constant. Most interestingly, small-radius magnetic white dwarfs remain super-Chandrasekhar even if their luminosity decreases to as low as about 10^{-20} solar luminosity. However, their large-radius counterparts in the same mass-radius relation merge with Chandrasekhar's result at low L. Hence, we argue for the possibility of highly magnetized, low luminous super-Chandrasekhar mass white dwarfs which, owing to their faintness, can be practically hidden.