Equation of state and surface thermal emission of magnetized white dwarfs

Abstract

AbstractThe observation and theoretical study of massive magnetized white dwarfs is one of the most important topics in the field of astronomy. This paper aims to obtain a coupled magneto‐thermal evolution model of magnetized white dwarfs (B‐WDs). As a fiducial model, we choose a non‐magnetized WD with a baryonic mass M0 = 1.37 M⊙ (M⊙ is the solar mass) for comparison with the magnetized cases. Firstly, we give an overview of the WD cooling, then study the equation of the state of a B‐WD. We find that the WD mass increases with magnetic field strength B, while its radius decreases with B, and the minimum of B required to reach the Chandrasecka limit is about 3.2 × 1014 G. Finally, by introducing the magnetic‐to‐thermal conversion coefficient ξ, and taking the temperature effect on the stellar radius into consideration, we calculate the luminosities of thermal photons Lph and surface effective temperature, Teff due to Ohmic dissipation for B‐WDs. According to our calculations, magnetic field decay can definitely maintain a long‐term thermal evolution for massive B‐WDs. This study will be useful for the study of internal thermal evolution and internal stability of B‐WDs in the future.