Mass–radius relation at the approximate temperature of WD1 (26,000 K) for different compositions. The purple dashed curve is the expected core composition of WD1 formed from the expected mixture due to carbon burning including the effects of electron capture. Solid blue band shows the best fit and 1σ region for the radius obtained from photometry, while the orange and green bands show the same for the surface gravity and gravitational redshift determined from spectroscopy.