Fermi-LAT Observations of fast rotating, magnetic white dwarfs J191213.72-441045.1 and EUVE J0317-85.5

We report the possible detection of pulsed 𝛾-ray emission from one confirmed white dwarf pulsar J191213.72-441045.1 and a candidate white dwarf pulsar EUVE J0317-85.5 using ∼15 years of data from the Fermi-LAT observatory. Pulsed 𝛾-ray emission in the 0.5-10 GeV energy range from J191213.72-441045.1 were detected at a period of 𝑃=319.99±0.35s with a -log(Pr)=6.76 which corresponds to a significance of ∼4.37𝜎 using the H-test Test Statistic. This H-test Test Statistic avoids the application of statistical penalties to the periodogram. The phase-folded 𝛾-ray light curve on this period is remarkably in phase with the recent optical observations of J191213.72-441045.1 suggesting that the pulsed 𝛾-rays and optical photons might be emanating from the same region in J191213.72-441045.1. Pulsed 𝛾-ray emission in the 0.5-10 GeV energy range were also found from the isolated, highly magnetic white dwarf EUVE J0317-85.5 at the period of 𝑃=724.65±0.54s with a -log(Pr)=5.02 which corresponds to significance of ∼3.72𝜎 using the H-test Test Statistic. The phase-folded 𝛾-ray light curve on this period is also in phase with recent optical observations of EUVE J0317-85.5 using the BOOTES-6 robotic telescope. We propose that the pulsed 𝛾-ray emission in the 0.5-10 GeV energy range from both of these fast spinning, magnetic white dwarfs is likely produced by the curvature radiation mechanism based on recent studies suggesting that fast spinning, magnetic white dwarfs to be possible low-level 𝛾-ray emitters.