Speaker
Description
We report the possible detection of γ-ray pulsations from both the recently
discovered ∼4.03 hour binary system J1912-4410 which consists of a white dwarf
rotating at Pspin=319.34903(8)s (∼5.32 minutes, Pelisoli et al. 2023) with an M-
dwarf companion and the 725.5(8)s (∼12 minutes, Ferarrio et al. 1997) rotating,
isolated white dwarf EUVE J0317-855 using ∼15 years of observations from the
Fermi -LAT telescope. Pulsed emission in the energy range 0.5-10 GeV was
found at a period Pspin=319.3491(3)s which corresponds to the spin period of
the white dwarf in J1912-4410. No significant pulsations in the γ-rays were
found at the beat frequency or other orbital sideband frequencies. The γ-ray
light curve of J1912-4410 folded on the detected period is aligned with recent
MeerKAT radio light curves using the same spin ephemeris which might suggest
that the radio and γ-ray photons are produced at the same regions on the white
dwarf. The folded γ-ray light curve of J1912-4410 at energy 0.1-500 GeV are
also aligned with the radio light curves but also show a faint peak at phase ∼0.5
which we interpret as pulsed γ-ray emission from the second magnetic pole of
the white dwarf in J1912-4410. Pulsed γ-ray emission from EUVE J0317-855
were also detected at a spin period Pspin=725.500(4)s and its first harmonic
P=362.750(1)s. The first harmonic was found to be more prominent in the 0.5-
10 GeV energy band whereas the spin period is more prominent in the 0.1-500
GeV band. These results suggest that fast spinning, highly magnetized white
dwarfs that are isolated or in binary systems might mimic the behaviour that
is seen from pulsars.
