Exploring PSR J0901-4046 as an ultra-slowly rotating neutron star versus a white dwarf

The source PSR J0901-4046 shows a very long rotational period, of $\approx 75.88$ s. In fact, its long period suggests that it could be a white dwarf. We examine the properties of the source and compare the outcomes under the hypotheses of the source being a highly magnetized white dwarf (B-WD) and neutron star. We find that assuming it to be a B-WD with a surface field $\sim {10}^{10}$ G explains many properties, including its storage/rotational energy, explaining luminosity. On the contrary, the neutron star-based idea, particularly if examined under the conventional spin down mechanism, requires an unusually high surface magnetic field $\gtrsim {10}^{14}$ G, even exceeding ${10}^{16}$ G, depending on the obliquity angle and emission mechanism. The source also sits very close to AR Sco, a white dwarf pulsar, in the period and period-derivative plane. We suggest that the source is a B-WD. Along with AR Sco, it being a B-WD constrains the death line model. B-WD hypothesis alleviates the necessity of an unusually high magnetic field hindering pair production for PSR J0901-4046 under the neutron star hypothesis. We argue that some rotation-powered pulsars with extreme properties may possibly be white dwarfs rather than neutron stars.