Recently discovered periodic radio transient may be a rare white dwarf pulsar, study finds

Tomasz Nowakowski is a writer for Phys.org.

A new study suggests that a recently discovered periodic radio Transient source may be a rare white dwarf. The paper was published on the arXiv pre-print server.

The rotating neutron stars emit a beam of radiation. They are usually detected in the form of short bursts of radio emission.

Astronomers theorize that a rotating magnetic white dwarf might show activity similar to a pulsar. Only one white dwarf pulsar has been found so far, as it contains a rapidly spinningWD bombarding its red dwarf companion with powerful beams of electrical particles and radiation. The system will fade twice every two minutes because of this.

A recently discovered pulsar has a spin period of 1,091 seconds. Transient radio bursts with durations of about a month are displayed, while the pulse width can be between 30 to 60 seconds. The rotational power of this pulsar was calculated to be less than 12 octillion erg/s, which is much smaller than the luminosity of the radio emission that is estimated to be about 40,000 erg/s.

The long period of radio pulsars and single neutron stars from other populations does not exceed 20 seconds. A previous study suggested that the long period may be the result of long-term evolution in the fallback disk model, when a neutron star evolve with a fallback disk and a magnetic dipole.

According to the study, the peculiar properties of GLEAM-XJ162759.5 may be explained by the fact that it is a white dwarf. He focused on the mean radiated power of the source as it exceeded the upper limit on its spin-down power by more than an order of magnitude.

It is impossible for a rotation-powered object to emit more than 1 percent of its spindown power as coherent radio emission. He thinks that the peculiarity could be explained by the long rotation period and theWD pulsar scenario.

"White dwarf have moments of inertia ∼ 10⁵⁰ g cm², about five orders of magnitude greater than that of a neutron star, increasing the estimated spindown power to ∼ 10³³ ergs/s, sufficient to power the radio emission with plausible (<<1)>

The temporal substructure of at least one of the pulse of GLEAM-XJ162759.5 indicates a large radius of curvature of the magnetic field lines, which supports his hypothesis.

In his concluding remarks, he noted that his finding opens the possibility that many white dwarfs may be WD pulsars. In order to confirm this, he suggests low frequencies of radio observations.

More information: J. I. Katz, GLEAM-X J16279.5-523504.3 as a White Dwarf Pulsar. arXiv:2203.08112v2 [astro-ph.SR], arxiv.org/abs/2203.08112

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