DOI

https://doi.org/10.48717/ep58-vy55

Project

EB115

Title

e-EVN: EB115A, RSM06B

Abstract

A new class of pulsating radio sources with unusually large periods ($\gtrsim 10\,$min) has recently been identified. Although only six such sources are known, their large radio luminosity, long period, and in some cases high period derivatives, appear inconsistent with a rotationally powered neutron star progenitor. Instead, a white dwarf or magnetar progenitor has been suggested. Here we request 36 hours of EVN astrometric measurements of a newly discovered 70-minute period radio source that is nearly 100% circularly polarised. Such high circular polarisation is unusual for this new class of object, raising the intriguing possibility that emission from this new source could instead be powered by the electron-cyclotron maser instability from a nearby brown dwarf or free-floating exoplanet. Our proposed observations will critically discriminate between the brown dwarf and compact object hypotheses via a trigonometric parallax and proper motion measurement. If the compact object hypothesis is confirmed, the proposed data will also provide the necessary astrometric constraints to plan follow-up optical and infrared observations to conclusively test the white dwarf hypothesis.