Landing page for project EP125

HD220242 is an F5 type star, and is the only main-sequence star other than an M dwarf or an RS CVn star that has been detected with highly circularly polarized emission in the LOFAR Two-metre Sky Survey. Radial velocity measurements and Gaia data suggest that HD220242 hosts a companion, but its nature is under debate. Sparse radial velocity data suggests a main-sequence companion, while astrometric analyses of Gaia-Hipparcos data favour a brown dwarf in a very close orbit, or a low-mass stellar companion at an orbital distance from 3 to 10 au. We propose L-band e-EVN observations aimed at detecting the radio emission from HD220242. Whether the companion is a brown dwarf or a main sequence star, the outcome has strong implications: If the companion is a brown dwarf in the so-called desert, this will constrain formation and migration theories, and will test scaling laws that predict the radio flux of exoplanets. Alternatively, the confirmation of a main sequence star companion will be a puzzling finding, given its very high radio loudness in the LOFAR band, and will require to understand better the energetics leading to coherent radio emission in those stars.

This data is part of the archive of VLBI data maintained by JIVE on behalf of the EVN, a network of radio telescopes located primarily in Europe and Asia, with additional antennas in South Africa. The EVN archive itself has the DOI https://doi.org/10.17616/R3Z197