Landing page for project EP137

HD 220242 is an F5V star and the only non–M-dwarf main-sequence object in the LoTSS Stokes-V survey showing strong circular polarization at 144 MHz. Recent RV+Hipparcos/Gaia modeling demonstrates that the known companion, HD 220242B, is a 0.619 Msun low-mass star on an 8.48 au orbit, ruling out a brown dwarf. In 2023 we detected a compact 1.7 GHz source at ~6.5 sigma, offset by ~300 mas (~21 au) from the propagated Gaia DR3 position, usiing the e-EVN, This separation is difficult to reconcile with the 8.5 au orbit and suggests either a background source or an additional bound component. LOFAR’s positional uncertainty also allows a common origin for the LOFAR and EVN signals. We therefore request two 6-h EVN L-band epochs separated by ~6 months, using dual polarization, to perform a decisive common-proper-motion (CPM) test and, if bound, measure relative astrometry to constrain a possible hierarchical triple. A non-CPM result will close the case (background source), while a CPM result will identify a new radio-emitting component and inform models of coherent radio emission in intermediate-mass multiple systems.

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