The TESS View of LOFAR Radio-emitting Stars

The recent detection of the M dwarf GJ 1151 at 144 MHz low radio frequencies using LOFAR has been interpreted as evidence of an exoplanet magnetically interacting with its host star. This would be the first exoplanet detected around a main-sequence star by a radio telescope. Radial velocity confirmation of such a planet has proven inconclusive and it remains possible that the radio emission could be generated by a stellar coronal process. Using data from TESS, we shed light on this question by probing the stellar activity and flares of GJ 1151 as well as 14 other M dwarfs detected by LOFAR. GJ 1151 and three other star–planet interaction candidates are found to be inactive, with no rotational modulation and few, if any, flares. The remainder of the LOFAR-detected M dwarfs flare frequently. We consider it unlikely that stellar activity is responsible for the bright, circularly polarized emission from GJ 1151 and its three analogs and support the star–planet magnetic interaction interpretation.