  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 fourteen 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.
