Magnetic Activities of GJ 1151: Flares in TESS Data and Radio Observation in uGMRT

Abstract GJ 1151 is a nearby (8 pc), quiescent mid-M dwarf (M 4.5V) of older age, made especially interesting by the hypothesized presence of a close-in planet invoked to explain its low-frequency radio emission. We analyzed the flaring activity of GJ 1151 to investigate its stellar atmosphere and magnetic properties using 2 minute short-cadence photometry from the Transiting Exoplanet Survey Satellite (TESS) and radio observations from the upgraded Giant Metrewave Radio Telescope (uGMRT). Analysis of TESS Sector 48 revealed three flare events, with bolometric flare energies estimated in the range of 10 30 –10 31 erg, showing that GJ 1151, previously regarded as optically inactive, does in fact exhibit flare activity, placing it in the lower-to-intermediate activity regime. Interestingly, we reported the first estimation of the most energetic flare energy to be (4.86 ± 0.19) × 10 31 erg that lasted for approximately 30 minutes, implying a minimum surface magnetic field strength of 45 G to power the event. We estimated the mean spot temperature to be approximately 2886 ± 837 K and the spot area to be 1.2% of the area of the star. The nondetection of radio emission at 1.36 GHz with the uGMRT suggests either time variability in the emission or the presence of a frequency cutoff in the 3 σ upper limit on its flux density of 105 μ Jy beam −1 in the emission mechanism, potentially governed by the changing magnetic environment of the star and the orbital configuration of its hypothesized planet.