Fig. 3: The model-independent constraints on the monochromatic signal.
From: Searching for ultralight dark matter conversion in solar corona using Low Frequency Array data

Model-independent 95% C.L. upper limits \({S}_{\lim }\) regarding photon frequency f are derived from LOFAR data on a constant monochromatic signal. The limits obtained from the observation data on 25 April 2015, 3 July 2015, and 3 September 2015 are represented by the blue, orange, and green curves, respectively.