Extended Data Fig. 4: Stacked GTC/MEGARA spectra.
From: A nebular origin for the persistent radio emission of fast radio bursts
From left to right, Hβ, [OIII] 5007 and Hα regions are presented. a, Stacked spectra from the six pixels in the FRB region (as shown in Extended Data Fig. 3). b, Stacked spectra of the entire galaxy. Individual spectra were shifted to align with the reference redshift (z = 0.0978) before stacking to compensate for any Hα-related velocity effect. Coloured vertical dotted lines mark the centroids of the three lines at the reference redshift. We observe an absorption line at approximately 5,493 Å. However, the nature of this spectral feature remains unrecognized by our analysis. This line is observed in each individual spectrum, too.
