tokens: in Section 3 and the recipe given in González Delgado et al. ( 2016 ). In a nutshell, for any given galaxy we compute the spaxel-to-spaxel mass of stars younger than 32 Myr. Then, by co-adding these masses over a given aperture we can estimate the average rate of star formation during this period. An extensive discussion about the optimal limiting age of the stellar population used to define the recent SFR is given in González Delgado et al. ( 2016 ). We tested the robustness of this assumption by repeating Fig. 1 using a limit of both 100 and 200 Myr. We find that the results are qualitatively in agreement. Our stellar population approach to compute the SFR is different from the usual H α luminosity proxy used in the literature (Kennicutt 1998 ; Catalán-Torrecilla et al. 2015 ). Nevertheless, it is most powerful for ETGs since it does not depend on the detection of emission lines. Fig. 1 also shows the SFR versus M ⋆ relation for our comparison sample of ellipticals (see Section 2 ) and for our ETGs without considering the bulge and disc components separately. It is worth noticing that, due to the optical coverage of the spectroscopic data, our SFR might be considered as upper limits for very low values of the SFR (see discussion in López Fernández et al. 2018 ; Bitsakis et al. 2019 ). This issue is more acute for our bulge SFR estimations, while it is almost negligible for the star-forming discs. However, this does not affect the main conclusions of this paper. Figure 1. Star formation rate (SFR) versus stellar mass ( M ⋆ ) distribution for our sample of ETGs. The measurements for bulges and discs are shown with red circles and blue stars, respectively. Black squares represent measurements of the same ETGs, but for the galaxy as a whole. Yellow triangles display the position of the sample of elliptical galaxies described in the text. The best fit to the SFMS from Elbaz et al. (Grey; 2007 ), Renzini Peng (Orange; 2015 ), González Delgado et al. (Navy; 2016 ), and Sánchez et al. (Green; 2019 ) are also shown for comparison. Downward arrows mark where the measured SFR is an upper limit (see text for details). It is clear from Fig. 1 that, whenever there is star formation in our ETGs, this is happening in the disc component and not in the bulge. We find that on average the specific SFR (sSFR) is smaller in bulges than in discs. The mean difference in logarithm accounts to at least 1.3 dex when integrated across the whole FoV of CALIFA. In addition, a qualitative comparison with literature values of the best fit to the SFMS at z ∼ 0 (Elbaz et al. 2007 ; Renzini Peng 2015 ; González Delgado et al. 2016 ; Sánchez et al. 2019 ) shows that several discs of our ETG sample are compatible (or over) with the SFMS, whereas bulges occupy the region of the diagram defined by retired galaxies (Crocker et al. 2011 ; Cano-Díaz et al. 2016 ; Sánchez et al. 2018 ), or even lower SFR values for a given stellar mass. In particular, we find that 30 discs and only
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