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Now we need an estimate of event rate. Note that apparent angular size is increased by lensed magnification so we don't want highly magnified lensed SNe.
Diego et al (20220 in paper about lensed type Ia say that photosphere radius after 1 mo is 10^-3 parsecs, or 3E15 cm. Too big! In retrospect this had to be true.
If these objects have comparable spectra, then to have comparable magnitudes their emitting areas have to be comparable.