tokens: by a Gaussian probability density function (PDF) with mean and standard deviation . For the flux limits, we used the 1 σ upper limits as as well as σ for the PDFs. All PDFs are set to zero for negative fluxes. Each of these Gaussian PDF representations of the measurements are corrected by the lens magnifications listed in Table 2 , using the intrinsic flux as simply the observed flux divided by the magnification and that the variance on the intrinsic flux is given by:Here is the estimated lensing magnification for each image. The uncertainties on the magnification factors quoted in Table 2 are not symmetric, and we therefore, conservatively, use the largest absolute value of the upper/lower magnification ranges as . The product of the individual magnification-corrected PDFs for each image gives us a representation of the intrinsic flux of the background source including information from both the detections and the upper limits. If any of the detections and/or upper flux limits were in disagreement such a product would be driven to 0. Within 3 σ, all of our measurements are in agreement with each other. Sampling the distribution resulting from taking the product of the individual PDFs, we obtain the combined intrinsic magnification-corrected line fluxes or line flux limits. In Table 3 , we quote the median value and 68% (∼1 σ ) confidence intervals for the final distribution. Comparing these values with the measurements performed directly on the stack also given in Table 3 scaled by the average HFF lens magnification of images A–E (), the de-magnified Ly α and C iv fluxes agree within the errors (especially if the large uncertainties on the magnification are folded into the error budget). The intrinsic flux limits appear to be roughly a factor of three tighter from the stack than from the Gaussian PDF if the uncertainties on the lens magnification are ignored. The tentative detection of the O iii ]-doublet in the stacks agree with the magnification-corrected flux limit set by the Gaussian PDF combination. 5.2. Interpreting UV Line Fluxes and EWs As mentioned in Section 1 , EWs and flux ratios of rest-frame UV lines are strongly correlated with the ionization strength and the gas-phase metallicity of the stellar populations dominating the SEDs of the emitters (e.g., Stark et al. 2015b , 2017 ; Feltre et al. 2016 ; Gutkin et al. 2016 ; Jaskot Ravindranath 2016 ; Mainali et al. 2017 ; Pérez-Montero Amorín 2017 ). Hence, the obtained flux ratios (limits) from the GLASS spectra can be used as an indicator of the physical properties of the multiply imaged source behind RXC J2248.7–4431 as described in the following. The C iii ] EW and the flux ratio between C iv and C iii ] are sensitive to the gas-phase metallicity and the ionization parameter of the stellar populations (Feltre et al. 2016 ; Gutkin et al. 2016 ; Jaskot Ravindranath 2016 ; Pérez-Montero Amorín 2017 ). From the GLASS spectra, we get rest-frame (1 σ ). As shown by Rigby et al. (
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