What exactly is it that is being magnified 50 times in this gravitational lensing observation? In the Los Angeles Times news item Scientists get a rare view of a type Ia supernova magnified 50 times what exactly is magnified 50 times? 

This supernova is really very far away. Is it somehow imaged by the gravitational lensing and being resolved — the actual supernova itself?

edit: I believe this is it, but it's behind a paywall (will confirm in due course): http://science.sciencemag.org/content/356/6335/291





above: From the Los Angeles Times. Photo credit: Joel Johansson



above: "This schematic image represents how light from a distant galaxy is distorted by the gravitational effects of a nearer foreground galaxy, which acts like a lens and makes the distant source appear distorted, but brighter, forming characteristic rings of light, known as Einstein rings. An analysis of the distortion has revealed that some of the distant star-forming galaxies are as bright as 40 trillion Suns, and have been magnified by the gravitational lens by up to 22 times. (Credit: ALMA ESO/NRAO/NAOJ, L. Calçada (ESO), Y. Hezaveh et al., edited and modified by Joel Johansson)" From the Los Angeles Times.
Reading through the full article, I see that the authors write


  we estimated the lensing amplification to be $\mu\sim52$.


This refers to the magnification factor. Essentially, it describes the solid angle of the image, as related to the solid angle of the source1:
$$\mu\equiv\frac{\theta}{\beta}\frac{d\theta}{d\beta}$$
Here's a diagram of the magnitudes of the angles:



Image courtesy of Wikipedia user Falcorian under the Creative Commons Attribution-Share Alike 3.0 Unported license.