As hinted at in the title, assuming the technology/means existed that could absorb energy fast enough, would it be possible to stop a star from going supernova, effectively “calming” it?
This is for a novel (not exactly a sci-fi one) but I’d like to keep in the realms of “technically possible”.
This is going to depend on the specifics of your story, but a supernova happens when a star runs out of easily fused fuel (hydrogen, helium).
If you want to prevent the supernova entirely and return the star to “normal,” that means removing all the heavy elements from a stellar core and adding lighter elements. I’m no scientist (or author), but turning back the clock like that is beyond my imagination.
Absorbing the energy for use in other applications? Any sufficiently advanced technology is indistinguishable from magic, so…maybe? You can probably hand wave that way. It won’t be 100% efficient, and whatever tech that’s absorbing that energy has to be able to contain a star. This one has at least some hypothetical support: https://en.wikipedia.org/wiki/Kardashev_scale
It reminds me of the Ringworld novels. I won’t rehash the entire plot, but basically an artificial structure is built that requires a material the author calls “scrith” that is essentially impossible with known physics, but a clever author can write around it well enough that it doesn’t get too much attention for its “magic” properties.