WD 0816–310

Among the polluted White Dwarf stars within 200 parsecs is WD 0816–310 alias SCR 0818−3110 or PM J08186−3110, at 19.4 parsecs. The new study doesn't cite Putirka / Siyi Xu on planetary mantles (tho' it cites an earlier Siyi Xu). I suspect this dwarf has no overlap with Putirka's set.

Its "cooling age" is 4.2 Gya; 2.5 masses before that, so between A0V and B9V for 600 My. And this one had more hydrogen than usual for a WD. This has been assumed pollution from hydrate ices like water, methane, and/or ammonia. I don't think Putirka had cited that paper.

Anyway the new study has this one as truly metal-polluted as well: Ca, Mg, Fe especially Mg. Usually when astronomers talk "metal" they mean anything higher than helium so would count oxygen, carbon, and nitrogen. This pollution is at least Vesta-mass.

More: the ratios look like chondrites. That's undifferentiated C-class rock like Pallas; Vesta proper is S (really P - for differentiated Marslike Planet). So this polluting mass is not counting what mass on its erstwhile Pallades wasn't metal. That may include silicon but assuredly includes carbon.

That, then, is why this paper does not overlap the others, on the planets' mantles. No differentiation means no mantles. Most worlds out in the soot zone perhaps even up to Mars' size stayed internally stiff. In the 600 My allotted them, they also did not mutually collide (as much). So they never differentiated; they stayed protoplanets to the end.

When the parent star went red, it expanded deep into what, here, would be the asteroid-belt. Gobbling... C-type asteroids, super-Pallades.