Do other Shards know when a Vessel dies?

[+Czernobog]

Taravangian seems to want to hide that Odium is no longer held by Rayse. Aside from Cultivation, who directly spoke with him, would the other shards see through this deception, or would Taravangian succeed in pretending to still be Rayse?

[Nebelskind]

If Frost is a Shard, which I’m not sure he is, then no: Hoid’s letter mentions the deaths of Devotion and Dominion as if Frost might not have noticed it. 

Harmony mentions in RoW that some Shards are hidden from him. So there’s a least a chance that the Vessels do not become aware when something like this happens. However, Odium does know that Harmony exists, and has merged two Shards, so there’s some level of awareness.

I’m not sure we know this for certain either way, but those are all the things I could remember that seemed related

[+robardin]

I suspect that something like a Shard being released and then taken up again would have reverberations in the Cosmere that those in tune with it would pick up on.

Not just other Shards, but very likely the members of the Ire, the 17th Shard, and "by now" the Ghostbloods. From Mistborn: Secret History we see that the Ire had carefully laid plans for "when" not "if" Preservation were dropped by its dying Vessel, and Khriss likewise knew it was "in the air" (albeit too dangerous for her to be personally and physically close to witnessing, due to Ruin's hostile presence).

That is different from knowing anything about the new Vessel. But unless Taravangian is extremely convincing, it's not going to pass muster if he tries to act like Rayse decided to give up the power and Descend, "just for a bit, right, to eat some food and see if it tasted the way I remembered it", before taking the Shard back up again.

At any rate, the Fused certainly know, or at least El does, who refers to the "newest Odium, who was so recently one of them [humans]" in his Musings on the Final Ten Days.