Guild Wars 2

I am in the middle of crafting the Bifrost. Can I get rid of all those star fragments I ran around and collected? And the Defender of Ascalon as well?

Unless it’s a crafting material, or not needed to unlock another collection item as with the HoT ones, then you should be able to.

Always check the wiki to make sure. .

https://wiki.guildwars2.com/wiki/Legendary_Weapons

From the wiki in regards to your question:

• The Jotun star fragments only drop once. Afterwards, you can sell them. It is not necessary to have them in your inventory to complete The Jotun Star.
• It is possible for multiple fragments to drop if you have not picked any of them up yet.
• Fusing the fragments does not remove them from your inventory, but all you can do with them at that point is sell them to a merchant.