The barbarian archetype Path of the Storm Herald from Xanathar's Guide to Everything has a class feature called Storm Aura (page 10):
Starting at 3rd level, you emanate an aura while you rage. The aura extends 10 feet from you in every direction, but not through total cover.
Your aura has an effect that activates when you enter your rage, and you can activate the effect again on each of your turns as a bonus action. Choose desert, sea, or tundra. Your aura's effect depends on that chosen environment. You can change your environment choice whenever you gain a level in this class.
If your aura's effects require a saving throw, the DC equals 8 + your proficiency bonus + your Constitution modifier.
The "Tundra" option is described as followed:
Tundra. Each creature of your choice in your aura gains 2 temporary hit points, as icy spirits inure it to suffering. The temporary hit points increase when you reach certain levels in this class, increasing to 3 at 5th level, 4 at 10th level, 5 at 15th level, and 6 at 20th level.
Usually, features linked to a barbarian's Rage end when the Rage ends, but from reading these, it appears to me as though these temporary hit points will stick around indefinitely afterwards.
Do these temporary hit points remain after the Rage ends?