SRD:Flaming Burst

Flaming Burst: A flaming burst weapon functions as a flaming weapon that also explodes with flame upon striking a successful critical hit. The fire does not harm the wielder. In addition to the extra fire damage from the flaming ability (see above), a flaming burst weapon deals an extra 1d10 points of fire damage on a successful critical hit. If the weapon’s critical multiplier is x3, add an extra 2d10 points of fire damage instead, and if the multiplier is x4, add an extra 3d10 points of fire damage. Bows, crossbows, and slings so crafted bestow the fire energy upon their ammunition.

Even if the flaming ability is not active, the weapon still deals its extra fire damage on a successful critical hit.

Strong evocation; CL 12th; Craft Magical Arms and Armor and flame blade, flame strike, or fireball; Price +2 bonus.