Yes! That is why research like the study I discussed in this article is so important. The gamma-ray signatures found do not seem to match that of a black hole (or other known gamma radiation signatures), but do match what we might expect from matter-antimatter annihilation. However, as one of the researchers mentioned, it would be easier to prove that these sources were actually a know gamma-ray source (such as a black hole) than to prove that they are from antistars, so more investigation into these sources will need to be done before any conclusions can be made.