'own' emphasizes that the thing that was done only by the pronoun (e.g., our, my, his, etc) without help from others.

I learned to tie my shoelaces on my own (by myself).

We did the research by ourselves / We did our own research (no one else helped us / just the people included in "ourselves" and "our")

As the other answers stated, it emphasizes 'who' did the research.

But to answer your question; "Why do we still need to use 'our' own? The answer is, you don't 'need' to use it. Using it adds exactness. Again, it emphasizes 'who' did the research. 

Short answer, it looks and sounds better and eliminates ambiguity when written with 'own.'

Research done by US - our own research.

Research done by ME - my own research.

Research done by YOU - your own research.

Research done by HIM - his own research.

Research done by HER - her own research.