Product of Friedel-Crafts cyclisation of (3-methylpent-4-en-1-yl)benzene
Though the question is old and pretty much answered in the comments, I ran into this question and draw the mechanism, so I thought about summarizing all that was brought up in an answer.

The carbocation is first formed on the secondary carbon. However, molecules are more stable when the charges are delocalized (this page talks about the stability of carbocations). When the positive charge is in the secondary carbon, it can only "share the burden" of having this charge with 2 neighbor carbons. So the tertiary carbon donates an hydrogen through a sigma to atomic orbital interaction (the sp3 hybdrization allows a π-type interaction) resulting in the more stable tertiary carbocation seen in the mechanism below:



Then the reaction follows analogously to the pathway you deduced for the 6 membered ring: First a π to atomic orbital interaction between the aromatic ring and the tertiary carbocation, which I believe to be the Rate Determining Step since it breaks the ring aromacity (bigger energy gap). Then finally the sigma to atomic interaction between the hydrogen and the ring carbocation, that restores aromaticity and releases the hydrogen.