I have an outbound flight from IAD to IST (then connecting to BUD). When I was checking in online last night, I discovered that my boarding pass shows *S. I am wondering whether I will be able to access to TK lounge in IST. I plan to have my United card showing both Platinum and Star Gold. On the return, I also want to take advantage of the express line from the IST terminal directly to the TK Lounge.

I wonder why my boarding pass shows *S. Has anyone encountered a similar case?