Maybe they ask you to fill out the W4 as single? That would be fine, as that only affects the tax withholding. But filing the return itself as single is wrong. Have a look at publication 519 <a rel="nofollow" target="_blank" href="
https://www.irs.gov/publications/p519/">https://www.irs.gov/publications/p519/</a>
for details on how to file. You can download all required forms from the internet. Also, some universities provide access to tax preparation software for their students and postdocs via Glacier. You should ask at the international office or student office. I looked at the treaty with Turkey and it seems, that your income would only be exempt, if it was paid from outside the US. The treaty (article 20 would be relevant) can be found here: <a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-trty/turkey.pdf">https://www.irs.gov/pub/irs-trty/turkey.pdf</a>
