Yes, it is.
1. Navigate to "Support" category on top of this page and click "software and drivers"
2. Type the hardware product you have purchased, for instance t620
3. Choose the thin client - t620 flexiable thin client and check the Operating System List
http://h20564.www2.hp.com/hpsc/swd/public/readIndex?sp4ts.oid=5404709&swLangOid=8&swEnvOid=4030