The union between Syria and Egypt came to be on February 22, 1958 with the signatures of President Quwwatli of Syria and Nasser of Egypt, after a public referendum in both countries. Nasser was President of the UAR, with Cairo as the capital. In 1958, it formed a loose federation with Yemen called the 'United Arab States'. In 1960, regional ministries in Syria were abolished by Nasser in favour of the central government. The union ended on Spetember 28, 1961 with Syrian secession after a military coup, and Yemen soon followed suit, although Egypt kept the name 'United Arab Republic' for another nine years. The flag consisted of three horizontal stripes of red, white, and black, with two green stars on the white stripe.
info from http://www.damascus-online.com/se/hist/united_arab_republic.htm and http://www.bartleby.com/65/un/UntdArRep.html