They are rising because Bitcoin is rising it is as simple as that. Look to Bitcoin for what the rest of the market will do, altcoins success and downfalls are usually tied to whatever Bitcoin is doing at the moment.
Since btc has crossed 8300$ the altcoin also have started to recover and many investors seems to be back in the market and thus the demand is rising continuously. Also a good time for traders to quickly make some quick gains in this rising prices.