England goalkeeper Fraser Forster does not know if he will still be at Celtic when they next play in Europe.
Norwich captain Sebastien Bassong has signed a new two-and-a-half-year contract.
The 34-year-old has barely featured under Michael Laudrup at City, starting just once since the Dane replaced Brendan Rodgers.
But Charlton boss Chris Powell has hinted at a permanent deal if Gower impresses in the club's final nine games.
He told the club website: "Mark is a midfielder I've had an eye on for a while.
"It's an area that I felt we needed someone just to come in and boost the numbers. He's got a good pedigree.
"He's a talented player, a good user of the ball and I think he will just add quality to the squad.
"I'm looking at him just to help us over the line for the rest of the season and then who knows? Maybe depending on how it goes he may be someone I look at for the future."