Kayal, 31, has joined the Championship side on a one-year loan deal, while Hemed, 32, who played 45 minutes in Saturday's 1-0 home win over Brentford, joined on a free transfer after a deal was agreed to cancel his contract with the Premier League club.
Although both players transfer forms were field two minutes after the deadlines, the FA approved both players to register with the Championship club.
Kayal said: “I promise to do everything to bring my experience and my quality to help Charlton win games.”
Kayal and Hemed both began their careers at Maccabi Haifa. Kayal played for Celtic and Hemed for Real Mallorca before they teamed up again to help Brighton win promotion to the Premier league. Hemed, 32, spent last season on loan with QPR. He scored 30 times in 97 league appearances for the Seagulls.
