Meaning of -AR in English
-ar BrE AmE ə, ɑː AmE ə r, ɑːr —In most words this ending is pronounced weak, ə AmE ə r ( ˈ cedar, ˈ stellar). In a few rarer or newer words it is pronounced strong, ɑː AmE \ ɑːr , either as an alternative or as the only form ( ˈ lumbar, ˈ radar).
Longman Pronunciation English Dictionary. Английский словарь произношений Longman. 2012