AADL is a standard for modeling embedded systems that is widely used in avionics and other safety-critical applications. However, AADL lacks a formal semantics, and this severely limits both unambiguous communication among model developers, and the development of simulators and formal analysis tools. In this work we present a formal object-based real-time concurrent semantics for a behavioral subset of AADL in rewriting logic, which includes the essential aspects of its behavior annex. Our semantics is directly executable in Real-Time Maude and provides an AADL simulator and LTL model checking tool called AADL2Maude. AADL2Maude is integrated with OSATE, so that OSATE's code generation facility is used to automatically transform AADL models into their corresponding Real-Time Maude specifications. Such transformed models can then be executed and model checked by Real-Time Maude. We present our semantics, and two case studies in which safety-critical properties are analyzed in AADL2Maude.