Air carrier flight crew reported while descending in Class B airspace they had a NMAC with an unidentified general aviation aircraft.
Synopsis
Air carrier flight crew reported while descending in Class B airspace they had a NMAC with an unidentified general aviation aircraft.
Narrative
During the descent into ZZZ on the RNAV STAR; in the vicinity of the ZZZZZ waypoint; we received a traffic advisory from ATC.Descending through 7;000ft to our assigned altitude of 6;000ft; we received a TCAS alert (TA).We noted the traffic on the TCAS display; started reducing our descent rate; and were able to visually identify the traffic at our 12 o'clock; moving to our 11 o'clock position; just a few hundred feet below and opposite direction. We then received a Resolution Advisory to 'adjust vertical speed'.I disconnected the autopilot and followed the RA vertical guidance while executing a slight turn to the right to increase separation.The traffic passed off our left wing within approximately 200ft. The traffic was a GA aircraft (Cessna; white with grey stripe). It did have its landing lights on and was maintaining a straight and level flight path.The Captain notified ATC of our responding to the RA.Once the RA was over and upon hearing the associated 'Clear of conflict' aural unit message; I complied with the most recent ATC instruction; re-engaged the autopilot; and resumed the arrival.The flight continued to ZZZ without incident.
Second reporter narrative
Upon descent into ZZZ on the RNAV [arrival]; we received a traffic advisory from ATC. Descending through 7;000ft to our assigned altitude of 6;00ft we received a TCAS alert. We noted the traffic on radar; PF reduced our descent rate; and we visually identify the traffic at 12 o'clock; moving to our 11 o'clock position; just below and opposite direction. We then received a Resolution Advisory to adjust vertical speed". My First Officer (PF) disconnected the auto pilot and followed the RA while executing a slight turn to the right to increase separation. Traffic passed off our left wing within approximately 200ft. The traffic was a GA aircraft (Cessna; white with grey stripe). Traffic did have landing lights on and was maintaining a straight and level path. Flight continued to ZZZ without incident."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.