Date: 201910
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Other Rejected Takeoff
Airspace: Class E ZZZ
ATC / advisory: CTAF ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Communication Breakdown; Confusion; Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Rejected Takeoff
Contributing factors: Procedure; Human Factors
Primary problem: Human Factors

Narrative: Departing ZZZ we rejected takeoff due to possible traffic conflict. Speed was about 100 knots. As we were taxiing with ground control to and approaching the end of Runway XX; a very short taxi. Ground control come onto the radio and closed the tower. The tower didn't advise us of any other traffic. I saw the one airplane taxiing to parking on foxtrot and a helicopter about 4 miles south of the field westbound; that was the only aircraft on TCAS. My FO got our release from ZZZ center and we already had our departure clearance. My FO made two announcements on COM one. One for about to taxi onto the runway for takeoff; and then just before starting the takeoff roll. At about 80 knots we heard on the radio something about Runway XX. We were both still monitoring com two with ground. Something didn't feel right and I rejected the take off and stopped the aircraft before crossing Runway XY. As we were slowing down I could see an aircraft [Aircraft Y] on runway XY that was also stopped. Aircraft Y was not visible from the start of the takeoff roll due to terrain between the runways. Neither aircraft crossed the other aircraft's runway. At this time I looked down and noticed that [the FO] had accidentally put in the wrong CTAF frequency and a 5 was replaced with an 8. After taxiing back to Runway XX and complying with Procedures for maintenance and BTMS of 4s and 3s. The flight departed and was normal.ATC not giving us all traffic on the field. FO accidentally putting in the wrong CTAF frequency. I didn't verify the correct frequency.ATC should call out all traffic on the field. Verify everything especially the normal routine things.


Second narrative: During taxi-out and approaching the runway; tower closed for the night. There were no traffic advisories from tower prior to closure. As I was switching frequencies to get our release; the Captain set Comm 2 to monitor. After getting a release from center; we completed checklists and I made two calls on Comm 1 to announce our intentions and take the runway. Durning the initial takeoff roll; we heard something on the radio about an aircraft [Aircraft Y] on Runway XX. Sensing something was wrong; We rejected the takeoff at 100 knots and stopped the aircraft prior to entering The crossing runway. As we slowed down; we could see [Aircraft Y] on Runway XY that had been previously blocked by terrain. Neither aircraft crossed the other's runway.At this point we realized that we had the incorrect frequency set in COM 1. A 5 was replaced with an 8. We taxied back to Runway XX to comply with the waiting period for departure and Mx procedure. We then took off without issue. Causes for this event included the transition from a controlled field to an uncontrolled field. We were unaware of another aircraft on the field that was ready to depart and only knew of traffic taxing inbound.Additionally; this left us with a last minute switch to CTAF which allowed little time for uncontrolled communication with aircraft in the area.I would recommend that before closing; tower should make a report so aircraft under their control become aware of other traffic that may become a factor. This report should be on the frequency that is to become the CTAF.


Synopsis: Air carrier flight crew reported aborting a takeoff due to another aircraft taking off from an intersecting runway.