Performance study and observation of the Crab Nebula with the HAWC Outrigger array

High Altitude Water Cherenkov Gamma-ray Observatory (HAWC) is a ground-based Water Cherenkov observatory and it has been operational since 2015 on the flanks of the Sierra Negra volcano, México. Beginning in 2017, we began deploying an array of outrigger tanks, which expanded the detector's area by about 4 times to nearly 0.1 km^2. Although smaller in size, outrigger tanks greatly improve the core location, direction, and energy reconstruction for showers falling near the main array, which substantially improves sensitivity, particularly in the crucial regime >100 TeV. In addition, the sensitivity to low-energy events was greatly improved with the information provided by the outrigger array, enhancing the ability of HAWC to detect transient events like Gamma-ray Burst(GRB). In this presentation, we will show the first observation of the Crab Nebula with the HAWC Outrigger array and the performance of HAWC with the Outrigger array.