The NuSTAR extragalactic surveys in the north ecliptic pole field

The JWST Deep Time-Domain Field (DTDF) in the North Ecliptic Pole (NEP) area is the newest and most promising survey for both time-domain studies and population studies with large cosmic lookback volume, which has vast multiwavelength observations from radio to X-rays. The NuSTAR extragalactic survey in the NEP field is the only hard X-ray survey in this field, which consists of 9 observations in three different epochs for a total exposure of 680 ks, covering about 0.17 square deg and overlapping with the Chandra data. The sensitivity of the survey at 50% coverage is 2.8e-14, 1.3e-14, 3.1e-14, 1.8e-14, and 5.2e-14 erg/cm²/s in the 3-24, 3-8, 8-24, 8-16, and 16-24 keV. Combining all five bands, we obtain a sample of 24 sources. The brightest target in the field of view is an NLSy1 galaxy at z=1.44 whose potential spectra variability has been monitored in multiple epochs with NuSTAR and Chandra. The intensive exposure enables us to study the high-energy cut-off thus the temperature of the X-ray emitting corona of this particular source, making it one of only 4 AGN at z>0.2 with high-energy cut-off measured. The current survey has shown that the NuSTAR NEP DTDF is a rich X-ray field, and another 800 ks was granted to perform time-domain study on this interesting field in the following year. In this talk, I will present the most updated results of the first 700 ks observation of the NuSTAR NEP survey.