Identification of an X-Ray Pulsar in the BeXRB System IGR J18219-1347

We report on observations of the candidate Be/X-ray binary (BeXRB) IGR J18219-1347 with the Swift/X-ray Telescope, the Nuclear Spectroscopic Telescope ARray, and the Neutron Star Interior Composition Explorer during Type-I outbursts in 2020 March and June. Our timing analysis revealed the spin period of a neutron star with P (spin) = 52.46 s. This periodicity, combined with the known orbital period of 72.4 days, indicates that the system is a BeXRB. Furthermore, by comparing the spectral energy distribution of the infrared counterpart to that of known BeXRBs, we confirm this classification and set a distance of approximately 10-15 kpc for the source. The broadband X-ray spectrum (1.5-50 keV) of the source is described by an absorbed power law with a photon index Gamma similar to 0.5 and a cutoff energy at similar to 13 keV.