Identification of an X-ray Pulsar in the BeXRB system IGR J18219$-$1347

TL;DR

This study confirms IGR J18219-1347 as a Be/X-ray binary through timing and spectral analysis, revealing a neutron star with a 52.46 s spin period and characterizing its broadband X-ray spectrum.

Contribution

First detection of the neutron star's spin period and classification of IGR J18219-1347 as a BeXRB using multi-instrument observations during outbursts.

Findings

Neutron star spin period of 52.46 seconds

System classified as BeXRB based on timing and IR data

X-ray spectrum characterized by a power-law with cutoff at 13 keV

Abstract

We report on observations of the candidate Be/X-ray binary IGR J18219$-$1347 with \textit{Swift}/XRT, \textit{NuSTAR}, and \textit{NICER} during Type-I outbursts in March and June 2020. Our timing analysis revealed the spin period of a neutron star with $P_\textrm{spin}=52.46$ s. This periodicity, combined with the known orbital period of $72.4$ d, indicates that the system is a BeXRB. Furthermore, by comparing the infrared counterpart's spectral energy distribution to known BeXRBs, we confirm this classification and set a distance of approximately $10-15$ kpc for the source. The source's broadband X-ray spectrum ($1.5-50$ keV) is described by an absorbed power-law with photon index $\Gamma$\,$\sim$\,$0.5$ and cutoff energy at $\sim$\,$13$ keV.