Broadband study of the Be/X-ray binary pulsar eRASSU J012422.9−724248 in the Magellanic Bridge, near the Eastern Wing of the Small Magellanic Cloud

Abstract The first four all-sky surveys with eROSITAthe soft X-ray instrument on board the Spektrum-Roentgen-Gamma (SRG) satellite revealed a new X-ray source, eRASSU J012422.9−724248, in the Magellanic Bridge, near the Eastern Wing of the Small Magellanic Cloud (SMC). We performed a broadband timing and spectral analysis using the optical and X-ray data of eRASSU J012422.9−724248. Using the X-ray observations with eROSITA, Swift, NuSTARand optical data from the optical Gravitational Lensing Experiment (OGLE) and the Las Cumbres Observatory (LCO), we confirm the nature of eRASSU J012422.9−724248as a Be/X-ray binary (BeXRB) pulsar in the Magellanic bridge. The position is coincident with that of an early-type star (OGLE ID SMC732.10.7). We detect the spin period at 341.71 s in NuSTARdata and infer a period of 63.65 days from the 15 year monitoring with OGLE, that we interpret as the orbital period of the system. A tentative CRSF at ∼12.3 keV is identified in NuSTARspectra with ∼1.8σ. The source appears to show a persistent X-ray luminosity and an optical magnitude transition on the long timescale. We propose eRASSU J012422.9−724248is a new member of the class of persistent BeXRBs.