Broad-band 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

The first four all-sky surveys with eROSITA, the 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 broad-band timing and spectral analysis using optical and X-ray data of eRASSU J012422.9--724248. Using X-ray observations from eROSITA, Swift, NuSTAR, together with optical data from the Optical Gravitational Lensing Experiment (OGLE) and the Las Cumbres Observatory (LCO), we confirm the nature of eRASSU J012422.9--724248 as 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 a spin period of $341.71,\mathrm{s}$ in the NuSTAR data and infer a period of $63.65,\mathrm{d}$ from 15 years of OGLE monitoring, which we interpret as the orbital period of the system. A tentative cyclotron resonance scattering feature (CRSF) at $\sim 12.3,\mathrm{keV}$ is identified in the NuSTAR spectra with a significance of $\sim 1.8\sigma$. The source appears to exhibit persistent X-ray luminosity and long-timescale optical magnitude variability. We propose that eRASSU J012422.9--724248 is a new member of the class of persistent BeXRBs.