Spectral and timing analysis of BeXRB eRASSU J050810.4-660653 recently discovered in the Large Magellanic Cloud (LMC)

Abstract

We have studied the Be/X-ray binary (BeXRB) pulsar eRASSU J050810.4-660653 recently discovered in the Large Magellanic Cloud (LMC). Timing and spectral features of the source have been discussed in detail using NuSTAR and XMM-Newton observations. Coherent pulsation of the source was detected at ~40.578 ± 0.001 s using NuSTAR observation. We analysed pulse profiles of the source in different energy bands using NuSTAR and XMM-Newton data. The pulse-profile evolved with time but was generally suggestive of a pencil-beam dominated pattern, which combined with the measured luminosity, indicates that the source may be accreting in the sub-critical regime. The pulse fraction follows a linearly increasing trend with photon energy and is anticorrelated with luminosity. In the 1-yr interval between the XMM and NuSTAR observations, the pulse period shortened by 0.021 s which could be consistent with spin-up or orbital Doppler effect. The average flux of the source in (3-50) keV energy range is found to be $\sim 5.56 \times 10^{-11}\, {\rm erg}\, {\rm cm}^{-2}\, \mathrm{s}^{-1}$ and the corresponding luminosity is $\sim 1.66 \times 10^{37}\, {\rm erg}\, \mathrm{s}^{-1}$. The variation of spectral parameters with pulse phase is studied using phase resolved spectroscopy which reveals that the observed photon index becomes harder with increasing flux.