Probing the emission mechanism and nature of the pulsating compact object in the X-ray binary SAX J1324.4−6200

Abstract

Recently, there has been renewed interest in the Be X-ray binary (Be/XRB) because of its spatial coincidence with a variable gamma -ray source detected by To explore more thoroughly its properties, new X-ray observations were carried out in 2023 by and satellites, jointly covering the energy range from $0.2-79$ keV. was caught at an X-ray flux of $ $ erg cm$^ $ s$^ $. The X-ray spectrum fits well with an absorbed power law with a high energy cutoff. Other acceptable fits require an additional blackbody component ($kT_ bb 1.1$ keV) or a Gaussian in absorption gabs keV). We measured a spin period of $175.8127 and an spin period of $175.862 We show that all the available spin period measurements of spanning 29 years, are highly correlated with time, resulting in a remarkably stable spin-down of $ P $ s s$^ $. We find that if hosts an accretion-powered pulsar, accretion torque models indicate a surface magnetic field of $ $ G. The X-ray properties emerging from our analysis strenghten the hypothesis that belongs to the small group of persistent Be/XRBs. We also performed radio observations with the Parkes Murriyang telescope, to search for radio pulsations. However, no radio pulsations compatible with the rotational ephemeris of were detected. We rule out the hypothesis that is a gamma -ray binary where the emission is produced by interactions between the pulsar and the companion winds. Other models commonly used to account for the production of $ in accreting pulsars cannot reproduce the bright emission from We examined other possible mechanisms behind the $ emission and note that there is a $ 0.5$<!PCT!> chance probability that an unknown extragalactic active galactic nucleus (AGN) observed through the Galactic plane may coincidentally fall within the error circle of the source and be responsible for the $ emission.