Broad-band analysis of X-ray pulsar 2S 1845–024

Abstract

<p>We present the results of a detailed investigation of the poorly studied X-ray pulsar 2S 1845−024 based on data obtained at the <i>NuSTAR</i> observatory during the type I outburst in 2017. Neither pulse phase-averaged nor phase-resolved spectra of the source show evidence for a cyclotron absorption feature. We also used data obtained from other X-ray observatories (<i>Swift</i>, <i>XMM</i>-<i>Newton</i> and <i>Chandra</i>) to study the spectral properties as a function of orbital phase. The analysis reveals a high hydrogen column density for the source reaching ∼10²⁴ cm⁻² around periastron. Using high-quality Chandra data we were able to obtain an accurate localization of 2S 1845−024 at 18^h48^m16^s.8 and Dec. = −2^◦25'25".1 (J2000), which allowed us to use infrared (IR) data to roughly classify the optical counterpart of the source as an OB supergiant at a distance of ≳15 kpc.<br></p>