We report the results of a comprehensive analysis of X-ray (Chandra and Swift observatories), optical (Southern African Large Telescope, SALT) and near-infrared (the VVV survey) observations of the Be/X-ray binary pulsar 2S1553-542. Accurate coordinates for the X-ray source are determined and are used to identify the faint optical/infrared counterpart for the first time. Using VVV and SALTICAM photometry, we have constructed the spectral energy distribution (SED) for this star and found a moderate NIR excess that is typical for Be stars and arises due to the presence of circumstellar material (disk). A comparison of the SED with those of known Be/X-ray binaries has allowed us to estimate the spectral type of the companion star as B1-2V and the distance to the system as >15 kpc. This distance estimation is supported by the X-ray data and makes 2S1553-542 one of the most distant X-ray binaries within the Milky Way, residing on the far side in the Scutum-Centaurus arm or even further.
@article{arxiv.1607.08605,
title = {2S1553-542: a Be/X-ray binary pulsar on the far side of the Galaxy},
author = {Alexander A. Lutovinov and David A. H. Buckley and Lee J. Townsend and Sergey S. Tsygankov and Jamie Kennea},
journal= {arXiv preprint arXiv:1607.08605},
year = {2016}
}
Comments
8 pages, 4 figures, accepted for publication in MNRAS