We present HI absorption spectra of the black hole candidate X-ray binary (XRB) MAXI J1348-630 using the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT. The ASKAP HI spectrum shows a maximum negative radial velocity (with respect to the local standard of rest) of −31±4 km s−1 for MAXI J1348-630, as compared to −50±4 km s−1 for a stacked spectrum of several nearby extragalactic sources. This implies a most probable distance of 2.2−0.6+0.5 kpc for MAXI J1348-630, and a strong upper limit of the tangent point distance at 5.3±0.1 kpc. Our preferred distance implies that MAXI J1348-630 reached 17±10 % of the Eddington luminosity at the peak of its outburst, and that the source transited from the soft to the hard X-ray spectral state at 2.5±1.5 % of the Eddington luminosity. The MeerKAT HI spectrum of MAXI J1348-630 (obtained from the older, low-resolution 4k mode) is consistent with the re-binned ASKAP spectrum, highlighting the potential of the eventual capabilities of MeerKAT for XRB spectral line studies.
@article{arxiv.2009.14419,
title = {Measuring the distance to the black hole candidate X-ray binary MAXI J1348-630 using HI absorption},
author = {J. Chauhan and J. C. A. Miller-Jones and W. Raja and J. R. Allison and P. F. L. Jacob and G. E. Anderson and F. Carotenuto and S. Corbel and R. Fender and A. Hotan and M. Whiting and P. A. Woudt and B. Koribalski and E. Mahony},
journal= {arXiv preprint arXiv:2009.14419},
year = {2020}
}