The M Supergiant High Mass X-Ray Binary 4U 1954+31
Abstract
The X-ray binary 4U 1954+31 has been classified as a Low Mass X-ray Binary (LMXB) containing a M giant and a neutron star (NS). It has also been included in the rare class of X-ray symbiotic binaries (SyXB). The Gaia parallax, infrared colors, spectral type, abundances, and orbital properties of the M star demonstrate that the cool star in this system is not a low mass giant but a high mass M supergiant. Thus, 4U 1954+31 is a High Mass X-ray Binary (HMXB) containing a late-type supergiant. It is the only known binary system of this type. The mass of the M I is 9 M giving an age of this system in the range 12 - 50 Myr with the NS no more than 43 Myr old. The spin period of the NS is one of the longest known, 5 hours. The existence of M I plus NS binary systems is in accord with stellar evolution theory, with this system a more evolved member of the HMXB population.
Cite
@article{arxiv.2010.01081,
title = {The M Supergiant High Mass X-Ray Binary 4U 1954+31},
author = {K. H. Hinkle and T. Lebzelter and F. C. Fekel and O. Straniero and R. R. Joyce and L. Prato and N. Karnath and N. Habel},
journal= {arXiv preprint arXiv:2010.01081},
year = {2020}
}
Comments
Accepted for publication in ApJ