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arXiv · 2010.01081

The M Supergiant High Mass X-Ray Binary 4U 1954+31

K. H. Hinkle·T. Lebzelter·F. C. Fekel·O. Straniero·R. R. Joyce·L. Prato·N. Karnath·N. Habel
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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$^{+6}_{-2}$ M$_\odot$ 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.

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K. H. Hinkle, T. Lebzelter, F. C. Fekel, O. Straniero, R. R. Joyce, L. Prato, N. Karnath, N. Habel. 2020-10-02. The M Supergiant High Mass X-Ray Binary 4U 1954+31. https://doi.org/10.3847/1538-4357%2Fabbe01

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