Outside those astronomical objects listed in Table 1, there is another X-ray source, which cannot be observed directly by XMM-Newton due to its high luminosity: Sco X-1 (or V818 Sco) .
Giacconi et al., "On the optical identification of SCO X-1," The Astrophysical Journal, vol.
Kallman et al., "Modeling the oxygen K absorption in the interstellar medium: an XMM-Newton view of Sco X-1," The Astrophysical Journal Letters, vol.
Sco X-1 is the brightest star in the night sky to X-ray eyes.
By combining recent measurements of Sco X-1's space motion with a model for the Milky Way's gravitational field, Mirabel and Rodrigues have made an educated guess about its past travels.
Mirabel and Rodrigues admit that Sco X-1 may instead have gotten its eccentric orbit from an impulsive kick when the neutron star's progenitor went supernova.