title: A Lunar Occultation of the Dust-Scattering Halo Around GX 5-1 Observed with ROSAT.
abstract: The x-ray source GX 5-1 in the galactic bulge has been observed with the position-sensitive proportional counter onboard the Röntgen satellite (ROSAT) during and after a lunar occultation. Extended emission around the source was unambiguously discovered while the central source was behind the lunar rim. This emission is interpreted as a dust-scattering halo around GX 5-1 that has a fractional intensity of 28 percent, implying a grain column density between GX 5-1 and Earth of approximately 3 x 10(10) per square centimeter. The halo derived from imaging during the ROSAT all-sky survey is identical to that obtained from the lunar occultation, thus demonstrating that the ROSAT x-ray mirror scattering has not changed as compared with the mirror properties as measured in preflight calibrations.
authors.forename: P
authors.initials: P
authors.lastname: Predehl
authors.forename: J H
authors.initials: JH
authors.lastname: Schmitt
authors.forename: S L
authors.initials: SL
authors.lastname: Snowden
authors.forename: J
authors.initials: J
authors.lastname: Trümper