Broad [O iii] in the globular cluster RZ 2109: X-ray ionized nova ejecta




We study the possibility that the very broad (∼1500 km s−1) and luminous (L5007∼ 1.4 × 1037 erg s−1) [O iii] line emission observed in the globular cluster RZ 2109 might be explained with the photoionization of nova ejecta by the bright (LX∼ 4 × 1039 erg s−1) X-ray source hosted in the same globular cluster. We find that such scenario is plausible and explains most of the features of the RZ 2109 spectrum (line luminosity, absence of H emission lines, peculiar asymmetry of the line profile); on the other hand, it requires the nova ejecta to be relatively massive (≳0.5 × 10−3 M), and the nova to be located at a distance ≲0.1 pc from the X-ray source. We also predict the time evolution of the RZ 2109 line emission, so that future observations can be used to test this scenario.