Variability of Markarian 1018: Seyfert 1.9 to Seyfert 1

Abstract

Simultaneous IUE and optical spectrophotometry of the Seyfert 1.9 galaxy Markarian 1018 is presented. The strength of H-beta(broad) has increased by a factor of 6.6 in 4 yr, and the galaxy now shows strong broad UV and optical line emission similar to that seen in normal Seyfert 1 galaxies, but with markedly asymmetric line profiles. As in other variable Seyfert galaxies, H-alpha emission has also increased but by a lesser amount than H-beta. Furthermore, Ly-alpha (not observed during the first epoch) is now quite strong relative to H-beta and H-alpha. Inspection of the line profiles reveals nearly identical blue asymmetric line profiles in all permitted lines; these show evidence of significant profile evolution over a 1 yr time scale. The present line ratios and the nature of their variability suggest that the enhancement in the broad-line emission is not caused by the removal of obscuring dust but by the 'lighting up' of the broad-line region.