A time-variable scattered component to broad Hα in the Seyfert 1 galaxy Mrk 509

Abstract

We present optical spectropolarimetry data for the Seyfert 1 galaxy Mrk 509 for three epochs: 1996 August and 1997 May and August. We confirm previous findings that broad Hα has a significantly greater width in the polarized flux spectrum than in total flux, and that the observed polarization is variable on relatively short time-scales, implying, for scattering, that at least some of the polarization originates in a compact region. We also find evidence that the observed changes in the degree of polarization (for the continuum and broad wings of Hα) and the associated position angle swing (for the continuum) are similar in pattern to previously observed polarimetry variations. We determine that a multicomponent scattering region is the most likely origin for the observed polarization of Mrk 509. The scattering appears to originate from three regions, which we identify with observed or expected components of the active galaxy. The proposed scenario is completely consistent with the unified theory of active galaxies.