Compton-thick X-ray absorption in the Seyfert galaxies Tololo 0109–383 and ESO 138–G1


★ NASA-supported undergraduate research associate.† E-mail: (MJC); (WNB)


We present analyses of the ASCA X-ray spectra of two Seyfert galaxies, Tololo 0109–383 and ESO 138–G1. In both cases, spectral fitting reveals two statistically acceptable continuum models: Compton reflection and partial covering. Both spectra have strong iron Kα lines, with equivalent widths greater than 1.5 keV. These large equivalent widths are suggestive of heavier obscuration than that directly indicated by the partial-covering models (≈2×1023 cm-2), with the actual column densities being ‘Compton-thick’ (i.e. NH≳1.5×1024 cm-2). We use the hard X-ray/[O iii] flux correlation for Seyferts and data from the literature to provide additional support for this hypothesis. Since Tololo 0109–383 is known to have optical type 1 characteristics such as broad Balmer line components and Fe ii emission, this result marks it as a notable object.