Markarian 1239: A Highly Polarized Narrow-Line Seyfert 1 Galaxy with a Steep X-Ray Spectrum and Strong Ne IX Emission*

摘要

We report the results of an XMM-Newton observation of the narrow-line Seyfert 1 galaxy Mrk 1239. This optically highly polarized AGN has one of the steepest X-ray spectra found in AGNs, with αX = +3.0 based on ROSAT PSPC data. The XMM-Newton EPIC pn and MOS data confirm this steep X-ray spectrum. The pn data are best fitted by a power law with a partial-covering absorption model suggesting two light paths between the continuum source and the observer, one indirect scattered one, which is less absorbed, and a highly absorbed direct light path. This result agrees with the wavelength-dependent degree of polarization in the optical/UV band. Residuals in the X-ray spectra of all three XMM-Newton EPIC detectors around 0.9 keV suggest the presence of an emission-line feature, most likely the Ne IX triplet. The detection of Ne IX and the nondetection of O VII/O VIII suggest a supersolar Ne/O ratio.