Proving strong magnetic fields near to the central black hole in the quasar PG0043+039 via cyclotron lines

Abstract

The optical luminous quasar PG0043+039 has not been detected before in deep X-ray observations indicating the most extreme optical-to-X-ray slope index ${\alpha }_{ox}$ of all quasars. This study aims to detect PG0043+039 in a deep X-ray exposure. Furthermore, we wanted to check out whether this object shows specific spectral properties in other frequency bands. We took deep X-ray (XMM-Newton), far-ultraviolet (HST), and optical (HET, SALT telescopes) spectra of PG0043+039 simultaneously in July 2013. We just detected PG0043+039 in our deep X-ray exposure. The steep ${\alpha }_{ox}=-2.37\pm 0.05$ gradient is consistent with an unusual steep gradient $F_{\nu }\sim {\nu }^{\alpha }$ with $\alpha =-2.67\pm 0.02$ seen in the UV/far-UV continuum. The optical/UV continuum flux has a clear maximum near 2500 Å. The UV spectrum is very peculiar because it shows broad humps in addition to known emission lines. A modeling of these observed humps with cyclotron lines can explain their wavelength positions, their relative distances, and their relative intensities. We derive plasma temperatures of T $\sim$ 3keV and magnetic field strengths of B $\sim$ 2 $\times 10^8$ G for the line-emitting regions close to the black hole.

4 pages, 3 figures, Astronomy & Astrophysics in press

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