2015A&A...577L...1K

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 α_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 α_ox=-2.37±0.05 gradient is consistent with an unusual steep gradient F_ν~ν^α with α=-2.67±0.02 seen in the UV/far-UV continuum. The optical/UV continuum flux has a clear maximum near 2500Å. 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∼3keV and magnetic field strengths of B ∼2x10⁸G for the line-emitting regions close to the black hole.