2015A&A...574A.117M

Multiwavelength observations have revealed the highly unusual properties of the γ-ray source PMNJ1603-4904, which are difficult to reconcile with any other well-established γ-ray source class. The object is either a very atypical blazar or a compact jet source seen at a larger angle to the line of sight. To determine the physical origin of the high-energy emission processes in PMNJ1603-4904, we study the X-ray spectrum in detail. We performed quasi-simultaneous X-ray observations with XMM-Newton and Suzaku in 2013 September. This resulted in the first high signal-to-noise X-ray spectrum of this source. The 2-10keV X-ray spectrum can be well described by an absorbed power law with an emission line at 5.44±0.05keV (observed frame). We interpret this feature as a Kα line from neutral iron and accordingly determine the redshift of PMNJ1603-4904 to be z=0.18±0.01, which corresponds to a luminosity distance of 872±54Mpc. The detection of a redshifted X-ray emission line further challenges the original BLLac classification of PMNJ1603-4904. This result suggests that the source is observed at a larger angle to the line of sight than expected for blazars, and thus the source would add to the elusive class of γ-ray loud misaligned-jet objects, possibly a γ-ray bright young radio galaxy.