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Description
In this paper, we characterize the first-ray flaring episode of the flat-spectrum radio quasar PKS 034-27 (z=0.991), as revealed by Fermi-LAT monitoring data, and the concurrent multi-wavelength variability observed from radio through X-rays. We studied the long- and short-term flux and spectral variability from PKS 0346-27 by producing-ray light curves with different time binning. We complement theFermi-LAT data with multi-wavelength observations from the Atacama Large MillimeterArray (radio mm-band), the Rapid Eye Mount telescope (near-infrared) and Swift (optical-UV and X-rays). This quasi-simultaneous multi-wavelength coverage allowed us to construct time-resolved spectral energy distributions (SEDs) of PKS 0346-27 and compare the broadband spectral properties of the source between different activity states using a one-zone leptonic emission model. PKS 0346-27 entered an elevated-ray activity state starting from the beginning of 2018. The high-state continued through-out the year, displaying the highest fluxes in May 2018. We find evidence of short-time scale variability down to approximately 1.5 hours, which constrains the-ray emission region to be compact. The extended flaring period was characterized by a persistently harder spectrum with respect to the quiescent state, indicating changes in the broadband spectral properties of the source. This was confirmed by the multi-wavelength observations, which show a shift in the position of the two SED peaks by approximately two orders of magnitude in energy and peak flux value. As a result, the non-thermal jet emission completely outshines the thermal contribution from the dust torus and accretion disk during the high state. The broadband SED of PKS 0346-27 transitions from a typical low-Synchrotron-Peaked (LSP) to the Intermediate-Synchrotron-Peaked (ISP) class, a behavior previously observed in other flaring-ray sources. Our one-zone leptonic emission model of the high-state SEDs constrains the gamma-ray emission region to have a lower magnetic field, larger radius, and higher maximum electron Lorentz factors with respect to the quiescent SED. Finally, we note that the bright and hard-ray spectrum observed during the peak of flaring activity in May 2018 implies that PKS 0346-27 could be a promising target for future ground-based Cherenkov observatories such as the Cherenkov Telescope Array (CTA). The CTA could detect such a flare in the low-energy tail of its energy range during a high state such as the one observed in May 2018.
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