2019A&A...627A.140A


Query : 2019A&A...627A.140A

2019A&A...627A.140A - Astronomy and Astrophysics, volume 627A, 140-140 (2019/7-1)

The large gamma-ray flare of the flat-spectrum radio quasar PKS 0346-27.

ANGIONI R., NESCI R., FINKE J.D., BUSON S. and CIPRINI S.

Abstract (from CDS):

Aims. In this paper, we characterize the first γ-ray flaring episode of the flat-spectrum radio quasar PKS 0346-27 (z=0.991), as revealed by Fermi-LAT monitoring data, and the concurrent multi-wavelength variability observed from radio through X-rays. Methods. We studied the long- and short-term flux and spectral variability from PKS 0346-27 by producing γ-ray light curves with different time binning. We complement the Fermi-LAT data with multi-wavelength observations from the Atacama Large Millimeter Array (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. Results. PKS 0346-27 entered an elevated γ-ray activity state starting from the beginning of 2018. The high-state continued throughout the year, displaying the highest fluxes in May 2018. We find evidence of short-time scale variability down to approximately 1.5h, which constrains the γ-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 γ-ray sources. Our one-zone leptonic emission model of the high-state SEDs constrains the γ-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 γ-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.

Abstract Copyright: © R. Angioni et al. 2019

Journal keyword(s): galaxies: active - galaxies: jets - quasars: individual: PKS 0346-27 - gamma rays: galaxies

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 7C 021804.09+354230.00 QSO 02 21 05.4920852208 +35 56 13.848581904   20.0 20.0 19.60   ~ 542 3
2 QSO B0346-279 QSO 03 48 38.14457039 -27 49 13.5657855   20.08 18.63 17.72   ~ 179 1
3 LB 2136 QSO 11 53 24.46663994 +49 31 08.8301372   17.94 17.66     ~ 480 1
4 7C 1441+2514 QSO 14 43 56.89220390 +25 01 44.4907165   19.5   19.7   ~ 135 1
5 QSO J2345-1555 BLL 23 45 12.4622049264 -15 55 07.836801888   19.21   18.48   ~ 154 1

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2023.09.27-15:57:45

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