Broadband study of blazar 1ES 1959+650 during flaring state in 2016

Abstract

Aims. The nearby TeV blazar 1ES 1959+650 (z=0.047) was reported to be in flaring state during June -July 2016 by Fermi-LAT, FACT, MAGIC and VERITAS collaborations. We studied the spectral energy distributions (SEDs) in different states of the flare during MJD 57530 -57589 using simultaneous multiwaveband data to understand the possible broadband emission scenario during the flare. Methods. The UV/optical and X-ray data from UVOT and XRT respectively on board Swift and high energy γ-ray data from Fermi-LAT are used to generate multiwaveband lightcurves as well as to obtain high flux states and quiescent state SEDs. The correlation and lag between different energy bands is quantified using discrete correlation function. The synchrotron self Compton (SSC) model was used to reproduce the observed SEDs during flaring and quiescent states of the source. Results. A decent correlation is seen between X-ray and high energy γ-ray fluxes. The spectral hardening with increase in the flux is seen in X-ray band. The powerlaw index vs flux plot in γ-ray band indicates the different emission regions for 0.1 -3 GeV and 3-300 GeV energy photons. Two zone SSC model satisfactorily fits the observed broadband SEDs. The inner zone is mainly responsible for producing synchrotron peak and high energy γ-ray part of the SED in all states. The second zone is mainly required to produce less variable optical/UV and low energy γ-ray emission. Conclusions. Conventional single zone SSC model does not satisfactorily explain broadband emission during observation period considered. There is an indication of two emission zones in the jet which are responsible for producing broadband emission from optical to high energy γ-rays.

Testing two-component models on very high-energy gamma-ray-emitting BL Lac objects

“…It has been suggested that the simple one-zone SSC model cannot reproduce the multiple flaring activity of 1ES 1959+650 and multiple-zone SSC models are favoured (Krawczynski et al 2004;Patel et al 2018). Those models are different from the one discussed here.…”

“…The application of multiplecomponent SSC models has therefore been suggested by many authors (e.g. Krawczynski et al 2004;Aleksić et al 2014;Tavecchio & Ghisellini 2016;Patel et al 2018). We used a two-component model with two interacting, co-spatial emission regions (core and blob) in order to mimic the so-called spinelayer SSC model described by Tavecchio & Ghisellini (2016).…”

“…Those models are different from the one discussed here. Krawczynski et al (2004) did not take into account the interaction between the two emission zones while Patel et al (2018) did not assume the co-spatiality of the emission regions. Finally, in both of these studies, the strength of the magnetic field was one order of magnitude lower than the value obtained from VLBI observations assuming equipartition.…”

Broadband characterisation of the very intense TeV flares of the blazar 1ES 1959+650 in 2016

“…Another strong VHE outburst during 2012 was reported by Aliu et al (2014) where an increased VHE flux was observed without a simultaneous activity in the X-ray and UV fluxes that could be explained by the reflected emission model similar to Böttcher (2005). Regarding the long-term behaviour in X-rays, the photon spectral index scatters below and above 2 when the spectra are fitted by a powerlaw (PL) function (Krawczynski et al 2004;Patel et al 2018). This behaviour of the PL index suggests that the low-energy peak of the SED moves around the X-ray band because the photon index of a PL is ∼2 at the peak energy of the SED.…”

Estudio observacional de la emisión óptica de blazares detectados a altas energías

“…1ES 1959+650 se aloja en una galaxia elíptica con una magnitud de M R = −23. Hasta el momento existen medidas aisladas de polarización óptica (P = 12.2 %, Sorcia et al 2013), aunque es una fuente bastante estudiada en todo el espectro electromagnético (Aliu et Zhang & Li 2017;Patel et al 2018). Para esta Tesis, el blazar fue observado durante 6 noches consecutivas durante los meses de julio y agosto de 2011 con el instrumento CAFOS (Sección 3.1.1).…”