Multiwavelength temporal and spectral study of TeV blazar 1ES 1727+502 during 2014–2021

Abstract

ABSTRACT One of the most important questions in blazar physics is the origin of broad-band emission and fast-flux variation. In this work, we studied the broad-band temporal and spectral properties of a TeV blazar 1ES 1727+502 and explore the one-zone synchrotron self-Compton (SSC) model to fit the broad-band spectral energy distribution (SED). We collected the long-term (2014–2021) multiband data that include both the low- and high-flux states of the source. The entire light curve is divided into three segments of different flux states and the best-fitting parameters obtained by broad-band SED modelling corresponding to three flux states were then compared. The TeV blazar 1ES 1727+502 has been observed to show the brightest flaring episode in the X-ray followed by the optical–UV and γ-rays. The fractional variability estimated during various segments behaves differently in multiple wavebands, suggesting a complex nature of emission in this source. This source has shown a range of variability time from days scale to month scale during this long period of observations between 2014 and 2021. A ‘harder-when-brighter’ trend is not prominent in the X-ray but seen in the optical–UV and an opposite trend is observed in the γ-ray. The complex nature of correlation among various bands is observed. The SED modelling suggests that the one-zone SSC emission model can reproduce the broad-band spectrum in the energy range from optical–UV to very high energy γ-ray.