Observers detect intraday variability of blazar 1ES 1426+42.8

Astronomers report the detection of intraday optical variability in a blazar known as 1ES 1426+42.8. The new findings, presented in a paper published in the September issue of Monthly Notices of the Royal Astronomical Societycould shed more light on the properties and nature of this blazar.

Blazars are very compact quasars associated with supermassive black holes (SMBHs) at the centers of active giant elliptical galaxies. They belong to a larger group of active galaxies that host active galactic nuclei (AGNs) and are the most numerous sources of extragalactic gamma-rays. Their characteristic features are relativistic jets pointed almost exactly toward Earth.

Based on their optical emission properties, astronomers divide blazars into two classes: flat-spectrum radio quasars (FSRQs), which exhibit prominent, broad optical emission lines, and BL Lacertae objects (BL Lacs), which do not.

1ES 1426+42.8 is a BL Lac with a redshift of 0.129, discovered in 1984. It is an extreme TeV source, with low power and a high synchrotron peak, above 100 keV. Since previous observations of 1ES 1426+42.8 have focused on its high-energy bands, the optical properties of this blazar remain poorly studied.

That’s why a team of astronomers led by Xin Chang of Yunnan University in China decided to explore 1ES 1426+42.8 in optical bands using Yunnan Observations’ 1.02-m optical telescope. They observed the blazar for 16 nights between 2021 and 2023.

Observations by Chang’s team detected an intradaily variability (IDV) of 1ES 1426+42.8 over seven days. The identified IDVs are intermittent and no correlation was found between light level and the presence or absence of these IDVs.

The astronomers explained that the observed IDV for 1ES 1426+42.8 can be interpreted as the result of a convolution of individual synchrotron pulses occurring in the turbulent jet of the blazar. In the case of 1ES 1426+42.8, the analysis conducted by the authors of the paper yields 80 pulses. The size distributions of the turbulent radiation cells, calculated from the fitting results, appear to range from 2.58 to 54.52 AU.

In general, the results obtained for 1ES 1426+42.8 suggest that turbulence exists in most regions of the jet. The cell size distribution was found to be continuous.

The study also detected a possible short-lived quasi-periodic oscillation (QPO) in the light curve of 1ES 1426+42.8. The QPO was identified on April 26, 2022, and had a period of about 58.55 minutes. QPOs are thought to occur when X-rays are emitted near the inner edge of an accretion disk in which gas swirls around a compact object such as a neutron star or black hole.

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