Researchers study flare activity in blazar S5 1803+78

(ORDO NEWS) — Using various space-based and ground-based observatories, astronomers have studied the flare activity seen in the blazar known as S5 1803+78. The results of this multi-wavelength study, published April 10 on the arXiv preprint server, shed more light on the properties of this source.

Blazars are very compact quasars associated with supermassive black holes (SMBHs) at the centers of active giant elliptical galaxies.

They belong to the larger group of active galaxies that host active galactic nuclei (AGNs) and are the most abundant extragalactic sources of gamma rays. Their characteristic feature is relativistic jets directed almost exactly towards the Earth.

Based on the properties of optical radiation, astronomers divide blazars into two classes: flat-spectrum radio quasars (FSRQs), which are characterized by prominent and broad optical emission lines, and BL Lacertae (BL Lacs) objects, which are not.

At a redshift of 0.684, S5 1803+78 is a blazar with a low synchrotron peak (LSP) of the BL Lac type. It demonstrates a periodicity of 6 years, which is associated with the helical motion of the jet. Previous observations have detected several large outbursts of this blazar with a possible period of about 3.5 years.

A team of astronomers led by Shruti Priya of the Indian Institute of Technology in Kharagpur, India, decided to conduct a multi-wavelength observing campaign for the object S5 1803+78 in order to better understand its flare behavior. To do this, they deployed several spacecraft and telescopes, including NASA‘s Swift, Fermi and NuSTAR or the TUBITAK National Observatory in Turkey.

“In this paper, we present a broadband source study by collecting data from radio to gamma radiation. Broadband SED [spectral energy distribution] simulations are performed to understand multiwavelength events at the source,” the researchers write.

By analyzing the light curve of the gamma ray S5 1803+78, the team was able to identify three outburst states from this source. They examined outbreak episodes from September 1, 2019. In April 2020, a large fiery outbreak was recorded, followed by several more similar episodes.

The fastest time scale of variability was found to be 0.95 days, and no significant correlation was found between gamma radiation, radio emission, and also X-ray emission.

According to the study, S5 1803+78 exhibits a so-called blue when brighter (BWB) trend. The highest photon energy during the big flare has been measured at 11.17 GeV. The study also showed that the flow does not show any significant correlation with the spectral index, and there is only a slight anti-correlation with the curvature index.

In general, the results obtained suggest that the emission region in S5 1803+78 is compact and located near the central supermassive black hole. The size of this area is estimated at about 100 trillion kilometers.

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