Fermi-LAT light curve for PKS 0402-362 at seven Penning days. Credit: Das et al., 2023.
Indian astronomers analyzed observational data of a gamma-ray blaze known as PKS 0402-362, which was collected over a time period of about 13 years. The study, published March 7 in the Monthly Notices of the Royal Astronomical Societyprovides important information regarding the long-term behavior of this Blazar.
Blazars are very compact quasars supermassive black holes (SMBHs) at the centers of active giant elliptical galaxies. They belong to a larger group of active host galaxies active galactic nuclei (AGN), the most massive extragalactic source of gamma rays. Their distinguishing features are relativistic jets directed almost exactly towards the Earth.
Based on their optical emission properties, astronomers divide blazars into two classes: Flat spectrum radio quasars (FSRQs) that have prominent, broad visual emission lines, and BL Lacertae (BL Lacs), which do not.
PKS 0402-362 (also known as 4FGL J0403.9-3605) is an FSRQ at a redshift of 1.42. the Blazar It is a persistent emitter of gamma rays, which has been monitored for years with NASA’s Fermi Gamma-ray Space Telescope.
In order to get more insights into the behavior of PKS 0402-362, a group of astronomers led by Avik Kumar Das of the Indian Institute of Science Education and Research Mohali in India decided to analyze a huge dataset of data obtained using Fermi’s Large Area Telescope (lat. ).
“We study the long-term behavior of the bright gamma-ray blaze PKS 0402-362. We collected nearly 13 years of Fermi-LAT data between August 2008 to January 2021 and identified three periods of bright gamma-ray activity,” the researchers wrote in the paper.
As noted in the study, the long-term monitoring campaign of PKS 0402-362 revealed multiple activity periods (AEs) of various durations spanning the 12 years of the observed time. Of the three selected eras, AE-1, AE-2, and AE-3, AE-2 turned out to be the brightest with over 20-fold more flux on average. Gamma rays flow.
Based on the data collected, astronomers have found that the size of the broadband region (BLR) for PKS 0402-362 is about 0.75 light-years across. By comparing this size with the location of the emission region, the authors concluded that the emission region is only at the boundary of the BLR.
The paper’s authors added that a long-term correlation study of PKS 0402-362 indicates that broadband emissions are spatial in common, and a covariance study indicates that they are produced within the BLR. They also found that, as in other known FSRQs, the accretion disk of PKS 0402-362 dominates the visible ultraviolet photoemission over the flare states of this star.
A dominant accretion disk has been observed for this source and is well fitted by a combination of synchrotron and thermal disk emission. This source has a strong accretion disk as also observed by Müller et al. (2018), which makes this source a good candidate for probing the jet disk connection, It is beyond the scope of this paper,” the study authors concluded.
more information:
Avik Kumar Das et al., Gamma-ray flares and broadband spectroscopy study of PKS 0402-362, Monthly Notices of the Royal Astronomical Society (2023). DOI: 10.1093/mnras/stad702. on arXiv: arxiv.org/pdf/2303.03039.pdf
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