Luminous gamma-ray flare detected from the blazar DA 193

January 3, 2019 by Tomasz Nowakowski, Phys.org report
**Luminous gamma-ray flare detected from the blazar DA 193
0.1−300 GeV test statistic map of DA 193, generated for the period MJD 54683−58137. Image scale is 0.05 degree per pixel and the black circle denotes the 95% positional uncertainty derived from the Fermi-LAT data analysis. The radio and optimized γ-ray positions are also shown, as labelled. Image credit: Paliya et al., 2018.

An international group of astronomers has detected an intense and extremely luminous gamma-ray flare from one of high-redshift blazars known as DA 193. The new detection, reported in a paper published December 18 on arXiv.org, is an uncommon finding as such bright flares are rarely observed from high-redshift sources.

Blazars, classified as members of a larger group of active galaxies that host  (AGN), are the most numerous extragalactic gamma-ray sources. Their characteristic features are relativistic jets pointed almost exactly toward the Earth. In general, blazars are perceived by astronomers as high-energy engines serving as natural laboratories to study particle acceleration, relativistic plasma processes, magnetic field dynamics and black hole physics.

Studies show that blazars (with redshifts above 2.0) hosting massive black holes and the most powerful relativistic jets are the most luminous ones. Finding and observing new blazars at high redshifts could be crucial for providing insights into many phenomena of the universe, including the evolution and space density of massive black holes.

A team of researchers led by Vaidehi S. Paliya of DESY research center in Zeuthen, Germany, investigated one such high-redshift . They used the Large Area Telescope (LAT) on board NASA's Fermi Gamma-ray Space Telescope and other instruments to characterize physical properties DA 193 – a blazar observed close to the galactic anti-center at a redshift of approximately 2.36. These observations resulted in the detection of significant gamma-ray emission from this object.

"In this work, we present the results of our study on another high-redshift blazar DA 193 (also known as 0552+398; z = 2.363, Wills & Wills 1976; McIntosh et al. 1999) which we have found as a new gamma-ray emitting object through our detailed Fermi-LAT analysis," the researchers wrote in the paper.

DA 193 underwent a significant GeV flare in the first week of 2018. According to the study, it was an extremely luminous gamma-ray flare with a luminosity of about 130 quindecillion erg/s.

The researchers note that such a GeV flare from a high-redshift blazar is a rare phenomenon. This is due to the fact that these blazars are generally faint in the gamma-ray band.

Notably, DA 193 has an extremely hard gamma-ray spectrum. "What makes this event a rare one is the observation of an extremely hard γ-ray spectrum (photon index = 1.7 ± 0.2), which is somewhat unexpected since high-redshift blazars typically exhibit a steep falling spectrum at GeV energies," the paper reads.

Trying to determine what caused such an intense and luminous flare from DA 193, the astronomers suggest that a change in the behavior of the underlying electron population could be responsible for the observed event. The team intends to use LAT for further continuous monitoring of the gamma-ray sky in order to find more powerful blazars showcasing luminous flares like DA 193. Studying such events could lead to a better understanding of radiative processes powering relativistic jets in blazars.

Explore further: Blazar LBQS 1319+0039 detected in hard X-rays

More information: Vaidehi S. Paliya et al. Detection of a gamma-ray flare from the high-redshift blazar DA 193. arXiv:1812.07350 [astro-ph.HE] arxiv.org/abs/1812.07350

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6 comments

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dirk_bruere
3.7 / 5 (3) Jan 03, 2019
"erg/s" ??? What century is this? Physics transitioned to SI (MKS) units decades ago.
And can we have "quindecillion" in power notation please. Despite being a physicist I am going to have to google that.
And having googled it, are we talking the US or British quindecillion?
rrwillsj
not rated yet Jan 03, 2019
dirk, you should also check with blazar DA 193
January 3, 2019
by Tomasz Nowakowski,
Phys.org

"... DA 193 underwent a significant GeV flare in the first week of 2018. According to the study, it was an extremely luminous gamma-ray flare with a luminosity of about 130 quindecillion erg/s. ..."

I did not find this exact phrase in the abstracts I read. Maybe I missed it?
Doesn't mean that it is incorrect. Possible language gap. Possible generational gap.

You will have to judge for yourself if it is relevant too your understanding of the conclusions from this research.

Considering the complexity of the material & my limited understanding of the underlying sciences? i was pleasantly surprised to not find more questions of meaning.

All too many of these pop-science press releases for popular consumption, are clumsily translated &/or rewritten.
By students in non-science majors for work-study programs.
Hungry students earning a few bucks.

MrBojangles
4.2 / 5 (5) Jan 03, 2019
"erg/s" ??? What century is this? Physics transitioned to SI (MKS) units decades ago.
And can we have "quindecillion" in power notation please. Despite being a physicist I am going to have to google that.
And having googled it, are we talking the US or British quindecillion?


This is astrophysics, where erg/s is still commonly used with luminosity, and not just by the author of this article.
RealScience
5 / 5 (2) Jan 03, 2019
@DB: The paper does not mention quindecillion, so that appears to be just the writer showing off by making a straightforward number obscure.

But yes, astronomers still use ergs (as well as light-years and parsecs and astronomical units that are not even metric).

The arxiv link will get you to the paper. This says:
In the first week of 2018, DA 193 underwent an extremely luminous GeV flare (Lγ = (1.3 ± 0.4) × 10^50 erg s−1

The conversion is 10^7 ergs per joule, so that's 1.3 x 10^43 J/s (or 1.3 x 10^43 Watts).
Solon
not rated yet Jan 03, 2019
Do the energy levels detected take into account the attenuation which must surely occur between observer and observed?
Da Schneib
3.3 / 5 (3) Jan 04, 2019
Scientific paper presents result that are unprecedented.

Trolls argue about ergs vs. Joules, because they can't do enough math to convert by 10⁷. Typical.

Can we talk about the blazar now, or is this going to turn into another 500 post trolling?

Worth mentioning that astrophysicists often present wavelength/frequency data as "per centimeters."

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