2023-12-29 23:10:00
On December 15, a major discovery was announced by the collaboration of Large-Sized Telescope (LST). Object OP 313 (quasar) was detected at very high energies, a first for LST-1. This detection marks an important milestone in the study of active galactic nuclei (AGN) and flat-spectrum quasars (FSRQ).
The LST collaboration announced the detection of the OP 313 source at very high energies with LST-1. Although OP 313 is known at lower energies, it has never been detected above 100 GeV. This detection makes OP 313 the most distant AGN ever detected by a Cherenkov telescope, demonstrating the exceptional performance of the LST prototype during its commissioning at the CTAO-Nord site on the island of La Palma, Spain .
OP 313 is what is known as a flat-spectrum quasar or FSRQ, a type of AGN. These are very luminous objects found at the centers of some galaxies, where a supermassive black hole devours the surrounding matter, creating powerful accretion disks and jets of light and relativistic particles.
An exceptional observation
LST-1 observed this source between December 10 and 14, following receiving an alert from satellite Fermi-LAT indicating unusually high activity in the low-energy gamma-ray regime. This activity was also confirmed in the optical range with different instruments. In just four days of data, the LST collaboration was able to detect the source above 100 Gigaelectronvolts (GeV), an energy level a billion times higher than the visible light humans can perceive.
Only nine quasars are known at very high energies, and OP 313 is now the tenth. In general, quasars are more difficult to detect at very high energies than other types of AGN. This is due not only to the brightness of their accretion disk which weakens the emission of gamma rays, but also because they are further away. In this case, OP 313 is located at a redshift of 0.997 or regarding 8 billion light years away, making it the most distant AGN and the second most distant source ever detected at very high energies. high.
The Large Telescope (LST)
The large telescope (LST) is one of three types of telescope that will be built to cover the entire energy range of the CTAO (from 20 GeV to 300 TeV).
The approved Alpha configuration of CTAO includes four LSTs arranged in the center of the Northern Hemisphere network. A plan to improve this configuration also includes two LSTs in the southern network, which are funded. These telescopes are optimized to cover low energy sensitivity between 20 and 150 GeV.
Each LST is a giant telescope 23 meters in diameter with a mirror area of around 400 square meters and a finely pixelated camera consisting of 1855 light sensors capable of detecting individual photons with high efficiency. Although the LST is 45 meters tall and weighs around 100 tonnes, it is extremely agile, capable of repositioning itself in 20 seconds to pick up brief, low-energy gamma ray signals.
Rendering of the CTAO Northern Hemisphere Network. Credit: Gabriel Pérez Díaz, IAC
The repositioning speed and low energy threshold provided by LSTs are essential for CTAO studies of transient gamma-ray sources in our galaxy and for the study of active galactic nuclei and long-shift gamma-ray bursts to the Red. The LST prototype, LST-1, is located at CTAO-North and is currently being commissioned. It is expected to become CTAO’s first telescope once it is commissioned and officially accepted.
Synthetic
The detection of OP 313 at very high energies by LST-1 marks an important step in the study of AGN and FSRQ. This discovery will allow scientists to improve their understanding of extragalactic background light (EBL), study magnetic fields within this type of source or delve into fundamental intergalactic physics.
For a better understanding
What is OP 313?
OP 313 is a flat-spectrum quasar, a type of active galactic nucleus. It is located approximately 8 billion light years from Earth.
What is LST-1?
The LST-1 is a large prototype telescope, currently being commissioned at the CTAO-North site on the island of La Palma, Spain.
What does detection at very high energies mean?
Detection at very high energies refers to the detection of gamma rays at energies above 100 GeV. It is an important area of study in astrophysics.
Why is this discovery important?
This discovery is important because it allows scientists to study very distant objects and better understand intergalactic physics.
What are the next steps ?
The LST collaboration will continue to observe this source with LST-1 to expand the dataset and obtain more precise analysis.
References
Large-Sized Telescope (LST) Collaboration. (2023)
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