Studying a supermassive black hole in our galaxy

(ORDO NEWS) — The supermassive black hole (SMBH) at the core of our galaxy, Sagittarius A * (Sag A *), has a modest size – only 4.15 million solar masses.

Recently, the Event Horizon Telescope (EHT) published an impressive submillimeter image of this hole, in a glowing environment.

Many galaxies have nuclear SMBHs that are thousands of times larger, such as the core of M87, which was imaged by the EHT in 2020.

But Sagittarius A* is relatively close to us, only twenty-five thousand light-years away, giving astronomers a unique opportunity to study the properties of the SMBH.

Episodic accretion and variable bursts of radiation provide clues about the nature of accretion, the size and location of each event in the black hole’s complex environment, and how the episodes can be related to each other and to properties of the black hole, such as its rotation.

Each wavelength carries certain information, and one of the key diagnostic tools is the time difference between flashes at different wavelengths, which allows you to trace where during the flash the development of various mechanisms occurs.

Sagittarius A* is close enough to have been observed on radio waves since its discovery in the 1950s; on average, Sagittarius A* accumulates material at a very low rate, a few hundredths of the mass of the Earth per year, but this is enough to cause variability, as well as brighter flares.

Astronomers have completed a time analysis of coordinated simultaneous observations of Sagittarius A* in the near infrared, X-ray and submillimeter regions.

Outbreaks were observed from 17 to 26 July 2019. The team notes that 2019 activity appears to reflect an unusually high accretion rate. Although some events were observed simultaneously, the submillimeter flare (ALMA) appeared about 20 minutes after the infrared and X-ray flares (Chandra).

Scientists are considering three scenarios: the infrared and X-ray emission in these flares arose as a result of the spiral rotation of charged particles in powerful magnetic fields; infrared and submillimeter radiation arose as a result of the first process, and X-ray radiation was obtained by the collision of infrared photons with charged particles moving at a speed close to the speed of light; and, finally, only submillimeter radiation resulted from the first process, while all other bands were generated by the second.

Unfortunately, ground-based observations cannot be continuous, and as a result, the peak time of the submillimeter flare emission was not observed, making it difficult to determine the time delay between it and the X-ray emission. which could testify to its occurrence in another place or as a result of another process.

The team, combining their findings with earlier variability studies, found one pattern in which infrared and X-rays are produced by a second process, and then submillimeter radiation from the first, in an expanding, cooling magnetized plasma.


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