FOR THE FIRST TIME: Scientists saw in detail black hole tearing a star

UNITED STATES, WASHINGTON (OBSERVATORY) — Scientists have witnessed an extremely rare event: the destruction of a star by a supermassive black hole. In a galaxy the size of the Milky Way, such a cataclysm occurs once in tens or hundreds of millennia.

This time, thanks to a happy coincidence, astronomers first traced the very beginning of the disaster. It is curious that the planet hunter TESS helped them in this.

The achievement is described in a scientific article published in the Astrophysical Journal by scientists from 22 research centers.

Recall in a nutshell that this happens when a celestial body approaches a predator approximately the distance between the Earth and the Sun. The side of the star turned towards the “monster” is attracted to it more strongly (since it is closer) than the opposite one.

The star does not withstand mechanical stress and breaks, literally stretching into a thread. Such a cataclysm is known as a tidal disruption event, or TDE (from the English phrase tidal disruption event). Throughout history, astronomers have observed only about 40 such disasters.

A new cataclysm occurred in the 2MASX galaxy J07001137-660225, located 375 million light-years from Earth in the constellation Flying Fish. The dead star probably had approximately solar mass, but the black hole that destroyed it was six million times more massive. Any boxer will confirm that the opponents are of different weights.

An important role in the discovery was played by the TESS space telescope, which we wrote about in detail. Recall that this instrument every half hour carefully measures the brightness of stars in a selected area to detect eclipses caused by exoplanets. Observation of each site lasts 27 days.

A by-product of this work is the discovery of all kinds of cosmic cataclysms that, by a lucky coincidence, occurred precisely in the part of the sky that TESS was observing at that moment. The data show how this point of the sky looked before the outbreak, and allow you to track its development in increments of half an hour for several days.

Researchers of various kinds of flare processes rarely get such rich observational material.

However, TESS does not transmit data to Earth in real time. Astronomers have to wait for the next communication session for several weeks. But it is extremely important to get information about the flash as soon as possible in order to connect instruments of various ranges to its study.

The sensational story with the first collision of neutron stars very clearly demonstrated this.

That is why, after the launch of TESS, the ASAS-SN project team began to devote more time to the sites that this planet hunter was currently observing. ASAS-SN is a wide field of view high-speed automatic telescope network designed to detect flash as quickly as possible.

The calculation was simple: if something interesting happens in this part of the sky, then the observers will notify their colleagues with all possible speed. And over time, the unique data from TESS will arrive in time, which saw everything from the very beginning, but could not tell about it in time.

That is exactly what happened on January 29, 2019, when telescopes recorded a flash that was designated ASASSN-19bt. Scientists quickly connected to this work several ground and space instruments operating in the optical, x-ray and ultraviolet ranges.

In addition, astronomers are incredibly lucky. The cataclysm happened not just in the current TESS site, but in the so-called continuous monitoring zone. This is the area of ​​the sky where several sites observed in turn overlap. Each such zone is surveyed for about a hundred days.

As a result, scientists received observations from this part of the sky from July 28, 2018. That is, continuous monitoring of the desired part of the sky began six months (!) Before the ASAS-SN network detected the outbreak.

“We closely monitored the areas of the sky observed by TESS with our ASAS-SN telescopes. But we were very lucky with this event that the portion of the sky that TESS constantly observes is small, and it was in it that one of the brightest TDEs happened we’ve ever seen, ” said co-author of the study, Patrick Vallely of Ohio University.“ Thanks to his fast detection with ASAS-SN [telescopes] and incredible TESS data, we were able to observe this TDE at much earlier stages than others [similar events]. It gives us some new pre representation of how TDE occur.”

The flash reached its maximum power in March 2019. At this moment, its luminosity was about one hundred billion solar. The maximum temperature of the remnants of the star reached 40 thousand degrees Celsius, which is almost eight times higher than on the surface of the Sun, but it quickly fell by half.

In their scientific article, the authors state that the development of ASASSN-19bt before the peak of brilliance was studied in more detail than any other TDE.

“The early TESS data allows us to see the glow of the [shattered star] very close to the black hole, much closer than we could see before,” says Valley.

Scientists were also convinced that the increase in brightness ASASSN-19bt was very smooth. According to TESS, the brightness began to increase 8.3 days before the event was detected by the ASAS-SN network. This fact confirmed that we are talking about the tidal destruction of a star, and not a flash of another type, for example, a supernova explosion.

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