Posted on January 11, 2019
"From the theory, we know that black holes and neutron stars are formed when a star dies, but we have never seen them immediately after birth. Never! "Raffaella Margutti, an assistant professor of physics and astronomy at Northwestern University, told the mysterious bright object that the astronomers gathered under the name" cow ". The "bulb" was sitting deep inside the explosion. It would be hard to see in a normal star explosion. But The Cow had very little weight, which allowed us to directly see the radiation of the central engine. "
Using the WM Keck Observatory in Maunakei, Hawaii, and the ATLAS Astronautics Institute at the University of Hawaii, the multi-institutional team now had evidence that they were probably caught in the exact moment when the star collapsed and formed a compact object, such as a black hole or a neutron star.
The cow shown in the above figure is visible as one of the two bright spots in the lower right quadrant of the spiral galaxy, classified as CGCG 137-068.
The stellar scales that are approaching and revolving around the horizon of the event caused an extremely bright shine. The research, which will be published at The Astrophysical Journal, was released today at a press conference at the 233rd meeting of the American Astronomical Society in Seattle.
This rare event will help astronomers better understand physics on the pitch at the first moments of the creation of a black hole or neutron star.
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"Based on X-rays and UV emissions, it may seem that the" cow "has caused a black hole that swallows a white dwarf. However, further observations of other wavelengths across the spectrum led to our interpretation that 'Cow' the actual formation of a black hole or neutron star, & # 39; & # 39; & # 39; said the main author Margutti, a member of the CIERA faculty (Center for Interdisciplinary Research and Research). for astrophysics).
The first sight was observed on June 16, when ATLAS telescopes at Haleakala and Maunaloa captured a spectacular light anomaly distant 200 million light-years away in the Hercule constellation. The building quickly deteriorated and then disappeared almost immediately.
The event attracted immediate international interest and left astronomers scratching their heads. "We thought it must be a supernova," said Margutti. "But what we have noticed has provoked our current perception of star death."
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First, the anomaly was unnaturally bright – 10 to 100 times brighter than the typical supernova. It also exploded and disappeared much faster than other known explosions of stars, with particles flying at 30,000 kilometers per second (or 10 percent of the light velocity).
In just 16 days, the facility has already given away most of its power. In the universe, where some phenomena last for millions and billions of years, two weeks are equal to the eye.
"We immediately knew that this source went from inactive to maximum luminosity in just a few days," said co-author Ryan Chornock, a physics and astronomy assistant at Ohio University. "It was enough that everyone was excited, because it was so unusual and according to astronomical standards it was very close."
With the help of Northwestern access to the Kecko double telescope, Marguttti's team looked at the image of the LRIS object at the Keck I telescope as well as at DEepos on Keck II. .
"Keck played a key role in determining the chemical composition and geometry of AT2018cow," said co-author Nathan Roth, a postdoctoral associate at the University of Maryland. "Kecko's unique niche is its ability to monitor the late behavior of the cow. This can be difficult; when the event expires more time, it becomes weaker. But with Kecko's later spectroscopy, we could pierce the "interior" of the explosion. This is very beautifully revealed by the red spectral characteristics AT2018cow. "
"The cow is an excellent example of the kind of observation that is becoming increasingly critical in astronomy: a quick response to transient events," says Keck Observatory chief researcher John O'Meara. "We look forward to pursuing new observation policies and telescopic instruments that enable us to be so fast in the sky and in science as we can."
The group also acquired optical images from the MMT Observatory in Arizona as well as the southern astrophysical research of the SOAR telescope in Chile.
When Margutti and her team examined the chemical composition of the cow, they found clear evidence of hydrogen and helium, which excluded models of compact converging objects – just like those that produce gravity waves.
"It took some time to get to know what we're seeing, I would say months," said co-author Brian Metzger, a professor of physics at Columbia University. "We tried several options and were forced to return to the drawing board several times. We finally could interpret the results, thanks to the hard work of our highly dedicated team.
Astronomers have traditionally studied stellar death in optical wavelengths using telescopes to capture visible light.
However, Margutt's team used a more holistic approach. When ATLAS noticed the object, the Margutti team quickly carried out further observations using various cows' observation cows in different wavelengths.
The researchers viewed the object in hard X-rays using the NASA's Nuclear Spectroscopic Telescope (NuSTAR) and the European Space Agency (ESA) of the INTEGRAL Intenational Lab for Astrophysics of Gamma Air (INTEGRAL) in soft X-rays (which are 10 times stronger than conventional X-rays (XMM-Newton) and in radio waves using a very large set of (VLAs) of the National Astronomical Observatory, which allowed them to continue exploring the anomaly long after its original visible light faded.
Margutti attaches a relatively naked cow to the potential discovery of this intergalactic secret. Although stars may collapse into black holes all the time, a large amount of material around newly born black holes blocks the vision of astronomers.
Fortunately, about 10 times less ebb around the cow spun around the typical starburst explosion. The lack of material enabled the astronomers to mirror straight to the "central engine" of the building, which proved to be a probable black hole or neutron star.
Margutt's team also benefited from the relative proximity of the star to the Earth. Though it was nested in a remote ground galaxy called the CGCG 137-068, astronomers consider it to be "just around the corner".
"Two hundred million light years are close to us," said Margutti. "This is the closest transient object of this kind that we have ever found."
Daily galaxy through Keck Observatory