Kilonovas are incredibly rare. According to astronomers, there may only be 10 of these in the Milky Way. However, they are incredibly strong and create heavy substances such as uranium, thorium and gold.
They are usually discovered after merging and emitting intense gamma-ray bursts (GRBs). However, SMARTS telescope users claim to have discovered a kilonova ancestor for the first time.
When two neutron stars, or a neutron star and a black hole combine, they cause a kilonova explosion. The stellar remnants of massive stars that exploded as supernovae are known as neutron stars. These are the smallest and densest celestial bodies known.
Progenitor kilonova stars have been discovered by astronomers 11,400 light-years away. They are known as CPD-29 2176 and were first discovered by NASA's Swift observatory.
However, they are incredibly powerful and create enormous more data from observations with the SMARTS 1,5-meter Telescope at the Cerro Tololo Inter-American Observatory in Chile.
An article titled "A high-mass X-ray binary derived from an ultra-stripped supernova" details the findings. The article was published in the journal Nature. Noel D. Richardson, assistant professor of physics and astronomy at Embry-Riddle Aeronautical University, is the lead author of the paper.
Currently, CPD-29 2176 does not consist of two neutron stars. The other is a massive star that is on the verge of going supernova and leaving behind a neutron star. One of them is a neutron star.
Conditions exist for a kilonova to occur within a million years, or possibly much later.
However, for the neutron star pair to fuse as a kilonova in the future, the second star would have to explode as an ultra-stripped supernova. The rarity of ultra-stripped supernovas is one of the factors contributing to the rarity of kilonovas. And as if that wasn't unusual enough, the neutron star that was already there was supposed to be a supernova.
When a normal supernova (SN) explodes, it releases a large amount of energy. The system's neutron star companion could be forced out of the system by the explosion, blocking the door to a future kilonova.
Since the neutron star SN leaves behind will be on its own, it will not have a chance to merge with another neutron star and explode as a kilonova.
But an ultra-ejected supernova (USSN) is different. When an SN is ultra-ejected, it has lost a significant amount of mass before it exploded. Mass is transferred to its stellar companion, and without that mass, the SN burst lacks the power necessary to eject its companion. These are very important features because binary stars are the most common type of stars massive enough to explode as SN.
What Are Kilonova Stars?
Any potential kilonova is largely dependent on interactions between two stars before one of them explodes as SN.
The final core mass of the SN is determined by changes in mass, stellar spin, and nuclear fusion. It produces an ultra-stripped supernova under ideal but rare conditions.
This is what happened on CPD-29 2176, and scientists doubt that the explosion of SN will generate enough energy to eject its neutron star mate. The current neutron star had to explode as a USSN in addition to the current massive star because otherwise it would have expelled its mate when it exploded as an SN. Therefore, two USSNs are required.
The current neutron star had to emerge before it ejected its mate from the system.
An ultra-stripped supernova is the best explanation for why these co-stars are orbiting so closely, according to Richardson, the study's lead author. The other star would also have to explode as an ultra-stripped supernova, so that the two neutron stars could one day eventually collide and fuse to produce a kilonova. This explains the rarity of kilonovas. Prerequisites are weaker SN bursts and mass stripping.
The researchers told the history of the system's development as well as what is likely to happen in the future.
First, a binary pair of two large blue stars is formed. One of the stars is always larger than the other; stars are never the same size.
As the larger star nears the end of its existence and swells, the smaller partner may drain some of the larger star's material and take up a significant portion of its outer atmosphere. The massive star then explodes as an ultra-ejected supernova, but it lacks the explosive power to eject its mate, leaving only a neutron star behind.
The current location of CPD-29 2176 is the level below. The larger star and neutron star that have not yet exploded are both present. Significant mass loss occurs as the neutron star empties the outer layers of the star. The situation has changed.
The remaining star will eventually lose most of its mass and explode as an ultra-stripped supernova about a million years later. The neutron star will not have enough power to drive its companion away. The neutron star he left behind will continue to orbit another neutron star until it spirals inward and eventually collides.
Astronomer and co-author André-Nicolas Chené from NOIRLab said: "Astronomers have long theorized about the exact conditions that could eventually lead to a kilonova." These new findings suggest that if one of the two sister neutron stars formed without a typical supernova explosion, merging is possible, at least under certain conditions.
The probability of something happening is extremely low. There are kilonovas though, so conditions must be right for them to occur. Therefore, every time we see a kilonova, we see an event that happens once in ten billion.
“We know there are at least 100 billion stars in the Milky Way, and there are probably hundreds of billions more. According to Chené, in essence, this extraordinary binary system is a one-ten-billion-one system. "Before our study, it was thought that a spiral galaxy like the Milky Way should contain only one or two such systems."
There's more to kilonovas than big bangs and gravitational waves. The heavy components of the universe are also a result of these events.
Thus, investigating them not only provides information about the conditions that lead to them, but also helps to elucidate the development of nucleosynthesis.
But to witness this kilonova event, humanity will have to endure an incredibly long time. It could take more than a million years for the star to go supernova in its ultra-ejected state. And when that happens, the two neutron stars have to be close enough to each other before a kilonova can occur. This is the time period and these are many different situations.
Now that astronomers have detected a kilonova, they can better identify these potential kilonova precursors. Along the way, they'll learn more about ultra-ejected supernovae.
According to Richardson, "this system shows that some neutron stars were created by just a small supernova hit." We'll learn more about how common systems like CPD-29 2176 are and how peaceful some stellar deaths can be, as well as whether these stars can die without producing conventional supernovae.
source: universetoday
Günceleme: 03/02/2023 17:37
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