This illustration shows an intermediate polar system, a type of two-star system to which the research team believes V1674 Hercules belongs. A stream of gas from the big companion star hits the accretion disk before flowing along the lines of a magnetic field to the white dwarf. Credit: Illustration by Mark Garlick
Most people are familiar with supernovae, spectacular stellar explosions that occur at the end of a massive star’s life and often lead to a black hole or neutron star. On the other hand, the new ones are much less known to the general public, although they appear much more often than the super-new ones, perhaps because they are usually not so dramatic.
New is the sudden, short-lived, dramatic lightening of a star. The star usually fades slowly to its original brightness in a few weeks or many months. Although the specific reasons for a new one can vary depending on the circumstances, they always include white dwarfs in close binary systems – two stars that orbit each other due to gravity.
Astronomers are now buzzing after watching the fastest new one ever recorded. The unusual event drew the attention of scientists to an even more unusual star. As they study it, they can find answers not only to the many confusing features of the new, but also to larger questions about the chemistry of our solar system, the death of the stars, and the evolution of the universe.
The research team, led by Professor Sumner Starfield of Arizona State University, Professor Charles Woodward of the University of Minnesota and researcher Mark Wagner of Ohio State University, co-authored a report published today (June 14, 2022). astronomical society.
New is a sudden explosion of bright light from a two-star system. Each new one is made up of a white dwarf – the very dense residual core of a star – and a close companion star. Over time, the white dwarf draws matter from its companion, which falls on the white dwarf. The white dwarf heats this material, causing an uncontrolled reaction that releases a burst of energy. The explosion launches matter at high speeds, which we observe as visible light.
The bright new one usually fades in a few weeks or more. On June 12, 2021, the new V1674 Hercules exploded so brightly that it was visible to the naked eye, but after just over a day it was weak again. It was as if someone had turned a flashlight on and off.
New events at this level of speed are rare, which makes this new valuable object of study.
“It was only about a day, and the previous fastest new one was the one we studied in 1991, the V838 Herculis, which went down in about two or three days,” said Starfield, an astrophysicist at ASU’s School of Earth and Space Research. .
While the world of astronomy is observing V1674 Hercules, other researchers have found that its speed is not its only unusual feature. The light and energy it sends out also pulsates like the sound of an echoing bell.
Every 501 seconds there is an oscillation that observers can see in both visible light waves and X-rays. A year after the explosion, the new one still shows this fluctuation and seems to last even longer. Starfield and his colleagues continue to study this oddity.
“The most unusual thing is that this flicker was visible before the explosion, but it was also obvious when the new one was about 10 magnitudes brighter,” said Wagner, who is also head of science at the Large Binocular Telescope Observatory. observation. the new one. “The mystery that people are trying to deal with is what drives this periodicity, that you will see it in this range of brightness in the system.”
The team also noticed something strange as they observed the matter ejected by the explosion of a new one – a kind of wind that may depend on the positions of the white dwarf and its accompanying star, shaping the flow of material in the space around the system.
Although the fastest new one is (literally) screaming, the reason it’s worth exploring is that the new ones can tell us important information about our solar system and even the universe as a whole.
A white dwarf collects and changes matter, then spice up the surrounding space with new material during a new explosion. This is an important part of the cycle of matter in space. Materials discarded from the new ones will eventually form new star systems. Such events have also helped shape our solar system, ensuring that the Earth is more than a lump of carbon.
“We’re always trying to figure out how the solar system came to be, where the chemical elements in the solar system come from,” says Starfield. “One of the things we will learn from this new one is, for example, how much lithium is produced by this explosion. We are now pretty sure that a significant portion of the lithium we have on Earth is produced by these types of explosions.
Sometimes a white dwarf star does not lose all its collected matter during the explosion of a new one, so with each cycle it gains mass. This would eventually make it unstable, and the white dwarf could generate a Type 1a supernova, one of the brightest events in the universe. Each type 1a supernova reaches the same level of brightness, so they are known as standard candles.
“Standard candles are so bright that we can see them at great distances in the universe. “Looking at how the brightness of light is changing, we can ask questions about how the universe is accelerating or about the overall three-dimensional structure of the universe,” says Woodward. “That’s one of the interesting reasons we’re studying some of these systems.”
In addition, the new ones can tell us more about how stars in binary systems evolved to death, a process that is not well understood. They also act as living laboratories, where scientists can see nuclear physics in action and test theoretical concepts.
The new surprise of the world of astronomy. This was not on the radar of scientists until Japanese amateur astronomer Seiji Ueda discovered and reported it.
Civic scientists are playing an increasingly important role in astronomy as well as modern technology. Although now too weak for other types of telescopes, the team can still observe the new one thanks to the wide aperture of the Large Binocular Telescope and other observatory equipment, including its pair of multi-object dual spectrographs and the outstanding high-resolution PEPSI spectrograph.
They plan to study the cause of the explosion and the processes that led to it, the reason for its record decline, the forces behind the observed wind and the reason for its pulsating brightness.
Reference: June 14, 2022, Research Notes of the American Astronomical Society. DOI: 10.3847 / 2515-5172 / ac779d
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