Explosive neutron star merger captured in millimeter light for the first time

In a first in radio astronomy, scientists have detected millimeter-wavelength light from a short-lived gamma-ray burst. This artist’s conception shows the merger between a neutron star and another star (seen as a disk, lower left) that caused an explosion resulting in the short-lived gamma-ray burst, GRB 211106A (white jet, middle), and left behind what scientists now know is one of the brightest afterglows ever recorded (semi-spherical shock wave middle right). While dust in the host galaxy obscured most of the visible light (shown as colors), millimeter light from the event (shown in green) was able to escape and reach the Atacama Large Millimeter/submillimeter Array (ALMA), giving scientists an unprecedented view. of this cosmic explosion. From the study, the team confirmed that GRB 211106A is one of the most energetic short-lived GRBs ever observed. Credit: ALMA (ESO/NAOJ/NRAO), M. Weiss (NRAO/AUI/NSF)

Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) – an international observatory co-operated by the National Radio Astronomy Observatory (NRAO) of the US National Science Foundation – have for the first time recorded millimeter wave light of a fiery explosion caused by the merger of a neutron star with another star. The team also confirmed that this flash of light was one of the most energetic short-lived gamma-ray bursts ever observed, leaving behind one of the brightest afterglows ever recorded. The research results will be published in an upcoming issue of Letters from the Astrophysical Journal.

Gamma-ray bursts (GRBs) are the brightest and most energetic explosions in the universe, capable of emitting more energy in seconds than our sun will emit in its entire lifetime. GRB 211106A belongs to a GRB subclass known as short-duration gamma-ray bursts. These explosions, which scientists believe are responsible for creating the heaviest elements in the universe, such as platinum and gold, result from the catastrophic merger of binary star systems containing a neutron star. “These mergers occur because of gravitational wave radiation that removes energy from the orbits of binary stars, causing the stars to spiral towards each other,” said Tanmoy Laskar, who will soon start working as a as assistant professor of physics and astronomy at the University of Utah. “The resulting explosion is accompanied by jets moving at near the speed of light. When one of these jets is pointed at Earth, we observe a short pulse of gamma radiation or a short-lived GRB .”

In the first-ever time-lapse movie of a short-lived gamma-ray burst in millimeter light, we see GRB 21106A captured with the Atacama Large Millimeter/submillimeter Array (ALMA). The millimeter light seen here indicates the location of the event in a distant host galaxy in images captured using the Hubble Space Telescope. The evolution of the luminosity of the millimetric light provides information on the energy and the geometry of the jets produced during the explosion. Credit: ALMA (ESO/NAOJ/NRAO), T. Laskar (Utah), S. Dagnello (NRAO/AUI/NSF)

A short-lived GRB typically only lasts a few tenths of a second. The scientists then look for an afterglow, an emission of light caused by the interaction of the jets with the surrounding gas. Even still, they are difficult to detect; only half a dozen short-lived GRBs have been detected at radio wavelengths, and so far none have been detected at millimeter wavelengths. Laskar, who led the research while an excellence fellow at Radboud University in the Netherlands, said the difficulty is the immense distance to the GRBs and the technological capabilities of the telescopes. “Short-lived GRB afterglows are very bright and energetic. But these outbursts take place in distant galaxies, which means the light they emit may be faint enough for our telescopes on Earth. Prior to ALMA, millimeter telescopes n weren’t sensitive enough to detect these afterglows.”

About 20 billion light-years from Earth, GRB 211106A is no exception. The light from this short-lived gamma-ray burst was so faint that while early X-ray observations with NASA’s Neil Gehrels Swift Observatory saw the explosion, the host galaxy was undetectable at that wavelength, and the scientists have not been able to determine exactly where the explosion came from. “The afterglow is essential for determining which galaxy a burst is coming from and for learning more about the burst itself. Initially, when only the equivalent of X-rays had been discovered, astronomers thought this burst might have come from. from a nearby galaxy,” he added. Laskar said, adding that a significant amount of dust in the area also obscured the object of detection in optical observations with the Hubble Space Telescope.

Each wavelength added a new dimension to the GRB scientists’ understanding, and the millimeter, in particular, was key to uncovering the truth about the burst. “Hubble observations revealed an unchanging field of galaxies. ALMA’s unparalleled sensitivity allowed us to more accurately pinpoint the location of the GRB within this field, and it turned out to be in a another faint galaxy, which is more distant. That, in turn, means that this short-lived gamma-ray burst is even more powerful than we first thought, making it one of the brightest and most energetic ever recorded,” Laskar said.

Wen-fai Fong, an assistant professor of physics and astronomy at Northwestern University, added, “This short gamma-ray burst was the first time we’ve attempted to observe such an event with ALMA. The afterglows for the short bursts are very hard to find, so After many years of observing these bursts, this startling discovery opens up a whole new area of ​​study, as it motivates us to observe many more with ALMA and other telescope arrays, in the future. .”

Joe Pesce, National Science Foundation program manager for NRAO/ALMA, said, “These observations are fantastic on many levels. They provide more information to help us understand enigmatic gamma-ray bursts (and the astrophysics of stars). neutrons in general), and they demonstrate how important and complementary multi-wavelength observations with space and terrestrial telescopes are for understanding astrophysical phenomena.”

And there’s still a lot of work to be done across multiple wavelengths, both with the new GRBs and with GRB 211106A, which could reveal additional surprises about these bursts. “The study of short-lived GRBs requires the rapid coordination of telescopes around the world and in space, operating at all wavelengths,” said Edo Berger, professor of astronomy at Harvard University.

“In the case of GRB 211106A, we used some of the most powerful telescopes available: ALMA, the National Science Foundation’s Karl G. Jansky Very Large Array (VLA), NASA’s Chandra X-ray Observatory, and the Hubble Space Telescope. With the now operational James Webb Space Telescope (JWST), and future 20-40 meter optical and radio telescopes such as the Next Generation VLA (ngVLA), we will be able to produce a complete picture of these cataclysmic events and study them from unprecedented distances. “

Laskar added, “With JWST, we can now take a spectrum of the host galaxy and know the distance easily, and in the future, we may also use JWST to capture infrared afterglows and study their chemical composition. With ngVLA, we we will be able to study the geometric structure of afterglows and the star-forming fuel found in their host environments in unprecedented detail.I am excited about these upcoming discoveries in our field.

Hawaii telescopes help uncover origins of shipwrecked gamma-ray bursts

More information:
Tanmoy Laskar et al, The First Short GRB Millimeter Afterglow: The Wide-Angled Jet of the Extremely Energetic SGRB 211106A. arXiv:2205.03419v2 [astro-ph.HE]arxiv.org/abs/2205.03419

Provided by the National Radio Astronomy Observatory

Quote: Explosive neutron star merger captured for the first time in millimeter light (2022, August 3) Retrieved August 4, 2022 from https://phys.org/news/2022-08-explosive-neutron-star-merger- captured.html

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