Out with a bang: Explosive neutron star merger captured for the first time in millimeter light
IMAGE: IN A FIRST FOR RADIO ASTRONOMY, SCIENTISTS HAVE DETECTED MILLIMETER-WAVELENGTH LIGHT FROM A SHORT-DURATION GAMMA-RAY BURST. THIS ARTIST'S CONCEPTION SHOWS THE MERGER BETWEEN A NEUTRON STAR AND ANOTHER STAR (SEEN AS A DISK, LOWER LEFT) WHICH CAUSED AN EXPLOSION RESULTING IN THE SHORT-DURATION GAMMA-RAY BURST, GRB 211106A (WHITE JET, MIDDLE), AND LEFT BEHIND WHAT SCIENTISTS NOW KNOW TO BE ONE OF THE MOST LUMINOUS AFTERGLOWS ON RECORD (SEMI-SPHERICAL SHOCK WAVE MID-RIGHT). WHILE DUST IN THE HOST GALAXY OBSCURED MOST OF THE VISIBLE LIGHT (SHOWN AS COLORS), MILLIMETER LIGHT FROM THE EVENT (DEPICTED 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-DURATION GRBS EVER OBSERVED. view more
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 US National Science Foundation’s National Radio Astronomy Observatory (NRAO)— have for the first time recorded millimeter-wavelength light from a fiery explosion caused by the merger of a neutron star with another star. The team also confirmed this flash of light to be one of the most energetic short-duration gamma-ray bursts ever observed, leaving behind one of the most luminous afterglows on record. The results of the research will be published in an upcoming edition of The Astrophysical Journal Letters.
Gamma-ray bursts (GRBs) are the brightest and most energetic explosions in the Universe, capable of emitting more energy in a matter of seconds than our Sun will emit during its entire lifetime. GRB 211106A belongs to a GRB sub-class known as short-duration gamma-ray bursts. These explosions— which scientists believe are responsible for the creation of 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 orbit of the binary stars, causing the stars to spiral in toward each other,” said Tanmoy Laskar, who will soon commence work as an Assistant Professor of Physics and Astronomy at the University of Utah. “The resulting explosion is accompanied by jets moving at close to the speed of light. When one of these jets is pointed at Earth, we observe a short pulse of gamma-ray radiation or a short-duration GRB.”
A short-duration GRB usually lasts only a few tenths of a second. Scientists then look for an afterglow, an emission of light caused by the interaction of the jets with surrounding gas. Even still, they’re difficult to detect; only half-a-dozen short-duration GRBs have been detected at radio wavelengths, and until now none had been detected in millimeter wavelengths. Laskar, who led the research while an Excellence Fellow at Radboud University in The Netherlands, said that the difficulty is the immense distance to GRBs, and the technological capabilities of telescopes. “Short-duration GRB afterglows are very luminous and energetic. But these explosions take place in distant galaxies which means the light from them can be quite faint for our telescopes on Earth. Before ALMA, millimeter telescopes were not sensitive enough to detect these afterglows.”
At roughly 20 billion light-years from Earth, GRB 211106A is no exception. The light from this short-duration 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 scientists weren’t able to determine exactly where the explosion was coming from. “Afterglow light is essential for figuring out which galaxy a burst comes from and for learning more about the burst itself. Initially, when only the X-ray counterpart had been discovered, astronomers thought that this burst might be coming from a nearby galaxy,” said Laskar, adding that a significant amount of dust in the area also obscured the object from detection in optical observations with the Hubble Space Telescope.
Each wavelength added a new dimension to scientists’ understanding of the GRB, and millimeter, in particular, was critical to uncovering the truth about the burst. “The Hubble observations revealed an unchanging field of galaxies. ALMA’s unparalleled sensitivity allowed us to pinpoint the location of the GRB in that field with more precision, and it turned out to be in another faint galaxy, which is further away. That, in turn, means that this short-duration gamma-ray burst is even more powerful than we first thought, making it one of the most luminous and energetic on record,” said Laskar.
Wen-fai Fong, an Assistant Professor of Physics and Astronomy at Northwestern University added, “This short gamma-ray burst was the first time we tried to observe such an event with ALMA. Afterglows for short bursts are very difficult to come by, so it was spectacular to catch this event shining so bright. After many years of observing these bursts, this surprising discovery opens up a new area of study, as it motivates us to observe many more of these with ALMA, and other telescope arrays, in the future.”
Joe Pesce, National Science Foundation Program Officer for NRAO/ALMA said, “These observations are fantastic on many levels. They provide more information to help us understand the enigmatic gamma-ray bursts (and neutron-star astrophysics in general), and they demonstrate how important and complementary multi-wavelength observations with space- and ground-based telescopes are in understanding astrophysical phenomena.”
And there’s plenty of work still to be done across multiple wavelengths, both with new GRBs and with GRB 211106A, which could uncover additional surprises about these bursts. “The study of short-duration 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 at unprecedented distances.”
Laskar added, "With JWST, we can now take a spectrum of the host galaxy and easily know the distance, and in the future, we could also use JWST to capture infrared afterglows and study their chemical composition. With ngVLA, we will be able to study the geometric structure of the afterglows and the star-forming fuel found in their host environments in unprecedented detail. I am excited about these upcoming discoveries in our field.”
Resource
“The First Short GRB Millimeter Afterglow: The Wide-Angled Jet of the Extremely Energetic SGRB 211106A,” Laskar et al (2022), The Astrophysical Journal Letters
About NRAO
The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
About ALMA
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
JOURNAL
The Astrophysical Journal Letters
ARTICLE TITLE
The First Short GRB Millimeter Afterglow: The Wide-Angled Jet of the Extremely Energetic SGRB 211106A
Explosive neutron star merger captured for first time in millimeter light
Flash is one of the most energetic short-duration gamma-ray bursts ever observed
Peer-Reviewed PublicationVIDEO: IN THE FIRST-EVER TIME-LAPSE MOVIE OF A SHORT-DURATION GAMMA-RAY BURST IN MILLIMETER-WAVELENGTH LIGHT, WE SEE GRB 21106A AS CAPTURED WITH THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY (ALMA). THE MILLIMETER LIGHT SEEN HERE PINPOINTS THE LOCATION OF THE EVENT TO A DISTANT HOST GALAXY IN IMAGES CAPTURED USING THE HUBBLE SPACE TELESCOPE. THE EVOLUTION OF THE MILLIMETER LIGHT’S BRIGHTNESS PROVIDES INFORMATION ON THE ENERGY AND GEOMETRY OF THE JETS PRODUCED IN THE EXPLOSION. view more
CREDIT: ALMA (ESO/NAOJ/NRAO), T. LASKAR (UTAH), S. DAGNELLO (NRAO/AUI/NSF)
For the first time, scientists have recorded millimeter-wavelength light from a fiery explosion caused by the merger of a neutron star with another star.
Led by Northwestern University and Radboud University in the Netherlands, the team also confirmed this flash as one of the most energetic short-duration gamma-ray bursts (GRBs) ever observed, leaving behind one of the most luminous afterglows on record.
Astrophysicists made the discovery with the Atacama Large Millimeter/submillimeter Array (ALMA), an international observatory operated by the National Science Foundation’s National Radio Astronomy Observatory (NRAO). Located in the high-altitude Atacama Desert in Chile, the ALMA array comprises 66 radio telescopes, making it the largest radio telescope in the world.
“This short gamma-ray burst was the first time we tried to observe such an event with ALMA,” said Northwestern’s Wen-fai Fong, principal investigator of the ALMA program. “Afterglows for short bursts are very difficult to come by, so it was spectacular to catch this event shining so brightly. After many years observing these bursts, this surprising discovery opens up a new area of study, as it motivates us to observe many more of these with ALMA and other telescope arrays in the future.”
The research will be published in an upcoming issue of the Astrophysical Journal Letters.
Fong is an assistant professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences and a key member of the Center for Interdisciplinary Exploration and Research in Astrophysics(CIERA). Northwestern coauthors include Alicia Rouco Escorial, Genevieve Schroeder, Jillian Rastinejad, Charles Kilpatrick, Kate Alexander and Anya Nugent.
Extreme energy
The brightest and most energetic explosions in the universe, GRBs are capable of emitting more energy in a matter of seconds than our sun will emit during its entire lifetime. In the new study, astrophysicists examined GRB 211106A, which belongs to a GRB subclass known as short-duration gamma ray bursts. Responsible for creating the heaviest elements in the universe, such as platinum and gold, these explosions result from a catastrophic merger of binary star systems containing at least one neutron star.
“These mergers are excellent sources of gravitational waves, making them premier multi-messenger cosmic sources that can be observed with gravitational waves and light,” Fong said. “While this GRB was out of the range of current gravitational wave observatories, we were still able to mobilize several observatories to capture its light in the millimeter, radio and X-ray wavelengths.”
“These mergers occur because of gravitational wave radiation that removes energy from the orbit of the binary stars, causing the stars to spiral in toward each other,” said the study’s lead author Tanmoy Laskar, an Excellence Fellow at Radboud University. “The resulting explosion is accompanied by jets moving at close to the speed of light. When one of these jets is pointed at Earth, we observe a short pulse of gamma-ray radiation or a short-duration GRB.”
The importance of millimeters
A short-duration GRB usually lasts only a few tenths of a second. After it fades, scientists look for an afterglow, an emission of light caused by the interaction of the jets with surrounding gas. Even still, short-duration GRBs are difficult to detect. Only half a dozen short-duration GRBs have been detected at radio wavelengths, and, until now, none had been detected in millimeter wavelengths.
“Millimeter wavelengths can tell us about the density of the environment around the GRB,” said Schroeder, study coauthor and graduate student in Fong’s research group. “And, when combined with the X-rays, they can tell us about the true energy of the explosion. Because emission at millimeter wavelengths can be detected for a longer time than in X-rays, the millimeter emission also can be used to determine the width of the GRB jet.”
“What makes GRB 211106A so special is it’s not only the first short-duration GRB that we detected in this wavelength, but also, thanks to the millimeter and radio detection, we could measure the opening angle of the jet,” added Rouco Escorial, study coauthor and postdoctoral fellow in CIERA. “The millimeter and radio bands provided us with information we needed to measure the jet opening angle. This is essential to infer the real rates of short GRBs in our universe and to compare them with the rates of binary neutron star or neutron star and black hole mergers.”
Because GRB 211106A occurred when the universe was just 40% of its current age, the light was particularly faint. Although NASA’s Neil Gehrels Swift Observatory detected the explosion with X-ray observations, the host galaxy was undetectable at that wavelength, leaving scientists unable to determine exactly where the explosion was coming from. NASA’s Hubble Space Telescope detected optical and infrared light from the host galaxy, while ALMA detected millimeter light from the afterglow. Each wavelength added a new dimension to scientists’ understanding of the GRB, and millimeter, in particular, was critical to uncovering the truth about the burst.
“The Hubble observations revealed an unchanging field of galaxies,” Laskar said. “ALMA’s unparalleled sensitivity allowed us to pinpoint the location of the GRB in that field with more precision, and it turned out to be in another faint galaxy, which is further away. That, in turn, means that this short-duration gamma-ray burst is even more powerful than we first thought, making it one of the most luminous and energetic on record.”
“ALMA shatters the playing field in terms of its capabilities at millimeter wavelengths and has enabled us to see the faint, dynamic universe in this type of light for the first time,” Fong said. “After a decade of observing short GRBs, it is truly amazing to witness the power of using these new technologies to unwrap surprise gifts from the universe.”
The study, “The first short GRB millimeter afterglow: The wide-angled jet of the extremely energetic SGRB 211106A,” was supported by the National Science Foundation (award numbers AST-1814782, AST-1909358 and AST-2047919), the David and Lucile Packard Foundation and NASA (award numbers NNM11AA01A and GO1-22059X).
JOURNAL
The Astrophysical Journal Letters
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
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