Scientists capture images of a neutron star merger for the first time

Scientists have recorded for the first time a millimeter-wave burst of light caused by the merger of a neutron star with another star.

Not only is this the first time scientists have successfully recorded a neutron star merger, but the team also confirmed that the resulting flash of light is one of the most energetic short-duration gamma-ray bursts ever observed and left one of the brightest afterglows on record.

The team, led by Northwestern University and Radboud University in the Netherlands, used the Atacama Large Millimeter/submillimeter Array (ALMA) for the observation. The ALMA array in Chile’s Atacama Desert consists of 66 radio telescopes, making it the largest such telescope in the world.

“This brief gamma-ray burst was the first time we attempted to observe such an event with ALMA,” says Northwestern’s Wen-fai Fong, principal investigator on the ALMA program.

“Afterglows for short bursts are very hard to come by, so to see this event shine so brightly was spectacular. After many years of observing these outbursts, this surprising discovery opens up a new area of ​​research as it motivates us to observe many more of them with ALMA and other telescope arrays in the future.”

As explained by the National Radio Astronomy Observatory (NRAO), gamma-ray bursts (GRBs) are the brightest and most energetic explosions in the universe and can emit more energy in seconds than the Sun will emit in its entire lifetime.

Short-duration GRBs typically last a fraction of a second, and although they eject a ton of energy and leave an afterglow — a light emission caused by the jets’ interaction with the surrounding gas — they’re still difficult to detect, lasting less than half an hour Dozens have ever been detected at radio wavelengths. So far, none had been detected in the millimeter wave range.

“Millimetre wavelengths can tell us about the density of the environment around the GRB,” says Genevieve Schroeder, co-author of the study and a PhD student in Fong’s research group.

“And combined with the X-rays, they can tell us something about the true energy of the explosion. Because emission can be detected at millimeter wavelengths longer than X-rays, millimeter emission can also be used to determine the width of the GRB jet.”

“What makes GRB 211106A so special is that not only is it the first short-duration GRB that we have detected in this wavelength, but thanks to millimeter and radio detection, we were also able to measure the aperture angle of the jet,” investigates Rouco Escorial Co -Author and postdoc at CIERA, adds.

“The millimeter and radio bands gave us the information we needed to measure the beam opening angle. This is important to derive the real rates of short GRBs in our Universe and compare them to the rates of neutron stars or neutron star black hole mergers.”

The explosion, named GR 211106A, which the scientists witnessed, happened when the universe was quite young: only 40% of its current age. As a result, the light from the explosion is incredibly dim.

“The light from this brief gamma-ray burst was so faint that early X-ray observations with NASA’s Neil Gehrels Swift Observatory spotted the explosion, but the host galaxy was undetectable at that wavelength and scientists were unable to pinpoint exactly where the explosion came from.” came,” writes the NRAO.

“Afterglow is essential for finding out which galaxy a burst originated from and for learning more about the burst itself. Initially, when only the X-ray counterpart had been detected, astronomers thought this burst might be coming from a nearby galaxy,” says Tanmoy Laskar, who will soon start work as an assistant professor of physics and astronomy at the University of Utah. and adds that a significant amount of surrounding dust obscured the object even in optical observations with the Hubble Space Telescope.

“The Hubble observations showed an unchanging galaxy field,” says Laskar. “ALMA’s unprecedented sensitivity allowed us to more accurately pinpoint the location of the GRB in this field, and it turned out to be in another faint galaxy, more distant. This in turn means this brief gamma-ray burst is even stronger than we first thought, making it one of the brightest and most energetic on record.”

The full research report on the observation will be published in a future issue of The Letters of the Astrophysical Journal.

Photo credit: ALMA (ESO/NAOJ/NRAO), M. Weiss (NRAO/AUI/NSF)