New Research Shows that Short Gamma-Ray Bursts are Powered through Formation of Neutron Stars as well as Black Holes

        An artist's impression of a gamma-ray burst powered by a neutron star. Credit: Nuria Jordana-Mitjans

An international collaboration led out of the University of Bath has reported early measurements of a short-duration gamma-ray burst that challenge the standard paradigm for these phenomena. The source, GRB 180618A, was observed with space-and ground-based telescopes to construct a time sequence of emission from gamma-ray through optical wavelengths.

Observations with the Large Binocular Telescope obtained by LBTO and INAF astronomers were used to locate the galaxy where the transient event occurred. Deep-field observations from the Large Binocular Cameras and high-precision spectroscopic data from the Multi-Object Double Spectrographs revealed a galactic trio 10.6 billion light years away. Further examination of the LBT data indicated that the GRB exploded at the outskirts of one of these galaxies.

Analysis of the measured GRB emission points to an origin from a wind nebula powered by a young, highly magnetized neutron star, known as a magnetar. Previous studies of short GRBs implicated the merger of a binary pair of neutron stars that form a black hole as the source of energy driving the explosion. The new results also point to the merger of a neutron star binary as the precipitating event, but with a product that is itself a massive neutron star, accompanied by a release of gravitational and magnetic energy. The conclusion is that at least two types of merger processes underlie short-duration gamma-ray bursts.

The new results are reported in the published article by Jordana-Mitjans et al. (2022), Astrophys. Jour., 939, 106

Red-Supergiant Supernova Images Reveal Secrets of an Earlier Universe

   The above image shows the light from the supernova behind the galaxy cluster Abell 370. Photo credit: Wenlei Chen, NASA

The above image shows the light from the supernova behind the galaxy cluster Abell 370. Photo credit: Wenlei Chen, NASA

A new study has measured the size of a star that exploded more than 11 billion years ago. Detailed images show the exploding star cooling and could help scientists learn more about the stars and galaxies present in the early universe.

The findings are published in Chen et al. (2022), Nature, 611, 256.

“This is the first detailed look at a supernova at a much earlier stage of the universe’s evolution,” said Patrick Kelly, a lead author of the paper and an associate professor in the University of Minnesota College of Science and Engineering. “It's very exciting because we can learn in detail about an individual star when the universe was less than a fifth of its current age, and begin to understand if the stars that existed many billions of years ago are different from the ones nearby.”

The red supergiant in question was about 500 times larger than the sun, and it’s located about 60 times farther away than any other supernova observed in this detail.

Using data from the Hubble Space Telescope and the Large Binocular Telescope, researchers were able to identify multiple detailed images of the red supergiant because of a phenomenon called gravitational lensing, where mass, such as that in a galaxy, bends light. This magnifies the light emitted from the star.

“The gravitational lens acts as a natural magnifying glass and multiplies Hubble’s power by a factor of eight,” Kelly said. “The images we captured show the supernova as it was at different ages separated by several days. We see the supernova rapidly cooling, which allows us to basically reconstruct what happened and study how the supernova cooled in its first few days with just one set of images. It enables us to see a rerun of a supernova.”

The researchers combined this discovery with another one of Kelly’s supernova discoveries from 2014 to estimate how many stars were exploding when the Universe was a small fraction of its current age. They found that there were likely many more supernovae than previously thought.

“Core-collapse supernovae mark the deaths of massive, short-lived stars. The number of core-collapse supernovae we detect can be used to understand how many massive stars were formed in galaxies when the Universe was much younger,” said Wenlei Chen, first author of the paper and a University of Minnesota postdoctoral researcher .

The research was funded by the National Science Foundation; the Hubble Space Telescope Cycle 27 Archival Research and Frontier Fields program; the World Premier International Research Center Initiative, MEXT, Japan; the United States-Israel Binational Science Foundation; the Ministry of Science & Technology, Israel; the Christopher R. Redlich Fund; and the University of California, Berkeley Miller Institute for Basic Research in Science.

Primordial Helium Research at the Large Binocular Telescope

A recent news story from Gonzaga University reports on research by Gonzaga Professor Erik Aver using the Large Binocular Telescope to study the primordial helium abundance. The work, conducted in collaboration with Richard Pogge at Ohio State University and Evan Skillman at the University of Minnesota, was recently awarded major support through a grant of $755k from the National Science Foundation.

The study will make use of LBT spectra of more than 40 metal-poor galaxies analyzed with advanced methods to measure a value for the primordial helium abundance with an uncertainty of approximately 0.5%. The resulting increase in precision will be significant as a constraint on proposed scenarios for extending the standard model of particle physics.