Bing Zhang contributes to understanding the physical mechanisms of fast radio bursts in three papers published in Nature.

Authored by Shane Bevell for the UNLV News Center, November 4, 2020.

Fast radio bursts, or FRBs – powerful, millisecond-duration radio waves coming from deep space outside the Milky Way Galaxy – have been among the most mysterious astronomical phenomena ever observed. Since FRBs were first discovered in 2007, astronomers from around the world have used radio telescopes to trace the bursts and look for clues on where they come from and how they’re produced.

UNLV astrophysicist Bing Zhang and international collaborators recently observed some of these mysterious sources, which led to a series of breakthrough discoveries reported in the journal Nature that may finally shed light into the physical mechanism of FRBs.

The first paper, for which Zhang is a corresponding author and leading theorist, was published in the Oct. 28 issue of Nature.

“There are two main questions regarding the origin of FRBs,” said Zhang, whose team made the observation using the Five-hundred-meter Aperture Spherical Telescope (FAST) in Guizhou, China. “The first is what are the engines of FRBs and the second is what is the mechanism to produce FRBs. We found the answer to the second question in this paper.”

Two competing theories have been proposed to interpret the mechanism of FRBs. One theory is that they’re similar to gamma-ray bursts (GRBs), the most powerful explosions in the universe. The other theory likens them more to radio pulsars, which are spinning neutron stars that emit bright, coherent radio pulses. The GRB-like models predict a non-varying polarization angle within each burst whereas the pulsar-like models predict variations of the polarization angle.

The team used FAST to observe one repeating FRB source and discovered 11 bursts from it. Surprisingly, seven of the 11 bright bursts showed diverse polarization angle swings during each burst. The polarization angles not only varied in each burst, the variation patterns were also diverse among bursts.

“Our observations essentially rules out the GRB-like models and offers support to the pulsar-like models,” said K.-J. Lee from the Kavli Institute for Astronomy and Astrophysics, Peking University, and corresponding author of the paper.

Four other papers on FRBs were published in Nature on Nov. 4. These include multiple research articles published by the FAST team led by Zhang and collaborators from the National Astronomical Observatories of China and Peking University. Researchers affiliated with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Survey for Transient Astronomical Radio Emission 2 (STARE2) group also partnered on the publications.

“Much like the first paper advanced our understanding of the mechanism behind FRBs, these papers solved the challenge of their mysterious origin,” explained Zhang.

Magnetars are incredibly dense, city-sized neutron stars that possess the most powerful magnetic fields in the universe. Magnetars occasionally make short X-ray or soft gamma-ray bursts through dissipation of magnetic fields, so they have been long speculated as plausible sources to power FRBs during high-energy bursts.

The first conclusive evidence of this came on April 28, 2020, when an extremely bright radio burst was detected from a magnetar sitting right in our backyard – at a distance of about 30,000 light years from Earth in the Milky Way Galaxy. As expected, the FRB was associated with a bright X-ray burst.

“We now know that the most magnetized objects in the universe, the so-called magnetars, can produce at least some or possibly all FRBs in the universe,” said Zhang.

The event was detected by CHIME and STARE2, two telescope arrays with many small radio telescopes that are suitable for detecting bright events from a large area of the sky.

Zhang’s team has been using FAST to observe the magnetar source for some time. Unfortunately, when the FRB occurred, FAST was not looking at the source. Nonetheless, FAST made some intriguing “non-detection” discoveries and reported them in one of the Nov. 4 Nature articles. During the FAST observational campaign, there were another 29 X-ray bursts emitted from the magnetar. However, none of these bursts were accompanied by a radio burst.

“Our non-detections and the detections by the CHIME and STARE2 teams delineate a complete picture of FRB-magnetar associations,” Zhang said.

To put it all into perspective, Zhang also worked with Nature to publish a single-author review of the various discoveries and their implications for the field of astronomy.

“Thanks to recent observational breakthroughs, the FRB theories can finally be reviewed critically,” said Zhang. “The mechanisms of producing FRBs are greatly narrowed down. Yet, many open questions remain. This will be an exciting field in the years to come.”

Read More

• "No pulsed radio emission during a bursting phase of a Galactic magnetar," published in the Nov. 4 issue of Nature.
• "The physical mechanisms of fast radio bursts," published in the Nov. 4 issue of Nature.
• "Diverse polarization angle swings from a repeating fast radio burst source," published in the Oct. 28 issue of Nature.

Ashkan Salamat's research about room-temperature superconductivity is one of 10 finalists in Physics World magazine's Breakthrough of the Year for 2020.

Ashkan Salamat's recent research about room-temperature superconductivity with colleague Ranga Dias from the University of Rochester was announced as one of 10 finalists in Physics World magazine's Breakthrough of the Year for 2020.

The announcement of the Breakthrough of the Year will be made Dec. 17.

This year’s Top 10 Breakthroughs were selected by a crack team of five Physics World editors, who have sifted through hundreds of research updates published on the website this year. In addition to having been reported in Physics World in 2020, selections must meet the following criteria:

• Significant advance in knowledge or understanding
• Importance of work for scientific progress and/or development of real-world applications
• Of general interest to Physics World readers

Rebecca Martin awarded NASA Exoplanets grant

Associate professor of Physics & Astronomy, Rebecca Martin, is the prinicipal investigator on a NASA Exoplanets grant that was awarded for $541,460 to study planet formation in binary star systems. Since most stars are in binaries, we need to understand how the binary affects the planet formation process in order to explain the properties of observed exoplanets.

Daniel Proga awarded NASA TCAN grant

Professor of Physics and Astronomy Daniel Proga was just awarded one of NASA's most prestigious research grants through the Theoretical and Computational Astrophysics Networks (TCAN) program. The grant totals $1,547,537 and will be shared with 4 other major research institutions: the Institute for Advanced Study, NASA's Goddard Space Flight Center, The University of Virginia, and the Flatiron Institute at the Center for Computational Astrophysics.

Professor Proga is the principal investigator and hence UNLV will be the head node of this network collaboration to advance the state of the art in modeling accretion processes in astrophysics. Specifically, the collaboration will develop algorithms and perform supercomputer simulations to understand exactly how the atmospheres of turbulent accretion disks should appear observationally, according to theory. It is well known that disk atmospheres around systems such as supermassive black holes and low mass X-ray binaries can be unbound, forming accretion disk winds. Professor Proga has spent much of his career understanding such disk winds, and this emphasis is apparent in the name of the collaboration: A New DAWN (Disk Accretion and Winds Network). The name also reflects the ambitious goals of the project, as the resulting modeling capability is expected to usher in a new dawn in understanding the physics of how matter is accreted and ejected from black holes, neutron stars, and newly born stars. The full UNLV team consists of Associate Professor of Physics and Astronomy and co-investigator Zhaohuan Zhu, Postdoctoral Researcher Tim Waters (who earned his PhD from UNLV in 2017), and graduate students Randall Dannen and Shalini Ganguly. This major grant will provide funding support for this team for a period of three years in addition to supporting two other postdoctoral researchers and several graduate students at the partnering research institutions.

Chao-Chin Yang awarded NASA TCAN grant

Assistant research professor Chao-Chin Yang was awarded a multi-institutional research grant by NASA through the Theoretical and Computational Astrophysics Networks (TCAN) program. Led by New Mexico State University, other collaborators include UNLV, University of Arizona, Iowa State University, and SETI Institute in the United States, and Max Planck Institute for Astronomy in Germany. Yang is a co-I/Institutional PI and will lead the UNLV node on the project. The grant totals $1.3 million with UNLV receiving $185,000. The team will investigate the influence of gas and dust dynamics in the protoplanetary disk around a newborn star on the formation of kilometer-scale planetary bodies — such as asteroids and comets in our own solar system — which are important intermediate building blocks of planets.

This award brings UNLV Physics & Astronomy's total active Theoretical and Computational Astrophysics Networks (TCAN) program awards to three. Meaning we have more active TCAN programs than any other institution in the US.

Ashkan Salamat and colleagues at UNLV and University of Rochester observe room-temperature superconductivity

Reported from the UNLV News Center press release release October 14 2020, Author: Natalie Bruzda.

Physicists from the University of Nevada, Las Vegas and the University of Rochester have made a breakthrough in the long sought-after quest for a room-temperature superconductor, what they call the “holy grail” of energy efficiency.

The research team led by University of Rochester physicist Ranga Dias in collaboration with Ashkan Salamat, assistant professor of physics and astronomy at UNLV, established room temperature superconductivity in a diamond anvil cell - a small, handheld, and commonly used research device that enables the compression of tiny materials to extreme pressures - pressures that you’d only find at the center of the Earth.

Though the phenomena observed by the research team and reported today as the cover story in the journal Nature was at an early stage, or fundamental level, the discovery has implications for how energy is stored and transmitted. It could also one day change how everyday technological devices - from laptops to MRI machines - are powered, how people and goods are transported, and how the whole of society could operate years into the future.

“It’s a revolutionary game changer,” said Salamat, who leads the Nevada Extreme Conditions Lab at UNLV, a newly formed, multidisciplinary group that explores fundamental experimental, computational, and engineering problems of materials under high pressure. “The discovery is new, and the technology is in its infancy and a vision of tomorrow, but the possibilities are endless. This could revolutionize the energy grid, and change every device that’s electronically driven.”

Superconductivity is a remarkable quantum phenomena as its hallmark properties include the expulsion of magnetic fields and zero resistance electrical flow, meaning that the energy current passing through a circuit is conducted infinitely and perfectly, with no loss of power.

Since its first observation in 1911, scientists have observed superconductivity only at very low temperatures — temperatures within a few degrees of absolute zero, (minus 273 degrees Celsius), which would make widespread and practical application unattainable. In 1968, however, scientists predicted that metallic hydrogen - accessed at very high pressures - could be the key ingredient to discovering superconductivity at or above room temperature.

"Because of the limits of low temperature, materials with such extraordinary properties have not quite transformed the world in the way that many might have imagined. However, our discovery will break down these barriers and open the door to many potential applications," Dias said in a University of Rochester release.

In Dias’ lab at the University of Rochester, the research team worked to chemically synthesize hydrogen in an effort to solve the century-old problem. Like a materials search engine, Salamat and Dias used the diamond anvil cell to scan through temperature and pressure space to find the right combination that would drive carbon sulfur hydrogen first into a metallic state, and then even further into a room-temperature superconducting state.

The U.S. energy grid, Salamat notes, which is made up of metallic cables loses about $20 billion a year to dissipating current. Though a metal like copper exhibits the least resistance of nearly all metals, it’s still resistant. Running current through copper and other metals generates heat, and as a consequence energy is lost (think of the heat exiting the bottom of your laptop).

Room-temperature superconductivity would allow current to flow through a closed loop forever, meaning that no energy would be lost. In the long distant future, such a state could enable a solar farm in the Southwest U.S. to transport energy to the East Coast with no loss, or MRI machines - which currently need liquid helium to operate - to be deployed to war zones. It could change how electronics are designed and built, and could revolutionize the transportation system.

Salamat calls it a “paradigm-shifting” discovery, which was made possible, in part, by the Early Career Award he received from the U.S. Department of Energy in 2019. The competitive DOE program bolsters financial support for exceptional talent during crucial early career years, when many scientists do their most formative work, and was the catalyst for Salamat to focus on the problem of identifying a room-temperature superconductor.

The discovery also dovetails perfectly into Salamat’s broader research priorities, which are identifying the precise makeup of metal superhydrides – extremely hydrogen-rich materials – and techniques to readily synthesize them.

The discovery of the room-temperature superconductor, Salamat said, was not what you would call a “eureka” moment, but rather, a methodical, targeted effort by he and Dias. They’re next step is to develop a protocol that releases the pressure for these materials while also retaining their superconducting properties.

To support their continued work on the problem, Dias and Salamat have started a new company, Unearthly Materials, to find a path to room temperature superconductors that can be produced at scale at ambient pressure.

“We live in a semiconductor society,” Salamat said. “With this kind of technology, you can take society from a semi-conducting society into a superconducting society.”

Coauthors on the Nature paper include Keith Lawler of UNLV's Nevada Extreme Conditions Lab; Elliot Snider, Nathan Dasenbrock-Gammon, Raymond McBride, Kevin Vencatasamy and Hiranya Vindana, all of the Dias lab at the University of Rochester; and Mathew Debessai of Intel Corporation.

Here is the publication in Nature where it was a cover feature. Room-temperature superconductivity in a carbonaceous sulfur hydride

The discovery has been widely reported including in these publications: Nature News, MIT Technology Review, Quanta magazine, Science magazine, New York Times, Nature podcast.

Additionally here is a nice interview with Ranga and Ash on Liv Boeree's Youtube channel.

Tim Waters appointed to working group on Athena X-Ray Observatory

Tim Waters has been appointed to be a member of the Athena X-Ray Observatory topical panel: SWG2.5: Physics of accretion, co-chaired by C. Done, J. Miller and C. Motch; this panel forms part of the SWG2: Energetic Universe working group, co-chaired by J. Aird, L. Brenneman and M. Cappi.

The Athena mission is scheduled to launch in 2031 and Tim as a member of the Physics of accretion working group aims to apply the simulations of X-ray binaries developed with Daniel Proga to make detailed predictions of the X-ray absorption lines that Athena should be able to resolve.

Athena Mission concept

The Athena mission will be a large X-ray observatory offering spatially-resolved X-ray spectroscopy and deep wide-field X-ray spectral imaging with performance greatly exceeding that offered by current X-ray observatories like XMM-Newton and Chandra, or by missions like Hitomi, XARM, and SRG/eROSITA.

Athena will be launched by an Ariane 6 vehicle, with equivalent or larger lift capability and fairing size to that of the Ariane 5 ECA. It will operate at the second Sun-Earth Lagrangian point (L2) in a large halo orbit, although the possibility of an L1 halo orbit is also being assessed. The operational orbit will be reached with a direct transfer trajectory towards L2, with limited delta-V demands, and it offers a very stable thermal environment as well as good instantaneous sky visibility and high observing efficiency.

Athena has a baseline mission lifetime of 4 years, although it is expected to be designed and have consumables for a longer time. Operations will be performed as in standard ESA science missions, with the Mission Operations Centre (MOC) at ESOC and the Science Operations Centre (SOC) at ESAC. The Instrument and Science Centre (ISC) associated with each of the two instruments will be in support of the SOC with regard to science ground segment activities.

Athena will be operated as an observatory, in a similar fashion to prior missions such as XMM-Newton and Herschel. Users will access the observatory via open proposal calls.

Science requirements

A detailed analysis of the scientific questions underlying the Hot and Energetic Universe theme sets the key performance parameters for the mission. Mapping the dynamics and chemical composition of hot gas in diffuse sources requires high spectral resolution (2.5 eV) imaging with large area and low background; the same capabilities also optimize the sensitivity to weak absorption and emission features needed to uncover the hot components of the intergalactic medium. High resolution X-ray spectroscopy of distant gamma-ray bursts (GRBs) will reveal the signature of the first generation of stars, provided that the observatory can be repointed within 4 hours of an external trigger. An angular resolution lower than 5” (Half Energy Width) is needed to disentangle contaminants (point-source and sub-clump) from extended thermal emission in clusters, groups and galaxies. The same angular resolution is needed to resolve the dominant core emission and smaller accreting structures in galaxy clusters and groups up to redshift z~2. This resolution, when combined with the mirror effective area, also provides the necessary flux sensitivity (~10-17 erg cm-2 s-1 in the 0.5-2 keV band) to uncover typical accreting SMBH at z>6. The area coverage needed to detect significant samples of these objects within a reasonable survey time demands a large field of view instrument, combined with excellent off-axis response for the X-ray optics. The spectral resolution of that instrument will reveal the most obscured black holes at the peak of the Universe’s activity at z=1-4. High timing resolution and high-count rate capability will shed new light on nearby accreting black hole systems.