Tuesday, June 14, 2022

A weird star produced the fastest nova on record

 A team of users of the Large Binocular Telescope has recorded the fastest nova ever. They hope to find answers to not only the nova’s many baffling traits, but to larger questions about our solar system and the universe.

Astronomers are buzzing after observing the fastest nova ever recorded. The unusual event drew scientists’ attention to an even more unusual star. As they study it, they may find answers to not only the nova’s many baffling traits, but to larger questions about the chemistry of our solar system, the death of stars and the evolution of the universe.

The research team, led by Arizona State University Regents Professor Sumner Starrfield, Professor Charles Woodward from University of Minnesota and Research Scientist Mark Wagner from The Ohio State University, co-authored a report published in the Research Notes of the American Astronomical Society.

 A nova is a sudden explosion of bright light from a two-star system. Every nova is created by a white dwarf — the very dense leftover core of a star — and a nearby companion star. Over time, the white dwarf draws matter from its companion, which falls onto the white dwarf. The white dwarf heats this material, causing an uncontrolled reaction that releases a burst of energy. The explosion shoots the matter away at high speeds, which we observe as visible light.

The bright nova usually fades over a couple of weeks or longer. On June 12, 2021, the nova V1674 Hercules burst so bright that it was visible to the naked eye — but in just over one day, it was faint once more. It was like someone flicked a flashlight on and off.

Nova events at this level of speed are rare, making this nova a precious study subject.

“It was only about one day, and the previous fastest nova was one we studied back in 1991, V838 Herculis, which declined in about two or three days,” says Starrfield, an astrophysicist in ASU’s School of Earth and Space Exploration.

As the astronomy world watched V1674 Hercules, other researchers found that its speed wasn’t its only unusual trait. The light and energy it sends out is also pulsing like the sound of a reverberating bell.

Every 501 seconds, there’s a wobble that observers can see in both visible light waves and X-rays. A year after its explosion, the nova is still showing this wobble, and it seems it’s been going on for even longer. Starrfield and his colleagues have continued to study this quirk.

The most unusual thing is that this oscillation was seen before the outburst, but it was also evident when the nova was some 10 magnitudes brighter,” says Wagner, who is also the head of science at the Large Binocular Telescope Observatory being used to observe the nova. “A mystery that people are trying to wrestle with is what’s driving this periodicity that you would see it over that range of brightness in the system.”

The team also noticed something strange as they monitored the matter ejected by the nova explosion — some kind of wind, which may be dependent on the positions of the white dwarf and its companion star, is shaping the flow of material into space surrounding the system.

This illustration shows an intermediate polar system, a type of two-star system that the research team thinks V1674 Hercules belongs to.  A flow of gas from the large companion star impacts an accretion disk before flowing along magnetic field lines onto the white dwarf.    Credit: Illustration by Mark Garlick. 


Though the fastest nova is (literally) flashy, the reason it’s worth further study is that novae can tell us important information about our solar system and even the universe as a whole.

A white dwarf collects and alters matter, then seasons the surrounding space with new material during a nova explosion. It’s an important part of the cycle of matter in space. The materials ejected by novae will eventually form new stellar systems. Such events helped form our solar system as well, ensuring that Earth is more than a lump of carbon.

 “We're always trying to figure out how the solar system formed, where the chemical elements in the solar system came from,” Starrfield says. “One of the things that we're going to learn from this nova is, for example, how much lithium was produced by this explosion. We're fairly sure now that a significant fraction of the lithium that we have on the Earth was produced by these kinds of explosions.”

Sometimes a white dwarf star doesn’t lose all of its collected matter during a nova explosion, so with each cycle, it gains mass. This would eventually make it unstable, and the white dwarf could generate a type 1a supernova, which is one of the brightest events in the universe. Each type 1a supernova reaches the same level of brightness, so they are known as standard candles.

“Standard candles are so bright that we can see them at great distances across the universe. By looking at how the brightness of light changes, we can ask questions about how the universe is accelerating or about the overall three-dimensional structure of the universe,” Woodward says. “This is one of the interesting reasons that we study some of these systems.”

Additionally, novae can tell us more about how stars in binary systems evolve to their death, a process that is not well understood. They also act as living laboratories where scientists can see nuclear physics in action and test theoretical concepts.

The nova took the astronomy world by surprise. It wasn’t on scientists’ radar until an amateur astronomer from Japan, Seidji Ueda, discovered and reported it.

MODS1 & MODS2, the pair of LBTO multi-object double spectrographs used by the team, seen while the telescope is pointed at horizon. Photo credit: Rick Pogge.

Citizen scientists play an increasingly important role in the field of astronomy, as does modern technology. Even though it is now too faint for other types of telescopes to see, the team is still able to monitor the nova thanks to the Large Binocular Telescope’s wide aperture and its observatory’s other equipment, including its pair of multi-object double spectrographs (MODS) and exceptional PEPSI high resolution spectrograph.

They plan to investigate the cause of the outburst and the processes that led to it, the reason for its record-breaking decline, the forces behind the observed wind, and the cause of its pulsing brightness.


Wednesday, June 8, 2022

AN UNEXPECTED GAMMA RAY BURST

An international group led by INAF researchers have confirmed that the gamma-ray burst GRB 200826A, which lasted less than two seconds – typical of short bursts – is associated with the explosion of a massive star, which is typical of long gamma-ray bursts. The study, involving also several universities and research institutes in Italy, is primarily based on data collected with the Large Binocular Telescope in Arizona, USA. The observations made the first ever use of adaptive optics to observe a supernova associated with a gamma-ray burst. 

Tuesday, May 31, 2022

Announcing the new Director of the Large Binocular Telescope

The Large Binocular Telescope Observatory, one of the largest and most advanced optical telescopes in the world, is proud to announce the appointment of its new Director, Prof. Joseph Shields, who will assume the position effective June 06, 2022.

Prof. Joseph Shields
Dr. Shields is currently Vice President for Research & Creative Activity and Dean of the Graduate College and the former Chair of the Department of Physics & Astronomy at  Ohio University.

Dr. Shields received his bachelors degree from the University of Kansas and his PhD in Astronomy from the University of California at Berkeley. He held a postdoctoral appointment at the Ohio State University and a Hubble Fellowship at the University of Arizona prior to joining the faculty at Ohio University. In his research, Shields studies the physics  of  supermassive black holes in galaxies, using both ground-based and space-based observatories. He is also interested  in the interstellar medium, star formation,  and supernovae. He is an author on more than 110 papers in the peer-reviewed literature, and served for four years as a Scientific Editor of the Astrophysical Journal.

The LBT Board of Directors appointed Prof. Shields to serve as the Observatory’s new director following an extensive international search.

“We are excited to welcome Joe and look forward to working with him to maintain the prominent position of LBT as a world-class astronomical facility,” stated Adriano Fontana, Chair of the LBT Board of Directors. “Joe has a unique combination of astronomical experience, scientific vision and managerial capabilities that make him the perfect match for LBT. Joe will build on the unique role of LBT in fostering new astronomical discoveries and the development of cutting-edge observational techniques associated with adaptive optics and interferometry.“

In accepting the Director position, Shields commented: “I am pleased and honoured to have the opportunity to lead the talented LBTO staff during the observatory’s next phase as a pioneer in the realm of extremely large optical telescopes.  The LBT has a storied history and vibrant future in technological innovation and astronomical discovery, enabled by the distinctive expertise of its partner institutions.”

The LBT Board of Directors also extended its appreciation to Dr. Christian Veillet, who successfully led the Observatory during the last ten years, completing the installation and commissioning of the initial suite of scientific instruments.

LBT is a unique astronomical facility. Located on Mt. Graham in southeast Arizona, at an elevation of 3200m/10000 ft, the LBT has  two 8.4m (27.5 feet) mirrors  side-by-side like a pair of binoculars for a combined collecting area of a single 11.8m (38.7 feet) telescope. This unique design gives it the capabilities of a 23-m (75.5 feet) telescope in some observing modes, making it the first of the next-generation extremely large telescopes.

The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, representing OSU, University of Notre Dame, University of Minnesota and University of Virginia.