Woodward research takes a look at the fastest nova on record
A research report, co-authored by Professor Charles Woodward of the School of Physics and Astronomy describes the unusual quirks of V1674 Hercules, the fastest nova ever on record. Apart from its unusual speed--the nova lasted about a day, when the previous record holder was spent in 2-3 days--the nova exhibited several other unusual traits that the researchers hope will help them learn more about nova physics in general.
A nova is a sudden explosion which results in a dramatic change in brightness from a two-star system. Novae are created on white dwarf stars — the very dense leftover core of solar-type stars at the end of their lifetimes — via interactions with its nearby companion star. Over time, the white dwarf draws matter from its companion, which falls onto the surface white dwarf. This material compresses and heats, causing an uncontrolled reaction that releases a burst of energy. The explosion ejects the matter away at high speeds, combined with a pulse of radiation (like that of a firework going off) observed as visible light (and at other wavelengths). Novae are important to study because they are part of the life cycle of matter in space and a because the systems which produce them can also create super novae. Cosmologists study novae and super novae because they are responsible for the creation and distribution of elements in the Universe and because they can be used to study the behavior of matter at energies far greater than can be reproduced on Earth.
The observers noticed a periodic flash of light or wobble in the nova. “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,” said Mark Wagner from The Ohio State University, one of the co authors and 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.
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 eventually makes the white dwarf core gravitationally unstable, and the white dwarf collapses upon itself generating a type Ia supernova, which, 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 said. “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.
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. 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 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.