U of S group joins worldwide effort to measure brightness of exploding star

On April 29, the sudden brightening of the dwarf nova V392 Persei was captured photographically in Japan, indicating it may have undergone a rare nova outburst. The eruption is only the second time that a previously known dwarf nova has transformed into a classical nova, said Stan Shadick, an astronomy lecturer in the College of Arts and Science’s Department of Physics and Engineering Physics.

The University of Saskatchewan Variable Star Research Group includes Shadick and fellow lecturer Daryl Janzen, as well as undergraduate students who have taken the Astronomy 213 hands-on telescope class. The purpose of the group is to involve undergraduate students in collecting research data about variable stars, including novae, exoplanet transits and eclipsing binary star systems.

The U of S students have measured the brightness of the nova on every clear evening since April 30, which was the first evening following its discovery on April 29.

“Their data is very useful in determining the luminosity behaviour of this exploding star,” said Shadick.

“The students are part of a worldwide campaign to monitor the star’s brightness variations in order to understand the physical processes involved in such nova eruptions. By combining our observations with those from other astronomers in northern Europe, we can search for any short-time variations in the behaviour of this star. This nova can be more easily observed from Canadian latitudes than more southerly locations within the U.S.”

When the star was a dwarf nova, its visual magnitude ranged from about 17 to 14. When it erupted as a classical nova, its magnitude brightened roughly 10,000 times to a peak magnitude of about 6, said Shadick.

“A dwarf nova occurs in a binary star system where a dense white dwarf star siphons hydrogen gas from a companion star,” said Shadick.

“The infalling gas forms a rotating accretion disk around the white dwarf star. This disk becomes unstable, causing brightness fluctuations that can be seen from Earth with our telescopes. In the case of a classical nova, gas from the accretion disk falls onto the white dwarf star. When sufficient gas is transferred onto the white dwarf star’s surface, its surface hydrogen ignites causing a hydrogen fusion explosion resulting in an even larger increase in brightness.”

Members of the U of S group are hopeful that they may eventually be able to obtain spectra of the nova, he added.

Any astronomy students who wish to participate in future studies of this nova should contact Daryl Janzen or Stan Shadick for details on any afternoon when the evening forecast shows clear skies.