Astronomers have spotted a “vampire star,” feeding on one of its brethren in a dwarf nova. A nova is an event marked by the sudden appearance of a bight, seemingly new star, which fades over a period of weeks or months. Traditional novae consist of a white dwarf feeding on a companion star, typically a main sequence, subgiant, or red giant star. As the white dwarf absorbs matter from its companion, gas begins to fall onto the white dwarf’s surface to create an atmosphere which is heated and begins to glow when fusion occurs.
What is unusual about this particular dwarf nova is that the white dwarf is feeding on one of its own, a brown dwarf. “The rare event we found was a super-outburst from the dwarf nova, which can be thought of as a vampire star system,” lead researcher Ryan Ridden-Harper of the Australian National University said in a statement. He and his colleagues discovered the event when pouring over data from the archive of the decommissioned Kepler Space Telescope.
An artist’s impression of a vampire system. NASA and L. Hustak (STSci)
“The incredible data from Kepler reveals a 30-day period during which the dwarf nova rapidly became 1,600 times brighter before dimming quickly and gradually returning to its normal brightness,” Ridden-Harper said. “The spike in brightness was caused by material stripped from the brown dwarf that’s being coiled around the white dwarf in a disk. That disk reached up to 11,700 degrees Celsius [21,092 degrees Fahrenheit] at the peak of the super-outburst.”
“The discovery of this dwarf nova was unexpected since it wasn’t what we were searching for, but it provided excellent data and new insights into these vampire star systems.”
To discover more about these vampire systems, the team wants to look at more data from the Kepler archive and from other sources like currently active telescopes. “The next steps for this project are to comb through all Kepler data and extend it to data from the Transiting Exoplanet Survey Satellite, which is known as TESS,” Ridden-Harper said. “This will give us the best understanding of the most rapid explosions in the universe. Along the way, we might discover some rare events that no other telescope could find.”
Kepler was able to observe some remarkable events during its term, from imaging dying stars to discovering exoplanets. But the archive of data it left behind is still providing surprises. “We’ve used it to see stars as they explode, the secret lives of black holes and now things previously missed — this vampire star that had been lurking in the darkness of space,” said Dr. Brad Tucker, supervisor of the project.
The findings are published in the Monthly Notices of the Royal Astronomical Society.