TWINKLING CATEGORY
The twinkle of stars dazzle everyone who set their eyes towards a clear, unpolluted night sky. Some twinkle more than others, so much, in fact, that they are classified as pulsating stars. A group of UCSB researchers recently discovered a new class of these pulsators.
“Many stars pulsate, even our sun does on a very small scale,” said UCSB researcher Thomas Kupfer who is leading the team of scientists. “Those with the largest brightness changes are usually radial pulsators, ‘breathing’ in and out as the entire star changes size.”
The four stars discovered by Dr. Kupfer and his colleagues change brightness by 10 to 20 percent, a high percentage for stars their size. They are the beating hearts in the sky, with the light reflecting on the changes of the size.
Another noteworthy fact about the four stars is that although their masses are about 25 to 35 percent of the sun, they are up to nine times hotter than the sun’s 10,000 F, making them subdwarf stars.
“That’s something you would not particularly expect to see,” said Dr. Kupfer.
Dr. Kupfer and his Caltech colleagues actually stumbled upon the new pulsators. They had been looking for binary stars — a pair of stars in which one star revolves around the other or both stars share a center to revolve around. Upon further observation of the four stars, the team realize that they were pulsators and not binary pairs.
The four stars, however, form their own pulsating category: hot subdwarf pulsators that pulsate every five minutes. Dr. Kupfer explained that previous research has not foreseen the existence of such stars, until now.
“Using high—cadence observations from the Zwicky Transient Facility (a sky survey at the Palomar Observatory near San Diego) at low Galactic latitudes,” write Dr. Kupfer and over 20 co—authors, “we have discovered a new class of pulsating, hot compact stars.”
Among the co—authors are more UCSB members: graduate student Evan Bauer and professor Lars Bildsten who has made a name for himself as an astrophysicist. With all the talent in this team, Dr. Kupfer told the News—Press that the research is still ongoing, with more excitement down the road. He and his team also continue to be on the lookout for binary pairs.
Dr. Kupfer is a postdoctoral scholar at UCSB’s Kavli Institute for Theoretical Physics. All his degrees are in physics. He attained his undergraduate and master’s degrees in Germany, where he is from; he obtained his PhD in the Netherlands.
The six—page report detailing the findings the team has gathered so far is called “A New Class of Large—amplitude Radial—mode Hot Subdwarf Pulsators” and is published in The Astrophysical Journal Letters. The research efforts that led to the discovery are supported by the National Science Foundation and the Gordon and Betty Moore Foundation. The Zwicky Transient Facility is funded by the National Science Foundation, NASA and the Heising—Simons Foundation. Other contributors include Caltech, the University of Washington, the University of Maryland, the Humboldt University of Berlin, the Weizmann Institute of Science and Boston University.
