A recent study by astronomers in Chile, published in Monthly Notices of the Royal Astronomical Society Letters, suggest that RR Lyrae stars are not as lonely as we once thought, according to a press release.
Binary systems are important in astrophysics "as their properties can be inferred with unparalleled accuracy from detailed analysis of their orbital properties," according to the Royal Astronomical Society (RAS). The lack of RR Lyrae in binary systems has made pinpointing their key characteristics more difficult. Theory has been used to fill the gap in knowledge.
An international research team led by experts of the Millennium Institute of Astrophysics (MAS) and the Pontificia Universidad Católica de Chile's Institute of Astrophysics (IA-PUC) have found evidence that these stars may not reject companionship as readily as initially thought. The team identified "as many as 20 candidate RR Lyrae binaries -- an increase of up to 2,000% with respect to previous tallies," according to the RAS. "Twelve of those candidates have enough measurements to conclude with high confidence that they do indeed consist of two stars orbiting each other."
"In the solar neighborhood, about every second star is in a binary. The problem with RR Lyrae variables is that for a long time only one of them was known to be in a long-period binary system. The fact that among 100,000 known RR Lyrae stars only one of them had been seen to have such a companion was something really intriguing for astronomers," said IA-PUC doctorial student and lead author Gergely Hajdu, according to the press release.
"The RR Lyrae stars pulsate regularly, significantly increasing, and then decreasing, their sizes, temperatures, and brightness, in a matter of just a few hours," said Hajdu, according to the press release. "When a pulsating star is in a binary system, the changes in brightness perceived by us can be affected by where exactly the star is in the course of its orbit around the companion. Thus, the starlight takes longer to reach us when it is at the farthest point along its orbit, and vice-versa. This subtle effect is what we have detected in our candidates."
"Our measurements were based on data published by the Polish OGLE Project," continued Hajdu, according to the press release. "The OGLE team have obtained their data using the 1.3m Warsaw telescope, located in Las Campanas Observatory, northern Chile, repeatedly observing the same patches of the sky for many years. Our 20 candidates were found analyzing the roughly 2,000 best observed RR Lyrae stars towards the central parts of the Milky Way. That's about 5% of the known ones. It was only thanks to the high quality of the OGLE data and the long timespan of these observations that we could finally find signs of companions around so many of these stars."
