News, July 2023
Cataclysmic variables are a key population of gravitational wave sources for LISA
Gravitational Waves from Cataclysmic Variable Stars Could Impact Future Space Mission
Figure 1 of the paper showing the orbital period distribution of CVs.
Gravitational waves are ripples in the fabric of spacetime caused by the motion of massive objects. They were first detected in 2015, confirming a prediction made by Albert Einstein a century earlier. Since then, scientists have been studying these waves to learn more about the universe. Now, a new study by Dr. Simone Scaringi from the Centre for Extragalactic Astronomy suggests that gravitational wave signals from a certain type of binary stars called cataclysmic variables (CVs) could have a significant impact on future space missions, including the upcoming Laser Interferometer Space Antenna (LISA) mission. CVs are binary star systems consisting of a white dwarf and a companion star. As matter from the companion star falls onto the white dwarf, it releases bursts of energy, producing bright flashes of light. These flashes can be observed in the electromagnetic spectrum, but Dr. Scaringi's study focuses on the gravitational waves emitted by these systems. The study estimates that at least three known CV systems will produce gravitational wave signals strong enough to be individually resolved within the first four years of LISA's operation. LISA is a space mission set to launch in 2034, with the goal of detecting gravitational waves in a lower frequency range than previous missions. In addition to these individual signals, CVs will also contribute significantly to the overall gravitational wave background detected by LISA. This means that the presence of gravitational waves from CVs could limit LISA's sensitivity to detecting signals from other sources in the same frequency range. The study also predicts a spike in the unresolved gravitational wave background at a frequency corresponding to the minimum orbital period of CVs. This excess noise could potentially impact the detection of other systems near this characteristic frequency. However, the amplitude and location of this excess noise spike can be used to measure the density of CVs in our Galaxy and their period bounce location, providing valuable information about these stellar systems. Overall, this study highlights the importance of considering the population of CVs in mission planning for LISA. By including these systems as both individual sources and generators of background noise, scientists can better understand their gravitational wave emission and characterize the CV population.