Using a 2.1-meter telescope at Kitt Peak National Observatory (USA), astronomers discovered a double star consisting of a pair of white dwarfs that make one turn around a common center of mass in just 6.91 minutes.
The whole system, according to scientists, would fit inside Saturn, and it is expected that soon it will become one of the strongest sources of gravitational waves, which will be recorded by the future space observatory of the European Space Agency “Laser Interferometer Space Antenna” (LISA). It is a record holder with the shortest circulation period among all known eclipsing doubles.
In the final stages of their evolution, the sun-like stars expand, becoming a red giant, and then a planetary nebula, in the heart of which there is a white dwarf – an object comparable in mass to the Sun, but compressed to the size of the Earth.
This scenario is typical for stars whose masses do not exceed the solar one 10 times, and not only for single ones, but also, as in this case, for binary ones, which form binary systems of white dwarfs.
It is assumed that such duets in very tight orbits, potentially being sources of gravitational waves, are relatively common, but for astronomers they remain practically elusive, and to date only a few such systems have been discovered.
Record holder among double white dwarfs
Fortunately, the recently launched review, which is carried out using telescopes of the Palomar Observatory (USA) and the Kitt Peak National Observatory, is changing this situation.
Every night, a 1.2-meter telescope at the Palomar Observatory scans the sky for objects that move, flicker, or otherwise change brightness. Then, in order to identify short-period eclipsing binary systems, the most promising candidates are followed by a 2.1-meter telescope at the Kitt-Peak National Observatory with the KPED instrument installed, which is designed to measure the speed and degree of change in the brightness of the sources.
This strategy led to the discovery of a system of two white dwarfs with the shortest period, designated ZTF J1539 + 5027. The smaller component of the duet is slightly larger than the Earth and inferior to the Sun in mass by about 40%. His companion is larger, but at the same time 5 times lighter than our star.
“When a dim star passes in front of a brighter star, it blocks most of its light, which leads to the seven-minute blink interval that we see in the ZTF data,” explained Kevin Burge, lead author of the California Institute of Technology (USA).
Astronomers note that the ZTF J1539 + 5027 system is a rare find, as it is one of the few currently known sources of gravitational waves that can be detected by the LISA observatory, whose launch is scheduled for 2034.
Eclipsing double white dwarfs with the shortest circulation period known
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