Study inspects unusual behavior of an X-ray binary
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Astronomers from the National Central University in Taiwan have investigated an unusual superorbital period variation of an X-ray binary known as 4U 1820-30. Results of the study, published September 13 on the preprint server arXiv, could help us better understand the nature of this system.
X-ray binaries are composed of a normal star or a white dwarf transferring mass onto a compact neutron star or a black hole. Based on the mass of the companion star, astronomers divide them into low-mass X-ray binaries (LMXBs) and high-mass X-ray binaries (HMXBs).
4U 1820-30 is an ultra-compact LMXB located near the center of globular cluster NGC 6624. It consists of a neutron star and a mass-losing companion—a helium white dwarf with a mass of 0.06–0.08 solar masses. The system has an orbital period of approximately 685 seconds.
