Physics and astrophysics really are a continuum of sciences where the boundaries are often blurred, with astronomers working at particle accelerators and physicists looking for their own particle accelerators in the sky.

In a new paper appearing in Physical Review Letters with first author Hiroki Yoneda, researchers look at the gamma-ray binary LS 5039. In general, we know that gamma-ray binaries are made of a massive star and some sort of a compact companion, like a neutron star or black hole. Understanding exactly what the companion star might be is fairly complicated, but LS 5039 offered researchers two powerful hints. 

Observations of the system discovered a pulse every nine seconds that is only visible in X-ray light. This is consistent with the behavior of a slowly rotating pulsar that is having its pulses in all other wavelengths masked by the companion star. They also detected extremely powerful Tera electron Volt gamma-ray photons that are consistent with a magnetic field three times more powerful than the magnetic field of a normal neutron star. This combination of a slow rotation and strong magnetic field indicates that the compact object in this particular system is a magnetar.

This is the first time a magnetar has been found in a binary system. The thirty-some-odd, previously-detected magnetars have all been isolated stars. It is unclear how common this kind of an arrangement may be, but now astronomers at least know what to look for when looking for paired off magnetars.

More Information

Kavil Institute for the Physics and Mathematics of the Universe press release 

“Sign of Hard X-Ray Pulsation from the Gamma-Ray Binary System LS 5039,” Hiroki Yoneda (1,2,3), Kazuo Makishima (1,2), Teruaki Enoto (4), Dmitry Khangulyan (5), Takahiro Matsumoto (1), & Tadayuki Takahashi (1,2), 2020 Sep. 8, Physical Review Letters (preprint on arxiv.org)