Researchers study hard X-ray emission from low-mass X-ray binaries of neutron stars

Correlation between the photon index (Γ) of a rigid X-ray tail and its flux (in ∼30–200 keV, in units of 109 ergs cm−2 s−1). The red, blue, and green circles represent the results for HB, NB and FB, respectively. Dotted lines are drawn using the least squares method. Panels (a) and (b) show the results of hard X-ray tails detected in HID1 and HID2, respectively. Credit: Astrophysical Journal (2023). DOI: 10.3847/1538-4357/accf91 With observational data from the Hard X-Ray Modulation Telescope (HXMT), China’s first X-ray astronomical satellite, Dr. Ding Guoqiang of the Xinjiang Observatory of the Chinese Academy of Sciences and collaborators researchers, studied the hard X-ray tails of low-mass X-ray binary stellar neutrons (NS-LMXB). Their findings were published in the Astrophysical Journal on June 12. In recent decades, observations from astronomical X-ray satellites have shown that the tails of hard X-rays above about 30 keV in Z sources, classified as NS-LMXB, are rarely detected. . The effective area of ​​the high-energy detector of the HXMT is up to 5000 cm2, and its observation data is very favorable for studying the hard X-ray tail of the Z source. The researchers systematically analyzed and tuned the high-energy spectrum of Scorpius X-1 (Z source) at 30–200 keV, observed by HXMT, and found a power law component in high-energy spectrum of eight observations. The results show that the power law component of Sco X-1, known as the X-ray hard tail, becomes stiff and weakens along the evolutionary trajectory in the hardness intensity graph. The coupling of the broadband spectrum (2–200 keV) suggests that Sco X-1’s stiff X-ray tail may be the result of an inverse comptonization that scatters X-ray photons emitted by surface neutrons. surface of the star by thermal electrons in the region between the neutron star and the accretion disk, and energetic electrons free-falling towards the neutron star in the converging stream towards the neutron star.

source: G. Q. Ding et al, Insight-HXMT Detections of Hard X-Ray Tails in Scorpius X-1, The Astrophysical Journal (2023). DOI: 10.3847/1538-4357/accf91