2018/10/31 by Sergey S. Tsygankov, Alicia Rouco Escorial, В. Ф. Сулейманов +8
Engineering · Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Compton scattering #Luminosity #Mechanics and Biomechanics Studies #Neutron star #Physics #Pulsar #Pulsars and Gravitational Waves Research #Scattering #X-ray pulsar #astro-ph.HE
paper · pdf · doi:10.1093/mnrasl/sly236
5 pages, 2 figures, accepted by MNRAS Letters
openalex publication_date 2018/12/15 · arxiv created 2018/12/20 · arxiv updated 2018/12/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract We report on the discovery of a dramatic change in the energy spectrum of the X-ray pulsar GX 304−1 appearing at low luminosity. Particularly, we found that the cut-off power-law spectrum typical for accreting pulsars, including GX 304−1 at higher luminosities of LX ∼ 1036–1037 erg s−1, transformed at lower luminosity of LX ∼ 1034 erg s−1 to a two-component spectrum peaking around 5 and 40 keV. We suggest that the observed transition corresponds to a change of the dominant mechanism responsible for the deceleration of the accretion flow. We argue that the accretion flow energy at low accretion rates is released in the atmosphere of the neutron star, and the low-energy component in the source spectrum corresponds to the thermal emission of the optically thick, heated atmospheric layers. The most plausible explanations for the high-energy component are either the cyclotron emission reprocessed by the magnetic Compton scattering or the thermal radiation of deep atmospheric layers partly Comptonized in the overheated upper layers. Alternative scenarios are also discussed.