A1 Refereed original research article in a scientific journal
Changes in the Nature of the Spectral Continuum and Stability of the Cyclotron Line in the X-ray Pulsar GRO J2058+42
Authors: Gorban AS, Molkov SV, Tsygankov SS, Mushtukov AA, Lutovinov AA
Publisher: PLEIADES PUBLISHING INC
Publication year: 2022
Journal: Astronomy Letters / Pis'ma v Astronomicheskii Zhurnal
Journal name in source: ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS
Journal acronym: ASTRON LETT+
Volume: 48
Issue: 4
First page : 256
Last page: 266
Number of pages: 11
ISSN: 1063-7737
eISSN: 1562-6873
DOI: https://doi.org/10.1134/S1063773722040028
Web address : https://link.springer.com/article/10.1134/S1063773722040028
Abstract
We present the results of our study of the transient X-ray pulsar GRO J2058+42 in a wide energy range in a state with a luminosity L-x similar or equal to 2.5 x 10(36) erg s(-1). We have found that the pulse profile of the source, along with the pulse fraction, changed significantly in comparison with the previous NuSTAR observations performed when the pulsar was brighter approximately by a factor of 10. The position of the cyclotron line at similar to 10 keV in a narrow phase interval is consistent with the observations in the high state. Spectral analysis has shown that at high luminosities L-x similar or equal to (2.7 - 3.2) x 10(37) erg s(-1) the spectrum has a shape typical of accreting pulsars, whereas a two-component model should be used to describe the spectrum when the luminosity drops approximately by an order of magnitude, to 2.5 x 10(36) erg s(-1). This behavior fits into the model in which the low-energy part of the spectrum is formed in a hot spot, while the high-energy one is formed as a result of resonant Compton scattering by the infalling matter in the accretion channel above the neutron star surface.
We present the results of our study of the transient X-ray pulsar GRO J2058+42 in a wide energy range in a state with a luminosity L-x similar or equal to 2.5 x 10(36) erg s(-1). We have found that the pulse profile of the source, along with the pulse fraction, changed significantly in comparison with the previous NuSTAR observations performed when the pulsar was brighter approximately by a factor of 10. The position of the cyclotron line at similar to 10 keV in a narrow phase interval is consistent with the observations in the high state. Spectral analysis has shown that at high luminosities L-x similar or equal to (2.7 - 3.2) x 10(37) erg s(-1) the spectrum has a shape typical of accreting pulsars, whereas a two-component model should be used to describe the spectrum when the luminosity drops approximately by an order of magnitude, to 2.5 x 10(36) erg s(-1). This behavior fits into the model in which the low-energy part of the spectrum is formed in a hot spot, while the high-energy one is formed as a result of resonant Compton scattering by the infalling matter in the accretion channel above the neutron star surface.
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