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BeppoSAX and RXTE Spectral Study of the Low-mass X-Ray Binary 4U 1705-44: Spectral Hardening during the Banana Branchстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 6 февраля 2017 г.
- Авторы: Seifina E., Titarchuk L., Shrader C., Shaposhnikov, N
- Журнал: Astrophysical Journal
- Том: 808
- Номер: 2
- Год издания: 2015
- Издательство: University of Chicago Press
- Местоположение издательства: United States
- Первая страница: 1
- Последняя страница: 16
- DOI: 10.1088/0004-637X/808/2/142
- Аннотация: We analyze the X-ray spectra of the atoll 4U 1705-44 when the source undergoes the island-banana state transition. We use the RXTE and BeppoSAX observations for this analysis. We demonstrate that the broadband energy spectral distributions for all evolutinary states can be fitted by a model consisting of two Comptonized components. One arises from the seed photons coming from a neutron star (NS) atmosphere at a temperature {{kT}}{{s}1}≲ 1.5 keV (herein Comptb1), and a second results from the seed photons of {T}{{s}2} ˜ 1.1-1.3 keV coming from the disk (herein Comptb2). We found that we needed to add a low-temperature blackbody and an iron-line (Gaussian) component to the model in order to obtain high-quality fits. The data analysis using this model indicates that the power-law photon index {{{Γ }}}1 of our model is always about 2, independently of the spectral state. Another parameter, {{{Γ }}}2, demonstrates a two-phase behavior depending on the spectral state. {{{Γ }}}2 is quasi-constant at {{{Γ }}}2˜ 2 when the electron temperature {{kT}}{{e}}(2)\lt 80 keV, and {{{Γ }}}2 is less than 2, in the range of 1.3\lt {{{Γ }}}2\lt 2, when {{kT}}{{e}}(2)\gt 80 keV. This phase is similar to that previously found in the Z-source Sco X-1. We interpret the decreasing index phase using a model in which a super-Eddington radiation pressure from the NS causes an expansion of the Compton cloud similar to that found previously in Sco X-1 during the Flaring branch.
- Добавил в систему: Титарчук Лев Григорьевич