Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray Variability
Gamma-ray binary systems, a subclass of high-mass X-ray binaries, show nonthermal emissions from radio to TeV. While efficient electron acceleration is considered to take place in them, the nature of the acceleration mechanism and the physical environments in these systems have been a long-standing...
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| Format: | Article |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acc175 |
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| author | Hiroki Yoneda Valenti Bosch-Ramon Teruaki Enoto Dmitry Khangulyan Paul S. Ray Tod Strohmayer Toru Tamagawa Zorawar Wadiasingh |
| author_facet | Hiroki Yoneda Valenti Bosch-Ramon Teruaki Enoto Dmitry Khangulyan Paul S. Ray Tod Strohmayer Toru Tamagawa Zorawar Wadiasingh |
| author_sort | Hiroki Yoneda |
| collection | DOAJ |
| description | Gamma-ray binary systems, a subclass of high-mass X-ray binaries, show nonthermal emissions from radio to TeV. While efficient electron acceleration is considered to take place in them, the nature of the acceleration mechanism and the physical environments in these systems have been a long-standing question. In this work, we report on long-term recurrent patterns in the short-term variability of the soft X-ray emission of LS 5039, one of the brightest gamma-ray binary systems. The Neutron star Interior Composition Explorer (NICER) observed LS 5039 four times from 2018 to 2021. By comparing them with the previous Suzaku and NuSTAR long-exposure observations, we studied the long-term evolution of the orbital light curve in the soft X-ray band. Although the observations by NICER and Suzaku are separated by ∼14 yr, i.e., more than 10 ^3 orbits, the orbital light curves show remarkable consistency after calculating their running averages with a window width ≳70 ks. Furthermore, all of the light curves show short-term variability with a timescale of ∼10 ks. Since the column density did not vary when the flux changed abruptly, such a short-term variability seems to be an intrinsic feature of the X-ray emission. We propose that the short-term variability is caused by clumps (or inhomogeneities) of the companion star wind impacting the X-ray production site. The observed timescale matches well with the lifetime of the clumps interacting with the pulsar wind and the dynamical timescale of the relativistic intrabinary shock in the pulsar wind scenario. |
| first_indexed | 2024-03-12T03:27:22Z |
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| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T03:27:22Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-d1e3a5eb3e664ce48fea015f8d13972c2023-09-03T13:33:45ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194827710.3847/1538-4357/acc175Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray VariabilityHiroki Yoneda0https://orcid.org/0000-0002-5345-5485Valenti Bosch-Ramon1https://orcid.org/0000-0002-6043-5079Teruaki Enoto2https://orcid.org/0000-0003-1244-3100Dmitry Khangulyan3https://orcid.org/0000-0002-7576-7869Paul S. Ray4https://orcid.org/0000-0002-5297-5278Tod Strohmayer5https://orcid.org/0000-0001-7681-5845Toru Tamagawa6https://orcid.org/0000-0002-8801-6263Zorawar Wadiasingh7https://orcid.org/0000-0002-9249-0515RIKEN Nishina Center , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan ; hiroki.yoneda@riken.jp; Julius-Maximilians-Universität Würzburg , Fakultät für Physik und Astronomie, Institut für Theoretische Physik und Astrophysik, Lehrstuhl für Astronomie, Emil-Fischer-Str. 31, D-97074 Würzburg, GermanyDepartament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos (ICC) , Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, E-08028 Barcelona, SpainExtreme natural phenomena RIKEN Hakubi Research Team, Cluster for Pioneering Research , RIKEN, Hirosawa 2-1, Wako, Saitama, 351-0198, JapanGraduate School of Artificial Intelligence and Science, Rikkyo University , Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, JapanU.S. Naval Research Laboratory , Washington, DC 20375, USAAstrophysics Science Division and Joint Space-Science Institute, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USARIKEN Nishina Center , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan ; hiroki.yoneda@riken.jpAstrophysics Science Division , NASA/GSFC, Greenbelt, MD 20771, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USAGamma-ray binary systems, a subclass of high-mass X-ray binaries, show nonthermal emissions from radio to TeV. While efficient electron acceleration is considered to take place in them, the nature of the acceleration mechanism and the physical environments in these systems have been a long-standing question. In this work, we report on long-term recurrent patterns in the short-term variability of the soft X-ray emission of LS 5039, one of the brightest gamma-ray binary systems. The Neutron star Interior Composition Explorer (NICER) observed LS 5039 four times from 2018 to 2021. By comparing them with the previous Suzaku and NuSTAR long-exposure observations, we studied the long-term evolution of the orbital light curve in the soft X-ray band. Although the observations by NICER and Suzaku are separated by ∼14 yr, i.e., more than 10 ^3 orbits, the orbital light curves show remarkable consistency after calculating their running averages with a window width ≳70 ks. Furthermore, all of the light curves show short-term variability with a timescale of ∼10 ks. Since the column density did not vary when the flux changed abruptly, such a short-term variability seems to be an intrinsic feature of the X-ray emission. We propose that the short-term variability is caused by clumps (or inhomogeneities) of the companion star wind impacting the X-ray production site. The observed timescale matches well with the lifetime of the clumps interacting with the pulsar wind and the dynamical timescale of the relativistic intrabinary shock in the pulsar wind scenario.https://doi.org/10.3847/1538-4357/acc175Compact binary starsX-ray binary starsGamma-ray sourcesX-ray sourcesHigh mass x-ray binary stars |
| spellingShingle | Hiroki Yoneda Valenti Bosch-Ramon Teruaki Enoto Dmitry Khangulyan Paul S. Ray Tod Strohmayer Toru Tamagawa Zorawar Wadiasingh Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray Variability The Astrophysical Journal Compact binary stars X-ray binary stars Gamma-ray sources X-ray sources High mass x-ray binary stars |
| title | Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray Variability |
| title_full | Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray Variability |
| title_fullStr | Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray Variability |
| title_full_unstemmed | Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray Variability |
| title_short | Unveiling Properties of the Nonthermal X-Ray Production in the Gamma-Ray Binary LS 5039 Using the Long-term Pattern of Its Fast X-Ray Variability |
| title_sort | unveiling properties of the nonthermal x ray production in the gamma ray binary ls 5039 using the long term pattern of its fast x ray variability |
| topic | Compact binary stars X-ray binary stars Gamma-ray sources X-ray sources High mass x-ray binary stars |
| url | https://doi.org/10.3847/1538-4357/acc175 |
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