Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources
Galactic diffuse X-ray emission (GDXE) can be spatially segmented into Galactic center X-ray emission (GCXE), Galactic ridge X-ray emission (GRXE), and Galactic bulge X-ray emission (GBXE). The X-ray spectra of GDXE are expressed by the assembly of compact X-ray sources, which are either white dwarf...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad0dff |
| _version_ | 1797344910177730560 |
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| author | Katsuji Koyama Masayoshi Nobukawa |
| author_facet | Katsuji Koyama Masayoshi Nobukawa |
| author_sort | Katsuji Koyama |
| collection | DOAJ |
| description | Galactic diffuse X-ray emission (GDXE) can be spatially segmented into Galactic center X-ray emission (GCXE), Galactic ridge X-ray emission (GRXE), and Galactic bulge X-ray emission (GBXE). The X-ray spectra of GDXE are expressed by the assembly of compact X-ray sources, which are either white dwarfs (WDs) or X-ray active stars consisting of binaries with late-type stars. WDs have either a strong magnetic field or a weak magnetic field. WDs and X-ray active stars are collectively called compact X-ray stars. However, spectral fittings by the assembly of all compact X-ray stars for GCXE, GRXE, and GBXE are rejected, leaving significant excess near the energies of the K α , He α , and Ly α lines. These excesses are found in the collisional ionization equilibrium (CIE) plasma. Thus, the spectra of GRXE and GBXE are improved by adding CIE supernova remnants (SNRs). However, the GCXE spectrum is still unacceptable, with significant data excess due to radiative recombination emission (recombining plasma (RP)). The GCXE fit is then significantly improved by adding aged RP-SNRs. Aged RP-SNRs are made by a past big flare of Sgr A* emitting either hard X-rays or low-energy cosmic rays. The big flares may excite Fe and Ni atoms in cold diffuse gas (cold matter (CM)) and emit fluorescent X-ray lines. The CIE-SNRs, RP-SNRs, and CM are called diffuse X-ray sources. This paper presents the spectral fits by the assembly of all the compact and diffuse X-ray sources together with high-quality spectra and a combined fit among all the GDXE of GCXE, GRXE, and GBXE. This provides the first scenario to quantitatively and comprehensively predict the origin of the GDXE spectra. |
| first_indexed | 2024-03-08T11:10:46Z |
| format | Article |
| id | doaj.art-c767925773b243ff90972cfc53f37fe9 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-08T11:10:46Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-c767925773b243ff90972cfc53f37fe92024-01-26T11:48:31ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01961220510.3847/1538-4357/ad0dffOrigin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray SourcesKatsuji Koyama0Masayoshi Nobukawa1https://orcid.org/0000-0003-1130-5363Department of Physics, Graduate School of Science, Kyoto University , Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, JapanFaculty of Education, Nara University of Education , Takabatake-cho, Nara 630-8528, Japan ; nobukawa@cc.nara-edu.ac.jpGalactic diffuse X-ray emission (GDXE) can be spatially segmented into Galactic center X-ray emission (GCXE), Galactic ridge X-ray emission (GRXE), and Galactic bulge X-ray emission (GBXE). The X-ray spectra of GDXE are expressed by the assembly of compact X-ray sources, which are either white dwarfs (WDs) or X-ray active stars consisting of binaries with late-type stars. WDs have either a strong magnetic field or a weak magnetic field. WDs and X-ray active stars are collectively called compact X-ray stars. However, spectral fittings by the assembly of all compact X-ray stars for GCXE, GRXE, and GBXE are rejected, leaving significant excess near the energies of the K α , He α , and Ly α lines. These excesses are found in the collisional ionization equilibrium (CIE) plasma. Thus, the spectra of GRXE and GBXE are improved by adding CIE supernova remnants (SNRs). However, the GCXE spectrum is still unacceptable, with significant data excess due to radiative recombination emission (recombining plasma (RP)). The GCXE fit is then significantly improved by adding aged RP-SNRs. Aged RP-SNRs are made by a past big flare of Sgr A* emitting either hard X-rays or low-energy cosmic rays. The big flares may excite Fe and Ni atoms in cold diffuse gas (cold matter (CM)) and emit fluorescent X-ray lines. The CIE-SNRs, RP-SNRs, and CM are called diffuse X-ray sources. This paper presents the spectral fits by the assembly of all the compact and diffuse X-ray sources together with high-quality spectra and a combined fit among all the GDXE of GCXE, GRXE, and GBXE. This provides the first scenario to quantitatively and comprehensively predict the origin of the GDXE spectra.https://doi.org/10.3847/1538-4357/ad0dffGalactic centerDiffuse x-ray backgroundInterstellar thermal emissionSupernova remnants |
| spellingShingle | Katsuji Koyama Masayoshi Nobukawa Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources The Astrophysical Journal Galactic center Diffuse x-ray background Interstellar thermal emission Supernova remnants |
| title | Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources |
| title_full | Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources |
| title_fullStr | Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources |
| title_full_unstemmed | Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources |
| title_short | Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources |
| title_sort | origin and composition of the galactic diffuse x ray emission spectra by unresolved x ray sources |
| topic | Galactic center Diffuse x-ray background Interstellar thermal emission Supernova remnants |
| url | https://doi.org/10.3847/1538-4357/ad0dff |
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