Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL
The question of the origin of the hard X-ray/soft gamma-ray emission in Centaurus A (Cen A) persists despite decades of observations. Results from X-ray instruments suggest a jet origin since the implied electron temperature ( kT _e ) would cause runaway pair production in the corona. In contrast, i...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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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/acfc23 |
| _version_ | 1797648002790195200 |
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| author | James Rodi E. Jourdain M. Molina J. P. Roques |
| author_facet | James Rodi E. Jourdain M. Molina J. P. Roques |
| author_sort | James Rodi |
| collection | DOAJ |
| description | The question of the origin of the hard X-ray/soft gamma-ray emission in Centaurus A (Cen A) persists despite decades of observations. Results from X-ray instruments suggest a jet origin since the implied electron temperature ( kT _e ) would cause runaway pair production in the corona. In contrast, instruments sensitive to soft gamma rays report electron temperatures indicating that a coronal origin may be possible. In this context, we analyzed archival INTEGRAL/IBIS-ISGRI and SPI data and observations from a 2022 Cen A monitoring program. Our analysis did not find any spectral variability. Thus we combined all observations for long-term average spectra, which were fit with a NuSTAR observation to study the 3.5 keV–2.2 MeV spectrum. Spectral fits using a CompTT model found kT _e ∼ 550 keV, near runaway pair production. The spectrum was also well described by a log-parabola to model synchrotron self-Compton emission from the jet. Additionally, a spectral fit with the 12 yr catalog Fermi/LAT spectrum using a log-parabola can explain the data up to ∼3 GeV. Above ∼3 GeV, a power-law excess is present, which has been previously reported in LAT/H.E.S.S. analysis. However, including a coronal spectral component can also describe the data well. In this scenario, the hard X-rays/soft gamma rays are due the corona and the MeV to GeV emission is due to the jet. |
| first_indexed | 2024-03-11T15:25:49Z |
| format | Article |
| id | doaj.art-0e8cba4a905f403296762a97bec2742c |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-11T15:25:49Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-0e8cba4a905f403296762a97bec2742c2023-10-27T14:06:07ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0195715110.3847/1538-4357/acfc23Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRALJames Rodi0https://orcid.org/0000-0003-2126-5908E. Jourdain1https://orcid.org/0000-0001-9932-3288M. Molina2https://orcid.org/0000-0003-0681-9984J. P. Roques3https://orcid.org/0000-0002-6529-4121INAF—Istituto di Astrofisica e Planetologia Spaziali , via Fosso del Cavaliere 100; I-00133 Roma, ItalyUniversité de Toulouse , UPS-OMP, IRAP, Toulouse, France; CNRS , IRAP, 9 Av. Colonel Roche, BP 44346, F-31028 Toulouse cedex 4, FranceIstituto di Astrofisica Spaziale e Fisica Cosmica di Milano , Milan, ItalyUniversité de Toulouse , UPS-OMP, IRAP, Toulouse, France; CNRS , IRAP, 9 Av. Colonel Roche, BP 44346, F-31028 Toulouse cedex 4, FranceThe question of the origin of the hard X-ray/soft gamma-ray emission in Centaurus A (Cen A) persists despite decades of observations. Results from X-ray instruments suggest a jet origin since the implied electron temperature ( kT _e ) would cause runaway pair production in the corona. In contrast, instruments sensitive to soft gamma rays report electron temperatures indicating that a coronal origin may be possible. In this context, we analyzed archival INTEGRAL/IBIS-ISGRI and SPI data and observations from a 2022 Cen A monitoring program. Our analysis did not find any spectral variability. Thus we combined all observations for long-term average spectra, which were fit with a NuSTAR observation to study the 3.5 keV–2.2 MeV spectrum. Spectral fits using a CompTT model found kT _e ∼ 550 keV, near runaway pair production. The spectrum was also well described by a log-parabola to model synchrotron self-Compton emission from the jet. Additionally, a spectral fit with the 12 yr catalog Fermi/LAT spectrum using a log-parabola can explain the data up to ∼3 GeV. Above ∼3 GeV, a power-law excess is present, which has been previously reported in LAT/H.E.S.S. analysis. However, including a coronal spectral component can also describe the data well. In this scenario, the hard X-rays/soft gamma rays are due the corona and the MeV to GeV emission is due to the jet.https://doi.org/10.3847/1538-4357/acfc23Active galactic nucleiGamma-rays |
| spellingShingle | James Rodi E. Jourdain M. Molina J. P. Roques Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL The Astrophysical Journal Active galactic nuclei Gamma-rays |
| title | Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL |
| title_full | Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL |
| title_fullStr | Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL |
| title_full_unstemmed | Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL |
| title_short | Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL |
| title_sort | centaurus a exploring the nature of the hard x ray soft gamma ray emission with integral |
| topic | Active galactic nuclei Gamma-rays |
| url | https://doi.org/10.3847/1538-4357/acfc23 |
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