Hard X-Ray Emission in Centaurus A

Rani, Bindu; Mundo, Sergio A; Mushotzky, R. F.; Lien, A. Y.; Gurwell, M. A.; Kim, Jae-Young

doi:10.3847/1538-4357/ac6fd4

Cited by 3 publications

(5 citation statements)

References 44 publications

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“…2581-2590) showed relatively soft spectra with photon indices of roughly 2.1 (SPI) and 2.0 (ISGRI), though the errors are large. During this period, the source was at its lowest flux level observed by INTEGRAL, which does not confirm the behavior reported by Rani et al (2022).…”

Section: Spectral Variabilitycontrasting

confidence: 88%

“…In their work on Cen A, Rani et al (2022) also showed that the 230 GHz flux correlates with the hard X-ray flux with no time lag. (Israel et al 2008 found similar results.)…”

Section: Comparison With Previous Workmentioning

confidence: 96%

“…Numerous authors have reported that Cen A's spectral shape does not change with flux (Jourdain et al 1993;Rothschild et al 2006Rothschild et al , 2011Beckmann et al 2011;Burke et al 2014). However, recent results from Swift/BAT reported spectral softening when the flux increased after 2013 (Rani et al 2022). Therefore, we searched for spectral variability in the INT-EGRAL data by fitting the SPI 25-70 keV and ISGRI 34-68 keV spectra independently to a power-law model.…”

Section: Spectral Variabilitymentioning

confidence: 99%

“…Note that Rani et al (2022) proposed a scenario where the peak energy of the jet overlaps with the corona component at ∼500 keV, thus hiding the corona component. However, we were not able to disentangle the presence of the two components with our data.…”

Section: Jet and Corona Scenariomentioning

confidence: 99%

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Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL

Rodi,

Jourdain,

Molina

et al. 2023

ApJ

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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.

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Section: Spectral Variabilitycontrasting

confidence: 88%

“…In their work on Cen A, Rani et al (2022) also showed that the 230 GHz flux correlates with the hard X-ray flux with no time lag. (Israel et al 2008 found similar results.)…”

Section: Comparison With Previous Workmentioning

confidence: 96%

Section: Spectral Variabilitymentioning

confidence: 99%

Section: Jet and Corona Scenariomentioning

confidence: 99%

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Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL

Rodi,

Jourdain,

Molina

et al. 2023

ApJ

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“…Many authors have reported that Cen A's spectrum does not change with flux [2,4,13,21,22]. In another side, Swift/BAT recently reported spectral softening after 2013 [17]. We searched for spectral variability in the INTEGRAL data by fitting the SPI 25 − 70 keV and ISGRI 34 − 68 keV spectra independently to a power-law model.…”

Section: Spectral Variabilitymentioning

confidence: 99%

Investigating the Nature of the Hard X-ray/Soft Gamma-ray Emission from Centaurus A

Rodi¹,

Jourdain²,

Molina³

et al. 2023

Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)

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The question of the origin of the hard X-ray/soft gamma-ray emission in Centaurus A (Cen A) persists despite decades of observations. Low energy results from X-ray instruments suggest a jet origin. In contrast, high energy X-ray/soft gamma-ray instruments find electron temperatures indicating a corona origin is possible. The spectral energy distribution (SED) peaks in this energy range so understanding the origin of this emission is critical to modelling it. We analyzed INTEGRAL/IBIS-ISGRI and SPI data and observations over nearly 20 years. We did not find any spectral variability so we combined all observations for long-term average spectra. A NuSTAR observation was also added to study the 3.5 keV − 2.2 MeV spectrum. Spectral fits using a CompTT model found 𝑘𝑇 𝑒 ∼ 520 keV, near pair-production runaway. The spectrum was also well described by a log-parabola to model synchrotron self-Compton emission (SSC) from the jet. Using a log-parabola can explain the data up to ∼ 3 GeV when including the 12-year catalog Fermi/LAT spectrum. Including a corona spectral component to model the hard X-rays/soft gamma-rays and a log-parabola for MeV to GeV emission can also well-describe the data, but the spectral parameters are poorly constrained. Thus, the hard X-ray/soft gamma-ray emission is likely due to SSC jet emission.

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Long-term hard X-ray variability properties of Swift-BAT blazars

Mundo,

Mushotzky

2023

Monthly Notices of the Royal Astronomical Society

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We present results from the first dedicated study in the time domain of the hard X-ray variability behavior of blazars on long timescales based on ∼13 years of continuous hard X-ray data in the 14-195 keV band. We use monthly-binned data from the recent 157-month Swift-BAT catalog to characterize the hard X-ray variability of 127 blazars and search for potential differences between the variability of BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs). A significant portion of the blazars in the sample (∼37 %) do not show statistically significant hard X-ray variability on monthly timescales, which is deeply at odds with previous studies that show that blazars are highly variable in the X-rays and other energy bands on a wide range of timescales. We also find that, on average, the FSRQs and BL Lacs for which we do detect variability exhibit similar flux variability; this suggests that the variability in these FSRQs is not necessarily driven by variations in the source function of scattered external radiation arriving from extended regions, and that it is instead possibly driven by processes that lead to variations in particle injection. In addition, only five blazars in our sample show significant spectral variability in the long-term light curves. For 3 blazars, we find that a power law that changes slope on monthly timescales is sufficient to characterize the variable hard X-ray spectrum, suggesting that, at least for some bright blazars, the long-term spectra in the hard X-rays may be described in a relatively simple fashion.

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Hard X-Ray Emission in Centaurus A

Cited by 3 publications

References 44 publications

Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL

Centaurus A: Exploring the Nature of the Hard X-Ray/Soft Gamma-Ray Emission with INTEGRAL

Investigating the Nature of the Hard X-ray/Soft Gamma-ray Emission from Centaurus A

Long-term hard X-ray variability properties of Swift-BAT blazars

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