The hard X-ray spectrum of soft X-ray-selected AGN

Page, M. J.

doi:10.1046/j.1365-8711.1998.01629.x

Cited by 4 publications

(4 citation statements)

References 6 publications

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“…∼0.3 keV, Menou & McClintock 2001). Finally, they are inconsistent with observed spectra from AGN, which in the 0.5-10 keV energy range are described by a simple power law (Page 1998) whereas the spectra of RX J0042.6+4115 require a second component. It would be hard to understand this object if it were in our Galaxy or in a distant background galaxy, whereas it is easily comprehensible as a member of M 31.…”

Section: Discussioncontrasting

confidence: 62%

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Tracing a Z-track in the M 31 X-ray binary RX J0042.6+4115

Barnard

Kolb

Osborne

2003

A&A

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Abstract. Four XMM-Newton observations of the core of M 31, spaced at 6 month intervals, show that the brightest point X-ray source, RX J0042.6+4115, has a 0.4-10 keV luminosity of ∼5× 10 38 erg s −1 , and exhibits significant variability in intensity and X-ray spectrum over a time scale of ∼100 s including hard flares; such behaviour is only observed in Z-sources and transient black hole binaries in our Galaxy. The lightcurves, X-ray spectra and hardness-intensity data from the four XMM-Newton observations all strongly suggest that it is a Z-source, bringing the total number of known Z-sources to nine.

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Section: Discussioncontrasting

confidence: 62%

“…Numbers in parentheses indicate 90% confidence errors on the last digit. by a simple power law (Page 1998) whereas the spectra of RX J0042.6+4115 require a second component.…”

Section: Discussionmentioning

confidence: 99%

Tracing a Z-track in the M 31 X-ray binary RX J0042.6+4115

Barnard

Kolb

Osborne

2003

A&A

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“…In contrast, the above spectral index is more consistent with the XRB spectrum (Gendreau et al 1995). Page (1998) studied the stacked spectrum of 34 soft X-ray selected QSOs from the RIXOS ROSAT survey using ASCA. He finds a spectral index of G ¼ 1:8^0:1 consistent with that of QSOs in the 2-10 keV band.…”

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 99%

ASCA observations of deep ROSAT fields - V. The X-ray spectrum of hard X-ray selected QSOs

Pappa¹,

Stewart²,

Georgantopoulos³

et al. 2001

Monthly Notices of the Royal Astronomical Society

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We present an analysis of the ROSAT and ASCA spectra of 21 broad‐line active galactic nuclei (AGN) quasi‐stellar objects (QSOs) with detected in the band with the ASCA GIS. The summed spectrum in the ASCA band is well described by a power law with , flatter than the average spectral index of bright QSOs and consistent with the spectrum of the X‐ray background in this band. The flat spectrum in the ASCA band could be explained by only a moderate absorption (∼ assuming the typical AGN spectrum, i.e. a power law with . This could in principle suggest that some of the highly obscured AGN, required by most X‐ray background synthesis models, may be associated with normal blue QSOs rather than narrow‐line AGN. However, the combined ASCA–ROSAT spectrum is well fit by a power‐law of with a spectral upturn at soft energies. It has been pointed out that such an upturn may be an artefact of uncertainties in the calibration of the ROSAT or ASCA detectors. Nevertheless, if real, it could imply that the above absorption model suggested by the ASCA data alone is ruled out. Then a large fraction of QSOs could have ‘concave’ spectra i.e. they gradually steepen towards softer energies. This result is in agreement with the BeppoSAX hardness ratio analysis of ∼100 hard X‐ray selected sources.

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“…A combined ASCA 2-10 keV spectrum of 13 unobscured ROSAT International X-Ray Optical Survey (RIXOS) AGNs (Page, 1998) has a photon index of 1:8 AE 0:1. Perola et al (2002) studied nine bright Seyfert 1 galaxies in the 0.1-200 keV band using BeppoSAX LECS+MECS+PDS data.…”

Section: Unobscured Agnsmentioning

confidence: 99%

Nonthermal Hard X‐Ray Emission in Galaxy Clusters Observed with theBeppoSAXPDS

Nevalainen¹,

Oosterbroek²,

Bonamente³

et al. 2004

ApJ

102

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We study the X-ray emission in a sample of galaxy clusters using the BeppoSAX PDS instrument in the 20-80 keV energy band. We estimate the nonthermal hard X-ray (HXR) cluster emission by modeling the thermal contribution from the cluster gas and the nonthermal contamination from the unobscured active galactic nuclei (AGNs) in the clusters. We also evaluate the systematic uncertainties due to the background fluctuations. Assuming negligible contamination from the obscured AGNs, the resulting nonthermal component is detected at a 2 level in $50% of the nonsignificantly AGN-contaminated clusters: A2142, A2199, A2256, A3376, Coma, Ophiuchus, and Virgo. The data are consistent with a scenario whereby relaxed clusters have no hard X-ray component of nonthermal origin, whereas merger clusters do, with a 20-80 keV luminosity of $10 43 -10 44 h À2 50 ergs s À1 . The co-added spectrum of the above clusters indicates a power-law spectrum for the HXR emission with a photon index of 2.8 þ0:3 À0:4 in the 12-115 keV band, and we find indication that it has extended distribution. These indications argue against significant contamination from obscured AGNs, which have harder spectra and a centrally concentrated distribution. These results are supportive of the assumption of the merger shock acceleration of electrons in clusters, which has been proposed as a possible origin of the nonthermal hard X-ray emission models. Assuming that the cosmic microwave background photons experience inverse Compton scattering from the merger-accelerated relativistic electrons and thus produce the observed HXR, the measured hard X-ray slope corresponds to a differential momentum spectra of the relativistic electrons with a slope of ¼ 3:8-5.0. In presence of cluster magnetic fields this relativistic electron population produces synchrotron emission with a spectral index of 1.4-2.1, consistent with radio halo observations of merger clusters. Thus both hard X-ray and radio observations of merger clusters are consistent with the inverse Compton model. The observed slope of the HXR emission is also consistent with that predicted by the nonthermal bremsstrahlung, which thus cannot be ruled out by the fit to the current data, even though this model requires an extreme, untenable cluster energetics. Assuming a centrally concentrated distribution of HXR emission, the data require a harder slope for the HXR spectrum, which is consistent with secondary electron models, but this model yields a worse fit to the PDS data and thus seems to be disfavored over the primary electron inverse Compton model.

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The hard X-ray spectrum of soft X-ray-selected AGN

Cited by 4 publications

References 6 publications

Tracing a Z-track in the M 31 X-ray binary RX J0042.6+4115

Tracing a Z-track in the M 31 X-ray binary RX J0042.6+4115

ASCA observations of deep ROSAT fields - V. The X-ray spectrum of hard X-ray selected QSOs

Nonthermal Hard X‐Ray Emission in Galaxy Clusters Observed with theBeppoSAXPDS

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