Equivalent width, shape and proper motion of the iron fluorescent line emission from molecular clouds as an indicator of the illuminating source X-ray flux history

Sunyaev, R.; Churazov, E.

doi:10.1046/j.1365-8711.1998.01684.x

Cited by 125 publications

(176 citation statements)

References 22 publications

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“…A mosaic with a higher S/N of the Galactic Center region may answer this point (Decourchelle et al 2003, in preparation). According to the formula of Sunyaev & Churazov (1998) and assuming a minimum projected distance, we obtained a line flux of about 10 −5 erg s −1 , i.e. approximatively 6 times lower than the very bright line emission observed from the giant molecular cloud Sgr B2 (5.6 × 10 −5 erg s −1 , Murakami et al 2001).…”

Section: Summary and Discussionmentioning

confidence: 68%

$\vec{XMM}$-$\vec{Newton}$ study of the persistent X-ray source 1E 1743.1–2843 located in the Galactic Center direction

Porquet

Rodríguez

Corbel

et al. 2003

A&A

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Abstract. We report the results of an XMM-Newton observation of the persistent X-ray source 1E 1743.1-2843, located in the Galactic Center (GC) direction. We determine the position of the source at α J2000 = 17 h 46 m 21.0 s , δ J2000 = −28 • 43 44 (with an uncertainty of 1.5 ), which is the most accurate to date, and will enable cross-identifications at other wavelengths. The source was bright during this observation (L 2−10 keV ∼ 2.7 × 10 36 d 2 10 kpc erg s −1 for a power-law continuum), with no significant variability. We propose that 1E 1743.1-2843 may be explained in terms of a black hole candidate in a low/hard state. There is an indication that the source exhibits different states from a comparison of our results with previous observations (e.g., ART-P, BeppoSAX). However, the present spectral analysis does not rule out the hypothesis of a neutron star low-mass X-ray binary as suggested previously. If 1E 1743.1-2843 is actually located in the GC region, we might expect to observe significant 6.4 keV fluorescent iron line emission from nearby molecular clouds (e.g., GCM+0.25+0.01).

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Section: Summary and Discussionmentioning

confidence: 68%

$\vec{XMM}$-$\vec{Newton}$ study of the persistent X-ray source 1E 1743.1–2843 located in the Galactic Center direction

Porquet

Rodríguez

Corbel

et al. 2003

A&A

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“…Being illuminated by powerful hard X-ray radiation from am outburst of the supermassive black hole at the Galactic Centre the neutral matter of molecular clouds can reflect and reprocess the radiation into the observed hard continuum and fluorescent 6.4 keV line emission (Sunyaev et al 1993, Sunyaev andChurazov 1998). Indeed, Revnivtsev et al (2004) associated the hard X-ray source IGR J17475-2822 discovered with the International Gamma-Ray Astrophysics Laboratory, INTEGRAL with the giant molecular cloud Sgr B2 in the Galactic Center vicinity.…”

Section: Galactic Center Clustersmentioning

confidence: 99%

Nonthermal particles and photons in starburst regions and superbubbles

Bykov

2014

Astron Astrophys Rev

118

102

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Starforming factories in galaxies produce compact clusters and loose associations of young massive stars. Fast radiation-driven winds and supernovae input their huge kinetic power into the interstellar medium in the form of highly supersonic and superalfvenic outflows. Apart from gas heating, collisionless relaxation of fast plasma outflows results in fluctuating magnetic fields and energetic particles. The energetic particles comprise a long-lived component which may contain a sizeable fraction of the kinetic energy released by the winds and supernova ejecta and thus modify the magnetohydrodynamic flows in the systems. We present a concise review of observational data and models of nonthermal emission from starburst galaxies, superbubbles, and compact clusters of massive stars. Efficient mechanisms of particle acceleration and amplification of fluctuating magnetic fields with a wide dynamical range in starburst regions are discussed. Sources of cosmic rays, neutrinos and multi-wavelength nonthermal emission associated with starburst regions including potential galactic "PeVatrons" are reviewed in the global galactic ecology context.

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“…4 and 5. & Churazov (1998) have shown that in the XRN model, the 6.4-keV line emission has to be accompanied by strong absorption above 7.1 keV, the minimum energy that a photon must have in order to be able to produce a K-shell vacancy in neutral Fe via the photoelectric effect. Moreover, because the primary source of ionisation is not seen directly by the observer, the EW of the line is expected to be very high, i.e.…”

Section: Sub-regions F1-f2-f3mentioning

confidence: 99%

“…Following the same approach as discussed by Sunyaev & Churazov (1998), Eq. (1) can be used to derive an expression for the separation, d, of the MC from the ionising source as:…”

Section: Placing Constraints On the Lightcurve Of Sgr A*mentioning

confidence: 99%

The X-ray lightcurve of Sagittarius A* over the past 150 years inferred from Fe-Kαline reverberation in Galactic centre molecular clouds

Capelli

Warwick

Porquet

et al. 2012

A&A

108

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Context. The spatial distribution and variability of Fe-Kα emission from molecular clouds in the Galactic centre region may provide an important key to the understanding of the recent history of Sgr A*. A very plausible interpretation is that this variability represents an echo in the reflected radiation from the clouds of a past episode of high activity in Sgr A*. Aims. We examine the temporal and spectral properties of nine Fe-Kα bright molecular clouds (three of which newly studied) within about 30 pc of Sgr A*, in order to understand and constrain the primary energising source of the Fe fluorescence. Methods. We collected all the archival XMM-Newton observations targeted at Sgr A*. The variability of the Fe-Kα line at 6.4-keV in specific cloud regions was investigated by spectrally fitting the data derived from the EPIC MOS cameras, after subtracting a modelled background. We have also studied the reflection imprints in time-averaged pn-spectra of each cloud. This involved measuring the equivalent width (EW) of the 6.4 keV line with respect to the underlying scattered continuum and the optical depth of the Fe-K absorption edge at 7.1 keV, superimposed on this same continuum. Finally we stacked the MOS spectra from two extended regions in order to quantify the east-west asymmetry apparent in the low-surface brightness diffuse Fe-Kα line emission. Results. Significant Fe-Kα variability was detected, with a spatial and temporal pattern consistent with that reported in previous studies. The main breakthrough that sets our paper apart from earlier contributions on this topic is the direct measurement of the column density and the Fe abundance of the MCs in our sample. All the spectra were characterised by a high EW of the Fe-Kα line and the presence of absorption at the Fe-K edge, both of which serve as tracers of X-ray illumination. We used the EW measurements to infer the average Fe abundance within the clouds to be 1.6 ± 0.1 times solar. The cloud column densities derived from the spectral analysis were typically of the order of 10 23 cm −2 , which is significantly higher than previous estimates. This in turn has a significant impact on the inferred geometry and time delays within the cloud system. The measured cloud parameters were used to set constraints on the past activity of Sgr A* and to investigate whether a contribution to the Fe fluorescence by cosmic-ray bombardment is plausible. Conclusions. Past X-ray activity of Sgr A* is the most likely source of ionisation within the molecular clouds in the innermost 30 pc of the Galaxy. In this scenario, the X-ray luminosity required to excite these reflection nebulae is of the order of 10 37 -10 38 erg s −1 , significantly lower than that estimated for the Sgr B2 molecular cloud. Moreover, the inferred Sgr A* lightcurve over the past 150 years shows a long-term downwards trend punctuated by occasional counter-trend brightening episodes of at least 5 years duration. Finally, we found that a contribution to the Fe fluorescence by X-ray transient binaries...

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Equivalent width, shape and proper motion of the iron fluorescent line emission from molecular clouds as an indicator of the illuminating source X-ray flux history

Cited by 125 publications

References 22 publications

$\vec{XMM}$-$\vec{Newton}$ study of the persistent X-ray source 1E 1743.1–2843 located in the Galactic Center direction

$\vec{XMM}$-$\vec{Newton}$ study of the persistent X-ray source 1E 1743.1–2843 located in the Galactic Center direction

Nonthermal particles and photons in starburst regions and superbubbles

The X-ray lightcurve of Sagittarius A* over the past 150 years inferred from Fe-Kαline reverberation in Galactic centre molecular clouds

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