THE ORIGIN OF THE 6.4 keV LINE EMISSION AND H
                    <sub>2</sub>
                    IONIZATION IN THE DIFFUSE MOLECULAR GAS OF THE GALACTIC CENTER REGION

Dogiel, V. A.; Chernyshov, Dmitry; Tatischeff, V.; Cheng, K. S.; Terrier, R.

doi:10.1088/2041-8205/771/2/l43

Cited by 18 publications

(29 citation statements)

References 42 publications

(48 reference statements)

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“…We see from the figure that this flux is negligible if E min = 100 keV. This conclusion is in a full agreement with results obtained by Dogiel et al (2013) (see Fig. 1 in that paper).…”

Section: 4 Kev Emission From Sgr B2 Produced By Subrelativistic Prosupporting

confidence: 92%

“…This effect is illustrated in Fig. 3 where we showed the energy range of subrelativistic protons which ionize the hydrogen gas and iron atoms (see for the ionization cross-sections Tatischeff, 2003;Dogiel et al, 2013).…”

Section: 4 Kev Emission From Sgr B2 Produced By Subrelativistic Promentioning

confidence: 80%

“…Therefore we conclude that the electrons are unable to provide the necessary rate of ionization in the GC region, and especially the necessary intensity of the 6.4 keV line from there (see Dogiel et al, 2013).…”

Section: Ionization By Cr Electrons In the Intercloud Medium Stationmentioning

confidence: 84%

“…• Our earlier analysis (Dogiel et al, 2013) showed that ionization of the diffuse hydrogen is provided by subrelativistic protons while the diffuse 6.4 keV line in the GC is generated by X-ray photons emitted by Sgr A*. An alternative interpretation was suggested by Yusef-Zadeh et al (2013a) who assumed that the ionization is provided by background electrons with E < 1 GeV whose spectrum was extrapolated from the radio data.…”

Section: Resultsmentioning

confidence: 99%

“…from Tatischeff (2003), n p (E p ) is the spectrum of primary protons, I(H 2 ) is the ionization potentials of hydrogen, E max p is the maximum energy of primary protons, and v p is the velocities of primary protons. As in Dogiel et al (2013) the contribution from knock-on electrons is neglected.…”

Section: 4 Kev Emission From Sgr B2 Produced By Subrelativistic Promentioning

confidence: 99%

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On the origin of the 6.4keV line in the Galactic Center region

Dogiel

Chernyshov

Kiselev

et al. 2014

Astroparticle Physics

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We analyse the 6.4 keV iron line component produced in the Galactic Center (GC) region by cosmic rays in dense molecular clouds (MCs) and in the diffuse molecular gas. We showed that this component, in principle, can be seen in several years in the direction of the cloud Srg B2. If this emission is produced by low energy CRs which ionize the interstellar molecular gas the intensity of the line is quite small, < 1%. However, we cannot exclude that local sources of CRs or X-ray photons nearby the cloud may provide much higher intensity of the line from there. Production of the line emission from molecular clouds depends strongly on processes of CR penetration into them. We show that turbulent motions of neutral gas may generate strong magnetic fluctuations in the clouds which prevent free penetration of CRs into the clouds from outside. We provide a special analysis of the line production by high energy electrons. We concluded that these electrons hardly provide the diffuse 6.4 keV line emission from the GC because their density is depleted by ionization losses. We do not exclude that local sources of electrons may provide an excesses of the 6.4 keV line emission in some molecular clouds and even reproduce a relatively short time variations of the iron line emission. However, we doubt whether a single electron source provides the simultaneous short time variability of the iron line emission from clouds which are distant from each other on hundred pc as observed for the GC clouds. An alternative speculation is that local electron sources could also provide the necessary effect of the line variations in different clouds that are seen simultaneously by chance that seems, however, very unlikely.

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“…We see from the figure that this flux is negligible if E min = 100 keV. This conclusion is in a full agreement with results obtained by Dogiel et al (2013) (see Fig. 1 in that paper).…”

Section: 4 Kev Emission From Sgr B2 Produced By Subrelativistic Prosupporting

confidence: 92%

Section: 4 Kev Emission From Sgr B2 Produced By Subrelativistic Promentioning

confidence: 80%

Section: Ionization By Cr Electrons In the Intercloud Medium Stationmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: 4 Kev Emission From Sgr B2 Produced By Subrelativistic Promentioning

confidence: 99%

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On the origin of the 6.4keV line in the Galactic Center region

Dogiel

Chernyshov

Kiselev

et al. 2014

Astroparticle Physics

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On the past activity of Sgr A*

et al. 2013

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Recent X-ray emission events in the Galactic center would be expected to generate an X-ray reflection response within the surrounding clouds of the central molecular zone, in the Galactic disk and even, if powerful enough, in clouds outside our Galaxy. We review here the current constraints on Sgr A*'s past activity obtained through this method, with particular emphasis on the strong evidence that has been gathered for multiple X-ray flashes during the past few hundred years.

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An X-ray survey of the central molecular zone: Variability of the Fe Kα emission line

Terrier

Clavel

Soldi

et al. 2018

A&A

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There is now abundant evidence that the luminosity of the Galactic super-massive black hole (SMBH) has not always been as low as it is nowadays. The observation of varying non-thermal diffuse X-ray emission in molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the SMBH. The observation of different variability timescales of the reflected emission in the Sgr A molecular complex can be well explained if the X-ray emission of at least two distinct and relatively short events (i.e. about 10 years or less) is currently propagating through the region. The number of such events or the presence of a long-duration illumination are open questions. Variability of the reflected emission all over of the central 300 pc, in particular in the 6.4 keV Fe Kα line, can bring strong constraints. To do so we performed a deep scan of the inner 300 pc with XMM-Newton in 2012. Together with all the archive data taken over the course of the mission, and in particular a similar albeit more shallow scan performed in 2000-2001, this allows for a detailed study of variability of the 6.4 keV line emission in the region, which we present here. We show that the overall 6.4 keV emission does not strongly vary on average, but variations are very pronounced on smaller scales. In particular, most regions showing bright reflection emission in 2000-2001 significantly decrease by 2012. We discuss those regions and present newly illuminated features. The absence of bright steady emission argues against the presence of an echo from an event of multi-centennial duration and most, if not all, of the emission can likely be explained by a limited number of relatively short (i.e. up to 10 years) events.

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THE ORIGIN OF THE 6.4 keV LINE EMISSION AND H ₂ IONIZATION IN THE DIFFUSE MOLECULAR GAS OF THE GALACTIC CENTER REGION

Cited by 18 publications

References 42 publications

On the origin of the 6.4keV line in the Galactic Center region

On the origin of the 6.4keV line in the Galactic Center region

On the past activity of Sgr A*

An X-ray survey of the central molecular zone: Variability of the Fe Kα emission line

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THE ORIGIN OF THE 6.4 keV LINE EMISSION AND H 2 IONIZATION IN THE DIFFUSE MOLECULAR GAS OF THE GALACTIC CENTER REGION

Cited by 18 publications

References 42 publications

On the origin of the 6.4keV line in the Galactic Center region

On the origin of the 6.4keV line in the Galactic Center region

On the past activity of Sgr A*

An X-ray survey of the central molecular zone: Variability of the Fe Kα emission line

Contact Info

Product

Resources

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THE ORIGIN OF THE 6.4 keV LINE EMISSION AND H ₂ IONIZATION IN THE DIFFUSE MOLECULAR GAS OF THE GALACTIC CENTER REGION