X‐Rays from Accelerated Ion Interactions

Tatischeff, V.; Ramaty, R.; Kozlovsky, B.

doi:10.1086/306118

Cited by 28 publications

(43 citation statements)

References 65 publications

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“…We used a steady-state, thick target model, in which accelerated electrons with given energy spectra are injected at a constant rate into the interaction region and produce atomic reactions as they slow down to energies below the thresholds of the various reactions (Tatischeff et al 1998). It includes the non-thermal X-ray emission from the secondary, knockon electrons, which mainly result from ionization of ambient H 2 molecules and He atoms.…”

Section: A Spectral Model Of Lecre Emissionmentioning

confidence: 99%

FADING HARD X-RAY EMISSION FROM THE GALACTIC CENTER MOLECULAR CLOUD Sgr B2

Terrier

Ponti

Bélanger

et al. 2010

ApJ

134

193

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The centre of our Galaxy harbours a 4 million solar mass black hole that is unusually quiet: its present X-ray luminosity is more than 10 orders of magnitude less than its Eddington luminosity. The observation of iron fluorescence and hard X-ray emission from some of the massive molecular clouds surrounding the Galactic Centre has been interpreted as an echo of a past 10 39 erg s −1 flare. Alternatively, low-energy cosmic rays propagating inside the clouds might account for the observed emission, through inverse bremsstrahlung of low energy ions or bremsstrahlung emission of low energy electrons. Here we report the observation of a clear decay of the hard X-ray emission from the molecular cloud Sgr B2 during the past 7 years thanks to more than 20 Ms of INTEGRAL exposure. This confirms the decay previously observed comparing the 6.4 keV line fluxes measured by various X-ray instruments, but without intercalibration effects. The measured decay time is 8.2 ± 1.7 years, compatible with the light crossing time of the molecular cloud core . Such a short timescale rules out inverse bremsstrahlung by cosmic-ray ions as the origin of the X ray emission. We also obtained 2-100 keV broadband X-ray spectra by combining INTEGRAL and XMM-Newton data and compared them with detailed models of X-ray emission due to irradiation of molecular gas by (i) low-energy cosmicray electrons and (ii) hard X-rays. Both models can reproduce the data equally well, but the time variability constraints and the huge cosmic ray electron luminosity required to explain the observed hard X-ray emission strongly favor the scenario in which the diffuse emission of Sgr B2 is scattered and reprocessed radiation emitted in the past by Sgr A*. The spectral index of the illuminating power-law source is found to be Γ ∼ 2 and its luminosity 1.5 − 5 × 10 39 erg s −1 , depending on the relative positions of Sgr B2 and Sgr A * . Using recent parallax measurements that place Sgr B2 in front of Sgr A * , we find that the period of intense activity of Sgr A * ended between 75 and 155 years ago.

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Section: A Spectral Model Of Lecre Emissionmentioning

confidence: 99%

FADING HARD X-RAY EMISSION FROM THE GALACTIC CENTER MOLECULAR CLOUD Sgr B2

Terrier

Ponti

Bélanger

et al. 2010

ApJ

134

193

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“…We assumed the X-ray production region to be neutral and of solar composition (Anders & Grevesse 1989) and considered the Ka and Kb lines from ambient C, N, O, Ne, Mg, Si, S, Ar, Ca, and Fe. The transition energies are given in Tatische † et al (1998, Table 6). The X-ray line production cross section can be written as…”

Section: X-rays From Lecre Interaction With the Ismmentioning

confidence: 99%

“…In addition to the bremsstrahlung continuum, LECRe produce nonthermal narrow X-ray emission lines below 10 keV via K-shell vacancy creation in ambient heavy atoms. Low-energy cosmic-ray ions (LECRi) also produce characteristic broad and narrow X-ray emission lines (Tatische †, Ramaty, & Kozlovsky 1998 and references therein ; Dogiel et al 1998). Their contribution to the Galactic ridge di †use emission has been considered by Tatische †, Ramaty, & Valinia (1999) and Tanaka et al (1999).…”

Section: Introductionmentioning

confidence: 99%

On the Origin of the Iron K Line in the Spectrum of the Galactic X‐Ray Background

Valinia

Tatischeff

Arnaud

et al. 2000

ApJ

Self Cite

114

129

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We propose a mechanism for the origin of the Galactic ridge X-ray background that naturally explains the properties of the Fe K line, speciÐcally the detection of the centroid line energy below 6.7 keV and the apparent broadness of the line. Motivated by recent evidence of nonthermal components in the spectrum of the Galactic X-ray/c-ray background, we consider a model that is a mixture of thermal plasma components of perhaps supernova origin and nonthermal emission from the interaction of low-energy cosmic-ray electrons (LECRe) with the interstellar medium. The LECRe may be accelerated in supernova explosions or by ambient interstellar plasma turbulence. Atomic collisions of fast electrons produce characteristic nonthermal, narrow X-ray emission lines that can explain the complex Galactic background spectrum. Using the ASCA GIS archival data from the Scutum arm region, we show that a two-temperature thermal plasma model with kT D 0.6 and D2.8 keV, plus a LECRe component models the data satisfactorily. Our analysis rules out a purely nonthermal origin for the emission. It also rules out a signiÐcant contribution from low-energy cosmic-ray ions, because their nonthermal X-ray production would be accompanied by a nuclear c-ray line di †use emission exceeding the upper limits obtained using OSSE, as well as by an excessive Galaxy-wide Be production rate. The proposed model naturally explains the observed complex line features and removes the difficulties associated with previous interpretations of the data which evoked a very hot thermal component (kT D 7 keV).

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“…Also, the presence of a hard continuum component is not in itself sufficient to demonstrate the presence of TeV particles. Hard components could be produced by any of a number of mechanisms: a hot thermal component, possibly associated with the forward shock (for most SNRs, ASCA lacks the bandwidth to discriminate between a thermal and nonthermal model), nonthermal bremsstrahlung (Asvarov et al 1990), bremsstrahlung from ions accelerated to MeV energy (Tatischeff, Ramaty, & Kozlovsky 1998), and even synchrotron emission from a hidden pulsar. The data from every SNR must be carefully scrutinized to determine whether the hard component truly arises from TeV electrons.…”

Section: Current Resultsmentioning

confidence: 99%

X-ray Emission as an Indicator of Cosmic ray Acceleration in Supernova Remnants

Petre¹,

Allen²,

Hwang³

et al. 2000

Symp. - Int. Astron. Union

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Abstract. X-ray observations over the past several years have led to the discovery of nonthermal X-ray emission arising in the shells of many young supernova remnants, including SN 1006, Cas A, and Tycho. This emission is thought to be synchrotron emission from electrons that have been shock accelerated to hundreds of TeV, and thus represents strong evidence that cosmic rays are accelerated in SNR shocks. The X-ray observations are corroborated by detection of TeV gamma rays from two of these remnants. A systematic investigation of young, shell-like remnants suggests that the nonthermal X-ray emission from shock-accelerated electrons is a common, if not ubiquitous, feature. We review the status of the X-ray observations and describe how they can be used to provide insight into the shock acceleration process.

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X‐Rays from Accelerated Ion Interactions

Cited by 28 publications

References 65 publications

FADING HARD X-RAY EMISSION FROM THE GALACTIC CENTER MOLECULAR CLOUD Sgr B2

FADING HARD X-RAY EMISSION FROM THE GALACTIC CENTER MOLECULAR CLOUD Sgr B2

On the Origin of the Iron K Line in the Spectrum of the Galactic X‐Ray Background

X-ray Emission as an Indicator of Cosmic ray Acceleration in Supernova Remnants

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