scholarly journals X-raying molecular clouds with a short flare: probing statistics of gas density and velocity fields

2020 ◽  
Vol 495 (1) ◽  
pp. 1414-1432 ◽  
Author(s):  
I Khabibullin ◽  
E Churazov ◽  
R Sunyaev ◽  
C Federrath ◽  
D Seifried ◽  
...  
Keyword(s):  
Generation X ◽  
Line Emission ◽  
Future Generation ◽  
Effective Area ◽  
Velocity Fields ◽  
High Spectral Resolution ◽  
Gas Density ◽  
X Ray ◽  
Cloud Parameters ◽  
Sgr A

ABSTRACT We take advantage of a set of molecular cloud simulations to demonstrate a possibility to uncover statistical properties of the gas density and velocity fields using reflected emission of a short (with duration much less than the cloud’s light-crossing time) X-ray flare. Such a situation is relevant for the Central Molecular Zone (CMZ) of our Galaxy where several clouds get illuminated by an ∼110 yr-old flare from the supermassive black hole Sgr A* . Due to shortness of the flare (Δt ≲ 1.6 yr), only a thin slice (Δz ≲ 0.5 pc) of the molecular gas contributes to the X-ray reflection signal at any given moment, and its surface brightness effectively probes the local gas density. This allows reconstructing the density probability distribution function over a broad range of scales with virtually no influence of attenuation, chemo-dynamical biases, and projection effects. Such a measurement is key to understanding the structure and star formation potential of the clouds evolving under extreme conditions in the CMZ. For cloud parameters similar to the currently brightest in X-ray reflection molecular complex Sgr A, the sensitivity level of the best available data is sufficient only for marginal distinction between solenoidal and compressive forcing of turbulence. Future-generation X-ray observatories with large effective area and high spectral resolution will dramatically improve on that by minimizing systematic uncertainties due to contaminating signals. Furthermore, measurement of the iron fluorescent line centroid with sub-eV accuracy in combination with the data on molecular line emission will allow direct investigation of the gas velocity field.

scholarly journals Molecular gas in the immediate vicinity of Sgr A* seen with ALMA

2016 ◽  
Vol 11 (S322) ◽  
pp. 129-132
Author(s):  
Lydia Moser ◽  
Álvaro Sánchez-Monge ◽  
Andreas Eckart ◽  
Miguel A. Requena-Torres ◽  
Macarena García-Marin ◽  
...  
Keyword(s):  
Galactic Center ◽  
Line Emission ◽  
Molecular Gas ◽  
Future Studies ◽  
X Ray ◽  
Circumnuclear Disk ◽  
Sgr A ◽  
Central Parsec ◽  
Cloud Cores ◽  
Cold Core

AbstractWe report serendipitous detections of line emission with ALMA in band 3, 6, and 7 in the central parsec of the Galactic center at an up to now highest resolution (<0.7″). Among the highlights are the very first and highly resolved images of sub-mm molecular emission of CS, H13CO+, HC3N, SiO, SO, C2H, and CH3OH in the immediate vicinity (~1″ in projection) of Sgr A* and in the circumnuclear disk (CND). The central association (CA) of molecular clouds shows three times higher CS/X (X: any other observed molecule) luminosity ratios than the CND suggesting a combination of higher excitation - by a temperature gradient and/or IR-pumping - and abundance enhancement due to UV- and/or X-ray emission. We conclude that the CA is closer to the center than the CND is and could be an infalling clump consisting of denser cloud cores embedded in diffuse gas. Moreover, we identified further regions in and outside the CND that are ideally suited for future studies in the scope of hot/cold core and extreme PDR/XDR chemistry and consequent star formation in the central few parsecs.

scholarly journals Investigation of laser-produced chlorine plasma radiation for non-monochromatic X-ray scattering experiments

2006 ◽  
Vol 24 (3) ◽  
pp. 335-345 ◽  
Author(s):  
M. SCHOLLMEIER ◽  
G. RODRÍGUEZ PRIETO ◽  
F.B. ROSMEJ ◽  
G. SCHAUMANN ◽  
A. BLAZEVIC ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Pyrolytic Graphite ◽  
Line Emission ◽  
Plasma Radiation ◽  
High Spectral Resolution ◽  
Crystal Spectrometer ◽  
X Ray ◽  
Dense Plasmas ◽  
X Ray Scattering ◽  
Ray Scattering

The chlorine Heαradiation of polyvinyl chloride (PVC) was investigated with respect to X-ray scattering experiments on dense plasmas. The X-ray source was a laser-produced plasma that was observed with a highly reflective highly oriented pyrolytic graphite (HOPG) crystal spectrometer as it is used in current x-ray scattering experiments on dense plasmas. The underlying dielectronic satellites of Heαcannot be resolved, therefore the plasma was observed at the same time with a focusing spectrometer with spatial resolution. To reconstruct the spectrum a simple model to calculate the spectral line emission based on dielectronic recombination and inner shell excitation of helium- and lithium-like ions was used. The analysis shows that chlorine dielectronic satellite emission is intense compared to Heαin laser-produced chlorine plasmas with a temperature of 300 eV in this wavelength range of Δλ = 0.07 Å (ΔE= 43 eV). The method proposed in this paper allows deducing experimentally the role of the underlying dielectronic satellites in the scatter spectrum measured with a HOPG crystal spectrometer. It is shown that the dielectronic satellites can be neglected when the scattering is measured with low spectral resolution in the non-collective regime. They are of major importance in the collective scatter regime where a high spectral resolution is necessary.

scholarly journals Observing Soft X-ray Line Emission from the Interstellar Medium with X-ray Calorimeter on a Sounding Rocket

1990 ◽  
Vol 115 ◽  
pp. 361-364
Author(s):  
J. Zhang ◽  
B. Edwards ◽  
M. Juda ◽  
R. Kelley ◽  
G. Madejski ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Supernova Remnants ◽  
Line Emission ◽  
Aluminum Foil ◽  
High Spectral Resolution ◽  
Sounding Rocket ◽  
Preliminary Design ◽  
High Quantum Efficiency ◽  
Equilibrium Plasma ◽  
X Ray

AbstractWe have been developing X-ray calorimeters that have high spectral resolution and high quantum efficiency. For an X-ray calorimeter working at 0.1 K, the energy resolution ideally can be as good as one eV for a practical detector. A detector with a resolution of 17 eV FWHM at 6 keV has been constructed. We expect to be able to improve this by a factor of two or more. With X-ray calorimeters flown on a sounding rocket, we should be able to observe soft X-ray line emission from the interstellar medium over the energy range 0.07 to 1 keV. Here we present a preliminary design for an X-ray calorimeter rocket experiment and the spectrum which might be observed from an equilibrium plasma. For later X-ray calorimeter sounding rocket experiments, we plan to add an aluminum foil mirror with collecting area of about 400 cm2 to observe line features from bright supernova remnants.

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

2018 ◽  
Vol 612 ◽  
pp. A102 ◽  
Author(s):  
R. Terrier ◽  
M. Clavel ◽  
S. Soldi ◽  
A. Goldwurm ◽  
G. Ponti ◽  
...  
Keyword(s):  
Line Emission ◽  
Molecular Complexes ◽  
Massive Black Hole ◽  
X Ray ◽  
Open Questions ◽  
Long Duration ◽  
Sgr A ◽  
Thermal Diffuse ◽  
Archive Data ◽  
Do So

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 yr 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 yr) events.

Iron K-Line Emission from X-Ray Binaries

1988 ◽  
Vol 102 ◽  
pp. 47-50
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
F. Nagase
Keyword(s):  
Accretion Disk ◽  
Radiative Recombination ◽  
Characteristic Temperature ◽  
Line Emission ◽  
Ionization Front ◽  
Continuum Radiation ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx&gt; 10 keV is likely due to fluorescence outside the He II ionization front.

scholarly journals Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*

2016 ◽  
Vol 461 (1) ◽  
pp. 552-559 ◽  
Author(s):  
S. Dibi ◽  
S. Markoff ◽  
R. Belmont ◽  
J. Malzac ◽  
J. Neilsen ◽  
...  
Keyword(s):  
Event Horizon ◽  
X Ray ◽  
Sgr A

scholarly journals NEAR-INFRARED AND X-RAY QUASI-PERIODIC OSCILLATIONS IN NUMERICAL MODELS OF Sgr A*

2012 ◽  
Vol 746 (1) ◽  
pp. L10 ◽  
Author(s):  
Joshua C. Dolence ◽  
Charles F. Gammie ◽  
Hotaka Shiokawa ◽  
Scott C. Noble
Keyword(s):  
Near Infrared ◽  
Numerical Models ◽  
Periodic Oscillations ◽  
X Ray ◽  
Sgr A

Nitrogen (N2) Implantation to Suppress Growth of Interfacial Oxide in Mocvd Bst and Sputtered Bst Films

1999 ◽  
Vol 567 ◽  
Author(s):  
Renee Nieh ◽  
Wen-Jie Qi ◽  
Yongjoo Jeon ◽  
Byoung Hun Lee ◽  
Aaron Lucas ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Interfacial Layer ◽  
Gate Dielectric ◽  
Nitrogen Concentration ◽  
Chemical Vapor ◽  
Future Generation ◽  
Oxide Thickness ◽  
Layer Growth ◽  
X Ray ◽  
Bst Films

ABSTRACTBa0.5Sr0.5TiO3 (BST) is one of the high-k candidates for replacing SiO2 as the gate dielectric in future generation devices. The biggest obstacle to scaling the equivalent oxide thickness (EOT) of BST is an interfacial layer, SixOy, which forms between BST and Si. Nitrogen (N2) implantation into the Si substrate has been proposed to reduce the growth of this interfacial layer. In this study, capacitors (Pt/BST/Si) were fabricated by depositing thin BST films (50Å) onto N2 implanted Si in order to evaluate the effects of implant dose and annealing conditions on EOT. It was found that N2 implantation reduced the EOT of RF magnetron sputtered and Metal Oxide Chemical Vapor Deposition (MOCVD) BST films by ∼20% and ∼33%, respectively. For sputtered BST, an implant dose of 1×1014cm−;2 provided sufficient nitrogen concentration without residual implant damage after annealing. X-ray photoelectron spectroscopy data confirmed that the reduction in EOT is due to a reduction in the interfacial layer growth. X-ray diffraction spectra revealed typical polycrystalline structure with (111) and (200) preferential orientations for both films. Leakage for these 50Å BST films is on the order of 10−8 to 10−5 A/cm2—lower than oxynitrides with comparable EOTs.

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