Laboratory Astrophysics Experiments in X-Ray Transfer Physics Relevant to Cosmic Accretion-Powered Sources

1988 ◽  
Vol 102 ◽  
pp. 67-70
Author(s):  
S.M. Kahn ◽  
W. Craig ◽  
J. Schachter ◽  
B. Wargelin ◽  
H. Kapteyn ◽  
...  
Keyword(s):  
Cross Sections ◽  
Surrounding Medium ◽  
Cataclysmic Variables ◽  
Laboratory Astrophysics ◽  
Time Resolved ◽  
X Ray ◽  
Laboratory Facility ◽  
Excitation Processes ◽  
Laboratory Astrophysics Experiments ◽  
Resonant Transitions

AbstractThe interpretation of upcoming cosmic soft X-ray spectroscopic observations may require a vast improvement in the state of our knowledge of basic atomic physics and radiation transfer processes, particularly for the important class of accretion-powered systems such as cataclysmic variables, X-ray binaries, and active galactic nuclei. For these sources, short wavelength spectral features are formed in the transfer of X-radiation from a powerful central source outward through a cooler, surrounding medium. The line emitting gas is photoionized and the level populations are determined largely by recombination cascades and photoexcitation as opposed to collisional effects. These processes can be rather complex and many uncertainties remain. We are developing a new approach to this problem using time-resolved studies of laser produced plasmas. Experiments which are currently underway include the measurements of: (a) inner and outer shell photoabsorption cross-sections of intermediate ions of abundant elements, and (b) fluorescent excitation processes due to wavelength coincidences of resonant transitions from different ions. In connection with this program, we have developed a novel reflection grating spectrometer coupled to a streak camera which provides high resolution spectra at soft X-ray and EUV wavelengths at the sub-nanosecond level. We describe our laboratory facility and some of our preliminary experimental results.

Electron–ion interactions for trapped highly charged Ge ions

2006 ◽  
Vol 84 (1) ◽  
pp. 67-81 ◽  
Author(s):  
G Machtoub ◽  
J.R. Crespo López-Urrutia ◽  
X Zhang ◽  
H Tawara
Keyword(s):  
Electron Beam ◽  
Cross Sections ◽  
Ion Trap ◽  
Dielectronic Recombination ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Theoretical Simulation ◽  
X Ray ◽  
New Information ◽  
Excitation Processes

A theoretical simulation of complex K X-ray spectra including those from dielectronic recombination and excitation processes is presented for trapped highly charged germanium ions ( Geq+, q = 27–30) interacting with a dense electron beam. We carried out numerical calculations of transition rates, level energies, transition wavelengths, resonance and collision strengths, and satellite intensity factors. Analytical results related to cross sections of B- through He-like Ge ions were obtained as well. The simulated spectra, including the contribution from different charge states of Ge27+–Ge30+, show good overall agreement over a wide electron energy range with the available X-ray measurements from the Heidelberg electron beam ion trap (EBIT). We have also predicted the electron impact excitation cross-section ratios for different transitions of Ge29+ and Ge30+ ions. It should be emphasized that the present analysis can also provide new information and clues of possible temperature measurements for EBIT and other plasma diagnostics.PACS No.: 32.30.Rj

scholarly journals Single-Shot X-Ray Coherent Diffractive Imaging of Superfluid He Nanodroplets

2014 ◽  
Vol 70 (a1) ◽  
pp. C289-C289
Author(s):  
Oliver Gessner ◽  
Christoph Bostedt ◽  
Andrey Vilesov
Keyword(s):  
Cross Sections ◽  
Direct Access ◽  
Single Shot ◽  
Diffractive Imaging ◽  
Helium Droplets ◽  
Helium Nanodroplets ◽  
Time Resolved ◽  
X Ray ◽  
Coherent Diffractive Imaging ◽  
Quantum Phenomena

Single-shot coherent diffractive imaging (CDI) experiments were performed on pure and doped helium nanodroplets using femtosecond X-ray pulses from the Linac Coherent Light Source (LCLS). The superfluid nature of helium droplets presents a rare opportunity to study the onset of macroscopic quantum phenomena in finite, sub-micron scale systems. Despite the small X-ray scattering cross sections of atomic helium, high-quality single-shot CDI data were obtained that give direct access to sizes and shapes of individual nanodroplets. The diffraction patterns from helium droplets doped with xenon atoms differ starkly from the patterns from pure droplets. Strong indications for the formation of complex xenon structures inside the superfluid helium environment are observed, giving access to information about the structure and aggregation dynamics of the dopant species. The results are discussed with respect to the hydrodynamic properties of the superfluid droplets and compared to those of classical drops. An outlook on femtosecond time-resolved CDI experiments to study dynamics in pure and Xe-doped He nanodroplets will be given based on a new undulator-based X-ray pump/X-ray probe technique that is currently under development at LCLS.

scholarly journals The obscured X-ray binaries V404 Cyg, Cyg X–3, V4641 Sgr, and GRS 1915+105

2020 ◽  
Vol 639 ◽  
pp. A13 ◽  
Author(s):  
K. I. I. Koljonen ◽  
J. A. Tomsick
Keyword(s):  
Large Scale ◽  
Surrounding Medium ◽  
The Other ◽  
Opening Angle ◽  
Spectral Evolution ◽  
Time Resolved ◽  
Orbital Inclination ◽  
X Ray ◽  
Geometrical Change ◽  
X Ray Binaries

Aims. V404 Cyg, Cyg X–3, V4641 Sgr, and GRS 1915+105 are among the brightest X-ray binaries and display complex behavior in their multiwavelength emission. Except for Cyg X–3, the other three sources have large accretion disks, and there is evidence of a high orbital inclination. Therefore, any large-scale geometrical change in the accretion disk can cause local obscuration events. On the other hand, Cyg X–3 orbits its Wolf-Rayet companion star inside the heavy stellar wind obscuring the X-ray source. We study here whether the peculiar X-ray spectra observed from all four sources can be explained by local obscuration events. Methods. We used spectra obtained with the Nuclear Spectroscopic Telescope Array and Rossi X-ray Timing Explorer to study the spectral evolution of the four luminous hard X-ray sources. We fit the time-averaged spectra, and also time-resolved spectra in case of V404 Cyg, with two physically motivated models describing either a scenario where all the intrinsic emission is reprocessed in the surrounding matter or where the emitter is surrounded by a thick torus with variable opening angle. Results. We show that the X-ray spectra during specific times are very similar in all four sources, likely arising from the high-density environments where they are embedded. The fitted models suggest that a low-luminosity phase preceding an intense flaring episode in the 2015 outburst of V404 Cyg is heavily obscured, but intrinsically very bright (super-Eddington) accretion state. Similar spectral evolution to that of V404 Cyg is observed from the recent X-ray state of GRS 1915+105 that presented unusually low luminosity. The modeling results point to a geometry change in the (outflowing) obscuring matter in V404 Cyg and GRS 1915+105, which is also linked to the radio (jet) evolution. Within the framework of the models, all sources display obscured X-ray emission, but with different intrinsic luminosities ranging from lower than 1% of the Eddington luminosity up to the Eddington limit. This indicates that different factors cause the obscuration. This work highlights the importance of taking the reprocessing of the X-ray emission in the surrounding medium into account in modeling the X-ray spectra. This may well take place in other sources as well.

scholarly journals Optical Studies of 10 Hard X-Ray-selected Cataclysmic Binaries

2022 ◽  
Vol 924 (2) ◽  
pp. 67
Author(s):  
Jules P. Halpern ◽  
John R. Thorstensen
Keyword(s):  
Cataclysmic Variables ◽  
Velocity Variation ◽  
Time Resolved ◽  
X Ray ◽  
Spin Period ◽  
Radial Velocity Variation ◽  
Cataclysmic Binaries ◽  
Orbital Periods ◽  
Magnetic Cataclysmic Variables ◽  
Optical Identifications

Abstract We conducted time-resolved optical spectroscopy and/or photometry of 10 cataclysmic binaries that were discovered in hard X-ray surveys, with the goal of measuring their orbital periods and searching for evidence that they are magnetic. Four of the objects in this study are new optical identifications: IGR J18017−3542, PBC J1841.1+0138, IGR J18434−0508, and Swift J1909.3+0124. A 311.8 s, coherent optical pulsation is detected from PBC J1841.1+0138, as well as eclipses with a period of 0.221909 days. A 152.49 s coherent period is detected from IGR J18434−0508. A probable period of 389 s is seen in IGR J18151−1052, in agreement with a known X-ray spin period. We also detect a period of 803.5 s in an archival X-ray observation of Swift J0717.8−2156. The last four objects are thus confirmed magnetic cataclysmic variables of the intermediate polar class. An optical period of 1554 s in AX J1832.3−0840 also confirms the known X-ray spin period, but a stronger signal at 2303 s is present whose interpretation is not obvious. We also studied the candidate intermediate polar Swift J0820.6−2805, which has low and high states differing by ≈4 mag and optical periods or quasi-periodic oscillations not in agreement with proposed X-ray periods. Of note is an unusually long 2.06-day orbital period for Swift J1909.3+0124, manifest in the radial velocity variation of photospheric absorption lines of an early K-type companion star. The star must be somewhat evolved if it is to fill its Roche lobe.

scholarly journals Dyson Orbitals within the fc-CVS-EOM-CCSD Framework

2019 ◽  
Author(s):  
Marta L. Vidal ◽  
Anna Krylov ◽  
Sonia Coriani
Keyword(s):  
Excited States ◽  
Cross Sections ◽  
Ground State ◽  
Equation Of Motion ◽  
Photoelectron Spectra ◽  
Coupled Cluster ◽  
Time Resolved ◽  
X Ray ◽  
Ccsd Method

We report on the implementation and illustrative applications of Dyson orbitals within the recently proposed frozen-core (fc) core-valence separated (CVS) equation-of-motion (EOM) coupled-cluster singles and doubles (CCSD) method, which enables efficient and accurate characterization of core-ionized states. Dyson orbitals are reduced quantities that can be interpreted as correlated states of the ejected/attached electron.<br>Dyson orbitals enter the expressions of various experimental observables, such as photoionization cross sections; thus, they are necessary for modeling photoelectron spectra.<br>Here we discuss the simulations of X-ray photoelectron spectra (XPS) and propose an approach to simulate time-resolved (TR-)XPS for probing excited states. <br>As illustrative examples, we present the simulation of the XPS of the ground state of adenine and of TR-XPS of the excited states of uracil.

LABORATORY ASTROPHYSICS EXPERIMENTS IN X-RAY TRANSFER PHYSICS RELEVANT TO COSMIC ACCRETION-POWERED SOURCES

1988 ◽  
Vol 49 (C1) ◽  
pp. C1-67-C1-70
Author(s):  
S. M. KAHN ◽  
W. CRAIG ◽  
J. SCHACHTER ◽  
B. WARGELIN ◽  
H. KAPTEYN ◽  
...  
Keyword(s):  
Laboratory Astrophysics ◽  
X Ray ◽  
Laboratory Astrophysics Experiments

scholarly journals High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare

2020 ◽  
Vol 641 ◽  
pp. A144 ◽  
Author(s):  
M. Lomaeva ◽  
V. Grinberg ◽  
M. Guainazzi ◽  
N. Hell ◽  
S. Bianchi ◽  
...  
Keyword(s):  
High Resolution ◽  
Stellar Wind ◽  
Emission Lines ◽  
High Mass ◽  
Time Resolved ◽  
X Ray ◽  
Multi Phase ◽  
Resonant Transitions ◽  
First Time ◽  
Charged Ions

Context. We present a ~130 ks observation of the prototypical wind-accreting, high-mass X-ray binary Vela X-1 collected with XMM-Newton at orbital phases between 0.12 and 0.28. A strong flare took place during the observation that allows us to investigate the reaction of the clumpy stellar wind to the increased X-ray irradiation. Aims. To examine the wind’s reaction to the flare, we performed both time-averaged and time-resolved analyses of the RGS spectrum and examined potential spectral changes. Methods. We focused on the high-resolution XMM-Newton RGS spectra and divided the observation into pre-flare, flare, and post-flare phases. We modeled the time-averaged and time-resolved spectra with phenomenological components and with the self-consistent photoionization models calculated via CLOUDY and XSTAR in the pre-flare phase, where strong emission lines due to resonant transitions of highly ionized ions are seen. Results. In the spectra, we find emission lines corresponding to K-shell transitions in highly charged ions of oxygen, neon, magnesium, and silicon as well as radiative recombination continua (RRC) of oxygen. Additionally, we observe potential absorption lines of magnesium at a lower ionization stage and features identified as iron L lines. The CLOUDY and XSTAR photoionization models provide contradictory results, either pointing towards uncertainties in theory or possibly a more complex multi-phase plasma, or both. Conclusions. We are able to demonstrate the existence of a plethora of variable narrow features, including the firm detection of oxygen lines and RRC that RGS enables to observe in this source for the first time. We show that Vela X-1 is an ideal source for future high-resolution missions, such as XRISM and Athena.

Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 766-767
Author(s):  
Eva-Maria Mandelkow ◽  
Eckhard Mandelkow ◽  
Joan Bordas
Keyword(s):  
Electron Microscopy ◽  
Dynamic Equilibrium ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Microtubule Growth ◽  
Ray Patterns ◽  
Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

Preparation And elemental analysis of ancient fibers

1987 ◽  
Vol 45 ◽  
pp. 410-411
Author(s):  
Allen Angel ◽  
Kathryn A. Jakes
Keyword(s):  
Cross Sections ◽  
Physical Structure ◽  
Energy Dispersive ◽  
Archaeological Sites ◽  
X Ray ◽  
Long Term Storage ◽  
Backscattered Electron ◽  
Electron Imaging

Fabrics recovered from archaeological sites often are so badly degraded that fiber identification based on physical morphology is difficult. Although diagenetic changes may be viewed as destructive to factors necessary for the discernment of fiber information, changes occurring during any stage of a fiber's lifetime leave a record within the fiber's chemical and physical structure. These alterations may offer valuable clues to understanding the conditions of the fiber's growth, fiber preparation and fabric processing technology and conditions of burial or long term storage (1).Energy dispersive spectrometry has been reported to be suitable for determination of mordant treatment on historic fibers (2,3) and has been used to characterize metal wrapping of combination yarns (4,5). In this study, a technique is developed which provides fractured cross sections of fibers for x-ray analysis and elemental mapping. In addition, backscattered electron imaging (BSI) and energy dispersive x-ray microanalysis (EDS) are utilized to correlate elements to their distribution in fibers.

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