7 research outputs found
Advances in Atomic Data for Neutron-Capture Elements
Neutron(n)-capture elements (atomic number Z>30), which can be produced in
planetary nebula (PN) progenitor stars via s-process nucleosynthesis, have been
detected in nearly 100 PNe. This demonstrates that nebular spectroscopy is a
potentially powerful tool for studying the production and chemical evolution of
trans-iron elements. However, significant challenges must be addressed before
this goal can be achieved. One of the most substantial hurdles is the lack of
atomic data for n-capture elements, particularly that needed to solve for their
ionization equilibrium (and hence to convert ionic abundances to elemental
abundances). To address this need, we have computed photoionization cross
sections and radiative and dielectronic recombination rate coefficients for the
first six ions of Se and Kr. The calculations were benchmarked against
experimental photoionization cross section measurements. In addition, we
computed charge transfer (CT) rate coefficients for ions of six n-capture
elements. These efforts will enable the accurate determination of nebular Se
and Kr abundances, allowing robust investigations of s-process enrichments in
PNe.Comment: To be published in IAU Symp. 283: Planetary Nebulae, an Eye to the
Future; 2 page
Heasim and Skyback Simulation Tools and Their Application to the Hitomi Mission
We present an introduction to the heasim multimission observation and skyback background, high-energy pseudo Monte Carlo astrophysical simulation tools. Heasim may be used to accurately and efficiently construct flexible image transport system (FITS) event files for simple or composite sources with a wide range of standard and user-defined spatial, spectral, and temporal characteristics. Skyback is designed to enable users to assess the impact of background discrete and diffuse emission on prospective observations, and skyback output may be directly input into heasim. We present a brief overview of heasim and skyback input, algorithms, usage, and output. We also introduce the sxsbranch tool that computes Hitomi soft X-ray spectrometer resolution grade branching ratios, emphasizing its application to simulations. We include several examples of particular relevance to the Hitomi mission
Erratum: "Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium, the Chandra Grating Spectra of XTE J1817-330" (2013, Apj, 768, 60)
In the published version of this paper, there are some minor inaccuracies in the absorption-line wavelengths listed in Table 4 as a result of a faulty reduction procedure of the Obs6615 spectrum. The shifts have been detected in a comparison with the wavelengths listed for this spectrum in the Chandra Transmission Grating Catalog and Archive (TGCat8). They are due to incorrect centroid positions of the zero-order image in both reductions as determined by the tgdetect utility which, when disentangled, yield the improved line positions of the amended Table 4 given below. It must also be pointed out that other quantitative findings of the original paper: 1. Table 5, p. 9: the column density (NH), ionization parameter, oxygen abundance of the warmabs model and the normalization and photon index of the power-law model; 2. Table 6, p. 9: the hydrogen column density of the warmabs fit; 3. Table 7, p. 9: the present oxygen equivalent widths of XTE J1817-330; and 4. Table 8, p. 10: the present oxygen column densities of XTE J1817-330 derived from both the curve of growth and warmabs model fit have been revised in the new light and are, within the estimated uncertainty ranges, in good accord with the new rendering
The first cut is the cheapest: optimizing Athena/X-IFU-like TES detectors resolution by filter truncation
The X-ray Integral Field Unit (X-IFU) instrument on the future ESA mission Athena X-ray Observatory is a cryogenic micro-calorimeter array of Transition Edge Sensor (TES) detectors designed to provide spatially-resolved high-resolution spectroscopy. The onboard reconstruction software provides energy, spatial location and arrival time of incoming X-ray photons hitting the detector. A new processing algorithm based on a truncation of the classical optimal filter and called 0-padding, has been recently
proposed aiming to reduce the computational cost without compromising energy resolution. Initial tests with simple synthetic data displayed promising results. This study explores the slightly better performance of the 0-padding filter and assess its final application to real data. The goal is to examine the larger sensitivity to instrumental conditions that was previously observed during the analysis of the simulations. This 0-padding technique is thoroughly tested using more realistic simulations and real data acquired from NASA and NIST laboratories employing X-IFU-like TES detectors. Different fitting methods are applied to the data, and a comparative analysis is performed to assess the energy resolution values obtained from these fittings. The 0-padding filter achieves energy resolutions as good as those obtained with standard filters, even with those of larger lengths, across different line complexes and instrumental conditions. This method proves to be useful for energy reconstruction of X-ray photons detected by the TES detectors provided proper corrections for baseline drift and jitter effects are applied. The finding is highly promising especially for onboard processing, offering efficiency in computational resources and facilitating the análisis of sources with higher count rates at high resolution.Fondo Europeo de Desarrollo Regional (FEDER)Ministerio de Ciencia e Innovación (España)Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu
The XSTAR Atomic Database
We describe the atomic database of the XSTAR spectral modeling code,
summarizing the systematic upgrades carried out in the past twenty years to
enable the modeling of K lines from chemical elements with atomic number and recent extensions to handle high-density plasmas. Such plasma
environments are found, for instance, in the inner region of accretion disks
round compact objects (neutron stars and black holes), which emit rich
information about the system physical properties. Our intention is to offer a
reliable modeling tool to take advantage of the outstanding spectral
capabilities of the new generation of X-ray space telescopes (e.g., XRISM and
ATHENA) to be launched in the coming years. Data curatorial aspects are
discussed and an updated list of reference sources is compiled to improve the
database provenance metadata. Two XSTAR spin-offs -- the ISMabs absorption
model and the uaDB database -- are also described.Comment: 36 pages, 11 figure