X-ray spectra of the Fe-L complex

Abstract

The Hitomi results for the Perseus cluster have shown that accurate atomic models are essential to the success of X-ray spectroscopic missions and just as important as the store of knowledge on instrumental calibration and astrophysical modeling. Preparing the models requires a multifaceted approach, including theoretical calculations, laboratory measurements, and calibration using real observations. In a previous paper, we presented a calculation of the electron impact cross sections on the transitions forming the Fe-L complex. In the present work, we systematically tested the calculation against cross-sections of ions measured in an electron beam ion trap experiment. A two-dimensional analysis in the electron beam energies and X-ray photon energies was utilized to disentangle radiative channels following dielectronic recombination, direct electron-impact excitation, and resonant excitation processes in the experimental data. The data calibrated through laboratory measurements were further fed into a global modeling of the Chandra grating spectrum of Capella. We investigated and compared the fit quality, as well as the sensitivity of the derived physical parameters to the underlying atomic data and the astrophysical plasma modeling. We further list the potential areas of disagreement between the observations and the present calculations, which, in turn, calls for renewed efforts with regard to theoretical calculations and targeted laboratory measurements.

The Metal Content of the Hot Atmospheres of Galaxy Groups

“…Nevertheless, RGS offers the unique advantage to reveal a glimpse of the main transitions populating the Fe-L complex at groups (and clusters) temperature regime(s). This is particularly essential, not only to refine our science prediction expected with micro-calorimeter instruments, like Resolve onboard XRISM (Section 4.2), but also to pursue the improvement of our spectral models in this crucial spectral band even before the release of XRISM, particularly by comparing updated atomic calculations with (i) laboratory measurements and (ii) state-of-the-art observational data [203,204].…”

“…Due to the relatively modest spatial resolution (with a HPD of 1.7 arcmin) and effective area, XRISM observations are ideally suited for studying the centers of nearby clusters and groups. Using these targets, together with dedicated laboratory measurements driven by these new observations (e.g., Reference [204,320]), it is expected that remaining uncertainties and differences between AtomDB and SPEXACT in modeling the Fe-L line emission will be ironed out early during the lifetime of the mission, whose expected launch is currently set for Japanese fiscal year 2022.…”

The metal content of the hot atmospheres of galaxy groups

“…This is particularly essential, not only to refine our science prediction expected with micro-calorimeter instruments like Resolve onboard XRISM (Sect. 4.2), but also to pursue the improvement of our spectral models in this crucial spectral band even before the release of XRISM, particularly by comparing updated atomic calculations with (i) laboratory measurements and (ii) state-of-the-art observational data (Gu et al, 2019(Gu et al, , 2020.…”

Observations of bright stars with AstroSat soft X-ray telescope

“…Capella has been studied quite extensively with a similarly low resolution CCD in the ASCA observatory (Brickhouse et al 2000) and also with very high spectral resolution instruments like Low Energy Transmission Grating (LETG) and High Energy Transmission Gratings (HETG) aboard Chandra Xray Observatory (Gu et al 2006;Raassen & Kaastra 2007). It is known to have a very complex X-ray spectrum that has been used to refine atomic data used in the plasma codes and also shows long term variations of $ 30-50% (Brickhouse et al 2000;Gu et al 2006;Raassen & Kaastra 2007;Gu et al 2020). In almost all these studies, one sees a continuous distribution of emission measures with a range of temperatures from very low (kT = 0.3 keV) to very high (kT = 4 keV) (Gu et al 2006;Raassen & Kaastra 2007), with two peaks: one at kT $ 0.55-0.70 keV and another broader peak at kT $ 1.7-2.2 keV.…”