L-SHELL DIELECTRONIC SATELLITE TRANSITIONS OF Fe XVII

Abstract

We have used the relativistic multi-reference Møller-Plesset perturbation theory to calculate the positions of the dielectronic satellite transitions involving doubly excited 3 3 configurations that are associated with the X-ray spectrum of Fe xvii. A comparison of these positions with the wavelengths employed in astrophysical modeling codes shows discrepancies of up to 36 mÅ. Inspection of the spectrum of Capella recorded with the high energy transmission grating on the Chandra X-Ray Observatory reveals several features enhanced by Fe xvi lines formed by dielectronic recombination, one of which may be of future diagnostic use as it is fairly well isolated and in large part formed by dielectronic recombination.

Comprehensive Laboratory Measurements Resolving the LMM Dielectronic Recombination Satellite Lines in Ne-like Fe xvii Ions

“…These differences highlight how crucial laboratory measurements are for testing different spectral models. This is important not only from the perspective of upcoming X-ray satellite missions XRISM (Tashiro et al 2018) and Athena (Barret et al 2016), which will soon provide high-resolution spectra using X-ray microcalorimeters (Durkin et al 2019), but also for interpreting available high-resolution spectra from the operating Chandra and XMM-Newton observatories (Gu et al 2020) needed for reliable plasma diagnostics (Beiersdorfer et al 2014(Beiersdorfer et al , 2018 4 with additional data provided by Nilsen (1989) and Beiersdorfer et al (2014).…”

“…It is thus crucial to accurately know these dielectronic satellites when diagnosing temperatures using collisional-radiative models (Savin & Laming 2002;Dudík et al 2019), such as AtomDB (Foster et al 2012) and SPEX (Kaastra et al 1996), or with the help of atomic databases like CHIANTI (Dere et al 2019) and OPEN-ADAS. 1 Except for direct observation of DR 3l5l and 3l6l satellites in Fe XXII-XXIV (Gu et al 2001), no laboratory wavelengths or intensities of Fe DR L-shell satellites are available, as mentioned in Beiersdorfer et al (2014). Only recently have DR cross sections for the 3lnl series for Fe XVII been published, with the purpose of investigating the 3d → 2p and 3s → 2p line ratios above the collision excitation threshold (Shah et al 2019).…”

Irreducible tensor form for the spin-photon coupling

“…The major cause of the small values of matrix elements is the small ν. To make ν large the satellite lines are a good example, for their wavelengths can be less than 21 (Å) [6,8]. In order to use the transitions with ν ≥ 1 we need to modify the definition of amplitudes.…”

“…In addition, we show that H ex AME can be split in two separate parts. One part is traditional in the sense that it does not vanish if the multipole moment of order l ∈ N is nonzero for at least one fixed l, while the second one is more "exotic" in the sense that it can be nonzero only if the multipole moment is nonzero for at least two different l. The latter case arises when, for example, one considers electronic satellite transitions produced by electron capture and subsequent radiative decay [6][7][8][9][10].…”

K-shell Emission from O vi Near 19 Å

“…The powerful grating spectrometers on board the Chandra X-ray Observatory and the XMM-Newton satellites have enabled high-resolution spectroscopic observations of compact, X-ray-emitting objects. Early emission line spectra from stellar coronae showed more spectral lines than had been cataloged in existing line lists (Raassen et al 2002), and many laboratory measurements have since been performed to augment the spectral databases (e.g., Lepson et al 2002Lepson et al , 2003Lepson et al , 2008Desai et al 2009;Gu et al 2011;Beiersdorfer & Lepson 2012;Beiersdorfer et al 2013Beiersdorfer et al , 2014aTräbert et al 2018). Special attention has been focused on the X-ray region below 25 Å (Savin et al 1996;Brown et al 1998Brown et al , 2002Wargelin et al 1998;Drake et al 1999;Gu et al 2007;Hell et al 2016;Beiersdorfer et al 2017), which contains the K-shell emission of elements between oxygen and iron as well as the L-shell emission of iron and nickel and which had shown deficiencies in the available data already after the launch of ASCA (Drake et al 1994;Fabian et al 1994;White et al 1994).…”