Neutron-Capture Element Abundances in Planetary Nebulae

Abstract

Nebular spectroscopy is a valuable tool for assessing the production of heavy elements by slow neutron(n)-capture nucleosynthesis (the s-process). Several transitions of n-capture elements have been identified in planetary nebulae (PNe) in the last few years, with the aid of sensitive, high-resolution, near-infrared spectrometers. Combined with optical spectroscopy, the newly discovered near-infrared lines enable more accurate abundance determinations than previously possible, and provide access to elements that had not previously been studied in PNe or their progenitors. Neutron-capture elements have also been detected in PNe in the Sagittarius Dwarf galaxy and in the Magellanic Clouds. In this brief review, I discuss developments in observational studies of s-process enrichments in PNe, with an emphasis on the last five years, and note some open questions and preliminary trends.

Planetary Nebulae: Sources of Enlightenment

“…The production of s-process elements in AGB stars is discussed in detail by Karakas & Lattanzio (2014, Section 3.7). In addition, readers can find a detailed review of neutroncapture element abundances in PNe in Sterling (2020a). For now we will briefly summarize the present picture.…”

Observing the signatures of AGB s-process nucleosynthesis in planetary nebulae: An origins story

“…These new lines were discovered at spectral resolving powers of R ≥ 30,000, rendering even weak lines visible against the continuum. Meanwhile, detections of optical emission lines of trans-iron elements have been accumulating in the literature (e.g., Sterling 2020;Kwitter and Henry 2022;Manea et al, 2022).…”

Accurate new atomic data for Galactic Surveys

“…Noble gases such as Ar have been observed in the Crab nebula as a molecular ion (Barlow et al (2013)). In the field of planetary nebulae, analysis of near-infrared emission spectra revealed the presence of Kr and Xe (Sterling (2020), Sterling et al (2017)).…”