Linemake: An Atomic and Molecular Line List Generator

The goals of this study are 1) to test the best theoretical transition probabilities for Ca I (a relatively light alkaline earth spectrum) from a modern ab initio calculation using configuration interaction plus many body perturbation theory against the best modern experimental transition probabilities, and 2) to produce as accurate and comprehensive a line list of Ca I transition probabilities as is currently possible based on this comparison. We report new Ca I radiative lifetime measurements from a laser-induced fluorescence (LIF) experiment and new emission branching fraction measurements from a 0.5 m focal length grating spectrometer with a detector array. We combine these data for upper levels that have both a new lifetime and new branching fractions to report log(gf)s for two multiplets consisting of nine transitions. Detailed comparisons are made between theory and experiment, including the measurements reported herein and a selected set of previously published experimental transition probabilities. We find that modern theory compares favorably to experimental measurements in most instances where such data exist. A final list of 202 recommended transition probabilities is presented, which covers lines of Ca I with wavelengths ranging from 2200 -10,000 Å. These are mostly selected from theory, but are augmented with high quality experimental measurements from this work and from the literature. The recommended transition probabilities are used in a redetermination of the Ca abundance in the Sun and in the metal-poor star HD 84937.1.

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“…Facility: HST (STIS), VLT (UVES) Software: linemake (Placco et al 2021), MOOG (Sneden 1973), SPECTRE (Fitzpatrick & Sneden 1987).…”

Section: Acknowledgementsmentioning

confidence: 99%

Atomic Transition Probabilities of Neutral Calcium*

Hartog

Lawler

Sneden

et al. 2021

ApJS

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“…Chemical abundances are determined using the 1D local thermodynamic equilibrium (LTE) ATLAS12 52 model atmospheres and MOOG spectrum synthesis code 53,54 . The spectral lines examined are listed in Extended Data Table 4, including their equivalent width measurements and atomic data from linemake 55 . The abundance uncertainties are estimated from the stellar parameter uncertainties, added in quadrature with an equivalent width measurement uncertainty.…”

Section: Spectroscopymentioning

confidence: 99%

A stellar stream remnant of a globular cluster below the metallicity floor

Martin,

Venn,

Aguado

et al. 2022

Preprint

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“…For Fe I, Fe II, O I, Mg I, Ca I, and Ti I, we adopted the atomic data from Jönsson et al (2017) when available to ensure our stellar parameters and α-abundances are on the same scale as their results. The atomic data for other species (Na I, Al I, Si I, K I, Sc II, V I, Mn I, Ni I, Zn I, Y II, Ba II, La II, Ce II, Eu II) were taken from linemake (Placco et al 2021), which keeps upto-date libraries of experimentally measured oscillator strengths.…”

Section: Observations and Abundance Analysismentioning

confidence: 99%

Evidence from Disrupted Halo Dwarfs that $r$-process Enrichment via Neutron Star Mergers is Delayed by $\gtrsim500$ Myrs

Naidu,

Ji,

Conroy

et al. 2021

Preprint

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The astrophysical origins of r-process elements remain elusive. Neutron star mergers (NSMs) and special classes of core-collapse supernovae (rCCSNe) are leading candidates. Due to these channels' distinct characteristic timescales (rCCSNe: prompt, NSMs: delayed), measuring r-process enrichment in galaxies of similar mass, but differing star-formation durations might prove informative. Two recently discovered disrupted dwarfs in the Milky Way's stellar halo, Kraken and Gaia-Sausage Enceladus (GSE), afford precisely this opportunity: both have M ≈ 10 8 M , but differing star-formation durations of ≈2 Gyrs and ≈3.6 Gyrs. Here we present R ≈ 50, 000 Magellan/MIKE spectroscopy for 31 stars from these systems, detecting the r-process element Eu in all stars. Stars from both systems have similar [Mg/H]≈ −1, but Kraken has a median [Eu/Mg]≈ −0.1 while GSE has an elevated [Eu/Mg]≈ 0.2. With simple models we argue NSM enrichment must be delayed by 500 − 1000 Myrs to produce this difference. rCCSNe must also contribute, especially at early epochs, otherwise stars formed during the delay period would be Eu-free. In this picture, rCCSNe account for ≈ 50% of the Eu in Kraken, ≈ 25% in GSE, and ≈ 15% in dwarfs with extended star-formation durations like Sagittarius. The inferred delay time for NSM enrichment is 10 − 100× longer than merger delay times from stellar population synthesis -this is not necessarily surprising because the enrichment delay includes time taken for NSM ejecta to be incorporated into subsequent generations of stars. For example, this may be due to natal kicks that result in r-enriched material deposited far from star-forming gas, which then takes ≈ 10 8 − 10 9 years to cool in these galaxies.

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Linemake: An Atomic and Molecular Line List Generator

Cited by 74 publications

References 3 publications

Atomic Transition Probabilities of Neutral Calcium*

Atomic Transition Probabilities of Neutral Calcium*

A stellar stream remnant of a globular cluster below the metallicity floor

Evidence from Disrupted Halo Dwarfs that $r$-process Enrichment via Neutron Star Mergers is Delayed by $\gtrsim500$ Myrs

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