A New Test of Copper and Zinc Abundances in Late-type Stars Using Ultraviolet Cu ii and Zn ii Lines*

Roederer, Ian U.; Barklem, P. S.

doi:10.3847/1538-4357/aab71f

Cited by 34 publications

(49 citation statements)

References 97 publications

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“…As for Cu, on the assumption that the lines of the majority species in the stellar atmosphere, Znii, are formed under condition that are close to LTE, then the difference of abundance between Znii and Zni can be taken as a proxy of the NLTE correction that has to be applied to the abundances derived from the Zni. For all the sample of of Roederer & Barklem (2018) the abundances derived from the two ions are very similar, implying small NLTE corrections, in agreement with the computations of Takeda et al (2005). For Fe the NLTE corrections at [Fe/H]≈ −2.0 are expected to be less than 0.1 dex for giants with log g ≥ 2.0 (Mashonkina et al 2016).…”

Section: Bd +80 • 245: the Key Element Znsupporting

confidence: 88%

“…Bonifacio et al (2010) have also shown that the UV resonance lines are strongly affected by granulation effects that go in the opposite direction: 3D corrections to the Cu abundance are always neg-5 https://koa.ipac.caltech.edu/ ative, while NLTE corrections are always positive. At the present time we are not able to perform a full 3D-NLTE computation, but we can gain some insight from the work of Roederer & Barklem (2018). Since Cuii is the majority species in the atmospeheres of these stars, we can assume that its lines form in conditions that are close to LTE, thus the difference between the LTE abundance of Cuii and that of Cui can be taken as a proxy of the NLTE correction for Cui.…”

Section: Bd +80 • 245: the Key Element Cumentioning

confidence: 99%

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Probing the existence of very massive first stars

Salvadori

Bonifacio

Caffau

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present a novel approach aimed at identifying the key chemical elements to search for the (missing) descendants of very massive first stars exploding as Pair Instability Supernovae (PISN). Our simple and general method consists in a parametric study accounting for the unknowns related to early cosmic star-formation and metalenrichment. Our approach allow us to define the most likely [Fe/H] and abundance ratios of long-lived stars born in inter-stellar media polluted by the nucleosynthetic products of PISN at a > 90%, 70%, and 50% level. In agreement with previous works, we show that the descendants of very massive first stars can be most likely found at [Fe/H]≈ −2. Further, we demonstrate that to search for an under-abundance of [(N, Cu, Zn)/Fe]< 0 is the key to identify these rare descendants. The "killing elements" N, Zn, and Cu are not produced by PISN, so that their sub-Solar abundance with respect to iron persists in environments polluted by further generations of normal core-collapse supernovae up to a 50% level. We show that the star BD +80 • 245, which has [Fe/H]= −2.2, [N/Fe]= −0.79, [Cu/Fe]= −0.75, and [Zn/Fe]= −0.12 can be the smoking gun of the chemical imprint from very massive first stars. To this end we acquired new spectra for BD +80 • 245 and re-analysed those available from the literature accounting for Non-Local Thermodynamic Equilibrium corrections for Cu. We discuss how to find more of these missing descendants in ongoing and future surveys to tightly constrain the mass distribution of the first stars.

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Section: Bd +80 • 245: the Key Element Znsupporting

confidence: 88%

Section: Bd +80 • 245: the Key Element Cumentioning

confidence: 99%

Probing the existence of very massive first stars

Salvadori

Bonifacio

Caffau

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Bergemann & Gehren 2008;Bergemann 2011;Hansen et al 2013), so we favor the abundances and ratios derived from lines of their ions. The [Cu/Fe] ratio, derived from one Cu i line, likely underestimates the true value by a few tenths of a dex (Korotin et al 2018;Roederer & Barklem 2018). Most heavy elements are detected in ionization states that represent a substantial fraction, if not a majority, of all atoms of each element.…”

Section: Abundance Analysismentioning

confidence: 99%

The R-Process Alliance: A Comprehensive Abundance Analysis of HD 222925, a Metal-poor Star with an Extreme R-process Enhancement of [Eu/H] = −0.14*

Roederer¹,

Sakari²,

Placco³

et al. 2018

ApJ

Self Cite

113

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We present a detailed abundance analysis of the bright (V = 9.02), metal-poor ([Fe/H] = −1.47 ± 0.08) field red horizontal-branch star HD 222925, which was observed as part of an ongoing survey by the R-Process Alliance. We calculate stellar parameters and derive abundances for 46 elements based on 901 lines examined in a high-resolution optical spectrum obtained using the Magellan Inamori Kyocera Echelle spectrograph. We detect 28 elements with 38 ≤ Z ≤ 90; their abundance pattern is a close match to the Solar r -process component. The distinguishing characteristic of HD 222925 is an extreme enhancement of r -process elements ([Eu/Fe] = +1.33 ± 0.08, [Ba/Eu] = −0.78 ± 0.10) in a moderately metal-poor star, so the abundance of r -process elements is the highest ([Eu/H] = −0.14 ± 0.09) in any known r -process-enhanced star. The abundance ratios among lighter (Z ≤ 30) elements are typical for metal-poor stars, indicating that production of these elements was dominated by normal Type II supernovae, with no discernible contributions from Type Ia supernovae or asymptotic giant branch stars. The chemical and kinematic properties of HD 222925 suggest it formed in a low-mass dwarf galaxy, which was enriched by a high-yield r -process event before being disrupted by interaction with the Milky Way.

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“…Atmosphere parameters of the program stars were taken from Roederer & Barklem (2018). Those parameters are listed in Table 2.…”

Section: Copper Abundance Analysismentioning

confidence: 99%

Copper abundance from Cu i and Cu ii lines in metal-poor star spectra: NLTE versus LTE

Коротин

Andrievsky

Zhukova

2018

Monthly Notices of the Royal Astronomical Society

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We checked consistency between the copper abundance derived in six metal-poor stars using UV Cu ii lines (which are assumed to form in LTE) and UV Cu i lines (treated in NLTE). Our program stars cover the atmosphere parameters which are typical for intermediate temperature dwarfs (effective temperature is in the range from approximately 5800 to 6100 K, surface garvity is from 3.6 to 4.5, metallicity is from about -1 to -2.6 dex). We obtained a good agreement between abundance from these two sets of the lines, and this testifies about reliability of our NLTE copper atomic model. We confirmed that no underabundace of this element is seen at low metallicities (the mean [Cu/Fe] value is about -0.2 dex, while as it follows from the previous LTE studies copper behaves as a secondary element and [Cu/Fe] ratio in the range of [Fe/H from -2 to -3 dex should be about -1 dex). According to our NLTE data the copper behaves as a primary element at low metallicity regime. We also conclude that our new NLTE copper abundance in metal-poor stars requires significant reconsideration of this element yields in the explosive nucleosynthesis.

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A New Test of Copper and Zinc Abundances in Late-type Stars Using Ultraviolet Cu ii and Zn ii Lines*

Cited by 34 publications

References 97 publications

Probing the existence of very massive first stars

Probing the existence of very massive first stars

The R-Process Alliance: A Comprehensive Abundance Analysis of HD 222925, a Metal-poor Star with an Extreme R-process Enhancement of [Eu/H] = −0.14*

Copper abundance from Cu i and Cu ii lines in metal-poor star spectra: NLTE versus LTE

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