The Abundance of Fluorine in the Hyades, NGC 752, and M67

Nault, Kristie A.; Pilachowski, Catherine A.

doi:10.1088/0004-6256/146/6/153

Cited by 23 publications

(23 citation statements)

References 48 publications

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“…The choice of the value of the solar Our abundances show less scatter in the trends than many previous investigations (see, e.g, Recio-Blanco et al 2012;Pilachowski & Pace 2015;Jönsson et al 2017b). For the narrow metallicity range of the open cluster giants in Nault & Pilachowski (2013), our results agree very well, with a clear increase at super-solar values, see Figure 4. Furthermore, our new abundances based on the Phoenix spectra show slightly smaller scatter, and a tighter correlation, than those determined by Jönsson et al (2017b), who analysed the same spectra (see the small grey dots in Figure 4).…”

Section: Fluorine Abundances and Ratios Versus Metallicitysupporting

confidence: 77%

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Fluorine in the Solar Neighborhood: The Need for Several Cosmic Sources

Ryde

Jönsson

Mace

et al. 2020

ApJ

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The cosmic origin of fluorine is still not well constrained. Several nucleosynthetic channels at different phases of stellar evolution have been suggested, but these must be constrained by observations. For this, the fluorine abundance trend with metallicity spanning a wide range is required. Our aim is to determine stellar abundances of fluorine for −1.1 < [Fe/H] < +0.4. We determine the abundances from HF lines in infrared K-band spectra (∼ 2.3 µm) of cool giants, observed with the IGRINS and Phoenix high-resolution spectrographs. We derive accurate stellar parameters for all our observed K giants, which is important since the HF lines are very temperature sensitive. We find that [F/Fe] is flat as a function of metallicity at [F/Fe]∼ 0, but increases as the metallicity increases. The fluorine slope shows a clear secondary behavior in this metallicity range. We also find that the [F/Ce] ratio is relatively flat for −0.6 < [Fe/H] < 0, and that for two metal-poor ([Fe/H] < −0.8), s-process element enhanced giants, we do not detect an elevated fluorine abundance. We interpret all these observational constraints to indicate that several major processes are at play for the cosmic budget of fluorine over time; from those in massive stars at low metallicities, through the asymptotic giant branch-star contribution at −0.6 < [Fe/H] < 0, to processes with increasing yields with metallicity at super-solar metallicities. The origins of the latter, and whether or not Wolf-Rayet stars and/or novae could contribute at super-solar metallicities, is currently not known. To quantify these observational results, theoretical modelling is required. More observations in the metal-poor region are required to clarify the processes there.

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Section: Fluorine Abundances and Ratios Versus Metallicitysupporting

confidence: 77%

“…See also the discussion inNault & Pilachowski (2013) about this value and a reevaluation of it due to the problems with the excitation potential of HF, now solved(Jönsson et al 2014b) …”

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confidence: 99%

Fluorine in the Solar Neighborhood: The Need for Several Cosmic Sources

Ryde

Jönsson

Mace

et al. 2020

ApJ

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“…As long as the excitation energy and partition function are consistent, both energies can be used for abundance determinations. Otherwise, there will be an ∼0.3 dex difference in abundance, just as Lucatello et al (2011), D'Orazi et al (2013, and Nault & Pilachowski (2013) showed. Since it is unclear which partition function is used in most works, it is difficult to compare the resulting abundance values.…”

Section: Line Datamentioning

confidence: 89%

Chemical evolution of fluorine in the bulge

Jönsson

Ryde

Harper

et al. 2014

A&A

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Context. Possible main formation sites of fluorine in the Universe include asymptotic giant branch (AGB) stars, the ν-process in Type II supernova, and/or Wolf-Rayet stars. The importance of the Wolf-Rayet stars has theoretically been questioned and they are probably not needed in modeling the chemical evolution of fluorine in the solar neighborhood. It has, however, been suggested that Wolf-Rayet stars are indeed needed to explain the chemical evolution of fluorine in the bulge. The molecular spectral data, needed to determine the fluorine abundance, of the often used HF-molecule has not been presented in a complete and consistent way and has recently been debated in the literature. Aims. We intend to determine the trend of the fluorine-oxygen abundance ratio as a function of a metallicity indicator in the bulge to investigate the possible contribution from Wolf-Rayet stars. Additionally, we present here a consistent HF line list for the K-and L-bands including the often used 23 358.33 Å line. Methods. High-resolution near-infrared spectra of eight K giants were recorded using the spectrograph CRIRES mounted at the VLT. A standard setting was used that covered the HF molecular line at 23 358.33 Å. The fluorine abundances were determined using spectral fitting. We also re-analyzed five previously published bulge giants observed with the Phoenix spectrograph on Gemini using our new HF molecular data. Results. We find that the fluorine-oxygen abundance in the bulge probably cannot be explained with chemical evolution models that only include AGB stars and the ν-process in supernovae Type II, that is a significant amount of fluorine production in Wolf-Rayet stars is most likely needed to explain the fluorine abundance in the bulge. For the HF line data, we find that a possible reason for the inconsistencies in the literature, where two different excitation energies were used, is two different definitions of the zero-point energy for the HF molecule and therefore also two accompanying different dissociation energies. Both line lists are correct as long as the corresponding consistent partition function is used in the spectral synthesis. However, we suspect this has not been the case in several earlier works, which led to fluorine abundances ∼0.3 dex too high. We present a line list for the K-and L-bands and an accompanying partition function.

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“…In sharp contrast, the H-deficient spectroscopic binary KS Per has an upper limit to the F abundance consistent with its initial abundance (Pandey 2006) confirming expectations that massive hot binaries like KS Per have an entirely different evolutionary history to the EHes and their relatives. and RCB stars (Nault & Pilachowski 2013;Li et al 2013;Maiorca et al 2014;Jönsson et al 2014;Jönsson et al 2017;Guerço et al 2019). Current uncertainty in the F vs Fe relation in Galactic normal stars should not affect the comparison of compositions of EHe, RCB and HdC stars with theoretical evolutionary scenarios; the F overabundance, in particular, dwarfs the current uncertainty.…”

Section: Fluorine Enrichmentmentioning

confidence: 95%

Detection of Fluorine in Hot Extreme Helium Stars

Bhowmick

Pandey

Lambert

2020

ApJ

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The main objective of this paper is to explore abundances of fluorine in hot Extreme Helium Stars (EHes). Overabundance of fluorine is a characteristic feature for cool EHes and R Coronae Borealis (RCB) stars and further enforces their close connection. For hot EHes this relationship with the cooler EHes, based on their fluorine abundance is unexplored. We present in this paper the first abundance estimates of fluorine determined from singly ionised fluorine lines (F ii) for 10 hot EHe stars from optical spectra. Fluorine abundances were determined using the F ii lines in two windows centered at 3505Å and 3850Å. Six of the 10 stars show significant enhancement of fluorine similar to the cool EHes. Two carbon-poor hot EHes show no signature of fluorine and have a significant low upper limit for the F abundance. These fluorine abundances are compared with the other elemental abundances observed in these stars which provide an idea about the formation and evolution of these stars. The trends of fluorine with C, O, and Ne show that significant helium burning after a CO-He white dwarf merger can account for a majority of the observed abundances. Predictions from simulations of white dwarf mergers are discussed in light of the observed abundances. Fig. 7.-Observed F ii in 3500Å and 3850Å of HD 144941 (solid line) with key lines marked. Synthetic spectra are shown for four fluorine abundanes.Fig. 11.-Observed F ii in 3500Å and 3850Å of HD 124448 (solid line) with key lines marked. Synthetic spectra are shown for four fluorine abundanes.

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The Abundance of Fluorine in the Hyades, NGC 752, and M67

Cited by 23 publications

References 48 publications

Fluorine in the Solar Neighborhood: The Need for Several Cosmic Sources

Fluorine in the Solar Neighborhood: The Need for Several Cosmic Sources

Chemical evolution of fluorine in the bulge

Detection of Fluorine in Hot Extreme Helium Stars

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