On the AGB stars of M 4: a robust disagreement between spectroscopic observations and theory

MacLean, B. T.; Campbell, Simon; Amarsi, A. M.; Nordlander, Thomas; Cottrell, P. L.; Silva, G. M. De; Lattanzio, John C.; Constantino, T.; D’Orazi, V.; Casagrande, Luca

doi:10.1093/mnras/sty2297

Cited by 13 publications

(11 citation statements)

References 84 publications

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“…: < δA(Na)> = -0.01 ± 0.04; with results from the infrared study by de Laverny & Recio-Blanco (2013a): < δA(Na)> = +0.11 ± 0.11 and with results fromMacLean et al (2018): < δA(Na)> = +0.04 ± 0.13. Our sodium abundances for ω Centauri are in agreement with the optical highresolution study bySmith et al (2000) having an average difference of < δA(Na)> = 0.03 ± 0.06.…”

supporting

confidence: 72%

Fluorine Abundances in the Globular Cluster M 4

Guerço,

Cunha,

Smith

et al. 2019

Preprint

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We present chemical abundances for the elements carbon, sodium, and fluorine in 15 red giants of the globular cluster M 4, as well as six red giants of the globular cluster ω Centauri. The chemical abundances were calculated in LTE via spectral synthesis. The spectra analyzed are high-resolution spectra obtained in the near-infrared region around λ2.3µm with the Phoenix spectrograph on the 8.1m Gemini South Telescope, the IGRINS spectrograph on the McDonald Observatory 2.7m Telescope, and the CRIRES spectrograph on the ESO 8.2m Very Large Telescope. The results indicate a significant reduction in the fluorine abundances when compared to previous values from the literature for M 4 and ω Centauri, due to a downward revision in the excitation potentials of the HF(1-0) R9 line used in the analysis. The fluorine abundances obtained for the M 4 red giants are found to be anti-correlated with those of Na, following the typical pattern of abundance variations seen in globular clusters between distinct stellar populations. In M 4, as the Na abundance increases by ∼+0.4 dex, the F abundance decreases by ∼-0.2 dex. A comparison with abundance predictions from two sets of stellar evolution models finds that the models predict somewhat less F depletion (∼-0.1 dex) for the same increase of +0.4 dex in Na.

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supporting

confidence: 72%

Fluorine Abundances in the Globular Cluster M 4

Guerço,

Cunha,

Smith

et al. 2019

Preprint

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“…As noted in Section 3, 6...376 is an asymptotic giant branch (AGB) star. There has been much discussion in the literature about differences in the abundances of stars on the AGB versus those on the RGB in globular clusters (Norris et al 1981;Campbell et al 2013Campbell et al , 2017MacLean et al 2016MacLean et al , 2018, in particular with respect to apparent differences in their derived metallicities and light element abundances (Lapenna et al 2016;Mucciarelli et al 2019). There are two related effects that are causing these discrepancies.…”

Section: Abundances On the Asymptotic Giant Branchmentioning

confidence: 99%

The GALAH Survey: Chemically tagging the Fimbulthul stream to the globular cluster ω Centauri

Simpson

Martell

Costa

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Using kinematics from Gaia and the large elemental abundance space of the second data release of the GALAH survey, we identify two new members of the Fimbulthul stellar stream, and chemically tag them to massive, multi-metallic globular cluster ω Centauri. Recent analysis of the second data release of Gaia had revealed the Fimbulthul stellar stream in the halo of the Milky Way. It had been proposed that the stream is associated with the ω Cen, but this proposition relied exclusively upon the kinematics and metallicities of the stars to make the association. In this work, we find our two new members of the stream to be metal-poor stars that are enhanced in sodium and aluminium, typical of second population globular cluster stars, but not otherwise seen in field stars. Furthermore, the stars share the s-process abundance pattern seen in ω Cen, which is rare in field stars. Apart from one star within 1.5 deg of ω Cen, we find no other stars observed by GALAH spatially near ω Cen or the Fimbulthul stream that could be kinematically and chemically linked to the cluster. Chemically tagging stars in the Fimbulthul stream to ω Cen confirms the earlier work, and further links this tidal feature in the Milky Way halo to ω Cen.

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“…Another still debated case is M4, for which the chemical analyses by MacLean et al (2016) and MacLean et al (2018) suggest a clear lack of 1P stars along the AGB (at variance with the RGB), while opposite results have been obtained by Lardo et al (2017), who found a comparable broadening of AGB and RGB sequences using the C UBI index sensitive to the light element abundances, and by Marino et al (2017), who detected the Na-O anticorrelation among the AGB stars using UVES-FLAMES spectra.…”

Section: Introductionmentioning

confidence: 95%

Confirming the Presence of Second-population Stars and the Iron Discrepancy along the AGB of the Globular Cluster NGC 6752^∗

Mucciarelli

Lapenna

Lardo

et al. 2019

ApJ

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Asymptotic giant branch (AGB) stars in the globular cluster NGC6752 have been found to exhibit some chemical peculiarities with respect to the red giant branch (RGB) stars. A discrepancy between [FeI/H] and [FeII/H] (not observed in RGB stars) has been detected adopting spectroscopic temperatures. Moreover, a possible lack of second-population stars along the AGB was claimed. The use of photometric temperatures based on (V-K) colors was proposed to erase this iron discrepancy. Also, ad hoc scenarios have been proposed to explain the absence of second-population AGB stars.Here we analyzed a sample of 19 AGB and 14 RGB stars of NGC6752 observed with the spectrographs UVES. The two temperature scales agree very well for the RGB stars while for the AGB stars there is a systematic offset of ∼100 K. We found that even if the photometric temperatures alleviate the iron discrepancy with respect to the spectroscopic ones, a systematic difference between [FeI/H] and [FeII/H] is still found among the AGB stars. An unexpected result is that the photometric temperatures do not satisfy the excitation equilibrium in the AGB stars. This suggests that standard 1D-LTE model atmospheres are unable to properly describe the thermal structure of AGB stars, at variance with the RGB stars.The use of photometric temperatures confirms the previous detection of second-population AGB stars in this cluster, with the presence of clear correlations/anticorrelations among the light element abundances. This firmly demonstrates that both first and second-population stars evolve along the AGB of NGC6752.Corresponding author: Alessio Mucciarelli alessio.mucciarelli2@unibo.it * Based on observations collected at the ESO-VLT under the programs 073.D-0211 and 095.D-0320.

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On the AGB stars of M 4: a robust disagreement between spectroscopic observations and theory

Cited by 13 publications

References 84 publications

Fluorine Abundances in the Globular Cluster M 4

Fluorine Abundances in the Globular Cluster M 4

The GALAH Survey: Chemically tagging the Fimbulthul stream to the globular cluster ω Centauri

Confirming the Presence of Second-population Stars and the Iron Discrepancy along the AGB of the Globular Cluster NGC 6752^∗

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On the AGB stars of M 4: a robust disagreement between spectroscopic observations and theory

Cited by 13 publications

References 84 publications

Fluorine Abundances in the Globular Cluster M 4

Fluorine Abundances in the Globular Cluster M 4

The GALAH Survey: Chemically tagging the Fimbulthul stream to the globular cluster ω Centauri

Confirming the Presence of Second-population Stars and the Iron Discrepancy along the AGB of the Globular Cluster NGC 6752∗

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Product

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Confirming the Presence of Second-population Stars and the Iron Discrepancy along the AGB of the Globular Cluster NGC 6752^∗