Abundances of neutron-capture elements in G 24-25

Liu, S.; Nissen, P. E.; Schuster, W. J.; Zhao, Gang; Chen, Y. Q.; Liang, Y. C.

doi:10.1051/0004-6361/201117909

Cited by 13 publications

(7 citation statements)

References 77 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Those works demonstrated that at low metallicities [hs/ls]∼1 can be obtained and that a good fit to a large number of s-process enriched CEMP stars can be found. In those calculations the 13 C pockets are artificially (Allen & Barbuy 2006, Smiljanic et al 2007, Liu et al 2009, Lebzelter et al 2013; open circles); CH stars (Smith et al 1993, Začs et al 2000, Goswami et al 2006, Pereira & Drake 2009, Goswami & Aoki 2010, Pereira & Drake 2011, Pereira et al 2012, Liu et al 2012, Karinkuzhi & Goswami 2014, Karinkuzhi & Goswami 2015, Goswami et al 2016; filled squares); CEMP-s stars (Preston & Sneden 2001, Aoki et al 2002b, Aoki et al 2002a, Lucatello 2004, Cohen et al 2006, Cohen et al 2013, Placco et al 2013, Roederer et al 2014; filled triangles); CEMP-rs stars (Aoki et al 2002c -25 -added after each TDU (with a constant mass extension) and the 13 C abundance is freely varied within the pockets (Gallino et al 1998). Within that framework, fits to observations are obtained with 13 C pockets characterized by very low 13 C abundances (see Figure 17 of Bisterzo et al 2011).…”

Section: The Cemp Casementioning

confidence: 99%

Constraints of the Physics of Low-Mass Agb Stars From Ch and Cemp Stars

Cristallo

Karinkuzhi

Goswami

et al. 2016

ApJ

View full text Add to dashboard Cite

We analyze a set of published elemental abundances from a sample of CH stars which are based on high resolution spectral analysis of ELODIE and SUBARU/HDS spectra. All the elemental abundances were derived from local thermodynamic equilibrium analysis using model atmospheres, and thus, they represent the largest homogeneous abundance data available for CH stars up to date. For this reason, we can use the set to constrain the physics and the nucleosynthesis occurring in low mass AGB stars. CH stars have been polluted in the past from an already extinct AGB companion and thus show s-process enriched surfaces. We discuss the effects induced on the -2 -surface AGB s-process distributions by different prescriptions for convection and rotation. Our reference theoretical FRUITY set fits only part of the observations. Moreover, the s-process observational spread for a fixed metallicity cannot be reproduced. At [Fe/H]>-1, a good fit is found when rotation and a different treatment of the inner border of the convective envelope are simultaneously taken into account. In order to increase the statistics at low metallicities, we include in our analysis a selected number of CEMP stars and, therefore, we compute additional AGB models down to [Fe/H]=-2.85. Our theoretical models are unable to attain the large [hs/ls] ratios characterizing the surfaces of those objects. We speculate on the reasons for such a discrepancy, discussing the possibility that the observed distribution is a result of a proton mixing episode leading to a very high neutron density (the so-called i-process).

show abstract

Section: The Cemp Casementioning

confidence: 99%

Constraints of the Physics of Low-Mass Agb Stars From Ch and Cemp Stars

Cristallo

Karinkuzhi

Goswami

et al. 2016

ApJ

View full text Add to dashboard Cite

show abstract

“…Thus, their low lithium abundance could be due to merging with a companion star causing Li-depleted gas to be mixed into the stellar atmosphere. The third star, G 24-25, is an s-process rich star probably due to mass transfer from a former AGB component (Liu et al 2012), which also brings Li-depleted gas into the atmosphere. HD 106516 and G 24-25 are singlelined spectroscopic binaries (Latham et al 2002;Ducati et al 2011) supporting the mass transfer hypothesis as an explanation of the abnormally low lithium abundance.…”

Section: Lithium Versus Mass and Heavy-element Fractionmentioning

confidence: 99%

Two distinct halo populations in the solar neighborhood

Nissen

Schuster

2012

A&A

Self Cite

View full text Add to dashboard Cite

Context. A previous study of F and G main-sequence stars in the solar neighborhood has revealed the existence of two distinct halo populations with a clear separation in [α/Fe] for the metallicity range −1.4 < [Fe/H] < −0.7. Taking into account the kinematics and ages of the stars, some Galactic formation models suggest that the "high-alpha" halo stars were formed in situ, whereas the "lowalpha" stars have been accreted from satellite galaxies. Aims. In this paper we investigate if there is a systematic difference in the lithium abundances of stars belonging to the high-and low-alpha halo populations. Methods. Equivalent widths of the Li i 6707.8 Å resonance line are measured from high resolution VLT/UVES and NOT/FIES spectra and used to derive Li abundances on the basis of MARCS model atmospheres. Furthermore, masses of the stars are determined from the log T eff -log g diagram by interpolating between evolutionary tracks based on Yonsei-Yale models.Results. There is no significant systematic difference in the lithium abundances of high-and low-alpha stars. For the large majority of stars with masses 0.7 < M/M < 0.9 and heavy-element mass fractions 0.001 < ∼ Z < 0.006, the lithium abundance is well fitted by a relation A(Li) = a 0 + a 1 M + a 2 Z + a 3 M Z, where a 0 , a 1 , a 2 , and a 3 are constants. Extrapolating this relation to Z = 0 leads to a lithium abundance close to the primordial value predicted from standard Big Bang nucleosynthesis calculations and the WMAP baryon density. The relation, however, does not apply to stars with metallicities below [Fe/H] −1.5. Conclusions. We suggest that metal-rich halo stars were formed with a lithium abundance close to the primordial value, and that lithium in their atmospheres has been depleted in time with an approximately linear dependence on stellar mass and Z. The lack of a systematic difference in the Li abundances of high-and low-alpha stars indicates that an environmental effect is not important for the destruction of lithium.

show abstract

“…Unfortunately, no Eu abundance is given for these stars. G 24-25 is a CH metal-poor subgiant ([Fe/H] = −1.4) studied by Liu et al (2012;yellow diamod), with a period of P = 3452 ± 67 days (Latham et al 2002).…”

mentioning

confidence: 99%