Planetary nebulae in the Small Magellanic Cloud

Abstract

We analyse the planetary nebulae (PNe) population of the Small Magellanic Cloud (SMC), based on evolutionary models of stars with metallicities in the range 10 −3 ≤ Z ≤ 4 × 10 −3 and mass 0.9 M < M < 8 M , evolved through the asymptotic giant branch (AGB) phase. The models used account for dust formation in the circumstellar envelope. To characterise the PNe sample of the SMC, we compare the observed abundances of the various species with the final chemical composition of the AGB models: this study allows us to identify the progenitors of the PNe observed, in terms of mass and chemical composition. According to our interpretation, most of the PNe descend from low-mass (M < 2M ) stars, which become carbon rich, after experiencing repeated third dredge-up episodes, during the AGB phase. A fraction of the PNe showing the signature of advanced CNO processing are interpreted as the progeny of massive AGB stars, with mass above ∼ 6M , undergoing strong hot bottom burning. The differences with the chemical composition of the PNe population of the Large Magellanic Cloud (LMC) is explained on the basis of the diverse star formation history and age-metallicity relation of the two galaxies. The implications of the present study for some still highly debated points regarding the AGB evolution are also commented.

Chemodynamics of newly identified giants with a globular cluster like abundance patterns in the bulge, disc, and halo of the Milky Way

“…In this work, we have selected a sub-sample of metal-poor ([Fe/H] < ∼ −0.7) red giants in the first Payne data release of APO-GEE abundances (Ting et al 2018, hereafter Payne-APOGEE) that satisfy the following quality cuts to further ensure reliable parameter/abundance derivation:…”

“…The Payne routine (see Ting et al 2018) simultaneously derives best-fit values for all atmospheric parameters and abundances using neural networks, with the parameter space of the training set restricted to [Fe/H] > ∼ − 1.5. For the same reason as in Fernández-Trincado et al (2016b and Schiavon et al (2017a), we remove stars with [C/Fe] > +0.15, because such stars are not typically found in globular clusters, and we want to minimize the contamination by objects such as CH stars (e.g., Karinkuzhi & Goswami 2015), leaving us with a total of 6,289 giants with metallicities in the range −1.5 < [Fe/H] < −0.7.…”

“…Atmospheric parameters from spectroscopy: In order to provide a consistent chemical analysis, we re-determine the chemical abundances assuming as input the effective temperature (T eff ), surface gravity (log g), and metallicity ([Fe/H]) as derived by the Payne-APOGEE runs (see e.g., Ting et al 2018).…”

An investigation of C, N, and Na abundances in red giant stars of the Sculptor dwarf spheroidal galaxy

“…In order to explain these light element abundance variations, several types of stars have been proposed as possible polluters. The most popu-lar are intermediate-mass asymptotic giant branch (AGB) stars D'Antona et al 1983;Ventura et al 2001) and/or super-AGB stars (Pumo et al 2008;Ventura & D'Antona 2011;D'Antona et al 2016), supermassive stars (Denissenkov & Hartwick 2013) and fast rotating massive stars (FRMS) (Norris 2004;Maeder & Meynet 2006;Decressin et al 2007Decressin et al , 2009). These stars allow a hot H-burning environment, a mechanism to bring the processed material to the surface (convection and rotational mixing for AGBs and FRMS, respectively), and a way to release this material into the intra-cluster medium at a velocity sufficiently low to avoid escaping from the cluster potential well.…”

Effects of the Metallicity on Li and B Production in Supernova Neutrino Process

“…The neutrino spallation process of He and C in massive stars during Type II supernovae (SNe II) explosions contributes to the production of 7 Li and 11 B in the Galaxy [1,2]. This process, as well as the 3 He(α,γ) 7 Be reaction [3,4] in asymptotic giant branch stars [5], red giants [6], and novae [7], and the production of LiBeB isotopes in cosmic ray nucleosynthesis via the spallation of CNO and α + α fusion [8,9], is, therefore, important in Galactic chemical evolution of light elements. SN explosions are energized by neutrinos emitted from the proto-neutron star (NS), and neutrino reactions with nuclei in the stellar interior produces a number of rare stable nuclei including 7 Li, 11 B, 138 La, and 180 Ta [1,2,10] as well as short-lived nuclei 92 Nb and 98 Tc [11][12][13].…”