tokens: can differ from a standard average value, depending on stochastically sampled explosions that have enriched a given galaxy. In addition, inhomogeneous mixing of gas results in different element abundance ratios in the next generation of stars. The same is true for other element abundance ratios, such as [Mg/Ca] or [Na/Mg]. Since there are model predictions of explosions of Pop iii stars, producing low [Na/Mg], we suggest them to be responsible for the low [Na/Mg] detected in MP stars. We failed to fit abundance patterns of any of our sample stars with a single nucleosynthesis event, however, we suggest that a small number of SN ii explosions including those with low [Na/Mg] contributed to the abundances found in the investigated stars. A comparison of observed relative [El/Mg] abundance ratios with nucleosynthesis predictions should be performed with a caution. We note that our sample stars are too metal rich to be fitted with yields from only one explosion. For each selected model, its metallicity is about [Fe/H]≃ −3, which is lower compared to that of the sample stars (−2.5 [Fe/H] −2.1). Magg et al. ( 2020 ) estimated analytically a limit for the dilution of metals produced by a single SN and recommended to account for not only element-to-element abundance ratios, but also the absolute abundance values when fitting stellar abundance patterns with nucleosynthesis yields. In their calculations, the following assumptions were adopted: the SN being alone and isolated, the explosions being spherical and well-mixed, and the surrounding medium being homogeneous. The latter assumption is not always fulfilled (see for example Chiaki Tominaga 2020 ). We also note that to date there is no a metal-poor star, whose extensive abundance pattern is reasonably well fitted with the yields from a single nucleosynthesis episode, despite many attempts that were made (see for example, Tominaga et al. 2007 ; Placco et al. 2015 ; Hansen et al. 2020a ). 5.3 Neutron-capture elements in classical and ultrafaint dwarf galaxies In the majority of EMP stars, n-capture elements are represented by Sr and Ba. A number of the Galactic studies reported on a large scatter of [Sr/Ba], of about 2 dex, which decreases with increasing [Ba/H] (Honda et al. 2004 ; François et al. 2007 ; Andrievsky et al. 2011 ). In classical dSphs, abundances of Sr and Ba at the lowest metallicity are at or below the lowest values in the MW halo, however, the [Sr/Fe] and [Ba/Fe] ratios increase toward the solar ratio as [Fe/H] increases, similarly to that for the MW halo (Cohen Huang 2009 , 2010 ; Jablonka et al. 2015 ; Mashonkina et al. 2017b ). Very low abundances of Sr and Ba were reported for the majority of UFDs (Frebel et al. 2010 ; Simon et al. 2010 ; Gilmore et al. 2013 ; Koch et al. 2013 ; Koch Rich 2014 ; Ji et al. 2016c , a ; Nagasawa et al. 2018 ). In the UFDs, the [Sr/Fe] and [Ba/Fe] ratios do not rise with metallicity, they scatter around a mean floor level of −1 and −0.7,
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula O O O O O O O O O O B-Formula I-Formula I-Formula B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O B-CelestialObjectRegion I-CelestialObjectRegion O O O O O O O O O O O O O O O O O O O B-CelestialObjectRegion I-CelestialObjectRegion B-Citation I-Citation I-Citation O B-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O