tokens: et al. 2017 ). This implies that low- and intermediate-mass stars in such a late evolutionary phase are often old and hence metal-poor on average. The distributions of [Fe/H] and [S, Zn/H] are very similar in the LMC and in our Galaxy (see Fig. 7 ), indicating that depletion and hence dust-gas segregation and subsequent gas accretion, is very similar in both environments. On average the LMC has a lower metallicity than the Galaxy but it does not affect the efficiency of the depletion process. Additionally, in none of the systems, there is an evidence that the abundances of the s-process elements, systematically deviate from the abundance of elements with similar dust-condensation temperature. A good tracer of the depletion which is independent of the initial metallicity is the [Zn/Ti] abundance ratio. Zn and Ti are both Fe-peak elements and have the same nucleosynthetic history. If only nucleosynthesis determines the abundances ratios, (i.e. no selective depletion of elements), then [Zn/Ti] will remain zero. Since Ti is likely to be more strongly depleted than Zn, [Zn/Ti] is an ideal indicator of depletion. Therefore, we define the efficiency of depletion as a function of [Zn/Ti]. In principle [Zn/Fe] can also be used as a proxy for depletion; however, Ti has a higher dust condensation temperature and hence more easily depleted than Fe. So we define the efficiency of depletion as a function of [Zn/Ti]. Strongly depleted sources are defined such that [Zn/Ti] ≳ 1.5. Mildly depleted sources are defined as those with 0.5 ≲ [Zn/Ti] ≲ 1.5 while sources with [Zn/Ti] ≲ 0.5 are considered to show little or no depletion. In Fig. 8 we show the spread in [Zn/Ti] abundance ratios as a function of T eff for the LMC post-AGB sources (left-hand panel) and the depleted Galactic sources (right-hand panel). We find that the LMC as well as Galactic post-AGB stars show a large spread in depletion patterns, ranging from strongly depleted to stars with mild and no depletion. The plots also show that there is no clear trend in the efficiency of depletion with respect to T eff . The advantage of the LMC sample is their accurately derived luminosities. The derived photospheric luminosities of the LMC sample of depleted objects show that chemical depletion is active over a range of luminosities (see Section 5 and Fig. 8 , left-hand panel). Hence we can conclude that there is also no clear trend in the efficiency of depletion with respect to luminosity ( L ph ) of the star. Figure 8. Left: The [Zn/Ti] abundance as a function of T eff for the depleted sources in the LMC. Right: The [Zn/Ti] abundance as a function of T eff for the depleted post-AGB stars in the LMC (black filled circles) and their Galactic analogues (magenta filled squares). The dashed line represents the limit of what we call ‘strongly depleted’ while the dotted line marks our definition of ‘mild depletion’. In the case of the Galactic sources, majority of these objects show the presence of a stable
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