Star formation metal-enhanced

The resulting [Ca/Fe] versus [Fe/H] plot is shown in Fig. 1, where except for a few outliers that will have to be manually inspected, a clear trend appears [Ca/Fe] slowly rises with [Fe/H] until it reaches a maximum and then declines again for the most metal-rich stars (RGB-a according to [4]). This nicely confirms a previous finding by [8] and [9]. If the metal-rich stars have evolved within the cluster in a process of self-enrichment, the only way to lower their a-enhancement would be SNe type la intervention. No simple explanation is provided for the rise of [Ca/Fe] at low [Fe/H], although a series of star formation bursts should be the likely cause. 

Some of these problems are addressed in the inverse wind scenario of Pipino and Matteucci (2004), in which they allow for inflow and assume ad hoc that, the higher the mass of the galaxy, the shorter the infall and especially the star formation timescales. This makes the more massive objects older, in the sense that star formation is stopped by a terminal wind at earlier times, permitting enhanced metallicities and a/Fe ratios in the framework of the classical Salpeter(O.l) IMF. Abundance gradients within elliptical galaxies are reproduced within their very considerable uncertainties by an outside-in scenario in which star formation... 

The comparison of coronal and photospheric abundances in cool stars is a very important tool in the interpretation of the physics of the corona. Active stars show a very different pattern to that followed by low activity stars such as the Sun, being the First Ionization Potential (FIP) the main variable used to classify the elements. The overall solar corona shows the so-called FIP effect the elements with low FIP (<10 eV, like Ca, N, Mg, Fe or Si), are enhanced by a factor of 4, while elements with higher FIP (S, C, O, N, Ar, Ne) remain at photospheric levels. The physics that yields to this pattern is still a subject of debate. In the case of the active stars (see [2] for a review), the initial results seemed to point towards an opposite trend, the so called Inverse FIP effect , or the MAD effect (for Metal Abundance Depletion). In this case, the elements with low FIP have a substantial depletion when compared to the solar photosphere, while elements with high FIP have same levels (the ratio of Ne and Fe lines of similar temperature of formation in an X-ray spectrum shows very clearly this effect). However, most of the results reported to date lack from their respective photospheric counterparts, raising doubts on how real is the MAD effect. 

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