From chemical abundance analysis of stars in the Sagittarius dwarf spheroidal galaxy ( Sgr ) , we conclude that the alpha-element deficiencies can not be due to the Type Ia supernova ( SNIa ) time-delay scenario of Tinsley ( 1979 ) .
Instead , the evidence points to low [ \alpha /Fe ] ratios resulting from an initial mass function ( IMF ) deficient in the highest mass stars .
The critical evidence is the 0.4 dex deficiency of [ O/Fe ] , [ Mg/Fe ] and other hydrostatic elements , contrasting with the normal trend of r-process [ Eu/Fe ] _ { r } with [ Fe/H ] .
Supporting evidence comes from the hydrostatic element ( O , Mg , Na , Al , Cu ) [ X/Fe ] ratios , which are inconsistent with iron added to the Milky Way ( MW ) disk trends .
Also , the ratio of hydrostatic to explosive ( Si , Ca , Ti ) element abundances suggests a relatively top-light IMF .
Abundance similarities with the LMC , Fornax and IC 1613 , suggest that their alpha-element deficiencies also resulted from IMFs lacking the most massive SNII .

For such a top-light IMF , the normal trend of r-process [ Eu/Fe ] _ { r } with [ Fe/H ] , as seen in Sgr , indicates that massive Type II supernovae ( \buildrel > \over { \sim } 30M _ { \odot } ) can not be major sources of r-process elements .

High [ La/Y ] ratios , consistent with leaky-box chemical evolution , are confirmed but \sim 0.3 dex larger than theoretical AGB predictions .
This may be due to the ^ { 13 } C pocket mass , or a difference between MW and Sgr AGB stars .
Sgr has the lowest [ Rb/Zr ] ratios known , consistent with low-mass ( \buildrel < \over { \sim } 2M _ { \odot } ) AGB stars near [ Fe/H ] = - 0.6 , likely resulting from leaky-box chemical evolution .

The [ Cu/O ] trend in Sgr and the MW suggest that Cu yields increase with both metallicity and stellar mass , as expected from Cu production by the weak s-process in massive stars .

Finally , we present an updated hfs line list , an abundance analysis of Arcturus , and further develop our error analysis formalism .