Zinc abundances in galactic bulge stars

Zinc is overabundant in metal-poor stars (Cayrel et al. 2004), being partially produced by neutron addition. It decreases with increasing metallicity, similarly to alpha-elements. In order to trace its abundance, the derivation of Zn abundance in different stellar populations, and varying metallicities, helps understanding its nucleosynthesis processes. Zn is also the main element of reference to derive the metallicity from absorption lines in quasars (QSOs), which allows to compare their evolution as a function of redshift and metallicity in metal-poor stars. In the present work, we derive Zn abundances for a sample of 56 bulge field stars, observed at high resolution with the FLAMES-UVES spectrograph. The mean wavelength coverage is 4800-6800 ˚A, at a resolution R ∼ 45000. The atmospheric parameters effective temperature, gravity and metallicity were derived in Zoccali et al. (2008) and Hill et al. (2011). Recently we have analysed the manganese abundances of this sample (Barbuy et al. 2013). To compute the Zn abundances we use spectrum synthesis, for the lines ZnI 4810.53 and 6362.34 ˚A. the named q-Maxwellian model (Soares et al. 2006, Physica A, 364, 413), a power-law type distribution function that adjusts the distribution of the projected rotational velocity. Then we compare the different distributions of V sin i obtained for different B − V intervals with the distribution model using the Kolmogorov-Smirnov statistical test to find the best fit. Results revealed that, as overall trend, low B−V tends to exhibit q > 1 values while q < 1 for high B−V for all classes of stars under study. Specifically, this point indicates rotation distributions with long tails due to the percentage of stars with relatively high speed for low B − V , and tailless distributions for stars of high B − V . Furthermore, it is a general behavior that binaries present q values slightly higher than singles indicating that their rotation distributions are wider than the single ones. As another broad trend, binaries tend to have q < 1 values later than their fellow-colors. In addition, there exists an inversion point in B − V , from which q > 1 regime switches to q < 1 regime, that is higher the more evolved is the luminosity class