We calculated new estimates of the Delta VHBbump parameter for 15 Galactic Globular Clusters (GGCs) using accurate ground-based photometric data. We enlarged our sample with literature data and we obtained a sample of 62 GGCs covering a wide metallicity range (-2.16le [M/H]le -0.58 dex). To compare the data with the theory we used theoretical models from \citet{pie04} and two different metallicity scales. We found that the observed values are higher (˜0.4 mag) than the canonical predictions. Moreover, the discepancy increases in the \citet{ki03} metallicity scale and it decreases in the \citet{cg97} scale. We investigated also the impact of CNONa extreme mixture and higher He-enhanced abundance (Y=0.30). The use of these models is not in the direction to explain the observed discrepancy.
On the Galactic globular cluster Delta VHBbump parameter
DEGL'INNOCENTI, SCILLA;PRADA MORONI, PIER GIORGIO;
2010-01-01
Abstract
We calculated new estimates of the Delta VHBbump parameter for 15 Galactic Globular Clusters (GGCs) using accurate ground-based photometric data. We enlarged our sample with literature data and we obtained a sample of 62 GGCs covering a wide metallicity range (-2.16le [M/H]le -0.58 dex). To compare the data with the theory we used theoretical models from \citet{pie04} and two different metallicity scales. We found that the observed values are higher (˜0.4 mag) than the canonical predictions. Moreover, the discepancy increases in the \citet{ki03} metallicity scale and it decreases in the \citet{cg97} scale. We investigated also the impact of CNONa extreme mixture and higher He-enhanced abundance (Y=0.30). The use of these models is not in the direction to explain the observed discrepancy.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
