Bibcode
Tang, B.; Cohen, Roger; Geisler, Douglas; Schiavon, Ricardo P.; Majewski, Steven R.; Villanova, Sandro; Carrera, R.; Zamora, O.; Garcia-Hernandez, D.; Shetrone, Matthew D.; Frinchaboy, Peter M.; Fernandez Trincado, Jose Gregorio; APOGEE Team
Bibliographical reference
American Astronomical Society, AAS Meeting #229, id.221.03
Advertised on:
1
2017
Citations
0
Refereed citations
0
Description
Multiple populations revealed in globular clusters (GCs) are important
windows to the formation and evolution of these stellar systems. The
metal-rich GCs in the Galactic bulge are an indispensable part of this
picture, but the high optical extinction in this region has prevented
extensive research. In this work, we use the high resolution
near-infrared (NIR) spectroscopic data from APOGEE to study the chemical
abundances of NGC 6553, which is one of the most metal-rich bulge GCs.
We identify ten red giants as cluster members using their positions,
radial velocities, iron abundances, and NIR photometry. Our sample stars
show a mean radial velocity of -0.14 km/s, and a mean [Fe/H] of -0.15.
We clearly separate two populations of stars in C and N in this GC for
the first time. NGC 6553 is the most metal-rich GC where the multiple
stellar population phenomenon is found until now. Substantial chemical
variations are also found in Na, O, and Al. However, the two populations
show similar Si, Ca, and iron-peak element abundances. Therefore, we
infer that the CNO, NeNa, and MgAl cycles have been activated, but the
MgAl cycle is too weak to show its effect on Mg. The Si leakage from the
MgAl cycle is negligible. Type Ia and Type II supernovae do not seem to
have significantly polluted the second generation stars. Comparing the
APOGEE results with other GC studies, we find that NGC 6553 shows
similar chemical variations as other relatively metal-rich GCs. We also
confront current GC formation theories with our results, and suggest
possible avenues for improvement in the models.