3 years ago

H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522.

M. Shetrone, D. Minniti, D. A. García-Hernández, R. Carrera, A. Almeida, R. J. Oelkers, S. R. Majewski, G. Zasowski, Sz. Mészáros, B. Tang, R. R. Lane, J. Sobeck, A. Rojas-Arriagada, S. Villanova, A. J. Burgasser, D. R. G. Schleicher, F. R. Hearty, D. Geisler, F. Dell'Agli, R. E. Cohen, J. Alonso-Garcia, T. Masseron, A. Manchado, Diogo Souto, A. Roman-Lopes, K. Cunha, R. P. Schiavon, P. Longa-Peña, R. E. Mennickent, Inese I. Ivans, F. Santana, T. C. Beers, O. Zamora, Sten Hasselquist, M. Schultheis, J. Schiappacasse Ulloa, J. G. Fernández-Trincado

We present elemental abundance analysis of high-resolution spectra for five giant stars, deriving Fe, Mg, Al, C, N, O, Si and Ce abundances, and spatially located within the innermost regions of the bulge globular cluster NGC 6522, based on H-band spectra taken with the multi-object APOGEEnorth spectrograph from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Of the five cluster candidates, four stars are confirmed to have second-generation (SG) abundance patterns, with the basic pattern of depletion in C and Mg simultaneous with enrichment in N and Al as seen in other SG globular cluster populations at similar metallicity. In agreement with the most recent optical studies, the NGC 6522 stars analyzed exhibit (when available) only mild overabundances of the s-process element Ce, contradicting the idea of the NGC 6522 stars being formed from gas enriched by spinstars and indicating that other stellar sources such as massive AGB stars could be the primary intra-cluster medium polluters. The peculiar abundance signature of SG stars have been observed in our data, confirming the presence of multiple generations of stars in NGC 6522.

Publisher URL: http://arxiv.org/abs/1801.07136

DOI: arXiv:1801.07136v1

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