Gemini/Phoenix H-band analysis of the globular cluster AL 3^★

¹ Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil
e-mail: b.barbuy@iag.usp.br
² UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
³ IfA, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
⁴ Instituto de Astronomía, Universidad Nacional Autónoma de México, A. P. 106, 22800, Ensenada, B. C., Mexico
⁵ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile
⁶ Millennium Institute of Astrophysics, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
⁷ Departamento de Ciencias Fisicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernandez Concha 700, Las Condes, Santiago, Chile
⁸ Vatican Observatory, 00120 Vatican City State, Italy
⁹ Instituto de Alta Investigación, Sede Esmeralda, Universidad de Tarapacá, Av. Luis Emilio Recabarren 2477, Iquique, Chile
¹⁰ Università di Padova, Dipartimento di Fisica e Astronomia, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
¹¹ INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹² Universidade Federal do Rio Grande do Sul, Departamento de Astronomia, 15051, Porto Alegre 91501-970, Brazil

Received: 26 October 2020
Accepted: 9 February 2021

Abstract

Context. The globular cluster AL 3 is old and located in the inner bulge. Three individual stars were observed with the Phoenix spectrograph at the Gemini South telescope. The wavelength region contains prominent lines of CN, OH, and CO, allowing the derivation of C, N, and O abundances of cool stars.

Aims. We aim to derive C, N, O abundances of three stars in the bulge globular cluster AL 3, and additionally in stars of NGC 6558 and HP 1. The spectra of AL 3 allows us to derive the cluster’s radial velocity.

Methods. For AL 3, we applied a new code to analyse its colour-magnitude diagram. Synthetic spectra were computed and compared to observed spectra for the three clusters.

Results. We present a detailed identification of lines in the spectral region centred at 15 555 Å, covering the wavelength range 15 525–15 590 Å. C, N, and O abundances are tentatively derived for the sample stars.