Abundances of P, S, and K in 58 bulge spheroid stars from APOGEE

¹ Universidade de São Paulo, IAG, Departamento de Astronomia, 05508-090 São Paulo, Brazil
² Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden
³ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁴ Instituto de Astrofísica de Canarias, C/Via Lactea s/n, 38205 La Laguna, Tenerife, Spain
⁵ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁶ Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile
⁷ University of Arizona, Steward Observatory, Tucson, AZ 85719, USA
⁸ Observatório Nacional, rua General José Cristino 77, São Cristóvão, Rio de Janeiro 20921-400, Brazil
⁹ NSF NOIRLab, 950 N. Cherry Ave., Tucson, AZ 85719, USA
¹⁰ Instituto de Astronomía, Universidad Nacional Autónoma de México, A. P. 106, C.P. 22800, Ensenada, B. C., Mexico
¹¹ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, Potsdam, 14482, Germany
¹² Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970 Porto Alegre, Brazil
¹³ Department of Physics and Astronomy and JINA Center for the Evolution of the Elements (JINA-CEE), University of Notre Dame, Notre Dame, IN 46556, USA
¹⁴ Departament de Física Quãntica i Astrofísica (FQA), Universitat de Barcelona (UB), Martí i Franquès, 1, 08028 Barcelona, Spain
¹⁵ Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
¹⁶ Institut d’Estudis Espacials de Catalunya (IEEC), Edifici RDIT, Campus UPC, 08860 Castelldefels (Barcelona), Spain
¹⁷ Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF, UK
¹⁸ Instituto de Astrofísica, Facultad de Ciencias Exactas, Universidad Andres Bello, Fernández Concha 700, Las Condes, Santiago, Chile
¹⁹ Vatican Observatory, Vatican City State 00120, Italy
²⁰ Departamento de Astronomía, Casilla 160-C, Universidad de Concepción, Chile
²¹ Departamento de Astronomía, Facultad de Ciencias, Universidad de La Serena. Av. Avenida Raúl Bitrán S/N, La Serena, Chile
²² Universidade Federal de Sergipe, Av. Marechal Rondon, S/N, 49000-000 São Cristóvão, SE, Brazil
²³ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Macul, Casilla 306, Santiago 22, Chile
²⁴ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
²⁵ Centro de Astronomía (CITEVA), Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1270300, Chile

^★ Corresponding author.

Received: 28 May 2025
Accepted: 14 July 2025

Abstract

Context. We have previously studied several elements in 58 selected bulge spheroid stars, based on spectral lines in the H band. We now derive the abundances of the less studied elements phosphorus (P; Z=15), sulphur (S; Z=16), and potassium (K; Z=19).

Aims. The abundances of P, S, and K in 58 bulge spheroid stars are compared both with the results of a previous analysis of the data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), and with a few available studies of these elements.

Methods. We derived the individual abundances through spectral synthesis, using the stellar physical parameters available for our sample from the DR17 release of the APOGEE project. We provide recommendations for the best lines to be used for the studied elements among those in the H-band. We also compare the present results, together with literature data, with chemical-evolution models. Finally, the neutrino-process was taken into account for the suitable fit to the odd-Z elements P and K.

Results. We confirm that the H-band has useful lines for the derivation of the elements P, S, and K in moderately metal-poor stars. The abundances, plotted together with literature results from high-resolution spectroscopy, indicate that moderately enhanced phosphorus stars are found, reminiscent of results obtained for thick disc and halo stars of metallicity [Fe/H]≈−1.0. Therefore, for the first time, we identify that this effect occurs in the old stars from the bulge spheroid. Sulphur is an α-element and behaves as such. Potassium and sulphur both exhibit some star-to-star scatter, but fit within the expectations of chemical evolution models.