Precise distances from OGLE-IV member RR Lyrae stars in six bulge globular clusters

Autor(es)

Oliveira, R. A. P. ^[1] ; Ortolani, S. ^{[2, 3, 4]} ; Barbuy, B. ^[1] ; Kerber, L. O. ^[5] ; Maia, F. F. S. ^[6] ; Bica, E. ^[7] ; Cassisi, S. ^{[8, 9]} ; Souza, S. O. ^[1] ; Perez-Villegas, A. ^[10]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, IAG, Rua Matao 1226, Cidade Univ, BR-05508900 Sao Paulo - Brazil

^[2] INAF Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua - Italy

^[3] Univ Padua, Dipartimento Fis & Astron, Vicolo Osservatorio 2, I-35122 Padua - Italy

^[4] Ctr Ateneo & Att Spaziali Giuseppe Colombo CISAS, Via Venezia 15, I-35131 Padua - Italy

^[5] Univ Estadual Santa Cruz, Rodovia Jorge Amado Km 16, BR-45662000 Ilheus, BA - Brazil

^[6] Univ Fed Rio de Janeiro, Av Athos Silveira 149, Cidade Univ, BR-21941909 Rio De Janeiro - Brazil

^[7] Univ Fed Rio Grande do Sul, Dept Astron, CP 15051, BR-91501970 Porto Alegre, RS - Brazil

^[8] Ist Nazl Fis Nucl, Sez Pisa, Largo Pontecorvo 3, I-56127 Pisa - Italy

^[9] INAF Astron Observ Abruzzo, Via M Maggini SN, I-64100 Teramo - Italy

^[10] Univ Nacl Autonoma Mexico, Inst Astron, AP 106, Ensenada 22800, Baja California - Mexico

• Tipo de documento: Artigo Científico
• Fonte: Astronomy & Astrophysics; v. 657, JAN 21 2022.
• Citações Web of Science: 0

Resumo

Context. RR Lyrae stars are useful standard candles allowing one to derive accurate distances for old star clusters. Based on the recent catalogues from OGLE-IV and Gaia Early Data Release 3 (EDR3), the distances can be improved for a few bulge globular clusters. Aims. The aim of this work is to derive an accurate distance for the following six moderately metal-poor, relatively high-reddening bulge globular clusters: NGC 6266, NGC 6441, NGC 6626, NGC 6638, NGC 6642, and NGC 6717. Methods. We combined newly available OGLE-IV catalogues of variable stars containing mean I magnitudes, with Clement's previous catalogues containing mean V magnitudes, and with precise proper motions from Gaia EDR3. Astrometric membership probabilities were computed for each RR Lyrae, in order to select those compatible with the cluster proper motions. Applying luminosity-metallicity relations derived from BaSTI alpha-enhanced models (He-enhanced for NGC 6441 and canonical He for the other clusters), we updated the distances with relatively low uncertainties. Results. Distances were derived with the I and V bands, with a 5-8% precision. We obtained 6.6 kpc, 13.1 kpc, 5.6 kpc, 9.6 kpc, 8.2 kpc, and 7.3 kpc for NGC 6266, NGC 6441, NGC 6626, NGC 6638, NGC 6642, and NGC 6717, respectively. The results are in excellent agreement with the literature for all sample clusters, considering the uncertainties. Conclusions. The present method of distance derivation, based on recent data of member RR Lyrae stars, updated BaSTI models, and robust statistical methods, proved to be consistent. A larger sample of clusters will be investigated in a future work. (AU)

• Processo FAPESP: 18/22181-0 - Gradientes de idade e metalicidade dos aglomerados estelares da Ponte de Magalhães
• Beneficiário: Raphael Augusto Pereira de Oliveira
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 18/22044-3 - Aglomerados globulares do bojo: relíquias da formação e evolução da galáxia
• Beneficiário: Stefano Oliveira de Souza
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto