NGC 6426: Colour-Magnitude diagram and variable star population as indicators of metallicity, distance, and age
Year: 2026
Type: preprint
Abstract: We present new VI CCD photometry of the globular cluster NGC 6426. The membership status of all point sources and, in particular, of all the variables in the field of view is discussed, including four recently detected variables. The double mode nature of variables V3 and V9 is confirmed and their periods are calculated. The presence of a cluster member anomalous Cepheid (V17) is reported. Employing only likely members we produce a decontaminated colour-magnitude diagram (CMD) differentially dereddened, which enables us to compare it with theoretical predictions and to study the variable stars distribution. The mean cluster metallicity and distance were calculated via the RR Lyrae V-band light curve Fourier decomposition and an I-band calibration of the Period-Magnitude-Metallicity relation. Further, a comparison using a Bayesian approach between theoretical isochrones of Dartmouth Stellar Evolution Database (DSED), with a deep HST CMD, gave us independent estimates of distance modulus, metallicity, colour excess, and cluster age.
Source: arXiv (Cornell University)
Institutions: Universidad Nacional Autónoma de México, National Institute of Astrophysics, Optics and Electronics, Secretaría de Ciencia Tecnología e Innovación, Secretaría de Ciencia, Humanidades, Tecnología e Innovación, Universidad Autónoma de Baja California, Indian Institute of Astrophysics, Universidad Nacional de Córdoba, Argentine National Observatory
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221152390