Zwicky Transient Facility and Globular Clusters: The Period–Luminosity and Period–Wesenheit Relations for SX Phoenicis Variables in the gri Band

Creators: Ngeow, Chow-Choong; Bhardwaj, Anupam; Graham, Matthew J.; Healy, Brian F.; Laher, Russ R.; Riddle, Reed; Wold, Avery

Abstract

SX Phoenicis (SXP) variables are short-period pulsating stars that exhibit a period–luminosity (PL) relation. We derived the gri-band PL and extinction-free period–Wesenheit (PW) relations, as well as the period-color and reddening-free period-Q-index relations for 47 SXP stars located in 21 globular clusters, using the optical light curves taken from Zwicky Transient Facility. These empirical relations were derived for the first time in the gri filters except for the g-band PL relation. We used our gi-band PL and PW relations to derive a distance modulus to Crater II dwarf spheroidal which hosts one SXP variable. Assuming that the fundamental and first-overtone pulsation mode for the SXP variable in Crater II, we found distance moduli of 20.03 ± 0.23 mag and 20.37 ± 0.24 mag, respectively, using the PW relation, where the latter is in excellent agreement with independent RR Lyrae based distance to Crater II dwarf galaxy.

Additional Information

© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. We thank the useful discussions and comments from an anonymous referee that improved the manuscript. We are thankful for funding from the National Science and Technology Council (Taiwan) under the contracts 107-2119-M-008-014-MY2, 107-2119-M-008-012, 108-2628-M-007-005-RSP, and 109-2112-M-008-014-MY3. Based on observations obtained with the Samuel Oschin Telescope 48 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. Z.T.F. is supported by the National Science Foundation under grants No. AST-1440341 and AST-2034437, and a collaboration including current partners Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. This research has made use of the SIMBAD database and the VizieR catalog access tool, operated at CDS, Strasbourg, France. This research made use of Astropy, 11 a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013, 2018, 2022). Facility: PO:1.2 m. - Software: astropy (Astropy Collaboration et al. 2013, 2018, 2022), dustmaps (Green 2018), gatspy (VanderPlas & Ivezić 2015), Matplotlib (Hunter 2007), NumPy (Harris et al. 2020), SciPy (Virtanen et al. 2020), statsmodels (Seabold & Perktold 2010).

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