Zwicky Transient Facility and Globular Clusters: The Period-Luminosity and Period-Wesenheit Relations for Type II Cepheids

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We present the first gri-band period-luminosity (PL) and period-Wesenheit (PW) relations for 37 Type II Cepheids (hereafter TIIC) located in 18 globular clusters based on photometric data from the Zwicky Transient Facility.

• We also updated BV IJHK-band absolute magnitudes for 58 TIIC in 24 globular clusters using the latest homogeneous distances to the globular clusters.
• The slopes of g/r/i and B/V/I band PL relations are found to be statistically consistent when using the same sample of distance and reddening.
• We employed the calibration of ri-band PL/PW relations in globular clusters to estimate a distance to M31 based on a sample of ~270 TIIC from the PAndromeda project.