Gaia DR3 Open Cluster Cepheids: A Unified Catalog with Calibrated Period–Age and Period–Wesenheit Relations

Abstract Classical Cepheids (CCs) in Galactic open clusters (OCs) provide essential observational constraints for calibrating the period–age relation (PAR) and the period–Wesenheit relation (PWR) of CCs. However, distant and long-period OC Cepheids remain limited, while the confirmed samples still require more precise determinations of their physical properties, such as ages and extinctions. In this work, we present a comprehensive census of OC Cepheids based on an extensive sample of distant OCs from Gaia Data Release 3 (DR3). By combining astrometric and photometric membership analyses, we identified 110 CCs associated with 102 OCs, of which 41 CCs across 37 OCs were classified as OC Cepheids, while the remaining cases were considered candidate or rejected associations. Our results are consistent with previous studies, while 4 of the 41 OC Cepheids are newly reported here. Using updated cluster parameters derived from manual isochrone fitting, we primarily refined the PAR to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>logAge</mml:mi> </mml:math> = (−0.595 ± 0.044) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>P</mml:mi> </mml:math> + (8.430 ± 0.042) and recalibrated the PWR to W G = (−3.615 ± 0.083) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>P</mml:mi> </mml:math> + (−2.379 ± 0.096). This study expands the sample of confirmed and candidate OC Cepheids. The newly longest-period confirmed OC Cepheid is BM Per (CWNU 3123) with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>P</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.36</mml:mn> </mml:math> , and two newly confirmed longest-period OC Cepheid candidates have distances exceeding 6 kpc. Moreover, the PAR and PWR are improved by incorporating refined OC ages and updated parallaxes, respectively.