New theoretical predictions on Type II Cepheids: towards a self consistent Pop. II distance scale
arXiv:2509.13552 · doi:10.1051/0004-6361/202556458
Abstract
Type II Cepheids are pulsating stars that can be used as standard candles for old stellar populations due to their characteristic Period-Luminosity and Period-Luminosity-Colour relations. They are traditionally divided in 3 sub-classes, namely BL Her, W Vir and RV Tauri. In this paper we focus on the first two sub-classes, to provide a new theoretical scenario and develop tools and relations to be adopted in distance scale and old stellar populations studies. We have built new nonlinear convective pulsation models of Type II Cepheids, computed along selected stellar evolution tracks and spanning a wide range of pulsation period and stellar parameters. Three chemical compositions have been taken into account. For each assumed Z and Y, models have been computed following stellar evolution predictions for off Zero Age Horizontal Branch evolution of stellar masses lower than typical RR Lyrae stars, crossing the classical instability strip as BL Her or W Vir pulsating stars. A new theoretical prediction for the instability strip boundaries of these classes of variable stars has been obtained together with their dependence on metal abundance. The predicted light and radial velocity curves have been computed along the evolution inside the strip, showing how the amplitude and the morphology are affected by the position relative to the edges and by the luminosity and mass values. The transformation of bolometric light curves into various photometric systems allowed us to provide new theoretical Period-Luminosity and Period-Wesenheit relations for BL Her and W Vir. These relations are consistent with previously published RR Lyrae model results but with a smaller metallicity dependence. Moreover, the application of the inferred theoretical relations to Magellanic and Galactic Type II Cepheid data provides results in good agreement with some independent distance estimates in the literature.
Accepted for publication on A&A
References in corpus (34)
- Gaia Data Release 3: Summary of the content and survey properties
- A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team
- Low Temperature Opacities
- Tensions between the Early and the Late Universe
- Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
- A distance to the Large Magellanic Cloud that is precise to one per cent
- Measurements of the Hubble Constant: Tensions in Perspective
- Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
- The influence of chemical composition on the properties of Cepheid stars. II-The iron content
- On a new theoretical framework for RR Lyrae stars I: the metallicity dependence
- A distance determination to the Small Magellanic Cloud with an accuracy of better than 2 percent based on late-type eclipsing binary stars
- A re-classification of Cepheids in the Gaia Data Release 2
- Nonlinear Investigation of the Pulsational Properties of RR Lyrae Variables
- The period-luminosity relation for type II Cepheids in globular clusters
- Gaia DR3: Specific processing and validation of all-sky RR Lyrae and Cepheid stars -- The Cepheid sample
- Metal Rich RR Lyrae Variables: II. The Pulsational Scenario
- The VMC Survey. XIII. Type II Cepheids in the Large Magellanic Cloud
- Cepheids and other short-period variables near the Galactic Centre
- A Classical Cepheid in a LMC eclipsing binary: evidence of shortcomings in current stellar evolutionary models?
- An updated metal-dependent theoretical scenario for Classical Cepheids
- The period-luminosity and period-radius relations of Type II and anomalous Cepheids
- Synthetic properties of bright metal-poor variables. II. BL Her stars
- On the Impact of Helium Content on the RR Lyrae Distance Scale
- An empirical mass-loss law for Population II giants from the Spitzer-IRAC survey of Galactic globular clusters
- Evolutionary and pulsation properties of Type II Cepheids
- Metallicity Effects on RR Lyrae Variables
- The evolutionary nature of RV Tauri stars in the SMC and LMC
- Cepheid metallicity in the Leavitt law (C-MetaLL) survey -- III. Simultaneous derivation of the Gaia parallax offset and Period-Luminosity-Metallicity coefficients
- Updated pulsation models for BL Herculis stars
- New type II Cepheids from VVV data towards the Galactic center
- Zwicky Transient Facility and Globular Clusters: The Period-Luminosity and Period-Wesenheit Relations for Type II Cepheids
- Precise Empirical Determination of Metallicity Dependence of Near-infrared Period-Luminosity Relations for RR Lyrae Variables
- Physical properties of galactic RV Tauri stars from Gaia DR2 data
- The model fitting of Gaia DR3 Classical Cepheid light and radial velocity curves