Updated pulsation models for BL Herculis stars

Abstract

Population II pulsatingvariables play a relevant role both as distance indicators and as tracers of the properties of old stellar populations. In this paper we present an update and homogeneous pulsational scenario for a wide range of stellar parameters typical of BL Her stars i.e., Population II Cepheids with periods shorter than 8 days. To this purpose, we adopt a nonlinear convective hydrodinamical code evaluate the stability and full amplitude behaviour of an extensive set of BL Her pulsation models. Various assumptions of mass, luminosity and metallicity consistent with the most recent evolutionary prescriptions, are adopted. We obtain the theoretical instability strip for both fundamental and first overtone pulsators and present a detailed atlas of light/radial-velocity curves. Some relations for the boundaries of the instability strip and for the dependence of the absolute magnitude on period, mass and color, as well as the fundamental period-amplitude relations are derived.Finally, we provide the theoretical period-radius relation for BL Her and find that it is in excellent agreement with the empirical relation by Burki & Meylan and consistent with the one holding for shorter periods for RR Lyrae stars.

7 pages, accepted for publication in A&A

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Cited by in corpus (14)

• Gaia Data Release 1. Testing the parallaxes with local Cepheids and RR Lyrae stars
• Old-Aged Stellar Population Distance Indicators
• The VMC Survey. XIII. Type II Cepheids in the Large Magellanic Cloud
• Discovery of period doubling in BL Herculis stars of the OGLE survey. Observations and theoretical models
• High-precision distance measurements with classical pulsating stars
• Evolutionary and pulsation properties of Type II Cepheids
• The Carina Project. VI. The helium burning variable stars
• A theoretical framework of BL Her stars. I. Effect of metallicity and convection parameters on period-luminosity and period-radius relations
• Blue straggler masses from pulsation properties. II. Topology of the Instability Strip
• The stellar photosphere-hydrogen ionization front interaction in Classical Pulsators: a theoretical explanation for observed period-colour relations
• A theoretical framework for BL Her stars III. A case study: Robust light curve optimisation in the LMC
• A theoretical framework for BL Her stars IV. New period-luminosity relations in the Rubin-LSST filters
• New theoretical predictions on Type II Cepheids: towards a self consistent Pop. II distance scale
• Variable Stars in M31 Stellar Clusters from the Panchromatic Hubble Andromeda Treasury