Synthetic properties of bright metal-poor variables. II. BL Her stars

Abstract

We investigate the properties of the so-called BL Her stars, i.e., Population II Cepheids with periods shorter than 8 days, using updated pulsation models and evolutionary tracks computed adopting a metal abundance in the range of Z=0.0001 to Z=0.004. We derive the predicted Period-Magnitude (PM) and Period-Wesenheit (PW) relations at the various photometric bands and we show that the slopes of these relations are in good agreement with the slopes determined by observed variables in Galactic globular clusters, independently of the adopted M_V(RR)-[Fe/H] relation to get the cluster RR Lyrae-based distance. Moreover, we show that also the distances provided by the predicted PM and PW relations for BL Her stars agree within the errors with the RR Lyrae based values. The use of the predicted relations with W Vir stars, which are Population II Cepheids with periods longer than 8 days, provides no clear evidence for or against a change in the PM and PW slopes around P~10 days.

arXiv comment12 pages, 6 figures, 6 tables, accepted for publication in A&A on date 16/05/2007

References in corpus (24)

• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Color Transformations for the 2MASS Second Incremental Data Release
• A large stellar evolution database for population synthesis studies. II. Stellar models and isochrones for an alpha-enhanced metal distribution
• Ultraviolet Radiation from Evolved Stellar Populations -- I. Models
• The initial Helium content of Galactic Globular Cluster stars from the R-parameter: comparison with the CMB constraint
• Cepheid pulsation models at varying metallicity and DY/DZ
• Color transformations and bolometric corrections for Galactic halo stars: alpha-enhanced vs scaled-solar results
• RR Lyrae stars in Galactic globular clusters.III. Pulsational predictions for metal content Z=0.0001 to Z=0.006
• Globular Cluster Distances from RR Lyrae Stars
• The Initial Helium Abundance of the Galactic Globular Cluster System
• The period-luminosity relation for type II Cepheids in globular clusters
• RR Lyrae stars in Galactic globular clusters. II. A theoretical approach to variables in M3
• Pulsation and evolutionary masses of classical Cepheids. I. Milky Way variables
• HST Snaphot Study of Variable Stars in Globular Clusters: Inner Region of NGC 6441
• Theoretical models for Bump Cepheids
• A pulsational distance to Omega Centauri based on Near-Infrared Period-Luminosity relations of RR Lyrae stars
• Updated pulsation models for anomalous Cepheids
• The Red Giant Branch Luminosity Function Bump
• RR Lyrae-based calibration of the Globular Cluster Luminosity Function
• A Homogenous Set of Globular Cluster Relative Distances and Reddenings
• Bright metal-poor variables: why "Anomalous" Cepheids?
• The RR Lyrae U Com as a test for nonlinear pulsation models
• Near-Infrared Observations of RR Lyrae variables in Galactic Globular Clusters: I. The case of M92
• Synthetic properties of bright metal-poor variables. I. "Anomalous" Cepheids

Cited by in corpus (31)

• Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
• The distance to the Galactic Centre based on Population-II Cepheids and RR Lyrae stars
• The Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441: new insights from UV observations
• Old-Aged Stellar Population Distance Indicators
• The VMC Survey. XIII. Type II Cepheids in the Large Magellanic Cloud
• Period-Luminosity Relations for Type II Cepheids and their Application
• Anomalous Cepheids in the Large Magellanic Cloud: Insight into their origin and connection with the star formation history
• The period-luminosity and period-radius relations of Type II and anomalous Cepheids
• Survey of non-linear hydrodynamic models of type-II Cepheids
• High-precision distance measurements with classical pulsating stars
• Evolutionary and pulsation properties of Type II Cepheids
• The ancient stellar population of M32: RR Lyr Variable stars confirmed
• Structure and kinematics of Type II Cepheids in the Galactic bulge based on near-infrared VVV data
• Variable Stars in the Cetus dSph Galaxy: Population Gradients and Connections with the Star Formation History
• On the separation between RR Lyrae and Type II Cepheids and their importance for distance determination: the case of $\omega$ Cen
• Analysing the spectral energy distributions of Galactic classical Cepheids
• Luminosities and infrared excess in Type II and anomalous Cepheids in the Large and Small Magellanic Clouds
• Blue straggler masses from pulsation properties. II. Topology of the Instability Strip
• A theoretical framework of BL Her stars. I. Effect of metallicity and convection parameters on period-luminosity and period-radius relations
• New type II Cepheids from VVV data towards the Galactic center
• An absolute calibration of the near-infrared Period-Luminosity Relations of Type II Cepheids in the Milky Way and in the Large Magellanic Cloud
• Zwicky Transient Facility and Globular Clusters: The Period-Luminosity and Period-Wesenheit Relations for Type II Cepheids
• Near-IR period-luminosity relations for pulsating stars in $\omega$ Centauri (NGC 5139)
• Homogeneous Photometry VI: Variable Stars in the Leo I Dwarf Spheroidal Galaxy
• Variable Stars in Local Group Galaxies. IV. RR Lyrae stars in the central regions of the low-density galaxy Crater II
• CCD \emph{VI} time-series of the extremely metal poor globular cluster M92: revisiting its variable star population
• V371 Per - A Thick-Disk, Short-Period F/1O Cepheid
• 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
• Period-Luminosity Relations for Galactic Type II Cepheids in the Sloan bands
• New theoretical predictions on Type II Cepheids: towards a self consistent Pop. II distance scale